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Myoediting: Towards a CRISPR/Cas9-based Treatment for DMD-associated Dilated Cardiomyopathy

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Review of “Correction of diverse muscular dystrophy mutations in human engineered heart muscle by single-site genome editing” from Science Advances by Stuart P. Atkinson

Dilated cardiomyopathy (DCM) represents one of the leading cause of death in patients with Duchenne muscular dystrophy (DMD) [1], a disorder caused by a wide range of mutational events in the X-linked Dystrophin (DMD) gene. The correction of these mutations via CRISPR/Cas9-gene editing could restore lost function to the affected cardiomyocytes (CMs); however, such an approach would require a correction strategy applicable to the wide range of mutational events associated with DMD.

Researchers from the laboratories of Chengzu Long and Eric N. Olson (University of Texas, USA) now report on a novel strategy to work past this problem and return lost function to DMD cardiomyocytes [2]: CRISPR/Cas9-mediated exon skipping, or as the authors have christened this new advance, myoediting. Previous studies demonstrated that skipping of specific exons can rescue dystrophin function in a majority of DMD patients [3] and now, Long et al. have established that myoediting can promote the expression of in-frame dystrophin proteins in CMs differentiated from DMD patient-derived induced pluripotent stem cells (iPSCs) [4]. 

The authors began their new study by screening for guide (g)RNAs that could abolish conserved RNA splice sites throughout the Dystrophin gene by introducing insertion/deletion mutations, thereby promoting the skipping of exons containing common mutations. They then applied this new myoediting approach to iPSCs generated by recombinant Sendai viral vectors expressing reprogramming factors and patient-derived peripheral blood mononuclear cells. 

Excitingly, myoediting of iPSCs carrying a large deletion mutation (exons 48 to 50), a pseudo-exon mutation (exon 47A), and a large duplication mutation (exons 55 to 59) led to the restored expression of in-frame dystrophin mRNA and Dystrophin protein in CMs differentiated from the corrected iPSCs. Even more excitingly, the study then confirmed that three-dimensional engineered heart muscle (EHM) constructed with corrected CMs displayed contractile behavior, suggesting that myoediting may represent a potentially exciting means to treat DCM in DMD patients.

To discover the future applications of myoediting, potentially including in vivo applications, stay tuned to the Stem Cells Portal!

References

  1. Fayssoil A, Nardi O, Orlikowski D, et al., Cardiomyopathy in Duchenne muscular dystrophy: pathogenesis and therapeutics. Heart Failure Reviews 2009;15:103.
  2. Aartsma-Rus A, Ginjaar IB, and Bushby K, The importance of genetic diagnosis for Duchenne muscular dystrophy. J Med Genet 2016;53:145-51.
  3. Aartsma-Rus A, Fokkema I, Verschuuren J, et al., Theoretic applicability of antisense-mediated exon skipping for Duchenne muscular dystrophy mutations. Human Mutation 2009;30:293-299.
  4. Long C, Li H, Tiburcy M, et al., Correction of diverse muscular dystrophy mutations in human engineered heart muscle by single-site genome editing. Science Advances 2018;4.