Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder primarily affecting male children and resulting in progressive degeneration and attempted regeneration of muscle with replacement of myofibers by adipose and fibrotic tissue. DMD patients have mutations in the DMD gene encoding for the large cytoskeletal protein dystrophin, which plays an essential role in the dystrophin-glycoprotein complex (DGC) as a structural connector within cardiac and skeletal muscle. The absence of dystrophin and DGC proteins leads to increased membrane fragility, dysregulation of calcium homeostasis, oxidative damage in muscle cells, and finally, premature death of the patients. Rhabdomyosarcoma (RMS), a soft tissue sarcoma arising from subpopulations of muscle cells and their precursors, has previously been reported in DMD patients and mouse models of DMD. Here, we report a case series of RMS arising from skeletal muscles in a Dmd-mutated (Dmdmdx) rat model developed using transcription activator-like effector nucleases targeting exon 23 of the Dmd gene on a Sprague Dawley background. Subcutaneous firm masses were noted grossly in 8 male Dmdmdx rats aged 6 to 17 months. The histologic findings were consistent with a sarcoma of skeletal muscle, with a population of small round cells in addition to spindle-shaped cells and occasional large multinucleated cells. The neoplasms were immunoreactive for myogenin, MyoD1, and desmin. Histology and immunohistochemistry supported the diagnosis of RMS. This represents a potentially novel animal model of DMD-associated RMS.

Severe dilated cardiomyopathy in females with dystrophinopathy : a case series of nine patients.

The DMD gene is best known for its product dystrophin, a large rod-shaped protein that plays a critical role in muscular membrane strength and integrity. Mutations affecting dystrophin lead to Duchenne muscular dystrophy, a fatal X-linked disease characterized by muscular weakness and breakdown. In addition to the full-length dystrophin product that is most often associated with disease, the DMD gene also encodes multiple shorter isoforms of dystrophin with diverse functions. One isoform in particular, Dp71, has been increasingly found to play a wide variety of roles throughout the body. In this narrative review, we consolidate the numerous studies on Dp71 to provide a comprehensive foundation for future work. We outline and summarize the current state of knowledge on the role of Dp71 in the brain, the retina, and skeletal muscles, identifying current knowns and unknowns in the field. We also explore Dp71-based therapies currently being tested in the pre-clinical landscape and identify potential limitations for clinical translation.

Clinical spectrum and genetic landscape of duchenne muscular dystrophy in Azerbaijan.

Duchenne muscular dystrophy (DMD) is the most common, lethal X-linked neuromuscular disorder of childhood and is caused by mutations in the Dmd gene that disrupt dystrophin expression. Although adeno-associated virus-mediated gene therapies hold tremendous promise for DMD treatment, their clinical applications have been limited by dose-dependent vector and genome-level toxicities. Here, we developed and tested a single-vector adenine base editing strategy as a potentially safer genome editing approach to recode the pathogenic nonsense mutation into a benign missense mutation in mdx4cv DMD mouse model. Delivered using a muscle-tropic adeno-associated virus (MyoAAV) at a clinically-feasible dose (4E13 VG/kg), this strategy enabled detectable molecular recoding of the mdx4cv mutation in mice ranging in age from 3 days to 6 months. Yet, the overall efficiency and therapeutic impact of in vivo base editing with this system was highest in mice treated at the juvenile stage, with animals administered MyoAAV vectors at 3 weeks of age showing robust recovery of dystrophin expression and significant improvement in muscle contractile properties only one month later. Notably, introduction of adenine base editors either earlier in development, in neonatal mice, or later, in adulthood, yielded substantially lower editing efficiencies, particularly in muscle satellite cells whose editing is essential to ensure durable rescue of dystrophin expression in growing and regenerating muscle. Taken together, these results demonstrate the therapeutic potential of single-vector adenine base editing for DMD and underscore the importance of recipient age and disease stage in achieving optimal treatment outcomes for this and other genetic muscle disorders.

