Genetic studies in American Indians from Arizona previously identified a population specific Arg1420 His mutation in ABCC8 which causes hyperinsulinemic hypoglycemia in infancy. The His allele is carried by 3% of this population and associates with increased birthweight, suggesting increased insulin secretion in-utero, and doubles the risk of type 2 diabetes, a disease characterized by reduced insulin secretion. To model the contrary effects of this mutation, we used gene-edited induced pluripotent stem cell (iPSC) derived pancreatic islet-like cells. An iPS cell line created from an American Indian heterozygous for the mutation was gene-edited using CRISPR-CAS9 to generate iPSCs homozygous for the risk (His) and the non-risk (Arg) allele. Multiple iPSC lines for each genotype were differentiated towards pancreatic islet-like cells using a seven-stage differentiation protocol and the effect of the mutation on islet function were assessed. Higher insulin secretion was observed from the His-allele carrying islet-like cells when stimulated with low glucose (2mM) after 1 and 2 weeks of maturation, consistent with a clinical phenotype of hyperinsulinemia in His-allele carriers. Stimulation with 20mM glucose resulted in increased insulin secretion after 2 weeks of maturation only in the Arg-allele (non-risk) carrying islets while no increase was seen in the His-allele carrying islets, consistent with its role in T2D risk. Treatment with diazoxide significantly reduced insulin secretion with no difference between the genotypes. Single cell RNA sequencing of islet-like cells cultured for an extended time (4 weeks) identified many differentially expressed genes in cells with the mutant vs. reference allele that could potentially reveal the mechanism of the increased future T2D risk including G6PC2, a known negative regulator of glucose-stimulated insulin secretion, in beta-like cells and CRH, which has been linked to increased T2D risk, in alpha-like cells.
A.K.Nair: None. M.Traurig: None. J.Sutherland: Stock/Shareholder; Bristol-Myers Squibb Company, Johnson & Johnson, Pfizer Inc. R.G.Nelson: None. C.Bogardus: None. L.Baier: None.