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Caleca L, Colombo M, van Overeem Hansen T, Lázaro C, Manoukian S, Parsons MT, Spurdle AB, Radice P. GFP-Fragment Reassembly Screens for the Functional Characterization of Variants of Uncertain Significance in Protein Interaction Domains of the BRCA1 and BRCA2 Genes. Cancers (Basel) 2019; 11:E151. [PMID: 30696104 PMCID: PMC6406614 DOI: 10.3390/cancers11020151] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 01/22/2019] [Indexed: 01/14/2023] Open
Abstract
Genetic testing for BRCA1 and BRCA2 genes has led to the identification of many unique variants of uncertain significance (VUS). Multifactorial likelihood models that predict the odds ratio for VUS in favor or against cancer causality, have been developed, but their use is conditioned by the amount of necessary data, which are difficult to obtain if a variant is rare. As an alternative, variants mapping to the coding regions can be examined using in vitro functional assays. BRCA1 and BRCA2 proteins promote genome protection by interacting with different proteins. In this study, we assessed the functional effect of two sets of variants in BRCA genes by exploiting the green fluorescent protein (GFP)-reassembly in vitro assay, which was set-up to test the BRCA1/BARD1, BRCA1/UbcH5a, and BRCA2/DSS1 interactions. Based on the findings observed for the validation panels of previously classified variants, BRCA1/UbcH5a and BRCA2/DSS1 binding assays showed 100% sensitivity and specificity in identifying pathogenic and non-pathogenic variants. While the actual efficiency of these assays in assessing the clinical significance of BRCA VUS has to be verified using larger validation panels, our results suggest that the GFP-reassembly assay is a robust method to identify variants affecting normal protein functioning and contributes to the classification of VUS.
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Affiliation(s)
- Laura Caleca
- Unit of Molecular Bases of Genetic Risk and Genetic Testing, Department of Research, Fondazione IRCCS Istituto Nazionale dei Tumori, 20133 Milan, Italy.
| | - Mara Colombo
- Unit of Molecular Bases of Genetic Risk and Genetic Testing, Department of Research, Fondazione IRCCS Istituto Nazionale dei Tumori, 20133 Milan, Italy.
| | - Thomas van Overeem Hansen
- Center for Genomic Medicine, Copenhagen University Hospital, Rigshospitalet, 2100 Copenhagen, Denmark.
- Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, 2100 Copenhagen, Denmark.
| | - Conxi Lázaro
- Hereditary Cancer Program, Catalan Institute of Oncology. Program in Molecular Mechanisms and Experimental Therapy in Oncology (Oncobell), IDIBELL, Hospitalet de Llobregat, 08900 Barcelona, Spain.
- Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), 28029 Madrid, Spain.
| | - Siranoush Manoukian
- Unit of Medical Genetics, Department of Medical Oncology and Hematology, Fondazione IRCCS Istituto Nazionale dei Tumori, 20133 Milan, Italy.
| | - Michael T Parsons
- Department of Genetics and Computational Biology, QIMR Berghofer Medical Research Institute, Brisbane 4029, Australia.
| | - Amanda B Spurdle
- Department of Genetics and Computational Biology, QIMR Berghofer Medical Research Institute, Brisbane 4029, Australia.
| | - Paolo Radice
- Unit of Molecular Bases of Genetic Risk and Genetic Testing, Department of Research, Fondazione IRCCS Istituto Nazionale dei Tumori, 20133 Milan, Italy.
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2
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Caleca L, Catucci I, Figlioli G, De Cecco L, Pesaran T, Ward M, Volorio S, Falanga A, Marchetti M, Iascone M, Tondini C, Zambelli A, Azzollini J, Manoukian S, Radice P, Peterlongo P. Two Missense Variants Detected in Breast Cancer Probands Preventing BRCA2-PALB2 Protein Interaction. Front Oncol 2018; 8:480. [PMID: 30410870 PMCID: PMC6210650 DOI: 10.3389/fonc.2018.00480] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 10/08/2018] [Indexed: 12/13/2022] Open
Abstract
PALB2 (partner and localizer of BRCA2) was initially identified as a binding partner of BRCA2. It interacts also with BRCA1 forming a complex promoting DNA repair by homologous recombination. Germline pathogenic variants in BRCA1, BRCA2 and PALB2 DNA repair genes are associated with high risk of developing breast cancer. Mutation screening in these breast cancer predisposition genes is routinely performed and allows the identification of individuals who carry pathogenic variants and are at risk of developing the disease. However, variants of uncertain significance (VUSs) are often detected and establishing their pathogenicity and clinical relevance remains a central challenge for the risk assessment of the carriers and the clinical decision-making process. Many of these VUSs are missense variants leading to single amino acid substitutions, whose impact on protein function is uncertain. Typically, VUSs are rare and due to the limited genetic, clinical, and pathological data the multifactorial approaches used for classification cannot be applied. Thus, these variants can only be characterized through functional analyses comparing their effect with that of normal and mutant gene products used as positive and negative controls. The two missense variants BRCA2:c.91T >G (p.Trp31Gly) and PALB2:c.3262C >T (p.Pro1088Ser) were detected in two breast cancer probands originally ascertained at Breast Cancer Units of Institutes located in Milan and Bergamo (Northern Italy), respectively. These variants were located in the BRCA2-PALB2 interacting domains, were predicted to be deleterious by in silico analyses, and were very rare and clinically not classified. Therefore, we initiate to study their functional effect by exploiting a green fluorescent protein (GFP)-reassembly in vitro assay specifically designed to test the BRCA2-PALB2 interaction. This functional assay proved to be easy to develop, robust and reliable. It also allows testing variants located in different genes. Results from these functional analyses showed that the BRCA2:p.Trp31Gly and the PALB2:p.Pro1088Ser prevented the BRCA2-PALB2 binding. While caution is warranted when the interpretation of the clinical significance of rare VUSs is based on functional studies only, our data provide initial evidences in favor of the possibility that these variants are pathogenic.
