DLK1 and diabetes mellitus: Signature genes included previously reported beta-specific genes like NKX6-1, DLK1, and ADCYAP1 (Fig. 3C, right) and alpha cell–specific genes like IRX2, LOXL4, and DPP4, a cell surface receptor and diabetes drug target (Dorrell et al. 2011a; Bramswig et al. 2013; Nica et al. 2013; Blodgett et al. 2015).