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Bodea GO, Botto JM, Ferreiro ME, Sanchez-Luque FJ, de Los Rios Barreda J, Rasmussen J, Rahman MA, Fenlon LR, Jansz N, Gubert C, Gerdes P, Bodea LG, Ajjikuttira P, Da Costa Guevara DJ, Cumner L, Bell CC, Kozulin P, Billon V, Morell S, Kempen MJHC, Love CJ, Saha K, Palmer LM, Ewing AD, Jhaveri DJ, Richardson SR, Hannan AJ, Faulkner GJ. LINE-1 retrotransposons contribute to mouse PV interneuron development. Nat Neurosci 2024:10.1038/s41593-024-01650-2. [PMID: 38773348 DOI: 10.1038/s41593-024-01650-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 04/14/2024] [Indexed: 05/23/2024]
Abstract
Retrotransposons are mobile DNA sequences duplicated via transcription and reverse transcription of an RNA intermediate. Cis-regulatory elements encoded by retrotransposons can also promote the transcription of adjacent genes. Somatic LINE-1 (L1) retrotransposon insertions have been detected in mammalian neurons. It is, however, unclear whether L1 sequences are mobile in only some neuronal lineages or therein promote neurodevelopmental gene expression. Here we report programmed L1 activation by SOX6, a transcription factor critical for parvalbumin (PV) interneuron development. Mouse PV interneurons permit L1 mobilization in vitro and in vivo, harbor unmethylated L1 promoters and express full-length L1 mRNAs and proteins. Using nanopore long-read sequencing, we identify unmethylated L1s proximal to PV interneuron genes, including a novel L1 promoter-driven Caps2 transcript isoform that enhances neuron morphological complexity in vitro. These data highlight the contribution made by L1 cis-regulatory elements to PV interneuron development and transcriptome diversity, uncovered due to L1 mobility in this milieu.
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Affiliation(s)
- Gabriela O Bodea
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia.
- Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, Queensland, Australia.
| | - Juan M Botto
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
| | - Maria E Ferreiro
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
| | - Francisco J Sanchez-Luque
- Institute of Parasitology and Biomedicine 'López-Neyra', Spanish National Research Council, Granada, Spain
| | | | - Jay Rasmussen
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
| | - Muhammed A Rahman
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
| | - Laura R Fenlon
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
| | - Natasha Jansz
- Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, Queensland, Australia
| | - Carolina Gubert
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Patricia Gerdes
- Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, Queensland, Australia
| | - Liviu-Gabriel Bodea
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
| | - Prabha Ajjikuttira
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
| | - Darwin J Da Costa Guevara
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
- Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, Queensland, Australia
| | - Linda Cumner
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
| | - Charles C Bell
- Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, Queensland, Australia
| | - Peter Kozulin
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
| | - Victor Billon
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
- Biology Department, École Normale Supérieure Paris-Saclay, Gif-sur-Yvette, France
| | - Santiago Morell
- Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, Queensland, Australia
- Department of Genetics, University of Cambridge, Cambridge, UK
| | - Marie-Jeanne H C Kempen
- MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh, Western General Hospital, Edinburgh, UK
| | - Chloe J Love
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Karabi Saha
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, USA
| | - Lucy M Palmer
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
- Florey Department of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Adam D Ewing
- Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, Queensland, Australia
| | - Dhanisha J Jhaveri
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
- Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, Queensland, Australia
| | - Sandra R Richardson
- Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, Queensland, Australia
| | - Anthony J Hannan
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Geoffrey J Faulkner
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia.
- Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, Queensland, Australia.
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2
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Toda T, Bedrosian TA, Schafer ST, Cuoco MS, Linker SB, Ghassemzadeh S, Mitchell L, Whiteley JT, Novaresi N, McDonald AH, Gallina IS, Yoon H, Hester ME, Pena M, Lim C, Suljic E, AlFatah Mansour A, Boulard M, Parylak SL, Gage FH. Long interspersed nuclear elements safeguard neural progenitors from precocious differentiation. Cell Rep 2024; 43:113774. [PMID: 38349791 PMCID: PMC10948021 DOI: 10.1016/j.celrep.2024.113774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Revised: 11/30/2023] [Accepted: 01/24/2024] [Indexed: 02/15/2024] Open
Abstract
Long interspersed nuclear element-1 (L1 or LINE-1) is a highly abundant mobile genetic element in both humans and mice, comprising almost 20% of each genome. L1s are silenced by several mechanisms, as their uncontrolled expression has the potential to induce genomic instability. However, L1s are paradoxically expressed at high levels in differentiating neural progenitor cells. Using in vitro and in vivo techniques to modulate L1 expression, we report that L1s play a critical role in both human and mouse brain development by regulating the rate of neural differentiation in a reverse-transcription-independent manner.
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Affiliation(s)
- Tomohisa Toda
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA; Laboratory of Neural Epigenomics, Institute of Medical Physics and Micro-tissue Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany; Nuclear Architecture in Neural Plasticity and Aging Laboratory, German Center for Neurodegenerative Diseases, 01307 Dresden, Germany.
| | - Tracy A Bedrosian
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA; Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Simon T Schafer
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA; Department of Psychiatry and Psychotherapy, School of Medicine and Health, Technical University of Munich, Munich, Germany; TUM Center for Organoid Systems (COS), Munich Institute of Biomedical Engineering, Garching, Germany
| | - Michael S Cuoco
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA; Computational Neural DNA Dynamics Lab, Department of Cognitive Science, University of California, San Diego, San Diego, CA, USA; Bioinformatics and Systems Biology Graduate Program, University of California, San Diego, San Diego, CA, USA
| | - Sara B Linker
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Saeed Ghassemzadeh
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Lisa Mitchell
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Jack T Whiteley
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Nicole Novaresi
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Aidan H McDonald
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Iryna S Gallina
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Hyojung Yoon
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Mark E Hester
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Monique Pena
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA; Department of Psychiatry and Psychotherapy, School of Medicine and Health, Technical University of Munich, Munich, Germany; TUM Center for Organoid Systems (COS), Munich Institute of Biomedical Engineering, Garching, Germany
| | - Christina Lim
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Emelia Suljic
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Abed AlFatah Mansour
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Matthieu Boulard
- Epigenetics & Neurobiology Unit, EMBL Rome, European Molecular Biology Laboratory, Via Ramarini 32, 00015 Monterotondo, Italy
| | - Sarah L Parylak
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Fred H Gage
- Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
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3
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Bona N, Crossan GP. Fanconi anemia DNA crosslink repair factors protect against LINE-1 retrotransposition during mouse development. Nat Struct Mol Biol 2023; 30:1434-1445. [PMID: 37580626 PMCID: PMC10584689 DOI: 10.1038/s41594-023-01067-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 07/13/2023] [Indexed: 08/16/2023]
Abstract
Long interspersed nuclear element 1 (LINE-1) is the only autonomous retrotransposon in humans and new integrations are a major source of genetic variation between individuals. These events can also lead to de novo germline mutations, giving rise to heritable genetic diseases. Recently, a role for DNA repair in regulating these events has been identified. Here we find that Fanconi anemia (FA) DNA crosslink repair factors act in a common pathway to prevent retrotransposition. We purify recombinant SLX4-XPF-ERCC1, the crosslink repair incision complex, and find that it cleaves putative nucleic acid intermediates of retrotransposition. Mice deficient in upstream crosslink repair signaling (FANCA), a downstream component (FANCD2) or the nuclease XPF-ERCC1 show increased LINE-1 retrotransposition in vivo. Organisms limit retrotransposition through transcriptional silencing but this protection is attenuated during early development leaving the zygote vulnerable. We find that during this window of vulnerability, DNA crosslink repair acts as a failsafe to prevent retrotransposition. Together, our results indicate that the FA DNA crosslink repair pathway acts together to protect against mutation by restricting LINE-1 retrotransposition.
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4
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Lee Y, Ha U, Moon S. Ongoing endeavors to detect mobilization of transposable elements. BMB Rep 2022. [PMID: 35725016 PMCID: PMC9340088 DOI: 10.5483/bmbrep.2022.55.7.088] [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] [Indexed: 11/20/2022] Open
Abstract
Transposable elements (TEs) are DNA sequences capable of mobilization from one location to another in the genome. Since the discovery of ‘Dissociation (Dc) locus’ by Barbara McClintock in maize (1), mounting evidence in the era of genomics indicates that a significant fraction of most eukaryotic genomes is composed of TE sequences, involving in various aspects of biological processes such as development, physiology, diseases and evolution. Although technical advances in genomics have discovered numerous functional impacts of TE across species, our understanding of TEs is still ongoing process due to challenges resulted from complexity and abundance of TEs in the genome. In this mini-review, we briefly summarize biology of TEs and their impacts on the host genome, emphasizing importance of understanding TE landscape in the genome. Then, we introduce recent endeavors especially in vivo retrotransposition assays and long read sequencing technology for identifying de novo insertions/TE polymorphism, which will broaden our knowledge of extraordinary relationship between genomic cohabitants and their host.
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Affiliation(s)
- Yujeong Lee
- Department of Biological Sciences, Kangwon National University, Chuncheon 24341, Korea
| | - Una Ha
- Department of Biological Sciences, Kangwon National University, Chuncheon 24341, Korea
| | - Sungjin Moon
- Department of Biological Sciences, Kangwon National University, Chuncheon 24341, Korea
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5
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Abstract
Transposable elements (TEs) are mobile sequences that engender widespread mutations and thus are a major hazard that must be silenced. The most abundant active class of TEs in mammalian genomes is long interspersed element class 1 (LINE1). Here, we report that LINE1 transposition is suppressed in the male germline by transcription factors encoded by a rapidly evolving X-linked homeobox gene cluster. LINE1 transposition is repressed by many members of this RHOX transcription factor family, including those with different patterns of expression during spermatogenesis. One family member-RHOX10-suppresses LINE1 transposition during fetal development in vivo when the germline would otherwise be susceptible to LINE1 activation because of epigenetic reprogramming. We provide evidence that RHOX10 suppresses LINE transposition by inducing Piwil2, which encodes a key component in the Piwi-interacting RNA pathway that protects against TEs. The ability of RHOX transcription factors to suppress LINE1 is conserved in humans but is lost in RHOXF2 mutants from several infertile human patients, raising the possibility that loss of RHOXF2 causes human infertility by allowing uncontrolled LINE1 expression in the germline. Together, our results support a model in which the Rhox gene cluster is in an evolutionary arms race with TEs, resulting in expansion of the Rhox gene cluster to suppress TEs in different biological contexts.
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6
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Chen D, Cremona MA, Qi Z, Mitra RD, Chiaromonte F, Makova KD. Human L1 Transposition Dynamics Unraveled with Functional Data Analysis. Mol Biol Evol 2021; 37:3576-3600. [PMID: 32722770 DOI: 10.1093/molbev/msaa194] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Long INterspersed Elements-1 (L1s) constitute >17% of the human genome and still actively transpose in it. Characterizing L1 transposition across the genome is critical for understanding genome evolution and somatic mutations. However, to date, L1 insertion and fixation patterns have not been studied comprehensively. To fill this gap, we investigated three genome-wide data sets of L1s that integrated at different evolutionary times: 17,037 de novo L1s (from an L1 insertion cell-line experiment conducted in-house), and 1,212 polymorphic and 1,205 human-specific L1s (from public databases). We characterized 49 genomic features-proxying chromatin accessibility, transcriptional activity, replication, recombination, etc.-in the ±50 kb flanks of these elements. These features were contrasted between the three L1 data sets and L1-free regions using state-of-the-art Functional Data Analysis statistical methods, which treat high-resolution data as mathematical functions. Our results indicate that de novo, polymorphic, and human-specific L1s are surrounded by different genomic features acting at specific locations and scales. This led to an integrative model of L1 transposition, according to which L1s preferentially integrate into open-chromatin regions enriched in non-B DNA motifs, whereas they are fixed in regions largely free of purifying selection-depleted of genes and noncoding most conserved elements. Intriguingly, our results suggest that L1 insertions modify local genomic landscape by extending CpG methylation and increasing mononucleotide microsatellite density. Altogether, our findings substantially facilitate understanding of L1 integration and fixation preferences, pave the way for uncovering their role in aging and cancer, and inform their use as mutagenesis tools in genetic studies.
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Affiliation(s)
- Di Chen
- Intercollege Graduate Degree Program in Genetics, The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Marzia A Cremona
- Department of Statistics, The Pennsylvania State University, University Park, PA.,Department of Operations and Decision Systems, Université Laval, Québec, Canada
| | - Zongtai Qi
- Department of Genetics and Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, MO
| | - Robi D Mitra
- Department of Genetics and Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, MO
| | - Francesca Chiaromonte
- Department of Statistics, The Pennsylvania State University, University Park, PA.,EMbeDS, Sant'Anna School of Advanced Studies, Pisa, Italy.,The Huck Institutes of the Life Sciences, Center for Medical Genomics, The Pennsylvania State University, University Park, PA
| | - Kateryna D Makova
- The Huck Institutes of the Life Sciences, Center for Medical Genomics, The Pennsylvania State University, University Park, PA.,Department of Biology, The Pennsylvania State University, University Park, PA
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7
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Gu Z, Liu Y, Zhang Y, Cao H, Lyu J, Wang X, Wylie A, Newkirk SJ, Jones AE, Lee M, Botten GA, Deng M, Dickerson KE, Zhang CC, An W, Abrams JM, Xu J. Silencing of LINE-1 retrotransposons is a selective dependency of myeloid leukemia. Nat Genet 2021; 53:672-682. [PMID: 33833453 PMCID: PMC8270111 DOI: 10.1038/s41588-021-00829-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 02/26/2021] [Indexed: 02/07/2023]
Abstract
Transposable elements or transposons are major players in genetic variability and genome evolution. Aberrant activation of long interspersed element-1 (LINE-1 or L1) retrotransposons is common in human cancers, yet their tumor-type-specific functions are poorly characterized. We identified MPHOSPH8/MPP8, a component of the human silencing hub (HUSH) complex, as an acute myeloid leukemia (AML)-selective dependency by epigenetic regulator-focused CRISPR screening. Although MPP8 is dispensable for steady-state hematopoiesis, MPP8 loss inhibits AML development by reactivating L1s to induce the DNA damage response and cell cycle exit. Activation of endogenous or ectopic L1s mimics the phenotype of MPP8 loss, whereas blocking retrotransposition abrogates MPP8-deficiency-induced phenotypes. Expression of AML oncogenic mutations promotes L1 suppression, and enhanced L1 silencing is associated with poor prognosis in human AML. Hence, while retrotransposons are commonly recognized for their cancer-promoting functions, we describe a tumor-suppressive role for L1 retrotransposons in myeloid leukemia.
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Affiliation(s)
- Zhimin Gu
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Pediatrics, Harold C. Simmons Comprehensive Cancer Center and Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Yuxuan Liu
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Pediatrics, Harold C. Simmons Comprehensive Cancer Center and Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Yuannyu Zhang
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Pediatrics, Harold C. Simmons Comprehensive Cancer Center and Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Hui Cao
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Pediatrics, Harold C. Simmons Comprehensive Cancer Center and Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Junhua Lyu
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Pediatrics, Harold C. Simmons Comprehensive Cancer Center and Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Xun Wang
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Annika Wylie
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Simon J Newkirk
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, USA
| | - Amanda E Jones
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Michael Lee
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Pediatrics, Harold C. Simmons Comprehensive Cancer Center and Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Giovanni A Botten
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Pediatrics, Harold C. Simmons Comprehensive Cancer Center and Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Mi Deng
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Kathryn E Dickerson
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Pediatrics, Harold C. Simmons Comprehensive Cancer Center and Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Cheng Cheng Zhang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Wenfeng An
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, USA
| | - John M Abrams
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jian Xu
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Department of Pediatrics, Harold C. Simmons Comprehensive Cancer Center and Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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8
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Kayesh MEH, Hashem MA, Tsukiyama-Kohara K. Toll-Like Receptor and Cytokine Responses to Infection with Endogenous and Exogenous Koala Retrovirus, and Vaccination as a Control Strategy. Curr Issues Mol Biol 2021; 43:52-64. [PMID: 33946297 PMCID: PMC8928999 DOI: 10.3390/cimb43010005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 04/28/2021] [Accepted: 04/28/2021] [Indexed: 02/07/2023] Open
Abstract
Koala populations are currently declining and under threat from koala retrovirus (KoRV) infection both in the wild and in captivity. KoRV is assumed to cause immunosuppression and neoplastic diseases, favoring chlamydiosis in koalas. Currently, 10 KoRV subtypes have been identified, including an endogenous subtype (KoRV-A) and nine exogenous subtypes (KoRV-B to KoRV-J). The host’s immune response acts as a safeguard against pathogens. Therefore, a proper understanding of the immune response mechanisms against infection is of great importance for the host’s survival, as well as for the development of therapeutic and prophylactic interventions. A vaccine is an important protective as well as being a therapeutic tool against infectious disease, and several studies have shown promise for the development of an effective vaccine against KoRV. Moreover, CRISPR/Cas9-based genome editing has opened a new window for gene therapy, and it appears to be a potential therapeutic tool in many viral infections, which could also be investigated for the treatment of KoRV infection. Here, we discuss the recent advances made in the understanding of the immune response in KoRV infection, as well as the progress towards vaccine development against KoRV infection in koalas.
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Affiliation(s)
- Mohammad Enamul Hoque Kayesh
- Transboundary Animal Diseases Centre, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima 890-0065, Japan; (M.E.H.K.); (M.A.H.)
- Department of Microbiology and Public Health, Faculty of Animal Science and Veterinary Medicine, Patuakhali Science and Technology University, Barishal 8210, Bangladesh
| | - Md Abul Hashem
- Transboundary Animal Diseases Centre, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima 890-0065, Japan; (M.E.H.K.); (M.A.H.)
- Department of Health, Chattogram City Corporation, Chattogram 4000, Bangladesh
- Laboratory of Animal Hygiene, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima 890-0065, Japan
| | - Kyoko Tsukiyama-Kohara
- Transboundary Animal Diseases Centre, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima 890-0065, Japan; (M.E.H.K.); (M.A.H.)
- Laboratory of Animal Hygiene, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima 890-0065, Japan
- Correspondence: ; Tel.: +81-99-285-3589
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9
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Damert A. LINE-1 ORF1p does not determine substrate preference for human/orangutan SVA and gibbon LAVA. Mob DNA 2020; 11:27. [PMID: 32676128 PMCID: PMC7353768 DOI: 10.1186/s13100-020-00222-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 07/06/2020] [Indexed: 12/28/2022] Open
Abstract
Background Non-autonomous VNTR (Variable Number of Tandem Repeats) composite retrotransposons – SVA (SINE-R-VNTR-Alu) and LAVA (L1-Alu-VNTR-Alu) – are specific to hominoid primates. SVA expanded in great apes, LAVA in gibbon. Both SVA and LAVA have been shown to be mobilized by the autonomous LINE-1 (L1)-encoded protein machinery in a cell-based assay in trans. The efficiency of human SVA retrotransposition in vitro has, however, been considerably lower than would be expected based on recent pedigree-based in vivo estimates. The VNTR composite elements across hominoids – gibbon LAVA, orangutan SVA_A descendants and hominine SVA_D descendants – display characteristic structures of the 5′ Alu-like domain and the VNTR. Different partner L1 subfamilies are currently active in each of the lineages. The possibility that the lineage-specific types of VNTR composites evolved in response to evolutionary changes in their autonomous partners, particularly in the nucleic acid binding L1 ORF1-encoded protein, has not been addressed. Results Here I report the identification and functional characterization of a highly active human SVA element using an improved mneo retrotransposition reporter cassette. The modified cassette (mneoM) minimizes splicing between the VNTR of human SVAs and the neomycin phosphotransferase stop codon. SVA deletion analysis provides evidence that key elements determining its mobilization efficiency reside in the VNTR and 5′ hexameric repeats. Simultaneous removal of the 5′ hexameric repeats and part of the VNTR has an additive negative effect on mobilization rates. Taking advantage of the modified reporter cassette that facilitates robust cross-species comparison of SVA/LAVA retrotransposition, I show that the ORF1-encoded proteins of the L1 subfamilies currently active in gibbon, orangutan and human do not display substrate preference for gibbon LAVA versus orangutan SVA versus human SVA. Finally, I demonstrate that an orangutan-derived ORF1p supports only limited retrotransposition of SVA/LAVA in trans, despite being fully functional in L1 mobilization in cis. Conclusions Overall, the analysis confirms SVA as a highly active human retrotransposon and preferred substrate of the L1-encoded protein machinery. Based on the results obtained in human cells coevolution of L1 ORF1p and VNTR composites does not appear very likely. The changes in orangutan L1 ORF1p that markedly reduce its mobilization capacity in trans might explain the different SVA insertion rates in the orangutan and hominine lineages, respectively.
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Affiliation(s)
- Annette Damert
- Primate Genetics Laboratory, German Primate Center, Leibniz Institute for Primate Research, Göttingen, Germany
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10
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Bravo JI, Nozownik S, Danthi PS, Benayoun BA. Transposable elements, circular RNAs and mitochondrial transcription in age-related genomic regulation. Development 2020; 147:dev175786. [PMID: 32527937 PMCID: PMC10680986 DOI: 10.1242/dev.175786] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Our understanding of the molecular regulation of aging and age-related diseases is still in its infancy, requiring in-depth characterization of the molecular landscape shaping these complex phenotypes. Emerging classes of molecules with promise as aging modulators include transposable elements, circRNAs and the mitochondrial transcriptome. Analytical complexity means that these molecules are often overlooked, even though they exhibit strong associations with aging and, in some cases, may directly contribute to its progress. Here, we review the links between these novel factors and age-related phenotypes, and we suggest tools that can be easily incorporated into existing pipelines to better understand the aging process.
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Affiliation(s)
- Juan I Bravo
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA
- Graduate Program in the Biology of Aging, University of Southern California, Los Angeles, CA 90089, USA
| | - Séverine Nozownik
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA
- Magistère européen de Génétique, Université Paris Diderot-Paris 7, Paris 75014, France
| | - Prakroothi S Danthi
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA
| | - Bérénice A Benayoun
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA 90089, USA
- USC Norris Comprehensive Cancer Center, Epigenetics and Gene Regulation, Los Angeles, CA 90089, USA
- USC Stem Cell Initiative, Los Angeles, CA 90089, USA
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11
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Newkirk SJ, Kong L, Jones MM, Habben CE, Dilts VL, Ye P, An W. Subfamily-specific quantification of endogenous mouse L1 retrotransposons by droplet digital PCR. Anal Biochem 2020; 601:113779. [PMID: 32442414 DOI: 10.1016/j.ab.2020.113779] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Revised: 05/06/2020] [Accepted: 05/14/2020] [Indexed: 11/18/2022]
Abstract
Long interspersed element type 1 (LINE-1; L1) mobilizes during early embryogenesis, neurogenesis, and germ cell development, accounting for 25% of disease-causing heritable insertions and 98% of somatic insertions in cancer. To better understand the regulation and impact of L1 mobilization in the genome, reliable methods for measuring L1 copy number variation (CNV) are needed. Here we present a comprehensive analysis of a droplet digital PCR (ddPCR) based method for quantifying endogenous mouse L1. We provide experimental evidence that ddPCR assays can be designed to target specific L1 subfamilies using diagnostic single nucleotide polymorphisms (SNPs). The target and off-target L1 subfamilies form distinct droplet clusters, which were experimentally verified using both synthetic gene fragments and endogenous L1 derived plasmid clones. We further provide a roadmap for in silico assay design and evaluation of target specificity, ddPCR testing, and optimization for L1 CNV quantification. The assay can achieve a sensitivity of 5% CNV with 8 technical replicates. With 24 technical replicates, it can detect 2% CNV because of the increased precision. The same approach will serve as a guide for the development of ddPCR based assays for quantifying human L1 copy number and any other high copy genomic target sequences.
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Affiliation(s)
- Simon J Newkirk
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, United States.
| | - Lingqi Kong
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, United States.
| | - Mason M Jones
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, United States.
| | - Chase E Habben
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, United States.
| | - Victoria L Dilts
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, United States.
| | - Ping Ye
- Department of Pharmacy Practice, South Dakota State University, Brookings, SD, 57007, United States; Avera Research Institute, Sioux Falls, SD, 57108, United States.
| | - Wenfeng An
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, United States.
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12
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Lou C, Goodier JL, Qiang R. A potential new mechanism for pregnancy loss: considering the role of LINE-1 retrotransposons in early spontaneous miscarriage. Reprod Biol Endocrinol 2020; 18:6. [PMID: 31964400 PMCID: PMC6971995 DOI: 10.1186/s12958-020-0564-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 01/07/2020] [Indexed: 12/14/2022] Open
Abstract
LINE1 retrotransposons are mobile DNA elements that copy and paste themselves into new sites in the genome. To ensure their evolutionary success, heritable new LINE-1 insertions accumulate in cells that can transmit genetic information to the next generation (i.e., germ cells and embryonic stem cells). It is our hypothesis that LINE1 retrotransposons, insertional mutagens that affect expression of genes, may be causal agents of early miscarriage in humans. The cell has evolved various defenses restricting retrotransposition-caused mutation, but these are occasionally relaxed in certain somatic cell types, including those of the early embryo. We predict that reduced suppression of L1s in germ cells or early-stage embryos may lead to excessive genome mutation by retrotransposon insertion, or to the induction of an inflammatory response or apoptosis due to increased expression of L1-derived nucleic acids and proteins, and so disrupt gene function important for embryogenesis. If correct, a novel threat to normal human development is revealed, and reverse transcriptase therapy could be one future strategy for controlling this cause of embryonic damage in patients with recurrent miscarriages.
