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Cellular and Molecular Life Sciences :... Jun 2008New approaches to understanding and designing treatments for Duchenne muscular dystrophy (DMD) may emerge from two hypotheses outlined here. The proposal that growing... (Review)
Review
New approaches to understanding and designing treatments for Duchenne muscular dystrophy (DMD) may emerge from two hypotheses outlined here. The proposal that growing skeletal muscle is more susceptible to necrosis than adult muscle raises the possibility that less intensive treatments may be sufficient to protect muscles during the adult phase. The second proposal is that a different balance of cell and molecular events contributes to acute necrosis (e.g. resulting from exercise) compared with chronic damage of dystrophic muscle. Validation of such differences presents the potential for more specific targeting of drugs or nutritional interventions to events downstream of the dystrophin deficiency. A deeper understanding of the events arising as an early consequence of dystrophin deficiency in these two situations may strengthen approaches to therapy for DMD designed to improve muscle function and the quality of life.
Topics: Animals; Diet Therapy; Dystrophin; Humans; Muscle, Skeletal; Muscular Dystrophy, Duchenne
PubMed: 18327663
DOI: 10.1007/s00018-008-7574-8 -
Proceedings of the National Academy of... Oct 2015The 427-kDa protein dystrophin is expressed in striated muscle where it physically links the interior of muscle fibers to the extracellular matrix. A range of mutations...
The 427-kDa protein dystrophin is expressed in striated muscle where it physically links the interior of muscle fibers to the extracellular matrix. A range of mutations in the DMD gene encoding dystrophin lead to a severe muscular dystrophy known as Duchenne (DMD) or a typically milder form known as Becker (BMD). Patients with nonsense mutations in dystrophin are specifically targeted by stop codon read-through drugs, whereas out-of-frame deletions and insertions are targeted by exon-skipping therapies. Both treatment strategies are currently in clinical trials. Dystrophin missense mutations, however, cause a wide range of phenotypic severity in patients. The molecular and cellular consequences of such mutations are not well understood, and there are no therapies specifically targeting this genotype. Here, we have modeled two representative missense mutations, L54R and L172H, causing DMD and BMD, respectively, in full-length dystrophin. In vitro, the mutation associated with the mild phenotype (L172H) caused a minor decrease in tertiary stability, whereas the L54R mutation associated with a severe phenotype had a more dramatic effect. When stably expressed in mammalian muscle cells, the mutations caused steady-state decreases in dystrophin protein levels inversely proportional to the tertiary stability and directly caused by proteasomal degradation. Both proteasome inhibitors and heat shock activators were able to increase mutant dystrophin to WT levels, establishing the new cell lines as a platform to screen for potential therapeutics personalized to patients with destabilized dystrophin.
Topics: Animals; Blotting, Western; Cell Line; Dystrophin; Heat-Shock Proteins; Humans; Limonins; Muscle Fibers, Skeletal; Muscular Dystrophy, Duchenne; Mutation, Missense; Phenotype; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Protein Stability; Proteolysis; Reverse Transcriptase Polymerase Chain Reaction
PubMed: 26392559
DOI: 10.1073/pnas.1508755112 -
International Journal of Molecular... Dec 2020Dystrophin-deficient cardiomyopathy (DDC) is currently the leading cause of death in patients with dystrophinopathies. Targeting myocardial fibrosis (MF) has become a... (Review)
Review
Dystrophin-deficient cardiomyopathy (DDC) is currently the leading cause of death in patients with dystrophinopathies. Targeting myocardial fibrosis (MF) has become a major therapeutic goal in order to prevent the occurrence of DDC. We aimed to review and summarize the current evidence about the role of the renin-angiotensin-aldosterone system (RAAS) in the development and perpetuation of MF in DCC. We conducted a comprehensive search of peer-reviewed English literature on PubMed about this subject. We found increasing preclinical evidence from studies in animal models during the last 20 years pointing out a central role of RAAS in the development of MF in DDC. Local tissue RAAS acts directly mainly through its main fibrotic component angiotensin II (ANG2) and its transducer receptor (AT1R) and downstream TGF-b pathway. Additionally, it modulates the actions of most of the remaining pro-fibrotic factors involved in DDC. Despite limited clinical evidence, RAAS blockade constitutes the most studied, available and promising therapeutic strategy against MF and DDC. Conclusion: Based on the evidence reviewed, it would be recommendable to start RAAS blockade therapy through angiotensin converter enzyme inhibitors (ACEI) or AT1R blockers (ARBs) alone or in combination with mineralocorticoid receptor antagonists (MRa) at the youngest age after the diagnosis of dystrophinopathies, in order to delay the occurrence or slow the progression of MF, even before the detection of any cardiovascular alteration.
