Reduced GIRK2 expression is predicted to affect the excitability of neurons. As expected, we found no differences in membrane capacitance, membrane resistance, spontaneous excitatory postsynaptic potential (sEPSC) frequencies or amplitudes, or spontaneous action potential (AP) firing (Fig. 3F). However, we observed increased excitability in the AF group (p = 1.2 × 10–5, Fig. 3G). Less current injection, using a ramp technique, was required for the AF group to shift the resting membrane potential (RMP) of neurons held at −65 mV, producing more AP firing, compared with the UN group (p = 2.0 × 10–9, Fig. 3G.d). Therefore, the KCNJ6 variant haplotype group (AF) exhibited increased neurite area, reduced neurite GIRK2 expression, and greater excitability. Other neuronal properties were unchanged, suggesting that overall neuron differentiation status was similar.
