 CAMs of the immunoglobulin superfamily (IgSF), which includes L1/NgCAM and neurofascin, are particularly promising, because they are expressed in the developing nervous system on neurons or Schwann cells.They are known to serve as guidance cues and mediate neuronal differentiation.Neurotrophic factors such as NGF and growth differentiation factor 5 (GDF-5), however, are well established as promoters of regeneration "in vivo".