SUN-738 Establishing the Link Between Genetic Variations of Estrogen Receptor 2 and Unexplained Infertility

Background: Unexplained or idiopathic infertility comprises approximately 30% of couples who present with infertility. This has led to investigations seeking to determine the cause(s) of this important diagnosis of exclusion. Estrogen’s role in reproduction has been well- established. Estrogens bind to two hormone receptors (namely estrogen receptor-alpha and estrogen receptor-beta), which are distributed differentially throughout the body. Specifically, the estrogen receptor-beta, coded by the Estrogen Receptor 2 (ESR2) gene, is highly expressed in granulosa cells and growing follicles. The one female patient reported with an ESR2 mutation presented with hypergonadotropic hypogonadism. However, subfertility with inefficient ovulation and resistance to exogenous ovulatory stimulation is seen in an ESR2 knockout mouse model. We therefore hypothesized that less severe ESR2 variants could lead to a normal female phenotype and pubertal development but could be a cause subfertility. Methods: DNA samples from 200 women with unexplained infertility were obtained from the Assessment of Multiple Intrauterine Gestations from Ovarian Stimulation (AMIGOS) clinical trial, which investigated optimal ovulation induction medications for unexplained infertility. These samples were subjected to targeted next-generation sequencing (NGS) for the ESR2 gene. Likely pathogenic variants that occurred with a minor allele frequency of < 0.01 in the gnomAD database and a Combined Annotation Dependent Depletion (CADD) score of > 20 were selected for confirmation by Sanger sequencing. Results: From the 200 patient samples, five heterozygous missense variants and one heterozygous in-frame deletion identified by targeted NGS were confirmed by Sanger sequencing. Further studies will need to be performed in vitro to confirm the likely pathogenicity of these variants. Conclusion: These studies raise the possibility that If these variants in ESR2 that impair estrogen signaling, they could be a potential newly recognized etiology of unexplained infertility in women with unexplained infertility. Conclusion: These studies raise the possibility that variants in ESR2 that impair estrogen signaling could be a potential newly recognized etiology of unexplained infertility in women.