Many studies have focused on gut microbiota as a regulator of α-synuclein misfolding and transmission towards the brain via the vagus nerve (Sampson et al., 2016; Bhattacharyya et al., 2019; Chiang and Lin, 2019) and results have revealed differences in gut microbiota between PD patients and healthy controls suggesting a role of the gut microbiome in PD pathogenesis (Scheperjans et al., 2015; Unger et al., 2016; Lin A. et al., 2018). The gene discussed is SNCA; the disease is Parkinson disease.