Estrogen-Related Receptor γ (ERRγ) Mediates Oxygen-Dependent Induction of Aromatase (CYP19) Gene Expression during Human Trophoblast Differentiation

Differentiation of human cytotrophoblasts to syncytiotrophoblast and the associated induction of aromatase/hCYP19 gene expression are dependent upon a critical O(2) tension; however, the underlying molecular mechanisms remain undefined. In this study, we provide compelling evidence that expression of the orphan nuclear receptor, estrogen-related receptor gamma (ERR gamma), is also O2 dependent, induced during human syncytiotrophoblast differentiation, and plays an obligatory role in the induction of placenta-specific hCYP19I. 1 gene expression. Treatment with the selective ERR gamma agonist, DY131, or overexpression of ERR gamma, stimulated hCYP19 expression in syncytiotrophoblast. Overexpression of ERR gamma prevented effects of hypoxia to repress hCYP19 gene expression in cultured trophoblasts. Conversely, small interfering RNA-mediated knockdown of endogenous ERR gamma in primary trophoblasts markedly inhibited hCYP19 expression. Promoter and site-directed mutagenesis studies in transfected placental cells identified a nuclear receptor element within placenta-specific hCYP19 promoter I. 1 required for ERR gamma-stimulated activity. Recruitment of endogenous ERR gamma to the nuclear receptor element region in hCYP19 promoter during trophoblast differentiation, assessed by chromatin immunoprecipitation, was prevented by hypoxia. Deferoxamine-induced hypoxia-inducible factor-1 alpha (HIF-1 alpha) levels decreased ERR gamma expression, whereas knockdown of endogenous HIF-1 alpha prevented ERR gamma suppression by hypoxia. Chromatin immunoprecipitation analysis of trophoblasts cultured in hypoxia revealed recruitment of HIF-1 alpha to one of two putative hypoxia response elements in the ERR gamma promoter, providing in vivo evidence of a direct HIF-1 alpha involvement in ERR gamma expression. Collectively, these novel findings identify ERR gamma as an O(2)-dependent transcription factor and HIF-1 alpha target gene that serves a critical role in the induction of hCYP19 expression during human trophoblast differentiation. (Molecular Endocrinology 25: 1513-1526, 2011)