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Westervelt N, Yoest A, Sayed S, Von Zimmerman M, Kaps K, Chadwick BP. Deletion of the XIST promoter from the human inactive X chromosome compromises polycomb heterochromatin maintenance. Chromosoma 2021; 130:177-197. [PMID: 33745031 DOI: 10.1007/s00412-021-00754-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 02/01/2021] [Accepted: 02/21/2021] [Indexed: 10/21/2022]
Abstract
Silencing most gene expression from all but one X chromosome in female mammals provides a means to overcome X-linked gene expression imbalances with males. Central to establishing gene silencing on the inactivated X chromosome are the actions of the long non-coding RNA XIST that triggers the repackaging of the chosen X into facultative heterochromatin. While understanding the mechanisms through which XIST expression is regulated and mediates its affects has been a major focus of research since its discovery, less is known about the role XIST plays in maintaining chromatin at the human inactive X chromosome (Xi). Here, we use genome engineering to delete the promoter of XIST to knockout expression from the Xi in non-cancerous diploid human somatic cells. Although some heterochromatin features exhibit limited change at the Xi, two of those assessed showed significant reductions including histone H2A monoubiquitylation at lysine 119 and histone H3 trimethylation at lysine 27, both of which are covalent histone modifications catalyzed by the polycomb repressive complexes 1 and 2 respectively. Coupled with these reductions, we observed an occasional gain of euchromatin signatures on Xp, but despite these signs of chromatin instability, we did not observe appreciable changes in the reactivation of genes from the Xi. Collectively, these data are consistent with maintenance of dosage compensation at the Xi involving multiple redundant layers of gene silencing.
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Affiliation(s)
- Natalia Westervelt
- Department of Biological Science, Florida State University, 319 Stadium Drive, King 3076, Tallahassee, FL, 32306-4295, USA
| | - Andrea Yoest
- Department of Biological Science, Florida State University, 319 Stadium Drive, King 3076, Tallahassee, FL, 32306-4295, USA
| | - Sadia Sayed
- Department of Biological Science, Florida State University, 319 Stadium Drive, King 3076, Tallahassee, FL, 32306-4295, USA
| | - Marina Von Zimmerman
- Department of Biological Science, Florida State University, 319 Stadium Drive, King 3076, Tallahassee, FL, 32306-4295, USA
| | - Kelly Kaps
- Department of Biological Science, Florida State University, 319 Stadium Drive, King 3076, Tallahassee, FL, 32306-4295, USA
| | - Brian P Chadwick
- Department of Biological Science, Florida State University, 319 Stadium Drive, King 3076, Tallahassee, FL, 32306-4295, USA.
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2
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Hagen SH, Henseling F, Hennesen J, Savel H, Delahaye S, Richert L, Ziegler SM, Altfeld M. Heterogeneous Escape from X Chromosome Inactivation Results in Sex Differences in Type I IFN Responses at the Single Human pDC Level. Cell Rep 2020; 33:108485. [PMID: 33296655 PMCID: PMC7833293 DOI: 10.1016/j.celrep.2020.108485] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 09/11/2020] [Accepted: 11/12/2020] [Indexed: 12/28/2022] Open
Abstract
Immune responses differ between women and men, and type I interferon (IFN) responses following Toll-like receptor 7 (TLR7) stimulation are higher in women. The precise mechanisms driving these sex differences in immunity are unknown. To investigate possible genetic factors, we quantify escape from X chromosome inactivation (XCI) for TLR7 and four other genes (RPS6KA3, CYBB, BTK, and IL13RA1) at the single plasmacytoid dendritic cell (pDC) level. We observe escape from XCI for all investigated genes, leading to biallelic expression patterns. pDCs with biallelic gene expression have significantly higher mRNA levels of the respective genes. Unstimulated pDCs with biallelic TLR7 expression exhibit significantly higher IFNα/β mRNA levels, and IFNα exposure results in significantly increased IFNα/β protein production by pDCs. These results identify unanticipated heterogeneity in escape from XCI of several genes in pDCs and highlight the important contribution of X chromosome factors to sex differences in type I IFN responses, which might explain observed sex differences in human diseases.
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Affiliation(s)
- Sven Hendrik Hagen
- Research Department Virus Immunology, Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Martinistrasse 52, Hamburg 20251, Germany
| | - Florian Henseling
- Research Department Virus Immunology, Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Martinistrasse 52, Hamburg 20251, Germany
| | - Jana Hennesen
- Technology Platform Flow Cytometry/FACS, Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Martinistrasse 52, Hamburg 20251, Germany
| | - Hélène Savel
- University of Bordeaux, Inserm, Bordeaux Population Health Research Center, UMR1219 and Inria, team SISTM, Bordeaux, France
| | - Solenne Delahaye
- University of Bordeaux, Inserm, Bordeaux Population Health Research Center, UMR1219 and Inria, team SISTM, Bordeaux, France
| | - Laura Richert
- University of Bordeaux, Inserm, Bordeaux Population Health Research Center, UMR1219 and Inria, team SISTM, Bordeaux, France
| | - Susanne Maria Ziegler
- Research Department Virus Immunology, Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Martinistrasse 52, Hamburg 20251, Germany
| | - Marcus Altfeld
- Research Department Virus Immunology, Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Martinistrasse 52, Hamburg 20251, Germany.
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3
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Wang D, Tang L, Wu Y, Fan C, Zhang S, Xiang B, Zhou M, Li X, Li Y, Li G, Xiong W, Zeng Z, Guo C. Abnormal X chromosome inactivation and tumor development. Cell Mol Life Sci 2020; 77:2949-2958. [PMID: 32040694 PMCID: PMC11104905 DOI: 10.1007/s00018-020-03469-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2019] [Revised: 01/17/2020] [Accepted: 01/21/2020] [Indexed: 12/13/2022]
Abstract
During embryonic development, one of the two X chromosomes of a mammalian female cell is randomly inactivated by the X chromosome inactivation mechanism, which is mainly dependent on the regulation of the non-coding RNA X-inactive specific transcript at the X chromosome inactivation center. There are three proteins that are essential for X-inactive specific transcript to function properly: scaffold attachment factor-A, lamin B receptor, and SMRT- and HDAC-associated repressor protein. In addition, the absence of X-inactive specific transcript expression promotes tumor development. During the process of chromosome inactivation, some tumor suppressor genes escape inactivation of the X chromosome and thereby continue to play a role in tumor suppression. A well-functioning tumor suppressor gene on the idle X chromosome in women is one of the reasons they have a lower propensity to develop cancer than men, women thereby benefit from this enhanced tumor suppression. This review will explore the mechanism of X chromosome inactivation, discuss the relationship between X chromosome inactivation and tumorigenesis, and consider the consequent sex differences in cancer.
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Affiliation(s)
- Dan Wang
- Department of Stomatology, NHC Key Laboratory of Carcinogenesis, Xiangya Hospital, Central South University, Changsha, Hunan, China
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
- Hunan Key Laboratory of Nonresolving Inflammation and Cancer, Disease Genome Research Center, The Third Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Le Tang
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Yingfen Wu
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Chunmei Fan
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Shanshan Zhang
- Department of Stomatology, NHC Key Laboratory of Carcinogenesis, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Bo Xiang
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Ming Zhou
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Xiaoling Li
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Yong Li
- Department of Medicine, Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, Texas, USA
| | - Guiyuan Li
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Wei Xiong
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Zhaoyang Zeng
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China
| | - Can Guo
- Department of Stomatology, NHC Key Laboratory of Carcinogenesis, Xiangya Hospital, Central South University, Changsha, Hunan, China.
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute, Central South University, Changsha, Hunan, China.
- Hunan Key Laboratory of Nonresolving Inflammation and Cancer, Disease Genome Research Center, The Third Xiangya Hospital, Central South University, Changsha, Hunan, China.
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Chadwick BP. Characterization of chromatin at structurally abnormal inactive X chromosomes reveals potential evidence of a rare hybrid active and inactive isodicentric X chromosome. Chromosome Res 2019; 28:155-169. [PMID: 31776830 DOI: 10.1007/s10577-019-09621-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 11/12/2019] [Accepted: 11/14/2019] [Indexed: 02/07/2023]
Abstract
X chromosome structural abnormalities are relatively common in Turner syndrome patients, in particular X isochromosomes. Reports over the last five decades examining asynchronous DNA replication between the normal X and isochromosome have clearly established that the structurally abnormal chromosome is the inactive X chromosome (Xi). Here the organization of chromatin at a deleted X chromosome, an Xq isochromosome, and two isodicentric chromosomes were examined. Consistent with previous differential staining methods, at interphase, the X isochromosome and isodicentric X chromosomes frequently formed bipartite Barr bodies, observed by fluorescence microscopy using numerous independent bona fide markers of Xi heterochromatin. At metaphase, with the exception of the pseudoautosomal region and the duplicated locus of the macrosatellite DXZ4 (if present on the abnormal X chromosome based on break points), euchromatin markers were absent from the Xi, whereas histone variant macroH2A formed reproducible banded mirror-image chromosomes. Unexpectedly, the isodicentric chromosome in 46,X,idic(X)(q28) cells, which carry a near full-length q-arm-to-q-arm fused chromosome, showed at interphase very rare instances of Xi chromatin bodies that were separated by large distances in the nucleus. Further examination using immunofluorescence and FISH support the possibility that these rare cells may represent ones in which one half of the isodicentric chromosome is active and the other half is inactive.
