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Mahdouani M, Zhuri D, Sezginer Guler H, Hmida D, Sana M, Azaza M, Ben Said M, Masmoudi S, Hmila F, Youssef S, Ben Sghaier R, Brieger A, Zeuzem S, Saad A, Gurkan H, Yalcintepe S, Gribaa M, Plotz G. Functional analysis of MMR gene VUS from potential Lynch syndrome patients. PLoS One 2024; 19:e0304141. [PMID: 38843250 PMCID: PMC11156341 DOI: 10.1371/journal.pone.0304141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 05/06/2024] [Indexed: 06/09/2024] Open
Abstract
Lynch syndrome is caused by inactivating variants in DNA mismatch repair genes, namely MLH1, MSH2, MSH6 and PMS2. We have investigated five MLH1 and one MSH2 variants that we have identified in Turkish and Tunisian colorectal cancer patients. These variants comprised two small deletions causing frameshifts resulting in premature stops which could be classified pathogenic (MLH1 p.(His727Profs*57) and MSH2 p.(Thr788Asnfs*11)), but also two missense variants (MLH1 p.(Asn338Ser) and p.(Gly181Ser)) and two small, in-frame deletion variants (p.(Val647-Leu650del) and p.(Lys678_Cys680del)). For such small coding genetic variants, it is unclear if they are inactivating or not. We here provide clinical description of the variant carriers and their families, and we performed biochemical laboratory testing on the variant proteins to test if their stability or their MMR activity are compromised. Subsequently, we compared the results to in-silico predictions on structure and conservation. We demonstrate that neither missense alteration affected function, while both deletion variants caused a dramatic instability of the MLH1 protein, resulting in MMR deficiency. These results were consistent with the structural analyses that were performed. The study shows that knowledge of protein function may provide molecular explanations of results obtained with functional biochemical testing and can thereby, in conjunction with clinical information, elevate the evidential value and facilitate clinical management in affected families.
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Affiliation(s)
- Marwa Mahdouani
- Laboratory of Cytogenetics, Molecular Genetics and Human Reproduction Biology, Farhat Hached University Hospital, Sousse, Tunisia
- Higher Institute of Biotechnology of Monastir, University of Monastir, Monastir, Tunisia
| | - Drenushe Zhuri
- Department of Medical Genetics, Trakya University School of Medicine, Edirne, Turkey
| | - Hazal Sezginer Guler
- Department of Medical Genetics, Trakya University School of Medicine, Edirne, Turkey
| | - Dorra Hmida
- Laboratory of Cytogenetics, Molecular Genetics and Human Reproduction Biology, Farhat Hached University Hospital, Sousse, Tunisia
- Faculty of Medicine Ibn El Jazzar of Sousse, University of Sousse, Sousse, Tunisia
| | - Mokni Sana
- Faculty of Medicine Ibn El Jazzar of Sousse, University of Sousse, Sousse, Tunisia
- Department of Dermatology and Venerology, Farhat Hached University Hospital, Sousse, Tunisia
| | - Mohamed Azaza
- Department of General Surgery, Sahloul University Hospital, Sousse, Tunisia
| | - Mariem Ben Said
- Laboratory of Molecular and Cellular Screening Processes, Center of Biotechnology of Sfax, Sfax, Tunisia
| | - Saber Masmoudi
- Laboratory of Molecular and Cellular Screening Processes, Center of Biotechnology of Sfax, Sfax, Tunisia
| | - Fahmi Hmila
- Faculty of Medicine Ibn El Jazzar of Sousse, University of Sousse, Sousse, Tunisia
- Department of General and Digestive Surgery, Farhat Hached University Hospital, Sousse, Tunisia
| | - Sabri Youssef
- Department of General Surgery, Farhat Hached University Hospital, Sousse, Tunisia
| | - Rihab Ben Sghaier
- Laboratory of Cytogenetics, Molecular Genetics and Human Reproduction Biology, Farhat Hached University Hospital, Sousse, Tunisia
- Higher Institute of Biotechnology of Monastir, University of Monastir, Monastir, Tunisia
| | - Angela Brieger
- Biomedical Research Laboratory, Medical Clinic 1, University Hospital, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Stefan Zeuzem
- Biomedical Research Laboratory, Medical Clinic 1, University Hospital, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Ali Saad
- Laboratory of Cytogenetics, Molecular Genetics and Human Reproduction Biology, Farhat Hached University Hospital, Sousse, Tunisia
- Faculty of Medicine Ibn El Jazzar of Sousse, University of Sousse, Sousse, Tunisia
| | - Hakan Gurkan
- Department of Medical Genetics, Trakya University School of Medicine, Edirne, Turkey
| | - Sinem Yalcintepe
- Department of Medical Genetics, Trakya University School of Medicine, Edirne, Turkey
| | - Moez Gribaa
- Laboratory of Cytogenetics, Molecular Genetics and Human Reproduction Biology, Farhat Hached University Hospital, Sousse, Tunisia
- Faculty of Medicine Ibn El Jazzar of Sousse, University of Sousse, Sousse, Tunisia
| | - Guido Plotz
- Biomedical Research Laboratory, Medical Clinic 1, University Hospital, Goethe University Frankfurt, Frankfurt am Main, Germany
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Firnau MB, Plotz G, Zeuzem S, Brieger A. Key role of phosphorylation sites in ATPase domain and Linker region of MLH1 for DNA binding and functionality of MutLα. Sci Rep 2023; 13:12503. [PMID: 37532794 PMCID: PMC10397344 DOI: 10.1038/s41598-023-39750-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 07/30/2023] [Indexed: 08/04/2023] Open
Abstract
MutLα is essential for human DNA mismatch repair (MMR). It harbors a latent endonuclease, is responsible for recruitment of process associated proteins and is relevant for strand discrimination. Recently, we demonstrated that the MMR function of MutLα is regulated by phosphorylation of MLH1 at serine (S) 477. In the current study, we focused on S87 located in the ATPase domain of MLH1 and on S446, S456 and S477 located in its linker region. We analysed the phosphorylation-dependent impact of these amino acids on DNA binding, MMR ability and thermal stability of MutLα. We were able to demonstrate that phosphorylation at S87 of MLH1 inhibits DNA binding of MutLα. In addition, we detected that its MMR function seems to be regulated predominantly via phosphorylation of serines in the linker domain, which are also partially involved in the regulation of DNA binding. Furthermore, we found that the thermal stability of MutLα decreased in relation to its phosphorylation status implying that complete phosphorylation might lead to instability and degradation of MLH1. In summary, we showed here, for the first time, a phosphorylation-dependent regulation of DNA binding of MutLα and hypothesized that this might significantly impact its functional regulation during MMR in vivo.
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Affiliation(s)
- May-Britt Firnau
- Goethe University Frankfurt, University Hospital, Medical Clinic 1, Biomedical Research Laboratory, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany
| | - Guido Plotz
- Goethe University Frankfurt, University Hospital, Medical Clinic 1, Biomedical Research Laboratory, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany
| | - Stefan Zeuzem
- Goethe University Frankfurt, University Hospital, Medical Clinic 1, Biomedical Research Laboratory, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany
| | - Angela Brieger
- Goethe University Frankfurt, University Hospital, Medical Clinic 1, Biomedical Research Laboratory, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany.
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Wolf K, Kosinski J, Gibson TJ, Wesch N, Dötsch V, Genuardi M, Cordisco EL, Zeuzem S, Brieger A, Plotz G. A conserved motif in the disordered linker of human MLH1 is vital for DNA mismatch repair and its function is diminished by a cancer family mutation. Nucleic Acids Res 2023; 51:6307-6320. [PMID: 37224528 PMCID: PMC10325900 DOI: 10.1093/nar/gkad418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 04/26/2023] [Accepted: 05/17/2023] [Indexed: 05/26/2023] Open
Abstract
DNA mismatch repair (MMR) is essential for correction of DNA replication errors. Germline mutations of the human MMR gene MLH1 are the major cause of Lynch syndrome, a heritable cancer predisposition. In the MLH1 protein, a non-conserved, intrinsically disordered region connects two conserved, catalytically active structured domains of MLH1. This region has as yet been regarded as a flexible spacer, and missense alterations in this region have been considered non-pathogenic. However, we have identified and investigated a small motif (ConMot) in this linker which is conserved in eukaryotes. Deletion of the ConMot or scrambling of the motif abolished mismatch repair activity. A mutation from a cancer family within the motif (p.Arg385Pro) also inactivated MMR, suggesting that ConMot alterations can be causative for Lynch syndrome. Intriguingly, the mismatch repair defect of the ConMot variants could be restored by addition of a ConMot peptide containing the deleted sequence. This is the first instance of a DNA mismatch repair defect conferred by a mutation that can be overcome by addition of a small molecule. Based on the experimental data and AlphaFold2 predictions, we suggest that the ConMot may bind close to the C-terminal MLH1-PMS2 endonuclease and modulate its activation during the MMR process.
