AAV-mediated interneuron-specific gene replacement for Dravet syndrome

Abstract

AbstractDravet syndrome (DS) is a devastating developmental epileptic encephalopathy marked by treatment-resistant seizures, developmental delay, intellectual disability, motor deficits, and a 10-20% rate of premature death. Most DS patients harbor loss-of-function mutations in one copy ofSCN1A, which has been associated with inhibitory neuron dysfunction. Here we developed an interneuron-targeting AAV humanSCN1Agene replacement therapy using cell class-specific enhancers. We generated a split-intein fusion form ofSCN1Ato circumvent AAV packaging limitations and deliverSCN1Avia a dual vector approach using cell class-specific enhancers. These constructs produced full-length NaV1.1 protein and functional sodium channels in HEK293 cells and in brain cellsin vivo. After packaging these vectors into enhancer-AAVs and administering to mice, immunohistochemical analyses showed telencephalic GABAergic interneuron-specific and dose-dependent transgene biodistribution. These vectors conferred strong dose-dependent protection against postnatal mortality and seizures in two DS mouse models carrying independent loss-of-function alleles ofScn1a,at two independent research sites, supporting the robustness of this approach. No mortality or toxicity was observed in wild-type mice injected with single vectors expressing either the N-terminal or C-terminal halves ofSCN1A, or the dual vector system targeting interneurons. In contrast, nonselective neuronal targeting ofSCN1Aconferred less rescue against mortality and presented substantial preweaning lethality. These findings demonstrate proof-of-concept that interneuron-specific AAV-mediatedSCN1Agene replacement is sufficient for significant rescue in DS mouse models and suggest it could be an effective therapeutic approach for patients with DS.