Soluble retinal proteins associated with photoreceptor cell death in the rd mouse

In the mouse, the homozygous presence of the rd gene results in the genetically programmed death of the photoreceptor cells of the retina. Using congenic strains of mice and a novel, sensitive, immunological approach for visualizing unique retinal proteins, we identified four bands of protein whose concentrations are regulated by the homozygous presence of the gene for retinal degeneration. Since these proteins (with apparent molecular weights of 23, 33, 55, and 69 kD) are present in normal adult mouse retinas and absent from rodless retinas, and from other mouse non-retinal tissues including brain, heart, kidney and liver, the data support the identification of these proteins as being retina specific. These proteins are not peculiar to the normal mouse retina; but rather, all four (23, 33, 55 and 69 kD) are common to rat retina; three (23, 33, and 55 kD) are common to bovine retina; and presently at least two, 23 and 69 kD, are clearly detectable in normal, adult human retina. The temporal appearance and disappearance of the four retinal specific protein bands coincide with the morphological maturation and degeneration of the photoreceptor cell population. Collectively, the present data suggest that one or more may be photoreceptor specific. These observations present the first step in the identification and characterization of specific soluble proteins correlated with the biochemical phenotype of the rd gene and the death of photoreceptor cells of the retina.