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MELODI is the European platform dedicated to low-dose radiation risk research. From 7 October through 10 October 2013 the Fifth MELODI Workshop took place in Brussels, Belgium. The workshop offered the opportunity to 221 unique participants originating from 22 countries worldwide to update their knowledge and discuss radiation research issues through 118 oral and 44 poster presentations. In addition, the MELODI 2013 workshop was reaching out to the broader radiation protection community, rather than only the low-dose community, with contributions from the fields of radioecology, emergency and recovery preparedness, and dosimetry. In this review, we summarise the major scientific conclusions of the workshop, which are important to keep the MELODI strategic research agenda up-to-date and which will serve to establish a joint radiation protection research roadmap for the future.

// Christophe Badie 1 , Agnieszka Blachowicz 2 , Zarko Barjaktarovic 3 , Rosemary Finnon 1 , Arlette Michaux 4 , Hakan Sarioglu 5 , Natalie Brown 1 , Grainne Manning 1 , M. Abderrafi Benotmane 4 , Soile Tapio 3 , Joanna Polanska 2 , Simon D. Bouffler 1 1 Radiation Effects Department, Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton, UK 2 Faculty of Automatic Control, Electronics and Computer Science, Silesian University of Techology, Gliwice, Poland 3 Helmholtz Zentrum Munchen, German Research Center for Environmental Health GmbH, Radiation Proteomics Group, Institute of Radiation Biology, Neuherberg, Germany 4 Radiobiology Unit, Institute for Environment, Health and Safety, Belgian Nuclear Research Centre (SCK•.CEN), Mol, Belgium 5 Helmholtz Zentrum Munchen, German Research Center for Environmental Health GmbH, Research Unit Protein Science, Neuherberg, Germany Correspondence to: Simon D. Bouffler, email: simon.bouffler@phe.gov.uk Keywords: ionising radiation, acute myeloid leukaemia, mouse, gene expression, protein expression Received: February 11, 2016 Accepted: May 09, 2016 Published: May 26, 2016 ABSTRACT A combined transcriptome and proteome analysis of mouse radiation-induced AMLs using two primary AMLs, cell lines from these primaries, another cell line and its in vivo passage is reported. Compared to haematopoietic progenitor and stem cells (HPSC), over 5000 transcriptome alterations were identified, 2600 present in all materials. 55 and 3 alterations were detected in the proteomes of the cell lines and primary/ in vivo passage material respectively, with one common to all materials. In cell lines, approximately 50% of the transcriptome changes are related to adaptation to cell culture, and in the proteome this proportion was higher. An AML ‘signature’ of 17 genes/proteins commonly deregulated in primary AMLs and cell lines compared to HPSCs was identified and validated using human AML transcriptome data. This also distinguishes primary AMLs from cell lines and includes proteins such as Coronin 1, pontin/RUVBL1 and Myeloperoxidase commonly implicated in human AML. C-Myc was identified as having a key role in radiation leukaemogenesis. These data identify novel candidates relevant to mouse radiation AML pathogenesis, and confirm that pathways of leukaemogenesis in the mouse and human share substantial commonality.

In view of long-haul space exploration missions, the European Space Agency initiated the Micro-Ecological Life Support System Alternative (MELiSSA) project targeting the total recycling of organic waste produced by the astronauts into oxygen, water and food using a loop of bacterial and higher plant bioreactors. In that purpose, the alpha-proteobacterium, Rhodospirillum rubrum S1H, was sent twice to the International Space Station and was analyzed post-flight using a newly developed R. rubrum whole genome oligonucleotide microarray and high throughput gel-free proteomics with Isotope-Coded Protein Label technology. Moreover, in an effort to identify a specific response of R. rubrum S1H to space flight, simulation of microgravity and space-ionizing radiation were performed on Earth under identical culture set-up and growth conditions as encountered during the actual space journeys. Transcriptomic and proteomic data were integrated and permitted to put forward the importance of medium composition and culture set-up on the response of the bacterium to space flight-related environmental conditions. In addition, we showed for the first time that a low dose of ionizing radiation (2 mGy) can induce a significant response at the transcriptomic level, although no change in cell viability and only a few significant differentially expressed proteins were observed. From the MELiSSA perspective, we could argue the effect of microgravity to be minimized, whereas R. rubrum S1H could be more sensitive to ionizing radiation during long-term space exploration mission.

