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

Ana C Fierro125*, Raphaël Thuret12, Laurent Coen3, Muriel Perron12, Barbara A Demeneix3, Maurice Wegnez12, Gabor Gyapay4, Jean Weissenbach4, Patrick Wincker4, André Mazabraud12 and Nicolas Pollet125*

Author Affiliations

1 CNRS UMR 8080, F-91405 Orsay, France

2 Univ Paris Sud, F-91405 Orsay, France

3 CNRS UMR 5166, Evolution des Régulations Endocriniennes, USM 501, Département Régulations, Développement et Diversité Moléculaire, Muséum National d'Histoire Naturelle, 7 rue Cuvier, 75231 Paris Cedex 5, France

4 Genoscope and CNRS UMR 8030, 2 rue Gaston Crémieux CP5706, 91057 Evry, France

5 Programme d'Épigénomique, Univ Evry, Tour Évry 2, 10è étage, 523 Terrasses de l'Agora, 91034 Evry cedex, France

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BMC Genomics 2007, 8:118  doi:10.1186/1471-2164-8-118

Published: 16 May 2007



The western African clawed frog Xenopus tropicalis is an anuran amphibian species now used as model in vertebrate comparative genomics. It provides the same advantages as Xenopus laevis but is diploid and has a smaller genome of 1.7 Gbp. Therefore X. tropicalis 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 X. tropicalis.


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.


These cDNA sequences permit in silico 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 X. tropicalis 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.