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Go KO, Kim YZ. Brain Invasion and Trends in Molecular Research on Meningioma. Brain Tumor Res Treat 2023; 11:47-58. [PMID: 36762808 PMCID: PMC9911709 DOI: 10.14791/btrt.2022.0044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Revised: 01/06/2023] [Accepted: 01/09/2023] [Indexed: 02/05/2023] Open
Abstract
Meningiomas are the most common primary brain tumors in adults. The treatment of non-benign meningiomas remains a challenging task, and after the publication of the 2021 World Health Organization classification, the importance of molecular biological classification is emerging. In this article, we introduce the mechanisms of brain invasion in atypical meningioma and review the genetic factors involved along with epigenetic regulation. First, it is important to understand the three major steps for brain invasion of meningeal cells: 1) degradation of extracellular matrix by proteases, 2) promotion of tumor cell migration to resident cells by adhesion molecules, and 3) neovascularization and supporting cells by growth factors. Second, the genomic landscape of meningiomas should be analyzed by major categories, such as germline mutations in NF2 and somatic mutations in non-NF2 genes (TRAF7, KLF4, AKT1, SMO, and POLR2A). Finally, epigenetic alterations in meningiomas are being studied, with a focus on DNA methylation, histone modification, and RNA interference. Increasing knowledge of the molecular landscape of meningiomas has allowed the identification of prognostic and predictive markers that can guide therapeutic decision-making processes and the timing of follow-up.
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Affiliation(s)
- Kyeong-O Go
- Department of Neurosurgery, Gyeongsang National University Hospital, Gyeongsang National University College of Medicine, Jinju, Korea
| | - Young Zoon Kim
- Division of Neuro Oncology and Department of Neurosurgery, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea.
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2
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Libertini G, Corbi G, Shubernetskaya O, Ferrara N. Is Human Aging a Form of Phenoptosis? BIOCHEMISTRY. BIOKHIMIIA 2022; 87:1446-1464. [PMID: 36717439 DOI: 10.1134/s0006297922120033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
A much debated question is whether aging is the cumulative consequence of degenerative factors insufficiently opposed by natural selection, or, on the contrary, an ordered process, genetically determined and regulated, modeled by natural selection, and for which the definition of phenoptotic phenomenon would be entirely appropriate. In this review, theoretical arguments and empirical data about the two hypotheses are exposed, with more evidence in support of the thesis of aging as a form of phenoptosis. However, as the thesis of aging as an adaptive and programmed phenomenon necessarily requires the existence of specific mechanisms that determine to age, such as the subtelomere-telomere theory proposed for this purpose, the evidence supporting the mechanisms described by this theory is reported. In particular, it is highlighted that the recent interpretation of the role of TERRA sequences in the context of subtelomere-telomere theory is a fundamental point in supporting the hypothesized mechanisms. Furthermore, some characteristics of the mechanisms proposed by the theory, such as epigenetic modifications in aging, gradual cell senescence, cell senescence, limits in cell duplications, and fixed size of the telomeric heterochromatin hood, are exposed in their compatibility with both the thesis of aging as phenoptotic phenomenon and the opposite thesis. In short, aging as a form of phenoptosis appears a scientifically sound hypothesis while the opposite thesis should clarify the meaning of various phenomena that appear to invalidate it.
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Affiliation(s)
- Giacinto Libertini
- Italian Society for Evolutionary Biology (SIBE), Asti, 14100, Italy. .,Department of Translational Medical Sciences, Federico II University of Naples, Naples, 80131, Italy
| | - Graziamaria Corbi
- Department of Medicine and Health Sciences, University of Molise, Campobasso, 86100, Italy. .,Italian Society of Gerontology and Geriatrics (SIGG), Firenze, 50129, Italy
| | - Olga Shubernetskaya
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, 117997, Russia.
| | - Nicola Ferrara
- Department of Translational Medical Sciences, Federico II University of Naples, Naples, 80131, Italy. .,Istituti Clinici Scientifici Maugeri SPA - Società Benefit, IRCCS, Telese Terme, BN, 82037, Italy
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3
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Bauer M, Payer B, Filion GJ. Causality in transcription and genome folding: Insights from X inactivation. Bioessays 2022; 44:e2200105. [PMID: 36028473 DOI: 10.1002/bies.202200105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 08/11/2022] [Accepted: 08/14/2022] [Indexed: 11/10/2022]
Abstract
The spatial organization of genomes is becoming increasingly understood. In mammals, where it is most investigated, this organization ties in with transcription, so an important research objective is to understand whether gene activity is a cause or a consequence of genome folding in space. In this regard, the phenomena of X-chromosome inactivation and reactivation open a unique window of investigation because of the singularities of the inactive X chromosome. Here we focus on the cause-consequence nexus between genome conformation and transcription and explain how recent results about the structural changes associated with inactivation and reactivation of the X chromosome shed light on this problem.
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Affiliation(s)
- Moritz Bauer
- Oncode Institute, Hubrecht Institute-KNAW and University Medical Center Utrecht, Utrecht, The Netherlands
| | - Bernhard Payer
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain.,Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Guillaume J Filion
- Dept. Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada
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Libertini G, Shubernetskaya O, Corbi G, Ferrara N. Is Evidence Supporting the Subtelomere-Telomere Theory of Aging? BIOCHEMISTRY. BIOKHIMIIA 2021; 86:1526-1539. [PMID: 34937532 DOI: 10.1134/s0006297921120026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The telomere theory tries to explain cellular mechanisms of aging as mainly caused by telomere shortening at each duplication. The subtelomere-telomere theory overcomes various shortcomings of telomere theory by highlighting the essential role of subtelomeric DNA in aging mechanisms. The present work illustrates and deepens the correspondence between assumptions and implications of subtelomere-telomere theory and experimental results. In particular, it is investigated the evidence regarding the relationships between aging and (i) epigenetic modifications; (ii) oxidation and inflammation; (iii) telomere protection; (iv) telomeric heterochromatin hood; (v) gradual cell senescence; (vi) cell senescence; and (vii) organism decline with telomere shortening. The evidence appears broadly in accordance or at least compatible with the description and implications of the subtelomere-telomere theory. In short, phenomena of cellular aging, by which the senescence of the whole organism is determined in various ways, appear substantially dependent on epigenetic modifications regulated by the subtelomere-telomere-telomeric hood-telomerase system. These phenomena appear to be not random, inevitable, and irreversible but rather induced and regulated by genetically determined mechanisms, and modifiable and reversible by appropriate methods. All this supports the thesis that aging is a genetically programmed and regulated phenoptotic phenomenon and is against the opposite thesis of aging as caused by random and inevitable degenerative factors.
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Affiliation(s)
- Giacinto Libertini
- Member of the Italian Society for Evolutionary Biology (SIBE), Asti, 14100, Italy. .,Department of Translational Medical Sciences, Federico II University of Naples, Naples, 80131, Italy
| | - Olga Shubernetskaya
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, 117997, Russia.
| | - Graziamaria Corbi
- Department of Medicine and Health Sciences, University of Molise, Campobasso, 86100, Italy. .,Italian Society of Gerontology and Geriatrics (SIGG), Firenze, 50129, Italy
| | - Nicola Ferrara
- Department of Translational Medical Sciences, Federico II University of Naples, Naples, 80131, Italy. .,Istituti Clinici Scientifici Maugeri SPA - Società Benefit, IRCCS, Telese Terme, BN, 82037, Italy
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5
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Gao Y, Wang X, Li S, Zhang Z, Li X, Lin F. Identification of a DNA Methylation-Based Prognostic Signature for Patients with Triple-Negative Breast Cancer. Med Sci Monit 2021; 27:e930025. [PMID: 34003815 PMCID: PMC8140526 DOI: 10.12659/msm.930025] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Aberrant DNA methylation is an important biological regulatory mechanism in malignant tumors. However, it remains underutilized for establishing prognostic models for triple-negative breast cancer (TNBC). MATERIAL AND METHODS Methylation data and expression data downloaded from The Cancer Genome Atlas (TCGA) were used to identify differentially methylated sites (DMSs). The prognosis-related DMSs were selected by univariate Cox regression analysis. Functional enrichment was analyzed using DAVID. A protein-protein interaction (PPI) network was constructed using STRING. Finally, a methylation-based prognostic signature was constructed using LASSO method and further validated in 2 validation cohorts. RESULTS Firstly, we identified 743 DMSs corresponding to 332 genes, including 357 hypermethylated sites and 386 hypomethylated sites. Furthermore, we selected 103 prognosis-related DMSs by univariate Cox regression. Using a LASSO algorithm, we established a 5-DMSs prognostic signature in TCGA-TNBC cohort, which could classify TNBC patients with significant survival difference (log-rank p=4.97E-03). Patients in the high-risk group had shorter overall survival than patients in the low-risk group. The excellent performance was validated in GSE78754 (HR=2.42, 95%CI: 1.27-4.59, log-rank P=0.0055). Moreover, for disease-free survival, the prognostic performance was verified in GSE141441 (HR=2.09, 95%CI: 1.28-3.44, log-rank P=0.0027). Multivariate Cox regression analysis indicated that the 5-DMSs signature could serve as an independent risk factor. CONCLUSIONS We constructed a 5-DMSs signature with excellent performance for the prediction of disease-free survival and overall survival, providing a guide for clinicians in directing personalized therapeutic regimen selection of TNBC patients.
