title: Hagfish leukocytes express a paired receptor family with a variable domain resembling those of antigen receptors.
abstract: Jawed vertebrates are equipped with TCR and BCR with the capacity to rearrange their V domains. By contrast, jawless vertebrates, represented by hagfish and lampreys, apparently lack such receptors. We describe in this study a family of hagfish genes carrying a single V-type domain resembling those of TCR/BCR. This multigene family, which we call agnathan paired receptors resembling Ag receptors (APAR), is expressed in leukocytes and predicted to encode a group of membrane glycoproteins with organizations characteristic of paired Ig-like receptors, consisting of activating and inhibitory forms. APAR has a J region in its V-type domain, and its V and J regions are encoded in a single exon. Thus, APAR is a member of the emerging families of diversified, innate immune-type receptors with TCR/BCR-like V-type domains and has many of the features expected for a primordial TCR/BCR-like receptor. The extracellular domain of APAR may be descended from a V-type domain postulated to have acquired recombination signal sequences in a jawed vertebrate lineage.
authors.affiliation: Department of Biosystems Science, School of Advanced Sciences, Graduate University for Advanced Studies (Sokendai), Hayama, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Tadasu
authors.initials: T
authors.lastname: Shin-I
authors.forename: Asao
authors.initials: A
authors.lastname: Fujiyama
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kohara
authors.forename: Masanori
authors.initials: M
authors.lastname: Kasahara
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005091:Exons; D018628:Gene Dosage; D016678:Genome; D006196:Hagfishes / Q000235:genetics / Q000276:immunology*; D007133:Immunoglobulin Joining Region / Q000737:chemistry / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000737:chemistry* / Q000235:genetics; D007438:Introns; D007962:Leukocytes / Q000276:immunology* / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000276:immunology; D009928:Organ Specificity / Q000235:genetics / Q000276:immunology; D017434:Protein Structure, Tertiary / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D011946:Receptors, Antigen / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D011947:Receptors, Antigen, B-Cell / Q000737:chemistry; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
chemical_list: D007133:Immunoglobulin Joining Region; D007135:Immunoglobulin Variable Region; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011946:Receptors, Antigen; D011947:Receptors, Antigen, B-Cell; D011948:Receptors, Antigen, T-Cell