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Current Journal of Neurology Oct 2023Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are inherited X-linked disorders resulting from alterations in the dystrophin gene....
Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are inherited X-linked disorders resulting from alterations in the dystrophin gene. Genotype-phenotype matching studies have revealed a link between disease severity, the amount of muscle dystrophin, and the extent of mutation/deletion on the dystrophin gene. This study aimed to assess the relationship between genetic alterations in the dystrophin gene and the clinical status of patients with dystrophinopathies among the Iranian population. This cross-sectional study examined 54 patients with muscle weakness caused by abnormalities in the dystrophin gene at a hospital affiliated to Isfahan University of Medical Sciences, Isfahan, Iran, in 2021. The participants' demographic information, including age, family history of muscle dystrophies, and family history of other medical diseases as well as the type of muscular dystrophy were recorded. Furthermore, the number and region of deleted exons based on dystrophy types were also evaluated using multiplex ligation-dependent probe amplification (MLPA). The patients' gaits were also assessed as using a wheelchair, the presence of waddling gaits, or toe gaits. The patients' clinical status and the coexistence of pulmonary, bulbar, and mental conditions were also examined and compared between the two groups of dystrophinopathies. In this study, 54 patients with dystrophinopathy with the mean age of 16.63 ± 12.10 years were evaluated, of whom 22 (40.7%) and 30 (55.6%) patients were classified as BMD and DMD, respectively. The most affected regions with deleted exons were exons 45-47 (n = 5) and 45-48 (n = 4) in patients with BMD, while exons 45, 48-52, 51-55, and 53 (2 cases per exon) were the most common affected exons in patients with DMD. Further analyses revealed that deletions in exons 45-47 and 51-55 were significantly associated with older and younger ages at the onset of becoming wheelchair-bound in patients with dystrophy, respectively. The hotspot range in both BMD and DMD was within exons 45-55 (n = 15 for each group); 63% of the patients had alterations on the dystrophin gene within this range [30 patients (68.18%) in the BMD group, 15 patients (53.57%) in the DMD group]. Exon deletion was the most common genetic alteration in patients with dystrophinopathies. No significant difference was observed between DMD and BMD regarding the number of deleted exons. Deletions in exons 45-47 and 51-55 were linked to later and earlier onset of becoming wheelchair-bound, respectively.
PubMed: 38425356
DOI: 10.18502/cjn.v22i4.14528 -
Journal of Veterinary Internal Medicine 2024X-linked muscular dystrophy in cats (FXMD) is an uncommon disease, with few reports describing its pathogenic genetic variants. A 9-year-old castrated male domestic...
X-linked muscular dystrophy in cats (FXMD) is an uncommon disease, with few reports describing its pathogenic genetic variants. A 9-year-old castrated male domestic shorthair cat was presented with persistent muscle swelling and breathing difficulty from 3 years of age. Serum activity of alanine aminotransferase, aspartate transaminase, and creatine kinase were abnormally high. Physical and neurological examinations showed muscle swelling in the neck and proximal limb, slow gait, and occasional breathing difficulties. Electromyography showed pseudomyotonic discharges and complex repetitive discharges with a "dive-bomber" sound. Histopathology revealed muscle necrosis and regeneration. Whole-genome sequencing identified a novel and unique hemizygous nonsense genetic variant, c.8333G > A in dystrophin (DMD), potentially causing a premature termination codon (p.Trp2778Ter). Based on a combination of clinical and histological findings and the presence of the DMD nonsense genetic variant, this case was considered FXMD, which showed mild clinical signs and long-term survival, even though immunohistochemical characterization was lacking.
Topics: Cats; Male; Animals; Dystrophin; Muscular Dystrophy, Duchenne; Codon, Nonsense; Electromyography; Disease Progression; Cat Diseases
PubMed: 38415938
DOI: 10.1111/jvim.17024 -
Acta Myologica : Myopathies and... 2023Duchenne Muscular Dystrophy (DMD) includes predictable phases requiring dedicated standard treatments. Therapeutic strategies feature corticosteroids or the more recent...
Duchenne Muscular Dystrophy (DMD) includes predictable phases requiring dedicated standard treatments. Therapeutic strategies feature corticosteroids or the more recent gene therapy/stop codon read-through. Ataluren (Translarna) is an oral drug promoting the readthrough of premature stop codons caused by nonsense mutation (nm) in order to produce full-length dystrophin. It was licensed by EMA in 2014 for ambulatory patients with nmDMD aged ≥ 5 years. Our aim is to report data on long-term ataluren use in Italian patients with nmDMD, with emphasis on continuity of the treatment after loss of ambulation (LoA). Four DMD patients aged between 16 and 24 years who lost ambulation between 12 and 14 years continued to take ataluren after LoA. The oldest patient, aged 24 years, is still taking a few steps. Even in those experiencing motor decline, PUL-test performances were stable and respiratory function satisfactory in all; two patients developed severe cardiomyopathy, stable in one. Therapeutic continuity with ataluren should be offered to all nmDMD patients after LoA given its favourable safety and efficacy profile. However, further research is recommended to identify additional clinically meaningful outcomes and treatment goals following LoA.
