The comet assay, DNA damage, DNA repair and cytotoxicity: hedgehogs are not always dead

Lorenzo, Yolanda; Costa, Solange; Collins, Andrew R.; Azqueta, Amaya
July 2013
Mutagenesis;Jul2013, Vol. 28 Issue 4, p427
Academic Journal
DNA damage is commonly measured at the level of individual cells using the so-called comet assay (single-cell gel electrophoresis). As the frequency of DNA breaks increases, so does the fraction of the DNA extending towards the anode, forming the comet tail. Comets with almost all DNA in the tail are often referred to as ‘hedgehog’ comets and are widely assumed to represent apoptotic cells. We review the literature and present theoretical and empirical arguments against this interpretation. The level of DNA damage in these comets is far less than the massive fragmentation that occurs in apoptosis. ‘Hedgehog’ comets are formed after moderate exposure of cells to, for example, H2O2, but if the cells are incubated for a short period, ‘hedgehogs’ are no longer seen. We confirm that this is not because DNA has degraded further and been lost from the gel, but because the DNA is repaired. The comet assay may detect the earliest stages of apoptosis, but as it proceeds, comets disappear in a smear of unattached DNA. It is clear that ‘hedgehogs’ can correspond to one level on a continuum of genotoxic damage, are not diagnostic of apoptosis and should not be regarded as an indicator of cytotoxicity.


Related Articles

  • Genotoxicity and cytotoxicity induced by municipal effluent in multiple organs of Wistar rats. da Silva, Victor; Moura, Carolina; Ribeiro, Flavia; Cesar, Augusto; Pereira, Camilo; Silva, Marcelo; Vilegas, Wagner; Ribeiro, Daniel // Environmental Science & Pollution Research;Nov2014, Vol. 21 Issue 22, p13069 

    The aim of this study was to evaluate cytotoxicity and genotoxicity in multiple organs of rats induced by municipal effluent released by submarine outfall in city of Santos. A total of 20 male Wistar rats were exposed to effluents by drinking water ad libitum at concentrations of 0, 10, 50, and...

  • Granzyme A, which causes single-stranded DNA damage, targets the double-strand break repair protein Ku70. Pengcheng Zhu; Dong Zhang; Chowdhury, Dipanjan; Martinvalet, Denis; Keefe, Dennis; Lianfa Shi; Lieberman, Judy // EMBO Reports;Apr2006, Vol. 7 Issue 4, p431 

    Granzyme A (GzmA) induces caspase-independent cell death with morphological features of apoptosis. Here, we show that GzmA at nanomolar concentrations cleaves Ku70, a key double-strand break repair (DSBR) protein, in target cells. Ku70 is cut after Arg301, disrupting Ku complex binding to DNA....

  • Cytotoxicity and genotoxicity of capecitabine in head and neck cancer and normal cells. Wisniewska-Jarosinska, Maria; Sliwinski, Tomasz; Kasznicki, Jacek; Kaczmarczyk, Dariusz; Krupa, Renata; Bloch, Karolina; Drzewoski, Jozef; Chojnacki, Jan; Blasiak, Janusz; Morawiec-Sztandera, Alina // Molecular Biology Reports;Aug2011, Vol. 38 Issue 6, p3679 

    The interaction between a chemical and a cell may strongly depend on whether this cell is normal or pathological. Side effects of anticancer drugs may sometimes overcome their benefit action, so it is important to investigate their effect in both the target and normal cells. Capecitabine...

  • Undetectable role of oxidative DNA damage in cell cycle, cytotoxic and clastogenic effects of Cr(VI) in human lung cells with restored ascorbate levels. Reynolds, Mindy; Armknecht, Susan; Johnston, Tatiana; Zhitkovich, Anatoly // Mutagenesis;Jul2012, Vol. 27 Issue 4, p437 

    Cultured human cells are invaluable biological models for mechanistic studies of genotoxic chemicals and drugs. Continuing replacement of animals in toxicity testing will further increase the importance of in vitro cell systems, which should accurately reproduce key in vivo characteristics of...

  • Evaluation of effect during cell isolation process in alkaline comet assay using epidermal skin cells. Tomoyasu Toyoizumi; Mika Watanabe; Hajime Sui; Yuzuki Nakagawa; Ryo Ohta; Kohji Yamakage // Journal of Toxicological Sciences;Dec2012, Vol. 37 Issue 6, p1267 

    The aim of the present study was to evaluate the effect of the cell isolation process in the alkaline comet assay using epidermal skin cells. When we explored the cell isolation method for the alkaline comet assay using the 3-dimensional (3D) human epidermal skin model, we found that DNA damage...

  • Genotoxic effect induced by hydrogen peroxide in human hepatoma cells using comet assay. Benhusein, Ghazalla M.; Mutch, Elaine; Aburawi, Suher; Williams, Faith M. // Libyan Journal of Medicine;Mar2010, Vol. 5 Issue 5, p1 

    Background: Hydrogen peroxide (H2O2) is a common reactive oxygen intermediate generated by various forms of oxidative stress. Aim: The aim of this study was to investigate the DNA damage capacity of H2O2 in HepG2 cells. Methods: Cells were treated with H2O2 at concentrations of 25 μM or 50...

  • Evaluación biológica de una fracción de la esponja marina Topsentia ophiraphidites del Caribe colombiano. Blandón G., Lina; Márquez F., Diana; López O., Juan; Márquez F., Maria // Revista MVZ Córdoba;Supp2013, Vol. 18 Issue Supplement, p3633 

    Objective. To evaluate the antiproliferative and genotoxic activity of a fraction (T4 fraction) of the Colombian Caribbean marine sponge Topsentia ophiraphidites, with cytotoxic activity. Materials and methods. T4 fraction from the marine sponge Topsentia ophiraphidites was provided by the group...

  • Induction of DNA breaks and apoptosis in crosslink-hypersensitive V79 cells by the cytostatic β-D-glucosyl-ifosfamide mustard. Becker, R.; Ritter, A.; Eichhorn, U.; Lips, J.; Bertram, B.; Wiessler, M.; Zdzienicka, M.Z.; Kaina, B. // British Journal of Cancer;1/7/2002, Vol. 86 Issue 1, p130 

    To study molecular aspects of cytotoxicity of the anticancer drug β-D-glucose-ifosfamide mustard we investigated the potential of the agent to induce apoptosis and DNA breakage. Since β-D-glucose-ifosfamide mustard generates DNA interstrand crosslinks, we used as an in vitro model system a...

  • Cytotoxicity, DNA damage, and apoptosis induced by titanium dioxide nanoparticles in human non-small cell lung cancer A549 cells. Wang, Yurong; Cui, Haiyan; Zhou, Jiaping; Li, Fengjuan; Wang, Jinju; Chen, Mianhua; Liu, Qingdai // Environmental Science & Pollution Research;Apr2015, Vol. 22 Issue 7, p5519 

    Concerns about the risk of titanium dioxide nanoparticles (TiO NPs) to human health and environment are gradually increasing due to their wide range of applications. In this study, cytotoxicity, DNA damage, and apoptosis induced by TiO NPs (5 nm) in A549 cells were investigated. The...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics