A genome-wide DNA methylation analysis of isolated human pancreatic islet cells harvested from donors with and without T2D revealed 853 unique differential DNA methylation genes, including 17 genes previously identified in GWAS such as TCF7L2, THADA, KCNQ1, FTO, and IRS1 associated with the risk of T2D (105). Here, TCF7L2 is linked to type 2 diabetes mellitus.