Movie S1.

Control axons possess motile growth cones. Representative transmitted light, 63× time-lapse movie of an E15.5 control growth cone, imaged over 5 min with one frame every 5 s. Control growth cones show a gain in position indicated by movement of their lamellipodia (red arrowheads mark the leading edge of a lamellipodium). Black arrows denote filopodia. (Scale bar, 10 µm.)