ZFIN ID: ZDB-PUB-110119-6
Pax2/8 proteins coordinate sequential induction of otic and epibranchial placodes through differential regulation of foxi1, sox3 and fgf24
Padanad, M.S., and Riley, B.B.
Date: 2011
Source: Developmental Biology   351(1): 90-98 (Journal)
Registered Authors: Padanad, Mahesh, Riley, Bruce
Keywords: zebrafish, heat shock, Fgf, Pax2/5/8, SoxB1
MeSH Terms:
  • Animals
  • Branchial Region/embryology*
  • Ear, Inner/embryology*
  • Fibroblast Growth Factors/genetics*
  • Fibroblast Growth Factors/physiology
  • Forkhead Transcription Factors/genetics*
  • Forkhead Transcription Factors/physiology
  • Ganglia/embryology
  • Gene Expression Regulation, Developmental
  • PAX2 Transcription Factor/physiology
  • Paired Box Transcription Factors/physiology
  • SOXB1 Transcription Factors/genetics
  • SOXB1 Transcription Factors/physiology
  • Transcription Factors/genetics
  • Transcription Factors/physiology*
  • Zebrafish/embryology*
  • Zebrafish Proteins/genetics*
  • Zebrafish Proteins/physiology
PubMed: 21215261 Full text @ Dev. Biol.
Vertebrate cranial placodes contribute vitally to development of sensory structures of the head. Amongst posterior placodes, the otic placode forms the inner ear whereas nearby epibranchial placodes produce sensory ganglia within branchial clefts. Though diverse in fate, these placodes show striking similarities in their early regulation. In zebrafish, both are initiated by localized Fgf signaling plus the ubiquitous competence factor Foxi1, and both express pax8 and sox3 in response. It has been suggested that Fgf initially induces a common otic/epibranchial field, which later subdivides in response to other signals. However, we find that otic and epibranchial placodes form at different times and by distinct mechanisms. Initially, Fgf from surrounding tissues induces otic expression of pax8 and sox3, which cooperate synergistically to establish otic fate. Subsequently, pax8 works with related genes pax2a/pax2b to downregulate otic expression of foxi1, a necessary step for further otic development. Additionally, pax2/8 activate otic expression of fgf24, which induces epibranchial expression of sox3. Knockdown of fgf24 or sox3 causes severe epibranchial deficiencies but has little effect on otic development. These findings clarify the roles of pax8 and sox3 and support a model whereby the otic placode forms first and induces epibranchial placodes through an Fgf-relay.