The role of α-synuclein in PD is not clear, but it is presumed to play a central pathogenic role, as demonstrated by the fact that mutations or duplications/triplications of the gene (SNCA) cause rare familial forms of PD11, coupled with many independent studies showing the detrimental effects of manipulating α-synuclein in cell and animal models12,13. Here, SNCA is linked to Parkinson disease.