Duchenne muscular dystrophy (DMD) is a fatal X-linked muscle-wasting disorder caused by protein truncating mutations in the dystrophin gene. Antisense oligomer induced removal of an exon carrying a nonsense mutation, or exons flanking frame-shifting deletions, the most common type of DMD mutation, has been shown to generate an in-frame message and an internally deleted, but functional protein. Becker muscular dystrophy (BMD) is an allelic disorder typically caused by in-frame deletions of one or more exons, most commonly in the first two thirds of the gene. The severity of BMD varies from borderline DMD to asymptomatic, and the dystrophin genes in mildly affected BMD patients provide an indication of functional exon combinations. At least one third of DMD cases result from duplications, micro-insertions/deletions and single base changes that alter splice site recognition or cause premature termination of translation. This project will address the design and application of antisense oligomers for induced exon skipping, for those DMD cases caused by non-deletion mutations. Patient cell lines will be transfected with test compounds and exon skipping assessed. Exon skipping strategies will be modified to maximize induced dystrophin quality and quantity, as permitted by the context of each particular dystrophin gene lesion.
The specific aims are to: 7 Optimise antisense oligomers to remove exons carrying sequence variations (disease-causing or neutral polymorphims) that would otherwise compromise exon skipping. 7 Develop exon skipping strategies appropriate to DMD cases caused by pseudo-exon incorporation or duplications of one or more exons. 7 Develop transient animal models to identify functionally significant dystrophin domains, according to exon boundaries, to facilitate design of optimal exon skipping strategies.
Duchenne muscular dystrophy is a relentlessly progressive, fatal disease for which there is no effective treatment. Specific exon removal has the potential to greatly reduce the severity of DMD, and restoration of dystrophin expression, even of partial function in a DMD patient is expected to result in a BMD-like phenotype, and reduce morbidity and extend life expectancy. This application seeks to develop personalised exon skipping therapies for the one third of DMD patients who have non-deletion mutations. Exon skipping should be made available to all patients who could benefit, not only those with the more common exon deletion mutations.
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