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Smirnov D, Konstantinovskiy N, Prokisch H. Integrative omics approaches to advance rare disease diagnostics. J Inherit Metab Dis 2023; 46:824-838. [PMID: 37553850 DOI: 10.1002/jimd.12663] [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] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 07/26/2023] [Accepted: 07/27/2023] [Indexed: 08/10/2023]
Abstract
Over the past decade high-throughput DNA sequencing approaches, namely whole exome and whole genome sequencing became a standard procedure in Mendelian disease diagnostics. Implementation of these technologies greatly facilitated diagnostics and shifted the analysis paradigm from variant identification to prioritisation and evaluation. The diagnostic rates vary widely depending on the cohort size, heterogeneity and disease and range from around 30% to 50% leaving the majority of patients undiagnosed. Advances in omics technologies and computational analysis provide an opportunity to increase these unfavourable rates by providing evidence for disease-causing variant validation and prioritisation. This review aims to provide an overview of the current application of several omics technologies including RNA-sequencing, proteomics, metabolomics and DNA-methylation profiling for diagnostics of rare genetic diseases in general and inborn errors of metabolism in particular.
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Affiliation(s)
- Dmitrii Smirnov
- School of Medicine, Institute of Human Genetics, Technical University of Munich, Munich, Germany
- Institute of Neurogenomics, Computational Health Center, Helmholtz Munich, Neuherberg, Germany
| | - Nikita Konstantinovskiy
- School of Medicine, Institute of Human Genetics, Technical University of Munich, Munich, Germany
| | - Holger Prokisch
- School of Medicine, Institute of Human Genetics, Technical University of Munich, Munich, Germany
- Institute of Neurogenomics, Computational Health Center, Helmholtz Munich, Neuherberg, Germany
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2
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Yépez VA, Mertes C, Müller MF, Klaproth-Andrade D, Wachutka L, Frésard L, Gusic M, Scheller IF, Goldberg PF, Prokisch H, Gagneur J. Detection of aberrant gene expression events in RNA sequencing data. Nat Protoc 2021; 16:1276-96. [PMID: 33462443 DOI: 10.1038/s41596-020-00462-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 11/06/2020] [Indexed: 12/20/2022]
Abstract
RNA sequencing (RNA-seq) has emerged as a powerful approach to discover disease-causing gene regulatory defects in individuals affected by genetically undiagnosed rare disorders. Pioneering studies have shown that RNA-seq could increase the diagnosis rates over DNA sequencing alone by 8-36%, depending on the disease entity and tissue probed. To accelerate adoption of RNA-seq by human genetics centers, detailed analysis protocols are now needed. We present a step-by-step protocol that details how to robustly detect aberrant expression levels, aberrant splicing and mono-allelic expression in RNA-seq data using dedicated statistical methods. We describe how to generate and assess quality control plots and interpret the analysis results. The protocol is based on the detection of RNA outliers pipeline (DROP), a modular computational workflow that integrates all the analysis steps, can leverage parallel computing infrastructures and generates browsable web page reports.
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Abstract
Both copy number variations (CNVs) and chromothripsis are phenomena that involve complex genomic rearrangements. Chromothripsis results in CNVs and other structural changes. CNVs are frequently observed in the human genome. Studies on CNVs have been increasing exponentially; the Database of Genomic Variants shows an increase in the number of data published on structural variations added to the database in the last 15 years. CNVs may be a result of replicative and non-replicative mechanisms, and are hypothesized to serve important roles in human health and disease. Chromothripsis is a phenomena of chromosomal rearrangement following chromosomal breaks at multiple locations and involves impaired DNA repair. In 2011, Stephens et al coined the term chromothripsis for this type of fragmenting event. Several proposed mechanisms have been suggested to underlie chromothripsis, such as p53 inactivation, micronuclei formation, abortive apoptosis and telomere fusions in telomere crisis. Chromothripsis gives rise to normal or abnormal phenotypes. In this review, constitutional chromothripsis, which may coexist with multiple de novo CNVs are described and discussed. This reviews aims to summarize recent advances in our understanding of CNVs and chromothripsis, and describe the effects of these phenomena on human health and birth defects.
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Affiliation(s)
- Aldina Brás
- Centre for Toxicogenomics and Human Health (ToxOmics), Genetics, Oncology and Human Toxicology, NOVA Medical School, Faculty of Medical Sciences, NOVA University of Lisbon, Lisbon 1169-056, Portugal
| | - António Sebastião Rodrigues
- Centre for Toxicogenomics and Human Health (ToxOmics), Genetics, Oncology and Human Toxicology, NOVA Medical School, Faculty of Medical Sciences, NOVA University of Lisbon, Lisbon 1169-056, Portugal
| | - José Rueff
- Centre for Toxicogenomics and Human Health (ToxOmics), Genetics, Oncology and Human Toxicology, NOVA Medical School, Faculty of Medical Sciences, NOVA University of Lisbon, Lisbon 1169-056, Portugal
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Abstract
BACKGROUND Inadvertent sample swaps are a real threat to data quality in any medium to large scale omics studies. While matches between samples from the same individual can in principle be identified from a few well characterized single nucleotide polymorphisms (SNPs), omics data types often only provide low to moderate coverage, thus requiring integration of evidence from a large number of SNPs to determine if two samples derive from the same individual or not. METHODS We select about six thousand SNPs in the human genome and develop a Bayesian framework that is able to robustly identify sample matches between next generation sequencing data sets. RESULTS We validate our approach on a variety of data sets. Most importantly, we show that our approach can establish identity between different omics data types such as Exome, RNA-Seq, and MethylCap-Seq. We demonstrate how identity detection degrades with sample quality and read coverage, but show that twenty million reads of a fairly low quality RNA-Seq sample are still sufficient for reliable sample identification. CONCLUSION Our tool, SMASH, is able to identify sample mismatches in next generation sequencing data sets between different sequencing modalities and for low quality sequencing data.
