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Wolf G, de Iaco A, Sun MA, Bruno M, Tinkham M, Hoang D, Mitra A, Ralls S, Trono D, Macfarlan TS. KRAB-zinc finger protein gene expansion in response to active retrotransposons in the murine lineage. eLife 2020; 9:56337. [PMID: 32479262 PMCID: PMC7289599 DOI: 10.7554/elife.56337] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 05/31/2020] [Indexed: 11/13/2022] Open
Abstract
The Krüppel-associated box zinc finger protein (KRAB-ZFP) family diversified in mammals. The majority of human KRAB-ZFPs bind transposable elements (TEs), however, since most TEs are inactive in humans it is unclear whether KRAB-ZFPs emerged to suppress TEs. We demonstrate that many recently emerged murine KRAB-ZFPs also bind to TEs, including the active ETn, IAP, and L1 families. Using a CRISPR/Cas9-based engineering approach, we genetically deleted five large clusters of KRAB-ZFPs and demonstrate that target TEs are de-repressed, unleashing TE-encoded enhancers. Homozygous knockout mice lacking one of two KRAB-ZFP gene clusters on chromosome 2 and chromosome 4 were nonetheless viable. In pedigrees of chromosome 4 cluster KRAB-ZFP mutants, we identified numerous novel ETn insertions with a modest increase in mutants. Our data strongly support the current model that recent waves of retrotransposon activity drove the expansion of KRAB-ZFP genes in mice and that many KRAB-ZFPs play a redundant role restricting TE activity.
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Affiliation(s)
- Gernot Wolf
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, United States
| | - Alberto de Iaco
- School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Ming-An Sun
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, United States
| | - Melania Bruno
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, United States
| | - Matthew Tinkham
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, United States
| | - Don Hoang
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, United States
| | - Apratim Mitra
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, United States
| | - Sherry Ralls
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, United States
| | - Didier Trono
- School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Todd S Macfarlan
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, United States
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Fukuda K, Shinkai Y. SETDB1-Mediated Silencing of Retroelements. Viruses 2020; 12:E596. [PMID: 32486217 PMCID: PMC7354471 DOI: 10.3390/v12060596] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 05/28/2020] [Accepted: 05/28/2020] [Indexed: 12/11/2022] Open
Abstract
SETDB1 (SET domain bifurcated histone lysine methyltransferase 1) is a protein lysine methyltransferase and methylates histone H3 at lysine 9 (H3K9). Among other H3K9 methyltransferases, SETDB1 and SETDB1-mediated H3K9 trimethylation (H3K9me3) play pivotal roles for silencing of endogenous and exogenous retroelements, thus contributing to genome stability against retroelement transposition. Furthermore, SETDB1 is highly upregulated in various tumor cells. In this article, we describe recent advances about how SETDB1 activity is regulated, how SETDB1 represses various types of retroelements such as L1 and class I, II, and III endogenous retroviruses (ERVs) in concert with other epigenetic factors such as KAP1 and the HUSH complex and how SETDB1-mediated H3K9 methylation can be maintained during replication.
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Affiliation(s)
- Kei Fukuda
- Cellular Memory Laboratory, RIKEN Cluster for Pioneering Research, RIKEN, Wako 351-0198, Japan
| | - Yoichi Shinkai
- Cellular Memory Laboratory, RIKEN Cluster for Pioneering Research, RIKEN, Wako 351-0198, Japan
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53
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Li X, Wang X, Cheng Z, Zhu Q. AGO2 and its partners: a silencing complex, a chromatin modulator, and new features. Crit Rev Biochem Mol Biol 2020; 55:33-53. [DOI: 10.1080/10409238.2020.1738331] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Xiaojing Li
- Xiangya School of Pharmaceutical Sciences, Central South University, Changsha, Hunan, China
| | - Xueying Wang
- Xiangya School of Pharmaceutical Sciences, Central South University, Changsha, Hunan, China
| | - Zeneng Cheng
- Xiangya School of Pharmaceutical Sciences, Central South University, Changsha, Hunan, China
| | - Qubo Zhu
- Xiangya School of Pharmaceutical Sciences, Central South University, Changsha, Hunan, China
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54
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Ectopic expression of the Stabilin2 gene triggered by an intracisternal A particle (IAP) element in DBA/2J strain of mice. Mamm Genome 2020; 31:2-16. [PMID: 31912264 PMCID: PMC7060167 DOI: 10.1007/s00335-019-09824-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 12/29/2019] [Indexed: 12/21/2022]
Abstract
Stabilin2 (Stab2) encodes a large transmembrane protein which is predominantly expressed in the liver sinusoidal endothelial cells (LSECs) and functions as a scavenger receptor for various macromolecules including hyaluronans (HA). In DBA/2J mice, plasma HA concentration is ten times higher than in 129S6 or C57BL/6J mice, and this phenotype is genetically linked to the Stab2 locus. Stab2 mRNA in the LSECs was significantly lower in DBA/2J than in 129S6, leading to reduced STAB2 proteins in the DBA/2J LSECs. We found a retrovirus-derived transposable element, intracisternal A particle (IAP), in the promoter region of Stab2DBA which likely interferes with normal expression in the LSECs. In contrast, in other tissues of DBA/2J mice, the IAP drives high ectopic Stab2DBA transcription starting within the 5′ long terminal repeat of IAP in a reverse orientation and continuing through the downstream Stab2DBA. Ectopic transcription requires the Stab2-IAP element but is dominantly suppressed by the presence of loci on 59.7–73.0 Mb of chromosome (Chr) 13 from C57BL/6J, while the same region in 129S6 requires additional loci for complete suppression. Chr13:59.9–73 Mb contains a large number of genes encoding Krüppel-associated box-domain zinc-finger proteins that target transposable elements-derived sequences and repress their expression. Despite the high amount of ectopic Stab2DBA transcript in tissues other than liver, STAB2 protein was undetectable and unlikely to contribute to the plasma HA levels of DBA/2J mice. Nevertheless, the IAP insertion and its effects on the transcription of the downstream Stab2DBA exemplify that stochastic evolutional events could significantly influence susceptibility to complex but common diseases.
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55
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Bertozzi TM, Ferguson-Smith AC. Metastable epialleles and their contribution to epigenetic inheritance in mammals. Semin Cell Dev Biol 2020; 97:93-105. [PMID: 31551132 DOI: 10.1016/j.semcdb.2019.08.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 08/15/2019] [Accepted: 08/20/2019] [Indexed: 02/02/2023]
Abstract
Many epigenetic differences between individuals are driven by genetic variation. Mammalian metastable epialleles are unusual in that they show variable DNA methylation states between genetically identical individuals. The occurrence of such states across generations has resulted in their consideration by many as strong evidence for epigenetic inheritance in mammals, with the classic Avy and AxinFu mouse models - each products of repeat element insertions - being the most widely accepted examples. Equally, there has been interest in exploring their use as epigenetic biosensors given their susceptibility to environmental compromise. Here we review the classic murine metastable epialleles as well as more recently identified candidates, with the aim of providing a more holistic understanding of their biology. We consider the extent to which epigenetic inheritance occurs at metastable epialleles and explore the limited mechanistic insights into the establishment of their variable epigenetic states. We discuss their environmental modulation and their potential relevance in genome regulation. In light of recent whole-genome screens for novel metastable epialleles, we point out the need to reassess their biological relevance in multi-generational studies and we highlight their value as a model to study repeat element silencing as well as the mechanisms and consequences of mammalian epigenetic stochasticity.
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Affiliation(s)
- Tessa M Bertozzi
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
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56
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Legoff L, D’Cruz SC, Tevosian S, Primig M, Smagulova F. Transgenerational Inheritance of Environmentally Induced Epigenetic Alterations during Mammalian Development. Cells 2019; 8:cells8121559. [PMID: 31816913 PMCID: PMC6953051 DOI: 10.3390/cells8121559] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 11/29/2019] [Accepted: 12/02/2019] [Indexed: 12/11/2022] Open
Abstract
Genetic studies traditionally focus on DNA as the molecule that passes information on from parents to their offspring. Changes in the DNA code alter heritable information and can more or less severely affect the progeny's phenotype. While the idea that information can be inherited between generations independently of the DNA's nucleotide sequence is not new, the outcome of recent studies provides a mechanistic foundation for the concept. In this review, we attempt to summarize our current knowledge about the transgenerational inheritance of environmentally induced epigenetic changes. We focus primarily on studies using mice but refer to other species to illustrate salient points. Some studies support the notion that there is a somatic component within the phenomenon of epigenetic inheritance. However, here, we will mostly focus on gamete-based processes and the primary molecular mechanisms that are thought to contribute to epigenetic inheritance: DNA methylation, histone modifications, and non-coding RNAs. Most of the rodent studies published in the literature suggest that transgenerational epigenetic inheritance through gametes can be modulated by environmental factors. Modification and redistribution of chromatin proteins in gametes is one of the major routes for transmitting epigenetic information from parents to the offspring. Our recent studies provide additional specific cues for this concept and help better understand environmental exposure influences fitness and fidelity in the germline. In summary, environmental cues can induce parental alterations and affect the phenotypes of offspring through gametic epigenetic inheritance. Consequently, epigenetic factors and their heritability should be considered during disease risk assessment.
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Affiliation(s)
- Louis Legoff
- Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environnement et travail)—UMR_S 1085, F-35000 Rennes, France; (L.L.); (S.C.D.); (M.P.)
| | - Shereen Cynthia D’Cruz
- Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environnement et travail)—UMR_S 1085, F-35000 Rennes, France; (L.L.); (S.C.D.); (M.P.)
| | - Sergei Tevosian
- University of Florida, Department of Physiological Sciences Box 100144, 1333 Center Drive, Gainesville, FL 32610, USA;
| | - Michael Primig
- Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environnement et travail)—UMR_S 1085, F-35000 Rennes, France; (L.L.); (S.C.D.); (M.P.)
| | - Fatima Smagulova
- Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environnement et travail)—UMR_S 1085, F-35000 Rennes, France; (L.L.); (S.C.D.); (M.P.)
- Correspondence:
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Abstract
Endogenous retroviruses (ERVs) consist of interspersed genomic elements derived from retroviral infections that invaded our ancestral germ lines. Notably, ERVs compose 8 to 10% of the human and mouse genomes. Until recently, ERVs were considered unimportant, so-called “junk” DNA. However, this naïve characterization has changed dramatically as distinct ERV-related functions are revealed in heath and disease. In this study, we demonstrate that chronic ERV activation is associated with cognitive impairment, measured with hippocampus-related tasks, in a mouse model. We confirm these findings in an independent mouse model of acute retroviral activation and show that cognitive deficits are mitigated in the absence of the retroviral RNA sensor protein MAVS. Our results point to an underappreciated therapeutic modality for impaired cognition. Retrotransposons compose a staggering 40% of the mammalian genome. Among them, endogenous retroviruses (ERV) represent sequences that closely resemble the proviruses created from exogenous retroviral infection. ERVs make up 8 to 10% of human and mouse genomes and range from evolutionarily ancient sequences to recent acquisitions. Studies in Drosophila have provided a causal link between genomic retroviral elements and cognitive decline; however, in mammals, the role of ERVs in learning and memory remains unclear. Here we studied 2 independent murine models for ERV activation: muMT strain (lacking B cells and antibody production) and intracerebroventricular injection of streptozotocin (ICVI-STZ). We conducted behavioral assessments (contextual fear memory and spatial learning), as well as gene and protein analysis (RNA sequencing, PCR, immunohistochemistry, and western blot assays). Mice lacking mitochondrial antiviral-signaling protein (MAVS) and mice lacking stimulator of IFN genes protein (STING), 2 downstream sensors of ERV activation, provided confirmation of ERV impact. We found that muMT mice and ICVI-STZ mice induced hippocampal ERV activation, as shown by increased gene and protein expression of the Gag sequence of the transposable element intracisternal A-particle. ERV activation was accompanied by significant hippocampus-related memory impairment in both models. Notably, the deficiency of the MAVS pathway was protective against ICVI-STZ–induced cognitive pathology. Overall, our results demonstrate that ERV activation is associated with cognitive impairment in mice. Moreover, they provide a molecular target for strategies aimed at attenuating retroviral element sensing, via MAVS, to treat dementia and neuropsychiatric disorders.
