FAST AXONAL-TRANSPORT IS REQUIRED FOR GROWTH CONE ADVANCE

GROWTH cones are capable of advancing despite linkage to a stationary axonal cytoskeleton in chick and murine dorsal root ganglion neurites1 ,2. Several lines of evidence point to the growth cone as the site of cytoskeletal elongation3,4. Fast axonal transport is probably the mean s by which cytoskeletal elements5 or cofactors are rapidly moved throu gh the axon. We report that direct, but reversible, inhibition of fast axonal transport with laser optical tweezers inhibits growth cone mot ility if cytoskeletal attachment to the cell body is maintained. Advan cement ceases after a distance-dependent lag period which correlates w ith the rate of fast axonal transport. But severing the axonal cytoske leton with the laser tweezers allows growth cones to advance considera bly further. We suggest that axon elongation requires fast axonal tran sport but growth cone motility does not.