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1
Straub, Volker, Jill A. Rafael, Jeffrey S. Chamberlain y Kevin P. Campbell. "Animal Models for Muscular Dystrophy Show Different Patterns of Sarcolemmal Disruption". Journal of Cell Biology 139, n.º 2 (20 de octubre de 1997): 375–85. http://dx.doi.org/10.1083/jcb.139.2.375.
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Genetic defects in a number of components of the dystrophin–glycoprotein complex (DGC) lead to distinct forms of muscular dystrophy. However, little is known about how alterations in the DGC are manifested in the pathophysiology present in dystrophic muscle tissue. One hypothesis is that the DGC protects the sarcolemma from contraction-induced damage. Using tracer molecules, we compared sarcolemmal integrity in animal models for muscular dystrophy and in muscular dystrophy patient samples. Evans blue, a low molecular weight diazo dye, does not cross into skeletal muscle fibers in normal mice. In contrast, mdx mice, a dystrophin-deficient animal model for Duchenne muscular dystrophy, showed significant Evans blue accumulation in skeletal muscle fibers. We also studied Evans blue dispersion in transgenic mice bearing different dystrophin mutations, and we demonstrated that cytoskeletal and sarcolemmal attachment of dystrophin might be a necessary requirement to prevent serious fiber damage. The extent of dye incorporation in transgenic mice correlated with the phenotypic severity of similar dystrophin mutations in humans. We furthermore assessed Evans blue incorporation in skeletal muscle of the dystrophia muscularis (dy/dy) mouse and its milder allelic variant, the dy2J/dy2J mouse, animal models for congenital muscular dystrophy. Surprisingly, these mice, which have defects in the laminin α2-chain, an extracellular ligand of the DGC, showed little Evans blue accumulation in their skeletal muscles. Taken together, these results suggest that the pathogenic mechanisms in congenital muscular dystrophy are different from those in Duchenne muscular dystrophy, although the primary defects originate in two components associated with the same protein complex.
2
Cui, Chang-Hao, Taro Uyama, Kenji Miyado, Masanori Terai, Satoru Kyo, Tohru Kiyono y Akihiro Umezawa. "Menstrual Blood-derived Cells Confer Human Dystrophin Expression in the Murine Model of Duchenne Muscular Dystrophy via Cell Fusion and Myogenic Transdifferentiation". Molecular Biology of the Cell 18, n.º 5 (mayo de 2007): 1586–94. http://dx.doi.org/10.1091/mbc.e06-09-0872.
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Duchenne muscular dystrophy (DMD), the most common lethal genetic disorder in children, is an X-linked recessive muscle disease characterized by the absence of dystrophin at the sarcolemma of muscle fibers. We examined a putative endometrial progenitor obtained from endometrial tissue samples to determine whether these cells repair muscular degeneration in a murine mdx model of DMD. Implanted cells conferred human dystrophin in degenerated muscle of immunodeficient mdx mice. We then examined menstrual blood–derived cells to determine whether primarily cultured nontransformed cells also repair dystrophied muscle. In vivo transfer of menstrual blood–derived cells into dystrophic muscles of immunodeficient mdx mice restored sarcolemmal expression of dystrophin. Labeling of implanted cells with enhanced green fluorescent protein and differential staining of human and murine nuclei suggest that human dystrophin expression is due to cell fusion between host myocytes and implanted cells. In vitro analysis revealed that endometrial progenitor cells and menstrual blood–derived cells can efficiently transdifferentiate into myoblasts/myocytes, fuse to C2C12 murine myoblasts by in vitro coculturing, and start to express dystrophin after fusion. These results demonstrate that the endometrial progenitor cells and menstrual blood–derived cells can transfer dystrophin into dystrophied myocytes through cell fusion and transdifferentiation in vitro and in vivo.
3
Steen, Michelle S., Marvin E. Adams, Yan Tesch y Stanley C. Froehner. "Amelioration of Muscular Dystrophy by Transgenic Expression of Niemann-Pick C1". Molecular Biology of the Cell 20, n.º 1 (enero de 2009): 146–52. http://dx.doi.org/10.1091/mbc.e08-08-0811.
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Duchenne muscular dystrophy (DMD) and other types of muscular dystrophies are caused by the loss or alteration of different members of the dystrophin protein complex. Understanding the molecular mechanisms by which dystrophin-associated protein abnormalities contribute to the onset of muscular dystrophy may identify new therapeutic approaches to these human disorders. By examining gene expression alterations in mouse skeletal muscle lacking α-dystrobrevin (Dtna−/−), we identified a highly significant reduction of the cholesterol trafficking protein, Niemann-Pick C1 (NPC1). Mutations in NPC1 cause a progressive neurodegenerative, lysosomal storage disorder. Transgenic expression of NPC1 in skeletal muscle ameliorates muscular dystrophy in the Dtna−/− mouse (which has a relatively mild dystrophic phenotype) and in the mdx mouse, a model for DMD. These results identify a new compensatory gene for muscular dystrophy and reveal a potential new therapeutic target for DMD.
4
Peter, Angela K., Jamie L. Marshall y Rachelle H. Crosbie. "Sarcospan reduces dystrophic pathology: stabilization of the utrophin–glycoprotein complex". Journal of Cell Biology 183, n.º 3 (3 de noviembre de 2008): 419–27. http://dx.doi.org/10.1083/jcb.200808027.
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Mutations in the dystrophin gene cause Duchenne muscular dystrophy and result in the loss of dystrophin and the entire dystrophin–glycoprotein complex (DGC) from the sarcolemma. We show that sarcospan (SSPN), a unique tetraspanin-like component of the DGC, ameliorates muscular dystrophy in dystrophin-deficient mdx mice. SSPN stabilizes the sarcolemma by increasing levels of the utrophin–glycoprotein complex (UGC) at the extrasynaptic membrane to compensate for the loss of dystrophin. Utrophin is normally restricted to the neuromuscular junction, where it replaces dystrophin to form a functionally analogous complex. SSPN directly interacts with the UGC and functions to stabilize utrophin protein without increasing utrophin transcription. These findings reveal the importance of protein stability in the prevention of muscular dystrophy and may impact the future design of therapeutics for muscular dystrophies.
5
Chen, Yi-Wen, Po Zhao, Rehannah Borup y Eric P. Hoffman. "Expression Profiling in the Muscular Dystrophies". Journal of Cell Biology 151, n.º 6 (11 de diciembre de 2000): 1321–36. http://dx.doi.org/10.1083/jcb.151.6.1321.
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We used expression profiling to define the pathophysiological cascades involved in the progression of two muscular dystrophies with known primary biochemical defects, dystrophin deficiency (Duchenne muscular dystrophy) and α-sarcoglycan deficiency (a dystrophin-associated protein). We employed a novel protocol for expression profiling in human tissues using mixed samples of multiple patients and iterative comparisons of duplicate datasets. We found evidence for both incomplete differentiation of patient muscle, and for dedifferentiation of myofibers to alternative lineages with advancing age. One developmentally regulated gene characterized in detail, α-cardiac actin, showed abnormal persistent expression after birth in 60% of Duchenne dystrophy myofibers. The majority of myofibers (∼80%) remained strongly positive for this protein throughout the course of the disease. Other developmentally regulated genes that showed widespread overexpression in these muscular dystrophies included embryonic myosin heavy chain, versican, acetylcholine receptor α-1, secreted protein, acidic and rich in cysteine/osteonectin, and thrombospondin 4. We hypothesize that the abnormal Ca2+ influx in dystrophin- and α-sarcoglycan–deficient myofibers leads to altered developmental programming of developing and regenerating myofibers. The finding of upregulation of HLA-DR and factor XIIIa led to the novel identification of activated dendritic cell infiltration in dystrophic muscle; these cells mediate immune responses and likely induce microenvironmental changes in muscle. We also document a general metabolic crisis in dystrophic muscle, with large scale downregulation of nuclear-encoded mitochondrial gene expression. Finally, our expression profiling results show that primary genetic defects can be identified by a reduction in the corresponding RNA.
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Yeadon, J. E., H. Lin, S. M. Dyer y S. J. Burden. "Dystrophin is a component of the subsynaptic membrane." Journal of Cell Biology 115, n.º 4 (15 de noviembre de 1991): 1069–76. http://dx.doi.org/10.1083/jcb.115.4.1069.
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A subsynaptic protein of Mr approximately 300 kD is a major component of Torpedo electric organ postsynaptic membranes and copurifies with the AChR and the 43-kD subsynaptic protein. mAbs against this protein react with neuromuscular synapses in higher vertebrates, but not at synapses in dystrophic muscle. The Torpedo 300-kD protein comigrates in SDS-PAGE with murine dystrophin and reacts with antibodies against murine dystrophin. The sequence of a partial cDNA isolated by screening an expression library with mAbs against the Torpedo 300-kD protein shows striking homology to mammalian dystrophin, and in particular to the b isoform of dystrophin. These results indicate that dystrophin is a component of the postsynaptic membrane at neuromuscular synapses and raise the possibility that loss of dystrophin from synapses in dystrophic muscle may have consequences that contribute to muscular dystrophy.
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Teramoto, Naomi, Hidetoshi Sugihara, Keitaro Yamanouchi, Katsuyuki Nakamura, Koichi Kimura, Tomoko Okano, Takanori Shiga et al. "Pathological evaluation of rats carrying in-frame mutations in the dystrophin gene: a new model of Becker muscular dystrophy". Disease Models & Mechanisms 13, n.º 9 (28 de agosto de 2020): dmm044701. http://dx.doi.org/10.1242/dmm.044701.
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ABSTRACTDystrophin, encoded by the DMD gene on the X chromosome, stabilizes the sarcolemma by linking the actin cytoskeleton with the dystrophin-glycoprotein complex (DGC). In-frame mutations in DMD cause a milder form of X-linked muscular dystrophy, called Becker muscular dystrophy (BMD), characterized by the reduced expression of truncated dystrophin. So far, no animal model with in-frame mutations in Dmd has been established. As a result, the effect of in-frame mutations on the dystrophin expression profile and disease progression of BMD remains unclear. In this study, we established a novel rat model carrying in-frame Dmd gene mutations (IF rats) and evaluated the pathology. We found that IF rats exhibited reduced expression of truncated dystrophin in a proteasome-independent manner. This abnormal dystrophin expression caused dystrophic changes in muscle tissues but did not lead to functional deficiency. We also found that the expression of additional dystrophin named dpX, which forms the DGC in the sarcolemma, was associated with the appearance of truncated dystrophin. In conclusion, the outcomes of this study contribute to the further understanding of BMD pathology and help elucidate the efficiency of dystrophin recovery treatments in Duchenne muscular dystrophy, a more severe form of X-linked muscular dystrophy.
