AAV6-mediated Systemic shRNA Delivery Reverses Disease in a Mouse Model of Facioscapulohumeral Muscular Dystrophy

Dulbecco Telethon Institute and Division of Regenerative Medicine, San Raffaele Scientific Institute, Milano, Italy.
Molecular Therapy (Impact Factor: 6.23). 08/2011; 19(11):2055-64. DOI: 10.1038/mt.2011.153
Source: PubMed


Treatment of dominantly inherited muscle disorders remains a difficult task considering the need to eliminate the pathogenic gene product in a body-wide fashion. We show here that it is possible to reverse dominant muscle disease in a mouse model of facioscapulohumeral muscular dystrophy (FSHD). FSHD is a common form of muscular dystrophy associated with a complex cascade of epigenetic events following reduction in copy number of D4Z4 macrosatellite repeats located on chromosome 4q35. Several 4q35 genes have been examined for their role in disease, including FRG1. Overexpression of FRG1 causes features related to FSHD in transgenic mice and the FRG1 mouse is currently the only available mouse model of FSHD. Here we show that systemic delivery of RNA interference expression cassettes in the FRG1 mouse, after the onset of disease, led to a dose-dependent long-term FRG1 knockdown without signs of toxicity. Histological features including centrally nucleated fibers, fiber size reduction, fibrosis, adipocyte accumulation, and inflammation were all significantly improved. FRG1 mRNA knockdown resulted in a dramatic restoration of muscle function. Through RNA interference (RNAi) expression cassette redesign, our method is amenable to targeting any pathogenic gene offering a viable option for long-term, body-wide treatment of dominant muscle disease in humans.

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    • "For example, the choice of the specific sequence encoded by the shRNA can affect not only siRNA efficiency but can also modulate overall toxicity [10], [17], [22]. In this regard we have recently shown that two separate shRNA sequences are effective at targeting the FRG1 transgene in a mouse model for FSHD [25]. Recent results in several systems suggest that miR30-based hairpins may display less toxicity than vectors based on simpler shRNA hairpins [41], [42]; JRC et al, submitted. "
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    • "FSHD region gene 1 (FRG1) is one of the proteins proposed to be involved in FSHD (Van Deutekom et al. 1996). FRG1-overexpressing mice are an animal model for FSHD, displaying a phenotype that strikingly resembles the functional and structural characteristics of FSHD (Gabellini et al. 2006; Bortolanza et al. 2011). Thick Tokuyasu sections of vastus lateralis muscle of FRG1-overexpressing mice were imaged with FM. "
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