Showing papers on "Sister chromatid exchange published in 2017"
TL;DR: Low-input methylase-assisted bisulfite sequencing and single-cell MAB-seq are described, capable of profiling 5fC and 5caC at genome scale using ∼100 cells and single cells, respectively, and allowing the simultaneous high-resolution mapping of sister chromatid exchange (SCE), facilitating the study of this type of genomic rearrangement.
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.
37 citations
TL;DR: Results of the present study demonstrate the cytogenetic damage in peripheral blood lymphocytes of oncology department personnel to avoid potential health hazards caused by cytostatic agents.
Abstract: Objective: Concern exists regarding the possible hazards to the personnel handling anti-neoplastic drugs. The purpose of the present study was to assess the genotoxicity induced by anti-neoplastic agents in oncology department personnel. Materials and methods: To do this, the frequency of chromosomal aberrations (CAs) induced in peripheral blood lymphocytes was assessed at G0 phase of the cell cycle using metaphase analysis, cytokinesis block-micronucleus (MN) assay and sister chromatid exchange (SCE) assay. These cytogenetic end points were measured among 71 nurses in oncology department and 10 drugstore personnel handling and preparing anti-neoplastic drugs. The results were compared to those of 74 matched nurses for age and sex not exposed to any anti-neoplastic agents. Results: There was no significant difference between the age of study subjects and control group (p > 0.05). The results showed that the mean frequency of cytogenetic damages in terms of CAs [chromatid breaks (p = 0.01), chromos...
36 citations
TL;DR: It is provided the first quantifiable evidence that most spontaneous SCE events in wild-type cells are not due to the repair of DNA double-strand breaks, which is an indicator of elevated recombination activity and of genome instability, which are a hallmark of cancer.
Abstract: Homologous recombination involving sister chromatids is the most accurate, and thus most frequently used, form of recombination-mediated DNA repair. Despite its importance, sister chromatid recombination is not easily studied because it does not result in a change in DNA sequence, making recombination between sister chromatids difficult to detect. We have previously developed a novel DNA template strand sequencing technique, called Strand-seq, that can be used to map sister chromatid exchange (SCE) events genome-wide in single cells. An increase in the rate of SCE is an indicator of elevated recombination activity and of genome instability, which is a hallmark of cancer. In this study, we have adapted Strand-seq to detect SCE in the yeast Saccharomyces cerevisiae. We provide the first quantifiable evidence that most spontaneous SCE events in wild-type cells are not due to the repair of DNA double-strand breaks.
33 citations
TL;DR: It is shown that constitutive signaling driven by mutated FLT3 and JAK2 confers interchromosomal homologous recombination (iHR), a precedent for CN-LOH, and therapeutic reduction of ROS may thus prevent leukemic progression and relapse in myeloid malignancies.
Abstract: Acquired copy neutral LOH (CN-LOH) is a frequent occurrence in myeloid malignancies and is often associated with resistance to standard therapeutic modalities and poor survival. Here, we show that constitutive signaling driven by mutated FLT3 and JAK2 confers interchromosomal homologous recombination (iHR), a precedent for CN-LOH. Using a targeted recombination assay, we determined significant iHR activity in internal tandem duplication FLT3 (FLT3-ITD) and JAK2V617F-mutated cells. Sister chromatid exchanges, a surrogate measure of iHR, was significantly elevated in primary FLT3-ITD normal karyotype acute myeloid leukemia (NK-AML) compared with wild-type FLT3 NK-AML. HR was harmonized to S phase of the cell cycle to repair broken chromatids and prevent iHR. Increased HR activity in G0 arrested primary FLT3-ITD NK-AML in contrast to wild-type FLT3 NK-AML. Cells expressing mutated FLT3-ITD demonstrated a relative increase in mutation frequency as detected by thymidine kinase (TK) gene mutation assay. Moreover, resistance was associated with CN-LOH at the TK locus. Treatment of FLT3-ITD- and JAK2V617F-mutant cells with the antioxidant N-acetylcysteine diminished reactive oxygen species (ROS), restoring iHR and HR levels. Our findings show that mutated FLT3-ITD and JAK2 augment ROS production and HR, shifting the cellular milieu toward illegitimate recombination events such as iHR and CN-LOH. Therapeutic reduction of ROS may thus prevent leukemic progression and relapse in myeloid malignancies. Cancer Res; 77(7); 1697-708. ©2017 AACR.