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Spaulding, HR, C. Ballmann, JC Quindry, MB Hudson y JT Selsby. "Autophagy in the heart is enhanced and independent of disease progression in mus musculus dystrophinopathy models". JRSM Cardiovascular Disease 8 (enero de 2019): 204800401987958. http://dx.doi.org/10.1177/2048004019879581.
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Background Duchenne muscular dystrophy is a muscle wasting disease caused by dystrophin gene mutations resulting in dysfunctional dystrophin protein. Autophagy, a proteolytic process, is impaired in dystrophic skeletal muscle though little is known about the effect of dystrophin deficiency on autophagy in cardiac muscle. We hypothesized that with disease progression autophagy would become increasingly dysfunctional based upon indirect autophagic markers. Methods Markers of autophagy were measured by western blot in 7-week-old and 17-month-old control (C57) and dystrophic (mdx) hearts. Results Counter to our hypothesis, markers of autophagy were similar between groups. Given these surprising results, two independent experiments were conducted using 14-month-old mdx mice or 10-month-old mdx/Utrn± mice, a more severe model of Duchenne muscular dystrophy. Data from these animals suggest increased autophagosome degradation. Conclusion Together these data suggest that autophagy is not impaired in the dystrophic myocardium as it is in dystrophic skeletal muscle and that disease progression and related injury is independent of autophagic dysfunction.
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Ibrahim Sory, P., T. Sidi, L. Guida, K. Boureima, M. Alassane Bameye, T. Mohomodine Ibrahim, K. Abdoulaye y C. Idrissa Ahmadou. "Dystrophie Musculaire de Duchenne: Aspects cliniques, biologiques et évolutifs à propos de cinq cas dans le service de Rhumatologie au CHU du Point G." Rhumatologie Africaine Francophone 6, n.º 2 (19 de enero de 2024): 18–23. http://dx.doi.org/10.62455/raf.v6i2.53.
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Résumé
La dystrophie musculaire de Duchenne (DMD) due à la non expression de la dystrophine est liée au chromosome X. Décrite au 19e siècle, est la plus courante dystrophie musculaire de l’enfant [1, 2]. L’incidence est estimée à 30 cas pour 100 000 naissances [1, 2].
But- étudier les caractères cliniques, biologiques et évolutifs de la dystrophie musculaire de Duchenne.
Patients et Méthodes :
Il s’est agi d’une étude rétrospective portant sur 5 dossiers de DMD, colligés en 7 ans.
Résultats
Nous rapportons cinq dossiers de garçons colligés entre 2005 et 2012,
2012, d’âge moyen de 7 ans avec des extrêmes de 1 et 12 ans. L’hypertrophie des mollets et la présence d’un signe de Gowers chez 4/5 patients. Le caractère familial était présent chez 2 garçons âgés de 5 et 10 ans à l’inclusion dont un mariage consanguin. L’examen anatomopathologique musculaire a conclu à des lésions dystrophiques. L’immunohistochimie n’a pas trouvé d’expression de la dystrophine. La corticothérapie précocement instituée à 0,5 mg/kg/jour associée à la rééducation kinésithérapie a maintenu l’autonomie des patients.
Conclusion
La corticothérapie retarderait les complications cardio-pulmonaires. Associée à la rééducation kinésithérapie et aux conseils pratiques elle a diminué les chutes.
Mots clés : Dystrophie – Musculaire – Duchenne, Rhumatologie Bamako
Abstract:
Introduction Duchenne’s muscular dystrophy (DMD) caused by no dystrophin expression is linked to X chromosome. Described in the 19th century, it is the most common muscular dystrophy of the child [1, 2]. The incidence is estimated at 30 cases per 100 000 births [1, 2]. Goal - Study clinical, biological and evolutive aspects of the Duchenne's Muscular Dystrophy.
Patients and Methods:
It was a retrospective study about 5 cases of DMD, collected in 7 years [2005-2012].
Results During our study from the period of 2005 to 2012, we had 5 cases of boys with an average age of 7 years and the extreme age from 1 year to 12 years. The calf’s hypertrophy and the presence of a Gowers’s sign in 4/5 patients. Family caracteristic was present in two boys aged 5 and 10 years with a consanguineous marriage. Muscular Histological examination concluded dystrophic lesions. The immunohistiochemistry found no expression of dystrophin. Corticosteroids early established at 0.5 mg / kg / day combined with physiotherapy rehabilitation maintained the autonomy of patients. .
Conclusion Corticosteroids would slow douwn cardiopulmonary complications. Associated with the physiotherapy rehabilitation and practical advice, it has decreased falls.
Keywords: Duchenne’s muscular dystrophy, Rheumatology, Bamako
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Zabłocka, Barbara, Dariusz C. Górecki y Krzysztof Zabłocki. "Disrupted Calcium Homeostasis in Duchenne Muscular Dystrophy: A Common Mechanism behind Diverse Consequences". International Journal of Molecular Sciences 22, n.º 20 (13 de octubre de 2021): 11040. http://dx.doi.org/10.3390/ijms222011040.
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Duchenne muscular dystrophy (DMD) leads to disability and death in young men. This disease is caused by mutations in the DMD gene encoding diverse isoforms of dystrophin. Loss of full-length dystrophins is both necessary and sufficient for causing degeneration and wasting of striated muscles, neuropsychological impairment, and bone deformities. Among this spectrum of defects, abnormalities of calcium homeostasis are the common dystrophic feature. Given the fundamental role of Ca2+ in all cells, this biochemical alteration might be underlying all the DMD abnormalities. However, its mechanism is not completely understood. While abnormally elevated resting cytosolic Ca2+ concentration is found in all dystrophic cells, the aberrant mechanisms leading to that outcome have cell-specific components. We probe the diverse aspects of calcium response in various affected tissues. In skeletal muscles, cardiomyocytes, and neurons, dystrophin appears to serve as a scaffold for proteins engaged in calcium homeostasis, while its interactions with actin cytoskeleton influence endoplasmic reticulum organisation and motility. However, in myoblasts, lymphocytes, endotheliocytes, and mesenchymal and myogenic cells, calcium abnormalities cannot be clearly attributed to the loss of interaction between dystrophin and the calcium toolbox proteins. Nevertheless, DMD gene mutations in these cells lead to significant defects and the calcium anomalies are a symptom of the early developmental phase of this pathology. As the impaired calcium homeostasis appears to underpin multiple DMD abnormalities, understanding this alteration may lead to the development of new therapies. In fact, it appears possible to mitigate the impact of the abnormal calcium homeostasis and the dystrophic phenotype in the total absence of dystrophin. This opens new treatment avenues for this incurable disease.
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Zabłocka, Barbara, Dariusz C. Górecki y Krzysztof Zabłocki. "Disrupted Calcium Homeostasis in Duchenne Muscular Dystrophy: A Common Mechanism behind Diverse Consequences". International Journal of Molecular Sciences 22, n.º 20 (13 de octubre de 2021): 11040. http://dx.doi.org/10.3390/ijms222011040.
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Duchenne muscular dystrophy (DMD) leads to disability and death in young men. This disease is caused by mutations in the DMD gene encoding diverse isoforms of dystrophin. Loss of full-length dystrophins is both necessary and sufficient for causing degeneration and wasting of striated muscles, neuropsychological impairment, and bone deformities. Among this spectrum of defects, abnormalities of calcium homeostasis are the common dystrophic feature. Given the fundamental role of Ca2+ in all cells, this biochemical alteration might be underlying all the DMD abnormalities. However, its mechanism is not completely understood. While abnormally elevated resting cytosolic Ca2+ concentration is found in all dystrophic cells, the aberrant mechanisms leading to that outcome have cell-specific components. We probe the diverse aspects of calcium response in various affected tissues. In skeletal muscles, cardiomyocytes, and neurons, dystrophin appears to serve as a scaffold for proteins engaged in calcium homeostasis, while its interactions with actin cytoskeleton influence endoplasmic reticulum organisation and motility. However, in myoblasts, lymphocytes, endotheliocytes, and mesenchymal and myogenic cells, calcium abnormalities cannot be clearly attributed to the loss of interaction between dystrophin and the calcium toolbox proteins. Nevertheless, DMD gene mutations in these cells lead to significant defects and the calcium anomalies are a symptom of the early developmental phase of this pathology. As the impaired calcium homeostasis appears to underpin multiple DMD abnormalities, understanding this alteration may lead to the development of new therapies. In fact, it appears possible to mitigate the impact of the abnormal calcium homeostasis and the dystrophic phenotype in the total absence of dystrophin. This opens new treatment avenues for this incurable disease.
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Koenig, Xaver, Janine Ebner y Karlheinz Hilber. "Voltage-Dependent Sarcolemmal Ion Channel Abnormalities in the Dystrophin-Deficient Heart". International Journal of Molecular Sciences 19, n.º 11 (23 de octubre de 2018): 3296. http://dx.doi.org/10.3390/ijms19113296.
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Mutations in the gene encoding for the intracellular protein dystrophin cause severe forms of muscular dystrophy. These so-called dystrophinopathies are characterized by skeletal muscle weakness and degeneration. Dystrophin deficiency also gives rise to considerable complications in the heart, including cardiomyopathy development and arrhythmias. The current understanding of the pathomechanisms in the dystrophic heart is limited, but there is growing evidence that dysfunctional voltage-dependent ion channels in dystrophin-deficient cardiomyocytes play a significant role. Herein, we summarize the current knowledge about abnormalities in voltage-dependent sarcolemmal ion channel properties in the dystrophic heart, and discuss the potentially underlying mechanisms, as well as their pathophysiological relevance.
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Pelosi, Laura, Laura Forcina, Carmine Nicoletti, Bianca Maria Scicchitano y Antonio Musarò. "Increased Circulating Levels of Interleukin-6 Induce Perturbation in Redox-Regulated Signaling Cascades in Muscle of Dystrophic Mice". Oxidative Medicine and Cellular Longevity 2017 (2017): 1–10. http://dx.doi.org/10.1155/2017/1987218.
