Duchenne Muscular Dystrophy Onset Research Articles

Downregulation of Dystrophin Expression Occurs across Diverse Tumors, Correlates with the Age of Onset, Staging and Reduced Survival of Patients.

Altered dystrophin expression was found in some tumors and recent studies identified a developmental onset of Duchenne muscular dystrophy (DMD). Given that embryogenesis and carcinogenesis share many mechanisms, we analyzed a broad spectrum of tumors to establish whether dystrophin alteration evokes related outcomes. Transcriptomic, proteomic, and mutation datasets from fifty tumor tissues and matching controls (10,894 samples) and 140 corresponding tumor cell lines were analyzed. Interestingly, dystrophin transcripts and protein expression were found widespread across healthy tissues and at housekeeping gene levels. In 80% of tumors, DMD expression was reduced due to transcriptional downregulation and not somatic mutations. The full-length transcript encoding Dp427 was decreased in 68% of tumors, while Dp71 variants showed variability of expression. Notably, low expression of dystrophins was associated with a more advanced stage, older age of onset, and reduced survival across different tumors. Hierarchical clustering analysis of DMD transcripts distinguished malignant from control tissues. Transcriptomes of primary tumors and tumor cell lines with low DMD expression showed enrichment of specific pathways in the differentially expressed genes. Pathways consistently identified: ECM-receptor interaction, calcium signaling, and PI3K-Akt are also altered in DMD muscle. Therefore, the importance of this largest known gene extends beyond its roles identified in DMD, and certainly into oncology.

Delayed onset of Duchenne muscular dystrophy in a case of 22-year male with normal developmental milestone

Delayed onset of Duchenne muscular dystrophy in a case of 22-year male with normal developmental milestone

Re-examination of therapeutic management of muscular dystrophies using a vascular smooth muscle-centered approach.

In contrast to the long-standing focus on the pathophysiology of skeletal muscles in the hunt for a cure for Duchenne muscular dystrophy (DMD), we opine that the malfunctioning of dystrophin produced by vascular smooth muscle is a major contributor to the pathology of the illness. We believe that a biological response modifier glucan (BRMG), which has been shown in clinical studies of DMD to boost the expression of vascular smooth muscle dystrophin and provide anti-fibrotic and anti-inflammatory effects, may play a key role in reducing the pathogenesis of DMD. According to the evaluation of biomarkers, this BRMG, which is safe and side-effect-free, reduces the pathogenesis of DMD. We describe the possible mechanisms of action by which this BRMG helps in alleviating the symptoms of DMD by targeting smooth muscle dystrophin, in addition to its advantages over other therapeutic modalities, as well as how it can serve as a valuable adjunct to existing therapies. We suggest that using BRMG adjuncts that target smooth muscle dystrophin would be a potential therapeutic approach that prolongs the lifespan and extends the duration of ambulation from the onset of DMD. Further studies are needed to validate this hypothesis.

Myogenesis modelled by human pluripotent stem cells: a multi-omic study of Duchenne myopathy early onset.

