The ability of a cell to modify its membrane composition to interact with other cells,such as neurons and/or glial cells appears to be critical for the development,remodeling and repair of the nervous system.Among many candidate molecules,evidences have been found to consider the association of poly-α2,8-sialic acid (PSA) with the neural cell adhesion molecule (NCAM) as a key factor of such abilities.Notably,PSA-NCAM,is re-expressed in several pathological situations such as aggressive tumors of neuroectodermal origin,regenerating muscles and sprouting axons.Observation based either on enzymatic destruction of PSA by endonenraminidase (EndoN) or the use of mutant mice for polysialyltransferase responsible for PSA synthesis indicate that PSA is required for morphogenesis and tissue remodelling.Thus,the carbohydrate PSA emerges as an important permissive factor for dynamic changes in cell surface interaction and represents one of the potential targets for therapeutic approaches to promote plasticity (gain of function) or control cell migration (loss of function).