Prenatal Androgenization Modifies H3K9me3 Binding in the Promoter of the Androgen Receptor Gene in the Arcuate Nucleus of the Adult Female Mouse

Animal models have shown that prenatal exposure to excess androgens is associated with the development of polycystic ovary syndrome (PCOS) features. We have identified that prenatally androgenized (PNA) mice modelling PCOS show suppressed androgen receptor mRNA (Ar) expression in the arcuate nucleus (ARC) across development. This could contribute to PCOS-related impaired gonadal steroid hormone feedback to GnRH neurons. However, the mechanism of Ar mRNA suppression following PNA is not determined. We performed a chromatin immunoprecipitation (ChIP) assay coupled with quantitative PCR (qPCR) to investigate histone and transcription factor binding within the Ar gene promoter or enhancer regions in the ARC of female mice at postnatal day (P)60 or gestational day (GD)18.5. In comparison to adult vehicle control (VEH) mice, our ChIP-qPCR revealed that H3K9me3, a repressive histone mark, was increased in adult PNA mice at the promoter regions of the Ar gene. H3K27ac, an active histone mark, and SP1, a transcription factor that acts as a positive regulator of gene expression, were unchanged in the same regions. Increased H3K9me3 seen at the promoter region in adult PNA mice, however, was not observed in the GD18.5 mice ARC following PNA. These results suggest that the deposition of H3K9me3 on the Ar promoter is unlikely to be established by PNA at the time of excess androgen exposure, and instead is likely to be established later in postnatal development or in adulthood. These data provide greater understanding of the developmental mechanisms and timeline underpinning PNA-mediated female dysfunction and PCOS-like reproductive physiology.