Neuromuscular Disorders - Articles in Press

A case of myelopathy, myopathy, peripheral neuropathy and subcortical grey matter degeneration associated with recessive compound heterozygous POLG1 mutations - Corrected Proof

P. McKelvie, R. Marotta, D.R. Thorburn, J. Chin, S. Punchihewa, S. Collins — 2012-02-22

Abstract: This 54year old woman presented with symptoms of sensory ataxic neuropathy, with cerebellar features. She developed further weakness, visual disturbances with diplopia, dysarthria and dysphasia. After her death at 66years, she was found to have compound heterozygous mutations of POLG1 gene in muscle, and Southern blot showed low levels of multiple deletions of mitochondrial DNA. Neuropathological examination showed profound dorsal column and dorsal spinocerebellar tract degeneration, degeneration of dorsal root ganglia and Clarke’s nucleus in spinal cord and severe predominantly sensory peripheral neuropathy. The brain showed severe neuronal loss and gliosis in substantia nigra, medial posterior thalamus and head of caudate. Excess numbers of COX-negative fibres and “ragged-red” fibres were found in five skeletal muscles sampled.

Mutation spectrum and phenotypic manifestation in FSHD Greek patients - Corrected Proof

2012-02-22

Abstract: Facioscapulohumeral Muscular Dystrophy (FSHD) is a genetic myopathy with a remarkable intra- and inter-familial clinical heterogeneity. This study reports the clinical and genetic analysis of 133 individuals from 71 unrelated Greek families based on a revised Clinical Severity Score (rCSS) index which was developed for clinical assessment regarding the disease progression. A high ratio (31/62, 50%) of probands’ family members was found to be asymptomatic or minimally affected gene carriers of a contracted 4q allele. Moreover, a notable clinical variability of FSHD is reported concerning the detection of an identical de novo 13kb EcoRI fragment in monozygotic twins, as well as indications of founder effect. This is the first survey that presents data of FSHD families from an East Mediterranean country supporting the speculation that the prevalence of disease might be significantly underestimated and that synergistic factors could play an essential role on the progression of the disease.

Sun, Surf and Science - Corrected Proof

Jane Miller, Susan Brown — 2012-02-17

Algarve, the ultimate sunshine haven: deep blue sea and azure skies, vivid green golf courses; sweet nemesis for ex-pat Brits and a serious challenge to the activities of the World Muscle Society’s Triple ‘E’ Society, of Education, Enjoyment and Excitement that found itself pitched against the attractions of the Quadruple ‘S’ Society: seascape, sunshine, sandals and socks, where portly, supine sunbathers soak up the golden sunrays, knotted handkerchiefs on heads, trousers rolled up to the knees, warm beer balanced on their bellies.

Experimental validation of in silico predicted KCNA1, KCNA2, KCNA6 and KCNQ2 genes for association studies of peripheral nerve hyperexcitability syndrome in Jack Russell Terriers - Corrected Proof

Mario Van Poucke, An E. Vanhaesebrouck, Luc J. Peelman, Luc Van Ham — 2012-02-16

Abstract: KCNA1, KCNA2, KCNA6 and KCNQ2 are associated with peripheral nerve hyperexcitability in humans. In order to determine if these genes are also involved in Jack Russell Terriers with a similar syndrome characterized by myokymia and neuromyotonia, their predicted canine orthologs were first validated experimentally. They were found either incompletely or even incorrectly annotated, mainly due to gaps in the canine genomic sequence and insufficient transcript data. Canine KCNQ2 was found to contain 20 coding exons, of which three are not described in humans. It encodes for at least 14 different transcript variants in the frontal cortex of a single dog, of which only four are also described in humans. Mutation detection in Jack Russell Terriers diagnosed with peripheral nerve hyperexcitability revealed no pathogenetic relevant structural mutations. However, the four missense sequence variations and the 14 transcript variants of KCNQ2 will contribute to the study of the functional diversity of voltage-gated potassium channels.

Fetal acetylcholine receptor inactivation syndrome and maternal myasthenia gravis: A case report - Corrected Proof

2012-02-10

Abstract: Fetal acetylcholine receptor inactivation syndrome is a rare condition occurring in newborns of myasthenic mothers, characterized by bulbar and facial weakness after recovery from the generalized muscle weakness. Antibodies against fetal subunit of acetylcholine receptor seem to have a pathogenetic role leading to long-lasting injury in vulnerable muscle groups. We report a girl, born to a myasthenic mother, who presented with this peculiar phenotype associated with high titers of antibodies specific to the fetal acetylcholine receptor. Although the infant had partial clinical improvement she died prematurely of aspiration pneumonia. We believe that this is a rare but possibly unrecognized condition that should be considered in newborns with persistent myasthenic features even in asymptomatic mothers, and clinicians should consider supportive intervention to avoid fatal complications.

