Fig. 7.

Computational modeling of cell-pair inversion. (A,B) Sketch of the two-cell computational model. Each cell freely rotates around a circle of a fixed radius, with its angle with respect to the x-axis (representing the A-P axis) as the degree of freedom for each cell. The arrows in each cell indicate the direction as +1 or −1 for anti-clockwise and clockwise movement, respectively. Each cell is attracted to one and only one Gaussian well. The depth of each well determines the strength with which its corresponding cell is attracted. The depth of one well can be different from the other. (A) In the asymmetrical model both cells have their attractive wells on opposite sides of the A-P axis. (B) In the symmetrical model both attractive wells lie on one side of the system, leading to a competition. (C,D) Two typical trajectories of the inverting pair in cumulative angle, as defined in Fig. 2C, for the asymmetrical and symmetrical model, respectively. The background colors indicate the phases of the process: blue (Phase 1), orange (Phase 2), green (Phase 3). (E) Distribution of final angles predicted by both models. Well depths are 0 and 50 (relative well depth=0) for the asymmetric model, and 50 and 20 (relative well depth=0.4) for the asymmetric model. (F,G) The final angle (F) and the noise (G) predicted by the asymmetric (symmetric) model are robust (sensitive) against the relative well depth. The depth of the reference well was fixed at 50 in these simulations. Asymmetric and symmetric models are represented in blue and red, respectively. Box plots show median values (middle bars) and first (Q1) to third (Q3) interquartile ranges (boxes); upper whisker is either 1.5× the interquartile range or the maximum value (whichever is the smallest) and lower whisker is either 1.5× the interquartile range or the minimum value (whichever is the biggest).