The dynamic spindle matrix.

Chromosome segregation during mitosis is mediated by the mitotic spindle, a structure composed of microtubules associated with a variety of proteins. Additionally, a distinct biochemical milieu, the 'spindle matrix', has long been proposed to assist this process and recent work provided compelling evidence for its existence in living animal cells. Here we focus on the dynamic properties of such a matrix, highlighting its roles in the spatial and temporal control of mitotic fidelity in respect to recent findings in different systems. Based on these findings and on theoretical principles behind molecular crowding, we challenge the idea of the spindle matrix as one functional entity and propose that some observed phenomena associated with this elusive structure could simply be a consequence of intrinsic cellular architecture and cytoplasmic 'compartmentalization' during mitosis.