CRISPR/Cas therapy tested in porcine DMD model

Duchenne muscular dystrophy (DMD) is the most common lethal inherited X-chromosomal muscular disease, occurring in one of 3,800–6,000 live male births. DMD is caused by loss-of-function mutations in the DMD gene (ca. 2.5 Mb, 79 exons) that lead to a shift in its reading frame, out-of-frame transcripts and loss of the essential muscle cytoskeletal protein dystrophin. The hotspots for mutations are in the regions of exons 3–7 and of exons 45–55. DMD is characterized by progressive muscle weakness and wasting: patients present first symptoms before the age of 5 years, lose ambulation around the age of 12 years and die of respiratory or heart failure in the second to fourth decade of life. A porcine DMD model developed at CiMM resembles a frequent human DMD mutation (loss of exon 52) and biochemical, clinical and pathological features of the human disease. In an interdisciplinary research team with scientists at TUM and HMGU, the team has for the first time succeeded in correcting the mutated DMD gene in living pigs. Using CRISPR/Cas delivered intramuscularly by adeno-associated viral vectors (AAV9-Cas9-gE51), DMD exon 51 was additionally deleted, resulting in expression of a shortened dystrophin (DMDΔ51–52) and improved skeletal muscle function. Moreover, systemic application of AAV9-Cas9-gE51 led to widespread dystrophin expression in muscle, including diaphragm and heart, prolonging survival and reducing arrhythmogenic vulnerability. The ability of Cas9-mediated exon excision to improve DMD pathology in this clinically severe large animal model paves the way for new treatment approaches in patients with this devastating disease. The same pig model has recently been used to validate detection of collagens by multispectral optoacoustic tomography as an imaging biomarker for progression of DMD (Regensburger et al., Nat Med 2019).

https://doi.org/10.1038/s41591-019-0738-2