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Affiliation(s)
- Karla Wolf
- Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, 60590, Germany
| | - Jan Kosinski
- European Molecular Biology Laboratory (EMBL), Centre for Structural Systems Biology (CSSB), Hamburg, 22607, Germany
| | - Toby J Gibson
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Heidelberg, 69117, Germany
| | - Nicole Wesch
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt am Main, 60438, Germany
| | - Volker Dötsch
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt am Main, 60438, Germany
| | - Maurizio Genuardi
- UOC Genetica Medica, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome00168, Italy
| | - Emanuela Lucci Cordisco
- Dipartimento di Scienze della Vita e di Sanità Pubblica, Università Cattolica del Sacro Cuore, Rome00168, Italy
| | - Stefan Zeuzem
- Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, 60590, Germany
| | - Angela Brieger
- Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, 60590, Germany
| | - Guido Plotz
- Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, 60590, Germany
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Rath A, Radecki AA, Rahman K, Gilmore RB, Hudson JR, Cenci M, Tavtigian SV, Grady JP, Heinen CD. A calibrated cell-based functional assay to aid classification of MLH1 DNA mismatch repair gene variants. Hum Mutat 2022; 43:2295-2307. [PMID: 36054288 PMCID: PMC9772141 DOI: 10.1002/humu.24462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 06/21/2022] [Accepted: 08/30/2022] [Indexed: 01/25/2023]
Abstract
Functional assays provide important evidence for classifying the disease significance of germline variants in DNA mismatch repair genes. Numerous laboratories, including our own, have developed functional assays to study mismatch repair gene variants. However, previous assays are limited due to the model system employed, the manner of gene expression, or the environment in which function is assessed. Here, we developed a human cell-based approach for testing the function of variants of uncertain significance (VUS) in the MLH1 gene. Using clustered regularly interspaced short palindromic repeats gene editing, we knocked in MLH1 VUS into the endogenous MLH1 loci in human embryonic stem cells. We examined their impact on RNA and protein, including their ability to prevent microsatellite instability and instigate a DNA damage response. A statistical clustering analysis determined the range of functions associated with known pathogenic or benign variants, and linear regression was performed using existing odds in favor of pathogenicity scores for these control variants to calibrate our functional assay results. By converting the functional outputs into a single odds in favor of pathogenicity score, variant classification expert panels can use these results to readily reassess these VUS. Ultimately, this information will guide proper diagnosis and disease management for suspected Lynch syndrome patients.
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Affiliation(s)
- Abhijit Rath
- Center for Molecular Oncology, UConn Health, Farmington, CT
| | | | - Kaussar Rahman
- Center for Molecular Oncology, UConn Health, Farmington, CT
| | - Rachel B. Gilmore
- Department of Genetics and Genome Sciences, UConn Health, Farmington, CT
| | - Jonathan R. Hudson
- Department of Genetics and Genome Sciences, UConn Health, Farmington, CT
| | - Matthew Cenci
- Center for Molecular Oncology, UConn Health, Farmington, CT
| | - Sean V. Tavtigian
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT
| | - James P. Grady
- Connecticut Institute for Clinical and Translational Science, UConn Health, Farmington, CT
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5
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Mahdouani M, Ben Ahmed S, Hmila F, Rais H, Ben Sghaier R, Saad H, Ben Said M, Masmoudi S, Hmida D, Brieger A, Zeuzem S, Saad A, Gribaa M, Plotz G. Functional characterization of MLH1 missense variants unveils mechanisms of pathogenicity and clarifies role in cancer. PLoS One 2022; 17:e0278283. [PMID: 36454741 PMCID: PMC9714755 DOI: 10.1371/journal.pone.0278283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 10/28/2022] [Indexed: 12/05/2022] Open
Abstract
Lynch syndrome is a heritable condition caused by a heterozygous germline inactivating mutation of the DNA mismatch repair (MMR) genes, most commonly the MLH1 gene. However, one third of the identified alterations are missense variants, for which the clinical significance is unclear in many cases. We have identified three MLH1 missense alterations (p.(Glu736Lys), p.(Pro640Thr) and p.(Leu73Pro)) in six individuals from large Tunisian families. For none of these alterations, a classification of pathogenicity was available, consequently diagnosis, predictive testing and targeted surveillance in affected families was impossible. We therefore performed functional laboratory testing using a system testing stability as well as catalytic activity that includes clinically validated reference variants. Both p.(Leu73Pro) and p.(Pro640Thr) were found to be non-functional due to severe defects in protein stability and catalytic activity. In contrast, p.(Glu736Lys) was comparable to the wildtype protein and therefore considered a neutral substitution. Analysis of residue conservation and of the structural roles of the substituted residues corroborated these findings. In conjunction with the available clinical data, two variants fulfil classification criteria for class 4 "likely pathogenic". The findings of this work clarify the mechanism of pathogenicity of two unclear MLH1 variants and enables predictive testing and targeted surveillance in members of carrier families worldwide.
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Affiliation(s)
- Marwa Mahdouani
- Laboratory of Human Cytogenetics, Molecular Genetics and Reproductive Biology, Farhat Hached University Hospital, Sousse, Tunisia
- Higher Institute of Biotechnology of Monastir, University of Monastir, Monastir, Tunisia
| | - Slim Ben Ahmed
- Department of Oncology, Farhat Hached University Hospital, Sousse, Tunisia
- Faculty of Medicine Ibn El Jazzar of Sousse, University of Sousse, Sousse, Tunisia
| | - Fahmi Hmila
- Faculty of Medicine Ibn El Jazzar of Sousse, University of Sousse, Sousse, Tunisia
- Department of General and Digestive Surgery, Farhat Hached University Hospital, Sousse, Tunisia
| | - Henda Rais
- Medical Service, Salah Azaiez Institute, Tunis, Tunisia
| | - Rihab Ben Sghaier
- Laboratory of Human Cytogenetics, Molecular Genetics and Reproductive Biology, Farhat Hached University Hospital, Sousse, Tunisia
- Higher Institute of Biotechnology of Monastir, University of Monastir, Monastir, Tunisia
| | - Hanene Saad
- Laboratory of Human Cytogenetics, Molecular Genetics and Reproductive Biology, Farhat Hached University Hospital, Sousse, Tunisia
- Higher Institute of Biotechnology of Monastir, University of Monastir, Monastir, Tunisia
| | - Mariem Ben Said
- Laboratory of Molecular and Cellular Screening Processes, Centre of Biotechnology of Sfax, Sfax, Tunisia
| | - Saber Masmoudi
- Laboratory of Molecular and Cellular Screening Processes, Centre of Biotechnology of Sfax, Sfax, Tunisia
| | - Dorra Hmida
- Laboratory of Human Cytogenetics, Molecular Genetics and Reproductive Biology, Farhat Hached University Hospital, Sousse, Tunisia
- Faculty of Medicine Ibn El Jazzar of Sousse, University of Sousse, Sousse, Tunisia
| | - Angela Brieger
- Biomedical Research Laboratory, Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, Germany
| | - Stefan Zeuzem
- Biomedical Research Laboratory, Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, Germany
| | - Ali Saad
- Laboratory of Human Cytogenetics, Molecular Genetics and Reproductive Biology, Farhat Hached University Hospital, Sousse, Tunisia
- Faculty of Medicine Ibn El Jazzar of Sousse, University of Sousse, Sousse, Tunisia
| | - Moez Gribaa
- Laboratory of Human Cytogenetics, Molecular Genetics and Reproductive Biology, Farhat Hached University Hospital, Sousse, Tunisia
- Faculty of Medicine Ibn El Jazzar of Sousse, University of Sousse, Sousse, Tunisia
| | - Guido Plotz
- Biomedical Research Laboratory, Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, Germany
- * E-mail:
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Combinatorial approach of in silico and in vitro evaluation of MLH1 variant associated with Lynch syndrome like metastatic colorectal cancer. Biosci Rep 2020; 40:224895. [PMID: 32432717 PMCID: PMC7269917 DOI: 10.1042/bsr20200225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 05/06/2020] [Accepted: 05/12/2020] [Indexed: 11/23/2022] Open
Abstract
Colorectal cancer (CRC) is the third most developing cancer worldwide and Lynch syndrome (LS) accounts for 3–4% of CRC. Genetic alteration in any of DNA mismatch repair (MMR) gene is the major cause of LS that disrupt the normal upstream and downstream MMR events. Germline mutation of MLH1 in heterozygous state have an increased risk for CRC. Defective MMR pathway mostly results in microsatellite instability (MSI) that occurs in high percentage of CRC associated tumors. Here, we reported a patient with LS like metastatic CRC (mCRC) associated with other related cancers. Whole exome sequencing (WES) of the proband was performed to identify potential causative gene. Genetic screening validated by Sanger sequencing identified a heterozygous missense mutation in exon 12 of MLH1 (c.1151T>A, p.V384D). The clinical significance of identified variant was elucidated on the basis of clinicopathological data, computational predictions and various in vitro functional analysis. In silico predictions classified the variant to be deleterious and evolutionary conserved. In vitro functional studies revealed a significant decrease in protein expression because of stability defect leading to loss of MMR activity. Mutant residue found in MutL transducer domain of MLH1 that localized in the nucleus but translocation was not found to be significantly disturbed. In conclusion, our study give insight into reliability of combinatorial prediction approach of in silico and in vitro expression analysis. Hence, we highlighted the pathogenic correlation of MLH1 variant with LS associated CRC as well as help in earlier diagnosis and surveillance for improved management and genetic counselling.
