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Nat Med. 2017 Aug;23(8):984-989. doi: 10.1038/nm.4367. Epub 2017 Jul 17.

Correction of a splicing defect in a mouse model of congenital muscular dystrophy type 1A using a homology-directed-repair-independent mechanism.

Author information

Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, Canada.
Department of Molecular Genetics, University of Toronto, Canada.
Deep Genomics, Toronto, Canada.
The Centre for Applied Genomics (TCAG), The Hospital for Sick Children Research Institute, Toronto, Canada.
Department of Electrical and Computer Engineering and Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada.
Heart & Stroke Richard Lewar Centre of Excellence in Cardiovascular Research, Toronto, Canada.
Department of Pediatrics, University of Toronto and The Hospital for Sick Children, Toronto, Canada.


Splice-site defects account for about 10% of pathogenic mutations that cause Mendelian diseases. Prevalence is higher in neuromuscular disorders (NMDs), owing to the unusually large size and multi-exonic nature of genes encoding muscle structural proteins. Therapeutic genome editing to correct disease-causing splice-site mutations has been accomplished only through the homology-directed repair pathway, which is extremely inefficient in postmitotic tissues such as skeletal muscle. Here we describe a strategy using nonhomologous end-joining (NHEJ) to correct a pathogenic splice-site mutation. As a proof of principle, we focus on congenital muscular dystrophy type 1A (MDC1A), which is characterized by severe muscle wasting and paralysis. Specifically, we correct a splice-site mutation that causes the exclusion of exon 2 from Lama2 mRNA and the truncation of Lama2 protein in the dy2J/dy2J mouse model of MDC1A. Through systemic delivery of adeno-associated virus (AAV) carrying clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 genome-editing components, we simultaneously excise an intronic region containing the mutation and create a functional donor splice site through NHEJ. This strategy leads to the inclusion of exon 2 in the Lama2 transcript and restoration of full-length Lama2 protein. Treated dy2J/dy2J mice display substantial improvement in muscle histopathology and function without signs of paralysis.

[Indexed for MEDLINE]

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