[Evaluation of variants of unknown significance in the BRCA2 gene]
M Heczková1, E Macháčková, M Jirsa
1Centrum experimentální medicíny, Institut klinické a experimentální medicíny, Praha.
Background:
Endogenous processes and exogenous agents cause constant DNA damage. DNA double-strand breaks are among the most serious types of damage. They are mainly repaired by homologous recombination, where the BRCA2 protein plays a dominant role. Heterozygous germline BRCA2 mutations predispose to breast, ovarian, pancreatic and other types of cancer. The presence of a pathogenic mutation in patients or their family members warrants close surveillance and prophylactic surgery. Apart from clearly pathogenic mutations, variants leading only to a single amino acid substitution are often identified. Since the influence of these variants on cancer risk is unknown, they represent a major clinical problem.
Aims:
The aim of this paper is to summarize the current possibilities of predicting pathogenicity of BRCA2 variants. In some cases, genetic methods are able to classify variants with high probability; however, their use is often limited by low frequency of the variants or inaccessibility of samples for mRNA isolation or DNA from family members. Alternatively, functional assays performed in various cellular models may be employed. Multiple functional tests and cellular models are presented and characterized, including their advantages and limitations. A new model of human syngeneic cell lines developed by the authors is presented, in which one BRCA2 allele is deleted and the variant is introduced into the other allele by homologous recombination. This model has the potential to evaluate function of variants without some of the unwanted effects of the other models. Currently, this model is being applied to variants identified in patients with hereditary cancer predisposition in the Masaryk Memorial Cancer Institute.
Conclusion:
Functional assays in cellular models including a new model of syngeneic cell lines described by the authors have a great potential in evaluating clinical importance of unclassified variants in the BRCA2 gene, especially in cases where genetic tests are not applicable.
Insights
Predicting the cancer risk of BRCA2 gene variants is challenging. New functional assays in cellular models, including a novel syngeneic cell line, show promise for classifying uncertain variants when genetic tests fail.
Area of Science:
- Genetics and Genomics
- Molecular Biology
- Cancer Research
Context:
- DNA double-strand breaks are critical DNA lesions repaired by homologous recombination.
- The BRCA2 protein is essential for homologous recombination and DNA repair.
- Germline BRCA2 mutations significantly increase the risk of various cancers, including breast, ovarian, and pancreatic cancers.
Purpose:
- To review current methods for predicting the pathogenicity of BRCA2 variants.
- To highlight the limitations of genetic testing for variant classification.
- To introduce and evaluate functional assays and cellular models for assessing BRCA2 variant function.
Summary:
- Genetic methods can classify some BRCA2 variants but are often limited by sample availability or variant frequency.
- Functional assays in cellular models offer an alternative approach to assess variant pathogenicity.
- A novel syngeneic cell line model was developed to evaluate BRCA2 variants with reduced confounding factors.
Impact:
- Functional assays, particularly the new syngeneic cell line model, can help determine the clinical significance of unclassified BRCA2 variants.
- This approach is especially valuable when traditional genetic testing methods are not feasible.
- Improved variant classification aids in cancer risk assessment and patient management for hereditary cancer predisposition.
Related Concept Videos
01:05Cancer-Critical Genes II: Tumor Suppressor Genes
When the function of certain critical genes, especially those involved in cell cycle regulation and cell growth signaling cascades, gets disrupted, it upsets the cell cycle progression. Such cells with unchecked cell cycles start proliferating uncontrollably and eventually develop into tumors.
Such genes that act...
01:05Cancer-Critical Genes II: Tumor Suppressor Genes
When the function of certain critical genes, especially those involved in cell cycle regulation and cell growth signaling cascades, gets disrupted, it upsets the cell cycle progression. Such cells with unchecked cell cycles start proliferating uncontrollably and eventually develop into tumors.
Such genes that act...
02:26Comparing Copy Number Variations and SNPs
Copy number variations or CNVs are the structural variations that cover more than 1kb of DNA sequence. The single nucleotide polymorphism (SNP), on the other hand, is a single nucleotide change or a point mutation that is found in more than 1%...
01:27Principles of Pharmacogenetics: Types of Genetic Variants