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Affiliation(s)
- Chao Lou
- Department of Genetics, Northwest Women’s and Children’s Hospital, 1616 Yanxiang Road, Xi’an, Shaanxi Province People’s Republic of China
| | - John L. Goodier
- 0000 0001 2171 9311grid.21107.35McKusick-Nathans Deartment of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD USA
| | - Rong Qiang
- Department of Genetics, Northwest Women’s and Children’s Hospital, 1616 Yanxiang Road, Xi’an, Shaanxi Province People’s Republic of China
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13
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Adney EM, Ochmann MT, Sil S, Truong DM, Mita P, Wang X, Kahler DJ, Fenyö D, Holt LJ, Boeke JD. Comprehensive Scanning Mutagenesis of Human Retrotransposon LINE-1 Identifies Motifs Essential for Function. Genetics 2019; 213:1401-1414. [PMID: 31666291 PMCID: PMC6893370 DOI: 10.1534/genetics.119.302601] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Accepted: 10/22/2019] [Indexed: 12/19/2022] Open
Abstract
Long Interspersed Nuclear Element-1 (LINE-1, L1) is the only autonomous active transposable element in the human genome. The L1-encoded proteins ORF1p and ORF2p enable the element to jump from one locus to another via a "copy-and-paste" mechanism. ORF1p is an RNA-binding protein, and ORF2p has endonuclease and reverse transcriptase activities. The huge number of truncated L1 remnants in the human genome suggests that the host has likely evolved mechanisms to prevent full L1 replication, and thereby decrease the proliferation of active elements and reduce the mutagenic potential of L1. In turn, L1 appears to have a minimized length to increase the probability of successful full-length replication. This streamlining would be expected to lead to high information density. Here, we describe the construction and initial characterization of a library of 538 consecutive trialanine substitutions that scan along ORF1p and ORF2p to identify functionally important regions. In accordance with the streamlining hypothesis, retrotransposition was overall very sensitive to mutations in ORF1p and ORF2p; only 16% of trialanine mutants retained near-wild-type (WT) activity. All ORF1p mutants formed near-WT levels of mRNA transcripts and 75% formed near-WT levels of protein. Two ORF1p mutants presented a unique nucleolar-relocalization phenotype. Regions of ORF2p that are sensitive to mutagenesis but lack phylogenetic conservation were also identified. We provide comprehensive information on the regions most critical to retrotransposition. This resource will guide future studies of intermolecular interactions that form with RNA, proteins, and target DNA throughout the L1 life cycle.
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Affiliation(s)
- Emily M Adney
- Institute for Systems Genetics, NYU Langone Health, New York 10016
- Department of Biochemistry and Molecular Pharmacology, NYU Langone Health, New York 10016
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Matthias T Ochmann
- Institute for Systems Genetics, NYU Langone Health, New York 10016
- Department of Biochemistry and Molecular Pharmacology, NYU Langone Health, New York 10016
- Division of Medical Biotechnology, Paul Ehrlich Institute, Langen 63225, Germany
| | - Srinjoy Sil
- Institute for Systems Genetics, NYU Langone Health, New York 10016
- Department of Biochemistry and Molecular Pharmacology, NYU Langone Health, New York 10016
| | - David M Truong
- Institute for Systems Genetics, NYU Langone Health, New York 10016
- Department of Biochemistry and Molecular Pharmacology, NYU Langone Health, New York 10016
| | - Paolo Mita
- Institute for Systems Genetics, NYU Langone Health, New York 10016
- Department of Biochemistry and Molecular Pharmacology, NYU Langone Health, New York 10016
| | - Xuya Wang
- Institute for Systems Genetics, NYU Langone Health, New York 10016
- Department of Biochemistry and Molecular Pharmacology, NYU Langone Health, New York 10016
| | - David J Kahler
- High Throughput Biology Laboratory, NYU Langone Health, New York 10016
| | - David Fenyö
- Institute for Systems Genetics, NYU Langone Health, New York 10016
- Department of Biochemistry and Molecular Pharmacology, NYU Langone Health, New York 10016
| | - Liam J Holt
- Institute for Systems Genetics, NYU Langone Health, New York 10016
- Department of Biochemistry and Molecular Pharmacology, NYU Langone Health, New York 10016
| | - Jef D Boeke
- Institute for Systems Genetics, NYU Langone Health, New York 10016
- Department of Biochemistry and Molecular Pharmacology, NYU Langone Health, New York 10016
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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14
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piRNA-Guided CRISPR-like Immunity in Eukaryotes. Trends Immunol 2019; 40:998-1010. [DOI: 10.1016/j.it.2019.09.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 09/17/2019] [Accepted: 09/17/2019] [Indexed: 02/07/2023]
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15
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Hassanin AAI, Tavera-Garcia M, Moorthy B, Zhou GD, Ramos KS. Lung genotoxicity of benzo(a)pyrene in vivo involves reactivation of LINE-1 retrotransposon and early reprogramming of oncogenic regulatory networks. Am J Physiol Lung Cell Mol Physiol 2019; 317:L816-L822. [PMID: 31596105 DOI: 10.1152/ajplung.00304.2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Several lines of evidence have implicated long interspersed nuclear element-1 (LINE-1) retroelement in the onset and progression of lung cancer. Retrotransposition-dependent mechanisms leading to DNA mobilization give rise to insertion mutations and DNA deletions, whereas retrotransposition-independent mechanisms disrupt epithelial programming and differentiation. Previous work by our group established that tobacco carcinogens such as benzo(a)pyrene (BaP) reactivate LINE-1 in bronchial epithelial cells through displacement of nucleosome remodeling and deacetylase (NuRD) corepressor complexes and interference with retinoblastoma-regulated epigenetic signaling. Whether LINE-1 in coordination with other genes within its regulatory network contributes to the in vivo genotoxic response to BaP remains largely unknown. Evidence is presented here that intratracheal instillation of ORFeusLSL mice with BaP alone or in combination with adenovirus (adeno)-CRE recombinase is genotoxic to the lung and associated with activation of the human LINE-1 transgene present in these mice. LINE-1 reactivation modulated the expression of genes involved in oncogenic signaling, and these responses were most pronounced in female mice compared with males and synergized by adeno-CRE recombinase. This is the first report linking LINE-1 and genes within its oncogenic regulatory network with early sexually dimorphic responses of the lung in vivo.
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Affiliation(s)
- A A I Hassanin
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, University of Arizona College of Medicine, Tucson, Arizona.,Department of Animal Wealth Development, Faculty of Veterinary Medicine, Suez Canal University, Ismailia, Egypt
| | - M Tavera-Garcia
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, University of Arizona College of Medicine, Tucson, Arizona
| | - B Moorthy
- Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - G D Zhou
- Institute of Biosciences and Technology, Texas A&M University Health Science Center, Houston, Texas
| | - K S Ramos
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, University of Arizona College of Medicine, Tucson, Arizona.,Institute of Biosciences and Technology, Texas A&M University Health Science Center, Houston, Texas
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16
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Kuroki-Kami A, Nichuguti N, Yatabe H, Mizuno S, Kawamura S, Fujiwara H. Targeted gene knockin in zebrafish using the 28S rDNA-specific non-LTR-retrotransposon R2Ol. Mob DNA 2019; 10:23. [PMID: 31139267 PMCID: PMC6530143 DOI: 10.1186/s13100-019-0167-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 05/13/2019] [Indexed: 02/07/2023] Open
Abstract
Background Although most of long interspersed elements (LINEs), one class of non-LTR-retrotransposons, are integrated into the host genome randomely, some elements are retrotransposed into the specific sequences of the genomic regions, such as rRNA gene (rDNA) clusters, telomeric repeats and other repetitive sequenes. Most of the sequence-specific LINEs have been reported mainly among invertebrate species and shown to retrotranspose into the specific sequences in vivo and in vitro systems. Recenlty, 28S rDNA-specific LINE R2 elements are shown to be distributed among widespread vertebrate species, but the sequence-specific retrotransposition of R2 has never been demonstrated in vertebrates. Results Here we cloned a full length unit of R2 from medaka fish Oryzias latipes, named R2Ol, and engineered it to a targeted gene integration tool in zebrafish. By injecting R2Ol-encoding mRNA into zebrafish embryos, R2Ol retrotransposed precisely into the target site at high efficiency (98%) and was transmitted to the next generation at high frequency (50%). We also generated transgenic zebrafish carrying the enhanced green fluorescent protein (EGFP) reporter gene in 28S rDNA target by the R2Ol retrotransposition system. Conclusions Sequence-specific LINE retrotransposes into the precise sequence using target primed reverse transcription (TPRT), possibly providing an alternative and effective targeted gene knockin method in vertebrates. Electronic supplementary material The online version of this article (10.1186/s13100-019-0167-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Azusa Kuroki-Kami
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Bioscience Bldg., Kashiwanoha 5-1-5, Kashiwa, Chiba, 277-8562 Japan
| | - Narisu Nichuguti
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Bioscience Bldg., Kashiwanoha 5-1-5, Kashiwa, Chiba, 277-8562 Japan
| | - Haruka Yatabe
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Bioscience Bldg., Kashiwanoha 5-1-5, Kashiwa, Chiba, 277-8562 Japan
| | - Sayaka Mizuno
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Bioscience Bldg., Kashiwanoha 5-1-5, Kashiwa, Chiba, 277-8562 Japan
| | - Shoji Kawamura
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Bioscience Bldg., Kashiwanoha 5-1-5, Kashiwa, Chiba, 277-8562 Japan
| | - Haruhiko Fujiwara
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Bioscience Bldg., Kashiwanoha 5-1-5, Kashiwa, Chiba, 277-8562 Japan
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17
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Wang Z, McSwiggin H, Newkirk SJ, Wang Y, Oliver D, Tang C, Lee S, Wang S, Yuan S, Zheng H, Ye P, An W, Yan W. Insertion of a chimeric retrotransposon sequence in mouse Axin1 locus causes metastable kinky tail phenotype. Mob DNA 2019; 10:17. [PMID: 31073336 PMCID: PMC6500023 DOI: 10.1186/s13100-019-0162-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Accepted: 04/21/2019] [Indexed: 12/12/2022] Open
Abstract
Background Transposable elements (TEs) make up > 50% of the human genome, and the majority of retrotransposon insertions are truncated and many are located in introns. However, the effects of retrotransposition on the host genes remain incompletely known. Results We report here that insertion of a chimeric L1 (cL1), but not IAP solo LTR, into intron 6 of Axin1 using CRIPSR/Cas9 induced the kinky tail phenotype with ~ 80% penetrance in heterozygous Axin cL1 mice. Both penetrant (with kinky tails) and silent (without kinky tails) Axin cL1 mice, regardless of sex, could transmit the phenotype to subsequent generations with similar penetrance (~ 80%). Further analyses revealed that a longer Axin1 transcript isoform containing partial cL1-targeted intron was present in penetrant, but absent in silent and wild type mice, and the production of this unique Axin1 transcript appeared to correlate with altered levels of an activating histone modification, H3K9ac. Conclusions The mechanism for Axin cL1 mice is different from those previously identified in mice with spontaneous retrotransposition of IAP, e.g., Axin Fu and A vy , both of which have been associated with DNA methylation changes. Our data suggest that Axin1 locus is sensitive to genetic and epigenetic alteration by retrotransposons and thus, ideally suited for studying the effects of new retrotransposition events on target gene function in mice.
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Affiliation(s)
- Zhuqing Wang
- 1Department of Physiology and Cell Biology, University of Nevada School of Medicine Center for Molecular Medicine, Room 207B 1664 North Virginia Street MS/0575, Reno, NV 89557 USA
| | - Hayden McSwiggin
- 1Department of Physiology and Cell Biology, University of Nevada School of Medicine Center for Molecular Medicine, Room 207B 1664 North Virginia Street MS/0575, Reno, NV 89557 USA
| | - Simon J Newkirk
- 3Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD 57007 USA
| | - Yue Wang
- 1Department of Physiology and Cell Biology, University of Nevada School of Medicine Center for Molecular Medicine, Room 207B 1664 North Virginia Street MS/0575, Reno, NV 89557 USA
| | - Daniel Oliver
- 1Department of Physiology and Cell Biology, University of Nevada School of Medicine Center for Molecular Medicine, Room 207B 1664 North Virginia Street MS/0575, Reno, NV 89557 USA
| | - Chong Tang
- 1Department of Physiology and Cell Biology, University of Nevada School of Medicine Center for Molecular Medicine, Room 207B 1664 North Virginia Street MS/0575, Reno, NV 89557 USA
| | - Sandy Lee
- 1Department of Physiology and Cell Biology, University of Nevada School of Medicine Center for Molecular Medicine, Room 207B 1664 North Virginia Street MS/0575, Reno, NV 89557 USA
| | - Shawn Wang
- 1Department of Physiology and Cell Biology, University of Nevada School of Medicine Center for Molecular Medicine, Room 207B 1664 North Virginia Street MS/0575, Reno, NV 89557 USA
| | - Shuiqiao Yuan
- 1Department of Physiology and Cell Biology, University of Nevada School of Medicine Center for Molecular Medicine, Room 207B 1664 North Virginia Street MS/0575, Reno, NV 89557 USA
| | - Huili Zheng
- 1Department of Physiology and Cell Biology, University of Nevada School of Medicine Center for Molecular Medicine, Room 207B 1664 North Virginia Street MS/0575, Reno, NV 89557 USA
| | - Ping Ye
- 2Avera McKennan Hospital and University Health Center, Sioux Falls, SD 57108 USA.,3Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD 57007 USA
| | - Wenfeng An
- 3Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD 57007 USA
| | - Wei Yan
- 1Department of Physiology and Cell Biology, University of Nevada School of Medicine Center for Molecular Medicine, Room 207B 1664 North Virginia Street MS/0575, Reno, NV 89557 USA.,4Department of Obstetrics and Gynecology, University of Nevada, Reno School of Medicine, Reno, NV 89557 USA.,5Department of Biology, University of Nevada, Reno, Reno, NV 89557 USA
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18
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Dynamic Methylation of an L1 Transduction Family during Reprogramming and Neurodifferentiation. Mol Cell Biol 2019; 39:MCB.00499-18. [PMID: 30692270 PMCID: PMC6425141 DOI: 10.1128/mcb.00499-18] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 01/11/2019] [Indexed: 01/28/2023] Open
Abstract
The retrotransposon LINE-1 (L1) is a significant source of endogenous mutagenesis in humans. In each individual genome, a few retrotransposition-competent L1s (RC-L1s) can generate new heritable L1 insertions in the early embryo, primordial germ line, and germ cells. L1 retrotransposition can also occur in the neuronal lineage and cause somatic mosaicism. Although DNA methylation mediates L1 promoter repression, the temporal pattern of methylation applied to individual RC-L1s during neurogenesis is unclear. Here, we identified a de novo L1 insertion in a human induced pluripotent stem cell (hiPSC) line via retrotransposon capture sequencing (RC-seq). The L1 insertion was full-length and carried 5' and 3' transductions. The corresponding donor RC-L1 was part of a large and recently active L1 transduction family and was highly mobile in a cultured-cell L1 retrotransposition reporter assay. Notably, we observed distinct and dynamic DNA methylation profiles for the de novo L1 and members of its extended transduction family during neuronal differentiation. These experiments reveal how a de novo L1 insertion in a pluripotent stem cell is rapidly recognized and repressed, albeit incompletely, by the host genome during neurodifferentiation, while retaining potential for further retrotransposition.
