Prognosis of Right Ventricular Systolic Dysfunction in Patients With Duchenne Muscular Dystrophy.

Background Chronic respiratory failure and heart involvement may occur in Duchenne muscular dystrophy. We aimed to assess the prognostic value of the right ventricular (RV) systolic dysfunction in patients with Duchenne muscular dystrophy. Methods and Results We studied 90 genetically proven patients with Duchenne muscular dystrophy from 2010 to 2019, to obtain respiratory function and Doppler echocardiographic RV systolic function. Prognostic value was assessed in terms of death and cardiac events. The median age was 27.5 years, and median forced vital capacity was at 10% of the predicted value: 83 patients (92%) were on home mechanical ventilation. An RV systolic dysfunction was found in 46 patients (51%). In patients without RV dysfunction at inclusion, a left ventricular systolic dysfunction at inclusion was associated with a higher risk of developing RV dysfunction during follow-up with an odds ratio of 4.5 (P=0.03). RV systolic dysfunction was significantly associated with cardiac events, mainly acute heart failure (62%) and cardiogenic shock (23%). In a multivariable Cox model, the adjusted hazard ratio was 4.96 (95% CI [1.09-22.6]; P=0.04). In terms of death, we found a significant difference between patients with RV dysfunction versus patients without RV dysfunction in the Kaplan-Meier curves (log-rank P=0.045). Conclusions RV systolic dysfunction is frequently present in patients with Duchenne muscular dystrophy and is associated with increased risk of cardiac events, irrespective of left ventricular dysfunction and mechanical ventilation. Registration URL: https://www.clinicaltrials.org; unique identifier: NCT02501083.

High-Throughput Digital Image Analysis Reveals Distinct Patterns of Dystrophin Expression in Dystrophinopathy Patients.

Duchenne muscular dystrophy (DMD) is an incurable disease caused by out-of-frame DMD gene deletions while in frame deletions lead to the milder Becker muscular dystrophy (BMD). In the last decade several antisense oligonucleotides drugs have been developed to induce a partially functional internally deleted dystrophin, similar to that produced in BMD, and expected to ameliorate the disease course. The pattern of dystrophin expression and functionality in dystrophinopathy patients is variable due to multiple factors, such as molecular functionality of the dystrophin and its distribution. To benchmark the success of therapeutic intervention, a clear understanding of dystrophin expression patterns in dystrophinopathy patients is vital. Recently, several groups have used innovative techniques to quantify dystrophin in muscle biopsies of children but not in patients with milder BMD. This study reports on dystrophin expression using both Western blotting and an automated, high-throughput, image analysis platform in DMD, BMD, and intermediate DMD/BMD skeletal muscle biopsies. Our results found a significant correlation between Western blot and immunofluorescent quantification indicating consistency between the different methodologies. However, we identified significant inter- and intradisease heterogeneity of patterns of dystrophin expression in patients irrespective of the amount detected on blot, due to variability in both fluorescence intensity and dystrophin sarcolemmal circumference coverage. Our data highlight the heterogeneity of the pattern of dystrophin expression in BMD, which will assist the assessment of dystrophin restoration therapies.

FHL1 is a key player of chikungunya virus tropism and pathogenesis.

Chikungunya is an infectious disease caused by the chikungunya virus (CHIKV), an alphavirus transmitted to humans by Aedes mosquitoes, and for which there is no licensed vaccine nor antiviral treatments. By using a loss-of-function genetic screen, we have recently identified the FHL1 protein as an essential host factor for CHIKV tropism and pathogenesis. FHL1 is highly expressed in muscles cells and fibroblasts, the main CHIKV-target cells. FHL1 interacts with the viral protein nsP3 and plays a critical role in CHIKV genome amplification. Experiments in vivo performed in FHL1-deficient mice have shown that these animals are resistant to infection and do not develop muscular lesions. Altogether these observations, published in the journal Nature [1], show that FHL1 is a key host factor for CHIKV pathogenesis and identify the interaction between FHL1 and nsP3 as a promising target for the development of new antiviral strategies.

Le chikungunya est une maladie infectieuse causée par le virus chikungunya (CHIKV), un alphavirus transmis à l'Homme par les moustiques Aedes et contre lequel il n'existe ni vaccin, ni traitements antiviraux. En utilisant une approche de crible génétique par perte de fonction, nous avons récemment identifié la protéine FHL1 comme un facteur cellulaire essentiel pour le tropisme et la pathogénèse du CHIKV. FHL1 est une molécule présente majoritairement dans les cellules musculaires et les fibroblastes, les cibles privilégiées de CHIKV. FHL1 interagit avec la protéine virale nsP3 et joue un rôle décisif dans le mécanisme d'amplification du génome de CHIKV. Des expériences in vivo chez des souris déficientes pour FHL1 ont montré que ces animaux sont résistants à l'infection et ne développent pas de lésions musculaires. L'ensemble de ces observations publiées dans la revue Nature [1] montrent que FHL1 est un facteur cellulaire clé pour la pathogénèse de CHIKV et identifient l'interaction entre FHL1 et nsp3 comme une cible prometteuse pour le développement de nouvelles stratégies antivirales.

