S. Sacconi

Clinical features of facioscapulohumeral muscular dystrophy 2.

Objective: In some 5% of patients with facioscapulohumeral muscular dystrophy (FSHD), no D4Z4 repeat contraction on chromosome 4q35 is observed. Such patients, termed patients with FSHD2, show loss of DNA methylation and heterochromatin markers at the D4Z4 repeat that are similar to patients with D4Z4 contractions (FSHD1). This commonality suggests that a change in D4Z4 chromatin structure unifies FSHD1 and FSHD2. The aim of our study was to critically evaluate the clinical features in patients with FSHD2 in order to establish whether these patients are phenotypically identical to FSHD1 and to establish the effects of the (epi-) genotype on the phenotype. Methods: This cross-sectional study studied 33 patients with FSHD2 from 27 families, the largest cohort described to date. All patients were clinically assessed using a standardized clinical evaluation form. Genotype analysis was performed by pulsed field gel electrophoresis and PCR; D4Z4 methylation was studied by methylation-sensitive Southern blot analysis. Results: FSHD2 is identical to FSHD1 in its clinical presentation. Notable differences include a higher incidence (67%) of sporadic cases and the absence of gender differences in disease severity in FSHD2. Overall, average disease severity in FSHD2 was similar to that reported in FSHD1 and was not influenced by D4Z4 repeat size. In FSHD2, a small effect of the degree of hypomethylation on disease severity was observed. Conclusions: Clinically, patients with FSHD2 are indistinguishable from patients with FSHD1. The present data suggest that FSHD1 and FSHD2 are the result of the same pathophysiologic process.

Coenzyme Q10 is frequently reduced in muscle of patients with mitochondrial myopathy

Coenzyme Q(10) (CoQ(10)) deficiency has been associated with an increasing number of clinical phenotypes. Whereas primary CoQ(10) defects are related to mutations in ubiquinone biosynthetic genes, which are now being unraveled, and respond well to CoQ(10) supplementation, the etiologies, and clinical phenotypes related to secondary deficiencies are largely unknown. The purpose of this multicenter study was to evaluate the frequency of muscle CoQ(10) deficiency in a cohort of 76 patients presenting with clinically heterogeneous mitochondrial phenotypes which included myopathy among their clinical features. A reliable diagnostic tool based on HPLC quantification was employed to measure muscle CoQ(10) levels. A significant proportion of these patients (28 over 76) displayed CoQ(10) deficiency that was clearly secondary in nine patients, who harbored a pathogenic mutation of mitochondrial DNA. This study provides a rationale for future therapeutic trials on the effect of CoQ(10) supplementation in patients with mitochondrial diseases presenting with myopathy among clinical features.

A novel CRYAB mutation resulting in multisystemic disease.

Mutations in the CRYAB gene, encoding alpha-B crystallin, cause distinct clinical phenotypes including isolated posterior polar cataract, myofibrillar myopathy, cardiomyopathy, or a multisystemic disorder combining all these features. Genotype/phenotype correlations are still unclear. To date, multisystemic involvement has been reported only in kindred harboring the R120G substitution. We report a novel CRYAB mutation, D109H, associated with posterior polar cataract, myofibrillar myopathy and cardiomyopathy in a two-generation family with five affected individuals. Age of onset, clinical presentation, and muscle abnormalities were very similar to those described in the R120G family. Alpha-B crystallin may form dimers and acts as a chaperone for a number of proteins. It has been suggested that the phenotypic diversity could be related to the various interactions between target proteins of individual mutant residues. Molecular modeling indicates that residues D109 and R120 interact with each other during dimerization of alpha-B crystallin; interestingly, the two substitutions affecting these residues (D109H and R120G) are associated with the same clinical phenotype, thus suggesting a similar pathogenic mechanism. We propose that impairment of alpha-B crystallin dimerization may also be relevant to the pathogenesis of these disorders.

DUX4 and DUX4 downstream target genes are expressed in fetal FSHD muscles

Facioscapulohumeral muscular dystrophy (FSHD) is one of the most prevalent adult muscular dystrophies. The common clinical signs usually appear during the second decade of life but when the first molecular dysregulations occur is still unknown. Our aim was to determine whether molecular dysregulations can be identified during FSHD fetal muscle development. We compared muscle biopsies derived from FSHD1 fetuses and the cells derived from some of these biopsies with biopsies and cells derived from control fetuses. We mainly focus on DUX4 isoform expression because the expression of DUX4 has been confirmed in both FSHD cells and biopsies by several laboratories. We measured DUX4 isoform expression by using qRT-PCR in fetal FSHD1 myotubes treated or not with an shRNA directed against DUX4 mRNA. We also analyzed DUX4 downstream target gene expression in myotubes and fetal or adult FSHD1 and control quadriceps biopsies. We show that both DUX4-FL isoforms are already expressed in FSHD1 myotubes. Interestingly, DUX4-FL expression level is much lower in trapezius than in quadriceps myotubes, which is confirmed by the level of expression of DUX4 downstream genes. We observed that TRIM43 and MBD3L2 are already overexpressed in FSHD1 fetal quadriceps biopsies, at similar levels to those observed in adult FSHD1 quadriceps biopsies. These results indicate that molecular markers of the disease are already expressed during fetal life, thus opening a new field of investigation for mechanisms leading to FSHD.

