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 (By similarity). Interacts with NOTCH1 (By similarity). Interacts with CNTNAP1 in cis form and TNR (PubMed:9118959, PubMed:9081628). Binds to the carbonic-anhydrase like domain of PTPRZ1 (PubMed:7628014). Detected in a complex with NRCAM and PTPRB (By similarity). Interacts with TASOR (By similarity). Expressed by neurons, oligodendrocytes and their progenitors (at protein level). Myelination regulates the expression being down-regulated when neurons are in contact with Schwann cells. Belongs to the immunoglobulin superfamily. Contactin family.