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Zhang M, Sun W, You X, Xu D, Wang L, Yang J, Li E, He S. LINE-1 repression in Epstein-Barr virus-associated gastric cancer through viral-host genome interaction. Nucleic Acids Res 2023; 51:4867-4880. [PMID: 36942479 PMCID: PMC10250212 DOI: 10.1093/nar/gkad203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 03/07/2023] [Accepted: 03/12/2023] [Indexed: 03/23/2023] Open
Abstract
Long INterspersed Element 1 (LINE-1 or L1) acts as a major remodeling force in genome regulation and evolution. Accumulating evidence shows that virus infection impacts L1 expression, potentially impacting host antiviral response and diseases. The underlying regulation mechanism is unclear. Epstein-Barr virus (EBV), a double-stranded DNA virus linked to B-cell and epithelial malignancies, is known to have viral-host genome interaction, resulting in transcriptional rewiring in EBV-associated gastric cancer (EBVaGC). By analyzing publicly available datasets from the Gene Expression Omnibus (GEO), we found that EBVaGC has L1 transcriptional repression compared with EBV-negative gastric cancer (EBVnGC). More specifically, retrotransposition-associated young and full-length L1s (FL-L1s) were among the most repressed L1s. Epigenetic alterations, especially increased H3K9me3, were observed on FL-L1s. H3K9me3 deposition was potentially attributed to increased TASOR expression, a key component of the human silencing hub (HUSH) complex for H3K9 trimethylation. The 4C- and HiC-seq data indicated that the viral DNA interacted in the proximity of the TASOR enhancer, strengthening the loop formation between the TASOR enhancer and its promoter. These results indicated that EBV infection is associated with increased H3K9me3 deposition, leading to L1 repression. This study uncovers a regulation mechanism of L1 expression by chromatin topology remodeling associated with viral-host genome interaction in EBVaGC.
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Affiliation(s)
- Mengyu Zhang
- State Key Laboratory of Pharmaceutical Biotechnology, Medical School, Nanjing University, Nanjing 210093, China
- Jiangsu Key Laboratory of Molecular Medicine, Medical School, Nanjing University, Nanjing 210093, China
- Yancheng Medical Research Center, Medical School, Nanjing University, Yancheng 224000, China
| | - Weikang Sun
- State Key Laboratory of Pharmaceutical Biotechnology, Medical School, Nanjing University, Nanjing 210093, China
- Jiangsu Key Laboratory of Molecular Medicine, Medical School, Nanjing University, Nanjing 210093, China
| | - Xiaoxin You
- State Key Laboratory of Pharmaceutical Biotechnology, Medical School, Nanjing University, Nanjing 210093, China
- Jiangsu Key Laboratory of Molecular Medicine, Medical School, Nanjing University, Nanjing 210093, China
| | - Dongge Xu
- State Key Laboratory of Pharmaceutical Biotechnology, Medical School, Nanjing University, Nanjing 210093, China
- Jiangsu Key Laboratory of Molecular Medicine, Medical School, Nanjing University, Nanjing 210093, China
| | - Lingling Wang
- State Key Laboratory of Pharmaceutical Biotechnology, Medical School, Nanjing University, Nanjing 210093, China
- Jiangsu Key Laboratory of Molecular Medicine, Medical School, Nanjing University, Nanjing 210093, China
| | - Jingping Yang
- State Key Laboratory of Pharmaceutical Biotechnology, Medical School, Nanjing University, Nanjing 210093, China
- Jiangsu Key Laboratory of Molecular Medicine, Medical School, Nanjing University, Nanjing 210093, China
| | - Erguang Li
- State Key Laboratory of Pharmaceutical Biotechnology, Medical School, Nanjing University, Nanjing 210093, China
- Jiangsu Key Laboratory of Molecular Medicine, Medical School, Nanjing University, Nanjing 210093, China
- Institute of Medical Virology, Nanjing Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210093, China
- Shenzhen Research Institute of Nanjing University, Shenzhen 518000, China
| | - Susu He
- State Key Laboratory of Pharmaceutical Biotechnology, Medical School, Nanjing University, Nanjing 210093, China
- Jiangsu Key Laboratory of Molecular Medicine, Medical School, Nanjing University, Nanjing 210093, China
- Yancheng Medical Research Center, Medical School, Nanjing University, Yancheng 224000, China
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2
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Batcher K, Varney S, Raudsepp T, Jevit M, Dickinson P, Jagannathan V, Leeb T, Bannasch D. Ancient segmentally duplicated LCORL retrocopies in equids. PLoS One 2023; 18:e0286861. [PMID: 37289743 PMCID: PMC10249811 DOI: 10.1371/journal.pone.0286861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 05/25/2023] [Indexed: 06/10/2023] Open
Abstract
LINE-1 is an active transposable element encoding proteins capable of inserting host gene retrocopies, resulting in retro-copy number variants (retroCNVs) between individuals. Here, we performed retroCNV discovery using 86 equids and identified 437 retrocopy insertions. Only 5 retroCNVs were shared between horses and other equids, indicating that the majority of retroCNVs inserted after the species diverged. A large number (17-35 copies) of segmentally duplicated Ligand Dependent Nuclear Receptor Corepressor Like (LCORL) retrocopies were present in all equids but absent from other extant perissodactyls. The majority of LCORL transcripts in horses and donkeys originate from the retrocopies. The initial LCORL retrotransposition occurred 18 million years ago (17-19 95% CI), which is coincident with the increase in body size, reduction in digit number, and changes in dentition that characterized equid evolution. Evolutionary conservation of the LCORL retrocopy segmental amplification in the Equidae family, high expression levels and the ancient timeline for LCORL retrotransposition support a functional role for this structural variant.
