Localization of the growth-associated phosphoprotein GAP-43 (B-50, F1) in the human cerebral cortex.

The growth-associated phosphoprotein GAP-43 is a component of the presynaptic membrane that has been linked to the development and functional modulation of neuronal connections. A monospecific antibody raised against rat GAP-43 was used here to study the distribution of the protein in cortical and subcortical areas of the human brain. On Western blots, the antibody recognized a synaptosomal plasma membrane protein that had an apparent molecular weight and isoelectric point similar to GAP-43 of other species. In brain tissue reacted with the antibody, the heaviest immunoreactivity was found in associative areas of the neocortex, particularly within layers 1 and 6, in the molecular layer of the dentate gyrus, the caudate putamen, and the amygdala. In contrast, primary sensory or motor regions of the cortex, portions of dorsal thalamus, and cerebellum showed only light staining. Staining was generally confined to the neuropil, which showed punctate labeling, whereas most neuronal somata and fiber bundles were unreactive. The pronounced variations in GAP-43 immunostaining among various areas of the human brain may reflect different potentials for functional and/or structural remodeling.