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Affiliation(s)
- Yinqi Gao
- Department of Breast Surgery, Capital Medical University Electric Power Teaching Hospital, Beijing, China (mainland)
| | - Xuelong Wang
- Department of Thoracic Surgery, Capital Medical University Electric Power Teaching Hospital, Beijing, China (mainland)
| | - Shihui Li
- Department of Breast Surgery, Capital Medical University Electric Power Teaching Hospital, Beijing, China (mainland)
| | - Zhiqiang Zhang
- Department of Breast Surgery, Capital Medical University Electric Power Teaching Hospital, Beijing, China (mainland)
| | - Xuefei Li
- Department of Breast Surgery, Capital Medical University Electric Power Teaching Hospital, Beijing, China (mainland)
| | - Fangcai Lin
- Department of Breast Surgery, Capital Medical University Electric Power Teaching Hospital, Beijing, China (mainland)
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Abstract
Introduction Although bibliometric analyses have been performed in the past on cancer and genomics, little is known about the most frequently cited articles specifically related to cancer epigenetics. Therefore, the purpose of this study is to use citation count to identify those papers in the scientific literature that have made key contributions in the field of cancer epigenetics and identify key driving forces behind future investigations. Materials and methods The Thomas Reuters Web of Science services was queried for the years 1980-2018 without language restrictions. Articles were sorted in descending order of the number of times they were cited in the Web of Science database by other studies, and all titles and abstracts were screened to identify the research areas of the top 100 articles. The number of citations per year was calculated. Results We identified the 100 most-cited articles on cancer epigenetics, which collectively had been cited 147,083 times at the time of this writing. The top-cited article was cited 7,124 times, with an average of 375 citations per year since publication. In the period 1980-2018, the most prolific years were the years 2006 and 2010, producing nine articles, respectively. Twenty-eight unique journals contributed to the 100 articles, with the Nature journal contributing most of the articles (n=22). The most common country of article origin was the United States of America (n=78), followed by Germany (n=4), Switzerland (n=4), Japan (n=3), Spain (n=2), and United Kingdom (n=2). Conclusions In this study, the 100 most-cited articles in cancer epigenetics were examined, and the contributions from various authors, specialties, and countries were identified. Cancer epigenetics is a rapidly growing scientific field impacting translational research in cancer screening, diagnosis, classification, prognosis, and targeted treatments. Recognition of important historical contributions to this field may guide future investigations.
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Affiliation(s)
- Ignacio Jusue-Torres
- Neurosurgery, Loyola University Chicago, Stritch School of Medicine, Chicago, USA
| | | | - Malcolm V Brock
- Surgery, Johns Hopkins University School of Medicine, Baltimore, USA
| | - Alicia Hulbert
- Surgery, University of Illinois at Chicago, Chicago, USA
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Watson KS, Hulbert A, Henderson V, Chukwudozie IB, Aponte-Soto L, Lerner L, Martinez E, Kim S, Winn RA. Lung Cancer Screening and Epigenetics in African Americans: The Role of the Socioecological Framework. Front Oncol 2019; 9:87. [PMID: 30915271 PMCID: PMC6423082 DOI: 10.3389/fonc.2019.00087] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 01/30/2019] [Indexed: 11/13/2022] Open
Abstract
Lung cancer is the leading cause of cancer morbidity and mortality in the U.S. and racial/ethnic minorities carry the greatest burden of lung cancer disparities with African Americans (AAs) impacted disproportionately. Inequities in lung cancer health disparities are often associated with multiple bio-behavioral and socio-cultural factors among racial/ethnic minorities. Epigenetic research has advanced the understanding of the intersectionality between biological and socio-cultural factors in lung cancer disparities among AAs. However, gaps exist in the engagement of diverse populations in epigenetic lung cancer research, which poses a challenge in ensuring the generalizability and implementation of epigenetic research in populations that carry an unequal cancer burden. Grounding epigenetic lung cancer research within a socio-ecological framework may prove promising in implementing a multi-level approach to community engagement, screening, navigation, and research participation among AAs. The University of Illinois Cancer Center (UI Cancer Center) is employing an evidence–based (EB) model of community/patient engagement utilizing the socio-ecological model (SEM) to develop a culturally sensitive epigenetic lung cancer research program that addresses multiple factors that impact lung cancer outcomes in AAs. By implementing epigenetic research within a group of Federally Qualified Health Centers (FQHCs) guided by the SEM, the UI Cancer Center is proposing a new pathway in mitigating lung cancer disparities in underserved communities. At the individual level, the framework examines tobacco use among patients at FQHCs (the organizational level) and also tailors epigenetic research to explore innovative biomarkers in high risk populations. Interpersonal interventions use Patient Navigators to support navigation to EB tobacco cessation resources and lung cancer screening. Community level support within the SEM is developed by ongoing partnerships with local and national partners such as the American Lung Association (ALA) and the American Cancer Society (ACS). Lastly, at the policy level, the UI Cancer Center acknowledges the role of policy implications in lung cancer screening and advocates for policies and screening recommendations that examine the current guidelines from the United States Preventive Services Task Force (USPTF).
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Affiliation(s)
| | - Alicia Hulbert
- Cancer Center, University of Illinois at Chicago, Chicago, IL, United States.,Department of Surgery, University of Illinois at Chicago, Chicago, IL, United States
| | - Vida Henderson
- Cancer Center, University of Illinois at Chicago, Chicago, IL, United States
| | | | - Lisa Aponte-Soto
- Cancer Center, University of Illinois at Chicago, Chicago, IL, United States
| | - Lane Lerner
- Cancer Center, University of Illinois at Chicago, Chicago, IL, United States
| | - Erica Martinez
- Cancer Center, University of Illinois at Chicago, Chicago, IL, United States
| | - Sage Kim
- Division of Health Policy and Administration, School of Public Health, University of Illinois at Chicago, Chicago, IL, United States
| | - Robert A Winn
- Cancer Center, University of Illinois at Chicago, Chicago, IL, United States.,Department of Surgery, University of Illinois at Chicago, Chicago, IL, United States.,Division of Pulmonary, Critical Care, Sleep and Allergy, University of Illinois at Chicago, Chicago, IL, United States
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8
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Wippermann A, Noll T. DNA methylation in CHO cells. J Biotechnol 2017; 258:206-210. [DOI: 10.1016/j.jbiotec.2017.08.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 08/06/2017] [Accepted: 08/07/2017] [Indexed: 01/22/2023]
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Exploring genetic moderators and epigenetic mediators of contextual and family effects: From Gene × Environment to epigenetics. Dev Psychopathol 2016; 28:1333-1346. [PMID: 27692009 DOI: 10.1017/s0954579416000882] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In the current manuscript, we provide an overview of a research program at the University of Georgia's Center for Family Research designed to expand upon rapid and ongoing developments in the fields of genetics and epigenetics. By placing those developments in the context of translational research on family and community determinants of health and well-being among rural African Americans, we hope to identify novel, modifiable environments and biological processes. In the first section of the article, we review our earlier work on genotypic variation effects on the association between family context and mental and physical health outcomes as well as differential responses to family-based intervention. We then transition to discuss our more recent research on the association of family and community environments with epigenetic processes. In this second section of the article, we begin by briefly reviewing terminology and basic considerations before describing evidence that early environments may influence epigenetic motifs that potentially serve as mediators of long-term effects of early family and community environments on longer term health outcomes. We also provide evidence that genotype may sometimes influence epigenetic outcomes. Finally, we describe our recent efforts to use genome-wide characterization of epigenetic patterns to better understand the biological impact of protective parenting on long-term shifts in inflammatory processes and its potential implications for young adult health. As will be clear, research on epigenetics as a mediator of the connections between family/community processes and a range of health outcomes is still in its infancy, but the potential to develop important insights regarding mechanisms linking modifiable environments to biological processes and long-term health outcomes already is coming into view.
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10
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Ordered chromatin changes and human X chromosome reactivation by cell fusion-mediated pluripotent reprogramming. Nat Commun 2016; 7:12354. [PMID: 27507283 PMCID: PMC4987517 DOI: 10.1038/ncomms12354] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 06/24/2016] [Indexed: 12/17/2022] Open
Abstract
Erasure of epigenetic memory is required to convert somatic cells towards pluripotency. Reactivation of the inactive X chromosome (Xi) has been used to model epigenetic reprogramming in mouse, but human studies are hampered by Xi epigenetic instability and difficulties in tracking partially reprogrammed iPSCs. Here we use cell fusion to examine the earliest events in the reprogramming-induced Xi reactivation of human female fibroblasts. We show that a rapid and widespread loss of Xi-associated H3K27me3 and XIST occurs in fused cells and precedes the bi-allelic expression of selected Xi-genes by many heterokaryons (30–50%). After cell division, RNA-FISH and RNA-seq analyses confirm that Xi reactivation remains partial and that induction of human pluripotency-specific XACT transcripts is rare (1%). These data effectively separate pre- and post-mitotic events in reprogramming-induced Xi reactivation and reveal a complex hierarchy of epigenetic changes that are required to reactivate the genes on the human Xi chromosome. Reactivation of the inactive X chromosome (Xi) has modelled epigenetic reprogramming in mouse. Here, by using cell fusion between human female fibroblasts and mouse embryonic stem cells, the authors show a complex hierarchy of epigenetic changes that are required to reactivate the genes on the human Xi chromosome.
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Lévesque N, Leclerc D, Gayden T, Lazaris A, De Jay N, Petrillo S, Metrakos P, Jabado N, Rozen R. Murine diet/tissue and human brain tumorigenesis alter Mthfr/MTHFR 5'-end methylation. Mamm Genome 2016; 27:122-34. [PMID: 26951114 DOI: 10.1007/s00335-016-9624-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 02/25/2016] [Indexed: 12/31/2022]
Abstract
Polymorphisms and decreased activity of methylenetetrahydrofolate reductase (MTHFR) are linked to disease, including cancer. However, epigenetic regulation has not been thoroughly studied. Our goal was to generate DNA methylation profiles of murine/human MTHFR gene regions and examine methylation in brain and liver tumors. Pyrosequencing in four murine tissues revealed minimal DNA methylation in the CpG island. Higher methylation was seen in liver or intestine in the CpG island shore 5' to the upstream translational start site or in another region 3' to the downstream start site. In the latter region, there was negative correlation between expression and methylation. Three orthologous regions were investigated in human MTHFR, as well as a fourth region between the two translation start sites. We found significantly increased methylation in three regions (not the CpG island) in pediatric astrocytomas compared with control brain, with decreased expression in tumors. Methylation in hepatic carcinomas was also increased in the three regions compared with normal liver, but the difference was significant for only one CpG. This work, the first overview of the Mthfr/MTHFR epigenetic landscape, suggests regulation through methylation in some regions, demonstrates increased methylation/decreased expression in pediatric astrocytomas, and should serve as a resource for future epigenetic studies.
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Affiliation(s)
- Nancy Lévesque
- Departments of Human Genetics and Pediatrics, The Research Institute of the McGill University Health Centre, McGill University, 1001 Décarie Blvd., Bloc E, Rm E M0.3211, Montreal, H4A 3J1, Canada
| | - Daniel Leclerc
- Departments of Human Genetics and Pediatrics, The Research Institute of the McGill University Health Centre, McGill University, 1001 Décarie Blvd., Bloc E, Rm E M0.3211, Montreal, H4A 3J1, Canada
| | - Tenzin Gayden
- Division of Experimental Medicine, Departments of Pediatrics and Human Genetics, The Research Institute of the McGill University Health Centre, McGill University, 1001 Décarie Blvd., Montreal, H4A 3J1, Canada
| | - Anthoula Lazaris
- Department of Surgery, The Research Institute of the McGill University Health Centre, McGill University, 1001 Décarie Blvd., Montreal, H4A 3J1, Canada
| | - Nicolas De Jay
- Division of Experimental Medicine, Departments of Pediatrics and Human Genetics, The Research Institute of the McGill University Health Centre, McGill University, 1001 Décarie Blvd., Montreal, H4A 3J1, Canada
| | - Stephanie Petrillo
- Department of Surgery, The Research Institute of the McGill University Health Centre, McGill University, 1001 Décarie Blvd., Montreal, H4A 3J1, Canada
| | - Peter Metrakos
- Department of Surgery, The Research Institute of the McGill University Health Centre, McGill University, 1001 Décarie Blvd., Montreal, H4A 3J1, Canada
| | - Nada Jabado
- Division of Experimental Medicine, Departments of Pediatrics and Human Genetics, The Research Institute of the McGill University Health Centre, McGill University, 1001 Décarie Blvd., Montreal, H4A 3J1, Canada
| | - Rima Rozen
- Departments of Human Genetics and Pediatrics, The Research Institute of the McGill University Health Centre, McGill University, 1001 Décarie Blvd., Bloc E, Rm E M0.3211, Montreal, H4A 3J1, Canada.
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The lncRNA Firre anchors the inactive X chromosome to the nucleolus by binding CTCF and maintains H3K27me3 methylation. Genome Biol 2015; 16:52. [PMID: 25887447 PMCID: PMC4391730 DOI: 10.1186/s13059-015-0618-0] [Citation(s) in RCA: 187] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 02/23/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In mammals, X chromosome genes are present in one copy in males and two in females. To balance the dosage of X-linked gene expression between the sexes, one of the X chromosomes in females is silenced. X inactivation is initiated by upregulation of the lncRNA (long non-coding RNA) Xist and recruitment of specific chromatin modifiers. The inactivated X chromosome becomes heterochromatic and visits a specific nuclear compartment adjacent to the nucleolus. RESULTS Here, we show a novel role for the lncRNA Firre in anchoring the inactive mouse X chromosome and preserving one of its main epigenetic features, H3K27me3. Similar to Dxz4, Firre is X-linked and expressed from a macrosatellite repeat locus associated with a cluster of CTCF and cohesin binding sites, and is preferentially located adjacent to the nucleolus. CTCF binding present initially in both male and female mouse embryonic stem cells is lost from the active X during development. Knockdown of Firre disrupts perinucleolar targeting and H3K27me3 levels in mouse fibroblasts, demonstrating a role in maintenance of an important epigenetic feature of the inactive X chromosome. No X-linked gene reactivation is seen after Firre knockdown; however, a compensatory increase in the expression of chromatin modifier genes implicated in X silencing is observed. Further experiments in female embryonic stem cells suggest that Firre does not play a role in X inactivation onset. CONCLUSIONS The X-linked lncRNA Firre helps to position the inactive X chromosome near the nucleolus and to preserve one of its main epigenetic features.
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Wan J, Oliver VF, Wang G, Zhu H, Zack DJ, Merbs SL, Qian J. Characterization of tissue-specific differential DNA methylation suggests distinct modes of positive and negative gene expression regulation. BMC Genomics 2015; 16:49. [PMID: 25652663 PMCID: PMC4331481 DOI: 10.1186/s12864-015-1271-4] [Citation(s) in RCA: 110] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 01/22/2015] [Indexed: 01/20/2023] Open
Abstract
Background DNA methylation plays an important role in regulating gene expression during many biological processes. However, the mechanism of DNA-methylation-dependent gene regulation is not fully understood. Here, we explore two possible DNA methylation regulatory mechanisms with opposite modes of gene expression regulation. Results By comparing the genome-wide methylation and expression patterns in different tissues, we find that majority of tissue-specific differentially methylated regions (T-DMRs) are negatively correlated with expression of their associated genes (negative T-DMRs), consistent with the classical dogma that DNA methylation suppresses gene expression; however, a significant portion of T-DMRs are positively correlated with gene expression (positive T-DMRs). We observe that the positive T-DMRs have similar genomic location as negative T-DMRs, except that the positive T-DMRs are more enriched in the promoter regions. Both positive and negative T-DMRs are enriched in DNase I hypersensitivity sites (DHSs), suggesting that both are likely to be functional. The CpG sites of both positive and negative T-DMRs are also more evolutionarily conserved than the genomic background. Interestingly, the putative target genes of the positive T-DMR are enriched for negative regulators such as transcriptional repressors, suggesting a novel mode of indirect DNA methylation inhibition of expression through transcriptional repressors. Likewise, two distinct sets of DNA sequence motifs exist for positive and negative T-DMRs, suggesting that two distinct sets of transcription factors (TFs) are involved in positive and negative regulation mediated by DNA methylation. Conclusions We find both negative and positive association between T-DMRs and gene expression, which implies the existence of two different mechanisms of DNA methylation-dependent gene regulation. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1271-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jun Wan
- Department of Ophthalmology, Wilmer Institute, Johns Hopkins University School of Medicine, Baltimore, MA, USA.
| | - Verity F Oliver
- Department of Ophthalmology, Wilmer Institute, Johns Hopkins University School of Medicine, Baltimore, MA, USA.
| | - Guohua Wang
- Department of Ophthalmology, Wilmer Institute, Johns Hopkins University School of Medicine, Baltimore, MA, USA.
| | - Heng Zhu
- Department of Pharmacology and Molecular Science, Johns Hopkins University School of Medicine, Baltimore, MA, USA.
| | - Donald J Zack
- Department of Ophthalmology, Wilmer Institute, Johns Hopkins University School of Medicine, Baltimore, MA, USA. .,Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MA, USA. .,Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MA, USA. .,Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MA, USA. .,Institut de la Vision, Université Pierre et Marie Curie, 17 rue Moreau, Paris, France.
| | - Shannath L Merbs
- Department of Ophthalmology, Wilmer Institute, Johns Hopkins University School of Medicine, Baltimore, MA, USA.
| | - Jiang Qian
- Department of Ophthalmology, Wilmer Institute, Johns Hopkins University School of Medicine, Baltimore, MA, USA.
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14
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Peeters SB, Cotton AM, Brown CJ. Variable escape from X-chromosome inactivation: identifying factors that tip the scales towards expression. Bioessays 2014; 36:746-56. [PMID: 24913292 PMCID: PMC4143967 DOI: 10.1002/bies.201400032] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In humans over 15% of X-linked genes have been shown to ‘escape’ from X-chromosome inactivation (XCI): they continue to be expressed to some extent from the inactive X chromosome. Mono-allelic expression is anticipated within a cell for genes subject to XCI, but random XCI usually results in expression of both alleles in a cell population. Using a study of allelic expression from cultured lymphoblasts and fibroblasts, many of which showed substantial skewing of XCI, we recently reported that the expression of genes lies on a contiunuum between those that are subject to inactivation, and those that escape. We now review allelic expression studies from mouse, and discuss the variability in escape seen in both humans and mice in genic expression levels, between X chromosomes and between tissues. We also discuss current knowledge of the heterochromatic features, DNA elements and three-dimensional topology of the inactive X that contribute to the balance of expression from the otherwise inactive X chromosome.
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Affiliation(s)
- Samantha B Peeters
- Department of Medical Genetics, Molecular Epigenetics Group, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
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15
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Kim YZ. Altered histone modifications in gliomas. Brain Tumor Res Treat 2014; 2:7-21. [PMID: 24926467 PMCID: PMC4049557 DOI: 10.14791/btrt.2014.2.1.7] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 03/16/2014] [Accepted: 03/21/2014] [Indexed: 12/24/2022] Open
Abstract
Gliomas are the most frequently occurring primary brain tumors in adults. Although they exist in different malignant stages, including histologically benign forms and highly aggressive states, most gliomas are clinically challenging for neuro-oncologists because of their infiltrative growth patterns and inherent relapse tendency with increased malignancy. Once this disease reaches the glioblastoma multiforme stage, the prognosis of patients is dismal: median survival time is 15 months. Extensive genetic analyses of glial tumors have revealed a variety of deregulated genetic pathways involved in DNA repair, apoptosis, cell migration/adhesion, and cell cycle. Recently, it has become evident that epigenetic alterations may also be an important factor for glioma genesis. Of epigenetic marks, histone modification is a key mark that regulates gene expression and thus modulates a wide range of cellular processes. In this review, I discuss the neuro-oncological significance of altered histone modifications and modifiers in glioma patients while briefly overviewing the biological roles of histone modifications.
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Affiliation(s)
- Young Zoon Kim
- Division of Neuro-Oncology, Department of Neurosurgery, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea
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16
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Shimoda N, Izawa T, Yoshizawa A, Yokoi H, Kikuchi Y, Hashimoto N. Decrease in cytosine methylation at CpG island shores and increase in DNA fragmentation during zebrafish aging. AGE (DORDRECHT, NETHERLANDS) 2014; 36:103-15. [PMID: 23736955 PMCID: PMC3889898 DOI: 10.1007/s11357-013-9548-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 05/20/2013] [Indexed: 05/13/2023]
Abstract
Age-related changes in DNA methylation have been demonstrated in mammals, but it remains unclear as to the generality of this phenomenon in vertebrates, which is a criterion for the fundamental cause of senescence. Here we showed that the zebrafish genome gradually and clearly lost methylcytosine in somatic cells, but not in male germ cells during aging, and that age-dependent hypomethylation preferentially occurred at a particular domain called the CpG island shore, which is associated with vertebrates' genes and has been shown to be hypomethylated in humans with age. We also found that two CpG island shores hypomethylated in zebrafish oocytes were de novo methylated in fertilized eggs, which suggests that the zebrafish epigenome is reset upon fertilization, enabling new generations to restart with a heavily methylated genome. Furthermore, we observed an increase in cleavage of the zebrafish genome to an oligonucleosome length in somatic cells from the age of 12 months, which is suggestive of an elevated rate of apoptosis in the senescent stage.
