The spindle matrix through the cell cycle in Drosophila.

A spindle matrix has long been proposed to provide structural support for counterbalancing force production and a substrate for essential mitotic factors. For years the molecular identity of such a structure remained elusive. Recently a complex of nuclear proteins that reorganize into a spindle-like structure during prophase through metaphase that shows characteristics of a spindle matrix has been identified in Drosophila. We review how these results support the concept of a spindle matrix and discuss its possible function(s) during mitosis. Importantly, these molecules also appear to play critical roles during interphase in nuclear organization and function. Given that during cell division the entire nucleus undergoes a dynamic and tightly orchestrated reorganization, the reorganization of spindle matrix components during mitosis may comprise one phase of a continuum of "nuclear architectural remodeling events" that can be considered to extend throughout the entire cell cycle, even in the absence of a defined nucleus.