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Sample records for atm ataxia telangiectasia

  1. Atm reactivation reverses ataxia telangiectasia phenotypes in vivo.

    Science.gov (United States)

    Di Siena, Sara; Campolo, Federica; Gimmelli, Roberto; Di Pietro, Chiara; Marazziti, Daniela; Dolci, Susanna; Lenzi, Andrea; Nussenzweig, Andre; Pellegrini, Manuela

    2018-02-22

    Hereditary deficiencies in DNA damage signaling are invariably associated with cancer predisposition, immunodeficiency, radiation sensitivity, gonadal abnormalities, premature aging, and tissue degeneration. ATM kinase has been established as a central player in DNA double-strand break repair and its deficiency causes ataxia telangiectasia, a rare, multi-system disease with no cure. So ATM represents a highly attractive target for the development of novel types of gene therapy or transplantation strategies. Atm tamoxifen-inducible mouse models were generated to explore whether Atm reconstitution is able to restore Atm function in an Atm-deficient background. Body weight, immunodeficiency, spermatogenesis, and radioresistance were recovered in transgenic mice within 1 month from Atm induction. Notably, life span was doubled after Atm restoration, mice were protected from thymoma and no cerebellar defects were observed. Atm signaling was functional after DNA damage in vivo and in vitro. In summary, we propose a new Atm mouse model to investigate novel therapeutic strategies for ATM activation in ataxia telangiectasia disease.

  2. ATM (ataxia-telangiectasia mutated) abnormality and diseases

    International Nuclear Information System (INIS)

    Takagi, Masatoshi; Nakata, Shinichiro; Mizutani, Shuki

    2007-01-01

    Ataxia-Telangiectasia (A-T) is an autosomal recessive inherited disease due to mutation of ATM gene on chromosome 11q22.3, with major symptoms of ataxia, telangiectasia, immunodeficiency and frequent complication of cancer, and the cells have characters of chromosomal break, high sensitivity to radiation and inappropriate continuation of DNA synthesis after radiation. This review describes past and present studies of ATM functions with clinical features in the following order: Clinical symptoms and epidemiology; ATM gene mutation in A-T patients, mainly by frame-shift (80-90%); ATM, whose gene consisted from 66 exons (150 kb), functions in phosphoinositide-3-kinase related kinase family which protecting cells from stress and integrating their system, at response to DNA double strand break, and in the cell cycle checkpoints at G1/S, S and G2/M phases; ATM nonsense/missense mutations in embryonic cells leading to carcinogenesis and role of ATM in the suppression of carcinogenesis in somatic cells; Chromosomal translocation which relating to carcinogenesis, by functional defect of ATM; and Other functions of ATM in neuronal growth, immunodeficiency, carbohydrate and lipid metabolism, early senescence, and virus infection. ATM is thus an essential molecule to maintain growth and homeostasis. (T.I.)

  3. Neurodegeneration in ataxia-telangiectasia: Multiple roles of ATM kinase in cellular homeostasis.

    Science.gov (United States)

    Choy, Kay Rui; Watters, Dianne J

    2018-01-01

    Ataxia-telangiectasia (A-T) is characterized by neuronal degeneration, cancer, diabetes, immune deficiency, and increased sensitivity to ionizing radiation. A-T is attributed to the deficiency of the protein kinase coded by the ATM (ataxia-telangiectasia mutated) gene. ATM is a sensor of DNA double-strand breaks (DSBs) and signals to cell cycle checkpoints and the DNA repair machinery. ATM phosphorylates numerous substrates and activates many cell-signaling pathways. There has been considerable debate about whether a defective DNA damage response is causative of the neurological aspects of the disease. In proliferating cells, ATM is localized mainly in the nucleus; however, in postmitotic cells such as neurons, ATM is mostly cytoplasmic. Recent studies reveal an increasing number of roles for ATM in the cytoplasm, including activation by oxidative stress. ATM associates with organelles including mitochondria and peroxisomes, both sources of reactive oxygen species (ROS), which have been implicated in neurodegenerative diseases and aging. ATM is also associated with synaptic vesicles and has a role in regulating cellular homeostasis and autophagy. The cytoplasmic roles of ATM provide a new perspective on the neurodegenerative process in A-T. This review will examine the expanding roles of ATM in cellular homeostasis and relate these functions to the complex A-T phenotype. Developmental Dynamics 247:33-46, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  4. Radiosensitivity in ataxia-telangiectasia

    International Nuclear Information System (INIS)

    Lavin, M.F.; Khanna, K.K.; Watters, D.

    1998-01-01

    Full text: Radiosensitivity is a major hallmark of the human genetic disorder ataxia-telangiectasia. This hypersensitivity to ionizing radiation has been demonstrated in vitro after exposure of patients to therapeutic thought to be the major factor contculture. Clearly an understanding of the nature of the molecular defect in ataxia-telangiectasia will be of considerable assistance in delineating additional pathways that determine cellular radiosensitivity/radioresistance. Furthermore, since patients with this syndrome are also predisposed to developing a number of leukaemias and lymphomas the possible connection between radiosensitivity and cancer predisposition is of interest. Now that the gene (ATM) responsible for this genetic disease has been cloned and identified, progress is being made in determining the role of the ATM protein in mediating the effects of cellular exposure to ionizing radiation and other forms of redox stress. Proteins such as the product of the tumour suppressor gene p53 and the proto-oncogene c-Abl (a protein tyrosine kinase) have been shown to interact with ATM. Since several intermediate steps in both the p53 and c-Abl pathways, activated by ionizing radiation, are known it will be possible to map the position of ATM in these pathways and describe its mechanism of action. What are the clinical implications of understanding the molecular basis of the defect in ataxia-telangiectasia? As outlined above since radiosensitivity is a universal characteristic of A-T understanding the mechanism of action of ATM will provide additional information or radiation signalling in human cells. With this information it may be possible to sensitize tumour cells to radiation and thus increase the therapeutic benefit of radiotherapy. This might involve the use of small molecules that would interfere with the normal ATM controlled pathways and thus sensitize cells to radiation or alternatively it might involve the efficient introduction of ATM anti-sense c

  5. Radiosensitivity in ataxia-telangiectasia

    Energy Technology Data Exchange (ETDEWEB)

    Lavin, M.F. [Royal Brisbane Hospital, QLD (Australia). Queensland Institute of Medical Research and The Department of Surgery; Khanna, K.K.; Watters, D. [Royal Brisbane Hospital, QLD (Australia). Queensland Institute of Medical Research

    1998-12-31

    Full text: Radiosensitivity is a major hallmark of the human genetic disorder ataxia-telangiectasia. This hypersensitivity to ionizing radiation has been demonstrated in vitro after exposure of patients to therapeutic thought to be the major factor contculture. Clearly an understanding of the nature of the molecular defect in ataxia-telangiectasia will be of considerable assistance in delineating additional pathways that determine cellular radiosensitivity/radioresistance. Furthermore, since patients with this syndrome are also predisposed to developing a number of leukaemias and lymphomas the possible connection between radiosensitivity and cancer predisposition is of interest. Now that the gene (ATM) responsible for this genetic disease has been cloned and identified, progress is being made in determining the role of the ATM protein in mediating the effects of cellular exposure to ionizing radiation and other forms of redox stress. Proteins such as the product of the tumour suppressor gene p53 and the proto-oncogene c-Abl (a protein tyrosine kinase) have been shown to interact with ATM. Since several intermediate steps in both the p53 and c-Abl pathways, activated by ionizing radiation, are known it will be possible to map the position of ATM in these pathways and describe its mechanism of action. What are the clinical implications of understanding the molecular basis of the defect in ataxia-telangiectasia? As outlined above since radiosensitivity is a universal characteristic of A-T understanding the mechanism of action of ATM will provide additional information or radiation signalling in human cells. With this information it may be possible to sensitize tumour cells to radiation and thus increase the therapeutic benefit of radiotherapy. This might involve the use of small molecules that would interfere with the normal ATM controlled pathways and thus sensitize cells to radiation or alternatively it might involve the efficient introduction of ATM anti-sense c

  6. The ATM gene and the radiobiology of ataxia-telangiectasia

    International Nuclear Information System (INIS)

    Jorgensen, T.J.; Shiloh, Y.

    1996-01-01

    Ataxia-telangiectasia (A-T) is the classic human genetic disease involving severe ionizing radiation sensitivity and as such has been intensely studied by radiation biologists over the years. Unlike its counterpart for UV light sensitivity -xeroderma pigmentosum - A-T has no obvious DNA repair defect; and there has been much speculation as to the mechanism underlying the altered radioresponses associated with this disease. The gene defective in A-T (ATM) has recently been cloned, and its primary coding sequence determined. The primary sequence of the ATM protein suggests that it has some regulatory functions related to cellular radioresponse and maintenance of genomic stability, and shares these functions with a growing family of other proteins in various organisms. At this juncture it is appropriate to review our current knowledge about the radiobiology of A-T and reflect on the possible radiobiological mechanisms that are suggested by the ATM gene itself. This article will attempt briefly to review current knowledge about the radiobiology of A-T and to introduce new speculations about underlying radiobiological mechanisms that are suggested by the primary amino acid sequence of the predicted ATM gene product. (Author)

  7. Health risks for ataxia-telangiectasia mutated heterozygotes : a systematic review, meta-analysis and evidence-based guideline

    NARCIS (Netherlands)

    van Os, N J H; Roeleveld, N; Weemaes, C M R; Jongmans, M C J; Janssens, G O; Taylor, A M R; Hoogerbrugge, N; Willemsen, Michel A A P

    Ataxia-telangiectasia (AT) is an autosomal recessive neurodegenerative disorder with immunodeficiency and an increased risk of developing cancer, caused by mutations in the ataxia-telangiectasia mutated (ATM) gene. Logically, blood relatives may also carry a pathogenic ATM mutation. Female carriers

  8. Cutaneous granulomatosis and combined immunodeficiency revealing Ataxia-Telangiectasia: a case report

    OpenAIRE

    Folgori, Laura; Scarselli, Alessia; Angelino, Giulia; Ferrari, Francesca; Antoccia, Antonio; Chessa, Luciana; Finocchi, Andrea

    2010-01-01

    Abstract Ataxia-telangiectasia (A-T) is a complex multisystem disorder characterized by progressive neurological impairment, variable immunodeficiency and oculo-cutaneous telangiectasia. A-T is a member of chromosomal breakage syndromes and it is caused by a mutation in the ataxia-telangiectasia mutated (ATM) gene. Because of a wide clinical heterogeneity, A-T is often difficult to diagnose in children. We report an unusual case of a 3-year-old boy affected by A-T who presented exclusively wi...

  9. Role of ataxia-telangiectasia mutated (ATM) in porcine oocyte in vitro maturation.

    Science.gov (United States)

    Lin, Zi-Li; Kim, Nam-Hyung

    2015-06-01

    Ataxia-telangiectasia mutated (ATM) is critical for the DNA damage response, cell cycle checkpoints, and apoptosis. Significant effort has focused on elucidating the relationship between ATM and other nuclear signal transducers; however, little is known about the connection between ATM and oocyte meiotic maturation. We investigated the function of ATM in porcine oocytes. ATM was expressed at all stages of oocyte maturation and localized predominantly in the nucleus. Furthermore, the ATM-specific inhibitor KU-55933 blocked porcine oocyte maturation, reducing the percentages of oocytes that underwent germinal vesicle breakdown (GVBD) and first polar body extrusion. KU-55933 also decreased the expression of DNA damage-related genes (breast cancer 1, budding uninhibited by benzimidazoles 1, and P53) and reduced the mRNA and protein levels of AKT and other cell cycle-regulated genes that are predominantly expressed during G2/M phase, including bone morphogenetic protein 15, growth differentiation factor 9, cell division cycle protein 2, cyclinB1, and AKT. KU-55933 treatment decreased the developmental potential of blastocysts following parthenogenetic activation and increased the level of apoptosis. Together, these data suggested that ATM influenced the meiotic and cytoplasmic maturation of porcine oocytes, potentially by decreasing their sensitivity to DNA strand breaks, stimulating the AKT pathway, and/or altering the expression of other maternal genes. © 2015 International Federation for Cell Biology.

  10. Ataxia telangiectasia: a review

    Directory of Open Access Journals (Sweden)

    Cynthia Rothblum-Oviatt

    2016-11-01

    Full Text Available Abstract Definition of the disease Ataxia telangiectasia (A-T is an autosomal recessive disorder primarily characterized by cerebellar degeneration, telangiectasia, immunodeficiency, cancer susceptibility and radiation sensitivity. A-T is often referred to as a genome instability or DNA damage response syndrome. Epidemiology The world-wide prevalence of A-T is estimated to be between 1 in 40,000 and 1 in 100,000 live births. Clinical description A-T is a complex disorder with substantial variability in the severity of features between affected individuals, and at different ages. Neurological symptoms most often first appear in early childhood when children begin to sit or walk. They have immunological abnormalities including immunoglobulin and antibody deficiencies and lymphopenia. People with A-T have an increased predisposition for cancers, particularly of lymphoid origin. Pulmonary disease and problems with feeding, swallowing and nutrition are common, and there also may be dermatological and endocrine manifestations. Etiology A-T is caused by mutations in the ATM (Ataxia Telangiectasia, Mutated gene which encodes a protein of the same name. The primary role of the ATM protein is coordination of cellular signaling pathways in response to DNA double strand breaks, oxidative stress and other genotoxic stress. Diagnosis The diagnosis of A-T is usually suspected by the combination of neurologic clinical features (ataxia, abnormal control of eye movement, and postural instability with one or more of the following which may vary in their appearance: telangiectasia, frequent sinopulmonary infections and specific laboratory abnormalities (e.g. IgA deficiency, lymphopenia especially affecting T lymphocytes and increased alpha-fetoprotein levels. Because certain neurological features may arise later, a diagnosis of A-T should be carefully considered for any ataxic child with an otherwise elusive diagnosis. A diagnosis of A-T can be confirmed by the

  11. Ataxia-telangiectasia: future prospects

    Directory of Open Access Journals (Sweden)

    Chaudhary MW

    2014-09-01

    Full Text Available Mohammed Wajid Chaudhary, Raidah Saleem Al-Baradie Pediatric Neurology, Neurosciences Centre, King Fahad Specialist Hospital, Dammam, Kingdom of Saudi Arabia Abstract: Ataxia-telangiectasia (A-T is an autosomal recessive multi-system disorder caused by mutation in the ataxia-telangiectasia mutated gene (ATM. ATM is a large serine/threonine protein kinase, a member of the phosphoinositide 3-kinase-related protein kinase (PIKK family whose best-studied function is as master controller of signal transduction for the DNA damage response (DDR in the event of double strand breaks (DSBs. The DDR rapidly recognizes DNA lesions and initiates the appropriate cellular programs to maintain genome integrity. This includes the coordination of cell-cycle checkpoints, transcription, translation, DNA repair, metabolism, and cell fate decisions, such as apoptosis or senescence. DSBs can be generated by exposure to ionizing radiation (IR or various chemical compounds, such as topoisomerase inhibitors, or can be part of programmed generation and repair of DSBs via cellular enzymes needed for the generation of the antibody repertoire as well as the maturation of germ cells. AT patients have immunodeficiency, and are sterile with gonadal dysgenesis as a result of defect in meiotic recombination. In the cells of nervous system ATM has additional role in vesicle dynamics as well as in the maintenance of the epigenetic code of histone modifications. Moderate levels of ATM are associated with prolonged lifespan through resistance to oxidative stress. ATM inhibitors are being viewed as potential radiosensitizers as part of cancer radiotherapy. Though there is no cure for the disease at present, glucocorticoids have been shown to induce alternate splicing site in the gene for ATM partly restoring its activity, but their most effective timing in the disease natural history is not yet known. Gene therapy is promising but large size of the gene makes it technically difficult

  12. Hashimoto thyroiditis associated with ataxia telangiectasia.

    Science.gov (United States)

    Patiroglu, Turkan; Gungor, Hatice Eke; Unal, Ekrem; Kurtoglu, Selim; Yikilmaz, Ali; Patiroglu, Tahir

    2012-01-01

    Ataxia telangiectasia is a rare genetic disease characterized by neurological manifestations, infections, and cancers. In addition to these cardinal features, different autoimmune diseases can be seen in patients with ataxia telangiectasia. Although there were reports of positive autoimmune thyroid antibodies associated with ataxia telangiectasia, to our knowledge, we report the first cases of nodular Hashimoto thyroiditis in two patients with ataxia telangiectasia in the English medical literature. These cases illustrate that despite the rarity of nodular Hashimoto thyroiditis associated with ataxia telangiectasia, physicians should be aware of this possibility. Furthermore, thyroid examination of patient with ataxia telangiectasia is recommended for early diagnosis.

  13. Targeted disruption of Ataxia-telangiectasia mutated gene in miniature pigs by somatic cell nuclear transfer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young June; Ahn, Kwang Sung; Kim, Minjeong; Kim, Min Ju; Park, Sang-Min; Ryu, Junghyun; Ahn, Jin Seop; Heo, Soon Young; Kang, Jee Hyun; Choi, You Jung [Department of Nanobiomedical Science and BK21 PLUS NBM Global Research Center for Regenerative Medicine, Dankook University, Cheonan (Korea, Republic of); Choi, Seong-Jun [Institute of Tissue Regeneration Engineering, Dankook University, Cheonan (Korea, Republic of); Shim, Hosup, E-mail: shim@dku.edu [Department of Nanobiomedical Science and BK21 PLUS NBM Global Research Center for Regenerative Medicine, Dankook University, Cheonan (Korea, Republic of); Institute of Tissue Regeneration Engineering, Dankook University, Cheonan (Korea, Republic of); Department of Physiology, Dankook University School of Medicine, Cheonan (Korea, Republic of)

    2014-10-03

    Highlights: • ATM gene-targeted pigs were produced by somatic cell nuclear transfer. • A novel large animal model for ataxia telangiectasia was developed. • The new model may provide an alternative to the mouse model. - Abstract: Ataxia telangiectasia (A-T) is a recessive autosomal disorder associated with pleiotropic phenotypes, including progressive cerebellar degeneration, gonad atrophy, and growth retardation. Even though A-T is known to be caused by the mutations in the Ataxia telangiectasia mutated (ATM) gene, the correlation between abnormal cellular physiology caused by ATM mutations and the multiple symptoms of A-T disease has not been clearly determined. None of the existing ATM mouse models properly reflects the extent to which neurological degeneration occurs in human. In an attempt to provide a large animal model for A-T, we produced gene-targeted pigs with mutations in the ATM gene by somatic cell nuclear transfer. The disrupted allele in the ATM gene of cloned piglets was confirmed via PCR and Southern blot analysis. The ATM gene-targeted pigs generated in the present study may provide an alternative to the current mouse model for the study of mechanisms underlying A-T disorder and for the development of new therapies.

  14. Targeted disruption of Ataxia-telangiectasia mutated gene in miniature pigs by somatic cell nuclear transfer

    International Nuclear Information System (INIS)

    Kim, Young June; Ahn, Kwang Sung; Kim, Minjeong; Kim, Min Ju; Park, Sang-Min; Ryu, Junghyun; Ahn, Jin Seop; Heo, Soon Young; Kang, Jee Hyun; Choi, You Jung; Choi, Seong-Jun; Shim, Hosup

    2014-01-01

    Highlights: • ATM gene-targeted pigs were produced by somatic cell nuclear transfer. • A novel large animal model for ataxia telangiectasia was developed. • The new model may provide an alternative to the mouse model. - Abstract: Ataxia telangiectasia (A-T) is a recessive autosomal disorder associated with pleiotropic phenotypes, including progressive cerebellar degeneration, gonad atrophy, and growth retardation. Even though A-T is known to be caused by the mutations in the Ataxia telangiectasia mutated (ATM) gene, the correlation between abnormal cellular physiology caused by ATM mutations and the multiple symptoms of A-T disease has not been clearly determined. None of the existing ATM mouse models properly reflects the extent to which neurological degeneration occurs in human. In an attempt to provide a large animal model for A-T, we produced gene-targeted pigs with mutations in the ATM gene by somatic cell nuclear transfer. The disrupted allele in the ATM gene of cloned piglets was confirmed via PCR and Southern blot analysis. The ATM gene-targeted pigs generated in the present study may provide an alternative to the current mouse model for the study of mechanisms underlying A-T disorder and for the development of new therapies

  15. Brain glucose metabolism in adults with ataxia-telangiectasia and their asymptomatic relatives.

    Science.gov (United States)

    Volkow, Nora D; Tomasi, Dardo; Wang, Gene-Jack; Studentsova, Yana; Margus, Brad; Crawford, Thomas O

    2014-06-01

    Ataxia-telangiectasia is a recessive genetic disorder (ATM is the mutated gene) of childhood with severe motor impairments and whereas homozygotes manifest the disorder, heterozygotes are asymptomatic. Structural brain imaging and post-mortem studies in individuals with ataxia-telangiectasia have reported cerebellar atrophy; but abnormalities of motor control characteristic of extrapyramidal dysfunction suggest impairment of broader motor networks. Here, we investigated possible dysfunction in other brain areas in individuals with ataxia-telangiectasia and tested for brain changes in asymptomatic relatives to assess if heterozygocity affects brain function. We used positron emission tomography and (18)F-fluorodeoxyglucose to measure brain glucose metabolism (quantified as µmol/100 g/min), which serves as a marker of brain function, in 10 adults with ataxia-telangiectasia, 19 non-affected adult relatives (12 siblings, seven parents) and 29 age-matched healthy controls. Statistical parametric mapping and region of interest analyses were used to compare individuals with ataxia-telangiectasia, asymptomatic relatives, and unrelated controls. We found that participants with ataxia-telangiectasia had lower metabolism in cerebellar hemispheres (14%, P brain stimulation. Our finding of decreased metabolism in vermis and hippocampus of asymptomatic relatives suggests that heterozygocity influences the function of these brain regions. Published by Oxford University Press on behalf of the Guarantors of Brain 2014. This work is written by US Government employees and is in the public domain in the US.

  16. Ataxia telangiectasia derived iPS cells show preserved x-ray sensitivity and decreased chromosomal instability

    OpenAIRE

    Fukawatase, Yoshihiro; Toyoda, Masashi; Okamura, Kohji; Nakamura, Ken-ichi; Nakabayashi, Kazuhiko; Takada, Shuji; Yamazaki-Inoue, Mayu; Masuda, Akira; Nasu, Michiyo; Hata, Kenichiro; Hanaoka, Kazunori; Higuchi, Akon; Takubo, Kaiyo; Umezawa, Akihiro

    2014-01-01

    Ataxia telangiectasia is a neurodegenerative inherited disease with chromosomal instability and hypersensitivity to ionizing radiation. iPS cells lacking ATM (AT-iPS cells) exhibited hypersensitivity to X-ray irradiation, one of the characteristics of the disease. While parental ataxia telangiectasia cells exhibited significant chromosomal abnormalities, AT-iPS cells did not show any chromosomal instability in vitro for at least 80 passages (560 days). Whole exome analysis also showed a compa...

  17. Telomere length, ATM mutation status and cancer risk in Ataxia-Telangiectasia families.

    Science.gov (United States)

    Renault, Anne-Laure; Mebirouk, Noura; Cavaciuti, Eve; Le Gal, Dorothée; Lecarpentier, Julie; d'Enghien, Catherine Dubois; Laugé, Anthony; Dondon, Marie-Gabrielle; Labbé, Martine; Lesca, Gaetan; Leroux, Dominique; Gladieff, Laurence; Adenis, Claude; Faivre, Laurence; Gilbert-Dussardier, Brigitte; Lortholary, Alain; Fricker, Jean-Pierre; Dahan, Karin; Bay, Jacques-Olivier; Longy, Michel; Buecher, Bruno; Janin, Nicolas; Zattara, Hélène; Berthet, Pascaline; Combès, Audrey; Coupier, Isabelle; Hall, Janet; Stoppa-Lyonnet, Dominique; Andrieu, Nadine; Lesueur, Fabienne

    2017-10-01

    Recent studies have linked constitutive telomere length (TL) to aging-related diseases including cancer at different sites. ATM participates in the signaling of telomere erosion, and inherited mutations in ATM have been associated with increased risk of cancer, particularly breast cancer. The goal of this study was to investigate whether carriage of an ATM mutation and TL interplay to modify cancer risk in ataxia-telangiectasia (A-T) families.The study population consisted of 284 heterozygous ATM mutation carriers (HetAT) and 174 non-carriers (non-HetAT) from 103 A-T families. Forty-eight HetAT and 14 non-HetAT individuals had cancer, among them 25 HetAT and 6 non-HetAT were diagnosed after blood sample collection. We measured mean TL using a quantitative PCR assay and genotyped seven single-nucleotide polymorphisms (SNPs) recurrently associated with TL in large population-based studies.HetAT individuals were at increased risk of cancer (OR = 2.3, 95%CI = 1.2-4.4, P = 0.01), and particularly of breast cancer for women (OR = 2.9, 95%CI = 1.2-7.1, P = 0.02), in comparison to their non-HetAT relatives. HetAT individuals had longer telomeres than non-HetAT individuals (P = 0.0008) but TL was not associated with cancer risk, and no significant interaction was observed between ATM mutation status and TL. Furthermore, rs9257445 (ZNF311) was associated with TL in HetAT subjects and rs6060627 (BCL2L1) modified cancer risk in HetAT and non-HetAT women.Our findings suggest that carriage of an ATM mutation impacts on the age-related TL shortening and that TL per se is not related to cancer risk in ATM carriers. TL measurement alone is not a good marker for predicting cancer risk in A-T families. © The Author 2017. Published by Oxford University Press.

  18. Cutaneous granulomatosis and combined immunodeficiency revealing Ataxia-Telangiectasia: a case report

    Directory of Open Access Journals (Sweden)

    Antoccia Antonio

    2010-04-01

    Full Text Available Abstract Ataxia-telangiectasia (A-T is a complex multisystem disorder characterized by progressive neurological impairment, variable immunodeficiency and oculo-cutaneous telangiectasia. A-T is a member of chromosomal breakage syndromes and it is caused by a mutation in the ataxia-telangiectasia mutated (ATM gene. Because of a wide clinical heterogeneity, A-T is often difficult to diagnose in children. We report an unusual case of a 3-year-old boy affected by A-T who presented exclusively with extensive cutaneous granulomatosis and severe combined immunodeficiency, without neurological abnormalities, at the time of diagnosis. This case clearly emphasizes the variable presentation of A-T syndrome and highlights the difficulties in the early diagnosis of A-T. A-T should be considered in children with evidence of combined humoral and cellular immunodeficiency associated with unexplained skin granulomatous lesions, even in the absence of the classic features of this syndrome.

  19. Ataxia-telangiectasia mutated (ATM) deficiency decreases reprogramming efficiency and leads to genomic instability in iPS cells

    Energy Technology Data Exchange (ETDEWEB)

    Kinoshita, Taisuke [Department of Cell Differentiation, The Sakaguchi Laboratory, School of Medicine, Keio University, Tokyo 160-8582 (Japan); Nagamatsu, Go, E-mail: gonag@sc.itc.keio.ac.jp [Department of Cell Differentiation, The Sakaguchi Laboratory, School of Medicine, Keio University, Tokyo 160-8582 (Japan); Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012 (Japan); Kosaka, Takeo [Department of Urology, School of Medicine, Keio University, Tokyo 160-8582 (Japan); Takubo, Keiyo [Department of Cell Differentiation, The Sakaguchi Laboratory, School of Medicine, Keio University, Tokyo 160-8582 (Japan); Hotta, Akitsu [Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012 (Japan); Department of Reprogramming Science, Center for iPS Cell Research and Application (CiRA), Kyoto University, Kyoto (Japan); Ellis, James [Ontario Human iPS Cell Facility, Molecular Genetics, University of Toronto, Developmental and Stem Cell Biology, SickKids, Toronto, Canada MG1L7 (Canada); Suda, Toshio, E-mail: sudato@sc.itc.keio.ac.jp [Department of Cell Differentiation, The Sakaguchi Laboratory, School of Medicine, Keio University, Tokyo 160-8582 (Japan)

    2011-04-08

    Highlights: {yields} iPS cells were induced with a fluorescence monitoring system. {yields} ATM-deficient tail-tip fibroblasts exhibited quite a low reprogramming efficiency. {yields} iPS cells obtained from ATM-deficient cells had pluripotent cell characteristics. {yields} ATM-deficient iPS cells had abnormal chromosomes, which were accumulated in culture. -- Abstract: During cell division, one of the major features of somatic cell reprogramming by defined factors, cells are potentially exposed to DNA damage. Inactivation of the tumor suppressor gene p53 raised reprogramming efficiency but resulted in an increased number of abnormal chromosomes in established iPS cells. Ataxia-telangiectasia mutated (ATM), which is critical in the cellular response to DNA double-strand breaks, may also play an important role during reprogramming. To clarify the function of ATM in somatic cell reprogramming, we investigated reprogramming in ATM-deficient (ATM-KO) tail-tip fibroblasts (TTFs). Although reprogramming efficiency was greatly reduced in ATM-KO TTFs, ATM-KO iPS cells were successfully generated and showed the same proliferation activity as WT iPS cells. ATM-KO iPS cells had a gene expression profile similar to ES cells and WT iPS cells, and had the capacity to differentiate into all three germ layers. On the other hand, ATM-KO iPS cells accumulated abnormal genome structures upon continuous passages. Even with the abnormal karyotype, ATM-KO iPS cells retained pluripotent cell characteristics for at least 20 passages. These data indicate that ATM does participate in the reprogramming process, although its role is not essential.

  20. Ataxia-telangiectasia mutated (ATM) deficiency decreases reprogramming efficiency and leads to genomic instability in iPS cells

    International Nuclear Information System (INIS)

    Kinoshita, Taisuke; Nagamatsu, Go; Kosaka, Takeo; Takubo, Keiyo; Hotta, Akitsu; Ellis, James; Suda, Toshio

    2011-01-01

    Highlights: → iPS cells were induced with a fluorescence monitoring system. → ATM-deficient tail-tip fibroblasts exhibited quite a low reprogramming efficiency. → iPS cells obtained from ATM-deficient cells had pluripotent cell characteristics. → ATM-deficient iPS cells had abnormal chromosomes, which were accumulated in culture. -- Abstract: During cell division, one of the major features of somatic cell reprogramming by defined factors, cells are potentially exposed to DNA damage. Inactivation of the tumor suppressor gene p53 raised reprogramming efficiency but resulted in an increased number of abnormal chromosomes in established iPS cells. Ataxia-telangiectasia mutated (ATM), which is critical in the cellular response to DNA double-strand breaks, may also play an important role during reprogramming. To clarify the function of ATM in somatic cell reprogramming, we investigated reprogramming in ATM-deficient (ATM-KO) tail-tip fibroblasts (TTFs). Although reprogramming efficiency was greatly reduced in ATM-KO TTFs, ATM-KO iPS cells were successfully generated and showed the same proliferation activity as WT iPS cells. ATM-KO iPS cells had a gene expression profile similar to ES cells and WT iPS cells, and had the capacity to differentiate into all three germ layers. On the other hand, ATM-KO iPS cells accumulated abnormal genome structures upon continuous passages. Even with the abnormal karyotype, ATM-KO iPS cells retained pluripotent cell characteristics for at least 20 passages. These data indicate that ATM does participate in the reprogramming process, although its role is not essential.

  1. Ataxia telangiectasia mutated (ATM) interacts with p400 ATPase for an efficient DNA damage response.

    Science.gov (United States)

    Smith, Rebecca J; Savoian, Matthew S; Weber, Lauren E; Park, Jeong Hyeon

    2016-11-04

    Ataxia telangiectasia mutated (ATM) and TRRAP proteins belong to the phosphatidylinositol 3-kinase-related kinase family and are involved in DNA damage repair and chromatin remodeling. ATM is a checkpoint kinase that is recruited to sites of DNA double-strand breaks where it phosphorylates a diverse range of proteins that are part of the chromatin and DNA repair machinery. As an integral subunit of the TRRAP-TIP60 complexes, p400 ATPase is a chromatin remodeler that is also targeted to DNA double-strand break sites. While it is understood that DNA binding transcriptional activators recruit p400 ATPase into a regulatory region of the promoter, how p400 recognises and moves to DNA double-strand break sites is far less clear. Here we investigate a possibility whether ATM serves as a shuttle to deliver p400 to break sites. Our data indicate that p400 co-immunoprecipitates with ATM independently of DNA damage state and that the N-terminal domain of p400 is vital for this interaction. Heterologous expression studies using Sf9 cells revealed that the ATM-p400 complex can be reconstituted without other mammalian bridging proteins. Overexpression of ATM-interacting p400 regions in U2OS cells induced dominant negative effects including the inhibition of both DNA damage repair and cell proliferation. Consistent with the dominant negative effect, the stable expression of an N-terminal p400 fragment showed a decrease in the association of p400 with ATM, but did not alter the association of p400 with TRRAP. Taken together, our findings suggest that a protein-protein interaction between ATM and p400 ATPase occurs independently of DNA damage and contributes to efficient DNA damage response and repair.

  2. A novel pathogenic variant in an Iranian Ataxia telangiectasia family revealed by next-generation sequencing followed by in silico analysis.

    Science.gov (United States)

    Tabatabaiefar, Mohammad Amin; Alipour, Paria; Pourahmadiyan, Azam; Fattahi, Najmeh; Shariati, Laleh; Golchin, Neda; Mohammadi-Asl, Javad

    2017-08-15

    Ataxia telangiectasia (A-T) is a neurodegenerative autosomal recessive disorder with the main characteristics of progressive cerebellar degeneration, sensitivity to ionizing radiation, immunodeficiency, telangiectasia, premature aging, recurrent sinopulmonary infections, and increased risk of malignancy, especially of lymphoid origin. Ataxia Telangiectasia Mutated gene, ATM, as a causative gene for the A-T disorder, encodes the ATM protein, which plays an important role in the activation of cell-cycle checkpoints and initiation of DNA repair in response to DNA damage. Targeted next-generation sequencing (NGS) was performed on an Iranian 5-year-old boy presented with truncal and limb ataxia, telangiectasia of the eye, Hodgkin lymphoma, hyper pigmentation, total alopecia, hepatomegaly, and dysarthria. Sanger sequencing was used to confirm the candidate pathogenic variants. Computational docking was done using the HEX software to examine how this change affects the interactions of ATM with the upstream and downstream proteins. Three different variants were identified comprising two homozygous SNPs and one novel homozygous frameshift variant (c.80468047delTA, p.Thr2682ThrfsX5), which creates a stop codon in exon 57 leaving the protein truncated at its C-terminal portion. Therefore, the activation and phosphorylation of target proteins are lost. Moreover, the HEX software confirmed that the mutated protein lost its interaction with upstream and downstream proteins. The variant was classified as pathogenic based on the American College of Medical Genetics and Genomics guideline. This study expands the spectrum of ATM pathogenic variants in Iran and demonstrates the utility of targeted NGS in genetic diagnostics. Copyright © 2017. Published by Elsevier B.V.

  3. [Ataxia telangiectasia: review of 13 new cases].

    Science.gov (United States)

    Valbuena, O; Póo, P; Campistol, J; Vernet, A; Fernández-Alvarez, E; Sierra, I; Gean, E

    1996-01-01

    We report the review of 13 patients who were diagnosed of ataxia telangiectasia before 6 years of age. All of them manifested cerebelous ataxia, oculocutaneus telangiectasias (11), sinopulmonary infections (9), dystonia (9), oculomotor apraxia (9) and Burkitt linfoma (1). We analyse the most common presentation of the disease in early stages and the complementary studies performed. The prompt diagnosis allow us a better control of infections, malignant process and finally the possibility of genetic counseling.

  4. DNA strand breakage repair in ataxia telangiectasia fibroblast-like cells

    Energy Technology Data Exchange (ETDEWEB)

    Vincent, Jr, R A; Sheridan, III, R B; Huang, P C [Johns Hopkins Univ., Baltimore, Md. (USA). Dept. of Environmental and Biophysical Sciences

    1975-12-01

    Human diploid fibroblast-like cells derived from four patients with the genetic disease ataxia telangiectasia and from two non-mutant donors were examined for the repair of x-ray induced strand breaks in DNA. The ataxia telangiectasia cultures showed no significant differences from the non-mutant cultures in the kinetics and extent of strand repair. This suggests that the increased spontaneous and x-ray induced chromatid aberrations observed in ataxia telangiectasia cells are not caused by a defect in the repair of single strand breaks as might be suspected from a general model of aberration production.

  5. Role of chromatin structure modulation by the histone deacetylase inhibitor trichostatin A on the radio-sensitivity of ataxia telangiectasia

    Energy Technology Data Exchange (ETDEWEB)

    Meschini, Roberta, E-mail: meschini@unitus.it; Morucci, Elisa; Berni, Andrea; Lopez-Martinez, Wilner; Palitti, Fabrizio

    2015-07-15

    Highlights: • Role of chromatin compaction on chromosomal instability. • Reduced radiation-induced clastogenicity in Ataxia telangiectasia cell lines. • Histone tails hyperacetylation reduces heterochromatin content favouring DSBs repair. - Abstract: At present, a lot is known about biochemical aspects of double strand breaks (DBS) repair but how chromatin structure affects this process and the sensitivity of DNA to DSB induction is still an unresolved question. Ataxia telangiectasia (A-T) patients are characterised by very high sensitivity to DSB-inducing agents such as ionising radiation. This radiosensitivity is revealed with an enhancement of chromosomal instability as a consequence of defective DNA repair for a small fraction of breaks located in the heterochromatin, where they are less accessible. Besides, recently it has been reported that Ataxia Telangiectasia Mutated (ATM) mediated signalling modifies chromatin structure. In order to study the impact of chromatin compaction on the chromosomal instability of A-T cells, the response to trichostatin-A, an histone deacetylase inhibitor, in normal and A-T lymphoblastoid cell lines was investigated testing its effect on chromosomal aberrations, cell cycle progression, DNA damage and repair after exposure to X-rays. The results suggest that the response to both trichostatin-A pre- and continuous treatments is independent of the presence of either functional or mutated ATM protein, as the reduction of chromosomal damage was found also in the wild-type cell line. The presence of trichostatin-A before exposure to X-rays could give rise to prompt DNA repair functioning on chromatin structure already in an open conformation. Differently, trichostatin-A post-treatment causing hyperacetylation of histone tails and reducing the heterochromatic DNA content might diminish the requirement for ATM and favour DSBs repair reducing chromosomal damage only in A-T cells. This fact could suggest that trichostatin-A post

  6. Case Report: Neuro-Imaging Findings in Ataxia Telangiectasia

    Directory of Open Access Journals (Sweden)

    Farhad Mahvelati

    2004-06-01

    Full Text Available Ataxia Telangiectasia (AT is an autosomal recessive inherited disorder in which cutaneous and scleral Telangiectasia, cerebellar ataxia and immunodeficiency occur. There is a high incidence of development of malignant tumors, mainly lymphomas. Cerebellar atrophy is the most prominent abnormality and is shown better by magnetic resonance imaging (MRI than CT-Scan. Intracranial hemorrhage occurs rarely. We report a 7 years old boy who admitted for recurrent pulmonary infections. His examination showed ataxic gait with decreased deep tendon reflexes in lower extremities. He had telangiectasia in the eyes and his speech was slurred and difficult. Brain MRI showed cerebellar atrophy with diffuse hyperintensity in white matter, most prominent in occipital region, which was suggestive of leukodystrophy. This white matter change was not reported before in AT.

  7. Bladder Wall Telangiectasia in a Patient with Ataxia-Telangiectasia and How to Manage?

    Directory of Open Access Journals (Sweden)

    Fatma Deniz Aygün

    2015-01-01

    Full Text Available Ataxia-telangiectasia (A-T is a rare neurodegenerative, inherited disease causing severe morbidity. Oculocutaneous telangiectasias are almost constant findings among the affected cases as telangiectasia is considered the main clinical finding for diagnosis. Vascular abnormalities in organs have been reported infrequently but bladder wall telangiectasias are extremely rare. We aimed to report recurrent hemorrhage from bladder wall telangiectasia in a 9-year-old boy with A-T who had received intravenous cyclophosphamide for non-Hodgkin’s lymphoma. Since A-T patients are known to be more susceptible to chemical agents, we suggested that possibly cyclophosphamide was the drug which induced bladder wall injury in this patient.

  8. NAD+ Replenishment Improves Lifespan and Healthspan in Ataxia Telangiectasia Models via Mitophagy and DNA Repair.

    Science.gov (United States)

    Fang, Evandro Fei; Kassahun, Henok; Croteau, Deborah L; Scheibye-Knudsen, Morten; Marosi, Krisztina; Lu, Huiming; Shamanna, Raghavendra A; Kalyanasundaram, Sumana; Bollineni, Ravi Chand; Wilson, Mark A; Iser, Wendy B; Wollman, Bradley N; Morevati, Marya; Li, Jun; Kerr, Jesse S; Lu, Qiping; Waltz, Tyler B; Tian, Jane; Sinclair, David A; Mattson, Mark P; Nilsen, Hilde; Bohr, Vilhelm A

    2016-10-11

    Ataxia telangiectasia (A-T) is a rare autosomal recessive disease characterized by progressive neurodegeneration and cerebellar ataxia. A-T is causally linked to defects in ATM, a master regulator of the response to and repair of DNA double-strand breaks. The molecular basis of cerebellar atrophy and neurodegeneration in A-T patients is unclear. Here we report and examine the significance of increased PARylation, low NAD + , and mitochondrial dysfunction in ATM-deficient neurons, mice, and worms. Treatments that replenish intracellular NAD + reduce the severity of A-T neuropathology, normalize neuromuscular function, delay memory loss, and extend lifespan in both animal models. Mechanistically, treatments that increase intracellular NAD + also stimulate neuronal DNA repair and improve mitochondrial quality via mitophagy. This work links two major theories on aging, DNA damage accumulation, and mitochondrial dysfunction through nuclear DNA damage-induced nuclear-mitochondrial signaling, and demonstrates that they are important pathophysiological determinants in premature aging of A-T, pointing to therapeutic interventions. Published by Elsevier Inc.

  9. Glutamine deprivation induces interleukin-8 expression in ataxia telangiectasia fibroblasts.

    Science.gov (United States)

    Kim, Min-Hyun; Kim, Aryung; Yu, Ji Hoon; Lim, Joo Weon; Kim, Hyeyoung

    2014-05-01

    To investigate whether glutamine deprivation induces expression of inflammatory cytokine interleukin-8 (IL-8) by determining NF-κB activity and levels of oxidative indices (ROS, reactive oxygen species; hydrogen peroxide; GSH, glutathione) in fibroblasts isolated from patients with ataxia telangiectasia (A-T). We used A-T fibroblasts stably transfected with empty vector (Mock) or with human full-length ataxia telangiectasia mutated (ATM) cDNA (YZ5) and mouse embryonic fibroblasts (MEFs) transiently transfected with ATM small interfering RNA (siRNA) or with non-specific control siRNA. The cells were cultured with or without glutamine or GSH. ROS levels were determined using a fluorescence reader and confocal microscopy. IL-8 or murine IL-8 homolog, keratinocyte chemoattractant (KC), and hydrogen peroxide levels in the medium were determined by enzyme-linked immunosorbent assay and colorimetric assay. GSH level was assessed by enzymatic assay, while IL-8 (KC) mRNA level was measured by reverse transcription-polymerase chain reaction (RT-PCR) and/or quantitative real-time PCR. NF-κB DNA-binding activity was determined by electrophoretic mobility shift assay. Catalase activity and ATM protein levels were determined by O2 generation and Western blotting. While glutamine deprivation induced IL-8 expression and increased NF-κB DNA-binding activity in Mock cells, both processes were decreased by treatment of cells with glutamine or GSH or both glutamine and GSH. Glutamine deprivation had no effect on IL-8 expression or NF-κB DNA-binding activity in YZ5 cells. Glutamine-deprived Mock cells had higher oxidative stress indices (increases in ROS and hydrogen peroxide, reduction in GSH) than glutamine-deprived YZ5 cells. In Mock cells, glutamine deprivation-induced oxidative stress indices were suppressed by treatment with glutamine or GSH or both glutamine and GSH. GSH levels and catalase activity were lower in Mock cells than YZ5 cells. MEFs transfected with ATM siRNA and

  10. Identification of ATM Protein Kinase Phosphorylation Sites by Mass Spectrometry.

    Science.gov (United States)

    Graham, Mark E; Lavin, Martin F; Kozlov, Sergei V

    2017-01-01

    ATM (ataxia-telangiectasia mutated) protein kinase is a key regulator of cellular responses to DNA damage and oxidative stress. DNA damage triggers complex cascade of signaling events leading to numerous posttranslational modification on multitude of proteins. Understanding the regulation of ATM kinase is therefore critical not only for understanding the human genetic disorder ataxia-telangiectasia and potential treatment strategies, but essential for deciphering physiological responses of cells to stress. These responses play an important role in carcinogenesis, neurodegeneration, and aging. We focus here on the identification of DNA damage inducible ATM phosphorylation sites to understand the importance of autophosphorylation in the mechanism of ATM kinase activation. We demonstrate the utility of using immunoprecipitated ATM in quantitative LC-MS/MS workflow with stable isotope dimethyl labeling of ATM peptides for identification of phosphorylation sites.

  11. Studies of ATM Kinase Activity Using Engineered ATM Sensitive to ATP Analogues (ATM-AS).

    Science.gov (United States)

    Enari, Masato; Matsushima-Hibiya, Yuko; Miyazaki, Makoto; Otomo, Ryo

    2017-01-01

    Ataxia-telangiectasia mutated (ATM) protein is a member of the phosphatidylinositol 3-phosphate kinase (PI3-K)-related protein kinase (PIKK) family and is implicated in the initiation of signaling pathways following DNA double strand breaks (DSBs) elicited by exposure to ionizing irradiation (IR) or radiomimetic compounds. Loss of function of the ATM gene product results in the human genetic disorder ataxia-telangiectasia (A-T) characterized by neurodegeneration, immunodeficiency, genomic instability, and cancer predisposition. In response to DSBs, ATM is activated and phosphorylates Ser/Thr-Gln (S/T-Q) sequences on numerous proteins participating in DNA-damage responses. Among these proteins, phosphorylation of the tumor suppressor p53 at Ser15 is known as a target for ATM, which leads to the dissociation of MDM2, an E3 ubiquitin ligase, from p53 to prevent MDM2-dependent p53 degradation. Ser46 on p53 is phosphorylated in response to DSBs and contributes to the preferential transactivation of pro-apoptotic genes, such as p53AIP1, Noxa, and PUMA, to prevent tumor formation. Our group have shown that not only ATM preferentially phosphorylates S/T-Q sequences, but also Ser46, which is a noncanonical site with an S-P sequence for ATM. Ser46 on p53 is directly phosphorylated by ATM in a p53 conformation-dependent manner using the ATP analogue-accepting ATM mutant (ATM-AS) system. This protocol summarizes an approach to identify direct numerous targets for ATM kinase and is used to elucidate ATM signaling pathways in the DNA damage responses.

  12. ROS-activated ATM-dependent phosphorylation of cytoplasmic substrates identified by large scale phosphoproteomics screen

    DEFF Research Database (Denmark)

    Kozlov, Sergei V; Waardenberg, Ashley J; Engholm-Keller, Kasper

    2016-01-01

    ATM (ataxia-telangiectasia, mutated) protein plays a central role in phosphorylating a network of proteins in response to DNA damage. These proteins function in signalling pathways designed to maintain the stability of the genome and minimize the risk of disease by controlling cell cycle checkpoi......ATM (ataxia-telangiectasia, mutated) protein plays a central role in phosphorylating a network of proteins in response to DNA damage. These proteins function in signalling pathways designed to maintain the stability of the genome and minimize the risk of disease by controlling cell cycle...... checkpoints, initiating DNA repair and regulating gene expression. ATM kinase can be activated by a variety of stimuli, including oxidative stress. Here we confirmed activation of cytoplasmic ATM by autophosphorylation at multiple sites. Then we employed a global quantitative phosphoproteomics approach...... to identify cytoplasmic proteins altered in their phosphorylation state in control and A-T (ataxia-telangiectasia) cells in response to oxidative damage. We demonstrated that ATM was activated by oxidative damage in the cytoplasm as well as in the nucleus and identified a total of 9,833 phosphorylation sites...

  13. Motor pathway degeneration in young ataxia telangiectasia patients: A diffusion tractography study

    Directory of Open Access Journals (Sweden)

    Ishani Sahama

    2015-01-01

    Conclusions: Whole tract analysis of the corticomotor, corticospinal and somatosensory pathways in ataxia telangiectasia showed significant white matter degeneration along the entire length of motor circuits, highlighting that ataxia–telangiectasia gene mutation impacts the cerebellum and multiple other motor circuits in young patients.

  14. Activation of ATM by DNA Damaging Agents

    National Research Council Canada - National Science Library

    Kurz, Ebba U; Lees-Miller, Susan P

    2004-01-01

    Ataxia-telangiectasia mutated (ATM) is a serine/threonine protein kinase that acts as a master switch controlling the cell cycle in response to ionizing radiation-induced DNA double-strand breaks (DSBs...

  15. Activation of ATM by DNA Damaging Agents

    National Research Council Canada - National Science Library

    Kurz, Ebba U; Lees-Miller, Susan P

    2005-01-01

    Ataxia-telangiectasia mutated (ATM) is a serine/threonine protein kinase that acts as a master switch controlling the cell cycle in response to ionizing radiation-induced DNA double-strand breaks (DSBs...

  16. Imaging study of lymphoreticular tumor development in ataxia-telangiectasia and Nijmegen breakage syndrome; Estudio por imagen del desarrollo de tumores linforreticulares en la ataxia telangiectasia y el sindrome de Nijmegen

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Leon, M. I.; Ceres-Ruiz, L.; Cuesta, M. A.; Garcia-Martin, F. J. [Hospital Materno-Infantil C.H.U. Carlos Haya. Malaga (Spain)

    2003-07-01

    Ataxia-telangiectasia (AT), or Louis-Bar syndrome, is an autosomal recessive illness characterized by progressive cerebellar ataxia, oculo-cutaneous telangiectasia, immunodeficiency combined with susceptibility to sinopulmonary infections and high incidence of neoplastic development. Nijmegen breakage syndrome (NBS) is a variant of AT, is also an autosomal recessive illness that presents cerebellar ataxia, as well as combined immunodeficiency and a tendency toward tumor development. Contrary to Louis-Bar syndrome, it doesn't present telangiectasia and exhibits a characteristics phenotype (short stature, bird-like face and microcephaly). Both entities are classified as syndrome of chromosomal instability or chromosomal fragility, a group which also includes Bloom syndrome and Fanconi anemia. All of these show an increase in the frequency of neoplastic pathologies, mainly lymphoid tumors. We present three patients,two with AT and one with NBS, who developed different lymphoma types in the course of the illness. We highlight the most outstanding aspects from a clinical-radiological point of view. (Author) 17 refs.

  17. Imaging study of lymphoreticular tumor development in ataxia-telangiectasia and Nijmegen breakage syndrome

    International Nuclear Information System (INIS)

    Martinez-Leon, M. I.; Ceres-Ruiz, L.; Cuesta, M. A.; Garcia-Martin, F. J.

    2003-01-01

    Ataxia-telangiectasia (AT), or Louis-Bar syndrome, is an autosomal recessive illness characterized by progressive cerebellar ataxia, oculo-cutaneous telangiectasia, immunodeficiency combined with susceptibility to sinopulmonary infections and high incidence of neoplastic development. Nijmegen breakage syndrome (NBS) is a variant of AT, is also an autosomal recessive illness that presents cerebellar ataxia, as well as combined immunodeficiency and a tendency toward tumor development. Contrary to Louis-Bar syndrome, it doesn't present telangiectasia and exhibits a characteristics phenotype (short stature, bird-like face and microcephaly). Both entities are classified as syndrome of chromosomal instability or chromosomal fragility, a group which also includes Bloom syndrome and Fanconi anemia. All of these show an increase in the frequency of neoplastic pathologies, mainly lymphoid tumors. We present three patients,two with AT and one with NBS, who developed different lymphoma types in the course of the illness. We highlight the most outstanding aspects from a clinical-radiological point of view. (Author) 17 refs

  18. Gastric outlet obstruction due to adenocarcinoma in a patient with Ataxia-Telangiectasia syndrome: a case report and review of the literature

    Directory of Open Access Journals (Sweden)

    Hammond Sue

    2009-03-01

    Full Text Available Abstract Background Ataxia-Telangiectasia syndrome is characterized by progressive cerebellar dysfunction, conjuctival and cutaneous telangiectasias, severe immune deficiencies, premature aging and predisposition to cancer. Clinical and radiographic evaluation for malignancy in ataxia-telangiectasia patients is usually atypical, leading to delays in diagnosis. Case presentation We report the case of a 20 year old ataxia-telangiectasia patient with gastric adenocarcinoma that presented as complete gastric outlet obstruction. Conclusion A literature search of adenocarcinoma associated with ataxia-telangiectasia revealed 6 cases. All patients presented with non-specific gastrointestinal complaints suggestive of ulcer disease. Although there was no correlation between immunoglobulin levels and development of gastric adenocarcinoma, the presence of chronic gastritis and intestinal metaplasia seem to lead to the development of gastric adenocarcinoma. One should consider adenocarcinoma in any patient with ataxia-telangiectasia who presents with non-specific gastrointestinal complaints, since this can lead to earlier diagnosis.

  19. Common ataxia telangiectasia mutated haplotypes and risk of breast cancer: a nested case–control study

    International Nuclear Information System (INIS)

    Tamimi, Rulla M; Hankinson, Susan E; Spiegelman, Donna; Kraft, Peter; Colditz, Graham A; Hunter, David J

    2004-01-01

    The ataxia telangiectasia mutated (ATM) gene is a tumor suppressor gene with functions in cell cycle arrest, apoptosis, and repair of DNA double-strand breaks. Based on family studies, women heterozygous for mutations in the ATM gene are reported to have a fourfold to fivefold increased risk of breast cancer compared with noncarriers of the mutations, although not all studies have confirmed this association. Haplotype analysis has been suggested as an efficient method for investigating the role of common variation in the ATM gene and breast cancer. Five biallelic haplotype tagging single nucleotide polymorphisms are estimated to capture 99% of the haplotype diversity in Caucasian populations. We conducted a nested case–control study of breast cancer within the Nurses' Health Study cohort to address the role of common ATM haplotypes and breast cancer. Cases and controls were genotyped for five haplotype tagging single nucleotide polymorphisms. Haplotypes were predicted for 1309 cases and 1761 controls for which genotype information was available. Six unique haplotypes were predicted in this study, five of which occur at a frequency of 5% or greater. The overall distribution of haplotypes was not significantly different between cases and controls (χ 2 = 3.43, five degrees of freedom, P = 0.63). There was no evidence that common haplotypes of ATM are associated with breast cancer risk. Extensive single nucleotide polymorphism detection using the entire genomic sequence of ATM will be necessary to rule out less common variation in ATM and sporadic breast cancer risk

  20. Clinical and genetic features of ataxia-telangiectasia

    International Nuclear Information System (INIS)

    Bundey, S.

    1994-01-01

    There are several variants of ataxia-telangiectasia (A-T): classical A-T with marked radiation sensitivity; classical A-T with intermediate levels of radiation sensitivity; mild A-T with intermediate levels of radiation sensitivity; A-T without telangiectasia; A-T without oculomoto apraxia; and A-T with microcephaly. These disorders are probably caused by different allelic mutations, because affected sibs resemble the index patients, and because there is an association of certain haplo-types of 11q22-23 with specific phenotypes. The Nijmegen Breakage Syndrome, with its lack of ataxia, seems on clinical grounds to be a different disorder. Although A-T is almost always inherited as an autosomal recessive, there are some unusual features; an unexpectedly low parental consanguinity rate, an incidence in sibs that is < 0.25, and occurrence of disease in many different races and in the offspring of mixed race unions. Moreover, looking at haplotypes from 63 UK patients, there is a remarkably low incidence of homozygosity. An autosomal recessive condition that is deficient in parental consanguinity, and in homozygosity for the region around the gene, can be explained by J.H. Edwards' hypothesis that homozygosity for alleles at a neighbouring locus are lethal early in embryogenesis. Other possible mechanisms to explain the unusual genetic features are discussed. (author)

  1. Breast cancer risk in ataxia telangiectasia (AT) heterozygotes: haplotype study in French AT families

    Science.gov (United States)

    Janin, N; Andrieu, N; Ossian, K; Laugé, A; Croquette, M-F; Griscelli, C; Debré, M; Bressac-de-Paillerets, B; Aurias, A; Stoppa-Lyonnet, D

    1999-01-01

    Epidemiological studies in ataxia telangiectasia (AT) families have suggested that AT heterozygotes could have an increased cancer risk, especially breast cancer (BC) in women. It has also been suggested that an increased sensibility of AT heterozygotes to the effect of ionizing radiation could be responsible for the increased BC risk. BC relative risk (RR) estimation in AT heterozygotes within families ascertained through AT children is presented here. Family data collected included demographic characteristics, occurrence of cancers, past radiation exposures and blood samples. DNA samples were studied using seven ATM linked microsatellites markers allowing AT haplotypes reconstitution. The relative risk of BC was assessed using French estimated incidence rates. A significant increase risk of BC is found among obligate ATM heterozygotes with a point estimate of 3.32 (P = 0.002). BC relative risk calculated according to age is significantly increased among the obligate ATM heterozygotes female relatives with an age ≤ 44 years (RR = 4.55, P = 0.005). The BC relative risk is statistically borderline among the obligate ATM heterozygote female relatives with an age ≥ 45 years (RR = 2.48, P = 0.08). The estimated BC relative risk among ATM heterozygotes is consistent with previously published data. However, the increased risk is only a little higher than classical reproductive risk factors and similar to the risk associated with a first-degree relative affected by BC. © 1999 Cancer Research Campaign PMID:10362113

  2. The Development of Ataxia Telangiectasia Mutated Kinase Inhibitors

    Czech Academy of Sciences Publication Activity Database

    Andrs, M.; Kobarecny, J.; Nepovimova, E.; Jun, D.; Hodný, Zdeněk; Moravcová, Simona; Hanzlíková, Hana; Kuca, K.

    2014-01-01

    Roč. 14, č. 10 (2014), s. 805-811 ISSN 1389-5575 R&D Projects: GA MŠk(CZ) CZ.1.07/2.3.00/30.0044 Grant - others:MH CZ - DRO (University Hospital Hradec Kralove(CZ) 00179906 Institutional support: RVO:68378050 Keywords : Ataxia telangiectasia mutated * cancer * chemosensitization * DNA damage response Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.903, year: 2014

  3. Complementation analysis of ataxia-telangiectasia

    International Nuclear Information System (INIS)

    Jaspers, N.G.; Painter, R.B.; Paterson, M.C.; Kidson, C.; Inoue, T.

    1985-01-01

    In a number of laboratories genetic analysis of ataxia-telangiectasia (AT) has been performed by studying the expression of the AT phenotype in fused somatic cells or mixtures of cell-free extracts from different patients. Complementation of the defective response to ionizing radiation was observed frequently, considering four different parameters for radiosensitivity in AT. The combined results from studies on cultured fibroblasts or lymphoblastoid cells from 17 unrelated families revealed the presence of at least four and possibly nine complementation groups. These findings suggest that there is an extensive genetic heterogeneity in AT. More extensive studies are needed for an integration of these data and to provide a set of genetically characterized cell strains for future research of the AT genetic defect

  4. Cell biological study on ataxia-telangiectasia

    International Nuclear Information System (INIS)

    Ohta, Shigeru; Katsura, Tadahiko; Shimada, Morimi; Shima, Akihiro; Chishiro, Hiroko; Kasahara, Yoshitaka.

    1985-01-01

    Diagnosis of ataxia-telangiectasia (AT) has largely been dependent on the clinical findings such as cerebellar ataxia, telangiectasia, and immunological deficiency. However, diagnosis of AT by these ordinary criteria is sometimes not sufficient because of the lack of immunological abnormalities. We examined three cases of AT by ordinary clinical criteria and also by X-ray sensitivity of cultured skin fibroblasts. Case 1, a 9-year-old boy, revealed typical clinical features of AT. However, he had no abnormality in serum IgA or IgE. Case 2, a 10-year-old boy, showed decreased serum IgA level. Case 3, a 19-year-old female, had typical clinical features of AT with normal serum IgA, and developed papillary adenocarcinoma of thyroid which was surgically removed. Fibroblast strains derived from these three cases of AT and from the parents of Case 3 were examined with regard to X-ray sensitivity. Three fibroblast strains derived from AT patients (AT homozygotes) showed remarkable hypersensitivity to X-ray. Fibroblast strains derived from the parents (AT heterozygotes) of Case 3, however, showed normal X-ray sensitivity. Recently, AT fibroblasts have been known to show hypersensitivity also to some mutagen like neocarzinostazin as reported by Shiloh et al. Fibroblasts from Case 3 revealed hypersensitivity to neocarzinostazin. However, the sensitivity of the strains from AT heterozygotes (the parents of Case 3) showed no apparent difference from that of control cells. The assay system for mutagen is quite unstable and proper conditioning of the seeding cell number is important for the carrier detection. However, the diagnosis of AT homozygotes was definitely established by X-ray irradiation to cultured fibroblasts from patients. (author)

  5. Absence of Wip1 partially rescues Atm deficiency phenotypes in mice

    Science.gov (United States)

    Darlington, Yolanda; Nguyen, Thuy-Ai; Moon, Sung-Hwan; Herron, Alan; Rao, Pulivarthi; Zhu, Chengming; Lu, Xiongbin; Donehower, Lawrence A.

    2011-01-01

    Wildtype p53-Induced Phosphatase 1 (WIP1) is a serine/threonine phosphatase that dephosphorylates proteins in the ataxia telangiectasia mutated (ATM)-initiated DNA damage response pathway. WIP1 may play a homeostatic role in ATM signaling by returning the cell to a normal pre-stress state following completion of DNA repair. To better understand the effects of WIP1 on ATM signaling, we crossed Atm-deficient mice to Wip1-deficient mice and characterized phenotypes of the double knockout progeny. We hypothesized that the absence of Wip1 might rescue Atm deficiency phenotypes. Atm null mice, like ATM-deficient humans with the inherited syndrome ataxia telangiectasia, exhibit radiation sensitivity, fertility defects, and are T-cell lymphoma prone. Most double knockout mice were largely protected from lymphoma development and had a greatly extended lifespan compared to Atm null mice. Double knockout mice had increased p53 and H2AX phosphorylation and p21 expression compared to their Atm null counterparts, indicating enhanced p53 and DNA damage responses. Additionally, double knockout splenocytes displayed reduced chromosomal instability compared to Atm null mice. Finally, doubly null mice were partially rescued from infertility defects observed in Atm null mice. These results indicate that inhibition of WIP1 may represent a useful strategy for cancer treatment in general and A-T patients in particular. PMID:21765465

  6. A TAD closer to ATM.

    Science.gov (United States)

    Aymard, Francois; Legube, Gaëlle

    2016-05-01

    Ataxia telangiectasia mutated (ATM) has been known for decades as the main kinase mediating the DNA double-strand break response. Our recent findings suggest that its major role at the sites of breaks likely resides in its ability to modify both the local chromatin landscape and the global chromosome organization in order to promote repair accuracy.

  7. Multifunctional Role of ATM/Tel1 Kinase in Genome Stability: From the DNA Damage Response to Telomere Maintenance

    Science.gov (United States)

    2014-01-01

    The mammalian protein kinase ataxia telangiectasia mutated (ATM) is a key regulator of the DNA double-strand-break response and belongs to the evolutionary conserved phosphatidylinositol-3-kinase-related protein kinases. ATM deficiency causes ataxia telangiectasia (AT), a genetic disorder that is characterized by premature aging, cerebellar neuropathy, immunodeficiency, and predisposition to cancer. AT cells show defects in the DNA damage-response pathway, cell-cycle control, and telomere maintenance and length regulation. Likewise, in Saccharomyces cerevisiae, haploid strains defective in the TEL1 gene, the ATM ortholog, show chromosomal aberrations and short telomeres. In this review, we outline the complex role of ATM/Tel1 in maintaining genomic stability through its control of numerous aspects of cellular survival. In particular, we describe how ATM/Tel1 participates in the signal transduction pathways elicited by DNA damage and in telomere homeostasis and its importance as a barrier to cancer development. PMID:25247188

  8. Ataxia Telangiectasia-Mutated (ATMPolymorphisms and Risk of Lung Cancer in a Chinese Population

    Directory of Open Access Journals (Sweden)

    Ajay A. Myneni

    2017-06-01

    Full Text Available BackgroundThe ataxia telangiectasia-mutated (ATM gene has a key role in DNA repair including activation and stabilization of p53, which implicates the importance of ATM polymorphisms in the development of cancer. This study aims to investigate the association of two ATM single-nucleotide polymorphisms (SNPs with lung cancer, as well as their potential interaction with p53 gene and other known risk factors of lung cancer.MethodsA population-based case–control study was conducted in Taiyuan city, China with 399 cases and 466 controls matched on the distribution of age and sex of cases. The two ATM gene SNPs, ATMrs227060 and ATMrs228589 as well as p53 gene SNP, p53rs1042522 were genotyped using Sequenom platform. Unconditional logistic regression models were used to estimate crude and adjusted odds ratios (aOR and 95% confidence intervals (CIs. Adjusted models controlled for age, sex, and smoking status.ResultsThe study showed that TT genotype of ATMrs227060 (aOR = 1.58, 95% CI: 1.06–2.35 and AA genotype of ATMrs228589 were significantly associated with lung cancer (aOR = 1.50, 95% CI: 1.08–2.08 in a recessive model. Additionally, carrying variant genotypes of ATMrs227060 (TT, ATMrs228589 (AA, and p53rs1042522 (CC concomitantly was associated with much higher risk (aOR = 3.68, 95% CI: 1.43–9.45 of lung cancer than carrying variant genotypes of any one of the above three SNPs. We also found multiplicative and additive interaction between tea drinking and ATMrs227060 in association with lung cancer.ConclusionThis study indicates that ATM gene variants might be associated with development of lung cancer in Chinese population. These results need to be validated in larger and different population samples.

  9. ATM-Deficient Colorectal Cancer Cells Are Sensitive to the PARP Inhibitor Olaparib.

    Science.gov (United States)

    Wang, Chen; Jette, Nicholas; Moussienko, Daniel; Bebb, D Gwyn; Lees-Miller, Susan P

    2017-04-01

    The ataxia telangiectasia mutated (ATM) protein kinase plays a central role in the cellular response to DNA damage. Loss or inactivation of both copies of the ATM gene (ATM) leads to ataxia telangiectasia, a devastating childhood condition characterized by neurodegeneration, immune deficiencies, and cancer predisposition. ATM is also absent in approximately 40% of mantle cell lymphomas (MCLs), and we previously showed that MCL cell lines with loss of ATM are sensitive to poly-ADP ribose polymerase (PARP) inhibitors. Next-generation sequencing of patient tumors has revealed that ATM is altered in many human cancers including colorectal, lung, prostate, and breast. Here, we show that the colorectal cancer cell line SK-CO-1 lacks detectable ATM protein expression and is sensitive to the PARP inhibitor olaparib. Similarly, HCT116 colorectal cancer cells with shRNA depletion of ATM are sensitive to olaparib, and depletion of p53 enhances this sensitivity. Moreover, HCT116 cells are sensitive to olaparib in combination with the ATM inhibitor KU55933, and sensitivity is enhanced by deletion of p53. Together our studies suggest that PARP inhibitors may have potential for treating colorectal cancer with ATM dysfunction and/or colorectal cancer with mutation of p53 when combined with an ATM kinase inhibitor. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  10. ATM haplotypes and cellular response to DNA damage: association with breast cancer risk and clinical radiosensitivity.

    NARCIS (Netherlands)

    Angele, S.; Romestaing, P.; Moullan, N.; Vuillaume, M.; Chapot, B.; Friesen, M.; Jongmans, W.; Cox, D.G.; Pisani, P.; Gerard, J.P.; Hall, J.

    2003-01-01

    The ATM gene, mutated in the cancer-prone and radiation-sensitive syndrome ataxia-telangiectasia (AT), could predispose to breast cancer (BC) development and adverse radiotherapy responses. Sixteen ATM variants were genotyped in 254 BC cases, 70 of whom were adverse radiotherapy responders (RS-BC),

  11. ATM signaling and 53BP1

    International Nuclear Information System (INIS)

    Zgheib, Omar; Huyen, Yentram; DiTullio, Richard A.; Snyder, Andrew; Venere, Monica; Stavridi, Elena S.; Halazonetis, Thanos D.

    2005-01-01

    The ATM (mutated in Ataxia-Telangiectasia) protein kinase is an important player in signaling the presence of DNA double strand breaks (DSBs) in higher eukaryotes. Recent studies suggest that ATM monitors the presence of DNA DSBs indirectly, through DNA DSB-induced changes in chromatin structure. One of the proteins that sense these chromatin structure changes is 53BP1, a DNA damage checkpoint protein conserved in all eukaryotes and the putative ortholog of the S. cerevisiae RAD9 protein. We review here the mechanisms by which ATM is activated in response to DNA DSBs, as well as key ATM substrates that control cell cycle progression, apoptosis and DNA repair

  12. CT and MR imaging of splenic leiomyoma in a child with ataxia telangiectasia

    Energy Technology Data Exchange (ETDEWEB)

    Coskun, M. [Dept. of Radiology, Hacettepe University Hospital, Ankara (Turkey); Aydingoez, Ue. [Dept. of Radiology, Hacettepe University Hospital, Ankara (Turkey); Tacal, T. [Dept. of Radiology, Hacettepe University Hospital, Ankara (Turkey); Ariyuerek, M. [Dept. of Radiology, Hacettepe University Hospital, Ankara (Turkey); Demirkazik, F. [Dept. of Radiology, Hacettepe University Hospital, Ankara (Turkey); Oguzkurt, L. [Dept. of Radiology, Hacettepe University Hospital, Ankara (Turkey)

    1995-02-01

    Computed tomographic and magnetic resonance imaging findings of a splenic leiomyoma in an 8-year-old boy with ataxia telangiectasia are presented. This is the first reported case of a splenic leiomyoma in the literature. (orig.)

  13. CT and MR imaging of splenic leiomyoma in a child with ataxia telangiectasia

    International Nuclear Information System (INIS)

    Coskun, M.; Aydingoez, Ue.; Tacal, T.; Ariyuerek, M.; Demirkazik, F.; Oguzkurt, L.

    1995-01-01

    Computed tomographic and magnetic resonance imaging findings of a splenic leiomyoma in an 8-year-old boy with ataxia telangiectasia are presented. This is the first reported case of a splenic leiomyoma in the literature. (orig.)

  14. Morphology and genomic hallmarks of breast tumours developed by ATM deleterious variant carriers.

    Science.gov (United States)

    Renault, Anne-Laure; Mebirouk, Noura; Fuhrmann, Laetitia; Bataillon, Guillaume; Cavaciuti, Eve; Le Gal, Dorothée; Girard, Elodie; Popova, Tatiana; La Rosa, Philippe; Beauvallet, Juana; Eon-Marchais, Séverine; Dondon, Marie-Gabrielle; d'Enghien, Catherine Dubois; Laugé, Anthony; Chemlali, Walid; Raynal, Virginie; Labbé, Martine; Bièche, Ivan; Baulande, Sylvain; Bay, Jacques-Olivier; Berthet, Pascaline; Caron, Olivier; Buecher, Bruno; Faivre, Laurence; Fresnay, Marc; Gauthier-Villars, Marion; Gesta, Paul; Janin, Nicolas; Lejeune, Sophie; Maugard, Christine; Moutton, Sébastien; Venat-Bouvet, Laurence; Zattara, Hélène; Fricker, Jean-Pierre; Gladieff, Laurence; Coupier, Isabelle; Chenevix-Trench, Georgia; Hall, Janet; Vincent-Salomon, Anne; Stoppa-Lyonnet, Dominique; Andrieu, Nadine; Lesueur, Fabienne

    2018-04-17

    The ataxia telangiectasia mutated (ATM) gene is a moderate-risk breast cancer susceptibility gene; germline loss-of-function variants are found in up to 3% of hereditary breast and ovarian cancer (HBOC) families who undergo genetic testing. So far, no clear histopathological and molecular features of breast tumours occurring in ATM deleterious variant carriers have been described, but identification of an ATM-associated tumour signature may help in patient management. To characterise hallmarks of ATM-associated tumours, we performed systematic pathology review of tumours from 21 participants from ataxia-telangiectasia families and 18 participants from HBOC families, as well as copy number profiling on a subset of 23 tumours. Morphology of ATM-associated tumours was compared with that of 599 patients with no BRCA1 and BRCA2 mutations from a hospital-based series, as well as with data from The Cancer Genome Atlas. Absolute copy number and loss of heterozygosity (LOH) profiles were obtained from the OncoScan SNP array. In addition, we performed whole-genome sequencing on four tumours from ATM loss-of-function variant carriers with available frozen material. We found that ATM-associated tumours belong mostly to the luminal B subtype, are tetraploid and show LOH at the ATM locus at 11q22-23. Unlike tumours in which BRCA1 or BRCA2 is inactivated, tumours arising in ATM deleterious variant carriers are not associated with increased large-scale genomic instability as measured by the large-scale state transitions signature. Losses at 13q14.11-q14.3, 17p13.2-p12, 21p11.2-p11.1 and 22q11.23 were observed. Somatic alterations at these loci may therefore represent biomarkers for ATM testing and harbour driver mutations in potentially 'druggable' genes that would allow patients to be directed towards tailored therapeutic strategies. Although ATM is involved in the DNA damage response, ATM-associated tumours are distinct from BRCA1-associated tumours in terms of morphological

  15. ATM, radiation, and the risk of second primary breast cancer.

    Science.gov (United States)

    Bernstein, Jonine L; Concannon, Patrick

    2017-10-01

    It was first suggested more than 40 years ago that heterozygous carriers for the human autosomal recessive disorder Ataxia-Telangiectasia (A-T) might also be at increased risk for cancer. Subsequent studies have identified the responsible gene, Ataxia-Telangiectasia Mutated (ATM), characterized genetic variation at this locus in A-T and a variety of different cancers, and described the functions of the ATM protein with regard to cellular DNA damage responses. However, an overall model of how ATM contributes to cancer risk, and in particular, the role of DNA damage in this process, remains lacking. This review considers these questions in the context of contralateral breast cancer (CBC). Heterozygous carriers of loss of function mutations in ATM that are A-T causing, are at increased risk of breast cancer. However, examination of a range of genetic variants, both rare and common, across multiple cancers, suggests that ATM may have additional effects on cancer risk that are allele-dependent. In the case of CBC, selected common alleles at ATM are associated with a reduced incidence of CBC, while other rare and predicted deleterious variants may act jointly with radiation exposure to increase risk. Further studies that characterize germline and somatic ATM mutations in breast cancer and relate the detected genetic changes to functional outcomes, particularly with regard to radiation responses, are needed to gain a complete picture of the complex relationship between ATM, radiation and breast cancer.

  16. ATM-Dependent Phosphorylation of MEF2D Promotes Neuronal Survival after DNA Damage

    Science.gov (United States)

    Chan, Shing Fai; Sances, Sam; Brill, Laurence M.; Okamoto, Shu-ichi; Zaidi, Rameez; McKercher, Scott R.; Akhtar, Mohd W.; Nakanishi, Nobuki

    2014-01-01

    Mutations in the ataxia telangiectasia mutated (ATM) gene, which encodes a kinase critical for the normal DNA damage response, cause the neurodegenerative disorder ataxia-telangiectasia (AT). The substrates of ATM in the brain are poorly understood. Here we demonstrate that ATM phosphorylates and activates the transcription factor myocyte enhancer factor 2D (MEF2D), which plays a critical role in promoting survival of cerebellar granule cells. ATM associates with MEF2D after DNA damage and phosphorylates the transcription factor at four ATM consensus sites. Knockdown of endogenous MEF2D with a short-hairpin RNA (shRNA) increases sensitivity to etoposide-induced DNA damage and neuronal cell death. Interestingly, substitution of endogenous MEF2D with an shRNA-resistant phosphomimetic MEF2D mutant protects cerebellar granule cells from cell death after DNA damage, whereas an shRNA-resistant nonphosphorylatable MEF2D mutant does not. In vivo, cerebella in Mef2d knock-out mice manifest increased susceptibility to DNA damage. Together, our results show that MEF2D is a substrate for phosphorylation by ATM, thus promoting survival in response to DNA damage. Moreover, dysregulation of the ATM–MEF2D pathway may contribute to neurodegeneration in AT. PMID:24672010

  17. Susceptibility of ATM-deficient pancreatic cancer cells to radiation.

    Science.gov (United States)

    Ayars, Michael; Eshleman, James; Goggins, Michael

    2017-05-19

    Ataxia telangiectasia mutated (ATM) is inactivated in a significant minority of pancreatic ductal adenocarcinomas and may be predictor of treatment response. We determined if ATM deficiency renders pancreatic cancer cells more sensitive to fractionated radiation or commonly used chemotherapeutics. ATM expression was knocked down in three pancreatic cancer cell lines using ATM-targeting shRNA. Isogenic cell lines were tested for sensitivity to several chemotherapeutic agents and radiation. DNA repair kinetics were analyzed in irradiated cells using the comet assay. We find that while rendering pancreatic cancer cells ATM-deficient did not significantly change their sensitivity to several chemotherapeutics, it did render them exquisitely sensitized to radiation. Pancreatic cancer ATM status may help predict response to radiotherapy.

  18. Sugammadex reversal of rocuronium-induced neuromuscular block in a patient with ataxia-telangiectasia

    International Nuclear Information System (INIS)

    Kang, E.; Jung, J.W.

    2015-01-01

    A 17-year-old adolescent with ataxia-telangiectasia was scheduled to have laparoscopic colectomy for a resection of colon cancer. He had symptoms and signs of dyspnea, generalized dystonia, dysmetria, ataxia, and telangiectasia on the orbit. General anesthesia was performed, and rocuronium 30 mg was administered for muscle relaxation. Deep neuromuscular block (post-tetanic count: 0-8) was maintained for 95 minutes without additional rocuronium. On completion of surgery, sugammadex 80 mg was injected and train-of-four ratio was 0.93 at 210 seconds after administration. The tracheal tube was removed 5 min after the end of surgery. He recovered full spontaneous respiration and voluntary movements within 1 minute after extubation. After the surgery, he transferred to the intensive care unit and discharged 14 days after the surgery without any concrete problem. The reversal of rocuronium induced neuromuscular block by sugammadex was fast, complete, and recovered to the initial preoperative level of neuromuscular function in this patient. (author)

  19. ATM deficiency results in accumulation of DNA-topoisomerase I covalent intermediates in neural cells.

    Directory of Open Access Journals (Sweden)

    Meryem Alagoz

    Full Text Available Accumulation of peptide-linked DNA breaks contributes to neurodegeration in humans. This is typified by defects in tyrosyl DNA phosphodiesterase 1 (TDP1 and human hereditary ataxia. TDP1 primarily operates at single-strand breaks (SSBs created by oxidative stress or by collision of transcription machinery with topoisomerase I intermediates (Top1-CCs. Cellular and cell-free studies have shown that Top1 at stalled Top1-CCs is first degraded to a small peptide resulting in Top1-SSBs, which are the primary substrates for TDP1. Here we established an assay to directly compare Top1-SSBs and Top1-CCs. We subsequently employed this assay to reveal an increased steady state level of Top1-CCs in neural cells lacking Atm; the protein mutated in ataxia telangiectasia. Our data suggest that the accumulation of endogenous Top1-CCs in Atm-/- neural cells is primarily due to elevated levels of reactive oxygen species. Biochemical purification of Top1-CCs from neural cell extract and the use of Top1 poisons further confirmed a role for Atm during the formation/resolution of Top1-CCs. Finally, we report that global transcription is reduced in Atm-/- neural cells and fails to recover to normal levels following Top1-mediated DNA damage. Together, these data identify a distinct role for ATM during the formation/resolution of neural Top1-CCs and suggest that their accumulation contributes to the neuropathology of ataxia telangiectasia.

