Showing papers on "Sister chromatid exchange published in 2020"
TL;DR: It is proposed that DDX11 is a DNA helicase protecting against G4 induced double-stranded breaks and concomitant loss of cohesion, possibly at DNA replication forks.
Abstract: Warsaw Breakage Syndrome (WABS) is a rare disorder related to cohesinopathies and Fanconi anemia, caused by bi-allelic mutations in DDX11. Here, we report multiple compound heterozygous WABS cases, each displaying destabilized DDX11 protein and residual DDX11 function at the cellular level. Patient-derived cell lines exhibit sensitivity to topoisomerase and PARP inhibitors, defective sister chromatid cohesion and reduced DNA replication fork speed. Deleting DDX11 in RPE1-TERT cells inhibits proliferation and survival in a TP53-dependent manner and causes chromosome breaks and cohesion defects, independent of the expressed pseudogene DDX12p. Importantly, G-quadruplex (G4) stabilizing compounds induce chromosome breaks and cohesion defects which are strongly aggravated by inactivation of DDX11 but not FANCJ. The DNA helicase domain of DDX11 is essential for sister chromatid cohesion and resistance to G4 stabilizers. We propose that DDX11 is a DNA helicase protecting against G4 induced double-stranded breaks and concomitant loss of cohesion, possibly at DNA replication forks.
27 citations
TL;DR: It is demonstrated that SCE-FISH frequency at fragile sites is a sensitive indicator of replication stress, and that large-scale genome organization influences DNA repair pathway choice.
Abstract: Chromosomal fragile sites are genomic loci sensitive to replication stress which accumulate high levels of DNA damage, and are frequently mutated in cancers. Fragile site damage is thought to arise from the aberrant repair of spontaneous replication stress, however successful fragile site repair cannot be calculated using existing techniques. Here, we report a new assay measuring recombination-mediated repair at endogenous genomic loci by combining a sister chromatid exchange (SCE) assay with fluorescent in situ hybridization (SCE-FISH). Using SCE-FISH, we find that endogenous and exogenous replication stress generated unrepaired breaks and SCEs at fragile sites. We also find that distinct sources of replication stress induce distinct patterns of breakage: ATR inhibition induces more breaks at early replicating fragile sites (ERFS), while ERFS and late-replicating common fragile sites (CFS) are equally fragile in response to aphidicolin. Furthermore, SCEs were suppressed at fragile sites near centromeres in response to replication stress, suggesting that genomic location influences DNA repair pathway choice. SCE-FISH also measured successful recombination in human primary lymphocytes, and identificed the proto-oncogene BCL2 as a replication stress-induced fragile site. These findings demonstrate that SCE-FISH frequency at fragile sites is a sensitive indicator of replication stress, and that large-scale genome organization influences DNA repair pathway choice.
21 citations
TL;DR: It is pointed out that being exposed to FA at high concentrations show cytotoxicity, and no genotoxic effects were seen in human lymphocytes in vitro using CA, SCE and MN assays.
Abstract: Fusaric acid (FA) is produced by several Fusarium species and is commonly found in grains. This investigation was performed to evaluate the cytotoxic and genotoxic effects of FA either in human cer...
18 citations
TL;DR: A follow-up study of a cohort of workers from a coke plant compared with a control group from the same industrial area was conducted in 2019, finding significant risk of death for all causes and chromosomal aberrations were found.
