Across the 13 brain tissues in GTEx, we observed the highest DNMT3B gene expression levels in cerebellum (median log10 RPKM=0.304) and cerebellar hemisphere (median log10 RPKM=0.298), compared to median log10 RPKM≤−0.325 for all other brain tissues (Supplementary Figure 5). Moreover, across the brain tissues, rs910083 was most significantly associated with DNMT3B gene expression levels in cerebellum (P=3.0×10−6) and cerebellar hemisphere (P=7.0×10−7), with the C allele associated with higher DNMT3B expression (Figure 3 and Supplementary Table 5). We replicated this pattern in the Brain eQTL Almanac, where DNMT3B mRNA transcript expression levels were highest in cerebellar cortex (Supplementary Figure 6)—the outer layer of the cerebellum that comprises most of its volume. Consistent with GTEx, rs910083-C was associated with increased DNMT3B mRNA transcript expression levels specifically in cerebellar cortex (P=0.028).
