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Restricted and non-essential redundancy of RNAi and piRNA pathways in mouse oocytes. PLoS Genet 2019; 15:e1008261. [PMID: 31860668 PMCID: PMC6944382 DOI: 10.1371/journal.pgen.1008261] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 01/06/2020] [Accepted: 12/02/2019] [Indexed: 11/19/2022] Open
Abstract
Germline genome defense evolves to recognize and suppress retrotransposons. One of defensive mechanisms is the PIWI-associated RNA (piRNA) pathway, which employs small RNAs for sequence-specific repression. The loss of the piRNA pathway in mice causes male sterility while females remain fertile. Unlike spermatogenic cells, mouse oocytes posses also RNA interference (RNAi), another small RNA pathway capable of retrotransposon suppression. To examine whether RNAi compensates the loss of the piRNA pathway, we produced a new RNAi pathway mutant DicerSOM and crossed it with a catalytically-dead mutant of Mili, an essential piRNA gene. Normal follicular and oocyte development in double mutants showed that RNAi does not suppress a strong ovarian piRNA knock-out phenotype. However, we observed redundant and non-redundant targeting of specific retrotransposon families illustrating stochasticity of recognition and targeting of invading retrotransposons. Intracisternal A Particle retrotransposon was mainly targeted by the piRNA pathway, MaLR and RLTR10 retrotransposons were targeted mainly by RNAi. Double mutants showed accumulations of LINE-1 retrotransposon transcripts. However, we did not find strong evidence for transcriptional activation and mobilization of retrotransposition competent LINE-1 elements suggesting that while both defense pathways are simultaneously expendable for ovarian oocyte development, yet another transcriptional silencing mechanism prevents mobilization of LINE-1 elements. Retrotransposons are mobile genomic parasites causing mutations. Germ cells need protection against retrotransposons to prevent heritable transmission of their new insertions. The piRNA pathway is an ancient germline defense system analogous to acquired immunity: once a retrotransposon jumps into a piRNA-producing locus, which provides a kind of a “genomic sensor” for actively transposing elements, it is recognized and suppressed. Remarkably, the murine piRNA pathway is essential for spermatogenesis but not oocyte development. In contrast, zebrafish lacking the piRNA pathway do not develop any germ cells. It was hypothesized that RNA interference pathway could rescue oocyte development in mice lacking the piRNA pathway. RNA interference also targets retrotransposons and is particularly enhanced in mouse oocytes. To test this hypothesis, we engineered mice lacking both pathways and observed that oocytes in these mice develop normally, which argues against the hypothesis. Furthermore, analysis of individual retrotransposon groups revealed that in specific cases the two pathways mutually compensate each other. However, this redundancy apparently evolved stochastically and is restricted to specific retrotransposon groups. Finally, our results indicate that there must be yet another layer of retrotransposon silencing in mouse oocytes, which prevents high retrotransposon activity in the absence of piRNA and RNA interference pathways.
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52
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Li XZ. What can PIWI-interacting RNA research learn from chickens, and vice versa? CANADIAN JOURNAL OF ANIMAL SCIENCE 2019. [DOI: 10.1139/cjas-2018-0252] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
P-element induced wimpy testis (PIWI) interacting RNA (piRNA) are essential for fertility, by protecting the integrity of the germ-line genome via silencing of transposable elements (TE). Because new TE are constantly invading the host genome, piRNA-producing loci are under continuous pressure to undergo rapid evolution. This arms race between TE and piRNA is a prime example of the genome being more plastic than previously thought. Historically, the study of piRNA and TE has benefited from the use of diverse model organisms, including worms, fruit fly, zebrafish, frogs, and mice. In domestic chickens, we recently identified a new mode of piRNA acquisition in which the host hijacks and converts a pre-existing provirus into a piRNA-producing locus to defend against Avian leukosis virus, an adaptive immune strategy similar to the prokaryotic CRISPR–Cas [clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas)] system. This finding reveals a previously unrecognized mechanism of the host piRNA repertoire to rapidly evolve and target TE specifically. In this review, we will focus on both the unique and common features of chicken piRNA, as well as the advantages of using chickens as a model system, to address fundamental questions regarding piRNA acquisition in hosts. We will also comment on the potential application of piRNA for improving poultry health and reproductive efficiency.
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Affiliation(s)
- Xin Zhiguo Li
- Center for RNA Biology: From Genome to Therapeutics, Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
- Center for RNA Biology: From Genome to Therapeutics, Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
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53
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Tharp ME, Bortvin A. De novo DNA Methylation: Who's Your DADdy? Trends Genet 2019; 35:785-787. [PMID: 31597610 DOI: 10.1016/j.tig.2019.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 09/06/2019] [Indexed: 11/30/2022]
Abstract
DNA methylation regulates the organization and function of the genome. Yamanaka et al. now report that de novo methylation of male germ cells of mice involves the transient opening of heterochromatin at megabase-size differentially accessible domains (DADs). This chromatin remodeling likely facilitates de novo methylation of the germ cell genome.
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Affiliation(s)
- Marla E Tharp
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD 21218, USA; Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Alex Bortvin
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD 21218, USA.
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54
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Broad Heterochromatic Domains Open in Gonocyte Development Prior to De Novo DNA Methylation. Dev Cell 2019; 51:21-34.e5. [PMID: 31474564 DOI: 10.1016/j.devcel.2019.07.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 03/28/2019] [Accepted: 07/24/2019] [Indexed: 02/03/2023]
Abstract
Facultative heterochromatin forms and reorganizes in response to external stimuli. However, how the initial establishment of such a chromatin state is regulated in cell-cycle-arrested cells remains unexplored. Mouse gonocytes are arrested male germ cells, at which stage the genome-wide DNA methylome forms. Here, we discovered transiently accessible heterochromatin domains of several megabases in size in gonocytes and named them differentially accessible domains (DADs). Open DADs formed in gene desert and gene cluster regions, primarily at transposons, with the reprogramming of histone marks, suggesting DADs as facultative heterochromatin. De novo DNA methylation took place with two waves in gonocytes: the first region specific and the second genome-wide. DADs were resistant to the first wave and their opening preceded the second wave. In addition, the higher-order chromosome architecture was reorganized with less defined chromosome compartments in gonocytes. These findings suggest that multiple layers of chromatin reprogramming facilitate de novo DNA methylation.
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55
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The diverse roles of DNA methylation in mammalian development and disease. Nat Rev Mol Cell Biol 2019; 20:590-607. [PMID: 31399642 DOI: 10.1038/s41580-019-0159-6] [Citation(s) in RCA: 1159] [Impact Index Per Article: 231.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/08/2019] [Indexed: 12/22/2022]
Abstract
DNA methylation is of paramount importance for mammalian embryonic development. DNA methylation has numerous functions: it is implicated in the repression of transposons and genes, but is also associated with actively transcribed gene bodies and, in some cases, with gene activation per se. In recent years, sensitive technologies have been developed that allow the interrogation of DNA methylation patterns from a small number of cells. The use of these technologies has greatly improved our knowledge of DNA methylation dynamics and heterogeneity in embryos and in specific tissues. Combined with genetic analyses, it is increasingly apparent that regulation of DNA methylation erasure and (re-)establishment varies considerably between different developmental stages. In this Review, we discuss the mechanisms and functions of DNA methylation and demethylation in both mice and humans at CpG-rich promoters, gene bodies and transposable elements. We highlight the dynamic erasure and re-establishment of DNA methylation in embryonic, germline and somatic cell development. Finally, we provide insights into DNA methylation gained from studying genetic diseases.
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56
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Abstract
Maintenance of genome stability requires control over the expression of transposable elements (TEs), whose activity can have substantial deleterious effects on the host. Chemical modification of DNA is a commonly used strategy to achieve this, and it has long been argued that the emergence of 5-methylcytosine (5mC) in many species was driven by the requirement to silence TEs. Potential roles in TE regulation have also been suggested for other DNA modifications, such as N6-methyladenine and oxidation derivatives of 5mC, although the underlying mechanistic relationships are poorly understood. Here, we discuss current evidence implicating DNA modifications and DNA-modifying enzymes in TE regulation across different species.
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Affiliation(s)
- Özgen Deniz
- Blizard Institute, Barts and The London School of Medicine and Dentistry, QMUL, London, UK
| | - Jennifer M Frost
- Blizard Institute, Barts and The London School of Medicine and Dentistry, QMUL, London, UK
| | - Miguel R Branco
- Blizard Institute, Barts and The London School of Medicine and Dentistry, QMUL, London, UK.
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57
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Ozata DM, Gainetdinov I, Zoch A, O'Carroll D, Zamore PD. PIWI-interacting RNAs: small RNAs with big functions. Nat Rev Genet 2019; 20:89-108. [PMID: 30446728 DOI: 10.1038/s41576-018-0073-3] [Citation(s) in RCA: 666] [Impact Index Per Article: 133.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In animals, PIWI-interacting RNAs (piRNAs) of 21-35 nucleotides in length silence transposable elements, regulate gene expression and fight viral infection. piRNAs guide PIWI proteins to cleave target RNA, promote heterochromatin assembly and methylate DNA. The architecture of the piRNA pathway allows it both to provide adaptive, sequence-based immunity to rapidly evolving viruses and transposons and to regulate conserved host genes. piRNAs silence transposons in the germ line of most animals, whereas somatic piRNA functions have been lost, gained and lost again across evolution. Moreover, most piRNA pathway proteins are deeply conserved, but different animals employ remarkably divergent strategies to produce piRNA precursor transcripts. Here, we discuss how a common piRNA pathway allows animals to recognize diverse targets, ranging from selfish genetic elements to genes essential for gametogenesis.
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Affiliation(s)
- Deniz M Ozata
- RNA Therapeutics Institute and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA, USA
| | - Ildar Gainetdinov
- RNA Therapeutics Institute and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA, USA
| | - Ansgar Zoch
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Dónal O'Carroll
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.,Wellcome Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, UK
| | - Phillip D Zamore
- RNA Therapeutics Institute and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA, USA.
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58
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Abstract
Germ cells undergo epigenome reprogramming for proper development of the next generation. The achievement of in vitro germ cell derivation from human and mouse pluripotent stem cells and further differentiation in a plane culture and in aggregation with gonadal somatic cells offers unprecedented opportunities for investigation of the germ cell development. Moreover, advances in low-input/single-cell genomics have enabled detailed investigation of epigenome dynamics during germ cell development. These technologies have advanced our knowledge of epigenome reprogramming during the specification and development of primordial germ cells, their sex differentiation, and gametogenesis. Key findings include details of chromatin remodeling and transcriptional regulation, progressive and comprehensive DNA demethylation, and tight links between DNA demethylation and histone marks during the development of primordial germ cells, acquisition of unique totipotent epigenome during oogenesis (e.g., broad H3K4me3 domains and low-level three-dimensional genomic organization), and unexpected organization of the sperm genome. Moreover, these studies suggest the importance of epigenome analyses for in-depth evaluations of in vitro gametogenesis.
