OR15-2 A Novel Upstream Enhancer Acts Synergistically with GnRH and Activin to Increase FSHβ Transcription

Abstract

Polycystic ovary syndrome (PCOS) is the most common cause of female infertility and is associated with an increased risk of type 2 diabetes and cardiovascular disease. Understanding the etiology of PCOS is crucial to relieve this tremendous health burden. Twin studies estimate that 70% of PCOS etiology can be explained by genetic factors, motivating studies to identify these factors. Recent genome wide association studies identified a PCOS risk locus that encompasses the gene encoding the follicle-stimulating hormone beta (FSHβ) subunit. The most significant single nucleotide polymorphism (SNP) within this locus, rs11031006 (rs06), resides within a region of DNA (~450 base pairs) that is highly conserved among mammals. As FSH supplementation can restore ovulation in some PCOS patients, deficient FSH signaling may be a causative factor of anovulation and potentially other facets of PCOS. FSH transcription and release is stimulated by gonadotropin-releasing hormone (GnRH) produced in the hypothalamus, as well as activin produced by the gonads and pituitary. We previously hypothesized that the conserved region containing rs06 acts as an enhancer of FSHβ transcription, and we determined through luciferase reporter assays that this highly conserved region enhances transcription ~2 fold compared to the minimal FSHβ promoter alone for human and 2.5 fold for mouse. The rs06 SNP minor allele further increased both mouse and human FSHβ luciferase expression. In the present study, we sought to identify interactions between the enhancer and the hormones, GnRH and activin. With DNA constructs from both human and mouse, we identified synergistic interactions between the enhancer and GnRH- or activin-induction of FSHβ. These interactions were maintained after mutation of the rs06 site to the minor allele, suggesting that this SNP alters basal and not hormone-induced FSHβ transcription. We are currently investigating the effect of the enhancer and rs06 on activin/GnRH synergy. Overall, our findings provide evidence that the enhancer functions as a novel mediator of activin and GnRH regulation of FSHβ transcription in both human and mouse.