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Affiliation(s)
- Brian P Chadwick
- Department of Biological Science, Florida State University, 319 Stadium Drive, King 3076, Tallahassee, FL, 32306-4295, USA.
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5
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Stork C, Li Z, Lin L, Zheng S. Developmental Xist induction is mediated by enhanced splicing. Nucleic Acids Res 2019; 47:1532-1543. [PMID: 30496473 PMCID: PMC6379716 DOI: 10.1093/nar/gky1198] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 11/12/2018] [Accepted: 11/15/2018] [Indexed: 11/12/2022] Open
Abstract
X-inactive-specific transcript (Xist) is a long noncoding RNA (lncRNA) essential for inactivating one of the two X chromosomes in mammalian females. Random X chromosome inactivation is mediated by Xist RNA expressed from the inactive X chromosome. We found that Xist RNA is unspliced in naïve embryonic stem (ES) cells. Upon differentiation, Xist splicing becomes efficient across all exons independent of transcription, suggesting interdependent or coordinated removal of Xist introns. In female cells with mutated polypyrimidine tract binding protein 1 (Ptbp1), differentiation fails to substantially upregulate mature Xist RNA because of a defect in Xist splicing. We further found both Xist129 and XistCAS RNA are unspliced in Mus musculus 129SvJ/Mus castaneous (CAS) hybrid female ES cells. Upon differentiation, Xist129 exhibits a higher splicing efficiency than XistCAS, likely contributing to preferential inhibition of the X129 chromosome. Single cell analysis shows that the allelic choice of Xist splicing is linked to the inactive X chromosome. We conclude post-transcriptional control of Xist RNA splicing is an essential regulatory step of Xist induction. Our studies shed light on the developmental roles of splicing for nuclear-retained Xist lncRNA and suggest inefficient Xist splicing is an additional fail-safe mechanism to prevent Xist activity in ES cells.
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Affiliation(s)
- Cheryl Stork
- Graduate Program in Cell, Molecular and Developmental Biology, University of California, Riverside, Riverside, CA 92521, USA
| | - Zhelin Li
- Graduate Program in Genetics, Genomics and Bioinformatics, University of California, Riverside, Riverside, CA 92521, USA
| | - Lin Lin
- Division of Biomedical Sciences, University of California, Riverside, Riverside, CA 92521, USA
| | - Sika Zheng
- Graduate Program in Cell, Molecular and Developmental Biology, University of California, Riverside, Riverside, CA 92521, USA.,Graduate Program in Genetics, Genomics and Bioinformatics, University of California, Riverside, Riverside, CA 92521, USA.,Division of Biomedical Sciences, University of California, Riverside, Riverside, CA 92521, USA
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6
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Jacob R, Zander S, Gutschner T. The Dark Side of the Epitranscriptome: Chemical Modifications in Long Non-Coding RNAs. Int J Mol Sci 2017; 18:ijms18112387. [PMID: 29125541 PMCID: PMC5713356 DOI: 10.3390/ijms18112387] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 11/05/2017] [Accepted: 11/06/2017] [Indexed: 12/20/2022] Open
Abstract
The broad application of next-generation sequencing technologies in conjunction with improved bioinformatics has helped to illuminate the complexity of the transcriptome, both in terms of quantity and variety. In humans, 70–90% of the genome is transcribed, but only ~2% carries the blueprint for proteins. Hence, there is a huge class of non-translated transcripts, called long non-coding RNAs (lncRNAs), which have received much attention in the past decade. Several studies have shown that lncRNAs are involved in a plethora of cellular signaling pathways and actively regulate gene expression via a broad selection of molecular mechanisms. Only recently, sequencing-based, transcriptome-wide studies have characterized different types of post-transcriptional chemical modifications of RNAs. These modifications have been shown to affect the fate of RNA and further expand the variety of the transcriptome. However, our understanding of their biological function, especially in the context of lncRNAs, is still in its infancy. In this review, we will focus on three epitranscriptomic marks, namely pseudouridine (Ψ), N6-methyladenosine (m6A) and 5-methylcytosine (m5C). We will introduce writers, readers, and erasers of these modifications, and we will present methods for their detection. Finally, we will provide insights into the distribution and function of these chemical modifications in selected, cancer-related lncRNAs.
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Affiliation(s)
- Roland Jacob
- Faculty of Medicine, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany.
| | - Sindy Zander
- Faculty of Medicine, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany.
| | - Tony Gutschner
- Faculty of Medicine, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany.
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Carrel L, Brown CJ. When the Lyon(ized chromosome) roars: ongoing expression from an inactive X chromosome. Philos Trans R Soc Lond B Biol Sci 2017; 372:20160355. [PMID: 28947654 PMCID: PMC5627157 DOI: 10.1098/rstb.2016.0355] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/24/2017] [Indexed: 12/21/2022] Open
Abstract
A tribute to Mary Lyon was held in October 2016. Many remarked about Lyon's foresight regarding many intricacies of the X-chromosome inactivation process. One such example is that a year after her original 1961 hypothesis she proposed that genes with Y homologues should escape from X inactivation to achieve dosage compensation between males and females. Fifty-five years later we have learned many details about these escapees that we attempt to summarize in this review, with a particular focus on recent findings. We now know that escapees are not rare, particularly on the human X, and that most lack functionally equivalent Y homologues, leading to their increasingly recognized role in sexually dimorphic traits. Newer sequencing technologies have expanded profiling of primary tissues that will better enable connections to sex-biased disorders as well as provide additional insights into the X-inactivation process. Chromosome organization, nuclear location and chromatin environments distinguish escapees from other X-inactivated genes. Nevertheless, several big questions remain, including what dictates their distinct epigenetic environment, the underlying basis of species differences in escapee regulation, how different classes of escapees are distinguished, and the roles that local sequences and chromosome ultrastructure play in escapee regulation.This article is part of the themed issue 'X-chromosome inactivation: a tribute to Mary Lyon'.
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Affiliation(s)
- Laura Carrel
- Department of Biochemistry and Molecular Biology, Penn State College of Medicine, 500 University Drive, Mail code H171, Hershey, PA 17033, USA
| | - Carolyn J Brown
- Department of Medical Genetics, Molecular Epigenetics Group, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, Canada BC V6T 1Z3
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8
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Affiliation(s)
- Chao-Po Lin
- Division of Cellular and Developmental Biology, Department of Molecular and Cell Biology, University of California, Berkeley, California 94705
| | - Lin He
- Division of Cellular and Developmental Biology, Department of Molecular and Cell Biology, University of California, Berkeley, California 94705
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9
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Yang T, Yildirim E. Epigenetic and LncRNA-Mediated Regulation of X Chromosome Inactivation and Its Impact on Pathogenesis. CURRENT PATHOBIOLOGY REPORTS 2017. [DOI: 10.1007/s40139-017-0120-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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10
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Abstract
The recognition of functional roles for transcribed long non-coding RNA (lncRNA) has provided a new dimension to our understanding of cellular physiology and disease pathogenesis. LncRNAs are a large group of structurally complex RNA genes that can interact with DNA, RNA, or protein molecules to modulate gene expression and to exert cellular effects through diverse mechanisms. The emerging knowledge regarding their functional roles and their aberrant expression in disease states emphasizes the potential for lncRNA to serve as targets for therapeutic intervention. In this concise review, we outline the mechanisms of action of lncRNAs, their functional cellular roles, and their involvement in disease. Using liver cancer as an example, we provide an overview of the emerging opportunities and potential approaches to target lncRNA-dependent mechanisms for therapeutic purposes.
