Unknown,Transcriptomics,Genomics,Proteomics

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Gamma radiation induces Life stage-dependent reprotoxicity in Caenorhabditis elegans via impairment of spermatogenesis

ABSTRACT: 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.

INSTRUMENT(S): Illumina HiSeq 4000

ORGANISM(S): Caenorhabditis elegans

SUBMITTER: Fabian Grammes

PROVIDER: E-MTAB-8004 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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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Gamma radiation induces Life stage-dependent reprotoxicity in Caenorhabditis elegans via impairment of spermatogenesis

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