Atlas of ACE2 gene expression reveals novel insights into transmission of SARS-CoV-2.

The recent pandemic, COVID-19, is caused by a novel coronavirus, SARS-CoV-2, with elusive origin. SARS-CoV-2 infects mammalian cells via ACE2, a transmembrane protein. Therefore, the conservation and expression patterns of ACE2 may provide valuable insights into tracing the carriers of SARS-CoV-2. In this work, we analyzed the conservation of ACE2 and its expression pattern among various mammalian species that are close to human beings. We show that mammalian ACE2 gene is deeply conserved at both DNA and peptide levels, suggesting that a broad range of mammals can potentially host SARS-CoV-2. We further report that ACE2 expression in certain human tissues are consistent with clinical symptoms of COVID-19 patients. Furthermore, we have built the first atlas of ACE2 expression in various common mammals, which shows that ACE2 expresses in mammalian tissues in a species-specific manner. Most notably, we observe exceptionally high expression of ACE2 in external body parts of cats and dogs, suggesting that these household pet animals could be vulnerable to viral infections and/or may serve as intermediate hosts, thus yielding novel insights into the transmission of SARS-CoV-2.