This Article Full Text (PDF) Other Versions of this Article: MCB.01791-07v1 28/10/3465    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Google Scholar Articles by Schisler, J. C. Articles by Newgard, C. B. PubMed PubMed Citation Articles by Schisler, J. C. Articles by Newgard, C. B.

 Previous Article  |  Next Article 

Mol. Cell. Biol. doi:10.1128/MCB.01791-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Stimulation of Human and Rat Islet -cell Proliferation with Retention of Function by the Homeodomain Transcription Factor Nkx6.1

Sarah W. Stedman Nutrition and Metabolism Center, Departments of Pharmacology and Cancer Biology, Medicine, and Biochemistry, Duke University Medical Center, Durham, NC 27704; Department of Internal Medicine, Division of Endocrinology and Metabolism, University of Virginia Health System, Charlottesville, VA 22903; Islet Cell Laboratory, Baylor University Medical Center, Dallas, TX 75226

^* To whom correspondence should be addressed. Email: newga002{at}mc.duke.edu.

	Abstract

The homeodomain transcription factor Nkx6.1 plays an important role in pancreatic islet -cell development, but its effects on adult -cell function, survival, and proliferation are not well understood. In the current study, we demonstrate that treatment of primary rat pancreatic islets with a recombinant adenovirus containing the Nkx6.1 cDNA (AdCMV-Nkx6.1) causes dramatic increases in ³H-methyl thymidine and 5-bromo-2'-deoxyuridine (BrdU) incorporation, and in the number of cells/islet relative to islets treated with a control adenovirus (AdCMV-GAL), whereas suppression of Nkx6.1 expression reduces thymidine incorporation. Immunolocalization studies reveal that > 80% of BrdU-positive cells in AdCMV-Nkx6.1-treated islets are -cells. Microarray, real-time PCR, and immunoblot analyses reveal that overexpression of Nkx6.1 in rat islets causes concerted up-regulation of a cadre of cell cycle control genes, including cyclins A, B, and E, and several regulatory kinases. Cyclin E is upregulated earlier than the other cyclins, and adenovirus-mediated overexpression of cyclin E is shown to be sufficient to activate islet cell proliferation. Moreover, chromatin immunoprecipitation assays demonstrate direct interaction of Nkx6.1 with the cyclin A2 and B1 genes. Overexpression of Nkx6.1 in rat islets caused a clear enhancement of glucose-stimulated insulin secretion (GSIS), whereas overexpression of Nkx6.1 in human islets caused a doubling of ³H-thymidine incorporation with complete retention of GSIS. We conclude that Nkx6.1 is among the very rare factors capable of stimulating -cell replication with retention or enhancement of function, properties that may be exploitable for expansion of -cell mass in treatment of both major forms of diabetes.