Identification and functional analysis of mutations in the hepatocyte nuclear factor-1alpha gene in anti-islet autoantibody-negative Japanese patients with type 1 diabetes.
Mutations in the hepatocyte nuclear factor-1alpha (HNF-1alpha) gene are the cause of maturity-onset diabetes of the young type 3 (MODY 3), which is characterized by a severe impairment of insulin secretion and early onset of the disease. Although the majority of patients with type 1 diabetes have type 1A, immune-mediated diabetes, there is a significant percentage of the patients who have no evidence of an autoimmune disorder at the onset of disease. The aim of this study was to estimate the prevalence of MODY 3 in antiislet autoantibody negative patients with type 1 diabetes. From a large population-based sample of unrelated Japanese patients with type 1 diabetes, 28 patients who lacked autoantibodies to glutamic acid decarboxylase, islet cell antigen 512/insulinoma-associated antigen-2, phogrin (phosphate homolog of granules of insulinoma)/insulinoma-associated antigen-2beta, and insulin at the onset of type 1 diabetes were examined by PCR-based direct sequencing of the 10 exons, flanking introns, and the promoter region of the HNF-1alpha gene. Two (7.1%) of 28 autoantibody-negative patients with type 1 diabetes were identified as carrying mutations in the HNF-1alpha gene. One patient carried a frameshift mutation (Pro379fsdelCT) in exon 6, and another patient carried a novel 2-bp substitution at nucleotides +45 (G to A) and +46 (C to A) from the transcriptional site of the promoter region. These mutations were identified in heterozygous form and were not identified in 64 unrelated healthy control subjects or 54 unrelated islet autoantibody-positive patients with type 1 diabetes. Functional analysis of the mutant HNF-1alpha gene indicated that the Pro379fsdelCT mutation had no transcriptional trans-activation activity and acted in a dominant negative manner. The +45/46 GC to AA mutation in the promoter region showed reduced promoter activity by 10-20% compared to the wild-type sequence. In conclusion, about 7% of Japanese diabetic patients lacking antiislet autoantibodies initially classified as having type 1 diabetes could have diabetes caused by mutations in the HNF-1alpha gene.
Kawasaki
E
E
First Department of Internal Medicine, Nagasaki University School of Medicine, Japan. f1196@cc.nagasaki-u.ac.jp
Sera
Y
Y
Yamakawa
K
K
Abe
T
T
Ozaki
M
M
Uotani
S
S
Ohtsu
N
N
Takino
H
H
Yamasaki
H
H
Yamaguchi
Y
Y
Matsuura
N
N
Eguchi
K
K
D000293:Adolescent; D000328:Adult; D001323:Autoantibodies / Q000032:analysis / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D004247:DNA / Q000032:analysis / Q000235:genetics; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics* / Q000276:immunology; D005260:Female; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D006801:Humans; D007515:Islets of Langerhans / Q000276:immunology*; D007564:Japan; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000502:physiology*; D009687:Nuclear Proteins / Q000235:genetics*; D010375:Pedigree; D011110:Polymorphism, Genetic / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*
D001323:Autoantibodies; D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; C496495:HNF1B protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; D009687:Nuclear Proteins; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta; D004247:DNA