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Nuclear β‐catenin promotes non‐neural ectoderm and posterior cell fates in amphioxus embryos
Author(s) -
Holland Linda Z.,
Panfilio Kristen A.,
Chastain Roger,
Schubert Michael,
Holland Nicholas D.
Publication year - 2005
Publication title -
developmental dynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.634
H-Index - 141
eISSN - 1097-0177
pISSN - 1058-8388
DOI - 10.1002/dvdy.20473
Subject(s) - biology , neurula , blastula , gastrulation , chordate , ectoderm , wnt signaling pathway , neuroectoderm , neural plate , microbiology and biotechnology , beta catenin , neurulation , neural development , embryo , embryogenesis , anatomy , embryonic stem cell , vertebrate , genetics , mesoderm , signal transduction , gene
In vertebrate development, Wnt/β‐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 β‐catenin from the invertebrate chordate amphioxus. The exon/intron organization of β‐catenin is highly conserved between amphioxus and other animals including a cnidarian, but not Drosophila . In development, amphioxus β‐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/β‐catenin signaling, had no detectable effect on axial patterning when applied before the late blastula stage, suggesting that a role for β‐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 β‐catenin are around the blastopore. In the early neurula, β‐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, down‐regulation of Wnt/β‐catenin signaling in the neural plate is necessary for maintenance of the neuroectoderm and that a major evolutionarily conserved role of Wnt/β‐catenin signaling is to specify posterior identity and pattern the anterior/posterior axis. Developmental Dynamics 233:1430–1443, 2005. © 2005 Wiley‐Liss, Inc.