Topics: Animals; Cardiomyopathies; Dystrophin; Humans; Renin-Angiotensin System
PubMed: 33396334
DOI: 10.3390/ijms22010356 -
Annals of Neurology Aug 2022Duchenne muscular dystrophy is associated with various degrees of cognitive impairment and behavioral disturbances. Emotional and memory deficits also constitute...
OBJECTIVES
Duchenne muscular dystrophy is associated with various degrees of cognitive impairment and behavioral disturbances. Emotional and memory deficits also constitute reliable outcome measures to assess efficacy of treatments in the mdx mouse lacking the muscle and neuronal full-length dystrophins. The present study aimed to evaluate whether these deficits could be alleviated by the restoration of brain dystrophin.
METHODS
We performed intracerebroventricular administration of a new potent tricyclo-DNA antisense oligonucleotide (tcDNA-ASO) containing a full phosphodiester backbone conjugated to a palmitic acid moiety (tcDNA-ASO), designed to skip the mutated exon 23 of mdx mice.
RESULTS
We first show that the tcDNA-ASO rescues expression of brain dystrophin to 10-30% of wild-type levels and significantly reduces the abnormal unconditioned fear responses in mdx mice in a dose-dependent manner, 5 weeks post-injection. Exon skipping efficiency, ASO biodistribution, protein restoration and effect on the fear response were optimal with a dose of 400 μg at 6-7 weeks post-injection, with synaptic-like expression in brain tissues such as the hippocampus and amygdala. Furthermore, this dose of tcDNA-ASO restored long-term memory retention of mdx mice in an object recognition task, but only had minor effects on fear conditioning.
INTERPRETATION
These results suggest for the first time that postnatal re-expression of brain dystrophin could reverse or at least alleviate some cognitive deficits associated with Duchenne muscular dystrophy. ANN NEUROL 2022;92:213-229.
Topics: Animals; Brain; Disease Models, Animal; Dystrophin; Exons; Mice; Mice, Inbred mdx; Muscular Dystrophy, Duchenne; Oligonucleotides; Oligonucleotides, Antisense; Tissue Distribution
PubMed: 35587226
DOI: 10.1002/ana.26409 -
The Journal of Clinical Investigation Jan 1994
Topics: Adult; Animals; Child; Cytoskeletal Proteins; Dystroglycans; Dystrophin; Glycoproteins; Humans; Male; Membrane Glycoproteins; Molecular Weight; Muscles; Muscular Dystrophies; Rabbits
PubMed: 8282811
DOI: 10.1172/JCI116973 -
Molecular Therapy : the Journal of the... May 2011Duchenne muscular dystrophy (DMD) is a genetic disease affecting about one in every 3,500 boys. This X-linked pathology is due to the absence of dystrophin in muscle... (Review)
Review
Duchenne muscular dystrophy (DMD) is a genetic disease affecting about one in every 3,500 boys. This X-linked pathology is due to the absence of dystrophin in muscle fibers. This lack of dystrophin leads to the progressive muscle degeneration that is often responsible for the death of the DMD patients during the third decade of their life. There are currently no curative treatments for this disease but different therapeutic approaches are being studied. Gene therapy consists of introducing a transgene coding for full-length or a truncated version of dystrophin complementary DNA (cDNA) in muscles, whereas pharmaceutical therapy includes the use of chemical/biochemical substances to restore dystrophin expression or alleviate the DMD phenotype. Over the past years, many potential drugs were explored. This led to several clinical trials for gentamicin and ataluren (PTC124) allowing stop codon read-through. An alternative approach is to induce the expression of an internally deleted, partially functional dystrophin protein through exon skipping. The vectors and the methods used in gene therapy have been continually improving in order to obtain greater encapsidation capacity and better transduction efficiency. The most promising experimental approaches using pharmaceutical and gene therapies are reviewed in this article.
