Clinical and Molecular Spectrum Associated with COL6A3 c.7447A>G p.(Lys2483Glu) Variant: Elucidating its Role in Collagen VI-related Myopathies

International audienceBackground: Dominant and recessive autosomal pathogenic variants in the three major genes (COL6A1-A2-A3) encoding the extracellular matrix protein collagen VI underlie a group of myopathies ranging from early-onset severe conditions (Ullrich congenital muscular dystrophy) to milder forms maintaining independent ambulation (Bethlem myopathy). Diagnosis is based on the combination of clinical presentation, muscle MRI, muscle biopsy, analysis of collagen VI secretion, and COL6A1-A2-A3 genetic analysis, the interpretation of which can be challenging. Objective: To refine the phenotypical spectrum associated with the frequent COL6A3 missense variant c.7447A>G (p.Lys2483Glu). Methods: We report the clinical and molecular findings in 16 patients: 12 patients carrying this variant in compound heterozygosity with another COL6A3 variant, and four homozygous patients. Results: Patients carrying this variant in compound heterozygosity with a truncating COL6A3 variant exhibit a phenotype consistent with COL6-related myopathies (COL6-RM), with joint contractures, proximal weakness and skin abnormalities. All remain ambulant in adulthood and only three have mild respiratory involvement. Most show typical muscle MRI findings. In five patients, reduced collagen VI secretion was observed in skin fibroblasts cultures. All tested parents were unaffected heterozygous carriers. Conversely, two out of four homozygous patients did not present with the classical COL6-RM clinical and imaging findings. Collagen VI immunolabelling on cultured fibroblasts revealed rather normal secretion in one and reduced secretion in another. Muscle biopsy from one homozygous patient showed myofibrillar disorganization and rimmed vacuoles. Conclusions: In light of our results, we postulate that the COL6A3 variant c.7447A>G may act as a modulator of the clinical phenotype. Thus, in patients with a typical COL6-RM phenotype, a second variant must be thoroughly searched for, while for patients with atypical phenotypes further investigations should be conducted to exclude alternative causes. This works expands the clinical and molecular spectrum of COLVI-related myopathies

OPA1 mutations induce mitochondrial DNA instability and optic atrophy 'plus' phenotypes.

International audienceMutations in OPA1, a dynamin-related GTPase involved in mitochondrial fusion, cristae organization and control of apoptosis, have been linked to non-syndromic optic neuropathy transmitted as an autosomal-dominant trait (DOA). We here report on eight patients from six independent families showing that mutations in the OPA1 gene can also be responsible for a syndromic form of DOA associated with sensorineural deafness, ataxia, axonal sensory-motor polyneuropathy, chronic progressive external ophthalmoplegia and mitochondrial myopathy with cytochrome c oxidase negative and Ragged Red Fibres. Most remarkably, we demonstrate that these patients all harboured multiple deletions of mitochondrial DNA (mtDNA) in their skeletal muscle, thus revealing an unrecognized role of the OPA1 protein in mtDNA stability. The five OPA1 mutations associated with these DOA 'plus' phenotypes were all mis-sense point mutations affecting highly conserved amino acid positions and the nuclear genes previously known to induce mtDNA multiple deletions such as POLG1, PEO1 (Twinkle) and SLC25A4 (ANT1) were ruled out. Our results show that certain OPA1 mutations exert a dominant negative effect responsible for multi-systemic disease, closely related to classical mitochondrial cytopathies, by a mechanism involving mtDNA instability

Effect of enzyme replacement therapy with alglucosidase alfa (Myozyme (R)) in 12 patients with advanced late-onset Pompe disease

International audienceThe efficacy of enzyme replacement therapy (ERT) in patients at an advanced stage of Pompe disease has only been addressed in a few studies. Our objective was to assess the long term effects of ERT in a cohort of patients with severe Pompe disease.We identified patients from the French Pompe Registry with severe respiratory failure and permanent wheelchair use (assisted walk for a few meters was allowed) when starting ERT. Patients' medical records were collected and reviewed and respiratory and motor functions, before ERT initiation and upon last evaluation were compared.Twelve patients (7 males) were identified. Median age at symptom onset was 24years [IQR=15.5; 36.0]. At baseline ventilation was invasive in 11 patients and noninvasive in one, with a median ventilation time of 24h [IQR=21.88; 24.00] (min 20; max 24). ERT was initiated at a median age of 52.5years [IQR=35.75; 66.50]. Median treatment duration was 55months [IQR=39.5; 81.0]. During observational period no adverse reaction to ERT was recorded, five patients (41.67%) died, three decreased their ventilation time by 30, 60 and 90min and two increased their assisted walking distance, by 80 and 20m.Some patients at a very advanced stage of Pompe disease may show a mild benefit from ERT, in terms of increased time of autonomous ventilation and of enlarged distance in assisted walk. ERT can be initiated in these patients in order to retain their current level of independence and ability to perform daily life activities

Mutation spectrum in the large GTPase dynamin 2, and genotype–phenotype correlation in autosomal dominant centronuclear myopathy

Centronuclear myopathy (CNM) is a genetically heterogeneous disorder associated with general skeletal muscle weakness, type I fiber predominance and atrophy, and abnormally centralized nuclei. Autosomal dominant CNM is due to mutations in the large GTPase dynamin 2 ( DNM2 ), a mechanochemical enzyme regulating cytoskeleton and membrane trafficking in cells. To date, 40 families with CNM‐related DNM2 mutations have been described, and here we report 60 additional families encompassing a broad genotypic and phenotypic spectrum. In total, 18 different mutations are reported in 100 families and our cohort harbors nine known and four new mutations, including the first splice‐site mutation. Genotype–phenotype correlation hypotheses are drawn from the published and new data, and allow an efficient screening strategy for molecular diagnosis. In addition to CNM, dissimilar DNM2 mutations are associated with Charcot–Marie–Tooth (CMT) peripheral neuropathy (CMTD1B and CMT2M), suggesting a tissue‐specific impact of the mutations. In this study, we discuss the possible clinical overlap of CNM and CMT, and the biological significance of the respective mutations based on the known functions of dynamin 2 and its protein structure. Defects in membrane trafficking due to DNM2 mutations potentially represent a common pathological mechanism in CNM and CMT. Hum Mutat 33:949–959, 2012. © 2012 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92087/1/22067_ftp.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/92087/2/humu_22067_sm_SuppInfo.pd

Convergence of patient- and physician-reported outcomes in the French National Registry of Facioscapulohumeral Dystrophy

International audienceFacioscapulohumeral muscular dystrophy (FSHD) is among the most prevalent muscular dystrophies and currently has no treatment. Clinical and genetic heterogeneity are the main challenges to a full comprehension of the physiopathological mechanism. Improving our knowledge of FSHD is crucial to the development of future therapeutic trials and standards of care. National FSHD registries have been set up to this end. The French National Registry of FSHD combines a clinical evaluation form (CEF) and a self-report questionnaire (SRQ), filled out by a physician with expertise in neuromuscular dystrophies and by the patient, respectively. Aside from favoring recruitment, our strategy was devised to improve data quality. Indeed, the pairwise comparison of data from 281 patients for 39 items allowed for evaluating data accuracy. Kappa or intra-class coefficient (ICC) values were calculated to determine the correlation between answers provided in both the CEF and SRQ. Results Patients and physicians agreed on a majority of questions common to the SRQ and CEF (24 out of 39). Demographic, diagnosis- and care-related questions were generally answered consistently by the patient and the medical practitioner (kappa or ICC values of most items in these groups were greater than 0.8). Muscle function-related items, i.e. FSHD-specific signs, showed an overall medium to poor correlation between data provided in the two forms; the distribution of agreements in this section was markedly spread out and ranged from poor to good. In particular, there was very little agreement regarding the assessment of facial motricity and the presence of a winged scapula. However, patients and physicians agreed very well on the Vignos and Brooke scores. The report of symptoms not specific to FSHD showed general poor consistency. Conclusions Patient and physician answers are largely concordant when addressing quantitative and objective items. Consequently, we updated collection forms by relying more on patient-reported data where appropriate. We hope the revised forms will reduce data collection time while ensuring the same quality standard. With the advent of artificial intelligence and automated decision-making, high-quality and reliable data are critical to develop top-performing algorithms to improve diagnosis, care, and evaluate the efficiency of upcoming treatments