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Endogenous Retroviruses Activity as a Molecular Signature of Neurodevelopmental Disorders. Int J Mol Sci 2019; 20:ijms20236050. [PMID: 31801288 PMCID: PMC6928979 DOI: 10.3390/ijms20236050] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Revised: 11/26/2019] [Accepted: 11/28/2019] [Indexed: 12/20/2022] Open
Abstract
Human endogenous retroviruses (HERVs) are genetic elements resulting from relics of ancestral infection of germline cells, now recognized as cofactors in the etiology of several complex diseases. Here we present a review of findings supporting the role of the abnormal HERVs activity in neurodevelopmental disorders. The derailment of brain development underlies numerous neuropsychiatric conditions, likely starting during prenatal life and carrying on during subsequent maturation of the brain. Autism spectrum disorders, attention deficit hyperactivity disorders, and schizophrenia are neurodevelopmental disorders that arise clinically during early childhood or adolescence, currently attributed to the interplay among genetic vulnerability, environmental risk factors, and maternal immune activation. The role of HERVs in human embryogenesis, their intrinsic responsiveness to external stimuli, and the interaction with the immune system support the involvement of HERVs in the derailed neurodevelopmental process. Although definitive proofs that HERVs are involved in neurobehavioral alterations are still lacking, both preclinical models and human studies indicate that the abnormal expression of ERVs could represent a neurodevelopmental disorders-associated biological trait in affected individuals and their parents.
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59
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Tanave A, Imai Y, Koide T. Nested retrotransposition in the East Asian mouse genome causes the classical nonagouti mutation. Commun Biol 2019; 2:283. [PMID: 31396563 PMCID: PMC6677723 DOI: 10.1038/s42003-019-0539-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Accepted: 07/10/2019] [Indexed: 01/31/2023] Open
Abstract
Black coat color (nonagouti) is a widespread classical mutation in laboratory mouse strains. The intronic insertion of endogenous retrovirus VL30 in the nonagouti (a) allele of agouti gene was previously reported as the cause of the nonagouti phenotype. Here, we report agouti mouse strains from East Asia that carry the VL30 insertion, indicating that VL30 alone does not cause the nonagouti phenotype. We find that a rare type of endogenous retrovirus, β4, was integrated into the VL30 region at the a allele through nested retrotransposition, causing abnormal splicing. Targeted complete deletion of the β4 element restores agouti gene expression and agouti coat color, whereas deletion of β4 except for a single long terminal repeat results in black-and-tan coat color. Phylogenetic analyses show that the a allele and the β4 retrovirus originated from an East Asian mouse lineage most likely related to Japanese fancy mice. These findings reveal the causal mechanism and historic origin of the classical nonagouti mutation.
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Affiliation(s)
- Akira Tanave
- Mouse Genomics Resource Laboratory, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540 Japan
- Present Address: Laboratory for Mouse Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, 1–3 Yamadaoka, Suita, Osaka 565-0871 Japan
| | - Yuji Imai
- Mouse Genomics Resource Laboratory, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540 Japan
| | - Tsuyoshi Koide
- Mouse Genomics Resource Laboratory, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540 Japan
- Department of Genetics, SOKENDAI (The Graduate University for Advanced Studies), 1111 Yata, Mishima, Shizuoka 411-8540 Japan
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60
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Kong Q, Quan X, Du J, Tai Y, Liu W, Zhang J, Zhang X, Mu Y, Liu Z. Endo-siRNAs regulate early embryonic development by inhibiting transcription of long terminal repeat sequence in pig†. Biol Reprod 2019; 100:1431-1439. [PMID: 30883641 DOI: 10.1093/biolre/ioz042] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 02/21/2019] [Accepted: 03/16/2019] [Indexed: 11/12/2022] Open
Abstract
Activity of some endogenous retroviruses (ERVs) has been proven to be important for development of early mammalian embryo. However, abnormal activation of ERVs can also cause genetic diseases due to their ability to retrotranspose, so the regulatory mechanism to limit transcription of ERVs needs to be clarified. Endogenous small interfering RNA (endo-siRNA) has been reported to protect cells against transposable elements (TEs). Here, we determined the role of ERVs long terminal repeat sequences (LTRs) derived endo-siRNAs (LTR-siRNAs) on inhibition of the activity of ERVs during early embryonic development in pig. Seven most highly expressed LTR-siRNAs were identified in porcine zygote by high-throughput small RNA sequencing. We verified that the biogenesis of the LTR-siRNAs was DICER-dependent and they were generated from double-stranded RNA (dsRNA) formed by sense and antisense transcripts of LTRs. And, the expression of sense and antisense of LTRs might be due to the loss of DNA methylation at some LTR loci. Furthermore, we showed that the LTR-siRNAs could regulate early embryonic development by repression of LTRs expression at a post-transcriptional level. So, we propose here, during early embryonic development when epigenetic reprogramming occurs, the endo-siRNA pathway acts as a sophisticated balance of regulatory mechanism for ERV activity.
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Affiliation(s)
- Qingran Kong
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin, Harbin, China
| | - Xue Quan
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin, Harbin, China
| | - Jiawei Du
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin, Harbin, China
| | - Yurong Tai
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin, Harbin, China
| | - Wanxin Liu
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin, Harbin, China
| | - Jiaming Zhang
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin, Harbin, China
| | - Xiaolei Zhang
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin, Harbin, China
| | - Yanshuang Mu
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin, Harbin, China
| | - Zhonghua Liu
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin, Harbin, China
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61
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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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62
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Gagnier L, Belancio VP, Mager DL. Mouse germ line mutations due to retrotransposon insertions. Mob DNA 2019; 10:15. [PMID: 31011371 PMCID: PMC6466679 DOI: 10.1186/s13100-019-0157-4] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 04/01/2019] [Indexed: 12/24/2022] Open
Abstract
Transposable element (TE) insertions are responsible for a significant fraction of spontaneous germ line mutations reported in inbred mouse strains. This major contribution of TEs to the mutational landscape in mouse contrasts with the situation in human, where their relative contribution as germ line insertional mutagens is much lower. In this focussed review, we provide comprehensive lists of TE-induced mouse mutations, discuss the different TE types involved in these insertional mutations and elaborate on particularly interesting cases. We also discuss differences and similarities between the mutational role of TEs in mice and humans.
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Affiliation(s)
- Liane Gagnier
- Terry Fox Laboratory, BC Cancer and Department of Medical Genetics, University of British Columbia, V5Z1L3, Vancouver, BC Canada
| | - Victoria P. Belancio
- Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane Cancer Center, Tulane Center for Aging, New Orleans, LA 70112 USA
| | - Dixie L. Mager
- Terry Fox Laboratory, BC Cancer and Department of Medical Genetics, University of British Columbia, V5Z1L3, Vancouver, BC Canada
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Leandro J, Violante S, Argmann CA, Hagen J, Dodatko T, Bender A, Zhang W, Williams EG, Bachmann AM, Auwerx J, Yu C, Houten SM. Mild inborn errors of metabolism in commonly used inbred mouse strains. Mol Genet Metab 2019; 126:388-396. [PMID: 30709776 PMCID: PMC6535113 DOI: 10.1016/j.ymgme.2019.01.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 01/23/2019] [Accepted: 01/23/2019] [Indexed: 10/27/2022]
Abstract
Inbred mouse strains are a cornerstone of translational research but paradoxically many strains carry mild inborn errors of metabolism. For example, α-aminoadipic acidemia and branched-chain ketoacid dehydrogenase deficiency are known in C57BL/6J mice. Using RNA sequencing, we now reveal the causal variants in Dhtkd1 and Bckdhb, and the molecular mechanism underlying these metabolic defects. C57BL/6J mice have decreased Dhtkd1 mRNA expression due to a solitary long terminal repeat (LTR) in intron 4 of Dhtkd1. This LTR harbors an alternate splice donor site leading to a partial splicing defect and as a consequence decreased total and functional Dhtkd1 mRNA, decreased DHTKD1 protein and α-aminoadipic acidemia. Similarly, C57BL/6J mice have decreased Bckdhb mRNA expression due to an LTR retrotransposon in intron 1 of Bckdhb. This transposable element encodes an alternative exon 1 causing aberrant splicing, decreased total and functional Bckdhb mRNA and decreased BCKDHB protein. Using a targeted metabolomics screen, we also reveal elevated plasma C5-carnitine in 129 substrains. This biochemical phenotype resembles isovaleric acidemia and is caused by an exonic splice mutation in Ivd leading to partial skipping of exon 10 and IVD protein deficiency. In summary, this study identifies three causal variants underlying mild inborn errors of metabolism in commonly used inbred mouse strains.
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Affiliation(s)
- João Leandro
- Department of Genetics and Genomic Sciences, Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA
| | - Sara Violante
- Department of Genetics and Genomic Sciences, Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA; Mount Sinai Genomics, Inc, One Gustave L Levy Place #1497, New York, NY 10029, USA
| | - Carmen A Argmann
- Department of Genetics and Genomic Sciences, Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA
| | - Jacob Hagen
- Department of Genetics and Genomic Sciences, Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA
| | - Tetyana Dodatko
- Department of Genetics and Genomic Sciences, Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA
| | - Aaron Bender
- Department of Genetics and Genomic Sciences, Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA
| | - Wei Zhang
- Mount Sinai Genomics, Inc, One Gustave L Levy Place #1497, New York, NY 10029, USA
| | - Evan G Williams
- Department of Biology, Institute of Molecular Systems Biology, ETH Zürich, Zürich CH-8093, Switzerland
| | - Alexis M Bachmann
- Laboratory of Integrative and Systems Physiology, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Johan Auwerx
- Laboratory of Integrative and Systems Physiology, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Chunli Yu
- Department of Genetics and Genomic Sciences, Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA; Mount Sinai Genomics, Inc, One Gustave L Levy Place #1497, New York, NY 10029, USA
| | - Sander M Houten
- Department of Genetics and Genomic Sciences, Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA.