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Affiliation(s)
- Maximillian Westphal
- Interdisciplinary Biophysics Graduate Program, The Ohio State University, 484 W. 12th Avenue, Columbus, 43210, OH, USA
| | - David Frankhouser
- Biomedical Science Graduate Program, The Ohio State University, 333 W. 10th Avenue, Columbus, 43210, OH, USA.,Department of Diabetes Complications and Metabolism and Department of Population Sciences in the Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, 91010, CA, USA
| | - Carmine Sonzone
- Molecular, Cellular, and Developmental Biology Graduate Program, The Ohio State University, 484 W. 12th Avenue, Columbus, 43210, OH, USA
| | - Peter G Shields
- Molecular, Cellular, and Developmental Biology Graduate Program, The Ohio State University, 484 W. 12th Avenue, Columbus, 43210, OH, USA.,Department of Internal Medicine, The Ohio State University, 395 W. 12th Avenue, Columbus, 43210, OH, USA.,Comprehensive Cancer Center, The Ohio State University, 460 W. 10th Avenue, Columbus, 43210, OH, USA
| | - Pearlly Yan
- Department of Internal Medicine, The Ohio State University, 395 W. 12th Avenue, Columbus, 43210, OH, USA.,Comprehensive Cancer Center, The Ohio State University, 460 W. 10th Avenue, Columbus, 43210, OH, USA
| | - Ralf Bundschuh
- Interdisciplinary Biophysics Graduate Program, The Ohio State University, 484 W. 12th Avenue, Columbus, 43210, OH, USA. .,Department of Internal Medicine, The Ohio State University, 395 W. 12th Avenue, Columbus, 43210, OH, USA. .,Department of Physics, The Ohio State University, 191 W. Woodruff Avenue, Columbus, 43210, OH, USA. .,Department of Chemistry and Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, 43210, OH, USA. .,Center for RNA Biology, The Ohio State University, 484 W. 12th Avenue, Columbus, 43210, OH, USA.
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Perez-Rodriguez D, Kalyva M, Leija-Salazar M, Lashley T, Tarabichi M, Chelban V, Gentleman S, Schottlaender L, Franklin H, Vasmatzis G, Houlden H, Schapira AHV, Warner TT, Holton JL, Jaunmuktane Z, Proukakis C. Investigation of somatic CNVs in brains of synucleinopathy cases using targeted SNCA analysis and single cell sequencing. Acta Neuropathol Commun 2019; 7:219. [PMID: 31870437 PMCID: PMC6929293 DOI: 10.1186/s40478-019-0873-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Accepted: 12/17/2019] [Indexed: 12/17/2022] Open
Abstract
Synucleinopathies are mostly sporadic neurodegenerative disorders of partly unexplained aetiology, and include Parkinson's disease (PD) and multiple system atrophy (MSA). We have further investigated our recent finding of somatic SNCA (α-synuclein) copy number variants (CNVs, specifically gains) in synucleinopathies, using Fluorescent in-situ Hybridisation for SNCA, and single-cell whole genome sequencing for the first time in a synucleinopathy. In the cingulate cortex, mosaicism levels for SNCA gains were higher in MSA and PD than controls in neurons (> 2% in both diseases), and for MSA also in non-neurons. In MSA substantia nigra (SN), we noted SNCA gains in > 3% of dopaminergic (DA) neurons (identified by neuromelanin) and neuromelanin-negative cells, including olig2-positive oligodendroglia. Cells with CNVs were more likely to have α-synuclein inclusions, in a pattern corresponding to cell categories mostly relevant to the disease: DA neurons in Lewy-body cases, and other cells in the striatonigral degeneration-dominant MSA variant (MSA-SND). Higher mosaicism levels in SN neuromelanin-negative cells may correlate with younger onset in typical MSA-SND, and in cingulate neurons with younger death in PD. Larger sample sizes will, however, be required to confirm these putative findings. We obtained genome-wide somatic CNV profiles from 169 cells from the substantia nigra of two MSA cases, and pons and putamen of one. These showed somatic CNVs in ~ 30% of cells, with clonality and origins in segmental duplications for some. CNVs had distinct profiles based on cell type, with neurons having a mix of gains and losses, and other cells having almost exclusively gains, although control data sets will be required to determine possible disease relevance. We propose that somatic SNCA CNVs may contribute to the aetiology and pathogenesis of synucleinopathies, and that genome-wide somatic CNVs in MSA brain merit further study.
