ZFIN ID: ZDB-PUB-050804-2
Endoderm-derived Fgf3 is necessary and sufficient for inducing neurogenesis in the epibranchial placodes in zebrafish
Nechiporuk, A., Linbo, T., and Raible, D.W.
Date: 2005
Source: Development (Cambridge, England)   132(16): 3717-3730 (Journal)
Registered Authors: Linbo, Tor, Nechiporuk, Alex, Raible, David
Keywords: Fgf3, Foxi1, Epibranchial placodes, Cranial ganglia, Endoderm, Pharyngeal pouches, Placode induction, Neurogenesis
MeSH Terms:
  • Animals
  • Body Patterning
  • Embryonic Structures/anatomy & histology
  • Embryonic Structures/physiology*
  • Endoderm/metabolism*
  • Fibroblast Growth Factor 3
  • Fibroblast Growth Factors/genetics
  • Fibroblast Growth Factors/metabolism*
  • In Situ Hybridization
  • Morphogenesis*
  • Neurons/cytology
  • Neurons/physiology*
  • Oligonucleotides, Antisense/genetics
  • Oligonucleotides, Antisense/metabolism
  • Signal Transduction/physiology
  • Zebrafish/embryology*
  • Zebrafish/metabolism
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism*
PubMed: 16077091 Full text @ Development
In vertebrates, epibranchial placodes are transient ectodermal thickenings that contribute sensory neurons to the epibranchial ganglia. These ganglia innervate internal organs and transmit information on heart rate, blood pressure and visceral distension from the periphery to the central nervous system. Despite their importance, the molecular mechanisms that govern the induction and neurogenesis of the epibranchial placodes are only now being elucidated. In this study, we demonstrate that endoderm is required for neurogenesis of the zebrafish epibranchial placodes. Mosaic analyses confirm that endoderm is the source of the neurogenic signal. Using a morpholino knockdown approach, we find that fgf3 is required for the majority of placode cells to undergo neurogenesis. Tissue transplants demonstrate that fgf3 activity is specifically required in the endodermal pouches. Furthermore, ectopic fgf3 expression is sufficient for inducing phox2a-positive neurons in wild-type and endoderm-deficient embryos. Surprisingly, ectodermal foxi1 expression, a marker for the epibranchial placode precursors, is present in both endoderm-deficient embryos and fgf3 morphants, indicating that neither endoderm nor Fgf3 is required for initial placode induction. Based on these findings, we propose a model for epibranchial placode development in which Fgf3 is a major endodermal determinant required for epibranchial placode neurogenesis.