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19
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Schumann GG, Fuchs NV, Tristán-Ramos P, Sebe A, Ivics Z, Heras SR. The impact of transposable element activity on therapeutically relevant human stem cells. Mob DNA 2019; 10:9. [PMID: 30899334 PMCID: PMC6408843 DOI: 10.1186/s13100-019-0151-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Accepted: 02/27/2019] [Indexed: 12/11/2022] Open
Abstract
Human stem cells harbor significant potential for basic and clinical translational research as well as regenerative medicine. Currently ~ 3000 adult and ~ 30 pluripotent stem cell-based, interventional clinical trials are ongoing worldwide, and numbers are increasing continuously. Although stem cells are promising cell sources to treat a wide range of human diseases, there are also concerns regarding potential risks associated with their clinical use, including genomic instability and tumorigenesis concerns. Thus, a deeper understanding of the factors and molecular mechanisms contributing to stem cell genome stability are a prerequisite to harnessing their therapeutic potential for degenerative diseases. Chemical and physical factors are known to influence the stability of stem cell genomes, together with random mutations and Copy Number Variants (CNVs) that accumulated in cultured human stem cells. Here we review the activity of endogenous transposable elements (TEs) in human multipotent and pluripotent stem cells, and the consequences of their mobility for genomic integrity and host gene expression. We describe transcriptional and post-transcriptional mechanisms antagonizing the spread of TEs in the human genome, and highlight those that are more prevalent in multipotent and pluripotent stem cells. Notably, TEs do not only represent a source of mutations/CNVs in genomes, but are also often harnessed as tools to engineer the stem cell genome; thus, we also describe and discuss the most widely applied transposon-based tools and highlight the most relevant areas of their biomedical applications in stem cells. Taken together, this review will contribute to the assessment of the risk that endogenous TE activity and the application of genetically engineered TEs constitute for the biosafety of stem cells to be used for substitutive and regenerative cell therapies.
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Affiliation(s)
- Gerald G Schumann
- 1Division of Medical Biotechnology, Paul-Ehrlich-Institut, Paul-Ehrlich-Str.51-59, 63225 Langen, Germany
| | - Nina V Fuchs
- 2Host-Pathogen Interactions, Paul-Ehrlich-Institut, Paul-Ehrlich-Str. 51-59, 63225 Langen, Germany
| | - Pablo Tristán-Ramos
- 3GENYO. Centre for Genomics and Oncological Research, Pfizer/University of Granada/Andalusian Regional Government, PTS Granada-Avenida de la Ilustración, 114, 18016 Granada, Spain.,4Department of Biochemistry and Molecular Biology II, Faculty of Pharmacy, University of Granada, Campus Universitario de Cartuja, 18071 Granada, Spain
| | - Attila Sebe
- 1Division of Medical Biotechnology, Paul-Ehrlich-Institut, Paul-Ehrlich-Str.51-59, 63225 Langen, Germany
| | - Zoltán Ivics
- 1Division of Medical Biotechnology, Paul-Ehrlich-Institut, Paul-Ehrlich-Str.51-59, 63225 Langen, Germany
| | - Sara R Heras
- 3GENYO. Centre for Genomics and Oncological Research, Pfizer/University of Granada/Andalusian Regional Government, PTS Granada-Avenida de la Ilustración, 114, 18016 Granada, Spain.,4Department of Biochemistry and Molecular Biology II, Faculty of Pharmacy, University of Granada, Campus Universitario de Cartuja, 18071 Granada, Spain
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20
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Percharde M, Lin CJ, Yin Y, Guan J, Peixoto GA, Bulut-Karslioglu A, Biechele S, Huang B, Shen X, Ramalho-Santos M. A LINE1-Nucleolin Partnership Regulates Early Development and ESC Identity. Cell 2018; 174:391-405.e19. [PMID: 29937225 PMCID: PMC6046266 DOI: 10.1016/j.cell.2018.05.043] [Citation(s) in RCA: 304] [Impact Index Per Article: 50.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2017] [Revised: 03/20/2018] [Accepted: 05/17/2018] [Indexed: 01/07/2023]
Abstract
Transposable elements represent nearly half of mammalian genomes and are generally described as parasites, or "junk DNA." The LINE1 retrotransposon is the most abundant class and is thought to be deleterious for cells, yet it is paradoxically highly expressed during early development. Here, we report that LINE1 plays essential roles in mouse embryonic stem cells (ESCs) and pre-implantation embryos. In ESCs, LINE1 acts as a nuclear RNA scaffold that recruits Nucleolin and Kap1/Trim28 to repress Dux, the master activator of a transcriptional program specific to the 2-cell embryo. In parallel, LINE1 RNA mediates binding of Nucleolin and Kap1 to rDNA, promoting rRNA synthesis and ESC self-renewal. In embryos, LINE1 RNA is required for Dux silencing, synthesis of rRNA, and exit from the 2-cell stage. The results reveal an essential partnership between LINE1 RNA, Nucleolin, Kap1, and peri-nucleolar chromatin in the regulation of transcription, developmental potency, and ESC self-renewal.
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Affiliation(s)
- Michelle Percharde
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Center for Reproductive Sciences, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Chih-Jen Lin
- The University of Edinburgh, MRC Centre for Reproductive Health, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh, EH16 4TJ, Scotland, UK
| | - Yafei Yin
- Tsinghua-Peking Center for Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, China
| | - Juan Guan
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Gabriel A Peixoto
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Center for Reproductive Sciences, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Aydan Bulut-Karslioglu
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Center for Reproductive Sciences, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Steffen Biechele
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Center for Reproductive Sciences, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Bo Huang
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94143, USA; Chan Zuckerberg Biohub, San Francisco, CA 94158, USA
| | - Xiaohua Shen
- Tsinghua-Peking Center for Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, China
| | - Miguel Ramalho-Santos
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Center for Reproductive Sciences, University of California, San Francisco, San Francisco, CA 94143, USA.
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21
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Faulkner GJ, Billon V. L1 retrotransposition in the soma: a field jumping ahead. Mob DNA 2018; 9:22. [PMID: 30002735 PMCID: PMC6035798 DOI: 10.1186/s13100-018-0128-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 06/27/2018] [Indexed: 12/13/2022] Open
Abstract
Retrotransposons are transposable elements (TEs) capable of "jumping" in germ, embryonic and tumor cells and, as is now clearly established, in the neuronal lineage. Mosaic TE insertions form part of a broader landscape of somatic genome variation and hold significant potential to generate phenotypic diversity, in the brain and elsewhere. At present, the LINE-1 (L1) retrotransposon family appears to be the most active autonomous TE in most mammals, based on experimental data obtained from disease-causing L1 mutations, engineered L1 reporter systems tested in cultured cells and transgenic rodents, and single-cell genomic analyses. However, the biological consequences of almost all somatic L1 insertions identified thus far remain unknown. In this review, we briefly summarize the current state-of-the-art in the field, including estimates of L1 retrotransposition rate in neurons. We bring forward the hypothesis that an extensive subset of retrotransposition-competent L1s may be de-repressed and mobile in the soma but largely inactive in the germline. We discuss recent reports of non-canonical L1-associated sequence variants in the brain and propose that the elevated L1 DNA content reported in several neurological disorders may predominantly comprise accumulated, unintegrated L1 nucleic acids, rather than somatic L1 insertions. Finally, we consider the main objectives and obstacles going forward in elucidating the biological impact of somatic retrotransposition.
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Affiliation(s)
- Geoffrey J. Faulkner
- Mater Research Institute – University of Queensland, TRI Building, Woolloongabba, QLD 4102 Australia
- School of Biomedical Sciences, University of Queensland, Brisbane, QLD 4072 Australia
- Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072 Australia
| | - Victor Billon
- Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072 Australia
- Biology Department, École Normale Supérieure Paris-Saclay, 61 Avenue du Président Wilson, 94230 Cachan, France
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22
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Richardson SR, Faulkner GJ. Heritable L1 Retrotransposition Events During Development: Understanding Their Origins: Examination of heritable, endogenous L1 retrotransposition in mice opens up exciting new questions and research directions. Bioessays 2018; 40:e1700189. [PMID: 29709066 PMCID: PMC6681178 DOI: 10.1002/bies.201700189] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 03/04/2018] [Indexed: 01/08/2023]
Abstract
The retrotransposon Long Interspersed Element 1 (LINE-1 or L1) has played a major role in shaping the sequence composition of the mammalian genome. In our recent publication, "Heritable L1 retrotransposition in the mouse primordial germline and early embryo," we systematically assessed the rate and developmental timing of de novo, heritable endogenous L1 insertions in mice. Such heritable retrotransposition events allow L1 to exert an ongoing influence upon genome evolution. Here, we place our findings in the context of earlier studies, and highlight how our results corroborate, and depart from, previous research based on human patient samples and transgenic mouse models harboring engineered L1 reporter genes. In parallel, we outline outstanding questions regarding the stage-specificity, regulation, and functional impact of embryonic and germline L1 retrotransposition, and propose avenues for future research in this field.
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Affiliation(s)
- Sandra R. Richardson
- Mater Research Institute–University of QueenslandWoolloongabbaQueensland 4102Australia
| | - Geoffrey J. Faulkner
- Mater Research Institute–University of QueenslandWoolloongabbaQueensland 4102Australia
- Queensland Brain InstituteUniversity of QueenslandBrisbaneQueensland 4072Australia
- School of Biomedical SciencesUniversity of QueenslandBrisbaneQueensland 4072Australia
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23
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Chen C. A novel reporter mouse to monitor in vivo retrotransposition in the germline. Biol Reprod 2017; 97:335-336. [PMID: 29024952 DOI: 10.1093/biolre/iox111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 08/29/2017] [Indexed: 01/16/2023] Open
Affiliation(s)
- Chen Chen
- Department of Animal Science, Michigan State University, East Lansing, Michigan, USA.,Reproductive and Developmental Sciences Program, Michigan State University, East Lansing, Michigan, USA.,Department of Obstetrics, Gynecology and Reproductive Biology, Michigan State University, Grand Rapids, Michigan, USA
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24
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L1 Mosaicism in Mammals: Extent, Effects, and Evolution. Trends Genet 2017; 33:802-816. [PMID: 28797643 DOI: 10.1016/j.tig.2017.07.004] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 06/30/2017] [Accepted: 07/14/2017] [Indexed: 10/19/2022]
Abstract
The retrotransposon LINE-1 (long interspersed element 1, L1) is a transposable element that has extensively colonized the mammalian germline. L1 retrotransposition can also occur in somatic cells, causing genomic mosaicism, as well as in cancer. However, the extent of L1-driven mosaicism arising during ontogenesis is unclear. We discuss here recent experimental data which, at a minimum, fully substantiate L1 mosaicism in early embryonic development and neural cells, including post-mitotic neurons. We also consider the possible biological impact of somatic L1 insertions in neurons, the existence of donor L1s that are highly active ('hot') in specific spatiotemporal niches, and the evolutionary selection of donor L1s driving neuronal mosaicism.
