258-OR: DNA Methylation Regulates the Identity of Pancreatic Beta Cells

Abstract

Diabetes is associated with the loss of beta-cell identity and function. Thus, understanding the mechanisms that simultaneously regulate beta-cell function and identity is critical for developing beta-cell replacement therapies. In this study, we show that the de novo DNA methyltransferase, Dnmt3a, orchestrates beta-cell identity and function. Previously, we have shown that loss of Dnmt3a in pancreatic beta-cells prevents the developmental metabolic reprogramming, resulting in loss of glucose stimulated insulin secretion (GSIS). To gain insights into the role of new DNA methylation patterns established in early pancreas development, we deleted Dnmt3a in the embryonic pancreatic progenitors in mice. RNA sequencing of Dnmt3aKO and control islets in adult life revealed that loss of Dnmt3a in progenitors leads to dysregulation of key genes involved in the maintenance of beta-cell identity and function. Notably, loss of Dnmt3a led to the upregulation of Tyrosine Hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis, along with dysregulation of several genes involved in Dopamine signaling. Specifically, a large proportion of beta-cells in KO was marked by TH expression, compared to controls. Bisulfite sequencing analysis revealed that TH expression is repressed in beta-cells due to DNA methylation during differentiation of endocrine progenitors. In addition, the TH positive beta-cells displayed G2/M cell cycle arrest, along with elevated ER-stress markers. This alteration of cell identity was accompanied by impaired glucose tolerance and a GSIS profile resembling functionally immature beta-cells in the KO mice. The Dnmt3aKO mice did not show any significant change in beta-cell mass, while delta- and alpha- cell masses were increased at 7 month. Taken together, our results show that de novo methylation during early pancreatic development is critical for the establishment of beta-cell identity and function. Disclosure N. Parveen: None. J.K. Wang: None. S. Dhawan: None. Funding National Institutes of Health (R01DK120523)