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Affiliation(s)
- Nobuyoshi Shimoda
- />Department of Regenerative Medicine, National Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, 36-3 Gengo, Morioka, Ōbu, Aichi, 474-8522 Japan
| | - Toshiaki Izawa
- />Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Akio Yoshizawa
- />Research Institute for Radiation Biology and Medicine, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima, Hiroshima 739-8526 Japan
| | - Hayoto Yokoi
- />Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumi-Dori Amamiya-Machi, Aoba-Ku, Sendai 981-8555 Japan
| | - Yutaka Kikuchi
- />Department of Biological Science, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima, Hiroshima 739-8526 Japan
| | - Naohiro Hashimoto
- />Department of Regenerative Medicine, National Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, 36-3 Gengo, Morioka, Ōbu, Aichi, 474-8522 Japan
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17
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Intragenic DNA methylation in transcriptional regulation, normal differentiation and cancer. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1829:1161-74. [PMID: 23938249 DOI: 10.1016/j.bbagrm.2013.08.001] [Citation(s) in RCA: 157] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 08/02/2013] [Accepted: 08/05/2013] [Indexed: 02/06/2023]
Abstract
Ever since the discovery of DNA methylation at cytosine residues, the role of this so called fifth base has been extensively studied and debated. Until recently, the majority of DNA methylation studies focused on the analysis of CpG islands associated to promoter regions. However, with the upcoming possibilities to study DNA methylation in a genome-wide context, this epigenetic mark can now be studied in an unbiased manner. As a result, recent studies have shown that not only promoters but also intragenic and intergenic regions are widely modulated during physiological processes and disease. In particular, it is becoming increasingly clear that DNA methylation in the gene body is not just a passive witness of gene transcription but it seems to be actively involved in multiple gene regulation processes. In this review we discuss the potential role of intragenic DNA methylation in alternative promoter usage, regulation of short and long non-coding RNAs, alternative RNA processing, as well as enhancer activity. Furthermore, we summarize how the intragenic DNA methylome is modified both during normal cell differentiation and neoplastic transformation.
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18
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Walker CG, Littlejohn MD, Meier S, Roche JR, Mitchell MD. DNA methylation is correlated with gene expression during early pregnancy in Bos taurus. Physiol Genomics 2013; 45:276-86. [DOI: 10.1152/physiolgenomics.00145.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Coordinated regulation of endometrial gene expression is essential for successful pregnancy establishment. A nonreceptive uterine environment may be a key contributor to pregnancy loss, as the majority of pregnancy losses occur prior to embryo implantation. DNA methylation has been highlighted as a potential contributor in regulating early pregnancy events in the uterus. It was hypothesized that DNA methylation regulates expression of key genes in the uterus during pregnancy. The correlation between DNA methylation and gene expression was tested. Endometrial samples from fertile and subfertile dairy cow strains were obtained at day 17 of pregnancy or the reproductive cycle. Microarrays were used to characterize genome-wide DNA methylation profiles and data compared with previously published transcription profiles. 39% of DNA methylation probes assayed mapped to RefSeq genes with transcription measurements. Correlations among gene expression and DNA methylation were assessed, and the 1,000 most significant correlations used for subsequent analysis. Of these, 52% percent were negatively correlated with gene expression. When this gene list was compared with previously reported gene expression studies on the same tissues, 42% were differentially expressed when pregnant and cycling animals were compared, and 11% were differentially expressed when pregnant fertile and subfertile animals were compared. DNA methylation status was correlated with gene expression in several pathways implicated in early pregnancy events. Although these data do not provide direct evidence of a causative association between DNA methylation and gene expression, this study provides critical support for an effect of DNA methylation in early pregnancy events and highlights candidate genes for future studies.
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Affiliation(s)
- Caroline G. Walker
- DairyNZ Limited, Hamilton, New Zealand
- Liggins Institute, The University of Auckland, Grafton, New Zealand; and
| | | | | | | | - Murray D. Mitchell
- UQ Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
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19
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Beach SRH, Brody GH, Lei MK, Gibbons FX, Gerrard M, Simons RL, Cutrona CE, Philibert RA. Impact of child sex abuse on adult psychopathology: a genetically and epigenetically informed investigation. JOURNAL OF FAMILY PSYCHOLOGY : JFP : JOURNAL OF THE DIVISION OF FAMILY PSYCHOLOGY OF THE AMERICAN PSYCHOLOGICAL ASSOCIATION (DIVISION 43) 2013; 27:3-11. [PMID: 23421829 PMCID: PMC3813956 DOI: 10.1037/a0031459] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Genetic, environmental, and epigenetic influences and their transactions were examined in a sample of 155 women from the Iowa adoptee sample who had been removed from their biological parents shortly after birth and assessed when participants were an average of 41.10 years old. We observed an interactive effect of child sex abuse (CSA) and biological parent psychopathology (i.e., genetic load) on substance abuse as well as a main effect of CSA on substance abuse in adulthood. We also observed main effects of CSA and genetic load on depression and on antisocial characteristics. As predicted, CSA, but not genetic load or later substance abuse, was associated with epigenetic change. In addition, the interaction between genetic load and CSA predicted epigenetic change, indicating a potential genetic basis for a differential impact of CSA on epigenetic change. Finally, epigenetic change partially mediated the effect of CSA on antisocial characteristics. The results suggest the relevance of genetic and epigenetic processes for future theorizing regarding marital and family precursors of several forms of adult psychopathology. Implications for preventive intervention are discussed.
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Affiliation(s)
- Steven R H Beach
- Center for Family Research, University of Georgia, Athens, GA 30602, USA.
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20
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Cotton AM, Lam L, Affleck JG, Wilson IM, Peñaherrera MS, McFadden DE, Kobor MS, Lam WL, Robinson WP, Brown CJ. Chromosome-wide DNA methylation analysis predicts human tissue-specific X inactivation. Hum Genet 2011; 130:187-201. [PMID: 21597963 PMCID: PMC3132437 DOI: 10.1007/s00439-011-1007-8] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Accepted: 05/06/2011] [Indexed: 12/04/2022]
Abstract
X-chromosome inactivation (XCI) results in the differential marking of the active and inactive X with epigenetic modifications including DNA methylation. Consistent with the previous studies showing that CpG island-containing promoters of genes subject to XCI are approximately 50% methylated in females and unmethylated in males while genes which escape XCI are unmethylated in both sexes; our chromosome-wide (Methylated DNA ImmunoPrecipitation) and promoter-targeted methylation analyses (Illumina Infinium HumanMethylation27 array) showed the largest methylation difference (D = 0.12, p < 2.2 E-16) between male and female blood at X-linked CpG islands promoters. We used the methylation differences between males and females to predict XCI statuses in blood and found that 81% had the same XCI status as previously determined using expression data. Most genes (83%) showed the same XCI status across tissues (blood, fetal: muscle, kidney and nerual); however, the methylation of a subset of genes predicted different XCI statuses in different tissues. Using previously published expression data the effect of transcription on gene-body methylation was investigated and while X-linked introns of highly expressed genes were more methylated than the introns of lowly expressed genes, exonic methylation did not differ based on expression level. We conclude that the XCI status predicted using methylation of X-linked promoters with CpG islands was usually the same as determined by expression analysis and that 12% of X-linked genes examined show tissue-specific XCI whereby a gene has a different XCI status in at least one of the four tissues examined.
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Affiliation(s)
- Allison M. Cotton
- Department of Medical Genetics, University of British Columbia, Vancouver, BC Canada
- Molecular Epigenetics Group, Life Sciences Institute, Vancouver, BC Canada
| | - Lucia Lam
- Department of Medical Genetics, University of British Columbia, Vancouver, BC Canada
- Child and Family Research Institute, Vancouver, BC Canada
- Centre for Molecular Medicine and Therapeutics, Vancouver, BC Canada
| | - Joslynn G. Affleck
- Department of Medical Genetics, University of British Columbia, Vancouver, BC Canada
- Molecular Epigenetics Group, Life Sciences Institute, Vancouver, BC Canada
| | - Ian M. Wilson
- British Columbia Cancer Research Centre, Vancouver, BC Canada
- Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC Canada
| | - Maria S. Peñaherrera
- Department of Medical Genetics, University of British Columbia, Vancouver, BC Canada
- Child and Family Research Institute, Vancouver, BC Canada
| | | | - Michael S. Kobor
- Department of Medical Genetics, University of British Columbia, Vancouver, BC Canada
- Child and Family Research Institute, Vancouver, BC Canada
- Centre for Molecular Medicine and Therapeutics, Vancouver, BC Canada
| | - Wan L. Lam
- British Columbia Cancer Research Centre, Vancouver, BC Canada
- Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC Canada
| | - Wendy P. Robinson
- Department of Medical Genetics, University of British Columbia, Vancouver, BC Canada
- Child and Family Research Institute, Vancouver, BC Canada
| | - Carolyn J. Brown
- Department of Medical Genetics, University of British Columbia, Vancouver, BC Canada
- Molecular Epigenetics Group, Life Sciences Institute, Vancouver, BC Canada
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21
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Nugent BM, Schwarz JM, McCarthy MM. Hormonally mediated epigenetic changes to steroid receptors in the developing brain: implications for sexual differentiation. Horm Behav 2011; 59:338-44. [PMID: 20800064 PMCID: PMC3011040 DOI: 10.1016/j.yhbeh.2010.08.009] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 08/12/2010] [Accepted: 08/19/2010] [Indexed: 01/22/2023]
Abstract
The establishment of sex-specific neural morphology, which underlies sex-specific behaviors, occurs during a perinatal sensitive window in which brief exposure to gonadal steroid hormones produces permanent masculinization of the brain. In the rodent, estradiol derived from testicular androgens is a principal organizational hormone. The mechanism by which transient estradiol exposure induces permanent differences in neuronal anatomy has been widely investigated, but remains elusive. Epigenetic changes, such as DNA methylation, allow environmental influences to alter long-term gene expression patterns and therefore may be a potential mediator of estradiol-induced organization of the neonatal brain. Here we review data that demonstrate sex and estradiol-induced differences in DNA methylation on the estrogen receptor α (ERα), estrogen receptor β (ERβ), and progesterone receptor (PR) promoters in sexually dimorphic brain regions across development. Contrary to the overarching view of DNA methylation as a permanent modification directly tied to gene expression, these data demonstrate that methylation patterns on steroid hormone receptors change across the life span and do not necessarily predict expression. Although further exploration into the mechanism and significance of estradiol-induced alterations in DNA methylation patterns in the neonatal brain is necessary, these results provide preliminary evidence that epigenetic alterations can occur in response to early hormone exposure and may mediate estradiol-induced organization of sex differences in the neonatal brain.
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Affiliation(s)
- Bridget M Nugent
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD, USA.
