Tissue-Specific Expression of dmrt Genes in Embryos and Adults of the Platyfish Xiphophorus maculatus

The vertebrate dmrt gene family encodes transcription factors with a characteristic DNA-binding motif called the DM domain. The best studied member is dmrt1, which is involved in sexual development in fish and tetrapods. The cloning of dmrt5 from the platyfish Xiphophorus maculatus and the expression pattern of dmrt1, dmrt2a, dmrt4, and dmrt5 in adults and embryos are reported. Consistent with a role in sexual development, platyfish dmrt1 is expressed exclusively in adult testis. Interestingly, dmrt1 expression was detected in both spermatogonia and Sertoli cells. This contrasts with the situation in other fish, where dmrt1 is not expressed in both types of cells, and is reminiscent of the expression observed in other vertebrates. Certain expression patterns in platyfish embryos were similar to those found in other vertebrates, suggesting conserved functions of dmrt genes in vertebrate development. This was the case for dmrt2a/terra and dmrt4, presenting expression patterns compatible with roles in somitogenesis and olfactory system development, respectively. However, differences in expression during embryogenesis and in adult tissues were observed not only between fish and tetrapods, but also between fish species, illustrating the possible functional divergence of this gene family in fish and other vertebrates.