bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic linkage maps of the West African clawed frog Xenopus tropicalis
Authors: Kochan Kelli J. , Wright David A. , Schroeder Lisa J. , Shen Jianjun , Morizot Donald C. 
Published: January 2003

AbstractAmphibians, and particularly the African clawed frog Xenopus laevis, have been used for more than a century as models of vertebrate embryonic development. However, in many cases, elucidation of developmental functions of specific gene sequences could be severely impeded, because X. laevis is a tetraploid species, with multiple functional copies of many genes of interest. Recent studies have shifted focus to the West African or tropical clawed frog, X. tropicalis, the only known diploid species of the genus Xenopus. Here, we present two preliminary linkage maps, constructed by analysis of joint segregation of amplified fragment length polymorphism (AFLP) markers in a X. tropicalis interstrain hybrid. A total of 53 markers, including 51 AFLP markers and 2 isozyme markers, are presently assigned to 13 multipoint linkage groups on a map of the maternal strain, whereas 9 AFLP markers from the paternal strain are assigned to 3 linkage groups on a separate map. A dense genetic linkage map is essential in mapping new developmental mutants and determining their sequences by positional cloning. © 2002 Wiley‐Liss, Inc.
Genome‐wide examination of myoblast cell cycle withdrawal during differentiation
Authors: Shen Xun , Collier J. Michael , Hlaing Myint , Zhang Leanne , Delshad Elizabeth H. , Bristow James , Bernstein Harold S. 
Published: January 2003

AbstractSkeletal and cardiac myocytes cease division within weeks of birth. Although skeletal muscle retains limited capacity for regeneration through recruitment of satellite cells, resident populations of adult myocardial stem cells have not been identified. Because cell cycle withdrawal accompanies myocyte differentiation, we hypothesized that C2C12 cells, a mouse myoblast cell line previously used to characterize myocyte differentiation, also would provide a model for studying cell cycle withdrawal during differentiation. C2C12 cells were differentiated in culture medium containing horse serum and harvested at various time points to characterize the expression profiles of known cell cycle and myogenic regulatory factors by immunoblot analysis. BrdU incorporation decreased dramatically in confluent cultures 48 hr after addition of horse serum, as cells started to form myotubes. This finding was preceded by up‐regulation of MyoD, followed by myogenin, and activation of Bcl‐2. Cyclin D1 was expressed in proliferating cultures and became undetectable in cultures containing 40% fused myotubes, as levels of p21WAF1/Cip1 increased and α‐actin became detectable. Because C2C12 myoblasts withdraw from the cell cycle during myocyte differentiation following a course that recapitulates this process in vivo, we performed a genome‐wide screen to identify other gene products involved in this process. Using microarrays containing ∼10,000 minimally redundant mouse sequences that map to the UniGene database of the National Center for Biotechnology Information, we compared gene expression profiles between proliferating, differentiating, and differentiated C2C12 cells and verified candidate genes demonstrating differential expression by RT‐PCR. Cluster analysis of differentially expressed genes revealed groups of gene products involved in cell cycle withdrawal, muscle differentiation, and apoptosis. In addition, we identified several genes, including DDAH2 and Ly‐6A, whose expression specifically was up‐regulated during cell cycle withdrawal coincident with early myoblast differentiation. 2002 Wiley‐Liss, Inc.
Molecular components of the endoderm specification pathway in Xenopus tropicalis
Authors: D'Souza Anjali , Lee Monica , Taverner Nicola , Mason Julia , Carruthers Samantha , Smith James C. , Amaya Enrique , Papalopulu Nancy , Zorn Aaron M. 
Published: January 2003

AbstractXenopus laevis has been instrumental in elucidating a conserved molecular pathway that regulates vertebrate endoderm specification. However, loss‐of‐function analysis is required to resolve the precise function of the genes involved. For such analysis, antisense oligos and possibly forward genetics are likely to be more effective in the diploid species Xenopus tropicalis than in the pseudotetraploid Xenopus laevis. Here we have isolated most of the tropicalis genes in the endoderm specification pathway, specifically, tVegT, tMixer, tMix, tBix, tGata6, tSox17α, tSox17β, tFoxA1, tHex, and tCerberus, which lack the redundant copies that are found in laevis. In situ hybridization analysis has revealed identical expression patterns between the orthologous tropicalis and laevis endoderm genes, thus suggesting conserved genetic functions. Furthermore, we noted that the smaller tropicalis embryos gave better probe penetration than in laevis whole‐mount in situ hybridizations—allowing us to visualize transcripts in the deep endoderm in tropicalis, which is difficult in laevis. This study illustrates how an entire genetic pathway can be quickly transferred from laevis to tropicalis due to high sequence conservation between the sister species and the large number of tropicalis‐expressed sequence tags that are now available. © 2002 Wiley‐Liss, Inc.
Spatial and temporal expression of folate‐binding protein 1 (Fbp1) is closely associated with anterior neural tube closure in mice
Authors: Saitsu Hirotomo , Ishibashi Makoto , Nakano Hitoo , Shiota Kohei 
Published: January 2003

