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 'genesis' source. Mon, 06 Feb 2012 09:32:10 +0100 http://www.medworm.com/index.php?rid=5663350&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22017 AbstractThe Drosophila Jun N‐terminal kinase (JNK) gene basket (bsk) promoter contains a DNA replication‐related element (DRE) like sequence, raising the possibility of regulation by the DNA replication‐related element‐binding factor (DREF). Chromatin immunoprecipitation assays with anti‐DREF IgG showed the bsk gene promoter region to be effectively amplified. Luciferase transient expression assays revealed the DRE like sequence to be important for bsk gene promoter activity, and knockdown of DREF decreased the bsk mRNA level and the bsk gene promoter activity. Furthermore, knockdown of DREF in the notum compartment of wing discs by pannier‐GAL4 and UAS‐DREFIR resulted in a split thorax phenotype. Monitoring of JNK activity in the wing disc by LacZ expression in a puckered (p... genesis journals http://www.medworm.com/rss/comments.php?id=5663350 Wed, 01 Feb 2012 05:00:00 +0100 5663350 http://www.medworm.com/index.php?rid=5654722&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.21800 (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5654722 Wed, 01 Feb 2012 05:00:00 +0100 5654722 http://www.medworm.com/index.php?rid=5654721&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22016 AbstractMiniature is an extracellular zona pellucida domain‐containing protein, required for flattening of pupal wing epithelia in Drosophila. Here we show that Miniature also plays an important role in the post‐eclosion wing maturation processes triggered by the neurohormone bursicon. Wing expansion and epithelial apoptosis are drastically delayed in miniature loss‐of‐function mutants, and sped up upon overexpression of the protein in wings. Miniature acts upstream from the heterotrimeric Gs protein transducing the bursicon signal in wing epithelia. We propose that Miniature interacts with bursicon and regulates its diffusion through or stability within the wing tissue. © 2012 Wiley Periodicals, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5654721 Wed, 01 Feb 2012 05:00:00 +0100 5654721 http://www.medworm.com/index.php?rid=5602642&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22013 AbstractXenopus is an essential vertebrate model system for biomedical research that has contributed to important discoveries in many disciplines, including cell biology, molecular biology, physiology, developmental biology and neurobiology. However, unlike other model systems no central repository/stock center for Xenopus had been established until recently. Similar to mouse, zebrafish and fly communities, which have established stock centers, Xenopus researchers need to maintain and distribute rapidly growing numbers of inbred, mutant and transgenic frog strains, along with DNA and protein resources, and individual laboratories struggle to accomplish this efficiently. In the last five years two resource centers were founded to address this need: the European Xenopus Resource Center (EXRC... genesis journals http://www.medworm.com/rss/comments.php?id=5602642 Wed, 18 Jan 2012 05:00:00 +0100 5602642 http://www.medworm.com/index.php?rid=5567107&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22006 AbstractTransgenesis is an essential, powerful tool for investigating gene function and the activities of enhancers, promoters and transcription factors in the chromatin environment. In Xenopus, current methods generate germ‐line transgenics by random insertion, often resulting in mosaicism, position‐dependent variations in expression, and lab‐to‐lab differences in efficiency. We have developed and tested a Xenopus FLP‐FRT Recombinase Mediated Transgenesis (XFRMT) method. We demonstrate transgenesis of Xenopus laevis by FLP‐catalyzed recombination of donor plasmid cassettes into F1 tadpoles with host cassette transgenes. X‐FRMT provides a new method for generating transgenic Xenopus. Once Xenopus lines harboring single host cassettes are generated, X‐FRMT should allow for t... genesis journals http://www.medworm.com/rss/comments.php?id=5567107 Wed, 04 Jan 2012 05:00:00 +0100 5567107 http://www.medworm.com/index.php?rid=5567106&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22009 AbstractChemical genetics, or chemical biology, has become an increasingly powerful method for studying biological processes. The main objective of chemical genetics is the identification and use of small molecules that act directly on proteins, allowing rapid and reversible control of activity. These compounds are extremely powerful tools for researchers, particularly in biological systems that are not amenable to genetic methods. In addition, identification of small molecule interactions is an important step in the drug discovery process. Increasingly, the African frog Xenopus is being used for chemical genetic approaches. Here, we highlight the advantages of Xenopus as a first‐line in vivo model for chemical screening as well as for testing reverse engineering approaches. © 2012 Wile... genesis journals http://www.medworm.com/rss/comments.php?id=5567106 Wed, 04 Jan 2012 05:00:00 +0100 5567106 http://www.medworm.com/index.php?rid=5567105&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22008 AbstractThe Xenopus community has made concerted efforts over the last ten to twelve years systematically to improve the available sequence information for this amphibian model organism ideally suited to the study of early development in vertebrates. Here I review progress in the collection of both sequence data and physical clone reagents for protein coding genes. I conclude that we have cDNA sequences for around 50% and full‐length clones for about 35% of the genes in Xenopus tropicalis, and similar numbers but a smaller proportion for Xenopus laevis. In addition I demonstrate that the gaps in the current genome assembly create problems for the computational elucidation of gene sequences, and suggest some ways to ameliorate the effects of this. © 2012 Wiley‐Liss, Inc. (Source: genes... genesis journals http://www.medworm.com/rss/comments.php?id=5567105 Wed, 04 Jan 2012 05:00:00 +0100 5567105 http://www.medworm.com/index.php?rid=5567104&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22007 AbstractA decade after the human genome sequence, most vertebrate gene functions remain poorly understood, limiting benefits to human health from rapidly advancing genomic technologies. Systematic in vivo functional analysis is ideally suited to the experimentally accessible Xenopus embryo, which combines embryological accessibility with a broad range of transgenic, biochemical and gain‐of‐function assays. The diploid X. tropicalis adds loss‐of‐function genetics and enhanced genomics to this repertoire. In the last decade diverse phenotypes have been recovered from genetic screens, mutations have been cloned, and reverse genetics in the form of TILLING and targeted gene editing have been established. Simple haploid genetics and gynogenesis and the very large number of embryos produ... genesis journals http://www.medworm.com/rss/comments.php?id=5567104 Wed, 04 Jan 2012 05:00:00 +0100 5567104 http://www.medworm.com/index.php?rid=5642413&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22015 AbstractThe frog Xenopus has been vital for biomedical science for over 80 years, contributing to diverse fields from cell signaling, cell and developmental biology, to ion channel physiology and toxicology. Its experimentally‐manipulable oocytes and embryos provide abundant material for molecular and biochemical approaches for a wide range of gene discovery and protein function studies. In recent years, the Xenopus community has invested in key resources for functional genomics, including genomewide full‐length cDNA collections and genome assemblies as well as genetic tools. These assets combine with Xenopus' extensive range of functional assays to create exciting new research avenues with medical as well as basic applications. This review describes how these resources were developed ... genesis journals http://www.medworm.com/rss/comments.php?id=5642413 Sun, 01 Jan 2012 05:00:00 +0100 5642413 http://www.medworm.com/index.php?rid=5633820&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.21799 (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5633820 Sun, 01 Jan 2012 05:00:00 +0100 5633820 http://www.medworm.com/index.php?rid=5615667&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.21799 AbstractTransdifferentiation is the direct cell reprogramming of a differentiated cell into another specialized cell type. In the worm Caenorhabditis elegans, an epithelial‐to‐neuronal transdifferentiation (the “Reset button”) occurs naturally in vivo. See the review by Hajduskova et al. in this issue. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5615667 Sun, 01 Jan 2012 05:00:00 +0100 5615667 http://www.medworm.com/index.php?rid=5615666&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22014 In conclusion, our data demonstrate for the first time BNC1′s essential role in maintaining mouse spermatogenesis. © 2012 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5615666 Sun, 01 Jan 2012 05:00:00 +0100 5615666 http://www.medworm.com/index.php?rid=5510709&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22003 AbstractSOX10 is a well‐conserved and widely expressed transcription factor involved in the regulation of embryonic development and in the determination of cell fate. As it is expressed in neural crest cells, their derivatives and the oligodendrocyte lineage, mutations of the protein contribute to a variety of diseases like neurocristopathies, peripheral demyelinating neuropathies and melanoma. Here, we report the generation of an inducible Sox10‐iCreERT2 BAC transgenic mouse line that labels, depending on the timepoint of induction, distinct derivatives of the otic placode and the neural crest as well as cells of the oligodendrocyte lineage. Surprisingly, we could show a neural crest origin of pericytes in the brain. Besides its use for fate‐mapping, the Sox10‐iCreERT2 mouse line ... genesis journals http://www.medworm.com/rss/comments.php?id=5510709 Thu, 15 Dec 2011 05:00:00 +0100 5510709 http://www.medworm.com/index.php?rid=5499906&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22000 In this study, we analyzed the expression and function of the double‐stranded RNA‐binding protein Staufen2 in Xenopus laevis endoderm. We found that staufen2 was broadly expressed within the developing endoderm beginning at gastrulation becoming localized to the anterior endoderm at later stages. Through morpholino‐mediated knockdown, we demonstrate that Staufen2 function is required for proper formation of the stomach, liver and pancreas. We define that its function is required during gastrulation for proper patterning of the dorsal‐ventral axis and that it acts to regulate expression of BMP signaling components. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5499906 Mon, 12 Dec 2011 05:00:00 +0100 5499906 http://www.medworm.com/index.php?rid=5499905&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22001 (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5499905 Mon, 12 Dec 2011 05:00:00 +0100 5499905 http://www.medworm.com/index.php?rid=5481679&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20831 AbstractEpigenetic regulation defines the commitment and potential of cells, including the limitations in their competence to respond to inducing signals. This review discusses the developmental origins of chromatin state in Xenopus and other vertebrate species and provides an overview of its use in genome annotation. In most metazoans the embryonic genome is transcriptionally quiescent after fertilization. This involves nucleosome‐dense chromatin, repressors and a temporal deficiency in the transcription machinery. Active histone modifications such as H3K4me3 appear in pluripotent blastula embryos, whereas repressive marks such as H3K27me3 show a major increase in enrichment during late blastula and gastrula stages. The H3K27me3 modification set by Polycomb restricts ectopic lineage‐s... genesis journals http://www.medworm.com/rss/comments.php?id=5481679 Sun, 04 Dec 2011 05:00:00 +0100 5481679 http://www.medworm.com/index.php?rid=5602641&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22012 AbstractHere we report and characterize deep sequencing data and bioinformatics analysis, of small RNAs from X. tropicalis gastrula. A total of 17,553,124 reads with perfect match to the genome derived from 2,616,053 unique sequences were identified. Seventy seven percent of theses sequences were not found in previous reports from X. tropicalis oocytes and somatic tissues. Bioinformatics analyses indicate that a large fraction of the small RNAs are PIWI‐interacting RNAs. Up to 23.9% of small RNAs mapped to transposable elements and 27% to genic regions. Most of abundant transposable derived small RNAs are found in oocyte and gastrula libraries, suggesting that transposon needs to be silenced also during early development. Additionally, miRNAs were identified and many of them are not pres... genesis journals http://www.medworm.com/rss/comments.php?id=5602641 Thu, 01 Dec 2011 05:00:00 +0100 5602641 http://www.medworm.com/index.php?rid=5567103&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22010 AbstractUsing a combination of deep sequencing and bioinformatics approach, we for the first time identify miRNAs and their relative abundance in mature, metaphase II arrested eggs in X. laevis. We characterize 115 miRNAs that have been described either in X. tropicalis (85), X. laevis (9) or other vertebrate species (21) that also map to known Xenopus pre‐miRNAs and to the X. tropicalis genome. Additionally, 72 new X. laevis putative candidate miRNAs are identified based on mapping to X. tropicalis genome within regions that have the propensity to form hairpin loops. These data expand on the availability of genetic information in X. laevis and identifies target miRNAs for future functional studies. © 2012 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5567103 Thu, 01 Dec 2011 05:00:00 +0100 5567103 http://www.medworm.com/index.php?rid=5541612&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22005 AbstractMitotic recombination is an effective tool for generating mutant clones in somatic tissues. Due to difficulties associated with detecting and quantifying mutant clones in mice, this technique is limited to analysis of growth related phenotypes induced by loss function of tumor suppressor genes. Here, we used the polymorphic CD45.1/CD45.2 alleles on chromosome 1 as pan‐hematopoietic markers to track mosaic clones generated through mitotic recombination in developing T cells. We show that lineage specific mitotic recombination can be induced and reliably detected as CD45.1 or CD45.2 homozygous clones from the CD45.1/CD45.2 heterozygous background. We have applied this system in the analysis of a lethal mutation in the Dhx9 gene. Mosaic analysis revealed a stage specific role for Dh... genesis journals http://www.medworm.com/rss/comments.php?id=5541612 Thu, 01 Dec 2011 05:00:00 +0100 5541612 http://www.medworm.com/index.php?rid=5510708&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22004 AbstractViral infection has been associated with a starvation‐like state in Drosophila melanogaster. Since starvation and inhibiting TOR kinase activity in vivo result in blocked oocyte production, we hypothesized that viral infection would also result in compromised oogenesis. Wild‐type flies were injected with Flock House Virus (FHV) and survival and embryo production were monitored. Infected flies had a dose‐responsive loss of fecundity that corresponded to a global reduction in Akt/TOR signaling. Highly penetrant egg chamber destruction mid‐way through oogenesis was noted and FHV coat protein was detected within developing egg chambers. As seen with in vivo TOR inhibition, oogenesis was partially rescued in loss of function discs large and merlin mutants. As expected, mutants i... genesis journals http://www.medworm.com/rss/comments.php?id=5510708 Thu, 01 Dec 2011 05:00:00 +0100 5510708 http://www.medworm.com/index.php?rid=5499904&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.22002 AbstractRetinoic acid (RA) signaling is necessary for proper patterning and morphogenesis during embryonic development. Tissue specific RA signaling requires precise spatial and temporal synthesis of RA from retinal by retinaldehyde dehydrogenases (Raldh) and the conversion of retinol to retinal by retinol dehydrogenases (Rdh) of the short‐chain dehydrogenase/reducatase gene family (SDR). The SDR, retinol dehydrogenase 10 (RDH10), is a major contributor to retinal biosynthesis during mid‐gestation. We have identified a missense mutation in the Rdh10 gene (Rdh10m366Asp) using an N‐ethyl‐N‐nitrosourea (ENU)‐induced forward genetic screen that result in reduced RA levels and signaling during embryonic development. Rdh10m366Asp mutant embryos have unique phenotypes, such as edema, ... genesis journals http://www.medworm.com/rss/comments.php?id=5499904 Thu, 01 Dec 2011 05:00:00 +0100 5499904 http://www.medworm.com/index.php?rid=5481680&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20830 AbstractVascular systems in the woody stem of an apple tree. Xylem (in light brown) and phloem (in blue) arise from the cambium that resides between the two. Stem cells in the cambium actively divide in an asymmetric manner, and their daughters differentiate into xylem or phloem in response to the positional information. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5481680 Thu, 01 Dec 2011 05:00:00 +0100 5481680 http://www.medworm.com/index.php?rid=5481678&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20832 AbstractGdX (also named Ubl4A) is a house‐keeping gene located on the X chromosome and encodes a protein harboring a ubiquitin‐like domain in human and mouse. Although identified in 1988, the function of GdX remains unknown. To elucidate the role of GdX in vivo, we generated a conditional GdX knockout mouse in which exon 2 was flanked by two loxP sites. We obtained viable and fertile mice with homozygous GdXflox/flox or GdXflox/Y allele. Germ‐line transmission was confirmed by crossing the mouse bearing conditionally targeted allele with an EIIα‐Cre transgenic mouse. GdX was successfully depleted in tissues of EIIα‐Cre‐GdX‐null mice. GdX‐/‐ and GdX‐/Y mice are viable and exhibit normal development compared with wild‐type littermates within 6 months during our observ... genesis journals http://www.medworm.com/rss/comments.php?id=5481678 Thu, 01 Dec 2011 05:00:00 +0100 5481678 http://www.medworm.com/index.php?rid=5453122&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20827 AbstractThe rhythmic segmentation process of the presomitic mesoderm (PSM) orchestrates the formation of somites, the fundamental units for the vertebrate axial body plan. To aid the investigation of molecular components governing the conversion from PSM into somites, we generated a transgenic mouse line that expresses a tamoxifen (tmx) inducible CreERT2 under the control of a 2.5kb enhancer element of Tbx6, a gene essential for PSM formation and somite patterning. Combined with Cre reporters, this Tbx6;CreERT2 line displays robust tmx‐inducible Cre activity in the PSM at various embryonic stages. This tool should be useful for studying gene function during somitogenesis by either conditional inactivation or mis‐expression, and potentially coupled with cell marking. © 2011 Wiley‐Lis... genesis journals http://www.medworm.com/rss/comments.php?id=5453122 Sat, 26 Nov 2011 05:00:00 +0100 5453122 http://www.medworm.com/index.php?rid=5453121&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20828 AbstractPromoting ectopic development of pancreatic beta cells from other cell types is one of the strategies being pursued for the treatment of diabetes. To achieve this, a detailed outline of the molecular lineage that operates in pancreatic progenitor cells to generate beta cells over other endocrine cell types is necessary. Here, we demonstrate that early transient expression of the endocrine progenitor bHLH protein Neurogenin 3 (Ngn3) favors the promotion of pancreatic beta and delta cell fates over an alpha cell fate, while later transient expression promotes ectopic development of all three endocrine cell fates. We found that short‐term activation of Ngn3 in Xenopus laevis endoderm just after gastrulation was sufficient to promote both early and ectopic development of beta and del... genesis journals http://www.medworm.com/rss/comments.php?id=5453121 Sat, 26 Nov 2011 05:00:00 +0100 5453121 http://www.medworm.com/index.php?rid=5548752&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20825 AbstractTwo main classes of models address the earliest steps of left–right patterning: those postulating that asymmetry is initiated via cilia‐driven fluid flow in a multicellular tissue at gastrulation, and those postulating that asymmetry is amplified from intrinsic chirality of individual cells at very early embryonic stages. A recent study revealed that cultured human cells have consistent left–right (LR) biases that are dependent on apical‐basal polarity machinery. The ability of single cells to set up asymmetry suggests that cellular chirality could be converted to embryonic laterality by cilia‐independent polarity mechanisms in cell fields. To examine the link between cellular polarity and LR patterning in a vertebrate model organism, we probed the roles of apical‐basal... genesis journals http://www.medworm.com/rss/comments.php?id=5548752 Tue, 15 Nov 2011 05:00:00 +0100 5548752 http://www.medworm.com/index.php?rid=5602643&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20820 AbstractWith the growing use of genome‐wide screens for cis‐regulatory elements, there is a pressing need for platforms that enable fast and cost‐effective experimental validation of identified hits in relevant developmental and tissue contexts. Here, we describe a murine embryonic stem cell (ESC)‐based system that facilitates rapid analysis of putative transcriptional enhancers. Candidate enhancers are targeted with high efficiency to a defined genomic locus via recombinase‐mediated cassette exchange. Targeted ESCs are subsequently differentiated in vitro into desired cell types, where enhancer activity is monitored by reporter gene expression. As a proof of principle, we analyzed a previously characterized, Sonic hedgehog (Shh)‐dependent, V3 interneuron progenitor (pV3)‐spe... genesis journals http://www.medworm.com/rss/comments.php?id=5602643 Mon, 14 Nov 2011 05:00:00 +0100 5602643 http://www.medworm.com/index.php?rid=5415619&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20819 AbstractWe have developed a method of injecting Bacterial Artificial Chromosome (BAC) DNA into Xenopus embryos that is simple and efficient, and results in consistent and tissue‐specific expression of transgenes cloned into BAC vectors. Working with large pieces of DNA, as can be accommodated by BACs, is necessary when studying large or complex genes and conducive to studying the function of long‐range regulatory elements that act to control developmentally restricted gene expression. We recombineered fluorescent reporters into three Xenopus tropicalis BAC clones targeting three different genes and report that up to 60% of injected embryos express the reporter in a manner consistent with endogenous expression. The behavior of these BACs, which are replicated after injection, contrasts ... genesis journals http://www.medworm.com/rss/comments.php?id=5415619 Mon, 14 Nov 2011 05:00:00 +0100 5415619 http://www.medworm.com/index.php?rid=5415618&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20820 AbstractWith the growing use of genome‐wide screens for cis‐regulatory elements, there is a pressing need for platforms that enable fast and cost‐effective experimental validation of identified hits in relevant developmental and tissue contexts. Here, we describe a murine embryonic stem cell (ESC) based system that facilitates rapid analysis of putative transcriptional enhancers. Candidate enhancers are targeted with high efficiency to a defined genomic locus via recombinase‐mediated cassette exchange (RMCE). Targeted ESCs are subsequently differentiated in vitro into desired cell types, where enhancer activity is monitored by reporter gene expression. As a proof of principle, we analyzed a previously characterized, Sonic hedgehog (Shh)‐dependent, V3 interneuron progenitor (pV3)�... genesis journals http://www.medworm.com/rss/comments.php?id=5415618 Mon, 14 Nov 2011 05:00:00 +0100 5415618 http://www.medworm.com/index.php?rid=5415617&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20821 AbstractAmphibians including the South African clawed frog Xenopus laevis, its close relative Xenopus tropicalis, and the Mexican axolotl (Ambystoma mexicanum) are important vertebrate models for cell biology, development and regeneration. For the analysis of embryos and larva with altered gene expression in gain‐of‐function or loss‐of‐function studies histology is increasingly important. Here, we discuss plastic or resin embedding of embryos as valuable alternatives to conventional paraffin embedding. For example, microwave‐assisted tissue processing, combined with embedding in the glycol methacrylate Technovit 7100, is a fast, simple and reliable method to obtain state‐of‐the‐art histology with high resolution of cellular details in less than a day. Microwave‐processed ... genesis journals http://www.medworm.com/rss/comments.php?id=5415617 Mon, 14 Nov 2011 05:00:00 +0100 5415617 http://www.medworm.com/index.php?rid=5415616&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20822 In conclusion, this cell line baptized “Speedy” should prove useful to couple in vitro and in vivo biological studies in the X. tropicalis frog model. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5415616 Mon, 14 Nov 2011 05:00:00 +0100 5415616 http://www.medworm.com/index.php?rid=5415615&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20823 AbstractIn egglaying animals, embryonic development takes place within the highly specialized environment provided by the eggshell and its underlying extracellular matrix. Far from being simply a passive physical support, the eggshell is a key player in many early developmental events. Herein, we review current understanding of eggshell structure, biosynthesis and function in zygotic development of the nematode, C. elegans. Beginning at sperm contact or entry, eggshell layers are produced sequentially. The earlier outer layers are required for secretion or organization of inner layers, and layers differ in composition and function. Developmental events that depend on the eggshell include polyspermy barrier generation, high fidelity meiotic chromosome segregation, osmotic barrier synthesis,... genesis journals http://www.medworm.com/rss/comments.php?id=5415615 Mon, 14 Nov 2011 05:00:00 +0100 5415615 http://www.medworm.com/index.php?rid=5415614&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20824 AbstractCiliated epithelia are important in a wide variety of biological contexts where they generate directed fluid flow. Here we address the fundamental advances in understanding ciliated epithelia that have been achieved using Xenopus as a model system. Xenopus embryos are covered with a ciliated epithelium that propels fluid unidirectionally across their surface. The external nature of this tissue, coupled with the molecular tools available in Xenopus and the ease of microscopic analysis on intact animals has thrust Xenopus to the forefront of ciliated epithelia biology. We discuss advances in understanding the molecular regulators of ciliated epithelia cell fate as well as basic aspects of ciliated epithelia cell biology including ciliogenesis and cell polarity. © 2011 Wiley‐Liss, ... genesis journals http://www.medworm.com/rss/comments.php?id=5415614 Mon, 14 Nov 2011 05:00:00 +0100 5415614 http://www.medworm.com/index.php?rid=5453120&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20829 We report that SCF positive cells constitute a subpopulation in the visceral endoderm before gastrulation and time‐lapse imaging reveals that SCF monitors the nascent definitive endoderm during epithelialisation. After gastrulation, SCF marks the mid‐ and hindgut endoderm and vascular endothelial network, which can be imaged during establishment in allantois explant cultures. The SCF reporter is downregulated in the endoderm epithelium and upregulated in endothelial cells of the intestine, lung and pancreas during organogenesis. In summary, the generation of the Sox17‐mCherry reporter mouse line allows direct visualization of endoderm and vascular development in culture and the mouse embryo. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5453120 Tue, 01 Nov 2011 04:00:00 +0100 5453120 http://www.medworm.com/index.php?rid=5446415&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20826 AbstractIn order to facilitate the use of the new mutant resource developed in the mouse, we have generated Cre and FlpO deleter mice on a pure inbred C57BL/6N background. The new transgenic constructs were designed to drive either the Cre or FlpO recombinase, fused to a specific fluorescent marker (respectively the eGFP or the eYFP) and were inserted by homologous recombination in the neutral Rosa26 locus. They allow a rapid, cost‐effective and efficient identification of the carrier individuals through the co‐expression of the fluorescent marker. The recombination efficiency of the two deleter lines, Gt(ROSA)26Sor<tm1(ACTB‐cre,‐EGFP)Ics and Gt(ROSA)26Sor<tm2(CAG‐flpo,EYFP)Ics, was carefully evaluated using five loxP‐flanked or four FRT‐flanked alleles located at diffe... genesis journals http://www.medworm.com/rss/comments.php?id=5446415 Tue, 01 Nov 2011 04:00:00 +0100 5446415 http://www.medworm.com/index.php?rid=5415613&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20825 AbstractTwo main classes of models address the earliest steps of left‐right patterning: those postulating that asymmetry is initiated via cilia‐driven fluid flow in a multicellular tissue at gastrulation, and those postulating that asymmetry is amplified from intrinsic chirality of individual cells at very early embryonic stages. A recent study revealed that cultured human cells have consistent left‐right (LR) biases that are dependent on apical‐basal polarity machinery. The ability of single cells to set up asymmetry suggests that cellular chirality could be converted to embryonic laterality by cilia‐independent polarity mechanisms in cell fields. To examine the link between cellular polarity and LR patterning in a vertebrate model organism, we probed the roles of apical‐basal... genesis journals http://www.medworm.com/rss/comments.php?id=5415613 Tue, 01 Nov 2011 04:00:00 +0100 5415613 http://www.medworm.com/index.php?rid=5394511&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20818 AbstractCoronary artery sections from day 13.5 transgenic mouse pups were stained by immuno‐fluorescence for a‐smooth muscle actin (red) and counterstained with DAPI (green) to mark nuclei. The blue, β‐galactosidase‐positive cells express a Bmp2‐driven lacZ reporter gene that lacks a post‐transcriptional repressor conserved from mammals to fishes. See Kruithof et al., An In Vivo Map of Bone Morphogenetic Protein 2 Post‐transcriptional Repression in the Heart. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5394511 Tue, 01 Nov 2011 04:00:00 +0100 5394511 http://www.medworm.com/index.php?rid=5567114&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20813 AbstractThe Notch‐regulated ankyrin repeat protein (Nrarp) is a component of a negative feedback system that attenuates Notch pathway‐mediated signaling. In vertebrates, the timing and spacing of formation of the mesodermal somites are controlled by a molecular oscillator termed the segmentation clock. Somites are also patterned along the rostral‐caudal axis of the embryo. Here, we demonstrate that Nrarp‐deficient embryos and mice exhibit genetic background‐dependent defects of the axial skeleton. While progression of the segmentation clock occurred in Nrarp‐deficient embryos, they exhibited altered rostrocaudal patterning of the somites. In Nrarp mutant embryos, the posterior somite compartment was expanded. These studies confirm an anticipated, but previously undocumented rol... genesis journals http://www.medworm.com/rss/comments.php?id=5567114 Thu, 13 Oct 2011 04:00:00 +0100 5567114 http://www.medworm.com/index.php?rid=5320143&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20813 AbstractThe Notch‐regulated ankyrin repeat protein (Nrarp) is a component of a negative feedback system that attenuates Notch pathway‐mediated signaling. In vertebrates, the timing and spacing of formation of the mesodermal somites is controlled by a molecular oscillator termed the segmentation clock. Somites are also patterned along the rostral‐caudal axis of the embryo. Here we demonstrate that Nrarp‐deficient embryos and mice exhibit genetic background‐dependent defects of the axial skeleton. While progression of the segmentation clock occurred in Nrarp‐deficient embryos, they exhibited altered rostrocaudal patterning of the somites. In Nrarp mutant embryos, the posterior somite compartment was expanded. These studies confirm an anticipated, but previously undocumented role ... genesis journals http://www.medworm.com/rss/comments.php?id=5320143 Thu, 13 Oct 2011 04:00:00 +0100 5320143 http://www.medworm.com/index.php?rid=5320142&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20814 AbstractMorphological diversity arises during development through the actions and interactions of diverse developmental pathways. Among those, the Wnt pathway is known to contribute to diverse developmental processes such as segmentation and the morphogenesis of appendages. Here, we characterize a transcription factor in the Wnt pathway, pangolin (pan), to investigate the role of Wnt signaling in the development of evolutionarily novel body structures: the horns of beetles. Beetle horns are highly diverse in size, shape and number and develop principally from two major body regions: the head and prothorax. We investigate horns in two species of the genus Onthophagus using comparative in situ hybridization, larval RNA interference, and allometric measurements to analyze whether horn formati... genesis journals http://www.medworm.com/rss/comments.php?id=5320142 Thu, 13 Oct 2011 04:00:00 +0100 5320142 http://www.medworm.com/index.php?rid=5320141&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20815 AbstractProtein phosphatase 2A (PP2A) is one of the most abundant serine/threonine phosphatases, with a critical role in embryonic development and human disease. There are two isoforms of the catalytic subunit of PP2A, Ppp2ca and Ppp2cb. Null mutation of Ppp2ca leads to early embryonic lethality at E6.5, hindering functional study of PP2A beyond this stage. We generated conditional null alleles of Ppp2ca and Ppp2cb by flanking with loxP sites exons 3 to 5 of Ppp2ca and exon 3 of Ppp2cb. Ppp2cafl/fl mice did not display any visible phenotype. Homozygous mutants in which Cre‐mediated excision resulted in global deletion of Ppp2ca displayed embryonic lethality and developmental defects similar to those previously reported. Ppp2cbΔ/Δ mice generated by the same strategy did not display any ... genesis journals http://www.medworm.com/rss/comments.php?id=5320141 Thu, 13 Oct 2011 04:00:00 +0100 5320141 http://www.medworm.com/index.php?rid=5320140&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20816 AbstractThe proneural genes are fundamental regulators of neuronal development in all metazoans. A critical role of the fly proneural factor Atonal (AtoDm) is to induce photoreceptor neuron formation in Drosophila, whereas its murine homolog, Atonal7Mm (aka Ath5) is essential for the development of the ganglion cells of the vertebrate eye. Here, we identify the Bombyx mori ato homolog (atoBm). In a pattern strikingly reminiscent of atoDm, the atoBm mRNA is expressed as a stripe in the silkworm eye disc. Its DNA‐binding and protein‐protein interaction domain is highly homologous to the AtoDm bHLH. Targeted expression of AtoBm in the endogenous atoDm pattern rescues the eyeless phenotype of the fly ato1 mutant and its ectopic expression induces similar gain‐of‐function phenotypes as ... genesis journals http://www.medworm.com/rss/comments.php?id=5320140 Thu, 13 Oct 2011 04:00:00 +0100 5320140 http://www.medworm.com/index.php?rid=5320145&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20807 AbstractNo abtract. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5320145 Sat, 01 Oct 2011 04:00:00 +0100 5320145 http://www.medworm.com/index.php?rid=5320144&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20812 AbstractTranverse section of a E10.5 mouse embryo showing the dorsal aorta immunostained for CD‐31 (red) and DRAQ5TM (blue). (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5320144 Sat, 01 Oct 2011 04:00:00 +0100 5320144 http://www.medworm.com/index.php?rid=5320139&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20817 AbstractTransgenic mouse lines expressing Cre recombinase in a cell‐ and tissue‐specific manner are essential tools for studying gene function and for developing suitable models for human diseases. Here, we employed an expression cassette containing the full 5' untranslated region of the porcine insulin gene to generate a mouse line expressing Cre recombinase specifically in pancreatic β‐cells by pronuclear DNA microinjection. We obtained a founder animal that transmitted the construct to his descendants in a mendelian fashion and whose descendents showed a clear activation of β‐galactosidase expression in pancreatic β‐cells after crossing into the ROSA26 lacZ reporter mouse line. Cre expression in other organs was negative except for the kidney, intestine, and the cerebral po... genesis journals http://www.medworm.com/rss/comments.php?id=5320139 Sat, 01 Oct 2011 04:00:00 +0100 5320139 http://www.medworm.com/index.php?rid=5567113&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20811 AbstractThe availability of both the Xenopus tropicalis genome and the soon to be released Xenopus laevis genome provides a solid foundation for Xenopus developmental biologists. The Xenopus community has presently amassed expression data for ∼2,300 genes in the form of published images collected in the Xenbase, the principal Xenopus research database. A few of these genes have been examined in both X. tropicalis and X. laevis and the cross‐species comparison has been proven invaluable for studying gene function. A recently published work has yielded developmental expression profiles for the majority of Xenopus genes across fourteen developmental stages spanning the blastula, gastrula, neurula, and the tail‐bud. While this data was originally queried for global evolutionary and devel... genesis journals http://www.medworm.com/rss/comments.php?id=5567113 Wed, 28 Sep 2011 04:00:00 +0100 5567113 http://www.medworm.com/index.php?rid=5567112&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20810 AbstractOuter hair cells (OHCs) in the cochlea are crucial for the remarkable hearing sensitivity and frequency tuning. To understand OHC physiology and pathology, it is imperative to use mouse genetic tools to manipulate gene expression specifically in OHCs. Here, we generated two prestin knockin mouse lines: (1) the prestin‐CreERT2 line, with an internal ribosome entry site‐CreERT2‐FRT‐Neo‐FRT cassette inserted into the prestin locus after the stop codon, and (2) the prestin‐CreERT2‐NN line, with the FRT‐Neo‐FRT removed subsequently. We characterized the inducible Cre activity of both lines by crossing them with the reporter lines CAG‐eGFP and Ai6. Cre activity was induced with tamoxifen at various postnatal ages and only detected in OHCs, resembling the endogenous pr... genesis journals http://www.medworm.com/rss/comments.php?id=5567112 Mon, 26 Sep 2011 04:00:00 +0100 5567112 http://www.medworm.com/index.php?rid=5244762&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20808 AbstractMature oligodendrocytes are critical for myelin maintenance. To understand the molecular basis for this, genetic manipulation of mature oligodendrocytes is needed. Here we generated a mature oligodendrocyte tTA (tetracycline‐controlled transcriptional activator) mouse line which, in combination with a tTA‐dependent promoter line driving the expression of the desired transgene, can be used for gain‐of‐function studies. We used an oligodendrocyte promoter, the mouse proteolipid protein (PLP) promoter, to express mammalianized tTA, and generated a PLP‐mtTA mouse line. In adults, mtTA mRNA was predominantly detected in brain white matter where it co‐localized with PLP mRNA. mtTA‐mediated gene induction was confirmed by crossing to mice with a tTA‐dependent promoter driv... genesis journals http://www.medworm.com/rss/comments.php?id=5244762 Thu, 22 Sep 2011 04:00:00 +0100 5244762 http://www.medworm.com/index.php?rid=5567111&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20803 AbstractThe ubiquitin proteasome system (UPS) is the main proteolytic system of cells. Recent evidence suggests that the UPS plays a regulatory role in regeneration processes. Here, we explore the possibility that the UPS is involved during intestinal regeneration of the sea cucumber Holothuria glaberrima. These organisms can regenerate most of their digestive tract following a process of evisceration. Initially, we identified components of H. glaberrima UPS, including sequences for Rpn10, β3, and ubiquitin‐RPL40. Predicted proteins from the mRNA sequences showed high degree of conservation that ranged from 60% (Rpn10) to 98% (Ub‐RPL40). Microarrays and RT‐PCR experiments showed that these genes were upregulated during intestinal regeneration. In addition, we demonstrated expression... genesis journals http://www.medworm.com/rss/comments.php?id=5567111 Mon, 12 Sep 2011 04:00:00 +0100 5567111 http://www.medworm.com/index.php?rid=5567110&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20804 AbstractFluorescent protein (FP) reporter alleles are useful both for identifying and purifying specific cell populations in the mouse. Here, we report the generation of mouse embryonic stem cells that contain a pancreatic and duodenal homeobox 1 (Pdx1) loxed cassette acceptor (Pdx1LCA) allele and the use of recombinase‐mediated cassette exchange to derive mice that contain a Pdx1CFP (Cerulean) reporter allele. Mice with this allele exhibited cyan fluorescence within the previously well‐characterized Pdx1 expression domain in posterior foregut endoderm. Immunolabeling showed that endogenous Pdx1 was coexpressed with CFP at all time points examined. Furthermore, fluorescence‐activated cell sorting was used to isolate CFP‐positive cells from E11.5 and E18.5 embryonic tissues using bo... genesis journals http://www.medworm.com/rss/comments.php?id=5567110 Mon, 12 Sep 2011 04:00:00 +0100 5567110 http://www.medworm.com/index.php?rid=5567109&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20801 We report here the construction of Tubby‐RFP balancers for the X, 2nd and 3rd chromosomes of Drosophila melanogaster. The insertion of a 2xTb‐RFP transgene on the FM7c, CyO, and TM3 balancer chromosomes introduces two easily scorable, dominant, developmental markers. The strong Tb phenotype is visible to the naked eye at the larval L2, L3, and pupal stages. The RFP associated with the cuticle is easily detected at all stages from late embryo to adult with the use of a fluorescence stereomicroscope. The FM7c Bar 2xTb‐RFP, CyO Cy 2xTb‐RFP, and TM3 Sb 2xTb‐RFP balancers will greatly facilitate the analysis of lethals and other developmental mutants in L2/L3 larvae and pupae, but also provide coverage of other stages beginning in late embryogenesis through to the adult. genesis 00:1�... genesis journals http://www.medworm.com/rss/comments.php?id=5567109 Mon, 12 Sep 2011 04:00:00 +0100 5567109 http://www.medworm.com/index.php?rid=5216633&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20799 AbstractCre‐mediated apoptosis has been observed in many contexts in mice expressing Cre‐recombinase, and can confound the analysis of genetically engineered conditional mutant or transgenic alleles. Several mechanisms have been proposed to explain this phenomenon. We find that the degree of apoptosis induced correlates roughly with the copy number of loxP sites present in the genome and that some level of increased apoptosis accompanies the presence of even only a few loxP sites, as occurs in conditional floxed alleles. Cre‐induced apoptosis in this context is completely p53‐dependent, suggesting that the apoptosis is stimulated by p53 activation in response to DNA damage incurred during the process of Cre‐mediated recombination. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5216633 Mon, 12 Sep 2011 04:00:00 +0100 5216633 http://www.medworm.com/index.php?rid=5216632&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20800 AbstractGastrulation in vertebrates is a conserved process, which involves transition from cellular pluripotency to early precursors of ectoderm, mesoderm and endoderm. Pluripotency control during this stage is far from being understood. Recent genetic and transcriptomic studies in zebrafish suggest that the core pluripotency transcription factors Pou5f1 and transcription factors of the SoxB1 group are critically involved in large‐scale temporal coordination of gene expression during gastrulation. A significant number of evolutionary conserved target genes of Pou5f1 in zebrafish are also involved in stem‐cell circuit in mammalian ES cell cultures. Here, I will review the roles of Pou5f1 in development, discuss the evolutionary conservation of Pou5f1 functions, and their relation to plu... genesis journals http://www.medworm.com/rss/comments.php?id=5216632 Mon, 12 Sep 2011 04:00:00 +0100 5216632 http://www.medworm.com/index.php?rid=5216631&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20801 We report here the construction of Tubby‐RFP balancers for the X, 2nd and 3rd chromosomes of Drosophila melanogaster. The insertion of a 2xTb‐RFP transgene on the FM7c, CyO and TM3 balancer chromosomes introduces two easily scorable, dominant, developmental markers. The strong Tb phenotype is visible to the naked eye at the larval L2, L3 and pupal stages. The RFP associated with the cuticle is easily detected at all stages from late embryo to adult with the use of a fluorescence stereomicroscope. The FM7c Bar 2xTb‐RFP, CyO Cy 2xTb‐RFP and TM3 Sb 2xTb‐RFP balancers will greatly facilitate the analysis of lethals and other developmental mutants in L2/L3 larvae and pupae, but also provide coverage of other stages beginning in late embryogenesis through to the adult. © 2011 Wiley‐... genesis journals http://www.medworm.com/rss/comments.php?id=5216631 Mon, 12 Sep 2011 04:00:00 +0100 5216631 http://www.medworm.com/index.php?rid=5216630&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20802 AbstractTo gain insight into the roles of various genes in development and to circumvent embryonic lethality that hinders genetic studies, lineage tracing and conditional knockout techniques have been widely performed on mice using the increasing numbers of gene‐targeted Cre mouse lines. Employing the internal ribosome entry site (IRES) and the 2A peptide multicistronic expression strategies, we report two new Bapx1 mouse lines with functional Bapx1 whereby Cre and enhanced green fluorescence protein (EGFP) are expressed discretely under the control of the Bapx1 promoter. These mouse lines, when mated with the Rosa26R‐lacZ reporter line, can be used to trace the lineage of Bapx1‐expressing cells while stage‐specific, spatial expression of Bapx1 can be visualized by the EGFP fluores... genesis journals http://www.medworm.com/rss/comments.php?id=5216630 Mon, 12 Sep 2011 04:00:00 +0100 5216630 http://www.medworm.com/index.php?rid=5216629&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20803 