HMG20A and type 2 diabetes mellitus: We find that: (1) HMG20A is expressed in pancreatic islet beta cells, (2) HMG20A levels are decreased in T2DM islets, (3) high glucose stimulates HMG20A expression, (4) the T2DM-associated SNP within the 3′ UTR of the HMG20A transcript decreases luciferase activity, (5) HMG20A regulates key genes in beta cell function and maturity, and (6) HMG20A depletion impairs GSIS.