  20. Germline variants in the ATM gene and breast cancer susceptibility ...

    African Journals Online (AJOL)

    Chaymaa Marouf

    2017-03-06

    Mar 6, 2017 ... Results: We did not detect the ATM c.7271T > G and c.1066–6T > G (IVS10–6T > G) ..... [8] Lavin MF, Shiloh Y. The genetic defect in ataxia-telangiectasia. .... [36] Inskip HM, Kinlen LJ, Taylor AM, Woods CG, Arlett CF. Risk of ...

  1. DNA-repair synthesis in ataxia telangiectasia lymphoblastoid cells

    Energy Technology Data Exchange (ETDEWEB)

    Ford, M.D.; Houldsworth, J.; Lavin, M.F. (Queensland Univ., Brisbane (Australia). Dept. of Biochemistry)

    1981-12-01

    The ability of a number of Epstein-Barr virus-transformed lymphoblastoid cells from ataxia telangiectasia (AT) patients to repair ..gamma..-radiation damage to DNA was determined. All of these AT cells were previously shown to be hypersensitive to ..gamma..-radiation. Two methods were used to determine DNA-repair synthesis: isopycnic gradient analysis and a method employing hydroxyurea to inhibit semiconservative DNA synthesis. Control, AT heterozygote and AT homozygote cells were demonstrated to have similar capacities for repair of radiation damage to DNA. In addition at high radiation doses (10-40 krad) the extent of inhibition of DNA synthesis was similar in the different cell types.

  2. An HTRF® Assay for the Protein Kinase ATM.

    Science.gov (United States)

    Adams, Phillip; Clark, Jonathan; Hawdon, Simon; Hill, Jennifer; Plater, Andrew

    2017-01-01

    Ataxia telangiectasia mutated (ATM) is a serine/threonine kinase that plays a key role in the regulation of DNA damage pathways and checkpoint arrest. In recent years, there has been growing interest in ATM as a therapeutic target due to its association with cancer cell survival following genotoxic stress such as radio- and chemotherapy. Large-scale targeted drug screening campaigns have been hampered, however, by technical issues associated with the production of sufficient quantities of purified ATM and the availability of a suitable high-throughput assay. Using a purified, functionally active recombinant ATM and one of its physiological substrates, p53, we have developed an in vitro FRET-based activity assay that is suitable for high-throughput drug screening.

  3. ATM protein is located on presynaptic vesicles and its deficit leads to failures in synaptic plasticity.

    Science.gov (United States)

    Vail, Graham; Cheng, Aifang; Han, Yu Ray; Zhao, Teng; Du, Shengwang; Loy, Michael M T; Herrup, Karl; Plummer, Mark R

    2016-07-01

    Ataxia telangiectasia is a multisystemic disorder that includes a devastating neurodegeneration phenotype. The ATM (ataxia-telangiectasia mutated) protein is well-known for its role in the DNA damage response, yet ATM is also found in association with cytoplasmic vesicular structures: endosomes and lysosomes, as well as neuronal synaptic vesicles. In keeping with this latter association, electrical stimulation of the Schaffer collateral pathway in hippocampal slices from ATM-deficient mice does not elicit normal long-term potentiation (LTP). The current study was undertaken to assess the nature of this deficit. Theta burst-induced LTP was reduced in Atm(-/-) animals, with the reduction most pronounced at burst stimuli that included 6 or greater trains. To assess whether the deficit was associated with a pre- or postsynaptic failure, we analyzed paired-pulse facilitation and found that it too was significantly reduced in Atm(-/-) mice. This indicates a deficit in presynaptic function. As further evidence that these synaptic effects of ATM deficiency were presynaptic, we used stochastic optical reconstruction microscopy. Three-dimensional reconstruction revealed that ATM is significantly more closely associated with Piccolo (a presynaptic marker) than with Homer1 (a postsynaptic marker). These results underline how, in addition to its nuclear functions, ATM plays an important functional role in the neuronal synapse where it participates in the regulation of presynaptic vesicle physiology. Copyright © 2016 the American Physiological Society.

  4. Ataxia-telangiectasia gene (ATM) mutation heterozygosity in breast cancer: a narrative review.

    Science.gov (United States)

    Jerzak, K J; Mancuso, T; Eisen, A

    2018-04-01

    Despite the fact that heterozygosity for a pathogenic ATM variant is present in 1%-2% of the adult population, clinical guidelines to inform physicians and genetic counsellors about optimal management in that population are lacking. In this narrative review, we describe the challenges and controversies in the management of women who are heterozygous for a pathogenic ATM variant with respect to screening for breast and other malignancies, to choices for systemic therapy, and to decisions about radiation therapy. Given that the lifetime risk for breast cancer in women who are heterozygous for a pathogenic ATM variant is likely greater than 25%, those women should undergo annual mammographic screening starting at least by 40 years of age. For women in this group who have a strong family history of breast cancer, earlier screening with both magnetic resonance imaging and mammography should be considered. High-quality data to inform the management of established breast cancer in carriers of pathogenic ATM variants are lacking. Although deficiency in the ATM gene product might confer sensitivity to dna-damaging pharmaceuticals such as inhibitors of poly (adp-ribose) polymerase or platinum agents, prospective clinical trials have not been conducted in the relevant patient population. Furthermore, the evidence with respect to radiation therapy is mixed; some data suggest increased toxicity, and other data suggest improved clinical benefit from radiation in women who are carriers of a pathogenic ATM variant. As in the 2017 U.S. National Comprehensive Cancer Network guidelines, we recommend high-risk imaging for women in Ontario who are heterozygous for a pathogenic ATM variant. Currently, ATM carrier status should not influence decisions about systemic or radiation therapy in the setting of an established breast cancer diagnosis.

  5. Recent studies on the ATM gene

    International Nuclear Information System (INIS)

    Lavin, M.F.; Khanna, K.K.; Waters, D.

    1996-01-01

    Full text: Radiosensitivity is a universal characteristic of ataxia-telangiectasia (A-T), observed after exposure of patients and of cells in culture to radiation. This sensitivity is manifested as higher levels of radiation-induced chromosomal aberrations and reduced survival compared to controls. The gene for A-T was mapped to chromosome 11q 22-23 seven years ago and more recently we have been involved in the cloning of a single gene, ATM (ataxia-telangiectasia mutated), mutated in this syndrome. ATM is a large gene, approximately 150 kb in size, composed of 66 exons and codes for a major mRNA of 13 kb with a predicted open reading frame of 9.135 kb. It is not yet known what activity the ATM gene product possesses, but the ralatedness of this gene sequence to the phosphatidylinositol 3-kinase gene family supports a role for ATM in intracellular signalling. Considerable information is already available on defective signalling through the p53 damage-inducible pathway in A-T. This includes failure to arrest at either the G1/S or G2/M checkpoints as well as radioresistant DNA synthesis. A reduced and/or delayed response in the induction of p53 after exposure of A-T cells to ionizing radiation can account for the defective G1/S checkpoint. More recently we have demonstrated that the ATM gene product is involved in the control of multiple cell cycle checkpoints. Antibodies prepared against ATM peptides demonstrate the presence of a protein 350 kDa in size, which is the predicted size for this protein based on open reading frame of 9 kb. This protein is present both in the nucleus and in the cytoplasm where it is present in vesicular structures. As expected from mutation data the ATM protein is absent in cells from some patients with A-T. The cloning of the ATM gene will allow for screening of radiosensitive patients for mutations in this gene and will provide a means of identifying interacting proteins and thus an understanding of how it functions

  6. Study of ATM Phosphorylation by Cdk5 in Neuronal Cells.

    Science.gov (United States)

    She, Hua; Mao, Zixu

    2017-01-01

    The phosphatidylinositol-3-kinase-like kinase ATM (ataxia-telangiectasia mutated) plays a central role in coordinating the DNA damage responses including cell cycle checkpoint control, DNA repair, and apoptosis. Mutations of ATM cause a spectrum of defects ranging from neurodegeneration to cancer predisposition. We previously showed that Cdk5 (cyclin-dependent kinase 5) is activated by DNA damage and directly phosphorylates ATM at serine 794 in postmitotic neurons. Phosphorylation at serine 794 precedes and is required for ATM autophosphorylation at serine 1981, and activates ATM kinase activity. Cdk5-ATM pathway plays a crucial role in DNA damage-induced neuronal injury. This chapter describes protocols used in analyzing ATM phosphorylation by Cdk5 in CGNs (cerebellar granule neurons) and its effects on neuronal survival.

  7. Genetic and cellular features of ataxia telangiectasia

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, A M.R.; Byrd, P J; McConville, C M; Thacker, S [Birmingham Univ. (United Kingdom). CRC Dept. of Cancer Studies

    1994-01-01

    Ataxia telangiectasia (AT) is a developmental disorder in which many organ systems are affected. The children are recognized by a progressive cerebellar deterioration. The gene for AT has now been localized to a region of chromosome 11q22-23 of no more than 3Mb in size and its product appears to be involved directly or indirectly in some form of DNA recombination. Patients and their cells are unusually sensitive to ionizing radiation and various radiometric drugs. Observations on the progressive nature of the disorder, with loss of selected cells or failure to develop normally, might be compatible with the pathological effect of an inability to correctly regulate apoptosis in some cell lineages. While this is an intriguing speculation, there is, at present, no evidence for such a defect in AT. (author).

  8. Two Novel Mutations Associated With Ataxia-Telangiectasia Identified Using an Ion AmpliSeq Inherited Disease Panel

    Directory of Open Access Journals (Sweden)

    Maria V. Kuznetsova

    2017-10-01

    Full Text Available Ataxia-telangiectasia (A-T, or Louis-Bar syndrome, is a rare neurodegenerative disorder associated with immunodeficiency. For families with at least one affected child, timely A-T genotyping during any subsequent pregnancy allows the parents to make an informed decision about whether to continue to term when the fetus is affected. Mutations in the ATM gene, which is 150 kb long, give rise to A-T; more than 600 pathogenic variants in ATM have been characterized since 1990 and new mutations continue to be discovered annually. Therefore, limiting genetic screening to previously known SNPs by PCR or hybridization with microarrays may not identify the specific pathogenic genotype in ATM for a given A-T family. However, recent developments in next-generation sequencing technology offer prompt high-throughput full-length sequencing of genomic fragments of interest. This allows the identification of the whole spectrum of mutations in a gene, including any novel ones. We report two A-T families with affected children and current pregnancies. Both families are consanguineous and originate from Caucasian regions of Russia and Azerbaijan. Before our study, no ATM mutations had been identified in the older children of these families. We used ion semiconductor sequencing and an Ion AmpliSeq™ Inherited Disease Panel to perform complete ATM gene sequencing in a single member of each family. Then we compared the experimentally determined genotype with the affected/normal phenotype distribution in the whole family to provide unambiguous evidence of pathogenic mutations responsible for A-T. A single novel SNP was allocated to each family. In the first case, we found a mononucleotide deletion, and in the second, a mononucleotide insertion. Both mutations lead to truncation of the ATM protein product. Identification of the pathogenic mutation in each family was performed in a timely fashion, allowing the fetuses to be tested and diagnosed. The parents chose to

  9. Ataxia-telangiectasia mutated (ATM) silencing promotes neuroblastoma progression through a MYCN independent mechanism

    Science.gov (United States)

    Mandriota, Stefano J.; Valentijn, Linda J.; Lesne, Laurence; Betts, David R.; Marino, Denis; Boudal-Khoshbeen, Mary; London, Wendy B.; Rougemont, Anne-Laure; Attiyeh, Edward F.; Maris, John M.; Hogarty, Michael D.; Koster, Jan; Molenaar, Jan J.; Versteeg, Rogier

    2015-01-01

    Neuroblastoma, a childhood cancer with highly heterogeneous biology and clinical behavior, is characterized by genomic aberrations including amplification of MYCN. Hemizygous deletion of chromosome 11q is a well-established, independent marker of poor prognosis. While 11q22-q23 is the most frequently deleted region, the neuroblastoma tumor suppressor in this region remains to be identified. Chromosome bands 11q22-q23 contain ATM, a cell cycle checkpoint kinase and tumor suppressor playing a pivotal role in the DNA damage response. Here, we report that haploinsufficiency of ATM in neuroblastoma correlates with lower ATM expression, event-free survival, and overall survival. ATM loss occurs in high stage neuroblastoma without MYCN amplification. In SK-N-SH, CLB-Ga and GI-ME-N human neuroblastoma cells, stable ATM silencing promotes neuroblastoma progression in soft agar assays, and in subcutaneous xenografts in nude mice. This effect is dependent on the extent of ATM silencing and does not appear to involve MYCN. Our findings identify ATM as a potential haploinsufficient neuroblastoma tumor suppressor, whose inactivation mirrors the increased aggressiveness associated with 11q deletion in neuroblastoma. PMID:26053094

  10. Human iPSC-Derived Cerebellar Neurons from a Patient with Ataxia-Telangiectasia Reveal Disrupted Gene Regulatory Networks

    Directory of Open Access Journals (Sweden)

    Sam P. Nayler

    2017-10-01

    Full Text Available Ataxia-telangiectasia (A-T is a rare genetic disorder caused by loss of function of the ataxia-telangiectasia-mutated kinase and is characterized by a predisposition to cancer, pulmonary disease, immune deficiency and progressive degeneration of the cerebellum. As animal models do not faithfully recapitulate the neurological aspects, it remains unclear whether cerebellar degeneration is a neurodevelopmental or neurodegenerative phenotype. To address the necessity for a human model, we first assessed a previously published protocol for the ability to generate cerebellar neuronal cells, finding it gave rise to a population of precursors highly enriched for markers of the early hindbrain such as EN1 and GBX2, and later more mature cerebellar markers including PTF1α, MATH1, HOXB4, ZIC3, PAX6, and TUJ1. RNA sequencing was used to classify differentiated cerebellar neurons generated from integration-free A-T and control induced pluripotent stem cells. Comparison of RNA sequencing data with datasets from the Allen Brain Atlas reveals in vitro-derived cerebellar neurons are transcriptionally similar to discrete regions of the human cerebellum, and most closely resemble the cerebellum at 22 weeks post-conception. We show that patient-derived cerebellar neurons exhibit disrupted gene regulatory networks associated with synaptic vesicle dynamics and oxidative stress, offering the first molecular insights into early cerebellar pathogenesis of ataxia-telangiectasia.

  11. Ataxia-telangiectasia: the pattern of cerebellar atrophy on MRI

    International Nuclear Information System (INIS)

    Tavani, F.; Zimmerman, R.A.; Gatti, R.; Bingham, P.; Berry, G.T.; Sullivan, K.

    2003-01-01

    We describe MRI of the brain in 19 patients with ataxia-telangiectasia (AT) and correlate the appearances with the degree of neurologic deficit. We examined 10 male and nine female patients; 17 were aged between 2 and 12 years (mean 8 years) but a woman and her brother were 35 and 38 years old, and had a variant of AT. Ataxia was the first recognized sign of the disease in every patient. We detected the following patterns of cerebellar atrophy: in the youngest patient, aged 2 years, the study was normal; in the five next youngest patients 3-7 years of age, the lateral cerebellum and superior vermis showed the earliest changes of atrophy; and all but one of the other patients had moderate to marked diffuse atrophy of vermis and cerebellar hemispheres. There were 12 patients aged 9 years and above; one, who was normal, was 9 years old. The five patients who at the time of examination were unable to walk all had diffuse atrophy involving both vermis and cerebellar hemispheres. (orig.)

  12. Downregulated Ku70 and ATM associated to poor prognosis in colorectal cancer among Chinese patients

    Directory of Open Access Journals (Sweden)

    Lu YF

    2014-10-01

    Full Text Available Yuanfang Lu,1,2 Jingyan Gao,1,3 Yuanming Lu,1 1Department of Toxicology, School of Public Health, Guilin Medical University, Guangxi, People's Republic of China; 2Department of Clinical Research Center, Affiliated 2nd Hospital of Nanjing Medical University, Nanjing, People's Republic of China; 3Department of Human Anatomy and Histo-Embryology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China Background: Double-strand DNA breaks (DSBs are a key factor in carcinogenesis. The necessary repair of DSBs is pivotal in maintaining normal cell division. To address the relationship between altered expression of DSB repair of proteins Ku70 and ataxia-telangiectasia mutated (ATM in colorectal cancer (CRC, we examined the expression levels and patterns of Ku70 and ATM in CRC samples. Methods: Expression and coexpression of Ku70 and ATM were investigated by using real-time quantitative polymerase chain reaction assays and confirmed further with fluorescent immunohistochemistry in CRC and pericancerous samples from 112 Chinese patients. Results: Downexpression patterns for both Ku70 and ATM were found in the CRC samples and were significantly associated with advanced tumor node metastasis stage and decreased 5-year overall survival rate. Conclusion: Downregulated Ku70 and ATM were associated with poor disease-free survival. Loss of Ku70 and ATM expression might act as a biomarker to predict poor prognosis in patients with CRC. Keywords: DNA double-strand breaks, ataxia-telangiectasia mutated, Ku70, colorectal cancer

  13. ATM down-regulation is associated with poor prognosis in sporadic breast carcinomas

    DEFF Research Database (Denmark)

    Bueno, R C; Canevari, R A; Villacis, R A R

    2014-01-01

    BACKGROUND: Ataxia telangiectasia-mutated (ATM) gene downexpression has been reported in sporadic breast carcinomas (BC); however, the prognostic value and mechanisms of ATM deregulation remain unclear. PATIENTS AND METHODS: ATM and miRNAs (miR-26a, miR-26b, miR-203, miR-421, miR-664, miR-576-5p...... and miR-18a) expression levels were evaluated by quantitative real-time PCR (RT-qPCR) in 52 BC and 3 normal breast samples. ATM protein expression was assessed by immunohistochemistry in 968 BC and 35 adjacent normal breast tissues. ATM copy number alteration was detected by array comparative genomic...... hybridization (aCGH) in 42 tumours. RESULTS: Low ATM levels were associated with tumour grade. Absence of ATM protein expression was associated with distant metastasis (P ATM...

  14. Structure of the intact ATM/Tel1 kinase

    Science.gov (United States)

    Wang, Xuejuan; Chu, Huanyu; Lv, Mengjuan; Zhang, Zhihui; Qiu, Shuwan; Liu, Haiyan; Shen, Xuetong; Wang, Weiwu; Cai, Gang

    2016-05-01

    The ataxia-telangiectasia mutated (ATM) protein is an apical kinase that orchestrates the multifaceted DNA-damage response. Normally, ATM kinase is in an inactive, homodimer form and is transformed into monomers upon activation. Besides a conserved kinase domain at the C terminus, ATM contains three other structural modules, referred to as FAT, FATC and N-terminal helical solenoid. Here we report the first cryo-EM structure of ATM kinase, which is an intact homodimeric ATM/Tel1 from Schizosaccharomyces pombe. We show that two monomers directly contact head-to-head through the FAT and kinase domains. The tandem N-terminal helical solenoid tightly packs against the FAT and kinase domains. The structure suggests that ATM/Tel1 dimer interface and the consecutive HEAT repeats inhibit the binding of kinase substrates and regulators by steric hindrance. Our study provides a structural framework for understanding the mechanisms of ATM/Tel1 regulation as well as the development of new therapeutic agents.

  15. ATM supports gammaherpesvirus replication by attenuating type I interferon pathway.

    Science.gov (United States)

    Darrah, Eric J; Stoltz, Kyle P; Ledwith, Mitchell; Tarakanova, Vera L

    2017-10-01

    Ataxia-Telangiectasia mutated (ATM) kinase participates in multiple networks, including DNA damage response, oxidative stress, and mitophagy. ATM also supports replication of diverse DNA and RNA viruses. Gammaherpesviruses are prevalent cancer-associated viruses that benefit from ATM expression during replication. This proviral role of ATM had been ascribed to its signaling within the DNA damage response network; other functions of ATM have not been considered. In this study increased type I interferon (IFN) responses were observed in ATM deficient gammaherpesvirus-infected macrophages. Using a mouse model that combines ATM and type I IFN receptor deficiencies we show that increased type I IFN response in the absence of ATM fully accounts for the proviral role of ATM during gammaherpesvirus replication. Further, increased type I IFN response rendered ATM deficient macrophages more susceptible to antiviral effects of type II IFN. This study identifies attenuation of type I IFN responses as the primary mechanism underlying proviral function of ATM during gammaherpesvirus infection. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. The mammalian mid-pachytene checkpoint: meiotic arrest in spermatocytes with a mutation in Atm alone or in combination with a Trp53 (p53) or Cdkn1a (p21/cip1) mutation

    NARCIS (Netherlands)

    Ashley, T.; Westphal, C.; Plug-de Maggio, A.; de rooij, D. G.

    2004-01-01

    ATM, the protein product of the gene mutated in the human autosomal recessive disorder ataxia telangiectasia, is involved in detection of double strand breaks (DSBs) and is a key component of the damage surveillance network of cell cycle proteins. In somatic cells ATM phosphorylates many other

  17. Tyrosine 370 phosphorylation of ATM positively regulates DNA damage response

    Science.gov (United States)

    Lee, Hong-Jen; Lan, Li; Peng, Guang; Chang, Wei-Chao; Hsu, Ming-Chuan; Wang, Ying-Nai; Cheng, Chien-Chia; Wei, Leizhen; Nakajima, Satoshi; Chang, Shih-Shin; Liao, Hsin-Wei; Chen, Chung-Hsuan; Lavin, Martin; Ang, K Kian; Lin, Shiaw-Yih; Hung, Mien-Chie

    2015-01-01

    Ataxia telangiectasia mutated (ATM) mediates DNA damage response by controling irradiation-induced foci formation, cell cycle checkpoint, and apoptosis. However, how upstream signaling regulates ATM is not completely understood. Here, we show that upon irradiation stimulation, ATM associates with and is phosphorylated by epidermal growth factor receptor (EGFR) at Tyr370 (Y370) at the site of DNA double-strand breaks. Depletion of endogenous EGFR impairs ATM-mediated foci formation, homologous recombination, and DNA repair. Moreover, pretreatment with an EGFR kinase inhibitor, gefitinib, blocks EGFR and ATM association, hinders CHK2 activation and subsequent foci formation, and increases radiosensitivity. Thus, we reveal a critical mechanism by which EGFR directly regulates ATM activation in DNA damage response, and our results suggest that the status of ATM Y370 phosphorylation has the potential to serve as a biomarker to stratify patients for either radiotherapy alone or in combination with EGFR inhibition. PMID:25601159

  18. Regulation of ATM induction

    International Nuclear Information System (INIS)

    Clarke, R.A.; Fang, Z.M.; Kearsley, J.H.; Lee, C.S.; Sarris, M.; De Murrell, D.

    2000-01-01

    Full text: ATM, the tumour suppressor protein mutated in ataxia-telangiectasia, is of pivotal importance in controlling the cells primary response to ionising radiation (IR) induced DNA damage. Mutations in ATM which reduce the level of the ATM protein and/or compromise ATM functions are known to give rise to radiosensitivity and defective cell cycle checkpoint control. In response to DNA damage ATM kinase is rapidly activated and initiates downstream signalling to cell cycle control molecules including p53. To investigate additional mechanisms of ATM control we have employed ATM antisense expression in cultured cells, western analyses and immunohistochemistry in situ. We report that ATM can be up-regulated up to 10-fold following exposure to low levels of ionising radiation. ATM radiation-induction was radiation dose dependent while the rapidity of the response indicates a post translational pathway. The concurrent time frames for the radiation-induction of ATM levels and the activation of ATM kinase activity appear to be complimentary in boosting ATM's protective response to IR induced DNA damage, especially in ATM 'low expressing' systems. We also provide the first report of ATM misregulation in 2 cancer patients, indicating that ATM is not only radio-protective but has possible implications in cancer, particularly breast cancer. These results have particular importance in defining the regulation of the ATM protein as an: adaptive radio-response; radio-prognostic market in tumours and normal tissue, and breast cancer marker

  19. Functional link between DNA damage responses and transcriptional regulation by ATM in response to a histone deacetylase inhibitor TSA.

    Science.gov (United States)

    Lee, Jong-Soo

    2007-09-01

    Mutations in the ATM (ataxia-telangiectasia mutated) gene, which encodes a 370 kd protein with a kinase catalytic domain, predisposes people to cancers, and these mutations are also linked to ataxia-telangiectasia (A-T). The histone acetylaion/deacetylation- dependent chromatin remodeling can activate the ATM kinase-mediated DNA damage signal pathway (in an accompanying work, Lee, 2007). This has led us to study whether this modification can impinge on the ATM-mediated DNA damage response via transcriptional modulation in order to understand the function of ATM in the regulation of gene transcription. To identify the genes whose expression is regulated by ATM in response to histone deaceylase (HDAC) inhibition, we performed an analysis of oligonucleotide microarrays with using the appropriate cell lines, isogenic A-T (ATM(-)) and control (ATM(+)) cells, following treatment with a HDAC inhibitor TSA. Treatment with TSA reprograms the differential gene expression profile in response to HDAC inhibition in ATM(-) cells and ATM(+) cells. We analyzed the genes that are regulated by TSA in the ATM-dependent manner, and we classified these genes into different functional categories, including those involved in cell cycle/DNA replication, DNA repair, apoptosis, growth/differentiation, cell- cell adhesion, signal transduction, metabolism and transcription. We found that while some genes are regulated by TSA without regard to ATM, the patterns of gene regulation are differentially regulated in an ATM-dependent manner. Taken together, these finding indicate that ATM can regulate the transcription of genes that play critical roles in the molecular response to DNA damage, and this response is modulated through an altered HDAC inhibition-mediated gene expression.

  20. ATM splicing variants as biomarkers for low dose dexamethasone treatment of A-T.

    Science.gov (United States)

    Menotta, Michele; Biagiotti, Sara; Spapperi, Chiara; Orazi, Sara; Rossi, Luigia; Chessa, Luciana; Leuzzi, Vincenzo; D'Agnano, Daniela; Soresina, Annarosa; Micheli, Roberto; Magnani, Mauro

    2017-07-05

    Ataxia Telangiectasia (AT) is a rare incurable genetic disease, caused by biallelic mutations in the Ataxia Telangiectasia-Mutated (ATM) gene. Treatment with glucocorticoid analogues has been shown to improve the neurological symptoms that characterize this syndrome. Nevertheless, the molecular mechanism underlying the glucocorticoid action in AT patients is not yet understood. Recently, we have demonstrated that Dexamethasone treatment may partly restore ATM activity in AT lymphoblastoid cells by a new ATM transcript, namely ATMdexa1. In the present study, the new ATMdexa1 transcript was also identified in vivo, specifically in the PMBCs of AT patients treated with intra-erythrocyte Dexamethasone (EryDex). In these patients it was also possible to isolate new "ATMdexa1 variants" originating from canonical and non-canonical splicing, each containing the coding sequence for the ATM kinase domain. The expression of the ATMdexa1 transcript family was directly related to treatment and higher expression levels of the transcript in patients' blood correlated with a positive response to Dexamethasone therapy. Neither untreated AT patients nor untreated healthy volunteers possessed detectable levels of the transcripts. ATMdexa1 transcript expression was found to be elevated 8 days after the drug infusion, while it decreased 21 days after treatment. For the first time, the expression of ATM splicing variants, similar to those previously observed in vitro, has been found in the PBMCs of patients treated with EryDex. These findings show a correlation between the expression of ATMdexa1 transcripts and the clinical response to low dose dexamethasone administration.

  1. ATM induction insufficiency in a radiosensitive breast-cancer patient

    International Nuclear Information System (INIS)

    Clarke, R.A.; Fang, Z.H.; Marr, P.J.; Kearsley, J.H.; Papadatos, G.; Lee, C.S.; University of Sydney, Camperdown, NSW

    2002-01-01

    ATM induction insufficiency in a radiosensitive breast-cancer patient The ataxia telangiectasia (A-T) gene (ATM) is a dominant breast cancer gene with tumour suppressor activity. ATM also regulates cellular sensitivity to ionising radiation (IR) presumably through its role as a facilitator of DNA repair. In normal cells and tissues the ATM protein is rapidly induced by IR to threshold/maximum levels. The kinase function of the ATM protein is also rapidly activated in response to IR. The fact that women carriers of ATM mutations can have an increased risk of developing breast cancer and that many sporadic breast tumours have reduced levels of the ATM protein broadens the scope of ATM's tumour suppressor within the breast. This report describes the downregulation of ATM protein levels in a radiosensitive breast cancer patient. Postinduction ATM levels were up to tenfold lower in the patient's fresh tissues compared to normal controls. These results might indicate a much broader role for ATM anomalies in breast cancer aetiology. Copyright (2002) Blackwell Science Pty Ltd

  2. Premeiotic germ cell defect in seminiferous tubules of Atm-null testis

    International Nuclear Information System (INIS)

    Takubo, Keiyo; Hirao, Atsushi; Ohmura, Masako; Azuma, Masaki; Arai, Fumio; Nagamatsu, Go; Suda, Toshio

    2006-01-01

    Lifelong spermatogenesis is maintained by coordinated sequential processes including self-renewal of stem cells, proliferation of spermatogonial cells, meiotic division, and spermiogenesis. It has been shown that ataxia telangiectasia-mutated (ATM) is required for meiotic division of the seminiferous tubules. Here, we show that, in addition to its role in meiosis, ATM has a pivotal role in premeiotic germ cell maintenance. ATM is activated in premeiotic spermatogonial cells and the Atm-null testis shows progressive degeneration. In Atm-null testicular cells, differing from bone marrow cells of Atm-null mice, reactive oxygen species-mediated p16 Ink4a activation does not occur in Atm-null premeiotic germ cells, which suggests the involvement of different signaling pathways from bone marrow defects. Although Atm-null bone marrow undergoes p16 Ink4a -mediated cellular senescence program, Atm-null premeiotic germ cells exhibited cell cycle arrest and apoptotic elimination of premeiotic germ cells, which is different from p16 Ink4a -mediated senescence

  3. Early-stage apoptosis is associated with DNA-damage-independent ATM phosphorylation and chromatin decondensation in NIH3T3 fibroblasts

    DEFF Research Database (Denmark)

    Schou, Kenneth Bødtker; Schneider, Linda; Christensen, Søren Tvorup

    2008-01-01

    Chromatin condensation and degradation of DNA into internucleosomal DNA fragments are key hallmarks of apoptosis. The phosphorylation of protein kinase ataxia telangiectasia mutated (ATM) and histone H2A.X was recently shown to occur concurrently with apoptotic DNA fragmentation. We have used...... necrosis factor-alpha mixed with cycloheximide (TNF-alpha/CHX). In extension to previous findings, ATM phosphorylation was associated with chromatin decondensation, i.e., by loss of dense foci of constitutive heterochromatin. These results suggest that chromatin is decondensed and that ATM is activated...

  4. ATM facilitates mouse gammaherpesvirus reactivation from myeloid cells during chronic infection.

    Science.gov (United States)

    Kulinski, Joseph M; Darrah, Eric J; Broniowska, Katarzyna A; Mboko, Wadzanai P; Mounce, Bryan C; Malherbe, Laurent P; Corbett, John A; Gauld, Stephen B; Tarakanova, Vera L

    2015-09-01

    Gammaherpesviruses are cancer-associated pathogens that establish life-long infection in most adults. Insufficiency of Ataxia-Telangiectasia mutated (ATM) kinase leads to a poor control of chronic gammaherpesvirus infection via an unknown mechanism that likely involves a suboptimal antiviral response. In contrast to the phenotype in the intact host, ATM facilitates gammaherpesvirus reactivation and replication in vitro. We hypothesized that ATM mediates both pro- and antiviral activities to regulate chronic gammaherpesvirus infection in an immunocompetent host. To test the proposed proviral activity of ATM in vivo, we generated mice with ATM deficiency limited to myeloid cells. Myeloid-specific ATM deficiency attenuated gammaherpesvirus infection during the establishment of viral latency. The results of our study uncover a proviral role of ATM in the context of gammaherpesvirus infection in vivo and support a model where ATM combines pro- and antiviral functions to facilitate both gammaherpesvirus-specific T cell immune response and viral reactivation in vivo. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Characterization of glioma stem cells through multiple stem cell markers and their specific sensitization to double-strand break-inducing agents by pharmacological inhibition of ataxia telangiectasia mutated protein.

    Science.gov (United States)

    Raso, Alessandro; Vecchio, Donatella; Cappelli, Enrico; Ropolo, Monica; Poggi, Alessandro; Nozza, Paolo; Biassoni, Roberto; Mascelli, Samantha; Capra, Valeria; Kalfas, Fotios; Severi, Paolo; Frosina, Guido

    2012-09-01

    Previous studies have shown that tumor-driving glioma stem cells (GSC) may promote radio-resistance by constitutive activation of the DNA damage response started by the ataxia telangiectasia mutated (ATM) protein. We have investigated whether GSC may be specifically sensitized to ionizing radiation by inhibiting the DNA damage response. Two grade IV glioma cell lines (BORRU and DR177) were characterized for a number of immunocytochemical, karyotypic, proliferative and differentiative parameters. In particular, the expression of a panel of nine stem cell markers was quantified by reverse transcription-polymerase chain reaction (RT-PCR) and flow cytometry. Overall, BORRU and DR177 displayed pronounced and poor stem phenotypes, respectively. In order to improve the therapeutic efficacy of radiation on GSC, the cells were preincubated with a nontoxic concentration of the ATM inhibitors KU-55933 and KU-60019 and then irradiated. BORRU cells were sensitized to radiation and radio-mimetic chemicals by ATM inhibitors whereas DR177 were protected under the same conditions. No sensitization was observed after cell differentiation or to drugs unable to induce double-strand breaks (DSB), indicating that ATM inhibitors specifically sensitize glioma cells possessing stem phenotype to DSB-inducing agents. In conclusion, pharmacological inhibition of ATM may specifically sensitize GSC to DSB-inducing agents while sparing nonstem cells. © 2012 The Authors; Brain Pathology © 2012 International Society of Neuropathology.

  6. ATM signaling and genomic stability in response to DNA damage

    International Nuclear Information System (INIS)

    Lavin, Martin F.; Birrell, Geoff; Chen, Philip; Kozlov, Sergei; Scott, Shaun; Gueven, Nuri

    2005-01-01

    DNA double strand breaks represent the most threatening lesion to the integrity of the genome in cells exposed to ionizing radiation and radiomimetic chemicals. Those breaks are recognized, signaled to cell cycle checkpoints and repaired by protein complexes. The product of the gene (ATM) mutated in the human genetic disorder ataxia-telangiectasia (A-T) plays a central role in the recognition and signaling of DNA damage. ATM is one of an ever growing number of proteins which when mutated compromise the stability of the genome and predispose to tumour development. Mechanisms for recognising double strand breaks in DNA, maintaining genome stability and minimizing risk of cancer are discussed

  7. Phenotypic Analysis of ATM Protein Kinase in DNA Double-Strand Break Formation and Repair.

    Science.gov (United States)

    Mian, Elisabeth; Wiesmüller, Lisa

    2017-01-01

    Ataxia telangiectasia mutated (ATM) encodes a serine/threonine protein kinase, which is involved in various regulatory processes in mammalian cells. Its best-known role is apical activation of the DNA damage response following generation of DNA double-strand breaks (DSBs). When DSBs appear, sensor and mediator proteins are recruited, activating transducers such as ATM, which in turn relay a widespread signal to a multitude of downstream effectors. ATM mutation causes Ataxia telangiectasia (AT), whereby the disease phenotype shows differing characteristics depending on the underlying ATM mutation. However, all phenotypes share progressive neurodegeneration and marked predisposition to malignancies at the organismal level and sensitivity to ionizing radiation and chromosome aberrations at the cellular level. Expression and localization of the ATM protein can be determined via western blotting and immunofluorescence microscopy; however, detection of subtle alterations such as resulting from amino acid exchanges rather than truncating mutations requires functional testing. Previous studies on the role of ATM in DSB repair, which connects with radiosensitivity and chromosomal stability, gave at first sight contradictory results. To systematically explore the effects of clinically relevant ATM mutations on DSB repair, we engaged a series of lymphoblastoid cell lines (LCLs) derived from AT patients and controls. To examine DSB repair both in a quantitative and qualitative manners, we used an EGFP-based assay comprising different substrates for distinct DSB repair mechanisms. In this way, we demonstrated that particular signaling defects caused by individual ATM mutations led to specific DSB repair phenotypes. To explore the impact of ATM on carcinogenic chromosomal aberrations, we monitored chromosomal breakage at a breakpoint cluster region hotspot within the MLL gene that has been associated with therapy-related leukemia. PCR-based MLL-breakage analysis of HeLa cells

  8. Excision of gamma-ray induced thymine lesions by preparations from ataxia telangiectasia fibroblasts

    Energy Technology Data Exchange (ETDEWEB)

    Remsen, J F; Cerutti, P A [Florida Univ., Gainesville (USA). Inst. of Food and Agricultural Sciences; Florida Univ., Gainesville (USA). Dept. of Biochemistry)

    1977-04-01

    The capacity of whole cell sonicates of skin fibroblasts of normal individuals and patients with the autosomal recessive disease Ataxia telangiectasia (AT) to remove aerobic gamma-ray products of the 5,6-dihydroxydihydrothymine type (tsub(O/sub 2/)sup(..gamma..)) from exogenous DNA substrates was investigated. All four AT strains (AT CRL 1312, AT CRL 1343, AT GM 367, AT 4BI) possessed normal capabilities to excise tsub(O/sub 2/)sup(..gamma..) from irradiated bacteriophage DNA and irradiated chromatin isolated from normal and AT-skin fibroblasts.

  9. Regulation of the DNA Damage Response by DNA-PKcs Inhibitory Phosphorylation of ATM.

    Science.gov (United States)

    Zhou, Yi; Lee, Ji-Hoon; Jiang, Wenxia; Crowe, Jennie L; Zha, Shan; Paull, Tanya T

    2017-01-05

    Ataxia-telangiectasia mutated (ATM) regulates the DNA damage response as well as DNA double-strand break repair through homologous recombination. Here we show that ATM is hyperactive when the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) is chemically inhibited or when the DNA-PKcs gene is deleted in human cells. Pre-incubation of ATM protein with active DNA-PKcs also significantly reduces ATM activity in vitro. We characterize several phosphorylation sites in ATM that are targets of DNA-PKcs and show that phospho-mimetic mutations at these residues significantly inhibit ATM activity and impair ATM signaling upon DNA damage. In contrast, phospho-blocking mutations at one cluster of sites increase the frequency of apoptosis during normal cell growth. DNA-PKcs, which is integral to the non-homologous end joining pathway, thus negatively regulates ATM activity through phosphorylation of ATM. These observations illuminate an important regulatory mechanism for ATM that also controls DNA repair pathway choice. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. An ATM-independent S-phase checkpoint response involves CHK1 pathway

    Science.gov (United States)

    Zhou, Xiang-Yang; Wang, Xiang; Hu, Baocheng; Guan, Jun; Iliakis, George; Wang, Ya

    2002-01-01

    After exposure to genotoxic stress, proliferating cells actively slow down the DNA replication through a S-phase checkpoint to provide time for repair. We report that in addition to the ataxia-telangiectasia mutated (ATM)-dependent pathway that controls the fast response, there is an ATM-independent pathway that controls the slow response to regulate the S-phase checkpoint after ionizing radiation in mammalian cells. The slow response of S-phase checkpoint, which is resistant to wortmannin, sensitive to caffeine and UCN-01, and related to cyclin-dependent kinase phosphorylation, is much stronger in CHK1 overexpressed cells, and it could be abolished by Chk1 antisense oligonucleotides. These results provide evidence that the ATM-independent slow response of S-phase checkpoint involves CHK1 pathway.

  11. ATM-dependent pathways of chromatin remodelling and oxidative DNA damage responses.

    Science.gov (United States)

    Berger, N Daniel; Stanley, Fintan K T; Moore, Shaun; Goodarzi, Aaron A

    2017-10-05

    Ataxia-telangiectasia mutated (ATM) is a serine/threonine protein kinase with a master regulatory function in the DNA damage response. In this role, ATM commands a complex biochemical network that signals the presence of oxidative DNA damage, including the dangerous DNA double-strand break, and facilitates subsequent repair. Here, we review the current state of knowledge regarding ATM-dependent chromatin remodelling and epigenomic alterations that are required to maintain genomic integrity in the presence of DNA double-strand breaks and/or oxidative stress. We will focus particularly on the roles of ATM in adjusting nucleosome spacing at sites of unresolved DNA double-strand breaks within complex chromatin environments, and the impact of ATM on preserving the health of cells within the mammalian central nervous system.This article is part of the themed issue 'Chromatin modifiers and remodellers in DNA repair and signalling'. © 2017 The Author(s).

  12. ATM regulation of IL-8 links oxidative stress to cancer cell migration and invasion.

    Science.gov (United States)

    Chen, Wei-Ta; Ebelt, Nancy D; Stracker, Travis H; Xhemalce, Blerta; Van Den Berg, Carla L; Miller, Kyle M

    2015-06-01

    Ataxia-telangiectasia mutated (ATM) protein kinase regulates the DNA damage response (DDR) and is associated with cancer suppression. Here we report a cancer-promoting role for ATM. ATM depletion in metastatic cancer cells reduced cell migration and invasion. Transcription analyses identified a gene network, including the chemokine IL-8, regulated by ATM. IL-8 expression required ATM and was regulated by oxidative stress. IL-8 was validated as an ATM target by its ability to rescue cell migration and invasion defects in ATM-depleted cells. Finally, ATM-depletion in human breast cancer cells reduced lung tumors in a mouse xenograft model and clinical data validated IL-8 in lung metastasis. These findings provide insights into how ATM activation by oxidative stress regulates IL-8 to sustain cell migration and invasion in cancer cells to promote metastatic potential. Thus, in addition to well-established roles in tumor suppression, these findings identify a role for ATM in tumor progression.

  13. Identification of p32 as a novel substrate for ATM in heart

    International Nuclear Information System (INIS)

    Kato, Hisakazu; Takashima, Seiji; Asano, Yoshihiro; Shintani, Yasunori; Yamazaki, Satoru; Seguchi, Osamu; Yamamoto, Hiroyuki; Nakano, Atsushi; Higo, Shuichiro; Ogai, Akiko; Minamino, Tetsuo; Kitakaze, Masafumi; Hori, Masatsugu

    2008-01-01

    Chemotherapeutic agents to induce DNA damage have been limited to use due to severe side effects of cardiotoxicity. ATM (Ataxia-telangiectasia mutated) is an essential protein kinase in triggering DNA damage responses. However, it is unclear how the ATM-mediated DNA damage responses are involved in the cardiac cell damage. To elucidate these functions in heart, we searched for specific substrates of ATM from mouse heart homogenate. Combining an in vitro phosphorylation following anion-exchange chromatography with purification by reverse-phase high-performance liquid chromatography (HPLC), we successfully identified p32, an ASF/SF2-associated protein, as a novel substrate for ATM. An in vitro kinase assay using recombinant p32 revealed that ATM directly phosphorylated p32. Furthermore, we determined Ser 148 of p32 as an ATM phosphorylation site. Since p32 is known to regulate mRNA splicing and transcription, p32 phosphorylation by ATM might be a new transcriptional regulatory pathway for specific DNA damage responses in heart

  14. Phosphorylation of p300 by ATM controls the stability of NBS1

    International Nuclear Information System (INIS)

    Jang, Eun Ryoung; Choi, Jae Duk; Jeong, Gajin; Lee, Jong-Soo

    2010-01-01

    Acetyltransferase, p300 is a transcriptional cofactor of signal-responsive transcriptional regulation. The surveillance kinase ataxia-telangiectasia mutated (ATM) plays a central role in regulation of a wide range of cellular DNA damage responses. Here, we investigated whether and how ATM mediates phosphorylation of p300 in response to DNA damage and how p300 phosphorylation is functionally linked to DNA damage. ATM-phosphorylated p300 in vitro and in vivo, in response to DNA damage. Phosphorylation of p300 proteins was observed upon γ-irradiation in ATM + cells but not ATM - cells. Importantly, expression of nonphosphorylatable serine to alanine form of p300 (S106A) destabilized both p300 and NBS1 proteins, after DNA damage. These data demonstrate that ATM transduces a DNA damage signal to p300, and that ATM-dependent phosphorylation of p300 is required for stabilization of NBS1 proteins in response to DNA damage.

  15. Alterations in cellular energy metabolism associated with the antiproliferative effects of the ATM inhibitor KU-55933 and with metformin.

    Directory of Open Access Journals (Sweden)

    Mahvash Zakikhani

    Full Text Available KU-55933 is a specific inhibitor of the kinase activity of the protein encoded by Ataxia telangiectasia mutated (ATM, an important tumor suppressor gene with key roles in DNA repair. Unexpectedly for an inhibitor of a tumor suppressor gene, KU-55933 reduces proliferation. In view of prior preliminary evidence suggesting defective mitochondrial function in cells of patients with Ataxia Telangiectasia (AT, we examined energy metabolism of cells treated with KU-55933. The compound increased AMPK activation, glucose uptake and lactate production while reducing mitochondrial membrane potential and coupled respiration. The stimulation of glycolysis by KU-55933 did not fully compensate for the reduction in mitochondrial functions, leading to decreased cellular ATP levels and energy stress. These actions are similar to those previously described for the biguanide metformin, a partial inhibitor of respiratory complex I. Both compounds decreased mitochondrial coupled respiration and reduced cellular concentrations of fumarate, malate, citrate, and alpha-ketogluterate. Succinate levels were increased by KU-55933 levels and decreased by metformin, indicating that the effects of ATM inhibition and metformin are not identical. These observations suggest a role for ATM in mitochondrial function and show that both KU-55933 and metformin perturb the TCA cycle as well as oxidative phosphorylation.

  16. Reactive Oxygen Species (ROS)-Activated ATM-Dependent Phosphorylation of Cytoplasmic Substrates Identified by Large-Scale Phosphoproteomics Screen*

    Science.gov (United States)

    Kozlov, Sergei V.; Waardenberg, Ashley J.; Engholm-Keller, Kasper; Arthur, Jonathan W.; Graham, Mark E.; Lavin, Martin

    2016-01-01

    Ataxia-telangiectasia, mutated (ATM) protein plays a central role in phosphorylating a network of proteins in response to DNA damage. These proteins function in signaling pathways designed to maintain the stability of the genome and minimize the risk of disease by controlling cell cycle checkpoints, initiating DNA repair, and regulating gene expression. ATM kinase can be activated by a variety of stimuli, including oxidative stress. Here, we confirmed activation of cytoplasmic ATM by autophosphorylation at multiple sites. Then we employed a global quantitative phosphoproteomics approach to identify cytoplasmic proteins altered in their phosphorylation state in control and ataxia-telangiectasia (A-T) cells in response to oxidative damage. We demonstrated that ATM was activated by oxidative damage in the cytoplasm as well as in the nucleus and identified a total of 9,833 phosphorylation sites, including 6,686 high-confidence sites mapping to 2,536 unique proteins. A total of 62 differentially phosphorylated peptides were identified; of these, 43 were phosphorylated in control but not in A-T cells, and 19 varied in their level of phosphorylation. Motif enrichment analysis of phosphopeptides revealed that consensus ATM serine glutamine sites were overrepresented. When considering phosphorylation events, only observed in control cells (not observed in A-T cells), with predicted ATM sites phosphoSerine/phosphoThreonine glutamine, we narrowed this list to 11 candidate ATM-dependent cytoplasmic proteins. Two of these 11 were previously described as ATM substrates (HMGA1 and UIMCI/RAP80), another five were identified in a whole cell extract phosphoproteomic screens, and the remaining four proteins had not been identified previously in DNA damage response screens. We validated the phosphorylation of three of these proteins (oxidative stress responsive 1 (OSR1), HDGF, and ccdc82) as ATM dependent after H2O2 exposure, and another protein (S100A11) demonstrated ATM

  17. Radioresistance of chordoma cells is associated with the ATM/ATR pathway, in which RAD51 serves as an important downstream effector.

    Science.gov (United States)

    Zhang, Chao; Wang, Bing; Li, Lei; Li, Yawei; Li, Pengzhi; Lv, Guohua

    2017-09-01

    Surgery followed by radiotherapy is the standard treatment for chordomas, which are a rare but low-grade type of bone cancer arising from remnants of the embryonic notochord. However, disease recurrence following radiotherapy is common, most likely due to endogenous DNA repair mechanisms that promote cell survival upon radiation strikes. The ataxia telangiectasia mutated/ataxia telangiectasia mutated and Rad3 related (ATM/ATR)-mediated pathway has a critical role in DNA repair mechanisms; however, it has rarely been investigated in chordomas. In the present study, the expression of signal molecules related to the ATM/ATR pathway in chordoma tissues and adjacent normal tissues were initially examined using immunohistochemistry and western blot analysis. Chordoma U-CH1 and U-CH2 cells were subsequently used to investigate cell responses to ionizing radiation and the potential protective actions mediated by the ATM/ATR pathway. Phosphorylated (p)-ATM, p-ATR, γ-H2A histone family, member X (H2AX) and RAD51 were significantly upregulated in chordoma tissues relative to adjacent normal tissues (PATM, γ-H2AX and RAD51 expression in U-CH1 cells (PATM, p-ATR and RAD51 levels in U-CH2 cells (PATM/ATR pathway, in which RAD51 serves as an important downstream effector. Thus, RAD51 presents a promising therapeutic target for improving the outcome of radiotherapy treatment in chordomas.

  18. Absence of ERK5/MAPK7 delays tumorigenesis in Atm-/- mice.

    Science.gov (United States)

    Granados-Jaén, Alba; Angulo-Ibáñez, Maria; Rovira-Clavé, Xavier; Gamez, Celina Paola Vasquez; Soriano, Francesc X; Reina, Manuel; Espel, Enric

    2016-11-15

    Ataxia-telangiectasia mutated (ATM) is a cell cycle checkpoint kinase that upon activation by DNA damage leads to cell cycle arrest and DNA repair or apoptosis. The absence of Atm or the occurrence of loss-of-function mutations in Atm predisposes to tumorigenesis. MAPK7 has been implicated in numerous types of cancer with pro-survival and pro-growth roles in tumor cells, but its functional relation with tumor suppressors is not clear. In this study, we show that absence of MAPK7 delays death due to spontaneous tumor development in Atm-/- mice. Compared with Atm-/- thymocytes, Mapk7-/-Atm-/- thymocytes exhibited an improved response to DNA damage (increased phosphorylation of H2AX) and a restored apoptotic response after treatment of mice with ionizing radiation. These findings define an antagonistic function of ATM and MAPK7 in the thymocyte response to DNA damage, and suggest that the lack of MAPK7 inhibits thymic lymphoma growth in Atm-/- mice by partially restoring the DNA damage response in thymocytes.

  19. Tug of War between Survival and Death: Exploring ATM Function in Cancer

    Science.gov (United States)

    Stagni, Venturina; Oropallo, Veronica; Fianco, Giulia; Antonelli, Martina; Cinà, Irene; Barilà, Daniela

    2014-01-01

    Ataxia-telangiectasia mutated (ATM) kinase is a one of the main guardian of genome stability and plays a central role in the DNA damage response (DDR). The deregulation of these pathways is strongly linked to cancer initiation and progression as well as to the development of therapeutic approaches. These observations, along with reports that identify ATM loss of function as an event that may promote tumor initiation and progression, point to ATM as a bona fide tumor suppressor. The identification of ATM as a positive modulator of several signalling networks that sustain tumorigenesis, including oxidative stress, hypoxia, receptor tyrosine kinase and AKT serine-threonine kinase activation, raise the question of whether ATM function in cancer may be more complex. This review aims to give a complete overview on the work of several labs that links ATM to the control of the balance between cell survival, proliferation and death in cancer. PMID:24681585

  20. Tug of War between Survival and Death: Exploring ATM Function in Cancer

    Directory of Open Access Journals (Sweden)

    Venturina Stagni

    2014-03-01

    Full Text Available Ataxia-telangiectasia mutated (ATM kinase is a one of the main guardian of genome stability and plays a central role in the DNA damage response (DDR. The deregulation of these pathways is strongly linked to cancer initiation and progression as well as to the development of therapeutic approaches. These observations, along with reports that identify ATM loss of function as an event that may promote tumor initiation and progression, point to ATM as a bona fide tumor suppressor. The identification of ATM as a positive modulator of several signalling networks that sustain tumorigenesis, including oxidative stress, hypoxia, receptor tyrosine kinase and AKT serine-threonine kinase activation, raise the question of whether ATM function in cancer may be more complex. This review aims to give a complete overview on the work of several labs that links ATM to the control of the balance between cell survival, proliferation and death in cancer.

  1. Requirement of the ATM/p53 tumor suppressor pathway for glucose homeostasis.

    Science.gov (United States)

    Armata, Heather L; Golebiowski, Diane; Jung, Dae Young; Ko, Hwi Jin; Kim, Jason K; Sluss, Hayla K

    2010-12-01

    Ataxia telangiectasia (A-T) patients can develop multiple clinical pathologies, including neuronal degeneration, an elevated risk of cancer, telangiectasias, and growth retardation. Patients with A-T can also exhibit an increased risk of insulin resistance and type 2 diabetes. The ATM protein kinase, the product of the gene mutated in A-T patients (Atm), has been implicated in metabolic disease, which is characterized by insulin resistance and increased cholesterol and lipid levels, blood pressure, and atherosclerosis. ATM phosphorylates the p53 tumor suppressor on a site (Ser15) that regulates transcription activity. To test whether the ATM pathway that regulates insulin resistance is mediated by p53 phosphorylation, we examined insulin sensitivity in mice with a germ line mutation that replaces the p53 phosphorylation site with alanine. The loss of p53 Ser18 (murine Ser15) led to increased metabolic stress, including severe defects in glucose homeostasis. The mice developed glucose intolerance and insulin resistance. The insulin resistance correlated with the loss of antioxidant gene expression and decreased insulin signaling. N-Acetyl cysteine (NAC) treatment restored insulin signaling in late-passage primary fibroblasts. The addition of an antioxidant in the diet rendered the p53 Ser18-deficient mice glucose tolerant. This analysis demonstrates that p53 phosphorylation on an ATM site is an important mechanism in the physiological regulation of glucose homeostasis.

  2. ERS statement on the multidisciplinary respiratory management of ataxia telangiectasia

    Directory of Open Access Journals (Sweden)

    Jayesh M. Bhatt

    2015-12-01

    Full Text Available Ataxia telangiectasia (A-T is a rare, progressive, multisystem disease that has a large number of complex and diverse manifestations which vary with age. Patients with A-T die prematurely with the leading causes of death being respiratory diseases and cancer. Respiratory manifestations include immune dysfunction leading to recurrent upper and lower respiratory infections; aspiration resulting from dysfunctional swallowing due to neurodegenerative deficits; inefficient cough; and interstitial lung disease/pulmonary fibrosis. Malnutrition is a significant comorbidity. The increased radiosensitivity and increased risk of cancer should be borne in mind when requesting radiological investigations. Aggressive proactive monitoring and treatment of these various aspects of lung disease under multidisciplinary expertise in the experience of national multidisciplinary clinics internationally forms the basis of this statement on the management of lung disease in A-T. Neurological management is outwith the scope of this document.

  3. Small Molecules Targeting Ataxia Telangiectasia and Rad3-Related (ATR) Kinase: An Emerging way to Enhance Existing Cancer Therapy

    Czech Academy of Sciences Publication Activity Database

    Andrs, M.; Korábečný, J.; Nepovimova, E.; Jun, D.; Hodný, Zdeněk; Kuca, K.

    2016-01-01

    Roč. 16, č. 3 (2016), s. 200-208 ISSN 1568-0096 Institutional support: RVO:68378050 Keywords : Ataxia telangiectasia and Rad3-related kinase (ATR) * cancer * chemosensitization * DNA damage response * phosphatidylinositol 3-kinase-related protein kinases (PIKK) * radiosensitization * synthetic lethality Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.992, year: 2016

  4. Drosophila atm/telomere fusion is required for telomeric localization of HP1 and telomere position effect

    OpenAIRE

    Oikemus, Sarah R.; McGinnis, Nadine; Queiroz-Machado, Joana; Tukachinsky, Hanna; Takada, Saeko; Sunkel, Claudio E.; Brodsky, Michael H.

    2004-01-01

    Terminal deletions of Drosophila chromosomes can be stably protected from end-to-end fusion despite the absence of all telomere-associated sequences. The sequence-independent protection of these telomeres suggests that recognition of chromosome ends might contribute to the epigenetic protection of telomeres. In mammals, Ataxia Telangiectasia Mutated (ATM) is activated by DNA damage and acts through an unknown, telomerase-independent mechanism to regulate telomere length and protection. We dem...

  5. Structures of closed and open conformations of dimeric human ATM

    Science.gov (United States)

    Baretić, Domagoj; Pollard, Hannah K.; Fisher, David I.; Johnson, Christopher M.; Santhanam, Balaji; Truman, Caroline M.; Kouba, Tomas; Fersht, Alan R.; Phillips, Christopher; Williams, Roger L.

    2017-01-01

    ATM (ataxia-telangiectasia mutated) is a phosphatidylinositol 3-kinase–related protein kinase (PIKK) best known for its role in DNA damage response. ATM also functions in oxidative stress response, insulin signaling, and neurogenesis. Our electron cryomicroscopy (cryo-EM) suggests that human ATM is in a dynamic equilibrium between closed and open dimers. In the closed state, the PIKK regulatory domain blocks the peptide substrate–binding site, suggesting that this conformation may represent an inactive or basally active enzyme. The active site is held in this closed conformation by interaction with a long helical hairpin in the TRD3 (tetratricopeptide repeats domain 3) domain of the symmetry-related molecule. The open dimer has two protomers with only a limited contact interface, and it lacks the intermolecular interactions that block the peptide-binding site in the closed dimer. This suggests that the open conformation may be more active. The ATM structure shows the detailed topology of the regulator-interacting N-terminal helical solenoid. The ATM conformational dynamics shown by the structures represent an important step in understanding the enzyme regulation. PMID:28508083

  6. The Landscape of Somatic Genetic Alterations in Breast Cancers From ATM Germline Mutation Carriers.

    Science.gov (United States)

    Weigelt, Britta; Bi, Rui; Kumar, Rahul; Blecua, Pedro; Mandelker, Diana L; Geyer, Felipe C; Pareja, Fresia; James, Paul A; Couch, Fergus J; Eccles, Diana M; Blows, Fiona; Pharoah, Paul; Li, Anqi; Selenica, Pier; Lim, Raymond S; Jayakumaran, Gowtham; Waddell, Nic; Shen, Ronglai; Norton, Larry; Wen, Hannah Y; Powell, Simon N; Riaz, Nadeem; Robson, Mark E; Reis-Filho, Jorge S; Chenevix-Trench, Georgia

    2018-02-28

    Pathogenic germline variants in ataxia-telangiectasia mutated (ATM), a gene that plays a role in DNA damage response and cell cycle checkpoints, confer an increased breast cancer (BC) risk. Here, we investigated the phenotypic characteristics and landscape of somatic genetic alterations in 24 BCs from ATM germline mutation carriers by whole-exome and targeted sequencing. ATM-associated BCs were consistently hormone receptor positive and largely displayed minimal immune infiltrate. Although 79.2% of these tumors exhibited loss of heterozygosity of the ATM wild-type allele, none displayed high activity of mutational signature 3 associated with defective homologous recombination DNA (HRD) repair. No TP53 mutations were found in the ATM-associated BCs. Analysis of an independent data set confirmed that germline ATM variants and TP53 somatic mutations are mutually exclusive. Our findings indicate that ATM-associated BCs often harbor bi-allelic inactivation of ATM, are phenotypically distinct from BRCA1/2-associated BCs, lack HRD-related mutational signatures, and that TP53 and ATM genetic alterations are likely epistatic.

  7. Molecular diagnosis of known recessive ataxias by homozygosity mapping with SNP arrays.

    Science.gov (United States)

    H'mida-Ben Brahim, D; M'zahem, A; Assoum, M; Bouhlal, Y; Fattori, F; Anheim, M; Ali-Pacha, L; Ferrat, F; Chaouch, M; Lagier-Tourenne, C; Drouot, N; Thibaut, C; Benhassine, T; Sifi, Y; Stoppa-Lyonnet, D; N'Guyen, K; Poujet, J; Hamri, A; Hentati, F; Amouri, R; Santorelli, F M; Tazir, M; Koenig, M

    2011-01-01

    The diagnosis of rare inherited diseases is becoming more and more complex as an increasing number of clinical conditions appear to be genetically heterogeneous. Multigenic inheritance also applies to the autosomal recessive progressive cerebellar ataxias (ARCAs), for which 14 genes have been identified and more are expected to be discovered. We used homozygosity mapping as a guide for identification of the defective locus in patients with ARCA born from consanguineous parents. Patients from 97 families were analyzed with GeneChip Mapping 10K or 50K SNP Affymetrix microarrays. We identified six families homozygous for regions containing the autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) gene, two families homozygous for the ataxia-telangiectasia gene (ATM), two families homozygous for the ataxia with oculomotor apraxia type 1 (AOA1) gene, and one family homozygous for the AOA type 2 (AOA2) gene. Upon direct gene testing, we were able to identify a disease-related mutation in all families but one of the two kindred homozygous at the ATM locus. Although linkage analyses pointed to a single locus on chromosome 11q22.1-q23.1 for this family, clinical features, normal levels of serum alpha-foetoprotein as well as absence of mutations in the ATM gene rather suggest the existence of an additional ARCA-related gene in that interval. While the use of homozygosity mapping was very effective at pointing to the correct gene, it also suggests that the majority of patients harbor mutations either in the genes of the rare forms of ARCA or in genes yet to be identified.

  8. Establishment of cell lines derived from ataxia telangiectasia and xeroderma pigmentosum patients with high radiation sensitivity

    International Nuclear Information System (INIS)

    Hashimoto, Tomoko; Furuyama, Jun-ichi; Nakano, Yoshiro; Owada, M. Koji; Kakunaga, Takeo

    1986-01-01

    Four human fibroblast cell lines, three of which were derived from a patient with ataxia telangiectasia and the other from a patient with xeroderma pigmentosum, were established after transfection with cloned SV40 DNA. These 4 cell lines showed some phenotypes characteristic of neoplastically transformed cells, and had a human karyotype with heteromorphisms identical to those of the parental fibroblasts. Their sensitivity to the cytotoxic effects of γ-rays or ultraviolet irradiation was as high as those of their parental fibroblasts. (Auth.)

  9. Ataxia telangiectasia: LET dependence of cellular inactivation

    International Nuclear Information System (INIS)

    Blakely, E.A.; Tobias, C.A.

    1984-01-01

    Human Ataxia telangiectasia cells (AT 2SF line) have been irradiated in vitro under aerobic and hypoxic conditions with heavy-ion beams accelerated at the Berkeley Bevalac as a part of a study to characterize the radiation responses of genetically sensitive and resistant cell lines to high LET radiations. Results from track-segment exposures to neon, silicon, argon and iron ion beams accelerated to initial energies of from 225 to 670 MeV/amu provided an LET range between 30 to 1,000 KeV/μm. The data indicate: (1) The sensitivity of AT cells increases with increasing LET, similar to resistant human lines (e.g., T-1 cells). However, due to efficient repair, T-1 cells are more resistant than AT cells at LET values below 200 keV/μm; (2) Maximum cell kill occurs for both lines at 100-200 keV/μm; at higher LET the sensitivity of the two lines approach each other; (3) There is only small variation in the sensitivity of AT cells to particles of various atomic numbers at the same LET; differences are more pronounced in the LET domain between 50 and 200 keV/μm; and (4) AT cells have slightly lower OER values than T-1 cells in the range of LET studied below 200 keV/μm

  10. Loss of ATM kinase activity leads to embryonic lethality in mice.

    Science.gov (United States)

    Daniel, Jeremy A; Pellegrini, Manuela; Lee, Baeck-Seung; Guo, Zhi; Filsuf, Darius; Belkina, Natalya V; You, Zhongsheng; Paull, Tanya T; Sleckman, Barry P; Feigenbaum, Lionel; Nussenzweig, André

    2012-08-06

    Ataxia telangiectasia (A-T) mutated (ATM) is a key deoxyribonucleic acid (DNA) damage signaling kinase that regulates DNA repair, cell cycle checkpoints, and apoptosis. The majority of patients with A-T, a cancer-prone neurodegenerative disease, present with null mutations in Atm. To determine whether the functions of ATM are mediated solely by its kinase activity, we generated two mouse models containing single, catalytically inactivating point mutations in Atm. In this paper, we show that, in contrast to Atm-null mice, both D2899A and Q2740P mutations cause early embryonic lethality in mice, without displaying dominant-negative interfering activity. Using conditional deletion, we find that the D2899A mutation in adult mice behaves largely similar to Atm-null cells but shows greater deficiency in homologous recombination (HR) as measured by hypersensitivity to poly (adenosine diphosphate-ribose) polymerase inhibition and increased genomic instability. These results may explain why missense mutations with no detectable kinase activity are rarely found in patients with classical A-T. We propose that ATM kinase-inactive missense mutations, unless otherwise compensated for, interfere with HR during embryogenesis.

  11. Downregulation of ATM Gene and Protein Expression in Canine Mammary Tumors.

    Science.gov (United States)

    Raposo-Ferreira, T M M; Bueno, R C; Terra, E M; Avante, M L; Tinucci-Costa, M; Carvalho, M; Cassali, G D; Linde, S D; Rogatto, S R; Laufer-Amorim, R

    2016-11-01

    The ataxia telangiectasia mutated (ATM) gene encodes a protein associated with DNA damage repair and maintenance of genomic integrity. In women, ATM transcript and protein downregulation have been reported in sporadic breast carcinomas, and the absence of ATM protein expression has been associated with poor prognosis. The aim of this study was to evaluate ATM gene and protein expression in canine mammary tumors and their association with clinical outcome. ATM gene and protein expression was evaluated by reverse transcription-quantitative polymerase chain reaction and immunohistochemistry, respectively, in normal mammary gland samples (n = 10), benign mammary tumors (n = 11), nonmetastatic mammary carcinomas (n = 19), and metastatic mammary carcinomas (n = 11). Lower ATM transcript levels were detected in benign mammary tumors and carcinomas compared with normal mammary glands (P = .011). Similarly, lower ATM protein expression was observed in benign tumors (P = .0003), nonmetastatic mammary carcinomas (P ATM gene or protein levels were detected among benign tumors and nonmetastatic and metastatic mammary carcinomas (P > .05). The levels of ATM gene or protein expression were not significantly associated with clinical and pathological features or with survival. Similar to human breast cancer, the data in this study suggest that ATM gene and protein downregulation is involved in canine mammary gland tumorigenesis. © The Author(s) 2016.

  12. ATM directs DNA damage responses and proteostasis via genetically separable pathways.

    Science.gov (United States)

    Lee, Ji-Hoon; Mand, Michael R; Kao, Chung-Hsuan; Zhou, Yi; Ryu, Seung W; Richards, Alicia L; Coon, Joshua J; Paull, Tanya T

    2018-01-09

    The protein kinase ATM is a master regulator of the DNA damage response but also responds directly to oxidative stress. Loss of ATM causes ataxia telangiectasia, a neurodegenerative disorder with pleiotropic symptoms that include cerebellar dysfunction, cancer, diabetes, and premature aging. We genetically separated the activation of ATM by DNA damage from that by oxidative stress using separation-of-function mutations. We found that deficient activation of ATM by the Mre11-Rad50-Nbs1 complex and DNA double-strand breaks resulted in loss of cell viability, checkpoint activation, and DNA end resection in response to DNA damage. In contrast, loss of oxidative activation of ATM had minimal effects on DNA damage-related outcomes but blocked ATM-mediated initiation of checkpoint responses after oxidative stress and resulted in deficiencies in mitochondrial function and autophagy. In addition, expression of a variant ATM incapable of activation by oxidative stress resulted in widespread protein aggregation. These results indicate a direct relationship between the mechanism of ATM activation and its effects on cellular metabolism and DNA damage responses in human cells and implicate ATM in the control of protein homeostasis. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  13. Mobile phone signal exposure triggers a hormesis-like effect in Atm+/+ and Atm-/- mouse embryonic fibroblasts.

    Science.gov (United States)

    Sun, Chuan; Wei, Xiaoxia; Fei, Yue; Su, Liling; Zhao, Xinyuan; Chen, Guangdi; Xu, Zhengping

    2016-11-18

    Radiofrequency electromagnetic fields (RF-EMFs) have been classified by the International Agency for Research on Cancer as possible carcinogens to humans; however, this conclusion is based on limited epidemiological findings and lacks solid support from experimental studies. In particular, there are no consistent data regarding the genotoxicity of RF-EMFs. Ataxia telangiectasia mutated (ATM) is recognised as a chief guardian of genomic stability. To address the debate on whether RF-EMFs are genotoxic, we compared the effects of 1,800 MHz RF-EMF exposure on genomic DNA in mouse embryonic fibroblasts (MEFs) with proficient (Atm +/+ ) or deficient (Atm -/- ) ATM. In Atm +/+ MEFs, RF-EMF exposure for 1 h at an average special absorption rate of 4.0 W/kg induced significant DNA single-strand breaks (SSBs) and activated the SSB repair mechanism. This effect reduced the DNA damage to less than that of the background level after 36 hours of exposure. In the Atm -/- MEFs, the same RF-EMF exposure for 12 h induced both SSBs and double-strand breaks and activated the two repair processes, which also reduced the DNA damage to less than the control level after prolonged exposure. The observed phenomenon is similar to the hormesis of a toxic substance at a low dose. To the best of our knowledge, this study is the first to report a hormesis-like effect of an RF-EMF.

  14. The ATM signaling network in development and disease

    Science.gov (United States)

    Stracker, Travis H.; Roig, Ignasi; Knobel, Philip A.; Marjanović, Marko

    2013-01-01

    The DNA damage response (DDR) rapidly recognizes DNA lesions and initiates the appropriate cellular programs to maintain genome integrity. This includes the coordination of cell cycle checkpoints, transcription, translation, DNA repair, metabolism, and cell fate decisions, such as apoptosis or senescence (Jackson and Bartek, 2009). DNA double-strand breaks (DSBs) represent one of the most cytotoxic DNA lesions and defects in their metabolism underlie many human hereditary diseases characterized by genomic instability (Stracker and Petrini, 2011; McKinnon, 2012). Patients with hereditary defects in the DDR display defects in development, particularly affecting the central nervous system, the immune system and the germline, as well as aberrant metabolic regulation and cancer predisposition. Central to the DDR to DSBs is the ataxia-telangiectasia mutated (ATM) kinase, a master controller of signal transduction. Understanding how ATM signaling regulates various aspects of the DDR and its roles in vivo is critical for our understanding of human disease, its diagnosis and its treatment. This review will describe the general roles of ATM signaling and highlight some recent advances that have shed light on the diverse roles of ATM and related proteins in human disease. PMID:23532176

  15. ATM-mediated transcriptional and developmental responses to gamma-rays in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Lilian Ricaud

    Full Text Available ATM (Ataxia Telangiectasia Mutated is an essential checkpoint kinase that signals DNA double-strand breaks in eukaryotes. Its depletion causes meiotic and somatic defects in Arabidopsis and progressive motor impairment accompanied by several cell deficiencies in patients with ataxia telangiectasia (AT. To obtain a comprehensive view of the ATM pathway in plants, we performed a time-course analysis of seedling responses by combining confocal laser scanning microscopy studies of root development and genome-wide expression profiling of wild-type (WT and homozygous ATM-deficient mutants challenged with a dose of gamma-rays (IR that is sublethal for WT plants. Early morphologic defects in meristematic stem cells indicated that AtATM, an Arabidopsis homolog of the human ATM gene, is essential for maintaining the quiescent center and controlling the differentiation of initial cells after exposure to IR. Results of several microarray experiments performed with whole seedlings and roots up to 5 h post-IR were compiled in a single table, which was used to import gene information and extract gene sets. Sequence and function homology searches; import of spatio-temporal, cell cycling, and mutant-constitutive expression characteristics; and a simplified functional classification system were used to identify novel genes in all functional classes. The hundreds of radiomodulated genes identified were not a random collection, but belonged to functional pathways such as those of the cell cycle; cell death and repair; DNA replication, repair, and recombination; and transcription; translation; and signaling, indicating the strong cell reprogramming and double-strand break abrogation functions of ATM checkpoints. Accordingly, genes in all functional classes were either down or up-regulated concomitantly with downregulation of chromatin deacetylases or upregulation of acetylases and methylases, respectively. Determining the early transcriptional indicators of

  16. ATM function and its relationship with ATM gene mutations in chronic lymphocytic leukemia with the recurrent deletion (11q22.3-23.2).

    Science.gov (United States)

    Jiang, Y; Chen, H-C; Su, X; Thompson, P A; Liu, X; Do, K-A; Wierda, W; Keating, M J; Plunkett, W

    2016-09-02

    Approximately 10-20% of chronic lymphocytic leukemia (CLL) patients exhibit del(11q22-23) before treatment, this cohort increases to over 40% upon progression following chemoimmunotherapy. The coding sequence of the DNA damage response gene, ataxia-telangiectasia-mutated (ATM), is contained in this deletion. The residual ATM allele is frequently mutated, suggesting a relationship between gene function and clinical response. To investigate this possibility, we sought to develop and validate an assay for the function of ATM protein in these patients. SMC1 (structural maintenance of chromosomes 1) and KAP1 (KRAB-associated protein 1) were found to be unique substrates of ATM kinase by immunoblot detection following ionizing radiation. Using a pool of eight fluorescence in situ hybridization-negative CLL samples as a standard, the phosphorylation of SMC1 and KAP1 from 46 del (11q22-23) samples was analyzed using normal mixture model-based clustering. This identified 13 samples (28%) that were deficient in ATM function. Targeted sequencing of the ATM gene of these samples, with reference to genomic DNA, revealed 12 somatic mutations and 15 germline mutations in these samples. No strong correlation was observed between ATM mutation and function. Therefore, mutation status may not be taken as an indicator of ATM function. Rather, a direct assay of the kinase activity should be used in the development of therapies.

  17. The response of normal and ataxia-telangiectasia human fibroblasts to the lethal effects of far, mid and near ultraviolet radiations

    International Nuclear Information System (INIS)

    Keyse, S.M.; McAleer, M.A.; Davies, D.J.G.; Moss, S.H.

    1985-01-01

    The responses of two ataxia-telangiectasia (A-T) cell strains to the lethal effects of monochromatic far, mid and near ultraviolet radiations have been determined and compared with the responses of three normal human cell strains. The authors results confirm a previous observation that the A-T cell strain AT4BI is abnormally sensitive to the lethal effects of mid u.v. (313 nm) radiation. After far u.v. (254 nm) radiation the strain AT4BI exhibits a small but statistically significant increase in sensitivity compared to the normal strains. Of most interest, in terms of a mechanistic interpretation of the sensitivity of A-T strains, the survival responses of neither A-T strain tested to near u.v. (365 nm) radiation differed significantly from the mean response of the normal strains, although it is of interest that one normal strain (48BR) was found to be significantly more resistant to near u.v. radiation than any of the other strains tested. The results are discussed in terms of the possible induction of radiogenic lesions in DNA by ultraviolet radiations and the possible mechanisms of radiation sensitivity in ataxia-telangiectasia. (author)

  18. Poly(ADP-ribose) polymerase-1 inhibits ATM kinase activity in DNA damage response

    International Nuclear Information System (INIS)

    Watanabe, Fumiaki; Fukazawa, Hidesuke; Masutani, Mitsuko; Suzuki, Hiroshi; Teraoka, Hirobumi; Mizutani, Shuki; Uehara, Yoshimasa

    2004-01-01

    DNA double-strand breaks (DSB) mobilize DNA-repair machinery and cell cycle checkpoint by activating the ataxia-telangiectasia (A-T) mutated (ATM). Here we show that ATM kinase activity is inhibited by poly(ADP-ribose) polymerase-1 (PARP-1) in vitro. It was shown by biochemical fractionation procedure that PARP-1 as well as ATM increases at chromatin level after induction of DSB with neocarzinostatin (NCS). Phosphorylation of histone H2AX on serine 139 and p53 on serine 15 in Parp-1 knockout (Parp-1 -/- ) mouse embryonic fibroblasts (MEF) was significantly induced by NCS treatment compared with MEF derived from wild-type (Parp-1 +/+ ) mouse. NCS-induced phosphorylation of histone H2AX on serine 139 in Parp-1 -/- embryonic stem cell (ES) clones was also higher than that in Parp-1 +/+ ES clone. Furthermore, in vitro, PARP-1 inhibited phosphorylation of p53 on serine 15 and 32 P-incorporation into p53 by ATM in a DNA-dependent manner. These results suggest that PARP-1 negatively regulates ATM kinase activity in response to DSB

  19. Drosophila atm/telomere fusion is required for telomeric localization of HP1 and telomere position effect.

    Science.gov (United States)

    Oikemus, Sarah R; McGinnis, Nadine; Queiroz-Machado, Joana; Tukachinsky, Hanna; Takada, Saeko; Sunkel, Claudio E; Brodsky, Michael H

    2004-08-01

    Terminal deletions of Drosophila chromosomes can be stably protected from end-to-end fusion despite the absence of all telomere-associated sequences. The sequence-independent protection of these telomeres suggests that recognition of chromosome ends might contribute to the epigenetic protection of telomeres. In mammals, Ataxia Telangiectasia Mutated (ATM) is activated by DNA damage and acts through an unknown, telomerase-independent mechanism to regulate telomere length and protection. We demonstrate that the Drosophila homolog of ATM is encoded by the telomere fusion (tefu) gene. In the absence of ATM, telomere fusions occur even though telomere-specific Het-A sequences are still present. High levels of spontaneous apoptosis are observed in ATM-deficient tissues, indicating that telomere dysfunction induces apoptosis in Drosophila. Suppression of this apoptosis by p53 mutations suggests that loss of ATM activates apoptosis through a DNA damage-response mechanism. Loss of ATM reduces the levels of heterochromatin protein 1 (HP1) at telomeres and suppresses telomere position effect. We propose that recognition of chromosome ends by ATM prevents telomere fusion and apoptosis by recruiting chromatin-modifying complexes to telomeres.

  20. Molecular Imaging of the ATM Kinase Activity

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Terence M. [Department of Radiation Oncology, Ohio State University, Columbus, Ohio (United States); Nyati, Shyam [Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor, Michigan (United States); Center for Molecular Imaging, University of Michigan Medical Center, Ann Arbor, Michigan (United States); Ross, Brian D. [Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor, Michigan (United States); Department of Radiology, University of Michigan Medical Center, Ann Arbor, Michigan (United States); Rehemtulla, Alnawaz, E-mail: alnawaz@umich.edu [Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor, Michigan (United States); Center for Molecular Imaging, University of Michigan Medical Center, Ann Arbor, Michigan (United States); Department of Radiology, University of Michigan Medical Center, Ann Arbor, Michigan (United States)

    2013-08-01

    Purpose: Ataxia telangiectasia mutated (ATM) is a serine/threonine kinase critical to the cellular DNA-damage response, including from DNA double-strand breaks. ATM activation results in the initiation of a complex cascade of events including DNA damage repair, cell cycle checkpoint control, and survival. We sought to create a bioluminescent reporter that dynamically and noninvasively measures ATM kinase activity in living cells and subjects. Methods and Materials: Using the split luciferase technology, we constructed a hybrid cDNA, ATM-reporter (ATMR), coding for a protein that quantitatively reports on changes in ATM kinase activity through changes in bioluminescence. Results: Treatment of ATMR-expressing cells with ATM inhibitors resulted in a dose-dependent increase in bioluminescence activity. In contrast, induction of ATM kinase activity upon irradiation resulted in a decrease in reporter activity that correlated with ATM and Chk2 activation by immunoblotting in a time-dependent fashion. Nuclear targeting improved ATMR sensitivity to both ATM inhibitors and radiation, whereas a mutant ATMR (lacking the target phosphorylation site) displayed a muted response. Treatment with ATM inhibitors and small interfering (si)RNA-targeted knockdown of ATM confirm the specificity of the reporter. Using reporter expressing xenografted tumors demonstrated the ability of ATMR to report in ATM activity in mouse models that correlated in a time-dependent fashion with changes in Chk2 activity. Conclusions: We describe the development and validation of a novel, specific, noninvasive bioluminescent reporter that enables monitoring of ATM activity in real time, in vitro and in vivo. Potential applications of this reporter include the identification and development of novel ATM inhibitors or ATM-interacting partners through high-throughput screens and in vivo pharmacokinetic/pharmacodynamic studies of ATM inhibitors in preclinical models.

