The proposed research explores mechanisms that underly the pathobiology of inherited retinal disease. A variety of animal models for retinitis pigmentosa will be utilized. Employing the spontaneously- mutated mouse model, retinal degeneration slow (rds) as the genetic background for this work, we will study transgenic lines carrying the rds point mutation P216L on the (rds+/-) background. We used these animals in a preclinical trial for recombinant adeno-associate virus (rAAV)-vectored therapy with ciliary neurotrophic factor (CNTF), a cytokine that has well-documented photoreceptor rescue properties. This treatment produced morphological photoreceptor rescue but it changed the photoreceptor nuclear phenotype and reduced the a and b-wave amplitude of the eletroretinogram. We will conduct additional dose response studies to determine whether this side effect can be eliminated and also try to determine the mechanism of the observed effect. These animals will also be used for rAAV-vector, ribozyme-mediated gene therapy. We will use doxycycline-inducible transgenic mice in which a wild type rds rescue transgene can be activated on the rds-/- or rds+/- background at various stages during the evolution of retinal degeneration. This will allow us to determine the optimal time for genetic intervention in the disease processes. We will also use a doxycycline-inducible transgenic mouse model in which the P216L point mutation can be switched on at any doxycycline-inducible transgenic mouse model in which the P216L point mutation can be switched on at any point after birth. Additionally, we will utilize a transgenic mouse line that features an X chromosome- linked non-autonomous form of photoreceptor cell death. In these animals, rds-/- photoreceptors that express a wild type rds rescue transgene located on their X chromosome degenerate in the presence of neighboring cells that lack expression of the rescue transgene due to X chromosome inactivation. Our approach in the analysis of these animals will involve the use of DNA microarrays in an attempt to identify genes that respond to the presence of the point mutation in a deleterious way and to identify genes involved in the non-autonomous cell death observed in the X-linked transgenic model.
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