201
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Denker HW. Self-Organization of Stem Cell Colonies and of Early Mammalian Embryos: Recent Experiments Shed New Light on the Role of Autonomy vs. External Instructions in Basic Body Plan Development. Cells 2016; 5:E39. [PMID: 27792143 PMCID: PMC5187523 DOI: 10.3390/cells5040039] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 10/08/2016] [Accepted: 10/12/2016] [Indexed: 12/23/2022] Open
Abstract
"Organoids", i.e., complex structures that can develop when pluripotent or multipotent stem cells are maintained in three-dimensional cultures, have become a new area of interest in stem cell research. Hopes have grown that when focussing experimentally on the mechanisms behind this type of in vitro morphogenesis, research aiming at tissue and organ replacements can be boosted. Processes leading to the formation of organoids in vitro are now often addressed as self-organization, a term referring to the formation of complex tissue architecture in groups of cells without depending on specific instruction provided by other cells or tissues. The present article focuses on recent reports using the term self-organization in the context of studies on embryogenesis, specifically addressing pattern formation processes in human blastocysts attaching in vitro, or in colonies of pluripotent stem cells ("gastruloids"). These morphogenetic processes are of particular interest because, during development in vivo, they lead to basic body plan formation and individuation. Since improved methodologies like those employed by the cited authors became available, early embryonic pattern formation/self-organization appears to evolve now as a research topic of its own. This review discusses concepts concerning the involved mechanisms, focussing on autonomy of basic body plan development vs. dependence on external signals, as possibly provided by implantation in the uterus, and it addresses biological differences between an early mammalian embryo, e.g., a morula, and a cluster of pluripotent stem cells. It is concluded that, apart from being of considerable biological interest, the described type of research needs to be contemplated carefully with regard to ethical implications when performed with human cells.
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Affiliation(s)
- Hans-Werner Denker
- Institut für Anatomie, Universität Duisburg-Essen, Universitätsklinikum, Hufelandstr. 55, 45122 Essen, Germany.
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202
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MERVL/Zscan4 Network Activation Results in Transient Genome-wide DNA Demethylation of mESCs. Cell Rep 2016. [PMID: 27681430 DOI: 10.1016/j.celrep.2016.08.087.] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Mouse embryonic stem cells are dynamic and heterogeneous. For example, rare cells cycle through a state characterized by decondensed chromatin and expression of transcripts, including the Zscan4 cluster and MERVL endogenous retrovirus, which are usually restricted to preimplantation embryos. Here, we further characterize the dynamics and consequences of this transient cell state. Single-cell transcriptomics identified the earliest upregulated transcripts as cells enter the MERVL/Zscan4 state. The MERVL/Zscan4 transcriptional network was also upregulated during induced pluripotent stem cell reprogramming. Genome-wide DNA methylation and chromatin analyses revealed global DNA hypomethylation accompanying increased chromatin accessibility. This transient DNA demethylation was driven by a loss of DNA methyltransferase proteins in the cells and occurred genome-wide. While methylation levels were restored once cells exit this state, genomic imprints remained hypomethylated, demonstrating a potential global and enduring influence of endogenous retroviral activation on the epigenome.
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203
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Abstract
Embryonic pluripotency can be recapitulated in vitro by a spectrum of pluripotent stem cell states stabilized with different culture conditions. Their distinct spatiotemporal characteristics provide an unprecedented tool for the study of early human development. The newly unveiled ability of some stem cell types for crossing xeno-barriers will facilitate the generation of interspecies chimeric embryos from distant species, including humans. When combined with efficient zygote genome editing technologies, xenogeneic human pluripotent stem cells may also open new frontiers for regenerative medicine applications, including the possibility of generating human organs in animals via interspecies chimeric complementation.
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204
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Fukuda A, Mitani A, Miyashita T, Kobayashi H, Umezawa A, Akutsu H. Spatiotemporal dynamics of OCT4 protein localization during preimplantation development in mice. Reproduction 2016; 152:417-30. [PMID: 27495230 PMCID: PMC5064760 DOI: 10.1530/rep-16-0277] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 08/04/2016] [Indexed: 01/19/2023]
Abstract
Spatiotemporal expression of transcription factors is crucial for genomic reprogramming. Pou5f1 (Oct4) is an essential transcription factor for reprogramming. A recent study reported that OCT4A, which is crucial for establishment and maintenance of pluripotent cells, is expressed in oocytes, but maternal OCT4A is dispensable for totipotency induction. Whereas another study reported that OCT4B, which is not related to pluripotency, is predominantly expressed instead of OCT4A during early preimplantation phases in mice. To determine the expression states of OCT4 in murine preimplantation embryos, we conducted in-depth expression and functional analyses. We found that pluripotency-related OCT4 mainly localizes to the cytoplasm in early preimplantation phases, with no major nuclear localization until the 8–16-cell stage despite high expression in both oocytes and early embryos. RNA-sequencing analysis using oocytes and early preimplantation embryos could not identify the splice variants creating alternative forms of OCT4 protein. Forced expression of OCT4 in zygotes by the injection of polyadenylated mRNA clearly showed nuclear localization of OCT4 protein around 3–5-fold greater than physiological levels and impaired developmental competency in a dose-dependent manner. Embryos with modest overexpression of OCT4 could develop to the 16-cell stage; however, more than 50% of the embryos were arrested at this stage, similar to the results for OCT4 depletion. In contrast, extensive overexpression of OCT4 resulted in complete arrest at the 2-cell stage accompanied by downregulation of zygotically activated genes and repetitive elements related to the totipotent state. These results demonstrated that OCT4 protein localization was spatiotemporally altered during preimplantation development, and strict control of Oct4 protein levels was essential for proper totipotential reprogramming.
