The objective of the proposed research is to establish the cellular basis of active convergence (narrowing) and extension (lengthening) that occurs in early development of the amphibian, Xenopus laevis. This morphogenetic movement, convergent extension, is the major force-generating process in gastrulation and early notochord formation in amphibians and also occurs in fish, birds, mammals, and many invertebrates. In vertebrates, it is important in organizing the dorsal-ventral polarity of the animal, in the development of the nervous system, and in the subsequent events of epigenesis. Despite its importance, this morphogenetic movement is poorly described and its cellular basis is unknown. Preliminary evidence shows that in amphibians convergent extension occurs by intercalation of cells to form an array that is fewer cells in width and more in length.
My aims i n the proposed research are, firstly, to determine what pattern of intercalation occurs in the intact gastrula or in explants of the gastrula by monitoring the intercalation of cells labeled with a fluorescent cell lineage tracer with adjacent unlabeled cells. Secondly, I will use time-lapse video and cinemicrography to record directly, the cellular motile behavior that brings about intercalation, using a new culture medium and culture system that allows such direct observation of morphogenetic events previously hidden from view in the gastrula. Thirdly, I will show what details of morphology and ultrastructure are associated with specific behavioral events by fixing the cells during intercalation and processing identified groups of cells for electron microscopy. Fourthly, I will analyze the effect of several experimental manipulations, known to ffect convergent extension, on the detailed behavior of intercalating cells. Lastly, I will develop experimental conditions and methods necessary for analysis of the cytoskeleton and extracellular matrix involved in cell intercalation. The results will establish a cellular basis for this important morphogenetic process and prepare for molecular analyses to follow.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
1R01HD018979-01A1
Application #
3316118
Study Section
Cellular Biology and Physiology Subcommittee 1 (CBY)
Project Start
1985-08-01
Project End
1988-07-31
Budget Start
1985-08-01
Budget End
1986-07-31
Support Year
1
Fiscal Year
1985
Total Cost
Indirect Cost
Name
University of California Berkeley
Department
Type
Schools of Arts and Sciences
DUNS #
094878337
City
Berkeley
State
CA
Country
United States
Zip Code
94704
Winklbauer, R; Keller, R E (1996) Fibronectin, mesoderm migration, and gastrulation in Xenopus. Dev Biol 177:413-26
Wilson, P; Keller, R (1991) Cell rearrangement during gastrulation of Xenopus: direct observation of cultured explants. Development 112:289-300
Winklbauer, R (1990) Mesodermal cell migration during Xenopus gastrulation. Dev Biol 142:155-68
Adams, D S; Keller, R; Koehl, M A (1990) The mechanics of notochord elongation, straightening and stiffening in the embryo of Xenopus laevis. Development 110:115-30
Wilson, P A; Oster, G; Keller, R (1989) Cell rearrangement and segmentation in Xenopus: direct observation of cultured explants. Development 105:155-66
Hardin, J (1989) Local shifts in position and polarized motility drive cell rearrangement during sea urchin gastrulation. Dev Biol 136:430-45
Keller, R; Cooper, M S; Danilchik, M et al. (1989) Cell intercalation during notochord development in Xenopus laevis. J Exp Zool 251:134-54
Keller, R; Tibbetts, P (1989) Mediolateral cell intercalation in the dorsal, axial mesoderm of Xenopus laevis. Dev Biol 131:539-49
Hardin, J; Keller, R (1988) The behaviour and function of bottle cells during gastrulation of Xenopus laevis. Development 103:211-30
Hardin, J (1988) The role of secondary mesenchyme cells during sea urchin gastrulation studied by laser ablation. Development 103:317-24

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