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22
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Pai AA, Bell JT, Marioni JC, Pritchard JK, Gilad Y. A genome-wide study of DNA methylation patterns and gene expression levels in multiple human and chimpanzee tissues. PLoS Genet 2011; 7:e1001316. [PMID: 21383968 PMCID: PMC3044686 DOI: 10.1371/journal.pgen.1001316] [Citation(s) in RCA: 149] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Accepted: 01/21/2011] [Indexed: 12/22/2022] Open
Abstract
The modification of DNA by methylation is an important epigenetic mechanism that affects the spatial and temporal regulation of gene expression. Methylation patterns have been described in many contexts within and across a range of species. However, the extent to which changes in methylation might underlie inter-species differences in gene regulation, in particular between humans and other primates, has not yet been studied. To this end, we studied DNA methylation patterns in livers, hearts, and kidneys from multiple humans and chimpanzees, using tissue samples for which genome-wide gene expression data were also available. Using the multi-species gene expression and methylation data for 7,723 genes, we were able to study the role of promoter DNA methylation in the evolution of gene regulation across tissues and species. We found that inter-tissue methylation patterns are often conserved between humans and chimpanzees. However, we also found a large number of gene expression differences between species that might be explained, at least in part, by corresponding differences in methylation levels. In particular, we estimate that, in the tissues we studied, inter-species differences in promoter methylation might underlie as much as 12%-18% of differences in gene expression levels between humans and chimpanzees.
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Affiliation(s)
- Athma A. Pai
- Department of Human Genetics, University of Chicago, Chicago, Illinois, United States of America
| | - Jordana T. Bell
- Department of Human Genetics, University of Chicago, Chicago, Illinois, United States of America
| | - John C. Marioni
- Department of Human Genetics, University of Chicago, Chicago, Illinois, United States of America
| | - Jonathan K. Pritchard
- Department of Human Genetics, University of Chicago, Chicago, Illinois, United States of America
- Howard Hughes Medical Institute, University of Chicago, Chicago, Illinois, United States of America
| | - Yoav Gilad
- Department of Human Genetics, University of Chicago, Chicago, Illinois, United States of America
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23
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Illingworth RS, Gruenewald-Schneider U, Webb S, Kerr ARW, James KD, Turner DJ, Smith C, Harrison DJ, Andrews R, Bird AP. Orphan CpG islands identify numerous conserved promoters in the mammalian genome. PLoS Genet 2010; 6:e1001134. [PMID: 20885785 PMCID: PMC2944787 DOI: 10.1371/journal.pgen.1001134] [Citation(s) in RCA: 377] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Accepted: 08/23/2010] [Indexed: 01/23/2023] Open
Abstract
CpG islands (CGIs) are vertebrate genomic landmarks that encompass the promoters of most genes and often lack DNA methylation. Querying their apparent importance, the number of CGIs is reported to vary widely in different species and many do not co-localise with annotated promoters. We set out to quantify the number of CGIs in mouse and human genomes using CXXC Affinity Purification plus deep sequencing (CAP-seq). We also asked whether CGIs not associated with annotated transcripts share properties with those at known promoters. We found that, contrary to previous estimates, CGI abundance in humans and mice is very similar and many are at conserved locations relative to genes. In each species CpG density correlates positively with the degree of H3K4 trimethylation, supporting the hypothesis that these two properties are mechanistically interdependent. Approximately half of mammalian CGIs (>10,000) are “orphans” that are not associated with annotated promoters. Many orphan CGIs show evidence of transcriptional initiation and dynamic expression during development. Unlike CGIs at known promoters, orphan CGIs are frequently subject to DNA methylation during development, and this is accompanied by loss of their active promoter features. In colorectal tumors, however, orphan CGIs are not preferentially methylated, suggesting that cancer does not recapitulate a developmental program. Human and mouse genomes have similar numbers of CGIs, over half of which are remote from known promoters. Orphan CGIs nevertheless have the characteristics of functional promoters, though they are much more likely than promoter CGIs to become methylated during development and hence lose these properties. The data indicate that orphan CGIs correspond to previously undetected promoters whose transcriptional activity may play a functional role during development. In the decade since the sequence of the human genome was announced, efforts have been made to annotate all genes with their regulatory sequences. CpG islands are short regions containing the sequence CG at high density that map to regions controlling the expression of most human genes (known as promoters). Using a biochemical method, we have identified and mapped all CpG islands in the human and mouse genomes and find that over half are remote from known gene promoters—so-called “orphans.” Mice, which were thought to possess far fewer CpG islands than humans, turn out to have a very similar number. Surprisingly, orphan CpG islands in both species often mark hitherto unknown promoters. The activity of these novel promoters is particularly dynamic during normal development, as they are often silenced by DNA methylation. In colorectal cancers, however, aberrant DNA methylation affects all CpG islands equally.
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Affiliation(s)
- Robert S. Illingworth
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Shaun Webb
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Alastair R. W. Kerr
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Keith D. James
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Daniel J. Turner
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Colin Smith
- Neuropathology Unit, Division of Pathology, University of Edinburgh, Edinburgh, United Kingdom
| | - David J. Harrison
- Division of Pathology, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom
| | - Robert Andrews
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Adrian P. Bird
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
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24
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Poplinski A, Wieacker P, Kliesch S, Gromoll J. Severe XIST hypomethylation clearly distinguishes (SRY+) 46,XX-maleness from Klinefelter syndrome. Eur J Endocrinol 2010; 162:169-75. [PMID: 19812237 DOI: 10.1530/eje-09-0768] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE 46,XX-maleness affects 1 in 20 000 live male newborns resulting in infertility and hypergonadotrophic hypogonadism. Although the phenotypes of XX-males have been well described, the molecular nature of the X chromosomes remains elusive. We assessed the X inactivation status by DNA methylation analysis of four informative loci and compared those to Klinefelter syndrome (KS) and Turner syndrome. DESIGN AND METHODS Patient cohort consisted of ten sex-determining region of the Y (SRY+) XX-males, two (SRY-) XX-males, ten 47,XXY Klinefelter men, six 45,X Turner females and ten male and female control individuals each. Methylation analysis was carried out by bisulphite sequencing of DNA from peripheral blood lymphocytes analysing X-inactive-specific transcript (XIST), phosphoglycerate kinase 1 (PGK1), ferritin, heavy peptide-like 17 (FTHL17) and short stature homeobox (SHOX). RESULTS XIST methylation was 18% in (SRY+) XX-males, and thus they were severely hypomethylated compared to (SRY-) XX-males (48%; P<0.01), Klinefelter men (44%; P<0.01) and female controls (47%; P<0.01). Turner females and male controls displayed a high degree of XIST methylation of 98 and 94% respectively. Methylation of PGK1, undergoing X inactivation, was not significantly reduced in (SRY+) XX-males compared to female controls in spite of severe XIST hypomethylation (51 vs 69%; P>0.05). FTHL17, escaping X inactivation, but undergoing cell-type-specific inactivation was similarly methylated in XX-males (89%), KS patients (87%) and female controls (90%). SHOX, an X inactivation escapee located in the pseudoautosomal region, displays similarly low degrees of methylation for XX-males (7%), KS patients (7%) and female controls (9%). CONCLUSIONS XIST hypomethylation clearly distinguishes (SRY+) XX-males from Klinefelter men. It does not, however, impair appropriate epigenetic regulation of representative X-linked loci.
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MESH Headings
- Adolescent
- Adult
- Chromosomes, Human, X/genetics
- Chromosomes, Human, Y/genetics
- Cohort Studies
- DNA Methylation
- Epigenesis, Genetic/genetics
- Female
- Gonadal Dysgenesis, 46,XX/diagnosis
- Gonadal Dysgenesis, 46,XX/genetics
- Humans
- Klinefelter Syndrome/diagnosis
- Klinefelter Syndrome/genetics
- Male
- Middle Aged
- RNA, Long Noncoding
- RNA, Untranslated/genetics
- RNA, Untranslated/metabolism
- Sex-Determining Region Y Protein/genetics
- Young Adult
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Affiliation(s)
- Andreas Poplinski
- Centre of Reproductive Medicine and Andrology, University Clinics Münster, Münster, Germany
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25
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Nagarajan RP, Costello JF. Molecular epigenetics and genetics in neuro-oncology. Neurotherapeutics 2009; 6:436-46. [PMID: 19560734 PMCID: PMC3981537 DOI: 10.1016/j.nurt.2009.04.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 03/26/2009] [Accepted: 04/09/2009] [Indexed: 01/25/2023] Open
Abstract
Gliomas arise through genetic and epigenetic alterations of normal brain cells, although the exact cell of origin for each glioma subtype is unknown. The alteration-induced changes in gene expression and protein function allow uncontrolled cell division, tumor expansion, and infiltration into surrounding normal brain parenchyma. The genetic and epigenetic alterations are tumor subtype and tumor-grade specific. Particular alterations predict tumor aggressiveness, tumor response to therapy, and patient survival. Genetic alterations include deletion, gain, amplification, mutation, and translocation, which result in oncogene activation and tumor suppressor gene inactivation, or in some instances the alterations may simply be a consequence of tumorigenesis. Epigenetic alterations in brain tumors include CpG island hypermethylation associated with tumor suppressor gene silencing, gene-specific hypomethylation associated with aberrant gene activation, and genome-wide hypomethylation potentially leading to loss of imprinting, chromosomal instability, and cellular hyperproliferation. Other epigenetic alterations, such as changes in the position of histone variants and changes in histone modifications are also likely to be important in the molecular pathology of brain tumors. Given that histone deacetylases are targets for drugs that are already in clinical trial, surprisingly little is known about histone acetylation in primary brain tumors. Although a majority of epigenetic alterations are independent of genetic alterations, there is interaction on specific genes, signaling pathways and within chromosomal domains. Next-generation sequencing technology is now the method of choice for genomic and epigenome profiling, allowing more comprehensive understanding of genetic and epigenetic contributions to tumorigenesis in the brain.
