title: An amputation resets positional information to a proximal identity in the regenerating zebrafish caudal fin.
abstract: BACKGROUND
  Zebrafish has emerged as a powerful model organism to study the process of regeneration. This teleost fish has the ability to regenerate various tissues and organs like the heart, spinal cord, retina and fins. In this study, we took advantage of the existence of an excellent morphological reference in the zebrafish caudal fin, the bony ray bifurcations, as a model to study positional information upon amputation. We investigated the existence of positional information for bifurcation formation by performing repeated amputations at different proximal-distal places along the fin.
  
  
  RESULTS
  We show that, while amputations performed at a long distance from the bifurcation do not change its final proximal-distal position in the regenerated fin, consecutive amputations done at 1 segment proximal to the bifurcation (near the bifurcation) induce a positional reset and progressively shift its position distally. Furthermore, we investigated the potential role of Shh and Fgf signalling pathways in the determination of the bifurcation position and observed that they do not seem to be involved in this process.
  
  
  CONCLUSIONS
  Our results reveal that, an amputation near the bifurcation inhibits the formation of the regenerated bifurcation in the pre-amputation position, inducing a distalization of this structure. This shows that the positional memory for bony ray bifurcations depends on the proximal-distal level of the amputation.
authors.affiliation: Instituto de Medicina Molecular e Instituto de Histologia e Biologia do Desenvolvimento, Faculdade de Medicina da Universidade de Lisboa, Lisbon, 1649-028, Portugal.
authors.forename: Ana Sofia
authors.initials: AS
authors.lastname: Azevedo
authors.forename: Sara
authors.initials: S
authors.lastname: Sousa
authors.forename: António
authors.initials: A
authors.lastname: Jacinto
authors.forename: Leonor
authors.initials: L
authors.lastname: Saúde
mesh_terms: D058500:Animal Fins / Q000033:anatomy & histology / Q000502:physiology*; D000818:Animals; D030801:Animals, Genetically Modified; D005346:Fibroblast Growth Factors / Q000378:metabolism; D015870:Gene Expression; D005786:Gene Expression Regulation; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000096:biosynthesis / Q000235:genetics; D012038:Regeneration; D015398:Signal Transduction; D015027:Zebrafish / Q000033:anatomy & histology / Q000235:genetics / Q000502:physiology*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D053823:Hedgehog Proteins; D029961:Zebrafish Proteins; D005346:Fibroblast Growth Factors; D051496:Receptor, Fibroblast Growth Factor, Type 1