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COUP-TFII controls mouse pancreatic ?-cell mass through GLP-1-?-catenin signaling pathways.


ABSTRACT: BACKGROUND:The control of the functional pancreatic ?-cell mass serves the key homeostatic function of releasing the right amount of insulin to keep blood sugar in the normal range. It is not fully understood though how ?-cell mass is determined. METHODOLOGY/PRINCIPAL FINDINGS:Conditional chicken ovalbumin upstream promoter transcription factor II (COUP-TFII)-deficient mice were generated and crossed with mice expressing Cre under the control of pancreatic duodenal homeobox 1 (pdx1) gene promoter. Ablation of COUP-TFII in pancreas resulted in glucose intolerance. Beta-cell number was reduced at 1 day and 3 weeks postnatal. Together with a reduced number of insulin-containing cells in the ductal epithelium and normal ?-cell proliferation and apoptosis, this suggests decreased ?-cell differentiation in the neonatal period. By testing islets isolated from these mice and cultured ?-cells with loss and gain of COUP-TFII function, we found that COUP-TFII induces the expression of the ?-catenin gene and its target genes such as cyclin D1 and axin 2. Moreover, induction of these genes by glucagon-like peptide 1 (GLP-1) via ?-catenin was impaired in absence of COUP-TFII. The expression of two other target genes of GLP-1 signaling, GLP-1R and PDX-1 was significantly lower in mutant islets compared to control islets, possibly contributing to reduced ?-cell mass. Finally, we demonstrated that COUP-TFII expression was activated by the Wnt signaling-associated transcription factor TCF7L2 (T-cell factor 7-like 2) in human islets and rat ?-cells providing a feedback loop. CONCLUSIONS/SIGNIFICANCE:Our findings show that COUP-TFII is a novel component of the GLP-1 signaling cascade that increases ?-cell number during the neonatal period. COUP-TFII is required for GLP-1 activation of the ?-catenin-dependent pathway and its expression is under the control of TCF7L2.

SUBMITTER: Boutant M 

PROVIDER: S-EPMC3265526 | BioStudies | 2012-01-01

REPOSITORIES: biostudies

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