Social difficulties and care burden of adult Duchenne muscular dystrophy in Japan: a questionnaire survey based on the Japanese Registry of Muscular Dystrophy (Remudy)

BACKGROUND

Little is known about the social difficulties and health care needs of adult Duchenne muscular dystrophy (DMD) patients in Japan, as well as the financial and physical stress experienced by their caregivers. This study aimed to clarify the social circumstances surrounding adult DMD patients and assess the degree of involvement of family members in their care and the associated economic burden of the disorder in Japan.

METHODS

Adult DMD patients were identified through the Registry of Muscular Dystrophy (Remudy) in Japan and invited to complete a questionnaire together with a caregiver. Data on health care use, quality of life, work status, informal care, and household expenses were collected to estimate the costs associated with DMD from social and caregiver household perspectives.

RESULTS

In total, 234 (63.7%) of 367 adult DMD patients (mean age, 27.4 ± 6.0; range, 20-48 years) completed the questionnaire. Of these, 38 (21%) had developmental disorders (mental retardation, autism, and learning disorders), 57 (33%) experienced bullying in school, and 44 (77%) indicated the reason for bullying to be their physical handicap. Employment histories were noted by 72 (31%), although 23 (10%) lost their jobs mainly due to physical difficulties. Of the 234 patients, 164 (74%) lived with their relatives, and 78% of care time was supplied by family members, in particular, their mothers. The mean rate of care work provided by family members was 81%. Household income of families with an adult DMD patient was lower, whereas the rate of living with parent(s) and grandparent(s) was higher, in comparison with the general Japanese population.

CONCLUSIONS

Adult DMD patients in Japan experience many social difficulties from childhood up to adulthood. As adults, many DMD patients experience bullying and workplace difficulties. Families were found to provide most of the care and financial support for DMD patients. Our results suggest the need to improve public patient care systems, including financial support, to address the physical and economic burdens of care for adult DMD patients in Japan.

Evolution of neuropsychological and behavioral profile in a cohort of pediatric patients with Becker muscular dystrophy in a longitudinal study

It has long been reported that neuropsychological deficits may be present in dystrophinopathies, specifically non-progressive cognitive impairment and a global deficit in executive functions; this neurocognitive profile has been less explored in patients with Becker than Duchenne muscular dystrophy (BMD/DMD). We conducted a longitudinal study to explore the evolution of neuropsychological and behavioural profile in a cohort of paediatric BMD. Seventeen patients with BMD without intellectual disability were assessed using a full battery of tests, including intellectual, adaptive and executive functioning, language and behavioral features. Tests were performed at baseline and after 12 months. The results showed adequate cognitive and adaptive profile with falls in Working Memory, as well as lower scores in executive functions. An improvement was observed in Processing Speed. Behavioral questionnaires confirmed a negative trend, while in normal ranges. We found a statistically significant difference between T0 and T1 in some items exploring executive functions. No statistically significant difference was observed stratifying patients by mutation site or IQ level. In conclusion, our study suggests that BMD patients have a stable neurocognitive profile, while a deflection in the executive functions may be observed. We recommend a careful monitoring to intercept learning disabilities and promptly start a multimodal rehabilitation.

Epilepsy in dystrophinopathies: A retrospective cohort and review of the literature

OBJECTIVE

This study aimed to assess the prevalence and characteristics of epilepsy in dystrophinopathies within a cohort of 142 patients at a tertiary neuromuscular center in Istanbul, Turkey.

METHODS

We recorded the age at seizure onset, seizure type, family history, history of febrile seizures, treatment, and EEG results. Epilepsy was classified according to the latest International League Against Epilepsy (ILAE) classification.

RESULTS

Of the 142 DMD patients, 8 experienced epileptic seizures (5.6 %). The median age of the patients was 11 years (8.0-15.2). The median age for the first DMD symptoms was 24 months (16.5-37.5). All seizures were consistent with generalized tonic-clonic seizures. Three patients are currently on anti-seizure medication.

SIGNIFICANCE

The prevalence of epilepsy in our study (5.6 %) exceeds that of the general pediatric population (0.5-1 %). However, the frequency of febrile seizures in children with dystrophinopathy is similar to that of the general population.

Phenotypic features of genetically modified DMD-XKOXWT pigs

Introduction

Duchenne muscular dystrophy (DMD) is a hereditary neuromuscular disorder caused by mutation in the dystrophin gene (DMD) on the X chromosome. Female DMD carriers occasionally exhibit symptoms such as muscle weakness and heart failure. Here, we investigated the characteristics and representativeness of female DMD carrier (DMD-XKOXWT) pigs as a suitable disease model.

Methods

In vitro fertilization using sperm from a DMD-XKOY↔XWTXWT chimeric boar yielded DMD-XKOXWT females, which were used to generate F2 and F3 progeny, including DMD-XKOXWT females. F1-F3 piglets were genotyped and subjected to biochemical analysis for blood creatine kinase (CK), aspartate aminotransferase, and lactate dehydrogenase. Skeletal muscle and myocardial tissue were analyzed for the expression of dystrophin and utrophin, as well as for lymphocyte and macrophage infiltration.

Results

DMD-XKOXWT pigs exhibited various characteristics common to human DMD carrier patients, namely, asymptomatic hyperCKemia, dystrophin expression patterns in the skeletal and cardiac muscles, histopathological features of skeletal muscle degeneration, myocardial lesions in adulthood, and sporadic death. Pathological abnormalities observed in the skeletal muscles in DMD-XKOXWT pigs point to a frequent incidence of pathological abnormalities in the musculoskeletal tissues of latent DMD carriers. Our findings suggest a higher risk of myocardial abnormalities in DMD carrier women than previously believed.

Conclusions

We demonstrated that DMD-XKOXWT pigs could serve as a suitable large animal model for understanding the pathogenic mechanism in DMD carriers and developing therapies for female DMD carriers.

