scholarly journals Mutation-Based Therapeutic Strategies for Duchenne Muscular Dystrophy: From Genetic Diagnosis to Therapy

2019 ◽  
Vol 9 (1) ◽  
pp. 16 ◽  
Author(s):  
Akinori Nakamura
Keyword(s):  
Muscular Dystrophy ◽  
Single Gene ◽  
Genetic Diagnosis ◽  
Exon Skipping ◽  
Becker Muscular Dystrophy ◽  
Therapeutic Strategies ◽  
Severe Phenotype ◽  
Reading Frame ◽  
Dystrophin Expression ◽  
Dmd Gene

Duchenne and Becker muscular dystrophy (DMD/BMD) are X-linked muscle disorders caused by mutations of the DMD gene, which encodes the subsarcolemmal protein dystrophin. In DMD, dystrophin is not expressed due to a disruption in the reading frame of the DMD gene, resulting in a severe phenotype. Becker muscular dystrophy exhibits a milder phenotype, having mutations that maintain the reading frame and allow for the production of truncated dystrophin. To date, various therapeutic approaches for DMD have been extensively developed. However, the pathomechanism is quite complex despite it being a single gene disorder, and dystrophin is expressed not only in a large amount of skeletal muscle but also in cardiac, vascular, intestinal smooth muscle, and nervous system tissue. Thus, the most appropriate therapy would be complementation or restoration of dystrophin expression, such as gene therapy using viral vectors, readthrough therapy, or exon skipping therapy. Among them, exon skipping therapy with antisense oligonucleotides can restore the reading frame and yield the conversion of a severe phenotype to one that is mild. In this paper, I present the significance of molecular diagnosis and the development of mutation-based therapeutic strategies to complement or restore dystrophin expression.

scholarly journals Genotype–Phenotype Correlations in Duchenne and Becker Muscular Dystrophy Patients from the Canadian Neuromuscular Disease Registry

2020 ◽  
Vol 10 (4) ◽  
pp. 241
Author(s):  
Kenji Rowel Q. Lim ◽  
Quynh Nguyen ◽  
Toshifumi Yokota
Keyword(s):  
Muscular Dystrophy ◽  
Neuromuscular Disease ◽  
Becker Muscular Dystrophy ◽  
Neuromuscular Disorder ◽  
Test Results ◽  
Disease Registry ◽  
Reading Frame ◽  
Negative Results ◽  
Genetic Test Results ◽  
Dmd Gene

Duchenne muscular dystrophy (DMD) is a fatal neuromuscular disorder generally caused by out-of-frame mutations in the DMD gene. In contrast, in-frame mutations usually give rise to the milder Becker muscular dystrophy (BMD). However, this reading frame rule does not always hold true. Therefore, an understanding of the relationships between genotype and phenotype is important for informing diagnosis and disease management, as well as the development of genetic therapies. Here, we evaluated genotype–phenotype correlations in DMD and BMD patients enrolled in the Canadian Neuromuscular Disease Registry from 2012 to 2019. Data from 342 DMD and 60 BMD patients with genetic test results were analyzed. The majority of patients had deletions (71%), followed by small mutations (17%) and duplications (10%); 2% had negative results. Two deletion hotspots were identified, exons 3–20 and exons 45–55, harboring 86% of deletions. Exceptions to the reading frame rule were found in 13% of patients with deletions. Surprisingly, C-terminal domain mutations were associated with decreased wheelchair use and increased forced vital capacity. Dp116 and Dp71 mutations were also linked with decreased wheelchair use, while Dp140 mutations significantly predicted cardiomyopathy. Finally, we found that 12.3% and 7% of DMD patients in the registry could be treated with FDA-approved exon 51- and 53-skipping therapies, respectively.

scholarly journals Exon skipping induced by nonsense/frameshift mutations in DMD gene results in Becker muscular dystrophy

