Accurate classification of BRCA1 variants with saturation genome editing
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ABSTRACT:
PROVIDER: PRJNA481326 | ENA |
REPOSITORIES: ENA
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Project description:We describe the use of saturation genome editing to make and measure the effect of BRCA1 variants on protein function and splicing. We find the results accurately predict the clinical effects of variants.
2018-08-01 | GSE117159 | GEO
Project description:Variants of uncertain significance fundamentally limit the clinical utility of genetic information. The challenge they pose is epitomized by BRCA1, a tumour suppressor gene in which germline loss-of-function variants predispose women to breast and ovarian cancer. Although BRCA1 has been sequenced in millions of women, the risk associated with most newly observed variants cannot be definitively assigned. Here we use saturation genome editing to assay 96.5% of all possible single-nucleotide variants (SNVs) in 13 exons that encode functionally critical domains of BRCA1. Functional effects for nearly 4,000 SNVs are bimodally distributed and almost perfectly concordant with established assessments of pathogenicity. Over 400 non-functional missense SNVs are identified, as well as around 300 SNVs that disrupt expression. We predict that these results will be immediately useful for the clinical interpretation of BRCA1 variants, and that this approach can be extended to overcome the challenge of variants of uncertain significance in additional clinically actionable genes.
| S-EPMC6181777 | biostudies-literature
Project description:BRCA1 and BRCA2 classification of ovarian cancer
| PRJNA437914 | ENA
Project description:Inactivating germline BRCA1 and BRCA2 mutations confer a defect in homologous recombination DNA repair which was found to leave traces in tumor DNA copy number aberration (CNA) profiles. In analogy to previously trained breast cancer CNA classifiers that predicted association with BRCA1 and BRCA2 mutated cancer and benefit of high dose double strand break inducing chemotherapy, we trained BRCA1 and BRCA2 classifiers on CNA profiles of 50 BRCA1 mutated, 10 BRCA2 mutated and 13 non-familial ovarian cancers and investigated whether tumor type and mutation type independent classifiers could be trained. The cross validated area under the curve of the receiver/operator characteristic curve of ovarian cancer BRCA1 and BRCA2 classifiers were 0.67 (95% CI: 0.55-0.78) and 0.91 (95% CI: 0.79-1). These classifiers identified the majority of the samples with germline and somatic BRCA1 and BRCA2 mutations and BRCA1 promoter hypermethylation in the Cancer Genome Atlas (TCGA) dataset. Combining tumor type or mutated gene did not yield higher AUCs than single gene classifiers, although the ovarian BRCA1+BRCA2 classifier identified most BRCA1 and -2 mutated cases, including those in the TCGA dataset, and a combined breast and ovarian cancer BRCA1 classifier may improve response prediction to double strand break inducing chemotherapy.
2021-12-31 | GSE111688 | GEO
Project description:Single nucleotide variants are the most frequent type of sequence changes detected in the genome and these are frequently variants of uncertain significance (VUS). VUS are changes in DNA for which disease risk association is unknown. Thus, methods that classify the functional impact of a VUS can be used as evidence for variant interpretation. In the case of the breast and ovarian cancer specific tumor suppressor protein, BRCA1, pathogenic missense variants frequently score as loss of function in an assay for homology-directed repair (HDR) of DNA double-strand breaks. We previously published functional results using a multiplexed assay for 1056 amino acid substitutions residues 2-192 in the amino terminus of BRCA1. In this study, we have re-assessed the data from this multiplexed assay using an improved analysis pipeline. These new analysis methods yield functional scores for more variants in the first 192 amino acids of BRCA1, plus we report new results for BRCA1 amino acid residues 193-302. We now present the functional classification of 2172 BRCA1 variants in BRCA1 residues 2-302 using the multiplexed HDR assay. Comparison of the functional determinations of the missense variants with clinically known benign or pathogenic variants indicated 93% sensitivity and 100% specificity for this assay. The results from BRCA1 variants tested in this assay are a resource for clinical geneticists for evidence to evaluate VUS in BRCA1.
2023-06-12 | GSE234482 | GEO
Project description:We employed saturation genome editing (SGE) to assess the functional consequences of synonymous, missense, and nonsense variants across KARS1 exon 2. Deep DNA sequencing of fixed-amplicon PCR products targeting the endogenous KARS1 Exon 2 locus was used to determine variant frequencies as part of a larger study to identify a set of reproducible enrichment scores indicating effects of variants on KARS1 function.
2024-05-31 | GSE232151 | GEO
Project description:We employed saturation genome editing (SGE) to assess the functional consequences of synonymous, missense, and nonsense variants across KARS1 exon 2. Deep DNA sequencing of fixed-amplicon PCR products targeting the endogenous KARS1 Exon 2 locus was used to determine variant frequencies as part of a larger study to identify a set of reproducible enrichment scores indicating effects of variants on KARS1 function.