Interleukin 4 improved adipose-derived stem cells engraftment via interacting with fibro/adipogenic progenitors in dystrophic mice

Adipose-derived stem cells (ADSC) therapy shows promise as an effective treatment for dystrophinopathy. Fibro-/adipogenic progenitors (FAPs) play an essential role in the myogenesis of muscle satellite cells and contribute to muscle fibrosis and adipocyte infiltration. The interleukin 4 (IL-4) pathway acts as a switch that regulates the functions of FAPs. The interaction between FAPs and engrafted cells remains unclear. In this study, we used a co-culture system to investigate possible crosstalk between the FAPs of dystrophic mice and ADSC overexpressing IL4 (IL4-ADSC) and control ADSC. Systemic transplantation of IL4-ADSC and control ADSC in dystrophic mice was conducted for 16 weeks, after which motor function and molecular improvements were evaluated. Overexpression of IL4 in ADSC significantly promoted myogenesis in vitro, increasing the expression of Pax7, Myogenin, and MyHC. Co-culture indicated that although myoblasts derived from control ADSC promoted adipogenic and fibrogenic differentiation of FAPs, FAPs did not significantly affect myogenesis of ADSC-derived myoblasts. However, overexpression of IL4 in ADSC inhibited their myotube-dependent promotion of FAPs differentiation on the one hand and promoted FAPs to enhance myogenesis on the other. Dystrophic mice administered with IL4-ADSC-derived myoblasts displayed significantly better motor ability, more engrafted cells showing dystrophin expression, and less muscle fibrosis, intramuscular adipocytes, and macrophage infiltration than mice administered control-ADSC-derived myoblasts. In conclusion, IL4 activation enhanced the therapeutic potential of ADSC transplantation in dystrophic mice, possibly by improving the myogenesis of IL4-ADSC and altering the crosstalk between engrafted stem cells and resident FAPs.

Mitochondrial Calcium Uptake 1 (MICU1) Gene-Related Myopathy with Extrapyramidal Signs: A Clinico-Radiological Case Report from India

Myopathy with extrapyramidal signs (MPXPS) is a rarely reported entity worldwide, manifesting as a muscular dystrophy with movement disorders. It results from mutations in the mitochondrial calcium uptake 1 (MICU1) gene. We hereby describe a 17-year-old boy who presented with proximal myopathy, calf muscle hypertrophy, and skeletal deformities along with choreiform movements of his upper extremities. Muscle MRI revealed a distinctively early involvement of adductors with sparing of antero-lateral compartment of thigh. This report expands the clinico-radiological presentation and to the best of our knowledge, is the first report of MICU-related MPXPS from India.

Synaptic alterations as a neurodevelopmental trait of Duchenne muscular dystrophy

Dystrophinopaties, e.g., Duchenne muscular dystrophy (DMD), Becker muscular dystrophy and X-linked dilated cardiomyopathy are inherited neuromuscular diseases, characterized by progressive muscular degeneration, which however associate with a significant impact on general system physiology. The more severe is the pathology and its diversified manifestations, the heavier are its effects on organs, systems, and tissues other than muscles (skeletal, cardiac and smooth muscles). All dystrophinopaties are characterized by mutations in a single gene located on the X chromosome encoding dystrophin (Dp427) and its shorter isoforms, but DMD is the most devasting: muscular degenerations manifests within the first 4 years of life, progressively affecting motility and other muscular functions, and leads to a fatal outcome between the 20s and 40s. To date, after years of studies on both DMD patients and animal models of the disease, it has been clearly demonstrated that a significant percentage of DMD patients are also afflicted by cognitive, neurological, and autonomic disorders, of varying degree of severity. The anatomical correlates underlying neural functional damages are established during embryonic development and the early stages of postnatal life, when brain circuits, sensory and motor connections are still maturing. The impact of the absence of Dp427 on the development, differentiation, and consolidation of specific cerebral circuits (hippocampus, cerebellum, prefrontal cortex, amygdala) is significant, and amplified by the frequent lack of one or more of its lower molecular mass isoforms. The most relevant aspect, which characterizes DMD-associated neurological disorders, is based on morpho-functional alterations of selective synaptic connections within the affected brain areas. This pathological feature correlates neurological conditions of DMD to other severe neurological disorders, such as schizophrenia, epilepsy and autistic spectrum disorders, among others. This review discusses the organization and the role of the dystrophin-dystroglycan complex in muscles and neurons, focusing on the neurological aspect of DMD and on the most relevant morphological and functional synaptic alterations, in both central and autonomic nervous systems, described in the pathology and its animal models.

Intellectual disability in paediatric patients with genetic muscle diseases

The differential diagnosis of genetic muscle disease has become increasingly difficult due to the rapid progress in genetic medicine in recent years. Where classifications based on the clinical picture were attributed to one gene only a few years ago, today we know that a variety of clinical presentations can result from the same mutation and, conversely, various genes are associated with a similar phenotype. A significant consideration in assessing a patient with muscle weakness is the presence or absence of intellectual disability, thus narrowing the differential diagnostic approach in any child with an as yet undiagnosed muscle disease. Intellectual disability in neuromuscular diseases is often associated with behavioural disorders and may be correlated with abnormal brain imaging. Conversely, brain involvement can sometimes be seen without intellectual disability, but may be associated with an epilepsy risk and is helpful for the differential diagnosis. This review focuses on the three most common causes of paediatric muscle diseases with intellectual disability, dystrophinopathies, myotonic dystrophy type 1 and dystroglycanopathies. It also summarises differential diagnostic considerations when assessing a child with a genetic muscle disease and intellectual disability. The recent scientific literature on this topic is reviewed, the frequency of intellectual disability assessed, and specific clinical features are described. Where available, data on disease onset, progression and serum creatine kinase levels are presented and the pattern of muscle involvement described in an algorithm. Central nervous involvement and brain imaging analysis was reviewed and included.

Serum creatinine as a biomarker for dystrophinopathy: a cross-sectional and longitudinal study

Background

Dystrophinopathy, a common neuromuscular disorder, includes Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). Many researches are currently ongoing to develop curative approaches, which results in an urgent need for biomarkers of disease progression and treatment response. This study investigated whether the serum creatinine (SCRN) level can be used as a biomarker of disease progression in dystrophinopathy.

Methods

We enrolled 377 male patients with dystrophinopathy and 520 male non-dystrophinopathy controls in a cross-sectional study. From this cohort, 113 follow-up patients were enrolled in a longitudinal study. Patients’ demographic information, motor function, muscle fatty infiltration, and muscle dystrophin levels were evaluated. We investigated correlations between these parameters and SCRN levels, and determined changes in SCRN levels with maturation and with motor function changes.

Results

Our results showed SCRN levels correlated with motor function (FDR < 0.001) and timed test results (FDR between < 0.001–0.012), as well as with muscle fatty infiltration (FDR < 0.001) and dystrophin levels (FDR = 0.015 and 0.001). SCRN levels increased with maturation in control individuals; it slowly increased with maturation in patients with BMD but decreased generally with maturation in patients with DMD. The longitudinal study further demonstrated that SCRN levels were associated with motor function.

Conclusions

These findings indicated that the SCRN level is a promising biomarker for assessing disease progression in dystrophinopathy and could be used as a potential outcome measure in clinical trials.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02382-7.

Vitamin D Level Stability in Dystrophinopathy Patients on Vitamin D Supplementation

BACKGROUND

Expert guidelines recommend annual monitoring of 25-hydroxyvitamin D (25-OHD) and maintaining 25-OHD ≥30 ng/ml in patients with dystrophinopathies.

OBJECTIVE

We hypothesized that 25-OHD remains stable and requires less frequent monitoring in patients taking stable maintenance doses of vitamin D.

METHODS

We performed a retrospective cohort study, using the electronic health record to identify 26 patients with dystrophinopathies with a baseline 25-OHD ≥30 ng/mL and at least one additional 25-OHD measurement. These patients had received a stable dose of vitamin D for ≥3 months prior to their baseline 25-OHD measurement and throughout follow-up. The main outcome measured was the mean duration time the subjects spent with a 25-OHD ≥30 ng/mL.

RESULTS

Only 19% of patients dropped their 25-OHD to < 30 ng/ml, with a mean time to drop of 33 months and a median nadir 25-OHD of 28 ng/mL.

CONCLUSIONS

These results suggest that measurement of 25-OHD every 2-2.5 years may be sufficient in patients with a baseline 25-OHD ≥30 ng/mL and who are on a stable maintenance dose of vitamin D. Other patients may require more frequent assessments.

CCR2 improves homing and engraftment of adipose-derived stem cells in dystrophic mice

Background

Dystrophinopathy, a common neuromuscular disorder caused by the absence of dystrophin, currently lacks effective treatments. Systemic transplantation of adipose-derived stem cells (ADSCs) is a promising treatment approach, but its low efficacy remains a challenge. Chemokine system-mediated stem cell homing plays a critical role in systemic transplantation. Here, we investigated whether overexpression of a specific chemokine receptor could improve muscle homing and therapeutic effects of ADSC systemic transplantation in dystrophic mice.

Methods

We analysed multiple microarray datasets from the Gene Expression Omnibus to identify a candidate chemokine receptor and then evaluated the protein expression of target ligands in different tissues and organs of dystrophic mice. The candidate chemokine receptor was overexpressed using the lentiviral system in mouse ADSCs, which were used for systemic transplantation into the dystrophic mice, followed by evaluation of motor function, stem cell muscle homing, dystrophin expression, and muscle pathology.

Results

Chemokine-profile analysis identified C–C chemokine receptor (CCR)2 as the potential target for improving ADSC homing. We found that the levels of its ligands C–C chemokine ligand (CCL)2 and CCL7 were higher in muscles than in other tissues and organs of dystrophic mice. Additionally, CCR2 overexpression improved ADSC migration ability and maintained their multilineage-differentiation potentials. Compared with control ADSCs, transplantation of those overexpressing CCR2 displayed better muscle homing and further improved motor function, dystrophin expression, and muscle pathology in dystrophic mice.

Conclusions

These results demonstrated that CCR2 improved ADSC muscle homing and therapeutic effects following systemic transplantation in dystrophic mice.

Molecular diagnosis of dystrophinopathies in Morocco and report of six novel mutations

Dystrophinopathies are the most common genetic neuromuscular disorders during childhood, with an X-linked recessive inheritance pattern. Because of clinical and genetic heterogeneity of dystrophinopathies, genetic testing of dystrophin gene at Xp21.2 is constantly evolving. Multiplex Polymerase Chain Reaction (MPCR) is used in the first line to detect common exon deletions of dystrophin gene (accounting for 65% of mutations), followed by the Multiplex Ligation-dependent Probe Amplification (MLPA) technique to reveal deletions of exons outside the usual hotspot and duplications in male and female carriers. (MLPA adds another 10-15% positive cases to MPCR). Recently, Next Generation Sequencing allows to screen for rare large and point mutations. We report here, molecular analysis results of dystrophin gene during 27 years in a large Moroccan cohort of 356 patients, using the multiplex polymerase chain reaction (MPCR) to screen for hot-spot exon deletions. First applications of whole dystrophin gene sequencing in our lab lead to the identification of six novel mutations.

Proteomic and cell biological profiling of the renal phenotype of the mdx-4cv mouse model of Duchenne muscular dystrophy

The X-linked inherited muscle wasting disease Duchenne muscular dystrophy, which is caused by primary abnormalities in the membrane cytoskeletal protein dystrophin, is a multi-system disorder. Highly progressive forms of dystrophinopathy are associated with a complex secondary pathophysiology, including renal dysfunction. It was therefore of interest to carry out a systematic survey of potential proteome-wide changes in the kidney of the established mdx-4cv mouse model of dystrophinopathy. Of 5878 mass spectrometrically identified kidney proteins, 82 versus 142 proteins were shown to be decreased or increased, respectively, in association with muscular dystrophy. The most decreased versus increased protein species are the ACSM3 isoform of mitochondrial acyl-coenzyme A synthetase and the FABP1 isoform of fatty acid binding protein, respectively. Both proteomic findings were verified by immunofluorescence microscopy and immunoblot analysis. Interestingly, haematoxylin/eosin staining indicated diffuse whitish deposits in the mdx-4cv kidney, and an increased intensity of Sudan Black labelling of kidney cells revealed ectopic fat deposition. Although the proteomic results and cell biological findings do not demonstrate a direct functional link between increased FABP1 and fat accumulation, the results suggest that the up-regulation of FABP1 may be related to abnormal fat metabolism. This makes FABP1 potentially a novel pathobiochemical indicator for studying kidney abnormalities in the mdx-4cv model of dystrophinopathy.

Dystrophin R16/17 protein therapy restores sarcolemmal nNOS in trans and improves muscle perfusion and function

Background

Delocalization of neuronal nitric oxide synthase (nNOS) from the sarcolemma leads to functional muscle ischemia. This contributes to the pathogenesis in cachexia, aging and muscular dystrophy. Mutations in the gene encoding dystrophin result in Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). In many BMD patients and DMD patients that have been converted to BMD by gene therapy, sarcolemmal nNOS is missing due to the lack of dystrophin nNOS-binding domain.

Methods

Dystrophin spectrin-like repeats 16 and 17 (R16/17) is the sarcolemmal nNOS localization domain. Here we explored whether R16/17 protein therapy can restore nNOS to the sarcolemma and prevent functional ischemia in transgenic mice which expressed an R16/17-deleted human micro-dystrophin gene in the dystrophic muscle. The palmitoylated R16/17.GFP fusion protein was conjugated to various cell-penetrating peptides and produced in the baculovirus-insect cell system. The best fusion protein was delivered to the transgenic mice and functional muscle ischemia was quantified.

