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Measuring DNA modifications with the comet assay: a compendium of protocols. Nat Protoc 2023; 18:929-989. [PMID: 36707722 DOI: 10.1038/s41596-022-00754-y] [Citation(s) in RCA: 105] [Impact Index Per Article: 105.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 07/05/2022] [Indexed: 01/28/2023]
Abstract
The comet assay is a versatile method to detect nuclear DNA damage in individual eukaryotic cells, from yeast to human. The types of damage detected encompass DNA strand breaks and alkali-labile sites (e.g., apurinic/apyrimidinic sites), alkylated and oxidized nucleobases, DNA-DNA crosslinks, UV-induced cyclobutane pyrimidine dimers and some chemically induced DNA adducts. Depending on the specimen type, there are important modifications to the comet assay protocol to avoid the formation of additional DNA damage during the processing of samples and to ensure sufficient sensitivity to detect differences in damage levels between sample groups. Various applications of the comet assay have been validated by research groups in academia, industry and regulatory agencies, and its strengths are highlighted by the adoption of the comet assay as an in vivo test for genotoxicity in animal organs by the Organisation for Economic Co-operation and Development. The present document includes a series of consensus protocols that describe the application of the comet assay to a wide variety of cell types, species and types of DNA damage, thereby demonstrating its versatility.
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Rinkevich B, Ballarin L, Martinez P, Somorjai I, Ben‐Hamo O, Borisenko I, Berezikov E, Ereskovsky A, Gazave E, Khnykin D, Manni L, Petukhova O, Rosner A, Röttinger E, Spagnuolo A, Sugni M, Tiozzo S, Hobmayer B. A pan-metazoan concept for adult stem cells: the wobbling Penrose landscape. Biol Rev Camb Philos Soc 2022; 97:299-325. [PMID: 34617397 PMCID: PMC9292022 DOI: 10.1111/brv.12801] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 09/20/2021] [Accepted: 09/22/2021] [Indexed: 12/17/2022]
Abstract
Adult stem cells (ASCs) in vertebrates and model invertebrates (e.g. Drosophila melanogaster) are typically long-lived, lineage-restricted, clonogenic and quiescent cells with somatic descendants and tissue/organ-restricted activities. Such ASCs are mostly rare, morphologically undifferentiated, and undergo asymmetric cell division. Characterized by 'stemness' gene expression, they can regulate tissue/organ homeostasis, repair and regeneration. By contrast, analysis of other animal phyla shows that ASCs emerge at different life stages, present both differentiated and undifferentiated phenotypes, and may possess amoeboid movement. Usually pluri/totipotent, they may express germ-cell markers, but often lack germ-line sequestering, and typically do not reside in discrete niches. ASCs may constitute up to 40% of animal cells, and participate in a range of biological phenomena, from whole-body regeneration, dormancy, and agametic asexual reproduction, to indeterminate growth. They are considered legitimate units of selection. Conceptualizing this divergence, we present an alternative stemness metaphor to the Waddington landscape: the 'wobbling Penrose' landscape. Here, totipotent ASCs adopt ascending/descending courses of an 'Escherian stairwell', in a lifelong totipotency pathway. ASCs may also travel along lower stemness echelons to reach fully differentiated states. However, from any starting state, cells can change their stemness status, underscoring their dynamic cellular potencies. Thus, vertebrate ASCs may reflect just one metazoan ASC archetype.
