Abstracts

Rationale: Mutations in DNM1, encoding a GTPase involved in endocytosis, has been implicated in epileptic encephalopathy (EE). Dnm1^Ftfl/Ftfl mice model the severe intractable seizure and comorbidities observed in patients with DNM1 mutations. Due to the dominant negative nature of DNM1 and Dnm1^Ftfl mutations, a possible strategy is to eliminate the toxic allele utilizing a microRNA (scAAV9-miDnm1a), hypothesizing that this will at least alleviate the lethal seizure phenotype, and provide more permanent therapy. Methods: Dnm1^Ftfl/Ftfl mice were treated with scAAV9-miDnm1a, or saline via a single intracerebroventricular injection containing ~1.85x10¹¹ viral particles at birth. Knockdown was assessed via a RT-PCR restriction enzyme assay. Survival and development were observed daily.  Results: Dnm1^Ftfl/Ftfl(n= 9) start to fall behind heterozygous (n= 12) and wildtype (n= 12) littermates significantly in growth at postnatal day 10 (P10) (p= 0.0028; p= 0.0041, respectively), gradually regressing until death before weaning. Treatment with scAAV9-miDnm1a (n= 10) improved this growth deficit observed in Dnm1^Ftfl/Ftfl, but did not rescue growth to wild type and heterozygous levels. Notably, treatment with scAAV9-miDnm1a eliminated the severe ataxia, appeared to have decreased seizure occurrence, and extended the lifespan of Dnm1^Ftfl/Ftfl mice by 4-5 days on average with 30% of the treated animals living past weaning.  Conclusions: While this study is still in preliminary stages, there is enough evidence to suggest a plausible treatment approach not only for DNM1 EE but other EE mutations that progress during the early postnatal period. If successful, this study would pioneer the potential use of AAV9-mediated gene silencing therapy for EE patients carrying gain-of-function or dominant negative EE mutations. Funding: NIH R37 NS031348