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Affiliation(s)
- Raman P. Nagarajan
- grid.266102.10000000122976811Brain Tumor Research Center, Department of Neurosurgery, Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, 94143 San Francisco, California
| | - Joseph F. Costello
- grid.266102.10000000122976811Brain Tumor Research Center, Department of Neurosurgery, Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, 94143 San Francisco, California
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26
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Nagarajan RP, Costello JF. Epigenetic mechanisms in glioblastoma multiforme. Semin Cancer Biol 2009; 19:188-97. [PMID: 19429483 DOI: 10.1016/j.semcancer.2009.02.005] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Accepted: 02/11/2009] [Indexed: 11/26/2022]
Abstract
Glioblastoma multiforme (GBM) is an aggressive and lethal cancer, accounting for the majority of primary brain tumors in adults. GBMs are characterized by genetic alterations large and small, affecting genes that control cell growth, apoptosis, angiogenesis, and invasion. Epigenetic alterations also affect the expression of cancer genes alone, or in combination with genetic mechanisms. For example, in each GBM, hundreds of genes are subject to DNA hypermethylation at their CpG island promoters. A subset of GBMs is also characterized by locus-specific and genome-wide decrease in DNA methylation, or DNA hypomethylation. Other epigenetic alterations, such as changes in the position of histone variants and changes in histone modifications are also likely important in the molecular pathology of GBM, but somewhat surprisingly there are very limited data about these in GBM. Alterations in histone modifications are especially important to understand, given that histone deacetylases are targets for drugs that are in clinical trial for GBMs. The technological wave of next-generation sequencing will accelerate GBM epigenome profiling, allowing the direct integration of DNA methylation, histone modification and gene expression profiles. Ultimately, genomic and epigenomic data should provide new predictive markers of response and lead to more effective therapies for GBM.
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Affiliation(s)
- Raman P Nagarajan
- Brain Tumor Research Center, Department of Neurosurgery, Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA 94143, USA
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A novel CpG island set identifies tissue-specific methylation at developmental gene loci. PLoS Biol 2008; 6:e22. [PMID: 18232738 PMCID: PMC2214817 DOI: 10.1371/journal.pbio.0060022] [Citation(s) in RCA: 455] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Accepted: 12/13/2007] [Indexed: 12/13/2022] Open
Abstract
CpG islands (CGIs) are dense clusters of CpG sequences that punctuate the CpG-deficient human genome and associate with many gene promoters. As CGIs also differ from bulk chromosomal DNA by their frequent lack of cytosine methylation, we devised a CGI enrichment method based on nonmethylated CpG affinity chromatography. The resulting library was sequenced to define a novel human blood CGI set that includes many that are not detected by current algorithms. Approximately half of CGIs were associated with annotated gene transcription start sites, the remainder being intra- or intergenic. Using an array representing over 17,000 CGIs, we established that 6%–8% of CGIs are methylated in genomic DNA of human blood, brain, muscle, and spleen. Inter- and intragenic CGIs are preferentially susceptible to methylation. CGIs showing tissue-specific methylation were overrepresented at numerous genetic loci that are essential for development, including HOX and PAX family members. The findings enable a comprehensive analysis of the roles played by CGI methylation in normal and diseased human tissues. The human genome contains about 22,000 genes, each encoding one of the proteins required for human life. A particular cell type (e.g., blood, skin, etc.) expresses a specific subset of protein genes and silences the remainder. To shed light on the mechanisms that cause genes to be activated or shut down, we studied DNA sequences called “CpG islands” (CGIs). These sequences are found at over half of all human genes and can exist in either the active or silent state depending on the presence or absence of methyl groups on the DNA. We devised a method for purifying all CGIs and showed that, unexpectedly, only half occur at the beginning of genes near the promoter, the rest occurring within or between genes. Notably, methylation of CGIs causes stable gene silencing. We tested 17,000 CGIs in four human tissues and found that 6%–8% were methylated in each. Genes whose protein products play an essential role during embryonic development were preferentially methylated, suggesting that gene expression during development could be regulated by CGI methylation. CpG island methylation, an epigenetic phenomenon usually associated with abnormality in disease, is little characterised in the context of "normal" human cells. Here we highlight tissue-specific CpG Island methylation, which frequently associates with developmental genes.
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Anderson CL, Brown CJ. Epigenetic predisposition to expression of TIMP1 from the human inactive X chromosome. BMC Genet 2005; 6:48. [PMID: 16194278 PMCID: PMC1262707 DOI: 10.1186/1471-2156-6-48] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Accepted: 09/29/2005] [Indexed: 12/01/2022] Open
Abstract
Background X inactivation in mammals results in the transcriptional silencing of an X chromosome in females, and this inactive X acquires many of the epigenetic features of silent chromatin. However, not all genes on the inactive X are silenced, and we have examined the TIMP1 gene, which has variable inactivation amongst females. This has allowed us to examine the features permitting expression from the otherwise silent X by comparing inactive X chromosomes with and without TIMP1 expression. Results Expression was generally correlated with euchromatic chromatin features, including DNA hypomethylation, nuclease sensitivity, acetylation of histone H3 and H4 and hypomethylation of H3 at lysines 9 and 27. Demethylation of the TIMP1 gene by 5-azacytidine was able to induce expression from the inactive X chromosome in somatic cell hybrids, and this expression was also accompanied by features of active chromatin. Acetylated histone H3 continued to be observed even when expression was lost in cells that naturally expressed TIMP1; while acetylation was lost upon TIMP1 silencing in cells where expression from the inactive X had been induced by demethylation. Thus ongoing acetylation of inactive X chromosomes does not seem to be simply a 'memory' of expression. Conclusion We propose that acetylation of H3 is an epigenetic mark that predisposes to TIMP1 expression from the inactive X chromosome in some females.
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Affiliation(s)
- Catherine L Anderson
- Department of Medical Genetics, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, CANADA V6T 1Z3
| | - Carolyn J Brown
- Department of Medical Genetics, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, CANADA V6T 1Z3
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29
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Affiliation(s)
- Andrew P Feinberg
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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30
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Hansen RS. X inactivation-specific methylation of LINE-1 elements by DNMT3B: implications for the Lyon repeat hypothesis. Hum Mol Genet 2003; 12:2559-67. [PMID: 12925568 DOI: 10.1093/hmg/ddg268] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Lyon has proposed that long interspersed nuclear element 1 (LINE-1 or L1) repeats may be mediators for the spread of X chromosome inactivation. Cells from ICF patients who are deficient in one of the DNA methyltransferases, DNMT3B, provide an opportunity to explore and refine this hypothesis. Southern blot and bisulfite methylation analyses indicate that, in normal somatic cells, X-linked L1s are hypermethylated on both the active and inactive X chromosomes. In contrast, ICF syndrome cells with DNMT3B mutations have L1s that are hypomethylated on the inactive X, but not on the active X or autosomes. The DNMT3B methyltransferase, therefore, is required for methylation of L1 CpG islands on the inactive X, whereas methylation of the corresponding L1 loci on the active X, as well as most autosomal L1s, is accomplished by another DNA methyltransferase. This unique phenomenon of identical allelic modifications by different enzymes has not been previously observed. Apart from CpG island methylation, the ICF inactive X is basically normal in that it forms a Barr body, is associated with XIST RNA, mostly replicates late, and its X-inactivated genes are mostly silent. Because the unmethylated state of the ICF inactive X L1s probably reflects their methylation status at the time of X inactivation, these data suggest that unmethylated L1 elements, but not methylated L1s, may have a role in the spreading of X chromosome inactivation.
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Affiliation(s)
- R Scott Hansen
- Department of Medicine, Division of Medical Genetics, University of Washington, Seattle, 98195-7720, USA.
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31
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Abstract
The histone H4 acetylation status of the active X (Xa) and inactive X (Xi) chromosomes was investigated at the level of individual genes. A moderate level of acetylation was observed along the lengths of genes on both the Xi and Xa, regardless of their X inactivation status. However, this moderate level of acetylation was modified specifically in promoter regions. Transcriptionally active genes showed elevated levels of acetylation at their promoters on both the Xi and Xa. In contrast, promoters of X-inactivated genes were markedly hypoacetylated, which coincided with the methylation of adjacent CG dinucleotides. This promoter-specific hypoacetylation may be a key component of an X inactivation machinery that operates at the level of individual genes.
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Affiliation(s)
- S L Gilbert
- Department of Biology, Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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32
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Macleod D, Ali RR, Bird A. An alternative promoter in the mouse major histocompatibility complex class II I-Abeta gene: implications for the origin of CpG islands. Mol Cell Biol 1998; 18:4433-43. [PMID: 9671453 PMCID: PMC109029 DOI: 10.1128/mcb.18.8.4433] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Nonmethylated CpG islands are generally located at the 5' ends of genes, but a CpG island in the mouse major histocompatibility complex class II I-Abeta gene is remote from the promoter and covers exon 2. We have found that this CpG island includes a novel intronic promoter that is active in embryonic and germ cells. The resulting transcript potentially encodes a severely truncated protein which would lack the signal peptide and external beta1 domains. The functional significance of the internal CpG island may be to facilitate gene conversion, thereby sustaining the high level of polymorphism seen at exon 2. Deletions of the I-Abeta CpG island promoter reduce transcription and frequently lead to methylation of the CpG island in a transgenic mouse assay. These and other results support the idea that all CpG islands arise at promoters that are active in early embryonic cells.
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Affiliation(s)
- D Macleod
- Institute of Cell and Molecular Biology, University of Edinburgh, Edinburgh EH9 3JR, Scotland.
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33
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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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34
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Litt MD, Hansen RS, Hornstra IK, Gartler SM, Yang TP. 5-Azadeoxycytidine-induced chromatin remodeling of the inactive X-linked HPRT gene promoter occurs prior to transcription factor binding and gene reactivation. J Biol Chem 1997; 272:14921-6. [PMID: 9169463 DOI: 10.1074/jbc.272.23.14921] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
During the process of 5-aza-2'-deoxycytidine (5aCdr)-induced reactivation of the X-linked human hypoxanthine phosphoribosyltransferase (HPRT) gene on the inactive X chromosome, acquisition of a nuclease-sensitive chromatin conformation in the 5' region occurs before the appearance of HPRT mRNA. In vivo footprinting experiments reported here show that the 5aCdr-induced change in HPRT chromatin structure precedes the appearance of three footprints in the immediate 5' flanking region that are characteristic of the active HPRT allele. These and other data suggest the following sequence of events that lead to the reactivation of the HPRT gene after 5aCdr treatment: (a) hemi-demethylation of the promoter, (b) an "opening" of chromatin structure detectable as increased nuclease sensitivity, (c) transcription factor binding to the promoter, (d) assembly of the transcription complex, and (e) synthesis of HPRT RNA. This sequence of events supports the view that inactive X-linked genes are silenced by a repressive chromatin structure that prevents the binding of transcriptional activators to the promoter.
