A threshold effect of the major isoforms of NCAM on neurite outgrowth

• Published in: Nature (London) 1990-02, Vol.343 (6257), p.464-466
• Main Authors: Doherty, Patrick, Fruns, Manuel, Seaton, Patricia, Dickson, George, Barton, C. Howard, Sears, Thomas A, Walsh, Frank S
• Format: Article
• Language: English
• Subjects: Adhesion; Animals; Antibodies; Astrocytes; Axon guidance; Axonogenesis; Axons - physiology; Axons - ultrastructure; Biological and medical sciences; Brain; Cell adhesion; Cell adhesion & migration; Cell adhesion molecules; Cell Adhesion Molecules, Neuronal - genetics; Cell Adhesion Molecules, Neuronal - pharmacology; Cell morphology; Cells, Cultured; Cellular biology; Cerebellum; Cerebellum - ultrastructure; Cloning; Cones; Deoxyribonucleic acid; DNA; DNA - genetics; Dorsal root ganglia; Enzymes; Fundamental and applied biological sciences. Psychology; Gene Expression; Growth cones; Humanities and Social Sciences; Immunology; Isoforms; letter; Molecular and cellular biology; Monolayers; Morphology; multidisciplinary; Nervous system; Neural cell adhesion molecule; Neurofilaments; Neurons; Neurons - ultrastructure; Phosphatidylinositol; Phosphatidylinositol Diacylglycerol-Lyase; Phosphoric Diester Hydrolases - pharmacology; Rats; Rodents; Schwann cells; Science; Science (multidisciplinary); Skeletal muscle; Substrates; Transfection
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/343464a0

INTERACTIONS between recognition molecules on the surface of neuronal growth cones and guidance cues present in the local cellular environment are thought to account for the growth of neurites in the highly stereospecific manner that contributes to correct target cell innervation 1–3 . In vitro assays have been used to identify candidate molecular components of this system, either directly by demonstrating their ability to promote neurite outgrowth 4,5 , or indirectly by the ability of specific antibodies to inhibit neurite outgrowth 6–10 . The role of the neural cell adhesion molecule (NCAM) 2,11 in pathway finding is not fully understood. Some immunological studies support a positive role 6,8,9 ; others do not 7,10 , and it has been reported that purified NCAM does not support neurite outgrowth 4 . We have previously shown that an arbitrary biochemical index of neurite outgrowth, the relative level of immunoreactive neurofilament protein, is increased when human and rat dorsal root ganglion neurons are cultured on monolayers of cells expressing transfected human NCAM 12 . But, the complexity of growth precluded a simple morphological analysis and we did not determine the 'dose-response' relationship between NCAM expression and neuronal response. Here, we report on the morphology of rat cerebellar neurons cultured on monolayers of 3T3 cells transfected with complementary DNAs encoding all of the main NCAM isoforms found in cells such as astrocytes, Schwann cells and skeletal muscle 13 . The data indicate that both transmembrane and glycosyl-phosphatidylinositol linked NCAM isoforms are potent substrates for neurite extension. A critical threshold value of NCAM expression is required for increased neurite outgrowth. Above this threshold, small increases in NCAM induce substantial increases in neurite outgrowth.