Towards Novel Therapies For KCNT1-Associated Epileptic Encephalopathy
1 Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Bonn, Germany
2 Institute for Molecular and Behavioral Neuroscience, University of Cologne, Cologne, Germany
3 Institute for Experimental Epileptology and Cognition Research, University of Bonn, Bonn, Germany
4 Center for Molecular Neurobiology Hamburg (ZMNH), Hamburg, Germany
5 Fraunhofer Institute for Translational Medicine and Pharmacology, Hamburg, Germany
6 CECAD, University of Cologne, Cologne, Germany
Altered brain development through ion channelopathies can lead to lifelong cognitive deficits and therapy-refractory epilepsy. Gain-of-function (GoF) mutations in KCNT1, encoding sodium-gated KNa1.1 (Slack) potassium channels, are associated with early-onset therapy-resistant epilepsies, intellectual disability, and behavioral changes. However, therapeutic options for early infantile epileptic encephalopathies are limited and no specific KCNT1 blockers are available for patients. To address this urgent need, we tested identified KCNT1 blockers in vivo to prevent, attenuate or normalize epileptogenesis and associated comorbidities.
We identified candidate blockers in a high throughput screen (HTS) for repurposing FDA-approved drugs. Furthermore, we generated two knock-in mouse lines with patient-derived KCNT1 mutations exhibiting distinct GoF levels. Using telemetric electrocorticogram, multichannel-depth recordings, acute slice electrophysiology and behavioral tests, we characterized mutation-induced alterations and observed blocker effects. Mutant mice developed spontaneous generalized seizures, showed epilepsy-typical hippocampal changes such as reactive astrogliosis, increased perineuronal nets and neuropeptide Y (NPY) expression in the dentate gyrus. These were associated with increased locomotion, reduced anxiety, impaired memory, and altered interictal network activities, including reduced cortical theta power during sleep and wakefulness. As our HTS identified potent, brain-permeable KCNT1 blockers validated on human and mouse channels in vitro, we characterized their effects on ictal and interictal network activities. Chronic treatment in adult epileptic mice did not rescue seizure phenotypes suggesting that treatment must target epileptogenesis period during brain development. In summary, our results confirmed the face and etiological validity of our KCNT1 epilepsy models, which are now being used to characterize disease pathophysiology and test novel treatments.