Non-neuronal expression of SARS-CoV-2 entry genes in the olfactory system suggests mechanisms underlying COVID-19-associated anosmia

A subset of COVID-19 patients exhibit altered olfactory function. Here we analyze bulk and single cell RNA-Seq datasets to identify cell types in the olfactory epithelium and olfactory bulb that express cell entry molecules that mediate infection by SARS-CoV-2 (CoV-2), the causal agent in COVID-19. We find that samples from whole olfactory mucosa in species including mouse and human express two key genes involved in CoV-2 entry, ACE2 and TMPRSS2. However, neither olfactory sensory neurons nor olfactory bulb neurons express these genes, which are instead expressed in support cells, stem cells, and perivascular cells. These findings suggest that CoV-2 infection of non-neuronal cell types leads to anosmia and related disturbances in odor perception in COVID-19 patients.