Elucidation of the transmission of a novel mutation in BRCA1 (1125delCT) in a family with multiple cases of breast cancer.

In a family with multiple members affected by breast cancer we identified the novel mutation 1125delCT (exon 11) in BRCA1. Three out of three offsprings have the novel mutation while the mother affected by breast cancer does not carry the mutation. Linkage analysis revealed the transmission of the healthy haplotype from the mother to the three offsprings while the children inherited the mutated haplotype from the father. Our data document in an unquestionable way where the mutated haplotype was inherited from. In some families, although the transmission pathway seems obvious, the molecular analysis yields surprising results.

Inherited cancer predisposition syndromes in Greece.

Hereditary cancer syndromes comprise approximately 5-10% of diagnosed carcinomas. They are caused by mutations in specific genes. Carriers of mutations in these genes are at an increased risk of developing cancer at a young age. When there is a suspicion of a hereditary cancer predisposition syndrome a detailed family tree of the patient requesting screening is constructed. DNA is isolated from all available members of the family. Mutation detection is carried out on DNA from an affected family member. If a mutation is found the remaining family is screened. The genetic basis of a large number of inherited cancer predisposition syndromes is known. In this paper the focus is on mutations in genes responsible for colorectal cancer, meaning adenomatous polyposis coli (APC), which is involved in familial adenomatous polyposis and homo sapiens mutL homolog 1 (hMLH1) and homo sapiens mutS homolog 2 (hMSH2), involved in hereditary non-polyposis colorectal cancer. In addition, the genes responsible for inherited breast and/or ovarian cancer, breast cancer genes 1 and 2 (BRCA1 and BRCA2), and the rearranged during transfection protooncogene RET which is responsible for multiple endocrine neoplasia type 2 are discussed. In all cases emphasis is given to the data available on the Greek population.

Efficient testing of the RET gene by DHPLC analysis for MEN 2 syndrome in a cohort of patients.

BACKGROUND: Multiple Endocrine Neoplasia type 2 (MEN 2) is an autosomal dominant inherited syndrome characterized by a strong predisposition for developing endocrine tumors. MEN 2 is caused by germline mutations in the ret proto-oncogene. We investigated the feasibility of using the DHPLC technique in mutation detection of the ret gene in members of MTC families. We compared DHPLC analysis with direct sequencing with regard to sensitivity, reliability, cost and time. MATERIALS AND METHODS: Exons 10 and 11 were amplified with PCR from forty-three samples in seventeen unrelated Greek families and were analyzed for mutations by DHPLC and DNA sequencing. RESULTS: Eight PCR amplicons showed a distinct non-wild-type DHPLC profile. Sequence analysis confirmed different nucleotide variations: six of them were localized in exon 10 and two in exon 11. Mutations were detected in five out of seventeen families tested (29%). CONCLUSION: None of the alterations detected by direct sequencing was missed by DHPLC. We conclude that DHPLC is a fast, sensitive, cost-efficient and reliable method for the scanning of ret germline mutations.

Characterization of a novel large deletion and single point mutations in the BRCA1 gene in a Greek cohort of families with suspected hereditary breast cancer.

BACKGROUND: Germline mutations in BRCA1 and BRCA2 predispose to breast and ovarian cancer. A multitude of mutations have been described and are found to be scattered throughout these two large genes. We describe analysis of BRCA1 in 25 individuals from 18 families from a Greek cohort. METHODS: The approach used is based on dHPLC mutation screening of the BRCA1 gene, followed by sequencing of fragments suspected to carry a mutation including intron--exon boundaries. In patients with a strong family history but for whom no mutations were detected, analysis was extended to exons 10 and 11 of the BRCA2 gene, followed by MLPA analysis for screening for large genomic rearrangements. RESULTS: A pathogenic mutation in BRCA1 was identified in 5/18 (27.7 %) families, where four distinct mutations have been observed. Single base putative pathogenic mutations were identified by dHPLC and confirmed by sequence analysis in 4 families: 5382insC (in two families), G1738R, and 5586G > A (in one family each). In addition, 18 unclassified variants and silent polymorphisms were detected including a novel silent polymorphism in exon 11 of the BRCA1 gene. Finally, MLPA revealed deletion of exon 20 of the BRCA1 gene in one family, a deletion that encompasses 3.2 kb of the gene starting 21 bases into exon 20 and extending 3.2 kb into intron 20 and leads to skipping of the entire exon 20. The 3' breakpoint lies within an AluSp repeat but there are no recognizable repeat motifs at the 5' breakpoint implicating a mechanism different to Alu-mediated recombination, responsible for the majority of rearrangements in the BRCA1 gene. CONCLUSIONS: We conclude that a combination of techniques capable of detecting both single base mutations and small insertions/deletions and large genomic rearrangements is necessary in order to accurately analyze the BRCA1 gene in patients at high risk of carrying a germline mutation as determined by their family history. Furthermore, our results suggest that in those families with strong evidence of linkage to the BRCA1 locus in whom no point mutation has been identified re-examination should be carried out searching specifically for genomic rearrangements.