Acentric Fragments Research Articles

Application of FISH based G2-PCC assay for the cytogenetic assessment of high radiation dose exposures: Potential implications for rapid triage biodosimetry.

The main goal of this study is to test the utility of calyculin A induced G2-PCC assay as a biodosimetry triage tool for assessing a wide range of low and acute high radiation dose exposures of photons. Towards this initiative, chromosome aberrations induced by low and high doses of x-rays were evaluated and characterized in G2-prematurely condensed chromosomes (G2-PCCs) by fluorescence in situ hybridization (FISH) using human centromere and telomere specific PNA (peptide nucleic acid) probes. A dose dependent increase in the frequency of dicentric chromosomes was observed in the G2-PCCs up to 20 Gy of x-rays. The combined yields of dicentrics and rings in the G2-PCCs showed a clear dose dependency up to 20 Gy from 0.02/cell for 0.1 Gy to 14.98/cell for 20 Gy. Centric rings were observed more frequently than acentric ring chromosomes in the G2-PCCs at all the radiation doses from 1 Gy to 20 Gy. A head-to-head comparison was also performed by FISH on the yields of chromosome aberrations induced by different doses of x-rays (0 Gy -7.5 Gy) in colcemid arrested metaphase chromosomes and calyculin A induced G2-PCCs. In general, the frequencies of dicentrics, rings and acentric fragments were slightly higher in G2-PCCs than in colcemid arrested metaphase chromosomes at all the radiation doses, but the differences were not statistically significant. To reduce the turnaround time for absorbed radiation dose estimation, attempt was made to obtain G2-PCCs by reducing the culture time to 36 hrs. The absorbed doses estimated in x-rays irradiated (0,1,2 and 4 Gy) G2-PCCs after 36 hrs of culture were grossly like that of G2-PCCs and colcemid arrested metaphase chromosomes prepared after 48 hrs of culture. Our study indicates that the shortened version of calyculin A induced G2-PCC assay coupled with the FISH staining technique can serve as an effective triage biodosimetry tool for large-scale radiological/nuclear incidents.

Bleomycin-induced chromosomal aberrations in Epstein-Barr virus-transformed human lymphoblastoid cells

We have evaluated the induction of complete (i.e., without open ends) and incomplete (i.e., with non-rejoined or open ends) chromosomal aberrations by the radiomimetic antibiotic bleomycin (BLM) in human lymphoblastoid cells immortalized with the Epstein-Barr virus (EBV). An EBV-induced lymphoblastoid cell line (T-37) was exposed to BLM (10–200 µg/mL) for 2 h at 37ºC, and chromosomal aberrations were analyzed 24 h after treatment, using PNA-FISH with pan-telomeric and pan-centromeric probes. Both complete (multicentrics, rings, compound acentric fragments, and interstitial deletions) and incomplete (incomplete chromosomes or IC, and terminal acentric fragments or TAF) chromosomal aberrations increased significantly in BLM-exposed cells, although the concentration-response relationship was non-linear. Of the acentric fragments (ace) induced by BLM, 40 % were compound fragments (CF, ace +/+). TAF (ace, +/-) and interstitial fragments (IAF, ace -/-) were induced at similar frequencies (30 %). 230 ICE were induced by BLM, of which 52 % were IC and 48 % TAF. The average ratio between total incomplete chromosome elements (ICE) and multicentrics was 1.52. These findings suggest that human lymphoblastoid cells exhibit less repair capacity than human lymphocytes, with respect to BLM-induced ICE, and that chromosomal incompleteness is a common event following exposure of these cells to BLM.

