Abstract Body

Although alpha-synuclein is implicated in the pathogenesis of Parkinson’s disease and related disorders, it remains unclear whether specific conformations or levels of alpha-synuclein assemblies are toxic and how they cause progressive loss of human dopaminergic neurons. To address this issue, we used iPSC-derived dopaminergic neurons where endogenous alpha-synuclein was seeded with fibrils generated de novo or amplified from homogenates of brains affected with Parkinson’s disease (n=3) or multiple system atrophy (n=5). We showed that progressive neuronal loss in this model is dependent on alpha-synuclein levels and the conformation induced by specific strains. Transcriptomic analysis and isogenic correction of alpha-synuclein levels revealed the central role of alpha-synuclein in triggering neuronal death. We used proximity-dependent biotinylation in living cells and identified 56 differentially interacting proteins with endogenously assembled alpha-synuclein. We found that aggregates triggered with brain amplified fibrils evaded the Parkinson’s disease-associated deglycase DJ-1 and DJ-1 knockout enhanced aggregate-induced cell death in human dopaminergic neurons. Our results define parameters for iPSC-based modelling of alpha-synuclein pathology using disease-relevant fibrils and demonstrate how Parkinson’s disease-associated genes influence the phenotypic manifestation of strains in human neurons.