Pancreatic ?-cells within the islets of Langerhans are required for glucose-stimulated insulin secretion and glucose homeostasis. Dysfunctional ?-cell activity and identity results in diabetes mellitus (DM), a growing disease affecting millions of Americans, thus creating an enormous fiscal and health burden. Strategies to improve outcomes for the mounting number of diabetic patients and the possibility to replace destroyed and dysfunctional ?-cell mass requires a deep understanding of the complex programs that coordinate proper islet formation. Developing upon existing knowledge of how islet enriched transcription factors (TFs) coordinate signals that direct islet cell development will allow us to understand how such programs can be targeted for ?- cell replacement therapies. Pdx1, one of the most important TFs in the pancreas and developing islet, has been shown to recruit a diverse set of coregulators which could potentially modulate its activity. This proposal is focused around how the Pdx1 recruited ATP-dependent Swi/Snf chromatin remodeling complex modulates Pdx1 transcriptional activity in the developing islet. Previous work by the PI?s group revealed a critical role for Pdx1:Swi/Snf function in the developing pancreas and the mature ?-cell. Preliminary studies thus far have shown that conditional removal of one of the core Swi/Snf ATPase subunits (through Cre-LoxP technology) from developing endocrine progenitor cells results in glucose intolerance, ad libitum fed hyperglycemia and reduced serum insulin levels in mutant animals postnatally. This proposal will test the hypothesis that Pdx1-recruited Swi/Snf chromatin remodeling activities control chromatin accessibility and gene expression programs essential for endocrine progenitor cell expansion and postnatal islet cell function.
In Aim 1, the PI will use this novel transgenic animal model to determine islet cell function, expression of islet cell maturation markers, hormone secretion and hormone cell mass in adult pancreata.
In Aim 2, embryonic tissues from mutant animals will be used to determine changes in endocrine progenitor cell mass and hormone cell proliferation/apoptosis. The mechanistic actions of Swi/Snf on directing chromatin accessibility and gene expression programs in endocrine progenitors will be determined by ATAC-Seq, RNA-Seq and ChIP-qPCR analyses on flow-sorted Swi/Snf-deficient endocrine precursors. My extensive experience studying transcription factor coregulatory complexes and our available in vivo reagents make my lab uniquely suited to accomplish these Aims. Mechanisms defined by these studies will uncover key processes and unique gene expression signatures dependent on chromatin remodeling during endocrine development, which will provide instrumental knowledge to researchers developing new molecular targets and cell-based therapies to combat diabetes. Importantly, this proposal has also been designed to generate data and resources that the applicant will utilize in an R01 application defining how dysregulated enhancer function from Type 2 diabetic (T2D) islet donors are influenced by altered Pdx1:Swi/Snf actions.
To combat the ever-growing health and economic costs associated with diabetes, researchers are developing therapies to replace lost ?-cell mass that will improve the quality of life for diabetic patients. Accomplishing these goals requires fundamental knowledge of gene regulatory mechanisms that are essential for the production of functional islet ?-cells. Successful completion of our studies will provide novel evidence that the Swi/Snf chromatin remodeling complex governs chromatin accessibility and gene expression signatures in endocrine progenitor cells that are essential for islet cell development.
