Abstract for presentation at 11th International Congress of Human Genetics

Antisense oligonucleotide induced dystrophin expression in mdx mouse cardiac cells

  • Mr Joshua Steinhaus, University of Western Australia, Australia
  • Sue Fletcher, University of Western Australia, Australia
  • Ms Kaite Honeyman, University of Western Australia, Australia
  • Prof Leonard Arnolda, University of Western Australia, Australia
  • Ms Penny Harding, University of Western Australia, Australia
  • Dr Douglas McKitrick, University of Western Australia, Australia
  • Dr Vasyl Holobotovskyy, University of Western Australia, Australia
  • A/Prof Steve Wilton, University of Western Australia, Australia

    • Purpose: Duchenne muscular dystrophy (DMD) is the most common, serious form of muscular dystrophy, affecting skeletal muscle, heart, smooth muscle and non-muscle tissues, and treatment options are limited. Patients who lack dystrophin in their muscles become non-ambulant by the age of 12 years and do not normally survive their third decade, succumbing to cardiac or respiratory complications. The potential of transcript manipulation using antisense oligonucleotides (AOs) to overcome disease-causing mutations has been demonstrated. Exclusion of an exon/s to remove a mutation or restore the reading frame during processing of the dystrophin primary transcript can result in the synthesis of functional protein. Systemic administration of AO analogues to the mdx mouse restored dystrophin expression in skeletal and smooth muscle, but not in cardiac muscle. We evaluated AO-induced dystrophin expression in cultured mdx mouse cardiomyocytes and in vivo.
    Methods: The mdx mouse has a nonsense mutation in exon 23 of the dystrophin gene. AO analogues, directed to the donor splice site of exon 23, were applied to cultured cardiomyocytes derived from neonatal mdx mice and were also injected into adult mice.
    Results: AO induced skipping of exon 23 induced a shortened, in-frame dystrophin transcript in cultured mdx mouse cardiac and skeletal muscle cells. However, the AOs were less effective in cardiac cells than in skeletal muscle cells in vitro. Administration of AO analogues to mdx mice showed that although phosphorodiamidate morpholino oligonucleotides (PMO) preparations are taken up by cardiac muscle, dystrophin expression was minimal.
    Conclusions: This suggests that the low efficacy of AO induced exon skipping in cardiac muscle, compared to skeletal muscle reflects differences in splicing mechanics in different tissues, rather than limitations in uptake of the AO by cardiac muscle. These issues are currently under further investigation.

    Conference Organiser - ICMS Pty Ltd