Establishing and maintaining a robust population of functional hormone-secreting endocrine cells is critical for regulating blood glucose homeostasis, which remains a challenge for individuals with Type 1 and Type 2 diabetes. Traditionally, endocrine cells have been molecularly defined by their gene expression patterns; however, recent studies have revealed the previously unappreciated importance of co- and post-transcriptional RNA regulation, such as modification, localization, alternative splicing and transcript stability, in the specification and function of differentiated cells. Regulation of RNAs is emerging as a critical player in establishing and maintaining a robust population of functional hormone-secreting endocrine cells. RNA regulation, including splicing and stability, are coordinated by RNA-binding proteins (RBPs). Each RBP can have hundreds of targets within a cell, making their potential impact on cellular identity and function extensive. Recent studies have shown dysregulation of RBPs and aberrant mRNA splicing activity in islets of diabetic patients compared to healthy controls. Additionally, my preliminary data provides some of the first evidence that ? cell function requires specific RBPs. Furthermore, our lab has shown differential splicing of over 1,000 genes between endocrine cell types and my own analysis of cytokine treated human ? cells as a model of autoimmune destruction revealed 2,250 dysregulated splicing events, including an RBP, Rbfox2. Together these data point toward a previously unappreciated role for RBPs in endocrine cells and offers a new perspective to examine ? cell function. In this proposal I have outlined the evidence for the extensive impact of Rbfox2 regulation of ? cell function. Rbfox2 is enriched in endocrine cells of pancreatic islets and has a highly conserved RNA binding sequence making it an ideal candidate to evaluate RBP mediated RNA regulation in the ? cell. Conditional loss of Rbfox2 in the pancreas results in impaired blood glucose regulation without a significant change in islet cell numbers or morphology, suggesting that islet function is disrupted. Additionally, loss of Rbfox2 in ? cells results in aberrant splicing and/or differential expression of critical ? cell specific genes, including MafA. By furthering our understanding of the role of RBPs and alternative splicing in diabetes, this project provides a unique perspective on a complex disease and will ultimately push the boundaries of therapeutic treatments of diabetes. The experiments proposed will not only uncover how ? cell function is finetuned at the level of RNA but could potentially describe novel function for the Rbfox2 in regulating transcript stability.
Diabetes is one of the fastest growing diseases globally, with an average of 1.5 million new diagnoses each year. Fundamentally, diabetes is characterized by the inability to maintain blood glucose homeostasis due to loss and/or dysfunction of insulin-producing ? cells. The proposed research strategy will enhance our understanding of the formation and function of ? cells through the characterization of RNA regulation of critical ? cell genes.
