Paola Concolino1, Roberta Rizza2, Karl Hackmann3,4,5,6, Angelo Minucci2, Giovanni Luca Scaglione2, Maria De Bonis2, Alessandra Costella2, Cecilia Zuppi2, Evelin Schrock3,4,5,6, Ettore Capoluongo2. 1. Polo Scienze per Immagini, di Laboratorio e Infettivologiche, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario Agostino Gemelli, Largo Francesco Vito, 1-00168, Rome, Italy. paola.concolino@policlinicogemelli.it. 2. Polo Scienze per Immagini, di Laboratorio e Infettivologiche, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario Agostino Gemelli, Largo Francesco Vito, 1-00168, Rome, Italy. 3. Institut fuer Klinische Genetik, Medizinische Fakultaet Carl Gustav Carus, Technische Universitaet Dresden, Fetscherstr. 74, 01307, Dresden, Germany. 4. German Cancer Consortium (DKTK), Dresden, Germany. 5. German Cancer Research Center (DKFZ), Heidelberg, Germany. 6. National Center for Tumor Diseases (NCT), Dresden, Germany.
Abstract
INTRODUCTION: Many studies document the involvement of BRCA1/2 gene rearrangements in genetic predisposition to breast and ovarian cancer. Large genomic rearrangements (LGRs) of BRCA1 account for 0-27% of all disease-causing mutations in various populations, while LGRs in BRCA2 are rarer. Here, we describe a novel BRCA2 LGR, involving the duplication of exons 4-26, in an Italian family with hereditary breast and ovarian cancer (HBOC) syndrome. OBJECTIVE: Our purpose was to provide an effective characterization of this variant using a combination of different methods able to establish the exact breakpoints of the duplication. METHODS: A multiplex amplicon quantification (MAQ) assay was used as the primary screening method in the detection of LGRs. Array comparative genomic hybridization (CGH), reverse transcriptase polymerase chain reaction (RT-PCR) and long-range PCR were used for the careful characterization of the rearrangement and breakpoint regions. The Repeat Masker program was employed to identify Alu sequences at breakpoint junctions. RESULTS: Array CGH and long-range PCR strategies revealed that the BRCA2 exons 4-26 duplication (g.12016_87170dup) involved exactly 75,154 bp nucleotides between intron 3 and intron 26 of the gene. Given that no Alu repeats were found at the junction sites, we support the hypothesis that the new duplication could be the result of a microhomology-mediated event (MH) involving very short homologous sequences at an upstream breakpoint. DISCUSSION: LGR investigation is mandatory in BRCA1/2 routine testing in order to provide a complete result for a targeted therapeutic decision. Nevertheless, the characterization and classification of novel BRCA1/2 variants represents a crucial step in the support of genetic counselling. Our results, including a comprehensive co-segregation analysis, indicate that the novel duplication identifed has a pathogenic role and would be considered a causing-disease variant in genetic and oncologic counselling.
INTRODUCTION: Many studies document the involvement of BRCA1/2 gene rearrangements in genetic predisposition to breast and ovarian cancer. Large genomic rearrangements (LGRs) of BRCA1 account for 0-27% of all disease-causing mutations in various populations, while LGRs in BRCA2 are rarer. Here, we describe a novel BRCA2 LGR, involving the duplication of exons 4-26, in an Italian family with hereditary breast and ovarian cancer (HBOC) syndrome. OBJECTIVE: Our purpose was to provide an effective characterization of this variant using a combination of different methods able to establish the exact breakpoints of the duplication. METHODS: A multiplex amplicon quantification (MAQ) assay was used as the primary screening method in the detection of LGRs. Array comparative genomic hybridization (CGH), reverse transcriptase polymerase chain reaction (RT-PCR) and long-range PCR were used for the careful characterization of the rearrangement and breakpoint regions. The Repeat Masker program was employed to identify Alu sequences at breakpoint junctions. RESULTS: Array CGH and long-range PCR strategies revealed that the BRCA2 exons 4-26 duplication (g.12016_87170dup) involved exactly 75,154 bp nucleotides between intron 3 and intron 26 of the gene. Given that no Alu repeats were found at the junction sites, we support the hypothesis that the new duplication could be the result of a microhomology-mediated event (MH) involving very short homologous sequences at an upstream breakpoint. DISCUSSION: LGR investigation is mandatory in BRCA1/2 routine testing in order to provide a complete result for a targeted therapeutic decision. Nevertheless, the characterization and classification of novel BRCA1/2 variants represents a crucial step in the support of genetic counselling. Our results, including a comprehensive co-segregation analysis, indicate that the novel duplication identifed has a pathogenic role and would be considered a causing-disease variant in genetic and oncologic counselling.
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Authors: Giovanni Luca Scaglione; Paola Concolino; Maria De Bonis; Elisa De Paolis; Angelo Minucci; Gabriella Ferrandina; Giovanni Scambia; Ettore Capoluongo Journal: Int J Mol Sci Date: 2018-03-23 Impact factor: 5.923