![]() ![]() Nuclear β-catenin promotes non-neural ectoderm and posterior cell fates in amphioxus embryos. Conservation of BMP signaling in zebrafish mesoderm patterning. Bone morphogenetic protein 4: a ventralizing factor in early Xenopus development. Dorsoventral patterning in hemichordates: insights into early chordate evolution. ![]() The BMP/CHORDIN antagonism controls sensory pigment cell specification and differentiation in the ascidian embryo. Amphioxus goosecoid and the evolution of the head organizer and prechordal plate. Characterization of amphioxus amphivent, an evolutionarily conserved marker for chordate ventral mesoderm. Initial patterning of the central nervous system: how many organizers? Nature Rev. ![]() An anterior signalling centre in Xenopus revealed by the homeobox gene XHex. Amphioxus Evx genes: implications for the evolution of the midbrain–hindbrain boundary and the chordate tailbud. The ventral and posterior expression of the zebrafish homeobox gene eve1 is perturbed in dorsalized and mutant embryos. S., Joly, C., Schulte-Merker, S., Boulekbache, H. Left–right asymmetry in embryonic development: a comprehensive review. An amphioxus nodal gene ( AmphiNodal) with early symmetrical expression in the organizer and mesoderm and later asymmetrical expression associated with left-right axis formation. Homologues of Twisted gastrulation are extracellular cofactors in antagonism of BMP signalling. Twisted gastrulation can function as a BMP antagonist. Regulation of ADMP and BMP2/4/7 at opposite embryonic poles generates a self-regulating morphogenetic field. Regionally specific induction by the Spemann–Mangold organizer. The establishment of Spemann's organizer and patterning of the vertebrate embryo. Dorsal–ventral patterning and neural induction in Xenopus embryos. Experimental studies on the neural induction in amphioxus. Topographic changes in nascent and early mesoderm in amphioxus embryos studied by DiI labeling and by in situ hybridization for a Brachyury gene. Deuterostome phylogeny reveals monophyletic chordates and the new phylum Xenoturbellida. Multigene analyses of bilaterian animals corroborate the monophyly of Ecdysozoa, Lophotrochozoa, and Protostomia. Molecular phylogeny and divergence times of deuterostome animals. Did the first chordates organize without the organizer? Trends Genet. Evolution of the organizer and the chordate body plan. In light of recent phylogenetic analyses placing cephalochordates basally in the chordate lineage, we propose that separate signalling centres for patterning the D/V and A/P axes may be an ancestral chordate character. These results suggest evolutionary conservation of the mechanisms for both D/V and A/P patterning of the early gastrula. In addition, Wnt-antagonists (for example, Dkks and sFRP2-like) are expressed anteriorly, whereas Wnt genes themselves are expressed posteriorly, consistent with a role for Wnt signalling in anterior/posterior (A/P) patterning. Here we show that the gastrula of the cephalochordate amphioxus expresses dorsal/ventral (D/V) patterning genes (for example, bone morphogenetic proteins ( BMPs), Nodal and their antagonists) in patterns reminiscent of those of their vertebrate orthlogues, and that amphioxus embryos, like those of vertebrates, are ventralized by exogenous BMP protein. Although a topic of long-standing interest, the evolutionary origin of the organizer remains unclear. The organizer of the vertebrate gastrula is an important signalling centre that induces and patterns dorsal axial structures. ![]()
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