HighlightsWhat are the main findings?A 5′-TTCT-3′ motif in epegRNAs limits prime editing efficiency at the mdx-4cv and mdx-5cv Dmd loci.Silent substitution of this motif enhances editing efficiency up to 20–21% in C2C12 myoblasts.What are the implications of the main findings?epegRNA sequence features play a critical role in determining prime editing efficiency.Optimized epegRNAs provide a valuable framework for therapeutic DMD correction in both in vitro and in vivo studies.Duchenne muscular dystrophy (DMD) is a fatal X-linked neuromuscular disorder caused by mutations in the dystrophin gene. Prime editing is a versatile genome editing technology capable of introducing precise nucleotide changes without generating double-strand DNA breaks, making it a promising approach for correcting pathogenic point mutations. In this study, we applied prime editing to modify mdx-4cv and mdx-5cv mutation-equivalent sites in mouse C2C12 myoblasts in vitro. Initial editing efficiencies were unexpectedly low and were associated with the presence of a 5′-TTCT-3′ motif within engineered prime editing guide RNAs (epegRNAs). epegRNA designs containing this motif exhibited reduced prime editing efficiency, whereas silent substitution eliminating the motif significantly improved editing outcomes, indicating that specific sequence features within epegRNAs can influence editing performance. Rational redesign of epegRNAs to remove this motif substantially enhanced editing efficiency, achieving up to 20% modification at the 4cv target site using an NGG PAM and 21% editing at the 5cv locus using an NGAG PAM. These findings highlight an important sequence-dependent constraint in epegRNA design and provide practical guidance for optimizing prime editing strategies targeting Dmd mutations in vitro.

While genome-wide analyses in vertebrates suggest that transcription negatively regulates replication origin activation, thereby shaping the landscape of replication initiation, it remains unknown whether efficient replication origins can overcome this suppression at common fragile sites (CFSs). In this study, we addressed this question by inserting two model origins into the avian DMD CFS and a transcriptionally silent late-replicating region in DT40 cells. The DMD gene, which is neither transcribed nor fragile in wild-type cells, became fragile following transcriptional activation in a genetically engineered cell line. Previous molecular combing experiments have shown that transcription represses origin firing. Here, we demonstrate that a minimal origin remains partially active under basal transcription conditions, yet is fully inactivated upon transcriptional induction. In contrast, the efficient β-actin promoter/origin retains functionality despite transcriptional activation. The same functional hierarchy emerges in a late-replicating, transcriptionally silent, and non-fragile locus. These results define a class of robust origins that function across diverse chromosomal contexts and support the model in which CFSs arise from transcription-dependent repression of replication origin initiation across large, late-replicating genes. Our study also suggests that depletion of cis-elements specifying efficient replication origins contributes to the formation of late-replicating domains, whereas a high density establishes early-replicating regions.

Duchenne muscular dystrophy, caused by mutations in the DMD gene encoding dystrophin, is a severe progressive muscle-wasting disorder characterized by impaired muscle regeneration. We reveal the alternative splicing of transcription factor E2-alpha (encoding transcription factors E12 and E47) plays a pivotal role in myogenic progression. E47 is highly expressed in proliferating myoblasts and promotes proliferation, whereas E12 is upregulated during differentiation and drives myogenic commitment. Mechanistically, we identify the nuclear splicing factor polypyrimidine tract binding protein 1 as a key regulator of transcription factor E2-alpha mutually exclusive alternative splicing. Polypyrimidine tract binding protein 1 levels decline during normal myoblast differentiation, facilitating the switch from E47 to E12. However, in Duchenne muscular dystrophy patients and mdx mice, polypyrimidine tract binding protein 1 remains aberrantly elevated, resulting in dysregulated E47/E12 ratios (increased E47 and decreased E12), which disrupts myogenic differentiation and impairs muscle regeneration. Therapeutically, polypyrimidine tract binding protein 1 knockdown restores myoblast differentiation, enhances muscle repair, and improves muscle function in mdx mice. Furthermore, we demonstrate that dergrasyn, a deubiquitinase inhibitor, induces polypyrimidine tract binding protein 1 degradation, restores myogenic differentiation, and ameliorates dystrophic pathology. Our findings identify polypyrimidine tract binding protein 1 as a potential therapeutic target for Duchenne muscular dystrophy and highlight modulation of transcription factor E2-alpha splicing as a promising strategy to restore muscle regeneration.

