SNCA and Parkinsonism: α-synuclein has been linked to PD pathology by studies showing that SNCA mutations, including the A53T mutation, cause autosomal dominant PD (Polymeropoulos et al., 1997), and that α-synuclein is a risk factor for idiopathic PD (International Parkinson Disease Genomics Consortium, Nalls, 2011).