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Zuntini R, Cattani C, Pedace L, Miele E, Caraffi SG, Gardini S, Ficarelli E, Pizzi S, Radio FC, Barone A, Piana S, Bertolini P, Corradi D, Marinelli M, Longo C, Motolese A, Zuffardi O, Tartaglia M, Garavelli L. Case Report: Sequential postzygotic HRAS mutation and gains of the paternal chromosome 11 carrying the mutated allele in a patient with epidermal nevus and rhabdomyosarcoma: evidence of a multiple-hit mechanism involving HRAS in oncogenic transformation. Front Genet 2023; 14:1231434. [PMID: 37636262 PMCID: PMC10447906 DOI: 10.3389/fgene.2023.1231434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 08/01/2023] [Indexed: 08/29/2023] Open
Abstract
We report a 7-year-old boy born with epidermal nevi (EN) arranged according to Blaschko's lines involving the face and head, right upper limb, chest, and left lower limb, who developed a left paratesticular embryonal rhabdomyosarcoma at 18 months of age. Parallel sequencing identified a gain-of-function variant (c.37G>C, p.Gly13Arg) of HRAS in both epidermal nevus and tumor but not in leukocytes or buccal mucosal epithelial cells, indicating its postzygotic origin. The variant accounted for 33% and 92% of the total reads in the nevus and tumor DNA specimens, respectively, supporting additional somatic hits in the latter. DNA methylation (DNAm) profiling of the tumor documented a signature consistent with embryonal rhabdomyosarcoma and CNV array analysis inferred from the DNAm arrays and subsequent MLPA analysis demonstrated copy number gains of the entire paternal chromosome 11 carrying the mutated HRAS allele, likely as the result of paternal unidisomy followed by subsequent gain(s) of the paternal chromosome in the tumor. Other structural rearrangements were observed in the tumours, while no additional pathogenic variants affecting genes with role in the RAS-MAPK and PI3K-AKT-MTOR pathways were identified. Our findings provide further evidence of the contribution of "gene dosage" to the multistep process driving cell transformation associated with hyperactive HRAS function.
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Affiliation(s)
- Roberta Zuntini
- Medical Genetics Unit, Azienda USL, IRCCS, Arcispedale Santa Maria Nuova, Reggio Emilia, Italy
| | - Chiara Cattani
- Medical Genetics Unit, Azienda USL, IRCCS, Arcispedale Santa Maria Nuova, Reggio Emilia, Italy
| | - Lucia Pedace
- Department of Pediatric Hematology, Oncology and Cellular and Gene Therapy, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy
| | - Evelina Miele
- Department of Pediatric Hematology, Oncology and Cellular and Gene Therapy, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy
| | | | - Stefano Gardini
- Dermatology Unit, Azienda USL, IRCCS, Arcispedale Santa Maria Nuova, Reggio Emilia, Italy
| | - Elena Ficarelli
- Dermatology Unit, Azienda USL, IRCCS, Arcispedale Santa Maria Nuova, Reggio Emilia, Italy
| | - Simone Pizzi
- Molecular Genetics and Functional Genomics Research Unit, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy
| | - Francesca Clementina Radio
- Molecular Genetics and Functional Genomics Research Unit, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy
| | - Angelica Barone
- Paediatric Hematology Oncology Unit, University Hospital of Parma, Parma, Italy
| | - Simonetta Piana
- Department of Oncology and Advanced Technologies, Pathology Unit, Azienda USL, IRCCS, Arcispedale S Maria Nuova, Reggio Emilia, Italy
| | - Patrizia Bertolini
- Paediatric Hematology Oncology Unit, University Hospital of Parma, Parma, Italy
| | - Domenico Corradi
- Department of Medicine and Surgery, Unit of Pathology, University of Parma, Parma, Italy
| | - Maria Marinelli
- Medical Genetics Unit, Azienda USL, IRCCS, Arcispedale Santa Maria Nuova, Reggio Emilia, Italy
| | - Caterina Longo
- Department of Dermatology, University of Modena and Reggio Emilia, Modena, Italy
- Department of Oncology and Advanced Technologies, Unit of Dermatology, Azienda USL, IRCCS, Arcispedale S Maria Nuova, Reggio Emilia, Italy
| | - Alberico Motolese
- Dermatology Unit, Azienda USL, IRCCS, Arcispedale Santa Maria Nuova, Reggio Emilia, Italy
| | - Orsetta Zuffardi
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Marco Tartaglia
- Molecular Genetics and Functional Genomics Research Unit, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy
