Fig. 6

Posterior lateral line (pLL) axon degeneration is affected by the absence of Schwann cells or hair cells. Double transgenic larvae (brn3c::GFP/neuroD::GFP) were treated to remove Schwann cells (AG1478) or hair cells (laser ablation) prior to axotomy, and were examined after 24 hours to evaluate regeneration of the pLL nerve. (a) Control fish; red arrowheads indicate neuromasts; the nerve grew along its original path. (b) When Schwann cells were absent, axons regenerated after axotomy but many of them failed to grow along the normal trajectory (yellow arrowheads). (c) After physical ablation of hair cells in lateral line neuromasts (circle indicates position of ablated neuromast), axon regeneration was normal. (d) Axon regeneration was normal after inhibition of hair cell differentiation with the ath1a morpholino. (e) Ablation of neuromasts with CuSO₄ treatment produced erratic growth of regenerating axons (arrow), but the normal trajectory of neurites was restored when neuromast hair cells (arrowhead) regenerated. (f) The number of axons wandering outside of the normal pLL trajectory was quantified and compared across the different conditions as indicated. *Significant differences between treatments (one-way nonparametric ANOVA, P <0.05).