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Medicine and Health Sciences


We screened a 300,000-clone, random shRNA-expressing library and identified shRNA sequences that reverse the decreased growth/survival phenotype of primary Friedreich ataxia (FA) fibroblasts grown in mitochondrial stress media. One of the hit sequences, gFA2, increases frataxin expression ~2 fold, either as a vector-expressed shRNA or as a transfected siRNA. We randomly mutagenized gFA2 to create a gFA2 variant sub-library. We screened this sub-library in primary FA fibroblasts and identified two gFA2 variants, gFA2.8 and gFA2.10, that further increase frataxin expression. Microarray analyses of primary FA fibroblasts expressing another hit shRNA, gFA11, revealed alterations in ~350 mRNAs. Bioinformatic pathway analyses indicated significant changes in mRNAs involved in cytokine secretion; we confirmed significant changes in cytokine secretion induced by gFA11 biochemically. Ingenuity Pathway Analysis revealed that inhibition of a known transcription factor, or treatment of cells with a previously studied chemical compound, induced a statistically similar pattern of gene expression to that induced by gFA11. Inhibition of the transcription factor using a directed siRNA in primary FA fibroblasts, as well as treatment of the cells with the chemical compound, recapitulated the phenotype induced by gFA11, namely reversal of decreased growth/survival in mitochondrial stress media. We are currently planning similar microarray and bioinformatics analyses of the optimized versions of gFA2. Combined with microarray analyses and bioinformatic pattern-matching, our random, shRNA library screens potentially yield, 1) small-RNA therapeutic candidates, 2) conventional chemical-compound therapeutic candidates, 3) drug-target candidates, and 4) elucidation of disease mechanisms, which may inform additional therapeutic initiatives.


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