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Affiliation(s)
- Diego Perez-Rodriguez
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK
| | - Maria Kalyva
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK
| | - Melissa Leija-Salazar
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK
| | - Tammaryn Lashley
- Queen Square Brain Bank for Neurological disorders, UCL Queen Square Institute of Neurology, 1 Wakefield street, London, WC1N 1PJ, UK
| | - Maxime Tarabichi
- The Francis Crick Institute, Midland Road 1, London, NW1 1AT, UK
| | - Viorica Chelban
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
- National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG, UK
| | | | - Lucia Schottlaender
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
- National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG, UK
| | - Hannah Franklin
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK
| | - George Vasmatzis
- Center for Individualized Medicine, Department of Molecular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Henry Houlden
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
- National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG, UK
| | - Anthony H V Schapira
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK
| | - Thomas T Warner
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK
- Queen Square Brain Bank for Neurological disorders, UCL Queen Square Institute of Neurology, 1 Wakefield street, London, WC1N 1PJ, UK
- National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG, UK
| | - Janice L Holton
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK
- Queen Square Brain Bank for Neurological disorders, UCL Queen Square Institute of Neurology, 1 Wakefield street, London, WC1N 1PJ, UK
| | - Zane Jaunmuktane
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK
- Queen Square Brain Bank for Neurological disorders, UCL Queen Square Institute of Neurology, 1 Wakefield street, London, WC1N 1PJ, UK
- National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG, UK
| | - Christos Proukakis
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK.
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Oliver GR, Tang X, Schultz-Rogers LE, Vidal-Folch N, Jenkinson WG, Schwab TL, Gaonkar K, Cousin MA, Nair A, Basu S, Chanana P, Oglesbee D, Klee EW. A tailored approach to fusion transcript identification increases diagnosis of rare inherited disease. PLoS One 2019; 14:e0223337. [PMID: 31577830 PMCID: PMC6774566 DOI: 10.1371/journal.pone.0223337] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 09/18/2019] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND RNA sequencing has been proposed as a means of increasing diagnostic rates in studies of undiagnosed rare inherited disease. Recent studies have reported diagnostic improvements in the range of 7.5-35% by profiling splicing, gene expression quantification and allele specific expression. To-date however, no study has systematically assessed the presence of gene-fusion transcripts in cases of germline disease. Fusion transcripts are routinely identified in cancer studies and are increasingly recognized as having diagnostic, prognostic or therapeutic relevance. Isolated reports exist of fusion transcripts being detected in cases of developmental and neurological phenotypes, and thus, systematic application of fusion detection to germline conditions may further increase diagnostic rates. However, current fusion detection methods are unsuited to the investigation of germline disease due to performance biases arising from their development using tumor, cell-line or in-silico data. METHODS We describe a tailored approach to fusion candidate identification and prioritization in a cohort of 47 undiagnosed, suspected inherited disease patients. We modify an existing fusion transcript detection algorithm by eliminating its cell line-derived filtering steps, and instead, prioritize candidates using a custom workflow that integrates genomic and transcriptomic sequence alignment, biological and technical annotations, customized categorization logic, and phenotypic prioritization. RESULTS We demonstrate that our approach to fusion transcript identification and prioritization detects genuine fusion events excluded by standard analyses and efficiently removes phenotypically unimportant candidates and false positive events, resulting in a reduced candidate list enriched for events with potential phenotypic relevance. We describe the successful genetic resolution of two previously undiagnosed disease cases through the detection of pathogenic fusion transcripts. Furthermore, we report the experimental validation of five additional cases of fusion transcripts with potential phenotypic relevance. CONCLUSIONS The approach we describe can be implemented to enable the detection of phenotypically relevant fusion transcripts in studies of rare inherited disease. Fusion transcript detection has the potential to increase diagnostic rates in rare inherited disease and should be included in RNA-based analytical pipelines aimed at genetic diagnosis.
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Affiliation(s)
- Gavin R. Oliver
- Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Xiaojia Tang
- Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Laura E. Schultz-Rogers
- Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Noemi Vidal-Folch
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - W. Garrett Jenkinson
- Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Tanya L. Schwab
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Krutika Gaonkar
- Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Margot A. Cousin
- Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Asha Nair
- Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Shubham Basu
- Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Pritha Chanana
- Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Devin Oglesbee
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, United States of America
- Department of Medical Genetics, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Eric W. Klee
- Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, United States of America
- Department of Clinical Genomics, Mayo Clinic, Rochester, Minnesota, United States of America
- * E-mail:
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7
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Koltsova AS, Pendina AA, Efimova OA, Chiryaeva OG, Kuznetzova TV, Baranov VS. On the Complexity of Mechanisms and Consequences of Chromothripsis: An Update. Front Genet 2019; 10:393. [PMID: 31114609 PMCID: PMC6503150 DOI: 10.3389/fgene.2019.00393] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [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: 01/05/2019] [Accepted: 04/11/2019] [Indexed: 12/28/2022] Open
Abstract
In the present review, we focus on the phenomenon of chromothripsis, a new type of complex chromosomal rearrangements. We discuss the challenges of chromothripsis detection and its distinction from other chromoanagenesis events. Along with already known causes and mechanisms, we introduce aberrant epigenetic regulation as a possible pathway to chromothripsis. We address the issue of chromothripsis characteristics in cancers and benign tumours, as well as chromothripsis inheritance in cases of its occurrence in germ cells, zygotes and early embryos. Summarising the presented data on different phenotypic effect of chromothripsis, we assume that its consequences are most likely determined not by the chromosome shattering and reassembly themselves, but by the genome regions involved in the rearrangement.
