QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Munro, E. M. Articles by Odell, G. Search for Related Content PubMed PubMed Citation Articles by Munro, E. M. Articles by Odell, G.

Morphogenetic pattern formation during ascidian notochord formation is regulative and highly robust

¹ Department of Zoology, University of Washington, Seattle, WA 98195, USA
² Friday Harbor Labs, Friday Harbor, WA 98250, USA

*Author for correspondence at address 1 (e-mail: munroem{at}u.washington.edu)

Accepted 5 October 2001

The ascidian notochord forms through simultaneous invagination and convergent extension of a monolayer epithelial plate. Here we combine micromanipulation with time lapse and confocal microscopy to examine how notochord-intrinsic morphogenetic behaviors and interactions with surrounding tissues, determine these global patterns of movement. We show that notochord rudiments isolated at the 64-cell stage divide and become motile with normal timing; but, in the absence of interactions with non-notochordal tissues, they neither invaginate nor converge and extend. We find that notochord formation is robust in the sense that no particular neighboring tissue is required for notochord formation. Basal contact with either neural plate or anterior endoderm/lateral mesenchyme or posterior mesoderm are each alone sufficient to ensure that the notochord plate forms and extends a cylindrical rod. Surprisingly, the axis of convergent extension depends on the specific tissues that contact the notochord, as do other patterns of cell shape change, movement and tissue deformation that accompany notochord formation. We characterize one case in detail, namely, embryos lacking neural plates, in which a normal notochord forms but by an entirely different trajectory. Our results show ascidian notochord formation to be regulative in a fashion and to a degree never before appreciated. They suggest this regulative behavior depends on a complex interplay between morphogenetic tendencies intrinsic to the notochord plate and instructive and permissive interactions with surrounding tissues. We discuss mechanisms that could account for these data and what they imply about notochord morphogenesis and its evolution within the chordate phylum.

Key words: Ascidian, Notochord, Pattern formation, Morphogenesis

This article has been cited by other articles:

				A. M. Soviknes and J. C. Glover Continued Growth and Cell Proliferation Into Adulthood in the Notochord of the Appendicularian Oikopleura dioica Biol. Bull., February 1, 2008; 214(1): 17 - 28. [Abstract] [Full Text] [PDF]

				M. T. Veeman, Y. Nakatani, C. Hendrickson, V. Ericson, C. Lin, and W. C. Smith chongmague reveals an essential role for laminin-mediated boundary formation in chordate convergence and extension movements Development, January 1, 2008; 135(1): 33 - 41. [Abstract] [Full Text] [PDF]

				P. R. H. Steinmetz, F. Zelada-Gonzales, C. Burgtorf, J. Wittbrodt, and D. Arendt Polychaete trunk neuroectoderm converges and extends by mediolateral cell intercalation PNAS, February 20, 2007; 104(8): 2727 - 2732. [Abstract] [Full Text] [PDF]

				M. G Larman, C. B Sheehan, and D. K Gardner Calcium-free vitrification reduces cryoprotectant-induced zona pellucida hardening and increases fertilization rates in mouse oocytes Reproduction, January 1, 2006; 131(1): 53 - 61. [Abstract] [Full Text] [PDF]

				N. S. Glickman, C. B. Kimmel, M. A. Jones, and R. J. Adams Shaping the zebrafish notochord Development, March 1, 2003; 130(5): 873 - 887. [Abstract] [Full Text] [PDF]