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Functional Characterization of a Missense Variant of MLH1 Identified in Lynch Syndrome Pedigree. DISEASE MARKERS 2020; 2020:8360841. [PMID: 32076465 PMCID: PMC7008259 DOI: 10.1155/2020/8360841] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 12/23/2019] [Indexed: 12/30/2022]
Abstract
Lynch syndrome (LS) is the most common hereditary colorectal cancer (CRCs) inherited in an autosomal-dominant manner. Here, we reported a multigeneration Chinese family clinically diagnosed with LS according to the Amsterdam II criteria. To identify the underlying causative gene for LS in this family, whole-exome sequencing (WES) was performed. A germline missense variant (c.2054C>T:p.S685F) in exon 18 of MLH1 was successfully identified by WES. Sanger sequencing verified the results of WES and also confirmed the cosegregation of the MLH1 missense variant in all affected members of the family including two unaffected family members. Bioinformatic tools predicted the identified MLH1 variant as deleterious. Immunohistochemistry (IHC) staining showed loss of MLH1 and PMS2 protein expression. In vitro expression analysis also revealed that the identified MLH1 missense variant (c.2054C>T:p.S685F) results in reduced expression of both MLH1 and PMS2 proteins. Based on the American College of Medical Genetics and Genomics (ACMG) guidelines, the missense mutation c.2054C>T in MLH1 was classified as a “pathogenic” variant. Two unaffected family members were later recommended for colonoscopy and other important cancer diagnostic inspections every 1-2 years as both were at higher risk of LS. In conclusion, our findings widen the genotypic spectrum of MLH1 mutations responsible for LS. This study increases the phenotypic spectrum of LS which will certainly help the clinicians in diagnosing LS in multigeneration families. This study also puts emphasis on the importance of genetic counselling for the benefit of asymptomatic carriers of MMR gene variants who are at higher risk of LS.
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González-Acosta M, Hinrichsen I, Fernández A, Lázaro C, Pineda M, Plotz G, Capellá G. Validation of an in Vitro Mismatch Repair Assay Used in the Functional Characterization of Mismatch Repair Variants. J Mol Diagn 2019; 22:376-385. [PMID: 31881334 DOI: 10.1016/j.jmoldx.2019.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 09/27/2019] [Accepted: 12/05/2019] [Indexed: 10/25/2022] Open
Abstract
A significant proportion of DNA-mismatch repair (MMR) variants are classified as of unknown significance, precluding diagnosis. The in vitro MMR assay is used to assess their MMR capability, likely the most important function of an MMR protein. However, the robustness of the assay, crucial for its use in the clinical setting, has been rarely evaluated. The aim of the present work was to validate an in vitro MMR assay approach to the functional characterization of MMR variants, as a first step to meeting quality standards of diagnostic laboratories. The MMR assay was optimized by testing a variety of reagents and experimental conditions. Reference materials and standard operating procedures were established. To determine the intra- and interexperimental variability of the assay and its reproducibility among centers, independent transfections of six previously characterized MLH1 variants were performed in two independent laboratories. Reagents and conditions optimal for performing the in vitro MMR assay were determined. The validated assay demonstrated no significant intra- or interexperimental variability and good reproducibility between centers. We set up a robust in vitro MMR assay that can provide relevant in vitro functional evidence for MMR variant pathogenicity assessment, eventually improving the molecular diagnosis of hereditary cancer syndromes associated with MMR deficiency.
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Affiliation(s)
- Maribel González-Acosta
- Hereditary Cancer Program, the Catalan Institute of Oncology (ICO), Hereditary Cancer Group, Molecular Mechanisms and Experimental Therapy in Oncology Program, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), Ciber Oncología (CIBERONC) Instituto Salud Carlos III, L'Hospitalet de Llobregat, Barcelona, Spain
| | - Inga Hinrichsen
- Biomedical Research Laboratory, Department of Internal Medicine 1, Universitätsklinikum Frankfurt, Frankfurt, Germany
| | - Anna Fernández
- Hereditary Cancer Program, the Catalan Institute of Oncology (ICO), Hereditary Cancer Group, Molecular Mechanisms and Experimental Therapy in Oncology Program, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), Ciber Oncología (CIBERONC) Instituto Salud Carlos III, L'Hospitalet de Llobregat, Barcelona, Spain
| | - Conxi Lázaro
- Hereditary Cancer Program, the Catalan Institute of Oncology (ICO), Hereditary Cancer Group, Molecular Mechanisms and Experimental Therapy in Oncology Program, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), Ciber Oncología (CIBERONC) Instituto Salud Carlos III, L'Hospitalet de Llobregat, Barcelona, Spain
| | - Marta Pineda
- Hereditary Cancer Program, the Catalan Institute of Oncology (ICO), Hereditary Cancer Group, Molecular Mechanisms and Experimental Therapy in Oncology Program, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), Ciber Oncología (CIBERONC) Instituto Salud Carlos III, L'Hospitalet de Llobregat, Barcelona, Spain
| | - Guido Plotz
- Biomedical Research Laboratory, Department of Internal Medicine 1, Universitätsklinikum Frankfurt, Frankfurt, Germany
| | - Gabriel Capellá
- Hereditary Cancer Program, the Catalan Institute of Oncology (ICO), Hereditary Cancer Group, Molecular Mechanisms and Experimental Therapy in Oncology Program, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), Ciber Oncología (CIBERONC) Instituto Salud Carlos III, L'Hospitalet de Llobregat, Barcelona, Spain.
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9
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Houlleberghs H, Dekker M, Lusseveld J, Pieters W, van Ravesteyn T, Verhoef S, Hofstra RMW, Te Riele H. Three-step site-directed mutagenesis screen identifies pathogenic MLH1 variants associated with Lynch syndrome. J Med Genet 2019; 57:308-315. [PMID: 31784484 DOI: 10.1136/jmedgenet-2019-106520] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 10/12/2019] [Accepted: 10/16/2019] [Indexed: 12/30/2022]
Abstract
BACKGROUND Inactivating mutations in the MLH1 DNA mismatch repair (MMR) gene underlie 42% of Lynch syndrome (LS) cases. LS is a cancer predisposition causing early onset colorectal and endometrial cancer. Nonsense and frameshift alterations unambiguously cause LS. The phenotype of missense mutations that only alter a single amino acid is often unclear. These variants of uncertain significance (VUS) hinder LS diagnosis and family screening and therefore functional tests are urgently needed. We developed a functional test for MLH1 VUS termed 'oligonucleotide-directed mutation screening' (ODMS). METHODS The MLH1 variant was introduced by oligonucleotide-directed gene modification in mouse embryonic stem cells that were subsequently exposed to the guanine analogue 6-thioguanine to determine whether the variant abrogated MMR. RESUTS In a proof-of-principle analysis, we demonstrate that ODMS can distinguish pathogenic and non-pathogenic MLH1 variants with a sensitivity of >95% and a specificity of >91%. We subsequently applied the screen to 51 MLH1 VUS and identified 31 pathogenic variants. CONCLUSION ODMS is a reliable tool to identify pathogenic MLH1 variants. Implementation in clinical diagnostics will improve clinical care of patients with suspected LS and their relatives.
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Affiliation(s)
- Hellen Houlleberghs
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Marleen Dekker
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Jarnick Lusseveld
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Wietske Pieters
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Thomas van Ravesteyn
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Senno Verhoef
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Robert M W Hofstra
- Department of Clinical Genetics, Erasmus MC, Erasmus University Rotterdam, Rotterdam, The Netherlands
| | - Hein Te Riele
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
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10
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Morak M, Schaefer K, Steinke-Lange V, Koehler U, Keinath S, Massdorf T, Mauracher B, Rahner N, Bailey J, Kling C, Haeusser T, Laner A, Holinski-Feder E. Full-length transcript amplification and sequencing as universal method to test mRNA integrity and biallelic expression in mismatch repair genes. Eur J Hum Genet 2019; 27:1808-1820. [PMID: 31332305 DOI: 10.1038/s41431-019-0472-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 05/13/2019] [Accepted: 07/02/2019] [Indexed: 12/13/2022] Open
Abstract
In pathogenicity assessment, RNA-based analyses are important for the correct classification of variants, and require gene-specific cut-offs for allelic representation and alternative/aberrant splicing. Beside this, the diagnostic yield of RNA-based techniques capable to detect aberrant splicing or allelic loss due to intronic/regulatory variants has to be elaborated. We established a cDNA analysis for full-length transcripts (FLT) of the four DNA mismatch repair (MMR) genes to investigate the splicing pattern and transcript integrity with active/inhibited nonsense-mediated mRNA-decay (NMD). Validation was based on results from normal controls, samples with premature termination codons (PTC), samples with splice-site defects (SSD), and samples with pathogenic putative missense variants. The method was applied to patients with variants of uncertain significance (VUS) or unexplained immunohistochemical MMR deficiency. We categorized the allelic representation into biallelic (50 ± 10%) or allelic loss (≤10%), and >10% and <40% as unclear. We defined isoforms up to 10% and exon-specific exceptions as alternative splicing, set the cut-off for SSD in cDNA + P to 30-50%, and regard >10% and <30% as unclear. FLT cDNA analyses designated 16% of all putative missense variants and 12% of VUS as SSD, detected MMR-defects in 19% of the unsolved patients, and re-classified >30% of VUS. Our method allows a standardized, systematic cDNA analysis of the MMR FLTs to assess the pathogenicity mechanism of VUS on RNA level, which will gain relevance for precision medicine and gene therapy. Diagnostic accuracy will be enhanced by detecting MMR defects in hitherto unsolved patients. The data generated will help to calibrate a high-throughput NGS-based mRNA-analysis and optimize prediction programs.
