Instabilité du Génome et Prédisposition au Cancer

Publications de l’équipe

Année de publication : 2021

Åsa Ehlén, Gaetana Sessa, Sophie Zinn-Justin, Aura Carreira (2021 Mar 10)

The phospho-dependent role of BRCA2 on the maintenance of chromosome integrity.

Cell cycle (Georgetown, Tex.) : 1-12 : DOI : 10.1080/15384101.2021.1892994 En savoir plus

Chromosomal instability is a hallmark of cancer. The tumor suppressor protein BRCA2 performs an important role in the maintenance of genome integrity particularly in interphase; as a mediator of homologous recombination DNA repair pathway, it participates in the repair of DNA double-strand breaks, inter-strand crosslinks and replicative DNA lesions. BRCA2 also protects stalled replication forks from aberrant degradation. Defects in these functions lead to structural chromosomal aberrations. BRCA2 is a large protein containing highly disordered regions that are heavily phosphorylated particularly in mitosis. The functions of these modifications are getting elucidated and reveal emerging activities in chromosome alignment, chromosome segregation and abscission during cell division. Defects in these activities result in numerical chromosomal aberrations. In addition to BRCA2, other factors of the DNA damage response (DDR) participate in mitosis in close association with cell cycle kinases and phosphatases suggesting that the maintenance of genome integrity functions of these factors extends beyond DNA repair. Here we will discuss the regulation of BRCA2 functions through phosphorylation by cell cycle kinases particularly in mitosis, and illustrate with some examples how BRCA2 and other DDR proteins partially rewire their interactions, essentially via phosphorylation, to fulfill mitotic specific functions that ensure chromosome stability.

Gaetana Sessa, Belén Gómez-González, Sonia Silva, Carmen Pérez-Calero, Romane Beaurepere, Sonia Barroso, Sylvain Martineau, Charlotte Martin, Åsa Ehlén, Juan S Martínez, Bérangère Lombard, Damarys Loew, Stephan Vagner, Andrés Aguilera, Aura Carreira (2021 Feb 26)

BRCA2 promotes R-loop resolution by DDX5 helicase at DNA breaks to facilitate their repair by homologous recombination.

The EMBO journal : e106018 : DOI : 10.15252/embj.2020106018 En savoir plus

The BRCA2 tumor suppressor is a DNA double-strand break (DSB) repair factor essential for maintaining genome integrity. BRCA2-deficient cells spontaneously accumulate DNA-RNA hybrids, a known source of genome instability. However, the specific role of BRCA2 on these structures remains poorly understood. Here we identified the DEAD-box RNA helicase DDX5 as a BRCA2-interacting protein. DDX5 associates with DNA-RNA hybrids that form in the vicinity of DSBs, and this association is enhanced by BRCA2. Notably, BRCA2 stimulates the DNA-RNA hybrid-unwinding activity of DDX5 helicase. An impaired BRCA2-DDX5 interaction, as observed in cells expressing the breast cancer variant BRCA2-T207A, reduces the association of DDX5 with DNA-RNA hybrids, decreases the number of RPA foci, and alters the kinetics of appearance of RAD51 foci upon irradiation. Our findings are consistent with DNA-RNA hybrids constituting an impediment for the repair of DSBs by homologous recombination and reveal BRCA2 and DDX5 as active players in their removal.


Année de publication : 2020

(2020 Aug 26)

Monitoring Homologous Recombination Activity in Human Cells

.Methods Mol Biol : DOI : 10.1007/978-1-0716-0644-5_9 En savoir plus

DNA double-strand breaks (DSBs) are among the most toxic lesions. This type of DNA damage is repaired by two major pathways, homologous recombination (HR), operating only in S/G2 cell-cycle phases and nonhomologous end joining (NHEJ) which is operative throughout the cell cycle. Because HR is a template-directed repair, it is generally less prone to errors and/or translocations than NHEJ.The HR pathway involves several effector proteins and regulators that modulate the efficiency of repair and limit the repair outside S/G2 phase. Some of the genes coding for these proteins are frequently mutated in human diseases such as cancer, and pathogenic mutations or variants identified in patients often alter the HR proficiency of the cells.This chapter describes a cell-based gene-targeting reporter assay in human cells to evaluate the repair of a site-specific DSB by HR . In it, a promoter-less fluorescent protein is encoded in a plasmid flanked by two homology arms directed to a safe-harbour locus in the genome. The expression of the fluorescent protein is driven by the promoter of the endogenous locus enabling to quantify the efficiency of HR by flow cytometry. This approach can be used to determine the requirement of certain proteins, protein domains, or protein modifications for HR . It can also be used to functionally evaluate variants of the genes encoding these proteins such as BRCA1, BRCA2, RAD51C, and PALB2; which may help assess their pathogenicity. Here, we use the homologous recombination mediator BRCA2 to illustrate the assay.

