Paraxial mesoderm specifies zebrafish primary motoneuron subtype identity

Katherine E. Lewis, Judith S. Eisen

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


We provide the first analysis of how a segmentally reiterated pattern of neurons is specified along the anteroposterior axis of the vertebrate spinal cord by investigating how zebrafish primary motoneurons are patterned. Two identified primary motoneuron subtypes, MiP and CaP, occupy distinct locations within the ventral neural tube relative to overlying somites, express different genes and innervate different muscle territories. In all vertebrates examined so far, paraxial mesoderm-derived signals specify distinct motoneuron subpopulations in specific anteroposterior regions of the spinal cord. We show that signals from paraxial mesoderm also control the much finer-grained segmental patterning of zebrafish primary motoneurons. We examined primary motoneuron specification in several zebrafish mutants that have distinct effects on paraxial mesoderm development. Our findings suggest that in the absence of signals from paraxial mesoderm, primary motoneurons have a hybrid identity with respect to gene expression, and that under these conditions the CaP axon trajectory may be dominant.

Original languageEnglish (US)
Pages (from-to)891-902
Number of pages12
Issue number4
StatePublished - Feb 2004
Externally publishedYes


  • After eight
  • CaP
  • Fused somites
  • Knypek
  • MiP
  • Motoneurons
  • No tail
  • Somites
  • Spadetail
  • Spinal cord
  • Trilobite
  • You-too
  • Zebrafish
  • b380
  • b567

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology


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