Ice recovery assay for detection of Golgi-derived microtubules.

Proper organization of the microtubule cytoskeleton is essential for many cellular processes including maintenance of Golgi organization and cell polarity. Traditionally, the centrosome is considered to be the major microtubule organizing center (MTOC) of the cell; however, microtubule nucleation can also occur through centrosome-independent mechanisms. Recently, the Golgi has been described as an additional, centrosome-independent, MTOC with distinct cellular functions. Golgi-derived microtubules contribute to the formation of an asymmetric microtubule network, control Golgi organization, and support polarized trafficking and directed migration in motile cells. In this chapter, we present an assay using recovery from ice treatment to evaluate the potential of the Golgi, or other MTOCs, to nucleate microtubules. This technique allows for clear separation of distinct MTOCs and observation of newly nucleated microtubules at these locations, which are normally obscured by the dense microtubule network present at steady-state conditions. This type of analysis is important for discovery and characterization of noncentrosomal MTOCs and, ultimately, understanding of their unique cellular functions.