SNCA and Parkinson disease: The molecular basis of PD is inextricably linked to several key processes: the abnormal aggregation of alpha-synuclein, culminating in the formation of Lewy bodies; dysregulation of the ubiquitination process; and the emergence of oxidative stress as a consequence of mitochondrial dysfunction, which leads to the accumulation of pathological alpha-synuclein and the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS).