This study focused on the effect of an AUD- and endophenotype-linked KCNJ6 haplotype on neuronal function, with a goal of identifying mechanisms that could eventually drive therapeutic strategies. To retain the appropriate genetic background for individuals with AUD, we selected subjects from the NIAAA/COGA Sharing Repository, using both KCNJ6 haplotype and alcohol dependence as criteria (Table 1). By preparing iPSC from these subjects and inducing them to model excitatory neurons, we identified differences in KCNJ6 mRNA levels and GIRK2 immunoreactivity in individuals with variant KCNJ6 haplotypes. Gene expression differences predicted effects on neuronal signaling including synaptic function. The KCNJ6 haplotype was also associated with differences in neuron projection area and membrane excitability, but not in other measures of neuronal differentiation. Surprisingly, we found that ethanol exposure led to increased KCNJ6 mRNA and GIRK2 expression, paralleled by reduced or eliminated morphological and physiological differences. Reversal of KCNJ6 haplotype effects by ethanol could also be mimicked by overexpressing GIRK2. These results demonstrate that genetic variants enhancing risk of AUD, even if they do not alter protein sequence, can trigger neuronal mechanisms at the cellular level mirroring or predicting endophenotypes, here ERO, linked with AUD behavior.
