Phylogenetic and expression analysis of amphibian Xenopus Toll-like receptors |
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Authors: | Akihiro Ishii Miyuki Kawasaki Misako Matsumoto Shin Tochinai Tsukasa Seya |
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Institution: | (1) Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Kita-ku, Sapporo 060-8638, Japan;(2) Department of Natural History Sciences, Faculty of Science, Hokkaido University, Kita-ku, Sapporo 060-0810, Japan |
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Abstract: | 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.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Toll-like receptor Xenopus Evolution Phylogeny Innate immunity |
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