GAMMA-TUBULIN IN DIFFERENTIATED CELL-TYPES - LOCALIZATION IN THE VICINITY OF BASAL BODIES IN RETINAL PHOTORECEPTORS AND CILIATED EPITHELIA

Gamma-Tubulin, a newly discovered member of the tubulin superfamily re quired for microtubule nucleation, is associated with the centrosome(s ) throughout the vertebrate cell cycle. We have used a polyclonal anti body, generated against a highly conserved segment of gamma-tubulin, t o localize this protein in postmitotic, ciliated cells, in which the m ajor microtubule organizing centers are the basal bodies. Single-ciliu m photoreceptor cells from bovine retina contained a strongly immunore active species, with molecular characteristics of gamma-tubulin, in as sociation with a detergent-resistant, cytoskeletal fraction devoid of cytoplasmic microtubules. Gamma-Tubulin was discretely localized throu ghout the basal body region, extending opposite to the axonemal shaft, in mechanically detached rod outer segments and whole-mounted, connec ting cilium-derived axonemes. In multiciliated epithelia from bovine t rachea and oviduct, gamma-tubulin immunoreactivity was detected at the base of the cilia, where basal bodies are located. These results sugg est that this key centrosomal protein of mitotically active cells is a lso an integral component of microtubule organizing centers, required for the generation of the microtubule network in terminally differenti ated cells.