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Yamamoto M, Keino D, Sumii S, Yokosuka T, Goto H, Inui A, Sogo T, Kawakami M, Tanaka M, Yanagimachi M. Severe Hepatitis-associated Aplastic Anemia Following COVID-19 mRNA Vaccination. Intern Med 2023. [PMID: 36948624 DOI: 10.2169/internalmedicine.1308-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/24/2023] Open
Abstract
We herein report a case of hepatitis-associated aplastic anemia (HAAA) that occurred after severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) vaccination. In this patient, progressive pancytopenia observed two months after acute hepatitis following the second dose of the SARS-Cov-2 vaccine indicated the development of HAAA. Although some reports have suggested that SARS-Cov-2 vaccination may be involved in the development of autoimmune diseases, no cases of HAAA developing after SARS-Cov-2 vaccination have been reported. SARS-Cov-2 vaccination in children has only started relatively recently, so the range of side effects in children has not yet been thoroughly described. Therefore, we need to strengthen surveillance for symptoms of children who are vaccinated.
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Affiliation(s)
- Michio Yamamoto
- Division of Hematology/Oncology, Kanagawa Children's Medical Center, Japan
| | - Dai Keino
- Division of Hematology/Oncology, Kanagawa Children's Medical Center, Japan
| | - Shinichiro Sumii
- Department of Pediatric Hepatology and Gastroenterology, Saiseikai Yokohamashi Tobu Hospital, Japan
| | - Tomoko Yokosuka
- Division of Hematology/Oncology, Kanagawa Children's Medical Center, Japan
| | - Hiroaki Goto
- Division of Hematology/Oncology, Kanagawa Children's Medical Center, Japan
| | - Ayano Inui
- Department of Pediatric Hepatology and Gastroenterology, Saiseikai Yokohamashi Tobu Hospital, Japan
| | - Tsuyoshi Sogo
- Department of Pediatric Hepatology and Gastroenterology, Saiseikai Yokohamashi Tobu Hospital, Japan
| | - Makio Kawakami
- Department of Pathology, Narita Sekijyuji Hospital, Japan
| | - Mio Tanaka
- Division of Pathology, Kanagawa Children's Medical Center, Japan
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Genetic and Epigenetic Inheritance at Telomeres. EPIGENOMES 2022; 6:epigenomes6010009. [PMID: 35323213 PMCID: PMC8947350 DOI: 10.3390/epigenomes6010009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 02/21/2022] [Accepted: 03/08/2022] [Indexed: 12/17/2022] Open
Abstract
Transgenerational inheritance can occur at telomeres in distinct contexts. Deficiency for telomerase or telomere-binding proteins in germ cells can result in shortened or lengthened chromosome termini that are transmitted to progeny. In human families, altered telomere lengths can result in stem cell dysfunction or tumor development. Genetic inheritance of altered telomeres as well as mutations that alter telomeres can result in progressive telomere length changes over multiple generations. Telomeres of yeast can modulate the epigenetic state of subtelomeric genes in a manner that is mitotically heritable, and the effects of telomeres on subtelomeric gene expression may be relevant to senescence or other human adult-onset disorders. Recently, two novel epigenetic states were shown to occur at C. elegans telomeres, where very low or high levels of telomeric protein foci can be inherited for multiple generations through a process that is regulated by histone methylation.Together, these observations illustrate that information relevant to telomere biology can be inherited via genetic and epigenetic mechanisms, although the broad impact of epigenetic inheritance to human biology remains unclear.
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3
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Del Brío Castillo R, Bleesing J, McCormick T, Squires JE, Mazariegos GV, Squires J, McKiernan PJ. Successful liver transplantation in short telomere syndromes without bone marrow failure due to DKC1 mutation. Pediatr Transplant 2020; 24:e13695. [PMID: 32166868 DOI: 10.1111/petr.13695] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 02/08/2020] [Accepted: 02/15/2020] [Indexed: 11/26/2022]
Abstract
Short telomere syndromes are a heterogenous spectrum of disorders leading to premature cellular aging. These may involve bone marrow failure, adult-onset idiopathic pulmonary fibrosis, and liver disease, and classical entities such as dyskeratosis congenita. We report a patient who presented with common variable immunodeficiency at 3 years of age and autoimmune cytopenias at 8 years of age. He was found to have short telomeres, and genetic testing confirmed a hemizygous mutation NM_001363.4: c.-142C > G in DKC1 gene. He subsequently developed cirrhosis with severe portal hypertension and hepatopulmonary syndrome, prompting liver transplantation at 11 years of age. He remains well 10 years after transplant with no progression of bone marrow failure or progressive lung disease. In conclusion, short telomere syndromes should be considered as a potential cause of pediatric liver disease of unknown etiology, and in severe cases, isolated liver transplantation may be both appropriate and successful.
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Affiliation(s)
| | - Jacob Bleesing
- Immunodeficiency and Histiocytosis Program, Cincinnati Children's Hospital, Cincinnati, OH, USA
| | | | - James E Squires
- Division of Gastroenterology, Hepatology and Nutrition, UPMC Children's Hospital of Pittsburgh, Pittsburgh, PA, USA
| | - George V Mazariegos
- Division of Pediatric Transplantation, Hillman Center for Pediatric Transplantation, UPMC Children's Hospital of Pittsburgh, Pittsburgh, PA, USA
| | - Judy Squires
- Department of Radiology, UPMC Children's Hospital of Pittsburgh, Pittsburgh, PA, USA
| | - Patrick J McKiernan
- Division of Gastroenterology, Hepatology and Nutrition, UPMC Children's Hospital of Pittsburgh, Pittsburgh, PA, USA
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4
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Structural, functional, and stability change predictions in human telomerase upon specific point mutations. Sci Rep 2019; 9:8707. [PMID: 31213647 PMCID: PMC6581908 DOI: 10.1038/s41598-019-45206-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 06/03/2019] [Indexed: 11/29/2022] Open
Abstract
Overexpression of telomerase is one of the hallmarks of human cancer. Telomerase is important for maintaining the integrity of the ends of chromosomes, which are called telomeres. A growing number of human disease syndromes are associated with organ failure caused by mutations in telomerase (hTERT or hTR). Mutations in telomerase lead to telomere shortening by decreasing the stability of the telomerase complex, reducing its accumulation, or directly affecting its enzymatic activity. In this work, potential human telomerase mutations were identified by a systematic computational approach. Moreover, molecular docking methods were used to predict the effects of these mutations on the affinity of certain ligands (C_9i, C_9k, 16A, and NSC749234). The C_9k inhibitor had the best binding affinity for wild-type (WT) telomerase. Moreover, C_9i and C_9k had improved interactions with human telomerase in most of the mutant models. The R631 and Y717 residues of WT telomerase formed interactions with all studied ligands and these interactions were also commonly found in most of the mutant models. Residues forming stable interactions with ligands in molecular dynamics (MD) were traced, and the MD simulations showed that the C_9k ligand formed different conformations with WT telomerase than the C_9i ligand.
