Cellular site of expression and genetic interaction of the rd and the rds loci in the retina of the mouse.

In the retina of mice, the two genes, rd and rds, produce retinal degeneration. Depending on allelic combination and gene dosage at these loci, four different genotypes with distinct phenotypic traits and rates of photoreceptor cell loss are recognized. The cellular site of gene action and the nature of interaction, resulting in the variegation of the retinal phenotypes have been analyzed by comparing gene expression in the retina of pure line (unigenotypic) mice, and in the retina of chimaeric mice, experimentally produced by aggregating embryos of different genotypic constitution. The findings suggest that both rd and rds genes act intracellularly within the photoreceptor cells. The primary expression of the genes, producing specific phenotypic alterations of the photoreceptor cells, are invariant and are not affected by extracellular factors. The lethal effects of the genes, on the other hand, resulting in specified rates of photoreceptor cell death, are influenced by both genetic (intracellular), and environmental factors.