Hepatocyte nuclear factor-4 gamma - cDNA sequence, gene organization, and mutation screening in early-onset autosomal-dominant type 2 diabetes

The aim of this study was to investigate whether mutations in hepatocyte nu clear factor (HNF)-4(gamma), a transcription factor homologous to HNF-4 alp ha, contribute to the etiology of early-onset type 2 diabetes. Linkage betw een diabetes and two polymorphic markers at the HNF-4 gamma locus (D8S286 a nd D8S548) was evaluated in 32 multigenerational families with early-onset autosomal-dominant type 2 diabetes unlinked to known maturity-onset diabete s of the young genes. Total logarithm of odds (LOD) scores were strongly ne gative (-50.3 at D8S286 and -46.2 at D8S548), but linkage could not be excl uded in 15 families having LOD scores >-2.0. To screen these pedigrees for HNF-4 gamma mutations, the gene structure was defined. Because reverse tran scriptase-polymerase chain reaction experiments indicated that the first 1, 674 bp of the published cDNA sequence (3,248 bp) were a cloning artifact, t he correct cDNA sequence was determined by 5' rapid amplification of cDNA e nds (RACE) and primer extension assay. Based on the new cDNA sequence (1,73 1 bp), 11 exons were found. After screening the 5' flanking region and all coding exons for mutations, we identified several polymorphisms, one of whi ch affected the amino acid sequence (M190I). However, no mutations segregat ing with diabetes could be found in these families. Fire conclude that gene tic variability in the HNF-4 gamma gene is unlikely to play a major role in the etiology of early-onset autosomal-dominant type 2 diabetes.