Effects of chronic gamma irradiation : a multigenerational study using Caenorhabditis elegans

The assessment of environmental impact of exposure to ionizing radiation (natural and ubiquitous phenomenon enriched by human activities) has become a major concern. However, this environmental risk assessment is currently hampered by the lack of knowledge, and hence, is often based on extrapolation from data obtained for acute exposure. Studies on chronic exposure over several generations are so needed to understand the disturbances related to ionizing radiation and their possible consequences on the population. Regarding this background, we assessed the effects of chronic exposure to ionizing radiation over three generations of the ubiquitous nematode Caenorhabditis elegans. In this study C. elegans were chronically and individually exposed to gamma radiation (dose rates ranging from 6.6 to 42.7 mGy/h). The evolution of growth and reproduction (here, cumulated number of larvae per individual) of individuals were followed daily. Comparisons within and between the generations of C. elegans subjected to different exposure statuses: (i) three generations continuously exposed (F0, F1, and F2) and (ii) parental generation exposed (F0) and the following generations placed in recovery (F1' and F2') were performed. Our experiment showed no significant difference in growth between the control and the exposed individuals whatever the generation and the exposed status. However we observed a decrease in the reproductive ability between F0 and F2 at the highest dose rate (42.7 mGy/h). We also observed significant differences in the same generation subjected to different exposure statuses (exposed (F1) or recovery (F1')). Surprisingly, the non-exposed generation (F1') laid out less number of eggs than the exposed generation (F1). Our results confirmed that reproduction is the most sensitive endpoint affected by ionizing radiation and revealed transgenerational effects from parental exposure in the second generation (F1') and the third generation (F2). Using these results on reproduction, molecular and cellular effects of chronic exposure to ionizing radiations on germline are examined to better understand the mechanisms underlying the observed effects