BackgroundDuchenne muscular dystrophy (DMD) causes severe disability of children and death of young men, with an incidence of approximately 1/5000 male births. Symptoms appear in early childhood, with a diagnosis made mostly around 4 years old, a time where the amount of muscle damage is already significant, preventing early therapeutic interventions that could be more efficient at halting disease progression. In the meantime, the precise moment at which disease phenotypes arise—even asymptomatically—is still unknown. Thus, there is a critical need to better define DMD onset as well as its first manifestations, which could help identify early disease biomarkers and novel therapeutic targets.MethodsWe have used both human tissue‐derived myoblasts and human induced pluripotent stem cells (hiPSCs) from DMD patients to model skeletal myogenesis and compared their differentiation dynamics with that of healthy control cells by a comprehensive multi‐omic analysis at seven time points. Results were strengthened with the analysis of isogenic CRISPR‐edited human embryonic stem cells and through comparisons against published transcriptomic and proteomic datasets from human DMD muscles. The study was completed with DMD knockdown/rescue experiments in hiPSC‐derived skeletal muscle progenitor cells and adenosine triphosphate measurement in hiPSC‐derived myotubes.ResultsTranscriptome and miRnome comparisons combined with protein analyses demonstrated that hiPSC differentiation (i) leads to embryonic/foetal myotubes that mimic described DMD phenotypes at the differentiation endpoint and (ii) homogeneously and robustly recapitulates key developmental steps—mesoderm, somite, and skeletal muscle. Starting at the somite stage, DMD dysregulations concerned almost 10% of the transcriptome. These include mitochondrial genes whose dysregulations escalate during differentiation. We also describe fibrosis as an intrinsic feature of DMD skeletal muscle cells that begins early during myogenesis. All the omics data are available online for exploration through a graphical interface at https://muscle‐dmd.omics.ovh/.ConclusionsOur data argue for an early developmental manifestation of DMD whose onset is triggered before the entry into the skeletal muscle compartment, data leading to a necessary reconsideration of dystrophin roles during muscle development. This hiPSC model of skeletal muscle differentiation offers the possibility to explore these functions as well as find earlier DMD biomarkers and therapeutic targets.

BETs inhibition attenuates oxidative stress and preserves muscle integrity in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) affects 1 in 3500 live male births. To date, there is no effective cure for DMD, and the identification of novel molecular targets involved in disease progression is important to design more effective treatments and therapies to alleviate DMD symptoms. Here, we show that protein levels of the Bromodomain and extra-terminal domain (BET) protein BRD4 are significantly increased in the muscle of the mouse model of DMD, the mdx mouse, and that pharmacological inhibition of the BET proteins has a beneficial outcome, tempering oxidative stress and muscle damage. Alterations in reactive oxygen species (ROS) metabolism are an early event in DMD onset and they are tightly linked to inflammation, fibrosis, and necrosis in skeletal muscle. By restoring ROS metabolism, BET inhibition ameliorates these hallmarks of the dystrophic muscle, translating to a beneficial effect on muscle function. BRD4 direct association to chromatin regulatory regions of the NADPH oxidase subunits increases in the mdx muscle and JQ1 administration reduces BRD4 and BRD2 recruitment at these regions. JQ1 treatment reduces NADPH subunit transcript levels in mdx muscles, isolated myofibers and DMD immortalized myoblasts. Our data highlight novel functions of the BET proteins in dystrophic skeletal muscle and suggest that BET inhibitors may ameliorate the pathophysiology of DMD.

Efficacy of Multi-exon Skipping Treatment in Duchenne Muscular Dystrophy Dog Model Neonates

Duchenne muscular dystrophy (DMD) is caused by mutations in DMD, which codes for dystrophin. Because the progressive and irreversible degeneration of muscle occurs from childhood, earlier therapy is required to prevent dystrophic progression. Exon skipping by antisense oligonucleotides called phosphorodiamidate morpholino oligomers (PMOs), which restores the DMD reading frame and dystrophin expression, is a promising candidate for use in neonatal patients, yet the potential remains unclear. Here, we investigate the systemic efficacy and safety of early exon skipping in dystrophic dog neonates. Intravenous treatment of canine X-linked muscular dystrophy in Japan dogs with a 4-PMO cocktail resulted in ∼3%-27% in-frame exon 6-9 skipping and dystrophin restoration across skeletal muscles up to 14% of healthy levels. Histopathology was ameliorated with the reduction of fibrosis and/or necrosis area and centrally nucleated fibers, significantly in the diaphragm. Treatment induced cardiac multi-exon skipping, though dystrophin rescue was not detected. Functionally, treatment led to significant improvement in the standing test. Toxicity was not observed from blood tests. This is the first study to demonstrate successful multi-exon skipping treatment and significant functional improvement in dystrophic dogs. Early treatment was most beneficial for respiratory muscles, with implications for addressing pulmonary malfunction in patients.