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Affiliation(s)
- Kazuki Kurimoto
- Department of Embryology, Nara Medical University, Nara, Japan.
| | - Mitinori Saitou
- Institute for the Advanced Study of Human Biology (ASHBi), Kyoto University, Kyoto, Japan; Department of Anatomy and Cell Biology, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Center for iPS Cell Research and Application, Kyoto University, Kyoto, Japan
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59
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Zhou M, Smith AD. Subtype classification and functional annotation of L1Md retrotransposon promoters. Mob DNA 2019; 10:14. [PMID: 31007728 PMCID: PMC6454616 DOI: 10.1186/s13100-019-0156-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/28/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND L1Md retrotransposons are the most abundant and active transposable elements in the mouse genome. The promoters of many L1Md retrotransposons are composed of tandem repeats called monomers. The number of monomers varies between retrotransposon copies, thus making it difficult to annotate L1Md promoters. Duplication of monomers contributes to the maintenance of L1Md promoters during truncation-prone retrotranspositions, but the associated mechanism remains unclear. Since the current classification of monomers is based on limited data, a comprehensive monomer annotation is needed for supporting functional studies of L1Md promoters genome-wide. RESULTS We developed a pipeline for de novo monomer detection and classification. Identified monomers are further classified into subtypes based on their sequence profiles. We applied this pipeline to genome assemblies of various rodent species. A major monomer subtype of the lab mouse was also found in other Mus species, implying that such subtype has emerged in the common ancestor of involved species. We also characterized the positioning pattern of monomer subtypes within individual promoters. Our analyses indicate that the subtype composition of an L1Md promoter can be used to infer its transcriptional activity during male germ cell development. CONCLUSIONS We identified subtypes for all monomer types using comprehensive data, greatly expanding the spectrum of monomer variants. The analysis of monomer subtype positioning provides evidence supporting both previously proposed models of L1Md promoter expansion. The transcription silencing of L1Md promoters differs between promoter types, which supports a model involving distinct suppressive pathways rather than a universal mechanism for retrotransposon repression in gametogenesis.
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Affiliation(s)
- Meng Zhou
- Molecular and Computational Biology Section, Division of Biological Sciences, University of Southern California, Los Angeles, USA
| | - Andrew D. Smith
- Molecular and Computational Biology Section, Division of Biological Sciences, University of Southern California, Los Angeles, USA
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60
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Aarabi M, Christensen KE, Chan D, Leclerc D, Landry M, Ly L, Rozen R, Trasler J. Testicular MTHFR deficiency may explain sperm DNA hypomethylation associated with high dose folic acid supplementation. Hum Mol Genet 2019; 27:1123-1135. [PMID: 29360980 DOI: 10.1093/hmg/ddy021] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 01/09/2018] [Indexed: 12/24/2022] Open
Abstract
Supplementation with high doses of folic acid, an important mediator of one-carbon transfers for DNA methylation, is used clinically to improve sperm parameters in infertile men. We recently detected an unexpected loss of DNA methylation in the sperm of idiopathic infertile men after 6 months of daily supplementation with 5 mg folic acid (>10× the daily recommended intake-DRI), exacerbated in men homozygous for a common variant in the gene encoding an important enzyme in folate metabolism, methylenetetrahydrofolate reductase (MTHFR 677C>T). To investigate the epigenomic impact and mechanism underlying effects of folic acid on male germ cells, wild-type and heterozygote mice for a targeted inactivation of the Mthfr gene were fed high-dose folic acid (10× the DRI) or control diets (CDs) for 6 months. No changes were detected in general health, sperm counts or methylation of imprinted genes. Reduced representation bisulfite sequencing revealed sperm DNA hypomethylation in Mthfr+/- mice on the 10× diets. Wild-type mice demonstrated sperm hypomethylation only with a very high dose (20×) of folic acid for 12 months. Testicular MTHFR protein levels decreased significantly in wild-type mice on the 20× diet but not in those on the 10× diet, suggesting a possible role for MTHFR deficiency in sperm DNA hypomethylation. In-depth analysis of the folic acid-exposed sperm DNA methylome suggested mouse/human susceptibility of sequences with potential importance to germ cell and embryo development. Our data provide evidence for a similar cross-species response to high dose folic acid supplementation, of sperm DNA hypomethylation, and implicate MTHFR downregulation as a possible mechanism.
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Affiliation(s)
- Mahmoud Aarabi
- Department of Human Genetics, McGill University, Montreal, QC H4A 3J1, Canada.,Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, QC H4A 3J1, Canada
| | - Karen E Christensen
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, QC H4A 3J1, Canada
| | - Donovan Chan
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, QC H4A 3J1, Canada
| | - Daniel Leclerc
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, QC H4A 3J1, Canada
| | - Mylène Landry
- Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, QC H4A 3J1, Canada
| | - Lundi Ly
- Department of Human Genetics, McGill University, Montreal, QC H4A 3J1, Canada.,Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, QC H4A 3J1, Canada
| | - Rima Rozen
- Department of Human Genetics, McGill University, Montreal, QC H4A 3J1, Canada.,Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, QC H4A 3J1, Canada.,Department of Pediatrics, McGill University, Montreal, QC H4A 3J1, Canada
| | - Jacquetta Trasler
- Department of Human Genetics, McGill University, Montreal, QC H4A 3J1, Canada.,Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, QC H4A 3J1, Canada.,Department of Pediatrics, McGill University, Montreal, QC H4A 3J1, Canada.,Department of Pharmacology & Therapeutics, McGill University, Montreal, QC H4A 3J1, Canada
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61
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Relationship between PIWIL4-Mediated H3K4me2 Demethylation and piRNA-Dependent DNA Methylation. Cell Rep 2018; 25:350-356. [DOI: 10.1016/j.celrep.2018.09.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 06/22/2018] [Accepted: 09/07/2018] [Indexed: 11/22/2022] Open
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62
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Watanabe T, Cui X, Yuan Z, Qi H, Lin H. MIWI2 targets RNAs transcribed from piRNA-dependent regions to drive DNA methylation in mouse prospermatogonia. EMBO J 2018; 37:e95329. [PMID: 30108053 PMCID: PMC6138435 DOI: 10.15252/embj.201695329] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 07/06/2018] [Accepted: 07/09/2018] [Indexed: 12/24/2022] Open
Abstract
Argonaute/Piwi proteins can regulate gene expression via RNA degradation and translational regulation using small RNAs as guides. They also promote the establishment of suppressive epigenetic marks on repeat sequences in diverse organisms. In mice, the nuclear Piwi protein MIWI2 and Piwi-interacting RNAs (piRNAs) are required for DNA methylation of retrotransposon sequences and some other sequences. However, its underlying molecular mechanisms remain unclear. Here, we show that piRNA-dependent regions are transcribed at the stage when piRNA-mediated DNA methylation takes place. MIWI2 specifically interacts with RNAs from these regions. In addition, we generated mice with deletion of a retrotransposon sequence either in a representative piRNA-dependent region or in a piRNA cluster. Both deleted regions were required for the establishment of DNA methylation of the piRNA-dependent region, indicating that piRNAs determine the target specificity of MIWI2-mediated DNA methylation. Our results indicate that MIWI2 affects the chromatin state through base-pairing between piRNAs and nascent RNAs, as observed in other organisms possessing small RNA-mediated epigenetic regulation.
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Affiliation(s)
- Toshiaki Watanabe
- Yale Stem Cell Center and Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Xiekui Cui
- Yale Stem Cell Center and Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Zhongyu Yuan
- Zhiyuan College, Shanghai Jiaotong University, Shanghai, China
| | - Hongying Qi
- Yale Stem Cell Center and Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Haifan Lin
- Yale Stem Cell Center and Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
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63
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Defective germline reprogramming rewires the spermatogonial transcriptome. Nat Struct Mol Biol 2018; 25:394-404. [PMID: 29728652 PMCID: PMC6086329 DOI: 10.1038/s41594-018-0058-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 03/21/2018] [Indexed: 01/13/2023]
Abstract
Defective germline reprogramming in Miwi2- and Dnmt3l-deficient mice results in the failure to reestablish transposon silencing, meiotic arrest and progressive loss of spermatogonia. Here we sought to understand the molecular basis for this spermatogonial dysfunction. Through a combination of imaging, conditional genetics and transcriptome analysis, we demonstrate that germ cell elimination in the respective mutants arises due to defective de novo genome methylation during reprogramming rather than a function for the respective factors within spermatogonia. In both Miwi2-/- and Dnmt3l-/- spermatogonia the intracisternal-A particle (IAP) family of endogenous retroviruses is de-repressed, but in contrast to meiotic cells DNA damage is not observed. Instead we find that unmethylated IAP promoters rewire the spermatogonial transcriptome by driving expression of neighboring genes. Finally, spermatogonial numbers, proliferation and differentiation are altered in Miwi2-/- and Dnmt3l-/- mice. In summary, defective reprogramming deregulates the spermatogonial transcriptome and may underlie spermatogonial dysfunction.
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64
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Mustafin RN, Khusnutdinova EK. The Role of Transposable Elements in Emergence of Metazoa. BIOCHEMISTRY (MOSCOW) 2018; 83:185-199. [PMID: 29625540 DOI: 10.1134/s000629791803001x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Systems initially emerged for protecting genomes against insertions of transposable elements and represented by mechanisms of splicing regulation, RNA-interference, and epigenetic factors have played a key role in the evolution of animals. Many studies have shown inherited transpositions of mobile elements in embryogenesis and preservation of their activities in certain tissues of adult organisms. It was supposed that on the emergence of Metazoa the self-regulation mechanisms of transposons related with the gene networks controlling their activity could be involved in intercellular cell coordination in the cascade of successive divisions with differentiated gene expression for generation of tissues and organs. It was supposed that during evolution species-specific features of transposons in the genomes of eukaryotes could form the basis for creation of dynamically related complexes of systems for epigenetic regulation of gene expression. These complexes could be produced due to the influence of noncoding transposon-derived RNAs on DNA methylation, histone modifications, and processing of alternative splicing variants, whereas the mobile elements themselves could be directly involved in the regulation of gene expression in cis and in trans. Transposons are widely distributed in the genomes of eukaryotes; therefore, their activation can change the expression of specific genes. In turn, this can play an important role in cell differentiation during ontogenesis. It is supposed that transposons can form a species-specific pattern for control of gene expression, and that some variants of this pattern can be favorable for adaptation. The presented data indicate the possible influence of transposons in karyotype formation. It is supposed that transposon localization relative to one another and to protein-coding genes can influence the species-specific epigenetic regulation of ontogenesis.
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65
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Qu J, Hodges E, Molaro A, Gagneux P, Dean MD, Hannon GJ, Smith AD. Evolutionary expansion of DNA hypomethylation in the mammalian germline genome. Genome Res 2018; 28:145-158. [PMID: 29259021 PMCID: PMC5793779 DOI: 10.1101/gr.225896.117] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 12/14/2017] [Indexed: 01/08/2023]
Abstract
DNA methylation in the germline is among the most important factors influencing the evolution of mammalian genomes. Yet little is known about its evolutionary rate or the fraction of the methylome that has undergone change. We compared whole-genome, single-CpG DNA methylation profiles in sperm of seven species-human, chimpanzee, gorilla, rhesus macaque, mouse, rat, and dog-to investigate epigenomic evolution. We developed a phylo-epigenetic model for DNA methylation that accommodates the correlation of states at neighboring sites and allows for inference of ancestral states. Applying this model to the sperm methylomes, we uncovered an overall evolutionary expansion of the hypomethylated fraction of the genome, driven both by the birth of new hypomethylated regions and by extensive widening of hypomethylated intervals in ancestral species. This expansion shows strong lineage-specific aspects, most notably that hypomethylated intervals around transcription start sites have evolved to be considerably wider in primates and dog than in rodents, whereas rodents show evidence of a greater trend toward birth of new hypomethylated regions. Lineage-specific hypomethylated regions are enriched near sets of genes with common developmental functions and significant overlap across lineages. Rodent-specific and primate-specific hypomethylated regions are enriched for binding sites of similar transcription factors, suggesting that the plasticity accommodated by certain regulatory factors is conserved, despite substantial change in the specific sites of regulation. Overall our results reveal substantial global epigenomic change in mammalian sperm methylomes and point to a divergence in trans-epigenetic mechanisms that govern the organization of epigenetic states at gene promoters.
