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Constitutive Heterochromatin in Eukaryotic Genomes: A Mine of Transposable Elements. Cells 2022; 11:cells11050761. [PMID: 35269383 PMCID: PMC8909793 DOI: 10.3390/cells11050761] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/10/2022] [Accepted: 02/18/2022] [Indexed: 12/22/2022] Open
Abstract
Transposable elements (TEs) are abundant components of constitutive heterochromatin of the most diverse evolutionarily distant organisms. TEs enrichment in constitutive heterochromatin was originally described in the model organism Drosophila melanogaster, but it is now considered as a general feature of this peculiar portion of the genomes. The phenomenon of TE enrichment in constitutive heterochromatin has been proposed to be the consequence of a progressive accumulation of transposable elements caused by both reduced recombination and lack of functional genes in constitutive heterochromatin. However, this view does not take into account classical genetics studies and most recent evidence derived by genomic analyses of heterochromatin in Drosophila and other species. In particular, the lack of functional genes does not seem to be any more a general feature of heterochromatin. Sequencing and annotation of Drosophila melanogaster constitutive heterochromatin have shown that this peculiar genomic compartment contains hundreds of transcriptionally active genes, generally larger in size than that of euchromatic ones. Together, these genes occupy a significant fraction of the genomic territory of heterochromatin. Moreover, transposable elements have been suggested to drive the formation of heterochromatin by recruiting HP1 and repressive chromatin marks. In addition, there are several pieces of evidence that transposable elements accumulation in the heterochromatin might be important for centromere and telomere structure. Thus, there may be more complexity to the relationship between transposable elements and constitutive heterochromatin, in that different forces could drive the dynamic of this phenomenon. Among those forces, preferential transposition may be an important factor. In this article, we present an overview of experimental findings showing cases of transposon enrichment into the heterochromatin and their positive evolutionary interactions with an impact to host genomes.
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West RJH, Sharpe JL, Voelzmann A, Munro AL, Hahn I, Baines RA, Pickering-Brown S. Co-expression of C9orf72 related dipeptide-repeats over 1000 repeat units reveals age- and combination-specific phenotypic profiles in Drosophila. Acta Neuropathol Commun 2020; 8:158. [PMID: 32894207 PMCID: PMC7487709 DOI: 10.1186/s40478-020-01028-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 08/19/2020] [Indexed: 02/08/2023] Open
Abstract
A large intronic hexanucleotide repeat expansion (GGGGCC) within the C9orf72 (C9orf72-SMCR8 Complex Subunit) locus is the most prevalent genetic cause of both Frontotemporal Dementia (FTD) and Motor Neuron Disease (MND). In patients this expansion is typically hundreds to thousands of repeat units in length. Repeat associated non-AUG translation of the expansion leads to the formation of toxic, pathological Dipeptide-Repeat Proteins (DPRs). To date there remains a lack of in vivo models expressing C9orf72 related DPRs with a repeat length of more than a few hundred repeats. As such our understanding of how physiologically relevant repeat length DPRs effect the nervous system in an ageing in vivo system remains limited. In this study we generated Drosophila models expressing DPRs over 1000 repeat units in length, a known pathological length in humans. Using these models, we demonstrate each DPR exhibits a unique, age-dependent, phenotypic and pathological profile. Furthermore, we show co-expression of specific DPR combinations leads to distinct, age-dependent, phenotypes not observed through expression of single DPRs. We propose these models represent a unique, in vivo, tool for dissecting the molecular mechanisms implicated in disease pathology, opening up new avenues in the study of both MND and FTD.