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Duchenne muscular dystrophy (DMD) is an X-linked genetic disease in which dystrophin gene is mutated, resulting in dysfunctional or absent dystrophin protein. The pathology of dystrophic muscle includes degeneration, necrosis with inflammatory cell invasion, regeneration, and fibrous and fatty changes. Nevertheless, the mechanisms by which the absence of dystrophin leads to muscle degeneration remain to be fully elucidated. An imbalance between oxidant and antioxidant systems has been proposed as a secondary effect of DMD. However, the significance and precise extent of the perturbation in redox signaling cascades is poorly understood. We report that mdx dystrophic mice are able to activate a compensatory antioxidant response at the presymptomatic stage of the disease. In contrast, increased circulating levels of IL-6 perturb the redox signaling cascade, even prior to the necrotic stage, leading to severe features and progressive nature of muscular dystrophy.
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Blake, Derek J., Andrew Weir, Sarah E. Newey y Kay E. Davies. "Function and Genetics of Dystrophin and Dystrophin-Related Proteins in Muscle". Physiological Reviews 82, n.º 2 (1 de abril de 2002): 291–329. http://dx.doi.org/10.1152/physrev.00028.2001.
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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 α-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.
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Meyers, Tatyana A., Jackie A. Heitzman y DeWayne Townsend. "DMD carrier model with mosaic dystrophin expression in the heart reveals complex vulnerability to myocardial injury". Human Molecular Genetics 29, n.º 6 (24 de enero de 2020): 944–54. http://dx.doi.org/10.1093/hmg/ddaa015.
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Abstract Duchenne muscular dystrophy (DMD) is a devastating neuromuscular disease that causes progressive muscle wasting and cardiomyopathy. This X-linked disease results from mutations of the DMD allele on the X-chromosome resulting in the loss of expression of the protein dystrophin. Dystrophin loss causes cellular dysfunction that drives the loss of healthy skeletal muscle and cardiomyocytes. As gene therapy strategies strive toward dystrophin restoration through micro-dystrophin delivery or exon skipping, preclinical models have shown that incomplete restoration in the heart results in heterogeneous dystrophin expression throughout the myocardium. This outcome prompts the question of how much dystrophin restoration is sufficient to rescue the heart from DMD-related pathology. Female DMD carrier hearts can shed light on this question, due to their mosaic cardiac dystrophin expression resulting from random X-inactivation. In this work, a dystrophinopathy carrier mouse model was derived by breeding male or female dystrophin-null mdx mice with a wild type mate. We report that these carrier hearts are significantly susceptible to injury induced by one or multiple high doses of isoproterenol, despite expressing ~57% dystrophin. Importantly, only carrier mice with dystrophic mothers showed mortality after isoproterenol. These findings indicate that dystrophin restoration in approximately half of the heart still allows for marked vulnerability to injury. Additionally, the discovery of divergent stress-induced mortality based on parental origin in mice with equivalent dystrophin expression underscores the need for better understanding of the epigenetic, developmental, and even environmental factors that may modulate vulnerability in the dystrophic heart.
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Betts, Corinne A., Aarti Jagannath, Tirsa LE van Westering, Melissa Bowerman, Subhashis Banerjee, Jinhong Meng, Maria Sofia Falzarano et al. "Dystrophin involvement in peripheral circadian SRF signalling". Life Science Alliance 4, n.º 10 (13 de agosto de 2021): e202101014. http://dx.doi.org/10.26508/lsa.202101014.
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Absence of dystrophin, an essential sarcolemmal protein required for muscle contraction, leads to the devastating muscle-wasting disease Duchenne muscular dystrophy. Dystrophin has an actin-binding domain, which binds and stabilises filamentous-(F)-actin, an integral component of the RhoA-actin-serum-response-factor-(SRF) pathway. This pathway plays a crucial role in circadian signalling, whereby the suprachiasmatic nucleus (SCN) transmits cues to peripheral tissues, activating SRF and transcription of clock-target genes. Given dystrophin binds F-actin and disturbed SRF-signalling disrupts clock entrainment, we hypothesised dystrophin loss causes circadian deficits. We show for the first time alterations in the RhoA-actin-SRF-signalling pathway, in dystrophin-deficient myotubes and dystrophic mouse models. Specifically, we demonstrate reduced F/G-actin ratios, altered MRTF levels, dysregulated core-clock and downstream target-genes, and down-regulation of key circadian genes in muscle biopsies from Duchenne patients harbouring an array of mutations. Furthermore, we show dystrophin is absent in the SCN of dystrophic mice which display disrupted circadian locomotor behaviour, indicative of disrupted SCN signalling. Therefore, dystrophin is an important component of the RhoA-actin-SRF pathway and novel mediator of circadian signalling in peripheral tissues, loss of which leads to circadian dysregulation.
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Vieira, Natassia M., Janelle M. Spinazzola, Matthew S. Alexander, Yuri B. Moreira, Genri Kawahara, Devin E. Gibbs, Lillian C. Mead, Sergio Verjovski-Almeida, Mayana Zatz y Louis M. Kunkel. "Repression of phosphatidylinositol transfer protein α ameliorates the pathology of Duchenne muscular dystrophy". Proceedings of the National Academy of Sciences 114, n.º 23 (22 de mayo de 2017): 6080–85. http://dx.doi.org/10.1073/pnas.1703556114.
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Duchenne muscular dystrophy (DMD) is a progressive muscle wasting disease caused by X-linked inherited mutations in the DYSTROPHIN (DMD) gene. Absence of dystrophin protein from the sarcolemma causes severe muscle degeneration, fibrosis, and inflammation, ultimately leading to cardiorespiratory failure and premature death. Although there are several promising strategies under investigation to restore dystrophin protein expression, there is currently no cure for DMD, and identification of genetic modifiers as potential targets represents an alternative therapeutic strategy. In a Brazilian golden retriever muscular dystrophy (GRMD) dog colony, two related dogs demonstrated strikingly mild dystrophic phenotypes compared with those typically observed in severely affected GRMD dogs despite lacking dystrophin. Microarray analysis of these “escaper” dogs revealed reduced expression of phosphatidylinositol transfer protein-α (PITPNA) in escaper versus severely affected GRMD dogs. Based on these findings, we decided to pursue investigation of modulation of PITPNA expression on dystrophic pathology in GRMD dogs, dystrophin-deficient sapje zebrafish, and human DMD myogenic cells. In GRMD dogs, decreased expression of Pitpna was associated with increased phosphorylated Akt (pAkt) expression and decreased PTEN levels. PITPNA knockdown by injection of morpholino oligonucleotides in sapje zebrafish also increased pAkt, rescued the abnormal muscle phenotype, and improved long-term sapje mutant survival. In DMD myotubes, PITPNA knockdown by lentiviral shRNA increased pAkt and increased myoblast fusion index. Overall, our findings suggest PIPTNA as a disease modifier that accords benefits to the abnormal signaling, morphology, and function of dystrophic skeletal muscle, and may be a target for DMD and related neuromuscular diseases.
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Law, D. J., D. L. Allen y J. G. Tidball. "Talin, vinculin and DRP (utrophin) concentrations are increased at mdx myotendinous junctions following onset of necrosis". Journal of Cell Science 107, n.º 6 (1 de junio de 1994): 1477–83. http://dx.doi.org/10.1242/jcs.107.6.1477.
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Duchenne muscular dystrophy (DMD) and the myopathy seen in the mdx mouse both result from absence of the protein dystrophin. Structural similarities between dystrophin and other cytoskeletal proteins, its enrichment at myotendinous junctions, and its indirect association with laminin mediated by a transmembrane glycoprotein complex suggest that one of dystrophin's functions in normal muscle is to form one of the links between the actin cytoskeleton and the extracellular matrix. Unlike Duchenne muscular dystrophy patients, mdx mice suffer only transient muscle necrosis, and are able to regenerate damaged muscle tissue. The present study tests the hypothesis that mdx mice partially compensate for dystrophin's absence by upregulating one or more dystrophin-independent mechanisms of cytoskeleton-membrane association. Quantitative analysis of immunoblots of adult mdx muscle samples showed an increase of approximately 200% for vinculin and talin, cytoskeletal proteins that mediate thin filament-membrane interactions at myotendinous junctions. Blots also showed an increase (143%) in the dystrophin-related protein called utrophin, another myotendinous junction constituent, which may be able to substitute for dystrophin directly. Muscle samples from 2-week-old animals, a period immediately preceding the onset of muscle necrosis, showed no significant differences in protein concentration between mdx and controls. Quantitative analyses of confocal images of myotendinous junctions from mdx and control muscles show significantly higher concentrations of talin and vinculin at the myotendinous junctions of mdx muscle. These findings indicate that mdx mice may compensate in part for the absence of dystrophin by increased expression of other molecules that subsume dystrophin's mechanical function.
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Bergman, Robert L., Karen D. Inzana, William E. Monroe, Linda G. Shell, Ling A. Liu, Eva Engvall y G. Diane Shelton. "Dystrophin-Deficient Muscular Dystrophy in a Labrador Retriever". Journal of the American Animal Hospital Association 38, n.º 3 (1 de mayo de 2002): 255–61. http://dx.doi.org/10.5326/0380255.
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Sex-linked muscular dystrophy associated with dystrophin deficiency has been reported in several breeds of dogs and is best characterized in the golden retriever. In this case report, a young, male Labrador retriever with dystrophin-deficient muscular dystrophy is presented. Clinical signs included generalized weakness, lingual hypertrophy, and dysphagia. Electromyographic abnormalities including complex repetitive discharges were present. Serum creatine kinase concentration was dramatically elevated. Histopathological changes within a muscle biopsy specimen confirmed a dystrophic myopathy, and dystrophin deficiency was demonstrated by immunohisto-chemical staining. While X-linked muscular dystrophy has not previously been reported in the Labrador retriever, a hereditary myopathy with an autosomal recessive mode of inheritance has been characterized. A correct diagnosis and classification of these two disorders are critical for breeders and owners since both the mode of inheritance and the prognosis differ.
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Bellayou, Hanane, Khalil Hamzi, Mohamed Abdou Rafai, Mehdi Karkouri, Ilham Slassi, Houssine Azeddoug y Sellama Nadifi. "Duchenne and Becker Muscular Dystrophy: Contribution of a Molecular and Immunohistochemical Analysis in Diagnosis in Morocco". Journal of Biomedicine and Biotechnology 2009 (2009): 1–5. http://dx.doi.org/10.1155/2009/325210.
