Enrichment analysis of the 270 marker mRNAs in cluster 4 showed that their functions were significantly enriched in oxidative phosphorylation, ATP metabolic process, nucleoside triphosphate metabolic process, mitochondrial protein complex, mitochondrial inner membrane, inner mitochondrial membrane protein complex, NADH dehydrogenase activity, Parkinson disease, oxidative phosphorylation, and Huntington disease (Figure 7(c)). The gene discussed is ENSG00000254051; the disease is Huntington disease.