To directly compare the two MOR genotypes in identical genetic backgrounds, eliminating the impact of secondary genetic variation, we generated two sets of isogenic human stem cell lines using CRISPR/Cas9 gene targeting. We first targeted the MOR locus in a well-characterized human H1 ES cell line, which is homozygous for the major allele (A118), using a sgRNA targeting the antisense DNA strand along with a 140bp single stranded oligodeoxynucleotide carrying G118 (Fig. 2A–B). Simultaneously, we converted one patient iPS cell line which is homozygous for the G118 allele to a homozygous A118 genotype with an alternative strategy utilizing direct transduction of guide RNA and Cas9 protein into the subject cell line (Fig. 2C–D). We isolated two clones (Supplemental Fig. 2A–C) with no detectable off-target effects from each targeting scheme. Inhibitory iN cells generated from isogenic lines are positive for MAP2, Synapsin and VGAT (Fig. 2E–F) and exhibit similar intrinsic membrane properties (Supplemental Fig. 2D–E) as well as sIPSC and AP properties in both genotypes (Supplemental Figs. 2F–G, Supplemental Figs. 3A–C).The densities and sizes of synapses were also not significantly different