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Affiliation(s)
- Baruch Rinkevich
- Israel Oceanographic & Limnological ResearchNational Institute of OceanographyPOB 9753, Tel ShikmonaHaifa3109701Israel
| | - Loriano Ballarin
- Department of BiologyUniversity of PadovaVia Ugo Bassi 58/BPadova35121Italy
| | - Pedro Martinez
- Departament de Genètica, Microbiologia i EstadísticaUniversitat de BarcelonaAv. Diagonal 643Barcelona08028Spain
- Institut Català de Recerca i Estudis Avançats (ICREA)Passeig Lluís Companys 23Barcelona08010Spain
| | - Ildiko Somorjai
- School of BiologyUniversity of St AndrewsSt Andrews, FifeKY16 9ST, ScotlandUK
| | - Oshrat Ben‐Hamo
- Israel Oceanographic & Limnological ResearchNational Institute of OceanographyPOB 9753, Tel ShikmonaHaifa3109701Israel
| | - Ilya Borisenko
- Department of Embryology, Faculty of BiologySaint‐Petersburg State UniversityUniversity Embankment, 7/9Saint‐Petersburg199034Russia
| | - Eugene Berezikov
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center GroningenAntonius Deusinglaan 1Groningen9713 AVThe Netherlands
| | - Alexander Ereskovsky
- Department of Embryology, Faculty of BiologySaint‐Petersburg State UniversityUniversity Embankment, 7/9Saint‐Petersburg199034Russia
- Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale (IMBE), Aix Marseille University, CNRS, IRD, Avignon UniversityJardin du Pharo, 58 Boulevard Charles LivonMarseille13007France
- Koltzov Institute of Developmental Biology of Russian Academy of SciencesUlitsa Vavilova, 26Moscow119334Russia
| | - Eve Gazave
- Université de Paris, CNRS, Institut Jacques MonodParisF‐75006France
| | - Denis Khnykin
- Department of PathologyOslo University HospitalBygg 19, Gaustad Sykehus, Sognsvannsveien 21Oslo0188Norway
| | - Lucia Manni
- Department of BiologyUniversity of PadovaVia Ugo Bassi 58/BPadova35121Italy
| | - Olga Petukhova
- Collection of Vertebrate Cell CulturesInstitute of Cytology, Russian Academy of SciencesTikhoretsky Ave. 4St. Petersburg194064Russia
| | - Amalia Rosner
- Israel Oceanographic & Limnological ResearchNational Institute of OceanographyPOB 9753, Tel ShikmonaHaifa3109701Israel
| | - Eric Röttinger
- Université Côte d'Azur, CNRS, INSERM, Institute for Research on Cancer and Aging, Nice (IRCAN)Nice06107France
- Université Côte d'Azur, Federative Research Institute – Marine Resources (IFR MARRES)28 Avenue de ValroseNice06103France
| | - Antonietta Spagnuolo
- Department of Biology and Evolution of Marine OrganismsStazione Zoologica Anton DohrnVilla ComunaleNaples80121Italy
| | - Michela Sugni
- Department of Environmental Science and Policy (ESP)Università degli Studi di MilanoVia Celoria 26Milan20133Italy
| | - Stefano Tiozzo
- Sorbonne Université, CNRS, Laboratoire de Biologie du Développement de Villefranche‐sur‐mer (LBDV)06234 Villefranche‐sur‐MerVillefranche sur MerCedexFrance
| | - Bert Hobmayer
- Institute of Zoology and Center for Molecular Biosciences, University of InnsbruckTechnikerstrInnsbruck256020Austria
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MiR-185 targets POT1 to induce telomere dysfunction and cellular senescence. Aging (Albany NY) 2020; 12:14791-14807. [PMID: 32687062 PMCID: PMC7425516 DOI: 10.18632/aging.103541] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Accepted: 06/01/2020] [Indexed: 12/20/2022]
Abstract
Protection of telomere 1 (POT1), the telomeric single-stranded DNA (ssDNA)-binding protein in the shelterin complex, has been implicated in the DNA damage response, tumorigenesis and aging. Telomere dysfunction induced by telomere deprotection could accelerate cellular senescence in primary human cells. While previous work demonstrated the biological mechanism of POT1 in aging and cancer, how POT1 is posttranscriptionally regulated remains largely unknown. To better understand the POT1 regulatory axis, we performed bioinformatic prediction, and selected candidates were further confirmed by dual-luciferase reporter assay. Collectively, our results revealed that miR-185 can significantly reduce POT1 mRNA and protein levels by directly targeting the POT1 3’-untranslated region (3’-UTR). Overexpression of miR-185 increased telomere dysfunction-induced foci (TIF) signals in both cancer cells and primary human fibroblasts. Elevated miR-185 led to telomere elongation in the telomerase-positive cell line HTC75, which was phenotypically consistent with POT1 knocking down. Moreover, miR-185 accelerated the replicative senescence process in primary human fibroblasts in a POT1-dependent manner. Interestingly, increased serum miR-185 could represent a potential aging-related biomarker. Taken together, our findings reveal miR-185 as a novel aging-related miRNA that targets POT1 and provide insight into the telomere and senescence regulatory network at both the intracellular and extracellular levels.
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DNA damage and tissue repair: What we can learn from planaria. Semin Cell Dev Biol 2018; 87:145-159. [PMID: 29727725 DOI: 10.1016/j.semcdb.2018.04.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 04/22/2018] [Accepted: 04/30/2018] [Indexed: 12/21/2022]
Abstract
Faithful renewal of aging and damaged tissues is central to organismal lifespan. Stem cells (SCs) generate the cellular progeny that replenish adult tissues across the body but this task becomes increasingly compromised over time. The age related decline in SC-mediated tissue maintenance is a multifactorial event that commonly affects genome integrity. The presence of DNA damage in SCs that are under continuous demand to divide poses a great risk for age-related disorders such as cancer. However, performing analysis of SCs with genomic instability and the DNA damage response during tissue renewal present significant challenges. Here we introduce an alternative experimental system based on the planaria flatworm Schmidtea mediterranea to address at the organismal level studies intersecting SC-mediated tissue renewal in the presence of genomic instability. Planaria have abundant SCs (neoblasts) that maintain high rates of cellular turnover and a variety of molecular tools have been developed to induce DNA damage and dissect how neoblasts respond to this stressor. S. mediterranea displays high evolutionary conservation of DNA repair mechanisms and signaling pathways regulating adult SCs. We describe genetically induced-DNA damage models and highlight body-wide signals affecting cellular decisions such as survival, proliferation, and death in the presence of genomic instability. We also discuss transcriptomic changes in the DNA damage response during injury repair and propose DNA repair as key component of tissue regeneration. Additional studies using planaria will provide insights about mechanisms regulating survival and growth of cells with DNA damage during tissue renewal and regeneration.
