Duchenne and Becker muscular dystrophy: contribution of a molecular and immunohistochemical analysis in diagnosis in Morocco

Duchenne and Becker muscular dystrophy: Cellular mechanisms, image analysis, and computational models: A review

The muscle is the principal tissue that is capable to transform potential energy into kinetic energy. This process is due to the transformation of chemical energy into mechanical energy to enhance the movements and all the daily activities. However, muscular tissues can be affected by some pathologies associated with genetic alterations that affect the expression of proteins. As the muscle is a highly organized structure in which most of the signaling pathways and proteins are related to one another, pathologies may overlap. Duchenne muscular dystrophy (DMD) is one of the most severe muscle pathologies triggering degeneration and muscle necrosis. Several mathematical models have been developed to predict muscle response to different scenarios and pathologies. The aim of this review is to describe DMD and Becker muscular dystrophy in terms of cellular behavior and molecular disorders and to present an overview of the computational models implemented to understand muscle behavior with the aim of improving regenerative therapy.

Casimersen (AMONDYS 45™): An Antisense Oligonucleotide for Duchenne Muscular Dystrophy

Casimersen (AMONDYS 45TM) is an antisense oligonucleotide of the phosphorodiamidate morpholino oligomer subclass developed by Sarepta therapeutics. It was approved by the Food and Drug Administration (FDA) in February 2021 to treat Duchenne muscular dystrophy (DMD) in patients whose DMD gene mutation is amenable to exon 45 skipping. Administered intravenously, casimersen binds to the pre-mRNA of the DMD gene to skip a mutated region of an exon, thereby producing an internally truncated yet functional dystrophin protein in DMD patients. This is essential in maintaining the structure of a myocyte membrane. While casimersen is currently continuing in phase III of clinical trials in various countries, it was granted approval by the FDA under the accelerated approval program due to its observed increase in dystrophin production. This article discusses the pathophysiology of DMD, summarizes available treatments thus far, and provides a full drug review of casimersen (AMONDYS 45TM).

Investigation of outcome measures and anomalous lower extremity in osteoarthritis patients with Jumpstart nutrition® supplementation

Background

Osteoarthritis (OA) is characterized by cartilage and synovial inflammation as well as anomalous lower extremity leading to joint pain, and impairment in lifestyle and epidemic of obesity. This study aimed to use the Jumpstart Nutrition® supplement (JNS) for achieving symmetry of aberrant lower extremity and improving the outcome measures in the management of OA.

Methods

This week-twelve registry included 108 patients treated with JNS mainly comprised of calcium, phosphorus, magnesium, vitamin-K2, coenzyme-Q10, vitamin-C, boswellic acids, and curcumin mixed with soy and whey proteins (experimental group) and 72 were treated with symptomatic slow-acting drugs (control group) for chronic OA confirmed with radiological images. The outcome measures (Visual analogue scale, Western Ontario and McMaster Universities Osteoarthritis Index, Knee-injury Osteoarthritis Outcomes Scale, and Body mass index), and anomalous lower extremity included bilateral: knee gaps between biceps femoris-short head and surface of the bed, diameters of muscles at the calf, the thigh, 4cm above and below the patella, angles of straight leg raising, knee- flexion and-extension in supine were evaluated with appropriate protocol at week-0 and at week-12 for both the groups.

Results

After week-12, risk ratios of studied lower extremity, and mean ±standard deviation of all outcome measures were significantly improved (p<0.0001), and Kellgren-Lawrence scale (KLS) was upgraded to ≥2 in experimental group compared to control.

Conclusions

This registry study indicates that JNS can be used to achieve symmetry of studied lower extremity and to improve the outcome measures safely as an effective management of OA patients confirmed with radiological images correlated with KLS.