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5
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Turning Uridines around: Role of rRNA Pseudouridylation in Ribosome Biogenesis and Ribosomal Function. Biomolecules 2018; 8:biom8020038. [PMID: 29874862 PMCID: PMC6023024 DOI: 10.3390/biom8020038] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 05/28/2018] [Accepted: 05/31/2018] [Indexed: 01/09/2023] Open
Abstract
Ribosomal RNA (rRNA) is extensively edited through base methylation and acetylation, 2'-O-ribose methylation and uridine isomerization. In human rRNA, 95 uridines are predicted to by modified to pseudouridine by ribonucleoprotein complexes sharing four core proteins and differing for a RNA sequence guiding the complex to specific residues to be modified. Most pseudouridylation sites are placed within functionally important ribosomal domains and can influence ribosomal functional features. Information obtained so far only partially explained the degree of regulation and the consequences of pseudouridylation on ribosomal structure and function in different physiological and pathological conditions. This short review focuses on the available evidence in this topic, highlighting open questions in the field and perspectives that the development of emerging techniques is offering.
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6
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Abstract
Telomere length (TL) predicts the onset of cellular senescence in vitro but the diagnostic utility of TL measurement in clinical settings is not fully known. We tested the value of TL measurement by flow cytometry and FISH (flowFISH) in patients with mutations in telomerase and telomere maintenance genes. TL had a discrete and reproducible normal range with definable upper and lower boundaries. While TL above the 50th age-adjusted percentile had a 100% negative predictive value for clinically relevant mutations, the lower threshold in mutation carriers was age-dependent, and adult mutation carriers often overlapped with the lowest decile of controls. The extent of telomere shortening correlated with the age at diagnosis as well as the short telomere syndrome phenotype. Extremely short TL caused bone marrow failure and immunodeficiency in children and young adults, while milder defects manifested as pulmonary fibrosis-emphysema in adults. We prospectively examined whether TL altered treatment decisions for newly diagnosed idiopathic bone marrow failure patients and found abnormally short TL enriched for patients with mutations in some inherited bone marrow failure genes, such as RUNX1, in addition to telomerase and telomere maintenance genes. The result was actionable, altering the choice of treatment regimen and/or hematopoietic stem cell donor in one-fourth of the cases (9 of 38, 24%). We conclude that TL measurement by flowFISH, when used for targeted clinical indications and in limited settings, can influence treatment decisions in ways that improve outcome.
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7
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Abstract
The importance of telomere length to human health, aging, and cancer continues to be underappreciated. This review examines some basics of telomere biology and relates how telomere function, telomerase activity, and mutations in TERC or TERT are involved in bone marrow failure, leukemias, and other cancers. Given the challenge to obtain accurate data on telomerase activity and telomere length in specific cell types, the situation in acute myeloid leukemia (AML) remains puzzling. In most cancers, telomerase levels are increased after cells have encountered a "telomere crisis," which is typically associated with poor prognosis. Cells emerging from "telomere crisis" have defective DNA damage responses, resulting, for example, from loss of p53. Such cells often express elevated telomerase levels as a result of point mutations in the TERT promoter or amplification of the TERT gene. While telomeres in AML blasts are typically shorter than expected for normal leukocytes, most AML cells do not show evidence of having gone through a "telomere crisis." In chronic myeloid leukemia (CML), the difference between the telomere length in nonmalignant T cells and malignant blasts from the same patient was found to correlate with the remaining duration of the chronic phase. This observation supports that a mitotic clock is ticking in CML stem cells and that disease progression in CML heralds the onset of a "telomere crisis." The presence of very short telomeres in tumor cells was found to predict disease progression in chronic lymphocytic leukemia, myeloma, and various solid tumors. In view of these findings longitudinal studies of telomere length in AML appear worthwhile.
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8
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Hoffman H, Rice C, Skordalakes E. Structural Analysis Reveals the Deleterious Effects of Telomerase Mutations in Bone Marrow Failure Syndromes. J Biol Chem 2017; 292:4593-4601. [PMID: 28154186 DOI: 10.1074/jbc.m116.771204] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 01/27/2017] [Indexed: 12/17/2022] Open
Abstract
Naturally occurring mutations in the ribonucleoprotein reverse transcriptase, telomerase, are associated with the bone marrow failure syndromes dyskeratosis congenita, aplastic anemia, and idiopathic pulmonary fibrosis. However, the mechanism by which these mutations impact telomerase function remains unknown. Here we present the structure of the human telomerase C-terminal extension (or thumb domain) determined by the method of single-wavelength anomalous diffraction to 2.31 Å resolution. We also used direct telomerase activity and nucleic acid binding assays to explain how naturally occurring mutations within this portion of telomerase contribute to human disease. The single mutations localize within three highly conserved regions of the telomerase thumb domain referred to as motifs E-I (thumb loop and helix), E-II, and E-III (the FVYL pocket, comprising the hydrophobic residues Phe-1012, Val-1025, Tyr-1089, and Leu-1092). Biochemical data show that the mutations associated with dyskeratosis congenita, aplastic anemia, and idiopathic pulmonary fibrosis disrupt the binding between the protein subunit reverse transcriptase of the telomerase and its nucleic acid substrates leading to loss of telomerase activity and processivity. Collectively our data show that although these mutations do not alter the overall stability or expression of telomerase reverse transcriptase, these rare genetic disorders are associated with an impaired telomerase holoenzyme that is unable to correctly assemble with its nucleic acid substrates, leading to incomplete telomere extension and telomere attrition, which are hallmarks of these diseases.
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Affiliation(s)
- Hunter Hoffman
- From the Department of Gene Expression and Regulation, Wistar Institute, Philadelphia, Pennsylvania 19104 and
| | - Cory Rice
- From the Department of Gene Expression and Regulation, Wistar Institute, Philadelphia, Pennsylvania 19104 and.,the Department of Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Emmanuel Skordalakes
- From the Department of Gene Expression and Regulation, Wistar Institute, Philadelphia, Pennsylvania 19104 and .,the Department of Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
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9
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Abstract
The incidence of many types of cancer arising in organs with non-reproductive functions is significantly higher in male populations than in female populations, with associated differences in survival. Occupational and/or behavioural factors are well-known underlying determinants. However, cellular and molecular differences between the two sexes are also likely to be important. In this Opinion article, we focus on the complex interplay that sex hormones and sex chromosomes can have in intrinsic control of cancer-initiating cell populations, the tumour microenvironment and systemic determinants of cancer development, such as the immune system and metabolism. A better appreciation of these differences between the two sexes could be of substantial value for cancer prevention as well as treatment.