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Affiliation(s)
- Laura Caleca
- Unit of Molecular Bases of Genetic Risk and Genetic Testing, Department of Research, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Irene Catucci
- Genome Diagnostics Program, IFOM the FIRC Institute of Molecular Oncology, Milan, Italy
| | - Gisella Figlioli
- Genome Diagnostics Program, IFOM the FIRC Institute of Molecular Oncology, Milan, Italy
| | - Loris De Cecco
- Platform of Integrated Biology, Department of Applied Research and Technology Development, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Tina Pesaran
- Ambry Genetics, Department of Clinical Diagnostics, Aliso Viejo, CA, United States
| | - Maggie Ward
- Cancer Outreach and Risk Assessment, Via Christi Hospitals, Wichita, KS, United States
| | - Sara Volorio
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Milan, Italy.,Cogentech Cancer Genetics Test Laboratory, Milan, Italy
| | - Anna Falanga
- Department of Immunohematology and Transfusion Medicine, Azienda Ospedaliera Papa Giovanni XXIII, Bergamo, Italy
| | | | - Maria Iascone
- USSD Laboratorio Genetica Medica, Azienda Ospedaliera Papa Giovanni XXIII, Bergamo, Italy
| | - Carlo Tondini
- Unit of Medical Oncology, Azienda Ospedaliera Papa Giovanni XXIII, Bergamo, Italy
| | - Alberto Zambelli
- Unit of Medical Oncology, Azienda Ospedaliera Papa Giovanni XXIII, Bergamo, Italy
| | - Jacopo Azzollini
- Unit of Medical Genetics, Department of Medical Oncology and Hematology, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Siranoush Manoukian
- Unit of Medical Genetics, Department of Medical Oncology and Hematology, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Paolo Radice
- Unit of Molecular Bases of Genetic Risk and Genetic Testing, Department of Research, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Paolo Peterlongo
- Genome Diagnostics Program, IFOM the FIRC Institute of Molecular Oncology, Milan, Italy
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3
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Ernst C, Hahnen E, Engel C, Nothnagel M, Weber J, Schmutzler RK, Hauke J. Performance of in silico prediction tools for the classification of rare BRCA1/2 missense variants in clinical diagnostics. BMC Med Genomics 2018; 11:35. [PMID: 29580235 PMCID: PMC5870501 DOI: 10.1186/s12920-018-0353-y] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 03/19/2018] [Indexed: 01/10/2023] Open
Abstract
Background The use of next-generation sequencing approaches in clinical diagnostics has led to a tremendous increase in data and a vast number of variants of uncertain significance that require interpretation. Therefore, prediction of the effects of missense mutations using in silico tools has become a frequently used approach. Aim of this study was to assess the reliability of in silico prediction as a basis for clinical decision making in the context of hereditary breast and/or ovarian cancer. Methods We tested the performance of four prediction tools (Align-GVGD, SIFT, PolyPhen-2, MutationTaster2) using a set of 236 BRCA1/2 missense variants that had previously been classified by expert committees. However, a major pitfall in the creation of a reliable evaluation set for our purpose is the generally accepted classification of BRCA1/2 missense variants using the multifactorial likelihood model, which is partially based on Align-GVGD results. To overcome this drawback we identified 161 variants whose classification is independent of any previous in silico prediction. In addition to the performance as stand-alone tools we examined the sensitivity, specificity, accuracy and Matthews correlation coefficient (MCC) of combined approaches. Results PolyPhen-2 achieved the lowest sensitivity (0.67), specificity (0.67), accuracy (0.67) and MCC (0.39). Align-GVGD achieved the highest values of specificity (0.92), accuracy (0.92) and MCC (0.73), but was outperformed regarding its sensitivity (0.90) by SIFT (1.00) and MutationTaster2 (1.00). All tools suffered from poor specificities, resulting in an unacceptable proportion of false positive results in a clinical setting. This shortcoming could not be bypassed by combination of these tools. In the best case scenario, 138 families would be affected by the misclassification of neutral variants within the cohort of patients of the German Consortium for Hereditary Breast and Ovarian Cancer. Conclusion We show that due to low specificities state-of-the-art in silico prediction tools are not suitable to predict pathogenicity of variants of uncertain significance in BRCA1/2. Thus, clinical consequences should never be based solely on in silico forecasts. However, our data suggests that SIFT and MutationTaster2 could be suitable to predict benignity, as both tools did not result in false negative predictions in our analysis. Electronic supplementary material The online version of this article (10.1186/s12920-018-0353-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Corinna Ernst
- Center for Familial Breast and Ovarian Cancer, Center for Integated Oncology (CIO), Medical Faculty, University Hospital Cologne, Kerpener Straße 34, Cologne, 50931, Germany
| | - Eric Hahnen
- Center for Familial Breast and Ovarian Cancer, Center for Integated Oncology (CIO), Medical Faculty, University Hospital Cologne, Kerpener Straße 34, Cologne, 50931, Germany
| | - Christoph Engel
- Institute of Medical Informatics, Statistics and Epidemiology (IMISE), Leipzig, Germany
| | - Michael Nothnagel
- Cologne Center for Genomics, University of Cologne, Cologne, Germany
| | - Jonas Weber
- Center for Familial Breast and Ovarian Cancer, Center for Integated Oncology (CIO), Medical Faculty, University Hospital Cologne, Kerpener Straße 34, Cologne, 50931, Germany
| | - Rita K Schmutzler
- Center for Familial Breast and Ovarian Cancer, Center for Integated Oncology (CIO), Medical Faculty, University Hospital Cologne, Kerpener Straße 34, Cologne, 50931, Germany
| | - Jan Hauke
- Center for Familial Breast and Ovarian Cancer, Center for Integated Oncology (CIO), Medical Faculty, University Hospital Cologne, Kerpener Straße 34, Cologne, 50931, Germany.
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4
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Weiderpass E, Tyczynski JE. Epidemiology of Patients with Ovarian Cancer with and Without a BRCA1/2 Mutation. Mol Diagn Ther 2016; 19:351-64. [PMID: 26476542 DOI: 10.1007/s40291-015-0168-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Ovarian cancer survival rates have improved only slightly in recent decades; however, treatment of this disease is expected to undergo rapid change as strategies incorporating molecular-targeted therapies enter clinical practice. Carriers of deleterious mutations (defined as a harmful mutation) in either the BRCA1 or BRCA2 gene (BRCAm) have a significantly increased risk of developing ovarian cancer. Epidemiology data in large (>500 patients) unselected ovarian cancer populations suggest that the expected incidence rate for BRCAm in this population is 12-14 %. Patients with a BRCAm are typically diagnosed at a younger age than those without a BRCAm. Associations with BRCAm vary according to ethnicity, with women of Ashkenazi Jewish descent being 10 times more likely to have a BRCAm than the general population. In terms of survival, patients with invasive epithelial ovarian cancer who have a BRCAm may have improved overall survival compared with patients who do not carry a BRCAm. Although genetic testing for BRCAm remains relatively uncommon in ovarian cancer patients, testing is becoming cheaper and increasingly accessible; however, this approach is not without numerous social, ethical and policy issues. Current guidelines recommend BRCAm testing in specific ovarian cancer patients only; however, with the emergence of treatments that are targeted at patients with a BRCAm, genetic testing of all patients with high-grade serous ovarian cancer may lead to improved patient outcomes in this patient population. Knowledge of BRCAm status could, therefore, help to inform treatment decisions and identify relatives at increased risk of developing cancer.
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Affiliation(s)
- Elisabete Weiderpass
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, PO Box 281, 171 77, Stockholm, Sweden. .,Department of Community Medicine, Faculty of Health Sciences, University of Tromsø, The Arctic University of Norway, Tromsø, Norway. .,Department of Research, Cancer Registry of Norway, Oslo, Norway. .,Genetic Epidemiology Group, Folkhälsan Research Center, Helsinki, Finland.
