Meyer-Alert Henriette, Wiseman Steve, Tang Song, Hecker Markus, Hollert Henner
Institute for Environmental Research, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany.
Toxicology Centre, University of Saskatchewan, 44 Campus Drive, Saskatoon, Saskatchewan S7N 5B3, Canada; Department of Biological Sciences and Water Institute for Sustainable Environments (WISE), University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada.
Ecotoxicol Environ Saf. 2021 Jan 15;208:111716. doi: 10.1016/j.ecoenv.2020.111716. Epub 2020 Dec 11.
Although withdrawn from the market in the 1980s, polychlorinated biphenyls (PCBs) are still found ubiquitously in the aquatic environment and pose a serious risk to biota due to their teratogenic potential. In fish, early life-stages are often considered most sensitive with regard to their exposure to PCBs and other dioxin-like compounds. However, little is known about the molecular drivers of the frequently observed teratogenic effects. Therefore, the aims of our study were to: (1) characterize the baseline transcriptome profiles at different embryonic life-stages in zebrafish (Danio rerio); and (2) to identify the molecular response to PCB exposure and life-stage specific-effects of the chemical on associated processes. For both objectives, embryos were sampled at 12, 48, and 96 h post-fertilization (hpf) and subjected to Illumina sequence-by-synthesis and RNAseq analysis. Results revealed that with increasing age more genes and related pathways were upregulated both in terms of number and magnitude. Yet, other transcripts followed an opposite pattern with greater transcript abundance at the earlier time points. Additionally, embryos were exposed to PCB126, a potent agonist of the aryl hydrocarbon receptor (AHR). ClueGO network analysis revealed significant enrichment of genes associated with basic cell metabolism, communication, and homeostasis as well as eye development, muscle formation, and skeletal formation. We selected eight genes involved in the affected pathways for an in-depth characterization of their regulation throughout normal embryogenesis and after exposure to PCB126 by quantification of transcript abundances every 12 h until 118 hpf. Among these, fgf7 and c9 stood out because of their strong upregulation by PCB126 exposure at 48 and 96 hpf, respectively. Cyp2aa12 was upregulated from 84 hpf on. Fabp10ab, myhz1.1, col8a1a, sulf1, and opn1sw1 displayed specific regulation depending on the developmental stage. Overall, we demonstrate that (1) the developmental transcriptome of zebrafish is highly dynamic, and (2) dysregulation of gene expression by exposure to PCB126 was significant and in several cases not directly connected to AHR-signaling. Hence, this study improves the understanding of linkages between molecular events and apical outcomes that are of regulatory relevance.
尽管多氯联苯（PCBs）在20世纪80年代已退出市场，但在水生环境中仍普遍存在，因其致畸潜力对生物群构成严重风险。在鱼类中，早期生命阶段通常被认为对多氯联苯和其他二噁英类化合物的暴露最为敏感。然而，对于频繁观察到的致畸效应的分子驱动因素知之甚少。因此，我们研究的目的是：（1） 表征斑马鱼（Danio rerio）不同胚胎生命阶段的基线转录组图谱；（2） 确定对多氯联苯暴露的分子反应以及该化学物质对相关过程的生命阶段特异性影响。为了实现这两个目标，在受精后12、48和96小时（hpf）对胚胎进行采样，并进行Illumina合成测序和RNAseq分析。结果显示，随着年龄的增长，无论是在数量还是幅度上，上调的基因和相关通路都更多。然而，其他转录本则呈现相反的模式，在较早的时间点转录本丰度更高。此外，胚胎暴露于多氯联苯126，一种芳烃受体（AHR）的强效激动剂。ClueGO网络分析显示，与基本细胞代谢、通讯和稳态以及眼睛发育、肌肉形成和骨骼形成相关的基因显著富集。我们选择了受影响通路中的八个基因，通过在118 hpf之前每12小时定量转录本丰度，深入表征它们在正常胚胎发育过程中以及暴露于多氯联苯126后的调控情况。其中，fgf7和c9尤为突出，因为它们分别在48和96 hpf时因暴露于多氯联苯126而强烈上调。Cyp2aa12从84 hpf开始上调。Fabp10ab、myhz1.1、col8a1a、sulf1和opn1sw1根据发育阶段表现出特定的调控。总体而言，我们证明了（1）斑马鱼的发育转录组具有高度动态性，（2）暴露于多氯联苯126导致的基因表达失调很显著，并且在某些情况下与AHR信号传导没有直接联系。因此，本研究增进了对分子事件与具有监管相关性的顶端结果之间联系的理解。
