Authors :
Presenting Author: Mona Safari, PhD Student – Fralin Biomedical Institute
Goeun Jang, MSN – Fralin Biomedical Institute
Matthew Weston, Ph.D. – Fralin Biomedical Institute
Amy Shore, Ph.D. – Fralin Biomedical Institute
Jessica Urbanczyk, MD – Fralin Biomedical Institute
Pranav Mathkar, Ph.D. Student – Fralin Biomedical Institute
Rationale:
Variants in the KCNT1 gene, which encodes a Na+-activated-K+ channel, are known to cause severe epileptic conditions, including Epilepsy of Infancy with Migrating Focal Seizures (EIMFS) and Sleep-Related Hypermotor Epilepsy (SHE). These forms of epilepsy are characterized by early onset, resistance to conventional medications, and significant impact on patient quality of life. KCNT1 mutations result in a gain-of-function (GOF) effect, leading to increased K+ efflux, neuronal network impairment, and seizure activity. Previous studies on variants such as Y777H, which primary causes SHE, suggest selective impairment of GABAergic neurons, which become hypoexcitable, while glutamatergic neurons remain unaffected. In contrast, studies on the R455H variant, which primarily causes EIMFS found that both GABAergic and glutamatergic neurons are affected, resulting in widespread network dysfunction.
Methods:
R428Q, which primarily causes EIMFS, is one of the most recurrent KCNT1 variants, but is unstudied in an animal model. To address this, we created a R428Q knock-in mouse model. EEG recordings showed that homozygous mice had frequent generalized seizures, whereas heterozygous mice had rare seizures. To investigate the cellular basis of these seizures, we explored the development of excitatory neuron excitability in Kcnt1 R428Q mice. We injected these mice with a CamkII-AAV8 virus at P0-P2 to target excitatory neurons and subsequently measured cortical excitability at early developmental stages (P14-P25) and in adulthood (P35-P45).
Results:
Our results reveal that the excitatory neurons in Kcnt1 R428Q mice are hyperexcitable, with significantly increased action potential firing rates at high levels of current injection, but no changes in subthreshold excitability. This hyperexcitability could contribute to the severe seizure phenotype observed in these mice, indicating a mechanism of network dysfunction different from that seen in other Kcnt1 variants. Conclusions:
Future experiments will determine whether the excitability of cortical inhibitory neurons is also impaired in this model and how each neuron type contributes to seizures. These findings will provide new insights into the pathophysiology of KCNT1-related epilepsies and guide future efforts to develop targeted therapeutic strategies for these devastating conditions.Funding: R01NS130042