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Ghanim GE, Sekne Z, Balch S, van Roon AMM, Nguyen THD. 2.7 Å cryo-EM structure of human telomerase H/ACA ribonucleoprotein. Nat Commun 2024; 15:746. [PMID: 38272871 PMCID: PMC10811338 DOI: 10.1038/s41467-024-45002-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 01/03/2024] [Indexed: 01/27/2024] Open
Abstract
Telomerase is a ribonucleoprotein (RNP) enzyme that extends telomeric repeats at eukaryotic chromosome ends to counterbalance telomere loss caused by incomplete genome replication. Human telomerase is comprised of two distinct functional lobes tethered by telomerase RNA (hTR): a catalytic core, responsible for DNA extension; and a Hinge and ACA (H/ACA) box RNP, responsible for telomerase biogenesis. H/ACA RNPs also have a general role in pseudouridylation of spliceosomal and ribosomal RNAs, which is critical for the biogenesis of the spliceosome and ribosome. Much of our structural understanding of eukaryotic H/ACA RNPs comes from structures of the human telomerase H/ACA RNP. Here we report a 2.7 Å cryo-electron microscopy structure of the telomerase H/ACA RNP. The significant improvement in resolution over previous 3.3 Å to 8.2 Å structures allows us to uncover new molecular interactions within the H/ACA RNP. Many disease mutations are mapped to these interaction sites. The structure also reveals unprecedented insights into a region critical for pseudouridylation in canonical H/ACA RNPs. Together, our work advances understanding of telomerase-related disease mutations and the mechanism of pseudouridylation by eukaryotic H/ACA RNPs.
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Affiliation(s)
| | - Zala Sekne
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
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2
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Revy P, Kannengiesser C, Bertuch AA. Genetics of human telomere biology disorders. Nat Rev Genet 2023; 24:86-108. [PMID: 36151328 DOI: 10.1038/s41576-022-00527-z] [Citation(s) in RCA: 43] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/11/2022] [Indexed: 01/24/2023]
Abstract
Telomeres are specialized nucleoprotein structures at the ends of linear chromosomes that prevent the activation of DNA damage response and repair pathways. Numerous factors localize at telomeres to regulate their length, structure and function, to avert replicative senescence or genome instability and cell death. In humans, Mendelian defects in several of these factors can result in abnormally short or dysfunctional telomeres, causing a group of rare heterogeneous premature-ageing diseases, termed telomeropathies, short-telomere syndromes or telomere biology disorders (TBDs). Here, we review the TBD-causing genes identified so far and describe their main functions associated with telomere biology. We present molecular aspects of TBDs, including genetic anticipation, phenocopy, incomplete penetrance and somatic genetic rescue, which underlie the complexity of these diseases. We also discuss the implications of phenotypic and genetic features of TBDs on fundamental aspects related to human telomere biology, ageing and cancer, as well as on diagnostic, therapeutic and clinical approaches.
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Affiliation(s)
- Patrick Revy
- INSERM UMR 1163, Laboratory of Genome Dynamics in the Immune System, Equipe Labellisée Ligue Nationale contre le Cancer, Paris, France.
- Université Paris Cité, Imagine Institute, Paris, France.
| | - Caroline Kannengiesser
- APHP Service de Génétique, Hôpital Bichat, Paris, France
- Inserm U1152, Université Paris Cité, Paris, France
| | - Alison A Bertuch
- Departments of Paediatrics and Molecular & Human Genetics, Baylor College of Medicine, Houston, TX, USA
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3
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Telomerase RNA recruits RNA polymerase II to target gene promoters to enhance myelopoiesis. Proc Natl Acad Sci U S A 2021; 118:2015528118. [PMID: 34353901 DOI: 10.1073/pnas.2015528118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dyskeratosis congenita (DC) is a rare inherited bone marrow failure and cancer predisposition syndrome caused by mutations in telomerase or telomeric proteins. Here, we report that zebrafish telomerase RNA (terc) binds to specific DNA sequences of master myeloid genes and controls their expression by recruiting RNA Polymerase II (Pol II). Zebrafish terc harboring the CR4-CR5 domain mutation found in DC patients hardly interacted with Pol II and failed to regulate myeloid gene expression in vivo and to increase their transcription rates in vitro. Similarly, TERC regulated myeloid gene expression and Pol II promoter occupancy in human myeloid progenitor cells. Strikingly, induced pluripotent stem cells derived from DC patients with a TERC mutation in the CR4-CR5 domain showed impaired myelopoiesis, while those with mutated telomerase catalytic subunit differentiated normally. Our findings show that TERC acts as a transcription factor, revealing a target for therapeutic intervention in DC patients.
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4
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Nagpal N, Agarwal S. Telomerase RNA processing: Implications for human health and disease. Stem Cells 2020; 38:10.1002/stem.3270. [PMID: 32875693 PMCID: PMC7917152 DOI: 10.1002/stem.3270] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 08/11/2020] [Indexed: 11/11/2022]
Abstract
Telomeres are composed of repetitive DNA sequences that are replenished by the enzyme telomerase to maintain the self-renewal capacity of stem cells. The RNA component of human telomerase (TERC) is the essential template for repeat addition by the telomerase reverse transcriptase (TERT), and also serves as a scaffold for several factors comprising the telomerase ribonucleoprotein (RNP). Unique features of TERC regulation and function have been informed not only through biochemical studies but also through human genetics. Disease-causing mutations impact TERC biogenesis at several levels including RNA transcription, post-transcriptional processing, folding, RNP assembly, and trafficking. Defects in TERC reduce telomerase activity and impair telomere maintenance, thereby causing a spectrum of degenerative diseases called telomere biology disorders (TBDs). Deciphering mechanisms of TERC dysregulation have led to a broader understanding of noncoding RNA biology, and more recently points to new therapeutic strategies for TBDs. In this review, we summarize over two decades of work revealing mechanisms of human telomerase RNA biogenesis, and how its disruption causes human diseases.
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Affiliation(s)
- Neha Nagpal
- Division of Hematology/Oncology and Stem Cell Program, Boston Children’s Hospital, Boston, Massachusetts
- Pediatric Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
- Harvard Initiative for RNA Medicine and Department of Pediatrics, Harvard Medical School, Boston, Massachusetts
- Harvard Stem Cell Institute, Boston, Massachusetts
| | - Suneet Agarwal
- Division of Hematology/Oncology and Stem Cell Program, Boston Children’s Hospital, Boston, Massachusetts
- Pediatric Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
- Harvard Initiative for RNA Medicine and Department of Pediatrics, Harvard Medical School, Boston, Massachusetts
- Harvard Stem Cell Institute, Boston, Massachusetts
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5
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Wu Z, Giudice V, Chen J, Sun W, Lin Z, Keyvanfar K, Talasani N, Kajigaya S, Feng X, Young NS. Interleukin-18 plays a dispensable role in murine and likely also human bone marrow failure. Exp Hematol 2018; 69:54-64.e2. [PMID: 30316805 DOI: 10.1016/j.exphem.2018.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 10/06/2018] [Accepted: 10/08/2018] [Indexed: 01/11/2023]
Abstract
Interleukin-18 (IL-18), also known as interferon-gamma (IFN-γ)-inducing factor, is involved in Th1 responses and regulation of immunity. Accumulating evidence implicates IL-18 in autoimmune diseases, but little is known of its role in acquired aplastic anemia (AA), the immune-mediated destruction of bone marrow (BM) hematopoietic stem and progenitor cells (HSPCs). IL-18 protein levels were significantly elevated in sera of severe AA (SAA) patients, including both responders and nonresponders assayed before treatment, and decreased after treatment. IL-18 receptor (IL-18R) was expressed on HSPCs. Co-culture of human BM CD34+ cells from healthy donors with IL-18 upregulated genes in the helper T-cell and Notch signaling pathways and downregulated genes in the cell cycle regulation, telomerase, and IL-6 signaling pathways. Plasma IL-18 levels were also elevated in murine models of immune-mediated BM failure. However, deletion of IL-18 in donor lymph node cells or deletions of either IL-18 or IL-18R in recipients did not attenuate elevations of circulating IFN-γ, tumor necrosis factor-alpha, or IL-6, nor did they alleviate BM failure. In summary, our findings suggest that, although increased circulating IL-18 is a feature of SAA, it may reflect an aberrant immune response but be dispensable to the pathogenesis of AA.
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Affiliation(s)
- Zhijie Wu
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Valentina Giudice
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Jichun Chen
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Wanling Sun
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Zenghua Lin
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Keyvan Keyvanfar
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Nidhi Talasani
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Sachiko Kajigaya
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Xingmin Feng
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
| | - Neal S Young
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
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6
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Understanding the evolving phenotype of vascular complications in telomere biology disorders. Angiogenesis 2018; 22:95-102. [DOI: 10.1007/s10456-018-9640-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 08/06/2018] [Indexed: 12/23/2022]
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Abstract
Purpose of Review Clonal hematopoiesis of indeterminate potential (CHIP) is a common, age-associated condition characterized by the acquisition of somatic mutations. This concise review explores our current understanding of the mechanisms that influence the development of clonality with aging and its potential malignant and non-malignant clinical implications. Recent Findings Aging of the hematopoietic system results in phenotypic changes that favor clonal dominance. Cell-extrinsic factors provide additional selective pressures that further shape clonal architecture. Even so, small clones with candidate driver mutations appear to be ubiquitous with age and largely benign in the absence of strong selective pressures. Benign clonal expansion may compensate for the loss of regenerative HSC capacity as we age. Summary CHIP is a marker of aging that reflects the biologic interplay between HSC aging and cell-extrinsic factors. The clinical significance of CHIP is highly variable and dependent on clinical context. Distinguishing the causal relationships and confounding factors that regulate clonal behavior will be essential to define the mechanistic role of CHIP in aging and potentially mitigate its clinical consequences.
