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Kell L, Simon AK, Alsaleh G, Cox LS. The central role of DNA damage in immunosenescence. FRONTIERS IN AGING 2023; 4:1202152. [PMID: 37465119 PMCID: PMC10351018 DOI: 10.3389/fragi.2023.1202152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 06/22/2023] [Indexed: 07/20/2023]
Abstract
Ageing is the biggest risk factor for the development of multiple chronic diseases as well as increased infection susceptibility and severity of diseases such as influenza and COVID-19. This increased disease risk is linked to changes in immune function during ageing termed immunosenescence. Age-related loss of immune function, particularly in adaptive responses against pathogens and immunosurveillance against cancer, is accompanied by a paradoxical gain of function of some aspects of immunity such as elevated inflammation and increased incidence of autoimmunity. Of the many factors that contribute to immunosenescence, DNA damage is emerging as a key candidate. In this review, we discuss the evidence supporting the hypothesis that DNA damage may be a central driver of immunosenescence through senescence of both immune cells and cells of non-haematopoietic lineages. We explore why DNA damage accumulates during ageing in a major cell type, T cells, and how this may drive age-related immune dysfunction. We further propose that existing immunosenescence interventions may act, at least in part, by mitigating DNA damage and restoring DNA repair processes (which we term "genoprotection"). As such, we propose additional treatments on the basis of their evidence for genoprotection, and further suggest that this approach may provide a viable therapeutic strategy for improving immunity in older people.
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Affiliation(s)
- Loren Kell
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- Botnar Institute for Musculoskeletal Sciences, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, United Kingdom
- The Kennedy Institute of Rheumatology, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, United Kingdom
| | - Anna Katharina Simon
- The Kennedy Institute of Rheumatology, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, United Kingdom
- Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Ghada Alsaleh
- Botnar Institute for Musculoskeletal Sciences, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, United Kingdom
- The Kennedy Institute of Rheumatology, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, United Kingdom
| | - Lynne S. Cox
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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2
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Teissier T, Temkin V, Pollak RD, Cox LS. Crosstalk Between Senescent Bone Cells and the Bone Tissue Microenvironment Influences Bone Fragility During Chronological Age and in Diabetes. Front Physiol 2022; 13:812157. [PMID: 35388291 PMCID: PMC8978545 DOI: 10.3389/fphys.2022.812157] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 01/27/2022] [Indexed: 01/10/2023] Open
Abstract
Bone is a complex organ serving roles in skeletal support and movement, and is a source of blood cells including adaptive and innate immune cells. Structural and functional integrity is maintained through a balance between bone synthesis and bone degradation, dependent in part on mechanical loading but also on signaling and influences of the tissue microenvironment. Bone structure and the extracellular bone milieu change with age, predisposing to osteoporosis and increased fracture risk, and this is exacerbated in patients with diabetes. Such changes can include loss of bone mineral density, deterioration in micro-architecture, as well as decreased bone flexibility, through alteration of proteinaceous bone support structures, and accumulation of senescent cells. Senescence is a state of proliferation arrest accompanied by marked morphological and metabolic changes. It is driven by cellular stress and serves an important acute tumor suppressive mechanism when followed by immune-mediated senescent cell clearance. However, aging and pathological conditions including diabetes are associated with accumulation of senescent cells that generate a pro-inflammatory and tissue-destructive secretome (the SASP). The SASP impinges on the tissue microenvironment with detrimental local and systemic consequences; senescent cells are thought to contribute to the multimorbidity associated with advanced chronological age. Here, we assess factors that promote bone fragility, in the context both of chronological aging and accelerated aging in progeroid syndromes and in diabetes, including senescence-dependent alterations in the bone tissue microenvironment, and glycation changes to the tissue microenvironment that stimulate RAGE signaling, a process that is accelerated in diabetic patients. Finally, we discuss therapeutic interventions targeting RAGE signaling and cell senescence that show promise in improving bone health in older people and those living with diabetes.
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Affiliation(s)
- Thibault Teissier
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Vladislav Temkin
- Division of Medicine, Department of Endocrinology and Metabolism, The Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Rivka Dresner Pollak
- Division of Medicine, Department of Endocrinology and Metabolism, The Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Lynne S. Cox
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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3
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Barros PR, Costa TJ, Akamine EH, Tostes RC. Vascular Aging in Rodent Models: Contrasting Mechanisms Driving the Female and Male Vascular Senescence. FRONTIERS IN AGING 2021; 2:727604. [PMID: 35821995 PMCID: PMC9261394 DOI: 10.3389/fragi.2021.727604] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Accepted: 08/25/2021] [Indexed: 12/12/2022]
Abstract
Increasing scientific interest has been directed to sex as a biological and decisive factor on several diseases. Several different mechanisms orchestrate vascular function, as well as vascular dysfunction in cardiovascular and metabolic diseases in males and females. Certain vascular sex differences are present throughout life, while others are more evident before the menopause, suggesting two important and correlated drivers: genetic and hormonal factors. With the increasing life expectancy and aging population, studies on aging-related diseases and aging-related physiological changes have steeply grown and, with them, the use of aging animal models. Mouse and rat models of aging, the most studied laboratory animals in aging research, exhibit sex differences in many systems and physiological functions, as well as sex differences in the aging process and aging-associated cardiovascular changes. In the present review, we introduce the most common aging and senescence-accelerated animal models and emphasize that sex is a biological variable that should be considered in aging studies. Sex differences in the cardiovascular system, with a focus on sex differences in aging-associated vascular alterations (endothelial dysfunction, remodeling and oxidative and inflammatory processes) in these animal models are reviewed and discussed.
