Figure 3.

Neuronal regeneration of the zebrafish differentiating cerebellum is very efficient. A–F, Lateral views. Surgical excision of the differentiating cerebellum at 36 hpf leads to the absence of GFP-fluorescent neuronal URL-derived cells in transgenic gata1:GFP 781 strain embryos at 59 hpf (B), indicating that the cerebellum including the URL is removed completely. The presence of some GFP-fluorescent cells in the previous left cerebellar domain in a few embryos (C; same embryo as shown in B) ensures that GFP expression in the cerebellum has been activated as in nonoperated transgenic embryos (A) some time before the examination. In 89% (n = 38) of transgenic embryos that were allowed to recover after surgical removal of the cerebellum at 36 hpf and lacking GFP-expressing neuronal cells at 59 hpf, numerous GFP-fluorescent neurons could be found along the MHB, forming clusters in the ventral cerebellar region at 6 dpf (E) (note that pictures from the right cerebellar side displayed in B and E were taken from the same larvae) similar to the cerebellum in nonoperated transgenic counterparts (D) or the left cerebellar side of the operated specimen (F). cb, Cerebellum; mes, mesencephalon; ot, optic tectum; rh, rhombencephalon; WT, wild type.