Acute axon removal causes delayed SC expansion. (A) NMJ with single-cell labeling before two-photon laser–induced axonal degeneration (SCs pseudocolored in white, magenta, and yellow). The axon was severed at the second node of Ranvier away from the synapse (white arrow indicating direction; not in frame). (B) Time-lapse recording over a period of 5 h shows AAD (note fragmentation after 1 h), which led to local SC outgrowth (orange arrowheads; shown in area boxed in A). (C and D) Fixation after 5 h and staining for BTX reveal local outgrowth along several NMJ branches (orange arrowheads in D show fixed SC channel only in the area boxed in C). The timers shown represent hours/minutes. Bars, 5 µm.