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Affiliation(s)
- Monika Morak
- Medizinische Klinik und Poliklinik IV, Campus Innenstadt, Klinikum der Universität München, Ziemssenstr. 1, 80336, Munich, Germany. .,MGZ - Medical Genetics Center, Bayerstr. 3-5, 80335, Munich, Germany.
| | - Kerstin Schaefer
- Medizinische Klinik und Poliklinik IV, Campus Innenstadt, Klinikum der Universität München, Ziemssenstr. 1, 80336, Munich, Germany
| | - Verena Steinke-Lange
- Medizinische Klinik und Poliklinik IV, Campus Innenstadt, Klinikum der Universität München, Ziemssenstr. 1, 80336, Munich, Germany.,MGZ - Medical Genetics Center, Bayerstr. 3-5, 80335, Munich, Germany
| | - Udo Koehler
- MGZ - Medical Genetics Center, Bayerstr. 3-5, 80335, Munich, Germany
| | - Susanne Keinath
- Medizinische Klinik und Poliklinik IV, Campus Innenstadt, Klinikum der Universität München, Ziemssenstr. 1, 80336, Munich, Germany
| | - Trisari Massdorf
- Medizinische Klinik und Poliklinik IV, Campus Innenstadt, Klinikum der Universität München, Ziemssenstr. 1, 80336, Munich, Germany.,MGZ - Medical Genetics Center, Bayerstr. 3-5, 80335, Munich, Germany
| | - Brigitte Mauracher
- Medizinische Klinik und Poliklinik IV, Campus Innenstadt, Klinikum der Universität München, Ziemssenstr. 1, 80336, Munich, Germany
| | - Nils Rahner
- Medical Faculty, Institute of Human Genetics, Heinrich-Heine University, Düsseldorf, Germany
| | - Jessica Bailey
- Clinical Genetics, St. George's University Hospital NHS Foundation Trust, London, UK
| | | | - Tanja Haeusser
- MGZ - Medical Genetics Center, Bayerstr. 3-5, 80335, Munich, Germany
| | - Andreas Laner
- MGZ - Medical Genetics Center, Bayerstr. 3-5, 80335, Munich, Germany
| | - Elke Holinski-Feder
- Medizinische Klinik und Poliklinik IV, Campus Innenstadt, Klinikum der Universität München, Ziemssenstr. 1, 80336, Munich, Germany. .,MGZ - Medical Genetics Center, Bayerstr. 3-5, 80335, Munich, Germany.
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11
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Köger N, Brieger A, Hinrichsen IM, Zeuzem S, Plotz G. Analysis of MUTYH alternative transcript expression, promoter function, and the effect of human genetic variants. Hum Mutat 2019; 40:472-482. [PMID: 30653782 DOI: 10.1002/humu.23709] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 12/14/2018] [Accepted: 01/14/2019] [Indexed: 01/07/2023]
Abstract
The human DNA repair gene MUTYH, whose mutational loss causes a colorectal polyposis and cancer predisposition, contains three alternative first exons. In order to analyze alternative transcription and the effect of genetic alterations found in humans, we established a cell-based minigene experimental model supporting transcription and splicing and thoroughly verified its functionality. We identified highly conserved promoter areas and inactivated them in the minigene, and also introduced six human variants. Moreover, the potential contribution of CpG island methylation and specific transcription factors on MUTYH transcription was addressed. The findings allowed to attribute regulatory roles to three conserved motifs in the promoter: an M4 motif, a transcription factor IIB recognition element, and a GC box. Moreover, the data showed that three patient variants compromised MUTYH expression and therefore have the potential to cause pathogenic effects. We did not find evidence for a biologically relevant contribution of CpG island methylation or a direct transcriptional activation by DNA damage. Besides insight into the regulation of MUTYH transcription, the work therefore provides a functional MUTYH minigene experimental system suitable as a diagnostic tool for analyzing patient variants, and a functional map of the promotor that also can facilitate pathogenicity classifications of human variants.
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Affiliation(s)
- Nicole Köger
- Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinikum, Frankfurt, Germany
| | - Angela Brieger
- Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinikum, Frankfurt, Germany
| | - Inga M Hinrichsen
- Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinikum, Frankfurt, Germany
| | - Stefan Zeuzem
- Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinikum, Frankfurt, Germany
| | - Guido Plotz
- Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinikum, Frankfurt, Germany
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12
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A functional assay-based procedure to classify mismatch repair gene variants in Lynch syndrome. Genet Med 2018; 21:1486-1496. [PMID: 30504929 DOI: 10.1038/s41436-018-0372-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 11/07/2018] [Indexed: 01/07/2023] Open
Abstract
PURPOSE To enhance classification of variants of uncertain significance (VUS) in the DNA mismatch repair (MMR) genes in the cancer predisposition Lynch syndrome, we developed the cell-free in vitro MMR activity (CIMRA) assay. Here, we calibrate and validate the assay, enabling its integration with in silico and clinical data. METHODS Two sets of previously classified MLH1 and MSH2 variants were selected from a curated MMR gene database, and their biochemical activity determined by the CIMRA assay. The assay was calibrated by regression analysis followed by symmetric cross-validation and Bayesian integration with in silico predictions of pathogenicity. CIMRA assay reproducibility was assessed in four laboratories. RESULTS Concordance between the training runs met our prespecified validation criterion. The CIMRA assay alone correctly classified 65% of variants, with only 3% discordant classification. Bayesian integration with in silico predictions of pathogenicity increased the proportion of correctly classified variants to 87%, without changing the discordance rate. Interlaboratory results were highly reproducible. CONCLUSION The CIMRA assay accurately predicts pathogenic and benign MMR gene variants. Quantitative combination of assay results with in silico analysis correctly classified the majority of variants. Using this calibration, CIMRA assay results can be integrated into the diagnostic algorithm for MMR gene variants.
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13
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Non-Coding Variants in BRCA1 and BRCA2 Genes: Potential Impact on Breast and Ovarian Cancer Predisposition. Cancers (Basel) 2018; 10:cancers10110453. [PMID: 30453575 PMCID: PMC6266896 DOI: 10.3390/cancers10110453] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 11/04/2018] [Accepted: 11/12/2018] [Indexed: 12/21/2022] Open
Abstract
BRCA1 and BRCA2 are major breast cancer susceptibility genes whose pathogenic variants are associated with a significant increase in the risk of breast and ovarian cancers. Current genetic screening is generally limited to BRCA1/2 exons and intron/exon boundaries. Most identified pathogenic variants cause the partial or complete loss of function of the protein. However, it is becoming increasingly clear that variants in these regions only account for a small proportion of cancer risk. The role of variants in non-coding regions beyond splice donor and acceptor sites, including those that have no qualitative effect on the protein, has not been thoroughly investigated. The key transcriptional regulatory elements of BRCA1 and BRCA2 are housed in gene promoters, untranslated regions, introns, and long-range elements. Within these sequences, germline and somatic variants have been described, but the clinical significance of the majority is currently unknown and it remains a significant clinical challenge. This review summarizes the available data on the impact of variants on non-coding regions of BRCA1/2 genes and their role on breast and ovarian cancer predisposition.
