I. Injection of Sup35 fibrils into the striatum of wild-type mice caused α-synopathy and PD-like motor impairment.II. In vitro and in vivo, Sup35-seeded α-syn fibrils outperformed pure α-syn fibrils in terms of seeding activity and neurotoxicity. These data suggest that the yeast prion protein Sup35 causes α-synopathy in PD. This evidence concerns the gene PRNP and Parkinson disease.