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25
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26
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Abstract
Transposable elements give rise to interspersed repeats, sequences that comprise most of our genomes. These mobile DNAs have been historically underappreciated - both because they have been presumed to be unimportant, and because their high copy number and variability pose unique technical challenges. Neither impediment now seems steadfast. Interest in the human mobilome has never been greater, and methods enabling its study are maturing at a fast pace. This Review describes the activity of transposable elements in human cancers, particularly long interspersed element-1 (LINE-1). LINE-1 sequences are self-propagating, protein-coding retrotransposons, and their activity results in somatically acquired insertions in cancer genomes. Altered expression of transposable elements and animation of genomic LINE-1 sequences appear to be hallmarks of cancer, and can be responsible for driving mutations in tumorigenesis.
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Affiliation(s)
- Kathleen H Burns
- Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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27
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Transposable elements in cancer. NATURE REVIEWS. CANCER 2017. [PMID: 28642606 DOI: 10.1038/nrc.2017.35+[doi]] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Transposable elements give rise to interspersed repeats, sequences that comprise most of our genomes. These mobile DNAs have been historically underappreciated - both because they have been presumed to be unimportant, and because their high copy number and variability pose unique technical challenges. Neither impediment now seems steadfast. Interest in the human mobilome has never been greater, and methods enabling its study are maturing at a fast pace. This Review describes the activity of transposable elements in human cancers, particularly long interspersed element-1 (LINE-1). LINE-1 sequences are self-propagating, protein-coding retrotransposons, and their activity results in somatically acquired insertions in cancer genomes. Altered expression of transposable elements and animation of genomic LINE-1 sequences appear to be hallmarks of cancer, and can be responsible for driving mutations in tumorigenesis.
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28
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Abstract
The PIWI-interacting RNA (piRNA) pathway is essential for retrotransposon silencing. In piRNA-deficient mice, L1-overexpressing male germ cells exhibit excessive DNA damage and meiotic defects. It remains unknown whether L1 expression simply highlights piRNA deficiency or actually drives the germ-cell demise. Specifically, the sheer abundance of genomic L1 copies prevents reliable quantification of new insertions. Here, we developed a codon-optimized L1 transgene that is controlled by an endogenous mouse L1 promoter. Importantly, DNA methylation dynamics of a single-copy transgene were indistinguishable from those of endogenous L1s. Analysis of Mov10l1-/- testes established that de novo methylation of the L1 transgene required the intact piRNA pathway. Consistent with loss of DNA methylation and programmed reduction of H3K9me2 at meiotic onset, the transgene showed 1,400-fold increase in RNA expression and consequently 70-fold increase in retrotransposition in postnatal day 14 Mov10l1-/- germ cells compared with the wild-type. Analysis of adult Mov10l1-/- germ-cell fractions indicated a stage-specific increase of retrotransposition in the early meiotic prophase. However, extrapolation of the transgene data to endogenous L1s suggests that it is unlikely insertional mutagenesis alone accounts for the Mov10l1-/- phenotype. Indeed, pharmacological inhibition of reverse transcription did not rescue the meiotic defect. Cumulatively, these results establish the occurrence of productive L1 mobilization in the absence of an intact piRNA pathway but leave open the possibility of processes preceding L1 integration in triggering meiotic checkpoints and germ-cell death. Additionally, our data suggest that many heritable L1 insertions originate from individuals with partially compromised piRNA defense.
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29
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The Role of Somatic L1 Retrotransposition in Human Cancers. Viruses 2017; 9:v9060131. [PMID: 28561751 PMCID: PMC5490808 DOI: 10.3390/v9060131] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 05/09/2017] [Accepted: 05/22/2017] [Indexed: 02/06/2023] Open
Abstract
The human LINE-1 (or L1) element is a non-LTR retrotransposon that is mobilized through an RNA intermediate by an L1-encoded reverse transcriptase and other L1-encoded proteins. L1 elements remain actively mobile today and continue to mutagenize human genomes. Importantly, when new insertions disrupt gene function, they can cause diseases. Historically, L1s were thought to be active in the germline but silenced in adult somatic tissues. However, recent studies now show that L1 is active in at least some somatic tissues, including epithelial cancers. In this review, we provide an overview of these recent developments, and examine evidence that somatic L1 retrotransposition can initiate and drive tumorigenesis in humans. Recent studies have: (i) cataloged somatic L1 activity in many epithelial tumor types; (ii) identified specific full-length L1 source elements that give rise to somatic L1 insertions; and (iii) determined that L1 promoter hypomethylation likely plays an early role in the derepression of L1s in somatic tissues. A central challenge moving forward is to determine the extent to which L1 driver mutations can promote tumor initiation, evolution, and metastasis in humans.
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30
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Kannan M, Li J, Fritz SE, Husarek KE, Sanford JC, Sullivan TL, Tiwary PK, An W, Boeke JD, Symer DE. Dynamic silencing of somatic L1 retrotransposon insertions reflects the developmental and cellular contexts of their genomic integration. Mob DNA 2017; 8:8. [PMID: 28491150 PMCID: PMC5424313 DOI: 10.1186/s13100-017-0091-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 05/03/2017] [Indexed: 02/15/2023] Open
Abstract
Background The ongoing mobilization of mammalian transposable elements (TEs) contributes to natural genetic variation. To survey the epigenetic control and expression of reporter genes inserted by L1 retrotransposition in diverse cellular and genomic contexts, we engineered highly sensitive, real-time L1 retrotransposon reporter constructs. Results Here we describe different patterns of expression and epigenetic controls of newly inserted sequences retrotransposed by L1 in various somatic cells and tissues including cultured human cancer cells, mouse embryonic stem cells, and tissues of pseudofounder transgenic mice and their progeny. In cancer cell lines, the newly inserted sequences typically underwent rapid transcriptional gene silencing, but they lacked cytosine methylation even after many cell divisions. L1 reporter expression was reversible and oscillated frequently. Silenced or variegated reporter expression was strongly and uniformly reactivated by treatment with inhibitors of histone deacetylation, revealing the mechanism for their silencing. By contrast, de novo integrants retrotransposed by L1 in pluripotent mouse embryonic stem (ES) cells underwent rapid silencing by dense cytosine methylation. Similarly, de novo cytosine methylation also was identified at new integrants when studied in several distinct somatic tissues of adult founder mice. Pre-existing L1 elements in cultured human cancer cells were stably silenced by dense cytosine methylation, whereas their transcription modestly increased when cytosine methylation was experimentally reduced in cells lacking DNA methyltransferases DNMT1 and DNMT3b. As a control, reporter genes mobilized by piggyBac (PB), a DNA transposon, revealed relatively stable and robust expression without apparent silencing in both cultured cancer cells and ES cells. Conclusions We hypothesize that the de novo methylation marks at newly inserted sequences retrotransposed by L1 in early pre-implantation development are maintained or re-established in adult somatic tissues. By contrast, histone deacetylation reversibly silences L1 reporter insertions that had mobilized at later timepoints in somatic development and differentiation, e.g., in cancer cell lines. We conclude that the cellular contexts of L1 retrotransposition can determine expression or silencing of newly integrated sequences. We propose a model whereby reporter expression from somatic TE insertions reflects the timing, molecular mechanism, epigenetic controls and the genomic, cellular and developmental contexts of their integration. Electronic supplementary material The online version of this article (doi:10.1186/s13100-017-0091-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Manoj Kannan
- Department of Biological Sciences, Birla Institute of Technology and Science Pilani, Pilani, 333031 Rajasthan India.,Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA.,Present Address: Birla Institute of Technology and Science, Pilani, Dubai campus, Dubai, United Arab Emirates
| | - Jingfeng Li
- Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA.,Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH USA.,Department of Internal Medicine, The Ohio State University, Columbus, OH USA
| | - Sarah E Fritz
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH USA.,Present Address: National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD USA
| | - Kathryn E Husarek
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH USA.,Present Address: Aventiv Research, Inc., Columbus, OH USA
| | - Jonathan C Sanford
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH USA.,Present Address: Drug Safety Research and Development, Pfizer, Inc., Groton, CT USA
| | - Teresa L Sullivan
- Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA
| | - Pawan Kumar Tiwary
- Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA.,Present Address: Biocon, Bangalore, India
| | - Wenfeng An
- Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, MD USA.,Present Address: Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD USA
| | - Jef D Boeke
- Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, MD USA.,Present Address: Institute for Systems Genetics, New York University Langone Medical Center, New York, NY USA
| | - David E Symer
- Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA.,Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH USA.,Human Cancer Genetics Program, and Department of Biomedical Informatics, The Ohio State University, Columbus, OH USA.,Human Cancer Genetics Program, Department of Cancer Biology and Genetics, and Department of Biomedical Informatics, The Ohio State University, Tzagournis Research Facility, Room 440, 420 West 12th Ave, Columbus, OH 43210 USA
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31
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Richardson SR, Gerdes P, Gerhardt DJ, Sanchez-Luque FJ, Bodea GO, Muñoz-Lopez M, Jesuadian JS, Kempen MJHC, Carreira PE, Jeddeloh JA, Garcia-Perez JL, Kazazian HH, Ewing AD, Faulkner GJ. Heritable L1 retrotransposition in the mouse primordial germline and early embryo. Genome Res 2017; 27:1395-1405. [PMID: 28483779 PMCID: PMC5538555 DOI: 10.1101/gr.219022.116] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Accepted: 05/02/2017] [Indexed: 12/31/2022]
Abstract
LINE-1 (L1) retrotransposons are a noted source of genetic diversity and disease in mammals. To expand its genomic footprint, L1 must mobilize in cells that will contribute their genetic material to subsequent generations. Heritable L1 insertions may therefore arise in germ cells and in pluripotent embryonic cells, prior to germline specification, yet the frequency and predominant developmental timing of such events remain unclear. Here, we applied mouse retrotransposon capture sequencing (mRC-seq) and whole-genome sequencing (WGS) to pedigrees of C57BL/6J animals, and uncovered an L1 insertion rate of ≥1 event per eight births. We traced heritable L1 insertions to pluripotent embryonic cells and, strikingly, to early primordial germ cells (PGCs). New L1 insertions bore structural hallmarks of target-site primed reverse transcription (TPRT) and mobilized efficiently in a cultured cell retrotransposition assay. Together, our results highlight the rate and evolutionary impact of heritable L1 retrotransposition and reveal retrotransposition-mediated genomic diversification as a fundamental property of pluripotent embryonic cells in vivo.
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Affiliation(s)
- Sandra R Richardson
- Mater Research Institute-University of Queensland, Woolloongabba QLD 4102, Australia
| | - Patricia Gerdes
- Mater Research Institute-University of Queensland, Woolloongabba QLD 4102, Australia
| | - Daniel J Gerhardt
- Mater Research Institute-University of Queensland, Woolloongabba QLD 4102, Australia.,Invenra, Incorporated, Madison, Wisconsin 53719, USA
| | - Francisco J Sanchez-Luque
- Mater Research Institute-University of Queensland, Woolloongabba QLD 4102, Australia.,Department of Genomic Medicine, GENYO, Centre for Genomics and Oncological Research, Pfizer-University of Granada-Andalusian Regional Government, PTS Granada, 18016 Granada, Spain
| | - Gabriela-Oana Bodea
- Mater Research Institute-University of Queensland, Woolloongabba QLD 4102, Australia
| | - Martin Muñoz-Lopez
- Department of Genomic Medicine, GENYO, Centre for Genomics and Oncological Research, Pfizer-University of Granada-Andalusian Regional Government, PTS Granada, 18016 Granada, Spain
| | - J Samuel Jesuadian
- Mater Research Institute-University of Queensland, Woolloongabba QLD 4102, Australia
| | | | - Patricia E Carreira
- Mater Research Institute-University of Queensland, Woolloongabba QLD 4102, Australia
| | | | - Jose L Garcia-Perez
- Department of Genomic Medicine, GENYO, Centre for Genomics and Oncological Research, Pfizer-University of Granada-Andalusian Regional Government, PTS Granada, 18016 Granada, Spain.,Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, United Kingdom
| | - Haig H Kazazian
- Institute of Genetic Medicine and Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Adam D Ewing
- Mater Research Institute-University of Queensland, Woolloongabba QLD 4102, Australia
| | - Geoffrey J Faulkner
- Mater Research Institute-University of Queensland, Woolloongabba QLD 4102, Australia.,School of Biomedical Sciences.,Queensland Brain Institute, University of Queensland, Brisbane QLD 4072, Australia
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32
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Lazaros L, Kitsou C, Kostoulas C, Bellou S, Hatzi E, Ladias P, Stefos T, Markoula S, Galani V, Vartholomatos G, Tzavaras T, Georgiou I. Retrotransposon expression and incorporation of cloned human and mouse retroelements in human spermatozoa. Fertil Steril 2017; 107:821-830. [PMID: 28139237 DOI: 10.1016/j.fertnstert.2016.12.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 12/14/2016] [Accepted: 12/17/2016] [Indexed: 12/19/2022]
Abstract
OBJECTIVE To investigate the expression of long interspersed element (LINE) 1, human endogenous retrovirus (HERV) K10, and short interspersed element-VNTR-Alu element (SVA) retrotransposons in ejaculated human spermatozoa by means of reverse-transcription (RT) polymerase chain reaction (PCR) analysis as well as the potential incorporation of cloned human and mouse active retroelements in human sperm cell genome. DESIGN Laboratory study. SETTING University research laboratories and academic hospital. PATIENT(S) Normozoospermic and oligozoospermic white men. INTERVENTION(S) RT-PCR analysis was performed to confirm the retrotransposon expression in human spermatozoa. Exogenous retroelements were tagged with a plasmid containing a green fluorescence (EGFP) retrotransposition cassette, and the de novo retrotransposition events were tested with the use of PCR, fluorescence-activated cell sorting analysis, and confocal microscopy. MAIN OUTCOME MEASURE(S) Retroelement expression in human spermatozoa, incorporation of cloned human and mouse active retroelements in human sperm genome, and de novo retrotransposition events in human spermatozoa. RESULT(S) RT-PCR products of expressed human LINE-1, HERV-K10, and SVA retrotransposons were observed in ejaculated human sperm samples. The incubation of human spermatozoa with either retrotransposition-active human LINE-1 and HERV-K10 or mouse reverse transcriptase-deficient VL30 retrotransposons tagged with an EGFP-based retrotransposition cassette led to EGFP-positive spermatozo; 16.67% of the samples were positive for retrotransposition. The respective retrotransposition frequencies for the LINE-1, HERV-K10, and VL30 retrotransposons in the positive samples were 0.34 ± 0.13%, 0.37 ± 0.17%, and 0.30 ± 0.14% per sample of 10,000 spermatozoa. CONCLUSION(S) Our results show that: 1) LINE-1, HERV-K10, and SVA retrotransposons are transcriptionally expressed in human spermatozoa; 2) cloned active retroelements of human and mammalian origin can be incorporated in human sperm genome; 3) active reverse transcriptases exist in human spermatozoa; and 4) de novo retrotransposition events occur in human spermatozoa.
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Affiliation(s)
- Leandros Lazaros
- Laboratory of Medical Genetics of Human Reproduction, Medical School, Ioannina University, Ioannina, Greece; Medical Genetics and Assisted Reproduction Unit, Department of Obstetrics and Gynecology, Ioannina University Hospital, Ioannina, Greece; Genesis-Genoma Lab, Chalandri-Athens, Greece
| | - Chrysoula Kitsou
- Laboratory of Medical Genetics of Human Reproduction, Medical School, Ioannina University, Ioannina, Greece
| | - Charilaos Kostoulas
- Laboratory of Medical Genetics of Human Reproduction, Medical School, Ioannina University, Ioannina, Greece
| | - Sofia Bellou
- Foundation for Research & Technology-Hellas Institute of Molecular Biology and Biotechnology, Department of Biomedical Research, Ioannina, Greece
| | - Elissavet Hatzi
- Medical Genetics and Assisted Reproduction Unit, Department of Obstetrics and Gynecology, Ioannina University Hospital, Ioannina, Greece
| | - Paris Ladias
- Laboratory of Medical Genetics of Human Reproduction, Medical School, Ioannina University, Ioannina, Greece
| | - Theodoros Stefos
- Medical Genetics and Assisted Reproduction Unit, Department of Obstetrics and Gynecology, Ioannina University Hospital, Ioannina, Greece
| | - Sofia Markoula
- Laboratory of Medical Genetics of Human Reproduction, Medical School, Ioannina University, Ioannina, Greece
| | - Vasiliki Galani
- Department of Anatomy-Histology-Embryology, Medical School, Ioannina University, Ioannina, Greece
| | - Georgios Vartholomatos
- Hematology Laboratory, Molecular Biology Unit, Ioannina University Hospital, Ioannina, Greece
| | - Theodore Tzavaras
- Department of General Biology, Medical School, Ioannina University, Ioannina, Greece
| | - Ioannis Georgiou
- Laboratory of Medical Genetics of Human Reproduction, Medical School, Ioannina University, Ioannina, Greece; Medical Genetics and Assisted Reproduction Unit, Department of Obstetrics and Gynecology, Ioannina University Hospital, Ioannina, Greece.
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33
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Abstract
Retrotransposons have generated about 40 % of the human genome. This review examines the strategies the cell has evolved to coexist with these genomic "parasites", focussing on the non-long terminal repeat retrotransposons of humans and mice. Some of the restriction factors for retrotransposition, including the APOBECs, MOV10, RNASEL, SAMHD1, TREX1, and ZAP, also limit replication of retroviruses, including HIV, and are part of the intrinsic immune system of the cell. Many of these proteins act in the cytoplasm to degrade retroelement RNA or inhibit its translation. Some factors act in the nucleus and involve DNA repair enzymes or epigenetic processes of DNA methylation and histone modification. RISC and piRNA pathway proteins protect the germline. Retrotransposon control is relaxed in some cell types, such as neurons in the brain, stem cells, and in certain types of disease and cancer, with implications for human health and disease. This review also considers potential pitfalls in interpreting retrotransposon-related data, as well as issues to consider for future research.
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Affiliation(s)
- John L. Goodier
- McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD USA 212051
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34
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McLaughlin RN, Gable JT, Wittkopp CJ, Emerman M, Malik HS. Conservation and Innovation of APOBEC3A Restriction Functions during Primate Evolution. Mol Biol Evol 2016; 33:1889-901. [PMID: 27189538 DOI: 10.1093/molbev/msw070] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
LINE-1 (long interspersed element-1) retroelements are the only active autonomous endogenous retroelements in human genomes. Their retrotransposition activity has created close to 50% of the current human genome. Due to the apparent costs of this proliferation, host genomes have evolved multiple mechanisms to curb LINE-1 retrotransposition. Here, we investigate the evolution and function of the LINE-1 restriction factor APOBEC3A, a member of the APOBEC3 cytidine deaminase gene family. We find that APOBEC3A genes have evolved rapidly under diversifying selection in primates, suggesting changes in APOBEC3A have been recurrently selected in a host-pathogen "arms race." Nonetheless, in contrast to previous reports, we find that the LINE-1 restriction activity of APOBEC3A proteins has been strictly conserved throughout simian primate evolution in spite of its pervasive diversifying selection. Based on these results, we conclude that LINE-1s have not driven the rapid evolution of APOBEC3A in primates. In contrast to this conserved LINE-1 restriction, we find that a subset of primate APOBEC3A genes have enhanced antiviral restriction. We trace this gain of antiviral restriction in APOBEC3A to the common ancestor of a subset of Old World monkeys. Thus, APOBEC3A has not only maintained its LINE-1 restriction ability, but also evolved a gain of antiviral specificity against other pathogens. Our findings suggest that while APOBEC3A has evolved to restrict additional pathogens, only those adaptive amino acid changes that leave LINE-1 restriction unperturbed have been tolerated.
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Affiliation(s)
| | - Jacob T Gable
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA
| | - Cristina J Wittkopp
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA Department of Microbiology, University of Washington, Seattle
| | - Michael Emerman
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA
| | - Harmit S Malik
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, WA
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35
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Honda T, Tomonaga K. Endogenous non-retroviral RNA virus elements evidence a novel type of antiviral immunity. Mob Genet Elements 2016; 6:e1165785. [PMID: 27510928 PMCID: PMC4964890 DOI: 10.1080/2159256x.2016.1165785] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 03/10/2016] [Indexed: 10/25/2022] Open
Abstract
Vertebrate genomes contain many virus-related sequences derived from both retroviruses and non-retroviral RNA and DNA viruses. Such non-retroviral RNA sequences are possibly produced by reverse-transcription and integration of viral mRNAs of ancient RNA viruses using retrotransposon machineries. We refer to this process as transcript reversion. During an ancient bornavirus infection, transcript reversion may have left bornavirus-related sequences, known as endogenous bornavirus-like nucleoproteins (EBLNs), in the genome. We have recently demonstrated that all Homo sapiens EBLNs are expressed in at least one tissue. Because species with EBLNs appear relatively protected against infection by a current bornavirus, Borna disease virus, it is speculated that EBLNs play some roles in antiviral immunity, as seen with some endogenous retroviruses. EBLNs can function as dominant negative forms of viral proteins, small RNAs targeting viral sequences, or DNA or RNA elements modulating the gene expression. Growing evidence reveals that various RNA viruses are reverse-transcribed and integrated into the genome of infected cells, suggesting transcript reversion generally occurs during ongoing infection. Considering this, transcript reversion-mediated interference with related viruses may be a novel type of antiviral immunity in vertebrates. Understanding the biological significance of transcript reversion will provide novel insights into host defenses against viral infections.
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Affiliation(s)
- Tomoyuki Honda
- Department of Viral Oncology, Institute for Virus Research, Kyoto University , Kyoto, Japan
| | - Keizo Tomonaga
- Department of Viral Oncology, Institute for Virus Research, Kyoto University , Kyoto, Japan
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Parrish NF, Fujino K, Shiromoto Y, Iwasaki YW, Ha H, Xing J, Makino A, Kuramochi-Miyagawa S, Nakano T, Siomi H, Honda T, Tomonaga K. piRNAs derived from ancient viral processed pseudogenes as transgenerational sequence-specific immune memory in mammals. RNA (NEW YORK, N.Y.) 2015; 21:1691-1703. [PMID: 26283688 PMCID: PMC4574747 DOI: 10.1261/rna.052092.115] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 07/08/2015] [Indexed: 06/04/2023]
Abstract
Endogenous bornavirus-like nucleoprotein elements (EBLNs) are sequences within vertebrate genomes derived from reverse transcription and integration of ancient bornaviral nucleoprotein mRNA via the host retrotransposon machinery. While species with EBLNs appear relatively resistant to bornaviral disease, the nature of this association is unclear. We hypothesized that EBLNs could give rise to antiviral interfering RNA in the form of PIWI-interacting RNAs (piRNAs), a class of small RNA known to silence transposons but not exogenous viruses. We found that in both rodents and primates, which acquired their EBLNs independently some 25-40 million years ago, EBLNs are present within piRNA-generating regions of the genome far more often than expected by chance alone (ℙ = 8 × 10(-3)-6 × 10(-8)). Three of the seven human EBLNs fall within annotated piRNA clusters and two marmoset EBLNs give rise to bona fide piRNAs. In both rats and mice, at least two of the five EBLNs give rise to abundant piRNAs in the male gonad. While no EBLNs are syntenic between rodent and primate, some of the piRNA clusters containing EBLNs are; thus we deduce that EBLNs were integrated into existing piRNA clusters. All true piRNAs derived from EBLNs are antisense relative to the proposed ancient bornaviral nucleoprotein mRNA. These observations are consistent with a role for EBLN-derived piRNA-like RNAs in interfering with ancient bornaviral infection. They raise the hypothesis that retrotransposon-dependent virus-to-host gene flow could engender RNA-mediated, sequence-specific antiviral immune memory in metazoans analogous to the CRISPR/Cas system in prokaryotes.
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Affiliation(s)
- Nicholas F Parrish
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan
| | - Kan Fujino
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan
| | - Yusuke Shiromoto
- Department of Pathology, Medical School and Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan
| | - Yuka W Iwasaki
- Department of Molecular Biology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Hongseok Ha
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
| | - Jinchuan Xing
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
| | - Akiko Makino
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan Center for Emerging Virus Research, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan
| | - Satomi Kuramochi-Miyagawa
- Department of Pathology, Medical School and Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan
| | - Toru Nakano
- Department of Pathology, Medical School and Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan
| | - Haruhiko Siomi
- Department of Molecular Biology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Tomoyuki Honda
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan Department of Tumor Viruses, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
| | - Keizo Tomonaga
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan Department of Tumor Viruses, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan Department of Mammalian Regulatory Network, Graduate School of Biostudies, Kyoto University, Kyoto 606-8507, Japan
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Grandi FC, Rosser JM, Newkirk SJ, Yin J, Jiang X, Xing Z, Whitmore L, Bashir S, Ivics Z, Izsvák Z, Ye P, Yu YE, An W. Retrotransposition creates sloping shores: a graded influence of hypomethylated CpG islands on flanking CpG sites. Genome Res 2015; 25:1135-46. [PMID: 25995269 PMCID: PMC4509998 DOI: 10.1101/gr.185132.114] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 05/19/2015] [Indexed: 11/25/2022]
Abstract
Long interspersed elements (LINEs), through both self-mobilization and trans-mobilization of short interspersed elements and processed pseudogenes, have made an indelible impact on the structure and function of the human genome. One consequence is the creation of new CpG islands (CGIs). In fact, more than half of all CGIs in the genome are associated with repetitive DNA, three-quarters of which are derived from retrotransposons. However, little is known about the epigenetic impact of newly inserted CGIs. We utilized a transgenic LINE-1 mouse model and tracked DNA methylation dynamics of individual germline insertions during mouse development. The retrotransposed GFP marker sequence, a strong CGI, is hypomethylated in male germ cells but hypermethylated in somatic tissues, regardless of genomic location. The GFP marker is similarly methylated when delivered into the genome via the Sleeping Beauty DNA transposon, suggesting that the observed methylation pattern may be independent of the mode of insertion. Comparative analyses between insertion- and non-insertion-containing alleles further reveal a graded influence of the retrotransposed CGI on flanking CpG sites, a phenomenon that we described as "sloping shores." Computational analyses of human and mouse methylomic data at single-base resolution confirm that sloping shores are universal for hypomethylated CGIs in sperm and somatic tissues. Additionally, the slope of a hypomethylated CGI can be affected by closely positioned CGI neighbors. Finally, by tracing sloping shore dynamics through embryonic and germ cell reprogramming, we found evidence of bookmarking, a mechanism that likely determines which CGIs will be eventually hyper- or hypomethylated.