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Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked recessive disorders caused by mutations of the DMD gene located at Xp21. In DMD patients, dystrophin is virtually absent; whereas BMD patients have 10% to 40% of the normal amount. Deletions in the dystrophin gene represent 65% of mutations in DMD/BMD patients. To explain the contribution of immunohistochemical and genetic analysis in the diagnosis of these dystrophies, we present 10 cases of DMD/BMD with particular features. We have analyzed the patients with immunohistochemical staining and PCR multiplex to screen for exons deletions. Determination of the quantity and distribution of dystrophin by immunohistochemical staining can confirm the presence of dystrophinopathy and allows differentiation between DMD and BMD, but dystrophin staining is not always conclusive in BMD. Therefore, only identification involved mutation by genetic analysis can establish a correct diagnosis.
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Gumerson, Jessica D. y Daniel E. Michele. "The Dystrophin-Glycoprotein Complex in the Prevention of Muscle Damage". Journal of Biomedicine and Biotechnology 2011 (2011): 1–13. http://dx.doi.org/10.1155/2011/210797.
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Muscular dystrophies are genetically diverse but share common phenotypic features of muscle weakness, degeneration, and progressive decline in muscle function. Previous work has focused on understanding how disruptions in the dystrophin-glycoprotein complex result in muscular dystrophy, supporting a hypothesis that the muscle sarcolemma is fragile and susceptible to contraction-induced injury in multiple forms of dystrophy. Although benign in healthy muscle, contractions in dystrophic muscle may contribute to a higher degree of muscle damage which eventually overwhelms muscle regeneration capacity. While increased susceptibility of muscle to mechanical injury is thought to be an important contributor to disease pathology, it is becoming clear that not all DGC-associated diseases share this supposed hallmark feature. This paper outlines experimental support for a function of the DGC in preventing muscle damage and examines the evidence that supports novel functions for this complex in muscle that when impaired, may contribute to the pathogenesis of muscular dystrophy.
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Spiro, Alfred J. "Muscular Dystrophy". Pediatrics In Review 16, n.º 11 (1 de noviembre de 1995): 437. http://dx.doi.org/10.1542/pir.16.11.437.
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Several varieties of muscular dystrophy can be distinguished on clinical, genetic, morphologic, and physiologic grounds. The classification includes Duchenne and Becker muscular dystrophies, both X-linked disorders; facioscapulohumeral muscular dystrophy, which is autosomal dominant; and limb-girdle muscular dystrophy, generally autosomal recessive. Duchenne muscular dystrophy (DMD), which occurs in approximately 1 in 3500 live male births, has no recognizable signs or symptoms at birth. However, markedly elevated serum creatine kinase always is demonstrable, even at birth. A molecular diagnosis can be made at any time in the patient's lifetime by demonstrating the defect in the dystrophin gene, the absence of dystrophin in a muscle biopsy, and the characteristic morphologic abnormalities.
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Ohlendieck, K. y K. P. Campbell. "Dystrophin-associated proteins are greatly reduced in skeletal muscle from mdx mice." Journal of Cell Biology 115, n.º 6 (15 de diciembre de 1991): 1685–94. http://dx.doi.org/10.1083/jcb.115.6.1685.
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Dystrophin, the protein product of the human Duchenne muscular dystrophy gene, exists in skeletal muscle as a large oligomeric complex that contains four glycoproteins of 156, 50, 43, and 35 kD and a protein of 59 kD. Here, we investigated the relative abundance of each of the components of the dystrophin-glycoprotein complex in skeletal muscle from normal and mdx mice, which are missing dystrophin. Immunoblot analysis using total muscle membranes from control and mdx mice of ages 1 d to 30 wk found that all of the dystrophin-associated proteins were greatly reduced (80-90%) in mdx mouse skeletal muscle. The specificity of the loss of the dystrophin-associated glycoproteins was demonstrated by the finding that the major glycoprotein composition of skeletal muscle membranes from normal and mdx mice was identical. Furthermore, skeletal muscle membranes from the dystrophic dy/dy mouse exhibited a normal density of dystrophin and dystrophin-associated proteins. Immunofluorescence microscopy confirmed the results from the immunoblot analysis and showed a drastically reduced density of dystrophin-associated proteins in mdx muscle cryosections compared with normal and dy/dy mouse muscle. Therefore, our results demonstrate that all of the dystrophin-associated proteins are significantly reduced in mdx skeletal muscle and suggest that the loss of dystrophin-associated proteins is due to the absence of dystrophin and not due to secondary effects of muscle fiber degradation.
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Echigoya, Yusuke, Akinori Nakamura, Tetsuya Nagata, Nobuyuki Urasawa, Kenji Rowel Q. Lim, Nhu Trieu, Dharminder Panesar et al. "Effects of systemic multiexon skipping with peptide-conjugated morpholinos in the heart of a dog model of Duchenne muscular dystrophy". Proceedings of the National Academy of Sciences 114, n.º 16 (3 de abril de 2017): 4213–18. http://dx.doi.org/10.1073/pnas.1613203114.
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Duchenne muscular dystrophy (DMD) is a lethal genetic disorder caused by an absence of the dystrophin protein in bodywide muscles, including the heart. Cardiomyopathy is a leading cause of death in DMD. Exon skipping via synthetic phosphorodiamidate morpholino oligomers (PMOs) represents one of the most promising therapeutic options, yet PMOs have shown very little efficacy in cardiac muscle. To increase therapeutic potency in cardiac muscle, we tested a next-generation morpholino: arginine-rich, cell-penetrating peptide-conjugated PMOs (PPMOs) in the canine X-linked muscular dystrophy in Japan (CXMDJ) dog model of DMD. A PPMO cocktail designed to skip dystrophin exons 6 and 8 was injected intramuscularly, intracoronarily, or intravenously into CXMDJ dogs. Intravenous injections with PPMOs restored dystrophin expression in the myocardium and cardiac Purkinje fibers, as well as skeletal muscles. Vacuole degeneration of cardiac Purkinje fibers, as seen in DMD patients, was ameliorated in PPMO-treated dogs. Although symptoms and functions in skeletal muscle were not ameliorated by i.v. treatment, electrocardiogram abnormalities (increased Q-amplitude and Q/R ratio) were improved in CXMDJ dogs after intracoronary or i.v. administration. No obvious evidence of toxicity was found in blood tests throughout the monitoring period of one or four systemic treatments with the PPMO cocktail (12 mg/kg/injection). The present study reports the rescue of dystrophin expression and recovery of the conduction system in the heart of dystrophic dogs by PPMO-mediated multiexon skipping. We demonstrate that rescued dystrophin expression in the Purkinje fibers leads to the improvement/prevention of cardiac conduction abnormalities in the dystrophic heart.
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Corrado, K., J. A. Rafael, P. L. Mills, N. M. Cole, J. A. Faulkner, K. Wang y J. S. Chamberlain. "Transgenic mdx mice expressing dystrophin with a deletion in the actin-binding domain display a "mild Becker" phenotype." Journal of Cell Biology 134, n.º 4 (15 de agosto de 1996): 873–84. http://dx.doi.org/10.1083/jcb.134.4.873.
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The functional significance of the actin-binding domain of dystrophin, the protein lacking in patients with Duchenne muscular dystrophy, has remained elusive. Patients with deletions of this domain (domain I) typically express low levels of the truncated protein. Whether the moderate to severe phenotypes associated with such deletions result from loss of an essential function, or from reduced levels of a functional protein, is unclear. To address this question, we have generated transgenic mice that express wild-type levels of a dystrophin deleted for the majority of the actin-binding domain. The transgene derived protein lacks amino acids 45-273, removing 2 of 3 in vitro identified actin interacting sites and part of hinge 1. Examination of the effect of this deletion in mice lacking wild-type dystrophin (mdx) suggests that a functional domain I is not essential for prevention of a dystrophic phenotype. However, in contrast to deletions in the central rod domain and to full-length dystrophin, both of which are functional at only 20% of wild-type levels, proteins with a deletion in domain I must be expressed at high levels to prevent a severe dystrophy. These results are also in contrast to the severe dystrophy resulting from truncation of the COOH-terminal domain that links dystrophin to the extracellular matrix. The mild phenotype observed in mice with domain I-deletions indicates that an intact actin-binding domain is not essential, although it does contribute to an important function of dystrophin. These studies also suggest the link between dystrophin and the subsarcolemmal cytoskeleton involves more than a simple attachment of domain I to actin filaments.
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Spinazzola, Janelle M., Matthias R. Lambert, Devin E. Gibbs, James R. Conner, Georgia L. Krikorian, Prithu Pareek, Carlo Rago y Louis M. Kunkel. "Effect of serotonin modulation on dystrophin-deficient zebrafish". Biology Open 9, n.º 8 (27 de julio de 2020): bio053363. http://dx.doi.org/10.1242/bio.053363.
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ABSTRACTDuchenne muscular dystrophy (DMD) is a progressive muscle-wasting disease caused by mutation of the dystrophin gene. Pharmacological therapies that function independently of dystrophin and complement strategies aimed at dystrophin restoration could significantly improve patient outcomes. Previous observations have suggested that serotonin pathway modulation ameliorates dystrophic pathology, and re-application of serotonin modulators already used clinically would potentially hasten availability to DMD patients. In our study, we used dystrophin-deficient sapje and sapje-like zebrafish models of DMD for rapid and easy screening of several classes of serotonin pathway modulators as potential therapeutics. None of the candidate drugs tested significantly decreased the percentage of zebrafish exhibiting the dystrophic muscle phenotype in the short-term birefringence assay or lengthened the lifespan in the long-term survival assay. Although we did not identify an effective drug, we believe our data is of value to the DMD research community for future studies, and there is evidence that suggests serotonin modulation may still be a viable treatment strategy with further investigation. Given the widespread clinical use of selective serotonin reuptake inhibitors, tricyclic antidepressants and reversible inhibitors of monoamine oxidase, their reapplication to DMD is an attractive strategy in the field's pursuit to identify pharmacological therapies to complement dystrophin restoration strategies.
