Expression of Epigenetic Reporters During Wound Closure in Drosophila larvae. Aimee E. Anderson, Sirisha Burra, Michael J. Galko. Biochemistry and Molecular Biology, University of Texas MD Anderson Cancer Center, Houston, TX.

   Epidermal wound closure is essential to reestablish a barrier between the animal and the outside environment. Proper closure requires a complex and tightly orchestrated series of events including coordinated changes in gene expression. Chromatin modification is one likely mechanism by which the expression of multiple genes can be altered simultaneously but a comprehensive and functional study of the role of chromatin modifying factors during wound closure has not been undertaken in any system. Profound chromatin modifications are mediated by two major groups of proteins: the repressive Polycomb Group (PcG) factors and the activating trithorax Group (trxG) members. In mice, certain PcG members are down regulated at the wound edge, while expression of some trxG factors is increased. These data suggest that the acute stress of wounding provokes a transcriptional response that requires regulation at the level of chromatin. To understand the role of epigenetic factors in wound closure, we undertook a reporter screen to identify histone-modifying proteins whose expression levels change in response to wounding. We screened 55 publicly available GFP- or YFP-tagged protein traps (targeting 33 distinct polypeptides) from the FlyTrap and Cambridge Protein Trap Insertion collections, for up- or down-regulation in wound-edge epidermal cells four hours after wounding. Remarkably, we identified 16 lines, representing seven distinct proteins, whose expression was sharply reduced in the nuclei of epidermal cells adjacent to the wound edge. These include proteins with known roles in both transcriptional repression (Mi-2, Sin3A, Sap130, and Mip120) and activation (Spt6, Kismet and Osa). These results suggest that epigenetic regulation of wound closure is a complex process requiring both up and down regulation of target genes, and implicates protein degradation as a regulatory mechanism in this process. We hope to be able to report on functional analysis of some of these genes, as well as whether reporter down-regulation is controlled by known wound closure pathways such as JNK and Pvr signaling.