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Fig. 4. Lamellipodial crawling versus purse-string closure of an in vitro
epithelial wound. (A) A temporal series that illustrates how the contractile
actin purse-string acts to draw a wound epidermis closed. The individual actin
filaments (green bars) anchor to adherens junctions (blue rectangles) formed
between adjacent cells. Contraction of the actin cable in each cell leads to
apical cell constriction and reduced wound circumference. As wound closure
proceeds, some cells are squeezed out of the front row such that fewer
epithelial cells remain in the front row. The remaining cells form new
adherens junctions and apical actin cable contraction continues until the
contralateral cells meet and fuse. Asterisks indicate cells that will be lost
from the leading edge; nuclei are red. (B) Repair of wounds made in monolayers
of the gut epithelial cell line Caco2BBE is achieved by
lamellipodial crawling or actin purse-string contraction, or a combination of
both. In this wound, one group of leading-edge cells is being drawn forwards
by contraction of an actin cable (arrows), as occurs during embryonic repair;
while other cells are clearly extending lamellae (arrowheads) and crawling
forwards, as occurs during repair of an adult skin wound [image courtesy of
Jane Brock; reproduced, with permission, from Jacinto et al.
(Jacinto et al., 2000)]. Green
staining is fluorescein isothiocyanate/phalloidin-tagged filamentous actin;
red staining is the nuclear dye 7AAD.
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