The vertebrate retina is a well-characterized area of the central nervous system that offers many advantages for studies of development. Specialized sensory cells, the rod photoreceptors are essential for vision and can suffer from several types of degeneration. Factors that affect the development of rods may also affect their survival and function. As well, it will be crucial to understand how to promote rod differentiation for therapies aimed at rod replacement. Rod photoreceptor has been studied by examining the effect of exogenous factors on developing retinal tissue in vitro. Experiments that probe the interaction of these factors with retinal progenitors and the mechanism by which these factors affect rod photoreceptor development will be carried out. The regulation of a novel, photoreceptor-specific gene, Crx, will also be examined. The effects of the factors identified in the previous funding period on Crx expression will be analyzed. As well, the cis-acting regulatory regions of Crx and the cognate factors will be sought. The data thus obtained may be of value in potentiating rod survival, regeneration and/or replacement in such degenerative diseases as retinitis pigmentosa.