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SMARCAD1 ATPase activity is required to silence endogenous retroviruses in embryonic stem cells. Nat Commun 2019; 10:1335. [PMID: 30902974 PMCID: PMC6430823 DOI: 10.1038/s41467-019-09078-0] [Citation(s) in RCA: 225] [Impact Index Per Article: 45.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 02/19/2019] [Indexed: 12/14/2022] Open
Abstract
Endogenous retroviruses (ERVs) can confer benefits to their host but present a threat to genome integrity if not regulated correctly. Here we identify the SWI/SNF-like remodeler SMARCAD1 as a key factor in the control of ERVs in embryonic stem cells. SMARCAD1 is enriched at ERV subfamilies class I and II, particularly at active intracisternal A-type particles (IAPs), where it preserves repressive histone methylation marks. Depletion of SMARCAD1 results in de-repression of IAPs and adjacent genes. Recruitment of SMARCAD1 to ERVs is dependent on KAP1, a central component of the silencing machinery. SMARCAD1 and KAP1 occupancy at ERVs is co-dependent and requires the ATPase function of SMARCAD1. Our findings uncover a role for the enzymatic activity of SMARCAD1 in cooperating with KAP1 to silence ERVs. This reveals ATP-dependent chromatin remodeling as an integral step in retrotransposon regulation in stem cells and advances our understanding of the mechanisms driving heterochromatin establishment. Tight regulation of retrotransposons such as endogenous retroviruses (ERVs) is essential for genome and transcriptome integrity. Here, the authors show that the ATPase function of the chromatin remodeler SMARCAD1 facilitates the binding of KAP1 to ERVs and is required for their repression in embryonic stem cells.
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Treger RS, Pope SD, Kong Y, Tokuyama M, Taura M, Iwasaki A. The Lupus Susceptibility Locus Sgp3 Encodes the Suppressor of Endogenous Retrovirus Expression SNERV. Immunity 2019; 50:334-347.e9. [PMID: 30709743 DOI: 10.1016/j.immuni.2018.12.022] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 10/18/2018] [Accepted: 12/17/2018] [Indexed: 12/24/2022]
Abstract
Elevated endogenous retrovirus (ERV) transcription and anti-ERV antibody reactivity are implicated in lupus pathogenesis. Overproduction of non-ecotropic ERV (NEERV) envelope glycoprotein gp70 and resultant nephritis occur in lupus-prone mice, but whether NEERV mis-expression contributes to lupus etiology is unclear. Here we identified suppressor of NEERV (Snerv) 1 and 2, Krüppel-associated box zinc-finger proteins (KRAB-ZFPs) that repressed NEERV by binding the NEERV long terminal repeat to recruit the transcriptional regulator KAP1. Germline Snerv1/Snerv2 deletion increased activating chromatin modifications, transcription, and gp70 expression from NEERV loci. F1 crosses of lupus-prone New Zealand Black (NZB) and 129 mice to Snerv1/Snerv2-/- mice failed to restore NEERV repression, demonstrating that loss of SNERV underlies the lupus autoantigen gp70 overproduction that promotes nephritis in susceptible mice and that SNERV encodes for Sgp3 (in NZB mice) and Gv-1 loci (in 129 mice). Increased ERV expression in lupus patients inversely correlated with three putative ERV-suppressing KRAB-ZFPs, suggesting that loss of KRAB-ZFP-mediated ERV control may contribute to human lupus pathogenesis.
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Affiliation(s)
- Rebecca S Treger
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Scott D Pope
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Yong Kong
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Molecular Biophysics and Biochemistry, W.M. Keck Foundation Biotechnology Resource Laboratory, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Maria Tokuyama
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Manabu Taura
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Akiko Iwasaki
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
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Thomas J, Perron H, Feschotte C. Variation in proviral content among human genomes mediated by LTR recombination. Mob DNA 2018; 9:36. [PMID: 30568734 PMCID: PMC6298018 DOI: 10.1186/s13100-018-0142-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 11/29/2018] [Indexed: 01/23/2023] Open
Abstract
Background Human endogenous retroviruses (HERVs) occupy a substantial fraction of the genome and impact cellular function with both beneficial and deleterious consequences. The vast majority of HERV sequences descend from ancient retroviral families no longer capable of infection or genomic propagation. In fact, most are no longer represented by full-length proviruses but by solitary long terminal repeats (solo LTRs) that arose via non-allelic recombination events between the two LTRs of a proviral insertion. Because LTR-LTR recombination events may occur long after proviral insertion but are challenging to detect in resequencing data, we hypothesize that this mechanism is a source of genomic variation in the human population that remains vastly underestimated. Results We developed a computational pipeline specifically designed to capture dimorphic proviral/solo HERV allelic variants from short-read genome sequencing data. When applied to 279 individuals sequenced as part of the Simons Genome Diversity Project, the pipeline retrieves most of the dimorphic loci previously reported for the HERV-K(HML2) subfamily as well as dozens of additional candidates, including members of the HERV-H and HERV-W families previously involved in human development and disease. We experimentally validate several of these newly discovered dimorphisms, including the first reported instance of an unfixed HERV-W provirus and an HERV-H locus driving a transcript (ESRG) implicated in the maintenance of embryonic stem cell pluripotency. Conclusions Our findings indicate that human proviral content exhibit more extensive interindividual variation than previously recognized, which has important bearings for deciphering the contribution of HERVs to human physiology and disease. Because LTR retroelements and LTR recombination are ubiquitous in eukaryotes, our computational pipeline should facilitate the mapping of this type of genomic variation for a wide range of organisms. Electronic supplementary material The online version of this article (10.1186/s13100-018-0142-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jainy Thomas
- 1Department of Human Genetics, University of Utah School of Medicine, 15 North 2030 East, Rm 5100, Salt Lake City, UT 84112 USA
| | - Hervé Perron
- GeNeuro, Plan-les-Ouates, Geneva, Switzerland.,3Université Claude Bernard, Lyon, France
| | - Cédric Feschotte
- 4Department of Molecular Biology and Genetics, Cornell University, 107 Biotechnology Building, Ithaca, NY 14853 USA
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67
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Bourque G, Burns KH, Gehring M, Gorbunova V, Seluanov A, Hammell M, Imbeault M, Izsvák Z, Levin HL, Macfarlan TS, Mager DL, Feschotte C. Ten things you should know about transposable elements. Genome Biol 2018; 19:199. [PMID: 30454069 PMCID: PMC6240941 DOI: 10.1186/s13059-018-1577-z] [Citation(s) in RCA: 619] [Impact Index Per Article: 103.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Transposable elements (TEs) are major components of eukaryotic genomes. However, the extent of their impact on genome evolution, function, and disease remain a matter of intense interrogation. The rise of genomics and large-scale functional assays has shed new light on the multi-faceted activities of TEs and implies that they should no longer be marginalized. Here, we introduce the fundamental properties of TEs and their complex interactions with their cellular environment, which are crucial to understanding their impact and manifold consequences for organismal biology. While we draw examples primarily from mammalian systems, the core concepts outlined here are relevant to a broad range of organisms.
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Affiliation(s)
- Guillaume Bourque
- Department of Human Genetics, McGill University, Montréal, Québec, H3A 0G1, Canada.
- Canadian Center for Computational Genomics, McGill University, Montréal, Québec, H3A 0G1, Canada.
| | - Kathleen H Burns
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Mary Gehring
- Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02142, USA
| | - Vera Gorbunova
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Andrei Seluanov
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Molly Hammell
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
| | - Michaël Imbeault
- Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK
| | - Zsuzsanna Izsvák
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125, Berlin, Germany
| | - Henry L Levin
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland, USA
| | - Todd S Macfarlan
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland, USA
| | - Dixie L Mager
- Terry Fox Laboratory, British Columbia Cancer Agency and Department of Medical Genetics, University of BC, Vancouver, BC, V5Z1L3, Canada
| | - Cédric Feschotte
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14850, USA.
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68
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Human Endogenous Retrovirus-K HML-2 integration within RASGRF2 is associated with intravenous drug abuse and modulates transcription in a cell-line model. Proc Natl Acad Sci U S A 2018; 115:10434-10439. [PMID: 30249655 DOI: 10.1073/pnas.1811940115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
HERV-K HML-2 (HK2) has been proliferating in the germ line of humans at least as recently as 250,000 years ago, with some integrations that remain polymorphic in the modern human population. One of the solitary HK2 LTR polymorphic integrations lies between exons 17 and 18 of RASGRF2, a gene that affects dopaminergic activity and is thus related to addiction. Here we show that this antisense HK2 integration (namely RASGRF2-int) is found more frequently in persons who inject drugs compared with the general population. In a Greek HIV-1-positive population (n = 202), we found RASGRF2-int 2.5 times (14 versus 6%) more frequently in patients infected through i.v. drug use compared with other transmission route controls (P = 0.03). Independently, in a United Kingdom-based hepatitis C virus-positive population (n = 184), we found RASGRF2-int 3.6 times (34 versus 9.5%) more frequently in patients infected during chronic drug abuse compared with controls (P < 0.001). We then tested whether RASGRF2-int could be mechanistically responsible for this association by modulating transcription of RASGRF2 We show that the CRISPR/Cas9-mediated insertion of HK2 in HEK293 cells in the exact RASGRF2 intronic position found in the population resulted in significant transcriptional and phenotypic changes. We also explored mechanistic features of other intronic HK2 integrations and show that HK2 LTRs can be responsible for generation of cis-natural antisense transcripts, which could interfere with the transcription of nearby genes. Our findings suggest that RASGRF2-int is a strong candidate for dopaminergic manipulation, and emphasize the importance of accurate mapping of neglected HERV polymorphisms in human genomic studies.
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69
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Tartaglione AM, Cipriani C, Chiarotti F, Perrone B, Balestrieri E, Matteucci C, Sinibaldi-Vallebona P, Calamandrei G, Ricceri L. Early Behavioral Alterations and Increased Expression of Endogenous Retroviruses Are Inherited Across Generations in Mice Prenatally Exposed to Valproic Acid. Mol Neurobiol 2018; 56:3736-3750. [DOI: 10.1007/s12035-018-1328-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 08/22/2018] [Indexed: 12/12/2022]
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70
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Transposons, p53 and Genome Security. Trends Genet 2018; 34:846-855. [PMID: 30195581 DOI: 10.1016/j.tig.2018.08.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 07/31/2018] [Accepted: 08/07/2018] [Indexed: 12/16/2022]
Abstract
p53, the most commonly mutated tumor suppressor, is a transcription factor known to regulate proliferation, senescence, and apoptosis. Compelling studies have found that p53 may prevent oncogenesis through effectors that are unrelated to these canonical processes and recent findings have uncovered ancient roles for p53 in the containment of mobile elements. Together, these developments raise the possibility that some p53-driven cancers could result from unrestrained transposons. Here, we explore evidence linking conserved features of p53 biology to the control of transposons. We also show how p53-deficient cells can be exploited to probe the behavior of transposons and illustrate how unrestrained transposons incited by p53 loss might contribute to human malignancies.
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71
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Russell SJ, Stalker L, LaMarre J. PIWIs, piRNAs and Retrotransposons: Complex battles during reprogramming in gametes and early embryos. Reprod Domest Anim 2018; 52 Suppl 4:28-38. [PMID: 29052331 DOI: 10.1111/rda.13053] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Gamete and embryo development are indispensable processes for successful reproduction. Cells involved in these processes acquire pluripotency, the ability to differentiate into multiple different cell types, through a series of events known as reprogramming that lead to profound changes in histone and DNA methylation. While essential for pluripotency, this epigenetic remodelling removes constraints that normally limit the expression of genomic sequences known as transposable elements (TEs). Unconstrained TE expression can lead to many deleterious consequences including infertility, so organisms have evolved complex and potent mechanistic arsenals to target and suppress TE expression during reprogramming. This review will focus on the control of transposable elements in gametes and embryos, and one important TE suppressing system known as the PIWI pathway. This broadly conserved, small RNA-targeted silencing mechanism appears critical for fertility in many species and may participate in multiple aspects of gene regulation in reproduction and other contexts.
