Guidance of optic axons in vivo by a preformed adhesive pathway on neuroepithelial endfeet.

Antibodies against the neural cell adhesion molecule (NCAM) were used in vivo both to localize NCAM antigenic determinants in developing tissues of the chicken visual system and to perturb cell-cell adhesion during growth of optic fibers to the tectum. The immunohistochemical studies revealed a staining pattern on neuroepithelial cells which coincided with certain regions of the presumptive route for optic axons, not only with respect to the overall pathway from the eye to the tectum, but also in the preferential distribution of the antigen on the marginal endfeet which are contacted by optic axon growth cones. The antibody-perturbation studies, which involved intraocular injection of anti-NCAM Fab at embryonic Day 3.5, demonstrated that inhibition of NCAM-mediated adhesion results in a dramatic distortion of growth cone-neuroepithelial cell relationships and consequently of the optic pathway. Together, these studies suggest that guidance of optic axons along the margin of the brain is at least in part influenced by a preformed adhesive pathway on neuroepithelial cells associated with NCAM antigens.