Synaptic alterations as a neurodevelopmental trait of Duchenne muscular dystrophy

Electrocardiographic and Autonomic Nervous System Changes after Changes in the Posture of Children and Adolescents with Duchenne Muscular Dystrophy

BACKGROUND

Duchenne Muscular Dystrophy (DMD) is a rare inherited neuromuscular disease. At first, cardiac involvement may be asymptomatic. Therefore, assessing patients using non-invasive methods can help detect any changes.

OBJECTIVES

Analyze the electrocardiogram (ECG) test and heart rate variability (HRV) of the DMD group and compare the information with that of the age-matched control group.

METHODS

A prospective study with 27 male patients with DMD (11.9 years old), who underwent clinical evaluation, ECG, echocardiogram, and Holter monitoring. ECG (200% increase) was assessed by two independent observers. HRV was measured over time (24 h) and in the frequency domain, in the supine and sitting positions. The healthy group consisted of nine patients (11.0 years old). A value of p < 0.05 was considered statistically significant.

RESULTS

The mean ejection fraction (EF) was 60% (34 to 71%). The Kappa coefficient for ECG measurements ranged from 0.64 to 1.00. An increase in the R/S ratio in V1 was observed in 25.9% of the subjects, pathological Q wave in 29.6%, and fragmented QRS in 22.2% in inferior/high lateral regions, with a negative correlation with EF (p = 0.006). There was low HRV, without the influence of any variable, including treatment. With the change in position, there was an increase in HR (p = 0.004), but there was no change in HRV. The LF/HF ratio was 2.7 in the DMD group and 0.7 in the control group (p = 0.002).

CONCLUSIONS

In DMD subjects, prominent R waves in V1 and changes in the inferior/high lateral regions occurred in almost 30% of the cases. Lower vagal tone was observed without the influence of the variables age, ejection fraction, QT dispersion, and treatment. Despite the increase in HR, there was no adequate HRV response to the change in position.

The unconditioned fear response in vertebrates deficient in dystrophin

Dystrophin loss due to mutations in the Duchenne muscular dystrophy (DMD) gene is associated with a wide spectrum of neurocognitive comorbidities, including an aberrant unconditioned fear response to stressful/threat stimuli. Dystrophin-deficient animal models of DMD demonstrate enhanced stress reactivity that manifests as sustained periods of immobility. When the threat is repetitive or severe in nature, dystrophinopathy phenotypes can be exacerbated and even cause sudden death. Thus, it is apparent that enhanced sensitivity to stressful/threat stimuli in dystrophin-deficient vertebrates is a legitimate cause of concern for patients with DMD that could impact neurocognition and pathophysiology. This review discusses our current understanding of the mechanisms and consequences of the hypersensitive fear response in preclinical models of DMD and the potential challenges facing clinical translatability.

How Can Proteomics Help to Elucidate the Pathophysiological Crosstalk in Muscular Dystrophy and Associated Multi-System Dysfunction?

This perspective article is concerned with the question of how proteomics, which is a core technique of systems biology that is deeply embedded in the multi-omics field of modern bioresearch, can help us better understand the molecular pathogenesis of complex diseases. As an illustrative example of a monogenetic disorder that primarily affects the neuromuscular system but is characterized by a plethora of multi-system pathophysiological alterations, the muscle-wasting disease Duchenne muscular dystrophy was examined. Recent achievements in the field of dystrophinopathy research are described with special reference to the proteome-wide complexity of neuromuscular changes and body-wide alterations/adaptations. Based on a description of the current applications of top-down versus bottom-up proteomic approaches and their technical challenges, future systems biological approaches are outlined. The envisaged holistic and integromic bioanalysis would encompass the integration of diverse omics-type studies including inter- and intra-proteomics as the core disciplines for systematic protein evaluations, with sophisticated biomolecular analyses, including physiology, molecular biology, biochemistry and histochemistry. Integrated proteomic findings promise to be instrumental in improving our detailed knowledge of pathogenic mechanisms and multi-system dysfunction, widening the available biomarker signature of dystrophinopathy for improved diagnostic/prognostic procedures, and advancing the identification of novel therapeutic targets to treat Duchenne muscular dystrophy.

