Age-dependent differences in cognin regeneration on embryonic retina cells: immunolabeling and SEM studies

The retina cognin (a glycoprotein isolated from the surface membrane of neural retina cells of chick embryos and postulated to mediate self-recognition and histogenetic association of retina cells) has been visualized by SEM on the surface of embryonic retina cells in vitro following immunolabeling of the cells with antibodies to the purified cognin and with polystyrene latex microbeads. Trypsin dissociation of retina tissue into separated cells resulted in cognin depletion from the cell surface; following incubation at 37 degrees C the cells regenerated the cognin. Regeneration was fastest and most abundant on cells from the youngest retinas examined; it declined markedly with the embryonic age of the cells, suggesting an age-dependent decrease in cell capacity for cognin formation. Evidence is discussed that the rate and amount of cognin regeneration on the cell surface are temporally-causally correlated with the capacity of the cells to reaggregate into retinotypic tissue. The results support the suggested role of the cognin in the mechanism of self-affinity and morphogenetic association of embryonic neural retinal cells.