DNA samples were genotyped on the Illumina Human 1M beadchip (Illumina) by the Center for Inherited Diseases Research (CIDR) at Johns Hopkins University. A thorough data-cleaning procedure was applied, including using HapMap controls, detection of gender and chromosomal anomalies, hidden relatedness, population structure, missing call rates, batch effects, Mendelian error detection, duplication error detection and Hardy–Weinberg equilibrium.33 A total of 948 658 SNPs passed data cleaning procedures.
