SF-1 Is Required In TGF-β3-induced 17β-estradiol Synthesis In Mouse Ovrian Granulosa Cells

The transforming growth factor-β(TGF-β) superfamily members are indicated to play key roles in ovarian follicular development, such as granulosa cell (GC) proliferation, estrogens and progesterone production. However, little is known about the roles of TGF-β3 in follicular development. In this study, we found that both the mRNA and the protein of TGF-β3 were predominantly expressed in GCs of mouse ovarian follicles, and TGF-β3 significantly promoted estradiol (E₂) release in a dose-dependent manner. Immunofluorescence and Western blot studies also demonstrated that the TGF-β3-induced E₂ release is due to the enhanced expression of Cyp19a1 (a key rate-limiting enzyme for estrogens biosyntheses), which is mediated by Smad-dependent signal pathway, since the phosphorylation and the translocation of Smad protein are need for this progress. In addition, the orphan nuclear receptor steroidogenic factor-1 (SF-1) was required in TGF-β3-induced Cyp19a1 expression and E₂ synthesis, because the knock-down of SF-1 totally abolished both the Cyp19a1 expression and E₂ release promoted by TGF-β3. Additionally, as evidenced by chromatin immunoprecipitation (ChIP) assays, TGF-β3 enhanced the binding of SF-1 to endogenous ovary-specific Cyp19a1 PII promoter, followed by activation of Cyp19a1 expression and E₂ release. Taken together, our data provide mechanistic insights into the roles of SF-1 in TGF-β3-mediated E₂ synthesis. Understanding of potential cross-points between extracellular signals affecting estrogens production will help to discover new therapeutic targets in estrogens-related diseases.