Growth-associated protein-43 (GAP-43) is a growth-related presynaptic protein that is highly expressed in the human hippocampus and is known to play an important role in the regulation of axonal growth, synaptic plasticity, learning, and memory.[30] Previous studies have found that GAP-43 is closely related to AD and is involved in the pathophysiology of AD. This evidence concerns the gene GAP43 and Alzheimer disease.