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Affiliation(s)
- Jianghan Qu
- Molecular and Computational Biology Section, Division of Biological Sciences, University of Southern California, Los Angeles, California 90089, USA
| | - Emily Hodges
- Department of Biochemistry and Vanderbilt Genetics Institute, Vanderbilt University, Nashville, Tennessee 37232, USA
| | - Antoine Molaro
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
| | - Pascal Gagneux
- Division of Comparative Pathology and Medicine, Department of Pathology, Glycobiology Research and Training Center, University of California San Diego, La Jolla, California 92093, USA
| | - Matthew D Dean
- Molecular and Computational Biology Section, Division of Biological Sciences, University of Southern California, Los Angeles, California 90089, USA
| | - Gregory J Hannon
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
- Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, University of Cambridge, Cambridge CB2 0RE, United Kingdom
- The New York Genome Center, New York, New York 10013, USA
| | - Andrew D Smith
- Molecular and Computational Biology Section, Division of Biological Sciences, University of Southern California, Los Angeles, California 90089, USA
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66
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Illum LRH, Bak ST, Lund S, Nielsen AL. DNA methylation in epigenetic inheritance of metabolic diseases through the male germ line. J Mol Endocrinol 2018; 60:R39-R56. [PMID: 29203518 DOI: 10.1530/jme-17-0189] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 12/04/2017] [Indexed: 12/26/2022]
Abstract
The global rise in metabolic diseases can be attributed to a complex interplay between biology, behavior and environmental factors. This article reviews the current literature concerning DNA methylation-based epigenetic inheritance (intergenerational and transgenerational) of metabolic diseases through the male germ line. Included are a presentation of the basic principles for DNA methylation in developmental programming, and a description of windows of susceptibility for the inheritance of environmentally induced aberrations in DNA methylation and their associated metabolic disease phenotypes. To this end, escapees, genomic regions with the intrinsic potential to transmit acquired paternal epigenetic information across generations by escaping the extensive programmed DNA demethylation that occurs during gametogenesis and in the zygote, are described. The ongoing descriptive and functional examinations of DNA methylation in the relevant biological samples, in conjugation with analyses of non-coding RNA and histone modifications, hold promise for improved delineation of the effect size and mechanistic background for epigenetic inheritance of metabolic diseases.
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Affiliation(s)
| | - Stine Thorhauge Bak
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Department of Clinical Medicine, Endocrinology and Diabetes, Aarhus University Hospital, Aarhus, Denmark
| | - Sten Lund
- Department of Clinical Medicine, Endocrinology and Diabetes, Aarhus University Hospital, Aarhus, Denmark
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67
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Platt RN, Vandewege MW, Ray DA. Mammalian transposable elements and their impacts on genome evolution. Chromosome Res 2018; 26:25-43. [PMID: 29392473 PMCID: PMC5857283 DOI: 10.1007/s10577-017-9570-z] [Citation(s) in RCA: 141] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 12/12/2017] [Accepted: 12/28/2017] [Indexed: 12/22/2022]
Abstract
Transposable elements (TEs) are genetic elements with the ability to mobilize and replicate themselves in a genome. Mammalian genomes are dominated by TEs, which can reach copy numbers in the hundreds of thousands. As a result, TEs have had significant impacts on mammalian evolution. Here we summarize the current understanding of TE content in mammal genomes and find that, with a few exceptions, most fall within a predictable range of observations. First, one third to one half of the genome is derived from TEs. Second, most mammalian genomes are dominated by LINE and SINE retrotransposons, more limited LTR retrotransposons, and minimal DNA transposon accumulation. Third, most mammal genome contains at least one family of actively accumulating retrotransposon. Finally, horizontal transfer of TEs among lineages is rare. TE exaptation events are being recognized with increasing frequency. Despite these beneficial aspects of TE content and activity, the majority of TE insertions are neutral or deleterious. To limit the deleterious effects of TE proliferation, the genome has evolved several defense mechanisms that act at the epigenetic, transcriptional, and post-transcriptional levels. The interaction between TEs and these defense mechanisms has led to an evolutionary arms race where TEs are suppressed, evolve to escape suppression, then are suppressed again as the defense mechanisms undergo compensatory change. The result is complex and constantly evolving interactions between TEs and host genomes.
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Affiliation(s)
- Roy N Platt
- Department of Biological Sciences, Texas Tech University, Lubbock, TX, USA.
| | | | - David A Ray
- Department of Biological Sciences, Texas Tech University, Lubbock, TX, USA
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68
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Ernst C, Odom DT, Kutter C. The emergence of piRNAs against transposon invasion to preserve mammalian genome integrity. Nat Commun 2017; 8:1411. [PMID: 29127279 PMCID: PMC5681665 DOI: 10.1038/s41467-017-01049-7] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 08/14/2017] [Indexed: 01/09/2023] Open
Abstract
Transposable elements (TEs) contribute to the large amount of repetitive sequences in mammalian genomes and have been linked to species-specific genome innovations by rewiring regulatory circuitries. However, organisms need to restrict TE activity to ensure genome integrity, especially in germline cells to protect the transmission of genetic information to the next generation. This review features our current understandings of mammalian PIWI-interacting RNAs (piRNAs) and their role in TE regulation in spermatogenesis. Here we discuss functional implication and explore additional molecular mechanisms that inhibit transposon activity and altogether illustrate the paradoxical arms race between genome evolution and stability.
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Affiliation(s)
- Christina Ernst
- University of Cambridge, Cancer Research UK Cambridge Institute, Robinson Way, Cambridge, CB2 0RE, UK
| | - Duncan T Odom
- University of Cambridge, Cancer Research UK Cambridge Institute, Robinson Way, Cambridge, CB2 0RE, UK
| | - Claudia Kutter
- Department of Microbiology, Tumor and Cell Biology, Science for Life Laboratory, Karolinska Institute, Nobels väg 16, 171 77, Stockholm, Sweden.
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69
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Lyko F. The DNA methyltransferase family: a versatile toolkit for epigenetic regulation. Nat Rev Genet 2017; 19:81-92. [PMID: 29033456 DOI: 10.1038/nrg.2017.80] [Citation(s) in RCA: 830] [Impact Index Per Article: 118.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The DNA methyltransferase (DNMT) family comprises a conserved set of DNA-modifying enzymes that have a central role in epigenetic gene regulation. Recent studies have shown that the functions of the canonical DNMT enzymes - DNMT1, DNMT3A and DNMT3B - go beyond their traditional roles of establishing and maintaining DNA methylation patterns. This Review analyses how molecular interactions and changes in gene copy numbers modulate the activity of DNMTs in diverse gene regulatory functions, including transcriptional silencing, transcriptional activation and post-transcriptional regulation by DNMT2-dependent tRNA methylation. This mechanistic diversity enables the DNMT family to function as a versatile toolkit for epigenetic regulation.
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Affiliation(s)
- Frank Lyko
- Division of Epigenetics, DKFZ-ZMBH Alliance, German Cancer Research Center, Im Neuenheimer Feld 580, 69120 Heidelberg, Germany
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70
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MacLennan M, García-Cañadas M, Reichmann J, Khazina E, Wagner G, Playfoot CJ, Salvador-Palomeque C, Mann AR, Peressini P, Sanchez L, Dobie K, Read D, Hung CC, Eskeland R, Meehan RR, Weichenrieder O, García-Pérez JL, Adams IR. Mobilization of LINE-1 retrotransposons is restricted by Tex19.1 in mouse embryonic stem cells. eLife 2017; 6:e26152. [PMID: 28806172 PMCID: PMC5570191 DOI: 10.7554/elife.26152] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2017] [Accepted: 07/11/2017] [Indexed: 12/21/2022] Open
Abstract
Mobilization of retrotransposons to new genomic locations is a significant driver of mammalian genome evolution, but these mutagenic events can also cause genetic disorders. In humans, retrotransposon mobilization is mediated primarily by proteins encoded by LINE-1 (L1) retrotransposons, which mobilize in pluripotent cells early in development. Here we show that TEX19.1, which is induced by developmentally programmed DNA hypomethylation, can directly interact with the L1-encoded protein L1-ORF1p, stimulate its polyubiquitylation and degradation, and restrict L1 mobilization. We also show that TEX19.1 likely acts, at least in part, through promoting the activity of the E3 ubiquitin ligase UBR2 towards L1-ORF1p. Moreover, loss of Tex19.1 increases L1-ORF1p levels and L1 mobilization in pluripotent mouse embryonic stem cells, implying that Tex19.1 prevents de novo retrotransposition in the pluripotent phase of the germline cycle. These data show that post-translational regulation of L1 retrotransposons plays a key role in maintaining trans-generational genome stability in mammals.