Sub-region analysis of DMD gene in cases with idiopathic generalized epilepsy

Gene sub-region encoded protein domain is the basic unit for protein structure and function. The DMD gene is the largest coding gene in humans, with its phenotype relevant to idiopathic generalized epilepsy. We hypothesized variants clustered in sub-regions of idiopathic generalized epilepsy genes and investigated the relationship between the DMD gene and idiopathic generalized epilepsy. Whole exome sequencing was performed in 106 idiopathic generalized epilepsy individuals. DMD variants were filtered with variant type, allele frequency, in silico prediction, hemizygous or homozygous status in the population, inheritance mode, and domain location. Variants located at the sub-regions were selected by the subRVIS software. The pathogenicity of variants was evaluated by the American College of Medical Genetics and Genomics criteria. Articles on functional studies related to epilepsy for variants clustered protein domains were reviewed. In sub-regions of the DMD gene, two variants were identified in two unrelated cases with juvenile absence epilepsy or juvenile myoclonic epilepsy. The pathogenicity of both variants was uncertain significance. Allele frequency of both variants in probands with idiopathic generalized epilepsy reached statistical significance compared with the population (Fisher's test, p = 2.02 × 10-6, adjusted α = 4.52 × 10-6). The variants clustered in the spectrin domain of dystrophin, which binds to glycoprotein complexes and indirectly affects ion channels contributing to epileptogenesis. Gene sub-region analysis suggests a weak association between the DMD gene and idiopathic generalized epilepsy. Functional analysis of gene sub-region helps infer the pathogenesis of idiopathic generalized epilepsy.

Differential expression profiles of plasma exosomal microRNAs in dilated cardiomyopathy with chronic heart failure

As one of the most prevalent heritable cardiovascular diseases, dilated cardiomyopathy (DCM) induces cardiac insufficiency and dysfunction. Although genetic mutation has been identified one of the causes of DCM, the usage of genetic biomarkers such as RNAs for DCM early diagnosis is still being overlooked. In addition, the alternation of RNAs could reflect the progression of the diseases, as an indicator for the prognosis of patients. Therefore, it is beneficial to develop genetic based diagnostic tool for DCM. RNAs are often unstable within circulatory system, leading to the infeasibility for clinical application. Recently discovered exosomal miRNAs have the stability that is then need for diagnostic purpose. Hence, fully understanding of the exosomal miRNA within DCM patients is vital for clinical translation. In this study, we employed the next generation sequencing based on the plasma exosomal miRNAs to comprehensively characterize the miRNAs expression in plasma exosomes from DCM patients exhibiting chronic heart failure (CHF) compared to healthy individuals. A complex landscape of differential miRNAs and target genes in DCM with CHF patients were identified. More importantly, we discovered that 92 differentially expressed miRNAs in DCM patients undergoing CHF were correlated with several enriched pathways, including oxytocin signalling pathway, circadian entrainment, hippo signalling pathway-multiple species, ras signalling pathway and morphine addiction. This study reveals the miRNA expression profiles in plasma exosomes in DCM patients with CHF, and further reveal their potential roles in the pathogenesis of it, presenting a new direction for clinical diagnosis and management of DCM patients with CHF.

Dystrophin Short Product, Dp71, Interacts with AQP4 and Kir4.1 Channels in the Mouse Cerebellar Glial Cells in Contrast to Dp427 at Inhibitory Postsynapses in the Purkinje Neurons

