ACE2 and COVID-19: Since the SARS-CoV-2 must bind to angiotensin-converting enzyme 2 (ACE2) to enter and infect host cells in humans (Zhou et al., 2020a; Shang et al., 2020b; Walls et al., 2020b; Wang et al., 2020e; Lan et al., 2020), the expression (partly determined by the stage of development) and body localization of ACE2 are important to understand COVID-19 symptoms and disease (Hamming et al., 2004; Yang et al., 2020b; Ni et al., 2020) (Figure 1A).