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Affiliation(s)
- Alla S Koltsova
- D.O. Ott Research Institute of Obstetrics, Gynecology and Reproductology, Saint Petersburg, Russia.,Department of Genetics and Biotechnology, Saint Petersburg State University, Saint Petersburg, Russia
| | - Anna A Pendina
- D.O. Ott Research Institute of Obstetrics, Gynecology and Reproductology, Saint Petersburg, Russia
| | - Olga A Efimova
- D.O. Ott Research Institute of Obstetrics, Gynecology and Reproductology, Saint Petersburg, Russia
| | - Olga G Chiryaeva
- D.O. Ott Research Institute of Obstetrics, Gynecology and Reproductology, Saint Petersburg, Russia
| | - Tatyana V Kuznetzova
- D.O. Ott Research Institute of Obstetrics, Gynecology and Reproductology, Saint Petersburg, Russia
| | - Vladislav S Baranov
- D.O. Ott Research Institute of Obstetrics, Gynecology and Reproductology, Saint Petersburg, Russia.,Department of Genetics and Biotechnology, Saint Petersburg State University, Saint Petersburg, Russia
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Bagadia M, Chandradoss KR, Jain Y, Singh H, Lal M, Sandhu KS. Evolutionary Loss of Genomic Proximity to Conserved Noncoding Elements Impacted the Gene Expression Dynamics During Mammalian Brain Development. Genetics 2019; 211:1239-54. [PMID: 30796012 DOI: 10.1534/genetics.119.301973] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Accepted: 02/14/2019] [Indexed: 01/05/2023] Open
Abstract
Conserved noncoding elements (CNEs) have a significant regulatory influence on their neighboring genes. Loss of proximity to CNEs through genomic rearrangements can, therefore, impact the transcriptional states of the cognate genes. Yet, the evolutionary implications of such chromosomal alterations have not been studied. Through genome-wide analysis of CNEs and the cognate genes of representative species from five different mammalian orders, we observed a significant loss of genes' linear proximity to CNEs in the rat lineage. The CNEs and the genes losing proximity had a significant association with fetal, but not postnatal, brain development as assessed through ontology terms, developmental gene expression, chromatin marks, and genetic mutations. The loss of proximity to CNEs correlated with the independent evolutionary loss of fetus-specific upregulation of nearby genes in the rat brain. DNA breakpoints implicated in brain abnormalities of germline origin had significant representation between a CNE and the gene that exhibited loss of proximity, signifying the underlying developmental tolerance of genomic rearrangements that allowed the evolutionary splits of CNEs and the cognate genes in the rodent lineage. Our observations highlighted a nontrivial impact of chromosomal rearrangements in shaping the evolutionary dynamics of mammalian brain development and might explain the loss of brain traits, like cerebral folding of the cortex, in the rodent lineage.
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Piazza A, Heyer WD. Homologous Recombination and the Formation of Complex Genomic Rearrangements. Trends Cell Biol 2019; 29:135-149. [PMID: 30497856 PMCID: PMC6402879 DOI: 10.1016/j.tcb.2018.10.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 10/28/2018] [Accepted: 10/29/2018] [Indexed: 12/13/2022]
Abstract
The maintenance of genome integrity involves multiple independent DNA damage avoidance and repair mechanisms. However, the origin and pathways of the focal chromosomal reshuffling phenomena collectively referred to as chromothripsis remain mechanistically obscure. We discuss here the role, mechanisms, and regulation of homologous recombination (HR) in the formation of simple and complex chromosomal rearrangements. We emphasize features of the recently characterized multi-invasion (MI)-induced rearrangement (MIR) pathway which uniquely amplifies the initial DNA damage. HR intermediates and cellular contexts that endanger genomic stability are discussed as well as the emerging roles of various classes of nucleases in the formation of genome rearrangements. Long-read sequencing and improved mapping of repeats should enable better appreciation of the significance of recombination in generating genomic rearrangements.
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Affiliation(s)
- Aurèle Piazza
- Department of Microbiology and Molecular Genetics, University of California, Davis, CA 95616, USA; Spatial Regulation of Genomes, Department of Genomes and Genetics, Centre National de la Recherche Scientifique (CNRS) Unité Mixte de Recherche 3525, Institut Pasteur, 75015 Paris, France
| | - Wolf-Dietrich Heyer
- Department of Microbiology and Molecular Genetics, University of California, Davis, CA 95616, USA; Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA.
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10
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DU ZF, Li PF, Zhao JQ, Cao ZL, Li F, Ma JM, Qi XP. Genetic diagnosis of a Chinese multiple endocrine neoplasia type 2A family through whole genome sequencing. J Biosci 2017; 42:209-18. [PMID: 28569245 DOI: 10.1007/s12038-017-9686-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Approximately 98% of patients with multiple endocrine neoplasia type 2A (MEN 2A) have an identifiable RET mutation. Prophylactic or early total thyroidectomy or pheochromocytoma/parathyroid removal in patients can be preventative or curative and has become standard management. The general strategy for RET screening on family members at risk is to sequence the most commonly affected exons and, if negative, to extend sequencing to additional exons. However, different families with MEN 2A due to the same RET mutation often have significant variability in the clinical exhibition of disease and aggressiveness of the MTC, which implies additional genetic loci exsit beyond RET coding region. Whole genome sequencing (WGS) greatly expands the breadth of screening from genes associated with a particular disease to the whole genome and, potentially, all the information that the genome contains about diseases or traits. This is presumably due to additive effect of disease modifying factors. In this study, we performed WGS on a typical Chinese MEN 2A proband and identified the pathogenic RET p.C634R mutation. We also identified several neutral variants within RET and pheochromocytoma-related genes. Moreover, we found several interesting structural variants including genetic deletions (RSPO1, OVCH2 and AP3S1, etc.) and fusion transcripts (FSIP1-BAZ2A, etc.).
