Phylogenetic and expression analysis of amphibian Xenopus Toll-like receptors
Phylogenetic and expression analysis of amphibian Xenopus Toll-like receptors
复制标题
DOI：
10.1007/s00251-007-0193-y
复制
发表时间：
2007-04-01
期刊：
影响因子：
3.2
通讯作者：
Seya, Tsukasa
中科院分区：
文献类型：
--
作者：
Ishii, Akihiro;Kawasaki, Miyuki;Seya, Tsukasa
无尾两栖动物南非爪蛙(Xenopus Laevis)被用来研究免疫系统，因为它拥有一套以T和B淋巴细胞和免疫球蛋白为代表的获得性免疫系统。在两栖动物的幼虫和变态阶段，获得性免疫系统一直受到损害。另一方面，先天性免疫系统在蝌蚪中的作用尚不清楚。最近，昆虫Toll蛋白同源物，即Toll样受体(TLRs)，被鉴定为识别脊椎动物微生物模式分子的传感器。热带非洲爪哇的全基因组分析支持TLR基因在青蛙中的存在。在本研究中，我们在同源性的基础上对最新的基因组组装版本4.1中的20个青蛙TLR基因核苷酸序列进行了注释，并鉴定了预测的青蛙TLR蛋白的cDNA。系统发育分析表明，蛙类的TLR包括鱼类和哺乳动物类型的TLR。我们发现，蛙类TLRs在蝌蚪和成年蛙中都有结构性表达。我们的结果表明，尽管蝌蚪的获得性免疫系统受损，但包括TLRs在内的固有系统可以保护蝌蚪免受微生物的侵袭。这是关于TLRs在最原始的陆地动物(如两栖动物)中的特性的第一份报告。
An anuran amphibian, South African clawed frog (Xenopus laevis), is used to study the immune system, as it possesses a set of acquired immune system represented by T and B lymphocytes and the immunoglobulins. The acquired immune system is impaired throughout the larva and the metamorphosis stage in the amphibians. On the other hand, the role of innate immune system in the tadpole remains unclear. Recently, insect Toll protein homologues, namely, Toll-like receptors (TLRs), have been identified as sensors recognizing microbe-pattern molecules in vertebrates. Whole-genome analysis of Xenopus tropicalis supported the existence of the tlr genes in the frog. In this study, we annotated 20 frog tlr gene nucleotide sequences from the latest genome assembly version 4.1 on the basis of homology and identified cDNAs of the predicted frog TLR proteins. Phylogenetic analysis showed that the repertoire of the frog TLRs consisted of both fish- and mammalian-type TLRs. We showed that the frog TLRs are constitutively expressed in the tadpole as well as in the adult frog. Our results suggest that tadpoles are protected from microbes by the innate system that includes TLRs, despite impaired acquired immune system in tadpoles. This is the first report on the properties of TLRs in the most primitive terrestrial animals like amphibia.