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Critical Role of Egr Transcription Factors in Regulating Insulin Biosynthesis, Blood Glucose Homeostasis, and Islet Size.
MedLine Citation:
PMID:  22597533     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Expression of early growth response protein (Egr)-1, a protein of the Egr family of zinc finger transcription factors, is stimulated in glucose-treated pancreatic β-cells and insulinoma cells. The purpose of this study was to elucidate the role of Egr transcription factors in pancreatic β-cells in vivo. To overcome the problem associated with redundancy of functions between Egr proteins, conditional transgenic mice were generated expressing a dominant-negative mutant of Egr-1 in pancreatic β-cells. The Egr-1 mutant interferes with DNA binding of all Egr proteins and thus impairs the biological functions of the entire Egr family. Expression of the Egr-1 mutant reduced expression of TGFβ and basic fibroblast growth factor, known target genes of Egr-1, whereas the expression of Egr-1, Egr-3, Ets-like gene-1, and specificity protein-3 was not changed in the presence of the Egr-1 mutant. Expression of the homeobox protein pancreas duodenum homeobox-1, a major regulator of insulin biosynthesis, was reduced in islets expressing the Egr-1 mutant. Accordingly, insulin mRNA and protein levels were reduced by 75 or 25%, respectively, whereas expression of glucagon and somatostatin was not altered after expression of the Egr-1 mutant in β-cells. Glucose tolerance tests revealed that transgenic mice expressing the Egr-1 mutant in pancreatic β-cells displayed impaired glucose tolerance. In addition, increased caspase-3/7 activity was detected as a result of transgene expression, leading to a 20% decrease of the size of the islets. These results show that Egr proteins play an important role in controlling insulin biosynthesis, glucose homeostasis, and islet size of pancreatic β-cells in vivo.
Authors:
Isabelle Müller; Oliver G Rössler; Christine Wittig; Michael D Menger; Gerald Thiel
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-5-17
Journal Detail:
Title:  Endocrinology     Volume:  -     ISSN:  1945-7170     ISO Abbreviation:  -     Publication Date:  2012 May 
Date Detail:
Created Date:  2012-5-18     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0375040     Medline TA:  Endocrinology     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Departments of Medical Biochemistry and Molecular Biology (I.M., O.G.R., G.T.), and Clinical and Experimental Surgery (C.W., M.D.M.), University of Saarland Medical Center, D-66421 Homburg, Germany.
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