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Guiraud, Simon, Benjamin Edwards, Arran Babbs, Sarah E. Squire, Adam Berg, Lee Moir, Matthew J. Wood y Kay E. Davies. "The potential of utrophin and dystrophin combination therapies for Duchenne muscular dystrophy". Human Molecular Genetics 28, n.º 13 (5 de marzo de 2019): 2189–200. http://dx.doi.org/10.1093/hmg/ddz049.
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Abstract Duchenne muscular dystrophy (DMD) is a lethal neuromuscular disorder caused by loss of dystrophin. Several therapeutic modalities are currently in clinical trials but none will achieve maximum functional rescue and full disease correction. Therefore, we explored the potential of combining the benefits of dystrophin with increases of utrophin, an autosomal paralogue of dystrophin. Utrophin and dystrophin can be co-expressed and co-localized at the same muscle membrane. Wild-type (wt) levels of dystrophin are not significantly affected by a moderate increase of utrophin whereas higher levels of utrophin reduce wt dystrophin, suggesting a finite number of actin binding sites at the sarcolemma. Thus, utrophin upregulation strategies may be applied to the more mildly affected Becker patients with lower dystrophin levels. Whereas increased dystrophin in wt animals does not offer functional improvement, overexpression of utrophin in wt mice results in a significant supra-functional benefit over wt. These findings highlight an additive benefit of the combined therapy and potential new unique roles of utrophin. Finally, we show a 30% restoration of wt dystrophin levels, using exon-skipping, together with increased utrophin levels restores dystrophic muscle function to wt levels offering greater therapeutic benefit than either single approach alone. Thus, this combination therapy results in additive functional benefit and paves the way for potential future combinations of dystrophin- and utrophin-based strategies.
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Spaulding, Hannah R., Tiffany Quindry, Kayleen Hammer, John C. Quindry y Joshua T. Selsby. "Nutraceutical and pharmaceutical cocktails did not improve muscle function or reduce histological damage in D2-mdx mice". Journal of Applied Physiology 127, n.º 4 (1 de octubre de 2019): 1058–66. http://dx.doi.org/10.1152/japplphysiol.00162.2019.
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Progressive muscle injury and weakness are hallmarks of Duchenne muscular dystrophy. We showed previously that quercetin (Q) partially protected dystrophic limb muscles from disease-related injury. As quercetin activates PGC-1α through Sirtuin-1, an NAD+-dependent deacetylase, the depleted NAD+ in dystrophic skeletal muscle may limit quercetin efficacy; hence, supplementation with the NAD+ donor, nicotinamide riboside (NR), may facilitate quercetin efficacy. Lisinopril (Lis) protects skeletal muscle and improves cardiac function in dystrophin-deficient mice; therefore, it was included in this study to evaluate the effects of lisinopril used with quercetin and NR. Our purpose was to determine the extent to which Q, NR, and Lis decreased dystrophic injury. We hypothesized that Q, NR, or Lis alone would improve muscle function and decrease histological injury and when used in combination would have additive effects. Muscle function of 11-mo-old DBA (healthy), D2-mdx (dystrophin-deficient), and D2-mdx mice was assessed after treatment with Q, NR, and/or Lis for 7 mo. To mimic typical pharmacology of patients with Duchenne muscular dystrophy, a group was treated with prednisolone (Pred) in combination with Q, NR, and Lis. At 11 mo of age, dystrophin deficiency decreased specific tension and tetanic force in the soleus and extensor digitorum longus muscles and was not corrected by any treatment. Dystrophic muscle was more sensitive to contraction-induced injury, which was partially offset in the QNRLisPred group, whereas fatigue was similar between all groups. Treatments did not decrease histological damage. These data suggest that treatment with Q, NR, Lis, and Pred failed to adequately maintain dystrophic limb muscle function or decrease histological damage. NEW & NOTEWORTHY Despite a compelling rationale and previous evidence to the contrary in short-term investigations, quercetin, nicotinamide riboside, or Lisinopril, alone or in combination, failed to restore muscle function or decrease histological injury in dystrophic limb muscle from D2-mdx mice after long-term administration. Importantly, we also found that in the D2-mdx model, an emerging and relatively understudied model of Duchenne muscular dystrophy dystrophin deficiency caused profound muscle dysfunction and histopathology in skeletal muscle.
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Hilton, Stephanie, Matthias Christen, Thomas Bilzer, Vidhya Jagannathan, Tosso Leeb y Urs Giger. "Dystrophin (DMD) Missense Variant in Cats with Becker-Type Muscular Dystrophy". International Journal of Molecular Sciences 24, n.º 4 (6 de febrero de 2023): 3192. http://dx.doi.org/10.3390/ijms24043192.
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Muscular dystrophy due to dystrophin deficiency in humans is phenotypically divided into a severe Duchenne and milder Becker type. Dystrophin deficiency has also been described in a few animal species, and few DMD gene variants have been identified in animals. Here, we characterize the clinical, histopathological, and molecular genetic aspects of a family of Maine Coon crossbred cats with clinically mild and slowly progressive muscular dystrophy. Two young adult male littermate cats exhibited abnormal gait and muscular hypertrophy with macroglossia. Serum creatine kinase activities were highly increased. Histopathologically, dystrophic skeletal muscle exhibited marked structural changes including atrophic, hypertrophic, and necrotic muscle fibers. Immunohistochemistry showed irregularly reduced expression of dystrophin but the staining of other muscle proteins such as β- and γ-sarcoglycans as well as desmin was also diminished. Whole genome sequencing of one affected cat and genotyping of the littermate found both to be hemizygous mutant at a single DMD missense variant (c.4186C>T). No other protein-changing variants in candidate genes for muscular dystrophy were detected. In addition, one clinically healthy male littermate was hemizygous wildtype, while the queen and one female littermate were clinically healthy, but heterozygous. The predicted amino acid exchange (p.His1396Tyr) resides in a conserved central rod spectrin domain of dystrophin. Various protein modeling programs did not predict major disruption of the dystrophin protein by this substitution, but the altered charge of the region may still affect protein function. This study represents the first genotype-to-phenotype correlation of Becker-type dystrophin deficiency in companion animals.
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Wehling, Michelle, Melissa J. Spencer y James G. Tidball. "A nitric oxide synthase transgene ameliorates muscular dystrophy in mdx mice". Journal of Cell Biology 155, n.º 1 (1 de octubre de 2001): 123–32. http://dx.doi.org/10.1083/jcb.200105110.
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Dystrophin-deficient muscles experience large reductions in expression of nitric oxide synthase (NOS), which suggests that NO deficiency may influence the dystrophic pathology. Because NO can function as an antiinflammatory and cytoprotective molecule, we propose that the loss of NOS from dystrophic muscle exacerbates muscle inflammation and fiber damage by inflammatory cells. Analysis of transgenic mdx mice that were null mutants for dystrophin, but expressed normal levels of NO in muscle, showed that the normalization of NO production caused large reductions in macrophage concentrations in the mdx muscle. Expression of the NOS transgene in mdx muscle also prevented the majority of muscle membrane injury that is detectable in vivo, and resulted in large decreases in serum creatine kinase concentrations. Furthermore, our data show that mdx muscle macrophages are cytolytic at concentrations that occur in dystrophic, NOS-deficient muscle, but are not cytolytic at concentrations that occur in dystrophic mice that express the NOS transgene in muscle. Finally, our data show that antibody depletions of macrophages from mdx mice cause significant reductions in muscle membrane injury. Together, these findings indicate that macrophages promote injury of dystrophin-deficient muscle, and the loss of normal levels of NO production by dystrophic muscle exacerbates inflammation and membrane injury in muscular dystrophy.
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Nogami, Ken'ichiro, Yusuke Maruyama, Fusako Sakai-Takemura, Norio Motohashi, Ahmed Elhussieny, Michihiro Imamura, Satoshi Miyashita et al. "Pharmacological activation of SERCA ameliorates dystrophic phenotypes in dystrophin-deficient mdx mice". Human Molecular Genetics 30, n.º 11 (5 de abril de 2021): 1006–19. http://dx.doi.org/10.1093/hmg/ddab100.
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Abstract Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder characterized by progressive muscular weakness because of the loss of dystrophin. Extracellular Ca2+ flows into the cytoplasm through membrane tears in dystrophin-deficient myofibers, which leads to muscle contracture and necrosis. Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) takes up cytosolic Ca2+ into the sarcoplasmic reticulum, but its activity is decreased in dystrophic muscle. Here, we show that an allosteric SERCA activator, CDN1163, ameliorates dystrophic phenotypes in dystrophin-deficient mdx mice. The administration of CDN1163 prevented exercise-induced muscular damage and restored mitochondrial function. In addition, treatment with CDN1163 for 7 weeks enhanced muscular strength and reduced muscular degeneration and fibrosis in mdx mice. Our findings provide preclinical proof-of-concept evidence that pharmacological activation of SERCA could be a promising therapeutic strategy for DMD. Moreover, CDN1163 improved muscular strength surprisingly in wild-type mice, which may pave the new way for the treatment of muscular dysfunction.
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Sazani, Peter, Kirk P. Van Ness, Doreen L. Weller, Duane Poage, Keith Nelson y and Stephen B. Shrewsbury. "Chemical and Mechanistic Toxicology Evaluation of Exon Skipping Phosphorodiamidate Morpholino Oligomers in mdx Mice". International Journal of Toxicology 30, n.º 3 (mayo de 2011): 322–33. http://dx.doi.org/10.1177/1091581811403504.
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AVI-4658 is a phosphorodiamidate morpholino oligomer (PMO) designed to induce skipping of dystrophin exon 51 and restore its expression in patients with Duchenne muscular dystrophy (DMD). Preclinically, restoration of dystrophin in the dystrophic mdx mouse model requires skipping of exon 23, achieved with the mouse-specific PMO, AVI-4225. Herein, we report the potential toxicological consequences of exon skipping and dystrophin restoration in mdx mice using AVI-4225. We also evaluated the toxicological effects of AVI-4658 in both mdx and wild-type mice. In both studies, animals were dosed once weekly for 12 weeks up to the maximum feasible dose of 960 mg/kg per injection. Both AVI-4658 and AVI-4225 were well-tolerated at all doses. Findings in AVI-4225-treated animals were generally limited to mild renal tubular basophilia/vacuolation, without any significant changes in renal function and with evidence of reversing. No toxicity associated with the mechanism of action of AVI-4225 in a dystrophic animal was observed.
