Genetic interactions underlying otic placode induction and formation

The formation of the otic placode is a complex process requiring multiple inductive signals. In zebrafish, fgf3 and fgf8, dlx3b and dlx4b, and foxi1 have been identified as the earliest‐acting genes in this process. fgf3 and fgf8 are required as inductive signals, whereas dlx3b, dlx4b, and foxi1 app...

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Bibliographic Details
Published in:Developmental dynamics 2004-07, Vol.230 (3), p.419-433
Main Authors: Solomon, Keely S., Kwak, Su‐Jin, Fritz, Andreas
Format: Article
Language:English
Subjects:
Animals
Danio rerio
dlx3b
dlx4b
Ear - embryology
Embryo, Nonmammalian
Embryonic Induction - drug effects
Epistasis, Genetic
fgf3
fgf8
foxi1
Gene Expression Regulation, Developmental
Models, Biological
Oligodeoxyribonucleotides, Antisense - pharmacology
otic placode
Signal Transduction
zebrafish
Zebrafish - embryology
Zebrafish Proteins - genetics
Zebrafish Proteins - metabolism
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Summary:The formation of the otic placode is a complex process requiring multiple inductive signals. In zebrafish, fgf3 and fgf8, dlx3b and dlx4b, and foxi1 have been identified as the earliest‐acting genes in this process. fgf3 and fgf8 are required as inductive signals, whereas dlx3b, dlx4b, and foxi1 appear to act directly within otic primordia. We have investigated potential interactions among these genes. Depletion of either dlx3b and dlx4b or foxi1 leads to a delay of pax2a expression in the otic primordia and reduction of the otic vesicle. Depletion of both foxi1 and dlx3b results in a complete ablation of otic placode formation. A strong synergistic interaction is also observed among foxi1, fgf3, and fgf8, and a weaker interaction among dlx3b, fgf3, and fgf8. Misexpression of foxi1 can induce expression of pax8, an early marker for the otic primordia, in embryos treated with an inhibitor of fibroblast growth factor (FGF) signaling. Conversely, morpholino knockdown of foxi1 blocks ectopic pax8 expression and otic vesicle formation induced by misexpression of fgf3 and/or fgf8. The observed genetic interactions suggest a model in which foxi1 and dlx3b/dlx4b act in independent pathways together with distinct phases of FGF signaling to promote otic placode induction and development. Developmental Dynamics 230:419–433, 2004. © 2004 Wiley‐Liss, Inc.
ISSN:1058-8388
1097-0177
DOI:10.1002/dvdy.20067