Yan Shi-yan, Zhou Xiao-yan, Cai San-jun, Yu Bao-hua, Zhang Tai-ming, Li Xiao-mei, Lu Yong-ming, Zhou Heng-hua, Mo Shan-jing, Du Xiang, Shi Da-ren
Department of Pathology, Cancer Hospital, Fudan University, Shanghai, 200032 PR China.
Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 2007 Dec;24(6):640-5.
To detect the germline mutation of mismatch repair gene (MSH6) in hereditary nonpolyposis colorectal cancer (HNPCC) kindreds fulfilling different clinical criteria.
The germline mutations of MSH6 gene were detected by PCR based DNA sequencing in 39 unrelated HNPCC probands fulfilling different clinical criteria in which MSH2 and MLH1 mutations were excluded. The exons with missense mutations were analyzed using PCR sequencing in the germline genomic DNA of 137 healthy persons. The expression of MSH6 protein was detected by Envision immunohistochemistry staining in the tumor tissues of the mutational probands.
Six germline mutations of MSH6 gene were detected in 39 probands of Chinese HNPCC kindreds, and the mutations distributed in the exon 4, 6, 9 and 10. Four out of six mutations were missense mutation, one was nonsense mutation and the remaining one was insertion mutation in splice site. The results of sequecing for the exons with above four missense mutations in 137 healthy persons' genomic DNA showed that 5 of 137 persons had the missense mutation of c.3488 A to T at codon 1163 of the 6th exon. The mutational rate was approximately 3.65% (5/137), so the mutation could be a single nucleotide polymorphism (SNP). The remaining missense mutations were not found in any germline genomic DNA of 137 healthy persons. Positive expression of MSH6 protein had been identified in the tumor of the SNP proband while the tumors had negative MSH6 protein expression in the rest probands of germline mutation MSH6 gene. The types of mutations and their potential significance were determined by comparing the following databases: http://www.ncbi.nlm.nih.gov/, http://www.ensembl.org/homo-sapies, and http://www.insight-group.org. Five out of the six mutations had not been reported previously and they were new pathological mutations, the rest one was a new SNP.
Germline mutations of MSH6 gene may play an important role in Chinese HNPCC kindreds fulfilling different clinical criteria. It is necessary to analyze the germline mutations of MSH6 gene using sequencing to identify HNPCC families in the probands in which MSH2 and MLH1 mutation were excluded.
检测符合不同临床标准的遗传性非息肉病性结直肠癌（HNPCC）家系中错配修复基因（MSH6）的胚系突变。
采用基于聚合酶链反应（PCR）的DNA测序技术，对39例符合不同临床标准且排除了MSH2和MLH1突变的无关HNPCC先证者进行MSH6基因的胚系突变检测。对137名健康人的胚系基因组DNA中存在错义突变的外显子进行PCR测序分析。采用Envision免疫组化染色法检测突变先证者肿瘤组织中MSH6蛋白的表达。
在39例中国HNPCC家系的先证者中检测到6个MSH6基因的胚系突变，这些突变分布在外显子4、6、9和10。6个突变中有4个为错义突变，1个为无义突变，另1个为剪接位点插入突变。对137名健康人基因组DNA中上述4个错义突变所在外显子进行测序的结果显示，137人中有5人第6外显子第1163密码子处存在c.3488 A到T的错义突变。突变率约为3.65%（5/137），因此该突变可能是单核苷酸多态性（SNP）。在137名健康人的任何胚系基因组DNA中均未发现其余错义突变。在SNP先证者的肿瘤中检测到MSH6蛋白阳性表达，而在其余MSH6基因胚系突变先证者的肿瘤中MSH6蛋白表达为阴性。通过比较以下数据库确定突变类型及其潜在意义：http://www.ncbi.nlm.nih.gov/、http://www.ensembl.org/homo-sapies和http://www.insight-group.org。这6个突变中有5个以前未报道过，是新的病理性突变，其余1个是新的SNP。
MSH6基因的胚系突变可能在符合不同临床标准的中国HNPCC家系中起重要作用。对于排除了MSH2和MLH1突变的先证者，有必要采用测序方法分析MSH6基因的胚系突变以鉴定HNPCC家系。
