Thesis: After the nuclear accidents at Chernobyl and Fukushima, radiation protection of the environment is a major concern. Studies show an increased sensitivity to ionizing radiation (IR) during development. However, there are few data on the molecular mechanisms leading to the effects of IR on embryogenesis. In this context, the objective of this thesis is to better understand the effects of exposure to IR on the development of zebrafish. Part of this work has focused on studying the effects of IR at an early stage of development. For this, a multi-omics approach with the study of the transcriptome and the methylome has been implemented. These results, highlight potential effects on the development of the central nervous system (CNS) and muscles. The other part of this work focused on assessing the effects of IR exposure at later developmental stages using a system biology approach. The results obtained at the different scales highlight effects on the retinoic acid pathway, the development of the CNS and muscles. This work has shown effects of IR on the development of the CNS and muscles from early development at the molecular level. These effects are confirmed at later stages of development. This study suggests that the molecular effects observed during early development are predictive of the effects observed at later developmental stages. In addition, this thesis work allows to propose a model of "Adverse Outcome Pathway" where the deregulation of the retinoic acid pathway by exposure to IR will lead to effects on the development of the CNS and muscles