title: Characterization of four novel BRCA2 large genomic rearrangements in Spanish breast/ovarian cancer families: review of the literature, and reevaluation of the genetic mechanisms involved in their origin.
abstract: Large genomic rearrangements (LGRs) at the BRCA2 locus explain a non-negligible proportion of hereditary breast and ovarian cancer (HBOC) syndromes. The multiplex ligation and probe amplification (MLPA) assay has permitted in recent years to identify several families carrying LGRs at this locus, but very few such alterations have been fully characterized at the molecular level. Yet, molecular characterization is essential to identify recurrent alterations, to analyze the genetic mechanisms underlying such alterations, or to investigate potential genotype/phenotype relationships. We have used MLPA to identify BRCA2 LGRs in 7 out of 813 Spanish HBOC families previously tested negative for BRCA1 and BRCA2 small genomic alterations (substitutions and indels) and BRCA1 LGRs. We used a combination of long-range PCR, restriction mapping, and cDNA analysis to characterize the alterations at the molecular level. We found that Del Exon1-Exon2, Del Exon12-Exon16 and Del Exon22-Exon24 explain one family each, while Del Exon2 appears to be a Spanish founder mutation explaining four independent families. Finally, we have combined our data with a comprehensive review of the literature to reevaluate the genetic mechanisms underlying LGRs at the BRCA2 locus. Our study substantially increases the spectrum of BRCA2 LGRs fully characterized at the molecular level. Further on, we provide data to suggest that non-allelic homologous recombination has been overestimated as a mechanism underlying these alterations, while the opposite might be true for microhomology-mediated events.
authors.affiliation: Laboratorio de Oncología Molecular, Instituto de Investigación Sanitaria San Carlos, Hospital Clínico San Carlos, C/Martín Lagos s/n, 28040 Madrid, Spain.
authors.forename: Gorka
authors.initials: G
authors.lastname: Ruiz de Garibay
authors.forename: Sara
authors.initials: S
authors.lastname: Gutiérrez-Enríquez
authors.forename: Pilar
authors.initials: P
authors.lastname: Garre
authors.forename: Sandra
authors.initials: S
authors.lastname: Bonache
authors.forename: Atocha
authors.initials: A
authors.lastname: Romero
authors.forename: Laura
authors.initials: L
authors.lastname: Palomo
authors.forename: Ana
authors.initials: A
authors.lastname: Sánchez de Abajo
authors.forename: Javier
authors.initials: J
authors.lastname: Benítez
authors.forename: Judith
authors.initials: J
authors.lastname: Balmaña
authors.forename: Pedro
authors.initials: P
authors.lastname: Pérez-Segura
authors.forename: Eduardo
authors.initials: E
authors.lastname: Díaz-Rubio
authors.forename: Orland
authors.initials: O
authors.lastname: Díez
authors.forename: Trinidad
authors.initials: T
authors.lastname: Caldés
authors.forename: Miguel
authors.initials: M
authors.lastname: de la Hoya
mesh_terms: D019313:BRCA1 Protein / Q000235:genetics; D024682:BRCA2 Protein / Q000235:genetics*; D001483:Base Sequence; D056905:Chromosome Breakpoints; D004252:DNA Mutational Analysis; D005091:Exons; D005260:Female; D006239:Haplotypes; D061325:Hereditary Breast and Ovarian Cancer Syndrome / Q000235:genetics*; D006801:Humans; D010375:Pedigree; D011995:Recombination, Genetic; D016415:Sequence Alignment; D017384:Sequence Deletion; D013030:Spain
chemical_list: D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D024682:BRCA2 Protein; C551750:BRCA2 protein, human