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Affiliation(s)
- Ryan J. H. West
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, S10 2HQ UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN UK
| | - Joanne L. Sharpe
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - André Voelzmann
- Division of Molecular and Cellular Function, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Anna L. Munro
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Ines Hahn
- Division of Molecular and Cellular Function, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Richard A. Baines
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Stuart Pickering-Brown
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
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Wang SH, Elgin SCR. The impact of genetic background and cell lineage on the level and pattern of gene expression in position effect variegation. Epigenetics Chromatin 2019; 12:70. [PMID: 31722719 PMCID: PMC6852933 DOI: 10.1186/s13072-019-0314-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Accepted: 10/28/2019] [Indexed: 01/17/2023] Open
Abstract
Background Chromatin-based transcriptional silencing is often described as a stochastic process, largely because of the mosaic expression observed in position effect variegation (PEV), where a euchromatic reporter gene is silenced in some cells as a consequence of juxtaposition with heterochromatin. High levels of variation in PEV phenotypes are commonly observed in reporter stocks. To ascertain whether background mutations are the major contributors to this variation, we asked how much of the variation is determined by genetic variants segregating in the population, examining both the level and pattern of expression using the fruit fly, Drosophila melanogaster, as the model. Results Using selective breeding of a fourth chromosome PEV reporter line, 39C-12, we isolated two inbred lines exhibiting contrasting degrees of variegation (A1: low expression, D1: high expression). Within each inbred population, remarkable similarity is observed in the degree of variegation: 90% of the variation between the two inbred lines in the degree of silencing can be explained by genotype. Further analyses suggest that this result reflects the combined effect of multiple independent trans-acting loci. While the initial observations are based on a PEV phenotype scored in the fly eye (hsp70-white reporter), similar degrees of silencing were observed using a beta-gal reporter scored across the whole fly. Further, the pattern of variegation becomes almost identical within each inbred line; significant pigment enrichment in the same quadrant of the eye was found for both A1 and D1 lines despite different degrees of expression. Conclusions The results indicate that background genetic variants play the major role in determining the variable degrees of PEV commonly observed in laboratory stocks. Interestingly, not only does the degree of variegation become consistent in inbred lines, the patterns of variegation also appear similar. Combining these observations with the spreading model for local heterochromatin formation, we propose an augmented stochastic model to describe PEV in which the genetic background drives the overall level of silencing, working with the cell lineage-specific regulatory environment to determine the on/off probability at the reporter locus in each cell. This model acknowledges cell type-specific events in the context of broader genetic impacts on heterochromatin formation.
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Affiliation(s)
- Sidney H Wang
- Center for Human Genetics, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA.
| | - Sarah C R Elgin
- Department of Biology, Washington University, St Louis, MO, 63130, USA.
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Drinnenberg IA, Berger F, Elsässer SJ, Andersen PR, Ausió J, Bickmore WA, Blackwell AR, Erwin DH, Gahan JM, Gaut BS, Harvey ZH, Henikoff S, Kao JY, Kurdistani SK, Lemos B, Levine MT, Luger K, Malik HS, Martín-Durán JM, Peichel CL, Renfree MB, Rutowicz K, Sarkies P, Schmitz RJ, Technau U, Thornton JW, Warnecke T, Wolfe KH. EvoChromo: towards a synthesis of chromatin biology and evolution. Development 2019; 146:146/19/dev178962. [PMID: 31558570 DOI: 10.1242/dev.178962] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Over the past few years, interest in chromatin and its evolution has grown. To further advance these interests, we organized a workshop with the support of The Company of Biologists to debate the current state of knowledge regarding the origin and evolution of chromatin. This workshop led to prospective views on the development of a new field of research that we term 'EvoChromo'. In this short Spotlight article, we define the breadth and expected impact of this new area of scientific inquiry on our understanding of both chromatin and evolution.