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Affiliation(s)
- Andrea Clocchiatti
- Cutaneous Biology Research Center, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA
| | - Elisa Cora
- Department of Biochemistry, University of Lausanne, Epalinges, CH-1066, Switzerland
| | - Yosra Zhang
- Cutaneous Biology Research Center, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA; and the Department of Biochemistry, University of Lausanne, Epalinges, CH-1066, Switzerland
| | - G Paolo Dotto
- Cutaneous Biology Research Center, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA; and the Department of Biochemistry, University of Lausanne, Epalinges, CH-1066, Switzerland
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10
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Singh M, Wang Z, Cascio D, Feigon J. Structure and interactions of the CS domain of human H/ACA RNP assembly protein Shq1. J Mol Biol 2015; 427:807-823. [PMID: 25553844 PMCID: PMC4323627 DOI: 10.1016/j.jmb.2014.12.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 12/13/2014] [Accepted: 12/16/2014] [Indexed: 12/27/2022]
Abstract
Shq1 is an essential protein involved in the early steps of biogenesis and assembly of H/ACA ribonucleoprotein particles (RNPs). Shq1 binds to dyskerin (Cbf5 in yeast) at an early step of H/ACA RNP assembly and is subsequently displaced by the H/ACA RNA. Shq1 contains an N-terminal CS and a C-terminal Shq1-specific domain (SSD). Dyskerin harbors many mutations associated with dyskeratosis congenita. Structures of yeast Shq1 SSD bound to Cbf5 revealed that only a subset of these mutations is in the SSD binding site, implicating another subset in the putative CS binding site. Here, we present the crystal structure of human Shq1 CS (hCS) and the nuclear magnetic resonance (NMR) and crystal structures of hCS containing a serine substitution for proline 22 that is associated with some prostate cancers. The structure of hCS is similar to yeast Shq1 CS domain (yCS) and consists of two β-sheets that form an immunoglobulin-like β-sandwich fold. The N-terminal affinity tag sequence AHHHHHH associates with a neighboring protein in the crystal lattice to form an extra β-strand. Deletion of this tag was required to get spectra suitable for NMR structure determination, while the tag was required for crystallization. NMR chemical shift perturbation (CSP) experiments with peptides derived from putative CS binding sites on dyskerin and Cbf5 revealed a conserved surface on CS important for Cbf5/dyskerin binding. A HADDOCK (high-ambiguity-driven protein-protein docking) model of a Shq1-Cbf5 complex that defines the position of CS domain in the pre-H/ACA RNP was calculated using the CSP data.
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Affiliation(s)
- Mahavir Singh
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Zhonghua Wang
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Duilio Cascio
- University of California Los Angeles-Department of Energy (UCLA-DOE) Institute for Genomics and Proteomics, University of California, Los Angeles, CA 90095, USA
| | - Juli Feigon
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA; University of California Los Angeles-Department of Energy (UCLA-DOE) Institute for Genomics and Proteomics, University of California, Los Angeles, CA 90095, USA.
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11
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Dai J, Cai H, Zhuang Y, Wu Y, Min H, Li J, Shi Y, Gao Q, Yi L. Telomerase gene mutations and telomere length shortening in patients with idiopathic pulmonary fibrosis in a Chinese population. Respirology 2014; 20:122-8. [PMID: 25346280 DOI: 10.1111/resp.12422] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 06/09/2014] [Accepted: 08/21/2014] [Indexed: 12/14/2022]
Affiliation(s)
- Jinghong Dai
- Department of Respiratory Medicine; Nanjing Drum Tower Hospital Affiliated to Medical School of Nanjing University; Nanjing China
- Jiangsu Key Laboratory of Molecular Medicine; Medical School of Nanjing University; Nanjing China
| | - Hourong Cai
- Department of Respiratory Medicine; Nanjing Drum Tower Hospital Affiliated to Medical School of Nanjing University; Nanjing China
| | - Yi Zhuang
- Department of Respiratory Medicine; Nanjing Drum Tower Hospital Affiliated to Medical School of Nanjing University; Nanjing China
| | - Yongzheng Wu
- Jiangsu Key Laboratory of Molecular Medicine; Medical School of Nanjing University; Nanjing China
| | - Haiyan Min
- Jiangsu Key Laboratory of Molecular Medicine; Medical School of Nanjing University; Nanjing China
| | - Jinheng Li
- Department of Medicine Science; Jinling Hospital; Medical School of Nanjing University; Nanjing China
| | - Yi Shi
- Department of Respiratory and Critical Care Medicine; Jinling Hospital; Medical School of Nanjing University; Nanjing China
| | - Qian Gao
- Jiangsu Key Laboratory of Molecular Medicine; Medical School of Nanjing University; Nanjing China
| | - Long Yi
- Department of Respiratory Medicine; Nanjing Drum Tower Hospital Affiliated to Medical School of Nanjing University; Nanjing China
- Jiangsu Key Laboratory of Molecular Medicine; Medical School of Nanjing University; Nanjing China
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12
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Moinho R, Brett A, Ferreira G, Lemos S. Pneumococcal vaccine failure: can it be a primary immunodeficiency? BMJ Case Rep 2014; 2014:bcr2014204714. [PMID: 24925540 PMCID: PMC4069748 DOI: 10.1136/bcr-2014-204714] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/25/2014] [Indexed: 12/25/2022] Open
Abstract
Vaccine failure is a rare condition and the need to investigate a primary immunodeficiency is controversial. We present the case of a 4-year-old boy, with complete antipneumococcal vaccination, who had necrotising pneumonia with pleural effusion and severe pancytopaenia with need for transfusion. A vaccine-serotype Streptococcus pneumoniae was isolated in the blood culture. On follow-up, detailed medical history, laboratory and genetic investigation led to the diagnosis of X linked dyskeratosis congenita. Dyskeratosis congenita is an inherited disorder that causes shortening or dysfunction of telomeres, affecting mainly rapidly dividing cells (particularly in the skin and haematopoietic system). It leads to bone marrow failure, combined immunodeficiency and predisposition to cancer. The confirmation of this diagnosis allows genetic counselling and medical monitoring of these patients, in order to detect early complications such as bone marrow aplasia or malignancies.
