The mitotic spindle is composed of microtubules and numerous proteins, all tightly regulated in order to provide the structure and dynamics required for accurate chromosome segregation. TPX2 is a microtubule-associated protein that was recently shown to be transported along microtubules from kinetochores, where microtubules reach chromosomes, to the spindle poles. Image above shows TPX2 (red) transported along microtubules (green) to spindle poles in a normal cell (top), compared to its more even distribution along microtubules when dynein, a microtubule motor, is inhibited (bottom).
Reference: Nan Ma, U. S. Tulu, Nick P. Ferenz, Carey Fagerstrom, Andrew Wilde, and Patricia Wadsworth. Authors’ Molecular Biology of the Cell paper can be found here.