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Affiliation(s)
- S J Russell
- Department of Biomedical Sciences, University of Guelph, Guelph, ON, Canada
| | - L Stalker
- Department of Biomedical Sciences, University of Guelph, Guelph, ON, Canada
| | - J LaMarre
- Department of Biomedical Sciences, University of Guelph, Guelph, ON, Canada
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72
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Berrens RV, Andrews S, Spensberger D, Santos F, Dean W, Gould P, Sharif J, Olova N, Chandra T, Koseki H, von Meyenn F, Reik W. An endosiRNA-Based Repression Mechanism Counteracts Transposon Activation during Global DNA Demethylation in Embryonic Stem Cells. Cell Stem Cell 2018; 21:694-703.e7. [PMID: 29100015 PMCID: PMC5678422 DOI: 10.1016/j.stem.2017.10.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 08/14/2017] [Accepted: 10/12/2017] [Indexed: 12/28/2022]
Abstract
Erasure of DNA methylation and repressive chromatin marks in the mammalian germline leads to risk of transcriptional activation of transposable elements (TEs). Here, we used mouse embryonic stem cells (ESCs) to identify an endosiRNA-based mechanism involved in suppression of TE transcription. In ESCs with DNA demethylation induced by acute deletion of Dnmt1, we saw an increase in sense transcription at TEs, resulting in an abundance of sense/antisense transcripts leading to high levels of ARGONAUTE2 (AGO2)-bound small RNAs. Inhibition of Dicer or Ago2 expression revealed that small RNAs are involved in an immediate response to demethylation-induced transposon activation, while the deposition of repressive histone marks follows as a chronic response. In vivo, we also found TE-specific endosiRNAs present during primordial germ cell development. Our results suggest that antisense TE transcription is a “trap” that elicits an endosiRNA response to restrain acute transposon activity during epigenetic reprogramming in the mammalian germline. Global DNA demethylation in embryonic stem cells leads to transposon activation Transposon activation increases the abundance of sense/antisense transcripts ARGONAUTE2-bound endosiRNAs accumulate at high levels for acute repression Longer-term transposon repression depends on repressive histone marks
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Affiliation(s)
- Rebecca V Berrens
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK; University of Cambridge, The Old Schools, Trinity Lane, Cambridge CB2 1TN, UK.
| | - Simon Andrews
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | | | - Fátima Santos
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK; University of Cambridge, The Old Schools, Trinity Lane, Cambridge CB2 1TN, UK
| | - Wendy Dean
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | - Poppy Gould
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | - Jafar Sharif
- RIKEN Research Center for Allergy and Immunology, 1-7-22 Suehiro-cho, Tsurumi, Yokohama, 230-0045 Kanagawa, Japan
| | - Nelly Olova
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | - Tamir Chandra
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | - Haruhiko Koseki
- RIKEN Research Center for Allergy and Immunology, 1-7-22 Suehiro-cho, Tsurumi, Yokohama, 230-0045 Kanagawa, Japan
| | | | - Wolf Reik
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK; University of Cambridge, The Old Schools, Trinity Lane, Cambridge CB2 1TN, UK; Wellcome Trust Sanger Institute, Hinxton CB10 1SA, UK.
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73
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Fukuda K, Okuda A, Yusa K, Shinkai Y. A CRISPR knockout screen identifies SETDB1-target retroelement silencing factors in embryonic stem cells. Genome Res 2018; 28:846-858. [PMID: 29728365 PMCID: PMC5991520 DOI: 10.1101/gr.227280.117] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 04/26/2018] [Indexed: 12/16/2022]
Abstract
In mouse embryonic stem cells (mESCs), the expression of provirus and endogenous retroelements is epigenetically repressed. Although many cellular factors involved in retroelement silencing have been identified, the complete molecular mechanism remains elusive. In this study, we performed a genome-wide CRISPR screen to advance our understanding of retroelement silencing in mESCs. The Moloney murine leukemia virus (MLV)–based retroviral vector MSCV-GFP, which is repressed by the SETDB1/TRIM28 pathway in mESCs, was used as a reporter provirus, and we identified more than 80 genes involved in this process. In particular, ATF7IP and the BAF complex components are linked with the repression of most of the SETDB1 targets. We characterized two factors, MORC2A and RESF1, of which RESF1 is a novel molecule in retroelement silencing. Although both factors are recruited to repress provirus, their roles in repression are different. MORC2A appears to function dependent on repressive epigenetic modifications, while RESF1 regulates repressive epigenetic modifications associated with SETDB1. Our genome-wide CRISPR screen cataloged genes which function at different levels in silencing of SETDB1-target retroelements and provides a useful resource for further molecular studies.
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Affiliation(s)
- Kei Fukuda
- Cellular Memory Laboratory, Cluster for Pioneering Research, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Akihiko Okuda
- Division of Developmental Biology, Research Center for Genomic Medicine, Saitama Medical University, 1397-1 Yamane Hidaka Saitama 350-1241, Japan
| | - Kosuke Yusa
- Wellcome Sanger Institute, Hinxton, Cambridge, CB10 1SA, United Kingdom
| | - Yoichi Shinkai
- Cellular Memory Laboratory, Cluster for Pioneering Research, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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74
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Schauer SN, Carreira PE, Shukla R, Gerhardt DJ, Gerdes P, Sanchez-Luque FJ, Nicoli P, Kindlova M, Ghisletti S, Santos AD, Rapoud D, Samuel D, Faivre J, Ewing AD, Richardson SR, Faulkner GJ. L1 retrotransposition is a common feature of mammalian hepatocarcinogenesis. Genome Res 2018; 28:639-653. [PMID: 29643204 PMCID: PMC5932605 DOI: 10.1101/gr.226993.117] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 03/26/2018] [Indexed: 12/15/2022]
Abstract
The retrotransposon Long Interspersed Element 1 (LINE-1 or L1) is a continuing source of germline and somatic mutagenesis in mammals. Deregulated L1 activity is a hallmark of cancer, and L1 mutagenesis has been described in numerous human malignancies. We previously employed retrotransposon capture sequencing (RC-seq) to analyze hepatocellular carcinoma (HCC) samples from patients infected with hepatitis B or hepatitis C virus and identified L1 variants responsible for activating oncogenic pathways. Here, we have applied RC-seq and whole-genome sequencing (WGS) to an Abcb4 (Mdr2)-/- mouse model of hepatic carcinogenesis and demonstrated for the first time that L1 mobilization occurs in murine tumors. In 12 HCC nodules obtained from 10 animals, we validated four somatic L1 insertions by PCR and capillary sequencing, including TF subfamily elements, and one GF subfamily example. One of the TF insertions carried a 3' transduction, allowing us to identify its donor L1 and to demonstrate that this full-length TF element retained retrotransposition capacity in cultured cancer cells. Using RC-seq, we also identified eight tumor-specific L1 insertions from 25 HCC patients with a history of alcohol abuse. Finally, we used RC-seq and WGS to identify three tumor-specific L1 insertions among 10 intra-hepatic cholangiocarcinoma (ICC) patients, including one insertion traced to a donor L1 on Chromosome 22 known to be highly active in other cancers. This study reveals L1 mobilization as a common feature of hepatocarcinogenesis in mammals, demonstrating that the phenomenon is not restricted to human viral HCC etiologies and is encountered in murine liver tumors.
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Affiliation(s)
- Stephanie N Schauer
- Mater Research Institute-University of Queensland, Woolloongabba, QLD 4102, Australia
| | - Patricia E Carreira
- Mater Research Institute-University of Queensland, Woolloongabba, QLD 4102, Australia
| | - Ruchi Shukla
- Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom
| | - Daniel J Gerhardt
- Mater Research Institute-University of Queensland, Woolloongabba, QLD 4102, Australia
- Invenra, Incorporated, Madison, Wisconsin 53719, USA
| | - Patricia Gerdes
- Mater Research Institute-University of Queensland, Woolloongabba, QLD 4102, Australia
| | - 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
| | - Paola Nicoli
- Department of Experimental Oncology, European Institute of Oncology, 20146 Milan, Italy
| | - Michaela Kindlova
- Mater Research Institute-University of Queensland, Woolloongabba, QLD 4102, Australia
| | | | - Alexandre Dos Santos
- INSERM, U1193, Paul-Brousse University Hospital, Hepatobiliary Centre, Villejuif 94800, France
- Université Paris-Sud, Faculté de Médecine, Villejuif 94800, France
| | - Delphine Rapoud
- INSERM, U1193, Paul-Brousse University Hospital, Hepatobiliary Centre, Villejuif 94800, France
- Université Paris-Sud, Faculté de Médecine, Villejuif 94800, France
| | - Didier Samuel
- INSERM, U1193, Paul-Brousse University Hospital, Hepatobiliary Centre, Villejuif 94800, France
- Université Paris-Sud, Faculté de Médecine, Villejuif 94800, France
| | - Jamila Faivre
- INSERM, U1193, Paul-Brousse University Hospital, Hepatobiliary Centre, Villejuif 94800, France
- Université Paris-Sud, Faculté de Médecine, Villejuif 94800, France
- Assistance Publique-Hôpitaux de Paris (AP-HP), Pôle de Biologie Médicale, Paul-Brousse University Hospital, Villejuif 94800, France
| | - Adam D Ewing
- Mater Research Institute-University of Queensland, Woolloongabba, QLD 4102, Australia
| | - Sandra R Richardson
- 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, University of Queensland, Brisbane, QLD 4072, Australia
- Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072, Australia
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75
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Zeng L, Kortschak RD, Raison JM, Bertozzi T, Adelson DL. Superior ab initio identification, annotation and characterisation of TEs and segmental duplications from genome assemblies. PLoS One 2018; 13:e0193588. [PMID: 29538441 PMCID: PMC5851578 DOI: 10.1371/journal.pone.0193588] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 02/14/2018] [Indexed: 11/21/2022] Open
Abstract
Transposable Elements (TEs) are mobile DNA sequences that make up significant fractions of amniote genomes. However, they are difficult to detect and annotate ab initio because of their variable features, lengths and clade-specific variants. We have addressed this problem by refining and developing a Comprehensive ab initio Repeat Pipeline (CARP) to identify and cluster TEs and other repetitive sequences in genome assemblies. The pipeline begins with a pairwise alignment using krishna, a custom aligner. Single linkage clustering is then carried out to produce families of repetitive elements. Consensus sequences are then filtered for protein coding genes and then annotated using Repbase and a custom library of retrovirus and reverse transcriptase sequences. This process yields three types of family: fully annotated, partially annotated and unannotated. Fully annotated families reflect recently diverged/young known TEs present in Repbase. The remaining two types of families contain a mixture of novel TEs and segmental duplications. These can be resolved by aligning these consensus sequences back to the genome to assess copy number vs. length distribution. Our pipeline has three significant advantages compared to other methods for ab initio repeat identification: 1) we generate not only consensus sequences, but keep the genomic intervals for the original aligned sequences, allowing straightforward analysis of evolutionary dynamics, 2) consensus sequences represent low-divergence, recently/currently active TE families, 3) segmental duplications are annotated as a useful by-product. We have compared our ab initio repeat annotations for 7 genome assemblies to other methods and demonstrate that CARP compares favourably with RepeatModeler, the most widely used repeat annotation package.
