Golgi lands new role

When it comes to microtubule organization, centrosomes have the lead role. But, as Andrey Efimov, Irina Kaverina (Vanderbilt University Medical Center, Nashville, TN), Alexey Kharitonov (Austrian Academy of Sciences, Vienna, Austria), and colleagues now report, the Golgi shares some of the limelight. Unlike centrosomes, this new-found organizer doesn't symmetrically radiate microtubules from center stage, but instead directs its performance to one cell edge.

Microtubules do not start growing spontaneously in cells; they rely on supporting protein machinery to nucleate tubulin building blocks and kick off polymerization. To find their origins, Efimov et al. tracked the growth of new microtubules in living cells. They found that the majority of new microtubules radiated out from a central position in the cell that is consistent with centrosomes.

A significant proportion of nucleation events, however, appeared to occur...