APOD and Parkinson disease: Supplementary Table S1 lists the 55 upregulated genes. Moreover, Supplementary Table S2shows the 50 downregulated genes. A heat map depicted that these DEGs could distinguish PD patients from healthy individuals (Figure 4E). We further intersected the upregulated genes with all other marker genes in the cell–cell communication network. As a result, five upregulated marker genes were identified, including ANGPT2, APOD, HSP90AA1, HSPA1A, and PDE1C (Figure 4F). Figure 4G shows their ligand–receptor interactions in all cell clusters.