Developmental biologists have long been trying to determine mechanisms underlying the development of vertebrate retina. One of the most fundamental questions to be asked is what are the factors determining or influencing the fate of progenitor cells (e.g. what determines whether the cells become cones instead of rods). Cadherins, in addition to being responsible for adhesion between many types of cells, may also play key roles in cell differentiation, axon pathfinding and synapse formation. Our preliminary results show that both N- and R-cadherins are located in the teleost retina at a time when retinal cells are proliferating and differentiating, and when retinal ganglion cell axons are migrating out of the retina toward their major target in the brain, the optic tectum. The proposed study will first examine the developmental profiles of these two cadherins in the visual system to look for correlations between the distribution of these molecules and the major morphogenetic events of the system. Functional analysis using either cadherin antibodies in an organ culture system or injection of antisense nucleotides to block cadherin mRNA will be employed to assess the role(s) of these cadherin molecules in the development of teleost visual structures.