Identification Of The Mutations In The Two Single-gene Disease Families

Gene mutations in human gene can cause various diseases. The human autosomal dominant brachydactyly type B(BDB) and autosomal dominant polycystic kidney disease(PKD) are due to gene mutation on chromosome. In order to reduce the damage which familial hereditary disease cause, modern molecular biology techniques can be used to find disease-causing mutation to prevent individuals carrying the disease-causing gene from borning.This issue is the molecular genetics research of two large single-gene dominant hereditary diseases, involing pedigree analysis, localization of genes, gene mutations analysis.First, to identify the mutation in ROR2 that caused brachydactyly type B1(BDB1). BDB1 is caused by mutations in the orphan tyrosine kinase receptor, ROR2 on chromosome 9q22. The protein encoded by this gene is a receptor protein tyrosine kinase and type I transmembrane protein that belongs to the ROR2 subfamily of cell surface receptors. In this study, two large Chinese families, one is six-generation Chinese family; the other is eight-generation Chinese family. According to the previous report, the mutation in the two families is consistent. Thus, we selected some microsatellite(STR)markers around the disease-causing gene ROR2 of BDB1. PCR amplification products were denatured and then polyacrylamide gel electrophoresis, analysis of the allele fragments, heplotype construction, choosing two-point linkage analysis, LOD scores were calculated using the MLINK component of the LINKAGE program package. Linkage analysis showed that the causative mutation in the two families was linked to marker D9S753, the LOD score is 3.41 at a recombination fraction of 0. DNA sequence analysis revealed a heterozygous mutation,the mutation is in the 9 exon of ROR2, c.2247G>A(p.W749X), which converts amino acid 749 from tryptophan to a premature stop.Second, to identify the mutation in PKD1 that caused polycystic kidney disease (PKD). PKD is an autosomal dominant hereditary disease, it can be divided into autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD). The family we studied is an autosomal dominant polycystic kidney diseases family, the mutation gene is PKD1, locating on the 16p13.3,about 85%of ADPKD is ADPKD1.The mutation is in the 31 exon of PKD1, c.3368G>A(p.D1123N), which converts amino acid 3368 from Asp to Asn.The result of first study, preparing for prenatal diagnosis by identifying the desease-causing mutation. The result of second study proved the mutation type is the first case in northwest of China, further more, this result proved the PKD in clinical and genetics heterogeneity.