Lavigne uncovered clues to a key element of nervous system construction. He proved that axons, the long, tubelike carriers of messages from nerve cells to target cells, are guided to the targets by molecules called chemoattractants. It really is like a sign that says, 'This way to San Francisco Airport,' and depending on who you are and where you want to go, you will decide whether or not to go that way. Tessier-Lavigne and other researchers now think that netrins can be used to coax healthy nerves into injured areas. At the University of Florida-Gainesville, for instance, scientists have induced nerve regeneration in the injured spinal cords of rats by grafting in cells that had been engineered to produce netrins.
Further studies are ongoing to determine whether the netrins actually caused the nerve growth.
But bridging the gap isn't that simple. Other molecules present in the body, called chemorepellents, appear to prevent nerve regrowth. Scientists at McGill University are trying to outflank the repellents with a vaccine. If scientists will have to intervene in guidance as well, it will take longer.