  1. Quantitative and Dynamic Imaging of ATM Kinase Activity.

    Science.gov (United States)

    Nyati, Shyam; Young, Grant; Ross, Brian Dale; Rehemtulla, Alnawaz

    2017-01-01

    Ataxia telangiectasia mutated (ATM) is a serine/threonine kinase critical to the cellular DNA-damage response, including DNA double-strand breaks (DSBs). ATM activation results in the initiation of a complex cascade of events facilitating DNA damage repair, cell cycle checkpoint control, and survival. Traditionally, protein kinases have been analyzed in vitro using biochemical methods (kinase assays using purified proteins or immunological assays) requiring a large number of cells and cell lysis. Genetically encoded biosensors based on optical molecular imaging such as fluorescence or bioluminescence have been developed to enable interrogation of kinase activities in live cells with a high signal to background. We have genetically engineered a hybrid protein whose bioluminescent activity is dependent on the ATM-mediated phosphorylation of a substrate. The engineered protein consists of the split luciferase-based protein complementation pair with a CHK2 (a substrate for ATM kinase activity) target sequence and a phospho-serine/threonine-binding domain, FHA2, derived from yeast Rad53. Phosphorylation of the serine residue within the target sequence by ATM would lead to its interaction with the phospho-serine-binding domain, thereby preventing complementation of the split luciferase pair and loss of reporter activity. Bioluminescence imaging of reporter expressing cells in cultured plates or as mouse xenografts provides a quantitative surrogate for ATM kinase activity and therefore the cellular DNA damage response in a noninvasive, dynamic fashion.

  2. The association between ATM IVS 22-77 T>C and cancer risk: a meta-analysis.

    Directory of Open Access Journals (Sweden)

    Lin Zhao

    Full Text Available BACKGROUND AND OBJECTIVES: It has become increasingly clear that ATM (ataxia-telangiectasia-mutated safeguards genome stability, which is a cornerstone of cellular homeostasis, and ATM IVS 22-77 T>C affects the normal activity of ATM proteins. However, the association between the ATM IVS 22-77 T>C genetic variant and cancer risk is controversial. Therefore, we conducted a systematic meta-analysis to estimate the overall cancer risk associated with the polymorphism and to quantify any potential between-study heterogeneity. METHODS: A total of nine studies including 4,470 cases and 4,862 controls were analyzed for ATM IVS 22-77 T>C association with cancer risk in this meta-analysis. Heterogeneity among articles and their publication bias were also tested. RESULTS: Our results showed that no association reached the level of statistical significance in the overall risk. Interestingly, in the stratified analyses, we observed an inverse relationship in lung and breast cancer. CONCLUSION: Further functional research on the ATM mechanism should be performed to explain the inconsistent results in different cancer types.

  3. Distinct roles of ATM and ATR in the regulation of ARP8 phosphorylation to prevent chromosome translocations.

    Science.gov (United States)

    Sun, Jiying; Shi, Lin; Kinomura, Aiko; Fukuto, Atsuhiko; Horikoshi, Yasunori; Oma, Yukako; Harata, Masahiko; Ikura, Masae; Ikura, Tsuyoshi; Kanaar, Roland; Tashiro, Satoshi

    2018-05-08

    Chromosomal translocations are hallmarks of various types of cancers and leukemias. However, the molecular mechanisms of chromosome translocations remain largely unknown. The ataxia-telangiectasia mutated (ATM) protein, a DNA damage signaling regulator, facilitates DNA repair to prevent chromosome abnormalities. Previously, we showed that ATM deficiency led to the 11q23 chromosome translocation, the most frequent chromosome abnormalities in secondary leukemia. Here, we show that ARP8, a subunit of the INO80 chromatin remodeling complex, is phosphorylated after etoposide treatment. The etoposide-induced phosphorylation of ARP8 is regulated by ATM and ATR, and attenuates its interaction with INO80. The ATM-regulated phosphorylation of ARP8 reduces the excessive loading of INO80 and RAD51 onto the breakpoint cluster region. These findings suggest that the phosphorylation of ARP8, regulated by ATM, plays an important role in maintaining the fidelity of DNA repair to prevent the etoposide-induced 11q23 abnormalities. © 2018, Sun et al.

  4. Hyperoxia activates ATM independent from mitochondrial ROS and dysfunction.

    Science.gov (United States)

    Resseguie, Emily A; Staversky, Rhonda J; Brookes, Paul S; O'Reilly, Michael A

    2015-08-01

    High levels of oxygen (hyperoxia) are often used to treat individuals with respiratory distress, yet prolonged hyperoxia causes mitochondrial dysfunction and excessive reactive oxygen species (ROS) that can damage molecules such as DNA. Ataxia telangiectasia mutated (ATM) kinase is activated by nuclear DNA double strand breaks and delays hyperoxia-induced cell death through downstream targets p53 and p21. Evidence for its role in regulating mitochondrial function is emerging, yet it has not been determined if mitochondrial dysfunction or ROS activates ATM. Because ATM maintains mitochondrial homeostasis, we hypothesized that hyperoxia induces both mitochondrial dysfunction and ROS that activate ATM. In A549 lung epithelial cells, hyperoxia decreased mitochondrial respiratory reserve capacity at 12h and basal respiration by 48 h. ROS were significantly increased at 24h, yet mitochondrial DNA double strand breaks were not detected. ATM was not required for activating p53 when mitochondrial respiration was inhibited by chronic exposure to antimycin A. Also, ATM was not further activated by mitochondrial ROS, which were enhanced by depleting manganese superoxide dismutase (SOD2). In contrast, ATM dampened the accumulation of mitochondrial ROS during exposure to hyperoxia. Our findings suggest that hyperoxia-induced mitochondrial dysfunction and ROS do not activate ATM. ATM more likely carries out its canonical response to nuclear DNA damage and may function to attenuate mitochondrial ROS that contribute to oxygen toxicity. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  5. MicroRNA-223 Enhances Radiation Sensitivity of U87MG Cells In Vitro and In Vivo by Targeting Ataxia Telangiectasia Mutated

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Liping; Zhu, Ji [Departments of Radiation Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai (China); Zaorsky, Nicholas G. [Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania (United States); Deng, Yun [Departments of Radiation Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai (China); Wu, Xingzhong [Department of Biochemistry and Molecular Biology, Shanghai Medical College, Fudan University, Shanghai (China); Liu, Yong [Departments of Radiation Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai (China); Liu, Fangqi; Cai, Guoxiang; Gu, Weilie [Department of Colorectal Cancer, Fudan University, Shanghai Cancer Center, Shanghai (China); Shen, Lijun [Departments of Radiation Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai (China); Zhang, Zhen, E-mail: zhenzhang6@hotmail.com [Departments of Radiation Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai (China)

    2014-03-15

    Purpose: Ataxia telangiectasia mutated (ATM) protein is important in the DNA damage response because it repairs radiation-induced damage in cancers. We examined the effect of microRNA-223 (miR-223), a regulator of ATM expression, on radiation sensitivity of cancer cells. Methods and Materials: Human embryonic kidney 293 T (293T) cells were infected with pLL3.7-miR-223 plasmid to generate the pLL3.7-miR-223 and -empty virus (EV) lentivirus (miR-223 and EV). A dual luciferase assay in which the reporter contained wild-type 3′ untranslated region (UTR) of ATM was performed. U87MG cells were infected with miR-223 or EV to establish the overexpressed stable cell lines (U87-223 or U87-EV, respectively). Cells were irradiated in vitro, and dose enhancement ratios at 2 Gy (DER{sub 2}) were calculated. Hind legs of BALB/c athymic mice were injected with U87-223 or U87-EV cells; after 2 weeks, half of the tumors were irradiated. Tumor volumes were tracked for a total of 5 weeks. Results: The dual luciferase reporter assay showed a significant reduction in luciferase activity of 293T cells cotransfected with miR-223 and the ATM 3′UTR compared to that in EV control. Overexpression of miR-223 in U87MG cells showed that ATM expression was significantly downregulated in the U87-223 cells compared to that in U87-EV (ATM/β-actin mRNA 1.0 vs 1.5, P<.05). U87-223 cells were hypersensitive to radiation compared to U87-EV cells in vitro (DER{sub 2} = 1.32, P<.01). Mice injected with miR-223-expressing tumors had almost the same tumors after 3 weeks (1.5 cm{sup 3} vs 1.7 cm{sup 3}). However, irradiation significantly decreased tumor size in miR-223-expressing tumors compared to those in controls (0.033 cm{sup 3} vs 0.829 cm{sup 3}). Conclusions: miR-223 overexpression downregulates ATM expression and sensitizes U87 cells to radiation in vitro and in vivo. MicroRNA-223 may be a novel cancer-targeting therapy, although its cancer- and patient-specific roles are

  6. Pulmonary function in adolescents with ataxia telangiectasia.

    Science.gov (United States)

    McGrath-Morrow, Sharon; Lefton-Greif, Maureen; Rosquist, Karen; Crawford, Thomas; Kelly, Amber; Zeitlin, Pamela; Carson, Kathryn A; Lederman, Howard M

    2008-01-01

    Pulmonary complications are common in adolescents with ataxia telangiectasia (A-T), however objective measurements of lung function may be difficult to obtain because of underlying bulbar weakness, tremors, and difficulty coordinating voluntary respiratory maneuvers. To increase the reliability of pulmonary testing, minor adjustments were made to stabilize the head and to minimize leaks in the system. Fifteen A-T adolescents completed lung volume measurements by helium dilution. To assess for reproducibility of spirometry testing, 10 A-T adolescents performed spirometry on three separate occasions. Total lung capacity (TLC) was normal or just mildly decreased in 12/15 adolescents tested. TLC correlated positively with functional residual capacity (FRC), a measurement independent of patient effort (R2=0.71). The majority of individuals had residual volumes (RV) greater than 120% predicted (10/15) and slow vital capacities (VC) less than 70% predicted (9/15). By spirometry, force vital capacity (FVC) and forced expiratory volume in 1 sec (FEV1) values were reproducible in the 10 individuals who underwent testing on three separate occasions (R=0.97 and 0.96 respectively). Seven of the 10 adolescents had FEV1/FVC ratios>90%. Lung volume measurements from A-T adolescents revealed near normal TLC values with increased RV and decreased VC values. These findings indicate a decreased ability to expire to residual volume rather then a restrictive defect. Spirometry was also found to be reproducible in A-T adolescents suggesting that spirometry testing may be useful for tracking changes in pulmonary function over time in this population. Copyright (c) 2007 Wiley-Liss, Inc.

  7. Loss of tumour-specific ATM protein expression is an independent prognostic factor in early resected NSCLC.

    Science.gov (United States)

    Petersen, Lars F; Klimowicz, Alexander C; Otsuka, Shannon; Elegbede, Anifat A; Petrillo, Stephanie K; Williamson, Tyler; Williamson, Chris T; Konno, Mie; Lees-Miller, Susan P; Hao, Desiree; Morris, Don; Magliocco, Anthony M; Bebb, D Gwyn

    2017-06-13

    Ataxia-telangiectasia mutated (ATM) is critical in maintaining genomic integrity. In response to DNA double-strand breaks, ATM phosphorylates downstream proteins involved in cell-cycle checkpoint arrest, DNA repair, and apoptosis. Here we investigate the frequency, and influence of ATM deficiency on outcome, in early-resected non-small cell lung cancer (NSCLC). Tissue microarrays, containing 165 formalin-fixed, paraffin-embedded resected NSCLC tumours from patients diagnosed at the Tom Baker Cancer Centre, Calgary, Canada, between 2003 and 2006, were analyzed for ATM expression using quantitative fluorescence immunohistochemistry. Both malignant cell-specific ATM expression and the ratio of ATM expression within malignant tumour cells compared to that in the surrounding tumour stroma, defined as the ATM expression index (ATM-EI), were measured and correlated with clinical outcome. ATM loss was identified in 21.8% of patients, and was unaffected by clinical pathological variables. Patients with low ATM-EI tumours had worse survival outcomes compared to those with high ATM-EI (p ATM-deficient patients may derive greater benefit from guideline-recommended adjuvant chemotherapy following surgical resection. Taken together, these results indicate that ATM loss seems to be an early event in NSCLC carcinogenesis and is an independent prognostic factor associated with worse survival in stage II/III patients.

  8. ATM regulates Cdt1 stability during the unperturbed S phase to prevent re-replication

    Science.gov (United States)

    Iwahori, Satoko; Kohmon, Daisuke; Kobayashi, Junya; Tani, Yuhei; Yugawa, Takashi; Komatsu, Kenshi; Kiyono, Tohru; Sugimoto, Nozomi; Fujita, Masatoshi

    2014-01-01

    Ataxia-telangiectasia mutated (ATM) plays crucial roles in DNA damage responses, especially with regard to DNA double-strand breaks (DSBs). However, it appears that ATM can be activated not only by DSB, but also by some changes in chromatin architecture, suggesting potential ATM function in cell cycle control. Here, we found that ATM is involved in timely degradation of Cdt1, a critical replication licensing factor, during the unperturbed S phase. At least in certain cell types, degradation of p27Kip1 was also impaired by ATM inhibition. The novel ATM function for Cdt1 regulation was dependent on its kinase activity and NBS1. Indeed, we found that ATM is moderately phosphorylated at Ser1981 during the S phase. ATM silencing induced partial reduction in levels of Skp2, a component of SCFSkp2 ubiquitin ligase that controls Cdt1 degradation. Furthermore, Skp2 silencing resulted in Cdt1 stabilization like ATM inhibition. In addition, as reported previously, ATM silencing partially prevented Akt phosphorylation at Ser473, indicative of its activation, and Akt inhibition led to modest stabilization of Cdt1. Therefore, the ATM-Akt-SCFSkp2 pathway may partly contribute to the novel ATM function. Finally, ATM inhibition rendered cells hypersensitive to induction of re-replication, indicating importance for maintenance of genome stability. PMID:24280901

  9. Cellular and molecular response to irradiation in ataxia telangiectasia and in Fanconi's anemia

    International Nuclear Information System (INIS)

    Ridet, A.; Guillouf, C.; Duchaud, E.; Moustacchi, E.; Rosselli, F.

    1997-01-01

    Ataxia telangiectasia (AT) and Fanconi anemia (FA) are recessive genetic diseases featuring chromosomal instability, increased predisposition to cancer and in vitro hypersensitivity to ionizing radiation (AT) or DNA cross-linking agents (FA). Moreover, an in vivo hypersensitivity to γ-rays exposure was reported in both syndromes. Cellular response to irradiation includes growth arrest (cell cycle modification) and cell death (by apoptosis or necrosis). Since it is generally accepted that apoptosis modulates cellular sensitivity to genotoxic stress, it was of interest to investigate the contribution of apoptosis in determining FA and AT responses to DNA Damaging Agents. The results support the contention that the in vivo hypersensitivity to radiation in these syndromes is not related to a higher rate of apoptotic cells but could be to a higher necrotic response triggering inflammatory reactions in the patients affected by this syndromes. (authors)

  10. TP53 and ATM mRNA expression in skin and skeletal muscle after low-level laser exposure.

    Science.gov (United States)

    Guedes de Almeida, Luciana; Sergio, Luiz Philippe da Silva; de Paoli, Flavia; Mencalha, Andre Luiz; da Fonseca, Adenilson de Souza

    2017-08-01

    Low-level lasers are widespread in regenerative medicine, but the molecular mechanisms involved in their biological effects are not fully understood, particularly those on DNA stability. Therefore, this study aimed to investigate mRNA expression of genes related to DNA genomic stability in skin and skeletal muscle tissue from Wistar rats exposed to low-level red and infrared lasers. For this, TP53 (Tumor Protein 53) and ATM (Ataxia Telangiectasia Mutated gene) mRNA expressions were evaluated by real-time quantitative PCR (RT-qPCR) technique 24 hours after low-level red and infrared laser exposure. Our data showed that relative TP53 mRNA expression was not significantly altered in both tissues exposed to lasers. For ATM, relative mRNA expression in skin tissue was not significantly altered, but in muscle tissue, laser exposure increased relative ATM mRNA expression. Low-level red and infrared laser radiations alter ATM mRNA expression related to DNA stability in skeletal muscle tissue.

  11. Defect in radiation signal transduction in ataxia-telangiectasia

    International Nuclear Information System (INIS)

    Lavin, M.F.

    1994-01-01

    Exposure of mammalian cells to ionizing radiation causes a delay in progression through the cycle at several checkpoints. Cells from patients with ataxia-telangiectasia (A-T) ignore these checkpoint controls postirradiation. The tumour suppressor gene product p53 plays a key role at the G 1 /S checkpoint preventing the progression of cells into S phase. The induction of p53 by radiation is reduced and/or delayed in A-T cells, which appears to account for the failure of delay at the G 1 /S checkpoint. We have investigated further this defect in radiation signal transduction in A-T. While the p53 response was defective after radiation, agents that interfered with cell cycle progression such as mimosine, aphidicolin and deprivation of serum led to a normal p53 response in A-T cells. None of these agents caused breaks in DNA, as determined by pulse-field gel electrophoresis, in order to elicit the response. Since this pathway is mediated by protein kinases, we investigated the activity of several of these enzymes in control and A-T cells. Ca +2 -dependent and -independent protein kinase C activities were increased by radiation to the same extent in the two cell types, a variety of serine/threonine protein kinase activities were approximately the same and anti-tyrosine antibodies failed to reveal any differences in protein phosphorylation between A-T and control cells. (author)

  12. Stable radioresistance in ataxia-telangiectasia cells containing DNA from normal human cells

    International Nuclear Information System (INIS)

    Kapp, L.N.; Painter, R.B.

    1989-01-01

    SV40-transformed ataxia-telangiectasia (AT) cells were transfected with a cosmid containing a normal human DNA library and selectable marker, the neo gene, which endows successfully transformed mammalian cells with resistance to the antibiotic G418. Cells from this line were irradiated with 50 Gy of X-rays and fused with non-transfected AT cells. Among the G418-resistant colonies recovered was one stably resistant to radiation. Resistance to ionizing radiation of both primary transfectant line and its fusion derivative was intermediate between that of AT cells and normal cells, as assayed by colony-forming ability and measurement of radiation-induced G 2 chromatic aberrations; both cell lines retained AT-like radioresistant DNA synthesis. Results suggest that, because radioresistance in transfected cells was not as great as in normal human cells, two hallmarks of AT, radiosensitivity and radioresistant DNA synthesis, may still be the result of a single defective AT gene. (author)

  13. ATM-Dependent Phosphorylation of All Three Members of the MRN Complex: From Sensor to Adaptor.

    Science.gov (United States)

    Lavin, Martin F; Kozlov, Sergei; Gatei, Magtouf; Kijas, Amanda W

    2015-10-23

    The recognition, signalling and repair of DNA double strand breaks (DSB) involves the participation of a multitude of proteins and post-translational events that ensure maintenance of genome integrity. Amongst the proteins involved are several which when mutated give rise to genetic disorders characterised by chromosomal abnormalities, cancer predisposition, neurodegeneration and other pathologies. ATM (mutated in ataxia-telangiectasia (A-T) and members of the Mre11/Rad50/Nbs1 (MRN complex) play key roles in this process. The MRN complex rapidly recognises and locates to DNA DSB where it acts to recruit and assist in ATM activation. ATM, in the company of several other DNA damage response proteins, in turn phosphorylates all three members of the MRN complex to initiate downstream signalling. While ATM has hundreds of substrates, members of the MRN complex play a pivotal role in mediating the downstream signalling events that give rise to cell cycle control, DNA repair and ultimately cell survival or apoptosis. Here we focus on the interplay between ATM and the MRN complex in initiating signaling of breaks and more specifically on the adaptor role of the MRN complex in mediating ATM signalling to downstream substrates to control different cellular processes.

  14. Mode of ATM-dependent suppression of chromosome translocation

    Energy Technology Data Exchange (ETDEWEB)

    Yamauchi, Motohiro, E-mail: motoyama@nagasaki-u.ac.jp [Graduate School of Biomedical Sciences, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523 (Japan); Suzuki, Keiji; Oka, Yasuyoshi; Suzuki, Masatoshi; Kondo, Hisayoshi; Yamashita, Shunichi [Graduate School of Biomedical Sciences, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523 (Japan)

    2011-12-09

    Highlights: Black-Right-Pointing-Pointer We addressed how ATM suppresses frequency of chromosome translocation. Black-Right-Pointing-Pointer We found ATM/p53-dependent G1 checkpoint suppresses translocation frequency. Black-Right-Pointing-Pointer We found ATM and DNA-PKcs function in a common pathway to suppress translocation. -- Abstract: It is well documented that deficiency in ataxia telangiectasia mutated (ATM) protein leads to elevated frequency of chromosome translocation, however, it remains poorly understood how ATM suppresses translocation frequency. In the present study, we addressed the mechanism of ATM-dependent suppression of translocation frequency. To know frequency of translocation events in a whole genome at once, we performed centromere/telomere FISH and scored dicentric chromosomes, because dicentric and translocation occur with equal frequency and by identical mechanism. By centromere/telomere FISH analysis, we confirmed that chemical inhibition or RNAi-mediated knockdown of ATM causes 2 to 2.5-fold increase in dicentric frequency at first mitosis after 2 Gy of gamma-irradiation in G0/G1. The FISH analysis revealed that ATM/p53-dependent G1 checkpoint suppresses dicentric frequency, since RNAi-mediated knockdown of p53 elevated dicentric frequency by 1.5-fold. We found ATM also suppresses dicentric occurrence independently of its checkpoint role, as ATM inhibitor showed additional effect on dicentric frequency in the context of p53 depletion and Chk1/2 inactivation. Epistasis analysis using chemical inhibitors revealed that ATM kinase functions in the same pathway that requires kinase activity of DNA-dependent protein kinase catalytic subunit (DNA-PKcs) to suppress dicentric frequency. From the results in the present study, we conclude that ATM minimizes translocation frequency through its commitment to G1 checkpoint and DNA double-strand break repair pathway that requires kinase activity of DNA-PKcs.

  15. Conditional abrogation of Atm in osteoclasts extends osteoclast lifespan and results in reduced bone mass.

    Science.gov (United States)

    Hirozane, Toru; Tohmonda, Takahide; Yoda, Masaki; Shimoda, Masayuki; Kanai, Yae; Matsumoto, Morio; Morioka, Hideo; Nakamura, Masaya; Horiuchi, Keisuke

    2016-09-28

    Ataxia-telangiectasia mutated (ATM) kinase is a central component involved in the signal transduction of the DNA damage response (DDR) and thus plays a critical role in the maintenance of genomic integrity. Although the primary functions of ATM are associated with the DDR, emerging data suggest that ATM has many additional roles that are not directly related to the DDR, including the regulation of oxidative stress signaling, insulin sensitivity, mitochondrial homeostasis, and lymphocyte development. Patients and mice lacking ATM exhibit growth retardation and lower bone mass; however, the mechanisms underlying the skeletal defects are not fully understood. In the present study, we generated mutant mice in which ATM is specifically inactivated in osteoclasts. The mutant mice did not exhibit apparent developmental defects but showed reduced bone mass due to increased osteoclastic bone resorption. Osteoclasts lacking ATM were more resistant to apoptosis and showed a prolonged lifespan compared to the controls. Notably, the inactivation of ATM in osteoclasts resulted in enhanced NF-κB signaling and an increase in the expression of NF-κB-targeted genes. The present study reveals a novel function for ATM in regulating bone metabolism by suppressing the lifespan of osteoclasts and osteoclast-mediated bone resorption.

  16. ATM regulates 3-methylpurine-DNA glycosylase and promotes therapeutic resistance to alkylating agents.

    Science.gov (United States)

    Agnihotri, Sameer; Burrell, Kelly; Buczkowicz, Pawel; Remke, Marc; Golbourn, Brian; Chornenkyy, Yevgen; Gajadhar, Aaron; Fernandez, Nestor A; Clarke, Ian D; Barszczyk, Mark S; Pajovic, Sanja; Ternamian, Christian; Head, Renee; Sabha, Nesrin; Sobol, Robert W; Taylor, Michael D; Rutka, James T; Jones, Chris; Dirks, Peter B; Zadeh, Gelareh; Hawkins, Cynthia

    2014-10-01

    Alkylating agents are a first-line therapy for the treatment of several aggressive cancers, including pediatric glioblastoma, a lethal tumor in children. Unfortunately, many tumors are resistant to this therapy. We sought to identify ways of sensitizing tumor cells to alkylating agents while leaving normal cells unharmed, increasing therapeutic response while minimizing toxicity. Using an siRNA screen targeting over 240 DNA damage response genes, we identified novel sensitizers to alkylating agents. In particular, the base excision repair (BER) pathway, including 3-methylpurine-DNA glycosylase (MPG), as well as ataxia telangiectasia mutated (ATM), were identified in our screen. Interestingly, we identified MPG as a direct novel substrate of ATM. ATM-mediated phosphorylation of MPG was required for enhanced MPG function. Importantly, combined inhibition or loss of MPG and ATM resulted in increased alkylating agent-induced cytotoxicity in vitro and prolonged survival in vivo. The discovery of the ATM-MPG axis will lead to improved treatment of alkylating agent-resistant tumors. Inhibition of ATM and MPG-mediated BER cooperate to sensitize tumor cells to alkylating agents, impairing tumor growth in vitro and in vivo with no toxicity to normal cells, providing an ideal therapeutic window. ©2014 American Association for Cancer Research.

  17. ATM-deficiency increases genomic instability and metastatic potential in a mouse model of pancreatic cancer.

    Science.gov (United States)

    Drosos, Yiannis; Escobar, David; Chiang, Ming-Yi; Roys, Kathryn; Valentine, Virginia; Valentine, Marc B; Rehg, Jerold E; Sahai, Vaibhav; Begley, Lesa A; Ye, Jianming; Paul, Leena; McKinnon, Peter J; Sosa-Pineda, Beatriz

    2017-09-11

    Germline mutations in ATM (encoding the DNA-damage signaling kinase, ataxia-telangiectasia-mutated) increase Familial Pancreatic Cancer (FPC) susceptibility, and ATM somatic mutations have been identified in resected human pancreatic tumors. Here we investigated how Atm contributes to pancreatic cancer by deleting this gene in a murine model of the disease expressing oncogenic Kras (Kras G12D ). We show that partial or total ATM deficiency cooperates with Kras G12D to promote highly metastatic pancreatic cancer. We also reveal that ATM is activated in pancreatic precancerous lesions in the context of DNA damage and cell proliferation, and demonstrate that ATM deficiency leads to persistent DNA damage in both precancerous lesions and primary tumors. Using low passage cultures from primary tumors and liver metastases we show that ATM loss accelerates Kras-induced carcinogenesis without conferring a specific phenotype to pancreatic tumors or changing the status of the tumor suppressors p53, p16 Ink4a and p19 Arf . However, ATM deficiency markedly increases the proportion of chromosomal alterations in pancreatic primary tumors and liver metastases. More importantly, ATM deficiency also renders murine pancreatic tumors highly sensitive to radiation. These and other findings in our study conclusively establish that ATM activity poses a major barrier to oncogenic transformation in the pancreas via maintaining genomic stability.

  18. Cellular and molecular response to irradiation in ataxia telangiectasia and in Fanconi`s anemia

    Energy Technology Data Exchange (ETDEWEB)

    Ridet, A.; Guillouf, C.; Duchaud, E.; Moustacchi, E.; Rosselli, F. [Institut Curie-Recherche, UMR 218, CNRS, 75 - Paris (France)

    1997-03-01

    Ataxia telangiectasia (AT) and Fanconi anemia (FA) are recessive genetic diseases featuring chromosomal instability, increased predisposition to cancer and in vitro hypersensitivity to ionizing radiation (AT) or DNA cross-linking agents (FA). Moreover, an in vivo hypersensitivity to {gamma}-rays exposure was reported in both syndromes. Cellular response to irradiation includes growth arrest (cell cycle modification) and cell death (by apoptosis or necrosis). Since it is generally accepted that apoptosis modulates cellular sensitivity to genotoxic stress, it was of interest to investigate the contribution of apoptosis in determining FA and AT responses to DNA Damaging Agents. The results support the contention that the in vivo hypersensitivity to radiation in these syndromes is not related to a higher rate of apoptotic cells but could be to a higher necrotic response triggering inflammatory reactions in the patients affected by this syndromes. (authors)

  19. ATM-Dependent Hyper-Radiosensitivity in Mammalian Cells Irradiated by Heavy Ions

    International Nuclear Information System (INIS)

    Xue Lian; Yu Dong; Furusawa, Yoshiya; Cao Jianping; Okayasu, Ryuichi; Fan Saijun

    2009-01-01

    Purpose: Low-dose hyper-radiosensitivity (HRS) and the later appearing radioresistance (termed induced radioresistance [IRR]) was mainly studied in low linear energy transfer (LET) radiation with survival observation. The aim of this study was to find out whether equivalent hypersensitivity occurred in high LET radiation, and the roles of ataxia telangiectasia mutated (ATM) kinase. Methods and Materials: Survival and mutation were measured by clonogenic assay and HPRT mutation assay. ATM Ser1981 activation was detected by Western blotting and immunofluorescent staining. Pretreatment of specific ATM inhibitor (10 μM KU55933) and activator (20 μg/mL chloroquine) before carbon radiation were adopted to explore the involvement of ATM. The roles of ATM were also investigated in its G2/M checkpoint function with histone H3 phosphorylation analysis and flow cytometric assay, and DNA double strand break (DSB) repair function measured using γ-H2AX foci assay. Results: HRS/IRR was observed with survival and mutation in normal human skin fibroblast cells by carbon ions, while impaired in cells with intrinsic ATM deficiency or normal cells modified with specific ATM activator or inhibitor before irradiation. The dose-response pattern of ATM kinase activation was concordant with the transition from HRS to IRR. The ATM-dependent 'early' G2 checkpoint arrest and DNA DSB repair efficiency could explain the difference between HRS and IRR. Conclusions: These data demonstrate that the HRS/IRR by carbon ion radiation is an ATM-dependent phenomenon in the cellular response to DNA damage.

  20. Workshop on The Epidemiology of the ATM Gene: Impact on Breast Cancer Risk and Treatment, Present Status and Future Focus, Lillehammer, Norway, 29 June 2002

    International Nuclear Information System (INIS)

    Bernstein, Jonine L; Seminara, Daniela; Børresen-Dale, Anne-Lise

    2002-01-01

    The role of ataxia-telangiectasia mutated (ATM) heterozygosity in cancer is uncertain. In vitro studies of cells from ATM heterozygotes provide strong evidence of radiation sensitivity. Some, but not all, clinical studies suggest an increased risk of breast cancer among ATM gene carriers, and this risk may be greater among those exposed to radiation. This possible excess risk of breast cancer associated with ATM heterozygosity constitutes the basis for several genetic epidemiological studies designed to clarify the role that the ATM gene plays in the etiology of breast and other cancers. The primary focus of this international, multidisciplinary, National Cancer Institute-sponsored workshop was to discuss ongoing and planned epidemiologic studies aimed at understanding the complexities of the ATM gene and its role in carcinogenesis. The invited participants were from diverse disciplines including molecular and clinical genetics, radiation biology and physics, epidemiology, biostatistics, pathology, and medicine. In the present meeting report, the aims of each project are described

  1. ATM is required for the repair of Topotecan-induced replication-associated double-strand breaks

    International Nuclear Information System (INIS)

    Köcher, Sabrina; Spies-Naumann, Anja; Kriegs, Malte; Dahm-Daphi, Jochen; Dornreiter, Irena

    2013-01-01

    Purpose: DNA replication is a promising target for anti-cancer therapies. Therefore, the understanding of replication-associated DNA repair mechanisms is of great interest. One key factor of DNA double-strand break (DSB) repair is the PIK kinase Ataxia-Telangiectasia Mutated (ATM) but it is still unclear whether ATM is involved in the repair of replication-associated DSBs. Here, we focused on the involvement of ATM in homology-directed repair (HDR) of indirect DSBs associated with replication. Material and methods: Experiments were performed using ATM-deficient and -proficient human cells. Replication-associated DSBs were induced with Topotecan (TPT) and compared with γ-irradiation (IR). Cell survival was measured by clonogenic assay. Overall DSB repair and HDR were evaluated by detecting residual γH2AX/53BP1 and Rad51 foci, respectively. Cell cycle distribution was analysed by flow cytometry and protein expression by Western blot. Results: ATM-deficiency leads to enhanced numbers of residual DSBs, resulting in a pronounced S/G2-block and decreased survival upon TPT-treatment. In common with IR, persisting Rad51 foci were detected following TPT-treatment. Conclusions: These results demonstrate that ATM is essentially required for the completion of HR-mediated repair of TPT-induced DSBs formed indirectly at replication forks

  2. Familial study of ataxia telangiectasia. Heterozygotes identification on the basis of sensitivity of gamma-irradiated cultures to caffeine post-treatment

    International Nuclear Information System (INIS)

    Pawlak, A.L.; Kotecki, M.

    1994-01-01

    The effects of caffeine (CF), γ-irradiation + CF post-treatment on chromosomal aberrations were studied in lymphocyte cultures from a patient with ataxia telangiectasia (AT), his parents and brother. In the studied family both the homozygotes and the obligatory heterozygotes of AT showed increased sensitivity to CF post-treatment. Individual differences in sensitivity to γ-irradiation + CF post-treatment proved to be correlated with the sensitivity of non-irradiated cells to CF treatment, but not to γ-irradiation. (author). 19 refs, 1 fig., 1 tab

  3. Familial study of ataxia telangiectasia. Heterozygotes identification on the basis of sensitivity of gamma-irradiated cultures to caffeine post-treatment

    Energy Technology Data Exchange (ETDEWEB)

    Pawlak, A.L.; Kotecki, M. [Polska Akademia Nauk, Poznan (Poland). Zaklad Genetyki Czlowieka; Ignatowicz, R. [Centrum Zdrowia Dziecka, Warsaw (Poland)

    1994-12-31

    The effects of caffeine (CF), {gamma}-irradiation + CF post-treatment on chromosomal aberrations were studied in lymphocyte cultures from a patient with ataxia telangiectasia (AT), his parents and brother. In the studied family both the homozygotes and the obligatory heterozygotes of AT showed increased sensitivity to CF post-treatment. Individual differences in sensitivity to {gamma}-irradiation + CF post-treatment proved to be correlated with the sensitivity of non-irradiated cells to CF treatment, but not to {gamma}-irradiation. (author). 19 refs, 1 fig., 1 tab.

  4. Squalene Inhibits ATM-Dependent Signaling in γIR-Induced DNA Damage Response through Induction of Wip1 Phosphatase.

    Directory of Open Access Journals (Sweden)

    Naoto Tatewaki

    Full Text Available Ataxia telangiectasia mutated (ATM kinase plays a crucial role as a master controller in the cellular DNA damage response. Inhibition of ATM leads to inhibition of the checkpoint signaling pathway. Hence, addition of checkpoint inhibitors to anticancer therapies may be an effective targeting strategy. A recent study reported that Wip1, a protein phosphatase, de-phosphorylates serine 1981 of ATM during the DNA damage response. Squalene has been proposed to complement anticancer therapies such as chemotherapy and radiotherapy; however, there is little mechanistic information supporting this idea. Here, we report the inhibitory effect of squalene on ATM-dependent DNA damage signals. Squalene itself did not affect cell viability and the cell cycle of A549 cells, but it enhanced the cytotoxicity of gamma-irradiation (γIR. The in vitro kinase activity of ATM was not altered by squalene. However, squalene increased Wip1 expression in cells and suppressed ATM activation in γIR-treated cells. Consistent with the potential inhibition of ATM by squalene, IR-induced phosphorylation of ATM effectors such as p53 (Ser15 and Chk1 (Ser317 was inhibited by cell treatment with squalene. Thus, squalene inhibits the ATM-dependent signaling pathway following DNA damage through intracellular induction of Wip1 expression.

  5. Inhibition of DNA-PKcs enhances radiosensitivity and increases the levels of ATM and ATR in NSCLC cells exposed to carbon ion irradiation.

    Science.gov (United States)

    Yang, Lina; Liu, Yuanyuan; Sun, Chao; Yang, Xinrui; Yang, Zhen; Ran, Juntao; Zhang, Qiuning; Zhang, Hong; Wang, Xinyu; Wang, Xiaohu

    2015-11-01

    Non-small cell lung cancer (NSCLC) exhibits radioresistance to conventional rays, due to its DNA damage repair systems. NSCLC may potentially be sensitized to radiation treatment by reducing those factors that continuously enhance the repair of damaged DNA. In the present study, normal lung fibroblast MRC-5 and lung cancer A549 cells were treated with NU7026 and CGK733, which are inhibitors of the DNA-dependent protein kinase catalytic subunit (PKcs) and ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related (ATR), respectively, followed by exposure to X-rays and carbon ion irradiation. The cytotoxic activity, cell survival rate, DNA damage repair ability, cell cycle arrest and apoptosis rate of the treated cells were analyzed with MTT assay, colony formation assay, immunofluorescence and flow cytometry, respectively. The transcription and translation levels of the ATM, ATR and DNA-PKcs genes were detected by reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. The results indicated that the radiosensitivity and DNA repair ability of A549 cells were reduced, and the percentages of apoptotic cells and those arrested at the G 2 /M phase of the cell cycle were significantly increased, following ionizing radiation with inhibitor-pretreatment. The expression levels of ATM, ATR, DNA-PKcs and phosphorylated histone H2AX, a biomarker for DNA double-strand breaks, were all upregulated at the transcriptional or translational level in A549 cells treated with carbon ion irradiation, compared with the control and X-rays-treated cells. In addition, the treatment with 5-50 µM NU7026 or CGK733 did not produce any obvious cytotoxicity in MRC-5 cells, and the effect of the DNA-PKcs-inhibitor on enhancing the radiosensitivity of A549 cells was stronger than that observed for the ATM and ATR-inhibitor. These findings demonstrated a minor role for ATM and ATR in radiation-induced cell death, since the upregulation of

  6. DNA-PK, ATM and ATR collaboratively regulate p53-RPA interaction to facilitate homologous recombination DNA repair.

    Science.gov (United States)

    Serrano, M A; Li, Z; Dangeti, M; Musich, P R; Patrick, S; Roginskaya, M; Cartwright, B; Zou, Y

    2013-05-09

    Homologous recombination (HR) and nonhomologous end joining (NHEJ) are two distinct DNA double-stranded break (DSB) repair pathways. Here, we report that DNA-dependent protein kinase (DNA-PK), the core component of NHEJ, partnering with DNA-damage checkpoint kinases ataxia telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR), regulates HR repair of DSBs. The regulation was accomplished through modulation of the p53 and replication protein A (RPA) interaction. We show that upon DNA damage, p53 and RPA were freed from a p53-RPA complex by simultaneous phosphorylations of RPA at the N-terminus of RPA32 subunit by DNA-PK and of p53 at Ser37 and Ser46 in a Chk1/Chk2-independent manner by ATR and ATM, respectively. Neither the phosphorylation of RPA nor of p53 alone could dissociate p53 and RPA. Furthermore, disruption of the release significantly compromised HR repair of DSBs. Our results reveal a mechanism for the crosstalk between HR repair and NHEJ through the co-regulation of p53-RPA interaction by DNA-PK, ATM and ATR.

  7. Low ATM protein expression and depletion of p53 correlates with olaparib sensitivity in gastric cancer cell lines

    Science.gov (United States)

    Kubota, Eiji; Williamson, Christopher T; Ye, Ruiqiong; Elegbede, Anifat; Peterson, Lars; Lees-Miller, Susan P; Bebb, D Gwyn

    2014-01-01

    Small-molecule inhibitors of poly (ADP-ribose) polymerase (PARP) have shown considerable promise in the treatment of homologous recombination (HR)-defective tumors, such as BRCA1- and BRCA2-deficient breast and ovarian cancers. We previously reported that mantle cell lymphoma cells with deficiency in ataxia telangiectasia mutated (ATM) are sensitive to PARP-1 inhibitors in vitro and in vivo. Here, we report that PARP inhibitors can potentially target ATM deficiency arising in a solid malignancy. We show that ATM protein expression varies between gastric cancer cell lines, with NUGC4 having significantly reduced protein levels. Significant correlation was found between ATM protein expression and sensitivity to the PARP inhibitor olaparib, with NUGC4 being the most sensitive. Moreover, reducing ATM kinase activity using a small-molecule inhibitor (KU55933) or shRNA-mediated depletion of ATM protein enhanced olaparib sensitivity in gastric cancer cell lines with depletion or inactivation of p53. Our results demonstrate that ATM is a potential predictive biomarker for PARP-1 inhibitor activity in gastric cancer harboring disruption of p53, and that combined inhibition of ATM and PARP-1 is a rational strategy for expanding the utility of PARP-1 inhibitors to gastric cancer with p53 disruption. PMID:24841718

  8. Complex control of ATM in response to radiation damage to DNA

    International Nuclear Information System (INIS)

    Lavin, M.F.; Beamish, H.; Chen, P.; Keating, K.; Scott, S.; Spring, K.; Kozlov, S.; Walters, D.

    2000-01-01

    Full text: The human genetic disorder ataxia-telangiectasia is characterized by neurodegeneration, immunodeficiency, extreme sensitivity to ionizing radiation, abnormalities in cell cycle checkpoints and a predisposition to develop leukemias and lymphomas. It appears likely that the basis of the hypersensitivity to ionizing radiation is due to defective sensing of double strand breaks in DNA and as a consequence a failure to repair all of these breaks. After exposure of cells to radiation the kinase activity of pre-existing ATM protein is rapidly activated leading to the radiation-induced phosphoylation of a number of important substrates including p53, c-Abl, BRCA1, NBS1 and chk2. Defective phosphorylation of BRCA1 and NBS1 is associated with increased sensitivity to ionizing radiation. We have also demonstrated that a reduction in the amount of ATM protein using antisense ATM cDNA transfection prior to exposure to radiation also sensitizes cells. This was further confirmed by treating human lymphoblastoid cells with EGF prior to radiation exposure. Furthermore radiation reverses the downregulation of ATM by EGF over a 3 hour period. Under these conditions cells are still sensitized to radiation since the restoration of ATM kinase activity is slower than that arising from activation of existing protein. Alterations in the amount of ATM protein are also observed in response to mitogenic agents. Thus it is evident that ATM protein and kinase activity are regulated in a complex fashion and this appears to vary in different tissues. The implications for altering ATM for therapeutic benefit will be discussed

  9. Lyn tyrosine kinase promotes silencing of ATM-dependent checkpoint signaling during recovery from DNA double-strand breaks

    International Nuclear Information System (INIS)

    Fukumoto, Yasunori; Kuki, Kazumasa; Morii, Mariko; Miura, Takahito; Honda, Takuya; Ishibashi, Kenichi; Hasegawa, Hitomi; Kubota, Sho; Ide, Yudai; Yamaguchi, Noritaka; Nakayama, Yuji; Yamaguchi, Naoto

    2014-01-01

    Highlights: • Inhibition of Src family kinases decreased γ-H2AX signal. • Inhibition of Src family increased ATM-dependent phosphorylation of Chk2 and Kap1. • shRNA-mediated knockdown of Lyn increased phosphorylation of Kap1 by ATM. • Ectopic expression of Src family kinase suppressed ATM-mediated Kap1 phosphorylation. • Src is involved in upstream signaling for inactivation of ATM signaling. - Abstract: DNA damage activates the DNA damage checkpoint and the DNA repair machinery. After initial activation of DNA damage responses, cells recover to their original states through completion of DNA repair and termination of checkpoint signaling. Currently, little is known about the process by which cells recover from the DNA damage checkpoint, a process called checkpoint recovery. Here, we show that Src family kinases promote inactivation of ataxia telangiectasia mutated (ATM)-dependent checkpoint signaling during recovery from DNA double-strand breaks. Inhibition of Src activity increased ATM-dependent phosphorylation of Chk2 and Kap1. Src inhibition increased ATM signaling both in G2 phase and during asynchronous growth. shRNA knockdown of Lyn increased ATM signaling. Src-dependent nuclear tyrosine phosphorylation suppressed ATM-mediated Kap1 phosphorylation. These results suggest that Src family kinases are involved in upstream signaling that leads to inactivation of the ATM-dependent DNA damage checkpoint

  10. DNA damage checkpoint kinase ATM regulates germination and maintains genome stability in seeds.

    Science.gov (United States)

    Waterworth, Wanda M; Footitt, Steven; Bray, Clifford M; Finch-Savage, William E; West, Christopher E

    2016-08-23

    Genome integrity is crucial for cellular survival and the faithful transmission of genetic information. The eukaryotic cellular response to DNA damage is orchestrated by the DNA damage checkpoint kinases ATAXIA TELANGIECTASIA MUTATED (ATM) and ATM AND RAD3-RELATED (ATR). Here we identify important physiological roles for these sensor kinases in control of seed germination. We demonstrate that double-strand breaks (DSBs) are rate-limiting for germination. We identify that desiccation tolerant seeds exhibit a striking transcriptional DSB damage response during germination, indicative of high levels of genotoxic stress, which is induced following maturation drying and quiescence. Mutant atr and atm seeds are highly resistant to aging, establishing ATM and ATR as determinants of seed viability. In response to aging, ATM delays germination, whereas atm mutant seeds germinate with extensive chromosomal abnormalities. This identifies ATM as a major factor that controls germination in aged seeds, integrating progression through germination with surveillance of genome integrity. Mechanistically, ATM functions through control of DNA replication in imbibing seeds. ATM signaling is mediated by transcriptional control of the cell cycle inhibitor SIAMESE-RELATED 5, an essential factor required for the aging-induced delay to germination. In the soil seed bank, seeds exhibit increased transcript levels of ATM and ATR, with changes in dormancy and germination potential modulated by environmental signals, including temperature and soil moisture. Collectively, our findings reveal physiological functions for these sensor kinases in linking genome integrity to germination, thereby influencing seed quality, crucial for plant survival in the natural environment and sustainable crop production.

  11. ATM Polymorphisms Are Associated With Risk of Radiation-Induced Pneumonitis

    International Nuclear Information System (INIS)

    Zhang Li; Yang Ming; Bi Nan; Fang Mingjing; Sun Tong; Ji Wei; Tan Wen; Zhao Lujun; Yu Dianke; Lin Dongxin; Wang Luhua

    2010-01-01

    Purpose: Since the ataxia telangiectasia mutated (ATM) protein plays crucial roles in repair of double-stranded DNA breaks, control of cell cycle checkpoints, and radiosensitivity, we hypothesized that variations in this gene might be associated with radiation-induced pneumonitis (RP). Methods and Materials: A total of 253 lung cancer patients receiving thoracic irradiation between 2004 and 2006 were included in this study. Common Terminology Criteria for Adverse Events version 3.0 was used to grade RP. Five haplotype-tagging single nucleotide polymorphisms (SNPs) in the ATM gene were genotyped using DNA from blood lymphocytes. Hazard ratios (HRs) and 95% confidence intervals (CIs) of RP for genotypes were computed by the Cox model, adjusted for clinical factors. The function of the ATM SNP associated with RP was examined by biochemical assays. Results: During the median 22-month follow-up, 44 (17.4%) patients developed grade ≥ 2 RP. In multivariate Cox regression models adjusted for other clinical predictors, we found two ATM variants were independently associated with increased RP risk. They were an 111G > A) polymorphism (HR, 2.49; 95% CI, 1.07-5.80) and an ATM 126713G > A polymorphism (HR, 2.47; 95% CI, 1.16-5.28). Furthermore, genotype-dependent differences in ATM expression were demonstrated both in cell lines (p < 0.001) and in individual lung tissue samples (p = 0.003), which supported the results of the association study. Conclusions: Genetic polymorphisms of ATM are significantly associated with RP risk. These variants might exert their effect through regulation of ATM expression and serve as independent biomarkers for prediction of RP in patients treated with thoracic radiotherapy.

  12. Nbn and atm cooperate in a tissue and developmental stage-specific manner to prevent double strand breaks and apoptosis in developing brain and eye.

    Directory of Open Access Journals (Sweden)

    Paulo M G Rodrigues

    Full Text Available Nibrin (NBN or NBS1 and ATM are key factors for DNA Double Strand Break (DSB signaling and repair. Mutations in NBN or ATM result in Nijmegen Breakage Syndrome and Ataxia telangiectasia. These syndromes share common features such as radiosensitivity, neurological developmental defects and cancer predisposition. However, the functional synergy of Nbn and Atm in different tissues and developmental stages is not yet understood. Here, we show in vivo consequences of conditional inactivation of both genes in neural stem/progenitor cells using Nestin-Cre mice. Genetic inactivation of Atm in the central nervous system of Nbn-deficient mice led to reduced life span and increased DSBs, resulting in increased apoptosis during neural development. Surprisingly, the increase of DSBs and apoptosis was found only in few tissues including cerebellum, ganglionic eminences and lens. In sharp contrast, we showed that apoptosis associated with Nbn deletion was prevented by simultaneous inactivation of Atm in developing retina. Therefore, we propose that Nbn and Atm collaborate to prevent DSB accumulation and apoptosis during development in a tissue- and developmental stage-specific manner.

  13. Impaired recovery and mutagenic SOS-like responses in ataxia telangiectasia cells

    Energy Technology Data Exchange (ETDEWEB)

    Hilgers, G. (Universite Libre de Bruxelles (Belgium) Rijksuniversiteit Leiden (Netherlands)); Abrahams, P.J. (Rijksuniversiteit Leiden (Netherlands)); Chen, Y.Q. (Universite Libre de Bruxelles (Belgium)); Schouten, R. (Rijksuniversiteit Leiden (Netherlands)); Cornelis, J.J. (Universite Libre de Bruxelles (Belgium) Institut Pasteur, 75 - Paris (France)); Lowe, J.E. (Sussex Univ., Brighton (UK)); Eb, A.J. van der (Rijksuniversiteit Leiden (Netherlands)); Rommelaere, J. (Universite Libre de Bruxelles (Belgium) Institut Pasteur, 75 - Paris (France))

    1989-01-01

    Radiosensitive fibroblasts from patients with ataxia telangiectasia (AT) were studied for their proficiency in two putative eukaryotic SOS-like responses, namely the enhanced reactivation (ER) and enhanced mutagenesis of damaged viruses infecting pre-irradiated versus mock-treated cells. A previous report indicated that, unlike normal human cells, a line of AT fibroblasts (AT5BIVA) could not be induced to express ER of damaged parvovirus H-1, a single-stranded DNA virus, by UV- or X-irradiation. In the present study, AT5BIVA fibroblasts were also distinguished from normal cells by the inability of the former to achieve enhanced mutagenesis of damaged H-1 virus upon cell UV-irradiation. In contrast, dose-response and time-course experiments revealed normal levels of ER of Herpes simplex virus 1, a double-stranded DNA virus, in X- or UV-irradiated AT5BIVA cells. Taken together, these data point to a possible deficiency of AT cells in a conditioned mutagenic process that contributes to a greater extent to the recovery of damaged single-stranded than double-stranded DNA. Such a defect may concern the replication of damaged DNA or the generation of signals promoting the latter process and may be related to the lack of radiation-induced delay that is typical of AT cell DNA synthesis. (author).

  14. Impaired recovery and mutagenic SOS-like responses in ataxia telangiectasia cells

    International Nuclear Information System (INIS)

    Hilgers, G.; Abrahams, P.J.; Chen, Y.Q.; Schouten, R.; Cornelis, J.J.; Lowe, J.E.; Eb, A.J. van der; Rommelaere, J.

    1989-01-01

    Radiosensitive fibroblasts from patients with ataxia telangiectasia (AT) were studied for their proficiency in two putative eukaryotic SOS-like responses, namely the enhanced reactivation (ER) and enhanced mutagenesis of damaged viruses infecting pre-irradiated versus mock-treated cells. A previous report indicated that, unlike normal human cells, a line of AT fibroblasts (AT5BIVA) could not be induced to express ER of damaged parvovirus H-1, a single-stranded DNA virus, by UV- or X-irradiation. In the present study, AT5BIVA fibroblasts were also distinguished from normal cells by the inability of the former to achieve enhanced mutagenesis of damaged H-1 virus upon cell UV-irradiation. In contrast, dose-response and time-course experiments revealed normal levels of ER of Herpes simplex virus 1, a double-stranded DNA virus, in X- or UV-irradiated AT5BIVA cells. Taken together, these data point to a possible deficiency of AT cells in a conditioned mutagenic process that contributes to a greater extent to the recovery of damaged single-stranded than double-stranded DNA. Such a defect may concern the replication of damaged DNA or the generation of signals promoting the latter process and may be related to the lack of radiation-induced delay that is typical of AT cell DNA synthesis. (author)

  15. The role of the neuro-astro-vascular unit in the etiology of Ataxia Telangiectasia

    Directory of Open Access Journals (Sweden)

    Leenoy eMeshulam

    2012-09-01

    Full Text Available The growing recognition that brain pathologies do not affect neurons only but rather are, to a large extent, pathologies of glial cells as well as of the vasculature opens to new perspectives in our understanding of genetic disorders of the CNS. To validate the role of the neuron-glial-vascular unit in the etiology of genome instability disorders, we report about cell death and morphological aspects of neuro-glia networks and the associated vasculature in a mouse model of Ataxia Telangiectasia (A-T, a human genetic disorder that induces severe motor impairment. We found that AT-mutated protein deficiency was consistent with aberrant astrocytic morphology and alterations of the vasculature, often accompanied by reactive gliosis. Interestingly similar findings could also be reported in the case of other genetic disorders. These observations bolster the notion that astrocyte-specific pathologies, hampered vascularization and astrocyte-endothelium interactions in the CNS could play a crucial role in the etiology of genome instability brain disorders and could underlie neurodegeneration.

  16. Molecular and functional characterization of a human ATM gene analogue at Arabidopsis thaliana; Caracterisation moleculaire et Fonctionnelle d'un Homologue du gene humain ATM chez Arabidopsis thaliana

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, V.

    2001-12-15

    The human ATM gene, whose inactivation is responsible for the human disease ataxia telangiectasia is conserved throughout the Eukaryotes and plays an important role in the cellular responses to DNA damage, in particular to DNA double-strand breaks (DSBs). Here we describe the identification of an Arabidopsis thaliana homologue of ATM (AtATM), and the molecular and cytological characterization of plants, hereafter called atm, carrying a disrupting T-DNA insertion in this gene. AtATM covers a 32 kb region on chromosome 3. The AtATM transcript has a complex structure, is 12 kb long and formed by 79 exons. The transcriptional level of AtATM is very low in all the tissues tested, and does not vary after exposure to ionizing radiations (IR). In atm plants, the protein is not detected suggesting the mutants are null. The atm mutants are partially sterile. Aberrant segregation of chromosomes during meiosis I on both male and female sides account for this sterility. However, meiotic recombination frequency is normal. Mutant plants are also hypersensitive to gamma rays and methyl methane sulfonate, but not to UV-B, pointing to a specific defect of atm mutants in the response to DNA DSBs. In plants, ionizing radiations induce a strong, rapid and transient transcriptional activation of genes involved in the cellular response to or the repair of DSBs. This transcriptional regulation of AtRAD51, AtPARP1, atGR1 and AtL1G4 is lost in the atm mutants . The absence of AtRAD51 induction associated with ionizing radiation sensitivity suggest that AtAtm play an important function in DSB repair by homologous recombination. In addition we show that homologous intra-chromosomal recombination frequency is elevated in the mutant comparing to wild-type, with or without gamma irradiation. These results show the implication of AtAtm in the genomic stability. (author)

  17. An Immunotherapeutic Approach to the Treatment and Prevention of Breast Cancer, Based on Epidermal Growth Factor Receptor Variant, Type III

    Science.gov (United States)

    1999-05-01

    clofibrate [CLF] for 3-60 days to induce hepatic hyperplasia, and 4-chloro-6-(2,3 xylidino)-2-pyrimidinyl-thio(N-ß-hydroxyethyl) acetamide [BR931] for 10...XIV List of Abbreviations aa Amino Acid ABs Alveolar Buds ABC ATP-Binding Cassette Ad Adenovirus APC Antigen Presenting Cell AT Ataxia...Telangiectasia ATCC American Type Culture Collection ATM Ataxia Telangiectasia, Mutated BCA Bicinchoninic Acid BDC Bile Duct Carcinomas BrdU

  18. Rejoining of DNA double-strand breaks in human fibroblasts and its impairment in one ataxia telangiectasia and two Fanconi strains

    International Nuclear Information System (INIS)

    Coquerelle, T.M.; Weibezahn, K.F.

    1981-01-01

    Using the technique of neutral elution through polycarbonate filters as a measure of DNA length, and hence of the number of double-strand breaks incurred as a result of radiation damage, we found that normal human fibroblasts rejoin 50% of all breaks within only 3 min (37 degrees C). This fast rejoining was impaired in fibroblasts from one patient with Ataxia telangiectasia and in fibroblasts from two patients with Fanconi's anemia. Also the number of residual breaks after several hours of repair was higher than in control cells. Other cases with the same diseases were normal in their rejoining of double-strand breaks

  19. Radiotherapy induces cell cycle arrest and cell apoptosis in nasopharyngeal carcinoma via the ATM and Smad pathways.

    Science.gov (United States)

    Li, Ming-Yi; Liu, Jin-Quan; Chen, Dong-Ping; Li, Zhou-Yu; Qi, Bin; He, Lu; Yu, Yi; Yin, Wen-Jin; Wang, Meng-Yao; Lin, Ling

    2017-09-02

    Nasopharyngeal carcinoma (NPC) is a common malignant neoplasm of the head and neck which is harmful to human's health. Radiotherapy is commonly used in the treatment of NPC and it induces immediate cell cycle arrest and cell apoptosis. However, the mechanism remains unknown. Evidences suggested the activation of Ataxia telangiectasia mutated (ATM) pathway and Smad pathway are 2 of the important crucial mediators in the function of radiotherapy. In this study, we performed in vitro assays with human nasopharyngeal carcinoma CNE-2 cells and in vivo assays with nude mice to investigate the role of the ATM and Smad pathways in the treatment of nasopharyngeal carcinoma with radiotherapy. The results suggested that radiation induced activation of ATM pathway by inducing expression of p-ATM, p-CHK1, p-CHK2, p15 and inhibiting expression of p-Smad3. In addition, Caspase3 expression was increased while CDC25A was decreased, leading to cell cycle arrest and cell apoptosis. On the other hand, activation of Smad3 can inhibited the ATM pathway and attenuated the efficacy of radiation. In summary, we suggest that both ATM and Smad pathways contribute to the cell cycle arrest and cell apoptosis during nasopharyngeal carcinoma cells treated with radiation.

  20. Gamma-ray induced inhibition of DNA synthesis in ataxia telangiectasia fibroblasts is a function of excision repair capacity

    International Nuclear Information System (INIS)

    Smith, P.J.; Paterson, M.C.

    1980-01-01

    The extent of the deficiency in γ-ray induced DNA repair synthesis in an ataxia telangiectasia (AT) human fibroblast strain was found to show no oxygen enhancement, consistent with a defect in the repair of base damage. Repair deficiency, but not repair proficiency, in AT cells was accompanied by a lack of inhibition of DNA synthesis by either γ-rays or the radiomimetic drug bleomycin. Experiments with 4-nitroquinoline 1-oxide indicated that lack of inhibition was specific for radiogenic-type damage. Thus excision repair, perhaps by DNA strand incision or chromatin modification, appears to halt replicon initiation in irradiated repair proficient cells whereas in repair defective AT strains this putatively important biological function is inoperative

  1. The depletion of ATM inhibits colon cancer proliferation and migration via B56γ2-mediated Chk1/p53/CD44 cascades.

    Science.gov (United States)

    Liu, Rui; Tang, Jiajia; Ding, Chaodong; Liang, Weicheng; Zhang, Li; Chen, Tianke; Xiong, Yan; Dai, Xiaowei; Li, Wenfeng; Xu, Yunsheng; Hu, Jin; Lu, Liting; Liao, Wanqin; Lu, Xincheng

    2017-04-01

    Ataxia-telangiectasia mutated (ATM) protein kinase is a major guardian of genomic stability, and its well-established function in cancer is tumor suppression. Here, we report an oncogenic role of ATM. Using two isogenic sets of human colon cancer cell lines that differed only in their ATM status, we demonstrated that ATM deficiency significantly inhibits cancer cell proliferation, migration, and invasion. The tumor-suppressive function of ATM depletion is not modulated by the compensatory activation of ATR, but it is associated with B56γ2-mediated Chk1/p53/CD44 signaling pathways. Under normal growth conditions, the depletion of ATM prevents B56γ2 ubiquitination and degradation, which activates PP2A-mediated Chk1/p53/p21 signaling pathways, leading to senescence and cell cycle arrest. CD44 was validated as a novel ATM target based on its ability to rescue cell migration and invasion defects in ATM-depleted cells. The activation of p53 induced by ATM depletion suppresses CD44 transcription, thus resulting in epithelial-mesenchymal transition (EMT) and cell migration suppression. Our study suggests that ATM has tumorigenic potential in post-formed colon neoplasia, and it supports ATM as an appealing target for improving cancer therapy. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Evidence for the Deregulation of Protein Turnover Pathways in Atm-Deficient Mouse Cerebellum: An Organotypic Study.

    Science.gov (United States)

    Kim, Catherine D; Reed, Ryan E; Juncker, Meredith A; Fang, Zhide; Desai, Shyamal D

    2017-07-01

    Interferon-stimulated gene 15 (ISG15), an antagonist of the ubiquitin pathway, is elevated in cells and brain tissues obtained from ataxia telangiectasia (A-T) patients. Previous studies reveal that an elevated ISG15 pathway inhibits ubiquitin-dependent protein degradation, leading to activation of basal autophagy as a compensatory mechanism for protein turnover in A-T cells. Also, genotoxic stress (ultraviolet [UV] radiation) deregulates autophagy and induces aberrant degradation of ubiquitylated proteins in A-T cells. In the current study, we show that, as in A-T cells, ISG15 protein expression is elevated in cerebellums and various other tissues obtained from Atm-compromised mice in an Atm-allele-dependent manner (Atm+/+ Atm+/- Atm-/-). Notably, in cerebellums, the brain part primarily affected in A-T, levels of ISG15 were significantly greater (3-fold higher) than cerebrums obtained from the same set of mice. Moreover, as in A-T cell culture, UV induces aberrant degradation of ubiquitylated proteins and autophagy in Atm-deficient, but not in Atm-proficient, cerebellar brain slices grown in culture. Thus, the ex vivo organotypic A-T mouse brain culture model mimics that of an A-T human cell culture model and could be useful for studying the role of ISG15-dependent proteinopathy in cerebellar neurodegeneration, a hallmark of A-T in humans. © 2017 American Association of Neuropathologists, Inc. All rights reserved.

  3. Cell and Molecular Biology of Ataxia Telangiectasia Heterozygous Human Mammary Epithelial Cells Irradiated in Culture

    Science.gov (United States)

    Richmond, Robert C.

    2001-01-01

    Autologous isolates of cell types from obligate heterozygotes with the autosomal disorder ataxia-telangiectasia (A-T)were used to begin a tissue culture model for assessing pathways of radiation-induced cancer formation in this target tissue. This was done by establishing cultures of stromal fibroblasts and long-term growth human mammary epithelial cells (HMEC) in standard 2-dimensional tissue culture in order to establish expression of markers detailing early steps of carcinogenesis. The presumptive breast cancer susceptibility of A-T heterozygotes as a sequel to damage caused by ionizing radiation provided reason to study expression of markers in irradiated HMEC. Findings from our study with HMEC have included determination of differences in specific protein expression amongst growth phase (e.g., log vs stationary) and growth progression (e.g., pass 7 vs pass 9), as well as differences in morphologic markers within populations of irradiated HMEC (e.g., development of multinucleated cells).

  4. Phospho-SMC1 in-Cell ELISA based Detection of Ataxia Telangiectasia

    Directory of Open Access Journals (Sweden)

    Majid Zaki dizaji

    2016-12-01

    Full Text Available BackgroundAtaxia telangiectasia (A-T is a common genetically inherited cause of early childhood-onset ataxia. The infrequency of this disease, vast phenotype variation, disorders with features similar to those of A-T, and lack of definite laboratory test, make diagnosis difficult.  In addition, there is no rapid reliable laboratory method for identifying A-T heterozygotes, who susceptible to ionizing radiation (IR, atherosclerosis, diabetes, and cancers. We used SMC1pSer966 (pSMC1 in-cell colorimetric ELISA to diagnosis and screen in A-T families.Materials and Methods: With informed consent, 2cc peripheral blood was collected from the 15 A-T patients, their parents, and 24 healthy controls with no family history of malignancy, diabetes, and atherosclerosis. Extracted peripheral blood mononuclear cells (PBMCs were cultured in poly-L-Lysine treated 96-well plate with density of 70,000 cells per well. SMC1 phosphorylation was evaluated with cell-based ELISA kit 1 hour after 5 Gy IR and the pSMC1data normalized with Glyceraldehyde-3-phosphate dehydrogenase (GAPDH.Results: SMC1 phosphorylation was significantly low in A-T`s PBMC (mean + standard deviation [SD]: 0.075 + 0.034 in comparison to carriers (mean + SD: 0.190 + 0.060 and healthy controls (mean + SD: 0.312 +0.081, but unluckily could only discriminate A-T patients (Area Under the Curve -receiver operating characteristic [AUC-ROC]: 1.00, 1.00-1.00. This method in spite of rapidness and simplicity showed poor imprecision (22.49% coefficient of variation [CV] for intraday imprecision.Conclusion: It seems pSMC1 assessment by in-cell ELISA can be used for detection of A-T patients, but it may not sensitive enough for identification of carriers. This ELISA test is very simple, rapid, and requires less than 2cc blood. Thus it may be proposed for the early differential diagnosis of A-T as an alternative method.

  5. ATM kinase sustains breast cancer stem-like cells by promoting ATG4C expression and autophagy.

    Science.gov (United States)

    Antonelli, Martina; Strappazzon, Flavie; Arisi, Ivan; Brandi, Rossella; D'Onofrio, Mara; Sambucci, Manolo; Manic, Gwenola; Vitale, Ilio; Barilà, Daniela; Stagni, Venturina

    2017-03-28

    The efficacy of Ataxia-Telangiectasia Mutated (ATM) kinase signalling inhibition in cancer therapy is tempered by the identification of new emerging functions of ATM, which suggests that the role of this protein in cancer progression is complex. We recently demonstrated that this tumor suppressor gene could act as tumor promoting factor in HER2 (Human Epidermal Growth Factor Receptor 2) positive breast cancer. Herein we put in evidence that ATM expression sustains the proportion of cells with a stem-like phenotype, measured as the capability to form mammospheres, independently of HER2 expression levels. Transcriptomic analyses revealed that, in mammospheres, ATM modulates the expression of cell cycle-, DNA repair- and autophagy-related genes. Among these, the silencing of the autophagic gene, autophagy related 4C cysteine peptidase (ATG4C), impairs mammosphere formation similarly to ATM depletion. Conversely, ATG4C ectopic expression in cells silenced for ATM expression, rescues mammospheres growth. Finally, tumor array analyses, performed using public data, identify a significant correlation between ATM and ATG4C expression levels in all human breast cancer subtypes, except for the basal-like one.Overall, we uncover a new connection between ATM kinase and autophagy regulation in breast cancer. We demonstrate that, in breast cancer cells, ATM and ATG4C are essential drivers of mammosphere formation, suggesting that their targeting may improve current approaches to eradicate breast cancer cells with a stem-like phenotype.

  6. Rats with a missense mutation in Atm display neuroinflammation and neurodegeneration subsequent to accumulation of cytosolic DNA following unrepaired DNA damage.

    Science.gov (United States)

    Quek, Hazel; Luff, John; Cheung, KaGeen; Kozlov, Sergei; Gatei, Magtouf; Lee, C Soon; Bellingham, Mark C; Noakes, Peter G; Lim, Yi Chieh; Barnett, Nigel L; Dingwall, Steven; Wolvetang, Ernst; Mashimo, Tomoji; Roberts, Tara L; Lavin, Martin F

    2017-04-01

    Mutations in the ataxia-telangiectasia (A-T)-mutated ( ATM ) gene give rise to the human genetic disorder A-T, characterized by immunodeficiency, cancer predisposition, and neurodegeneration. Whereas a series of animal models recapitulate much of the A-T phenotype, they fail to present with ataxia or neurodegeneration. We describe here the generation of an Atm missense mutant [amino acid change of leucine (L) to proline (P) at position 2262 (L2262P)] rat by intracytoplasmic injection (ICSI) of mutant sperm into oocytes. Atm -mutant rats ( Atm L2262P/L2262P ) expressed low levels of ATM protein, suggesting a destabilizing effect of the mutation, and had a significantly reduced lifespan compared with Atm +/+ Whereas these rats did not show cerebellar atrophy, they succumbed to hind-limb paralysis (45%), and the remainder developed tumors. Closer examination revealed the presence of both dsDNA and ssDNA in the cytoplasm of cells in the hippocampus, cerebellum, and spinal cord of Atm L2262P/L2262P rats. Significantly increased levels of IFN-β and IL-1β in all 3 tissues were indicative of DNA damage induction of the type 1 IFN response. This was further supported by NF-κB activation, as evidenced by p65 phosphorylation (P65) and translocation to the nucleus in the spinal cord and parahippocampus. Other evidence of neuroinflammation in the brain and spinal cord was the loss of motor neurons and the presence of increased activation of microglia. These data provide support for a proinflammatory phenotype that is manifested in the Atm mutant rat as hind-limb paralysis. This mutant represents a useful model to investigate the importance of neuroinflammation in A-T. © Society for Leukocyte Biology.

  7. MiR-2964a-5p binding site SNP regulates ATM expression contributing to age-related cataract risk.

    Science.gov (United States)

    Rong, Han; Gu, Shanshan; Zhang, Guowei; Kang, Lihua; Yang, Mei; Zhang, Junfang; Shen, Xinyue; Guan, Huaijin

    2017-10-17

    This study was to explore the involvement of DNA repair genes in the pathogenesis of age-related cataract (ARC). We genotyped nine single nucleotide polymorphisms (SNPs) of genes responsible to DNA double strand breaks (DSBs) in 804 ARC cases and 804 controls in a cohort of eye diseases in Chinese population and found that the ataxia telangiectasia mutated ( ATM ) gene-rs4585:G>T was significantly associated with ARC risk. An in vitro functional test found that miR-2964a-5p specifically down-regulated luciferase reporter expression and ATM expression in the cell lines transfected with rs4585 T allele compared to rs4585 G allele. The molecular assay on human tissue samples discovered that ATM expression was down-regulated in majority of ARC tissues and correlated with ATM genotypes. In addition, the Comet assay of cellular DNA damage of peripheral lymphocytes indicated that individuals carrying the G allele (GG/GT) of ATM -rs4585 had lower DNA breaks compared to individuals with TT genotype. These findings suggested that the SNP rs4585 in ATM might affect ARC risk through modulating the regulatory affinity of miR-2964a-5p. The reduced DSBs repair might be involved in ARC pathogenesis.

  8. ATM Protein Physically and Functionally Interacts with Proliferating Cell Nuclear Antigen to Regulate DNA Synthesis*

    Science.gov (United States)

    Gamper, Armin M.; Choi, Serah; Matsumoto, Yoshihiro; Banerjee, Dibyendu; Tomkinson, Alan E.; Bakkenist, Christopher J.

    2012-01-01

    Ataxia telangiectasia (A-T) is a pleiotropic disease, with a characteristic hypersensitivity to ionizing radiation that is caused by biallelic mutations in A-T mutated (ATM), a gene encoding a protein kinase critical for the induction of cellular responses to DNA damage, particularly to DNA double strand breaks. A long known characteristic of A-T cells is their ability to synthesize DNA even in the presence of ionizing radiation-induced DNA damage, a phenomenon termed radioresistant DNA synthesis. We previously reported that ATM kinase inhibition, but not ATM protein disruption, blocks sister chromatid exchange following DNA damage. We now show that ATM kinase inhibition, but not ATM protein disruption, also inhibits DNA synthesis. Investigating a potential physical interaction of ATM with the DNA replication machinery, we found that ATM co-precipitates with proliferating cell nuclear antigen (PCNA) from cellular extracts. Using bacterially purified ATM truncation mutants and in vitro translated PCNA, we showed that the interaction is direct and mediated by the C terminus of ATM. Indeed, a 20-amino acid region close to the kinase domain is sufficient for strong binding to PCNA. This binding is specific to ATM, because the homologous regions of other PIKK members, including the closely related kinase A-T and Rad3-related (ATR), did not bind PCNA. ATM was found to bind two regions in PCNA. To examine the functional significance of the interaction between ATM and PCNA, we tested the ability of ATM to stimulate DNA synthesis by DNA polymerase δ, which is implicated in both DNA replication and DNA repair processes. ATM was observed to stimulate DNA polymerase activity in a PCNA-dependent manner. PMID:22362778

  9. ATM and ATR play complementary roles in the behavior of excitatory and inhibitory vesicle populations.

    Science.gov (United States)

    Cheng, Aifang; Zhao, Teng; Tse, Kai-Hei; Chow, Hei-Man; Cui, Yong; Jiang, Liwen; Du, Shengwang; Loy, Michael M T; Herrup, Karl

    2018-01-09

    ATM (ataxia-telangiectasia mutated) and ATR (ATM and Rad3-related) are large PI3 kinases whose human mutations result in complex syndromes that include a compromised DNA damage response (DDR) and prominent nervous system phenotypes. Both proteins are nuclear-localized in keeping with their DDR functions, yet both are also found in cytoplasm, including on neuronal synaptic vesicles. In ATM- or ATR-deficient neurons, spontaneous vesicle release is reduced, but a drop in ATM or ATR level also slows FM4-64 dye uptake. In keeping with this, both proteins bind to AP-2 complex components as well as to clathrin, suggesting roles in endocytosis and vesicle recycling. The two proteins play complementary roles in the DDR; ATM is engaged in the repair of double-strand breaks, while ATR deals mainly with single-strand damage. Unexpectedly, this complementarity extends to these proteins' synaptic function as well. Superresolution microscopy and coimmunoprecipitation reveal that ATM associates exclusively with excitatory (VGLUT1 + ) vesicles, while ATR associates only with inhibitory (VGAT + ) vesicles. The levels of ATM and ATR respond to each other; when ATM is deficient, ATR levels rise, and vice versa. Finally, blocking NMDA, but not GABA, receptors causes ATM levels to rise while ATR levels respond to GABA, but not NMDA, receptor blockade. Taken together, our data suggest that ATM and ATR are part of the cellular "infrastructure" that maintains the excitatory/inhibitory balance of the nervous system. This idea has important implications for the human diseases resulting from their genetic deficiency.

  10. Modulation of proteostasis counteracts oxidative stress and affects DNA base excision repair capacity in ATM-deficient cells.

    Science.gov (United States)

    Poletto, Mattia; Yang, Di; Fletcher, Sally C; Vendrell, Iolanda; Fischer, Roman; Legrand, Arnaud J; Dianov, Grigory L

    2017-09-29

    Ataxia telangiectasia (A-T) is a syndrome associated with loss of ATM protein function. Neurodegeneration and cancer predisposition, both hallmarks of A-T, are likely to emerge as a consequence of the persistent oxidative stress and DNA damage observed in this disease. Surprisingly however, despite these severe features, a lack of functional ATM is still compatible with early life, suggesting that adaptation mechanisms contributing to cell survival must be in place. Here we address this gap in our knowledge by analysing the process of human fibroblast adaptation to the lack of ATM. We identify profound rearrangement in cellular proteostasis occurring very early on after loss of ATM in order to counter protein damage originating from oxidative stress. Change in proteostasis, however, is not without repercussions. Modulating protein turnover in ATM-depleted cells also has an adverse effect on the DNA base excision repair pathway, the major DNA repair system that deals with oxidative DNA damage. As a consequence, the burden of unrepaired endogenous DNA lesions intensifies, progressively leading to genomic instability. Our study provides a glimpse at the cellular consequences of loss of ATM and highlights a previously overlooked role for proteostasis in maintaining cell survival in the absence of ATM function. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  11. Molecular and functional characterization of a human ATM gene analogue at Arabidopsis thaliana

    International Nuclear Information System (INIS)

    Garcia, V.

    2001-12-01

    The human ATM gene, whose inactivation is responsible for the human disease ataxia telangiectasia is conserved throughout the Eukaryotes and plays an important role in the cellular responses to DNA damage, in particular to DNA double-strand breaks (DSBs). Here we describe the identification of an Arabidopsis thaliana homologue of ATM (AtATM), and the molecular and cytological characterization of plants, hereafter called atm, carrying a disrupting T-DNA insertion in this gene. AtATM covers a 32 kb region on chromosome 3. The AtATM transcript has a complex structure, is 12 kb long and formed by 79 exons. The transcriptional level of AtATM is very low in all the tissues tested, and does not vary after exposure to ionizing radiations (IR). In atm plants, the protein is not detected suggesting the mutants are null. The atm mutants are partially sterile. Aberrant segregation of chromosomes during meiosis I on both male and female sides account for this sterility. However, meiotic recombination frequency is normal. Mutant plants are also hypersensitive to gamma rays and methyl methane sulfonate, but not to UV-B, pointing to a specific defect of atm mutants in the response to DNA DSBs. In plants, ionizing radiations induce a strong, rapid and transient transcriptional activation of genes involved in the cellular response to or the repair of DSBs. This transcriptional regulation of AtRAD51, AtPARP1, atGR1 and AtL1G4 is lost in the atm mutants . The absence of AtRAD51 induction associated with ionizing radiation sensitivity suggest that AtAtm play an important function in DSB repair by homologous recombination. In addition we show that homologous intra-chromosomal recombination frequency is elevated in the mutant comparing to wild-type, with or without gamma irradiation. These results show the implication of AtAtm in the genomic stability. (author)

  12. Ataxia-telangiectasia cells are not uniformly deficient in poly(ADP-ribose) synthesis following X-irradiation

    International Nuclear Information System (INIS)

    Zwelling, L.A.; Kerrigan, D.; Mattern, M.R.

    1983-01-01

    The synthesis of poly(adenosine diphosphoribose [poly(ADP-R)] follows the DNA strand breakage produced by a number of physical and chemical agents, including X-radiation, and may be important for repair of several types of DNA damage. The reduction or abolition of its synthesis following X-irradiation might explain the enhanced sensitivity of ataxia-telangiectasia (A-T) cells to X-ray. We have examined 8 lines of human fibroblasts (including 4 A-T lines) for stimulation of the synthesis of poly(ADP-R) by X-irradiation. Similar amounts of X-ray-stimulated synthesis of poly(ADP-R) were detected in 4 lines of A-T fibroblasts, and in fibrolasts from a xeroderma pigmentosum (XP) patient, a Fanconi's anemia (FA) patient and 2 normal patients. 6 lines of human lymphoblastoid lines were also examined for X-ray-stimulated poly(ADP-R) synthesis. 4 A-T lines displayed an unusually high synthesis of poly(ADP-R) in unirradiated cells compared with 2 normal lines. (orig./AJ)

  13. Ataxia-telangiectasia cells are not uniformly deficient in poly(ADP-ribose) synthesis following X-irradiation

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    Zwelling, L.A.; Kerrigan, D. (National Cancer Inst., Bethesda, MD (USA). Lab. of Molecular Pharmacology); Mattern, M.R. (National Cancer Inst., Bethesda, MD (USA). Lab. of Molecular Carcinogenesis)

    1983-04-01

    The synthesis of poly(adenosine diphosphoribose (poly(ADP-R)) follows the DNA strand breakage produced by a number of physical and chemical agents, including X-radiation, and may be important for repair of several types of DNA damage. The reduction or abolition of its synthesis following X-irradiation might explain the enhanced sensitivity of ataxia-telangiectasia (A-T) cells to X-ray. We have examined 8 lines of human fibroblasts (including 4 A-T lines) for stimulation of the synthesis of poly(ADP-R) by X-irradiation. Similar amounts of X-ray-stimulated synthesis of poly(ADP-R) were detected in 4 lines of A-T fibroblasts, and in fibrolasts from a xeroderma pigmentosum (XP) patient, a Fanconi's anemia (FA) patient and 2 normal patients. 6 lines of human lymphoblastoid lines were also examined for X-ray-stimulated poly(ADP-R) synthesis. 4 A-T lines displayed an unusually high synthesis of poly(ADP-R) in unirradiated cells compared with 2 normal lines.

