Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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In vivo assessment of ROS production and oxidative stress effects induced by chronic exposure to gamma radiation in C. elegans

ABSTRACT: Ionizing radiation-induced changes to the redox balance does not only represent a risk for the cellular homeostasis, but can also induce a drastic modulation in the overall signalling system of cells. In the current study, effects of chronic exposure to ionizing gamma radiation were assessed in the radioresistant nematode Caenorhabditis elegans in order to understand whether antioxidant defences (AODs) could ameliorate radical formation, or if increased ROS levels would cause oxidative damage. This analysis was accompanied by phenotypical as well as molecular investigations, via assessment of reproductive capacity and somatic growth and differential gene expression through RNA sequencing. The use of a fluorescent reporter strain (sod1::gfp) and two ratiometric biosensors (Hyper and Grx1-roGFP2) demonstrated increased ROS production (H2O2) and activation of AODs (SOD1 and GPx) in vivo. The data indicate that at dose-rates ≤10 mGy/h defence mechanisms were able to prevent the manifestation of oxidative stress. In contrast, at dose-rates ≥40 mGy/h the constant formation of radicals induced a redox shift, which lead to oxidative damage responses, including changes in mitochondrial metabolism and functions, protein degradation, lipid metabolism, collagen synthesis and modulation of transcription. Moreover, genotoxic effects were among the most over-represented functions affected by chronic gamma irradiation, as indicated by differential regulation of genes involved in DNA damage, DNA repair, cell-cycle checkpoints, chromosome segregation and chromatin remodelling. Ultimately, the exposure to gamma radiation caused reprotoxic effects, with >20% reduction in the number of offspring per adult hermaphrodite at dose-rates ≥40 mGy/h, accompanied by the down-regulation of more than 300 genes related to reproductive system, meiotic functions and gamete development and fertilization.

INSTRUMENT(S): Illumina HiSeq 4000

ORGANISM(S): Caenorhabditis elegans

SUBMITTER: Fabian Grammes

PROVIDER: E-MTAB-8284 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:In the current study a systematic investigation of life stage, tissue and cell dependent sensitivity to ionizing radiation in the nematode Caenorhabditis elegans was conducted. This revealed that individuals that have reached the post-mitotic L4 stage showed no significant effects with respect to mortality, morbidity or reproduction when subjected to either acute dose ≤6 Gy(1500 mGy/h) or chronic exposure ≤4 Gy( ≤ 100 mGy/h). In contrast, chronic exposure from embryo to young adult stage caused a dose and dose rate dependent reprotoxicitiy with 43% reduction in total brood size at 6.7Gy (107 mGy/h). Systematic targeted irradiation of developmental stages showed that exposure during L1 to young L4 was sufficient to induce reprotoxic effects. Exposure during these stages was associated with a dose rate dependent genotoxic effects on gonads with 1.7 to 3.2 fold increase in germ cell apoptosis in larvae subjected to 40-100 mGy/h, respectively. Importantly, exposure to gamma radiation significantly impaired spermatogenesis in a dose rate dependent manner. The observed reduction in the number of spermatids accounted for xx% of the reprotoxic effects, thus signifying spermatids as the most radiosensitive cell type in C. elegans. Molecular responses analyzed by RNAseq of nematodes irradiated from L1 to L4 stage revealed a significant enrichment of genes related to both male and hermaphrodite reproductive processes. Gene network analysis identified adverse genotoxic effects related to down-regulation of genes required for spindle formation and sperm meiosis/maturation, including smz-1, smz-2 and htas-1. The expression of a subset of 28 set-17 regulated Major Sperm Proteins (MSP) required for spermatids production was correlated to the reduction in reproduction and the number of spermatids, thus corroborating the impairment of spermatogenesis as the major cause of gamma radiation induced life-stage dependent reprotoxic effect. Furthermore, the progeny of irradiated nematodes showed significant embryonal DNA damage that was associated with persistent effect on somatic growth. Unexpectedly, these nematodes did however maintain much of their reproductive capacity in spite of the reduced growth.

