Synapse formation in retina is influenced by molecules that identify cell position.

Molecules that identify cell type and position in the nervous system were detected by monoclonal antibodies. One molecule, TOP, is distributed in a 35-fold topographic gradient from the dorsoposterior margin to the ventroanterior margin of avian retina. The gradient is present in young embryos, increases with retinal growth, and persists in the adult. TOP molecules are present on most or all cells of retina. The number of TOP molecules detected per cell varies continuously along the axis of the antigen gradient. Thus, TOP can be used to identify position in the plane of retina along that axis. Other antigens that identify cell type and position across the thickness of retina also were detected. Molecules that mark such cellular organization may represent a neuronal recognition system. Antibodies were used to examine the role of markers of cell position in development of the nervous system. Antibody to TOP from hybridoma cells that were injected into in vivo embryo eyes diffused into the retina and bound in a topographic gradient of Ab.TOP complexes. Synapse formation in retina was inhibited in the presence of anti-TOP antibody. This suggests that TOP is involved in synapse formation and that recognition of position by neurons is necessary for normal synapse formation.