Widespread transneuronal propagation of α-synucleinopathy triggered in olfactory bulb mimics prodromal Parkinson’s disease

Parkinson's disease (PD) is characterized by the progressive appearance of intraneuronal Lewy aggregates, which are primarily composed of misfolded α-synuclein (α-syn). The aggregates are believed to propagate via neural pathways following a stereotypical pattern, starting in the olfactory bulb (OB) and gut. We hypothesized that injection of fibrillar α-syn into the OB of wild-type mice would recreate the sequential progression of Lewy-like pathology, while triggering olfactory deficits. We demonstrate that injected α-syn fibrils recruit endogenous α-syn into pathological aggregates that spread transneuronally over several months, initially in the olfactory network and later in distant brain regions. The seeded inclusions contain posttranslationally modified α-syn that is Thioflavin S positive, indicative of amyloid fibrils. The spreading α-syn pathology induces progressive and specific olfactory deficits. Thus, we demonstrate that propagating α-syn pathology triggered in the OB is functionally detrimental. Collectively, we have created a mouse model of prodromal PD.