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Affiliation(s)
- Soo J Park
- Moores Cancer Center, University of California, San Diego, La Jolla, CA
| | - Rafael Bejar
- Moores Cancer Center, University of California, San Diego, La Jolla, CA
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8
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El Beshlawy A, Said F, El Ansary M, Hamdy M, Abdel-Azim K, Abdel-Razek ARA, Abulata N, Abdel-Salam A. Telomerase enzyme activity in Egyptian children with bone marrow failure and response to immunosuppressive therapy. Blood Cells Mol Dis 2017; 63:58-61. [PMID: 28160733 DOI: 10.1016/j.bcmd.2017.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2016] [Revised: 01/23/2017] [Accepted: 01/24/2017] [Indexed: 11/26/2022]
Affiliation(s)
| | - Fadwa Said
- Clinical and Chemical Pathology Department, Cairo University, Egypt.
| | - Mervat El Ansary
- Clinical and Chemical Pathology Department, Cairo University, Egypt.
| | - Mona Hamdy
- Pediatric Hematology Department, Cairo University, Egypt.
| | | | | | - Nelly Abulata
- Clinical and Chemical Pathology Department, Cairo University, Egypt.
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9
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Bangru S, Kalsotra A. Advances in analyzing RNA diversity in eukaryotic transcriptomes: peering through the Omics lens. F1000Res 2016; 5:2668. [PMID: 27909578 PMCID: PMC5112568 DOI: 10.12688/f1000research.9511.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/08/2016] [Indexed: 12/12/2022] Open
Abstract
Alternative splicing, polyadenylation, and chemical modifications of RNA generate astonishing complexity within eukaryotic transcriptomes. The last decade has brought numerous advances in sequencing technologies that allow biologists to investigate these phenomena with greater depth and accuracy while reducing time and cost. A commensurate development in biochemical techniques for the enrichment and analysis of different RNA variants has accompanied the advancement of global sequencing analysis platforms. Here, we present a detailed overview of the latest biochemical methods, along with bioinformatics pipelines that have aided in identifying different RNA variants. We also highlight the ongoing developments and challenges associated with RNA variant detection and quantification, including sample heterogeneity and isolation, as well as 'Omics' big data handling.
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Affiliation(s)
- Sushant Bangru
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Illinois, USA
| | - Auinash Kalsotra
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Illinois, USA; Institute of Genomic Biology, University of Illinois at Urbana-Champaign, Illinois, USA; College of Medicine, University of Illinois at Urbana-Champaign, Illinois, USA
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10
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Boyraz B, Bellomo CM, Fleming MD, Cutler CS, Agarwal S. A novel TERC CR4/CR5 domain mutation causes telomere disease via decreased TERT binding. Blood 2016; 128:2089-2092. [PMID: 27587879 PMCID: PMC5073186 DOI: 10.1182/blood-2016-04-710160] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Affiliation(s)
- Baris Boyraz
- Division of Hematology/Oncology and Stem Cell Program, Boston Children's Hospital, Boston, MA
- Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA
- Harvard Stem Cell Institute, Boston, MA
- Department of Pediatrics, Harvard Medical School, Boston, MA
- Department of Basic Oncology, Hacettepe University Cancer Institute, Ankara, Turkey
| | | | - Mark D Fleming
- Department of Pathology, Boston Children's Hospital, Boston, MA; and
| | - Corey S Cutler
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA
| | - Suneet Agarwal
- Division of Hematology/Oncology and Stem Cell Program, Boston Children's Hospital, Boston, MA
- Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA
- Harvard Stem Cell Institute, Boston, MA
- Department of Pediatrics, Harvard Medical School, Boston, MA
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11
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Melicher D, Buzas EI, Falus A. Genetic and epigenetic trends in telomere research: a novel way in immunoepigenetics. Cell Mol Life Sci 2015; 72:4095-109. [PMID: 26190020 PMCID: PMC11113282 DOI: 10.1007/s00018-015-1991-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Revised: 06/25/2015] [Accepted: 07/10/2015] [Indexed: 01/09/2023]
Abstract
Telomeres are protective heterochromatic structures that cap the end of linear chromosomes and play a key role in preserving genomic stability. Telomere length represents a balance between processes that shorten telomeres during cell divisions with incomplete DNA replication and the ones that lengthen telomeres by the action of telomerase, an RNA-protein complex with reverse transcriptase activity which adds telomeric repeats to DNA molecule ends. Telomerase activity and telomere length have a crucial role in cellular ageing and in the pathobiology of several human diseases attracting intense research. The last few decades have witnessed remarkable advances in our understanding about telomeres, telomere-associated proteins, and the biogenesis and regulation of the telomerase holoenzyme complex, as well as about telomerase activation and the telomere-independent functions of telomerase. Emerging data have revealed that telomere length can be modified by genetic and epigenetic factors, sex hormones, reactive oxygen species and inflammatory reactions. It has become clear that, in order to find out more about the factors influencing the rate of telomere attrition in vivo, it is crucial to explore both genetic and epigenetic mechanisms. Since the telomere/telomerase assembly is under the control of multiple epigenetic influences, the unique design of twin studies could help disentangle genetic and environmental factors in the functioning of the telomere/telomerase system. It is surprising that the literature on twin studies investigating this topic is rather scarce. This review aims to provide an overview of some important immune response- and epigenetics-related aspects of the telomere/telomerase system demanding more research, while presenting the available twin data published in connection with telomere research so far. By emphasising what we know and what we still do not know in these areas, another purpose of this review is to urge more twin studies in telomere research.
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Affiliation(s)
- Dora Melicher
- Department of Genetics, Cell and Immunobiology, Semmelweis University, Budapest, Hungary
| | - Edit I Buzas
- Department of Genetics, Cell and Immunobiology, Semmelweis University, Budapest, Hungary
| | - Andras Falus
- Department of Genetics, Cell and Immunobiology, Semmelweis University, Budapest, Hungary.
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12
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Chen J, Bryant MA, Dent JJ, Sun Y, Desierto MJ, Young NS. Hematopoietic lineage skewing and intestinal epithelia degeneration in aged mice with telomerase RNA component deletion. Exp Gerontol 2015; 72:251-60. [PMID: 26523501 DOI: 10.1016/j.exger.2015.10.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 10/19/2015] [Accepted: 10/28/2015] [Indexed: 11/17/2022]
Abstract
A deletion of a telomerase RNA component (Terc(-/-)) in C57BL/6 (B6) mice resulted in hematopoietic lineage skewing with increased neutrophils and CD11b(+) myeloid cells and decreased red blood cells and CD45R(+) B lymphocytes when animals reach ages older than 12 months. There was no decline in bone marrow (BM) c-Kit(+)Sca-1(+)Lin(-) (KSL) cells in old Terc(-/-) mice, and the lineage skewing phenomenon was not transferred when BM cells from old Terc(-/-) donors were transplanted into young B6 recipients. Necropsy and histological examinations found minimal to no change in the lung, spleen and liver but detected severe epithelia degeneration, ulceration and infection in small and large intestines, leading to enteritis, typhlitis and colitis in old Terc(-/-) mice. In a mouse model of dextran-sulfate-sodium-induced typhlitis and colitis, development of intestinal pathology was associated with increases in neutrophils and CD11b(+) myeloid cells and a decrease in CD45R(+) B cells, similar to those observed in old Terc(-/-) mice. Treatment of 11-13 month old Terc(-/-) mice with antibiotic trimethoprim-sulfa water reduced neutrophils and myeloid cells and increased B lymphocytes in the blood, indicating that mitigation of intestinal infection and inflammation could alleviate hematological abnormalities in old Terc(-/-) animals.
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Affiliation(s)
- Jichun Chen
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States.
| | - Mark A Bryant
- Division of Veterinary Resources, Office of Research Services, National Institutes of Health, Bethesda, MD 20892, United States
| | - James J Dent
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - Yu Sun
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States; Hematology Department, Second Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China
| | - Marie J Desierto
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - Neal S Young
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States
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13
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Raval A, Behbehani GK, Nguyen LXT, Thomas D, Kusler B, Garbuzov A, Ramunas J, Holbrook C, Park CY, Blau H, Nolan GP, Artandi SE, Mitchell BS. Reversibility of Defective Hematopoiesis Caused by Telomere Shortening in Telomerase Knockout Mice. PLoS One 2015; 10:e0131722. [PMID: 26133370 PMCID: PMC4489842 DOI: 10.1371/journal.pone.0131722] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 06/04/2015] [Indexed: 01/08/2023] Open
Abstract
Telomere shortening is common in bone marrow failure syndromes such as dyskeratosis congenita (DC), aplastic anemia (AA) and myelodysplastic syndromes (MDS). However, improved knowledge of the lineage-specific consequences of telomere erosion and restoration of telomere length in hematopoietic progenitors is required to advance therapeutic approaches. We have employed a reversible murine model of telomerase deficiency to compare the dependence of erythroid and myeloid lineage differentiation on telomerase activity. Fifth generation Tert-/- (G5 Tert-/-) mice with shortened telomeres have significant anemia, decreased erythroblasts and reduced hematopoietic stem cell (HSC) populations associated with neutrophilia and increased myelopoiesis. Intracellular multiparameter analysis by mass cytometry showed significantly reduced cell proliferation and increased sensitivity to activation of DNA damage checkpoints in erythroid progenitors and in erythroid-biased CD150hi HSC, but not in myeloid progenitors. Strikingly, Cre-inducible reactivation of telomerase activity restored hematopoietic stem and progenitor cell (HSPC) proliferation, normalized the DNA damage response, and improved red cell production and hemoglobin levels. These data establish a direct link between the loss of TERT activity, telomere shortening and defective erythropoiesis and suggest that novel strategies to restore telomerase function may have an important role in the treatment of the resulting anemia.