  14. Effects of hyperthermia and ionizing radiation in normal and ataxia telangiectasia human fibroblast lines

    International Nuclear Information System (INIS)

    Mitchel, R.E.J.; Chan, A.; Smith, B.P.; Child, S.D.; Paterson, M.C.

    1984-01-01

    The effects of 45 0 C hyperthermia and γ radiation have been studied in three normal human fibroblast lines (GM38, GM730, WI38) and compared to the effects in two lines derived from patients with the hereditary disease ataxia telangiectasia (AR3BI, AT5BI). All lines, both normal and γ-sensitive AT, showed a similar resistance to killing by heat alone, suggesting that the defect responsible for the increased radiation sensitivity in AT lines does not confer increased heat sensitivity. Shouldered survival curves were obtained in each case indicating the ability to accumulate sublethal heat damage. All normal and AT cell lines exhibited increased resistance to the lethal effects of heat in response to a thermal stress, indicating that the defect that causes radiosensitivity in AT cell lines does not prevent the induction of thermotolerance. It was hypothesized that in normal cells, this heat treatment inactivates the process which is already defective in AT lines, and that this process may be required for the proper rejoining of double-strand breaks produced during the repair of other radiation-induced lesions

  15. Effect of caffeine on γ-ray induced G2 delay in ataxia telangiectasia

    International Nuclear Information System (INIS)

    Bates, P.R.; Lavin, M.F.

    1985-01-01

    Exposure of normal control and ataxia-telangiectasia (A-T) lymphoblastoid cell lines to ionizing radiation gives rise to an increase in the proportion of G2 phase cells. The size and extent of the G2 phase block is greater in A-T cells than in normal cells. Caffeine has a similar overall effect in control and A-T cell lines in reducing the G2 arrest observed after ionizing radiation. While the proportion of cells accumulated in G2 in A-T cells is considerably greater than in controls, addition of caffeine at the time of maximal G2 block brings about a return of G2 phase cell numbers to unirradiated values in 3 hours in both cell types. In normal control cells the caffeine-mediated decrease in G2 cells is reflected by an increase in mitotic cells. These mitotic cells have a higher frequency of chromosome aberrations compared to cells harvested in the absence of caffeine. Similarly in A-T cells addition of caffeine to irradiated cultures, delayed in G2 phase, increased the number of mitotic cells and the frequency of chromosome aberrations. (author)

  16. The effect of MRN complex and ATM kinase inhibitors on Zebrafish embryonic development

    Science.gov (United States)

    Kumaran, Malina; Fazry, Shazrul

    2018-04-01

    Zebrafish is an ideal animal model to study developmental biology due to its transparent embryos and rapid development stages of embryogenesis. Here we investigate the role of DNA damage proteins, specifically Mre11/Rad50/NBN (MRN) complex and ataxia-telangiectasia mutated (ATM) kinase during embryogenesis by inhibiting its function using specific MRN complex (Mirin) and ATM Kinase inhibitors (Ku60019 and Ku55933). Zebrafish embryos at midblastula transition (MBT) stage are treated with Mirin, Ku60019 and Ku55933. The embryonic development of the embryos was monitored at 24 hours-post fertilisation (hpf), 48 hpf and 72 hpf. We observed that at the lowest concentrations (3 µM of Mirin, 1.5 nM of Ku60019 and 3 nM of Ku55933), the inhibitors treated embryos have 100% survivability. However, with increasing inhibitor concentration, the survivability drops. Control or mock treatment of all embryos shows 100 % survivability rate. This study suggests that DNA damage repair proteins may be crucial for normal zebrafish embryo development and survival.

  17. Contribution of canonical nonhomologous end joining to chromosomal rearrangements is enhanced by ATM kinase deficiency.

    Science.gov (United States)

    Bhargava, Ragini; Carson, Caree R; Lee, Gabriella; Stark, Jeremy M

    2017-01-24

    A likely mechanism of chromosomal rearrangement formation involves joining the ends from two different chromosomal double-strand breaks (DSBs). These events could potentially be mediated by either of two end-joining (EJ) repair pathways [canonical nonhomologous end joining (C-NHEJ) or alternative end joining (ALT-EJ)], which cause distinct rearrangement junction patterns. The relative role of these EJ pathways during rearrangement formation has remained controversial. Along these lines, we have tested whether the DNA damage response mediated by the Ataxia Telangiectasia Mutated (ATM) kinase may affect the relative influence of C-NHEJ vs. ALT-EJ on rearrangement formation. We developed a reporter in mouse cells for a 0.4-Mbp deletion rearrangement that is formed by EJ between two DSBs induced by the Cas9 endonuclease. We found that disruption of the ATM kinase causes an increase in the frequency of the rearrangement as well as a shift toward rearrangement junctions that show hallmarks of C-NHEJ. Furthermore, ATM suppresses rearrangement formation in an experimental condition, in which C-NHEJ is the predominant EJ repair event (i.e., expression of the 3' exonuclease Trex2). Finally, several C-NHEJ factors are required for the increase in rearrangement frequency caused by inhibition of the ATM kinase. We also examined ATM effectors and found that H2AX shows a similar influence as ATM, whereas the influence of ATM on this rearrangement seems independent of 53BP1. We suggest that the contribution of the C-NHEJ pathway to the formation of a 0.4-Mbp deletion rearrangement is enhanced in ATM-deficient cells.

  18. Inhibition of TGFbeta1 Signaling Attenutates ATM Activity inResponse to Genotoxic Stress

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    Kirshner, Julia; Jobling, Michael F.; Pajares, Maria Jose; Ravani, Shraddha A.; Glick, Adam B.; Lavin, Martin J.; Koslov, Sergei; Shiloh, Yosef; Barcellos-Hoff, Mary Helen

    2006-09-15

    Ionizing radiation causes DNA damage that elicits a cellular program of damage control coordinated by the kinase activity of ataxia telangiectasia mutated protein (ATM). Transforming growth factor {beta}1 (TGF{beta}), which is activated by radiation, is a potent and pleiotropic mediator of physiological and pathological processes. Here we show that TGF{beta} inhibition impedes the canonical cellular DNA damage stress response. Irradiated Tgf{beta}1 null murine epithelial cells or human epithelial cells treated with a small molecule inhibitor of TGF{beta} type I receptor kinase exhibit decreased phosphorylation of Chk2, Rad17 and p53, reduced {gamma}H2AX radiation-induced foci, and increased radiosensitivity compared to TGF{beta} competent cells. We determined that loss of TGF{beta} signaling in epithelial cells truncated ATM autophosphorylation and significantly reduced its kinase activity, without affecting protein abundance. Addition of TGF{beta} restored functional ATM and downstream DNA damage responses. These data reveal a heretofore undetected critical link between the microenvironment and ATM that directs epithelial cell stress responses, cell fate and tissue integrity. Thus, TGF{beta}1, in addition to its role in homoeostatic growth control, plays a complex role in regulating responses to genotoxic stress, the failure of which would contribute to the development of cancer; conversely, inhibiting TGF{beta} may be used to advantage in cancer therapy.

  19. MicroRNA203a suppresses glioma tumorigenesis through an ATM-dependent interferon response pathway.

    Science.gov (United States)

    Yang, Chuan He; Wang, Yinan; Sims, Michelle; Cai, Chun; He, Ping; Häcker, Hans; Yue, Junming; Cheng, Jinjun; Boop, Frederick A; Pfeffer, Lawrence M

    2017-12-22

    Glioblastoma (GBM) is a deadly and incurable brain tumor. Although microRNAs (miRNAs) play critical roles in regulating the cancer cell phenotype, the underlying mechanisms of how they regulate tumorigenesis are incompletely understood. We previously showed that miR-203a is expressed at relatively low levels in GBM patients, and ectopic miR-203a expression in GBM cell lines inhibited cell proliferation and migration, increased sensitivity to apoptosis induced by interferon (IFN) or temozolomide in vitro , and inhibited GBM tumorigenesis in vivo . Here we show that ectopic expression of miR-203a in GBM cell lines promotes the IFN response pathway as evidenced by increased IFN production and IFN-stimulated gene (ISG) expression, and high basal tyrosine phosphorylation of multiple STAT proteins. Importantly, we identified that miR-203a directly suppressed the protein levels of ataxia-telangiectasia mutated (ATM) kinase that negatively regulates IFN production. We found that high ATM expression in GBM correlates with poor patient survival and that ATM expression is inversely correlated with miR-203a expression. Knockout of ATM expression and inhibition of ATM function in GBM cell lines inhibited cell proliferation and migration, increased sensitivity to apoptosis induced by therapeutic agents in vitro , and markedly suppressed GBM tumor growth and promoted animal survival. In contrast, restoring ATM levels in GBM cells ectopically expressing miR-203a increased tumorigenicity and decreased animal survival. Our study suggests that low miR-203a expression in GBM suppresses the interferon response through an ATM-dependent pathway.

  20. Body composition, muscle strength and hormonal status in patients with ataxia telangiectasia: a cohort study.

    Science.gov (United States)

    Pommerening, H; van Dullemen, S; Kieslich, M; Schubert, R; Zielen, S; Voss, S

    2015-12-09

    Ataxia-telangiectasia (A-T) is a devastating human autosomal recessive disorder that causes progressive cerebellar ataxia, immunodeficiency, premature aging, chromosomal instability and increased cancer risk. Affected patients show growth failure, poor weight gain, low body mass index (BMI), myopenia and increased fatigue during adolescence. The prevalence of alterations in body composition, muscle strength and hormonal status has not been well described in classical A-T patients. Additionally, no current guidelines are available for the assessment and management of these changes. We analyzed body composition, manual muscle strength and hormonal status in 25 A-T patients and 26 age-matched, healthy controls. Bioelectrical impedance analysis (BIA) was performed to evaluate the body composition, fat-free mass (FFM), body cell mass (BCM), extracellular matrix (ECM), phase angle (PhA), fat mass (FM) and ECM to BCM ratio. Manual muscle strength was measured using a hydraulic hand dynamometer. The BMI, FFM and PhA were significantly lower in A-T patients than in controls (BMI 16.56 ± 3.52 kg/m(2) vs. 19.86 ± 3.54 kg/m(2); Z-Score: -1.24 ± 1.29 vs. 0.05 ± 0.92, p body composition, characterized by depleted BMI, PhA and BCM; by the need to sit in a wheelchair; by altered hormone levels; and by poor muscle strength, is a major factor underlying disease progression and increased fatigue in A-T patients. ClinicalTrials.gov NCT02345200.

  1. Potentiation by caffeine of x-ray damage to cultured human skin fibroblasts from normal subjects and ataxia-telangiectasia patients

    International Nuclear Information System (INIS)

    Furcinitti, P.S.

    1983-01-01

    Caffeine was found to potentiate x-ray-induced killing of human diploid fibroblasts from a normal subject and an ataxia-telangiectasia (AT) patient when it was present at 2 mM concentration for 30 to 66 h postirradiation. The dose-modifying factor for caffeine-treated normal cells had an average value of 1.26 +- 0.13 which did not vary significantly with treatment time or x-ray dose. The dose-modifying factor for caffeine-treated AT cells was 1.12 +- 0.12 at 30 h, rose to 1.66 +- 0.17 at 41 h, and decreased to 1.31 +- 0.13 at 66 h. Thus no clear difference was observed between these two cell strains' susceptibility to postirradiation caffeine treatment

  2. Atm heterozygous mice are more sensitive to radiation-induced cataracts than are their wild-type counterparts

    Science.gov (United States)

    Worgul, Basil V.; Smilenov, Lubomir; Brenner, David J.; Junk, Anna; Zhou, Wei; Hall, Eric J.

    2002-01-01

    It is important to know whether the human population includes genetically predisposed radiosensitive subsets. In vitro studies have shown that cells from individuals homozygous for ataxia telangiectasia (A-T) are much more radiosensitive than cells from unaffected individuals. Although cells heterozygous for the ATM gene (ATM(+/-)) may be slightly more radiosensitive in vitro, it remained to be determined whether the greater susceptibility of ATM(+/-) cells translates into an increased sensitivity for late effects in vivo, though there is a suggestion that radiotherapy patients that are heterozygous for the ATM gene may be more at risk of developing late normal tissue damage. We chose cataractogenesis in the lens as a means to assay for the effects of ATM deficiency in a late-responding tissue. One eye of wild-type, Atm heterozygous and homozygous knockout mice was exposed to 0.5-, 1.0-, 2.0-, or 4.0-Gy x rays. The animals were followed weekly for cataract development by conventional slit-lamp biomicroscopy. Cataract development in the animals of all three groups was strongly dependent on dose. The lenses of homozygous mice were the first to opacify at any given dose. Most important in the present context is that cataracts appeared earlier in the heterozygous versus wild-type animals. The data suggest that ATM heterozygotes in the human population may also be radiosensitive. This may influence the choice of individuals destined to be exposed to higher than normal doses of radiation, such as astronauts, and may also suggest that radiotherapy patients who are ATM heterozygotes could be predisposed to increased late normal tissue damage.

  3. Critical involvement of the ATM-dependent DNA damage response in the apoptotic demise of HIV-1-elicited syncytia.

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    Jean-Luc Perfettini

    Full Text Available DNA damage can activate the oncosuppressor protein ataxia telangiectasia mutated (ATM, which phosphorylates the histone H2AX within characteristic DNA damage foci. Here, we show that ATM undergoes an activating phosphorylation in syncytia elicited by the envelope glycoprotein complex (Env of human immunodeficiency virus-1 (HIV-1 in vitro. This was accompanied by aggregation of ATM in discrete nuclear foci that also contained phospho-histone H2AX. DNA damage foci containing phosphorylated ATM and H2AX were detectable in syncytia present in the brain or lymph nodes from patients with HIV-1 infection, as well as in a fraction of blood leukocytes, correlating with viral status. Knockdown of ATM or of its obligate activating factor NBS1 (Nijmegen breakage syndrome 1 protein, as well as pharmacological inhibition of ATM with KU-55933, inhibited H2AX phosphorylation and prevented Env-elicited syncytia from undergoing apoptosis. ATM was found indispensable for the activation of MAP kinase p38, which catalyzes the activating phosphorylation of p53 on serine 46, thereby causing p53 dependent apoptosis. Both wild type HIV-1 and an HIV-1 mutant lacking integrase activity induced syncytial apoptosis, which could be suppressed by inhibiting ATM. HIV-1-infected T lymphoblasts from patients with inactivating ATM or NBS1 mutations also exhibited reduced syncytial apoptosis. Altogether these results indicate that apoptosis induced by a fusogenic HIV-1 Env follows a pro-apoptotic pathway involving the sequential activation of ATM, p38MAPK and p53.

  4. Promoter Hypermethylation of the ATM Gene as a Novel Biomarker for Breast Cancer

    Science.gov (United States)

    Begam, Nasrin; Jamil, Kaiser; Raju, Suryanarayana G

    2017-11-26

    Background: Breast cancer may be induced by activation of protooncogenes to oncogenes and in many cases inactivation of tumor suppressor genes. Ataxia telangiectasia mutated (ATM) is an important tumor suppressor gene which plays central roles in the maintenance of genomic integrity by activating cell cycle checkpoints and promoting repair of double-strand breaks of DNA. In breast cancer, decrease ATM expression correlates with a poor outcome; however, the molecular mechanisms underlying downregulation are still unclear. Promoter hypermethylation may contribute in downregulation. Hence the present investigation was designed to evaluate promoter methylation and expression of the ATM gene in breast cancer cases, and to determine links with clinical and demographic manifestations, in a South Indian population. Methods: Tumor biopsy samples were collected from 50 pathologically confirmed sporadic breast cancer cases. DNA was isolated from tumor and adjacent non-tumorous regions, and sodium bisulfite conversion and methylation-specific PCR were performed using MS-PCR primers for the ATM promoter region. In addition, ATM mRNA expression was also analyzed for all samples using real-time PCR. Results: Fifty eight percent (58%) of cancer tissue samples showed promoter hypermethylation for the ATM gene, in contrast to only 4.44% of normal tissues (p= 0.0001). Furthermore, ATM promoter methylation was positively associated with age (p = 0.01), tumor size (p=0.045) and advanced stage of disease i.e. stages III and IV (p =0.019). An association between promoter hypermethylation and lower expression of ATM mRNA was also found (p=0.035). Conclusion: We report for the first time that promoter hypermethylation of ATM gene may be useful as a potential new biomarker for breast cancer, especially in the relatively young patients. Creative Commons Attribution License

  5. The orally active and bioavailable ATR kinase inhibitor AZD6738 potentiates the anti-tumor effects of cisplatin to resolve ATM-deficient non-small cell lung cancer in vivo.

    Science.gov (United States)

    Vendetti, Frank P; Lau, Alan; Schamus, Sandra; Conrads, Thomas P; O'Connor, Mark J; Bakkenist, Christopher J

    2015-12-29

    ATR and ATM are DNA damage signaling kinases that phosphorylate several thousand substrates. ATR kinase activity is increased at damaged replication forks and resected DNA double-strand breaks (DSBs). ATM kinase activity is increased at DSBs. ATM has been widely studied since ataxia telangiectasia individuals who express no ATM protein are the most radiosensitive patients identified. Since ATM is not an essential protein, it is widely believed that ATM kinase inhibitors will be well-tolerated in the clinic. ATR has been widely studied, but advances have been complicated by the finding that ATR is an essential protein and it is widely believed that ATR kinase inhibitors will be toxic in the clinic. We describe AZD6738, an orally active and bioavailable ATR kinase inhibitor. AZD6738 induces cell death and senescence in non-small cell lung cancer (NSCLC) cell lines. AZD6738 potentiates the cytotoxicity of cisplatin and gemcitabine in NSCLC cell lines with intact ATM kinase signaling, and potently synergizes with cisplatin in ATM-deficient NSCLC cells. In contrast to expectations, daily administration of AZD6738 and ATR kinase inhibition for 14 consecutive days is tolerated in mice and enhances the therapeutic efficacy of cisplatin in xenograft models. Remarkably, the combination of cisplatin and AZD6738 resolves ATM-deficient lung cancer xenografts.

  6. Murine scid cells complement ataxia-telangiectasia cells and show a normal port-irradiation response of DNA synthesis

    International Nuclear Information System (INIS)

    Komatsu, K.; Yoshida, M.; Okumura, Y.

    1993-01-01

    The murine severe combined immunodeficient mutation (scid) is characterized by a lack of both B and T cells, due to a deficit in lymphoid variable-(diversity)-joining (V(D)J) rearrangement. Scid cells are highly sensitive to both radiation-induced killing and chromosomal aberrations. Significantly reduced D 0 and n values were demonstrated in scid cells and were similar to ataxia-telangiectasia (AT) cells (a unique human disease conferring whole body radiosensitivity). However, the kinetics of DNA synthesis after irradiation were different between the two cell types. In contrast with the radioresistant DNA synthesis of AT cells, DNA synthesis of scid cells was markedly inhibited after irradiation. The existence of different mutations was also supported by evidence of complementation in somatic cell hybrids between scid cells and AT cells. Results indicate that the radiobiological character of scid is similar to AT but is presumably caused by different mechanisms. (author)

  7. Ataxia crónica en pediatría

    Directory of Open Access Journals (Sweden)

    Ricardo Erazo Torricelli

    2013-09-01

    Full Text Available Las ataxias crónicas constituyen un grupo heterogéneo de enfermedades, que afectan al niño a diferentes edades. Así las formas congénitas, generalmente no progresivas, se observan desde los primeros meses de vida y se expresan por hipotonía y retraso motor, mucho antes de que la ataxia se haga evidente. La resonancia magnética cerebral puede ser diagnóstica en algunos cuadros, como ocurre con el síndrome de Joubert. El grupo de ataxias hereditarias progresivas, en constante expansión, suelen comenzar después del período del lactante. Los signos clínicos destacables son la apraxia ocular y la inestabilidad de la marcha que pueden asociarse a telangiectasias oculocutáneas (ataxia-telangiectasia o a neuropatía sensitiva (ataxia de Friedreich. En esta revisión se describen en forma sucinta las ataxias congénitas y en forma más detallada las causas principales de ataxias hereditarias progresivas autosómicas recesivas, autosómicas dominantes y mitocondriales. Se destaca la importancia del estudio genético, que es la clave para lograr el diagnóstico en la mayoría de estas enfermedades. Aunque aún no hay tratamiento para la mayoría de las ataxias hereditarias progresivas, algunas sí lo tienen, como la enfermedad de Refsum, déficit de vitamina E, déficit de Coenzima Q10, por lo cual el diagnóstico en estos casos es aún más relevante. En la actualidad, el diagnóstico de los cuadros de ataxia hereditaria del niño aún no tratable es fundamental para lograr un manejo adecuado, determinar un pronóstico preciso y dar a la familia un consejo genético oportuno.

  8. ATM regulates NF-κB-dependent immediate-early genes via RelA Ser 276 phosphorylation coupled to CDK9 promoter recruitment

    Science.gov (United States)

    Fang, Ling; Choudhary, Sanjeev; Zhao, Yingxin; Edeh, Chukwudi B; Yang, Chunying; Boldogh, Istvan; Brasier, Allan R.

    2014-01-01

    Ataxia-telangiectasia mutated (ATM), a member of the phosphatidylinositol 3 kinase-like kinase family, is a master regulator of the double strand DNA break-repair pathway after genotoxic stress. Here, we found ATM serves as an essential regulator of TNF-induced NF-kB pathway. We observed that TNF exposure of cells rapidly induced DNA double strand breaks and activates ATM. TNF-induced ROS promote nuclear IKKγ association with ubiquitin and its complex formation with ATM for nuclear export. Activated cytoplasmic ATM is involved in the selective recruitment of the E3-ubiquitin ligase β-TrCP to phospho-IκBα proteosomal degradation. Importantly, ATM binds and activates the catalytic subunit of protein kinase A (PKAc), ribosmal S6 kinase that controls RelA Ser 276 phosphorylation. In ATM knockdown cells, TNF-induced RelA Ser 276 phosphorylation is significantly decreased. We further observed decreased binding and recruitment of the transcriptional elongation complex containing cyclin dependent kinase-9 (CDK9; a kinase necessary for triggering transcriptional elongation) to promoters of NF-κB-dependent immediate-early cytokine genes, in ATM knockdown cells. We conclude that ATM is a nuclear damage-response signal modulator of TNF-induced NF-κB activation that plays a key scaffolding role in IκBα degradation and RelA Ser 276 phosphorylation. Our study provides a mechanistic explanation of decreased innate immune response associated with A-T mutation. PMID:24957606

  9. Effects of radiation therapy for Hodgkin's disease in a child with ataxia telangiectasia: a clinical, biological and pathologic study

    International Nuclear Information System (INIS)

    Pritchard, J.; Sandland, M.R.; Breatnach, F.B.; Pincott, J.R.; Cox, R.; Husband, P.

    1982-01-01

    Stage I lymphocyte-predominant Hodgkin's disease was diagnosed in a 44-month-old girl. Although immune deficiency was suspected and IgA deficiency demonstrated, the diagnosis of an ataxia-telangiectasia (AT)-like syndrome was not confirmed until eight weeks later when results of studies on the radiosensitivity of cultured skin fibroblasts were available. The child had none of the usual physical stigmata of AT. Severe acute radiation damage followed the treatment of this child with standard doses of radiation therapy. Clinical, pathologic, and radiobiologic correlations are drawn. The diagnosis of a malignant lymphoma disorder in children under the age of five should alert clinicians to the possibility of immune deficiency and, even in the absence of classical physical signs, to AT in particular. Suggestions for the management of future similar cases are put forward

  10. Germline variants in the ATM gene and breast cancer susceptibility in Moroccan women: A meta-analysis

    Directory of Open Access Journals (Sweden)

    Chaymaa Marouf

    2017-10-01

    Full Text Available Background: The ATM gene encoding a large protein kinase is mutated in ataxia-telangiectasia (AT, an autosomale recessive disease characterized by neurological and immunological symptoms, and cancer predisposition. Previous studies suggest that heterozygous carriers of ATM mutations have an increased risk of breast cancer compared with non carriers, but the contribution of specific variants has been difficult to estimate. However, two functional ATM variants, c.7271T > G and c.1066–6T > G (IVS10–6T > G, are associated with increased risk for the development of breast cancer. Methods: To investigate the role of ATM in breast cancer susceptibility, we genotyped 163 case patients with breast cancer and 150 healthy control individuals for the c.7271T > G and c.1066–6T > G (IVS10–6T > G ATM variants using polymerase chain reaction (PCR-restriction fragment length polymorphism (RFLP analysis. Results: We did not detect the ATM c.7271T > G and c.1066–6T > G (IVS10–6T > G mutations in any of 150 healthy control individuals and 163 breast cancer patients, including 59 women diagnosed with breast cancer at an early age ( G (IVS10–6T > G mutation and the rare c.7271T > G variant are not a risk factor for developing breast cancer in the Moroccan population. Larger and/or combined association studies are needed to clarify this issue. Keywords: Breast cancers, ATM gene, Germline mutation, Genetic susceptibility, Moroccan population

  11. Cisplatin-mediated radiosensitization of non-small cell lung cancer cells is stimulated by ATM inhibition

    International Nuclear Information System (INIS)

    Toulany, Mahmoud; Mihatsch, Julia; Holler, Marina; Chaachouay, Hassan; Rodemann, H. Peter

    2014-01-01

    Background and purpose: Cisplatin activates ataxia-telangiectasia-mutated (ATM), a protein with roles in DNA repair, cell cycle progression and autophagy. We investigated the radiosensitizing effect of cisplatin with respect to its effect on ATM pathway activation. Material and methods: Non-small cell lung cancer cells (NSCLC) cell lines (A549, H460) and human fibroblast (ATM-deficient AT5, ATM-proficient 1BR3) cells were used. The effects of cisplatin combined with irradiation on ATM pathway activity, clonogenicity, DNA double-strand break (DNA-DSB) repair and cell cycle progression were analyzed with Western blotting, colony formation and γ-H2AX foci assays as well as FACS analysis, respectively. Results: Cisplatin radiosensitized H460 cells, but not A549 cells. Radiosensitization of H460 cells was not due to impaired DNA-DSB repair, increased apoptosis or cell cycle dysregulation. The lack of radiosensitization demonstrated for A549 cells was associated with cisplatin-mediated stimulation of ATM (S1981) and AMPKα (T172) phosphorylation and autophagy. However, in both cell lines inhibition of ATM and autophagy by KU-55933 and chloroquine diphosphate (CQ) respectively resulted in a significant radiosensitization. Combined treatment with the AMPK inhibitor compound-C led to radiosensitization of A549 but not of H460 cells. As compared to the treatment with KU-55933 alone, radiosensitivity of A549 cells was markedly stimulated by the combination of KU-55933 and cisplatin. However, the combination of CQ and cisplatin did not modulate the pattern of radiation sensitivity of A549 or H460 cells. In accordance with the results that cisplatin via stimulation of ATM activity can abrogate its radiosensitizing effect, ATM deficient cells were significantly sensitized to ionizing radiation by cisplatin. Conclusion: The results obtained indicate that ATM targeting can potentiate cisplatin-induced radiosensitization

  12. Constitutive phosphorylation of ATM in lymphoblastoid cell lines from patients with ICF syndrome without downstream kinase activity.

    Science.gov (United States)

    Goldstine, Jimena V; Nahas, Shareef; Gamo, Kristin; Gartler, Stanley M; Hansen, R Scott; Roelfsema, Jeroen H; Gatti, Richard A; Marahrens, York

    2006-04-08

    Double strand DNA breaks in the genome lead to the activation of the ataxia-telangiectasia mutated (ATM) kinase in a process that requires ATM autophosphorylation at serine-1981. ATM autophosphorylation only occurs if ATM is previously acetylated by Tip60. The activated ATM kinase phosphorylates proteins involved in arresting the cell cycle, including p53, and in repairing the DNA breaks. Chloroquine treatment and other manipulations that produce chromatin defects in the absence of detectable double strand breaks also trigger ATM phosphorylation and the phosphorylation of p53 in primary human fibroblasts, while other downstream substrates of ATM that are involved in the repair of DNA double strand breaks remain unphosphorylated. This raises the issue of whether ATM is constitutively activated in patients with genetic diseases that display chromatin defects. We examined lymphoblastoid cell lines (LCLs) generated from patients with different types of chromatin disorders: Immunodeficiency, Centromeric instability, Facial anomalies (ICF) syndrome, Coffin Lowry syndrome, Rubinstein Taybi syndrome and Fascioscapulohumeral Muscular Dystrophy. We show that ATM is phosphorylated on serine-1981 in LCLs derived from ICF patients but not from the other syndromes. The phosphorylated ATM in ICF cells did not phosphorylate the downstream targets NBS1, SMC1 and H2AX, all of which require the presence of double strand breaks. We demonstrate that ICF cells respond normally to ionizing radiation, ruling out the possibility that genetic deficiency in ICF cells renders activated ATM incapable of phosphorylating its downstream substrates. Surprisingly, p53 was also not phosphorylated in ICF cells or in chloroquine-treated wild type LCLs. In this regard the response to chromatin-altering agents differs between primary fibroblasts and LCLs. Our findings indicate that although phosphorylation at serine-1981 is essential in the activation of the ATM kinase, serine-1981 phosphorylation is

  13. A pharmacological screen for compounds that rescue the developmental lethality of a Drosophila ATM mutant.

    Science.gov (United States)

    Rimkus, Stacey A; Wassarman, David A

    2018-01-01

    Ataxia-telangiectasia (A-T) is a neurodegenerative disease caused by mutation of the A-T mutated (ATM) gene. ATM encodes a protein kinase that is activated by DNA damage and phosphorylates many proteins, including those involved in DNA repair, cell cycle control, and apoptosis. Characteristic biological and molecular functions of ATM observed in mammals are conserved in Drosophila melanogaster. As an example, conditional loss-of-function ATM alleles in flies cause progressive neurodegeneration through activation of the innate immune response. However, unlike in mammals, null alleles of ATM in flies cause lethality during development. With the goals of understanding biological and molecular roles of ATM in a whole animal and identifying candidate therapeutics for A-T, we performed a screen of 2400 compounds, including FDA-approved drugs, natural products, and bioactive compounds, for modifiers of the developmental lethality caused by a temperature-sensitive ATM allele (ATM8) that has reduced kinase activity at non-permissive temperatures. Ten compounds reproducibly suppressed the developmental lethality of ATM8 flies, including Ronnel, which is an organophosphate. Ronnel and other suppressor compounds are known to cause mitochondrial dysfunction or to inhibit the enzyme acetylcholinesterase, which controls the levels of the neurotransmitter acetylcholine, suggesting that detrimental consequences of reduced ATM kinase activity can be rescued by inhibiting the function of mitochondria or increasing acetylcholine levels. We carried out further studies of Ronnel because, unlike the other compounds that suppressed the developmental lethality of homozygous ATM8 flies, Ronnel was toxic to the development of heterozygous ATM8 flies. Ronnel did not affect the innate immune response of ATM8 flies, and it further increased the already high levels of DNA damage in brains of ATM8 flies, but its effects were not harmful to the lifespan of rescued ATM8 flies. These results provide

  14. The rate of DNA synthesis in normal human and ataxia telangiectasia cells after exposure to X-irradiation

    International Nuclear Information System (INIS)

    Wit, J. de; Bootsma, D.; Jaspers, N.G.J.; Rijksverdedigingsorganisatie TNO, Rijswijk

    1981-01-01

    The rate of DNA synthesis was studied in normal cell strains and in strains from patients suffering from the inherited disorder ataxia telangiectasia (AT). After exposure to relatively low doses of oxic X-rays (0- 4 krad) DNA synthesis was depressed in AT cell strains to a significantly lesser extent than in normal cells. This response was observed in both an excision-deficient and an excision-proficient strain. In contrast, there was no difference in DNA-synthesis inhibition between AT and normal cells after UV exposure. After X-irradiation of cells from patients with xeroderma pigmentosum, both complementation group A and XP variants, the observed rate of DNA synthesis was equal to that in normal cells. An exception was the strain XP3BR which has been shown to be X-ray-sensitive. This strain exhibited diminished DNA synthesis inhibition after X-ray doses below 1 krad. These data suggest a relationship between hypersensitivity to X-rays and diminished depression of DNA synthesis. (orig.)

  15. Abnormal levels of UV-induced unscheduled DNA synthesis in ataxia telangiectasia cells after exposure to ionizing radiation

    International Nuclear Information System (INIS)

    Jaspers, N.G.J.; Nederlandse Centrale Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek, Rijswijk. Medical Biological Lab.); Bootsma, D.

    1982-01-01

    In cultured cells from normal individuals and from patients having ataxia telangiectasia (AT) the rate of unscheduled DNA synthesis (UDS) induced by UV light was investigated by autoradiography. The number of grains in 6 different AT cell strains was similar to that observed in normal cells. Exposure of normal cells to doses of X-rays up to 20 krad had no influence on the rate of UV-induced UDS. In contrast, the UV-induced UDS was significantly modified in AT cells by treatment with X-rays. In AT cell strains that were reported to have reduced levels of γ-ray-induced repair DNA synthesis ('excision-deficient' AT cells) the effect of X-rays on UV-induced UDS was inhibitory, whereas UV-induced UDS was stimulated by X-ray exposure in 'excision-proficient' AT cell strains. Different UV and X-ray dose-response relationships were seen in the two categories of AT cell strains. (orig./AJ)

  16. The effect of caffeine on X-ray-induced mitotic delay in normal human and ataxia-telangiectasia fibroblasts

    International Nuclear Information System (INIS)

    Zampetti-Bosseler, F.; Scott, D.

    1985-01-01

    The authors previously showed that radiation-sensitive fibroblasts from ataxia-telangiectasia (A-T) patients sustain less G 2 delay after X-irradiation than normal fibroblasts. Caffeine is known to reduce the amount of X-ray-induced delay in various mammalian cell types. It is proposed that A-T cells have an altered chromatin structure, similar to that of caffeine-treated normal cells and that this results in a failure of A-T cells to delay their progression through the cell cycle to allow time for DNA repair. The authors now show that caffeine treatment after X-irradiation reduces G 2 delay in both A-T and normal cells. The authors confirm the results previously obtained on lymphocytes that caffeine potentiates the chromosome-damaging effects of X-rays in both A-T and normal fibroblasts. These and other data suggest that the radiation responses of A-T cells and of caffeine-treated normal cells are caused by different mechanisms. (Auth.)

  17. Kinetics of chromatid aberrations in G2 ataxia-telangiectasia cells exposed to X-rays and ara A

    International Nuclear Information System (INIS)

    Mozdarani, Hossein; Bryant, P.E.

    1989-01-01

    The cytogenetic effects of X-rays alone or in combination with 9-β-D-arabinofuranosyladenine (ara A) were studied in an immortalized fibroblastic line of ataxia-telangiectasia (A-T) cells. It is postulated that the kinetics of disappearance (rejoining) of chromatid deletions with postirradiation incubation time reflects the underlying repair of dsb, and is inhibited by ara A. The rejoining kinetics for deletions in A-T was similar to that found in a previous study of normal human fibroblasts (Mozdarani and Bryant 1987). The number of deletions in X-irradiated A-T cells at 1.5 h before fixation was found to be higher by a factor of approximately 2 than that found previously in normals, indicating that in A-T a higher rate of conversion of dsb into chromatid deletions occurs. The frequency of exchanges induced in G2 A-T cells was similarly enhanced but, unlike the situation in normal cells, ara A was found to cause only a slight increase in this frequency. (author)

  18. Dual inhibition of ATR and ATM potentiates the activity of trabectedin and lurbinectedin by perturbing the DNA damage response and homologous recombination repair.

    Science.gov (United States)

    Lima, Michelle; Bouzid, Hana; Soares, Daniele G; Selle, Frédéric; Morel, Claire; Galmarini, Carlos M; Henriques, João A P; Larsen, Annette K; Escargueil, Alexandre E

    2016-05-03

    Trabectedin (Yondelis®, ecteinascidin-743, ET-743) is a marine-derived natural product approved for treatment of advanced soft tissue sarcoma and relapsed platinum-sensitive ovarian cancer. Lurbinectedin is a novel anticancer agent structurally related to trabectedin. Both ecteinascidins generate DNA double-strand breaks that are processed through homologous recombination repair (HRR), thereby rendering HRR-deficient cells particularly sensitive. We here characterize the DNA damage response (DDR) to trabectedin and lurbinectedin in HeLa cells. Our results show that both compounds activate the ATM/Chk2 (ataxia-telangiectasia mutated/checkpoint kinase 2) and ATR/Chk1 (ATM and RAD3-related/checkpoint kinase 1) pathways. Interestingly, pharmacological inhibition of Chk1/2, ATR or ATM is not accompanied by any significant improvement of the cytotoxic activity of the ecteinascidins while dual inhibition of ATM and ATR strongly potentiates it. Accordingly, concomitant inhibition of both ATR and ATM is an absolute requirement to efficiently block the formation of γ-H2AX, MDC1, BRCA1 and Rad51 foci following exposure to the ecteinascidins. These results are not restricted to HeLa cells, but are shared by cisplatin-sensitive and -resistant ovarian carcinoma cells. Together, our data identify ATR and ATM as central coordinators of the DDR to ecteinascidins and provide a mechanistic rationale for combining these compounds with ATR and ATM inhibitors.

  19. The ATM and ATR inhibitors CGK733 and caffeine suppress cyclin D1 levels and inhibit cell proliferation

    International Nuclear Information System (INIS)

    Alao, John P; Sunnerhagen, Per

    2009-01-01

    The ataxia telangiectasia mutated (ATM) and the ATM- related (ATR) kinases play a central role in facilitating the resistance of cancer cells to genotoxic treatment regimens. The components of the ATM and ATR regulated signaling pathways thus provide attractive pharmacological targets, since their inhibition enhances cellular sensitivity to chemo- and radiotherapy. Caffeine as well as more specific inhibitors of ATM (KU55933) or ATM and ATR (CGK733) have recently been shown to induce cell death in drug-induced senescent tumor cells. Addition of these agents to cancer cells previously rendered senescent by exposure to genotoxins suppressed the ATM mediated p21 expression required for the survival of these cells. The precise molecular pharmacology of these agents however, is not well characterized. Herein, we report that caffeine, CGK733, and to a lesser extent KU55933, inhibit the proliferation of otherwise untreated human cancer and non-transformed mouse fibroblast cell lines. Exposure of human cancer cell lines to caffeine and CGK733 was associated with a rapid decline in cyclin D1 protein levels and a reduction in the levels of both phosphorylated and total retinoblastoma protein (RB). Our studies suggest that observations based on the effects of these compounds on cell proliferation and survival must be interpreted with caution. The differential effects of caffeine/CGK733 and KU55933 on cyclin D1 protein levels suggest that these agents will exhibit dissimilar molecular pharmacological profiles

  20. Transition in Survival From Low-Dose Hyper-Radiosensitivity to Increased Radioresistance Is Independent of Activation of ATM SER1981 Activity

    International Nuclear Information System (INIS)

    Krueger, Sarah A.; Collis, Spencer J.; Joiner, Michael C.; Wilson, George D.; Marples, Brian

    2007-01-01

    Purpose: The molecular basis of low-dose hyper-radiosensitivity (HRS) is only partially understood. The aim of this study was to define the roles of ataxia telangiectasia mutated (ATM) activity and the downstream ATM-dependent G 2 -phase cell cycle checkpoint in overcoming HRS and triggering radiation resistance. Methods and Materials: Survival was measured using a high-resolution clonogenic assay. ATM Ser1981 activation was measured by Western blotting. The role of ATM was determined in survival experiments after molecular (siRNA) and chemical (0.4 mM caffeine) inhibition and chemical (20 μg/mL chloroquine, 15 μM genistein) activation 4-6 h before irradiation. Checkpoint responsiveness was assessed in eight cell lines of differing HRS status using flow cytometry to quantify the progression of irradiated (0-2 Gy) G 2 -phase cells entering mitosis, using histone H3 phosphorylation analysis. Results: The dose-response pattern of ATM activation was concordant with the transition from HRS to radioresistance. However, ATM activation did not play a primary role in initiating increased radioresistance. Rather, a relationship was discovered between the function of the downstream ATM-dependent early G 2 -phase checkpoint and the prevalence and overcoming of HRS. Four cell lines that exhibited HRS failed to show low-dose ( 2 -phase checkpoint. These data suggest that clinical exploitation of HRS could be achieved by combining radiotherapy with chemotherapeutic agents that modulate this cell cycle checkpoint

  1. Expression and clinical significance of ATM and PUMA gene in patients with colorectal cancer.

    Science.gov (United States)

    Xiong, Hui; Zhang, Jiangnan

    2017-12-01

    The expression of ataxia-telangiectasia mutated (ATM) and p53 upregulated modulator of apoptosis (PUMA) genes in patients with colorectal cancer were investigated, to explore the correlation between the expression of ATM and PUMA and tumor development, to evaluate the clinical significance of ATM and PUMA in the treatment of colorectal cancer. Quantitative real-time PCR was used to detect the expression of ATM and PUMA in tumor tissue and adjacent healthy tissue of 67 patients with colorectal cancer and in normal colorectal tissue of 33 patients with colorectal polyps at mRNA level. The expression level of ATM mRNA in colorectal cancer tissues was significantly higher than that in normal mucosa tissues and adjacent non-cancerous tissue (P≤0.05), while no significant differences in expression level of ATM mRNA were found between normal mucosa tissues and adjacent noncancerous tissue (P=0.07). There was a negative correlation between the expression of ATM mRNA and the degree of differentiation of colorectal cancer (r= -0.312, P=0.013), while expression level of ATM mRNA was not significantly correlated with the age, sex, tumor invasion, lymph node metastasis or clinical stage (P>0.05). Expression levels of PUMA mRNA in colorectal cancer tissues, adjacent noncancerous tissue and normal tissues were 0.68±0.07, 0.88±0.04 and 1.76±0.06, respectively. Expression level of PUMA mRNA in colorectal cancer tissues and adjacent noncancerous tissue was significantly lower than that in normal colorectal tissues (PATM mRNA is expressed abnormally in colorectal cancer tissues. Expression of PUMA gene in colorectal carcinoma is downregulated, and is negatively correlated with the occurrence of cancer.

  2. Normal rejoining of DNA strand breaks in ataxia telangiectasia fibroblast lines after low x-ray exposure

    International Nuclear Information System (INIS)

    Hariharan, P.V.; Eleczko, S.; Smith, B.P.; Paterson, M.C.

    1981-01-01

    The alkaline elution method was used to measure the enzymatic repair of x-ray-induced DNA strand breaks in skin fibroblasts derived from human subjects afflicted with ataxia telangiectasia (AT). Monolayer cultures of normal control and AT cell lines were exposed acutely to moderately lethal (250-rad) and highly lethal (1250-rad) doses of 250-kV x rays under aerobic conditions. Upon receiving 250 rad, the control fibroblasts from a clinically normal donor rejoined all detectable single-strand breaks (plus alkali-labile bonds) within 30 to 60 min of incubation. When challenged with 1250 rad the kinetics of strand rejoining by the normal control cells were biphasic. For both exposures, no significant difference in either the rate or the extent of strand rejoining was detected between the normal cell line (GM38) and three mutant cell lines (AT2BE, AT3BI, AT4BI) belonging to the three known genetic complementation groups in AT. It would thus appear that the enhanced radiosensitivity of cultured AT cells does not stem from faulty rejoining of radiogenic DNA strand breaks

  3. Identification of 4 ataxia telangiectasia cell lines hypersensitive to. gamma. -irradiation but not to hydrogen peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Cantoni, O.; Sestili, P.; Santoro, M.P.; Tannoia, M.C.; Cattabeni, F. (Universita degli Studi di Urbino (Italy). Istituto di Farmacologia e Farmacognosia and Centro di Farmacologia Oncologia Sperimentale); Novelli, G.; Dallapiccola, B. (Universit degli Studi di Urbino (Italy). Cattedra di Genetica); Fiorilli, M. (Universita di Roma ' La Sapienze' (Italy). Cattedra di Allergologia e Immunologia Clinica)

    1989-09-01

    The effct of hydrogen peroxide on the rate of semi-conservative DNA synthesis in ataxia telangiectasia (AT) and normal human lymphoblastoid cells was investigated. The rate of DNA synthesis in AT cells was not depressed to a lesser extent than in normal cells, as might have been expected since H{sub 2O2} is a radiomimetic agent. On the contrary, 4 AT cell lines displayed a higher sensitivity to the inhibitory effect of H{sub 2O2} on DNA synthesis than 2 normal cell lines. Comparable levels of cytotoxicity were detected in cell vaibility studies. Furthermore, neither the level of DNA breakage produced by H{sub 2O2}, nor the rate of repair of these lesions was signigicantly different in normal and AT cells. Together, these results indicate that the AT cell lines utilized in this study are not hypersensitive to the oxidant. It is suggested that H-2-O-2 may not induce lethality via the direct ation of the hydroxyl radical (OH). (Author). 20 refs.; 3 figs.; 1 tab.

  4. Identification of 4 ataxia telangiectasia cell lines hypersensitive to γ-irradiation but not to hydrogen peroxide

    International Nuclear Information System (INIS)

    Cantoni, O.; Sestili, P.; Santoro, M.P.; Tannoia, M.C.; Cattabeni, F.; Novelli, G.; Dallapiccola, B.; Fiorilli, M.

    1989-01-01

    The effct of hydrogen peroxide on the rate of semi-conservative DNA synthesis in ataxia telangiectasia (AT) and normal human lymphoblastoid cells was investigated. The rate of DNA synthesis in AT cells was not depressed to a lesser extent than in normal cells, as might have been expected since H 2O2 is a radiomimetic agent. On the contrary, 4 AT cell lines displayed a higher sensitivity to the inhibitory effect of H 2O2 on DNA synthesis than 2 normal cell lines. Comparable levels of cytotoxicity were detected in cell vaibility studies. Furthermore, neither the level of DNA breakage produced by H 2O2 , nor the rate of repair of these lesions was signigicantly different in normal and AT cells. Together, these results indicate that the AT cell lines utilized in this study are not hypersensitive to the oxidant. It is suggested that H-2-O-2 may not induce lethality via the direct ation of the hydroxyl radical (OH). (Author). 20 refs.; 3 figs.; 1 tab

  5. The effect of ATM kinase inhibition on the initial response of human dental pulp and periodontal ligament mesenchymal stem cells to ionizing radiation.

    Science.gov (United States)

    Cmielova, Jana; Havelek, Radim; Kohlerova, Renata; Soukup, Tomas; Bruckova, Lenka; Suchanek, Jakub; Vavrova, Jirina; Mokry, Jaroslav; Rezacova, Martina

    2013-07-01

    This study evaluates early changes in human mesenchymal stem cells (MSC) isolated from dental pulp and periodontal ligament after γ-irradiation and the effect of ataxia-telangiectasia mutated (ATM) inhibition. MSC were irradiated with 2 and 20 Gy by (60)Co. For ATM inhibition, specific inhibitor KU55933 was used. DNA damage was measured by Comet assay and γH2AX detection. Cell cycle distribution and proteins responding to DNA damage were analyzed 2-72 h after the irradiation. The irradiation of MSC causes an increase in γH2AX; the phosphorylation was ATM-dependent. Irradiation activates ATM kinase, and the level of p53 protein is increased due to its phosphorylation on serine15. While this phosphorylation of p53 is ATM-dependent in MSC, the increase in p53 was not prevented by ATM inhibition. A similar trend was observed for Chk1 and Chk2. The increase in p21 is greater without ATM inhibition. ATM inhibition also does not fully abrogate the accumulation of irradiated MSC in the G2-phase of the cell-cycle. In irradiated MSC, double-strand breaks are tagged quickly by γH2AX in an ATM-dependent manner. Although phosphorylations of p53(ser15), Chk1(ser345) and Chk2(thr68) are ATM-dependent, the overall amount of these proteins increases when ATM is inhibited. In both types of MSC, ATM-independent mechanisms for cell-cycle arrest in the G2-phase are triggered.

  6. Analysis of Chromosomal Aberrations after Low and High Dose Rate Gamma Irradiation in ATM or NBS Suppressed Human Fibroblast Cells

    Science.gov (United States)

    Hada, M.; Huff, J. L.; Patel, Z.; Pluth, J. M.; George, K. A.; Cucinotta, F. A.

    2009-01-01

    A detailed understanding of the biological effects of heavy nuclei is needed for space radiation protection and for cancer therapy. High-LET radiation produces more complex DNA lesions that may be non-repairable or that may require additional processing steps compared to endogenous DSBs, increasing the possibility of misrepair. Interplay between radiation sensitivity, dose, and radiation quality has not been studied extensively. Previously we studied chromosome aberrations induced by low- and high- LET radiation in several cell lines deficient in ATM (ataxia telangactasia mutated; product of the gene that is mutated in ataxia telangiectasia patients) or NBS (nibrin; product of the gene mutated in the Nijmegen breakage syndrome), and gliomablastoma cells that are proficient or lacking in DNA-dependent protein kinase (DNA-PK) activity. We found that the yields of both simple and complex chromosomal aberrations were significantly increased in the DSB repair defective cells compared to normal cells. The increased aberrations observed for the ATM and NBS defective lines was due to a significantly larger quadratic dose-response term compared to normal fibroblasts for both simple and complex aberrations, while the linear dose-response term was significantly higher in NBS cells only for simple exchanges. These results point to the importance of the functions of ATM and NBS in chromatin modifications that function to facilitate correct DSB repair and minimize aberration formation. To further understand the sensitivity differences that were observed in ATM and NBS deficient cells, in this study, chromosomal aberration analysis was performed in normal lung fibroblast cells treated with KU-55933, a specific ATM kinase inhibitor, or Mirin, an MRN complex inhibitor involved in activation of ATM. We are also testing siRNA knockdown of these proteins. Normal and ATM or NBS suppressed cells were irradiated with gamma-rays and chromosomes were collected with a premature chromosome

  7. Identification of ataxia telangiectasia heterozygotes by flow cytometric analysis of X-ray damage

    International Nuclear Information System (INIS)

    Rudolph, N.S.

    1989-01-01

    Flow cytometry was used to identify heterozygotes for the autosomal recessive DNA-repair deficiency disease ataxia telangiectasia (AT). Confluent G 0 /G 1 fibroblasts from 4 homozygotes (at/at), 5 obligate heterozygates (at/+) and 7 presumed normal (+/+) were X-irradiated with 200 Rad and subcultured immediately in medium containing 5-bromodeoxyuridine (BrdU). Cells were harvested 72 h later and stained with fluoresceinated anti-BrdU antibody to identify cells that had entered S phase. They were counterstained with propidium iodide to measure total DNA content. On the basis of relative release from G 0 /G 1 , the at/+ strains as a group were distinguished from both the presumed +/+ strains and at/at strains, although the individual values for some strains did show overlap between genotypes. When 10 cell strains were coded and analyzed in 'blind' experiments, all 4 heterozygotes were correctly assigned. By a similar assay in which exponentially growing cultures were pulsed briefly with BrdU 8 h after irradiation with 400 Rad and then harvested immediately, presumed +/+ cells as a group could be distinguished from at/at cells but not from at/- cells. This combination of assays assists in the identification of all 3 AT genotypes. This should be of both basic and diagnostic use, particularly in families known to segregate AT. (author). 37 refs.; 3 figs.; 5 tabs

  8. Radiation-induced chromosome aberrations and cell killing in normal human fibroblasts and ataxia telangiectasia fibroblasts

    International Nuclear Information System (INIS)

    Kawata, T.; Saito, M.; Uno, T.; Ito, H.; Shigematsu, N.

    2003-01-01

    Full text: When cells are held in a non-dividing state (G0) after irradiation, an enhanced survival can be observed compared to that of immediate plating. A change of survival depending on post irradiation condition is known to be repair of potentially lethal damage (RPLD). The effects of confluent holding recovery (24-h incubation following irradiation) on chromosome aberrations in normal human fibroblasts (AG1522) and ataxia telangiectasia fibroblasts (GM02052C) were examined. A chemical-induced premature chromosome condensation (PCC) technique with fluorescent in situ hybridization (FISH) was applied to study chromosome aberrations in G2 and M-phase. Results from cell survival showed that the capacity for potentially lethal damage repair was normal in AG1522 cells but very little in GM02052C cells. The frequency of chromosome aberrations in AG1522 cells decreased when cells were allowed to repair for 24-h. Especially complex type exchanges were found to decrease markedly at high doses (4Gy and 6Gy). However, the frequency of chromosome aberrations including complex type exchanges showed little decrease in GM02052C cells. Confluent holding can effectively reduce chromosome aberrations, especially complex type exchanges in normal cells

  9. Targeting Werner syndrome protein sensitizes U-2 OS osteosarcoma cells to selenium-induced DNA damage response and necrotic death

    DEFF Research Database (Denmark)

    Cheng, Wen-Hsing; Wu, Ryan T Y; Wu, Min

    2012-01-01

    to MSeA-induced necrotic death. Co-treatment with the ataxia-telangiectasia mutated (ATM) kinase inhibitor KU55933 desensitized the control shRNA cells, but not WRN shRNA cells, to MSeA treatment. WRN did not affect MSeA-induced ATM phosphorylation on Ser-1981 or H2A.X phosphorylation on Ser-139...

  10. Type I IFN-related NETosis in ataxia telangiectasia and Artemis deficiency.

    Science.gov (United States)

    Gul, Ersin; Sayar, Esra Hazar; Gungor, Bilgi; Eroglu, Fehime Kara; Surucu, Naz; Keles, Sevgi; Guner, Sukru Nail; Findik, Siddika; Alpdundar, Esin; Ayanoglu, Ihsan Cihan; Kayaoglu, Basak; Geckin, Busra Nur; Sanli, Hatice Asena; Kahraman, Tamer; Yakicier, Cengiz; Muftuoglu, Meltem; Oguz, Berna; Cagdas Ayvaz, Deniz Nazire; Gursel, Ihsan; Ozen, Seza; Reisli, Ismail; Gursel, Mayda

    2017-11-16

    Pathological inflammatory syndromes of unknown etiology are commonly observed in ataxia telangiectasia (AT) and Artemis deficiency. Similar inflammatory manifestations also exist in patients with STING-associated vasculopathy in infancy (SAVI). We sought to test the hypothesis that the inflammation-associated manifestations observed in patients with AT and Artemis deficiency stem from increased type I IFN signature leading to neutrophil-mediated pathological damage. Cytokine/protein signatures were determined by ELISA, cytometric bead array, or quantitative PCR. Stat1 phosphorylation levels were determined by flow cytometry. DNA species accumulating in the cytosol of patients' cells were quantified microscopically and flow cytometrically. Propensity of isolated polymorhonuclear granulocytes to form neutrophil extracellular traps (NETs) was determined using fluorescence microscopy and picogreen assay. Neutrophil reactive oxygen species levels and mitochondrial stress were assayed using fluorogenic probes, microscopy, and flow cytometry. Type I and III IFN signatures were elevated in plasma and peripheral blood cells of patients with AT, Artemis deficiency, and SAVI. Chronic IFN production stemmed from the accumulation of DNA in the cytoplasm of AT and Artemis-deficient cells. Neutrophils isolated from patients spontaneously produced NETs and displayed indicators of oxidative and mitochondrial stress, supportive of their NETotic tendencies. A similar phenomenon was also observed in neutrophils from healthy controls exposed to patient plasma samples or exogeneous IFN-α. Type I IFN-mediated neutrophil activation and NET formation may contribute to inflammatory manifestations observed in patients with AT, Artemis deficiency, and SAVI. Thus, neutrophils represent a promising target to manage inflammatory syndromes in diseases with active type I IFN signature. Copyright © 2017 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights

  11. Effect of ATM heterozygosity on heritable DNA damage in mice following paternal F0 germline irradiation

    International Nuclear Information System (INIS)

    Baulch, Janet E.; Li, M.-W.; Raabe, Otto G.

    2007-01-01

    The ataxia telangiectasia mutated (ATM) gene product maintains genome integrity and initiates cellular DNA repair pathways following exposures to genotoxic agents. ATM also plays a significant role in meiotic recombination during spermatogenesis. Fertilization with sperm carrying damaged DNA could lead to adverse effects in offspring including developmental defects or increased cancer susceptibility. Currently, there is little information regarding the effect of ATM heterozygosity on germline DNA repair and heritable effects of paternal germline-ionizing irradiation. We used neutral pH comet assays to evaluate spermatozoa 45 days after acute whole-body irradiation of male mice (0.1 Gy, attenuated 137 Cs γ rays) to determine the effect of ATM heterozygosity on delayed DNA damage effects of Type A/B spermatogonial irradiation. Using the neutral pH sperm comet assay, significant irradiation-related differences were found in comet tail length, percent tail DNA and tail extent moment, but there were no observed differences in effect between wild-type and ATM +/- mice. However, evaluation of spermatozoa from third generation descendants of irradiated male mice for heritable chromatin effects revealed significant differences in DNA electrophoretic mobility in the F 3 descendants that were based upon the irradiated F 0 sire's genotype. In this study, radiation-induced chromatin alterations to Type A/B spermatogonia, detected in mature sperm 45 days post-irradiation, led to chromatin effects in mature sperm three generations later. The early cellular response to and repair of DNA damage is critical and appears to be affected by ATM zygosity. Our results indicate that there is potential for heritable genetic or epigenetic changes following Type A/B spermatogonial irradiation and that ATM heterozygosity increases this effect

  12. The production and repair of double strand breaks in cells from normal humans and patients with ataxia telangiectasia

    International Nuclear Information System (INIS)

    Lehman, A.R.; Stevens, S.

    1977-01-01

    The production and repair of double strand breaks induced by γ-rays in the DNA of human fibroblasts have been measured by sedimentation in sucrose gradients under non-denaturing conditions. Unirradiated DNA formed a rapidly sedimenting gel. Low doses of radiation released freely sedimenting DNA molecules from this gel. Higher doses reduced the rate of sedimentation of the free DNA due to the introduction of double strand breaks. The breakage efficiency was 1 break/1.3x10 10 daltons of DNA/krad. Postirradiation incubation after a high dose of radiation resulted in an increase in molecular weight of the free DNA molecules, and after a low dose the rapidly-sedimenting gel was reformed. These data suggest that double strand breaks are repaired in human fibroblasts. No significant differences were found between fibroblasts from two normal donors and four patients with the radiosensitive disorder, ataxia telangiectasia, in either the production or repair of double strand breaks

  13. miR-181a promotes G1/S transition and cell proliferation in pediatric acute myeloid leukemia by targeting ATM.

    Science.gov (United States)

    Liu, Xiaodan; Liao, Wang; Peng, Hongxia; Luo, Xuequn; Luo, Ziyan; Jiang, Hua; Xu, Ling

    2016-01-01

    Abnormal expression of miRNAs is intimately related to a variety of human cancers. The purpose of this study is to confirm the expression of miR-181a and elucidate its physiological function and mechanism in pediatric acute myeloid leukemia (AML). Pediatric AML patients and healthy controls were enrolled, and the expression of miR-181a and ataxia telangiectasia mutated (ATM) in tissues were examined using quantitative PCR. Moreover, cell proliferation and cell cycle were evaluated in several cell lines (HL60, NB4 and K562) by using flow cytometry after transfected with miR-181a mimics and inhibitors, or ATM siRNA and control siRNA. Finally, ATM as the potential target protein of miR-181a was examined. We found that miR-181a was significantly increased in pediatric AML, which showed an inverse association with ATM expression. Overexpressed miR-181a in cell lines significantly enhanced cell proliferation, as well as increased the ratio of S-phase cells by miR-181a mimics transfection in vitro. Luciferase activity of the reporter construct identified ATM as the direct molecular target of miR-181a. ATM siRNA transfection significantly enhanced cell proliferation and increased the ratio of S-phase cells in vitro. The results revealed novel mechanism through which miR-181a regulates G1/S transition and cell proliferation in pediatric AML by regulating the tumor suppressor ATM, providing insights into the molecular mechanism in pediatric AML.

  14. Effects of exogenous ATM gene on mRNA expression of human telomerase reverse transcriptase in AT cells induced by irradiation

    International Nuclear Information System (INIS)

    Sheng Fangjun; Cao Jianping; Luo Jialin; Zhu Wei; Liu Fenju; Feng Shuang; Song Jianyuan; Li Chong

    2005-01-01

    The study is to observe effects of exogenous ATM gene on mRNA expression of hTERT (human telomerase reverse transcriptase) in fibroblast cells (AT5BIVA cells) from skin of Ataxia-telangiectasia (AT) patients and to study the regulation of ATM to hTERT. Using reverse transcription polymerase chain reaction (RT-PCR), mRNA expression of hTERT in AT, PEBS7-AT, ATM + -AT and GM cells irradiated with 0 and 3 Gy of 60 Co γ-rays were examined respectively. The difference of the mRNA expression of hTERT among AT, PEBS7-AT, ATM + -AT and GM cells were analyzed. Difference of the mRNA expression of hTERT between 0 Gy and 3 Gy groups was analyzed, too. The results showed that the mRNA expression of hTERT in GM cells was negative, but positive mRNA expression of hTERT in AT cells. The mRNA expression of hTERT in ATM + -AT cells decreased significantly (p 60 Co γ-rays, the mRNA expression of hTERT in GM cells was positive, and that in AT, PEBS7-AT, ATM + -AT cells was increased (p + -AT cells was lower than that in AT and PEBS7-AT cells respectively (p<0.05). It is postulated that exogenous ATM is able to downregulate the mRNA expression of hTERT in AT cells, ionizing radiation can induce the mRNA expression of hTERT in cells and telomerase anticipates the repair of damaged DNA. (authors)

  15. Cooperative Enhancement of Radiosensitivity After Combined Treatment of 17-(Allylamino)-17-Demethoxygeldanamycin and Celecoxib in Human Lung and Colon Cancer Cell Lines

    Science.gov (United States)

    Kim, Young-Mee

    2012-01-01

    We investigated whether the combined treatment of 17-(allylamino)-17-demethoxygeldanamycin (17-AAG), an inhibitor of heat-shock protein 90 (hsp90), and celecoxib, an inhibitor of cyclooxygenase-2, can cooperatively enhance the radiosensitivity of various human cancer cells. Combined treatment with 17-AAG and celecoxib, at clinically relevant concentrations, cooperatively induced radiosensitization in all tested cancer cells, but not in normal cells. Cooperative radiosensitization by the drug combination was also shown in a human tumor xenograft system. We found that ataxia-telangiectasia and rad3-related (ATR) and ataxia-telangiectasia mutated (ATM) are novel client proteins of hsp90. Combined treatment with 17-AAG and celecoxib cooperatively induced downregulation of ATR and ATM. In conclusion, combined treatment with 17-AAG and celecoxib at clinically relevant concentrations may significantly enhance the therapeutic efficacy of ionizing radiation. PMID:21830942

  16. Ataxia Telangiectasia - A Report of a case in Port Harcourt

    African Journals Online (AJOL)

    TNHJOURNALPH

    ocularand cutaneous telangiectasia, and a predisposition to ... complications because early management with monitoring of lung ... Blymphoid malignancy and hypersensitivity to ionizing radiation. 4 Data on the prevalence of A-T in Nigeria is limited. Few cases of A-T have been reported in Nigeria. 5 The prevalence.

  17. ATM and checkpoint responses to DNA double strand breaks

    International Nuclear Information System (INIS)

    Khanna, K.K.

    2003-01-01

    DNA damage checkpoints can be classified into G1/S, intra-S and G2/M checkpoints, so named according to the cell cycle transitions that they regulate. DNA damage incurred during the G1 or G2 phase of the cell cycle leads to growth arrest at the G1/S and G2/M phase boundaries, respectively, whereas genotoxic stress during S phase results in the transient suppression of DNA synthesis. In mammals, ATM (ataxia-telangiectasia mutated) is a protein kinase that controls all checkpoint responses to DNA damage. ATM is a versatile kinase which uses various means to regulate a given checkpoint pathway. It has been shown to act upon several proteins within the same pathway, many times controlling several different modifications of the same protein or using several different targets to arrive at the same end point. Some of the ATM targets act as adaptors by recruiting additional substrates for ATM. ATM controls two types of responses in G1. The p53-dependent responses inhibit Cyclin/Cdk activity by transcriptional induction of p21, whereas p53-independent responses inhibit CDKs through degradation of Cdc25A to maintain CdK2 inhibitory phosphorylation. In regulating p53, ATM directly phosphorylates p53 on Ser15, which likely causes p53 transcriptional activation, concurrently activating other kinases that phosphorylate p53 at other sites such as Ser20, which reduces the ability of MDM2 to bind p53, thus promoting its stability. ATM further ensures p53 stability by phosphorylating MDM2. At least six ATM targets, namely CHK2, CHK1, NBS1, BRCA1, SMC1 and FANCD2, have been implicated in the control of S-phase checkpoint. Cdc25A is the downstream effector of CHK1 and CHK2, though the underlying mechanism for control of intra S-phase checkpoint by other targets remain obscure. G2 checkpoint prevents mitotic entry solely through inhibitory phosphorylation of Cdc2/Cdk1. Several ATM targets including CHK1, CHK2, BRCA1, MDC1 and p53BP1 have been implicated in the control of G2/M

  18. p38 MAPK-Mediated Bmi-1 Down-Regulation and Defective Proliferation in ATM-Deficient Neural Stem Cells Can Be Restored by Akt Activation

    Science.gov (United States)

    Kim, Jeesun; Hwangbo, Jeon; Wong, Paul K. Y.

    2011-01-01

    A-T (ataxia telangiectasia) is a genetic disease caused by a mutation in the Atm (A-T mutated) gene that leads to neurodegeneration. Despite an increase in the numbers of studies in this area in recent years, the mechanisms underlying neurodegeneration in human A-T are still poorly understood. Previous studies demonstrated that neural stem cells (NSCs) isolated from the subventricular zone (SVZ) of Atm -/- mouse brains show defective self-renewal and proliferation, which is accompanied by activation of chronic p38 mitogen-activated protein kinase (MAPK) and a lower level of the polycomb protein Bmi-1. However, the mechanism underlying Bmi-1 down-regulation and its relevance to defective proliferation in Atm-/- NSCs remained unclear. Here, we show that over-expression of Bmi-1 increases self-renewal and proliferation of Atm-/- NSCs to normal, indicating that defective proliferation in Atm-/- NSCs is a consequence of down-regulation of Bmi-1. We also demonstrate that epidermal growth factor (EGF)-induced Akt phosphorylation renders Bmi-1 resistant to the proteasomal degradation, leading to its stabilization and accumulation in the nucleus. However, inhibition of the Akt-dependent Bmi-1 stabilizing process by p38 MAPK signaling reduces the levels of Bmi-1. Treatment of the Atm-/- NSCs with a specific p38 MAPK inhibitor SB203580 extended Bmi-1 posttranscriptional turnover and H2A ubiquitination in Atm-/- NSCs. Our observations demonstrate the molecular basis underlying the impairment of self-renewal and proliferation in Atm-/- NSCs through the p38 MAPK-Akt-Bmi-1-p21 signaling pathway. PMID:21305053

  19. Excision repair in ataxia telangiectasia, Fanconi's anemia, Cockayne syndrome, and Bloom's syndrome after treatment with ultraviolet radiation and N-acetoxy-2-acetylaminofluorene

    International Nuclear Information System (INIS)

    Ahmed, F.E.; Setlow, R.B.

    1978-01-01

    Excision repair of damage due to ultraviolet radiation, N-acetoxy-2-acetylaminofluorene and a combination of both agents was studied in normal human fibroblasts and various cells from cancer prone patients (ataxia telangiectasia, Fanconi's anemia, Cockayne syndrome and Bloom's syndrome). Three methods giving similar results were used: unscheduled DNA synthesis by radioautography, photolysis of bromodeoxyuridine incorporated into parental DNA during repair, and loss of sites sensitive to an ultraviolet endonuclease. All cell lines were proficient in repair of ultraviolet and acetoxy acetylaminofluorene damage and at saturation doses of both agents repair was additive. We interpret these data as indicating that the rate limiting step in excision repair of ultraviolet and acetoxy acetylaminofluorene is different and that there are different enzyme(s) working on incision of both types of damages. (Auth.)

  20. Ataxia-telangiectasia-mutated (ATM) and NBS1-dependent phosphorylation of Chk1 on Ser-317 in response to ionizing radiation

    DEFF Research Database (Denmark)

    Gatei, Magtouf; Sloper, Katie; Sørensen, Claus Storgaard

    2003-01-01

    . In mammalian cells, evidence has been presented that Chk1 is devoted to the ATR signaling pathway and is modified by ATR in response to replication inhibition and UV-induced damage, whereas Chk2 functions primarily through ATM in response to ionizing radiation (IR), suggesting that Chk2 and Chk1 might have...

  1. Effect of silencing of ATM expression by siRNA on radiosensitivity of human lung adenocarcinoma A549 cells

    International Nuclear Information System (INIS)

    Liu Xiaoqun; Qiao Tiankui

    2014-01-01

    Objective: To investigate the effect of silencing of ataxia-telangiectasia mutated (ATM) expression by plasmid-mediated RNA interference on the radiosensitivity of human lung adenocarcinoma A 549 cells. Methods: Eukaryotic expression plasmid containing ATM small interfering RNA (siRNA) (pSilencer2.1-ATM), as well as pSilencer2.1-nonspecific, was constructed.Lung adenocarcinoma A 549 cells were divided into positive group, negative group,and control group to be transfected with pSilencer2.1-ATM, pSilencer2.1-nonspecific, and no plasmid, respectively. The mRNA and protein expression of ATM was measured by RT-PCR and Western blot, respectively. The change in cell radiosensitivity was observed by colony-forming assay. Cell cycle and cell apoptosis were analyzed by flow cytometry. Results: The eukaryotic expression plasmid containing ATM siRNA was successfully constructed. The RT-PCR and Western blot demonstrated that the expression of ATM was down-regulated in the positive group. The sensitization enhancement ratios (D 0 ratios) for the positive group and negative group were 1.50 and 1.01, respectively. The flow cytometry revealed that the proportions of A 549 cells in G 1 and G 2 /M phases were significantly lower in the positive group than in the control group (51.27% vs 61.85%, P = 0.012; 6.34% vs 10.91%, P = 0.008) and that the apoptosis rate was significantly higher in the positive group than in the control group and negative group (49.31% vs 13.58%, P = 0.000; 49.31% vs 13.17%, P = 0.000). Conclusions: Silencing of ATM expression may increase the radiosensitivity of human lung adenocarcinoma A 549 cells, probably by affecting the cell cycle and promoting cell apoptosis. (authors)

  2. Noncanonical ATM Activation and Signaling in Response to Transcription-Blocking DNA Damage.

    Science.gov (United States)

    Marteijn, Jurgen A; Vermeulen, Wim; Tresini, Maria

    2017-01-01

    Environmental genotoxins and metabolic byproducts generate DNA lesions that can cause genomic instability and disrupt tissue homeostasis. To ensure genomic integrity, cells employ mechanisms that convert signals generated by stochastic DNA damage into organized responses, including activation of repair systems, cell cycle checkpoints, and apoptotic mechanisms. DNA damage response (DDR) signaling pathways coordinate these responses and determine cellular fates in part, by transducing signals that modulate RNA metabolism. One of the master DDR coordinators, the Ataxia Telangiectasia Mutated (ATM) kinase, has a fundamental role in mediating DNA damage-induced changes in mRNA synthesis. ATM acts by modulating a variety of RNA metabolic pathways including nascent RNA splicing, a process catalyzed by the spliceosome. Interestingly, ATM and the spliceosome influence each other's activity in a reciprocal manner by a pathway that initiates when transcribing RNA polymerase II (RNAPII) encounters DNA lesions that prohibit forward translocation. In response to stalling of RNAPII assembly of late-stage spliceosomes is disrupted resulting in increased splicing factor mobility. Displacement of spliceosomes from lesion-arrested RNA polymerases facilitates formation of R-loops between the nascent RNA and DNA adjacent to the transcription bubble. R-loops signal for noncanonical ATM activation which in quiescent cells occurs in absence of detectable dsDNA breaks. In turn, activated ATM signals to regulate spliceosome dynamics and AS genome wide.This chapter describes the use of fluorescence microscopy methods that can be used to evaluate noncanonical ATM activation by transcription-blocking DNA damage. First, we present an immunofluorescence-detection method that can be used to evaluate ATM activation by autophosphorylation, in fixed cells. Second, we present a protocol for Fluorescence Recovery After Photobleaching (FRAP) of GFP-tagged splicing factors, a highly sensitive and

  3. Patients with an inherited syndrome characterized by immunodeficiency, microcephaly, and chromosomal instability: genetic relationship to ataxia telangiectasia

    International Nuclear Information System (INIS)

    Jaspers, N.G.; Taalman, R.D.; Baan, C.

    1988-01-01

    Fibroblast cultures from six unrelated patients having a familial type of immunodeficiency combined with microcephaly, developmental delay, and chromosomal instability were studied with respect to their response to ionizing radiation. The cells from five of them resembled those from individuals with ataxia telangiectasia (AT) in that they were two to three times more radiosensitive on the basis of clonogenic cell survival. In addition, after exposure to either X-rays or bleomycin, they showed an inhibition of DNA replication that was less pronounced than that in normal cells and characteristic of AT fibroblasts. However, the patients are clinically very different from AT patients, not showing any signs of neurocutaneous symptoms. Genetic complementation studies in fused cells, with the radioresistant DNA synthesis used as a marker, showed that the patients' cells could complement representatives of all presently known AT complementation groups. Furthermore, they were shown to constitute a genetically heterogeneous group as well. It is concluded that these patients are similar to AT patients with respect to cytological parameters. The clinical differences between these patients and AT patients are a reflection of genetic heterogeneity. The data indicate that the patients suffer from a chromosome-instability syndrome that is distinct from AT

  4. S phase entry causes homocysteine-induced death while ataxia telangiectasia and Rad3 related protein functions anti-apoptotically to protect neurons.

    Science.gov (United States)

    Ye, Weizhen; Blain, Stacy W

    2010-08-01

    A major phenotype seen in neurodegenerative disorders is the selective loss of neurons due to apoptotic death and evidence suggests that inappropriate re-activation of cell cycle proteins in post-mitotic neurons may be responsible. To investigate whether reactivation of the G1 cell cycle proteins and S phase entry was linked with apoptosis, we examined homocysteine-induced neuronal cell death in a rat cortical neuron tissue culture system. Hyperhomocysteinaemia is a physiological risk factor for a variety of neurodegenerative diseases, including Alzheimer's disease. We found that in response to homocysteine treatment, cyclin D1, and cyclin-dependent kinases 4 and 2 translocated to the nucleus, and p27 levels decreased. Both cyclin-dependent kinases 4 and 2 regained catalytic activity, the G1 gatekeeper retinoblastoma protein was phosphorylated and DNA synthesis was detected, suggesting transit into S phase. Double-labelling immunofluorescence showed a 95% co-localization of anti-bromodeoxyuridine labelling with apoptotic markers, demonstrating that those cells that entered S phase eventually died. Neurons could be protected from homocysteine-induced death by methods that inhibited G1 phase progression, including down-regulation of cyclin D1 expression, inhibition of cyclin-dependent kinases 4 or 2 activity by small molecule inhibitors, or use of the c-Abl kinase inhibitor, Gleevec, which blocked cyclin D and cyclin-dependent kinase 4 nuclear translocation. However, blocking cell cycle progression post G1, using DNA replication inhibitors, did not prevent apoptosis, suggesting that death was not preventable post the G1-S phase checkpoint. While homocysteine treatment caused DNA damage and activated the DNA damage response, its mechanism of action was distinct from that of more traditional DNA damaging agents, such as camptothecin, as it was p53-independent. Likewise, inhibition of the DNA damage sensors, ataxia-telangiectasia mutant and ataxia telangiectasia and Rad

  5. ATM Polymorphisms Predict Severe Radiation Pneumonitis in Patients With Non-Small Cell Lung Cancer Treated With Definitive Radiation Therapy

    International Nuclear Information System (INIS)

    Xiong, Huihua; Liao, Zhongxing; Liu, Zhensheng; Xu, Ting; Wang, Qiming; Liu, Hongliang; Komaki, Ritsuko; Gomez, Daniel; Wang, Li-E; Wei, Qingyi

    2013-01-01

    Purpose: The ataxia telangiectasia mutated (ATM) gene mediates detection and repair of DNA damage. We investigated associations between ATM polymorphisms and severe radiation-induced pneumonitis (RP). Methods and Materials: We genotyped 3 potentially functional single nucleotide polymorphisms (SNPs) of ATM (rs1801516 [D1853N/5557G>A], rs189037 [-111G>A] and rs228590) in 362 patients with non-small cell lung cancer (NSCLC), who received definitive (chemo)radiation therapy. The cumulative severe RP probabilities by genotypes were evaluated using the Kaplan-Meier analysis. The associations between severe RP risk and genotypes were assessed by both logistic regression analysis and Cox proportional hazard model with time to event considered. Results: Of 362 patients (72.4% of non-Hispanic whites), 56 (15.5%) experienced grade ≥3 RP. Patients carrying ATM rs189037 AG/GG or rs228590 TT/CT genotypes or rs189037G/rs228590T/rs1801516G (G-T-G) haplotype had a lower risk of severe RP (rs189037: GG/AG vs AA, adjusted hazard ratio [HR] = 0.49, 95% confidence interval [CI], 0.29-0.83, P=.009; rs228590: TT/CT vs CC, HR=0.57, 95% CI, 0.33-0.97, P=.036; haplotype: G-T-G vs A-C-G, HR=0.52, 95% CI, 0.35-0.79, P=.002). Such positive findings remained in non-Hispanic whites. Conclusions: ATM polymorphisms may serve as biomarkers for susceptibility to severe RP in non-Hispanic whites. Large prospective studies are required to confirm our findings

  6. ATM Expression Predicts Veliparib and Irinotecan Sensitivity in Gastric Cancer by Mediating P53-Independent Regulation of Cell Cycle and Apoptosis.

    Science.gov (United States)

    Subhash, Vinod Vijay; Tan, Shi Hui; Yeo, Mei Shi; Yan, Fui Leng; Peethala, Praveen C; Liem, Natalia; Krishnan, Vaidehi; Yong, Wei Peng

    2016-12-01

    Identification of synthetically lethal cellular targets and synergistic drug combinations is important in cancer chemotherapy as they help to overcome treatment resistance and increase efficacy. The Ataxia Telangiectasia Mutated (ATM) kinase is a nuclear protein that plays a major role in the initiation of DNA repair signaling and cell-cycle check points during DNA damage. Although ATM was shown to be associated with poor prognosis in gastric cancer, its implications as a predictive biomarker for cancer chemotherapy remain unexplored. The present study evaluated ATM-induced synthetic lethality and its role in sensitization of gastric cancer cells to PARP and TOP1 inhibitors, veliparib (ABT-888) and irinotecan (CPT-11), respectively. ATM expression was detected in a panel of gastric cell lines, and the IC 50 against each inhibitors was determined. The combinatorial effect of ABT-888 and CPT-11 in gastric cancer cells was also determined both in vitro and in vivo ATM deficiency was found to be associated with enhanced sensitivity to ABT-888 and CPT-11 monotherapy, hence suggesting a mechanism of synthetic lethality. Cells with high ATM expression showed reduced sensitivity to monotherapy; however, they showed a higher therapeutic effect with ABT-888 and CPT-11 combinatorial therapy. Furthermore, ATM expression was shown to play a major role in cellular homeostasis by regulating cell-cycle progression and apoptosis in a P53-independent manner. The present study highlights the clinical utility of ATM expression as a predictive marker for sensitivity of gastric cancer cells to PARP and TOP1 inhibition and provides a deeper mechanistic insight into ATM-dependent regulation of cellular processes. Mol Cancer Ther; 15(12); 3087-96. ©2016 AACR. ©2016 American Association for Cancer Research.

  7. ATM Is Required for the Prolactin-Induced HSP90-Mediated Increase in Cellular Viability and Clonogenic Growth After DNA Damage.

