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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 -
Neurotherapeutics : the Journal of the... Oct 2023Duchenne muscular dystrophy (DMD) is the most common childhood form of muscular dystrophy. It is caused by mutations in the DMD gene, leading to reduced or absent... (Review)
Review
Duchenne muscular dystrophy (DMD) is the most common childhood form of muscular dystrophy. It is caused by mutations in the DMD gene, leading to reduced or absent expression of the dystrophin protein. Clinically, this results in loss of ambulation, cardiomyopathy, respiratory failure, and eventually death. In the past decades, the use of corticosteroids has slowed down the disease progression. More recently, the development of genetically mediated therapies has emerged as the most promising treatment for DMD. These strategies include exon skipping with antisense oligonucleotides, gene replacement therapy with adeno-associated virus, and gene editing with CRISPR (clustered regularly interspaced short palindromic repeats) technology. In this review, we highlight the most up-to-date therapeutic progresses in the field, with emphasis on past and recent experiences, as well as the latest clinical results of DMD micro-dystrophin gene therapy. Additionally, we discuss the lessons learned along the way and the challenges encountered, all of which have helped advance the field, with the potential to finally alleviate such a devastating disease.
Topics: Humans; Child; Muscular Dystrophy, Duchenne; Dystrophin; Gene Editing; Exons; Genetic Therapy
PubMed: 37673849
DOI: 10.1007/s13311-023-01423-y -
BioDrugs : Clinical Immunotherapeutics,... Jan 2024Duchenne muscular dystrophy is a devastating disease that leads to progressive muscle loss and premature death. While medical management focuses mostly on symptomatic... (Comparative Study)
Comparative Study Review
Duchenne muscular dystrophy is a devastating disease that leads to progressive muscle loss and premature death. While medical management focuses mostly on symptomatic treatment, decades of research have resulted in first therapeutics able to restore the affected reading frame of dystrophin transcripts or induce synthesis of a truncated dystrophin protein from a vector, with other strategies based on gene therapy and cell signaling in preclinical or clinical development. Nevertheless, recent reports show that potentially therapeutic dystrophins can be immunogenic in patients. This raises the question of whether a dystrophin paralog, utrophin, could be a more suitable therapeutic protein. Here, we compare dystrophin and utrophin amino acid sequences and structures, combining published data with our extended in silico analyses. We then discuss these results in the context of therapeutic approaches for Duchenne muscular dystrophy. Specifically, we focus on strategies based on delivery of micro-dystrophin and micro-utrophin genes with recombinant adeno-associated viral vectors, exon skipping of the mutated dystrophin pre-mRNAs, reading through termination codons with small molecules that mask premature stop codons, dystrophin gene repair by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9)-mediated genetic engineering, and increasing utrophin levels. Our analyses highlight the importance of various dystrophin and utrophin domains in Duchenne muscular dystrophy treatment, providing insights into designing novel therapeutic compounds with improved efficacy and decreased immunoreactivity. While the necessary actin and β-dystroglycan binding sites are present in both proteins, important functional distinctions can be identified in these domains and some other parts of truncated dystrophins might need redesigning due to their potentially immunogenic qualities. Alternatively, therapies based on utrophins might provide a safer and more effective approach.
Topics: Humans; Dystrophin; Genetic Therapy; Muscular Dystrophy, Duchenne; Utrophin
PubMed: 37917377
DOI: 10.1007/s40259-023-00632-3 -
Progress in Retinal and Eye Research Jul 2023Duchenne muscular dystrophy (DMD) is caused by X-linked inherited or de novo DMD gene mutations predominantly affecting males who develop early-onset muscle... (Review)
Review
Duchenne muscular dystrophy (DMD) is caused by X-linked inherited or de novo DMD gene mutations predominantly affecting males who develop early-onset muscle degeneration, severely affecting their quality of life and leading to reduced life expectancy. DMD patients may also develop proliferative retinopathy, cataract, ERG abnormalities, altered contrast sensitivity, color vision losses, and elevated flash detection thresholds during dark adaptation. Depending on the position of the genetic alteration in the large DMD gene, it is associated with a lack of the full-length dystrophin protein possibly with an additional loss of one or several other dystrophins, which are normally transcribed from internal promoters in retina and crystalline lens. During the last decades, the properties of the dystrophins have been characterized in patients with different genetic alterations and in genetic mouse models of DMD. The complex expression pattern of the dystrophins in photoreceptors, Müller glial cells and astrocytes, likely influences synaptic transmission, ionic balance and vascular integrity of the retina. However, the specific function of each retinal dystrophin remains largely unknown. This review describes the current knowledge on dystrophin expression, the putative molecular, structural, and physiological properties of retinal dystrophins, and the main clinical implications associated with the loss of dystrophins in DMD patients and mouse models. Current data and working hypotheses warrant future research on retinal dystrophins to increase our understanding of dystrophin function in the central nervous system in general and to unveil new retinal mechanisms and therapeutic avenues for retinal diseases.