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14
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Weßbecher IM, Hinrichsen I, Funke S, Oellerich T, Plotz G, Zeuzem S, Grus FH, Biondi RM, Brieger A. DNA mismatch repair activity of MutLα is regulated by CK2-dependent phosphorylation of MLH1 (S477). Mol Carcinog 2018; 57:1723-1734. [DOI: 10.1002/mc.22892] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 06/22/2018] [Accepted: 08/18/2018] [Indexed: 12/15/2022]
Affiliation(s)
- Isabel M. Weßbecher
- Medical Clinic I; Biomedical Research Laboratory; Goethe-University; Frankfurt Germany
| | - Inga Hinrichsen
- Medical Clinic I; Biomedical Research Laboratory; Goethe-University; Frankfurt Germany
| | - Sebastian Funke
- Department of Ophthalmology; Experimental Ophthalmology; University Medical Center; Gutenberg University; Mainz Germany
| | - Thomas Oellerich
- Department of Medicine II, Hematology/Oncology; Goethe-University; Frankfurt Germany
| | - Guido Plotz
- Medical Clinic I; Biomedical Research Laboratory; Goethe-University; Frankfurt Germany
| | - Stefan Zeuzem
- Medical Clinic I; Biomedical Research Laboratory; Goethe-University; Frankfurt Germany
| | - Franz H. Grus
- Department of Ophthalmology; Experimental Ophthalmology; University Medical Center; Gutenberg University; Mainz Germany
| | - Ricardo M. Biondi
- Medical Clinic I; Biomedical Research Laboratory; Goethe-University; Frankfurt Germany
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET-Partner Institute of the Max Planck Society; Buenos Aires Argentina
| | - Angela Brieger
- Medical Clinic I; Biomedical Research Laboratory; Goethe-University; Frankfurt Germany
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15
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Liu Q, Thoms JAI, Nunez AC, Huang Y, Knezevic K, Packham D, Poulos RC, Williams R, Beck D, Hawkins NJ, Ward RL, Wong JWH, Hesson LB, Sloane MA, Pimanda JE. Disruption of a -35 kb Enhancer Impairs CTCF Binding and MLH1 Expression in Colorectal Cells. Clin Cancer Res 2018; 24:4602-4611. [PMID: 29898989 DOI: 10.1158/1078-0432.ccr-17-3678] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 04/17/2018] [Accepted: 06/06/2018] [Indexed: 11/16/2022]
Abstract
Purpose:MLH1 is a major tumor suppressor gene involved in the pathogenesis of Lynch syndrome and various sporadic cancers. Despite their potential pathogenic importance, genomic regions capable of regulating MLH1 expression over long distances have yet to be identified.Experimental Design: Here, we use chromosome conformation capture (3C) to screen a 650-kb region flanking the MLH1 locus to identify interactions between the MLH1 promoter and distal regions in MLH1-expressing and nonexpressing cells. Putative enhancers were functionally validated using luciferase reporter assays, chromatin immunoprecipitation, and CRISPR-Cas9-mediated deletion of endogenous regions. To evaluate whether germline variants in the enhancer might contribute to impaired MLH1 expression in patients with suspected Lynch syndrome, we also screened germline DNA from a cohort of 74 patients with no known coding mutations or epimutations at the MLH1 promoter.Results: A 1.8-kb DNA fragment, 35 kb upstream of the MLH1 transcription start site enhances MLH1 gene expression in colorectal cells. The enhancer was bound by CTCF and CRISPR-Cas9-mediated deletion of a core binding region impairs endogenous MLH1 expression. A total of 5.4% of suspected Lynch syndrome patients have a rare single-nucleotide variant (G > A; rs143969848; 2.5% in gnomAD European, non-Finnish) within a highly conserved CTCF-binding motif, which disrupts enhancer activity in SW620 colorectal carcinoma cells.Conclusions: A CTCF-bound region within the MLH1-35 enhancer regulates MLH1 expression in colorectal cells and is worthy of scrutiny in future genetic screening strategies for suspected Lynch syndrome associated with loss of MLH1 expression. Clin Cancer Res; 24(18); 4602-11. ©2018 AACR.
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Affiliation(s)
- Qing Liu
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
| | - Julie A I Thoms
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
- School of Medical Sciences, UNSW Sydney, Sydney, New South Wales, Australia
| | - Andrea C Nunez
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
| | - Yizhou Huang
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
- Centre for Health Technologies and the School of Software, University of Technology, Sydney, New South Wales, Australia
| | - Kathy Knezevic
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
| | - Deborah Packham
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
| | - Rebecca C Poulos
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
| | - Rachel Williams
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
- Hereditary Cancer Clinic, Prince of Wales Hospital, Randwick, New South Wales, Australia
| | - Dominik Beck
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
- Centre for Health Technologies and the School of Software, University of Technology, Sydney, New South Wales, Australia
| | - Nicholas J Hawkins
- School of Medical Sciences, UNSW Sydney, Sydney, New South Wales, Australia
- School of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Robyn L Ward
- School of Medicine, The University of Queensland, Brisbane, Queensland, Australia
- Level 3, Brian Wilson Chancellery, The University of Queensland, Brisbane, Queensland, Australia
| | - Jason W H Wong
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia
| | - Luke B Hesson
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia.
- Genome.One, Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Darlinghurst, New South Wales, Australia
| | - Mathew A Sloane
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia.
- Australian Museum, Sydney, New South Wales, Australia
| | - John E Pimanda
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Sydney, Sydney, New South Wales, Australia.
- School of Medical Sciences, UNSW Sydney, Sydney, New South Wales, Australia
- Department of Haematology, Prince of Wales Hospital, Randwick, New South Wales, Australia
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16
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Köger N, Paulsen L, López-Kostner F, Della Valle A, Vaccaro CA, Palmero EI, Alvarez K, Sarroca C, Neffa F, Kalfayan PG, Gonzalez ML, Rossi BM, Reis RM, Brieger A, Zeuzem S, Hinrichsen I, Dominguez-Valentin M, Plotz G. Evaluation of MLH1 variants of unclear significance. Genes Chromosomes Cancer 2018. [PMID: 29520894 DOI: 10.1002/gcc.22536] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Inactivating mutations in the MLH1 gene cause the cancer predisposition Lynch syndrome, but for small coding genetic variants it is mostly unclear if they are inactivating or not. Nine such MLH1 variants have been identified in South American colorectal cancer (CRC) patients (p.Tyr97Asp, p.His112Gln, p.Pro141Ala, p.Arg265Pro, p.Asn338Ser, p.Ile501del, p.Arg575Lys, p.Lys618del, p.Leu676Pro), and evidence of pathogenicity or neutrality was not available for the majority of these variants. We therefore performed biochemical laboratory testing of the variant proteins and compared the results to protein in silico predictions on structure and conservation. Additionally, we collected all available clinical information of the families to come to a conclusion concerning their pathogenic potential and facilitate clinical diagnosis in the affected families. We provide evidence that four of the alterations are causative for Lynch syndrome, four are likely neutral and one shows compromised activity which can currently not be classified with respect to its pathogenic potential. The work demonstrates that biochemical testing, corroborated by congruent evolutionary and structural information, can serve to reliably classify uncertain variants when other data are insufficient.
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Affiliation(s)
- Nicole Köger
- Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinik Frankfurt, Frankfurt, Germany
| | - Lea Paulsen
- Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinik Frankfurt, Frankfurt, Germany
| | | | - Adriana Della Valle
- Hospital Fuerzas Armadas, Grupo Colaborativo Uruguayo, Investigación de Afecciones Oncológicas Hereditarias (GCU), Montevideo, Uruguay
| | | | - Edenir Inêz Palmero
- Barretos Cancer Hospital, Molecular Oncology Research Center, Barretos, São Paulo, Brazil.,Barretos School of Health Sciences-FACISB, Barretos, São Paulo, Brazil
| | - Karin Alvarez
- Laboratorio de Oncología y Genética Molecular, Clínica Los Condes, Santiago, Chile
| | - Carlos Sarroca
- Hospital Fuerzas Armadas, Grupo Colaborativo Uruguayo, Investigación de Afecciones Oncológicas Hereditarias (GCU), Montevideo, Uruguay
| | - Florencia Neffa
- Hospital Fuerzas Armadas, Grupo Colaborativo Uruguayo, Investigación de Afecciones Oncológicas Hereditarias (GCU), Montevideo, Uruguay
| | | | - Maria Laura Gonzalez
- Hereditary Cancer Program (PROCANHE), Hospital Italiano, Buenos Aires, Argentina
| | | | - Rui Manuel Reis
- Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinik Frankfurt, Frankfurt, Germany.,Life and Health Sciences Q5 753 Research Institute (ICVS), Health Sciences School, University of Minho, Braga, 754, Portugal.,ICVS/3B's-PT Government Associate Laboratory, Braga, Guimarães, 755, Portugal
| | - Angela Brieger
- Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinik Frankfurt, Frankfurt, Germany
| | - Stefan Zeuzem
- Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinik Frankfurt, Frankfurt, Germany
| | - Inga Hinrichsen
- Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinik Frankfurt, Frankfurt, Germany
| | - Mev Dominguez-Valentin
- Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Guido Plotz
- Biomedizinisches Forschungslabor, Medizinische Klinik 1, Universitätsklinik Frankfurt, Frankfurt, Germany
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17
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Nykamp K, Anderson M, Powers M, Garcia J, Herrera B, Ho YY, Kobayashi Y, Patil N, Thusberg J, Westbrook M, Topper S. Sherloc: a comprehensive refinement of the ACMG-AMP variant classification criteria. Genet Med 2017; 19:1105-1117. [PMID: 28492532 PMCID: PMC5632818 DOI: 10.1038/gim.2017.37] [Citation(s) in RCA: 478] [Impact Index Per Article: 68.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 02/28/2017] [Indexed: 01/05/2023] Open
Abstract
PurposeThe 2015 American College of Medical Genetics and Genomics-Association for Molecular Pathology (ACMG-AMP) guidelines were a major step toward establishing a common framework for variant classification. In practice, however, several aspects of the guidelines lack specificity, are subject to varied interpretations, or fail to capture relevant aspects of clinical molecular genetics. A simple implementation of the guidelines in their current form is insufficient for consistent and comprehensive variant classification.MethodsWe undertook an iterative process of refining the ACMG-AMP guidelines. We used the guidelines to classify more than 40,000 clinically observed variants, assessed the outcome, and refined the classification criteria to capture exceptions and edge cases. During this process, the criteria evolved through eight major and minor revisions.ResultsOur implementation: (i) separated ambiguous ACMG-AMP criteria into a set of discrete but related rules with refined weights; (ii) grouped certain criteria to protect against the overcounting of conceptually related evidence; and (iii) replaced the "clinical criteria" style of the guidelines with additive, semiquantitative criteria.ConclusionSherloc builds on the strong framework of 33 rules established by the ACMG-AMP guidelines and introduces 108 detailed refinements, which support a more consistent and transparent approach to variant classification.