Åsa Ehlén, Charlotte Martin, Simona Miron, Manon Julien, François-Xavier Theillet, Virginie Ropars, Gaetana Sessa, Romane Beaurepere, Virginie Boucherit, Patricia Duchambon, Ahmed El Marjou, Sophie Zinn-Justin, Aura Carreira (2020 Apr 14)

Proper chromosome alignment depends on BRCA2 phosphorylation by PLK1.

Nature communications : 1819 : DOI : 10.1038/s41467-020-15689-9 En savoir plus

The BRCA2 tumor suppressor protein is involved in the maintenance of genome integrity through its role in homologous recombination. In mitosis, BRCA2 is phosphorylated by Polo-like kinase 1 (PLK1). Here we describe how this phosphorylation contributes to the control of mitosis. We identify a conserved phosphorylation site at T207 of BRCA2 that constitutes a bona fide docking site for PLK1 and is phosphorylated in mitotic cells. We show that BRCA2 bound to PLK1 forms a complex with the phosphatase PP2A and phosphorylated-BUBR1. Reducing BRCA2 binding to PLK1, as observed in BRCA2 breast cancer variants S206C and T207A, alters the tetrameric complex resulting in unstable kinetochore-microtubule interactions, misaligned chromosomes, faulty chromosome segregation and aneuploidy. We thus reveal a role of BRCA2 in the alignment of chromosomes, distinct from its DNA repair function, with important consequences on chromosome stability. These findings may explain in part the aneuploidy observed in BRCA2-mutated tumors.


Année de publication : 2018

Sandrine M Caputo, Mélanie Léone, Francesca Damiola, Asa Ehlen, Aura Carreira, Pascaline Gaidrat, Alexandra Martins, Rita D Brandão, Ana Peixoto, Ana Vega, Claude Houdayer, Capucine Delnatte, Myriam Bronner, Danièle Muller, Laurent Castera, Marine Guillaud-Bataille, Inge Søkilde, Nancy Uhrhammer, Sophie Demontety, Hélène Tubeuf, Gaïa Castelain, , Uffe Birk Jensen, Ambre Petitalot, Sophie Krieger, Cédrick Lefol, Virginie Moncoutier, Nadia Boutry-Kryza, Henriette Roed Nielsen, Olga Sinilnikova, Dominique Stoppa-Lyonnet, Amanda B Spurdle, Manuel R Teixeira, Florence Coulet, Mads Thomassen, Etienne Rouleau (2018 Apr 3)

Full in-frame exon 3 skipping of BRCA2 confers high risk of breast and/or ovarian cancer.

Oncotarget : 17334-17348 : DOI : 10.18632/oncotarget.24671 En savoir plus

Germline pathogenic variants in the gene are associated with a cumulative high risk of breast/ovarian cancer. Several variants result in complete loss of the exon-3 at the transcript level. The pathogenicity of these variants and the functional impact of loss of exon 3 have yet to be established. As a collaboration of the COVAR clinical trial group (France), and the ENIGMA consortium for investigating breast cancer gene variants, this study evaluated 8 variants resulting in complete deletion of exon 3. Clinical information for 39 families was gathered from Portugal, France, Denmark and Sweden. Multifactorial likelihood analyses were conducted using information from 293 patients, for 7 out of the 8 variants (including 6 intronic). For all variants combined the likelihood ratio in favor of causality was 4.39*10. These results provide convincing evidence for the pathogenicity of all examined variants that lead to a total exon 3 skipping, and suggest that other variants that result in complete loss of exon 3 at the molecular level could be associated with a high risk of cancer comparable to that associated with classical pathogenic variants in or gene. In addition, our functional study shows, for the first time, that deletion of exon 3 impairs the ability of cells to survive upon Mitomycin-C treatment, supporting lack of function for the altered BRCA2 protein in these cells. Finally, this study demonstrates that any variant leading to expression of only delta-exon 3 will be associated with an increased risk of breast and ovarian cancer.