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Affiliation(s)
- Marie MacLennan
- MRC Human Genetics Unit,
MRC Institute of Genetics and Molecular Medicine,
University of Edinburgh, Edinburgh, United
Kingdom
| | - Marta García-Cañadas
- Centro de Genómica e
Investigación Oncológica (GENYO), Pfizer-Universidad de
Granada-Junta de Andalucía, PTS Granada, Granada,
Spain
| | - Judith Reichmann
- MRC Human Genetics Unit,
MRC Institute of Genetics and Molecular Medicine,
University of Edinburgh, Edinburgh, United
Kingdom
| | - Elena Khazina
- Department of
Biochemistry, Max Planck Institute for Developmental
Biology, Tübingen, Germany
| | - Gabriele Wagner
- Department of
Biochemistry, Max Planck Institute for Developmental
Biology, Tübingen, Germany
| | - Christopher J Playfoot
- MRC Human Genetics Unit,
MRC Institute of Genetics and Molecular Medicine,
University of Edinburgh, Edinburgh, United
Kingdom
| | - Carmen Salvador-Palomeque
- Centro de Genómica e
Investigación Oncológica (GENYO), Pfizer-Universidad de
Granada-Junta de Andalucía, PTS Granada, Granada,
Spain
| | - Abigail R Mann
- MRC Human Genetics Unit,
MRC Institute of Genetics and Molecular Medicine,
University of Edinburgh, Edinburgh, United
Kingdom
| | - Paula Peressini
- Centro de Genómica e
Investigación Oncológica (GENYO), Pfizer-Universidad de
Granada-Junta de Andalucía, PTS Granada, Granada,
Spain
| | - Laura Sanchez
- Centro de Genómica e
Investigación Oncológica (GENYO), Pfizer-Universidad de
Granada-Junta de Andalucía, PTS Granada, Granada,
Spain
| | - Karen Dobie
- MRC Human Genetics Unit,
MRC Institute of Genetics and Molecular Medicine,
University of Edinburgh, Edinburgh, United
Kingdom
| | - David Read
- MRC Human Genetics Unit,
MRC Institute of Genetics and Molecular Medicine,
University of Edinburgh, Edinburgh, United
Kingdom
| | - Chao-Chun Hung
- MRC Human Genetics Unit,
MRC Institute of Genetics and Molecular Medicine,
University of Edinburgh, Edinburgh, United
Kingdom
| | - Ragnhild Eskeland
- Department of
Biosciences, University of Oslo,
Oslo,
Norway
- Norwegian Center for
Stem Cell Research, Department of Immunology, Oslo
University Hospital, Oslo, Norway
| | - Richard R Meehan
- MRC Human Genetics Unit,
MRC Institute of Genetics and Molecular Medicine,
University of Edinburgh, Edinburgh, United
Kingdom
| | - Oliver Weichenrieder
- Department of
Biochemistry, Max Planck Institute for Developmental
Biology, Tübingen, Germany
| | - Jose Luis García-Pérez
- MRC Human Genetics Unit,
MRC Institute of Genetics and Molecular Medicine,
University of Edinburgh, Edinburgh, United
Kingdom
- Centro de Genómica e
Investigación Oncológica (GENYO), Pfizer-Universidad de
Granada-Junta de Andalucía, PTS Granada, Granada,
Spain
| | - Ian R Adams
- MRC Human Genetics Unit,
MRC Institute of Genetics and Molecular Medicine,
University of Edinburgh, Edinburgh, United
Kingdom
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71
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Switching of dominant retrotransposon silencing strategies from posttranscriptional to transcriptional mechanisms during male germ-cell development in mice. PLoS Genet 2017; 13:e1006926. [PMID: 28749988 PMCID: PMC5549759 DOI: 10.1371/journal.pgen.1006926] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 08/08/2017] [Accepted: 07/15/2017] [Indexed: 12/13/2022] Open
Abstract
Mammalian genomes harbor millions of retrotransposon copies, some of which are transpositionally active. In mouse prospermatogonia, PIWI-interacting small RNAs (piRNAs) combat retrotransposon activity to maintain the genomic integrity. The piRNA system destroys retrotransposon-derived RNAs and guides de novo DNA methylation at some retrotransposon promoters. However, it remains unclear whether DNA methylation contributes to retrotransposon silencing in prospermatogonia. We have performed comprehensive studies of DNA methylation and polyA(+) RNAs (transcriptome) in developing male germ cells from Pld6/Mitopld and Dnmt3l knockout mice, which are defective in piRNA biogenesis and de novo DNA methylation, respectively. The Dnmt3l mutation greatly reduced DNA methylation levels at most retrotransposons, but its impact on their RNA abundance was limited in prospermatogonia. In Pld6 mutant germ cells, although only a few retrotransposons exhibited reduced DNA methylation, many showed increased expression at the RNA level. More detailed analysis of RNA sequencing, nascent RNA quantification, profiling of cleaved RNA ends, and the results obtained from double knockout mice suggest that PLD6 works mainly at the posttranscriptional level. The increase in retrotransposon expression was larger in Pld6 mutants than it was in Dnmt3l mutants, suggesting that RNA degradation by the piRNA system plays a more important role than does DNA methylation in prospermatogonia. However, DNA methylation had a long-term effect: hypomethylation caused by the Pld6 or Dnmt3l mutation resulted in increased retrotransposon expression in meiotic spermatocytes. Thus, posttranscriptional silencing plays an important role in the early stage of germ cell development, then transcriptional silencing becomes important in later stages. In addition, intergenic and intronic retrotransposon sequences, in particular those containing the antisense L1 promoters, drove ectopic expression of nearby genes in both mutant spermatocytes, suggesting that retrotransposon silencing is important for the maintenance of not only genomic integrity but also transcriptomic integrity. Retrotransposons are a class of transposable elements, of which mobility has mutagenic potential. Therefore, it is important to regulate the expression of retrotransposons for maintaining the genomic integrity. In male germ cells, DNA methylation and the piRNA system are thought to play roles in retrotransposon silencing. However, genome-wide DNA methylation is once erased (in primordial germ cells) and reestablished (in prospermatogonia) during development. In prospermatogonia, piRNAs guide de novo DNA methylation at some retrotransposons. To clarify the contribution of DNA methylation and the piRNA system to retrotransposon silencing in the course of male germ cell development, we analyzed DNA methylation and RNA expression in Dnmt3l and Pld6 knockout mice, which are defective in de novo DNA methylation and piRNA biogenesis, respectively. Our results reveal that, in prospermatogonia, the piRNA system works mainly at the posttranscriptional level, and plays a more important role than does DNA methylation in retrotransposon silencing. However, DNA methylation becomes much more important in later stages when germ cells enter meiosis (in spermatocytes). We also found that hypomethylated retrotransposons can drive ectopic expression of nearby genes; therefore, their transcriptional silencing by DNA methylation is important for maintaining the transcriptomic integrity as well.
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72
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Saint-Leandre B, Clavereau I, Hua-Van A, Capy P. Transcriptional polymorphism ofpiRNA regulatory genes underlies themarineractivity inDrosophila simulanstestes. Mol Ecol 2017; 26:3715-3731. [DOI: 10.1111/mec.14145] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 12/28/2016] [Indexed: 02/03/2023]
Affiliation(s)
- Bastien Saint-Leandre
- Laboratoire Evolution, Génomes, Comportement, Ecologie CNRS; Univ. Paris-Sud, IRD; Université Paris-Saclay; Gif-sur-Yvette Cedex France
| | - Isabelle Clavereau
- Laboratoire Evolution, Génomes, Comportement, Ecologie CNRS; Univ. Paris-Sud, IRD; Université Paris-Saclay; Gif-sur-Yvette Cedex France
| | - Aurelie Hua-Van
- Laboratoire Evolution, Génomes, Comportement, Ecologie CNRS; Univ. Paris-Sud, IRD; Université Paris-Saclay; Gif-sur-Yvette Cedex France
| | - Pierre Capy
- Laboratoire Evolution, Génomes, Comportement, Ecologie CNRS; Univ. Paris-Sud, IRD; Université Paris-Saclay; Gif-sur-Yvette Cedex France
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73
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Abstract
The PIWI-interacting RNA (piRNA) pathway is essential for retrotransposon silencing. In piRNA-deficient mice, L1-overexpressing male germ cells exhibit excessive DNA damage and meiotic defects. It remains unknown whether L1 expression simply highlights piRNA deficiency or actually drives the germ-cell demise. Specifically, the sheer abundance of genomic L1 copies prevents reliable quantification of new insertions. Here, we developed a codon-optimized L1 transgene that is controlled by an endogenous mouse L1 promoter. Importantly, DNA methylation dynamics of a single-copy transgene were indistinguishable from those of endogenous L1s. Analysis of Mov10l1-/- testes established that de novo methylation of the L1 transgene required the intact piRNA pathway. Consistent with loss of DNA methylation and programmed reduction of H3K9me2 at meiotic onset, the transgene showed 1,400-fold increase in RNA expression and consequently 70-fold increase in retrotransposition in postnatal day 14 Mov10l1-/- germ cells compared with the wild-type. Analysis of adult Mov10l1-/- germ-cell fractions indicated a stage-specific increase of retrotransposition in the early meiotic prophase. However, extrapolation of the transgene data to endogenous L1s suggests that it is unlikely insertional mutagenesis alone accounts for the Mov10l1-/- phenotype. Indeed, pharmacological inhibition of reverse transcription did not rescue the meiotic defect. Cumulatively, these results establish the occurrence of productive L1 mobilization in the absence of an intact piRNA pathway but leave open the possibility of processes preceding L1 integration in triggering meiotic checkpoints and germ-cell death. Additionally, our data suggest that many heritable L1 insertions originate from individuals with partially compromised piRNA defense.
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74
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Comparative Principles of DNA Methylation Reprogramming during Human and Mouse In Vitro Primordial Germ Cell Specification. Dev Cell 2017; 39:104-115. [PMID: 27728778 PMCID: PMC5064768 DOI: 10.1016/j.devcel.2016.09.015] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2015] [Revised: 08/24/2016] [Accepted: 09/14/2016] [Indexed: 12/22/2022]
Abstract
Primordial germ cell (PGC) development is characterized by global epigenetic remodeling, which resets genomic potential and establishes an epigenetic ground state. Here we recapitulate PGC specification in vitro from naive embryonic stem cells and characterize the early events of epigenetic reprogramming during the formation of the human and mouse germline. Following rapid de novo DNA methylation during priming to epiblast-like cells, methylation is globally erased in PGC-like cells. Repressive chromatin marks (H3K9me2/3) and transposable elements are enriched at demethylation-resistant regions, while active chromatin marks (H3K4me3 or H3K27ac) are more prominent at regions that demethylate faster. The dynamics of specification and epigenetic reprogramming show species-specific differences, in particular markedly slower reprogramming kinetics in the human germline. Differences in developmental kinetics may be explained by differential regulation of epigenetic modifiers. Our work establishes a robust and faithful experimental system of the early events of epigenetic reprogramming and regulation in the germline.
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75
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Vasiliauskaitė L, Vitsios D, Berrens RV, Carrieri C, Reik W, Enright AJ, O'Carroll D. A MILI-independent piRNA biogenesis pathway empowers partial germline reprogramming. Nat Struct Mol Biol 2017; 24:604-606. [PMID: 28530707 PMCID: PMC5898609 DOI: 10.1038/nsmb.3413] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 04/26/2017] [Indexed: 12/30/2022]
Abstract
In mice, the PIWI-piRNA pathway is essential to re-establish transposon silencing during male germline reprogramming. The cytoplasmic PIWI protein MILI mediates piRNA-guided transposon RNA cleavage as well as piRNA amplification. MIWI2-bound piRNAs and its nuclear localization are proposed to be dependent upon MILI function. Here, we demonstrate the existence of a piRNA biogenesis pathway that in the absence of MILI sustains partial MIWI2 function and reprogramming activity.
