Validation of known differences in gene expression between mouse and human alpha and beta cells. We assessed the expression of two sets of genes, Mafa/Mafb and Ucn3/Crh, that markedly differ in distribution between alpha and beta cells in mouse (A) and human (B) islets. Mafa is restricted to beta cells of both species, while Mafb is selectively expressed in mouse alpha cells (A), but expressed in human beta cells as well (B). Ucn3 is highly selective for mouse beta cells while Crh is detected in neither mouse islet population (A, C, D). By contrast, UCN3 expression is a common feature of human alpha and beta cells, while CRH is enriched in human alpha cells (B, E, F). Human RNA-seq data are from . See also Additional file 7 for single channel images.