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Affiliation(s)
- Kevin Batcher
- Department of Population Health and Reproduction, University of California Davis, Davis, CA, United States of America
| | - Scarlett Varney
- Department of Population Health and Reproduction, University of California Davis, Davis, CA, United States of America
| | - Terje Raudsepp
- Veterinary Integrative Biosciences, School of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America
| | - Matthew Jevit
- Veterinary Integrative Biosciences, School of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America
| | - Peter Dickinson
- Department of Surgical and Radiological Sciences, University of California Davis, Davis, CA, United States of America
| | - Vidhya Jagannathan
- Institute of Genetics, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Tosso Leeb
- Institute of Genetics, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Danika Bannasch
- Department of Population Health and Reproduction, University of California Davis, Davis, CA, United States of America
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Batcher K, Varney S, York D, Blacksmith M, Kidd JM, Rebhun R, Dickinson P, Bannasch D. Recent, full-length gene retrocopies are common in canids. Genome Res 2022; 32:gr.276828.122. [PMID: 35961775 PMCID: PMC9435743 DOI: 10.1101/gr.276828.122] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 07/19/2022] [Indexed: 02/03/2023]
Abstract
Gene retrocopies arise from the reverse transcription and insertion into the genome of processed mRNA transcripts. Although many retrocopies have acquired mutations that render them functionally inactive, most mammals retain active LINE-1 sequences capable of producing new retrocopies. New retrocopies, referred to as retro copy number variants (retroCNVs), may not be identified by standard variant calling techniques in high-throughput sequencing data. Although multiple functional FGF4 retroCNVs have been associated with skeletal dysplasias in dogs, the full landscape of canid retroCNVs has not been characterized. Here, retroCNV discovery was performed on a whole-genome sequencing data set of 293 canids from 76 breeds. We identified retroCNV parent genes via the presence of mRNA-specific 30-mers, and then identified retroCNV insertion sites through discordant read analysis. In total, we resolved insertion sites for 1911 retroCNVs from 1179 parent genes, 1236 of which appeared identical to their parent genes. Dogs had on average 54.1 total retroCNVs and 1.4 private retroCNVs. We found evidence of expression in testes for 12% (14/113) of the retroCNVs identified in six Golden Retrievers, including four chimeric transcripts, and 97 retroCNVs also had significantly elevated F ST across dog breeds, possibly indicating selection. We applied our approach to a subset of human genomes and detected an average of 4.2 retroCNVs per sample, highlighting a 13-fold relative increase of retroCNV frequency in dogs. Particularly in canids, retroCNVs are a largely unexplored source of genetic variation that can contribute to genome plasticity and that should be considered when investigating traits and diseases.
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Affiliation(s)
- Kevin Batcher
- Department of Population Health and Reproduction, University of California, Davis, Davis, California 95616, USA
| | - Scarlett Varney
- Department of Population Health and Reproduction, University of California, Davis, Davis, California 95616, USA
| | - Daniel York
- Department of Surgical and Radiological Sciences, University of California, Davis, Davis, California 95616, USA
| | - Matthew Blacksmith
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - Jeffrey M Kidd
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
- Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - Robert Rebhun
- Department of Surgical and Radiological Sciences, University of California, Davis, Davis, California 95616, USA
| | - Peter Dickinson
- Department of Surgical and Radiological Sciences, University of California, Davis, Davis, California 95616, USA
| | - Danika Bannasch
- Department of Population Health and Reproduction, University of California, Davis, Davis, California 95616, USA
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4
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Miller D, Chen J, Liang J, Betrán E, Long M, Sharakhov IV. Retrogene Duplication and Expression Patterns Shaped by the Evolution of Sex Chromosomes in Malaria Mosquitoes. Genes (Basel) 2022; 13:genes13060968. [PMID: 35741730 PMCID: PMC9222922 DOI: 10.3390/genes13060968] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 05/23/2022] [Accepted: 05/25/2022] [Indexed: 12/19/2022] Open
Abstract
Genes that originate during evolution are an important source of novel biological functions. Retrogenes are functional copies of genes produced by retroduplication and as such are located in different genomic positions. To investigate retroposition patterns and retrogene expression, we computationally identified interchromosomal retroduplication events in nine portions of the phylogenetic history of malaria mosquitoes, making use of species that do or do not have classical sex chromosomes to test the roles of sex-linkage. We found 40 interchromosomal events and a significant excess of retroduplications from the X chromosome to autosomes among a set of young retrogenes. These young retroposition events occurred within the last 100 million years in lineages where all species possessed differentiated sex chromosomes. An analysis of available microarray and RNA-seq expression data for Anopheles gambiae showed that many of the young retrogenes evolved male-biased expression in the reproductive organs. Young autosomal retrogenes with increased meiotic or postmeiotic expression in the testes tend to be male biased. In contrast, older retrogenes, i.e., in lineages with undifferentiated sex chromosomes, do not show this particular chromosomal bias and are enriched for female-biased expression in reproductive organs. Our reverse-transcription PCR data indicates that most of the youngest retrogenes, which originated within the last 47.6 million years in the subgenus Cellia, evolved non-uniform expression patterns across body parts in the males and females of An. coluzzii. Finally, gene annotation revealed that mitochondrial function is a prominent feature of the young autosomal retrogenes. We conclude that mRNA-mediated gene duplication has produced a set of genes that contribute to mosquito reproductive functions and that different biases are revealed after the sex chromosomes evolve. Overall, these results suggest potential roles for the evolution of meiotic sex chromosome inactivation in males and of sexually antagonistic conflict related to mitochondrial energy function as the main selective pressures for X-to-autosome gene reduplication and testis-biased expression in these mosquito lineages.
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Affiliation(s)
- Duncan Miller
- Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA; (D.M.); (J.L.)
| | - Jianhai Chen
- Department of Ecology and Evolution, University of Chicago, Chicago, IL 60637, USA;
| | - Jiangtao Liang
- Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA; (D.M.); (J.L.)
| | - Esther Betrán
- Department of Biology, University of Texas at Arlington, Arlington, TX 76019, USA;
| | - Manyuan Long
- Department of Ecology and Evolution, University of Chicago, Chicago, IL 60637, USA;
- Correspondence: (M.L.); (I.V.S.)
| | - Igor V. Sharakhov
- Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA; (D.M.); (J.L.)
- Department of Genetics and Cell Biology, Tomsk State University, 634050 Tomsk, Russia
- Correspondence: (M.L.); (I.V.S.)
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5
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The Role of Transposable Elements of the Human Genome in Neuronal Function and Pathology. Int J Mol Sci 2022; 23:ijms23105847. [PMID: 35628657 PMCID: PMC9148063 DOI: 10.3390/ijms23105847] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 05/17/2022] [Accepted: 05/19/2022] [Indexed: 12/13/2022] Open
Abstract
Transposable elements (TEs) have been extensively studied for decades. In recent years, the introduction of whole-genome and whole-transcriptome approaches, as well as single-cell resolution techniques, provided a breakthrough that uncovered TE involvement in host gene expression regulation underlying multiple normal and pathological processes. Of particular interest is increased TE activity in neuronal tissue, and specifically in the hippocampus, that was repeatedly demonstrated in multiple experiments. On the other hand, numerous neuropathologies are associated with TE dysregulation. Here, we provide a comprehensive review of literature about the role of TEs in neurons published over the last three decades. The first chapter of the present review describes known mechanisms of TE interaction with host genomes in general, with the focus on mammalian and human TEs; the second chapter provides examples of TE exaptation in normal neuronal tissue, including TE involvement in neuronal differentiation and plasticity; and the last chapter lists TE-related neuropathologies. We sought to provide specific molecular mechanisms of TE involvement in neuron-specific processes whenever possible; however, in many cases, only phenomenological reports were available. This underscores the importance of further studies in this area.
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Domazet-Lošo T. mRNA Vaccines: Why Is the Biology of Retroposition Ignored? Genes (Basel) 2022; 13:719. [PMID: 35627104 PMCID: PMC9141755 DOI: 10.3390/genes13050719] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 04/14/2022] [Accepted: 04/15/2022] [Indexed: 02/07/2023] Open
Abstract
The major advantage of mRNA vaccines over more conventional approaches is their potential for rapid development and large-scale deployment in pandemic situations. In the current COVID-19 crisis, two mRNA COVID-19 vaccines have been conditionally approved and broadly applied, while others are still in clinical trials. However, there is no previous experience with the use of mRNA vaccines on a large scale in the general population. This warrants a careful evaluation of mRNA vaccine safety properties by considering all available knowledge about mRNA molecular biology and evolution. Here, I discuss the pervasive claim that mRNA-based vaccines cannot alter genomes. Surprisingly, this notion is widely stated in the mRNA vaccine literature but never supported by referencing any primary scientific papers that would specifically address this question. This discrepancy becomes even more puzzling if one considers previous work on the molecular and evolutionary aspects of retroposition in murine and human populations that clearly documents the frequent integration of mRNA molecules into genomes, including clinical contexts. By performing basic comparisons, I show that the sequence features of mRNA vaccines meet all known requirements for retroposition using L1 elements-the most abundant autonomously active retrotransposons in the human genome. In fact, many factors associated with mRNA vaccines increase the possibility of their L1-mediated retroposition. I conclude that is unfounded to a priori assume that mRNA-based therapeutics do not impact genomes and that the route to genome integration of vaccine mRNAs via endogenous L1 retroelements is easily conceivable. This implies that we urgently need experimental studies that would rigorously test for the potential retroposition of vaccine mRNAs. At present, the insertional mutagenesis safety of mRNA-based vaccines should be considered unresolved.
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Affiliation(s)
- Tomislav Domazet-Lošo
- Laboratory of Evolutionary Genetics, Division of Molecular Biology, Ruđer Bošković Institute, Bijenička Cesta 54, HR-10000 Zagreb, Croatia;
- School of Medicine, Catholic University of Croatia, Ilica 242, HR-10000 Zagreb, Croatia
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7
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Zhang W, Tautz D. Tracing the origin and evolutionary fate of recent gene retrocopies in natural populations of the house mouse. Mol Biol Evol 2021; 39:6481550. [PMID: 34940842 PMCID: PMC8826619 DOI: 10.1093/molbev/msab360] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Although the contribution of retrogenes to the evolution of genes and genomes has long been recognized, the evolutionary patterns of very recently derived retrocopies that are still polymorphic within natural populations have not been much studied so far. We use here a set of 2,025 such retrocopies in nine house mouse populations from three subspecies (Mus musculus domesticus, M. m. musculus, and M. m. castaneus) to trace their origin and evolutionary fate. We find that ancient house-keeping genes are significantly more likely to generate retrocopies than younger genes and that the propensity to generate a retrocopy depends on its level of expression in the germline. Although most retrocopies are detrimental and quickly purged, we focus here on the subset that appears to be neutral or even adaptive. We show that retrocopies from X-chromosomal parental genes have a higher likelihood to reach elevated frequencies in the populations, confirming the notion of adaptive effects for “out-of-X” retrogenes. Also, retrocopies in intergenic regions are more likely to reach higher population frequencies than those in introns of genes, implying a more detrimental effect when they land within transcribed regions. For a small subset of retrocopies, we find signatures of positive selection, indicating they were involved in a recent adaptation process. We show that the population-specific distribution pattern of retrocopies is phylogenetically informative and can be used to infer population history with a better resolution than with SNP markers.
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Affiliation(s)
- Wenyu Zhang
- Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Biology, August-Thienemann-Str. 2, Plön, D-24306, Germany
| | - Diethard Tautz
- Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Biology, August-Thienemann-Str. 2, Plön, D-24306, Germany
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8
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Feliciello I, Procino A. mRNA vaccines: Why and how they should be modified. JOURNAL OF BIOLOGICAL RESEARCH - BOLLETTINO DELLA SOCIETÀ ITALIANA DI BIOLOGIA SPERIMENTALE 2021. [DOI: 10.4081/jbr.2021.10072] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The COVID-19 pandemic has stimulated the production of different therapeutic approaches for the resolution of coronavirus infections. On one hand, nanobiomolecules have been proposed as bait material for viruses,1,2 on the other hand unconventional messenger RNA vaccines have been produced like SARS-CoV-2 mRNA vaccines (BioNTech/Pfizer BNT162b2 and Moderna mRNA-1273). [...]
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9
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Kazachenka A, Kassiotis G. SARS-CoV-2-Host Chimeric RNA-Sequencing Reads Do Not Necessarily Arise From Virus Integration Into the Host DNA. Front Microbiol 2021; 12:676693. [PMID: 34149667 PMCID: PMC8206523 DOI: 10.3389/fmicb.2021.676693] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 05/05/2021] [Indexed: 12/11/2022] Open
Abstract
The human genome bears evidence of extensive invasion by retroviruses and other retroelements, as well as by diverse RNA and DNA viruses. High frequency of somatic integration of the RNA virus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into the DNA of infected cells was recently suggested, based on a number of observations. One key observation was the presence of chimeric RNA-sequencing (RNA-seq) reads between SARS-CoV-2 RNA and RNA transcribed from human host DNA. Here, we examined the possible origin specifically of human-SARS-CoV-2 chimeric reads in RNA-seq libraries and provide alternative explanations for their origin. Chimeric reads were frequently detected also between SARS-CoV-2 RNA and RNA transcribed from mitochondrial DNA or episomal adenoviral DNA present in transfected cell lines, which was unlikely the result of SARS-CoV-2 integration. Furthermore, chimeric reads between SARS-CoV-2 RNA and RNA transcribed from nuclear DNA were highly enriched for host exonic, rather than intronic or intergenic sequences and often involved the same, highly expressed host genes. Although these findings do not rule out SARS-CoV-2 somatic integration, they nevertheless suggest that human-SARS-CoV-2 chimeric reads found in RNA-seq data may arise during library preparation and do not necessarily signify SARS-CoV-2 reverse transcription, integration in to host DNA and further transcription.