This study aims to evaluate the clinical management of incidental findings of copy number variations (CNVs) in the DMD gene detected through prenatal single nucleotide polymorphism array (SNP-array). Prenatal SNP-array testing was performed on samples exhibiting CNVs in the DMD locus, followed by parental analysis using the same technique. Additionally, multiplex ligation-dependent probe amplification (MLPA) testing was conducted on prenatal cases and their parents. Pregnancy outcomes were documented, and postnatal follow-up was conducted. SNP-array analysis identified copy number variations at Xp21 affecting either the entire DMD gene or only a portion of it in 14 fetuses. In 11 cases, MLPA testing confirmed the presence of deletions or duplications detected by the SNP-array. High-density SNP-array platforms with low reporting thresholds may incidentally detect a subset of exon-level copy number variations involving the DMD gene during routine prenatal testing and thereby contribute to early recognition of potential dystrophinopathy-related variants. Suspected DMD-related CNVs, especially exon-level alterations, require confirmation by targeted assays such as MLPA or next-generation sequencing, together with cautious clinical interpretation. Assessing the pathogenicity of prenatally detected DMD copy number variations remains challenging, particularly for duplications, which require careful evaluation. Furthermore, the sequential, time-intensive nature of confirmatory and familial studies often limits definitive risk assessment within the prenatal decision-making window, and introduces broader familial implications that must be navigated through careful, multidisciplinary counseling.

Duchenne muscular dystrophy is the hereditary progressive neuromuscular disease associated with mutations in the DMD gene encoding dystrophin protein and is characterized by striated muscles and cardiomyocytes impairment. It is X-linked recessive disorder and more prevalent in males. Females are carriers of the pathological mutation. It leads to impediment to diagnosis of this disease in women. Mild and severe clinical manifestations can also appear in women and they are attributable to chromosomal aberrations on the short arm of X-chromosome (Xp21.2) and skewed X-chromosome inactivation. The article presents a case of Duchenne muscular dystrophy in a girl with a nonsense mutation in the DMD gene. Primary diagnosis was suspected by gastroenterologist due to elevated levels of creatine phosphokinase and transaminase. The importance of diagnosis in preclinical stage of the disease is highlighted, moreover it became significantly relevant with appeared therapeutic options for patients with this mutation.

Becker muscular dystrophy (BMD) is caused primarily by in-frame mutations in the DMD gene. Phenotype varies from asymptomatic to severe; manifestations may include muscle weakness, scoliosis, cardiac involvement, loss of ambulation, respiratory impairment, cognitive dysfunction, and premature death. This study aimed to characterize the frequency and age at occurrence of these milestones. A systematic literature review (SLR) was refreshed in 2022 using MEDLINE and EMBASE to identify articles describing the natural history of BMD. The proportion of patients experiencing clinical milestones was reported by 'life-stage' age groups (0-17; 18-40; 41+ years) using patient-level data from the general BMD population; age at each milestone's occurrence as mean (standard deviation [SD]). From 4948 abstracts screened, 121 publications were included. Among 36 general BMD population studies, by age 41+ years (lifetime-risk proxy), 93.6% experienced muscle weakness; 69.4% cardiac involvement; 55.6% scoliosis; 47.4% loss of ambulation; and 33.3% ventilation. Decreased cognitive function or cognitive dysfunction were reported in 41% across all ages. Among those experiencing milestones (79 studies), mean (SD) age at symptom onset was 12.5 (9.7); muscle weakness, 19.9 (11.7); scoliosis, 24.9 (3.1); cardiac involvement, 31.9 (13.4); loss of ambulation, 33.3 (13.5); ventilation, 35.7 (12.2); and death at 55.6 (19.4) years. Data availability ranged from three to 1079 patients/outcome. This SLR highlights the variability in disease presentation in BMD. Stratifying BMD populations into phenotype groups based on the full spectrum of clinical manifestations may better capture disease progression and enhance comparability across studies.Included clinical trials:ClinicalTrials.gov NCT01070511 (https://clinicaltrials.gov/study/NCT01070511), ClinicalTrials.gov NCT02147639 (https://clinicaltrials.gov/study/NCT02147639?term=Becker%20Muscular%20Dystrophy&intr=Sodium%20Nitrate&rank=3), ClinicalTrials.gov NCT01350154 and EudraCT number: 2010-024659-10 (https://clinicaltrials.gov/study/NCT01350154?term=NCT01350154&rank=1; https://www.clinicaltrialsregister.eu/ctr-search/trial/2010-024659-10/results).