Catharina von Nicolai, Åsa Ehlén, Juan S Martinez, Aura Carreira (2018 Apr 1)

Dissecting the Recombination Mediator Activity of BRCA2 Using Biochemical Methods.

Methods in enzymology : 479-511 : DOI : S0076-6879(17)30356-7 En savoir plus

Homologous recombination (HR) is an essential pathway to restart stalled replication forks, repair spontaneous DNA double-strand breaks, and generate genetic diversity. Together with genetic studies in model organisms, the development of purification protocols and biochemical assays has allowed investigators to begin to understand how the complex machinery of HR functions. At the core of the HR process is the recombination enzyme RecA in bacteria or RAD51 and DMC1 in eukaryotes. The main steps of HR can be reconstituted in vitro and involve: (1) The formation of a ssDNA-RAD51 complex into a helical structure termed the nucleoprotein filament after one DNA strand has been resected at the site of the break. (2) The homologous DNA pairing with an intact copy of the damaged chromatid to form a joint molecule also called displacement loop (D-loop). (3) The exchange of DNA strands and de novo DNA synthesis to restore the damaged/lost DNA. (4) The resolution of joint molecules by nucleolytic cleavage. The human tumor suppressor BRCA2 is a mediator of HR as it actively facilitates the DNA transactions of the recombination proteins RAD51 and DMC1 in a variety of ways: It stabilizes ssDNA-RAD51/DMC1 nucleoprotein filaments. It limits the assembly of RAD51 on dsDNA. It facilitates the replacement of replication protein A by RAD51. The result of these activities is a net increase of DNA strand exchange products as observed in vitro. Here, we describe some of the biochemical assays used to dissect the mediator activities of BRCA2.


Année de publication : 2017

Hermela Shimelis, Romy L S Mesman, Catharina Von Nicolai, Asa Ehlen, Lucia Guidugli, Charlotte Martin, Fabienne Mgr Calleja, Huong Meeks, Emily Hallberg, Jamie Hinton, Jenna Lilyquist, Chunling Hu, Cora M Aalfs, Kristiina Aittomaki, Irene L Andrulis, Hoda Anton-Culver, Volker Arndt, Matthias W Beckmann, Javier J Benitez, Natalia Bogdanova, Stig E Bojesen, Manjeet K Bolla, Anne-Lise Borresen-Dale, Hiltrud Brauch, Paul Brennan, Hermann Brenner, Annegien Broeks, Barbara Brouwers, Thomas Bruning, Barbara Burwinkel, Jenny Chang-Claude, Georgia Chenevix-Trench, Ching-Yu Cheng, Ji-Yeob Choi, J Margriet Collée, Angela Cox, Simon S Cross, Kamila Czene, Hatef Darabi, Joe Dennis, Thilo Dork, Isabel Dos Santos Silva, Alison M Dunning, Peter A Fasching, Jonine D Figueroa, Henrik Flyger, Montserrat Garcia-Closas, Graham G Giles, Gord Glendon, Pascal Guenel, Christopher A Haiman, Per Hall, Ute Hamann, Mikael Hartman, Frans B L Hogervorst, Antoinette Hollestelle, John L Hopper, Hidemi Ito, Anna Jakubowska, Daehee Kang, Veli-Matti Kosma, Vessela Kristensen, Kah-Nyin Lai, Diether Lambrechts, Loic Le Marchand, Jingmei Li, Annika Lindblom, Artitaya Lophatananon, Jan Lubinski, Eva Machackova, Arto Mannermaa, Sara Margolin, Frederik Marme, Keitaro Matsuo, Hui Miao, Kyriaki Michailidou, Roger L Milne, Kenneth Muir, Susan L Neuhausen, Heli Nevanlinna, Janet E Olson, Curtis Olswold, Jan C Oosterwijk, Ana Osorio, Paolo Peterlongo, Julian Peto, Paul D P Pharoah, Katri Pylkäs, Paolo Radice, Muhammad U Rashid, Valerie Rhenius, Anja Rudolph, Suleeporn Sangrajrang, Elinor J Sawyer, Marjanka K Schmidt, Minouk J Schoemaker, Caroline M Seynaeve, Mitul Shah, Chen-Yang Shen, Martha J Shrubsole, Xiao-Ou Shu, Susan L Slager, Melissa C Southey, Daniel O Stram, Anthony J Swerdlow, Soo Hwang Teo, Ian Tomlinson, Diana Torres, Therese Truong, Christi J van Asperen, Lizet E van der Kolk, Qin Wang, Robert Winqvist, Anna H Wu, Jyh-Cherng Yu, Wei Zheng, Ying Zheng, Jennifer Leary, Logan C Walker, Lenka Foretova, Florentia Fostira, Kathleen Claes, Liliana Varesco, Setareh Moghadasi, Douglas F Easton, Amanda B Spurdle, Peter Devilee, Harry Vrieling, Alvaro N Monteiro, David E Goldgar, Aura Carreira, Maaike P G Vreeswijk, Fergus J Couch (2017 Jun 1)

