The Difference Is Clear

Abstract

CELL BIOLOGY The microtubules that make up the mitotic spindle are connected at the pole to the centrosome and at the equator to the central region of the chromosome, the kinetochore. The dynamic behavior of microtubules is controlled largely by what goes on at their ends. O'Toole et al. examined the structure and placement of microtubule ends in relation to their centrosome or kinetochore targets during mitosis. Using high-voltage electron tomography, they found that the ends of the microtubules that were associated with the centrosome could be either closed (conical) or open (flared), and they suggest that these conformations correspond to the absence or presence of components that would promote microtubule dynamics. Most of the microtubules had closed ends and were distributed uniformly around the centrioles in the centrosome. Open-ended microtubules were more likely to be aimed toward kinetochores. Further work will be required to define more precisely the functional consequences of these differences. — SMH J. Cell Biol. 163, 451 (2003).