Immunofluorescence indicates that DLK1 is beta cell specific in human but not mouse islets (Li et al. 2016), and FACS-enriched mouse beta cells show low expression of Dlk1 in comparison to other sorted islet alpha and delta cells (DiGruccio et al. 2016), potentially implicating a unique role of this gene in human T2D progression. The gene discussed is DLK1; the disease is type 2 diabetes mellitus.