Unknown,Transcriptomics,Genomics,Proteomics

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Characterization of gene expression profiles at low and very low doses of ionizing radiation

ABSTRACT: The aim of the present study is to analyze by microarray techniques how gene expression is modulated after exposure to low and very low doses of ionizing radiation, to evaluate if the pattern of gene expression shows dose dependence, and to search for putative regulatory mechanisms behind the observed gene-expression modifications.For this, whole blood samples from five healthy donors diluted in IMDM (1:10) were exposed at six doses between 5 and 500 mGy. Total RNA extraction from CD4+ lymphocytes was done at four different post-irradiation times (150, 300, 450 and 600 min). After mRNA amplification, aRNAs were hybridized on 4x44k DNA microarrays. The results indicated that up-regulation were twice than down-regulation. Surprisingly, the number of modulated genes doesnM-bM-^@M-^Yt seem to change drastically with dose, even at the lowest dose of 5 mGy. Clustering analysis revealed seven gene expression clusters with different dose dependence profiles. The functional analysis showed that the genes which increased their expression with the dose were related to p53 pathway and DNA damage response. This could be observed from 25 mGy, but becomes very clear at doses equal or greater than 100 mGy. On the other hand, genes with a constant modulation of their expression in all the tested doses were related to cellular respiration, ATP metabolic process and chromatin organization. These latter molecular mechanisms seem to be triggered at very low doses (5-25 mGy). In-silico promoter analysis seems to confirm the implication of transcription factors related to the pathways mentioned above. Human whole blood samples from 5 healthy donors were diluted in IMDM medium (1:10) and exposed to 500,100,50,25,10 and 5 mGy of Cobalt 60 gamma-rays. Gene expression alterations were measured 150, 300, 450 and 600 min post exposure after negative cell sorting of lymphocytes TCD4+ cells.

ORGANISM(S): Homo sapiens

SUBMITTER: Gaetan GRUEL

PROVIDER: E-GEOD-43151 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Characterization of gene expression profiles at low and very low doses of ionizing radiation.

Nosel Ingrid I Vaurijoux Aurélie A Barquinero Joan-Francesc JF Gruel Gaetan G

DNA repair 20130516 7

The aim of the present study is to analyse by microarray techniques how gene expression is modulated after exposure to low and very low doses of ionizing radiation, to evaluate if the pattern of gene expression shows dose dependence, and to search for putative regulatory mechanisms behind the observed gene-expression modifications. For this, whole blood samples from five healthy donors were exposed in six doses between 5 and 500mGy. Total RNA extraction from CD4(+) lymphocytes was done at four d ...[more]

PMID: 23683873

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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.

Project description:Background: The effects of dose-rate and its implications on radiation biodosimetry methods are not well studied in the context of large-scale radiological scenarios. There are significant health risks to individuals exposed to an acute dose in such an event, but the most realistic scenario would be a combination of exposure to both high and low dose-rates, from both external and internal radioactivity. It is important therefore, to understand the biological response to prolonged exposure; and further, discover biomarkers that can be used to estimate the extent of damage from low-dose rate exposure and propose appropriate clinical treatment. Methods: We irradiated human whole blood ex vivo to three doses, 0.56 Gy, 2.25 Gy and 4.45 Gy, using two dose rates: 1.1Gy/min and 3.1mGy/min. After 24 hours, we isolated RNA from blood cells and hybridized these to Agilent Whole Human genome microarrays. We validated the microarray results using qRT-PCR. Results: Microarray results showed that there were 454 significantly differentially expressed genes after prolonged exposure to all doses. After acute exposure, 598 genes were differentially expressed to all doses combined. Gene ontology terms enriched in both sets of genes were related to immune processes and B cell mediated immunity. Genes responding to acute exposure was also enriched in functions related to natural killer cell activation and cell-to-cell signaling. As expected, p53 pathway was found to be significantly enriched at all doses and by both dose-rates of radiation. Prediction algorithms were able to distinguish between low dose-rate and acute exposures, on the basis of a group of genes. These maybe candidates for preliminary testing as markers for differences in gene expression based on dose-rate. Radiation induced gene expression was measured in ex vivo irradiated human blood, at the 24hr time point after irradiation. Doses (0.56 Gy, 2.2 Gy and 4.45 Gy) were delivered by two dose rates, acute dose rate of 1Gy/min and low dose rate of 3.1 mGy/min.

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Characterization of gene expression profiles at low and very low doses of ionizing radiation

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Characterization of gene expression profiles at low and very low doses of ionizing radiation.

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