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Affiliation(s)
- M D Litt
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida 32610, USA
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35
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Abstract
Tumorigenesis begins with the disregulated growth of an abnormal cell that has acquired the ability to divide more rapidly than its normal counterparts (Nowell, P.C. (1976) Science, 194, 23-28 [1]). Alterations in global levels and regional changes in the patterns of DNA methylation are among the earliest and most frequent events known to occur in human cancers (Feinberg and Vogelstein (1983) Nature, 301, 89-92 ([2]); Gama-Sosa, M.A. et al. (1983) Nucleic Acids Res., 11, 6883-6894 ([3]); Jones, P.A. (1986) Cancer Res., 46, 461-466 [4]). These changes in methylation may impair the proper expression and/or function of cell-cycle regulatory genes and thus confer a selective growth advantage to affected cells. Developments in the field of cancer research over the past few years have led to an increased understanding of the role DNA methylation may play in tumorigenesis. Many of these studies have investigated two major mechanisms by which DNA methylation may lead to aberrant cell cycle control: (1) through the generation of transition mutations via deamination-driven events resulting in the inactivation of tumor suppressor genes, or (2) by altering levels of gene expression through epigenetic effects at CpG islands. The mechanisms by which the normal function of growth regulatory genes may become affected by the mutagenic and epigenetic properties of DNA methylation will be discussed in the framework of recent discoveries in the field.
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Affiliation(s)
- M L Gonzalgo
- Department of Biochemistry and Molecular Biology, USC/Norris Comprehensive Cancer Center, University of Southern California, School of Medicine, Los Angeles 90033, USA
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36
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Litt MD, Hornstra IK, Yang TP. In vivo footprinting and high-resolution methylation analysis of the mouse hypoxanthine phosphoribosyltransferase gene 5' region on the active and inactive X chromosomes. Mol Cell Biol 1996; 16:6190-9. [PMID: 8887649 PMCID: PMC231622 DOI: 10.1128/mcb.16.11.6190] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
To investigate potential mechanisms regulating the hypoxanthine phosphoribosyltransferase (HPRT) gene by X-chromosome inactivation, we performed in vivo footprinting and high-resolution DNA methylation analysis on the 5' region of the active and inactive mouse HPRT alleles and compared these results with those from the human HPRT gene. We found multiple footprinted sites on the active mouse HPRT allele and no footprints on the inactive allele. Comparison of the footprint patterns of the mouse and human HPRT genes demonstrated that the in vivo binding of regulatory proteins between these species is generally conserved but not identical. Detailed nucleotide sequence comparison of footprinted regions in the mouse and human genes revealed a novel 9-bp sequence associated with transcription factor binding near the transcription sites of both genes, suggesting the identification of a new conserved initiator element. Ligation-mediated PCR genomic sequencing showed that all CpG dinucleotides examined on the active allele are unmethylated, while the majority of CpGs on the inactive allele are methylated and interspersed with a few hypomethylated sites. This pattern of methylation on the inactive mouse allele is notably different from the unusual methylation pattern of the inactive human gene, which exhibited strong hypomethylation specifically at GC boxes. These studies, in conjunction with other genomic sequencing studies of X-linked genes, demonstrate that (i) the active alleles are essentially unmethylated, (ii) the inactive alleles are hypermethylated, and (iii) the high-resolution methylation patterns of the hypermethylated inactive alleles are not strictly conserved. There is no obvious correlation between the pattern of methylated sites on the inactive alleles and the pattern of binding sites for transcription factors on the active alleles. These results are discussed in relationship to potential mechanisms of transcriptional regulation by X-chromosome inactivation.
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Affiliation(s)
- M D Litt
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville 32610, USA
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37
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Wei LN, Lee CH. Demethylation in the 5'-flanking region of mouse cellular retinoic acid binding protein-I gene is associated with its high level of expression in mouse embryos and facilitates its induction by retinoic acid in P19 embryonal carcinoma cells. Dev Dyn 1994; 201:1-10. [PMID: 7528580 DOI: 10.1002/aja.1002010102] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The mouse cellular retinoic acid binding protein-I (CRABP-I) gene is specifically up-regulated by retinoic acid (RA) in P19 mouse embryonal carcinoma cells, and its expression in animals is spatially and temporally restricted to RA-sensitive tissues during embryonic development. This study demonstrates that, in adult mouse tissues and P19 cells where the expression of CRABP-I is detected at the basal level, the 5'-flanking region of the CRABP-I gene is hypermethylated at the C residues of all the Hpa II sites. Conversely, in mouse embryos during early stages of development when the expression of CRABP-I gene is detected at a much higher level, this region is demethylated at these Hpa II sites. In P19, enhancement on the RA-induced up-regulation of CRABP-I can be observed in cells treated with 5-azacytidine (5-AzaC) in conjunction with RA, where partial demethylation in the 5'-flanking region of CRABP-I gene is observed. Nuclear run-on experiments indicate that increased message levels of CRABP-I in P19 cells can be accounted for, at least partially, by increases in its transcription rates. The induction of retinoic acid receptor (RAR) beta by RA can also be enhanced by 5-AzaC, but to a much lesser degree. In contrast, all the Hpa II sites in the structural gene portion, at least in the first two exons, are fully demethylated at the C residues.
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Affiliation(s)
- L N Wei
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis 55455
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38
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Abstract
CpG methylation is known to suppress transcription. This repression is generally thought to be related to alterations of chromatin structure that are specified by the methylation. The nature of these chromatin alterations is unknown. Moreover, it has not been clear if the methylation repression occurs in an all-or-none fashion at some critical methylation density, or if intermediate densities of methylation can give intermediate levels of repression. Here I report a stable episomal system which recapitulates many dynamic features of methylation observed in the genome. I have determined the extent of transcriptional repression as a function of four densities of CpG methylation. I find that the repression is a graded but exponential function of the CpG methylation density such that low levels of methylation yield a 67 to 90% inhibition of gene expression. Higher levels of methylation extinguished gene expression completely. Transcription from methylated minichromosomes can be increased by butyrate treatment, suggesting that histone acetylation can reverse some of the repression specified by the methylated state. Sites of preferential demethylation occurred and may have resulted from transcription factor binding or DNA looping.
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39
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Abstract
CpG methylation is known to suppress transcription. This repression is generally thought to be related to alterations of chromatin structure that are specified by the methylation. The nature of these chromatin alterations is unknown. Moreover, it has not been clear if the methylation repression occurs in an all-or-none fashion at some critical methylation density, or if intermediate densities of methylation can give intermediate levels of repression. Here I report a stable episomal system which recapitulates many dynamic features of methylation observed in the genome. I have determined the extent of transcriptional repression as a function of four densities of CpG methylation. I find that the repression is a graded but exponential function of the CpG methylation density such that low levels of methylation yield a 67 to 90% inhibition of gene expression. Higher levels of methylation extinguished gene expression completely. Transcription from methylated minichromosomes can be increased by butyrate treatment, suggesting that histone acetylation can reverse some of the repression specified by the methylated state. Sites of preferential demethylation occurred and may have resulted from transcription factor binding or DNA looping.
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Affiliation(s)
- C L Hsieh
- Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, Missouri 63110
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40
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High-resolution methylation analysis of the human hypoxanthine phosphoribosyltransferase gene 5' region on the active and inactive X chromosomes: correlation with binding sites for transcription factors. Mol Cell Biol 1994. [PMID: 8289817 DOI: 10.1128/mcb.14.2.1419] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
DNA methylation within GC-rich promoters of constitutively expressed X-linked genes is correlated with transcriptional silencing on the inactive X chromosome in female mammals. For most X-linked genes, X chromosome inactivation results in transcriptionally active and inactive alleles occupying each female nucleus. To examine mechanisms responsible for maintaining this unique system of differential gene expression, we have analyzed the methylation of individual cytosine residues in the 5' CpG island of the human hypoxanthine phosphoribosyltransferase (HPRT) gene on the active and inactive X chromosomes. Methylation analysis of 142 CpG dinucleotides by genomic sequencing was carried out on purified DNA using the cytosine-specific Maxam and Gilbert DNA sequencing reaction in conjunction with ligation-mediated PCR. These studies demonstrate the 5' CpG islands of active and 5-azacytidine-reactivated alleles are essentially unmethylated while the inactive allele is hypermethylated. The inactive allele is completely methylated at nearly all CpG dinucleotides except in a 68-bp region containing four adjacent GC boxes where most CpG dinucleotides are either unmethylated or partially methylated. Curiously, these GC boxes exhibit in vivo footprints only on the active X chromosome, not on the inactive X. The methylation pattern of the inactive HPRT gene is strikingly different from that reported for the inactive X-linked human phosphoglycerate kinase gene which exhibits methylation at all CpG sites in the 5' CpG island. These results suggest that the position of methylated CpG dinucleotides, the density of methylated CpGs, the length of methylated regions, and/or chromatin structure associated with methylated DNA may have a role in repressing the activity of housekeeping promoters on the inactive X chromosome. The pattern of DNA methylation on the inactive human HPRT gene may also provide insight into the process of inactivating the gene early in female embryogenesis.
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41
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Hornstra IK, Yang TP. High-resolution methylation analysis of the human hypoxanthine phosphoribosyltransferase gene 5' region on the active and inactive X chromosomes: correlation with binding sites for transcription factors. Mol Cell Biol 1994; 14:1419-30. [PMID: 8289817 PMCID: PMC358497 DOI: 10.1128/mcb.14.2.1419-1430.1994] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
DNA methylation within GC-rich promoters of constitutively expressed X-linked genes is correlated with transcriptional silencing on the inactive X chromosome in female mammals. For most X-linked genes, X chromosome inactivation results in transcriptionally active and inactive alleles occupying each female nucleus. To examine mechanisms responsible for maintaining this unique system of differential gene expression, we have analyzed the methylation of individual cytosine residues in the 5' CpG island of the human hypoxanthine phosphoribosyltransferase (HPRT) gene on the active and inactive X chromosomes. Methylation analysis of 142 CpG dinucleotides by genomic sequencing was carried out on purified DNA using the cytosine-specific Maxam and Gilbert DNA sequencing reaction in conjunction with ligation-mediated PCR. These studies demonstrate the 5' CpG islands of active and 5-azacytidine-reactivated alleles are essentially unmethylated while the inactive allele is hypermethylated. The inactive allele is completely methylated at nearly all CpG dinucleotides except in a 68-bp region containing four adjacent GC boxes where most CpG dinucleotides are either unmethylated or partially methylated. Curiously, these GC boxes exhibit in vivo footprints only on the active X chromosome, not on the inactive X. The methylation pattern of the inactive HPRT gene is strikingly different from that reported for the inactive X-linked human phosphoglycerate kinase gene which exhibits methylation at all CpG sites in the 5' CpG island. These results suggest that the position of methylated CpG dinucleotides, the density of methylated CpGs, the length of methylated regions, and/or chromatin structure associated with methylated DNA may have a role in repressing the activity of housekeeping promoters on the inactive X chromosome. The pattern of DNA methylation on the inactive human HPRT gene may also provide insight into the process of inactivating the gene early in female embryogenesis.