The aim of studies under way in our laboratory is to investigate whether heterozygous mutations in genes involved in such important cellular processes as cell cycle regulation, apoptosis and DNA repair may influence the radiation sensitivity of early mammalian embryos. The embryonic stage chosen for our first investigations is the zygote (first day of gestation). This stage occurs while women cannot be aware of pregnancy. Moreover, in contradiction with a long standing dogma of teratology, various kinds of malformations were previously found in mouse fetuses from particular (wild-type) strains after X-irradiation at the zygote stage. Our studies mainly concentrate on external congenital anomalies, cytokine secretion in the amniotic fluid and chromosomal instability. Measuring cytokines in the amniotic will enable us to determine whether developmental abnormalities are accompanied by changes in the levels of particular cytokines, as suggested by the few available data. On the other hand, chromosome instability has been recently reported in mouse fetuses from different strains, after x-irradiation at the zygote stage. The gene currently under study is P53, the "genome guardian". The P53 mutation was introduced in the CF1 strain, whose wild-type zygotes had been previously shown by us to be sensitive to radiation induction of congenital anomalies (Jacquet et al., Mutation Res., 332, 73-87, 1995). P53 (+/+ x -/-) or P53 (+/+ x +/-) matings were performed from 7.30 till 9.30 am and the females showing a vaginal plug were x-irradiated with either 0.2 or 0.4 Gy 2 h after presumed fertilization. A number of them were sacrificed on day 8 of gestation, their gastrula stage embryos were collected and their embryonic parts were cultured for 7 h in the presence of colchicine. The cells were then fixed and cytogenetically analyzed. Other females were sacrificed on day 19 of gestation. Pre- and post-implantation losses were recorded, amniotic fluid surrounding the fetuses was collected for cytokine analysis and the living fetuses were weighed and examined under the stereomicroscope for the presence of congenital anomalies. When needed (+/+ x +/- matings), the tails of the fetuses were collected for genotype analysis. So far, and although our results have still to be completed, the P53 mutation did not seem to result into the development of a chromosomal instability and/or to higher levels of congenital anomalies in irradiated embryos. (Partially funded by the research contract n° CO-90 06 2024.00 between SCK•CEN and the Federal Agency for Nuclear Control).

Human lymphocyte subpopulations differ in their cellular responses to ionizing radiation. To shed light on the molecular basis of this effect, we characterized the transcriptional response to 1 Gy X-rays of CD4+ T lymphocytes. Of 18,433 genes tested, 102 were modulated more than 1.5-fold. The majority of the strongly activated genes were p53 targets involved in DNA repair and apoptosis. The expression of three of these genes was further tested by quantitative RT-PCR in lymphocyte subpopulations [CD4+ and CD8+ T, CD19+ B, CD56+ natural killer cells and peripheral blood lymphocytes (PBLs)] from ten adult donors. In contrast to DDB2, TNFRSF10B and BAX were differentially modulated among the subpopulations and the PBLs, being more activated in irradiated CD19+ B and CD8+ T lymphocytes. The level of BAX activation in the various subpopulations correlated with the sensitivity of the cells to radiation, suggesting its possible role in the differential radiosensitivity of hematopoietic cell subsets.

Radiation therapy is a clinical treatment modality where ionizing radiation is used to treat patients with malignant neoplasms. The goal is to deliver a measured dose of radiation to a defined volume with minimal damage to surrounding normal tissue, resulting in eradication of the tumor. Radiotherapy is generally given in divided doses or fractionated. Molecular biology methods have enhanced our ability to investigate the response of cells to ionizing radiation. These methods can be applied to tissue-culture systems or to biopsies from patients both to develop a quick and easy way to predict the radiosensitivity of a patient and to understand how cells respond to stress produced by ionizing radiation. In this review we will mainly explain two major mechanisms involved in human individual radiosensitivity: the DNA-damage repair defect mechanism and the DNA-repair signaling via cell cycle checkpoint defect.