NovelMLH1andMSH2germline mutations in the first HNPCC families identified in Slovakia

Abstract

Hereditary nonpolyposis colorectal cancer (HNPCC) is a dominantly-inherited cancer predisposition syndrome, in which the susceptibility to cancer of the colon, endometrium and ovary is linked to germline mutations in DNA mismatch repair (MMR) genes. We have recently initiated a cancer prevention program in suspected HNPCC families in the Slovak Republic. The first ten families fulfilling Amsterdam criteria or Bethesda guidelines were screened for germline mutations in MLH1 and MSH2, two MMR genes most frequently mutated in HNPCC families. Six mutations were identified, five of which have not been reported previously. Two of the three new mutations in MLH1 (c.380+2T>A; c.307-2A>C) were absent from 100 chromosomes of healthy controls and probably cause a splicing defect, while the third was a 1 bp deletion (c.1261delA). In the MSH2 gene, one new nonsense (c.1030C>T [p.Q344X]) and one missense (c.524T>C [p.L175P]) mutation were identified. This latter variant was not found in 104 alleles of healthy control individuals. Moreover, a previously-reported pathogenic mutation (c.677G>T [p.R226L]) was found in one kindred. The clinical data and the genotypic and phenotypic evaluation of the tumors indicate that all the new alterations are pathogenic HNPCC mutations.

Redundant DNA methylation in colorectal cancers of Lynch‐syndrome patients

“…interscience.wiley. Germline mutations consist of 9 novel (cases 1, 2,3,8,11,13,18,21,26) and 6 recurrent (6,14,16,19,20,22) mutations in MLH1 or MSH2 genes and they were described previously in two articles (Bartosova et al, 2003;Zavodna et al, 2006); one patient (code 15) manifests the same germline mutation as in the case 21 (unpublished result).…”

“…These patients manifested MSI-H phenotype, absence of MMR protein expression, and presence of LOH in MMR genes, as described (Alemayehu et al, 2007). In most of them, the novel or recurrent pathogenic germline mutations in MLH1 or MSH2 were detected by genomic sequencing (Bartosova et al, 2003;Zavodna et al, 2006). DNA isolated from blood samples of five healthy persons up to 50 years and five individuals of advanced age were used as controls.…”

Partial loss of heterozygosity events at the mutated gene in tumors from MLH1/MSH2 large genomic rearrangement carriers

“…Taking into account all mutations identified so far (28 mutations in total), including the mutations found in this study, the LGRs account for 25% of clearly pathogenic changes in MMR genes from Slovakian HNPCC families. The large deletion in the MLH1 gene, a del5-6, has not been reported in other populations and, as a single mutation, represents only 6.7% (1 of 15) of all MLH1 mutations, while LGRs in the MSH2 gene account for 50% (6 of 12) of all MSH2 mutation-positive cases [30-32] (one family with inherited MSH6 mutation is unpublished). Although large duplications in MMR genes seem to occur much less frequently than deletions [18,39-43], we uncovered one duplication of exons 5 and 6 affecting the MSH2 gene in our relatively small cohort.…”

“…To date, among 58 clinically well-defined Slovak HNPCC families, 21 clearly pathogenic MMR gene mutations have been identified by applying direct DNA genomic sequencing [30,31]. As DNA sequencing fails to detect LGRs, it is possible that in some of these patients, an LGR is responsible for HNPCC.…”

Multiplex SNaPshot Genotyping for Detecting Loss of Heterozygosity in the Mismatch-Repair Genes MLH1 and MSH2 in Microsatellite-Unstable Tumors

“…Patients 1-42 were known carriers of pathogenic germline mutations in MLH1 or MSH2 (20)(21)(22)(23)(24)(25)(26). Patients 43-67 were suspected HNPCC probands.…”