An Ancient, MHC-Linked, Nonclassical Class I Lineage in Cartilaginous Fish
An Ancient, MHC-Linked, Nonclassical Class I Lineage in Cartilaginous Fish
复制标题
DOI：
10.4049/jimmunol.1901025
复制
发表时间：
2020-02-15
影响因子：
4.4
通讯作者：
Verissimo, Ana
中科院分区：
文献类型：
--
作者：
Almeida, Tereza;Esteves, Pedro J.;Verissimo, Ana
软骨鱼或软骨鱼类是最古老的有颌脊椎动物，具有基于 MHC 和 Ig 超家族 AgR 的适应性免疫系统。在这个有颌脊椎动物的基础类群中，我们鉴定出了第三种非经典 MHC I 类谱系 (UDA)，该谱系存在于两个主要软骨亚类——全头鱼（鲣鱼）和板鳃亚纲（鲨鱼、鳐鱼和鳐鱼）中分析的所有物种中。 UDA 的推导氨基酸序列具有九个典型不变残基中的八个，这些残基与大多数经典 I 类椎骨 (UAA) 中发现的结合肽的 N 和 C 末端结合；此外，其他预测的 28 个肽结合残基在所有软骨鱼 UDA 序列中都完全保守。 UDA 与 UAA 的不同之处在于其不同的组织分布和较低的表达水平，并且与高度多态性的 UAA 不同，UDA 是单态或寡态的。 UDA 在软骨鱼中的拷贝数较低，但在全头斑鼠鱼 (Hydrolagus colliei) 中为多拷贝。利用护士鲨 (Ginglymostoma cirratum) 家族，我们发现 UDA 与 MHC 相关，但可通过与紧密相连的 UAA、TAP 和 LMP 基因簇（大多数非哺乳动物脊椎动物中发现的所谓 I 类区域）重组而分离。 UDA 预测了与其他脊椎动物中某些非经典 I 类基因相似的结构特征，并且与多态性经典 I 类基因不同，我们预计它可能与一组保守的专门肽结合。
Cartilaginous fishes, or chondrichthyans, are the oldest jawed vertebrates that have an adaptive immune system based on the MHC and Ig superfamily-based AgR. In this basal group of jawed vertebrates, we identified a third nonclassical MHC class I lineage (UDA), which is present in all species analyzed within the two major cartilaginous subclasses, Holocephali (chimaeras) and Elasmobranchii (sharks, skates, and rays). The deduced amino acid sequences of UDA have eight out of nine typically invariant residues that bind to the N and C termini of bound peptide found in most vertebrae classical class I (UAA); additionally, the other predicted 28 peptide-binding residues are perfectly conserved in all elasmobranch UDA sequences. UDA is distinct from UAA in its differential tissue distribution and its lower expression levels and is mono- or oligomorphic unlike the highly polymorphic UAA. UDA has a low copy number in elasmobranchs but is multicopy in the holocephalan spotted ratfish (Hydrolagus colliei). Using a nurse shark (Ginglymostoma cirratum) family, we found that UDA is MHC linked but separable by recombination from the tightly linked cluster of UAA, TAP, and LMP genes, the so-called class I region found in most nonmammalian vertebrates. UDA has predicted structural features that are similar to certain nonclassical class I genes in other vertebrates, and, unlike polymorpic classical class I, we anticipate that it may bind to a conserved set of specialized peptides.