25 citations
TL;DR: It is found that Hmr and Lhr are required in D. melanogaster for detachment of sister chromatids during anaphase, and not for a centromere defect causing hybrid lethality.
Abstract: Crosses between Drosophila melanogaster females and Drosophila simulans males produce hybrid sons that die at the larval stage. This hybrid lethality is suppressed by loss-of-function mutations in the D. melanogaster Hybrid male rescue (Hmr) or in the D. simulans Lethal hybrid rescue (Lhr) genes. Previous studies have shown that Hmr and Lhr interact with heterochromatin proteins and suppress expression of transposable elements within D. melanogaster It also has been proposed that Hmr and Lhr function at the centromere. We examined mitotic divisions in larval brains from Hmr and Lhr single mutants and Hmr; Lhr double mutants in D. melanogaster In none of the mutants did we observe defects in metaphase chromosome alignment or hyperploid cells, which are hallmarks of centromere or kinetochore dysfunction. In addition, we found that Hmr-HA and Lhr-HA do not colocalize with centromeres either during interphase or mitotic division. However, all mutants displayed anaphase bridges and chromosome aberrations resulting from the breakage of these bridges, predominantly at the euchromatin-heterochromatin junction. The few dividing cells present in hybrid males showed fuzzy and irregularly condensed chromosomes with unresolved sister chromatids. Despite this defect in condensation, chromosomes in hybrids managed to align on the metaphase plate and undergo anaphase. We conclude that there is no evidence for a centromeric function of Hmr and Lhr within D. melanogaster nor for a centromere defect causing hybrid lethality. Instead, we find that Hmr and Lhr are required in D. melanogaster for detachment of sister chromatids during anaphase.
21 citations
TL;DR: The study shows that some of the basic properties of recombination differ considerably between single-copy and tandemly-repeated genes.
Abstract: In the yeast Saccharomyces cerevisiae, the genes encoding the metallothionein protein Cup1 are located in a tandem array on chromosome VIII. Using a diploid strain that is heterozygous for an insertion of a selectable marker (URA3) within this tandem array, and heterozygous for markers flanking the array, we measured interhomolog recombination and intra/sister chromatid exchange in the CUP1 locus. The rate of intra/sister chromatid recombination exceeded the rate of interhomolog recombination by >10-fold. Loss of the Rad51 and Rad52 proteins, required for most interhomolog recombination, led to a relatively small reduction of recombination in the CUP1 array. Although interhomolog mitotic recombination in the CUP1 locus is elevated relative to the average genomic region, we found that interhomolog meiotic recombination in the array is reduced compared to most regions. Lastly, we showed that high levels of copper (previously shown to elevate CUP1 transcription) lead to a substantial elevation in rate of both interhomolog and intra/sister chromatid recombination in the CUP1 array; recombination events that delete the URA3 insertion from the CUP1 array occur at a rate of >10−3/division in unselected cells. This rate is almost three orders of magnitude higher than observed for mitotic recombination events involving single-copy genes. In summary, our study shows that some of the basic properties of recombination differ considerably between single-copy and tandemly-repeated genes.
20 citations
TL;DR: It is found that the chemoresistant nasopharyngeal carcinoma cells, derived from chronic treatment of cisplatin, show elevated expression of TIP60 and the depletion of Tip60 significantly reduces sister chromatid exchange, a measurement of HR efficiency.