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Affiliation(s)
- Atsushi Fukuda
- Center for Regenerative MedicineNational Research Institute for Child Health and Development, Setagaya, Tokyo, Japan
| | - Atsushi Mitani
- Center for Regenerative MedicineNational Research Institute for Child Health and Development, Setagaya, Tokyo, Japan
| | - Toshiyuki Miyashita
- Department of Molecular GeneticsKitasato University Graduate School of Medical Sciences, Minami, Sagamihara, Kanagawa, Japan
| | - Hisato Kobayashi
- NODAI Genome Research CenterTokyo University of Agriculture, Setagaya-ku, Tokyo, Japan
| | - Akihiro Umezawa
- Center for Regenerative MedicineNational Research Institute for Child Health and Development, Setagaya, Tokyo, Japan
| | - Hidenori Akutsu
- Center for Regenerative MedicineNational Research Institute for Child Health and Development, Setagaya, Tokyo, Japan Department of Stem Cell ResearchFukushima Medical University, 1 Hikarigaoka, Fukushima City, Fukushima, Japan
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205
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Wang B, Pfeiffer MJ, Drexler HCA, Fuellen G, Boiani M. Proteomic Analysis of Mouse Oocytes Identifies PRMT7 as a Reprogramming Factor that Replaces SOX2 in the Induction of Pluripotent Stem Cells. J Proteome Res 2016; 15:2407-21. [PMID: 27225728 DOI: 10.1021/acs.jproteome.5b01083] [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] [Indexed: 12/21/2022]
Abstract
The reprogramming process that leads to induced pluripotent stem cells (iPSCs) may benefit from adding oocyte factors to Yamanaka's reprogramming cocktail (OCT4, SOX2, KLF4, with or without MYC; OSK(M)). We previously searched for such facilitators of reprogramming (the reprogrammome) by applying label-free LC-MS/MS analysis to mouse oocytes, producing a catalog of 28 candidates that are (i) able to robustly access the cell nucleus and (ii) shared between mature mouse oocytes and pluripotent embryonic stem cells. In the present study, we hypothesized that our 28 reprogrammome candidates would also be (iii) abundant in mature oocytes, (iv) depleted after the oocyte-to-embryo transition, and (v) able to potentiate or replace the OSKM factors. Using LC-MS/MS and isotopic labeling methods, we found that the abundance profiles of the 28 proteins were below those of known oocyte-specific and housekeeping proteins. Of the 28 proteins, only arginine methyltransferase 7 (PRMT7) changed substantially during mouse embryogenesis and promoted the conversion of mouse fibroblasts into iPSCs. Specifically, PRMT7 replaced SOX2 in a factor-substitution assay, yielding iPSCs. These findings exemplify how proteomics can be used to prioritize the functional analysis of reprogrammome candidates. The LC-MS/MS data are available via ProteomeXchange with identifier PXD003093.
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Affiliation(s)
- Bingyuan Wang
- Key Laboratory of Farm Animal Genetic Resources and Germplasm Innovation of Ministry of Agriculture, Institute of Animal Science, Chinese Academy of Agricultural Sciences , Beijing 100193, China
| | - Martin J Pfeiffer
- Max Planck Institute for Molecular Biomedicine , Röntgenstraße 20, 48149 Münster, Germany
| | - Hannes C A Drexler
- Max Planck Institute for Molecular Biomedicine , Bioanalytical Mass Spectrometry Facility, Röntgenstraße 20, 48149 Münster, Germany
| | - Georg Fuellen
- Institute for Biostatistics and Informatics in Medicine and Ageing Research, Rostock University Medical Center, 18057 Rostock, Germany
| | - Michele Boiani
- Max Planck Institute for Molecular Biomedicine , Röntgenstraße 20, 48149 Münster, Germany
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206
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Göke J, Ng HH. CTRL+INSERT: retrotransposons and their contribution to regulation and innovation of the transcriptome. EMBO Rep 2016; 17:1131-44. [PMID: 27402545 DOI: 10.15252/embr.201642743] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 06/20/2016] [Indexed: 12/25/2022] Open
Abstract
The human genome contains millions of fragments from retrotransposons-highly repetitive DNA sequences that were once able to "copy and paste" themselves to other regions in the genome. However, the majority of retrotransposons have lost this capacity through acquisition of mutations or through endogenous silencing mechanisms. Without this imminent threat of transposition, retrotransposons have the potential to act as a major source of genomic innovation. Indeed, large numbers of retrotransposons have been found to be active in specific contexts: as gene regulatory elements and promoters for protein-coding genes or long noncoding RNAs, among others. In this review, we summarise recent findings about retrotransposons, with implications in gene expression regulation, the expansion of gene isoform diversity and the generation of long noncoding RNAs. We highlight key examples that demonstrate their role in cellular identity and their versatility as markers of cell states, and we discuss how their dysregulation may contribute to the formation of and possibly therapeutic response in human cancers.
