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Comprehensive Physiology Jul 2015The dystrophin complex stabilizes the plasma membrane of striated muscle cells. Loss of function mutations in the genes encoding dystrophin, or the associated proteins,... (Review)
Review
The dystrophin complex stabilizes the plasma membrane of striated muscle cells. Loss of function mutations in the genes encoding dystrophin, or the associated proteins, trigger instability of the plasma membrane, and myofiber loss. Mutations in dystrophin have been extensively cataloged, providing remarkable structure-function correlation between predicted protein structure and clinical outcomes. These data have highlighted dystrophin regions necessary for in vivo function and fueled the design of viral vectors and now, exon skipping approaches for use in dystrophin restoration therapies. However, dystrophin restoration is likely more complex, owing to the role of the dystrophin complex as a broad cytoskeletal integrator. This review will focus on dystrophin restoration, with emphasis on the regions of dystrophin essential for interacting with its associated proteins and discuss the structural implications of these approaches.
Topics: Animals; Dystrophin; Dystrophin-Associated Proteins; Genetic Therapy; Humans; Muscular Dystrophies
PubMed: 26140716
DOI: 10.1002/cphy.c140048 -
Physiological Reviews Apr 2002The X-linked muscle-wasting disease Duchenne muscular dystrophy is caused by mutations in the gene encoding dystrophin. There is currently no effective treatment for the... (Review)
Review
The X-linked muscle-wasting disease Duchenne muscular dystrophy is caused by mutations in the gene encoding dystrophin. There is currently no effective treatment for the disease; however, the complex molecular pathology of this disorder is now being unravelled. Dystrophin is located at the muscle sarcolemma in a membrane-spanning protein complex that connects the cytoskeleton to the basal lamina. Mutations in many components of the dystrophin protein complex cause other forms of autosomally inherited muscular dystrophy, indicating the importance of this complex in normal muscle function. Although the precise function of dystrophin is unknown, the lack of protein causes membrane destabilization and the activation of multiple pathophysiological processes, many of which converge on alterations in intracellular calcium handling. Dystrophin is also the prototype of a family of dystrophin-related proteins, many of which are found in muscle. This family includes utrophin and alpha-dystrobrevin, which are involved in the maintenance of the neuromuscular junction architecture and in muscle homeostasis. New insights into the pathophysiology of dystrophic muscle, the identification of compensating proteins, and the discovery of new binding partners are paving the way for novel therapeutic strategies to treat this fatal muscle disease. This review discusses the role of the dystrophin complex and protein family in muscle and describes the physiological processes that are affected in Duchenne muscular dystrophy.
Topics: Animals; Dystrophin; Humans; Muscle Proteins; Muscle, Skeletal; Muscular Dystrophies
PubMed: 11917091
DOI: 10.1152/physrev.00028.2001 -
Molecular Therapy : the Journal of the... Oct 2018Duchenne muscular dystrophy (DMD) is a lethal muscle disease caused by dystrophin gene mutation. Conceptually, replacing the mutated gene with a normal one would cure... (Review)
Review
Duchenne muscular dystrophy (DMD) is a lethal muscle disease caused by dystrophin gene mutation. Conceptually, replacing the mutated gene with a normal one would cure the disease. However, this task has encountered significant challenges due to the enormous size of the gene and the distribution of muscle throughout the body. The former creates a hurdle for viral vector packaging and the latter begs for whole-body therapy. To address these obstacles, investigators have invented the highly abbreviated micro-dystrophin gene and developed body-wide systemic gene transfer with adeno-associated virus (AAV). Numerous microgene configurations and various AAV serotypes have been explored in animal models in many laboratories. Preclinical data suggests that intravascular AAV micro-dystrophin delivery can significantly ameliorate muscle pathology, enhance muscle force, and attenuate dystrophic cardiomyopathy in animals. Against this backdrop, several clinical trials have been initiated to test the safety and tolerability of this promising therapy in DMD patients. While these trials are not powered to reach a conclusion on clinical efficacy, findings will inform the field on the prospects of body-wide DMD therapy with a synthetic micro-dystrophin AAV vector. This review discusses the history, current status, and future directions of systemic AAV micro-dystrophin therapy.
Topics: Dependovirus; Dystrophin; Genetic Therapy; Genetic Vectors; Humans; Muscle, Skeletal; Muscular Dystrophy, Duchenne
PubMed: 30093306
DOI: 10.1016/j.ymthe.2018.07.011 -
International Journal of Molecular... Feb 2022Duchenne muscular dystrophy (DMD) is an X-linked recessive neuromuscular disorder with a prevalence of approximately 1 in 3500-5000 males. DMD manifests as... (Review)
Review
Duchenne muscular dystrophy (DMD) is an X-linked recessive neuromuscular disorder with a prevalence of approximately 1 in 3500-5000 males. DMD manifests as childhood-onset muscle degeneration, followed by loss of ambulation, cardiomyopathy, and death in early adulthood due to a lack of functional dystrophin protein. Out-of-frame mutations in the dystrophin gene are the most common underlying cause of DMD. Gene editing via the clustered regularly interspaced short palindromic repeats (CRISPR) system is a promising therapeutic for DMD, as it can permanently correct DMD mutations and thus restore the reading frame, allowing for the production of functional dystrophin. The specific mechanism of gene editing can vary based on a variety of factors such as the number of cuts generated by CRISPR, the presence of an exogenous DNA template, or the current cell cycle stage. CRISPR-mediated gene editing for DMD has been tested both in vitro and in vivo, with many of these studies discussed herein. Additionally, novel modifications to the CRISPR system such as base or prime editors allow for more precise gene editing. Despite recent advances, limitations remain including delivery efficiency, off-target mutagenesis, and long-term maintenance of dystrophin. Further studies focusing on safety and accuracy of the CRISPR system are necessary prior to clinical translation.
Topics: Animals; CRISPR-Cas Systems; Disease Models, Animal; Dystrophin; Frameshift Mutation; Gene Editing; Humans; Male; Muscular Dystrophy, Duchenne; Reading Frames; Translational Research, Biomedical
PubMed: 35163754
DOI: 10.3390/ijms23031832 -
Science (New York, N.Y.) Oct 2018Mutations in the gene encoding dystrophin, a protein that maintains muscle integrity and function, cause Duchenne muscular dystrophy (DMD). The deltaE50-MD dog model of...
Mutations in the gene encoding dystrophin, a protein that maintains muscle integrity and function, cause Duchenne muscular dystrophy (DMD). The deltaE50-MD dog model of DMD harbors a mutation corresponding to a mutational "hotspot" in the human gene. We used adeno-associated viruses to deliver CRISPR gene editing components to four dogs and examined dystrophin protein expression 6 weeks after intramuscular delivery ( = 2) or 8 weeks after systemic delivery ( = 2). After systemic delivery in skeletal muscle, dystrophin was restored to levels ranging from 3 to 90% of normal, depending on muscle type. In cardiac muscle, dystrophin levels in the dog receiving the highest dose reached 92% of normal. The treated dogs also showed improved muscle histology. These large-animal data support the concept that, with further development, gene editing approaches may prove clinically useful for the treatment of DMD.
Topics: Adenoviridae; Animals; CRISPR-Cas Systems; Disease Models, Animal; Dogs; Dystrophin; Female; Gene Editing; Gene Transfer Techniques; Male; Muscular Dystrophy, Duchenne
PubMed: 30166439
DOI: 10.1126/science.aau1549 -
International Journal of Molecular... Aug 2022Duchenne muscular dystrophy (DMD) is the most common fatal muscle disease, with an estimated incidence of 1/3500-1/5000 male births, and it is associated with mutations...
Duchenne muscular dystrophy (DMD) is the most common fatal muscle disease, with an estimated incidence of 1/3500-1/5000 male births, and it is associated with mutations in the X-linked gene encoding dystrophin, the largest known human gene. There is currently no cure for DMD. The large size of the gene hampers exogenous gene addition and delivery. The genetic correction of DMD patient-derived induced pluripotent stem cells (DMD-iPSCs) and differentiation into suitable cells for transplantation is a promising autologous therapeutic strategy for DMD. In this study, using CRISPR/Cas9, the full-length dystrophin coding sequence was reconstructed in an exon-50-deleted DMD-iPSCs by the targeted addition of exon 50 at the junction of exon 49 and intron 49 via homologous-directed recombination (HDR), with a high targeting efficiency of 5/15, and the genetically corrected iPSCs were differentiated into cardiomyocytes (iCMs). Importantly, the full-length dystrophin expression and membrane localization were restored in genetically corrected iPSCs and iCMs. Thus, this is the first study demonstrating that full-length dystrophin can be restored in iPSCs and iCMs via targeted exon addition, indicating potential clinical prospects for DMD gene therapy.
Topics: Dystrophin; Exons; Humans; Induced Pluripotent Stem Cells; Male; Muscular Dystrophy, Duchenne; Myocytes, Cardiac
PubMed: 36012442
DOI: 10.3390/ijms23169176 -
Disease Models & Mechanisms Mar 2015Duchenne muscular dystrophy (DMD) is a progressive muscle-wasting disorder. It is caused by loss-of-function mutations in the dystrophin gene. Currently, there is no... (Review)
Review
Duchenne muscular dystrophy (DMD) is a progressive muscle-wasting disorder. It is caused by loss-of-function mutations in the dystrophin gene. Currently, there is no cure. A highly promising therapeutic strategy is to replace or repair the defective dystrophin gene by gene therapy. Numerous animal models of DMD have been developed over the last 30 years, ranging from invertebrate to large mammalian models. mdx mice are the most commonly employed models in DMD research and have been used to lay the groundwork for DMD gene therapy. After ~30 years of development, the field has reached the stage at which the results in mdx mice can be validated and scaled-up in symptomatic large animals. The canine DMD (cDMD) model will be excellent for these studies. In this article, we review the animal models for DMD, the pros and cons of each model system, and the history and progress of preclinical DMD gene therapy research in the animal models. We also discuss the current and emerging challenges in this field and ways to address these challenges using animal models, in particular cDMD dogs.
