Waves of actomyosin assembly and constriction help repair epithelial wounds, Antunes et al. reveal.
When epithelial tissues are punctured, the cells around the wound edge assemble an actomyosin cable that constricts like a purse string to draw the wound closed. The events that lead up to cable formation are poorly understood, however, prompting Antunes et al. to study the earliest stages of the wound response in the epithelial notum of Drosophila pupae.
Live imaging revealed that, within minutes of wounding, cells set back from the wound initiated a wave of actin filament assembly that flowed through neighboring cells toward the wound edge. These actin filaments recruited myosin II and drove a wave of apical cell constriction that propagated into the epithelial cells surrounding the wound. Depleting cells of the actin-nucleating formin protein Dia or the contractility-promoting kinase ROCK blocked the waves of actin polymerization and cell constriction, inhibiting actomyosin cable assembly and wound closure.
Calcium signaling forms a key part of the early wound response in many tissues. Knocking down the calcium channel TRPM diminished the influx of calcium into cells surrounding epithelial wounds, impairing actomyosin flow and cable assembly. Down-regulating the calcium-activated, actin-severing protein Gelsolin had a similar effect, suggesting that calcium may initiate actomyosin flow by inducing the remodeling of existing actin filaments. Senior author Antonio Jacinto now wants to investigate in more detail how calcium signals and mechanical forces guide actomyosin flow toward the wound edge to promote cable assembly and wound healing.
Text by Ben Short