Single cells and multicellular tissues rapidly heal wounds. These processes are considered distinct, but one mode of healing-Rho GTPase-dependent formation and closure of a purse string of actin filaments (F-actin) and myosin-2 around wounds-occurs in single cells [1, 2] and in epithelia [3-10]. Here, we show that wounding of one cell in Xenopus embryos elicits Rho GTPase activation around the wound and at the nearest cell-cell junctions in the neighbor cells. F-actin and myosin-2 accumulate at the junctions and around the wound itself, and as the resultant actomyosin array closes over the wound site, junctional F-actin and myosin-2 become mechanically integrated with the actin and myosin-2 around the wound, forming a hybrid purse string. When cells are ablated rather than wounded, Rho GTPase activation and F-actin accumulation occur at cell-cell junctions surrounding the ablated cell, and the purse string closes the hole in the epithelium. Elevation of intracellular free calcium, an essential upstream signal for the single-cell wound response [2, 11], also occurs at the cell-cell contacts and in neighbor cells. Thus, the single and multicellular purse string wound responses represent points on a signaling and mechanical continuum that are integrated by cell-cell junctions. © 2009 Elsevier Ltd. All rights reserved.
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