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Affiliation(s)
- Lu Zeng
- School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
| | - R. Daniel Kortschak
- School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Joy M. Raison
- School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Terry Bertozzi
- School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
- Evolutionary Biology Unit, South Australian Museum, Adelaide, SA 5005, Australia
| | - David L. Adelson
- School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
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76
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Platt RN, Vandewege MW, Ray DA. Mammalian transposable elements and their impacts on genome evolution. Chromosome Res 2018; 26:25-43. [PMID: 29392473 PMCID: PMC5857283 DOI: 10.1007/s10577-017-9570-z] [Citation(s) in RCA: 139] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 12/12/2017] [Accepted: 12/28/2017] [Indexed: 12/22/2022]
Abstract
Transposable elements (TEs) are genetic elements with the ability to mobilize and replicate themselves in a genome. Mammalian genomes are dominated by TEs, which can reach copy numbers in the hundreds of thousands. As a result, TEs have had significant impacts on mammalian evolution. Here we summarize the current understanding of TE content in mammal genomes and find that, with a few exceptions, most fall within a predictable range of observations. First, one third to one half of the genome is derived from TEs. Second, most mammalian genomes are dominated by LINE and SINE retrotransposons, more limited LTR retrotransposons, and minimal DNA transposon accumulation. Third, most mammal genome contains at least one family of actively accumulating retrotransposon. Finally, horizontal transfer of TEs among lineages is rare. TE exaptation events are being recognized with increasing frequency. Despite these beneficial aspects of TE content and activity, the majority of TE insertions are neutral or deleterious. To limit the deleterious effects of TE proliferation, the genome has evolved several defense mechanisms that act at the epigenetic, transcriptional, and post-transcriptional levels. The interaction between TEs and these defense mechanisms has led to an evolutionary arms race where TEs are suppressed, evolve to escape suppression, then are suppressed again as the defense mechanisms undergo compensatory change. The result is complex and constantly evolving interactions between TEs and host genomes.
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Affiliation(s)
- Roy N Platt
- Department of Biological Sciences, Texas Tech University, Lubbock, TX, USA.
| | | | - David A Ray
- Department of Biological Sciences, Texas Tech University, Lubbock, TX, USA
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77
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Deniz Ö, de la Rica L, Cheng KCL, Spensberger D, Branco MR. SETDB1 prevents TET2-dependent activation of IAP retroelements in naïve embryonic stem cells. Genome Biol 2018; 19:6. [PMID: 29351814 PMCID: PMC5775534 DOI: 10.1186/s13059-017-1376-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 12/07/2017] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Endogenous retroviruses (ERVs), which are responsible for 10% of spontaneous mouse mutations, are kept under control via several epigenetic mechanisms. The H3K9 histone methyltransferase SETDB1 is essential for ERV repression in embryonic stem cells (ESCs), with DNA methylation also playing an important role. It has been suggested that SETDB1 protects ERVs from TET-dependent DNA demethylation, but the relevance of this mechanism for ERV expression remains unclear. Moreover, previous studies have been performed in primed ESCs, which are not epigenetically or transcriptionally representative of preimplantation embryos. RESULTS We use naïve ESCs to investigate the role of SETDB1 in ERV regulation and its relationship with TET-mediated DNA demethylation. Naïve ESCs show an increased dependency on SETDB1 for ERV silencing when compared to primed ESCs, including at the highly mutagenic intracisternal A particles (IAPs). We find that in the absence of SETDB1, TET2 activates IAP elements in a catalytic-dependent manner. Surprisingly, TET2 does not drive changes in DNA methylation levels at IAPs, suggesting that it regulates these retrotransposons indirectly. Instead, SETDB1 depletion leads to a TET2-dependent loss of H4R3me2s, which is indispensable for IAP silencing during epigenetic reprogramming. CONCLUSIONS Our results demonstrate a novel and unexpected role for SETDB1 in protecting IAPs from TET2-dependent histone arginine demethylation.
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Affiliation(s)
- Özgen Deniz
- Blizard Institute, Barts and The London School of Medicine and Dentistry, QMUL, London, E1 2AT, UK
| | - Lorenzo de la Rica
- Blizard Institute, Barts and The London School of Medicine and Dentistry, QMUL, London, E1 2AT, UK.,Present address: The Royal Society, 6-9 Carlton House Terrace, London, SW1Y 5AG, UK
| | - Kevin C L Cheng
- Blizard Institute, Barts and The London School of Medicine and Dentistry, QMUL, London, E1 2AT, UK
| | - Dominik Spensberger
- Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK.,Present address: Gene Targeting Facility, Babraham Institute, Cambridge, CB22 3AT, UK
| | - Miguel R Branco
- Blizard Institute, Barts and The London School of Medicine and Dentistry, QMUL, London, E1 2AT, UK.
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78
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High expression of Endogenous Retroviruses from intrauterine life to adulthood in two mouse models of Autism Spectrum Disorders. Sci Rep 2018; 8:629. [PMID: 29330412 PMCID: PMC5766538 DOI: 10.1038/s41598-017-19035-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 12/12/2017] [Indexed: 12/19/2022] Open
Abstract
Retroelements, such as Human Endogenous Retroviruses (HERVs), have been implicated in many complex diseases, including neurological and neuropsychiatric disorders. Previously, we demonstrated a distinctive expression profile of specific HERV families in peripheral blood mononuclear cells from Autistic Spectrum Disorders (ASD) patients, suggesting their involvement in ASD. Here we used two distinct ASD mouse models: inbred BTBR T+tf/J mice and CD-1 outbred mice prenatally exposed to valproic acid. Whole embryos, blood and brain samples from the offspring were collected at different ages and the expression of several ERV families (ETnI, ETnII-α, ETnII-β, ETnII-γ, MusD and IAP), proinflammatory cytokines (IL-1β, IL-6 and TNF-α) and Toll-like receptors (TLR3 and TLR4) was assessed. In the two distinct mouse models analysed, the transcriptional activity of the ERV families was significant higher in comparison with corresponding controls, in whole embryos, blood and brain samples. Also the expression levels of the proinflammatory cytokines and TLRs were significantly higher than controls. Current results are in agreement with our previous findings in ASD children, supporting the hypothesis that ERVs may serve as biomarkers of atypical brain development. Moreover, the changes in ERVs and proinflammatory cytokines expression could be related with the autistic-like traits acquisition in the two mouse models.
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79
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Oh C, Ryoo J, Park K, Kim B, Daly MB, Cho D, Ahn K. A central role for PI3K-AKT signaling pathway in linking SAMHD1-deficiency to the type I interferon signature. Sci Rep 2018; 8:84. [PMID: 29311560 PMCID: PMC5758801 DOI: 10.1038/s41598-017-18308-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 12/08/2017] [Indexed: 11/08/2022] Open
Abstract
The autoimmune disorder Aicardi-Goutières syndrome (AGS) is characterized by a constitutive type I interferon response. SAMHD1 possesses both dNTPase and RNase activities and mutations in SAMHD1 cause AGS; however, how SAMHD1-deficiency causes the type I interferon response in patients with AGS remains unknown. Here, we show that endogenous RNA substrates accumulated in the absence of SAMHD1 act as a major immunogenic source for the type I interferon response. Reconstitution of SAMHD1-negative human cells with wild-type but not RNase-defective SAMHD1 abolishes spontaneous type I interferon induction. We further identify that the PI3K/AKT/IRF3 signaling pathway is essential for the type I interferon response in SAMHD1-deficient human monocytic cells. Treatment of PI3K or AKT inhibitors dramatically reduces the type I interferon signatures in SAMHD1-deficient cells. Moreover, SAMHD1/AKT1 double knockout relieves the type I interferon signatures to the levels observed for wild-type cells. Identification of AGS-related RNA sensing pathway provides critical insights into the molecular pathogenesis of the type I interferonopathies such as AGS and overlapping autoimmune disorders.
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Affiliation(s)
- Changhoon Oh
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea
- Center for RNA Research, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of the Interdisciplinary Program in Genetic Engineering, Seoul National University, Seoul, 08826, Republic of Korea
| | - Jeongmin Ryoo
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea
- Center for RNA Research, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
| | - Kiwon Park
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea
| | - Baek Kim
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, 30322, USA
| | - Michele B Daly
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, 30322, USA
| | - DongYeon Cho
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea
- Center for RNA Research, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
| | - Kwangseog Ahn
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea.
- Center for RNA Research, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea.
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80
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Shimosuga KI, Fukuda K, Sasaki H, Ichiyanagi K. Locus-specific hypomethylation of the mouse IAP retrotransposon is associated with transcription factor-binding sites. Mob DNA 2017; 8:20. [PMID: 29255492 PMCID: PMC5729234 DOI: 10.1186/s13100-017-0105-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 12/01/2017] [Indexed: 01/23/2023] Open
Abstract
Background Intracisternal A particle (IAP) is one of the most transpositionally active retrotransposons in the mouse genome, but its expression varies between cell types. This variation is believed to arise from differences in the epigenetic state (e.g., DNA methylation) of the 5′ long terminal repeat (LTR), where transcription starts. However, owing to the high copy number and high sequence similarity between copies, it is difficult to analyze the epigenetic states of individual IAP LTRs in a comprehensive manner. Results We have developed a method called Target Enrichment after Post-Bisulfite Adaptor Tagging (TEPBAT) to analyze the DNA methylation states of a large number of individual retrotransposon copies at once. Using this method, we determined the DNA methylation levels of >8500 copies of genomic IAP LTRs (almost all copies that we aimed to target by the PCR primers) in the sperm and tail. This revealed that the vast majority of the LTRs were heavily methylated in both sperm and tail; however, hypomethylated copies were more frequently found in the sperm than in the tail. Interestingly, most of these hypomethylated LTRs were solo-type, belonged to specific IAP subfamilies, and carried binding sites for transcription factors (TFs) that are active in male germ cells. Conclusions The current study revealed subfamily- and locus-specific hypomethylation of IAP LTRs, and suggests that binding of TFs is involved in the protection from DNA methylation, whereas the IAP internal sequence enhances methylation. Furthermore, the study demonstrated that TEPBAT offers a cost-effective method for a variety of DNA methylome studies that focus on retrotransposon sequences. Electronic supplementary material The online version of this article (10.1186/s13100-017-0105-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ken-Ichi Shimosuga
- Division of Epigenomics and Development, Medical Institute of Bioregulation, and Epigenome Network Research Center, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582 Japan.,Trygroup Incorporated, 1-8-10 Kudankita, Chiyoda-ku, Tokyo, 102-0073 Japan
| | - Kei Fukuda
- Division of Epigenomics and Development, Medical Institute of Bioregulation, and Epigenome Network Research Center, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582 Japan.,Cellular Memory Laboratory, RIKEN, Wako, Saitama, 351-0198 Japan
| | - Hiroyuki Sasaki
- Division of Epigenomics and Development, Medical Institute of Bioregulation, and Epigenome Network Research Center, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582 Japan
| | - Kenji Ichiyanagi
- Division of Epigenomics and Development, Medical Institute of Bioregulation, and Epigenome Network Research Center, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582 Japan.,Laboratory of Genome and Epigenome Dynamics, Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan
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81
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Miller WB. Biological information systems: Evolution as cognition-based information management. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 134:1-26. [PMID: 29175233 DOI: 10.1016/j.pbiomolbio.2017.11.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 11/16/2017] [Accepted: 11/21/2017] [Indexed: 01/08/2023]
Abstract
An alternative biological synthesis is presented that conceptualizes evolutionary biology as an epiphenomenon of integrated self-referential information management. Since all biological information has inherent ambiguity, the systematic assessment of information is required by living organisms to maintain self-identity and homeostatic equipoise in confrontation with environmental challenges. Through their self-referential attachment to information space, cells are the cornerstone of biological action. That individualized assessment of information space permits self-referential, self-organizing niche construction. That deployment of information and its subsequent selection enacted the dominant stable unicellular informational architectures whose biological expressions are the prokaryotic, archaeal, and eukaryotic unicellular forms. Multicellularity represents the collective appraisal of equivocal environmental information through a shared information space. This concerted action can be viewed as systematized information management to improve information quality for the maintenance of preferred homeostatic boundaries among the varied participants. When reiterated in successive scales, this same collaborative exchange of information yields macroscopic organisms as obligatory multicellular holobionts. Cognition-Based Evolution (CBE) upholds that assessment of information precedes biological action, and the deployment of information through integrative self-referential niche construction and natural cellular engineering antecedes selection. Therefore, evolutionary biology can be framed as a complex reciprocating interactome that consists of the assessment, communication, deployment and management of information by self-referential organisms at multiple scales in continuous confrontation with environmental stresses.
