P17

Therapeutic research in dysferlinopathies: Progress in gene therapy

A Dangreaux(1) N Da Silva(1) O Ballouhey(1) S Courrier(1) M Bartoli(1,2)

1:Aix-Marseille University; 2:Inserm

Dysferlinopathies are rare degenerative genetic muscle diseases that exist in two main forms : the Miyoshi Myopathy and the LGMDR2 (2B). Both are caused by recessive mutations in the DYSF gene and are characterized by muscular weakness, atrophy, and high levels of creatine kinase in the blood. Dysferlin is a large transmembrane protein whose key function is membrane repair in muscle cells. There is currently no etiological treatment for patients, only supportive care. Fifteen years ago, a large homozygous deletion in the gene was observed in a female patient with a late onset presentation and very moderate dysferlinopathy. This mini-gene enables the production of a truncated but partially functional protein. Given the limited encapsidation capacity of AAVs, this mini-gene would enable a gene therapy approach with only the part of the gene required for membrane repair. Following the discovery of this patient, we compared different constructs in vitro with a laser wound membrane repair assay in dysferlin-deficient cells. We are now testing our most effective mini-gene in a pre-clinical gene therapy trial in a mouse model that has already been characterized. Eight-week-old dysferlin-deficient mice were injected intramuscularly and we are analyzing their muscle strength every months post-injection. We are also studying protein expression and localization, the histology of their quadriceps and the possible hepatotoxicity of our treatment. If these initial results are promising, we will repeat the trial using systemic administration method and a new vector.