Abstract: A follow-up study of a cohort of workers from a coke plant compared with a control group from the same industrial area was conducted in 2019. The recruitment and environmental and biomarker measurements were performed during 1993/1994. The environmental concentrations of polycyclic aromatic hydrocarbons (PAH), B(a)P, pyrene and nitro-PAH were measured. Personal data were collected via an individual semi-structured questionnaire by a trained physician. All biomarkers were measured after a specific blood drawing for every test. Significant risks (ORs) were observed for nitro-PAH (≥0.12 µg/m3) [OR = 7.96 (1.01–62.82)], urinary 1-hydroxypyrene (1-OHpy) (≥0.99 µmoles/moles of creatinine) [OR = 11.71 (1.47–92.90)], PAH DNA adducts (P32) (≥2.69 adducts/108 nucleotides) [OR = 5.46 (1.17–25.58)], total nitro-PAH hemoglobin adducts (≥161.68 fg/µg of Hb) [OR = 5.92 (1.26–27.86)], sister chromatid exchange (SCE) with TCR (≥377.84 SCE/cell chromosomes) [OR = 13.06 (3.95–93.10)], sister chromatid exchange with T (≥394.72 total SCE) [OR = 13.06 (3.95–93.10)], and sister chromatid exchange with X (≥8.19 mean SCE) [OR = 13.06 (3.95–93.10)]. Significant risk of death for all causes and chromosomal aberrations (48 h) (OR = 7.19 [1.19–43.44]) or micronuclei in culture at 48 h (OR = 3.86 [1.04–14.38]) were also found.
13 citations
TL;DR: It is demonstrated that elevated concentrations (similar to manufacturers suggested concentration; >5–10 μM) of EdU treatment were toxic to the cell cultures, particularly in cells with a defect in homologous recombination repair, and EdU should be administered with additional precautions.
Abstract: BrdU (bromodeoxyuridine) and EdU (ethynyldeoxyuridine) have been largely utilized as the means of monitoring DNA replication and cellular division. Although BrdU induces gene and chromosomal mutations and induces sensitization to photons, EdU‘s effects have not been extensively studied yet. Therefore, we investigated EdU’s potential cytotoxic and mutagenic effects and its related underlying mechanisms when administered to Chinese hamster ovary (CHO) wild type and DNA repair-deficient cells. EdU treatment displayed a higher cytotoxicity and genotoxicity than BrdU treatment. Cells with defective homologous recombination repair displayed a greater growth delay and severe inhibition of clonogenicity with EdU compared to wild type and other DNA repair-deficient cells. Inductions of sister chromatid exchange and hypoxanthine phosphorybosyl transferase (HPRT) mutation were observed in EdU-incorporated cells as well. Interestingly, on the other hand, EdU did not induce sensitization to photons to the same degree as BrdU. Our results demonstrate that elevated concentrations (similar to manufacturers suggested concentration; >5–10 μM) of EdU treatment were toxic to the cell cultures, particularly in cells with a defect in homologous recombination repair. Therefore, EdU should be administered with additional precautions.
13 citations
TL;DR: NB-UVB is less cytotoxic and genotoxic than BB-UVBs, but can still produce genot toxic effects even at noncytotoxic doses, and SCE and HPRT mutation frequencies were observed to rise in noncyTotoxic dosages of NB- UVB exposure.
Abstract: Phototherapy using narrowband ultraviolet-B (NB-UVB) has been shown to be more effective than conventional broadband UVB (BB-UVB) in treating a variety of skin diseases. To assess the difference in carcinogenic potential between NB-UVB and BB-UVB, we investigated the cytotoxicity via colony formation assay, genotoxicity via sister chromatid exchange (SCE) assay, mutagenicity via hypoxanthine phosphoribosyltransferase (HPRT) mutation assay, as well as cyclobutane pyrimidine dimer (CPD) formation and reactive oxygen species (ROS) generation in Chinese hamster ovary (CHO) and their NER mutant cells. The radiation dose required to reduce survival to 10% (D10 value) demonstrated BB-UVB was 10 times more cytotoxic than NB-UVB, and revealed that NB-UVB also induces DNA damage repaired by nucleotide excision repair. We also found that BB-UVB more efficiently induced SCEs and HPRT mutations per absorbed energy dosage (J/m2) than NB-UVB. However, SCE and HPRT mutation frequencies were observed to rise in noncytotoxic dosages of NB-UVB exposure. BB-UVB and NB-UVB both produced a significant increase in CPD formation and ROS formation (p < 0.05); however, higher dosages were required for NB-UVB. These results suggest that NB-UVB is less cytotoxic and genotoxic than BB-UVB, but can still produce genotoxic effects even at noncytotoxic doses.
