Khaoula El Marzkioui "Size determination and role of the steroid hormone ecdysone during wing growth of Drosophila"

Khaoula El Marzkioui obtained her master in cell biology at the university of Cergy (France). Then, she pursued her PhD in developmental biology at the Curie Institute (France), in the team of Pierre Léopold in which she focused on understanding organ growth control. Understanding how organs achieve their final size during development is a fundamental yet unresolved question in biology. This process involves both mass increase and growth cessation, but the mechanisms driving growth arrest are not fully understood. Studies on Drosophila imaginal tissues suggest that the current model is that size determination is accomplished at the end of the larval phase, coinciding with the decline in cell proliferation during the larva-to-pupa transition (LPT), our research shows that tissue growth continues into the pupal stage. We found that discs double in mass after LPT, with growth shifting from coupled cell growth and proliferation to cell growth alone, therefore uncoupling proliferation arrest from growth. Further analysis emphasizes the Insulin/IGF pathway's role, indicating that the current wing development model needs revision and providing new insights into growth arrest and organ size regulation. Additionally, we explored the role of the steroid hormone ecdysone in growth control. Our findings align with recent studies indicating that ecdysone is essential for tissue growth during the larval stage, especially when ecdysone levels are low. At the end of larval development, rising ecdysone levels trigger proliferation arrest and we show that growth becomes independent of ecdysone signaling suggesting a functional-dose dependent switch in ecdysone signaling.