Tritium (³H) is a radioactive isotope of hydrogen. In the environment, the most common form of tritium is tritiated water (HTO). The present study aimed to identify early biomarkers of HTO contamination through the use of an aquatic model, the zebrafish (Danio rerio). We used the zebrafish embryo-larvae model to investigate the modes of action of HTO exposure at dose rates of 0.4 and 4 mGy/h, dose rates expected to induce deleterious effects on fish. Zebrafish were exposed to HTO from 3 hpf (hours post fertilization) to 96 hpf. The transcriptomic effects were investigated 24 h and 96 h after the beginning of the contamination, using mRNAseq. Results suggested an impact of HTO contamination, regardless of the dose rate, on genes involved in muscle contraction (tnnt2d, tnni2a.4, slc6a1a or atp2a1l) and eye opacity (crygm2d9, crygmxl1, mipb or lim2.3) after 24 h of contamination. Interestingly, an opposite differential expression was highlighted in genes playing a role in muscle contraction and eye opacity in 24 hpf embryos when comparing dose rates, suggesting an onset of DNA protective mechanisms. The expression of h2afx and ddb2 involved in DNA repair was enhanced in response to HTO exposure. The entrainment of circadian clock and the response to H₂O₂ signalling pathways were enriched at 96 hpf at 0.4 mGy/h and in both stages after 4 mGy/h. Genes involved in ROS scavenging were differentially expressed only after 24 h of exposure for the lowest dose rate, suggesting the onset of early protective mechanisms against oxidative stress. Effects highlighted on muscle at the molecular scale were confirmed at a higher biological scale, as electron microscopy observations revealed sarcomere impairments in 96 hpf larvae for both dose rates. Together with other studies, the present work provides useful data to better understand modes of action of tritium on zebrafish embryos-larvae.

（（³ H）是氢的放射性同位素。在环境中，最常见的of形式是tri水（HTO）。本研究旨在通过使用水生模型斑马鱼（Danio rerio）来识别HTO污染的早期生物标记。我们使用斑马鱼胚胎-幼虫模型研究了HTO暴露在0.4和4 mGy / h的剂量率下的作用模式，该剂量率预计会对鱼类造成有害影响。斑马鱼暴露于HTO的时间从3 hpf（受精后数小时）到96hpf。使用mRNAseq对污染开始后24小时和96小时的转录组效应进行了研究。结果表明，无论剂量率高低，HTO污染都会对参与肌肉收缩的基因产生影响（tnnt2d，tnni2a.4，slc6a1a或atp2a11l）和污染24小时后的眼睛混浊（crygm2d9，crygmxl1，mipb或lim2.3）。有趣的是，当比较剂量率时，在24 hpf胚胎的肌肉收缩和眼不透明性中起作用的基因中，一个相反的差异表达被突出显示出来，提示了DNA保护机制的开始。响应HTO暴露，参与DNA修复的h2afx和ddb2的表达增强。昼夜节律时钟的夹带和对H ₂ O ₂的响应信号通路在96 hpf时以0.4 mGy / h富集，并且在4 mGy / h之后的两个阶段均富集。仅在最低剂量率的暴露24小时后，参与ROS清除的基因才有差异表达，这表明了针对氧化应激的早期保护机制的开始。在更高的生物学规模上证实了在分子尺度上对肌肉产生的影响，因为电子显微镜观察显示两种剂量率的96 hpf幼虫均出现肌节损伤。与其他研究一起，本工作提供了有用的数据，以更好地了解of对斑马鱼胚胎-幼虫的作用方式。