Preferential adhesion of tectal membranes to anterior embryonic chick retina neurites

Recognition between cells during embryogenesis is essential for the formation of precisely patterned neuronal networks such as the projection of axons from the retina on to the tectum in the avian optical system. A gradient of adhesion between retinal and tectal cells has been detected, with cells from the dorsal area of the neural retina adhering preferentially to cells of the ventral half of the visual tecta and vice versa (for review see ref. 1). This has supported the idea that topological relationships between cells are established through markers on the cell surface 2 . Such findings are based on adhesion between cell bodies, whereas it is only the axon tip of the retina ganglion cell which makes contact with and presumably recognizes tectal cells. Here, we have used a system in which outgrowing neurites from the retina were exposed to tectal cell surfaces in vitro and found a striking antero-posterior polarity in the chick retina.