Retinal ganglion cells do not extend axons by default: promotion by neurotrophic signaling and electrical activity

Neuron. 2002 Feb 28;33(5):689-702. doi: 10.1016/s0896-6273(02)00602-5.


We investigate the signaling mechanisms that induce retinal ganglion cell (RGC) axon elongation by asking whether surviving neurons extend axons by default. We show that bcl-2 overexpression is sufficient to keep purified RGCs alive in the absence of any glial or trophic support. The bcl-2-expressing RGCs do not extend axons or dendrites unless signaled to do so by single peptide trophic factors. Axon growth stimulated by peptide trophic factors is remarkably slow but is profoundly potentiated by physiological levels of electrical activity spontaneously generated within embryonic explants or mimicked on a multielectrode silicon chip. These findings demonstrate that these surviving neurons do not constitutively extend axons and provide insight into the signals that may be necessary to promote CNS regeneration.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Axons / physiology*
  • Cell Culture Techniques / methods
  • Cell Survival / drug effects*
  • Cell Survival / physiology
  • Cells, Cultured
  • Colforsin / pharmacology
  • Culture Media, Conditioned
  • Electrophysiology / methods
  • Enzyme Inhibitors / pharmacology
  • Extracellular Matrix / chemistry
  • Extracellular Matrix / metabolism
  • Fluorescent Dyes / metabolism
  • Growth Substances / pharmacology*
  • Humans
  • Peptides / pharmacology*
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Retinal Ganglion Cells / cytology
  • Retinal Ganglion Cells / physiology*
  • Signal Transduction / physiology*
  • Visual Pathways / cytology
  • Visual Pathways / metabolism


  • Culture Media, Conditioned
  • Enzyme Inhibitors
  • Fluorescent Dyes
  • Growth Substances
  • Peptides
  • Proto-Oncogene Proteins c-bcl-2
  • Colforsin