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Affiliation(s)
- I K Hornstra
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville 32610
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42
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Gartler SM, Goldman MA. Reactivation of inactive X-linked genes. DEVELOPMENTAL GENETICS 1994; 15:504-14. [PMID: 7530612 DOI: 10.1002/dvg.1020150609] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- S M Gartler
- Department of Medicine, University of Washington, Seattle 98195
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43
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Tommasi S, LeBon JM, Riggs AD, Singer-Sam J. Methylation analysis by genomic sequencing of 5' region of mouse Pgk-1 gene and a cautionary note concerning the method. SOMATIC CELL AND MOLECULAR GENETICS 1993; 19:529-41. [PMID: 7510422 DOI: 10.1007/bf01233380] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We have used genomic sequencing aided by ligation-mediated PCR (LMPCR) to assay for 5-methylcytosine in the CpG-rich promoter region of the mouse X-linked phosphoglycerate kinase gene (Pgk-1). Earlier studies showed that there was very heavy methylation of CpG dinucleotides in the CpG-rich promoter of the human PGK1 gene on the inactive X chromosome (the Xi), but that these same sites were completely unmethylated on the active X chromosome (the Xa). For mouse Pgk-1, previous restriction enzyme analysis had shown apparently complete methylation of only one cytosine in the promoter region on the Xi, at HpaII site H7, which is located in the untranslated region, 28 nucleotides upstream of the translation start site. We analyzed this potentially critical region by combining the use of HpaII with LMPCR, and find that the CpG dinucleotides near H7 are either unmethylated or only partially methylated on the Xi. LMPCR analysis of male and female DNA over a 490-bp sequence including the promoter and enhancer extend the finding of relative hypomethylation on the mouse Xi to include all CpG dinucleotides in this region. These results are relevant to the role of DNA methylation in stabilizing the inactive state of chromatin. In addition, we find that caution must be exercised in using LMPCR for methylation analysis of some sequences. A DNA concentration-dependent band-suppression artifact can incorrectly suggest methylation of both CpG and nonCpG dinucleotides.
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Affiliation(s)
- S Tommasi
- Biology Department, Beckman Research Institute of the City of Hope, Duarte, California 91010
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44
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Dandolo L, Stewart CL, Mattei MG, Avner PR. Inactivation of an X-linked transgene in murine extraembryonic and adult tissues. Development 1993; 118:641-9. [PMID: 8223283 DOI: 10.1242/dev.118.2.641] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Transgenes located on the X chromosome have been used to study the mechanisms involved in X-chromosome inactivation. Analysis of the transgenic mouse strain M-TKneo1 carrying a neomycin resistance gene inserted in the X chromosome showed that, in adult somatic tissues, this transgene is subject to X-inactivation and to de novo methylation as other endogenous X-linked genes. During mouse embryogenesis, X-linked genes show a preferential paternal inactivation in extraembryonic tissues, whereas these genes are subject to random inactivation in embryonic tissues. It has been suggested that, in the mouse, the extraembryonic tissues carry a parental imprint at the time of inactivation. The study of the neo transgene expression in extraembryonic endoderm has shown not only that neo is inactivated but also that, at the RNA level, paternal inactivation of the transgene seems essentially complete. The differences between our results and previously obtained results with a mouse alpha-fetoprotein transgene, which was only inactivated in neonatal tissues but not in extraembryonic tissues, are discussed.
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45
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Cooper GE, Bishop PL, Turker MS. Hemidemethylation is sufficient for chromatin relaxation and transcriptional activation of methylated aprt gene in mouse P19 embryonal carcinoma cell line. SOMATIC CELL AND MOLECULAR GENETICS 1993; 19:221-9. [PMID: 7687384 DOI: 10.1007/bf01233070] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A series of clones displaying a high-frequency "switching" phenotype for expression of the adenine phosphoribosyltransferase (aprt) gene was previously isolated from the P19 mouse embryonal carcinoma stem cell line. In a subset of these clones, loss of aprt expression was correlated with increased DNA methylation, a nuclease-resistant chromatin conformation, and loss of RNA transcription; reactivation was associated with a reversal of these parameters. In this report, the role of DNA methylation in transcriptional inactivation was studied in the H22D3 clone. The cells of this clone contain a single inactive aprt allele that is methylated. Mass cultures of H22D3 were treated with 2-deoxy-5'-azacytidine (5aCdr) and found to reactivate aprt at frequencies ranging from 60 to 90%. Treated cultures were then assayed over time for aprt mRNA, chromatin conformation, and DNA methylation of the aprt gene. These studies demonstrated that 5aCdr treatment resulted in promoter region-specific hemidemethylation and chromatin relaxation starting at 12 h. This was followed by the appearance of RNA transcripts at 18 h and increasing levels of APRT enzymatic activity at 36 h after treatment. Complete demethylation occurred significantly later. Experiments in which cells were treated with 5aCdr for varying periods of time demonstrated that a single round of analog incorporation was sufficient for transcriptional reactivation of aprt in H22D3.
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Affiliation(s)
- G E Cooper
- Department of Microbiology & Immunology, University of Kentucky College of Medicine, Lexington 40536
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46
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Affiliation(s)
- J Singer-Sam
- Beckman Research Institute, City of Hope, Duarte, CA 91010
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47
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Affiliation(s)
- A Yeivin
- Department of Cellular Biochemistry, Hebrew University, Hadassah Medical School, Jerusalem, Israel
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Multiple in vivo footprints are specific to the active allele of the X-linked human hypoxanthine phosphoribosyltransferase gene 5' region: implications for X chromosome inactivation. Mol Cell Biol 1992. [PMID: 1448069 DOI: 10.1128/mcb.12.12.5345] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dosage compensation of X-linked genes in male and female mammals is accomplished by random inactivation of one X chromosome in each female somatic cell. As a result, a transcriptionally active allele and a transcriptionally inactive allele of most X-linked genes reside within each female nucleus. To examine the mechanism responsible for maintaining this unique system of differential gene expression, we have analyzed the differential binding of regulatory proteins to the 5' region of the human hypoxanthine phosphoribosyltransferase (HPRT) gene on the active and inactive X chromosomes. Studies of DNA-protein interactions associated with the transcriptionally active and inactive HPRT alleles were carried out in intact cultured cells by in vivo footprinting by using ligation-mediated polymerase chain reaction and dimethyl sulfate. Analysis of the active allele demonstrates at least six footprinted regions, whereas no footprints were detected on the inactive allele. Of the footprints on the active allele, at least four occur over canonical GC boxes or Sp1 consensus binding sites, one is associated with a potential AP-2 binding site, and another is associated with a DNA sequence not previously reported to interact with a sequence-specific DNA-binding factor. While no footprints were observed for the HPRT gene on the inactive X chromosome, reactivation of the inactive allele with 5-azacytidine treatment restored the in vivo footprint pattern found on the active allele. Results of these experiments, in conjunction with recent studies on the X-linked human PGK-1 gene, bear implications for models of X chromosome inactivation.
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Hornstra IK, Yang TP. Multiple in vivo footprints are specific to the active allele of the X-linked human hypoxanthine phosphoribosyltransferase gene 5' region: implications for X chromosome inactivation. Mol Cell Biol 1992; 12:5345-54. [PMID: 1448069 PMCID: PMC360472 DOI: 10.1128/mcb.12.12.5345-5354.1992] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Dosage compensation of X-linked genes in male and female mammals is accomplished by random inactivation of one X chromosome in each female somatic cell. As a result, a transcriptionally active allele and a transcriptionally inactive allele of most X-linked genes reside within each female nucleus. To examine the mechanism responsible for maintaining this unique system of differential gene expression, we have analyzed the differential binding of regulatory proteins to the 5' region of the human hypoxanthine phosphoribosyltransferase (HPRT) gene on the active and inactive X chromosomes. Studies of DNA-protein interactions associated with the transcriptionally active and inactive HPRT alleles were carried out in intact cultured cells by in vivo footprinting by using ligation-mediated polymerase chain reaction and dimethyl sulfate. Analysis of the active allele demonstrates at least six footprinted regions, whereas no footprints were detected on the inactive allele. Of the footprints on the active allele, at least four occur over canonical GC boxes or Sp1 consensus binding sites, one is associated with a potential AP-2 binding site, and another is associated with a DNA sequence not previously reported to interact with a sequence-specific DNA-binding factor. While no footprints were observed for the HPRT gene on the inactive X chromosome, reactivation of the inactive allele with 5-azacytidine treatment restored the in vivo footprint pattern found on the active allele. Results of these experiments, in conjunction with recent studies on the X-linked human PGK-1 gene, bear implications for models of X chromosome inactivation.
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Affiliation(s)
- I K Hornstra
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville 32610
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Hemimethylation and hypersensitivity are early events in transcriptional reactivation of human inactive X-linked genes in a hamster x human somatic cell hybrid. Mol Cell Biol 1992. [PMID: 1380647 DOI: 10.1128/mcb.12.9.3819] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Reactivation of the hypoxanthine phosphoribosyltransferase (HPRT) gene on an inactive human X chromosome in a somatic cell hybrid was analyzed following exposure to 5-aza-2'-deoxycytidine. Hemimethylation and chromatin hypersensitivity in the 5' CpG island appeared by 6 h after exposure and continued to increase for 24 h in an exponentially growing cell culture. These results imply that the conformation of inactive chromatin requires a symmetrically methylated 5' G+C-rich promoter region. In addition, quantitative analysis of the time course patterns suggest that chromatin sensitivity changes may depend on strand-specific demethylation. Symmetrically demethylated DNA was first detected at 24 h and continued to increase until 48 h. HPRT mRNA was first detected at 24 h and increased in a biphasic pattern until 48 h. These results suggest that hemimethylation permits nuclease attack but not transcription factor binding, which requires symmetrically demethylated DNA. We also show that in G1-arrested cells, 5-aza-2'-deoxycytidine has no effect on methylation, chromatin conformation, or transcription. We conclude that reactivation of the HPRT gene present on the inactive X chromosome of a somatic cell hybrid involves the initial events of DNA hemimethylation and chromatin hypersensitivity at the 5' CpG island, followed by symmetrical demethylation and transcriptional reactivation.
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