177-OR: The Swi/Snf Chromatin Remodeling Complex Controls the Specification, Expansion, and Differentiation of Pancreatic Endocrine Progenitor Cells

Abstract

A key feature of type 1 and type 2 diabetes is insufficient functional β-cell mass. Strategies to augment functional β-cell mass include directed differentiation of embryonic stem cells towards a β-cell fate, which requires extensive knowledge of the transcriptional programs governing endocrine cell differentiation in vivo. Pdx1, an essential transcription factor involved in pancreas formation, endocrine progenitor cell expansion and β-cell function, dynamically recruits coregulators to drive gene expression programs in those cells vital for its activity. Pdx1 binds to numerous coregulators in the β-cell, including the ATP-dependent Swi/Snf chromatin remodeling complex. Previous work by our group revealed a critical role for Pdx1:Swi/Snf in both the developing pancreas and mature β-cell. Here we interrogate the role of Swi/Snf on governing Pdx1-dependent gene expression programs and chromatin accessibility in pancreatic endocrine cell development. We developed a mouse model to eliminate the activity of the two core ATPase subunits of Swi/Snf, Brg1 and Brm from endocrine progenitor cells using Neurogenin3-Cre (Δendo). Conditional knockout of Brg1 (Brg1ΔendoBrm+/-) from endocrine progenitor cells leads to severe glucose intolerance, ad-libitum fed hyperglycemia, reduced serum insulin, compromised glucose stimulated insulin secretion from isolated islets and reduced islet mass in 4-week old animals. Whereas Brg1Δendo/+Brm-/- mice are normal, remarkably, no DKOΔendo (double knockout (DKO): targeted both Brg1 and Brm) mice have been found at weaning, suggesting loss of all Swi/Snf activity from the endocrine progenitor cell pool is postnatally lethal. Future experiments will be directed at determining how Swi/Snf controls Pdx1-dependent gene expression programs and chromatin accessibility in endocrine progenitor cells that are critical for islet cell expansion, differentiation and maturation. Disclosure J. Spaeth: None. R. K. Davidson: None. N. Casey: None. Funding National Institutes of Health (R03DK127129, K01DK115633)