Joint analysis revealed 43 tissue-conserved genes (Fig. 4G and Supplementary Table 3), of which MDH2 and OGDHL, which encode key metabolic enzymes of TCA cycle (Figs. 1D, 2K, 4H and S1C), were significantly downregulated in both PD transcriptome data and cell model. The gene discussed is MDH2; the disease is Parkinson disease.