Novo Nordisk Fonden - Uncovering the molecular basis for nutritional reprogramming of the endocrine pancreas using novel in situ and genome-wide approaches - Advanced Grant 2015

Several lines of evidence indicate that prolonged nutrient overload not only stimulate insulin secretion, but also reprograms the genome of pancreatic β-cells. Initially this helps the β-cells to adapt to the increased demand for insulin, but this may also drive nutrient toxicity and lead to β-cell dedifferentiation and failure, eventually resulting in type 2 diabetes (T2D). Most studies addressing this phenomenon have used β-cell model systems, and the in vivo studies that have been performed are based on isolated islets, which have been cultured ex vivo briefly to recover from isolation stresses. This is known to introduce artifacts, and further, islets represent an average of all cell types in the islet, not only the β-cell. Thus, insight into β-cell-specific reprogramming in vivo in response to nutrients and during development of T2D is lacking.In this project, we will adapt a newly developed method (creTRAP) for in situ cell-type-specific transcriptomic profiling to the study of nutritional reprogramming of β-cells. We will generate mice with β-cell-specific ribosome labeling, which will allow us to analyze the β-cell transcriptome without prior isolation and culturing. Using creTRAP, we will generate the first in situ genome-wide maps of temporal adaptive and pathogenic changes in β- cell gene expression and enhancer activity in response to high fat diet (HFD). Based on this, we will identify novel regulators and determine their role in mediating the adaptive and pathogenic effects of HFD by in vivo loss-of function analyses using the unique features of creTRAP. Finally, we will investigate if our findings hold true in humans as well. In conclusion, in this project we will introduce a new powerful method to the study of the endocrine pancreas, and we will use it to generate novel insight into the nutrient-induced reprogramming of β- cells. We expect these studies will have profound impact on our understanding of the etiology of T2D.