BRCA2 hypomorphic missense variants confer moderate risks of breast cancer.

Cancer research : DOI : 10.1158/0008-5472.CAN-16-2568 En savoir plus

Breast cancer risks conferred by many germline missense variants in the BRCA1 and BRCA2 genes, often referred to as variants of uncertain significance (VUS), have not been established. In this study, associations between 19 BRCA1 and 33 BRCA2 missense substitution variants and breast cancer risk were investigated through a breast cancer case control study using genotyping data from 38 studies of predominantly European ancestry (41,890 cases and 41,607 controls) and nine studies of Asian ancestry (6,269 cases and 6,624 controls). The BRCA2 c.9104A>C, p.Tyr3035Ser (OR=2.52, p=0.04) and BRCA1 c.5096G>A, p.Arg1699Gln (OR=4.29, p=0.009) variant were associated with moderately increased risks of breast cancer among Europeans, whereas BRCA2 c.7522G>A, p.Gly2508Ser (OR=2.68, p=0.004) and c.8187G>T, p.Lys2729Asn (OR=1.4, p=0.004) were associated with moderate and low risks of breast cancer among Asians. Functional characterization of the BRCA2 variants using four quantitative assays showed reduced BRCA2 activity for p.Tyr3035Ser compared to wildtype. Overall, our results show how BRCA2 missense variants that influence protein function can confer clinically relevant, moderately increased risks of breast cancer, with potential implications for risk management guidelines in women with these specific variants.


Année de publication : 2016

Catharina von Nicolai, Åsa Ehlén, Charlotte Martin, Xiaodong Zhang, Aura Carreira (2016 Sep 15)

A second DNA binding site in human BRCA2 promotes homologous recombination.

Nature communications : 12813 : DOI : 10.1038/ncomms12813 En savoir plus

BRCA2 tumour-suppressor protein is well known for its role in DNA repair by homologous recombination (HR); assisting the loading of RAD51 recombinase at DNA double-strand breaks. This function is executed by the C-terminal DNA binding domain (CTD) which binds single-stranded (ss)DNA, and the BRC repeats, which bind RAD51 and modulate its assembly onto ssDNA. Paradoxically, analysis of cells resistant to DNA damaging agents missing the CTD restore HR proficiency, suggesting another domain may take over its function. Here, we identify a region in the N terminus of BRCA2 that exhibits DNA binding activity (NTD) and provide evidence for NTD promoting RAD51-mediated HR. A missense variant detected in breast cancer patients located in the NTD impairs HR stimulation on dsDNA/ssDNA junction containing substrates. These findings shed light on the function of the N terminus of BRCA2 and have implications for the evaluation of breast cancer variants.

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Juan S Martinez, Catharina von Nicolai, Taeho Kim, Åsa Ehlén, Alexander V Mazin, Stephen C Kowalczykowski, Aura Carreira (2016 Mar 29)

BRCA2 regulates DMC1-mediated recombination through the BRC repeats.