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Koenig, Xaver, Lena Rubi, Gerald J. Obermair, Rene Cervenka, Xuan B. Dang, Peter Lukacs, Stefan Kummer et al. "Enhanced currents through L-type calcium channels in cardiomyocytes disturb the electrophysiology of the dystrophic heart". American Journal of Physiology-Heart and Circulatory Physiology 306, n.º 4 (15 de febrero de 2014): H564—H573. http://dx.doi.org/10.1152/ajpheart.00441.2013.
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Duchenne muscular dystrophy (DMD), induced by mutations in the gene encoding for the cytoskeletal protein dystrophin, is an inherited disease characterized by progressive muscle weakness. Besides the relatively well characterized skeletal muscle degenerative processes, DMD is also associated with cardiac complications. These include cardiomyopathy development and cardiac arrhythmias. The current understanding of the pathomechanisms in the heart is very limited, but recent research indicates that dysfunctional ion channels in dystrophic cardiomyocytes play a role. The aim of the present study was to characterize abnormalities in L-type calcium channel function in adult dystrophic ventricular cardiomyocytes. By using the whole cell patch-clamp technique, the properties of currents through calcium channels in ventricular cardiomyocytes isolated from the hearts of normal and dystrophic adult mice were compared. Besides the commonly used dystrophin-deficient mdx mouse model for human DMD, we also used mdx-utr mice, which are both dystrophin- and utrophin-deficient. We found that calcium channel currents were significantly increased, and channel inactivation was reduced in dystrophic cardiomyocytes. Both effects enhance the calcium influx during an action potential (AP). Whereas the AP in dystrophic mouse cardiomyocytes was nearly normal, implementation of the enhanced dystrophic calcium conductance in a computer model of a human ventricular cardiomyocyte considerably prolonged the AP. Finally, the described dystrophic calcium channel abnormalities entailed alterations in the electrocardiograms of dystrophic mice. We conclude that gain of function in cardiac L-type calcium channels may disturb the electrophysiology of the dystrophic heart and thereby cause arrhythmias.
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EBIHARA, SATORU, GHIABE-HENRI GUIBINGA, RENALD GILBERT, JOSEPHINE NALBANTOGLU, BERNARD MASSIE, GEORGE KARPATI y BASIL J. PETROF. "Differential effects of dystrophin and utrophin gene transfer in immunocompetent muscular dystrophy (mdx) mice". Physiological Genomics 3, n.º 3 (8 de septiembre de 2000): 133–44. http://dx.doi.org/10.1152/physiolgenomics.2000.3.3.133.
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Ebihara, Satoru, Ghiabe-Henri Guibinga, Renald Gilbert, Josephine Nalbantoglu, Bernard Massie, George Karpati, and Basil J. Petrof. Differential effects of dystrophin and utrophin gene transfer in immunocompetent muscular dystrophy (mdx) mice. Physiol Genomics 3: 133–144, 2000.—Duchenne muscular dystrophy (DMD) is a fatal disease caused by defects in the gene encoding dystrophin. Dystrophin is a cytoskeletal protein, which together with its associated protein complex, helps to protect the sarcolemma from mechanical stresses associated with muscle contraction. Gene therapy efforts aimed at supplying a normal dystrophin gene to DMD muscles could be hampered by host immune system recognition of dystrophin as a “foreign” protein. In contrast, a closely related protein called utrophin is not foreign to DMD patients and is able to compensate for dystrophin deficiency when overexpressed throughout development in transgenic mice. However, the issue of which of the two candidate molecules is superior for DMD therapy has remained an open question. In this study, dystrophin and utrophin gene transfer effects on dystrophic muscle function were directly compared in the murine (mdx) model of DMD using E1/E3-deleted adenovirus vectors containing either a dystrophin (AdV-Dys) or a utrophin (AdV-Utr) transgene. In immunologically immature neonatal animals, AdV-Dys and AdV-Utr improved tibialis anterior muscle histopathology, force-generating capacity, and the ability to resist injury caused by high-stress contractions to an equivalent degree. By contrast, only AdV-Utr was able to achieve significant improvement in force generation and the ability to resist stress-induced injury in the soleus muscle of immunocompetent mature mdx animals. In addition, in mature mdx mice, there was significantly greater transgene persistence and reduced inflammation with utrophin compared to dystrophin gene transfer. We conclude that dystrophin and utrophin are largely equivalent in their intrinsic abilities to prevent the development of muscle necrosis and weakness when expressed in neonatal mdx animals with an immature immune system. However, because immunity against dystrophin places an important limitation on the efficacy of dystrophin gene replacement in an immunocompetent mature host, the use of utrophin as an alternative to dystrophin gene transfer in this setting appears to offer a significant therapeutic advantage.
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Beckers, Evy, Ine Cornelis, Sofie F. M. Bhatti, Pascale Smets, G. Diane Shelton, Ling T. Guo, Luc Peelman y Bart J. G. Broeckx. "A Nonsense Variant in the DMD Gene Causes X-Linked Muscular Dystrophy in the Maine Coon Cat". Animals 12, n.º 21 (25 de octubre de 2022): 2928. http://dx.doi.org/10.3390/ani12212928.
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(1) Feline dystrophin-deficient muscular dystrophy (ddMD) is a fatal disease characterized by progressive weakness and degeneration of skeletal muscles and is caused by variants in the DMD gene. To date, only two feline causal variants have been identified. This study reports two cases of male Maine coon siblings that presented with muscular hypertrophy, growth retardation, weight loss, and vomiting. (2) Both cats were clinically examined and histopathology and immunofluorescent staining of the affected muscle was performed. DMD mRNA was sequenced to identify putative causal variants. (3) Both cats showed a significant increase in serum creatine kinase activity. Electromyography and histopathological examination of the muscle samples revealed abnormalities consistent with a dystrophic phenotype. Immunohistochemical testing revealed the absence of dystrophin, confirming the diagnosis of dystrophin-deficient muscular dystrophy. mRNA sequencing revealed a nonsense variant in exon 11 of the feline DMD gene, NC_058386.1 (XM_045050794.1): c.1180C>T (p.(Arg394*)), which results in the loss of the majority of the dystrophin protein. Perfect X-linked segregation of the variant was established in the pedigree. (4) ddMD was described for the first time in the Maine coon and the c.1180C>T variant was confirmed as the causal variant.
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Menke, A. y H. Jockusch. "Extent of shock-induced membrane leakage in human and mouse myotubes depends on dystrophin". Journal of Cell Science 108, n.º 2 (1 de febrero de 1995): 727–33. http://dx.doi.org/10.1242/jcs.108.2.727.
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A lack of the cytoskeletal protein dystrophin causes muscle fiber necrosis in Duchenne/Becker muscular dystrophies (DMD/BMD) and in murine X-linked muscular dystrophy (MDX). However, no overt disease symptoms are observed in dystrophin-less cultured myotubes, and the biological function of dystrophin in normal muscle cells is still unknown. In this work, we have extended our studies on a model system, using hypoosmotic shock to determine stress resistance of muscle cells. In frozen sections of control human and mouse myotubes, dystrophin was shown to be localized at the cell periphery as in mature muscle fibers. Dystrophin-less DMD and MDX myotubes were more susceptible to hypoosmotic shock than controls, as monitored by the uptake of external horseradish peroxidase and release of the soluble enzymes creatinine kinase or pyruvate kinase and of radiolabelled proteins. Control experiments indicated that this difference is not due to differences in metabolism or ion fluxes. Treatment with cytochalasin D drastically increased the shock sensitivity of myotubes and abolished the difference between dystrophin-less and control cells. These results lend further support to the suggested stabilizing role of dystrophin in the context of the membrane-cytoskeletal complex.
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Kochergin-Nikitskiy, K. S., S. A. Smirnikhina y A. V. Lavrov. "Stages of research and development of therapeutic approaches for Duchenne myodystrophy. Part II: etiotropic approaches". Neuromuscular Diseases 14, n.º 2 (24 de mayo de 2024): 44–52. http://dx.doi.org/10.17650/2222-8721-2024-14-2-44-52.
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Duchenne muscular dystrophy is one of the most common inherited muscular dystrophies. The cause of this disease with an X‑linked recessive type of inheritance is mutations in the DMD gene, leading to the absence of the dystrophin protein this gene encodes or its impaired function. Loss of dystrophin leads to severe degenerative processes in patients, especially in muscle tissue, with impaired muscle function, loss of ability to move independently, respiratory failure, cardiomyopathies, etc.The collective efforts of many researchers over the years since the 19th century, when the diseases was described, not allowed to achieve a cure or significantly influencing the trajectory of the illness. The only notable impact on the disease course has come with the integration of corticosteroid medications into Duchenne muscular dystrophy therapy. While their application can decelerate disease progression and extend the average life expectancy up to 30–40 years, it comes with substantial adversely affects influencing patients’ quality of life.Certain hopes were associated in recent decades with the development of etiotropic therapy for Duchenne muscular dystrophy, aimed at restoration of the dystrophin’s function. Some of such approaches were based on the overcoming of the effect of premature stop codons in the DMD gene using aminoglycoside antibiotics, ataluren, etc. Several subsequent studies were conducted to explore the applicability of exon‑skipping approaches in the dystrophin gene, aimed at excluding exons carrying pathogenic genetic variants. The rationale for these studies was the available information about a milder course of the disease associated with a truncated but functional dystrophin. The possibility of the pathology correction by means of introduction of the exogenous functional DMD gene copy from the outside (gene replacement therapy) has been under study since the beginning of the 20th century. One of the most promising directions in recent years was the development of approaches related to genome editing, which, unlike the methods mentioned above, allows for the permanent correction of the underlying cause of genetic diseases. Some of corresponding drugs have already received approval, while others, related to gene therapy, are at the stage of clinical trials.
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Murphy, Sandra, Margit Zweyer, Rustam R. Mundegar, Dieter Swandulla y Kay Ohlendieck. "Chemical crosslinking analysis of β-dystroglycan in dystrophin-deficient skeletal muscle". HRB Open Research 1 (30 de mayo de 2018): 17. http://dx.doi.org/10.12688/hrbopenres.12846.1.
