MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Current Topics in Developmental Biology' source. Thu, 09 Feb 2012 14:32:06 +0100 http://www.medworm.com/index.php?rid=5672581&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22305157%26dopt%3DAbstract Authors: Cadigan KM Abstract Wnts are conserved, secreted signaling proteins that can influence cell behavior by stabilizing β-catenin. Accumulated β-catenin enters the nucleus, where it physically associates with T-cell factor (TCF) family members to regulate target gene expression in many developmental and adult tissues. Recruitment of β-catenin to Wnt response element (WRE) chromatin converts TCFs from transcriptional repressors to activators. This review will outline the complex interplay between factors contributing to TCF repression and coactivators working with β-catenin to regulate Wnt targets. In addition, three variations of the standard transcriptional switch model will be discussed. One is the Wnt/β-catenin symmetry pathway in Caenorhabditis elegans, where Wnt-medi... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5672581 Thu, 09 Feb 2012 15:36:04 +0100 5672581 http://www.medworm.com/index.php?rid=5672580&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22305158%26dopt%3DAbstract Authors: Wang S, Samakovlis C Abstract The Grainy head (Grh) family of transcription factors is characterized by a unique DNA-binding domain that binds to a conserved consensus sequence. Nematodes and flies have a single grh gene, whereas mice and humans have evolved three genes encoding Grainy head-like (Grhl) factors. We review the biological function of Grh in different animals and the mechanisms modulating its activity. grh and grhl genes play a remarkably conserved role in epithelial organ development and extracellular barrier repair after tissue damage. Recent studies in flies and vertebrates suggest that Grh factors may be primary determinants of cell adhesion and epithelial tissue formation. Grh proteins can dimerize and act as activators or repressors in different developm... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5672580 Thu, 09 Feb 2012 15:36:04 +0100 5672580 http://www.medworm.com/index.php?rid=5672579&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22305159%26dopt%3DAbstract Authors: Turki-Judeh W, Courey AJ Abstract Drosophila Groucho (Gro) is the founding member of a family of metazoan corepressors. Gro mediates repression through interactions with a myriad of DNA-binding repressor proteins to direct the silencing of genes involved in many developmental processes, including neurogenesis and patterning of the main body axis, as well as receptor tyrosine kinase/Ras/MAPK, Notch, Wingless (Wg)/Wnt, and Decapentaplegic (Dpp) signaling. Gro mediates repression by multiple molecular mechanisms, depending on the regulatory context. Because Gro is a broadly expressed nuclear factor, whereas its repressor partners display restricted temporal and spatial distribution, it was presumed that this corepressor played permissive rather than instructive roles in devel... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5672579 Thu, 09 Feb 2012 15:36:04 +0100 5672579 http://www.medworm.com/index.php?rid=5672578&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22305160%26dopt%3DAbstract Authors: Evans NC, Swanson CI, Barolo S Abstract This review focuses on a single cis-regulatory element: the sparkling eye enhancer of the Drosophila dPax2 gene. sparkling responds to Notch and EGFR signaling, along with other direct regulatory inputs, to drive gene expression that is restricted to cone cells of the developing fly retina. Functional, genetic, biochemical, evolutionary, and bioinformatic analyses have revealed surprising properties of sparkling, which may provide new insights into cis-regulatory logic and mechanisms of transcriptional activation. These properties include: a very high density of regulatory information and a correspondingly low "junk" content; an unexpectedly complex combinatorial code; tight functional constraints on enhancer organization, paradoxica... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5672578 Thu, 09 Feb 2012 15:36:04 +0100 5672578 http://www.medworm.com/index.php?rid=5672577&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22305161%26dopt%3DAbstract Authors: Aerts S Abstract Transcription factors (TFs) are key proteins that decode the information in our genome to express a precise and unique set of proteins and RNA molecules in each cell type in our body. These factors play a pivotal role in all biological processes, including the determination of a cell's fate during development and the maintenance of a cell's physiological function. To achieve this, a TF binds to specific DNA sequences in the noncoding part of the genome, recruits chromatin modifiers and cofactors, and directs the transcription initiation rate of its "target genes." Therefore, a key challenge in deciphering a transcriptional switch is to identify the direct target genes of the master regulators that control the switch, the cis-regulatory elements implementin... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5672577 Thu, 09 Feb 2012 15:36:04 +0100 5672577 http://www.medworm.com/index.php?rid=5672576&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22305162%26dopt%3DAbstract Authors: Wang W, Christiaen L Abstract The study of cis-regulatory DNAs that control developmental gene expression is integral to the modeling of comprehensive genomic regulatory networks for embryogenesis. Ascidian embryos provide a unique opportunity for the analysis of cis-regulatory DNAs with cellular resolution in the context of a simple but typical chordate body plan. Here, we review landmark studies that have laid the foundations for the study of transcriptional enhancers, among other cis-regulatory DNAs, and their roles in ascidian development. The studies using ascidians of the Ciona genus have capitalized on a unique electroporation technique that permits the simultaneous transfection of hundreds of fertilized eggs, which develop rapidly and express transgenes with little... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5672576 Thu, 09 Feb 2012 15:36:04 +0100 5672576 http://www.medworm.com/index.php?rid=5672575&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22305163%26dopt%3DAbstract Authors: Estella C, Voutev R, Mann RS Abstract Animal appendages require a proximodistal (PD) axis, which forms orthogonally from the two main body axes, anteroposterior and dorsoventral. In this review, we discuss recent advances that begin to provide insights into the molecular mechanisms controlling PD axis formation in the Drosophila leg. In this case, two morphogens, Wingless (Wg) and Decapentaplegic (Dpp), initiate a genetic cascade that, together with growth of the leg imaginal disc, establishes the PD axis. The analysis of cis-regulatory modules (CRMs) that control the expression of genes at different positions along the PD axis has been particularly valuable in dissecting this complex process. From these experiments, it appears that only one concentration of Wg and Dpp are... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5672575 Thu, 09 Feb 2012 15:36:04 +0100 5672575 http://www.medworm.com/index.php?rid=5672574&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22305164%26dopt%3DAbstract Authors: Maurange C Abstract The mechanisms underlying the temporal specification of neural stem cells (NSCs), a process by which a single progenitor can generate different types of neurons and glia in an invariant order, are still poorly understood in mammals. However, in the past decade, work on Drosophila NSCs, called neuroblasts, has identified a series of sequentially expressed transcription factors that lies at the heart of this phenomenon. Here, I highlight some key findings that illuminate the role of these transcription factors during development and the regulatory principles allowing them not only to promote neuronal diversity but also to control the final number of neurons in the different regions of the nervous system. Ultimately, and given recent evidences of evolution... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5672574 Thu, 09 Feb 2012 15:36:04 +0100 5672574 http://www.medworm.com/index.php?rid=5672573&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22305165%26dopt%3DAbstract Authors: Moreno-Risueno MA, Van Norman JM, Benfey PN Abstract Development of multicellular organisms requires specification of diverse cell types. In plants, development is continuous and because plant cells are surrounded by rigid cell walls, cell division and specification of daughter cell fate must be carefully orchestrated. During embryonic and postembryonic plant development, the specification of cell types is determined both by positional cues and cell lineage. The establishment of distinct transcriptional domains is a fundamental mechanism for determining different cell fates. In this review, we focus on four examples from recent literature of switches operating in cell fate decisions that are regulated by transcriptional mechanisms. First, we highlight a transcriptional mec... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5672573 Thu, 09 Feb 2012 15:36:04 +0100 5672573 http://www.medworm.com/index.php?rid=5672572&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22305166%26dopt%3DAbstract Authors: Quan XJ, Ramaekers A, Hassan BA Abstract It is now widely recognized that as cells of developing tissues transition through successive states of decreasing pluripotency into a state of terminal differentiation, they undergo significant changes in their gene expression profiles. Interestingly, these successive states of increasing differentiation are marked by the spatially and temporally restricted expression of sets of transcription factors. Each wave of transcription factors not only signals the arrival of a given stage in cellular differentiation, but it is also necessary for the activation of the next set of transcription factors, creating the appearance of a smooth, directed, and deterministic genetic program of cellular differentiation. Until recently, however, it wa... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5672572 Thu, 09 Feb 2012 15:36:04 +0100 5672572 http://www.medworm.com/index.php?rid=5672571&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22305167%26dopt%3DAbstract Authors: de Joussineau C, Bataillé L, Jagla T, Jagla K Abstract Understanding gene regulatory pathways underlying diversification of cell types during development is one of the major challenges in developmental biology. Progressive specification of mesodermal lineages that are at the origin of body wall muscles in Drosophila embryos has been extensively studied during past years, providing an attractive framework for dissecting cell type diversification processes. In particular, it has been found that muscle founder cells that are at the origin of individual muscles display specific expression of transcription factors that control diversification of muscle types. These factors, encoded by genes collectively called muscle identity genes, are activated in discrete subsets of muscle ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5672571 Thu, 09 Feb 2012 15:36:04 +0100 5672571 http://www.medworm.com/index.php?rid=5672570&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22305168%26dopt%3DAbstract Authors: Plaza S, Payre F PMID: 22305168 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5672570 Thu, 09 Feb 2012 15:36:04 +0100 5672570 http://www.medworm.com/index.php?rid=5414108&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22074600%26dopt%3DAbstract Authors: Raphael AR, Talbot WS Abstract Myelin is a vertebrate adaptation that allows for the rapid propagation of action potentials along axons. Specialized glial cells-oligodendrocytes in the central nervous system (CNS) and Schwann cells in the peripheral nervous system (PNS)-form myelin by repeatedly wrapping axon segments. Debilitating diseases result from the disruption of myelin, including multiple sclerosis and Charcot-Marie-Tooth peripheral neuropathies. The process of myelination involves extensive communication between glial cells and the associated neurons. The past few years have seen important progress in understanding the molecular basis of the signals that coordinate the development of these fascinating cells. This review highlights recent advances in myelination de... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5414108 Thu, 17 Nov 2011 12:42:02 +0100 5414108 http://www.medworm.com/index.php?rid=5414107&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22074601%26dopt%3DAbstract Authors: Buechling T, Boutros M Abstract Wnt signaling is one of the most important developmental signaling pathways that controls cell fate decisions and tissue patterning during early embryonic and later development. It is activated by highly conserved Wnt proteins that are secreted as palmitoylated glycoproteins and act as morphogens to form a concentration gradient across a developing tissue. Wnt proteins regulate transcriptional and posttranscriptional processes depending on the distance of their origin and activate distinct intracellular cascades, commonly referred to as canonical (β-catenin-dependent) and noncanonical (β-catenin-independent) pathways. Therefore, the secretion and the diffusion of Wnt proteins needs to be tightly regulated to induce short- and long-range do... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5414107 Thu, 17 Nov 2011 12:42:02 +0100 5414107 http://www.medworm.com/index.php?rid=5414106&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22074602%26dopt%3DAbstract Authors: Johnson JE, Macdonald RJ Abstract Notch-dependent CSL transcription complexes control essential biological processes such as cell proliferation, differentiation, and cell-fate decisions in diverse developmental systems. The orthologous proteins CBF1/Rbpj (mammalian), Su(H) (Drosophila), and Lag-1 (Caenorhabditis elegans) compose the CSL family of sequence-specific DNA-binding transcription factors. The CSL proteins are best known for their role in canonical Notch signaling. However, CSL factors also form transcription complexes that can function independent of Notch signaling and include repression and activation of target gene transcription. Because the different complexes share CSL as a DNA-binding subunit, they can control overlapping sets of genes; but they can also co... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5414106 Thu, 17 Nov 2011 12:42:02 +0100 5414106 http://www.medworm.com/index.php?rid=5414105&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22074603%26dopt%3DAbstract Authors: Matise MP, Wang H Abstract Sonic Hedgehog (Shh) is one of three mammalian orthologs of the Hedgehog (Hh) family of secreted proteins first identified for their role in patterning the Drosophila embryo. In this review, we will highlight some of the outstanding questions regarding how Shh signaling controls embryonic development. We will mainly consider its role in the developing mammalian central nervous system (CNS) where the pathway plays a critical role in orchestrating the specification of distinct cell fates within ventral regions, a process of exquisite complexity that is necessary for the proper wiring and hence function of the mature system. Embryonic development is a process that plays out in both the spatial and the temporal dimensions, and it is becoming increasi... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5414105 Thu, 17 Nov 2011 12:42:02 +0100 5414105 http://www.medworm.com/index.php?rid=5414104&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22074604%26dopt%3DAbstract Authors: Sahores M, Salinas PC Abstract Synapse formation is a critical step in the assembly of neuronal circuits. Both secreted and membrane-associated proteins contribute to the assembly and maturation of synapses. In addition, neuronal activity regulates the formation of neuronal circuits through the stimulation of growth factor secretion and the localization of receptors such as NMDA and AMPA receptors (NMDAR and AMPAR, respectively). Little is known, however, about the role of activity in the localization and function of receptors for synaptogenic molecules. Wnts are secreted proteins that play a role in synapse formation by regulating pre- and postsynaptic assembly at central and peripheral synapses. Wnts can signal through different receptors including Frizzleds (Fzs), the L... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5414104 Thu, 17 Nov 2011 12:42:02 +0100 5414104 http://www.medworm.com/index.php?rid=5414103&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22074605%26dopt%3DAbstract Authors: Holstein TW, Watanabe H, Ozbek S Abstract The determination of the body axis in the last common ancestor of bilaterian animals is still a matter of debate. While Hox genes pattern the formation of the primary, anteroposterior body axis in bilaterians, there is growing evidence from lower metazoans that the Wnt/β-catenin pathway acts as the primordial signaling system in this process. This review summarizes molecular data from recent genomic analyses of basal model organisms with a focus on the evolution of signaling pathways involved in the establishment of the primary and successive body axes during early metazoan evolution. PMID: 22074605 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5414103 Thu, 17 Nov 2011 12:42:02 +0100 5414103 http://www.medworm.com/index.php?rid=5414102&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22074606%26dopt%3DAbstract Authors: Stricker S, Mundlos S Abstract Skeletal malformations are among the most frequent developmental disturbances in humans. In the past years, progress has been made in unraveling the molecular mechanisms that govern skeletal development by the use of animal models as well as by the identification of numerous mutations that cause human skeletal syndromes. Receptor tyrosine kinases have critical roles in embryonic development. During formation of the skeletal system, the fibroblast growth factor receptor (FGFR) family plays major roles in the formation of cranial, axial, and appendicular bones. Another player of relevance to skeletal development is the unusual receptor tyrosine kinase ROR2, the function of which is as interesting as it is complex. In this chapter, we review the... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5414102 Thu, 17 Nov 2011 12:42:02 +0100 5414102 http://www.medworm.com/index.php?rid=5414101&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22074607%26dopt%3DAbstract Authors: Birchmeier C PMID: 22074607 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=5414101 Thu, 17 Nov 2011 12:42:02 +0100 5414101 http://www.medworm.com/index.php?rid=4899225&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21621065%26dopt%3DAbstract Authors: Murphy M, Kardon G Muscle development, growth, and regeneration take place throughout vertebrate life. In amniotes, myogenesis takes place in four successive, temporally distinct, although overlapping phases. Understanding how embryonic, fetal, neonatal, and adult muscle are formed from muscle progenitors and committed myoblasts is an area of active research. In this review we examine recent expression, genetic loss-of-function, and genetic lineage studies that have been conducted in the mouse, with a particular focus on limb myogenesis. We synthesize these studies to present a current model of how embryonic, fetal, neonatal, and adult muscle are formed in the limb. PMID: 21621065 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4899225 Mon, 06 Jun 2011 14:15:04 +0100 4899225 http://www.medworm.com/index.php?rid=4899224&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21621066%26dopt%3DAbstract Authors: Kikuchi K, Rubin BP, Keller C Rhabdomyosarcomas (RMS) are very heterogeneous tumors that can be divided into three major groups: alveolar rhabdomyosarcoma, embryonal rhabdomyosarcoma, and pleomorphic rhabdomyosarcoma. Concerted efforts over the past a decade have led to an understanding of the genetic underpinnings of many human tumors through genetically engineered models; however, left largely behind in this effort have been rare tumors with poorly understood chromosomal abnormalities including the vast majority of RMS lacking a pathognomonic translocation, i.e. fusion-negative RMS. In this chapter, we review the characteristic genetic abnormalities associated with human RMS and the genetically engineered animal models for these fusion-negative RMS. We explore not only how s... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4899224 Mon, 06 Jun 2011 14:15:04 +0100 4899224 http://www.medworm.com/index.php?rid=4899223&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21621067%26dopt%3DAbstract Authors: Sartorelli V, Juan AH Satellite cells (SCs) are the main source of adult skeletal muscle stem cells responsible for muscle growth and regeneration. By interpreting extracellular cues, developmental regulators control quiescence, proliferation, and differentiation of SCs by influencing coordinate gene expression. The scope of this review is limited to the description and discussion of protein complexes that introduce and decode heritable histone and chromatin modifications and how these modifications are relevant for SC biology. PMID: 21621067 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4899223 Mon, 06 Jun 2011 14:15:04 +0100 4899223 http://www.medworm.com/index.php?rid=4899041&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21621068%26dopt%3DAbstract Authors: Peterson JM, Bakkar N, Guttridge DC Muscle development, growth, and maintenance require an intricate and timely series of events initiated through a multitude of signaling pathways. The very nature of skeletal muscle requires tremendous plasticity to accommodate the need for anabolism or catabolism, and deregulation of these processes may be a tipping point in the development or progression of various skeletal muscle disorders. Among the relevant signaling pathways, NF-κB has emerged as a critical factor involved in various facets of muscle homeostasis. In this review, we summarize the NF-κB signaling pathway and provide a fresh perspective into the regulation and function of this transcription factor, underlying both the physiological and pathophysiological states of skelet... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4899041 Mon, 06 Jun 2011 14:15:04 +0100 4899041 http://www.medworm.com/index.php?rid=4898967&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21621069%26dopt%3DAbstract Authors: Mounier R, Chrétien F, Chazaud B The fate of stem cell is regulated by cues received from the surrounding area. Recently, the concept of "stem cell zone"-rather than a predefined niche-introduced the notion of dynamic and permanent interactions between stem cells and their microenvironment. In adult skeletal muscle, satellite cells are considered as the main stem cells responsible for muscle repair and maintenance. They are localized close to vessels regardless their state of activation and differentiation. Moreover, the number of satellite cells is positively correlated to the capillarization of the myofiber. Angiogenesis has been known for a long time to be essential for muscle repair. However, relationships between vessel cells and satellite/myogenic cells that govern myog... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4898967 Mon, 06 Jun 2011 14:15:04 +0100 4898967 http://www.medworm.com/index.php?rid=4898892&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21621070%26dopt%3DAbstract Authors: Paylor B, Natarajan A, Zhang RH, Rossi F Although classical dogma dictates that satellite cells are the primary cell type involved in skeletal muscle regeneration, alternative cell types such as a variety of inflammatory and stromal cells are also actively involved in this process. A model describing myogenic cells as direct contributors to regeneration and nonmyogenic cells from other developmental sources as important accessories has emerged, with similar systems having been described in numerous other tissues in the body. Increasing evidence supports the notion that inflammatory cells function as supportive accessory cells, and are not merely involved in clearing damage following skeletal muscle injury. Additionally, recent studies have highlighted the role of tissue reside... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4898892 Mon, 06 Jun 2011 14:15:04 +0100 4898892 http://www.medworm.com/index.php?rid=4898805&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21621071%26dopt%3DAbstract Authors: Serrano AL, Mann CJ, Vidal B, Ardite E, Perdiguero E, Muñoz-Cánoves P The repair of an injured tissue is a complex biological process involving the coordinated activities of tissue-resident and infiltrating cells in response to local and systemic signals. Following acute tissue injury, inflammatory cell infiltration and activation/proliferation of resident stem cells is the first line of defense to restore tissue homeostasis. However, in the setting of chronic tissue damage, such as in Duchenne Muscular Dystrophy, inflammatory infiltrates persist, the ability of stem cells (satellite cells) is blocked and fibrogenic cells are continuously activated, eventually leading to the conversion of muscle into nonfunctional fibrotic tissue. This review explores our current understandi... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4898805 Mon, 06 Jun 2011 14:15:04 +0100 4898805 http://www.medworm.com/index.php?rid=4898561&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21621072%26dopt%3DAbstract Authors: Posey AD, Demonbreun A, McNally EM Myoblast fusion contributes to muscle growth in development and during regeneration of mature muscle. Myoblasts fuse to each other as well as to multinucleate myotubes to enlarge the myofiber. The molecular mechanisms of myoblast fusion are incompletely understood. Adhesion, apposition, and membrane fusion are accompanied by cytoskeletal rearrangements. The ferlin family of proteins is implicated in human muscle disease and has been implicated in fusion events in muscle, including myoblast fusion, vesicle trafficking and membrane repair. Dysferlin was the first mammalian ferlin identified and it is now known that there are six different ferlins. Loss-of-function mutations in the dysferlin gene lead to limb girdle muscular dystrophy and the mi... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4898561 Mon, 06 Jun 2011 14:15:04 +0100 4898561 http://www.medworm.com/index.php?rid=4898480&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21621073%26dopt%3DAbstract Authors: Lefta M, Wolff G, Esser KA Almost all organisms ranging from single cell bacteria to humans exhibit a variety of behavioral, physiological, and biochemical rhythms. In mammals, circadian rhythms control the timing of many physiological processes over a 24-h period, including sleep-wake cycles, body temperature, feeding, and hormone production. This body of research has led to defined characteristics of circadian rhythms based on period length, phase, and amplitude. Underlying circadian behaviors is a molecular clock mechanism found in most, if not all, cell types including skeletal muscle. The mammalian molecular clock is a complex of multiple oscillating networks that are regulated through transcriptional mechanisms, timed protein turnover, and input from small molecules. At ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4898480 Mon, 06 Jun 2011 14:15:04 +0100 4898480 http://www.medworm.com/index.php?rid=4898388&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21621074%26dopt%3DAbstract Authors: Hall MN, Corbett AH, Pavlath GK Proper skeletal muscle function is dependent on spatial and temporal control of gene expression in multinucleated myofibers. In addition, satellite cells, which are tissue-specific stem cells that contribute critically to repair and maintenance of skeletal muscle, are also required for normal muscle physiology. Gene expression in both myofibers and satellite cells is dependent upon nuclear proteins that require facilitated nuclear transport. A unique challenge for myofibers is controlling the transcriptional activity of hundreds of nuclei in a common cytoplasm yet achieving nuclear selectivity in transcription at specific locations such as neuromuscular synapses and myotendinous junctions. Nucleocytoplasmic transport of macromolecular cargoes is... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4898388 Mon, 06 Jun 2011 14:15:04 +0100 4898388 http://www.medworm.com/index.php?rid=4745463&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21501746%26dopt%3DAbstract Authors: Labouesse M PMID: 21501746 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4745463 Sun, 24 Apr 2011 22:15:03 +0100 4745463 http://www.medworm.com/index.php?rid=4745462&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21501747%26dopt%3DAbstract Authors: Lindemann CB The cilia and flagella of eukaryotic cells are complex filamentous organelles that undulate rapidly and produce propulsive force against the fluids that surround the living cell. They provide a number of important functions in the life cycle of higher organisms including humans. A flagellum propels the spermatozoa to the site of fertilization and cilia move the egg through the oviduct to the uterus and have a role in left-right asymmetry in the developing embryo and contribute to normal brain morphology. The geometric clutch hypothesis is a mechanistic explanation of how the repetitive bending of cilia and flagella is generated. This chapter recounts the events leading to the development of the geometric clutch hypothesis, explores the conceptual framework of the ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4745462 Sun, 24 Apr 2011 22:15:03 +0100 4745462 http://www.medworm.com/index.php?rid=4745461&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21501748%26dopt%3DAbstract Authors: Supatto W, Vermot J Embryonic development involves the cellular integration of chemical and physical stimuli. A key physical input is the mechanical stress generated during embryonic morphogenesis. This process necessitates tensile forces at the tissue scale such as during axis elongation and budding, as well as at the cellular scale when cells migrate and contract. Furthermore, cells can generate forces using motile cilia to produce flow. Cilia-driven flows are critical throughout embryonic development but little is known about the diversity of the forces they exert and the role of the mechanical stresses they generate. In this chapter, through an examination of zebrafish development, we highlight what is known about the role of hydrodynamics mediated by beating cilia and exa... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4745461 Sun, 24 Apr 2011 22:15:03 +0100 4745461 http://www.medworm.com/index.php?rid=4745460&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21501749%26dopt%3DAbstract Authors: Kruse K, Riveline D Major transformations of cells during embryonic development are traditionally associated with the activation or inhibition of genes and with protein modifications. The contributions of mechanical properties intrinsic to the matter an organism is made of, however, are often overlooked. The emerging field "physics of living matter" is addressing active material properties of the cytoskeleton and tissues like the spontaneous generation of stress, which may lead to shape changes and tissue flows, and their implications for embryonic development. Here, we discuss spontaneous mechanical oscillations to present some basic elements for understanding this physics, and we illustrate its application to developing embryos. We highlight the role of state diagrams to qua... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4745460 Sun, 24 Apr 2011 22:15:03 +0100 4745460 http://www.medworm.com/index.php?rid=4745459&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21501750%26dopt%3DAbstract We present here different key aspects of cortical forces: their physical nature, some rules governing their emergence, and how their deployment at cell surfaces drives important morphogenetic movements in epithelia. We review a wide range of literature combining genetic/molecular, biophysical and modeling approaches, which explore essential features of cortical force generation and transmission in tissues. PMID: 21501750 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4745459 Sun, 24 Apr 2011 22:15:03 +0100 4745459 http://www.medworm.com/index.php?rid=4745458&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21501751%26dopt%3DAbstract Authors: Lye CM, Sanson B During morphogenesis, tissues are shaped by cell behaviors such as apical cell constriction and cell intercalation, which are the result of cell intrinsic forces, but are also shaped passively by forces acting on the cells. The latter extrinsic forces can be produced either within the deforming tissue by the tissue-scale integration of intrinsic forces, or outside the tissue by other tissue movements or by fluid flows. Here we review the intrinsic and extrinsic forces that sculpt the epithelium of early Drosophila embryos, focusing on three conserved morphogenetic processes: tissue internalization, axis extension, and segment boundary formation. Finally, we look at how the actomyosin cytoskeleton forms force-generating structures that power these three morphog... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4745458 Sun, 24 Apr 2011 22:15:03 +0100 4745458 http://www.medworm.com/index.php?rid=4745457&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21501752%26dopt%3DAbstract Authors: Krens SF, Heisenberg CP During the development of multicellular organisms, cell fate specification is followed by the sorting of different cell types into distinct domains from where the different tissues and organs are formed. Cell sorting involves both the segregation of a mixed population of cells with different fates and properties into distinct domains, and the active maintenance of their segregated state. Because of its biological importance and apparent resemblance to fluid segregation in physics, cell sorting was extensively studied by both biologists and physicists over the last decades. Different theories were developed that try to explain cell sorting on the basis of the physical properties of the constituent cells. However, only recently the molecular and cellular ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4745457 Sun, 24 Apr 2011 22:15:03 +0100 4745457 http://www.medworm.com/index.php?rid=4745456&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21501753%26dopt%3DAbstract Authors: Davidson LA Morphogenesis requires the spatial and temporal control of embryo mechanics, including force production and mechanical resistance to those forces, to coordinate tissue deformation and large-scale movements. Thus, biomechanical processes play a key role in directly shaping the embryo. Additional roles for embryo mechanics during development may include the patterning of positional information and to provide feedback to ensure the success of morphogenetic movements in shaping the larval body and organs. To understand the multiple roles of mechanics during development requires familiarity with engineering principles of the mechanics of structures, the viscoelastic properties of biomaterials, and the integration of force and stress within embryonic structures as morpho... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4745456 Sun, 24 Apr 2011 22:15:03 +0100 4745456 http://www.medworm.com/index.php?rid=4745455&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21501754%26dopt%3DAbstract We describe the genetic, mechanical, and magnetic tools that have allowed the testing of mechanical induction in development by a step-by-step uncoupling of genetic inputs from mechanical inputs in embryogenesis. We discuss the known underlying molecular mechanisms involved in such mechanotransduction processes, including the Armadillo/β-catenin activation of Twist and the Fog-dependent stabilization of Myosin-II. These mechanotransduction processes are associated with a variety of physiological functions, such as mid-gut differentiation, mesoderm invagination and skeletal joint differentiation in embryogenesis, cell migration and internal pressure regulation during oogenesis, and meristem morphogenesis. We describe how the conservation of associated mechanosensitive pathways in embryonic... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4745455 Sun, 24 Apr 2011 22:15:03 +0100 4745455 http://www.medworm.com/index.php?rid=4087780&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20959160%26dopt%3DAbstract Authors: Cagan RL, Reh TA PMID: 20959160 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4087780 Fri, 22 Oct 2010 17:25:03 +0100 4087780 http://www.medworm.com/index.php?rid=4087779&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20959161%26dopt%3DAbstract Authors: Kumar JP The road to producing an eye begins with the decision to commit a population of cells to adopting an eye tissue fate, the process of retinal determination. Over the past decade and a half, a network of transcription factors has been found to mediate this process in all seeing animals. This retinal determination network is known to regulate not only tissue fate but also cell proliferation, pattern formation, compartment boundary establishment, and even retinal cell specification. The compound eye of the fruit fly, Drosophila melanogaster, has proven to be an excellent experimental system to study the mechanisms by which this network regulates organogenesis and tissue patterning. In fact the founding members of most of the gene families that make up this network were fi... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4087779 Fri, 22 Oct 2010 17:25:03 +0100 4087779 http://www.medworm.com/index.php?rid=4087778&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20959162%26dopt%3DAbstract Authors: Zuber ME Vertebrate eyes begin as a small patch of cells at the most anterior end of the early brain called the eye field. If these cells are removed from an amphibian embryo, the eyes do not form. If the eye field is transplanted to another location on the embryo or cultured in a dish, it forms eyes. These simple cut and paste experiments were performed at the beginning of the last century and helped to define the embryonic origin of the vertebrate eye. The genes necessary for eye field specification and eventual eye formation, by contrast, have only recently been identified. These genes and the molecular mechanisms regulating the initial formation of the Xenopus laevis eye field are the subjects of this review. PMID: 20959162 [PubMed - in process] (Source: Current Topics... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4087778 Fri, 22 Oct 2010 17:25:03 +0100 4087778 http://www.medworm.com/index.php?rid=4087777&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20959163%26dopt%3DAbstract Authors: Fuhrmann S Organogenesis of the eye is a multistep process that starts with the formation of optic vesicles followed by invagination of the distal domain of the vesicles and the overlying lens placode resulting in morphogenesis of the optic cup. The late optic vesicle becomes patterned into distinct ocular tissues: the neural retina, retinal pigment epithelium (RPE), and optic stalk. Multiple congenital eye disorders, including anophthalmia or microphthalmia, aniridia, coloboma, and retinal dysplasia, stem from disruptions in embryonic eye development. Thus, it is critical to understand the mechanisms that lead to initial specification and differentiation of ocular tissues. An accumulating number of studies demonstrate that a complex interplay between inductive signals provide... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4087777 Fri, 22 Oct 2010 17:25:03 +0100 4087777 http://www.medworm.com/index.php?rid=4087776&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20959164%26dopt%3DAbstract Authors: Bao S Cells are sequentially recruited during formation of the Drosophila compound eye. A few simple rules are reiteratively utilized to control successive steps of eye assembly. Two themes emerge: the interplay between cell signaling and competence determines diversity of cell types and selective cell adhesion determines spatial patterns of cells. Cell signaling through competence creates signaling relays, which sequentially trigger differentiation of all cell types. Selective cell adhesion, on the other hand, provides forces to drive cells into energy-favored spatial configurations. Organ formation is nevertheless a complex process. The complexity lies in the spatial, temporal, and quantitative precision of gene expression. Many challenging questions remain. PMID: 209591... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4087776 Fri, 22 Oct 2010 17:25:03 +0100 4087776 http://www.medworm.com/index.php?rid=4087775&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20959165%26dopt%3DAbstract Authors: Charlton-Perkins M, Cook TA In the past, vast differences in ocular structure, development, and physiology throughout the animal kingdom led to the widely accepted notion that eyes are polyphyletic, that is, they have independently arisen multiple times during evolution. Despite the dissimilarity between vertebrate and invertebrate eyes, it is becoming increasingly evident that the development of the eye in both groups shares more similarity at the genetic level than was previously assumed, forcing a reexamination of eye evolution. Understanding the molecular underpinnings of cell type specification during Drosophila eye development has been a focus of research for many labs over the past 25 years, and many of these findings are nicely reviewed in Chapters 1 and 4. A somewhat ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4087775 Fri, 22 Oct 2010 17:25:03 +0100 4087775 http://www.medworm.com/index.php?rid=4087774&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20959166%26dopt%3DAbstract Authors: Davis DM, Dyer MA Neurogenesis in the retina occurs via the coordination of proliferation, cell cycle exit and differentiation of retinal progenitor cells. Until recently, it was widely assumed that once a retinal progenitor cell produced a postmitotic neuron, there was no possibility for cell-cycle re-entry. However, recent studies have shown that mature differentiated horizontal neurons with reduced Rb pathway function can re-enter the cell cycle and proliferate while maintaining their differentiated features. This chapter will explore the molecular and cellular mechanisms that help to keep differentiated retinal neurons and glia postmitotic. We propose that there are cell-type specific barriers to cell-cycle re-entry by differentiated neurons and these may include apoptosis... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4087774 Fri, 22 Oct 2010 17:25:03 +0100 4087774 http://www.medworm.com/index.php?rid=4087773&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20959167%26dopt%3DAbstract Authors: Jenny A Planar cell polarity (PCP) signaling regulates the establishment of polarity within the plane of an epithelium and allows cells to obtain directional information. Its results are as diverse as the determination of cell fates, the generation of asymmetric but highly aligned structures (e.g., stereocilia in the human ear or hairs on a fly wing), or the directional migration of cells during convergent extension during vertebrate gastrulation. Aberrant PCP establishment can lead to human birth defects or kidney disease. PCP signaling is governed by the noncanonical Wnt or Fz/PCP pathway. Traditionally, PCP establishment has been best studied in Drosophila, mainly due to the versatility of the fly as a genetic model system. In Drosophila, PCP is essential for the orientatio... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4087773 Fri, 22 Oct 2010 17:25:03 +0100 4087773 http://www.medworm.com/index.php?rid=4087772&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20959168%26dopt%3DAbstract Authors: Josten NJ, Huberman AD All information about the visual world is conveyed to the brain by a single type of neurons at the back of the eye called retinal ganglion cells (RGCs). Understanding how RGC axons locate and wire up with their targets is therefore critical to understanding visual development. In recent years, several important technological and conceptual advances have been made in this area, and yet, many fundamental questions remain unanswered. Indeed, while much is now known about how RGC axons pathfind at the optic chiasm and form retinotopic maps within their targets, how RGCs select their overall targets in the first place is poorly understood. Moreover, the signals that direct mammalian RGC axons to their appropriate layer within those targets remain unknown. The... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=4087772 Fri, 22 Oct 2010 17:25:03 +0100 4087772 http://www.medworm.com/index.php?rid=3954618&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816390%26dopt%3DAbstract Authors: PMID: 20816390 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954618 Fri, 10 Sep 2010 14:09:05 +0100 3954618 http://www.medworm.com/index.php?rid=3954617&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816391%26dopt%3DAbstract Authors: Artavanis-Tsakonas S, Muskavitch MA Proliferating investigations of the Notch pathway have given rise to the Notch "field," which has grown exponentially over the past 30 years. This field, founded by investigations of embryology and genetics in Drosophila, now encompasses many metazoa, including humans. The increasingly diverse scope of the field has engendered an expanding understanding that normal Notch pathway function is central to most developmental decision-making in animals, and that pathway dysfunction is implicated in many diseases, including cancer. We provide a personal view of the foundations and rapid evolution of the Notch field; and we discuss a variety of outstanding conundrums and questions regarding Notch biology, for which answers will be found and refined ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954617 Fri, 10 Sep 2010 14:09:05 +0100 3954617 http://www.medworm.com/index.php?rid=3954616&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816392%26dopt%3DAbstract Authors: Kovall RA, Blacklow SC Notch proteins are the receptors in a highly conserved signal transduction system used to communicate signals between cells that contact each other. Studies investigating structure-function relationships in Notch signaling have gained substantial momentum in recent years. Here, we summarize the current understanding of the molecular logic of Notch signal transduction, emphasizing structural and biochemical studies of Notch receptors, their ligands, and complexes of intracellular Notch proteins with their target transcription factors. Recent advances in the structure-based modulation of Notch-signaling activity are also discussed. PMID: 20816392 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954616 Fri, 10 Sep 2010 14:09:05 +0100 3954616 http://www.medworm.com/index.php?rid=3954615&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816393%26dopt%3DAbstract Authors: D'Souza B, Meloty-Kapella L, Weinmaster G Notch signaling induced by canonical Notch ligands is critical for normal embryonic development and tissue homeostasis through the regulation of a variety of cell fate decisions and cellular processes. Activation of Notch signaling is normally tightly controlled by direct interactions with ligand-expressing cells, and dysregulated Notch signaling is associated with developmental abnormalities and cancer. While canonical Notch ligands are responsible for the majority of Notch signaling, a diverse group of structurally unrelated noncanonical ligands has also been identified that activate Notch and likely contribute to the pleiotropic effects of Notch signaling. Soluble forms of both canonical and noncanonical ligands have been isolated, ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954615 Fri, 10 Sep 2010 14:09:05 +0100 3954615 http://www.medworm.com/index.php?rid=3954614&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816394%26dopt%3DAbstract Authors: Stanley P, Okajima T Notch and the DSL Notch ligands Delta and Serrate/Jagged are glycoproteins with a single transmembrane domain. The extracellular domain (ECD) of both Notch receptors and Notch ligands contains numerous epidermal growth factor (EGF)-like repeats which are post-translationally modified by a variety of glycans. Inactivation of a subset of genes that encode glycosyltransferases which initiate and elongate these glycans inhibits Notch signaling. In the formation of developmental boundaries in Drosophila and mammals, in mouse T-cell and marginal zone B-cell development, and in co-culture Notch signaling assays, the regulation of Notch signaling by glycans is to date a cell-autonomous effect of the Notch-expressing cell. The regulation of Notch signaling by glyca... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954614 Fri, 10 Sep 2010 14:09:05 +0100 3954614 http://www.medworm.com/index.php?rid=3954613&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816395%26dopt%3DAbstract Authors: Yamamoto S, Charng WL, Bellen HJ Notch signaling occurs through direct interaction between Notch, the receptor, and its ligands, presented on the surface of neighboring cells. Endocytosis has been shown to be essential for Notch signal activation in both signal-sending and signal-receiving cells, and numerous genes involved in vesicle trafficking have recently been shown to act as key regulators of the pathway. Defects in vesicle trafficking can lead to gain- or loss-of-function defects in a context-dependent manner. Here, we discuss how endocytosis and vesicle trafficking regulate Notch signaling in both signal-sending and signal-receiving cells. We will introduce the key players in different trafficking steps, and further illustrate how they impact the signal outcome. Some o... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954613 Fri, 10 Sep 2010 14:09:05 +0100 3954613 http://www.medworm.com/index.php?rid=3954612&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816396%26dopt%3DAbstract Authors: Jorissen E, De Strooper B gamma-secretase is the crucial proteolytic activity that releases the Notch intracellular domain and is therefore a central player in the canonical Notch-signaling transduction pathway. We discuss here briefly the discovery of gamma-secretase and what is known on its structure and function. Recent work also indicates that the assembly and activity of gamma-secretase might be regulated by novel cell biological mechanisms. Finally we explore the recent insight that there are several gamma-secretase complexes in mammalian and discuss possibilities to use gamma-secretase as a drug target in Alzheimer's disease and cancer. PMID: 20816396 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954612 Fri, 10 Sep 2010 14:09:05 +0100 3954612 http://www.medworm.com/index.php?rid=3954611&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816397%26dopt%3DAbstract Authors: Tanigaki K, Honjo T RBP-J/Su(H)/Lag1, the main transcriptional mediator of Notch signaling, binds DNA with the consensus sequence YRTGDGAD. Notch target genes can be controlled by two opposing activities of RBP-J. The interaction of the Notch intracellular domain with RBP-J induces a weak transcriptional activation and requires an additional tissue-specific transcriptional activator such as bHLH proteins or GATA to mediate strong target gene expression. For example, during Drosophila sensory organ precursor (SOP) cell development, proneural bHLH interacts with Da, a Drosophila orthologue of E2A, to form a tissue-specific activator of Su(H), the Drosophila orthologue of RBP-J. This complex and Su(H) act synergistically to promote the epidermal cell fate. In contrast, a complex ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954611 Fri, 10 Sep 2010 14:09:05 +0100 3954611 http://www.medworm.com/index.php?rid=3954610&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816398%26dopt%3DAbstract Authors: Bray S, Bernard F The proteolytic cleavages elicited by activation of the Notch receptor release an intracellular fragment, Notch intracellular domain, which enters the nucleus to activate the transcription of targets. Changes in transcription are therefore a major output of this pathway. However, the Notch outputs clearly differ from cell type to cell type. In this review we discuss current understanding of Notch targets, the mechanisms involved in their transcriptional regulation, and what might underlie the activation of different sets of targets in different cell types. PMID: 20816398 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954610 Fri, 10 Sep 2010 14:09:05 +0100 3954610 http://www.medworm.com/index.php?rid=3954609&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816399%26dopt%3DAbstract Authors: Gridley T Notch signaling is an evolutionarily conserved, intercellular signaling mechanism that plays myriad roles during vascular development and physiology in vertebrates. These roles include the regulation of arteriovenous specification and differentiation in both endothelial cells and vascular smooth muscle cells, regulation of blood vessel sprouting and branching during normal and pathological angiogenesis, and the physiological responses of vascular smooth muscle cells. Defects in Notch signaling also cause inherited vascular diseases, such as the degenerative vascular disorder cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy. This review summarizes recent studies that highlight the multiple roles the Notch signaling pathway pla... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954609 Fri, 10 Sep 2010 14:09:05 +0100 3954609 http://www.medworm.com/index.php?rid=3954608&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816400%26dopt%3DAbstract Authors: Kageyama R, Niwa Y, Shimojo H, Kobayashi T, Ohtsuka T Notch signaling regulates many dynamic processes; accordingly, expression of genes in this pathway is also dynamic. In mouse embryos, one dynamic process regulated by Notch is somite segmentation, which occurs with a 2-h periodicity. This periodic event is regulated by a biological clock called the segmentation clock, which involves cyclic expression of the Notch effector gene Hes7. Loss of Hes7 expression and sustained expression of Hes7 result in identical and severe somite defects, suggesting that Hes7 oscillation is required for proper somite segmentation. Mathematical models of this oscillator have been used to generate and test hypothesis, helping to uncover the role of negative feedback in regulating the oscillator. ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954608 Fri, 10 Sep 2010 14:09:05 +0100 3954608 http://www.medworm.com/index.php?rid=3954607&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816401%26dopt%3DAbstract Authors: Macgrogan D, Nus M, Pompa JL The Notch-signaling pathway is involved in multiple processes during vertebrate cardiac development. Cardiomyocyte differentiation, patterning of the different cardiac regions, valve development, ventricular trabeculation, and outflow tract development have all been shown to depend on the activity of specific Notch-signaling elements. From these studies, it becomes obvious that Notch regulates in a cell autonomous or non-cell autonomous manner different signaling pathways, pointing to a role for Notch as a signal coordinator during cardiogenesis. While most of the research has concentrated on Notch signaling in the myocardium, the importance of Notch activity in the cardiac endothelium (endocardium) must not be overlooked. Endocardial Notch activit... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954607 Fri, 10 Sep 2010 14:09:05 +0100 3954607 http://www.medworm.com/index.php?rid=3954606&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816402%26dopt%3DAbstract Authors: Liu J, Sato C, Cerletti M, Wagers A Stem cells are rare and unique precursor cells that participate in the building and rebuilding of tissues and organs during embryogenesis, postnatal growth, and injury repair. Stem cells are distinctively endowed with the ability to both self-renew and differentiate, such that they can replenish the stem cell pool while continuing to produce the differentiated daughter cells that are essential for tissue function. Stem cell self-renewal/differentiation decisions must be carefully controlled during organogenesis, tissue homeostasis, and regeneration, as failure in stem cell maintenance or activation can lead to progressive tissue wasting, while unchecked self-renewal is a hallmark of many cancers. Here, we review evidence implicating the Notc... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954606 Fri, 10 Sep 2010 14:09:05 +0100 3954606 http://www.medworm.com/index.php?rid=3954605&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816403%26dopt%3DAbstract Authors: Koch U, Radtke F In recent years a substantial body of evidence derived from not only preclinical but also clinical studies has accumulated in support of Notch signaling playing important oncogenic roles in several types of cancer. The finding that activating Notch mutations are frequently found in patients suffering from acute lymphoblastic leukemia is one of the best examples for a critical role of Notch signaling in cancer, a fact that motivated many researchers and clinicians to study the role of Notch also in solid tumors. Hence Notch signaling has gained increasing attention as a potential therapeutic target. In this book chapter we would like to discuss our current knowledge of Notch signaling within different types of solid cancers as well as advantages and disadvantag... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954605 Fri, 10 Sep 2010 14:09:05 +0100 3954605 http://www.medworm.com/index.php?rid=3954604&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20816404%26dopt%3DAbstract Authors: Heitzler P Early genetics in flies revealed that Notch is a complex pleiotropic locus. We now know that Notch is a receptor that plays prominent roles during development and functions locally in many tissues to instruct cell fate decisions. Drosophila has been an excellent model to identify genetically the elements that contribute to the canonical Notch signaling transduction machinery defined as DSL-Notch-CSL-MAML axis. This core pathway is required in many biological events in all animals. Though the canonical Notch pathway is relatively simple, and as the steps of the events are now more deeply understood, an increasing number of reports in the last decade show that many other molecules can influence Notch signaling, some by competing with a given element of the cascade. Th... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3954604 Fri, 10 Sep 2010 14:09:05 +0100 3954604 http://www.medworm.com/index.php?rid=3869412&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705176%26dopt%3DAbstract Authors: PMID: 20705176 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869412 Tue, 17 Aug 2010 01:03:03 +0100 3869412 http://www.medworm.com/index.php?rid=3869411&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705177%26dopt%3DAbstract Authors: Peris CI, Rademacher EH, Weijers D Embryogenesis in plants transforms the zygote into a relatively simple structure, the seedling, which contains all tissues and organs that later form the mature plant body. Despite a profound diversity in cell division patterns among plant species, embryogenesis yields remarkably homologous seedling architectures. In this review, we describe the formative events during plant embryogenesis and discuss the molecular mechanisms that regulate these processes, focusing on Arabidopsis. Even though only a relatively small number of factors are known that regulate each patterning step, a picture emerges where locally acting transcription factors and intercellular signaling contribute to the specification and spatio-temporal coordination of the variou... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869411 Tue, 17 Aug 2010 01:03:03 +0100 3869411 http://www.medworm.com/index.php?rid=3869410&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705178%26dopt%3DAbstract Authors: Kami C, Lorrain S, Hornitschek P, Fankhauser C Plants are sessile and photo-autotrophic; their entire life cycle is thus strongly influenced by the ever-changing light environment. In order to sense and respond to those fluctuating conditions higher plants possess several families of photoreceptors that can monitor light from UV-B to the near infrared (far-red). The molecular nature of UV-B sensors remains unknown, red (R) and far-red (FR) light is sensed by the phytochromes (phyA-phyE in Arabidopsis) while three classes of UV-A/blue photoreceptors have been identified: cryptochromes, phototropins, and members of the Zeitlupe family (cry1, cry2, phot1, phot2, ZTL, FKF1, and LKP2 in Arabidopsis). Functional specialization within photoreceptor families gave rise to members optim... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869410 Tue, 17 Aug 2010 01:03:03 +0100 3869410 http://www.medworm.com/index.php?rid=3869409&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705179%26dopt%3DAbstract Authors: Bennett T, Scheres B In this review, we analyze progress in understanding the mechanisms of root meristem development and function. The formation of embryonic and lateral roots, together with the remarkable regenerative ability of roots, seems to be linked to an auxin-dependent patterning mechanism, the "reflux loop," that can act at least partly independently of cellular context. A major feature of root formation is the production of the "structural initials," the center of the developing root. These cells form an organizing center (OC), the quiescent center (QC), which is needed for meristem activity. The exact role of the QC remains somewhat unclear, though it maintains a stem cell (SC) state in adjacent cells and acts as a long-term SC pool itself. SCs in the root can be d... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869409 Tue, 17 Aug 2010 01:03:03 +0100 3869409 http://www.medworm.com/index.php?rid=3869408&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705180%26dopt%3DAbstract Authors: Ha CM, Jun JH, Fletcher JC The shoot apical meristem (SAM) generates above-ground aerial organs throughout the lifespan of higher plants. In order to fulfill this function, the meristem must maintain a balance between the self-renewal of a reservoir of central stem cells and organ initiation from peripheral cells. The activity of the pluripotent stem cell population in the SAM is dynamically controlled by complex, overlapping signaling networks that include the feedback regulation of meristem maintenance genes and the signaling of plant hormones. Organ initiation likewise requires the function of multifactor gene regulatory networks, as well as instructive cues from the plant hormone auxin and reciprocal signals from the shoot meristem. Floral meristems (FMs) are products of t... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869408 Tue, 17 Aug 2010 01:03:03 +0100 3869408 http://www.medworm.com/index.php?rid=3869407&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705181%26dopt%3DAbstract Authors: Kidner CA, Timmermans MC Most leaves are dorsiventrally flattened and develop clearly defined upper and lower surfaces. Light capturing is the specialization of the adaxial or upper surface and the abaxial or lower surface is specialized for gas exchange (Fig. 5.1). This division into adaxial and abaxial domains is also key for the outgrowth of the leaf blade or lamina, which occurs along the boundary between the upper and lower sides. How this polarity is set up is not clear but genetic analysis in a range of species suggests that several highly conserved interlocking pathways are involved. Positional information from the meristem is reinforced by signaling through the epidermal layer as the meristem grows away from the leaf primordium. Opposing ta-siRNA and miRNA gradients h... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869407 Tue, 17 Aug 2010 01:03:03 +0100 3869407 http://www.medworm.com/index.php?rid=3869406&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705182%26dopt%3DAbstract Authors: Koenig D, Sinha N Leaf shape is a highly variable trait. Ancestrally, all leaves are proposed to have derived from modifications of branched shoot systems. The formation of blade, smooth margins or serrations on the blade, or distinct leaflets that are the characteristic features of some leaves provides an opportunity to study the generation of morphogenesis in organs that are evolutionarily homologous and yet developmentally distinct in patterning. Intense research in several model species with distinct leaf morphologies has revealed a complex network of genes that interact to pattern the leaf. Several parallels between leaf patterning and shoot patterning exist. The plant growth hormone auxin is emerging as a key player in the specification of both shoot and leaf patterning.... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869406 Tue, 17 Aug 2010 01:03:03 +0100 3869406 http://www.medworm.com/index.php?rid=3869405&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705183%26dopt%3DAbstract Authors: Breuninger H, Lenhard M Plant organs grow to characteristic, species-specific sizes and shapes. At the cellular level, organ growth is initially characterized by cell proliferation, which gives way to cell expansion at later stages. Using mainly Arabidopsis thaliana as a model species, a number of factors have been isolated in recent years that promote or restrict organ growth, with the altered organ size being associated with changes in cell number, in cell size, or in both. However, cells in an organ do not appear to follow a strictly autonomous program of proliferation and expansion, and their behavior is coordinated in at least three different respects: normally sized organs can be formed consisting of altered numbers of cells with compensatory changes in the size of the i... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869405 Tue, 17 Aug 2010 01:03:03 +0100 3869405 http://www.medworm.com/index.php?rid=3869404&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705184%26dopt%3DAbstract Authors: Scarpella E, Helariutta Y Reticulate tissue systems exist in most multicellular organisms, and the principles underlying the formation of cellular networks have fascinated philosophers, mathematicians, and biologists for centuries. In particular, the beautiful and varied arrangements of vascular tissues in plants have intrigued mankind since antiquity, yet the organizing signals have remained elusive. Plant vascular tissues form systems of interconnected cell files throughout the plant body. Vascular cells are aligned with one another along continuous lines, and vascular tissues differentiate at reproducible positions within organ environments. However, neither the precise path of vascular differentiation nor the exact geometry of vascular networks is fixed or immutable. Sever... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869404 Tue, 17 Aug 2010 01:03:03 +0100 3869404 http://www.medworm.com/index.php?rid=3869403&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705185%26dopt%3DAbstract Authors: Dong J, Bergmann DC Stomata are epidermal pores used for water and gas exchange between a plant and the atmosphere. Both the entry of carbon dioxide for photosynthesis and the evaporation of water that drives transpiration and temperature regulation are modulated by the activities of stomata. Each stomatal pore is surrounded by two highly specialized cells called guard cells (GCs), and may also be associated with neighboring subsidiary cells; this entire unit is referred to as the stomatal complex. Generation of GCs requires stereotyped asymmetric and symmetric cell divisions, and the pattern of stomatal complexes in the epidermis follows a "one-cell-spacing rule" (one complex almost never touches another one). Both stomatal formation and patterning are highly regulated by a n... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869403 Tue, 17 Aug 2010 01:03:03 +0100 3869403 http://www.medworm.com/index.php?rid=3869402&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705186%26dopt%3DAbstract Authors: Balkunde R, Pesch M, Hülskamp M The aerial organs of plants typically produce trichomes that may adopt various functions, including light, wind, frost, and herbivore protection. Trichomes are of epidermal origin regularly distributed on the surface. The mechanism by which trichome differentiation is triggered in individual cells in a field of protodermal cells is best studied in Arabidopsis thaliana. The genetic analysis has revealed a number of key genes controlling this patterning process, and further molecular analysis has enabled the in-depth cell-biological and biochemical analysis. The established models explain trichome patterning by the mutual interaction between positive and negative factors. Three activators, a bHLH (helix-loop-helix), a R2R3 MYB-related transcrip... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869402 Tue, 17 Aug 2010 01:03:03 +0100 3869402 http://www.medworm.com/index.php?rid=3869401&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705187%26dopt%3DAbstract Authors: Albani MC, Coupland G In plants the switch from vegetative growth to flowering involves a major transition in the development of the shoot apex. This transition can occur once, in annual species, or repeatedly, in perennial plants. In annuals, flowering is associated with senescence and death of the whole plant, whereas perennials flower in consecutive years and maintain vegetative development after flowering. The perennial life strategy depends on differential behavior of meristems on a single plant so that some remain in the vegetative state while others undergo the floral transition. A. thaliana provides a powerful model system for understanding the mechanisms of flowering in annuals. Here we review the events that occur in the meristem of A. thaliana during the floral tran... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869401 Tue, 17 Aug 2010 01:03:03 +0100 3869401 http://www.medworm.com/index.php?rid=3869400&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705188%26dopt%3DAbstract Authors: Nag A, Jack T microRNAs (miRNAs) are small approximately 21-nucleotide RNAs that function posttranscriptionally to regulate gene activity. miRNAs function by binding to complementary sites in target genes causing mRNA degradation and/or translational repression of the target. Since the discovery of miRNAs in plants in 2002 much has been learned about the function of these small regulatory RNAs. miRNAs function broadly to control many aspects of plant biology and plant development. This review focuses on the role of miRNAs in flower development. miRNAs function throughout flower development, from the earliest stages (floral induction) to very late stages (floral organ cell type specification). miRNAs such as miR156 and miR172 play a key role in vegetative phase change and in th... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869400 Tue, 17 Aug 2010 01:03:03 +0100 3869400 http://www.medworm.com/index.php?rid=3869399&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20705189%26dopt%3DAbstract This article reviews recent progress in understanding the mechanisms underlying gametophytic development and function in flowering plants. The focus is on genes and molecules involved in the processes of initiation, growth, cell specification, and fertilization of the male and female gametophytes derived primarily from studies in model systems. PMID: 20705189 [PubMed - as supplied by publisher] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3869399 Tue, 17 Aug 2010 01:03:03 +0100 3869399 http://www.medworm.com/index.php?rid=3853283&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20691845%26dopt%3DAbstract Authors: Koopman P PMID: 20691845 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3853283 Wed, 11 Aug 2010 08:06:03 +0100 3853283 http://www.medworm.com/index.php?rid=3853282&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20691846%26dopt%3DAbstract Authors: Vincent SD, Buckingham ME The formation of the heart is a complex morphogenetic process that depends on the spatiotemporally regulated contribution of cardiac progenitor cells. These mainly derive from the splanchnic mesoderm of the first and second heart field (SHF), with an additional contribution of neurectodermally derived neural crest cells that are critical for the maturation of the arterial pole of the heart. The origin and distinguishing characteristics of the two heart fields, as well as the relation of the SHF to the proepicardial organ and to a proposed third heart field are still subjects of debate. In the last ten years many genes that function in the SHF have been identified, leading to the establishment of a gene regulatory network in the mouse embryo. It is bec... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3853282 Wed, 11 Aug 2010 08:06:03 +0100 3853282 http://www.medworm.com/index.php?rid=3853281&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20691847%26dopt%3DAbstract Authors: Chappell JC, Bautch VL Vertebrate development depends on the formation of intricate vascular networks at numerous sites and in precise patterns; these vascular networks supply oxygen and nutrients to the rapidly expanding tissues of the embryo. Embryonic blood vessels are composed of endothelial cells and pericytes that organize and expand into highly branched conduits. Proper development of the vasculature requires heterogeneity in the response of endothelial cells to angiogenic cues provided by other tissues and organs. The pathogenesis of vascular diseases results from genetic mutations in pathways that provide these cues and in signals that coordinate endothelial heterogeneity during blood vessel formation. Here we provide a brief overview of different aspects of blood ves... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3853281 Wed, 11 Aug 2010 08:06:03 +0100 3853281 http://www.medworm.com/index.php?rid=3853280&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20691848%26dopt%3DAbstract Authors: Warburton D, El-Hashash A, Carraro G, Tiozzo C, Sala F, Rogers O, Langhe SD, Kemp PJ, Riccardi D, Torday J, Bellusci S, Shi W, Lubkin SR, Jesudason E Developmental lung biology is a field that has the potential for significant human impact: lung disease at the extremes of age continues to cause major morbidity and mortality worldwide. Understanding how the lung develops holds the promise that investigators can use this knowledge to aid lung repair and regeneration. In the decade since the "molecular embryology" of the lung was first comprehensively reviewed, new challenges have emerged-and it is on these that we focus the current review. Firstly, there is a critical need to understand the progenitor cell biology of the lung in order to exploit the potential of stem cells for t... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3853280 Wed, 11 Aug 2010 08:06:03 +0100 3853280 http://www.medworm.com/index.php?rid=3853279&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20691849%26dopt%3DAbstract Authors: Heath JK The vertebrate intestine is a complex and highly specialized organ comprising tissues derived from all three germ layers. While a description of the morphological events underlying the consolidation and organization of the endoderm, mesoderm, and ectoderm-derived cells into a multi-layered, continuously renewing organ has been available for several decades, only recently has a strong genetic framework for this process started to emerge, and as yet it remains incomplete. This review highlights the roles played by a number of transcription factors and signaling pathways in the development of the vertebrate intestine from the moment the definitive endoderm is formed. These molecular pathways often interact with each other and play multiple roles at different stages of in... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3853279 Wed, 11 Aug 2010 08:06:03 +0100 3853279 http://www.medworm.com/index.php?rid=3853278&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20691850%26dopt%3DAbstract Authors: Little M, Georgas K, Pennisi D, Wilkinson L The mammalian kidney may well be one of the most complex organs of postnatal life. Each adult human kidney contains on average more than one million functional filtration units, the nephrons, residing within a specialized cellular interstitium. Each kidney also contains over 25 distinct cell types, each of which must be specifically aligned with respect to each other to ensure both normal development and ultimately, normal renal function. Despite this complexity, the development of the kidney can be simplistically described as the coordinate formation of two distinct sets of tubules. These tubules develop cooperatively with each other in time and space, yet represent two distinct but classical types of tubulogenesis. The first of the... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3853278 Wed, 11 Aug 2010 08:06:03 +0100 3853278 http://www.medworm.com/index.php?rid=3853277&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20691851%26dopt%3DAbstract Authors: Wainwright EN, Wilhelm D In mammals, biological differences between males and females, which influence many aspects of their physical, social, and psychological environments, are solely determined genetically. In the presence of a Y chromosome, the gonadal primordium will differentiate into a testis, whereas in the absence of the Y chromosome an ovary will develop. Testis and ovary subsequently direct the differentiation of all secondary sex characteristics down the male and female pathway, respectively. The male-determining factor on the Y chromosome, SRY, was identified some 20 years ago. Since then, significant progress has been made toward understanding the molecular and cellular pathways that result in the formation of a testis. Here, we review what is known about testis ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3853277 Wed, 11 Aug 2010 08:06:03 +0100 3853277 http://www.medworm.com/index.php?rid=3853276&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20691852%26dopt%3DAbstract Authors: Liu CF, Liu C, Yao HH Despite its significant role in oocyte generation and hormone production in adulthood, the ovary, with regard to its formation, has received little attention compared to its male counterpart, the testis. With the exception of germ cells, which undergo a female-specific pattern of meiosis, morphological changes in the fetal ovary are subtle. Over the past 40 years, a number of hypotheses have been proposed for the organogenesis of the mammalian ovary. It was not until the turn of the millennium, thanks to the advancement of genetic and genomic approaches, that pathways for ovary organogenesis that consist of positive and negative regulators have started to emerge. Through the action of secreted factors (R-spondin1, WNT4, and follistatin) and transcription ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3853276 Wed, 11 Aug 2010 08:06:03 +0100 3853276 http://www.medworm.com/index.php?rid=3853275&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20691853%26dopt%3DAbstract We describe numerous skeletal malformation and degeneration diseases that occur in humans as a result of mutations in regulatory genes, and explain how these diseases both help and motivate us to further decipher skeletogenic processes. Upon discussing current knowledge and gaps in knowledge in the control of skeletogenesis, we highlight ultimate research goals and propose research priorities and approaches for future endeavors. PMID: 20691853 [PubMed - as supplied by publisher] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3853275 Wed, 11 Aug 2010 08:06:03 +0100 3853275 http://www.medworm.com/index.php?rid=3853274&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20691854%26dopt%3DAbstract Authors: Butterfield NC, McGlinn E, Wicking C The limb has long been considered a paradigm for organogenesis because of its simplicity and ease of manipulation. However, it has become increasingly clear that the processes required to produce a perfectly formed limb involve complex molecular interactions across all three axes of limb development. Old models have evolved with acquisition of molecular knowledge, and in more recent times mathematical modeling approaches have been invoked to explain the precise spatio-temporal regulation of gene networks that coordinate limb patterning and outgrowth. This review focuses on recent advances in our understanding of vertebrate limb development, highlighting the signaling interactions required to lay down the pattern on which the processes of di... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3853274 Wed, 11 Aug 2010 08:06:03 +0100 3853274 http://www.medworm.com/index.php?rid=3853273&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20691855%26dopt%3DAbstract Authors: Graw J The vertebrate eye comprises tissues from different embryonic origins: the lens and the cornea are derived from the surface ectoderm, but the retina and the epithelial layers of the iris and ciliary body are from the anterior neural plate. The timely action of transcription factors and inductive signals ensure the correct development of the different eye components. Establishing the genetic basis of eye defects in zebrafishes, mouse, and human has been an important tool for the detailed analysis of this complex process. A single eye field forms centrally within the anterior neural plate during gastrulation; it is characterized on the molecular level by the expression of "eye-field transcription factors." The single eye field is separated into two, forming the optic vesi... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=3853273 Wed, 11 Aug 2010 08:06:03 +0100 3853273 http://www.medworm.com/index.php?rid=2782432&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19737639%26dopt%3DAbstract Authors: Lecuit T PMID: 19737639 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2782432 Thu, 10 Sep 2009 19:48:02 +0100 2782432 http://www.medworm.com/index.php?rid=2782431&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19737640%26dopt%3DAbstract Authors: Borghi N, James Nelson W A major challenge in developmental biology is to understand how cellular processes that result from expression of the genetic program determine the material properties and shape transformations of tissues during morphogenesis. Cell/cell adhesion is critical in development, and it controls many aspects of tissue rearrangements that support morphogenesis. Intercellular adhesion not only allows cells to adhere together but also supports structure and function compartmentalization on the scale of cell assemblies, tissues, and organs. In metazoans, cadherins comprise a major class of cell/cell adhesion proteins. They form Ca(2+)-dependent, homophilic adhesive contacts between neighboring cells that results in remodeling of the underlying cortical cytoskelet... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2782431 Thu, 10 Sep 2009 19:48:02 +0100 2782431 http://www.medworm.com/index.php?rid=2782430&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19737641%26dopt%3DAbstract Authors: Nishimura T, Takeichi M Morphogenesis of epithelial tissues involves various forms of reshaping of cell layers, such as invagination or bending, convergent extension, and epithelial-mesenchymal transition. At the cellular level, these processes include changes in the shape, position, and assembly pattern of cells. During such morphogenetic processes, epithelial sheets in general maintain their multicellular architecture, implying that they must engage the mechanisms to change the spatial relationship with their neighbors without disrupting the junctions. A major junctional structure in epithelial tissues is the "adherens junction," which is composed of cadherin adhesion receptors and associated proteins including F-actin. The adherens junctions are required for the firm associ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2782430 Thu, 10 Sep 2009 19:48:02 +0100 2782430 http://www.medworm.com/index.php?rid=2782429&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19737642%26dopt%3DAbstract Authors: Harris TJ, Sawyer JK, Peifer M One key challenge for cell and developmental biologists is to determine how the cytoskeletal toolkit is used to build embryonic tissues and organs. Here, we review recent progress in meeting this challenge, focusing on epithelial morphogenesis in the Drosophila embryo as a model. We outline how actin and microtubule networks are regulated by embryonic patterning systems, and how they affect cell shape, cell behavior, and cell-cell interactions to shape epithelial structures. We focus on the formation of the first epithelium at cellularization, the assembly of junctions, apical constriction of cells in the ventral furrow, cell intercalation in the germband, and epithelial sheet migration during dorsal closure. These events provide models for uncov... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2782429 Thu, 10 Sep 2009 19:48:02 +0100 2782429 http://www.medworm.com/index.php?rid=2782428&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19737643%26dopt%3DAbstract Authors: Gibson WT, Gibson MC Epithelia are sheets of tightly adherent cells that line both internal and external surfaces in a vast array of metazoans. During development, an intrinsic consequence of coupling tight adhesion with cellular proliferation is the emergence of an epithelial form characterized by a stereotyped distribution of polygonal cell shapes. Despite the near universality of this constraint on cell shape and tissue organization, very little is known about the possible implications of cell pattern geometry for mechanical properties of tissues or key biological processes, such as planar polarization, tissue remodeling, and cell division. In this chapter, through an examination of increasingly complex models, we highlight what is known about the role of mitotic proliferat... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2782428 Thu, 10 Sep 2009 19:48:02 +0100 2782428 http://www.medworm.com/index.php?rid=2782427&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19737644%26dopt%3DAbstract Authors: Cagan R The Drosophila eye is one of nature's most beautiful structures and one of its most useful. It has emerged as a favored model for understanding the processes that direct cell fate specification, patterning, and morphogenesis. Though composed of thousands of cells, each fly eye is a simple repeating pattern of perhaps a dozen cell types arranged in a hexagonal array that optimizes coverage of the visual field. This simple structure combined with powerful genetic tools make the fly eye an ideal model to explore the relationships between local cell fate specification and global tissue patterning. In this chapter, I discuss the basic principles that have emerged from three decades of close study. We now understand at a useful level some of the basic principles of cell fate... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2782427 Thu, 10 Sep 2009 19:48:02 +0100 2782427 http://www.medworm.com/index.php?rid=2782426&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19737645%26dopt%3DAbstract Authors: Baer MM, Chanut-Delalande H, Affolter M Biological tubes are integral components of many organs. Based on their cellular organization, tubes can be divided into three types: multicellular, unicellular, and intracellular. The mechanisms by which these tubes form during development vary significantly, in many cases even for those sharing a similar final architecture. Here, we present recent advances in studying cellular and molecular aspects of tubulogenesis in different organisms. PMID: 19737645 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2782426 Thu, 10 Sep 2009 19:48:02 +0100 2782426 http://www.medworm.com/index.php?rid=2782425&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19737646%26dopt%3DAbstract Authors: Yin C, Ciruna B, Solnica-Krezel L During vertebrate gastrulation, coordinated cell movements shape the basic body plan. Key components of gastrulation are convergence and extension (C&E) movements, which narrow and lengthen the embryonic tissues, respectively. The rates of C&E movements differ significantly according to the position and the stage of gastrulation. Here, we review the distinct cellular behaviors that define the spatial and temporal patterns of C&E movements, with the special emphasis on zebrafish. We also summarize the molecular regulation of these cellular behaviors and the interplay between different signaling pathways that drive C&E. Finally, to ensure efficient C&E movements, cells must achieve mediolaterally-elongated cell morphology and... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2782425 Thu, 10 Sep 2009 19:48:02 +0100 2782425 http://www.medworm.com/index.php?rid=2675039&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19651299%26dopt%3DAbstract Authors: PMID: 19651299 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2675039 Thu, 06 Aug 2009 20:52:03 +0100 2675039 http://www.medworm.com/index.php?rid=2675038&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19651300%26dopt%3DAbstract Authors: Maeda RK, Karch F In his 1978 seminal paper, Ed Lewis described a series of mutations that affect the segmental identities of the segments forming the posterior two-thirds of the Drosophila body plan. In each class of mutations, particular segments developed like copies of a more-anterior segment. Genetic mapping of the different classes of mutations led to the discovery that their arrangement along the chromosome paralleled the body segments they affect along the anteroposterior axis of the fly. As all these mutations mapped to the same cytological location, he named this chromosomal locus after its founding mutation. Thus the first homeotic gene (Hox) cluster became known as the bithorax complex (BX-C). Even before the sequencing of the BX-C, the fact that these similar muta... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2675038 Thu, 06 Aug 2009 20:52:03 +0100 2675038 http://www.medworm.com/index.php?rid=2675037&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19651301%26dopt%3DAbstract Authors: Gehring WJ, Kloter U, Suga H In this chapter, we consider the question of how the ordered clusters of Hox genes arose during evolution. Since ordered Hox clusters are found in all major superphyla, we have to assume that the Hox clusters arose before the Cambrian "explosion" giving rise to all of these taxa. Based on his studies of the bithorax complex (BX-C) in Drosophila Lewis considered the ground state to be the mesothoracic segment (T2) since the deletion of all of the genes of the BX-C leads to a transformation of all segments from T3 to A8/9 (the last abdominal segment) into T2 segments. We define the developmental ground state genetically, by assuming that loss-of-function mutants lead to transformations toward the ground state, whereas gain-of-function mutants lead to... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2675037 Thu, 06 Aug 2009 20:52:03 +0100 2675037 http://www.medworm.com/index.php?rid=2675036&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19651302%26dopt%3DAbstract Authors: Mann RS, Lelli KM, Joshi R Hox proteins are well known for executing highly specific functions in vivo, but our understanding of the molecular mechanisms underlying gene regulation by these fascinating proteins has lagged behind. The premise of this review is that an understanding of gene regulation-by any transcription factor-requires the dissection of the cis-regulatory elements that they act upon. With this goal in mind, we review the concepts and ideas regarding gene regulation by Hox proteins and apply them to a curated list of directly regulated Hox cis-regulatory elements that have been validated in the literature. Our analysis of the Hox-binding sites within these elements suggests several emerging generalizations. We distinguish between Hox cofactors, proteins that bi... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2675036 Thu, 06 Aug 2009 20:52:03 +0100 2675036 http://www.medworm.com/index.php?rid=2675035&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19651303%26dopt%3DAbstract Authors: Tümpel S, Wiedemann LM, Krumlauf R In the vertebrate central nervous system, the hindbrain is an important center for coordinating motor activity, posture, equilibrium, sleep patterns, and essential unconscious functions, such as breathing rhythms and blood circulation. During development, the vertebrate hindbrain depends upon the process of segmentation or compartmentalization to create and organize regional properties essential for orchestrating its highly conserved functional roles. The process of segmentation in the hindbrain differs from that which functions in the paraxial mesoderm to generate somites and the axial skeleton. In the prospective hindbrain, cells in the neural epithelia transiently alter their ability to interact with their neighbors, resulting in the ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2675035 Thu, 06 Aug 2009 20:52:03 +0100 2675035 http://www.medworm.com/index.php?rid=2675034&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19651304%26dopt%3DAbstract Authors: Narita Y, Rijli FM The mammalian hindbrain is the seat of regulation of several vital functions that involve many of the organ systems of the body. Such functions are controlled through the activity of intricate arrays of neuronal circuits and connections. The establishment of ordered patterns of neuronal specification, migration, and axonal topographic connectivity during development is crucial to build such a complex network of circuits and functional connectivity in the mature hindbrain. The early development of the vertebrate hindbrain proceeds according to a fundamental metameric partitioning along the anteroposterior axis into cellular compartments known as rhombomeres. Such an organization has been highly conserved in vertebrate evolution and has a fundamental impact on... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2675034 Thu, 06 Aug 2009 20:52:03 +0100 2675034 http://www.medworm.com/index.php?rid=2675033&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19651305%26dopt%3DAbstract Authors: Dasen JS, Jessell TM Motor behaviors are the primary means by which animals interact with their environment, forming the final output of most central nervous system (CNS) activity. The neural circuits that govern basic locomotor functions appear to be genetically hard wired and are comprised of discrete groups of neurons residing within the spinal cord. These local microcircuits coordinate simple reflexive behaviors in response to sensory stimuli and underlie the generation of rhythmic patterns of neural activity necessary for walking. In recent years there have been significant advances in understanding the genetic and molecular programs that determine the specificity of neural connections within the spinal cord that are critical for the emergence of coordinate motor behavior... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2675033 Thu, 06 Aug 2009 20:52:03 +0100 2675033 http://www.medworm.com/index.php?rid=2675032&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19651306%26dopt%3DAbstract Authors: Iimura T, Denans N, Pourquié O The vertebrate spine exhibits two striking characteristics. The first one is the periodic arrangement of its elements-the vertebrae-along the anteroposterior axis. This segmented organization is the result of somitogenesis, which takes place during organogenesis. The segmentation machinery involves a molecular oscillator-the segmentation clock-which delivers a periodic signal controlling somite production. During embryonic axis elongation, this signal is displaced posteriorly by a system of traveling signaling gradients-the wavefront-which depends on the Wnt, FGF, and retinoic acid pathways. The other characteristic feature of the spine is the subdivision of groups of vertebrae into anatomical domains, such as the cervical, thoracic, lumbar,... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2675032 Thu, 06 Aug 2009 20:52:03 +0100 2675032 http://www.medworm.com/index.php?rid=2675031&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19651307%26dopt%3DAbstract Authors: Young T, Deschamps J Cdx and Hox gene families descend from the same ProtoHox cluster, already present in the common ancestors of bilaterians and cnidarians, and thought to act by providing anteroposterior (A-P) positional identity to axial tissues in all bilaterians. Mouse Cdx and Hox genes still exhibit common features in their early expression and function. The initiation and early shaping of Hox and Cdx transcriptional domains in mouse embryos are very similar, in keeping with their common involvement in conveying A-P information to the nascent tissues during embryonic axial elongation. Considerations of the impact on axial patterning of the early expression phase of these genes that correlates with the temporally collinear expression of 3'-5'Hox genes suggest that it is c... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2675031 Thu, 06 Aug 2009 20:52:03 +0100 2675031 http://www.medworm.com/index.php?rid=2675030&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19651308%26dopt%3DAbstract Authors: Wellik DM The axial skeleton in all vertebrates is comprised of similar structures that extend from anterior to posterior along the body axis: the occipital skull bones, cervical, thoracic, lumbar, sacral and caudal vertebrae. Despite significant changes in the number and size of these elements during vertebrate evolution, the basic character of these anatomical elements, as well as the order in which they appear, has remained strikingly similar. Extensive expression analysis, classic embryology experiments in chick and targeted loss-of-function mutant analyses in mice have clearly demonstrated that Hox genes are key regulators of morphology along the axial skeleton. The cumulative data from this work provides an emerging understanding of Hox gene function in patterning the ve... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2675030 Thu, 06 Aug 2009 20:52:03 +0100 2675030 http://www.medworm.com/index.php?rid=2547232&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19361686%26dopt%3DAbstract Authors: Jeffery WR PMID: 19361686 [PubMed - indexed for MEDLINE] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547232 Sun, 28 Jun 2009 04:17:03 +0100 2547232 http://www.medworm.com/index.php?rid=2547231&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19361687%26dopt%3DAbstract Authors: Nikitina N, Sauka-Spengler T, Bronner-Fraser M The neural crest is a multipotent migratory embryonic cell population that is present in all vertebrates, but missing from basal chordates. In this chapter, we discuss recent work in amphioxus, ascidians, lamprey, and gnathostomes that reflects the current state of knowledge of the evolutionary origin of this fascinating cell population. We summarize recent evidence for the ongoing diversification of the neural crest in several vertebrate species, with particular reference to studies in nontraditional vertebrate model organisms. PMID: 19361687 [PubMed - indexed for MEDLINE] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547231 Sun, 28 Jun 2009 04:17:03 +0100 2547231 http://www.medworm.com/index.php?rid=2547230&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19361688%26dopt%3DAbstract Authors: Zhang G, Eames BF, Cohn MJ Major advances in the molecular genetics, paleobiology, and the evolutionary developmental biology of vertebrate skeletogenesis have improved our understanding of the early evolution and development of the vertebrate skeleton. These studies have involved genetic analysis of model organisms, human genetics, comparative developmental studies of basal vertebrates and nonvertebrate chordates, and both cladistic and histological analyses of fossil vertebrates. Integration of these studies has led to renaissance in the area of skeletal development and evolution. Among the major findings that have emerged is the discovery of an unexpectedly deep origin of the gene network that regulates chondrogenesis. In this chapter, we discuss recent progress in each the... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547230 Sun, 28 Jun 2009 04:17:03 +0100 2547230 http://www.medworm.com/index.php?rid=2547229&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19361689%26dopt%3DAbstract Authors: Haag ES A number of major adaptations in animals have been mediated by alteration of germ cells and their immediate derivatives, the gametes. Here, several such cases are discussed, including examples from echinoderms, vertebrates, insects, and nematodes. A feature of germ cells that make their development (and hence evolution) distinct from the soma is the prominent role played by posttranscriptional controls of mRNA translation in the regulation of proliferation and differentiation. This presents a number of special challenges for investigation of the evolution of germline development. Caenorhabditis nematodes represent a particularly favorable system for addressing these challenges, both because of technical advantages and (most importantly) because of natural variation in ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547229 Sun, 28 Jun 2009 04:17:03 +0100 2547229 http://www.medworm.com/index.php?rid=2547228&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19361690%26dopt%3DAbstract Authors: Kramer EM The number of genetically tractable plant model systems is rapidly increasing, thanks to the decreasing cost of sequencing and the wide amenability of plants to stable transformation and other functional approaches. In this chapter, I discuss emerging model systems from throughout the land plant phylogeny and consider how their unique attributes are contributing to our understanding of development, evolution, and ecology. These new models are being developed using two distinct strategies: in some cases, they are selected because of their close relationship to the established models, while in others, they are chosen with the explicit intention of exploring distantly related plant lineages. Such complementary approaches are yielding exciting new results that shed light... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547228 Sun, 28 Jun 2009 04:17:03 +0100 2547228 http://www.medworm.com/index.php?rid=2547227&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19361691%26dopt%3DAbstract Authors: Lambert JD The spiralian developmental program is a highly conserved mode of early development that is characterized by regularities in cleavage pattern, fate map, and larval morphology. It is found in a number of animal phyla, and was likely present in the last common ancestor of the large superphylum Lophotrochozoa. Despite this key position for understanding the evolution of development in animals, and the intrinsic advantages for using spiralian embryos to study embryonic development and asymmetric cell division, very little is known about the molecular mechanisms of spiralian embryogenesis. The snail Ilyanassa has typical spiralian development, as well as a number of practical and experimental advantages that have made it a useful model for understanding spiralian embryog... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547227 Sun, 28 Jun 2009 04:17:03 +0100 2547227 http://www.medworm.com/index.php?rid=2547226&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19361692%26dopt%3DAbstract Authors: Moczek AP Understanding how development and ecology shape organismal evolution is a central goal of evolutionary developmental biology. This chapter highlights a class of traits and organisms that are emerging as new models in evo-devo and eco-devo research: beetle horns and horned beetles. Horned beetles are morphologically diverse, ecologically rich, and developmentally and genetically increasingly accessible. Recent studies have begun to take advantage of these attributes and are starting to link the microevolution of horned beetle development to the macroevolution of novel features, and to identify the genetic, developmental, and ecological mechanisms, and the interactions between them, that mediate organismal innovation and diversification in natural populations. Here, I ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547226 Sun, 28 Jun 2009 04:17:03 +0100 2547226 http://www.medworm.com/index.php?rid=2547225&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19361693%26dopt%3DAbstract Authors: Raff RA, Snoke Smith M Marine invertebrate embryos and larvae are diverse and can evolve rapidly, providing a link between early developmental and evolutionary mechanisms. We here discuss the role of evolutionary changes in axis formation, which is a crucial part of the patterning of marine embryos and larvae. We focus on sea urchin embryos, where axial features are well defined and subject to active current investigation. The genetic control of processes of formation of the three axial systems, animal-vegetal, dorsal-ventral, and left-right, is becoming established for species that undergo development via the feeding pluteus larva. These species represent the primitive condition among living sea urchins. We compare their developmental processes to the highly modified developm... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547225 Sun, 28 Jun 2009 04:17:03 +0100 2547225 http://www.medworm.com/index.php?rid=2547224&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19361694%26dopt%3DAbstract Authors: Jeffery WR The teleost Astyanax mexicanus is a single species consisting of two radically different forms: a sighted pigmented surface-dwelling form (surface fish) and a blind depigmented cave-dwelling form (cavefish). The two forms of Astyanax have favorable attributes, including descent from a common ancestor, ease of laboratory culture, and the ability to perform genetic analysis, permitting their use as a model system to explore questions in evolution and development. Here, we review current research on the molecular, cellular, and developmental mechanisms underlying the loss of eyes and pigmentation in Astyanax cavefish. Although functional eyes are lacking in adults, cavefish embryos begin to develop eye primordia, which subsequently degenerate. The major cause of eye de... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547224 Sun, 28 Jun 2009 04:17:03 +0100 2547224 http://www.medworm.com/index.php?rid=2547223&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19427515%26dopt%3DAbstract Authors: Simpson HD, Mortimer D, Goodhill GJ Proper wiring up of the nervous system is critical to the development of organisms capable of complex and adaptable behaviors. Besides the many experimental advances in determining the cellular and molecular machinery that carries out this remarkable task precisely and robustly, theoretical approaches have also proven to be useful tools in analyzing this machinery. A quantitative understanding of these processes can allow us to make predictions, test hypotheses, and appraise established concepts in a new light. Three areas that have been fruitful in this regard are axon guidance, retinotectal mapping, and activity-dependent development. This chapter reviews some of the contributions made by mathematical modeling in these areas, illustrated b... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547223 Sun, 28 Jun 2009 04:17:03 +0100 2547223 http://www.medworm.com/index.php?rid=2547222&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19427517%26dopt%3DAbstract Authors: Batista-Brito R, Fishell G The central goal of this manuscript is to survey our present knowledge of how cortical interneuron subtypes are generated. To achieve this, we will first define what is meant by subtype diversity. To this end, we begin by considering the mature properties that differentiate between the different populations of cortical interneurons. This requires us to address the difficulties involved in determining which characteristics allow particular interneurons to be assigned to distinct subclasses. Having grappled with this thorny issue, we will then proceed to review the progressive events in development involved in the generation of interneuron diversity. Starting with their origin and specification within the subpallium, we will follow them up through the ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547222 Sun, 28 Jun 2009 04:17:03 +0100 2547222 http://www.medworm.com/index.php?rid=2547221&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19427518%26dopt%3DAbstract Authors: Dasen JS The emergence of coordinated locomotor behaviors in vertebrates relies on the establishment of selective connections between discrete populations of neurons present in the spinal cord and peripheral nervous system. The assembly of the circuits necessary for movement presumably requires the generation of many unique cell types to accommodate the intricate connections between motor neurons, sensory neurons, interneurons, and muscle. The specification of diverse neuronal subtypes is mediated largely through networks of transcription factors that operate within progenitor and postmitotic cells. Selective patterns of transcription factor expression appear to define the cell-type-specific cellular programs that govern the axonal guidance decisions and synaptic specificities... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547221 Sun, 28 Jun 2009 04:17:03 +0100 2547221 http://www.medworm.com/index.php?rid=2547220&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19427519%26dopt%3DAbstract Authors: Li Y, Mu Y, Gage FH The hippocampal formation is widely studied in part because of its distinct and highly laminar organization as well as its demonstrated fundamental role in learning and memory. The dentate gyrus of the hippocampal formation is one of two recognized brain regions that continually generate new neurons in adulthood. In this chapter, we review the basic structure of hippocampal cellular components and circuitry, the properties of stem cells and their progeny in the dentate gyrus, and the known mechanisms and timing of their maturation and integration into the adult circuitry. We also address the functional implication of neurogenesis in the adult hippocampus. PMID: 19427519 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547220 Sun, 28 Jun 2009 04:17:03 +0100 2547220 http://www.medworm.com/index.php?rid=2547219&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19427520%26dopt%3DAbstract Authors: Bénard C, Hobert O Neuronal circuitries established in development must persist throughout life. This poses a serious challenge to the structural integrity of an embryonically patterned nervous system as an animal dramatically increases its size postnatally, remodels parts of its anatomy, and incorporates new neurons. In addition, body movements, injury, and ageing generate physical stress on the nervous system. Specific molecular pathways maintain intrinsic properties of neurons in the mature nervous system. Other factors ensure that the overall organization of entire neuronal ensembles into ganglia and fascicles is appropriately maintained upon external challenges. Here, we discuss different molecules underlying these neuronal maintenance mechanisms, with a focus on les... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=2547219 Sun, 28 Jun 2009 04:17:03 +0100 2547219 http://www.medworm.com/index.php?rid=1362394&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18282514%26dopt%3DAbstract Authors: Bieker JJ PMID: 18282514 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1362394 Thu, 10 Apr 2008 09:55:10 +0100 1362394 http://www.medworm.com/index.php?rid=1245047&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18282514%26dopt%3DAbstract Authors: Bieker JJ PMID: 18282514 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1245047 Wed, 20 Feb 2008 21:12:47 +0100 1245047 http://www.medworm.com/index.php?rid=1245046&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18282515%26dopt%3DAbstract Authors: McGrath K, Palis J Red cells are required not only for adult well-being but also for survival and growth of the mammalian embryo beyond early postimplantation stages of development. The embryo's first "primitive" erythroid cells, derived from a transient wave of committed progenitors, emerge from the yolk sac as immature precursors and differentiate as a semisynchronous cohort in the bloodstream. Surprisingly, this maturational process in the mammalian embryo is characterized by globin gene switching and ultimately by enucleation. The yolk sac also synthesizes a second transient wave of "definitive" erythroid progenitors that enter the bloodstream and seed the liver of the fetus. At the same time, hematopoietic stem cells within the embryo also seed the liver and are the presu... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1245046 Wed, 20 Feb 2008 21:12:47 +0100 1245046 http://www.medworm.com/index.php?rid=1245045&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18282516%26dopt%3DAbstract Authors: Manwani D, Bieker JJ Erythroblastic islands are specialized microenvironmental compartments within which definitive mammalian erythroblasts proliferate and differentiate. These islands consist of a central macrophage that extends cytoplasmic protrusions to a ring of surrounding erythroblasts. The interaction of cells within the erythroblastic island is essential for both early and late stages of erythroid maturation. It has been proposed that early in erythroid maturation the macrophages provide nutrients, proliferative and survival signals to the erythroblasts, and phagocytose extruded erythroblast nuclei at the conclusion of erythroid maturation. There is also accumulating evidence for the role of macrophages in promoting enucleation itself. The central macrophages are ident... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1245045 Wed, 20 Feb 2008 21:12:47 +0100 1245045 http://www.medworm.com/index.php?rid=1245044&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18282517%26dopt%3DAbstract Authors: Wozniak RJ, Bresnick EH Epigenetic mechanisms involving dynamic changes in posttranslational histone modifications commonly control gene transcription and therefore the execution of all cellular differentiation programs. The differentiation of hematopoietic stem cells into specific progenitor cells and the diverse blood cell types represents a particularly powerful system for the study of epigenetic mechanisms. The hematopoietic system allows one to define mechanisms underlying the establishment and regulation of histone modification patterns covering entire genes and/or chromosomes at distinct stages of differentiation. This chapter reviews progress in elucidating principles underlying epigenetic control of complex loci, specifically focusing on genes differentially expressed... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1245044 Wed, 20 Feb 2008 21:12:47 +0100 1245044 http://www.medworm.com/index.php?rid=1245043&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18282518%26dopt%3DAbstract Authors: Ginder GD, Gnanapragasam MN, Mian OY The sequence complexity of the known vertebrate genomes alone is insufficient to account for the diversity between individuals of a species. Although our knowledge of vertebrate biology has evolved substantially with the growing compilation of sequenced genomes, understanding the temporal and spatial regulation of genes remains fundamental to fully exploiting this information. The importance of epigenetic factors in gene regulation was first hypothesized decades ago when biologists posited that methylation of DNA could heritably alter gene expression [Holliday and Pugh, 1975. Science187(4173), 226-232; Riggs, 1975. Cytogenet. and Cell Genet.14(1), 9-25; Scarano et al., 1967. Proc. Natl. Acad. Sci. USA57(5), 1394-1400)]. It was subsequently ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1245043 Wed, 20 Feb 2008 21:12:47 +0100 1245043 http://www.medworm.com/index.php?rid=1245042&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18282519%26dopt%3DAbstract Authors: de Laat W, Klous P, Kooren J, Noordermeer D, Palstra RJ, Simonis M, Splinter E, Grosveld F The history of globin research is marked by a series of contributions seminal to our understanding of the genome, its function, and its relation to disease. For example, based on studies on hemoglobinopathies, it was understood that gene expression can be under the control of DNA elements that locate away from the genes on the linear chromosome template. Recent technological developments have allowed the demonstration that these regulatory DNA elements communicate with the genes through physical interaction, which loops out the intervening chromatin fiber. Subsequent studies showed that the spatial organization of the beta-globin locus dynamically changes in relation to differences in ge... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1245042 Wed, 20 Feb 2008 21:12:47 +0100 1245042 http://www.medworm.com/index.php?rid=1245041&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18282520%26dopt%3DAbstract Authors: Wrighting DM, Andrews NC Erythrocytes require iron to perform their duty as oxygen carriers. Mammals have evolved a mechanism to maintain systemic iron within an optimal range that fosters erythroid development and function while satisfying other body iron needs. This chapter reviews erythroid iron uptake and utilization as well as systemic factors that influence iron availability. One of these factors is hepcidin, a circulating peptide hormone that maintains iron homeostasis. Elevated levels of hepcidin in the bloodstream effectively shut off iron absorption by disabling the iron exporter ferroportin. Conversely, low levels of circulating hepcidin allow ferroportin to export iron into the bloodstream. Aberrations in hepcidin expression or responsiveness to hepcidin result in ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1245041 Wed, 20 Feb 2008 21:12:47 +0100 1245041 http://www.medworm.com/index.php?rid=1245040&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18282521%26dopt%3DAbstract Authors: Cokić VP, Schechter AN Nitric oxide (NO) is a diffusible free radical generated primarily by NO synthases (NOS), isoenzymes that convert the l-arginine and molecular oxygen to citrulline and NO in cells. Endothelial cells as well as macrophages, components of hematopoietic microenvironment and potent NO producers, play an active role in the modulation of human hematopoietic cell growth and differentiation. A role of NO in erythroid cell differentiation has been postulated based on demonstration that NO inhibits growth, differentiation, and hemoglobinization of erythroid primary cells. Endothelial NOS (eNOS) mRNA and protein levels, as well as bioactivity, decrease during erythroid differentiation, concomitantly with the elevation of hemoglobin levels. Human red blood cel... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1245040 Wed, 20 Feb 2008 21:12:47 +0100 1245040 http://www.medworm.com/index.php?rid=1245039&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18282522%26dopt%3DAbstract Authors: Ellis SR, Lipton JM Diamond Blackfan anemia (DBA) is an inherited hypoplastic anemia that typically presents in the first year of life. The genes identified to date that are mutated in DBA encode ribosomal proteins, and in these cases ribosomal protein haploinsufficiency gives rise to the disease. The developmental timing of DBA presentation suggests that the changes in red blood cell production that occur around the time of birth trigger a pathophysiological mechanism, likely linked to defective ribosome synthesis, which precipitates the hematopoietic phenotype. Variable presentation of other clinical phenotypes in DBA patients indicates that other developmental pathways may also be affected by ribosomal protein haploinsufficiency and that the involvement of these pathways is... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1245039 Wed, 20 Feb 2008 21:12:47 +0100 1245039 http://www.medworm.com/index.php?rid=1189988&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023722%26dopt%3DAbstract Authors: Schnell S, Maini PK, Newman SA, Newman TJ PMID: 18023722 [PubMed - indexed for MEDLINE] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1189988 Thu, 31 Jan 2008 09:02:02 +0100 1189988 http://www.medworm.com/index.php?rid=1041364&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023722%26dopt%3DAbstract Authors: Schnell S, Maini PK, Newman SA, Newman TJ PMID: 18023722 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041364 Wed, 21 Nov 2007 15:05:16 +0100 1041364 http://www.medworm.com/index.php?rid=1041363&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023723%26dopt%3DAbstract Authors: Meinhardt H An inroad into an understanding of the complex molecular interactions on which development is based can be achieved by uncovering the minimum requirements that describe elementary steps and their linkage. Organizing regions and other signaling centers can be generated by reactions that involve local self-enhancement coupled to antagonistic reactions of longer range. More complex patterns result from a chaining of such reactions in which one pattern generates the prerequisites for the next. Patterning along the single axis of radial symmetric animals including the small freshwater polyp hydra can be explained in this way. The body pattern of such ancestral organisms evolved into the brain of higher organisms, while trunk and midline formation are later evolutionary ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041363 Wed, 21 Nov 2007 15:05:16 +0100 1041363 http://www.medworm.com/index.php?rid=1041362&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023724%26dopt%3DAbstract Authors: Umulis D, O'Connor MB, Othmer HG PMID: 18023724 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041362 Wed, 21 Nov 2007 15:05:16 +0100 1041362 http://www.medworm.com/index.php?rid=1041361&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023725%26dopt%3DAbstract We describe processes operating in the embryo from whole embryo scale, the tissue-scale, to the cellular and extracellular matrix scale. We focus on describing cells, their behaviors and the unique microenvironments they traverse during gastrulation and discuss the role of tissue mechanics in these processes. PMID: 18023725 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041361 Wed, 21 Nov 2007 15:05:16 +0100 1041361 http://www.medworm.com/index.php?rid=1041360&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023726%26dopt%3DAbstract Authors: Chuai M, Weijer CJ Formation of the primitive streak is one of the key events in the early development of amniote embryos. The streak is the site where during gastrulation the mesendoderm cells ingress to take up their correct topographical positions in the embryo. The process of streak formation can be conveniently observed in the chick embryo, where the streak forms as an accumulation of cells in the epiblast in the posterior pole of the embryo and extends subsequently in anterior direction until it covers 80% of the epiblast. A prerequisite for streak formation is the differentiation of mesoderm, which is induced in the epiblast at the interface between the posterior Area Opaca and Area Pellucida in a sickle shaped domain overlying Koller's sickle. Current views on the mole... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041360 Wed, 21 Nov 2007 15:05:16 +0100 1041360 http://www.medworm.com/index.php?rid=1041359&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023727%26dopt%3DAbstract Authors: Newman TJ This paper is comprised of two parts. In the first we provide a brief overview of grid-free methods for modeling multicellular systems. We focus on an approach based on Langevin equations, in which inertia is ignored, and stochastic effects on cell motion are included. The discussion starts with simpler models, in which cells are modeled as adhesive spheres. We then turn to more sophisticated approaches in which nontrivial cell shape is accommodated, including the recently introduced Subcellular Element Model, in which each cell is described as a cluster of adhesively coupled over-damped subcellular elements, representing patches of cytoskeleton. In the second part of the paper we illustrate the use of a standard grid-free cell-based model to computationally probe in... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041359 Wed, 21 Nov 2007 15:05:16 +0100 1041359 http://www.medworm.com/index.php?rid=1041358&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023728%26dopt%3DAbstract Authors: Baker RE, Schnell S, Maini PK Somitogenesis is the process of division of the anterior-posterior vertebrate embryonic axis into similar morphological units known as somites. These segments generate the prepattern which guides formation of the vertebrae, ribs and other associated features of the body trunk. In this work, we review and discuss a series of mathematical models which account for different stages of somite formation. We begin by presenting current experimental information and mechanisms explaining somite formation, highlighting features which will be included in the models. For each model we outline the mathematical basis, show results of numerical simulations, discuss their successes and shortcomings and avenues for future exploration. We conclude with a brief disc... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041358 Wed, 21 Nov 2007 15:05:16 +0100 1041358 http://www.medworm.com/index.php?rid=1041357&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023729%26dopt%3DAbstract Authors: Glazier JA, Zhang Y, Swat M, Zaitlen B, Schnell S During gastrulation in vertebrates, mesenchymal cells at the anterior end of the presomitic mesoderm (PSM) periodically compact, transiently epithelialize and detach from the posterior PSM to form somites. In the prevailing clock-and-wavefront model of somitogenesis, periodic gene expression, particularly of Notch and Wnt, interacts with an FGF8-based thresholding mechanism to determine cell fates. However, this model does not explain how cell determination and subsequent differentiation translates into somite morphology. In this paper, we use computer simulations of chick somitogenesis to show that experimentally-observed temporal and spatial patterns of adhesive N-CAM and N-cadherin and repulsive EphA4-ephrinB2 pairs suffice ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041357 Wed, 21 Nov 2007 15:05:16 +0100 1041357 http://www.medworm.com/index.php?rid=1041356&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023730%26dopt%3DAbstract Authors: Lubkin SR Branching morphogenesis is ubiquitous and important in creating bulk transport systems. Branched ducts can be generated by several different mechanisms including growth, cell rearrangements, contractility, adhesion changes, and other mechanisms. We have developed several models of the mechanics of cleft formation, which we review. We discuss the implications of several candidate mechanisms and review what has been found in models and in experiments. PMID: 18023730 [PubMed - in process] (Source: Current Topics in Developmental Biology) Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041356 Wed, 21 Nov 2007 15:05:16 +0100 1041356 http://www.medworm.com/index.php?rid=1041355&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023731%26dopt%3DAbstract Authors: Czirok A, Zamir EA, Szabo A, Little CD Living organisms, from bacteria to vertebrates, are well known to generate sophisticated multicellular patterns. Numerous recent interdisciplinary studies have focused on the formation and regulation of these structures. Advances in automatized microscopy allow the time-resolved tracking of embryonic development at cellular resolution over an extended area covering most of the embryo. The resulting images yield simultaneous information on the motion of multiple tissue components-both cells and extracellular matrix (ECM) fibers. Recent studies on ECM displacements in bird embryos resulted in a method to distinguish tissue deformation and cell-autonomous motion. Patterning of the primary vascular plexus results from a collective action of p... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041355 Wed, 21 Nov 2007 15:05:16 +0100 1041355 http://www.medworm.com/index.php?rid=1041354&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023732%26dopt%3DAbstract Authors: Miura T Vertebrate lung has tree-like structure which facilitates gas exchange. After discovery of the involvement of several key toolkit genes-FGF10, BMP4, and Shh, huge amount of molecular information on lung development is now available. However, how their interactions result in a branched structure has not been elucidated. Recently, some studies have utilized mathematical models to understand the mechanism of branching morphogenesis, and we now have some models which are reliable enough to make experimental predictions in the in vitro system. In addition, a different type of modeling, which generates tree-like branching pattern by repeatedly applying a set of simple rules iteratively, is also utilized to model lung function. In this review, I focus on how these models can ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041354 Wed, 21 Nov 2007 15:05:16 +0100 1041354 http://www.medworm.com/index.php?rid=1041353&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023733%26dopt%3DAbstract Authors: Newman SA, Christley S, Glimm T, Hentschel HG, Kazmierczak B, Zhang YT, Zhu J, Alber M Dynamical systems in which geometrically extended model cells produce and interact with diffusible (morphogen) and nondiffusible (extracellular matrix) chemical fields have proved very useful as models for developmental processes. The embryonic vertebrate limb is an apt system for such mathematical and computational modeling since it has been the subject of hundreds of experimental studies, and its normal and variant morphologies and spatiotemporal organization of expressed genes are well known. Because of its stereotypical proximodistally generated increase in the number of parallel skeletal elements, the limb lends itself to being modeled by Turing-type systems which are capable of produci... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041353 Wed, 21 Nov 2007 15:05:16 +0100 1041353 http://www.medworm.com/index.php?rid=1041352&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023734%26dopt%3DAbstract Authors: Salazar-Ciudad I One of the aims of developmental biology is to understand how a single egg cell gives rise to the complex spatial distributions of cell types and extracellular components of the adult phenotype. This review discusses the main genetic and epigenetic interactions known to play a role in tooth development and how they can be integrated into coherent models. Along the same lines, several hypotheses about aspects of tooth development that are currently not well understood are evaluated. This is done from their morphological consequences from the model and how these fit known morphological variation and change during tooth development. Thus the aim of this review is two-fold. On one hand the model and its comparison with experimental evidence will be used to outline... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041352 Wed, 21 Nov 2007 15:05:16 +0100 1041352 http://www.medworm.com/index.php?rid=1041351&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023735%26dopt%3DAbstract Authors: Meyer-Hermann M Mathematical methods in Biology are of increasing relevance for understanding the control and the dynamics of biological systems with medical relevance. In particular, agent-based methods turn more and more important because of fast increasing computational power which makes even large systems accessible. An overview of different mathematical methods used in Theoretical Biology is provided and a novel agent-based method for cell mechanics based on Delaunay-triangulations and Voronoi-tessellations is explained in more detail: The Delaunay-Object-Dynamics method. It is claimed that the model combines physically realistic cell mechanics with a reasonable computational load. The power of the approach is illustrated with two examples, avascular tumor growth and gene... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041351 Wed, 21 Nov 2007 15:05:16 +0100 1041351 http://www.medworm.com/index.php?rid=1041350&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023736%26dopt%3DAbstract Authors: Hatzikirou H, Deutsch A Understanding the precise interplay of moving cells with their typically heterogeneous environment is crucial for central biological processes as embryonic morphogenesis, wound healing, immune reactions or tumor growth. Mathematical models allow for the analysis of cell migration strategies involving complex feedback mechanisms between the cells and their microenvironment. Here, we introduce a cellular automaton (especially lattice-gas cellular automaton-LGCA) as a microscopic model of cell migration together with a (mathematical) tensor characterization of different biological environments. Furthermore, we show how mathematical analysis of the LGCA model can yield an estimate for the cell dispersion speed within a given environment. Novel imaging techn... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041350 Wed, 21 Nov 2007 15:05:16 +0100 1041350 http://www.medworm.com/index.php?rid=1041349&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023737%26dopt%3DAbstract Authors: Grima R In the past few decades, it has become increasingly popular and important to utilize mathematical models to understand how microscopic intercellular interactions lead to the macroscopic pattern formation ubiquitous in the biological world. Modeling methodologies come in a large variety and presently it is unclear what is their interrelationship and the assumptions implicit in their use. They can be broadly divided into three categories according to the spatial scale they purport to describe: the molecular, the cellular and the tissue scales. Most models address dynamics at the tissue-scale, few address the cellular scale and very few address the molecular scale. Of course there would be no dissent between models or at least the underlying assumptions would be known if ... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041349 Wed, 21 Nov 2007 15:05:16 +0100 1041349 http://www.medworm.com/index.php?rid=1041348&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023738%26dopt%3DAbstract Authors: Flenner E, Marga F, Neagu A, Kosztin I, Forgacs G A distinguishing feature of a multicellular living system is that it operates at various scales, from the intracellular to organismal. Genes and molecules set up the conditions for the physical processes to act, in particular to shape the embryo. As development continues the changes brought about by the physical processes lead to changes in gene expression. It is this coordinated interplay between genetic and generic (i.e., physical and chemical) processes that constitutes the modern understanding of early morphogenesis. It is natural to assume that in this multiscale process the smaller defines the larger. In case of biophysical properties, in particular, those at the subcellular level are expected to give rise to those at the... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041348 Wed, 21 Nov 2007 15:05:16 +0100 1041348 http://www.medworm.com/index.php?rid=1041347&cid=s_35505_62_f&fid=35505&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023739%26dopt%3DAbstract Authors: Bellomo N, Forni G This chapter deals with the modeling and simulation of large systems of interacting entities whose microscopic state includes not only geometrical and mechanical variables (typically position and velocity), but also biological functions or specific activities. The main issue looks at the development of a biological mathematical theory for multicellular systems. The first part is devoted to the derivation of mathematical structures to be properly used to model a variety of biological phenomena with special focus on immune competition. Then, some specific applications are proposed referring to the competition between neoplastic and immune cells. Finally, the last part is devoted to research perspectives towards the objective of developing a mathematical-biolog... Current Topics in Developmental Biology journals http://www.medworm.com/rss/comments.php?id=1041347 Wed, 21 Nov 2007 15:05:16 +0100 1041347