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Thiruvalluvan M, Barghouth PG, Tsur A, Broday L, Oviedo NJ. SUMOylation controls stem cell proliferation and regional cell death through Hedgehog signaling in planarians. Cell Mol Life Sci 2018; 75:1285-1301. [PMID: 29098326 PMCID: PMC7083543 DOI: 10.1007/s00018-017-2697-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 10/21/2017] [Accepted: 10/24/2017] [Indexed: 12/15/2022]
Abstract
Mechanisms underlying anteroposterior body axis differences during adult tissue maintenance and regeneration are poorly understood. Here, we identify that post-translational modifications through the SUMO (Small Ubiquitin-like Modifier) machinery are evolutionarily conserved in the Lophotrocozoan Schmidtea mediterranea. Disruption of SUMOylation in adult animals by RNA-interference of the only SUMO E2 conjugating enzyme Ubc9 leads to a systemic increase in DNA damage and a remarkable regional defect characterized by increased cell death and loss of the posterior half of the body. We identified that Ubc9 is mainly expressed in planarian stem cells (neoblasts) but it is also transcribed in differentiated cells including neurons. Regeneration in Ubc9(RNAi) animals is impaired and associated with low neoblast proliferation. We present evidence indicating that Ubc9-induced regional cell death is preceded by alterations in transcription and spatial expression of repressors and activators of the Hedgehog signaling pathway. Our results demonstrate that SUMOylation acts as a regional-specific cue to regulate cell fate during tissue renewal and regeneration.
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Affiliation(s)
- Manish Thiruvalluvan
- Department of Molecular and Cell Biology, University of California, 5200 North Lake Road, Merced, CA, 95343, USA
- Quantitative and Systems Biology Graduate Program, University of California, Merced, USA
| | - Paul G Barghouth
- Department of Molecular and Cell Biology, University of California, 5200 North Lake Road, Merced, CA, 95343, USA
- Quantitative and Systems Biology Graduate Program, University of California, Merced, USA
| | - Assaf Tsur
- Department of Cell and Developmental Biology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Limor Broday
- Department of Cell and Developmental Biology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Néstor J Oviedo
- Department of Molecular and Cell Biology, University of California, 5200 North Lake Road, Merced, CA, 95343, USA.
- Quantitative and Systems Biology Graduate Program, University of California, Merced, USA.
- Health Sciences Research Institute, University of California, Merced, USA.
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Sahu S, Dattani A, Aboobaker AA. Secrets from immortal worms: What can we learn about biological ageing from the planarian model system? Semin Cell Dev Biol 2017; 70:108-121. [PMID: 28818620 DOI: 10.1016/j.semcdb.2017.08.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 08/07/2017] [Accepted: 08/09/2017] [Indexed: 12/12/2022]
Abstract
Understanding how some animals are immortal and avoid the ageing process is important. We currently know very little about how they achieve this. Research with genetic model systems has revealed the existence of conserved genetic pathways and molecular processes that affect longevity. Most of these established model organisms have relatively short lifespans. Here we consider the use of planarians, with an immortal life-history that is able to entirely avoid the ageing process. These animals are capable of profound feats of regeneration fueled by a population of adult stem cells called neoblasts. These cells are capable of indefinite self-renewal that has underpinned the evolution of animals that reproduce only by fission, having disposed of the germline, and must therefore be somatically immortal and avoid the ageing process. How they do this is only now starting to be understood. Here we suggest that the evidence so far supports the hypothesis that the lack of ageing is an emergent property of both being highly regenerative and the evolution of highly effective mechanisms for ensuring genome stability in the neoblast stem cell population. The details of these mechanisms could prove to be very informative in understanding how the causes of ageing can be avoided, slowed or even reversed.
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Affiliation(s)
- Sounak Sahu
- Department of Zoology, South Parks Road, University of Oxford, Oxford OX1 3PS, UK
| | - Anish Dattani
- Department of Zoology, South Parks Road, University of Oxford, Oxford OX1 3PS, UK
| | - A Aziz Aboobaker
- Department of Zoology, South Parks Road, University of Oxford, Oxford OX1 3PS, UK.
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