We also examined loci that showed a nominal genetic correlation across multiple disorder pairs, and found these loci also harbored GW hits for respective phenotypes. The locus at 17q12 shared among multiple disorders contains a GW hit for BD (17:36809344-38877404) ascribed to candidate gene ERBB2 (Hou et al. 2016). This gene and its relatives encode receptor tyrosine kinases that interact with a family of growth factors called neuregulins to regulate the assembly of neural circuitry, myelination, neurotransmission and synaptic plasticity. A large body of evidence implicates both ligands and receptors from these families as susceptibility genes for SZ and BD (Mei & Nave 2014). Notably, ERBB2 overlaps with GW hits for multiple autoimmune disorders, though these have been attributed to different genes in the region. Another locus at 1q32.1 (1:200137649-201589975) contains GW hits for multiple autoimmune disorders (including celiac disease, CD, multiple sclerosis, and UC) and is near candidate genes C1orf106, CACNA1S, GPR25, and KIF21B. Genetic disruptions of voltage-gated calcium channels, including CACNA1S, are well-established susceptibility factors in psychiatric and neurological disorders (Schmunk & Gargus 2013; Heyes et al. 2015).
