Sex Lethal Gene Manipulates Gonadal Development of Medaka, , Through Estrogenic Interventions

Germ cells are pivotal for gonadal sexuality maintenance and reproduction. Sex lethal (), the somatic sex determining gene of , is the known regulator and initiator of germ cell femininity in invertebrates. However, the role of the Sxl homologue has rarely been investigated in vertebrates. So, we used medaka to clarify the role of in vertebrate gonadogenesis and sexuality and identified two Sxl homologues, i.e., Sxl1a and Sxl1b. We found that specifically expresses in the primordial germ cells (PGC), ovary, (early gonia and oocytes), while distributions are ubiquitous. An mRNA overexpression of accelerated germ cell numbers in 10 DAH XY fish, and knockdown (KD), on the other hand, induced PGC mis-migration, aberrant PGC structuring and ultimately caused significant germ cell reduction in XX fish. Using an in vitro promoter analysis and in vivo steroid treatment, we found a strong link between and estrogenic germ cell-population maintenance. Further, using -KD and -knockout fish, we determined that acts through and controls PGC sexuality. Cumulatively, our study highlights the novel role of in germ cell maintenance and sexual identity assignment and thus might become a steppingstone to understanding the commonalities of animal sexual development.