GAP-43: A Gene for Neuronal Remodeling

The mammalian neuron is post-mitotic for most of the animal’s life. The brain’s adaptation to its microenvironment during these many years does not rely upon selective expansion of appropriate clones, as occurs with lymphocytes, but rather is due to changes in connectivity, often with physical changes in synaptic structure. This “plasticity” is most evident during development (Bailey and Chen, 1983; Cotman and Nieto-Sampedro, 1984; Greenough et al., 1986), but persists for the life of the animal (Purves and Lichtman, 1980; Purves et al., 1987). It is reasonable to presume that particular sets of genes are expressed coordinately during these long-term changes in nerve terminal structure. Growth of the neuron during development and repair also involves structural changes in the nerve, and is likely to depend upon sets of “growth-associated” genes (Skene, 1984, 1989).