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Affiliation(s)
- Aparna Raval
- Stanford Cancer Institute and Division of Hematology, Department of Medicine, Stanford University, Stanford, CA, 94305, United States of America
| | - Gregory K. Behbehani
- Stanford Cancer Institute and Division of Hematology, Department of Medicine, Stanford University, Stanford, CA, 94305, United States of America
- Baxter Laboratory for Stem Cell Biology, Department of Microbiology and Immunology Stanford University, School of Medicine, Stanford, CA, 94305, United States of America
| | - Le Xuan Truong Nguyen
- Stanford Cancer Institute and Division of Hematology, Department of Medicine, Stanford University, Stanford, CA, 94305, United States of America
| | - Daniel Thomas
- Stanford Cancer Institute and Division of Hematology, Department of Medicine, Stanford University, Stanford, CA, 94305, United States of America
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, CA, 94035, United States of America
| | - Brenda Kusler
- Stanford Cancer Institute and Division of Hematology, Department of Medicine, Stanford University, Stanford, CA, 94305, United States of America
| | - Alina Garbuzov
- Department of Genetics, Stanford University, Stanford, CA, 94305, United States of America
| | - John Ramunas
- Baxter Laboratory for Stem Cell Biology, Department of Microbiology and Immunology Stanford University, School of Medicine, Stanford, CA, 94305, United States of America
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, CA, 94035, United States of America
| | - Colin Holbrook
- Baxter Laboratory for Stem Cell Biology, Department of Microbiology and Immunology Stanford University, School of Medicine, Stanford, CA, 94305, United States of America
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, CA, 94035, United States of America
| | - Christopher Y. Park
- Human Oncology and Pathogenesis Program and Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, 10065, United States of America
| | - Helen Blau
- Baxter Laboratory for Stem Cell Biology, Department of Microbiology and Immunology Stanford University, School of Medicine, Stanford, CA, 94305, United States of America
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, CA, 94035, United States of America
| | - Garry P. Nolan
- Baxter Laboratory for Stem Cell Biology, Department of Microbiology and Immunology Stanford University, School of Medicine, Stanford, CA, 94305, United States of America
| | - Steven E. Artandi
- Departments of Medicine and Biochemistry, Stanford University, Stanford, CA, 94305, United States of America
| | - Beverly S. Mitchell
- Stanford Cancer Institute and Division of Hematology, Department of Medicine, Stanford University, Stanford, CA, 94305, United States of America
- * E-mail:
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14
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Marrone A, Dokal I. Dyskeratosis congenita: a disorder of telomerase deficiency and its relationship to other diseases. ACTA ACUST UNITED AC 2014. [DOI: 10.1586/17469872.1.3.463] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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15
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Paiva RMA, Calado RT. Telomere dysfunction and hematologic disorders. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 125:133-57. [PMID: 24993701 DOI: 10.1016/b978-0-12-397898-1.00006-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Aplastic anemia is a disease in which the hematopoietic stem cell fails to adequately produce peripheral blood cells, causing pancytopenia. In some cases of acquired aplastic anemia and in inherited type of aplastic anemia, dyskeratosis congenita, telomere biology gene mutations and telomere shortening are etiologic. Telomere erosion hampers the ability of hematopoietic stem and progenitor cells to adequately replicate, clinically resulting in bone marrow failure. Additionally, telomerase mutations and short telomeres are genetic risk factors for the development of some hematologic cancers, including myelodysplastic syndrome, acute myeloid leukemia, and chronic lymphocytic leukemia.
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Affiliation(s)
- Raquel M A Paiva
- Department of Internal Medicine, University of São Paulo at Ribeirão Preto School of Medicine, Ribeirão Preto, São Paulo, Brazil
| | - Rodrigo T Calado
- Department of Internal Medicine, University of São Paulo at Ribeirão Preto School of Medicine, Ribeirão Preto, São Paulo, Brazil
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16
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Yang L, Mailloux A, Rollison DE, Painter JS, Maciejewski J, Paquette RL, Loughran TP, McGraw K, Makishima H, Radhakrishnan R, Wei S, Ren X, Komrokji R, List AF, Epling-Burnette PK. Naive T-cells in myelodysplastic syndrome display intrinsic human telomerase reverse transcriptase (hTERT) deficiency. Leukemia 2012; 27:897-906. [PMID: 23072779 PMCID: PMC4346223 DOI: 10.1038/leu.2012.300] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Telomeres are specialized structures providing chromosome integrity during cellular division along with protection against premature senescence and apoptosis. Accelerated telomere attrition in patients with myelodysplastic syndrome (MDS) occurs by an undefined mechanism. Although the MDS clone originates within the myeloid compartment, T-lymphocytes display repertoire contraction and loss of naive T-cells. The replicative lifespan of T-cells is stringently regulated by telomerase activity. In MDS cases, we show that purified CD3+ T-cells have significantly shorter telomere length and reduced proliferative capacity upon stimulation compared with controls. To understand the mechanism, telomerase enzymatic activity and telomerase reverse transcriptase (hTERT), gene expression were compared in MDS cases (n=35) and healthy controls (n=42) within different T-cell compartments. Telomerase activity is greatest in naive T-cells illustrating the importance of telomere repair in homeostatic repertoire regulation. Compared with healthy controls, MDS cases had lower telomerase induction (P<0.0001) that correlated with significantly lower hTERT mRNA (P<0.0001), independent of age and disease stratification. hTERT mRNA deficiency affected naive but not memory T-cells, and telomere erosion in MDS occurred without evidence of an hTERT-promoter mutation, copy number variation or deletion. Telomerase insufficiency may undermine homeostatic control within the hematopoietic compartment and promote a change in the T-cell repertoire in MDS.
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Affiliation(s)
- L Yang
- Immunology Program at the H Lee Moffitt Cancer Center, Tampa, FL, USA
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Touzot F, Le Guen T, de Villartay JP, Revy P. Nouvelles formes de dyskératoses congénitales. Med Sci (Paris) 2012; 28:618-24. [DOI: 10.1051/medsci/2012286015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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18
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Mason PJ, Bessler M. The genetics of dyskeratosis congenita. Cancer Genet 2011; 204:635-45. [PMID: 22285015 PMCID: PMC3269008 DOI: 10.1016/j.cancergen.2011.11.002] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 11/11/2011] [Accepted: 11/13/2011] [Indexed: 01/18/2023]
Abstract
Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome associated with characteristic mucocutaneous features and a variable series of other somatic abnormalities. The disease is heterogeneous at the genetic and clinical levels. Determination of the genetic basis of DC has established that the disease is caused by a number of genes, all of which encode products involved in telomere maintenance, either as part of telomerase or as part of the shelterin complex that caps and protects telomeres. There is overlap at the genetic and clinical levels with other, more common conditions, including aplastic anemia (AA), pulmonary fibrosis (PF), and liver cirrhosis. Although part of the spectrum of disorders known to be associated with DC, it has emerged that mutations in telomere maintenance genes can lead to the development of AA and PF in the absence of other DC features. Here we discuss the genetics of DC and its relationship to disease presentation.
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Affiliation(s)
- Philip J Mason
- Division of Hematology, Department of Pediatrics, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, USA.
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19
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Podlevsky JD, Chen JJL. It all comes together at the ends: telomerase structure, function, and biogenesis. Mutat Res 2011; 730:3-11. [PMID: 22093366 DOI: 10.1016/j.mrfmmm.2011.11.002] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 10/30/2011] [Accepted: 11/01/2011] [Indexed: 12/18/2022]
Abstract
Telomerase is a reverse transcriptase specialized in the addition of telomeric DNA repeats onto the ends of chromosomes. Telomere extension offsets the loss of telomeric repeats from the failure of DNA polymerases to fully replicate linear chromosome ends. Telomerase functions as a ribonucleoprotein, requiring an integral telomerase RNA (TR) component, in addition to the catalytic telomerase reverse transcriptase (TERT). Extensive studies have identified numerous structural and functional features within the TR and TERT essential for activity. A number of accessory proteins have also been identified with various functions in enzyme biogenesis, localization, and regulation. Understanding the molecular mechanism of telomerase function has significance for the development of therapies for telomere-mediated disorders and cancer. Here we review telomerase structural and functional features, and the techniques for assessing telomerase dysfunction.
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Affiliation(s)
- Joshua D Podlevsky
- Department of Chemistry & Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA
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20
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Abstract
Telomerase is a unique reverse transcriptase that catalyzes the addition of telomere DNA repeats onto the 3' ends of linear chromosomes and plays a critical role in maintaining genome stability. Unlike other reverse transcriptases, telomerase is unique in that it is a ribonucleoprotein complex, where the RNA component [telomerase RNA (TR)] not only provides the template for the synthesis of telomere DNA repeats but also plays essential roles in catalysis, accumulation, TR 3'-end processing, localization, and holoenzyme assembly. Biochemical studies have identified TR elements essential for catalysis that share remarkably conserved secondary structures across different species as well as species-specific domains for other functions, paving the way for high-resolution structure determination of TRs. Over the past decade, structures of key elements from the core, conserved regions 4 and 5, and small Cajal body specific RNA domains of human TR have emerged, providing significant insights into the roles of these RNA elements in telomerase function. Structures of all helical elements of the core domain have been recently reported, providing the basis for a high-resolution model of the complete core domain. We review this progress to determine the overall architecture of human telomerase RNA.
