Intersection of Drosophila innate immunity and epidermal wound response in the serine proteolytic pathway. Michelle T. Juarez, Rachel A. Patterson, William McGinnis. University of California, San Diego, La Jolla, CA.

   After injury to the animal epidermis a variety of genes are transcriptionally activated in nearby cells to regenerate the missing cells and facilitate barrier repair. The range and types of diffusible wound signals that are produced by damaged epidermis and function to activate repair genes during epidermal regeneration remains a subject of very active study in many animals. In Drosophila embryos, we have discovered that serine protease function is locally activated around wound sites, and is also required for localized activation of epidermal repair genes. Conversely, the serine protease trypsin is sufficient to induce a striking global epidermal wound response without inflicting cell death or compromising the integrity of the epithelial barrier. Genetic analyses combined with the trypsin treatment have placed serine protease activity downstream of a hydrogen peroxide response signal and upstream of a well-characterized pathway that regulates the transcriptional response to epidermal wounds genes (grainy head, Flotillin-2, Dual oxidase, Src42A). We used the trypsin wounding treatment as an amplification tool to more fully understand the changes in the Drosophila transcriptome that occur after epidermal injury. By comparing our array results with similar results on mammalian skin wounding we can see which evolutionarily conserved pathways are activated after epidermal wounding in very diverse animals. Our innovative serine protease-mediated wounding protocol allowed us to identify 8 additional genes that are activated in epidermal cells in the immediate vicinity of puncture wounds, and the functions of many of these genes suggest novel genetic pathways that may control epidermal wound repair. Additionally, our data augments the evidence that clean puncture wounding can mount a powerful innate immune transcriptional response, with different innate immune genes being activated either in epidermal cells in the immediate vicinity of wounds; in all epidermal cells; in the developing fat body; or in multiple tissues.