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Affiliation(s)
| | - George Kassiotis
- Retroviral Immunology, The Francis Crick Institute, London, United Kingdom
- Department of Infectious Disease, St Mary’s Hospital, Imperial College London, London, United Kingdom
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The mutational load in natural populations is significantly affected by high primary rates of retroposition. Proc Natl Acad Sci U S A 2021; 118:2013043118. [PMID: 33526666 PMCID: PMC8017666 DOI: 10.1073/pnas.2013043118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The phenomenon of retroposition (the reintegration of reverse-transcribed RNA into the genome) has been well studied in comparisons between species and has been identified as a source of evolutionary innovation. However, less attention has been paid to possible negative effects of retroposition. To trace the evolutionary dynamics of these negative effects, our study uses a unique genomic dataset of house mouse populations. It reveals that the initial retroposition rate is very high and that most of these newly transposed retrocopies have a deleterious impact, apparently through modifying the expression of their parental genes. In humans, this effect is expected to cause disease alleles, and we propose that genetic screening should include the search for newly transposed retrocopies. Gene retroposition is known to contribute to patterns of gene evolution and adaptations. However, possible negative effects of gene retroposition remain largely unexplored since most previous studies have focused on between-species comparisons where negatively selected copies are mostly not observed, as they are quickly lost from populations. Here, we show for natural house mouse populations that the primary rate of retroposition is orders of magnitude higher than the long-term rate. Comparisons with single-nucleotide polymorphism distribution patterns in the same populations show that most retroposition events are deleterious. Transcriptomic profiling analysis shows that new retroposed copies become easily subject to transcription and have an influence on the expression levels of their parental genes, especially when transcribed in the antisense direction. Our results imply that the impact of retroposition on the mutational load has been highly underestimated in natural populations. This has additional implications for strategies of disease allele detection in humans.
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Cancer, Retrogenes, and Evolution. Life (Basel) 2021; 11:life11010072. [PMID: 33478113 PMCID: PMC7835786 DOI: 10.3390/life11010072] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Revised: 01/14/2021] [Accepted: 01/15/2021] [Indexed: 12/18/2022] Open
Abstract
This review summarizes the knowledge about retrogenes in the context of cancer and evolution. The retroposition, in which the processed mRNA from parental genes undergoes reverse transcription and the resulting cDNA is integrated back into the genome, results in additional copies of existing genes. Despite the initial misconception, retroposition-derived copies can become functional, and due to their role in the molecular evolution of genomes, they have been named the “seeds of evolution”. It is convincing that retrogenes, as important elements involved in the evolution of species, also take part in the evolution of neoplastic tumors at the cell and species levels. The occurrence of specific “resistance mechanisms” to neoplastic transformation in some species has been noted. This phenomenon has been related to additional gene copies, including retrogenes. In addition, the role of retrogenes in the evolution of tumors has been described. Retrogene expression correlates with the occurrence of specific cancer subtypes, their stages, and their response to therapy. Phylogenetic insights into retrogenes show that most cancer-related retrocopies arose in the lineage of primates, and the number of identified cancer-related retrogenes demonstrates that these duplicates are quite important players in human carcinogenesis.
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Pan CT, Lin YS. MicroRNA retrocopies generated via L1-mediated retrotransposition in placental mammals help to reveal how their parental genes were transcribed. Sci Rep 2020; 10:20612. [PMID: 33244051 PMCID: PMC7692494 DOI: 10.1038/s41598-020-77381-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 11/10/2020] [Indexed: 02/07/2023] Open
Abstract
In mammalian genomes, most retrocopies emerged via the L1 retrotransposition machinery. The hallmarks of an L1-mediated retrocopy, i.e., the intronlessness, the presence of a 3′ poly-A tail, and the TSDs at both ends, were frequently used to identify retrotransposition events. However, most previous studies only focused on protein-coding genes as their possible parental sources and thus only a few retrocopies derived from non-coding genes were reported. Remarkably, none of them was from microRNAs. Here in this study, we found several retrocopies generated from the mir-302–367 cluster gene (MIR302CHG), and identified a novel alternatively spliced exon encoding mir-302a. The other recognized microRNA retrotransposition events are primate-specific with mir-373 and mir-498 as their parental genes. The 3′ poly-A tracts of these two retrocopy groups were directly attached to the end of the microRNA precursor homologous regions, which suggests that their parental transcripts might alternatively terminate at the end of mir-373 and mir-498. All the three parental microRNAs are highly expressed in specific tissues with elevated retrotransposon activity, such as the embryonic stem cells and the placenta. This might be the reason that our first microRNA retrocopy findings were derived from these three microRNA genes.
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Affiliation(s)
- Cheng-Tsung Pan
- Institute of Bioinformatics and Systems Biology, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Yeong-Shin Lin
- Institute of Bioinformatics and Systems Biology, National Chiao Tung University, Hsinchu, 300, Taiwan. .,Department of Biological Science and Technology, College of Biological Science and Technology, National Chiao Tung University, Hsinchu, 300, Taiwan. .,Center For Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Chiao Tung University, Hsinchu, 300, Taiwan.
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Cadmium Uptake, MT Gene Activation and Structure of Large-Sized Multi-Domain Metallothioneins in the Terrestrial Door Snail Alinda biplicata (Gastropoda, Clausiliidae). Int J Mol Sci 2020; 21:ijms21051631. [PMID: 32120996 PMCID: PMC7084494 DOI: 10.3390/ijms21051631] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 02/20/2020] [Accepted: 02/24/2020] [Indexed: 02/06/2023] Open
Abstract
Terrestrial snails (Gastropoda) possess Cd-selective metallothioneins (CdMTs) that inactivate Cd2+ with high affinity. Most of these MTs are small Cysteine-rich proteins that bind 6 Cd2+ equivalents within two distinct metal-binding domains, with a binding stoichiometry of 3 Cd2+ ions per domain. Recently, unusually large, so-called multi-domain MTs (md-MTs) were discovered in the terrestrial door snail Alinda biplicata (A.b.). The aim of this study is to evaluate the ability of A.b. to cope with Cd stress and the potential involvement of md-MTs in its detoxification. Snails were exposed to increasing Cd concentrations, and Cd-tissue concentrations were quantified. The gene structure of two md-MTs (9md-MT and 10md-MT) was characterized, and the impact of Cd exposure on MT gene transcription was quantified via qRT PCR. A.b. efficiently accumulates Cd at moderately elevated concentrations in the feed, but avoids food uptake at excessively high Cd levels. The structure and expression of the long md-MT genes of A.b. were characterized. Although both genes are intronless, they are still transcribed, being significantly upregulated upon Cd exposure. Overall, our results contribute new knowledge regarding the metal handling of Alinda biplicata in particular, and the potential role of md-MTs in Cd detoxification of terrestrial snails, in general.