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Affiliation(s)
- Fiorella C Grandi
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA
| | - James M Rosser
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA
| | - Simon J Newkirk
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA; Department of Pharmaceutical Sciences, South Dakota State University, Brookings, South Dakota 57007, USA
| | - Jun Yin
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA
| | - Xiaoling Jiang
- The Children's Guild Foundation Down Syndrome Research Program, Department of Cancer Genetics and Genetics Program, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Zhuo Xing
- The Children's Guild Foundation Down Syndrome Research Program, Department of Cancer Genetics and Genetics Program, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Leanne Whitmore
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA
| | - Sanum Bashir
- Max Delbrück Center for Molecular Medicine, 13092 Berlin, Germany
| | - Zoltán Ivics
- Division of Medical Biotechnology, Paul Ehrlich Institute, 63225 Langen, Germany
| | - Zsuzsanna Izsvák
- Max Delbrück Center for Molecular Medicine, 13092 Berlin, Germany
| | - Ping Ye
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA
| | - Y Eugene Yu
- The Children's Guild Foundation Down Syndrome Research Program, Department of Cancer Genetics and Genetics Program, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Wenfeng An
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, South Dakota 57007, USA
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The Broad-Spectrum Antiviral Protein ZAP Restricts Human Retrotransposition. PLoS Genet 2015; 11:e1005252. [PMID: 26001115 PMCID: PMC4441479 DOI: 10.1371/journal.pgen.1005252] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 04/29/2015] [Indexed: 12/13/2022] Open
Abstract
Intrinsic immunity describes the set of recently discovered but poorly understood cellular mechanisms that specifically target viral pathogens. Their discovery derives in large part from intensive studies of HIV and SIV that revealed restriction factors acting at various stages of the retroviral life cycle. Recent studies indicate that some factors restrict both retroviruses and retrotransposons but surprisingly in ways that may differ. We screened known interferon-stimulated antiviral proteins previously untested for their effects on cell culture retrotransposition. Several factors, including BST2, ISG20, MAVS, MX2, and ZAP, showed strong L1 inhibition. We focused on ZAP (PARP13/ZC3HAV1), a zinc-finger protein that targets viruses of several families, including Retroviridae, Tiloviridae, and Togaviridae, and show that ZAP expression also strongly restricts retrotransposition in cell culture through loss of L1 RNA and ribonucleoprotein particle integrity. Association of ZAP with the L1 ribonucleoprotein particle is supported by co-immunoprecipitation and co-localization with ORF1p in cytoplasmic stress granules. We also used mass spectrometry to determine the protein components of the ZAP interactome, and identified many proteins that directly interact and colocalize with ZAP, including MOV10, an RNA helicase previously shown to suppress retrotransposons. The detection of a chaperonin complex, RNA degradation proteins, helicases, post-translational modifiers, and components of chromatin modifying complexes suggest mechanisms of ZAP anti-retroelement activity that function in the cytoplasm and perhaps also in the nucleus. The association of the ZAP ribonucleoprotein particle with many interferon-stimulated gene products indicates it may be a key player in the interferon response. Retrotransposons are mobile DNA elements that duplicate themselves by a "copy and paste" mechanism using an RNA intermediate. They are insertional mutagens that have had profound effects on genome evolution, fostering DNA deletions, insertions and rearrangements, and altering gene expression. LINE-1 retrotransposons occupy 17% of human DNA, although it is believed that only about 100 remain competent for retrotransposition in any individual. The cell has evolved defenses restricting retrotransposition, involving in some cases interferon-stimulated genes (ISGs) that are part of the innate immune system that protects the cell from viral infections. We screened a panel of ISGs and found several to strongly limit retrotransposition in a cell culture assay. Our investigations increase understanding of how ZAP, an important restriction factor against positive- and negative-strand RNA and some DNA viruses, also interacts with human retrotransposons to prevent genome mutation. Microscopy and immunoprecipitation show a close association of ZAP protein with the L1 ribonucleoprotein particle, as well as MOV10, an RNA helicase that also inhibits retrotransposons. A detailed examination of the ZAP protein interactome reveals many other ISGs that directly bind ZAP, and suggests new directions for exploring the mechanisms of ZAP-mediated anti-retroelement activity.
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Abstract
Long-terminal repeat (LTR)-retrotransposons generate a copy of their DNA (cDNA) by reverse transcription of their RNA genome in cytoplasmic nucleocapsids. They are widespread in the eukaryotic kingdom and are the evolutionary progenitors of retroviruses [1]. The Ty1 element of the budding yeast Saccharomyces cerevisiae was the first LTR-retrotransposon demonstrated to mobilize through an RNA intermediate, and not surprisingly, is the best studied. The depth of our knowledge of Ty1 biology stems not only from the predominance of active Ty1 elements in the S. cerevisiae genome but also the ease and breadth of genomic, biochemical and cell biology approaches available to study cellular processes in yeast. This review describes the basic structure of Ty1 and its gene products, the replication cycle, the rapidly expanding compendium of host co-factors known to influence retrotransposition and the nature of Ty1's elaborate symbiosis with its host. Our goal is to illuminate the value of Ty1 as a paradigm to explore the biology of LTR-retrotransposons in multicellular organisms, where the low frequency of retrotransposition events presents a formidable barrier to investigations of retrotransposon biology.
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Exploiting the power of LINE-1 retrotransposon mutagenesis for identification of genes involved in embryonic stem cell differentiation. Stem Cell Rev Rep 2014; 10:408-16. [PMID: 24610122 PMCID: PMC4008784 DOI: 10.1007/s12015-014-9500-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Identifying the genes or epigenetic factors that control the self-renewal and differentiation of stem cells is critical to understanding the molecular basis of cell commitment. Although a number of insertional mutagenesis vectors have been developed for identifying gene functions in animal models, the L1 retrotransposition system offers additional advantages as a tool to disrupt genes in embryonic stem cells in order to identify their functions and the phenotypes associated with them. Recent advances in producing synthetic versions of L1 retrotransposon vector system and the optimization of techniques to accurately identify retrotransposon integration sites have increased their utility for gene discovery applications. We have developed a novel episomal, nonviral L1 retrotransposon vector using scaffold/matrix attachment regions that provides stable, sustained levels of retrotransposition in cell cultures without being affected by epigenetic silencing or from some of the common problems of vector integration. This modified vector contains a GFP marker whose expression occurs only after successful gene disruption events and thus the cells with disrupted genes can be easily picked for functional analysis. Here we present a method to disrupt gene function in embryonic stem cells that aid in the identification of genes involved in stem cell differentiation processes. The methods presented here can be easily adapted to the study of other types of cancer stem cells or induced pluripotent stem cells using the L1 retrotransposon as an insertional mutagen.
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Arokium H, Kamata M, Kim S, Kim N, Liang M, Presson AP, Chen IS. Deep sequencing reveals low incidence of endogenous LINE-1 retrotransposition in human induced pluripotent stem cells. PLoS One 2014; 9:e108682. [PMID: 25289675 PMCID: PMC4188539 DOI: 10.1371/journal.pone.0108682] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 09/03/2014] [Indexed: 01/27/2023] Open
Abstract
Long interspersed element-1 (LINE-1 or L1) retrotransposition induces insertional mutations that can result in diseases. It was recently shown that the copy number of L1 and other retroelements is stable in induced pluripotent stem cells (iPSCs). However, by using an engineered reporter construct over-expressing L1, another study suggests that reprogramming activates L1 mobility in iPSCs. Given the potential of human iPSCs in therapeutic applications, it is important to clarify whether these cells harbor somatic insertions resulting from endogenous L1 retrotransposition. Here, we verified L1 expression during and after reprogramming as well as potential somatic insertions driven by the most active human endogenous L1 subfamily (L1Hs). Our results indicate that L1 over-expression is initiated during the reprogramming process and is subsequently sustained in isolated clones. To detect potential somatic insertions in iPSCs caused by L1Hs retotransposition, we used a novel sequencing strategy. As opposed to conventional sequencing direction, we sequenced from the 3′ end of L1Hs to the genomic DNA, thus enabling the direct detection of the polyA tail signature of retrotransposition for verification of true insertions. Deep coverage sequencing thus allowed us to detect seven potential somatic insertions with low read counts from two iPSC clones. Negative PCR amplification in parental cells, presence of a polyA tail and absence from seven L1 germline insertion databases highly suggested true somatic insertions in iPSCs. Furthermore, these insertions could not be detected in iPSCs by PCR, likely due to low abundance. We conclude that L1Hs retrotransposes at low levels in iPSCs and therefore warrants careful analyses for genotoxic effects.
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Affiliation(s)
- Hubert Arokium
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Masakazu Kamata
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Sanggu Kim
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Namshin Kim
- Korean Bioinformation Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea
| | - Min Liang
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Angela P. Presson
- Department of Biostatistics, University of California Los Angeles School of Public Health, University of California Los Angeles, Los Angeles, California, United States of America
| | - Irvin S. Chen
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, United States of America
- * E-mail:
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Retrotransposons in pluripotent cells: Impact and new roles in cellular plasticity. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1849:417-26. [PMID: 25042909 DOI: 10.1016/j.bbagrm.2014.07.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 07/08/2014] [Accepted: 07/10/2014] [Indexed: 12/27/2022]
Abstract
Transposable Elements are pieces of DNA able to mobilize from one location to another within genomes. Although they constitute more than 50% of the human genome, they have been classified as selfish DNA, with the only mission to spread within genomes and generate more copies of themselves that will ensure their presence over generations. Despite their remarkable prevalence, only a minor group of transposable elements remain active in the human genome and can sporadically be associated with the generation of a genetic disorder due to their ongoing mobility. Most of the transposable elements identified in the human genome corresponded to fixed insertions that no longer move in genomes. As selfish DNA, transposable element insertions accumulate in cell types where genetic information can be passed to the next generation. Indeed, work from different laboratories has demonstrated that the main heritable load of TE accumulation in humans occurs during early embryogenesis. Thus, active transposable elements have a clear impact on our pluripotent genome. However, recent findings suggest that the main proportion of fixed non-mobile transposable elements might also have emerging roles in cellular plasticity. In this concise review, we provide an overview of the impact of currently active transposable elements in our pluripotent genome and further discuss new roles of transposable elements (active or not) in regulating pluripotency. This article is part of a Special Issue entitled: Stress as a fundamental theme in cell plasticity.
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Yang L, Brunsfeld J, Scott L, Wichman H. Reviving the dead: history and reactivation of an extinct l1. PLoS Genet 2014; 10:e1004395. [PMID: 24968166 PMCID: PMC4072516 DOI: 10.1371/journal.pgen.1004395] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 04/07/2014] [Indexed: 11/18/2022] Open
Abstract
Although L1 sequences are present in the genomes of all placental mammals and marsupials examined to date, their activity was lost in the megabat family, Pteropodidae, ∼24 million years ago. To examine the characteristics of L1s prior to their extinction, we analyzed the evolutionary history of L1s in the genome of a megabat, Pteropus vampyrus, and found a pattern of periodic L1 expansion and quiescence. In contrast to the well-characterized L1s in human and mouse, megabat genomes have accommodated two or more simultaneously active L1 families throughout their evolutionary history, and major peaks of L1 deposition into the genome always involved multiple families. We compared the consensus sequences of the two major megabat L1 families at the time of their extinction to consensus L1s of a variety of mammalian species. Megabat L1s are comparable to the other mammalian L1s in terms of adenosine content and conserved amino acids in the open reading frames (ORFs). However, the intergenic region (IGR) of the reconstructed element from the more active family is dramatically longer than the IGR of well-characterized human and mouse L1s. We synthesized the reconstructed element from this L1 family and tested the ability of its components to support retrotransposition in a tissue culture assay. Both ORFs are capable of supporting retrotransposition, while the IGR is inhibitory to retrotransposition, especially when combined with either of the reconstructed ORFs. We dissected the inhibitory effect of the IGR by testing truncated and shuffled versions and found that length is a key factor, but not the only one affecting inhibition of retrotransposition. Although the IGR is inhibitory to retrotransposition, this inhibition does not account for the extinction of L1s in megabats. Overall, the evolution of the L1 sequence or the quiescence of L1 is unlikely the reason of L1 extinction.
