Duchenne muscular dystrophy: Case report and review

SKR, Kulandaivelu US, Alavala RR, Manne R. Study of Clinical Features and Diagnosis Pattern of Duchene Muscular Dystrophy in Southern India

Background  Duchene muscular dystrophy (DMD) is an X-linked progressive muscle disorder that is characterized by proximal muscle weakness followed by a premature death in young boys. There is a low index of reports on diagnosis ratio and clinical features in Southern India.

Objective  The present study aimed to conduct an observational survey on preliminary analysis, family history, associated complaints, and diagnosis ratio of DMD in southern regions of India.

Materials and Methods  A systematic observation and survey were conducted on clinically confirmed DMD patients registered between 2019 and 2021 through the questionnaire. The questionnaire and pattern of study were identified by exploring published and unpublished studies available from electronic databases and critical assessment criteria considered by physicians. Preliminary analysis such as onset criteria, motor difficulties, milestone delay; family history and consanguinity analysis; chief complaints (ambulatory status, lordosis, respiratory, and cardiac outcomes), associated complaints such as enlarged tongue, oral hygiene, behavioral problems; and other similar parameters were studied. An assessment of the diagnosis rate and pattern was performed.

Statistical analysis  The data were reviewed and interpreted through statistical methods mean ± standard deviation represented as a percentage.

Results  In total, 400 DMD patients were included and 250 participated in the study. The onset age group was 2 to 5 years in 37% of the population. Milestone delay was seen in 86%; consanguinity marriage of parents was reported in 39%. Frequent falls were reported in 62% in 5 to 8 years old group. Wheelchair status was reported in 65% in 9 to 12 years old. Cervical and lumbar lordoses were seen in 57 and 69%, respectively, in above 13 years old. Respiratory and cardiac complications were 88 and 78% reported in above 13 years old, respectively. Other major associated complaints such as enlarged tongue were reported in 79%. Fifty-one percent underwent genetic diagnosis and 79% of the population underwent serum creatine phosphokinase (CPK) analysis for the confirmation of DMD.

Conclusion  In this study population of South India, milestone delay was a major observation. Although there was a slight margin, family history shows “no blood relation among parents” in the majority of the study population. Chief complaints were predominantly severe above 13-year age group population. Serum CPK was the first choice for the first investigation, which is followed by a genetic diagnosis.

C-X-C motif chemokine ligand 12: a potential therapeutic target in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked recessive disease caused by a mutant dystrophin protein. DMD patients undergo gradual progressive paralysis until death. Chronic glucocorticoid therapy remains one of the main treatments for DMD, despite the significant side effects. However, its mechanisms of action remain largely unknown. We used bioinformatics tools to identify pathogenic genes involved in DMD and glucocorticoid target genes. Two gene expression profiles containing data from DMD patients and healthy controls (GSE38417 and GSE109178) were downloaded for further analysis. Differentially expressed genes (DEGs) between DMD patients and controls were identified using GEO2R, and glucocorticoid target genes were predicted from the Pharmacogenetics and Pharmacogenomics Knowledge Base. Surprisingly, only one gene, CXCL12 (C-X-C motif chemokine ligand 12), was both a glucocorticoid target and a DEG. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, Gene Ontology term enrichment analysis, and gene set enrichment analysis were performed. A protein-protein interaction network was constructed and hub genes identified using the Search Tool for the Retrieval of Interacting Genes (STRING) database and Cytoscape. Enriched pathways involving the DEGs, including CXCL12, were associated with the immune response and inflammation. Levels of CXCL12 and its receptor CXCR4 (C-X-C motif chemokine receptor 4) were increased in X-linked muscular dystrophy (mdx) mice (DMD models) but became significantly reduced after prednisone treatment. Metformin also reduced the expression of CXCL12 and CXCR4 in mdx mice. In conclusion, the CXCL12-CXCR4 pathway may be a potential target for DMD therapy.

