Duchenne muscular dystrophy (DMD) causes progressive muscle weakness and gradually leads to contracture development, both resulting in functional decline. It is not known how passive range of motion (ROM) is associated with upper extremity (UE) function over time within individuals. For clinical care it is important to investigate whether changes in UE-ROM are associated with changes in UE-function to better inform and guide parents/patients for therapy. Boys with DMD aged >5 years were eligible for this prospective, multicenter study. Bilateral passive UE-ROM outcomes: wrist extension (range:-90°;100°), supination (range:-90°;90°), elbow extension (range:+15°;-150°), shoulder flexion (range:0°;180°), and Performance of the Upper Limb (PUL1.2, range:0-74 points) were collected 6-monthly for up to 4 years. ROM-total was computed (ROM-outcomes sum, range:-660°;770°). Changes over time were tested using mixed-linear-models and within-individual association between UE-ROM and UE-function using repeated-measure-correlations. Ninety boys participated. Mean baseline age was 9.5 years (SD:3.7), 58 (64.4%) were ambulant, 78 (86.7%) used steroids. Mean ROM-total was 646° (SD:99.7°) and mean PUL-score 63 points (SD:10.0). ROM-total and PUL-score decreased over time; -50° (p=0.001) and -11 points (p<0.001). Weak correlations were found between PUL and elbow extension (rrm=0.31, p<0.001) and ROM-total (rrm=0.33, p<0.001), but not with other ROM-outcomes (rrm<0.2, p>0.05). Even though UE-ROM and UE-function deteriorate over time there is only a weak within-individual association between both. Loss of strength probably precedes loss of passive UE-ROM but there may be an interplay between UE-ROM, strength and function. Further research is needed to investigate this interplay. It is important to address UE contracture prevention in DMD to prevent secondary problems (e.g., pain, difficulty clothing and positioning etc.) but staying active may also be important to help preserve UE-function.

Sarcoglycanopathies are among the most frequent and severe forms of autosomal recessive forms of limb-girdle muscular dystrophies (LGMDs) with childhood onset. Four subtypes are known: LGMDR3, LGMDR4, LGMDR5 and LGMDR6, which are caused, respectively, by mutations in the SGCA, SGCB, SGCG and SGCD genes. We present the clinical variability of LGMD 2C/R5 among a genetically homogeneous group of 57 patients, belonging to 35 pedigrees. Molecular genetic analysis showed that all 57 patients were homozygous for the C283Y variant. The muscles of the pelvic girdle and the trunk were affected early and were more severely affected, followed by the shoulder girdle. Macroglossia, hypertrophy of the calves, scapular winging and lumbar hyperlordosis were common in the ambulatory phase. A great intra and interfamilial variability in the clinical presentation of LGMD 2C/R5 was observed, despite having the same underlying molecular defect. Females demonstrated a relatively milder clinical course compared to males. Mean creatine phosphokinase (CK) CK levels were 20 times above normal values. Muscle computer tomography (CT) CT or MRIs showed earlier and more severe involvement of the flexor proximal limb muscles in comparison to extensor muscles.

Friedreichʼs ataxia (FA) is caused by a variant of the Frataxin ( FXN ) gene, leading to its downregulation and progressively impaired cardiac and neurological function. Current gold-standard clinical scales use simplistic behavioral assessments, which require 18- to 24-month-long trials to determine if therapies are beneficial. Here we captured full-body movement kinematics from patients with wearable sensors, enabling us to define digital behavioral features based on the data from nine FA patients (six females and three males) and nine age- and sex-matched controls, who performed the 8-m walk (8-MW) test and 9-hole peg test (9 HPT). We used machine learning to combine these features to longitudinally predict the clinical scores of the FA patients, and compared these with two standard clinical assessments, Spinocerebellar Ataxia Functional Index (SCAFI) and Scale for the Assessment and Rating of Ataxia (SARA). The digital behavioral features enabled longitudinal predictions of personal SARA and SCAFI scores 9 months into the future and were 1.7 and 4 times more precise than longitudinal predictions using only SARA and SCAFI scores, respectively. Unlike the two clinical scales, the digital behavioral features accurately predicted FXN gene expression levels for each FA patient in a cross-sectional manner. Our work demonstrates how data-derived wearable biomarkers can track personal disease trajectories and indicates the potential of such biomarkers for substantially reducing the duration or size of clinical trials testing disease-modifying therapies and for enabling behavioral transcriptomics.

