Meta‐Analysis of Genomewide Association Studies Reveals Genetic Variants for Hip Bone Geometry

Hip geometry (HG) is an important predictor of fracture. We performed a meta-analysis of GWAS studies in adults to identify genetic variants that are associated with proximal femur geometry phenotypes. We analyzed four phenotypes: 1) Femoral neck length; 2) Neck-shaft angle; 3) Femoral neck width, and 4) Femoral neck section modulus, estimated from DXA scans using algorithms of hip structure analysis. In the Discovery stage, 10 cohort studies were included in the fixed-effect meta-analysis, with up to 18,719 men and women ages 16-93 years. Association analyses were performed with ~ 2.5 million polymorphismsunder an additive model adjusted for age and body mass index; an additional analysis also adjusted for height. Replication analyses of meta-GWAS significant loci (at genome-wide significance, GWS, threshold p≤5x10-8) were performed in 7 additional cohorts in-silico. In meta-analysis not adjusting for height (combined Discovery and Replication stages), GWS associations were found on chr. 4 (in HHIP), chr. 8 (C8orf34), chr. 13 (FAM10A4 and DLEU2), and chr. 20 (inDDX27). The height-adjusted meta-analysis showed significant associations at 5p15 (IRX1 and ADAMTS16); 5q35 near FGFR4; at 12p11 (in CCDC91); 11q13 (near LRP5 and PPP6R3 (rs7102273)). Several HG signals overlapped with bone mineral density (BMD), including JAG1 on chr. 20, near TNFRSF11B (chr. 8), SOX6 and LRP5 (chr. 11). Chr. 11 SNP rs7102273 was associated with any-type fracture (p = 7.5 x 10-5). We used bone transcriptome data and discovered several significant eQTLs, including rs7102273 and PPP6R3 expression (p=0.0007), and rs6556301 (intergenic, chr.5) and PDLIM7 expression(p=0.005). In conclusion, we found associations between HG measures and several genes being part of biological pathways relevant to BMD and fractures. The results provide a defined set of genes facilitating further experimental exploration and validation to understand biological mechanisms underlying human bone geometry and etiology of bone fragility.