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82
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Schiavo G, Hoffmann OI, Ribani A, Utzeri VJ, Ghionda MC, Bertolini F, Geraci C, Bovo S, Fontanesi L. A genomic landscape of mitochondrial DNA insertions in the pig nuclear genome provides evolutionary signatures of interspecies admixture. DNA Res 2017; 24:487-498. [PMID: 28460080 PMCID: PMC5737481 DOI: 10.1093/dnares/dsx019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 04/02/2017] [Indexed: 12/26/2022] Open
Abstract
Nuclear DNA sequences of mitochondrial origin (numts) are derived by insertion of mitochondrial DNA (mtDNA), into the nuclear genome. In this study, we provide, for the first time, a genome picture of numts inserted in the pig nuclear genome. The Sus scrofa reference nuclear genome (Sscrofa10.2) was aligned with circularized and consensus mtDNA sequences using LAST software. A total of 430 numt sequences that may represent 246 different numt integration events (57 numt regions determined by at least two numt sequences and 189 singletons) were identified, covering about 0.0078% of the nuclear genome. Numt integration events were correlated (0.99) to the chromosome length. The longest numt sequence (about 11 kbp) was located on SSC2. Six numts were sequenced and PCR amplified in pigs of European commercial and local pig breeds, of the Chinese Meishan breed and in European wild boars. Three of them were polymorphic for the presence or absence of the insertion. Surprisingly, the estimated age of insertion of two of the three polymorphic numts was more ancient than that of the speciation time of the Sus scrofa, supporting that these polymorphic sites were originated from interspecies admixture that contributed to shape the pig genome.
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Affiliation(s)
- Giuseppina Schiavo
- Department of Agricultural and Food Sciences, Division of Animal Sciences, University of Bologna, 40127 Bologna, Italy
| | - Orsolya Ivett Hoffmann
- Ruminant Genome Biology Group, NARIC, Agricultural Biotechnology Center, H-2100?Gödöllo, Hungary
| | - Anisa Ribani
- Department of Agricultural and Food Sciences, Division of Animal Sciences, University of Bologna, 40127 Bologna, Italy
| | - Valerio Joe Utzeri
- Department of Agricultural and Food Sciences, Division of Animal Sciences, University of Bologna, 40127 Bologna, Italy
| | - Marco Ciro Ghionda
- Department of Agricultural and Food Sciences, Division of Animal Sciences, University of Bologna, 40127 Bologna, Italy
| | - Francesca Bertolini
- Department of Agricultural and Food Sciences, Division of Animal Sciences, University of Bologna, 40127 Bologna, Italy
| | - Claudia Geraci
- Department of Agricultural and Food Sciences, Division of Animal Sciences, University of Bologna, 40127 Bologna, Italy
| | - Samuele Bovo
- Department of Agricultural and Food Sciences, Division of Animal Sciences, University of Bologna, 40127 Bologna, Italy
| | - Luca Fontanesi
- Department of Agricultural and Food Sciences, Division of Animal Sciences, University of Bologna, 40127 Bologna, Italy
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83
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Abstract
Krüppel-associated box domain zinc finger proteins (KRAB-ZFPs) are the largest family of transcriptional regulators in higher vertebrates. Characterized by an N-terminal KRAB domain and a C-terminal array of DNA-binding zinc fingers, they participate, together with their co-factor KAP1 (also known as TRIM28), in repression of sequences derived from transposable elements (TEs). Until recently, KRAB-ZFP/KAP1-mediated repression of TEs was thought to lead to irreversible silencing, and the evolutionary selection of KRAB-ZFPs was considered to be just the host component of an arms race against TEs. However, recent advances indicate that KRAB-ZFPs and their TE targets also partner up to establish species-specific regulatory networks. Here, we provide an overview of the KRAB-ZFP gene family, highlighting how its evolutionary history is linked to that of TEs, and how KRAB-ZFPs influence multiple aspects of development and physiology.
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Affiliation(s)
- Gabriela Ecco
- School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Station19, 1015 Lausanne, Switzerland
| | - Michael Imbeault
- School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Station19, 1015 Lausanne, Switzerland
| | - Didier Trono
- School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Station19, 1015 Lausanne, Switzerland
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84
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Identification of Candidate Genes for Generalized Tonic-Clonic Seizures in Noda Epileptic Rat. Behav Genet 2017; 47:609-619. [PMID: 28936718 DOI: 10.1007/s10519-017-9870-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 09/08/2017] [Indexed: 12/31/2022]
Abstract
The Noda epileptic rat (NER) exhibits generalized tonic-clonic seizures (GTCS). A genetic linkage analysis identified two GTCS-associated loci, Ner1 on Chr 1 and Ner3 on Chr 5. The wild-type Ner1 and Ner3 alleles suppressed GTCS when combined in double-locus congenic lines, but not when present in single-locus congenic lines. Global expression analysis revealed that cholecystokinin B receptor (Cckbr) and suppressor of tumorigenicity 5 (St5), which map within Ner1, and PHD finger protein 24 (Phf24), which maps within Ner3, were significantly downregulated in NER. De novo BAC sequencing detected an insertion of an endogenous retrovirus sequence in intron 2 of the Phf24 gene in the NER genome, and PHF24 protein was almost absent in the NER brain. Phf24 encodes a Gαi-interacting protein involved in GABAB receptor signaling pathway. Based on these findings, we conclude that Cckbr, St5, and Phf24 are strong candidate genes for GTCS in NER.
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85
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Palanza KM, Radden LA, Rabah MA, Nguyen TV, Kohm AC, Connor ME, Ricci MM, Stewart JJ, Eragene S, King TR. The rough fur (ruf) mutation in mice is an allele of myelin protein zero-like 3 (Mpzl3). ACTA ACUST UNITED AC 2017. [DOI: 10.1080/23312025.2017.1370058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Kenneth M. Palanza
- Department of Biomolecular Sciences, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06053, USA
| | - Legairre A. Radden
- Department of Biomolecular Sciences, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06053, USA
| | - Mohammed A. Rabah
- Department of Biomolecular Sciences, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06053, USA
| | - Tu V. Nguyen
- Department of Biomolecular Sciences, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06053, USA
| | - Audra C. Kohm
- Department of Biomolecular Sciences, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06053, USA
| | - Malcolm E. Connor
- Department of Biomolecular Sciences, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06053, USA
| | - Morgan M. Ricci
- Department of Biomolecular Sciences, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06053, USA
| | - Jachius J. Stewart
- Department of Biomolecular Sciences, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06053, USA
| | - Sidney Eragene
- Department of Biomolecular Sciences, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06053, USA
| | - Thomas R. King
- Department of Biomolecular Sciences, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06053, USA
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86
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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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87
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Franke V, Ganesh S, Karlic R, Malik R, Pasulka J, Horvat F, Kuzman M, Fulka H, Cernohorska M, Urbanova J, Svobodova E, Ma J, Suzuki Y, Aoki F, Schultz RM, Vlahovicek K, Svoboda P. Long terminal repeats power evolution of genes and gene expression programs in mammalian oocytes and zygotes. Genome Res 2017; 27:1384-1394. [PMID: 28522611 PMCID: PMC5538554 DOI: 10.1101/gr.216150.116] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 05/15/2017] [Indexed: 12/11/2022]
Abstract
Retrotransposons are "copy-and-paste" insertional mutagens that substantially contribute to mammalian genome content. Retrotransposons often carry long terminal repeats (LTRs) for retrovirus-like reverse transcription and integration into the genome. We report an extraordinary impact of a group of LTRs from the mammalian endogenous retrovirus-related ERVL retrotransposon class on gene expression in the germline and beyond. In mouse, we identified more than 800 LTRs from ORR1, MT, MT2, and MLT families, which resemble mobile gene-remodeling platforms that supply promoters and first exons. The LTR-mediated gene remodeling also extends to hamster, human, and bovine oocytes. The LTRs function in a stage-specific manner during the oocyte-to-embryo transition by activating transcription, altering protein-coding sequences, producing noncoding RNAs, and even supporting evolution of new protein-coding genes. These functions result, for example, in recycling processed pseudogenes into mRNAs or lncRNAs with regulatory roles. The functional potential of the studied LTRs is even higher, because we show that dormant LTR promoter activity can rescue loss of an essential upstream promoter. We also report a novel protein-coding gene evolution-D6Ertd527e-in which an MT LTR provided a promoter and the 5' exon with a functional start codon while the bulk of the protein-coding sequence evolved through a CAG repeat expansion. Altogether, ERVL LTRs provide molecular mechanisms for stochastically scanning, rewiring, and recycling genetic information on an extraordinary scale. ERVL LTRs thus offer means for a comprehensive survey of the genome's expression potential, tightly intertwining with gene expression and evolution in the germline.