Topics: Humans; Adolescent; Young Adult; Adult; Muscular Dystrophy, Duchenne; Codon, Nonsense; Dystrophin; Oxadiazoles; Walking
PubMed: 38406379
DOI: 10.36185/2532-1900-396 -
Biomedicines Feb 2024The muscle-tendon junction (MTJ) is a highly specific tissue interface where the muscle's fascia intersects with the extracellular matrix of the tendon. The MTJ... (Review)
Review
The muscle-tendon junction (MTJ) is a highly specific tissue interface where the muscle's fascia intersects with the extracellular matrix of the tendon. The MTJ functions as the particular structure facilitating the transmission of force from contractive muscle fibers to the skeletal system, enabling movement. Considering that the MTJ is continuously exposed to constant mechanical forces during physical activity, it is susceptible to injuries. Ruptures at the MTJ often accompany damage to both tendon and muscle tissues. In this review, we attempt to provide a precise definition of the MTJ, describe its subtle structure in detail, and introduce therapeutic approaches related to MTJ tissue engineering. We hope that our detailed illustration of the MTJ and summary of the representative research achievements will help researchers gain a deeper understanding of the MTJ and inspire fresh insights and breakthroughs for future research.
PubMed: 38398025
DOI: 10.3390/biomedicines12020423 -
Cardiovascular Research May 2024The microtubule (MT) network plays a major role in the transport of the cardiac sodium channel Nav1.5 to the membrane, where the latter associates with interacting...
AIMS
The microtubule (MT) network plays a major role in the transport of the cardiac sodium channel Nav1.5 to the membrane, where the latter associates with interacting proteins such as dystrophin. Alterations in MT dynamics are known to impact on ion channel trafficking. Duchenne muscular dystrophy (DMD), caused by dystrophin deficiency, is associated with an increase in MT detyrosination, decreased sodium current (INa), and arrhythmias. Parthenolide (PTL), a compound that decreases MT detyrosination, has shown beneficial effects on cardiac function in DMD. We here investigated its impact on INa and Nav1.5 subcellular distribution.
METHODS AND RESULTS
Ventricular cardiomyocytes (CMs) from wild-type (WT) and mdx (DMD) mice were incubated with either 10 µM PTL, 20 µM EpoY, or dimethylsulfoxide (DMSO) for 3-5 h, followed by patch-clamp analysis to assess INa and action potential (AP) characteristics in addition to immunofluorescence and stochastic optical reconstruction microscopy (STORM) to investigate MT detyrosination and Nav1.5 cluster size and density, respectively. In accordance with previous studies, we observed increased MT detyrosination, decreased INa and reduced AP upstroke velocity (Vmax) in mdx CMs compared to WT. PTL decreased MT detyrosination and significantly increased INa magnitude (without affecting INa gating properties) and AP Vmax in mdx CMs, but had no effect in WT CMs. Moreover, STORM analysis showed that in mdx CMs, Nav1.5 clusters were decreased not only in the grooves of the lateral membrane (LM; where dystrophin is localized) but also at the LM crests. PTL restored Nav1.5 clusters at the LM crests (but not at the grooves), indicating a dystrophin-independent trafficking route to this subcellular domain. Interestingly, Nav1.5 cluster density was also reduced at the intercalated disc (ID) region of mdx CMs, which was restored to WT levels by PTL. Treatment of mdx CMs with EpoY, a specific MT detyrosination inhibitor, also increased INa density, while decreasing the amount of detyrosinated MTs, confirming a direct mechanistic link.
CONCLUSION
Attenuating MT detyrosination in mdx CMs restored INa and enhanced Nav1.5 localization at the LM crest and ID. Hence, the reduced whole-cell INa density characteristic of mdx CMs is not only the consequence of the lack of dystrophin within the LM grooves but is also due to reduced Nav1.5 at the LM crest and ID secondary to increased baseline MT detyrosination. Overall, our findings identify MT detyrosination as a potential therapeutic target for modulating INa and subcellular Nav1.5 distribution in pathophysiological conditions.
Topics: Animals; NAV1.5 Voltage-Gated Sodium Channel; Myocytes, Cardiac; Mice, Inbred mdx; Action Potentials; Microtubules; Muscular Dystrophy, Duchenne; Disease Models, Animal; Tubulin Modulators; Mice, Inbred C57BL; Cells, Cultured; Sesquiterpenes; Male; Sodium
PubMed: 38395031
DOI: 10.1093/cvr/cvae043 -
Skeletal Muscle Feb 2024Human iPSC-derived 3D-tissue-engineered-skeletal muscles (3D-TESMs) offer advanced technology for disease modelling. However, due to the inherent genetic heterogeneity...
