SNCA and Parkinson disease: In one study, membrane-associated sodium dodecyl sulfate soluble full-length 17 kDa and high molecular weight alpha-synuclein species were only slightly increased in PD patients as compared to healthy subjects (Tong et al., 2010) whereas in another study total alpha-synuclein was suggested to be 11-fold increased in fresh frozen protein extracts (Shehadeh et al., 2009).