An analysis of induction of the ear from foreign ectoderm in the salamander embryo

Yntema, C. L.

doi:10.1002/jez.1401130110

Cited by 109 publications

(37 citation statements)

References 17 publications

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“…FGF signals act over a prolonged period during the early steps of otic placode induction (Phillips et al, 2001;Leger and Brand, 2002) and in later aspects of patterning and differentiation (Kwak et al, 2002;Leger and Brand, 2002). The characteristics of FGF signaling fit well with previous data suggesting that otic placode induction is an extended process requiring signals from multiple tissues (Yntema, 1950;Herbrand et al, 1998;Groves and Bronner-Fraser, 2000).…”

Section: Introductionsupporting

confidence: 76%

Genetic interactions underlying otic placode induction and formation

Solomon

Kwak

Fritz

2004

Developmental Dynamics

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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.

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Section: Introductionsupporting

confidence: 76%

Genetic interactions underlying otic placode induction and formation

Solomon

Kwak

Fritz

2004

Developmental Dynamics

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“…Previous studies have implicated signals from the mesendoderm in the induction of individual placodes, namely the olfactory, lens and otic primordia (Zwilling, 1940;Raven and Kloos, 1945;Yntema, 1950;Yntema, 1955;Jacobson, 1963a;OrtsLlorca and Jimenez-Collado, 1971;Henry and Grainger, 1990;Gallagher et al, 1996). However, owing to the lack of molecular markers, species differences and different timing of the experiments, its precise role remained ill defined.…”

Section: Discussionmentioning

confidence: 99%

A balance of FGF, BMP and WNT signalling positions the future placode territory in the head

Litsiou

Hanson

Streit³

2005

Development

256

391

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The sensory nervous system in the vertebrate head arises from two different cell populations: neural crest and placodal cells. By contrast, in the trunk it originates from neural crest only. How do placode precursors become restricted exclusively to the head and how do multipotent ectodermal cells make the decision to become placodes or neural crest? At neural plate stages,future placode cells are confined to a narrow band in the head ectoderm, the pre-placodal region (PPR). Here, we identify the head mesoderm as the source of PPR inducing signals, reinforced by factors from the neural plate. We show that several independent signals are needed: attenuation of BMP and WNT is required for PPR formation. Together with activation of the FGF pathway, BMP and WNT antagonists can induce the PPR in naïve ectoderm. We also show that WNT signalling plays a crucial role in restricting placode formation to the head. Finally, we demonstrate that the decision of multipotent cells to become placode or neural crest precursors is mediated by WNT proteins:activation of the WNT pathway promotes the generation of neural crest at the expense of placodes. This mechanism explains how the placode territory becomes confined to the head, and how neural crest and placode fates diversify.

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“…The otic placode is a transient structure, giving rise to the otic vesicle, which then proliferates and differentiates to form specialized cell types necessary for hearing and balance. Transplantation experiments in chick (Waddington, 1937) and amphibians (Jacobson, 1966;Yntema, 1933;Yntema, 1950) have shown that competence to form an otic placode is initially broadly distributed throughout the ectoderm that lies laterally to the neural plate. This region of competence becomes increasingly restricted as an ongoing response to multiple, overlapping signals emanating from surrounding tissues (Jacobson, 1963).…”

Section: Introductionmentioning

confidence: 99%

Zebrafishfoxi1mediates otic placode formation and jaw development

et al. 2003

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The otic placode is a transient embryonic structure that gives rise to the inner ear. Although inductive signals for otic placode formation have been characterized, less is known about the molecules that respond to these signals within otic primordia. Here, we identify a mutation in zebrafish, hearsay, which disrupts the initiation of placode formation. We show that hearsay disrupts foxi1, a forkhead domain-containing gene, which is expressed in otic precursor cells before placodes become visible; foxi1 appears to be the earliest marker known for the otic anlage. We provide evidence that foxi1 regulates expression of pax8, indicating a very early role for this gene in placode formation. In addition, foxi1 is expressed in the developing branchial arches, and jaw formation is disrupted in hearsay mutant embryos.

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An analysis of induction of the ear from foreign ectoderm in the salamander embryo

Cited by 109 publications

References 17 publications

Genetic interactions underlying otic placode induction and formation

Genetic interactions underlying otic placode induction and formation

A balance of FGF, BMP and WNT signalling positions the future placode territory in the head

Zebrafishfoxi1mediates otic placode formation and jaw development

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