Modeling gene-specific therapy of intractable childhood epileptic encephalopathy

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Project Summary Early onset pharmacoresistant epileptic encephalopathies (EE) are often caused by de novo variants in neuronal protein genes. Dynamin 1 (encoded by DNM1), a key neuron-specific GTPase involved in endocytosis, is a prototypical example of both the disease and its intractable nature, whereby pathogenic dominant-negative missense mutations cause intractable seizures, developmental delays and cognitive impairment. We study the Dnm1Ftfl (“fitful”) model of DNM1 EE, which mimics key disease features and provides a compelling platform to develop and test gene therapies. For DNM1 and other genetic EE where the mutation exerts a genetically dominant effect, supplying the wildtype copy of the mutated product is expected to be of limited, if any, benefit. Thus, elimination or alteration of the mutated product is a more logical recourse. We have begun to model dominant negative gene silencing therapy via microRNAs shuttled through neurotrophic self-complementary adeno-associated viral (AAV) vectors for the treatment of genetically dominant EE, utilizing the Dnm1Ftfl mouse model. We hypothesize that this approach will rescue the core disease phenotypes, including lethal seizures and major comorbidities and provide a more permanent therapy option. Preliminary treatment of homozygous fitful mice via intracerebroventricular neonatal injection, remedied developmental deficits, decreased severe seizure-associated lethality, and extended lifespan. To propel this project forward, our aims are to: 1) optimize our rescue of the disease-defining core phenotypes of fitful mice towards full rescue; 2) identify neuronal structural and functional defects that culminates in the core phenotypes; and 3) assess rescue of neuronal structural and functional defects with scAAV9-miDnm1a treatment. Successful completion of these aims will inform on a possible treatment for both the seizure phenotype, and associated developmental delays while providing a generalizable approach for other similar EE models, informing future clinical applications.