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Samadi M, Beigi L, Yadegari F, Ansari AM, Majidzadeh-A K, Eskordi M, Farahmand L. Recognition of functional genetic polymorphism using ESE motif definition: a conservative evolutionary approach to CYP2D6/CYP2C19 gene variants. Genetica 2022; 150:289-297. [PMID: 35913522 DOI: 10.1007/s10709-022-00161-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 03/24/2022] [Indexed: 11/04/2022]
Abstract
Although predicting the effects of variants near intron-exon boundaries is relatively straightforward, predicting the functional Exon Splicing Enhancers (ESEs) and the possible effects of variants within ESEs remains a challenge. Considering the essential role of CYP2D6/CYP2C19 genes in drug metabolism, we attempted to identify variants that are most likely to disrupt splicing through their effect on these ESEs. ESEs were predicted in these two genes using ESEfinder 3.0, incorporating a series of filters (increased threshold and evolutionary conservation). Finally, reported mutations were evaluated for their potential to disrupt splicing by affecting these ESEs. Initially, 169 and 243 ESEs were predicted for CYP2C19/CYP2D6, respectively. However, applying the filters, the number of predicted ESEs was reduced to 26 and 19 in CYP2C19/CYP2D6, respectively. Comparing prioritized predicted ESEs with known sequence variants in CYP2C19/CYP2D6 genes highlights 18 variations within conserved ESEs for each gene. We found good agreement in cases where such predictions could be compared to experimental evidence. In total, we prioritized a subset of mutational changes in CYP2C19/CYP2D6 genes that may affect the function of these genes and lead to altered drug responses. Clinical studies and functional analysis for investigating detailed functional consequences of the mentioned mutations and their phenotypic outcomes is mostly recommended.
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Affiliation(s)
- Mitra Samadi
- Recombinant Proteins Department, Breast Cancer Research Center, Motamed Cancer Institute, ACECR, Tehran, Iran
| | - Laleh Beigi
- Recombinant Proteins Department, Breast Cancer Research Center, Motamed Cancer Institute, ACECR, Tehran, Iran
| | - Fatemeh Yadegari
- Recombinant Proteins Department, Breast Cancer Research Center, Motamed Cancer Institute, ACECR, Tehran, Iran
| | - Alireza Madjid Ansari
- Recombinant Proteins Department, Breast Cancer Research Center, Motamed Cancer Institute, ACECR, Tehran, Iran
| | - Keivan Majidzadeh-A
- Recombinant Proteins Department, Breast Cancer Research Center, Motamed Cancer Institute, ACECR, Tehran, Iran
| | - Maryam Eskordi
- Recombinant Proteins Department, Breast Cancer Research Center, Motamed Cancer Institute, ACECR, Tehran, Iran
| | - Leila Farahmand
- Recombinant Proteins Department, Breast Cancer Research Center, Motamed Cancer Institute, ACECR, Tehran, Iran.
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Fraile-Bethencourt E, Valenzuela-Palomo A, Díez-Gómez B, Acedo A, Velasco EA. Identification of Eight Spliceogenic Variants in BRCA2 Exon 16 by Minigene Assays. Front Genet 2018; 9:188. [PMID: 29881398 PMCID: PMC5977032 DOI: 10.3389/fgene.2018.00188] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 05/08/2018] [Indexed: 11/17/2022] Open
Abstract
Genetic testing of BRCA1 and BRCA2 identifies a large number of variants of uncertain clinical significance whose functional and clinical interpretations pose a challenge for genetic counseling. Interestingly, a relevant fraction of DNA variants can disrupt the splicing process in cancer susceptibility genes. We have tested more than 200 variants throughout 19 BRCA2 exons mostly by minigene assays, 54% of which displayed aberrant splicing, thus confirming the utility of this assay to check genetic variants in the absence of patient RNA. Our goal was to investigate BRCA2 exon 16 with a view to characterizing spliceogenic variants recorded at the mutational databases. Seventy-two different BIC and UMD variants were analyzed with NNSplice and Human Splicing Finder, 12 of which were selected because they were predicted to disrupt essential splice motifs: canonical splice sites (ss; eight variants) and exonic/intronic splicing enhancers (four variants). These 12 candidate variants were introduced into the BRCA2 minigene with seven exons (14–20) by site-directed mutagenesis and then transfected into MCF-7 cells. Seven variants (six intronic and one missense) induced complete abnormal splicing patterns: c.7618-2A>T, c.7618-2A>G, c.7618-1G>C, c.7618-1G>A, c.7805G>C, c.7805+1G>A, and c.7805+3A>C, as well as a partial anomalous outcome by c.7802A>G. They generated at least 10 different transcripts: Δ16p44 (alternative 3’ss 44-nt downstream; acceptor variants), Δ16 (exon 16-skipping; donor variants), Δ16p55 (alternative 3’ss 55-nt downstream), Δ16q4 (alternative 5’ss 4-nt upstream), Δ16q100 (alternative 5’ss 4-nt upstream), ▾16q20 (alternative 5’ss 20-nt downstream), as well as minor (Δ16p93 and Δ16,17p69) and uncharacterized transcripts of 893 and 954 nucleotides. Isoforms Δ16p44, Δ16, Δ16p55, Δ16q4, Δ16q100, and ▾16q20 introduced premature termination codons which presumably inactivate BRCA2. According to the guidelines the American College of Medical Genetics and Genomics these eight variants could be classified as pathogenic or likely pathogenic whereas the Evidence-based Network for the Interpretation of Germline Mutant Alleles rules suggested seven class 4 and one class 3 variants. In conclusion, our study highlights the relevance of splicing functional assays by hybrid minigenes for the clinical classification of genetic variations. Hence, we provide new data about spliceogenic variants of BRCA2 exon 16 that are directly correlated with breast cancer susceptibility.