Proceedings of the National Academy of Sciences of the United States of America : 3515-20 : DOI : 10.1073/pnas.1601691113 En savoir plus

In somatic cells, BRCA2 is needed for RAD51-mediated homologous recombination. The meiosis-specific DNA strand exchange protein, DMC1, promotes the formation of DNA strand invasion products (joint molecules) between homologous molecules in a fashion similar to RAD51. BRCA2 interacts directly with both human RAD51 and DMC1; in the case of RAD51, this interaction results in stimulation of RAD51-promoted DNA strand exchange. However, for DMC1, little is known regarding the basis and functional consequences of its interaction with BRCA2. Here we report that human DMC1 interacts directly with each of the BRC repeats of BRCA2, albeit most tightly with repeats 1-3 and 6-8. However, BRC1-3 bind with higher affinity to RAD51 than to DMC1, whereas BRC6-8 bind with higher affinity to DMC1, providing potential spatial organization to nascent filament formation. With the exception of BRC4, each BRC repeat stimulates joint molecule formation by DMC1. The basis for this stimulation is an enhancement of DMC1-ssDNA complex formation by the stimulatory BRC repeats. Lastly, we demonstrate that full-length BRCA2 protein stimulates DMC1-mediated DNA strand exchange between RPA-ssDNA complexes and duplex DNA, thus identifying BRCA2 as a mediator of DMC1 recombination function. Collectively, our results suggest unique and specialized functions for the BRC motifs of BRCA2 in promoting homologous recombination in meiotic and mitotic cells.


Année de publication : 2015

Juan S Martinez, Céline Baldeyron, Aura Carreira (2015 Nov 13)

Molding BRCA2 function through its interacting partners.

Cell cycle (Georgetown, Tex.) : 3389-95 : DOI : 10.1080/15384101.2015.1093702 En savoir plus

The role of the tumor suppressor BRCA2 has been shaped over 2 decades thanks to the discovery of its protein and nucleic acid partners, biochemical and structural studies of the protein, and the functional evaluation of germline variants identified in breast cancer patients. Yet, the pathogenic and functional effect of many germline mutations in BRCA2 remains undetermined, and the heterogeneity of BRCA2-associated tumors challenges the identification of causative variants that drive tumorigenesis. In this review, we propose an overview of the established and emerging interacting partners and functional pathways attributed to BRCA2, and we speculate on how variants altering these functions may contribute to cancer susceptibility.


Année de publication : 2014

Martin Dutertre, Sarah Lambert, Aura Carreira, Mounira Amor-Guéret, Stéphan Vagner (2014 Mar 1)

DNA damage: RNA-binding proteins protect from near and far.

Trends in biochemical sciences : 141-9 : DOI : 10.1016/j.tibs.2014.01.003 En savoir plus

Recent work, including large-scale genetic and molecular analyses, identified RNA-binding proteins (RBPs) as major players in the prevention of genome instability. These studies show that RBPs prevent harmful RNA/DNA hybrids and are involved in the DNA damage response (DDR), from DNA repair to cell survival decisions. Indeed, specific RBPs allow the selective regulation of DDR genes at multiple post-transcriptional levels (from pre-mRNA splicing/polyadenylation to mRNA stability/translation) and are directly involved in DNA repair. These multiple activities are mediated by RBP binding to mRNAs, nascent transcripts, noncoding RNAs, and damaged DNA. Finally, because DNA damage modifies RBP localization and binding to different RNA/DNA molecules, we propose that upon DNA damage, RBPs coordinately regulate various aspects of both RNA and DNA metabolism.

Lucia Guidugli, Aura Carreira, Sandrine M Caputo, Asa Ehlen, Alvaro Galli, Alvaro N A Monteiro, Susan L Neuhausen, Thomas V O Hansen, Fergus J Couch, Maaike P G Vreeswijk, (2014 Feb 1)

Functional assays for analysis of variants of uncertain significance in BRCA2.

Human mutation : 151-64 : DOI : 10.1002/humu.22478 En savoir plus

Missense variants in the BRCA2 gene are routinely detected during clinical screening for pathogenic mutations in patients with a family history of breast and ovarian cancer. These subtle changes frequently remain of unknown clinical significance because of the lack of genetic information that may help establish a direct correlation with cancer predisposition. Therefore, alternative ways of predicting the pathogenicity of these variants are urgently needed. Since BRCA2 is a protein involved in important cellular mechanisms such as DNA repair, replication, and cell cycle control, functional assays have been developed that exploit these cellular activities to explore the impact of the variants on protein function. In this review, we summarize assays developed and currently utilized for studying missense variants in BRCA2. We specifically depict details of each assay, including variants of uncertain significance analyzed, and describe a validation set of (genetically) proven pathogenic and neutral missense variants to serve as a golden standard for the validation of each assay. Guidelines are proposed to enable implementation of laboratory-based methods to assess the impact of the variant on cancer risk.


Année de publication : 2013

Antony M Carr, Sarah Lambert, Aura Carreira (2013 Nov 29)

Replication stress-induced genome instability: the dark side of replication maintenance by homologous recombination.

Journal of molecular biology : 4733-44 : DOI : 10.1016/j.jmb.2013.04.023 En savoir plus

Homologous recombination (HR) is an evolutionary-conserved mechanism involved in a subtle balance between genome stability and diversity. HR is a faithful DNA repair pathway and has been largely characterized in the context of double-strand break (DSB) repair. Recently, multiple functions for the HR machinery have been identified at arrested forks. These are evident across different organisms and include replication fork-stabilization and fork-restart functions. Interestingly, a DSB appears not to be a prerequisite for HR-mediated replication maintenance. HR has the ability to rebuild a replisome at inactivated forks, but perhaps surprisingly, the resulting replisome is liable to intrastrand and interstrand switches leading to replication errors. Here, we review our current understanding of the replication maintenance function of HR. The error proneness of these pathways leads us to suggest that the origin of replication-associated genome instability should be re-evaluated.


Année de publication : 2011

Aura Carreira, Stephen C Kowalczykowski (2011 Jun 28)

Two classes of BRC repeats in BRCA2 promote RAD51 nucleoprotein filament function by distinct mechanisms.

Proceedings of the National Academy of Sciences of the United States of America : 10448-53 : DOI : 10.1073/pnas.1106971108 En savoir plus

The human tumor suppressor protein BRCA2 plays a key role in recombinational DNA repair. BRCA2 recruits RAD51 to sites of DNA damage through interaction with eight conserved motifs of approximately 35 amino acids, the BRC repeats; however, the specific function of each repeat remains unclear. Here, we investigated the function of the individual BRC repeats by systematically analyzing their effects on RAD51 activities. Our results reveal the existence of two categories of BRC repeats that display unique functional characteristics. One group, comprising BRC1, -2, -3, and -4, binds to free RAD51 with high affinity. The second group, comprising BRC5, -6, -7, and -8, binds to free RAD51 with low affinity but binds to the RAD51-ssDNA filament with high affinity. Each member of the first group reduces the ATPase activity of RAD51, whereas none of the BRC repeats of the second group affects this activity. Thus, through different mechanisms, both types of BRC repeats bind to and stabilize the RAD51 nucleoprotein filament on ssDNA. In addition, members of the first group limit binding of RAD51 to duplex DNA, where members of the second group do not. Only the first group enhances DNA strand exchange by RAD51. Our results suggest that the two groups of BRC repeats have differentially evolved to ensure efficient formation of a nascent RAD51 filament on ssDNA by promoting its nucleation and growth, respectively. We propose that the BRC repeats cooperate in a partially redundant but reinforcing manner to ensure a high probability of RAD51 filament formation.


Année de publication : 2010

Ryan B Jensen, Aura Carreira, Stephen C Kowalczykowski (2010 Oct 7)

Purified human BRCA2 stimulates RAD51-mediated recombination.

Nature : 678-83 : DOI : 10.1038/nature09399 En savoir plus

Mutation of the breast cancer susceptibility gene, BRCA2, leads to breast and ovarian cancers. Mechanistic insight into the functions of human BRCA2 has been limited by the difficulty of isolating this large protein (3,418 amino acids). Here we report the purification of full-length BRCA2 and show that it both binds RAD51 and potentiates recombinational DNA repair by promoting assembly of RAD51 onto single-stranded DNA (ssDNA). BRCA2 acts by targeting RAD51 to ssDNA over double-stranded DNA, enabling RAD51 to displace replication protein-A (RPA) from ssDNA and stabilizing RAD51-ssDNA filaments by blocking ATP hydrolysis. BRCA2 does not anneal ssDNA complexed with RPA, implying it does not directly function in repair processes that involve ssDNA annealing. Our findings show that BRCA2 is a key mediator of homologous recombination, and they provide a molecular basis for understanding how this DNA repair process is disrupted by BRCA2 mutations, which lead to chromosomal instability and cancer.