title: Mesodermal Fgf10b cooperates with other fibroblast growth factors during induction of otic and epibranchial placodes in zebrafish.
abstract: BACKGROUND
  Vertebrate otic and epibranchial placodes develop in close proximity in response to localized fibroblast growth factor (Fgf) signaling. Although less is known about epibranchial induction, the process of otic induction in highly conserved, with important roles for Fgf3 and Fgf8 reported in all species examined. Fgf10 is also critical for otic induction in mouse, but the only zebrafish ortholog examined to date, fgf10a, is not expressed early enough to play such a role. A second zebrafish ortholog, fgf10b, has not been previously examined.
  
  
  RESULTS
  We find that zebrafish fgf10b is expressed at tailbud stage in paraxial cephalic mesoderm beneath prospective epibranchial tissue, lateral to the developing otic placode. Knockdown of fgf10b does not affect initial otic induction but impairs subsequent accumulation of otic cells. Formation of epibranchial placodes and ganglia are also moderately impaired. Combinatorial disruption of fgf10b and fgf3 exacerbates the deficiency of otic cells and eliminates epibranchial induction entirely. Disruption of fgf10b and fgf24 also strongly reduces, but does not eliminate, epibranchial induction.
  
  
  CONCLUSIONS
  fgf10b participates in a late phase of otic induction and, in combination with fgf3, is especially critical for epibranchial induction.
authors.affiliation: Biology Department, Texas A&M University, College Station, Texas.
authors.forename: Kirstin
authors.initials: K
authors.lastname: Maulding
authors.forename: Mahesh S
authors.initials: MS
authors.lastname: Padanad
authors.forename: Jennifer
authors.initials: J
authors.lastname: Dong
authors.forename: Bruce B
authors.initials: BB
authors.lastname: Riley
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000235:genetics; D001934:Branchial Region / Q000196:embryology* / Q000378:metabolism; D004423:Ear / Q000196:embryology*; D004625:Embryo, Nonmammalian; D004627:Embryonic Induction / Q000235:genetics*; D051526:Fibroblast Growth Factor 10 / Q000502:physiology; D051518:Fibroblast Growth Factor 3 / Q000502:physiology*; D005346:Fibroblast Growth Factors / Q000502:physiology*; D008648:Mesoderm / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology / Q000235:genetics; D029961:Zebrafish Proteins / Q000502:physiology*
chemical_list: D051526:Fibroblast Growth Factor 10; D051518:Fibroblast Growth Factor 3; D029961:Zebrafish Proteins; C520413:fgf10a protein, zebrafish; C489200:fgf3 protein, zebrafish; D005346:Fibroblast Growth Factors
keywords: cranial placodes; epibranchial ganglia; otic vesicle; pax2a; phox2a; sox3