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21
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Hematopoietic stem cell development, aging and functional failure. Int J Hematol 2011; 94:3-10. [DOI: 10.1007/s12185-011-0856-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 03/04/2011] [Accepted: 04/06/2011] [Indexed: 12/28/2022]
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22
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Alder JK, Cogan JD, Brown AF, Anderson CJ, Lawson WE, Lansdorp PM, Phillips JA, Loyd JE, Chen JJL, Armanios M. Ancestral mutation in telomerase causes defects in repeat addition processivity and manifests as familial pulmonary fibrosis. PLoS Genet 2011; 7:e1001352. [PMID: 21483807 PMCID: PMC3069110 DOI: 10.1371/journal.pgen.1001352] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2010] [Accepted: 02/23/2011] [Indexed: 01/05/2023] Open
Abstract
The telomerase reverse transcriptase synthesizes new telomeres onto chromosome ends by copying from a short template within its integral RNA component. During telomere synthesis, telomerase adds multiple short DNA repeats successively, a property known as repeat addition processivity. However, the consequences of defects in processivity on telomere length maintenance are not fully known. Germline mutations in telomerase cause haploinsufficiency in syndromes of telomere shortening, which most commonly manifest in the age-related disease idiopathic pulmonary fibrosis. We identified two pulmonary fibrosis families that share two non-synonymous substitutions in the catalytic domain of the telomerase reverse transcriptase gene hTERT: V791I and V867M. The two variants fell on the same hTERT allele and were associated with telomere shortening. Genealogy suggested that the pedigrees shared a single ancestor from the nineteenth century, and genetic studies confirmed the two families had a common founder. Functional studies indicated that, although the double mutant did not dramatically affect first repeat addition, hTERT V791I-V867M showed severe defects in telomere repeat addition processivity in vitro. Our data identify an ancestral mutation in telomerase with a novel loss-of-function mechanism. They indicate that telomere repeat addition processivity is a critical determinant of telomere length and telomere-mediated disease.
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Affiliation(s)
- Jonathan K. Alder
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Joy D. Cogan
- Department of Pediatrics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Andrew F. Brown
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, United States of America
| | - Collin J. Anderson
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - William E. Lawson
- Department of Medicine, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Peter M. Lansdorp
- Terry Fox Laboratory and Department of Medicine, University of British Columbia, Vancouver, Canada
| | - John A. Phillips
- Department of Pediatrics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - James E. Loyd
- Department of Medicine, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Julian J.-L. Chen
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, United States of America
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | - Mary Armanios
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
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23
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Koziel JE, Fox MJ, Steding CE, Sprouse AA, Herbert BS. Medical genetics and epigenetics of telomerase. J Cell Mol Med 2011; 15:457-67. [PMID: 21323862 PMCID: PMC3922369 DOI: 10.1111/j.1582-4934.2011.01276.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Accepted: 02/01/2011] [Indexed: 12/13/2022] Open
Abstract
Telomerase is a specialized reverse transcriptase that extends and maintains the terminal ends of chromosomes, or telomeres. Since its discovery in 1985 by Nobel Laureates Elizabeth Blackburn and Carol Greider, thousands of articles have emerged detailing its significance in telomere function and cell survival. This review provides a current assessment on the importance of telomerase regulation and relates it in terms of medical genetics. In this review, we discuss the recent findings on telomerase regulation, focusing on epigenetics and non-coding RNAs regulation of telomerase, such as microRNAs and the recently discovered telomeric-repeat containing RNA transcripts. Human genetic disorders that develop due to mutations in telomerase subunits, the role of single nucleotide polymorphisms in genes encoding telomerase components and diseases as a result of telomerase regulation going awry are also discussed. Continual investigation of the complex regulation of telomerase will further our insight into the use of controlling telomerase activity in medicine.
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Affiliation(s)
- Jillian E Koziel
- Department of Medical and Molecular Genetics, Indiana University School of MedicineIndianapolis, IN, USA
| | - Melanie J Fox
- Department of Medical and Molecular Genetics, Indiana University School of MedicineIndianapolis, IN, USA
| | - Catherine E Steding
- Department of Medical and Molecular Genetics, Indiana University School of MedicineIndianapolis, IN, USA
| | - Alyssa A Sprouse
- Department of Pharmacology and Toxicology, Indiana University School of MedicineIndianapolis, IN, USA
| | - Brittney-Shea Herbert
- Department of Medical and Molecular Genetics, Indiana University School of MedicineIndianapolis, IN, USA
- Department of Pharmacology and Toxicology, Indiana University School of MedicineIndianapolis, IN, USA
- Indiana University Melvin and Bren Simon Cancer Center, Indiana University School of MedicineIndianapolis, IN, USA
- Indiana University Center for Regenerative Biology and Medicine, Indiana University School of MedicineIndianapolis, IN, USA
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24
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Kirwan M, Vulliamy T, Marrone A, Walne AJ, Beswick R, Hillmen P, Kelly R, Stewart A, Bowen D, Schonland SO, Whittle AM, McVerry A, Gilleece M, Dokal I. Defining the pathogenic role of telomerase mutations in myelodysplastic syndrome and acute myeloid leukemia. Hum Mutat 2010; 30:1567-73. [PMID: 19760749 DOI: 10.1002/humu.21115] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The primary pathology in many cases of myelodysplasia (MDS) and acute myeloid leukemia (AML) remains unknown. In some cases, two or more affected members have been identified in the same family. To date, mutations in two genes have been directly implicated: the hematopoietic transcription factors RUNX1 (runt-related transcription factor 1) and CEBPA (CCATT-box enhancer binding protein alpha). However, there are also other familial cases of MDS/AML where the genetic basis remains unknown. Both MDS, and to a lesser extent AML, have been observed in cases of the bone marrow failure syndrome dyskeratosis congenita, in which telomerase mutations have been identified. Recently, an increased incidence of telomerase reverse transcriptase mutations has been reported in a series of de novo AML. We have now identified novel mutations in the telomerase RNA (TERC) or telomerase reverse transcriptase component (TERT) within 4 of 20 families presenting with familial MDS/AML. Functional analysis has demonstrated that all mutations adversely impact on telomerase activity in vitro, and affected individuals have short telomeres. These families, in conjunction with a review of previously published cases, help to further define the pathological role of telomerase mutations in MDS/AML and have implications for the biology, treatment and screening regimen of de novo cases.
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Affiliation(s)
- Michael Kirwan
- Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Barts and The London Children's Hospital, United Kingdom
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25
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Abstract
Stem cells are rare and unique precursor cells that participate in the building and rebuilding of tissues and organs during embryogenesis, postnatal growth, and injury repair. Stem cells are distinctively endowed with the ability to both self-renew and differentiate, such that they can replenish the stem cell pool while continuing to produce the differentiated daughter cells that are essential for tissue function. Stem cell self-renewal/differentiation decisions must be carefully controlled during organogenesis, tissue homeostasis, and regeneration, as failure in stem cell maintenance or activation can lead to progressive tissue wasting, while unchecked self-renewal is a hallmark of many cancers. Here, we review evidence implicating the Notch signaling pathway, an evolutionarily conserved cell fate determinant with widespread roles in a variety of tissues and organisms, as a crucial regulator of stem cell behavior. As discussed below, this pathway plays varied and critical roles at multiple stages of organismal development, in lineage-specific differentiation of pluripotent embryonic stem cells, and in controlling stem cell numbers and activity in the context of age-related tissue degeneration, injury-induced tissue repair, and malignancy.
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26
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Robart AR, Collins K. Investigation of human telomerase holoenzyme assembly, activity, and processivity using disease-linked subunit variants. J Biol Chem 2009; 285:4375-86. [PMID: 20022961 DOI: 10.1074/jbc.m109.088575] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
After the initial discovery of human telomerase deficiency in the X-linked form of the bone marrow failure syndrome dyskeratosis congenita, mutations in genes encoding telomerase subunits have been identified in patients with a wide spectrum of disorders. Structure/function studies of disease-linked variants of human telomerase RNA (hTR) or telomerase reverse transcriptase (TERT) have exploited in vitro reconstitution of the enzyme catalytic core and/or a PCR-amplified activity assay readout that would not reflect alterations of cellular RNP assembly efficiency, telomeric primer recognition, and/or repeat addition processivity. Here we used telomerase reconstitution in vivo and direct telomeric-repeat primer extension activity assays to compare the ribonucleoprotein (RNP) assembly and activity properties of disease-linked subunit variants in holoenzyme context. Analysis of a large panel of hTR variants revealed numerous biochemical mechanisms for telomerase loss of function, including reduced association of hTR with TERT, reduced RNP catalytic activity, or loss in fidelity of telomeric repeat synthesis. An absolute correlation exists between hTR loss of function and hematopoietic deficiency, but there is no readily apparent telomerase deficiency imposed by an hTR variant linked to pulmonary fibrosis. Some disease-linked TERT variants have altered properties of holoenzyme assembly or repeat addition processivity, but other TERT variants linked to either pulmonary fibrosis or hematopoietic deficiency retained normal hTR interaction and RNP catalytic activity. Combined with additional hTR structure/function studies, our results establish a new resolution of insight into hTR structural requirements for hTR-TERT interaction and for the catalytic cycle of human telomerase holoenzyme.
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Affiliation(s)
- Aaron R Robart
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3200, USA
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27
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Ashbridge B, Orte A, Yeoman JA, Kirwan M, Vulliamy T, Dokal I, Klenerman D, Balasubramanian S. Single-molecule analysis of the human telomerase RNA.dyskerin interaction and the effect of dyskeratosis congenita mutations. Biochemistry 2009; 48:10858-65. [PMID: 19835419 PMCID: PMC2778356 DOI: 10.1021/bi901373e] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Revised: 10/01/2009] [Indexed: 11/29/2022]
Abstract
It has been proposed that human telomerase RNA (hTR) interacts with dyskerin, prior to assembly of the telomerase holoenzyme. The direct interaction of dyskerin and hTR has not been demonstrated and is an experimentally challenging research problem because of difficulties in expressing and purifying dyskerin in quantities that are useful for biophysical analysis. By orthogonally labeling dyskerin and hTR, we have been able to employ single-molecule two-color coincidence detection (TCCD) to observe directly the formation of a dyskerin.hTR complex. By systematic deletion of hTR subdomains, we have gained insights into the RNA sites required for interaction with dyskerin. We then investigated mutated forms of hTR and dyskerin that are associated with dyskeratosis congenita (DC), on the basis of clinical genetics studies, for their effects on the dyskerin.hTR interaction. Dyskerin mutations associated with X-linked DC resulted in significant impairment of the dyskerin.hTR interaction, whereas mutations in hTR associated with autosomal dominant (AD) DC did not affect the interaction. We propose that disruption of the dyskerin.hTR interaction may contribute to X-linked DC.
