Lean and obese women with Polycystic Ovary Syndrome (PCOS) display different clinical characteristics, implying a different pathophysiology depending on body mass index (BMI). PCOS phenotypes, stratified by BMI, are potentially genetically distinct.
This study aimed to detect genotype differences between lean and overweight/obese PCOS-affected women and explore distinctions in genetic architecture based on BMI.
Case-control genome-wide association study (GWAS) data from Caucasian PCOS-affected women and controls were pooled from six international PCOS research groups, and separated according to three BMI stratifications (lean BMI<25kg/m2, overweight BMI >25-<30kg/m2 and obese BMI >30kg/m2). A meta-analysis of GWAS data (Meta-GWAS) from each BMI tier was performed.
The population comprised 257,155 women (6,273 cases and 250,822 controls) from Australian, American, Netherlands, Estonian and Finnish cohorts. Almost half of the population (47.1%, n=120,983) were of lean BMI. Two genetic loci meeting genome-wide significance (p<5x10-8) for lean PCOS were identified - rs12000707, within DENND1A (9q33.3; p=1.55x10-12) and rs2228260 within XBP1 (22q12.1; p=3.68x10-8). DENND1A is a well-recognised genetic risk locus for PCOS and is associated with hyperandrogenism and ovulatory dysfunction. XBP1 is involved in glucose and lipid metabolism, suggesting a plausible biological link with PCOS. The signal at XBP1 is part of a large linkage disequilibrium (LD) block containing other genes, including CHEK2, with putative PCOS involvement.
Gene-based association testing identified C8orf49 as significantly associated with lean PCOS. C8orf49 is located in close proximity to two other genes previously implicated in PCOS, GATA4 and NEIL2, and may be part of a PCOS-susceptibility gene cluster on chromosome 8. The association between these genetic loci and lean PCOS is a novel finding.
The SNPs and genes identified in this study provide further evidence of distinct genetic architecture underlying lean and overweight/obese PCOS. The identification of loci associated specifically with lean PCOS is of significant interest.