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Kelsey AD, Yang C, Leung D, Minks J, Dixon-McDougall T, Baldry SEL, Bogutz AB, Lefebvre L, Brown CJ. Impact of flanking chromosomal sequences on localization and silencing by the human non-coding RNA XIST. Genome Biol 2015; 16:208. [PMID: 26429547 PMCID: PMC4591629 DOI: 10.1186/s13059-015-0774-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 09/10/2015] [Indexed: 01/07/2023] Open
Abstract
Background X-chromosome inactivation is a striking example of epigenetic silencing in which expression of the long non-coding RNA XIST initiates the heterochromatinization and silencing of one of the pair of X chromosomes in mammalian females. To understand how the RNA can establish silencing across millions of basepairs of DNA we have modelled the process by inducing expression of XIST from nine different locations in human HT1080 cells. Results Localization of XIST, depletion of Cot-1 RNA, perinuclear localization, and ubiquitination of H2A occurs at all sites examined, while recruitment of H3K9me3 was not observed. Recruitment of the heterochromatic features SMCHD1, macroH2A, H3K27me3, and H4K20me1 occurs independently of each other in an integration site-dependent manner. Silencing of flanking reporter genes occurs at all sites, but the spread of silencing to flanking endogenous human genes is variable in extent of silencing as well as extent of spread, with silencing able to skip regions. The spread of H3K27me3 and loss of H3K27ac correlates with the pre-existing levels of the modifications, and overall the extent of silencing correlates with the ability to recruit additional heterochromatic features. Conclusions The non-coding RNA XIST functions as a cis-acting silencer when expressed from nine different locations throughout the genome. A hierarchy among the features of heterochromatin reveals the importance of interaction with the local chromatin neighborhood for optimal spread of silencing, as well as the independent yet cooperative nature of the establishment of heterochromatin by the non-coding XIST RNA. Electronic supplementary material The online version of this article (doi:10.1186/s13059-015-0774-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Angela D Kelsey
- Department of Medical Genetics, Molecular Epigenetics Group, Life Sciences Institute, University of British Columbia, Vancouver, Canada.
| | - Christine Yang
- Department of Medical Genetics, Molecular Epigenetics Group, Life Sciences Institute, University of British Columbia, Vancouver, Canada.
| | - Danny Leung
- Ludwig Institute for Cancer Research, University of California at San Diego School of Medicine, La Jolla, CA, USA. .,Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
| | - Jakub Minks
- Department of Medical Genetics, Molecular Epigenetics Group, Life Sciences Institute, University of British Columbia, Vancouver, Canada.
| | - Thomas Dixon-McDougall
- Department of Medical Genetics, Molecular Epigenetics Group, Life Sciences Institute, University of British Columbia, Vancouver, Canada.
| | - Sarah E L Baldry
- Department of Medical Genetics, Molecular Epigenetics Group, Life Sciences Institute, University of British Columbia, Vancouver, Canada.
| | - Aaron B Bogutz
- Department of Medical Genetics, Molecular Epigenetics Group, Life Sciences Institute, University of British Columbia, Vancouver, Canada.
| | - Louis Lefebvre
- Department of Medical Genetics, Molecular Epigenetics Group, Life Sciences Institute, University of British Columbia, Vancouver, Canada.
| | - Carolyn J Brown
- Department of Medical Genetics, Molecular Epigenetics Group, Life Sciences Institute, University of British Columbia, Vancouver, Canada.
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12
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Fatima R, Akhade VS, Pal D, Rao SMR. Long noncoding RNAs in development and cancer: potential biomarkers and therapeutic targets. MOLECULAR AND CELLULAR THERAPIES 2015; 3:5. [PMID: 26082843 PMCID: PMC4469312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 05/19/2015] [Indexed: 11/21/2023]
Abstract
Long noncoding RNAs are emerging as key players in various fundamental biological processes. We highlight the varied molecular mechanisms by which lncRNAs modulate gene expression in diverse cellular contexts and their role in early mammalian development in this review. Furthermore, it is being increasingly recognized that altered expression of lncRNAs is specifically associated with tumorigenesis, tumor progression and metastasis. We discuss various lncRNAs implicated in different cancer types with a focus on their clinical applications as potential biomarkers and therapeutic targets in the pathology of diverse cancers.
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Affiliation(s)
- Roshan Fatima
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur, Bangalore 560064 India
| | - Vijay Suresh Akhade
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur, Bangalore 560064 India
| | - Debosree Pal
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur, Bangalore 560064 India
| | - Satyanarayana MR Rao
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur, Bangalore 560064 India
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13
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Fatima R, Akhade VS, Pal D, Rao SM. Long noncoding RNAs in development and cancer: potential biomarkers and therapeutic targets. MOLECULAR AND CELLULAR THERAPIES 2015; 3:5. [PMID: 26082843 PMCID: PMC4469312 DOI: 10.1186/s40591-015-0042-6] [Citation(s) in RCA: 203] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 05/19/2015] [Indexed: 02/07/2023]
Abstract
Long noncoding RNAs are emerging as key players in various fundamental biological processes. We highlight the varied molecular mechanisms by which lncRNAs modulate gene expression in diverse cellular contexts and their role in early mammalian development in this review. Furthermore, it is being increasingly recognized that altered expression of lncRNAs is specifically associated with tumorigenesis, tumor progression and metastasis. We discuss various lncRNAs implicated in different cancer types with a focus on their clinical applications as potential biomarkers and therapeutic targets in the pathology of diverse cancers.
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Affiliation(s)
- Roshan Fatima
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur, Bangalore 560064 India
| | - Vijay Suresh Akhade
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur, Bangalore 560064 India
| | - Debosree Pal
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur, Bangalore 560064 India
| | - Satyanarayana Mr Rao
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur, Bangalore 560064 India
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14
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Karreth FA, Reschke M, Ruocco A, Ng C, Chapuy B, Léopold V, Sjoberg M, Keane TM, Verma A, Ala U, Tay Y, Wu D, Seitzer N, Velasco-Herrera MDC, Bothmer A, Fung J, Langellotto F, Rodig SJ, Elemento O, Shipp MA, Adams DJ, Chiarle R, Pandolfi PP. The BRAF pseudogene functions as a competitive endogenous RNA and induces lymphoma in vivo. Cell 2015; 161:319-32. [PMID: 25843629 DOI: 10.1016/j.cell.2015.02.043] [Citation(s) in RCA: 255] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 12/19/2014] [Accepted: 02/02/2015] [Indexed: 12/14/2022]
Abstract
Research over the past decade has suggested important roles for pseudogenes in physiology and disease. In vitro experiments demonstrated that pseudogenes contribute to cell transformation through several mechanisms. However, in vivo evidence for a causal role of pseudogenes in cancer development is lacking. Here, we report that mice engineered to overexpress either the full-length murine B-Raf pseudogene Braf-rs1 or its pseudo "CDS" or "3' UTR" develop an aggressive malignancy resembling human diffuse large B cell lymphoma. We show that Braf-rs1 and its human ortholog, BRAFP1, elicit their oncogenic activity, at least in part, as competitive endogenous RNAs (ceRNAs) that elevate BRAF expression and MAPK activation in vitro and in vivo. Notably, we find that transcriptional or genomic aberrations of BRAFP1 occur frequently in multiple human cancers, including B cell lymphomas. Our engineered mouse models demonstrate the oncogenic potential of pseudogenes and indicate that ceRNA-mediated microRNA sequestration may contribute to the development of cancer.
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Affiliation(s)
- Florian A Karreth
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Markus Reschke
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Anna Ruocco
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Christopher Ng
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Bjoern Chapuy
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA
| | - Valentine Léopold
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Marcela Sjoberg
- Experimental Cancer Genetics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton CB10 1HH, UK
| | - Thomas M Keane
- Experimental Cancer Genetics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton CB10 1HH, UK
| | - Akanksha Verma
- Department of Physiology and Biophysics, Institute for Computational Biomedicine, Weill Cornell Medical College, New York, NY 10021, USA
| | - Ugo Ala
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Yvonne Tay
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - David Wu
- Meyer Cancer Center, Weill Cornell Medical College, New York, NY 10021, USA
| | - Nina Seitzer
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | | | - Anne Bothmer
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Jacqueline Fung
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Fernanda Langellotto
- Department of Pathology, Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Scott J Rodig
- Department of Pathology, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Olivier Elemento
- Department of Physiology and Biophysics, Institute for Computational Biomedicine, Weill Cornell Medical College, New York, NY 10021, USA
| | - Margaret A Shipp
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA
| | - David J Adams
- Experimental Cancer Genetics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton CB10 1HH, UK
| | - Roberto Chiarle
- Department of Pathology, Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; Department of Molecular Biotechnology and Health Sciences, University of Torino, 10124 Torino, Italy
| | - Pier Paolo Pandolfi
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
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15
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Irie N, Tang WWC, Azim Surani M. Germ cell specification and pluripotency in mammals: a perspective from early embryogenesis. Reprod Med Biol 2014; 13:203-215. [PMID: 25298745 PMCID: PMC4182624 DOI: 10.1007/s12522-014-0184-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 05/19/2014] [Indexed: 12/01/2022] Open
Abstract
Germ cells are unique cell types that generate a totipotent zygote upon fertilization, giving rise to the next generation in mammals and many other multicellular organisms. How germ cells acquire this ability has been of considerable interest. In mammals, primordial germ cells (PGCs), the precursors of sperm and oocytes, are specified around the time of gastrulation. PGCs are induced by signals from the surrounding extra-embryonic tissues to the equipotent epiblast cells that give rise to all cell types. Currently, the mechanism of PGC specification in mammals is best understood from studies in mice. Following implantation, the epiblast cells develop as an egg cylinder while the extra-embryonic ectoderm cells which are the source of important signals for PGC specification are located over the egg cylinder. However, in most cases, including humans, the epiblast cells develop as a planar disc, which alters the organization and the source of the signaling for cell fates. This, in turn, might have an effect on the precise mechanism of PGC specification in vivo as well as in vitro using pluripotent embryonic stem cells. Here, we discuss how the key early embryonic differences between rodents and other mammals may affect the establishment of the pluripotency network in vivo and in vitro, and consequently the basis for PGC specification, particularly from pluripotent embryonic stem cells in vitro.
