SNCA and Parkinson disease: Vagus nerve-mediated translocation of a-syn aggregations from the gut to the brain was observed after injections of human recombinant a-syn from PD patients into rats’ intestinal walls (Holmqvist et al., 2014), or the peritoneal cavity of a-synuclein overexpressing (ASO) mice (Breid et al., 2016).