    Science.gov (United States)

    Karayazi Atici, Ödül; Urbanska, Anna; Gopinathan, Sesha Gopal; Boutillon, Florence; Goffin, Vincent; Shemanko, Carrie S

    2018-02-01

    Prolactin (PRL) acts as a survival factor for breast cancer cells, but the PRL signaling pathway and the mechanism are unknown. Previously, we identified the master chaperone, heat shock protein 90 (HSP90) α, as a prolactin-Janus kinase 2 (JAK2)-signal transducer and activator of transcription 5 (STAT5) target gene involved in survival, and here we investigated the role of HSP90 in the mechanism of PRL-induced viability in response to DNA damage. The ataxia-telangiectasia mutated kinase (ATM) protein plays a critical role in the cellular response to double-strand DNA damage. We observed that PRL increased viability of breast cancer cells treated with doxorubicin or etoposide. The increase in cellular resistance is specific to the PRL receptor, because the PRL receptor antagonist, Δ1-9-G129R-hPRL, prevented the increase in viability. Two different HSP90 inhibitors, 17-allylamino-17-demethoxygeldanamycin and BIIB021, reduced the PRL-mediated increase in cell viability of doxorubicin-treated cells and led to a decrease in JAK2, ATM, and phosphorylated ATM protein levels. Inhibitors of JAK2 (G6) and ATM (KU55933) abolished the PRL-mediated increase in cell viability of DNA-damaged cells, supporting the involvement of each, as well as the crosstalk of ATM with the PRL pathway in the context of DNA damage. Drug synergism was detected between the ATM inhibitor (KU55933) and doxorubicin and between the HSP90 inhibitor (BIIB021) and doxorubicin. Short interfering RNA directed against ATM prevented the PRL-mediated increase in cell survival in two-dimensional cell culture, three-dimensional collagen gel cultures, and clonogenic cell survival, after doxorubicin treatment. Our results indicate that ATM contributes to the PRL-JAK2-STAT5-HSP90 pathway in mediating cellular resistance to DNA-damaging agents. Copyright © 2018 Endocrine Society.

  8. The ATM homologue MEC1 is required for phosphorylation of replication protein A in yeast

    International Nuclear Information System (INIS)

    Brush, G.S.; Morrow, D.M.; Hieter, P.; Kelly, T.J.

    1996-01-01

    Replication protein A (RPA) is a highly conserved single-stranded DNA-binding protein, required for cellular DNA replication, repair, and recombination. In human cells, RPA is phosphorylated during the S and G2 phases of the cell cycle and also in response to ionizing or ultraviolet radiation. Saccharomyces cerevisiae exhibits a similar pattern of cell cycle-regulated RPA phosphorylation, and our studies indicate that the radiation-induced reactions occur in yeast as well. We have examined yeast RPA phosphorylation during the normal cell cycle and in response to environmental insult, and have demonstrated that the checkpoint gene MEC1 is required for the reaction under all conditions tested. Through examination of several checkpoint mutants, we have placed RPA phosphorylation in a novel pathway of the DNA damage response. MEC1 is similar in sequence to human ATM, the gene mutated in patients with ataxia-telangiectasia (A-T). A-T cells are deficient in multiple checkpoint pathways and are hypersensitive to killing by ionizing radiation. Because A-T cells exhibit a delay in ionizing radiation-induced RPA phosphorylation, our results indicate a functional similarity between MEC1 and ATM, and suggest that RPA phosphorylation is involved in a conserved eukaryotic DNA damage-response pathway defective in A-T

  9. Naphthalimides Induce G2 Arrest Through the ATM-Activated Chk2-Executed Pathway in HCT116 Cells

    Directory of Open Access Journals (Sweden)

    Hong Zhu

    2009-11-01

    Full Text Available Naphthalimides, particularly amonafide and 2-(2-dimethylamino-6-thia-2-aza-benzo[def]chrysene-1,3-diones (R16, have been identified to possess anticancer activities and to induce G2-M arrest through inhibiting topoisomerase II accompanied by Chk1 degradation. The current study was designed to precisely dissect the signaling pathway(s responsible for the naphthalimide-induced cell cycle arrest in human colon carcinoma HCT116 cells. Using phosphorylated histone H3 and mitotic protein monoclonal 2 as mitosis markers, we first specified the G2 arrest elicited by the R16 and amonafide. Then, R16 and amonafide were revealed to induce phosphorylation of the DNA damage sensor ataxia telangiectasia-mutated (ATM responding to DNA double-strand breaks (DSBs. Inhibition of ATM by both the pharmacological inhibitor caffeine and the specific small interference RNA (siRNA rescued the G2 arrest elicited by R16, indicating its ATM-dependent characteristic. Furthermore, depletion of Chk2, but not Chk1 with their corresponding siRNA, statistically significantly reversed the R16- and amonafide-triggered G2 arrest. Moreover, the naphthalimides phosphorylated Chk2 in an ATM-dependent manner but induced Chk1 degradation. These data indicate that R16 and amonafide preferentially used Chk2 as evidenced by the differential ATM-executed phosphorylation of Chk1 and Chk2. Thus, a clear signaling pathway can be established, in which ATM relays the DNA DSBs signaling triggered by the naphthalimides to the checkpoint kinases, predominantly to Chk2,which finally elicits G2 arrest. The mechanistic elucidation not only favors the development of the naphthalimides as anticancer agents but also provides an alternative strategy of Chk2 inhibition to potentiate the anticancer activities of these agents.

  10. Hsp90α regulates ATM and NBN functions in sensing and repair of DNA double-strand breaks.

    Science.gov (United States)

    Pennisi, Rosa; Antoccia, Antonio; Leone, Stefano; Ascenzi, Paolo; di Masi, Alessandra

    2017-08-01

    The molecular chaperone heat shock protein 90 (Hsp90α) regulates cell proteostasis and mitigates the harmful effects of endogenous and exogenous stressors on the proteome. Indeed, the inhibition of Hsp90α ATPase activity affects the cellular response to ionizing radiation (IR). Although the interplay between Hsp90α and several DNA damage response (DDR) proteins has been reported, its role in the DDR is still unclear. Here, we show that ataxia-telangiectasia-mutated kinase (ATM) and nibrin (NBN), but not 53BP1, RAD50, and MRE11, are Hsp90α clients as the Hsp90α inhibitor 17-(allylamino)-17-demethoxygeldanamycin (17-AAG) induces ATM and NBN polyubiquitination and proteosomal degradation in normal fibroblasts and lymphoblastoid cell lines. Hsp90α-ATM and Hsp90α-NBN complexes are present in unstressed and irradiated cells, allowing the maintenance of ATM and NBN stability that is required for the MRE11/RAD50/NBN complex-dependent ATM activation and the ATM-dependent phosphorylation of both NBN and Hsp90α in response to IR-induced DNA double-strand breaks (DSBs). Hsp90α forms a complex also with ph-Ser1981-ATM following IR. Upon phosphorylation, NBN dissociates from Hsp90α and translocates at the DSBs, while phThr5/7-Hsp90α is not recruited at the damaged sites. The inhibition of Hsp90α affects nuclear localization of MRE11 and RAD50, impairs DDR signaling (e.g., BRCA1 and CHK2 phosphorylation), and slows down DSBs repair. Hsp90α inhibition does not affect DNA-dependent protein kinase (DNA-PK) activity, which possibly phosphorylates Hsp90α and H2AX after IR. Notably, Hsp90α inhibition causes H2AX phosphorylation in proliferating cells, this possibly indicating replication stress events. Overall, present data shed light on the regulatory role of Hsp90α on the DDR, controlling ATM and NBN stability and influencing the DSBs signaling and repair. © 2017 Federation of European Biochemical Societies.

  11. Plasma induced DNA damage: Comparison with the effects of ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Lazović, S.; Maletić, D.; Puač, N.; Malović, G.; Petrović, Z. Lj. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Leskovac, A.; Filipović, J.; Joksić, G. [Department of Physical Chemistry, Vinča Institute of Nuclear Sciences, University of Belgrade, 11001 Belgrade (Serbia)

    2014-09-22

    We use human primary fibroblasts for comparing plasma and gamma rays induced DNA damage. In both cases, DNA strand breaks occur, but of fundamentally different nature. Unlike gamma exposure, contact with plasma predominantly leads to single strand breaks and base-damages, while double strand breaks are mainly consequence of the cell repair mechanisms. Different cell signaling mechanisms are detected confirming this (ataxia telangiectasia mutated - ATM and ataxia telangiectasia and Rad3 related - ATR, respectively). The effective plasma doses can be tuned to match the typical therapeutic doses of 2 Gy. Tailoring the effective dose through plasma power and duration of the treatment enables safety precautions mainly by inducing apoptosis and consequently reduced frequency of micronuclei.

  12. Nutritional status of patients with ataxia-telangiectasia: A case for early and ongoing nutrition support and intervention.

    Science.gov (United States)

    Ross, Lynda J; Capra, Sandra; Baguley, Brenton; Sinclair, Kate; Munro, Kate; Lewindon, Peter; Lavin, Martin

    2015-08-01

    Ataxia-telangiectasia (A-T) is a rare genomic syndrome resulting in severe disability. Chronic childhood disorders can profoundly influence growth and development. Nutrition-related issues in A-T are not well described, and there are no nutritional guidelines. This study investigated the nutrition-related characteristics and behaviours of Australian A-T patients attending a national clinic. A cross-sectional analysis of 13 A-T patients (nine females; aged: 4-23 years): nutritional status was assessed by anthropometric and body cell mass (BCM) calculations. Parents reported their child's diet history and physical and behavioural factors that affect nutrition including fatigue and need for assistance. Ten (77%) had short stature (height for age z scores nutritional barriers as chronic tiredness and the need for care giver assistance with meals. This study confirms profound malnutrition in Australian A-T patients. Poor intakes and diet quality suggest the need for early nutrition intervention. Ongoing support for families and early discussions on tube feeding are required to address changing needs in childhood and likely nutritional decline into adulthood. A prospective study is required to assess feasibility and effectiveness of nutrition interventions in young people with A-T. © 2015 The Authors. Journal of Paediatrics and Child Health © 2015 Paediatrics and Child Health Division (Royal Australasian College of Physicians).

  13. Prenatal diagnosis of ataxia-telangiectasia and Nijmegen Breakage Syndrome by the assay of radioresistant DNA synthesis

    International Nuclear Information System (INIS)

    Kleijer, W.J.; Kraan, M. van der; Los, F.J.; Jaspers, N.G.J.

    1994-01-01

    Prenatal diagnosis was performed in 16 pregnancies at risk of ataxia-telangiectasia (A-T) or Nijmegen Breakage Syndrome (NBS). Radioresistant DNA synthesis (RDS) was investigated in cultured chorionic villus (CV) cells and/or amniotic fluid (AF) cells. In four pregnancies, an affected foetus was diagnosed with increased RDS in cultured CV cells. In three of the four cases confirmation of the diagnosis was obtained by analysis of AF cells and/or skin fibroblasts from the foetus cultured after termination of the pregnancy; in the fourth case a fibroblast culture from the aborted foetus failed. In one case, only AF cells could be analysed in a late stage of pregnancy; pregnancy was terminated due to intermediate/equivocal results but the foetus fibroblasts showed normal RDS. Normal RDS was demonstrated in the other 11 pregnancies at 25% risk either by analysis of CB cells (nine cases) or of AF cells (two cases). In some cases the (normal) results on the CV cells were corroborated by subsequent analysis of Af cells. The results suggest that RDS analysis of CV cells allows reliable prenatal diagnosis of A-T/NBS. However, amniocentesis may be necessary to confirm normal results on CV cells if the foetus is female (because of the risk of maternal cell contamination) or in the rare case of equivocal results. (author)

  14. DNA-PKcs, ATM, and ATR Interplay Maintains Genome Integrity during Neurogenesis.

    Science.gov (United States)

    Enriquez-Rios, Vanessa; Dumitrache, Lavinia C; Downing, Susanna M; Li, Yang; Brown, Eric J; Russell, Helen R; McKinnon, Peter J

    2017-01-25

    The DNA damage response (DDR) orchestrates a network of cellular processes that integrates cell-cycle control and DNA repair or apoptosis, which serves to maintain genome stability. DNA-PKcs (the catalytic subunit of the DNA-dependent kinase, encoded by PRKDC), ATM (ataxia telangiectasia, mutated), and ATR (ATM and Rad3-related) are related PI3K-like protein kinases and central regulators of the DDR. Defects in these kinases have been linked to neurodegenerative or neurodevelopmental syndromes. In all cases, the key neuroprotective function of these kinases is uncertain. It also remains unclear how interactions between the three DNA damage-responsive kinases coordinate genome stability, particularly in a physiological context. Here, we used a genetic approach to identify the neural function of DNA-PKcs and the interplay between ATM and ATR during neurogenesis. We found that DNA-PKcs loss in the mouse sensitized neuronal progenitors to apoptosis after ionizing radiation because of excessive DNA damage. DNA-PKcs was also required to prevent endogenous DNA damage accumulation throughout the adult brain. In contrast, ATR coordinated the DDR during neurogenesis to direct apoptosis in cycling neural progenitors, whereas ATM regulated apoptosis in both proliferative and noncycling cells. We also found that ATR controls a DNA damage-induced G 2 /M checkpoint in cortical progenitors, independent of ATM and DNA-PKcs. These nonoverlapping roles were further confirmed via sustained murine embryonic or cortical development after all three kinases were simultaneously inactivated. Thus, our results illustrate how DNA-PKcs, ATM, and ATR have unique and essential roles during the DDR, collectively ensuring comprehensive genome maintenance in the nervous system. The DNA damage response (DDR) is essential for prevention of a broad spectrum of different human neurologic diseases. However, a detailed understanding of the DDR at a physiological level is lacking. In contrast to many in

  15. Silencing of ATM expression by siRNA technique contributes to glioma stem cell radiosensitivity in vitro and in vivo.

    Science.gov (United States)

    Li, Yan; Li, Luchun; Wu, Zhijuan; Wang, Lulu; Wu, Yongzhong; Li, Dairong; Ma, Uiwen; Shao, Jianghe; Yu, Huiqing; Wang, Donglin

    2017-07-01

    Evidence has shown that both high expression of the ataxia-telangiectasia mutated (ATM) gene and glioma stem cells (GSCs) are responsible for radioresistance in glioma. Thus, we hypothesized that brain tumor radiosensitivity may be enhanced via silencing of the ATM gene in GSCs. In the present study we successfully induced GSCs from two cell lines and used CD133 and nestin to identify GSCs. A lentivirus was used to deliver siRNA-ATMPuro (A group) to GSCs prior to radiation, while siRNA-HKPuro (N group) and GSCs (C group) were used as negative and blank controls, respectively. RT-qPCR and western blotting were performed to verify the efficiency of the siRNA-ATM technique. The expression of the ATM gene and ATM protein were significantly downregulated post-transfection. Cell Counting Kit-8 (CCK-8) and colony formation assays revealed that the A group demonstrated weak cell proliferation and lower survival fractions post-irradiation compared to the C/N groups. Flow cytometry was used to examine the percentage of cell apoptosis and G2 phase arrest, which were both higher in the A group than in the C/N groups. We found that the comet tail percentage evaluated by comet assay was higher in the A group than in the C/N groups. After radiation treatment, three radiosensitive genes [p53, proliferating cell nuclear antigen (PCNA), survivin] exhibited a decreasing tendency as determined by RT-qPCR. Mice underwent subcutaneous implantation, followed by radiation, and the resulting necrosis and hemorrhage were more obvious in the A group than in the N groups. In conclusion, silencing of ATM via the siRNA technique improved radiosensitivity of GSCs both in vitro and in vivo.

  16. Ataxia telangiectasia: un desorden multisistémico con inestabilidad cromosómica y predisposición al cáncer

    Directory of Open Access Journals (Sweden)

    M. Guzmán

    1994-12-01

    Full Text Available El síndrome de ataxia telangiectasia (A-T fue descrito por Syllaba y Henneren 1926 y redescrito en 1941 por Louis Bar (1,2. Es una entidad autosómica recesiva que afecta a hombres y mujeres en igual proporción. La expresividad del gen A-Tes variable y la incidencia familiares alta (1,2. Se ha estimado que la frecuencia de individuos homocigotos (afectados para el gen A-T, es de 1/40.000 nacidos vivos y 1% de la población general serían heterocigotos (portadores. Sin embargo, la incidencia en la población se puede incrementar ya que los homocigotos pueden tener descendencia. Es así como se estima que en la población blanca de Estados Unidos los heterocigotos podrían llegar a constituir el 1,4% de la población (2,3. Otros autores estiman una frecuencia de heterocigotos mucho más alta entre 0,68% y 7,7% de la población (4.

  17. DNA-mediated gene transfer into human diploid fibroblasts derived from normal and ataxia-telangiectasia donors: parameters for DNA transfer and properties of DNA transformants

    International Nuclear Information System (INIS)

    Debenham, P.G.; Webb, M.B.T.; Masson, W.K.; Cox, R.

    1984-01-01

    An investigation was made of the feasibility of DNA-mediated gene transfer into human diploid fibroblasts derived from patients with the radiation sensitive syndrome ataxia-telangiectasia (A-T) and from a normal donor. Although they are markedly different in their growth characteristics, both normal and A-T strains give similar frequencies for DNA transfer in a model system using the recombinant plasmid pSV2-gpt. pSV2-gpt DNA transformants arise with a frequency between 10 -5 and 10 -4 per viable cell. Analysis of such transformants, although possible, is severely handicapped by the limited clonal life span of diploid human cells. Despite these problems it may be concluded that diploid human fibroblasts are competent recipients for DNA-mediated gene transfer and the putative repair deficiency of A-T does not markedly effect the efficiency of this process. (author)

  18. Ionizing radiation-induced phosphorylation of RPA p34 is deficient in ataxia telangiectasia and reduced in aged normal fibroblasts

    International Nuclear Information System (INIS)

    Xinbo Cheng; Nge Cheong; Ya Wang; Iliakis, George

    1996-01-01

    Replication protein A (RPA, also called human single stranded DNA binding protein, hSSB) is a trimeric, multifunctional protein complex involved in DNA replication, DNA repair and recombination. Phosphorylation of RPA p34 subunit is observed after exposure of cells to radiation and other DNA damaging agents, which implicates the protein not only in repair but also in the regulation of replication on damaged DNA template. Here, we show that the phosphorylation observed in RPA p34 after exposure to ionizing radiation, X- or γ-rays, is reduced and occurs later in primary fibroblasts from patients suffering from ataxia telangiectasia (AT), as compared to normal fibroblasts. We also show that in primary normal human fibroblasts, radiation-induced phosphorylation of RPA p34 is 'age'-dependent and decreases significantly as cultures senesce. Radiation-induced phosphorylation of RPA p34 is nearly absent in non-cycling cells, while the expression of p21 cip1/waf1/sdi1 remains inducible. The results demonstrate a growth-stage and culture-age dependency in radiation-induced RPA p34 phosphorylation, and suggest the operation of a signal transduction pathway that is inactivated in senescing or quiescent fibroblasts and defective in AT cells

  19. Study on effects of ATM gene on expression of hTERT in AT cells exposed to 60Co γ-rays

    International Nuclear Information System (INIS)

    Cao Jianping; Sheng Fangjun; Zhu Wei; Feng Shuang; Eckardt-Schupp, F.; Luo Jialin

    2005-01-01

    Objective: To study the effects of exogenous ATM gene on mRNA and protein expression of hTERT (human telomerase reverse transcriptase, hTERT) of a fibroblast cell line (AT5BIVA cells, At cells for short) established from skin of the ataxia telangiectasia (AT) patients. Methods: After the following cells had been exposed to 0, 1, 3, 5 Gy of 60 Co γ-rays, RT-PCR and Western blotting were used to observe the mRNA and protein expressions of hTERT in AT, PEBS7(blank vector)-AT, ATM + (AT gene mutated)-AT and GM cells, respectively. The GM(GM0639) cells were used as the normal control in this experiment. Results: Except for GM cells, there were mRNA and protein expressions of hTERT in all AT, PEBS7-AT and ATM + -AT cells before exposure to ionizing radiation. However, the mRNA and protein expressions of hTERT in ATM + -AT cells were significantly lower than those in AT cells, but still higher than those in GM cells (P + -AT and GM cells were increased dose-dependently from 1 Gy to 5 Gy. At the same dose point, the mRNA expression of hTERT in ATM + -AT cells was significantly lower than that of AT cells. Conclusion: Exogenous ATM gene can down-regulate mRNA and protein expressions of hTERT in AT cells no matter where the latter have been exposed to ionizing radiation or not. The mRNA and protein expressions of hTERT in cells can be induced by ionizing radiation in a dose- dependent manner. Telomerase is speculated on to participate in the repair of DNA damaged induced by ionizing radiation. (authors)

  20. ATM-activated autotaxin (ATX) propagates inflammation and DNA damage in lung epithelial cells: a new mode of action for silica-induced DNA damage?

    Science.gov (United States)

    Zheng, Huiyuan; Högberg, Johan; Stenius, Ulla

    2017-12-07

    Silica exposure is a common risk factor for lung cancer. It has been claimed that key elements in cancer development are activation of inflammatory cells that indirectly induce DNA damage and proliferative stimuli in respiratory epithelial cells. We studied DNA damage induced by silica particles in respiratory epithelial cells and focused the role of the signaling enzyme autotaxin (ATX). A549 and 16 bronchial epithelial cells (16HBE) lung epithelial cells were exposed to silica particles. Reactive oxygen species (ROS), NOD-like receptor family pyrin domain containing-3 (NLRP3) inflammasome activation, ATX, ataxia telangiectasia mutated (ATM), and DNA damage (γH2AX, pCHK1, pCHK2, comet assay) were end points. Low doses of silica induced NLRP3 activation, DNA damage accumulation, and ATM phosphorylation. A novel finding was that ATM induced ATX generation and secretion. Not only silica but also rotenone, camptothecin and H2O2 activated ATX via ATM, suggesting that ATX is part of a generalized ATM response to double-strand breaks (DSBs). Surprisingly, ATX inhibition mitigated DNA damage accumulation at later time points (6-16 h), and ATX transfection caused NLRP3 activation and DNA damage. Furthermore, the product of ATX enzymatic activity, lysophosphatidic acid, recapitulated the effects of ATX transfection. These data indicate an ATM-ATX-dependent loop that propagates inflammation and DSB accumulation, making low doses of silica effective inducers of DSBs in epithelial cells. We conclude that an ATM-ATX axis interconnects DSBs with silica-induced inflammation and propagates these effects in epithelial cells. Further studies of this adverse outcome pathway may give an accurate assessment of the lowest doses of silica that causes cancer. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  1. In Vivo and In Vitro Effects of ATM/ATR Signaling Pathway on Proliferation, Apoptosis, and Radiosensitivity of Nasopharyngeal Carcinoma Cells.

    Science.gov (United States)

    Wang, Ming; Liu, Gang; Shan, Guo-Ping; Wang, Bing-Bing

    2017-08-01

    The study investigated the ability of ataxia-telangiectasia mutated (ATM)/Rad3-related (ATR) signaling pathway to influence the proliferation, apoptosis, and radiosensitivity of nasopharyngeal carcinoma (NPC) cells. NPC tissues and corresponding adjacent normal tissues were collected from 143 NPC patients. The NPC CNE2 cells were assigned into a control group, X-ray group, CGK-733 group, and X-ray+CGK-733 group. The mRNA levels of ATM and ATR were evaluated using quantitative real-time polymerase chain reaction (qRT-PCR) and the protein levels of ATM and ATR using western blotting. The positive expression of ATM and ATR in tissues and nude mouse tumor tissues was determined by immunohistochemistry. Cell proliferation, migration, invasion, and apoptosis rates were analyzed by the 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide (MTT) assay, scratch test, transwell assay, and flow cytometry, respectively. A nude mouse model of NPC was established to observe tumor volume and growth. The mRNA levels of ATR and ATM and the expression of ATR and ATM protein in NPC tissues were significantly higher than those in adjacent normal tissues. The colony formation assay showed that the colony-forming rate decreased, showing radiation dose-dependent and CGK-733 concentration-dependent manners. Expression of ATM, ATR, Chk1, and Chk2 was evidently increased in the X-ray, CGK-733, and X-ray+CGK-733groups compared with the control group, and the aforementioned expression was highest in the X-ray+CGK-733 group among the four groups. The cell proliferation, invasion, and migration were decreased, tumor volume decreased and cell apoptosis increased in the X-ray, CGK-733, and X-ray+CGK-733 groups compared with the control group; the X-ray+CGK-733 group exhibited lowest cell proliferation, invasion and migration, smallest tumor volume, and highest cell apoptosis among the four groups. Inhibition of ATM/ATR signaling pathway reduces proliferation and enhances apoptosis and

  2. Tyrosyl-DNA Phosphodiesterase I a critical survival factor for neuronal development and homeostasis.

    Science.gov (United States)

    van Waardenburg, Robert C A M

    2016-01-01

    Tyrosyl-DNA phosphodiesterase I (TDP1), like most DNA repair associated proteins, is not essential for cell viability. However, dysfunctioning TDP1 or ATM (ataxia telangiectasia mutated) results in autosomal recessive neuropathology with similar phenotypes, including cerebellar atrophy. Dual inactivation of TDP1 and ATM causes synthetic lethality. A TDP1H 493 R catalytic mutant is associated with spinocerebellar ataxia with axonal neuropathy (SCAN1), and stabilizes the TDP1 catalytic obligatory enzyme-DNA covalent complex. The ATM kinase activates proteins early on in response to DNA damage. Tdp1-/- and Atm-/- mice exhibit accumulation of DNA topoisomerase I-DNA covalent complexes (TOPO1-cc) explicitly in neuronal tissue during development. TDP1 resolves 3'- and 5'-DNA adducts including trapped TOPO1-cc and TOPO1 protease resistant peptide-DNA complex. ATM appears to regulate the response to TOPO1-cc via a noncanonical function by regulating SUMO/ubiquitin-mediated TOPO1 degradation. In conclusion, TDP1 and ATM are critical factors for neuronal cell viability via two independent but cooperative pathways.

  3. EBV-encoded miRNAs target ATM-mediated response in nasopharyngeal carcinoma.

    Science.gov (United States)

    Lung, Raymond W-M; Hau, Pok-Man; Yu, Ken H-O; Yip, Kevin Y; Tong, Joanna H-M; Chak, Wing-Po; Chan, Anthony W-H; Lam, Ka-Hei; Lo, Angela Kwok-Fung; Tin, Edith K-Y; Chau, Shuk-Ling; Pang, Jesse C-S; Kwan, Johnny S-H; Busson, Pierre; Young, Lawrence S; Yap, Lee-Fah; Tsao, Sai-Wah; To, Ka-Fai; Lo, Kwok-Wai

    2018-04-01

    Nasopharyngeal carcinoma (NPC) is a highly invasive epithelial malignancy that is prevalent in southern China and Southeast Asia. It is consistently associated with latent Epstein-Barr virus (EBV) infection. In NPC, miR-BARTs, the EBV-encoded miRNAs derived from BamH1-A rightward transcripts, are abundantly expressed and contribute to cancer development by targeting various cellular and viral genes. In this study, we establish a comprehensive transcriptional profile of EBV-encoded miRNAs in a panel of NPC patient-derived xenografts and an EBV-positive NPC cell line by small RNA sequencing. Among the 40 miR-BARTs, predominant expression of 22 miRNAs was consistently detected in these tumors. Among the abundantly expressed EBV-miRNAs, BART5-5p, BART7-3p, BART9-3p, and BART14-3p could negatively regulate the expression of a key DNA double-strand break (DSB) repair gene, ataxia telangiectasia mutated (ATM), by binding to multiple sites on its 3'-UTR. Notably, the expression of these four miR-BARTs represented more than 10% of all EBV-encoded miRNAs in tumor cells, while downregulation of ATM expression was commonly detected in all of our tested sequenced samples. In addition, downregulation of ATM was also observed in primary NPC tissues in both qRT-PCR (16 NP and 45 NPC cases) and immunohistochemical staining (35 NP and 46 NPC cases) analysis. Modulation of ATM expression by BART5-5p, BART7-3p, BART9-3p, and BART14-3p was demonstrated in the transient transfection assays. These findings suggest that EBV uses miRNA machinery as a key mechanism to control the ATM signaling pathway in NPC cells. By suppressing these endogenous miR-BARTs in EBV-positive NPC cells, we further demonstrated the novel function of miR-BARTs in inhibiting Zta-induced lytic reactivation. These findings imply that the four viral miRNAs work co-operatively to modulate ATM activity in response to DNA damage and to maintain viral latency, contributing to the tumorigenesis of NPC. © 2017 The Authors

  4. IFN-γ Induces Mimic Extracellular Trap Cell Death in Lung Epithelial Cells Through Autophagy-Regulated DNA Damage.

    Science.gov (United States)

    Lin, Chiou-Feng; Chien, Shun-Yi; Chen, Chia-Ling; Hsieh, Chia-Yuan; Tseng, Po-Chun; Wang, Yu-Chih

    2016-02-01

    Treatment of interferon-γ (IFN-γ) causes cell growth inhibition and cytotoxicity in lung epithelial malignancies. Regarding the induction of autophagy related to IFN-γ signaling, this study investigated the link between autophagy and IFN-γ cytotoxicity. In A549 human lung cancer cells, IFN-γ treatment induced concurrent apoptotic and nonapoptotic events. Unexpectedly, the nonapoptotic cells present mimic extracellular trap cell death (ETosis), which was regulated by caspase-3 and by autophagy induction through immunity-related GTPase family M protein 1 and activating transcription factor 6. Furthermore, IFN-γ signaling controlled mimic ETosis through a mechanism involving an autophagy- and Fas-associated protein with death domain-controlled caspase-8/-3 activation. Following caspase-mediated lamin degradation, IFN-γ caused DNA damage-associated ataxia telangiectasia and Rad3-related protein (ATR)/ataxia telangiectasia mutated (ATM)-regulated mimic ETosis. Upon ATR/ATM signaling, peptidyl arginine deiminase 4 (PAD4)-mediated histone 3 citrullination promoted mimic ETosis. Such IFN-γ-induced effects were defective in PC14PE6/AS2 human lung cancer cells, which were unsusceptible to IFN-γ-induced autophagy. Due to autophagy-based caspase cascade activation, IFN-γ triggers unconventional caspase-mediated DNA damage, followed by ATR/ATM-regulated PAD4-mediated histone citrullination during mimic ETosis in lung epithelial malignancy.

  5. Mislocalization of the MRN complex prevents ATR signaling during adenovirus infection

    DEFF Research Database (Denmark)

    Carson, Christian T; Orazio, Nicole I; Lee, Darwin V

    2009-01-01

    The protein kinases ataxia-telangiectasia mutated (ATM) and ATM-Rad3 related (ATR) are activated in response to DNA damage, genotoxic stress and virus infections. Here we show that during infection with wild-type adenovirus, ATR and its cofactors RPA32, ATRIP and TopBP1 accumulate at viral...... during virus infection, which is independent of Mre11 nuclease activity and recruitment of RPA/ATR/ATRIP/TopBP1. Unlike other damage scenarios, we found that ATM and ATR signaling are not dependent on each other during infection. We identify a region of the viral E4orf3 protein responsible...

  6. Arecoline-induced phosphorylated p53 and p21(WAF1) protein expression is dependent on ATM/ATR and phosphatidylinositol-3-kinase in clone-9 cells.

    Science.gov (United States)

    Chou, Wen-Wen; Guh, Jinn-Yuh; Tsai, Jung-Fa; Hwang, Chi-Ching; Chiou, Shean-Jaw; Chuang, Lea-Yea

    2009-06-01

    Betel-quid use is associated with liver cancer whereas its constituent arecoline is cytotoxic, genotoxic, and induces p53-dependent p21(WAF1) protein expression in Clone-9 cells (rat hepatocytes). The ataxia telangiectasia mutated (ATM)/rad3-related (ATR)-p53-p21(WAF1) and the phosphatidylinositol-3-kinase (PI3K)-mammalian target of rapamycin (mTOR) pathways are involved in the DNA damage response and the pathogenesis of cancers. Thus, we studied the role of ATM/ATR and PI3K in arecoline-induced p53 and p21(WAF1) protein expression in Clone-9 cells. We found that arecoline (0.5 mM) activated the ATM/ATR kinase at 30 min. The arecoline-activated ATM/ATR substrate contained p-p53Ser15. Moreover, arecoline only increased the levels of the p-p53Ser6, p-p53Ser15, and p-p53Ser392 phosphorylated p53 isoforms among the known isoforms. ATM shRNA attenuated arecoline-induced p-p53Ser15 and p21(WAF1) at 24 h. Arecoline (0.5 mM) increased phosphorylation levels of p-AktSer473 and p-mTORSer2448 at 30-60 min. Dominant-negative PI3K plasmids attenuated arecoline-induced p21(WAF1), but not p-p53Ser15, at 24 h. Rapamycin attenuated arecoline-induced phosphrylated p-p53Ser15, but not p21(WAF1), at 24 h. ATM shRNA, but not dominant-negative PI3K plasmids, attenuated arecoline-induced p21(WAF1) gene transcription. We conclude that arecoline activates the ATM/ATR-p53-p21(WAF1) and the PI3K/Akt-mTOR-p53 pathways in Clone-9 cells. Arecoline-induced phosphorylated p-p53Ser15 expression is dependent on ATM whereas arecoline-induced p21(WAF1) protein expression is dependent on ATM and PI3K. Moreover, p21(WAF1) gene is transcriptionally induced by arecoline-activated ATM. (c) 2009 Wiley-Liss, Inc.

  7. ATM localization and gene expression in the adult mouse eye.

    Science.gov (United States)

    Leemput, Julia; Masson, Christel; Bigot, Karine; Errachid, Abdelmounaim; Dansault, Anouk; Provost, Alexandra; Gadin, Stéphanie; Aoufouchi, Said; Menasche, Maurice; Abitbol, Marc

    2009-01-01

    High levels of metabolism and oxygen consumption in most adult murine ocular compartments, combined with exposure to light and ultraviolet (UV) radiation, are major sources of oxidative stress, causing DNA damage in ocular cells. Of all mammalian body cells, photoreceptor cells consume the largest amount of oxygen and generate the highest levels of oxidative damage. The accumulation of such damage throughout life is a major factor of aging tissues. Several multiprotein complexes have recently been identified as the major sensors and mediators involved in the maintenance of DNA integrity. The activity of these complexes initially seemed to be restricted to dividing cells, given their ultimate role in major cell cycle checkpoints. However, it was later established that they are also active in post-mitotic cells. Recent findings demonstrate that the DNA damage response (DDR) is essential for the development, maintenance, and normal functioning of the adult central nervous system. One major molecular factor in the DDR is the protein, ataxia telangiectasia mutated (ATM). It is required for the rapid induction of cellular responses to DNA double-strand breaks. These cytotoxic DNA lesions may be caused by oxidative damage. To understand how ATM prevents oxidative stress and participates in the maintenance of genomic integrity and cell viability of the adult retina, we determined the ATM expression patterns and studied its localization in the adult mouse eye. Atm gene expression was analyzed by RT-PCR experiments and its localization by in situ hybridization on adult mouse ocular and cerebellar tissue sections. ATM protein expression was determined by western blot analysis of proteins homogenates extracted from several mouse tissues and its localization by immunohistochemistry experiments performed on adult mouse ocular and cerebellar tissue sections. In addition, subcellular localization was realized by confocal microscopy imaging of ocular tissue sections, with a special

  8. Oxidative stress, mitochondrial abnormalities and antioxidant defense in Ataxia-telangiectasia, Bloom syndrome and Nijmegen breakage syndrome

    Directory of Open Access Journals (Sweden)

    Mateusz Maciejczyk

    2017-04-01

    Full Text Available Rare pleiotropic genetic disorders, Ataxia-telangiectasia (A-T, Bloom syndrome (BS and Nijmegen breakage syndrome (NBS are characterised by immunodeficiency, extreme radiosensitivity, higher cancer susceptibility, premature aging, neurodegeneration and insulin resistance. Some of these functional abnormalities can be explained by aberrant DNA damage response and chromosomal instability. It has been suggested that one possible common denominator of these conditions could be chronic oxidative stress caused by endogenous ROS overproduction and impairment of mitochondrial homeostasis. Recent studies indicate new, alternative sources of oxidative stress in A-T, BS and NBS cells, including NADPH oxidase 4 (NOX4, oxidised low-density lipoprotein (ox-LDL or Poly (ADP-ribose polymerases (PARP. Mitochondrial abnormalities such as changes in the ultrastructure and function of mitochondria, excess mROS production as well as mitochondrial damage have also been reported in A-T, BS and NBS cells. A-T, BS and NBS cells are inextricably linked to high levels of reactive oxygen species (ROS, and thereby, chronic oxidative stress may be a major phenotypic hallmark in these diseases. Due to the presence of mitochondrial disturbances, A-T, BS and NBS may be considered mitochondrial diseases. Excess activity of antioxidant enzymes and an insufficient amount of low molecular weight antioxidants indicate new pharmacological strategies for patients suffering from the aforementioned diseases. However, at the current stage of research we are unable to ascertain if antioxidants and free radical scavengers can improve the condition or prolong the survival time of A-T, BS and NBS patients. Therefore, it is necessary to conduct experimental studies in a human model.

  9. Calcium dysregulation and Cdk5-ATM pathway involved in a mouse model of fragile X-associated tremor/ataxia syndrome.

    Science.gov (United States)

    Robin, Gaëlle; López, José R; Espinal, Glenda M; Hulsizer, Susan; Hagerman, Paul J; Pessah, Isaac N

    2017-07-15

    Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurological disorder that affects premutation carriers with 55-200 CGG-expansion repeats (preCGG) in FMR1, presenting with early alterations in neuronal network formation and function that precede neurodegeneration. Whether intranuclear inclusions containing DNA damage response (DDR) proteins are causally linked to abnormal synaptic function, neuronal growth and survival are unknown. In a mouse that harbors a premutation CGG expansion (preCGG), cortical and hippocampal FMRP expression is moderately reduced from birth through adulthood, with greater FMRP reductions in the soma than in the neurite, despite several-fold elevation of Fmr1 mRNA levels. Resting cytoplasmic calcium concentration ([Ca2+]i) in cultured preCGG hippocampal neurons is chronically elevated, 3-fold compared to Wt; elevated ROS and abnormal glutamatergic responses are detected at 14 DIV. Elevated µ-calpain activity and a higher p25/p35 ratio in the cortex of preCGG young adult mice indicate abnormal Cdk5 regulation. In support, the Cdk5 substrate, ATM, is upregulated by 1.5- to 2-fold at P0 and 6 months in preCGG brain, as is p-Ser1981-ATM. Bax:Bcl-2 is 30% higher in preCGG brain, indicating a greater vulnerability to apoptotic activation. Elevated [Ca2+]i, ROS, and DDR signals are normalized with dantrolene. Chronic [Ca2+]i dysregulation amplifies Cdk5-ATM signaling, possibly linking impaired glutamatergic signaling and DDR to neurodegeneration in preCGG brain. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  10. Sterigmatocystin-induced DNA damage triggers G2 arrest via an ATM/p53-related pathway in human gastric epithelium GES-1 cells in vitro.

    Directory of Open Access Journals (Sweden)

    Donghui Zhang

    Full Text Available Sterigmatocystin (ST, which is commonly detected in food and feed commodities, is a mutagenic and carcinogenic mycotoxin that has been recognized as a possible human carcinogen. Our previous study showed that ST can induce G2 phase arrest in GES-1 cells in vitro and that the MAPK and PI3K signaling pathways are involved in the ST-induced G2 arrest. It is now widely accepted that DNA damage plays a critical role in the regulation of cell cycle arrest and apoptosis. In response to DNA damage, a complex signaling network is activated in eukaryotic cells to trigger cell cycle arrest and facilitate DNA repair. To further explore the molecular mechanism through which ST induces G2 arrest, the current study was designed to precisely dissect the role of DNA damage and the DNA damage sensor ataxia telangiectasia-mutated (ATM/p53-dependent pathway in the ST-induced G2 arrest in GES-1 cells. Using the comet assay, we determined that ST induces DNA damage, as evidenced by the formation of DNA comet tails, in GES-1 cells. We also found that ST induces the activation of ATM and its downstream molecules, Chk2 and p53, in GES-1 cells. The ATM pharmacological inhibitor caffeine was found to effectively inhibit the activation of the ATM-dependent pathways and to rescue the ST-induced G2 arrest in GES-1 cells, which indicating its ATM-dependent characteristic. Moreover, the silencing of the p53 expression with siRNA effectively attenuated the ST-induced G2 arrest in GES-1 cells. We also found that ST induces apoptosis in GES-1 cells. Thus, our results show that the ST-induced DNA damage activates the ATM/53-dependent signaling pathway, which contributes to the induction of G2 arrest in GES-1 cells.

  11. Avances en el tratamiento de las ataxias crónicas

    Directory of Open Access Journals (Sweden)

    María Celeste Buompadre

    2013-09-01

    Full Text Available Las ataxias crónicas cerebelosas autosómicas recesivas constituyen el grupo más amplio de ataxias hereditarias, con presentación principalmente en la edad pediátrica, se caracterizan por degeneración o desarrollo anormal del cerebelo y de la médula espinal. Hasta el momento el tratamiento etiológico está disponible sólo para algunas formas: aquellas con defecto metabólico conocido como la abetalipoproteinemia, la ataxia con deficiencia de vitamina E y la xantomatosis cerebrotendinosa. En estas entidades la modificación de la dieta, el suplemento con vitaminas E y A principalmente y la administración de ácido quenodexocicólico pueden cambiar el curso de la enfermedad. En la mayoría de los otros tipos de ataxia el tratamiento es solo de soporte, como por ejemplo el uso de antioxidantes y quelantes del hierro en la ataxia de Friederich con el objetivo de disminuir los depósitos de hierro mitocondriales, de corticoides en la ataxia telangiectasia y de ubiquinona /coenzima Q10 en la ataxia por deficiencia de coenzima Q-10. Si bien hasta el momento ningún tratamiento es curativo para la mayoría de las ataxias crónicas autosómico recesivas, el diagnóstico precoz de estas entidades se asocia con una mejor respuesta a las diferentes drogas.

  12. INTS3 controls the hSSB1-mediated DNA damage response

    OpenAIRE

    Skaar, Jeffrey R.; Richard, Derek J.; Saraf, Anita; Toschi, Alfredo; Bolderson, Emma; Florens, Laurence; Washburn, Michael P.; Khanna, Kum Kum; Pagano, Michele

    2009-01-01

    Human SSB1 (single-stranded binding protein 1 [hSSB1]) was recently identified as a part of the ataxia telangiectasia mutated (ATM) signaling pathway. To investigate hSSB1 function, we performed tandem affinity purifications of hSSB1 mutants mimicking the unphosphorylated and ATM-phosphorylated states. Both hSSB1 mutants copurified a subset of Integrator complex subunits and the uncharacterized protein LOC58493/c9orf80 (henceforth minute INTS3/hSSB-associated element [MISE]). The INTS3?MISE?h...

  13. Deficient expression of enhanced reactivation of parvovirus H-1 in ataxia telangiectasia cells irradiated with X-rays or u.v. light

    International Nuclear Information System (INIS)

    Gilgers, Genevieve; Chen, Y.Q.; Cornelis, J.J.; Rommelaere, Jean

    1987-01-01

    Cells of patients with ataxia telangiectasia (AT), an inherited disease characterized by a high propensity to cancer, are hypersensitive to ionizing radiation. We investigated whether the hyper-radiosensitivity of AT cells correlated with a defect in their constitutive and/or conditional ability to rescue a damaged exogenous virus. For that purpose, parvovirus H-1, a single-stranded DNA virus whose intranuclear replication mostly relies on host cell functions, was used as a probe. The survival of u.v.-or γ-irradiated H-1 was measured in X-, u.v.-or mock-irradiated human cells of normal (NB-E) or AT (AT5BIVA) origin. γ-Irradiated H-1 survived to similar extents in untreated normal and AT cell lines. Both X- and u.v.-irradiation induced normal cells to achieve an enhanced reactivation (ER) of γ- or u.v.-damaged H-1. In contrast, neither dose-effect curves nor time course revealed significant levels of ER expression after X- or u.v.-irradiation in AT5BIVA cells. Our results suggest that the impairment of ER of damaged parvoviruses may constitute a marker of the AT cell phenotype and be related to the radiosensitivity of AT cells. (author)

  14. Deficient expression of enhanced reactivation of parvovirus H-1 in ataxia telangiectasia cells irradiated with X-rays or u. v. light

    Energy Technology Data Exchange (ETDEWEB)

    Hilgers, G.; Chen, Y.Q.; Cornelis, J.J.; Rommelaere, J.

    1987-02-01

    Cells of patients with ataxia telangiectasia (AT), an inherited disease characterized by a high propensity to cancer, are hypersensitive to ionizing radiation. We investigated whether the hyper-radiosensitivity of AT cells correlated with a defect in their constitutive and/or conditional ability to rescue a damaged exogenous virus. For that purpose, parvovirus H-1, a single-stranded DNA virus whose intranuclear replication mostly relies on host cell functions, was used as a probe. The survival of u.v.- or gamma-irradiated H-1 was measured in X-, u.v.- or mock-irradiated human cells of normal (NB-E) or AT (AT5BIVA) origin. gamma-Irradiated H-1 survived to similar extents in untreated normal and AT cell lines. Both X- and u.v.-irradiation induced normal cells to achieve an enhanced reactivation (ER) of gamma- or u.v.-damaged H-1. In contrast, neither dose-effect curves nor time course revealed significant levels of ER expression after X- or u.v.-irradiation in AT5BIVA cells. Our results suggest that the impairment of ER of damaged parvoviruses may constitute a marker of the AT cell phenotype and be related to the radiosensitivity of AT cells.

  15. Nedd4 family interacting protein 1 (Ndfip1) is required for ubiquitination and nuclear trafficking of BRCA1-associated ATM activator 1 (BRAT1) during the DNA damage response.

    Science.gov (United States)

    Low, Ley-Hian; Chow, Yuh-Lit; Li, Yijia; Goh, Choo-Peng; Putz, Ulrich; Silke, John; Ouchi, Toru; Howitt, Jason; Tan, Seong-Seng

    2015-03-13

    During injury, cells are vulnerable to apoptosis from a variety of stress conditions including DNA damage causing double-stranded breaks. Without repair, these breaks lead to aberrations in DNA replication and transcription, leading to apoptosis. A major response to DNA damage is provided by the protein kinase ATM (ataxia telangiectasia mutated) that is capable of commanding a plethora of signaling networks for DNA repair, cell cycle arrest, and even apoptosis. A key element in the DNA damage response is the mobilization of activating proteins into the cell nucleus to repair damaged DNA. BRAT1 is one of these proteins, and it functions as an activator of ATM by maintaining its phosphorylated status while also keeping other phosphatases at bay. However, it is unknown how BRAT1 is trafficked into the cell nucleus to maintain ATM phosphorylation. Here we demonstrate that Ndfip1-mediated ubiquitination of BRAT1 leads to BRAT1 trafficking into the cell nucleus. Without Ndfip1, BRAT1 failed to translocate to the nucleus. Under genotoxic stress, cells showed increased expression of both Ndfip1 and phosphorylated ATM. Following brain injury, neurons show increased expression of Ndfip1 and nuclear translocation of BRAT1. These results point to Ndfip1 as a sensor protein during cell injury and Ndfip1 up-regulation as a cue for BRAT1 ubiquitination by Nedd4 E3 ligases, followed by nuclear translocation of BRAT1. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  16. Dysphonia and vocal fold telangiectasia in hereditary hemorrhagic telangiectasia.

    Science.gov (United States)

    Chang, Joseph; Yung, Katherine C

    2014-11-01

    This case report is the first documentation of dysphonia and vocal fold telangiectasia as a complication of hereditary hemorrhagic telangiectasia (HHT). Case report of a 40-year-old man with HHT presenting with 2 years of worsening hoarseness. Hoarseness corresponded with a period of anticoagulation. Endoscopy revealed vocal fold scarring, vocal fold telangiectasias, and plica ventricular is suggestive of previous submucosal vocal fold hemorrhage and subsequent counterproductive compensation with ventricular phonation. Hereditary hemorrhagic telangiectasia may present as dysphonia with vocal fold telangiectasias and place patients at risk of vocal fold hemorrhage. © The Author(s) 2014.

  17. Comparison of Selected Parameters of Redox Homeostasis in Patients with Ataxia-Telangiectasia and Nijmegen Breakage Syndrome

    Directory of Open Access Journals (Sweden)

    Barbara Pietrucha

    2017-01-01

    Full Text Available This study compared the antioxidant status and major lipophilic antioxidants in patients with ataxia-telangiectasia (AT and Nijmegen breakage syndrome (NBS. Total antioxidant status (TAS, total oxidant status (TOS, oxidative stress index (OSI, and concentrations of coenzyme Q10 (CoQ10 and vitamins A and E were estimated in the plasma of 22 patients with AT, 12 children with NBS, and the healthy controls. In AT patients, TAS (median 261.7 μmol/L was statistically lower but TOS (496.8 μmol/L was significantly elevated in comparison with the healthy group (312.7 μmol/L and 311.2 μmol/L, resp.. Tocopherol (0.8 μg/mL and CoQ10 (0.1 μg/mL were reduced in AT patients versus control (1.4 μg/mL and 0.3 μg/mL, resp.. NBS patients also displayed statistically lower TAS levels (290.3 μmol/L, while TOS (404.8 μmol/L was comparable to the controls. We found that in NBS patients retinol concentration (0.1 μg/mL was highly elevated and CoQ10 (0.1 μg/mL was significantly lower in comparison with those in the healthy group. Our study confirms disturbances in redox homeostasis in AT and NBS patients and indicates a need for diagnosing oxidative stress in those cases as a potential disease biomarker. Decreased CoQ10 concentration found in NBS and AT indicates a need for possible supplementation.

  18. Upregulated ATM gene expression and activated DNA crosslink-induced damage response checkpoint in Fanconi anemia: implications for carcinogenesis.

    Science.gov (United States)

    Yamamoto, Kazuhiko; Nihrane, Abdallah; Aglipay, Jason; Sironi, Juan; Arkin, Steven; Lipton, Jeffrey M; Ouchi, Toru; Liu, Johnson M

    2008-01-01

    Fanconi anemia (FA) predisposes to hematopoietic failure, birth defects, leukemia, and squamous cell carcinoma of the head and neck (HNSCC) and cervix. The FA/BRCA pathway includes 8 members of a core complex and 5 downstream gene products closely linked with BRCA1 or BRCA2. Precancerous lesions are believed to trigger the DNA damage response (DDR), and we focused on the DDR in FA and its putative role as a checkpoint barrier to cancer. In primary fibroblasts with mutations in the core complex FANCA protein, we discovered that basal expression and phosphorylation of ATM (ataxia telangiectasia mutated) and p53 induced by irradiation (IR) or mitomycin C (MMC) were upregulated. This heightened response appeared to be due to increased basal levels of ATM in cultured FANCA-mutant cells, highlighting the new observation that ATM can be regulated at the transcriptional level in addition to its well-established activation by autophosphorylation. Functional analysis of this response using gamma-H2AX foci as markers of DNA double-stranded breaks (DSBs) demonstrated abnormal persistence of only MMC- and not IR-induced foci. Thus, we describe a processing defect that leads to general DDR upregulation but specific persistence of DNA crosslinker-induced damage response foci. Underscoring the significance of these findings, we found resistance to DNA crosslinker-induced cell cycle arrest and apoptosis in a TP53-mutant, patient-derived HNSCC cell line, whereas a lymphoblastoid cell line derived from this same individual was not mutated at TP53 and retained DNA crosslinker sensitivity. Our results suggest that cancer in FA may arise from selection for cells that escape from a chronically activated DDR checkpoint.

  19. Ionizing radiation: down regulation of 'atm' by 2 Deoxy-D-Glucose: a dose and time dependent study

    International Nuclear Information System (INIS)

    Lahiri, S.S.; Saxena, N.; Hambarde, S.

    2014-01-01

    Exposure to Ionizing Radiation (IR) cause cell death, but it also help in radio-sensitization of cancer cells, by causing oxidative stress and DNA damage, primarily by double strand breaks. Ataxia telangiectasia mutated (atm) gene is involved in DNA double strand breaks, sensory and repair pathways. Therefore, inhibition of its expression, can lead to useful radio-sensitization of cancerous cells. Metabolic inhibitor 2-Deoxy-D-Glucose (2-DG) block glycolysis and modulates protein glycosylation (2-DG). This cause sensitization of cancer cells to radiation, which help in effective reduction in the essential dose of therapeutic ionizing radiation required for the treatment of cancer. The transcription factor Sp-1 involved, is also down-regulated by 2-DG. We have studied the effect of 2-DG at varied concentrations, applied at different pre, simultaneous as well as post irradiation time intervals with 2 Gy, 5 Gy or 10 Gy (lethal dose) of ionizing radiations. Expressions of 'atm' gene in response to the drug and/or IR of different doses were studied. Response was studied at different post irradiation time intervals, in the levels of mRNA, protein and cell survival. It was observed that exposure of human glioma cells (BMG1) to 2 Gy, 5 Gy or 10 Gy of IR alone, had differential and dose dependent effect on 'atm' expression. The 'atm' level was significantly down regulated by 2-DG, in non-irradiated as well as gamma ray irradiated cells. It was observed that BMG1 cells when treated with 2-DG and exposed to irradiation, there was no net significant alteration (normalcy was restored) in the expression level of 'atm'. It was also observed that the extent of down-regulation by pre-treatment with 2-DG, was greater than post-treatment. This work has great significance in the application of clinically relevant low dose radiotherapy for the treatment of cancer. (author)

  20. Homeostatic regulation of meiotic DSB formation by ATM/ATR

    International Nuclear Information System (INIS)

    Cooper, Tim J.; Wardell, Kayleigh; Garcia, Valerie; Neale, Matthew J.

    2014-01-01

    Ataxia–telangiectasia mutated (ATM) and RAD3-related (ATR) are widely known as being central players in the mitotic DNA damage response (DDR), mounting responses to DNA double-strand breaks (DSBs) and single-stranded DNA (ssDNA) respectively. The DDR signalling cascade couples cell cycle control to damage-sensing and repair processes in order to prevent untimely cell cycle progression while damage still persists [1]. Both ATM/ATR are, however, also emerging as essential factors in the process of meiosis; a specialised cell cycle programme responsible for the formation of haploid gametes via two sequential nuclear divisions. Central to achieving accurate meiotic chromosome segregation is the introduction of numerous DSBs spread across the genome by the evolutionarily conserved enzyme, Spo11. This review seeks to explore and address how cells utilise ATM/ATR pathways to regulate Spo11-DSB formation, establish DSB homeostasis and ensure meiosis is completed unperturbed

  1. Homeostatic regulation of meiotic DSB formation by ATM/ATR

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, Tim J.; Wardell, Kayleigh; Garcia, Valerie; Neale, Matthew J., E-mail: m.neale@sussex.ac.uk

    2014-11-15

    Ataxia–telangiectasia mutated (ATM) and RAD3-related (ATR) are widely known as being central players in the mitotic DNA damage response (DDR), mounting responses to DNA double-strand breaks (DSBs) and single-stranded DNA (ssDNA) respectively. The DDR signalling cascade couples cell cycle control to damage-sensing and repair processes in order to prevent untimely cell cycle progression while damage still persists [1]. Both ATM/ATR are, however, also emerging as essential factors in the process of meiosis; a specialised cell cycle programme responsible for the formation of haploid gametes via two sequential nuclear divisions. Central to achieving accurate meiotic chromosome segregation is the introduction of numerous DSBs spread across the genome by the evolutionarily conserved enzyme, Spo11. This review seeks to explore and address how cells utilise ATM/ATR pathways to regulate Spo11-DSB formation, establish DSB homeostasis and ensure meiosis is completed unperturbed.

  2. Effects of X-irradiation on cell-cycle progression, induction of chromosomal aberrations and cell killing in ataxia telangiectasia (AT) fibroblasts

    International Nuclear Information System (INIS)

    Nagasawa, H.; Little, J.B.; Latt, S.A.; Lalande, M.E.

    1985-01-01

    Survival, cumulative labeling indices, chromosomal aberrations and cell-cycle distribution by flow microfluorometry (FMF) were studied in fibroblasts from normal and three ataxia telangiectasia (AT) families after X-irradiation during density-inhibition of growth and immediate release by subculture to low density. Homozygotic AT (proband) fibroblasts were very hypersensitive to cell killing by X-irradiation. Fibroblasts from AT heterozygotes (parents) were minimally hypersensitive, with D 0 's slightly lower than those for normal fibroblasts. There were three different response groups for a G 1 phase block induced by 400 rad of X-rays: (1) minimal or no G 1 block was observed in AT homozygote cell strains; (2) 10-20% of the cells were blocked in G 1 in normal cell strains; and (3) 50% or more of the cells were blocked in AT heterozygote strains. FMF profiles and cumulative labeling indices showed that homozygotic AT cells irradiated in plateau phase moved into the S-phase following subculture with no additional delay over non-irradiated controls. Homozygotic AT cells showed not only a 4-5 times higher frequency of X-ray-induced chromosomal aberrations than normal strains, but approximately 30% of these were of the chromatid-type. There were no differences in the frequency or type of X-ray-induced chromosomal aberrations between normal and heterozygotic AT cells. (orig.)

  3. Recombinational DNA repair and human disease

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Larry H.; Schild, David

    2002-11-30

    We review the genes and proteins related to the homologous recombinational repair (HRR) pathway that are implicated in cancer through either genetic disorders that predispose to cancer through chromosome instability or the occurrence of somatic mutations that contribute to carcinogenesis. Ataxia telangiectasia (AT), Nijmegen breakage syndrome (NBS), and an ataxia-like disorder (ATLD), are chromosome instability disorders that are defective in the ataxia telangiectasia mutated (ATM), NBS, and Mre11 genes, respectively. These genes are critical in maintaining cellular resistance to ionizing radiation (IR), which kills largely by the production of double-strand breaks (DSBs). Bloom syndrome involves a defect in the BLM helicase, which seems to play a role in restarting DNA replication forks that are blocked at lesions, thereby promoting chromosome stability. The Werner syndrome gene (WRN) helicase, another member of the RecQ family like BLM, has very recently been found to help mediate homologous recombination. Fanconi anemia (FA) is a genetically complex chromosomal instability disorder involving seven or more genes, one of which is BRCA2. FA may be at least partially caused by the aberrant production of reactive oxidative species. The breast cancer-associated BRCA1 and BRCA2 proteins are strongly implicated in HRR; BRCA2 associates with Rad51 and appears to regulate its activity. We discuss in detail the phenotypes of the various mutant cell lines and the signaling pathways mediated by the ATM kinase. ATM's phosphorylation targets can be grouped into oxidative stress-mediated transcriptional changes, cell cycle checkpoints, and recombinational repair. We present the DNA damage response pathways by using the DSB as the prototype lesion, whose incorrect repair can initiate and augment karyotypic abnormalities.

  4. Recombinational DNA repair and human disease

    International Nuclear Information System (INIS)

    Thompson, Larry H.; Schild, David

    2002-01-01

    We review the genes and proteins related to the homologous recombinational repair (HRR) pathway that are implicated in cancer through either genetic disorders that predispose to cancer through chromosome instability or the occurrence of somatic mutations that contribute to carcinogenesis. Ataxia telangiectasia (AT), Nijmegen breakage syndrome (NBS), and an ataxia-like disorder (ATLD), are chromosome instability disorders that are defective in the ataxia telangiectasia mutated (ATM), NBS, and Mre11 genes, respectively. These genes are critical in maintaining cellular resistance to ionizing radiation (IR), which kills largely by the production of double-strand breaks (DSBs). Bloom syndrome involves a defect in the BLM helicase, which seems to play a role in restarting DNA replication forks that are blocked at lesions, thereby promoting chromosome stability. The Werner syndrome gene (WRN) helicase, another member of the RecQ family like BLM, has very recently been found to help mediate homologous recombination. Fanconi anemia (FA) is a genetically complex chromosomal instability disorder involving seven or more genes, one of which is BRCA2. FA may be at least partially caused by the aberrant production of reactive oxidative species. The breast cancer-associated BRCA1 and BRCA2 proteins are strongly implicated in HRR; BRCA2 associates with Rad51 and appears to regulate its activity. We discuss in detail the phenotypes of the various mutant cell lines and the signaling pathways mediated by the ATM kinase. ATM's phosphorylation targets can be grouped into oxidative stress-mediated transcriptional changes, cell cycle checkpoints, and recombinational repair. We present the DNA damage response pathways by using the DSB as the prototype lesion, whose incorrect repair can initiate and augment karyotypic abnormalities

  5. Activation of eNOS in endothelial cells exposed to ionizing radiation involves components of the DNA damage response pathway

    Energy Technology Data Exchange (ETDEWEB)

    Nagane, Masaki; Yasui, Hironobu; Sakai, Yuri; Yamamori, Tohru [Laboratory of Radiation Biology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818 (Japan); Niwa, Koichi [Laboratory of Biochemistry, Department of Food and Cosmetic Science, Faculty of Bioindustry, Tokyo University of Agriculture, Abashiri 099-2493 (Japan); Hattori, Yuichi [Department of Molecular and Medical Pharmacology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194 (Japan); Kondo, Takashi [Department of Radiological Sciences, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194 (Japan); Inanami, Osamu, E-mail: inanami@vetmed.hokudai.ac.jp [Laboratory of Radiation Biology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818 (Japan)

    2015-01-02

    Highlights: • eNOS activity is increased in BAECs exposed to X-rays. • ATM is involved in this increased eNOS activity. • HSP90 modulates the radiation-induced activation of ATM and eNOS. - Abstract: In this study, the involvement of ataxia telangiectasia mutated (ATM) kinase and heat shock protein 90 (HSP90) in endothelial nitric oxide synthase (eNOS) activation was investigated in X-irradiated bovine aortic endothelial cells. The activity of nitric oxide synthase (NOS) and the phosphorylation of serine 1179 of eNOS (eNOS-Ser1179) were significantly increased in irradiated cells. The radiation-induced increases in NOS activity and eNOS-Ser1179 phosphorylation levels were significantly reduced by treatment with either an ATM inhibitor (Ku-60019) or an HSP90 inhibitor (geldanamycin). Geldanamycin was furthermore found to suppress the radiation-induced phosphorylation of ATM-Ser1181. Our results indicate that the radiation-induced eNOS activation in bovine aortic endothelial cells is regulated by ATM and HSP90.

  6. Involvement of DNA-PK and ATM in radiation- and heat-induced DNA damage recognition and apoptotic cell death

    International Nuclear Information System (INIS)

    Tomita, Masanori

    2010-01-01

    Exposure to ionizing radiation and hyperthermia results in important biological consequences, e.g. cell death, chromosomal aberrations, mutations, and DNA strand breaks. There is good evidence that the nucleus, specifically cellular DNA, is the principal target for radiation-induced cell lethality. DNA double-strand breaks (DSBs) are considered to be the most serious type of DNA damage induced by ionizing radiation. On the other hand, verifiable mechanisms which can lead to heat-induced cell death are damage to the plasma membrane and/or inactivation of heat-labile proteins caused by protein denaturation and subsequent aggregation. Recently, several reports have suggested that DSBs can be induced after hyperthermia because heat-induced phosphorylated histone H2AX (γ-H2AX) foci formation can be observed in several mammalian cell lines. In mammalian cells, DSBs are repaired primarily through two distinct and complementary mechanisms: non-homologous end joining (NHEJ), and homologous recombination (HR) or homology-directed repair (HDR). DNA-dependent protein kinase (DNA-PK) and ataxia-telangiectasia mutated (ATM) are key players in the initiation of DSB repair and phosphorylate and/or activate many substrates, including themselves. These phosphorylated substrates have important roles in the functioning of cell cycle checkpoints and in cell death, as well as in DSB repair. Apoptotic cell death is a crucial cell suicide mechanism during development and in the defense of homeostasis. If DSBs are unrepaired or misrepaired, apoptosis is a very important system which can protect an organism against carcinogenesis. This paper reviews recently obtained results and current topics concerning the role of DNA-PK and ATM in heat- or radiation-induced apoptotic cell death. (author)

  7. Lack of effect of inhibitors of DNA synthesis/repair on the ionizing radiation-induced chromosomal damage in G[sub 2] stage of ataxia telangiectasia cells

    Energy Technology Data Exchange (ETDEWEB)

    Antoccia, A. (Univ. ' La Sapienza' , Rome (Italy). Dipt. di Genetica e Biologia Molecolare); Palitti, F.; Raggi, T. (Univ. del Tuscia, Viterbo (Italy). Dipt. di Agrobiologia ed Agrochimica); Catena, C. (ENEA, Casaccia (Italy). Centro Ricerche Energia); Tanzarella, C. (Rome Univ. 3 (Italy). Dipt. di Biologia)

    1994-09-01

    The relationship between the repair processes occurring at the G[sub 2] phase of the cell cycle and cytogenetic damage in ataxia telangiectasia (AT) cells was studied. Lymphoblastoid cells derived from normal, heterozygote AT (HzAT) and three AT patients were exposed to X-rays or fission neutrons and post-treated with inhibitors of DNA synthesis/repair, such as inhibitors of DNA polymerases [alpha], [sigma] and [epsilon] (cytosine arabinoside, ara-C; aphidicolin, APC; buthylphenyl-guanine, BuPdG) or ribonucleotide reductase (hydroxyurea HU). A strong increase of radiation-induced chromosomal aberrations was observed in normal and HzAT cells post-treated with ara-C, APC and HU, but not in the presence of BuPdG. No enhancing effect was observed in cells derived from AT patients, except for HU post-irradiation treatment. These results suggest that the enzymes that can be inhibited by these agents are not directly involved in the repair of radiation damage induced in G[sub 2] cells from AT patients, indicating that probably the AT cells that we used lack the capability to transform the primary DNA lesions into reparable products, or that AT cells might contain a mutated form of DNA polymerase resistant to the inhibitors. (author).

  8. ATM status of the clinically radio-hypersensitive

    International Nuclear Information System (INIS)

    Clarke, R. A.; Hasnain, H.; Goozee, G.; Alvandi, R.; Miller, A.; Kearsley, J.H.; Farrell, A.; Bittell, G.; Chen, P.; Lavin, M.

    1996-01-01

    The aim of this study was to characterise the response to ionising radiation of normal tissues from patients that display early and acute hypersensitivity to radiotherapy. Methods include cell proliferation assay using MTT, induced chromosomal aberration testing, cell cycle response to radiation via FACs, mutation analysis of Ataxia Telangiectasia (AT) gene, p53 and AT Western analysis. It is now well appreciated that standard clinical doses (1.8-2 Gy per fraction per day) produce predictable acute and late toxicity in most patients. Occasionally, however, the standard clinical dose produces acute and late toxicity which can exceed the norm both in their extent and timing. The study confirmed the innate cellular radiosensitivity of the clinically radio-hypersensitive patients. No indication of AT gene mutations was found

  9. The Future of Radiobiology.

    Science.gov (United States)

    Kirsch, David G; Diehn, Max; Kesarwala, Aparna H; Maity, Amit; Morgan, Meredith A; Schwarz, Julie K; Bristow, Robert; Demaria, Sandra; Eke, Iris; Griffin, Robert J; Haas-Kogan, Daphne; Higgins, Geoff S; Kimmelman, Alec C; Kimple, Randall J; Lombaert, Isabelle M; Ma, Li; Marples, Brian; Pajonk, Frank; Park, Catherine C; Schaue, Dörthe; Bernhard, Eric J

    2018-04-01

    Innovation and progress in radiation oncology depend on discovery and insights realized through research in radiation biology. Radiobiology research has led to fundamental scientific insights, from the discovery of stem/progenitor cells to the definition of signal transduction pathways activated by ionizing radiation that are now recognized as integral to the DNA damage response (DDR). Radiobiological discoveries are guiding clinical trials that test radiation therapy combined with inhibitors of the DDR kinases DNA-dependent protein kinase (DNA-PK), ataxia telangiectasia mutated (ATM), ataxia telangiectasia related (ATR), and immune or cell cycle checkpoint inhibitors. To maintain scientific and clinical relevance, the field of radiation biology must overcome challenges in research workforce, training, and funding. The National Cancer Institute convened a workshop to discuss the role of radiobiology research and radiation biologists in the future scientific enterprise. Here, we review the discussions of current radiation oncology research approaches and areas of scientific focus considered important for rapid progress in radiation sciences and the continued contribution of radiobiology to radiation oncology and the broader biomedical research community.

  10. Enhanced radiosensitivity of cultured fibroblasts from ataxia telangiectasia heterozygotes manifested by defective colony-forming ability and reduced DNA repair replication after hypoxic γ-irradiation

    International Nuclear Information System (INIS)

    Paterson, M.C.; Anderson, A.K.; Smith, B.P.; Smith, P.J.

    1979-01-01

    We have measured the sensitivity to γ-ray inactivation of diploid skin fibroblasts cultured from 10 persons in four families with ataxia telangiectasia (AT). Persons heterozygous for AT, including parents of afflicted patients, are not as yet detectable by any specific clinical or laboratory marker but are believed to constitute a substantial portion of the middle-aged cancer population. In one AT family, fibroblast strains from both parents exhibited a colony-forming ability after hypoxic irradiation which was intermediate between that displayed by five control strains from normal children and that from the affected child. In the remaining three families, cultures from only one parent were available; one parental strain displayed an intermediate survival capacity as above, whereas the other two responded normally. The homozygous recessive strains from the five afflicted children in the four families were all equally hypersensitive to hypoxic γ-ray inactivation. The three presumed AT heterozygous strains that displayed intermediate rayiosensitivity also carried out γ-rad-induced DNA repair replication to an extent intermediate between those in normals and AT homozygotes. These findings suggest that a numerically significant, cancer-prone subpopulation of humans carrying one normal and one abnormal AT gene may also be moderately sensitive to lethal effects of hypoxic γ-rays due to a defect in the enzymatic repair of DNA

  11. Sequence analysis of the ATM gene in 20 patients with RTOG grade 3 or 4 acute and/or late tissue radiation side effects

    International Nuclear Information System (INIS)

    Oppitz, Ulrich; Bernthaler, Ulrike; Schindler, Detlev; Sobeck, Alexandra; Hoehn, Holger; Platzer, Matthias; Rosenthal, Andre; Flentje, Michael

    1999-01-01

    Purpose: Patients with ataxia-telangiectasia (A-T) show greatly increased radiation sensitivity and cancer predisposition. Family studies imply that the otherwise clinically silent heterozygotes of this autosomal recessive disease run a 3.5 to 3.8 higher risk of developing cancer. In vitro studies suggest moderately increased cellular radiation sensitivity of A-T carriers. They may also show elevated clinical radiosensitivity. We retrospectively examined patients who presented with severe adverse reactions during or after standard radiation treatment for mutations in the gene responsible for A-T, ATM, considering a potential means of future identification of radiosensitive individuals prospectively to adjust dosage schedules. Material and Methods: We selected 20 cancer patients (breast, 11; rectum, 2; ENT, 2; bladder, 1; prostate, 1; anus, 1; astrocytoma, 1; Hodgkins lymphoma, 1) with Grade 3 to 4 (RTOG) acute and/or late tissue radiation side effects by reaction severity. DNA from the peripheral blood of patients was isolated. All 66 exons and adjacent intron regions of the ATM gene were PCR-amplified and examined for mutations by a combination of agarose gel electrophoresis, single-stranded conformational polymorphism (SSCP) analysis, and exon-scanning direct sequencing. Results: Only 2 of the patients revealed altogether four heteroallelic sequence variants. The latter included two single-base deletions in different introns, a single-base change causing an amino acid substitution in an exon, and a large insertion in another intron. Both the single-base deletions and the single-base change represent known polymorphisms. The large insertion was an Alu repeat, shown not to give rise to altered gene product. Conclusions: Despite high technical efforts, no unequivocal ATM mutation was detected. Nevertheless, extension of similar studies to larger and differently composed cohorts of patients suffering severe adverse effects of radiotherapy, and application of new

  12. Polychlorinated biphenyl quinone induces oxidative DNA damage and repair responses: The activations of NHEJ, BER and NER via ATM-p53 signaling axis

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Hui; Shi, Qiong; Song, Xiufang; Fu, Juanli; Hu, Lihua; Xu, Demei; Su, Chuanyang; Xia, Xiaomin; Song, Erqun; Song, Yang, E-mail: songyangwenrong@hotmail.com

    2015-07-01

    Our previous studies demonstrated that polychlorinated biphenyl (PCB) quinone induced oxidative DNA damage in HepG2 cells. To promote genomic integrity, DNA damage response (DDR) coordinates cell-cycle transitions, DNA repair and apoptosis. PCB quinone-induced cell cycle arrest and apoptosis have been documented, however, whether PCB quinone insult induce DNA repair signaling is still unknown. In this study, we identified the activation of DDR and corresponding signaling events in HepG2 cells upon the exposure to a synthetic PCB quinone, PCB29-pQ. Our data illustrated that PCB29-pQ induces the phosphorylation of p53, which was mediated by ataxia telangiectasia mutated (ATM) protein kinase. The observed phosphorylated histone H2AX (γ-H2AX) foci and the elevation of 8-hydroxy-2′-deoxyguanosine (8-OHdG) indicated that DDR was stimulated by PCB29-pQ treatment. Additionally, we found PCB29-pQ activates non-homologous end joining (NHEJ), base excision repair (BER) and nucleotide excision repair (NER) signalings. However, these repair pathways are not error-free processes and aberrant repair of DNA damage may cause the potential risk of carcinogenesis and mutagenesis. - Highlights: • Polychlorinated biphenyl quinone induces oxidative DNA damage in HepG2 cells. • The elevation of γ-H2AX and 8-OHdG indicates the activation of DNA damage response. • ATM-p53 signaling acts as the DNA damage sensor and effector. • Polychlorinated biphenyl quinone activates NHEJ, BER and NER signalings.

  13. Lead (Pb) induced ATM-dependent mitophagy via PINK1/Parkin pathway.

    Science.gov (United States)

    Gu, Xueyan; Qi, Yongmei; Feng, Zengxiu; Ma, Lin; Gao, Ke; Zhang, Yingmei

    2018-07-01

    Lead (Pb), a widely distributed environmental pollutant, is known to induce mitochondrial damage as well as autophagy in vitro and in vivo. In this study, we found that Pb could trigger mitophagy in both HEK293 cells and the kidney cortex of male Kunming mice. However, whether ataxia telangiectasis mutated (ATM) which is reported to be linked with PTEN-induced putative kinase 1 (PINK1)/Parkin pathway (a well-characterized mitophagic pathway) participates in the regulation of Pb-induced mitophagy and its exact role remains enigmatic. Our results indicated that Pb activated ATM in vitro and in vivo, and further in vitro studies showed that ATM could co-localize with PINK1 and Parkin in cytosol and interact with PINK1. Knockdown of ATM by siRNA blocked Pb-induced mitophagy even under the circumstance of enhanced accumulation of PINK1 and mitochondrial Parkin. Intriguingly, elevation instead of reduction in phosphorylation level of PINK1 and Parkin was observed in response to ATM knockdown and Pb did not contribute to the further increase of their phosphorylation level, implying that ATM indirectly regulated PINK1/Parkin pathway. These findings reveal a novel mechanism for Pb toxicity and suggest the regulatory importance of ATM in PINK1/Parkin-mediated mitophagy. Copyright © 2018 Elsevier B.V. All rights reserved.

  14. Radiation 2006. In association with the Polymer Division, Royal Australian Chemical Institute. Incorporating the 21st AINSE Radiation Chemistry Conference and the 18th Radiation Biology Conference, conference handbook

    International Nuclear Information System (INIS)

    Lavin, M. F.; Luff, J.; Peng, Cheng; Chen, P.; Gueven, N.; Bottle, S.; Hosokawa, K.

    2006-01-01

    Full text: Ataxia-telangiectasia (A-T) is an autosomal recessive genetic disorder characterized by immunodeficiency, cancer predisposition and neurological degeneration. Cells from A-T patients are hypersensitive to radiation, display cell cycle checkpoint defects and genome instability. The gene product defective in this syndrome, ATM, is activated by double strand breaks in DNA and signals these to the DNA repair machinery and the cell cycle checkpoints via a series of phosphorylated intermediates including p53, Chk2, Nbs1 and SMC1. It has been suggested that the neurodegenerative phenotype in A-T patients arises as a consequence of oxidative stress. This is supported by observations that A-T patients have significantly reduced levels of total antioxidant capacity and that A-T cells in culture are more sensitive to oxidative stress that normal cells. We have demonstrated that in vitro survival of cerebellar Purkinje cells of Atm-mutant mice is significantly reduced compared to their wild-type littermates and most neurons from these animals have dramatically reduced dendritic branching. We also showed that in vitro administration of the antioxidant 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl (CTMIO) to Atm-deficient mice reduced the rate of cell death of Purkinje cells and enhanced dendritogenesis to wild-type levels. Intraperitoneal administration of this antioxidant throughout pregnancy enhanced survival of Purkinje cell neurons from Atm-disrupted animals and protected against oxidative stress in older animals as determined by levels of nitro-tyrosinated proteins and amount of catalase activity in the cerebellum. This antioxidant, a member of the nitroxide group, is a stable, free radical, capable of scavenging reactive oxygen species and may also circumvent Fenton-derived pathways by oxidizing the metals involved. We have recently demonstrated that CTMIO correct neuro-behavioural deficits in these mice and reduces oxidative damage to Purkinje cells. We

  15. Polymorphism rs189037C > T in the promoter region of the ATM gene may associate with reduced risk of T2DM in older adults in China: a case control study.

    Science.gov (United States)

    Ding, Xiang; Hao, Qiukui; Yang, Ming; Chen, Tie; Chen, Shanping; Yue, Jirong; Leng, Sean X; Dong, Birong

    2017-08-14

    Recent evidence indicates that ataxia telangiectasia mutated (ATM) is a cytoplasmic protein that involves in insulin signaling pathways. When ATM gene is mutated, this event appears to contribute to the development of insulin resistance and type 2 diabetes mellitus (T2DM). Up to date, little information about the relationship between ATM gene polymorphism and T2DM is available. This study aimed to explore potential association between a genetic variant [single nucleotide polymorphism (SNP), i.e. rs189037C > T] in the ATM promoter region and T2DM in older adults in China. We conducted a 1:1 age- and sex-matched case-control study. It enrolled 160 patients including 80 type 2 diabetic and 80 nondiabetic patients who were aged 60 years and above. Genotyping of the polymorphism rs189037 in the promoter of the ATM gene was performed using polymerase chain reaction-restriction fragment length polymorphism. Chi-square test or Fisher's exact test (when an expected cell count was ATM rs189037 polymorphism and T2DM (P = 0.037). The frequency of CT genotype is much higher in patients without T2DM than in diabetics (60.0% versus 40.0%, P = 0.012). After adjustment of the major confounding factors, such difference remained significant (OR for non-T2DM is 2.62, 95%CI = 1.05-6.53, P = 0.038). Similar effect of CT genotype on T2DM was observed in male population (adjusted: OR = 0.27, 95%CI = 0.09-0.84, P = 0.024). In addition, the percentage of TT genotype in diabetics with coronary artery disease (CAD) was considerably lower than in those without CAD (17.9% versus 61.5%, P = 0.004). Our study suggests that the ATM rs189037 polymorphism is associated with reduced risk of T2DM in older adult population in China. Specifically, CT heterozygote seems to be associated with a lower risk of T2DM than CC or TT genotype, especially in male older adults. Moreover, TT genotype may reduce the risk of CAD in diabetic patients.

  16. Ataxia Telangiectasia

    Science.gov (United States)

    ... is the measurement of "fetal proteins," or serum alpha-fetoprotein , in the blood. These are proteins that are ... than 95 percent) have elevated levels of serum alpha-fetoprotein. When other causes of elevations of alpha-fetoprotein ...

  17. Ataxia Telangiectasia

    Science.gov (United States)

    ... the hair, difficulty swallowing, and delayed physical and sexual development. Children with A-T usually have normal or ... the hair, difficulty swallowing, and delayed physical and sexual development. Children with A-T usually have normal or ...

  18. How Human Papillomavirus Replication and Immune Evasion Strategies Take Advantage of the Host DNA Damage Repair Machinery.

