Watching nuclei move: Insights into how kinesin-1 and dynein function together.

Moving nuclei to specific intracellular locations is central to many cell and developmental processes. However, the molecular mechanisms of nuclear migration are poorly understood. We took advantage of the ability to film nuclear migration events in Caenorhabditis elegans embryos to gain insights into the mechanisms of nuclear migration. Mutations in unc-83 blocked the initiation of nuclear migration. UNC-83 recruits kinesin-1 and dynein to the nuclear envelope. Live imaging of mutants showed that kinein-1 provides the major force to move nuclei. Dynein is responsible to move nuclei backwards or to mediate nuclear rolling to by pass cellular roadblocks that impede efficient migration. Live imaging was also used to analyze the microtubule network, which is highly polarized and dynamic. This detailed mechanism of nuclear migration may be applicable to nuclear migration in other systems and for the movement of other large cellular cargo.