Epigenetic Regulation of Transdetermination in Drosophila Imaginal Discs
Final Report Abstract
In this project we studied regeneration of imaginal discs in Drosophila to assess the molecular processes underlying cellular reprogramming. Regeneration of Drosophila imaginal discs occurs in an epimorphic manner. Following fragmentation of imaginal discs, cells at the wound site activate a restoration program through wound healing, regenerative cell proliferation and eventually reprogram the cellular identity to rebuild the lost patterning. Several genetic approaches to dissect the early events in disc regeneration have identified prospective genes and signaling pathways, including Wg, Myc, or Hippo signaling. In addition, transcriptome analyses of regenerating disc cells have been conducted to identify genes that function in the regeneration process. Although these studies by other groups considerably contributed to our knowledge on early disc regeneration, our understanding on how each molecular process therein is regulated and how regeneration is coordinately organized is still not conclusive. In particular the interplay of signaling cascades, driving these early regenerative steps, is not well understood. Here we investigated transcriptome profiles of regenerating cells in the early phase of twenty-four hours after wounding. In order not to miss small, yet significant gene expression changes in regenerating cells, we further isolated the local area involved in the regeneration process. This meticulous sampling procedure made it possible to produce samples of pure regenerating disc cell and assess detailed gene expression changes in the early regeneration process. We observed that upd, wg, and dpp, the ligand coding genes for JAK/STAT, Wg and Dpp signaling pathways respectively, are becoming sequentially activated in JNK signaling dependent manner. We found that the JAK/STAT signaling indeed activated at the wound site and promotes regenerative cell proliferation in collaboration with Wingless signaling. We are currently analyzing mutations of cis-regulatory elements, which lack putative activation protein-1 (AP-1, the JNK signaling effector) binding sequences from the upd or wg locus, to investigate the signaling transmission from JNK signaling to the other signaling pathways. In addition, we demonstrated that the expression of Insuline-like peptide 8 (Ilp8) in early regenerating discs, which encodes the paracrine peptide to delay the onset of pupariation, are regulated by JAK/STAT signaling. Our findings suggest that JAK/STAT signaling has a pivotal role to coordinate the regenerative disc growth and Ilp8-mediated signaling controlling overall organism development. Taken together, our findings suggest that several signaling pathways are sequentially activated and required for promoting regenerative cellular reprogramming
Publications
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(2011). Epigenetic reprogramming during tissue regeneration. FEBS Lett 585, 1617–1624
Katsuyama, T., and Paro, R.
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(2013). An efficient strategy for TALEN-mediated genome engineering in Drosophila. Nucleic Acids Res 41 (17), p. e163
Katsuyama, T., Akmammedov, A., Seimiya, M., Hess, S.C., Sievers, C., and Paro, R.
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(2013). Innate immune cells are dispensable for regenerative growth of imaginal discs. Mech Dev 130, 112–121
Katsuyama, T., and Paro, R.
