Contactins mediate cell surface interactions during nervous system development. Involved in the formation of paranodal axo-glial junctions in myelinated peripheral nerves and in the signaling between axons and myelinating glial cells via its association with CNTNAP1. Participates in oligodendrocytes generation by acting as a ligand of NOTCH1. Its association with NOTCH1 promotes NOTCH1 activation through the released notch intracellular domain (NICD) and subsequent translocation to the nucleus. Interaction with TNR induces a repulsion of neurons and an inhibition of neurite outgrowth. Monomer. Interacts with CNTNAP1 in cis form (By similarity). Binds to the carbonic-anhydrase like domain of PTPRZ1 (PubMed:20133774). Interacts with NOTCH1 and TNR (PubMed:7678967, PubMed:14567914). Detected in a complex with NRCAM and PTPRB (PubMed:11564762). Interacts with TASOR (PubMed:31112734). Expressed in the ovary and in Sertoli cells of the testis. F3 shares with L1, N-CAM, MAG, and other cell adhesion molecules from nervous tissue the L2/HNK-1 carbohydrate epitope. Belongs to the immunoglobulin superfamily. Contactin family.