Figure 6

Inhibition of dynamic microtubules prevents RNP granule movement into the growth cone periphery. Embryos were injected with fluorescently labeled UTP (Cy3-UTP) at the four to eight-cell stage to visualize ribonucleoprotein (RNP) granules. Cultured stage 24/25 retinal explants positive for Cy3-UTP-labeled RNP granules were selected for time-lapse imaging on an inverted spinning disk confocal system (60× water immersion objective, 5-s acquisition interval) and treated on-stage with cytoskeletal disrupting drugs. Prior to colchicine treatment, RNP granules were trafficked to the growth cone periphery (arrowheads, top row in (A)). However, colchicine treatment acutely blocked RNP granule movement into the peripheral domain (bottom row in (A), 8 out of 10 growth cones). In contrast, cytochalasin D treatment did not affect RNP granule trafficking to the periphery (arrowheads in bottom row of (B), 8 out of 11 growth cones). Representative frames per minute from before and 5 min after colchicine (panels in A) or cytochalasin D (panels in B) treatment are shown. Numbers in the lower left of each image represent time in minutes.