Topics: Male; Mice; Animals; Dystrophin; Muscular Dystrophy, Duchenne; Quality of Life; Retina; Retinal Diseases
PubMed: 36404230
DOI: 10.1016/j.preteyeres.2022.101137 -
Cell Cycle (Georgetown, Tex.) 2015
Topics: Animals; Dystrophin; Female; Humans; Male; Muscular Dystrophies; Sarcoma
PubMed: 26101897
DOI: 10.1080/15384101.2015.1064676 -
Cell Reports Nov 2023Duchenne muscular dystrophy (DMD) is a severe genetic disease caused by the loss of the dystrophin protein. Exon skipping is a promising strategy to treat DMD by...
Duchenne muscular dystrophy (DMD) is a severe genetic disease caused by the loss of the dystrophin protein. Exon skipping is a promising strategy to treat DMD by restoring truncated dystrophin. Here, we demonstrate that base editors (e.g., targeted AID-mediated mutagenesis [TAM]) are able to efficiently induce exon skipping by disrupting functional redundant exonic splicing enhancers (ESEs). By developing an unbiased and high-throughput screening to interrogate exonic sequences, we successfully identify novel ESEs in DMD exons 51 and 53. TAM-CBE (cytidine base editor) induces near-complete skipping of the respective exons by targeting these ESEs in patients' induced pluripotent stem cell (iPSC)-derived cardiomyocytes. Combined with strategies to disrupt splice sites, we identify suitable single guide RNAs (sgRNAs) with TAM-CBE to efficiently skip most DMD hotspot exons without substantial double-stranded breaks. Our study thus expands the repertoire of potential targets for CBE-mediated exon skipping in treating DMD and other RNA mis-splicing diseases.
Topics: Humans; Dystrophin; RNA, Guide, CRISPR-Cas Systems; Muscular Dystrophy, Duchenne; RNA Splicing; Exons
PubMed: 37906593
DOI: 10.1016/j.celrep.2023.113340 -
Biophysical Journal Aug 2018We have used pulsed electron paramagnetic resonance, calorimetry, and molecular dynamics simulations to examine the structural mechanism of binding for dystrophin's...
We have used pulsed electron paramagnetic resonance, calorimetry, and molecular dynamics simulations to examine the structural mechanism of binding for dystrophin's N-terminal actin-binding domain (ABD1) and compare it to utrophin's ABD1. Like other members of the spectrin superfamily, dystrophin's ABD1 consists of two calponin-homology (CH) domains, CH1 and CH2. Several mutations within dystrophin's ABD1 are associated with the development of severe degenerative muscle disorders Duchenne and Becker muscular dystrophies, highlighting the importance of understanding its structural biology. To investigate structural changes within dystrophin ABD1 upon binding to actin, we labeled the protein with spin probes and measured changes in inter-CH domain distance using double-electron electron resonance. Previous studies on the homologous protein utrophin showed that actin binding induces a complete structural opening of the CH domains, resulting in a highly ordered ABD1-actin complex. In this study, double-electron electron resonance shows that dystrophin ABD1 also undergoes a conformational opening upon binding F-actin, but this change is less complete and significantly more structurally disordered than observed for utrophin. Using molecular dynamics simulations, we identified a hinge in the linker region between the two CH domains that grants conformational flexibility to ABD1. The conformational dynamics of both dystrophin's and utrophin's ABD1 showed that compact conformations driven by hydrophobic interactions are preferred and that extended conformations are energetically accessible through a flat free-energy surface. Considering that the binding free energy of ABD1 to actin is on the order of 6-7 kcal/mole, our data are compatible with a mechanism in which binding to actin is largely dictated by specific interactions with CH1, but fine tuning of the binding affinity is achieved by the overlap between conformational ensembles of ABD1 free and bound to actin.
