A dystrophic Duchenne mouse model for testing human antisense oligonucleotides

Duchenne muscular dystrophy(DMD) is a severe muscle-wasting disease generally caused by reading framedisrupting mutations in the DMD gene resulting in loss of functional dystrophinprotein. The reading framecan be restored by antisense oligonucleotide (AON)-mediated exon skipping, allowing production of internally deleted, but partially functional dystrophinproteins as found in the less severe Becker muscular dystrophy. Due to genetic variation between species, mouse models with mutations in the murine genes are of limited use to test and further optimize human specific AONs in vivo. To address this we have generated the del52hDMD/ mdx mouse. This model carries both murine and human DMD genes. However, mouse dystrophinexpression is abolished due to a stop mutation in exon23, while the expression of human dystrophinis abolished due to a deletion of exon52. The del52hDMD/mdx model, like mdx, shows signs of muscle dystrophyon a histological level and phenotypically mild functional impairment. Local administration of human specific vivo morpholinosinduces exon skippingand dystrophinrestoration in these mice. Depending on the number of mismatches, occasional skipping of the murine Dmd gene, albeit at low levels, could be observed. Unlike previous models, the del52hDMD/mdx model enables the in vivo analysis of human specific AONs targeting exon51 or exon53 on RNA and protein level and muscle quality and function. Therefore, it will be a valuable tool for optimizing human specific AONs and genome editingapproaches for DMD.