Many examples have been described of individuals and families carrying deleterious mutations in more than one proven breast cancer susceptibility gene; one such example is the co-observation of mutations.21,25 This study demonstrates the power of massively parallel sequencing in the Dxd discovery of additional breast cancer susceptibility genes when used with an appropriate study design. unaccounted for.1 Recently, exome sequencing has been demonstrated to be a powerful tool for identifying the underlying cause of rare Mendelian disorders. However, Rabbit Polyclonal to OR5K1 diseases such as breast cancer present substantially increased complexity in terms of locus, allelic and phenotypic heterogeneity, and relationships between genotype and phenotype. As part of a collaborative (Leiden University Medical Centre, the Spanish National Cancer Center, and The University of Melbourne) project involving the exome capture and massively parallel sequencing of multiple-case breast-cancer-affected Dxd families, we applied whole-exome sequencing to DNA from multiple affected relatives from 13 families (family structure and sample availability were considered before the affected relatives were chosen). Bioinformatic analysis of the resulting exome sequences identified a protein-truncating mutation, c.651_652del (p.Cys217?), in X-ray repair cross complementing Dxd gene-2 ([MIM 600375; “type”:”entrez-nucleotide”,”attrs”:”text”:”NM_005431.1″,”term_id”:”4885656″,”term_text”:”NM_005431.1″NM_005431.1]) in the peripheral-blood DNA of a man participating in the Australian Breast Cancer Family Registry2 (ABCFR; Figure?1A); this man (III-4 in Figure?1A) had been diagnosed with breast cancer at 29?years of age, and his mother (II-3), sister (III-5), and cousin (III-1) had been diagnosed with breast cancer at 37, 41, and 34 years of age, respectively. The cousin (III-1), who had also been selected for exome sequencing, did not carry this mutation, the sister’s DNA was Sanger sequenced and was found to carry the mutation, and there was no?DNA available for testing of the mother. Exome sequencing of three individuals from a family participating in a Dutch research study of multiple-case breast-cancer-affected families identified a probably deleterious missense mutation (c.271C T [p.Arg91Trp] in Mutations Mutation status is indicated for all family members for whom a DNA sample was available. Cancer diagnosis and age of onset are indicated for affected members. Asterisks indicate that DNA underwent exome sequencing (libraries for 50?bp fragment reads were prepared according to the SOLiD Baylor protocol 2.1 and the Nimblegen exome-capture protocol v.1.2 with some variations). The following abbreviations are used: BC, breast cancer (black filled symbols); PC, pancreatic cancer; BwC, bowel cancer; UC, uterine cancer; MM, malignant melanoma; UK, unknown age; BlC, bladder cancer; OC, ovarian cancer; BCC, basal cell carcinoma; L, lung cancer; (all gray-filled symbols); V, verified cancer (via cancer registry or pathology report); and wt, wild-type. Some symbols represent more than one Dxd person as indicated by a numeral. Open in a separate window Figure?2 XRCC2 Multiple-Sequence Alignment Centered on Position Arg91 Missense substitutions observed in this interval are given with the missense residue directly above the corresponding human reference sequence residue. The following abbreviations are used: Hsap, mutations c.651_652del (p.Cys217?) and c.271C T (p.Arg91Trp) in Dxd 1,344 cases and 1,436 controls from the Melbourne Collaborative Cohort Study3 (MCCS) and the ABCFR revealed one control (II-2, Figure?1C) who carried c.651_652del (p.Cys217?). Intriguingly, this control individual’s sister (II-1) was diagnosed with breast cancer at 63 years of age, and her mother (I-2) was diagnosed with melanoma at 69 years of age (Figure?1C, Tables 1 and ?and22). Table 1 Mutation Screening in Multiple-Case Breast Cancer Families Variantsc.70_80del (p.Cys24Serfs?13). dThis carrier of p.Arg91Trp was identified through both the ABFCR multiple-case family screening and the BCFR-IARC (Breast Cancer Family Registry-International Agency for Research on Cancer) case-control screening. eFamily included in the exome-sequencing phase. Table 2 Case-Control Mutation Screening Applied to the BCFR Population-Based Study Variantsparalog, was cloned because of its ability.