Cartilaginous fish class II genes reveal unprecedented old allelic lineages and confirm the late evolutionary emergence of DM.
Cartilaginous fish class II genes reveal unprecedented old allelic lineages and confirm the late evolutionary emergence of DM.
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DOI：
10.1016/j.molimm.2020.10.003
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发表时间：
2020-12
影响因子：
3.6
通讯作者：
Veríssimo A
中科院分区：
文献类型：
--
作者：
Almeida T;Gaigher A;Muñoz-Mérida A;Neves F;Castro LFC;Flajnik MF;Ohta Y;Esteves PJ;Veríssimo A
软骨鱼类（银鲛、鳐和鲨鱼）是现存最基本的有颌脊椎动物，具有基于主要组织相容性复合体（MHC）的适应性免疫系统。尽管是脊椎动物适应性免疫进化中的一个关键分类群，但尚未对该组的MHC II类基因进行全面表征。我们进行了广泛的生物信息学搜索的转录组和软骨鱼靶向MHC II类序列的基因组的分类学上不同的数据集。从所有分析的分类群中检索到II类α和IIβ序列，并显示出经典II类基因的典型特征。免疫球蛋白超家族结构域的系统发育树显示了两个不同的和非常古老的血统II类基因在Selachians（鲨鱼），起源于> 3.5亿年前。发现了IIα和IIβ基因的谱系特异性对的紧密连锁，证实了先前的结果，来自不同谱系的基因作为等位基因分离。从这些数据中没有检索到非经典II类DM序列，经典II类序列缺乏与DM分子相互作用的保守残基，支持DM系统仅在导致四足动物的叶鳍鱼谱系中出现的说法。基于我们的搜索方法，其他不同的II类基因是不太可能在软骨鱼。
Cartilaginous fish (chimaeras, rays and sharks) are the most basal extant jawed vertebrates with an adaptive immune system based on the Major Histocompatibility Complex (MHC). Despite being a key taxon in the evolution of vertebrate adaptive immunity, no comprehensive characterization of MHC class II genes has been undertaken for the group. We performed extensive bioinformatic searches on a taxonomically diverse dataset of transcriptomes and genomes of cartilaginous fish targeting MHC class II sequences. Class IIα and IIβ sequences were retrieved from all taxa analyzed and showed typical features of classical class II genes. Phylogenetic trees of the immunoglobulin superfamily domain showed two divergent and remarkably ancient lineages of class II genes in Selachians (sharks), originating >350 million years ago. Close linkage of lineage-specific pairs of IIα and IIβ genes was found, confirming previous results, with genes from distinct lineages segregating as alleles. Nonclassical class II DM sequences were not retrieved from these data and classical class II sequences lacked the conserved residues shown to interact with DM molecules, supporting claims that the DM system arose only in the lobe-finned fish lineage leading to tetrapods. Based on our search methods, other divergent class II genes are unlikely in cartilaginous fish.
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影响因子：
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作者：
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通讯作者：
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