AbstractPericonceptional folate supplementation is widely believed to have significant preventive effects on the production of neural tube defects. Folate‐binding protein 1 (FBP1) is one of the membrane proteins that mediate cellular uptake of folate. Although recent studies suggest that Fbp1 is essential for neural tube closure, the pattern of Fbp1 expression in embryonic tissues has not been examined in detail. To elucidate how Fbp1 contributes to neural tube closure, we examined the spatial and temporal expression patterns of Fbp1 in the developing neural folds and tube of mouse embryos by in situ hybridization. Fbp1 showed a distinct expression pattern in the neural folds, which preceded initiation of neural tube closure at the cervical region and the prosencephalic/mesencephalic boundary. Fbp1 expression was mainly localized to the most dorsal regions of the neural folds where fusion was to occur. With proceeding of neural fold fusion, Fbp1 expression extended to the adjacent unfused neural folds. In the rhombencephalon, robust expression of Fbp1 was observed in rhombomere2 (r2) and r6, suggesting its roles in development of neural crest cells. Fbp1 also showed intense expression in the yolk sac, indicating that FBP1 may mediate transferring maternal folate to embryos during neurulation. These findings indicate close association between Fbp1 and anterior neural tube closure. © 2002 Wiley‐Liss, Inc.
In ovo electroporation of Crim1 in the developing chick spinal cord
Authors: Kolle Gabriel , Jansen Annemieke , Yamada Toshiya , Little Melissa 
Published: January 2003

AbstractThe novel mammalian gene Crim1 encodes a transmembrane bound protein with similarity to the secreted bone morphogenetic protein (BMP) antagonists, vertebrate Chordin, and its Drosophila homologue short gastrulation. Crim1 is expressed in the neural tube in mouse in a restricted pattern, but its function in central nervous system development is largely unknown. We isolated the chicken Crim1 orthologue and analyzed its expression in the developing neural tube. Chicken CRIM1 shares strong homology to human/mouse CRIM1 and C. elegans CRIM1‐like proteins. Crim1 is expressed in a similar but not identical pattern to that in the developing spinal cord of mouse, including the notochord, floor plate, motor neurons, and the roof plate. Unlike follistatin, a secreted inhibitor of BMPs, in ovo electroporation of CRIM1, as a full‐length transmembrane bound or secreted ectodomain was not sufficient to disrupt early patterning of the neural tube. However, ectodomain CRIM1 overexpression leads to an approximate 50% decrease in populations of specific ventral neuronal populations, including ISL‐1+ motor neurons, CHX‐10+ V1, and EN‐1+ V2 interneurons. © 2002 Wiley‐Liss, Inc.
Pronephric duct extension in amphibian embryos: Migration and other mechanisms
Authors: Drawbridge Julie , Meighan Christopher M. , Lumpkins Rebecca , Kite Mary E. 
Published: January 2003

AbstractInitiation of excretory system development in all vertebrates requires (1) delamination of the pronephric and pronephric duct rudiments from intermediate mesoderm at the ventral border of anterior somites, and (2) extension of the pronephric duct to the cloaca. Pronephric duct extension is the central event in nephric system development; the pronephric duct differentiates into the tubule that carries nephric filtrate out of the body and induces terminal differentiation of adult kidneys. Early studies concluded that pronephric ducts formed by means of in situ segregation of pronephric duct tissue from lateral mesoderm ventral to the forming somites; more recent studies highlight caudal migration of the pronephric duct as the major morphogenetic mechanism. The purpose of this review is to provide the historical background on studies of the mechanisms of amphibian pronephric duct extension, to review evidence showing that different amphibians perform pronephric duct morphogenesis in different ways, and to suggest future studies that may help illuminate the molecular basis of the mechanisms that have evolved in amphibians to extend the pronephric duct to the cloaca. © 2002 Wiley‐Liss, Inc.
T‐box gene products are required for mesenchymal induction of epithelial branching in the embryonic mouse lung
Authors: Cebra‐Thomas Judith A. , Bromer Jason , Gardner Rose , Lam Gordon K. , Sheipe Hillary , Gilbert Scott F. 
Published: January 2003

