Figure 1.

The expression of the ACE2 and interferon gene depends on the methylation rate of the CpG islands in the DNA promotor sequence. Susceptible individuals, mostly men, the elderly, and smokers, show a hypomethylation pattern of the ACE2 and interferon genes (lower part), whereas women, children, and non-smokers show DNA hypermethylation and lower expression of ACE2 and interferon proteins (upper part). The higher presence of ACE2 on epithelial cells and interferon makes people more susceptible to SARS-CoV-2 infection and increases disease severity, whereas a low presence of ACE2 and interferon seems to offer disease protection.