Combining Protein Expression and Molecular Data Improves Mutation Characterization of Dystrophinopathies

Duchenne and Becker muscular dystrophy are X-linked recessive inherited disorders characterized by progressive weakness due to skeletal muscle degeneration. Different mutations in the DMD gene, which encodes for dystrophin protein, are responsible for these disorders. The aim of our study was to investigate the relationship between type, size, and location of the mutation that occurs in the DMD gene and their effect on dystrophin protein expression in a cohort of 40 male dystrophinopathy patients and nine females, possible carriers. We evaluated the expression of dystrophin by immunofluorescence and immunoblotting. The mutational spectrum of the DMD gene was established by MLPA for large copy number variants, followed by HRM analysis for point mutations and sequencing of samples with an abnormal melting profile. MLPA revealed 30 deletions (75%) and three duplications (7.5%). HRM analysis accounted for seven-point mutations (17.5%). We also report four novel small mutations (c. 8507G>T, c.3021delG, c.9563_9563+1insAGCATGTTTATGATACAGCA, c.7661-60T>A) in DMD gene. Our work shows that the DNA translational open reading frame and the location of the mutation both influence the expression of dystrophin and disease severity phenotype. The proposed algorithm used in this study demonstrates its accuracy for the characterization of dystrophinopathy patients.

Diagnostic Value of Dystrophin Immunostaining in the Diagnosis of Duchenne and Becker Muscular Dystrophy Patients

Background: Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked recessive muscular disorders caused by the absence or reduction of the muscle cytoskeletal protein dystrophin. Standard procedures to detect deletion and duplication of the DMD gene use Multiplex Ligation-Dependent Probe Amplification (MLPA). However, genetic testing, such as MLPA, is not covered by the national insurance scheme in Indonesia. Immunohistochemical (IHC) staining of dystrophin from muscle biopsy in the form of Formalin-Fixed Paraffin-Embedded (FFPE) specimens can be an alternative method to detect dystrophin expression in protein levels to establish the diagnosis of DMD or BMD. Objectives: To determinate sensitivity, specificity and accuracy of IHC analysis of dystrophin in DMD/BMD patient in comparison with the standard genetic testing, MLPA. Methods: Twenty-six patients enrolled in this study were clinically diagnosed as DMD/BMD in Dr. Sardjito Hospital and Universitas Gadjah Mada Academic Hospital. Genomic DNA was isolated from 3 mL of EDTA-peripheral whole blood samples. The deletion and duplication of DMD genes were detected by MLPA. IHC examination was performed using a specific antibody dystrophin (DYS2). Complete loss of dystrophin staining indicated DMD, while partial loss of dystrophin staining indicated BMD. MLPA result was used as the gold standard to determine sensitivity, specificity, and accuracy of IHC technique using a 2x2 table. Results: MLPA results revealed 18 (18/26; 69.3%) patients with deletion and 3 (3/26; 11.5%) patients with duplication. Five (5/26; 19.2%) patients who showed no deletion nor duplication were excluded from the analysis. Among 21 patients with deletion or duplication, 18 (18/21; 85.7%) patients were out-of-frame (DMD) and 3 (3/21; 14.3%) patients were in-frame (BMD). Six patients showed a discrepancy between the IHC and MLPA results with 9.5% (2/21) false positive and 19% (4/21) false negative. The sensitivity of dystrophin IHC was 77.78%, specificity 33.33%, positive predictive value 87.5%, negative predictive value 20%, and accuracy 71.43%. Conclusion: Muscle biopsy followed by IHC can be one of the diagnostic tools to diagnose BMD or DMD, with high sensitivity. The protein-based strategy is probably the most efficient way to approach the diagnosis of Duchenne and Becker muscular dystrophy in limited health care settings.

Early Identification of DMD in the Setting of West Syndrome

Duchene muscular dystrophy (DMD) is the most common muscular dystrophy in childhood, affecting ∼1:5000 male live births worldwide. DMD is a genetic disorder with X-linked recessive inheritance pattern characterized by a severe muscular phenotype with progressive muscle weakness and atrophy due to pathogenic variations within the DMD gene. Two cases are reported to date in the literature of individuals with a diagnosis of both DMD and West syndrome; neither of which had the degree of additional genetic abnormalities that our patient demonstrates. We present a male infant with West syndrome, and multiple pathogenic variants, the ominous one being in the DMD gene. This case adds to confirming that West syndrome expands the spectrum of epilepsy that may be present in DMD patients. Additionally, this case can identify how the early use of steroids may shed light on effects of early symptomatic treatment of DMD.

