Figure 2.

Poleward fluxes of SAC components diverge in multipolar spindle until spindle-pole clustering causes fluxes to converge. (KT) Kinetochore; (SP) spindle pole. (A) Spindle pole signal in multipolar spindles before and after the final kinetochore attachment. (B) Final steady-state signals at the spindle pole for each intermediate spindle configuration during spindle pole clustering. Microtubule density in the overlapped spindle area (heavier red shade) is doubled (see Appendix C). (A and B) Computations are performed on static geometries with examples given in the cartoons. (Magenta arrows on cartoons) Streaming proteins flux toward the spindle poles. (Dashed lines on plots) Signal threshold at spindle pole necessary to trigger SAC silencing. (C and D) Poleward flux intensities in multipolar spindles (C) and spindle pole clustering (D). (Color maps) Absolute flux intensity of streaming proteins at the transverse plane through the spindle poles. Flux intensity quickly decreases away from the spindle pole. The crescents right outside the spindle pole show the difference between flux intensities in different cases. In all simulations, the kinetochore positions are chosen to maximize symmetry; the geometry is then reduced according to the symmetry to improve computational efficiency. This treatment is viable because the model results barely depend on the positions of the kinetochores inside the spindle (Fig. S1).