Biology Reference
In-Depth Information
FIGURE 17.1
Dorsal closure in the embryo of D. melanogaster. The embryo is covered by an epithelial epidermis
(grey) except at the dorsal 'hole'. This hole in the epidermis is covered by amnioserosa cells (yellow), also epithelial,
which disappear as the epidermal edges advance and seal the hole up.
other actin-organizing small GTPases, Rac and cdc42, and cable formation fails in embryos
carrying dominant-negative versions of either of these proteins,
4
actin and myosin instead
forming complexes located apparently randomly in the cell periphery. The connection
between Rac and cdc42, which are normally associated with protrusive actin in lammelipo-
dia and filopodia, and the formation of actin-myosin cables, is not fully understood in this
FIGURE 17.2
Leading edge actin bands in dorsal closure. (a) Alternation of actin filaments (green) and cell
junctions (orange) connects adjacent cells mechanically to form a tissue-scale contractile apparatus. (b) The
circumferential contractile forces (green) produce a resultant radial force (red).
