title: The keratin-related Ouroboros proteins function as immune antigens mediating tail regression in Xenopus metamorphosis.
abstract: Tail resorption during amphibian metamorphosis has been thought to be controlled mainly by a cell-autonomous mechanism of programmed cell death triggered by thyroid hormone. However, we have proposed a role for the immune response in metamorphosis, based on the finding that syngeneic grafts of tadpole tail skin into adult Xenopus animals are rejected by T cells. To test this, we identified two tail antigen genes called ouro1 and ouro2 that encode keratin-related proteins. Recombinant Ouro1 and Ouro2 proteins generated proliferative responses in vitro in T cells isolated from naive adult Xenopus animals. These genes were expressed specifically in the tail skin at the climax of metamorphosis. Overexpression of ouro1 and ouro2 induced T-cell accumulation and precocious tail degeneration after full differentiation of adult-type T cells when overexpressed in the tail region. When the expression of ouro1 and ouro2 were knocked down, tail skin tissue remained even after metamorphosis was complete. Our findings indicate that Ouro proteins participate in the process of tail regression as immune antigens and highlight the possibility that the acquired immune system contributes not only to self-defense but also to remodeling processes in vertebrate morphogenesis.
authors.affiliation: Department of Biology, Faculty of Science, Niigata University, Niigata 950-2181, Japan.
authors.forename: Katsuki
authors.initials: K
authors.lastname: Mukaigasa
authors.forename: Akira
authors.initials: A
authors.lastname: Hanasaki
authors.forename: Mitsugu
authors.initials: M
authors.lastname: Maéno
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fujii
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Hayashida
authors.forename: Mari
authors.initials: M
authors.lastname: Itoh
authors.forename: Makoto
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Shin
authors.initials: S
authors.lastname: Tochinai
authors.forename: Masayuki
authors.initials: M
authors.lastname: Hatta
authors.forename: Kazuya
authors.initials: K
authors.lastname: Iwabuchi
authors.forename: Masanori
authors.initials: M
authors.lastname: Taira
authors.forename: Kazunori
authors.initials: K
authors.lastname: Onoé
authors.forename: Yumi
authors.initials: Y
authors.lastname: Izutsu
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D000941:Antigens / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D049109:Cell Proliferation; D018507:Gene Expression Regulation, Developmental; D007633:Keratins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008675:Metamorphosis, Biological; D008969:Molecular Sequence Data; D012867:Skin / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D013623:Tail / Q000254:growth & development / Q000276:immunology / Q000378:metabolism*; D014158:Transcription, Genetic; D029867:Xenopus Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014982:Xenopus laevis / Q000235:genetics / Q000254:growth & development* / Q000276:immunology / Q000378:metabolism*
chemical_list: D000941:Antigens; C544963:Ouro1 protein, Xenopus; C544964:Ouro2 protein, Xenopus; D029867:Xenopus Proteins; D007633:Keratins