Furthermore, pathologic α-synuclein aggregates are first detected in the gastrointestinal tract and submandibular glands during the prodromal stage of PD rather than in the SN [9,10], thereby leading to the hypothesis that environmental insults (i.e., toxins or pathogens) may first affect the ENS, causing local α-synuclein aggregation. The gene discussed is SNCA; the disease is Parkinson disease.