A guide to writing systematic reviews of rare disease treatments to generate FAIR-compliant datasets: building a Treatabolome.

BACKGROUND: Rare diseases are individually rare but globally affect around 6% of the population, and in over 70% of cases are genetically determined. Their rarity translates into a delayed diagnosis, with 25% of patients waiting 5 to 30 years for one. It is essential to raise awareness of patients and clinicians of existing gene and variant-specific therapeutics at the time of diagnosis to avoid that treatment delays add up to the diagnostic odyssey of rare diseases' patients and their families. AIMS: This paper aims to provide guidance and give detailed instructions on how to write homogeneous systematic reviews of rare diseases' treatments in a manner that allows the capture of the results in a computer-accessible form. The published results need to comply with the FAIR guiding principles for scientific data management and stewardship to facilitate the extraction of datasets that are easily transposable into machine-actionable information. The ultimate purpose is the creation of a database of rare disease treatments ("Treatabolome") at gene and variant levels as part of the H2020 research project Solve-RD. RESULTS: Each systematic review follows a written protocol to address one or more rare diseases in which the authors are experts. The bibliographic search strategy requires detailed documentation to allow its replication. Data capture forms should be built to facilitate the filling of a data capture spreadsheet and to record the application of the inclusion and exclusion criteria to each search result. A PRISMA flowchart is required to provide an overview of the processes of search and selection of papers. A separate table condenses the data collected during the Systematic Review, appraised according to their level of evidence. CONCLUSIONS: This paper provides a template that includes the instructions for writing FAIR-compliant systematic reviews of rare diseases' treatments that enables the assembly of a Treatabolome database that complement existing diagnostic and management support tools with treatment awareness data.

Clinical Phenotypes of DMD Exon 51 Skip Equivalent Deletions: A Systematic Review.

BACKGROUND: Eteplirsen, the first FDA-approved RNA-modifying therapy for DMD, is applicable to ∼13% of patients with DMD. Because multiple exonic deletions are amenable to exon 51 skipping, the isoforms resulting from the various exon 51-skipped transcripts may vary in stability, function, and phenotype. OBJECTIVE/METHODS: We conducted a detailed review of dystrophinopathy published literature and unpublished databases to compile phenotypic features of patients with exon 51 "skip-equivalent" deletions. RESULTS: Theoretically, 48 different in-frame transcripts may result from exon 51 skipping. We found sufficient clinical information on 135 patients carrying mutations that would result in production of 11 (23%) of these transcripts, suggesting the remainder have not been identified in vivo. The majority had mild phenotypes: BMD (n = 81) or isolated dilated cardiomyopathy (n = 3). Particularly interesting are the asymptomatic (n = 10) or isolated hyperCKemia (n = 20) patients with deletions of exons 45- 51, 48- 51, 49- 51 and 50- 51. Finally, 16 (12%) had more severe phenotypes described as intermediate (n = 2) or DMD (n = 14), and 6 reports had no definitive phenotype. CONCLUSIONS: This review shows that the majority of exon 51 "skip-equivalent" deletions result in milder (BMD) phenotypes and supports that exon 51 skipping therapy could provide clinical benefit, although we acknowledge that other factors, such as age at treatment initiation or ongoing standard of care, may influence the degree of benefit.

Effects of Home Mechanical Ventilation on Left Ventricular Function in Sarcoglycanopathies (Limb Girdle Muscular Dystrophies).