AbstractThe ubiquitin proteasome system (UPS) is the main proteolytic system of cells. Recent evidence suggests that the UPS plays a regulatory role in regeneration processes. Here we explore the possibility that the UPS is involved during intestinal regeneration of the sea cucumber Holothuria glaberrima. These organisms can regenerate most of their digestive tract following a process of evisceration. Initially, we identified components of H. glaberrima UPS, including sequences for Rpn10, β3 and ubiquitin‐RPL40. Predicted proteins from the mRNA sequences showed high degree of conservation that ranged from 60% (Rpn10) to 98% (Ub‐RPL40). Microarrays and RT‐PCR experiments showed that these genes were up‐regulated during intestinal regeneration. In addition, we demonstrated expressio... genesis journals http://www.medworm.com/rss/comments.php?id=5216629 Mon, 12 Sep 2011 04:00:00 +0100 5216629 http://www.medworm.com/index.php?rid=5266889&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20811 AbstractThe availability of both the Xenopus tropicalis genome and the soon to be released Xenopus laevis genome provides a solid foundation for Xenopus developmental biologists. The Xenopus community has presently amassed expression data for ∼2,300 genes in the form of published images collected in the Xenbase, the principal Xenopus research database. A few of these genes have been examined in both X. tropicalis and X. laevis and the cross‐species comparison has been proven invaluable for studying gene function. A recently published work has yielded developmental expression profiles for the majority of Xenopus genes across fourteen developmental stages spanning the blastula, gastrula, neurula, and the tail‐bud. While this data was originally queried for global evolutionary and devel... genesis journals http://www.medworm.com/rss/comments.php?id=5266889 Thu, 01 Sep 2011 04:00:00 +0100 5266889 http://www.medworm.com/index.php?rid=5256163&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20810 AbstractOuter hair cells (OHCs) in the cochlea are crucial for the remarkable hearing sensitivity and frequency tuning. To understand OHC physiology and pathology, it is imperative to use mouse genetic tools to manipulate gene expression specifically in OHCs. Here, we generated 2 prestin knockin mouse lines: 1) the prestin‐CreERT2 line, with an internal ribosome entry site (IRES)‐CreERT2‐FRT‐Neo‐FRT cassette inserted into the prestin locus after the stop codon, and 2) the prestin‐CreERT2‐NN line, with the FRT‐Neo‐FRT removed subsequently. We characterized the inducible Cre activity of both lines by crossing them with the reporter lines CAG‐eGFP and Ai6. Cre activity was induced with tamoxifen at various postnatal ages and only detected in OHCs, resembling the endogenous... genesis journals http://www.medworm.com/rss/comments.php?id=5256163 Thu, 01 Sep 2011 04:00:00 +0100 5256163 http://www.medworm.com/index.php?rid=5244761&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20809 AbstractXenopus laevis provides a unique animal model, alternative to mouse, to study immunology. Even though, several methodologies have been developed for the generation of transgenic Xenopus, to date none have been adapted for the Xenopus laevis/gilli (LG) isogenetic clones that are essential for immunological studies. Since LG clones are generated via gynogenesis, transgenic methods using transgene integration into the sperm nuclei are not suited. Therefore, we have tested three alternative methods for LG transgenesis: the phiC31 integrase, the Sleeping Beauty transposase and the I‐SceI meganuclease. All three techniques produced transgenic LG clones; however, the I‐SceI meganuclease was most effective. It resulted in high transgenesis efficiency (35‐50%), bright non‐mosaic GFP... genesis journals http://www.medworm.com/rss/comments.php?id=5244761 Thu, 01 Sep 2011 04:00:00 +0100 5244761 http://www.medworm.com/index.php?rid=5231314&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20806 AbstractAchieving controlled reprogramming of differentiated cells into a desired cell type would open new opportunities in stem cell biology and regenerative medicine. Experimentation on cell reprogramming requires a model in which cell conversion can be induced and tracked individually. The tiny nematode, Caenorhabditis elegans, owing to its known cellular lineage, allows the study of direct cell type conversion with a single‐cell resolution. Indeed, recent advances have shown that despite its invariant cell lineage, cellular identities can be reprogrammed, leading to cell conversion in vivo. In addition, natural transdifferentiation events occur in the worm, providing a powerful model for the study of cellular plasticity in a physiological cellular microenvironment. Here we review pio... genesis journals http://www.medworm.com/rss/comments.php?id=5231314 Thu, 01 Sep 2011 04:00:00 +0100 5231314 http://www.medworm.com/index.php?rid=5216635&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20797 AbstractNo abtract. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5216635 Thu, 01 Sep 2011 04:00:00 +0100 5216635 http://www.medworm.com/index.php?rid=5216634&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20805 AbstractConfocal images of hindbrain neurons in two‐day old wild type (left) and tshz3b mRNA‐injected (right) zebrafish embryos. The two top panels show the GFP‐positive branchiomotor neurons (green) of Tg(isl1:GFP) embryos co‐stained with the zn‐5 antibody against Alcam a (red). The bottom two panels highlight the hindbrain reticulospinal neurons as visualized using the rmo44 α‐Neurofilament‐medium antibody. Overexpression of tshz3b perturbs the normal segmental patterning of these neurons. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5216634 Thu, 01 Sep 2011 04:00:00 +0100 5216634 http://www.medworm.com/index.php?rid=5216628&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20804 (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5216628 Thu, 01 Sep 2011 04:00:00 +0100 5216628 http://www.medworm.com/index.php?rid=5567108&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20794 AbstractSkeletal muscle fibers vary in contractile and metabolic properties. Four main fiber types are present in mammalian trunk and limb muscles; they are called I, IIA, IIX, and IIB, ranging from slowest‐ to fastest‐contracting. Individual muscles contain stereotyped proportions of two or more fiber types. Fiber type is determined by a combination of nerve‐dependent and ‐independent influences, leading to formation of “homogeneous motor units” in which all branches of a single motor neuron form synapses on fibers of a single type. Fiber type composition of muscles can be altered in adulthood by multiple factors including exercise, denervation, hormones, and aging. To facilitate analysis of muscle development, plasticity, and innervation, we generated transgenic mouse lines i... genesis journals http://www.medworm.com/rss/comments.php?id=5567108 Fri, 26 Aug 2011 04:00:00 +0100 5567108 http://www.medworm.com/index.php?rid=5167589&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20791 AbstractBased on deletion and complementation mapping and DNA sequencing, a new recessive fully penetrant mutation (DNApol‐εpl10R), causing prolonged larval life and larval/early pupal lethality, is identified as the first mutant allele of the DNApol‐ε(CG6768) gene of Drosophila melanogaster. A same‐sense base pair substitution in exon 1 of the DNApol‐ε gene is associated with retention of the first intron and significant reduction in DNApol‐ε transcripts in DNApol‐εpl10R homozygotes. Homozygous mutant larvae show small imaginal discs with fewer cells and reduced polyteny in salivary glands, presumably because of the compromised DNA polymerase function following exhaustion of the maternal contribution. Extremely small and rare DNApol‐εpl10R homozygous somatic clones in ... genesis journals http://www.medworm.com/rss/comments.php?id=5167589 Thu, 25 Aug 2011 23:00:00 +0100 5167589 http://www.medworm.com/index.php?rid=5167588&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20792 AbstractEach mammalian female cell transcriptionally inactivates one X chromosome to balance X‐linked gene dosage between males and females. This phenomenon, called X chromosome inactivation, is a perfect epigenetic event, in which two chromosomes with identical DNA sequences are solely distinguished by epigenetic modifications. In this case, epigenetic marks, such as histone modifications, histone variants, DNA methylation, and ncRNAs, are all enriched on one chromosome, the inactive X chromosome (Xi), to establish its chromosome‐wide gene silencing. At face value, it seems that the gene silencing mechanism of Xi is well understood. However, the “silence” of Xi in somatic cells is so tightly maintained that it remains largely intact even after almost all known epigenetic modificat... genesis journals http://www.medworm.com/rss/comments.php?id=5167588 Thu, 25 Aug 2011 23:00:00 +0100 5167588 http://www.medworm.com/index.php?rid=5167587&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20793 AbstractThe hypothalamic mammillary region is critical for spatial memory and vestibular processing. Pitx2 encodes a paired‐like transcription factor that is highly expressed in the developing mammillary region and is required for subthalamic nucleus formation. Here we analyzed a loss of function Pitx2‐TaulacZ knock‐in allele to study the effects of Pitx2 deficiency on neuronal projections in the embryonic mammillary region. Pitx2‐expressing neurons contribute axons to principal mammillary, mammillotegmental and mammillotectal tracts. Embryos with Pitx2 deficiency exhibit axonal fibers in the principal mammillary tract that are improperly bundled and disorganized, yet project caudally toward the tectum and tegmentum. Embryos with Nestin‐Cre mediated conditional Pitx2 deficiency e... genesis journals http://www.medworm.com/rss/comments.php?id=5167587 Thu, 25 Aug 2011 23:00:00 +0100 5167587 http://www.medworm.com/index.php?rid=5167586&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20794 AbstractSkeletal muscle fibers vary in contractile and metabolic properties. Four main fiber types are present in mammalian trunk and limb muscles; they are called I, IIA, IIX and IIB, ranging from slowest‐ to fastest‐contracting. Individual muscles contain stereotyped proportions of two or more fiber types. Fiber type is determined by a combination of nerve‐dependent and –independent influences, leading to formation of “homogeneous motor units” in which all branches of a single motor neuron form synapses on fibers of a single type. Fiber type composition of muscles can be altered in adulthood by multiple factors including exercise, denervation, hormones and aging. To facilitate analysis of muscle development, plasticity and innervation, we generated transgenic mouse lines in w... genesis journals http://www.medworm.com/rss/comments.php?id=5167586 Thu, 25 Aug 2011 23:00:00 +0100 5167586 http://www.medworm.com/index.php?rid=5189779&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20798 AbstractThe Notch1 receptor plays a critical role in cell fate decisions during development. Activation of Notch signaling has been implicated in several types of cancer, particularly T‐cell acute lymphoblastic leukemia (T‐ALL). Consequently, several transgenic mouse strains have been made to study the role of Notch1 in T‐ALL. However, the existing Notch1 transgenic lines mimic a translocation event found in only ˜1% of T‐ALL cases. Here we describe three novel NOTCH1 transgenic mouse strains that have Cre‐inducible expression of the entire human NOTCH1 locus, each possessing a common mutation found in T‐ALL. Unlike existing Notch1 transgenic strains, these NOTCH1 transgenic strains express full‐length receptors from an endogenous human promoter that should be susceptible to... genesis journals http://www.medworm.com/rss/comments.php?id=5189779 Sun, 31 Jul 2011 23:00:00 +0100 5189779 http://www.medworm.com/index.php?rid=5178660&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20789 AbstractThe Transforming Growth Factor beta (TGFβ) pathway is involved in embryonic development and several inherited and acquired human diseases. The gene for TGFβ3 (Tgfb3) encodes one of the 3 ligands for TGFβ receptors. It is widely expressed in the embryo and its mutation or misexpression is found in human diseases. Tgfb3−/− mice die at birth from cleft palate, precluding functional studies in adults. Here, we generated mice in which exon 6 of Tgfb3 was flanked with LoxP sites (Tgfb3flox/flox). The mice were normal and fertile. EIIa‐Cre‐mediated deletion of exon 6 in Tgfb3flox/flox mice efficiently generated Tgfb3 conditional knockout (Tgfb3cko/cko) mice which died at birth from the same cleft palate defect as Tgfb3−/− mice, indicating that the conditional and knockout a... genesis journals http://www.medworm.com/rss/comments.php?id=5178660 Sun, 31 Jul 2011 23:00:00 +0100 5178660 http://www.medworm.com/index.php?rid=5167585&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20795 AbstractA key question about the development of multicellular organisms is how they precisely control the complex pattern formation during their growth. For plants to grow for many years, a tight balance between pluripotent dividing cells and cells undergoing differentiation should be maintained within stem cell populations. In this process, cell‐cell communication plays a central role by creating positional information for proper cell type patterning. Cell‐type specific gene regulatory networks govern differentiation of cells into particular cell types. In this review, we will provide a comprehensive overview of emerging key signaling and regulatory programs in the stem cell population that direct morphogenesis of plant vascular tissues. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5167585 Sun, 31 Jul 2011 23:00:00 +0100 5167585 http://www.medworm.com/index.php?rid=5115631&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20788 (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5115631 Sun, 31 Jul 2011 23:00:00 +0100 5115631 http://www.medworm.com/index.php?rid=5115630&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20790 AbstractA montage of images from the 29th annual Molecular Embryology of the Mouse course, which took place at Cold Spring Harbor June 8th – 28th 2011. The montage was put together by, and features the work of, the students on the course. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5115630 Sun, 31 Jul 2011 23:00:00 +0100 5115630 http://www.medworm.com/index.php?rid=5084510&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20786 AbstractThe role of hedgehog (HH) signaling in reproductive tract development was studied in mice in which a dominant active allele of the signal transducer smoothened (SmoM2) was conditionally expressed in the Müllerian duct and ovary. Mutant females are infertile, primarily because they fail to ovulate. Levels of mRNA for targets of HH signaling, Gli1, Ptch1 and Hhip, were elevated in reproductive tracts of 24‐day old mutant mice, confirming over‐activation of HH signaling. The tracts of mutant mice developed abnormally. The uterine luminal epithelium had a simple columnar morphology in control mice, but in mutants contained stratified squamous cells typical of the cervix and vagina. In mutant mice, the number of uterine glands were reduced and the oviducts were not coiled. Expressi... genesis journals http://www.medworm.com/rss/comments.php?id=5084510 Sun, 31 Jul 2011 23:00:00 +0100 5084510 http://www.medworm.com/index.php?rid=5004701&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20783 We report that src64 is maternally expressed in the Drosophila embryo and acts primarily as a maternal gene during cellularization. However, we show that src64 has some zygotic activity during late cellularization. By using compound chromosomes to generate embryos with wild‐type levels of maternal src64 activity, we show that this zygotic activity is normally nonessential. We also report the identification of an alternate src64 transcript. Expression of this transcript is not affected by the src64Δ17 deletion mutation, explaining the presence of low levels of src64 activity observed in src64Δ17 mutants. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5004701 Tue, 05 Jul 2011 23:00:00 +0100 5004701 http://www.medworm.com/index.php?rid=5004700&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20784 AbstractCell‐cell signaling and adhesion are critical for establishing tissue architecture during development and for maintaining tissue architecture and function in the adult. Defects in adhesion and signaling can result in mislocalization of cells, uncontrolled proliferation and improper differentiation, leading to tissue overgrowth, tumor formation and cancer metastasis. An important example is found in the germline. Germ cells that are not incorporated into the gonad exhibit a greater propensity for forming germ cell tumors, and defects in germline development can reduce fertility. While much attention is given to germ cells, their development into functional gametes depends upon somatic gonadal cells. The study of model organisms has provided great insights into how somatic gonadal ... genesis journals http://www.medworm.com/rss/comments.php?id=5004700 Tue, 05 Jul 2011 23:00:00 +0100 5004700 http://www.medworm.com/index.php?rid=5084509&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20787 AbstractEater is a transmembrane protein that mediates phagocytosis in Drosophila. eater was identified in a microarray analysis of genes down‐regulated in S2 cells, in which Serpent had been knocked down by RNAi. The gene was shown to be expressed predominantly in plasmatocytes after embryonic development. We have extensively analyzed the transcriptional enhancer controlling eater expression with the following findings: the enhancer reproduces the plasmatocyte expression pattern of the gene as verified by anti‐P1 antibody staining and a 526‐basepair DNA region is active in lymph gland and hemolymph plasmatocytes. This DNA contains several GATA elements that serve as putative binding sites for Serpent. Site‐directed mutagenesis of two of these GATA sites abolishes eater expression ... genesis journals http://www.medworm.com/rss/comments.php?id=5084509 Thu, 30 Jun 2011 23:00:00 +0100 5084509 http://www.medworm.com/index.php?rid=5004703&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20776 (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=5004703 Thu, 30 Jun 2011 23:00:00 +0100 5004703 http://www.medworm.com/index.php?rid=5004699&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20785 AbstractGenetic studies have shown that ephrin‐B2 and its cognate EphB4 receptor are necessary for normal embryonic angiogenesis. Moreover, there is overwhelming evidence that ephrin‐B2 is involved in tumor vascularization, yet its role in adult angiogenesis has been difficult to track genetically. Here we report the generation of transgenic mice that over‐express EfnB2 specifically in endothelial cells (ECs). We show that exogenous expression of EfnB2 under the control of the Tie2 promoter/enhancer regions in ECs does not affect viability or growth of the transgenic animals. We further show that targeted expression of EfnB2 in ECs is not sufficient to rescue severe cardiovascular defects at mid‐gestation stages but rescues early embryonic lethality associated with loss‐of‐func... genesis journals http://www.medworm.com/rss/comments.php?id=5004699 Thu, 30 Jun 2011 23:00:00 +0100 5004699 http://www.medworm.com/index.php?rid=5153437&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20780 AbstractThe ovaries of early embryos (40 days post coitum/p.c.) of the bat Carollia perspicillata contain numerous germ‐line cysts, which are composed of 10 to 12 sister germ cells (cystocytes). Variability in the number of cystocytes within the cyst and between the cysts (defying the Giardina rule) indicates that the mitotic divisions of the cystoblast are asynchronous in this bat species. Serial section analysis showed that the cystocytes are interconnected via intercellular bridges that are atypical, strongly elongated, short‐lived, and rich in microtubule bundles and microfilaments. During slightly later stages of embryonic development (44–46 days p.c.), somatic cells penetrate the cyst, and their cytoplasmic projections separate individual oocytes. Separated oocytes surrounded b... genesis journals http://www.medworm.com/rss/comments.php?id=5153437 Wed, 15 Jun 2011 23:00:00 +0100 5153437 http://www.medworm.com/index.php?rid=4918971&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20777 AbstractLarge‐scale functional genomics in mice is becoming feasible through projects to develop conditional knockout alleles for every gene. Inducible neuron‐specific gene knockout in such mice will permit the analysis of neuronal phenotypes while circumventing developmental defects or embryonic lethality. Here we describe a transgenic line, termed SLICK‐H, that facilitates widespread inducible conditional genetic manipulation within most populations of projection neurons. In SLICK‐H mice, the Thy1 promoter drives robust and relatively uniform expression of a drug‐inducible form of cre recombinase throughout the peripheral and central nervous system. This permits efficient induction of cre‐mediated genetic manipulation upon tamoxifen administration in adult mice. Importantly, ... genesis journals http://www.medworm.com/rss/comments.php?id=4918971 Thu, 09 Jun 2011 23:00:00 +0100 4918971 http://www.medworm.com/index.php?rid=4950550&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20774 AbstractImages of multiply labeled fluorescent samples provide unique insights into the localization of molecules, cells, and tissues. The ability to image multiple channels simultaneously at high speed without cross talk is limited to a few colors and requires dedicated multichannel or multispectral detection procedures. Simpler microscopes, in which each color is imaged sequentially, produce a much lower frame rate. Here, we describe a technique to image, at high frame rate, multiply labeled samples that have a repeating motion. We capture images in a single channel at a time over one full occurrence of the motion then repeat acquisition for other channels over subsequent occurrences. We finally build a high‐speed multichannel image sequence by combining the images after applying a nor... genesis journals http://www.medworm.com/rss/comments.php?id=4950550 Wed, 01 Jun 2011 23:00:00 +0100 4950550 http://www.medworm.com/index.php?rid=4973929&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20781 AbstractIn flies, the zinc‐finger protein Teashirt promotes trunk segmental identities, in part, by repressing the expression and function of anterior hox paralog group (PG) 1‐4 genes that specify head fates. Anterior‐posterior patterning of the vertebrate hindbrain also requires Hox PG 1‐4 function, but the role of vertebrate teashirt‐related genes in this process has not been investigated. In this work, we use overexpression and structure‐function analyses to show that zebrafish tshz3b antagonizes Hox‐dependent hindbrain segmentation. Ectopic Tshz3b perturbs the specification of rhombomere identities and leads to the caudal expansion of r1, the only rhombomere whose identity is specified independently of Hox function. This overexpression phenotype does not require the homeo... genesis journals http://www.medworm.com/rss/comments.php?id=4973929 Tue, 31 May 2011 23:00:00 +0100 4973929 http://www.medworm.com/index.php?rid=4943408&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20780 AbstractThe ovaries of early embryos (40 days after fertilization) of the bat Carollia perspicillata contain numerous germ‐line cysts, which are composed of 10 to 12 sister germ cells (cystocytes). The variability in the number of cystocytes within the cyst and between the cysts (that defies the Giardina rule) indicates that the mitotic divisions of the cystoblast are asynchronous in this bat species. The serial section analysis showed that the cystocytes are interconnected via intercellular bridges that are atypical, strongly elongated, short‐lived, and rich in microtubule bundles and microfilaments. During the later stages of embryonic development (44‐46 days after fertilization), the somatic cells penetrate the cyst, and their cytoplasmic projections separate individual oocytes. S... genesis journals http://www.medworm.com/rss/comments.php?id=4943408 Tue, 31 May 2011 23:00:00 +0100 4943408 http://www.medworm.com/index.php?rid=4918973&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20775 (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4918973 Tue, 31 May 2011 23:00:00 +0100 4918973 http://www.medworm.com/index.php?rid=4918972&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20779 AbstractTwo puppies, carrying an inducible eGFP transgene, delivered from the Tet‐on eGFP mother reported in Kim et al in this issue. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4918972 Tue, 31 May 2011 23:00:00 +0100 4918972 http://www.medworm.com/index.php?rid=4918970&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20778 AbstractBone Morphogenetic Proteins (BMPs) perform a variety of functions during development. Considering a single BMP, what enables its multiple roles in tissues of varied sizes and shapes? What regulates the spatial distribution and activity patterns of the BMP in these different developmental contexts? Some BMP functions require controlling spread of the BMP morphogen, while others require formation of localized, high concentration peaks of BMP activity. Here we review work in Drosophila that describes spatial regulation of the BMP encoded by decapentaplegic (dpp) in different developmental contexts. We concentrate on extracellular modulation of BMP function and discuss the mechanisms that generate concentrated peaks of Dpp activity, subdivide territories of different activity levels or... genesis journals http://www.medworm.com/rss/comments.php?id=4918970 Tue, 31 May 2011 23:00:00 +0100 4918970 http://www.medworm.com/index.php?rid=4890313&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20773 AbstractWe generated transgenic mice bearing a tamoxifen‐dependent Cre recombinase expressed under the control of the dopamine‐β‐hydroxylase promoter. By crossing to the ROSA26 reporter mice we show that tamoxifen‐induced Cre recombinase in adult mice specifically activates β‐galactosidase expression in differentiated noradrenergic neurons of the central and peripheral nervous system. Tamoxifen application in adult mice did not induce β‐galactosidase activity in parasympathetic neurons that transiently express DBH during development. Thus, this transgenic mouse line represents a valuable tool to study gene function in mature noradrenergic neurons by conditional inactivation. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4890313 Tue, 31 May 2011 23:00:00 +0100 4890313 http://www.medworm.com/index.php?rid=4793488&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20767 AbstractA number of heat shock proteins (HSPs), including Hsp70 and Hsp110, function as molecular chaperones within intestinal epithelial cells that line the mammalian digestive system. HSPs confer cellular protection against environmental stress induced by chemical toxins or pathogens. There is interest in how members of this protein family might influence the progression of inflammatory bowel disease. Using the zebrafish model system, we report the expression of the duplicated hspa4 genes within the intestinal epithelium. The hspa4 genes belong to the Hsp110 family. We show that under inflammatory stress conditions within the gut, expression of these genes is up‐regulated in a similar manner to that previously observed for mammalian Hsp70. Because of the amenability of the zebrafish to... genesis journals http://www.medworm.com/rss/comments.php?id=4793488 Thu, 05 May 2011 23:00:00 +0100 4793488 http://www.medworm.com/index.php?rid=4774381&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20761 AbstractInitiation of BMP signaling is dependent upon activation of type I BMP receptor by constitutively active type II BMP receptor. Three type II BMP receptors have been identified; Acvr2a and Acvr2b serve as receptors for BMPs and for activin‐like ligands while BMPR‐II functions only as a BMP receptor. As BMP signaling is required for endochondral ossification and loss of either Acvr2a or Acvr2b is not associated with deficits in limb development, we hypothesized that BMPR‐II would be essential for BMP signaling during skeletogenesis. We removed BMPR‐II from early limb mesoderm by crossing BMPR‐II floxed mice with those carrying the Prx1‐Cre transgene. Mice lacking limb expression of BMPR‐II have normal skeletons that could not be distinguished from control littermates. F... genesis journals http://www.medworm.com/rss/comments.php?id=4774381 Sun, 01 May 2011 23:00:00 +0100 4774381 http://www.medworm.com/index.php?rid=4890319&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20771 AbstractThe fluorescent marking of immature (blue) and hypertrophic (red) chondrocytes in an E17.5 mouse embryo by the Collagen, type II, alpha 1 promoter driving the expression of enhanced cyan fluorescent protein (blue) and the Collagen, type X, alpha 1 BAC driving the expression of mCherry fluorescent protein (red), respectively. See the article by Maye et al. in this issue. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4890319 Sat, 30 Apr 2011 23:00:00 +0100 4890319 http://www.medworm.com/index.php?rid=4890312&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20774 AbstractImages of multiply‐labeled fluorescent samples provide unique insights into the localization of molecules, cells, and tissues. The ability to image multiple channels simultaneously at high speed without cross talk is limited to a few colors and requires dedicated multi‐channel or multi‐spectral detection procedures. Simpler microscopes, in which each color is imaged sequentially, produce a much lower frame rate. Here, we describe a technique to image, at high frame rate, multiply‐labeled samples that have a repeating motion. We capture images in a single channel at a time over one full occurrence of the motion then repeat acquisition for other channels over subsequent occurrences. We finally build a high‐speed multi‐channel image sequence by combining the images after a... genesis journals http://www.medworm.com/rss/comments.php?id=4890312 Sat, 30 Apr 2011 23:00:00 +0100 4890312 http://www.medworm.com/index.php?rid=4882198&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20772 In conclusion, transgenic RFP female dogs exhibited normal reproductive ability and expression of the transgene was demonstrated in F1 and F2 generations. Am. J. Hematol., 2011. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4882198 Sat, 30 Apr 2011 23:00:00 +0100 4882198 http://www.medworm.com/index.php?rid=4838150&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20770 (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4838150 Sat, 30 Apr 2011 23:00:00 +0100 4838150 http://www.medworm.com/index.php?rid=4826978&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20725 In this study, we addressed this issue and we report on the generation of a MART‐1::Cre BAC transgenic mouse line, in which the expression of Cre recombinase is controlled by regulatory elements of the pigment cell‐specific gene MART‐1 (mlana). When MART‐1::Cre BAC transgenic mice were bred with the ROSA26‐R reporter line, ß‐galactosidase expression was observed in RPE from E12.5 onwards, and in melanocyte precursors from E17.5, indicating that the MART‐1::Cre line provides Cre recombinase activity in pigment‐producing cells rather than in a particular lineage. In addition, breeding of this mouse line to mice carrying a conditional allele of RBP‐Jκ corroborated the reported phenotypes in both pigment cell lineages, inducing hair greying and microphthalmia. Our results t... genesis journals http://www.medworm.com/rss/comments.php?id=4826978 Sat, 30 Apr 2011 23:00:00 +0100 4826978 http://www.medworm.com/index.php?rid=5153436&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20763 AbstractDuring the early stages of body axis extension, retinoic acid (RA) synthesized in somites by Raldh2 represses caudal fibroblast growth factor (FGF) signaling to limit the tailbud progenitor zone. Excessive RA down‐regulates Fgf8 and triggers premature termination of body axis extension, suggesting that endogenous RA may function in normal termination of body axis extension. Here, we demonstrate that Raldh2−/− mouse embryos undergo normal down‐regulation of tailbud Fgf8 expression and termination of body axis extension in the absence of RA. Interestingly, Raldh2 expression in wild‐type tail somites and tailbud from E10.5 onwards does not result in RA activity monitored by retinoic acid response element (RARE)‐lacZ. Treatment of wild‐type tailbuds with physiological lev... genesis journals http://www.medworm.com/rss/comments.php?id=5153436 Thu, 28 Apr 2011 23:00:00 +0100 5153436 http://www.medworm.com/index.php?rid=4766948&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20763 AbstractDuring the early stages of body axis extension, retinoic acid (RA) synthesized in somites by Raldh2 represses caudal FGF signaling to limit the tailbud progenitor zone. Excessive RA down‐regulates Fgf8 and triggers premature termination of body axis extension, suggesting that endogenous RA may function in normal termination of body axis extension. Here, we demonstrate that Raldh2‐/‐ mouse embryos undergo normal down‐regulation of tailbud Fgf8 expression and termination of body axis extension. Interestingly, Raldh2 expression in tail somites and tailbud from E10.5 onwards does not result in RA activity monitored by RARE‐lacZ. Treatment of tailbuds with physiological levels of RA or retinaldehyde induces RARE‐lacZ activity, validating the sensitivity of RARE‐lacZ and de... genesis journals http://www.medworm.com/rss/comments.php?id=4766948 Thu, 28 Apr 2011 23:00:00 +0100 4766948 http://www.medworm.com/index.php?rid=4766947&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20764 AbstractProximal spinal muscular atrophy (SMA) is caused by low levels of the SMN protein, encoded by the Survival Motor Neuron genes (SMN1 and SMN2). Mouse models of SMA can be rescued by increased SMN expression, but the timing of SMN replacement for complete rescue is unknown. Studies in zebrafish predict restoration of SMN function during embryogenesis may be important for axonal pathfinding, while the mouse models and normal human disease progression suggest that post‐natal treatment may be sufficient for amelioration of disease. To evaluate the timing for SMN replacement we have generated a stably integrated Cre‐inducible SMN mouse in which expression of full length SMN2 occurs after tamoxifen administration. Our temporally inducible SMN transgene is able to express SMN in embryo... genesis journals http://www.medworm.com/rss/comments.php?id=4766947 Thu, 28 Apr 2011 23:00:00 +0100 4766947 http://www.medworm.com/index.php?rid=4766946&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20765 AbstractThe hippocampus is crucial for higher brain functions, such as learning, memory and emotion. Many diseases like epilepsy and Down's syndrome are associated with abnormalities in early hippocampal development. Additionally, adult dentate neurogenesis is thought to be defective in several classes of psychiatric disorders. However, the mechanisms regulating hippocampal development and adult neurogenesis remain unclear. One of the limitations to studying these processes is the scarcity of available specific mouse tools. Here, we report an inducible transgenic Cre mouse line, Frizzled 9‐CreER™, in which tamoxifen administration induces Cre recombinant. Our data show that Cre is expressed in the developing hippocampal primordium, confined to the granule cell layer at P20 and further ... genesis journals http://www.medworm.com/rss/comments.php?id=4766946 Thu, 28 Apr 2011 23:00:00 +0100 4766946 http://www.medworm.com/index.php?rid=5153435&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20759 AbstractInducible Cre recombination is a powerful technology that allows for spatial and temporal modulation of gene expression in vivo. Diseases of the cardiac conduction system (CCS) pose a significant clinical burden but are not currently well understood at the molecular level. To enable inducible recombination in the murine CCS, we created a minK:CreERT2 bacterial artificial chromosome (BAC) transgenic mouse line. Cre activity is present after tamoxifen administration in the atrioventricular (AV) node, AV bundle, and bundle branches of adult transgenic mice. We anticipate that by enabling inducible recombination specifically in the AV node, bundle, and bundle branches, minK:CreERT2 BAC transgenic mice will prove useful in advancing our understanding of CCS disease and function. genesis... genesis journals http://www.medworm.com/rss/comments.php?id=5153435 Sun, 17 Apr 2011 23:00:00 +0100 5153435 http://www.medworm.com/index.php?rid=4730839&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20748 AbstractTo facilitate dynamic imaging of neural crest (NC) lineages and discrimination of individual cells in the enteric nervous system (ENS) where close juxtaposition often complicates viewing, we generated a mouse BAC transgenic line that drives a Histone2BVenus (H2BVenus) reporter from Sox10 regulatory regions. This strategy does not alter the endogenous Sox10 locus and thus facilitates analysis of normal NC development. Our Sox10‐H2BVenus BAC transgene exhibits temporal, spatial, and cell‐type specific expression that reflects endogenous Sox10 patterns. Individual cells exhibiting nuclear‐localized fluorescence of the H2BVenus reporter are readily visualized in both fixed and living tissue and are amenable to isolation by fluorescence activated cell sorting (FACS). FACS‐isolat... genesis journals http://www.medworm.com/rss/comments.php?id=4730839 Sun, 17 Apr 2011 23:00:00 +0100 4730839 http://www.medworm.com/index.php?rid=4730838&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20756 AbstractPostovulatory mammalian oocytes age significantly in culture. B6D2F1 or ICR strain mouse oocytes were collected 16 h after hCG injection and then cultured for up to 40 h post hCG at 37 °C under 5% CO2 in air. After intracytoplasmic sperm injection (ICSI), B6D2F1 and ICR oocytes lost full‐term developmental potential by 30 h and 26 h after hCG administration, respectively. However, using supplementation with 10 mM caffeine or 1–5 μM of MG132, we could obtain live offspring from oocytes at 34 h (BDF1, 5–21%) or 28 h (ICR, 5–18%), whereas none were obtained from untreated aged oocytes. Caffeine maintained normal meiotic spindle morphology, whereas MG132 maintained maturation‐promoting factor activity. These treatments did not affect the potential of fresh oocytes for ferti... genesis journals http://www.medworm.com/rss/comments.php?id=4730838 Sun, 17 Apr 2011 23:00:00 +0100 4730838 http://www.medworm.com/index.php?rid=4730837&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20757 AbstractThe Bmp2 3'untranslated region (UTR) sequence bears a sequence conserved between mammals and fishes that can post‐transcriptionally activate or repress protein synthesis. We developed a map of embryonic cells in the mouse where this potent Bmp2 regulatory sequence functions by using a lacZ reporter transgene with a 3′UTR bearing two loxP sites flanking the ultra‐conserved sequence. Cre‐recombinase‐mediated deletion of the ultra‐conserved sequence caused strong ectopic expression in proepicardium, epicardium and epicardium‐derived cells (EPDC) and in tissues with known epicardial contributions (coronary vessels and valves). Transient transfections of reporters in the epicardial/mesothelial cell (EMC) line confirmed this repression. Ectopic expression of the recombined ... genesis journals http://www.medworm.com/rss/comments.php?id=4730837 Sun, 17 Apr 2011 23:00:00 +0100 4730837 http://www.medworm.com/index.php?rid=4730836&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20758 AbstractLive‐imaging is an essential tool to visualize live cells and monitor their behaviors during development. This technology demands a variety of mouse reporter lines, each uniquely expressing a fluorescent protein. Here, we developed an R26R‐RG reporter mouse line that conditionally and simultaneously expresses mCherry and EGFP in nuclei and plasma membranes, respectively, from the Rosa26 locus. The intensity and resolution of mCherry nuclear localization and EGFP membrane localization were demonstrated to be sufficient for live‐imaging with embryos that express RG (mCherry and EGFP) ubiquitously and specifically in fetal Sertoli cells. The conditional R26R‐RG reporter mouse line should be a useful tool for labeling nuclei and membranes simultaneously in distinct cell populat... genesis journals http://www.medworm.com/rss/comments.php?id=4730836 Sun, 17 Apr 2011 23:00:00 +0100 4730836 http://www.medworm.com/index.php?rid=4730835&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20759 AbstractInducible Cre recombination is a powerful technology that allows for spatial and temporal modulation of gene expression in vivo. Diseases of the cardiac conduction system (CCS) pose a significant clinical burden but are not currently well understood at the molecular level. To enable inducible recombination in the murine cardiac conduction system (CCS), we created a minK:CreERT2 bacterial artificial chromosome (BAC) transgenic mouse line. Cre activity is present after tamoxifen administration in the atrioventricular (AV) node, AV bundle, and bundle branches of adult transgenic mice. We anticipate that by enabling inducible recombination specifically in the AV node, bundle, and bundle branches, minK:CreERT2 BAC transgenic mice will prove useful in advancing our understanding of CCS d... genesis journals http://www.medworm.com/rss/comments.php?id=4730835 Sun, 17 Apr 2011 23:00:00 +0100 4730835 http://www.medworm.com/index.php?rid=4801108&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20769 AbstractWith the intention to modulate gene expression in vascular mural cells of remodeling vessels, we generated and characterized transgenic mouse lines with Cre recombinase under the control of the platelet‐derived growth factor receptor‐ß promoter, referred to as Tg(Pdgfrb‐Cre)35Vli. Transgenic mice were crossed with the Gt(ROSA)26Sortm1Sor strain and examined for Cre activation by ß‐galactosidase activity, which was compared with endogenous Pdgfrb expression. In addition, Pdgfrb‐Cre mice were used to drive expression of a conditional myc‐tagged Cthrc1 transgene. There was good overlap of ß‐galactosidase activity with endogenous Pdgfrb immunoreactivity. However, dedifferentiation of vascular mural cells induced by carotid artery ligation revealed a dramatic discrepanc... genesis journals http://www.medworm.com/rss/comments.php?id=4801108 Thu, 31 Mar 2011 23:00:00 +0100 4801108 http://www.medworm.com/index.php?rid=4793487&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20768 AbstractMuch is known regarding the role of Indian hedgehog (Ihh) in endochondral ossification, where Ihh regulates multiple steps of chondrocyte differentiation. The Ihh−/− phenotype is most notable for severely foreshortened limbs and a complete absence of mature osteoblasts. A far less explored phenotype in the Ihh−/− mutant is found in the calvaria, where bones form predominately through intramembranous ossification. We investigated the role of Ihh in calvarial bone ossification, finding that proliferation was largely unaffected. Instead, our results indicate that Ihh is a pro‐osteogenic factor that positively regulates intramembranous ossification. We confirmed through histologic and quantitative gene analysis that loss of Ihh results in reduction of cranial bone size and al... genesis journals http://www.medworm.com/rss/comments.php?id=4793487 Thu, 31 Mar 2011 23:00:00 +0100 4793487 http://www.medworm.com/index.php?rid=4774380&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20762 AbstractEpigenetics is defined as the study of heritable changes in gene expression that are not accompanied by changes in the DNA sequence. Epigenetic mechanisms include histone post‐translational modifications, histone variant incorporation, non‐coding RNAs, and nucleosome remodeling and exchange. In addition, the functional compartmentalization of the nucleus also contributes to epigenetic regulation of gene expression.Studies on the molecular mechanisms underlying epigenetic phenomena and their biological function have relied on various model systems, including yeast, plants, flies and cultured mammalian cells. Here we will expose the reader to the current understanding of epigenetic regulation in the roundworm C. elegans. We will review recent models of nuclear organization and it... genesis journals http://www.medworm.com/rss/comments.php?id=4774380 Thu, 31 Mar 2011 23:00:00 +0100 4774380 http://www.medworm.com/index.php?rid=4766945&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20766 This study characterized a 125‐bp mnx1 enhancer to direct gene expression in spinal cord motor neurons. A promoter containing three copies of the 125‐bp mnx1 enhancer was generated in a Tol2 vector and used to drive EGFP expression either directly or in combination with the Gal4/UAS transcriptional activation system. Both methods induced protein expression for up to five days after fertilization, allowing the observation of the dendritic tree and axonal arborization of single motor neurons within a somitic segment in fixed and live animals. The use of the 125‐bp mnx1 promoter for transient transgenic expression or for the generation of stable transgenic fish lines will facilitate the study of motor neuron development and neurodegenerative processes. © 2011 Wiley‐Liss, Inc. (Source... genesis journals http://www.medworm.com/rss/comments.php?id=4766945 Thu, 31 Mar 2011 23:00:00 +0100 4766945 http://www.medworm.com/index.php?rid=4740603&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20754 We describe the development of transgenic quail that express various fluorescent proteins in targeted manners and their use as a model system that integrates advanced imaging approaches with conventional and emerging molecular genetics technologies. We also review the progression and complications of past fate mapping techniques that led us to generate transgenic quail which permit dynamic imaging of amniote embryogenesis with unprecedented sub‐cellular resolution. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4740603 Thu, 31 Mar 2011 23:00:00 +0100 4740603 http://www.medworm.com/index.php?rid=4730834&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20760 Abstractin vivo study of embryonic morphogenesis tremendously benefits from recent advances in live microscopy and computer analyses. Quantitative and automated investigation of morphogenetic processes opens the field to high‐content and high‐throughput strategies. Following experimental workflow currently developed in cell biology, we identify the key challenges for applying such strategies in developmental biology. We review the recent progress in embryo preparation and manipulation, live imaging, data registration, image segmentation, feature computation and data mining dedicated to the study of embryonic morphogenesis. We discuss a selection of pioneering studies tackling the current methodological bottlenecks and illustrating the investigation of morphogenetic processes in vivo us... genesis journals http://www.medworm.com/rss/comments.php?id=4730834 Thu, 31 Mar 2011 23:00:00 +0100 4730834 http://www.medworm.com/index.php?rid=4718478&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20752 (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4718478 Thu, 31 Mar 2011 23:00:00 +0100 4718478 http://www.medworm.com/index.php?rid=4718477&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20755 AbstractImages of craniofacial development from frog, fish, chick and mouse embryos, provided by the authors of this special issue. Please read the articles for details. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4718477 Thu, 31 Mar 2011 23:00:00 +0100 4718477 http://www.medworm.com/index.php?rid=5153439&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20750 AbstractTcf21 is a Class II bHLH family member with essential roles in the formation of the lungs, kidneys, gonads, spleen, and heart. Here, we report the utility of a mouse line with targeted insertion of a tamoxifen‐inducible Cre recombinase, MerCreMer at the Tcf21 locus. This mouse line will permit the inducible expression of Cre recombinase in Tcf21‐expressing cells. Using ROSA26 reporter mice, we show that Cre recombinase is specifically and robustly activated in multiple Tcf21‐expressing tissues during embryonic and postnatal development. The expression profile in the kidney is particularly dynamic with the ability to cause recombination in mesangial cells at one time of induction and podocytes at another time. These features make the Tcf21‐driven inducible Cre line (Tcf21iCr... genesis journals http://www.medworm.com/rss/comments.php?id=5153439 Tue, 22 Mar 2011 00:00:00 +0100 5153439 http://www.medworm.com/index.php?rid=4620633&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20749 AbstractPhosphorylation of the alpha (α) subunit of the eukaryotic initiation factor 2 (eIF2) at serine 51 is an important mechanism of translational control in response to various forms of environmental stress. In metazoans, eIF2α phosphorylation is mediated by four kinases each of which become activated by distinct stimuli. Previous work established that expression of a chimera protein comprising of the bacteria Gyrase B N‐terminal (GyrB) domain fused to the kinase domain (KD) of the eIF2α kinase PKR is capable of inducing eIF2α phosphorylation in cultured cells after treatment with the antibiotic coumermycin. Herein, we report the development of transgenic mice expressing the fusion protein GyrB.PKR ubiquitously. Treatment of mice with coumermycin induces eIF2α phosphorylation in... genesis journals http://www.medworm.com/rss/comments.php?id=4620633 Tue, 22 Mar 2011 00:00:00 +0100 4620633 http://www.medworm.com/index.php?rid=5153438&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20746 AbstractThe serotonergic (5‐HT) system modulates many behaviors and has been implicated in psychiatric disorders, but the density of 5‐HT processes has complicated analyses. We have used regulatory regions from the Tryptophan hydroxylase 1 (Tph1) gene to drive expression of LoxP‐flanked placental alkaline phosphatase (PLAP) to generate the Tph1‐Lox‐PLAP reporter mouse line. In these mice, PLAP is expressed in the hindbrain raphe nuclei and in peripheral tissues known to express Tph1. Tph1 is expressed at low levels in neurons. While, in Tph1‐Lox‐PLAP mice, most PLAP‐expressing neurons are monoaminergic, PLAP was expressed in only 5–10% of neurons expressing the predominant neuronal 5‐HT biosynthetic enzyme Tph2, serotonin transporter (SERT) or aromatic amino acid decarb... genesis journals http://www.medworm.com/rss/comments.php?id=5153438 Tue, 15 Mar 2011 00:00:00 +0100 5153438 http://www.medworm.com/index.php?rid=4589148&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20745 AbstractFragile X syndrome (FXS) is the most common form of inherited mental retardation and is caused by the loss of function for Fragile X Mental Retardation Protein (FMRP), a selective RNA‐binding protein with a demonstrated role in the localized translation of target mRNAs at synapses. Several recent studies provide compelling evidence for a new role of FMRP in the development of the nervous system, during neurogenesis. Using a multi‐faceted approach and a variety of model systems ranging from cultured neurospheres and progenitor cells to in vivo Drosophila and mouse models these reports indicate that FMRP is required for neural stem and progenitor cell proliferation, differentiation, survival as well as regulation of gene expression. Here we compare and contrast these recent repor... genesis journals http://www.medworm.com/rss/comments.php?id=4589148 Mon, 14 Mar 2011 00:00:00 +0100 4589148 http://www.medworm.com/index.php?rid=4558359&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20743 AbstractLyl1 codes for a bHLH protein that is an important regulator of hematopoietic stem cell function. An existing mutant allele of Lyl1 features a lacZ gene inserted in‐frame into the fourth exon, leaving behind the N‐terminus and the DNA‐binding basic region, resulting in a translated chimeric protein. Here, we have generated a null allele, which allowed us to examine residual function of the N‐terminus in the absence of a bHLH region. The new Lyl1‐/‐ mouse model exhibited a reduced ability to generate lymphoid lineages and a somewhat more severe hematopoietic repopulation defect when transplanting purified hematopoietic stem cells. Our data show that in the absence of the HLH but presence of the N‐terminus, residual function of the Lyl1 is detectable but relatively mino... genesis journals http://www.medworm.com/rss/comments.php?id=4558359 Tue, 08 Mar 2011 00:00:00 +0100 4558359 http://www.medworm.com/index.php?rid=4675243&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20742 (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4675243 Tue, 01 Mar 2011 00:00:00 +0100 4675243 http://www.medworm.com/index.php?rid=4651059&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20753 AbstractA series of conditional reporter mouse lines were established in which specific organelles were labeled with fluorescent proteins. Subcellular localization and intensity of twenty‐eight fluorescent fusion‐protein constructs were surveyed in cell lines, and sixteen constructs then were selected to generate mouse lines. The fusion cDNAs were inserted into the ROSA26 genomic locus next to the stop sequences flanked with loxP so that fluorescent proteins were expressed under the ubiquitous ROSA26 transcriptional machinery when the loxP sequences were recombined with Cre. The subcellular localization and intensity of the fusion product in each reporter mouse line were examined by ubiquitously expressing them in E7.5 embryos. Twelve reporter lines, that mark nucleus, mitochondria, Go... genesis journals http://www.medworm.com/rss/comments.php?id=4651059 Tue, 01 Mar 2011 00:00:00 +0100 4651059 http://www.medworm.com/index.php?rid=4635252&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20751 AbstractSection through the intestine of a P3 (postnatal day 3) Afp::mCherry; Afp::GFP double transgenic mouse. Red and green fluorescent reporter‐expressing cells are located in the endoderm layer along villi, but excluded from the crypt stem cell zone. See the article by Viotti at al. in this issue. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4635252 Tue, 01 Mar 2011 00:00:00 +0100 4635252 http://www.medworm.com/index.php?rid=4620634&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20689 In this study, we investigated the extent that fully modified 2′‐O‐methyl oligonucleotides (2′‐OMe oligos) that can function as translation inhibiting reagents in vivo, using Xenopus and zebrafish embryos. We find that oligos against Xenopus β‐catenin, wnt11, and bmp4 and against zebrafish chordin (chd), which can efficiently and specifically generate embryonic loss‐of‐function phenotypes comparable with morpholino injection and other methods. These results show that fully modified 2′‐OMe oligos can function as RNase‐H independent antisense reagents in vertebrate embryos and can thus serve as an alternative modification to morpholinos in some cases. genesis 49:117–123, 2011. © 2010 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4620634 Tue, 01 Mar 2011 00:00:00 +0100 4620634 http://www.medworm.com/index.php?rid=4620632&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20750 AbstractTcf21 is a class II bHLH family member with essential roles in the formation of the lungs, kidneys, gonads, spleen, and heart. Here, we report the utility of a mouse line with targeted insertion of a tamoxifen‐inducible Cre recombinase, MerCreMer at the Tcf21 locus. This mouse line will permit the inducible expression of Cre recombinase in Tcf21‐expressing cells. Using ROSA26 reporter mice, we show that Cre recombinase is specifically and robustly activated in multiple Tcf21‐expressing tissues during embryonic and postnatal development. The expression profile in the kidney is particularly dynamic with the ability to cause recombination in mesangial cells at one time of induction and podocytes at another time. These features make the Tcf21‐driven inducible Cre line (Tcf21iCr... genesis journals http://www.medworm.com/rss/comments.php?id=4620632 Tue, 01 Mar 2011 00:00:00 +0100 4620632 http://www.medworm.com/index.php?rid=4516124&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20739 AbstractThe homeobox gene Lbx1 not only plays critical roles in myogenesis and neurogenesis during embryonic development but is also expressed in activated satellite cells of adult mice. To address the potential postnatal functions of Lbx1, we generated conditional Lbx1‐null mice using the Cre‐loxP system. We generated a mouse in which exon 2 of Lbx1 was floxed (Lbx1flox/flox), followed by cross‐breeding between the Lbx1flox/flox mouse and either a transgenic mouse where a tamoxifen‐inducible Cre‐recombinase (Cre) was ubiquitously expressed, or a Myf5Cre mouse where Cre was inserted into the Myf5 locus. In both Lbx1‐null mouse lines generated, Pax3‐expressing limb muscle precursor cells were seriously reduced during embryonic development and eventually the limb extensor muscl... genesis journals http://www.medworm.com/rss/comments.php?id=4516124 Thu, 24 Feb 2011 00:00:00 +0100 4516124 http://www.medworm.com/index.php?rid=4516123&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20740 AbstractParkinson's disease (PD) is the second most common neurodegenerative disorder in humans. It affects one percent of the population over sixty‐five years old. Its causes are environmental and genetic. As the world population ages, there is an urgent need for better and more detailed animal models for this kind of diseases. In this work we show that the use of transgenic Drosophila is comparable to more complicated and costly animal models such as mice. The Drosophila model behaves very similar to the equivalent transgenic mice model. We show that both Synphilin‐1 and alpha‐synuclein are toxic by themselves, but when co‐expressed, they suppress their toxicity reciprocally. Importantly, the symptoms induced in the fly can be treated and partially reverted using standard PD phar... genesis journals http://www.medworm.com/rss/comments.php?id=4516123 Thu, 24 Feb 2011 00:00:00 +0100 4516123 http://www.medworm.com/index.php?rid=4505974&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20736 AbstractIn the mid‐1980's live‐cell imaging was changed by the introduction of video techniques, allowing new ways to collect and store data. The increased resolution obtained by manipulating video signals, the ability to use time‐lapse videocassette recorders to study events that happen over long time intervals, and the introduction of fluorescent probes and sensitive video cameras opened research avenues previously unavailable. The author gives a personal account of this evolution, focusing on cell migration studies at the Marine Biological Laboratory 25 years ago. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4505974 Tue, 22 Feb 2011 00:00:00 +0100 4505974 http://www.medworm.com/index.php?rid=4505973&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20737 We report the creation of a transgenic dog that conditionally expresses eGFP (enhanced green fluorescent protein) under the regulation of doxycycline. Briefly, fetal fibroblasts transfected with a Tet‐on eGFP vector were used for somatic cell nuclear transfer. Subsequently reconstructed oocytes were transferred to recipients. Three clones having transgenes were born and one dog was alive. The dog showed all features of inducible expression of eGFP upon doxycycline administration, and successful breeding resulted in eGFP‐positive puppies, confirming stable insertion of the transgene into the genome. This inducible dog model will be useful for a variety of medical research studies. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4505973 Tue, 22 Feb 2011 00:00:00 +0100 4505973 http://www.medworm.com/index.php?rid=4505972&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20734 We report here the generation of conditional mutant mice containing two loxP sites flanking Exon 2 of the Osr1 gene. Mice homozygous for this targeted Osr1fneo allele are normal and fertile. Crossing the Osr1fneo/fneo mice with the EIIa‐Cre transgenic mice resulted in Cre‐mediated deletion of the loxP‐flanked Exon2 in the germ line and mice homozygous for this deletion recapitulated the Osr1 null mutant phenotypes. The Osr1fneo conditional mice will be valuable for tissue‐specific analysis of the roles of Osr1 in embryonic and postnatal developmental processes. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4505972 Tue, 22 Feb 2011 00:00:00 +0100 4505972 http://www.medworm.com/index.php?rid=4481317&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20730 AbstractOne of challenges in the field of developmental biology is to understand how spatially and/or temporally coordinated expression of genes is controlled at the chromosomal level. It remains controversial whether genes expressed in a given tissue are randomly distributed throughout a given animal genome, or instead resolve into clusters. Here we used microarray analysis to identify more than 1,700 genes that are expressed preferentially in each of 11 organs of the chordate Ciona intestinalis adult, and determined the location of these genes on the 14 pairs of Ciona chromosomes. In spite of extensive mapped gene analysis, we only confirmed small clusters containing two or three genes. Our result indicates that organ‐specific genes are distributed rather evenly all over chromosomes, s... genesis journals http://www.medworm.com/rss/comments.php?id=4481317 Tue, 15 Feb 2011 00:00:00 +0100 4481317 http://www.medworm.com/index.php?rid=4481316&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20731 AbstractWnt/β‐catenin signaling initiates taste papilla development in mouse embryos, however, its involvement in taste cell turnover in adult mice has not been explored. Here we used the BATGAL reporter mouse model, which carries an engineered allele in which the LacZ gene is expressed in the presence of activated β‐catenin, to determine the responsiveness of adult taste bud cells to canonical Wnt signaling. Double immunostaining with markers of differentiated taste cells revealed that a subset of type I, II and III taste cells express β‐galactosidase. Using in situ hybridization, we showed that β‐catenin activates the transcription of the LacZ gene mainly in intragemmal basal cells that are immature taste cells, identified by their expression of Sonic Hedgehog (Shh). Finally,... genesis journals http://www.medworm.com/rss/comments.php?id=4481316 Tue, 15 Feb 2011 00:00:00 +0100 4481316 http://www.medworm.com/index.php?rid=4481315&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20732 AbstractPodosomes and invadopodia are actin‐rich protrusions of the plasma membrane important for matrix degradation and cell migration. Most of the information in this field has been obtained in cancer cells, where the presence of invadopodia has been related to increased invasiveness and metastatic potential. The importance of the related podosome structure in other pathological or physiological processes that require cell invasion is relatively unexplored. Recent evidence indicates that essential components of podosomes are responsible for several human syndromes, some of which are characterized by serious