Introduction: Sex determination is an essential process for the production of dimorphic gametes, sperms and eggs. The sex determination genes in gonadal somatic cells have been well studied, but nothing is known about the mechanism of germline sex determination in vertebrates. We have tackled a totally unaddressed issue using medaka.
Materials and methods: Using transgenic medaka in which germ cells were labeled with EGFP, three different types of germ cells, stem-type, cystic, and meiotic germ cells, were isolated by flowcytometry, followed by RNA-Seq analysis. The expression of candidate genes was screened by in situ hybridization, and the functional analysis was performed.
Results and discussion: We identified an oocytesperm switch gene, which was initially expressed in germ cells of indifferent gonad in both XX and XY embryos but totally disappeared during male development. The loss-of-function of homozygous XX mutants produced sperms instead of oocytes during the sex differentiation. These results suggest that germline sex determination occurs by repressing the spermatogenesis. This is the first report of the mechanism of germline sex determination in vertebrates and provides an important insight into the sex determination processes between germ cells and somatic cells.
02 - 04 Sep 2014
World Congress of Reproductive Biology