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Affiliation(s)
- Ines A Drinnenberg
- Institut Curie, Paris Sciences et Lettres Research University, Centre National de la Recherche Scientifique UMR 3664, Paris 75005, France
| | - Frédéric Berger
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenter, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Simon J Elsässer
- Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden
| | - Peter R Andersen
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), Dr. Bohrgasse 3, 1030 Vienna, Austria
| | - Juan Ausió
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8W 3P6, Canada
| | - Wendy A Bickmore
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK
| | | | - Douglas H Erwin
- Department of Paleobiology, MRC-121, National Museum of Natural History, Washington, DC 20013-7012, USA
| | - James M Gahan
- Sars Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgt. 55, 5008 Bergen, Norway
| | - Brandon S Gaut
- Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA 92697, USA
| | - Zachary H Harvey
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Steven Henikoff
- Division of Basic Sciences and Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Joyce Y Kao
- Center for Genomics and Systems Biology, New York University, 12 Waverly Place, New York, NY 10003, USA.,Institute of Molecular Systems Biology, Swiss Federal Institute of Technology (ETH) Zürich, Otto-Stern-Weg 3, 8093 Zürich, Switzerland
| | - Siavash K Kurdistani
- Department of Biological Chemistry, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Bernardo Lemos
- Program in Molecular and Integrative Physiological Sciences, Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA
| | - Mia T Levine
- Department of Biology, Epigenetics Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Karolin Luger
- Howard Hughes Medical Institute and Department of Biochemistry, CU Boulder, Boulder, CO 80303, USA
| | - Harmit S Malik
- Division of Basic Sciences and Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - José M Martín-Durán
- Queen Mary University of London, School of Biological and Chemical Sciences, Mile End Road, London E1 4NS, UK
| | - Catherine L Peichel
- Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland
| | - Marilyn B Renfree
- School of BioSciences, The University of Melbourne, Melbourne, 3010 VIC, Australia
| | - Kinga Rutowicz
- Institute of Plant and Microbial Biology, Zurich-Basel Plant Science Center, University of Zurich, 8092 Zürich, Switzerland
| | - Peter Sarkies
- MRC London Institute of Medical Sciences and Institute of Clinical Sciences, IMperial College London, Du Cane Road, London W12 0NN, UK
| | - Robert J Schmitz
- Department of Genetics, University of Georgia, Athens, GA 30602, USA
| | - Ulrich Technau
- Department for Molecular Evolution and Development, Centre of Organismal Systems Biology, University of Vienna, Vienna A-1090, Austria
| | - Joseph W Thornton
- Department of Human Genetics, and Department of Ecology and Evolution, University of Chicago, Chicago, IL 60637 USA
| | - Tobias Warnecke
- MRC London Institute of Medical Sciences and Institute of Clinical Sciences, IMperial College London, Du Cane Road, London W12 0NN, UK
| | - Kenneth H Wolfe
- Conway Institute and School of Medicine, University College Dublin, Dublin 4, Ireland
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The Drosophila Dot Chromosome: Where Genes Flourish Amidst Repeats. Genetics 2019; 210:757-772. [PMID: 30401762 PMCID: PMC6218221 DOI: 10.1534/genetics.118.301146] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 08/17/2018] [Indexed: 11/18/2022] Open
Abstract
The F element of the Drosophila karyotype (the fourth chromosome in Drosophila melanogaster) is often referred to as the "dot chromosome" because of its appearance in a metaphase chromosome spread. This chromosome is distinct from other Drosophila autosomes in possessing both a high level of repetitious sequences (in particular, remnants of transposable elements) and a gene density similar to that found in the other chromosome arms, ∼80 genes distributed throughout its 1.3-Mb "long arm." The dot chromosome is notorious for its lack of recombination and is often neglected as a consequence. This and other features suggest that the F element is packaged as heterochromatin throughout. F element genes have distinct characteristics (e.g, low codon bias, and larger size due both to larger introns and an increased number of exons), but exhibit expression levels comparable to genes found in euchromatin. Mapping experiments show the presence of appropriate chromatin modifications for the formation of DNaseI hypersensitive sites and transcript initiation at the 5' ends of active genes, but, in most cases, high levels of heterochromatin proteins are observed over the body of these genes. These various features raise many interesting questions about the relationships of chromatin structures with gene and chromosome function. The apparent evolution of the F element as an autosome from an ancestral sex chromosome also raises intriguing questions. The findings argue that the F element is a unique chromosome that occupies its own space in the nucleus. Further study of the F element should provide new insights into chromosome structure and function.
