SNCA and Parkinson disease: The SNCA rs356219 polymorphism codes for α-synuclein levels, with the G risk allele associated with higher transformed plasma α-synuclein (Mata et al., 2010; Emelyanov et al., 2018), reduced striatal binding potential (Huertas et al., 2017), and increased risk for PD (Goris et al., 2007; Trotta et al., 2012; Zhang et al., 2018).