Contactins mediate cell surface interactions during nervous system development. Has some neurite outgrowth-promoting activity. Interacts with PTPRG. Specifically expressed in brain. Not expressed in peripheral tissues such as heart, lung, liver, spleen, kidney and skeletal muscle. In brain, it is restricted to subsets of neurons such as Purkinje cells of the cerebellum, granule cells of the dentate gyrus, and neurons in the superficial layers of the cerebral cortex. Weakly or not expressed from E12 to E20. Expressed at much higher level from postnatal day 2, reaching a maximum level in adult brain. Belongs to the immunoglobulin superfamily. Contactin family.