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Affiliation(s)
- Vedran Franke
- Bioinformatics Group, Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, 10000, Zagreb, Croatia
| | - Sravya Ganesh
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Rosa Karlic
- Bioinformatics Group, Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, 10000, Zagreb, Croatia
| | - Radek Malik
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Josef Pasulka
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Filip Horvat
- Bioinformatics Group, Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, 10000, Zagreb, Croatia
| | - Maja Kuzman
- Bioinformatics Group, Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, 10000, Zagreb, Croatia
| | - Helena Fulka
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Marketa Cernohorska
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Jana Urbanova
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Eliska Svobodova
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Jun Ma
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Yutaka Suzuki
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8562, Japan
| | - Fugaku Aoki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8562, Japan
| | - Richard M Schultz
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Kristian Vlahovicek
- Bioinformatics Group, Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, 10000, Zagreb, Croatia
| | - Petr Svoboda
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
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88
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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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89
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Coskran TM, Jiang Z, Klaunig JE, Mager DL, Obert L, Robertson A, Tsinoremas N, Wang Z, Gosink M. Induction of endogenous retroelements as a potential mechanism for mouse-specific drug-induced carcinogenicity. PLoS One 2017; 12:e0176768. [PMID: 28472135 PMCID: PMC5417610 DOI: 10.1371/journal.pone.0176768] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 04/17/2017] [Indexed: 11/23/2022] Open
Abstract
A number of chemical compounds have been shown to induce liver tumors in mice but not in other species. While several mechanisms for this species-specific tumorigenicity have been proposed, no definitive mechanism has been established. We examined the effects of the nongenotoxic rodent hepatic carcinogen, WY-14,643, in male mice from a high liver tumor susceptible strain (C3H/HeJ), and from a low tumor susceptible strain (C57BL/6). WY-14,643, a PPARα activator induced widespread increases in the expression of some endogenous retroelements, namely members of LTR and LINE elements in both strains. The expression of a number of known retroviral defense genes was also elevated. We also demonstrated that basal immune-mediated viral defense was elevated in C57BL/6 mice (the resistant strain) and that WY-14,643 further activated those immuno-defense processes. We propose that the previously reported >100X activity of retroelements in mice drives mouse-specific tumorigenicity. We also propose that C57BL/6's competent immune to retroviral activation allows it to remove cells before the activation of these elements can result in significant chromosomal insertions and mutation. Finally, we showed that WY-14,643 treatment induced gene signatures of DNA recombination in the sensitive C3H/HeJ strain.
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Affiliation(s)
- Timothy M. Coskran
- Drug Safety Research & Development, Pfizer Inc., Groton, Connecticut, United States of America
| | - Zhijie Jiang
- Department of Computer Science, University of Miami, Miami, Florida, United States of America
| | - James E. Klaunig
- Environmental Health, Indiana University, Bloomington, Indiana, United States of America
| | - Dixie L. Mager
- Terry Fox Laboratory, BC Cancer Agency, Vancouver, British Columbia, Canada
| | - Leslie Obert
- GlaxoSmithKline plc, King of Prussia, Pennsylvania, United States of America
| | - Andrew Robertson
- Drug Safety Research & Development, Pfizer Inc., Groton, Connecticut, United States of America
| | - Nicholas Tsinoremas
- Department of Computer Science, University of Miami, Miami, Florida, United States of America
| | - Zemin Wang
- Environmental Health, Indiana University, Bloomington, Indiana, United States of America
| | - Mark Gosink
- Drug Safety Research & Development, Pfizer Inc., Groton, Connecticut, United States of America
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90
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Hu T, Zhu X, Pi W, Yu M, Shi H, Tuan D. Hypermethylated LTR retrotransposon exhibits enhancer activity. Epigenetics 2017; 12:226-237. [PMID: 28165867 DOI: 10.1080/15592294.2017.1289300] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
LTR retrotransposons are repetitive DNA elements comprising ∼10% of the human genome. They are silenced by hypermethylation of cytosines in CpG dinucleotides and are considered parasitic DNA serving no useful function for the host genome. However, hypermethylated LTRs contain enhancer and promoter sequences and can promote tissue-specific transcription of cis-linked genes. To resolve the apparent paradox of hypermethylated LTRs possessing transcriptional activities, we studied the ERV-9 LTR retrotransposon located at the 5' border of the transcriptionally active β-globin gene locus in human erythroid progenitor and erythroleukemia K562 cells. We found that the ERV-9 LTR, containing 65 CpGs in 1.7 kb DNA, was hypermethylated (with > 90% methylated CpGs). Hypermethylated LTR possessed transcriptional enhancer activity, since in vivo deletion of the LTR by CRISPR-cas9 suppressed transcription of the globin genes by > 50%. ChIP-qPCR and ChIP-seq studies showed that the hypermethylated LTR enhancer spanning recurrent CCAATCG and GATA motifs associated respectively with key transcription factors (TFs) NF-Y and GATA-1 and -2 at reduced levels, compared with the unmethylated LTR in transfected LTR-reporter gene plasmids. Electrophoretic mobility shift assays with methylated LTR enhancer probe showed that the methylated probe bound both NF-Y and GATA-1 and -2 with lower affinities than the unmethylated enhancer probe. Thus, hypermethylation drastically reduced, but did not totally abolish, the binding affinities of the enhancer motifs to the key TFs to assemble the LTR-pol II transcription complex that activated transcription of cis-linked genes at reduced efficiency.
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Affiliation(s)
- Tianxiang Hu
- a Department of Biochemistry and Molecular Biology , Medical College of Georgia, Augusta University , Augusta , GA , USA
| | - Xingguo Zhu
- a Department of Biochemistry and Molecular Biology , Medical College of Georgia, Augusta University , Augusta , GA , USA
| | - Wenhu Pi
- a Department of Biochemistry and Molecular Biology , Medical College of Georgia, Augusta University , Augusta , GA , USA
| | - Miao Yu
- b Georgia Cancer Center , Medical College of Georgia, Augusta University , Augusta , GA , USA
| | - Huidong Shi
- b Georgia Cancer Center , Medical College of Georgia, Augusta University , Augusta , GA , USA
| | - Dorothy Tuan
- a Department of Biochemistry and Molecular Biology , Medical College of Georgia, Augusta University , Augusta , GA , USA
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91
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da Silva KR, Mariotto S, Centofante L, Parise-Maltempi PP. Chromosome mapping of a Tc1-like transposon in species of the catfish Ancistrus. COMPARATIVE CYTOGENETICS 2017; 11:65-79. [PMID: 28919950 PMCID: PMC5599695 DOI: 10.3897/compcytogen.v11i1.10519] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 11/28/2016] [Indexed: 06/07/2023]
Abstract
The Tc1 mariner element is widely distributed among organisms and have been already described in different species of fish. The genus Ancistrus (Kner, 1854) has 68 nominal species and is part of an interesting taxonomic and cytogenetic group, as well as presenting a variation of chromosome number, ranging from 2n=34 to 54 chromosomes, and the existence of simple and multiple sex chromosome system and the occurrence of chromosomal polymorphisms involving chromosomes that carry the nucleolus organizer region. In this study, a repetitive element by restriction enzyme, from Ancistrus sp.1 "Flecha" was isolated, which showed similarity with a transposable element Tc1-mariner. Its chromosomal location is distributed in heterochromatic regions and along the chromosomal arms of all specimens covered in this study, confirming the pattern dispersed of this element found in other studies carried out with other species. Thus, this result reinforces the hypothesis that the sequence AnDraI is really a dispersed element isolated. As this isolated sequence showed the same pattern in all species which have different sex chromosomes systems, including in all sex chromosomes, we could know that it is not involved in sex chromosome differentiation.
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Affiliation(s)
- Keteryne Rodrigues da Silva
- Laboratório de Citogenética Animal – Universidade Estadual Paulista “Júlio de Mesquita Filho” Campus de Rio Claro – Av 24A, 1515 Jardim Bela Vista- 13600-000- Rio Claro/SP, Brasil
| | - Sandra Mariotto
- Instituto Federal de Ciências e Tecnologia do Mato Grosso, campus de Cuiabá – Bela Vista, MT, Brasil
| | - Liano Centofante
- Instituto de Biociências, UFMT Universidade Federal de Mato Grosso, Cuiabá, MT, Brasil
| | - Patricia Pasquali Parise-Maltempi
- Laboratório de Citogenética Animal – Universidade Estadual Paulista “Júlio de Mesquita Filho” Campus de Rio Claro – Av 24A, 1515 Jardim Bela Vista- 13600-000- Rio Claro/SP, Brasil
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92
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Evsikov AV, Marín de Evsikova C. Friend or Foe: Epigenetic Regulation of Retrotransposons in Mammalian Oogenesis and Early Development. THE YALE JOURNAL OF BIOLOGY AND MEDICINE 2016; 89:487-497. [PMID: 28018140 PMCID: PMC5168827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Epigenetics is the study of phenotypic variation arising from developmental and environmental factors regulating gene transcription at molecular, cellular, and physiological levels. A naturally occurring biological process driven by epigenetics is the egg-to-embryo developmental transition when two fully differentiated adult cells - egg and sperm - revert to an early stem cell type with totipotency but subsequently differentiates into pluripotent embryonic stem cells that give rise to any cell type. Transposable elements (TEs) are active in mammalian oocytes and early embryos, and this activity, albeit counterintuitive because TEs can lead to genomic instability in somatic cells, correlates to successful development. TEs bridge genetic and epigenetic landscapes because TEs are genetic elements whose silencing and de-repression are regulated by epigenetic mechanisms that are sensitive to environmental factors. Ultimately, transposition events can change size, content, and function of mammalian genomes. Thus, TEs act beyond mutagenic agents reshuffling the genomes, and epigenetic regulation of TEs may act as a proximate mechanism by which evolutionary forces increase a species' hidden reserve of epigenetic and phenotypic variability facilitating the adaptation of genomes to their environment.
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Affiliation(s)
- Alexei V. Evsikov
- To whom all correspondence should be addressed: Caralina Marín de Evsikova, Alexei V. Evsikov, Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd., MDC07, Tampa, FL 33612, CMdE: ; (813) 974 2248; AVE: ; (813) 974 6922, Fax: 813-974-7357
| | - Caralina Marín de Evsikova
- To whom all correspondence should be addressed: Caralina Marín de Evsikova, Alexei V. Evsikov, Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd., MDC07, Tampa, FL 33612, CMdE: ; (813) 974 2248; AVE: ; (813) 974 6922, Fax: 813-974-7357
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93
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Muñoz-Lopez M, Vilar-Astasio R, Tristan-Ramos P, Lopez-Ruiz C, Garcia-Pérez JL. Study of Transposable Elements and Their Genomic Impact. Methods Mol Biol 2016; 1400:1-19. [PMID: 26895043 DOI: 10.1007/978-1-4939-3372-3_1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Transposable elements (TEs) have been considered traditionally as junk DNA, i.e., DNA sequences that despite representing a high proportion of genomes had no evident cellular functions. However, over the last decades, it has become undeniable that not only TE-derived DNA sequences have (and had) a fundamental role during genome evolution, but also TEs have important implications in the origin and evolution of many genomic disorders. This concise review provides a brief overview of the different types of TEs that can be found in genomes, as well as a list of techniques and methods used to study their impact and mobilization. Some of these techniques will be covered in detail in this Method Book.
