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PMID:14757644

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Citation

Phillips, BT, Storch, EM, Lekven, AC and Riley, BB (2004) A direct role for Fgf but not Wnt in otic placode induction. Development 131:923-31

Abstract

Induction of the otic placode, which gives rise to all tissues comprising the inner ear, is a fundamental aspect of vertebrate development. A number of studies indicate that fibroblast growth factor (Fgf), especially Fgf3, is necessary and sufficient for otic induction. However, an alternative model proposes that Fgf must cooperate with Wnt8 to induce otic differentiation. Using a genetic approach in zebrafish, we tested the roles of Fgf3, Fgf8 and Wnt8. We demonstrate that localized misexpression of either Fgf3 or Fgf8 is sufficient to induce ectopic otic placodes and vesicles, even in embryos lacking Wnt8. Wnt8 is expressed in the hindbrain around the time of otic induction, but loss of Wnt8 merely delays expression of preotic markers and otic vesicles form eventually. The delay in otic induction correlates closely with delayed expression of fgf3 and fgf8 in the hindbrain. Localized misexpression of Wnt8 is insufficient to induce ectopic otic tissue. By contrast, global misexpression of Wnt8 causes development of supernumerary placodes/vesicles, but this reflects posteriorization of the neural plate and consequent expansion of the hindbrain expression domains of Fgf3 and Fgf8. Embryos that misexpress Wnt8 globally but are depleted for Fgf3 and Fgf8 produce no otic tissue. Finally, cells in the preotic ectoderm express Fgf (but not Wnt) reporter genes. Thus, preotic cells respond directly to Fgf but not Wnt8. We propose that Wnt8 serves to regulate timely expression of Fgf3 and Fgf8 in the hindbrain, and that Fgf from the hindbrain then acts directly on preplacodal cells to induce otic differentiation.

Links

PubMed Online version:10.1242/dev.00978

Keywords

Animals; Cytoskeletal Proteins; Ear/embryology; Embryonic Induction/physiology; Fibroblast Growth Factors/physiology; Genes, Reporter; Proteins/physiology; Proto-Oncogene Proteins/physiology; Rhombencephalon/embryology; Wnt Proteins; Zebrafish/embryology; Zebrafish Proteins

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

DANRE:FGF8A

involved_in

GO:0030177: positive regulation of Wnt signaling pathway

ECO:0000316: genetic interaction evidence used in manual assertion

ZFIN:ZDB-GENE-980526-178

P

Seeded From UniProt

complete

DANRE:FGF8A

involved_in

GO:0030916: otic vesicle formation

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

DANRE:FGF3

involved_in

GO:0030177: positive regulation of Wnt signaling pathway

ECO:0000316: genetic interaction evidence used in manual assertion

ZFIN:ZDB-GENE-990415-72

P

Seeded From UniProt

complete

DANRE:FGF3

involved_in

GO:0030916: otic vesicle formation

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

DANRE:FGF3

involved_in

GO:0009953: dorsal/ventral pattern formation

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

DANRE:FGF3

involved_in

GO:0043049: otic placode formation

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

DANRE:WNT8A

involved_in

GO:0009952: anterior/posterior pattern specification

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

DANRE:WNT8A

involved_in

GO:0045743: positive regulation of fibroblast growth factor receptor signaling pathway

ECO:0000315: mutant phenotype evidence used in manual assertion

ZFIN:ZDB-GENO-020130-1

P

Seeded From UniProt

complete

See also

References

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