Contactins mediate cell surface interactions during nervous system development. Has some neurite outgrowth-promoting activity. May be involved in synaptogenesis. Interacts with PTPRG. Mainly expressed in brain. Highly expressed in cerebellum and weakly expressed in corpus callosum, caudate nucleus, amygdala and spinal cord. Also expressed in testis, pancreas, thyroid, uterus, small intestine and kidney. Not expressed in skeletal muscle. Isoform 2 is weakly expressed in cerebral cortex. By retinoic acid, suggesting that it may act in response to differentiating agents. A chromosomal aberration involving CNTN4 has been found in a boy with characteristic physical features of 3p deletion syndrome (3PDS). Translocation t(3;10)(p26;q26). 3PDS is a rare contiguous gene disorder involving the loss of the telomeric portion of the short arm of chromosome 3 and characterized by developmental delay, growth retardation, and dysmorphic features. Belongs to the immunoglobulin superfamily. Contactin family.