RETHINKING ANAPHASE - WHERE PAC-MAN FAILS AND WHY A ROLE FOR THE SPINDLE MATRIX IS LIKELY

The ''Pac-Man'' model for explaining chromosome movement is based on t hree main tenets: (i) the force that moves chromosomes is generated at the kinetochore; (ii) disassembly of the microtubules (MTs) of the ki netochore fibre generates poleward movement; and (iii) the energy requ ired for this movement comes from MT disassembly. We show that these t enets are not valid in some and perhaps many situations. Thus, the Pac -Man model is inadequate and misleading as the central basis for expla ining chromosomal motion generally. We argue that multiple mechanisms are involved in mitotic function and that a contractile/elastic spindl e matrix is likely involved not only in anchoring kinetochore fibres, but also by exerting force on them. This view of the spindle matrix sh ares some features with the ''tensegrity'' model already formulated as a basis for understanding interphase cell behaviour.