title: Characterization of hMLH1 and hMSH2 gene dosage alterations in Lynch syndrome patients.
abstract: OBJECTIVE
  A significant proportion of Lynch syndrome cases are believed to be due to large genomic alterations in the mismatch repair genes hMLH1 and hMSH2. However, previous studies have not adequately identified the frequency and scope of such mutations, and routine clinical Lynch syndrome testing often does not include analysis for these mutations. Our aim was to characterize hMLH1 and hMSH2 genomic rearrangements in a large population of suspected Lynch syndrome patients.
  
  
  METHODS
  A total of 365 samples from probands referred for genetic testing for Lynch syndrome were analyzed for the presence of large genomic alterations in hMLH1 or hMSH2 by using a combination of techniques. Samples with a deletion in exons 1-6 in hMSH2 were further characterized by polymerase chain reaction to establish the presence of the hMSH2 American founder deletion.
  
  
  RESULTS
  An hMLH1 or hMSH2 mutation was identified in 153 cases, and, of these, 12 of 67 (17.9%) and 39 of 86 (45.3%) had a large genomic alteration in hMLH1 and hMSH2, respectively. Overall, 6 different hMLH1 and 12 different hMSH2 deletions/duplications, including 10 novel mutations, were identified. Analysis of the hMSH2 exon 1-6 deletion samples showed that 13 of 18 (72.2%) had the American founder deletion.
  
  
  CONCLUSIONS
  These data show a high frequency and diverse spectrum of large genomic alterations in hMLH1 and hMSH2 in suspected Lynch syndrome patients. Thus, a comprehensive mutation identification strategy that includes the ability to detect large genomic rearrangements is imperative for the clinical genetic identification of Lynch syndrome patients and families.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
authors.forename: Linnea M
authors.initials: LM
authors.lastname: Baudhuin
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Ferber
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Winters
authors.forename: Kelle J
authors.initials: KJ
authors.lastname: Steenblock
authors.forename: Russell L
authors.initials: RL
authors.lastname: Swanson
authors.forename: Amy J
authors.initials: AJ
authors.lastname: French
authors.forename: Malinda L
authors.initials: ML
authors.lastname: Butz
authors.forename: Stephen N
authors.initials: SN
authors.lastname: Thibodeau
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017668:Age of Onset; D002352:Carrier Proteins; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D005091:Exons; D005260:Female; D018628:Gene Dosage; D006801:Humans; D008297:Male; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009363:Neoplasm Proteins / Q000235:genetics*; D009679:Nuclear Family; D009687:Nuclear Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D012189:Retrospective Studies; D017384:Sequence Deletion
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein