Key result
Skeletal muscle-restricted CAPN3 expression prevents cardiac toxicity and reverses pathology in mice.
Why the study?
Genetic defects in calpain3 cause limb-girdle muscular dystrophy type 2A, and unrestricted CAPN3 gene transfer induces cardiac toxicity in a murine model.
Restricting calpain3 gene expression to skeletal muscle using specific promoters and microRNA targets prevents fatal cardiac toxicity while maintaining therapeutic efficacy in a murine model of muscular dystrophy.
Answers are grounded in this paper and cite their sources.
May enable safer gene therapy for muscular dystrophy; leaves open clinical translation.
BACKGROUND: Genetic defects in calpain3 (CAPN3) lead to limb-girdle muscular dystrophy type 2A, a disease of the skeletal muscle that affects predominantly the proximal limb muscles. We previously demonstrated the potential of adeno-associated virus-mediated transfer of the CAPN3 gene to correct the pathological signs in a murine model for limb-girdle muscular dystrophy type 2A after intramuscular and locoregional administrations. METHODS AND RESULTS: Here, we showed that intravenous injection of calpain3-expressing vector in mice can induce mortality in a dose-dependent manner. An anatomopathological investigation revealed large areas of fibrosis in the heart that we related to unregulated proteolytic activity of calpain3. To circumvent this toxicity, we developed new adeno-associated virus vectors with skeletal muscle-restricted expression by using new muscle-specific promoters that include the CAPN3 promoter itself and by introducing a target sequence of the cardiac-specific microRNA-208a in the cassette. Our results show that CAPN3 transgene expression can be successfully suppressed in the cardiac tissue, preventing the cardiac toxicity, whereas expression of the transgene in skeletal muscle reverts the pathological signs of calpain3 deficiency. CONCLUSIONS: The molecular strategies used in this study may be useful for any gene transfer strategy with potential toxicity in the heart.
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Roudaut et al. (2013) studied Limb-girdle muscular dystrophy type 2A (murine model). Adeno-associated virus vectors with skeletal muscle-restricted expression of CAPN3 vs. Unrestricted calpain3-expressing vector was evaluated on Cardiac toxicity and pathological signs of calpain3 deficiency. Skeletal muscle-restricted expression of CAPN3 using muscle-specific promoters and a cardiac-specific microRNA-208a target sequence prevented cardiac toxicity and reverted pathological signs in mice.
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