Genotyping was performed at the Genome Technology Access Center at Washington University School of Medicine in St. Louis (http://gtac.wustl.edu/) using the Illumina Human OmniExpress array 12.VI (Illumina, San Diego, CA, USA). A total of 707,557 autosomal SNPs passed quality control (Wang et al., 2013). SNPs with a minor allele frequency (MAF) below 5% (n=115,872) were excluded from further analysis. EIGENSTRAT was utilized in the HapMap European reference samples to identify ethnic stratification within the sample.