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Affiliation(s)
- Lina Vasiliauskaitė
- European Molecular Biology Laboratory (EMBL), Monterotondo, Italy.,MRC Centre for Regenerative Medicine, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | | | | | - Claudia Carrieri
- European Molecular Biology Laboratory (EMBL), Monterotondo, Italy.,MRC Centre for Regenerative Medicine, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Wolf Reik
- Epigenetics Programme, Babraham Institute, Cambridge, UK.,Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK
| | | | - Dónal O'Carroll
- European Molecular Biology Laboratory (EMBL), Monterotondo, Italy.,MRC Centre for Regenerative Medicine, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
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76
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Kannan M, Li J, Fritz SE, Husarek KE, Sanford JC, Sullivan TL, Tiwary PK, An W, Boeke JD, Symer DE. Dynamic silencing of somatic L1 retrotransposon insertions reflects the developmental and cellular contexts of their genomic integration. Mob DNA 2017; 8:8. [PMID: 28491150 PMCID: PMC5424313 DOI: 10.1186/s13100-017-0091-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 05/03/2017] [Indexed: 02/15/2023] Open
Abstract
Background The ongoing mobilization of mammalian transposable elements (TEs) contributes to natural genetic variation. To survey the epigenetic control and expression of reporter genes inserted by L1 retrotransposition in diverse cellular and genomic contexts, we engineered highly sensitive, real-time L1 retrotransposon reporter constructs. Results Here we describe different patterns of expression and epigenetic controls of newly inserted sequences retrotransposed by L1 in various somatic cells and tissues including cultured human cancer cells, mouse embryonic stem cells, and tissues of pseudofounder transgenic mice and their progeny. In cancer cell lines, the newly inserted sequences typically underwent rapid transcriptional gene silencing, but they lacked cytosine methylation even after many cell divisions. L1 reporter expression was reversible and oscillated frequently. Silenced or variegated reporter expression was strongly and uniformly reactivated by treatment with inhibitors of histone deacetylation, revealing the mechanism for their silencing. By contrast, de novo integrants retrotransposed by L1 in pluripotent mouse embryonic stem (ES) cells underwent rapid silencing by dense cytosine methylation. Similarly, de novo cytosine methylation also was identified at new integrants when studied in several distinct somatic tissues of adult founder mice. Pre-existing L1 elements in cultured human cancer cells were stably silenced by dense cytosine methylation, whereas their transcription modestly increased when cytosine methylation was experimentally reduced in cells lacking DNA methyltransferases DNMT1 and DNMT3b. As a control, reporter genes mobilized by piggyBac (PB), a DNA transposon, revealed relatively stable and robust expression without apparent silencing in both cultured cancer cells and ES cells. Conclusions We hypothesize that the de novo methylation marks at newly inserted sequences retrotransposed by L1 in early pre-implantation development are maintained or re-established in adult somatic tissues. By contrast, histone deacetylation reversibly silences L1 reporter insertions that had mobilized at later timepoints in somatic development and differentiation, e.g., in cancer cell lines. We conclude that the cellular contexts of L1 retrotransposition can determine expression or silencing of newly integrated sequences. We propose a model whereby reporter expression from somatic TE insertions reflects the timing, molecular mechanism, epigenetic controls and the genomic, cellular and developmental contexts of their integration. Electronic supplementary material The online version of this article (doi:10.1186/s13100-017-0091-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Manoj Kannan
- Department of Biological Sciences, Birla Institute of Technology and Science Pilani, Pilani, 333031 Rajasthan India.,Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA.,Present Address: Birla Institute of Technology and Science, Pilani, Dubai campus, Dubai, United Arab Emirates
| | - Jingfeng Li
- Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA.,Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH USA.,Department of Internal Medicine, The Ohio State University, Columbus, OH USA
| | - Sarah E Fritz
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH USA.,Present Address: National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD USA
| | - Kathryn E Husarek
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH USA.,Present Address: Aventiv Research, Inc., Columbus, OH USA
| | - Jonathan C Sanford
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH USA.,Present Address: Drug Safety Research and Development, Pfizer, Inc., Groton, CT USA
| | - Teresa L Sullivan
- Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA
| | - Pawan Kumar Tiwary
- Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA.,Present Address: Biocon, Bangalore, India
| | - Wenfeng An
- Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, MD USA.,Present Address: Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD USA
| | - Jef D Boeke
- Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, MD USA.,Present Address: Institute for Systems Genetics, New York University Langone Medical Center, New York, NY USA
| | - David E Symer
- Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA.,Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH USA.,Human Cancer Genetics Program, and Department of Biomedical Informatics, The Ohio State University, Columbus, OH USA.,Human Cancer Genetics Program, Department of Cancer Biology and Genetics, and Department of Biomedical Informatics, The Ohio State University, Tzagournis Research Facility, Room 440, 420 West 12th Ave, Columbus, OH 43210 USA
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77
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Barau J, Teissandier A, Zamudio N, Roy S, Nalesso V, Hérault Y, Guillou F, Bourc’his D. The DNA methyltransferase DNMT3C protects male germ cells from transposon activity. Science 2016; 354:909-912. [DOI: 10.1126/science.aah5143] [Citation(s) in RCA: 210] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 10/19/2016] [Indexed: 12/23/2022]
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78
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Roles for small noncoding RNAs in silencing of retrotransposons in the mammalian brain. Proc Natl Acad Sci U S A 2016; 113:12697-12702. [PMID: 27791114 DOI: 10.1073/pnas.1609287113] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Piwi-interacting RNAs (piRNAs), long thought to be restricted to germline, have recently been discovered in neurons of Aplysia, with a role in the epigenetic regulation of gene expression underlying long-term memory. We here ask whether piwi/piRNAs are also expressed and have functional roles in the mammalian brain. Large-scale RNA sequencing and subsequent analysis of protein expression revealed the presence in brain of several piRNA biogenesis factors including a mouse piwi (Mili), as well as small RNAs, albeit at low levels, resembling conserved piRNAs in mouse testes [primarily LINE1 (long interspersed nuclear element1) retrotransposon-derived]. Despite the seeming low expression of these putative piRNAs, single-base pair CpG methylation analyses across the genome of Mili/piRNA-deficient (Mili-/- ) mice demonstrate that brain genomic DNA is preferentially hypomethylated within intergenic areas and LINE1 promoter areas of the genome. Furthermore, Mili mutant mice exhibit behavioral deficits such as hyperactivity and reduced anxiety. These results suggest that putative piRNAs exist in mammalian brain, and similar to the role of piRNAs in testes, they may be involved in the silencing of retrotransposons, which in brain have critical roles in contributing to genomic heterogeneity underlying adaptation, stress response, and brain pathology. We also describe the presence of another class of small RNAs in the brain, with features of endogenous siRNAs, which may have taken over the role of invertebrate piRNAs in their capacity to target both transposons, as well as protein-coding genes. Thus, RNA interference through gene and retrotransposon silencing previously encountered in Aplysia may also have potential roles in the mammalian brain.
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79
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Long HK, King HW, Patient RK, Odom DT, Klose RJ. Protection of CpG islands from DNA methylation is DNA-encoded and evolutionarily conserved. Nucleic Acids Res 2016; 44:6693-706. [PMID: 27084945 PMCID: PMC5001583 DOI: 10.1093/nar/gkw258] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 03/09/2016] [Accepted: 04/01/2016] [Indexed: 12/19/2022] Open
Abstract
DNA methylation is a repressive epigenetic modification that covers vertebrate genomes. Regions known as CpG islands (CGIs), which are refractory to DNA methylation, are often associated with gene promoters and play central roles in gene regulation. Yet how CGIs in their normal genomic context evade the DNA methylation machinery and whether these mechanisms are evolutionarily conserved remains enigmatic. To address these fundamental questions we exploited a transchromosomic animal model and genomic approaches to understand how the hypomethylated state is formed in vivo and to discover whether mechanisms governing CGI formation are evolutionarily conserved. Strikingly, insertion of a human chromosome into mouse revealed that promoter-associated CGIs are refractory to DNA methylation regardless of host species, demonstrating that DNA sequence plays a central role in specifying the hypomethylated state through evolutionarily conserved mechanisms. In contrast, elements distal to gene promoters exhibited more variable methylation between host species, uncovering a widespread dependence on nucleotide frequency and occupancy of DNA-binding transcription factors in shaping the DNA methylation landscape away from gene promoters. This was exemplified by young CpG rich lineage-restricted repeat sequences that evaded DNA methylation in the absence of co-evolved mechanisms targeting methylation to these sequences, and species specific DNA binding events that protected against DNA methylation in CpG poor regions. Finally, transplantation of mouse chromosomal fragments into the evolutionarily distant zebrafish uncovered the existence of a mechanistically conserved and DNA-encoded logic which shapes CGI formation across vertebrate species.
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Affiliation(s)
- Hannah K Long
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DS, UK
| | - Hamish W King
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK
| | - Roger K Patient
- Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DS, UK
| | - Duncan T Odom
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, CB2 0RE, UK
| | - Robert J Klose
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK
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80
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Abstract
Retrotransposons have generated about 40 % of the human genome. This review examines the strategies the cell has evolved to coexist with these genomic "parasites", focussing on the non-long terminal repeat retrotransposons of humans and mice. Some of the restriction factors for retrotransposition, including the APOBECs, MOV10, RNASEL, SAMHD1, TREX1, and ZAP, also limit replication of retroviruses, including HIV, and are part of the intrinsic immune system of the cell. Many of these proteins act in the cytoplasm to degrade retroelement RNA or inhibit its translation. Some factors act in the nucleus and involve DNA repair enzymes or epigenetic processes of DNA methylation and histone modification. RISC and piRNA pathway proteins protect the germline. Retrotransposon control is relaxed in some cell types, such as neurons in the brain, stem cells, and in certain types of disease and cancer, with implications for human health and disease. This review also considers potential pitfalls in interpreting retrotransposon-related data, as well as issues to consider for future research.
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Affiliation(s)
- John L. Goodier
- McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD USA 212051
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81
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Cui X, Jing X, Wu X, Yan M, Li Q, Shen Y, Wang Z. DNA methylation in spermatogenesis and male infertility. Exp Ther Med 2016; 12:1973-1979. [PMID: 27698683 DOI: 10.3892/etm.2016.3569] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 04/06/2016] [Indexed: 12/12/2022] Open
Abstract
Infertility is a significant problem for human reproduction, with males and females equally affected. However, the molecular mechanisms underlying male infertility remain unclear. Spermatogenesis is a highly complex process involving mitotic cell division, meiosis cell division and spermiogenesis; during this period, unique and extensive chromatin and epigenetic modifications occur to bring about specific epigenetic profiles in spermatozoa. It has recently been suggested that the dysregulation of epigenetic modifications, in particular the methylation of sperm genomic DNA, may serve an important role in the development of numerous diseases. The present study is a comprehensive review on the topic of male infertility, aiming to elucidate the association between sperm genomic DNA methylation and poor semen quality in male infertility. In addition, the current status of the genetic and epigenetic determinants of spermatogenesis in humans is discussed.