AbstractThe regulation of signaling pathways is a prerequisite for coordinating the induction between mesenchymal and epithelial tissues during morphogenesis. Mesenchymal FGF10 is known to be an important paracrine factor regulating the branching morphogenesis of the bronchial epithelium. By using antisense oligonucleotides (AS ODNs) and in vitro culture of embryonic lungs, we demonstrate that the transcription factors Tbx4 and Tbx5 are critical for the expression of mesenchymal FGF10. Treatment of embryonic lung cultures with AS ODNs to Tbx4 and Tbx5 reduces the level of these transcripts, suppresses Fgf10 expression in the mesenchyme, and completely eliminates the formation of new lung branches. If FGF10 is locally replaced in these AS ODN‐treated lungs, epithelial branching is restored. These studies provide evidence that the production of branching signals by the lung mesenchyme is mediated by T‐box genes. © 2002 Wiley‐Liss, Inc.
Drosophila NAB (dNAB) is an orphan transcriptional co‐repressor required for correct CNS and eye development
Authors: Clements Mark , Duncan Dianne , Milbrandt Jeffrey 
Published: January 2003

AbstractThe mammalian NAB proteins have been identified previously as potent co‐repressors of the EGR family of zinc finger transcription factors. Drosophila NAB (dNAB), like its mammalian counterparts, binds EGR1 and represses EGR1‐mediated transcriptional activation from a synthetic promoter. In contrast, dNAB does not bind the Drosophila EGR‐related protein klumpfuss. dnab RNA is expressed exclusively in a subset of neuroblasts in the embryonic and larval central nervous system (CNS), as well as in several larval imaginal disc tissues. Here, we describe the creation of targeted deletion mutations in the dnab gene and the identification of additional, EMS‐induced dnab mutations by genetic complementation analysis. Null alleles in dnab cause larval locomotion defects and early larval lethality (L1–L2). A putative hypomorphic allele in dnab instead causes early adult lethality due to severe locomotion defects. In the dnab ‐/‐ CNS, axon outgrowth/guidance and glial development appear normal; however, a subset of eve+ neurons forms in reduced numbers. In addition, mosaic analysis in the eye reveals that dnab ‐/‐ clones are either very small or absent. Similarly, dNAB overexpression in the eye causes eyes to be very small with few ommatidia. These dramatic eye‐specific phenotypes will prove useful for enhancer/suppressor screens to identify dnab‐interacting genes. © 2002 Wiley‐Liss, Inc.
Cyclops‐independent floor plate differentiation in zebrafish embryos
Authors: Albert Stéphanie , Müller Ferenc , Fischer Nadine , Biellmann Dominique , Neumann Carl , Blader Patrick , Strähle Uwe 
Published: January 2003

AbstractIn zebrafish, development of the ventral neural tube depends on the Nodal‐related signal Cyclops (Cyc). One‐day‐old cyc mutant embryos lack the medial floor plate (MFP). We show here that cells expressing MFP marker genes differentiate gradually in cyc mutant embryos in a delayed manner during the second day of development. This late differentiation is restricted to the hindbrain and spinal cord and depends on an intact Hedgehog (Hh) signalling pathway. Cells expressing MFP marker genes in cyc mutant embryos appear to be derived from lateral floor plate (LFP) cells as they coexpress LFP and MFP marker genes. This finding suggests that the correct temporal development of the MFP is required for the distinction of LFP and MFP cells in wild‐type embryos. © 2002 Wiley‐Liss, Inc.
Rho‐associated kinases play an essential role in cardiac morphogenesis and cardiomyocyte proliferation
Authors: Zhao Zhiyong , Rivkees Scott A. 
Published: January 2003

