A novel missense mutation in the homeodomain of the hepatocyte nuclear factor-1alpha/maturity-onset diabetes of the young 3 in a Japanese early-onset type 2 diabetic patient and time-course of glucose-stimulated insulin secretion

Mutations in the genes encoding the transcription factors hepatocyte nuclear factor 1 alpha (HNF1A) and 4 alpha (HNF4A) in maturity-onset diabetes of the young

Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes mellitus characterized by autosomal dominant inheritance, early age of onset (often <25 years of age), and pancreatic beta-cell dysfunction. MODY is both clinically and genetically heterogeneous, with six different genes identified to date; glucokinase (GCK), hepatocyte nuclear factor-1 alpha (HNF1A, or TCF1), hepatocyte nuclear factor-4 alpha (HNF4A), insulin promoter factor-1 (IPF1 or PDX1), hepatocyte nuclear factor-1 beta (HNF1B or TCF2), and neurogenic differentiation 1 (NEUROD1). Mutations in the HNF1A gene are a common cause of MODY in the majority of populations studied. A total of 193 different mutations have been described in 373 families. The most common mutation is Pro291fs (P291fsinsC) in the polycytosine (poly C) tract of exon 4, which has been reported in 65 families. HNF4A mutations are rarer; 31 mutations reported in 40 families. Sensitivity to treatment with sulfonylurea tablets is a feature of both HNF1A and HNF4A mutations. The identification of an HNF1A or 4A gene mutation confirms a diagnosis of MODY and has important implications for clinical management.

The private hepatocyte nuclear factor-1alpha G319S variant is associated with plasma lipoprotein variation in Canadian Oji-Cree

We previously showed an extremely strong association between type 2 diabetes and a private polymorphism, namely G319S, in the hepatocyte nuclear transcription factor (HNF)-1alpha. Because HNF-1alpha is involved in the transcription of several apolipoprotein genes, we tested for an association between the private HNF1A G319S variant and plasma lipoproteins in a sample of 55 unrelated Oji-Cree subjects with type 2 diabetes and 175 unrelated Oji-Cree subjects without type 2 diabetes. In Oji-Cree subjects with type 2 diabetes, we found that the HNF1A G319S genotype was significantly associated with lower plasma concentrations of total cholesterol, low density lipoprotein cholesterol, and apolipoprotein (apo) B. In Oji-Cree subjects without type 2 diabetes, we found that the HNF1A G319S genotype was significantly associated with higher plasma concentrations of high density lipoprotein cholesterol and apo AI. There were no associations with plasma triglycerides or lipoprotein(a). Regression analysis indicated that the HNF1A genotype accounted for approximately 10% of the variation in the apo B-related traits in the diabetic subjects and for approximately 5% of the variation in the apo AI-related traits in the nondiabetic subjects. Furthermore, the regression model indicated that the HNF1A S319 allele affected these traits in a dominant manner in subjects with and without type 2 diabetes. These findings provide the first evidence that a rare variant in a nuclear transcription factor is associated with variation in plasma lipoprotein traits.

The hepatic nuclear factor-1alpha G319S variant is associated with early-onset type 2 diabetes in Canadian Oji-Cree

Mutations in the gene encoding hepatic nuclear factor-1alpha (HNF-1alpha) have been found in patients with maturity-onset diabetes of the young. We identified a new variant in the HNF-1alpha gene, namely G319S, in Ontario Oji-Cree with type 2 diabetes. G319S is within the proline II-rich domain of the trans-activation site of HNF-1alpha and alters a glycine residue that is conserved throughout evolution. S319 was absent from 990 alleles taken from subjects representing six other ethnic groups, suggesting that it is private for Oji-Cree. We found that 1) the S319 allele was significantly more prevalent in diabetic than nondiabetic Oji-Cree (0.209 vs. 0.087; P = 0.000001); 2) S319/S319 homozygotes and S319/G319 heterozygotes, respectively, had odds ratios for type 2 diabetes of 4.00 (95% confidence interval, 2.65-6.03) and 1.97 (95% confidence interval, 1.44-2.70) compared with G319/G319 homozygotes; 3) there was a significant difference in the mean age of onset of type 2 diabetes, with G319/G319, S319/G319, and S319/S319 subjects affected in the fifth, fourth, and third decades of life, respectively. In subjects with type 2 diabetes, we also found significantly lower body mass index and significantly higher post-challenge plasma glucose in S319/S319 and S319/G319 compared with G319/G319 subjects. Finally, among nondiabetic subjects, S319/G319 heterozygotes had significantly lower plasma insulin than G319/G319 homozygotes. The presence of the private HNF-1alpha G319S variant in a large number of Oji-Cree with type 2 diabetes and its strong association with type 2 diabetes susceptibility are unique among human populations. Also, G319S is associated with a distinct form of type 2 diabetes, characterized by onset at an earlier age, lower body mass, and a higher postchallenge plasma glucose.