Tonge David A, Pountney David J, Leclere Pascal G, Zhu Ning, Pizzey John A
GKT School of Biomedical Sciences, King's College London, Guy's Hospital Campus, London Bridge, London SE1 1UL, UK.
Dev Biol. 2004 Jan 1;265(1):169-80. doi: 10.1016/j.ydbio.2003.09.016.
The mechanisms for directing axons to their targets in developing limbs remain largely unknown though recent studies in mice have demonstrated the importance of neurotrophins in this process. We now report that in co-cultures of larval Xenopus laevis limb buds with spinal cords and dorsal root ganglia of Xenopus and axolotl (Ambystoma mexicanum) axons grow directly to the limb buds over distances of up to 800 microm and in particular to sheets of epidermal cells which migrate away from the limb buds and also tail segments in culture. This directed axonal growth persists in the presence of trk-IgG chimeras, which sequester neurotrophins, and k252a, which blocks their actions mediated via trk receptors. These findings indicate that developing limb buds in Xenopus release diffusible factors other than neurotrophins, able to attract growth of sensory and motor axons over long distances.
