Résumé :
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Mutations in the dystrophin gene cause Duchenne muscular dystrophy, the most common severe childhood muscular pathology. With antisense sequences linked to a modified U7 small nuclear RNA, we achieved persistent exon skipping that removes the mutated exon and re-establishes the open reading frame on the dystrophin messenger RNA of the mdx mouse model for Duchenne dystrophy (Goyenvalle et al., Science. 2004). This strategy is promising but will always concern patients for which exon skipping restores a shorter but functional protein. We are therefore developing a novel RNA repair strategy by trans-splicing allowing the replacement of the mutated exon by its normal version.The trans-splicing approach is based on the Spliceosome-mediated RNA trans-splicing (SMaRT, Intronn, Puttaraju et al., Nature Biotech. 1999), an emerging technology based on a trans-splicing molecule that forces the splicing to occur between the mutated endogenous pre-messenger RNA and an exogenous therapeutic RNA molecule which brings the normal sequence.We applied this strategy in mdx dystrophic mouse to replace the mutated exon 23 by its normal version. After intramuscular injections of AAV1 vectors expressing trans-splicing molecules, we detected by RT-PCR analysis the presence of repaired transcripts. We are currently working on the optimization of the different elements of the trans-splicing molecule and the detection of wild-type protein by western-blot. Those results are promising as a novel therapeutical strategy to treat DMD patients that can not be included in any exon skipping strategies.
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