TCF7L2 and type 2 diabetes mellitus: These include reported diabetes loci, such as TCF7L2, FTO and KCNQ1. Furthermore, we found 102 genes that showed both differential DNA methylation and gene expression in T2D islets, including CDKN1A, PDE7B, SEPT9 and EXOC3L2. Finally, we provide functional proof that identified candidate genes directly affect insulin secretion and exocytosis in pancreatic β-cells as well as glucagon secretion in α-cells.