Cardiac and respiratory function may be impaired in sarcoglycanopathies, a subgroup of muscular dystrophies due to sarcoglycan proteins (α, ß, γ, and δ) genes mutations. Management of patients with restrictive respiratory failure mainly relies on home mechanical ventilation (HMV). Little is known about the cardiac effects of prolonged mechanical ventilation in patients with muscular dystrophy and restrictive respiratory insufficiency. We aimed to assess the effects of HMV on cardiac function in sarcoglycanopathies. We retrospectively included 10 genetically proven patients with sarcoglycanopathy followed at the HMV unit of the Raymond Poincare University Hospital (4 patients with α-sarcoglycanopathy and 6 patients with γ-sarcoglycanopathy). We collected cardiorespiratory clinical baseline data and left ventricular ejection fraction (LVEF) at baseline before initiation of HMV and at the end of follow-up. At baseline, median age was 30.5 years (27 to 39) and median pulmonary vital capacity was 27% of the predicted value (21 to 36). Forty percent of the patients had documented sleep apnea. Cardiomyopathy, defined as LVEF <50%, was found in 3 patients with γ-sarcoglycanopathy. After a median follow-up of 3 years (1.0 to 4.5), there was a significant increase in LVEF after initiation of HMV, that is, 62% (48 to 65) versus 53% (45.5 to 56.5) (p = 0.0039). In conclusion, HMV in sarcoglycanopathies is not harmful and may protect left ventricular function by its thoracic physiological effects.

Clinical profiles and prognosis of acute heart failure in adult patients with dystrophinopathies on home mechanical ventilation.

AIMS: Duchenne muscular dystrophy (DMD) is characterized by respiratory and heart involvements. In the context of permanently wheelchair bound and on mechanical ventilation (MV) patients, the clinical presentation of acute heart failure (AHF) syndrome may be atypical. We sought to describe clinical and genetic profiles and to determine prognosis of DMD and Becker muscular dystrophy (BMD) patients on home MV (HMV), hospitalized for AHF. METHODS AND RESULTS: We included genetically proven DMD and BMD patients on HMV admitted for AHF. A total of 13 patients (11 DMD and 2 BMD) fulfilled the inclusion criteria. Median age was 34.0 [interquartile range (IQR) 26.0; 40.0] years. Median pulmonary vital capacity was 9.0% (6.0; 15.0) of predicted value. Long-term invasive ventilation was performed in 69% of patients. All the 11 DMD patients carried out-of-frame DMD gene mutations. At admission, dyspnoea was present in 46%, lipothymia in 23%, and abdominal discomfort in 38.4% of patients. A total of 53.8% of patients showed anasarca. Cardiogenic shock presentation was found in six patients (46%). Ejection fraction was severely altered [median 25% (IQR 20; 30)]. Intra-hospital mortality rate was 30%, reaching 53.8 % after 1 year. Previous episodes of AHF ≥ 2 were associated with intra-hospital mortality (P = 0.025). In patients with cardiogenic shock, intra-hospital mortality rate was 66.6%, reaching 83.3% after 1 year. CONCLUSIONS: In adult DMD and BMD patients with severe ejection fraction alteration and on HMV, admitted for AHF, right cardiac signs are frequent. The intra-hospital and 1 year mortality rate was high and was associated with previous episodes of AHF ≥ 2.

Assessment of the structural and functional impact of in-frame mutations of the DMD gene, using the tools included in the eDystrophin online database.

BACKGROUND: Dystrophin is a large essential protein of skeletal and heart muscle. It is a filamentous scaffolding protein with numerous binding domains. Mutations in the DMD gene, which encodes dystrophin, mostly result in the deletion of one or several exons and cause Duchenne (DMD) and Becker (BMD) muscular dystrophies. The most common DMD mutations are frameshift mutations resulting in an absence of dystrophin from tissues. In-frame DMD mutations are less frequent and result in a protein with partial wild-type dystrophin function. The aim of this study was to highlight structural and functional modifications of dystrophin caused by in-frame mutations. METHODS AND RESULTS: We developed a dedicated database for dystrophin, the eDystrophin database. It contains 209 different non frame-shifting mutations found in 945 patients from a French cohort and previous studies. Bioinformatics tools provide models of the three-dimensional structure of the protein at deletion sites, making it possible to determine whether the mutated protein retains the typical filamentous structure of dystrophin. An analysis of the structure of mutated dystrophin molecules showed that hybrid repeats were reconstituted at the deletion site in some cases. These hybrid repeats harbored the typical triple coiled-coil structure of native repeats, which may be correlated with better function in muscle cells. CONCLUSION: This new database focuses on the dystrophin protein and its modification due to in-frame deletions in BMD patients. The observation of hybrid repeat reconstitution in some cases provides insight into phenotype-genotype correlations in dystrophin diseases and possible strategies for gene therapy. The eDystrophin database is freely available: http://edystrophin.genouest.org/.

Clinical and genetic heterogeneity in laminopathies.