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Affiliation(s)
- Paula R. Barros
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Tiago J. Costa
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Eliana H. Akamine
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
- *Correspondence: Rita C. Tostes, ; Eliana H. Akamine,
| | - Rita C. Tostes
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
- *Correspondence: Rita C. Tostes, ; Eliana H. Akamine,
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4
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Wu Z, Zhang W, Song M, Wang W, Wei G, Li W, Lei J, Huang Y, Sang Y, Chan P, Chen C, Qu J, Suzuki K, Belmonte JCI, Liu GH. Differential stem cell aging kinetics in Hutchinson-Gilford progeria syndrome and Werner syndrome. Protein Cell 2018; 9:333-350. [PMID: 29476423 PMCID: PMC5876188 DOI: 10.1007/s13238-018-0517-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 02/08/2018] [Indexed: 01/12/2023] Open
Abstract
Hutchinson-Gilford progeria syndrome (HGPS) and Werner syndrome (WS) are two of the best characterized human progeroid syndromes. HGPS is caused by a point mutation in lamin A (LMNA) gene, resulting in the production of a truncated protein product-progerin. WS is caused by mutations in WRN gene, encoding a loss-of-function RecQ DNA helicase. Here, by gene editing we created isogenic human embryonic stem cells (ESCs) with heterozygous (G608G/+) or homozygous (G608G/G608G) LMNA mutation and biallelic WRN knockout, for modeling HGPS and WS pathogenesis, respectively. While ESCs and endothelial cells (ECs) did not present any features of premature senescence, HGPS- and WS-mesenchymal stem cells (MSCs) showed aging-associated phenotypes with different kinetics. WS-MSCs had early-onset mild premature aging phenotypes while HGPS-MSCs exhibited late-onset acute premature aging characterisitcs. Taken together, our study compares and contrasts the distinct pathologies underpinning the two premature aging disorders, and provides reliable stem-cell based models to identify new therapeutic strategies for pathological and physiological aging.
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Affiliation(s)
- Zeming Wu
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China.,National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Weiqi Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China.,National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital of Capital Medical University, Beijing, 100053, China
| | - Moshi Song
- University of Chinese Academy of Sciences, Beijing, 100049, China.,State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Wei Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Gang Wei
- Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Wei Li
- National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital of Capital Medical University, Beijing, 100053, China
| | - Jinghui Lei
- National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital of Capital Medical University, Beijing, 100053, China
| | - Yu Huang
- Department of Medical genetics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China
| | - Yanmei Sang
- Department of Pediatric Endocrinology and Genetic Metabolism, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, 100045, China
| | - Piu Chan
- National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital of Capital Medical University, Beijing, 100053, China
| | - Chang Chen
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jing Qu
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Keiichiro Suzuki
- Institute for Advanced Co-Creation Studies, Osaka University, Osaka, 560-8531, Japan. .,Graduate School of Engineering Science, Osaka University, Osaka, 560-8531, Japan.
| | | | - Guang-Hui Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China. .,National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital of Capital Medical University, Beijing, 100053, China. .,Key Laboratory of Regenerative Medicine of Ministry of Education, Institute of Aging and Regenerative Medicine, Jinan University, Guangzhou, 510632, China.
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5
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Ahmed MS, Ikram S, Bibi N, Mir A. Hutchinson-Gilford Progeria Syndrome: A Premature Aging Disease. Mol Neurobiol 2017; 55:4417-4427. [PMID: 28660486 DOI: 10.1007/s12035-017-0610-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 05/10/2017] [Indexed: 12/15/2022]
Abstract
Progeria is sporadic, very rare, autosomal dominant, deadly childhood disorder. It is one of the progeroid syndromes also known as Hutchinson-Gilford progeria syndrome (HGPS). Aging is a developmental process that begins with fertilization and ends up with death involving a lot of environmental and genetic factors. The disease firstly involves premature aging and then death from complications of atherosclerosis such as myocardial infarction, stroke, atherosclerosis, or heart failure. The lifespan of the patient is normally up to teen age or early twenties. It is usually not inherited because a patient normally dies before the age of reproduction. The most important genetic linkage between progeria and aging is shortening of telomere ends with each replication cycle. The patients are normally observed to have extremely short telomeres. Currently, 90% of the patients are said to have de novo point mutations in the LMNA gene that substitute cytosine with thymine and have been found in individuals with HGPS. Lmna encodes lamins A and C, and the A-type lamins have important structural function in the nuclear envelope. The most common type of HGPS mutation is located at codon 608 (G608G). It could not be diagnosed at birth, but after the age of 2 years, visible, prominent symptoms can be observed. Still, lot of research is needed to solve this mystery; hopefully, future research on HGPS would provide important clues for progeria and other fatal age-related disorders.