Paroxysmal neuromyotonia: A new sporadic channelopathy - Corrected Proof

2012-02-06

Abstract: Neuromyotonia is a heterogeneous group of genetic and autoimmune channelopathies resulting in hyperexcitability of peripheral nerves. We report an unusual case of neuromyotonia, which to our knowledge has not been previously described. The patient developed intermittent attacks of severe painful muscle stiffness accompanied by sweating, myokymia and raised serum creatine kinase. Genetic analysis of KCNA1, KCNQ2 and SCN4A genes did not identify pathogenic mutation. Serum voltage-gated potassium channel antibody was also negative. He was successfully treated with acetazolamide and carbamazepine. This appears to be a new neuromuscular disease, “paroxysmal neuromyotonia”, the etiology of which is still unknown.

Two common mutations (p.Gln832X and c.663+1G>C) account for about a third of the DYSF mutations in Korean patients with dysferlinopathy - Corrected Proof

2012-02-01

Abstract: Dysferlinopathy refers to autosomal recessive muscular dystrophies caused by mutations in dysferlin gene (DYSF). It includes two major distinct disorders, Miyoshi myopathy and limb-girdle muscular dystrophy type 2B. Twenty-three Korean patients were recruited. Full sequence analysis of DYSF detected 10 novel and 9 known mutations. The p.Gln832X showed the highest allele frequency (10/46) as a unique recurrent mutation among Korean population, and two common mutations (p.Gln832X and c.663+1G>C) accounted for 34.8% of the identified mutations. Korean DYSF mutations appeared to cluster in the N-terminal region. Notably, none of homozygous mutations was found in this study. Clinical features were similar to previous reports showing onset in early adulthood, high serum CK and inflammatory reactions on muscle pathology. In Miyoshi myopathy, gastrocnemius muscle was first affected on muscle CT scans, and anterior lower legs and thigh muscles were then affected with disease progression. Despite the genetic variety of DYSF mutations, clinical features were rather invariable among the patients.

Comparison of skeletal muscle pathology and motor function of dystrophin and utrophin deficient mouse strains - Corrected Proof

2012-01-30

Abstract: The genetic defect of mdx mice resembles that of Duchenne muscular dystrophy, although their functional performance and life expectancy is nearly normal. By contrast, mice lacking utrophin and dystrophin (mdx/utrn −/−) are severely affected and die prematurely. Mice with one utrophin allele (mdx/utrn +/−) are more severely affected than mdx mice, but outlive mdx/utrn −/− mice. We subjected mdx/utrn +/+, +/−, −/− and wild type males to a 12week functional test regime of four different functional tests. Mdx/utrn +/+ and +/− mice completed the regime, while mdx/utrn −/− mice died prematurely. Mdx/utrn +/− mice performed significantly worse compared to mdx/utrn +/+ mice in functional tests. Creatine kinase levels, percentage of fibrotic/necrotic tissue, morphology of neuromuscular synapses and expression of biomarker genes were comparable, whereas mdx/utrn +/− and −/− mice had increased levels of regenerating fibers. This makes mdx/utrn +/− mice valuable for testing the benefit of potential therapies on muscle function parameters.

Cerebral and muscle MRI abnormalities in myotonic dystrophy - Corrected Proof

2012-01-30

Abstract: Pathophysiological mechanisms underlying the clinically devastating CNS features of myotonic dystrophy (DM) remain more enigmatic and controversial than do the muscle abnormalities of this common form of muscular dystrophy. To better define CNS and cranial muscle changes in DM, we used quantitative volumetric and diffusion tensor MRI methods to measure cerebral and masticatory muscle differences between controls (n=5) and adults with either congenital (n=5) or adult onset (n=5) myotonic dystrophy type 1 and myotonic dystrophy type 2 (n=5). Muscle volumes were diminished in DM1 and strongly correlated with reduced white matter integrity and gray matter volume. Moreover, correlation of reduced fractional anisotropy (white matter integrity) and gray matter volume in both DM1 and DM2 suggests that these abnormalities may share a common underlying pathophysiological mechanism. Further quantitative temporal and spatial characterization of these features will help delineate developmental and progressive neurological components of DM, and help determine the causative molecular and cellular mechanisms.

