Disruption of the autism-associated gene SCN2A alters synaptic development and neuronal signaling in patient iPSC-glutamatergic neurons

SUMMARY SCN2A is an autism spectrum disorder (ASD) risk gene and encodes a voltage-gated sodium channel. However, the impact of autism-associated SCN2A de novo variants on human neuron development is unknown. We studied SCN2A using isogenic SCN2A -/- induced pluripotent stem cells (iPSCs), and patient-derived iPSCs harboring a p.R607* or a C-terminal p.G1744* de novo truncating variant. We used Neurogenin2 to generate excitatory glutamatergic neurons and found that SCN2A +/ p . R607 * and SCN2A -/- neurons displayed a reduction in synapse formation and excitatory synaptic activity using multielectrode arrays and electrophysiology. However, the p.G1744* variant, which leads to early-onset seizures in addition to ASD, altered action-potential dynamics but not synaptic activity. Proteomic and functional analysis of SCN2A +/ p . R607 * neurons revealed defects in neuronal morphology and bioenergetic pathways, which were not present in SCN2A +/ p . G1744 * neurons. Our study reveals that SCN2A de novo variants can have differential impact on human neuron function and signaling. HIGHTLIGHTS - Isogenic SCN2A -/- neurons display intrinsic hyperexcitability and impaired excitatory synapse function - SCN2A +/ p . R607 * variant reduces excitatory synapse function in patient neurons - C-terminal SCN2A +/ p . G1744 * variant enhances action potential properties but not synaptic transmission in patient neurons - SCN2A +/ p . R607 * variant display impacts on morphological and bioenergetic signaling networks through proteomic and functional analysis eTOC - Brown et al. examined Autism-associated SCN2A variants using patient-derived iPSC NGN2-neurons. They discover that genetic variants differentially impact neuronal development and synaptic function, and highlight neuronal and bioenergetic signaling networks underlying SCN2A loss-of-function.