not report testing IREB2, a gene previously associated with COPD [11], [36]. The specific IREB2 SNPs associated in GWAS (rs13180) [11] and in a candidate gene analysis of differentially expressed genes (rs2656069) [36] were in only moderate LD (r2 = 0.44) with each other, implying independent effects on IREB2 expression. The IREB2 and CHRNA5 eQTL SNPs were not in LD with each other, suggesting the presence of at least two COPD susceptibility genes on chromosome 15q25. Previous studies have similarly used eQTL analyses to add functional information about genes identified through GWAS, including studies of asthma [7], celiac disease [46], and Crohn's disease [47]. However, these prior studies have examined gene expression in blood cells, and not primary disease tissues.
