Isogenic human iPSC pairs reveal a neuronal subtype-specific and genetic background-independent mechanism of SCN1A epilepsy

Over 1250 mutations in SCN1A , the voltage-gated sodium channel gene Nav1.1, are associated with seizure disorders including GEFS+ and Dravet Syndrome (DS). To evaluate how a specific mutation, independent of genetic background, causes seizure activity we generated two pairs of isogenic human iPSC lines by CRISPR/Cas9 gene editing. One pair is a control line from an unaffected sibling, and the mutated control carrying the GEFS+ K1270T SCN1A mutation. The second pair is a GEFS+ patient line with the K1270T mutation, and the corrected patient line. By comparing the electrophysiological properties in inhibitory and excitatory iPSC-derived neurons from these pairs, we found the K1270T mutation causes gene dosage-dependent and cell type-specific alterations in sodium current density and evoked firing, resulting in hyperactive neural networks. We also identified differences associated with genetic background and interaction between the mutation and genetic background. Dual isogenic iPSC-derived neuronal cultures provide a novel platform for developing patient-specific anti-seizure therapies.