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 requires understanding the complex programs that coordinate a proper insulin release in response to changing blood glucose levels. Developing upon existing knowledge of how islet enriched transcription factors (TFs) coordinate signals that influence gene regulatory programs will allow us to understand how such programs are dramatically altered in islet ?-cells of diabetes patients. Pdx1, one of the most important TFs in the developing and postnatal ?-cell, has been shown to recruit a diverse set of coregulators which could potentially modulate its activity. This proposal is focused around how Pdx1:coregulator interactions are influential to normal ?-cell function and are altered in pathophysiological conditions associated with Type 2 diabetes (T2DM). The Swi/Snf ATP-dependent chromatin remodeling complex was found to interact with and control a subset of Pdx1 target genes in a glucose dependent manner in vitro. Preliminary studies demonstrate that conditional removal of Swi/Snf activity from mature islet ?-cells significantly impacts ?-cell function and identity in vivo. Moreover, our lab found that Pdx1:Swi/Snf interactions are compromised in human T2DM donor samples, which suggests that, in general, Pdx1:coregulator interactions are sensitive to the diabetic milieu. This proposal will test the overall hypothesis that ?-cell activity is regulated by coregulators whose interactions with Pdx1 are dynamically controlled by physiological and pathophysiological conditions.
In Aim 1, the applicant will utilize unbiased genome-wide RNA-Sequencing, targeted ChIP, ChIP-ReChIP and bioinformatics approaches to define the genes and pathways regulated by Pdx1:Swi/Snf in mature ?-cells using transgenic Swi/Snf knockout mice. Moreover, the influence of Swi/Snf on human Pdx1 and ?-cell action will be investigated.
Aim 2 will evaluate the influence other Pdx1-recruited coregulators have on human and mouse ?-cell function.
In Aim 3, the applicant will test how metabolic stress associated with T2DM affects Pdx1:Swi/Snf complex formation using in vivo rodent models of T2DM and human islets. With this K01 Career Developmental Award, the applicant will be able to continue to focus their time on the Aims outlined in this proposal. A significant amount of career training and research data will be acquired while at the Vanderbilt University, which is more than equipped with the intellectual knowledge of faculty and core facilities to carry out all of the proposed studies. Moreover, the candidate will develop the tools and skills necessary to answer many of the questions raised by these Aims and generate interesting data to be further developed into his own research program as an independent investigator.
Combatting the ever-growing health and economic costs associated with diabetes, it is necessary to obtain full knowledge of how the disease, specifically beta cell dysfunction and loss of identity, ultimately result in beta cell failure. Accurate gene expression programs within the beta cell are mediated by islet enriched transcription factors and recruited coregulators, whose dynamic interactions are predicted to be compromised in the pathophysiological conditions associated with diabetes. The studies herein aim to define the importance of the Swi/Snf chromatin remodeling complex and other coregulators on regulating the activity of the Pancreas Duodenum Homeobox-1 transcription factor in physiological and pathophysiological conditions associated with Type 2 diabetes.
