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First published online 17 November 2004
doi: 10.1242/dev.01542

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Regional requirements for Dishevelled signaling during Xenopus gastrulation: separable effects on blastopore closure, mesendoderm internalization and archenteron formation

Andrew J. Ewald^1,*, Sara M. Peyrot², J. Michael Tyszka¹, Scott E. Fraser¹ and John B. Wallingford^3,

¹ Department of Biology and Biological Imaging Center, California Institute of Technology, Pasadena, CA 91125, USA
² Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
³ Department of Molecular, Cell and Developmental Biology and Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA

Author for correspondence (e-mail: wallingford{at}mail.utexas.edu)

Accepted 21 October 2004

During amphibian gastrulation, the embryo is transformed by the combined actions of several different tissues. Paradoxically, many of these morphogenetic processes can occur autonomously in tissue explants, yet the tissues in intact embryos must interact and be coordinated with one another in order to accomplish the major goals of gastrulation: closure of the blastopore to bring the endoderm and mesoderm fully inside the ectoderm, and generation of the archenteron. Here, we present high-resolution 3D digital datasets of frog gastrulae, and morphometrics that allow simultaneous assessment of the progress of convergent extension, blastopore closure and archenteron formation in a single embryo. To examine how the diverse morphogenetic engines work together to accomplish gastrulation, we combined these tools with time-lapse analysis of gastrulation, and examined both wild-type embryos and embryos in which gastrulation was disrupted by the manipulation of Dishevelled (Xdsh) signaling. Remarkably, although inhibition of Xdsh signaling disrupted both convergent extension and blastopore closure, mesendoderm internalization proceeded very effectively in these embryos. In addition, much of archenteron elongation was found to be independent of Xdsh signaling, especially during the second half of gastrulation. Finally, even in normal embryos, we found a surprising degree of dissociability between the various morphogenetic processes that occur during gastrulation. Together, these data highlight the central role of PCP signaling in governing distinct events of Xenopus gastrulation, and suggest that the loose relationship between morphogenetic processes may have facilitated the evolution of the wide variety of gastrulation mechanisms seen in different amphibian species.

Key words: Gastrulation, Dishevelled, Morphogenesis, Xenopus

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