Diagnostic challenges in facioscapulohumeral muscular dystrophy.

The diagnosis of facioscapulohumeral muscular dystrophy (FSHD) can be difficult due to its clinical variability and complex genetic cause. We present three challenging cases: one misdiagnosis of FSHD, one patient with FSHD resembling mitochondrial myopathy, and one patient with combined FSHD and limb girdle muscular dystrophy 2A. Detailed clinical and genetic evaluation, including 4qA/4qB allele determination, may be needed for the diagnosis of FSHD.

Cytosolic 5′-nucleotidase 1A autoantibody profile and clinical characteristics in inclusion body myositis

Objectives Autoantibodies directed against cytosolic 5′-nucleotidase 1A have been identified in many patients with inclusion body myositis. This retrospective study investigated the association between anticytosolic 5′-nucleotidase 1A antibody status and clinical, serological and histopathological features to explore the utility of this antibody to identify inclusion body myositis subgroups and to predict prognosis. Materials and methods Data from various European inclusion body myositis registries were pooled. Anticytosolic 5′-nucleotidase 1A status was determined by an established ELISA technique. Cases were stratified according to antibody status and comparisons made. Survival and mobility aid requirement analyses were performed using Kaplan-Meier curves and Cox proportional hazards regression. Results Data from 311 patients were available for analysis; 102 (33%) had anticytosolic 5′-nucleotidase 1A antibodies. Antibody-positive patients had a higher adjusted mortality risk (HR 1.89, 95% CI 1.11 to 3.21, p=0.019), lower frequency of proximal upper limb weakness at disease onset (8% vs 23%, adjusted OR 0.29, 95% CI 0.12 to 0.68, p=0.005) and an increased prevalence of excess of cytochrome oxidase deficient fibres on muscle biopsy analysis (87% vs 72%, adjusted OR 2.80, 95% CI 1.17 to 6.66, p=0.020), compared with antibody-negative patients. Interpretation Differences were observed in clinical and histopathological features between anticytosolic 5′-nucleotidase 1A antibody positive and negative patients with inclusion body myositis, and antibody-positive patients had a higher adjusted mortality risk. Stratification of inclusion body myositis by anticytosolic 5′-nucleotidase 1A antibody status may be useful, potentially highlighting a distinct inclusion body myositis subtype with a more severe phenotype.

Copper and bezafibrate cooperate to rescue cytochrome c oxidase deficiency in cells of patients with sco2 mutations

BackgroundMutations in SCO2 cause cytochrome c oxidase deficiency (COX) and a fatal infantile cardioencephalomyopathy. SCO2 encodes a protein involved in COX copper metabolism; supplementation with copper salts rescues the defect in patients’ cells. Bezafibrate (BZF), an approved hypolipidemic agent, ameliorates the COX deficiency in mice with mutations in COX10, another COX-assembly gene.MethodsWe have investigated the effect of BZF and copper in cells with SCO2 mutations using spectrophotometric methods to analyse respiratory chain activities and a luciferase assay to measure ATP production..ResultsIndividual mitochondrial enzymes displayed different responses to BZF. COX activity increased by about 40% above basal levels (both in controls and patients), with SCO2 cells reaching 75-80% COX activity compared to untreated controls. The increase in COX was paralleled by an increase in ATP production. The effect was dose-dependent: it was negligible with 100 μM BZF, and peaked at 400 μM BZF. Higher BZF concentrations were associated with a relative decline of COX activity, indicating that the therapeutic range of this drug is very narrow. Combined treatment with 100 μM CuCl2 and 200 μM BZF (which are only marginally effective when administered individually) achieved complete rescue of COX activity in SCO2 cells.ConclusionsThese data are crucial to design therapeutic trials for this otherwise fatal disorder. The additive effect of copper and BZF will allow to employ lower doses of each drug and to reduce their potential toxic effects. The exact mechanism of action of BZF remains to be determined.