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5
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Riahi A, Messaoudi A, Mrad R, Fourati A, Chabouni-Bouhamed H, Kharrat M. Molecular characterization, homology modeling and docking studies of the R2787H missense variation in BRCA2 gene: Association with breast cancer. J Theor Biol 2016; 403:188-196. [DOI: 10.1016/j.jtbi.2016.05.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 03/12/2016] [Accepted: 05/04/2016] [Indexed: 10/21/2022]
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6
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Vallée MP, Di Sera TL, Nix DA, Paquette AM, Parsons MT, Bell R, Hoffman A, Hogervorst FBL, Goldgar DE, Spurdle AB, Tavtigian SV. Adding In Silico Assessment of Potential Splice Aberration to the Integrated Evaluation of BRCA Gene Unclassified Variants. Hum Mutat 2016; 37:627-39. [PMID: 26913838 PMCID: PMC4907813 DOI: 10.1002/humu.22973] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 01/29/2016] [Indexed: 01/05/2023]
Abstract
Clinical mutation screening of the cancer susceptibility genes BRCA1 and BRCA2 generates many unclassified variants (UVs). Most of these UVs are either rare missense substitutions or nucleotide substitutions near the splice junctions of the protein coding exons. Previously, we developed a quantitative method for evaluation of BRCA gene UVs—the “integrated evaluation”—that combines a sequence analysis‐based prior probability of pathogenicity with patient and/or tumor observational data to arrive at a posterior probability of pathogenicity. One limitation of the sequence analysis‐based prior has been that it evaluates UVs from the perspective of missense substitution severity but not probability to disrupt normal mRNA splicing. Here, we calibrated output from the splice‐site fitness program MaxEntScan to generate spliceogenicity‐based prior probabilities of pathogenicity for BRCA gene variants; these range from 0.97 for variants with high probability to damage a donor or acceptor to 0.02 for exonic variants that do not impact a splice junction and are unlikely to create a de novo donor. We created a database http://priors.hci.utah.edu/PRIORS/ that provides the combined missense substitution severity and spliceogenicity‐based probability of pathogenicity for BRCA gene single‐nucleotide substitutions. We also updated the BRCA gene Ex‐UV LOVD, available at http://hci‐exlovd.hci.utah.edu, with 77 re‐evaluable variants.
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Affiliation(s)
- Maxime P Vallée
- Department of Molecular Medicine, CHUQ Research Center, Quebec City, Canada
| | - Tonya L Di Sera
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah
| | - David A Nix
- ARUP Laboratories, University of Utah School of Medicine, Salt Lake City, Utah
| | - Andrew M Paquette
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah
| | | | - Russel Bell
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah
| | - Andrea Hoffman
- QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | | | - David E Goldgar
- Department of Dermatology, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah
| | | | - Sean V Tavtigian
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah
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7
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Hauke J, Engel C, Wappenschmidt B, Müller CR, Hahnen E. Klassifizierung von „variants of unknown significance“ (VUS) beim familiären Brust- und Eierstockkrebs. MED GENET-BERLIN 2015. [DOI: 10.1007/s11825-015-0049-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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8
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Tavtigian SV, Chenevix-Trench G. Growing recognition of the role for rare missense substitutions in breast cancer susceptibility. Biomark Med 2014; 8:589-603. [PMID: 24796624 DOI: 10.2217/bmm.13.143] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Most cancer susceptibility genes function as tumor suppressors; accordingly, the focus of mutation screening in breast cancer families has been to identify protein-truncating mutations. However, it is now clear that, for some breast cancer susceptibility genes, a significant proportion of the burden of disease comes from rare missense substitutions. Among genes that have been extensively evaluated, BRCA1, BRCA2, PALB2 and BRIP1 stand as examples where the majority of mutations lead to protein truncation;TP53 provides a counter example, where the majority of pathogenic variants are missense substitutions. In ATM and CHEK2, missense substitutions are probably equally or more important in terms of their frequency and attributable risk. Therefore, ongoing efforts to identify new susceptibility genes should not ignore missense variation.
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Affiliation(s)
- Sean V Tavtigian
- Huntsman Cancer Institute and Department of Oncological Sciences, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
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9
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BRCA-associated ovarian cancer: from molecular genetics to risk management. BIOMED RESEARCH INTERNATIONAL 2014; 2014:787143. [PMID: 25136623 PMCID: PMC4129974 DOI: 10.1155/2014/787143] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 07/08/2014] [Accepted: 07/10/2014] [Indexed: 01/12/2023]
Abstract
Ovarian cancer (OC) mostly arises sporadically, but a fraction of cases are associated with mutations in BRCA1 and BRCA2 genes. The presence of a BRCA mutation in OC patients has been suggested as a prognostic and predictive factor. In addition, the identification of asymptomatic carriers of such mutations offers an unprecedented opportunity for OC prevention.
This review is aimed at exploring the current knowledge on epidemiological and molecular aspects of BRCA-associated OC predisposition, on pathology and clinical behavior of OC occurring in BRCA mutation carriers, and on the available options for managing asymptomatic carriers.
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10
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Challenges in assessing pathogenicity based on frequency of variants in mismatch repair genes: an extreme case of a MSH2 variant and a meta-analysis. Gene 2014; 546:421-4. [PMID: 24933000 DOI: 10.1016/j.gene.2014.06.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 04/30/2014] [Accepted: 06/13/2014] [Indexed: 11/21/2022]
Abstract
The clinical interpretation of variants in mismatch repair (MMR) genes associated with Lynch syndrome can be confusing when the functional nature of the variant is not clearly defined. We report an extreme case where a polymorphism in the MSH2 gene which had a low minor allele frequency, was misclassified as a mutation based on low evidential methods in the database and previous publications. We expanded this experience to perform a systematic meta-analysis in order to investigate other variants that have potentially been misclassified. Our results suggested that the interpretation of pathogenicity should be more cautious and emphasized the need for solid validation through multiple analyses including functional analysis for variants in MMR genes.
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11
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Multifactorial likelihood assessment of BRCA1 and BRCA2 missense variants confirms that BRCA1:c.122A>G(p.His41Arg) is a pathogenic mutation. PLoS One 2014; 9:e86836. [PMID: 24489791 PMCID: PMC3904950 DOI: 10.1371/journal.pone.0086836] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 12/13/2013] [Indexed: 11/22/2022] Open
Abstract
Rare exonic, non-truncating variants in known cancer susceptibility genes such as BRCA1 and BRCA2 are problematic for genetic counseling and clinical management of relevant families. This study used multifactorial likelihood analysis and/or bioinformatically-directed mRNA assays to assess pathogenicity of 19 BRCA1 or BRCA2 variants identified following patient referral to clinical genetic services. Two variants were considered to be pathogenic (Class 5). BRCA1:c.4484G> C(p.Arg1495Thr) was shown to result in aberrant mRNA transcripts predicted to encode truncated proteins. The BRCA1:c.122A>G(p.His41Arg) RING-domain variant was found from multifactorial likelihood analysis to have a posterior probability of pathogenicity of 0.995, a result consistent with existing protein functional assay data indicating lost BARD1 binding and ubiquitin ligase activity. Of the remaining variants, seven were determined to be not clinically significant (Class 1), nine were likely not pathogenic (Class 2), and one was uncertain (Class 3).These results have implications for genetic counseling and medical management of families carrying these specific variants. They also provide additional multifactorial likelihood variant classifications as reference to evaluate the sensitivity and specificity of bioinformatic prediction tools and/or functional assay data in future studies.
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12
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Hansen MF, Neckmann U, Lavik LAS, Vold T, Gilde B, Toft RK, Sjursen W. A massive parallel sequencing workflow for diagnostic genetic testing of mismatch repair genes. Mol Genet Genomic Med 2014; 2:186-200. [PMID: 24689082 PMCID: PMC3960061 DOI: 10.1002/mgg3.62] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 11/21/2013] [Accepted: 12/02/2013] [Indexed: 11/11/2022] Open
Abstract
The purpose of this study was to develop a massive parallel sequencing (MPS) workflow for diagnostic analysis of mismatch repair (MMR) genes using the GS Junior system (Roche). A pathogenic variant in one of four MMR genes, (MLH1, PMS2, MSH6, and MSH2), is the cause of Lynch Syndrome (LS), which mainly predispose to colorectal cancer. We used an amplicon-based sequencing method allowing specific and preferential amplification of the MMR genes including PMS2, of which several pseudogenes exist. The amplicons were pooled at different ratios to obtain coverage uniformity and maximize the throughput of a single-GS Junior run. In total, 60 previously identified and distinct variants (substitutions and indels), were sequenced by MPS and successfully detected. The heterozygote detection range was from 19% to 63% and dependent on sequence context and coverage. We were able to distinguish between false-positive and true-positive calls in homopolymeric regions by cross-sample comparison and evaluation of flow signal distributions. In addition, we filtered variants according to a predefined status, which facilitated variant annotation. Our study shows that implementation of MPS in routine diagnostics of LS can accelerate sample throughput and reduce costs without compromising sensitivity, compared to Sanger sequencing.
