Evolutionarily conserved Wingless signaling pathway is regulated by newly identified newt genes to trigger regeneration response in Drosophila.
Notophthalmus viridescens possess amazing regeneration capabilities but due to lack of available genetic tools the mechanism driving such regeneration has not been well understood. Here we used Drosophila imaginal discs to study regenerative role of five newly identified newt proteins that have new sequence motifs. These proteins were identified by denovo assembly of newt transcriptome combined with proteomic validation. Using transgenic approach these genes were misexpressed in developing eye field of early as well as late eye Drosophila mutants where cell death was induced in photoreceptor cells during early 2nd instar (in early eye mutants) and late 3rd instar (in late eye mutants) stage, respectively. The penetrance of mutant phenotype was 0%. Strikingly, Newt genes when expressed in the background of such mutants show significant regeneration of missing eye tissue. Even more, these genes having signal peptides, exhibited non-autonomous regeneration as shown by domain specific misexpression on candidate genes, and flip out clones. Using Retinal determination (RD) fate markers, we demonstrated that regeneration response was restricted only to fly eye field. These regenerated tissues (eyes) showed 6 ± 1.5 folds increase in mitotic index as compared to the mutants. In comparison, there was only 1-fold downregulation of cell death, suggesting that newt regeneration genes employ cell proliferation function to promote regeneration. Additionally, downregulation in apoptosis is preventing regenerated tissue from further death. Using RNA sequencing, we identified the role of signaling pathway that has been perturbed by newt genes to induce regeneration in Drosophila. We found that member of evolutionarily conserved Wnt/Wingless (Wg) pathway exhibit 4-fold downregulation of expression. Additionally, the genes related to the molecular class of development, apoptosis and cell cycle were highly enriched. Using immunohistochemistry we verified RNA Seq results, and found that Wg is significantly downregulated by these newt genes to promote regeneration. Perturbing positive and negative regulators of Wg signaling pathway and blocking Wg transport revealed that newt genes regulate Wg/Wnt pathway in regenerative response. Our results demonstrate a unique class of genes present in Newts which employ conserved pathways to trigger regeneration response, and also provided a novel platform to bridge the gap of unraveling the mechanism behind regeneration tool kit from newts.
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Stander Symposium poster
"Evolutionarily conserved Wingless signaling pathway is regulated by newly identified newt genes to trigger regeneration response in Drosophila." (2019). Stander Symposium Posters. 1602.