NFASC, also known as neurofascin, belongs to the immunoglobulin superfamily, L1/neurofascin/NgCAM family. It contains 5 fibronectin type-III domains and 6 Ig-like C2-type (immunoglobulin-like) domains. NFASC functions in neurite outgrowth, neurite fasciculation, and organization of the axon initial segment (AIS) and nodes of Ranvier on axons during early development. Both the AIS and nodes of Ranvier contain high densities of voltage-gated Na+ (Nav) channels which are clustered by interactions with cytoskeletal and scaffolding proteins including this protein, gliomedin, ankyrin 3 (ankyrin-G), and betaIV spectrin. NFASC links the AIS extracellular matrix to the intracellular cytoskeleton.