Exploring nervous system transcriptomes during embryogenesis and metamorphosis in Xenopus tropicalis using EST analysis

<p>Abstract</p> <p>Background</p> <p>The western African clawed frog <it>Xenopus tropicalis </it>is an anuran amphibian species now used as model in vertebrate comparative genomics. It provides the same advantages as <it>Xenopus laevis </it>but is diploid and has a smaller genome of 1.7 Gbp. Therefore <it>X. tropicalis </it>is more amenable to systematic transcriptome surveys. We initiated a large-scale partial cDNA sequencing project to provide a functional genomics resource on genes expressed in the nervous system during early embryogenesis and metamorphosis in <it>X. tropicalis</it>.</p> <p>Results</p> <p>A gene index was defined and analysed after the collection of over 48,785 high quality sequences. These partial cDNA sequences were obtained from an embryonic head and retina library (30,272 sequences) and from a metamorphic brain and spinal cord library (27,602 sequences). These ESTs are estimated to represent 9,693 transcripts derived from an estimated 6,000 genes. Comparison of these cDNA sequences with protein databases indicates that 46% contain their start codon. Further annotation included Gene Ontology functional classification, InterPro domain analysis, alternative splicing and non-coding RNA identification. Gene expression profiles were derived from EST counts and used to define transcripts specific to metamorphic stages of development. Moreover, these ESTs allowed identification of a set of 225 polymorphic microsatellites that can be used as genetic markers.</p> <p>Conclusion</p> <p>These cDNA sequences permit <it>in silico </it>cloning of numerous genes and will facilitate studies aimed at deciphering the roles of cognate genes expressed in the nervous system during neural development and metamorphosis. The genomic resources developed to study <it>X. tropicalis </it>biology will accelerate exploration of amphibian physiology and genetics. In particular, the model will facilitate analysis of key questions related to anuran embryogenesis and metamorphosis and its associated regulatory processes.</p

Étude de la régulation du gène elrD au cours de la neurogenèse chez Xenopus laevis (caractérisation de deux promoteurs)

PARIS-BIUSJ-Thèses (751052125) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Subcellular distribution of Xenopus XEL-1 protein, a member of the neuron-specific ELAV/Hu family, revealed by epitope tagging.

International audienceDrosophila and vertebrate elav/Hu genes are involved in the development and the maintenance of the nervous system. They all encode proteins that contain three RNA recognition motifs (RRM) and are thus expected to play a role in RNA metabolism. Drosophila ELAV and RBP9 proteins were reported to be exclusively distributed in nuclei of neurons, whereas known human Hu proteins display a bipartite nuclear and cytoplasmic distribution. We have previously isolated a member of this family in Xenopus, Xel-1, that is exclusively expressed in neural tissues from the early tailbud stage onward. In the present study, we report on the subcellular distribution of XEL-1 protein using myc epitope tagging, a strategy allowing the study of a single member of the ELAV/Hu family. We show that the subcellular distribution of exogenous XEL-1 protein in neural tissues depends on developmental stages. In the neural tube at the neurula stage, where endogenous Xel-1 is not expressed, exogenous tagged XEL-1 protein is localized in both the nucleus and the cytoplasm. At the tailbud stage, where endogenous Xel-1 is expressed, exogenous tagged XEL-1 protein is localized essentially in the cytoplasm of neural tube cells. In contrast, exogenous Drosophila ELAV protein localizes to the nucleus at all stages in Xenopus embryos. The variability in the subcellular localization of ELAV/Hu proteins in different species may have functional implications

XSEB4R, a novel RNA-binding protein involved in retinal cell differentiation downstream of bHLH proneural genes.

RNA-binding proteins play key roles in the post-transcriptional regulation of gene expression but so far they have not been studied extensively in the context of developmental processes. We report on the molecular cloning and spatio-temporal expression of a novel RNA-binding protein, XSEB4R, which is strongly expressed in the nervous system. This study is focused on the analysis of Xseb4R in the context of primary neurogenesis and retinogenesis. To study Xseb4R function during eye development, we set up a new protocol allowing in vivo lipofection of antisense morpholino oligonucleotides into the retina. The resulting XSEB4R knockdown causes an impairment of neuronal differentiation, with an increase in the number of glial cells. By contrast, our gain-of-function analysis demonstrates that Xseb4R strongly promotes neural differentiation. We also showed a similar function during primary neurogenesis. Consistent with this proneural effect, we found that in the open neural plate Xseb4R expression is upregulated by the proneural gene XNgnr1, as well as by the differentiation gene XNeuroD, but is inhibited by the Notch/Delta pathway. Altogether, our results suggest for the first time a proneural effect for a RNA-binding protein involved in the genetic network of retinogenesis.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Adaptation des organismes aux pollutions metalliques Approche moleculaire et genetique par l'etude des metalloproteines

Available at INIST (FR), Document Supply Service, under shelf-number : RP 185 (2603) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc