Fellowship/Muniappan: Identification for miRNAsRegulated by Beta-Cell Transcription Factors

Production and secretion of insulin by the pancreatic beta cells is essential for proper glucose homeostasis. Defects associated with this process lead to the metabolic disorder diabetes, which is a major cause of cardiovascular diseases. Recent studies indicate that a novel population of small cellular RNAs, termed microRNAs (miRNAs), may play an important role in the development of type 1 and 2 diabetes. Recent data suggest that miRNAs regulate insulin secretion and pancreas development, and dysregulation of these miRNAs may lead to diabetes. For example, miR-375 has been discovered to be specifically expressed in pancreatic beta cells and to be important for insulin secretion. The function of most miRNAs in beta cells are yet to be investigated. Beta-cell transcription factors POX-I, NeuroDl and MafA play an important role in maintaining beta-cell function. However, it is not known whether these transcription factors are involved in regulation of beta-cell specific miRNAs. To address this question, we transfected liver cells with the beta-cell specific transcription factors PDX-1, NeuroDl and MafA adenoviruses and screened for miRNAs with increased or decreased expression levels compared to GFP (control virus) expressing liver cells. The miRNAs idiñfifiéd b~Tthiii&è&ri W&è Iidáidfo~thë1~è*frëii1bWáñd~[üöäSiiéJlitiöiiiifthéähöiiatiëétâöill - line MIN6. The major goal of this application is to analyze the expression and glucose regulation of the identified miRNAs in pancreatic islets of normal and diabetic animals and to characterize their role in beta-cell function. Therefore, the two specific aims of this project are: (1) To analyze the glucose-dependent expression of the identified miRNAs in pancreatic islets of normal and diabetic animals, such as NOD mice (type 1 diabetes model) and db/db mice (type 2 diabetes model) (2) To characterize the role of the validated miRNAs with respect to insulin production and secretion. Our long-term goal will be to identify the target mRNA5 for the validated miRNJAs, which is beyond the scope of this one-year extension application. The data obtained from this proposal may lead to the discovery of novel type I and 2 diabetic biomarkers and contribute to the development of potential therapeutic applications to treat or prevent diabetes and its associated complications, such as cardiovascular disease and stroke.