In summary, we found correlated gene expression of four genes encoding GABAA receptor subunits located in a 1.4 Mb region of chr4p12, with GABAA gene expression levels significantly associated with a tag-SNP for this region that has been linked to AD. The endophenotype of low mRNA expression for the chr4p12 GABAA gene cluster in this iPSC in vitro model may be a more useful marker than the diagnosis of AD to identify functional polymorphisms in this region. Our results suggest that such functional variants may produce behavioral effects relevant to AD via effects on GABAA gene expression in the developing nervous system. This work supports the utility of iPSCs as a model system to explore previously unknown molecular effects of genetic variation associated with risk for neuropsychiatric disease. Limitations of such models include the need to examine multiple donor and iPSC lines to address inter- and intra-cell line variability and the limited ability of cultures to replicate the prolonged and complex development of the human nervous system in vivo. Finally, our finding that nearly half of iPSC lines produce neural