Mitotic Errors Increase Radiation Sensitivity in Multiple Cancer Cell Types and in Laryngeal Cancer Patients

Chromosomal instability (CIN) arises from continual mitotic errors over the course of multiple cell divisions and is common in cancer. When CIN is increased beyond a maximally tolerated threshold it leads to cell death due to loss of both copies of one or more essential chromosomes. Combining two independent insults that each cause tolerable levels of CIN results in high CIN, cell death and tumor suppression. Because radiation causes CIN, we hypothesize that pre-existing CIN sensitizes tumor cells to radiation therapy. We characterized CIN in 4 HPV+ and 4 HPV- head and neck (HNC), 4 cervical, and 2 breast cancer cell lines before and 24 hours after 2 Gy of radiation. CIN was quantified by scoring lagging, bridge, and misaligned chromosomes, centrosome amplification, and multipolar spindles using immunofluorescence microscopy. To test our hypothesis, we created isogenic CIN and non-CIN HeLa and FaDu cells by knocking down the mitotic checkpoint protein Mad1, which induces lagging chromosomes, and by using MCF10A cells expressing tet-inducible polo-like kinase 4 (PLK4) to induce centrosome amplification. Clonogenic assays and murine tumor growth curves were used to determine radiation sensitivity in vitro and in vivo respectively. 6-chromosome FISH was used to quantify CIN and test if it was associated with local recurrence (LR) in a cohort of 29 laryngeal cancer patients treated with definitive (chemo)radiation. Significant differences were determined using a two-tailed student's t-test or Fisher's exact test. A total of 2 Gy of radiation significantly increased lagging, bridge, and misaligned chromosomes and induced centrosome amplification in all cancer cell types in vitro and in vivo. Most abnormal chromosomes after radiation were acentric fragments, which are known to missegregate. Mad1 knockdown in HeLa and FaDu cells increased CIN and led to significantly increased radiation sensitivity compared to their wild-type counterparts. PLK4 overexpression in MCF10A cells led to centrosome amplification and multipolar spindles, which also increased radiation sensitivity. Additionally, mitotic errors were significantly correlated with radiation response in both HPV+ and HPV- patient derived xenograft (PDX) HNC tumors. Finally, patients with laryngeal tumors with CIN below the median of the cohort had a 31% rate of LR after therapy, while tumors with CIN greater than or equal to the median had a LR rate of only 6%. Cancer cells with higher CIN are more sensitive to radiation therapy in vitro and in vivo. This was true for different types of mitotic errors and in different cancer models implying this is likely tumor type agnostic. Importantly, laryngeal tumors with higher baseline levels of CIN had an improved response to definitive radiation therapy, implying increased radiation sensitivity. These studies have potential implications for personalization of radiation dose.

Preliminary study of chromosome aberrations using Giemsa, two-colour fish, and micronucleus assays in lymphocytes of individuals living in elevated radon concentration areas.

The frequencies of unstable and stable chromosome aberrations and micronuclei were examined in peripheral blood samples from 10 individuals living in elevated radon concentration areas (Takandeang Village, Mamuju, Indonesia). Blood samples from 10 people living in Topoyo Village were used as a control group. For unstable chromosome aberration analysis, a dicentric chromosome assay was conducted using conventional Giemsa staining. Chromosomal painting of chromosomes 1 and 4 using the fluorescence in situ hybridisation technique was also applied to four subjects to assess the stable chromosome aberration. Our study showed no significant increases across all groups in dicentric and other unstable chromosome aberrations, such as rings and acentric fragments. Translocations were found in one person from Takandeang Village and two Topoyo Village inhabitants. The translocations found in the subjects from Takandeang Village were due more to aging factors than to radon exposure. The number of micronuclei per 1000 binucleus cells in Takandeang Village inhabitants was not significantly different than that in the control group (p=0.943). A more comprehensive analysis should be conducted in a subsequent study by increasing the number of study donors and the number of metaphases to be analysed in both dicentric chromosome assay and fluorescence in situ hybridisation assays. Such research could provide valid information on the cytogenetic effects of elevated indoor radon exposure.

SETD2 safeguards the genome against isochromosome formation.

Isochromosomes are mirror-imaged chromosomes with simultaneous duplication and deletion of genetic material which may contain two centromeres to create isodicentric chromosomes. Although isochromosomes commonly occur in cancer and developmental disorders and promote genome instability, mechanisms that prevent isochromosomes are not well understood. We show here that the tumor suppressor and methyltransferase SETD2 is essential to prevent these errors. Using cellular and cytogenetic approaches, we demonstrate that loss of SETD2 or its epigenetic mark, histone H3 lysine 36 trimethylation (H3K36me3), results in the formation of isochromosomes as well as isodicentric and acentric chromosomes. These defects arise during DNA replication and are likely due to faulty homologous recombination by RAD52. These data provide a mechanism for isochromosome generation and demonstrate that SETD2 and H3K36me3 are essential to prevent the formation of this common mutable chromatin structure known to initiate a cascade of genomic instability in cancer.

Cytogenetic disorders of winter wheat root meristem cells under the action of moderate and high concentrations of N-nitroso-N-methylurea

Aim. To study the frequency and spectrum of the cytogenetic disorders in Triticum aestivum L., induced by the effect of moderate and high concentrations of N-nitroso-N-methylurea. Methods. The seeds of winter wheat of cultivars Albatros odeskyi and Zymoiarka were treated with water solution of N-nitroso-N-methylurea in such concentrations as 0.005 %, 0.01 %, 0.025 %. A cytogenetic analysis of the cells of a root meristem was made with help of an anatelophase method. Results. The frequency of mitoses with chromosome aberrations amounted to 2.74–23.05 %, and it depended on the concentration of a mutagen and a plant genotype. A significant increase of the frequency of the aberrant cells was recorded as a result of the effect of the mutagen in the concentration 0.025 %, which was associated with a radiometric impact caused by the influence of a chemical mutagen in a high concentration. The spectrum of cytogenetic disorders contained mostly acentric fragments, the bridges of a chromatid type and the chromosomes which lagged behind. As the super-mutagen concentration increased, the spectrum expansion of the cytogenetic disorders took place at the expense of the even acentric fragments, micro-nuclei and acentric rings. Conclusions. The frequency of the chromosome aberrations, induced by the effect of NMU, exceeds the control level by 3.5–39.7 times, and it depends directly on the concentration of a chemical mutagen. N-nitroso-N-methylurea in the concentration equal to 0.025 % shows a radiometric effect which classifies a mentioned amount of the concentration of a super-mutagen as a high one. A serious increase of the indicator of the number of aberrations per aberrant cell appeared to be typical only when it was under the effect of a chemical mutagen in the highest concentration.

Analysis of chromosome aberrations in peripheral blood lymphocyte of medical radiation workers in a tertiary hospital

Objective: To analyze the level of chromosome aberration in lymphocytes of medical radiation workers and its influencing factors. Methods: From July to September 2020, 252 medical workers in a tertiary hospital were selected as the study subjects and 107 preserviceworkers were selected as the control group. The Chromosomal aberrations of peripheral blood lymphocytes were measured using conventional cytogenetic analysis method, and the differences were analyzed. Results: The frequencies of dicentric puls centric ring, total chromosome-type aberrations, and abnormal detection rate in the radiation group were significantly higher than those in the control group (Z=2.59, 3.74, 9.99, P<0.05). There was significant difference in the frequencies of dicentric plus centric ring and total chromosome-type aberrations among different types of work (χ(2)=8.59, 8.17, 11.39, P<0.05), and the frequencies of dicentric plus centric ring were significantly higher in the interventional radiology group than those in diagnostic radiology (χ(2)=2.90, P<0.05), While the rates of acentric fragment and total chromosome-type aberrations were significantly higher in the nuclear medicine group than those in diagnostic radiology (χ(2)=2.81, 3.19, P<0.05). The difference in the abnormal detection rate of chromosome aberrations between different types of work was statistically significant (P<0.05), and the rate in the interventional radiology group was significantly higher than that in the diagnostic radiology group (χ(2)=7.66, P<0.05). There was no significant difference in chromosome aberration level and abnormal detection rate among different working ages (P>0.05). Poisson regression analysis indicated that the type of work is a risk factor for chromosomal aberration [IRR=2.31 (nuclear medicine group), 1.66 (Radiation therapy), and 1.78 (interventional group) ; P<0.05]. Conclusion: Ionizing radiation causes certain radiation damage to medical radiology workers, and the frequencies of chromosome aberration in the radiation workers of nuclear medicine and interventional radiology groups are relatively high, so radiation protection should be strengthened to ensure the health of relevant workers.

Abstract PR012: SETD2 safeguards the genome against isochromosome formation

Abstract Chromosome mis-segregation during cell division occurs in diverse tumor types, promoting aneuploidy and intratumoral genetic heterogeneity. While the mechanisms that govern chromosome segregation are well-established, how changes in the activities of tumor suppressors or oncogenes drive mitotic errors remain poorly understood. Loss of the tumor suppressor SETD2, the methyltransferase responsible for tri-methylation of histone 3 lysine 36 (H3K36me3), correlates with clear cell renal cell carcinoma (ccRCC) tumors exhibiting extensive intratumoral heterogeneity. Yet, how loss of H3K36me3 or SETD2 promotes heterogeneity is unknown. Here, we show that loss of SETD2 promotes chromosome mis-segregation during mitosis and interphase DNA bridges driven by the formation of dicentric chromosomes. Cytogenetic analyses revealed that these dicentrics loss were largely comprised of mirror-imaged isodicentric chromosomes that contain two active centromeres. In addition to isodicentrics, cells lacking SETD2 or H36K36me3 generated iso- and acentric chromosomes, however loss of SETD2 protein additionally caused chromosome instability. These data directly link loss of a tumor suppressor to these mutable chromatin structures that initiate intratumor heterogeneity by promoting gross chromosomal rearrangements. Citation Format: Frank M. Mason, Anteneh T. Tebeje, Emily S. Kounlavong, Rashmi Dahiya, Logan Vlach, Tiffany Guess, Ruhee Dere, Ryoma Ohi, Peter Ly, Cheryl L. Walker, W. Kimryn Rathmell. SETD2 safeguards the genome against isochromosome formation [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr PR012.

Recombinase-independent chromosomal rearrangements between dispersed inverted repeats in Saccharomyces cerevisiae meiosis.

DNA double-strand break (DSB) repair by homologous recombination (HR) uses a DNA template with similar sequence to restore genetic identity. Allelic DNA repair templates can be found on the sister chromatid or homologous chromosome. During meiotic recombination, DSBs preferentially repair from the homologous chromosome, with a proportion of HR events generating crossovers. Nevertheless, regions of similar DNA sequence exist throughout the genome, providing potential DNA repair templates. When DSB repair occurs at these non-allelic loci (termed ectopic recombination), chromosomal duplications, deletions and rearrangements can arise. Here, we characterize in detail ectopic recombination arising between a dispersed pair of inverted repeats in wild-type Saccharomyces cerevisiae at both a local and a chromosomal scale-the latter identified via gross chromosomal acentric and dicentric chromosome rearrangements. Mutation of the DNA damage checkpoint clamp loader Rad24 and the RecQ helicase Sgs1 causes an increase in ectopic recombination. Unexpectedly, additional mutation of the RecA orthologues Rad51 and Dmc1 alters-but does not abolish-the type of ectopic recombinants generated, revealing a novel class of inverted chromosomal rearrangement driven by the single-strand annealing pathway. These data provide important insights into the role of key DNA repair proteins in regulating DNA repair pathway and template choice during meiosis.

Detection of complex chromosome rearrangements using optical genome mapping

Chromosomal structural variations (SVs) are a main cause of human genetic disease. Currently, karyotype, chromosomal microarray analysis (CMA), and fluorescent in situ hybridization (FISH) form the backbone of current routine diagnostics (CRD). These methods have their own limitations. CRD cannot identify cryptic balanced SVs and complex SVs even if these techniques were performed either simultaneously or in a sequential manner. Optical genome mapping (OGM) is a novel technology that can identify several classes of SVs with higher resolution, but studies on the applicability of OGM and its comparison with CRD are inadequate for difficult and complicated chromosomal SVs are lacking. Herein, seven patients with definite complicated SVs involving at least two breakpoints (BPs) were recruited for this study. The results of BPs and SVs from OGM were compared with those from CRD. The results showed that all BPs of five samples and partial BPs of two samples were detected by OGM. The undetected BPs were all close to the repeat-rich gap region. Besides, OGM also detected additional SVs including a cryptic balanced translocation, two additional complex chromosomal rearrangement (CCR). OGM yielded the additional information, such as the orientation of acentric fragments, BP positions, and genes mapped in the BP region for all the cases. The accuracy of additional SVs and BPs detected by OGM was verified by FISH panel and next-generation sequencing and Sanger sequencing. Taken together, OGM exhibit a better performance in detecting chromosomal SVs compared to the CRD. We suggested that OGM method should be utilized in the clinical examination to improve the efficiency and accuracy of genetic disease diagnosis, supplemented by FISH or karyotyping to compensate for the SVs in the repeat-rich gap region if necessary.

Chromosomal aberrations induced by Mitomycin C in canine lymphocytes

Chromosomal aberrations comprise an abnormal number of chromosomes as well as changes in the structure of the chromosomes. Aberrations in the structure of chromosomes, such as gaps and breaks in chromatids and chromosomes, acentric fragments, telomeric associations, deletions, early chromatid-separation and large scale effects, such as pulverized metaphases, and sticky metaphases. In this study, the effect of Mitomycin C, a recognized clastogen on human lymphocytes, was assayed in cultures of canine lymphocytes, an animal species that is flourishing in comparative medicine. Blood cultures were performed on samples from a male and a female dog. Cytotoxicity using the mitotic index and genotoxicity testing were performed with 0.25 µg/ml Mitomycin C. The total chromosomal aberrations were significantly higher due to the effect of Mitomycin C (P=0.0247). The number of chromatid breaks nearly quintupled, while pulverized metaphases were found to be six times more frequent, and endoduplicated cells were three times higher than in negative control cultures. The quantitatively most relevant chromosomal aberration was the presence of sticky metaphases, related to adverse effects in chromatin proteins. The potential use of canine lymphocytes for chromosomal aberration assay is emphasized in the evaluation or re-evaluation of the genotoxic in vitro effect of xenobiotics, to evidence chromosomal damage.

Chromosome damage in regions with different levels of air pollution.

Air pollution is an important environmental factor influencing human health. In this study, we compared chromosome damage in city policemen from three cities in the Czech Republic: industrial Ostrava characterized by high levels of benzo[a]pyrene, Prague with heavy traffic emitting nitrogen oxides, and relatively clean Ceske Budejovice located in an area with predominantly agricultural activity. Chromosomal aberrations in lymphocytes were evaluated by fluorescence in situ hybridization with painting probes for chromosomes 1, 2, 3, and 4 in spring and autumn. An increase in the frequency of unstable chromosome aberrations, that is, dicentric chromosomes and acentric fragments, was observed in spring samples from Ostrava (p = .014 and p = .044, respectively) and Prague (p = .002 and p = .006, respectively) in comparison with Ceske Budejovice. The difference was significant only for samples taken after the winter period, when the concentration of pollutants in the air increases due to poor dispersion conditions. An increased frequency of dicentric chromosomes was observed in spring compared to autumn in both Ostrava and Prague (p = .017 and p = .023, respectively), but not in Ceske Budejovice. More breakpoints were observed on chromosome 1 than on the other chromosomes examined (p < .001). The number of breakpoints in the heterochromatin region 1p11-q12 was lower than in other parts of chromosome 1 (p < .001), suggesting a protective function of heterochromatin against damage. Our study showed, that air pollution increased the frequency of unstable chromosome aberrations, especially dicentric chromosomes. However, we did not show an effect on stable chromosome rearrangements.

