RPE65 and retinal degeneration: To determine if the decrease in the transcript levels of visual and phototransduction genes in the Mfrprd6 mutant was a non-specific effect of the disease process that occurs during retinal degeneration, we examined the levels of visual cycle and phototransduction pathway transcripts in two unrelated retinal degeneration models with mutations in the retina-specific gene, Tulp1 or the RPE-specific gene, Rpe65. Homozygous Tulp1 (Tulp1tvrm124) mutant mice model early onset retinal degeneration and have characteristically shorter OSs at P14 [21], comparable to those observed in Mfrprd6 mutants.