Required for gap junction formation (By similarity). Required, with CNTNAP1, for radial and longitudinal organization of myelinated axons (PubMed:25378149). Plays a role in the formation of functional distinct domains critical for saltatory conduction of nerve impulses in myelinated nerve fibers. Demarcates the juxtaparanodal region of the axo-glial junction (Probable) (PubMed:25378149). Interacts (via C-terminus) with KCNA2. Expressed in the juxtaparadonal region. In sciatic nerve predominantly found at the juxtaparanodal regions (at protein level). Detected at postnatal day 8 in sciatic nerve at the paranodes and the juxtaparanodal region. Is progressively translocated to the adjacent juxtaparanodal region until it becomes completely absent from the paranodes in the adult. Mutants don't show difference of Ranvier nodes length and width compared to wild-type littermates. Double mutants CNTNAP1 and CNTNAP2 have wider Ranvier nodes. Belongs to the neurexin family.