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Palmio J.,University of Tampere | Evila A.,University of Helsinki | Chapon F.,University of Caen Lower Normandy | Tasca G.,Don Carlo Gnocchi ONLUS Foundation | And 27 more authors.
Journal of Neurology, Neurosurgery and Psychiatry | Year: 2014

Objective Several families with characteristic features of hereditary myopathy with early respiratory failure (HMERF) have remained without genetic cause. This international study was initiated to clarify epidemiology and the genetic underlying cause in these families, and to characterise the phenotype in our large cohort. Methods DNA samples of all currently known families with HMERF without molecular genetic cause were obtained from 12 families in seven different countries. Clinical, histopathological and muscle imaging data were collected and five biopsy samples made available for further immunohistochemical studies. Genotyping, exome sequencing and Sanger sequencing were used to identify and confirm sequence variations. Results All patients with clinical diagnosis of HMERF were genetically solved by five different titin mutations identified. One mutation has been reported while four are novel, all located exclusively in the FN3 119 domain (A150) of A-band titin. One of the new mutations showed semirecessive inheritance pattern with subclinical myopathy in the heterozygous parents. Typical clinical features were respiratory failure at mid-adulthood in an ambulant patient with very variable degree of muscle weakness. Cytoplasmic bodies were retrospectively observed in all muscle biopsy samples and these were reactive for myofibrillar proteins but not for titin. Conclusions We report an extensive collection of families with HMERF with five different mutations in exon 343 of TTN, which establishes this exon as the primary target for molecular diagnosis of HMERF. Our relatively large number of new families and mutations directly implies that HMERF is not extremely rare, not restricted to Northern Europe and should be considered in undetermined myogenic respiratory failure.

Wallgren-Pettersson C.,University of Helsinki | Sewry C.A.,Institute of Child Health | Sewry C.A.,Wolfson Center for Inherited Neuromuscular Diseases | Nowak K.J.,University of Western Australia | Laing N.G.,University of Western Australia
Seminars in Pediatric Neurology | Year: 2011

Nemaline myopathy constitutes a continuous spectrum of primary skeletal muscle disorders named after the Greek word for thread, nema. The diagnosis is based on muscle weakness, combined with visualization of nemaline bodies on muscle biopsy. The patients' muscle weakness is usually generalized, but there may be a selective pattern of more pronounced weakness, and, most importantly, respiratory muscles may be especially weak. Histologically, additional features may coexist with the nemaline bodies. There are 7 known causative genes. The function of the most recently identified gene is unknown, but the other 6 encoded proteins are associated with the muscle thin filament. The 2 most common causes of nemaline myopathy are recessive mutations in nebulin and de novo dominant mutations in skeletal muscle α-actin. At least 1 further gene remains to be identified. Patient care is based on managing the clinical symptoms. Animal models are helping to gain insight into pathogenesis, and a variety of therapeutic approaches are being investigated. © 2011 Elsevier Inc.

Rodriguez Cruz P.M.,John Radcliffe Hospital | Rodriguez Cruz P.M.,Weatherall Institute of Molecular Medicine | Sewry C.,Institute of Child Health and Great Ormond Street Hospital | Sewry C.,Wolfson Center for Inherited Neuromuscular Diseases | And 5 more authors.
Neuromuscular Disorders | Year: 2014

Congenital myopathies are a clinically and genetically heterogeneous group of disorders characterized by early onset hypotonia, weakness and characteristic, but not pathognomonic, structural abnormalities in muscle fibres. The clinical features overlap with muscular dystrophies, myofibrillar myopathies, neurogenic conditions and congenital myasthenic syndromes. We describe a case of cap myopathy with myasthenic features due to a mutation in the TPM2 gene that responded to anticholinesterase therapy. We also review other published cases of congenital myopathies with neuromuscular transmission abnormalities. This report expands the spectrum of congenital myopathies with secondary neuromuscular transmission defects. The recognition of these cases is important since these conditions can benefit from treatment with drugs enhancing neuromuscular transmission. © 2014 Elsevier B.V.

Logan C.V.,St Jamess Hospital | Szabadkai G.,University College London | Szabadkai G.,National Research Council Italy | Sharpe J.A.,University College London | And 34 more authors.
Nature Genetics | Year: 2014

Mitochondrial Ca 2+ uptake has key roles in cell life and death. Physiological Ca 2+ signaling regulates aerobic metabolism, whereas pathological Ca 2+ overload triggers cell death. Mitochondrial Ca 2+ uptake is mediated by the Ca 2+ uniporter complex in the inner mitochondrial membrane, which comprises MCU, a Ca 2+ -selective ion channel, and its regulator, MICU1. Here we report mutations of MICU1 in individuals with a disease phenotype characterized by proximal myopathy, learning difficulties and a progressive extrapyramidal movement disorder. In fibroblasts from subjects with MICU1 mutations, agonist-induced mitochondrial Ca 2+ uptake at low cytosolic Ca 2+ concentrations was increased, and cytosolic Ca 2+ signals were reduced. Although resting mitochondrial membrane potential was unchanged in MICU1-deficient cells, the mitochondrial network was severely fragmented. Whereas the pathophysiology of muscular dystrophy and the core myopathies involves abnormal mitochondrial Ca 2+ handling, the phenotype associated with MICU1 deficiency is caused by a primary defect in mitochondrial Ca 2+ signaling, demonstrating the crucial role of mitochondrial Ca 2+ uptake in humans. © 2014 Nature America, Inc.

Sewry C.A.,Institute of Child Health | Sewry C.A.,Wolfson Center for Inherited Neuromuscular Diseases
Acta Neuropathologica | Year: 2010

Muscular dystrophies are clinically, genetically, and molecularly a heterogeneous group of neuromuscular disorders. Considerable advances have been made in recent years in the identification of causative genes, the differentiation of the different forms and in broadening the understanding of pathogenesis. Muscle pathology has an important role in these aspects, but correlation of the pathology with clinical phenotype is essential. Immunohistochemistry has a major role in differential diagnosis, particularly in recessive forms where an absence or reduction in protein expression can be detected. Several muscular dystrophies are caused by defects in genes encoding sarcolemmal proteins, several of which are known to interact. Others are caused by defects in nuclear membrane proteins or enzymes. Assessment of both primary and secondary abnormalities in protein expression is useful, in particular the hypoglycosylation of alpha-dystroglycan. In dominantly inherited muscular dystrophies it is rarely possible to detect a change in the expression of the primary defective protein; an exception to this is caveolin-3. © 2010 Springer-Verlag.

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