SNCA was significantly downregulated in two independent datasets (Fig. 2A-B), SLC31A1, SLC31A2 and MT4 are not significantly differentially expressed in the GSE176405 dataset (Figure S1) (G1 group and red represent healthy samples, G2 group and blue represent COVID-19 samples, P < 0.05 and FC > 1.50 or < 0.67 is considered to have significant differences). Here, MT4 is linked to COVID-19.