Topics: Dystrophin; Genetic Therapy; Gentamicins; Humans; Male; Muscle Fibers, Skeletal; Muscular Dystrophy, Duchenne; Oxadiazoles
PubMed: 21468001
DOI: 10.1038/mt.2011.59 -
International Journal of Experimental... Feb 2021Dystrophin deficiency makes the sarcolemma fragile and susceptible to degeneration in Duchenne muscular dystrophy. The proteasome is a multimeric protease complex and is...
Dystrophin deficiency makes the sarcolemma fragile and susceptible to degeneration in Duchenne muscular dystrophy. The proteasome is a multimeric protease complex and is central to the regulation of cellular proteins. Previous studies have shown that proteasome inhibition improved pathological changes in mdx mice. Ixazomib is the first oral proteasome inhibitor used as a therapy in multiple myeloma. This study investigated the effects of ixazomib on the dystrophic muscle of mdx mice. MDX mice were treated with ixazomib (7.5 mg/kg/wk by gavage) or 0.2 mL of saline for 12 weeks. The Kondziela test was performed to measure muscle strength. The tibialis anterior (TA) and diaphragm (DIA) muscles were used for morphological analysis, and blood samples were collected for biochemical measurement. We observed maintenance of the muscle strength in the animals treated with ixazomib. Treatment with ixazomib had no toxic effect on the mdx mouse. The morphological analysis showed a reduction in the inflammatory area and fibres with central nuclei in the TA and DIA muscles and an increase in the number of fibres with a diameter of 20 µm in the DIA muscle after treatment with ixazomib. There was an increase in the expression of dystrophin and utrophin in the TA and DIA muscles and a reduction in the expression of osteopontin and TGF-β in the DIA muscle of mdx mice treated with ixazomib. Ixazomib was thus shown to increase the expression of dystrophin and utrophin associated with improved pathological and functional changes in the dystrophic muscles of mdx mice.
Topics: Animals; Boron Compounds; Dystrophin; Glycine; Mice, Inbred mdx; Muscle, Skeletal; Muscular Dystrophy, Duchenne; Protease Inhibitors; Utrophin; Mice
PubMed: 33296126
DOI: 10.1111/iep.12383 -
Current Gene Therapy Jun 2012The muscular dystrophies collectively represent a major health challenge, as few significant treatment options currently exist for any of these disorders. Recent years... (Review)
Review
The muscular dystrophies collectively represent a major health challenge, as few significant treatment options currently exist for any of these disorders. Recent years have witnessed a proliferation of novel approaches to therapy, spanning increased testing of existing and new pharmaceuticals, DNA delivery (both anti-sense oligonucleotides and plasmid DNA), gene therapies and stem cell technologies. While none of these has reached the point of being used in clinical practice, all show promise for being able to impact different types of muscular dystrophies. Our group has focused on developing direct gene replacement strategies to treat recessively inherited forms of muscular dystrophy, particularly Duchenne and Becker muscular dystrophy (DMD/BMD). Both forms of dystrophy are caused by mutations in the dystrophin gene and all cases can in theory be treated by gene replacement using synthetic forms of the dystrophin gene. The major challenges for success of this approach are the development of a suitable gene delivery shuttle, generating a suitable gene expression cassette able to be carried by such a shuttle, and achieving safe and effective delivery without elicitation of a destructive immune response. This review summarizes the current state of the art in terms of using adeno-associated viral vectors to deliver synthetic dystrophin genes for the purpose of developing gene therapy for DMD.
Topics: Dependovirus; Dystrophin; Gene Expression; Gene Transfer Techniques; Genetic Therapy; Genetic Vectors; Humans; Immunity, Active; Muscular Dystrophy, Duchenne; Mutation
PubMed: 22533379
DOI: 10.2174/156652312800840603 -
Brain : a Journal of Neurology Dec 2011Duchenne muscular dystrophy is caused by mutations in the DMD gene that disrupt the open reading frame and prevent the full translation of its protein product,...
