The genes septin-9 (Sept9), cyclin-dependent kinase inhibitor 1A (Cdkn1a), and phosphodiesterase-7B (Pde7b) were selected based on their potential role in islet function and DM, along with their differential DNA methylation in multiple CpG sites and differential expression in T2DM islets. The gene discussed is CDKN1A; the disease is diabetes mellitus.