Regulation of Damage-Responsive Maturity-Silenced enhancers in Drosophila
Authors: John Quinn; Robin Harris
Affiliation: Arizona State University
Keywords: k. regeneration; e. enhancers
Regeneration is a complex process that occurs in a variety of different organisms. In early larval stages, the imaginal discs of Drosophila – the precursors to the adult appendages – have a significant capacity to regenerate that is lost as the organism matures. Using a genetic ablation method established by our group we have found that several genes involved in disc regeneration are regulated by damage-responsive and maturity-silenced (DRMS) enhancers. These regulatory elements are activated upon damage to induce regenerative gene expression, but epigenetically silenced as the organism approaches pupariation. The goal of my research is to investigate what specific signals activate DRMS enhancers and how they become progressively silenced as discs mature.
The genes wg and Wnt6 are activated during regeneration and controlled by a single DRMS enhancer (DRMSWnt). We found that JNK signaling is necessary for the activation of DRMSWnt but not sufficient, since developmental JNK signaling does not activate the enhancer. The cells contributing to regeneration co-express both JNK and JAK/STAT consistent with previous data that shows these pathways are important for regeneration. Using a GFP reporter for DRMSWnt we found that reducing JAK/STAT pathway activity via STAT92E RNAi decreases damage-induced activation of the reporter, suggesting a role for JAK/STAT in the activation of the enhancer. Although, this decrease indicates that JAK/STAT is involved in regeneration, it does not show whether STAT is directly interacting with the enhancer DNA. To test this interaction, we generated a DRMSWnt-GFP lacking the consensus transcription factor binding sites to STAT92E, which shows a similar reduction in GFP to that seen with STAT RNAi. To understand the dynamics of how JAK/STAT activates DRMS we examined how a reduction in STAT might affect regeneration over a 48hr period. Our results show that STAT is required for full enhancer activity and does not preferentially work at a certain point of regeneration.
Going forward, we are overexpressing the JAK/STAT pathway elements to determine the necessity and sufficiency in DRMS enhancer activation and whether it can improve regeneration. Furthermore, we are also testing whether this genetic relationship is relevant to other DRMS enhancers that we have identified.