SNCA and Parkinson disease: It is known that duplication or triplication of the SNCA gene accelerates the onset and progression of PD symptoms (Singleton et al., 2003), and even nonmutated WT α-Syn can cause dopamine neuronal cell death or PD-like motor deficits depending on its expression level (St Martin et al., 2007; Oliveras-Salvá et al., 2013; Richter et al., 2023).