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Affiliation(s)
- Eugenia Fraile-Bethencourt
- Splicing and Genetic Susceptibility to Cancer, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, Valladolid, Spain
| | - Alberto Valenzuela-Palomo
- Splicing and Genetic Susceptibility to Cancer, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, Valladolid, Spain
| | - Beatriz Díez-Gómez
- Splicing and Genetic Susceptibility to Cancer, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, Valladolid, Spain
| | - Alberto Acedo
- Splicing and Genetic Susceptibility to Cancer, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, Valladolid, Spain.,Biome Makers Inc., San Francisco, CA, United States
| | - Eladio A Velasco
- Splicing and Genetic Susceptibility to Cancer, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, Valladolid, Spain
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Garre P, Martín L, Sanz J, Romero A, Tosar A, Bando I, Llovet P, Diaque P, García-Paredes B, Díaz-Rubio E, de la Hoya M, Caldés T. BRCA2 gene: a candidate for clinical testing in familial colorectal cancer type X. Clin Genet 2014; 87:582-7. [PMID: 24814045 DOI: 10.1111/cge.12427] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 05/09/2014] [Accepted: 05/09/2014] [Indexed: 01/19/2023]
Abstract
Familial colorectal cancer type X (FCCX) encompasses a group of families with dominant inheritance pattern of colorectal cancer (CRC) but no alteration in any known CRC susceptibility gene. Therefore, the explanation of their susceptibility is a priority to offer an accurate genetic counseling. We screened the 27 coding exons and exon-intron boundaries of BRCA2 in 48 FCCX probands. We identified 29 variants including a frameshift mutation. Deleterious variant c.3847_3848delGT p.(Val1283Lysfs*2) showed cosegregation with disease as well as loss of heterozygosity (LOH) in CRC tumor DNA. This is the first evidence of germline BRCA2 pathogenic mutation associated with CRC risk. Furthermore, missense variants c.502C>A p.(Pro168Thr), c.5744C>T p.(Thr1915Met) and c.7759C>T p.(Leu2587Phe) were proposed as candidate risk alleles based on cosegregation, LOH tumor analysis and in silico testing.
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Affiliation(s)
- P Garre
- Laboratorio de Oncología Molecular, Hospital Clínico San Carlos, IdISSC, Madrid, Spain
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Di Giacomo D, Gaildrat P, Abuli A, Abdat J, Frébourg T, Tosi M, Martins A. Functional analysis of a large set of BRCA2 exon 7 variants highlights the predictive value of hexamer scores in detecting alterations of exonic splicing regulatory elements. Hum Mutat 2013; 34:1547-57. [PMID: 23983145 DOI: 10.1002/humu.22428] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 08/14/2013] [Indexed: 11/06/2022]
Abstract
Exonic variants can alter pre-mRNA splicing either by changing splice sites or by modifying splicing regulatory elements. Often these effects are difficult to predict and are only detected by performing RNA analyses. Here, we analyzed, in a minigene assay, 26 variants identified in the exon 7 of BRCA2, a cancer predisposition gene. Our results revealed eight new exon skipping mutations in this exon: one directly altering the 5' splice site and seven affecting potential regulatory elements. This brings the number of splicing regulatory mutations detected in BRCA2 exon 7 to a total of 11, a remarkably high number considering the total number of variants reported in this exon (n = 36), all tested in our minigene assay. We then exploited this large set of splicing data to test the predictive value of splicing regulator hexamers' scores recently established by Ke et al. (). Comparisons of hexamer-based predictions with our experimental data revealed high sensitivity in detecting variants that increased exon skipping, an important feature for prescreening variants before RNA analysis. In conclusion, hexamer scores represent a promising tool for predicting the biological consequences of exonic variants and may have important applications for the interpretation of variants detected by high-throughput sequencing.
