Zebrafish Foxi1 provides a neuronal ground state during inner ear induction preceding the Dlx3b/4b-regulated sensory lineage

Development. 2013 May;140(9):1936-45. doi: 10.1242/dev.087718.

Abstract

Vertebrate inner ear development is a complex process that involves the induction of a common territory for otic and epibranchial precursors and their subsequent segregation into otic and epibranchial cell fates. In zebrafish, the otic-epibranchial progenitor domain (OEPD) is induced by Fgf signaling in a Foxi1- and Dlx3b/4b-dependent manner, but the functional differences of Foxi1 and Dlx3b/4b in subsequent cell fate specifications within the developing inner ear are poorly understood. Based on pioneer tracking (PioTrack), a novel Cre-dependent genetic lineage tracing method, and genetic data, we show that the competence to embark on a neuronal or sensory fate is provided sequentially and very early during otic placode induction. Loss of Foxi1 prevents neuronal precursor formation without affecting hair cell specification, whereas loss of Dlx3b/4b inhibits hair cell but not neuronal precursor formation. Consistently, in Dlx3b/4b- and Sox9a-deficient b380 mutants almost all otic epithelial fates are absent, including sensory hair cells, and the remaining otic cells adopt a neuronal fate. Furthermore, the progenitors of the anterior lateral line ganglia also arise from the OEPD in a Foxi1-dependent manner but are unaffected in the absence of Dlx3b/4b or in b380 mutants. Thus, in addition to otic fate Foxi1 provides neuronal competence during OEPD induction prior to and independently of the Dlx3b/4b-mediated sensory fate of the developing inner ear.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Genetically Modified / embryology
  • Animals, Genetically Modified / genetics
  • Animals, Genetically Modified / metabolism
  • Cell Lineage
  • Ear, Inner / embryology*
  • Ear, Inner / physiology
  • Embryo, Nonmammalian / drug effects
  • Embryo, Nonmammalian / metabolism
  • Embryo, Nonmammalian / physiology
  • Forkhead Transcription Factors / genetics
  • Forkhead Transcription Factors / metabolism*
  • Gene Expression Regulation, Developmental
  • Genes, Reporter
  • Hair Cells, Auditory / metabolism*
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism*
  • Immunohistochemistry
  • Morpholinos / administration & dosage
  • Neurogenesis
  • Neurons / metabolism
  • Neurons / physiology
  • PAX2 Transcription Factor / genetics
  • PAX2 Transcription Factor / metabolism
  • Promoter Regions, Genetic
  • SOX9 Transcription Factor / genetics
  • SOX9 Transcription Factor / metabolism
  • Transcription, Genetic
  • Zebrafish / embryology
  • Zebrafish / metabolism*
  • Zebrafish / physiology
  • Zebrafish Proteins / genetics
  • Zebrafish Proteins / metabolism*

Substances

  • Forkhead Transcription Factors
  • Homeodomain Proteins
  • Morpholinos
  • PAX2 Transcription Factor
  • SOX9 Transcription Factor
  • Sox9a protein, zebrafish
  • Zebrafish Proteins
  • dlx3b protein, zebrafish
  • foxi1 protein, zebrafish
  • pax2a protein, zebrafish