Abstract
Purpose: :
Usher syndrome is characterized by congenital deafness associated with retinitis pigmentosa (RP). Mutations in the myosin VIIa gene (MYO7a) cause a common and severe subtype of Usher syndrome (USH1B). Shaker1 mice have mutant Myo7a andare widely accepted animal models for USH1B. They are deaf and have vestibular dysfunction but do not develop photoreceptor degeneration. The goal of this study was to investigate abnormalities of photoreceptors in shaker1 mice.
Methods: :
Immunocytochemistry and hydroethidine-based detection of intracellular superoxide production were used. Photoreceptor cell densities under various conditions of light/dark exposures were evaluated.
Results: :
In shaker1 mice, the rod transducin translocation is delayed due to a shift of its light activation threshold to a higher level. Even moderate light exposure can induce oxidative damage and significant rod degeneration in shaker1 mice. Shaker1 mice reared under a moderate light/dark cycle develop severe retinal degeneration in less than 6 months
Conclusions: :
These findings demonstrate that, contrary to earlier studies, shaker-1 mice possess a robust retinal phenotype which may link to defective rod protein translocation. Importantly USH1B animal models are thus likely vulnerable to light induced photoreceptor damage even under moderate light.
Keywords: retinal degenerations: cell biology • photoreceptors • signal transduction