Abstract for presentation at 11th International Congress of Human Genetics

Making sense in spite of nonsense: a splice intervention therapy for Duchenne Muscular Dystrophy

  • A/Prof Steve Wilton, Australian Neuromuscular Research Institute, QE II Medical Centre, Nedlands, WA, Australia
  • Ms Abbie Fall, Australian Neuromuscular Research Institute, QE II Medical Centre, Nedlands, WA, Australia
  • Ms Penny Harding, Australian Neuromuscular Research Institute, QE II Medical Centre, Nedlands, WA, Australia
  • Mr Graham McClorey, Australian Neuromuscular Research Institute, QE II Medical Centre, Nedlands, WA, Australia
  • Mr Russell Johnsen, Australian Neuromuscular Research Institute, QE II Medical Centre, Nedlands, WA, Australia
  • Dr Patrick Iversen, AVI BioPharma, Corvallis, Oregon, United States
  • Dr Susan Fletcher, Australian Neuromuscular Research Institute, QE II Medical Centre, Nedlands, WA, Australia

    • Purpose: There is currently no effective treatment for Duchenne muscular dystrophy (DMD), the most common serious childhood form of muscle wasting. DMD arises from mutations which cause premature termination of translation in the dystrophin gene transcript. Becker muscular dystrophy also arises from dystrophin mutations, but the majority of these defects do not disrupt the reading frame, thereby allowing synthesis of a semi-functional protein. Substantial dystrophin coding regions may be lost with only minimal symptoms, unequivocally demonstrating considerable flexibility in which exons can be retained to direct production of a functional protein. This protein coding redundancy opens the possibility of splicing manipulation during pre-mRNA processing as a therapeutic intervention to address DMD mutations.
    Methods: Antisense oligonucleotides (AOs) have been designed to target splicing motifs across the human dystrophin pre-mRNA to induce a splicing blockade, thereby removing selected exons from the mature mRNA. Exons with nonsense mutations can be skipped, or exons flanking genomic deletions may be removed to restore the reading-frame. AO development was undertaken in vitro and in human muscle explants.
    Results: We have generated a panel of AOs capable of inducing skipping of over 65 exons within the human dystrophin gene transcript. Every exon targeted in vitro could be removed from the mature mRNA in a dose dependant and reproducable manner. No single splicing motif has been identified as a consistent amenable target.
    Conclusions: Preliminary studies in murine animal models have been more than encouraging, especially after morpholino AOs were administered systemically. Phase I and II clinical trials evaluating morpholino AOs to down-regulate expression of targeted genes through translation blockade have shown a high degree of safety. This available clinical data will be applied to Phase I trials being implemented to address common frame-shifting mutations responsible for DMD. Should splicing manipulation prove efficacious for an intractable disorder such as DMD, there is great potential for AO application to address many other conditions involving either aberrant or inappropriate alternative splicing.

    Conference Organiser - ICMS Pty Ltd