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Overcoming challenges and dogmas to understand the functions of pseudogenes. Nat Rev Genet 2019; 21:191-201. [DOI: 10.1038/s41576-019-0196-1] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/05/2019] [Indexed: 01/08/2023]
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15
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Bim LV, Navarro FCP, Valente FOF, Lima-Junior JV, Delcelo R, Dias-da-Silva MR, Maciel RMB, Galante PAF, Cerutti JM. Retroposed copies of RET gene: a somatically acquired event in medullary thyroid carcinoma. BMC Med Genomics 2019; 12:104. [PMID: 31288802 PMCID: PMC6617568 DOI: 10.1186/s12920-019-0552-1] [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: 01/07/2019] [Accepted: 06/17/2019] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Different pathogenic germline mutations in the RET oncogene are identified in MEN 2, a hereditary syndrome characterized by medullary thyroid carcinoma (MTC) and other endocrine tumors. Although genetic predisposition is recognized, not all RET mutation carriers will develop the disease during their lifetime or, likewise, RET mutation carriers belonging to the same family may present clinical heterogeneity. It has been suggested that a single germline mutation might not be sufficient for development of MEN 2-associated tumors and a somatic bi-allelic alteration might be required. Here we investigated the presence of somatic second hit mutation in the RET gene in MTC. METHODS We integrated Multiplex Ligation-dependent Probe Amplification (MLPA) and whole exome sequencing (WES) to search for copy number alteration (CNA) in the RET gene in MTC samples and medullary thyroid cell lines (TT and MZ-CR-1). We next found reads spanning exon-exon boundaries on RET, an indicative of retrocopy. We subsequently searched for RET retrocopies in the human reference genome (GRCh37) and in the 1000 Genomes Project data, by looking for reads reporting joined exons in the RET locus or distinct genomic regions. To determine RET retrocopy specificity and recurrence, DNA isolated from sporadic and MEN 2-associated MTC (n = 37), peripheral blood (n = 3) and papillary thyroid carcinomas with RET fusion (n = 10) samples were tested using PCR-sequencing methodology. RESULTS Through MLPA we have found evidence of CNA in the RET gene in MTC samples and MTC cell lines. WES analysis reinforced the presence of the CNA and hinted for a retroposed copy of RET not found in the human reference genome and 1.000 Genomes Project. Extended analysis confirmed the presence of a somatic MTC-related retrocopy of RET in both sporadic and hereditary tumors. We further unveiled a recurrent (28%) novel point mutation (p.G548 V) found exclusively in the retrocopy of RET. The mutation was also found in cDNA of mutated samples, suggesting it might be functional. CONCLUSION We here report a somatic specific RET retroposed copy in MTC samples and cell lines. Our results support the idea that generation of retrocopies in somatic cells is likely to contribute to MTC genesis and progression.
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Affiliation(s)
- Larissa V Bim
- Laboratório As Bases Genéticas dos Tumores da Tiroide, Universidade Federal de São Paulo, São Paulo, SP, Brazil
| | - Fábio C P Navarro
- Centro de Oncologia Molecular, Hospital Sírio-libanês, São Paulo, SP, Brazil.,Departamento de Bioquímica, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Flávia O F Valente
- Laboratório de Endocrinologia Molecular e Translacional, Universidade Federal de São Paulo, São Paulo, SP, Brazil
| | - José V Lima-Junior
- Laboratório As Bases Genéticas dos Tumores da Tiroide, Universidade Federal de São Paulo, São Paulo, SP, Brazil
| | - Rosana Delcelo
- Departamento de Patologia, Universidade Federal de São Paulo, São Paulo, SP, Brazil
| | - Magnus R Dias-da-Silva
- Laboratório de Endocrinologia Molecular e Translacional, Universidade Federal de São Paulo, São Paulo, SP, Brazil
| | - Rui M B Maciel
- Laboratório de Endocrinologia Molecular e Translacional, Universidade Federal de São Paulo, São Paulo, SP, Brazil
| | - Pedro A F Galante
- Centro de Oncologia Molecular, Hospital Sírio-libanês, São Paulo, SP, Brazil
| | - Janete M Cerutti
- Laboratório As Bases Genéticas dos Tumores da Tiroide, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
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Shapiro JA. Living Organisms Author Their Read-Write Genomes in Evolution. BIOLOGY 2017; 6:E42. [PMID: 29211049 PMCID: PMC5745447 DOI: 10.3390/biology6040042] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 11/17/2017] [Accepted: 11/28/2017] [Indexed: 12/18/2022]
Abstract
Evolutionary variations generating phenotypic adaptations and novel taxa resulted from complex cellular activities altering genome content and expression: (i) Symbiogenetic cell mergers producing the mitochondrion-bearing ancestor of eukaryotes and chloroplast-bearing ancestors of photosynthetic eukaryotes; (ii) interspecific hybridizations and genome doublings generating new species and adaptive radiations of higher plants and animals; and, (iii) interspecific horizontal DNA transfer encoding virtually all of the cellular functions between organisms and their viruses in all domains of life. Consequently, assuming that evolutionary processes occur in isolated genomes of individual species has become an unrealistic abstraction. Adaptive variations also involved natural genetic engineering of mobile DNA elements to rewire regulatory networks. In the most highly evolved organisms, biological complexity scales with "non-coding" DNA content more closely than with protein-coding capacity. Coincidentally, we have learned how so-called "non-coding" RNAs that are rich in repetitive mobile DNA sequences are key regulators of complex phenotypes. Both biotic and abiotic ecological challenges serve as triggers for episodes of elevated genome change. The intersections of cell activities, biosphere interactions, horizontal DNA transfers, and non-random Read-Write genome modifications by natural genetic engineering provide a rich molecular and biological foundation for understanding how ecological disruptions can stimulate productive, often abrupt, evolutionary transformations.
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Affiliation(s)
- James A Shapiro
- Department of Biochemistry and Molecular Biology, University of Chicago GCIS W123B, 979 E. 57th Street, Chicago, IL 60637, USA.
