|Abstract:||Parkinson’s Disease (PD) is the second most common neurodegenerative disease after Alzheimer’s disease. It affects 1-2% of the total world population with more than 500,000 patients in the US. PD is a progressive disorder that selectively affects the dopaminergic neurons in the substantia nigra of brain. Since dopamine is the neurotransmitter responsible for controlling balance and movement of the body, patients affected by PD experience symptoms such as tremors, bradykinesia, limb rigidity, gait and balance problems. A common pathogenic mechanism in both familial and sporadic forms of PD is the accumulation of the protein α-synuclein in the brain basal ganglia. SNCA, the gene encoding α-synuclein, when mutated or overexpressed causes misfolding of α-synuclein, which forms toxic aggregates known as Lewy bodies, a characteristic pathological finding in PD. There is no cure for PD and the only treatment available is symptomatic therapy. Therefore, there is a critical need to engineer novel approaches for treating PD.
A potential strategy to prevent neurotoxicity in PD is to force the affected cells to produce less toxic isoforms of SNCA by skipping the exons that encode for the domains responsible for aggregation. Thus, one potential approach to treat PD is skipping exon 3 in SNCA, which has been shown to decrease α-synuclein aggregation. We have recently demonstrated that CRISPR-Cas9 base editors can be used to induce exon skipping by mutating the conserved “AG” dinucleotide within the splice acceptor site preceding each exon. Here we demonstrate skipping of exon 3 in the SNCA gene in mammalian cells in culture by A>G and C>T base editors, which decreased SNCA aggregation. We also demonstrate that skipping of SNCA exon 3 can be accomplished using split base editors that are compatible with in vivo delivery. Overall, these results demonstrate development of a novel gene therapy to treat PD.