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Affiliation(s)
- Naoko Irie
- Wellcome Trust/Cancer Research UK, Gurdon InstituteUniversity of CambridgeTennis Court RoadCB2 1QNCambridgeUK
| | - Walfred W. C. Tang
- Wellcome Trust/Cancer Research UK, Gurdon InstituteUniversity of CambridgeTennis Court RoadCB2 1QNCambridgeUK
| | - M. Azim Surani
- Wellcome Trust/Cancer Research UK, Gurdon InstituteUniversity of CambridgeTennis Court RoadCB2 1QNCambridgeUK
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16
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Alvarez-Dominguez JR, Hu W, Gromatzky AA, Lodish HF. Long noncoding RNAs during normal and malignant hematopoiesis. Int J Hematol 2014; 99:531-41. [PMID: 24609766 DOI: 10.1007/s12185-014-1552-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 01/25/2014] [Accepted: 02/18/2014] [Indexed: 11/28/2022]
Abstract
Long noncoding RNAs (lncRNAs) are increasingly recognized to contribute to cellular development via diverse mechanisms during both health and disease. Here, we highlight recent progress on the study of lncRNAs that function in the development of blood cells. We emphasize lncRNAs that regulate blood cell fates through epigenetic control of gene expression, an emerging theme among functional lncRNAs. Many of these noncoding genes and their targets become dysregulated during malignant hematopoiesis, directly implicating lncRNAs in blood cancers such as leukemia. In a few cases, dysregulation of an lncRNA alone leads to malignant hematopoiesis in a mouse model. Thus, lncRNAs may be not only useful as markers for the diagnosis and prognosis of cancers of the blood, but also as potential targets for novel therapies.
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17
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An active isodicentric x chromosome in a case of refractory anaemia with ring sideroblasts associated with marked thrombocytosis. Case Rep Genet 2014; 2014:205318. [PMID: 24592338 PMCID: PMC3926399 DOI: 10.1155/2014/205318] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Accepted: 12/11/2013] [Indexed: 11/17/2022] Open
Abstract
Refractory anaemia with ring sideroblasts and marked thrombocytosis (RARS-T) is a provisional entity in the World Health Organization (WHO) classification. It displays features characteristic of both myelodysplastic syndrome and myeloproliferative neoplasia plus ring sideroblasts ≥15% and marked thrombocytosis. Most patients with RARS-T show a normal karyotype. We report a 76-year-old woman diagnosed with RARS-T (76% of ring sideroblasts) with JAK2 (V617F) mutation and a load of 30-40%. Classical and molecular cytogenetic (FISH) studies of a bone marrow sample revealed the presence of isodicentric X chromosome [(idic(X)(q13)]. Moreover, HUMARA assay showed the idic(X)(q13) as the active X chromosome. This finding was correlated with the cytochemical finding of ring sideroblasts. To our knowledge, this is the first reported case of an active isodicentric X in a woman with RARS-T.
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18
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Yildirim E, Kirby JE, Brown DE, Mercier FE, Sadreyev RI, Scadden DT, Lee JT. Xist RNA is a potent suppressor of hematologic cancer in mice. Cell 2013; 152:727-42. [PMID: 23415223 PMCID: PMC3875356 DOI: 10.1016/j.cell.2013.01.034] [Citation(s) in RCA: 365] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Revised: 12/04/2012] [Accepted: 01/23/2013] [Indexed: 02/06/2023]
Abstract
X chromosome aneuploidies have long been associated with human cancers, but causality has not been established. In mammals, X chromosome inactivation (XCI) is triggered by Xist RNA to equalize gene expression between the sexes. Here we delete Xist in the blood compartment of mice and demonstrate that mutant females develop a highly aggressive myeloproliferative neoplasm and myelodysplastic syndrome (mixed MPN/MDS) with 100% penetrance. Significant disease components include primary myelofibrosis, leukemia, histiocytic sarcoma, and vasculitis. Xist-deficient hematopoietic stem cells (HSCs) show aberrant maturation and age-dependent loss. Reconstitution experiments indicate that MPN/MDS and myelofibrosis are of hematopoietic rather than stromal origin. We propose that Xist loss results in X reactivation and consequent genome-wide changes that lead to cancer, thereby causally linking the X chromosome to cancer in mice. Thus, Xist RNA not only is required to maintain XCI but also suppresses cancer in vivo.
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Affiliation(s)
- Eda Yildirim
- Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA
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19
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The WSTF-ISWI chromatin remodeling complex transiently associates with the human inactive X chromosome during late S-phase prior to BRCA1 and γ-H2AX. PLoS One 2012; 7:e50023. [PMID: 23166813 PMCID: PMC3498190 DOI: 10.1371/journal.pone.0050023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 10/16/2012] [Indexed: 01/08/2023] Open
Abstract
Replicating the genome prior to each somatic cell division not only requires precise duplication of the genetic information, but also accurately reestablishing the epigenetic signatures that instruct how the genetic material is to be interpreted in the daughter cells. The mammalian inactive X chromosome (Xi), which is faithfully inherited in a silent state in each daughter cell, provides an excellent model of epigenetic regulation. While much is known about the early stages of X chromosome inactivation, much less is understood with regards to retaining the Xi chromatin through somatic cell division. Here we report that the WSTF-ISWI chromatin remodeling complex (WICH) associates with the Xi during late S-phase as the Xi DNA is replicated. Elevated levels of WICH at the Xi is restricted to late S-phase and appears before BRCA1 and γ-H2A.X. The sequential appearance of WICH and BRCA1/γ-H2A.X implicate each as performing important but distinct roles in the maturation and maintenance of heterochromatin at the Xi.
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20
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Ellatif SKA, Gutschner T, Diederichs S. Long Noncoding RNA Function and Expression in Cancer. REGULATORY RNAS 2012:197-226. [DOI: 10.1007/978-3-642-22517-8_8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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21
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Ellatif SKA, Gutschner T, Diederichs S. Long Noncoding RNA Function and Expression in Cancer. REGULATORY RNAS 2012:197-226. [DOI: 10.1007/978-3-662-45801-3_8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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22
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Abstract
BACKGROUND X inactive-specific transcript (XIST) RNA is involved in X chromosome silencing in female cells and allows X chromosome equilibration with males. X inactive-specific transcript expression has been found to be dysregulated in a variety of human cancers when compared to normal cells; meanwhile, the inactivated X chromosome has been noted to be conspicuously absent in human cancer specimens, whereas X chromosome duplications are widely noted. The specific pathways whereby changes in X chromosome status and XIST expression occur in cancer remain incompletely described. Nevertheless, a role for XIST in BRCA1-mediated epigenetic activity has been proposed. METHODS Here we review the data regarding XIST expression and X chromosome status in a variety of female, male, and non-sex-related human cancers. CONCLUSIONS It is not yet known whether X chromosome duplication, XIST dysregulation, and over-expression of X-linked genes represent important factors in tumorgenesis or are simply a consequence of overall epigenetic instability in these cancers.
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23
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X-chromosome inactivation: molecular mechanisms from the human perspective. Hum Genet 2011; 130:175-85. [PMID: 21553122 DOI: 10.1007/s00439-011-0994-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Accepted: 04/15/2011] [Indexed: 10/18/2022]
Abstract
X-chromosome inactivation is an epigenetic process whereby one X chromosome is silenced in mammalian female cells. Since it was first proposed by Lyon in 1961, mouse models have been valuable tools to uncover the molecular mechanisms underlying X inactivation. However, there are also inherent differences between mouse and human X inactivation, ranging from sequence content of the X inactivation center to the phenotypic outcomes of X-chromosome abnormalities. X-linked gene dosage in males, females, and individuals with X aneuploidies and X/autosome translocations has demonstrated that many human genes escape X inactivation, implicating cis-regulatory elements in the spread of silencing. We discuss the potential nature of these elements and also review the elements in the X inactivation center involved in the early events in X-chromosome inactivation.
