TRANSPORT AND TURNOVER OF MICROTUBULES IN FROG NEURONS DEPEND ON THE PATTERN OF AXONAL GROWTH

The transport of axonal microtubules in growing neurites has been a co ntroversial issue because of clear but conflicting results obtained wi th fluorescence-marking techniques. We have attempted to resolve the d iscordance via analysis of the relationship between apparent microtubu le translocation and cell adhesion. Neuronal cultures were prepared fr om Xenopus embryos 1 d after injection of Cy3-conjugated tubulin into one of the blastomeres of two-cell-stage embryos. Anterograde transloc ation of axonal microtubules was observed in neurons cultured on a lam inin-coated surface, in agreement with previously published data for X enopus embryonic neurons. However, when neuronal cultures were prepare d on a concanavalin A-treated surface, the axonal microtubules were st ationary, as reported for all other neurons investigated previously. N euronal cultures prepared on laminin-and concanavalin A-coated surface s also demonstrated dramatic differences in the pattern of axonal grow th, dynamics of axonal microtubules, and response to brefeldin A treat ment. Our findings suggest that transport and dynamics of axonal micro tubules may be directly affected by the mechanical tension produced by growth cone activity.