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Affiliation(s)
- Jonathan Göke
- Computational and Systems Biology, Genome Institute of Singapore, Singapore
| | - Huck Hui Ng
- Gene Regulation Laboratory, Genome Institute of Singapore, Singapore Department of Biochemistry, National University of Singapore, Singapore Department of Biological Sciences, National University of Singapore, Singapore School of Biological Sciences, Nanyang Technological University, Singapore
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207
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The landscape of accessible chromatin in mammalian preimplantation embryos. Nature 2016; 534:652-7. [DOI: 10.1038/nature18606] [Citation(s) in RCA: 424] [Impact Index Per Article: 53.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Accepted: 05/27/2016] [Indexed: 12/28/2022]
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208
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Abstract
Organism viability relies on the stable maintenance of specific chromatin landscapes, established during development, that shape cell functions and identities by driving distinct gene expression programs. Yet epigenome maintenance is challenged during transcription, replication, and repair of DNA damage, all of which elicit dynamic changes in chromatin organization. Here, we review recent advances that have shed light on the specialized mechanisms contributing to the restoration of epigenome structure and function after DNA damage in the mammalian cell nucleus. By drawing a parallel with epigenome maintenance during replication, we explore emerging concepts and highlight open issues in this rapidly growing field. In particular, we present our current knowledge of molecular players that support the coordinated maintenance of genome and epigenome integrity in response to DNA damage, and we highlight how nuclear organization impacts genome stability. Finally, we discuss possible functional implications of epigenome plasticity in response to genotoxic stress.
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Affiliation(s)
- Juliette Dabin
- Epigenome Integrity Group, UMR 7216 CNRS, Paris Diderot University, Sorbonne Paris Cité, 75013 Paris Cedex 13, France
| | - Anna Fortuny
- Epigenome Integrity Group, UMR 7216 CNRS, Paris Diderot University, Sorbonne Paris Cité, 75013 Paris Cedex 13, France
| | - Sophie E Polo
- Epigenome Integrity Group, UMR 7216 CNRS, Paris Diderot University, Sorbonne Paris Cité, 75013 Paris Cedex 13, France.
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209
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Thompson PJ, Macfarlan TS, Lorincz MC. Long Terminal Repeats: From Parasitic Elements to Building Blocks of the Transcriptional Regulatory Repertoire. Mol Cell 2016; 62:766-76. [PMID: 27259207 PMCID: PMC4910160 DOI: 10.1016/j.molcel.2016.03.029] [Citation(s) in RCA: 162] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The life cycle of endogenous retroviruses (ERVs), also called long terminal repeat (LTR) retrotransposons, begins with transcription by RNA polymerase II followed by reverse transcription and re-integration into the host genome. While most ERVs are relics of ancient integration events, "young" proviruses competent for retrotransposition-found in many mammals, but not humans-represent an ongoing threat to host fitness. As a consequence, several restriction pathways have evolved to suppress their activity at both transcriptional and post-transcriptional stages of the viral life cycle. Nevertheless, accumulating evidence has revealed that LTR sequences derived from distantly related ERVs have been exapted as regulatory sequences for many host genes in a wide range of cell types throughout mammalian evolution. Here, we focus on emerging themes from recent studies cataloging the diversity of ERV LTRs acting as important transcriptional regulatory elements in mammals and explore the molecular features that likely account for LTR exaptation in developmental and tissue-specific gene regulation.
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Affiliation(s)
- Peter J Thompson
- Department of Medical Genetics, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Todd S Macfarlan
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, USA.
| | - Matthew C Lorincz
- Department of Medical Genetics, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
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210
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Clément C, Vassias I, Ray-Gallet D, Almouzni G. Functional Characterization of Histone Chaperones Using SNAP-Tag-Based Imaging to Assess De Novo Histone Deposition. Methods Enzymol 2016; 573:97-117. [PMID: 27372750 DOI: 10.1016/bs.mie.2016.04.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Histone chaperones-key actors in the dynamic organization of chromatin-interact with the various histone variants to ensure their transfer in and out of chromatin. In vitro chromatin assembly assays and isolation of protein complexes using tagged histone variants provided first clues concerning their binding specificities and mode of action. Here, we describe an in vivo method using SNAP-tag-based imaging to assess the de novo deposition of histones and the role of histone chaperones. This method exploits cells expressing SNAP-tagged histones combined with individual cell imaging to visualize directly de novo histone deposition in vivo. We show how, by combining this method with siRNA-based depletion, we could assess the function of two distinct histone chaperones. For this, we provide the details of the method as applied in two examples to characterize the function of the histone chaperones CAF-1 and HIRA. In both cases, we document the impact of their depletion on the de novo deposition of the histone variants H3.1 and H3.3, first in a normal context and second in response to DNA damage. We discuss how this cellular assay offers means to define in a systematic manner the function of any chosen chaperone with respect to the deposition of a given histone variant.