In vitro assessment of the antioxidative, toxicological and antimicrobial properties of battery of parabens

The aim of this study was to evaluate antioxidative features using 2,2-diphenyl-1-pycrylhydrazyl free radical (DPPH•) scavenging method, bovine serum albumin (BSA)-binding properties with usage of spectrofluorimetric method, proliferative and cyto/genotoxic status by use of chromosome aberration test, and antimicrobial potential using broth microdilution method, followed by resazurin assay of benzyl-, isopropyl-, isobutyl and phenylparaben in vitro. Our results showed that all parabens had significant antiradical scavenger activity compared to p-hydroxybenzoic acid (PHBA) precursor. Higher mitotic index for benzyl-, isopropyl and isobutylparaben (250 µg/mL) in comparison with control was demonstrated. An increase in the frequency of acentric fragments in lymphocytes treated with benzylparaben and isopropylparaben (125 and 250 µg/mL), and isobutylparaben (250 µg/mL) was observed. Isobutylparaben (250 µg/mL) induced higher number of dicentric chromosomes. An increased number of minute fragments in lymphocytes exposed to benzylparaben (125 and 250 µg/mL) was found. A significant difference in the frequency of chromosome pulverization, between phenylparaben (250 µg/mL) and control, was detected. Benzylparaben (250 µg/mL) and phenylparaben (62.5 µg/mL) caused an increase in the number of apoptotic cells, while isopropylparaben (62.5, 125 and 250 µg/mL) and isobutylparaben (62.5 and 125 µg/mL) induced higher frequency of necrosis. Minimum inhibitory concentration (MIC) of tested parabens ranged 15.62–250 µg/mL for bacteria, and 125–500 µg/mL for the yeast. Minimum microbiocidal concentration ranged 31.25 to 500 µg/mL, and 250 to 1000 µg/mL in bacteria and fungi respectively. The lowest MICs for bacteria were observed for phenyl- (15.62 µg/mL) and isopropylparaben (31.25 µg/mL) against Enterococcus faecalis.

CIP2A and TOPBP1: Molecular lassos that herd pulverized micronuclear chromosomes

Lin etal.1 demonstrate that acentric chromosome fragments generated within micronuclei are tethered by the CIP2A-TOPBP1 complex during mitosis, thus promoting clustered segregation of the fragments to a single daughter cell nucleus and facilitating re-ligation with limited chromosomal scattering and loss.

Mitotic clustering of pulverized chromosomes from micronuclei

Complex genome rearrangements can be generated by the catastrophic pulverization of missegregated chromosomes trapped within micronuclei through a process known as chromothripsis1–5. As each chromosome contains a single centromere, it remains unclear how acentric fragments derived from shattered chromosomes are inherited between daughter cells during mitosis6. Here we tracked micronucleated chromosomes with live-cell imaging and show that acentric fragments cluster in close spatial proximity throughout mitosis for asymmetric inheritance by a single daughter cell. Mechanistically, the CIP2A–TOPBP1 complex prematurely associates with DNA lesions within ruptured micronuclei during interphase, which poises pulverized chromosomes for clustering upon mitotic entry. Inactivation of CIP2A–TOPBP1 caused acentric fragments to disperse throughout the mitotic cytoplasm, stochastically partition into the nucleus of both daughter cells and aberrantly misaccumulate as cytoplasmic DNA. Mitotic clustering facilitates the reassembly of acentric fragments into rearranged chromosomes lacking the extensive DNA copy-number losses that are characteristic of canonical chromothripsis. Comprehensive analysis of pan-cancer genomes revealed clusters of DNA copy-number-neutral rearrangements—termed balanced chromothripsis—across diverse tumour types resulting in the acquisition of known cancer driver events. Thus, distinct patterns of chromothripsis can be explained by the spatial clustering of pulverized chromosomes from micronuclei.