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Affiliation(s)
- Muhammad Saad Ahmed
- Department of Bioinformatics and Biotechnology, Faculty of Basic and Applied Sciences, International Islamic University, Islamabad, Pakistan.,Department of Biological Engineering/Institute of Biotransformation and Synthetic Biosystem, School of Life Sciences, Beijing Institute of Technology, Beijing, 100081, People's Republic of China
| | - Sana Ikram
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology & Business University (BTBU), 11 Fucheng Road, Beijing, 100048, People's Republic of China
| | - Nousheen Bibi
- Department of Bioinformatics, Hazara University, Mansehra, Pakistan.,National Center for Bioinformatics, Quaid-e-Azam University, Islamabad, Pakistan
| | - Asif Mir
- Department of Bioinformatics and Biotechnology, Faculty of Basic and Applied Sciences, International Islamic University, Islamabad, Pakistan.
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6
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Kõks S, Dogan S, Tuna BG, González-Navarro H, Potter P, Vandenbroucke RE. Mouse models of ageing and their relevance to disease. Mech Ageing Dev 2016; 160:41-53. [PMID: 27717883 DOI: 10.1016/j.mad.2016.10.001] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 09/26/2016] [Accepted: 10/03/2016] [Indexed: 12/28/2022]
Abstract
Ageing is a process that gradually increases the organism's vulnerability to death. It affects different biological pathways, and the underlying cellular mechanisms are complex. In view of the growing disease burden of ageing populations, increasing efforts are being invested in understanding the pathways and mechanisms of ageing. We review some mouse models commonly used in studies on ageing, highlight the advantages and disadvantages of the different strategies, and discuss their relevance to disease susceptibility. In addition to addressing the genetics and phenotypic analysis of mice, we discuss examples of models of delayed or accelerated ageing and their modulation by caloric restriction.
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Affiliation(s)
- Sulev Kõks
- University of Tartu, Tartu, Estonia and Estonian University of Life Sciences, Tartu, Estonia.
| | - Soner Dogan
- Yeditepe University, School of Medicine, Department of Medical Biology, Istanbul, Turkey.
| | - Bilge Guvenc Tuna
- Yeditepe University, School of Medicine, Department of Biophysics, Istanbul, Turkey.
| | - Herminia González-Navarro
- Institute of Health Research-INCLIVA, 46010 Valencia, Spain and CIBER de Diabetes y Enfermedades Metabólicas (CIBERDEM), 28029 Madrid, Spain.
| | - Paul Potter
- Mammalian Genetics Unit, MRC Harwell, Oxfordshire, UK.
| | - Roosmarijn E Vandenbroucke
- Inflammation Research Center, VIB, Ghent, Belgium, Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium.
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7
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Ibrahim B, Sheerin AN, Jennert-Burston K, Bird JLE, Massala MV, Illsley M, James SE, Faragher RGA. Absence of premature senescence in Werner's syndrome keratinocytes. Exp Gerontol 2016; 83:139-47. [PMID: 27492502 DOI: 10.1016/j.exger.2016.07.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 07/29/2016] [Accepted: 07/31/2016] [Indexed: 11/29/2022]
Abstract
Werner's syndrome (WS) is an autosomal recessive genetic disorder caused by loss of function mutation in wrn and is a useful model of premature in vivo ageing. Cellular senescence is a plausible causal mechanism of mammalian ageing and, at the cellular level, WS fibroblasts show premature senescence resulting from a combination of telomeric attrition and replication fork stalling. Over 90% of WS fibroblast cultures achieve <20 population doublings (PD) in vitro compared to wild type human fibroblast cultures. It has been proposed that some cell types, capable of proliferation, will fail to show a premature senescence phenotype in response to wrn mutations. To test this hypothesis, human dermal keratinocytes (derived from both WS and wild type patients) were cultured long term. WS Keratinocytes showed a replicative lifespan in excess of 100 population doublings but maintained functional growth arrest mechanisms based on p16 and p53. The karyotype of the cells was superficially normal and the cultures retained markers characteristic of keratinocyte holoclones (stem cells) including p63 expression and telomerase activity. Accordingly we conclude that, in contrast to WS fibroblasts, WS keratinocytes do not demonstrate slow growth rates or features of premature senescence. These findings suggest that the epidermis is among the tissue types that do not display symptoms of premature ageing caused by loss of function of wrn. This is in support that Werner's syndrome is a segmental progeroid syndrome.
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Affiliation(s)
- Badr Ibrahim
- School of Pharmacy and biomolecular sciences, stress, ageing and diseases research group, College of life, health and physical sciences, University of Brighton, Cockcroft Building, Brighton, BN149HJ, England.
| | - Angela N Sheerin
- School of Pharmacy and biomolecular sciences, stress, ageing and diseases research group, College of life, health and physical sciences, University of Brighton, Cockcroft Building, Brighton, BN149HJ, England.
| | - Katrin Jennert-Burston
- School of Pharmacy and biomolecular sciences, stress, ageing and diseases research group, College of life, health and physical sciences, University of Brighton, Cockcroft Building, Brighton, BN149HJ, England.
| | - Joe L E Bird
- School of Pharmacy and biomolecular sciences, stress, ageing and diseases research group, College of life, health and physical sciences, University of Brighton, Cockcroft Building, Brighton, BN149HJ, England.
