KCNC1 and KCNG2, loci containing some of the most significantly associated SNPs, encode potassium voltage-gated channel subunits. Another locus, PITPNM3, encodes a protein that is involved in phosphatidylinositol transport, but that also binds calcium. Variants located ~196 kb upstream from PPP3CA were associated with OD in the case-control model (although not GWS) in both populations (rs6419156, PAA=1.4×10−6, PEA=5.6×10−7); the effect directions were opposite, suggesting that population-specific causal variants or a single causal variant occurring on distinct haplotypes may be responsible. PPP3CA encodes a calcium-dependent, calmodulin-stimulated protein phosphatase involved in calcium signaling. (A trinucleotide repeat at this locus was reported to be nominally associated to SD in AAs but not EAs (21)).
