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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.
- Source :
-
Diabetes . Aug2009, Vol. 58 Issue 8, p1929-1935. 7p. 1 Diagram, 1 Chart, 2 Graphs. - Publication Year :
- 2009
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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