inositol polyphosphate phosphatase 4A (INPP4A) in cis. The gene INPP4A has been shown to protect neurons from excitotoxic cell death and to maintain the functional integrity of the brain 26. Remarkably, a previous study has shown that increased excitotoxicity may account for disease progression in Bipolar Disorder 27. The gene INPP4A encodes one of the enzymes involved in the phosphatidylinositol signaling pathway, which is a target for the effects of lithium 28. We obtained replication of the association in the independent WTCCC GWA study. We also found the SNP was a cis eQTL for UNC50 (p = 0.009). It is worth noting that considering SNPs that are both cis mQTLs and cis eQTLs even if the methylation and expression targets are not the same gene may increase power to detect an association in genome-wide studies of Bipolar Disorder by further reducing the multiple testing burden and providing a potentially more robust genetic association finding.