Artificial intelligence has the potential to revolutionize healthcare, yet clinical trials in neurological diseases continue to rely on subjective, semiquantitative and motivation-dependent endpoints for drug development. To overcome this limitation, we collected a digital readout of whole-body movement behavior of patients with Duchenne muscular dystrophy (DMD) ( n = 21) and age-matched controls ( n = 17). Movement behavior was assessed while the participant engaged in everyday activities using a 17-sensor bodysuit during three clinical visits over the course of 12 months. We first defined new movement behavioral fingerprints capable of distinguishing DMD from controls. Then, we used machine learning algorithms that combined the behavioral fingerprints to make cross-sectional and longitudinal disease course predictions, which outperformed predictions derived from currently used clinical assessments. Finally, using Bayesian optimization, we constructed a behavioral biomarker, termed the KineDMD ethomic biomarker, which is derived from daily-life behavioral data and whose value progresses with age in an S-shaped sigmoid curve form. The biomarker developed in this study, derived from digital readouts of daily-life movement behavior, can predict disease progression in patients with muscular dystrophy and can potentially track the response to therapy.

Background: Hypertrophic cardiomyopathy (HCM) is a life-threatening inherited heart disease characterized by left ventricular hypertrophy and diastolic dysfunction. The most common cause of HCM is genetic variants in MYBPC3 , encoding cardiac myosin binding protein C (cMyBP-C), a sarcomeric protein with structural and regulatory roles. The majority of MYBPC3 gene variants are truncating leading to protein haploinsufficiency. Hypothesis: Transfer of a functional copy of MYBPC3 to heart muscle deficient in cMyBP-C will lead to sustained improvements in cardiac function. Aims: To determine whether BMN 293 (AAV-hMYBPC3) can restore cMyBP-C levels in the sarcomere and halt and/or reverse disease progression in non-clinical models of genetic HCM due to MYPBC3 deficiency. Methods: BMN 293 is an adeno-associated virus (AAV) vector that encodes wild-type human MYBPC3 under the control of a cardiomyocyte-selective promoter. We transduced human iPSC-derived cardiomyocytes and engineered heart tissues (EHTs) carrying a compound heterozygous truncating MYBPC3 mutation (MYBPC3 -/- ) with BMN 293 and assessed cMyBP-C levels and contractile parameters. We also systemically administered BMN 293 to MYBPC3 -/- mice and assessed cardiac distribution of human cMyBP-C by molecular and histological methods and determined its impact on left ventricular hypertrophy and function by echocardiography and other imaging techniques. Results: BMN 293 transduction of human iPSC MYBPC3 -/- cardiomyocytes and EHTs resulted in high levels of human MYBPC3 mRNA and cMyBP-C protein, correct incorporation of cMyBP-C into the sarcomere, and complete normalization of contractile kinetics. BMN 293 was well tolerated in MYBPC3 -/- mice and resulted in uniform restoration of cMyBP-C expression throughout the heart and significant correction of structural and functional cardiac abnormalities. Conclusions: A single IV infusion of BMN 293 to MYBPC3 -/- mice resulted in early and sustained reduction in left ventricular hypertrophy and durable improvements in diastolic function.

