Furthermore, several studies have described elevated levels of oligomeric α-synuclein in cerebrospinal fluid (CSF) in PD patients compared to control subjects (Tokuda et al., 2006; Park et al., 2011; Aasly et al., 2014; Hansson et al., 2014; Parnetti et al., 2014). Here, SNCA is linked to Parkinson disease.