10 citations
TL;DR: The genotoxic potential of MET was evaluated by using chromosome aberrations, sister chromatid exchanges, and micronucleus assays in human peripheral lymphocytes as well as comet assay in isolated lymphocytes to show that MET had a mild genot toxic effect, especially at a long treatment period and higher concentrations in human lymphocytes in vitro.
Abstract: Metformin (MET) is the first-choice antidiabetic drug for type 2 diabetes mellitus treatment. In this study, the genotoxic potential of MET was evaluated by using chromosome aberrations (CAs), sist...
7 citations
TL;DR: For the first time, an induced pluripotent cell line is derived from a Bloom syndrome patient retaining the specific sister-chromatid exchange feature as a unique tool to model the pathology.
4 citations
TL;DR: It is proposed that ZGRF1 promotes repair of replication-blocking DNA lesions through stimulation of homologous recombination and is a 5′-to-3′ helicase that catalyzes D-loop dissociation and Holliday junction branch migration.
4 citations
TL;DR: A detailed protocol for differential labeling sister chromatids in barley cells that is based on the incorporation and simple detection of EdU is reported, enabling an analysis of the effects of two model agents—maleic acid hydrazide and gamma rays—on the formation of SCEs.
Abstract: This study is the example of using 5-ethynyl-2`-deoxyuridine (EdU) for detecting sister chromatid exchanges (SCEs) at chromosomal level. Here we report a detailed protocol for differential labeling sister chromatids in barley (Hordeum vulgare, 2n=14) cells that is based on the incorporation and simple detection of EdU. The perfect distinguishing of sister chromatids enabled an analysis of the effects of two model agents - maleic acid hydrazide (MH) and gamma rays, on the formation of SCEs. Using this method, we demonstrated the high sensitivity of barley cells to maleic hydrazide, which is expressed as an increased level of SCEs. A gamma ray induced only slightly more SCEs in the treated cells than in the control cells. The possible mechanisms of MH and gamma ray action in respect to distinguishing chromatids using EdU are discussed. Recommendation for SCEs visualization using EdU as an easy and quick method that can be successfully adapted to other plant species and potentially for human genotoxicity studies is presented.
3 citations
TL;DR: Investigation of the genotoxic and cytotoxic effects of temephos on human peripheral blood lymphocytes using the cytokinesis-block micronucleus (CBMN) and sister chromatid exchange assays concluded that temepos was not cytotoxicity at concentrations of 25, 50 and 75 μg/ml, however, it may have a genot toxic potential in human peripheral lymphocytes.
Abstract: Genotoxic effects of pesticides are of great concern for public health due to
the fact that they are widely used for both domestic and industrial
purposes. Temephos is a member of organophosphorus pesticides, which is the
most widely used group of chemicals against both agricultural and domestic
insects. We therefore aimed in the present study to investigate the
genotoxic and cytotoxic effects of temephos on human peripheral blood
lymphocytes, using the cytokinesis-block micronucleus (CBMN) and sister
chromatid exchange assays. The results showed that micronucleus (MN)
frequency increased at concentrations of 50 and 75 μg/ml although it was not
found statically significant (p>0.05). We found that sister chromatid
exchange (SCE) values at concentrations of 50 and 75 μg/ ml were
significantly higher than those obtained for the control (p<0.01). We also
analyzed associations between temephos exposure and mitotic index (MI),
proliferation index (PI), and cell blocked proliferation index (CBPI). There
was no significant change in these values at the tested concentrations
(p>0.05). It can be concluded that temephos was not cytotoxic at
concentrations of 25, 50 and 75 μg/ml. However, it may have a genotoxic
potential in human peripheral lymphocytes.