A potential alternative genetic model more consistent with these results would include a cis-acting genetic locus influencing expression of the chr4p12 GABAA gene cluster paired with a random, mitotically-stable, allelic expression bias. In this model, a stochastic clonal allelic expression bias for the chromosome carrying a cis-acting repressive functional variant linked with the rs279858*C-allele would determine Cluster 1 vs. 2 membership for a given iPSC line. Support for a model that includes allelic expression bias in this region was obtained using RT-qPCR and TaqMan allele-specific probes to examine neural cell RNA from 16 Cluster 2 cell lines heterozygous for exonic SNPs in at least one of the chr4p12 GABAA genes (GABRG1, GABRA2, GABRA4 and GABRB1). We observed allelic imbalance [a 50% or greater increase in RNA from one of the two alleles, i.e. >±0.5ΔCT (Serre et al., 2008, Jeffries et al., 2012)] in chr4p12 GABAA RNA expression compared to fibroblast genomic DNA in 7 of 16 lines (44%). In contrast, 0 of 11 lines (0%) heterozygous for an exonic SNP in the AKR1C3 gene (chr10p15) showed an imbalance in expression
