MON-156 A Point Mutation Upstream of Fshb Alters Fertility in Female Mice

Abstract Disclosure: K.J. Tonsfeldt: None. S. Bohaczuk: None. T.I. Slaiwa: None. G. Dunn: None. D.L. Gillette: None. S. Yeo: None. C.V. Shi: None. J. Cassin: None. V.G. Thackray: None. P.L. Mellon: None. Follicle-stimulating hormone (FSH) regulates gametogenesis and hormone synthesis and is required for fertility. FSH is composed of a common alpha subunit and a specific beta subunit encoded by FSHB/Fshb. Recent GWAS studies have identified a lead single nucleotide polymorphism (SNP), rs11031006(G/A), associated with polycystic ovary syndrome, age of natural menopause, and dizygotic twinning. Of note, these traits are all linked to FSH levels, and rs11031006 is located 26 kb upstream of the human FSHB transcriptional start site. In investigating this region, we discovered an evolutionarily conserved enhancer of FSHB/Fshb containing the rs11031006 site, in which the minor SNP increases enhancer activity in vitro. To explore the effects of this enhancer in vivo, we used CRISPR/Cas9 to generate two mouse lines, one containing a deletion of the entire upstream enhancer (located 17kb upstream of the mouse Fshb TSS, FshbeD777), and one with a G>A point mutation at the equivalent base in mice (SNP06_G>A). A full characterization of the large enhancer deletion reveals no changes in puberty, fertility, serum FSH or LH levels, or pituitary Fshb or Lhb mRNA levels. Similarly, the point mutation mouse had no changes in puberty, serum FSH or LH levels, or pituitary Fshb or Lhb mRNA levels, but did show a premature decline in fecundity. These mice displayed significantly fewer litters born in 120 days (3.8 ± 1.0 vs 3.0 ± 0.8, p < 0.05), with a normal time to first litter, but longer intervals in the timing of subsequent litters. At 10 months of age, the SNP06_G>A mice trended towards longer diestrus and shorter estrus, and had longer estrous cycles compared to their wild-type counterparts (5.3 ± 0.6 vs 6.8 ± 1.2 days, p < 0.01). Our on-going studies are examining the potential mechanisms for these phenotypes. Overall, the G>A mutation within the mouse 17 kb upstream enhancer may contribute to FSH expression later in life but is dispensable in younger mice. Presentation: Monday, July 14, 2025