Fig 1: Increased excitatory transmission and altered GABA currents in G2019S KI cortical neurons. (A-C) Whole-cell patch-clamp recordings of neurons in DIV21 CTX cultures from KI mice. (A) Example traces of mEPSCs. (B) Quantification of mean mEPSC amplitude and frequency shows no significant difference in amplitude, but significantly higher frequency of events in KI neurons (**p = 0.01 by Student's t-test). (C) Cumulative probability analysis found no significant differences in mEPSC amplitudes, but revealed a significant main effect of genotype and interaction between IEI and genotype (2-way RM-ANOVA, **p = 0.01, ****p = 0.0001, values between 40 and 200 ms were also significant by Bonferroni post-test ***p = 0.001), due to shorter IEIs (indicative of higher frequency) in KI neurons. (D) Cultures were stained (as in Figure 2) for MAP2 (green) and VGluT1 (blue) and PSD-95 (red). Left: 60× 2-times zoom of individual neuron staining. Right: expanded ROI from the 63× image showing synaptic markers overlayed with and without MAP2. Co-clusters are highlighted (white arrow heads). (E) KI neuronal densities were similar to those of NT littermates as were total dendritic areas (not shown), there were no differences (or trends) in the density of VGluT1 clusters, PSD-95 clusters or co-clusters (glutamate synapses). Similarly there were no differences in the density, size or intensity of synapsin 1 (Syn1) clusters, present at all glutamatergic and inhibitory synapses. (F) Example traces of miniature inhibitory post-synaptic currents (mIPSCs). (G) Quantification of mean mIPSC amplitude and frequency shows trends, but no significant differences in event amplitude or frequency of events in KI neurons. (H) Cumulative probability analysis revealed a highly significant interaction (and nearly significant genotype effect) due to increased mIPSC amplitudes in KI neurons (2-way RM-ANOVA, ****p = 0.0001, values between 25 and 35pA were significant by Bonferroni post-test **p = 0.01). There was no significant main effect of genotype on mIPSC IEIs or interaction (despite a trend to higher frequency) in KI neurons.