As shown in the KEGG enrichment analysis (Figure 5B), Clusters 1, 3 and 4 were enriched in the TGF‐β signalling pathway, mTOR signalling pathway, PI3K‐Akt signalling pathway, autophagy, various metabolic processes (steroid, protein synthesis, and cholesterol metabolism), and neurodegenerative pathways (Parkinson's disease, Alzheimer's disease, and amyotrophic lateral sclerosis). Here, TGFB1 is linked to Parkinson disease.