Furthermore, expression of PD-associated (e.g., SNCA, MAPT) (Klein and Westenberger 2012) and other neurodegenerative disease–associated genes (e.g., BCL2, CLU) (Satou et al. 1995; Killick et al. 2014) were significantly elevated with the inferred disease progression but did not display a significant difference by global comparison between PD patients and aged healthy donors (Supplemental Fig. S3C). Here, SNCA is linked to neurodegenerative disease.