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Affiliation(s)
- Rita Moinho
- Hospital Pediátrico de Coimbra, Centro Hospitalar e Universitário de coimbra, Coimbra, Portugal
| | - Ana Brett
- Hospital Pediátrico de Coimbra, Centro Hospitalar e Universitário de coimbra, Coimbra, Portugal
| | - Gisela Ferreira
- Department of Serviço de Hematologia, Centro Hospitalar e Universitário de coimbra, Coimbra, Portugal
| | - Sónia Lemos
- Hospital Pediátrico de Coimbra, Centro Hospitalar e Universitário de coimbra, Coimbra, Portugal
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13
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Raiser DM, Narla A, Ebert BL. The emerging importance of ribosomal dysfunction in the pathogenesis of hematologic disorders. Leuk Lymphoma 2013; 55:491-500. [DOI: 10.3109/10428194.2013.812786] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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14
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Roberts AR, Huang E, Jones L, Daxinger L, Chong S, Whitelaw E. Non-telomeric epigenetic and genetic changes are associated with the inheritance of shorter telomeres in mice. Chromosoma 2013; 122:541-54. [DOI: 10.1007/s00412-013-0427-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 06/28/2013] [Accepted: 07/01/2013] [Indexed: 12/22/2022]
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15
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Carrillo J, Martínez P, Solera J, Moratilla C, González A, Manguán-García C, Aymerich M, Canal L, del Campo M, Dapena J, Escoda L, García-Sagredo J, Martín-Sala S, Rives S, Sevilla J, Sastre L, Perona R. High resolution melting analysis for the identification of novel mutations in DKC1 and TERT genes in patients with dyskeratosis congenita. Blood Cells Mol Dis 2012; 49:140-6. [DOI: 10.1016/j.bcmd.2012.05.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 04/23/2012] [Indexed: 12/27/2022]
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Abstract
PURPOSE OF REVIEW Despite blood or marrow transplantation (BMT) being arguably the most active modality against hematologic malignancies, relapses remain the major reason for failure. Many cancers have now been shown to harbor cells that are phenotypically and biologically similar to normal cells with self-renewal capacity; these so-called cancer stem cells (CSCs) typically constitute only a small fraction of the total tumor burden, but are hypothesized to be responsible for relapse after conventional-dose therapy. Here, we review whether CSCs may have relevance to BMT. RECENT FINDINGS CSCs appear to be relatively resistant to standard anticancer therapies in vitro. The often-dramatic responses induced by chemotherapy in most hematologic malignancies are likely a consequence of their impressive activity against the bulk tumor cells. Although the clinical importance of CSCs remains unproven, new evidence suggests that the limited durability of many of these responses reflect resistant CSCs. It is possible that CSCs are also relatively resistant to both high-dose myeloablative conditioning and allogeneic graft-versus-tumor effects. Data on the ability of most hematologic CSCs to circulate even early in the natural history of a malignancy also raises concerns about contamination of autografts contributing to relapse. SUMMARY Emerging data for the first time suggest CSCs may be responsible for relapse, even after BMT. However, BMT may be a particularly compelling setting to test CSC-targeting strategies because it provides the most effective clinical debulking of hematologic malignancies, and because CSC-targeting strategies may also enhance allogeneic antitumor immunity.
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17
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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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18
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Walne AJ, Dokal I. Telomerase dysfunction and dyskeratosis congenita. Cytotechnology 2011; 45:13-22. [PMID: 19003239 DOI: 10.1007/s10616-004-5121-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2004] [Accepted: 09/21/2004] [Indexed: 01/04/2023] Open
Abstract
Dyskeratosis congenita (DC) is a multi system bone marrow failure syndrome characterized by muco-cutaneous abnormalities and an increased predisposition to malignancy. It exhibits considerable clinical and genetic heterogeneity. X-linked recessive, autosomal dominant and autosomal recessive forms of the disease are recognized. The X-linked recessive form is due to mutations in dyskerin, which is a component of both small nucleolar ribonuclear protein particles and the telomerase complex. Autosomal dominant DC is due to mutations in the RNA component of telomerase, TERC. As dyskerin and TERC are both components of the telomerase complex and all patients with DC have short telomeres it appears that the principal pathology in DC relates to telomerase dysfunction. The gene or genes involved in the recessive form of DC remain elusive, though genes whose products are required for telomere maintenance remain strong candidates. The study of DC has highlighted the critical role of telomerase and the consequences, including premature aging and malignancy, of its dysfunction.
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Affiliation(s)
- Amanda J Walne
- Department of Haematology, Division of Investigative Science, Faculty of Medicine, Imperial College London, Hammersmith Hospital, Du Cane Road, London, W12 ONN, United Kingdom,
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19
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Parry EM, Alder JK, Lee SS, Phillips JA, Loyd JE, Duggal P, Armanios M. Decreased dyskerin levels as a mechanism of telomere shortening in X-linked dyskeratosis congenita. J Med Genet 2011; 48:327-33. [PMID: 21415081 PMCID: PMC3088476 DOI: 10.1136/jmg.2010.085100] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Dyskeratosis congenita (DC) is a premature ageing syndrome characterised by short telomeres. An X-linked form of DC is caused by mutations in DKC1 which encodes dyskerin, a telomerase component that is essential for telomerase RNA stability. However, mutations in DKC1 are identifiable in only half of X-linked DC families. A four generation family with pulmonary fibrosis and features of DC was identified. Affected males showed the classic mucocutaneous features of DC and died prematurely from pulmonary fibrosis. Although there were no coding sequence or splicing variants, genome wide linkage analysis of 16 individuals across four generations identified significant linkage at the DKC1 locus, and was accompanied by reduced dyskerin protein levels in affected males. Decreased dyskerin levels were associated with compromised telomerase RNA levels and very short telomeres. These data identify decreased dyskerin levels as a novel mechanism of DC, and indicate that intact dyskerin levels, in the absence of coding mutations, are critical for telomerase RNA stability and for in vivo telomere maintenance.
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Affiliation(s)
- Erin M Parry
- Department of Oncology and Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine Baltimore, Maryland, USA
- Medical Scientist Training Progra, Johns Hopkins University School of Medicine Baltimore, Maryland, USA
| | - Jonathan K Alder
- Department of Oncology and Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine Baltimore, Maryland, USA
| | - Stella S Lee
- Pre-doctoral Training Program in Human Genetics, Johns Hopkins University School of Medicine Baltimore, Maryland, USA
| | - John A Phillips
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - James E Loyd
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Priya Duggal
- Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Mary Armanios
- Department of Oncology and Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine Baltimore, Maryland, USA
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine Baltimore, Maryland, USA
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20
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Abstract
Skin is a self-renewing tissue that is required to go through extensive proliferation throughout the lifespan of an organism. Telomere shortening acts as a mitotic clock that prevents aberrant proliferation such as cancer. A consequence of this protection is cellular senescence and ageing. The telomerase enzyme complex maintains telomere length in germline cells and in cancer cells. Telomerase is also active in certain somatic cells such as those in the epidermis but is almost undetectable in the dermis. Increasing evidence indicates that telomerase plays a significant role in maintenance of skin function and proliferation. Mutations in telomerase component genes in the disease dyskeratosis congenita result in numerous epidermal abnormalities. Studies also indicate that telomerase activity in epidermal stem cells might have roles that go beyond telomere elongation. Telomeres in skin cells may be particularly susceptible to accelerated shortening because of both proliferation and DNA-damaging agents such as reactive oxygen species. Skin might present an accessible tissue for manipulation of telomerase activity and telomere length with the potential of ameliorating skin diseases associated with ageing.
