Figure 4.

The factors that influence spindle size. (a) Roles of the parameters of MT dynamics in governing spindle length, including: (i) growing velocity v₁, (ii) shrinking velocity v₂, (iii) rescue rate k₁, and (iv) catastrophe rate k₂. (b) Role of the slipping of MTs on cortex in governing the spindle length. Here, ξ is the friction coefficient associated with the slipping in Eq. 2. (c) Spindle length increases with the binding rate of the cortical dyneins $k_b^{-}$, which is normalized by the binding rate of the cortical kinesins. (d) Spindle length increases with the pushing force on the antiparallel MTs. Because the antiparallel MTs are simulated separately in 2D simulations, we change the parameter A in Eq. 20, which corresponds to the parameters of the cross-linker dynamics. (e) Spindle size decreases with the pulling force generated by the MTs bound to the kinetochores. Here, we change both the binding rates of kinetochores $k_{b,c}^{-}$ and chromosome kinesins $k_{b,c}^{+}$. The ranges of parameters are shown in Table S1. On the left of the dotted line, the stable spindle cannot be assembled. (f) The attachment asymmetry can regulate spindle length. $k_{0,c}^{-}$ is the unloaded unbinding rate of dyneins that connect MTs and chromosome. (g) The mass conservation of tubulin regulates spindle length. The label k_c is the concentration coefficient defined in Eq. 18. (h) Spindle length increases with chromosome size (or equivalently chromosome number when chromosome size is fixed). The lengths of the meiosis II spindle and the mitosis stage 1 spindle were measured from the experimental results (7) and compared with our simulation. Both chromosome size L_c and spindle length L_s are normalized by cell length L. To see this figure in color, go online.