Two populations of microtubules have different functions during cytokinesis.
During interphase, microtubules radiate from centrosomes in all directions. But after chromosome segregation a structure called the central spindle forms. It provides the signals that place the actin-based cytokinetic furrow in the right place and then orchestrates its actions.
The authors take a close look at the central spindle in living fly spermatocytes and find that this structure, previously thought to be uniform, is composed of two populations of microtubules. These peripheral and interior microtubules were both geographically and biochemically distinct, with only the interior microtubules associated with the Orbit/Mast protein.
In mutants with reduced levels of Orbit protein, formation of the interior bundle of central spindle microtubules was defective. As...
