MTHFR and COVID-19: In both shared gene lists, the top positions were occupied by CLCN6, MTHFR, C10orf107, FES, and FURIN. Gene expression analysis of shared gene sets highlighted the sigmoid colon as the most relevant to the association of COVID-19 death (Figure 2A), suggesting that the disruption of gut homeostasis in the course of COVID-19 (Varshney et al., 2021) may contribute to COVID-19 mortality disproportionally.