AbstractRho‐associated coiled‐coil kinases (ROCKs), initially identified as effectors for Rho GTPases, play a role in cardiac cell physiology and are also expressed in the developing heart. However, their role in cardiac development is not known. To investigate the role of these kinases in cardiac development, we examined cardiac development in cultured murine embryos treated with the ROCK inhibitor Y27632. After inhibition of ROCK activity, we found disturbed cardiac chamber formation and trabeculation. To further examine the mechanisms by which ROCK blockade causes cardiac hypoplasia, we assessed programmed cell death and cell proliferation in the hearts. We found decreased cell proliferation in the Y27632‐treated hearts, but no changes in programmed cell death. We further observed that ROCK inhibition decreased cardiac myocyte proliferation, suggesting that ROCK kinases regulate cardiomyocyte division. To identify factors involved in ROCK action in regulation of cardiac cell division, we examined expression of cell cycle proteins by using Western blot analysis. We found that ROCK blockade decreased expression of cell cycle proteins, cyclin D3, CDK6, and p27KIP1 in the hearts and cardiomyocytes, which are required for initiation of cell cycle and G1/S phase transition. These observations show that ROCK kinases play a role in cardiac development and that ROCK kinases regulate cardiac cell proliferation and cell cycle protein expression. © 2002 Wiley‐Liss, Inc.
Heart‐selective expression of the chicken FK506‐binding protein (FKBP) 12.6 gene during embryonic development
Authors: Yazawa Shigenobu , Obata Koji , Iio Akio , Koide Masafumi , Yokota Mitsuhiro , Sasaki Shin‐Ichi , Kagami Hiroshi , Ono Tamao 
Published: January 2003

AbstractFKBP12.6, a member of the family of FK506‐binding proteins, selectively associates with the cardiac isoform of the ryanodine receptor and thereby stabilizes this Ca2+ release channel. A chicken FKBP12.6 (chFKBP12.6) cDNA was cloned and shown to encode a protein of 108 amino acids. The deduced amino acid sequence of chFKBP12.6 is 91–92% identical to those of mammalian FKBP12.6 proteins. Northern blot analysis revealed that chFKBP12.6 mRNA is largely restricted to the heart during embryonic development and that the abundance of this mRNA in the heart decreases, and it becomes restricted to the atrium during cardiogenesis. In situ hybridization revealed that chFKBP12.6 mRNA is localized to the precardiac mesoderm before formation of the primitive heart tube. Expression of the chFKBP12.6 gene was initially apparent throughout the developing multichambered heart but became restricted to the atria before hatching. Reverse transcription and polymerase chain reaction analysis demonstrated that chFKBP12.6 mRNA is present in the embryo from early gastrulation and is most abundant immediately after the onset of the heartbeat. These observations suggest that the chFKBP12.6 gene is expressed before heart morphogenesis to play a role in excitation–contraction coupling in cardiomyocytes and that the function of the encoded protein becomes increasingly restricted to the atrium during embryonic development. © 2002 Wiley‐Liss, Inc.
Developmental expression of the HNK‐1 carbohydrate epitope on aggrecan during chondrogenesis
Authors: Domowicz Miriam S. , Mueller Melissa M. , Novak Todd E. , Schwartz Lauren E. , Schwartz Nancy B. 
Published: January 2003

AbstractPreviously, we showed that the HNK‐1 carbohydrate epitope is expressed on aggrecan synthesized in the notochord but not in mature cartilage. In the present study, we demonstrate that in immature cartilage (embryonic day 6) the HNK‐1 epitope is also expressed predominantly on aggrecan proteoglycan molecules. This finding was verified by using an aggrecan‐deficient mutant, the nanomelic chick, which lacks HNK‐1 immunostaining in the extracellular matrix of dividing and hypertrophic chondrocytes as late as embryonic day 12. By using both biochemical and immunologic approaches, the initially prominent expression of the HNK‐1 epitope is down‐regulated as development of limb and vertebral cartilage proceeds, so that by embryonic day 14 no HNK‐1 is detectable. Localization changes with development and the HNK‐1–aggrecan matrix becomes restricted to dividing and hypertrophic chondrocytes and is particularly concentrated in the intraterritorial matrix. Concomitant with the temporal and spatial decreases in HNK‐1, there is a significant increase in keratan‐sulfate content and the aggrecan‐borne HNK‐1 epitope is closely associated with proteolytic peptides that contain keratan sulfate chains, rather than chondroitin sulfate chains or carbohydrate‐free domains. Lastly, the diminution in HNK‐1 expression is consistent with a reduction in mRNA transcripts specific for at least one of the key enzymes in HNK‐1 oligosaccharide biosynthesis, the HNK‐1 sulfotransferase. These findings indicate that the HNK‐1 carbohydrate may be a common modifier of several proteoglycans (such as aggrecan) that are usually expressed early in development, and that HNK‐1 addition to these molecules may be regulated by tissue‐ and temporal‐specific expression of requisite sulfotransferases and glycosyltransferases. © 2002 Wiley‐Liss, Inc.
T‐box binding site mediates the dorsal activation of myf‐5 in Xenopus gastrula embryos
Authors: Lin Gu Fa , Geng Xin , Chen Ying , Qu Bin , Wang Fubin , Hu Ruiying , Ding Xiaoyan 
Published: January 2003

