Identification and functional characterization of a novel mutation of hepatocyte nuclear factor-1α gene in a Korean family with MODY3

Abstract

Aims/hypothesis. After screening 16 Korean families with early onset Type 2 diabetes in search for hepatocyte nuclear factor (HNF)-1α gene mutation, we identified a novel missense mutation (R263L) associated with MODY phenotype. We studied the biological characteristics of the mutation and the potential functional consequences based on the crystallographic structure of HNF-1α in complex with DNA. Methods. DNA from subjects with a familial form of early onset diabetes was isolated and HNF-1α was sequenced. The R263L substitution was generated by PCR-based sited-directed mutagenesis. Functional and biochemical studies were conducted by reporter assay using glucose-transporter type 2 (GLUT2) or insulin promoters and electrophoretic mobility shift assay, respectively. Results. Transfection of wild-type HNF-1α increased the reporter activities of GLUT2 and insulin promoters in NIH3T3 and SK-Hep1 cells, while R263L mutant was defective in transactivation of those promoters. Both wild-type HNF-1α and R263L mutant could not transactivate GLUT2 and insulin promoters in MIN6N8 insulinoma cells. R263L mutant had a defective cooperation with its heterodimeric partner HNF-1β or coactivator p300. R263L mutant protein displayed greatly reduced DNA binding ability, despite its comparable protein stability to the wild-type HNF-1α. Conclusion/interpretation. These results suggest that the mutation of HNF-1α at codon 263 from arginine to leucine leads to the development of MODY3 through decreased insulin production and defective glucose sensing. These findings are in good agreement with the crystal structure in which R263 makes hydrogen bonds with phosphorus atoms of DNA backbone to mediate the stable binding of HNF-1α homeodomain to the promoter. [Diabetologia (2003) 46:721-727]

Structural Basis of Disease-Causing Mutations in Hepatocyte Nuclear Factor 1β,

“…It has been reported that the R295H mutant exhibited target-specific effects of activation in which the transactivation potential of R295H on the HNF4α promoter reached to wild-type transactivation level, while transactivation of either Afp or albumin promoter by this mutant were barely detectable (49). In other studies, the corresponding mutants R263C/L in HNF1α showed greatly reduced DNA binding activity as a result of these more drastic substitutions (52,53).…”

Genetic and clinical characteristics of Korean maturity-onset diabetes of the young (MODY) patients

“…Among the 69 patients, only 10 patients had autosomal dominant inheritance of type 2 DM in at least three generations. Kim et al [16]. reported that one patient (6.3%) with an HNF-1a R267L mutation was detected among 16 unrelated patients diagnosed with type 2 DM before the age of 35 years who had autosomal dominant inheritance of type 2 DM in at least two generations.…”

Epigenetics: A Molecular Link Between Environmental Factors and Type 2 Diabetes

“…The chromatin remodeling involves recruitment of HATs (e.g., p300/CBP), resulting in hyperacetylation of histones at specific promoters, including GLUT2 and pyruvate kinase, in β-cells (86–88). Interestingly, a missense mutation (R263L) in the HNF1A gene that is associated with a MODY phenotype results in reduced affinity for p300 (89). Moreover, MODY mutations in the HNF1B gene influence the capacity of HNF1β to bind proteins with HAT activity and may thereby affect the chromatin structure (90).…”