NEURAL CELL ADHESION MOLECULES OF THE IMMUNOGLOBULIN SUPERFAMILY: Role in Axon Growth and Guidance

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Abstract
▪ Abstract NCAM, L1, and DCC—immunoglobulin cell adhesion molecules (Ig CAMs)—are widely expressed during development. Many workers have dismissed a role for such molecules in the control of axonal growth and guidance because they do not show highly restricted expression patterns. Yet evidence from a number of model systems suggests all three CAMs play a role in the development of specific projections in the nervous system. For example, there is a reduction in mossy fiber tracts in the hippocampus of mice that lack NCAM, a requirement for DCC in the response of commissural neurons to a floor plate–derived chemoattractant, and a loss of corticospinal tracts in humans who carry mutations in the L1 gene. The above paradox might be explained by the observation that differential post-translational processing can modulate CAMs function and that alternative splicing can generate functionally distinct isoforms of a CAM. Activation of the FGF tyrosine kinase receptor is required for the responses stimulated by NCA...