Less kinesin, more condensation

Kinesin motors drag cargos, including chromosomes, but do not normally reshape those cargos. But on page 613, Mazumdar et al. demonstrate that a human chromokinesin HKIF4A is needed to establish the correct condensation state of chromosomes.

Chromokinesins are localized along chromosome arms and are thought, at least in some cases, to act as part of the polar wind: they walk along microtubules away from centrosomes, thus dragging their chromosome cargos toward the middle of the mitotic spindle. The authors depleted HKIF4A from human fibroblast cells using antibodies and RNAi. They observed numerous mitotic defects including misaligned chromosomes, incomplete chromosome separation during anaphase, and disorganized spindles. The resulting daughter cells had a high rate of aneuploidy.

When the authors visually examined the chromosomes in RNAi-treated cells, they saw that chromosomes were hypercondensed relative to those in control cells....