The phenotype of dysferlin-deficient mice is not rescued by adeno-associated virus-mediated transfer of anoctamin 5.

Mutations in dysferlin and anoctamin 5 are the cause of muscular disorders, with the main presentations as limb-girdle muscular dystrophy or Miyoshi type of distal myopathy. Both these proteins have been implicated in sarcolemmal resealing. On the basis of similarities in associated phenotypes and protein functions, we tested the hypothesis that ANO5 protein could compensate for dysferlin absence. We first defined that the main transcript of ANO5 expressed in skeletal muscle is the 22-exon full-length isoform, and we demonstrated that dysferlin-deficient (Dysf (prmd)) mice have lower Ano5 expression levels, an observation that further enhanced the rational of the tested hypothesis. We then showed that AAV-mediated transfer of human ANO5 (hANO5) did not lead to apparent toxicity in wild-type mice. Finally, we demonstrated that AAV-hANO5 injection was not able to compensate for dysferlin deficiency in the Dysf (prmd) mouse model or improve the membrane repair defect seen in the absence of dysferlin. Consequently, overexpressing hANO5 does not seem to provide a valuable therapeutic strategy for dysferlin deficiency.

A naturally occurring human minidysferlin protein repairs sarcolemmal lesions in a mouse model of dysferlinopathy.

Dysferlinopathies are autosomal recessive, progressive muscle dystrophies caused by mutations in DYSF, leading to a loss or a severe reduction of dysferlin, a key protein in sarcolemmal repair. Currently, no etiological treatment is available for patients affected with dysferlinopathy. As for other muscular dystrophies, gene therapy approaches based on recombinant adeno-associated virus (rAAV) vectors are promising options. However, because dysferlin messenger RNA is far above the natural packaging size of rAAV, full-length dysferlin gene transfer would be problematic. In a patient presenting with a late-onset moderate dysferlinopathy, we identified a large homozygous deletion, leading to the production of a natural "minidysferlin" protein. Using rAAV-mediated gene transfer into muscle, we demonstrated targeting of the minidysferlin to the muscle membrane and efficient repair of sarcolemmal lesions in a mouse model of dysferlinopathy. Thus, as previously demonstrated in the case of dystrophin, a deletion mutant of the dysferlin gene is also functional, suggesting that dysferlin's structure is modular. This minidysferlin protein could be used as part of a therapeutic strategy for patients affected with dysferlinopathies.