Project description:Although radiation effects have been extensively studied, the biological effects of low-dose radiation (LDR) are controversial. This study investigates LDR-induced alterations in locomotive behavior and gene expression profiles of Drosophila melanogaster. We measured locomotive behavior using larval pupation height and rapid iterative negative geotaxis (RING) assay after exposure to 0.1 Gy gamma-radiation (dose rate of 16.7 mGy/h). We also observed chronic LDR effects on development (pupation and eclosion rates) and longevity (life span). To identify chronic LDR effects on gene expression, we performed whole-genome expression analysis using gene-expression microarrays, and confirmed the results using quantitative real-time PCR. Pupation height was significantly higher after LDR treatment at the first larval instar. Locomotive behavior of male flies was significantly greater approximately 3M-BM--5 weeks after LDR, but pupation and eclosion rates and life spans were not significantly different. Genome-wide expression analysis identified 344 genes that were differentially expressed in irradiated larvae compared with those of controls. We identified several genes belonging to larval behavior functional groups such as locomotive behavior and oxidation reduction, and genes involved in conventional functional groups modulated by irradiation such as defense response, sensory and perception. Four candidate genes were confirmed as differentially expressed genes in irradiated larvae using qRT-PCR. These data suggest that LDR stimulates locomotion-related genes, and these genes can be used as potential markers for LDR. Eggs were collected from 5-day-old female flies and cultivated for 24 h on standard medium. Then, twenty larvae were manually selected and seeded on fresh standard medium in a new vial. After transfer, the experimental group of first-instar larvae was immediately irradiated with chronic gamma-radiation at a dose rate of 16.7 mGy/h. After treatment, gamma-irradiated flies and non-irradiated control flies were maintained in the same incubator at 25degC.

Project description:Following nuclear accidents and the increasing use of radionuclides, environmental radiation radiological protection is a source of major concern, particularly in the context of low doses. Ionizing radiation (IR) may lead to genetic mutations, chromosomal rearrangements and epigenetic modifications. The present study focuses on the in vivo effects of low to moderate doses of IR on zebrafish early embryonic development. The effects of IR on the transcriptome were studied at the shield stage (6 hours post-fertilization, hpf) and at dose rates from 50 mGy/h to 0.005 mGy/h. The effects on the methylome by whole genome bisulfite sequencing were investigated at the same stage and at dose rates of 50 mGy/h and 5 mGy/h.IR exposure impacted the expression of genes involved in germ layers specification during gastrulation of zebrafish embryos. Moreover, changes in mitochondrial energetic metabolism were detected at all dose rates. Different transcriptomic responses were observed between groups irradiated at the two highest dose rates, 50 mGy/h and 5 mGy/h and those irradiated at the three lower dose rates. However, the transcriptomic analysis revealed an impact of IR on development, neurogenesis and muscular development at 50 mGy/h, 5 mGy/h and 0.5 mGy/h. The global level of methylation was not changed after exposure to IR, and no widespread changes in transposable elements were detected. Rather, we observed that IR induced loci specific demethylation in the promoter of genes involved in development, neurogenesis and myogenesis. Interestingly, this promoter hypomethylation was equally associated with a change in gene expression. In this study, both DMR and gene expression analysis pointed toward a specific deregulation of genes involved in development, neurogenesis and myogenesis. The modification of the methylation pattern in promoters of genes involved in central nervous system development and muscle development seems to be responsible of transcriptomic changes. This study confirms previous results obtained at later developmental stages, showing that neurogenesis and muscle development were also impacted at 50 mGy/h, 5 mGy/h and 0.5 mGy/h with phenotypic alterations in terms of muscle histology and swimming behaviour. This suggests that early developmental perturbations are predictive of functional defects at later developmental stages.

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In vivo assessment of ROS production and oxidative stress effects induced by chronic exposure to gamma radiation in C. elegans

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