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Affiliation(s)
- Keith Nykamp
- Invitae Corporation, San Francisco, California, USA
| | | | | | - John Garcia
- Invitae Corporation, San Francisco, California, USA
| | | | - Yuan-Yuan Ho
- Invitae Corporation, San Francisco, California, USA
| | | | - Nila Patil
- Invitae Corporation, San Francisco, California, USA
| | | | | | | | - Scott Topper
- Invitae Corporation, San Francisco, California, USA
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18
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Tricarico R, Kasela M, Mareni C, Thompson BA, Drouet A, Staderini L, Gorelli G, Crucianelli F, Ingrosso V, Kantelinen J, Papi L, De Angioletti M, Berardi M, Gaildrat P, Soukarieh O, Turchetti D, Martins A, Spurdle AB, Nyström M, Genuardi M. Assessment of the InSiGHT Interpretation Criteria for the Clinical Classification of 24 MLH1 and MSH2 Gene Variants. Hum Mutat 2016; 38:64-77. [PMID: 27629256 DOI: 10.1002/humu.23117] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 09/04/2016] [Accepted: 09/09/2016] [Indexed: 01/15/2023]
Abstract
Pathogenicity assessment of DNA variants in disease genes to explain their clinical consequences is an integral component of diagnostic molecular testing. The International Society for Gastrointestinal Hereditary Tumors (InSiGHT) has developed specific criteria for the interpretation of mismatch repair (MMR) gene variants. Here, we performed a systematic investigation of 24 MLH1 and MSH2 variants. The assessments were done by analyzing population frequency, segregation, tumor molecular characteristics, RNA effects, protein expression levels, and in vitro MMR activity. Classifications were confirmed for 15 variants and changed for three, and for the first time determined for six novel variants. Overall, based on our results, we propose the introduction of some refinements to the InSiGHT classification rules. The proposed changes have the advantage of homogenizing the InSIGHT interpretation criteria with those set out by the Evidence-based Network for the Interpretation of Germline Mutant Alleles (ENIGMA) consortium for the BRCA1/BRCA2 genes. We also observed that the addition of only few clinical data was sufficient to obtain a more stable classification for variants considered as "likely pathogenic" or "likely nonpathogenic." This shows the importance of obtaining as many as possible points of evidence for variant interpretation, especially from the clinical setting.
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Affiliation(s)
- Rossella Tricarico
- Department of Biomedical, Experimental and Clinical Sciences, Medical Genetics Unit, University of Florence, Florence, Italy.,Cancer Epigenetics and Cancer Biology Programs, Fox Chase Cancer Center, Philadelphia, Pennsylvania
| | - Mariann Kasela
- Department of Biosciences, Division of Genetics, University of Helsinki, Helsinki, Finland
| | | | - Bryony A Thompson
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah.,Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Victoria, Australia
| | - Aurélie Drouet
- Inserm-U1079-IRIB, Normandy Centre for Genomic and Personalized Medicine, University of Rouen, Rouen, France
| | - Lucia Staderini
- Department of Biomedical, Experimental and Clinical Sciences, Medical Genetics Unit, University of Florence, Florence, Italy.,Microbiology and Virology Department, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy
| | - Greta Gorelli
- Department of Biomedical, Experimental and Clinical Sciences, Medical Genetics Unit, University of Florence, Florence, Italy
| | - Francesca Crucianelli
- Department of Biomedical, Experimental and Clinical Sciences, Medical Genetics Unit, University of Florence, Florence, Italy
| | - Valentina Ingrosso
- Department of Biomedical, Experimental and Clinical Sciences, Medical Genetics Unit, University of Florence, Florence, Italy
| | - Jukka Kantelinen
- Department of Biosciences, Division of Genetics, University of Helsinki, Helsinki, Finland
| | - Laura Papi
- Department of Biomedical, Experimental and Clinical Sciences, Medical Genetics Unit, University of Florence, Florence, Italy
| | - Maria De Angioletti
- Cancer Genetics and Gene Transfer - Core Research Laboratory, Istituto Toscano Tumori, Florence, Italy.,ICCOM-CNR, Sesto Fiorentino, Italy
| | - Margherita Berardi
- Cancer Genetics and Gene Transfer - Core Research Laboratory, Istituto Toscano Tumori, Florence, Italy
| | - Pascaline Gaildrat
- Inserm-U1079-IRIB, Normandy Centre for Genomic and Personalized Medicine, University of Rouen, Rouen, France
| | - Omar Soukarieh
- Inserm-U1079-IRIB, Normandy Centre for Genomic and Personalized Medicine, University of Rouen, Rouen, France
| | - Daniela Turchetti
- Medical Genetics, Department of Medical and Surgical Sciences (DIMEC), University of Bologna, Bologna, Italy
| | - Alexandra Martins
- Inserm-U1079-IRIB, Normandy Centre for Genomic and Personalized Medicine, University of Rouen, Rouen, France
| | - Amanda B Spurdle
- Genetics and Computational Biology Department, QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Minna Nyström
- Department of Biosciences, Division of Genetics, University of Helsinki, Helsinki, Finland
| | - Maurizio Genuardi
- Department of Biomedical, Experimental and Clinical Sciences, Medical Genetics Unit, University of Florence, Florence, Italy.,Institute of Genomic Medicine, A. Gemelli School of Medicine, Medical Genetics Unit, Catholic University of the Sacred Heart, Rome, Italy
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19
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Liu Q, Thompson BA, Ward RL, Hesson LB, Sloane MA. Understanding the Pathogenicity of Noncoding Mismatch Repair Gene Promoter Variants in Lynch Syndrome. Hum Mutat 2016; 37:417-26. [DOI: 10.1002/humu.22971] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Accepted: 02/05/2016] [Indexed: 01/04/2023]
Affiliation(s)
- Qing Liu
- Adult Cancer Program; Lowy Cancer Research Centre and Prince of Wales Clinical School; UNSW Australia; Sydney New South Wales Australia
| | - Bryony A. Thompson
- Huntsman Cancer Institute; University of Utah; Salt Lake City Utah
- Centre for Epidemiology and Biostatistics; Melbourne School of Population and Global Health; University of Melbourne; Melbourne Victoria Australia
| | - Robyn L. Ward
- Adult Cancer Program; Lowy Cancer Research Centre and Prince of Wales Clinical School; UNSW Australia; Sydney New South Wales Australia
- Level 3 Brian Wilson Chancellery; The University of Queensland; Brisbane Queensland Australia
| | - Luke B. Hesson
- Adult Cancer Program; Lowy Cancer Research Centre and Prince of Wales Clinical School; UNSW Australia; Sydney New South Wales Australia
| | - Mathew A. Sloane
- Adult Cancer Program; Lowy Cancer Research Centre and Prince of Wales Clinical School; UNSW Australia; Sydney New South Wales Australia
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20
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Clinical and Molecular Characterization of Brazilian Patients Suspected to Have Lynch Syndrome. PLoS One 2015; 10:e0139753. [PMID: 26437257 PMCID: PMC4593564 DOI: 10.1371/journal.pone.0139753] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 09/15/2015] [Indexed: 12/30/2022] Open
Abstract
Lynch syndrome (LS) accounts for 3–5% of all colorectal cancers (CRC) and is inherited in an autosomal dominant fashion. This syndrome is characterized by early CRC onset, high incidence of tumors in the ascending colon, excess of synchronous/metachronous tumors and extra-colonic tumors. Nowadays, LS is regarded of patients who carry deleterious germline mutations in one of the five mismatch repair genes (MMR), mostly in MLH1 and MSH2, but also in MSH6, PMS1 and PMS2. To comprehensively characterize 116 Brazilian patients suspected for LS, we assessed the frequency of germline mutations in the three minor genes MSH6, PMS1 and PMS2 in 82 patients negative for point mutations in MLH1 and MSH2. We also assessed large genomic rearrangements by MLPA for detecting copy number variations (CNVs) in MLH1, MSH2 and MSH6 generating a broad characterization of MMR genes. The complete analysis of the five MMR genes revealed 45 carriers of pathogenic mutations, including 25 in MSH2, 15 in MLH1, four in MSH6 and one in PMS2. Eleven novel pathogenic mutations (6 in MSH2, 4 in MSH6 and one in PMS2), and 11 variants of unknown significance (VUS) were found. Mutations in the MLH1 and MSH2 genes represented 89% of all mutations (40/45), whereas the three MMR genes (MSH6, PMS1 and PMS2) accounted for 11% (5/45). We also investigated the MLH1 p.Leu676Pro VUS located in the PMS2 interaction domain and our results revealed that this variant displayed no defective function in terms of cellular location and heterodimer interaction. Additionally, we assessed the tumor phenotype of a subset of patients and also the frequency of CRC and extra-colonic tumors in 2,365 individuals of the 116 families, generating the first comprehensive portrait of the genetic and clinical aspects of patients suspected of LS in a Brazilian cohort.