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Affiliation(s)
- Beth Ashbridge
- University Chemical Laboratories, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
| | - Angel Orte
- University Chemical Laboratories, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
| | - Justin A. Yeoman
- University Chemical Laboratories, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
| | - Michael Kirwan
- Centre for Paediatrics, Institute of Cell and Molecular Science, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, London E1 2AT, U.K
| | - Tom Vulliamy
- Centre for Paediatrics, Institute of Cell and Molecular Science, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, London E1 2AT, U.K
| | - Inderjeet Dokal
- Centre for Paediatrics, Institute of Cell and Molecular Science, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, London E1 2AT, U.K
| | - David Klenerman
- University Chemical Laboratories, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
| | - Shankar Balasubramanian
- University Chemical Laboratories, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
- School of Clinical Medicine, University of Cambridge, Cambridge CB2 0SP, U.K
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28
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Calado RT, Regal JA, Kajigaya S, Young NS. Erosion of telomeric single-stranded overhang in patients with aplastic anaemia carrying telomerase complex mutations. Eur J Clin Invest 2009; 39:1025-32. [PMID: 19674077 PMCID: PMC6738339 DOI: 10.1111/j.1365-2362.2009.02209.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
BACKGROUND Loss-of-function mutations in telomerase complex genes reduce telomerase activity and shorten overall telomere length in leucocytes, and they can clinically manifest as bone marrow failure (aplastic anaemia and dyskeratosis congenita) and familial pulmonary fibrosis. Telomeres are constituted of double-stranded tandem TTAGGG repeats followed by a 3' G-rich single-stranded overhang, a crucial telomeric structural component responsible for the t-loop formation. MATERIALS AND METHODS We investigated the length of telomeric overhangs in 25 healthy individuals from 0 to 76 years of age, 16 patients with aplastic anaemia, and 13 immediate relatives using a non-denaturing in-gel method and the telomere-oligonucleotide ligation assay. RESULTS Telomeric overhang lengths were constant from birth to eighth decade of life in healthy subjects, in contrast to overall telomere length, which shortened with ageing. Most patients with marrow failure and a telomerase gene mutation showed marked erosion of telomeric overhang associated with critically short telomeres; in other aplastic patients with normal genotypes, normal overall telomere lengths and who responded to immunosuppressive therapy, telomeric overhangs were maintained. CONCLUSIONS Telomeric overhang erosion does not participate in physiological ageing but support a role for eroded telomeric overhangs and abnormal telomere structure in pathological shortening of telomeres, especially caused by loss-of-function telomerase mutations. Disrupted telomere structure caused by short telomeric overhangs may contribute to the mechanisms of abnormal haematopoietic compartment senescence and chromosomal instability in human bone marrow failure.
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Affiliation(s)
- R T Calado
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1202, USA.
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Hills M, Lansdorp PM. Short telomeres resulting from heritable mutations in the telomerase reverse transcriptase gene predispose for a variety of malignancies. Ann N Y Acad Sci 2009; 1176:178-90. [PMID: 19796246 DOI: 10.1111/j.1749-6632.2009.04565.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Telomeres are composed of long arrays of TTAGGG repeats and associated proteins that act as a protective cap for chromosome ends. The length of telomere repeats is set in the germline but decreases in somatic cells, primarily as a function of DNA replication. Progressive telomere shortening limits stem cell divisions and probably acts as a tumor suppressor mechanism. Using a sensitive PCR method to detect the length of individual telomere repeats on specific chromosomes, we confirmed that telomere length decreases from primitive to more differentiated human cell types within the hematopoietic hierarchy. Genetic mutations in the components of telomerase (the RNA template sequence hTERC, reverse transcriptase hTERT, and Syskerin DKC1) have recently been implicated in a variety of bone marrow failure syndromes, idiopathic pulmonary fibrosis, and more recently, acute myeloid leukemia (AML). The majority of mutations discovered in AML patients were heritable and resulted in partial loss of telomerase activity, a finding counterintuitive to the requirement of telomerase in cancer cells. We have found heritable hypomorphic TERT mutations in other cancers as well, and we propose that such mutations result in short telomeres and premature loss of stem cells. Loss of normal stem cells could provide strong selection for abnormal cells incapable of responding to DNA damage signals originating from short telomeres. Such cells will have a DNA repair defect resulting in genomic instability and a mutator phenotype. Our findings point to an intimate connection between senescence and cancer and highlight the important role of telomeres in the biology of normal and malignant human cells.
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Affiliation(s)
- Mark Hills
- Terry Fox Laboratory, BC Cancer Agency, Vancouver, British Columbia, Canada
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30
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Abstract
The telomeres of most eukaryotes are characterized by guanine-rich repeats synthesized by the reverse transcriptase telomerase. Complete loss of telomerase is tolerated for several generations in most species, but modestly reduced telomerase levels in human beings are implicated in bone marrow failure, pulmonary fibrosis and a spectrum of other diseases including cancer. Differences in telomerase deficiency phenotypes between species most likely reflect a tumour suppressor function of telomeres in long-lived mammals that does not exist as such in short-lived organisms. Another puzzle provided by current observations is that family members with the same genetic defect, haplo-insufficiency for one of the telomerase genes, can present with widely different diseases. Here, the crucial role of telomeres and telomerase in human (stem cell) biology is discussed from a Darwinian perspective. It is proposed that the variable phenotype and penetrance of heritable human telomerase deficiencies result from additional environmental, genetic and stochastic factors or combinations thereof.
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Sex hormones, acting on the TERT gene, increase telomerase activity in human primary hematopoietic cells. Blood 2009; 114:2236-43. [PMID: 19561322 DOI: 10.1182/blood-2008-09-178871] [Citation(s) in RCA: 260] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Androgens have been used in the treatment of bone marrow failure syndromes without a clear understanding of their mechanism of action. Blood counts of patients with dyskeratosis congenita or aplastic anemia with mutations in telomerase genes can improve with androgen therapy. Here we observed that exposure in vitro of normal peripheral blood lymphocytes and human bone marrow-derived CD34(+) cells to androgens increased telomerase activity, coincident with higher TERT mRNA levels. Cells from patients who were heterozygous for telomerase mutations had low baseline telomerase activity, which was restored to normal levels by exposure to androgens. Estradiol had an effect similar to androgens on TERT gene expression and telomerase enzymatic activity. Tamoxifen abolished the effects of both estradiol and androgens on telomerase function, and letrozole, an aromatase inhibitor, blocked androgen effects on telomerase activity. Conversely, flutamide, an androgen receptor antagonist, did not affect androgen stimulation of telomerase. Down-regulation by siRNA of estrogen receptor-alpha (ER alpha), but not ER beta, inhibited estrogen-stimulated telomerase function. Our results provide a mechanism for androgen therapy in bone marrow failure: androgens appear to regulate telomerase expression and activity mainly by aromatization and through ER alpha. These findings have potential implications for the choice of current androgenic compounds and the development of future agents for clinical use.
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Trahan C, Dragon F. Dyskeratosis congenita mutations in the H/ACA domain of human telomerase RNA affect its assembly into a pre-RNP. RNA (NEW YORK, N.Y.) 2009; 15:235-243. [PMID: 19095616 PMCID: PMC2648702 DOI: 10.1261/rna.1354009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Accepted: 10/30/2008] [Indexed: 05/27/2023]
Abstract
Dyskeratosis congenita (DC) is an inherited disorder that implicates defects in the biology of telomeres, which are maintained by telomerase, a ribonucleoprotein with reverse transcriptase activity. Like all H/ACA RNAs, the H/ACA domain of nascent human telomerase RNA (hTR) forms a pre-RNP with H/ACA proteins NAF1, dyskerin, NOP10, and NHP2 in vivo. To assess the pre-RNP assembly of hTR mutants that poorly accumulate in vivo, we developed an in vitro system that uses components of human origin. Pre-RNPs were reconstituted with synthetic (32)P-labeled RNAs and (35)S-labeled proteins produced in rabbit reticulocyte lysate, and immunoprecipitations were carried out to analyze RNP formation. We show that human NAF1 cannot bind directly to the H/ACA domain of hTR, and requires the core trimer dyskerin-NOP10-NHP2 to be efficiently incorporated into the pre-RNP. This order of assembly seems common to H/ACA RNAs since it was observed with snoRNA ACA36 and scaRNA U92, which are predicted to guide pseudouridylation of 18S rRNA and U2 snRNA, respectively. However, the processing H/ACA snoRNA U17 did not conform to this rule, as NAF1 alone was able to bind it. We also provide the first evidence that DC-related mutations of hTR C408G and Delta378-451 severely impair pre-RNP assembly. Integrity of boxes H and ACA of hTR are also crucial for pre-RNP assembly, while the CAB box is dispensable. Our results offer new insights into the defects caused by some mutations located in the H/ACA domain of hTR.
