Gene therapies alleviate absence epilepsy associated withScn2adeficiency in DBA/2J mice

Mutations in the voltage-gated sodium channel geneSCN2A, which encodes the Na_V1.2 channel, cause severe epileptic seizures. Patients withSCN2Aloss-of-function (LoF) mutations, such as protein-truncating mutations, often experience later-onset and drug-resistant epilepsy, highlighting an urgent unmet clinical need for new therapies. We previously developed a gene-trapScn2a(Scn2a^gt/gt) mouse model with a global Na_V1.2 reduction in the widely used C57BL/6N (B6) strain. Although these mice display multiple behavioral abnormalities, EEG recordings indicated only mild epileptiform discharges, possibly attributable to the seizure-resistant characteristics associated with the B6 strain. To enhance the epileptic phenotype, we derived congenicScn2a^gt/gtmice in the seizure-susceptible DBA/2J (D2J) strain. Notably, we found that these mice exhibit prominent spontaneous absence seizures, marked by both short and long spike-wave discharges (SWDs). Restoring Na_V1.2 expression in adult mice substantially reduced their SWDs, suggesting the possibility ofSCN2Agene replacement therapy during adulthood. RNA sequencing revealed significant alterations in gene expression in theScn2a^gt/gtmice, in particular a broad downregulation of voltage-gated potassium channel (K_V) genes, including K_V1.1. The reduction of K_V1.1 expression was further validated in human cerebral organoids withSCN2Adeficiency, highlighting K_V1.1 as a promising therapeutic target for refractory seizures associated withSCN2Adysfunction. Importantly, delivery of exogenous human K_V1.1 expression via adeno-associated virus (AAV) in D2JScn2a^gt/gtmice substantially reduced absence seizures. Together, these findings underscore the influence of mouse strain on seizure severity and highlight the potential of targeted gene therapies for treatingSCN2Adeficiency-related epilepsies.