The characteristics and expression profile of gonadal soma-derived factor (gsdf/Gsdf) during androgen-induced reversible sex change in the protogynous orange-spotted grouper, Epinephelus coioides

Abstract

Gonadal soma-derived factor (gsdf) is a teleost- and gonad-specific growth factor involved in gonadal differentiation and early germline cell development. In protogynous grouper, the androgen-induced precocious male phase is transient, and a reversible sex change (induced male-to-female change) occurs after chemical withdrawal. In this study, we used MT (17 alpha-methyltestosterone)-induced bi-directional sex change to understand the role of Gsdf signaling in the sexual differentiation of orange-spotted grouper, Epinephelus coioides. Our results showed that the expression of gsdf was higher in the MT-induced male (functional male) than in the control female (primary oocyte stage). Conversely, high gsdf expression was also found in the transient phase of reversible induced male-to-female sex change (dormant gonad). Furthermore, gsdf/Gsdf was expressed in the Sertoli cells surrounding the spermatogonia and the somatic cells surrounding the oogonia. gsdf/Gsdf expression was also found in the somatic cells surrounding the spermatogonia-like cells in the transient phase of induced male-to-female sex change. Recombinant Gsdf (rGsdf) was produced and specific anti-Gsdf antiserum was obtained. Moreover, the proliferation activities of the oogonia were decreased by rGsdf in in vitro ovarian tissue culture (equivalent to 1.125 mg crude protein extracted from 37.5 mg testicular tissue/ml). Conversely, the treatment of ovarian tissue culture with rGsdf did not affect the expression levels of female and male sex-related genes (equivalent to 1.125 mg crude protein extracted from 37.5 mg testicular tissue/ml). Taken together, our data suggest that Gsdf signaling is related to the arrest of proliferation activity in early-stage germline cells but is not directly related to sexual phase determination.