Nuclear beta-catenin promotes non-neural ectoderm and posterior cell fates in amphioxus embryos

Holland, LZ, Panfilio KA, Chastain R, Schubert M, Holland ND.  2005.  Nuclear beta-catenin promotes non-neural ectoderm and posterior cell fates in amphioxus embryos. Developmental Dynamics. 233:1430-1443.

Date Published:



amphioxus, animal-vegetal axis, axial patterning, beta-catenin, brachyury, chordate evolution, convergent, deuterostome evolution, developmental expression, dorsoventral axis, extension movements, gastrulation movements, gene-expression, lithium, sea-urchin embryo, wnt, wnt signaling pathway, wnt/beta-catenin, xenopus tail bud


In vertebrate development, Wnt/beta-catenin signaling has an early role in specification of dorsal/anterior identity and a late one in posterior specification. To understand the evolution of these roles, we cloned beta-catenin from the invertebrate chordate amphioxus. The exon/intron organization of beta-catenin is highly conserved between amphioxus and other animals including a cnidarian, but not Drosophila. In development, amphioxus P-catenin is concentrated in all nuclei from the 16-cell stage until the onset of gastrulation when it becomes undetectable in presumptive mesendoderm. Li+, which up-regulates Wnt/beta-catenin signaling, had no detectable effect on axial patterning when applied before the late blastula stage, suggesting that a role for P-catenin in specification of dorsal/anterior identity may be a vertebrate innovation. From the mid-gastrula through the neurula stage, the highest levels of nuclear R-catenin are around the blastopore. In the early neurula, P-catenin is down-regulated in the neural plate, but remains high in adjacent non-neural ectoderm. Embryos treated with Li+ at the late blastula stage are markedly posteriorized and lack a neural plate. These results suggest that in amphioxus, as in vertebrates, downregulation of Wnt/beta-catenin signaling in the neural plate is necessary for maintenance of the neuroectoderm and that a major evolutionarily conserved role of Wnt/beta-catenin signaling is to specify posterior identity and pattern the anterior/posterior axis. (c) 2005 Wiley-Liss, Inc.