title: Uncertain pathogenicity of MSH2 variants N127S and G322D challenges their classification.
abstract: Hereditary non-polyposis colorectal cancer (HNPCC) is associated with germline mutations in mismatch repair (MMR) genes. Inherited missense mutations, however, complicate the diagnostics because they do not always cause unambiguous predisposition to cancer. This leads to variable and contradictory interpretations of their pathogenicity. Here, we establish evidence for the functionality of the 2 frequently reported variations, MSH2 N127S and G322D, which have been described both as pathogenic and non-pathogenic in literature and databases. We report the results of 3 different functional analyses characterizing the biochemical properties of these protein variants in vitro. We applied an immunoprecipitation assay to assess the MSH2-MSH6 interaction, a bandshift assay to study mismatch recognition and binding, and a MMR assay for repair efficiency. None of the experiments provided evidence on reduced functionality of these proteins as compared to wild-type MSH2. Our data demonstrate that MSH2 N127S and G322D per se are not sufficient to trigger MMR deficiency. This together with variable clinical phenotypes in the mutation carriers suggest no or only low cancer risk in vivo.
authors.affiliation: Department of Biological and Environmental Sciences, Genetics, University of Helsinki, Helsinki, Finland.
authors.forename: Saara
authors.initials: S
authors.lastname: Ollila
authors.forename: Denis
authors.initials: D
authors.lastname: Dermadi Bebek
authors.forename: Marc
authors.initials: M
authors.lastname: Greenblatt
authors.forename: Minna
authors.initials: M
authors.lastname: Nyström
mesh_terms: D001216:Asparagine; D001224:Aspartic Acid; D001661:Biliary Tract Neoplasms / Q000235:genetics; D015153:Blotting, Western; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics*; D053843:DNA Mismatch Repair; D004268:DNA-Binding Proteins / Q000235:genetics; D016889:Endometrial Neoplasms / Q000235:genetics; D005260:Female; D020022:Genetic Predisposition to Disease; D018095:Germ-Line Mutation; D005998:Glycine; D006801:Humans; D047468:Immunoprecipitation; D051718:MutS Homolog 2 Protein / Q000235:genetics*; D010190:Pancreatic Neoplasms / Q000235:genetics; D012694:Serine; D035501:Uncertainty
chemical_list: D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; D001224:Aspartic Acid; D012694:Serine; D001216:Asparagine; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein; D005998:Glycine