title: DNA repair capacity is impaired in healthy BRCA1 heterozygous mutation carriers.
abstract: BRCA1 germline mutations increase the lifetime risk of developing breast and ovarian cancers. However, taking into account the differences in disease manifestation among mutation carriers, it is probable that different BRCA1 mutations have distinct haploinsufficiency effects and lead to the formation of different phenotypes. Using lymphoblastoid cell lines derived from heterozygous BRCA1 mutation carriers and non-carriers, we investigated the haploinsufficiency effects of various mutation types using qPCR, immunofluorescence, and microarray technology. Lymphoblastoid cell lines carrying a truncating mutation showed significantly lower BRCA1 mRNA and protein levels and higher levels of gamma-H2AX than control cells or those harboring a missense mutation, indicating greater spontaneous DNA damage. Cells carrying either BRCA1 mutation type showed impaired RAD51 foci formation, suggesting defective repair in mutated cells. Moreover, compared to controls, cell lines carrying missense mutations displayed a more distinct expression profile than cells with truncating mutations, which is consistent with different mutations giving rise to distinct phenotypes. Alterations in the immune response pathway in cells harboring missense mutations point to possible mechanisms of breast cancer initiation in carriers of these mutations. Our findings offer insight into how various heterozygous mutations in BRCA1 could lead to impairment of BRCA1 function and provide strong evidence of haploinsufficiency in BRCA1 mutation carriers.
authors.affiliation: Human Genetics Group, Human Cancer Genetics Programme, Spanish National Cancer Research Centre (CNIO), C/Melchor Fernández Almagro 3, 28029, Madrid, Spain.
authors.forename: Tereza
authors.initials: T
authors.lastname: Vaclová
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Gómez-López
authors.forename: Fernando
authors.initials: F
authors.lastname: Setién
authors.forename: José María García
authors.initials: JM
authors.lastname: Bueno
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Macías
authors.forename: Alicia
authors.initials: A
authors.lastname: Barroso
authors.forename: Miguel
authors.initials: M
authors.lastname: Urioste
authors.forename: Manel
authors.initials: M
authors.lastname: Esteller
authors.forename: Javier
authors.initials: J
authors.lastname: Benítez
authors.forename: Ana
authors.initials: A
authors.lastname: Osorio
mesh_terms: D000483:Alleles; D019313:BRCA1 Protein / Q000235:genetics* / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D016000:Cluster Analysis; D004260:DNA Repair; D005260:Female; D015870:Gene Expression; D020869:Gene Expression Profiling; D053263:Gene Regulatory Networks; D057895:Haploinsufficiency; D006579:Heterozygote; D006657:Histones / Q000378:metabolism; D006801:Humans; D009154:Mutation; D051135:Rad51 Recombinase / Q000378:metabolism; D059467:Transcriptome
chemical_list: D019313:BRCA1 Protein; D006657:Histones; D051135:Rad51 Recombinase