Title: HNF1A Deficiency Impairs Beta-cell Fate, Granule Maturation and Function
Description: Mutations in HNF1A cause Maturity Onset Diabetes of the Young type 3, the second most frequent form of diabetes caused by single gene mutation. We generated human stem cell-derived pancreatic endocrine cells with clinically pathogenic mutations in HNF1A and show that HNF1A deficiency impairs endocrine cell fate, insulin granule maturation and the secretion of insulin in response to glucose. Single-cell RNA sequencing reveals that HNF1A orchestrates a network of genes involved in β-cell fate, granule maturation, glucose metabolism, calcium ion binding and hormone exocytosis. In both patients and stem cell-derived β-cells, HNF1A deficiency altered the stoichiometry of secreted insulin to c-peptide. Sulfonylurea, used in the treatment of these patients, restored both insulin secretion and stoichiometry. The uncoupling of insulin and c-peptide secretion as described here questions the common practice of using c-peptide as a proxy to evaluate β-cell function. We also demonstrate that correction of the HNF1A mutations restores function, providing a path to cell-based replacement therapy.