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11
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Lin CY, Shukla A, Grady JP, Fink JL, Dray E, Duijf PHG. Translocation Breakpoints Preferentially Occur in Euchromatin and Acrocentric Chromosomes. Cancers (Basel) 2018; 10:cancers10010013. [PMID: 29316705 PMCID: PMC5789363 DOI: 10.3390/cancers10010013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [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: 10/27/2017] [Revised: 12/11/2017] [Accepted: 01/05/2018] [Indexed: 12/12/2022] Open
Abstract
Chromosomal translocations drive the development of many hematological and some solid cancers. Several factors have been identified to explain the non-random occurrence of translocation breakpoints in the genome. These include chromatin density, gene density and CCCTC-binding factor (CTCF)/cohesin binding site density. However, such factors are at least partially interdependent. Using 13,844 and 1563 karyotypes from human blood and solid cancers, respectively, our multiple regression analysis only identified chromatin density as the primary statistically significant predictor. Specifically, translocation breakpoints preferentially occur in open chromatin. Also, blood and solid tumors show markedly distinct translocation signatures. Strikingly, translocation breakpoints occur significantly more frequently in acrocentric chromosomes than in non-acrocentric chromosomes. Thus, translocations are probably often generated around nucleoli in the inner nucleoplasm, away from the nuclear envelope. Importantly, our findings remain true both in multivariate analyses and after removal of highly recurrent translocations. Finally, we applied pairwise probabilistic co-occurrence modeling. In addition to well-known highly prevalent translocations, such as those resulting in BCR-ABL1 (BCR-ABL) and RUNX1-RUNX1T1 (AML1-ETO) fusion genes, we identified significantly underrepresented translocations with putative fusion genes, which are probably subject to strong negative selection during tumor evolution. Taken together, our findings provide novel insights into the generation and selection of translocations during cancer development.
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Affiliation(s)
- Cheng-Yu Lin
- University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
| | - Ankit Shukla
- University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
| | - John P Grady
- University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
| | - J Lynn Fink
- University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
| | - Eloise Dray
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
- Mater Research Institute-The University of Queensland, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
| | - Pascal H G Duijf
- University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
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12
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Zhao Y, Song WM, Zhang F, Zhou MM, Zhang W, Walsh MJ, Zhang B. Distinct distributions of genomic features of the 5’ and 3’ partners of coding somatic cancer gene fusions: arising mechanisms and functional implications. Oncotarget 2017; 8:66769-66783. [PMID: 28977995 PMCID: PMC5620135 DOI: 10.18632/oncotarget.10734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Accepted: 06/06/2016] [Indexed: 11/25/2022] Open
Abstract
The genomic features and arising mechanisms of coding cancer somatic gene fusions (CSGFs) largely remain elusive. In this study, we show the gene origin stratification pattern of CSGF partners that fusion partners in human cancers are significantly enriched for genes with the gene age ofEuteleostomes and with the gene family age of Bilateria. GC skew (a measurement of G, C nucleotide content bias, (G-C)/(G+C)) is a useful measurement to indicate the DNA leading strand, lagging strand, replication origin, and replication terminal and DNA-RNA R-loop formation. We find that GC skew bias at the 5 prime (5′) but not the 3 prime (3’) partners of CSGFs, coincident with the polarity feature of gene expression breadth that the 5’ partners are more ubiquitous while the 3’ fusion partners are more tissue specific in general. We reveal distinct length and composition distributions of 5’ and 3’ of CSGFs, including sequence features corresponded to the 5’ untranslated regions (UTRs), 3’ UTRs, and the N-terminal sequences of the encoded proteins. Oncogenic somatic gene fusions are most enriched for the 5’ and 3’ genes’ somatic amplification alongside a substantial proportion of other types of combinations. At the function level, 5’ partners of CSGFs appear more likely to be tumour suppressor genes while many 3’ partners appear to be proto-oncogene. Such distinct polarities of CSGFs at the evolutionary, structural, genomic and functional levels indicate the heterogeneous arsing mechanisms of CSGFs including R-loops and suggest potential novel targeted therapeutics specific to CSGF functional categories.
