Neural cell adhesion molecule （NCAM）, also called CD56, is a homophilic binding glycoprotein expressed on the surface of neurons, glia and skeletal muscle. CD56 is thought to signal to induce neurite outgrowth via the fibroblast growth factor receptor （FGFR） and act upon the p59Fyn signaling pathway. In nerves, CD56 regulates homophilic （like-like） interactions between neurons and between neurons and muscle; it associates with fibroblast growth factor receptor （FGFR） and stimulates tyrosine kinase activity of receptor to induce neurite outgrowth. When neural crest cells stop making CD56 and N-cadherin, and start displaying integrin receptors, cells separate and migrate. During hematopoiesis, CD56 is the prototypic marker of NK cells, also present on subset of CD4+ T cells and CD8+ T cells. In cell adhesion, CD56 contributes to cell-cell adhesion or cell-matrix adhesion during embryonic development.