121Fig. 4.2 Dynamic changes in spindle morphology during the cell cycle. The spindle apparatus
begins to form before metaphase. During metaphase, interpolar microtubules (ipMTs) link the
spindle poles, and short metaphase asters (ma) form that are too short to reach the cortex (Wühr
et al. 2010 ). Asters during anaphase appear to be much more developed, reaching a wider radius.
A zone of microtubule exclusion, the microtubule interaction zone, forms in the region in which
asters meet and which presages the furrow (arrows). AurB, a CPC protein, shows recruitment of
this complex to the spindle midzone (arrowhead at late anaphase) and at the tip of FMA tubules in
more distal regions of the furrow (arrowhead in telophase; see also Yabe et al. 2009 ). A zone of
microtubule exclusion, the microtubule interaction zone, forms in the region in which asters meet
and which presages the furrow (arrows). Microtubules in red, AurB in green, DNA in blue. Figure
adapted from Yabe et al. ( 2009 )
4 Vertebrate Embryonic Cleavage Pattern Determination