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Paper of the Month

May 2020

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Somatic gene editing ameliorates skeletal and cardiac muscle failure in pig and human models of Duchenne muscular dystrophy. Nature Medicine, DZHK authors: A. Moretti, P. Hoppmann, A. B. Meier, T. Bozoglu, A. Baehr, C. M. Schneider, D. Sinnecker, K. Klett, F. Abdel Rahman, T. Haufe, S. Sun , V. Jurisch, R. Hinkel, R. Dirschinger, E. Martens, C. Jilek, G. Santamaria, B. Campbell, A. Wolf, T. Ziegler, S. Lee, T. Dorn, A. Dendorfer, K. L. Laugwitz, E. Wolf, and C. Kupatt

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Duchenne muscular dystrophy (DMD) represents the most frequent hereditary childhood myopathy, leading to progressive muscle degeneration and weakness, and to premature death due to respiratory and cardiac failure. The X-chromosomal location of DMD renders 1 in 3,500 to 5,000 male newborns affected.

The vast majority of patients carry frameshift mutations in the DMD gene encoding dystrophin (DMD), which are mainly exon deletions. Recently, Crispr/Cas9-based gene editing strategies have demonstrated an efficient and permanent genomic correction in murine mdx models. Moreover, intravenous (i.v.) application of AAV9 delivering CRISPR/Cas9 components in a beagle model of DMD (exon 50 deficiency) proved successful in restoring expression of a shortened dystrophin in various muscles, including the heart. However, functional data have not been reported as of yet.

In a consortium of DZHK-scientists from Internal Medicine at TUM as well as LMU and Helmholtz-Munich, pigs of a transgenic strain lacking dystrophin exon 52 were investigated with regard to skeletal muscle function and electrophysiological stability of the heart. The researchers were able to demonstrate that a systemic infusion of AAV9-Crispr-Cas9 combined with appropriate guide RNAs sufficed to express a shortened, but stable dystrophin in many muscles, including the diaphragm and heart.

Moreover, high-resolution electrophysiological mapping in the diseased pigs, which died of sudden cardiac death no later than 105 days after birth, revealed a large area of vulnerable myocardium. This area was found reduced by the AAV9-Cas9-gRNA treatment, extending life span of the treatment group significantly. Consistently, human iPS-derived cardiomyocytes subjected to analogous AAV6-Cas9-gRNA transduction demonstrated dystrophin expression combined with a normalization of calcium handling. These findings demonstrate in preclinical large animal experiments,  that gene editing by Crispr-Cas9 in DMD is capable of inducing dystrophin expression, and improving heart and skeletal muscle functions.