L5: A carbohydrate epitope involved in neural development

Summry— The L5 carbohydrate epitope is developmentally regulated in the vertebrate nervous system, both at very early stages (neural induction) and during postnatal development. Here, we review the evidence indicating that, during gastrulation, L5 may be a marker for cells competent to respond to neural inducing signals emanating from Hensen's node (the ‘organizer’) and that it may itself be involved in the response to neural induction. In postnatal cerebellar development, when L5 is found on astrocytes, it participates in the outgrowth of astrocytic processes on extracellular matrix components. Finally, we indicate the structural relatedness of the L5 carbohydrate and Lex, CD15 and SSEA‐1.