Conversely, pancreatic polypeptide cells (gamma cells), pancreatic alpha cells, and keratinocytes show similarly robust ACE2 expression but have not been strongly associated with ACE2 in the literature. This combination suggests either a biological novelty or an experimental artifact. We note that the strong ACE2 expression in pancreatic cell types is derived from only one murine study (Figure 2—figure supplement 1; Tabula Muris Consortium et al., 2018), while ACE2 expression is not observed in gamma or alpha cells from scRNAseq of human pancreatic islets (Figure 2—figure supplement 1; Segerstolpe et al., 2016; Grün et al., 2016; Muraro et al., 2016). While we cannot determine the validity of either observation, this example demonstrates how knowledge synthesis can automatically surface discordant biological signals for further evaluation.