BACKGROUND
Human iPSC-derived 3D-tissue-engineered-skeletal muscles (3D-TESMs) offer advanced technology for disease modelling. However, due to the inherent genetic heterogeneity among human individuals, it is often difficult to distinguish disease-related readouts from random variability. The generation of genetically matched isogenic controls using gene editing can reduce variability, but the generation of isogenic hiPSC-derived 3D-TESMs can take up to 6 months, thereby reducing throughput.
METHODS
Here, by combining 3D-TESM and shRNA technologies, we developed a disease modelling strategy to induce distinct genetic deficiencies in a single hiPSC-derived myogenic progenitor cell line within 1 week.
RESULTS
As proof of principle, we recapitulated disease-associated pathology of Duchenne muscular dystrophy and limb-girdle muscular dystrophy type 2A caused by loss of function of DMD and CAPN3, respectively. shRNA-mediated knock down of DMD or CAPN3 induced a loss of contractile function, disruption of tissue architecture, and disease-specific proteomes. Pathology in DMD-deficient 3D-TESMs was partially rescued by a candidate gene therapy treatment using micro-dystrophin, with similar efficacy compared to animal models.
CONCLUSIONS
These results show that isogenic shRNA-based humanized 3D-TESM models provide a fast, cheap, and efficient tool to model muscular dystrophies and are useful for the preclinical evaluation of novel therapies.
Topics: Animals; Humans; Muscle, Skeletal; Muscular Dystrophy, Duchenne; Muscular Dystrophies, Limb-Girdle; Muscle Contraction; RNA, Small Interfering
PubMed: 38389096
DOI: 10.1186/s13395-024-00335-5 -
BMC Neurology Feb 2024This paper details the results of an evaluation of the level of consensus amongst clinicians on the use of ataluren in both ambulatory and non-ambulatory patients with...
The role of ataluren in the treatment of ambulatory and non-ambulatory children with nonsense mutation duchenne muscular dystrophy - a consensus derived using a modified Delphi methodology in Eastern Europe, Greece, Israel and Sweden.
BACKGROUND
This paper details the results of an evaluation of the level of consensus amongst clinicians on the use of ataluren in both ambulatory and non-ambulatory patients with nonsense mutation Duchenne muscular dystrophy (nmDMD). The consensus was derived using a modified Delphi methodology that involved an exploration phase and then an evaluation phase.
METHODS
The exploration phase involved 90-minute virtual 1:1 interviews of 12 paediatric neurologists who cared for 30-120 DMD patients each and had patient contact every one or two weeks. The respondents managed one to ten nmDMD patients taking ataluren. The Discussion Guide for the interviews can be viewed as Appendix A. Following the exploration phase interviews, the interview transcripts were analysed by an independent party to identify common themes, views and opinions and developed 43 draft statements that the Steering Group (authors) reviewed, refined and endorsed a final list of 42 statements. Details of the recruitment of participants for the exploration and evaluation phases can be found under the Methods section.
RESULTS
A consensus was agreed (> 66% of respondents agreeing) for 41 of the 42 statements using results from a consensus survey of healthcare professionals (n = 20) experienced in the treatment of nmDMD.
CONCLUSIONS
The statements with a high consensus suggest that treatment with ataluren should be initiated as soon as possible to delay disease progression and allow patients to remain ambulatory for as long as possible. Ataluren is indicated for the treatment of Duchenne muscular dystrophy that results from a nonsense mutation in the dystrophin gene, in ambulatory patients aged 2 years and older (see Summary of Product Characteristics for each country).
Topics: Child; Humans; Muscular Dystrophy, Duchenne; Codon, Nonsense; Greece; Sweden; Israel; Consensus; Dystrophin; Europe, Eastern; Oxadiazoles
PubMed: 38383326
DOI: 10.1186/s12883-024-03570-x -
Applied Magnetic Resonance Mar 2024Here we review applications of site-directed spin labeling (SDSL) with engineered cysteines in proteins, to study the structural dynamics of muscle and non-muscle...
