Cloning of cDNA for newt WT1 and the differential expression during spermatogenesis of the Japanese newt, Cynops pyrrhogaster

To investigate the function of Wilms' tumor 1 (WT1) during spermatogenesis, cDNA for newt WT1 homolog was cloned and the expression of WT1 in newt tes tes was examined. The cDNA is 2089 bp in length and encodes 426 amino acid (aa) residues. The deduced aa sequence shares 76 and 79% homology with huma n and Xenopus WT1, respectively. Northern blot analysis shows that WT1 mRNA , 3.2 and 4.5 kb in length, are expressed in the testis and kidney. Both WT 1 mRNA species are detected in various stages of spermatogenesis, but the 3 .2 kb mRNA is highly expressed in spermatogonia and mature sperm stages, wh ile the amount of 4.5 kb mRNA is almost constant throughout spermatogenesis . in situ hybridization reveals that WT1 mRNA is localized in Sertoli cells . Moreover; immunohistochemical analysis shows that WT1 protein is highly e xpressed in the nuclei of Sertoli cells in early spermatogonia and mature s perm stages, but not in pericystic cells or germ cells. These results sugge st that WT1 is involved in the regulation of gene expression in Sertoli cel ls, depending on the spermatogenic stage.