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21
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A founder MLH1 mutation in Lynch syndrome families from Piedmont, Italy, is associated with an increased risk of pancreatic tumours and diverse immunohistochemical patterns. Fam Cancer 2015; 13:401-13. [PMID: 24802709 DOI: 10.1007/s10689-014-9726-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The MLH1 c.2252_2253delAA mutation was found in 11 unrelated families from a restricted area south-west of Turin among 140 families with mutations in the mismatch repair genes. The mutation is located in the highly conserved C-terminal region, responsible for dimerization with the PMS2 protein. Twenty-five tumour tissues from 61 individuals with the c.2252_2253delAA mutation were tested for microsatellite instability (MSI) and protein expression. We compared the clinical features of these families versus the rest of our cohort and screened for a founder effect. All but one tumours showed the MSI-high mutator phenotype. Normal, focal and lack of MLH1 staining were observed in 16, 36 and 48 % of tumours, respectively. PMS2 expression was always lost. The mutation co-segregated with Lynch syndrome-related cancers in all informative families. All families but one fulfilled Amsterdam criteria, a frequency higher than in other MLH1 mutants. This was even more evident for AC II (72.7 vs. 57.5 %). Moreover, all families had at least one colon cancer diagnosed before 50 years and one case with multiple Lynch syndrome-related tumours. Interestingly, a statistically significant (p = 0.0057) higher frequency of pancreatic tumours was observed compared to families with other MLH1 mutations: 8.2 % of affected individuals versus 1.6 %. Haplotype analysis demonstrated a common ancestral origin of the mutation, which originated about 1,550 years ago. The mutation is currently classified as having an uncertain clinical significance. Clinical features, tissue analysis and co-segregation with disease strongly support the hypothesis that the MLH1 c.2252_2253delAA mutation has a pathogenic effect.
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22
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Hesson LB, Packham D, Kwok CT, Nunez AC, Ng B, Schmidt C, Fields M, Wong JWH, Sloane MA, Ward RL. Lynch syndrome associated with two MLH1 promoter variants and allelic imbalance of MLH1 expression. Hum Mutat 2015; 36:622-30. [PMID: 25762362 PMCID: PMC4682451 DOI: 10.1002/humu.22785] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 03/03/2015] [Indexed: 12/27/2022]
Abstract
Lynch syndrome is a hereditary cancer syndrome caused by a constitutional mutation in one of the mismatch repair genes. The implementation of predictive testing and targeted preventative surveillance is hindered by the frequent finding of sequence variants of uncertain significance in these genes. We aimed to determine the pathogenicity of previously reported variants (c.-28A>G and c.-7C>T) within the MLH1 5′untranslated region (UTR) in two individuals from unrelated suspected Lynch syndrome families. We investigated whether these variants were associated with other pathogenic alterations using targeted high-throughput sequencing of the MLH1 locus. We also determined their relationship to gene expression and epigenetic alterations at the promoter. Sequencing revealed that the c.-28A>G and c.-7C>T variants were the only potentially pathogenic alterations within the MLH1 gene. In both individuals, the levels of transcription from the variant allele were reduced to 50% compared with the wild-type allele. Partial loss of expression occurred in the absence of constitutional epigenetic alterations within the MLH1 promoter. We propose that these variants may be pathogenic due to constitutional partial loss of MLH1 expression, and that this may be associated with intermediate penetrance of a Lynch syndrome phenotype. Our findings provide further evidence of the potential importance of noncoding variants in the MLH1 5′UTR in the pathogenesis of Lynch syndrome.
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Affiliation(s)
- Luke B Hesson
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Australia, Sydney, New South Wales, Australia
| | - Deborah Packham
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Australia, Sydney, New South Wales, Australia
| | - Chau-To Kwok
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Australia, Sydney, New South Wales, Australia
| | - Andrea C Nunez
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Australia, Sydney, New South Wales, Australia
| | - Benedict Ng
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Australia, Sydney, New South Wales, Australia
| | - Christa Schmidt
- Department of Pathology and Medical Genetics, St. Olavs University Hospital, Trondheim
| | - Michael Fields
- Royal North Shore Hospital, Sydney, New South Wales, Australia
| | - Jason W H Wong
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Australia, Sydney, New South Wales, Australia
| | - Mathew A Sloane
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Australia, Sydney, New South Wales, Australia
| | - Robyn L Ward
- Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, UNSW Australia, Sydney, New South Wales, Australia.,Level 3 Brian Wilson Chancellery, The University of Queensland, Brisbane, Queensland, Australia
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23
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Hinrichsen I, Schäfer D, Langer D, Köger N, Wittmann M, Aretz S, Steinke V, Holzapfel S, Trojan J, König R, Zeuzem S, Brieger A, Plotz G. Functional testing strategy for coding genetic variants of unclear significance in MLH1 in Lynch syndrome diagnosis. Carcinogenesis 2014; 36:202-11. [PMID: 25477341 DOI: 10.1093/carcin/bgu239] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Lynch syndrome is caused by inactivating mutations in the MLH1 gene, but genetic variants of unclear significance frequently preclude diagnosis. Functional testing can reveal variant-conferred defects in gene or protein function. Based on functional defect frequencies and clinical applicability of test systems, we developed a functional testing strategy aimed at efficiently detecting pathogenic defects in coding MLH1 variants. In this strategy, tests of repair activity and expression are prioritized over analyses of subcellular protein localization and messenger RNA (mRNA) formation. This strategy was used for four unclear coding MLH1 variants (p.Asp41His, p.Leu507Phe, p.Gln689Arg, p.Glu605del + p.Val716Met). Expression was analyzed using a transfection system, mismatch repair (MMR) activity by complementation in vitro, mRNA formation by reverse transcriptase-PCR in carrier lymphocyte mRNA, and subcellular localization with dye-labeled fusion constructs. All tests included clinically meaningful controls. The strategy enabled efficient identification of defects in two unclear variants: the p.Asp41His variant showed loss of MMR activity, whereas the compound variant p.Glu605del + p.Val716Met had a defect of expression. This expression defect was significantly stronger than the pathogenic expression reference variant analyzed in parallel, therefore the defect of the compound variant is also pathogenic. Interestingly, the expression defect was caused additively by both of the compound variants, at least one of which is non-pathogenic when occurring by itself. Tests were neutral for p.Leu507Phe and p.Gln689Arg, and the results were consistent with available clinical data. We finally discuss the improved sensitivity and efficiency of the applied strategy and its limitations in analyzing unclear coding MLH1 variants.