| | - Livia Garavelli
- Medical Genetics Unit, Azienda USL, IRCCS, Arcispedale Santa Maria Nuova, Reggio Emilia, Italy
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Rydzanicz M, Glinkowski W, Walczak A, Koppolu A, Kostrzewa G, Gasperowicz P, Pollak A, Stawiński P, Płoski R. Postzygotic mosaicism of a novel PTPN11 mutation in monozygotic twins discordant for metachondromatosis. Am J Med Genet A 2022; 188:1482-1487. [PMID: 35112464 DOI: 10.1002/ajmg.a.62670] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 12/16/2021] [Accepted: 01/11/2022] [Indexed: 01/05/2023]
Abstract
Genetic mosaicism caused by postzygotic mutations is of a great interest due to its role in human disease. Monozygotic twins arising from a single zygote are considered as genetically identical, and any differences likely to be caused by postzygotic events. Thus, phenotypically discordant monozygotic twins offer a unique opportunity to study genotype-phenotype correlation. Here, we present a three-generation family starting from a pair of monozygotic twins discordant for metachondromatosis due to postzygotic p.(Gln175His) variant in the PTPN11 gene. Both phenotypically discordant monozygotic twins harbor p.(Gln175His), however significant differences in mosaic ratio is observed not only between twins, but also within different tissue types within one individual. Phenotypic manifestation of p.(Gln175His) in examined family clearly depends on allele variant fraction (VAF). Individuals harboring constitutional mutation (VAF 50%) present typical metachondromatosis. Milder phenotype is observed in twin harboring high-level mosaicism in the tissue of ectodermal origin (VAF 45%), but not in a blood (VAF 5%). Finally, her twin sister harboring low-level mosaicism in blood (VAF 2%) and nonblood (VAF 12%) tissues is phenotypically normal. Our results provide insights into biological role of mosaicism in disease and further support the usefulness of nonblood tissues as an optimal source of DNA for the identification of postzygotic mutations in phenotypically discordant monozygotic twins.
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Affiliation(s)
| | - Wojciech Glinkowski
- Center of Excellence "TeleOrto" for Telediagnostics and Treatment of Disorders and Injuries of the Locomotor System, Department of Medical Informatics and Telemedicine, Medical University of Warsaw, Warsaw, Poland
| | - Anna Walczak
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
| | - Agnieszka Koppolu
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland.,Postgraduate School of Molecular Medicine, Medical University of Warsaw, Warsaw, Poland
| | - Grażyna Kostrzewa
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
| | - Piotr Gasperowicz
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
| | - Agnieszka Pollak
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
| | - Piotr Stawiński
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
| | - Rafał Płoski
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
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Abstract
Autism spectrum disorder (ASD) is a genetically heterogenous neurodevelopmental disorder. In the early years of next-generation sequencing, de novo germline variants were shown to contribute to ASD risk. These germline mutations are present in all of the cells of an affected individual and can be detected in any tissue, including clinically accessible DNA sources such as blood or saliva. In recent years, studies have also implicated de novo somatic variants in ASD risk. These somatic mutations arise postzygotically and are present in only a subset of the cells of an affected individual. Depending on the developmental time and progenitor cell in which a somatic mutation occurs, it may be detectable in some tissues and not in others. Somatic mutations detectable at relatively low sequencing coverage in clinically accessible tissues are suggested to contribute to 3-5% of simplex ASD diagnoses, and "brain limited" somatic mutations have been identified in postmortem ASD brain tissue. Somatic mutations likely represent the genetic diagnosis in a proportion of otherwise unexplained individuals with ASD, and brain limited somatic mutations can be used as markers to discover risk genes, cell types, brain regions, and cellular pathways important for ASD pathogenesis and to potentially target for therapeutics.
