SNCA and Parkinson disease: In fact, the now over 20 genes shown to influence the risk for PD are frequently upstream of α-synuclein expression or proteinopathy links (Billingsley et al., 2018; Chang et al., 2017; Nalls et al., 2014; Simon-Sanchez et al., 2009; Thomas et al., 2023), indicating that various biological mechanisms are interacting to generate a late stage pathology.