Quantification of asymmetric microtubule nucleation at subcellular structures.

Cell polarization is important for multiple physiological processes. In polarized cells, microtubules (MTs) are organized into a spatially polarized array. Generally, in nondifferentiated cells, it is assumed that MTs are symmetrically nucleated exclusively from centrosome [microtubule organizing center (MTOC)] and then reorganized into the asymmetric array. We have recently identified the Golgi complex as an additional MTOC that asymmetrically nucleates MTs toward one side of the cell. Methods used for alternative MTOC identification include microtubule regrowth after complete drug-induced depolymerization and tracking of growing microtubules using fluorescently labeled MT +TIP binding proteins in living cells. These approaches can be used for quantification of MT nucleation sites at diverse subcellular structures.