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Affiliation(s)
- Daniela Di Giacomo
- Inserm U1079, University of Rouen, Institute for Research and Innovation in Biomedicine, Rouen, France; Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, Italy
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Wappenschmidt B, Becker AA, Hauke J, Weber U, Engert S, Köhler J, Kast K, Arnold N, Rhiem K, Hahnen E, Meindl A, Schmutzler RK. Analysis of 30 putative BRCA1 splicing mutations in hereditary breast and ovarian cancer families identifies exonic splice site mutations that escape in silico prediction. PLoS One 2012; 7:e50800. [PMID: 23239986 PMCID: PMC3519833 DOI: 10.1371/journal.pone.0050800] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 10/25/2012] [Indexed: 12/12/2022] Open
Abstract
Screening for pathogenic mutations in breast and ovarian cancer genes such as BRCA1/2, CHEK2 and RAD51C is common practice for individuals from high-risk families. However, test results may be ambiguous due to the presence of unclassified variants (UCV) in the concurrent absence of clearly cancer-predisposing mutations. Especially the presence of intronic or exonic variants within these genes that possibly affect proper pre-mRNA processing poses a challenge as their functional implications are not immediately apparent. Therefore, it appears necessary to characterize potential splicing UCV and to develop appropriate classification tools. We investigated 30 distinct BRCA1 variants, both intronic and exonic, regarding their spliceogenic potential by commonly used in silico prediction algorithms (HSF, MaxEntScan) along with in vitro transcript analyses. A total of 25 variants were identified spliceogenic, either causing/enhancing exon skipping or activation of cryptic splice sites, or both. Except from a single intronic variant causing minor effects on BRCA1 pre-mRNA processing in our analyses, 23 out of 24 intronic variants were correctly predicted by MaxEntScan, while HSF was less accurate in this cohort. Among the 6 exonic variants analyzed, 4 severely impair correct pre-mRNA processing, while the remaining two have partial effects. In contrast to the intronic alterations investigated, only half of the spliceogenic exonic variants were correctly predicted by HSF and/or MaxEntScan. These data support the idea that exonic splicing mutations are commonly disease-causing and concurrently prone to escape in silico prediction, hence necessitating experimental in vitro splicing analysis.
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Affiliation(s)
- Barbara Wappenschmidt
- Division of Molecular Gynaeco-Oncology, Department of Gynaecology and Obstetrics, University Hospital of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Alexandra A. Becker
- Division of Molecular Gynaeco-Oncology, Department of Gynaecology and Obstetrics, University Hospital of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Jan Hauke
- Division of Molecular Gynaeco-Oncology, Department of Gynaecology and Obstetrics, University Hospital of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
- Institute of Human Genetics, University of Cologne, Cologne, Germany
| | - Ute Weber
- Division of Molecular Gynaeco-Oncology, Department of Gynaecology and Obstetrics, University Hospital of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Stefanie Engert
- Department of Gynaecology and Obstetrics, Klinikum rechts der Isar at the Technical University, Munich, Germany
| | - Juliane Köhler
- Division of Molecular Gynaeco-Oncology, Department of Gynaecology and Obstetrics, University Hospital of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Karin Kast
- Department of Gynecology and Obstetrics, Technical University of Dresden, Dresden, Germany
| | - Norbert Arnold
- Division of Oncology, Department of Gynaecology and Obstetrics, University Hospital Schleswig-Holstein, Christian-Albrechts-University, Kiel, Germany
| | - Kerstin Rhiem
- Division of Molecular Gynaeco-Oncology, Department of Gynaecology and Obstetrics, University Hospital of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Eric Hahnen
- Division of Molecular Gynaeco-Oncology, Department of Gynaecology and Obstetrics, University Hospital of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Alfons Meindl
- Department of Gynaecology and Obstetrics, Klinikum rechts der Isar at the Technical University, Munich, Germany
| | - Rita K. Schmutzler
- Division of Molecular Gynaeco-Oncology, Department of Gynaecology and Obstetrics, University Hospital of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
- * E-mail:
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Jin P, Cai R, Zhou X, Li-Ling J, Ma F. Features of missense/nonsense mutations in exonic splicing enhancer sequences from cancer-related human genes. Mutat Res 2012; 740:6-12. [PMID: 23123687 DOI: 10.1016/j.mrfmmm.2012.10.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2011] [Revised: 08/31/2012] [Accepted: 10/19/2012] [Indexed: 11/18/2022]
