A model for the focusing of spindle MT minus ends by Asp. Asp binds to spindle MT ends from the early phases of mitosis and cross-links them. Ncd is a more general and dynamic spindle MT cross-linker and does not function specifically at the pole (the halftime of recovery after Ncd-GFP photobleaching was 2.5 s; Goshima et al., 2005a). When spindle MTs are nucleated at the pole, these MTs are immediately focused by the action of polar Asp. Spindle MTs are also nucleated in a polarized manner in the body of the spindle in an augmin-dependent manner. Those MT ends are also decorated by Asp, cross-linked with other MTs, and translocated to the pole by the action of spindle MT flux driven by the kinesin-5 sliding motor (blue arrows) or CLASP- and kinesin-13–dependent kinetochore MT treadmilling (orange arrows). Asp also ensures the focusing of these intraspindle MTs. Centrosomes would serve as an extra source of polar MTs on which Ncd and Asp function (not described in this diagram).