Pathway analysis of subpopulation marker genes showed over-representation of key cellular processes known to be implicated in PD pathology, such as energy production (e.g., ATP1B1, ENO1 and ENO2), cholesterol metabolism (e.g., DHCR24, CYB5R3 and HDLBP), iron transport (e.g., FTL, FTH1 and SLC22A17), oxidative stress (e.g., CHCHD10, CLU and SOD1) and transcripts linked to the UPR (including chaperones, e.g., HSPA8 and HSP90AA1) (Fig. 2D, E; Supplementary Fig. 3; Supplementary Table 6). This evidence concerns the gene HSPA8 and Parkinson disease.