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24
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Sato K, Torimoto Y, Hosoki T, Ikuta K, Takahashi H, Yamamoto M, Ito S, Okamura N, Ichiki K, Tanaka H, Shindo M, Hirai K, Mizukami Y, Otake T, Fujiya M, Sasaki K, Kohgo Y. Loss of ABCB7 gene: pathogenesis of mitochondrial iron accumulation in erythroblasts in refractory anemia with ringed sideroblast with isodicentric (X)(q13). Int J Hematol 2011; 93:311-318. [PMID: 21380928 DOI: 10.1007/s12185-011-0786-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 02/08/2011] [Accepted: 02/09/2011] [Indexed: 11/28/2022]
Abstract
An isodicentric (X)(q13) (idicXq13) is a rare, acquired chromosomal abnormality originated by deletion of the long arm from Xq13 (Xq13-qter), and is found in female patients with hematological disorders involving increased ringed sideroblasts (RSs), which are characterized by mitochondrial iron accumulation around the erythroblast nucleus. The cause of increased RSs in idicXq13 patients is not fully understood. Here, we report the case of a 66-year-old female presenting with refractory anemia with ringed sideroblasts (RARS), and idicXq13 on G-banded analysis. We identify the loss of the ABCB7 (ATP-binding cassette subfamily B member-7) gene, which is located on Xq13 and is involved in mitochondrial iron transport to the cytosol, by fluorescent in situ hybridization (FISH) analysis and the decreased expression level of ABCB7 mRNA in the patient's bone marrow cells. Further FISH analyses showed that the ABCB7 gene is lost only on the active X-chromosome, not on the inactive one. We suggest that loss of ABCB7 due to deletion of Xq13-qter at idicXq13 formation may have contributed to the increased RSs in this patient. These findings suggest that loss of the ABCB7 gene may be a pathogenetic factor underlying mitochondrial iron accumulation in RARS patients with idicXq13.
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Affiliation(s)
- Kazuya Sato
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan.
| | - Yoshihiro Torimoto
- Oncology Center, Asahikawa Medical University Hospital, Asahikawa, Hokkaido, Japan
| | - Takaaki Hosoki
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
| | - Katsuya Ikuta
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
| | - Hiroyuki Takahashi
- Department of Medical Laboratory and Blood Center, Asahikawa Medical University Hospital, Asahikawa, Hokkaido, Japan
| | - Masayo Yamamoto
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
| | - Satoshi Ito
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
| | - Naoka Okamura
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
| | - Kazuhiko Ichiki
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
| | - Hiroki Tanaka
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
| | - Motohiro Shindo
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
| | | | - Yusuke Mizukami
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
| | - Takaaki Otake
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
| | - Mikihiro Fujiya
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
| | - Kastunori Sasaki
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
| | - Yutaka Kohgo
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2 jo 1 chome 1-1, Asahikawa, Hokkaido, 078-8510, Japan
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25
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Abstract
A simple model, termed "occlusis", is presented here to account for both cell fate restriction during somatic development and reestablishment of pluripotency during reproduction. The model makes three assertions: (1) A gene's transcriptional potential can assume one of two states: the "competent" state, wherein the gene is responsive to, and can be activated by, trans-acting factors in the cellular milieu, and the "occluded" state, wherein the gene is blocked by cis-acting, chromatin-based mechanisms from responding to trans-acting factors such that it remains silent irrespective of whether transcriptional activators are present in the milieu. (2) As differentiation proceeds in somatic lineages, lineage-inappropriate genes shift progressively and irreversibly from competent to occluded state, thereby leading to the restriction of cell fate. (3) During reproduction, global deocclusion takes place in the germline and/or early zygotic cells to reset the genome to the competent state in order to facilitate a new round of organismal development.
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Affiliation(s)
- Bruce T Lahn
- Department of Human Genetics, Howard Hughes Medical Institute, University of Chicago, Chicago, IL, USA.
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26
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Active chromatin marks are retained on X chromosomes lacking gene or repeat silencing despite XIST/Xist expression in somatic cell hybrids. PLoS One 2010; 5:e10787. [PMID: 20520737 PMCID: PMC2875404 DOI: 10.1371/journal.pone.0010787] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Accepted: 04/27/2010] [Indexed: 02/01/2023] Open
Abstract
Background X-chromosome inactivation occurs early in mammalian development and results in the inactive X chromosome acquiring numerous hallmarks of heterochromatin. While XIST is a key player in the inactivation process, the method of action of this ncRNA is yet to be determined. Methodology/Principal Findings To assess which features of heterochromatin may be directly recruited by the expression and localization of the XIST RNA we have analyzed a mouse/human somatic cell hybrid in which expression of human and mouse XIST/Xist has been induced from the active X by demethylation. Such hybrids had previously been demonstrated to disconnect XIST/Xist expression from gene silencing and we confirm maintenance of X-linked gene expression, even close to the Xist locus, despite the localized expression of mouse Xist. Conclusions/Significance Loss of the active chromatin marks H3 acetylation and H3 lysine 4 methylation was not observed upon XIST/Xist expression, nor was there a gain of DNA methylation; thus these marks of facultative heterochromatin are not solely dependent upon Xist expression. Cot-1 holes, regions of depleted RNA hybridization with a Cot-1 probe, were observed upon Xist expression; however, these were at reduced frequency and intensity in these somatic cells. Domains of human Cot-1 transcription were observed corresponding to the human chromosomes in the somatic cell hybrids. The Cot-1 domain of the X was not reduced with the expression of XIST, which fails to localize to the human X chromosome in a mouse somatic cell background. The human inactive X in a mouse/human hybrid cell also shows delocalized XIST expression and an ongoing Cot-1 domain, despite X-linked gene silencing. These results are consistent with recent reports separating Cot-1 silencing from genic silencing, but also demonstrate repetitive element expression from an otherwise silent X chromosome in these hybrid cells.
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27
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Paulsson K, Haferlach C, Fonatsch C, Hagemeijer A, Andersen MK, Slovak ML, Johansson B. The idic(X)(q13) in myeloid malignancies: breakpoint clustering in segmental duplications and association with TET2 mutations. Hum Mol Genet 2010; 19:1507-14. [DOI: 10.1093/hmg/ddq024] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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28
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Adeyinka A, Smoley S, Fink S, Sanchez J, Van Dyke DL, Dewald G. Isochromosome (X)(p10) in hematologic disorders: FISH study of 14 new cases show three types of centromere signal patterns. ACTA ACUST UNITED AC 2008; 179:25-30. [PMID: 17981211 DOI: 10.1016/j.cancergencyto.2007.07.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2007] [Revised: 07/06/2007] [Accepted: 07/11/2007] [Indexed: 10/22/2022]
Abstract
Though X chromosome anomalies are uncommon in hematologic malignancies, isodicentric X chromosomes, idic(X)(q13), with break and fusion points at Xq13 are well known among older females with de novo myelodysplasia. In contrast, only 17 patients with X isochromosomes involving break and fusion points at the centromere i(X)(p10) have been published, to our knowledge. We present 14 new patients with i(X)(p10) identified by G-banding and further characterized by fluorescence in situ hybridization (FISH) using probes for the X p-arm, X alpha-satellite DNA (DXZ1), and the XIST gene (Xq13). These anomalies each had an X p-arm probe signal on either side of a single centromeric FISH signal, thus they are monocentric isochromosomes. On the basis of FISH, the following three centromeric patterns were identified: (1) centromere signal same size as normal X, (2) centromere signal larger than normal X, and (3) centromere signal smaller than normal X. These centromere patterns may be related to the mechanism of i(X)(p10) formation. In 9 (64%) of 14 patients, the i(X)(p10) was the sole anomaly, attesting to its pathogenic potential. Our series, when collated with information on previously reported cases of i(X)(p10), show that this anomaly is associated with females with a median age 74 years, though patients from 3.75 to 49 years, including a 17-year-old in the present cohort, have been described. i(X)(p10) is observed in a wide range of hematologic malignancies, including myeloid and lymphoid disorders, as well as a patient with therapy-related AML in the present series. i(X)(p10) has been reported in occasional males, indicating that this anomaly can arise from active X chromosomes. It is not known whether i(X)(p10) arises randomly from the active or inactive X chromosome in female patients.
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Affiliation(s)
- Adewale Adeyinka
- Cytogenetics Laboratory, Department of Medical Genetics, Henry Ford Health System, 2799 West Grand Boulevard, Detroit, MI 48202, USA.
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29
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Chadwick BP, Lane TF. BRCA1 associates with the inactive X chromosome in late S-phase, coupled with transient H2AX phosphorylation. Chromosoma 2005; 114:432-9. [PMID: 16240122 DOI: 10.1007/s00412-005-0029-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2005] [Revised: 09/05/2005] [Accepted: 09/12/2005] [Indexed: 10/25/2022]
Abstract
The BRCA1 tumor suppressor gene encodes an E3-ubiquitin ligase that has been implicated in several distinct biochemical processes. As the cell cycle progresses, BRCA1 proteins interact transiently with nuclear foci containing DNA replication and DNA double-strand repair machinery. A hallmark of these foci is the presence of S139 phosphorylated histone H2AX. BRCA1 was recently shown to associate with facultative heterochromatin at the inactive X chromosome (Xi), where it may play a role in maintaining gene silencing. As the kinetics of this interaction has not been described, we sought to establish whether association of BRCA1 with the Xi also correlated with replication. Here we demonstrate that the interaction of BRCA1 and the Xi is transient, occurring during late S-phase. This interaction is concomitant with the presence of distinct foci of S139 phospho-H2AX and specifically corresponds with late replication of the Xi. BRCA1 and phospho-H2AX appear on the Xi immediately adjacent to CAF-1, a known marker of replication fork activity. Taken together, these data implicate BRCA1 and the H2AX kinase in replication of facultative heterochromatin on the Xi, most likely in a fashion similar to that performed at sites of DNA replication and double-strand break repair observed on somatic chromosomes.
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Affiliation(s)
- Brian P Chadwick
- Department of Cell Biology, Duke University Medical Center & Institute for Genome Science and Policy, Durham, NC 27710, USA.
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30
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Chadwick BP, Willard HF. Multiple spatially distinct types of facultative heterochromatin on the human inactive X chromosome. Proc Natl Acad Sci U S A 2004; 101:17450-5. [PMID: 15574503 PMCID: PMC534659 DOI: 10.1073/pnas.0408021101] [Citation(s) in RCA: 176] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2004] [Indexed: 11/18/2022] Open
Abstract
Heterochromatin is defined classically by condensation throughout the cell cycle, replication in late S phase and gene inactivity. Facultative heterochromatin is of particular interest, because its formation is developmentally regulated as a result of cellular differentiation. The most extensive example of facultative heterochromatin is the mammalian inactive X chromosome (Xi). A variety of histone variants and covalent histone modifications have been implicated in defining the organization of the Xi heterochromatic state, and the features of Xi heterochromatin have been widely interpreted as reflecting a redundant system of gene silencing. However, here we demonstrate that the human Xi is packaged into at least two nonoverlapping heterochromatin types, each characterized by specific Xi features: one defined by the presence of Xi-specific transcript RNA, the histone variant macroH2A, and histone H3 trimethylated at lysine 27 and the other defined by H3 trimethylated at lysine 9, heterochromatin protein 1, and histone H4 trimethylated at lysine 20. Furthermore, regions of the Xi packaged in different heterochromatin types are characterized by different patterns of replication in late S phase. The arrangement of facultative heterochromatin into spatially and temporally distinct domains has implications for both the establishment and maintenance of the Xi and adds a previously unsuspected degree of epigenetic complexity.
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Affiliation(s)
- Brian P Chadwick
- Institute for Genome Sciences and Policy, Department of Molecular Genetics and Microbiology, Duke University, Durham, NC 27708, USA
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31
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Chadwick BP, Willard HF. Barring gene expression after XIST: maintaining facultative heterochromatin on the inactive X. Semin Cell Dev Biol 2003; 14:359-67. [PMID: 15015743 DOI: 10.1016/j.semcdb.2003.09.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
X chromosome inactivation refers to the developmentally regulated process of silencing gene expression from all but one X chromosome per cell in female mammals in order to equalize the levels of X chromosome derived gene expression between the sexes. While much attention has focused on the genetic and epigenetic events early in development that initiate the inactivation process, it is also important to understand the events that ensure maintenance of the inactive state through subsequent cell divisions. Gene silencing at the inactive X chromosome is irreversible in somatic cells and is achieved through the formation of facultative heterochromatin (visible as the Barr body) that is remarkably stable and faithfully preserved. Here we review the many features of inactive X chromatin in terminally differentiated cells and address the highly redundant mechanisms of maintaining the inactive X chromatin.
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Affiliation(s)
- Brian P Chadwick
- Department of Molecular Genetics & Microbiology, Institute for Genome Sciences and Policy, 103 Research Drive, Box 3382, Duke University Medical Center Durham, NC 27710, USA.
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32
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Abstract
Dosage compensation in mammals is achieved by the transcriptional inactivation of one X chromosome in female cells. From the time X chromosome inactivation was initially described, it was clear that several mechanisms must be precisely integrated to achieve correct regulation of this complex process. X-inactivation appears to be triggered upon differentiation, suggesting its regulation by developmental cues. Whereas any number of X chromosomes greater than one is silenced, only one X chromosome remains active. Silencing on the inactive X chromosome coincides with the acquisition of a multitude of chromatin modifications, resulting in the formation of extraordinarily stable facultative heterochromatin that is faithfully propagated through subsequent cell divisions. The integration of all these processes requires a region of the X chromosome known as the X-inactivation center, which contains the Xist gene and its cis-regulatory elements. Xist encodes an RNA molecule that plays critical roles in the choice of which X chromosome remains active, and in the initial spread and establishment of silencing on the inactive X chromosome. We are now on the threshold of discovering the factors that regulate and interact with Xist to control X-inactivation, and closer to an understanding of the molecular mechanisms that underlie this complex process.
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Affiliation(s)
- Kathrin Plath
- Department of Biochemistry & Biophysics, University of California San Francisco, San Francisco, California 94143, USA.
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33
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Gray BA, Cornfield D, Bent-Williams A, Zori RT. Translocation (X;20)(q13.1;q13.3) as a primary chromosomal finding in two patients with myelocytic disorders. CANCER GENETICS AND CYTOGENETICS 2003; 141:169-74. [PMID: 12606138 DOI: 10.1016/s0165-4608(02)00764-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Reports of X chromosome translocations, as primary chromosomal changes associated with hematologic disorders, remain relatively uncommon. Herein, we report the detection, by conventional cytogenetic methods, of a cytogenetically identical t(X;20) in two different patients with hematologic disorders (probable myelodysplasia and polycythemia vera/acute myelocytic leukemia). In both cases, this translocation appeared as the primary clonal chromosome abnormality, with breakpoints occurring in the long arms of both the X chromosome and chromosome 20 (Xq13.1 and 20q13.3, respectively). Further characterization and comparison of the translocation chromosome products of these two cases by use of fluorescence in situ hybridization techniques is also described. Similar previously reported cytogenetically cases and the potential that this specific rearrangement may represent a nonrandom chromosomal finding are discussed.
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Affiliation(s)
- Brian A Gray
- Department of Pediatrics, College of Medicine, University of Florida, Gainesville, FL, USA
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34
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Chadwick BP, Valley CM, Willard HF. Histone variant macroH2A contains two distinct macrochromatin domains capable of directing macroH2A to the inactive X chromosome. Nucleic Acids Res 2001; 29:2699-705. [PMID: 11433014 PMCID: PMC55781 DOI: 10.1093/nar/29.13.2699] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Chromatin on the inactive X chromosome (Xi) of female mammals is enriched for the histone variant macroH2A that can be detected at interphase as a distinct nuclear structure referred to as a macro chromatin body (MCB). Green fluorescent protein-tagged and Myc epitope-tagged macroH2A readily form an MCB in the nuclei of transfected female, but not male, cells. Using targeted disruptions, we have identified two macrochromatin domains within macroH2A that are independently capable of MCB formation and association with the Xi. Complete removal of the non-histone C-terminal tail does not reduce the efficiency of association of the variant histone domain of macroH2A with the Xi, indicating that the histone portion alone can target the Xi. The non-histone domain by itself is incapable of MCB formation. However, when directed to the nucleosome by fusion to core histone H2A or H2B, the non-histone tail forms an MCB that appears identical to that of the endogenous protein. Mutagenesis of the non-histone portion of macroH2A localized the region required for MCB formation and targeting to the Xi to an approximately 190 amino acid region.
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Affiliation(s)
- B P Chadwick
- Department of Genetics, Case Western Reserve University School of Medicine and Center for Human Genetics and Research Institute, University Hospitals of Cleveland, 10900 Euclid Avenue, Cleveland, OH 44106-4955, USA
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35
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Csankovszki G, Nagy A, Jaenisch R. Synergism of Xist RNA, DNA methylation, and histone hypoacetylation in maintaining X chromosome inactivation. J Cell Biol 2001; 153:773-84. [PMID: 11352938 PMCID: PMC2192370 DOI: 10.1083/jcb.153.4.773] [Citation(s) in RCA: 368] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2001] [Accepted: 04/02/2001] [Indexed: 12/01/2022] Open
Abstract
Xist RNA expression, methylation of CpG islands, and hypoacetylation of histone H4 are distinguishing features of inactive X chromatin. Here, we show that these silencing mechanisms act synergistically to maintain the inactive state. Xist RNA has been shown to be essential for initiation of X inactivation, but not required for maintenance. We have developed a system in which the reactivation frequency of individual X-linked genes can be assessed quantitatively. Using a conditional mutant Xist allele, we provide direct evidence for that loss of Xist RNA destabilizes the inactive state in somatic cells, leading to an increased reactivation frequency of an X-linked GFP transgene and of the endogenous hypoxanthine phosphoribosyl transferase (Hprt) gene in mouse embryonic fibroblasts. Demethylation of DNA, using 5-azadC or by introducing a mutation in Dnmt1, and inhibition of histone hypoacetylation using trichostatin A further increases reactivation in Xist mutant fibroblasts, indicating a synergistic interaction of X chromosome silencing mechanisms.