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Background: In Duchenne muscular dystrophy, primary abnormalities in the membrane cytoskeletal protein dystrophin trigger the loss of sarcolemmal linkage between the extracellular matrix component laminin-211 and the intracellular cortical actin membrane cytoskeleton. The disintegration of the dystrophin-associated glycoprotein complex renders the plasma membrane of contractile fibres more susceptible to micro-rupturing, which is associated with abnormal calcium handling and impaired cellular signalling in dystrophinopathy. Methods: The oligomerisation pattern of β-dystroglycan, an integral membrane protein belonging to the core dystrophin complex, was studied using immunoprecipitation and chemical crosslinking analysis. A homo-bifunctional and non-cleavable agent with water-soluble and amine-reactive properties was employed to study protein oligomerisation in normal versus dystrophin-deficient skeletal muscles. Crosslinker-induced protein oligomerisation was determined by a combination of gel-shift analysis and immunoblotting. Results: Although proteomics was successfully applied for the identification of dystroglycan as a key component of the dystrophin-associated glycoprotein complex in the muscle membrane fraction, mass spectrometric analysis did not efficiently recognize this relatively low-abundance protein after immunoprecipitation or chemical crosslinking. As an alternative approach, comparative immunoblotting was used to evaluate the effects of chemical crosslinking. Antibody decoration of the crosslinked microsomal protein fraction from wild type versus the mdx-4cv mouse model of dystrophinopathy revealed oligomers that contain β-dystroglycan. The protein exhibited a comparable reduction in gel electrophoretic mobility in both normal and dystrophic samples. The membrane repair proteins dysferlin and myoferlin, which are essential components of fibre regeneration and counteract the dystrophic phenotype, were also shown to exist in high-molecular mass complexes. Conclusions: The muscular dystrophy-related reduction in the concentration of β-dystroglycan, which forms in conjunction with its extracellular binding partner α-dystroglycan a critical plasmalemmal receptor for laminin-211, does not appear to alter its oligomeric status. Thus, independent of direct interactions with dystrophin, this sarcolemmal glycoprotein appears to exist in a supramolecular assembly in muscle.
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Holland, Ashling y Kay Ohlendieck. "Proteomic Profiling of the Dystrophin-DeficientmdxPhenocopy of Dystrophinopathy-Associated Cardiomyopathy". BioMed Research International 2014 (2014): 1–15. http://dx.doi.org/10.1155/2014/246195.
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Cardiorespiratory complications are frequent symptoms of Duchenne muscular dystrophy, a neuromuscular disorder caused by primary abnormalities in the dystrophin gene. Loss of cardiac dystrophin initially leads to changes in dystrophin-associated glycoproteins and subsequently triggers secondarily sarcolemmal disintegration, fibre necrosis, fibrosis, fatty tissue replacement, and interstitial inflammation. This results in progressive cardiac disease, which is the cause of death in a considerable number of patients afflicted with X-linked muscular dystrophy. In order to better define the molecular pathogenesis of this type of cardiomyopathy, several studies have applied mass spectrometry-based proteomics to determine proteome-wide alterations in dystrophinopathy-associated cardiomyopathy. Proteomic studies included both gel-based and label-free mass spectrometric surveys of dystrophin-deficient heart muscle from the establishedmdxanimal model of dystrophinopathy. Comparative cardiac proteomics revealed novel changes in proteins associated with mitochondrial energy metabolism, glycolysis, signaling, iron binding, antibody response, fibre contraction, basal lamina stabilisation, and cytoskeletal organisation. This review summarizes the importance of studying cardiomyopathy within the field of muscular dystrophy research, outlines key features of themdxheart and its suitability as a model system for studying cardiac pathogenesis, and discusses the impact of recent proteomic findings for exploring molecular and cellular aspects of cardiac abnormalities in inherited muscular dystrophies.
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Wells, Dominic J., Aurora Ferrer y Kim E. Wells. "Immunological hurdles in the path to gene therapy for Duchenne muscular dystrophy". Expert Reviews in Molecular Medicine 4, n.º 23 (4 de noviembre de 2002): 1–23. http://dx.doi.org/10.1017/s146239940200515x.
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Patients with Duchenne muscular dystrophy (DMD), an X-linked lethal muscle-wasting disease, have abnormal expression of the protein dystrophin within their muscle fibres. In the mdx mouse model of this condition, both germline and neonatal somatic gene transfers of dystrophin cDNAs have demonstrated the potential of gene therapy in treating DMD. However, in many DMD patients, there appears to be no dystrophin expression when muscle biopsies are immunostained or western blots are performed. This raises the possibility that the expression of dystrophin following gene transfer might trigger a destructive immune response against this ‘neoantigen’. Immune responses can also be generated against the gene transfer vector used to transfect the dystrophic muscle, and the combined immune response could further damage the already inflamed muscle. These problems are now beginning to be investigated in immunocompetent mdx mice. Although much work remains to be done, there are promising indications that these immune responses might not prove as much of a concern as originally envisaged.
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Iwata, Yuko, Yuki Katanosaka, Yuji Arai, Kazuo Komamura, Kunio Miyatake y Munekazu Shigekawa. "A novel mechanism of myocyte degeneration involving the Ca2+-permeable growth factor–regulated channel". Journal of Cell Biology 161, n.º 5 (9 de junio de 2003): 957–67. http://dx.doi.org/10.1083/jcb.200301101.
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Disruption of the dystrophin–glycoprotein complex caused by genetic defects of dystrophin or sarcoglycans results in muscular dystrophy and/or cardiomyopathy in humans and animal models. However, the key early molecular events leading to myocyte degeneration remain elusive. Here, we observed that the growth factor–regulated channel (GRC), which belongs to the transient receptor potential channel family, is elevated in the sarcolemma of skeletal and/or cardiac muscle in dystrophic human patients and animal models deficient in dystrophin or δ-sarcoglycan. However, total cell GRC does not differ markedly between normal and dystrophic muscles. Analysis of the properties of myotubes prepared from δ-sarcoglycan–deficient BIO14.6 hamsters revealed that GRC is activated in response to myocyte stretch and is responsible for enhanced Ca2+ influx and resultant cell damage as measured by creatine phosphokinase efflux. We found that cell stretch increases GRC translocation to the sarcolemma, which requires entry of external Ca2+. Consistent with these findings, cardiac-specific expression of GRC in a transgenic mouse model produced cardiomyopathy due to Ca2+ overloading, with disease expression roughly parallel to sarcolemmal GRC levels. The results suggest that GRC is a key player in the pathogenesis of myocyte degeneration caused by dystrophin–glycoprotein complex disruption.
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Morotti, Marta, Alessandro Gaeta, Cristina Limatola, Myriam Catalano, Maria Amalia Di Castro y Francesca Grassi. "Early Developmental Changes of Muscle Acetylcholine Receptors Are Little Influenced by Dystrophin Absence in mdx Mouse". Life 12, n.º 11 (12 de noviembre de 2022): 1861. http://dx.doi.org/10.3390/life12111861.
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Dystrophin is a cytoskeletal protein contributing to the organization of the neuromuscular junction. In Duchenne muscular dystrophy, due to dystrophin absence, the distribution of endplate acetylcholine receptors (AChRs) becomes disorganized. It is still debated whether this is due to the absence of dystrophin or to the repeated damage/regeneration cycles typical of dystrophic muscle. We addressed this controversy studying the endplate in the first 3 postnatal weeks, when muscle damage in dystrophic (mdx) mice is minimal. By synaptic and extra-synaptic patch-clamp recordings in acutely dissociated mdx and wt muscle fibers, we recorded unitary events due to openings of AChR-channels containing the γ and ε subunit. We also examined AChR distribution at the endplate by immunofluorescence assays. No differences between wt and mdx fibers were found in the γ/ε switch, nor in the AChR organization at the endplates up to 21 postnatal days. Conversely, we detected a delayed appearance and disappearance of patches with high channel opening frequency in mdx fibers. Our data emphasize that the innervation-dependent γ/ε switch and AChR organization in the endplate are not affected by the absence of dystrophin, while extra-synaptic AChR cluster formation and disassembly could be differentially regulated in mdx mice.
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Hack, Andrew A., Chantal T. Ly, Fang Jiang, Cynthia J. Clendenin, Kirsten S. Sigrist, Robert L. Wollmann y Elizabeth M. McNally. "γ-Sarcoglycan Deficiency Leads to Muscle Membrane Defects and Apoptosis Independent of Dystrophin". Journal of Cell Biology 142, n.º 5 (7 de septiembre de 1998): 1279–87. http://dx.doi.org/10.1083/jcb.142.5.1279.
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γ-Sarcoglycan is a transmembrane, dystrophin-associated protein expressed in skeletal and cardiac muscle. The murine γ-sarcoglycan gene was disrupted using homologous recombination. Mice lacking γ-sarcoglycan showed pronounced dystrophic muscle changes in early life. By 20 wk of age, these mice developed cardiomyopathy and died prematurely. The loss of γ-sarcoglycan produced secondary reduction of β- and δ-sarcoglycan with partial retention of α- and ε-sarcoglycan, suggesting that β-, γ-, and δ-sarcoglycan function as a unit. Importantly, mice lacking γ-sarco- glycan showed normal dystrophin content and local- ization, demonstrating that myofiber degeneration occurred independently of dystrophin alteration. Furthermore, β-dystroglycan and laminin were left intact, implying that the dystrophin–dystroglycan–laminin mechanical link was unaffected by sarcoglycan deficiency. Apoptotic myonuclei were abundant in skeletal muscle lacking γ-sarcoglycan, suggesting that programmed cell death contributes to myofiber degeneration. Vital staining with Evans blue dye revealed that muscle lacking γ-sarcoglycan developed membrane disruptions like those seen in dystrophin-deficient muscle. Our data demonstrate that sarcoglycan loss was sufficient, and that dystrophin loss was not necessary to cause membrane defects and apoptosis. As a common molecular feature in a variety of muscular dystrophies, sarcoglycan loss is a likely mediator of pathology.
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Watchko, Jon F., Terrence L. O'Day y Eric P. Hoffman. "Functional characteristics of dystrophic skeletal muscle: insights from animal models". Journal of Applied Physiology 93, n.º 2 (1 de agosto de 2002): 407–17. http://dx.doi.org/10.1152/japplphysiol.01242.2001.