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Affiliation(s)
- Christian Trahan
- Département des Sciences Biologiques and Centre de Recherche BioMed, Université du Québec à Montréal, Canada
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33
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Constitutional hypomorphic telomerase mutations in patients with acute myeloid leukemia. Proc Natl Acad Sci U S A 2009; 106:1187-92. [PMID: 19147845 DOI: 10.1073/pnas.0807057106] [Citation(s) in RCA: 143] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Loss-of-function mutations in telomerase complex genes can cause bone marrow failure, dyskeratosis congenita, and acquired aplastic anemia, both diseases that predispose to acute myeloid leukemia. Loss of telomerase function produces short telomeres, potentially resulting in chromosome recombination, end-to-end fusion, and recognition as damaged DNA. We investigated whether mutations in telomerase genes also occur in acute myeloid leukemia. We screened bone marrow samples from 133 consecutive patients with acute myeloid leukemia and 198 controls for variations in TERT and TERC genes. An additional 89 patients from a second cohort, selected based on cytogenetic status, and 528 controls were further examined for mutations. A third cohort of 372 patients and 384 controls were specifically tested for one TERT gene variant. In the first cohort, 11 patients carried missense TERT gene variants that were not present in controls (P < 0.0001); in the second cohort, TERT mutations were associated with trisomy 8 and inversion 16. Mutation germ-line origin was demonstrated in 5 patients from whom other tissues were available. Analysis of all 3 cohorts (n = 594) for the most common gene variant (A1062T) indicated a prevalence 3 times higher in patients than in controls (n = 1,110; P = 0.0009). Introduction of TERT mutants into telomerase-deficient cells resulted in loss of enzymatic activity by haploinsufficiency. Inherited mutations in TERT that reduce telomerase activity are risk factors for acute myeloid leukemia. We propose that short and dysfunctional telomeres limit normal stem cell proliferation and predispose for leukemia by selection of stem cells with defective DNA damage responses that are prone to genome instability.
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34
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Chakraborty S, Sun CL, Francisco L, Sabado M, Li L, Chang KL, Forman S, Bhatia S, Bhatia R. Accelerated telomere shortening precedes development of therapy-related myelodysplasia or acute myelogenous leukemia after autologous transplantation for lymphoma. J Clin Oncol 2009; 27:791-8. [PMID: 19124806 DOI: 10.1200/jco.2008.17.1033] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
PURPOSE Therapy-related myelodysplasia or acute myelogenous leukemia (t-MDS/AML) is a lethal complication of autologous hematopoietic stem-cell transplantation (aHCT) for Hodgkin's lymphoma (HL) and non-Hodgkin's lymphoma (NHL). Here, we investigated the hypothesis that accelerated telomere shortening after aHCT could contribute to the development of t-MDS/AML. PATIENTS AND METHODS A prospective longitudinal cohort was constructed to investigate the sequence of cellular and molecular abnormalities leading to development of t-MDS/AML after aHCT for HL/NHL. This cohort formed the sampling frame for a nested case-control study to compare changes in telomere length in serial blood samples from patients who developed t-MDS/AML with matched controls who did not develop t-MDS/AML. RESULTS An initial increase in telomere length at day 100 after aHCT was followed by an accelerated telomere shortening in t-MDS/AML patients when compared with controls. These telomere alterations preceded the onset of t-MDS and were independent of other known risk factors associated with development of t-MDS/AML on multivariate analysis. Additionally, we observed reduced generation of committed progenitors in patients who developed t-MDS/AML, indicating that these telomere alterations were associated with reduced regenerative capacity of hematopoietic stem cells. CONCLUSION The development of t-MDS/AML after aHCT is associated with and preceded by markedly altered telomere dynamics in hematopoietic cells. Accelerated telomere loss in patients developing t-MDS/AML may reflect increased clonal proliferation and/or altered telomere regulation in premalignant cells. Genetic instability associated with shortened telomeres may contribute to leukemic transformation in t-MDS/AML.
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Affiliation(s)
- Sujata Chakraborty
- Department of Stem Cell and Leukemia Research, Division of Population Sciences, City of Hope National Medical Center, Duarte, CA 91010, USA
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Abstract
Telomeres play a central role in cell fate and aging by adjusting the cellular response to stress and growth stimulation on the basis of previous cell divisions and DNA damage. At least a few hundred nucleotides of telomere repeats must "cap" each chromosome end to avoid activation of DNA repair pathways. Repair of critically short or "uncapped" telomeres by telomerase or recombination is limited in most somatic cells and apoptosis or cellular senescence is triggered when too many "uncapped" telomeres accumulate. The chance of the latter increases as the average telomere length decreases. The average telomere length is set and maintained in cells of the germline which typically express high levels of telomerase. In somatic cells, telomere length is very heterogeneous but typically declines with age, posing a barrier to tumor growth but also contributing to loss of cells with age. Loss of (stem) cells via telomere attrition provides strong selection for abnormal and malignant cells, a process facilitated by the genome instability and aneuploidy triggered by dysfunctional telomeres. The crucial role of telomeres in cell turnover and aging is highlighted by patients with 50% of normal telomerase levels resulting from a mutation in one of the telomerase genes. Short telomeres in such patients are implicated in a variety of disorders including dyskeratosis congenita, aplastic anemia, pulmonary fibrosis, and cancer. Here the role of telomeres and telomerase in human aging and aging-associated diseases is reviewed.
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Affiliation(s)
- Geraldine Aubert
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
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Characterization of primitive hematopoietic cells from patients with dyskeratosis congenita. Blood 2008; 111:4523-31. [PMID: 18310499 DOI: 10.1182/blood-2007-10-120204] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Dyskeratosis congenita (DC) is an inherited bone marrow (BM) failure syndrome associated with mutations in telomerase genes and the acquisition of shortened telomeres in blood cells. To investigate the basis of the compromised hematopoiesis seen in DC, we analyzed cells from granulocyte colony-stimulating factor mobilized peripheral blood (mPB) collections from 5 members of a family with autosomal dominant DC with a hTERC mutation. Premobilization BM samples were hypocellular, and percentages of CD34(+) cells in marrow and mPB collections were significantly below values for age-matched controls in 4 DC subjects. Directly clonogenic cells, although present at normal frequencies within the CD34(+) subset, were therefore absolutely decreased. In contrast, even the frequency of long-term culture-initiating cells within the CD34(+) DC mPB cells was decreased, and the telomere lengths of these cells were also markedly reduced. Nevertheless, the different lineages of mature cells were produced in normal numbers in vitro. These results suggest that marrow failure in DC is caused by a reduction in the ability of hematopoietic stem cells to sustain their numbers due to telomere impairment rather than a qualitative defect in their commitment to specific lineages or in the ability of their lineage-restricted progeny to execute normal differentiation programs.
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Abstract
Acquired and congenital aplastic anemias recently have been linked molecularly and pathophysiologically by abnormal telomere maintenance. Telomeres are repeated nucleotide sequences that cap the ends of chromosomes and protect them from damage. Telomeres are eroded with cell division, but in hematopoietic stem cells, maintenance of their length is mediated by telomerase. Accelerated telomere shortening is virtually universal in dyskeratosis congenita, caused by mutations in genes encoding components of telomerase or telomere-binding protein (TERT, TERC, DKC1, NOP10, or TINF2). About one-third of patients with acquired aplastic anemia also have short telomeres, which in some cases associate with TERT or TERC mutations. These mutations cause low telomerase activity, accelerated telomere shortening, and diminished proliferative capacity of hematopoietic progenitors. As in other genetic diseases, additional environmental, genetic, and epigenetic modifiers must contribute to telomere erosion and ultimately to disease phenotype. Short telomeres also may cause genomic instability and malignant progression in these marrow failure syndromes. Identification of short telomeres has potential clinical implications: it may be useful in dyskeratosis congenita diagnosis, in suggesting mutations in patients with acquired aplastic anemia, and for selection of suitable hematopoietic stem cell family donors for transplantation in telomerase-deficient patients.
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Dyskeratosis congenita: The diverse clinical presentation of mutations in the telomerase complex. Biochimie 2008; 90:122-30. [DOI: 10.1016/j.biochi.2007.07.017] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Accepted: 07/22/2007] [Indexed: 12/23/2022]
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Xie M, Mosig A, Qi X, Li Y, Stadler PF, Chen JJL. Structure and function of the smallest vertebrate telomerase RNA from teleost fish. J Biol Chem 2007; 283:2049-59. [PMID: 18039659 DOI: 10.1074/jbc.m708032200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Telomerase extends chromosome ends by copying a short template sequence within its intrinsic RNA component. Telomerase RNA (TR) from different groups of species varies dramatically in sequence and size. We report here the bioinformatic identification, secondary structure comparison, and functional analysis of the smallest known vertebrate TRs from five teleost fishes. The teleost TRs (312-348 nucleotides) are significantly smaller than the cartilaginous fish TRs (478-559 nucleotides) and tetrapod TRs. This remarkable length reduction of teleost fish TRs correlates positively with the genome size, reflecting an unusual structural plasticity of TR during evolution. The teleost TR consists of a compact three-domain structure, lacking most of the sequences in regions that are variable in other vertebrate TR structures. The medaka and fugu TRs, when assembled with their telomerase reverse transcriptase (TERT) protein counterparts, reconstituted active and processive telomerase enzymes. Titration analysis of individual RNA domains suggests that the efficient assembly of the telomerase complex is influenced more by the telomerase reverse transcriptase (TERT) binding of the CR4-CR5 domain than the pseudoknot domain of TR. The remarkably small teleost fish TR further expands our understanding about the evolutionary divergence of vertebrate TR.