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Affiliation(s)
- Xiangrong Cui
- Reproductive Medicine Center, Children's Hospital of Shanxi and Women Health Center of Shanxi, Taiyuan, Shanxi 030000, P.R. China; Division of Clinical Microbiology The Center Hospital of Linfen, Linfen, Shanxi 041000, P.R. China
| | - Xuan Jing
- Clinical Laboratory, Shanxi Province People's Hospital, Taiyuan, Shanxi 030001, P.R. China
| | - Xueqing Wu
- Reproductive Medicine Center, Children's Hospital of Shanxi and Women Health Center of Shanxi, Taiyuan, Shanxi 030000, P.R. China
| | - Meiqin Yan
- Reproductive Medicine Center, Children's Hospital of Shanxi and Women Health Center of Shanxi, Taiyuan, Shanxi 030000, P.R. China
| | - Qiang Li
- Reproductive Medicine Center, Children's Hospital of Shanxi and Women Health Center of Shanxi, Taiyuan, Shanxi 030000, P.R. China
| | - Yan Shen
- Reproductive Medicine Center, Children's Hospital of Shanxi and Women Health Center of Shanxi, Taiyuan, Shanxi 030000, P.R. China
| | - Zhenqiang Wang
- Reproductive Medicine Center, Children's Hospital of Shanxi and Women Health Center of Shanxi, Taiyuan, Shanxi 030000, P.R. China
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82
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Kneitz S, Mishra RR, Chalopin D, Postlethwait J, Warren WC, Walter RB, Schartl M. Germ cell and tumor associated piRNAs in the medaka and Xiphophorus melanoma models. BMC Genomics 2016; 17:357. [PMID: 27183847 PMCID: PMC4869193 DOI: 10.1186/s12864-016-2697-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 05/06/2016] [Indexed: 11/10/2022] Open
Abstract
Background A growing number of studies report an abnormal expression of Piwi-interacting RNAs (piRNAs) and the piRNA processing enzyme Piwi in many cancers. Whether this finding is an epiphenomenon of the chaotic molecular biology of the fast dividing, neoplastically transformed cells or is functionally relevant to tumorigenesisis is difficult to discern at present. To better understand the role of piRNAs in cancer development small laboratory fish models can make a valuable contribution. However, little is known about piRNAs in somatic and neoplastic tissues of fish. Results To identify piRNA clusters that might be involved in melanoma pathogenesis, we use several transgenic lines of medaka, and platyfish/swordtail hybrids, which develop various types of melanoma. In these tumors Piwi, is expressed at different levels, depending on tumor type. To quantify piRNA levels, whole piRNA populations of testes and melanomas of different histotypes were sequenced. Because no reference piRNA cluster set for medaka or Xiphophorus was yet available we developed a software pipeline to detect piRNA clusters in our samples and clusters were selected that were enriched in one or more samples. We found several loci to be overexpressed or down-regulated in different melanoma subtypes as compared to hyperpigmented skin. Furthermore, cluster analysis revealed a clear distinction between testes, low-grade and high-grade malignant melanoma in medaka. Conclusions Our data imply that dysregulation of piRNA expression may be associated with development of melanoma. Our results also reinforce the importance of fish as a suitable model system to study the role of piRNAs in tumorigenesis. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2697-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Susanne Kneitz
- Physiological Chemistry I, Biocenter, University of Würzburg, Am Hubland, 97074, Würzburg, Germany.
| | - Rasmi R Mishra
- Physiological Chemistry I, Biocenter, University of Würzburg, Am Hubland, 97074, Würzburg, Germany
| | | | - John Postlethwait
- Institute of Neuroscience, University of Oregon, 1425 E. 13th Avenue, Eugene, OR, 97403, USA
| | - Wesley C Warren
- Genome Sequencing Center, Washington University School of Medicine, 4444 Forest Park Blvd., St Louis, MO, 63108, USA
| | - Ronald B Walter
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, 419 Centennial Hall, Texas State University, 601 University Drive, San Marcos, TX, 78666, USA
| | - Manfred Schartl
- Physiological Chemistry I, Biocenter, University of Würzburg, Am Hubland, 97074, Würzburg, Germany.,Comprehensive Cancer Center Mainfranken, University Clinic Würzburg, Josef Schneider Straße 6, D-97074, Würzburg, Germany.,Texas Institute for Advanced Study and Department of Biology, Texas A&M University, College Station, Texas, 77843, USA
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83
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Ni K, Dansranjavin T, Rogenhofer N, Oeztuerk N, Deuker J, Bergmann M, Schuppe HC, Wagenlehner F, Weidner W, Steger K, Schagdarsurengin U. TET enzymes are successively expressed during human spermatogenesis and their expression level is pivotal for male fertility. Hum Reprod 2016; 31:1411-24. [PMID: 27141042 DOI: 10.1093/humrep/dew096] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 04/07/2016] [Indexed: 12/22/2022] Open
Abstract
STUDY QUESTION Are ten-eleven-translocation (TET) 1-3 family enzymes involved in human spermatogenesis and do they impact male fertility? SUMMARY ANSWER TET1, TET2 and TET3 are successively expressed at different stages of human spermatogenesis, and their expression levels associate with male fertility. WHAT IS KNOWN ALREADY Spermatogenesis is a complex cell differentiation process accompanied by a drastic epigenetic remodeling. TET1-3 dioxygenases are essential for active DNA demethylation in the paternal pronucleus and in embryonic stem cells. STUDY DESIGN, SIZE, DURATION Expression of TET1-3 mRNAs and proteinss and 5-hydroxymethylcytosine (5-hmC) proteins were analyzed in human testis tissues from men with obstructive azoospermia and exhibiting histologically normal spermatogenesis. Ejaculated spermatozoa from normozoospermic healthy volunteers, the 'controls' (TET1: n = 58; TET2-3: n = 63), and subfertile men who participated with their female partners in an ICSI-program, the 'patients' (TET1: n = 66; TET2-3: n = 64), were analyzed concerning the stored TET1-3 mRNAs, and the values were correlated to semen parameters and ICSI-outcomes. PARTICIPANTS/MATERIALS, SETTING, METHODS Testis sections were used for in situ hybridization (ISH) and immunohistochemical (IHC) studies to determine TET1-3 mRNA and protein expression, and for immunofluorescence (IF) detection of 5-hmC. Sperm samples from controls were analyzed by western blot, immunocytochemistry (ICC) and RT-PCR concerning the presence of non-degraded TET1-3 protein and mRNA. Sperm samples from controls and patients were used for quantitative TET1-3 mRNA analyses (reverse transcription-polymerase chain reaction) and for comparative statistical evaluations under consideration of semen parameters and ICSI-outcome (pregnancy). MAIN RESULTS AND THE ROLE OF CHANCE During human spermatogenesis TET1-3 proteins are successively expressed: TET2 is expressed in the cytoplasm of late pachytene spermatocytes of Stage V, TET1 starts to be expressed in the nuclei of Step 1 round spermatids at Stage I, and TET3 starts to be expressed in the nuclei of Step 3 round spermatids at Stage III. Five-hmC appears only in Step 5 elongated spermatids. All three TETs are still detectable at the mRNA and protein level in sperm cells in considerable amounts. Control men generally exhibited higher levels of TET1-3 in sperm. TET1- and TET3-mRNA levels in sperm were significantly negatively correlated with age (P = 0.0025 and P = 0.0343) and positively correlated with progressive sperm motility (P = 0.0007 and P = 0.018). All TETs showed a significant association with sperm concentration (P < 0.03). Patients diagnosed with oligozoospermia and/or asthenozoospermia (TET1: n = 35; TET2-3: n = 32) showed significantly reduced TET1-3 in sperm in comparison to controls (P = 0.003, P = 0.041 and P = 0.028), but not compared with normozoospermic patients. Levels of TET3 in sperm was significantly associated with high-fertilization rates (P = 0.009). Concerning ICSI-outcome, the lowest levels of TET1-3 mRNAs in sperm were found in the non-pregnant group. Increased TET2 in sperm was significantly associated with pregnancy (P = 0.006). LIMITATIONS, REASONS FOR CAUTION Our results concerning the association of the mRNA level of TETs in ejaculated sperm cells to different fertility parameters are descriptive. Further studies clarifying the reasons for decreased TET1-3 levels in subfertile men and their effect on their sperm methylome are essential. WIDER IMPLICATIONS OF THE FINDINGS The study gives a substantial indication that in human spermiogenesis, an active DNA demethylation process occurs with an involvement of TET enzymes, and that the level of TET1-3 expression is pivotal for male fertility. STUDY FUNDING Research grant from the German Research Foundation (DFG) to U.S. (SCHA1531/1-1 and SCHA1531/2-1). COMPETING INTERESTS None.
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Affiliation(s)
- Kai Ni
- Department of Urology, Pediatric Urology and Andrology, Justus Liebig University Giessen, Rudolf-Buchheim Str. 7, 35392 Giessen, Germany
| | - Temuujin Dansranjavin
- Department of Urology, Pediatric Urology and Andrology, Justus Liebig University Giessen, Rudolf-Buchheim Str. 7, 35392 Giessen, Germany
| | - Nina Rogenhofer
- Division of Gynecological Endocrinology and Reproductive Medicine, Department of Gynecology and Obstetrics, Clinical Centre of Ludwig Maximilians University, Campus Grosshadern, Marchioninistr. 15, 81377 Munich, Germany
| | - Nihan Oeztuerk
- Department of Urology, Pediatric Urology and Andrology, Justus Liebig University Giessen, Rudolf-Buchheim Str. 7, 35392 Giessen, Germany
| | - Johanna Deuker
- Division of Pulmonary Pharmacotherapy, Universities of Giessen and Marburg Lung Center (UGMLC), Justus Liebig University Giessen, Aulweg 130, 35392 Giessen, Germany
| | - Martin Bergmann
- Institute of Veterinary Anatomy, Histology and Embryology, Justus Liebig University Giessen, Frankfurter Str. 94, 35392 Giessen, Germany
| | - Hans-Christian Schuppe
- Department of Urology, Pediatric Urology and Andrology, Justus Liebig University Giessen, Rudolf-Buchheim Str. 7, 35392 Giessen, Germany
| | - Florian Wagenlehner
- Department of Urology, Pediatric Urology and Andrology, Justus Liebig University Giessen, Rudolf-Buchheim Str. 7, 35392 Giessen, Germany
| | - Wolfgang Weidner
- Department of Urology, Pediatric Urology and Andrology, Justus Liebig University Giessen, Rudolf-Buchheim Str. 7, 35392 Giessen, Germany
| | - Klaus Steger
- Department of Urology, Pediatric Urology and Andrology, Justus Liebig University Giessen, Rudolf-Buchheim Str. 7, 35392 Giessen, Germany
| | - Undraga Schagdarsurengin
- Department of Urology, Pediatric Urology and Andrology, Justus Liebig University Giessen, Rudolf-Buchheim Str. 7, 35392 Giessen, Germany
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84
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Czech B, Hannon GJ. One Loop to Rule Them All: The Ping-Pong Cycle and piRNA-Guided Silencing. Trends Biochem Sci 2016; 41:324-337. [PMID: 26810602 PMCID: PMC4819955 DOI: 10.1016/j.tibs.2015.12.008] [Citation(s) in RCA: 300] [Impact Index Per Article: 37.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 12/17/2015] [Accepted: 12/22/2015] [Indexed: 01/06/2023]
Abstract
The PIWI-interacting RNA (piRNA) pathway is a conserved defense mechanism that protects the genetic information of animal germ cells from the deleterious effects of molecular parasites, such as transposons. Discovered nearly a decade ago, this small RNA silencing system comprises PIWI-clade Argonaute proteins and their associated RNA-binding partners, the piRNAs. In this review, we highlight recent work that has advanced our understanding of how piRNAs preserve genome integrity across generations. We discuss the mechanism of piRNA biogenesis, give an overview of common themes as well as differences in piRNA-mediated silencing between species, and end by highlighting known and emerging functions of piRNAs.
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Affiliation(s)
- Benjamin Czech
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, University of Cambridge, Cambridge, CB2 0RE, UK.
| | - Gregory J Hannon
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, University of Cambridge, Cambridge, CB2 0RE, UK.
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85
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Yang F, Wang PJ. Multiple LINEs of retrotransposon silencing mechanisms in the mammalian germline. Semin Cell Dev Biol 2016; 59:118-125. [PMID: 26957474 DOI: 10.1016/j.semcdb.2016.03.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 02/29/2016] [Accepted: 03/01/2016] [Indexed: 02/07/2023]
Abstract
Retrotransposons play an important role in genome evolution but pose acute challenges to host genome integrity, particularly in early stage germ cells where epigenetic control is relaxed to permit genome-wide reprogramming. In most species, the inability to silence retrotransposons in the germline is usually associated with sterility. LINE1 is the most abundant retrotransposon type in the mammalian genome. Mammalian germ cells employ multiple mechanisms to suppress retrotransposon activity, including small non-coding piRNAs, DNA methylation, and repressive histone modifications. Novel factors contributing to the epigenetic silencing of retrotransposons in the germline continue to be identified. Recent studies have provided insight into how epigenetic changes associated with retrotransposon activation impact on fertility.
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Affiliation(s)
- Fang Yang
- Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, PA 19104, USA
| | - P Jeremy Wang
- Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, PA 19104, USA.
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86
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Molaro A, Malik HS. Hide and seek: how chromatin-based pathways silence retroelements in the mammalian germline. Curr Opin Genet Dev 2016; 37:51-58. [PMID: 26821364 DOI: 10.1016/j.gde.2015.12.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 12/02/2015] [Accepted: 12/14/2015] [Indexed: 01/07/2023]
Abstract
Retroelements comprise a major fraction of most mammalian genomes. To protect their fitness and stability, hosts must keep retroelements in check in their germline. In most tissues mobile element insertions are decorated with chromatin modifications suggestive of transcriptional silencing. However, germline cells undergo massive chromatin reprogramming events, which erase repressive chromatin marks and necessitate de novo re-establishment of silencing. How do host genomes achieve the discrimination necessary for this de novo silencing? A series of recent studies have revealed aspects of the multi-pronged strategy that mammalian genomes use to identify and silence retroelements. These strategies include the use of small RNA-guides, of specialized DNA-binding protein adaptors and of proteins that repair chromatin discontinuities caused by retroelement insertions. Genetic analyses reveal the importance of these mechanisms of protection, each of which specializes in silencing retroelements of different evolutionary ages. Together, these strategies allow mammalian genomes to withstand the high burden of their parasites.
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Affiliation(s)
- Antoine Molaro
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, United States
| | - Harmit S Malik
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, United States; Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, United States.
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87
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Luo LF, Hou CC, Yang WX. Small non-coding RNAs and their associated proteins in spermatogenesis. Gene 2015; 578:141-57. [PMID: 26692146 DOI: 10.1016/j.gene.2015.12.020] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 11/30/2015] [Accepted: 12/08/2015] [Indexed: 12/26/2022]
Abstract
The importance of the gene regulation roles of small non-coding RNAs and their protein partners is of increasing focus. In this paper, we reviewed three main small RNA species which appear to affect spermatogenesis. MicroRNAs (miRNAs) are single stand RNAs derived from transcripts containing stem-loops and hairpins which target corresponding mRNAs and affect their stability or translation. Many miRNA species have been found to be related to normal male germ cell development. The biogenesis of piRNAs is still largely unknown but several models have been proposed. Some piRNAs and PIWIs target transposable elements and it is these that may be active in regulating translation or stem cell maintenance. endo-siRNAs may also participate in sperm development. Some possible interactions between different kinds of small RNAs have even been suggested. We also show that male germ granules are seen to have a close relationship with a considerable number of mRNAs and small RNAs. Those special structures may also participate in sperm development.
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Affiliation(s)
- Ling-Feng Luo
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Cong-Cong Hou
- School of Marine Sciences, Ningbo University, Ningbo, Zhejiang 315211, China
| | - Wan-Xi Yang
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
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88
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A Small RNA-Based Immune System Defends Germ Cells against Mobile Genetic Elements. Stem Cells Int 2015; 2016:7595791. [PMID: 26681955 PMCID: PMC4670677 DOI: 10.1155/2016/7595791] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 06/11/2015] [Indexed: 11/17/2022] Open
Abstract
Transposons are mobile genetic elements that threaten the survival of species by destabilizing the germline genomes. Limiting the spread of these selfish elements is imperative. Germ cells employ specialized small regulatory RNA pathways to restrain transposon activity. PIWI proteins and Piwi-interacting RNAs (piRNAs) silence transposons at the transcriptional and posttranscriptional level with loss-of-function mutant animals universally exhibiting sterility often associated with germ cell defects. This short review aims to illustrate basic strategies of piRNA-guided defense against transposons. Mechanisms of piRNA silencing are most readily studied in Drosophila melanogaster, which serves as a model to delineate molecular concepts and as a reference for mammalian piRNA systems. PiRNA pathways utilize two major strategies to handle the challenges of transposon control: (1) the hard-wired molecular memory of prior transpositions enables recognition of mobile genetic elements and discriminates transposons from host genes; (2) a feed-forward adaptation mechanism shapes piRNA populations to selectively combat the immediate threat of transposon transcripts. In flies, maternally contributed PIWI-piRNA complexes bolster both of these lines of defense and ensure transgenerational immunity. While recent studies have provided a conceptual framework of what could be viewed as an ancient immune system, we are just beginning to appreciate its many molecular innovations.
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89
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Yu Y, Gu J, Jin Y, Luo Y, Preall JB, Ma J, Czech B, Hannon GJ. Panoramix enforces piRNA-dependent cotranscriptional silencing. Science 2015; 350:339-42. [PMID: 26472911 PMCID: PMC4722808 DOI: 10.1126/science.aab0700] [Citation(s) in RCA: 133] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The Piwi-interacting RNA (piRNA) pathway is a small RNA-based innate immune system that defends germ cell genomes against transposons. In Drosophila ovaries, the nuclear Piwi protein is required for transcriptional silencing of transposons, though the precise mechanisms by which this occurs are unknown. Here we show that the CG9754 protein is a component of Piwi complexes that functions downstream of Piwi and its binding partner, Asterix, in transcriptional silencing. Enforced tethering of CG9754 to nascent messenger RNA transcripts causes cotranscriptional silencing of the source locus and the deposition of repressive chromatin marks. We have named CG9754 "Panoramix," and we propose that this protein could act as an adaptor, scaffolding interactions between the piRNA pathway and the general silencing machinery that it recruits to enforce transcriptional repression.
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Affiliation(s)
- Yang Yu
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA. Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Jiaqi Gu
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA. Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA. State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Biochemistry, School of Life Sciences, Fudan University, Shanghai, China
| | - Ying Jin
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | - Yicheng Luo
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA. Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Jonathan B Preall
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA. Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Jinbiao Ma
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Biochemistry, School of Life Sciences, Fudan University, Shanghai, China
| | - Benjamin Czech
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA. Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA. Cancer Research UK Cambridge Institute, Li Ka Shing Centre, University of Cambridge, Cambridge, UK
| | - Gregory J Hannon
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA. Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA. Cancer Research UK Cambridge Institute, Li Ka Shing Centre, University of Cambridge, Cambridge, UK. The New York Genome Center, 101 Avenue of the Americas, New York, NY 10013, USA.
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90
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Nagamori I, Kobayashi H, Shiromoto Y, Nishimura T, Kuramochi-Miyagawa S, Kono T, Nakano T. Comprehensive DNA Methylation Analysis of Retrotransposons in Male Germ Cells. Cell Rep 2015; 12:1541-7. [PMID: 26321633 DOI: 10.1016/j.celrep.2015.07.060] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Revised: 07/06/2015] [Accepted: 07/28/2015] [Indexed: 11/25/2022] Open
Abstract
De novo DNA methylation of retrotransposons is critical for silencing. Here, we use DNA methylation analysis to examine retrotransposons in mouse male germ cells. DNA methylation of long interspersed nuclear elements (LINEs) is dependent on piRNA, and younger LINEs exhibit greater piRNA dependence. In contrast, most long terminal repeat (LTR) retrotransposons produce lower levels of piRNAs and do not show significant piRNA dependence. The relationship between DNA methylation and corresponding piRNA expression of several LTR retrotransposons was reduced in Mili-null cells, but not Miwi2-null cells. These observations raise the possibility of piRNA-dependent DNA methylation without Miwi2. Therefore, it appears that the molecular mechanisms of the gene silencing of retrotransposons are more complicated than previously thought.
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Affiliation(s)
- Ippei Nagamori
- Department of Pathology, Medical School, Osaka University, Suita, Osaka 565-0871, Japan
| | - Hisato Kobayashi
- NODAI Genome Research Center, Tokyo University of Agriculture, Setagaya-ku, Tokyo 156-8502, Japan
| | - Yusuke Shiromoto
- Department of Pathology, Medical School, Osaka University, Suita, Osaka 565-0871, Japan; Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan
| | - Toru Nishimura
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Satomi Kuramochi-Miyagawa
- Department of Pathology, Medical School, Osaka University, Suita, Osaka 565-0871, Japan; Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan
| | - Tomohiro Kono
- Department of Bioscience, Tokyo University of Agriculture, Setagaya-ku, Tokyo 156-8502, Japan
| | - Toru Nakano
- Department of Pathology, Medical School, Osaka University, Suita, Osaka 565-0871, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan; Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan.
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91
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Manakov SA, Pezic D, Marinov GK, Pastor WA, Sachidanandam R, Aravin AA. MIWI2 and MILI Have Differential Effects on piRNA Biogenesis and DNA Methylation. Cell Rep 2015; 12:1234-43. [PMID: 26279574 PMCID: PMC4554733 DOI: 10.1016/j.celrep.2015.07.036] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 07/02/2015] [Accepted: 07/16/2015] [Indexed: 01/30/2023] Open
Abstract
In developing male germ cells, prospermatogonia, two Piwi proteins, MILI and MIWI2, use Piwi-interacting RNA (piRNA) guides to repress transposable element (TE) expression and ensure genome stability and proper gametogenesis. In addition to their roles in post-transcriptional TE repression, both proteins are required for DNA methylation of TE sequences. Here, we analyzed the effect of Miwi2 deficiency on piRNA biogenesis and transposon repression. Miwi2 deficiency had only a minor impact on piRNA biogenesis; however, the piRNA profile of Miwi2-knockout mice indicated overexpression of several LINE1 TE families that led to activation of the ping-pong piRNA cycle. Furthermore, we found that MILI and MIWI2 have distinct functions in TE repression in the nucleus. MILI is responsible for DNA methylation of a larger subset of TE families than MIWI2 is, suggesting that the proteins have independent roles in establishing DNA methylation patterns.
