GnRH Regulates Sex Differentiation in Sebastes schlegelii Through TGF-β/MAPK Signaling Pathways.

Sex determination and gonadal differentiation are essential for vertebrate development and reproduction. Fish, with both genetic and environmental sex-determining mechanisms, serve as ideal models for exploring environmental effects on gonadal development. The hypothalamic-pituitary-gonadal (HPG) axis is involved in sex differentiation, but its role as a key mediator in temperature-dependent sex differentiation remains unclear. Sebastes schlegelii is an economically important marine fish species along the northern coast of China. It exhibits obvious sexual growth dimorphism and typical temperature-dependent sex differentiation, making it an excellent model for investigating the mechanism of sex differentiation. In this study, individuals of S. schlegelii at the sex differentiation stage were treated with a GnRH receptor antagonist and subjected to transcriptome sequencing analysis. The results revealed that GnRH may regulate sex differentiation through steroid biosynthesis, TGF-β and MAPK signaling pathways. We identified several key genes, including srd5, bmp8a, bmp2, fgf23, pdgfra, and egfr, which may affect gonadal differentiation by acting on core sex-determining genes and steroidogenesis. In conclusion, GnRH precisely mediates the process of sex differentiation by modulating the TGF-β signaling pathway, the MAPK signaling pathway, and local gonadal steroidogenic networks.