mRNA Profiling of Rat Islet Tumors Reveals Nkx 6.1 as a β-Cell-specific Homeodomain Transcription Factor

doi:10.1074/jbc.271.31.18749

mRNA Profiling of Rat Islet Tumors Reveals Nkx 6.1 as a β-Cell-specific Homeodomain Transcription Factor*

From the Hagedorn Research Institute, Niels Steensensvej 6, DK-2820 Gentofte, Denmark

^‡ To whom correspondence should be addressed. Tel.: 45-31680860; Fax: 45-44438000; E-mail: odm{at}hrl.dk

Abstract

Development of a high capacity multiplex reverse transcriptase-polymerase chain reaction protocol has allowed us to screen lineage related rat islet tumors classified as α-, β-, and δ-like as judged by their hormone profile for differential expression of more than 50 selected genes. We find that in addition to insulin the insulinoma express the normal β-cell markers Pdx-1, IAPP, and Glut-2, and that these markers are absent from the glucagonoma: a reflection of the normal α-cell. Furthermore, this study suggests that the GLP-1, glucagon, GIP, IGF-1, and insulin receptors as well as E-cadherin, R-cadherin, Id-1, and Id-2 are differentially expressed within the islet of Langerhans. Importantly, insulinoma-specific expression of the recently cloned homeodomain protein Nkx 6.1 predicted β-cell-specific expression in the normal islet. Immunohistochemistry using antibodies raised against recombinant Nkx 6.1 did indeed localize Nkx 6.1 expression exclusively to the nuclei of normal islet β-cells. Apart from pancreatic islets only the antral part of the stomach contained Nkx 6.1 mRNA. We conclude that multiplex reverse transcriptase-polymerase chain reaction-based mRNA profiling is a powerful tool to identify differentially expressed genes within phenotypically related cells and propose that Nkx 6.1 is involved in specifying the unique characteristics of the β-cell.

Footnotes

↵* This work was supported by the Danish National Research Foundation (Centre for Gene Regulation and Plasticity in the Neuroendocrine Network) and Kræftens Bekæmpelse. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

RT-PCR

reverse transcriptase-polymerase chain reaction

PCR

polmerase chain reaction

CGRP

calcitonin gene-related peptide

CREB

cAMP-responsive element-binding protein

GH

growth hormone

GIP

gastric inhibitory peptide

GLP-1

glucagon like peptide-1

Glut

glucose transporter

GST

glutathione S-transferase

HLH

helix-loop-helix

IAPP

islet amyloid polypeptide

IEF-1

insulin enhancer factor-1

IGF-1

insulin like growth factor-1

NCAM

neural cell adhesion molecule

Pdx-1

pancreatic duodenal homeodomain factor-1

PP

pancreatic polypeptide

-R (suffix)

receptor.
↵² A. Øster, J. Jensen, P. Serup, O. D. Madsen, and L.-I. Larsson, manuscript in preparation.
- Received December 29, 1995.
- Revision received May 2, 1996.