four tissues of the six tissues tested for OPRM1 favored the hypothesis that only a genetic association with OA at this locus is present (Fig. 5H2, Supplementary Table 15). However, in the cerebellum, where OPRM1 is most highly expressed and for which S-PrediXcan predicted differential expression by OA, the greatest posterior probabilities favored hypotheses for both the OA-associated locus and cis-eQTL traits being associated, but with different causal variants (H3) or a shared single causal variant (H4). Among the three genes at the PPP6C-centered locus, PPP6C shows the highest levels of gene expression in brain tissues (Supplementary Fig. 17b–d) and the greatest support for colocalization of OA-associated variants with cis-eQTLs for PPP6C (Fig. 5, Supplementary Table 15). In contrast, the analysis for RABEPK uniformly indicated that the OA-associated variants do not colocalize with the RABEPK cis-eQTLs. The analyses for SCAI showed mixed results, indicating the OA-associated variants have a moderate probability of colocalization with SCAI cis-eQTLs for some tissues (cortex, frontal cortex, and hippocampus) but not for most, and not as high a probability as for PPP6C. For FURIN, the null hypothesis of neither trait being associated in this region has the highest posterior probability across all tested brain tissues
