ACE2 and infection: Protein overexpression studies have demonstrated that ACE2 facilitates SARS-CoV-2 infection (Zhou et al., 2020), while mice with engineered human ACE2 are susceptible to infection (Yinda et al., 2021), and it has been suggested that the distribution of ACE2 receptor expression across different tissues contributes to differential virus susceptibility (e.g., lung tissue and alveolar cells) (Zhang et al., 2020a).