Molecular mechanisms of successful axon pathfinding during CNS regeneration in the visual system of adult zebrafish (360G-Wellcome-078052_Z_05_Z)

Adult zebrafish, in contrast to mammals, are capable of regenerating CNS tracts. Thus, regeneration of the optic projection in zebrafish can be used to study the factors required for axon regrowth such as those that determine correct pathfinding and retinotopic mapping on the tectum during axonal regeneration. We will analyse (re-)expression of axon guidance molecules and their receptors on retinal ganglion cells (RGCs) known to play a role in axon pathfinding during development, such as ephrins/eph, semaphorins/neuropilins, slits/robos, neogenin/RGM by in situ hybridisation. By comparing expression profiles on DNA micro-arrays of different retinal sectors during regeneration we will analyse (re-)expression of other, possibly unknown receptors for topographic cues. We will test the function of these systems using anti-sense "morpholino" oligonucleotide assisted knock down in the developing and adult retina. Anterograde tracing will reveal pathfinding and mapping errors. Additionally, we will analyse adult regeneration in mutants of RGC axon pathfinding, focussing on the astray/robo2 mutant, which displays pathfinding errors of RGC axons during development. These analyses should provide insight into the mechanisms that need to be (re-)activated to achieve target specific growth of axons during development and regeneration in the adult CNS.