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Affiliation(s)
- Erin M Buckingham
- Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA
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21
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[Senescence and cellular immortality]. Bull Cancer 2010; 97:1275-83. [PMID: 21051314 DOI: 10.1684/bdc.2010.1205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Senescence was originally described from the observation of the limited ability of normal cells to grow in culture, and may be generated by telomere erosion, accumulation of DNA damages, oxidative stress and modulation of oncogenes or tumor suppressor genes. Senescence corresponds to a cellular response aiming to control tumor progression by limiting cell proliferation and thus constitutes an anticancer barrier. Senescence is observed in pre-malignant tumor stages and disappears from malignant tumors. Agents used in standard chemotherapy also have the potential to induce senescence, which may partly explain their therapeutic activities. It is possible to restore senescence in tumors using targeted therapies that triggers telomere dysfunction or reactivates suppressor genes functions, which are essential for the onset of senescence.
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22
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Mather KA, Jorm AF, Parslow RA, Christensen H. Is telomere length a biomarker of aging? A review. J Gerontol A Biol Sci Med Sci 2010; 66:202-13. [PMID: 21030466 DOI: 10.1093/gerona/glq180] [Citation(s) in RCA: 283] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Telomeres, the DNA-protein structures located at the ends of chromosomes, have been proposed to act as a biomarker of aging. In this review, the human evidence that telomere length is a biomarker of aging is evaluated. Although telomere length is implicated in cellular aging, the evidence suggesting telomere length is a biomarker of aging in humans is equivocal. More studies examining the relationships between telomere length and mortality and with measures that decline with "normal" aging in community samples are required. These studies would benefit from longitudinal measures of both telomere length and aging-related parameters.
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Affiliation(s)
- Karen Anne Mather
- Centre for Mental Health Research, Australian National University, Canberra, Australia.
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23
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Baran I, Nalcaci R, Kocak M. Dyskeratosis congenita: clinical report and review of the literature. Int J Dent Hyg 2010; 8:68-74. [PMID: 20096085 DOI: 10.1111/j.1601-5037.2009.00364.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Dyskeratosis congenita (DKC) is an inherited disorder that usually presents in males, consisting of the triad of leukoplakia of the mucous membranes, nails dystrophy and skin pigmentation. Oral and dental abnormalities may also be present. Most cases are X-linked autosomal dominant, but recessive forms have also been reported. This study describes herein a case in which the classic triad of signs was present, along with the development of leukoplakia in the buccal mucosa. Our patient, a 25-year-old man, presented with several characteristic systemic features of this condition, together with the following oral features: hypodontia, delayed dental eruption, short blunt roots, extensive caries, gingival inflammation and bleeding, loss of alveolar bone and buccal mucosa with leukoplakia and irregular ulcers. The patient was given full preventive care. The primary teeth were extracted under local anaesthesia. After establishing optimal oral health, oral hygiene instructions were given to the patient and he was rehabilitated with fixed and removable partial denture. Prosthetic treatments were carried out after establishing optimal oral health. This treatment option appears beneficial in this patient, resulting in rehabilitation of occlusion and less mechanical irritation to the oral mucosa.
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Affiliation(s)
- I Baran
- Department of Prosthetic Dentistry, Faculty of Dentistry, Kirikkale University, Kirikkale, Turkey.
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24
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Abstract
Ribosomopathies compose a collection of disorders in which genetic abnormalities cause impaired ribosome biogenesis and function, resulting in specific clinical phenotypes. Congenital mutations in RPS19 and other genes encoding ribosomal proteins cause Diamond-Blackfan anemia, a disorder characterized by hypoplastic, macrocytic anemia. Mutations in other genes required for normal ribosome biogenesis have been implicated in other rare congenital syndromes, Schwachman-Diamond syndrome, dyskeratosis congenita, cartilage hair hypoplasia, and Treacher Collins syndrome. In addition, the 5q- syndrome, a subtype of myelodysplastic syndrome, is caused by a somatically acquired deletion of chromosome 5q, which leads to haploinsufficiency of the ribosomal protein RPS14 and an erythroid phenotype highly similar to Diamond-Blackfan anemia. Acquired abnormalities in ribosome function have been implicated more broadly in human malignancies. The p53 pathway provides a surveillance mechanism for protein translation as well as genome integrity and is activated by defects in ribosome biogenesis; this pathway appears to be a critical mediator of many of the clinical features of ribosomopathies. Elucidation of the mechanisms whereby selective abnormalities in ribosome biogenesis cause specific clinical syndromes will hopefully lead to novel therapeutic strategies for these diseases.
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25
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Armanios M, Alder JK, Parry EM, Karim B, Strong MA, Greider CW. Short telomeres are sufficient to cause the degenerative defects associated with aging. Am J Hum Genet 2009; 85:823-32. [PMID: 19944403 DOI: 10.1016/j.ajhg.2009.10.028] [Citation(s) in RCA: 184] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 10/20/2009] [Accepted: 10/24/2009] [Indexed: 11/30/2022] Open
Abstract
Telomerase function is critical for telomere maintenance. Mutations in telomerase components lead to telomere shortening and progressive bone marrow failure in the premature aging syndrome dyskeratosis congenita. Short telomeres are also acquired with aging, yet the role that they play in mediating age-related disease is not fully known. We generated wild-type mice that have short telomeres. In these mice, we identified hematopoietic and immune defects that resembled those present in dyskeratosis congenita patients. When mice with short telomeres were interbred, telomere length was only incrementally restored, and even several generations later, wild-type mice with short telomeres still displayed degenerative defects. Our findings implicate telomere length as a unique heritable trait that, when short, is sufficient to mediate the degenerative defects of aging, even when telomerase is wild-type.
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Affiliation(s)
- Mary Armanios
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
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26
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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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27
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Erythrocyte scaffolding protein p55/MPP1 functions as an essential regulator of neutrophil polarity. Proc Natl Acad Sci U S A 2009; 106:19842-7. [PMID: 19897731 DOI: 10.1073/pnas.0906761106] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
As mediators of innate immunity, neutrophils respond to chemoattractants by adopting a highly polarized morphology. Efficient chemotaxis requires the formation of one prominent pseudopod at the cell front characterized by actin polymerization, while local inhibition suppresses the formation of rear and lateral protrusions. This asymmetric control of signaling pathways is required for directional migration along a chemotactic gradient. Here, we identify the MAGUK protein p55/MPP1 as a mediator of the frontness signal required for neutrophil polarization. We developed a p55 knockout (p55(-/-)) mouse model, and demonstrate that p55(-/-) neutrophils form multiple transient pseudopods upon chemotactic stimulation, and do not migrate efficiently in vitro. Upon agonist stimulation, p55 is rapidly recruited to the leading edge of neutrophils in mice and humans. Total F-actin polymerization, along with Rac1 and RhoA activation, appear to be normal in p55(-/-) neutrophils. Importantly, phosphorylation of Akt is significantly decreased in p55(-/-) neutrophils upon chemotactic stimulation. The activity of immunoprecipitated phosphatidylinositol 3-kinase gamma (PI3Kgamma), responsible for chemoattractant-induced synthesis of PIP(3) and Akt phosphorylation, is unperturbed in p55(-/-) neutrophils. Although the total amount of PIP(3) is normal in p55(-/-) neutrophils, PIP(3) is diffusely localized and forms punctate aggregates in activated p55(-/-) neutrophils, as compared to its accumulation at the leading edge membrane in the wild type neutrophils. Together, these results show that p55 is required for neutrophil polarization by regulating Akt phosphorylation through a mechanism that is independent of PI3Kgamma activity.
