Figure 1.

Schematic representation of the RGC axonal and dendritic growth response in relation to time after ONC in untreated or mTOR/MMP inhibited adult zebrafish.

(A) Immediately after injury, retinal synapses degenerate and RGC dendrites retract, depicted as a negative growth response, shown in red. Directly after dendrite shrinkage, RGC axons start to regrow, inducing a positive growth response, shown in green, eventually resulting in optic tectum reinnervation and target contact initiation. This, in turn, triggers the dendrites to shift their negative growth response to a positive one and to establish new synaptic contacts, finally leading to restoration of vision. (B) Retinal mTOR or MMP inhibition prevents retinal synapse degradation and dendrite collapsing after ONC, shown in a grey color for an unchanged growth response. This dendritic preservation consecutively delays the initiation of axonal regrowth, resulting in a retarded optic tectum reinnervation. Here the effect on target contact initiation was not studied. ONC: Optic nerve crush; RGC: retinal ganglion cell; dpi: day(s) post-injury; mTOR: mechanistic target of rapamycin; MMP: matrix metalloproteinases.