GAP43 protein, also known as growth-associated protein 43, is a crucial molecule in the nervous system. It is predominantly expressed in neurons and plays a vital role in axonal growth and regeneration. During the development of the nervous system, GAP43 is highly expressed in growth cones at the tips of growing axons, where it helps to mediate the interactions between the axon and its surrounding environment, guiding the direction of axonal extension. In the adult nervous system, its expression can be upregulated in response to injury, facilitating the repair and reconnection of damaged neural circuits. Additionally, GAP43 is involved in synaptic plasticity, contributing to the strengthening and remodeling of synapses, which is essential for learning and memory processes. Its phosphorylation and dephosphorylation states can regulate its function, and alterations in GAP43 levels or activity have been implicated in various neurological disorders, making it an important target for research in neuroregeneration and neurodegenerative diseases.