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Asif-Laidin A, Delmarre V, Laurentie J, Miller WJ, Ronsseray S, Teysset L. Short and long-term evolutionary dynamics of subtelomeric piRNA clusters in Drosophila. DNA Res 2017; 24:459-472. [PMID: 28459978 PMCID: PMC5737368 DOI: 10.1093/dnares/dsx017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Accepted: 03/29/2017] [Indexed: 12/31/2022] Open
Abstract
Two Telomeric Associated Sequences, TAS-R and TAS-L, form the principal subtelomeric repeat families identified in Drosophila melanogaster. They are PIWI-interacting RNA (piRNA) clusters involved in repression of Transposable Elements. In this study, we revisited TAS structural and functional dynamics in D. melanogaster and in related species. In silico analysis revealed that TAS-R family members are composed of previously uncharacterized domains. This analysis also showed that TAS-L repeats are composed of arrays of a region we have named "TAS-L like" (TLL) identified specifically in one TAS-R family member, X-TAS. TLL were also present in other species of the melanogaster subgroup. Therefore, it is possible that TLL represents an ancestral subtelomeric piRNA core-cluster. Furthermore, all D. melanogaster genomes tested possessed at least one TAS-R locus, whereas TAS-L can be absent. A screen of 110 D. melanogaster lines showed that X-TAS is always present in flies living in the wild, but often absent in long-term laboratory stocks and that natural populations frequently lost their X-TAS within 2 years upon lab conditioning. Therefore, the unexpected structural and temporal dynamics of subtelomeric piRNA clusters demonstrated here suggests that genome organization is subjected to distinct selective pressures in the wild and upon domestication in the laboratory.
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Affiliation(s)
- Amna Asif-Laidin
- Sorbonne Universités, UPMC University of Paris 06, CNRS, Biologie du Développement Paris-Seine, Institut de Biologie Paris-Seine (LBD-IBPS), 75005 Paris, France
| | - Valérie Delmarre
- Sorbonne Universités, UPMC University of Paris 06, CNRS, Biologie du Développement Paris-Seine, Institut de Biologie Paris-Seine (LBD-IBPS), 75005 Paris, France
| | - Jeanne Laurentie
- Sorbonne Universités, UPMC University of Paris 06, CNRS, Biologie du Développement Paris-Seine, Institut de Biologie Paris-Seine (LBD-IBPS), 75005 Paris, France
| | - Wolfgang J. Miller
- Lab Genome Dynamics, Department for Cell & Developmental Biology, Center of Anatomy and Cell Biology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Stéphane Ronsseray
- Sorbonne Universités, UPMC University of Paris 06, CNRS, Biologie du Développement Paris-Seine, Institut de Biologie Paris-Seine (LBD-IBPS), 75005 Paris, France
| | - Laure Teysset
- Sorbonne Universités, UPMC University of Paris 06, CNRS, Biologie du Développement Paris-Seine, Institut de Biologie Paris-Seine (LBD-IBPS), 75005 Paris, France
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Lee YCG, Karpen GH. Pervasive epigenetic effects of Drosophila euchromatic transposable elements impact their evolution. eLife 2017; 6. [PMID: 28695823 PMCID: PMC5505702 DOI: 10.7554/elife.25762] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 06/09/2017] [Indexed: 12/21/2022] Open
Abstract
Transposable elements (TEs) are widespread genomic parasites, and their evolution has remained a critical question in evolutionary genomics. Here, we study the relatively unexplored epigenetic impacts of TEs and provide the first genome-wide quantification of such effects in D. melanogaster and D. simulans. Surprisingly, the spread of repressive epigenetic marks (histone H3K9me2) to nearby DNA occurs at >50% of euchromatic TEs, and can extend up to 20 kb. This results in differential epigenetic states of genic alleles and, in turn, selection against TEs. Interestingly, the lower TE content in D. simulans compared to D. melanogaster correlates with stronger epigenetic effects of TEs and higher levels of host genetic factors known to promote epigenetic silencing. Our study demonstrates that the epigenetic effects of euchromatic TEs, and host genetic factors modulating such effects, play a critical role in the evolution of TEs both within and between species. DOI:http://dx.doi.org/10.7554/eLife.25762.001 The DNA inside an organism encodes all the instructions needed for the organism to develop and work properly. Organisms carefully organize and maintain their DNA (collectively known as the genome) so that the genetic information remains intact and the cell can understand the instructions. However, there are some pieces of DNA that are capable of moving around the genome. For example, pieces known as transposable elements can make new copies of themselves and jump into new locations in the genome. Most transposons do not appear to have any important roles, and in fact they are usually harmful to organisms. Despite this, transposons are present in the genomes of almost all species. The number of transposons in a genome varies greatly between individuals and species, but it is not clear why this is the case. Organisms have evolved ways to limit the damage caused by transposons. For example, many cells package regions of DNA containing transposons into a tightly packed structure known as heterochromatin. However, this type of DNA packaging sometimes spreads to neighboring sections of DNA. This is a problem because cells are not usually able to read the information contained within heterochromatin. This means that transposons can prevent some instructions from being produced when they should be. Lee and Karpen used fruit flies to investigate to what extent transposons harm organisms by changing the way DNA is packaged, and whether this influences how transposons evolve. The experiments show that that more than half of the transposons in fruit flies cause neighboring sections of DNA to be packaged into heterochromatin. This can negatively impact up to 20% of genes in the genome. As a result, transposons that have harmful effects on DNA packaging are more likely to be lost from the fly population during evolution than transposons that do not have harmful effects. Fruit fly species containing transposons that tend to package more neighboring sections of DNA into heterochromatin generally have fewer transposons than genomes containing less harmful transposons. The findings of Lee and Karpen provide new insight as to why the numbers of transposons vary among organisms. The next challenge is to find out whether transposons that alter how DNA is packaged are also common in primates and other animals. DOI:http://dx.doi.org/10.7554/eLife.25762.002
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Affiliation(s)
- Yuh Chwen G Lee
- Division of Biological Systems and Engineering, Lawrence Berkeley National Laboratory, Berkeley, United States.,Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, United States
| | - Gary H Karpen
- Division of Biological Systems and Engineering, Lawrence Berkeley National Laboratory, Berkeley, United States.,Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, United States
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Sensitivity of Allelic Divergence to Genomic Position: Lessons from the Drosophila tan Gene. G3-GENES GENOMES GENETICS 2016; 6:2955-62. [PMID: 27449514 PMCID: PMC5015952 DOI: 10.1534/g3.116.032029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
To identify genetic variants underlying changes in phenotypes within and between species, researchers often utilize transgenic animals to compare the function of alleles in different genetic backgrounds. In Drosophila, targeted integration mediated by the ΦC31 integrase allows activity of alternative alleles to be compared at the same genomic location. By using the same insertion site for each transgene, position effects are generally assumed to be controlled for because both alleles are surrounded by the same genomic context. Here, we test this assumption by comparing the activity of tan alleles from two Drosophila species, D. americana and D. novamexicana, at five different genomic locations in D. melanogaster. We found that the relative effects of these alleles varied among insertion sites, with no difference in activity observed between them at two sites. One of these sites simply silenced both transgenes, but the other allowed expression of both alleles that was sufficient to rescue a mutant phenotype yet failed to reveal the functional differences between the two alleles. These results suggest that more than one insertion site should be used when comparing the activity of transgenes because failing to do so could cause functional differences between alleles to go undetected.
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