Dystrophin is the causative gene for Duchenne and Becker muscular dystrophy (DMD/BMD), and it produces full-length and short dystrophin, Dp427 and Dp71, respectively, in the brain. The existence of the different dystrophin molecular complexes has been known for a quarter century, so it is necessary to derive precise expression profiles of the molecular complexes in the brain to elucidate the mechanism of cognitive symptoms in DMD/BMD patients. In order to investigate the Dp71 expression profile in cerebellum, we employed Dp71-specific tag-insertion mice, which allowed for the specific detection of endogenous Dp71 in the immunohistochemical analysis and found its expressions in the glial cells, Bergmann glial (BG) cells, and astrocytes, whereas Dp427 was exclusively expressed in the inhibitory postsynapses within cerebellar Purkinje cells (PCs). Interestingly, we found different cell-type dependent dystrophin molecular complexes; i.e., glia-associated Dp71 was co-expressed with dystroglycan (DG) and dystrobrevinα, whereas synapse-associated Dp427 was co-expressed with DG and dystrobrevinβ. Furthermore, we investigated the molecular relationship of Dp71 to the AQP4 water channel and the Kir4.1 potassium channel, and found biochemical associations of Dp71 with AQP4 and Kir4.1 in both the cerebellum and cerebrum. Immunohistochemical and cytochemical investigations revealed partial co-localizations of Dp71 with AQP4 and Kir4.1 in the glial cells, indicating Dp71 interactions with the channels in the BG cells and astrocytes. Taken together, different cell-types, glial cells and Purkinje neurons, in the cerebellum express different dystrophin molecular complexes, which may contribute to pathological and physiological processes through the regulation of the water/ion channel and inhibitory postsynapses.

Global prevalence of intellectual developmental disorder in dystrophinopathies: A systematic review and meta-analysis

AIM

To estimate the global prevalence of intellectual developmental disorder (IDD) and the IDD prevalence-genotype association in Becker muscular dystrophy (BMD) or Duchenne muscular dystrophy (DMD) according to the affected isoforms of the DMD gene: Dp427, Dp140, Dp71.

METHOD

Systematic searches in MEDLINE, Scopus, Web of Science, and the Cochrane Library were conducted from inception of each database to March 2022. Observational studies that determined the prevalence of IDD in the population with BMD or DMD were included. Meta-analyses of IDD prevalence and prevalence ratios of the IDD-genotype association were conducted.

RESULTS

Forty-nine studies were included. The prevalence of IDD in BMD was 8.0% (95% confidence interval 5.0-11.0), and in DMD it was 22.0% (18.0-27.0). Meta-analyses of IDD-genotype association showed a deleterious association between IDD and the number of isoforms affected in DMD, with a prevalence ratio = 0.43 (0.28-0.64) and 0.17 (0.09-0.34) for Dp140⁺ /Dp71⁺ versus Dp140^- /Dp71⁺ and Dp140⁺ /Dp71⁺ versus Dp140^- /Dp71^- comparisons respectively. However, in BMD, there was no association for Dp140⁺ /Dp71⁺ versus Dp140^- /Dp71⁺ .

INTERPRETATION

There is a high prevalence of IDD in BMD and DMD. Moreover, the number of isoforms affected is strongly and negatively associated with the prevalence of IDD in DMD.

Abnormal Expression of Synaptic and Extrasynaptic GABAA Receptor Subunits in the Dystrophin-Deficient mdx Mouse

Duchenne muscular dystrophy (DMD) is a neurodevelopmental disorder primarily caused by the loss of the full-length Dp427 dystrophin in both muscle and brain. The basis of the central comorbidities in DMD is unclear. Brain dystrophin plays a role in the clustering of central gamma-aminobutyric acid A receptors (GABA_ARs), and its loss in the mdx mouse alters the clustering of some synaptic subunits in central inhibitory synapses. However, the diversity of GABAergic alterations in this model is still fragmentary. In this study, the analysis of in vivo PET imaging of a benzodiazepine-binding site radioligand revealed that the global density of central GABA_ARs is unaffected in mdx compared with WT mice. In contrast, semi-quantitative immunoblots and immunofluorescence confocal imaging in tissue sections revealed complex and differential patterns of alterations of the expression levels and/or clustered distribution of a variety of synaptic and extrasynaptic GABA_AR subunits in the hippocampus, cerebellum, cortex, and spinal cord. Hence, dystrophin loss not only affects the stabilization of synaptic GABA_ARs but also influences the subunit composition of GABA_ARs subtypes at both synaptic and extrasynaptic sites. This study provides new molecular outcome measures and new routes to evaluate the impact of treatments aimed at compensating alterations of the nervous system in DMD.