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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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29
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Abstract
Telomeres and telomerase were initially discovered in pursuit of questions about how the ends of chromosomes are maintained. The implications of these discoveries to age-related disease have emerged in recent years with the recognition of a group of telomere-mediated syndromes. Telomere-mediated disease was initially identified in the context of dyskeratosis congenita, a rare syndrome of premature aging. More recently, mutations in telomerase components were identified in adults with idiopathic pulmonary fibrosis. These findings have revealed that the spectrum of telomere-mediated disease is broad and includes clinical presentations in both children and adults. We have previously proposed that these disorders be collectively considered as syndromes of telomere shortening. Here, the spectrum of these disorders and the unique telomere genetics that underlies them are reviewed. I also propose broader clinical criteria for defining telomere-mediated syndromes outside of dyskeratosis congenita, with the goal of facilitating their diagnosis and highlighting their pathophysiology.
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Affiliation(s)
- Mary Armanios
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21285, USA.
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30
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Jones RJ. Cancer stem cells-clinical relevance. J Mol Med (Berl) 2009; 87:1105-10. [PMID: 19816664 DOI: 10.1007/s00109-009-0534-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 08/29/2009] [Accepted: 08/31/2009] [Indexed: 02/06/2023]
Abstract
Therapeutic advances over the past three decades now allow most cancer patients to achieve major clinical responses. Although clinical responses can clearly decrease side effects and improve quality of life, most cancer patients still eventually relapse and die of their disease. Many cancers have now been shown to harbor cells that are phenotypically and biologically similar to normal cells with self-renewal capacity; these so-called cancer stem cells (CSC) typically constitute only a small fraction of the total tumor burden, but theoretically harbor all the self-renewal capacity. Moreover, the CSC appears to be relatively resistant to standard anticancer therapies by co-opting normal stem cells' intrinsic defense mechanisms, such as quiescence, efflux pumps, and detoxifying enzymes. However, the clinical importance of CSC, if any, remains unproven. Nevertheless, emerging evidence suggests that initial responses in cancer represent therapeutic effectiveness against the bulk cancer cells, while the rare CSC is responsible for relapse. Better understanding of the biology of CSC, as well as reexamining both our preclinical and clinical drug development paradigms to include the CSC concept, has the potential to revolutionize the treatment of many cancers.
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Affiliation(s)
- Richard J Jones
- Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Room 244, Bunting-Blaustein Cancer Research Building, 1650 Orleans St, Baltimore, MD 21231, USA.
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31
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Abstract
PURPOSE To develop a model for the initiation of human tumourigenesis that is consistent with various observations that are difficult to reconcile with current models. CONCLUSIONS A novel model of tumourigenesis was developed that includes three basic postulates: (1) tumourigenesis is initiated by recombinogenic DNA lesions, (2) potentially recombinogenic DNA lesions in transcribed regions of the genome can be converted into chromosomal rearrangements and (3) chromosomal rearrangements alone are insufficient for tumourigenesis but can initiate a mutator/recombinator phenotype.
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Affiliation(s)
- I R Radford
- Radiation Oncology Division, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne, Victoria 3002, Australia.
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32
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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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33
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Gourronc FA, Robertson MM, Herrig AK, Lansdorp PM, Goldman FD, Klingelhutz AJ. Proliferative defects in dyskeratosis congenita skin keratinocytes are corrected by expression of the telomerase reverse transcriptase, TERT, or by activation of endogenous telomerase through expression of papillomavirus E6/E7 or the telomerase RNA component, TERC. Exp Dermatol 2009; 19:279-88. [PMID: 19558498 DOI: 10.1111/j.1600-0625.2009.00916.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Dyskeratosis congenita (DC) is characterized by the triad of reticulate skin pigmentation, nail dystrophy and leukoplakia. Epidermal atrophy, hair growth defects, bone marrow failure and increased risk of cancer are also common in DC patients. DC is caused by mutations in genes encoding for telomerase complex factors. Although there is an association of epidermal abnormalities with DC, epidermal cells from DC donors have not been previously characterized. We have isolated skin keratinocytes from affected members of a family with an autosomal dominant form of DC that is caused by a mutation in the RNA component of telomerase, TERC. Here, we demonstrate that, similar to DC fibroblasts from these donors, DC keratinocytes have short telomeres and a short lifespan. DC keratinocytes also exhibited impaired colony forming efficiency (CFE) and migration capacity. Exogenous expression of the reverse transcriptase (RT) component of telomerase, TERT, activated telomerase levels to half that of TERT expressing normal cells and maintained telomeres at a short length with concomitant extension of lifespan. Unlike fibroblasts, transduction of human papillomavirus type 16 E6/E7 genes into DC keratinocytes activated telomerase to half that of E6/E7 expressing normal cells, and robust proliferation was observed. While expression of TERC has no measurable effect on telomerase in fibroblasts, expression of TERC in keratinocytes upregulated telomerase activity and, rarely, allowed rescue of proliferative defects. Our results point to important differences between DC fibroblasts and keratinocytes and show, for the first time, that expression of TERC can increase the lifespan of primary human epithelial cells.
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Recent insights into the molecular mechanisms involved in aging and the malignant transformation of adult stem/progenitor cells and their therapeutic implications. Ageing Res Rev 2009; 8:94-112. [PMID: 19114129 DOI: 10.1016/j.arr.2008.12.001] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Accepted: 12/04/2008] [Indexed: 02/07/2023]
Abstract
Recent advancements in tissue-resident adult stem/progenitor cell research have revealed that enhanced telomere attrition, oxidative stress, ultraviolet radiation exposure and oncogenic events leading to severe DNA damages and genomic instability may occur in these immature and regenerative cells during chronological aging. Particularly, the alterations in key signaling components controlling their self-renewal capacity and an up-regulation of tumor suppressor gene products such as p16(INK4A), p19(ARF), ataxia-telangiectasia mutated (ATM) kinase, p53 and/or the forkhead box O (FOXOs) family of transcription factors may result in their dysfunctions, growth arrest and senescence or apoptotic death during the aging process. These molecular events may culminate in a progressive decline in the regenerative functions and the number of tissue-resident adult stem/progenitor cells, and age-related disease development. Conversely, the telomerase re-activation and accumulation of numerous genetic and/or epigenetic alterations in adult stem/progenitor cells with advancing age may result in their immortalization and malignant transformation into highly leukemic or tumorigenic cancer-initiating cells and cancer initiation. Therefore, the cell-replacement and gene therapies and molecular targeting of aged and dysfunctional adult stem/progenitor cells including their malignant counterpart, cancer-initiating cells, hold great promise for treating and even curing diverse devastating human diseases. These diseases include premature aging diseases, hematopoietic, cardiovascular, musculoskeletal, pulmonary, ocular, urogenital, neurodegenerative and skin disorders and aggressive and recurrent cancers.
