Comparative Study of X-Ray and UV Induced Cytotoxicity, DNA Repair, and Mutagenesis in Down's Syndrome and Normal Fibroblasts

Abstract

Summawre~airs chromosomal breaks (4). It was also re~orted that leukoUtilizing six age-matched human fibroblast cell strains (three normal and three Down's syndrome) cytotoxicity, DNA repair, and X-ray mutagenesis were measured. There was no significant difference in the colony-forming ability after ultraviolet (UV) or X-irradiation between normal and Down's fibroblasts. Similarly, UV-induced unscheduled DNA synthesis was not significantly different between normal and Down's cells. Finally, a comparison between the spontaneous and X-ray induced mutation frequency at the hypoxanthine-guanine phosphoribosyl transferase locus demonstrated no difference between the two cell types (normal and Down's). cy;es from Down's syndrome patients exhibitid lower levels of UV-induced DNA repair synthesis (unscheduled DNA synthesis) than did leukocytes from normal controls (10).In an attempt to further investigate the problem, the authors report here a series of experiments to measure: (1) colony-forming ability, i.e., survival, of Down's and normal fibroblasts exposed to either UV or X-irradiation, (2) unscheduled DNA synthesis (excision repair) of Down's and normal fibroblasts after exposure to UV, and (3) spontaneous and X-ray induced mutation frequencies at the hypoxanthine-guanine phosphoribosyltransferase (HGPRT) locus in Down's and normal fibroblasts. Speculation MATERIALS AND METHODS Down's syndrome has long been recognized as a cancer-pronePrimary fibroblast cultures of age-and sex-matched normal and human syndrome. Chromosomal radiosensitivity indicated the pos-Down's syndrome individuals were provided by Dr. D. Segal sibility of faulty DNA repair leading to the accumulation of (Department of Pediatrics, University of Alberta, Edmonton, Alsomatic mutations. Because no biologic differences were detected berta). These cell strains have previously been examined in terms in fibroblasts, the predisposition to cancer (especially leukemia) in of their in vitro cell cycle, origin, and growth (18). The LeschDown's syndrome might be due to abnormal DNA repair in the Nyhan cells (GM 1362) were obtained from the Human Genetic white blood cells of these individuals.Mutant Cell Repository (Camden, NJ). The cells were grown in modified Eagle's medium (Earle's balanced salt solution with a 50% increase of essential amino acids and vitamins) supplemented It has been recognized now for many years that children with with "nonessential" amino acids (1Wo increase), 1 mM sodium Down's syndrome are at an increased risk for neoplasia, especially pyruvate, and 10% heat inactivated fetal calf serum. Under inculeukemia (8,9,14,15,20,22). In addition, chromosomes from bation conditions of 5% Con in humidxed air at 37OC the cells individuals who are trisomic for chromosome 21 exhibit an in-had a generation time of approximately 24 hr. creased aberration frequency (exchange type) after exposure toThe cell survival experiments were conducted similarly for UV gamma rays (17). Chromosomes from Down's syndrome individ-and X-irradiation. To determine th...

Human trisomy 21 fibroblasts rescue methotrexate toxic effect after treatment with 5‐methyl‐tetrahydrofolate and 5‐formyl‐tetrahydrofolate

“…Nerve cells, germ cells, embryonal stem cells (ES), cancer cells, or other cell types with trisomy 21 genotype are not commercially available or retrievable from the biobanks, and often they derive from induced-pluripotent stem cells (iPSC) which could suffer deep genotype rearrangements (Sobol et al, 2015) or spontaneous chromosome loss (Li et al, 2012), avoiding the identification of the alterations caused only by the trisomic genotype we are interested in. In addition, cultured children and adult skin fibroblasts have been extensively used over decades to model cellular and molecular features of trisomy 21, for example, among others: cell proliferation (Kimura et al, 2005;Segal & McCoy, 1974), enzyme activity (Chadefaux et al, 1985;Cox, 1965;Feaster, Kwok, & Epstein, 1977;Sinet, Lejeune, & Jerome, 1979;Zatorska & Jozwiak, 2002), gene expression (Sullivan et al, 2016;Urakami et al, 1996), sensitivity to radiation and DNA repair (Kedziora, Sibinska, Rozga, & Bartosz, 1986;Necchi et al, 2015;Steiner & Woods, 1982;Yotti, Glover, Trosko, & Segal, 1980). FA was tested to confirm the null effect on trisomy 21 cell lines, previously observed by other authors, when it was administered in vitro (Blehaut et al, 2010).…”

Defective DNA repair and increased chromatin binding of DNA repair factors in Down syndrome fibroblasts

“…However, the information regarding the ability of DS cells to repair oxidative DNA damage has been in general neglected [39]. In fact, only a few works have dealt with this particular issue [11,23], having previous reports been focused mainly on SSBR [20] and NER processes [21]. Here, we report that primary DS fibroblasts, from both fetal and adult donors, exhibited the activation of a DNA damage response, which was observed in basal growth conditions, suggesting that the checkpoint was activated by an endogenous source of stress.…”

“…In previous studies, it was verified that DS cells exhibited more frequent chromosomal aberrations in response to different types of DNA damaging agents, as compared with control cells [19]. However, the analysis of DNA repair efficiency in DS cells provided contrasting results, in particular for DNA repair induced by X-ray or UV-induced DNA damage [19][20][21], probably also because of an inter-individual variability, and the possible influence of the donor age [22]. In addition, no information on the repair of oxidative damage was available.…”