Abstract: The Fanconi anemia pathway in coordination with homologous recombination is essential to repair interstrand crosslinks (ICLs) caused by cisplatin. TIP60 belongs to the MYST family of acetyltransferases and is involved in DNA repair and regulation of gene transcription. Although the physical interaction between the TIP60 and FANCD2 proteins has been identified that is critical for ICL repair, it is still elusive whether TIP60 regulates the expression of FA and HR genes. In this study, we found that the chemoresistant nasopharyngeal carcinoma cells, derived from chronic treatment of cisplatin, show elevated expression of TIP60. Furthermore, TIP60 binds to the promoters of FANCD2 and BRCA1 by using the chromatin immunoprecipitation experiments and promote the expression of FANCD2 and BRCA1. Importantly, the depletion of TIP60 significantly reduces sister chromatid exchange, a measurement of HR efficiency. The similar results were also shown in the FNACD2-, and BRCA1-deficient cells. Additionally, these TIP60-deficient cells encounter more frequent stalled forks, as well as more DNA double-strand breaks resulting from the collapse of stalled forks. Taken together, our results suggest that TIP60 promotes the expression of FA and HR genes that are important for ICL repair and the chemoresistant phenotype under chronic treatment with cisplatin.
13 citations
TL;DR: Findings reveal a new function of PARP-1 in sister chromatid disjunction during mitosis in cohesin-depleted BS cells, regardless of BLM expression status.
Abstract: Bloom Syndrome (BS) is a rare genetic disease characterized by high levels of chromosomal instability and an increase in cancer risk. Cytidine deaminase (CDA) expression is downregulated in BS cells, leading to an excess of cellular dC and dCTP that reduces basal PARP-1 activity, compromising optimal Chk1 activation and reducing the efficiency of downstream checkpoints. This process leads to the accumulation of unreplicated DNA during mitosis and, ultimately, ultrafine anaphase bridge (UFB) formation. BS cells also display incomplete sister chromatid disjunction when depleted of cohesin. Using a combination of fluorescence in situ hybridization and chromosome spreads, we investigated the possible role of CDA deficiency in the incomplete sister chromatid disjunction in cohesin-depleted BS cells. The decrease in basal PARP-1 activity in CDA-deficient cells compromised sister chromatid disjunction in cohesin-depleted cells, regardless of BLM expression status. The observed incomplete sister chromatid disjunction may be due to the accumulation of unreplicated DNA during mitosis in CDA-deficient cells, as reflected in the changes in centromeric DNA structure associated with the decrease in basal PARP-1 activity. Our findings reveal a new function of PARP-1 in sister chromatid disjunction during mitosis.
11 citations
26 Mar 2017
TL;DR: It is demonstrated that DNA damaging agents that cause DSBs stimulate DNA damage-associated SCE by RAD5-independent mechanisms, while several potent agents that generate bulky DNA adducts stimulate SCE in budding yeast mutants by multiple RAD 5-dependent mechanisms.
Abstract: Sister chromatids are preferred substrates for recombinational repair after cells are exposed to DNA damage. While some agents directly cause double-strand breaks (DSBs), others form DNA base adducts which stall or impede the DNA replication fork. We asked which types of DNA damage can stimulate SCE in budding yeast mutants defective in template switch mechanisms and whether PCNA polyubiquitination functions are required for DNA damage-associated SCE after exposure to potent recombinagens. We measured spontaneous and DNA damage-associated unequal sister chromatid exchange (uSCE) in yeast strains containing two fragments of his3 after exposure to MMS, 4-NQO, UV, X rays, and HO endonuclease-induced DSBs. We determined whether other genes in the pathway for template switching, including UBC13, MMS2, SGS1, and SRS2 were required for DNA damage-associated SCE. RAD5 was required for DNA damage-associated SCE after exposure to UV, MMS, and 4-NQO, but not for spontaneous, X-ray-associated, or HO endonuclease-induced SCE. While UBC13, MMS2, and SGS1 were required for MMS and 4NQO-associated SCE, they were not required for UV-associated SCE. DNA damage-associated recombination between his3 recombination substrates on non-homologous recombination was enhanced in rad5 mutants. These results demonstrate that DNA damaging agents that cause DSBs stimulate SCE by RAD5-independent mechanisms, while several potent agents that generate bulky DNA adducts stimulate SCE by multiple RAD5-dependent mechanisms. We suggest that DSB-associated recombination that occurs in G2 is RAD5-independent.
8 citations
TL;DR: It was concluded that Anilofos has genotoxic and cytotoxic effects in human peripheral lymphocytes and this pesticide decreased mitotic index and nuclear division index significantly.
Abstract: We aimed to evaluate the mutagenic effect of Anilofos, organophosphate pesticide, by using Ames/Salmonella/microsome test. Its cytotoxic and genotoxic effects were also determined by chromosome aberration (CA), sister chromatid exchange (SCE) and micronucleus (MN) test in human peripheral blood lymphocytes. In the Ames test, five different concentrations of Anilofos were examined on TA97, TA98, TA100 and TA102 strains in the absence and presence of S9 fraction. According to the results all concentrations of this pesticide have not shown any mutagenic activity on TA97, TA100 and TA102 strains in the absence and presence of S9 fraction. But, 10, 100 and 1000 µg/plate concentrations of Anilofos were determined to be mutagenic on TA98 strain without S9 fraction. Lymphocytes were treated with various concentrations (25, 50, 100 and 200 µg/ml) of Anilofos for 24 and 48 h. The results of the assays showed that Anilofos did not induce SCE frequency, replication index and MN formation at all concentrations for both treatment periods. Anilofos significantly increased CA frequency at 100 and 200 µg/ml concentrations at 24 h treatment periods and at 50, 100 and 200 µg/ml concentrations in 48 h treatment periods. Additionally, it was determined that this pesticide decreased mitotic index and nuclear division index significantly. It was concluded that Anilofos has genotoxic and cytotoxic effects in human peripheral lymphocytes.
7 citations
TL;DR: Hispidin did not increase the frequency of chromosome aberrations, micronuclei, or primary DNA damage in human lymphocytes in vitro and did not produce reverse mutation in bacterial cells, however, inhuman lymphocytes were identified a statistically significant dose-dependent increase in sister chromatid exchange frequency and a decrease in replication index and nuclear division index values.
Abstract: Antioxidant and genotoxic properties of hispidin isolated from the Phaeolus schweinitzii mushroom were evaluated with various assays. Hispidin demonstrated strong free radical scavenging, oxygen radical absorbance capacity, and ferric-reducing antioxidant power; in all applied assays, hispidin exhibited antioxidant capacity similar to or higher than that of the reference antioxidant Trolox. Genotoxic activity of hispidin was assessed using different end points: chromosome aberrations, micronuclei, sister chromatid exchanges, and primary DNA damage (detected by the comet assay) in human lymphocytes in vitro, and gene mutations in the Salmonella/microsome test. Hispidin did not increase the frequency of chromosome aberrations, micronuclei, or primary DNA damage in human lymphocytes in vitro and did not produce reverse mutation in bacterial cells. However, we identified in human lymphocytes a statistically significant dose-dependent increase in sister chromatid exchange frequency and a decrease in replication index and nuclear division index values.
TL;DR: The reported reduction of H3K79 methylation in response to UV exposure in Saccharomyces cerevisiae points to the existence of a novel histone crosstalk pathway that is important for the regulation of UV-induced DNA damage repair.
Abstract: Histone post-translational modifications play vital roles in a variety of nuclear processes, including DNA repair. It has been previously shown that histone H3K79 methylation is important for the cellular response to DNA damage caused by ultraviolet (UV) radiation, with evidence that specific methylation states play distinct roles in UV repair. Here, we report that H3K79 methylation is reduced in response to UV exposure in Saccharomyces cerevisiae. This reduction is specific to the dimethylated state, as trimethylation levels are minimally altered by UV exposure. Inhibition of this reduction has a deleterious effect on UV-induced sister chromatid exchange, suggesting that H3K79 dimethylation levels play a regulatory role in UV repair. Further evidence implicates an additional role for H3K79 dimethylation levels in error-free translesion synthesis, but not in UV-induced G1/S checkpoint activation or double-stranded break repair. Additionally, we find that H3K79 dimethylation levels are influenced by acetylatable lysines on the histone H4 N-terminal tail, which are hyperacetylated in response to UV exposure. Preclusion of H4 acetylation prevents UV-induced reduction of H3K79 dimethylation, and similarly has a negative effect on UV-induced sister chromatid exchange. These results point to the existence of a novel histone crosstalk pathway that is important for the regulation of UV-induced DNA damage repair.
TL;DR: It is indicated that both OXC and its metabolites have cytotoxic, cytostatic and genotoxic potential on human peripheral blood lymphocyte cultures under the experimental conditions.
Abstract: There has been considerable debate about the relationship between epilepsy and cancer. Oxcarbazepine (OXC) is used for treating certain types of seizures in patients with epilepsy. There ha...
TL;DR: It can be suggested that V2O3 induces a genotoxic effect at the centromere level, indicating that it is a cause of aneuploidy that is capable of altering cell cycle progression.
Abstract: Vanadium is a widely distributed metal in the Earth’s surface and is released into the environment by either natural or anthropogenic causes. Vanadium (III) oxide (V2O3) is present in the environment, and many organisms are exposed to this compound; however, its effects at the cellular and genetic levels are still unknown. Therefore, in this study, the ability of V2O3 to induce chromosomal damage and impair cell proliferation was tested on human leukocytes in vitro. The cultures cells were treated for 48 h with different concentrations 2, 4, 8 or 16 μg/mL of V2O3, and we use the sister chromatid exchange’s (SCE) test and the viability assay to evaluate the effects.In the results, no change was observed in either the viability or the frequency of SCE; however, a significant increase was observed in the incidence of premature chromatid separation (PCS), and a decrease was observed in both the mitotic index (MI) and the replication index (RI). Therefore, it can be suggested that V2O3 induces a genoto...
TL;DR: Macrolide antibiotic roxithromycin did not have genotoxic and oxidative stress effects in human-cultured lymphocytes as well as in chromosome aberration and micronucleus tests.
Abstract: Macrolide antibiotic roxithromycin was evaluated in terms of its genotoxic, cytotoxic and oxidative stress effects. For this purpose; 25, 50, 100 and 200 μg/mL concentrations of roxithromycin were dissolved in dimethyl sulfoxide and treated to human peripheral blood lymphocytes for two different treatment periods (24 and 48 h). In chromosome aberration (CA) and micronucleus (MN) tests, roxithromycin did not show genotoxic effect. But it induced sister chromatid exchange (SCE) at the highest concentration (200 μg/mL) for the 24-h treatment period and at all concentrations (except 25 μg/mL) for the 48-h treatment period. Looking at cytotoxic effect of roxithromycin, statistically insignificant decreases on mitotic index and proliferation index were observed. Roxithromycin decreased nuclear division index (NDI) at highest two concentrations (100 and 200 μg/mL) for the 24-h treatment period and at all concentrations (expect 25 μg/mL) for the 48-h treatment period. Total oxidant values, total antioxida...
TL;DR: It is indicated that OFX has cytotoxic, cytostatic and genotoxic potential especially at higher concentrations on human peripheral blood lymphocyte cultures under the experimental conditions.
Abstract: Ofloxacin (OFX), a second-generation of quinolones, is a broad-spectrum flouroquinolone antibiotic used in the treatment of various bacterial infections. In this article, we aimed to investigate the cytotoxic and genotoxic potentials of OFX in cultured human peripheral lymphocytes. The cytotoxicity and genotoxicity of OFX on human peripheral blood lymphocytes were examined in vitro by sister chromatid exchange (SCE), chromosomal aberrations (CAs) and micronucleus (MN) tests. Cultures were treated with 30, 60 and 120 μg/ml of OFX for 48 h. Dimethylsulfoxide (DMSO) was used as a solvent control. OFX decreased the mitotic index (MI) and nuclear division index (NDI) significantly, especially at higher concentrations (60 and 120 μg/ml) compared with solvent control. OFX significantly induced CAs at all concentrations and SCEs at higher concentrations (60 and 120 μg/ml) compared with solvent control. In conclusion, our results indicated that OFX has cytotoxic, cytostatic and genotoxic potential especially at higher concentrations on human peripheral blood lymphocyte cultures under the experimental conditions.
