title: Mutations affecting thymus organogenesis in Medaka, Oryzias latipes.
abstract: The thymus is an organ for T lymphocyte maturation and is indispensable for the establishment of a highly developed immune system in vertebrates. In order to genetically dissect thymus organogenesis, we carried out a large-scale mutagenesis screening for Medaka mutations affecting recombination activating gene 1 (rag1) expression in the developing thymus. We identified 24 mutations, defining at least 13 genes, which led to a marked reduction of rag1 expression in the thymus. As thymus development depends on pharyngeal arches, we classified those mutations into three classes according to the defects in the pharyngeal arches. Class 1 mutants had no or slight morphological abnormalities in the pharyngeal arches, implying that the mutations may include defects in such thymus-specific events as lymphocyte development and thymic epithelial cell maturation. Class 2 mutants had abnormally shaped pharyngeal arches. Class 3 mutants showed severely attenuated pharyngeal arch development. In Class 2 and Class 3 mutants, the defects in thymus development may be due to abnormal pharyngeal arch development. Those mutations are expected to be useful for identifying the molecular mechanisms underlying thymus organogenesis.
authors.affiliation: Division of Experimental Immunology, Institute for Genome Research, University of Tokushima, 3-18-15 Kuramoto, Tokushima 770-8503, Japan.
authors.forename: Norimasa
authors.initials: N
authors.lastname: Iwanami
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Takahama
authors.forename: Sanae
authors.initials: S
authors.lastname: Kunimatsu
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.forename: Rie
authors.initials: R
authors.lastname: Takei
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ishikura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Suwa
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Niwa
authors.forename: Takao
authors.initials: T
authors.lastname: Sasado
authors.forename: Chikako
authors.initials: C
authors.lastname: Morinaga
authors.forename: Akihito
authors.initials: A
authors.lastname: Yasuoka
authors.forename: Tomonori
authors.initials: T
authors.lastname: Deguchi
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Hirose
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yoda
authors.forename: Thorsten
authors.initials: T
authors.lastname: Henrich
authors.forename: Osamu
authors.initials: O
authors.lastname: Ohara
authors.forename: Hisato
authors.initials: H
authors.lastname: Kondoh
authors.forename: Makoto
authors.initials: M
authors.lastname: Furutani-Seiki
mesh_terms: D000818:Animals; D001934:Branchial Region / Q000002:abnormalities / Q000196:embryology; D015870:Gene Expression / Q000502:physiology; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D016654:Genes, RAG-1 / Q000502:physiology; D009154:Mutation; D009990:Oryzias / Q000002:abnormalities / Q000196:embryology* / Q000235:genetics*; D013950:Thymus Gland / Q000002:abnormalities / Q000196:embryology* / Q000378:metabolism