2020 ◽  
Vol 139 (2) ◽  
pp. 247-255 ◽  
Author(s):  
Mariko Okubo ◽  
Satoru Noguchi ◽  
Shinichiro Hayashi ◽  
Harumasa Nakamura ◽  
Hirofumi Komaki ◽  
...  
Keyword(s):  
Duchenne Muscular Dystrophy ◽  
Muscular Dystrophy ◽  
Nonsense Mutation ◽  
Frameshift Mutation ◽  
Exon Skipping ◽  
Becker Muscular Dystrophy ◽  
Intronic Sequence ◽  
Frameshift Mutations ◽  
Dmd Gene ◽  
Accurate Quantification

AbstractDuchenne muscular dystrophy (DMD) is caused by a nonsense or frameshift mutation in the DMD gene, while its milder form, Becker muscular dystrophy (BMD) is caused by an in-frame deletion/duplication or a missense mutation. Interestingly, however, some patients with a nonsense mutation exhibit BMD phenotype, which is mostly attributed to the skipping of the exon containing the nonsense mutation, resulting in in-frame deletion. This study aims to find BMD cases with nonsense/frameshift mutations in DMD and to investigate the exon skipping rate of those nonsense/frameshift mutations. We searched for BMD cases with nonsense/frameshift mutations in DMD in the Japanese Registry of Muscular Dystrophy. For each DMD mutation identified, we constructed minigene plasmids containing one exon with/without a mutation and its flanking intronic sequence. We then introduced them into HeLa cells and measured the skipping rate of transcripts of the minigene by RT-qPCR. We found 363 cases with a nonsense/frameshift mutation in DMD gene from a total of 1497 dystrophinopathy cases in the registry. Among them, 14 had BMD phenotype. Exon skipping rates were well correlated with presence or absence of dystrophin, suggesting that 5% exon skipping rate is critical for the presence of dystrophin in the sarcolemma, leading to milder phenotypes. Accurate quantification of the skipping rate is important in understanding the exact functions of the nonsense/frameshift mutations in DMD and for interpreting the phenotypes of the BMD patients.

scholarly journals The lncRNA 44s2 Study Applicability to the Design of 45-55 Exon Skipping Therapeutic Strategy for DMD

Biomedicines ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 219
Author(s):  
Elena Gargaun ◽  
Sestina Falcone ◽  
Guilhem Solé ◽  
Julien Durigneux ◽  
Andoni Urtizberea ◽  
...  
Keyword(s):  
Muscular Dystrophy ◽  
Gene Mutations ◽  
Exon Skipping ◽  
Becker Muscular Dystrophy ◽  
Protein Stabilization ◽  
Progressive Muscular Dystrophy ◽  
Dilatative Cardiomyopathy ◽  
Proliferation And Differentiation ◽  
Dmd Gene ◽  
Dystrophin Protein

In skeletal muscle, long noncoding RNAs (lncRNAs) are involved in dystrophin protein stabilization but also in the regulation of myocytes proliferation and differentiation. Hence, they could represent promising therapeutic targets and/or biomarkers for Duchenne and Becker muscular dystrophy (DMD/BMD). DMD and BMD are X-linked myopathies characterized by a progressive muscular dystrophy with or without dilatative cardiomyopathy. Two-thirds of DMD gene mutations are represented by deletions, and 63% of patients carrying DMD deletions are eligible for 45 to 55 multi-exons skipping (MES), becoming BMD patients (BMDΔ45-55). We analyzed the genomic lncRNA presence in 38 BMDΔ45-55 patients and characterized the lncRNA localized in introns 44 and 55 of the DMD gene. We highlighted that all four lncRNA are differentially expressed during myogenesis in immortalized and primary human myoblasts. In addition, the lncRNA44s2 was pointed out as a possible accelerator of differentiation. Interestingly, lncRNA44s expression was associated with a favorable clinical phenotype. These findings suggest that lncRNA44s2 could be involved in muscle differentiation process and become a potential disease progression biomarker. Based on these results, we support MES45-55 therapy and propose that the design of the CRISPR/Cas9 MES45-55 assay consider the lncRNA sequences bordering the exonic 45 to 55 deletion.

