Photoreceptor-specific mRNAs in mice carrying different allelic combinations at the rd and rds loci

Several retinal mRNAs encoding photoreceptor-specific proteins have been examined in congenic lines of mice carrying different allelic combinations at the rd and rds loci, to determine how mRNA expression is affected by the presence of both the rd and rds genes together or by the presence of one or two rd and rds alleles in the visual cells. Slot blots with retinal RNA from 9 to 30 days old C3H +/+, +/+; rd/+, +/+; rd/rd, +/+; +/+, +/rds; +/+, rds/rds; and the rd/rd, rds/rds double homozygous mutant mice were hybridized successively to several [32P]cDNA probes encoding proteins involved in phototransduction. The increases and decreases in the levels of mRNA coding for opsin, the alpha-subunit of transducin, 48 kDa protein and the beta-subunit of cGMP-phosphodiesterase in the heterozygous and homozygous rds and rd mouse retinas reflected the growth and degeneration of the photoreceptor cells. The heterozygous rd mouse (rd/+, +/+) retina expressed cGMP-phosphodiesterase beta mRNA levels halfway between those in the control (+/+, +/+) and homozygous (rd/rd, +/+) mice, indicating a possible dosage effect. The double homozygous mutant (rd/rd, rds/rds) showed intermediate levels between those observed in the two homozygotes for all mRNAs studied, suggesting a possible interaction between the rd and rds genes.