| | - M V Massala
- Department of Dermatology, University of Sassari, Viale S Pietro No 43, 09100 Sassari, Italy, Department of Human and Hereditary Pathology, Section of General Biology and Medical Genetics, University of Pavia, Pavia
| | - Matthew Illsley
- School of Pharmacy and biomolecular sciences, stress, ageing and diseases research group, College of life, health and physical sciences, University of Brighton, Cockcroft Building, Brighton, BN149HJ, England.
| | - S Elizabeth James
- School of Pharmacy and biomolecular sciences, stress, ageing and diseases research group, College of life, health and physical sciences, University of Brighton, Cockcroft Building, Brighton, BN149HJ, England.
| | - Richard G A Faragher
- School of Pharmacy and biomolecular sciences, stress, ageing and diseases research group, College of life, health and physical sciences, University of Brighton, Cockcroft Building, Brighton, BN149HJ, England.
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8
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Lees H, Walters H, Cox LS. Animal and human models to understand ageing. Maturitas 2016; 93:18-27. [PMID: 27372369 DOI: 10.1016/j.maturitas.2016.06.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 06/07/2016] [Accepted: 06/08/2016] [Indexed: 12/12/2022]
Abstract
Human ageing is the gradual decline in organ and tissue function with increasing chronological time, leading eventually to loss of function and death. To study the processes involved over research-relevant timescales requires the use of accessible model systems that share significant similarities with humans. In this review, we assess the usefulness of various models, including unicellular yeasts, invertebrate worms and flies, mice and primates including humans, and highlight the benefits and possible drawbacks of each model system in its ability to illuminate human ageing mechanisms. We describe the strong evolutionary conservation of molecular pathways that govern cell responses to extracellular and intracellular signals and which are strongly implicated in ageing. Such pathways centre around insulin-like growth factor signalling and integration of stress and nutritional signals through mTOR kinase. The process of cellular senescence is evaluated as a possible underlying cause for many of the frailties and diseases of human ageing. Also considered is ageing arising from systemic changes that cannot be modelled in lower organisms and instead require studies either in small mammals or in primates. We also touch briefly on novel therapeutic options arising from a better understanding of the biology of ageing.
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Affiliation(s)
- Hayley Lees
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Hannah Walters
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Lynne S Cox
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK.
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9
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Abstract
Progeroid mouse models display phenotypes in multiple organ systems that suggest premature aging and resemble features of natural aging of both mice and humans. The prospect of a significant increase in the global elderly population within the next decades has led to the emergence of "geroscience," which aims at elucidating the molecular mechanisms involved in aging. Progeroid mouse models are frequently used in geroscience as they provide insight into the molecular mechanisms that are involved in the highly complex process of natural aging. This review provides an overview of the most commonly reported nonneoplastic macroscopic and microscopic pathologic findings in progeroid mouse models (eg, osteoporosis, osteoarthritis, degenerative joint disease, intervertebral disc degeneration, kyphosis, sarcopenia, cutaneous atrophy, wound healing, hair loss, alopecia, lymphoid atrophy, cataract, corneal endothelial dystrophy, retinal degenerative diseases, and vascular remodeling). Furthermore, several shortcomings in pathologic analysis and descriptions of these models are discussed. Progeroid mouse models are valuable models for aging, but thorough knowledge of both the mouse strain background and the progeria-related phenotype is required to guide interpretation and translation of the pathology data.
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Affiliation(s)
- L Harkema
- Dutch Molecular Pathology Center, Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - S A Youssef
- Dutch Molecular Pathology Center, Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - A de Bruin
- Dutch Molecular Pathology Center, Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands Department of Pediatrics, Division of Molecular Genetics, University Medical Center Groningen, Groningen, The Netherlands
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10
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Physiological and pathological consequences of cellular senescence. Cell Mol Life Sci 2014; 71:4373-86. [PMID: 25080110 PMCID: PMC4207941 DOI: 10.1007/s00018-014-1691-3] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 07/21/2014] [Accepted: 07/23/2014] [Indexed: 12/11/2022]
Abstract
Cellular senescence, a permanent state of cell cycle arrest accompanied by a complex phenotype, is an essential mechanism that limits tumorigenesis and tissue damage. In physiological conditions, senescent cells can be removed by the immune system, facilitating tumor suppression and wound healing. However, as we age, senescent cells accumulate in tissues, either because an aging immune system fails to remove them, the rate of senescent cell formation is elevated, or both. If senescent cells persist in tissues, they have the potential to paradoxically promote pathological conditions. Cellular senescence is associated with an enhanced pro-survival phenotype, which most likely promotes persistence of senescent cells in vivo. This phenotype may have evolved to favor facilitation of a short-term wound healing, followed by the elimination of senescent cells by the immune system. In this review, we provide a perspective on the triggers, mechanisms and physiological as well as pathological consequences of senescent cells.
