CDNA CLONING AND ITS PRONEPHROS-SPECIFIC EXPRESSION OF THE WILMS-TUMOR SUPPRESSOR GENE, WT1, FROM XENOPUS-LAEVIS

The Wilms' tumor suppressor gene, WT1, plays a crucial role during ear ly urogenital development in mammals. To elucidate the function of WT1 in other vertebrates, we isolated the Xenopus WT1 homolog (XeWT1) fro m a testis cDNA library. Comparison of the XeWT1 protein with other WT 1 proteins revealed that the zinc finger domain of XeWT1 is identical to that of the human WT1 except for the first two amino acid residues. An alternative splice II site, located between the third and the four th zinc finger is also conserved. In the transcriptional regulatory re gion, however, three domains, a glycine stretch, a proline stretch and one alternative splice site which are present in the mammalian WT1, a re not conserved in amphibians. The XeWT1 gene is expressed in testis and kidney, and whole mount in situ hybridization revealed that the on set of the WT1 gene expression coincides with the early stages of pron ephros development in Xenopus. These findings implicate the involvemen t of WT1 protein during urogenital development in amphibians as well a s in mammals.