Unusual multisystemic involvement and a novel BAG3 mutation revealed by NGS screening in a large cohort of myofibrillar myopathies

BackgroundMyofibrillar myopathies (MFM) are a group of phenotypically and genetically heterogeneous neuromuscular disorders, which are characterized by protein aggregations in muscle fibres and can be associated with multisystemic involvement.MethodsWe screened a large cohort of 38 index patients with MFM for mutations in the nine thus far known causative genes using Sanger and next generation sequencing (NGS). We studied the clinical and histopathological characteristics in 38 index patients and five additional relatives (nu2009=u200943) and particularly focused on the associated multisystemic symptoms.ResultsWe identified 14 heterozygous mutations (diagnostic yield of 37%), among them the novel p.Pro209Gln mutation in the BAG3 gene, which was associated with onset in adulthood, a mild phenotype and an axonal sensorimotor polyneuropathy, in the absence of giant axons at the nerve biopsy. We revealed several novel clinical phenotypes and unusual multisystemic presentations with previously described mutations: hearing impairment with a FLNC mutation, dysphonia with a mutation in DES and the first patient with a FLNC mutation presenting respiratory insufficiency as the initial symptom. Moreover, we described for the first time respiratory insufficiency occurring in a patient with the p.Gly154Ser mutation in CRYAB. Interestingly, we detected a polyneuropathy in 28% of the MFM patients, including a BAG3 and a MYOT case, and hearing impairment in 13%, including one patient with a FLNC mutation and two with mutations in the DES gene. In four index patients with a mutation in one of the MFM genes, typical histological findings were only identified at the ultrastructural level (29%).ConclusionsWe conclude that extraskeletal symptoms frequently occur in MFM, particularly cardiac and respiratory involvement, polyneuropathy and/or deafness. BAG3 mutations should be considered even in cases with a mild phenotype or an adult onset. We identified a genetic defect in one of the known genes in less than half of the MFM patients, indicating that more causative genes are still to be found. Next generation sequencing techniques should be helpful in achieving this aim.

A.P.3

Myofibrillar myopathies (MFM) are a group of phenotypically and genetically heterogenous neuromuscular disorders, which are characterized by protein aggregations in muscle fibres and can be associated with respiratory and/or extraskeletal involvement. We screened a large cohort of 38 index patients with MFM for mutations in the nine thus far known causative genes using Sanger and next generation sequencing (NGS). We studied the clinical and histopathological characteristics in 38 index patients and five additional relatives ( n =43) and particularly focused on the associated extraskeletal symptoms. We identified 14 heterozygous mutations (diagnostic yield of 37%), among them the novel p.Pro209Gln mutation in the BAG3 gene, which was associated with a mild phenotype and an axonal sensorimotor polyneuropathy. We detected a polyneuropathy in 28% of the MFM patients, including a BAG3 and a MYOT case, hearing loss in 13%, including one patient with a FLNC mutation and two with mutations in the DES gene, dysphonia with a DES mutation and the first patient with a FLNC mutation presenting respiratory insufficiency as the initial symptom. Moreover, we described for the first time respiratory insufficiency occurring in a patient with the p.Gly154Ser mutation in CRYAB. In four index patients with a mutation in one of the MFM genes, typical histological findings were only identified at the ultrastructural level (29%). We conclude that extraskeletal symptoms frequently occur in MFM, particularly polyneuropathy, deafness, cardiac and respiratory involvement. In case of muscle weakness and extraskeletal symptoms the presence of a MFM should be considered. We identified a genetic defect in one of the known genes in less than half of the MFM patients, indicating that more causative genes are still to be found. Next generation sequencing techniques should be helpful in achieving this aim.

P.16.3 DUX4 and DUX4 downstream target genes are expressed in fetal FSHD muscles

The facio scapulo humeral dystrophy (FSHD) is the third most prevalent muscular dystrophy. The common clinical signs usually appear during the second decade of life but when the first molecular dysregulations occur is still unknown. Our aim was to determine whether molecular dysregulations can be identified during FSHD fetal muscle development. We compared 2 muscle biopsies coming from one FSHD fetus and the cells derived from these biopsies with biopsies and cells coming from control fetuses. We mainly focus on DUX4 isoform expression since the expression of DUX4 has been confirmed in both FSHD cells and biopsies by several laboratories. We measured by qRT-PCR DUX4 isoforms expression in fetal FSDH myotubes treated or not with a shRNA directed against DUX4 mRNA. We also analyzed DUX4 downstream genes expression in myotubes and fetal or adult FSDH and control quadriceps biopsies. We show that DUX4-FL is not expressed in control myotubes whereas it is expressed FSHD myotubes. Interestingly, DUX4-FL expression level is much lower in trapezius than in quadriceps myotubes which is confirmed by the level of expression of DUX4 downstream genes: We observed that TRIM43 and MBD3L2 are already overexpressed in FSHD fetal quadriceps biopsies, at similar levels at those observed in adult FSHD quadriceps biopsies. These results indicate that molecular markers of the disease are already expressed during fetal life, raising the question as to the role of DUX4 in the onset and progression of FSHD.