Becker muscular dystrophy (BMD) is an X-linked recessive myopathy caused by pathogenic variants of the dystrophin-encoding DMD gene. The clinical presentation of BMD encompasses four clinical subtypes: limb-girdle muscle weakness, quadriceps myopathy, isolated cramp-pain syndrome, and asymptomatic hyper-creatine kinase-emia. Patients may also present with cardiopulmonary involvement, neuropsychological issues, joint contractures, and spinal deformities. Diagnosis primarily relies on genetic testing and/or muscle biopsies. The treatment and management of BMD requires comprehensive and multidisciplinary interventions involving specialists in neurology, cardiology, respiratory medicine, rehabilitation medicine, orthopedics, gastroenterology, anesthesiology, clinical nutrition, psychology, and medical genetics. This coordinated approach aims to preserve patients' motor function, bone/joint function, cardiopulmonary function, and digestive function, while maintaining a good nutritional status and psychological well-being. To standardize the diagnosis, treatment, and management of BMD in China, a joint committee comprising multidisciplinary experts from the Chinese Medical Association Rare Disease Branch and the Beijing Medical Association Rare Disease Branch was established. This committee formulated the Chinese expert consensus on the diagnosis and treatment of BMD, with the primary objectives of improving patient quality of life and reducing the disease burden.

A five-year-old boy with clinical features of Duchenne muscular dystrophy was found to have a rare de novo DMD exon 2-9 duplication. Reporting such atypical duplications improves genotype-phenotype interpretation and highlights the need for multidisciplinary care, particularly in resource-limited settings.

Base editors (BEs) enable precise base substitutions, but their size exceeds the packaging capacity of adeno-associated virus (AAV), impeding in vivo applications. Here we design a split BE system that recruits deaminases to Cas9 nickase via coiled-coil heterodimers, resulting in various coiled-coil heterodimers-mediated base editors (CC-BEs), including cytidine base editor (CC-CBE), adenine base editor (CC-ABE), and their derivatives. We reveal that CC-BEs maintain and even improve the editing efficiency of the original unsplit BEs across various cell types and editing scopes, achieving maximum enhancements of 9.6-fold in human immortalized cells and 12.4-fold in primary somatic cells for CC-CBE. Using CC-ABE, we validate in vivo editing efficiency and successfully achieve A-to-G conversion in the Pcsk9 and Dmd genes via dual-AAV vectors in mice. Altogether, we develop a simple and universal strategy to address the challenges posed by the large size of BEs without compromising editing efficiency for base substitutions in vivo.

Duchenne muscular dystrophy is the most severe form of hereditary myopathies in boys, caused by mutations in the DMD gene, located on the X chromosome at the Xp21.2–p21.1 locus and encoding the dystrophin protein. The most common mutations are deletions of one or more exons (about 70 % of cases), which disrupt the reading frame and lead to the synthesis of a shortened and non-functional dystrophin protein, which causes the breakdown of skeletal muscle fibers (rhabdomyolysis) and progressive muscle weakness. The disease clinically manifests at the age of 2–5 years and rapidly progresses to the loss of the ability to walk independently by 8–12 years and death in the second or third decade of life due to respiratory and cardiac failure. The authors present Russian experience in the use of a gene therapy drug for the treatment of Duchenne muscular dystrophy using the exon skipping method, exemplified by the only registered drug of this class in Russia for Duchenne muscular dystrophy therapy – viltolarsen (Viltepso®).

