Cytokinesis microtubule organisers at a glance.

Cytokinesis is a fundamental step of cell proliferation, and its high-fidelity completion is crucial for stable maintenance of the genome (Ganem et al., 2007; Lacroix and Maddox, 2012). Anti-parallel microtubule bundle structures such as the central spindle and the midbody play various important roles throughout cytokinesis, from positioning of cleavage furrow to final separation of the two daughter cells (Barr and Gruneberg, 2007; Glotzer, 2009; Fededa and Gerlich, 2012). Although a large number of different factors that are important for abscission, including membrane trafficking machinery, localise to the midzone during cytokinesis (Caballe and Martin-Serrano, 2011; Guizetti and Gerlich, 2010; Neto and Gould, 2011), here we focus on the current understanding of protein– protein interactions between microtubule organisers and their regulators that form cytokinetic microtubule structures. During anaphase, a barrel-shaped array of bundles of interpolar microtubules appears between the segregating chromosomes (Barr and Gruneberg, 2007; Glotzer, 2009). Although this structure has been referred to in different ways, such as ‘midzone microtubule bundles’, here we call it the ‘central spindle’ (Douglas and Mishima, 2010). It is made of two sets of microtubules that come from each half of the mitotic spindle with their plus ends at the centre and form interdigitating anti-parallel overlaps referred to as the ‘stem body’ (see Poster). In some cell types, especially in larger cells such as blastomeres of sea urchin embryos, growth of non-spindle microtubules that emanate from spindle poles (astral microtubules) towards the cell cortex is also promoted after the onset of anaphase (von Dassow et al., 2009). When astral microtubules from opposite poles meet at the equatorial region, they also form anti-parallel bundles. Irrespective of their origins, both of these anti-parallel microtubule bundle structures play important roles in specifying the cleavage furrow by recruiting cytokinesis effectors, such as activator(s) of Rho GTPase, the