A ring of RhoA-activated myosin-2 (green) inside a ring of active Cdc42 (red) pulls the actin cytoskeleton over a wound.
A wounded cell, such as the frog oocyte system used by the authors, rapidly repairs its broken membrane by an onslaught of exocytosis. After sealing the hole, the cell must rebuild the actin cytoskeleton underneath the new membrane. This is partly accomplished by stretching the undamaged surrounding cytoskeleton inward over the wound, which requires actomyosin-based contraction.
The authors now see that this inward motion of actin is coordinated by ring-like patterns of the active form of two rho GTPase family members known to regulate actin dynamics. The appearance of these rings—an inner loop of RhoA-GTP circumscribed by a halo of Cdc42-GTP—preceded actin accumulation and occurred...
