To identify neuronal properties affected by KCNJ6 haplotype, we focused on three aspects: morphology, expression of GIRK2, and physiological properties. A detailed analysis of neuronal morphology is essential to rule out differences affecting excitability [45]. Most measures of basic neuronal morphology did not exhibit differences by haplotype, including soma size, circularity, and solidity, which describe the most fundamental aspects of neuron shape (Fig. 3B.a–c). However, neurite area, as determined by βIII-tubulin-staining, reflecting the number and/or branching of neurites per cell, increased in the AF group (p = 0.018; Fig. 3B.d), with example images from individual cell lines in Fig. 3C. Results are plotted for each cell line or aggregated by KCNJ6 haplotype. As predicted by KCNJ6 mRNA expression (Fig. 1J), GIRK2 immunoreactivity was decreased in the AF group (Fig. 3D), measured by puncta counts (p = 0.0012; Fig. 3D.a), puncta circularity (p = 0.007; Fig. 3D.c), and solidity (p = 0.037; Fig. 3D.d) but not puncta size (Fig. 3D.b). No difference was found by sex. These results demonstrate an overall decrease in GIRK2 in neuronal processes in the AF (KCNJ6 variant allele) group.
