Changes in the position of the nucleus inside the cell are associated with migration, polarisation and responses to shear stress. Moreover, alterations in nuclear localisation are also linked to diseases that range from dysplasia to cancer. Microtubules and actin filaments are both important in nuclear anchorage and movement. Now, Sandrine Etienne-Manneville and colleagues (p. ) provide evidence that intermediate filaments are a key component of actin-driven nuclear positioning. Rearrangements of the actin network result in the accumulation of intermediate filaments around the nuclear envelope – an effect that is lost when disrupting the actin cytoskeleton. By contrast, disruption of the intermedite filament actin network by combined depletion of vimentin, nestin and the glial fibrillary acidic protein (GFAP) does not affect actin structures, but does perturb nuclear positioning. In addition, the lack of intermediate filaments results in a decrease in nuclear velocity and a less-direct pattern of movement, and it inhibits nuclear rotation. Thus, intermediate filaments have a fundamental role in nuclear positioning inside the cell. On the basis of their observations, the authors propose that actin drives the polarised perinuclear build-up of intermediate filaments, which then push against the nuclear envelope and move the nucleus around the cell.
