Insulin Gene Mutations Resulting in Early-Onset Diabetes: Marked Differences in Clinical Presentation, Metabolic Status, and Pathogenic Effect Through Endoplasmic Reticulum Retention
- Gargi Meur1,
- Albane Simon2,
- Nasret Harun1,
- Marie Virally3,
- Aurélie Dechaume4,
- Amélie Bonnefond4,
- Sabrina Fetita5,
- Andrei I. Tarasov1,
- Pierre-Jean Guillausseau3,
- Trine Welløv Boesgaard6,
- Oluf Pedersen6,7,8,
- Torben Hansen6,9,
- Michel Polak2,
- Jean-François Gautier5,
- Philippe Froguel4,10,
- Guy A. Rutter1 and
- Martine Vaxillaire4
- 1Section of Cell Biology, Division of Medicine, Imperial College London, London, U.K.;
- 2Universite Paris Descartes, INSERM U845, Pediatric Endocrinology, Hopital Necker Enfants Malades Paris, Paris, France;
- 3Department of Endocrinology and Diabetes, Lariboisière Hospital, University Paris-Diderot Paris-7, Paris, France;
- 4Centre National de la Recherche Scientifique-UMR8090, Lille Institute of Biology, Lille 2 University, Pasteur Institute, Lille, France;
- 5Department of Endocrinology and Diabetes, Clinical Investigation Center CIC9504, Saint-Louis Hospital, INSERM, U872, University Paris-Diderot Paris-7, Paris, France;
- 6Hagedorn Research Institute and Steno Diabetes Center, Gentofte, Denmark;
- 7Faculty of Health Science, University of Aarhus, Aarhus, Denmark;
- 8Institute of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark;
- 9Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark;
- 10Genomic Medicine, Hammersmith Hospital, Imperial College, London, U.K.
- Corresponding authors: Guy A. Rutter, g.rutter{at}imperial.ac.uk, or Philippe Froguel, froguel{at}mail-good.pasteur-lille.fr.
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A.S., N.H., and M.V. contributed equally to this work.
Abstract
OBJECTIVE Heterozygous mutations in the human preproinsulin (INS) gene are a cause of nonsyndromic neonatal or early-infancy diabetes. Here, we sought to identify INS mutations associated with maturity-onset diabetes of the young (MODY) or nonautoimmune diabetes in mid-adult life, and to explore the molecular mechanisms involved.
RESEARCH DESIGN AND METHODS The INS gene was sequenced in 16 French probands with unexplained MODY, 95 patients with nonautoimmune early-onset diabetes (diagnosed at <35 years) and 292 normoglycemic control subjects of French origin. Three identified insulin mutants were generated by site-directed mutagenesis of cDNA encoding a preproinsulin–green fluorescent protein (GFP) (C-peptide) chimera. Intracellular targeting was assessed in clonal β-cells by immunocytochemistry and proinsulin secretion, by radioimmunoassay. Spliced XBP1 and C/EBP homologous protein were quantitated by real-time PCR.
RESULTS A novel coding mutation, L30M, potentially affecting insulin multimerization, was identified in five diabetic individuals (diabetes onset 17–36 years) in a single family. L30M preproinsulin-GFP fluorescence largely associated with the endoplasmic reticulum (ER) in MIN6 β-cells, and ER exit was inhibited by ∼50%. Two additional mutants, R55C (at the B/C junction) and R6H (in the signal peptide), were normally targeted to secretory granules, but nonetheless caused substantial ER stress.
CONCLUSIONS We describe three INS mutations cosegregating with early-onset diabetes whose clinical presentation is compatible with MODY. These led to the production of (pre)proinsulin molecules with markedly different trafficking properties and effects on ER stress, demonstrating a range of molecular defects in the β-cell.
Footnotes
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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- Received July 27, 2009.
- Accepted November 24, 2009.
- © 2010 by the American Diabetes Association.
