Three-dimensional organization of stable microtubules and the Golgi apparatus in the somata of developing chick sensory neurons.

Microtubules play a role important in regulating cell shape and in mediating organelle movements. These functions are especially important in elaborately branched neurons, which have many stable microtubules that are resistant to cold and to microtubule depolymerizing drugs. We examined the three-dimensional organization of microtubules in cell bodies of cultured chick embryo sensory neurons, using confocal laser scanning microscopy. Microtubules were visualized with antibodies against alpha-tubulin and post-translationally modified forms of alpha-tubulin that accumulate in older microtubules. Optical sections were collected through neuronal somata, and the images were reconstructed in three dimensions. In neuronal perikarya a dense network of older microtubules is co-localized with the Golgi apparatus. This complex of the Golgi and older microtubules usually lies beneath the cell nucleus and is oriented toward the substratum. From this region, older microtubules extend into each neurite. A cage of older microtubules extends around the nucleus to the top of the perikaryon. The stability of these microtubules was confirmed by their resistance to the depolymerizing drug, nocodazole. This arrangement of stable microtubules in a developing neuron provides a supporting cytoskeleton and a transport pathway for movement of cytoplasmic components between the Golgi apparatus, the perikaryon and developing neurites.