Project description:The aim of this study is to identify sites occupied by Pdx1 throughout key stages in mouse and human pancreatic development as well as during in vitro differentiation of human ES cells.
Project description:The aim of this experiment was to observe the transcriptional profile of mouse islets during development (at timepoints E18.5, P10, Adult). RNA-seq was performed on the same RNA that was used for an earlier microarray. No MARIS sorting.
Project description:Remarkable advancements in protocol development have been achieved to manufacture insulin-secreting islets from human pluripotent stem cells. Distinct from current approaches, we devised a tunable strategy to generate islet spheroids enriched for major islet cell types by incorporating PDX1+ cell budding morphogenesis into the differentiation process of staged transcriptional programming. In this process that appears to mimic normal islet morphogenesis, the differentiating islet spheroids self-organize with endocrine cells that are intermingled or arranged in a core-mantle architecture, accompanied with functional heterogeneity. Through in vitro modelling of human pancreas development, we illustrate the importance of PDX1 in eliciting cell budding morphogenesis, and the requirement for EphB3/4 signaling. We show how RFX6 deficiency affects pancreatic patterning and uncover an expected role of RFX6 in early pancreas morphology. The tunable differentiation system and stem cell-derived islet models described in this work may facilitate addressing fundamental questions in islet biology and probing human pancreas diseases.
Project description:Pancreatic neuroendocrine tumors (PanNET) were classified into grades (G) 1-3 by the World Health Organization in 2017, but the precise mechanisms of PanNET initiation and progression have remained unclear. In this study, we used a genetically engineered mouse model to investigate the mechanisms of PanNET formation. Although pancreas-specific deletion of the Rb gene (Pdx1-Cre;Rbf/f) in mice did not affect pancreatic exocrine cells, the α-cell/β-cell ratio of islet cells was decreased at 8 months of age. During long-term observation (18-20 months), mice formed well-differentiated PanNET with a Ki67-labeling index of 2.7%. In contrast, pancreas-specific induction of a p53 mutation (Pdx1-Cre;Trp53R172H) had no effect on pancreatic exocrine and endocrine tissues, but simultaneous induction of a p53 mutation with Rb gene deletion (Pdx1-Cre;Trp53R172H;Rb f/f) resulted in the formation of aggressive PanNET with a Ki67-labeling index of 24.7% over the short-term (4 months). In Pdx1-Cre;Trp53R172H;Rb f/f mice, mRNA expression of Pten and Tsc2, negative regulators of the mTOR pathway, significantly decreased in the islet cells, and activation of the mTOR pathway was confirmed in subsequently formed PanNET. Thus, by manipulating Rb and p53 genes, we established a multistep progression model from dysplastic islet to indolent PanNET and aggressive metastatic PanNET in mice. These observations suggest that Rb and p53 have distinct roles in the development of PanNET.
Project description:Transcription factors positively and/or negatively impact gene expression by recruiting coregulatory factors, which interact through protein-protein binding. Here we demonstrate that mouse pancreas size and islet β cell function are controlled by the ATP-dependent Swi/Snf chromatin-remodeling coregulatory complex that physically associates with Pdx1, a diabetes-linked transcription factor essential to pancreatic morphogenesis and adult islet-cell function and maintenance. Early embryonic deletion of just the Swi/Snf Brg1 ATPase subunit reduced multipotent pancreatic progenitor cell proliferation and resulted in pancreas hypoplasia. In contrast, removal of both Swi/Snf ATPase subunits, Brg1 and Brm, were required to compromise adult islet β cell activity, which included whole animal glucose intolerance, hyperglycemia and impaired insulin secretion. Notably, lineage-tracing analysis revealed that these Swi/Snf deficient β cells lost the ability to produce insulin and other key metabolic genes, yet the expression levels of many essential islet-enriched transcription factors were unaffected. Swi/Snf was necessary for Pdx1 binding to the insulin enhancer, demonstrating the importance of this association in mediating chromatin accessibility. These results illustrate how fundamental the Pdx1:Swi/Snf coregulator complex is in the pancreas and we discuss how disrupting their association could influence Type 1 and Type 2 diabetes susceptibility.
Project description:We anticipated that the identification of cis-regulatory regions active in pancreatic islets would help increase our understanding of islet biology and the pathology of diabetes. Towards this end we used histone H3 lysine 4 monomethylation-based nucleosome predictions genome-wide, in conjunction with binding data for PDX1, FOXA2, MAFA, and NEUROD1, to identify 3,654 putative enhancers that are H3K4me1-enriched uniquely in islets as compared to 14 other tissue or cell-types. We show that these islet-specific enhancers are associated with genes with significantly higher islet specificity than genes associated with non-specific enhancers. Further, islet-specific enhancers were not enriched for typical active or repressive histone methylations in embryonic stem cells and liver, suggesting they are formed by de novo histone methylation during pancreas development. We also identify a subset of enhancers bivalently marked by both H3K4me1 and H3K27me3 in adult pancreatic islets. Further, we show that islet-specific enhancers triple- or quadruple- bound by PDX1, MAFA, NEUROD1 and/or FOXA2 are associated with genes with particularly high islet-specificity, and that these loci are enriched in regions with functional activity in islet cell types. Finally, we demonstrate that cytokines reduce H3K4me1 enrichment levels at selected triple- or quadruple-bound islet-specific enhancers, suggesting that epigenetic changes may contribute to cytokine-induced b-cell dysfunction. In conjunction with data from Hoffman et al Genome Research 2010, an analysis of histone modifications and transcription factor binding sites to identify enhancer regions
Project description:Transcription factor pancreatic and duodenal homeobox 1 (Pdx1) plays an essential role in the pancreas to regulate its development and maintain proper islet function. However, less is known about the function of Pdx1 in the small intestine. We aim to investigate the role of Pdx1 in mature proximal small intestine by profiling the expression of genes differentially regulated in response to Pdx1 inactivation restricted to the intestinal epithelium in mice.
Project description:To get a more complete picture of the transcriptional changes associated with Pdx1 loss in ?-cells, we conducted an mRNA microarray comparing normal islet ?-cells and a-cells to the reprogrammed cells from PKO mice. Islet beta cells are from mice which has a single copy of Pdx1 flox (Pdx1L/+) allele, but is considered normal based on normal islet morphology, gene profiling, and euglycemic status. We chose to use heterozygous mice as control to avoid the litter effect. Islet alpha cells are from normal mice. To enrich for genes directly affected by Pdx1 loss, we chose the early time-point for analysis of PKO mice (5d after TAM administration). Control mRNA profiling was performed on FACS sorted islet YFP+ ?-cells and a-cells obtained from 2 month-old glucagon-Cre; RosaYFP and RIP-CreER; Pdx1fl/+, RosaYFP mice, respectively.
Project description:Transcription factor pancreatic and duodenal homeobox 1 (Pdx1) plays an essential role in the pancreas to regulate its development and maintain proper islet function. However, less is known about the function of Pdx1 in the small intestine. We aim to investigate the role of Pdx1 in mature proximal small intestine by profiling the expression of genes differentially regulated in response to Pdx1 inactivation restricted to the intestinal epithelium in mice. Pdx1 was conditionally inactivated in the intestinal epithelium of Pdx1flox/flox;VilCre mice, by crossing mutant mice homozygous for loxP site-flanked Pdx1 alleles with transgenic mice expressing Cre recombinase under the control of the mouse villin 1 gene promoter. Total RNA was isolated from the first five centimeters of the small intestine from adult Pdx1flox/flox;VilCre and littermate control mice. Microarray analysis was performed to investigate genome-wide transcriptional profiles in the proximal small intestine.