Chromosome Movements During Cell-Division: Possible involvement of actin filaments

In this chapter I concentrate on the question of whether or not actin is involved in producing force for chromosome movements during cell-division. the data to date concern whether or not actin is a genuine spindle component: these data will be considered in detail. By way of introduction, I first review some of the basic and generally agreed upon aspects of mitosis, such as the forces involved, the role of chromosomal spindle fibres, and so on. Then I briefly summarize the main hypotheses in which microtubules are considered to be the force producing agents, and I briefly summarize my view of the status of these hypotheses. Finally, I discuss critically and in detail the electron microscopic and light microscopic data which suggest that actin is a component of chromosomal spindle fibres. I discuss also the negative evidences, and I discuss the counter-arguments that are used to argue that actin is not a component of spindles. I conclude that actin is probably a spindle component, and is probably involved in chromosome movement. However, none of the evidences for actin being a spindle component are unequivocal, and I disucss the kinds of data that need to be obtained to substantiate that actin is a spindle fibre component and that actin is involved in producing the force for chromosome movement.