Catastrophe gradient drives anaphase B

It takes a polar catastrophe—oodles of them, actually—to get through anaphase, suggest Cheerambathur et al. on page 995. Their modeling reveals that concentrating microtubule catastrophes near the spindle poles might drive the second half of anaphase.

Anaphase in fly cells is a two-step process: first the chromosomes migrate to the poles (anaphase A), then the spindle lengthens, pushing the DNA further apart (anaphase B). To understand the microtubule changes that lead to anaphase B, the authors combined modeling studies with in vivo observations of microtubule dynamics.

The experimental studies revealed that microtubule plus ends became concentrated in the central spindle at the onset of anaphase B. The changes were driven by cell cycle–regulated signaling pathways, not by any intrinsic properties of microtubules.

Determining which spindle proteins are targeted by these...