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35
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Hoareau-Aveilla C, Henry Y, Leblanc T. [Dyskeratosis congenita, a disease caused by defective telomere maintenance]. Med Sci (Paris) 2008; 24:390-8. [PMID: 18405638 DOI: 10.1051/medsci/2008244390] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Dyskeratosis congenita (DC), also called Zinsser-Cole-Engman syndrome, is a rare, often fatal, inherited disease described for the first time at the dermatological level by Zinsser in 1906. It is a very polymorphous disease at the clinical level, with several modes of inheritance. Several clinical symptoms of the disease can appear after a latency period. These features render DC particularly difficult to diagnose. Mutations of several genes can cause DC, four of them having been identified so far. However, for a majority of patients, the affected gene has not been found. Remarkably, all identified genes (DKC1, hTERC, hTERT, and NOP10) encode components of telomerase, all required for telomere length maintenance. DC is thus a unique clinical model for the study of the roles of telomerase and telomeres. Moreover, proteins encoded by the DKC1 and NOP10 genes are also components of so-called box H/ACA RNPs required for ribosome synthesis and pre-mRNA processing. Alterations of these processes could contribute to the symptoms of DC patients carrying mutations in DKC1 or NOP10.
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Affiliation(s)
- Coralie Hoareau-Aveilla
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, Université de Toulouse, UPS, 118 route de Narbonne, 31062 Toulouse cedex 09, France
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36
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Roobrouck VD, Ulloa-Montoya F, Verfaillie CM. Self-renewal and differentiation capacity of young and aged stem cells. Exp Cell Res 2008; 314:1937-44. [DOI: 10.1016/j.yexcr.2008.03.006] [Citation(s) in RCA: 202] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Accepted: 03/06/2008] [Indexed: 12/30/2022]
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37
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Engin H, Kuzu I, Ustündağ Y, Aydemir S, Aköz AG, Kilinçarslan D. Dyskeratosis congenita associated with hypocellular myelodysplastic syndrome: a case report. Am J Med Sci 2007; 334:206-8. [PMID: 17873535 DOI: 10.1097/maj.0b013e3181405e51] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A 16-year-old female patient presented with complaints of malaise, dizziness, syncope, and nausea of 1-week duration. On dermatologic examination there were telangiectasias, atrophic areas, and poikiloderma with both hypopigmentation and hyperpigmentation on the neck and the proximal parts of the thighs. The bone marrow biopsy specimen showed hypocellularity and dysplastic megakaryocytic and erythroid elements, findings consistent with hypocellular myelodysplastic syndrome, which was further confirmed by cytogenetic studies. Thereafter, she was referred for allogeneic bone marrow transplantation.
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Affiliation(s)
- Hüseyin Engin
- Karaelmas University Faculty of Medicine, Department of Internal Medicine, Zonguldak, Turkey.
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38
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Scheinfeld MH, Lui YW, Kolb EA, Engel HM, Gomes WA, Weidenheim KM, Bello JA. The neuroradiological findings in a case of Revesz syndrome. Pediatr Radiol 2007; 37:1166-70. [PMID: 17874088 DOI: 10.1007/s00247-007-0592-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2007] [Revised: 07/03/2007] [Accepted: 07/13/2007] [Indexed: 10/22/2022]
Abstract
Revesz syndrome is a variant of dyskeratosis congenita characterized by aplastic anemia, retinopathy, and central nervous system abnormalities. We describe a 3-year-old boy in whom the spectrum of neuroimaging findings, including intracranial calcifications, cerebellar hypoplasia and unusual brain lesions were found by biopsy to be gliosis despite their enhancement and progression. In patients with dyskeratosis-related syndromes, non-neoplastic parenchymal brain lesions occur and gliosis should be considered in the differential diagnosis for progressive enhancing brain lesions. Should this finding be confirmed consistently in additional cases, brain biopsy could potentially be avoided.
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Affiliation(s)
- Meir H Scheinfeld
- Department of Radiology, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY 10467, USA.
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39
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Walne AJ, Dokal I. Dyskeratosis Congenita: a historical perspective. Mech Ageing Dev 2007; 129:48-59. [PMID: 18054794 DOI: 10.1016/j.mad.2007.10.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2007] [Revised: 10/18/2007] [Accepted: 10/24/2007] [Indexed: 12/29/2022]
Abstract
"Dyskeratosis Congenita (DC) also known as Zinsser-Engman-Cole syndrome is a rare multi-system bone marrow failure syndrome characterised by mucocutaneous abnormalities and an increased predisposition to cancer". This is a common definition of DC but how did this definition arise? The aim of this review is to follow the development of DC and associated diseases from its first reported description in the early 20th century to the current understanding of the genes involved and its pathophysiology in 2007 in a chronological order. Although this review is not intended to be an exhaustive citation of the literature available it does provide a summary of the key developments, citing particularly the earlier reports of each development.
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Affiliation(s)
- Amanda J Walne
- 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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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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Strategies to eliminate cancer stem cells. ERNST SCHERING FOUNDATION SYMPOSIUM PROCEEDINGS 2007. [PMID: 17939303 DOI: 10.1007/2789_2007_052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register]
Abstract
Therapeutic advances over the past three decades now allow most cancer patients to achieve major clinical responses. Although clinical responses can clearly decrease side effects and improve quality of life, most cancer patients still eventually relapse and die of their disease. Emerging data suggest that initial responses in cancer represent therapeutic effectiveness against the differentiated cancer cells making up the bulk of the tumor, while rare biologically distinct cancer stem cells resistant to the therapies are responsible for relapse. Better understanding the biology of cancer stem cells, and reexamining both our preclinical and clinical drug development paradigms to include the cancer stem cell concept, have the potential to revolutionize the treatment of many cancers.
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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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43
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Benoit S, Kraemer D, Bröcker EB, Goebeler M. [Dyskeratosis congenita in a 40-year-old patient]. DER HAUTARZT 2007; 57:313-5. [PMID: 15789197 DOI: 10.1007/s00105-005-0937-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A 40-year-old patient with a 3-year history of thrombocytopenia was admitted with reticulated and speckled hyper- and hypopigmentations especially on the upper trunk. Aplasia or dystrophy of the fingernails and toenails as well as atresia of the lacrimal ducts were noted. Examination of the oropharynx revealed multiple mucosal leukoplakias and loss of almost all teeth. Based on these observations the diagnosis of X-linked dyskeratosis congenita (Zinsser-Cole-Engman syndrome, OMIM #305000) was made and confirmed by sequencing of the dyskerin 1 (DKC1) gene which revealed a missense mutation in exon 11.