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Affiliation(s)
- Yongzhong Zhao
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, NY 10029, USA
- Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, NY 10029, USA
| | - Won-Min Song
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, NY 10029, USA
- Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, NY 10029, USA
| | - Fan Zhang
- Department of Medicine, Icahn School of Medicine at Mount Sinai, NY 10029, USA
| | - Ming-Ming Zhou
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, NY 10029, USA
| | - Weijia Zhang
- Department of Medicine, Icahn School of Medicine at Mount Sinai, NY 10029, USA
| | - Martin J. Walsh
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, NY 10029, USA
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, NY 10029, USA
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Bin Zhang
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, NY 10029, USA
- Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, NY 10029, USA
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13
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Middelkamp S, van Heesch S, Braat AK, de Ligt J, van Iterson M, Simonis M, van Roosmalen MJ, Kelder MJE, Kruisselbrink E, Hochstenbach R, Verbeek NE, Ippel EF, Adolfs Y, Pasterkamp RJ, Kloosterman WP, Kuijk EW, Cuppen E. Molecular dissection of germline chromothripsis in a developmental context using patient-derived iPS cells. Genome Med 2017; 9:9. [PMID: 28126037 PMCID: PMC5270341 DOI: 10.1186/s13073-017-0399-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [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: 07/12/2016] [Accepted: 01/06/2017] [Indexed: 12/18/2022] Open
Abstract
Background Germline chromothripsis causes complex genomic rearrangements that are likely to affect multiple genes and their regulatory contexts. The contribution of individual rearrangements and affected genes to the phenotypes of patients with complex germline genomic rearrangements is generally unknown. Methods To dissect the impact of germline chromothripsis in a relevant developmental context, we performed trio-based RNA expression analysis on blood cells, induced pluripotent stem cells (iPSCs), and iPSC-derived neuronal cells from a patient with de novo germline chromothripsis and both healthy parents. In addition, Hi-C and 4C-seq experiments were performed to determine the effects of the genomic rearrangements on transcription regulation of genes in the proximity of the breakpoint junctions. Results Sixty-seven genes are located within 1 Mb of the complex chromothripsis rearrangements involving 17 breakpoints on four chromosomes. We find that three of these genes (FOXP1, DPYD, and TWIST1) are both associated with developmental disorders and differentially expressed in the patient. Interestingly, the effect on TWIST1 expression was exclusively detectable in the patient’s iPSC-derived neuronal cells, stressing the need for studying developmental disorders in the biologically relevant context. Chromosome conformation capture analyses show that TWIST1 lost genomic interactions with several enhancers due to the chromothripsis event, which likely led to deregulation of TWIST1 expression and contributed to the patient’s craniosynostosis phenotype. Conclusions We demonstrate that a combination of patient-derived iPSC differentiation and trio-based molecular profiling is a powerful approach to improve the interpretation of pathogenic complex genomic rearrangements. Here we have applied this approach to identify misexpression of TWIST1, FOXP1, and DPYD as key contributors to the complex congenital phenotype resulting from germline chromothripsis rearrangements. Electronic supplementary material The online version of this article (doi:10.1186/s13073-017-0399-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sjors Middelkamp
- Center for Molecular Medicine and Cancer Genomics Netherlands, Division Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, Utrecht, 3584CG, The Netherlands
| | - Sebastiaan van Heesch
- Center for Molecular Medicine and Cancer Genomics Netherlands, Division Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, Utrecht, 3584CG, The Netherlands.,Cardiovascular and Metabolic Sciences, Max-Delbrück-Center for Molecular Medicine (MDC) in the Helmholtz Association, Robert-Rössle-Strasse 10, Berlin, 13125, Germany
| | - A Koen Braat
- Department of Cell Biology, Center for Molecular Medicine and Regenerative Medicine Center, University Medical Center Utrecht, Uppsalalaan 6, Utrecht, 3584CT, The Netherlands
| | - Joep de Ligt
- Center for Molecular Medicine and Cancer Genomics Netherlands, Division Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, Utrecht, 3584CG, The Netherlands
| | - Maarten van Iterson
- Department of Molecular Epidemiology, Leiden University Medical Center, Einthovenweg 20, Leiden, 2333ZC, The Netherlands
| | - Marieke Simonis
- Cergentis B.V., Yalelaan 62, Utrecht, 3584CM, The Netherlands
| | - Markus J van Roosmalen
- Center for Molecular Medicine and Cancer Genomics Netherlands, Division Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, Utrecht, 3584CG, The Netherlands
| | - Martijn J E Kelder
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Road, Edinburgh, EH4 2XU, UK
| | - Evelien Kruisselbrink
- Department of Pediatric Pulmonology & Laboratory of Translational Immunology, Wilhelmina Children's Hospital, University Medical Centre, Lundlaan 6, Utrecht, 3584EA, The Netherlands
| | - Ron Hochstenbach
- Center for Molecular Medicine and Cancer Genomics Netherlands, Division Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, Utrecht, 3584CG, The Netherlands
| | - Nienke E Verbeek
- Department of Genetics, University Medical Center Utrecht, Lundlaan 6, Utrecht, 3584EA, The Netherlands
| | - Elly F Ippel
- Department of Genetics, University Medical Center Utrecht, Lundlaan 6, Utrecht, 3584EA, The Netherlands
| | - Youri Adolfs
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Universiteitsweg 100, Utrecht, 3584CG, The Netherlands
| | - R Jeroen Pasterkamp
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Universiteitsweg 100, Utrecht, 3584CG, The Netherlands
| | - Wigard P Kloosterman
- Center for Molecular Medicine and Cancer Genomics Netherlands, Division Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, Utrecht, 3584CG, The Netherlands
| | - Ewart W Kuijk
- Center for Molecular Medicine and Cancer Genomics Netherlands, Division Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, Utrecht, 3584CG, The Netherlands.
| | - Edwin Cuppen
- Center for Molecular Medicine and Cancer Genomics Netherlands, Division Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, Utrecht, 3584CG, The Netherlands.
