title: In-frame dystrophin following exon 51-skipping improves muscle pathology and function in the exon 52-deficient mdx mouse.
abstract: A promising therapeutic approach for Duchenne muscular dystrophy (DMD) is exon skipping using antisense oligonucleotides (AOs). In-frame deletions of the hinge 3 region of the dystrophin protein, which is encoded by exons 50 and 51, are predicted to cause a variety of phenotypes. Here, we performed functional analyses of muscle in the exon 52-deleted mdx (mdx52) mouse, to predict the function of in-frame dystrophin following exon 51-skipping, which leads to a protein lacking most of hinge 3. A series of AOs based on phosphorodiamidate morpholino oligomers was screened by intramuscular injection into mdx52 mice. The highest splicing efficiency was generated by a two-oligonucleotide cocktail targeting both the 5' and 3' splice sites of exon 51. After a dose-escalation study, we systemically delivered this cocktail into mdx52 mice seven times at weekly intervals. This induced 20-30% of wild-type (WT) dystrophin expression levels in all muscles, and was accompanied by amelioration of the dystrophic pathology and improvement of skeletal muscle function. Because the structure of the restored in-frame dystrophin resembles human dystrophin following exon 51-skipping, our results are encouraging for the ongoing clinical trials for DMD. Moreover, the therapeutic dose required can provide a suggestion of the theoretical equivalent dose for humans.
authors.affiliation: Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Yoshitsugu
authors.initials: Y
authors.lastname: Aoki
authors.forename: Akinori
authors.initials: A
authors.lastname: Nakamura
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Yokota
authors.forename: Takashi
authors.initials: T
authors.lastname: Saito
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Okazawa
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Nagata
authors.forename: Shin'ichi
authors.initials: S
authors.lastname: Takeda
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D003402:Creatine Kinase / Q000097:blood; D016189:Dystrophin / Q000502:physiology*; D005091:Exons / Q000502:physiology*; D020869:Gene Expression Profiling; D015316:Genetic Therapy; D007124:Immunoenzyme Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology*; D020388:Muscular Dystrophy, Duchenne / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D020411:Oligonucleotide Array Sequence Analysis; D016376:Oligonucleotides, Antisense / Q000627:therapeutic use*; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D015415:Biomarkers; D016189:Dystrophin; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D003402:Creatine Kinase
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