Movie S2.

Ikbkap−/− axons possess more branched and less motile growth cones than axons in control littermates. Representative transmitted light, 63× time-lapse movie of an E15.5 Ikbkap−/− growth cone, imaged over 5 min with one frame every 5 s. Like the growth cones of control DRG neurons, mutant Ikbkap−/− growth cones have motile filopodia (black arrows), but the filopodia in the mutants are longer and more abundant than those in control neurons. Mutant growth cones also rarely show a gain in position, as indicated by the lack of movement of their lamellipodia (red arrowheads mark the leading edge of a lamellipodium). (Scale bar, 10 µm.)