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Affiliation(s)
- C Clément
- Institut Curie, PSL Research University, CNRS, UMR3664, Equipe Labellisée Ligue contre le Cancer, Paris, France; Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR3664, Paris, France
| | - I Vassias
- Institut Curie, PSL Research University, CNRS, UMR3664, Equipe Labellisée Ligue contre le Cancer, Paris, France; Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR3664, Paris, France
| | - D Ray-Gallet
- Institut Curie, PSL Research University, CNRS, UMR3664, Equipe Labellisée Ligue contre le Cancer, Paris, France; Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR3664, Paris, France
| | - G Almouzni
- Institut Curie, PSL Research University, CNRS, UMR3664, Equipe Labellisée Ligue contre le Cancer, Paris, France; Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR3664, Paris, France.
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211
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Corujo D, Mas G, Malinverni R, Di Croce L, Buschbeck M. Barcelona conference on epigenetics and cancer 2015: Coding and non-coding functions of the genome. Epigenetics 2016; 11:95-100. [PMID: 26996885 DOI: 10.1080/15592294.2015.1131377] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The Barcelona Conference on Epigenetics and Cancer (BCEC) entitled "Coding and Non-Coding functions of the Genome" took place October 29-30, 2015 in Barcelona. The 2015 BCEC was the third edition of a series of annual conferences jointly organized by 5 leading research centers in Barcelona together with B-Debate, an initiative of BioCat. Luciano Di Croce from the Center for Genomic Regulation and Marcus Buschbeck from the Josep Carreras Leukemia Research Institute put together the scientific program with a particular focus on the role of non-coding RNAs in enhancer regulation, epigenetic control by Polycomb complexes, histone variants, and nuclear organization. In one and a half days, 22 talks and 56 posters were presented to an audience of 215 participants.
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Affiliation(s)
- David Corujo
- a Josep Carreras Leukaemia Research Institute (IJC), Campus ICO - Germans Trias i Pujol, Campus Can Ruti, Crta. Can Ruti, Cami de les Escoles , Badalona , Spain
| | - Gloria Mas
- b Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr. Aiguader 88 , Barcelona , Spain.,c Universitat Pompeu Fabra (UPF) , Barcelona , Spain
| | - Roberto Malinverni
- a Josep Carreras Leukaemia Research Institute (IJC), Campus ICO - Germans Trias i Pujol, Campus Can Ruti, Crta. Can Ruti, Cami de les Escoles , Badalona , Spain
| | - Luciano Di Croce
- b Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr. Aiguader 88 , Barcelona , Spain.,c Universitat Pompeu Fabra (UPF) , Barcelona , Spain.,d Institució Catalana de Recerca i Estudis Avançats, Passeig Lluis Companys 23 , Barcelona , Spain
| | - Marcus Buschbeck
- a Josep Carreras Leukaemia Research Institute (IJC), Campus ICO - Germans Trias i Pujol, Campus Can Ruti, Crta. Can Ruti, Cami de les Escoles , Badalona , Spain
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212
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Ooga M, Fulka H, Hashimoto S, Suzuki MG, Aoki F. Analysis of chromatin structure in mouse preimplantation embryos by fluorescent recovery after photobleaching. Epigenetics 2016; 11:85-94. [PMID: 26901819 DOI: 10.1080/15592294.2015.1136774] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Zygotes are totipotent cells that have the ability to differentiate into all cell types. It is believed that this ability is lost gradually and differentiation occurs along with the progression of preimplantation development. Here, we hypothesized that the loose chromatin structure is involved in the totipotency of one-cell stage embryos and that the change from loose to tight chromatin structure is associated with the loss of totipotency. To address this hypothesis, we investigated the mobility of eGFP-tagged histone H2B (eGFP-H2B), which is an index for the looseness of chromatin, during preimplantation development based on fluorescent recovery after photobleaching (FRAP) analysis. The highest mobility of eGFP-H2B was observed in pronuclei in 1-cell stage embryos and mobility gradually decreased during preimplantation development. The decrease in mobility between the 1- and 2-cell stages depended on DNA synthesis in 2-cell stage embryos. In nuclear transferred embryos, chromatin in the pseudopronuclei loosened to a level comparable to the pronuclei in 1-cell stage embryos. These results indicated that the mobility of eGFP-H2B is negatively correlated with the degree of differentiation of preimplantation embryos. Therefore, we suggest that highly loosened chromatin is involved in totipotency of 1-cell embryos and the loss of looseness is associated with differentiation during preimplantation development.
