Subjects were selected from the NIAAA/COGA Sharing Repository of the Collaborative Study on the Genetics of Alcoholism (COGA) project with characteristics summarized in Table 1. Selection criteria consisted of KCNJ6 SNP genotype, DSM-IV diagnosis of AUD, sex, and availability of frozen lymphocytes in the repository. All subjects were of European ancestry. See Supplementary Methods for details. The previously-described protocol for generating glutamatergic human induced neurons (iN) [27–29] was modified. To obtain cultures with enhanced levels of spontaneous activity, we minimized the time of Ngn2 induction to reduce alternate cell identities [30] and fed cultures with a low-molality medium for at least 30 days post-induction [31] as described in the Supplementary Methods. Cultures of iN typically exhibited resting membrane potentials averaging −40 mV with the presence of synaptic markers, spontaneous action potentials, and synaptic activity.Table 1Subjects selected for iPSC.GroupIDSexDSMIV Dxrs702859 Synonymousrs702860 Intronicrs2835872 IntronicAF376MAffectedGGGGAA246MAffectedGGGGAA351FAffectedGGGGAA233FAffectedGGGGAAUN472MUnaffectedAAAAGG384MUnaffectedAAAAGG451FUnaffectedAAAAGG420FUnaffectedAAAAGGThe ID is a three-digit code that is not traceable to the subject identity. Genotypes for listed SNPs were obtained from GWAS studies [8]. SNP genotypes were confirmed by iPSC genomic DNA PCR and Sanger sequencing.