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Affiliation(s)
- Martin Muñoz-Lopez
- Department of Human DNA Variability, Pfizer/University of Granada and Andalusian Regional Government Center for Genomics and Oncology (GENYO), Avda Ilustracion 114, PTS Granada, 18016, Granada, Spain.
| | - Raquel Vilar-Astasio
- Department of Human DNA Variability, Pfizer/University of Granada and Andalusian Regional Government Center for Genomics and Oncology (GENYO), Avda Ilustracion 114, PTS Granada, 18016, Granada, Spain
| | - Pablo Tristan-Ramos
- Department of Human DNA Variability, Pfizer/University of Granada and Andalusian Regional Government Center for Genomics and Oncology (GENYO), Avda Ilustracion 114, PTS Granada, 18016, Granada, Spain
| | - Cesar Lopez-Ruiz
- Department of Human DNA Variability, Pfizer/University of Granada and Andalusian Regional Government Center for Genomics and Oncology (GENYO), Avda Ilustracion 114, PTS Granada, 18016, Granada, Spain
| | - Jose L Garcia-Pérez
- -Genyo (Center for Genomics and Oncological Research), Pfizer/Universidad de Granada/Junta de Andalucia. PTS Granada, Spain-Institute of Genetics and Molecular Medicine (IGMM), University of Edinburgh,, Edinburgh, UK
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94
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Babaian A, Mager DL. Endogenous retroviral promoter exaptation in human cancer. Mob DNA 2016; 7:24. [PMID: 27980689 PMCID: PMC5134097 DOI: 10.1186/s13100-016-0080-x] [Citation(s) in RCA: 142] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 11/11/2016] [Indexed: 12/13/2022] Open
Abstract
Cancer arises from a series of genetic and epigenetic changes, which result in abnormal expression or mutational activation of oncogenes, as well as suppression/inactivation of tumor suppressor genes. Aberrant expression of coding genes or long non-coding RNAs (lncRNAs) with oncogenic properties can be caused by translocations, gene amplifications, point mutations or other less characterized mechanisms. One such mechanism is the inappropriate usage of normally dormant, tissue-restricted or cryptic enhancers or promoters that serve to drive oncogenic gene expression. Dispersed across the human genome, endogenous retroviruses (ERVs) provide an enormous reservoir of autonomous gene regulatory modules, some of which have been co-opted by the host during evolution to play important roles in normal regulation of genes and gene networks. This review focuses on the “dark side” of such ERV regulatory capacity. Specifically, we discuss a growing number of examples of normally dormant or epigenetically repressed ERVs that have been harnessed to drive oncogenes in human cancer, a process we term onco-exaptation, and we propose potential mechanisms that may underlie this phenomenon.
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Affiliation(s)
- Artem Babaian
- Terry Fox Laboratory, British Columbia Cancer Agency, 675 West 10th Avenue, Vancouver, BC V5Z1L3 Canada ; Department of Medical Genetics, University of British Columbia, Vancouver, BC Canada
| | - Dixie L Mager
- Terry Fox Laboratory, British Columbia Cancer Agency, 675 West 10th Avenue, Vancouver, BC V5Z1L3 Canada ; Department of Medical Genetics, University of British Columbia, Vancouver, BC Canada
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95
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Tan S, Cardoso-Moreira M, Shi W, Zhang D, Huang J, Mao Y, Jia H, Zhang Y, Chen C, Shao Y, Leng L, Liu Z, Huang X, Long M, Zhang YE. LTR-mediated retroposition as a mechanism of RNA-based duplication in metazoans. Genome Res 2016; 26:1663-1675. [PMID: 27934698 PMCID: PMC5131818 DOI: 10.1101/gr.204925.116] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 10/18/2016] [Indexed: 01/09/2023]
Abstract
In a broad range of taxa, genes can duplicate through an RNA intermediate in a process mediated by retrotransposons (retroposition). In mammals, L1 retrotransposons drive retroposition, but the elements responsible for retroposition in other animals have yet to be identified. Here, we examined young retrocopies from various animals that still retain the sequence features indicative of the underlying retroposition mechanism. In Drosophila melanogaster, we identified and de novo assembled 15 polymorphic retrocopies and found that all retroposed loci are chimeras of internal retrocopies flanked by discontinuous LTR retrotransposons. At the fusion points between the mRNAs and the LTR retrotransposons, we identified shared short similar sequences that suggest the involvement of microsimilarity-dependent template switches. By expanding our approach to mosquito, zebrafish, chicken, and mammals, we identified in all these species recently originated retrocopies with a similar chimeric structure and shared microsimilarities at the fusion points. We also identified several retrocopies that combine the sequences of two or more parental genes, demonstrating LTR-retroposition as a novel mechanism of exon shuffling. Finally, we found that LTR-mediated retrocopies are immediately cotranscribed with their flanking LTR retrotransposons. Transcriptional profiling coupled with sequence analyses revealed that the sense-strand transcription of the retrocopies often lead to the origination of in-frame proteins relative to the parental genes. Overall, our data show that LTR-mediated retroposition is highly conserved across a wide range of animal taxa; combined with previous work from plants and yeast, it represents an ancient and ongoing mechanism continuously shaping gene content evolution in eukaryotes.
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Affiliation(s)
- Shengjun Tan
- Key Laboratory of Zoological Systematics and Evolution and State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | | | - Wenwen Shi
- Key Laboratory of Zoological Systematics and Evolution and State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Dan Zhang
- Key Laboratory of Zoological Systematics and Evolution and State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jiawei Huang
- Key Laboratory of Zoological Systematics and Evolution and State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yanan Mao
- Key Laboratory of Zoological Systematics and Evolution and State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Hangxing Jia
- Key Laboratory of Zoological Systematics and Evolution and State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yaqiong Zhang
- Key Laboratory of Zoological Systematics and Evolution and State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Chunyan Chen
- Key Laboratory of Zoological Systematics and Evolution and State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yi Shao
- Key Laboratory of Zoological Systematics and Evolution and State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liang Leng
- Key Laboratory of Zoological Systematics and Evolution and State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhonghua Liu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Xun Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Manyuan Long
- Department of Ecology and Evolution, The University of Chicago, Chicago, Illinois 60637, USA
| | - Yong E Zhang
- Key Laboratory of Zoological Systematics and Evolution and State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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96
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Abstract
Despite often being classified as selfish or junk DNA, transposable elements (TEs) are a group of abundant genetic sequences that have a significant impact on mammalian development and genome regulation. In recent years, our understanding of how pre-existing TEs affect genome architecture, gene regulatory networks and protein function during mammalian embryogenesis has dramatically expanded. In addition, the mobilization of active TEs in selected cell types has been shown to generate genetic variation during development and in fully differentiated tissues. Importantly, the ongoing domestication and evolution of TEs appears to provide a rich source of regulatory elements, functional modules and genetic variation that fuels the evolution of mammalian developmental processes. Here, we review the functional impact that TEs exert on mammalian developmental processes and discuss how the somatic activity of TEs can influence gene regulatory networks.
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Affiliation(s)
- Jose L Garcia-Perez
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, UK
- Department of Genomic Medicine, GENYO, Centre for Genomics & Oncology (Pfizer - University of Granada & Andalusian Regional Government), PTS Granada, Avda. de la Ilustración 114, Granada 18016, Spain
| | - Thomas J Widmann
- Department of Genomic Medicine, GENYO, Centre for Genomics & Oncology (Pfizer - University of Granada & Andalusian Regional Government), PTS Granada, Avda. de la Ilustración 114, Granada 18016, Spain
| | - Ian R Adams
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, UK
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97
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Abstract
In the last 20 years research in Immunology underwent fundamental changes. Most importantly, the identification of the key role of innate immune pattern recognition receptors (PRRs) that recognize evolutionarily conserved molecular patterns on infectious pathogens. This results in priming of innate immune cells, which in turn activate and direct the adaptive immune response. Progress in innate immune recognition instigated the current working hypothesis, that recognition of endogenous ligands by PRRs results in innate immune cell activation (autoinflammation) or activation of adaptive cells, with self-reactive antigen receptors (autoimmunity). In particular, nucleic acid-sensing innate immune receptors seem to be prime candidates for a mechanistic understanding of autoreactive activation of the immune system. However, it remains uncertain what the actual source of nucleic acid ligands is and what other signals are needed to drive activation of autoreactive innate immune cells and break self-tolerance of the adaptive immune system. Here, I will review our present understanding about whether the infection with exogenous retroviruses or the reactivation of endogenous retroviruses might play an etiological role in certain autoimmune conditions of humans and murine experimental models.
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Affiliation(s)
- Philipp Yu
- Institute of Immunology, Philipps-Universität Marburg, Marburg, Germany
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98
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Abstract
The germ track is the cellular path by which genes are transmitted to future generations whereas somatic cells die with their body and do not leave direct descendants. Transposable elements (TEs) evolve to be silent in somatic cells but active in the germ track. Thus, the performance of most bodily functions by a sequestered soma reduces organismal costs of TEs. Flexible forms of gene regulation are permissible in the soma because of the self-imposed silence of TEs, but strict licensing of transcription and translation is maintained in the germ track to control proliferation of TEs. Delayed zygotic genome activation (ZGA) and maternally inherited germ granules are adaptations that enhance germ-track security. Mammalian embryos exhibit very early ZGA associated with extensive mobilization of retroelements. This window of vulnerability to retrotransposition in early embryos is an indirect consequence of evolutionary conflicts within the mammalian genome over postzygotic maternal provisioning.
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Affiliation(s)
- David Haig
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.
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99
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Distribution patterns and impact of transposable elements in genes of green algae. Gene 2016; 594:151-159. [PMID: 27614292 DOI: 10.1016/j.gene.2016.09.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 09/01/2016] [Accepted: 09/06/2016] [Indexed: 11/23/2022]
Abstract
Transposable elements (TEs) are DNA sequences able to transpose in the host genome, a remarkable feature that enables them to influence evolutive trajectories of species. An investigation about the TE distribution and TE impact in different gene regions of the green algae species Chlamydomonas reinhardtii and Volvox carteri was performed. Our results indicate that TEs are very scarce near introns boundaries, suggesting that insertions in this region are negatively selected. This contrasts with previous results showing enrichment of tandem repeats in introns boundaries and suggests that different evolutionary forces are acting in these different classes of repeats. Despite the relatively low abundance of TEs in the genome of green algae when compared to mammals, the proportion of poly(A) sites derived from TEs found in C. reinhardtii was similar to that described in human and mice. This fact, associated with the enrichment of TEs in gene 5' and 3' flanks of C. reinhardtii, opens up the possibility that TEs may have considerably contributed for gene regulatory sequences evolution in this species. Moreover, it was possible identify several instances of TE exonization for C. reinhardtii, with a particularly interesting case from a gene coding for Condensin II, a protein involved in the maintenance of chromosomal structure, where the addition of a transposomal PHD finger may contribute to binding specificity of this protein. Taken together, our results suggest that the low abundance of TEs in green algae genomes is correlated with a strict negative selection process, combined with the retention of copies that contribute positively with gene structures.
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100
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Kassiotis G, Stoye JP. Immune responses to endogenous retroelements: taking the bad with the good. Nat Rev Immunol 2016; 16:207-19. [PMID: 27026073 DOI: 10.1038/nri.2016.27] [Citation(s) in RCA: 165] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The ultimate form of parasitism and evasion of host immunity is for the parasite genome to enter the germ line of the host species. Retroviruses have invaded the host germ line on the grandest scale, and this is evident in the extraordinary abundance of endogenous retroelements in the genome of all vertebrate species that have been studied. Many of these endogenous retroelements have retained viral characteristics; some also the capacity to replicate and, consequently, the potential to trigger host innate and adaptive immune responses. However, although retroelements are mainly recognized for their pathogenic potential, recent evidence suggests that this 'enemy within' may also have beneficial roles in tuning host immune reactivity. In this Review, we discuss how the immune system recognizes and is shaped by endogenous retroelements.
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Affiliation(s)
- George Kassiotis
- Retroviral Immunology, the Francis Crick Institute, Mill Hill Laboratory, London NW7 1AA, UK.,Department of Medicine, Faculty of Medicine, Imperial College London, London W2 1PG, UK
| | - Jonathan P Stoye
- Department of Medicine, Faculty of Medicine, Imperial College London, London W2 1PG, UK.,Retrovirus-Host Interactions, the Francis Crick Institute, Mill Hill Laboratory, London NW7 1AA, UK
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