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Affiliation(s)
- Mingyi Xie
- Department of Chemistry & Biochemistry and School of Life Sciences, Arizona State University, Tempe, Arizona 85287, USA
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40
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Zimmermann S, Martens UM. Telomeres, senescence, and hematopoietic stem cells. Cell Tissue Res 2007; 331:79-90. [PMID: 17960423 DOI: 10.1007/s00441-007-0469-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2007] [Accepted: 07/10/2007] [Indexed: 01/01/2023]
Abstract
The replicative lifespan of normal somatic cells is restricted by the erosion of telomeres, which are protective caps at the ends of linear chromosomes. The loss of telomeres induces antiproliferative signals that eventually lead to cellular senescence. The enzyme complex telomerase can maintain telomeres, but its expression is confined to highly proliferative cells such as stem cells and tumor cells. The immense regenerative capacity of the hematopoietic system is provided by a distinct type of adult stem cell: hematopoietic stem cells (HSCs). Although blood cells have to be produced continuously throughout life, the HSC pool seems not to be spared by aging processes. Indeed, limited expression of telomerase is not sufficient to prevent telomere shortening in these cells, which is thought ultimately to limit their proliferative capacity. In this review, we discuss the relevance of telomere maintenance for the hematopoietic stem cell compartment and consider potential functions of telomerase in this context. We also present possible clinical applications of telomere manipulation in HSCs and new insights affecting the aging of the hematopoietic stem cell pool and replicative exhaustion.
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Affiliation(s)
- Stefan Zimmermann
- Department of Hematology/Oncology, Freiburg University Medical Center, Hugstetterstrasse 55, 79106, Freiburg, Germany.
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41
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Identification and functional characterization of novel telomerase variant alleles in Japanese patients with bone-marrow failure syndromes. Blood Cells Mol Dis 2007; 40:185-191. [PMID: 17936651 DOI: 10.1016/j.bcmd.2007.08.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2007] [Revised: 06/14/2007] [Accepted: 08/02/2007] [Indexed: 11/21/2022]
Abstract
As the incidence of bone-marrow failure syndromes (BMFS) is 2-3x higher in East Asia than in the West, we examined peripheral blood or marrow cells of 100 Japanese patients for possible pathogenic mutations in the two main components of the telomere-synthesizing enzyme telomerase (hTERC RNA and hTERT protein) that have recently been implicated in the disease pathogenesis. We analyzed samples collected from 34 patients with acquired aplastic anemia (AA), 66 patients with myelodysplastic syndromes (MDS) and 120 healthy controls. In addition to two polymorphic germ-line sequence changes (n-771A/G and n-714 C insertion) in the promoter region of hTERC and eleven hTERT polymorphisms that were identified in both patients and healthy individuals, we found a novel germ-line C323T mutation in the hTERC RNA in an MDS patient only. This heterozygous C323T mutation abolished telomerase enzymatic activity and functioned in a haploinsufficiency manner to modulate telomerase activity in cells. In summary, this study reports a novel telomerase natural variant that abolishes telomerase function, which may lead to telomere shortening and marrow hypocellularity in patients with BMFS. This study also highlights the rarity of genetic alterations in BMFS patients in Japan, which suggests that other factors may play a more prominent role in the disease pathogenesis in East Asia.
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Baerlocher GM, Vulto I, de Jong G, Lansdorp PM. Flow cytometry and FISH to measure the average length of telomeres (flow FISH). Nat Protoc 2007; 1:2365-76. [PMID: 17406480 DOI: 10.1038/nprot.2006.263] [Citation(s) in RCA: 312] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Telomeres have emerged as crucial cellular elements in aging and various diseases including cancer. To measure the average length of telomere repeats in cells, we describe our protocols that use fluorescent in situ hybridization (FISH) with labeled peptide nucleic acid (PNA) probes specific for telomere repeats in combination with fluorescence measurements by flow cytometry (flow FISH). Flow FISH analysis can be performed using commercially available flow cytometers, and has the unique advantage over other methods for measuring telomere length of providing multi-parameter information on the length of telomere repeats in thousands of individual cells. The accuracy and reproducibility of the measurements is augmented by the automation of most pipetting (aspiration and dispensing) steps, and by including an internal standard (control cells) with a known telomere length in every tube. The basic protocol for the analysis of nucleated blood cells from 22 different individuals takes about 12 h spread over 2-3 days.
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Affiliation(s)
- Gabriela M Baerlocher
- Terry Fox Laboratory, British Columbia Cancer Agency, 675 West 10th Avenue, Vancouver, British Columbia, V5Z 1L3, Canada.
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Garcia CK, Wright WE, Shay JW. Human diseases of telomerase dysfunction: insights into tissue aging. Nucleic Acids Res 2007; 35:7406-16. [PMID: 17913752 PMCID: PMC2190725 DOI: 10.1093/nar/gkm644] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
There are at least three human diseases that are associated with germ-line mutations of the genes encoding the two essential components of telomerase, TERT and TERC. Heterozygous mutations of these genes have been described for patients with dyskeratosis congenita, bone marrow failure and idiopathic pulmonary fibrosis. In this review, we will detail the clinical similarities and difference of these diseases and review the molecular phenotypes observed. The spectrum of mutations in TERT and TERC varies for these diseases and may in part explain the clinical differences observed. Environmental insults and genetic modifiers that accelerate telomere shortening and increase cell turnover may exaggerate the effects of telomerase haploinsufficiency, contributing to the variability of age of onset as well as tissue-specific organ pathology. A central still unanswered question is whether telomerase dysfunction and short telomeres are a much more prominent factor than previously suspected in other adult-onset, age-related diseases. Understanding the biological effects of these mutations may ultimately lead to novel treatments for these patients.
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Affiliation(s)
- Christine Kim Garcia
- McDermott Center for Human Growth and Development and the Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine and Department of Cell Biology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
| | - Woodring E. Wright
- McDermott Center for Human Growth and Development and the Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine and Department of Cell Biology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
| | - Jerry W. Shay
- McDermott Center for Human Growth and Development and the Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine and Department of Cell Biology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
- *To whom correspondence should be addressed.+1 214-648-3282+1 214-648-8694
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Marrone A, Walne A, Tamary H, Masunari Y, Kirwan M, Beswick R, Vulliamy T, Dokal I. Telomerase reverse-transcriptase homozygous mutations in autosomal recessive dyskeratosis congenita and Hoyeraal-Hreidarsson syndrome. Blood 2007; 110:4198-205. [PMID: 17785587 PMCID: PMC2882230 DOI: 10.1182/blood-2006-12-062851] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dyskeratosis congenita (DC) is a multisystem bone marrow failure syndrome characterized by a triad of mucocutaneous abnormalities and an increased predisposition to malignancy. X-linked DC is due to mutations in DKC1, while heterozygous mutations in TERC (telomerase RNA component) and TERT (telomerase reverse transcriptase) have been found in autosomal dominant DC. Many patients with DC remain uncharacterized, particularly families displaying autosomal recessive (AR) inheritance. We have now identified novel homozygous TERT mutations in 2 unrelated consanguineous families, where the index cases presented with classical DC or the more severe variant, Hoyeraal-Hreidarsson (HH) syndrome. These TERT mutations resulted in reduced telomerase activity and extremely short telomeres. As these mutations are homozygous, these patients are predicted to have significantly reduced telomerase activity in vivo. Interestingly, in contrast to patients with heterozygous TERT mutations or hemizygous DKC1 mutations, these 2 homozygous TERT patients were observed to have higher-than-expected TERC levels compared with controls. Collectively, the findings from this study demonstrate that homozygous TERT mutations, resulting in a pure but severe telomerase deficiency, produce a phenotype of classical AR-DC and its severe variant, the HH syndrome.
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Affiliation(s)
- Anna Marrone
- Academic Unit of Paediatrics, Institute of Cell and Molecular Science, Barts and The London, Queen Mary’s School of Medicine and Dentistry, London, United Kingdom
| | - Amanda Walne
- Academic Unit of Paediatrics, Institute of Cell and Molecular Science, Barts and The London, Queen Mary’s School of Medicine and Dentistry, London, United Kingdom
| | - Hannah Tamary
- Department of Paediatric Haematology, Schneider Children’s Medical Center of Israel, Sackler School of Medicine, Tel Aviv University, Petah-Tikva, Israel
| | - Yuka Masunari
- Academic Unit of Paediatrics, Institute of Cell and Molecular Science, Barts and The London, Queen Mary’s School of Medicine and Dentistry, London, United Kingdom
| | - Michael Kirwan
- Academic Unit of Paediatrics, Institute of Cell and Molecular Science, Barts and The London, Queen Mary’s School of Medicine and Dentistry, London, United Kingdom
| | - Richard Beswick
- Academic Unit of Paediatrics, Institute of Cell and Molecular Science, Barts and The London, Queen Mary’s School of Medicine and Dentistry, London, United Kingdom
| | - Tom Vulliamy
- Academic Unit of Paediatrics, Institute of Cell and Molecular Science, Barts and The London, Queen Mary’s School of Medicine and Dentistry, London, United Kingdom
| | - Inderjeet Dokal
- Academic Unit of Paediatrics, Institute of Cell and Molecular Science, Barts and The London, Queen Mary’s School of Medicine and Dentistry, London, United Kingdom
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Abstract
Dyskeratosis congenita (DKC) is a bone marrow failure (BMF) with characteristic physical anomalies, and is typically diagnosed in childhood. Some forms of DKC are known to be caused by mutations occurring in DKC1, telomerase RNA component (TERC), and telomerase reverse transcriptase (TERT). These genes are the main constituents of the telomerase complex that plays a role in replicating telomeres and stabilizing them against shortening. Mutations in these genes could shorten telomeres and impair the proliferative capacity of hematopoietic stem cells, eventually causing DKC. Recently, mutations in TERC and TERT have been reported in some cases of aplastic anemia (AA) and myelodysplastic syndrome (MDS). These cases are considered to be atypical forms of DKC that develop slowly in adulthood without characteristic physical anomalies. Genetic tests are essential in diagnosing this late-presenting DKC and determining the appropriate treatment. This article reviews mutations in the telomerase complex and their connections with DKC and bone marrow failures.
