The larval ascidian nervous system: the chordate brain from its small beginnings

Meinertzhagen, Ian A.; Okamura, Yasushi

doi:10.1016/s0166-2236(00)01851-8

Cited by 154 publications

(120 citation statements)

References 62 publications

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“…The numerous advantages of Ciona as an experimental organism include a compact genome, invariant cell lineages, rapid development and simple transgenesis methods (Lemaire, 2011;Satoh, 2003). The cellular simplicity of the Ciona CNS makes it an ideal model for understanding the development and function of chordate-specific neuronal networks Meinertzhagen and Okamura, 2001).…”

Section: Introductionmentioning

confidence: 99%

Neural tube patterning by Ephrin, FGF and Notch signaling relays

et al. 2011

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Section: Introductionmentioning

confidence: 99%

Neural tube patterning by Ephrin, FGF and Notch signaling relays

et al. 2011

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“…The ascidian larval CNS consists, along the anteriorposterior axis, of a sensory vesicle, neck, visceral ganglion and tail nerve cord ( Fig. 1) (for reviews, see Lemaire et al, 2002;Meinertzhagen and Okamura, 2001;Meinertzhagen et al, 2004). The entire CNS consists of only around 330 cells.…”

Section: Introductionmentioning

confidence: 99%

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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“…(B-J)Embryos electroporated with either the 2.4 kb Ci-Tbx6b CRM (B-D), the 862 bp fragment (E-G) or the 2.4 kb CRM carrying mutations in all Ci-Macho1-binding sites (H-J) were fixed at the 32-cell (B,E,H), 110-cell (C,F,I), or early neurula (D,G,J) stage and hybridized in situ with a lacZ probe. Stained blastomeres are labeled only on one side of the embryos (Conklin, 1905;Meinertzhagen and Okamura, 2001). (K)The 266 bp proximal region of the Ci-Tbx6b CRM (orange in A) contains putative binding sites for CREB (blue diamond), T-box (red oval) and bHLH ('AC'-core E-box; pink triangle) transcription factors.…”

Section: The Proximal Region Of the Ci-tbx6b Crm Recapitulates The Lamentioning

confidence: 99%

Temporal regulation of the muscle gene cascade by Macho1 and Tbx6 transcription factors in Ciona intestinalis

Kugler¹,

Gazdoiu²,

Oda-Ishii³

et al. 2010

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SummaryFor over a century, muscle formation in the ascidian embryo has been representative of 'mosaic' development. The molecular basis of muscle-fate predetermination has been partly elucidated with the discovery of Macho1, a maternal zinc-finger transcription factor necessary and sufficient for primary muscle development, and of its transcriptional intermediaries Tbx6b and Tbx6c. However, the molecular mechanisms by which the maternal information is decoded by cis-regulatory modules (CRMs) associated with muscle transcription factor and structural genes, and the ways by which a seamless transition from maternal to zygotic transcription is ensured, are still mostly unclear. By combining misexpression assays with CRM analyses, we have identified the mechanisms through which Ciona Macho1 (Ci-Macho1) initiates expression of Ci-Tbx6b and Ci-Tbx6c, and we have unveiled the cross-regulatory interactions between the latter transcription factors. Knowledge acquired from the analysis of the Ci-Tbx6b CRM facilitated both the identification of a related CRM in the Ci-Tbx6c locus and the characterization of two CRMs associated with the structural muscle gene fibrillar collagen 1 (CiFCol1). We use these representative examples to reconstruct how compact CRMs orchestrate the muscle developmental program from pre-localized ooplasmic determinants to differentiated larval muscle in ascidian embryos.

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The larval ascidian nervous system: the chordate brain from its small beginnings

Cited by 154 publications

References 62 publications

Neural tube patterning by Ephrin, FGF and Notch signaling relays

Neural tube patterning by Ephrin, FGF and Notch signaling relays

Patterning across the ascidian neural plate by lateral Nodal signalling sources

Temporal regulation of the muscle gene cascade by Macho1 and Tbx6 transcription factors in Ciona intestinalis

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