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Affiliation(s)
- S Benoit
- Klinik und Poliklinik für Haut- und Geschlechtskrankheiten, Universität Würzburg
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44
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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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Armanios MY, Chen JJL, Cogan JD, Alder JK, Ingersoll RG, Markin C, Lawson WE, Xie M, Vulto I, Phillips JA, Lansdorp PM, Greider CW, Loyd JE. Telomerase mutations in families with idiopathic pulmonary fibrosis. N Engl J Med 2007; 356:1317-26. [PMID: 17392301 DOI: 10.1056/nejmoa066157] [Citation(s) in RCA: 905] [Impact Index Per Article: 53.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BACKGROUND Idiopathic pulmonary fibrosis is progressive and often fatal; causes of familial clustering of the disease are unknown. Germ-line mutations in the genes hTERT and hTR, encoding telomerase reverse transcriptase and telomerase RNA, respectively, cause autosomal dominant dyskeratosis congenita, a rare hereditary disorder associated with premature death from aplastic anemia and pulmonary fibrosis. METHODS To test the hypothesis that familial idiopathic pulmonary fibrosis may be caused by short telomeres, we screened 73 probands from the Vanderbilt Familial Pulmonary Fibrosis Registry for mutations in hTERT and hTR. RESULTS Six probands (8%) had heterozygous mutations in hTERT or hTR; mutant telomerase resulted in short telomeres. Asymptomatic subjects with mutant telomerase also had short telomeres, suggesting that they may be at risk for the disease. We did not identify any of the classic features of dyskeratosis congenita in five of the six families. CONCLUSIONS Mutations in the genes encoding telomerase components can appear as familial idiopathic pulmonary fibrosis. Our findings support the idea that pathways leading to telomere shortening are involved in the pathogenesis of this disease.
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Affiliation(s)
- Mary Y Armanios
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA.
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Mahiques L, Febrer I, Vilata JJ, Fortea JM. A case of dyskeratosis congenita associated with schizophrenia and two malignancies. J Eur Acad Dermatol Venereol 2007; 20:1159-61. [PMID: 16987292 DOI: 10.1111/j.1468-3083.2006.01660.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Shervington A, Patel R, Lu C, Cruickshanks N, Lea R, Roberts G, Dawson T, Shervington L. Telomerase subunits expression variation between biopsy samples and cell lines derived from malignant glioma. Brain Res 2007; 1134:45-52. [PMID: 17196947 DOI: 10.1016/j.brainres.2006.11.093] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Revised: 11/29/2006] [Accepted: 11/30/2006] [Indexed: 01/12/2023]
Abstract
Although scientific advances have recognised the prognostic power of telomerase activity in different cancers, as yet there has been no investigation regarding the expression variation of telomerase subunits in glioma tissues and cell lines. In this study, a recurrent anaplastic ependymoma and seven glioblastoma biopsy samples, four cell lines and four controls including two normal brain tissues were analysed for telomerase subunit expression profiles together with telomerase activity. Since telomerase activity is linked to tumourgenesis, the genes were analysed with respect to their expression variation. TEP1 was expressed in all glioma cell lines and 70% of glioblastoma tissues, in addition to the control brain tissues. Tankyrase was expressed in 85% of the glioblastoma tissues and was down-regulated in the recurrent anaplastic ependymoma tissue control cell lines. However, it was expressed in the control tissues. Dyskerin was expressed in all cell lines and tissues apart from U87-MG and NHA cells and the recurrent anaplastic ependymoma tissue. As expected, PARP1 and GAPDH showed constitutive expression throughout all cell lines and tissues since both are known to be housekeeping genes. hTERT was expressed in all glioma cell lines and tissues but was absent in the control cells and tissues. Telomerase activity was absent in IPDDC-A2 cells and 57% of the glioblastoma tissues. These results suggest that hTERT expression and not telomerase activity possibly represents a simple and reliable biological diagnostic tool.
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Affiliation(s)
- Amal Shervington
- Department of Biological Sciences, University of Central Lancashire, and Neurosurgery Department, Royal Preston Hospital, UK.
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48
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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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49
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Abstract
Objective clinical responses to anticancer treatments often do not translate into substantial improvements in overall survival. Recent data suggesting many cancers arise from rare self-renewing cells (cancer stem cells) that are biologically distinct from their more numerous differentiated progeny, may explain this paradox. Current anticancer therapies have been developed to target the bulk of the tumor mass (i.e., the differentiated cancer cells). Although treatments directed against the bulk of the cancer may produce dramatic responses, they are unlikely to result in long-term remissions if the rare cancer stem cells are also not targeted. Better understanding the biology of cancer stem cells as well reexamining both our preclinical and clinical drug development paradigms to include the cancer stem cell concept, have the potential to revolutionize the treatment of many cancers.
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50
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Kittur N, Darzacq X, Roy S, Singer RH, Meier UT. Dynamic association and localization of human H/ACA RNP proteins. RNA (NEW YORK, N.Y.) 2006; 12:2057-62. [PMID: 17135485 PMCID: PMC1664726 DOI: 10.1261/rna.249306] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Mammalian H/ACA RNPs are essential for ribosome biogenesis, pre-mRNA splicing, and telomere maintenance. To form mature RNA-protein complexes, one H/ACA RNA associates with four core proteins. In the cell, this process is assisted by at least one nuclear assembly factor, NAF1. Here we report several unanticipated dynamic aspects of H/ACA RNP proteins. First, when overexpressed, NAF1 delocalizes to the cytoplasm. However, its nucleocytoplasmic shuttling properties remain unaffected. These observations demonstrate a subtle equilibrium between NAF1 expression levels and the availability of NAF1 nuclear binding sites. Second, although NAF1 is excluded from mature RNPs in nucleoli and Cajal bodies, NAF1 associates with mature H/ACA RNA in cell lysates. This association occurs post-lysis because it is observed even when NAF1 and the H/ACA RNA are expressed in separate cells. This documents a protein-RNP association in cell lysates that is absent from intact cells. Third, in similar experiments, all H/ACA core proteins, except NAP57, exchange with their exogenous counterparts, portraying an unexpected dynamic picture of H/ACA RNPs. Finally, the irreversible association of only NAP57 with H/ACA RNA and the conundrum that only NAP57 is mutated in X-linked dyskeratosis congenita (even though most core proteins are required for maintaining H/ACA RNAs) may be more than a coincidence.
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Affiliation(s)
- Nupur Kittur
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York, New York 10461, USA
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