title: Missense variants in hMLH1 identified in patients from the German HNPCC consortium and functional studies.
abstract: Missense mutations of the DNA mismatch repair gene MLH1 are found in a significant fraction of patients with Lynch syndrome (hereditary nonpolyposis colorectal cancer, HNPCC) and their pathogenicity often remains unclear. We report here all 88 MLH1 missense variants identified in families from the German HNPCC consortium with clinical details of these patients/families. We investigated 23 MLH1 missense variants by two functional in vivo assays in yeast; seven map to the ATPase and 16 to the protein interaction domain. In the yeast-2-hybrid (Y2H) assay three variants in the ATPase and twelve variants in the interaction domain showed no or a reduced interaction with PMS2; seven showed a normal and one a significantly higher interaction. Using the Lys2A (14) reporter system to study the dominant negative mutator effect (DNE), 16 variants showed no or a low mutator effect, suggesting that these are nonfunctional, three were intermediate and four wild type in this assay. The DNE and Y2H results were concordant for all variants in the interaction domain, whereas slightly divergent results were obtained for variants in the ATPase domain. Analysis of the stability of the missense proteins in yeast and human embryonic kidney cells (293T) revealed a very low expression for seven of the variants in yeast and for nine in human cells. In total 15 variants were classified as deleterious, five were classified as variants of unclassified significance (VUS) and three were basically normal in the functional assays, P603R, K618R, Q689R, suggesting that these are neutral.
authors.affiliation: Institute of Human Genetics and Anthropology, Heinrich Heine University and University Hospital Duesseldorf, Postfach 101007, 40001 Duesseldorf, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Hardt
authors.forename: Sven Boris
authors.initials: SB
authors.lastname: Heick
authors.forename: Beate
authors.initials: B
authors.lastname: Betz
authors.forename: Timm
authors.initials: T
authors.lastname: Goecke
authors.forename: Haniyeh
authors.initials: H
authors.lastname: Yazdanparast
authors.forename: Robin
authors.initials: R
authors.lastname: Küppers
authors.forename: Kati
authors.initials: K
authors.lastname: Servan
authors.forename: Verena
authors.initials: V
authors.lastname: Steinke
authors.forename: Nils
authors.initials: N
authors.lastname: Rahner
authors.forename: Monika
authors.initials: M
authors.lastname: Morak
authors.forename: Elke
authors.initials: E
authors.lastname: Holinski-Feder
authors.forename: Christoph
authors.initials: C
authors.lastname: Engel
authors.forename: Gabriela
authors.initials: G
authors.lastname: Möslein
authors.forename: Hans-Konrad
authors.initials: HK
authors.lastname: Schackert
authors.forename: Magnus
authors.initials: M
authors.lastname: von Knebel Doeberitz
authors.forename: Christian
authors.initials: C
authors.lastname: Pox
authors.forename: Johannes H
authors.initials: JH
authors.lastname: Hegemann
authors.forename: Brigitte
authors.initials: B
authors.lastname: Royer-Pokora
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics; D002478:Cells, Cultured; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics*; D053843:DNA Mismatch Repair; D006801:Humans; D000070957:MutL Protein Homolog 1; D020125:Mutation, Missense; D009687:Nuclear Proteins / Q000235:genetics*; D017434:Protein Structure, Tertiary; D020798:Two-Hybrid System Techniques; D015003:Yeasts / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D000251:Adenosine Triphosphatases; D000070957:MutL Protein Homolog 1