Parallel to gene expression quantification, genomic DNA was extracted from whole-blood samples collected at the time of recruitment. The Gentra Puregene Blood Kit (Qiagen) was used to separate and lyse white blood cells for purification of DNA from blood biospecimens. Extracted DNA elutes were normalized at 50 ng/μL and further analyzed in a 96-well plate format. Samples were hybridized to either HumanOmniExpress or HumanOmni2.5 BeadChips (Illumina, San Diego, CA), and the iScan system (Illumina, San Diego, CA) was used to scan the arrays. Genotypes were then called in GenomeStudio (Illumina). Samples genotyped on the larger platform, HumanOmni2.5, were scaled back to the overlap with HumanOmniExpress coverage. Genotypes with GenCall (GC) scores <0.2 and samples with call rates <95% were excluded as failed markers and samples, respectively. Only SNPs with call rates >95%, minor allele frequency (MAF) >5%, and Hardy–Weinberg equilibrium χ2 P values greater than 10−6 were considered. Raw genotyping data are available on request.
