Maturity-onset diabetes of the young (MODY) is an autosomal dominant form of early-onset Type II (non±insulin±dependent) diabetes mellitus. Five different forms of MODY have been identified [1]. Hepatocyte nuclear factor (HNF)-1a/MODY3, a homeodomain-containing transcription factor, functions as a homodimer or a heterodimer with structurally related HNF-1b/MODY5. Hepatocyte nuclear factor-4a/MODY1, a member of the nuclear receptor superfamily, is a positive regulator of HNF-1a gene transcription. Insulin promoter factor-1 (IPF1)/ MODY4, which is required for pancreatic development and insulin gene transcription, regulates the expression of the gene encoding glucokinase/MODY2. Recently, characterization of HNF-1a-knockout mice and insulinoma cells overexpressing HNF-1a and its dominant-negative mutant indicated that HNF-1a is essential for insulin gene transcription and beta-cell glycolytic signalling [2,3]. The functional relation of proteins encoded by these MODY genes suggests the importance of the HNF-transcription cascade in determining beta-cell function. Diabetologia (2000) 43: 121±124
Short communicationCloning of cDNA and the gene encoding human hepatocyte nuclear factor (HNF)-3b and mutation screening in Japanese subjects with maturity-onset diabetes of the young Abstract Aims/hypothesis. Molecular defects of the genes for transcription factors, hepatocyte nuclear factor (HNF)-4a, HNF-1a, HNF-1b and insulin promoter factor-1 cause maturity-onset diabetes of the young (MODY1, 3, 5, and 4, respectively). This suggests the HNF-related transcription cascade is important in insulin secretion which is induced by glucose. These genes and the gene encoding glycolytic enzyme glucokinase (MODY2) are, however, responsible for only 15±20 % of cases of MODY in the Japanese. Searching for a novel form of MODY in this population, we cloned a new candidate gene encoding human HNF-3b, a winged helix transcription factor, which also belongs to the same HNF-transcription cascade. Methods. The cDNA clone for human HNF-3b was isolated from a liver cDNA library. The gene was also cloned from a genomic library and its organization and chromosomal localization were determined. We screened 68 Japanese subjects with MODY/early-onset diabetes for mutations in this gene. Results. Human HNF-3b is composed of 457 amino acids. The human gene, which was mapped to the segment 30 cR from SHGC-37 039 on chromosome 20 p by radiation hybrid mapping, spans approximately 4.5 kb and consists of three exons. Direct sequencing of the exons and flanking regions identified one missense mutation A328 V and seven polymorphisms, although the functional significance of the mutation in the pathogenesis of diabetes is not known. Conclusion/interpretation. The characterization of the structure of the HNF-3b gene and its mapping in the framework of markers will be helpful in genetic studies of the various forms of diabetes mellitus. [Diabetologia (2000) Corresponding author: J. Takeda, MD Laboratory of Molecular Genetics, Department of Cell Biology, I...