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Affiliation(s)
- Sergei A Manakov
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Dubravka Pezic
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Georgi K Marinov
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - William A Pastor
- Department of Molecular, Cell and Developmental Biology, University of California Los Angeles, 610 Charles E. Young Drive East, Los Angeles, CA 90095, USA
| | - Ravi Sachidanandam
- Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, NY 10029, USA
| | - Alexei A Aravin
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
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92
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Grandi FC, Rosser JM, Newkirk SJ, Yin J, Jiang X, Xing Z, Whitmore L, Bashir S, Ivics Z, Izsvák Z, Ye P, Yu YE, An W. Retrotransposition creates sloping shores: a graded influence of hypomethylated CpG islands on flanking CpG sites. Genome Res 2015; 25:1135-46. [PMID: 25995269 PMCID: PMC4509998 DOI: 10.1101/gr.185132.114] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 05/19/2015] [Indexed: 11/25/2022]
Abstract
Long interspersed elements (LINEs), through both self-mobilization and trans-mobilization of short interspersed elements and processed pseudogenes, have made an indelible impact on the structure and function of the human genome. One consequence is the creation of new CpG islands (CGIs). In fact, more than half of all CGIs in the genome are associated with repetitive DNA, three-quarters of which are derived from retrotransposons. However, little is known about the epigenetic impact of newly inserted CGIs. We utilized a transgenic LINE-1 mouse model and tracked DNA methylation dynamics of individual germline insertions during mouse development. The retrotransposed GFP marker sequence, a strong CGI, is hypomethylated in male germ cells but hypermethylated in somatic tissues, regardless of genomic location. The GFP marker is similarly methylated when delivered into the genome via the Sleeping Beauty DNA transposon, suggesting that the observed methylation pattern may be independent of the mode of insertion. Comparative analyses between insertion- and non-insertion-containing alleles further reveal a graded influence of the retrotransposed CGI on flanking CpG sites, a phenomenon that we described as "sloping shores." Computational analyses of human and mouse methylomic data at single-base resolution confirm that sloping shores are universal for hypomethylated CGIs in sperm and somatic tissues. Additionally, the slope of a hypomethylated CGI can be affected by closely positioned CGI neighbors. Finally, by tracing sloping shore dynamics through embryonic and germ cell reprogramming, we found evidence of bookmarking, a mechanism that likely determines which CGIs will be eventually hyper- or hypomethylated.
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Affiliation(s)
- Fiorella C Grandi
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA
| | - James M Rosser
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA
| | - Simon J Newkirk
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA; Department of Pharmaceutical Sciences, South Dakota State University, Brookings, South Dakota 57007, USA
| | - Jun Yin
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA
| | - Xiaoling Jiang
- The Children's Guild Foundation Down Syndrome Research Program, Department of Cancer Genetics and Genetics Program, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Zhuo Xing
- The Children's Guild Foundation Down Syndrome Research Program, Department of Cancer Genetics and Genetics Program, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Leanne Whitmore
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA
| | - Sanum Bashir
- Max Delbrück Center for Molecular Medicine, 13092 Berlin, Germany
| | - Zoltán Ivics
- Division of Medical Biotechnology, Paul Ehrlich Institute, 63225 Langen, Germany
| | - Zsuzsanna Izsvák
- Max Delbrück Center for Molecular Medicine, 13092 Berlin, Germany
| | - Ping Ye
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA
| | - Y Eugene Yu
- The Children's Guild Foundation Down Syndrome Research Program, Department of Cancer Genetics and Genetics Program, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Wenfeng An
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, South Dakota 57007, USA
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93
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Jin Y, Tam OH, Paniagua E, Hammell M. TEtranscripts: a package for including transposable elements in differential expression analysis of RNA-seq datasets. Bioinformatics 2015. [PMID: 26206304 DOI: 10.1093/bioinformatics/btv422] [Citation(s) in RCA: 337] [Impact Index Per Article: 37.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
MOTIVATION Most RNA-seq data analysis software packages are not designed to handle the complexities involved in properly apportioning short sequencing reads to highly repetitive regions of the genome. These regions are often occupied by transposable elements (TEs), which make up between 20 and 80% of eukaryotic genomes. They can contribute a substantial portion of transcriptomic and genomic sequence reads, but are typically ignored in most analyses. RESULTS Here, we present a method and software package for including both gene- and TE-associated ambiguously mapped reads in differential expression analysis. Our method shows improved recovery of TE transcripts over other published expression analysis methods, in both synthetic data and qPCR/NanoString-validated published datasets. AVAILABILITY AND IMPLEMENTATION The source code, associated GTF files for TE annotation, and testing data are freely available at http://hammelllab.labsites.cshl.edu/software. CONTACT mhammell@cshl.edu. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Ying Jin
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
| | - Oliver H Tam
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
| | - Eric Paniagua
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
| | - Molly Hammell
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
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94
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Wasik KA, Tam OH, Knott SR, Falciatori I, Hammell M, Vagin VV, Hannon GJ. RNF17 blocks promiscuous activity of PIWI proteins in mouse testes. Genes Dev 2015; 29:1403-15. [PMID: 26115953 PMCID: PMC4511215 DOI: 10.1101/gad.265215.115] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 06/03/2015] [Indexed: 01/21/2023]
Abstract
PIWI proteins and their associated piRNAs protect germ cells from the activity of mobile genetic elements. Two classes of piRNAs—primary and secondary—are defined by their mechanisms of biogenesis. Primary piRNAs are processed directly from transcripts of piRNA cluster loci, whereas secondary piRNAs are generated in an adaptive amplification loop, termed the ping-pong cycle. In mammals, piRNA populations are dynamic, shifting as male germ cells develop. Embryonic piRNAs consist of both primary and secondary species and are mainly directed toward transposons. In meiotic cells, the piRNA population is transposon-poor and largely restricted to primary piRNAs derived from pachytene piRNA clusters. The transition from the embryonic to the adult piRNA pathway is not well understood. Here we show that RNF17 shapes adult meiotic piRNA content by suppressing the production of secondary piRNAs. In the absence of RNF17, ping-pong occurs inappropriately in meiotic cells. Ping-pong initiates piRNA responses against not only transposons but also protein-coding genes and long noncoding RNAs, including genes essential for germ cell development. Thus, the sterility of Rnf17 mutants may be a manifestation of a small RNA-based autoimmune reaction.
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Affiliation(s)
- Kaja A Wasik
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, New York 11724, USA; Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, New York 11724, USA
| | - Oliver H Tam
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, New York 11724, USA
| | - Simon R Knott
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, New York 11724, USA; Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, New York 11724, USA
| | - Ilaria Falciatori
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, New York 11724, USA; Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, New York 11724, USA
| | - Molly Hammell
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, New York 11724, USA
| | - Vasily V Vagin
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, New York 11724, USA; Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, New York 11724, USA
| | - Gregory J Hannon
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, New York 11724, USA; Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, New York 11724, USA; Cancer Research UK Cambridge Institute, Li Ka Shing Centre, University of Cambridge, Cambridge CB2 0RE, United Kingdom
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95
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Developmental windows of susceptibility for epigenetic inheritance through the male germline. Semin Cell Dev Biol 2015; 43:96-105. [DOI: 10.1016/j.semcdb.2015.07.006] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 07/20/2015] [Indexed: 02/02/2023]
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96
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Chen YCA, Aravin AA. Non-Coding RNAs in Transcriptional Regulation: The review for Current Molecular Biology Reports. ACTA ACUST UNITED AC 2015; 1:10-18. [PMID: 26120554 DOI: 10.1007/s40610-015-0002-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Transcriptional gene silencing guided by small RNAs is a process conserved from protozoa to mammals. Small RNAs loaded into Argonaute family proteins direct repressive histone modifications or DNA cytosine methylation to homologous regions of the genome. Small RNA-mediated transcriptional silencing is required for many biological processes, including repression of transposable elements, maintaining the genome stability/integrity, and epigenetic inheritance of gene expression. Here we will summarize the current knowledge about small RNA biogenesis and mechanisms of transcriptional regulation in plants, Drosophila, C. elegans and mice. Furthermore, a rapidly growing number long non-coding RNAs (lncRNAs) have been implicated as important players in transcription regulation. We will discuss current models for long non-coding RNA-mediated gene regulation.
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Affiliation(s)
- Yung-Chia Ariel Chen
- California Institute of Technology, Division of Biology and Biological Engineering, 147-75, 1200 E. California Blvd., Pasadena, CA 91125, USA
| | - Alexei A Aravin
- California Institute of Technology, Division of Biology and Biological Engineering, 147-75, 1200 E. California Blvd., Pasadena, CA 91125, USA
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97
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O'Doherty AM, McGettigan PA. Epigenetic processes in the male germline. Reprod Fertil Dev 2015; 27:725-38. [DOI: 10.1071/rd14167] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 08/01/2014] [Indexed: 12/12/2022] Open
Abstract
Sperm undergo some of the most extensive chromatin modifications seen in mammalian biology. During male germline development, paternal DNA methylation marks are erased and established on a global scale through waves of demethylation and de novo methylation. As spermatogenesis progresses, the majority of the histones are removed and replaced by protamines, enabling a tighter packaging of the DNA and transcriptional shutdown. Following fertilisation, the paternal genome is rapidly reactivated, actively demethylated, the protamines are replaced with histones and the embryonic genome is activated. The development of new assays, made possible by high-throughput sequencing technology, has resulted in the revisiting of what was considered settled science regarding the state of DNA packaging in mammalian spermatozoa. Researchers have discovered that not all histones are replaced by protamines and, in certain experiments, various species of RNA have been detected in what was previously considered transcriptionally quiescent spermatozoa. Most controversially, several groups have suggested that environmental modifications of the epigenetic state of spermatozoa may operate as a non-DNA-based form of inheritance, a process known as ‘transgenerational epigenetic inheritance’. Other developments in the field include the increased focus on the involvement of short RNAs, such as microRNAs, long non-coding RNAs and piwi-interacting RNAs. There has also been an accumulation of evidence illustrating associations between defects in sperm DNA packaging and disease and fertility. In this paper we review the literature, recent findings and areas of controversy associated with epigenetic processes in the male germline, focusing on DNA methylation dynamics, non-coding RNAs, the biology of sperm chromatin packaging and transgenerational inheritance.
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98
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Marchal C, Miotto B. Emerging Concept in DNA Methylation: Role of Transcription Factors in Shaping DNA Methylation Patterns. J Cell Physiol 2014; 230:743-51. [DOI: 10.1002/jcp.24836] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 10/01/2014] [Indexed: 02/04/2023]
Affiliation(s)
- Claire Marchal
- Université Paris Diderot; Sorbonne Paris Cité; Epigenetics and Cell Fate; Paris France
| | - Benoit Miotto
- Université Paris Diderot; Sorbonne Paris Cité; Epigenetics and Cell Fate; Paris France
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99
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MORC1 represses transposable elements in the mouse male germline. Nat Commun 2014; 5:5795. [PMID: 25503965 PMCID: PMC4268658 DOI: 10.1038/ncomms6795] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Accepted: 11/07/2014] [Indexed: 12/30/2022] Open
Abstract
The Microrchidia (Morc) family of GHKL ATPases are present in a wide variety of prokaryotic and eukaryotic organisms but are of largely unknown function. Genetic screens in Arabidopsis thaliana have identified Morc genes as important repressors of transposons and other DNA-methylated and silent genes. MORC1-deficient mice were previously found to display male-specific germ cell loss and infertility. Here we show that MORC1 is responsible for transposon repression in the male germline in a pattern that is similar to that observed for germ cells deficient for the DNA methyltransferase homologue DNMT3L. Morc1 mutants show highly localized defects in the establishment of DNA methylation at specific classes of transposons, and this is associated with failed transposon silencing at these sites. Our results identify MORC1 as an important new regulator of the epigenetic landscape of male germ cells during the period of global de novo methylation. The Microrchidia (Morc) family of GHKL ATPases are important repressors of transposons and other DNA-methylated and silent genes in A. thaliana. Here, the authors show that MORC1 is responsible for repression and methylation of specific classes of transposons in the mouse male germline.
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