title: Notochord-derived hedgehog is essential for tail regeneration in Xenopus tadpole.
abstract: BACKGROUND
  Appendage regeneration in amphibians is regulated by the combinatorial actions of signaling molecules. The requirement of molecules secreted from specific tissues is reflected by the observation that the whole process of regeneration can be inhibited if a certain tissue is removed from the amputated stump. Interestingly, urodeles and anurans show different tissue dependencies during tail regeneration. The spinal cord is essential for tail regeneration in urodele but not in anuran larva, whereas the notochord but not the spinal cord is essential for tail regeneration in anuran tadpoles. Sonic hedgehog is one of the signaling molecules responsible for such phenomenon in axolotl, as hedgehog signaling is essential for overall tail regeneration and sonic hedgehog is exclusively expressed in the spinal cord. In order to know whether hedgehog signaling is involved in the molecular mechanism underlying the inconsistent tissue dependency for tail regeneration between anurans and urodeles, we investigated expression of hedgehog signal-related genes in the regenerating tail of Xenopus tadpole and examined the effect of the hedgehog signal inhibitor, cyclopamine, on the tail regeneration.
  
  
  RESULTS
  In Xenopus, sonic hedgehog is expressed exclusively in the notochord but not in the spinal cord of the regenerate. Overall regeneration was severely impaired in cyclopamine-treated tadpoles. Notochord maturation in the regenerate, including cell alignment and vacuolation, and myofiber formation were inhibited. Proliferation of spinal cord cells in the neural ampulla and of mesenchymal cells was also impaired.
  
  
  CONCLUSIONS
  As in the axolotl, hedgehog signaling is required for multiple steps in tail regeneration in the Xenopus tadpole, although the location of the Shh source is quite different between the two species. This difference in Shh localization is the likely basis for the differing tissue requirement for tail regeneration between urodeles and anurans.
authors.affiliation: Department of Life Science, Graduate school of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori Akou, Hyogo 678-1297, Japan. yuka.taniguchi@crt-dresden.de.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Taniguchi
authors.forename: Kenji
authors.initials: K
authors.lastname: Watanabe
authors.forename: Makoto
authors.initials: M
authors.lastname: Mochii
mesh_terms: D000818:Animals; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins / Q000235:genetics*; D017403:In Situ Hybridization; D007814:Larva / Q000235:genetics / Q000502:physiology; D009672:Notochord / Q000378:metabolism*; D012038:Regeneration / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D058630:Spinal Cord Regeneration / Q000235:genetics / Q000502:physiology; D013623:Tail / Q000378:metabolism / Q000502:physiology* / Q000601:surgery; D014704:Veratrum Alkaloids / Q000494:pharmacology; D029867:Xenopus Proteins / Q000235:genetics*; D014982:Xenopus laevis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D053823:Hedgehog Proteins; D014704:Veratrum Alkaloids; D029867:Xenopus Proteins; C000541:cyclopamine