Functions and Mechanisms of Action of the Medaka Sex-Determining Gene

点击翻译按钮获取中文摘要

We previously identified PG17 as the leading candidate for the medaka sex-determining gene. To definitively identify PG17 as a sex-determining gene, we injected one-cell stage medaka embryos with a genomic DNA fragment carrying PG17. The transgenic embryos were bred until secondary sexual characters were observed. We found that all XX transgenic fish were male, showing that PG17 is sufficient to induce male development. The present data combined with our previous data indicate that PG17 is the sex-determining gene of medaka and named it DMY.DMY mRNA and protein are expressed specifically in the somatic cells (Sertoli cells) surrounding primordial germ cells (PGC) in the early gonadal primordium, before morphological sex differences are apparent. DMRT1, another DM domain gene that is also involved in male development in other vertebrates, is expressed in spermatogonium-supporting cells after testicular differentiation (20-30 days after hatching). These results strongly suggest that DMY regulates PGC proliferation and differentiation sex-specifically during early gonadal differentiation of XY individuals and that DMRT1 regulates spermatogonial differentiation.Because Sry transgenic mice are sterile and because DMY transgenic XX medakas are fertile, i.e., fully functional males, DMY transgenic medakas are the first transgenic vertebrates known to undergo complete sex reversal.