Topics: Actins; Dystrophin; Electron Spin Resonance Spectroscopy; Molecular Dynamics Simulation; Protein Binding; Protein Domains
PubMed: 30007583
DOI: 10.1016/j.bpj.2018.05.039 -
Bosnian Journal of Basic Medical... Jul 2015Mutations of the dystrophin DMD gene, essentially deletions of one or several exons, are the cause of two devastating and to date incurable diseases, Duchenne (DMD) and... (Review)
Review
Mutations of the dystrophin DMD gene, essentially deletions of one or several exons, are the cause of two devastating and to date incurable diseases, Duchenne (DMD) and Becker (BMD) muscular dystrophies. Depending upon the preservation or not of the reading frame, dystrophin is completely absent in DMD, or present in either a mutated or a truncated form in BMD. DMD is a severe disease which leads to a premature death of the patients. Therapy approaches are evolving with the aim to transform the severe DMD in the BMD form of the disease by restoring the expression of a mutated or truncated dystrophin. These therapies are based on the assumption that BMD is a mild disease. However, this is not completely true as BMD patients are more or less severely affected and no molecular basis of this heterogeneity of the BMD form of the disease is yet understood. The aim of this review is to report for the correlation between dystrophin structures in BMD deletions in view of this heterogeneity and to emphasize that examining BMD patients in details is highly relevant to anticipate for DMD therapy effects.
Topics: Dystrophin; Humans; Muscular Dystrophy, Duchenne; Mutation
PubMed: 26295289
DOI: 10.17305/bjbms.2015.636 -
Gene Therapy Nov 2022Duchenne muscular dystrophy (DMD) is a lethal, degenerative muscle disorder caused by mutations in the DMD gene, leading to severe reduction or absence of the protein...
Duchenne muscular dystrophy (DMD) is a lethal, degenerative muscle disorder caused by mutations in the DMD gene, leading to severe reduction or absence of the protein dystrophin. Gene therapy strategies that aim to increase expression of a functional dystrophin protein (mini-dystrophin) are under investigation. The ability to accurately quantify dystrophin/mini-dystrophin is essential in assessing the level of gene transduction. We demonstrated the validation and application of a novel peptide immunoaffinity liquid chromatography-tandem mass spectrometry (IA-LC-MS/MS) assay. Data showed that dystrophin expression in Becker muscular dystrophy and DMD tissues, normalized against the mean of non-dystrophic control tissues (n = 20), was 4-84.5% (mean 32%, n = 20) and 0.4-24.1% (mean 5%, n = 20), respectively. In a DMD rat model, biceps femoris tissue from dystrophin-deficient rats treated with AAV9.hCK.Hopti-Dys3978.spA, an adeno-associated virus vector containing a mini-dystrophin transgene, showed a dose-dependent increase in mini-dystrophin expression at 6 months post-dose, exceeding wildtype dystrophin levels at high doses. Validation data showed that inter- and intra-assay precision were ≤20% (≤25% at the lower limit of quantification [LLOQ]) and inter- and intra-run relative error was within ±20% (±25% at LLOQ). IA-LC-MS/MS accurately quantifies dystrophin/mini-dystrophin in human and preclinical species with sufficient sensitivity for immediate application in preclinical/clinical trials.
Topics: Humans; Rats; Animals; Dystrophin; Muscular Dystrophy, Duchenne; Chromatography, Liquid; Tandem Mass Spectrometry; Muscle, Skeletal; Genetic Therapy
PubMed: 34737451
DOI: 10.1038/s41434-021-00300-7 -
Proceedings of the National Academy of... Jan 2023Dystrophin is essential for muscle health: its sarcolemmal absence causes the fatal, X-linked condition, Duchenne muscular dystrophy (DMD). However, its normal, spatial...
Dystrophin is essential for muscle health: its sarcolemmal absence causes the fatal, X-linked condition, Duchenne muscular dystrophy (DMD). However, its normal, spatial organization remains poorly understood, which hinders the interpretation of efficacy of its therapeutic restoration. Using female reporter mice heterozygous for fluorescently tagged dystrophin (), we here reveal that dystrophin distribution is unexpectedly compartmentalized, being restricted to myonuclear-defined sarcolemmal territories extending ~80 µm, which we called "basal sarcolemmal dystrophin units (BSDUs)." These territories were further specialized at myotendinous junctions, where both transcripts and dystrophin protein were enriched. Genome-level correction in X-linked muscular dystrophy mice via CRISPR/Cas9 gene editing restored a mosaic of separated dystrophin domains, whereas transcript-level correction, following treatment with tricyclo-DNA antisense oligonucleotides, restored dystrophin initially at junctions before extending along the entire fiber-with levels ~2% sufficient to moderate the dystrophic process. We conclude that widespread restoration of fiber dystrophin is likely critical for therapeutic success in DMD, perhaps most importantly, at muscle-tendon junctions.
Topics: Female; Mice; Animals; Dystrophin; Muscular Dystrophy, Duchenne; Muscles; Gene Editing; Treatment Outcome; Mice, Inbred mdx; Muscle, Skeletal; Disease Models, Animal
PubMed: 36595689
DOI: 10.1073/pnas.2206324120