Coupling Mechanical Deformations and Planar Cell Polarity to Create Regular Patterns in the Zebrafish Retina
Figure 2
Defining the orientational order parameter Q4.
Top two panels of A and B represent disordered cell packing; the bottom two panels of A and B represent ordered cell packing. A) A cross (blue) is placed at the geometric center of each cell profile, and the local fourfold orientation is chosen by minimizing the mean square distance between neighboring cells and the arms of the cross (red lines). One neighboring cell is chosen in each quadrant (dashed lines). B) The orientation of the crosses varies less in an ordered packing. C) The magnitude of the fourth order parameter ranges from 0 to 1 and increases as variability in the orientation of the crosses decreases. (See also Methods.)