Duchenne muscular dystrophy is caused by mutations in the DMD gene that disrupt the open reading frame and prevent the full translation of its protein product, dystrophin. Restoration of the open reading frame and dystrophin production can be achieved by exon skipping using antisense oligonucleotides targeted to splicing elements. This approach aims to transform the Duchenne muscular dystrophy phenotype to that of the milder disorder, Becker muscular dystrophy, typically caused by in-frame dystrophin deletions that allow the production of an internally deleted but partially functional dystrophin. There is ongoing debate regarding the functional properties of the different internally deleted dystrophins produced by exon skipping for different mutations; more insight would be valuable to improve and better predict the outcome of exon skipping clinical trials. To this end, we have characterized the clinical phenotype of 17 patients with Becker muscular dystrophy harbouring in-frame deletions relevant to on-going or planned exon skipping clinical trials for Duchenne muscular dystrophy and correlated it to the levels of dystrophin, and dystrophin-associated protein expression. The cohort of 17 patients, selected exclusively on the basis of their genotype, included 4 asymptomatic, 12 mild and 1 severe patient. All patients had dystrophin levels of >40% of control and significantly higher dystrophin (P = 0.013), β-dystroglycan (P = 0.025) and neuronal nitric oxide synthase (P = 0.034) expression was observed in asymptomatic individuals versus symptomatic patients with Becker muscular dystrophy. Furthermore, grouping the patients by deletion, patients with Becker muscular dystrophy with deletions with an end-point of exon 51 (the skipping of which could rescue the largest group of Duchenne muscular dystrophy deletions) showed significantly higher dystrophin levels (P = 0.034) than those with deletions ending with exon 53. This is the first quantitative study on both dystrophin and dystrophin-associated protein expression in patients with Becker muscular dystrophy with deletions relevant for on-going exon skipping trials in Duchenne muscular dystrophy. Taken together, our results indicate that all varieties of internally deleted dystrophin assessed in this study have the functional capability to provide a substantial clinical benefit to patients with Duchenne muscular dystrophy.
Topics: Adolescent; Adult; Aged; Child; Cohort Studies; Dystrophin; Exons; Female; Genotype; Humans; Male; Middle Aged; Muscular Dystrophy, Duchenne; Open Reading Frames; Phenotype; Retrospective Studies; Severity of Illness Index
PubMed: 22102647
DOI: 10.1093/brain/awr291 -
Scientific Reports Mar 2017Duchenne Muscular Dystrophy (DMD) is caused by a lack of dystrophin expression in patient muscle fibres. Current DMD gene therapy strategies rely on the expression of...
Duchenne Muscular Dystrophy (DMD) is caused by a lack of dystrophin expression in patient muscle fibres. Current DMD gene therapy strategies rely on the expression of internally deleted forms of dystrophin, missing important functional domains. Viral gene transfer of full-length dystrophin could restore wild-type functionality, although this approach is restricted by the limited capacity of recombinant viral vectors. Lentiviral vectors can package larger transgenes than adeno-associated viruses, yet lentiviral vectors remain largely unexplored for full-length dystrophin delivery. In our work, we have demonstrated that lentiviral vectors can package and deliver inserts of a similar size to dystrophin. We report a novel approach for delivering large transgenes in lentiviruses, in which we demonstrate proof-of-concept for a 'template-switching' lentiviral vector that harnesses recombination events during reverse-transcription. During this work, we discovered that a standard, unmodified lentiviral vector was efficient in delivering full-length dystrophin to target cells, within a total genomic load of more than 15,000 base pairs. We have demonstrated gene therapy with this vector by restoring dystrophin expression in DMD myoblasts, where dystrophin was expressed at the sarcolemma of myotubes after myogenic differentiation. Ultimately, our work demonstrates proof-of-concept that lentiviruses can be used for permanent full-length dystrophin gene therapy, which presents a significant advancement in developing an effective treatment for DMD.
Topics: Cell Line; Child, Preschool; Dystrophin; Genetic Therapy; Genetic Vectors; Humans; Lentivirus; Muscular Dystrophy, Duchenne; Myoblasts; Templates, Genetic; Transduction, Genetic; Transgenes
PubMed: 28303972
DOI: 10.1038/srep44775