Sister chromatid exchange

About: Sister chromatid exchange is a research topic. Over the lifetime, 3187 publications have been published within this topic receiving 90029 citations. The topic is also known as: replication-born DSB repair by SCE & GO:1990414.

Simultaneous mapping of active DNA demethylation and sister chromatid exchange in single cells.

Abstract: To understand mammalian active DNA demethylation, various methods have been developed to map the genomic distribution of the demethylation intermediates 5-formylcysotine (5fC) and 5-carboxylcytosine (5caC). However, the majority of these methods requires a large number of cells to begin with. In this study, we describe low-input methylase-assisted bisulfite sequencing (liMAB-seq ) and single-cell MAB-seq (scMAB-seq), capable of profiling 5fC and 5caC at genome scale using ∼100 cells and single cells, respectively. liMAB-seq analysis of preimplantation embryos reveals the oxidation of 5mC to 5fC/5caC and the positive correlation between chromatin accessibility and processivity of ten-eleven translocation (TET) enzymes. scMAB-seq captures the cell-to-cell heterogeneity of 5fC and 5caC and reveals the strand-biased distribution of 5fC and 5caC. scMAB-seq also allows the simultaneous high-resolution mapping of sister chromatid exchange (SCE), facilitating the study of this type of genomic rearrangement. Therefore, our study not only establishes new methods for the genomic mapping of active DNA demethylation using limited numbers of cells or single cells but also demonstrates the utilities of the methods in different biological contexts.

Evaluation of chromosome aberrations, sister chromatid exchange and micronuclei in patients with type-1 diabetes mellitus

Abstract: Oxidative stress-induced DNA damage seems to play a role in the pathogenesis of type-1 diabetes mellitus and its complications. Several in vitro assays have been used to measure the DNA damage produced by oxidative stress. In the present study, we aimed to investigate the frequency of sister chromatid exchange (SCE), chromosomal aberrations (CA) and micronuclei (MN) in type-1 diabetes mellitus patients compared with healthy controls. SCE, CA and MN tests were carried out with the blood-cell cultures from 35 type-1 diabetic patients and 15 healthy, age- and sex-matched control subjects. The mean age of the type-1 diabetic patients was 31.89 ± 10.01 years, with a mean duration of the diabetes of 7.8 ± 6.02 years. The mean level of HbA1c of the type-1 diabetic patients was 8.37 ± 1.36%. Only three (8.5%) patients with type-1 diabetes mellitus had an HbA1c level below 7%. Patients with type-1 diabetes mellitus showed a higher frequency of SCE compared with controls (5.44 ± 1.47 and 2.54 ± 0.82, respectively, p < 0.001), but there was no significant correlation between the duration of diabetes, HbA1c and SCE. No significant difference was found in CA or MN frequency in type-1 diabetic patients compared with controls. In conclusion, these results suggest that type-1 diabetes mellitus is a condition with genomic instability characterized by an increased level of SCE. Hyperglycemia-induced oxidative stress may be the underlying factor of the increased SCE frequency.

Sister chromatid exchanges induced in rabbit lymphocytes by ethylene oxide after inhalation exposure.

Abstract: Ethylene oxide, which is the simplest epoxide and an extremely important commercial compound, has been used by many investigators as a model compound to study mutagenicity by alkylation of DNA. Knowledge of in vivo dose-effect relations under experimental conditions may provide further insight into the dynamics of the sister chromatid exchange (SCE) response. It may also provide information on temporal aspects of sampling design for human worker populations. Groups of four male New Zealand white rabbits were exposed in inhalation chambers to 0, 10, 50, and 250 parts per million (ppm) ethylene oxide for 6 hr a day, 5 days a week, for 12 weeks. Peripheral blood samples were taken before the start of exposure, at intervals during exposure, and up to 15 weeks after the end of exposure to measure SCE rates in peripheral lymphocytes as well as standard hematological endpoints. Additionally, the level of reduced glutathione (GSH) in liver and blood was measured in a set of concurrently exposed animals at the end of the 12-week exposure. Results show that exposure to 10 ppm does not cause a detectable increase in SCE rates. However, exposure to 50 and 250 ppm does cause an increase in SCEs that decreases after exposure ends, but still remains above baseline levels 15 weeks after exposure. Hematological and GSH measurements did not differ between control and exposed groups. These results indicate that inhalation exposure to the mutagenic alkylating agent ethylene oxide results in a dose-related SCE effect, and that SCE is a more sensitive indicator of exposure than either standard hematological end points or GSH levels.

PARP Inhibitors in Clinical Use Induce Genomic Instability in Normal Human Cells.

Abstract: Poly(ADP-ribose) polymerases (PARPs) are the first proteins involved in cellular DNA repair pathways to be targeted by specific inhibitors for clinical benefit. Tumors harboring genetic defects in homologous recombination (HR), a DNA double-strand break (DSB) repair pathway, are hypersensitive to PARP inhibitors (PARPi). Early phase clinical trials with PARPi have been promising in patients with advanced BRCA1 or BRCA2-associated breast, ovary and prostate cancer and have led to limited approval for treatment of BRCA-deficient ovary cancer. Unlike HR-defective cells, HR-proficient cells manifest very low cytotoxicity when exposed to PARPi, although they mount a DNA damage response. However, the genotoxic effects on normal human cells when agents including PARPi disturb proficient cellular repair processes have not been substantially investigated. We quantified cytogenetic alterations of human cells, including primary lymphoid cells and non-tumorigenic and tumorigenic epithelial cell lines, exposed to PARPi at clinically relevant doses by both sister chromatid exchange (SCE) assays and chromosome spreading. As expected, both olaparib and veliparib effectively inhibited poly-ADP-ribosylation (PAR), and caused marked hypersensitivity in HR-deficient cells. Significant dose-dependent increases in SCEs were observed in normal and non-tumorigenic cells with minimal residual PAR activity. Clinically relevant doses of the FDA-approved olaparib led to a marked increase of SCEs (5-10-fold) and chromatid aberrations (2-6-fold). Furthermore, olaparib potentiated SCE induction by cisplatin in normal human cells. Our data have important implications for therapies with regard to sustained genotoxicity to normal cells. Genomic instability arising from PARPi warrants consideration, especially if these agents will be used in people with early stage cancers, in prevention strategies or for non-oncologic indications.

Comparison of repair of O6-methylguanine produced by N-methyl-N'-nitro-N-nitrosoguanidine in mouse and human cells.

Abstract: The repair of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-produced O6-methylguanine (O6-MeG) in DNA and its correlation with MNNG-produced cell-killing and sister chromatid exchange (SCE) induction were compared in mouse and reference human tumor cell strains. As a result, mouse cell strains were divided into three groups: (i) cells proficient in O6-MeG-repair and insensitive to MNNG similar to human Mer+ Rem+ strains; (ii) cells deficient in O6-MeG-removal and sensitive to MNNG similar to human Mer-Rem- strains; (iii) cells deficient in O6-MeG-removal but insensitive to MNNG similar to some SV40-transformed human strains. Attempts at correlating lack of capacity for O6-MeG-removal, MNNG-sensitivity and high SCE induction showed that O6-MeG in DNA may be a lesion common to cell-killing and SCE induction only in mouse cells of groups i and ii. Levels of O6-MeG-DNA methyltransferase activity in mouse cells were measured and the enzyme had the same molecular weight as that in human cells.