Background Dystrophinopathy comprises a group of X‐linked recessive muscular disorders that primarily affect skeletal and/or cardiac muscles. Although more than 90% of dystrophinopathy patients exhibit detectable variants in the DMD gene, a small proportion of cases remain undiagnosed at the molecular level. Methods We employed an integrated multiomics approach, including RNA sequencing (RNA‐seq) of muscle tissue, optical genome mapping (OGM), short‐ and long‐read whole‐genome sequencing (WGS), and karyotype analysis to elucidate the genetic mechanism in a dystrophinopathy family. Results Integrated genomic analyses identified a balanced reciprocal translocation between Xp21.1 and 7q31.31 in the proband, with the X‐chromosomal breakpoint disrupting intron 20 of DMD . RNA sequencing of muscle tissue revealed severely reduced DMD transcript coverage downstream of the breakpoint, consistent with transcriptional interruption. Muscle immunohistochemistry showed absent dystrophin staining at the N‐terminus, rod domain, and C‐terminus, confirming loss of protein expression. The translocation was maternally inherited; the mother is a carrier with a dystrophinopathy phenotype. Conclusions We report the first male case of dystrophinopathy caused by an X;autosome translocation disrupting DMD , thereby expanding the mutational spectrum of this disorder. Our findings underscore the value of comprehensive genomic profiling in resolving diagnostically elusive dystrophinopathy cases.

BackgroundCardiac involvement is increasingly recognized in women carrying pathogenic variants in the dystrophin (DMD) gene, both Duchenne and Becker-associated, but the long-term natural history of cardiac structure, function, and conduction abnormalities in this group is not well understood. We conducted a prospective 7-year follow-up study to investigate the evolution of ventricular function, myocardial fibrosis, and arrhythmias.Methods34 women with confirmed pathogenic DMD gene variants (19 predicted to cause Duchenne muscular dystrophy and 15 Becker muscular dystrophy) underwent assessments after a mean of 7 years. Evaluations included cardiac magnetic resonance imaging with late gadolinium enhancement, 24-h Holter monitoring, 12-lead electrocardiography (ECG), cardiac biomarkers, and clinical examinations.ResultsAt the group level, left ventricular ejection fraction (LVEF) remained stable over follow-up (p = 0.403). Six women had a ≥ 5% change in LVEF: three improved with treatment, and three declined by 5–8%. Fibrosis was present in 9 women at both baseline and follow-up; 3 showed visual progression, and no new cases were identified. Although the median ventricular premature contractions per hour (VPC/h) increased from 0.23/h to 6.38/h (p < 0.001), this increase is likely not clinically meaningful as age-related increases in ventricular ectopy are also seen in healthy populations, and high-burden arrhythmias—according to prespecified thresholds—remained uncommon.ECG parameters remained stable (PR, QRS, and QTc unchanged), with no new bundle-branch blocks or high-grade atrioventricular block detected. No association was observed between LVEF, VPC/h, and supraventricular premature contraction per hour over the 7-year follow-up period.ConclusionsOver 7 years, women carrying pathogenic DMD gene variants have very little or no progression of cardiac findings (LVEF, fibrosis, and arrhythmias). Given these findings, frequent routine rhythm monitoring is not indicated. Follow-up should be risk-stratified: closer for women with symptoms, baseline high-burden ectopy, reduced LVEF, or pre-existing fibrosis; others can be reviewed at extended intervals.

