Accurate positioning of the mitotic spindle in the centre of the cells, critical for the generation of equally sized daughter cells, is mediated by a cortical dynein–dynactin complex pulling on astral microtubules. Kiyomitsu and Cheeseman have characterized the anaphase recruitment pathway for cortical dynein and discovered an unexpected role for the plasma membrane in centring the spindle. (Cell http://dx.doi.org/10.1016/j.cell.2013.06.010; 2013).

The recruitment of dynein–dynactin to the cortex in metaphase is known to require its cortical targeting factor LGN and the LGN-binding protein Gαi. However, the authors find that in anaphase, there is an LGN-dependent recruitment pathway that is independent of Gαi, but requires 4.1 G and R proteins and is suppressed by cyclin-dependent kinase (CDK) activity. Blocking both the LGN- and 4.1-dependent pathways for cortical dynein recruitment resulted in unequally sized cells after division, with small cells delaying their cell cycle. Anaphase spindle elongation was also impaired in cells depleted of both LGN and 4.1. Surprisingly, visualization of the plasma membrane during division revealed that in cells with an off-centred spindle, the plasma membrane elongated in an asymmetric fashion, leading to a correction of spindle position. Membrane blebs forming on the elongating membrane were partly responsible for this elongation, and the authors found a correlation between the proximity of chromatin to the cortex and elongation of the membrane. Further experimentation led the authors to suggest that a chromosome-derived Ran gradient reduces levels of Anillin and other cortical proteins, allowing membrane reorganisation.