An alternative hypothesis for the interaction of SNCA eQTL and an opportunistic pathogen is that eQTL controls alpha-synuclein concentration in the cell, bacteria triggers misfolding and aggregation of alpha-synuclein, and since misfolding and aggregation is directly dependent on the concentration of alpha-synuclein in the cell43, individuals with certain SNCA eQTL genotypes are at higher risk of developing PD pathology from gut-derived insults. This evidence concerns the gene SNCA and Parkinson disease.