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Affiliation(s)
- Lei Yang
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, United States of America
- Institute for Bioinformatics and Evolutionary Studies, University of Idaho, Moscow, Idaho, United States of America
| | - John Brunsfeld
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, United States of America
| | - LuAnn Scott
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, United States of America
| | - Holly Wichman
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, United States of America
- Institute for Bioinformatics and Evolutionary Studies, University of Idaho, Moscow, Idaho, United States of America
- * E-mail:
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Morrish TA, Bekbolysnov D, Velliquette D, Morgan M, Ross B, Wang Y, Chaney B, McQuigg J, Fager N, Maine IP. Multiple Mechanisms Contribute To Telomere Maintenance. JOURNAL OF CANCER BIOLOGY & RESEARCH 2013; 1:1012. [PMID: 25285314 PMCID: PMC4181876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The unlimited growth potential of tumors depends on telomere maintenance and typically depends on telomerase, an RNA-dependent DNA polymerase, which reverse transcribes the telomerase RNA template, synthesizing telomere repeats at the ends of chromosomes. Studies in various model organisms genetically deleted for telomerase indicate that several recombination-based mechanisms also contribute to telomere maintenance. Understanding the molecular basis of these mechanisms is critical since some human tumors form without telomerase, yet the sequence is maintained at the telomeres. Recombination-based mechanisms also likely contribute at some frequency to telomere maintenance in tumors expressing telomerase. Preventing telomere maintenance is predicted to impact tumor growth, yet inhibiting telomerase may select for the recombination-based mechanisms. Telomere recombination mechanisms likely involve altered or unregulated pathways of DNA repair. The use of some DNA damaging agents may encourage the use of these unregulated pathways of DNA repair to be utilized and may allow some tumors to generate resistance to these agents depending on which repair pathways are altered in the tumors. This review will discuss the various telomere recombination mechanisms and will provide rationale regarding the possibility that L1 retrotransposition may contribute to telomere maintenance in tumors lacking telomerase.
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Affiliation(s)
- Tammy A. Morrish
- Department of Biochemistry and Cancer Biology, University of Toledo, Toledo, OH 43614, USA
| | - Dulat Bekbolysnov
- Department of Biochemistry and Cancer Biology, University of Toledo, Toledo, OH 43614, USA
- Graduate Program in Microbiology and Immunology, University of Toledo, Toledo, OH 43614 USA
| | - David Velliquette
- Department of Biochemistry and Cancer Biology, University of Toledo, Toledo, OH 43614, USA
| | - Michelle Morgan
- Department of Biochemistry and Cancer Biology, University of Toledo, Toledo, OH 43614, USA
| | - Bryan Ross
- Department of Biochemistry and Cancer Biology, University of Toledo, Toledo, OH 43614, USA
| | - Yongheng Wang
- Department of Biological Sciences, University of Toledo, OH 43614, USA
| | - Benjamin Chaney
- Department of Biochemistry and Cancer Biology, University of Toledo, Toledo, OH 43614, USA
| | - Jessica McQuigg
- Department of Biochemistry and Cancer Biology, University of Toledo, Toledo, OH 43614, USA
| | - Nathan Fager
- Department of Biochemistry and Cancer Biology, University of Toledo, Toledo, OH 43614, USA
| | - Ira P. Maine
- Department of Biochemistry and Cancer Biology, University of Toledo, Toledo, OH 43614, USA
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Belan E. LINEs of evidence: noncanonical DNA replication as an epigenetic determinant. Biol Direct 2013; 8:22. [PMID: 24034780 PMCID: PMC3868326 DOI: 10.1186/1745-6150-8-22] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 09/06/2013] [Indexed: 12/17/2022] Open
Abstract
LINE-1 (L1) retrotransposons are repetitive elements in mammalian genomes. They are
capable of synthesizing DNA on their own RNA templates by harnessing reverse
transcriptase (RT) that they encode. Abundantly expressed full-length L1s and their
RT are found to globally influence gene expression profiles, differentiation state,
and proliferation capacity of early embryos and many types of cancer, albeit by yet
unknown mechanisms. They are essential for the progression of early development and
the establishment of a cancer-related undifferentiated state. This raises important
questions regarding the functional significance of L1 RT in these cell systems.
Massive nuclear L1-linked reverse transcription has been shown to occur in mouse
zygotes and two-cell embryos, and this phenomenon is purported to be DNA replication
independent. This review argues against this claim with the goal of understanding the
nature of this phenomenon and the role of L1 RT in early embryos and cancers.
Available L1 data are revisited and integrated with relevant findings accumulated in
the fields of replication timing, chromatin organization, and epigenetics, bringing
together evidence that strongly supports two new concepts. First, noncanonical
replication of a portion of genomic full-length L1s by means of L1 RNP-driven reverse
transcription is proposed to co-exist with DNA polymerase-dependent replication of
the rest of the genome during the same round of DNA replication in embryonic and
cancer cell systems. Second, the role of this mechanism is thought to be epigenetic;
it might promote transcriptional competence of neighboring genes linked to
undifferentiated states through the prevention of tethering of involved L1s to the
nuclear periphery. From the standpoint of these concepts, several hitherto
inexplicable phenomena can be explained. Testing methods for the model are
proposed.
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Affiliation(s)
- Ekaterina Belan
- Genetics Laboratory, Royal University Hospital, Saskatoon, SK S7N 0W8, Canada.
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Terasaki N, Goodier JL, Cheung LE, Wang YJ, Kajikawa M, Kazazian HH, Okada N. In vitro screening for compounds that enhance human L1 mobilization. PLoS One 2013; 8:e74629. [PMID: 24040300 PMCID: PMC3770661 DOI: 10.1371/journal.pone.0074629] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 08/05/2013] [Indexed: 12/31/2022] Open
Abstract
The Long interspersed element 1 (LINE1 or L1) retrotransposon constitutes 17% of the human genome. There are currently 80-100 human L1 elements that are thought to be active in any diploid human genome. These elements can mobilize into new locations of the genome, resulting in changes in genomic information. Active L1s are thus considered to be a type of endogenous mutagen, and L1 insertions can cause disease. Certain stresses, such as gamma radiation, oxidative stress, and treatment with some agents, can induce transcription and/or mobilization of retrotransposons. In this study, we used a reporter gene assay in HepG2 cells to screen compounds for the potential to enhance the transcription of human L1. We assessed 95 compounds including genotoxic agents, substances that induce cellular stress, and commercially available drugs. Treatment with 15 compounds increased the L1 promoter activity by >1.5-fold (p<0.05) after 6 or 24 hours of treatment. In particular, genotoxic agents (benzo[a]pyrene, camptothecin, cytochalasin D, merbarone, and vinblastine), PPARα agonists (bezafibrate and fenofibrate), and non-steroidal anti-inflammatory drugs (diflunisal, flufenamic acid, salicylamide, and sulindac) induced L1 promoter activity. To examine their effects on L1 retrotransposition, we developed a high-throughput real-time retrotransposition assay using a novel secreted Gaussia luciferase reporter cassette. Three compounds (etomoxir, WY-14643, and salicylamide) produced a significant enhancement in L1 retrotransposition. This is the first study to report the effects of a wide variety of compounds on L1 transcription and retrotransposition. These results suggest that certain chemical- and drug-induced stresses might have the potential to cause genomic mutations by inducing L1 mobilization. Thus, the risk of induced L1 transcription and retrotransposition should be considered during drug safety evaluation and environmental risk assessments of chemicals.
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Affiliation(s)
- Natsuko Terasaki
- Department of Biological Science, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
| | - John L. Goodier
- McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Ling E. Cheung
- McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Yue J. Wang
- McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Masaki Kajikawa
- Department of Biological Science, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
| | - Haig H. Kazazian
- McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Norihiro Okada
- Department of Biological Science, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
- Department of Life Sciences, National Cheng Kung University, Tainan, Taiwan
- * E-mail:
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Ranzani M, Annunziato S, Adams DJ, Montini E. Cancer gene discovery: exploiting insertional mutagenesis. Mol Cancer Res 2013; 11:1141-58. [PMID: 23928056 DOI: 10.1158/1541-7786.mcr-13-0244] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Insertional mutagenesis has been used as a functional forward genetics screen for the identification of novel genes involved in the pathogenesis of human cancers. Different insertional mutagens have been successfully used to reveal new cancer genes. For example, retroviruses are integrating viruses with the capacity to induce the deregulation of genes in the neighborhood of the insertion site. Retroviruses have been used for more than 30 years to identify cancer genes in the hematopoietic system and mammary gland. Similarly, another tool that has revolutionized cancer gene discovery is the cut-and-paste transposons. These DNA elements have been engineered to contain strong promoters and stop cassettes that may function to perturb gene expression upon integration proximal to genes. In addition, complex mouse models characterized by tissue-restricted activity of transposons have been developed to identify oncogenes and tumor suppressor genes that control the development of a wide range of solid tumor types, extending beyond those tissues accessible using retrovirus-based approaches. Most recently, lentiviral vectors have appeared on the scene for use in cancer gene screens. Lentiviral vectors are replication-defective integrating vectors that have the advantage of being able to infect nondividing cells, in a wide range of cell types and tissues. In this review, we describe the various insertional mutagens focusing on their advantages/limitations, and we discuss the new and promising tools that will improve the insertional mutagenesis screens of the future.
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Affiliation(s)
- Marco Ranzani
- San Raffaele-Telethon Institute for Gene Therapy, via Olgettina 58, 20132, Milan, Italy.
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48
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Grandi FC, An W. Non-LTR retrotransposons and microsatellites: Partners in genomic variation. Mob Genet Elements 2013; 3:e25674. [PMID: 24195012 PMCID: PMC3812793 DOI: 10.4161/mge.25674] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 07/07/2013] [Accepted: 07/09/2013] [Indexed: 01/10/2023] Open
Abstract
The human genome is laden with both non-LTR (long-terminal repeat) retrotransposons and microsatellite repeats. Both types of sequences are able to, either actively or passively, mutagenize the genomes of human individuals and are therefore poised to dynamically alter the human genomic landscape across generations. Non-LTR retrotransposons, such as L1 and Alu, are a major source of new microsatellites, which are born both concurrently and subsequently to L1 and Alu integration into the genome. Likewise, the mutation dynamics of microsatellite repeats have a direct impact on the fitness of their non-LTR retrotransposon parent owing to microsatellite expansion and contraction. This review explores the interactions and dynamics between non-LTR retrotransposons and microsatellites in the context of genomic variation and evolution.
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Affiliation(s)
- Fiorella C Grandi
- School of Molecular Biosciences and Center for Reproductive Biology; Washington State University; Pullman, WA USA
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Controlled insertional mutagenesis using a LINE-1 (ORFeus) gene-trap mouse model. Proc Natl Acad Sci U S A 2013; 110:E2706-13. [PMID: 23818630 DOI: 10.1073/pnas.1302504110] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
A codon-optimized mouse LINE-1 element, ORFeus, exhibits dramatically higher retrotransposition frequencies compared with its native long interspersed element 1 counterpart. To establish a retrotransposon-mediated mouse model with regulatable and potent mutagenic capabilities, we generated a tetracycline (tet)-regulated ORFeus element harboring a gene-trap cassette. Here, we show that mice expressing tet-ORFeus broadly exhibit robust retrotransposition in somatic tissues when treated with doxycycline. Consistent with a significant mutagenic burden, we observed a reduced number of double transgenic animals when treated with high-level doxycycline during embryogenesis. Transgene induction in skin resulted in a white spotting phenotype due to somatic ORFeus-mediated mutations that likely disrupt melanocyte development. The data suggest a high level of transposition in melanocyte precursors and consequent mutation of genes important for melanoblast proliferation, differentiation, or migration. These findings reveal the utility of a retrotransposon-based mutagenesis system as an alternative to existing DNA transposon systems. Moreover, breeding these mice to different tet-transactivator/reversible tet-transactivator lines supports broad functionality of tet-ORFeus because of the potential for dose-dependent, tissue-specific, and temporal-specific mutagenesis.
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Grandi FC, Rosser JM, An W. LINE-1-derived poly(A) microsatellites undergo rapid shortening and create somatic and germline mosaicism in mice. Mol Biol Evol 2012; 30:503-12. [PMID: 23125228 DOI: 10.1093/molbev/mss251] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Interspersed and tandem repeat sequences comprise the bulk of mammalian genomes. Interspersed repeats result from successive replication by transposable elements, such as Alu and long interspersed element type 1 (L1). Microsatellites are tandem repeats of 1-6 base pairs, among which poly(A) microsatellites are the most abundant in the human genome. The rise and fall of a microsatellite has been depicted as a life cycle. Previous studies have demonstrated that Alu and L1 insertions are a major source of A-rich microsatellites owing to the concurrent formation of a poly(A) DNA tract at the 3'-end of each insertion. The fate of such poly(A) tracts has been studied by surveying the length distribution of genomic resident Alu and L1 insertions. However, these cross-sectional studies provide no information about the tempo of mutation immediately after birth. In this study, de novo L1 insertions were created using a transgenic L1 mouse model and traced through generations to investigate the early life of poly(A) microsatellites. High frequencies of intra-individual and intergenerational shortening were observed for long poly(A) tracts, creating somatic and germline mosaicism at the insertion site, whereas little variation was observed for short poly(A) alleles. As poly(A) microsatellites are the major intrinsic signal for nucleosome positioning, their remarkable abundance and variability make them a significant source of epigenetic variation. Thus, the birth of poly(A) microsatellites from retrotransposons and the subsequent rapid and variable shortening represent a new way with which retrotransposons can modify the genetic and epigenetic architecture of our genome.
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Affiliation(s)
- Fiorella C Grandi
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, USA
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