Natural killer cell receptor genes in the family Equidae: not only Ly49.
Natural killer cell receptor genes in the family Equidae: not only Ly49.
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DOI：
10.1371/journal.pone.0064736
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Horin P
中科院分区：
文献类型：
--
作者：
Futas J;Horin P
自然杀伤(NK)细胞在免疫中具有重要作用。哺乳动物的NK识别可通过杀伤细胞免疫球蛋白样受体(KIR)和/或杀伤细胞凝集素样Ly49受体介导。编码高度可变的NK细胞受体(NKR)的基因代表着快速进化的基因组区域。在哺乳动物中没有观察到NKR基因的单一保守模式。在哺乳动物中存在的单拷贝低多态NKR基因可能在其他物种中扩展成高度多态的多基因家族。与其他非啮齿动物哺乳动物相比，马中似乎存在多个类似Ly49的基因，而在该物种中没有观察到有功能的KIR基因。在本研究中，寻找了Ly49和KIR，并对它们在整个马科中的进化进行了描述。检索到的基因组序列显示，在马、驴和斑马中至少存在5个高度保守的多态Ly49基因。这些发现证实了Ly49基因的扩增发生在整个家族中。在马的基因组中也发现了几个类似KIR的序列。除了先前发现的一个无功能的KIR-免疫球蛋白样转录本融合基因(KIR-ILTA)和两个假定的假基因外，还分析了一个类似KIR3DL的序列。与以前在马身上观察到的相反，KIR3DL序列、基因组结构和mRNA表达表明，所有的马匹都可能产生一个具有单一非突变免疫酪氨酸抑制基序(ITIM)结构域的功能性KIR受体蛋白分子。未发现KIR3DL基因存在正向选择的证据。系统发育分析包括犀牛和织锦的基因组DNA和推导的氨基酸KIR相关序列，表明在围趾目的不同科之间，甚至不同种之间存在差异。结果表明，Perissodactyla及其科具有扩展的Ly49基因和具有潜在功能的KIR基因的目的可能代表了NKR基因的一个有趣的进化生物学模式。
Natural killer (NK) cells have important functions in immunity. NK recognition in mammals can be mediated through killer cell immunoglobulin-like receptors (KIR) and/or killer cell lectin-like Ly49 receptors. Genes encoding highly variable NK cell receptors (NKR) represent rapidly evolving genomic regions. No single conservative model of NKR genes was observed in mammals. Single-copy low polymorphic NKR genes present in one mammalian species may expand into highly polymorphic multigene families in other species. In contrast to other non-rodent mammals, multiple Ly49-like genes appear to exist in the horse, while no functional KIR genes were observed in this species. In this study, Ly49 and KIR were sought and their evolution was characterized in the entire family Equidae. Genomic sequences retrieved showed the presence of at least five highly conserved polymorphic Ly49 genes in horses, asses and zebras. These findings confirmed that the expansion of Ly49 occurred in the entire family. Several KIR-like sequences were also identified in the genome of Equids. Besides a previously identified non-functional KIR-Immunoglobulin-like transcript fusion gene (KIR-ILTA) and two putative pseudogenes, a KIR3DL-like sequence was analyzed. In contrast to previous observations made in the horse, the KIR3DL sequence, genomic organization and mRNA expression suggest that all Equids might produce a functional KIR receptor protein molecule with a single non-mutated immune tyrosine-based inhibition motif (ITIM) domain. No evidence for positive selection in the KIR3DL gene was found. Phylogenetic analysis including rhinoceros and tapir genomic DNA and deduced amino acid KIR-related sequences showed differences between families and even between species within the order Perissodactyla. The results suggest that the order Perissodactyla and its family Equidae with expanded Ly49 genes and with a potentially functional KIR gene may represent an interesting model for evolutionary biology of NKR genes.
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