Evolutionary modification of mouth position in deuterostomes

Christiaen, Lionel; Jaszczyszyn, Yan; Kerfant, Marina; Kano, Shungo; Thermes, Violette; Joly, Jean Stéphane

doi:10.1016/j.semcdb.2007.06.002

Cited by 40 publications

(52 citation statements)

References 77 publications

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“…In addition, nodal, a gene involved in chordate left-right asymmetry, is expressed on the right side in chordates and the left side in sea urchins, further adding evidence to a body axis inversion in chordates (Swalla and Smith, 2008). This has led to the hypothesis that vertebrate evolution involved a rotation of the mouth of an enteropneust-like ancestor to the other side of the body on the same side as the gill slits (Christiaen et al, 2007;Lacalli, 2006;Lowe et al, 2006). However, following this scenario the neural tube would remain on the same side of the worm as the gill slits and the mouth or a ''hot zone'' of a neural organizing center must occur on the post oral dorsal side of the vertebrates (see details in Lacalli, 2006).…”

Section: Dorsal-ventral Axis Inversion or The Placement Of The Gill Smentioning

confidence: 99%

Man is but a worm: Chordate origins

Brown

Prendergast

Swalla

2008

Genesis

112

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Summary: The origin of chordates remains one of the major puzzles of zoology, even after more than a century of intense scientific inquiry, following Darwin's ''Origin of Species''. The chordates exhibit a unique body plan that evolved from a deuterostome ancestor some time before the Cambrian. Molecular data gathered from phylogenetics and developmental gene expression has changed our perception of the relationships within and between deuterostome phyla. Recent developmental gene expression data has shown that the chordates use similar gene families and networks to specify their anterior-posterior, dorsal-ventral and left-right body axes. The anterior-posterior axis is similarly established among deuterostomes and is determined by a related family of transcription factors, the Hox gene clusters and Wnt signaling pathways. In contrast, the dorsalventral axis is inverted in chordates, compared with other nonchordate invertebrates, while still determined by expression of BMP signaling pathway members and their antagonists. Finally, left-right asymmetries in diverse deuterostomes are determined by nodal signaling. These new data allow revised, testable hypotheses about our earliest ancestors. We present a new hypothesis for the origin of the chordates whereby the expansion of BMP during dorsal-ventral patterning allowed the evolution of noneural ectoderm and pharyngeal gill slits on the ventral side. We conclude that ''Man is but a worm . . . ,'' that our chordate ancestors were worm-like deposit and/or filter feeders with pharyngeal slits, and an anterior tripartite unsegmented neurosensory region. genesis 46:605-613,

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Section: Dorsal-ventral Axis Inversion or The Placement Of The Gill Smentioning

confidence: 99%

Man is but a worm: Chordate origins

Brown

Prendergast

Swalla

2008

Genesis

112

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“…4C,D). Six3/6, which encodes a homeodomain transcription factor, is normally expressed in row IV of the neural plate (Moret et al, 2005;Christiaen et al, 2007), but its expression is lost upon U0126 treatment (Fig. 4E,F).…”

Section: Research Articlementioning

confidence: 99%

“…Morphological, embryological and molecular evidence suggest that ascidian palps represent a rudimentary placode (Manni et al, 2004;. Another placode-like structure, the stomodeum, arises from the neural plate territory sandwiched between the palp placode and the anterior neural tube (Manni et al, 2005;Christiaen et al, 2007). The stomodeum gives rise to the oral siphon (mouth) of the adult and derives from the anterior neuropore .…”

Section: Introductionmentioning

confidence: 99%

FGF signaling establishes the anterior border of the Ciona neural tube

2012

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SUMMARYThe Ciona tadpole is constructed from simple, well-defined cell lineages governed by provisional gene networks that have been defined via extensive gene disruption assays. Here, we examine the patterning of the anterior neural plate, which produces placodal derivatives such as the adhesive palps and stomodeum, as well as the sensory vesicle (simple brain) of the Ciona tadpole. Evidence is presented that the doublesex-related gene DMRT is expressed throughout the anterior neural plate of neurulating embryos. It leads to the activation of FoxC and ZicL in the palp placode and anterior neural tube, respectively. This differential expression depends on FGF signaling, which inhibits FoxC expression in the anterior neural tube. Inhibition of FGF signaling leads to expanded expression of FoxC, the loss of ZicL, and truncation of the anterior neural tube.

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“…Preliminary data on the inhibition of the Nodal pathway in snails show that nodal regulates exclusively the asymmetric domain of Pitx expression, suggesting different independent enhancers for Pitx in snails, as described for vertebrates (Christiaen et al 2005(Christiaen et al , 2007.…”

Section: Nodal-pitx In Bilateriamentioning

confidence: 86%

“…In addition to asymmetric expression, Pitx is a stomodeal (mouth) marker for both chordates and echinoderms (Christiaen et al 2007). However, in another group of deuterostomes, hemichordates, this gene is expressed at the opposite end of the site of mouth formation (Lowe et al 2006).…”

Section: Nodal-pitx In Bilateriamentioning

confidence: 99%