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Affiliation(s)
- Masatoshi Ooga
- a Department of Integrated Biosciences , Graduate School of Frontier Sciences, The University of Tokyo , Kashiwa, Chiba , Japan
| | - Helena Fulka
- a Department of Integrated Biosciences , Graduate School of Frontier Sciences, The University of Tokyo , Kashiwa, Chiba , Japan.,b Department of Biology of Reproduction , Institute of Animal Science , Prague , Czech Republic
| | - Satoshi Hashimoto
- a Department of Integrated Biosciences , Graduate School of Frontier Sciences, The University of Tokyo , Kashiwa, Chiba , Japan
| | - Masataka G Suzuki
- a Department of Integrated Biosciences , Graduate School of Frontier Sciences, The University of Tokyo , Kashiwa, Chiba , Japan
| | - Fugaku Aoki
- a Department of Integrated Biosciences , Graduate School of Frontier Sciences, The University of Tokyo , Kashiwa, Chiba , Japan.,b Department of Biology of Reproduction , Institute of Animal Science , Prague , Czech Republic
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213
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Abstract
Differentiating somatic cells are progressively restricted to specialized functions during ontogeny, but they can be experimentally directed to form other cell types, including those with complete embryonic potential. Early nuclear reprogramming methods, such as somatic cell nuclear transfer (SCNT) and cell fusion, posed significant technical hurdles to precise dissection of the regulatory programmes governing cell identity. However, the discovery of reprogramming by ectopic expression of a defined set of transcription factors, known as direct reprogramming, provided a tractable platform to uncover molecular characteristics of cellular specification and differentiation, cell type stability and pluripotency. We discuss the control and maintenance of cellular identity during developmental transitions as they have been studied using direct reprogramming, with an emphasis on transcriptional and epigenetic regulation.
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214
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Abstract
After a spermatozoon enters an oocyte, maternal factors accumulated in the oocyte reprogram the genomes of the terminally differentiated oocyte and spermatozoon epigenetically and turn the zygote into a totipotent cell, with the capacity to differentiate into all types of somatic cells in a highly organized manner and generate the entire organism, a feature referred to as totipotency. Differentiation of the first lineage begins after three cleavages, when the early embryo compacts and becomes polarized, followed by segregation of the first lineages--the inner cell mass (ICM) and the trophectoderm (TE). To date, a full understanding of the molecular mechanisms that underlie the establishment of totipotency and the ICM/TE lineage segregation remains unclear. In this review, we discuss recent findings in the mechanism of transcriptional regulation networks and signaling pathways in the first lineage separation in the totipotent mouse embryo.
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Affiliation(s)
- Guangming Wu
- Department of Cell and Developmental Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany
| | - Hans R Schöler
- Department of Cell and Developmental Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany.
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215
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Cheloufi S, Elling U, Hopfgartner B, Jung YL, Murn J, Ninova M, Hubmann M, Badeaux AI, Euong Ang C, Tenen D, Wesche DJ, Abazova N, Hogue M, Tasdemir N, Brumbaugh J, Rathert P, Jude J, Ferrari F, Blanco A, Fellner M, Wenzel D, Zinner M, Vidal SE, Bell O, Stadtfeld M, Chang HY, Almouzni G, Lowe SW, Rinn J, Wernig M, Aravin A, Shi Y, Park PJ, Penninger JM, Zuber J, Hochedlinger K. The histone chaperone CAF-1 safeguards somatic cell identity. Nature 2016; 528:218-24. [PMID: 26659182 PMCID: PMC4866648 DOI: 10.1038/nature15749] [Citation(s) in RCA: 192] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 09/28/2015] [Indexed: 12/25/2022]
Abstract
Cellular differentiation involves profound remodeling of chromatic landscapes, yet the mechanisms by which somatic cell identity is subsequently maintained remain incompletely understood. To further elucidate regulatory pathways that safeguard the somatic state, we performed two comprehensive RNAi screens targeting chromatin factors during transcription factor-mediated reprogramming of mouse fibroblasts to induced pluripotent stem cells (iPSCs). Remarkably, subunits of the chromatin assembly factor-1 (CAF-1) complex emerged as the most prominent hits from both screens, followed by modulators of lysine sumoylation and heterochromatin maintenance. Optimal modulation of both CAF-1 and transcription factor levels increased reprogramming efficiency by several orders of magnitude and facilitated iPSC formation in as little as 4 days. Mechanistically, CAF-1 suppression led to a more accessible chromatin structure at enhancer elements early during reprogramming. These changes were accompanied by a decrease in somatic heterochromatin domains, increased binding of Sox2 to pluripotency-specific targets and activation of associated genes. Notably, suppression of CAF-1 also enhanced the direct conversion of B cells into macrophages and fibroblasts into neurons. Together, our findings reveal the histone chaperone CAF-1 as a novel regulator of somatic cell identity during transcription factor-induced cell fate transitions and provide a potential strategy to modulate cellular plasticity in a regenerative setting.