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11
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12
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Mason PA, Boubriak I, Robbins T, Lasala R, Saunders R, Cox LS. The Drosophila orthologue of progeroid human WRN exonuclease, DmWRNexo, cleaves replication substrates but is inhibited by uracil or abasic sites : analysis of DmWRNexo activity in vitro. AGE (DORDRECHT, NETHERLANDS) 2013; 35:793-806. [PMID: 22562358 PMCID: PMC3636389 DOI: 10.1007/s11357-012-9411-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Accepted: 04/17/2012] [Indexed: 05/31/2023]
Abstract
Werner syndrome (WS) is a rare late-onset premature ageing disease showing many of the phenotypes associated with normal ageing, and provides one of the best models for investigating cellular pathways that lead to normal ageing. WS is caused by mutation of WRN, which encodes a multifunctional DNA replication and repair helicase/exonuclease. To investigate the role of WRN protein's unique exonuclease domain, we have recently identified DmWRNexo, the fly orthologue of the exonuclease domain of human WRN. Here, we fully characterise DmWRNexo exonuclease activity in vitro, confirming 3'-5' polarity, demonstrating a requirement for Mg(2+), inhibition by ATP, and an ability to degrade both single-stranded DNA and duplex DNA substrates with 3' or 5' overhangs, or bubble structures, but with no activity on blunt ended DNA duplexes. We report a novel active site mutation that ablates enzyme activity. Lesional substrates containing uracil are partially cleaved by DmWRNexo, but the enzyme pauses on such substrates and is inhibited by abasic sites. These strong biochemical similarities to human WRN suggest that Drosophila can provide a valuable experimental system for analysing the importance of WRN exonuclease in cell and organismal ageing.
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Affiliation(s)
- Penelope A. Mason
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Ivan Boubriak
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Timothy Robbins
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Ralph Lasala
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
- Department of Life Sciences, The Open University, Milton Keynes, MK7 6AA UK
| | - Robert Saunders
- Department of Life Sciences, The Open University, Milton Keynes, MK7 6AA UK
| | - Lynne S. Cox
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
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13
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Duband-Goulet I, Woerner S, Gasparini S, Attanda W, Kondé E, Tellier-Lebègue C, Craescu CT, Gombault A, Roussel P, Vadrot N, Vicart P, Ostlund C, Worman HJ, Zinn-Justin S, Buendia B. Subcellular localization of SREBP1 depends on its interaction with the C-terminal region of wild-type and disease related A-type lamins. Exp Cell Res 2011; 317:2800-13. [PMID: 21993218 DOI: 10.1016/j.yexcr.2011.09.012] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 09/02/2011] [Accepted: 09/26/2011] [Indexed: 11/26/2022]
Abstract
Lamins A and C are nuclear intermediate filament proteins expressed in most differentiated somatic cells. Previous data suggested that prelamin A, the lamin A precursor, accumulates in some lipodystrophy syndromes caused by mutations in the lamin A/C gene, and binds and inactivates the sterol regulatory element binding protein 1 (SREBP1). Here we show that, in vitro, the tail regions of prelamin A, lamin A and lamin C bind a polypeptide of SREBP1. Such interactions also occur in HeLa cells, since expression of lamin tail regions impedes nucleolar accumulation of the SREBP1 polypeptide fused to a nucleolar localization signal sequence. In addition, the tail regions of A-type lamin variants that occur in Dunnigan-type familial partial lipodystrophy of (R482W) and Hutchison Gilford progeria syndrome (∆607-656) bind to the SREBP1 polypeptide in vitro, and the corresponding FLAG-tagged full-length lamin variants co-immunoprecipitate the SREBP1 polypeptide in cells. Overexpression of wild-type A-type lamins and variants favors SREBP1 polypeptide localization at the intranuclear periphery, suggesting its sequestration. Our data support the hypothesis that variation of A-type lamin protein level and spatial organization, in particular due to disease-linked mutations, influences the sequestration of SREBP1 at the nuclear envelope and thus contributes to the regulation of SREBP1 function.
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Affiliation(s)
- Isabelle Duband-Goulet
- Laboratoire du Stress et Pathologies du Cytosquelette, Université Paris Diderot-Paris 7, CNRS, Institut de Biologie Fonctionnelle et Adaptative, 4 rue M.A. Lagroua Weill Halle, 75205 Paris cedex 13, France
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14
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Bird JLE, Jennert-Burston KCB, Bachler MA, Mason PA, Lowe JE, Heo SJ, Campisi J, Faragher RGA, Cox LS. Recapitulation of Werner syndrome sensitivity to camptothecin by limited knockdown of the WRN helicase/exonuclease. Biogerontology 2011; 13:49-62. [PMID: 21786128 DOI: 10.1007/s10522-011-9341-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Accepted: 05/10/2011] [Indexed: 12/01/2022]
Abstract
WRN is a RecQ helicase with an associated exonuclease activity important in DNA metabolism, including DNA replication, repair and recombination. In humans, deficiencies in WRN function cause the segmental progeroid Werner syndrome (WS), in which patients show premature onset of many hallmarks of normal human ageing. At the cellular level, WRN loss results in rapid replicative senescence, chromosomal instability and sensitivity to various DNA damaging agents including the topoisomerase inhibitor, camptothecin (CPT). Here, we investigate the potential of using either transient or stable WRN knockdown as a means of sensitising cells to CPT. We show that targeting WRN mRNA for degradation by either RNAi or hammerhead ribozyme catalysis renders human fibroblasts as sensitive to CPT as fibroblasts derived from WS patients, and furthermore, we find altered cell cycle transit and nucleolar destabilisation in these cells following CPT treatment. Such WS-like phenotypes are observed despite very limited decreases in total WRN protein, suggesting that levels of WRN protein are rate-limiting for the cellular response to camptothecin. These findings have major implications for development of anti-WRN agents that may be useful in sensitising tumour cells to clinically relevant topoisomerase inhibitors.