Duchenne muscular dystrophy (DMD) is caused by the lack of dystrophin, but many patients have rare revertant fibers that express dystrophin. The skeletal muscle pathology of DMD patients includes immune cell infiltration and inflammatory cascades. There are several strategies to restore dystrophin in skeletal muscles of patients, including exon skipping and gene therapy. There is some evidence that dystrophin restoration leads to a reduction in immune cells, but dystrophin epitopes expressed in revertant fibers or following genome editing, cell therapy, or microdystrophin delivery after adeno-associated viral gene therapy may elicit T cell production in patients. This may affect the efficacy of the therapeutic intervention, and potentially lead to serious adverse events. To confirm and extend previous studies, we performed annual enzyme- linked immunospot interferon-gamma assays on peripheral blood mononuclear cells from 77 pediatric boys with DMD recruited into a natural history study, 69 of whom (89.6%) were treated with corticosteroids. T cell responses to dystrophin were quantified using a total of 368 peptides spanning the entire dystrophin protein, organized into nine peptide pools. Peptide mapping pools were used to further localize the immune response in one positive patient. Six (7.8%) patients had a T cell-mediated immune response to dystrophin at at least one time point. All patients who had a positive result had been treated with corticosteroids, either prednisolone or prednisone. Our results show that ∼8% of DMD individuals in our cohort have a pre-existing T cell-mediated immune response to dystrophin, despite steroid treatment. Although these responses are relatively low level, this information should be considered a useful immunological baseline before undertaking clinical trials and future DMD studies. We further highlight the importance for a robust, reproducible standard operating procedure for collecting, storing, and shipping samples from multiple centers to minimize the number of inconclusive data.

Two placebo-controlled trials of 52-week duration showed that idebenone consistently reduced respira- tory function decline rate in patients with DMD. Long-term data from the DELPHI-Extension (DELPHI-E) study and SYROS (DELOS patients who transitioned to idebenone under an Expanded Access Program) are now presented. The aim was to assess the consistency of the long-term effect of idebenone. 11 DELPHI-E and 18 SYROS patients with abnormal (<80%) forced vital capacity (as percent predicted, FVC%p) were treated with idebenone for an average of 2.0 and 4.2 years respectively. Annualized FVC%p decline rates were compared to untreated patients from SYROS or matched external controls. Mean (SD) baseline age was 13.6 (2.3) and 13.3 (2.7) years in DELPHI (N=11) and DELOS (N=18), respec- tively, and FVC%p was 47.2% (19.7%) and 58.7% (17.6%). For the first 2-year period, the average annual decline rate was comparable in treated patients (4.5% and 5.4% in DELPHI-E and SYROS) and lower than in untreated SYROS patients and external controls (7.9% untreated and 8.1% in CINRG-DNHS). During years 3–6, the annual decline rate was consistently lower than for matched controls. Treatment with idebenone resulted in a sustained reduction in the rate of decline in respiratory function. laurent.servais@paediatrics.ox.ac.uk

Muscular dystrophies due to heterozygous pathogenic variants in LMNA gene cover a broad spectrum of clinical presentations and severity with an age of onset ranging from the neonatal period to adulthood. The natural history of these conditions is not well defined, particularly in patients with congenital or early onset who arguably present with the highest disease burden. Thus the definition of natural history endpoints along with clinically revelant outcome measures is essential to establishing both clinical care planning and clinical trial readiness for this patient group. We designed a large international cross-sectional retrospective natural history study of patients with genetically proven muscle laminopathy who presented with symptoms before two years of age intending to identify and characterize an optimal clinical trial cohort with pertinent motor, cardiac and respiratory endpoints. Quantitative statistics were used to evaluate associations between LMNA variants and distinct clinical events. The study included 151 patients (median age at symptom onset 0.9 years, range: 0.0-2.0). Age of onset and age of death were significantly lower in patients who never acquired independent ambulation compared to patients who achieved independent ambulation. Most of the patients acquired independent ambulation (n = 101, 66.9%), and subsequently lost this ability (n = 86; 85%). The age of ambulation acquisition (median: 1.2 years, range: 0.8-4.0) and age of ambulation loss (median: 7 years, range: 1.2-38.0) were significantly associated with the age of the first respiratory interventions and the first cardiac symptoms. Respiratory and gastrointestinal interventions occurred during first decade while cardiac interventions occurred later. Genotype-phenotype analysis showed that the most common mutation, p.Arg249Trp (20%), was significantly associated with a more severe disease course. This retrospective natural history study of early onset LMNA-related muscular dystrophy confirms the progressive nature of the disorder, initially involving motor symptoms prior to onset of other symptoms (respiratory, orthopaedic, cardiac and gastrointestinal). The study also identifies subgroups of patients with a range of long-term outcomes. Ambulatory status was an important mean of stratification along with the presence or absence of the p.Arg249Trp mutation. These categorizations will be important for future clinical trial cohorts. Finally, this study furthers our understanding of the progression of early onset LMNA-related muscular dystrophy and provides important insights into the anticipatory care needs of LMNA-related respiratory and cardiac manifestations.

