G.P.78 Dystrophin isoforms with incomplete β dystroglycan and syntrophin binding domains retain partial function

Abstract

Duchenne muscular dystrophy (DMD) is an X-linked, relentlessly progressive muscle wasting disorder resulting from faulty production of the sub sarcolemmal protein, dystrophin. DMD has a predictable course and limited treatment options, with the majority of cases being caused by frame-shifting deletions of one or more of the 79 exons in the dystrophin gene, while deletions that do not disrupt the dystrophin reading frame generally cause the milder allelic disorder, Becker muscular dystrophy (BMD). Antisense oligomer (AO)-mediated splicing manipulation can remove specific exons during transcript processing and overcome DMD-causing dystrophin gene lesions to generate shorter, partially functional BMD-like dystrophin isoforms, and is showing promise as a therapy for DMD. Dystrophin gene structure in BMD patients with less severe phenotypes provides templates for potentially functional dystrophin isoforms. However, such mutations downstream of exon 55 are rare, and the probable consequences of AO-induced exon removal in this region are not known. We report that systemic administration of antisense phosphorodiamidate morpholino oligomer-cell penetrating peptide conjugates to wild-type C57BL/10ScSn mice can remove dystrophin exons to generate DMD- and BMD-like in vivo models for molecular, physiological and pathology evaluation. Exclusion of single exons and in-frame exon blocks, within the β dystroglycan and syntrophin binding domains, is helping to elucidate the relative importance of these regions to dystrophin function, and provide guidelines for the development of therapeutic exon skipping strategies.