Norwegian Veterinary Institute, P.O. Box 8146 Dep, 0033, Oslo, Norway.
Immunogenetics. 2021 Feb;73(1):79-91. doi: 10.1007/s00251-020-01190-6. Epub 2020 Nov 23.
Major histocompatibility complex (MHC) genes are key players in the adaptive immunity providing a defense against invading pathogens. Although the basic structures are similar when comparing mammalian and teleost MHC class II (MHCII) molecules, there are also clear-cut differences. Based on structural requirements, the teleosts non-classical MHCII molecules do not comply with a function similar to the human HLA-DM and HLA-DO, i.e., assisting in peptide loading and editing of classical MHCII molecules. We have previously studied the evolution of teleost class II genes identifying various lineages and tracing their phylogenetic occurrence back to ancient ray-finned fishes. We found no syntenic MHCII regions shared between cyprinids, salmonids, and neoteleosts, suggesting regional instabilities. Salmonids have experienced a unique whole genome duplication 94 million years ago, providing them with the opportunity to experiment with gene duplicates. Many salmonid genomes have recently become available, and here we set out to investigate how MHCII has evolved in salmonids using Northern pike as a diploid sister phyla, that split from the salmonid lineage prior to the fourth whole genome duplication (4WGD) event. We identified 120 MHCII genes in pike and salmonids, ranging from 11 to 20 genes per species analyzed where DB-group genes had the most expansions. Comparing the MHC of Northern pike with that of Atlantic salmon and other salmonids species provides a tale of gene loss, translocations, and genome rearrangements.
主要组织相容性复合体（MHC）基因是适应性免疫的关键参与者，为抵御入侵病原体提供防御。尽管哺乳动物和硬骨鱼类 MHC 类 II（MHCII）分子的基本结构相似，但也存在明显的差异。根据结构要求，硬骨鱼类非经典 MHCII 分子不符合类似于人类 HLA-DM 和 HLA-DO 的功能，即协助经典 MHCII 分子的肽加载和编辑。我们之前研究了硬骨鱼类 II 类基因的进化，确定了各种谱系，并追溯了它们的系统发生起源，可以追溯到古代的有鳍鱼类。我们在鲤鱼、鲑鱼和新鳍鱼类之间没有发现共享的 MHCII 区域，这表明区域不稳定。鲑鱼经历了 9400 万年前的独特全基因组复制，为它们提供了实验基因重复的机会。许多鲑鱼基因组最近已经可用，在这里，我们着手研究鲑鱼中 MHCII 是如何进化的，以北欧梭鲈作为二倍体姐妹门，它在第四次全基因组复制（4WGD）事件之前从鲑鱼谱系中分离出来。我们在梭鲈和鲑鱼中鉴定出 120 个 MHCII 基因，每个分析的物种从 11 到 20 个基因不等，其中 DB 组基因的扩张最多。将北欧梭鲈的 MHC 与大西洋鲑和其他鲑鱼物种的 MHC 进行比较，讲述了基因丢失、易位和基因组重排的故事。
