Postnatal development of photoreceptor proteins in mutant mice and Abyssinian cats with retinal degeneration

Using immunocytochemical techniques, development of opsin, transducin alpha and S-antigen in photoreceptor cells of the mice homozygous or heterozygous for the rd or rds genes has been found to be similar to that of control animals during the first postnatal week. Even though the absolute amounts of these proteins are low (eg. opsin in the rds retina) or decrease in the postnatal period (as in the rd retina), we can demonstrate their persistence during the entire degeneration process. In fact, the content of the proteins in the photoreceptor perikarya actually appear to be higher after postnatal day 11 in all mutants studied. Thus, one of the major manifestations of the mutant retinae is a loss of polarity of the photoreceptor cells at the time of ROS degeneration without a loss in the ability to synthesize these important proteins of the visual cycle. This correlates well with the apparent defect in IRBP secretion and its intracellular accumulation in mutant photoreceptor cells as previously observed (van Veen et al. 1986). In the Abyssinian cat model for progressive retinal atrophy, the development an cellular distribution of all the proteins studied are similar in affected and control retinae until the beginning of stage 2 of the disease. At this time, outer segments begin to degenerate and immunoreactivity increases in the photoreceptor perikarya. The IRBP content of the retina declines markedly at stage 2, preceding extensive loss of photoreceptors.