COMET WP4 - DELIVERABLE (D4.2): Joint Research Activities:Midterm report

The COMET deliverable D4.2 "Joint Research Activities: Midterm report" presents the results obtained to date in WP4. This WP is focussing on epigenetic effects and their possible role in the induction of transgenerational changes in organisms experiencing chronic exposure to low doses of ionizing radiation (IR). We hypothesise that (1) Exposure to gamma-irradiation results in a changed radio-sensitivity within and over generations (2) Epigenetic mechanisms underlie changes in radiosensitivity observed in gamma-irradiated organisms and (3) Epigenetic changes observed in gamma-irradiated organisms grown under controlled lab conditions are similar to epigenetic changes observed in areas affected by a nuclear accident, i.e. the Chernobyl Exclusion Zone (CEZ) and the Fukushima affected areas. Those hypotheses are investigated in model species representative of different environmental compartments: zebrafish, frog, earthworm and Arabidopsis thaliana plants. In addition, both laboratory experiments and field experiments are carried out. To ensure consistency of used protocols for performing analyses in different laboratories, it has been decided to study DNA methylation using Methylation Sensitive Amplified Fragment Length Polymorphism (MS-AFLP) as common method. In addition, DNA methylation in zebrafish and A. thaliana was determined at the genome-wide level using High Performance Liquid Chromatography–Tandem Mass Spectrometry (HPLC–MS/MS). To optimize the techniques, a pilot experiment was performed on zebrafish exposed to waterborne depleted uranium (DU). This experiment indicated that both MS-AFLP and HPLC–MS/MS are effective in assessing the effects of DU on the DNA methylation after chronic exposure to environmentally relevant DU concentrations. After the method optimization for all the organisms, the different organisms were exposed to radiation. From the results obtained so far, it is clear that the methylation status changes after exposure to IR. However, further analyses are still needed to identify the possible key role of epigenetic changes in the response of organisms to radiation. Concerning the field studies, a sampling campaign was done to establish a first overview of the earthworm diversity within the CEZ according to contamination level and habitat type. In addition, the effects of chronic exposure to IR on the Japanese tree frog (Hyla japonica) sampled in the Fukushima Daiichi contaminated areas was addressed. More sampling campaigns in CEZ and Fukushima will take place in spring and autumn of 2016. This will allow a greater understanding of the role of epigenetics in the biological responses to chronic exposure to IR by relating the changes in the epigenetic parameters to field based radionuclide exposure.