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Affiliation(s)
- Sihem Cheloufi
- Department of Molecular Biology, Cancer Center and Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Stem Cell and Regenerative Biology and Harvard Stem Cell Institute, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - Ulrich Elling
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna Biocenter (VBC), A-1030 Vienna, Austria
| | - Barbara Hopfgartner
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), A-1030 Vienna, Austria
| | - Youngsook L Jung
- Department of Biomedical Informatics, Harvard Medical School, Boston, Massachusetts 02115, USA.,Division of Genetics, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA
| | - Jernej Murn
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.,Division of Newborn Medicine, Boston Children's Hospital, Boston, Massachusetts 02115, USA
| | - Maria Ninova
- California Institute of Technology, Division of Biology and Biological Engineering, Pasadena, California 91125, USA
| | - Maria Hubmann
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna Biocenter (VBC), A-1030 Vienna, Austria
| | - Aimee I Badeaux
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.,Division of Newborn Medicine, Boston Children's Hospital, Boston, Massachusetts 02115, USA
| | - Cheen Euong Ang
- Institute for Stem Cell Biology and Regenerative Medicine, Department of Pathology and Department of Bioengineering, Stanford University, Stanford, California 94305, USA
| | - Danielle Tenen
- Department of Stem Cell and Regenerative Biology and Harvard Stem Cell Institute, Cambridge, Massachusetts 02138, USA.,Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts 02142, USA
| | - Daniel J Wesche
- Department of Molecular Biology, Cancer Center and Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Stem Cell and Regenerative Biology and Harvard Stem Cell Institute, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - Nadezhda Abazova
- Department of Molecular Biology, Cancer Center and Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Stem Cell and Regenerative Biology and Harvard Stem Cell Institute, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - Max Hogue
- Department of Molecular Biology, Cancer Center and Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Stem Cell and Regenerative Biology and Harvard Stem Cell Institute, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - Nilgun Tasdemir
- Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Justin Brumbaugh
- Department of Molecular Biology, Cancer Center and Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Stem Cell and Regenerative Biology and Harvard Stem Cell Institute, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - Philipp Rathert
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), A-1030 Vienna, Austria
| | - Julian Jude
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), A-1030 Vienna, Austria
| | - Francesco Ferrari
- Department of Biomedical Informatics, Harvard Medical School, Boston, Massachusetts 02115, USA.,Division of Genetics, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA
| | - Andres Blanco
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.,Division of Newborn Medicine, Boston Children's Hospital, Boston, Massachusetts 02115, USA
| | - Michaela Fellner
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), A-1030 Vienna, Austria
| | - Daniel Wenzel
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna Biocenter (VBC), A-1030 Vienna, Austria
| | - Marietta Zinner
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna Biocenter (VBC), A-1030 Vienna, Austria
| | - Simon E Vidal
- The Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, Department of Cell Biology, NYU School of Medicine, New York, New York 10016, USA
| | - Oliver Bell
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna Biocenter (VBC), A-1030 Vienna, Austria
| | - Matthias Stadtfeld
- The Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, Department of Cell Biology, NYU School of Medicine, New York, New York 10016, USA
| | - Howard Y Chang
- Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA.,Center for Personal Dynamic Regulomes and Program in Epithelial Biology, Stanford University School of Medicine, Stanford, California 94305, USA
| | | | - Scott W Lowe
- Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA.,Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - John Rinn
- Department of Stem Cell and Regenerative Biology and Harvard Stem Cell Institute, Cambridge, Massachusetts 02138, USA.,Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts 02142, USA
| | - Marius Wernig
- Institute for Stem Cell Biology and Regenerative Medicine, Department of Pathology and Department of Bioengineering, Stanford University, Stanford, California 94305, USA
| | - Alexei Aravin
- California Institute of Technology, Division of Biology and Biological Engineering, Pasadena, California 91125, USA
| | - Yang Shi
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.,Division of Newborn Medicine, Boston Children's Hospital, Boston, Massachusetts 02115, USA
| | - Peter J Park
- Department of Biomedical Informatics, Harvard Medical School, Boston, Massachusetts 02115, USA.,Division of Genetics, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA
| | - Josef M Penninger
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna Biocenter (VBC), A-1030 Vienna, Austria
| | - Johannes Zuber
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), A-1030 Vienna, Austria
| | - Konrad Hochedlinger
- Department of Molecular Biology, Cancer Center and Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Stem Cell and Regenerative Biology and Harvard Stem Cell Institute, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
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216
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Abstract
Embryonal totipotent cells can produce both embryonic and extraembryonic tissues and can generate whole organisms. In mice this level of genome plasticity is preserved in the 2-cell embryos, but is absent in embryonic cells from later stages of development. Recently it has been demonstrated that totipotent-like cells spontaneously appear in embryonic stem cell cultures and that the depletion of the histone chaperone Chromatin Assembly Factor I (CAF-I) increases the abundance of 2cell-like cells. On the other hand, earlier studies have demonstrated that CAF-I is necessary for epigenetic conversions at the telomeres of S. cerevisiae. This commentary proposes that the absence of CAF-I confers totipotency of embryonic cells and that its activation triggers chromatin changes that reset the epigenome toward cell differentiation.
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Affiliation(s)
- Krassimir Yankulov
- a Department of Molecular and Cellular Biology ; University of Guelph ; Guelph , Ontario , Canada
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217
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Abstract
Retroviral restriction is a complex phenomenon that, despite remarkable recent progress, is far from being well understood. In this Preview, we introduce an insightful study by Yang et al. that represents the first attempt to identify the global determinants of retroviral repression in pluripotent mammalian cells.
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Affiliation(s)
- Gernot Wolf
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, MD 20892, USA
| | - Todd S Macfarlan
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, MD 20892, USA.
