The Arrangement of Early Inductive Signals in Relation to Gastrulation; Results from Frog and Chick
Nieuwkoop and his students first showed clearly that specification of presumptive mesodermal territories in the amphibian embryo, and of their overall orientation, takes place by agency of signals deriving from the yolky vegetal zone (Nieuwkoop 1977, review). This process begins during (possibly early) blastula stages, and is progressive so that by onset of gastrulation, when the first movements begin to produce rearrangement in the induced territories, there is a significant geographical pattern and differential time schedule to these movements, as well as a pattern of differentiation capacities in the tissue when cultured in isolation (Keller et al. 1985; Dale and Slack 1987b). This pattern relates to the subsequent axes of organization of the body. Geographical regionalization on a finer scale is most advanced in a relatively narrow (ca. 90°) sector around the future dorsal midline, and is related to deep vs. superficial position within the blastula wall as well as to cells’ distances from initial sources of induction, i.e., to ‘height’ in the marginal zone towards the animal pole. As described by Keller and his associates (op. cit. and Keller 1986; Wilson et al. 1989) the role of this sector in gastrulation and neurulation and its capacities when developing in isolation entitle it to the designation ‘morphogenetic organ’.
KeywordsMarginal Zone Xenopus Laevis Xenopus Embryo Neural Induction Animal Pole
Unable to display preview. Download preview PDF.
- Cooke, J. 1989a. The early amphibian embryo: Evidence for activating and for modulating or self-limiting components in a signalling system that underlies pattern formation, p. 145–158. In: Cell to Cell Signalling. A. Goldbeter (Ed.). Academic Press, New York.Google Scholar
- Dale, L. and J.M.W. Slack. 1987a. Fate map for the 32-cell stage of Xenopus laevis. Development 99:197–210.Google Scholar
- Gerhart, J., T. Doniach, and R. Stewart. 1991. Organizing the Xenopus Organizer, p. 57–78. In: Gastrulation: Movements, Patterns, and Molecules. R. Keller, W.H. Clark, Jr., F. Griffin (Eds.). Plenum Press, New York.Google Scholar
- Meinhardt, H. 1982. Models of Biological Pattern Formation. Academic Press, London.Google Scholar
- New, D.A.T. 1955. A new technique for the cultivation of the chick embryo in vitro. J. Embryol. Exp. Morph. 3:326–331.Google Scholar
- Nieuwkoop, P.D. and J. Faber. 1967. Normal table of Xenopus laevis (Daudin). 2nd edition. North Holland, Amsterdam.Google Scholar
- Ruiz-Altaba, A. 1990. Neural expression of the Xenopus homeobox gene Xhox3: Evidence for a patterning neural signal that spreads through ectoderm. Development 108:595–604.Google Scholar
- Ruiz-Altaba, A. and D.A. Melton. 1989a. Bimodal and graded expression of the Xenopus homeobox gene Xhox3 during embryonic development. Development 106:173–183.Google Scholar
- Spemann, H. and H. Mangold. 1924. Uber Induktion von Embryonenanlagen durch Implantation Artfremder Organisatoren. Wilhelm Roux’s Arch. Dev. Biol. 100:599–638.Google Scholar
- Symes, K. and J.C. Smith. 1987. Gastrulation movements provide an early marker of mesoderm induction in Xenopus laevis. Development 101:339–350.Google Scholar