Asymptomatic Becker muscular dystrophy in a family with a multiexon deletion

Ferreiro, Verónica; Giliberto, Florencia; Muñiz, García M. Noelia; Francipane, Liliana; Marzese, Diego M.; Mampel, Alejandra; Roqué, María; Frechtel, Gustavo Daniel; Szijan, Irene

doi:10.1002/mus.21193

Cited by 53 publications

(46 citation statements)

References 12 publications

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“…First, it would be applicable to ∼63% of DMD patients with dystrophin deletion mutations (13). Second, the majority of individuals with a deletion of exons 45-55 of the DMD gene fall into the category of BMD patients with exceptionally mild, sometimes almost asymptomatic skeletal muscle involvement (12,13 (19). Such observations raise the hope that antisensemediated exon 45-55 skipping will have the potential not only to convert DMD patients to a mild BMD clinical phenotype but also to ameliorate the condition of some of the more severe BMD patients with mutations within the exon 45-55 hotspot region.…”

Section: Discussionmentioning

confidence: 99%

Bodywide skipping of exons 45–55 in dystrophic mdx52 mice by systemic antisense delivery

Aoki

Yokota

Nagata

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

142

124

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Duchenne muscular dystrophy (DMD), the commonest form of muscular dystrophy, is caused by lack of dystrophin. One of the most promising therapeutic approaches is antisense-mediated elimination of frame-disrupting mutations by exon skipping. However, this approach faces two major hurdles: limited applicability of each individual target exon and uncertain function and stability of each resulting truncated dystrophin. Skipping of exons 45-55 at the mutation hotspot of the DMD gene would address both issues. Theoretically it could rescue more than 60% of patients with deletion mutations. Moreover, spontaneous deletions of this specific region are associated with asymptomatic or exceptionally mild phenotypes. However, such multiple exon skipping of exons 45-55 has proved technically challenging. We have therefore designed antisense oligo (AO) morpholino mixtures to minimize self-or heteroduplex formation. These were tested as conjugates with cell-penetrating moieties (vivo-morpholinos). We have tested the feasibility of skipping exons 45-55 in H2K-mdx52 myotubes and in mdx52 mice, which lack exon 52. Encouragingly, with mixtures of 10 AOs, we demonstrated skipping of all 10 exons in vitro, in H2K-mdx52 myotubes and on intramuscular injection into mdx52 mice. Moreover, in mdx52 mice in vivo, systemic injections of 10 AOs induced extensive dystrophin expression at the subsarcolemma in skeletal muscles throughout the body, producing up to 15% of wild-type dystrophin protein levels, accompanied by improved muscle strength and histopathology without any detectable toxicity. This is a unique successful demonstration of effective rescue by exon 45-55 skipping in a dystrophin-deficient animal model. personalized medicine | nucleic acid therapy | molecular therapy | oligonucleotides | gene therapy D uchenne muscular dystrophy (DMD), the commonest form of muscular dystrophy, is characterized by progressive deterioration of muscle function (1). DMD is caused mainly by frame-shifting deletion or nonsense mutations in the DMD gene, which encodes the protein dystrophin (2). At the milder end of the disease spectrum, Becker muscular dystrophy (BMD) is a form of dystrophin deficiency that presents with a large spectrum of severities, from borderline DMD to almost asymptomatic cases. BMD typically results from in-frame deletions in the DMD gene that allow the expression of limited amounts of an internally truncated but partly functional protein (3).Skipping of exons in DMD muscle so as to restore an in-frame and asymptomatic or very mild Becker-like transcript is among the more promising therapeutic approaches to treatment of DMD (4). To this end, systemic administration of antisense oligonucleotides (AOs) targeting specific exon(s) in the DMD gene has been shown to restore the reading frame and induce body-wide production of partially functional BMD-like dystrophin in mouse and dog models of DMD (5-7). Recently, phase I/II human clinical trials with AOs targeting exon 51 have been completed (8, 9).Although promising, future developm...

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Section: Discussionmentioning

confidence: 99%

Bodywide skipping of exons 45–55 in dystrophic mdx52 mice by systemic antisense delivery

Aoki

Yokota

Nagata

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

142

124

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“…DMD and BMD mutations differentially affect the DMD gene: in DMD the mutations disrupt the reading frame, while mutations that cause BMD maintain the ORF (31,32) leading to the production of an internally deleted dystrophin protein. The size of the deletion does not correlate with the severity of the disease, as long as the reading frame rule is maintained (33)(34)(35)(36)(37)(38)(39)(40), and provided crucial domains of dystrophin such as the β-dystroglycan binding site are not removed by the deletion. While the central and distal rod domain is less vital for function (35), (some patients missing these domains only have very mild disease manifestations such as myalgia and muscle cramps, and mild weakness), in frame deletions that affect the binding of dystrophin to other proteins such as cytoskeletal actin or β-dystroglycan result in a severe phenotype (41,42).…”

Section: Becker Muscular Dystrophymentioning

confidence: 99%

Antisense Oligonucleotide-Mediated Exon Skipping for Duchenne Muscular Dystrophy: Progress and Challenges

Arechavala‐Gomeza¹,

Anthony²,

Morgan³

et al. 2012

CGT

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Duchenne muscular dystrophy (DMD) is the most common childhood neuromuscular disorder. It is caused by mutations in the DMD gene that disrupt the open reading frame (ORF) preventing the production of functional dystrophin protein. The loss of dystrophin ultimately leads to the degeneration of muscle fibres, progressive weakness and premature death. Antisense oligonucleotides (AOs) targeted to splicing elements within DMD pre-mRNA can induce the skipping of targeted exons, restoring the ORF and the consequent production of a shorter but functional dystrophin protein. This approach may lead to an effective disease modifying treatment for DMD and progress towards clinical application has been rapid. Less than a decade has passed between the first studies published in 1998 describing the use of AOs to modify the DMD gene in mice and the results of the first intramuscular proof of concept clinical trials. Whilst phase II and III trials are now underway, the heterogeneity of DMD mutations, efficient systemic delivery and targeting of AOs to cardiac muscle remain significant challenges. Here we review the current status of AO-mediated therapy for DMD, discussing the pre-clinical, clinical and regulatory hurdles and their possible solutions to expedite the translation of AO-mediated exon skipping therapy to clinic.

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“…In addition, multi-exon skipping will enable us to select the deletion patterns that optimize the functionality of the shortened dystrophin proteins. For example, deletion of DMD exons 45 -55 is associated with exceptionally mild symptoms or asymptomatic individuals 14,19,[60][61][62][63] . The multi-exon skipping of exons 45 -55 has already been demonstrated in a mouse model of DMD with an exon 52 deletion (mdx52) using systemic injections of vPMOs 22,26 .…”

Section: Discussionmentioning

confidence: 99%

Multi-exon Skipping Using Cocktail Antisense Oligonucleotides in the Canine X-linked Muscular Dystrophy

Nichols

Aoki

Kuraoka

et al. 2016

JoVE

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Duchenne muscular dystrophy (DMD) is one of the most common lethal genetic diseases worldwide, caused by mutations in the dystrophin (DMD) gene. Exon skipping employs short DNA/RNA-like molecules called antisense oligonucleotides (AONs) that restore the reading frame and produce shorter but functional proteins. However, exon skipping therapy faces two major hurdles: limited applicability (up to only 13% of patients can be treated with a single AON drug), and uncertain function of truncated proteins. These issues were addressed with a cocktail AON approach. While approximately 70% of DMD patients can be treated by single exon skipping (all exons combined), one could potentially treat more than 90% of DMD patients if multiple exon skipping using cocktail antisense drugs can be realized. The canine X-linked muscular dystrophy (CXMD) dog model, whose phenotype is more similar to human DMD patients, was used to test the systemic efficacy and safety of multi-exon skipping of exons 6 and 8. The CXMD dog model harbors a splice site mutation in intron 6, leading to a lack of exon 7 in dystrophin mRNA. To restore the reading frame in CXMD requires multi-exon skipping of exons 6 and 8; therefore, CXMD is a good middle-sized animal model for testing the efficacy and safety of multi-exon skipping. In the current study, a cocktail of antisense morpholinos targeting exon 6 and exon 8 was designed and it restored dystrophin expression in body-wide skeletal muscles. Methods for transfection/injection of cocktail oligos and evaluation of the efficacy and safety of multi-exon skipping in the CXMD dog model are presented.

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Asymptomatic Becker muscular dystrophy in a family with a multiexon deletion

Cited by 53 publications

References 12 publications

Bodywide skipping of exons 45–55 in dystrophic mdx52 mice by systemic antisense delivery

Bodywide skipping of exons 45–55 in dystrophic mdx52 mice by systemic antisense delivery

Antisense Oligonucleotide-Mediated Exon Skipping for Duchenne Muscular Dystrophy: Progress and Challenges

Multi-exon Skipping Using Cocktail Antisense Oligonucleotides in the Canine X-linked Muscular Dystrophy

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