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218
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Politz JCR, Scalzo D, Groudine M. The redundancy of the mammalian heterochromatic compartment. Curr Opin Genet Dev 2015; 37:1-8. [PMID: 26706451 DOI: 10.1016/j.gde.2015.10.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 10/26/2015] [Accepted: 10/28/2015] [Indexed: 01/05/2023]
Abstract
Two chromatin compartments are present in most mammalian cells; the first contains primarily euchromatic, early replicating chromatin and the second, primarily late-replicating heterochromatin, which is the subject of this review. Heterochromatin is concentrated in three intranuclear regions: the nuclear periphery, the perinucleolar space and in pericentromeric bodies. We review recent evidence demonstrating that the heterochromatic compartment is critically involved in global nuclear organization and the maintenance of genome stability, and discuss models regarding how this compartment is formed and maintained. We also evaluate our understanding of how heterochromatic sequences (herein named heterochromatic associated regions (HADs)) might be tethered within these regions and review experiments that reveal the stochastic nature of individual HAD positioning within the compartment. These investigations suggest a substantial level of functional redundancy within the heterochromatic compartment.
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Affiliation(s)
| | - David Scalzo
- Fred Hutchinson Cancer Research Center, Seattle, WA, United States
| | - Mark Groudine
- Fred Hutchinson Cancer Research Center, Seattle, WA, United States.
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219
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Gaume X, Torres-Padilla ME. Regulation of Reprogramming and Cellular Plasticity through Histone Exchange and Histone Variant Incorporation. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2015; 80:165-175. [PMID: 26582788 DOI: 10.1101/sqb.2015.80.027458] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Early embryonic cells are totipotent and can generate a complete organism including embryonic and extraembryonic tissues. After division, cells lose their potency as they move toward a pluripotent state characterized by decreased cellular plasticity. During this transition, drastic changes in transcriptional programs occur in parallel with global chromatin reorganization. The epigenetic mechanisms governing the changes in chromatin signatures during the transitions of cellular plasticity states are starting to be understood. Among these mechanisms, recent studies highlight the importance of histone variant incorporation and/or eviction from chromatin in the regulation of the chromatin state that is linked to cellular potential. In this review, we discuss the role of histone variants during in vivo and in vitro reprogramming events. These results sustain the hypothesis that histone variants and histone exchange are key actors in the establishment of cellular plasticity programs.
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Affiliation(s)
- Xavier Gaume
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM U964, U de S, F-67404 Illkirch, CU de Strasbourg, France
| | - Maria-Elena Torres-Padilla
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM U964, U de S, F-67404 Illkirch, CU de Strasbourg, France
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220
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Histone chaperone CAF-1 mediates repressive histone modifications to protect preimplantation mouse embryos from endogenous retrotransposons. Proc Natl Acad Sci U S A 2015; 112:14641-6. [PMID: 26546670 DOI: 10.1073/pnas.1512775112] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Substantial proportions of mammalian genomes comprise repetitive elements including endogenous retrotransposons. Although these play diverse roles during development, their appropriate silencing is critically important in maintaining genomic integrity in the host cells. The major mechanism for retrotransposon silencing is DNA methylation, but the wave of global DNA demethylation that occurs after fertilization renders preimplantation embryos exceptionally hypomethylated. Here, we show that hypomethylated preimplantation mouse embryos are protected from retrotransposons by repressive histone modifications mediated by the histone chaperone chromatin assembly factor 1 (CAF-1). We found that knockdown of CAF-1 with specific siRNA injections resulted in significant up-regulation of the retrotransposons long interspersed nuclear element 1, short interspersed nuclear element B2, and intracisternal A particle at the morula stage. Concomitantly, increased histone H2AX phosphorylation and developmental arrest of the majority (>95%) of embryos were observed. The latter was caused at least in part by derepression of retrotransposons, as treatment with reverse transcriptase inhibitors rescued some embryos. Importantly, ChIP analysis revealed that CAF-1 mediated the replacement of H3.3 with H3.1/3.2 at the retrotransposon regions. This replacement was associated with deposition of repressive histone marks, including trimethylation of histone H3 on lysine 9 (H3K9me3), H3K9me2, H3K27me3, and H4K20me3. Among them, H4K20me3 and H3K9me3 seemed to play predominant roles in retrotransposon silencing, as assessed by knockdown of specific histone methyltransferases and forced expression of unmethylatable mutants of H3.1K9 and H4K20. Our data thus indicate that CAF-1 is an essential guardian of the genome in preimplantation mouse embryos by deposition of repressive histone modifications via histone variant replacement.
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221
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Transposable elements at the center of the crossroads between embryogenesis, embryonic stem cells, reprogramming, and long non-coding RNAs. Sci Bull (Beijing) 2015; 60:1722-1733. [PMID: 26543668 PMCID: PMC4624819 DOI: 10.1007/s11434-015-0905-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 09/18/2015] [Indexed: 12/19/2022]
Abstract
Transposable elements (TEs) are mobile genomic sequences of DNA capable of autonomous and non-autonomous duplication. TEs have been highly successful, and nearly half of the human genome now consists of various families of TEs. Originally thought to be non-functional, these elements have been co-opted by animal genomes to perform a variety of physiological functions ranging from TE-derived proteins acting directly in normal biological functions, to innovations in transcription factor logic and influence on epigenetic control of gene expression. During embryonic development, when the genome is epigenetically reprogrammed and DNA-demethylated, TEs are released from repression and show embryonic stage-specific expression, and in human and mouse embryos, intact TE-derived endogenous viral particles can even be detected. A similar process occurs during the reprogramming of somatic cells to pluripotent cells: When the somatic DNA is demethylated, TEs are released from repression. In embryonic stem cells (ESCs), where DNA is hypomethylated, an elaborate system of epigenetic control is employed to suppress TEs, a system that often overlaps with normal epigenetic control of ESC gene expression. Finally, many long non-coding RNAs (lncRNAs) involved in normal ESC function and those assisting or impairing reprogramming contain multiple TEs in their RNA. These TEs may act as regulatory units to recruit RNA-binding proteins and epigenetic modifiers. This review covers how TEs are interlinked with the epigenetic machinery and lncRNAs, and how these links influence each other to modulate aspects of ESCs, embryogenesis, and somatic cell reprogramming.
