Generation and characterization of a novel mouse model of Becker Muscular Dystrophy with a deletion of exons 52 to 55

Becker Muscular Dystrophy (BMD) is a rare X-linked recessive neuromuscular disorder caused by in-frame deletions in the DMD gene that result in the production of a truncated, yet functional, dystrophin protein. BMD is often considered a milder form of Duchenne Muscular Dystrophy, in which mutations typically result in the disruption of the reading frame and the malfunction or loss of dystrophin. The consequences of BMD-causing in-frame deletions on the organism are more difficult to predict, especially in regard to long-term prognosis. Here, we employed CRISPR-Cas9 technology to generate a new Dmd del52-55 mouse model by deleting exons 52-55, resulting in a typical BMD-like in-frame deletion. To delineate the long-term effects of this deletion, we studied these mice over 52 weeks. Our results suggest that a truncated dystrophin is sufficient to maintain wildtype-like muscle and heart functions in young mice. However, the truncated protein appears insufficient to maintain normal muscle homeostasis and protect against exercise-induced damage at 52 weeks. To further delineate the effects of the exons 52-55 in-frame deletion, we performed RNA-Seq pre- and post-exercise and identified several differentially expressed pathways that could explain the abnormal muscle phenotype observed at 52 weeks in the BMD model. Summary StatementWe generated and characterized the long-term effects of a Becker Muscular Dystrophy-like in-frame deletion of exon 52 to 55 in mice.