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Muscular dystrophies are a clinically and genetically heterogeneous group of disorders that show myofiber degeneration and regeneration. Identification of animal models of muscular dystrophy has been instrumental in research on the pathogenesis, pathophysiology, and treatment of these disorders. We review our understanding of the functional status of dystrophic skeletal muscle from selected animal models with a focus on 1) the mdx mouse model of Duchenne muscular dystrophy, 2) the Bio 14.6 δ-sarcoglycan-deficient hamster model of limb-girdle muscular dystrophy, and 3) transgenic null mutant murine lines of sarcoglycan (α, β, δ, and γ) deficiencies. Although biochemical data from these models suggest that the dystrophin-sarcoglycan-dystroglycan-laminin network is critical for structural integrity of the myofiber plasma membrane, emerging studies of muscle physiology suggest a more complex picture, with specific functional deficits varying considerably from muscle to muscle and model to model. It is likely that changes in muscle structure and function, downstream of the specific, primary biochemical deficiency, may alter muscle contractile properties.
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Mázala, Davi A. G., Robert W. Grange y Eva R. Chin. "The role of proteases in excitation-contraction coupling failure in muscular dystrophy". American Journal of Physiology-Cell Physiology 308, n.º 1 (1 de enero de 2015): C33—C40. http://dx.doi.org/10.1152/ajpcell.00267.2013.
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Duchenne muscular dystrophy (DMD) is one of the most frequent types of muscular dystrophy. Alterations in intracellular calcium (Ca2+) handling are thought to contribute to the disease severity in DMD, possibly due to the activation of Ca2+-activated proteases. The purpose of this study was twofold: 1) to determine whether prolonged excitation-contraction (E-C) coupling disruption following repeated contractions is greater in animals lacking both dystrophin and utrophin ( mdx/Utr−/−) compared with mice lacking only dystrophin ( mdx); and 2) to assess whether protease inhibition can prevent E-C coupling failure following repeated tetani in these dystrophic mouse models. Excitation-contraction coupling was assessed using Fura-2 ratio, as an index of intracellular free Ca2+ concentration, in response to electrical stimulation of single muscle fibers from the flexor digitorum brevis muscle. Resting Fura-2 ratio was higher in dystrophic compared with control (Con) fibers, but peak Fura-2 ratios during stimulation were similar in dystrophic and Con fibers. One hour after a series of repeated tetani, peak Fura-2 ratios were reduced by 30 ± 5.6%, 23 ± 2%, and 36 ± 3.1% in mdx, mdx/Utr+/−, and mdx/Utr−/−, respectively, with the greatest reduction in mdx/Utr−/− fibers ( P < 0.05). Protease inhibition attenuated this decrease in peak Fura-2 ratio. These data indicate that E-C coupling impairment after repeated contractions is greatest in fibers lacking both dystrophin and utrophin and that prevention of protease activation can mitigate the prolonged E-C coupling impairment. These data further suggest that acute protease inhibition may be useful in reducing muscle weakness in DMD.
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Lu, Q. L., G. E. Morris, S. D. Wilton, T. Ly, O. V. Artem'yeva, P. Strong y T. A. Partridge. "Massive Idiosyncratic Exon Skipping Corrects the Nonsense Mutation in Dystrophic Mouse Muscle and Produces Functional Revertant Fibers by Clonal Expansion". Journal of Cell Biology 148, n.º 5 (6 de marzo de 2000): 985–96. http://dx.doi.org/10.1083/jcb.148.5.985.
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Conventionally, nonsense mutations within a gene preclude synthesis of a full-length functional protein. Obviation of such a blockage is seen in the mdx mouse, where despite a nonsense mutation in exon 23 of the dystrophin gene, occasional so-called revertant muscle fibers are seen to contain near-normal levels of its protein product. Here, we show that reversion of dystrophin expression in mdx mice muscle involves unprecedented massive loss of up to 30 exons. We detected several alternatively processed transcripts that could account for some of the revertant dystrophins and could not detect genomic deletion from the region commonly skipped in revertant dystrophin. This, together with exon skipping in two noncontiguous regions, favors aberrant splicing as the mechanism for the restoration of dystrophin, but is hard to reconcile with the clonal idiosyncrasy of revertant dystrophins. Revertant dystrophins retain functional domains and mediate plasmalemmal assembly of the dystrophin-associated glycoprotein complex. Physiological function of revertant fibers is demonstrated by the clonal growth of revertant clusters with age, suggesting that revertant dystrophin could be used as a guide to the construction of dystrophin expression vectors for individual gene therapy. The dystrophin gene in the mdx mouse provides a favored system for study of exon skipping associated with nonsense mutations.
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Niebrój-Dobosz, Irena y Irena Hausmanowa-Petrusewicz. "The involvement of oxidative stress in determining the severity and progress of pathological processes in dystrophin-deficient muscles." Acta Biochimica Polonica 52, n.º 2 (25 de mayo de 2005): 449–52. http://dx.doi.org/10.18388/abp.2005_3458.
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In both forms of muscular dystrophy, the severe Duchenne's muscular dystrophy (DMD) with lifespan shortened to about 20 years and the milder Becker dystrophy (BDM) with normal lifespan, the gene defect is located at chromosome locus Xp21. The location is the same in the experimental model of DMD in the mdx mice. As the result of the gene defect a protein called dystrophin is either not synthesized, or is produced in traces. Although the structure of this protein is rather well established there are still many controversies about the dystrophin function. The most accepted suggestion supposes that it stabilizes sarcolemma in the course of the contraction-relaxation cycle. Solving the problem of dystrophin function is a prerequisite for introduction of an effective therapy. Among the different factors which might be responsible for the appearance and progress of dystrophic changes in muscles there is an excessive action of oxidative stress. In this review data indicating the influence of oxidative stress on the severity of the pathologic processes in dystrophy are discussed. Several pieces of data indicating the action of oxidative damage to different macromolecules in DMD/BDM are presented. Special attention is devoted to the degree of oxidative damage to muscle proteins, the activity of neuronal nitric oxide synthase (nNOS) and their involvement in defining the severity of the dystrophic processes. It is indicated that the severity of the morbid process is related to the degree of oxidative damage to muscle proteins and the decrease of the nNOS activity in muscles. Estimation of the degree of the destructive action of oxidative stress in muscular dystrophy may be a useful marker facilitating introduction of an effective antioxidant therapy and regulation of nNOS activity.
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Kuno, Atsushi y Yoshiyuki Horio. "SIRT1: A Novel Target for the Treatment of Muscular Dystrophies". Oxidative Medicine and Cellular Longevity 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/6714686.
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Muscular dystrophies are inherited myogenic disorders accompanied by progressive skeletal muscle weakness and degeneration. Duchenne muscular dystrophy (DMD) is the most common and severe form of muscular dystrophy and is caused by mutations in the gene that encodes the cytoskeletal protein dystrophin. The treatment for DMD is limited to glucocorticoids, which are associated with multiple side effects. Thus, the identification of novel therapeutic targets is urgently needed. SIRT1 is an NAD+-dependent histone/protein deacetylase that plays roles in diverse cellular processes, including stress resistance and cell survival. Studies have shown that SIRT1 activation provides beneficial effects in the dystrophin-deficientmdxmouse, a model of DMD. SIRT1 activation leads to the attenuation of oxidative stress and inflammation, a shift from the fast to slow myofiber phenotype, and the suppression of tissue fibrosis. Although further research is needed to clarify the molecular mechanisms underlying the protective role of SIRT1 inmdxmice, we propose SIRT1 as a novel therapeutic target for patients with muscular dystrophies.
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Culligan, Kevin, Niamh Banville, Paul Dowling y Kay Ohlendieck. "Drastic reduction of calsequestrin-like proteins and impaired calcium binding in dystrophic mdx muscle". Journal of Applied Physiology 92, n.º 2 (1 de febrero de 2002): 435–45. http://dx.doi.org/10.1152/japplphysiol.00903.2001.
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Although the reduction in dystrophin-associated glycoproteins is the primary pathophysiological consequence of the deficiency in dystrophin, little is known about the secondary abnormalities leading to x-linked muscular dystrophy. As abnormal Ca2+ handling may be involved in myonecrosis, we investigated the fate of key Ca2+ regulatory membrane proteins in dystrophic mdx skeletal muscle membranes. Whereas the expression of the ryanodine receptor, the dihydropyridine receptor, the Ca2+-ATPase, and calsequestrin was not affected, a drastic decline in calsequestrin-like proteins of 150–220 kDa was observed in dystrophic microsomes using one-dimensional immunoblotting, two-dimensional immunoblotting with isoelectric focusing, diagonal two-dimensional blotting technique, and immunoprecipitation. In analogy, overall Ca2+ binding was reduced in the sarcoplasmic reticulum of dystrophic muscle. The reduction in Ca2+ binding proteins might be directly involved in triggering impaired Ca2+ sequestration within the lumen of the sarcoplasmic reticulum. Thus disturbed sarcolemmal Ca2+ fluxes seem to influence overall Ca2+homeostasis, resulting in distinct changes in the expression profile of a subset of Ca2+ handling proteins, which might be an important factor in the progressive functional decline of dystrophic muscle fibers.
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Anderson, Judy E. "Myotube phospholipid synthesis and sarcolemmal ATPase activity in dystrophic (mdx) mouse muscle". Biochemistry and Cell Biology 69, n.º 12 (1 de diciembre de 1991): 835–41. http://dx.doi.org/10.1139/o91-124.
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Phospholipid incorporation of 32P by primary myotube cultures and the tissue activity of sarcolemmal Na+/K+-transporting ATPase were studied to determine whether the absence of dystrophin from dystrophic (mdx) muscle would affect membrane lipid synthesis and membrane function. The incorporation of 32P by phospholipid as a ratio with total protein was greater in cultured dystrophic cells compared with control cells. The mdx cells also incorporated more 32P than control cells into phosphatidylethanolamine, which is thought to increase prior to myoblast fusion, and less into phosphatidylserine, phosphatidylinositol, and lysophosphatidylchoiine. There was no difference in total protein content or [3H]leucine or 32P incorporation into the aqueous fraction of dystrophic and control cells, although dystrophic cells incorporated less [35S]methionine into protein than controls. Isolated sarcolemma from mdx skeletal muscle tissue demonstrated a consistently greater specific activity of ouabain-sensitive Na+/K+-transporting ATPase than sarcolemmal preparations from control skeletal muscle. These observations suggest that cytoskeletal changes such as dystrophin deficiency may alter the differentiation of membrane composition and function.Key words: muscular dystrophy, mdx, myogenesis, sarcolemma, ouabain-sensitive ATPase, phospholipid.