Chromosomal fragile site breakage by EBV-encoded EBNA1 at clustered repeats.

Epstein-Barr virus (EBV) is an oncogenic herpesvirus associated with several cancers of lymphocytic and epithelial origin1-3. EBV encodes EBNA1, which binds to a cluster of 20 copies of an 18-base-pair palindromic sequence in the EBV genome4-6. EBNA1 also associates with host chromosomes at non-sequence-specific sites7, thereby enabling viral persistence. Here we show that the sequence-specific DNA-binding domain of EBNA1 binds to acluster of tandemly repeatedcopies of an EBV-like, 18-base-pair imperfect palindromic sequence encompassing a region of about 21 kilobases at human chromosome 11q23. In situ visualization of the repetitive EBNA1-binding site reveals aberrant structures on mitotic chromosomes characteristic of inherently fragile DNA. We demonstrate that increasing levels of EBNA1 binding trigger dose-dependent breakage at 11q23, producing a fusogenic centromere-containing fragment and an acentric distal fragment, with both mis-segregated into micronuclei in the next cell cycles. In cells latently infected with EBV, elevating EBNA1 abundance by as little as twofold was sufficient to trigger breakage at 11q23. Examination of whole-genome sequencing of EBV-associated nasopharyngeal carcinomas revealed that structural variants are highly enriched on chromosome 11. Presence of EBV is also shown to be associated with an enrichment of chromosome 11 rearrangements across 2,439 tumours from 38 cancer types. Our results identify a previously unappreciated link between EBV and genomic instability, wherein EBNA1-induced breakage at 11q23 triggers acquisition of structural variations in chromosome 11.

Cytogenetic features in adolescent girls with abnormal uterine bleeding which is comorbid with multi­factor diseases

Objective — to study the state of chromosomal apparatus in adolescent girls with abnormal uterine bleeding which is comorbid with multi-­factor diseases.&#x0D; Materials and methods. Cytogenetic analysis has been carried out in 25 girls aged 14 to 17 with abnormal uterine bleeding (AUB) which is comorbid with multifactor diseases (endocrine and nervous). The comparison group included 25 age-matching healthy girls. All the girls have been examined in the Laboratory of Medical Genetics of the Institute. Statistical processing of the study results has been carried out following the Student’s t­test with the use of Excel software package.&#x0D; Results and discussion. According to the data of cytogenetic analysis, it has been established that the total level of chromosome aberrations in blood lymphocytes of sick girls constituted 5.44 % and exceeded this value by a factor of 2.2 in comparison with the frequency in healthy girls. A 1.8-­fold increase of the number of chromosome aberrations was observed; among them the paired acentric fragments have been recorded twice as often. Chromatid­type aberrations in blood lymphocytes were observed in 2.9 times oftener in girls with AUB, mainly due to an increase in the number of single acentric fragments. The frequency of genomic disorders was 0.60 % that is five times more than their frequency in blood lymphocytes of healthy girls.&#x0D; Conclusions. Cytogenetic analysis conducted in adolescent girls with abnormal uterine bleeding and comorbid pathology have revealed an increase of the overall level of chromosome aberrations in comparison with healthy girls. Paired acentric fragments prevailed among chromosome aberrations, single acentric fragments prevailed among chromatid-­type aberrations, polyploid cells prevailed among genomic disorders.