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Affiliation(s)
- Joseph L E Bird
- School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, UK
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15
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Enabling enrichment analysis with the Human Disease Ontology. J Biomed Inform 2011; 44 Suppl 1:S31-S38. [PMID: 21550421 DOI: 10.1016/j.jbi.2011.04.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2011] [Revised: 04/12/2011] [Accepted: 04/22/2011] [Indexed: 01/30/2023]
Abstract
Advanced statistical methods used to analyze high-throughput data such as gene-expression assays result in long lists of "significant genes." One way to gain insight into the significance of altered expression levels is to determine whether Gene Ontology (GO) terms associated with a particular biological process, molecular function, or cellular component are over- or under-represented in the set of genes deemed significant. This process, referred to as enrichment analysis, profiles a gene set, and is widely used to make sense of the results of high-throughput experiments. Our goal is to develop and apply general enrichment analysis methods to profile other sets of interest, such as patient cohorts from the electronic medical record, using a variety of ontologies including SNOMED CT, MedDRA, RxNorm, and others. Although it is possible to perform enrichment analysis using ontologies other than the GO, a key pre-requisite is the availability of a background set of annotations to enable the enrichment calculation. In the case of the GO, this background set is provided by the Gene Ontology Annotations. In the current work, we describe: (i) a general method that uses hand-curated GO annotations as a starting point for creating background datasets for enrichment analysis using other ontologies; and (ii) a gene-disease background annotation set - that enables disease-based enrichment - to demonstrate feasibility of our method.
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16
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Geyfman M, Andersen B. Clock genes, hair growth and aging. Aging (Albany NY) 2010; 2:122-8. [PMID: 20375466 PMCID: PMC2871241 DOI: 10.18632/aging.100130] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Accepted: 03/17/2010] [Indexed: 05/06/2023]
Abstract
Hair follicles undergo continuous cycles of growth, involution and rest. This process, referred to as the hair growth cycle, has a periodicity of weeks to months. At the same time, skin and hair follicles harbor a functional circadian clock that regulates gene expression with a periodicity of approximately twenty four hours. In our recent study we found that circadian clock genes play a role in regulation of the hair growth cycle during synchronized hair follicle cycling, uncovering an unexpected connection between these two timing systems within skin. This work, therefore, indicates a role for circadian clock genes in a cyclical process of much longer periodicity than twenty four hours.
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Affiliation(s)
- Mikhail Geyfman
- Departments of Medicine and Biological Chemistry, University of California-Irvine, Irvine CA 92697, USA
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17
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Abstract
Ageing is a progressive failure of defence and repair processes that produces physiological frailty (the loss of organ reserve with age), loss of homeostasis and eventual death. Over the past ten years exceptional progress has been made in understanding both why the ageing process happens and the mechanisms that are responsible for it. The study of natural mutants that accelerate some, but not all, of the features of the human ageing process has now progressed to a degree that drug trials are either taking place or can be envisaged. Simultaneously, a series of mutations have been identified in different species that confer extended healthy life, indicating that the ageing process is much more malleable than might have been expected and that single interventions have the potential to delay the onset of multiple age-associated conditions. Data generated using these organisms have led to the formulation of a powerful new hypothesis, the ‘green theory’ of ageing. This proposes that a finite capacity to carry out broad-spectrum detoxification and recycling is the primary mechanistic limit on organismal lifespan. This is turn suggests important new experimental approaches and potential interventions designed to increase healthy lifespan.
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18
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Vulliamy TJ. Premature aging. Cell Mol Life Sci 2009; 66:3091-4. [PMID: 19618112 PMCID: PMC11115659 DOI: 10.1007/s00018-009-0091-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 07/01/2009] [Accepted: 07/02/2009] [Indexed: 10/20/2022]
Affiliation(s)
- Thomas J 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, UK.
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19
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Cox LS, Mattison JA. Increasing longevity through caloric restriction or rapamycin feeding in mammals: common mechanisms for common outcomes? Aging Cell 2009; 8:607-13. [PMID: 19678809 DOI: 10.1111/j.1474-9726.2009.00509.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Significant extension of lifespan in important mammalian species is bound to attract the attention not only of the aging research community, but also the media and the wider public. Two recent papers published by Harrison et al. (2009) in Nature and by Colman et al. (2009) in Science report increased longevity of mice fed with rapamycin and of rhesus monkeys undergoing caloric restriction, respectively. These papers have generated considerable debate in the aging community. Here we assess what is new about these findings, how they fit with our knowledge of lifespan extension from other studies and what prospects this new work holds out for improvements in human longevity and human health span.
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Affiliation(s)
- Lynne S Cox
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK.