scholarly journals Advances in Genetic Characterization and Genotype–Phenotype Correlation of Duchenne and Becker Muscular Dystrophy in the Personalized Medicine Era

2020 ◽  
Vol 10 (3) ◽  
pp. 111 ◽  
Author(s):  
Omar Sheikh ◽  
Toshifumi Yokota
Keyword(s):  
Muscular Dystrophy ◽  
Personalized Medicine ◽  
Genetic Diagnosis ◽  
Exon Skipping ◽  
Dystrophin Gene ◽  
Becker Muscular Dystrophy ◽  
Phenotype Correlation ◽  
Related Condition ◽  
Genotype Phenotype Correlation ◽  
Dystrophin Protein

Currently, Duchenne muscular dystrophy (DMD) and the related condition Becker muscular dystrophy (BMD) can be usually diagnosed using physical examination and genetic testing. While BMD features partially functional dystrophin protein due to in-frame mutations, DMD largely features no dystrophin production because of out-of-frame mutations. However, BMD can feature a range of phenotypes from mild to borderline DMD, indicating a complex genotype–phenotype relationship. Despite two mutational hot spots in dystrophin, mutations can arise across the gene. The use of multiplex ligation amplification (MLPA) can easily assess the copy number of all exons, while next-generation sequencing (NGS) can uncover novel or confirm hard-to-detect mutations. Exon-skipping therapy, which targets specific regions of the dystrophin gene based on a patient’s mutation, is an especially prominent example of personalized medicine for DMD. To maximize the benefit of exon-skipping therapies, accurate genetic diagnosis and characterization including genotype–phenotype correlation studies are becoming increasingly important. In this article, we present the recent progress in the collection of mutational data and optimization of exon-skipping therapy for DMD/BMD.

scholarly journals New Approach for Antisense Oligonucleotide-Mediated Exon Skipping in Duchenne Muscular Dystrophy

2012 ◽  
Vol 16 (4) ◽  
pp. 521-526
Author(s):  
Yoshitsugu Aoki ◽  
◽  
Tetsuya Nagata ◽  
Shin’ichi Takeda
Keyword(s):  
Duchenne Muscular Dystrophy ◽  
Muscular Dystrophy ◽  
Antisense Oligonucleotide ◽  
Antisense Oligonucleotides ◽  
Exon Skipping ◽  
New Approach ◽  
Reading Frame ◽  
Promising Therapeutic Approach ◽  
Dmd Gene ◽  
Dystrophin Protein

Duchenne Muscular Dystrophy (DMD) is a lethalmuscle disorder characterized by mutations in the DMD gene. These mutations primarily disrupt the reading frame, resulting in the absence of functional dystrophin protein. Exon skipping, which involves the use of antisense oligonucleotides is a promising therapeutic approach for DMD, and clinical trials on exon skipping are currently underway in DMD patients. Recently, stable and less-toxic antisense oligonucleotides with higher efficacy have been developed in mouse and dog models of DMD. This review highlights a new approach for antisense oligonucleotide-based therapeutics for DMD, particularly for exon skipping-based methods.

scholarly journals Multiple Exon Skipping in the Duchenne Muscular Dystrophy Hot Spots: Prospects and Challenges

2018 ◽  
Vol 8 (4) ◽  
pp. 41 ◽  
Author(s):  
Yusuke Echigoya ◽  
Kenji Rowel Q. Lim ◽  
Akinori Nakamura ◽  
Toshifumi Yokota
Keyword(s):  
Duchenne Muscular Dystrophy ◽  
Muscular Dystrophy ◽  
Exon Skipping ◽  
Becker Muscular Dystrophy ◽  
Therapeutic Modality ◽  
Therapeutic Concept ◽  
Patient Registration ◽  
Potential Therapeutic Application ◽  
Dmd Gene ◽  
Retrospective Database

