MBI PhD Oral Defense
Time: 4-5pm
Date: Tuesday, 14 October 2017
Venue: Level 5 Seminar Room, T-Lab
Supervisor: Assistant Professor Yusuke Toyama
Three-dimensional cell intercalation drives Drosophila germband extension
Throughout development, tissue exhibits robust morphological change, which is an integration of cellular level mechanics that evolve in time and in three-dimensional space. During Drosophila germband extension (GBE), it is known that the apical cell intercalation is driven by polarized apical adherens junction remodelling, which requires myosin II-mediated contraction, is the key mechanism for tissue elongation. However, it remains unclear whether the basolateral cell motility contributes, if any, to GBE. Here I characterize how cells coordinate their shape and movement in three dimensions during rosette formation, which is a hallmark of cell intercalation, and show that there are distinct apical and basolateral mechanisms that drive intercalation. As previously reported, the contraction of acto-myosin cable formed in subset of cells in rosette cluster, the anterior/posterior (A/P) cells, drives apical rosette formation. Whereas basolateral rosette formation is driven by cells mostly locate at the most dorsal/ventral part of the cell cluster (D/V cells); these cells exhibit wedge-shaped basolateral protrusions and migrate towards each other along the converging D/V axis. Surprisingly, the formation of basolateral rosette precedes that of apical rosette. The establishment of basal rosettes is independent of apical contractility, but rather requires Rac1-dependent cell motility. Furthermore, basolateral protrusions are associated with high level of phosphorylated Src42A. Reduction of Src42A by RNA interference leads to abnormal basal intercalation but retains apical rosette formation, which eventually results in delayed GBE. My study shows that in addition to apical contraction, active cell crawling mediated by basolateral protrusions play an important role in cell intercalation and contribute to GBE.
*Please note only panelists are permitted for the following examination*
