Cleavage furrow establishment - a preliminary to cylindrical shape change

Abstract

The predictable pattern of cell shape changes characterizing animal development must be a consequence of control mechanisms that are at least analogous to those operating in dividing cells. When cells change shape by an internal mechanism, it is implied that they also contain systems that will activate and deactivate the mechanism, localize it within the cell, insure proper timing, and impart the proper vectoral qualities. Experimental investigations designed to elucidate similar processes in dividing cells reveal that the physical mechanism that accomplishes cytokinesis is established at or near the equatorial cell surface by the mitotic apparatus. The process is completed by late metaphase or early anaphase. In cleaving eggs a pair of asters can substitute for the intact mitotic apparatus. The nature of the stimulus which apparently passes from the mitotic apparatus to the surface is presently unknown. It moves toward the surface at about 6 microns per minute and requires about 1 minute to establish the mechanism. The resulting equatorial contractile activity is initially isotropic but becomes anisolropic at the beginning of visible constriction. ©1973 by the American Society of Zoologists.