Abstract
Mutations in the dysferlin gene are the cause of Limb-girdle Muscular Dystrophy type 2B and Miyoshi Myopathy. The dysferlin protein has been implicated in sarcolemmal resealing, leading to the idea that the pathophysiology of dysferlin deficiencies is due to a deficit in membrane repair. Here, we show using two different approaches that fullfiling membrane repair as asseyed by laser wounding assay is not sufficient for alleviating the dysferlin deficient pathology. First, we generated a transgenic mouse overexpressing myoferlin to test the hypothesis that myoferlin, which is homologous to dysferlin, can compensate for the absence of dysferlin. The myoferlin overexpressors show no skeletal muscle abnormalities, and crossing them with a dysferlin-deficient model rescues the membrane fusion defect present in dysferlin-deficient mice in vitro. However, myoferlin overexpression does not correct muscle histology in vivo. Second, we report that AAV-mediated transfer of a minidysferlin, previously shown to correct the membrane repair deficit in vitro, also fails to improve muscle histology. Furthermore, neither myoferlin nor the minidysferlin prevented myofiber degeneration following eccentric exercise. Our data suggest that the pathogenicity of dysferlin deficiency is not solely related to impairment in sarcolemmal repair and highlight the care needed in selecting assays to assess potential therapies for dysferlinopathies.
Highlights
Mutations in dysferlin have been shown to lead to a variety of muscle phenotypes that range from mild to severe, including the prominent Limb-Girdle Muscular Dystrophy type 2B [LGMD2B; OMIM 253601; [1]] and Miyoshi Myopathy
We investigated the potency of two different strategies for reversing the myopathology of dysferlin deficiency: overexpression of myoferlin and associated viruses (AAV)-mediated transfer of a minidysferlin
We used a laser wounding assay of myofibers in tissue culture to assess the efficacy of these treatments in promoting sarcolemmal repair, histology to examine the dystrophic phenotype in vivo, and large strain injury to assess the susceptibility of skeletal muscles to damage from eccentric contractions
Summary
Mutations in dysferlin have been shown to lead to a variety of muscle phenotypes that range from mild to severe, including the prominent Limb-Girdle Muscular Dystrophy type 2B [LGMD2B; OMIM 253601; [1]] and Miyoshi Myopathy Electron microscopy analysis of muscle biopsies from LGMD2B or MM patients reveals numerous structural membrane defects such as disruption of the plasma membrane, alterations in the basal lamina and subsarcolemmal accumulation of vesicles [3]. Both naturally occurring and genetically engineered murine models of dysferlin deficiency show dystrophic changes and loss of membrane integrity [4,5,6]. Restoring dysferlin in muscle alone is sufficient to mitigate the dystrophic phenotype [11] suggesting that the primary defect due to the absence of dysferlin lies within the muscle fibers themselves, and not in cells of the immune system
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call