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Nijmegen breakage syndrome cells fail to induce the p53-mediated DNA damage response following exposure to ionizing radiation.

ABSTRACT: The functionality of the p53-mediated pathway, activated in response to DNA damage, has been assessed in primary fibroblast cell cultures and Epstein-Barr virus-transformed lymphoblastoid cell lines derived from Nijmegen breakage syndrome (NBS) patients. This autosomal recessive disease is characterized by microcephaly, growth and mental retardation, chromosomal instability, radiosensitivity, and high cancer incidence. The recent mapping of the NBS gene to chromosome 8q21 demonstrates that NBS is genetically distinct from ataxia telangiectasia (AT). Changes in p53 protein levels were significantly reduced and delayed in all the NBS fibroblast cell cultures and lymphoblastoid cell lines examined compared to normal cultures over a 4-h period postirradiation (5 Gy). The transcriptional activation of p21(WAF1/CIP1) mRNA was also lower in 12 NBS fibroblast cultures examined. In agreement with an abrogated p53 function, NBS cells exposed to ionizing radiation show an abnormal cell cycle arrest at G1-S and a prolonged accumulation of cells in the G2 phase. In contrast, exposure to the alkylating agent methyl methanesulfonate results in similar increases of p53 and p21(WAF1/CIP1) mRNA in both cell types. The ATM gene transcript was found to be expressed at similar levels in NBS and normal cells, whereas it was strongly reduced in the AT homozygote cells examined. These results suggest that the ATM gene product cannot substitute for that of the NBS gene in the signaling of cellular damage produced by ionizing radiation and that both are involved in the activation of p53. The suboptimal p53-mediated response could contribute to the high cancer risk and radiosensitivity seen in NBS patients.

SUBMITTER: Jongmans W

PROVIDER: S-EPMC232352 | biostudies-other | 1997 Sep

REPOSITORIES: biostudies-other

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Nijmegen breakage syndrome cells fail to induce the p53-mediated DNA damage response following exposure to ionizing radiation.

Jongmans W W Vuillaume M M Chrzanowska K K Smeets D D Sperling K K Hall J J

Molecular and cellular biology 19970901 9

The functionality of the p53-mediated pathway, activated in response to DNA damage, has been assessed in primary fibroblast cell cultures and Epstein-Barr virus-transformed lymphoblastoid cell lines derived from Nijmegen breakage syndrome (NBS) patients. This autosomal recessive disease is characterized by microcephaly, growth and mental retardation, chromosomal instability, radiosensitivity, and high cancer incidence. The recent mapping of the NBS gene to chromosome 8q21 demonstrates that NBS i ...[more]

PMID: 9271379

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Project description:Nijmegen breakage syndrome (NBS) is a rare autosomal recessive syndrome of chromosomal instability mainly characterized by microcephaly at birth, combined immunodeficiency and predisposition to malignancies. Due to a founder mutation in the underlying NBN gene (c.657_661del5) the disease is encountered most frequently among Slavic populations. The principal clinical manifestations of the syndrome are: microcephaly, present at birth and progressive with age, dysmorphic facial features, mild growth retardation, mild-to-moderate intellectual disability, and, in females, hypergonadotropic hypogonadism. Combined cellular and humoral immunodeficiency with recurrent sinopulmonary infections, a strong predisposition to develop malignancies (predominantly of lymphoid origin) and radiosensitivity are other integral manifestations of the syndrome. The NBN gene codes for nibrin which, as part of a DNA repair complex, plays a critical nuclear role wherever double-stranded DNA ends occur, either physiologically or as a result of mutagenic exposure. Laboratory findings include: (1) spontaneous chromosomal breakage in peripheral T lymphocytes with rearrangements preferentially involving chromosomes 7 and 14, (2) sensitivity to ionizing radiation or radiomimetics as demonstrated in vitro by cytogenetic methods or by colony survival assay, (3) radioresistant DNA synthesis, (4) biallelic hypomorphic mutations in the NBN gene, and (5) absence of full-length nibrin protein. Microcephaly and immunodeficiency are common to DNA ligase IV deficiency (LIG4 syndrome) and severe combined immunodeficiency with microcephaly, growth retardation, and sensitivity to ionizing radiation due to NHEJ1 deficiency (NHEJ1 syndrome). In fact, NBS was most commonly confused with Fanconi anaemia and LIG4 syndrome. Genetic counselling should inform parents of an affected child of the 25% risk for further children to be affected. Prenatal molecular genetic diagnosis is possible if disease-causing mutations in both alleles of the NBN gene are known. No specific therapy is available for NBS, however, hematopoietic stem cell transplantation may be one option for some patients. Prognosis is generally poor due to the extremely high rate of malignancies.

Project description:Ataxia-telangiectasia (AT) and Nijmegen breakage syndrome (NBS) belong to a group of primary immunodeficiency diseases (PI) characterized by premature aging, cerebral degeneration, immunoglobulin deficiency and higher cancer susceptibility. Despite the fact that oxidative stress has been demonstrated in vitro and in animal models of AT and NBS, the involvement of redox homeostasis disorders is still unclear in the in vivo phenotype of AT and NBS patients. Our study is the first to compare both enzymatic and non-enzymatic antioxidants as well as oxidative damage between AT and NBS subjects. Twenty two Caucasian children with AT and twelve patients with NBS were studied. Enzymatic and non-enzymatic antioxidants - glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase-1 (SOD) and uric acid (UA); redox status-total antioxidant capacity (TAC) and ferric reducing ability of plasma (FRAP); and oxidative damage products-8-hydroxy-2'-deoxyguanosine (8-OHdG), advanced glycation end products (AGE), advanced oxidation protein products (AOPP), 4-hydroxynonenal (4-HNE) protein adducts, and 8-isoprostanes (8-isop) were evaluated in serum or plasma samples. We showed that CAT, SOD and UA were significantly increased, while TAC and FRAP levels were statistically lower in the plasma of AT patients compared to controls. In NBS patients, only CAT activity was significantly elevated, while TAC was significantly decreased as compared to healthy children. We also showed higher oxidative damage to DNA (↑8-OHdG), proteins (↑AGE, ↑AOPP), and lipids (↑4-HNE, ↑8-isop) in both AT and NBS patients. Interestingly, we did not demonstrate any significant differences in the antioxidant defense and oxidative damage between AT and NBS patients. However, in AT children, we showed a positive correlation between 8-OHdG and the α-fetoprotein level as well as a negative correlation between 8-OHdG and IgA. In NBS, AGE was positively correlated with IgM and negatively with the IgG level. Summarizing, we demonstrated an imbalance in cellular redox homeostasis and higher oxidative damage in AT and NBS patients. Despite an increase in the activity/concentration of some antioxidants, the total antioxidant capacity is overwhelmed in children with AT and NBS and predisposes them to more considerable oxidative damage. Oxidative stress may play a major role in AT and NBS phenotype.

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Nijmegen breakage syndrome cells fail to induce the p53-mediated DNA damage response following exposure to ionizing radiation.

Publications

Nijmegen breakage syndrome cells fail to induce the p53-mediated DNA damage response following exposure to ionizing radiation.

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