INHIBITION OF MICROTUBULE NUCLEATION AT THE NEURONAL CENTROSOME COMPROMISES AXON GROWTH

We tested the dependence of axon growth on microtubule (MT) nucleation from the neuronal centrosome. Nocodazole diminished MTs in freshly pl ated neurons by >99%. Within 5 min of drug removal, MTs reassembled at the centrosome. This response was inhibited in cells microinjected wi th gamma-tubulin antibody. Within 2 hr of drug removal, uninjected neu rons grew >500 mu m of axon. In roughly half of the antibody-injected cells, axon growth was abolished and MT levels were reduced by similar to 87% compared with uninjected cells. In the other antibody-injected cells, axon growth was compromised but not abolished, and MT levels w ere reduced by similar to 38%. Thus inhibition of MT nucleation at the centrosome hindered MT reassembly, and depending on the severity of t his response, axon growth was either compromised or abolished.