[Study on the germline mutation of MSH6 gene in Chinese hereditary nonpolyposis colorectal cancer pedigrees using PCR based sequencing].
OBJECTIVE
To detect the germline mutation of mismatch repair gene (MSH6) in hereditary nonpolyposis colorectal cancer (HNPCC) kindreds fulfilling different clinical criteria.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Yan
Shi-yan
SY
Department of Pathology, Cancer Hospital, Fudan University, Shanghai, 200032 PR China.
Zhou
Xiao-yan
XY
Cai
San-jun
SJ
Yu
Bao-hua
BH
Zhang
Tai-ming
TM
Li
Xiao-mei
XM
Lu
Yong-ming
YM
Zhou
Heng-hua
HH
Mo
Shan-jing
SJ
Du
Xiang
X
Shi
Da-ren
DR
D000328:Adult; D044466:Asian People / Q000235:genetics; D020137:Base Pair Mismatch / Q000235:genetics*; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics* / Q000473:pathology; D004252:DNA Mutational Analysis; D045643:DNA Repair Enzymes / Q000235:genetics*; D005260:Female; D018095:Germ-Line Mutation / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D051719:MutS DNA Mismatch-Binding Protein / Q000235:genetics*; D051718:MutS Homolog 2 Protein / Q000235:genetics; D010375:Pedigree; D016133:Polymerase Chain Reaction
D051719:MutS DNA Mismatch-Binding Protein; D051718:MutS Homolog 2 Protein; D045643:DNA Repair Enzymes