Genotyping was performed by the Center for Inherited Disease Research (CIDR) at John Hopkins University using the Illumina® Infinium II assay protocol (Gunderson et al. 2006) for hybridization to Illumina® HumanHap 1M BeadChips (Illumina, San Diego, CA), with a blind duplicate reproducibility of 99.97% and 99.98% for the COGA and SAGE samples, respectively. Details are reported by Bierut et al. (2010) and Edenberg et al. (2010). Protocols and GWAS data for the COGA (n = 1,003,800 SNPs) and SAGE (n = 1,040,106 SNPs) samples are available on the National Center for Biotechnology Information (NCBI) database dbGaP. For each sample set, subjects were assigned to EA and AA population groups via principal component (PC) analysis of the genotype data, corresponding to two major population clusters observable in PC space (Table 1; Fig. S2 and S3).
