Scientists have long puzzled over nerve regeneration. Damaged nerves in the arms or legs often repair themselves after injury, but those in the brain or spine rarely do. Research in the past 2 decades has suggested that GAP-43, a compound in the growth-associated protein family, influences nerve regrowth. But in laboratory trials, injured animals induced to produce extra amounts of this compound show only meager signs of spinal cord repair. Another compound under investigation, a cortical-actin-associated protein, CAP-23, has also performed feebly.
However, a study in mice shows that when unleashed simultaneously on a severed nerve that leads into the spinal cord, the two proteins multiply their effect, researchers report in the January Nature Neuroscience. GAP-43 and CAP-23 together induce up to 60 times as much nerve regrowth as either engenders alone, says coauthor J.H. Pate Skene, a neurobiologist at Duke University Medical Center in Durham, N.C. The results sugg