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17
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Casola C, Betrán E. The Genomic Impact of Gene Retrocopies: What Have We Learned from Comparative Genomics, Population Genomics, and Transcriptomic Analyses? Genome Biol Evol 2017; 9:1351-1373. [PMID: 28605529 PMCID: PMC5470649 DOI: 10.1093/gbe/evx081] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/18/2017] [Indexed: 02/07/2023] Open
Abstract
Gene duplication is a major driver of organismal evolution. Gene retroposition is a mechanism of gene duplication whereby a gene’s transcript is used as a template to generate retroposed gene copies, or retrocopies. Intriguingly, the formation of retrocopies depends upon the enzymatic machinery encoded by retrotransposable elements, genomic parasites occurring in the majority of eukaryotes. Most retrocopies are depleted of the regulatory regions found upstream of their parental genes; therefore, they were initially considered transcriptionally incompetent gene copies, or retropseudogenes. However, examples of functional retrocopies, or retrogenes, have accumulated since the 1980s. Here, we review what we have learned about retrocopies in animals, plants and other eukaryotic organisms, with a particular emphasis on comparative and population genomic analyses complemented with transcriptomic datasets. In addition, these data have provided information about the dynamics of the different “life cycle” stages of retrocopies (i.e., polymorphic retrocopy number variants, fixed retropseudogenes and retrogenes) and have provided key insights into the retroduplication mechanisms, the patterns and evolutionary forces at work during the fixation process and the biological function of retrogenes. Functional genomic and transcriptomic data have also revealed that many retropseudogenes are transcriptionally active and a biological role has been experimentally determined for many. Finally, we have learned that not only non-long terminal repeat retroelements but also long terminal repeat retroelements play a role in the emergence of retrocopies across eukaryotes. This body of work has shown that mRNA-mediated duplication represents a widespread phenomenon that produces an array of new genes that contribute to organismal diversity and adaptation.
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Affiliation(s)
- Claudio Casola
- Department of Ecosystem Science and Management, Texas A&M University, TX
| | - Esther Betrán
- Department of Biology, University of Texas at Arlington, Arlington, TX
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18
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Watson CM, Camm N, Crinnion LA, Antanaviciute A, Adlard J, Markham AF, Carr IM, Charlton R, Bonthron DT. Characterization and Genomic Localization of a SMAD4 Processed Pseudogene. J Mol Diagn 2017; 19:933-940. [PMID: 28867604 DOI: 10.1016/j.jmoldx.2017.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 08/16/2017] [Indexed: 12/30/2022] Open
Abstract
Like many clinical diagnostic laboratories, the Yorkshire Regional Genetics Service undertakes routine investigation of cancer-predisposed individuals by high-throughput sequencing of patient DNA that has been target-enriched for genes associated with hereditary cancer. Accurate diagnosis using such reagents requires alertness regarding rare nonpathogenic variants that may interfere with variant calling. In a cohort of 2042 such cases, we identified 5 that initially appeared to be carriers of a 95-bp deletion of SMAD4 intron 6. More detailed analysis indicated that these individuals all carried one copy of a SMAD4 processed gene. Because of its interference with diagnostic analysis, we characterized this processed gene in detail. Whole-genome sequencing and confirmatory Sanger sequencing of junction PCR products were used to show that in each of the 5 cases, the SMAD4 processed gene was integrated at the same position on chromosome 9, located within the last intron of the SCAI gene. This rare polymorphic processed gene therefore reflects the occurrence of a single ancestral retrotransposition event. Compared to the reference SMAD4 mRNA sequence NM_005359.5 (https://www.ncbi.nlm.nih.gov/nucleotide), the 5' and 3' untranslated regions of the processed gene are both truncated, but its open reading frame is unaltered. Our experience leads us to advocate the use of an RNA-seq aligner as part of diagnostic assay quality assurance, since this allows recognition of processed pseudogenes in a comparatively facile automated fashion.
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Affiliation(s)
- Christopher M Watson
- Yorkshire Regional Genetics Service, St. James's University Hospital, Leeds, United Kingdom; MRC Medical Bioinformatics Centre, Leeds Institute for Data Analytics, St. James's University Hospital, Leeds, United Kingdom; MRC Single Cell Functional Genomics Centre, University of Leeds, St. James's University Hospital, Leeds, United Kingdom.
| | - Nick Camm
- Yorkshire Regional Genetics Service, St. James's University Hospital, Leeds, United Kingdom
| | - Laura A Crinnion
- Yorkshire Regional Genetics Service, St. James's University Hospital, Leeds, United Kingdom; MRC Medical Bioinformatics Centre, Leeds Institute for Data Analytics, St. James's University Hospital, Leeds, United Kingdom; MRC Single Cell Functional Genomics Centre, University of Leeds, St. James's University Hospital, Leeds, United Kingdom
| | - Agne Antanaviciute
- MRC Medical Bioinformatics Centre, Leeds Institute for Data Analytics, St. James's University Hospital, Leeds, United Kingdom
| | - Julian Adlard
- Yorkshire Regional Genetics Service, St. James's University Hospital, Leeds, United Kingdom
| | - Alexander F Markham
- MRC Medical Bioinformatics Centre, Leeds Institute for Data Analytics, St. James's University Hospital, Leeds, United Kingdom
| | - Ian M Carr
- MRC Medical Bioinformatics Centre, Leeds Institute for Data Analytics, St. James's University Hospital, Leeds, United Kingdom; MRC Single Cell Functional Genomics Centre, University of Leeds, St. James's University Hospital, Leeds, United Kingdom
| | - Ruth Charlton
- Yorkshire Regional Genetics Service, St. James's University Hospital, Leeds, United Kingdom
| | - David T Bonthron
- Yorkshire Regional Genetics Service, St. James's University Hospital, Leeds, United Kingdom; MRC Medical Bioinformatics Centre, Leeds Institute for Data Analytics, St. James's University Hospital, Leeds, United Kingdom; MRC Single Cell Functional Genomics Centre, University of Leeds, St. James's University Hospital, Leeds, United Kingdom
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Zhang Y, Li S, Abyzov A, Gerstein MB. Landscape and variation of novel retroduplications in 26 human populations. PLoS Comput Biol 2017; 13:e1005567. [PMID: 28662076 PMCID: PMC5510864 DOI: 10.1371/journal.pcbi.1005567] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 07/14/2017] [Accepted: 05/12/2017] [Indexed: 01/10/2023] Open
Abstract
Retroduplications come from reverse transcription of mRNAs and their insertion back into the genome. Here, we performed comprehensive discovery and analysis of retroduplications in a large cohort of 2,535 individuals from 26 human populations, as part of 1000 Genomes Phase 3. We developed an integrated approach to discover novel retroduplications combining high-coverage exome and low-coverage whole-genome sequencing data, utilizing information from both exon-exon junctions and discordant paired-end reads. We found 503 parent genes having novel retroduplications absent from the reference genome. Based solely on retroduplication variation, we built phylogenetic trees of human populations; these represent superpopulation structure well and indicate that variable retroduplications are effective population markers. We further identified 43 retroduplication parent genes differentiating superpopulations. This group contains several interesting insertion events, including a SLMO2 retroduplication and insertion into CAV3, which has a potential disease association. We also found retroduplications to be associated with a variety of genomic features: (1) Insertion sites were correlated with regular nucleosome positioning. (2) They, predictably, tend to avoid conserved functional regions, such as exons, but, somewhat surprisingly, also avoid introns. (3) Retroduplications tend to be co-inserted with young L1 elements, indicating recent retrotranspositional activity, and (4) they have a weak tendency to originate from highly expressed parent genes. Our investigation provides insight into the functional impact and association with genomic elements of retroduplications. We anticipate our approach and analytical methodology to have application in a more clinical context, where exome sequencing data is abundant and the discovery of retroduplications can potentially improve the accuracy of SNP calling.