BACKGROUND:Facioscapulohumeral dystrophy (FSHD) is caused by mutations leading to the aberrant expression of the DUX4 transcription factor in muscles. DUX4 was proposed to induce cell death, but the involvement of different death pathways is still discussed. A possible pro-apoptotic role of DUX4 was proposed, but as FSHD muscles are characterized by necrosis and inflammatory infiltrates, non-apoptotic pathways may be also involved.METHODS:We explored DUX4-mediated cell death by focusing on the role of one regulated necrosis pathway called necroptosis, which is regulated by RIPK3. We investigated the effect of necroptosis on cell death in vitro and in vivo experiments using RIPK3 inhibitors and a RIPK3-deficient transgenic mouse model.RESULTS:We showed in vitro that DUX4 expression causes a caspase-independent and RIPK3-mediated cell death in both myoblasts and myotubes. In vivo, RIPK3-deficient animals present improved body and muscle weights, a reduction of the aberrant activation of the DUX4 network genes, and an improvement of muscle histology.CONCLUSIONS:These results provide evidence for a role of RIPK3 in DUX4-mediated cell death and open new avenues of research.

Abstract Background Duchenne muscular dystrophy (DMD) is a lethal muscle disease detected in approximately 1:5000 male births. DMD is caused by mutations in the DMD gene, encoding a critical protein that links the cytoskeleton and the extracellular matrix in skeletal and cardiac muscles. The primary consequence of the disrupted link between the extracellular matrix and the myofibre actin cytoskeleton is thought to involve sarcolemma destabilization, perturbation of Ca2+ homeostasis, activation of proteases, mitochondrial damage, and tissue degeneration. A recently emphasized secondary aspect of the dystrophic process is a progressive metabolic change of the dystrophic tissue; however, the mechanism and nature of the metabolic dysregulation are yet poorly understood. In this study, we characterized a molecular mechanism of metabolic perturbation in DMD. Methods We sequenced plasma miRNA in a DMD cohort, comprising 54 DMD patients treated or not by glucocorticoid, compared with 27 healthy controls, in three groups of the ages of 4–8, 8–12, and 12–20 years. We developed an original approach for the biological interpretation of miRNA dysregulation and produced a novel hypothesis concerning metabolic perturbation in DMD. We used the mdx mouse model for DMD for the investigation of this hypothesis. Results We identified 96 dysregulated miRNAs (adjusted P‐value <0.1), of which 74 were up‐regulated and 22 were down‐regulated in DMD. We confirmed the dysregulation in DMD of Dystro‐miRs, Cardio‐miRs, and a large number of the DLK1‐DIO3 miRNAs. We also identified numerous dysregulated miRNAs yet unreported in DMD. Bioinformatics analysis of both target and host genes for dysregulated miRNAs predicted that lipid metabolism might be a critical metabolic perturbation in DMD. Investigation of skeletal muscles of the mdx mouse uncovered dysregulation of transcription factors of cholesterol and fatty acid metabolism (SREBP‐1 and SREBP‐2), perturbation of the mevalonate pathway, and the accumulation of cholesterol in the dystrophic muscles. Elevated cholesterol level was also found in muscle biopsies of DMD patients. Treatment of mdx mice with Simvastatin, a cholesterol‐reducing agent, normalized these perturbations and partially restored the dystrophic parameters. Conclusions This investigation supports that cholesterol metabolism and the mevalonate pathway are potential therapeutic targets in DMD.