Results

Among five candidate cell-penetrating peptides, the mutant HIV trans-acting activator of transcription (TAT) protein transduction domain (mTAT) was the best in transferring the R16/17.GFP protein to the muscle. Systemic delivery of the mTAT.R16/17.GFP protein to micro-dystrophin transgenic mice successfully restored sarcolemmal nNOS without inducing T cell infiltration. More importantly, R16/17 protein therapy effectively prevented treadmill challenge-induced force loss and improved muscle perfusion during contraction.

Conclusions

Our results suggest that R16/17 protein delivery is a highly promising therapy for muscle diseases involving sarcolemmal nNOS delocalizaton.

Electronic supplementary material

The online version of this article (10.1186/s10020-019-0101-6) contains supplementary material, which is available to authorized users.

Proteomic profiling of the mouse diaphragm and refined mass spectrometric analysis of the dystrophic phenotype

The diaphragm is a crucial muscle involved in active inspiration and whole body homeostasis. Previous biochemical, immunochemical and cell biological investigations have established the distribution and fibre type-specific expression of key diaphragm proteins. Building on these findings, it was of interest to establish the entire experimentally assessable diaphragm proteome and verify the presence of specific protein isoforms within this specialized subtype of skeletal muscle. A highly sensitive Orbitrap Fusion Tribrid mass spectrometer was used for the systematic identification of the mouse diaphragm-associated protein population. Proteomics established 2925 proteins by high confidence peptide identification. Bioinformatics was used to determine the distribution of the main protein classes, biological processes and subcellular localization within the diaphragm proteome. Following the establishment of the respiratory muscle proteome with special emphasis on protein isoform expression in the contractile apparatus, the extra-sarcomeric cytoskeleton, the extracellular matrix and the excitation-contraction coupling apparatus, the mass spectrometric analysis of the diaphragm was extended to the refined identification of proteome-wide changes in X-linked muscular dystrophy. The comparative mass spectrometric profiling of the dystrophin-deficient diaphragm from the mdx-4cv mouse model of Duchenne muscular dystrophy identified 289 decreased and 468 increased protein species. Bioinformatics was employed to analyse the clustering of changes in protein classes and potential alterations in interaction patterns of proteins involved in metabolism, the contractile apparatus, proteostasis and the extracellular matrix. The detailed pathoproteomic profiling of the mdx-4cv diaphragm suggests highly complex alterations in a variety of crucial cellular processes due to deficiency in the membrane cytoskeletal protein dystrophin.

Proteomic profiling of liver tissue from the mdx-4cv mouse model of Duchenne muscular dystrophy

Background

Duchenne muscular dystrophy is a highly complex multi-system disease caused by primary abnormalities in the membrane cytoskeletal protein dystrophin. Besides progressive skeletal muscle degeneration, this neuromuscular disorder is also associated with pathophysiological perturbations in many other organs including the liver. To determine potential proteome-wide alterations in liver tissue, we have used a comparative and mass spectrometry-based approach to study the dystrophic mdx-4cv mouse model of dystrophinopathy.

Methods

The comparative proteomic profiling of mdx-4cv versus wild type liver extracts was carried out with an Orbitrap Fusion Tribrid mass spectrometer. The distribution of identified liver proteins within protein families and potential protein interaction patterns were analysed by systems bioinformatics. Key findings on fatty acid binding proteins were confirmed by immunoblot analysis and immunofluorescence microscopy.

Results

The proteomic analysis revealed changes in a variety of protein families, affecting especially fatty acid, carbohydrate and amino acid metabolism, biotransformation, the cellular stress response and ion handling in the mdx-4cv liver. Drastically increased protein species were identified as fatty acid binding protein FABP5, ferritin and calumenin. Decreased liver proteins included phosphoglycerate kinase, apolipoprotein and perilipin. The drastic change in FABP5 was independently verified by immunoblotting and immunofluorescence microscopy.

Conclusions

The proteomic results presented here indicate that the intricate and multifaceted pathogenesis of the mdx-4cv model of dystrophinopathy is associated with secondary alterations in the liver affecting especially fatty acid transportation. Since FABP5 levels were also shown to be elevated in serum from dystrophic mice, this protein might be a useful indicator for monitoring liver changes in X-linked muscular dystrophy.

Chemical crosslinking analysis of β-dystroglycan in dystrophin-deficient skeletal muscle

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, as well as the caveolae-associated protein cavin-1, 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.

Characterization of Australian Labradoodle dystrophinopathy

In humans, dystrophin mutations cause the X-linked recessive disorder known as Duchenne muscular dystrophy (DMD). These mutations result in skeletal and cardiac muscle damage with mortality increasingly associated with cardiomyopathy. We have identified a novel dystrophin mutation in exon 21 in a line of Australian Labradoodles; affected dogs develop progressive clinical signs including poor weight gain and weight loss, gait abnormalities, exercise intolerance, skeletal muscle atrophy, macroglossa, ptyalism, dysphagia, kyphosis, and a plantigrade stance. Echocardiographic abnormalities include hyperechoic foci in the left ventricular papillary muscles, septal hypokinesis, and decreased left ventricular systolic and diastolic volume and internal diameter. Holter recordings found a Mobitz type II second-degree atrioventricular (AV) block in one affected dog. Analysis of phosphocreatine-to-ATP ratios (PCr/ATP) (obtained via cardiac magnetic resonance imaging and spectroscopy evaluation), found no statistically significant difference in the mean PCr/ATP between groups. Histopathologic skeletal muscle changes included fibrofatty infiltration, myocyte degeneration, necrosis, and regeneration, lymphohistiocytic inflammation, and mineralization; cardiac changes were limited to a focal area of mineralization adjacent to the sinoatrial node in the dog with a second-degree AV block. Due to rapidly progressive clinical signs, a severe phenotype, and potential for cardiac involvement, Australian Labradoodle dystrophinopathy may be a useful model to further study DMD pathogenesis.

Proteomic identification of elevated saliva kallikrein levels in the mdx-4cv mouse model of Duchenne muscular dystrophy

Dystrophinopathies are multi-system disorders that affect the skeletal musculature, the cardio-respiratory system and the central nervous system. The systematic screening of suitable biofluids for released or altered proteins promises new insights into the highly complex pathophysiology of X-linked muscular dystrophy. However, standard detection approaches using antibody-based assays often fail to reproducibly detect low-abundance protein isoforms in dilute biological fluids. In contrast, mass spectrometric screening approaches enable the proteome-wide identification of minor protein changes in biofluids. This report describes the findings from the comparative proteomic analysis of whole saliva samples from wild type versus the established mdx-4cv mouse model of highly progressive muscular dystrophy, focusing on the kallikrein protein family. Kallikrein-1 (Klk1) and 13 Klk1-related peptidases were identified in saliva and serum from normal mice. Comparative proteomics revealed elevated saliva levels of the Klk1-related peptidases Klk1-b1, Klk1-b5 and Klk-b22, as well as an increased Klk-1 concentration, which agrees with higher Klk-1 levels in serum from mdx-4cv mice. This indicates altered cellular signaling, extracellular matrix remodeling and an altered immune response in the mdx-4cv mouse, and establishes liquid biopsy procedures as suitable bioanalytical tools for the systematic survey of complex pathobiochemical changes in animal models of muscular dystrophy.