TL;DR: It is indicated that Casiopeina III-Ea® shows cytotoxic and clastogenic activity in bone marrow cells from treated mice.
Abstract: Casiopeina III-Ea® (Cas III-Ea®) is a chelated copper complex with antineoplastic activity that is capable of reducing tumor size and inducing antiproliferative and apoptotic effects However, little is known about its in vivo genotoxic effects Therefore, this study evaluated two cytogenetic and two proliferative parameters 24 h after the administration of Casiopeina III-Ea® to male CD-1 mice Three doses of Cas III-Ea® were administered by intraperitoneal injections of 169, 339 and 676 mg/kg (corresponding to 1/8, 1/4 and 1/2 of LD50, respectively) A reduction in the mitotic index (MI) and an increased numbers of cells with structural chromosomal aberrations (SCA) were detected Additionally, a low but significant increase in the frequency of sister chromatid exchange (SCE) was observed at the highest dose Changes in the DNA replication index (RI) were not observed These results indicate that Casiopeina III-Ea® shows cytotoxic and clastogenic activity in bone marrow cells from treated mice
TL;DR: Although in the assay the drug showed a lower effect, the present study agreed with a previous report that analyzed the amount of micronuclei in mouse peripheral blood, and it confirmed the relevance of evaluating the genotoxic effect of antidepressants, specifically duloxetine by applying diverse tests.
Abstract: Duloxetine is an antidepressant which has showed valuable results, particularly in patients with major depression. This type of drugs is known to require genotoxic studies as part of their preclinical safety evaluation. In the case of duloxetine, however, there have been controversial results. Therefore, we considered it worthwhile to extend studies on the matter in an attempt to reach a conclusion. The present assay was made in mouse bone marrow to evaluate the capacity of the drug to induce sister chromatid exchanges (SCE), as well as to modify the proliferation kinetics and the mitotic index. Three doses of the antidepressant were tested (2, 20, and 200 mg/kg), besides the control mice were administered with purified water, and the positive treated animals administered with 1 mg/kg of doxorubicin. The results indicated a moderate but significant increase of SCE with the three tested doses, no effect regarding the mitotic index and a small reduction in the proliferation kinetics. Although in our assay the drug showed a lower effect, the present study agreed with a previous report that analyzed the amount of micronuclei in mouse peripheral blood, and it confirmed the relevance of evaluating the genotoxic effect of antidepressants, specifically duloxetine by applying diverse tests.
TL;DR: The aim of the study was to analyse chromatin instability by determining the number and sites of spontaneous SCE in the karyotype of arctic and silver foxes and chromosomal polymorphism in the arctic fox and the modal number of B chromosomes in the silver fox were established.
Abstract: The sister chromatid exchange (SCE) test is a cytogenetic assay and is known as a biomonitoring test to analyse chromosome damage caused by exogenous factors. The aim of the study was to analyse chromatin instability by determining the number and sites of spontaneous SCE in the karyotype of arctic and silver foxes. Twenty-four animals: 12 arctic foxes (Vulpes lagopus) and 12 silver foxes (Vulpes vulpes) were investigated. The experiment used peripheral blood lymphocytes following in vitro culture. Karyotype evaluation in both fox species was made by RBA staining with modified Giemsa reagent. To analyse SCE, three different bromodeoxyuridine (BrdU) concentrations were added to the culture and the microscopic preparations were stained by the FPG technique. Based on these results, chromosomal polymorphism in the arctic fox and the modal number of B chromosomes in the silver fox were established. Spontaneous SCE in both fox species was observed at a concentration of 0.5 μg/ml BrdU. The number of spontaneous SCE averaged 0.65±0.55 SCE/cell in the arctic fox and 2.33±0.76 SCE/cell in the silver fox. Higher BrdU concentrations induced additional chromatin breaks. The arctic fox was characterized by a greater number of centromeric SCE in relation to the other SCE types. In the silver fox, centromeric and terminal SCE occurred at a similar frequency. No significant effect of the living environment and no effect of sex on increasing SCE frequency were found in either fox species.
