Molecular Scanning On HNF1β Genes In The Diabetes Pedigrees With Hepatic And Renal Cysts

Research background Monogenic diabetes have recently received attention,because of definiteness of pathogenic gene, high of exon rate, largeness of theirfamily heritability. Monogenic diabetes including Maturity-Onset Diabetes of theYoung (MODY), mitochondrial DNA mutations in diabetes, neonatal diabetes, geneticdefects of insulin such as the insulin receptor gene mutation. MODY belongs to aspecial type of diabetes which is an autosomal dominant genetic disease. Its mainmechanism of pathogenesis is the defection of glucose-stimulated β-cell. It is oftencharacterized by early onset which is often less than25years old, at least twogenerations of a family history of diabetes, less prone to ketone acidosis disease and atleast2years before dependent on insulin therapy. To date, at least13genes associatedwith MODY have been found, of which hepatocyte nuclear factor-1β gene(Hepatocyte Nuclear Factor1β, HNF1β) is a transcription factor regulating genesspecifically expressed in the liver. HNF1β can identify some specific targetsequence. By combination to cis-acting elements of the regulatory region, it can playthe role of activation or repression of target gene transcription. The gene of HNF1βis one of the genes of MODY5disease. Overseas research showed that the incidenceof MODY5was low and its clinical phenotype was complex and diverse. The mostcommon clinical phenotype were diabetes and renal cysts followed by liver phenotype.Domestic research on MODY is still on early stage. As so far, there is still no cleardata about which MODY subtypes is more common. Previous study demonstrated that the mutation of GCK and HNF1α gene could cause MODY2and MODY3subtypes.There is less report on MODY5subtypes，especially on MODY5pedigrees. Based onthe above researches, we analyzed part of patients from four diabetic pedigrees in ourhospital to explore whether clinical common familial diabetes is associated with thegene mutation of HNF1β. Meanwhile, the corresponding clinical subtype ofMODY5was analyzed in the present study to provide new ideas for the clinicaldiagnosis and treatment for MODY5.Objective In this study, HNF1β gene molecular was screened in four pedigreesof diabetic patients with hepatic or/and kidney cysts to explore whether MODY5genemutation existed in the four pedigrees and to definite the possible mutation point.Meanwhile, the relationship between the clinical phenotype of HNF1β gene andMODY5gene mutation was analyzed in the present study.Methods A total of12cases of the four pedigrees were selected in the study,including9cases of two pedigrees of diabete with hepatic and renal cysts (F1、F2),2cases of one pedigree of diabete with hepatic cyst (F3) and1proband case of onepedigrees of diabete with multiple cysts in the two kidneys (F4). The indexes ofheight, weight, blood glucose, blood lipids, blood pressure and other related indicatorswere measured in the subjects.5ml of peripheral blood was extracted withanticoagulant ethylene diamine tetra-acetic acid (EDTA). The DNA of peripheralblood was extracted by the method of improved chloroform-phenol and thepolymerase chain reaction (PCR) was was performed to amplify all the exons andexon／intron splice sites of HNF1β gene， and the products of PCR were directsequenced to identify specific nucleic acid mutations and their encoded amino acidmutations，20healthy members were selected as control group.Results1. Heterozygosity mutation c.1861C>T resulting in the conversion ofserine(S) into phenylalanine acid(F)(S547F) was identified in exon8of HNF1β genein two patients of F1pedigree, it was not found in the same location of the othersubjects. The detection rate of mutations in the pedigree is0.29(2/7).2. The codingregion mutation in HNF1β gene was not found in the F3lines, but a rare SNP of the HNF1β gene was found:+99C>T was only seen in this family, it was not found inthe same location of the control group, the detection rate of this snp in the pedigreewas0.17(2/12) and in all subjects was0.063(2/32).3. Mutations in the coding regionand the rare SNP were not found in the F2and F3pedigrees.4. Five kinds of SNPwere found in the four families: IVS7-115G>A, IVS8+102G>A, IVS8+155delA,IVS9-22T>C,+100G>A, the detection rate of thses snps in12family membersrespectively were.:0.25(3/12),0.5(6/12),0.5(6/12),0.42(5/12),0.58(7/12); and thedetection rate of thses snps in the control group were as follows:0.25(5/20),0.20(4/20),0.20(4/20),0.45(9/20),0.55(11/20).5. In F1pedigree, the three groups are asfollows: the group of diabetes members who carry S547F mutation and who did notcarry mutations in diabetes and the family members who blood sugar was normal,these three groups were compared, there was found this HNF1β gene mutationS547F was associated with kidney structural abnormalities and kidney function, otherindexes in these three groups of members were differences without statisticalsignificance. The proband and her son who carry the mutation of+99A> C in the F3family have high blood glucose, meanwhile the proband with hepatic cysts and herson with liver enzyme abnormalities.Conclusion One pedigree of MODY5was identified by the way of moleculargenetics. The domain mutant site was Located in the transactivation of S547F, whichcaused significant individual differences in the clinical phenotypes within thepedigree. The downstream regulatory sequences+99C> A polymorphism may beassociated with diabetes and liver disease but specific pathogenic mechanism remainsto be protein function studies confirmed.