Identification of a Polycystic ovary syndrome susceptibility variant in fibrillin-3 and association with a metabolic phenotype

Context: Polycystic ovary syndrome ( PCOS), the most common reproductive endocrine disorder of premenopausal women, is also associated with metabolic abnormalities including insulin resistance and an increased risk for diabetes mellitus. We previously mapped a PCOS susceptibility locus to chromosome 19p13.2 near the dinucleotide repeat marker D19S884. Objective: Our objective is to localize the chromosome 19p13.2 PCOS susceptibility locus and determine its impact on metabolic features of PCOS. Design: Resequencing and family-based association testing were used to examine the effect of sequence variation within 100 kb of D19S884 on the reproductive and metabolic phenotypes of PCOS. Setting: The study was conducted in an academic medical center. Subjects: Genetic analyses were performed on DNA obtained from1723 individuals in 412 families with 412 index cases and 43 affected sisters of predominantly European origin (> 94%). Genotype-phenotype associations were assessed in 601 women with PCOS and 168 brothers of affected women. Results: D19S884 allele 8 (A8) within intron 55 of the fibrillin-3 (FBN3) gene showed the strongest evidence for association with PCOS of 53 variants tested ( P-corrected = 0.0037). A8 was also associated with higher levels of fasting insulin and homeostasis model assessment for insulin resistance in women with PCOS and higher fasting levels of proinsulin and proinsulin/insulin ratio in brothers. Conclusions: These findings strongly suggest that A8 of D19S884 is the chromosome 19p13.2 PCOS susceptibility locus. The association of D19S884 with markers of insulin resistance and pancreatic beta-cell dysfunction suggests that the same variant contributes to the reproductive and metabolic abnormalities of PCOS in affected women and their brothers.