Novel Gain of Function Mouse Model of KCNT1-Related Epilepsy
KCNT1-related epilepsy is an autosomal dominant neurodevelopmental disorder resulting from de novo pathogenic variants in KCNT1 which encodes a sodium-gated potassium channel. These variants are associated with Epilepsy of Infancy with Migrating Focal Seizures (EIMFS) and Autosomal Dominant Nocturnal Frontal Lobe Epilepsy (ADNFLE). At least 64 human KCNT1 variants have been reported, the majority are gain-of-function and each has unique electrophysiological and epileptic characteristics. A multi-disciplinary collaboration generated a novel mouse model (C57BL/6-Kcnt1em1Bryd) that carries the G269S variant corresponding to the human G288S variant located within the coding region of the channel pore. We characterized network excitability of cultured cortical neurons from all three genotypes, since many KCNT1 mouse models require homozygosity for seizure detection. Kcnt1+/G269S neurons exhibited sustained hyperexcitability and hypersynchronous bursting versus Kcnt1+/+ controls, while Kcnt1G269S/G269S neurons showed early excessive bursting followed by network collapse by 28 days-in-vitro, suggesting excitotoxicity. Therefore, behavioral comparisons were conducted between Kcnt1+/G269S and Kcnt1+/+ mice including developmental milestones, motor and cognitive abilities, respiratory physiology, and seizure susceptibility. Kcnt1+/G269S displayed no abnormal gross motor abilities, poor coordination, erratic breathing, and increased apneas, as functional outcome measures. Critically, Kcnt1+/G269S were more susceptible to thermal-induced seizures in early life. In summary, these data: (i) provide a novel mouse model of KCNT1-related epilepsy, (ii) provide strong in vitro evidence of neuronal hyperexcitability, (iii) illustrate early-life seizures as a functional outcome measure, and (iv) lay the groundwork for future analysis of neural activity in vivo and modeling circuit level dynamics in vitro, in vivo, and in silico.