Expression of cdc25 phosphatases in the germ cells of the rat testis

cdc25A and cdc25C, which encode threonine/tyrosine phosphatases involved in cell cycle regulation, were found to be differentially localized in rat testicular germ cells during spermatogenesis. Northern blot analysis identified two cdc25A transcripts. A transcript of 3.8 kilobases (kb) was expressed in the early germ cells including spermatogonia, and a 3.3-kb transcript was highly expressed in spermatocytes and round spermatids. In situ hybridization showed that the levels of mRNA for cdc25A were highest in diplotene spermatocytes and round spermatids but were undetectable in Sertoli cells. Both transcripts for cdc25A increased with retinol treatment in the vitamin A-deficient testis. Immunolocalization showed that cdc25A protein was distributed in the cytoplasm of germ cells, whereas cdc25C was localized to the nucleus of late spermatocytes and round spermatids. Previous studies have identified two cdc25C transcripts of 2.1 kb and 1.9 kb, which were expressed in spermatocytes and round spermatids, respectively. These results suggest that cdc25A may function during mitosis of spermatogonia. Both cdc25A and cdc25C may function in the regulation of the meiotic cell cycle, although in different manners, as indicated by their subcellular localization.