TaqMan (Life Technologies) FAM- and VIC-labeled genotyping probe and primer sets targeting exonic SNPS in GABRG1 (rs976156, C__8723970_1_), GABRA2 (rs279858, C__2073557_1_), GABRA4 (rs7660336, C__11278069_10), GABRB1 (rs10028945, C__2119811_30), and AKR1C3 (rs12529, C__8723970_1_) were used to examine allelic expression bias of the chr4p12 GABAA cluster. 20µL TaqMan reactions containing 2µL of cDNA from iPSC-derived neural cells or genomic DNA from human fibroblasts were carried out in triplicate using Universal Master Mix II (Life Technologies) and an Applied Biosystems 7500 instrument. ΔCT values were generated as the difference between FAM- and VIC-probes for the iPSC-derived neural cell cDNA samples or heterozygote fibroblast gDNA for each SNP. Consistent with other studies (Lin et al., 2012, Serre et al., 2008), we used a threshold for allelic imbalance as a 50% increase in RNA from one of the two alleles (i.e. ±0.5ΔCT).
