title: Germline mutation analysis of MLH1 and MSH2 in Malaysian Lynch syndrome patients.
abstract: OBJECTIVE
  To investigate the protein expression profile of mismatch repair (MMR) genes in suspected cases of Lynch syndrome and to characterize the associated germline mutations.
  
  
  METHODS
  Immunohistochemical analysis of tumor samples was performed to determine the protein expression profile of MMR protein. Germline mutation screening was carried out on peripheral blood samples. The entire exon regions of MLH1 and MSH2 genes were amplified by polymerase chain reaction, screened by denaturing high performance liquid chromatography (dHPLC) and analyzed by DNA sequencing to characterize the germline mutations.
  
  
  RESULTS
  Three out of 34 tissue samples (8.8%) and four out of 34 tissue samples (11.8%) showed loss of nuclear staining by immunohistochemistry, indicating the absence of MLH1 and MSH2 protein expression in carcinoma cells, respectively. dHPLC analysis followed by DNA sequencing showed these samples to have germline mutations of MSH2 gene. However, no deleterious mutations were identified in any of the 19 exons or coding regions of MLH1 gene, but we were able to identify MLH1 promoter polymorphism, -93G > A (rs1800734), in 21 out of 34 patients (61.8%). We identified one novel mutation, transversion mutation c.2005G > C, which resulted in a missense mutation (Gly669Arg), a transversion mutation in exon 1, c.142G > T, which resulted in a nonsense mutation (Glu48Stop) and splice-site mutation, c.2006-6T > C, which was adjacent to exon 13 of MSH2 gene.
  
  
  CONCLUSIONS
  Germline mutations were identified in four Malaysian Lynch syndrome patients. Immunohistochemical analysis of tumor tissue proved to be a good pre-screening test before proceeding to germline mutation analysis of DNA MMR genes.
authors.affiliation: Human Genome Centre, School of Medical Sciences, University Sains Malaysia Health Campus, 16150 Kubang Kerian, Kelantan, Malaysia.
authors.forename: Mohd Nizam
authors.initials: MN
authors.lastname: Zahary
authors.forename: Gurjeet
authors.initials: G
authors.lastname: Kaur
authors.forename: Muhammad Radzi
authors.initials: MR
authors.lastname: Abu Hassan
authors.forename: Harjinder
authors.initials: H
authors.lastname: Singh
authors.forename: Venkatesh R
authors.initials: VR
authors.lastname: Naik
authors.forename: Ravindran
authors.initials: R
authors.lastname: Ankathil
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D001483:Base Sequence; D015179:Colorectal Neoplasms / Q000209:etiology / Q000235:genetics* / Q000473:pathology; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000150:complications / Q000235:genetics* / Q000473:pathology; D053843:DNA Mismatch Repair; D004252:DNA Mutational Analysis; D020022:Genetic Predisposition to Disease; D018095:Germ-Line Mutation; D006801:Humans; D008296:Malaysia; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics*; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C501486:MLH1 protein, human; D009687:Nuclear Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein