Trithorax is required for imaginal disc regeneration. Andrea Skinner, Rachel Smith-Bolton. Cell & Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL.

   Drosophila melanogaster is able to regenerate lost or damaged imaginal disc tissue prior to pupariation. To identify genes critical for regeneration, we performed a dominant modifier genetic screen in which tissue was ablated from the wing imaginal disc of early third instar larvae. The animals were then screened for adult wing size as a measure of regeneration. Through this screen, we found animals heterozygous for trithorax (trx) have reduced wing regeneration. Trx is thought to control active gene expression by regulating chromatin modifications. To understand how trx is important for regeneration, we are characterizing the impaired regeneration in trx/+ mutants and identifying genes regulated by trx after tissue damage. Thus far we have shown several processes are misregulated in trx/+ damaged tissue. First, on the organismal level, trx/+ regenerating animals do not delay entry into pupariation to the same extent as wild-type regenerating animals. Second, on the cellular level, more cells are in S phase both in the regeneration blastema and at a distance from the wound, where proliferation is normally suppressed. Third, on the molecular level, JNK signaling, which is normally required for regeneration, is significantly elevated. We will present our ongoing characterization of regeneration in trx/+ mutants as well as our working model for how regeneration fails despite increased numbers of proliferating cells and increased JNK signaling.