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20
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Faragher R. What could advances in the biology of ageing mean for the quality of later life? QUALITY IN AGEING AND OLDER ADULTS 2009. [DOI: 10.1108/14717794200900015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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21
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Roles of RECQ helicases in recombination based DNA repair, genomic stability and aging. Biogerontology 2008; 10:235-52. [PMID: 19083132 DOI: 10.1007/s10522-008-9205-z] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Accepted: 11/24/2008] [Indexed: 12/28/2022]
Abstract
The maintenance of the stability of genetic material is an essential feature of every living organism. Organisms across all kingdoms have evolved diverse and highly efficient repair mechanisms to protect the genome from deleterious consequences of various genotoxic factors that might tend to destabilize the integrity of the genome in each generation. One such group of proteins that is actively involved in genome surveillance is the RecQ helicase family. These proteins are highly conserved DNA helicases, which have diverse roles in multiple DNA metabolic processes such as DNA replication, recombination and DNA repair. In humans, five RecQ helicases have been identified and three of them namely, WRN, BLM and RecQL4 have been linked to genetic diseases characterized by genome instability, premature aging and cancer predisposition. This helicase family plays important roles in various DNA repair pathways including protecting the genome from illegitimate recombination during chromosome segregation in mitosis and assuring genome stability. This review mainly focuses on various roles of human RecQ helicases in the process of recombination-based DNA repair to maintain genome stability and physiological consequences of their defects in the development of cancer and premature aging.
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22
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Osorio FG, Obaya ÁJ, López-Otín C, Freije JMP. Accelerated ageing: from mechanism to therapy through animal models. Transgenic Res 2008; 18:7-15. [DOI: 10.1007/s11248-008-9226-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Accepted: 10/27/2008] [Indexed: 11/28/2022]
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23
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Boubriak I, Mason PA, Clancy DJ, Dockray J, Saunders RDC, Cox LS. DmWRNexo is a 3'-5' exonuclease: phenotypic and biochemical characterization of mutants of the Drosophila orthologue of human WRN exonuclease. Biogerontology 2008; 10:267-77. [PMID: 18956248 DOI: 10.1007/s10522-008-9181-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Accepted: 09/25/2008] [Indexed: 12/21/2022]
Abstract
The premature human ageing Werner's syndrome is caused by loss or mutation of the WRN helicase/exonuclease. We have recently identified the orthologue of the WRN exonuclease in flies, DmWRNexo, encoded by the CG7670 locus, and showed very high levels of mitotic recombination in a hypomorphic PiggyBac insertional mutant. Here, we report a novel allele of CG7670, with a point mutation resulting in the change of the conserved aspartate (229) to valine. Flies bearing this mutation show levels of mitotic recombination 20-fold higher than wild type. Molecular modelling suggests that D229 lies towards the outside of the molecule distant from the nuclease active site. We have produced recombinant protein of the D229V mutant, assayed its nuclease activity in vitro, and compared activity with that of wild type DmWRNexo and a D162A E164A double active site mutant we have created. We show for the first time that DmWRNexo has 3'-5' exonuclease activity and that mutation within the presumptive active site disrupts exonuclease activity. Furthermore, we show that the D229V mutant has very limited exonuclease activity in vitro. Using Drosophila, we can therefore analyse WRN exonuclease from enzyme activity in vitro through to fly phenotype, and show that loss of exonuclease activity contributes to genome instability.
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Affiliation(s)
- Ivan Boubriak
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK
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24
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Davis T, Kipling D. Assessing the role of stress signalling via p38 MAP kinase in the premature senescence of ataxia telangiectasia and Werner syndrome fibroblasts. Biogerontology 2008; 10:253-66. [PMID: 18830681 DOI: 10.1007/s10522-008-9179-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 09/18/2008] [Indexed: 10/21/2022]
Abstract
The premature ageing ataxia telangiectasia (AT) and Werner syndromes (WS) are associated with accelerated cellular ageing. Young WS fibroblasts have an aged appearance and activated p38 MAP kinase, and treatment with the p38 inhibitor SB230580 extends their lifespan to within the normal range. SB203580 also extends the replicative lifespan of normal adult dermal fibroblasts, however, the effect is much reduced when compared to WS cells, suggesting that WS fibroblasts undergo a form of stress-induced premature senescence (SIPS). A small lifespan extension is seen in AT cells, which is not significant compared to normal fibroblasts, and the majority of young AT cells do not have an aged appearance and lack p38 activation, suggesting that the premature ageing does not result from SIPS. The lack of p38 activation is supported by the clinical manifestation, since AT is not associated with inflammatory disease, whereas WS individuals are predisposed to atherosclerosis, type II diabetes and osteoporosis, conditions known to be associated with p38 activation.
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Affiliation(s)
- Terence Davis
- Department of Pathology, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK.
