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Identification of a Novel β-Cell Glucokinase (GCK) Promoter Mutation (-71G>C) That Modulates GCK Gene Expression Through Loss of Allele-Specific Sp1 Binding Causing Mild Fasting Hyperglycemia in Humans.

Authors :
Gašperíková, Daniela
Tribble, Nicolas D.
Staník, Juraj
Hučková, Miroslava
Mišovicová, Nadežda
van de Bunt, Martijn
Valentínová, Lucia
Barrow, Beryl A.
Barák, L'ubomir
Dobránsky, Radoslav
Bereczková, Eva
Michálek, Jozef
Wicks, Kate
Colclough, Kevin
Knight, Julian C.
Ellard, Sian
Klimeš, Iwar
Gloyn, Anna L.
Source :
Diabetes. Aug2009, Vol. 58 Issue 8, p1929-1935. 7p. 1 Diagram, 1 Chart, 2 Graphs.
Publication Year :
2009

Abstract

OBJECTIVE--Inactivating mutations in glucokinase (GCK) cause mild fasting hyperglycemia. Identification of a GCK mutation has implications for treatment and prognosis; therefore, it is important to identify these individuals. A significant number of patients have a phenotype suggesting a defect in glucokinase but no abnormality of GCK. We hypothesized that the GCK β-cell promoter region, which currently is not routinely screened, could contain pathogenic mutations; therefore, we sequenced this region in 60 such probands. RESEARCH DESIGN AND METHODS--The β-cell GCK promoter was sequenced in patient DNA. The effect of the identified novel mutation on GCK promoter activity was assessed using a luciferase reporter gene expression system. Electrophoretic mobility shift assays (EMSAs) were used to determine the impact of the mutation on Sp1 binding. RESULTS--A novel -71G>C mutation was identified in a nonconserved region of the human promoter sequence in six apparently unrelated probands. Family testing established cosegregation with fasting hyperglycemia (≥5.5 mmol/l) in 39 affected individuals. Haplotype analysis in the U.K. family and four of the Slovakian families demonstrated that the mutation had arisen independently. The mutation maps to a potential transcriptional activator binding site for Sp1. Reporter assays demonstrated that the mutation reduces promoter activity by up to fourfold. EMSAs demonstrated a dramatic reduction in Sp1 binding to the promoter sequence corresponding to the mutant allele. CONCLUSIONS--A novel p-cell GCK promoter mutation was identified that significantly reduces gene expression in vitro through loss of regulation by Sp1. To ensure correct diagnosis of potential GCK-MODY (maturity-onset diabetes of the young) cases, analysis of the β-cell GCK promoter should be included. Diabetes 58:1929-1935, 2009 [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00121797
Volume :
58
Issue :
8
Database :
Academic Search Index
Journal :
Diabetes
Publication Type :
Academic Journal
Accession number :
44148062
Full Text :
https://doi.org/10.2337/db09-0070