Gene therapy targeting striatal dysfunction for Parkinson’s disease

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Project Summary Parkinson’s disease (PD) is characterized by motor abnormalities primarily caused by loss of midbrain dopamine (DA) cells, which significantly modulate striatal neurons. DA depletion is thus associated with altered function of striatal projection neurons (SPNs). SPN dysregulation is evidenced by significant morphological and physiological changes, as shown in numerous ex-vivo and in-vivo studies. Furthermore, our studies in primate models and patients have revealed pathological hyperactivity of SPNs. A key contributor to this hyperactivity is the excitatory glutamate signaling. This has been recently demonstrated with selective striatal blockade of NMDARs. The block reduces hyperactivity and controls the altered neuronal responses to DA replacement. Furthermore, it has significant effects on parkinsonian motor symptoms. Therefore, data support that reducing NMDAR signaling on SPNs may have therapeutic effects in PD. Given the largely conserved structure of NMDARs across brain regions, pharmacotherapies are generally limited by widespread drug actions. We recently tested gene therapies targeting NMDAR subunit expression in the striatum. Our preliminary data generated with exploratory tests in rodents showed that, indeed, gene knockdown (KD) of GluN2 subunits may offer a novel therapeutic strategy to improve motor symptoms of PD. Thus, data support advanced preclinical studies of GluN2 gene KD in non-human primates (NHP) for extensive evaluation of this gene therapy in the gold-standard model of PD. In this project we plan to demonstrate “efficacy” of GluN2 gene KD for various motor and cognitive symptoms of PD. The studies will use primate MPTP models and shRNA viral vector injections in the striatum to suppress gene expression of GluN2 in SPNs. A battery of motor and cognitive tests will be used over a prolonged term post-virus administration to determine stable, chronic effects. Taking advantage of PD modeling in NHPs, different disease stages will also be evaluated. We also include additional outcome measures to evaluate “safety” of targeting the proper assembly of NMDAR in the striatum. Finally, we will validate this gene therapy with electrophysiology data demonstrating specific effects on altered SPN activity, and applying optogenetics. for cell resolution in NHP recordings. Overall, the research strategy in this proposal is based on optimal animal models, viral vectors of proven efficiency, extensive testing of motor, cognitive, and other behaviors, and precision tools for electrophysiology. We expect that results of these studies demonstrate efficacy and safety with translational data to support further development of striatal GluN2 gene therapy for PD.