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Affiliation(s)
- Yan Zhang
- Program in Computational Biology and Bioinformatics, Yale University, New Haven, Connecticut, United States of America
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, United States of America
- Department of Biomedical Informatics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Shantao Li
- Program in Computational Biology and Bioinformatics, Yale University, New Haven, Connecticut, United States of America
| | - Alexej Abyzov
- Department of Health Sciences Research, Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Mark B. Gerstein
- Program in Computational Biology and Bioinformatics, Yale University, New Haven, Connecticut, United States of America
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, United States of America
- Department of Computer Science, Yale University, New Haven, Connecticut, United States of America
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20
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Protein-Coding Genes' Retrocopies and Their Functions. Viruses 2017; 9:v9040080. [PMID: 28406439 PMCID: PMC5408686 DOI: 10.3390/v9040080] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Revised: 04/07/2017] [Accepted: 04/11/2017] [Indexed: 12/11/2022] Open
Abstract
Transposable elements, often considered to be not important for survival, significantly contribute to the evolution of transcriptomes, promoters, and proteomes. Reverse transcriptase, encoded by some transposable elements, can be used in trans to produce a DNA copy of any RNA molecule in the cell. The retrotransposition of protein-coding genes requires the presence of reverse transcriptase, which could be delivered by either non-long terminal repeat (non-LTR) or LTR transposons. The majority of these copies are in a state of “relaxed” selection and remain “dormant” because they are lacking regulatory regions; however, many become functional. In the course of evolution, they may undergo subfunctionalization, neofunctionalization, or replace their progenitors. Functional retrocopies (retrogenes) can encode proteins, novel or similar to those encoded by their progenitors, can be used as alternative exons or create chimeric transcripts, and can also be involved in transcriptional interference and participate in the epigenetic regulation of parental gene expression. They can also act in trans as natural antisense transcripts, microRNA (miRNA) sponges, or a source of various small RNAs. Moreover, many retrocopies of protein-coding genes are linked to human diseases, especially various types of cancer.
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21
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Wang Y. PlantRGDB: A Database of Plant Retrocopied Genes. PLANT & CELL PHYSIOLOGY 2017; 58:e2. [PMID: 28111365 DOI: 10.1093/pcp/pcw210] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 11/17/2016] [Indexed: 05/26/2023]
Abstract
RNA-based gene duplication, known as retrocopy, plays important roles in gene origination and genome evolution. The genomes of many plants have been sequenced, offering an opportunity to annotate and mine the retrocopies in plant genomes. However, comprehensive and unified annotation of retrocopies in these plants is still lacking. In this study I constructed the PlantRGDB (Plant Retrocopied Gene DataBase), the first database of plant retrocopies, to provide a putatively complete centralized list of retrocopies in plant genomes. The database is freely accessible at http://probes.pw.usda.gov/plantrgdb or http://aegilops.wheat.ucdavis.edu/plantrgdb. It currently integrates 49 plant species and 38,997 retrocopies along with characterization information. PlantRGDB provides a user-friendly web interface for searching, browsing and downloading the retrocopies in the database. PlantRGDB also offers graphical viewer-integrated sequence information for displaying the structure of each retrocopy. The attributes of the retrocopies of each species are reported using a browse function. In addition, useful tools, such as an advanced search and BLAST, are available to search the database more conveniently. In conclusion, the database will provide a web platform for obtaining valuable insight into the generation of retrocopies and will supplement research on gene duplication and genome evolution in plants.
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Affiliation(s)
- Yi Wang
- USDA-ARS, Western Regional Research Center, Crop Improvement and Genetics Research Unit, Albany, CA, USA
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA, USA
- USDA-ARS, Plant Gene Expression Center, Albany, CA, USA
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22
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Mori S, Hayashi M, Inagaki S, Oshima T, Tateishi K, Fujii H, Suzuki S. Identification of Multiple Forms of RNA Transcripts Associated with Human-Specific Retrotransposed Gene Copies. Genome Biol Evol 2016; 8:2288-96. [PMID: 27389689 PMCID: PMC5010893 DOI: 10.1093/gbe/evw156] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The human genome contains thousands of retrocopies, mostly as processed pseudogenes, which were recently shown to be prevalently transcribed. In particular, those specifically acquired in the human lineage are able to modulate gene expression in a manner that contributed to the evolution of human-specific traits. Therefore, knowledge of the human-specific retrocopies that are transcribed or their full-length transcript structure contributes to better understand human genome evolution. In this study, we identified 16 human-specific retrocopies that harbor 5' CpG islands by in silico analysis and showed that 12 were transcribed in normal tissues and cancer cell lines with a variety of expression patterns, including cancer-specific expression. Determination of the structure of the transcripts associated with the retrocopies revealed that none were transcribed from their 5' CpG islands, but rather, from inside the 3' UTR and the nearby 5' flanking region of the retrocopies as well as the promoter of neighboring genes. The multiple forms of the transcripts, such as chimeric and individual transcripts in both the sense and antisense orientation, might have introduced novel post-transcriptional regulation into the genome during human evolution. These results shed light on the potential role of human-specific retrocopies in the evolution of gene regulation and genomic disorders.