TL;DR: Both ZIP and its metabolites have cytotoxic, cytostatic and genotoxic potential on lymphocyte cultures under the experimental conditions, and further studies are necessary to make a possible risk assessment in patients receiving therapy with this drug.
Abstract: It has been stated that some antipsychotic drugs might cause genotoxic and carcinogenic effects. Ziprasidone (ZIP) is commonly used an antipsychotic drug. However, its genotoxicity and carcinogenicity data are very limited. The cytotoxicity and genotoxicity of ZIP on human peripheral blood lymphocytes were examined in vitro by sister chromatid exchange (SCE), chromosome aberration (CA) and micronucleus (MN) tests in this study. Lymphocyte cultures were treated with 50, 75 and 100 μg/ml of ZIP in the presence and absence of a metabolic activator (S9 mix). Dimethylsulfoxide was used as a solvent control. While the cells were treated with ZIP for 24 h and 48 h in cultures without S9 mix, the cultures with S9 mix were exposed to ZIP for 3 h. ZIP and its metabolites can exert cytotoxic activities due to significant decreases in mitotic index, proliferation index and nuclear division index in the presence and absence of S9 mix. Statistically significant increases in CAs, aberrant cells and MN values in ...
TL;DR: It is found that most spontaneous SCE events are not due to the repair of DNA double-strand breaks, contrary to what is commonly thought.
Abstract: Homologous recombination involving sister chromatids is the most accurate, and thus most frequently used, form of recombination-mediated DNA repair. Despite its importance, sister chromatid recombination is not easily studied because it does not result in a change in DNA sequence, making recombination between sister chromatids difficult to detect. We have previously developed a novel DNA template strand sequencing technique, called Strand-seq, that can be used to map sister chromatid exchange (SCE) events genome-wide in single cells. An increase in the rate of SCE is an indicator of elevated recombination activity and of genome instability, which is a hallmark of cancer. In this study, we have adapted Strand-seq to detect SCE in the yeast Saccharomyces cerevisiae. Contrary to what is commonly thought, we find that most spontaneous SCE events are not due to the repair of DNA double-strand breaks.
01 Jan 2017
TL;DR: Hereditary retinoblastoma lymphocytes appear more radiosensitive than sporadic retinOBlastoma, perhaps, reflecting the increased second malignancies in germinal mutation retin Oblastoma.
Abstract: Lymphocyte cultures were employed to assess the degree of spontaneous and induced chromosomal fragility in retinoblastoma. Sister chromatid exchange (SCEs) were scored in metaphases. Three unilateral, three bilateral, eleven family members and controls were studied. Retinoblastoma (RB) lymphocytes did not exhibit increased spontaneous fragility. X-irradiation (25-200 rad) did not significantly increase SCE in unilateral retinoblastoma lymphocytes when compared with controls (P > 0.50). However, bilaterally affected subjects and three unaffected relatives demonstrated a statistically significant increase in SCE (P < 0.01). In conclusion, hereditary retinoblastoma lymphocytes appear more radiosensitive than sporadic retinoblastoma, perhaps, reflecting the increased second malignancies in germinal mutation retinoblastoma. In addition, the analysis of radiation-induced SCE in peripheral blood lymphocytes of RB patients and family members may provide a valuable tool increasing the accuracy of genetic counseling for this disorder. Additional studies of RB patients and families are needed to assess the relevance of this approach to genetic counseling. Invest Ophthalmol Vis Sci 25:698-702, 1984 This study was undertaken in order to assess the degree of spontaneous and induced sister chromatid exchanges in retinoblastoma patients and family members as compared with controls. Recent studies have suggested that retinoblastoma patients and family members are at higher risk for the development of second nonocular malignancies, the most prevalent of which is osteogenic sarcoma of the femur. 1 " 7 Since
TL;DR: This study demonstrated that by in vitro sister chromatid exchange assay, Mimosa pudica crude bee pollen extract from Chiangmai, Northern Thailand, increased genotoxicity in human lymphocytes at concentrations of 0.005 and 0.5 μg/mL by 20% and 24% respectively, compared to the RPMI control.