Friedreich’s ataxia (FA) is a neurodegenerative disease caused by the epigenetic repression of the Frataxin gene modulating mitochondrial activity in the brain, which has a diffuse phenotypic impact on patients’ motor behavior. Therefore, with current gold-standard clinical scales, it requires 18–24 month-long clinical trials to determine if disease-modifying therapies are at all beneficial. Our high-performance monitoring approach captures the full-movement kinematics from human subjects using wearable body sensor networks from a cohort of FA patients during their regular clinical visits. We then use artificial intelligence to convert these movement data using universal behavior fingerprints into a digital biomarker of disease state. This enables us to predict two different ‘gold-standard’ clinical scores (SCAFI, SARA) that serve as primary clinical endpoints. Crucially, by performing gene expression analysis on each patient their personal Frataxin gene expression levels were poorly, if at all, correlated with their clinical scores – fundamentally failing to establish a link between disease mechanism (dysregulated gene expression) and measures to quantify it in the behavioral phenotype. In contrast, our wearable digital biomarker can accurately predict for each patient their personal FXN gene expression levels, demonstrating the sensitivity of our approach and the importance of FXN levels in FA. Therefore, our data-derived biomarker approach can not only cross-sectionally predict disease and their gene expression levels but also their longitudinal disease trajectory: it is sensitive and accurate enough to detect disease progression with much fewer subjects or shorter time scales than existing primary endpoints. Our work demonstrates that data-derived wearable biomarkers have the potential to substantially reduce clinical trial durations and a first in-human demonstration of reconstructing FXN gene expression levels from behavioral data alone.

The main aim was to explore the changes in hand-grip strength in patients with Duchenne muscular dystrophy (DMD) aged 5–29 years. Secondary aims were to test the effect of mutation, ambulatory status and glucocorticoid use on grip strength and its changes over time and to compute the number of subjects needed for a clinical trial to stabilize grip strength. The analysis was performed on data collected during five international natural history studies on a cohort of DMD patients. Two hundred and two patients with genetically proven DMD were pooled from five different natural history studies. Excepting 13 patients with only one visit, the mean duration of follow-up was 2.2 ± 1.6 years. A total of 977 measurement points were collected. Grip strength was measured on the dominant side with a high precision dynamometer. The analysis was performed using absolute values and normalized values expressed in percentage of predicted values for age. For absolute values, grip strength typically increased in ambulatory boys and decreased in non-ambulatory patients. However, when normalized, grip strength was already reduced at age 5 years and thereafter continued to fall away from normal values. The weaker the patients, the less strength they are prone to lose over again. Grip strength constitutes a sensitive and continuous outcome measure that can be used across all stages of DMD. Its measurement is easy to standardized, can be used in ambulatory and non-ambulatory patients and does not present any floor or ceiling effect. It is thus attractive as an outcome measure in therapeutic trials.

Aim: To perform cross-sectional and longitudinal miRNA profiling in plasma from Duchenne muscular dystrophy (DMD) subjects and find non-invasive biomarkers in DMD. Subjects/materials & methods: Plasma was collected from 14 age and sex matched controls and 46 DMD subjects. Free-circulating and extracellular vesicle (EV)-derived miRNA expression was measured by RT-qPCR. Results: Free-circulating and EVs derived miR-29c-3p and miR-133a-3p are dysregulated in DMD subjects. Free-circulating and EV-derived miR-29c-3p are reduced in DMD subjects undergoing daily corticosteroid treatment. Free-circulating miR-1-3p and miR-122-5p are longitudinally upregulated in ambulant DMD subjects. Conclusion: We detected novel free-circulating and EV-derived dysregulated miRNAs in plasma from DMD subjects and characterized the longitudinal profile of free-circulating miRNA on plasma from DMD subjects.