Current Genetic Survey and Potential Gene-Targeting Therapeutics for Neuromuscular Diseases

Neuromuscular diseases (NMDs) belong to a class of functional impairments that cause dysfunctions of the motor neuron-muscle functional axis components. Inherited monogenic neuromuscular disorders encompass both muscular dystrophies and motor neuron diseases. Understanding of their causative genetic defects and pathological genetic mechanisms has led to the unprecedented clinical translation of genetic therapies. Challenged by a broad range of gene defect types, researchers have developed different approaches to tackle mutations by hijacking the cellular gene expression machinery to minimize the mutational damage and produce the functional target proteins. Such manipulations may be directed to any point of the gene expression axis, such as classical gene augmentation, modulating premature termination codon ribosomal bypass, splicing modification of pre-mRNA, etc. With the soar of the CRISPR-based gene editing systems, researchers now gravitate toward genome surgery in tackling NMDs by directly correcting the mutational defects at the genome level and expanding the scope of targetable NMDs. In this article, we will review the current development of gene therapy and focus on NMDs that are available in published reports, including Duchenne Muscular Dystrophy (DMD), Becker muscular dystrophy (BMD), X-linked myotubular myopathy (XLMTM), Spinal Muscular Atrophy (SMA), and Limb-girdle muscular dystrophy Type 2C (LGMD2C).

The Effect of Vitamin D Supplementation on Skeletal Muscle in the mdx Mouse Model of Duchenne Muscular Dystrophy

Vitamin D (VitD) has shown to be beneficial in reversing muscle weakness and atrophy associated with VitD deficiency. Duchenne muscular dystrophy is characterized by worsening muscle weakness and muscle atrophy, with VitD deficiency commonly observed. This study aimed to investigate the effect of VitD supplementation on dystrophic skeletal muscle. Eight-week old female control (C57BL/10; n = 29) and dystrophic (C57BL/mdx; n = 23) mice were randomly supplemented with one of three VitD enriched diets (1000, 8000 & 20,000 IU/kg chow). Following a four-week feeding period, the extensor digitorum longus (EDL) and soleus muscles contractile and fatigue properties were tested ex vivo, followed by histological analysis. As expected, mdx muscles displayed higher mass yet lower specific forces and a rightward shift in their force frequency relationship consistent with dystrophic pathology. There was a trend for mdx muscle mass to be larger following the 20,000 IU/kg diet, but this did not result in improved force production. Fiber area in the EDL was larger in mdx compared to controls, and there were higher amounts of damage in both muscles, with VitD supplementation having no effect. Four weeks of VitD supplementation did not appear to have any impact upon dystrophic skeletal muscle pathology at this age.

Pathological Issues in Dystrophinopathy in the Age of Genetic Therapies

Dystrophinopathy is a class of genetic skeletal muscle disease characterized by myofiber degeneration and regeneration due to insufficient levels or functioning of dystrophin. Pathological evaluation for dystrophinopathy includes the identification of dystrophic skeletal muscle pathology and the immunohistochemical evaluation of dystrophin epitopes, but biopsies have become rare in recent years. However, the evaluation of dystrophin expression in the research setting has become critically important due to recent advances in genetic therapies, including exon skipping and gene therapy. Given the number of these therapies under evaluation in patients, it is likely that the traditional methods of evaluating dystrophinopathy will need to evolve in the near future. This review discusses current muscle biopsy diagnostic practices in dystrophinopathy and further focuses on how these practices have evolved in the context of therapeutic interventions for dystrophinopathy.

Mutation spectrum analysis of Duchenne/Becker muscular dystrophy in 68 families in Kuwait: The era of personalized medicine