Comparative gel-based proteomic analysis of chemically crosslinked complexes in dystrophic skeletal muscle

Duchenne muscular dystrophy is a highly progressive muscle wasting disease with a complex pathophysiology that is based on primary abnormalities in the dystrophin gene. In order to study potential changes in the oligomerization of high-molecular-mass protein complexes in dystrophic skeletal muscle, chemical crosslinking was combined with mass spectrometric analysis. The biochemical stabilization of protein interactions was carried out with the homo-bifunctional and amine-reactive agent bis[sulfosuccinimidyl]suberate, followed by protein shift analysis in one-dimensional gels. The proteomic approach identified 11 and 15 protein species in wild type versus dystrophic microsomal fractions, respectively, as well as eight common proteins, with an electrophoretic mobility shift to very high molecular mass following chemical crosslinking. In dystrophin-deficient preparations, several protein species with an increased tendency of oligomerisation were identified as components of the sarcolemma and its associated intra- and extracellular structures, as well as mitochondria. This included the sarcolemmal proteins myoferlin and caveolin, the cytoskeletal components vimentin and tubulin, extracellular collagen alpha-1(XII) and the mitochondrial trifunctional enzyme and oxoglutarate dehydrogenase. These changes are probably related to structural and metabolic adaptations, especially cellular repair processes, which agrees with the increased oligomerisation of myosin-3, myosin-9 and actin, and their role in cellular regeneration and structural adjustments in dystrophinopathy.

Social involvement issues in patients with Becker muscular dystrophy: A questionnaire survey of subjects from a patient registry

BACKGROUND

Little is known about the relationship between Becker Muscular Dystrophy (BMD) and developmental problems, school life, employment, and mental problems. We aimed to clarify whether BMD is a risk factor for developmental disorders, problematic behavior, psychiatric diseases, and other social difficulties in school life and employment.

METHODS

Adults with genetically or immunohistochemically confirmed BMD from the Registry of Muscular Dystrophy in Japan (REMUDY) were asked to complete a questionnaire regarding patient history, school life, employment, and mental problems.

RESULTS

In total, 125 (68.3%) of 183 participants with BMD (median age, 37.2 years) completed the questionnaire. Of these, ten had developmental disorders (mental retardation, autism, and speech disturbance). Fifty-eight (44%) experienced bullying in school, and 39 felt the reason for bullying was physical handicap. Sixteen participants experienced problematic behavior such as cutting class, domestic violence, violent incidents, suicide attempts, or self-mutilation. Employment histories were noted by 92 (73%), of whom 15 could not continue to work due to physical handicaps. Fifteen participants had psychiatric disorders, with 5, 3 and 1 having neurosis, depression, and bipolar disorder, respectively. The other 6 participants with psychiatric disorders did not specify their diagnoses. Patients carrying a Dp140 expression change had significantly more incidences of developmental disorders, but not bullying, problematic behavior, workplace difficulties, or psychiatric disorders.

CONCLUSIONS

Patients with BMD risk bullying and workplace difficulties, as well as developing psychiatric disorders. Parents, teachers, and supporters should be mindful of the daily environment of BMD patients and provide support to help them cope with stress.

Proteomic Profiling of the Dystrophin-Deficient Brain

Duchenne muscular dystrophy is a highly progressive neuromuscular disorder caused by primary abnormalities in the Dmd gene encoding the membrane cytoskeletal protein dystrophin. Dystrophinopathies are multi-systems disorders that are characterized by severe skeletal muscle wasting, with loss of independent ambulation in the early teenage years, followed by cardio-respiratory complications and premature death. Nonprogressive cognitive impairments are estimated to affect approximately one-third of dystrophic children. To identify the molecular mechanisms behind the impaired brain function in dystrophinopathy, liquid chromatography-based mass spectrometry offers an unbiased and technology-driven approach. In this chapter, we give a detailed description of a label-free mass spectrometric method to investigate proteome-wide changes in the dystrophin-deficient brain from a genetic mouse model of Duchenne muscular dystrophy.

Clinical Manifestations and Overall Management Strategies for Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder that causes progressive weakness and wasting of skeletal muscular and myocardium in boys due to mutation of dystrophin. The structural integrity of each individual skeletal and cardiac myocyte is significantly compromised upon physical stress due to the absence of dystrophin. The progressive destruction of systemic musculature and myocardium causes affected patients to develop multiple organ disabilities, including loss of ambulation, physical immobility, neuromuscular scoliosis, joint contracture, restrictive lung disease, obstructive sleep apnea, and cardiomyopathy. There are some central nervous system-related medical problems, as dystrophin is also expressed in the neuronal tissues. Although principal management is to mainly delay the pathological process, an enhanced understanding of underlying pathological processes has significantly improved quality of life and longevity for DMD patients. Future research in novel molecular approach is warranted to answer unanswered questions.

A rare subclinical or mild type of Becker muscular dystrophy caused by a single exon 48 deletion of the dystrophin gene

In the material of 227 families with Becker muscular dystrophy (BMD), we found nine non-consanguineous families with 17 male individuals carrying a rare mutation—a single exon 48 deletion of the dystrophin gene—who were affected with a very mild or subclinical form of BMD. They were usually detected thanks to accidental findings of elevated serum creatine phosphokinase (sCPK). A thorough clinical analysis of the carriers, both children (12) and adults (5), revealed in some of them muscle hypotonia (10/17) and/or very mild muscle weakness (9/17), as well as decreased tendon reflexes (6/17). Adults, apart from very mild muscle weakness and calf hypertrophy in some, had no significant abnormalities on neurological assessments and had good exercise tolerance. Parents of the children carriers of the exon 48 deletion are usually unaware of their children being affected, and possibly at risk of developing life-threatening cardiomyopathy. The same concerns the adult male carriers. Therefore, the authors postulate undertaking preventive measures such as cascade screening of the relatives of the probands. Newborn screening programmes of Duchenne muscular dystrophy (DMD)/BMD based on sCPK marked increase may be considered.

