Cloning, pattern of gonadal soma-derived factor mRNA in the orange-spotted grouper, Epinephelus coioides

The orange-spotted grouper (Epinephelus coioides), as a protogynous hermaphrodite, provides a novel model for understanding the mechanisms of sex determination and differentiation in teleosts. Gonadal soma-derived factor (gsdf), involved in early germ cell development, is a new member of the transforming growth factor-beta (TGF-β) superfamily. In this study, a 2364-bp long gsdf gene was cloned from E. coioides and there was further analysis of its tissue distribution and patterns of gene expression during the female phase, bisexual gonads stage and testis stage. The cellular localization of Gsdf during the early sexual differentiation stage was also analyzed. In addition, the expression levels of gsdf, dmrt1, foxl2 and cyp19a1a in gonads during the early sexual differentiation stage were analyzed by real-time PCR. Tissue distribution analysis showed that gsdf was only expressed in the testis and ovary. The gene expression showed that gsdf was expressed significantly higher in testes and bisexual gonads compared to ovaries. The early-stage ovary showed a significant fluorescence signal in the supporting cells surrounding gonium and oogonium, but not pre-vitellogenic oocytes, indicating that gsdf expression was restricted to morphologically undifferentiated supporting cells in the early stages of oogenesis. During the early sexual differentiation stage, Real-time PCR showed that both the expression levels of gsdf and dmrt1 were progressively increased and the expression levels of foxl2 and cyp19a1a were growing slowly. These results suggest that gsdf could have roles in the early sexual differentiation in hermaphroditic, E. coioides