Background: Duchenne and Becker Muscular Dystrophy (DMD/BMD) is an X-linked recessive inherited neuromuscular disease characterised by progressive muscle weakness and wasting due to variants in the DMD gene encoding dystrophin protein. This study aimed to evaluate the genetic and clinical characteristics of patients diagnosed with DMD/BMD who were found to have variants in the DMD gene by genetic analysis. Material and Methods: In this retrospective study, we evaluated 34 patients from 32 families diagnosed with dystrophinopathies, including 24 individuals (70.6%) with DMD and 10 individuals (29.4%) with BMD. Clinical, biochemical, and family history data were obtained from patient files. Genetic analyses were performed by multiple ligation-dependent probe amplification (MLPA) and Sanger sequencing. 15 mothers were segregated for carriage. Results: Exon deletion was detected in 79.4% of cases, and a small variant in 20.6%. The most common deletion sites were between exons 45-52. CK levels were found to be high in all patients. The mean age at diagnosis was 5 years. Segregation analysis showed that 12 of the mothers carried the variant detected in their children. Three new variants that had not been reported in the literature before were found in our cohort. Conclusions: Genetic analyses are valuable in diagnosis, phenotypic prediction, and family screening in DMD/BMD cases. In this study, the variant types and clinical features of DMD/BMD were analysed to contribute to the reported cases from Türkiye. Effective use of molecular diagnosis is important for early diagnosis and management.

Background: Duchenne/Becker muscular dystrophy (DMD/BMD) is associated with a wide spectrum of brain-related comorbidities. Methods: This retrospective study assesses the neuropsychiatric profile of DMD/BMD patients and the hypothesis of a functional-versus-structural approach of dystrophin gene variants/impaired isoforms in relation to brain comorbidities. Patients with documented mutation in the DMD gene and neuropsychiatric assessments were included. Seven comorbidities were analyzed based on variant location and dystrophin brain isoform disruption. The clustering of comorbidities and genotype–phenotype correlations were studied. Results: 264 DMD/BMD patients met inclusion criteria. 22 variants have never been described before. A high prevalence of neuropsychiatric comorbidities was identified in the cohort with higher values in patients with distal mutations. The number of comorbidities increased with the number of brain dystrophin isoforms predicted to be lost. Functional-versus-structural comparison revealed that Dp140 5′UTR variants might not affect protein expression. Epilepsy and intellectual disability (ID) showed significant association in this cohort. Neuropsychiatric phenotype varied greatly in patients with identical variants, even between siblings. Conclusions: This is one of the largest European cohorts for which all these comorbidities were studied in association with DMD gene mutation site and the first study of this kind performed on the Eastern European DMD/BMD population. Our group analyzed, for the first time, Dp140 5′UTR variants in relation to all neuropsychiatric phenotypes and showed that epilepsy and ID are strongly associated in DMD/DMB patients.

Background/Objectives: This study reports on findings from the first preconception screening performed in Russia and provides a comprehensive discussion of the significant results and challenges faced during the implementation of the project. Methods: Using a targeted sequencing panel of 33 genes (associated with 29 autosomal recessive and 4 X-linked diseases), we analyzed 165 couples considering pregnancy. The screening design also included analysis of the frequent pathogenic variants in the SMN1, DMD, CFTR, and CYP21A2 genes that may not be detected through the next-generation sequencing approach. The sequential screening protocol, wherein the female partner was tested first, was used. Results: The results revealed that 35.8% of women (n = 59) were carriers of at least one pathogenic or likely pathogenic (P/LP) variant, with 7.9% of women (n = 13) carrying variants in two or more genes. Notably, the analysis identified 5 deletions of exon 7 in the SMN1 gene, 1 deletion of the CYP21A2 gene, and 1 large duplication in the DMD gene in female participants. The most frequently identified pathogenic variants occurred in the CYP21A2, GJB2, SERPINA1, and ATP7B genes. The screening identified six couples (3.6% of the cohort) at high risk of having a child with an autosomal recessive or X-linked genetic disorder. Conclusions: This pilot study confirms the high clinical utility of the gene panel, effectively evaluating reproductive risk in couples without a known family history of monogenic diseases. The findings indicate that the observed frequencies of identified gene variants differ from those theoretically expected, with a notable percentage of identified couples being at relatively high risk. Furthermore, these results highlight the indispensable role of comprehensive genetic counseling both before and after testing to ensure an appropriate preconception testing algorithm and informed reproductive decision-making.