    Science.gov (United States)

    Bordignon, Valentina; Di Domenico, Enea Gino; Trento, Elisabetta; D'Agosto, Giovanna; Cavallo, Ilaria; Pontone, Martina; Pimpinelli, Fulvia; Mariani, Luciano; Ensoli, Fabrizio

    2017-12-19

    The DNA damage response (DDR) is a complex signalling network activated when DNA is altered by intrinsic or extrinsic agents. DDR plays important roles in genome stability and cell cycle regulation, as well as in tumour transformation. Viruses have evolved successful life cycle strategies in order to ensure a chronic persistence in the host, virtually avoiding systemic sequelae and death. This process promotes the periodic shedding of large amounts of infectious particles to maintain a virus reservoir in individual hosts, while allowing virus spreading within the community. To achieve such a successful lifestyle, the human papilloma virus (HPV) needs to escape the host defence systems. The key to understanding how this is achieved is in the virus replication process that provides by itself an evasion mechanism by inhibiting and delaying the host immune response against the viral infection. Numerous studies have demonstrated that HPV exploits both the ataxia-telangiectasia mutated (ATM) and ataxia-telangiectasia and rad3-related (ATR) DDR pathways to replicate its genome and maintain a persistent infection by downregulating the innate and cell-mediated immunity. This review outlines how HPV interacts with the ATM- and ATR-dependent DDR machinery during the viral life cycle to create an environment favourable to viral replication, and how the interaction with the signal transducers and activators of transcription (STAT) protein family and the deregulation of the Janus kinase (JAK)-STAT pathways may impact the expression of interferon-inducible genes and the innate immune responses.

  19. DNA damage response in nephrotoxic and ischemic kidney injury

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Mingjuan; Tang, Chengyuan [Department of Nephrology, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011 (China); Ma, Zhengwei [Department of Cellular Biology & Anatomy, Medical College of Georgia at Augusta University and Charlie Norwood VA Medical Center, Augusta, GA 30912 (United States); Huang, Shuang [Department of Anatomy and Cell Biology, University of Florida College of Medicine, Gainesville, FL (United States); Dong, Zheng, E-mail: zdong@augusta.edu [Department of Nephrology, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011 (China); Department of Cellular Biology & Anatomy, Medical College of Georgia at Augusta University and Charlie Norwood VA Medical Center, Augusta, GA 30912 (United States)

    2016-12-15

    DNA damage activates specific cell signaling cascades for DNA repair, cell cycle arrest, senescence, and/or cell death. Recent studies have demonstrated DNA damage response (DDR) in experimental models of acute kidney injury (AKI). In cisplatin-induced AKI or nephrotoxicity, the DDR pathway of ATR/Chk2/p53 is activated and contributes to renal tubular cell apoptosis. In ischemic AKI, DDR seems more complex and involves at least the ataxia telangiectasia mutated (ATM), a member of the phosphatidylinositol 3-kinase-related kinase (PIKK) family, and p53; however, while ATM may promote DNA repair, p53 may trigger cell death. Targeting DDR for kidney protection in AKI therefore relies on a thorough elucidation of the DDR pathways in various forms of AKI.

  20. Vertical transmission of macular telangiectasia type 2.

    Science.gov (United States)

    Delaere, Lien; Spielberg, Leigh; Leys, Anita M

    2012-01-01

    The purpose of this study was to report vertical transmission of macular telangiectasia type 2 and type 2 diabetes mellitus in 3 families. In this retrospective interventional case series, the charts of patients with inherited macular telangiectasia type 2 were reviewed. A large spectrum of presentations of macular telangiectasia type 2 was observed and has been studied with different techniques including best-corrected visual acuity, microperimetry, confocal blue reflectance fundus autofluorescence, fluorescein angiography, and time domain and spectral domain optical coherence tomography. Vertical transmission of macular telangiectasia type 2 and associated type 2 diabetes mellitus is described in 3 families. Symptomatic as well as asymptomatic eyes with macular telangiectasia type 2 were identified. In 2 families, a mother and son experienced visual loss and were diagnosed with macular telangiectasia type 2. All 4 patients had type 2 diabetes. Diabetic retinopathy was observed in one mother and her son. In the third family, the index patient was diagnosed macular telangiectasia type 2 after complaints of metamorphopsia. She and her family members had type 2 diabetes mellitus, and further screening of her family revealed familial macular telangiectasia type 2. None of the patients were treated for macular telangiectasia type 2. Macular telangiectasia type 2 may be more common than previously assumed, as vision can remain preserved and patients may go undiagnosed. Screening of family members is indicated, and detection of mild anomalies is possible using fundus autofluorescence and spectral domain optical coherence tomography.

  1. Phosphorylation of p53 at serine 15 in A549 pulmonary epithelial cells exposed to vanadate: Involvement of ATM pathway

    International Nuclear Information System (INIS)

    Suzuki, Katsura; Inageda, Kiyoshi; Nishitai, Gen; Matsuoka, Masato

    2007-01-01

    When A549 cells were exposed to sodium metavanadate (NaVO 3 ), the pentavalent species of vanadium (vanadate), phosphorylation of p53 protein at Ser15 was found in a time (8-48 h)- and dose (10-200 μM)-dependent manner. After the incubation with 50 or 100 μM NaVO 3 for 48 h, accumulation of p53 protein was accompanied with Ser15 phosphorylation. Among serines in p53 protein immunoprecipitated from A549 cells treated with 100 μM NaVO 3 for 48 h, only Ser15 was markedly phosphorylated. Treatment with other vanadate compounds, sodium orthovanadate (Na 3 VO 4 ) and ammonium metavanadate (NH 4 VO 3 ), also induced Ser15 phosphorylation and accumulation of p53 protein. While phosphorylation of extracellular signal-regulated protein kinase (ERK) was found in cells treated with NaVO 3 , treatment with U0126 did not suppress Ser15 phosphorylation. On the other hand, treatment with wortmannin or caffeine, the inhibitors to phosphatidylinositol 3-kinase related kinases (PIKKs), suppressed both NaVO 3 -induced Ser15 phosphorylation and accumulation of p53 protein. The silencing of ataxia telangiectasia mutated (ATM) expression using short-interference RNA resulted in the marked suppression of Ser15 phosphorylation in A549 cells exposed to NaVO 3 . However, treatment with antioxidants such as catalase and N-acetylcysteine did not suppress NaVO 3 -induced Ser15 phosphorylation. Transcriptional activation of p53 and DNA fragmentation in A549 cells treated with NaVO 3 were suppressed only slightly by S15A mutation, suggesting that Ser15 phosphorylation is not essential for these responses. The present results showed that vanadate induces the phosphorylation of p53 at Ser15 depending on ATM, one of the members of PIKK family, in this human pulmonary epithelial cell line

  2. Ataxia-telangiectasia mutated (ATM) silencing promotes neuroblastoma progression through a MYCN independent mechanism

    NARCIS (Netherlands)

    Mandriota, Stefano J.; Valentijn, Linda J.; Lesne, Laurence; Betts, David R.; Marino, Denis; Boudal-Khoshbeen, Mary; London, Wendy B.; Rougemont, Anne-Laure; Attiyeh, Edward F.; Maris, John M.; Hogarty, Michael D.; Koster, Jan; Molenaar, Jan J.; Versteeg, Rogier; Ansari, Marc; Gumy-Pause, Fabienne

    2015-01-01

    Neuroblastoma, a childhood cancer with highly heterogeneous biology and clinical behavior, is characterized by genomic aberrations including amplification of MYCN. Hemizygous deletion of chromosome 11q is a well-established, independent marker of poor prognosis. While 11q22-q23 is the most

  3. Genomic instability--an evolving hallmark of cancer.

    Science.gov (United States)

    Negrini, Simona; Gorgoulis, Vassilis G; Halazonetis, Thanos D

    2010-03-01

    Genomic instability is a characteristic of most cancers. In hereditary cancers, genomic instability results from mutations in DNA repair genes and drives cancer development, as predicted by the mutator hypothesis. In sporadic (non-hereditary) cancers the molecular basis of genomic instability remains unclear, but recent high-throughput sequencing studies suggest that mutations in DNA repair genes are infrequent before therapy, arguing against the mutator hypothesis for these cancers. Instead, the mutation patterns of the tumour suppressor TP53 (which encodes p53), ataxia telangiectasia mutated (ATM) and cyclin-dependent kinase inhibitor 2A (CDKN2A; which encodes p16INK4A and p14ARF) support the oncogene-induced DNA replication stress model, which attributes genomic instability and TP53 and ATM mutations to oncogene-induced DNA damage.

  4. Low dose ionizing radiation responses and knockdown of ATM kinase activity in glioma stem cells

    International Nuclear Information System (INIS)

    Lim, Y.C.; Roberts, T.; Day, B.; Kozlov, S.; Walker, D.; Lavin, M.; Harding, A.

    2009-01-01

    Genesis of new cells in the mammalian brain has previously been regarded as a negligible event; an assumption that long limited our understanding in the development of neoplasias. The recent discovery of perpetual lineages derived from neural stem cells has resulted in a new approach to studying the cellular behaviour of potential cancer stem cells in the brain. Glioblastoma multiforme (GBM), the most aggressive and lethal brain tumour is derived from a group of cancerous stem cells known as glioma stem cells. GBM cells are impervious to conventional therapies such as surgical resection and ionizing radiation because of their pluripotent and radioresistant properties. Thus in our study, we aim to investigate whether a combination of chemo- and radio- therapies is an effective treatment for glioma stem cells. The study utilizes a specific kinase inhibitor (ATMi) of the ATM (Ataxia-telangiectasia mutated) protein which is an essential protein in DNA-damage responses. In the presence of both low dose radiation and ATMi, glioma stem cells have rapid onset of cell death and reduction in growth. Since DNA damage can be inherited through cell division, accumulated DNA breaks in later generations may also lead to cell death. The limitation of conventional radiation therapy is that administration of fractionated (low) doses to reduce any potential harm to the surrounding healthy cells in the brain outweighs the benefits of high radiation doses to induce actual arrest in the propagation of malignant cells. Our study demonstrates a benefit in using low dose radiation combined with chemotherapy resulting in a reduction in malignancy of glioma stem cells. (author)

  5. Comparative human cellular radiosensitivity: I. The effect of SV40 transformation and immortalisation on the gamma-irradiation survival of skin derived fibroblasts from normal individuals and from ataxia-telangiectasia patients and heterozygotes.

    Science.gov (United States)

    Arlett, C F; Green, M H; Priestley, A; Harcourt, S A; Mayne, L V

    1988-12-01

    We have compared cell killing following 60Co gamma irradiation in 22 primary human fibroblast strains, nine SV40-immortalized human fibroblast lines and seven SV40-transformed pre-crisis human fibroblast cultures. We have examined material from normal individuals, from ataxia-telangiectasia (A-T) patients and from A-T heterozygotes. We have confirmed the greater sensitivity of A-T derived cells to gamma radiation. The distinction between A-T and normal cells is maintained in cells immortalized by SV40 virus but the immortal cells are more gamma radiation resistant than the corresponding primary fibroblasts. Cells transformed by plasmids (pSV3gpt and pSV3neo) expressing SV40 T-antigen, both pre- and post-crisis, show this increased resistance, indicating that it is expression of SV40 T-antigen, rather than immortalization per se which is responsible for the change. We use D0, obtained from a straight line fit, and D, estimated from a multitarget curve, as parameters to compare radiosensitivity. We suggest that both have their advantages; D0 is perhaps more reproducible, but D is more realistic when comparing shouldered and non-shouldered data.

  6. A critical role for topoisomerase IIb and DNA double strand breaks in transcription.

    Science.gov (United States)

    Calderwood, Stuart K

    2016-05-26

    Recent studies have indicated a novel role for topoisomerase IIb in transcription. Transcription of heat shock genes, serum-induced immediate early genes and nuclear receptor-activated genes, each required DNA double strands generated by topoisomerase IIb. Such strand breaks seemed both necessary and sufficient for transcriptional activation. In addition, such transcription was associated with initiation of the DNA damage response pathways, including the activation of the enzymes: ataxia-telangiectasia mutated (ATM), DNA-dependent protein kinase and poly (ADP ribose) polymerase 1. DNA damage response signaling was involved both in transcription and in repair of DNA breaks generated by topoisomerase IIb.

  7. Absence of ERK5/MAPK7 delays tumorigenesis in Atm−/− mice

    Science.gov (United States)

    Rovira-Clavé, Xavier; Gamez, Celina Paola Vasquez; Soriano, Francesc X.; Reina, Manuel; Espel, Enric

    2016-01-01

    Ataxia-telangiectasia mutated (ATM) is a cell cycle checkpoint kinase that upon activation by DNA damage leads to cell cycle arrest and DNA repair or apoptosis. The absence of Atm or the occurrence of loss-of-function mutations in Atm predisposes to tumorigenesis. MAPK7 has been implicated in numerous types of cancer with pro-survival and pro-growth roles in tumor cells, but its functional relation with tumor suppressors is not clear. In this study, we show that absence of MAPK7 delays death due to spontaneous tumor development in Atm−/− mice. Compared with Atm−/− thymocytes, Mapk7−/−Atm−/− thymocytes exhibited an improved response to DNA damage (increased phosphorylation of H2AX) and a restored apoptotic response after treatment of mice with ionizing radiation. These findings define an antagonistic function of ATM and MAPK7 in the thymocyte response to DNA damage, and suggest that the lack of MAPK7 inhibits thymic lymphoma growth in Atm−/− mice by partially restoring the DNA damage response in thymocytes. PMID:27793024

  8. DNA Repair Defects and Chromosomal Aberrations

    Science.gov (United States)

    Hada, Megumi; George, K. A.; Huff, J. L.; Pluth, J. M.; Cucinotta, F. A.

    2009-01-01

    Yields of chromosome aberrations were assessed in cells deficient in DNA doublestrand break (DSB) repair, after exposure to acute or to low-dose-rate (0.018 Gy/hr) gamma rays or acute high LET iron nuclei. We studied several cell lines including fibroblasts deficient in ATM (ataxia telangiectasia mutated; product of the gene that is mutated in ataxia telangiectasia patients) or NBS (nibrin; product of the gene mutated in the Nijmegen breakage syndrome), and gliomablastoma cells that are proficient or lacking in DNA-dependent protein kinase (DNA-PK) activity. Chromosomes were analyzed using the fluorescence in situ hybridization (FISH) chromosome painting method in cells at the first division post irradiation, and chromosome aberrations were identified as either simple exchanges (translocations and dicentrics) or complex exchanges (involving >2 breaks in 2 or more chromosomes). Gamma irradiation induced greater yields of both simple and complex exchanges in the DSB repair-defective cells than in the normal cells. The quadratic dose-response terms for both simple and complex chromosome exchanges were significantly higher for the ATM- and NBS-deficient lines than for normal fibroblasts. However, in the NBS cells the linear dose-response term was significantly higher only for simple exchanges. The large increases in the quadratic dose-response terms in these repair-defective cell lines points the importance of the functions of ATM and NBS in chromatin modifications to facilitate correct DSB repair and minimize the formation of aberrations. The differences found between ATM- and NBS-deficient cells at low doses suggest that important questions should with regard to applying observations of radiation sensitivity at high dose to low-dose exposures. For aberrations induced by iron nuclei, regression models preferred purely linear dose responses for simple exchanges and quadratic dose responses for complex exchanges. Relative biological effectiveness (RBE) factors of all of

  9. Breast cancer stem cell-like cells are more sensitive to ionizing radiation than non-stem cells: role of ATM.

    Directory of Open Access Journals (Sweden)

    Seog-Young Kim

    Full Text Available There are contradictory observations about the different radiosensitivities of cancer stem cells and cancer non-stem cells. To resolve these contradictory observations, we studied radiosensitivities by employing breast cancer stem cell (CSC-like MDA-MB231 and MDA-MB453 cells as well as their corresponding non-stem cells. CSC-like cells proliferate without differentiating and have characteristics of tumor-initiating cells [1]. These cells were exposed to γ-rays (1.25-8.75 Gy and survival curves were determined by colony formation. A final slope, D(0, of the survival curve for each cell line was determined to measure radiosensitivity. The D(0 of CSC-like and non-stem MDA-MB-453 cells were 1.16 Gy and 1.55 Gy, respectively. Similar results were observed in MDA-MB-231 cells (0.94 Gy vs. 1.56 Gy. After determination of radiosensitivity, we investigated intrinsic cellular determinants which influence radiosensitivity including cell cycle distribution, free-radical scavengers and DNA repair. We observed that even though cell cycle status and antioxidant content may contribute to differential radiosensitivity, differential DNA repair capacity may be a greater determinant of radiosensitivity. Unlike non-stem cells, CSC-like cells have little/no sublethal damage repair, a low intracellular level of ataxia telangiectasia mutated (ATM and delay of γ-H2AX foci removal (DNA strand break repair. These results suggest that low DNA repair capacity is responsible for the high radiosensitivity of these CSC-like cells.

  10. Clinical features of Hereditary Haemorrhagic Telangiectasia

    NARCIS (Netherlands)

    Hosman, A.E.

    2017-01-01

    Hereditary Haemorrhagic Telangiectasia (HHT), also known as Rendu-Osler-Weber disease (ROW), is an autosomal dominant disease with multi-systemic vascular dysplasia characterized by mucocutaneous telangiectasia, arteriovenous malformations and recurrent spontaneous epistaxis (nosebleeds). Most cases

  11. Requirement of ATR for maintenance of intestinal stem cells in aging Drosophila.

    Science.gov (United States)

    Park, Joung-Sun; Na, Hyun-Jin; Pyo, Jung-Hoon; Jeon, Ho-Jun; Kim, Young-Shin; Yoo, Mi-Ae

    2015-05-01

    The stem cell genomic stability forms the basis for robust tissue homeostasis, particularly in high-turnover tissues. For the genomic stability, DNA damage response (DDR) is essential. This study was focused on the role of two major DDR-related factors, ataxia telangiectasia-mutated (ATM) and ATM- and RAD3-related (ATR) kinases, in the maintenance of intestinal stem cells (ISCs) in the adultDrosophila midgut. We explored the role of ATM and ATR, utilizing immunostaining with an anti-pS/TQ antibody as an indicator of ATM/ATR activation, γ-irradiation as a DNA damage inducer, and the UAS/GAL4 system for cell type-specific knockdown of ATM, ATR, or both during adulthood. The results showed that the pS/TQ signals got stronger with age and after oxidative stress. The pS/TQ signals were found to be more dependent on ATR rather than on ATM in ISCs/enteroblasts (EBs). Furthermore, an ISC/EB-specific knockdown of ATR, ATM, or both decreased the number of ISCs and oxidative stress-induced ISC proliferation. The phenotypic changes that were caused by the ATR knockdown were more pronounced than those caused by the ATM knockdown; however, our data indicate that ATR and ATM are both needed for ISC maintenance and proliferation; ATR seems to play a bigger role than does ATM.

  12. Trovafloxacin-induced replication stress sensitizes HepG2 cells to tumor necrosis factor-alpha-induced cytotoxicity mediated by extracellular signal-regulated kinase and ataxia telangiectasia and Rad3-related

    International Nuclear Information System (INIS)

    Beggs, Kevin M.; Maiuri, Ashley R.; Fullerton, Aaron M.; Poulsen, Kyle L.; Breier, Anna B.; Ganey, Patricia E.; Roth, Robert A.

    2015-01-01

    Use of the fluoroquinolone antibiotic trovafloxacin (TVX) was restricted due to idiosyncratic, drug-induced liver injury (IDILI). Previous studies demonstrated that tumor necrosis factor-alpha (TNF) and TVX interact to cause death of hepatocytes in vitro that was associated with prolonged activation of c-Jun N-terminal kinase (JNK), activation of caspases 9 and 3, and DNA damage. The purpose of this study was to explore further the mechanism by which TVX interacts with TNF to cause cytotoxicity. Treatment with TVX caused cell cycle arrest, enhanced expression of p21 and impaired proliferation, but cell death only occurred after cotreatment with TVX and TNF. Cell death involved activation of extracellular signal-related kinase (ERK), which in turn activated caspase 3 and ataxia telangiectasia and Rad3-related (ATR), both of which contributed to cytotoxicity. Cotreatment of HepG2 cells with TVX and TNF caused double-strand breaks in DNA, and ERK contributed to this effect. Inhibition of caspase activity abolished the DNA strand breaks. The data suggest a complex interaction of TVX and TNF in which TVX causes replication stress, and the downstream effects are exacerbated by TNF, leading to hepatocellular death. These results raise the possibility that IDILI from TVX results from MAPK and ATR activation in hepatocytes initiated by interaction of cytokine signaling with drug-induced replication stress

  13. Splenic Involvement in Hereditary Hemorrhagic Telangiectasia

    Directory of Open Access Journals (Sweden)

    Susumu Takamatsu

    2016-01-01

    Full Text Available A 33-year-old man who presented with prolonged epigastric pain was referred to our hospital. He had experienced recurrent epistaxis and had a family history of hereditary hemorrhagic telangiectasia. Computed tomography and magnetic resonance imaging revealed splenomegaly and a 9 cm hypervascular mass in his spleen. Computed tomography also showed a pulmonary arteriovenous malformation and heterogeneous enhancement of the liver parenchyma, suggesting the presence of arteriosystemic shunts and telangiectases. Based on these findings, the patient was definitely diagnosed with hereditary hemorrhagic telangiectasia according to Curaçao criteria. He underwent splenectomy, and his symptoms disappeared after surgery. Pathological examination of the resected specimen revealed that the hypervascular lesion of the spleen was not a tumor but was composed of abnormal vessels associated with hereditary hemorrhagic telangiectasia. Symptomatic splenic involvement may be a rare manifestation of hereditary hemorrhagic telangiectasia but can be revealed by imaging modalities.

  14. miR-26b promotes granulosa cell apoptosis by targeting ATM during follicular atresia in porcine ovary.

    Directory of Open Access Journals (Sweden)

    Fei Lin

    Full Text Available More than 99% of ovarian follicles undergo atresia in mammals, but the mechanism of follicular atresia remains to be elucidated. In this study, we explored microRNA (miRNA regulation of follicular atresia in porcine ovary. A miRNA expression profile was constructed for healthy, early atretic, and progressively atretic follicles, and the differentially expressed miRNAs were selected and analyzed. We found that miR-26b, which was upregulated during follicular atresia, increased the number of DNA breaks and promoted granulosa cell apoptosis by targeting the ataxia telangiectasia mutated gene directly in vitro.

  15. Epstein-Barr Virus Hijacks DNA Damage Response Transducers to Orchestrate Its Life Cycle.

    Science.gov (United States)

    Hau, Pok Man; Tsao, Sai Wah

    2017-11-16

    The Epstein-Barr virus (EBV) is a ubiquitous virus that infects most of the human population. EBV infection is associated with multiple human cancers, including Burkitt's lymphoma, Hodgkin's lymphoma, a subset of gastric carcinomas, and almost all undifferentiated non-keratinizing nasopharyngeal carcinoma. Intensive research has shown that EBV triggers a DNA damage response (DDR) during primary infection and lytic reactivation. The EBV-encoded viral proteins have been implicated in deregulating the DDR signaling pathways. The consequences of DDR inactivation lead to genomic instability and promote cellular transformation. This review summarizes the current understanding of the relationship between EBV infection and the DDR transducers, including ATM (ataxia telangiectasia mutated), ATR (ATM and Rad3-related), and DNA-PK (DNA-dependent protein kinase), and discusses how EBV manipulates the DDR signaling pathways to complete the replication process of viral DNA during lytic reactivation.

  16. Ataxia with oculomotor apraxia type 2: clinical, biological and genotype/phenotype correlation study of a cohort of 90 patients.

    LENUS (Irish Health Repository)

    Anheim, M

    2009-10-01

    Ataxia with oculomotor apraxia type 2 (AOA2) is an autosomal recessive disease due to mutations in the senataxin gene, causing progressive cerebellar ataxia with peripheral neuropathy, cerebellar atrophy, occasional oculomotor apraxia and elevated alpha-feto-protein (AFP) serum level. We compiled a series of 67 previously reported and 58 novel ataxic patients who underwent senataxin gene sequencing because of suspected AOA2. An AOA2 diagnosis was established for 90 patients, originating from 15 countries worldwide, and 25 new senataxin gene mutations were found. In patients with AOA2, median AFP serum level was 31.0 microg\\/l at diagnosis, which was higher than the median AFP level of AOA2 negative patients: 13.8 microg\\/l, P = 0.0004; itself higher than the normal level (3.4 microg\\/l, range from 0.5 to 17.2 microg\\/l) because elevated AFP was one of the possible selection criteria. Polyneuropathy was found in 97.5% of AOA2 patients, cerebellar atrophy in 96%, occasional oculomotor apraxia in 51%, pyramidal signs in 20.5%, head tremor in 14%, dystonia in 13.5%, strabismus in 12.3% and chorea in 9.5%. No patient was lacking both peripheral neuropathy and cerebellar atrophy. The age at onset and presence of occasional oculomotor apraxia were negatively correlated to the progression rate of the disease (P = 0.03 and P = 0.009, respectively), whereas strabismus was positively correlated to the progression rate (P = 0.03). An increased AFP level as well as cerebellar atrophy seem to be stable in the course of the disease and to occur mostly at or before the onset of the disease. One of the two patients with a normal AFP level at diagnosis had high AFP levels 4 years later, while the other had borderline levels. The probability of missing AOA2 diagnosis, in case of sequencing senataxin gene only in non-Friedreich ataxia non-ataxia-telangiectasia ataxic patients with AFP level > or =7 microg\\/l, is 0.23% and the probability for a non-Friedreich ataxia non-ataxia-telangiectasia

  17. Ataxia with oculomotor apraxia type 2: clinical, biological and genotype/phenotype correlation study of a cohort of 90 patients.

    Science.gov (United States)

    Anheim, M; Monga, B; Fleury, M; Charles, P; Barbot, C; Salih, M; Delaunoy, J P; Fritsch, M; Arning, L; Synofzik, M; Schöls, L; Sequeiros, J; Goizet, C; Marelli, C; Le Ber, I; Koht, J; Gazulla, J; De Bleecker, J; Mukhtar, M; Drouot, N; Ali-Pacha, L; Benhassine, T; Chbicheb, M; M'Zahem, A; Hamri, A; Chabrol, B; Pouget, J; Murphy, R; Watanabe, M; Coutinho, P; Tazir, M; Durr, A; Brice, A; Tranchant, C; Koenig, M

    2009-10-01

    Ataxia with oculomotor apraxia type 2 (AOA2) is an autosomal recessive disease due to mutations in the senataxin gene, causing progressive cerebellar ataxia with peripheral neuropathy, cerebellar atrophy, occasional oculomotor apraxia and elevated alpha-feto-protein (AFP) serum level. We compiled a series of 67 previously reported and 58 novel ataxic patients who underwent senataxin gene sequencing because of suspected AOA2. An AOA2 diagnosis was established for 90 patients, originating from 15 countries worldwide, and 25 new senataxin gene mutations were found. In patients with AOA2, median AFP serum level was 31.0 microg/l at diagnosis, which was higher than the median AFP level of AOA2 negative patients: 13.8 microg/l, P = 0.0004; itself higher than the normal level (3.4 microg/l, range from 0.5 to 17.2 microg/l) because elevated AFP was one of the possible selection criteria. Polyneuropathy was found in 97.5% of AOA2 patients, cerebellar atrophy in 96%, occasional oculomotor apraxia in 51%, pyramidal signs in 20.5%, head tremor in 14%, dystonia in 13.5%, strabismus in 12.3% and chorea in 9.5%. No patient was lacking both peripheral neuropathy and cerebellar atrophy. The age at onset and presence of occasional oculomotor apraxia were negatively correlated to the progression rate of the disease (P = 0.03 and P = 0.009, respectively), whereas strabismus was positively correlated to the progression rate (P = 0.03). An increased AFP level as well as cerebellar atrophy seem to be stable in the course of the disease and to occur mostly at or before the onset of the disease. One of the two patients with a normal AFP level at diagnosis had high AFP levels 4 years later, while the other had borderline levels. The probability of missing AOA2 diagnosis, in case of sequencing senataxin gene only in non-Friedreich ataxia non-ataxia-telangiectasia ataxic patients with AFP level > or =7 microg/l, is 0.23% and the probability for a non-Friedreich ataxia non-ataxia-telangiectasia

  18. Hereditary haemorrhagic telangiectasia

    DEFF Research Database (Denmark)

    Kjeldsen, A D; Vase, P; Green, A

    1999-01-01

    Hereditary haemorrhagic telangiectasia (HHT) is a dominantly inherited disease characterized by telangiectatic lesions. The disease manifestations are variable and include epistaxis, gastrointestinal bleeding, pulmonary arteriovenous malformations and cerebral arteriovenous malformations. Early...

  19. Chromosomal radiosensitivity, cancer predisposition and response to radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Scott, D. [Christie Hospital, Manchester (United Kingdom). Paterson Inst. for Cancer Research

    2000-05-01

    Aim: This paper briefly summarizes the research on this topic, undertaken in the Department of Cancer Genetics, Paterson Institute for Cancer Research, Manchester, England, over the previous 6 years. We have investigated the possible role of radiosensitivity as a marker of cancer predisposition and response to radiotherapy in the general population. Results: We found that 42% (57/135) of breast cancer patients exhibit chromosomal radiosensitivity when lymphocytes are irradiated in the G{sub 2} phase of the cell cycle, compared with 6% (6/105) of healthy controls. These figures are much higher than the estimated frequencies of carriers of the ataxia-telangiectasia gene (heterozygotes) amongst breast cancer patients (<5%) and control (0.5%). We have also obtained evidence of heritability of G{sub 2} sensitivity by studying relatives of breast cancer cases. The pattern of inheritance is relatively simple and attributable to 1 or 2 genes segregating in each family. In a prospective study of 123 breast cancer patients, 9 (7%) had severe acute reactions to radiotherapy and their mean G{sub 2} sensitivity was significantly greater (p=0.001) than that of the remaining patients. In 16 patients with adverse acute reactions we found no mutations of the ataxia-telangiectasia gene (ATM). Using another chromosomal assay (micronucleus induction in G{sub 0} lymphocytes) we found that the mean radiosensitivity of patients with severe late reactions was higher than that of normal reactors. For example, 8 patients with severe fibrosis were more sensitive (p=0.055) than 39 patients with a normal response. However, the discriminatory power of these chromosomal assays is too low for them to be used alone in a clinical setting. Conclusion: Our results provide good evidence that genes other than ATM, that confer chromosomal radiosensitivity, are involved in low penetrance predisposition to breast cancer in a high proportion of cases and contribute to adverse reactions after radiotherapy

  20. Coordinate to Guard: Crosstalk of Phosphorylation, Sumoylation, and Ubiquitylation in DNA Damage Response

    International Nuclear Information System (INIS)

    Kuo, Ching-Ying; Shieh, Christine; Cai, Fei; Ann, David Kong

    2012-01-01

    Small ubiquitin-like modifier-1/2/3 (SUMO-1/2/3) and ubiquitin share similar structure and utilize analogous machinery for protein lysine conjugation. Although sumoylation and ubiquitylation have distinct functions, they are often tightly associated with each other to fine-tune protein fate in transducing signals to regulate a wide variety of cellular functions, including DNA damage response, cell proliferation, DNA replication, embryonic development, and cell differentiation. In this Perspective, we specifically highlight the role of sumoylation and ubiquitylation in ataxia-telangiectasia mutated (ATM) signaling in response to DNA double-strand breaks and hypothesize that ATM-induced phosphorylation is a unique node in regulating SUMO-targeted ubiquitylation in mammalian cells to combat DNA damage and to maintain genome integrity. A potential role for the coordination of three types of post-translational modification in dictating the tempo and extent of cellular response to genotoxic stress is speculated.

  1. Coordinate to Guard: Crosstalk of Phosphorylation, Sumoylation, and Ubiquitylation in DNA Damage Response

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, Ching-Ying [Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of City of Hope, Duarte, CA (United States); Department of Molecular Pharmacology, Beckman Research Institute of City of Hope, Duarte, CA (United States); Shieh, Christine; Cai, Fei [Eugene and Ruth Roberts Summer Student Academy, Beckman Research Institute of City of Hope, Duarte, CA (United States); Ann, David Kong, E-mail: dann@coh.org [Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of City of Hope, Duarte, CA (United States); Department of Molecular Pharmacology, Beckman Research Institute of City of Hope, Duarte, CA (United States); Eugene and Ruth Roberts Summer Student Academy, Beckman Research Institute of City of Hope, Duarte, CA (United States)

    2012-01-19

    Small ubiquitin-like modifier-1/2/3 (SUMO-1/2/3) and ubiquitin share similar structure and utilize analogous machinery for protein lysine conjugation. Although sumoylation and ubiquitylation have distinct functions, they are often tightly associated with each other to fine-tune protein fate in transducing signals to regulate a wide variety of cellular functions, including DNA damage response, cell proliferation, DNA replication, embryonic development, and cell differentiation. In this Perspective, we specifically highlight the role of sumoylation and ubiquitylation in ataxia-telangiectasia mutated (ATM) signaling in response to DNA double-strand breaks and hypothesize that ATM-induced phosphorylation is a unique node in regulating SUMO-targeted ubiquitylation in mammalian cells to combat DNA damage and to maintain genome integrity. A potential role for the coordination of three types of post-translational modification in dictating the tempo and extent of cellular response to genotoxic stress is speculated.

  2. No evidence for association of ataxia-telangiectasia mutated gene T2119C and C3161G amino acid substitution variants with risk of breast cancer

    International Nuclear Information System (INIS)

    Spurdle, Amanda B; Hopper, John L; Chen, Xiaoqing; McCredie, Margaret RE; Giles, Graham G; Newman, Beth; Chenevix-Trench, Georgia; Khanna, KumKum

    2002-01-01

    There is evidence that certain mutations in the double-strand break repair pathway ataxia-telangiectasia mutated gene act in a dominant-negative manner to increase the risk of breast cancer. There are also some reports to suggest that the amino acid substitution variants T2119C Ser707Pro and C3161G Pro1054Arg may be associated with breast cancer risk. We investigate the breast cancer risk associated with these two nonconservative amino acid substitution variants using a large Australian population-based case–control study. The polymorphisms were genotyped in more than 1300 cases and 600 controls using 5' exonuclease assays. Case–control analyses and genotype distributions were compared by logistic regression. The 2119C variant was rare, occurring at frequencies of 1.4 and 1.3% in cases and controls, respectively (P = 0.8). There was no difference in genotype distribution between cases and controls (P = 0.8), and the TC genotype was not associated with increased risk of breast cancer (adjusted odds ratio = 1.08, 95% confidence interval = 0.59–1.97, P = 0.8). Similarly, the 3161G variant was no more common in cases than in controls (2.9% versus 2.2%, P = 0.2), there was no difference in genotype distribution between cases and controls (P = 0.1), and the CG genotype was not associated with an increased risk of breast cancer (adjusted odds ratio = 1.30, 95% confidence interval = 0.85–1.98, P = 0.2). This lack of evidence for an association persisted within groups defined by the family history of breast cancer or by age. The 2119C and 3161G amino acid substitution variants are not associated with moderate or high risks of breast cancer in Australian women

  3. Evidence-based management of epistaxis in hereditary haemorrhagic telangiectasia.

    Science.gov (United States)

    Syed, I; Sunkaraneni, V S

    2015-05-01

    There are currently no guidelines in the UK for the specific management of hereditary haemorrhagic telangiectasia related epistaxis. The authors aimed to review the literature and provide an algorithm for the management of hereditary haemorrhagic telangiectasia related epistaxis. The Medline and Embase databases were interrogated on 15 November 2013 using the search items 'hereditary haemorrhagic telangiectasia' (title), 'epistaxis' (title) and 'treatment' (title and abstract), and limiting the search to articles published in English. A total of 46 publications were identified, comprising 1 systematic review, 2 randomised, controlled trials, 27 case series, 9 case reports, 4 questionnaire studies and 3 in vitro studies. There is a lack of high-level evidence for the use of many of the available treatments for the specific management of epistaxis in hereditary haemorrhagic telangiectasia. Current management should be based on a multidisciplinary team approach involving both a hereditary haemorrhagic telangiectasia physician and an ENT surgeon, especially when systemic therapy is being considered. The suggested treatment algorithm considers that the severity of epistaxis merits intervention at different levels of the treatment ladder. The patient should be assessed using a reproducible validated assessment tool, for example an epistaxis severity score, to guide treatment. More research is required, particularly in the investigation of topical agents targeting the development and fragility of telangiectasiae in hereditary haemorrhagic telangiectasia.

  4. Differential Processing of Low and High LET Radiation Induced DNA Damage: Investigation of Switch from ATM to ATR Signaling

    Science.gov (United States)

    Saha, Janapriya; Wang, Minli; Hada, Megumi; Cucinotta, Francis A.

    2011-01-01

    The members of the phosphatidylinositol kinase-like kinase family of proteins namely ataxia-telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR) are directly responsible for the maintenance of genomic integrity by mounting DDR through signaling and facilitating the recruitment of repair factors at the sites of DNA damage along with coordinating the deployment of cell cycle checkpoints to permit repair by phosphorylating Checkpoint kinase Chk1, Chk2 and p53. High LET radiation from GCR (Galactic Cosmic Rays) consisting mainly of protons and high energy and charged (HZE) particles from SPE (Solar Particle Event) pose a major health risk for astronauts on their space flight missions. The determination of these risks and the design of potential safeguards require sound knowledge of the biological consequences of lesion induction and the capability of the cells to counter them. We here strive to determine the coordination of ATM and ATR kinases at the break sites directly affecting checkpoint signaling and DNA repair and whether differential processing of breaks induced by low and high LET radiation leads to possible augmentation of swap of these damage sensors at the sites of DNA damage. Exposure of cells to IR triggers rapid autophosphorylation of serine-1981 that causes dimer dissociation and initiates monomer formation of ATM. ATM kinase activity depends on the disruption of the dimer, which allows access and phosphorylation of downstream ATM substrates like Chk2. Evidence suggests that ATM is activated by the alterations in higher-order chromatin structure although direct binding of ATM to DSB ends may be a crucial step in its activation. On the other hand, in case of ATR, RPA (replication protein A)-coated ssDNA (single-stranded DNA) generated as a result of stalled DNA replication or during processing of chromosomal lesions is crucial for the localization of ATR to sites of DNA damage in association with ATR-interacting protein (ATRIP). Although the

  5. NAD(+) Replenishment Improves Lifespan and Healthspan in Ataxia Telangiectasia Models via Mitophagy and DNA Repair

    DEFF Research Database (Denmark)

    Fang, Evandro Fei; Kassahun, Henok; Croteau, Deborah L

    2016-01-01

    and neurodegeneration in A-T patients is unclear. Here we report and examine the significance of increased PARylation, low NAD(+), and mitochondrial dysfunction in ATM-deficient neurons, mice, and worms. Treatments that replenish intracellular NAD(+) reduce the severity of A-T neuropathology, normalize neuromuscular...... function, delay memory loss, and extend lifespan in both animal models. Mechanistically, treatments that increase intracellular NAD(+) also stimulate neuronal DNA repair and improve mitochondrial quality via mitophagy. This work links two major theories on aging, DNA damage accumulation, and mitochondrial...

  6. Colorectal choriocarcinoma in a patient with probable Lynch syndrome

    Directory of Open Access Journals (Sweden)

    Viktor Hendrik Koelzer

    2016-11-01

    Full Text Available Background: Personalized therapy of colorectal cancer (CRC is influenced by morphological, molecular and host-related factors. Here we report the comprehensive clinicopathological and molecular analysis of a pure extra-gestational colorectal choriocarcinoma in a patient with probable Lynch syndrome.Case presentation: A 61 year old female with history of gastric cancer at age 36 presented with a transmurally invasive tumor of the right hemicolon and liver metastasis. A right hemicolectomy was performed. Histopathological analysis showed a mixed trophoblastic and syncytiotrophoblastic differentiation, consistent with choriocarcinoma. Disease progression was rapid under oxaliplatin, capecitabine, irinotecan (XELOXIRI and bevacizumab. Molecular phenotyping identified loss of the mismatch-repair (MMR protein PMS2, microsatellite instability, a lack of MLH1 promoter methylation and lack of of BRAF mutation suggestive of Lynch-Syndrome. Targeted next generation sequencing revealed an Ataxia Telangiectasia Mutated (ATM p.P604S missense mutation. A bleomycin, etoposide and cisplatin (BEP treatment protocol targeting germ-cell neoplasia lead to disease remission and prolonged survival of 34 months.Conclusions: Comprehensive immunohistochemical and genetic testing is essential to identify uncommon cancers possibly related to Lynch syndrome. For rare tumors, personalized therapeutic approaches should take both molecular and morphological information into account.Key words: Colorectal cancer, choriocarcinoma, histopathology, prognostic factors, Lynch syndrome, microsatellite instability, ataxia telangiectasia mutated, molecular pathology, next generation sequencing, personalized medicine

  7. In children with Friedreich ataxia, muscle and ataxia parameters are associated

    NARCIS (Netherlands)

    Sival, Deborah A.; Pouwels, Maria E.; van Brederode, Agnes; Maurits, Natasha M.; Verschuuren - Bemelmans, Corien C.; Brunt, Ewout R.; Sarvaas, Gideon J. Du Marchie; Verbeek, Renate J.; Brouwer, Oebele F.; van der Hoeven, Johannes H.

    Aim In children with Friedreich ataxia (FRDA), ataxia is assessed using the surrogate marker the International Cooperative Ataxia Rating Scale (ICARS). We aimed to determine whether ICARS scores in children with FRDA are confounded by muscle weakness. Method In 12 children with FRDA (10 males, two

  8. Elucidation on protection mechanism of living body from cellular obstacle due to radiation and its functional obstacle in a highly carcinogenic family

    International Nuclear Information System (INIS)

    Mizutani, Shuki; Asada, Minoru; Takagi, Masatoshi; Yamada, Takayuki

    1999-01-01

    Development of a serologic diagnostic method for patients with ataxia telangiectasia (AT) and its carriers who have abnormalities in AT gene was attempted in this study. The expression of ATM protein was examined in 18 cell lines derived from AT patients of homo-mutant, complex hetero-mutant and asymptomatic hetero mutant. The results showed that the expression of ATM protein was very little in these mutant lines; homo and complex hetero mutants and the rate of its expression in complex-hetero patients presenting with some AT insufficiencies was less than 40% at most. Therefore, diagnosis of AT patients would be possible in future using ATM antibody with some exceptions. In the previous year, the authors reported that lymphocytes derived from AT carriers had some cytological abnormalities, such as p53-phosphorylating activity, apoptosis, etc. However, the expression level of ATM protein in the carrier cells from 9 patients was nearly 60% at most. These results suggest that the use of anti-ATM antibody would allow detection of the carriers of ATM abnormalities and such carriers might include AT patients that can not be assigned into cytologically normal group. Furthermore, it was shown that the expression of ATM protein was decreased and cytological abnormalities were present in normal somatic cells from patients with T cell typed, acute lymphocytic leukemia. Thus, the ATM antibody is thought available for detection of AT carriers, who are difficult to be discriminated from its normally appearing patients. (M.N.)

  9. Screening for Ataxia-Telangiectasia Mutations in a Population-Based Sample of Women with Early-Onset Breast Cancer

    Science.gov (United States)

    1999-09-01

    and xeroderma pigmentosum in Britain. Cancer Res 1988;48:2929-32. 18 13. Stankovic T, Kidd AMJ, Sutcliffe A, McGuire GM, Robinson P, Weber P, et al...nested-PCR products of ATM nucleotide po - Nonsense and Missense Mutations with Indirect Effects sitions 500-1191 from cDNAs of AT113LA, AT140LA, and

  10. Abrogation of Wip1 expression by RITA-activated p53 potentiates apoptosis induction via activation of ATM and inhibition of HdmX

    Science.gov (United States)

    Spinnler, C; Hedström, E; Li, H; de Lange, J; Nikulenkov, F; Teunisse, A F A S; Verlaan-de Vries, M; Grinkevich, V; Jochemsen, A G; Selivanova, G

    2011-01-01

    Inactivation of the p53 tumour suppressor, either by mutation or by overexpression of its inhibitors Hdm2 and HdmX is the most frequent event in cancer. Reactivation of p53 by targeting Hdm2 and HdmX is therefore a promising strategy for therapy. However, Hdm2 inhibitors do not prevent inhibition of p53 by HdmX, which impedes p53-mediated apoptosis. Here, we show that p53 reactivation by the small molecule RITA leads to efficient HdmX degradation in tumour cell lines of different origin and in xenograft tumours in vivo. Notably, HdmX degradation occurs selectively in cancer cells, but not in non-transformed cells. We identified the inhibition of the wild-type p53-induced phosphatase 1 (Wip1) as the major mechanism important for full engagement of p53 activity accomplished by restoration of the ataxia telangiectasia mutated (ATM) kinase-signalling cascade, which leads to HdmX degradation. In contrast to previously reported transactivation of Wip1 by p53, we observed p53-dependent repression of Wip1 expression, which disrupts the negative feedback loop conferred by Wip1. Our study reveals that the depletion of both HdmX and Wip1 potentiates cell death due to sustained activation of p53. Thus, RITA is an example of a p53-reactivating drug that not only blocks Hdm2, but also inhibits two important negative regulators of p53 – HdmX and Wip1, leading to efficient elimination of tumour cells. PMID:21546907

  11. Abrogation of Wip1 expression by RITA-activated p53 potentiates apoptosis induction via activation of ATM and inhibition of HdmX.

    Science.gov (United States)

    Spinnler, C; Hedström, E; Li, H; de Lange, J; Nikulenkov, F; Teunisse, A F A S; Verlaan-de Vries, M; Grinkevich, V; Jochemsen, A G; Selivanova, G

    2011-11-01

    Inactivation of the p53 tumour suppressor, either by mutation or by overexpression of its inhibitors Hdm2 and HdmX is the most frequent event in cancer. Reactivation of p53 by targeting Hdm2 and HdmX is therefore a promising strategy for therapy. However, Hdm2 inhibitors do not prevent inhibition of p53 by HdmX, which impedes p53-mediated apoptosis. Here, we show that p53 reactivation by the small molecule RITA leads to efficient HdmX degradation in tumour cell lines of different origin and in xenograft tumours in vivo. Notably, HdmX degradation occurs selectively in cancer cells, but not in non-transformed cells. We identified the inhibition of the wild-type p53-induced phosphatase 1 (Wip1) as the major mechanism important for full engagement of p53 activity accomplished by restoration of the ataxia telangiectasia mutated (ATM) kinase-signalling cascade, which leads to HdmX degradation. In contrast to previously reported transactivation of Wip1 by p53, we observed p53-dependent repression of Wip1 expression, which disrupts the negative feedback loop conferred by Wip1. Our study reveals that the depletion of both HdmX and Wip1 potentiates cell death due to sustained activation of p53. Thus, RITA is an example of a p53-reactivating drug that not only blocks Hdm2, but also inhibits two important negative regulators of p53 - HdmX and Wip1, leading to efficient elimination of tumour cells.

  12. Wireless ATM : handover issues

    OpenAIRE

    Jiang, Fan; Käkölä, Timo

    1998-01-01

    Basic aspects of cellular systems and the ATM transmission technology are introduced. Wireless ATM is presented as a combination of radio ATM and mobile ATM. Radio ATM is a wireless extension of an ATM connection while mobile ATM contains the necessary extensions to ATM to support mobility. Because the current ATM technology does not support mobility, handover becomes one of the most important research issues for wireless ATM. Wireless ATM handover requirements are thus analysed. A handover s...

  13. Ataxia-Telangiectasia Children's Project

    Science.gov (United States)

    ... T CURE TEAM Walt Disney World® Marathon Weekend Star Wars™ Half Marathon - The Dark Side Pittsburgh Marathon Weekend Hess Lake Run Half Marathon Super Heroes Half Marathon Run Any Race What's New Exploring the Epidemiology of A-T in ...

  14. Fabrication and characterization of MCC [Materials Characterization Center] approved testing material---ATM-2, ATM-3, and ATM-4 glasses

    International Nuclear Information System (INIS)

    Wald, J.W.

    1988-03-01

    Materials Characterization Center glasses ATM-2, ATM-3, and ATM-4 are designed to simulate high-level waste glasses that are likely to result from the reprocessing of commercial nuclear reactor fuels. The three Approved Testing Materials (ATMs) are borosilicate glasses based upon the MCC-76-68 glass composition. One radioisotope was added to form each ATM. The radioisotopes added to form ATM-2, ATM-3, and ATM-4 were 241 Am, 237 Np, and 239 Pu, respectively. Each of the ATM lots was produced in a nominal lot size of 450 g from feed stock melted in a nitrogen-atmosphere glove box at 1200/degree/C in a platinum crucible. Each ATM was then cast into bars. Analyzed compositions of these glasses are listed. The nonradioactive elements were analyzed by inductively coupled argon plasma atomic emission spectroscopy (ICP), and the radioisotope analyses were done by alpha energy analysis. Results are discussed. 7 refs., 3 figs., 5 tabs

  15. The Heterochromatic Barrier to DNA Double Strand Break Repair: How to Get the Entry Visa

    Directory of Open Access Journals (Sweden)

    Aaron A. Goodarzi

    2012-09-01

    Full Text Available Over recent decades, a deep understanding of pathways that repair DNA double strand breaks (DSB has been gained from biochemical, structural, biophysical and cellular studies. DNA non-homologous end-joining (NHEJ and homologous recombination (HR represent the two major DSB repair pathways, and both processes are now well understood. Recent work has demonstrated that the chromatin environment at a DSB significantly impacts upon DSB repair and that, moreover, dramatic modifications arise in the chromatin surrounding a DSB. Chromatin is broadly divided into open, transcriptionally active, euchromatin (EC and highly compacted, transcriptionally inert, heterochromatin (HC, although these represent extremes of a spectrum. The HC superstructure restricts both DSB repair and damage response signaling. Moreover, DSBs within HC (HC-DSBs are rapidly relocalized to the EC-HC interface. The damage response protein kinase, ataxia telangiectasia mutated (ATM, is required for HC-DSB repair but is dispensable for the relocalization of HC-DSBs. It has been proposed that ATM signaling enhances HC relaxation in the DSB vicinity and that this is a prerequisite for HC-DSB repair. Hence, ATM is essential for repair of HC-DSBs. Here, we discuss how HC impacts upon the response to DSBs and how ATM overcomes the barrier that HC poses to repair.

  16. Very early disease manifestations of macular telangiectasia type 2

    NARCIS (Netherlands)

    Issa, P.C.; Heeren, T.F.C.; Kupitz, E.H.; Holz, F.G.; Berendschot, T.T.J.M.

    Background: To report very early morphologic and functional alterations in patients with macular telangiectasia type 2. Methods: Patients with asymmetric disease manifestations, in whom retinal alterations characteristic for macular telangiectasia type 2 were present in one but not in the apparently

  17. ATM-deficient human fibroblast cells are resistant to low levels of DNA double-strand break induced apoptosis and subsequently undergo drug-induced premature senescence

    International Nuclear Information System (INIS)

    Park, Jun; Jo, Yong Hwa; Cho, Chang Hoon; Choe, Wonchae; Kang, Insug; Baik, Hyung Hwan; Yoon, Kyung-Sik

    2013-01-01

    Highlights: ► A-T cells were not hypersensitive to low levels of DNA DSBs. ► A-T cells have enhanced Akt but defect in activation of p53 and apoptotic proteins. ► A-T cells underwent premature senescence after DNA damage accumulated. ► Chemotherapeutic effect in cancer therapy may be associated with premature senescence. -- Abstract: DNA DSBs are induced by IR or radiomimetic drugs such as doxorubicin. It has been indicated that cells from ataxia-telangiectasia patients are highly sensitive to radiation due to defects in DNA repair, but whether they have impairment in apoptosis has not been fully elucidated. A-T cells showed increased sensitivity to high levels of DNA damage, however, they were more resistant to low doses. Normal cells treated with combination of KU55933, a specific ATM kinase inhibitor, and doxorubicin showed increased resistance as they do in a similar manner to A-T cells. A-T cells have higher viability but more DNA breaks, in addition, the activations of p53 and apoptotic proteins (Bax and caspase-3) were deficient, but Akt expression was enhanced. A-T cells subsequently underwent premature senescence after treatment with a low dose of doxorubicin, which was confirmed by G2 accumulation, senescent morphology, and SA-β-gal positive until 15 days repair incubation. Finally, A-T cells are radio-resistant at low doses due to its defectiveness in detecting DNA damage and apoptosis, but the accumulation of DNA damage leads cells to premature senescence.

  18. A product of the bicistronic Drosophila melanogaster gene CG31241, which also encodes a trimethylguanosine synthase, plays a role in telomere protection.

    Science.gov (United States)

    Komonyi, Orban; Schauer, Tamas; Papai, Gabor; Deak, Peter; Boros, Imre M

    2009-03-15

    Although telomere formation occurs through a different mechanism in Drosophila compared with other organisms, telomere associations result from mutations in homologous genes, indicating the involvement of similar pathways in chromosome end protection. We report here that mutations of the Drosophila melanogaster gene CG31241 lead to high frequency chromosome end fusions. CG31241 is a bicistronic gene that encodes trimethylguanosine synthase (TGS1), which forms the m3G caps of noncoding small RNAs, and a novel protein, DTL. We show that although TGS1 has no role in telomere protection, DTL is localized at specific sites, including the ends of polytene chromosomes, and its loss results in telomere associations. Mutations of ATM- and Rad3-related (ATR) kinase suppress telomere fusions in the absence of DTL. Thus, genetic interactions place DTL in an ATR-related pathway in telomere protection. In contrast to ATR kinase, mutations of ATM (ataxia telangiectasia mutated) kinase, which acts in a partially overlapping pathway of telomere protection, do not suppress formation of telomere associations in the absence of DTL. Thus, uncovering the role of DTL will help to dissect the evolutionary conserved pathway(s) controlling ATM-ATR-related telomere protection.

  19. miR-30a can inhibit DNA replication by targeting RPA1 thus slowing cancer cell proliferation.

    Science.gov (United States)

    Zou, Zhenyou; Ni, Mengjie; Zhang, Jing; Chen, Yongfeng; Ma, Hongyu; Qian, Shihan; Tang, Longhua; Tang, Jiamei; Yao, Hailun; Zhao, Chengbin; Lu, Xiongwen; Sun, Hongyang; Qian, Jue; Mao, Xiaoting; Lu, Xulin; Liu, Qun; Zen, Juping; Wu, Hanbing; Bao, Zhaosheng; Lin, Shudan; Sheng, Hongyu; Li, Yunlong; Liang, Yong; Chen, Zhiqiang; Zong, Dan

    2016-07-15

    Cell proliferation was inhibited following forced over-expression of miR-30a in the ovary cancer cell line A2780DX5 and the gastric cancer cell line SGC7901R. Interestingly, miR-30a targets the DNA replication protein RPA1, hinders the replication of DNA and induces DNA fragmentation. Furthermore, ataxia telangiectasia mutated (ATM) and checkpoint kinase 2 (CHK2) were phosphorylated after DNA damage, which induced p53 expression, thus triggering the S-phase checkpoint, arresting cell cycle progression and ultimately initiating cancer cell apoptosis. Therefore, forced miR-30a over-expression in cancer cells can be a potential way to inhibit tumour development. © 2016 The Author(s). published by Portland Press Limited on behalf of the Biochemical Society.

  20. Middle infrared radiation induces G2/M cell cycle arrest in A549 lung cancer cells.

    Science.gov (United States)

    Chang, Hsin-Yi; Shih, Meng-Her; Huang, Hsuan-Cheng; Tsai, Shang-Ru; Juan, Hsueh-Fen; Lee, Si-Chen

    2013-01-01

    There were studies investigating the effects of broadband infrared radiation (IR) on cancer cell, while the influences of middle-infrared radiation (MIR) are still unknown. In this study, a MIR emitter with emission wavelength band in the 3-5 µm region was developed to irradiate A549 lung adenocarcinoma cells. It was found that MIR exposure inhibited cell proliferation and induced morphological changes by altering the cellular distribution of cytoskeletal components. Using quantitative PCR, we found that MIR promoted the expression levels of ATM (ataxia telangiectasia mutated), ATR (ataxia-telangiectasia and Rad3-related and Rad3-related), TP53 (tumor protein p53), p21 (CDKN1A, cyclin-dependent kinase inhibitor 1A) and GADD45 (growth arrest and DNA-damage inducible), but decreased the expression levels of cyclin B coding genes, CCNB1 and CCNB2, as well as CDK1 (Cyclin-dependent kinase 1). The reduction of protein expression levels of CDC25C, cyclin B1 and the phosphorylation of CDK1 at Thr-161 altogether suggest G(2)/M arrest occurred in A549 cells by MIR. DNA repair foci formation of DNA double-strand breaks (DSB) marker γ-H2AX and sensor 53BP1 was induced by MIR treatment, it implies the MIR induced G(2)/M cell cycle arrest resulted from DSB. This study illustrates a potential role for the use of MIR in lung cancer therapy by initiating DSB and blocking cell cycle progression.

  1. Frequency of the ATM IVS10-6T→G variant in Australian multiple-case breast cancer families

    International Nuclear Information System (INIS)

    Lindeman, Geoffrey J; Suthers, Graeme; Kirk, Judy; Hiew, Melody; Visvader, Jane E; Leary, Jennifer; Field, Michael; Gaff, Clara L; Gardner, RJ McKinlay; Trainor, Kevin; Cheetham, Glenice

    2004-01-01

    Germline mutations in the genes BRCA1 and BRCA2 account for only a proportion of hereditary breast cancer, suggesting that additional genes contribute to hereditary breast cancer. Recently a heterozygous variant in the ataxia–telangiectasia mutated (ATM) gene, IVS10-6T→G, was reported by an Australian multiple-case breast cancer family cohort study (the Kathleen Cuningham Foundation Consortium for Research into Familial Breast Cancer) to confer a substantial breast cancer risk. Although this variant can result in a truncated ATM product, its clinical significance as a high-penetrance breast cancer allele or its role as a low-penetrance risk-modifier is controversial. We determined the frequency of ATM IVS10-6T→G variants in a cohort of individuals affected by breast and/or ovarian cancer who underwent BRCA1 and BRCA2 genetic testing at four major Australian familial cancer clinics. Seven of 495 patients (1.4%) were heterozygous for the IVS10-6T→G variant; the carrier rate in unselected Australian women with no family history of breast cancer is reported to be 6 of 725 (0.83%) (P = 0.4). Two of the seven probands also harboured a pathogenic BRCA1 mutation and one patient had a BRCA1 unclassified variant of uncertain significance. These findings indicate that the ATM IVS10-6T→G variant does not seem to occur at a significantly higher frequency in affected individuals from high-risk families than in the general population. A role for this variant as a low-penetrance allele or as a modifying gene in association with other genes (such as BRCA1) remains possible. Routine testing for ATM IVS10-6T→G is not warranted in mutation screening of affected individuals from high-risk families

  2. A Case of Ataxia with Isolated Vitamin E Deficiency Initially Diagnosed as Friedreich’s Ataxia

    Directory of Open Access Journals (Sweden)

    Michael Bonello

    2016-01-01

    Full Text Available Ataxia with isolated vitamin E deficiency (AVED is a rare autosomal recessive condition that is caused by a mutation in the alpha tocopherol transfer protein gene. It is almost indistinguishable clinically from Friedreich’s ataxia but with appropriate treatment its devastating neurological features can be prevented. Patients can present with a progressive cerebellar ataxia, pyramidal spasticity, and evidence of a neuropathy with absent deep tendon reflexes. It is important to screen for this condition on initial evaluation of a young patient presenting with progressive ataxia and it should be considered in patients with a long standing ataxia without any diagnosis in view of the potential therapeutics and genetic counselling. In this case report we present a patient who was initially diagnosed with Friedreich’s ataxia but was later found to have AVED.

  3. Clinical neurogenetics: friedreich ataxia.

    Science.gov (United States)

    Collins, Abigail

    2013-11-01

    Friedreich ataxia is the most common autosomal recessive ataxia. It is a progressive neurodegenerative disorder, typically with onset before 20 years of age. Signs and symptoms include progressive ataxia, ascending weakness and ascending loss of vibration and joint position senses, pes cavus, scoliosis, cardiomyopathy, and arrhythmias. There are no disease-modifying medications to either slow or halt the progression of the disease, but research investigating therapies to increase endogenous frataxin production and decrease the downstream consequences of disrupted iron homeostasis is ongoing. Clinical trials of promising medications are underway, and the treatment era of Friedreich ataxia is beginning. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. Linking loss of sodium-iodide symporter expression to DNA damage

    Energy Technology Data Exchange (ETDEWEB)

    Lyckesvärd, Madeleine Nordén [Sahlgrenska Cancer Center, University of Gothenburg, Göteborg (Sweden); Department of Medical Chemistry and Cell Biology, University of Gothenburg, Göteborg (Sweden); Kapoor, Nirmal [Department of Medical Chemistry and Cell Biology, University of Gothenburg, Göteborg (Sweden); Ingeson-Carlsson, Camilla; Carlsson, Therese [Sahlgrenska Cancer Center, University of Gothenburg, Göteborg (Sweden); Department of Medical Chemistry and Cell Biology, University of Gothenburg, Göteborg (Sweden); Karlsson, Jan-Olof [Department of Medical Chemistry and Cell Biology, University of Gothenburg, Göteborg (Sweden); Postgård, Per; Himmelman, Jakob; Forssell-Aronsson, Eva [Department of Radiation Physics, University of Gothenburg, Göteborg (Sweden); Hammarsten, Ola [Department of Clinical Chemistry, University of Gothenburg, Göteborg (Sweden); Nilsson, Mikael, E-mail: mikael.nilsson@gu.se [Sahlgrenska Cancer Center, University of Gothenburg, Göteborg (Sweden); Department of Medical Chemistry and Cell Biology, University of Gothenburg, Göteborg (Sweden)

    2016-05-15

    Radiotherapy of thyroid cancer with I-131 is abrogated by inherent loss of radioiodine uptake due to loss of sodium iodide symporter (NIS) expression in poorly differentiated tumor cells. It is also known that ionizing radiation per se down-regulates NIS (the stunning effect), but the mechanism is unknown. Here we investigated whether loss of NIS-mediated iodide transport may be elicited by DNA damage. Calicheamicin, a fungal toxin that specifically cleaves double-stranded DNA, induced a full scale DNA damage response mediated by the ataxia-telangiectasia mutated (ATM) kinase in quiescent normal thyrocytes. At sublethal concentrations (<1 nM) calicheamicin blocked NIS mRNA expression and transepithelial iodide transport as stimulated by thyrotropin; loss of function occurred at a much faster rate than after I-131 irradiation. KU-55933, a selective ATM kinase inhibitor, partly rescued NIS expression and iodide transport in DNA-damaged cells. Prolonged ATM inhibition in healthy cells also repressed NIS-mediated iodide transport. ATM-dependent loss of iodide transport was counteracted by IGF-1. Together, these findings indicate that NIS, the major iodide transporter of the thyroid gland, is susceptible to DNA damage involving ATM-mediated mechanisms. This uncovers novel means of poor radioiodine uptake in thyroid cells subjected to extrinsic or intrinsic genotoxic stress. - Highlights: • DNA damage inhibits polarized iodide transport in normal thyroid cells. • Down-regulation of NIS expression is mediated by activation of the ATM kinase. • Long-term ATM inhibition also represses NIS-mediated iodide transport. • IGF-1 rescues NIS expression and iodide transport in DNA-damaged cells.

  5. Linking loss of sodium-iodide symporter expression to DNA damage

    International Nuclear Information System (INIS)

    Lyckesvärd, Madeleine Nordén; Kapoor, Nirmal; Ingeson-Carlsson, Camilla; Carlsson, Therese; Karlsson, Jan-Olof; Postgård, Per; Himmelman, Jakob; Forssell-Aronsson, Eva; Hammarsten, Ola; Nilsson, Mikael

    2016-01-01

    Radiotherapy of thyroid cancer with I-131 is abrogated by inherent loss of radioiodine uptake due to loss of sodium iodide symporter (NIS) expression in poorly differentiated tumor cells. It is also known that ionizing radiation per se down-regulates NIS (the stunning effect), but the mechanism is unknown. Here we investigated whether loss of NIS-mediated iodide transport may be elicited by DNA damage. Calicheamicin, a fungal toxin that specifically cleaves double-stranded DNA, induced a full scale DNA damage response mediated by the ataxia-telangiectasia mutated (ATM) kinase in quiescent normal thyrocytes. At sublethal concentrations (<1 nM) calicheamicin blocked NIS mRNA expression and transepithelial iodide transport as stimulated by thyrotropin; loss of function occurred at a much faster rate than after I-131 irradiation. KU-55933, a selective ATM kinase inhibitor, partly rescued NIS expression and iodide transport in DNA-damaged cells. Prolonged ATM inhibition in healthy cells also repressed NIS-mediated iodide transport. ATM-dependent loss of iodide transport was counteracted by IGF-1. Together, these findings indicate that NIS, the major iodide transporter of the thyroid gland, is susceptible to DNA damage involving ATM-mediated mechanisms. This uncovers novel means of poor radioiodine uptake in thyroid cells subjected to extrinsic or intrinsic genotoxic stress. - Highlights: • DNA damage inhibits polarized iodide transport in normal thyroid cells. • Down-regulation of NIS expression is mediated by activation of the ATM kinase. • Long-term ATM inhibition also represses NIS-mediated iodide transport. • IGF-1 rescues NIS expression and iodide transport in DNA-damaged cells.

  6. Video game-based coordinative training improves ataxia in children with degenerative ataxia.

    Science.gov (United States)

    Ilg, Winfried; Schatton, Cornelia; Schicks, Julia; Giese, Martin A; Schöls, Ludger; Synofzik, Matthis

    2012-11-13

    Degenerative ataxias in children present a rare condition where effective treatments are lacking. Intensive coordinative training based on physiotherapeutic exercises improves degenerative ataxia in adults, but such exercises have drawbacks for children, often including a lack of motivation for high-frequent physiotherapy. Recently developed whole-body controlled video game technology might present a novel treatment strategy for highly interactive and motivational coordinative training for children with degenerative ataxias. We examined the effectiveness of an 8-week coordinative training for 10 children with progressive spinocerebellar ataxia. Training was based on 3 Microsoft Xbox Kinect video games particularly suitable to exercise whole-body coordination and dynamic balance. Training was started with a laboratory-based 2-week training phase and followed by 6 weeks training in children's home environment. Rater-blinded assessments were performed 2 weeks before laboratory-based training, immediately prior to and after the laboratory-based training period, as well as after home training. These assessments allowed for an intraindividual control design, where performance changes with and without training were compared. Ataxia symptoms were significantly reduced (decrease in Scale for the Assessment and Rating of Ataxia score, p = 0.0078) and balance capacities improved (dynamic gait index, p = 0.04) after intervention. Quantitative movement analysis revealed improvements in gait (lateral sway: p = 0.01; step length variability: p = 0.01) and in goal-directed leg placement (p = 0.03). Despite progressive cerebellar degeneration, children are able to improve motor performance by intensive coordination training. Directed training of whole-body controlled video games might present a highly motivational, cost-efficient, and home-based rehabilitation strategy to train dynamic balance and interaction with dynamic environments in a large variety of young-onset neurologic

  7. Diagnostic criteria for hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber syndrome)

    DEFF Research Database (Denmark)

    Shovlin, C L; Guttmacher, A E; Buscarini, E

    2000-01-01

    Hereditary Hemorrhagic Telangiectasia (HHT) is easily recognized in individuals displaying the classical triad of epistaxis, telangiectasia, and a suitable family history, but the disease is more difficult to diagnosis in many patients. Serious consequences may result if visceral arteriovenous ma...... in this disorder. These criteria may be refined as molecular diagnostic tests become available in the next few years....... of the HHT Foundation International, Inc., we present consensus clinical diagnostic criteria. The four criteria (epistaxes, telangiectasia, visceral lesions and an appropriate family history) are carefully delineated. The HHT diagnosis is definite if three criteria are present. A diagnosis of HHT cannot...

  8. Spinocerebellar ataxias Ataxias espinocerebelares

    Directory of Open Access Journals (Sweden)

    Hélio A.G. Teive

    2009-12-01

    Full Text Available Spinocerebellar ataxias (SCAs constitute a heterogeneous group of neurodegenerative diseases characterized by progressive cerebellar ataxia in association with some or all of the following conditions: ophthalmoplegia, pyramidal signs, movement disorders, pigmentary retinopathy, peripheral neuropathy, cognitive dysfunction and dementia. OBJECTIVE: To carry out a clinical and genetic review of the main types of SCA. METHOD: The review was based on a search of the PUBMED and OMIM databases. RESULTS: Thirty types of SCAs are currently known, and 16 genes associated with the disease have been identified. The most common types are SCA type 3, or Machado-Joseph disease, SCA type 10 and SCA types 7, 2, 1 and 6. SCAs are genotypically and phenotypically very heterogeneous. A clinical algorithm can be used to distinguish between the different types of SCAs. CONCLUSIONS: Detailed clinical neurological examination of SCA patients can be of great help when assessing them, and the information thus gained can be used in an algorithm to screen patients before molecular tests to investigate the correct etiology of the disease are requested.As ataxias espinocerebelares (AECs compreendem um grupo heterogeneo de enfermidades neurodegenerativas, que se caracterizam pela presença de ataxia cerebelar progressiva, associada de forma variada com oftalmoplegia, sinais piramidais, distúrbios do movimento, retinopatia pigmentar, neuropatia periférica, disfunção cognitiva e demência. OBJETIVO: Realizar uma revisão clínico-genética dos principais tipos de AECs. MÉTODO: A revisão foi realizada através da pesquisa pelo sistema do PUBMED e do OMIM. RESULTADOS: Na atualidade existem cerca de 30 tipos de AECs, com a descoberta de 16 genes. Os tipos mais comuns são a AEC tipo 3, ou doença de Machado-Joseph, a AEC tipo 10, e as AECs tipo 7, 2 1, e 6. As AECs apresentam grande heterogeneidade genotípica e fenotípica. Pode-se utilizar um algoritmo clínico para a

  9. DNA-PK. The major target for wortmannin-mediated radiosensitization by the inhibition of DSB repair via NHEJ pathway

    International Nuclear Information System (INIS)

    Hashimoto, Mitsumasa; Rao, S.; Tokuno, Osamu; Utsumi, Hiroshi; Takeda, Shunichi

    2003-01-01

    The effect of wortmannin posttreatment was studied in cells derived from different species (hamster, mouse, chicken, and human) with normal and defective DNA-dependent protein kinase (DNA-PK) activity, cells with and without the ataxia telangiectasia mutated (ATM) gene, and cells lacking other regulatory proteins involved in the DNA double-strand break (DSB) repair pathways. Clonogenic assays were used to obtain all results. Wortmannin radiosensitization was observed in Chinese hamster cells (V79-B310H, CHO-K1), mouse mammary carcinoma cells (SR-1), transformed human fibroblast (N2KYSV), chicken B lymphocyte wild-type cells (DT40), and chicken Rad54 knockout cells (Rad54 -/- ). However, mouse mammary carcinoma cells (SX9) with defects in the DNA-PK and chicken DNA-PK catalytic subunit (DNA-PKcs) knockout cells (DNA-PKcs -/-/- ) failed to exhibit wortmannin radiosensitization. On the other hand, severe combined immunodeficiency (SCID) mouse cells (SC3VA2) exposed to wortmannin exhibited significant increases in radiosensitivity, possibly because of some residual function of DNA-PKcs. Moreover, the transformed human cells derived from AT patients (AT2KYSV) and chicken ATM knockout cells (ATM -/- ) showed pronounced wortmannin radiosensitization. These studies demonstrate confirm that the mechanism underlying wortmannin radiosensitization is the inhibition of DNA-PK, but not of ATM, thereby resulting in the inhibition of DSB repair via nonhomologous endjoining (NHEJ). (author)

  10. ATM and Internet protocol

    CERN Document Server

    Bentall, M; Turton, B

    1998-01-01

    Asynchronous Transfer Mode (ATM) is a protocol that allows data, sound and video being transferred between independent networks via ISDN links to be supplied to, and interpreted by, the various system protocols.ATM and Internet Protocol explains the working of the ATM and B-ISDN network for readers with a basic understanding of telecommunications. It provides a handy reference to everyone working with ATM who may not require the full standards in detail, but need a comprehensive guide to ATM. A substantial section is devoted to the problems of running IP over ATM and there is some discussion o

  11. Adult onset sporadic ataxias: a diagnostic challenge

    Directory of Open Access Journals (Sweden)

    Orlando Graziani Povoas Barsottini

    2014-03-01

    Full Text Available Patients with adult onset non-familial progressive ataxia are classified in sporadic ataxia group. There are several disease categories that may manifest with sporadic ataxia: toxic causes, immune-mediated ataxias, vitamin deficiency, infectious diseases, degenerative disorders and even genetic conditions. Considering heterogeneity in the clinical spectrum of sporadic ataxias, the correct diagnosis remains a clinical challenge. In this review, the different disease categories that lead to sporadic ataxia with adult onset are discussed with special emphasis on their clinical and neuroimaging features, and diagnostic criteria.

  12. Sleep disorders in cerebellar ataxias

    Directory of Open Access Journals (Sweden)

    José L. Pedroso

    2011-04-01

    Full Text Available Cerebellar ataxias comprise a wide range of etiologies leading to central nervous system-related motor and non-motor symptoms. Recently, a large body of evidence has demonstrated a high frequency of non-motor manifestations in cerebellar ataxias, specially in autosomal dominant spinocerebellar ataxias (SCA. Among these non-motor dysfunctions, sleep disorders have been recognized, although still under or even misdiagnosed. In this review, we highlight the main sleep disorders related to cerebellar ataxias focusing on REM sleep behavior disorder (RBD, restless legs syndrome (RLS, periodic limb movement in sleep (PLMS, excessive daytime sleepiness (EDS, insomnia and sleep apnea.

  13. Spinocerebellar ataxia 36 (SCA36): «Costa da Morte ataxia».

    Science.gov (United States)

    Arias, M; García-Murias, M; Sobrido, M J

    To describe the history of the discovery of SCA36 and review knowledge of this entity, which is currently the most prevalent hereditary ataxia in Galicia (Spain) owing to a founder effect. SCA36 is an autosomal dominant hereditary ataxia with late onset and slow progression. It presents with cerebellar ataxia, sensorineural hearing loss, and discrete motor neuron impairment (tongue atrophy with denervation, discrete pyramidal signs). SCA36 was first described in Japan (Asida River ataxia) and in Galicia(Costa da Morte ataxia). The condition is caused by a genetic mutation (intronic hexanucleotide repeat expansion) in the NOP56 gene on the short arm of chromosome 20 (20p13). Magnetic resonance image study initially shows cerebellar vermian atrophy that subsequently extends to the rest of the cerebellum and finally to the pontomedullary region of the brainstem without producing white matter lesions. Peripheral nerve conduction velocities are normal, and sensorimotor evoked potential studies show delayed conduction of stimuli to lower limbs. In patients with hearing loss, audiometric studies show a drop of >40dB in frequencies exceeding 2,500Hz. Auditory evoked potential studies may also show lack of waves I and II. Costa da Morte ataxia or SCA36 is the most prevalent SCA in the Spanish region of Galicia. Given the region's history of high rates of emigration, new cases may be diagnosed in numerous countries, especially in Latin America. Genetic studies are now available to patients and asymptomatic carriers. Since many people are at risk for this disease, we will continue our investigations aimed at elucidating the underlying pathogenic molecular mechanisms and discovering effective treatment. Copyright © 2014 Sociedad Española de Neurología. Publicado por Elsevier España, S.L.U. All rights reserved.

  14. From mild ataxia to huntington disease phenocopy: the multiple faces of spinocerebellar ataxia 17.

    Science.gov (United States)

    Koutsis, Georgios; Panas, Marios; Paraskevas, George P; Bougea, Anastasia M; Kladi, Athina; Karadima, Georgia; Kapaki, Elisabeth

    2014-01-01

    Introduction. Spinocerebellar ataxia 17 (SCA 17) is a rare autosomal dominant cerebellar ataxia (ADCA) caused by a CAG/CAA expansion in the TBP gene, reported from a limited number of countries. It is a very heterogeneous ADCA characterized by ataxia, cognitive decline, psychiatric symptoms, and involuntary movements, with some patients presenting with Huntington disease (HD) phenocopies. The SCA 17 expansion is stable during parent-child transmission and intrafamilial phenotypic homogeneity has been reported. However, significant phenotypic variability within families has also been observed. Report of the Family. We presently report a Greek family with a pathological expansion of 54 repeats at the SCA 17 locus that displayed remarkable phenotypic variability. Among 3 affected members, one presented with HD phenocopy; one with progressive ataxia, dementia, chorea, dystonia, and seizures, and one with mild slowly progressive ataxia with minor cognitive and affective symptoms. Conclusions. This is the first family with SCA 17 identified in Greece and highlights the multiple faces of this rare disorder, even within the same family.

  15. Recurrent Ataxia in Children and Adolescents.

    Science.gov (United States)

    Salman, Michael S; Klassen, Samantha F; Johnston, Janine L

    2017-07-01

    Recurrent ataxia is encountered infrequently in clinical pediatric neurology practise and presents with diagnostic challenges. It is caused by several disorders. Our aims were to describe the epidemiology and clinical features in children with recurrent ataxia. A retrospective review was undertaken in 185 children with chronic ataxia, who presented during 1991 to 2008. Several databases were searched to ensure optimum ascertainment. Patients with brain tumors or isolated disorders of the peripheral nerves or vestibular system were excluded. Recurrent ataxia was reported in 21 patients. Their age range was between 6 and 32.75 years (males=12). The crude period prevalence rate for the 18-year study period was 7.44/100,000. Eight patients had episodic ataxia and seven had inflammatory and metabolic disorders. In the rest the etiology was unknown. Many patients presented with ataxia, dizziness, and vertigo. The frequency and duration of the ataxic episodes varied from several per day to one every few months. Other clinical features included developmental delay and seizures. Neuroimaging in episodic ataxia was normal and abnormal in inflammatory or metabolic disorders. Acetazolamide provided symptomatic relief in patients with episodic ataxia, while steroids were beneficial in patients with an inflammatory etiology. One child with a metabolic disorder died. Recurrent ataxia is an uncommon presentation in children and mortality is rare. Genetic, metabolic, and inflammatory disorders should be considered in these patients. Neuroimaging is essential. Acetazolamide in selected patients provides good symptomatic relief.

  16. Targeting p38 Mitogen-Activated Protein Kinase Signaling Restores Subventricular Zone Neural Stem Cells and Corrects Neuromotor Deficits in Atm Knockout Mouse

    Science.gov (United States)

    Kim, Jeesun

    2012-01-01

    Ataxia-telangiectasia (A-T) is a progressive degenerative disorder that results in major neurological disability. In A-T patients, necropsy has revealed atrophy of cerebellar cortical layers along with Purkinje and granular cell loss. We have previously identified an oxidative stress-mediated increase in phospho-p38 mitogen-activated protein kinase (MAPK) and the resultant downregulation of Bmi-1 and upregulation of p21 as key components of the mechanism causing defective proliferation of neural stem cells (NSCs) isolated from the subventricular zone (SVZ) of Atm−/− mice. However, the in vivo aspect of alteration in SVZ tissue and the functional significance of p38MAPK activation in NSCs for neuropathogenesis of ATM deficiency remain unknown. Here we show that the NSC population was abnormally decreased in the SVZ of 3-month-old Atm−/− mice; this decrease was accompanied by p38MAPK activation. However, after a 2-month treatment with the p38MAPK inhibitor SB203580, starting at 1 month old, Atm−/− mice showed restoration of normal levels of Bmi-1 and p21 with the rescue of NSC population in the SVZ. In addition, treated Atm−/− mice exhibited more Purkinje cells in the cerebellum. Most importantly, motor coordination of Atm−/− mice was significantly improved in the treatment group. Our results show for the first time in vivo evidence of depleted NSCs in the SVZ of Atm−/− mice and also demonstrate that pharmacologic inhibition of p38MAPK signaling has the potential to treat neurological defects of A-T. This study provides a promising approach targeting the oxidative stress-dependent p38 signaling pathway not only for A-T but also for other neurodegenerative disorders. PMID:23197859

  17. From Mild Ataxia to Huntington Disease Phenocopy: The Multiple Faces of Spinocerebellar Ataxia 17

    Directory of Open Access Journals (Sweden)

    Georgios Koutsis

    2014-01-01

    Full Text Available Introduction. Spinocerebellar ataxia 17 (SCA 17 is a rare autosomal dominant cerebellar ataxia (ADCA caused by a CAG/CAA expansion in the TBP gene, reported from a limited number of countries. It is a very heterogeneous ADCA characterized by ataxia, cognitive decline, psychiatric symptoms, and involuntary movements, with some patients presenting with Huntington disease (HD phenocopies. The SCA 17 expansion is stable during parent-child transmission and intrafamilial phenotypic homogeneity has been reported. However, significant phenotypic variability within families has also been observed. Report of the Family. We presently report a Greek family with a pathological expansion of 54 repeats at the SCA 17 locus that displayed remarkable phenotypic variability. Among 3 affected members, one presented with HD phenocopy; one with progressive ataxia, dementia, chorea, dystonia, and seizures, and one with mild slowly progressive ataxia with minor cognitive and affective symptoms. Conclusions. This is the first family with SCA 17 identified in Greece and highlights the multiple faces of this rare disorder, even within the same family.

