MG53 AAV Constructs as a Gene Therapy for Dysferlinopathies
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Abstract
Plasma membrane repair is a conserved cellular process that uses various mechanisms to restore the barrier function of the plasma membrane when it is disrupted. This allows the cell to survive injuries that would usually compromise membrane integrity and result in death of the cell. Compromised plasma membrane repair responses or reduced membrane integrity characterize several muscular dystrophies, including the dysferlinopathies produced by mutations in the dysferlin gene that is directly involved in the plasma membrane repair process. The mitsugumin 53 (MG53/TRIM72) protein is a binding partner for dysferlin that is also involved in cellular membrane repair. Protein supplementation therapy with MG53 has been shown to be efficacious in ameliorating muscle damage accumulated in dysferlinopathic cells and mouse models, however recent discoveries on potential off target effects raise concerns about use of MG53 protein as a therapeutic. Delivery of modified MG53 constructs via an adeno-associated virus (AAV) vector as a therapeutic for dysferlinopathies may avoid these challenges. Here, our AAV backbone and respective MG53 construct’s DNA sequence were ligated to produce three AAV constructs. The plasmid DNA segments were ligated and each construct was confirmed using AAV-ITR sequencing. Appropriate protein expression was verified via transfection into C2C12 cells and western blot analysis. Further, a ballistic damage assay was conducted in HEK293 cells to monitor cell membrane repair capabilities of the plasmid constructs. After confirmation of the plasmid sequences and function in membrane repair, our plasmid was sent to a collaborating lab for packaging into AAV particles. Future studies will treat 3–9-month-old dysferlin deficient mice with one of the three related AAV vectors encoding for a different version of the MG53 protein to resolve if treatment of dysferlin deficient mice lead to transgene expression, improved muscle contractile force generation and restoration of normal muscle histology.