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A. M. Siddiqui, C. A. Wassif, F. D. Porter, M. J. Richards, S. J. Fliesler; A Systems-Level Approach to Temporal Transcriptional Profiling of Retinas in a Rat Model of Smith-Lemli-Opitz Syndrome. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3067.
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© ARVO (1962-2015); The Authors (2016-present)
Smith-Lemli-Opitz syndrome (SLOS) is a hereditary disease caused by defective cholesterol biosynthesis. An animal model of SLOS has been developed by treating rats with AY9944, an inhibitor of the affected enzyme in SLOS, which results in progressive retinal degeneration. We performed temporal transcriptional profiling of retinas from this SLOS rat model in comparison with age-matched controls.
Sprague Dawley rats were treated with AY9944 (s.c.) over a 3-mo course starting at birth; control rats received no drug. All animals were maintained under dim cyclic light and fed a cholesterol-free diet. At 1, 2, and 3 postnatal months, total RNA was extracted from individual retinas, and mRNA was amplified, labeled, and hybridized to Affymetrix GeneChip Rat Genome 230 2.0 arrays. Data were normalized using accuracy/precision-optimizing gcRMA algorithms, accounting for probe GC content. Retinas from AY9944-treated rats were compared to age-matched controls (N=3 per age/treatment); a two-way ANOVA was performed to assess gene expression variability with regard to AY9944 treatment and age (FDR ≤ 0.01). Five distinct differential groups were each partitioned into co-expression profile groups using a [gene x gene] vector matrix Pearson’s correlation algorithm written in R-script. Functional category enrichment for each gene profile group was statistically analyzed using a 2x2 Fisher’s Exact Test. Differential gene expression was validated by qRT-PCR using the ΔΔCt method.
Functional enrichment analysis revealed that genes involved in diverse biochemical pathways are affected, e.g., fatty acid metabolism, oxidative stress response, (anti-)apoptosis, visual transduction, and complement component activation; sterol metabolism genes were down-regulated at all ages (+AY9944 vs. control). Notably, the expression profiles of genes involved in oxidative stress response and apoptosis (up-regulated) were anti-correlated with profiles of anti-apoptotic genes (down-regulated).
Retinal degeneration in the SLOS rat model involves age-dependent differential regulation of multiple genes, consistent with global metabolic involvement beyond the primary defect in cholesterol biosynthesis. Oxidative stress and apoptotic cell death appear to be significant components of the degenerative process.
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