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Affiliation(s)
- Györgyi Csankovszki
- Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142
| | - András Nagy
- Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Rudolf Jaenisch
- Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142
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Chadwick BP, Willard HF. A novel chromatin protein, distantly related to histone H2A, is largely excluded from the inactive X chromosome. J Cell Biol 2001; 152:375-84. [PMID: 11266453 PMCID: PMC2199617 DOI: 10.1083/jcb.152.2.375] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Chromatin on the mammalian inactive X chromosome differs in a number of ways from that on the active X. One protein, macroH2A, whose amino terminus is closely related to histone H2A, is enriched on the heterochromatic inactive X chromosome in female cells. Here, we report the identification and localization of a novel and more distant histone variant, designated H2A-Bbd, that is only 48% identical to histone H2A. In both interphase and metaphase female cells, using either a myc epitope-tagged or green fluorescent protein-tagged H2A-Bbd construct, the inactive X chromosome is markedly deficient in H2A-Bbd staining, while the active X and the autosomes stain throughout. In double-labeling experiments, antibodies to acetylated histone H4 show a pattern of staining indistinguishable from H2A-Bbd in interphase nuclei and on metaphase chromosomes. Chromatin fractionation demonstrates association of H2A-Bbd with the histone proteins. Separation of micrococcal nuclease-digested chromatin by sucrose gradient ultracentrifugation shows cofractionation of H2A-Bbd with nucleosomes, supporting the idea that H2A-Bbd is incorporated into nucleosomes as a substitute for the core histone H2A. This finding, in combination with the overlap with acetylated forms of H4, raises the possibility that H2A-Bbd is enriched in nucleosomes associated with transcriptionally active regions of the genome. The distribution of H2A-Bbd thus distinguishes chromatin on the active and inactive X chromosomes.
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Affiliation(s)
- Brian P. Chadwick
- Department of Genetics, Case Western Reserve University School of Medicine and Center for Human Genetics and Research Institute, University Hospitals of Cleveland, Cleveland, Ohio 44106-4955
| | - Huntington F. Willard
- Department of Genetics, Case Western Reserve University School of Medicine and Center for Human Genetics and Research Institute, University Hospitals of Cleveland, Cleveland, Ohio 44106-4955
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37
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Abstract
A hypothesis explaining the known heterochromatin features--a compact DNA packaging, transcriptional inactivity, propensity to aggregate (stickiness) and position effect variegation-is described. The hypothesis is based on the assumption that DNA molecules in heterochromatin are topologically open and contain single-strand breaks in the regions with identical or similar primary sequences.
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Affiliation(s)
- A D Gruzdev
- Siberian Branch of the Russian Academy of Sciences, Institute of Cytology and Genetics, Novosibirsk, 630090, Russia.
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38
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Brown CJ, Robinson WP. The causes and consequences of random and non-random X chromosome inactivation in humans. Clin Genet 2000; 58:353-63. [PMID: 11140834 DOI: 10.1034/j.1399-0004.2000.580504.x] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
X chromosome (X) inactivation is a remarkable biological process including the choice and cis-limited inactivation of one X, as well as the stable maintenance of this silencing by epigenetic chromatin alterations. The process results in females generally being mosaic for two populations of cells--one with each parental X active. In this review, we discuss recent advances in our understanding of how inactivation works, as well as the causes and clinical implications of deviations from random inactivation.
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Affiliation(s)
- C J Brown
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada.
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39
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Rasmussen TP, Mastrangelo MA, Eden A, Pehrson JR, Jaenisch R. Dynamic relocalization of histone MacroH2A1 from centrosomes to inactive X chromosomes during X inactivation. J Cell Biol 2000; 150:1189-98. [PMID: 10974005 PMCID: PMC2175247 DOI: 10.1083/jcb.150.5.1189] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Histone variant macroH2A1 (macroH2A1) contains an NH(2)-terminal domain that is highly similar to core histone H2A and a larger COOH-terminal domain of unknown function. MacroH2A1 is expressed at similar levels in male and female embryonic stem (ES) cells and adult tissues, but a portion of total macroH2A1 protein localizes to the inactive X chromosomes (Xi) of differentiated female cells in concentrations called macrochromatin bodies. Here, we show that centrosomes of undifferentiated male and female ES cells harbor a substantial store of macroH2A1 as a nonchromatin-associated pool. Greater than 95% of centrosomes from undifferentiated ES cells contain macroH2A1. Cell fractionation experiments confirmed that macroH2A1 resides at a pericentrosomal location in close proximity to the known centrosomal proteins gamma-tubulin and Skp1. Retention of macroH2A1 at centrosomes was partially labile in the presence of nocodazole suggesting that intact microtubules are necessary for accumulation of macroH2A1 at centrosomes. Upon differentiation of female ES cells, Xist RNA expression became upregulated and monoallelic as judged by fluorescent in situ hybridization, but early Xist signals lacked associated macroH2A1. Xi acquired macroH2A1 soon thereafter as indicated by the colocalization of Xist RNA and macroH2A1. Accumulation of macroH2A1 on X chromosomes occurred with a corresponding loss of centrosomal macroH2A1. Our results define a sequence for the loading of macroH2A1 on the Xi and place this event in the context of differentiation and Xist expression. Furthermore, these results suggest a role for the centrosome in the X inactivation process.
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Affiliation(s)
| | | | - Amir Eden
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142
| | - John R. Pehrson
- University of Pennsylvania Veterinary School, Philadelphia, Pennsylvania 19104-6048
| | - Rudolf Jaenisch
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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40
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Van den Wyngaert I, de Vries W, Kremer A, Neefs J, Verhasselt P, Luyten WH, Kass SU. Cloning and characterization of human histone deacetylase 8. FEBS Lett 2000; 478:77-83. [PMID: 10922473 DOI: 10.1016/s0014-5793(00)01813-5] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
To date, seven different human histone deacetylases (HDACs) have been identified, which fall into two distinct classes. We have isolated and characterized a cDNA encoding a novel human HDAC, which we name HDAC8. HDAC8 shows a high degree of sequence similarity to HDAC1 and HDAC2 and thus belongs to the class I of HDACs. HDAC8 is expressed in a variety of tissues. Human cells overexpressing HDAC8 localize the protein in sub-nuclear compartments whereas HDAC1 shows an even nuclear distribution. In addition, the HDAC8 gene is localized on the X chromosome at position q13, which is close to the XIST gene and chromosomal breakpoints associated with preleukemia.
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Affiliation(s)
- I Van den Wyngaert
- Department of Advanced Bio-Technologies, Jansen Research Foundation, Turnhoutseweg 30, 2340 Beerse, Belgium
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41
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McDonell N, Ramser J, Francis F, Vinet MC, Rider S, Sudbrak R, Riesselman L, Yaspo ML, Reinhardt R, Monaco AP, Ross F, Kahn A, Kearney L, Buckle V, Chelly J. Characterization of a highly complex region in Xq13 and mapping of three isodicentric breakpoints associated with preleukemia. Genomics 2000; 64:221-9. [PMID: 10756090 DOI: 10.1006/geno.2000.6128] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The chromosomal abnormality represented by an isodicentric X chromosome [idic(X)(q13)] is associated with a subset of acute myeloid leukemia (AML) and preleukemia observed in elderly females. A previous study localized the breakpoints of two acquired isodicentric X chromosomes associated with myelodysplasia to a 450-kb region proximal to the XIST gene. Here we report the construction and extensive characterization of a reliable 1-Mb P1 artificial chromosome and bacterial artificial chromosome contig covering a highly problematic region in Xq13 that includes the previously described isodicentric breakpoint region. In addition to mapping of the brain-specific gene (NAP1L2) and the phosphoglyceryl kinase alpha subunit 1 gene (PHKA1) and generation and mapping of a large number of STSs throughout the contig, we have mapped a putative transcriptional regulatory protein (HDACL1), and 35 ESTs. Sequencing data, Southern blot analysis, and fiber-FISH analysis have permitted characterization of extensive region-specific duplications and triplications in addition to an unusually high concentration of long interspersed repeat elements, both of which could be implicated in isodicentric chromosome formation and other Xq13 chromosome aberrations. FISH analysis of metaphase chromosomes from two previously unpublished AML patients and one preleukemic patient using cosmid clones and selected subclones allowed mapping of the idic(X)(q13) breakpoints to a 100-kb interval, consistent with the involvement of an X-linked gene in the genesis of this form of preleukemia, disruption of which may represent a preliminary step in progression to AML. Assembly and physical mapping of this complex 1-Mb contig establish a foundation for ongoing sequencing and gene identification projects in the region.
