Project description:Objective: beta-cell dedifferentiation has been revealed as a pathological mechanism underlying pancreatic dysfunction in diabetes. However, exactly how such dedifferentiation process affects beta-cell gene expression and islet microenvironment remains incompletely understood Method: We performed bulk in islets obtained from beta-cell-specific miR-7a2 overexpressing mice (Tg7), a murine model of beta-cell dedifferentiation and diabetes. Results: Bulk RNA-seq revealed that beta-cell dedifferentiation is associated with the induction of genes associated with epithelial to mesenchymal transition (EMT) in pre-diabetic (2-week-old) and diabetic (12-week-old) Tg7mice. These molecular changes are associated with a weakening of beta-cell:beta-cell contacts, increased extracellular matrix (ECM) deposition and TGFb-dependent islet fibrosis. We find that the mesenchymal reprogramming of beta-cells is explained in part by the downregulation of Pdx1 and its inability to regulate a myriad of target genes preserving the epithelial cell phenotype. Notable among epithelial genes transactivated by Pdx1 is Ovol2, a transcriptional repressor of the EMT transcription factor ZEB2. Following compromised beta-cell identity, the reduction of Pdx1 mRNA levels decreases Ovol2 gene expression, which triggers mesenchymal reprogramming of beta-cells through the induction of Zeb2. Finally, we provided evidence that EMT signalling associated with the upregulation of Zeb2 expression is a molecular feature of islet of T2D subjects. Conclusions: Our study indicates that beta-cell dedifferentiation triggers a chronic response to tissue injury, which alters the pancreatic islet microenvironment and contribute to islet fibrosis. It suggests that regulators of EMT signalling may represent novel therapeutic targets for the treatment of beta-cell dysfunction and fibrosis in T2D.
Project description:Pancreas specific deletion of the Haster promoter region results in a variegated phenotype in pancreatic islets with overexpression or silencing of the Hnf1a gene. To determine the transcriptional consequence of the overexpression or silencing of Hnf1a is islet cells from the Haster pKO mice (Haster loxP/loxP;Pdx1-Cre), we performed scRNA-seq of pancreatic islets from control and adult female Haster pKO mice.
Project description:During pregnancy, the energy requirements of the fetus impose changes in maternal metabolism. Increasing insulin resistance in the mother maintains nutrient flow to the growing fetus, while prolactin and placental lactogen counterbalance this resistance and prevent maternal hyperglycemia by driving expansion of the maternal population of insulin-producing beta-cells. However, the exact mechanisms by which the lactogenic hormones drive beta-cell expansion remain uncertain. Here we show that serotonin acts downstream of lactogen signaling to drive beta-cell proliferation. Serotonin synthetic enzyme Tph1 and serotonin production increased sharply in beta-cells during pregnancy or after treatment with lactogens in vitro. Inhibition of serotonin synthesis by dietary tryptophan restriction or Tph inhibition blocked beta-cell expansion and induced glucose intolerance in pregnant mice without affecting insulin sensitivity. Expression of the Gq-linked serotonin receptor Htr2b in maternal islets increased during pregnancy and normalized just prior to parturition, while expression of the Gi-linked receptor Htr1d increased at the end of pregnancy and postpartum. Blocking Htr2b signaling in pregnant mice also blocked beta-cell expansion and caused glucose intolerance. These studies reveal an integrated signaling pathway linking beta-cell mass to anticipated insulin need during pregnancy. Modulators of this pathway, including medications and diet, may affect the risk of gestational diabetes. Analysis of poly(A)+ RNA from 3 biological replicates of pancreatic islets isolated from normal female and pregnant female mice
Project description:Pancreatic islet beta cell heterogeneity has been identified, which plays a pivotal role in the pathological alterations of pancreatic islets in type 2 diabetes (T2D) mice. However, pathological alterations of beta cells in type 2 diabetes (T2D) mice remain to be investigated. We isolated pancreatic islets from the control and T2D mice and conducted scRNA-seq analysis using the 10x Genomics platform. Pathological alterations of beta cells in T2D were also explored.
Project description:To gain insights into how pancreatic cells are programmed in vivo, we profiled RNA expression in pancreatic islets of pancreatic Ring1b conditional KO mice (conditional using a pancreas specfic Cre; Pdx1-Cre) and their littermate controls