Mutations in the LMNA gene encoding lamins A/C are responsible for more than ten different disorders called laminopathies which affect various tissues in an isolated (striated muscle, adipose tissue or peripheral nerve) or systemic (premature aging syndromes) fashion. Overlapping phenotypes are also observed. Associated with this wide clinical variability, there is also a large genetic heterogeneity, with 408 different mutations being reported to date. Whereas a few hotspot mutations emerge for some types of laminopathies, relationships between genotypes and phenotypes remain poor for laminopathies affecting the striated muscles. In addition, there is important intrafamilial variability, explained only in a few cases by digenism, thus suggesting an additional contribution from modifier genes. In this regard, a chromosomal region linked to the variability in the age at onset of myopathic symptoms in striated muscle laminopathies has recently been identified. This locus is currently under investigation to identify modifier variants responsible for this variability.

Cardioembolic stroke prompting diagnosis of LMNA-associated Emery-Dreifuss muscular dystrophy.

The diagnosis of Emery-Dreifuss muscular dystrophy (EDMD) is suggested by the combination of musculoskeletal weakness and wasting, joint contractures, and cardiac disease. Herein we report a patient in whom an ischemic stroke prompted the diagnosis of EDMD. A mutation in the LMNA gene (c.266G>T, p.Arg89Leu) was found. It had been reported previously exclusively with isolated cardiac disease, thus reinforcing the high phenotypic heterogeneity of laminopathies.

Contractures and hypertrophic cardiomyopathy in a novel FHL1 mutation.

We investigated a large German family (n = 37) with male members who had contractures, rigid spine syndrome, and hypertrophic cardiomyopathy. Muscle weakness or atrophy was not prominent in affected individuals. Muscle biopsy disclosed a myopathic pattern with cytoplasmic bodies. We used microsatellite markers and found linkage to a locus at Xq26-28, a region harboring the FHL1 gene. We sequenced FHL1 and identified a new missense mutation within the third LIM domain that replaces a highly conserved cysteine by an arginine (c.625T>C; p.C209R). Our finding expands the phenotypic spectrum of the recently identified FHL1-associated myopathies and widens the differential diagnosis of Emery-Dreifuss-like syndromes.

Genotype-phenotype analysis in 2,405 patients with a dystrophinopathy using the UMD-DMD database: a model of nationwide knowledgebase.

UMD-DMD France is a knowledgebase developed through a multicenter academic effort to provide an up-to-date resource of curated information covering all identified mutations in patients with a dystrophinopathy. The current release includes 2,411 entries consisting in 2,084 independent mutational events identified in 2,046 male patients and 38 expressing females, which corresponds to an estimated number of 39 people per million with a genetic diagnosis of dystrophinopathy in France. Mutations consist in 1,404 large deletions, 215 large duplications, and 465 small rearrangements, of which 39.8% are nonsense mutations. The reading frame rule holds true for 96% of the DMD patients and 93% of the BMD patients. Quality control relies on the curation by four experts for the DMD gene and related diseases. Data on dystrophin and RNA analysis, phenotypic groups, and transmission are also available. About 24% of the mutations are de novo events. This national centralized resource will contribute to a greater understanding of prevalence of dystrophinopathies in France, and in particular, of the true frequency of BMD, which was found to be almost half (43%) that of DMD. UMD-DMD is a searchable anonymous database that includes numerous newly developed tools, which can benefit to all the scientific community interested in dystrophinopathies. Dedicated functions for genotype-based therapies allowed the prediction of a new multiexon skipping (del 45-53) potentially applicable to 53% of the deleted DMD patients. Finally, such a national database will prove to be useful to implement the international global DMD patients' registries under development.

Meta-analysis of clinical characteristics of 299 carriers of LMNA gene mutations: do lamin A/C mutations portend a high risk of sudden death?

This study evaluated common clinical characteristics of patients with lamin A/C gene mutations that cause either isolated dilated cardiomyopathy or dilated cardiomyopathy in association with skeletal muscular dystrophy. We pooled clinical data of all published carriers of lamin A/C gene mutations as cause of skeletal and/or cardiac muscle disease and reviewed ECG findings. Cardiac dysrhythmias were reported in 92% of patients after the age of 30 years; heart failure was reported in 64% after the age of 50. Sudden death was the most frequently reported mode of death (46%) in both the cardiac and the neuromuscular phenotype. Carriers of lamin A/C gene mutations often received a pacemaker (28%). However, this intervention did not alter the rate of sudden death. Review of the ECG findings typically showed a low amplitude P wave and prolongation of the PR interval with a narrow QRS complex. This meta-analysis suggests that cardiomyopathy due to lamin A/C gene mutations portends a high risk of sudden death, and that this risk does not differ between subjects with predominantly cardiac or neuromuscular disease. This implies then that all carriers of a lamin A/C gene mutation need to be carefully screened with particular emphasis also on tachyarrhythmias. Prospective studies are needed to evaluate risk stratification and proper treatment strategies.