developmental defects involving the craniofacial area, skeleton and heart, and very poor prognosis. Here we will review them and discuss the possible role of podosomes as a player i... genesis journals http://www.medworm.com/rss/comments.php?id=4481315 Tue, 15 Feb 2011 00:00:00 +0100 4481315 http://www.medworm.com/index.php?rid=4675241&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20727 AbstractProper craniofacial development begins during gastrulation and requires the coordinated integration of each germ layer tissue (ectoderm, mesoderm, and endoderm) and its derivatives in concert with the precise regulation of cell proliferation, migration, and differentiation. Neural crest cells, which are derived from ectoderm, are a migratory progenitor cell population that generates most of the cartilage, bone, and connective tissue of the head and face. Neural crest cell development is regulated by a combination of intrinsic cell autonomous signals acquired during their formation, balanced with extrinsic signals from tissues with which the neural crest cells interact during their migration and differentiation. Although craniofacial anomalies are typically attributed to defects in ... genesis journals http://www.medworm.com/rss/comments.php?id=4675241 Tue, 08 Feb 2011 00:00:00 +0100 4675241 http://www.medworm.com/index.php?rid=4449231&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20726 AbstractThe closely related C. elegans MEG‐1 and MEG‐2 proteins localize to P granules during a brief period of embryogenesis when the germ lineage is being separated from the soma. Embryonic primordial germ cells still develop in the absence of MEG activity, but major defects emerge during larval stages when germ cells fail to proliferate or differentiate normally, resulting in sterility. To investigate meg‐1 function, we conducted a targeted RNAi screen for enhancers and suppressors of meg‐1 sterility. Here, we show that meg‐1 interacts with multiple pathways that promote germ cell proliferation and survival. Surprisingly, we found that two nanos family members had opposing effects on the meg‐1 phenotype. Loss of nos‐3 suppressed the meg‐1 phenotype, restoring fertility, ... genesis journals http://www.medworm.com/rss/comments.php?id=4449231 Tue, 08 Feb 2011 00:00:00 +0100 4449231 http://www.medworm.com/index.php?rid=4449230&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20727 AbstractProper craniofacial development begins during gastrulation and requires the coordinated integration of each germ layer tissue (ectoderm, mesoderm and endoderm) and its derivatives in concert with the precise regulation of cell proliferation, migration and differentiation. Neural crest cells, which are derived from ectoderm, are a migratory progenitor cell population that generates most of the cartilage, bone and connective tissue of the head and face. Neural crest cell development is regulated by a combination of intrinsic cell autonomous signals acquired during their formation, balanced with extrinsic signals from tissues with which the neural crest cells interact during their migration and differentiation. Although craniofacial anomalies are typically attributed to defects in neu... genesis journals http://www.medworm.com/rss/comments.php?id=4449230 Tue, 08 Feb 2011 00:00:00 +0100 4449230 http://www.medworm.com/index.php?rid=4449229&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20728 AbstractPrimary cilia are microtubule‐based organelles that serve as hubs for the transduction of various developmental signaling pathways including Hedgehog, Wnt, FGF and PDGF. Ciliary dysfunction contributes to a range of disorders, collectively known as the ciliopathies. Recently, interest has grown in these syndromes, particularly among craniofacial biologists, as many known and putative ciliopathies have severe craniofacial defects. Herein we discuss the current understanding of ciliary biology and craniofacial development in an attempt to gain insight into the molecular etiology for craniofacial ciliopathies, and uncover a characteristic ciliopathic craniofacial gestalt. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4449229 Tue, 08 Feb 2011 00:00:00 +0100 4449229 http://www.medworm.com/index.php?rid=4599305&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20747 AbstractThe p75NTR neurotrophin receptor has been implicated in multiple biological and pathological processes. While significant advances have recently been made in understanding the physiologic role of p75NTR, many details and aspects remain to be determined. This is in part because the two existing knockout mouse models (exons 3 or 4 deleted, respectively), both display features that defy definitive conclusions. Here we describe the generation of mice that carry a conditional p75NTR (p75NTR‐FX) allele made by flanking exons 4‐6, which encode the transmembrane and all cytoplasmic domains, by loxP sites. To validate this novel conditional allele, both neural crest‐specific p75NTR/Wnt1‐Cre mutants and conventional p75NTR null mutants were generated. Both mutants displayed abnormal ... genesis journals http://www.medworm.com/rss/comments.php?id=4599305 Tue, 01 Feb 2011 00:00:00 +0100 4599305 http://www.medworm.com/index.php?rid=4589147&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20746 AbstractThe serotonergic (5‐HT) system modulates many behaviors and has been implicated in psychiatric disorders, but the density of 5‐HT processes has complicated analyses. We have used regulatory regions from the Tryptophan hydroxylase 1 (Tph1) gene to drive expression of LoxP‐flanked placental alkaline phosphatase (PLAP) to generate the Tph1‐Lox‐PLAP reporter mouse line. In these mice, PLAP is expressed in the hindbrain raphe nuclei and in peripheral tissues known to express Tph1. Tph1 is expressed at low levels in neurons. While, in Tph1‐Lox‐PLAP mice, most PLAP‐expressing neurons are monoaminergic, PLAP was expressed in only 5‐10% of neurons expressing the predominant neuronal 5‐HT biosynthetic enzyme Tph2, serotonin transporter (SERT) or aromatic amino acid decarb... genesis journals http://www.medworm.com/rss/comments.php?id=4589147 Tue, 01 Feb 2011 00:00:00 +0100 4589147 http://www.medworm.com/index.php?rid=4558358&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20744 AbstractEpithelial‐mesenchymal interactions underlie the foundation for ectodermal appendage formation. Signal molecules such as BMPs and WNTs mediate crosstalk between the two tissue layers and coordinate both the induction and morphogenesis of ectodermal appendages. Here we analyzed the function of two BMP downstream transcription factors, Msx2 and Foxn1, in nail differentiation. First we show that Msx2 function is required during onychocyte (nail cell) terminal differentiation. Second, the Msx2/Foxn1/hair keratin pathway controlling hair differentiation is also conserved during onychocyte differentiation. Finally, the Msx2‐/‐;Foxn1‐/‐ double mutant nails exhibit a more severe phenotype than either single mutant including nail bed hyperplasia. Together, our data implicate impor... genesis journals http://www.medworm.com/rss/comments.php?id=4558358 Tue, 01 Feb 2011 00:00:00 +0100 4558358 http://www.medworm.com/index.php?rid=4534919&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20742 (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4534919 Tue, 01 Feb 2011 00:00:00 +0100 4534919 http://www.medworm.com/index.php?rid=4516122&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20741 AbstractCre‐loxP recombination is widely used for genetic manipulation of the mouse genome. Here, we report generation and characterization of a new Cre line, Stella‐Cre, where Cre expression cassette was targeted to the 3′ UTR of the Stella locus. Stella is specifically expressed in preimplantation embryos and in the germline. Cre‐loxP recombination efficiency in Stella‐Cre mice was investigated at several genomic loci including Rosa26, Jak2 and Npm1. At all the loci examined, we observed 100% Cre‐loxP recombination efficiency in the embryos and in the germline. Thus, Stella‐Cre mice serve as a very efficient deleter line. © 2011 Wiley‐Liss, Inc. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4516122 Tue, 01 Feb 2011 00:00:00 +0100 4516122 http://www.medworm.com/index.php?rid=4505976&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20706 (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4505976 Tue, 01 Feb 2011 00:00:00 +0100 4505976 http://www.medworm.com/index.php?rid=4505975&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20738 AbstractConfocal images of immunofluorescence showing the specific expression of Cx40‐Cre allele through the expression of RFP (Red) colocalizing with alpha‐actinin in green in Purkinje fibers of the ventricular conduction system and with PECAM (blue) in endothelial cells of coronary vessels. See the article by Beyer at al. in this issue. (Source: genesis) genesis journals http://www.medworm.com/rss/comments.php?id=4505975 Tue, 01 Feb 2011 00:00:00 +0100 4505975 http://www.medworm.com/index.php?rid=4505971&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20735 AbstractThe gelsolin related actin binding protein, Flii, is able to regulate wound healing; mice with decreased Flii expression show improved wound healing whereas mice with elevated Flii expression exhibit impaired wound healing. In both mice and humans Flii expression increases with age and amelioration of FLII activity represents a possible therapeutic strategy for improved wound healing in humans. Despite analysis of Flii function in a variety of organisms we know little of the molecular mechanisms underlying Flii action. Two new murine alleles of Flii have been produced to drive constitutive or tissue specific expression of Flii. Each strain is able to rescue the embryonic lethality associated with a Flii null allele and to impair wound healing. These strains provide valuable resourc... genesis journals http://www.medworm.com/rss/comments.php?id=4505971 Tue, 01 Feb 2011 00:00:00 +0100 4505971 http://www.medworm.com/index.php?rid=4410497&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20724 AbstractNormal patterning and morphogenesis of the complex skeletal structures of the skull requires an exquisite, reciprocal cross‐talk between the embryonic cephalic epithelia and mesenchyme. The mesenchyme associated with the jaws and the optic and olfactory capsules is derived from a Hox‐negative cranial neural crest (CNC) population that acts much as an equivalence group in its interactions with specific local cephalic epithelial signals. Craniofacial pattern and morphogenesis is therefore controlled in large part through the regulation of these local cephalic epithelial signals. Here we demonstrate that Pax6 is essential to the formation and maturation of the complex cephalic ectodermal patterning centers that govern the development and morphogenesis of the upper jaws and associa... genesis journals http://www.medworm.com/rss/comments.php?id=4410497 Fri, 28 Jan 2011 00:00:00 +0100 4410497 http://www.medworm.com/index.php?rid=4381445&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20721 AbstractDental patterns in vertebrates range from absence of teeth to multiple sets of teeth that are replaced throughout life. Despite this great variation, most of our understanding of tooth development is derived from studies on just a few model organisms. Here we introduce the reptile as an excellent model in which to study the molecular basis for early dental specification and, most importantly, for tooth replacement. We review recent snake studies that highlight the conserved role of Shh in marking the position of the odontogenic band. The distinctive molecular patterning of the dental lamina in the labial‐lingual and oral‐aboral axes is reviewed. We explain how these early signals help to specify the tooth‐forming and non‐tooth forming sides of the dental lamina as well as t... genesis journals http://www.medworm.com/rss/comments.php?id=4381445 Fri, 21 Jan 2011 00:00:00 +0100 4381445 http://www.medworm.com/index.php?rid=4381444&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20723 AbstractEpithelial invagination in many model systems is driven by apical cell constriction, mediated by actin and myosin II contraction regulated by GTPase activity. Here we investigate apical constriction during chick lens placode invagination. Inhibition of actin polymerization and myosin II activity by Cytochalasin D or blebbistatin prevents lens invagination. To further verify if lens placode invaginate through apical constriction, we analyzed the role o Rho‐ROCK pathway. Rho GTPases expression at the apical portion of the lens placode occurs with the same dynamics as that of the cytoskeleton. Overexpression of the pan‐Rho inhibitor C3 exotoxin abolished invagination and had a strong effect on apical myosin II enrichment and a mild effect on apical actin localization. In contrast,... genesis journals http://www.medworm.com/rss/comments.php?id=4381444 Fri, 21 Jan 2011 00:00:00 +0100 4381444 http://www.medworm.com/index.php?rid=4675240&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20718 AbstractA transgenic mouse line named iUBC‐KikGR was generated, which expresses the photoconvertible fluorescent protein Kikume Green‐Red (KikGR) under the control of the human Ubiquitin C promoter. KikGR is natively a green fluorophore, which can be converted into a red fluorophore upon exposure to UV light. KikGR is expressed broadly throughout transgenic embryos from the two‐cell stage onward and in the adult. Specificity of photoconversion can range from the entire embryo to a region of an organ, to a few individual cells, depending on the needs of the experimenter. Cell movements, tissue reorganization, and migration can then be observed in real time by culturing the tissue of interest as an explant on the microscope stage. The iUBC‐KikGR transgenic line represents a singular ... genesis journals http://www.medworm.com/rss/comments.php?id=4675240 Thu, 20 Jan 2011 00:00:00 +0100 4675240 http://www.medworm.com/index.php?rid=4376430&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20718 AbstractA transgenic mouse line named iUBC‐KikGR was generated which expresses the photoconvertible fluorescent protein Kikume Green‐Red (KikGR) under the control of the human Ubiquitin C promoter. KikGR is natively a green fluorophore which can be converted into a red fluorophore upon exposure to UV light. KikGR is expressed broadly throughout transgenic embryos from the 2‐cell stage onward, and in the adult. Specificity of photoconversion can range from the entire embryo, to a region of an organ, to a few individual cells, depending on the needs of the experimenter. Cell movements, tissue reorganization, and migration can then be observed in real time by culturing the tissue of interest as an explant on the microscope stage. The iUBC‐KikGR transgenic line represents a singular ge... genesis journals http://www.medworm.com/rss/comments.php?id=4376430 Thu, 20 Jan 2011 00:00:00 +0100 4376430 http://www.medworm.com/index.php?rid=4376429&cid=s_33772_50_f&fid=33772&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fdvg.20719 AbstractHIC1 (Hypermethylated In Cancer 1) is a tumor suppressor gene located on chromosome 17p13.3, a region frequently hypermethylated or deleted in human neoplasias. In the mouse, Hic1 is essential for embryonic development and exerts an anti‐tumor role in adult animals. Since Hic1‐deficient mice die perinatally, we generated a conditional Hic1 null allele by flanking the Hic1 coding region by loxP sites. When crossed to animals expressing Cre recombinase in a cell‐specific manner, the Hic1 conditional mice will provide new insights into the function of Hic1 in developing and mature tissues. Additionally, we used gene targeting to replace a sequence encoding amino acids 186 to 893 of Hic1 by citrine fluorescent protein cDNA. We demonstrate that the distribution of Hic1‐citrine f... genesis journals http://www.medworm.com/rss/comments.php?id=4376429 Thu, 20 Jan 2011 00:00:00 +0100 4376429