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25
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de Magalhães JP, Faragher RGA. Cell divisions and mammalian aging: integrative biology insights from genes that regulate longevity. Bioessays 2008; 30:567-78. [PMID: 18478536 DOI: 10.1002/bies.20760] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Despite recent progress in the identification of genes that regulate longevity, aging remains a mysterious process. One influential hypothesis is the idea that the potential for cell division and replacement are important factors in aging. In this work, we review and discuss this perspective in the context of interventions in mammals that appear to accelerate or retard aging. Rather than focus on molecular mechanisms, we interpret results from an integrative biology perspective of how gene products affect cellular functions, which in turn impact on tissues and organisms. We review evidence suggesting that mutations that give rise to features resembling premature aging tend to be associated with cellular phenotypes such as increased apoptosis or premature replicative senescence. In contrast, many interventions in mice that extend lifespan and might delay aging, including caloric restriction, tend to either hinder apoptosis or result in smaller animals and thus may be the product of fewer cell divisions. Therefore, it appears plausible that changes in the number of times that cells, and particularly stem cells, divide during an organism's lifespan influence longevity and aging. We discuss possible mechanisms related to this hypothesis and propose experimental paradigms.
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26
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Lutomska A, Lebedev A, Scharffetter-Kochanek K, Iben S. The transcriptional response to distinct growth factors is impaired in Werner syndrome cells. Exp Gerontol 2008; 43:820-6. [PMID: 18625297 DOI: 10.1016/j.exger.2008.06.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2007] [Revised: 04/16/2008] [Accepted: 06/12/2008] [Indexed: 10/21/2022]
Abstract
The Werner syndrome protein (WRN) is mutated in Werner syndrome (WS) and plays a role in telomere maintenance, DNA repair and transcription. WS represents a premature aging syndrome with severe growth retardation. Here we show that WRN is critically required to mediate the stimulatory effect of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-b) and epidermal growth factor (EGF) on the activity of RNA polymerase I (Pol I). Recombinant WRN specifically reconstitutes RNA polymerase I transcription in extracts from Werner syndrome fibroblasts in vitro. In addition, we identified a critical role for WRN during promoter clearance of Pol I transcription, but not in elongation. Notably, WRN was isolated in a complex with Pol I and was crosslinked to the unmethylated, active proportion of rDNA genes in quiescent cells suggesting a so far unknown role for WRN in epigenetic regulation. This together with alterations in Pol I transcription provide a novel mechanism possibly underlying at least in part the severe growth retardation and premature aging in Werner syndrome patients.
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Affiliation(s)
- Anna Lutomska
- Department of Dermatology and Allergic Diseases, University of Ulm, Maienweg 12, 89081 Ulm, Germany
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27
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Saunders RDC, Boubriak I, Clancy DJ, Cox LS. Identification and characterization of a Drosophila ortholog of WRN exonuclease that is required to maintain genome integrity. Aging Cell 2008; 7:418-25. [PMID: 18346216 PMCID: PMC2408639 DOI: 10.1111/j.1474-9726.2008.00388.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/07/2008] [Indexed: 01/08/2023] Open
Abstract
The premature human aging Werner syndrome (WS) is caused by mutation of the RecQ-family WRN helicase, which is unique in possessing also 3'-5' exonuclease activity. WS patients show significant genomic instability with elevated cancer incidence. WRN is implicated in restraining illegitimate recombination, especially during DNA replication. Here we identify a Drosophila ortholog of the WRN exonuclease encoded by the CG7670 locus. The predicted DmWRNexo protein shows conservation of structural motifs and key catalytic residues with human WRN exonuclease, but entirely lacks a helicase domain. Insertion of a piggyBac element into the 5' UTR of CG7670 severely reduces gene expression. DmWRNexo mutant flies homozygous for this insertional allele of CG7670 are thus severely hypomorphic; although adults show no gross morphological abnormalities, females are sterile. Like human WS cells, we show that the DmWRNexo mutant flies are hypersensitive to the topoisomerase I inhibitor camptothecin. Furthermore, these mutant flies show highly elevated rates of mitotic DNA recombination resulting from excessive reciprocal exchange. This study identifies a novel WRN ortholog in flies and demonstrates an important role for WRN exonuclease in maintaining genome stability.
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Affiliation(s)
- Robert D C Saunders
- Department of Biological Sciences, The Open University, Milton Keynes MK7 6AA, UK.
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28
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Jeyapalan JC, Sedivy JM. Cellular senescence and organismal aging. Mech Ageing Dev 2008; 129:467-74. [PMID: 18502472 DOI: 10.1016/j.mad.2008.04.001] [Citation(s) in RCA: 256] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2007] [Revised: 03/27/2008] [Accepted: 04/06/2008] [Indexed: 01/22/2023]
Abstract
Cellular senescence, first observed and defined using in vitro cell culture studies, is an irreversible cell cycle arrest which can be triggered by a variety of factors. Emerging evidence suggests that cellular senescence acts as an in vivo tumor suppression mechanism by limiting aberrant proliferation. It has also been postulated that cellular senescence can occur independently of cancer and contribute to the physiological processes of normal organismal aging. Recent data have demonstrated the in vivo accumulation of senescent cells with advancing age. Some characteristics of senescent cells, such as the ability to modify their extracellular environment, could play a role in aging and age-related pathology. In this review, we examine current evidence that links cellular senescence and organismal aging.
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Affiliation(s)
- Jessie C Jeyapalan
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
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29
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Garcia SN, Pereira-Smith O. MRGing Chromatin Dynamics and Cellular Senescence. Cell Biochem Biophys 2008; 50:133-41. [DOI: 10.1007/s12013-008-9006-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2007] [Accepted: 12/15/2007] [Indexed: 11/28/2022]
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