Forces are required for congression of chromosomes by microtubule spindles. Here, using super-resolution microscopy and computational modelling, the authors find that in addition to forces, torques caused by the microtubule motor protein kinesin-5 induce chirality and curves into the spindle.

Microtubules (MT) form higher-order structures such as asters, but the molecular pathway underlying aster formation remains unclear. Here authors demonstrate that the kinesin-14, HSET, clusters with soluble (nonMT) tubulin via its N-terminal tail domain and thereby promotes MT aster formation.

Single microtubules (MTs) can move chromosomes, but it is unclear why kinetochores bind up to 20 MTs. Here, the authors decrease the number of kinetochore MTs with BAL27862 and see lagging chromosomes, suggesting that numerous kinetochore MTs provide force ensuring robust chromosomal segregation.

Microtubule asters are positioned precisely within cells by forces generated by molecular motors, but it is unclear how these are integrated in space and time. Here the authors perform in vivo drag measurements and genetic manipulations to determine the balance of forces that position microtubule asters in C. elegans zygotes.