Mediates cell surface interactions during nervous system development. Expressed in brain. First detectable at 16 hours post-fertilization (hpf) in trigeminal and Rohon-Beard neurons. At 18-24 hpf, it is also weakly expressed in discrete cell clusters in the hindbrain, in the anterior lateral line/acoustic ganglion and in spinal motor neurons. Belongs to the immunoglobulin superfamily. Contactin family.