Affiliation(s)
- Ping Jin
- College of Life Science, Nanjing Normal University, Nanjing, China
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Biswas K, Das R, Eggington JM, Qiao H, North SL, Stauffer S, Burkett SS, Martin BK, Southon E, Sizemore SC, Pruss D, Bowles KR, Roa BB, Hunter N, Tessarollo L, Wenstrup RJ, Byrd RA, Sharan SK. Functional evaluation of BRCA2 variants mapping to the PALB2-binding and C-terminal DNA-binding domains using a mouse ES cell-based assay. Hum Mol Genet 2012; 21:3993-4006. [PMID: 22678057 DOI: 10.1093/hmg/dds222] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Single-nucleotide substitutions and small in-frame insertions or deletions identified in human breast cancer susceptibility genes BRCA1 and BRCA2 are frequently classified as variants of unknown clinical significance (VUS) due to the availability of very limited information about their functional consequences. Such variants can most reliably be classified as pathogenic or non-pathogenic based on the data of their co-segregation with breast cancer in affected families and/or their co-occurrence with a pathogenic mutation. Biological assays that examine the effect of variants on protein function can provide important information that can be used in conjunction with available familial data to determine the pathogenicity of VUS. In this report, we have used a previously described mouse embryonic stem (mES) cell-based functional assay to characterize eight BRCA2 VUS that affect highly conserved amino acid residues and map to the N-terminal PALB2-binding or the C-terminal DNA-binding domains. For several of these variants, very limited co-segregation information is available, making it difficult to determine their pathogenicity. Based on their ability to rescue the lethality of Brca2-deficient mES cells and their effect on sensitivity to DNA-damaging agents, homologous recombination and genomic integrity, we have classified these variants as pathogenic or non-pathogenic. In addition, we have used homology-based modeling as a predictive tool to assess the effect of some of these variants on the structural integrity of the C-terminal DNA-binding domain and also generated a knock-in mouse model to analyze the physiological significance of a residue reported to be essential for the interaction of BRCA2 with meiosis-specific recombinase, DMC1.
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Affiliation(s)
- Kajal Biswas
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
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Zago P, Buratti E, Stuani C, Baralle FE. Evolutionary connections between coding and splicing regulatory regions in the fibronectin EDA exon. J Mol Biol 2011; 411:1-15. [PMID: 21663748 DOI: 10.1016/j.jmb.2011.05.031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 05/16/2011] [Accepted: 05/20/2011] [Indexed: 01/03/2023]
Abstract
Research on exonic coding sequences has demonstrated that many substitutions at the amino acid level may also reflect profound changes at the level of splicing regulatory regions. These results have revealed that, for many alternatively spliced exons, there is considerable pressure to strike a balance between two different and sometimes conflicting forces: the drive to improve the quality and production efficiency of proteins and the maintenance of proper exon recognition by the splicing machinery. Up to now, the systems used to investigate these connections have mostly focused on short alternatively spliced exons that contain a high density of splicing regulatory elements. Although this is obviously a desirable feature in order to maximize the chances of spotting connections, it also complicates the process of drawing straightforward evolutionary pathways between different species (because of the numerous alternative pathways through which the same end point can be achieved). The alternatively spliced fibronectin extra domain A exon (also referred to as EDI or EIIIA) does not have these limitations, as its inclusion is already known to depend on a single exonic splicing enhancer element within its sequence. In this study, we have compared the rat and human fibronectin EDA exons with regard to RNA structure, exonic splicing enhancer strengths, and SR protein occupancy. The results gained from these analyses have then been used to perform an accurate evaluation of EDA sequences observed in a wide range of animal species. This comparison strongly suggests the existence of an evolutionary connection between changes at the nucleotide levels and the need to maintain efficient EDA recognition in different species.