Recently, several promising treatments have emerged for neuromuscular disorders, highlighting the need for robust biomarkers for monitoring therapeutic efficacy and maintenance of the therapeutic effect. Several studies have proposed circulating and tissue biomarkers, but none of them has been validated to monitor acute and long-term drug response. We previously described how the myostatin (MSTN) level is naturally downregulated in several neuromuscular diseases, including Duchenne muscular dystrophy (DMD). Here, we show that the dystrophin-deficient Golden Retriever muscular dystrophy (GRMD) dog model also presents an intrinsic loss of Mstn production in muscle. The abnormally low levels of Mstn observed in the GRMD dog puppies at 2 months were partially rescued at both mRNA and protein level after adeno-associated virus (AAV)-microdystrophin treatment in a dose-dependent manner. These results show that circulating Mstn is a robust and reliable quantitative biomarker, capable of measuring a therapeutic response to pharmaco-gene therapy in real time in the neuromuscular system, as well as a quantitative means for non-invasive follow-up of a therapeutic effect. Moreover, a 2-year follow-up also suggests that Mstn could be a longitudinal monitoring tool to follow maintenance or decrease of the therapeutic effect.

Duchenne Muscular Dystrophy (DMD) is a lethal muscle disorder, caused by mutations in the DMD gene and affects approximately 1:5000–6000 male births. In this report, we identified dysregulation of members of the Dlk1-Dio3 miRNA cluster in muscle biopsies of the GRMD dog model. Of these, we selected miR-379 for a detailed investigation because its expression is high in the muscle, and is known to be responsive to glucocorticoid, a class of anti-inflammatory drugs commonly used in DMD patients. Bioinformatics analysis predicts that miR-379 targets EIF4G2, a translational factor, which is involved in the control of mitochondrial metabolic maturation. We confirmed in myoblasts that EIF4G2 is a direct target of miR-379, and identified the DAPIT mitochondrial protein as a translational target of EIF4G2. Knocking down DAPIT in skeletal myotubes resulted in reduced ATP synthesis and myogenic differentiation. We also demonstrated that this pathway is GC-responsive since treating mice with dexamethasone resulted in reduced muscle expression of miR-379 and increased expression of EIF4G2 and DAPIT. Furthermore, miR-379 seric level, which is also elevated in the plasma of DMD patients in comparison with age-matched controls, is reduced by GC treatment. Thus, this newly identified pathway may link GC treatment to a mitochondrial response in DMD.

ObjectiveA hitherto undescribed phenotype of early onset muscular dystrophy associated with sensorineural hearing loss and primary ovarian insufficiency was initially identified in 2 siblings and in subsequent patients with a similar constellation of findings. The goal of this study was to understand the genetic and molecular etiology of this condition.MethodsWe applied whole exome sequencing (WES) superimposed on shared haplotype regions to identify the initial biallelic variants in GGPS1 followed by GGPS1 Sanger sequencing or WES in 5 additional families with the same phenotype. Molecular modeling, biochemical analysis, laser membrane injury assay, and the generation of a Y259C knock‐in mouse were done.ResultsA total of 11 patients in 6 families carrying 5 different biallelic pathogenic variants in specific domains of GGPS1 were identified. GGPS1 encodes geranylgeranyl diphosphate synthase in the mevalonate/isoprenoid pathway, which catalyzes the synthesis of geranylgeranyl pyrophosphate, the lipid precursor of geranylgeranylated proteins including small guanosine triphosphatases. In addition to proximal weakness, all but one patient presented with congenital sensorineural hearing loss, and all postpubertal females had primary ovarian insufficiency. Muscle histology was dystrophic, with ultrastructural evidence of autophagic material and large mitochondria in the most severe cases. There was delayed membrane healing after laser injury in patient‐derived myogenic cells, and a knock‐in mouse of one of the mutations (Y259C) resulted in prenatal lethality.InterpretationThe identification of specific GGPS1 mutations defines the cause of a unique form of muscular dystrophy with hearing loss and ovarian insufficiency and points to a novel pathway for this clinical constellation. ANN NEUROL 2020;88:332–347.