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222
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Wolf G, Greenberg D, Macfarlan TS. Spotting the enemy within: Targeted silencing of foreign DNA in mammalian genomes by the Krüppel-associated box zinc finger protein family. Mob DNA 2015; 6:17. [PMID: 26435754 PMCID: PMC4592553 DOI: 10.1186/s13100-015-0050-8] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 09/24/2015] [Indexed: 12/17/2022] Open
Abstract
Tandem C2H2-type zinc finger proteins (ZFPs) constitute the largest transcription factor family in animals. Tandem-ZFPs bind DNA in a sequence-specific manner through arrays of multiple zinc finger domains that allow high flexibility and specificity in target recognition. In tetrapods, a large proportion of tandem-ZFPs contain Krüppel-associated-box (KRAB) repression domains, which are able to induce epigenetic silencing through the KAP1 corepressor. The KRAB-ZFP family continuously amplified in tetrapods through segmental gene duplications, often accompanied by deletions, duplications, and mutations of the zinc finger domains. As a result, tetrapod genomes contain unique sets of KRAB-ZFP genes, consisting of ancient and recently evolved family members. Although several hundred human and mouse KRAB-ZFPs have been identified or predicted, the biological functions of most KRAB-ZFP family members have gone unexplored. Furthermore, the evolutionary forces driving the extraordinary KRAB-ZFP expansion and diversification have remained mysterious for decades. In this review, we highlight recent studies that associate KRAB-ZFPs with the repression of parasitic DNA elements in the mammalian germ line and discuss the hypothesis that the KRAB-ZFP family primarily evolved as an adaptive genomic surveillance system against foreign DNA. Finally, we comment on the computational, genetic, and biochemical challenges of studying KRAB-ZFPs and attempt to predict how these challenges may be soon overcome.
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Affiliation(s)
- Gernot Wolf
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, MD 20892 USA
| | - David Greenberg
- The Gladstone Institute of Virology and Immunology, University of California, San Francisco, CA 94158 USA ; Present address: Pacific Biosciences, 1380 Willow Road, Menlo Park, CA 94025 USA
| | - Todd S Macfarlan
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, MD 20892 USA
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223
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Hayashi M, Maehara K, Harada A, Semba Y, Kudo K, Takahashi H, Oki S, Meno C, Ichiyanagi K, Akashi K, Ohkawa Y. Chd5 Regulates MuERV-L/MERVL Expression in Mouse Embryonic Stem Cells Via H3K27me3 Modification and Histone H3.1/H3.2. J Cell Biochem 2015; 117:780-92. [PMID: 26359639 DOI: 10.1002/jcb.25368] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 09/09/2015] [Indexed: 12/12/2022]
Abstract
Chd5 is an essential factor for neuronal differentiation and spermatogenesis and is a known tumor suppressor. H3K27me3 and H3K4un are modifications recognized by Chd5; however, it remains unclear how Chd5 remodels chromatin structure. We completely disrupted the Chd5 locus using the CRISPR-Cas9 system to generate a 52 kbp long deletion and analyzed Chd5 function in mouse embryonic stem cells. Our findings show that Chd5 represses murine endogenous retrovirus-L (MuERV-L/MERVL), an endogenous retrovirus-derived retrotransposon, by regulating H3K27me3 and H3.1/H3.2 function.
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Affiliation(s)
- Masayasu Hayashi
- Department of Advanced Medical Initiatives, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan.,Department of Medicine and Biosystemic Science, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan
| | - Kazumitsu Maehara
- Department of Advanced Medical Initiatives, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan
| | - Akihito Harada
- Department of Advanced Medical Initiatives, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan
| | - Yuichiro Semba
- Department of Advanced Medical Initiatives, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan.,Department of Medicine and Biosystemic Science, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan
| | - Kensuke Kudo
- Department of Advanced Medical Initiatives, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan.,Department of Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Hidehisa Takahashi
- Department of Biochemistry, Hokkaido University Graduate School of Medicine, Hokkaido 060-8638, Japan
| | - Shinya Oki
- Department of Developmental Biology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Chikara Meno
- Department of Developmental Biology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Kenji Ichiyanagi
- Division of Epigenomics and Development, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Koichi Akashi
- Department of Medicine and Biosystemic Science, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan
| | - Yasuyuki Ohkawa
- Department of Advanced Medical Initiatives, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan
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224
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