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Affiliation(s)
- Paola Zago
- International Center for Genetic Engineering and Biotechnology, Trieste, Italy
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Whiley PJ, Pettigrew CA, Brewster BL, Walker LC, Spurdle AB, Brown MA. Effect of BRCA2 sequence variants predicted to disrupt exonic splice enhancers on BRCA2 transcripts. BMC MEDICAL GENETICS 2010; 11:80. [PMID: 20507642 PMCID: PMC2897790 DOI: 10.1186/1471-2350-11-80] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Accepted: 05/28/2010] [Indexed: 12/02/2022]
Abstract
Background Genetic screening of breast cancer patients and their families have identified a number of variants of unknown clinical significance in the breast cancer susceptibility genes, BRCA1 and BRCA2. Evaluation of such unclassified variants may be assisted by web-based bioinformatic prediction tools, although accurate prediction of aberrant splicing by unclassified variants affecting exonic splice enhancers (ESEs) remains a challenge. Methods This study used a combination of RT-PCR analysis and splicing reporter minigene assays to assess five unclassified variants in the BRCA2 gene that we had previously predicted to disrupt an ESE using bioinformatic approaches. Results Analysis of BRCA2 c.8308 G > A (p.Ala2770Thr) by mRNA analysis, and BRCA2 c.8962A > G (p.Ser2988Gly), BRCA2 c.8972G > A (p.Arg2991His), BRCA2 c.9172A > G (p.Ser3058Gly), and BRCA2 c.9213G > T (p.Glu3071Asp) by a minigene assay, revealed no evidence for aberrant splicing. Conclusions These results illustrate the need for improved methods for predicting functional ESEs and the potential consequences of sequence variants contained therein.
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Affiliation(s)
- Phillip J Whiley
- School of Chemistry and Molecular Biosciences, The University of Queensland, Australia
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Spurdle AB, Couch FJ, Hogervorst FBL, Radice P, Sinilnikova OM. Prediction and assessment of splicing alterations: implications for clinical testing. Hum Mutat 2008; 29:1304-13. [PMID: 18951448 PMCID: PMC2832470 DOI: 10.1002/humu.20901] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Sequence variants that may result in splicing alterations are a particular class of inherited variants for which consequences can be more readily assessed, using a combination of bioinformatic prediction methods and in vitro assays. There is also a general agreement that a variant would invariably be considered pathogenic on the basis of convincing evidence that it results in transcript(s) carrying a premature stop codon or an in-frame deletion disrupting known functional domain(s). This commentary discusses current practices used to assess the clinical significance of this class of variants, provides suggestions to improve assessment, and highlights the issues involved in routine assessment of potential splicing aberrations. We conclude that classification of sequence variants that may alter splicing is greatly enhanced by supporting in vitro analysis. Additional studies that assess large numbers of variants for induction of splicing aberrations and exon skipping are needed to define the contribution of splicing/exon skipping to cancer and disease. These studies will also provide the impetus for development of algorithms that better predict splicing patterns. To facilitate variant classification and development of more specific bioinformatic tools, we call for the deposition of all laboratory data from splicing analyses into national and international databases.
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Affiliation(s)
- Amanda B Spurdle
- Genetics and Population Health Division, Queensland Institute of Medical Research, Brisbane, Australia.
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Cvok ML, Cretnik M, Musani V, Ozretic P, Levanat S. New sequence variants in BRCA1 and BRCA2 genes detected by high-resolution melting analysis in an elderly healthy female population in Croatia. Clin Chem Lab Med 2008; 46:1376-83. [PMID: 18844490 DOI: 10.1515/cclm.2008.307] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND Mutations in BRCA1 and BRCA2 genes are associated with family predisposition to breast and ovarian cancer. Novel screening methods are required for efficient and rapid detection of sequence variants in cancer patients and their family members. METHODS The screening for variants in the breast and ovarian cancer susceptibility genes BRCA1 and BRCA2 in Croatia was performed by a high-resolution melting approach, which is based on differences in melting curves caused by variations in nucleotide sequence. This is the first screening in Croatia on elderly healthy women with no family history of cancer. BRCA1 screening was performed on 220 and BRCA2 screening on 115 samples. RESULTS In a population well beyond the average age of breast/ovarian cancer onset, 21 different sequence variants in the BRCA1 gene (one novel: c.5193+49_50delTA) and 36 variants in the BRCA2 gene (7 novel: c.459A>C, c.3318C>A, c.4412_ 4414delGAA, c.4790C>A, c.6264T>C, c.9087G>A, and c.9864A>G) were detected. CONCLUSIONS Nine BRCA1 and seven BRCA2 known variants appeared with such high frequencies that they could be declared as harmless in this population. Eight BRCA1 high frequency variants, located further from the promoter region, appear to be strongly correlated. Three novel variants that changed the amino acid sequence of the BRCA2 protein (two missense base substitutions, c.3318C>A and c.4790C>A, and one codon deletion c.4412_4414delGAA), appearing only once, were predicted to have no potential effect on protein structure and function.
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