Genetic variation in the hepatocyte nuclear factor-3β gene (HNF3B) does not contribute to maturity-onset diabetes of the young in French Caucasians

Mutations in genes encoding hepatocyte nuclear factor (HNF) are responsible for three of the five subtypes of maturity-onset diabetes of the young (MODY). This observation and molecular studies indicate that the HNF network is required for normal function of pancreatic beta-cells. This suggests that transcription factors involved in this complex network are candidates for genetic defects in MODY. Because the HNF-3 beta gene is implicated in this network, we screened it for mutations in 21 probands of French ancestry with clinical diagnosis of MODY and early-onset type 2 diabetes, All of the five known MODY genes, HNF-4 alpha, glucokinase, HNF-1 alpha; HNF-1 beta, and IPF1, were previously excluded as being the cause of diabetes in these families, By direct sequencing, we identified two transitions, an A-to-G rat position -213 and a C-to-T at position -63 in the promoter and exon 1, respectively, of the HNF-3 beta gene. A G-to-C transversion at position +32 in the intron 1 and three transitions, C-to-T at position 291, A to-G at position 837, and G-to-A at position 1188 in the exon 3, resulting in noncoding mutations Ala97Ala, Gly279Gly, and Gln396Gln, respectively, were also identified. The allele frequencies were not significantly different between a control group and MODY probands, Familial segregation studies and linkage analysis showed that; genetic variation in the HNF-3 beta gene is unlikely to be the cause of early-onset type 2 diabetes in these Caucasian families.