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Affiliation(s)
- Maren F Hansen
- Department of Laboratory Medicine, Children and Women's Health, Faculty of Medicine, Norwegian University of Science and Technology Trondheim, Norway
| | - Ulrike Neckmann
- Department of Laboratory Medicine, Children and Women's Health, Faculty of Medicine, Norwegian University of Science and Technology Trondheim, Norway
| | - Liss A S Lavik
- Department of Pathology and Medical Genetics, St. Olavs Hospital Trondheim, Norway
| | - Trine Vold
- Department of Pathology and Medical Genetics, St. Olavs Hospital Trondheim, Norway
| | - Bodil Gilde
- Department of Pathology and Medical Genetics, St. Olavs Hospital Trondheim, Norway
| | - Ragnhild K Toft
- Department of Laboratory Medicine, Children and Women's Health, Faculty of Medicine, Norwegian University of Science and Technology Trondheim, Norway
| | - Wenche Sjursen
- Department of Laboratory Medicine, Children and Women's Health, Faculty of Medicine, Norwegian University of Science and Technology Trondheim, Norway ; Department of Pathology and Medical Genetics, St. Olavs Hospital Trondheim, Norway
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13
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Thompson BA, Spurdle AB, Plazzer JP, Greenblatt MS, Akagi K, Al-Mulla F, Bapat B, Bernstein I, Capellá G, den Dunnen JT, du Sart D, Fabre A, Farrell MP, Farrington SM, Frayling IM, Frebourg T, Goldgar DE, Heinen CD, Holinski-Feder E, Kohonen-Corish M, Robinson KL, Leung SY, Martins A, Moller P, Morak M, Nystrom M, Peltomaki P, Pineda M, Qi M, Ramesar R, Rasmussen LJ, Royer-Pokora B, Scott RJ, Sijmons R, Tavtigian SV, Tops CM, Weber T, Wijnen J, Woods MO, Macrae F, Genuardi M. Application of a 5-tiered scheme for standardized classification of 2,360 unique mismatch repair gene variants in the InSiGHT locus-specific database. Nat Genet 2013; 46:107-115. [PMID: 24362816 DOI: 10.1038/ng.2854] [Citation(s) in RCA: 363] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 11/26/2013] [Indexed: 12/12/2022]
Abstract
The clinical classification of hereditary sequence variants identified in disease-related genes directly affects clinical management of patients and their relatives. The International Society for Gastrointestinal Hereditary Tumours (InSiGHT) undertook a collaborative effort to develop, test and apply a standardized classification scheme to constitutional variants in the Lynch syndrome-associated genes MLH1, MSH2, MSH6 and PMS2. Unpublished data submission was encouraged to assist in variant classification and was recognized through microattribution. The scheme was refined by multidisciplinary expert committee review of the clinical and functional data available for variants, applied to 2,360 sequence alterations, and disseminated online. Assessment using validated criteria altered classifications for 66% of 12,006 database entries. Clinical recommendations based on transparent evaluation are now possible for 1,370 variants that were not obviously protein truncating from nomenclature. This large-scale endeavor will facilitate the consistent management of families suspected to have Lynch syndrome and demonstrates the value of multidisciplinary collaboration in the curation and classification of variants in public locus-specific databases.
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Affiliation(s)
- Bryony A Thompson
- Department of Genetics and Computational Biology, QIMR Berghofer Medical Research Institute, Brisbane, Australia.,School of Medicine, University of Queensland, Brisbane, Australia
| | - Amanda B Spurdle
- Department of Genetics and Computational Biology, QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - John-Paul Plazzer
- Department of Colorectal Medicine and Genetics, Royal Melbourne Hospital, Australia
| | - Marc S Greenblatt
- Vermont Cancer Center, University of Vermont College of Medicine, Burlington, VT, USA
| | - Kiwamu Akagi
- Division of Molecular Diagnosis and Cancer Prevention, Saitama Cancer Center, Saitama, Japan
| | - Fahd Al-Mulla
- Department of Pathology, Faculty of Medicine, Health Sciences Center, Kuwait University, Safat, Kuwait
| | - Bharati Bapat
- Department of Lab Medicine and Pathobiology, University of Toronto, Canada
| | - Inge Bernstein
- Danish HNPCC Registry, Copenhagen, Denmark.,Surgical Gastroenterology Department, Aalborg University Hospital, Aalborg, Denmark
| | - Gabriel Capellá
- Hereditary Cancer Program, Catalan Institute of Oncology-IDIBELL, Barcelona, Spain
| | - Johan T den Dunnen
- Center of Human and Clinical Genetics, Leiden University Medical Centre, Leiden, The Netherlands
| | - Desiree du Sart
- Molecular Genetics Lab, Victorian Clinical Genetics Services, Murdoch Childrens Research Institute, Melbourne, Australia
| | - Aurelie Fabre
- INSERM UMR S910, Department of Medical Genetics and Functional Genomics, Marseille, France
| | - Michael P Farrell
- Department of Cancer Genetics, Mater Private Hospital, Dublin, Ireland
| | - Susan M Farrington
- Colon Cancer Genetics Group, Institute of Genetics and Molecular Medicine, University of Edinburgh, Scotland
| | - Ian M Frayling
- Institute of Medical Genetics, University Hospital of Wales, Cardiff, UK
| | - Thierry Frebourg
- Inserm U1079, Faculty of Medicine, Institute for Biomedical Research, University of Rouen, France
| | - David E Goldgar
- Department of Dermatology, University of Utah Medical School, Salt Lake City, UT, USA.,Huntsman Cancer Institute, Salt Lake City, UT, USA
| | - Christopher D Heinen
- Center for Molecular Medicine, UConn Health Center, Farmington, CT, USA.,Neag Comprehensive Cancer Center, UConn Health Center, Farmington, CT, USA
| | - Elke Holinski-Feder
- MGZ - Medizinisch Genetisches Zentrum, Munich, Germany.,Klinikum der Universität München, Campus Innenstadt, Medizinische Klinik und Poliklinik IV, Munich, Germany
| | - Maija Kohonen-Corish
- School of Medicine, University of Western Sydney, Sydney, Australia.,The Kinghorn Cancer Centre, Garvan Institute of Medical Research, Sydney, Australia.,St Vincent's Clinical School, University of NSW, Sydney, Australia
| | - Kristina Lagerstedt Robinson
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
| | - Suet Yi Leung
- Hereditary Gastrointestinal Cancer Genetic Diagnosis Laboratory, Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong
| | - Alexandra Martins
- Inserm U1079, University of Rouen, Institute for Research and Innovation in Biomedicine, Rouen, France
| | - Pal Moller
- Research Group on Inherited Cancer, Department of Medical Genetics, Oslo University Hospital, The Norwegian Radium Hospital, Oslo, Norway
| | - Monika Morak
- MGZ - Medizinisch Genetisches Zentrum, Munich, Germany.,Klinikum der Universität München, Campus Innenstadt, Medizinische Klinik und Poliklinik IV, Munich, Germany
| | - Minna Nystrom
- Division of Genetics, Department of Biosciences, University of Helsinki, Helsinki, Finland
| | - Paivi Peltomaki
- Department of Medical Genetics, Haartman Institute, University of Helsinki, Finland
| | - Marta Pineda
- Hereditary Cancer Program, Catalan Institute of Oncology-IDIBELL, Barcelona, Spain
| | - Ming Qi
- Center for Genetic and Genomic Medicine, The First Affiliated Hospital of Zhejiang University School of Medicine, James Watson Institute of Genomic Sciences, Beijing Genome Institute, China.,University of Rochester Medical Center, NY, USA
| | - Rajkumar Ramesar
- MRC Human Genetics Research Unit, Division of Human Genetics, Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, South Africa
| | | | | | - Rodney J Scott
- Discipline of Medical Genetics, Faculty of Health, University of Newcastle, The Hunter Medical Research Institute, NSW, Australia.,The Division of Molecular Medicine, Hunter Area Pathology Service, John Hunter Hospital, Newcastle, NSW, Australia
| | - Rolf Sijmons
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | | | - Carli M Tops
- Center of Human and Clinical Genetics, Leiden University Medical Centre, Leiden, The Netherlands
| | - Thomas Weber
- State University of New York at Downstate, Brooklyn, NY, USA
| | - Juul Wijnen
- Center of Human and Clinical Genetics, Leiden University Medical Centre, Leiden, The Netherlands
| | - Michael O Woods
- Discipline of Genetics, Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Finlay Macrae
- Department of Colorectal Medicine and Genetics, Royal Melbourne Hospital, Australia
| | - Maurizio Genuardi
- Department of Biomedical, Experimental and Clinical Sciences, University of Florence, Italy.,Fiorgen Foundation for Pharmacogenomics, Sesto Fiorentino, Italy
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14
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Shirts BH, Jacobson A, Jarvik GP, Browning BL. Large numbers of individuals are required to classify and define risk for rare variants in known cancer risk genes. Genet Med 2013; 16:529-34. [PMID: 24357849 DOI: 10.1038/gim.2013.187] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 10/25/2013] [Indexed: 01/24/2023] Open
Abstract
PURPOSE Up to half of unique genetic variants in genomic evaluations of familial cancer risk will be rare variants of uncertain significance. Classification of rare variants will be an ongoing issue as genomic testing becomes more common. METHODS We modified standard power calculations to explore sample sizes necessary to classify and estimate relative disease risk for rare variant frequencies (0.001-0.00001) and varying relative risk (20-1.5), using population-based and family-based designs focusing on breast and colon cancer. We required 80% power and tolerated a 10% false-positive rate because variants tested will be in known genes with high pretest probability. RESULTS Using population-based strategies, hundreds to millions of cases are necessary to classify rare cancer variants. Larger samples are necessary for less frequent and less penetrant variants. Family-based strategies are robust to changes in variant frequency and require between 8 and 1,175 individuals, depending on risk. CONCLUSION It is unlikely that most rare missense variants will be classifiable in the near future, and accurate relative risk estimates may never be available for very rare variants. This knowledge may alter strategies for communicating information about variants of uncertain significance to patients.
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Affiliation(s)
- Brian H Shirts
- Department of Laboratory Medicine, University of Washington, Seattle, Washington, USA
| | - Angela Jacobson
- Department of Laboratory Medicine, University of Washington, Seattle, Washington, USA
| | - Gail P Jarvik
- 1] Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, Washington, USA [2] Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Brian L Browning
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, Washington, USA
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15
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Parsons MT, Whiley PJ, Beesley J, Drost M, de Wind N, Thompson BA, Marquart L, Hopper JL, Jenkins MA, Brown MA, Tucker K, Warwick L, Buchanan DD, Spurdle AB. Consequences of germline variation disrupting the constitutional translational initiation codon start sites of MLH1 and BRCA2: Use of potential alternative start sites and implications for predicting variant pathogenicity. Mol Carcinog 2013; 54:513-22. [PMID: 24302565 DOI: 10.1002/mc.22116] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 11/03/2013] [Accepted: 11/07/2013] [Indexed: 12/21/2022]
Abstract
Variants that disrupt the translation initiation sequences in cancer predisposition genes are generally assumed to be deleterious. However, few studies have validated these assumptions with functional and clinical data. Two cancer syndrome gene variants likely to affect native translation initiation were identified by clinical genetic testing: MLH1:c.1A>G p.(Met1?) and BRCA2:c.67+3A>G. In vitro GFP-reporter assays were conducted to assess the consequences of translation initiation disruption on alternative downstream initiation codon usage. Analysis of MLH1:c.1A>G p.(Met1?) showed that translation was mostly initiated at an in-frame position 103 nucleotides downstream, but also at two ATG sequences downstream. The protein product encoded by the in-frame transcript initiating from position c.103 showed loss of in vitro mismatch repair activity comparable to known pathogenic mutations. BRCA2:c.67+3A>G was shown by mRNA analysis to result in an aberrantly spliced transcript deleting exon 2 and the consensus ATG site. In the absence of exon 2, translation initiated mostly at an out-of-frame ATG 323 nucleotides downstream, and to a lesser extent at an in-frame ATG 370 nucleotides downstream. Initiation from any of the downstream alternative sites tested in both genes would lead to loss of protein function, but further clinical data is required to confirm if these variants are associated with a high cancer risk. Importantly, our results highlight the need for caution in interpreting the functional and clinical consequences of variation that leads to disruption of the initiation codon, since translation may not necessarily occur from the first downstream alternative start site, or from a single alternative start site.
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Affiliation(s)
- Michael T Parsons
- Department of Genetics and Computational Biology, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - Phillip J Whiley
- Department of Genetics and Computational Biology, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - Jonathan Beesley
- Department of Genetics and Computational Biology, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - Mark Drost
- Department of Toxicogenetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Niels de Wind
- Department of Toxicogenetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Bryony A Thompson
- Department of Genetics and Computational Biology, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia.,School of Medicine, The University of Queensland, Herston, Queensland, Australia
| | - Louise Marquart
- Department of Population Health, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - John L Hopper
- Centre for MEGA Epidemiology, School of Population and Global Health, The University of Melbourne, Melbourne, Australia.,School of Public Health, Seoul National University, Seoul, Korea
| | - Mark A Jenkins
- Centre for MEGA Epidemiology, School of Population and Global Health, The University of Melbourne, Melbourne, Australia
| | | | - Melissa A Brown
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
| | - Kathy Tucker
- Hereditary Cancer Clinic, Prince of Wales Hospital, Randwick, Sydney, Australia
| | - Linda Warwick
- ACT Genetics Service, The Canberra Hospital, Canberra, Australia
| | - Daniel D Buchanan
- Department of Population Health, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - Amanda B Spurdle
- Department of Genetics and Computational Biology, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
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16
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You YN, Vilar E. Classifying MMR variants: time for revised nomenclature in Lynch syndrome. Clin Cancer Res 2013; 19:2280-2. [PMID: 23532885 DOI: 10.1158/1078-0432.ccr-13-0392] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Inactivating germline mutations in DNA mismatch repair (MMR) genes are diagnostic for Lynch syndrome. However, the clinical significance of missense variants is uncertain. A threshold level of compromised MLH1 expression, correlating with greater protein instability and MMR functional defect, has been identified to help classify the pathogenicity of missense variants.
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Affiliation(s)
- Y Nancy You
- Department of Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77230, USA.
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17
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Comparative in vitro and in silico analyses of variants in splicing regions of BRCA1 and BRCA2 genes and characterization of novel pathogenic mutations. PLoS One 2013; 8:e57173. [PMID: 23451180 PMCID: PMC3579815 DOI: 10.1371/journal.pone.0057173] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Accepted: 01/18/2013] [Indexed: 12/15/2022] Open
Abstract
Several unclassified variants (UVs) have been identified in splicing regions of disease-associated genes and their characterization as pathogenic mutations or benign polymorphisms is crucial for the understanding of their role in disease development. In this study, 24 UVs located at BRCA1 and BRCA2 splice sites were characterized by transcripts analysis. These results were used to evaluate the ability of nine bioinformatics programs in predicting genetic variants causing aberrant splicing (spliceogenic variants) and the nature of aberrant transcripts. Eleven variants in BRCA1 and 8 in BRCA2, including 8 not previously characterized at transcript level, were ascertained to affect mRNA splicing. Of these, 16 led to the synthesis of aberrant transcripts containing premature termination codons (PTCs), 2 to the up-regulation of naturally occurring alternative transcripts containing PTCs, and one to an in-frame deletion within the region coding for the DNA binding domain of BRCA2, causing the loss of the ability to bind the partner protein DSS1 and ssDNA. For each computational program, we evaluated the rate of non-informative analyses, i.e. those that did not recognize the natural splice sites in the wild-type sequence, and the rate of false positive predictions, i.e., variants incorrectly classified as spliceogenic, as a measure of their specificity, under conditions setting sensitivity of predictions to 100%. The programs that performed better were Human Splicing Finder and Automated Splice Site Analyses, both exhibiting 100% informativeness and specificity. For 10 mutations the activation of cryptic splice sites was observed, but we were unable to derive simple criteria to select, among the different cryptic sites predicted by the bioinformatics analyses, those actually used. Consistent with previous reports, our study provides evidences that in silico tools can be used for selecting splice site variants for in vitro analyses. However, the latter remain mandatory for the characterization of the nature of aberrant transcripts.
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18
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Thompson BA, Goldgar DE, Paterson C, Clendenning M, Walters R, Arnold S, Parsons MT, Walsh MD, Gallinger S, Haile RW, Hopper JL, Jenkins MA, LeMarchand L, Lindor NM, Newcomb PA, Thibodeau SN, Young JP, Buchanan DD, Tavtigian SV, Spurdle AB. A multifactorial likelihood model for MMR gene variant classification incorporating probabilities based on sequence bioinformatics and tumor characteristics: a report from the Colon Cancer Family Registry. Hum Mutat 2013; 34:200-9. [PMID: 22949379 PMCID: PMC3538359 DOI: 10.1002/humu.22213] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2012] [Accepted: 08/22/2012] [Indexed: 01/04/2023]
Abstract
Mismatch repair (MMR) gene sequence variants of uncertain clinical significance are often identified in suspected Lynch syndrome families, and this constitutes a challenge for both researchers and clinicians. Multifactorial likelihood model approaches provide a quantitative measure of MMR variant pathogenicity, but first require input of likelihood ratios (LRs) for different MMR variation-associated characteristics from appropriate, well-characterized reference datasets. Microsatellite instability (MSI) and somatic BRAF tumor data for unselected colorectal cancer probands of known pathogenic variant status were used to derive LRs for tumor characteristics using the Colon Cancer Family Registry (CFR) resource. These tumor LRs were combined with variant segregation within families, and estimates of prior probability of pathogenicity based on sequence conservation and position, to analyze 44 unclassified variants identified initially in Australasian Colon CFR families. In addition, in vitro splicing analyses were conducted on the subset of variants based on bioinformatic splicing predictions. The LR in favor of pathogenicity was estimated to be ~12-fold for a colorectal tumor with a BRAF mutation-negative MSI-H phenotype. For 31 of the 44 variants, the posterior probabilities of pathogenicity were such that altered clinical management would be indicated. Our findings provide a working multifactorial likelihood model for classification that carefully considers mode of ascertainment for gene testing.
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Affiliation(s)
- Bryony A. Thompson
- Department of Genetics and Population Health, Queensland Institute of Medical Research, Herston, Brisbane, Australia
- School of Medicine, University of Queensland, Brisbane, Australia
| | - David E. Goldgar
- Department of Dermatology, University of Utah School of Medicine, Salt Lake City, Utah
| | - Carol Paterson
- Department of Genetics and Population Health, Queensland Institute of Medical Research, Herston, Brisbane, Australia
| | - Mark Clendenning
- Department of Genetics and Population Health, Queensland Institute of Medical Research, Herston, Brisbane, Australia
| | - Rhiannon Walters
- Department of Genetics and Population Health, Queensland Institute of Medical Research, Herston, Brisbane, Australia
| | - Sven Arnold
- Department of Genetics and Population Health, Queensland Institute of Medical Research, Herston, Brisbane, Australia
| | - Michael T. Parsons
- Department of Genetics and Population Health, Queensland Institute of Medical Research, Herston, Brisbane, Australia
| | - Michael D. Walsh
- Department of Genetics and Population Health, Queensland Institute of Medical Research, Herston, Brisbane, Australia
| | - Steven Gallinger
- Cancer Care Ontario, Department of Surgery, Familial Gastrointestinal Cancer Registry, University of Toronto, Toronto, Ontario, Canada
| | - Robert W. Haile
- Department of Preventive Medicine, University of Southern California, Los Angeles, California
| | - John L. Hopper
- Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, University of Melbourne, Melbourne, Australia
| | - Mark A. Jenkins
- Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, University of Melbourne, Melbourne, Australia
| | - Loic LeMarchand
- Cancer Research Center of Hawaii, University of Hawaii at Manoa, Honolulu, Hawaii
| | - Noralane M. Lindor
- Department of Health Science Research, Mayo Clinic Arizona, Scottsdale, Arizona
| | - Polly A. Newcomb
- Prevention Program, Fred Hutchinson Cancer Research Center, Seattle, Washington
| | | | | | - Joanne P. Young
- Department of Genetics and Population Health, Queensland Institute of Medical Research, Herston, Brisbane, Australia
| | - Daniel D. Buchanan
- Department of Genetics and Population Health, Queensland Institute of Medical Research, Herston, Brisbane, Australia
| | - Sean V. Tavtigian
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah
| | - Amanda B. Spurdle
- Department of Genetics and Population Health, Queensland Institute of Medical Research, Herston, Brisbane, Australia
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19
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Bozzao C, Lastella P, Stella A. Anticipation in lynch syndrome: where we are where we go. Curr Genomics 2012; 12:451-65. [PMID: 22547953 PMCID: PMC3219841 DOI: 10.2174/138920211797904070] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 07/08/2011] [Accepted: 07/20/2011] [Indexed: 02/06/2023] Open
Abstract
Lynch syndrome (LS) is the most common form of inherited predisposition to develop cancer mainly in the colon and endometrium but also in other organ sites. Germline mutations in DNA mismatch repair (MMR) gene cause the transmission of the syndrome in an autosomal dominant manner. The management of LS patients is complicated by the large variation in age at cancer diagnosis which requires these patients to be enrolled in surveillance protocol starting as early as in their second decade of life. Several environmental and genetic factors have been proposed to explain this phenotypic heterogeneity, but the molecular mechanisms remain unknown. Although the presence of genetic anticipation in Lynch syndrome has been suspected since 15 years, only recently the phenomenon has been increasingly reported to be present in different cancer genetic syndromes including LS. While the biological basis of earlier cancer onset in successive generations remains poorly known, recent findings point to telomere dynamics as a mechanism significantly contributing to genetic anticipation in Lynch syndrome and in other familial cancers. In this review, we summarize the clinical and molecular features of Lynch syndrome, with a particular focus on the latest studies that have investigated the molecular mechanisms of genetic anticipation.
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Affiliation(s)
- Cristina Bozzao
- Medical Genetics Unit, Department of Biomedicine in Childhood, Università degli Studi di Bari "Aldo Moro", Bari, Italy
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20
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Rasmussen LJ, Heinen CD, Royer-Pokora B, Drost M, Tavtigian S, Hofstra RMW, de Wind N. Pathological assessment of mismatch repair gene variants in Lynch syndrome: past, present, and future. Hum Mutat 2012; 33:1617-25. [PMID: 22833534 DOI: 10.1002/humu.22168] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2012] [Accepted: 07/11/2012] [Indexed: 12/12/2022]
Abstract
Lynch syndrome (LS) is caused by germline mutations in DNA mismatch repair (MMR) genes and is the most prevalent hereditary colorectal cancer syndrome. A significant proportion of variants identified in MMR and other common cancer susceptibility genes are missense or noncoding changes whose consequences for pathogenicity cannot be easily interpreted. Such variants are designated as "variants of uncertain significance" (VUS). Management of LS can be significantly improved by identifying individuals who carry a pathogenic variant and thus benefit from screening, preventive, and therapeutic measures. Also, identifying family members that do not carry the variant is important so they can be released from the intensive surveillance. Determining which genetic variants are pathogenic and which are neutral is a major challenge in clinical genetics. The profound mechanistic knowledge on the genetics and biochemistry of MMR enables the development and use of targeted assays to evaluate the pathogenicity of variants found in suspected patients with LS. We describe different approaches for the functional analysis of MMR gene VUS and propose development of a validated diagnostic framework. Furthermore, we call attention to common misconceptions about functional assays and endorse development of an integrated approach comprising validated assays for diagnosis of VUS in patients suspected of LS.
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Affiliation(s)
- Lene Juel Rasmussen
- Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark.
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21
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Role of rare variants in undetermined multiple adenomatous polyposis and early-onset colorectal cancer. J Hum Genet 2012; 57:709-716. [PMID: 22875147 DOI: 10.1038/jhg.2012.99] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Some 15-20% of multiple adenomatous polyposis have no genetic explanation and 20-30% of colorectal cancer (CRC) cases are thought to be due to inherited multifactorial causes. Accumulation of deleterious effects of low-frequency dominant and independently acting variants may be a partial explanation for such patients. The aim of this study was to type a selection of rare and low-frequency variants (<5%) to elucidate their role in CRC susceptibility. A total of 1181 subjects were included (866 controls; 315 cases). Cases comprised UK (n=184) and French (n=131) patients with MAP (n=187) or early-onset CRC (n=128). Seventy variants in 17 genes were examined in cases and controls. The effect of the variant effect on protein function was investigated in silico. Out of the 70 variants typed, 36 (51%) were tested for association. Twenty-one variants were rare (minor allele frequency (MAF) <1%). Four rare variants were found to have a significantly higher MAF in cases (EXO1-12, MLH1-1, CTNNB1-1 and BRCA2-37, P<0.05) than in controls. Pooling all rare variants with a MAF <0.5% showed an excess risk in cases (odds ratio=3.2; 95% confidence interval=1.1-9.5; P=0.04). Rare variants are important risk factors in CRC and, as such, should be systematically assayed alongside common variation in the search for the genetic basis of complex diseases.
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22
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Collective evidence supports neutrality of BRCA1 V1687I, a novel sequence variant in the conserved THV motif of the first BRCT repeat. Breast Cancer Res Treat 2012; 134:435-41. [PMID: 22527099 DOI: 10.1007/s10549-012-2052-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 03/26/2012] [Indexed: 10/28/2022]
Abstract
Unambiguous classification of BRCA1 and BRCA2 variants of uncertain significance (VUS) is a challenging task that vexes health care providers and has profound implications for patients and their family members. Numerous VUS have been described to date, which await assessment of their functional, hence clinical, impact. As a result of a routine BRCA1/BRCA2 mutational screening, we identified a previously unreported BRCA1 sequence alteration [c.5178G>A (V1687I)] in a patient diagnosed with early onset triple negative breast cancer. The sequence alteration falls in the invariant THV motif of the BRCT domain. To investigate its significance, we applied an integrated approach that, in addition to genetic and histopathological data, included in silico analyses, comparative structural modeling and verification of BRCT-mediated interactions. In line with web-based algorithms that predicted the benign nature of BRCA1 V1687I, the three-dimensional model of the BRCA1 V1687I BRCT domain did not reveal any major structural changes relative to its wild-type counterpart, thus suggesting that BRCA1 V1687I has a negligible impact on both the local architecture and the overall stability of the protein. Consistently, the BRCA1 V1687I protein was properly expressed and localized to the nucleus, and it was still capable of binding three BRCT-interacting, DNA damage response, and repair partner proteins, namely BRIP1/FANCJ, CtIP, and Abraxas. Our collected evidence suggests that, although occurring in a highly conserved region, the BRCA1 V1687I variant is likely a benign sequence alteration.
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23
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Vallée MP, Francy TC, Judkins MK, Babikyan D, Lesueur F, Gammon A, Goldgar DE, Couch FJ, Tavtigian SV. Classification of missense substitutions in the BRCA genes: a database dedicated to Ex-UVs. Hum Mutat 2012; 33:22-8. [PMID: 21990165 PMCID: PMC3478957 DOI: 10.1002/humu.21629] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Accepted: 09/26/2011] [Indexed: 01/15/2023]
Abstract
Unclassified sequence variants (UVs) arising from clinical mutation screening of cancer susceptibility genes present a frustrating issue to clinical genetics services and the patients that they serve. We created an open-access database holding missense substitutions from the breast and ovarian cancer susceptibility genes BRCA1 and BRCA2. The main inclusion criterion is that each variant should have been assessed in a published work that used the Bayesian integrated evaluation of unclassified BRCA gene variants. Transfer of data on these substitutions from the original publications to our database afforded an opportunity to analyze the missense substitutions under a single model and to remove inconsistencies that arose during the evolution of the integrated evaluation over the last decade. This analysis also afforded the opportunity to reclassify these missense substitutions according to the recently published IARC 5-Class system. From an initial set of 248 missense substitutions, 31 were set aside due to nonnegligible probability to interfere with splicing. Of the remaining substitutions, 28 fell into one of the two pathogenic classes (IARC Class 4 or 5), 174 fell into one of the two nonpathogenic classes (IARC Class 1 or 2), and 15 remain in IARC Class 3, "Uncertain." The database is available at http://brca.iarc.fr/LOVD.
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Affiliation(s)
| | - Tiana C. Francy
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, USA
| | - Megan K. Judkins
- Graduate Program in Genetic Counseling, University of Utah School of Medicine, Salt Lake City, USA
| | - Davit Babikyan
- Laboratory of Cancer Genetics, Center of Medical Genetics and Primary Health Care, Yerevan, Armenia
| | | | - Amanda Gammon
- High Risk Cancer Clinics, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, USA
| | - David E. Goldgar
- Department of Family and Preventive Medicine, University of Utah School of Medicine, Salt Lake City, USA
| | - Fergus J. Couch
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, USA
| | - Sean V. Tavtigian
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, USA
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24
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Spurdle AB, Healey S, Devereau A, Hogervorst FBL, Monteiro ANA, Nathanson KL, Radice P, Stoppa-Lyonnet D, Tavtigian S, Wappenschmidt B, Couch FJ, Goldgar DE. ENIGMA--evidence-based network for the interpretation of germline mutant alleles: an international initiative to evaluate risk and clinical significance associated with sequence variation in BRCA1 and BRCA2 genes. Hum Mutat 2011; 33:2-7. [PMID: 21990146 DOI: 10.1002/humu.21628] [Citation(s) in RCA: 237] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Accepted: 09/26/2011] [Indexed: 12/27/2022]
Abstract
As genetic testing for predisposition to human diseases has become an increasingly common practice in medicine, the need for clear interpretation of the test results is apparent. However, for many disease genes, including the breast cancer susceptibility genes BRCA1 and BRCA2, a significant fraction of tests results in the detection of a genetic variant for which disease association is not known. The finding of an "unclassified" variant (UV)/variant of uncertain significance (VUS) complicates genetic test reporting and counseling. As these variants are individually rare, a large collaboration of researchers and clinicians will facilitate studies to assess their association with cancer predisposition. It was with this in mind that the ENIGMA consortium (www.enigmaconsortium.org) was initiated in 2009. The membership is both international and interdisciplinary, and currently includes more than 100 research scientists and clinicians from 19 countries. Within ENIGMA, there are presently six working groups focused on the following topics: analysis, clinical, database, functional, tumor histopathology, and mRNA splicing. ENIGMA provides a mechanism to pool resources, exchange methods and data, and coordinately develop and apply algorithms for classification of variants in BRCA1 and BRCA2. It is envisaged that the research and clinical application of models developed by ENIGMA will be relevant to the interpretation of sequence variants in other disease genes.
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25
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Dandapani M, Stoffel EM. CLINICAL MANAGEMENT OF FAMILIES WITH HEREDITARY COLORECTAL CANCER SYNDROMES. SEMINARS IN COLON AND RECTAL SURGERY 2011; 22:100-104. [PMID: 21743786 PMCID: PMC3129991 DOI: 10.1053/j.scrs.2010.12.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Hereditary colorectal cancer syndromes can be associated with a lifetime risk of CRC of >70% in the absence of specialized surveillance. Diagnosing a genetic predisposition to cancer allows clinicians to tailor cancer prevention strategies for patients and families at highest risk. Once a genetic syndrome has been identified in a family, communication with family members, timely implementation of screening tests and/or surgeries, and psychosocial support are all instrumental for effective cancer prevention.Molecular screening of tumors, computerized risk assessment models, and genetic testing can help clinicians identify individuals at risk for hereditary cancer syndromes. This review discusses some of the complexities involved in the diagnosis and management of families with hereditary CRC syndromes and provides strategies for coordinating clinical care.
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Affiliation(s)
- Monica Dandapani
- Cancer Risk and Prevention Clinic, Dana-Farber Cancer Institute, Boston, MA
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Abstract
PURPOSE Lynch syndrome is a genetic disease that predisposes to colorectal tumors, caused by mutation in mismatch repair genes. The use of genetic tests to identify mutation carriers does not always give perfectly clear results, as happens when an unclassified variant is found. This study aimed to define the pathogenic role of 35 variants present in MSH2, MLH1, MSH6, and PMS2 genes identified in our 15-year case study. METHODS We collected clinical and molecular data of all carriers, and then we analyzed the variants pathogenic role with web tools and molecular analyses. Using a Bayesian approach, we derived a posterior probability of pathogenicity and classified each variant according to a standardized five-class system. RESULTS The MSH2 p.Pro349Arg, p.Met688Arg, the MLH1 p.Gly67Arg, p.Thr82Ala, p.Lys618Ala, the MSH6 p.Ala1236Pro, and the PMS2 p.Arg20Gln were classified as pathogenic, and the MSH2 p.Cys697Arg and the PMS2 p.Ser46Ile were classified as likely pathogenic. Seven variants were likely nonpathogenic, 3 were nonpathogenic, and 16 remained uncertain. CONCLUSION Quantitative assessment of several parameters and their integration in a multifactorial likelihood model is the method of choice for classifying the variants. As such classifications can be associated with surveillance and testing recommendations, the results and the method developed in our study can be useful for helping laboratory geneticists in evaluation of genetic tests and clinicians in the management of carriers.
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Radice P, De Summa S, Caleca L, Tommasi S. Unclassified variants in BRCA genes: guidelines for interpretation. Ann Oncol 2011; 22 Suppl 1:i18-23. [PMID: 21285146 DOI: 10.1093/annonc/mdq661] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
In the last few years, several studies have focused on the interpretation of unclassified variants (UVs) of BRCA1 and BRCA2 genes. Analysis of UVs through a unique approach is not sufficient to understand their role in the development of tumors. Thus, it is clear that assembling results from different sources (genetic and epidemiological data, histopathological features, and in vitro and in silico analyses) represents a powerful way to classify such variants. Building reliable integrated models for UV classification requires the joining of many working groups to collaborative consortia, allowing data exchange and improvements of methods. This will lead to improvement in the predictivity of gene testing in BRCA1 and BRCA2 and, consequently, to an increase in the number of families that can be correctly classified as linked or unlinked to these genes, allowing more accurate genetic counseling and clinical management.
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Affiliation(s)
- P Radice
- Unit of Molecular Bases of Genetic Risk and Genetic Testing, Department of Preventive and Predictive Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milano, Italy.
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Kohonen-Corish MRJ, Macrae F, Genuardi M, Aretz S, Bapat B, Bernstein IT, Burn J, Cotton RGH, den Dunnen JT, Frebourg T, Greenblatt MS, Hofstra R, Holinski-Feder E, Lappalainen I, Lindblom A, Maglott D, Møller P, Morreau H, Möslein G, Sijmons R, Spurdle AB, Tavtigian S, Tops CMJ, Weber TK, de Wind N, Woods MO. Deciphering the colon cancer genes--report of the InSiGHT-Human Variome Project Workshop, UNESCO, Paris 2010. Hum Mutat 2011; 32:491-4. [PMID: 21387463 DOI: 10.1002/humu.21450] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 01/09/2011] [Indexed: 12/12/2022]
Abstract
The Human Variome Project (HVP) has established a pilot program with the International Society for Gastrointestinal Hereditary Tumours (InSiGHT) to compile all inherited variation affecting colon cancer susceptibility genes. An HVP-InSiGHT Workshop was held on May 10, 2010, prior to the HVP Integration and Implementation Meeting at UNESCO in Paris, to review the progress of this pilot program. A wide range of topics were covered, including issues relating to genotype-phenotype data submission to the InSiGHT Colon Cancer Gene Variant Databases (chromium.liacs.nl/LOVD2/colon_cancer/home.php). The meeting also canvassed the recent exciting developments in models to evaluate the pathogenicity of unclassified variants using in silico data, tumor pathology information, and functional assays, and made further plans for the future progress and sustainability of the pilot program.
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