Abstract
Purpose: :
To investigate the role of the Retinal Degeneration Slow (Rds)–specific mutant protein, R172W (associated with macular dystrophy), in the cone–dominated retina of the Neural Retina Leucine Zipper (Nrl)–deficient mouse lacking the endogenous Rds protein.
Methods: :
We generated mice carrying the R172W mutation in different genetic backgrounds: R172W+/+/Rds–/–/Nrl–/–, R172W+/–/Rds–/–/Nrl–/–, R172W+/+/Rds+/–/Nrl–/–, R172W+/–/Rds+/–/Nrl–/–. Light and electron microscopy (LM, EM) were used to examine retinal histology and ultrastructure. Electroretinography (ERG) was performed on mice at postnatal (P) day 30, 60 and 120 to assess retinal function. Immunohistochemistry (IHC) and immunogold labeling served to determine the localization of several retinal–specific proteins involved in outer segment (OS) formation and phototransduction. Biochemical analyses were performed to further characterize the fate of the mutant protein.
Results: :
R172W mutant Rds protein was detected by Western analysis in all genetic backgrounds. Preliminary examination of R172W in the Rds–/–/Nrl–/– background demonstrated altered scotopic and photopic ERG values as compared to the Rds–/–/Nrl–/– alone. Ultrastructural analyses revealed disorganized OS lamellae formation which labeled with anti–Rds and anti–S–cone opsin.
Conclusions: :
Mutant R172W Rds protein is synthesized and routed to the site of OS membrane assembly in the cone–dominated Nrl–deficient murine retina; however, OS morphogenesis is aberrant. Further biochemical analyses to determine the precise phenotypic defect caused by the R172W mutant protein will aid in the rational design of therapeutic strategies for treating Rds–associated macular dystrophy.
Keywords: retinal degenerations: cell biology • photoreceptors • retina