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.

Oxidative stress and DNA damage in the mechanism of fetal alcohol spectrum disorders

“…Hence, the prevalence of BRCA1‐deficient individuals is currently unknown, but likely greater than that estimated by mutational screening. The reported collective 65% BRCA1 deficiency (Baldeyron et al, ; Vaclova et al, ) likely varies considerably in any given human, but may be greater than the 28–40% decrease in BRCA1 protein in our cKO and KO Brca1 models, suggesting that conceptal variations in BRCA1 levels could be an important determinant of risk for FASD.…”

“…Though limited information is available, a variety of missense and truncating mutations exhibit a collective 65% deficiency in BRCA1 protein levels in human peripheral blood lymphocytes (Baldeyron et al, ; Vaclova et al, ). However, the degree of deficiency depends on the mutation (Baldeyron et al, ; Vaclova et al, ), where some individuals could have biallelic mutations with minimal BRCA1 expression/activity (Domchek et al, ). Most of the missense and truncating mutations in BRCA1 identified to date are commonly associated with breast and ovarian cancers.…”

Defects in homologous recombination repair behind the human diseases: FA and HBOC

“…In the long run, accumulated knowledge about segregation of the genotype and an individual's cancer susceptibility within families may eventually clarify the significance of VUS. At the moment, careful evaluation of DNA repair capacity in lymphocytes from cases with VUS might be useful (Pathania et al 2014, Vaclová et al 2015. It would be particularly useful to construct a collection of isogenic knock-in cells with candidate variants using the CRISPR-CAS9 system (Paquet et al 2016).…”

Fetal oxidative stress mechanisms of neurodevelopmental deficits and exacerbation by ethanol and methamphetamine

“…However, this reported prevalence only considers BRCA1 mutations related to cancer, and the actual incidence may be higher when considering BRCA1 mutations yet to be identified. Though limited information is available, in humans, a variety of missense and truncating mutations suggest up to a 65% deficiency in BRCA1 protein levels from peripheral blood lymphocytes (Baldeyron et al, ; Vaclova et al, ). This human level of BRCA1 deficiency is considerably greater than the 28‐40% deficiencies in our cKO and KO Brca1 models, suggesting that conceptal variations in BRCA1 levels could be an important determinant of risk for ASD and FASD.…”