鲟鱼和匙吻鲟(鲟形目)的免疫系统:利用染色体尺度下的基因组数据进行性总结

发布于 2021-04-09 10:31

鲟鱼(鲟鱼科)和匙吻鲟(匙吻鲟科)及其他分支脊椎动物的

主要免疫器官的系统发育和基因组学研究

摘要

鲟鱼的免疫研究对探究其进化历程和相关的应用研究（包括鱼子酱和肉制品的生产、野生鲟鱼的保护以及通过保育再引进等）具有重要意义。通过全面查阅免疫器官的相关文献，我们在脊椎动物系统发育和基因组学的背景下讨论了先天性和适应性免疫系统的激发过程。胸腺作为鲟鱼适应性免疫的关键器官，需要我们在未来对其进行更深入的分子生物学研究。同样，目前关于鲟鱼特异性心包和脑膜组织免疫功能的数据也十分缺乏。如果将免疫和内分泌功能综合起来看，鲟鱼的头肾类似于硬骨鱼的头肾。另外，我们还需要对最近发现的鲟鱼模式识别受体的下游调控通路做更进一步的研究。在本文中，我们首次汇总了有关鲟形目鱼类Toll样受体（TLRs）的数据信息。Toll样受体是在细胞膜和核内体中表达的I型跨膜糖蛋白，通过分子模式诱导启动炎症和宿主防御。鲟鱼的视黄酸诱导基因I样(RIG-like)受体是大多数不同类型细胞的RNA和病毒感染的关键感受器。与硬骨鱼类似，鲟鱼也拥有适应性免疫系统的主要组成部分，包括B细胞、免疫球蛋白、主要组织相容性复合物和T细胞的适应性细胞反应。但是，目前鲟鱼先天性和适应性免疫基因在不同器官的变化情况尚未得到充分研究。从基因组学的角度来看，本文展示的100个关键免疫基因的最新数据体现了鲟鱼特异性基因组复制后的多种进化轨迹，其中一些单拷贝基因与多拷贝基因形成对比，使其组织发生特异化、亚功能化或两者兼而有之成为可能。当然，本文得出的初步结论还需要通过进化生物信息学对涉及到的所有1000多个免疫基因进行进一步地检验。最后，本文刷新了我们对于鲟形目鱼类免疫系统的有关认知，指出了当前研究的重要空白领域，以期为未来鲟鱼的应用提供参考基础。

关键词

进化，基因组学，免疫基因，免疫器官，免疫系统，鲟鱼

Abstract

Sturgeon immunity is relevant for basic evolutionary and applied research, including caviar- and meat-producing aquaculture, protection of wild sturgeons and their re-introduction through conservation aquaculture. Starting from a comprehensive overview of immune organs, we discuss pathways of innate and adaptive immune systems in a vertebrate phylogenetic and genomic context. The thymus as a key organ of adaptive immunity in sturgeons requires future molecular studies. Likewise, data on immune functions of sturgeon-specific pericardial and meningeal tissues are largely missing. Integrating immunological and endocrine functions, the sturgeon head kidney resembles that of teleosts. Recently identified pattern recognition receptors in sturgeon require research on downstream regulation. We review first acipenseriform data on Toll-like receptors (TLRs), type I transmembrane glycoproteins expressed in membranes and endosomes, initiating inflammation and host defence by molecular pattern-induced activation. Retinoic acid-inducible gene-I-like (RIG-like) receptors of sturgeons present RNA and key sensors of virus infections in most cell types. Sturgeons and teleosts share major components of the adaptive immune system, including B cells, immunoglobulins, major histocompatibility complex and the adaptive cellular response by T cells. The ontogeny of the sturgeon innate and onset of adaptive immune genes in different organs remain understudied. In a genomics perspective, our new data on 100 key immune genes exemplify a multitude of evolutionary trajectories after the sturgeon-specific genome duplication, where some single-copy genes contrast with many duplications, allowing tissue specialization, sub-functionalization or both. Our preliminary conclusion should be tested by future evolutionary bioinformatics, involving all >1000 immunity genes. This knowledge update about the acipenseriform immune system identifies several important research gaps and presents a basis for future applications.

Key words: evolution, genomics, immune genes, immune organs, immune system, sturgeon.