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Project Topic
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The gene therapy pipeline is intransigently linked to vector efficacy. Due to a paucity of vectors capable of harboring large expression cassettes, several rare diseases have little hope of being targets of gene replacement. Here we will push multiple technological boundaries with the focused goal to cure Dravet syndrome (DS), a rare, monogenic neurological disorder. DS is a severe epileptic encephalopathy characterized by infantile onset, refractory seizures, mental, behavior and motor comorbidities, as well as increased risk of sudden death. In most cases, the genetic basis is haploinsufficiency caused by mutation in SCN1A, which encodes a voltage-dependent Na+ channel (NaV1.1). Due to the complex physiopathology of DS, etiological approaches such as gene therapy (GT) have unique chances to obtain a global improvement in the life of these patients. However, several challenges for DS treatment include the large (6 kb) SCN1A cDNA, which precludes efficient expression by some viral vectors, the theoretical possibility that supraphysiological NaV1.1 levels in non-neuronal cells could be harmful, infecting enough neurons in the pertinent regions, and providing long-term therapy. Our approaches will overcome these hurdles and ultimately provide proof of concept for the safety and efficacy of GT for DS. We will use helper-dependent adenovirus (HD-AdV) vectors, which have a >30 kb cloning capacity, allow long-term expression, and have preferential neuronal tropism and/or neuron-restricted expression. These vectors will contain a codon-optimized SCN1A cDNA under the control of regulatable and neuronal-specific promoter sequences. Treatment, via intracerebral vector administration in severely affected DS mice, will be initiated at different ages to determine the impact on neuronal excitability via in vivo and ex vivo electrophysiology. Modification of DS progression will focus on survival, seizures, cognition, behavior and motor abilities. Together, our studies will pave the way for clinical trials for DS and other rare
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