A conserved role for the MEK signalling pathway in neural tissue specification and posteriorisation in the invertebrate chordate, the ascidian<i>Ciona intestinalis</i>

Hudson, C. S.; Darras, Sébastien; Caillol, Danielle; Yasuo, Hitoyoshi; Lemaire, Patrick

doi:10.1242/dev.00200

Cited by 110 publications

(134 citation statements)

References 51 publications

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“…The present study identified the b6.5 blastomere as a Nodal signalling source, dependent on the specific activation of the Ci-Nodal gene in this blastomere by Ci-FGF9/16/20 signalling from vegetal blastomeres. However, ERK1/2 activation is observed in both b6.5 and a6.5 blastomeres, and an FGFresponse element of the Ci-Otx gene is able to drive expression of a reporter gene in both lineages (Bertrand et al, 2003;Hudson et al, 2003). We propose that the transcriptional activation of Ci-Nodal in b6.5 but not in a6.5 is due to a difference in competence between a-and b-line blastomeres to respond to FGF-signalling, as has been previously observed during the formation of anterior neural fates and sensory neurons (Hudson and Lemaire, 2001;Ohtsuka et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

“…The Ras/MEK/ERK/Ets signalling pathway, which is activated downstream of FGF-like signalling, has been implicated in posteriorisation of the neural tube (Akanuma and Nishida, 2003;Hudson et al, 2003). In embryos in which this signalling pathway is inhibited, markers of posterior neural fate are lost and a greater number of A-line cells express markers of the anterior CNS.…”

Section: Introductionmentioning

confidence: 99%

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Patterning across the ascidian neural plate by lateral Nodal signalling sources

2005

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Ascidians are invertebrate chordates with a simple larval tadpole form containing a notochord and an overlying dorsal neural tube. As in vertebrates,the neural tube of ascidian larvae displays positional differences along the rostral-caudal and dorsal-ventral axes in terms of neuronal cell types generated, morphology and gene expression. However, how these differences are established in this simple chordate remains largely unknown. In this study, we show that a single blastomere named b6.5, which is situated in a lateral position in the 32-cell-stage embryo, is a source of signal(s) required for patterning across the medial-lateral axis (future ventral-dorsal axis) of the neural plate. We identify this signal as a Ciona homologue of Nodal, Ci-Nodal. Transcriptional activation of Ci-Nodal in b6.5 depends upon vegetally derived Ci-FGF9/16/20. Using three distinct reagents to inhibit Nodal signals, we show that Nodal signalling is required for neural plate patterning across the medial-lateral axis and that, in the absence of this signal, the caudal-lateral part of the neural plate adopts a medial-like fate. Secondary muscle fate is similarly affected. We conclude that specification of the lateral neural plate is initiated by signalling sources laterally flanking the neural plate and involves a cell-fate choice between lateral and medial neural fates, with Nodal signalling promoting lateral fate. This role for Nodal signalling during ascidian neural plate patterning contrasts with that in vertebrates, where it is implicated in promoting a medial neural fate, the floor plate.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Patterning across the ascidian neural plate by lateral Nodal signalling sources

2005

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“…3b). Ci-Mnx is expressed in the ventral nerve cord-lineage cells in normal embryos (Hudson et al 2003; Fig. 3c).…”

Section: Alteration Of Gene Expression Pattern By Overexpression Of Cmentioning

confidence: 94%

Nodal regulates neural tube formation in the Ciona intestinalis embryo

Mita

Fujiwara

2007

Dev Genes Evol

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“…FGF signaling is mediated in vertebrate embryos by the Ras/MEK/MAPK cascade. In ascidians, these intermediates have been shown to play a conserved role during formation of the secondary notochord cells, as well as in the specification of the neural tissue (Kim and Nishida, 2001;Hudson et al, 2003).…”

Section: Larval Tissues Notochordmentioning

confidence: 99%

Ciona intestinalis: Chordate development made simple

2005

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Thanks to their transparent and rapidly developing mosaic embryos, ascidians (or sea squirts) have been a model system for embryological studies for over a century. Recently, ascidians have entered the postgenomic era, with the sequencing of the Ciona intestinalis genome and the accumulation of molecular resources that rival those available for fruit flies and mice. One strength of ascidians as a model system is their close similarity to vertebrates. Literature reporting molecular homologies between vertebrate and ascidian tissues has flourished over the past 15 years, since the first ascidian genes were cloned. However, it should not be forgotten that ascidians diverged from the lineage leading to vertebrates over 500 million years ago. Here, we review the main similarities and differences so far identified, at the molecular level, between ascidian and vertebrate tissues and discuss the evolution of the compact ascidian genome.

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A conserved role for the MEK signalling pathway in neural tissue specification and posteriorisation in the invertebrate chordate, the ascidianCiona intestinalis

Cited by 110 publications

References 51 publications

Patterning across the ascidian neural plate by lateral Nodal signalling sources

Patterning across the ascidian neural plate by lateral Nodal signalling sources

Nodal regulates neural tube formation in the Ciona intestinalis embryo

Ciona intestinalis: Chordate development made simple

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