Doctoral defence: Vi Ngan Tran "The Cellular Dynamics and Epithelial Morphogenesis in Drosophila Wing Development"

On August 21 at 13:15 Vi Ngan Tran will defend her doctoral thesis "The Cellular Dynamics and Epithelial Morphogenesis in Drosophila Wing Development“ for obtaining the degree of Doctor of Philosophy (in Developmental Biology).

Supervisor:
Professor Osamu Shimmi, University of Tartu

Opponent:
Doctor Barry Denholm, University of Edinburgh (the United Kingdom)

Summary:

Epithelial cells are crucial in developing animal organs and 3D tissue structures. However, we still do not fully understand how changes in cellular structure affect tissue morphogenesis. To gain insight into this process, we need a system that allows us to observe real-time changes in cell shape. This thesis investigates how changes in cell shape coordinate 3D morphogenesis during two stages of Drosophila melanogaster wing development: inflation and second apposition.

Our study discovered the intercellular connection Interplanar Amida Network (IPAN) during the inflation stage of pupal wing development. IPAN is a 3D meshwork structure that consists of dorsal and ventral cells with microtubule protrusions and microfilament extensions. It is critical for coordinated growth between two separated epitheliums. Changes in cell shape lead to a transition from non-centrosomal to centrosomal microtubule-organizing centers. IPAN provides a unique framework for 3D morphogenesis. In addition, the study also focuses on cell shape changes during microtubule protrusion disassembly. We found that α-Spectrin plays a crucial role in regulating apical relaxation via actomyosin networks, which is necessary for 3D tissue morphogenesis. Finally, the study investigated how cell shape alteration and Bone Morphogenetic Protein (BMP) signaling relate to posterior crossvein (PCV) morphogenesis in the Drosophila pupal wing. The results suggest that apical constriction refines BMP signals, differentiating cells into veins or intervein cells.

In summary, the study discussed in the doctoral thesis shed light on the questions of how cell shape changes coordinate 3D tissue morphogenesis, how IPAN helps to synchronize the division of dorsal and ventral wing epithelial cells through the loss of cell-cell contacts,  the relationship between α-spectrin and the "relaxation" of the apical part of the wing epithelial cell, and how apical cell constriction and cell shape change mediate competition for the BMP developmental signal that directs hindwing vein morphogenesis.

The defence can be followed in Zoom (Meeting ID: 986 6724 2462, Passcode: 995217).