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Affiliation(s)
- Saori Mori
- Epigenomics Division, Frontier Agriscience and Technology Center, Faculty of Agriculture, Shinshu University, Kami-Ina, Nagano, Japan
| | - Masaaki Hayashi
- Epigenomics Division, Frontier Agriscience and Technology Center, Faculty of Agriculture, Shinshu University, Kami-Ina, Nagano, Japan
| | - Shun Inagaki
- Epigenomics Division, Frontier Agriscience and Technology Center, Faculty of Agriculture, Shinshu University, Kami-Ina, Nagano, Japan
| | - Takuji Oshima
- Epigenomics Division, Frontier Agriscience and Technology Center, Faculty of Agriculture, Shinshu University, Kami-Ina, Nagano, Japan
| | - Ken Tateishi
- Epigenomics Division, Frontier Agriscience and Technology Center, Faculty of Agriculture, Shinshu University, Kami-Ina, Nagano, Japan
| | - Hiroshi Fujii
- Department of Interdisciplinary Genome Sciences and Cell Metabolism, Institute for Biomedical Sciences, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, Kami-Ina, Nagano, Japan
| | - Shunsuke Suzuki
- Epigenomics Division, Frontier Agriscience and Technology Center, Faculty of Agriculture, Shinshu University, Kami-Ina, Nagano, Japan Department of Interdisciplinary Genome Sciences and Cell Metabolism, Institute for Biomedical Sciences, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, Kami-Ina, Nagano, Japan
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23
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Abstract
Transposable elements have had a profound impact on the structure and function of mammalian genomes. The retrotransposon Long INterspersed Element-1 (LINE-1 or L1), by virtue of its replicative mobilization mechanism, comprises ∼17% of the human genome. Although the vast majority of human LINE-1 sequences are inactive molecular fossils, an estimated 80-100 copies per individual retain the ability to mobilize by a process termed retrotransposition. Indeed, LINE-1 is the only active, autonomous retrotransposon in humans and its retrotransposition continues to generate both intra-individual and inter-individual genetic diversity. Here, we briefly review the types of transposable elements that reside in mammalian genomes. We will focus our discussion on LINE-1 retrotransposons and the non-autonomous Short INterspersed Elements (SINEs) that rely on the proteins encoded by LINE-1 for their mobilization. We review cases where LINE-1-mediated retrotransposition events have resulted in genetic disease and discuss how the characterization of these mutagenic insertions led to the identification of retrotransposition-competent LINE-1s in the human and mouse genomes. We then discuss how the integration of molecular genetic, biochemical, and modern genomic technologies have yielded insight into the mechanism of LINE-1 retrotransposition, the impact of LINE-1-mediated retrotransposition events on mammalian genomes, and the host cellular mechanisms that protect the genome from unabated LINE-1-mediated retrotransposition events. Throughout this review, we highlight unanswered questions in LINE-1 biology that provide exciting opportunities for future research. Clearly, much has been learned about LINE-1 and SINE biology since the publication of Mobile DNA II thirteen years ago. Future studies should continue to yield exciting discoveries about how these retrotransposons contribute to genetic diversity in mammalian genomes.
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Inter-population Differences in Retrogene Loss and Expression in Humans. PLoS Genet 2015; 11:e1005579. [PMID: 26474060 PMCID: PMC4608704 DOI: 10.1371/journal.pgen.1005579] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 09/15/2015] [Indexed: 11/19/2022] Open
Abstract
Gene retroposition leads to considerable genetic variation between individuals. Recent studies revealed the presence of at least 208 retroduplication variations (RDVs), a class of polymorphisms, in which a retrocopy is present or absent from individual genomes. Most of these RDVs resulted from recent retroduplications. In this study, we used the results of Phase 1 from the 1000 Genomes Project to investigate the variation in loss of ancestral (i.e. shared with other primates) retrocopies among different human populations. In addition, we examined retrocopy expression levels using RNA-Seq data derived from the Ilumina BodyMap project, as well as data from lymphoblastoid cell lines provided by the Geuvadis Consortium. We also developed a new approach to detect novel retrocopies absent from the reference human genome. We experimentally confirmed the existence of the detected retrocopies and determined their presence or absence in the human genomes of 17 different populations. Altogether, we were able to detect 193 RDVs; the majority resulted from retrocopy deletion. Most of these RDVs had not been previously reported. We experimentally confirmed the expression of 11 ancestral retrogenes that underwent deletion in certain individuals. The frequency of their deletion, with the exception of one retrogene, is very low. The expression, conservation and low rate of deletion of the remaining 10 retrocopies may suggest some functionality. Aside from the presence or absence of expressed retrocopies, we also searched for differences in retrocopy expression levels between populations, finding 9 retrogenes that undergo statistically significant differential expression.
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Faber-Hammond JJ, Phillips RB, Brown KH. Comparative Analysis of the Shared Sex-Determination Region (SDR) among Salmonid Fishes. Genome Biol Evol 2015; 7:1972-87. [PMID: 26112966 PMCID: PMC4524489 DOI: 10.1093/gbe/evv123] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Salmonids present an excellent model for studying evolution of young sex-chromosomes. Within the genus, Oncorhynchus, at least six independent sex-chromosome pairs have evolved, many unique to individual species. This variation results from the movement of the sex-determining gene, sdY, throughout the salmonid genome. While sdY is known to define sexual differentiation in salmonids, the mechanism of its movement throughout the genome has remained elusive due to high frequencies of repetitive elements, rDNA sequences, and transposons surrounding the sex-determining regions (SDR). Despite these difficulties, bacterial artificial chromosome (BAC) library clones from both rainbow trout and Atlantic salmon containing the sdY region have been reported. Here, we report the sequences for these BACs as well as the extended sequence for the known SDR in Chinook gained through genome walking methods. Comparative analysis allowed us to study the overlapping SDRs from three unique salmonid Y chromosomes to define the specific content, size, and variation present between the species. We found approximately 4.1 kb of orthologous sequence common to all three species, which contains the genetic content necessary for masculinization. The regions contain transposable elements that may be responsible for the translocations of the SDR throughout salmonid genomes and we examine potential mechanistic roles of each one.
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Affiliation(s)
- Joshua J Faber-Hammond
- Department of Biology, Portland State University School of Biological Sciences, Washington State University Vancouver
| | - Ruth B Phillips
- School of Biological Sciences, Washington State University Vancouver Center for Reproductive Biology, Washington State University, Pullman
| | - Kim H Brown
- Department of Biology, Portland State University
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Abstract
Processed pseudogenes are copies of messenger RNAs that have been reverse transcribed into DNA and inserted into the genome using the enzymatic activities of active L1 elements. Processed pseudogenes generally lack introns, end in a 3’ poly A, and are flanked by target site duplications. Until recently, very few polymorphic processed pseudogenes had been discovered in mammalian genomes. Now several studies have found a number of polymorphic processed pseudogenes in humans. Moreover, processed pseudogenes can occur in somatic cells, including in various cancers and in early fetal development. One recent somatic insertion of a processed pseudogene has caused a Mendelian X-linked disease, chronic granulomatous disease.
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Affiliation(s)
- Haig H Kazazian
- Institute for Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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