Swimming Improves Memory and Antioxidant Defense in an Animal Model of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a genetic disease associated with progressive skeletal muscle degeneration. In humans, DMD has an early onset, causes developmental delays, and is a devastating disease that drastically diminishes the quality of life of young individuals affected. The objective of this study was to evaluate the effects of a swimming protocol on memory and oxidative stress in an animal model of DMD. Male mdx and wild-type mice aged ≥ 28 days were used in this study. The animals were trained for a stepped swimming protocol for four consecutive weeks. The swimming protocol significantly reduced the levels of lipid peroxidation and protein carbonylation in the gastrocnemius, hippocampus, and striatum in the exercised animals. It also prevented lipid peroxidation in the diaphragm. Moreover, it increased the free thiol levels in the gastrocnemius, the diaphragm, and all central nervous system structures. The results showed that the protocol that applied swimming as a low-intensity aerobic exercise for 4 weeks prevented aversive memory and habituation in mdx mice.

Vector-mediated expression of muscle specific kinase restores specific force to muscles in the mdx mouse model of Duchenne muscular dystrophy

NEW FINDINGS

What is the central question of this study? The (dystrophin-deficient) muscles of mdx mice generate less contractile force per cross-sectional area (specific force) than those of healthy wild-type mice: what is the influence of muscle specific kinase (MuSK) upon the properties of the tibialis anterior (TA) muscle in mdx mice? What is the main finding and its importance? Injection of adeno-associated viral vector encoding MuSK into the TA muscle of young mdx mice increased the specific force of the muscle, suggesting the MuSK signalling system has the potential to restore healthy growth to dystrophin-deficient muscles.

ABSTRACT

In the mdx mouse model of Duchenne muscular dystrophy, muscle fibres are fragile and prone to injury and degeneration. Compared to wild-type mice, muscles of mdx mice also develop less specific force (contractile force/cross-sectional area). We recently reported that injecting adeno-associated viral vector encoding muscle specific kinase (AAV-MuSK) into muscles of mdx mice increased utrophin expression and made the muscles more resistant to acute stretch-induced injury. Here we injected AAV-MuSK unilaterally into the tibialis anterior muscle of mdx mice at a younger age (4 weeks), and recorded contraction force from the muscles in situ at 12 weeks of age. Compared to contralateral empty-vector control muscles, muscles injected with AAV-MuSK produced 28% greater specific force (P = 0.0005). They did not undergo the compensatory hypertrophy that normally occurs in muscles of mdx mice. Injection of AAV encoding rapsyn (a downstream effector of MuSK signalling) caused no such improvement in muscle strength. Muscles injected with AAV-MuSK displayed a 10% reduction in the number of fibres with centralized nuclei (P = 0.0015). Our results in mdx mice suggest that elevating the expression of MuSK can reduce the incidence of muscle fibre regeneration and improve the strength of dystrophin-deficient muscles.

Various Aspects of a Gene Editing System-CRISPR-Cas9

The discovery of clustered, regularly interspaced short palindromic repeats (CRISPR) and their cooperation with CRISPR-associated (Cas) genes is one of the greatest advances of the century and has marked their application as a powerful genome engineering tool. The CRISPR-Cas system was discovered as a part of the adaptive immune system in bacteria and archaea to defend from plasmids and phages. CRISPR has been found to be an advanced alternative to zinc-finger nucleases (ZFN) and transcription activator-like effector nucleases (TALEN) for gene editing and regulation, as the CRISPR-Cas9 protein remains the same for various gene targets and just a short guide RNA sequence needs to be altered to redirect the site-specific cleavage. Due to its high efficiency and precision, the Cas9 protein derived from the type II CRISPR system has been found to have applications in many fields of science. Although CRISPR-Cas9 allows easy genome editing and has a number of benefits, we should not ignore the important ethical and biosafety issues. Moreover, any tool that has great potential and offers significant capabilities carries a level of risk of being used for non-legal purposes. In this review, we present a brief history and mechanism of the CRISPR-Cas9 system. We also describe on the applications of this technology in gene regulation and genome editing; the treatment of cancer and other diseases; and limitations and concerns of the use of CRISPR-Cas9.