Shih, John and Keller, Ray (1992) Patterns of cell motility in the organizer and dorsal mesoderm of Xenopus laevis. Development, 116 (4). pp. 915-930. ISSN 0950-1991. http://resolver.caltech.edu/CaltechAUTHORS:20120322-131746646
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In a companion paper (Shih, J. and Keller, R. (1992) Development 116, 901–914), we described a sequence of cell behaviors, called mediolateral intercalation behavior (MIB), that produces mediolateral cell intercalation, the process that drives convergence and extension of the axial and paraxial mesoderm of Xenopus. In this paper, we describe the pattern of expression of MIB in the mesoderm during gastrulation, using video image processing and recording of cell behavior in ‘shaved’, open-faced explants of the marginal zone. At midgastrula stage (10.5), MIB begins at two dorsolateral sites in the prospective anterior mesoderm and progresses medially along two arcs that lengthen toward and meet at the midline to form a single arc of cells expressing MIB, called the vegetal alignment zone (VgAZ). The notochordal-somitic mesodermal boundary forms within the VgAZ at stage 11, and then progresses animally and laterally, along the prospective anterior-posterior axis, eventually bounding a trapezoidal area the shape of the fate-mapped notochord. Meanwhile, from its origin in the VgAZ, MIB spreads in the prospective posterior direction along the lateral boundaries of both the notochordal and somitic mesoderm. From there it spreads medially in both tissues. Subsequently, vacuolation of notochord cells, and segmentation and expression of a somite-specific marker repeat the progression of mediolateral intercalation behavior. Thus cells in the posterior, medial regions of the notochordal and the somitic territories are the last to express mediolateral intercalation behavior and subsequent tissue differentiations. In explants that do not converge, these cells neither express mediolateral intercalation behavior nor differentiate. These facts suggest that progressions of MIB in the anterior-posterior and lateral-medial directions may be organized by signals emanating from the lateral somitic and notochordal boundaries. These signals may have limited range and may be dependent on convergence, driven by mediolateral cell intercalation, to bring cells within their range. In the embryo, the posterior progression of MIB results in arcs of convergence, anchored in the vegetal endoderm at each end, acting on the inside of the blastoporal lip to produce involution of the IMZ.
|Additional Information:||© 1992 The Company of Biologists Limited. Accepted 24 August 1992. This work was supported by NSF grant DCB89052 and NIH grant HD25594. We thank J. P. Trinkaus for his inspiration, his encouragement, and his pioneering work on the study of motility in embryos. We also thank Paul Wilson for his pointed criticism and support. Finally, we thank Jessica Bolker, Dr John Gerhart, Mary Constance Lane, Nan Ho, Susan Purcell, and Amy Sater for their insightful comments and suggestions.|
|Subject Keywords:||gastrulation, Xenopus, cell motility, boundary formation, cell alignment, cell intercalation, morphogenesis, tissue differentiation|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||17 Apr 2012 22:20|
|Last Modified:||26 Dec 2012 14:58|
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