Topics: Animals; Cardiomyopathies; Disease Models, Animal; Dystrophin; Genetic Therapy; Muscular Dystrophy, Duchenne; Neurons
PubMed: 25740330
DOI: 10.1242/dmm.018424 -
Precise correction of Duchenne muscular dystrophy exon deletion mutations by base and prime editing.Science Advances Apr 2021Duchenne muscular dystrophy (DMD) is a fatal muscle disease caused by the lack of dystrophin, which maintains muscle membrane integrity. We used an adenine base editor...
Duchenne muscular dystrophy (DMD) is a fatal muscle disease caused by the lack of dystrophin, which maintains muscle membrane integrity. We used an adenine base editor (ABE) to modify splice donor sites of the dystrophin gene, causing skipping of a common DMD deletion mutation of exon 51 (∆Ex51) in cardiomyocytes derived from human induced pluripotent stem cells, restoring dystrophin expression. Prime editing was also capable of reframing the dystrophin open reading frame in these cardiomyocytes. Intramuscular injection of ∆Ex51 mice with adeno-associated virus serotype-9 encoding ABE components as a split-intein trans-splicing system allowed gene editing and disease correction in vivo. Our findings demonstrate the effectiveness of nucleotide editing for the correction of diverse DMD mutations with minimal modification of the genome, although improved delivery methods will be required before these strategies can be used to sufficiently edit the genome in patients with DMD.
Topics: Animals; CRISPR-Cas Systems; Dystrophin; Exons; Gene Editing; Humans; Induced Pluripotent Stem Cells; Mice; Muscular Dystrophy, Duchenne; Sequence Deletion
PubMed: 33931459
DOI: 10.1126/sciadv.abg4910 -
Journal of Neuromuscular Diseases 2022Duchenne muscular dystrophy (DMD) is a rare, genetic disease caused by mutations in the DMD gene resulting in an absence of functional dystrophin protein. Viltolarsen,... (Clinical Trial)
Clinical Trial
BACKGROUND
Duchenne muscular dystrophy (DMD) is a rare, genetic disease caused by mutations in the DMD gene resulting in an absence of functional dystrophin protein. Viltolarsen, an exon 53 skipping therapy, has been shown to increase endogenous dystrophin levels. Herein, long-term (>2 years) functional outcomes in viltolarsen treated patients were compared to a matched historical control group.
OBJECTIVE
To evaluate long-term efficacy and safety of the anti-sense oligonucleotide viltolarsen in the treatment of patients with DMD amenable to exon 53 skipping therapy.
METHODS
This trial (NCT03167255) is the extension of a previously published 24-week trial in North America (NCT02740972) that examined dystrophin levels, timed function tests compared to a matched historical control group (Cooperative International Neuromuscular Research Group Duchenne Natural History Study, CINRG DNHS), and safety in boys 4 to < 10 years (N = 16) with DMD amenable to exon 53 skipping who were treated with viltolarsen. Both groups were treated with glucocorticoids. All 16 participants elected to enroll in this long-term trial (up to 192 weeks) to continue evaluation of motor function and safety.
RESULTS
Time to stand from supine and time to run/walk 10 meters showed stabilization from baseline through week 109 for viltolarsen-treated participants whereas the historical control group showed decline (statistically significant differences for multiple timepoints). Safety was similar to that observed in the previous 24-week trial, which was predominantly mild. There have been no treatment-related serious adverse events and no discontinuations.
CONCLUSIONS
Based on these results at over 2 years, viltolarsen can be a new treatment option for patients with DMD amenable to exon 53 skipping.
Topics: Dystrophin; Humans; Male; Muscular Dystrophy, Duchenne; Oligonucleotides; Oligonucleotides, Antisense
PubMed: 35634851
DOI: 10.3233/JND-220811 -
Genome Biology 2001A unique arrangement of domains makes up the common region of two otherwise very different proteins - long, elegant dystrophin, and its rather dumpy distant cousin,... (Review)
Review
A unique arrangement of domains makes up the common region of two otherwise very different proteins - long, elegant dystrophin, and its rather dumpy distant cousin, dystrobrevin. The two work in concert, forming the core of a large membrane-bound complex in all metazoa. Like many proteins, dystrophin and dystrobrevin have diversified in the vertebrate clade, as have their binding partners, yielding specialized complexes tailored to different cellular and subcellular locations. Disruption of several components of the complex is known to result in syndromes that include progressive myopathy, sometimes combined with cognitive defects; the best known of these is Duchenne muscular dystrophy. Despite a wealth of biochemical, cell biological and genetic information, the precise role of dystrophins, dystrobrevins and their collaborators remains unclear.
Topics: Animals; Cytoskeletal Proteins; Dystrophin; Dystrophin-Associated Proteins; Evolution, Molecular; Genes; Humans; Membrane Proteins; Muscular Dystrophy, Duchenne; Mutation; Neuropeptides; Phylogeny
PubMed: 11305946
DOI: 10.1186/gb-2001-2-4-reviews3006