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Affiliation(s)
- Inga Hinrichsen
- Biomedical Research Laboratory, Department of Internal Medicine 1 and Department of Human Genetics, Universitätsklinikum Frankfurt, Frankfurt D-60590, Germany, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Department of Internal Medicine 1, Universitätsklinikum Frankfurt D-60590, Frankfurt, Germany
| | - Dieter Schäfer
- Department of Human Genetics, Universitätsklinikum Frankfurt, Frankfurt D-60590, Germany
| | - Deborah Langer
- Biomedical Research Laboratory, Department of Internal Medicine 1 and Department of Human Genetics, Universitätsklinikum Frankfurt, Frankfurt D-60590, Germany, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Department of Internal Medicine 1, Universitätsklinikum Frankfurt D-60590, Frankfurt, Germany
| | - Nicole Köger
- Biomedical Research Laboratory, Department of Internal Medicine 1 and Department of Human Genetics, Universitätsklinikum Frankfurt, Frankfurt D-60590, Germany, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Department of Internal Medicine 1, Universitätsklinikum Frankfurt D-60590, Frankfurt, Germany
| | - Margarethe Wittmann
- Biomedical Research Laboratory, Department of Internal Medicine 1 and Department of Human Genetics, Universitätsklinikum Frankfurt, Frankfurt D-60590, Germany, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Department of Internal Medicine 1, Universitätsklinikum Frankfurt D-60590, Frankfurt, Germany
| | - Stefan Aretz
- Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and
| | - Verena Steinke
- Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and
| | - Stefanie Holzapfel
- Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and
| | - Jörg Trojan
- Department of Internal Medicine 1, Universitätsklinikum Frankfurt D-60590, Frankfurt, Germany
| | - Rainer König
- Department of Human Genetics, Universitätsklinikum Frankfurt, Frankfurt D-60590, Germany
| | - Stefan Zeuzem
- Department of Internal Medicine 1, Universitätsklinikum Frankfurt D-60590, Frankfurt, Germany
| | - Angela Brieger
- Biomedical Research Laboratory, Department of Internal Medicine 1 and Department of Human Genetics, Universitätsklinikum Frankfurt, Frankfurt D-60590, Germany, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Department of Internal Medicine 1, Universitätsklinikum Frankfurt D-60590, Frankfurt, Germany
| | - Guido Plotz
- Biomedical Research Laboratory, Department of Internal Medicine 1 and Department of Human Genetics, Universitätsklinikum Frankfurt, Frankfurt D-60590, Germany, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Department of Internal Medicine 1, Universitätsklinikum Frankfurt D-60590, Frankfurt, Germany
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24
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Pineda M, González-Acosta M, Thompson BA, Sánchez R, Gómez C, Martínez-López J, Perea J, Caldés T, Rodríguez Y, Landolfi S, Balmaña J, Lázaro C, Robles L, Capellá G, Rueda D. Detailed characterization of MLH1 p.D41H and p.N710D variants coexisting in a Lynch syndrome family with conserved MLH1 expression tumors. Clin Genet 2014; 87:543-8. [PMID: 25060679 DOI: 10.1111/cge.12467] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 07/18/2014] [Accepted: 07/22/2014] [Indexed: 12/26/2022]
Abstract
Lynch syndrome (LS) is an autosomal dominant cancer-susceptibility disease caused by inactivating germline mutations in mismatch repair (MMR) genes. Variants of unknown significance (VUS) are often detected in mutational analysis of MMR genes. Here we describe a large family fulfilling Amsterdam I criteria carrying two rare VUS in the MLH1 gene: c.121G > C (p.D41H) and c.2128A > G (p.N710D). Collection of clinico-pathological data, multifactorial analysis, in silico predictions, and functional analyses were used to elucidate the clinical significance of the identified MLH1 VUS. Only the c.121G > C variant cosegregated with LS-associated tumors in the family. Diagnosed colorectal tumors were microsatellite unstable although immunohistochemical staining revealed no loss of MMR proteins expression. Multifactorial likelihood analysis classified c.2128A > G as a non-pathogenic variant and c.121G > C as pathogenic. In vitro functional tests revealed impaired MMR activity and diminished expression of c.121G > C. Accordingly, the N710 residue is located in the unconserved MLH1 C-terminal domain, whereas D41 is highly conserved and located in the ATPase domain. The obtained results will enable adequate genetic counseling of c.121G > C and c.2128A > G variant carriers and their families. Furthermore, they exemplify how cumulative data and comprehensive analyses are mandatory to refine the classification of MMR variants.
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Affiliation(s)
- M Pineda
- Hereditary Cancer Program, Catalan Institute of Oncology, ICO-IDIBELL, Hospitalet de Llobregat, Barcelona, Spain
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25
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Abulí A, Bujanda L, Muñoz J, Buch S, Schafmayer C, Valeria Maiorana M, Veneroni S, van Wezel T, Liu T, Westers H, Esteban-Jurado C, Ocaña T, Piqué JM, Andreu M, Jover R, Carracedo A, Xicola RM, Llor X, Castells A, Dunlop M, Hofstra R, Lindblom A, Wijnen J, Peterlongo P, Hampe J, Ruiz-Ponte C, Castellví-Bel S. The MLH1 c.1852_1853delinsGC (p.K618A) variant in colorectal cancer: genetic association study in 18,723 individuals. PLoS One 2014; 9:e95022. [PMID: 24743384 PMCID: PMC3990597 DOI: 10.1371/journal.pone.0095022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Accepted: 03/21/2014] [Indexed: 12/25/2022] Open
Abstract
Colorectal cancer is one of the most frequent neoplasms and an important cause of mortality in the developed world. Mendelian syndromes account for about 5% of the total burden of CRC, being Lynch syndrome and familial adenomatous polyposis the most common forms. Lynch syndrome tumors develop mainly as a consequence of defective DNA mismatch repair associated with germline mutations in MLH1, MSH2, MSH6 and PMS2. A significant proportion of variants identified by screening these genes correspond to missense or noncoding changes without a clear pathogenic consequence, and they are designated as "variants of uncertain significance", being the c.1852_1853delinsGC (p.K618A) variant in the MLH1 gene a clear example. The implication of this variant as a low-penetrance risk variant for CRC was assessed in the present study by performing a case-control study within a large cohort from the COGENT consortium-COST Action BM1206 including 18,723 individuals (8,055 colorectal cancer cases and 10,668 controls) and a case-only genotype-phenotype correlation with several clinical and pathological characteristics restricted to the Epicolon cohort. Our results showed no involvement of this variant as a low-penetrance variant for colorectal cancer genetic susceptibility and no association with any clinical and pathological characteristics including family history for this neoplasm or Lynch syndrome.
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Affiliation(s)
- Anna Abulí
- Department of Gastroenterology, Hospital Clínic, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Catalonia, Spain
- Department of Gastroenterology, Hospital del Mar-IMIM (Hospital del Mar Medical Research Centre), Pompeu Fabra University, Barcelona, Catalonia, Spain
| | - Luis Bujanda
- Gastroenterology Department, Hospital Donostia, Networked Biomedical Research Centre for Hepatic and Digestive Diseases (CIBEREHD), Basque Country University, San Sebastián, Spain
| | - Jenifer Muñoz
- Department of Gastroenterology, Hospital Clínic, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Catalonia, Spain
| | - Stephan Buch
- Department of Medine I, University Hospital Dresden, Dresden, Germany
| | - Clemens Schafmayer
- Department of General and Thoracic Surgery, University Hospital Schleswig-Holstein, Kiel, Germany
| | | | - Silvia Veneroni
- Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Tom van Wezel
- Department of Pathology, Leiden University Medical Center, Leiden, The Netherlands
| | - Tao Liu
- Department of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden
| | - Helga Westers
- Department of Genetics, University Medical Center Groningen, Groningen, The Netherlands
| | - Clara Esteban-Jurado
- Department of Gastroenterology, Hospital Clínic, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Catalonia, Spain
| | - Teresa Ocaña
- Department of Gastroenterology, Hospital Clínic, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Catalonia, Spain
| | - Josep M. Piqué
- Department of Gastroenterology, Hospital Clínic, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Catalonia, Spain
| | - Montserrat Andreu
- Department of Gastroenterology, Hospital del Mar-IMIM (Hospital del Mar Medical Research Centre), Pompeu Fabra University, Barcelona, Catalonia, Spain
| | - Rodrigo Jover
- Department of Gastroenterology, Hospital General d'Alacant, Alicante, Spain
| | - Angel Carracedo
- Galician Public Foundation of Genomic Medicine (FPGMX), Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Genomics Medicine Group, Hospital Clínico, Santiago de Compostela, University of Santiago de Compostela, Galicia, Spain
- Center of Excellence in Genomic Medicine Research, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia
| | - Rosa M. Xicola
- Section of Digestive Diseases and Nutrition, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Xavier Llor
- Section of Digestive Diseases and Nutrition, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Antoni Castells
- Department of Gastroenterology, Hospital Clínic, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Catalonia, Spain
| | | | - Malcolm Dunlop
- Colon Cancer Genetics Group, Institute of Genetics and Molecular Medicine, University of Edinburgh and MRC Human Genetics Unit, Edinburgh, United Kingdom
| | - Robert Hofstra
- Department of Genetics, University Medical Center Groningen, Groningen, The Netherlands
| | - Annika Lindblom
- Department of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden
| | - Juul Wijnen
- Departments of Human Genetics and Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Paolo Peterlongo
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Milan, Italy
| | - Jochen Hampe
- Department of Medine I, University Hospital Dresden, Dresden, Germany
| | - Clara Ruiz-Ponte
- Galician Public Foundation of Genomic Medicine (FPGMX), Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Genomics Medicine Group, Hospital Clínico, Santiago de Compostela, University of Santiago de Compostela, Galicia, Spain
| | - Sergi Castellví-Bel
- Department of Gastroenterology, Hospital Clínic, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Catalonia, Spain
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26
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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: 354] [Impact Index Per Article: 32.2] [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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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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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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