Immunohistochemistry of sarcolemmal membrane-associated proteins in formalin-fixed and paraffin-embedded skeletal muscle tissue: a promising tool for the diagnostic evaluation of common muscular dystrophies

BACKGROUND

The analysis of fresh frozen muscle specimens is standard following routine muscle biopsy, but this service is not widely available in countries with limited medical facilities, such as Thailand. Nevertheless, immunohistochemistry (IHC) analysis is essential for the diagnosis of patients with a strong clinical suspicion of muscular dystrophy, in the absence of mutations detected by molecular genetics. As the successful labelling of sarcolemmal membrane-associated proteins in formalin-fixed and paraffin-embedded (FFPE) muscle sections using IHC staining has rarely been described, this study aimed to develop a reproducible IHC method for such an analysis.

METHODS

Thirteen cases were studied from the files of the Department of Pathology, Mahidol University. Diagnoses included three Duchenne muscular dystrophy (DMD), one Becker muscular dystrophy (BMD), one dysferlinopathy, and several not-specified muscular dystrophies. IHC was performed on FFPE sections at different thicknesses (3 μm, 5 μm, and 8 μm) using the heat-mediated antigen retrieval method with citrate/EDTA buffer, followed by an overnight incubation with primary antibodies at room temperature. Antibodies against spectrin, dystrophin (rod domain, C-terminus, and N-terminus), dysferlin, sarcoglycans (α, β, and γ), and β-dystroglycan were used. Frozen sections were tested in parallel for comparative analysis.

RESULTS

Antibodies labelling spectrin, dystrophin (rod domain and C-terminus), dysferlin, sarcoglycans (α, β, and γ), and β-dystroglycan clearly exhibited sarcolemmal staining in FFPE sections. However, staining of FFPE sections using the antibody directed against the N-terminus of dystrophin was unsuccessful. The absence of labeling for dystrophins and dysferlin in FFPE sections was documented in all three DMD patients and the dysferlinopathy patient. The BMD diagnosis could not be made using IHC in FFPE sections alone because of a lack of staining for the dystrophin N-terminus, indicating a limitation of this method.

CONCLUSIONS

We developed a reliable and reproducible IHC technique using FFPE muscle. This could become a valuable tool for the diagnosis of some muscular dystrophies, dystrophinopathies, sarcoglycanopathies (LGMD2D, LGMD2E, and LGMD2C), and dysferlinopathy, especially in situations where the analysis of fresh frozen muscle samples is not routinely available.

Perceived quality of life among caregivers of children with a childhood-onset dystrophinopathy: a double ABCX model of caregiver stressors and perceived resources

Background

Duchenne and Becker muscular dystrophies, collectively referred to as dystrophinopathies, are recessive X-linked disorders characterized by progressive muscle weakness and ultimately cardiac and respiratory failure. Immediate family members are often primary caregivers of individuals with a dystrophinopathy.

Methods

We explored the impact of this role by inviting primary caregivers (n = 209) of males diagnosed with childhood-onset dystrophinopathy who were identified by the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet) to complete a mailed questionnaire measuring perceived social support and stress, spirituality, and family quality of life (FQoL). Bivariate and multivariate analyses examined associations between study variables using the Double ABCX model as an analytic framework.

Results

Higher stressor pile-up was associated with lower perceived social support (r = -0.29, p < .001), availability of supportive family (r = -0.30, p < .001) or non-family (r = -0.19, p < .01) relationships, and higher perceived stress (r = 0.33, p < .001); but not with spirituality (r = -0.14, p > 0.05). FQoL was positively associated with all support measures (correlations ranged from: 0.25 to 0.58, p-values 0.01–0.001) and negatively associated with perceived stress and control (r = -0.49, p < .001). The association between stressor pile-up and FQoL was completely mediated through global perceived social support, supportive family relationships, and perceived stress and control; supportive non-family relationships did not remain statistically significant after controlling for other mediators.

Conclusions

Findings suggest caregiver adaptation to a dystrophinopathy diagnosis can be optimized by increased perceived control, supporting family resources, and creation of a healthy family identity. Our findings will help identify areas for family intervention and guide clinicians in identifying resources that minimize stress and maximize family adaptation.

Becker muscular dystrophy due to an intronic splicing mutation inducing a dual dystrophin transcript

We describe a 29-year-old patient who complained of left thigh muscle weakness since he was 23 and of moderate proximal weakness of both lower limbs with difficulty in climbing stairs and running since he was 27. Mild weakness of iliopsoas and quadriceps muscles and muscle atrophy of both the distal forearm and thigh were observed upon clinical examination. He harboured a novel c.1150-3C>G substitution in the DMD gene, affecting the intron 10 acceptor splice site and causing exon 11 skipping and an out-of-frame transcript. However, protein of normal molecular weight but in reduced amounts was observed on Western Blot analysis. Reverse transcription analysis on muscle RNA showed production, via alternative splicing, of a transcript missing exon 11 as well as a low abundant full-length transcript which is enough to avoid the severe Duchenne phenotype. Our study showed that a reduced amount of full length dystrophin leads to a mild form of Becker muscular dystrophy. These results confirm earlier findings that low amounts of dystrophin can be associated with a milder phenotype, which is promising for therapies aiming at dystrophin restoration.

Muscle redox disturbances and oxidative stress as pathomechanisms and therapeutic targets in early-onset myopathies

Because of their contractile activity and their high oxygen consumption and metabolic rate, skeletal muscles continually produce moderate levels of reactive oxygen and nitrogen species (ROS/RNS), which increase during exercise and are buffered by multiple antioxidant systems to maintain redox homeostasis. Imbalance between ROS/RNS production and elimination results in oxidative stress (OxS), which has been implicated in ageing and in numerous human diseases, including cancer, diabetes or age-related muscle loss (sarcopenia). The study of redox homeostasis in muscle was hindered by its lability, by the many factors influencing technical OxS measures and by ROS/RNS important roles in signaling pathways and adaptative responses to muscle contraction and effort, which make it difficult to define a threshold between physiological signaling and pathological conditions. In the last years, new tools have been developed that facilitate the study of these key mechanisms, and deregulation of redox homeostasis has emerged as a key pathogenic mechanism and potential therapeutic target in muscle conditions. This is in particular the case for early-onset myopathies, genetic muscle diseases which present from birth or early childhood with muscle weakness interfering with ambulation and often with cardiac or respiratory failure leading to premature death. Inherited defects of the reductase selenoprotein N in SEPN1-related myopathy leads to chronic OxS of monogenic origin as a primary disease pathomechanism. In myopathies associated with mutations of the genes encoding the calcium channel RyR1, the extracellular matrix protein collagen VI or the sarcolemmal protein dystrophin (Duchenne Muscular Dystrophy), OxS has been identified as a relevant secondary pathophysiological mechanism. OxS being drug-targetable, it represents an interesting therapeutic target for these incurable conditions, and following preclinical correction of the cell or animal model phenotype, the first clinical trials with the antioxidants N-acetylcysteine (SEPN1- and RYR1-related myopathies) or epigallocatechin-gallate (DMD) have been launched recently. In this review, we provide an overview of the mechanisms involved in redox regulation in skeletal muscle, the technical tools available to measure redox homeostasis in muscle cells, the bases of OxS as a primary or secondary pathomechanism in early-onset myopathies and the innovative clinical trials with antioxidants which are currently in progress for these so-far untreatable infantile muscle diseases. Progress in our knowledge of redox homeostasis defects in these rare muscle conditions may be useful as a model paradigm to understand and treat other conditions in which OxS is involved, including prevalent conditions with major socioeconomic impact such as insulin resistance, cachexia, obesity, sarcopenia or ageing.

