The Journal of Cell Biology, Vol 81, 301-315, Copyright © 1979 by The Rockefeller University Press
Cloned pigmented retinal epiehtlium. The role of microfilaments in the differentiation of cell shape
B Crawford
3-wk-old clones of pigmented epithelial cells from chick retina can be
divided into four zones on the basis of cellular morphology and
pigmentation. These zones appear to represent different stages in the
re-expression of differentiation: those cells with essentially no
differentiated characteristics are at the outer edge and those with the
greatest number are at the center. Cells of the colony exhibit three
different types of movement when analyzed by time-lapse
cinephotomicrography: focal contractions, extension and retraction of
apical protrusions, and undulations of the lateral membranes. All the cells
of the colony contain microfilaments, 4--7 nm in Diam, which are primarily
arranged as apical and basal webs. In addition, less well defined
filamentous networks are found in the apical protrusions and lateral
interdigitations. When colonies are treated with 10 micrograms/ml of the
drug cytochalasin B (CCB), the apical microfilament arrays are disrupted
and movement stops. Both phenomena are reversible upon removal of the drug.
During the process of redifferentiation, the cells change their shape from
squamous to cuboidal, and the greatest change is found where the colony
exhibits the greatest number of focal contractions. The evidence suggests
that the apical microfilament arrays are directly responsible for the
observed movements, particularly the focal contractions, and that focal
contractions contribute to the development of the differentiated cellular
shape. Possible roles for the other movements are discussed.
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