Fig. 6

Regenerating axons are repelled by persistent Wld^S-expressing fragments. Confocal time-lapse image stack projections of two neurons expressing Wld^S. (A-E) A neuron axotomized at 54 hpf. (A) Before axotomy (0 hours); (B-E) time-points post-axotomy. White arrow in B indicates site of axotomy. Red arrows indicate contact points between axons. White arrowheads in B and D indicate spontaneously pruned fragments. This series also shows an example of a rare instance when a regenerating axon crossed over a fragment (blue arrow), which also sometimes occurs in encounters between sister branches (Liu and Halloran, 2005; Sagasti et al., 2005) (see Movie 5 in the supplementary material). (F-J) A neuron axotomized at 30 hpf. White arrow in F indicates site of axotomy at 0.5 hours post-axotomy. Red arrow in G indicates filopodia from both the fragment and the intact axon extending out and contacting each other. These filopodia were repelled from each other and retracted back, as seen in H. Red arrow in I also indicates a point of contact from the fragment extending out to the intact axon, which retracts back, as seen in J (see Movie 6 in the supplementary material). Scale bars: 50 μm.