Bertolini Francesca, Jørgensen Michelle Grace Pinto, Henkel Christiaan, Dufour Sylvie, Tomkiewicz Jonna
National Institute of Aquatic Resources, Technical University of Denmark, Lyngby, Denmark.
Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway.
PLoS One. 2020 Aug 13;15(8):e0236438. doi: 10.1371/journal.pone.0236438. eCollection 2020.
The life cycle of European eel (Anguilla anguilla), a catadromous species, is complex and enigmatic. In nature, during the silvering process prior to their long spawning migration, reproductive development is arrested, and they cease feeding. In studies of reproduction using hormonal induction, eels are equivalently not feed. Therefore, in female eels that undergo vitellogenesis, the liver plays different, essential roles being involved both in vitellogenins synthesis and in reallocating resources for the maintenance of vital functions, performing the transoceanic reproductive migration and completing reproductive development. The present work aimed at unravelling the major transcriptomic changes that occur in the liver during induced vitellogenesis in female eels. mRNA-Seq data from 16 animals (eight before induced vitellogenesis and eight after nine weeks of hormonal treatment) were generated and differential expression analysis was performed comparing the two groups. This analysis detected 1,328 upregulated and 1,490 downregulated transcripts. Overrepresentation analysis of the upregulated genes included biological processes related to biosynthesis, response to estrogens, mitochondrial activity and localization, while downregulated genes were enriched in processes related to morphogenesis and development of several organs and tissues, including liver and immune system. Among key genes, the upregulated ones included vitellogenin genes (VTG1 and VTG2) that are central in vitellogenesis, together with ESR1 and two novel genes not previously investigated in European eel (LMAN1 and NUPR1), which have been linked with reproduction in other species. Moreover, several upregulated genes, such as CYC1, ELOVL5, KARS and ACSS1, are involved in the management of the effect of fasting and NOTCH, VEGFA and NCOR are linked with development, autophagy and liver maintenance in other species. These results increase the understanding of the molecular changes that occur in the liver during vitellogenesis in this complex and distinctive fish species, bringing new insights on European eel reproduction and broodstock management.
欧洲鳗鲡（Anguilla anguilla）是一种降河洄游鱼类，其生命周期复杂且神秘。在自然环境中，在进行漫长的产卵洄游之前的性腺成熟过程中，生殖发育会停滞，并且它们停止进食。在使用激素诱导进行繁殖研究时，鳗鱼同样不进食。因此，在经历卵黄发生的雌性鳗鱼中，肝脏发挥着不同的重要作用，既参与卵黄蛋白原的合成，又参与重新分配维持重要功能、进行跨洋生殖洄游和完成生殖发育所需的资源。本研究旨在揭示雌性鳗鱼在诱导卵黄发生过程中肝脏发生的主要转录组变化。生成了16只动物（8只在诱导卵黄发生前和8只在激素处理9周后）的mRNA测序数据，并对两组进行了差异表达分析。该分析检测到1328个上调转录本和1490个下调转录本。上调基因的过度表达分析包括与生物合成、雌激素反应、线粒体活性和定位相关的生物学过程，而下调基因则富集于与包括肝脏和免疫系统在内的多个器官和组织的形态发生和发育相关的过程。在关键基因中，上调的基因包括在卵黄发生中起核心作用的卵黄蛋白原基因（VTG1和VTG2），以及ESR1和两个以前未在欧洲鳗鲡中研究过的新基因（LMAN1和NUPR1），它们在其他物种中与繁殖有关。此外，一些上调基因，如CYC1、ELOVL5、KARS和ACSS1，参与禁食效应的管理，而NOTCH、VEGFA和NCOR在其他物种中与发育、自噬和肝脏维持有关。这些结果增进了对这种复杂而独特的鱼类在卵黄发生过程中肝脏发生的分子变化的理解，为欧洲鳗鲡的繁殖和亲鱼管理带来了新的见解。