Duchenne muscular dystrophy (DMD), a fatal X-linked recessive disorder, is caused mostly by frame-disrupting, out-of-frame deletions in the dystrophin (DMD) gene. Antisense oligonucleotide-mediated exon skipping is a promising therapy for DMD. Exon skipping aims to convert out-of-frame mRNA to in-frame mRNA and induce the production of internally-deleted dystrophin as seen in the less severe Becker muscular dystrophy. Currently, multiple exon skipping has gained special interest as a new therapeutic modality for this approach. Previous retrospective database studies represented a potential therapeutic application of multiple exon skipping. Since then, public DMD databases have become more useful with an increase in patient registration and advances in molecular diagnosis. Here, we provide an update on DMD genotype-phenotype associations using a global DMD database and further provide the rationale for multiple exon skipping development, particularly for exons 45–55 skipping and an emerging therapeutic concept, exons 3–9 skipping. Importantly, this review highlights the potential of multiple exon skipping for enabling the production of functionally-corrected dystrophin and for treating symptomatic patients not only with out-of-frame deletions but also those with in-frame deletions. We will also discuss prospects and challenges in multiple exon skipping therapy, referring to recent progress in antisense chemistry and design, as well as disease models.

scholarly journals High-Throughput Digital Image Analysis Reveals Distinct Patterns of Dystrophin Expression in Dystrophinopathy Patients

2021 ◽  
Author(s):  
Silvia Torelli ◽  
Domenic Scaglioni ◽  
Valentina Sardone ◽  
Matthew J Ellis ◽  
Joana Domingos ◽  
...  
Keyword(s):  
Image Analysis ◽  
Muscular Dystrophy ◽  
High Throughput ◽  
Expression Patterns ◽  
Becker Muscular Dystrophy ◽  
Clear Understanding ◽  
Incurable Disease ◽  
Dystrophin Expression ◽  
Dmd Gene ◽  
Muscle Biopsies

Abstract Duchenne muscular dystrophy (DMD) is an incurable disease caused by out-of-frame DMD gene deletions while in frame deletions lead to the milder Becker muscular dystrophy (BMD). In the last decade several antisense oligonucleotides drugs have been developed to induce a partially functional internally deleted dystrophin, similar to that produced in BMD, and expected to ameliorate the disease course. The pattern of dystrophin expression and functionality in dystrophinopathy patients is variable due to multiple factors, such as molecular functionality of the dystrophin and its distribution. To benchmark the success of therapeutic intervention, a clear understanding of dystrophin expression patterns in dystrophinopathy patients is vital. Recently, several groups have used innovative techniques to quantify dystrophin in muscle biopsies of children but not in patients with milder BMD. This study reports on dystrophin expression using both Western blotting and an automated, high-throughput, image analysis platform in DMD, BMD, and intermediate DMD/BMD skeletal muscle biopsies. Our results found a significant correlation between Western blot and immunofluorescent quantification indicating consistency between the different methodologies. However, we identified significant inter- and intradisease heterogeneity of patterns of dystrophin expression in patients irrespective of the amount detected on blot, due to variability in both fluorescence intensity and dystrophin sarcolemmal circumference coverage. Our data highlight the heterogeneity of the pattern of dystrophin expression in BMD, which will assist the assessment of dystrophin restoration therapies.

scholarly journals Effects of Chronic, Maximal Phosphorodiamidate Morpholino Oligomer (PMO) Dosing on Muscle Function and Dystrophin Restoration in a Mouse Model of Duchenne Muscular Dystrophy

2021 ◽  
pp. 1-13
Author(s):  
Margaret E. Benny Klimek ◽  
Maria Candida Vila ◽  
Katie Edwards ◽  
Jessica Boehler ◽  
James Novak ◽  
...  
Keyword(s):  
Duchenne Muscular Dystrophy ◽  
Muscular Dystrophy ◽  
Muscle Function ◽  
Imaging Techniques ◽  
Exon Skipping ◽  
Becker Muscular Dystrophy ◽  
Mdx Mice ◽  
High Dose ◽  
Combination Treatments ◽  
Dystrophin Expression