  18. Frontal ataxia in childhood.

    NARCIS (Netherlands)

    Erasmus, C.E.; Beems, T.; Rotteveel, J.J.

    2004-01-01

    Frontal ataxia may be the result of a unilateral frontal lesion. In this report three cases are presented with ataxia due to right frontal lesions. One case concerns a boy presenting with an unsteady gait and titubation of the trunk, mimicking developmental disequilibrium and with complex partial

  19. DNA synthesis in ataxia telangiectasia

    NARCIS (Netherlands)

    N.G.J. Jaspers (Nicolaas)

    1985-01-01

    textabstractAfter the discovery that cultured cells from AT patients are hypersensitive to ionizing radiation the suggestion was made that AT-could be the 1 X-ray-analogue 1 of xeroderma pigmentosum. The latter syndrome (XP) is characterized by hypersensitivity to short-wave UV-radiation, caused by

  20. DNA synthesis in ataxia telangiectasia

    OpenAIRE

    Jaspers, Nicolaas

    1985-01-01

    textabstractAfter the discovery that cultured cells from AT patients are hypersensitive to ionizing radiation the suggestion was made that AT-could be the 1 X-ray-analogue 1 of xeroderma pigmentosum. The latter syndrome (XP) is characterized by hypersensitivity to short-wave UV-radiation, caused by a reduced ability to properly remove UV-induced DNA damage. The evidence for a DNA repair defect in AT cells is not as strong as in the case of XP (see section 2.2.5 of this thesis). Different XP p...

  1. Speech in spinocerebellar ataxia.

    Science.gov (United States)

    Schalling, Ellika; Hartelius, Lena

    2013-12-01

    Spinocerebellar ataxias (SCAs) are a heterogeneous group of autosomal dominant cerebellar ataxias clinically characterized by progressive ataxia, dysarthria and a range of other concomitant neurological symptoms. Only a few studies include detailed characterization of speech symptoms in SCA. Speech symptoms in SCA resemble ataxic dysarthria but symptoms related to phonation may be more prominent. One study to date has shown an association between differences in speech and voice symptoms related to genotype. More studies of speech and voice phenotypes are motivated, to possibly aid in clinical diagnosis. In addition, instrumental speech analysis has been demonstrated to be a reliable measure that may be used to monitor disease progression or therapy outcomes in possible future pharmacological treatments. Intervention by speech and language pathologists should go beyond assessment. Clinical guidelines for management of speech, communication and swallowing need to be developed for individuals with progressive cerebellar ataxia. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Autosomal dominant hereditary ataxia in Sri Lanka

    OpenAIRE

    Sumathipala, Dulika S; Abeysekera, Gayan S; Jayasekara, Rohan W; Tallaksen, Chantal ME; Dissanayake, Vajira HW

    2013-01-01

    Background Spinocerebellar ataxias (SCA) are a group of hereditary neurodegenerative disorders. Prevalence of SCA subtypes differ worldwide. Autosomal dominant ataxias are the commonest types of inherited ataxias seen in Sri Lanka. The aim of the study is to determine the genetic etiology of patients with autosomal dominant ataxia in Sri Lanka and to describe the clinical features of each genetic subtype. Methods ...

  3. Diode laser for the treatment of telangiectasias following hemangioma involution.

    Science.gov (United States)

    Cerrati, Eric W; O, Teresa M; Chung, Hoyun; Waner, Milton

    2015-02-01

    Infantile hemangiomas are well known for their rapid growth during the first 6 to 9 months of life, followed by a spontaneous but slow involution. The standard of care is to treat these lesions at an early age with propranolol to expedite the involution process; however, surgery still remains an active component in the management. Medical treatment with propranolol or natural involution will often result in residual telangiectasias. We evaluated the efficacy of using a diode laser as a treatment for telangiectasias following cervicofacial infantile hemangioma involution. Case series with chart review. Tertiary care hospital and practice specializing in the care of vascular anomalies. Twenty patients, aged 4 months to 11 years (average 2.69 years), underwent treatment with a 532-nm diode laser to treat the residual telangiectasias following hemangioma involution. All procedures were performed in the operating room. To assess the efficacy, we independently evaluated pre- and posttreatment digital photographs and ranked them on a 0- to 4-point scale (0 = no change and 4 = complete response). Adverse reactions were also recorded. The telangiectasias showed considerable improvement following treatment. In more than half of the patients treated, the affected area demonstrated a complete response. No adverse reactions were noted. A 532-nm diode laser effectively treats the remaining telangiectasias following hemangioma involution. Whether used independently or in conjunction with other treatment modalities, the diode laser should be part of the surgical armamentarium when treating infantile hemangiomas. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2014.

  4. Friedreich's ataxia and other hereditary ataxias in Greece: an 18-year perspective.

    Science.gov (United States)

    Koutsis, Georgios; Kladi, Athina; Karadima, Georgia; Houlden, Henry; Wood, Nicholas W; Christodoulou, Kyproula; Panas, Marios

    2014-01-15

    Limited data exist on the spectrum of heredoataxias in Greece, including the prevalence and phenotype of Friedreich's ataxia (FRDA) and the prevalence and subtypes of dominant spinocerebellar ataxias (SCAs). We analyzed clinically and investigated genetically for FRDA and triplet-repeat expansion SCAs a consecutive series of 186 patients with suspected heredoataxia referred to Athens over 18 years. For prevalence estimates we included patients with molecular diagnosis from Cyprus that were absent from the Athens cohort. The minimum prevalence of FRDA was ~0.9/100,000, with clusters of high prevalence in Aegean islands. FRDA was diagnosed in 73 probands. The genotypic and phenotypic spectrum of FRDA was similar to other populations, with one patient compound heterozygote for a known point mutation in FXN (Asn146Lys). Undiagnosed recessive ataxias included FRDA-like and spastic ataxias. The minimum prevalence of dominant SCAs was ~0.7/100,000. SCA1 (4), SCA7 (4), SCA2, SCA6, and SCA17 (1 each) probands were identified. A molecular diagnosis was reached in 31% of dominant cases. Undiagnosed dominant patients included a majority of type III autosomal dominant cerebellar ataxias. FRDA is the commonest heredoataxia in the Greek population with prevalence towards the lower end of other European populations. Dominant SCAs are almost as prevalent. SCA1, SCA2, SCA6, SCA7 and SCA17 patients complete the spectrum of cases with a specific molecular diagnosis. © 2013.

  5. ATM technology and beyond

    Science.gov (United States)

    Cheung, Nim K.

    1993-01-01

    Networks based on Asynchronous Transfer Mode (ATM) are expected to provide cost-effective and ubiquitous infrastructure to support broadband and multimedia services. In this paper, we give an overview of the ATM standards and its associated physical layer transport technologies. We use the experimental HIPPI-ATM-SONET (HAS) interface in the Nectar Gigabit Testbed to illustrate how one can use the SONET/ATM public network to provide transport for bursty gigabit applications.

  6. The effect of piracetam on ataxia: clinical observations in a group of autosomal dominant cerebellar ataxia patients.

    Science.gov (United States)

    Ince Gunal, D; Agan, K; Afsar, N; Borucu, D; Us, O

    2008-04-01

    Autosomal dominant cerebellar ataxias are clinically and genetically heterogeneous neurodegenerative disorders. There is no known treatment to prevent neuronal cell death in these disorders. Current treatment is purely symptomatic; ataxia is one of the most disabling symptoms and represents the main therapeutic challenge. A previous case report suggesting benefit from administration of high dose piracetam inspired the present study of the efficacy of this agent in patients with cerebellar ataxia. Piracetam is a low molecular weight derivative of gamma-aminobutyric acid. Although little is known of its mode of action, its efficacy has been documented in a wide range of clinical indications, such as cognitive disorders, dementia, vertigo and dyslexia, as well as cortical myoclonus. The present report investigated the role of high dose piracetam in patients with cerebellar ataxia. Eight patients with autosomal dominant cerebellar ataxia were given intravenous piracetam 60 g/day by a structured protocol for 14 days. The baseline and end-of-the study evaluations were based on the International Cooperative Ataxia Rating Scale. Statistical analysis demonstrated a significant improvement in the patients' total score (P = 0.018) and a subscale analysis showed statistical significance for only the posture and gait disturbances item (P = 0.018). This study is providing good clinical observation in favour of high dose piracetam infusion to reduce the disability of the patients by improving their gait ataxia.

  7. Current concepts in the treatment of hereditary ataxias

    Directory of Open Access Journals (Sweden)

    Pedro Braga Neto

    2016-03-01

    Full Text Available ABSTRACT Hereditary ataxias (HA represents an extensive group of clinically and genetically heterogeneous neurodegenerative diseases, characterized by progressive ataxia combined with extra-cerebellar and multi-systemic involvements, including peripheral neuropathy, pyramidal signs, movement disorders, seizures, and cognitive dysfunction. There is no effective treatment for HA, and management remains supportive and symptomatic. In this review, we will focus on the symptomatic treatment of the main autosomal recessive ataxias, autosomal dominant ataxias, X-linked cerebellar ataxias and mitochondrial ataxias. We describe management for different clinical symptoms, mechanism-based approaches, rehabilitation therapy, disease modifying therapy, future clinical trials and perspectives, genetic counseling and preimplantation genetic diagnosis.

  8. Histone H2AX in DNA repair

    International Nuclear Information System (INIS)

    Lewandowska, H.; Szumiel, I.

    2002-01-01

    The paper reviews the recent reports on the role of the phosphorylated histone H2AX (γ-H2AX). The modification of this histone is an important part of the cellular response to the induction of DNA double strand brakes (DSB) by ionising radiation and other DSB-generating factors. In irradiated cells the modification is carried out mainly by ATM (ataxia-telangiectasia mutated) kinase, the enzyme that starts the alarm signalling upon induction of DSB.γ-H2AX molecules are formed within 1-3 min after irradiation and form foci at the sites of DSB. This seems to be necessary for the recruitment of repair factors that are later present in foci of damaged nuclei. Modification of a constant percentage of H2AX molecules per DSB takes place, corresponding to chromatin domains of megabase of DNA. (author)

  9. Receptor tyrosine kinase EphA5 is a functional molecular target in human lung cancer.

    Science.gov (United States)

    Staquicini, Fernanda I; Qian, Ming D; Salameh, Ahmad; Dobroff, Andrey S; Edwards, Julianna K; Cimino, Daniel F; Moeller, Benjamin J; Kelly, Patrick; Nunez, Maria I; Tang, Ximing; Liu, Diane D; Lee, J Jack; Hong, Waun Ki; Ferrara, Fortunato; Bradbury, Andrew R M; Lobb, Roy R; Edelman, Martin J; Sidman, Richard L; Wistuba, Ignacio I; Arap, Wadih; Pasqualini, Renata

    2015-03-20

    Lung cancer is often refractory to radiotherapy, but molecular mechanisms of tumor resistance remain poorly defined. Here we show that the receptor tyrosine kinase EphA5 is specifically overexpressed in lung cancer and is involved in regulating cellular responses to genotoxic insult. In the absence of EphA5, lung cancer cells displayed a defective G1/S cell cycle checkpoint, were unable to resolve DNA damage, and became radiosensitive. Upon irradiation, EphA5 was transported into the nucleus where it interacted with activated ATM (ataxia-telangiectasia mutated) at sites of DNA repair. Finally, we demonstrate that a new monoclonal antibody against human EphA5 sensitized lung cancer cells and human lung cancer xenografts to radiotherapy and significantly prolonged survival, thus suggesting the likelihood of translational applications. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  10. Clinical spectrum of early onset cerebellar ataxia with retained tendon reflexes: an autosomal recessive ataxia not to be missed Espectro clínico da ataxia cerebelar de início precoce com reflexos mantidos: uma ataxia autossômica recessiva para não ser esquecida

    Directory of Open Access Journals (Sweden)

    José Luiz Pedroso

    2013-06-01

    Full Text Available Autosomal recessive cerebellar ataxias are a heterogeneous group of neurological disorders. In 1981, a neurological entity comprised by early onset progressive cerebellar ataxia, dysarthria, pyramidal weakness of the limbs and retained or increased upper limb reflexes and knee jerks was described. This disorder is known as early onset cerebellar ataxia with retained tendon reflexes. In this article, we aimed to call attention for the diagnosis of early onset cerebellar ataxia with retained tendon reflexes as the second most common cause of autosomal recessive cerebellar ataxias, after Friedreich ataxia, and also to perform a clinical spectrum study of this syndrome. In this data, 12 patients from different families met all clinical features for early onset cerebellar ataxia with retained tendon reflexes. Dysarthria and cerebellar atrophy were the most common features in our sample. It is uncertain, however, whether early onset cerebellar ataxia with retained tendon reflexes is a homogeneous disease or a group of phenotypically similar syndromes represented by different genetic entities. Further molecular studies are required to provide definitive answers to the questions that remain regarding early onset cerebellar ataxia with retained tendon reflexes.As ataxias cerebelares autossômicas recessivas são um grupo heterogêneo de doenças neurológicas. Em 1981, foi descrita uma entidade neurológica incluindo ataxia cerebelar progressiva de início precoce, disartria, liberação piramidal e manutenção ou aumento dos reflexos tendíneos nos membros superiores e inferiores. Essa síndrome é conhecida como ataxia cerebelar de início precoce com reflexos mantidos. Neste artigo, o objetivo foi chamar a atenção para o diagnóstico de ataxia cerebelar de início precoce com reflexos mantidos como a segunda causa mais comum de ataxia cerebelar autossômica recessiva, após a ataxia de Friedreich, e também realizar um estudo do espectro cl

  11. The ovarian DNA damage repair response is induced prior to phosphoramide mustard-induced follicle depletion, and ataxia telangiectasia mutated inhibition prevents PM-induced follicle depletion

    Energy Technology Data Exchange (ETDEWEB)

    Ganesan, Shanthi, E-mail: shanthig@iastate.edu; Keating, Aileen F., E-mail: akeating@iastate.edu

    2016-02-01

    Phosphoramide mustard (PM) is an ovotoxic metabolite of cyclophosphamide and destroys primordial and primary follicles potentially by DNA damage induction. The temporal pattern by which PM induces DNA damage and initiation of the ovarian response to DNA damage has not yet been well characterized. This study investigated DNA damage initiation, the DNA repair response, as well as induction of follicular demise using a neonatal rat ovarian culture system. Additionally, to delineate specific mechanisms involved in the ovarian response to PM exposure, utility was made of PKC delta (PKCδ) deficient mice as well as an ATM inhibitor (KU 55933; AI). Fisher 344 PND4 rat ovaries were cultured for 12, 24, 48 or 96 h in medium containing DMSO ± 60 μM PM or KU 55933 (48 h; 10 nM). PM-induced activation of DNA damage repair genes was observed as early as 12 h post-exposure. ATM, PARP1, E2F7, P73 and CASP3 abundance were increased but RAD51 and BCL2 protein decreased after 96 h of PM exposure. PKCδ deficiency reduced numbers of all follicular stages, but did not have an additive impact on PM-induced ovotoxicity. ATM inhibition protected all follicle stages from PM-induced depletion. In conclusion, the ovarian DNA damage repair response is active post-PM exposure, supporting that DNA damage contributes to PM-induced ovotoxicity. - Highlights: • PM exposure induces DNA damage repair gene expression. • Inhibition of ATM prevented PM-induced follicle depletion. • PKCδ deficiency did not impact PM-induced ovotoxicity.

  12. [Hereditary hemorrhagic telangiectasia presenting with hematuria and severe anemia].

    Science.gov (United States)

    Paz, A; Goren, E; Segal, M

    1995-07-01

    A patient with hereditary hemorrhagic telangiectasia was admitted with hematuria and severe anemia after mild recurrent episodes of epistaxis. Telangiectasias were found in the skin and buccal and nasal mucosa. No defect in the coagulation mechanism was found; thrombocyte count and function were normal. On cystoscopy, tortuous engorged vessels, some actively bleeding, were seen in the trigonal mucosa. Biopsy showed enlarged vessels in the lamina propria. Electrocoagulation of the bleeding vessels stopped hematuria, but 6 months later it recurred. This time Nd-YAG laser was used to stop the bleeding after electrocoagulation was ineffective.

  13. Genetics Home Reference: hereditary hemorrhagic telangiectasia

    Science.gov (United States)

    ... Central OMIM: JUVENILE POLYPOSIS/HEREDITARY HEMORRHAGIC TELANGIECTASIA SYNDROME McDonald J, Bayrak-Toydemir P, Pyeritz RE. Hereditary hemorrhagic ... 10.1097/GIM.0b013e3182136d32. Review. Citation on PubMed McDonald J, Wooderchak-Donahue W, VanSant Webb C, Whitehead ...

  14. Aurora-B Mediated ATM Serine 1403 Phosphorylation Is Required For Mitotic ATM Activation and the Spindle Checkpoint

    OpenAIRE

    Yang, Chunying; Tang, Xi; Guo, Xiaojing; Niikura, Yohei; Kitagawa, Katsumi; Cui, Kemi; Wong, Stephen T.C.; Fu, Li; Xu, Bo

    2011-01-01

    The ATM kinase plays a critical role in the maintenance of genetic stability. ATM is activated in response to DNA damage and is essential for cell cycle checkpoints. Here, we report that ATM is activated in mitosis in the absence of DNA damage. We demonstrate that mitotic ATM activation is dependent on the Aurora-B kinase and that Aurora-B phosphorylates ATM on serine 1403. This phosphorylation event is required for mitotic ATM activation. Further, we show that loss of ATM function results in...

  15. Phenotype variability and early onset ataxia symptoms in spinocerebellar ataxia type 7: comparison and correlation with other spinocerebellar ataxias

    Directory of Open Access Journals (Sweden)

    Marcus Vinicius Cristino de Albuquerque

    2015-01-01

    Full Text Available The spinocerebellar ataxias (SCA are a group of neurodegenerative disorders characterized by heterogeneous clinical presentation. Spinocerebellar ataxia type 7 (SCA7 is caused by an abnormal CAG repeat expansion and includes cerebellar signs associated with visual loss and ophthalmoplegia. Marked anticipation and dynamic mutation is observed in SCA7. Moreover, phenotype variability and very early onset of symptoms may occur. In this article, a large series of Brazilian patients with different SCA subtypes was evaluated, and we compared the age of onset of SCA7 with other SCA. From the 26 patients with SCA7, 4 manifested their symptoms before 10-year-old. Also, occasionally the parents may have the onset of symptoms after their children. In conclusion, our study highlights the genetic anticipation phenomenon that occurs in SCA7 families. Patients with very early onset ataxia in the context of a remarkable family history, must be considered and tested for SCA7.

  16. Frontal ataxia in childhood.

    Science.gov (United States)

    Erasmus, C E; Beems, T; Rotteveel, J J

    2004-12-01

    Frontal ataxia may be the result of a unilateral frontal lesion. In this report three cases are presented with ataxia due to right frontal lesions. One case concerns a boy presenting with an unsteady gait and titubation of the trunk, mimicking developmental disequilibrium and with complex partial seizures. It proved to be caused by a small right-sided cavernoma in the middle frontal gyrus. After surgical intervention the symptoms and the seizures disappeared. Two subsequent cases concern teenage patients presenting with headache after an ENT infection and on physical examination mild dysmetric function of the upper limbs and slight disequilibrium, due to right-sided frontal lobe abscesses. After neurosurgical and antibiotic therapy the symptoms were relieved. The frontal origin of ataxia should be considered in children presenting with a "cerebellar syndrome". Frontal gait disorders consist of a clinical pattern of different gait disorders. The syndrome has been mentioned in the literature under different names. Our patients show signs compatible with the term frontal disequilibrium, a clinical pattern of frontal gait disorder. This assumes walking problems characterized by loss of control of motor planning, leading to imbalance. Remarkably, frontal ataxia may mimic developmental delay as demonstrated in the first case and may be the leading mild symptom in extensive frontal lobe damage as demonstrated by the two other cases. We suppose that frontal ataxia is the result of a disturbance in the cerebellar-frontal circuitries and an impairment of executive and planning functions of the basal ganglia-frontal lobe circuitry.

  17. Comparison of performance between TCP/IP over ATM e ATM nativo

    OpenAIRE

    Marcelo Silva Freitas

    2001-01-01

    Com o recente desenvolvimento de tecnologias de redes de altas taxas de transmissão, tais como Asynchronous Transfer Mode (ATM), o problema da carência por largura de banda foi solucionado. A questão atual é a implementação de sistemas que suportem os protocolos ATM de forma nativa e integral. Atualmente tem-se utilizado aplicativos tradicionais baseados nos protocolos TCP(UDP)/IP no topo da pilha de protocolos ATM. Tal modelo traz redundâncias que implicam diretamente em aumento de overhead ...

  18. DNA Damage-Induced Acetylation of Lysine 3016 of ATM Activates ATM Kinase Activity▿ †

    OpenAIRE

    Sun, Yingli; Xu, Ye; Roy, Kanaklata; Price, Brendan D.

    2007-01-01

    The ATM protein kinase is essential for cells to repair and survive genotoxic events. The activation of ATM's kinase activity involves acetylation of ATM by the Tip60 histone acetyltransferase. In this study, systematic mutagenesis of lysine residues was used to identify regulatory ATM acetylation sites. The results identify a single acetylation site at lysine 3016, which is located in the highly conserved C-terminal FATC domain adjacent to the kinase domain. Antibodies specific for acetyl-ly...

  19. Ataxias and Cerebellar or Spinocerebellar Degeneration

    Science.gov (United States)

    ... and conducts a broad range of basic and clinical research on cerebellar and spinocerebellar degeneration, including work aimed at finding the cause(s) of ataxias and ways to ... Publications Definition Ataxia ...

  20. Hereditary haemorrhagic telangiectasia: a cause of preventable morbidity and mortality.

    LENUS (Irish Health Repository)

    Brady, A P

    2012-01-31

    Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant condition whose effects are mediated through deficient blood vessel formation and regeneration, with multisystem involvement. Patients are usually aware of resulting skin telangiectasia and epistaxis, but are also exposed to dangers posed by occult vascular malformations in other organs. About 15-35% of HHT patients have pulmonary AVMs (PAVMs), 10% have cerebral AVMs (CAVMs), 25-33% suffer significant GI blood loss from GI tract telangiectasia, and an unknown but high percentage have liver involvement. In total, 10% of affected individuals die prematurely or suffer major disability from HHT, largely because of bleeding from CAVMs and PAVMs, or paradoxical embolization through PAVMs. Screening for and early intervention to treat occult PAVMs and CAVMs can largely eliminate these risks, and should be undertaken in a specialist centre. The National HHT Center in The Mercy University Hospital in Cork is the referral centre for HHT screening in Ireland.

  1. Biological significance of the focus on DNA damage checkpoint factors remained after irradiation of ionizing radiation

    International Nuclear Information System (INIS)

    Yamauchi, Motohiro; Suzuki, Keiji

    2005-01-01

    This paper reviews recent reports on the focus formation and participation to checkpoint of (such phosphorylated (P-d) as below) ATM and H2AX, MDC1, 53BP1 and NBS1, and discusses their role in DNA damage checkpoint induction mainly around authors' studies. When the cell is irradiated by ionizing radiation, the subtype histone like H2AX is P-d and the formed focus', seen in the nucleus on immuno-fluorographic observation, represents the P-d H2AX at the damaged site of DNA. The role of P-d ATM (the product of causative gene of ataxia-telangiectasia mutation, a protein kinase) has been first shown by laser beam irradiation. Described are discussions on the roles and functions after irradiation in focus formation and DNA damage checkpoint of P-d H2AX (a specific histone product by the radiation like γ-ray as above), P-d ATM, MDC1 (a mediator of DNA damage check point protein 1), 53BP1, (a p53 binding protein) and NBS1 (the product of the causative gene of Nijmegen Breakage Syndrome). Authors have come to point out the remained focal size increase as implications of the efficient repair of damaged DNA, and the second cycled p53 accumulation, of tumor suppression. Thus evaluation of biological significance of these aspects, scarcely noted hitherto, is concluded important. (S.I.)

  2. Cisplatinum and Taxol Induce Different Patterns of p53 Phosphorylation

    Directory of Open Access Journals (Sweden)

    Giovanna Damia

    2001-01-01

    Full Text Available Posttranslational modifications of p53 induced by two widely used anticancer agents, cisplatinum (DDP and taxol were investigated in two human cancer cell lines. Although both drugs were able to induce phosphorylation at serine 20 (Ser20, only DDP treatment induced p53 phosphorylation at serine 15 (Ser15. Moreover, both drug treatments were able to increase p53 levels and consequently the transcription of waf1 and mdm-2 genes, although DDP treatment resulted in a stronger inducer of both genes. Using two ataxia telangiectasia mutated (ATM cell lines, the role of ATM in druginduced p53 phosphorylations was investigated. No differences in drug-induced p53 phosphorylation could be observed, indicating that ATM is not the kinase involved in these phosphorylation events. In addition, inhibition of DNA-dependent protein kinase activity by wortmannin did not abolish p53 phosphorylation at Ser15 and Ser20, again indicating that DNA-PK is unlikely to be the kinase involved. After both taxol and DDP treatments, an activation of hCHK2 was found and this is likely to be responsible for phosphorylation at Ser20. In contrast, only DDP was able to activate ATR, which is the candidate kinase for phosphorylation of Ser15 by this drug. This data clearly suggests that differential mechanisms are involved in phosphorylation and activation of p53 depending on the drug type.

  3. Intact Mre11/Rad50/Nbs1 Complex Predicts Good Response to Radiotherapy in Early Breast Cancer

    International Nuclear Information System (INIS)

    Soederlund, Karin; Stal, Olle; Skoog, Lambert; Rutqvist, Lars Erik; Nordenskjoeld, Bo; Askmalm, Marie Stenmark

    2007-01-01

    Purpose: To investigate the expression and predictive role of the Mre11/Rad50/Nbs1 (MRN) complex and the ataxia-telangiectasia mutated protein (ATM) for the outcome of radiotherapy in breast cancer patients. Methods and Materials: The protein expression of ATM and the DNA repair proteins in the MRN complex were investigated using immunohistochemistry in tumors from 224 women with early breast cancer, who were randomized to receive postoperative radiotherapy or adjuvant chemotherapy. Results: Compared with normal breast tissue, the staining intensity of Mre11, Rad50, Nbs1, and ATM was reduced in a majority of the tumors. Weak expression of the MRN complex was correlated with high histologic grade and estrogen receptor negativity (p = 0.01 and p 0.0001, respectively). Radiotherapy significantly reduced the risk of local recurrence as compared with chemotherapy (p = 0.04). The greatest benefit of radiotherapy was seen in patients with moderate/strong expression of the MRN complex (relative risk = 0.27, 95% confidence interval = 0.098-0.72, p 0.009), whereas patients with negative/weak MRN expression had no benefit of radiotherapy compared with adjuvant chemotherapy. These results suggest that an intact MRN complex is important for the tumor cell eradicating effect of radiotherapy. Conclusions: Reduced expression of the MRN complex predicts a poor effect of radiotherapy in patients with early breast cancer

  4. Genetics Home Reference: ataxia with vitamin E deficiency

    Science.gov (United States)

    ... Conditions Ataxia with vitamin E deficiency Ataxia with vitamin E deficiency Printable PDF Open All Close All Enable ... view the expand/collapse boxes. Description Ataxia with vitamin E deficiency is a disorder that impairs the body's ...

  5. Hereditary hemorrhagic telangiectasia: genetics and molecular diagnostics in a new era

    Directory of Open Access Journals (Sweden)

    Jamie eMcDonald

    2015-01-01

    Full Text Available Hereditary hemorrhagic telangiectasia (HHT is a vascular dysplasia characterized by telangiectases and arteriovenous malformations (AVMs in particular locations described in consensus clinical diagnostic criteria published in 2000. Two genes in the transforming growth factor-beta (TGF-β signaling pathway, ENG and ACVRL1, were discovered almost two decades ago, and mutations in these genes have been reported to cause up to 85% of HHT. In our experience, approximately 96% of individuals with HHT have a mutation in these two genes, when published (Curaçao diagnostic criteria for HHT are strictly applied. More recently, two additional genes in the same pathway, SMAD4 and GDF2, have been identified in a much smaller number of patients with a similar or overlapping phenotype to HHT. Yet families still exist with compelling evidence of a hereditary telangiectasia disorder, but no identifiable mutation in a known gene. Recent availability of whole exome and genome testing has created new opportunities to facilitate gene discovery, identify genetic modifiers to explain clinical variability, and potentially define an increased spectrum of hereditary telangiectasia disorders. An expanded approach to molecular diagnostics for inherited telangiectasia disorders that incorporates a multi-gene next generation sequencing (NGS HHT panel is proposed.

  6. The Wireless ATM Architecture

    Directory of Open Access Journals (Sweden)

    R. Palitefka

    1998-06-01

    Full Text Available An overview of the proposed wireless ATM structure is provided. Wireless communication have been developed to a level where offered services can now be extended beyond voice and data. There are already wireless LANs, cordless systems offering data services and mobile data. Wireless LAN systems are basically planned for local, on-promises and in-house networking providing short distance radio or infrared links between computer system. The main challenge of wireless ATM is to harmonise the development of broadband wireless system with service B -ISDN/ATM and ATM LANs, and offer multimedia multiservice features for the support of time-sensitive voice communication, video, desktop multimedia applications, and LAN data traffic for the wireless user.

  7. Hereditary hemorrhagic telangiectasia clinical and molecular genetics

    NARCIS (Netherlands)

    Letteboer, T.G.W.

    2010-01-01

    Hereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber (ROW) syndrome is an autosomal dominant disease characterized by vascular malformations in multiple organ systems. HHT has an age-related penetrance and variable clinical expression. The clinical symptoms are caused by direct

  8. Targeting Ongoing DNA Damage in Multiple Myeloma: Effects of DNA Damage Response Inhibitors on Plasma Cell Survival

    Directory of Open Access Journals (Sweden)

    Ana Belén Herrero

    2017-05-01

    Full Text Available Human myeloma cell lines (HMCLs and a subset of myeloma patients with poor prognosis exhibit high levels of replication stress (RS, leading to DNA damage. In this study, we confirmed the presence of DNA double-strand breaks (DSBs in several HMCLs by measuring γH2AX and RAD51 foci and analyzed the effect of various inhibitors of the DNA damage response on MM cell survival. Inhibition of ataxia telangiectasia and Rad3-related protein (ATR, the main kinase mediating the response to RS, using the specific inhibitor VE-821 induced more cell death in HMCLs than in control lymphoblastoid cells and U266, an HMCL with a low level of DNA damage. The absence of ATR was partially compensated by ataxia telangiectasia-mutated protein (ATM, since chemical inhibition of both kinases using VE-821 and KU-55933 significantly increased the death of MM cells with DNA damage. We found that ATM and ATR are involved in DSB repair by homologous recombination (HR in MM. Inhibition of both kinases resulted in a stronger inhibition that may underlie cell death induction, since abolition of HR using two different inhibitors severely reduced survival of HMCLs that exhibit DNA damage. On the other hand, inhibition of the other route involved in DSB repair, non-homologous end joining (NHEJ, using the DNA-PK inhibitor NU7441, did not affect MM cell viability. Interestingly, we found that NHEJ inhibition did not increase cell death when HR was simultaneously inhibited with the RAD51 inhibitor B02, but it clearly increased the level of cell death when HR was inhibited with the MRE11 inhibitor mirin, which interferes with recombination before DNA resection takes place. Taken together, our results demonstrate for the first time that MM cells with ongoing DNA damage rely on an intact HR pathway, which thereby suggests therapeutic opportunities. We also show that inhibition of HR after the initial step of end resection might be more appropriate for inducing MM cell death, since it

  9. Frontal ataxia in childhood.

    OpenAIRE

    Erasmus, C.E.; Beems, T.; Rotteveel, J.J.

    2004-01-01

    Frontal ataxia may be the result of a unilateral frontal lesion. In this report three cases are presented with ataxia due to right frontal lesions. One case concerns a boy presenting with an unsteady gait and titubation of the trunk, mimicking developmental disequilibrium and with complex partial seizures. It proved to be caused by a small right-sided cavernoma in the middle frontal gyrus. After surgical intervention the symptoms and the seizures disappeared. Two subsequent cases concern teen...

  10. Maculopathy and spinocerebellar ataxia type 1

    DEFF Research Database (Denmark)

    Lebranchu, Pierre; Le Meur, Guylène; Magot, Armelle

    2013-01-01

    Autosomal dominant cerebellar ataxia is a rare heterogeneous group of diseases characterized by cerebellar symptoms, often associated with other multisystemic signs. Mild optic neuropathy has been associated with spinocerebellar ataxia type 1 (SCA1), but macular dysfunction has been reported...

  11. Requirement of Sequences outside the Conserved Kinase Domain of Fission Yeast Rad3p for Checkpoint Control

    Science.gov (United States)

    Chapman, Carolyn Riley; Evans, Sarah Tyler; Carr, Antony M.; Enoch, Tamar

    1999-01-01

    The fission yeast Rad3p checkpoint protein is a member of the phosphatidylinositol 3-kinase-related family of protein kinases, which includes human ATMp. Mutation of the ATM gene is responsible for the disease ataxia-telangiectasia. The kinase domain of Rad3p has previously been shown to be essential for function. Here, we show that although this domain is necessary, it is not sufficient, because the isolated kinase domain does not have kinase activity in vitro and cannot complement a rad3 deletion strain. Using dominant negative alleles of rad3, we have identified two sites N-terminal to the conserved kinase domain that are essential for Rad3p function. One of these sites is the putative leucine zipper, which is conserved in other phosphatidylinositol 3-kinase-related family members. The other is a novel motif, which may also mediate Rad3p protein–protein interactions. PMID:10512862

  12. Preliminary Study of Intravenous Amantadine Treatment for Ataxia Management in Patients with Probable Multiple System Atrophy with Predominant Cerebellar Ataxia

    Directory of Open Access Journals (Sweden)

    Jinyoung Youn

    2012-05-01

    Full Text Available Background and Purpose: Multiple system atrophy with predominant cerebellar ataxia is a disabling neurologic disease. However, effective management has not yet been established. We conducted a short-term, open-label preliminary study to assess the benefits of intravenous amantadine treatment in patients with probable multiple system atrophy with predominant cerebellar ataxia. Methods: Twenty patients (10 male, 10 female with probable multiple system atrophy with predominant cerebellar ataxia received 400 mg of amantadine by intravenous per day for 5 days. Ataxia severity was evaluated by the International Cooperative Ataxia Rating Scale before and after intravenous amantadine therapy and all subjects reported subjective improvement after intravenous amantadine treatment using a patient global impression scale. We analyzed the total and subscale scores by the ataxia scale and patient global impression scale. Results: The mean age was 57.4 years (range: 47–72 and the mean disease duration was 30.8 months (range: 11–79. The ataxia severity significantly decreased after intravenous amantadine therapy from 42.5 to 37.3 (p < 0.001. The mean patient global impression scale for improvement was 2.9 and there were no side effects of intravenous amantadine treatment observed. When we assessed responders, the duration of intravenous amantadine effect was more than 1 month in 4 subjects of 7 responders. Conclusions: Our findings suggest that intravenous amantadine treatment can be a safe management option in cerebellar ataxia, although the mechanism is unclear. Thus, further double-blind, long-term studies with a larger sample size are needed.

  13. Web Based ATM PVC Management

    NARCIS (Netherlands)

    van der Waaij, B.D.; Sprenkels, Ron; van Beijnum, Bernhard J.F.; Pras, Aiko

    1998-01-01

    This paper discusses the design of a public domain web based ATM PVC Management tool for the Dutch SURFnet research ATM network. The aim of this tool is to assists in the creation and deletion of PVCs through local and remote ATM network domains. The tool includes security mechanisms to restrict the

  14. Orphan Nuclear Receptor Small Heterodimer Partner Negatively Regulates Growth Hormone-mediated Induction of Hepatic Gluconeogenesis through Inhibition of Signal Transducer and Activator of Transcription 5 (STAT5) Transactivation*

    Science.gov (United States)

    Kim, Yong Deuk; Li, Tiangang; Ahn, Seung-Won; Kim, Don-Kyu; Lee, Ji-Min; Hwang, Seung-Lark; Kim, Yong-Hoon; Lee, Chul-Ho; Lee, In-Kyu; Chiang, John Y. L.; Choi, Hueng-Sik

    2012-01-01

    Growth hormone (GH) is a key metabolic regulator mediating glucose and lipid metabolism. Ataxia telangiectasia mutated (ATM) is a member of the phosphatidylinositol 3-kinase superfamily and regulates cell cycle progression. The orphan nuclear receptor small heterodimer partner (SHP: NR0B2) plays a pivotal role in regulating metabolic processes. Here, we studied the role of ATM on GH-dependent regulation of hepatic gluconeogenesis in the liver. GH induced phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6-phosphatase gene expression in primary hepatocytes. GH treatment and adenovirus-mediated STAT5 overexpression in hepatocytes increased glucose production, which was blocked by a JAK2 inhibitor, AG490, dominant negative STAT5, and STAT5 knockdown. We identified a STAT5 binding site on the PEPCK gene promoter using reporter assays and point mutation analysis. Up-regulation of SHP by metformin-mediated activation of the ATM-AMP-activated protein kinase pathway led to inhibition of GH-mediated induction of hepatic gluconeogenesis, which was abolished by an ATM inhibitor, KU-55933. Immunoprecipitation studies showed that SHP physically interacted with STAT5 and inhibited STAT5 recruitment on the PEPCK gene promoter. GH-induced hepatic gluconeogenesis was decreased by either metformin or Ad-SHP, whereas the inhibition by metformin was abolished by SHP knockdown. Finally, the increase of hepatic gluconeogenesis following GH treatment was significantly higher in the liver of SHP null mice compared with that of wild-type mice. Overall, our results suggest that the ATM-AMP-activated protein kinase-SHP network, as a novel mechanism for regulating hepatic glucose homeostasis via a GH-dependent pathway, may be a potential therapeutic target for insulin resistance. PMID:22977252

  15. Trial Watch: Targeting ATM–CHK2 and ATR–CHK1 pathways for anticancer therapy

    Science.gov (United States)

    Manic, Gwenola; Obrist, Florine; Sistigu, Antonella; Vitale, Ilio

    2015-01-01

    The ataxia telangiectasia mutated serine/threonine kinase (ATM)/checkpoint kinase 2 (CHEK2, best known as CHK2) and the ATM and Rad3-related serine/threonine kinase (ATR)/CHEK1 (best known as CHK1) cascades are the 2 major signaling pathways driving the DNA damage response (DDR), a network of processes crucial for the preservation of genomic stability that act as a barrier against tumorigenesis and tumor progression. Mutations and/or deletions of ATM and/or CHK2 are frequently found in tumors and predispose to cancer development. In contrast, the ATR–CHK1 pathway is often upregulated in neoplasms and is believed to promote tumor growth, although some evidence indicates that ATR and CHK1 may also behave as haploinsufficient oncosuppressors, at least in a specific genetic background. Inactivation of the ATM–CHK2 and ATR–CHK1 pathways efficiently sensitizes malignant cells to radiotherapy and chemotherapy. Moreover, ATR and CHK1 inhibitors selectively kill tumor cells that present high levels of replication stress, have a deficiency in p53 (or other DDR players), or upregulate the ATR–CHK1 module. Despite promising preclinical results, the clinical activity of ATM, ATR, CHK1, and CHK2 inhibitors, alone or in combination with other therapeutics, has not yet been fully demonstrated. In this Trial Watch, we give an overview of the roles of the ATM-CHK2 and ATR-CHK1 pathways in cancer initiation and progression, and summarize the results of clinical studies aimed at assessing the safety and therapeutic profile of regimens based on inhibitors of ATR and CHK1, the only 2 classes of compounds that have so far entered clinics. PMID:27308506

  16. The Influence of Genetic Stability on Aspergillus fumigatus Virulence and Azole Resistance

    Directory of Open Access Journals (Sweden)

    Thaila Fernanda dos Reis

    2018-01-01

    Full Text Available Genetic stability is extremely important for the survival of every living organism, and a very complex set of genes has evolved to cope with DNA repair upon DNA damage. Here, we investigated the Aspergillus fumigatus AtmA (Ataxia-telangiectasia mutated, ATM and AtrA kinases, and how they impact virulence and the evolution of azole resistance. We demonstrated that A. fumigatus atmA and atrA null mutants are haploid and have a discrete chromosomal polymorphism. The ΔatmA and ΔatrA strains are sensitive to several DNA-damaging agents, but surprisingly both strains were more resistant than the wild-type strain to paraquat, menadione, and hydrogen peroxide. The atmA and atrA genes showed synthetic lethality emphasizing the cooperation between both enzymes and their consequent redundancy. The lack of atmA and atrA does not cause any significant virulence reduction in A. fumigatus in a neutropenic murine model of invasive pulmonary aspergillosis and in the invertebrate alternative model Galleria mellonela. Wild-type, ΔatmA, and ΔatrA populations that were previously transferred 10 times in minimal medium (MM in the absence of voriconazole have not shown any significant changes in drug resistance acquisition. In contrast, ΔatmA and ΔatrA populations that similarly evolved in the presence of a subinhibitory concentration of voriconazole showed an ∼5–10-fold increase when compared to the original minimal inhibitory concentration (MIC values. There are discrete alterations in the voriconazole target Cyp51A/Erg11A or cyp51/erg11 and/or Cdr1B efflux transporter overexpression that do not seem to be the main mechanisms to explain voriconazole resistance in these evolved populations. Taken together, these results suggest that genetic instability caused by ΔatmA and ΔatrA mutations can confer an adaptive advantage, mainly in the intensity of voriconazole resistance acquisition.

  17. Linkage disequilibrium pattern of the ATM gene in breast cancer patients and controls; association of SNPs and haplotypes to radio-sensitivity and post-lumpectomy local recurrence

    International Nuclear Information System (INIS)

    Edvardsen, Hege; Tefre, Toril; Jansen, Laila; Vu, Phuong; Haffty, Bruce G; Fosså, Sophie D; Kristensen, Vessela N; Børresen-Dale, Anne-Lise

    2007-01-01

    The ATM protein is activated as a result of ionizing radiation, and genetic variants of the ATM gene may therefore affect the level of radiation-induced damage. Individuals heterozygous for ATM mutations have been reported to have an increased risk of malignancy, especially breast cancer. Norwegian breast cancer patients (272) treated with radiation (252 of which were evaluated for radiation-induced adverse side effects), 95 Norwegian women with no known history of cancer and 95 American breast cancer patients treated with radiation (44 of which developed ipsilateral breast tumour recurrence, IBTR) were screened for sequence variations in all exons of the ATM gene as well as known intronic variants by denaturating high performance liquid chromatography (dHPLC) followed by sequencing to determine the nature of the variant. A total of 56 variants were identified in the three materials combined. A borderline significant association with breast cancer risk was found for the 1229 T>C (Val>Ala) substitution in exon 11 (P-value 0.055) between the Norwegian controls and breast cancer patients as well as a borderline significant difference in haplotype distribution (P-value 0.06). Adverse side effects, such as: development of costal fractures and telangiectasias, subcutaneous and lung fibrosis, pleural thickening and atrophy were evaluated in the Norwegian patients. Significant associations were found for several of the identified variants such as rs1800058 (Leu > Phe) where a decrease in minor allele frequency was found with increasing level of adverse side effects for the clinical end-points pleural thickening and lung fibrosis, thus giving a protective effect. Overall our results indicate a role for variation in the ATM gene both for risk of developing breast cancer, and in radiation induced adverse side effects. No association could be found between risk of developing ipsilateral breast tumour recurrence and any of the sequence variants found in the American patient

  18. The benefits of a Neurogenetics clinic in an adult Academic Teaching Hospital.

    Science.gov (United States)

    Olszewska, Diana A; McVeigh, Terri; Fallon, Emer M; Pastores, Gregory M; Lynch, Tim

    2018-03-09

    Genetics is the backbone of Neurology, where a number of disorders have a genetic aetiology and are complex, requiring a dedicated Neurogenetics clinic. Genetics in the Republic of Ireland is under-resourced, with the lowest number of consultants per million of population in Europe. In November 2014, we established the monthly adult Neurogenetics clinic in Ireland, staffed by 2 consultants and 2 registrars from each speciality. We see patients with complex rare neurological conditions that may potentially have an underlying genetic basis, in the presence or absence of a family history. We performed a retrospective cohort analysis, reviewing symptoms and work-up data. Twenty-seven patients attended a pilot clinic over 12 months. Conditions encountered included Parkin-related PD, leucodystrophy, ataxia, fronto-temporal lobar degeneration, spinocerebellar ataxia type 6 (SCA6) and ataxia-telangiectasia. Identification of pathogenic mutations directed screening, treatment and facilitated onward genetic counselling (n = 10, 33%). A number of novel mutations were identified in MAPT gene ("missing tau mutation" McCarthy et al., Brain, 2015), SLCA1 gene and GRN (progranulin). Phenotypic features not previously reported were seen; e.g. writer's cramp in SCA6; paroxysmal myoclonus in the glucose transporter protein type 1 (GLUT1) deficiency. Breast cancer screening for ATM mutations carriers and referral to international experts in two undiagnosed patients were arranged. The establishment of a Neurogenetics clinic has addressed a gap in service and allowed identification of rare and atypical diagnoses.

  19. Genetics Home Reference: X-linked sideroblastic anemia and ataxia

    Science.gov (United States)

    ... linked sideroblastic anemia and ataxia X-linked sideroblastic anemia and ataxia Printable PDF Open All Close All ... the expand/collapse boxes. Description X-linked sideroblastic anemia and ataxia is a rare condition characterized by ...

  20. Gigabit ATM: another technical mistake?

    Science.gov (United States)

    Christ, Paul

    1998-09-01

    Once upon a time, or more precisely during February 1988 at the CCITT Seoul plenary, and definitely arriving as a revolution, ATM hit the hard-core B-ISDN circuit-switching gang. Initiated by the Telecoms' camp, but, surprisingly, soon to be pushed by computer minded people, ATM's generic technological history is somewhat richer than single-sided stories. Here are two classical elements of that history: Firstly, together with X.25, ATM suffers from the connection versus datagram dichotomy, well known for more than twenty years. Secondly, and lesser known, ATM's use of cells in support of the 'I' of B-ISDN was questioned from the very beginning by the packet switching camp. Furthermore, in this context, there are two other essential elements to be considered: Firstly, the exponential growth of the Internet and later intranets, using Internet technology, sparked by the success of the Web and the WINTEL alliance, resulted in a corresponding demand for both aggregate and end-system network bandwidth. Secondly, servers, historically restricted to the exclusive club of HIPPI-equipped supercomputers, suddenly become ordinary high-end PCs with 64-bit wide PCI busses -- definitely aiming at the Gigabit. Here, if your aim is for Gigabit ATM with 5000-transactions per second classical supercomputers, a 65K ATM MTU -- as implemented by Cray -- might be okay. Following Clark and others, another part of the story is the adoption and redefinition, by the IETF, of the Telecoms' notion of 'Integrated Services' and QoS mechanisms. The quest for low-delay IP packet forwarding, perhaps possible over ATM cut-throughs, has resulted in the switching versus/or integrated-with-routing movement. However, a blow for ATM may be the recent results concerning fast routing table lookup algorithms. This, by making Gigabit routing possible using ordinary Pentium processors may eventually render the much prophesized ATM switching performance unnecessary. Recently, with the rise of Gigabit Ethernet

  1. Protein phosphatase 5 is necessary for ATR-mediated DNA repair

    International Nuclear Information System (INIS)

    Kang, Yoonsung; Cheong, Hyang-Min; Lee, Jung-Hee; Song, Peter I.; Lee, Kwang-Ho; Kim, Sang-Yong; Jun, Jae Yeoul; You, Ho Jin

    2011-01-01

    Research highlights: → Serine/threonine protein phosphatase 5 (PP5) has been shown to participate in ataxia telangiectasia-mutated (ATM)- and ATR (ATM- and Rad3-related)-mediated checkpoint pathways, which plays an important role in the DNA damage response and maintenance of genomic stability. → However, it is not clear exactly how PP5 participates in this process. → Our results indicate that PP5 is more closely related with ATR-mediated pathway than ATM-mediated pathway in DNA damage repair. -- Abstract: Several recent studies have shown that protein phosphatase 5 (PP5) participates in cell cycle arrest after DNA damage, but its roles in DNA repair have not yet been fully characterized. We investigated the roles of PP5 in the repair of ultraviolet (UV)- and neocarzinostatin (NCS)-induced DNA damage. The results of comet assays revealed different repair patterns in UV- and NCS-exposed U2OS-PS cells. PP5 is only essential for Rad3-related (ATR)-mediated DNA repair. Furthermore, the phosphorylation of 53BP1 and BRCA1, important mediators of DNA damage repair, and substrates of ATR and ATM decreased in U2OS-PS cells exposed to UV radiation. In contrast, the cell cycle arrest proteins p53, CHK1, and CHK2 were normally phosphorylated in U2OS and U2OS-PS cells exposed to UV radiation or treated with NCS. In view of these results, we suggest that PP5 plays a crucial role in ATR-mediated repair of UV-induced DNA damage.

  2. Friedreich's ataxia cardiomyopathy: case based discussion and management issues.

    LENUS (Irish Health Repository)

    Hanley, A

    2010-04-01

    Cardiac involvement is common in Friedreich\\'s Ataxia and is a common cause of premature death. Evidence regarding treatment of congestive heart failure in patients with Friedreich\\'s Ataxia is lacking. The case of a 31-year-old male with advanced Friedreich\\'s Ataxia who presented with an acute diarrhoeal illness and features of acute heart failure is discussed. We then review the reported cardiac manifestations of Friedreich\\'s Ataxia and discuss management options.

  3. Characterizing POLG ataxia: clinics, electrophysiology and imaging.

    Science.gov (United States)

    Synofzik, Matthis; Srulijes, Karin; Godau, Jana; Berg, Daniela; Schöls, Ludger

    2012-12-01

    Mutations in the mitochondrial DNA polymerase gamma (POLG) cause a highly pleomorphic disease spectrum, and reports about their frequencies in ataxia populations yield equivocal results. This leads to uncertainties about the role of POLG genetics in the workup of patients with unexplained ataxia. A comprehensive characterization of POLG-associated ataxia (POLG-A) will help guide genetic diagnostics and advance our understanding of the disease processes underlying POLG-A. Thirteen patients with POLG-A were assessed by standardized clinical investigation, nerve conduction studies, motor-evoked potentials, magnetic resonance imaging (MRI) and transcranial sonography (TCS). The findings were compared with 13 matched patients with Friedreich's ataxia (FA). In addition to the well-known POLG-associated features of chronic external ophthalmoplegia (100 %), areflexia to the lower extremity (100 %), impaired vibration sense (100 %), bilateral ptosis (69 %) and epilepsy (38 %), also hyperkinetic movement disorders were frequent in POLG-A patients, including chorea (31 %), dystonia (31 %) and myoclonus (23 %). Similar to FA, polyneuropathy was of sensory axonal type (100 %). In contrast to FA, none of the POLG-A patients showed impaired central motor conduction. TCS demonstrated less enlargement of the fourth ventricle and more diffuse cerebellar hyperechogenicity in POLG-A. Corresponding to TCS, MRI revealed no or only mild cerebellar atrophy in most POLG-A patients (85 %). POLG ataxia presents with the clinical characteristics of both afferent and cerebellar ataxia. Cerebellar alterations diffusely involve various parts of the cerebellum, yet cerebellar atrophy is generally mild. POLG-A presents with a high load of distinct non-ataxia features, namely, sensory neuropathy, external ophthalmoplegia, ptosis, epilepsy and/or hyperkinetic movement disorders. Involvement of the corticospinal tract, however, is rare.

  4. Acute Cerebellar Ataxia Induced by Nivolumab

    Science.gov (United States)

    Kawamura, Reina; Nagata, Eiichiro; Mukai, Masako; Ohnuki, Yoichi; Matsuzaki, Tomohiko; Ohiwa, Kana; Nakagawa, Tomoki; Kohno, Mitsutomo; Masuda, Ryota; Iwazaki, Masayuki; Takizawa, Shunya

    2017-01-01

    A 54-year-old woman with adenocarcinoma of the lung and lymph node metastasis experienced nystagmus and cerebellar ataxia 2 weeks after initiating nivolumab therapy. An evaluation for several autoimmune-related antibodies and paraneoplastic syndrome yielded negative results. We eventually diagnosed the patient with nivolumab-induced acute cerebellar ataxia, after excluding other potential conditions. Her ataxic gait and nystagmus resolved shortly after intravenous steroid pulse therapy followed by the administration of decreasing doses of oral steroids. Nivolumab, an immune checkpoint inhibitor, is known to induce various neurological adverse events. However, this is the first report of acute cerebellar ataxia associated with nivolumab treatment. PMID:29249765

  5. Tumor germinal mixto con componentes de disgerminoma y coriocarcinoma de ovario en mujer adolescente con ataxiatelangiectasia

    Directory of Open Access Journals (Sweden)

    Eduardo Augusto Gálvez-Cuitiva

    2015-11-01

    días. Se suspendió la quimioterapia porque desarrolló choque séptico que puso en riesgo su vida. Por su enfermedad de base permaneció bajo vigilancia. Actualmente, 17 meses después, la paciente vive sin actividad tumoral.  Conclusión: existe asociación entre ataxia-telangiectasia, leucemia y linfomas. Se describe el caso clínico de una paciente con ataxia-telangiectasia y tumor germinal mixto con componente de disgerminoma y coriocarcinoma de ovario. Se propone establecer un tratamiento especial para estos pacientes inmunocomprometidos, con alto riesgo de cáncer pero, a la vez, de no tolerar los esquemas habituales.

  6. Novel targets for ATM-deficient malignancies

    Science.gov (United States)

    Winkler, Johannes; Hofmann, Kay; Chen, Shuhua

    2014-01-01

    Conventional chemo- and radiotherapies for the treatment of cancer target rapidly dividing cells in both tumor and non-tumor tissues and can exhibit severe cytotoxicity in normal tissue and impair the patient's immune system. Novel targeted strategies aim for higher efficacy and tumor specificity. The role of ATM protein in the DNA damage response is well known and ATM deficiency frequently plays a role in tumorigenesis and development of malignancy. In addition to contributing to disease development, ATM deficiency also renders malignant cells heavily dependent on other pathways that cooperate with the ATM-mediated DNA damage response to ensure tumor cell survival. Disturbing those cooperative pathways by inhibiting critical protein components allows specific targeting of tumors while sparing healthy cells with normal ATM status. We review druggable candidate targets for the treatment of ATM-deficient malignancies and the mechanisms underlying such targeted therapies. PMID:27308314

  7. Spinocerebellar ataxia-10 with paranoid schizophrenia

    Directory of Open Access Journals (Sweden)

    Bhavesh Trikamji

    2015-01-01

    Full Text Available Spino-cerebellar ataxia type 10 (SCA10 is an autosomal dominant disorder that is characterized by cerebellar ataxia, seizures and nystagmus with a fragmented pursuit. Schizophrenia has been reported with SCAs 1 and 2 yet in SCA 10, psychiatric manifestations are uncommon. We report a Hispanic family involving a father and his four children with SCA10 genetic mutation. Two of his children, a 20-year-old female and a 23-year-old male, presented with gradually progressive spino-cerebellar ataxia and paranoid schizophrenia. Neurological examination revealed ocular dysmetria, dysdiadokinesia, impaired finger-to-nose exam, gait ataxia and hyperreflexia in both the cases. Additionally, they had a history of psychosis with destructive behavior, depression and paranoid delusions with auditory hallucinations. Serology and CSF studies were unremarkable and MRI brain revealed cerebellar volume loss. Ultimately, a test for ATAXIN-10 mutation was positive thus confirming the diagnosis of SCA10 in father and his four children. We now endeavor to investigate the association between schizophrenia and SCA10.

  8. Gastrointestinal bleeding in patients with hereditary hemorrhagic telangiectasia

    DEFF Research Database (Denmark)

    Kjeldsen, A D; Kjeldsen, J

    2000-01-01

    Gastrointestinal bleeding occurs in a number of patients with hereditary hemorrhagic telangiectasia (HHT) and may lead to a high transfusion need. The aim of this study was to estimate the occurrence and severity of gastrointestinal bleeding in a geographically well defined HHT population....

  9. Aspectos moleculares das ataxias espinocerebelares autossomicas recessivas

    OpenAIRE

    Flavia Chagas Costa

    2000-01-01

    Resumo: As ataxias espinocerebelares (ABC) formam um grupo heterogêneo de doenças degenerativas que envolvem o sistema nervoso central. Esse grupo se caracteriza clinicamente por apresentar disfunção cerebelar manifestada por ataxia de marcha, incoordenação e disartria. Nos casos familiares, o padrão de herança é variável, podendo ser compatível com herança autossômica dominante (HAD) ou herança autossômica recessiva (HAR). Para as ataxias espinocerebelares com HAR existem três lócus identifi...

  10. 53BP1 loss suppresses the radiosensitizing effect of icotinib hydrochloride in colorectal cancer cells.

    Science.gov (United States)

    Huang, Ai; Yao, Jing; Liu, Tao; Lin, Zhenyu; Zhang, Sheng; Zhang, Tao; Ma, Hong

    2018-04-01

    This study aimed to investigate the influence of the expression of P53-binding protein 1 (53BP1), a key component in DNA damage repair pathways, on the radiosensitizing effect of icotinib hydrochloride in colorectal cancer and to elucidate the mechanisms underlying this influence. Real-time RT-PCR and Western blotting were performed to verify the gene-knockout effect of 53BP1 small hairpin RNA (ShRNA), and colony formation assay was employed to investigate the influence of 53BP1 downregulation on the radiosensitizing effect of icotinib hydrochloride in HCT116 cells. Cell apoptosis, cell cycle distributions, and histone H2AX (γ-H2AX) fluorescence foci after 53BP1 knockdown were evaluated. Relative protein expression in the ataxia telangiectasia mutated kinase (ATM)-checkpoint kinase-2 (CHK2)-P53 pathway was measured by Western blot analysis to unravel the molecular mechanisms linking the pathway to the above phenomena. Icotinib hydrochloride increased the radiosensitivity of HCT116 cells; however, this effect was suppressed by the downregulation of 53BP1 expression, a change that inhibited cell apoptosis, increased the percentage of HCT116 cells arrested in S-phase and inhibited the protein expression of key molecules in the ATM-CHK2-P53 apoptotic pathway. Our studies confirmed that the loss of 53BP1 serves as a negative regulator of the radiosensitizing effect of icotinib in part by suppressing the ATM-CHK2-P53 apoptotic pathway.

  11. Dose rate effect on low-dose hyper-radiosensitivity with cells in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Geon-Min; Kim, Eun-Hee [Seoul National University, Seoul (Korea, Republic of)

    2016-10-15

    Low-dose hyper-radiosensitivity (HRS) is the phenomenon that mammalian cells exhibit higher sensitivity to radiation at low doses (< 0.5 Gy) than expected by the linear-quadratic model. At doses above 0.5Gy, the cellular response is recovered to the level expected by the linear-quadratic model. This transition is called the increased radio-resistance (IRR). HRS was first verified using Chinese hamster V79 cells in vitro by Marples and has been confirmed in studies with other cell lines including human normal and tumor cells. HRS is known to be induced by inactivation of ataxia telangiectasia-mutated (ATM), which plays a key role in repairing DNA damages. Considering the connection between ATM and HRS, one can infer that dose rate may affect cellular response regarding HRS at low doses. In this study, we quantitated the effect of dose rate on HRS by clonogenic assay with normal and tumor cells. The HRS of cells at low dose exposures is a phenomenon already known. In this study, we observed HRS of rat normal diencephalon cells and rat gliosarcoma cells at doses below 1 Gy. In addition, we found that dose rate mattered. HRS occurred at low doses, but only when total dose was delivered at a rate below certain level.

  12. Movement disorders in hereditary ataxias.

    Science.gov (United States)

    Garcia Ruiz, Pedro J; Mayo, David; Hernandez, Jaime; Cantarero, Susana; Ayuso, Carmen

    2002-10-15

    Movement disorders are well known features of some dominant hereditary ataxias (HA), specially SCA3/Machado-Joseph disease and dentatorubropallidolusyan atrophy. However, little is known about the existence and classification of movement disorders in other dominant and recessive ataxias. We prospectively studied the presence of movement disorders in patients referred for HA over the last 3 years. Only those patients with a confirmed family history of ataxia were included. We studied 84 cases of HA, including 46 cases of recessive and 38 cases of dominant HA. Thirty out of 46 cases of recessive HA could be classified as: Friedreich ataxia (FA), 29 cases; vitamin E deficiency, 1 case. Twenty-three out of 38 cases of dominant HA could be classified as: SCA 2, 4 cases; SCA 3, 8 cases; SCA 6, 4 cases; SCA 7, 6 cases and SCA 8, 1 case. We observed movement disorders in 20/38 (52%) patients with dominant HA and 25/46 (54%) cases with recessive HA, including 16 patients (16/29) with FA. In general, postural tremor was the most frequent observed movement disorder (27 cases), followed by dystonia (22 cases). Five patients had akinetic rigid syndrome, and in 13 cases, several movement disorders coexisted. Movement disorders are frequent findings in HA, not only in dominant HA but also in recessive HA. Copyright 2002 Elsevier Science B.V.

  13. Hereditary syndromes with enhanced radiosensitivity

    International Nuclear Information System (INIS)

    Lohmann, D.

    2000-01-01

    Sensitivity to ionizing radiation is modified by heritable genetic factors. This is exemplified by heritable disorders that are characterized by predisposition to the development of neoplasms. Cells derived from patients with ataxia telangiectasia, Nijmegen breakage syndrome and ataxia telangiektasia-like disorder show a markedly changed reaction to exposure to ionizing radiation. Correspondingly, at least in patients with ataxia telangiectasia, an enhanced radiosensitivity that is of clinical importance has been observed. In addition to these recessive disorders, some autosomal dominant cancer predisposition syndromes are associated with increased radiosensitivity. As cells from these patients still have a normal allele (that is dominant over the mutant allele), the cellular phenotype is most often normal. Specifically, there is no overtly altered reaction in response to ionizing radiation. Nevertheless, two dominant cancer predisposition syndromes, namely hereditary retinoblastoma and naevoid basal cell carcinoma syndrome, are associated with a enhanced radiosensitivity as indicated by increased development of tumors following radiation therapy. (orig.) [de

  14. Caffeine markedly sensitizes human mesothelioma cell lines to pemetrexed

    Science.gov (United States)

    Min, Sang Hee; Goldman, I. David; Zhao, Rongbao

    2013-01-01

    Pemetrexed is a new generation antifolate approved for the treatment of mesothelioma and non-small cell lung cancer. Caffeine is known to augment radiation or chemotherapeutic drug-induced cell killing. The current study addresses the impact of caffeine on the activity of pemetrexed in mesothelioma cell lines. Caffeine enhanced pemetrexed activity in all four mesothelioma cell lines tested (H2052, H2373, H28 and MSTO-211H). Caffeine sensitized H2052 cells in a dose- and schedule-dependent manner, and was associated with a markedly decreased clonogenic survival. Caffeine sensitization occurred only in cells subjected to pulse, but not continuous, exposure to pemetrexed. Similar pemetrexed sensitization was also observed with the clinically better tolerated caffeine analog, theobromine. Pemetrexed sensitization by caffeine was associated with an increase in pemetrexed-induced phosphorylation of ataxia-telangiectasia-mutated (ATM) and Chk1. These data indicate that caffeine and its analog, theobromine, may be a useful approach to enhance pemetrexed-based chemotherapy. PMID:17594092

  15. The thyroid hormone receptor β induces DNA damage and premature senescence.

    Science.gov (United States)

    Zambrano, Alberto; García-Carpizo, Verónica; Gallardo, María Esther; Villamuera, Raquel; Gómez-Ferrería, Maria Ana; Pascual, Angel; Buisine, Nicolas; Sachs, Laurent M; Garesse, Rafael; Aranda, Ana

    2014-01-06

    There is increasing evidence that the thyroid hormone (TH) receptors (THRs) can play a role in aging, cancer and degenerative diseases. In this paper, we demonstrate that binding of TH T3 (triiodothyronine) to THRB induces senescence and deoxyribonucleic acid (DNA) damage in cultured cells and in tissues of young hyperthyroid mice. T3 induces a rapid activation of ATM (ataxia telangiectasia mutated)/PRKAA (adenosine monophosphate-activated protein kinase) signal transduction and recruitment of the NRF1 (nuclear respiratory factor 1) and THRB to the promoters of genes with a key role on mitochondrial respiration. Increased respiration leads to production of mitochondrial reactive oxygen species, which in turn causes oxidative stress and DNA double-strand breaks and triggers a DNA damage response that ultimately leads to premature senescence of susceptible cells. Our findings provide a mechanism for integrating metabolic effects of THs with the tumor suppressor activity of THRB, the effect of thyroidal status on longevity, and the occurrence of tissue damage in hyperthyroidism.

  16. Ataxia with Vitamin E Deficiency in Norway

    Directory of Open Access Journals (Sweden)

    Areej Elkamil

    2015-01-01

    Full Text Available Objective Ataxia with vitamin E deficiency (AVED is a rare autosomal recessive neurological disorder which usually starts in childhood. The clinical presentation is very similar to Friedreich ataxia, most patients have progressive truncal and extremity ataxia, areflexia, positive Babinski sign, dysarthria and sensory neuropathy. Methods We made an inquiry to our colleagues in Norway, we included information from a prevalence study published southern Norway and added data from our own known case. Results A newly published prevalence study of hereditary ataxias (total of 171 subjects found only one subject with AVED in Southeast Norway. We describe two more patients, one from the Central part and one from the Northern part of Norway. All 3 cases had age of onset in early childhood (age of 4–5 years and all experienced gait ataxia and dysarthria. The genetic testing confirmed that they had pathogenic mutations in the α-tocopherol transfer protein gene (TTPA. All were carriers of the non-sense c.400C > T mutation, one was homozygous for that mutation and the others were compound heterozygous, either with c.358G > A or c.513_514insTT. The homozygous carrier was by far the most severely affected case. Conclusions We estimate the occurrence of AVED in Norway to be at least 0.6 per million inhabitants. We emphasize that all patients who develop ataxia in childhood should be routinely tested for AVED to make an early diagnosis for initiating treatment with high dose vitamin E to avoid severe neurological deficits.

  17. Fragile X-associated tremor/ataxia syndrome.

    Science.gov (United States)

    Hoem, Gry; Koht, Jeanette

    2017-10-31

    Fragile X-associated tremor/ataxia syndrome (FXTAS) is a hereditary neurodegenerative disorder caused by a mutation on the X chromosome. The major signs and symptoms are tremor, ataxia and parkinsonism. Up to one in 2 000 persons over 50 years of age will develop the syndrome. There is reason to believe that too few individuals in Norway undergo testing for this condition.

  18. Functional Characterization of ATM Kinase Using Acetylation-Specific Antibodies.

    Science.gov (United States)

    Sun, Yingli; Du, Fengxia

    2017-01-01

    The activation of ATM is critical in the DNA double strand breaks repair pathway. Acetylation of ATM by Tip60 histone acetyltransferase (HAT) plays a key role in the activation of ATM kinase activity in response to DNA damage. ATM forms a stable complex with Tip60 through the FATC domain of ATM. Tip60 acetylates lysine3016 of ATM, and this acetylation induces the activation of ATM. Several techniques are included in the study of ATM acetylation by Tip60, such as in vitro kinase assay, systematic mutagenesis, western blots. Here, we describe how to study the acetylation of ATM using acetylation-specific antibodies.

  19. Acute Cerebellar Ataxia Induced by Nivolumab

    OpenAIRE

    Kawamura, Reina; Nagata, Eiichiro; Mukai, Masako; Ohnuki, Yoichi; Matsuzaki, Tomohiko; Ohiwa, Kana; Nakagawa, Tomoki; Kohno, Mitsutomo; Masuda, Ryota; Iwazaki, Masayuki; Takizawa, Shunya

    2017-01-01

    A 54-year-old woman with adenocarcinoma of the lung and lymph node metastasis experienced nystagmus and cerebellar ataxia 2 weeks after initiating nivolumab therapy. An evaluation for several autoimmune-related antibodies and paraneoplastic syndrome yielded negative results. We eventually diagnosed the patient with nivolumab-induced acute cerebellar ataxia, after excluding other potential conditions. Her ataxic gait and nystagmus resolved shortly after intravenous steroid pulse therapy follow...

  20. Genetics Home Reference: neuropathy, ataxia, and retinitis pigmentosa

    Science.gov (United States)

    ... Twitter Home Health Conditions NARP Neuropathy, ataxia, and retinitis pigmentosa Printable PDF Open All Close All Enable Javascript ... the expand/collapse boxes. Description Neuropathy, ataxia, and retinitis pigmentosa ( NARP ) is a condition that causes a variety ...

  1. Requirement of the Mre11 complex and exonuclease 1 for activation of the Mec1 signaling pathway.

    Science.gov (United States)

    Nakada, Daisuke; Hirano, Yukinori; Sugimoto, Katsunori

    2004-11-01

    The large protein kinases, ataxia-telangiectasia mutated (ATM) and ATM-Rad3-related (ATR), orchestrate DNA damage checkpoint pathways. In budding yeast, ATM and ATR homologs are encoded by TEL1 and MEC1, respectively. The Mre11 complex consists of two highly related proteins, Mre11 and Rad50, and a third protein, Xrs2 in budding yeast or Nbs1 in mammals. The Mre11 complex controls the ATM/Tel1 signaling pathway in response to double-strand break (DSB) induction. We show here that the Mre11 complex functions together with exonuclease 1 (Exo1) in activation of the Mec1 signaling pathway after DNA damage and replication block. Mec1 controls the checkpoint responses following UV irradiation as well as DSB induction. Correspondingly, the Mre11 complex and Exo1 play an overlapping role in activation of DSB- and UV-induced checkpoints. The Mre11 complex and Exo1 collaborate in producing long single-stranded DNA (ssDNA) tails at DSB ends and promote Mec1 association with the DSBs. The Ddc1-Mec3-Rad17 complex associates with sites of DNA damage and modulates the Mec1 signaling pathway. However, Ddc1 association with DSBs does not require the function of the Mre11 complex and Exo1. Mec1 controls checkpoint responses to stalled DNA replication as well. Accordingly, the Mre11 complex and Exo1 contribute to activation of the replication checkpoint pathway. Our results provide a model in which the Mre11 complex and Exo1 cooperate in generating long ssDNA tracts and thereby facilitate Mec1 association with sites of DNA damage or replication block.

  2. AT cells are not radiosensitive for simple chromosomal exchanges at low dose

    International Nuclear Information System (INIS)

    Hada, Megumi; Huff, Janice L.; Patel, Zarana S.; Kawata, Tetsuya; Pluth, Janice M.; George, Kerry A.; Cucinotta, Francis A.

    2011-01-01

    Cells deficient in ATM (product of the gene that is mutated in ataxia telangiectasia patients) or NBS (product of the gene mutated in the Nijmegen breakage syndrome) show increased yields of both simple and complex chromosomal aberrations after high doses (>0.5 Gy) of ionizing radiation (X-rays or γ-rays), however less is known on how these cells respond at low dose. Previously we had shown that the increased chromosome aberrations in ATM and NBS defective lines was due to a significantly larger quadratic dose-response term compared to normal fibroblasts for both simple and complex exchanges. The linear dose-response term for simple exchanges was significantly higher in NBS cells compared to wild type cells, but not for AT cells. However, AT cells have a high background level of exchanges compared to wild type or NBS cells that confounds the understanding of low dose responses. To understand the sensitivity differences for high to low doses, chromosomal aberration analysis was first performed at low dose-rates (0.5 Gy/d), and results provided further evidence for the lack of sensitivity for exchanges in AT cells below doses of 1 Gy. Normal lung fibroblast cells treated with KU-55933, a specific ATM kinase inhibitor, showed increased numbers of exchanges at a dose of 1 Gy and higher, but were similar to wild type cells at 0.5 Gy or below. These results were confirmed using siRNA knockdown of ATM. The present study provides evidence that the increased radiation sensitivity of AT cells for chromosomal exchanges found at high dose does not occur at low dose.

  3. Linkage disequilibrium pattern of the ATM gene in breast cancer patients and controls; association of SNPs and haplotypes to radio-sensitivity and post-lumpectomy local recurrence

    Directory of Open Access Journals (Sweden)

    Fosså Sophie D

    2007-07-01

    Full Text Available Abstract Background The ATM protein is activated as a result of ionizing radiation, and genetic variants of the ATM gene may therefore affect the level of radiation-induced damage. Individuals heterozygous for ATM mutations have been reported to have an increased risk of malignancy, especially breast cancer. Materials and methods Norwegian breast cancer patients (272 treated with radiation (252 of which were evaluated for radiation-induced adverse side effects, 95 Norwegian women with no known history of cancer and 95 American breast cancer patients treated with radiation (44 of which developed ipsilateral breast tumour recurrence, IBTR were screened for sequence variations in all exons of the ATM gene as well as known intronic variants by denaturating high performance liquid chromatography (dHPLC followed by sequencing to determine the nature of the variant. Results and Conclusion A total of 56 variants were identified in the three materials combined. A borderline significant association with breast cancer risk was found for the 1229 T>C (Val>Ala substitution in exon 11 (P-value 0.055 between the Norwegian controls and breast cancer patients as well as a borderline significant difference in haplotype distribution (P-value 0.06. Adverse side effects, such as: development of costal fractures and telangiectasias, subcutaneous and lung fibrosis, pleural thickening and atrophy were evaluated in the Norwegian patients. Significant associations were found for several of the identified variants such as rs1800058 (Leu > Phe where a decrease in minor allele frequency was found with increasing level of adverse side effects for the clinical end-points pleural thickening and lung fibrosis, thus giving a protective effect. Overall our results indicate a role for variation in the ATM gene both for risk of developing breast cancer, and in radiation induced adverse side effects. No association could be found between risk of developing ipsilateral breast tumour

  4. Dyspnea with anemia turned out to be a case of hereditary hemorrhagic telangiectasia

    Directory of Open Access Journals (Sweden)

    Amitabha Sengupta

    2013-01-01

    Full Text Available Hereditary hemorrhagic telangiectasia (HHT is a rare autosomal dominant inherited disorder of the vascular system. It can be asymptomatic but when symptomatic most common presentation being epistaxis. It can involve any organs of the body like lungs, skin, liver brain, GI mucosa etc. We are reporting a case of HHT presented to us with dyspnea and severe anemia. He had arteriovenous malformations of different visceral organs and telangiectasia of skin along with presence of similar history in first-degree relatives.

  5. Satellite ATM Networks: Architectures and Guidelines Developed

    Science.gov (United States)

    vonDeak, Thomas C.; Yegendu, Ferit

    1999-01-01

    An important element of satellite-supported asynchronous transfer mode (ATM) networking will involve support for the routing and rerouting of active connections. Work published under the auspices of the Telecommunications Industry Association (http://www.tiaonline.org), describes basic architectures and routing protocol issues for satellite ATM (SATATM) networks. The architectures and issues identified will serve as a basis for further development of technical specifications for these SATATM networks. Three ATM network architectures for bent pipe satellites and three ATM network architectures for satellites with onboard ATM switches were developed. The architectures differ from one another in terms of required level of mobility, supported data rates, supported terrestrial interfaces, and onboard processing and switching requirements. The documentation addresses low-, middle-, and geosynchronous-Earth-orbit satellite configurations. The satellite environment may require real-time routing to support the mobility of end devices and nodes of the ATM network itself. This requires the network to be able to reroute active circuits in real time. In addition to supporting mobility, rerouting can also be used to (1) optimize network routing, (2) respond to changing quality-of-service requirements, and (3) provide a fault tolerance mechanism. Traffic management and control functions are necessary in ATM to ensure that the quality-of-service requirements associated with each connection are not violated and also to provide flow and congestion control functions. Functions related to traffic management were identified and described. Most of these traffic management functions will be supported by on-ground ATM switches, but in a hybrid terrestrial-satellite ATM network, some of the traffic management functions may have to be supported by the onboard satellite ATM switch. Future work is planned to examine the tradeoffs of placing traffic management functions onboard a satellite as

  6. ATM-induced radiosensitization in vitro and in vivo

    International Nuclear Information System (INIS)

    Choi, E. K.; Ahn, S. D.; Rhee, Y. H.; Chung, H. S.; Ha, S. W; Song, C. W.; Griffin, R. J.; Park, H. J.

    2003-01-01

    It has been known that ATM plays a central role in response of cells to ionizing radiation by enhancing DNA repair. We have investigated the feasibility of increasing radiosensitivity of tumor cells with the use of ATM inhibitors such as caffeine, pentoxifylline and wortmannin. Human colorectal cancer RKO.C cells and RKO-ATM cells (RKO cells overexpressing ATM) were used in the present study. The clonogenic cell survival in vitro indicated that RKO-ATM cells were markedly radioresistant than RKO.C cells. Treatment with 3 mM of caffeine significantly increased the radiosensitivity of cells, particulary the RKO-ATM cells, so that the radiosensitivity of RKO.C cells and RKO-ATM cells were almost similar. The radiation induced G2/M arrest in RKO-ATM cells was noticeably longer than that in RKO.C cells and caffeine treatment significantly reduced the length of the radiation induced G2/M arrest in both RKO.C and RKO-ATM cells. Pentoxifylline and wortmannin were also less effective than caffeine to radiosensitize RKO.C or RKO-ATM cells. However, wortmannin was more effective than caffeine against human lung adenocarcinoma A549 cells indicating the efficacy of ATM inhibitor to increase radiosensitivity is cell line dependent. For in vivo study, RKO.C cells were injected s.c. into the hind-leg of BALB/c-nuslc nude mice, and allowed to grow to 130mm3 tumor. The mice were i.p. injected with caffeine solution or saline and the tumors irradiated with 10 Gy of X-rays. The radiation induced growth delay was markedly increased by 1-2 mg/g of caffeine. It was concluded that caffeine increases radiosensitivity of tumor cells by inhibiting ATM kinase function, thereby inhibiting DNA repair, that occurs during the G2/M arrest after radiation

  7. Comparison of γ i-irradiation-induced accumulation of ataxia telangiesctasia and control cells in G2 phase

    International Nuclear Information System (INIS)

    Bates, P.R.; Lavin, M.F.

    1989-01-01

    Recent reports from a number of laboratories have linked radiosensitivity in ataxia telangiectasia (AT) to a large and prolonged block of some cells in G 2 phase. Previous results from this laboratory, largely with one Epstein-Barr virus-transformed A-T lymphoblastoid cell line, presented evidence for a dramatic increase in the number of cells in G 2 phase over controls during a 24 h period post irradiation. We describe here a study of the effect of γ-radiation on G 2 phase delay in several A-T cell lines. Based on previous results with several cell lines 24 h post irradiation was selected as the optimum time to discriminate between G 2 phase delay in control and A-T cells. All A-T homozygotes showed a signigicantly greater number of cells in G 2 phase, 24 h post irradiation, than observed in controls. A more prolonged delay in G 2 phase after irradiation was seen in different A-T cell types that included lymphoblastoid cells, fibroblasts and SV40-transformed fibroblasts. At the radiation dose used it was not possibel to distinguish A-T heterozygotes from controls (Author). 28 refs.; 2 figs.; 1 tab

  8. Implementation of virtual LANs over ATM WANs

    Science.gov (United States)

    Braun, Torsten; Maehler, Martin

    1998-09-01

    Virtual LANs (VLANs) allow to interconnect users over campus or wide area networks and gives the users the impression as they would be connected to the same local area network (LAN). The implementation of VLANs is based on ATM Forum's LAN Emulation and LAN/ATM switches providing interconnection of emulated LANs over ATM and the LAN ports to which the user's end systems are attached to. The paper discusses possible implementation architectures and describes advanced features such as ATM short-cuts, QoS, and redundancy concepts.

