hPSCs model of Maturity Onset Diabetes of the Young caused by mutations in the transcription factor HNF1A (HNF1A-MODY), regulates the expression of genes required for the formation of dense-core insulin granules and calcium-dependent insulin secretion, demonstrating a basis to treat HNF1A-MODY patients with sulfonylureas. Here, HNF1A is linked to diabetes mellitus.