Here we review applications of site-directed spin labeling (SDSL) with engineered cysteines in proteins, to study the structural dynamics of muscle and non-muscle proteins, using and developing the electron paramagnetic resonance (EPR) spectroscopic techniques of dipolar EPR, double electron electron resonance (DEER), saturation transfer EPR (STEPR), and orientation measured by EPR. The SDSL technology pioneered by Wayne Hubbell and collaborators has greatly expanded the use of EPR, including the measurement of distances between spin labels covalently attached to proteins and peptides. The Thomas lab and collaborators have applied these techniques to elucidate dynamic interactions in the myosin-actin complex, myosin-binding protein C, calmodulin, ryanodine receptor, phospholamban, utrophin, dystrophin, β-III-spectrin, and Aurora kinase. The ability to design and engineer cysteines in proteins for site-directed covalent labeling has enabled the use of these powerful EPR techniques to measure distances, while showing that they are complementary with optical spectroscopy measurements.
PubMed: 38371230
DOI: 10.1007/s00723-023-01623-x -
Journal of Neuromuscular Diseases 2024Duchenne muscular dystrophy (DMD) and related dystrophinopathies are neuromuscular conditions with great unmet medical needs that require the development of effective...
Draft Guidance for Industry Duchenne Muscular Dystrophy, Becker Muscular Dystrophy, and Related Dystrophinopathies - Developing Potential Treatments for the Entire Spectrum of Disease.
BACKGROUND
Duchenne muscular dystrophy (DMD) and related dystrophinopathies are neuromuscular conditions with great unmet medical needs that require the development of effective medical treatments.
OBJECTIVE
To aid sponsors in clinical development of drugs and therapeutic biological products for treating DMD across the disease spectrum by integrating advancements, patient registries, natural history studies, and more into a comprehensive guidance.
METHODS
This guidance emerged from collaboration between the FDA, the Duchenne community, and industry stakeholders. It entailed a structured approach, involving multiple committees and boards. From its inception in 2014, the guidance underwent revisions incorporating insights from gene therapy studies, cardiac function research, and innovative clinical trial designs.
RESULTS
The guidance provides a deeper understanding of DMD and its variants, focusing on patient engagement, diagnostic criteria, natural history, biomarkers, and clinical trials. It underscores patient-focused drug development, the significance of dystrophin as a biomarker, and the pivotal role of magnetic resonance imaging in assessing disease progression. Additionally, the guidance addresses cardiomyopathy's prominence in DMD and the burgeoning field of gene therapy.
CONCLUSIONS
The updated guidance offers a comprehensive understanding of DMD, emphasizing patient-centric approaches, innovative trial designs, and the importance of biomarkers. The focus on cardiomyopathy and gene therapy signifies the evolving realm of DMD research. It acts as a crucial roadmap for sponsors, potentially leading to improved treatments for DMD.
Topics: Humans; Muscular Dystrophy, Duchenne; Cardiomyopathies; Exons; Biomarkers
PubMed: 38363616
DOI: 10.3233/JND-230219 -
Journal of Neuromuscular Diseases 2024Dilated cardiomyopathy (DCM) is a major complication of, and leading cause of mortality in Duchenne muscular dystrophy (DMD). Its severity, age at onset, and rate of...
BACKGROUND
Dilated cardiomyopathy (DCM) is a major complication of, and leading cause of mortality in Duchenne muscular dystrophy (DMD). Its severity, age at onset, and rate of progression display wide variability, whose molecular bases have been scarcely elucidated. Potential DCM-modifying factors include glucocorticoid (GC) and cardiological treatments, DMD mutation type and location, and variants in other genes.
METHODS AND RESULTS
We retrospectively collected 3138 echocardiographic measurements of left ventricular ejection fraction (EF), shortening fraction (SF), and end-diastolic volume (EDV) from 819 DMD participants, 541 from an Italian multicentric cohort and 278 from the Cooperative International Neuromuscular Group Duchenne Natural History Study (CINRG-DNHS). Using generalized estimating equation (GEE) models, we estimated the yearly rate of decrease of EF (-0.80%) and SF (-0.41%), while EDV increase was not significantly associated with age. Utilizing a multivariate generalized estimating equation (GEE) model we observed that mutations preserving the expression of the C-terminal Dp71 isoform of dystrophin were correlated with decreased EDV (-11.01 mL/m2, p = 0.03) while for dp116 were correlated with decreased EF (-4.14%, p = <0.001). The rs10880 genotype in the LTBP4 gene, previously shown to prolong ambulation, was also associated with increased EF and decreased EDV (+3.29%, p = 0.002, and -10.62 mL/m2, p = 0.008) with a recessive model.
CONCLUSIONS
We quantitatively describe the progression of systolic dysfunction progression in DMD, confirm the effect of distal dystrophin isoform expression on the dystrophin-deficient heart, and identify a strong effect of LTBP4 genotype of DCM in DMD.
Topics: Humans; Dystrophin; Haplotypes; Retrospective Studies; Stroke Volume; Ventricular Function, Left; Muscular Dystrophy, Duchenne; Cardiomyopathies; Protein Isoforms; Latent TGF-beta Binding Proteins
PubMed: 38363615
DOI: 10.3233/JND-230129