For quality control (QC), samples were excluded (n=367) due to call rates below 0.95, sex mismatch, duplicate discordance, contamination and genetic similarity (identity by state > 0.2). Population stratification was assessed by principal component analysis over the sample correlation matrix, based on 16,842 independent (LD-pruned) SNPs. We excluded samples when they diverged from the mean with at least 3 standard deviations (Z-score > 3) for the first five principal components.