Abstract 12541: Development of a Transgenic Rabbit Model of Dravet Syndrome

Abstract

Introduction: Sudden Unexpected Death in Epilepsy (SUDEP) is a leading cause of death in patients with epilepsy. While SUDEP mechanisms are not understood, there is evidence to implicate autonomic dysfunction and cardiac arrhythmias. Loss-of-function variants in SCN1A are linked to Dravet syndrome (DS). Importantly, SCN1A is expressed in both heart and brain in humans and rodents. Studies on Scn1a+/- DS mice and induced pluripotent stem cell (iPSC)-derived cardiac myocytes from DS patients show altered cardiac electrophysiology that serves as substrates for arrhythmias. However, no mouse or iPSC model can completely replicate the human DS phenotype. Hypothesis: Cardiac arrhythmias contribute to the mechanisms of SUDEP in a rabbit model of DS. Methods: We generate a New Zealand White (NZW) rabbit Scn1a deletion model using CRISPR-Cas9 gene editing. Rabbits were tested using video EEG/ECG telemetry as well as surface ECG under anesthesia. Optical mapping studies were performed in isolated hearts and patch clamp electrophysiology was performed in acutely isolated cardiac myocytes. Results: NZW Scn1a-/- kits died by postnatal day (P) 7-9 and showed bradycardia, long QT intervals, and AP prolongation. Cardiac myocytes isolated from NZW Scn1a+/- kits showed increased late sodium current compared to WT. We did not observe behavioral seizures or arrhythmias in NZW Scn1a+/- rabbits, which live normal life spans and breed normally. These data suggested, like mouse models, that the DS rabbit phenotype may be background strain dependent. To test this hypothesis, we crossed Scn1a+/- NZW rabbits to the Dutch Belted (DB) strain. We found that F1:NZW x DB Scn1a+/- rabbits have spontaneous seizures as well as pre- and post-ictal cardiac arrhythmia as assessed by video/EEG/ECG telemetry. Approximately 22% of the kits undergo premature death. Severe seizures are observed in adult animals, but to date no adults have died during seizures. Conclusions: F1:NZW x DB Scn1a+/- rabbits model DS in terms of seizures and SUDEP and are an optimal model to investigate neuro-cardiac mechanisms of SUDEP as well as to develop novel therapeutics for DS. To our knowledge, this is the first transgenic large animal model of a developmental and epileptic encephalopathy