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Vertebrate segmentation has been proposed as an evolutionary inheritance either from some metameric protostome or from a more closely related deuterostome. To address this question, we studied the developmental expression of AmphiEn, the engrailed gene of amphioxus, the closest living invertebrate relative of the vertebrates. In neurula embryos of(More)
The dynamic expression patterns of the single amphioxus Distal-less homolog (AmphiDll) during development are consistent with successive roles of this gene in global regionalization of the ectoderm, establishment of the dorsoventral axis, specification of migratory epidermal cells early in neurulation and the specification of forebrain. Such a multiplicity(More)
Recent studies of protochordates (ascidian tunicates and amphioxus) have given insights into possible ancestors of 2 of the characteristic features of the vertebrate head: neural crest and placodes. The neural crest probably evolved from cells on either side of the neural plate-epidermis boundary in a protochordate ancestral to the vertebrates. In(More)
The organizer of the vertebrate gastrula is an important signalling centre that induces and patterns dorsal axial structures. Although a topic of long-standing interest, the evolutionary origin of the organizer remains unclear. Here we show that the gastrula of the cephalochordate amphioxus expresses dorsal/ventral (D/V) patterning genes (for example, bone(More)
Amphioxus, the closest living invertebrate relative of the vertebrates, has a notochord, segmental axial musculature, pharyngeal gill slits and dorsal hollow nerve cord, but lacks neural crest. In amphioxus, as in vertebrates, exogenous retinoic acid (RA) posteriorizes the embryo. The mouth and gill slits never form, AmphiPax1, which is normally(More)
In developing chordates, retinoic acid (RA) signaling patterns the rostrocaudal body axis globally and affects gene expression locally in some differentiating cell populations. Here we focus on development of epidermal sensory neurons in an invertebrate chordate (amphioxus) to determine how RA signaling influences their rostrocaudal distribution and gene(More)
The full-length sequence and developmental expression of an amphioxus Wnt gene (AmphiWnt8) are described. In amphioxus embryos, the expression patterns of AmphiWnt8 suggest patterning roles in the forebrain, in the hindgut, and in the paraxial mesoderm that gives rise to the muscular somites. Phylogenetic analysis indicates that a single Wnt8 subfamily gene(More)
Amphioxus, as the closest living invertebrate relative of the vertebrates, can give insights into the evolutionary origin of the vertebrate body plan. Therefore, to investigate the evolution of genetic mechanisms for establishing and patterning the neuroectoderm, we cloned and determined the embryonic expression of two amphioxus transcription factors,(More)
To explore the evolution of myogenic regulatory factors in chordates, we isolated two MyoD family genes (AmphiMRF1 and AmphiMRF2) from amphioxus. AmphiMRF1 is first expressed at the late gastrula in the paraxial mesoderm. As the first somites form, expression is restricted to their myotomal region. In the early larva, expression is strongest in the most(More)