681B Poster - 10. Cell biology: Cytoskeleton, organelles and trafficking
Friday April 08, 2:00 PM - 4:00 PM

Authors:
Sierra Schwabach; Sally Horne-Badovinac

Affiliation: University of Chicago

Keywords:
r. cell migration; q. epithelial sheets

The collective migration of cells is a critical process during development, wound healing, and cancer metastasis. We study the highly coordinated collective migration of follicular epithelial cells in the Drosophila egg chamber, which helps to create the elliptical shape of the mature egg. During the formation of a new egg chamber, follicle cells initiate a collective migration perpendicular to the anterior-posterior (AP) axis. In many models of collective migration, a subset of the cells contact free space which can act as an external polarizing cue for the cells to start migrating. In contrast, the follicle cells form a topologically closed epithelium that lacks a free edge. As a result, the direction of follicle cell migration in each egg chamber is stochastic and can occur either clockwise or counterclockwise with respect to the AP axis. Follicle cell migration depends on a type of planar polarity, in which the atypical cadherin Fat2 localizes to the trailing edge of each cell and signals to the cell behind to promote migration. Interestingly, we know that the maintenance of Fat2’s planar polarized localization also requires migration of the tissue, which is driven by SCAR/WAVE-dependent protrusions at the leading edge of each follicle cell. This leads to our model that polarized Fat2 signaling and migration promote one another in a self-reinforcing, mutually dependent feedback loop. While we have a grasp on the mechanisms that promote follicle cell migration once it has started, it is unknown how follicle cells initiate collective migration without the existence of an external polarizing cue. We hypothesize that it is the interplay between motility and polarized Fat2 signaling that allows the tissue to self-organize and initiate collective migration. We have taken two different approaches to address this hypothesis. The first includes improving upon current live imaging methods to watch migration initiation unfold in its natural context. The second approach utilizes the GAL4/UAS system to delay migration initiation until the egg chambers are older and easier to image. Preliminary results from both methods will be discussed at the poster.