Impact of the Kcnt1 R428Q Mutation on Neuronal Subtype Excitability and Therapeutic Approaches in a Mouse Model

Abstract

Gain-of-function (GOF) mutations in KCNT1, encoding the sodium-activated potassium channel KNa1.1, are associated with severe developmental and epileptic encephalopathies, including epilepsy of infancy with migrating focal seizures (EIMFS). However, the cell-type–specific mechanisms underlying seizure generation and effective targeted therapies remain unclear. Here, we generated a mouse model carrying the Kcnt1-R409Q (human R428Q) mutation and found that this GOF variant selectively reduces the excitability of somatostatin (SST) interneurons, while excitatory neurons and parvalbumin (PV) interneurons remain largely unaffected. Selective expression of the mutation in medial ganglionic eminence (MGE)-derived interneurons was sufficient to recapitulate the seizure phenotype. We next tested a selective, high-potency KCNT1 inhibitor and found that it robustly suppressed seizures in vivo. Electrophysiological recordings revealed that KCNT1 inhibition increased interneuron excitability, reversing the hypoexcitability observed in mutant mice, while excitatory neuron function remained unchanged. To assess whether this approach extends to other channelopathies, we evaluated the compound in a Dravet syndrome model caused by loss-of-function of the NaV1.1 sodium channel (SCN1A). Treatment significantly reduced seizure frequency, decreased SUDEP incidence, and improved survival. At the cellular level, KCNT1 inhibition enhanced PV interneuron excitability, indicating a shared mechanism across distinct genetic epilepsies. Together, these findings identify KCNT1 as a key regulator of neuronal excitability and demonstrate that its inhibition can modulate circuit function and suppress seizures. This work highlights the potential of KCNT1 inhibition as a therapeutic approach for multiple forms of drug-resistant epilepsy.