Antecedent chromatin organization determines cGAS recruitment to ruptured micronuclei

Micronuclei (MN) are cytosolic bodies that sequester acentric fragments or mis-segregated chromosomes from the primary nucleus. Spontaneous rupture of the MN envelope allows recognition by the viral receptor cyclic GMP-AMP synthase (cGAS), initiating interferon signaling downstream of DNA damage. Here, we demonstrate that MN rupture is permissive but not sufficient for cGAS localization. Chromatin characteristics such as histone 3, lysine 79 dimethylation (H3K79me2) are present in the nucleus before DNA damage, retained in ruptured MN, and regulate cGAS recruitment. cGAS is further responsive to dynamic intra-MN processes occurring prior to rupture, including transcription. MN chromatin tethering via the nucleosome acidic patch is necessary for cGAS-dependent interferon signaling. Our data suggest that both damage-antecedent nuclear chromatin status and MN-contained chromatin organizational changes dictate cGAS recruitment and the magnitude of the cGAS-driven interferon cascade. Our work defines MN as integrative signaling hubs for the cellular response to genotoxic stress.

Medical personnel occupationally exposed to low-dose ionising radiation in Federation of Bosnia and Herzegovina: A cytogenetic study.

Medical radiation exposures have been reduced significantly with modern equipment and protection measures. Biomonitoring of medical personnel can provide information concerning possible effects of radiation exposure. However, chromosome aberration (CA) analysis is now recommended only when the estimated effective dose is 200 mSv or higher. In this retrospective study in Bosnia and Herzegovina, we have measured the cytogenetic status of medical workers and healthy volunteers (controls). Peripheral blood samples from 66 medical workers exposed to low-dose ionising radiation and 89 non-exposed volunteers were collected for chromosome aberrations (CA) analysis and the cytokinesis-block micronucleus (CBMN) assay. Higher rates of chromatid and chromosome breaks, acentric fragments, double minutes, micronuclei, and micronucleated binuclear cells were observed in the control group, while the rate of nucleoplasmic bridges was higher in the medical workers group.

Chromosome aberrations, micronucleus frequency, and catalase concentration in a population chronically exposed to high levels of radon

Purpose To deepen our knowledge on the effects of high levels of indoor radon exposure, we assessed the frequencies of unstable and stable chromosome aberrations and micronucleus (MN), as well as the concentration of an endogenous antioxidant (catalase, CAT), in blood samples of individuals chronically exposed to high indoor radon concentrations in Indonesia (Tande-Tande sub-village, Mamuju, West Sulawesi). Moreover, we also investigated the occurrence of a radio-adaptive response (RAR) in Tande-Tande sub-village inhabitants using the G2 MN assay. Materials and Methods The frequencies of dicentric (DC), acentric (AF), ring (R), and translocation (Tr) chromosomes in Tande-Tande inhabitants were compared to those in people living in a reference area with low levels of indoor radon levels (Topoyo village, Indonesia). The number of MN per 1000 binucleated cells (BNC) and CAT concentration per total protein was quantified and compared between groups. Lastly, we irradiated (2 Gy) phytohemagglutinin-stimulated samples in vitro and measured the frequency of MN to verify the occurrence of a RAR in Tande-Tande sub-village inhabitants. Results and Conclusion The frequencies of DC, AF, and Tr did not differ between Tande-Tande inhabitants and control subjects (p = 0.350, 0.521, 0.597). The frequency of MN in Tande-Tande inhabitants was significantly lower than that in the control group (p = 0.006). Similarly, CAT concentration in Tande-Tande inhabitants was also significantly lower than that in the control population (p < 0.001). Significant negative correlations were identified for MN number and CAT concentration versus indoor radon concentration, annual effective dose, or cumulative dose both within groups and when all data were analyzed together. Our findings indicate that, despite the high indoor radon levels, Tande-Tande inhabitants are not under oxidative stress, since this group had lower CAT concentration and MN frequency than those in the control group. The negative correlation between MN frequency and indoor radon concentration, annual effective dose, and cumulative dose suggests the occurrence of an RAR phenomenon in Tande-Tande sub-village inhabitants. This interpretation is also supported by the results of the G2 MN assay, which revealed lower MN frequencies after in vitro irradiation of samples from Tande-Tande sub-village inhabitants than those in samples from the control group (p = 0.0069, for cumulative MN frequency; p = 0.0146, for radiation-induced MN only).