Figure 8.

Model illustrating the function of astral microtubules in fission yeast. (A) In wild-type cells, the spindle forms at a random angle to the cell axis. (B) Astral microtubules (green lines) that polymerise from the extranuclear face of the SPBs (red circles) interact with a zone that surrounds the nucleus, which we term an AMIZ (open box). Spindle rotation is driven by simultaneous contact on both sides of the cell cortex. (C) An astral microtubule from one SPB contacts the CAR (closed box). This stabilises alignment of the spindle along the longitudinal axis of the cell. (D) Spindle elongation (anaphase B) and separation of sister chromatids (blue) occur co-incidentally. Astral microtubules maintain spindle angle and contribute to the rate of spindle elongation during anaphase B.