Novel role for Grainy head in the regulation of cytoskeletal and junctional dynamics during epithelial repair

Tissue repair is critical to maintain epithelial integrity and permeability. Simple epithelia repair relies on a combination of collective cell movements and the action of a contractile actomyosin cable at the wound edge that together promote the fast and efficient closure of tissue discontinuities. Grainy head (Grh) is an essential transcription factor that has been implicated both in the development and repair of epithelia. However, the genes and the molecular mechanisms that it controls remain poorly understood. Here we show that Grh knockdown disrupts actomyosin dynamics upon injury of the Drosophila pupa epithelial tissue. This leads to the formation of an ectopic actomyosin cable away from the wound edge and impaired wound closure. We also uncovered that E-Cadherin is downregulated in the Grh-depleted tissue around the wound, likely as a consequence of Dorsal/NF-κB misregulation, which also affects actomyosin cable formation. Our work highlights the importance of Grh as a stress response factor and its central role in the maintenance of epithelial characteristics for tissue repair by regulating cytoskeleton and E-Cadherin dynamics.