title: Apoptosis and differentiation of Xenopus tail-derived myoblasts by thyroid hormone.
abstract: The metamorphosis of anuran amphibians is induced by thyroid hormone (TH). To study the molecular mechanisms underlying tail regression during metamorphosis, we established a cell line, XL-B4, from a Xenopus laevis tadpole tail at a premetamorphic stage. The cells expressed myoblast markers and differentiated into myotubes in differentiation medium. XL-B4 cells expressing fluorescent proteins were transplanted into tadpole tails. At 5 days post-transplantation, fluorescence was observed in myotube-like structures, indicating that the myoblastic cells could contribute to skeletal muscle. Exposure of XL-B4 cells to the TH triiodothyronine (T3) for several days significantly induced apoptotic cell death. We then examined an early response of expression of genes involved in apoptosis or myogenesis to T3. Treatment of the cells with T3 increased transcription of genes for matrix metalloproteinase-9 (MMP-9) and thyroid hormone receptor beta. Interestingly, the T3-treatment also increased myoD transcripts, but decreased the amounts of myogenin mRNA and myosin heavy chain. Importantly, we also observed upregulation of myoD expression and downregulation of myogenin expression in tails, but not in hind limbs, when tadpoles at a premetamorphic stage were treated with T3 for 1 day. These results indicated that T3 could not only induce apoptosis, but also attenuate myogenesis in tadpole tails during metamorphosis.
authors: Department of BiosciencesSchool of Science, Kitasato University, 1-15-1 Kitasato, Minamiku, Sagamihara 252-0373, Japan.
authors: Kei
authors: K
authors: Tamura
authors: Department of BiosciencesSchool of Science, Kitasato University, 1-15-1 Kitasato, Minamiku, Sagamihara 252-0373, Japan.
authors: Shutaro
authors: S
authors: Takayama
authors: Department of BiosciencesSchool of Science, Kitasato University, 1-15-1 Kitasato, Minamiku, Sagamihara 252-0373, Japan.
authors: Takako
authors: T
authors: Ishii
authors: Department of BiosciencesSchool of Science, Kitasato University, 1-15-1 Kitasato, Minamiku, Sagamihara 252-0373, Japan.
authors: Shuuji
authors: S
authors: Mawaribuchi
authors: Department of BiosciencesSchool of Science, Kitasato University, 1-15-1 Kitasato, Minamiku, Sagamihara 252-0373, Japan.
authors: Nobuhiko
authors: N
authors: Takamatsu
authors: Department of BiosciencesSchool of Science, Kitasato University, 1-15-1 Kitasato, Minamiku, Sagamihara 252-0373, Japan ito@sci.kitasato-u.ac.jp.
authors: Michihiko
authors: M
authors: Ito
mesh_terms: D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation; D002460:Cell Line; D005260:Female; D015870:Gene Expression; D008297:Male; D032446:Myoblasts / Q000502:physiology*; D018008:Myogenin / Q000235:genetics / Q000378:metabolism; D013623:Tail; D014284:Triiodothyronine / Q000502:physiology*; D014982:Xenopus laevis
chemical_list: D018008:Myogenin; D014284:Triiodothyronine
keywords: Xenopus; apoptosis; metamorphosis; myoblast; myogenesis; thyroid hormone