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Nicholas M. Tran, Shiming Chen; Crx Overexpression Identified in a Knock-IN Mouse Model for Severe Forms of Crx-Associated Disease. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1636.
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Mutations in the transcription factor CRX have been associated with dominant retinal degeneration diseases of vastly different classification and severity including Retinitis Pigmentosa (RP), Cone-Rod Dystrophy (CRD) and Leber’s Congenital Amaurosis (LCA). To model distinct forms of disease, we have established two Knock-IN Crx mutation mouse models, Dominant Negative Low and High expression (DNL and DNH). DNL and DNH carry the same 2bp deletion mutation that results in a truncated CRX protein that loses transactivation. Genetically, DNL and DNH differ only in the presence or absence of a neomycin cassette in third intron of Crx. However, DNH yields a more severe dominant retinopathy than DNL. Our goal was to determine the mechanisms that modulate severity and pathology of retinal disease in the Crx DNH and DNL mice and how that will impact the design of therapeutic strategies.
The phenotypes of Crx DNH and DNL mice were characterized by morphology (histology, immunohistochemistry), retinal function (Electroretinogram), and gene expression (QRT-PCR, Microarray, Western Blot).
Crx DNH mice have severely impaired rod and cone function by one month of age and undergo rapid cone, slow rod degeneration. In contrast, DNL mice have moderately impaired cone function and slightly impaired rod function and undergo slow cone but no rod degeneration. Crx DNH also causes a stronger reduction in CRX target gene expression. Interestingly, Crx DNH causes overexpression of both the WT and mutant Crx alleles, indicating Crx’s transcriptional regulation is disrupted in these mice. Crx DNL mice, however, have normal Crx expression.
Crx DNH and DNL represent two distinct mouse models for dominant Crx disease. We have found that the same DN mutation can cause disease of different severity and pathology which correlated with the level of Crx expression. This finding identifies a novel target for therapeutic intervention and could greatly affect the design of appropriate therapeutic strategies.
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