title: Transcriptome analysis of hagfish leukocytes: a framework for understanding the immune system of jawless fishes.
abstract: Jawless fishes occupy a critical phylogenetic position in understanding the origin of the adaptive immune system. Here, we performed large-scale expressed sequence tag analysis of leukocytes isolated from the inshore hagfish Eptatretus burgeri. Although we found many immunity-related genes such as those involved in lymphocyte or hematopoietic cell signaling and development as well as cytokine and cytokine receptor genes, MHC molecules or antigen receptors were not identified. We characterized two hagfish cDNAs that closely resembled mammalian proteins with essential roles in adaptive immunity, one encoding a GATA3-like molecule and another encoding a Bruton's tyrosine kinase (Btk)-like molecule. The GATA3-like gene of hagfish was equidistant from GATA3 and GATA2 in jawed vertebrates. Similarly, the hagfish Btk-like molecule was not Btk itself, but qualified as a pre-duplicated form of Btk and Bmx in jawed vertebrates. In total, our work provides circumstantial evidence that adaptive immunity is unique to jawed vertebrates.
authors.affiliation: Department of Biosystems Science, School of Advanced Sciences, The Graduate University for Advanced Studies (Sokendai), Shonan Village, Hayama 240-0193, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Tadasu
authors.initials: T
authors.lastname: Shin-I
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; D016207:Cytokines / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D020224:Expressed Sequence Tags; D020869:Gene Expression Profiling; D006196:Hagfishes / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D007962:Leukocytes / Q000276:immunology / Q000378:metabolism*; D008969:Molecular Sequence Data; D046988:Proteasome Endopeptidase Complex / Q000276:immunology / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D018121:Receptors, Cytokine / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D014157:Transcription Factors / Q000276:immunology / Q000378:metabolism
chemical_list: D016207:Cytokines; D012333:RNA, Messenger; D018121:Receptors, Cytokine; D014157:Transcription Factors; D046988:Proteasome Endopeptidase Complex