GAP43 (growth associated protein 43, neuromodulin, B-50) is a component of the motile growth cones at the tips of elongating axons, and it is functionally associated with nerve growth, regeneration and plasticity. It is involved in axonal and dendritic filopodia induction. It is also important for learning, memory and information storage, and heterozygous loss of the GAP43 gene results in intellectual disability. In immunohistochemistry, it has membranous and cytoplasmic positivity in the central nervous system and in peripheral nerves. References: PLoS ONE. 9 (3): e92624, PMC: 3960265; Clinical Genetics. 53 (3): 220–2, PMID: 9630079; Front Cell Neurosci. 2017; 11: 266, PMID: 28912688