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14
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Pavlistova L, Izakova S, Zemanova Z, Bartuskova L, Langova M, Malikova P, Michalova K. Rare congenital chromosomal aberration dic(X;Y)(p22.33;p11.32) in a patient with primary myelofibrosis. Mol Cytogenet 2016; 9:67. [PMID: 27588041 PMCID: PMC5007838 DOI: 10.1186/s13039-016-0276-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [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: 07/04/2016] [Accepted: 08/09/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Constitutional translocations between sex chromosomes are rather rare in humans with breakpoints at Xp11 and Yq11 as the most frequent. Breakpoints on the short arm of the Y chromosome form one subgroup of t(X;Y), giving rise to a derived chromosome with the centromeres of both the X and Y chromosomes, dic(X;Y). Here, we report a rare congenital chromosomal aberration, 46,X,dic(X;Y)(p22.33;p11.32)[20]/45,X[10], in an adult male. CASE PRESENTATION Primary myelofibrosis, a malignant haematological disease, was diagnosed in a 63-year-old man following liver transplantation after hepatocellular carcinoma. By the analysis of the bone marrow sample, the karyotype 46,X,dic(X;Y)(p22.33;p11.32) was detected in all the mitoses analysed and verified with multicolour fluorescence in situ hybridization (mFISH). A cytogenetic examination of stimulated peripheral blood cells revealed the constitutional karyotype 46,X,dic(X;Y)(p22.33;p11.32)[20]/45,X[10]. The cell line 45,X was confirmed with FISH in 35 % of interphase nuclei. The SRY locus was present on the dicentric chromosome. A CGH/SNP array (Illumina) revealed a gain of 153,7 Mbp of the X chromosome and a 803-kbp microdeletion (including the SHOX gene), which were also confirmed with FISH. SHOX encodes a transcriptional factor that regulates the growth of the long bones. The deletion of the SHOX gene together with the Madelung deformity of the forearm and the short stature of the proband led to a diagnosis of Léri-Weill dyschondrosteosis (LWD). The gain of almost the whole X chromosome (153,7 Mbp) was considered a variant of Klinefelter syndrome (KS). The levels of gonadotropins and testosterone were consistent with gonadal dysfunction. A malformation of the right external ear was detected. CONCLUSIONS We have reported a structural aberration of the sex chromosomes, dic(X;Y)(p22.33;p11.32). The related genomic imbalance is associated with two known hereditary syndromes, LWD and a KS variant, identified in our proband at an advanced age. Because the breakpoints did not involve cancer genes, we inferred that the two malignancies in the proband were not caused by this abnormality. The possible influence of SHOX haploinsufficiency on the growth regulation of auricular chondrocytes is discussed.
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Affiliation(s)
- Lenka Pavlistova
- Center of Oncocytogenetics, Institute of Medical Biochemistry and Laboratory Diagnostics, General University Hospital and First Faculty of Medicine of Charles University, U Nemocnice 499/2, Prague 2, 128 08 Czech Republic
| | - Silvia Izakova
- Center of Oncocytogenetics, Institute of Medical Biochemistry and Laboratory Diagnostics, General University Hospital and First Faculty of Medicine of Charles University, U Nemocnice 499/2, Prague 2, 128 08 Czech Republic
| | - Zuzana Zemanova
- Center of Oncocytogenetics, Institute of Medical Biochemistry and Laboratory Diagnostics, General University Hospital and First Faculty of Medicine of Charles University, U Nemocnice 499/2, Prague 2, 128 08 Czech Republic
| | - Lucie Bartuskova
- Center of Oncocytogenetics, Institute of Medical Biochemistry and Laboratory Diagnostics, General University Hospital and First Faculty of Medicine of Charles University, U Nemocnice 499/2, Prague 2, 128 08 Czech Republic
| | - Martina Langova
- Department of Medical Genetics, Faculty Thomayer's Hospital, Vídeňská 800, 140 00 Prague 4, Czech Republic
| | - Pavlina Malikova
- Department of Clinical Hematology IKEM, Vídeňská 1958/9, 140 21 Prague 4, Czech Republic
| | - Kyra Michalova
- Center of Oncocytogenetics, Institute of Medical Biochemistry and Laboratory Diagnostics, General University Hospital and First Faculty of Medicine of Charles University, U Nemocnice 499/2, Prague 2, 128 08 Czech Republic ; Department of Cytogenetics, Institute of Hematology and Blood Transfusion, U Nemocnice 1, 128 08 Prague 2, Czech Republic
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15
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Storchová Z, Kloosterman WP. The genomic characteristics and cellular origin of chromothripsis. Curr Opin Cell Biol 2016; 40:106-113. [PMID: 27023493 DOI: 10.1016/j.ceb.2016.03.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 02/19/2016] [Accepted: 03/05/2016] [Indexed: 01/25/2023]
Abstract
Human genomes are continuously subjected to mutations, which can drive genetic diseases and cancer. An intriguing recent finding has been the discovery of chromothripsis, a spectacular and complex form of chromosome rearrangement that can occur in the genomes of cancer cells and patients with congenital diseases. Chromothripsis has been described in a large array of human cancers and various types of chromothripsis have appeared, which differ in complexity and genomic hallmarks. From the combined genomic data a consensus hypothesis has been inferred, involving aberrant DNA replication and chromosome shattering as the underlying processes explaining chromothripsis. In addition, recent work has established several cellular models that recapitulate chromothripsis under defined experimental conditions. One of these models indicates that chromothripsis can originate from DNA damage in micronuclei, providing an elegant explanation for the restriction of chromothriptic rearrangements to a single chromosome. Alternatively, chromothripsis can be caused by telomere crisis, a process that involves formation of dicentric chromosomes and chromatin bridges. Here, we summarize the genomic features of chromothripsis and we discuss experimental approaches that allow dissection of the chromothripsis process.
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Affiliation(s)
- Zuzana Storchová
- Group Maintenance of Genome Stability, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany; Department of Molecular Genetics, University of Kaiserslautern, Paul-Ehrlich Str. 24, 67653 Kaiserslautern, Germany
| | - Wigard P Kloosterman
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands.
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16
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Poot M. Gene Fusion due to Chromosome Misconnection May Seriously Affect Your Health. Mol Syndromol 2015; 6:55-7. [PMID: 26279648 DOI: 10.1159/000381081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/09/2015] [Indexed: 11/19/2022] Open
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17
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Poot M, Haaf T. Mechanisms of Origin, Phenotypic Effects and Diagnostic Implications of Complex Chromosome Rearrangements. Mol Syndromol 2015; 6:110-34. [PMID: 26732513 DOI: 10.1159/000438812] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/23/2015] [Indexed: 01/08/2023] Open
Abstract
Complex chromosome rearrangements (CCRs) are currently defined as structural genome variations that involve more than 2 chromosome breaks and result in exchanges of chromosomal segments. They are thought to be extremely rare, but their detection rate is rising because of improvements in molecular cytogenetic technology. Their population frequency is also underestimated, since many CCRs may not elicit a phenotypic effect. CCRs may be the result of fork stalling and template switching, microhomology-mediated break-induced repair, breakage-fusion-bridge cycles, or chromothripsis. Patients with chromosomal instability syndromes show elevated rates of CCRs due to impaired DNA double-strand break responses during meiosis. Therefore, the putative functions of the proteins encoded by ATM, BLM, WRN, ATR, MRE11, NBS1, and RAD51 in preventing CCRs are discussed. CCRs may exert a pathogenic effect by either (1) gene dosage-dependent mechanisms, e.g. haploinsufficiency, (2) mechanisms based on disruption of the genomic architecture, such that genes, parts of genes or regulatory elements are truncated, fused or relocated and thus their interactions disturbed - these mechanisms will predominantly affect gene expression - or (3) mixed mutation mechanisms in which a CCR on one chromosome is combined with a different type of mutation on the other chromosome. Such inferred mechanisms of pathogenicity need corroboration by mRNA sequencing. Also, future studies with in vitro models, such as inducible pluripotent stem cells from patients with CCRs, and transgenic model organisms should substantiate current inferences regarding putative pathogenic effects of CCRs. The ramifications of the growing body of information on CCRs for clinical and experimental genetics and future treatment modalities are briefly illustrated with 2 cases, one of which suggests KDM4C (JMJD2C) as a novel candidate gene for mental retardation.
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Affiliation(s)
- Martin Poot
- Department of Human Genetics, University of Würzburg, Würzburg, Germany
| | - Thomas Haaf
- Department of Human Genetics, University of Würzburg, Würzburg, Germany
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18
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Abstract
Chromosome structural variation (SV) is a normal part of variation in the human genome, but some classes of SV can cause neurodevelopmental disorders. Analysis of the DNA sequence at SV breakpoints can reveal mutational mechanisms and risk factors for chromosome rearrangement. Large-scale SV breakpoint studies have become possible recently owing to advances in next-generation sequencing (NGS) including whole-genome sequencing (WGS). These findings have shed light on complex forms of SV such as triplications, inverted duplications, insertional translocations, and chromothripsis. Sequence-level breakpoint data resolve SV structure and determine how genes are disrupted, fused, and/or misregulated by breakpoints. Recent improvements in breakpoint sequencing have also revealed non-allelic homologous recombination (NAHR) between paralogous long interspersed nuclear element (LINE) or human endogenous retrovirus (HERV) repeats as a cause of deletions, duplications, and translocations. This review covers the genomic organization of simple and complex constitutional SVs, as well as the molecular mechanisms of their formation.
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Affiliation(s)
- Brooke Weckselblatt
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - M Katharine Rudd
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA.
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19
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Weckselblatt B, Hermetz KE, Rudd MK. Unbalanced translocations arise from diverse mutational mechanisms including chromothripsis. Genome Res 2015; 25:937-47. [PMID: 26070663 PMCID: PMC4484391 DOI: 10.1101/gr.191247.115] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 05/15/2015] [Indexed: 12/17/2022]
Abstract
Unbalanced translocations are a relatively common type of copy number variation and a major contributor to neurodevelopmental disorders. We analyzed the breakpoints of 57 unique unbalanced translocations to investigate the mechanisms of how they form. Fifty-one are simple unbalanced translocations between two different chromosome ends, and six rearrangements have more than three breakpoints involving two to five chromosomes. Sequencing 37 breakpoint junctions revealed that simple translocations have between 0 and 4 base pairs (bp) of microhomology (n = 26), short inserted sequences (n = 8), or paralogous repeats (n = 3) at the junctions, indicating that translocations do not arise primarily from nonallelic homologous recombination but instead form most often via nonhomologous end joining or microhomology-mediated break-induced replication. Three simple translocations fuse genes that are predicted to produce in-frame transcripts of SIRPG-WWOX, SMOC2-PROX1, and PIEZO2-MTA1, which may lead to gain of function. Three complex translocations have inversions, insertions, and multiple breakpoint junctions between only two chromosomes. Whole-genome sequencing and fluorescence in situ hybridization analysis of two de novo translocations revealed at least 18 and 33 breakpoints involving five different chromosomes. Breakpoint sequencing of one maternally inherited translocation involving four chromosomes uncovered multiple breakpoints with inversions and insertions. All of these breakpoint junctions had 0–4 bp of microhomology consistent with chromothripsis, and both de novo events occurred on paternal alleles. Together with other studies, these data suggest that germline chromothripsis arises in the paternal genome and may be transmitted maternally. Breakpoint sequencing of our large collection of chromosome rearrangements provides a comprehensive analysis of the molecular mechanisms behind translocation formation.
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Affiliation(s)
- Brooke Weckselblatt
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | - Karen E Hermetz
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | - M Katharine Rudd
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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