Background: Phosphorodiamidate morpholino oligomer (PMO)-mediated exon skipping is currently used in clinical development to treat Duchenne muscular dystrophy (DMD), with four exon-skipping drugs achieving regulatory approval. Exon skipping elicits a truncated, but semi-functional dystrophin protein, similar to the truncated dystrophin expressed in patients with Becker Muscular dystrophy (BMD) where the disease phenotype is less severe than DMD. Despite promising results in both dystrophic animal models and DMD boys, restoration of dystrophin by exon skipping is highly variable, leading to contradictory functional outcomes in clinical trials. Objective: To develop optimal PMO dosing protocols that result in increased dystrophin and improved outcome measures in preclinical models of DMD. Methods: Tested effectiveness of multiple chronic, high dose PMO regimens using biochemical, histological, molecular, and imaging techniques in mdx mice. Results: A chronic, monthly regimen of high dose PMO increased dystrophin rescue in mdx mice and improved specific force in the extensor digitorum longus (EDL) muscle. However, monthly high dose PMO administration still results in variable dystrophin expression localized throughout various muscles. Conclusions: High dose monthly PMO administration restores dystrophin expression and increases muscle force; however, the variability of dystrophin expression at both the inter-and intramuscular level remains. Additional strategies to optimize PMO uptake including increased dosing frequencies or combination treatments with other yet-to-be-defined therapies may be necessary to achieve uniform dystrophin restoration and increases in muscle function.

Systemic administration of the antisense oligonucleotide NS-065/NCNP-01 for skipping of exon 53 in patients with Duchenne muscular dystrophy

2018 ◽  
Vol 10 (437) ◽  
pp. eaan0713 ◽  
Author(s):  
Hirofumi Komaki ◽  
Tetsuya Nagata ◽  
Takashi Saito ◽  
Satoru Masuda ◽  
Eri Takeshita ◽  
...  
Keyword(s):  
Clinical Trial ◽  
Duchenne Muscular Dystrophy ◽  
Muscular Dystrophy ◽  
Muscle Protein ◽  
Phase 1 ◽  
Exon Skipping ◽  
Muscle Disease ◽  
Dependent Manner ◽  
Reading Frame ◽  
Dystrophin Expression

Duchenne muscular dystrophy (DMD) is a lethal hereditary muscle disease caused by mutations in the gene encoding the muscle protein dystrophin. These mutations result in a shift in the open reading frame leading to loss of the dystrophin protein. Antisense oligonucleotides (ASOs) that induce exon skipping correct this frame shift during pre-mRNA splicing and partially restore dystrophin expression in mouse and dog models. We conducted a phase 1, open-label, dose-escalation clinical trial to determine the safety, pharmacokinetics, and activity of NS-065/NCNP-01, a morpholino ASO that enables skipping of exon 53. Ten patients with DMD (6 to 16 years old), carrying mutations in the dystrophin gene whose reading frame would be restored by exon 53 skipping, were administered NS-065/NCNP-01 at doses of 1.25, 5, or 20 mg/kg weekly for 12 weeks. The primary endpoint was safety; the secondary endpoints were pharmacokinetics and successful exon skipping. No severe adverse drug reactions were observed, and no treatment discontinuation occurred. Muscle biopsy samples were taken before and after treatment and compared by reverse transcription polymerase chain reaction (RT-PCR), immunofluorescence, and Western blotting to assess the amount of exon 53 skipping and dystrophin expression. NS-065/NCNP-01 induced exon 53 skipping in dystrophin-encoding mRNA in a dose-dependent manner and increased the dystrophin/spectrin ratio in 7 of 10 patients. Furthermore, the amount of exon skipping correlated with the maximum drug concentration in plasma (Cmax) and the area under the concentration-time curve in plasma (AUC0-t). These results indicate that NS-065/NCNP-01 has a favorable safety profile and promising pharmacokinetics warranting further study in a phase 2 clinical trial.

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