Duchenne and Becker muscular dystrophies (DMD/BMD) are X-linked recessive neuromuscular disorders characterized by progressive irreversible muscle weakness and atrophy that affect both skeletal and cardiac muscles. DMD/BMD is caused by mutations in the Dystrophin gene on the X chromosome, leading to the absence of the essential muscle protein Dystrophin in DMD. In BMD, Dystrophin is partially functioning with a shorter protein product. Recent advances in molecular therapies for DMD require precise genetic diagnoses because most therapeutic strategies are mutation-specific. Hence, early diagnosis is crucial to allow appropriate planning for patient care and treatment. In this study, data from DMD/BMD patients who attended the Kuwait Medical Genetic Center during the last 20 years was retrieved from a Kuwait neuromuscular registry and analyzed. We combined multiplex PCR and multiplex ligation-dependent probe amplification (MLPA) with Sanger sequencing to detect Dystrophin gene mutations. A total of 35 different large rearrangements, 2 deletion-insertions (Indels) and 4 substitution mutations were identified in the 68 unrelated families. The deletion and duplication rates were 66.2% and 4.4%, respectively. The analyzed data from our registry revealed that 11 (16%) of the DMD families will benefit from newly introduced therapies (Ataluren and exon 51 skipping). At the time of submitting this paper, two cases have already enrolled in Ataluren (Tranlsarna™) therapy, and one case has been enrolled in exon 51 skipping therapy.

Molecular Analysis-Based Genetic Characterization of a Cohort of Patients with Duchenne and Becker Muscular Dystrophy in Eastern China

Background:

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are common X-linked recessive neuromuscular disorders caused by mutations in dystrophin gene. Multiplex polymerase chain reaction (multiplex PCR) and multiplex ligation-dependent probe amplification (MLPA) are the most common methods for detecting dystrophin gene mutations. This study aimed to contrast the two methods and discern the genetic characterization of patients with DMD/BMD in Eastern China.

Methods:

We collected 121 probands, 64 mothers of probands, and 15 fetuses in our study. The dystrophin gene was detected by multiplex PCR primarily in 28 probands, and MLPA was used in multiplex PCR-negative cases subsequently. The dystrophin gene of the remaining 93 probands and 62 female potential carriers was tested by MLPA directly. In fetuses, multiplex PCR and MLPA were performed on 4 fetuses and 10 fetuses, respectively. In addition, sequencing was also performed in 4 probands with negative MLPA.

Results:

We found that 61.98% of the subjects had genetic mutations including deletions (50.41%) and duplications (11.57%). There were 43.75% of mothers as carriers of the mutation. In 15 fetuses, 2 out of 7 male fetuses were found to be unhealthy and 2 out of 8 female fetuses were found to be carriers. Exons 3–26 and 45–52 have the maximum frequency in mutation regions. In the frequency of exons individually, exon 47 and exon 50 were the most common in deleted regions and exons 5, 6, and 7 were found most frequently in duplicated regions.

Conclusions:

MLPA has better productivity and sensitivity than multiplex PCR. Prenatal diagnosis should be applied in DMD high-risk fetuses to reduce the disease incidence. Furthermore, it is the responsibility of physicians to inform female carriers the importance of prenatal diagnosis.

The trefoil with single fruit sign in muscle magnetic resonance imaging is highly specific for dystrophinopathies

BACKGROUND

The purpose of this study was to evaluate the diagnostic value of the trefoil (three leaflets formed by relative sparing of the sartorius, gracilis, and adductor longus) with single fruit sign (relative sparing of the semitendinosus) in the evaluation of thigh muscle magnetic resonance imaging (MRI) for dystrophinopathies.

METHODS

Five examiners blinded to any clinical data analyzed muscle MRI scans from 166 patients with dystrophinopathies (124 cases confirmed genetically and 42 cases confirmed by immunohistochemistry) and from 244 control patients, all treated in our hospital from 2011 to 2014. The controls were patients with other neuromuscular disorders and with dystrophinopathies excluded by genetic testing and/or muscle biopsy. Examiners assessed the presence or absence of the trefoil with single fruit sign approximately at the middle thigh cross-section. Results were analyzed for diagnostic accuracy and inter-examiner agreement.

RESULTS

Sensitivity of the trefoil with single fruit sign for all patients with dystrophinopathies was 41.6% (95% confidence interval (CI) of 34.0-49.5). However, specificity was 99.2% (95% CI 97.1-99.9). The positive predictive value (PPV) was 97.2% and negative predictive value (NPV) was 71.4%. Inter-examiner agreement was substantial (Kappa=0.66). The 69 dystrophinopathy patients whose MRIs exhibited the sign were significantly older than the 97 dystrophinopathy patients whose MRIs did not (Z=-3.970, P<0.001).

CONCLUSIONS

The trefoil with single fruit sign is a potential imaging marker for diagnosis of dystrophinopathies.