The 6-minute walk test, motor function measure and quantitative thigh muscle MRI in Becker muscular dystrophy: A cross-sectional study

Becker muscular dystrophy (BMD) has an incidence of 1 in 16 000 male births. This cross-sectional study investigated the relation between validated functional scores and quantitative MRI (qMRI) of thigh muscles in 20 ambulatory BMD patients, aged 18.3-60 years (mean 31.2; SD 11.1). Clinical assessments included the motor function measure (MFM) and its subscales, as well as timed function tests such as the 6-minute walk test (6MWT) and the timed 10-m run/walk test. Quantitative MRI of the thigh muscles included the mean fat fraction (MFF) using a 2-point Dixon (2-PD) technique, and transverse relaxation time (T2) measurements. The mean MFM value was 80.4%, SD 9.44 and the D1 subscore 54.5%, SD 19.9. The median 6MWT was 195m, IQR 160-330.2. The median 10-m run/walk test was 7.4 seconds, IQR 6.1-9.3. The mean fat fraction of the thigh muscles was 55.6%, SD 17.4%, mean T2 relaxation times of all muscles: 69.9 ms, SD 14.4. The flexors had the highest MFF and T2 relaxation times, followed by the extensors and the adductors. MFF and global T2 relaxation times were highly negatively correlated with the MFM total, D1-subscore and 6MWT, and positively correlated with the 10 m run/walk test time (p < 0.01). Age was not correlated with MFF, global T2 relaxation time or clinical assessments. Both MFF and T2 measures in the thigh muscle were well correlated with clinical function in BMD and may serve as a surrogate outcome measure in clinical trials.

The biochemical and mass spectrometric profiling of the dystrophin complexome from skeletal muscle

The development of advanced mass spectrometric methodology has decisively enhanced the analytical capabilities for studies into the composition and dynamics of multi-subunit protein complexes and their associated components. Large-scale complexome profiling is an approach that combines the systematic isolation and enrichment of protein assemblies with sophisticated mass spectrometry-based identification methods. In skeletal muscles, the membrane cytoskeletal protein dystrophin of 427 kDa forms tight interactions with a variety of sarcolemmal, cytosolic and extracellular proteins, which in turn associate with key components of the extracellular matrix and the intracellular cytoskeleton. A major function of this enormous assembly of proteins, including dystroglycans, sarcoglycans, syntrophins, dystrobrevins, sarcospan, laminin and cortical actin, is postulated to stabilize muscle fibres during the physical tensions of continuous excitation-contraction-relaxation cycles. This article reviews the evidence from recent proteomic studies that have focused on the characterization of the dystrophin-glycoprotein complex and its central role in the establishment of the cytoskeleton-sarcolemma-matrisome axis. Proteomic findings suggest a close linkage of the core dystrophin complex with a variety of protein species, including tubulin, vimentin, desmin, annexin, proteoglycans and collagens. Since the almost complete absence of dystrophin is the underlying cause for X-linked muscular dystrophy, a more detailed understanding of the composition, structure and plasticity of the dystrophin complexome may have considerable biomedical implications.

Label-free mass spectrometric analysis reveals complex changes in the brain proteome from the mdx-4cv mouse model of Duchenne muscular dystrophy

BACKGROUND

X-linked muscular dystrophy is a primary disease of the neuromuscular system. Primary abnormalities in the Dmd gene result in the absence of the full-length isoform of the membrane cytoskeletal protein dystrophin. Besides progressive skeletal muscle wasting and cardio-respiratory complications, developmental cognitive deficits and behavioural abnormalities are clinical features of Duchenne muscular dystrophy. In order to better understand the mechanisms that underlie impaired brain functions in Duchenne patients, we have carried out a proteomic analysis of total brain extracts from the mdx-4cv mouse model of dystrophinopathy.

RESULTS

The comparative proteomic profiling of the mdx-4cv brain revealed a significant increase in 39 proteins and a decrease in 7 proteins. Interesting brain tissue-associated proteins with an increased concentration in the mdx-4cv animal model were represented by the glial fibrillary acidic protein GFAP, the neuronal Ca(2+)-binding protein calretinin, annexin AnxA5, vimentin, the neuron-specific enzyme ubiquitin carboxyl-terminal hydrolase isozyme L1, the dendritic spine protein drebrin, the cytomatrix protein bassoon of the nerve terminal active zone, and the synapse-associated protein SAP97. Decreased proteins were identified as the nervous system-specific proteins syntaxin-1B and syntaxin-binding protein 1, as well as the plasma membrane Ca(2+)-transporting ATPase PMCA2 that is mostly found in the brain cortex. The differential expression patterns of GFAP, vimentin, PMCA2 and AnxA5 were confirmed by immunoblotting. Increased GFAP levels were also verified by immunofluorescence microscopy.

CONCLUSIONS

The large number of mass spectrometrically identified proteins with an altered abundance suggests complex changes in the mdx-4cv brain proteome. Increased levels of the glial fibrillary acidic protein, an intermediate filament component that is uniquely associated with astrocytes in the central nervous system, imply neurodegeneration-associated astrogliosis. The up-regulation of annexin and vimentin probably represent compensatory mechanisms involved in membrane repair and cytoskeletal stabilization in the absence of brain dystrophin. Differential alterations in the Ca(2+)-binding protein calretinin and the Ca(2+)-pumping protein PMCA2 suggest altered Ca(2+)-handling mechanisms in the Dp427-deficient brain. In addition, the proteomic findings demonstrated metabolic adaptations and functional changes in the central nervous system from the dystrophic phenotype. Candidate proteins can now be evaluated for their suitability as proteomic biomarkers and their potential in predictive, diagnostic, prognostic and/or therapy-monitoring approaches to treat brain abnormalities in dystrophinopathies.

