Association of genotypes of four RGS17 SNPs and RGS17 mRNA expression levels. The association between four RGS17 SNPs (rs9371276, rs9397585, rs6931160 and rs596359, which were significantly associated with substance dependence) and RGS17 mRNA expression levels was examined in 60 CEU (a) and 60 YRI (b) unrelated subjects. P values were calculated by linear regression analysis and adjusted by sex. The ends of the vertical lines indicate the minimum and maximum values. The lower hinge of the boxes indicates the 25th percentile, the upper hinge of the boxes indicates the 75th percentile, and the line in the boxes indicates the median value. “+” in the boxes refers to the mean expression level. X axis: RGS17 SNP genotypes; Y axis: RGS7 mRNA expression levels (mean ± SEM).