Viral-mediated expression of desmin mutants to create mouse models of myofibrillar myopathy

Abstract

BackgroundThe clinical features of myofibrillar myopathies display a wide phenotypic heterogeneity. To this date, no studies have evaluated this parameter due to the absence of pertinent animal models. By studying two mutants of desmin, which induce subtle phenotypic differences in patients, we address this issue using an animal model based on the use of adeno-associated virus (AAV) vectors carrying mutated desmin cDNA.MethodsAfter preparation of the vectors, they were injected directly into the tibialis anterior muscles of C57BL/6 mice to allow expression of wild-type (WT) or mutated (R406W or E413K) desmin. Measurements of maximal force were carried out on the muscle in situ and then the injected muscles were analyzed to determine the structural consequences of the desmin mutations on muscle structure (microscopic observations, histology and immunohistochemistry).ResultsInjection of AAV carrying WT desmin results in the expression of exogenous desmin in 98% of the muscle fibers without any pathological or functional perturbations. Exogenous WT and endogenous desmin are co-localized and no differences were observed compared to non-injected muscle. Expression of desmin mutants in mouse muscles induce morphological changes of muscle fibers (irregular shape and size) and the appearance of desmin accumulations around the nuclei (for R406W) or in subsarcolemmal regions of fibers (for E413K). These accumulations seem to occur and disrupt the Z-line, and a strong regeneration was observed in muscle expressing the R406W desmin, which is not the case for E413K. Moreover, both mutants of desmin studied here induce a decrease in muscle force generation capacity.ConclusionsIn this study we show that AAV-mediated expression of desmin mutants in mouse muscles recapitulate the aggregation features, the decrease in contractile function and the morphological changes observed in patients with myofibrillar myopathy. More importantly, our results suggest that the R406W desmin mutant induces a robust muscle regeneration, which is not the case for the E413K mutant. This difference could help to explain the phenotypic differences observed in patients. Our results highlight the heterogeneous pathogenic mechanisms between different desmin mutants and open the way for new advances in the study of myofibrillar myopathies.

The role and regulation of erythropoietin (EPO) and its receptor in skeletal muscle: how much do we really know?

“…This inducible model is able to overcome limitations of traditional gene targeting strategies and can down regulate the target of interest in a temporal and tissue-specific manner in the adult animal following tamoxifen administration. For over expression studies in adult animals, the use of adeno-associated viruses (AAV) has now become a popular method to deliver stable gene targets of interest into skeletal via intramuscular injection (Joanne et al, 2013) or systemically via intravenous (Katwal et al, 2013) or intraperitoneal administration (Charan et al, 2012). …”

Developmental Alterations in Heart Biomechanics and Skeletal Muscle Function in Desmin Mutants Suggest an Early Pathological Root for Desminopathies

“…Therefore, addressing whether there are mechanical mechanisms associated with desmin function that influence heart pumping and whether desmin aggregates affect these biomechanical mechanisms would help to solve this issue. To date, several mouse models of desmin-related myopathy, consisting of knockin mice carrying specific patient's point mutations, were generated, yet most of them did not present clear aggregate structures, and subsequent phenotypes were often associated to dominant-negative effects on the desmin network rather than to aggregate formation (Joanne et al, 2013;Kostareva et al, 2008;Raats et al, 1996). So far, desmin aggregation was observed in mouse cardiomyocytes carrying a specific desmin mutation (Wang et al, 2001a) or CRYAB mutation (Wang et al, 2001b).…”

Synemin acts as a regulator of signalling molecules in skeletal muscle hypertrophy

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