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Affiliation(s)
- N McDonell
- Institut Cochin de Génétique Moléculaire, INSERM Unité 129, CHU Cochin-Port-Royal, 24 Rue du Faubourg Saint Jacques, Paris, 75014, France
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42
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Mermoud JE, Costanzi C, Pehrson JR, Brockdorff N. Histone macroH2A1.2 relocates to the inactive X chromosome after initiation and propagation of X-inactivation. J Cell Biol 1999; 147:1399-408. [PMID: 10613899 PMCID: PMC2174253 DOI: 10.1083/jcb.147.7.1399] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The histone macroH2A1.2 has been implicated in X chromosome inactivation on the basis of its accumulation on the inactive X chromosome (Xi) of adult female mammals. We have established the timing of macroH2A1.2 association with the Xi relative to the onset of X-inactivation in differentiating murine embryonic stem (ES) cells using immuno-RNA fluorescence in situ hybridization (FISH). Before X-inactivation we observe a single macroH2A1.2-dense region in both undifferentiated XX and XY ES cells that does not colocalize with X inactive specific transcript (Xist) RNA, and thus appears not to associate with the X chromosome(s). This pattern persists through early stages of differentiation, up to day 7. Then the frequency of XY cells containing a macroH2A1.2-rich domain declines. In contrast, in XX cells there is a striking relocalization of macroH2A1.2 to the Xi. Relocalization occurs in a highly synchronized wave over a 2-d period, indicating a precisely regulated association. The timing of macroH2A1.2 accumulation on the Xi suggests it is not necessary for the initiation or propagation of random X-inactivation.
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Affiliation(s)
- J E Mermoud
- X-Inactivation Group, Medical Research Council Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital, London W12 0NN, United Kingdom.
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43
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Csankovszki G, Panning B, Bates B, Pehrson JR, Jaenisch R. Conditional deletion of Xist disrupts histone macroH2A localization but not maintenance of X inactivation. Nat Genet 1999; 22:323-4. [PMID: 10431231 DOI: 10.1038/11887] [Citation(s) in RCA: 294] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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44
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Affiliation(s)
- M F Lyon
- Medical Research Council, Mammalian Genetics Unit, Harwell, Didcot, Oxon, UK
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45
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Clemson CM, Chow JC, Brown CJ, Lawrence JB. Stabilization and localization of Xist RNA are controlled by separate mechanisms and are not sufficient for X inactivation. J Cell Biol 1998; 142:13-23. [PMID: 9660859 PMCID: PMC2133021 DOI: 10.1083/jcb.142.1.13] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/1997] [Revised: 05/04/1998] [Indexed: 02/08/2023] Open
Abstract
These studies address whether XIST RNA is properly localized to the X chromosome in somatic cells where human XIST expression is reactivated, but fails to result in X inactivation (Tinker, A.V., and C.J. Brown. 1998. Nucl. Acids Res. 26:2935-2940). Despite a nuclear RNA accumulation of normal abundance and stability, XIST RNA does not localize in reactivants or in naturally inactive human X chromosomes in mouse/ human hybrid cells. The XIST transcripts are fully stabilized despite their inability to localize, and hence XIST RNA localization can be uncoupled from stabilization, indicating that these are separate steps controlled by distinct mechanisms. Mouse Xist RNA tightly localized to an active X chromosome, demonstrating for the first time that the active X chromosome in somatic cells is competent to associate with Xist RNA. These results imply that species-specific factors, present even in mature, somatic cells that do not normally express Xist, are necessary for localization. When Xist RNA is properly localized to an active mouse X chromosome, X inactivation does not result. Therefore, there is not a strict correlation between Xist localization and chromatin inactivation. Moreover, expression, stabilization, and localization of Xist RNA are not sufficient for X inactivation. We hypothesize that chromosomal association of XIST RNA may initiate subsequent developmental events required to enact transcriptional silencing.
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Affiliation(s)
- C M Clemson
- Department of Cell Biology, University of Massachusetts Medical Center, Worcester, Massachusetts 01655, USA.
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46
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47
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Tinker AV, Brown CJ. Induction of XIST expression from the human active X chromosome in mouse/human somatic cell hybrids by DNA demethylation. Nucleic Acids Res 1998; 26:2935-40. [PMID: 9611238 PMCID: PMC147638 DOI: 10.1093/nar/26.12.2935] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
X chromosome inactivation occurs early in mammalian development to transcriptionally silence one of the pair of X chromosomes in females. The XIST RNA, a large untranslated RNA that is expressed solely from the inactive X chromosome, is implicated in the process of inactivation. As previous studies have shown that the XIST gene is methylated on the active X chromosome, we have treated a mouse/human somatic cell hybrid retaining an active human X chromosome with demethylating agents to determine whether expression of the human XIST gene could be induced. Stable expression of XIST was observed after several rounds of demethylation and stability of XIST expression correlated with the loss of methylation at the three sites analysed. We conclude that methylation is sufficient to inhibit expression of the XIST gene in somatic cell hybrids. No loss of expression was detected for eight other X-linked genes from the active X chromosome that was expressing XIST , suggesting that additional developmental or species-specific factors are required for the inactivation process.
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Affiliation(s)
- A V Tinker
- Department of Medical Genetics, University of British Columbia, 6174 University Boulevard, Vancouver, BC V6T 1Z3, Canada
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48
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Goto T, Monk M. Regulation of X-chromosome inactivation in development in mice and humans. Microbiol Mol Biol Rev 1998; 62:362-78. [PMID: 9618446 PMCID: PMC98919 DOI: 10.1128/mmbr.62.2.362-378.1998] [Citation(s) in RCA: 202] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Dosage compensation for X-linked genes in mammals is accomplished by inactivating one of the two X chromosomes in females. X-chromosome inactivation (XCI) occurs during development, coupled with cell differentiation. In somatic cells, XCI is random, whereas in extraembryonic tissues, XCI is imprinted in that the paternally inherited X chromosome is preferentially inactivated. Inactivation is initiated from an X-linked locus, the X-inactivation center (Xic), and inactivity spreads along the chromosome toward both ends. XCI is established by complex mechanisms, including DNA methylation, heterochromatinization, and late replication. Once established, inactivity is stably maintained in subsequent cell generations. The function of an X-linked regulatory gene, Xist, is critically involved in XCI. The Xist gene maps to the Xic, it is transcribed only from the inactive X chromosome, and the Xist RNA associates with the inactive X chromosome in the nucleus. Investigations with Xist-containing transgenes and with deletions of the Xist gene have shown that the Xist gene is required in cis for XCI. Regulation of XCI is therefore accomplished through regulation of Xist. Transcription of the Xist gene is itself regulated by DNA methylation. Hence, the differential methylation of the Xist gene observed in sperm and eggs and its recognition by protein binding constitute the most likely mechanism regulating imprinted preferential expression of the paternal allele in preimplantation embryos and imprinted paternal XCI in extraembryonic tissues. This article reviews the mechanisms underlying XCI and recent advances elucidating the functions of the Xist gene in mice and humans.
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Affiliation(s)
- T Goto
- Molecular Embryology Unit, Institute of Child Health, London WC1N 1EH, United Kingdom.
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49
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Abstract
X inactivation acts in female mammals to equalise X-linked gene dosage between XX females and XY males. X inactivation is controlled by a single X-linked cis-acting locus called the X inactivation centre (Xic). In 1991 the Xist gene was identified as a candidate for the Xic. Xist is expressed in all adult female tissues, but only from the allele on the inactive X. The Xist transcript does not encode a protein but remains sequestered within the nucleus and co-localises with the inactive X chromosome. Transgenic and knockout studies have shown that a genomic region covering only a few kilobases either side of Xist carries all of the functions attributed to the Xic. The major questions currently occupying researchers studying X inactivation are: how do cells count their number of X chromosomes to determine whether X inactivation is necessary, and how does the Xist transcript inactivate all genes on the X chromosome?
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Affiliation(s)
- G F Kay
- Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Australia.
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50
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Hansen RS, Canfield TK, Stanek AM, Keitges EA, Gartler SM. Reactivation of XIST in normal fibroblasts and a somatic cell hybrid: abnormal localization of XIST RNA in hybrid cells. Proc Natl Acad Sci U S A 1998; 95:5133-8. [PMID: 9560241 PMCID: PMC20226 DOI: 10.1073/pnas.95.9.5133] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The XIST gene, expressed only from the inactive X chromosome, is a critical component of X inactivation. Although apparently unnecessary for maintenance of inactivation, XIST expression is thought to be sufficient for inactivation of genes in cis even when XIST is located abnormally on another chromosome. This repression appears to involve the association of XIST RNA with the chromosome from which it is expressed. Reactivated genes on the inactive X chromosome, however, maintain expression in several somatic cell hybrid lines with stable expression of XIST. We describe here another example of an XIST-expressing human-hamster hybrid that lacks X-linked gene repression in which the human XIST gene present on an active X chromosome was reactivated by treatment with 5-aza-2'-deoxycytidine. These data raise the possibility that human XIST RNA does not function properly in human-rodent somatic cell hybrids. As part of our approach to address this question, we reactivated the XIST gene in normal male fibroblasts and then compared their patterns of XIST RNA localization by subcellular fractionation and in situ hybridization with those of hybrid cells. Although XIST RNA is nuclear in all cell types, we found that the in situ signals are much more diffuse in hybrids than in human cells. These data suggest that hybrids lack components needed for XIST localization and, presumably, XIST-mediated gene repression.
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Affiliation(s)
- R S Hansen
- Department of Medicine, University of Washington, Seattle, WA 98195, USA
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