SNCA and Parkinson disease: While the precise mechanisms of protein aggregation-induced neurodegeneration are under scrutiny (Spillantini et al., 1997; Luk et al., 2012a,b; Rodriguez et al., 2015), alpha-synuclein’s pivotal role in Parkinson’s pathology is evident from studies involving intracerebral injections of brain extracts from alpha-synuclein transgenic mice, which induced aggregation and neuropathology in recipients (Luk et al., 2012a,b).