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Affiliation(s)
- Hiroki Yamaguchi
- Department of Pathophysiological Management/Medical Oncology, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan.
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46
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Marrone A, Sokhal P, Walne A, Beswick R, Kirwan M, Killick S, Williams M, Marsh J, Vulliamy T, Dokal I. Functional characterization of novel telomerase RNA (TERC) mutations in patients with diverse clinical and pathological presentations. Haematologica 2007; 92:1013-20. [PMID: 17640862 PMCID: PMC2892775 DOI: 10.3324/haematol.11407] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Accepted: 05/15/2007] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND AND OBJECTIVES Functional characterization of heterozygous TERC (telomerase RNA component) and TERT (telomerase reverse transcriptase) mutations found in autosomal dominant dyskeratosis congenita (DC) and aplastic anemia (AA) shows that telomerase function is defective and that this is associated with short telomeres. This leads to reduced cell longevity with maximal impact on tissues with high proliferate potential. The aim of this study was to establish the role of TERC in the pathophysiology of uncharacterized patients with AA with some features of DC. DESIGN AND METHODS The TERC gene was screened for mutations by denaturing high performance liquid chromatography. To determine the functional significance of TERC mutations telomerase activity was assessed in an in vitro (TRAP) assay and telomere length of patients' samples was determined using Southern blot analysis. RESULTS This study led to the identification of four novel TERC mutations (G178A, C180T, D52-86 and G2C) and a recurrent TERC mutation (D110-113GACT). INTERPRETATION AND CONCLUSIONS Two of the de novo TERC mutations (G178A and C180T) found uniquely produce a clinical phenotype in the first generation, differing from previously published cases in which individuals in the first generation are usually asymptomatic. Curiously these mutations are located near the triple-helix domain of TERC. We also observed that the recurrent D110-113GACT can present with AA, myelodysplasia or leukemia. The D52-86 is associated with varied phenotypes including pulmonary disease (pulmonary fibrosis) as the first presentation. In summary, this study reports the functional characterization of several novel TERC mutations associated with varied hematologic and extra-hematologic presentations.
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Affiliation(s)
- Anna Marrone
- Academic Unit of Paediatrics, Institute of Cell and Molecular Science, Barts and The London,Queen Mary's School of Medicine and Dentistry, The Blizard Building, 4 Newark Street, London, E1 2AT, UK.
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47
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Westin ER, Chavez E, Lee KM, Gourronc FA, Riley S, Lansdorp PM, Goldman FD, Klingelhutz AJ. Telomere restoration and extension of proliferative lifespan in dyskeratosis congenita fibroblasts. Aging Cell 2007; 6:383-94. [PMID: 17381549 PMCID: PMC2225626 DOI: 10.1111/j.1474-9726.2007.00288.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Dyskeratosis congenita (DC), an inherited bone marrow failure syndrome, is caused by defects in telomerase. Somatic cells from DC patients have shortened telomeres and clinical symptoms are most pronounced in organs with a high cell turnover, including those involved in hematopoiesis and skin function. We previously identified an autosomal dominant (AD) form of DC that is caused by mutations in the telomerase RNA component (TER). In this study, we evaluated whether retroviral expression of TER and/or telomerase reverse transcriptase (TERT), the catalytic component of telomerase, could extend telomere length and rescue AD DC cells from a phenotype characteristic of early senescence. Exogenous TER expression, without TERT, could not activate telomerase in AD DC skin fibroblasts. Transduction of TERT alone, however, provided AD DC cells with sufficient telomerase activity to extend average telomere length and proliferative capacity. Interestingly, we found that expression of TER and TERT together resulted in extension of lifespan and higher levels of telomerase and longer telomeres than expression of TERT alone in both AD DC and normal cells. Our results provide evidence that AD DC cells can be rescued from defects in telomere maintenance and proliferation, and that coexpression of TERT and TER together provides a more efficient means to elongate telomeres than expression of TERT alone. Similar strategies may be useful for ameliorating the detrimental effects of telomere shortening in AD DC and other diseases associated with telomerase or telomere defects.
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Affiliation(s)
- Erik R. Westin
- Interdisciplinary Program in Genetics, University of Iowa, Iowa City, IA, USA
| | - Elizabeth Chavez
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
| | - Kimberly M. Lee
- Department of Microbiology, University of Iowa, Iowa City, IA, USA
| | | | - Soraya Riley
- Program in Molecular and Cellular Biology, University of Iowa, Iowa City, IA, USA
| | - Peter M. Lansdorp
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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Li X, Nishizuka H, Tsutsumi K, Imai Y, Kurihara Y, Uesugi S. Structure, interactions and effects on activity of the 5'-terminal region of human telomerase RNA. J Biochem 2007; 141:755-65. [PMID: 17387120 DOI: 10.1093/jb/mvm081] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Telomerase is an enzyme that catalyzes addition of telomeric repeat sequences to the 3'-termini of eukaryotic chromosome DNA. The catalytic core of telomerase consists of a protein component, telomerase reverse transcriptase (TERT), for the catalysis and an RNA component, telomerase RNA (TR), containing the template for the sequence. Human telomerase RNA (hTR) consists of 451 nucleotides (nt) and contains consecutive G-stretches in the 5'-terminal region. We examined the effects of the 5'-terminal sequence (nt 1-17) in hTR, which is assumed to be a single-stranded region (region 1), on interaction and telomerase activity in vitro. Mutation and binding experiments for hTR and its variants suggest that region 1 has repressive effects on telomerase activity by interaction with the region(s) in the 3'-half part. We prepared various hTR variants with mutations in region 1 and two possible target regions (region 2: nt 229-244; region 3: nt 284-297). Studies on these variants showed that region 1 can interact with regions 2 and 3 and the interactions between regions 1 and 3 may contribute to the repressive effects of region 1. We found that a mutation in region 2 markedly enhances telomerase activity. We also found that some deletion and sequence mutations in region 1 enhance the activity.
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Affiliation(s)
- Xianglan Li
- Department of Environment and Natural Sciences, Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
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49
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Thompson JE, Conlon JP, Yang X, Sanchez PV, Carroll M. Enhanced growth of myelodysplastic colonies in hypoxic conditions. Exp Hematol 2007; 35:21-31. [PMID: 17198870 PMCID: PMC3677695 DOI: 10.1016/j.exphem.2006.08.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Revised: 08/21/2006] [Accepted: 08/28/2006] [Indexed: 11/17/2022]
Abstract
OBJECTIVE To determine the response of bone marrow progenitor cells from patients with myelodysplastic syndromes (MDS) to culture in physiologic oxygen tension. METHODS Methylcellulose progenitor assays using both unfractionated bone marrow mononuclear cells (MNCs) and purified CD34(+) progenitors were performed in atmospheric oxygen (18.6% O(2)) or one of two levels of hypoxia (1% and 3% O(2)). Assays were performed using normal donor marrow, MDS patient marrow, acute myelogenous leukemia marrow or peripheral blood blasts, chronic phase chronic myelogenous leukemia (CML) marrow MNCs, and blast crisis CML peripheral blood. RESULTS The majority of MDS samples showed decreased colony-forming units (CFU) in 18.6% O(2) compared to normal controls, as expected. However, in either 1% or 3% O(2), 9 of 13 MDS samples demonstrated augmentation of CFUs beyond that observed in normal controls, with 6 of 13 demonstrating a greater than ninefold augmentation. This effect is cell autonomous, as it persisted after purification of CD34(+) progenitor cells. Additionally, the augmented response to physiologic oxygen tension is specific to MDS, as it was not observed in either acute or chronic myelogenous leukemia samples. CONCLUSION These results suggest that the reported decrease in MDS CFUs reflects greater sensitivity of MDS progenitors or their progeny to the nonphysiologic oxygen tensions routinely used in vitro, rather than a true decrease in progenitor frequency. Importantly, these experiments for the first time describe an experimental system that can be used to study the growth of primary cells from patients with MDS.
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Affiliation(s)
- James Edwin Thompson
- Division of Hematology and Oncology, University of Pennsylvania, Philadelphia, PA 19104-6160, USA.
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50
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Fleisig HB, Wong JMY. Telomerase as a clinical target: Current strategies and potential applications. Exp Gerontol 2007; 42:102-12. [PMID: 16814507 DOI: 10.1016/j.exger.2006.05.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2006] [Accepted: 05/05/2006] [Indexed: 01/19/2023]
Abstract
Chromosome ends are capped by telomeres, protective DNA-protein complexes that distinguish natural ends from random DNA breaks. Telomeres erode with each successive cell division, and such divisions cease once telomeres become critically short. This proliferation limit is important as a tumor suppressive mechanism, but also contributes to the degenerative conditions associated with cellular aging. In cell types that require continuous renewal, transient expression of telomerase delays proliferation arrest by the de novo synthesis of telomere repeats. Data from our work and others' has shown that deficient telomerase activity has a negative impact on normal human physiology. In the bone marrow failure syndrome dyskeratosis congenita, telomerase enzyme deficiency leads to the premature shortening of telomeres. Premature telomere shortening most grievously affects tissues that have a rapid turnover, such as the hematopoietic and epithelial compartments. In the most severe cases, compromised renewal of hematopoietic stem cells leads to bone marrow failure and premature death. Telomerase activation/replacement shows potential as a therapy for telomere maintenance deficiency syndromes, and in tissue engineering for the degenerative conditions that are associated with normal aging. Conversely, clinical researchers are developing telomerase inhibition therapies to treat tumors, which overcome the short-telomere barrier to unrestricted proliferation by over-expressing telomerase.
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Affiliation(s)
- Helen B Fleisig
- Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
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