Cell Geometry and PCP Signaling

Several observations indicate that PCP can propagate from cell to cell. Next to clones mutant for frizzled or Van gogh, genetically wild-type cells are seen to reverse polarity. Inside clones that fail to receive the global directional signal that orients cells with respect to the tissue axes, cells show a strong tendency to align with one another, and within small clones they almost always adopt the correct orientation with respect to the global axis, despite their inability to directly sense the global signal. Both of these phenomena reflect the tendency of cells toward local alignment. Local alignment is a logical consequence of the Fz competition feedback loop mechanism that we have described. We have evidence that this tendency to local propagation of polarity is strongly influenced by cell geometry, such that regularly hexagonally packed cells are much more likely than irregularly packed cells to propagate the signal correctly. We are applying a combination of biological experimentation and mathematical modeling to study the influence of cell geometry on PCP signaling.

In a related project, we are studying how fly wing cells transition from an irregularly packed array to the regular hexagonal packing that is observed prior to polarization. We are using live imaging, computer vision and computational methods together with genetics to address this problem.