BACKGROUND: The incidence of breast cancer has doubled over the past 20 years in the Czech Republic. Hereditary factors may be a cause of young onset, bilateral breast or ovarian cancer, and familial accumulation of the disease. BRCA1 and BRCA2 mutations account for an important fraction of hereditary breast and ovarian cancer cases. One thousand and ten unrelated high-risk probands with breast and/or ovarian cancer were analysed for the presence of a BRCA1 or BRCA2 gene mutation at the Masaryk Memorial Cancer Institute (Czech Republic) during 1999-2006. METHODS: The complete coding sequences and splice sites of both genes were screened, and the presence of large intragenic rearrangements in BRCA1 was verified. Putative splice-site variants were analysed at the cDNA level for their potential to alter mRNA splicing. RESULTS: In 294 unrelated families (29.1% of the 1,010 probands) pathogenic mutations were identified, with 44 different BRCA1 mutations and 41 different BRCA2 mutations being detected in 204 and 90 unrelated families, respectively. In total, three BRCA1 founder mutations (c.5266dupC; c.3700_3704del5; p.Cys61Gly) and two BRCA2 founder mutations (c.7913_7917del5; c.8537_8538del2) represent 52% of all detected mutations in Czech high-risk probands. Nine putative splice-site variants were evaluated at the cDNA level. Three splice-site variants in BRCA1 (c.302-3C>G; c.4185G>A and c.4675+1G>A) and six splice-site variants in BRCA2 (c.475G>A; c.476-2>G; c.7007G>A; c.8755-1G>A; c.9117+2T>A and c.9118-2A>G) were demonstrated to result in aberrant transcripts and are considered as deleterious mutations. CONCLUSION: This study represents an evaluation of deleterious genetic variants in the BRCA1 and 2 genes in the Czech population. The classification of several splice-site variants as true pathogenic mutations may prove useful for genetic counselling of families with high risk of breast and ovarian cancer.
- MeSH
- genetická predispozice k nemoci MeSH
- lidé MeSH
- mutace MeSH
- mutační analýza DNA MeSH
- nádory prsu u mužů epidemiologie genetika patologie MeSH
- nádory prsu epidemiologie genetika patologie MeSH
- nádory vaječníků epidemiologie genetika patologie MeSH
- protein BRCA1 genetika MeSH
- protein BRCA2 genetika MeSH
- rizikové faktory MeSH
- věk při počátku nemoci MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
BACKGROUND: Alterations in the highly penetrant cancer susceptibility gene BRCA1 are responsible for the majority of hereditary breast and/or ovarian cancers. However, the number of detected germline mutations has been lower than expected based upon genetic linkage data. Undetected deleterious mutations in the BRCA1 gene in some high-risk families could be due to the presence of intragenic rearrangements as deletions, duplications or insertions spanning whole exons. Standard PCR-based screening methods are mainly focused on detecting point mutations and small insertions/deletions, but large rearrangements might escape detection.The purpose of this study was to determine the type and frequency of large genomic rearrangements in the BRCA1 gene in hereditary breast and ovarian cancer cases in the Czech Republic. METHODS: Multiplex ligation-dependent probe amplification (MLPA) was used to examine BRCA1 rearrangements in 172 unrelated patients with hereditary breast and/or ovarian cancer syndrome without finding deleterious mutation after complete screening of whole coding regions of BRCA1/2 genes. Positive MLPA results were confirmed and located by long-range PCR. The breakpoints of detected rearrangements were characterized by sequencing. RESULTS: Six different large deletions in the BRCA1 gene were identified in 10 out of 172 unrelated high-risk patients: exons 1A/1B and 2 deletion; partial deletion of exon 11 and exon 12; exons 18 and 19 deletion; exon 20 deletion; exons 21 and 22 deletion; and deletion of exons 5 to 14. The breakpoint junctions were localized and further characterized. Destabilization and global unfolding of the mutated BRCT domains explain the molecular and genetic defects associated with the exon 20 in-frame deletion and the exon 21 and 22 in-frame deletion, respectively. CONCLUSION: Using MLPA, mutations were detected in 6% of high-risk patients previously designated as BRCA1/2 mutation-negative. The breakpoints of five out of six large deletions detected in Czech patients are novel. Screening for large genomic rearrangements in the BRCA1 gene in the Czech high-risk patients is highly supported by this study.
- MeSH
- bodová mutace MeSH
- delece genu MeSH
- DNA nádorová MeSH
- dospělí MeSH
- financování organizované MeSH
- genová přestavba MeSH
- geny BRCA1 MeSH
- lidé MeSH
- nádory prsu genetika MeSH
- nádory vaječníků genetika MeSH
- polymerázová řetězová reakce MeSH
- rodokmen MeSH
- syndrom MeSH
- zárodečné mutace MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- ženské pohlaví MeSH
- Geografické názvy
- Česká republika MeSH