Pathoproteomic profiling of the skeletal muscle matrisome in dystrophinopathy associated myofibrosis

The gradual accumulation of collagen and associated proteins of the extracellular matrix is a crucial myopathological parameter of many neuromuscular disorders. Progressive tissue damage and fibrosis play a key pathobiochemical role in the dysregulation of contractile functions and often correlates with poor motor outcome in muscular dystrophies. Following a brief introduction into the role of the extracellular matrix in skeletal muscles, we review here the proteomic profiling of myofibrosis and its intrinsic role in X-linked muscular dystrophy. Although Duchenne muscular dystrophy is primarily a disease of the membrane cytoskeleton, one of its most striking histopathological features is a hyperactive connective tissue and tissue scarring. We outline the identification of novel factors involved in the modulation of the extracellular matrix in muscular dystrophy, such as matricellular proteins. The establishment of novel proteomic markers will be helpful in improving the diagnosis, prognosis, and therapy monitoring in relation to fibrotic substitution of contractile tissue. In the future, the prevention of fibrosis will be crucial for providing optimum conditions to apply novel pharmacological treatments, as well as establish cell-based approaches or gene therapeutic interventions. The elimination of secondary abnormalities in the matrisome promises to reduce tissue scarring and the loss of skeletal muscle elasticity.

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.

Dystrophinopathy mimicking metabolic myopathies

Recurrent rhabdomyolysis warrants comprehensive evaluations to search for underlying muscle diseases, including metabolic myopathies, LPIN1-myopathy, RYR1-myopathy, and less commonly muscular dystrophies. The absence of weakness and the normal or minimally elevated creatine kinase levels between attacks are typical of metabolic myopathies, LPIN1-myopathy, and RYR1-myopathy, while the presence of weakness and the highly elevated creatine kinase levels between attacks point toward muscular dystrophies. Here we report a 32-year-old man with a one-year history of recurrent rhabdomyolysis, who had normal strength, slightly elevated baseline creatine kinase level, and normal muscle histopathology. All workups for metabolic myopathies, LPIN1-myopathy and RYR1-myopathy were unrevealing. Next generation sequencing of muscular dystrophy-related genes revealed a hemizygous deletion of exons 17-34 of the dystrophin-encoding gene. Immunohistochemical study revealed absent staining for the rod domain of dystrophin. Dystrophinopathy should be considered in patients with recurrent rhabdomyolysis despite the absence of fixed weakness or highly elevated resting creatine kinase level.

Left ventricular noncompaction cardiomyopathy in Duchenne muscular dystrophy carriers

Duchenne and Becker muscular dystrophies are X-linked hereditary myopathies secondary to a dystrophinopathy resulting in progressive cardiomyopathy and heart failure. The most commonly associated cardiac involvements in these patients are dilated cardiomyopathy and conduction abnormalities; however, recent studies have shown a high prevalence of left ventricular noncompaction cardiomyopathy in patients with Duchenne muscular dystrophy. Furthermore, there is increasing awareness of cardiomyopathy in female heterozygous dystrophinopathy carriers. We report a case series of two dystrophinopathy carriers with the dilated form of left ventricular noncompaction cardiomyopathy, a newly identified association. <Learning objective: Dystrophinopathy carriers can manifest cardiac disease in the form of cardiomyopathy. We present a novel finding of carriers who manifest their cardiomyopathy in the form of left ventricular noncompaction, dilated phenotype. This has been described previously in patients with Duchenne muscular dystrophy.>.

Comparative proteomic analysis of the contractile-protein-depleted fraction from normal versus dystrophic skeletal muscle

In basic and applied myology, gel-based proteomics is routinely used for studying global changes in the protein constellation of contractile fibers during myogenesis, physiological adaptations, neuromuscular degeneration, and the natural aging process. Since the main proteins of the actomyosin apparatus and its auxiliary sarcomeric components often negate weak signals from minor muscle proteins during proteomic investigations, we have here evaluated whether a simple prefractionation step can be employed to eliminate certain aspects of this analytical obstacle. To remove a large portion of highly abundant contractile proteins from skeletal muscle homogenates without the usage of major manipulative steps, differential centrifugation was used to decisively reduce the sample complexity of crude muscle tissue extracts. The resulting protein fraction was separated by two-dimensional gel electrophoresis, and 2D-landmark proteins were identified by mass spectrometry. To evaluate the suitability of the contractile-protein-depleted fraction for comparative proteomics, normal versus dystrophic muscle preparations were examined. The mass spectrometric analysis of differentially expressed proteins, as determined by fluorescence difference in-gel electrophoresis, identified 10 protein species in dystrophic mdx hindlimb muscles. Interesting new biomarker candidates included Hsp70, transferrin, and ferritin, whereby their altered concentration levels in dystrophin-deficient muscle were confirmed by immunoblotting.

Precordial R wave height does not correlate with echocardiographic findings in boys with Duchenne muscular dystrophy

OBJECTIVES

Cardiomyopathy (CM) is an inevitable consequence of Duchenne muscular dystrophy, and electrocardiographic changes, right ventricular hypertrophy in particular, have been proposed to serve as an early marker for CM. To evaluate this concept, we assessed the correlation between R wave height in lead V1 and echocardiographic findings in boys with Duchenne muscular dystrophy.

METHODS

Serial echocardiograms and electrocardiograms (n = 800) were performed during each clinic visit in a cohort of 155 boys with Duchenne muscular dystrophy. Precordial R wave height in lead V1 was measured. Echocardiographic parameters included ejection fraction (EF), shortening fraction, and left ventricular end-diastolic dimension. Data were analyzed using Pearson correlation and linear regression.

RESULTS

Ages ranged from 1.8 to 37.2 years (mean 14.7 ± 5.9 years). Seventy-one patients had CM and 318/800 echocardiograms had an EF < 55%. Older patients tended to have a lower EF, but there was no correlation between age and left ventricular end-diastolic dimension. R wave height in lead V1 correlated poorly with both left ventricular end-diastolic dimension (r = 0.096, P =.0078) and EF (r = 0.096, P =.0088) for the whole cohort as well as those studies demonstrating an EF <55% (left ventricular end-diastolic dimension r = 0.089, P =.12 and EF r = -0.044, P =.94). No individual patient demonstrated significant correlation between R wave height in lead V1 and left ventricular end-diastolic dimension or EF. Left ventricular end-diastolic dimension showed a moderate negative correlation with EF for the whole cohort (r = -0.394, P <.001) as well as those with an EF < 55% (r = -0.376, P <.001).

CONCLUSIONS

The precordial R wave height in V1 correlates poorly with the presence of depressed left ventricular function and is not prognostic for the development of CM. While not predictive for CM, the electrocardiogram remains vital to cardiac screening for boys with Duchenne muscular dystrophy due to risk for other cardiac manifestations such as arrhythmias.