Muscular Dystrophy: A Retrospective Evaluation of 15 Cases.

Objectives:The aim of this study was to investigate the clinical and laboratory findings of patients followed up with a diagnosis of Duchenne muscular dystrophy (DMD).Methods:This retrospective study included 15 boys diagnosed with muscular dystrophy at the Pediatric Neurology Department between July 2008 and July 2016. The presenting symptoms; level of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and creatine kinase (CK); ophthalmological findings; echocardiography (ECHO) results; findings on brain magnetic resonance imaging (MRI); genetic analysis results; and muscular biopsy findings were evaluated.Results:The mean age of the patients was 5.2±2.3 years (range: 11 months-8 years) and the mean age at the onset of DMD was 4.1±2.2 years (range: 10 months-6 years). The ALT level ranged between 67 and 527 IU/L, the AST between 44 and 455 IU/L, and the CK between 931 and 19,595 IU/L. The genetic analysis determined deletions in 12 (80%) and duplications in 2 (13%) patients.Conclusion:Parents with a DMD-affected child should be provided with genetic counseling in order to make decisions about future pregnancies.

Analyses of the presence of mutations in Dystrophin protein to predict their relative influences in the onset of Duchenne Muscular Dystrophy

Muscle plays a vital role in the life of vertebrates like humans. Muscle contraction is the only criterion required for locomotion. Muscle fibers also play a vital role as the provider of mechanical strength and act as a large repository of building blocks for protein synthesis in living beings. Muscles function as per the messages received from the extra-cellular signals. One of the central players responsible for capturing and transmission of extra-cellular signals to maintain the integrity of muscle function is the protein called Dystrophin (Dp). However, the wild type Dp protein accumulates some mutations which lead to a severe disease called Duchenne Muscular Dystrophy (DMD). The disease is so frequent that it is known to affect 1 in 3500 newborns per year. There are a number of reports that identify the mutations leading to DMD. Interestingly, it is also observed that the type of mutations affects the severity of the disease. But the biochemical mechanism of the DMD onset is still obscure. In the present scenario, an attempt has been made to analyze the mutations in the development of the disease. We analyzed the changes in secondary structure, solvent accessibility and stability of the Dp protein associated with the mutations. We tried to correlate the type of mutations with the severity of the disease. So far this is the first report that deals with the analyses of the mutations leading to DMD. This study would therefore be essential to come up with a plausible mechanism of DMD disease onset.

Abstract 286: Structural Determinants Of Thermodynamic Stability And Actin-binding Function Of Dystrophin And Utrophin

Muscular dystrophy (MD) is an incurable disease, and affects all types of muscles. The decreased function of heart muscles causes heart problems such as cardiomyopathy and congestive heart failure. A deficiency in functional dystrophin protein in muscle cells triggers the onset of Duchenne MD and Becker MD. Utrophin is the closest homologue of dystrophin and is being tested as a protein drug to replace the loss of functional dystrophin in human patients. However, utrophin is less stable and binds to actin through a different mode of contact when compared with dystrophin. To optimize utrophin as the protein drug, we first need to understand how its molecular structure controls its stability and function. Utrophin and dystrophin bind to actin using tandem calponin-homology (CH) domains at their N-terminus. Individual CH domains of utrophin and dystrophin are very similar in amino acid sequence and their three dimensional structures. The major difference is in their relative orientation around the linker region that connects the two CH domains. To determine the role of the linker, we designed constructs with linkers switched between utrophin and dystrophin. Our results indicate that the tandem CH domain of utrophin with dystrophin linker (UDL) is more stable than that of utrophin but less stable than that of dystrophin. Similarly, tandem CH domain of dystrophin with utrophin linker (DUL) is less stable than that of dystrophin but more stable than that of utrophin. Kinetic folding and unfolding studies suggest that the linker predominantly affects the folding rate rather than the unfolding rate. In addition to stability and folding, the linker also controls protein aggregation. UDL is more prone to aggregation when compared with that of utrophin, whereas DUL is less prone to aggregation when compared with that of dystrophin. These results indicate that the linker plays a major role in controlling the stability and function of tandem CH domains, and further suggests that it is possible to engineer utrophin to behave precisely like dystrophin based on their molecular structures.

Abstract 327: Utrophin Loss in the Absence of Dystrophin Induces Alterations in Cardiac-Related Protein Expression and Activity in the Heart and Muscle of Dystrophic Mice

Duchenne Muscular Dystrophy (DMD) is an x-linked recessive disorder that affects 1:3500 males. The disease is characterized by the absence of the dystrophin protein, leading to progressive muscular degeneration in both skeletal and cardiac muscle. DMD is recapitulated in mouse models, the most severe model lacking both dystrophin and its compensatory homolog, utrophin (mdx:utro). This model mimics the onset of DMD much more rapidly than mdx. Nitric oxide (NO) synthesis is significantly diminished in DMD and mdx skeletal muscle. We have identified previously unreported functional differences in neuronal nitric oxide synthase (NOS1)-related nitric oxide production in cardiac musculature in mdx:utro mice, caused by the absence of utrophin. We have quantified mechanistic differences in L-Arginine mediated nitric oxide production via NOS1 in mdx and mdx:utro myocytes isolated via Langendorff perfusion. Interestingly, L-arginine transport levels were increased in the presence of this amino acid and occurred concurrently with increases in the number of mRNA transcripts for the low-affinity cationic amino acid transporter, CAT-2A. As CAT activity is an obligate process for L-Arginine entry to the cardiac myocytes, this may represent a potential compensatory mechanism related to decreased nitric oxide production. We have also found manifestations of ectopic cardiac-related protein expression in the quadriceps muscle of mdx:utro mice. In these tissues, we have found ectopic expression of the cardiac isoform of the SERCA2a calcium pump predominantly expressed in the heart. Additionally, we have found expression of slow-twitch Type 1 cardiac myosin heavy chain, indicative of a fiber type switch event. We have shown that expression of both of these proteins is co-localized to specific muscle fibers. Our analyses indicate that the appearance of these proteins is directly correlated with the lowered expression of the fast-twitch calcium pump (SERCA1) and muscle fiber types (Type 2a and Type 2b). These findings illustrate important molecular consequences of the absence of utrophin in mouse models of DMD. Identification of compensatory corrective targets may bear important therapeutic potential in muscular dystrophy and its associated cardiomyopathy.

Fast-twitch skeletal muscles of dystrophic mouse pups are resistant to injury from acute mechanical stress.

Loss of the dystrophin-glycoprotein complex from muscle sarcolemma in Duchenne's muscular dystrophy (DMD) renders the membrane susceptible to mechanical injury, leaky to Ca(2+), and disrupts signaling, but the precise mechanism(s) leading to the onset of DMD remain unclear. To assess the role of mechanical injury in the onset of DMD, extensor digitorum longus (EDL) muscles from C57 (control), mdx, and mdx-utrophin-deficient [mdx:utrn(-/-); dystrophic] pups aged 9-12 days were subjected to an acute stretch-injury or no-stretch protocol in vitro. Before the stretches, isometric stress was attenuated for mdx:utrn(-/-) compared with control muscles at all stimulation frequencies (P < 0.05). During the stretches, EDL muscles for each genotype demonstrated similar mean stiffness values. After the stretches, isometric stress during a tetanus was decreased significantly for both mdx and mdx:utrn(-/-) muscles compared with control muscles (P < 0.05). Membrane injury assessed by uptake of procion orange dye was greater for dystrophic compared with control EDL (P < 0.05), but, within each genotype, the percentage of total cells taking up dye was not different for the no-stretch vs. stretch condition. These data suggest that the sarcolemma of maturing dystrophic EDL muscles are resistant to acute mechanical injury.