  9. Ataxia cerebelar aguda na criança Acute cerebellar ataxia in children

    Directory of Open Access Journals (Sweden)

    Valeriana Moura Ribeiro

    1968-03-01

    Full Text Available São relatados os casos de 6 crianças com ataxia cerebelar aguda. Admitem os autores a presença de um fator etiológico de caráter viral comum a todos êles, discutindo os mecanismos patogênicos com base nos casos da literatura. A evolução foi favorável em todos os pacientes, com regressão completa da sintomatologia, dentro do período de 6 a 60 dias.Clinical observations of 6 children with acute cerebellar ataxia and respective laboratorial data are reported. Considerations are made in order to support the hypothesis of involving virus. The evolution of the disorder was a nonfatal one and the patients regained normal cerebellar function within a period of 6 to 60 days.

  10. ATM in Europe: analysis of current status

    DEFF Research Database (Denmark)

    1999-01-01

    This deliverable provides an overview of the current status of the European market for ATM services. The offer of ATM services by principal operators in Belgium, Denmark, Finland, France, Germany, Greece, Italy, Norway, Portugal, Spain, Sweden and United Kingdom is described. In addition, a number...... of international providers of ATM in Europe are presented....

  11. Vascular Risk Factors and Clinical Progression in Spinocerebellar Ataxias

    Directory of Open Access Journals (Sweden)

    Raymond Y. Lo

    2015-02-01

    Full Text Available Background: The contributions of vascular risk factors to spinocerebellar ataxia (SCA are not known.Methods: We studied 319 participants with SCA 1, 2, 3, and 6 and repeatedly measured clinical severity using the Scale for Assessment and Rating of Ataxia (SARA for 2 years. Vascular risk factors were summarized by CHA2DS2-VASc scores as the vascular risk factor index. We employed regression models to study the effects of vascular risk factors on ataxia onset and progression after adjusting for age, sex, and pathological CAG repeats. Our secondary analyses took hyperlipidemia into account.Results: Nearly 60% of SCA participants were at low vascular risks with CHA2DS2-VASc = 0, and 31% scored 2 or greater. Higher CHA2DS2-VASc scores were not associated with either earlier onset or faster progression of ataxia. These findings were not altered after accounting for hyperlipidemia. Discussion: Vascular risks are not common in SCAs and are not associated with earlier onset or faster ataxia progression.

  12. NOTCH1 Inhibits Activation of ATM by Impairing the Formation of an ATM-FOXO3a-KAT5/Tip60 Complex.

    Science.gov (United States)

    Adamowicz, Marek; Vermezovic, Jelena; d'Adda di Fagagna, Fabrizio

    2016-08-23

    The DNA damage response (DDR) signal transduction pathway is responsible for sensing DNA damage and further relaying this signal into the cell. ATM is an apical DDR kinase that orchestrates the activation and the recruitment of downstream DDR factors to induce cell-cycle arrest and repair. We have previously shown that NOTCH1 inhibits ATM activation upon DNA damage, but the underlying mechanism remains unclear. Here, we show that NOTCH1 does not impair ATM recruitment to DNA double-strand breaks (DSBs). Rather, NOTCH1 prevents binding of FOXO3a and KAT5/Tip60 to ATM through a mechanism in which NOTCH1 competes with FOXO3a for ATM binding. Lack of FOXO3a binding to ATM leads to the loss of KAT5/Tip60 association with ATM. Moreover, expression of NOTCH1 or depletion of ATM impairs the formation of the FOXO3a-KAT5/Tip60 protein complex. Finally, we show that pharmacological induction of FOXO3a nuclear localization sensitizes NOTCH1-driven cancers to DNA-damage-induced cell death. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  13. Are lesions induced by ionizing radiation direct blocks to DNA chain elongation

    International Nuclear Information System (INIS)

    Painter, R.B.

    1983-01-01

    Ionizing radiation blocks DNA chain elongation in normal diploid fibroblasts but not in fibroblasts from patients with ataxia-telangiectasia, even though there are no differences in the damage induced between the two cell types. This difference suggests that radiation-induced lesions in DNA are not themselves blocks to chain elongation in ataxia cells and raises the possibility that in normal cells a mediator exists between DNA damage and chain termination

  14. Treatment for speech disorder in Friedreich ataxia and other hereditary ataxia syndromes.

    Science.gov (United States)

    Vogel, Adam P; Folker, Joanne; Poole, Matthew L

    2014-10-28

    Hereditary ataxia syndromes can result in significant speech impairment, a symptom thought to be responsive to treatment. The type of speech impairment most commonly reported in hereditary ataxias is dysarthria. Dysarthria is a collective term referring to a group of movement disorders affecting the muscular control of speech. Dysarthria affects the ability of individuals to communicate and to participate in society. This in turn reduces quality of life. Given the harmful impact of speech disorder on a person's functioning, treatment of speech impairment in these conditions is important and evidence-based interventions are needed. To assess the effects of interventions for speech disorder in adults and children with Friedreich ataxia and other hereditary ataxias. On 14 October 2013, we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE, EMBASE, CINAHL Plus, PsycINFO, Education Resources Information Center (ERIC), Linguistics and Language Behavior Abstracts (LLBA), Dissertation Abstracts and trials registries. We checked all references in the identified trials to identify any additional published data. We considered for inclusion randomised controlled trials (RCTs) or quasi-RCTs that compared treatments for hereditary ataxias with no treatment, placebo or another treatment or combination of treatments, where investigators measured speech production. Two review authors independently selected trials for inclusion, extracted data and assessed the risk of bias of included studies using the standard methodological procedures expected by The Cochrane Collaboration. The review authors collected information on adverse effects from included studies. We did not conduct a meta-analysis as no two studies utilised the same assessment procedures within the same treatment. Fourteen clinical trials, involving 721 participants, met the criteria for inclusion in the review. Thirteen studies compared a pharmaceutical treatment with placebo (or a

  15. Exome Capture Reveals ZNF423 and CEP164 Mutations, Linking Renal Ciliopathies to DNA Damage Response Signaling

    Czech Academy of Sciences Publication Activity Database

    Chaki, M.; Airik, R.; Ghosh, A.K.; Giles, R.H.; Bryja, Vítězslav

    2012-01-01

    Roč. 150, č. 3 (2012), s. 533-548 ISSN 0092-8674 Institutional support: RVO:68081707 Keywords : MULTIPOINT LINKAGE ANALYSIS * POLYCYSTIC KIDNEY -DISEASE * ATAXIA-TELANGIECTASIA Subject RIV: BO - Biophysics Impact factor: 31.957, year: 2012

  16. Wireless Connectivity to ATM Communication Grid

    National Research Council Canada - National Science Library

    Rajaravivarma, Veeramuthu

    1998-01-01

    The AFOSR funds were used to purchase a 12 port Fore ATM switch, ATM network interface cards, a SUN UltraSPARC workstation, Lucent WavePoint wireless bridge, and Lucent WaveLAN wireless network interface cards...

  17. The telomeric protein TRF2 binds the ATM kinase and can inhibit the ATM-dependent DNA damage response.

    Directory of Open Access Journals (Sweden)

    Jan Karlseder

    2004-08-01

    Full Text Available The telomeric protein TRF2 is required to prevent mammalian telomeres from activating DNA damage checkpoints. Here we show that overexpression of TRF2 affects the response of the ATM kinase to DNA damage. Overexpression of TRF2 abrogated the cell cycle arrest after ionizing radiation and diminished several other readouts of the DNA damage response, including phosphorylation of Nbs1, induction of p53, and upregulation of p53 targets. TRF2 inhibited autophosphorylation of ATM on S1981, an early step in the activation of this kinase. A region of ATM containing S1981 was found to directly interact with TRF2 in vitro, and ATM immunoprecipitates contained TRF2. We propose that TRF2 has the ability to inhibit ATM activation at telomeres. Because TRF2 is abundant at chromosome ends but not elsewhere in the nucleus, this mechanism of checkpoint control could specifically block a DNA damage response at telomeres without affecting the surveillance of chromosome internal damage.

  18. Chloroquine Improves Survival and Hematopoietic Recovery After Lethal Low-Dose-Rate Radiation

    International Nuclear Information System (INIS)

    Lim Yiting; Hedayati, Mohammad; Merchant, Akil A.; Zhang Yonggang; Yu, Hsiang-Hsuan M.; Kastan, Michael B.; Matsui, William; DeWeese, Theodore L.

    2012-01-01

    Purpose: We have previously shown that the antimalarial agent chloroquine can abrogate the lethal cellular effects of low-dose-rate (LDR) radiation in vitro, most likely by activating the ataxia-telangiectasia mutated (ATM) protein. Here, we demonstrate that chloroquine treatment also protects against lethal doses of LDR radiation in vivo. Methods and Materials: C57BL/6 mice were irradiated with a total of 12.8 Gy delivered at 9.4 cGy/hour. ATM null mice from the same background were used to determine the influence of ATM. Chloroquine was administered by two intraperitoneal injections of 59.4 μg per 17 g of body weight, 24 hours and 4 hours before irradiation. Bone marrow cells isolated from tibia, fibula, and vertebral bones were transplanted into lethally irradiated CD45 congenic recipient mice by retroorbital injection. Chimerism was assessed by flow cytometry. In vitro methylcellulose colony-forming assay of whole bone marrow cells and fluorescence activated cell sorting analysis of lineage depleted cells were used to assess the effect of chloroquine on progenitor cells. Results: Mice pretreated with chloroquine before radiation exhibited a significantly higher survival rate than did mice treated with radiation alone (80% vs. 31%, p = 0.0026). Chloroquine administration before radiation did not affect the survival of ATM null mice (p = 0.86). Chloroquine also had a significant effect on the early engraftment of bone marrow cells from the irradiated donor mice 6 weeks after transplantation (4.2% vs. 0.4%, p = 0.015). Conclusion: Chloroquine administration before radiation had a significant effect on the survival of normal but not ATM null mice, strongly suggesting that the in vivo effect, like the in vitro effect, is also ATM dependent. Chloroquine improved the early engraftment of bone marrow cells from LDR-irradiated mice, presumably by protecting the progenitor cells from radiation injury. Chloroquine thus could serve as a very useful drug for protection

  19. Genetics Home Reference: fragile X-associated tremor/ataxia syndrome

    Science.gov (United States)

    ... Share: Email Facebook Twitter Home Health Conditions FXTAS Fragile X-associated tremor/ataxia syndrome Printable PDF Open All ... Javascript to view the expand/collapse boxes. Description Fragile X-associated tremor/ataxia syndrome ( FXTAS ) is characterized by ...

  20. [Knockdown of DNA-PKcs inhibits cell cycle and its mechanism of drug-resistant Bel7402/5-Fu hepatocellular carcinoma cells].

    Science.gov (United States)

    Li, Dayu; Liu, Yun; Yu, Chunbo; Liu, Xiping; Fan, Fang

    2017-12-01

    Objective To study the effect of the knock-down of the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) on the cell cycle of the multidrug-resistant (MDR) Bel7402/5-Fu hepatocellular carcinoma cells and its MDR mechanism. Methods After cationic liposome-mediated siDNA-PKcs oligonucleotide transfection, the drug sensitivity of Bel7402/5-Fu cells to 5-fluorouracil (5-Fu) and adriamycin (ADM) was determined by MTT assay; the cell cycle were detected by flow cytometry; meanwhile, the protein expressions of cell cycle-related proteins P21, cell cycle protein B1 (cyclin B1), cell cycle division protein 2 (CDC2) were tested by Western blotting; the expressions of ataxia telangiectasia mutated (ATM) and p53 at both mRNA and protein levels were detected by real-time PCR and Western blot analysis. Results The MTT results showed siDNA-PKcs increased the chemotherapeutic sensitivity of Bel7402/5-Fu cells to 5-Fu and ADM. The flow cytometric analysis showed siDNA-PKcs decreased the percentage of S-phase cells but increased the percentage of G2/M phase cells. Western blotting showed siDNA-PKcs increased the protein expression of P21 but decreased cyclinB1 and CDC2 proteins. In addition, siDNA-PKcs also increased the expressions of ATM and p53. Conclusion DNA-PKcs silencing increases P21 while decreases cyclin B1 and CDC2 expressions, and finally induces G2/M phase arrest in Bel7402/5-Fu cells, which may be related to ATM-p53 signaling pathway.

  1. Very Late-Onset Friedreich Ataxia with Laryngeal Dystonia

    Directory of Open Access Journals (Sweden)

    Silvia Rota

    2014-12-01

    Full Text Available Friedreich ataxia (FRDA is an autosomal recessive neurodegenerative disorder characterized by progressive gait and limb ataxia, cerebellar, pyramidal and dorsal column involvement, visual defects, scoliosis, pes cavus and cardiomyopathy. It is caused by a homozygous guanine-adenine-adenine (GAA trinucleotide repeat expansion in intron 1 of the frataxin gene (FXN on chromosome 9q13-q21.1. Onset is usually in the first or second decade of life; however, late-onset cases of Freidreich ataxia (LOFA, after the age of 25 years, and very late-onset cases of Freidreich ataxia (VLOFA, after the age of 40 years, have been reported. VLOFA is quite rare and usually presents a milder progression of the disease. We report the case of a 64-year-old woman affected with VLOFA whose first symptoms (balance and gait disturbances occurred at the age of 44 years. At the age of 62 years, she started complaining of a slowly progressive dysphonia showing the clinical aspects of laryngeal dystonia. Molecular analysis showed a 210- and 230-trinucleotide GAA repeat expansion in the two alleles of the FXN gene. Laryngeal dystonia has been reported only in very few cases of ataxia syndrome and never before in FRDA patients. It may represent a rare clinical manifestation of VLOFA thus confirming the high variability of the clinical spectrum of FRDA.

  2. Brain abscesses and hereditary hemorrhagic telangiectasia

    International Nuclear Information System (INIS)

    Vives, Daniel A.; Bauni, Carlos E.; Mendoza, Monica E.

    2003-01-01

    Rendu-Osler-Weber disease or Hereditary Hemorrhagic Telangiectasia (HHT) is a generalized familial angiodysplastic disorder. The neurological manifestations of this entity are due to Central Nervous System vascular lesions or to complications of other visceral lesions such as pulmonary arteriovenous fistulae. This report describes two patients (males, 40 and 61 years old), with brain abscesses associated with HHT. The CT, MRI and Angiographic findings as well as the therapeutic approach are analyzed. Patients with brain abscess of unknown origin must be evaluated for the presence of lung vascular malformation in association with HHT. (author)

  3. CT and MR imaging of acute cerebellar ataxia

    International Nuclear Information System (INIS)

    Shoji, H.; Hirai, S.; Ishikawa, K.; Aramaki, M.; Sato, Y.; Abe, T.; Kojima, K.

    1991-01-01

    An adult female showed mild cerebellar ataxia and CSF pleocytosis following an acute infection of the upper respiratory tract, and was diagnosed as having acute cerebellar ataxia (ACA). CT and MR appearances in the acute stage revealed moderate swelling of the cerebellum and bilaterally increased signal intensity in the cerebellar cortex. (orig.)

  4. Prevalence of spinocerebellar ataxia 36 in a US population.

    Science.gov (United States)

    Valera, Juliana M; Diaz, Tatyana; Petty, Lauren E; Quintáns, Beatriz; Yáñez, Zuleima; Boerwinkle, Eric; Muzny, Donna; Akhmedov, Dmitry; Berdeaux, Rebecca; Sobrido, Maria J; Gibbs, Richard; Lupski, James R; Geschwind, Daniel H; Perlman, Susan; Below, Jennifer E; Fogel, Brent L

    2017-08-01

    To assess the prevalence and clinical features of individuals affected by spinocerebellar ataxia 36 (SCA36) at a large tertiary referral center in the United States. A total of 577 patients with undiagnosed sporadic or familial cerebellar ataxia comprehensively evaluated at a tertiary referral ataxia center were molecularly evaluated for SCA36. Repeat primed PCR and fragment analysis were used to screen for the presence of a repeat expansion in the NOP56 gene. Fragment analysis of triplet repeat primed PCR products identified a GGCCTG hexanucleotide repeat expansion in intron 1 of NOP56 in 4 index cases. These 4 SCA36-positive families comprised 2 distinct ethnic groups: white (European) (2) and Asian (Japanese [1] and Vietnamese [1]). Individuals affected by SCA36 exhibited typical clinical features with gait ataxia and age at onset ranging between 35 and 50 years. Patients also suffered from ataxic or spastic limbs, altered reflexes, abnormal ocular movement, and cognitive impairment. In a US population, SCA36 was observed to be a rare disorder, accounting for 0.7% (4/577 index cases) of disease in a large undiagnosed ataxia cohort.

  5. A 70-year-old male with peripheral neuropathy, ataxia and antigliadin antibodies shows improvement in neuropathy, but not ataxia, after intravenous immunoglobulin and gluten-free diet

    Directory of Open Access Journals (Sweden)

    Dharshan Anandacoomaraswamy

    2008-10-01

    Full Text Available Dharshan Anandacoomaraswamy1, Jagdeesh Ullal2, Aaron I Vinik21Department of Internal Medicine, Coney Island Hospital, Brooklyn, NY, USA; 2Strelitz Diabetes Center, Department of Internal Medicine, Eastern Virginia Medical School, Norfolk, VA, USAAbstract: This is a case of a 70-year-old man with severe peripheral neuropathy, type 2 diabetes and progressively worsening cerebellar ataxia. He was found to have circulating antigliadin and antireticulin antibodies compatible with celiac disease in the absence of intestinal pathology. The peripheral neuropathy improved with a gluten-free diet, antioxidants and intravenous immunoglobulin, whereas the ataxia did not. This case illustrates the need to test for celiac disease in patients with idiopathic ataxia and peripheral neuropathy and the need for alternative therapies for ataxia. Keywords: celiac disease, peripheral neuropathy, autoimmune disease, cerebellar ataxia, type 2 diabetes

  6. Low levels of endogenous or X-ray-induced DNA double-strand breaks activate apoptosis in adult neural stem cells.

    Science.gov (United States)

    Barazzuol, Lara; Rickett, Nicole; Ju, Limei; Jeggo, Penny A

    2015-10-01

    The embryonic neural stem cell compartment is characterised by rapid proliferation from embryonic day (E)11 to E16.5, high endogenous DNA double-strand break (DSB) formation and sensitive activation of apoptosis. Here, we ask whether DSBs arise in the adult neural stem cell compartments, the sub-ventricular zone (SVZ) of the lateral ventricles and the sub-granular zone (SGZ) of the hippocampal dentate gyrus, and whether they activate apoptosis. We used mice with a hypomorphic mutation in DNA ligase IV (Lig4(Y288C)), ataxia telangiectasia mutated (Atm(-/-)) and double mutant Atm(-/-)/Lig4(Y288C) mice. We demonstrate that, although DSBs do not arise at a high frequency in adult neural stem cells, the low numbers of DSBs that persist endogenously in Lig4(Y288C) mice or that are induced by low radiation doses can activate apoptosis. A temporal analysis shows that DSB levels in Lig4(Y288C) mice diminish gradually from the embryo to a steady state level in adult mice. The neonatal SVZ compartment of Lig4(Y288C) mice harbours diminished DSBs compared to its differentiated counterpart, suggesting a process selecting against unfit stem cells. Finally, we reveal high endogenous apoptosis in the developing SVZ of wild-type newborn mice. © 2015. Published by The Company of Biologists Ltd.

  7. Nuclear factor kB (NF-KB): signalosoma and its importance in cancer and inflammatories diseases

    International Nuclear Information System (INIS)

    Echeverri, Nancy P; Mockus, Ismena S

    2008-01-01

    The nuclear factor B (NF- B) is a dimer conformed by Rel family. NF- B is found in cytoplasm bound to inhibitor proteins (I B). I B are phosphorylated by different kinases who are part of signalosome as IeB kinases (IKK , IKK and NF- B essential modulator or NEMO), the mitogenic activated protein kinase (MAPK or p38) and NF-eB inducer kinase (NIK). These kinases are activated by different cytokines and ultraviolet light, I B phosphorylated induce their ubiquitination and proteosome degradation subsequently NF- B release and nucleus translocation. Nowadays, the NF- B activation by oxidative stress, genotoxic stress and DNA damage pathways. In contrast with the classical pathway, in this pathway there are a SUMOilation and nuclear translocation of NEMO. In nucleus NEMO interact with ataxia telangiectasia muted which is activated by chromatin changes and DNA damage. The complex ATM/NEMO is later translocated to cytoplasm where IKK is phosphorylated by ATM bringing to ubiquitination and thus NF- B releasing which is translocated to nucleus. NF- B induces survival rising antioxidants enzymes as superoxide dismutase, catalase and glutathione. These enzymes act in the control of oxidative species levels in the cell. NF- B over expression is related with inflammation and cancer. Nowadays, is development a pharmacological search which can act inhibiting NF- B signalosome molecules, not only to inflammatory disease whereas to radiotherapy and chemotherapy cancer resistance.

  8. Deletion of the B-B' and C-C' regions of inverted terminal repeats reduces rAAV productivity but increases transgene expression.

    Science.gov (United States)

    Zhou, Qingzhang; Tian, Wenhong; Liu, Chunguo; Lian, Zhonghui; Dong, Xiaoyan; Wu, Xiaobing

    2017-07-14

    Inverted terminal repeats (ITRs) of the adeno-associated virus (AAV) are essential for rescue, replication, packaging, and integration of the viral genome. While ITR mutations have been identified in previous reports, we designed a new truncated ITR lacking the B-B' and C-C' regions named as ITRΔBC and investigated its effects on viral genome replication, packaging, and expression of recombinant AAV (rAAV). The packaging ability was compared between ITRΔBC rAAV and wild-type (wt) ITR rAAV. Our results showed the productivity of ITRΔBC rAAV was reduced 4-fold, which is consistent with the 8-fold decrease in the replication of viral genomic DNA of ITRΔBC rAAV compared with wt ITR rAAV. Surprisingly, transgene expression was significantly higher for ITRΔBC rAAV. A preliminary exploration of the underlying mechanisms was carried out by inhibiting and degrading the ataxia telangiectasia mutated (ATM) protein and the Mre11 complex (MRN), respectively, since the rAAV expression was inhibited by the ATM and/or MRN through cis interaction or binding with wt ITRs. We demonstrated that the inhibitory effects were weakened on ITRΔBC rAAV expression. This study suggests deletion in ITR can affect the transgene expression of AAV, which provides a new way to improve the AAV expression through ITRs modification.

  9. Abnormal regulation of DNA replication and increased lethality in ataxia telangiectasia cells exposed to carcinogenic agents

    International Nuclear Information System (INIS)

    Jaspers, N.G.; de Wit, J.; Regulski, M.R.; Bootsma, D.

    1982-01-01

    The effect of different carcinogenic agents on the rate of semiconservative DNA replication in normal and ataxia telangiectasis (AT) cells was investigated. The rate of DNA synthesis in all AT cell strains tested was depressed to a significantly lesser extent than in normal cells after exposure to X-rays under oxia or hypoxia or to bleomycin, agents to which AT cells are hypersensitive. In contrast, inhibition of DNA replication in normal human and AT cells was similar after treatment with some DNA-methylating agents or mitomycin C. Colony-forming ability of AT cells treated with these agents was not different from normal cells. Treatment with 4-nitroquinoline 1-oxide elicited a variable response in both AT and normal cell strains. In some strains, including those shown to be hypersensitive to the drug by other workers, the inhibition of DNA synthesis was more pronounced than in other cell strains, but no significant difference between AT and normal cells could be detected. The rejoining of DNA strand breaks induced by X-rays, measured by DNA elution techniques, occurred within l2 hr after treatment and could not be correlated with the difference in DNA synthesis inhibition in AT and normal cells. After low doses of X-rays, AT cells rejoined single-strand breaks slightly more slowly than did normal cells. The rate of DNA replication in X-irradiation AT and normal cells was not affected by nicotinamide, an inhibitor of poly(adenosine diphosphate ribose) synthesis. These data indicate that the diminished inhibition of DNA replication in carcinogen-treated AT cells (a) is a general characteristic of all AT cell strains, (b) correlates with AT cellular hypersensitivity, (c) is not directly caused by the bulk of the DNA strand breaks produced by carcinogenic agents, and (d) is not based on differences in the induction of poly(adenosine diphosphate ribose) synthesis between X-irradiated AT and normal cells

  10. Functional and nonfunctional testing of ATM networks

    Science.gov (United States)

    Ricardo, Manuel; Ferreira, M. E. P.; Guimaraes, Francisco E.; Mamede, J.; Henriques, M.; da Silva, Jorge A.; Carrapatoso, E.

    1995-02-01

    ATM network will support new multimedia services that will require new protocols, those services and protocols will need different test strategies and tools. In this paper, the concepts of functional and non-functional testers of ATM networks are discussed, a multimedia service and its requirements are presented and finally, a summary description of an ATM network and of the test tool that will be used to validate it are presented.

  11. Synchronous and Asynchronous ATM Multiplexor Properties Comparsion

    OpenAIRE

    Jan Zabka

    2006-01-01

    The article is aimed to ATM multiplexor computer model utilisation. Based on simulation runs we try to review aspects of use a synchronous and asynchronous ATM multiplexors. ATM multiplexor is the input queuing model with three inputs. Synchronous multiplexor works without an input priority. Multiplexor inputs are served periodically. Asynchronous multiplexor model supports several queuing and priority mechanisms. CLR and CTD are basic performance parameters. Input cell flows are genera...

  12. ATM-induced radiosensitization in vitro and in vivo

    International Nuclear Information System (INIS)

    Song, C. W.; Griffin, R. J.; Park, H. J.; Chung, H. S.; Choi, E. K.; Ahn, S. D.; Rhee, Y. H.; Ha, S. W.

    2002-01-01

    It has been known that ATM plays a central role in response of cells to ionizing radiation by enhancing DNA repair. Based in large part on studies of the homologous proteins in yeast, it is predicted that ATM function as proximal signal transducers in G1, S, and G2 checkpoint pathways. With the exception of p53, the downstream components of these pathways remain largely undefined. We have investigated the feasibility of increasing radiosensitivity of tumor cells with the use of ATM inhibitors such as caffeine, pentoxifylline, and wortmannin. Also in an effort to examine and understand the molecular mechanism by which ATM might exert its cellular effects, we have expressed the full length wild type ATM in RKO cells

  13. NPP ATMS Snowfall Rate Product

    Science.gov (United States)

    Meng, Huan; Ferraro, Ralph; Kongoli, Cezar; Wang, Nai-Yu; Dong, Jun; Zavodsky, Bradley; Yan, Banghua

    2015-01-01

    Passive microwave measurements at certain high frequencies are sensitive to the scattering effect of snow particles and can be utilized to retrieve snowfall properties. Some of the microwave sensors with snowfall sensitive channels are Advanced Microwave Sounding Unit (AMSU), Microwave Humidity Sounder (MHS) and Advance Technology Microwave Sounder (ATMS). ATMS is the follow-on sensor to AMSU and MHS. Currently, an AMSU and MHS based land snowfall rate (SFR) product is running operationally at NOAA/NESDIS. Based on the AMSU/MHS SFR, an ATMS SFR algorithm has been developed recently. The algorithm performs retrieval in three steps: snowfall detection, retrieval of cloud properties, and estimation of snow particle terminal velocity and snowfall rate. The snowfall detection component utilizes principal component analysis and a logistic regression model. The model employs a combination of temperature and water vapor sounding channels to detect the scattering signal from falling snow and derive the probability of snowfall (Kongoli et al., 2015). In addition, a set of NWP model based filters is also employed to improve the accuracy of snowfall detection. Cloud properties are retrieved using an inversion method with an iteration algorithm and a two-stream radiative transfer model (Yan et al., 2008). A method developed by Heymsfield and Westbrook (2010) is adopted to calculate snow particle terminal velocity. Finally, snowfall rate is computed by numerically solving a complex integral. NCEP CMORPH analysis has shown that integration of ATMS SFR has improved the performance of CMORPH-Snow. The ATMS SFR product is also being assessed at several NWS Weather Forecast Offices for its usefulness in weather forecast.

  14. Introduction to multiprotocol over ATM (MPOA)

    Science.gov (United States)

    Fredette, Andre N.

    1997-10-01

    Multiprotocol over ATM (MPOA) is a new protocol specified by the ATM Forum. MPOA provides a framework for effectively synthesizing bridging and routing with ATM in an environment of diverse protocols and network technologies. The primary goal of MPOA is the efficient transfer of inter-subnet unicast data in a LAN Emulation (LANE) environment. MPOA integrates LANE and the next hop resolution protocol (NHRP) to preserve the benefits of LAN Emulation, while allowing inter-subnet, internetwork layer protocol communication over ATM VCCs without requiring routers in the data path. It reduces latency and the internetwork layer forwarding load on backbone routers by enabling direct connectivity between ATM-attached edge devices (i.e., shortcuts). To establish these shortcuts, MPOA uses both routing and bridging information to locate the edge device closest to the addressed end station. By integrating LANE and NHRP, MPOA allows the physical separation of internetwork layer route calculation and forwarding, a technique known as virtual routing. This separation provides a number of key benefits including enhanced manageability and reduced complexity of internetwork layer capable edge devices. This paper provides an overview of MPOA that summarizes the goals, architecture, and key attributes of the protocol. In presenting this overview, the salient attributes of LANE and NHRP are described as well.

  15. Connecting Remote Clusters with ATM

    Energy Technology Data Exchange (ETDEWEB)

    Hu, T.C.; Wyckoff, P.S.

    1998-10-01

    Sandia's entry into utilizing clusters of networked workstations is called Computational Plant or CPlant for short. The design of CPlant uses Ethernet to boot the individual nodes, Myrinet to communicate within a node cluster, and ATM to connect between remote clusters. This SAND document covers the work done to enable the use of ATM on the CPlant nodes in the Fall of 1997.

  16. Nuclear survivin and its relationship to DNA damage repair genes in non-small cell lung cancer investigated using tissue array.

    Directory of Open Access Journals (Sweden)

    Songliu Hu

    Full Text Available To investigate the predictive role and association of nuclear survivin and the DNA double-strand breaks repair genes in non-small cell lung cancer (NSCLC: DNA-dependent protein kinase catalytic subunit (DNA-PKcs, Ku heterodimeric regulatory complex 70-KD subunit (Ku70 and ataxia-telangiectasia mutated (ATM.The protein expression of nuclear survivin, DNA-PKcs, Ku70 and ATM were investigated using immunohistochemistry in tumors from 256 patients with surgically resected NSCLC. Furthermore, we analyzed the correlation between the expression of nuclear survivin, DNA-PKcs, Ku70 and ATM. Univariate and multivariate analyses were performed to determine the prognostic factors that inuenced the overall survival and disease-free survival of NSCLC.The expression of nuclear survivin, DNA-PKcs, Ku70 and ATM was significantly higher in tumor tissues than in normal tissues. By dichotomizing the specimens as expressing low or high levels of nuclear survivin, nuclear survivin correlated significantly with the pathologic stage (P = 0.009 and lymph node status (P = 0.004. The nuclear survivin levels were an independent prognostic factor for both the overall survival and the disease-free survival in univariate and multivariate analyses. Patients with low Ku70 and DNA-PKcs expression had a greater benefit from radiotherapy than patients with high expression of Ku70 (P = 0.012 and DNA-PKcs (P = 0.02. Nuclear survivin expression positively correlated with DNA-PKcs (P<0.001 and Ku70 expression (P<0.001.Nuclear survivin may be a prognostic factor for overall survival in patients with resected stage I-IIIA NSCLC. DNA-PKcs and Ku70 could predict the effect of radiotherapy in patients with NSCLC. Nuclear survivin may also stimulates DNA double-strand breaks repair by its interaction with DNA-PKcs and Ku70.

  17. Ionizing Radiation Activates AMP-Activated Kinase (AMPK): A Target for Radiosensitization of Human Cancer Cells

    International Nuclear Information System (INIS)

    Sanli, Toran; Rashid, Ayesha; Liu Caiqiong

    2010-01-01

    Purpose: Adenosine monophosphate (AMP)-activated kinase (AMPK) is a molecular energy sensor regulated by the tumor suppressor LKB1. Starvation and growth factors activate AMPK through the DNA damage sensor ataxia-telangiectasia mutated (ATM). We explored the regulation of AMPK by ionizing radiation (IR) and its role as a target for radiosensitization of human cancer cells. Methods and Materials: Lung, prostate, and breast cancer cells were treated with IR (2-8 Gy) after incubation with either ATM or AMPK inhibitors or the AMPK activator metformin. Then, cells were subjected to either lysis and immunoblotting, immunofluorescence microscopy, clonogenic survival assays, or cell cycle analysis. Results: IR induced a robust phosphorylation and activation of AMPK in all tumor cells, independent of LKB1. IR activated AMPK first in the nucleus, and this extended later into cytoplasm. The ATM inhibitor KU-55933 blocked IR activation of AMPK. AMPK inhibition with Compound C or anti-AMPK α subunit small interfering RNA (siRNA) blocked IR induction of the cell cycle regulators p53 and p21 waf/cip as well as the IR-induced G2/M arrest. Compound C caused resistance to IR, increasing the surviving fraction after 2 Gy, but the anti-diabetic drug metformin enhanced IR activation of AMPK and lowered the surviving fraction after 2 Gy further. Conclusions: We provide evidence that IR activates AMPK in human cancer cells in an LKB1-independent manner, leading to induction of p21 waf/cip and regulation of the cell cycle and survival. AMPK appears to (1) participate in an ATM-AMPK-p21 waf/cip pathway, (2) be involved in regulation of the IR-induced G2/M checkpoint, and (3) may be targeted by metformin to enhance IR responses.

  18. ATM protein is deficient in over 40% of lung adenocarcinomas.

    Science.gov (United States)

    Villaruz, Liza C; Jones, Helen; Dacic, Sanja; Abberbock, Shira; Kurland, Brenda F; Stabile, Laura P; Siegfried, Jill M; Conrads, Thomas P; Smith, Neil R; O'Connor, Mark J; Pierce, Andrew J; Bakkenist, Christopher J

    2016-09-06

    Lung cancer is the leading cause of cancer-related mortality in the USA and worldwide, and of the estimated 1.2 million new cases of lung cancer diagnosed every year, over 30% are lung adenocarcinomas. The backbone of 1st-line systemic therapy in the metastatic setting, in the absence of an actionable oncogenic driver, is platinum-based chemotherapy. ATM and ATR are DNA damage signaling kinases activated at DNA double-strand breaks (DSBs) and stalled and collapsed replication forks, respectively. ATM protein is lost in a number of cancer cell lines and ATR kinase inhibitors synergize with cisplatin to resolve xenograft models of ATM-deficient lung cancer. We therefore sought to determine the frequency of ATM loss in a tissue microarray (TMA) of lung adenocarcinoma. Here we report the validation of a commercial antibody (ab32420) for the identification of ATM by immunohistochemistry and estimate that 61 of 147 (41%, 95% CI 34%-50%) cases of lung adenocarcinoma are negative for ATM protein expression. As a positive control for ATM staining, nuclear ATM protein was identified in stroma and immune infiltrate in all evaluable cases. ATM loss in lung adenocarcinoma was not associated with overall survival. However, our preclinical findings in ATM-deficient cell lines suggest that ATM could be a predictive biomarker for synergy of an ATR kinase inhibitor with standard-of-care cisplatin. This could improve clinical outcome in 100,000's of patients with ATM-deficient lung adenocarcinoma every year.

  19. Defective fluid shear stress mechanotransduction mediates hereditary hemorrhagic telangiectasia

    Science.gov (United States)

    Baeyens, Nicolas; Larrivée, Bruno; Ola, Roxana; Hayward-Piatkowskyi, Brielle; Dubrac, Alexandre; Huang, Billy; Ross, Tyler D.; Coon, Brian G.; Min, Elizabeth; Tsarfati, Maya; Tong, Haibin; Eichmann, Anne

    2016-01-01

    Morphogenesis of the vascular system is strongly modulated by mechanical forces from blood flow. Hereditary hemorrhagic telangiectasia (HHT) is an inherited autosomal-dominant disease in which arteriovenous malformations and telangiectasias accumulate with age. Most cases are linked to heterozygous mutations in Alk1 or Endoglin, receptors for bone morphogenetic proteins (BMPs) 9 and 10. Evidence suggests that a second hit results in clonal expansion of endothelial cells to form lesions with poor mural cell coverage that spontaneously rupture and bleed. We now report that fluid shear stress potentiates BMPs to activate Alk1 signaling, which correlates with enhanced association of Alk1 and endoglin. Alk1 is required for BMP9 and flow responses, whereas endoglin is only required for enhancement by flow. This pathway mediates both inhibition of endothelial proliferation and recruitment of mural cells; thus, its loss blocks flow-induced vascular stabilization. Identification of Alk1 signaling as a convergence point for flow and soluble ligands provides a molecular mechanism for development of HHT lesions. PMID:27646277

  20. Human hereditary diseases associated with elevated frequency of chromosome aberrations

    International Nuclear Information System (INIS)

    Ejima, Yosuke

    1988-01-01

    Human recessive diseases collectively known as chromosome breakage syndromes include Fanconi's anemia, Bloom's syndrome and ataxia telangiectasia. Cells from these patients show chromosome instabilities both spontaneously and following treatments with radiations or certain chemicals, where defects in DNA metabolisms are supposed to be involved. Cells from patients with ataxia telangiectasia are hypersensitive to ionizing radiations, though DNA replication is less affected than in normal cells. Chromatid-type as well as chromosom-type aberrations are induced in cells irradiated in G 0 or G 1 phases. These unusual responses to radiations may provide clues for understanding the link between DNA replicative response and cellular radiosensitivity. Alterations in cellular radiosensitivity or spontaneous chromosome instabilities are observed in some patients with congenital chromosome anomalies or dominant diseases, where underlying defects may be different from those in recessive diseases. (author)

  1. Human hereditary diseases associated with elevated frequency of chromosome aberrations

    Energy Technology Data Exchange (ETDEWEB)

    Ejima, Yosuke; Ikushima, Takaji (ed.)

    1988-07-01

    Human recessive diseases collectively known as chromosome breakage syndromes include Fanconi's anemia, Bloom's syndrome and ataxia telangiectasia. Cells from these patients show chromosome instabilities both spontaneously and following treatments with radiations or certain chemicals, where defects in DNA metabolisms are supposed to be involved. Cells from patients with ataxia telangiectasia are hypersensitive to ionizing radiations, though DNA replication is less affected than in normal cells. Chromatid-type as well as chromosom-type aberrations are induced in cells irradiated in G/sub 0/ or G/sub 1/ phases. These unusual responses to radiations may provide clues for understanding the link between DNA replicative response and cellular radiosensitivity. Alterations in cellular radiosensitivity or spontaneous chromosome instabilities are observed in some patients with congenital chromosome anomalies or dominant diseases, where underlying defects may be different from those in recessive diseases.

  2. Telangiectasia hemorrágica hereditária e malformações arteriovenosas pulmonares - Embolização com rolhão vascular Amplatzer Hereditary hemorrhagic telangiectasia and pulmonary arteriovenous malformations - Embolization with Amplatzer vascular plug

    Directory of Open Access Journals (Sweden)

    Cláudia Sofia Santos

    2009-03-01

    Full Text Available As malformações arteriovenosas pulmonares (MAVP estão associadas a telangiectasia hemorrágica hereditária em cerca de 70% dos casos, podendo cursar com complicações neurológicas graves decorrentes do embolismo paradoxal potencial. A terapêutica das malformações é realizada no sentido de prevenir estas complicações. Descreve-se o caso clínico de uma doente com duas MAVP, no contexto de telangiectasia hemorrágica hereditária,submetida a embolização com o rolhão vascular Amplatzer. Este novo dispositivo é cada vez mais utilizado nestas situações, salientando-se algumas das suas características e vantagens em relação a outras técnicas de embolização mais frequentemente utilizadas.Pulmonary arteriovenous malformations (PAVMs are associated to hereditary hemorrhagic telangiectasia in about 70% of the cases. PAVMs are associated to serious neurologic complications, secondary to inherent paradoxical embolisms. Treatment of the malformations is done to prevent these complications. The authors report a clinical case of a patient with two PAVMs, with hereditary hemorrhagic telangiectasia, who was treated by embolization with na Amplatzer vascular plug, a new device increasingly used in these situations. The authors emphasise some of its characteristics and advantages when compared with other embolization techniques most commonly used.

  3. ATM Card Cloning and Ethical Considerations.

    Science.gov (United States)

    Kaur, Paramjit; Krishan, Kewal; Sharma, Suresh K; Kanchan, Tanuj

    2018-05-01

    With the advent of modern technology, the way society handles and performs monetary transactions has changed tremendously. The world is moving swiftly towards the digital arena. The use of Automated Teller Machine (ATM) cards (credit and debit) has led to a "cash-less society" and has fostered digital payments and purchases. In addition to this, the trust and reliance of the society upon these small pieces of plastic, having numbers engraved upon them, has increased immensely over the last two decades. In the past few years, the number of ATM fraud cases has increased exponentially. With the money of the people shifting towards the digital platform, ATM skimming has become a problem that has eventually led to a global outcry. The present review discusses the serious repercussions of ATM card cloning and the associated privacy, ethical and legal concerns. The preventive measures which need to be taken and adopted by the government authorities to mitigate the problem have also been discussed.

  4. Friedreich's ataxia mimicking hereditary motor and sensory neuropathy.

    Science.gov (United States)

    Panas, Marios; Kalfakis, Nikolaos; Karadima, Georgia; Davaki, Panagiota; Vassilopoulos, Demetris

    2002-11-01

    Four patients from three unrelated families, with clinical and electrophysiological findings compatible with the diagnosis of hereditary motor and sensory neuropathy, are presented. The molecular analysis showed that the affected individuals were homozygous for the mutation in the X25 gene, characteristic of Friedreich's ataxia. These patients seem to represent a form of Friedreich's ataxia mimicking Charcot-Marie-Tooth disease.

  5. Treatment of Hereditary Hemorrhagic Telangiectasia-Related Epistaxis.

    Science.gov (United States)

    Sautter, Nathan B; Smith, Timothy L

    2016-06-01

    Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disease with an incidence of 1:5000. Recurrent, spontaneous epistaxis is the most common presenting symptom. Severity of epistaxis varies widely, from mild, self-limited nosebleeds to severe, life-threatening nasal hemorrhage. Treatment of HHT-related epistaxis presents a challenge to the otolaryngologist due to the recurrent, persistent nature of epistaxis often requiring multiple treatments. Treatment modalities range from conservative topical therapies to more aggressive surgical treatments. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. ATM security via "Stargate" solution

    OpenAIRE

    Hensley, Katrina; Ludden, Fredrick

    1999-01-01

    Approved for public release, distribution unlimited. In today's world of integrating voice, video and data into a single network, Asynchronous Transfer Mode (ATM) networks have become prevalent in the Department of Defense. The Department of Defense's critical data will have to pass through public networks, which causes concern for security. This study presents an efficient solution aimed at authenticating communications over public ATM networks. The authenticating device, Stargate, utiliz...

  7. Fabrication and characterization of MCC approved testing material - ATM-1 glass

    International Nuclear Information System (INIS)

    Wald, J.W.

    1985-10-01

    The Materials Characterization Center Approved Testing Material ATM-1 is a borosilicate glass that incorporates nonradioactive constituents and uranium to represent high-level waste (HLW) resulting from the reprocessing of commercial nuclear reactor fuel. Its composition is based upon the simulated HLW glass type 76-68 to which depleted uranium has been added as UO 2 . Three separate lots of ATM-1 glass have been fabricated, designated ATM-1a, ATM-1b, and ATM-1c. Limited analyses and microstructural evaluations were conducted on each type. Each lot of ATM-1 glass was produced from a feedstock melted in an air atmosphere at between 1150 to 1200 0 C and cast into stress annealed rectangular bars. Bars of ATM-1a were nominally 1.3 x 1.3 x 7.6 cm (approx.36 g each), bars of ATM-1b were nominally 2 x 2.5 x 17.5 cm (approx.190 g each) and bars of ATM-1c were nominally 1.9 x 1.9 x 15 cm (approx.170 g each). Thirteen bars of ATM-1a, 14 bars of ATM-1b, and 6 bars of ATM-1c were produced. Twelve random samples from each of lots ATM-1a, ATM-1b, and ATM-1c were analyzed. The concentrations (except for U and Cs) were obtained by Inductively-Coupled Argon Plasma Atomic Emission Spectroscopy analysis. Cesium analysis was performed by Atomic Absorption Spectroscopy, while uranium was analyzed by Pulsed Laser Fluorometry. X-ray diffraction analysis of four samples indicated that lot ATM-1a had no detectable crystalline phases (<3 wt %), while ATM-1b and ATM-1c contained approx.3 to 5 wt % iron-chrome spinel crystals. These concentrations of secondary spinel component are not considered uncommon. Scanning electron microscopy examination of fracture surfaces revealed only a random, apparently crystalline, second phase (1-10 μm diam) and a random distribution of small voids or bubbles (approx.1 μm nominal diam)

  8. Missense mutations in ITPR1 cause autosomal dominant congenital nonprogressive spinocerebellar ataxia

    Directory of Open Access Journals (Sweden)

    Huang Lijia

    2012-09-01

    Full Text Available Abstract Background Congenital nonprogressive spinocerebellar ataxia is characterized by early gross motor delay, hypotonia, gait ataxia, mild dysarthria and dysmetria. The clinical presentation remains fairly stable and may be associated with cerebellar atrophy. To date, only a few families with autosomal dominant congenital nonprogressive spinocerebellar ataxia have been reported. Linkage to 3pter was demonstrated in one large Australian family and this locus was designated spinocerebellar ataxia type 29. The objective of this study is to describe an unreported Canadian family with autosomal dominant congenital nonprogressive spinocerebellar ataxia and to identify the underlying genetic causes in this family and the original Australian family. Methods and Results Exome sequencing was performed for the Australian family, resulting in the identification of a heterozygous mutation in the ITPR1 gene. For the Canadian family, genotyping with microsatellite markers and Sanger sequencing of ITPR1 gene were performed; a heterozygous missense mutation in ITPR1 was identified. Conclusions ITPR1 encodes inositol 1,4,5-trisphosphate receptor, type 1, a ligand-gated ion channel that mediates calcium release from the endoplasmic reticulum. Deletions of ITPR1 are known to cause spinocerebellar ataxia type 15, a distinct and very slowly progressive form of cerebellar ataxia with onset in adulthood. Our study demonstrates for the first time that, in addition to spinocerebellar ataxia type 15, alteration of ITPR1 function can cause a distinct congenital nonprogressive ataxia; highlighting important clinical heterogeneity associated with the ITPR1 gene and a significant role of the ITPR1-related pathway in the development and maintenance of the normal functions of the cerebellum.

  9. Ataxia rating scales are age-dependent in healthy children

    NARCIS (Netherlands)

    Brandsma, Rick; Spits, Anne H.; Kuiper, Marieke J.; Lunsing, Roelinka J.; Burger, Huibert; Kremer, Hubertus P.; Sival, Deborah A.

    AIM: To investigate ataxia rating scales in children for reliability and the effect of age and sex. METHOD: Three independent neuropaediatric observers cross-sectionally scored a set of paediatric ataxia rating scales in a group of 52 healthy children (26 males, 26 females) aged 4 to 16 years (mean

  10. Role of Oxidative Stress in Hepatocarcinogenesis Induced by Hepatitis C Virus

    Directory of Open Access Journals (Sweden)

    Kyoko Tsukiyama-Kohara

    2012-11-01

    Full Text Available Hepatitis C virus (HCV easily establishes chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC. During the progression of HCV infections, reactive oxygen species (ROS are generated, and these ROS then induce significant DNA damage. The role of ROS in the pathogenesis of HCV infection is still not fully understood. Recently, we found that HCV induced the expression of 3β-hydroxysterol ∆24-reductase (DHCR24. We also found that a HCV responsive region is present in the 5'-flanking genomic promoter region of DHCR24 and the HCV responsive region was characterized as (−167/−140. Moreover, the transcription factor Sp1 was found to bind to this region in response to oxidative stress under the regulation of ataxia telangiectasia mutated (ATM kinase. Overexpression of DHCR24 impaired p53 activity by suppression of acetylation and increased interaction with MDM2. This impairment of p53 suppressed the hydrogen peroxide-induced apoptotic response in hepatocytes. Thus, a target of oxidative stress in HCV infection is DHCR24 through Sp1, which suppresses apoptotic responses and increases tumorigenicity.

  11. A survey of IP over ATM architectures

    Energy Technology Data Exchange (ETDEWEB)

    Chen, H.; Tsang, R.; Brandt, J.; Hutchins, J.

    1997-07-01

    Over the past decade, the Internet has burgeoned into a worldwide information highway consisting of approximately 5 million hosts on over 45,000 interconnected networks. This unprecedented growth, together with the introduction of multimedia workstations, has spurred the development of innovative applications that require high speed, low latency, and real-time transport. Today`s Internet can neither scale in its bandwidth nor guarantee the Quality of Services (QoS) necessary to meet these performance requirements. Many network researchers propose to use the Asynchronous Transfer Mode (ATM) technology as the underlying infrastructure for the next generation of workgroup, campus, and enterprise IP networks. Since ATM is significantly different from today`s legacy network technologies, efficient implementation of IP over ATM is especially challenging. This tutorial paper covers several existing proposals that integrate IP over ATM.

  12. Differential responses to high- and low-dose ultraviolet-B stress in tobacco Bright Yellow-2 cells

    Science.gov (United States)

    Takahashi, Shinya; Kojo, Kei H.; Kutsuna, Natsumaro; Endo, Masaki; Toki, Seiichi; Isoda, Hiroko; Hasezawa, Seiichiro

    2015-01-01

    Ultraviolet (UV)-B irradiation leads to DNA damage, cell cycle arrest, growth inhibition, and cell death. To evaluate the UV-B stress–induced changes in plant cells, we developed a model system based on tobacco Bright Yellow-2 (BY-2) cells. Both low-dose UV-B (low UV-B: 740 J m−2) and high-dose UV-B (high UV-B: 2960 J m−2) inhibited cell proliferation and induced cell death; these effects were more pronounced at high UV-B. Flow cytometry showed cell cycle arrest within 1 day after UV-B irradiation; neither low- nor high-UV-B–irradiated cells entered mitosis within 12 h. Cell cycle progression was gradually restored in low-UV-B–irradiated cells but not in high-UV-B–irradiated cells. UV-A irradiation, which activates cyclobutane pyrimidine dimer (CPD) photolyase, reduced inhibition of cell proliferation by low but not high UV-B and suppressed high-UV-B–induced cell death. UV-B induced CPD formation in a dose-dependent manner. The amounts of CPDs decreased gradually within 3 days in low-UV-B–irradiated cells, but remained elevated after 3 days in high-UV-B–irradiated cells. Low UV-B slightly increased the number of DNA single-strand breaks detected by the comet assay at 1 day after irradiation, and then decreased at 2 and 3 days after irradiation. High UV-B increased DNA fragmentation detected by the terminal deoxynucleotidyl transferase dUTP nick end labeling assay 1 and 3 days after irradiation. Caffeine, an inhibitor of ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related (ATR) checkpoint kinases, reduced the rate of cell death in high-UV-B–irradiated cells. Our data suggest that low-UV-B–induced CPDs and/or DNA strand-breaks inhibit DNA replication and proliferation of BY-2 cells, whereas larger contents of high-UV-B–induced CPDs and/or DNA strand-breaks lead to cell death. PMID:25954287

  13. JS-K, a nitric oxide prodrug, induces DNA damage and apoptosis in HBV-positive hepatocellular carcinoma HepG2.2.15 cell.

    Science.gov (United States)

    Liu, Zhengyun; Li, Guangmin; Gou, Ying; Xiao, Dongyan; Luo, Guo; Saavedra, Joseph E; Liu, Jie; Wang, Huan

    2017-08-01

    Hepatocellular carcinoma (HCC) is the most important cause of cancer-related death, and 85% of HCC is caused by chronic HBV infection, the prognosis of patients and the reduction of HBV DNA levels remain unsatisfactory. JS-K, a nitric oxide-releasing diazeniumdiolates, is effective against various tumors, but little is known on its effects on HBV positive HCC. We found that JS-K reduced the expression of HBsAg and HBeAg in HBV-positive HepG2.2.15 cells. This study aimed to further examine anti-tumor effects of JS-K on HepG2.2.15 cells. The MTT assay and colony forming assay were used to study the cell growth inhibition of JS-K; scratch assay and transwell assay were performed to detect cell migration. The cell cycle was detected by flow cytometry. The immunofluorescence, flow cytometry analysis, and western blot were used to study DNA damage and cell apoptosis. JS-K inhibited HepG2.2.15 cell growth in a dose-dependent manner, suppressed cell colony formation and migration, arrested cells gather in the G2 phase. JS-K (1-20μM) increased the expression of DNA damage-associated protein phosphorylation H 2 AX (γH 2 AX), phosphorylation of checkpoint kinase 1 (p-Chk1), phosphorylation of checkpoint kinase 2 (p-Chk2), ataxia-telangiectasia mutated (ATM), phosphorylation of ataxia-telangiectasia mutated rad3-related (p-ATR) and apoptotic-associated proteins cleaved caspase-3, cleaved caspase-7, cleaved poly ADP-ribose polymerase (cleaved PARP). The study demonstrated JS-K is effective against HBV-positive HepG2.2.15 cells, the mechanisms are not only related to inhibition of HBsAg and HBeAg secretion, but also related with induction of DNA damage and apoptosis. JS-K is a promising anti-cancer candidate against HBV-positive HCC. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  14. Kaempferol induces DNA damage and inhibits DNA repair associated protein expressions in human promyelocytic leukemia HL-60 cells.

    Science.gov (United States)

    Wu, Lung-Yuan; Lu, Hsu-Feng; Chou, Yu-Cheng; Shih, Yung-Luen; Bau, Da-Tian; Chen, Jaw-Chyun; Hsu, Shu-Chun; Chung, Jing-Gung

    2015-01-01

    Numerous evidences have shown that plant flavonoids (naturally occurring substances) have been reported to have chemopreventive activities and protect against experimental carcinogenesis. Kaempferol, one of the flavonoids, is widely distributed in fruits and vegetables, and may have cancer chemopreventive properties. However, the precise underlying mechanism regarding induced DNA damage and suppressed DNA repair system are poorly understood. In this study, we investigated whether kaempferol induced DNA damage and affected DNA repair associated protein expression in human leukemia HL-60 cells in vitro. Percentages of viable cells were measured via a flow cytometry assay. DNA damage was examined by Comet assay and DAPI staining. DNA fragmentation (ladder) was examined by DNA gel electrophoresis. The changes of protein levels associated with DNA repair were examined by Western blotting. Results showed that kaempferol dose-dependently decreased the viable cells. Comet assay indicated that kaempferol induced DNA damage (Comet tail) in a dose-dependent manner and DAPI staining also showed increased doses of kaempferol which led to increased DNA condensation, these effects are all of dose-dependent manners. Western blotting indicated that kaempferol-decreased protein expression associated with DNA repair system, such as phosphate-ataxia-telangiectasia mutated (p-ATM), phosphate-ataxia-telangiectasia and Rad3-related (p-ATR), 14-3-3 proteins sigma (14-3-3σ), DNA-dependent serine/threonine protein kinase (DNA-PK), O(6)-methylguanine-DNA methyltransferase (MGMT), p53 and MDC1 protein expressions, but increased the protein expression of p-p53 and p-H2AX. Protein translocation was examined by confocal laser microscopy, and we found that kaempferol increased the levels of p-H2AX and p-p53 in HL-60 cells. Taken together, in the present study, we found that kaempferol induced DNA damage and suppressed DNA repair and inhibited DNA repair associated protein expression in HL-60

  15. Nuclear and cytoplasmic signalling in the cellular response to ionising radiation

    International Nuclear Information System (INIS)

    Szumiel, Irena

    2001-01-01

    DNA is the universal primary target for ionising radiation; however, the cellular response is highly diversified not only by differential DNA repair ability. The monitoring system for the ionising radiation-inflicted DNA damage consists of 3 apparently independently acting enzymes which are activated by DNA breaks: two protein kinases, ATM (ataxia telangiectasia mutated) and DNA-PK (DNA-dependent protein kinase) and a poly(ADP-ribose) polymerase, PARP-1. These 3 enzymes are the source of alarm signals, which affect to various extents DNA repair, progression through the cell cycle and eventually the pathway to cell death. Their functions probably are partly overlapping. On the side of DNA repair their role consists in recruiting and/or activating the repair enzymes, as well as preventing illegitimate recombination of the damaged sites. A large part of the nuclear signalling pathway, including the integrating role of TP53 has been revealed. Two main signalling pathways start at the plasma membrane: the MAPK/ERK (mitogen and extracellular signal regulated protein kinase family) 'survival pathway' and the SAPK/JNK (stress-activated protein kinase/c-Jun N-terminal kinase) 'cell death pathway'. The balance between them is likely to determine the cell's fate. An additional important 'survival pathway' starts at the insulin-like growth factor type I receptor (IGF-IR), involves phosphoinositide- 3 kinase and Akt kinase and is targeted at inactivation of the pro-apoptotic BAD protein. Interestingly, over-expression of IGF-IR almost entirely abrogates the extreme radiation sensitivity of ataxia telangiectasia cells. When DNA break rejoining is impaired, the cell is unconditionally radiation sensitive. The fate of a repair-competent cell is determined by the time factor: the cell cycle arrest should be long enough to ensure the completion of repair. Incomplete repair or misrepair may be tolerated, when generation of the death signal is prevented. So, the character and timing

  16. Spectrum of centrosome autoantibodies in childhood varicella and post-varicella acute cerebellar ataxia

    Directory of Open Access Journals (Sweden)

    Stinton Laura M

    2003-09-01

    Full Text Available Abstract Background Sera from children with post-varicella infections have autoantibodies that react with centrosomes in brain and tissue culture cells. We investigated the sera of children with infections and post-varicella ataxia and related conditions for reactivity to five recombinant centrosome proteins: γγ-enolase, pericentrin, ninein, PCM-1, and Mob1. Methods Sera from 12 patients with acute post-varicella ataxia, 1 with post-Epstein Barr virus (EBV ataxia, 5 with uncomplicated varicella infections, and other conditions were tested for reactivity to cryopreserved cerebellum tissue and recombinant centrosome proteins. The distribution of pericentrin in the cerebellum was studied by indirect immunofluorescence (IIF using rabbit antibodies to the recombinant protein. Antibodies to phospholipids (APL were detected by ELISA. Results Eleven of 12 children with post-varicella ataxia, 4/5 children with uncomplicated varicella infections, 1/1 with post-EBV ataxia, 2/2 with ADEM, 1/2 with neuroblastoma and ataxia, and 2/2 with cerebellitis had antibodies directed against 1 or more recombinant centrosome antigens. Antibodies to pericentrin were seen in 5/12 children with post-varicella ataxia but not in any of the other sera tested. IIF demonstrated that pericentrin is located in axons and centrosomes of cerebellar cells. APL were detected in 75% of the sera from children with post-varicella ataxia and 50% of children with varicella without ataxia and in none of the controls. Conclusion This is the first study to show the antigen specificity of anti-centrosome antibodies in children with varicella. Our data suggest that children with post-varicella ataxia have unique autoantibody reactivity to pericentrin.

  17. Treatment for ataxia in multiple sclerosis.

    Science.gov (United States)

    Mills, R J; Yap, L; Young, C A

    2007-01-24

    Disabling tremor or ataxia is common in multiple sclerosis (MS) and up to 80% of patients experience tremor or ataxia at some point during their disease. A variety of treatments are available, ranging from pharmacotherapy or stereotactic neurosurgery to neurorehabilitation. To assess the efficacy and tolerability of both pharmacological and non-pharmacologic treatments of ataxia in patients with MS. The following electronic resources were searched: Cochrane MS Group trials register (June 2006), the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 2, 2006), National Health Service National Research Register (NRR) including the Medical Research Council Clinical Trials Directory (Issue 2, 2006), MEDLINE (January 1996 to June 2006), and EMBASE (Jan 1988 to June 2006). Manual searches of bibliographies of relevant articles, pertinent medical and neurology journals and abstract books of major neurology and MS conferences (2001-2006) were also performed. Direct communication with experts and drug companies was sought. Blinded, randomised trials which were either placebo-controlled or which compared two or more treatments were included. Trials testing pharmacological agents must have had both participant and assessor blinding. Trials testing surgical interventions or effects of physiotherapy, where participants could not have been blinded to the treatment, must have had independent assessors who were blinded to the treatment. Cross-over trials were included. Three independent reviewers extracted data and the findings of the trials were summarised. A meta-analysis was not performed due to the inadequacy of outcome measures and methodological problems with the studies reviewed. Ten randomised controlled trials met the inclusion criteria. Six placebo-controlled studies (pharmacotherapy) and four comparative studies (one stereotactic neurosurgery and three neurorehabilitation) were reviewed. No standardised outcome measures were used across the studies. In

  18. Fragile X-associated tremor/ataxia syndrome: An under-recognised cause of tremor and ataxia.

    Science.gov (United States)

    Kalus, Sarah; King, John; Lui, Elaine; Gaillard, Frank

    2016-01-01

    Fragile X-associated tremor/ataxia syndrome (FXTAS) is a progressive degenerative movement disorder resulting from a fragile X "premutation", defined as 55-200 CGG repeats in the 5'-untranslated region of the FMR1 gene. The FMR1 premutation occurs in 1/800 males and 1/250 females, with FXTAS affecting 40-45% of male and 8-16% of female premutation carriers over the age of 50. FXTAS typically presents with kinetic tremor and cerebellar ataxia. FXTAS has a classical imaging profile which, in concert with clinical manifestations and genetic testing, participates vitally in its diagnosis. The revised FXTAS diagnostic criteria include two major radiological features. The "MCP sign", referring to T2 hyperintensity in the middle cerebellar peduncle, has long been considered the radiological hallmark of FXTAS. Recently included as a major radiological criterion in the diagnosis of FXTAS is T2 hyperintensity in the splenium of the corpus callosum. Other imaging features of FXTAS include T2 hyperintensities in the pons, insula and periventricular white matter as well as generalised brain and cerebellar atrophy. FXTAS is an under-recognised and misdiagnosed entity. In patients with unexplained tremor, ataxia and cognitive decline, the presence of middle cerebellar peduncle and/or corpus callosum splenium hyperintensity should raise suspicion of FXTAS. Diagnosis of FXTAS has important implications not only for the patient but also, through genetic counselling and testing, for future generations. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Ataxia rating scales are age-dependent in healthy children

    NARCIS (Netherlands)

    Brandsma, Rick; Spits, Anne H.; Kuiper, Marieke J.; Lunsing, Roelinka J.; Burger, Huibert; Kremer, Hubertus P.; Sival, Deborah A.; Barisic, N.; Baxter, P.; Brankovic-Sreckovic, V.; Calabrò, G. E.; Catsman-Berrevoets, C.; de Coo, Ifm; Craiu, D.; Dan, B.; Gburek-Augustat, J.; Kammoun-Feki, F.; Kennedy, C.; Mancini, F.; Mirabelli-Badenier, M.; Nemeth, A.; Newton, R.; Poll-The, B. T.; Steinlin, M.; Synofzik, M.; Topcu, M.; Triki, C.; Valente, E. M.

    2014-01-01

    To investigate ataxia rating scales in children for reliability and the effect of age and sex. Three independent neuropaediatric observers cross-sectionally scored a set of paediatric ataxia rating scales in a group of 52 healthy children (26 males, 26 females) aged 4 to 16 years (mean age 10y 5mo

  20. The history of spinocerebellar ataxia type 10 in Brazil: travels of a gene A história da ataxia espinocerebelar tipo 10 no Brasil: as viagens de um gene

    Directory of Open Access Journals (Sweden)

    Hélio A.G. Teive

    2007-12-01

    Full Text Available The authors report the history of spinocerebellar ataxia 10 (SCA10, since its first report in a large Portuguese-ancestry Family with autosomal dominant pure cerebellar ataxia, till the final identification of further families without Mexican ancestry. These families present a quite different phenotype from those SCA10 families described in Mexico.Os autores apresentam a história da descoberta da ataxia espinocerebelar tipo 10 (AEC10 no Brasil, desde o primeiro relato em uma família com ancestrais portugueses com ataxia cerebelar pura, autossômica dominante, até a identificação de famílias sem ancestrais mexicanos. Essas famílias apresentam um fenótipo de AEC10, com ataxia cerebelar "pura", distinta daquele descrito nas famílias no México.

  1. Ataxias agudas en la infancia

    Directory of Open Access Journals (Sweden)

    Yaline Betancourt Fursow

    2013-09-01

    Full Text Available La ataxia cerebelosa aguda infantil (ACAI es la forma más frecuente de complicación neurológica por el virus de la varicela.Descritas dentro del grupo de las cerebelitis agudas. Los objetivos de este estudio fueron: evaluar la presentación clínica, manejo y seguimiento de niños hospitalizados con ACAI en un hospital pediátrico terciario donde la inmunización para varicela no está disponible (parte I y describir los diagnósticos diferenciales de la cerebelitis aguda (parte II. Estudiamos 95 pacientes. Los criterios diagnósticos de ataxia aguda se basaron en: pérdida aguda de la coordinación o dificultad para la marcha con o sin nistagmo asociado y duración menor de 48 horas, en un niño previamente sano. Estos criterios se cumplían en todos los casos valorados, excepto en las ataxias secundarias a ingesta de tóxicos, en los que la duración debía ser menor de 24 horas para su inclusión en el estudio. Se registraron los datos en una historia clínica pediátrica y neurológica. Entre los pacientes inmunosuprimidos la incidencia mayor fue la complicación por varicela. La mayoría de los pacientes fueron varones. El rango de edad fue la preescolar, 5 años . El intervalo entre la presentación del rash y el ingreso fue de 1 a 3 días. El estudio de LCR se practicó en 59.5% de los casos. La TAC y la resonancia magnética cerebral (RM presentaron edema en el 33.3%. El aciclovir endovenoso fue utilizado en 23 pacientes; pero no hubo diferencias significativas en las manifestaciones clínicas y seguimiento entre tratados y no tratados. La ataxia fue la primera manifestación clínica. La estadía hospitalaria fue de 4 días (rango: 2-11 días.

  2. Clinical neurogenetics: autosomal dominant spinocerebellar ataxia.

    Science.gov (United States)

    Shakkottai, Vikram G; Fogel, Brent L

    2013-11-01

    The autosomal dominant spinocerebellar ataxias are a diverse and clinically heterogeneous group of disorders characterized by degeneration and dysfunction of the cerebellum and its associated pathways. Clinical and diagnostic evaluation can be challenging because of phenotypic overlap among causes, and a stratified and systematic approach is essential. Recent advances include the identification of additional genes causing dominant genetic ataxia, a better understanding of cellular pathogenesis in several disorders, the generation of new disease models that may stimulate development of new therapies, and the use of new DNA sequencing technologies, including whole-exome sequencing, to improve diagnosis. Copyright © 2013 Elsevier Inc. All rights reserved.

  3. ATM Quality of Service Tests for Digitized Video Using ATM Over Satellite: Laboratory Tests

    Science.gov (United States)

    Ivancic, William D.; Brooks, David E.; Frantz, Brian D.

    1997-01-01

    A digitized video application was used to help determine minimum quality of service parameters for asynchronous transfer mode (ATM) over satellite. For these tests, binomially distributed and other errors were digitally inserted in an intermediate frequency link via a satellite modem and a commercial gaussian noise generator. In this paper, the relation- ship between the ATM cell error and cell loss parameter specifications is discussed with regard to this application. In addition, the video-encoding algorithms, test configurations, and results are presented in detail.

  4. A Managerial Analysis of ATM in Facilitating Distance Education.

    Science.gov (United States)

    Littman, Marlyn Kemper

    In this paper, the fundamental characteristics and capabilities of ATM (Asynchronous Transfer Mode) networks in a distance learning environment are examined. Current and projected ATM applications are described, and issues and challenges associated with developing ATM networking solutions for instructional delivery are explored. Other topics…

  5. ATM: Restructing Learning for Deaf Students.

    Science.gov (United States)

    Keefe, Barbara; Stockford, David

    Governor Baxter School for the Deaf is one of six Maine pilot sites chosen by NYNEX to showcase asynchronous transfer mode (ATM) technology. ATM is a network connection that allows high bandwidth transmission of data, voice, and video. Its high speed capability allows for high quality two-way full-motion video, which is especially beneficial to a…

  6. ATM and KAT5 safeguard replicating chromatin against formaldehyde damage

    Science.gov (United States)

    Ortega-Atienza, Sara; Wong, Victor C.; DeLoughery, Zachary; Luczak, Michal W.; Zhitkovich, Anatoly

    2016-01-01

    Many carcinogens damage both DNA and protein constituents of chromatin, and it is unclear how cells respond to this compound injury. We examined activation of the main DNA damage-responsive kinase ATM and formation of DNA double-strand breaks (DSB) by formaldehyde (FA) that forms histone adducts and replication-blocking DNA-protein crosslinks (DPC). We found that low FA doses caused a strong and rapid activation of ATM signaling in human cells, which was ATR-independent and restricted to S-phase. High FA doses inactivated ATM via its covalent dimerization and formation of larger crosslinks. FA-induced ATM signaling showed higher CHK2 phosphorylation but much lower phospho-KAP1 relative to DSB inducers. Replication blockage by DPC did not produce damaged forks or detectable amounts of DSB during the main wave of ATM activation, which did not require MRE11. Chromatin-monitoring KAT5 (Tip60) acetyltransferase was responsible for acetylation and activation of ATM by FA. KAT5 and ATM were equally important for triggering of intra-S-phase checkpoint and ATM signaling promoted recovery of normal human cells after low-dose FA. Our results revealed a major role of the KAT5-ATM axis in protection of replicating chromatin against damage by the endogenous carcinogen FA. PMID:26420831

  7. Rapid and Complete Reversal of Sensory Ataxia by Gene Therapy in a Novel Model of Friedreich Ataxia.

    Science.gov (United States)

    Piguet, Françoise; de Montigny, Charline; Vaucamps, Nadège; Reutenauer, Laurence; Eisenmann, Aurélie; Puccio, Hélène

    2018-05-28

    Friedreich ataxia (FA) is a rare mitochondrial disease characterized by sensory and spinocerebellar ataxia, hypertrophic cardiomyopathy, and diabetes, for which there is no treatment. FA is caused by reduced levels of frataxin (FXN), an essential mitochondrial protein involved in the biosynthesis of iron-sulfur (Fe-S) clusters. Despite significant progress in recent years, to date, there are no good models to explore and test therapeutic approaches to stop or reverse the ganglionopathy and the sensory neuropathy associated to frataxin deficiency. Here, we report a new conditional mouse model with complete frataxin deletion in parvalbumin-positive cells that recapitulate the sensory ataxia and neuropathy associated to FA, albeit with a more rapid and severe course. Interestingly, although fully dysfunctional, proprioceptive neurons can survive for many weeks without frataxin. Furthermore, we demonstrate that post-symptomatic delivery of frataxin-expressing AAV allows for rapid and complete rescue of the sensory neuropathy associated with frataxin deficiency, thus establishing the pre-clinical proof of concept for the potential of gene therapy in treating FA neuropathy. Copyright © 2018 The American Society of Gene and Cell Therapy. Published by Elsevier Inc. All rights reserved.

  8. Macular telangiectasia type 2 (MacTel) in a 34-year-old patient.

    Science.gov (United States)

    Nicolai, Heleen; Wirix, Mieke; Spielberg, Leigh; Leys, Anita

    2014-09-23

    We report macular telangiectasia type 2 (MacTel) in a 34-year-old man, the youngest patient so far published with MacTel type 2. The patient presented with metamorphopsia and impaired reading ability. Diagnosis was based on bilateral abnormal macular autofluorescence, perifoveal telangiectasia with fluorescein angiographic hyperfluorescence without cystoid oedema, a small foveal avascular zone, asymmetric configuration of the foveal pit, disruptions in the inner segment/outer segment layer and hyper-reflective haze and spots in the outer nuclear layer. Although MacTel usually manifests with a slowly progressive decrease in visual acuity in the fifth to seventh decades of life, younger patients may occasionally be diagnosed with the disease. Awareness of subtle signs of the condition is essential for early diagnosis. 2014 BMJ Publishing Group Ltd.

  9. Methylation of the ATM promoter in glioma cells alters ionizing radiation sensitivity

    International Nuclear Information System (INIS)

    Roy, Kanaklata; Wang, Lilin; Makrigiorgos, G. Mike; Price, Brendan D.

    2006-01-01

    Glioblastomas are among the malignancies most resistant to radiation therapy. In contrast, cells lacking the ATM protein are highly sensitive to ionizing radiation. The relationship between ATM protein expression and radiosensitivity in 3 glioma cell lines was examined. T98G cells exhibited normal levels of ATM protein, whereas U118 and U87 cells had significantly lower levels of ATM and increased (>2-fold) sensitivity to ionizing radiation compared to T98G cells. The ATM promoter was methylated in U87 cells. Demethylation by azacytidine treatment increased ATM protein levels in the U87 cells and decreased their radiosensitivity. In contrast, the ATM promoter in U118 cells was not methylated. Further, expression of exogenous ATM did not significantly alter the radiosensitivity of U118 cells. ATM expression is therefore heterogeneous in the glioma cells examined. In conclusion, methylation of the ATM promoter may account for the variable radiosensitivity and heterogeneous ATM expression in a fraction of glioma cells

  10. Comparison of. gamma. i-irradiation-induced accumulation of ataxia telangiesctasia and control cells in G sub 2 phase

    Energy Technology Data Exchange (ETDEWEB)

    Bates, P.R. (Royal Brisbane Hospital, Herston (Australia)); Lavin, M.F. (Queensland Inst. of Medical Research, Brisbane (Australia))

    1989-09-01

    Recent reports from a number of laboratories have linked radiosensitivity in ataxia telangiectasia (AT) to a large and prolonged block of some cells in G{sub 2} phase. Previous results from this laboratory, largely with one Epstein-Barr virus-transformed A-T lymphoblastoid cell line, presented evidence for a dramatic increase in the number of cells in G{sub 2} phase over controls during a 24 h period post irradiation. We describe here a study of the effect of {gamma}-radiation on G{sub 2} phase delay in several A-T cell lines. Based on previous results with several cell lines 24 h post irradiation was selected as the optimum time to discriminate between G{sub 2} phase delay in control and A-T cells. All A-T homozygotes showed a signigicantly greater number of cells in G{sub 2} phase, 24 h post irradiation, than observed in controls. A more prolonged delay in G{sub 2} phase after irradiation was seen in different A-T cell types that included lymphoblastoid cells, fibroblasts and SV40-transformed fibroblasts. At the radiation dose used it was not possibel to distinguish A-T heterozygotes from controls (Author). 28 refs.; 2 figs.; 1 tab.

  11. Molecular and clinical study of a cohort of 110 Algerian patients with autosomal recessive ataxia.

    Science.gov (United States)

    Hamza, Wahiba; Ali Pacha, Lamia; Hamadouche, Tarik; Muller, Jean; Drouot, Nathalie; Ferrat, Farida; Makri, Samira; Chaouch, Malika; Tazir, Meriem; Koenig, Michel; Benhassine, Traki

    2015-06-12

    Autosomal recessive cerebellar ataxias (ARCA) are a complex group of neurodegenerative disorders with great genetic and phenotypic heterogeneity, over 30 genes/loci have been associated with more than 20 different clinical forms of ARCA. Genetic heterogeneity combined with highly variable clinical expression of the cerebellar symptoms and overlapping features complicate furthermore the etiological diagnosis of ARCA. The determination of the most frequent mutations and corresponding ataxias, as well as particular features specific to a population, are mandatory to facilitate and speed up the diagnosis process, especially when an appropriate treatment is available. We explored 166 patients (115 families) refered to the neurology units of Algiers central hospitals (Algeria) with a cerebellar ataxia phenotype segregating as an autosomal recessive pattern of inheritance. Genomic DNA was extracted from peripheral blood samples and mutational screening was performed by PCR and direct sequencing or by targeted genomic capture and massive parallel sequencing of 57 genes associated with inherited cerebellar ataxia phenotypes. In this work we report the clinical and molecular results obtained on a large cohort of Algerian patients (110 patients/76 families) with genetically determined autosomal recessive ataxia, representing 9 different types of ARCA and 23 different mutations, including 6 novel ones. The five most common ARCA in this cohort were Friedreich ataxia, ataxia with isolated vitamin E deficiency, ataxia with oculomotor apraxia type 2, autosomal recessive spastic ataxia of Charlevoix-Saguenay and ataxia with oculomotor apraxia type 1. We report here a large cohort of patients with genetically determined autosomal recessive ataxia and the first study of the genetic context of ARCA in Algeria. This study showed that in Algerian patients, the two most common types of ataxia (Friedreich ataxia and ataxia with isolated vitamin E deficiency) coexist with forms that may be

  12. [A sporadic case of episodic ataxia with nystagmus (EA-2)].

    Science.gov (United States)

    Namekawa, M; Takiyama, Y; Ueno, N; Nishizawa, M

    1998-05-01

    A 39-year-old man with episodic ataxia with nystagmus (EA-2) was reported. He showed intermittent cerebellar dysfunction, i.e., ataxia, nystagmus, dysarthria and vertigo, since he was 10 years old. Although this attack lasted for several hours, he was normal with exception of interictal nystagmus. His parents and sister showed no episodic ataxia. We ruled out the diseases, which may cause episodic ataxia, such as multiple sclerosis, vascular disorders, metabolic disorders and congenital anomalies. He was released from the attack by treatment with acetazolamide. EA-2 has been associated with mutations in the alpha 1A-voltage dependent calcium channel gene (CACNL1A4), which is also affected in familial hemiplegic migraine (FMH) and spinocerebellar ataxia type 6 (SCA6). In EA-2, frame-shift mutation leading to premature stop and splice-site mutation leading to truncated, non-functional channel protein have been reported. However, our patient did not have the mutations in the CACNL1A4 gene that were previously reported. In addition, our patient did not have an expanded CAG allele in the CACNL1A4 gene which is responsible for SCA6. Further examination is required to address whether a new mutation exists in the CACNL1A4 gene in our patient.

  13. Pretreatment of liver grafts in vivo by γ-aminobutyric acid receptor regulation reduces cold ischemia/warm reperfusion injury in rat

    Science.gov (United States)

    Hori, Tomohide; Gardner, Lindsay B.; Hata, Toshiyuki; Chen, Feng; Baine, Ann-Marie T.; Uemoto, Shinji; Nguyen, Justin H.

    2014-01-01

    Summary Background: Gamma-aminobutyric acid (GABA) is found throughout the body. The regulation of GABA receptor (GABAR) reduces oxidative stress (OS). Ischemia/reperfusion injury after orthotopic liver transplantation (OLT) causes OS-induced graft damage. The effects of GABAR regulation in donors in vivo were investigated. Material/Methods: Donor rats received saline, a GABAR agonist or GABAR antagonist 4 h before surgery. Recipient rats were divided into four groups according to the donor treatments: laparotomy, OLT with saline, OLT with GABAR agonist and OLT with GABAR antagonist. Histopathological, biochemical and immunohistological examinations were performed at 6, 12 and 24 h after OLT. Protein assays were performed at 6 h after OLT. The 4-hydroxynonenal (4-HNE), ataxia-telangiectasia mutated kinase (ATM), phosphorylated histone H2AX (γH2AX), phosphatidylinositol-3 kinase (PI3K), Akt and superoxide dismutase (SOD) were assessed by western blot analysis. Results: In the univariate analysis, histopathological and biochemical profiles verified that the GABAR agonist reduced graft damage. Immunohistology revealed that the GABAR agonist prevented the induction of apoptosis. Measurement of 4-4-HNE levels confirmed OS-induced damage after OLT, and the GABAR agonist improved this damage. In the γH2AX, PI3K, Akt and antioxidant enzymes (SODs), ATM and H2AX were greatly increased after OLT, and were reduced by the GABAR agonist. In the multivariate analyses between multiple groups, histopathological assessment, aspartate aminotransferase level, immunohistologi