title: Topological distribution of different forms of neural cell adhesion molecule in the developing chick visual system.
abstract: The cell adhesion molecule isolated from neural tissue (N-CAM) is a membrane glycoprotein which is directly involved in calcium-independent adhesion among nerve cells and their processes (for review see refs 1,2). N-CAM has an unusual carbohydrate moiety containing a large and variable amount of sialic acid, the variation reflecting both the type of tissue and its developmental age. N-CAM is believed to be a ligand in the formation of cell-cell bonds and a decrease in sialic acid content from 30% to 10% is associated with a marked enhancement of the molecule's binding activity. Antibodies to N-CAM block its function and inhibit or alter bundling of nerve fibres, retinal cell development and nerve-muscle interaction. Here we use micro-gel electrophoresis to compare N-CAM from several parts of the developing chick visual system. The results indicate that N-CAM from the retina of 5-10-day-old embryos already exists in a relatively sialic acid-poor form, whereas the tectum and optic nerve beyond the eye contain sialic acid-rich N-CAM until much later in development. These studies suggest that the perikaryon and proximal axon shaft of retinoganglion cells have N-CAM with a lower sialic acid content than the distal portion of the axons, and that resulting differences in neurite adhesivity may be an important factor in the formation of the optic system.
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000032:analysis*; D001370:Axonal Transport; D015815:Cell Adhesion Molecules; D002642:Chick Embryo; D009900:Optic Nerve / Q000196:embryology*; D009928:Organ Specificity; D012160:Retina / Q000196:embryology*; D012165:Retinal Ganglion Cells / Q000502:physiology; D012794:Sialic Acids / Q000032:analysis; D013477:Superior Colliculi / Q000196:embryology*
chemical_list: D000954:Antigens, Surface; D015815:Cell Adhesion Molecules; D012794:Sialic Acids