AbstractMyf‐5, a member of the muscle regulatory factor family of transcription factors, plays an important role in the determination, development, and differentiation of the skeletal muscle. Factors that regulate the expression of myf‐5 itself are not well understood. We show here that a T‐box binding site in the Xenopus myf‐5 promoter mediated the activation of myf‐5 expression through specific interaction with nuclear proteins of gastrula embryos. The T‐box binding site could be bound by and respond to T‐box proteins. T‐box genes could induce Xmyf‐5. The results suggest that T‐box proteins are involved in the specification of myogenic mesoderm and muscle development. © 2002 Wiley‐Liss, Inc.
Ci‐GATAa, a GATA‐class gene from the ascidian Ciona intestinalis: Isolation and developmental expression
Authors: D'Ambrosio Palmira , Fanelli Albertina , Pischetola Michele , Spagnuolo Antonietta 
Published: January 2003

AbstractMembers of the GATA family of zinc finger transcription factors have been shown to play important roles in controlling gene expression in a variety of cell types in many metazoan. Here, we describe the identification of Ci‐GATAa, a member of this gene family, in the ascidian Ciona intestinalis. Whole‐mount in situ hybridization showed that Ci‐GATAa was expressed in a highly dynamic manner. The maternal transcript was evenly distributed in the embryo during early stages of development; however, the signal gradually decreased until it disappeared at the 64‐cell stage. A zygotic transcript was detected at the 110‐cell stage in the blastomeres precursors of three different tissues (brain vesicle, mesenchyme, and trunk lateral cells) and the signal was conserved in these territories up to the larval stage, indicating an important role for Ci‐GATAa during ascidian differentiation. © 2002 Wiley‐Liss, Inc.
Chick limbs with mouse teeth: An effective in vivo culture system for tooth germ development and analysis
Authors: Koyama Eiki , Wu Changshan , Shimo Tsuyoshi , Pacifici Maurizio 
Published: January 2003

AbstractMouse tooth germ development is currently studied by three main approaches: in wild‐type and mutant mouse lines, after transplantation of tooth germs to ectopic sites, and in organ culture. The in vivo approaches are the most physiological but do not provide accessibility to tooth germs for further experimental manipulation. Organ cultures, although readily accessible, do not sustain full tooth germ development and are appropriate for short‐term analysis. Thus, we sought to establish a new approach that would combine experimental accessibility with sustained development. We implanted fragments of embryonic day 12 mouse embryo first branchial arch containing early bud stage tooth germs into the lateral mesenchyme of day 4–5 chick embryo wing buds in ovo. Eggs were reincubated, and implanted tissues were examined by histochemistry and in situ hybridization over time. The tooth germs underwent seemingly normal growth, differentiation, and morphogenesis. They reached the cap, bell, and crown stages in approximately 3, 6, and 10 days, respectively, mimicking in a striking manner native temporal patterns. To examine mechanisms regulating tooth germ development, we first implanted tooth germ fragments, microinjected them with neutralizing antibodies to the key signaling molecule Sonic hedgehog (Shh), and examined them over time. Tooth germ development was markedly delayed, as revealed by poor morphogenesis and lack of mature ameloblasts and odontoblasts displaying characteristic traits such as an elongated cell shape, nuclear relocalization, and amelogenin gene expression. These phenotypic changes began to be reversed upon further incubation. The data show that the limb bud represents an effective, experimentally accessible as well as economical system for growth and analysis of developing tooth germs. The inhibitory effects of Shh neutralizing antibody treatment are discussed in relation to roles of this signaling pathway proposed by this and other groups previously. © 2002 Wiley‐Liss, Inc.