Abstract: Bee pollen has been used as a food supplement and as a traditional medicine for thousands of years. Our study demonstrated that by in vitro sister chromatid exchange assay, Mimosa pudica crude bee ...
16 Feb 2017
TL;DR: The results suggested that cynarin may have antigenotoxic potential especially at highest concentrations, as indicated by the reduction in frequency of SCEs/cell in the three concentrations.
Abstract: Artichoke is a plant that is cultivated for its head and leaves which can be eaten as a vegetable. Numerous studies on artichokes have showed that it has health-protective effect such as hepatoprotective, antioxidant, hypocholesterolemic and anticarcinogenic activities. Cynarin is a polyphenol that is derivative of di-caffeoylquinic acids in artichoke. It has strong antioxidant activity. The present study was planned for the assessment of potential in vitro genotoxic and antigenotoxic effect of cynarin against mitomycin-C (MMC) by using sister chromatid exchange (SCE) assay in human lymphocytes. Peripheral lymphocytes were incubated with different concentrations of cynarin (6.25, 12.50, 25.00, 50.00, 100.00 µg/mL) alone and simultaneously with 0.2 µg/mL MMC for 24 and 48 hours. A negative, a solvent (50% methanol) and a positive control (MMC) were also maintained. Cynarin did not significantly increased the SCE/cell frequency at all the concentrations alone compared to control groups at both 24 h and 48 h (except 100 µg/mL). Simultaneous treatment of Cynarin and MMC significantly reduced the frequency of SCEs/cell in the three concentrations (12.50, 25.00 and 50.00 µg/mL) compared to positive control in both application times. Our results suggested that cynarin may have antigenotoxic potential especially at highest concentrations.
01 Jan 2017
TL;DR: Both baseline SCE and delta SCE were not different among patients with arsenic-induced diseases and healthy normal residents, indicating that hypersensitivity may have been due to previous arsenic exposure but was not associated with disease status.
Abstract: The objective of this study was to determine if cytogenetic markers can be used as indicators of prior exposure to arsenic compounds. Baseline sister chromatid exchange (SCE) and mitomycin C-induced (MMC) SCE were measured in four study populations recruited from a blackfoot (BF) disease endemic area, including 22 patients with cancer (CA) only, 8 patients with both BF disease and CA (BF+CA), 10 patients with BF disease only, and 26 healthy residents (HRs). Another group of 23 healthy, nonarsenic-exposed workers were recruited as external healthy controls (HCs). Characteristics of study population were collected by questionnaire, and 10 ml of venous blood were drawn for lymphocyte culture. The results showed that the frequencies of baseline SCE did not differ among the five study groups. The frequencies
TL;DR: It is proposed that BLM protects against genome instability by suppressing recombination at sites of G4 structures, particularly in transcribed regions of the genome.
Abstract: Bloom syndrome is a cancer predisposition disorder caused by mutations in the BLM helicase gene. Cells from persons with Bloom syndrome exhibit striking genomic instability characterized by excessive sister chromatid exchange events (SCEs). We applied single-cell DNA template strand-sequencing (Strand-seq) to map the genomic locations of SCEs at a resolution that is orders of magnitude better than was previously possible. Our results show that, in the absence of BLM, sister chromatid exchanges in human and murine cells do not occur randomly throughout the genome but are strikingly enriched at coding regions, specifically at sites of putative guanine quadruplex (G4) motifs in transcribed genes. We propose that BLM protects against genome instability by suppressing recombination at sites of G4 structures, particularly in transcribed regions of the genome.