Gastrulation in Xenopus:

Region-Specific Behaviors

The cellular analysis of gastrulation has led to several fundamental insights about morphogenesis. One of these is that region-specific behaviors are crucial for the successful completion of gastrulation. Different regions of the embryo perform different movements, often at the same time. The coordinated effects of these movements results in the overal changes in the embryo that occur during gastrulation. In amphibians, many of the fundamental insights intosuch region-specific behaviors have been gained by Ray Keller (now at the Univ. of Virginia) and his colleagues in Xenopus. Several key behaviors have been identified:

(1) Epiboly of the animal cap, which is accompanied by radial intercalation of its deep cells.

(2) Apical constriction of bottle cells, which contributes to the initial formation of the blastopore lip.

(3) Convergent extension of the involuting marginal zone, particularly the dorsal involuting marginal zone (DIMZ), resulting in involution of the presumptive mesoderm (deep cells) and the roof of the archenteron (superficial cells).

(4) Convergent extension of the non-involuting marginal zone (NIMZ). The dorsal region of the NIMZ ultimately becomes the neural plate.

(5) Directed migration of leading edge mesoderm cells. Dorsal leading edge mesoderm cells contribute head structures.

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