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Rath M, Spiegler S, Nath N, Schwefel K, Di Donato N, Gerber J, Korenke GC, Hellenbroich Y, Hehr U, Gross S, Sure U, Zoll B, Gilberg E, Kaderali L, Felbor U. Constitutional de novo and postzygotic mutations in isolated cases of cerebral cavernous malformations. Mol Genet Genomic Med 2016; 5:21-27. [PMID: 28116327 PMCID: PMC5241208 DOI: 10.1002/mgg3.256] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 10/02/2016] [Indexed: 11/07/2022] Open
Abstract
Background Cerebral cavernous malformations (CCM) are vascular lesions of the central nervous system that can be found in sporadic or autosomal dominantly inherited forms and manifest with headaches, seizures, and hemorrhagic stroke. The precise proportion of de novo mutations in the CCM1,CCM2, and CCM3 genes remains unknown. Methods We here present a series of six trios with de novo mutations that have been analyzed by amplicon deep sequencing to differentiate between constitutional and postzygotic mutations. Results In one case, allelic ratios clearly indicated mosaicism for a CCM3 splice site mutation found in blood and buccal mucosa of a 2‐year‐old boy with multiple CCMs. The remaining five de novo mutations proved to be constitutional. In addition to three CCM3, two CCM1, and one CCM2 de novo point mutations, a deletion of the entire CCM3 gene was identified in an index case that most likely originated from an early postzygotic event. These are the first high‐level mosaic mutations reported in blood samples of isolated CCM cases. Conclusion Our data demonstrate that de novo mutations in CCM1‐3 might be more frequent than previously thought. Furthermore, amplicon deep sequencing is useful to discriminate between patients with constitutional and postzygotic mutations, and thereby improves genetic counseling.
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Affiliation(s)
- Matthias Rath
- Department of Human Genetics University Medicine Greifswald and Interfaculty Institute of Genetics and Functional Genomics University of Greifswald Greifswald Germany
| | - Stefanie Spiegler
- Department of Human Genetics University Medicine Greifswald and Interfaculty Institute of Genetics and Functional Genomics University of Greifswald Greifswald Germany
| | - Neetika Nath
- Institute for Bioinformatics University Medicine Greifswald Greifswald Germany
| | - Konrad Schwefel
- Department of Human Genetics University Medicine Greifswald and Interfaculty Institute of Genetics and Functional Genomics University of Greifswald Greifswald Germany
| | - Nataliya Di Donato
- Institute for Clinical Genetics Faculty of Medicine Carl Gustav Carus TU Dresden Dresden Germany
| | - Johannes Gerber
- Department of Neuroradiology University Hospital Carl Gustav Carus Dresden Germany
| | - G Christoph Korenke
- Department of Neuropaediatrics Children's Hospital Oldenburg Oldenburg Germany
| | | | - Ute Hehr
- Center for and Institute of Human Genetics University of Regensburg Regensburg Germany
| | - Stephanie Gross
- Department of Neuropediatrics Justus-Liebig-University Gießen Germany
| | - Ulrich Sure
- Department of Neurosurgery University Hospital Essen University of Duisburg-Essen Essen Germany
| | - Barbara Zoll
- Institute of Human Genetics Georg August University Göttingen Germany
| | - Eberhard Gilberg
- Department of Human Genetics University Medicine Greifswald and Interfaculty Institute of Genetics and Functional Genomics University of Greifswald Greifswald Germany
| | - Lars Kaderali
- Institute for Bioinformatics University Medicine Greifswald Greifswald Germany
| | - Ute Felbor
- Department of Human Genetics University Medicine Greifswald and Interfaculty Institute of Genetics and Functional Genomics University of Greifswald Greifswald Germany
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Campbell IM, Shaw CA, Stankiewicz P, Lupski JR. Somatic mosaicism: implications for disease and transmission genetics. Trends Genet 2015; 31:382-92. [PMID: 25910407 DOI: 10.1016/j.tig.2015.03.013] [Citation(s) in RCA: 190] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 03/17/2015] [Accepted: 03/18/2015] [Indexed: 11/21/2022]
Abstract
Nearly all of the genetic material among cells within an organism is identical. However, single-nucleotide variants (SNVs), small insertions/deletions (indels), copy-number variants (CNVs), and other structural variants (SVs) continually accumulate as cells divide during development. This process results in an organism composed of countless cells, each with its own unique personal genome. Thus, every human is undoubtedly mosaic. Mosaic mutations can go unnoticed, underlie genetic disease or normal human variation, and may be transmitted to the next generation as constitutional variants. We review the influence of the developmental timing of mutations, the mechanisms by which they arise, methods for detecting mosaic variants, and the risk of passing these mutations on to the next generation.
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