2024-05-31 | GSE232150 | GEO
Project description:Background: The BRCA1 protein has been shown to play critical roles in several molecular pathways, but the specific defect(s) that promote breast and ovarian carcinogenesis remain a mystery. Furthermore, while mutations that result in a truncated protein can unequivocally be called disease-causing, many other variants mutations have poorly defined clinical significance. Given these factors, development of a functional assay for BRCA1 is a significant clinical priority, but presents significant biological challenges. Methodology and Significant Findings: We have developed a novel function-based assay for BRCA1 carrier identification by examining the effect of loss of a single copy of BRCA1 on global gene expression levels. Comparison of the gene expression profiles of undamaged, actively cycling EBV-transformed lymphocytes allowed accurate discrimination between BRCA1+/+ and BRCA1+/- cells. The best predictor was 100% (16/16) accurate in predicting BRCA1 status in an independent test set; the overall sensitivity and specificity of the test are 84% and 92%, respectively, when the training set data (53 samples) is also included. A set of 22 genes was identified by two distinct analytical approaches, including a set of 11 genes (TBX21, MX2, IFIT1, IFIT2, IFIT3, GLDC, F13A1, SOX4, LCK, HERC5, USP18) that could be linked in a single pathway encompassing cellular proliferation and development. By contrast, analysis of the same samples for global gene expression level changes following irradiation did not support the development of an accurate class predictor. Conclusions and Significance: Our results support the idea that the fundamental defect resulting from BRCA1 mutation is a reduction in cellular differentiation, and that changes in the DNA damage response require inactivation of the second BRCA1 allele. Given that the class predictor we have developed was based on unperturbed cells, this work could ultimately lead to the development of a rapid and accurate test for identification of BRCA1 mutation carriers.
2014-12-12 | GSE19541 | GEO
Project description:While new defects in BRCA1 are still being found, it is unclear whether current breast cancer diagnostics misses many BRCA1-associated cases. A reliable test that is able to indicate the involvement of BRCA1 deficiency in cancer genesis could support decision making in genetic counselling and clinical management. To find BRCA1-specific markers and explore the effectiveness of the current diagnostic strategy, we designed a classification method, validated it and examined whether we could find BRCA1-like breast tumours in a group of patients initially diagnosed as non-BRCA1/2 mutation carriers. A classifier was built based on array-CGH profiles of 18 BRCA1-related and 32 control breast tumours, and validated on independent sets of 16 BRCA1-related and 16 control breast carcinomas. Subsequently, we applied the classifier to 48 breast tumours of patients from Hereditary Breast and Ovarian Cancer (HBOC) families in whom no germ line BRCA1/BRCA2 mutations were identified. The classifier showed an accuracy of 91% when applied to the validation sets. In 48 non-BRCA1/2 patients, only two breast tumours presented a BRCA1-like CGH profile. Additional evidence for BRCA1 dysfunction was found in one of these tumours. We here describe the specific chromosomal aberrations in BRCA1-related breast carcinomas. We developed a predictive genetic test for BRCA1-association and show that BRCA1-related tumours can still be identified in HBOC families after routine DNA diagnostics.
2010-12-02 | GSE9021 | GEO
Project description:The pathogenicity of majority of variants identified in cancer-causing genes is unknown due to limited epidemiological data, hence they are considered to be variant of uncertain significance (VUS). To date, Breast Cancer gene-2 (BRCA2) has the highest number of VUSs, which has necessitated the development of several robust functional assays to determine their functional significance. Here we report the use of a humanized-mouse embryonic stem cell (mESC) line expressing a single copy of the human BRCA2 for a CRISPR-Cas9-based high-throughput functional assay. As a proof-of-principle, we have saturated 11 codons encoded by BRCA2 exons 3, 18, 19 and all possible single-nucleotide variants in exon 13 and multiplexed these variants for their functional categorization. Specifically, we used a pool of 180-mer single-stranded donor DNA to generate all possible combination of variants. Using a high throughput sequencing-based approach, we show a significant drop in the frequency of non-functional variants, whereas functional variants are enriched in the pool of the cells. We further demonstrate that variants with partial loss of BRCA2 function are sensitive to the DNA-damaging agents, cisplatin and olaparib, allowing us to discriminate between functional and intermediate variants. We have categorized 599 BRCA2 variants including 93-single nucleotide variants (SNVs) across the 11 codons, of which 28 are reported in ClinVar. We also functionally categorized 252 SNVs from exon 13 into 188 functional, 60 non-functional and 4 intermediate variants, demonstrating that saturation genome editing (SGE) coupled with drug sensitivity assays can enhance functional annotation of BRCA2 VUS.
2023-08-30 | GSE238143 | GEO