title: Cellular dynamics underlying regeneration of appropriate segment number during axolotl tail regeneration.
abstract: BACKGROUND
  Salamanders regenerate their tails after amputation anywhere along their length. How the system faithfully reconstitutes the original number of segments and length is not yet known.
  
  
  METHODS
  To gain quantitative insight into how the system regenerates the appropriate length, we amputated tails at 4 or 16 myotomes post-cloaca and measured blastema size, cell cycle kinetics via cumulative Bromodeoxyuridine (BrdU) incorporation and the method of Nowakowski, and myotome differentiation rate.
  
  
  RESULTS
  In early stages until day 15, blastema cells were all proliferative and divided at the same rate at both amputation levels. A larger blastema was formed in 4th versus 16th myotome amputations indicating a larger founding population. Myotome differentiation started at the same timepoint in the 4th and 16 th level blastemas. The rate of myotome formation was more rapid in 4th myotome blastemas so that by day 21 the residual blastema from the two amputation levels achieved equivalent size. At that time point, only a fraction of blastema cells remain in cycle, with the 4th myotome blastema harboring double the number of cycling cells as the 16th myotome blastema allowing it to grow faster and further reconstitute the larger number of missing myotomes.
  
  
  CONCLUSIONS
  These data suggest that there are two separable phases of blastema growth. The first is level-independent, with cells displaying unrestrained proliferation. In the second phase, the level-specific growth is revealed, where differing fractions of cells remain in the cell cycle over time.
authors.affiliation: Max-Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 105, 01307, Dresden, Germany. cdvincen@gmail.com.|Technische Universität Dresden, DFG Center for Regenerative Therapies, Fetscherstraße 105, 01307, Dresden, Germany. cdvincen@gmail.com.
authors.forename: Carr D
authors.initials: CD
authors.lastname: Vincent
authors.affiliation: Technische Universität Dresden, Center for Information Services and High Performance Computing, and Center for Advancing Electronics Dresden (cfaed), 01062, Dresden, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Rost
authors.affiliation: Technische Universität Dresden, DFG Center for Regenerative Therapies, Fetscherstraße 105, 01307, Dresden, Germany.
authors.forename: Wouter
authors.initials: W
authors.lastname: Masselink
authors.affiliation: Technische Universität Dresden, Center for Information Services and High Performance Computing, and Center for Advancing Electronics Dresden (cfaed), 01062, Dresden, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Brusch
authors.affiliation: Technische Universität Dresden, DFG Center for Regenerative Therapies, Fetscherstraße 105, 01307, Dresden, Germany. elly.tanaka@crt-dresden.de.
authors.forename: Elly M
authors.initials: EM
authors.lastname: Tanaka
mesh_terms: D000558:Ambystoma mexicanum / Q000196:embryology*; D000671:Amputation, Surgical; D000818:Animals; D002453:Cell Cycle / Q000235:genetics; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D009929:Organ Size / Q000235:genetics / Q000502:physiology*; D012038:Regeneration / Q000502:physiology*; D013623:Tail / Q000196:embryology* / Q000502:physiology