Dissecting the mechanisms behind biphasic beta cell disease caused by mutations in HNF1alpha

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Project Summary In order for the b-cell to precisely secrete insulin in response to glucose, glucose metabolism to ATP is tightly coupled to insulin secretion through the ATP-sensitive K (KATP) channel. Any disruption along this pathway leads to b-cell dysfunction and ensuing diabetes or, more rarely, congenital hyperinsulinism. While these diseases mostly arise from multiple factors, some cases are caused by single gene mutations, termed monogenic diseases. Interestingly, the same loss-of-function heterozygous mutations in the transcription factor HNF1a can result in both hyperinsulinism and diabetes, though presenting at different ages and through unknown mechanisms. In the proposed project, we will investigate the underlying causes of both HNF1a- related diabetes and hyperinsulinism. Our prior published work and additional preliminary data show that HNF1A-deficient human stem cell-derived β-cells exhibit increased basal and decreased glucose-stimulated insulin secretion, recapitulating the clinical disease. HNF1A-deficient β-cell models exhibited significantly decreased glycolysis, suggesting decreased ATP production in response to glucose. Expression analyses revealed broad defects in HNF1A-deficient β-cells in genes regulating cellular metabolism and decreased expression of KATP channel genes. Based on these previous findings, we hypothesize that HNF1a regulates both KATP channel expression and ATP production in response to glucose. Loss of HNF1a leads to uncoupling of glucose metabolism and insulin secretion at these two points in the insulin secretion cascade, impacting basal and stimulated insulin secretion in opposing directions and resulting in hyperinsulinism and diabetes, respectively. Using a novel and manipulatable human b-cell model system combined with a variety of analytical techniques, we will rigorously test our hypotheses and advance our knowledge of b-cell dysfunction in complex disease states. My long-term goal is to have a basic and translational research lab that studies the diseases resulting from pancreatic β-cell dysfunction. My proposed K08 project will help me learn new technical methods, develop a new intellectual foundation and generate preliminary data that will be instrumental in helping me start my own independent lab. I chose my co-mentors as they have complimentary research approaches and varied areas of expertise. I have a career development plan which relies on my extensive mentoring relationships, including regular interaction with my co-mentors and my advisory committee, which contains individuals within the local and national research community with varying areas of expertise. I have developed a plan of training which takes full advantage of the collaborative research environment at the Children’s Hospital of Philadelphia and University of Pennsylvania School of Medicine, including participation in trainings, seminars, and workshops to advance my knowledge base and professional skills.