When tubules aggregate - Corrected Proof

Hans H. Goebel — 2012-01-27

Within muscle fibres, tubules appear as microtubules, transverse tubules, and different components of the sarcotubular system, the latter consisting of longitudinal tubules and lateral or terminal sacs which, at special junctional connections, are situated on both sides of transverse tubules forming triads. Pathological structures related to the transverse tubules are honeycomb structures, both the transverse tubules and the honeycomb ones being labelled by extracellularly applied lanthanum or potassium ferrocyanide , thus, indicating an open connection between the interior of the muscle fibres and the extracellular space. Dyads or multiple incomplete or complete forms of triads, pentads or heptads, are pathological forms of triads. The pathological equivalent of the sarcotubular system is tubular aggregates. The derivation of tubular aggregates from the sarcotubular system can be established by electron microscopy showing continuity between tubular aggregates and the sarcotubular system where both border, and by immunohistochemical evidence of proteins that are common components of the sarcotubular system and tubular aggregates, i.e. SERCA (sarcoplasmic endoplasmic reticulum calcium ATPase) 1 and sarcalumenin in longitudinal tubules, calsequestrin in the terminal lateral sacs, and ryanodine receptor 1 and the 95 and 31kDa isoforms of triadin in the junctional parts of the sarcotubular system. Tubular aggregates are highly organised, often in a hexagonal fashion, the individual tubules of which are composed of cylindrically formed membranes. In addition, different components may be encountered within these single-walled tubules, multiple double-walled tubules, filaments, or an amorphous finely granular slightly electron-dense material. Based on these internal differences within the single-walled tubules, they may make up different tubular aggregates or appear mixed within different tubules of the tubular aggregates and have, hence, been differently subclassified as tubules I–III or up to five different forms . While the double-walled tubules seem to form the standard tubule of tubular aggregates for which the derivation from the sarcotubular system has been established by electron microscopy and immunohistochemistry, the morphogenesis and pathogenesis of the other subtypes are less well known.

Cardiac dysfunction and pathology in the dystrophin and utrophin-deficient mouse during development of dilated cardiomyopathy - Corrected Proof

Ju Lan Chun, Robert O’Brien, Suzanne E. Berry — 2012-01-24

Abstract: Cardiac involvement in Duchenne muscular dystrophy is asymptomatic until function is severely affected. Little is known about its evolution, and few animal models are available to study potential treatments. We therefore examined cardiac function and pathology in mdx/utrn−/− dystrophin/utrophin-deficient mice. Decreased left ventricular fractional shortening and ejection fraction, as well as increased end-diastolic volume, left ventricle dilation, and thinning of the ventricular wall and septum develop by 15weeks. Fibrosis is also detected in the outer region of both ventricle walls and the septum and ultrastructure analysis revealed abnormalities in mitochondrial organization, size, and shape. The functional changes observed are comparable to the evolution of dilated cardiomyopathy in Duchenne muscular dystrophy, indicating that mdx/utrn−/− dystrophin/utrophin-deficient mice are a possible phenotypic model for cardiomyopathy in Duchenne muscular dystrophy.

Cortical heterotopia in LGMD2I - Corrected Proof

Dimitri Renard, Carla Fernandez, Celine Bouchet-Seraphin, Pierre Labauge — 2012-01-24

A 40-year-old man, with a history of one generalized non-febrile seizure at the age of 4years, presented with slowly progressive proximal muscle weakness in the four limbs since the age of 12years and recent myalgia. Clinical examination confirmed that proximal symmetrical limb girdle weakness was predominant in the legs, together with bilateral moderate scapula alata and abdominal muscle weakness. Cognition was normal. CK level was 5400U/l. Transthoracic echocardiography showed a slightly dilated cardiomyopathy. A vital capacity of 70% of the expected value was seen on respiratory function tests. Deltoid muscle biopsy showed slight dystrophic changes, and immunohistochemical analysis revealed reduced staining for alpha-dystroglycan. Genetic analysis, performed in spite of normal alpha-dystroglycan muscle analysis on Western Blot, disclosed a homozygote C826A (Leu276Ileu) point mutation in the fukutin-related protein (FKRP) gene, which is the most frequent mutation found in limb girdle muscular dystrophy (LGMD) type 2I. In contrast to FKRP-related congenital muscular dystrophies, LGMD2I patients most often show normal cognition and absence of brain MRI abnormalities (although several cases with cognitive deficit and/or MRI changes have been reported) . Because of the history of seizure, a 3T brain MRI was performed, showing frontal subependymal lesions isointense to normal gray matter on all sequences consistent with cortical heterotopia, two frontal subcortical lesions isointense to normal gray matter on T1- and T2-weighted imaging and hyperintense on FLAIR sequences consistent with (sub)cortical dysplasia, and slight ventriculomegaly of the left lateral ventricle ().

Necklace fibers as histopathological marker in a patient with severe form of X-linked myotubular myopathy - Corrected Proof

2012-01-24

Abstract: X-linked myotubular myopathy due to mutations in the MTM1 gene is classically characterized by a severe neonatal phenotype and a typical muscle biopsy presenting globular and centrally located nuclei in muscle myofibers. Recently, four patients with mild late-onset form have been described, a male with a hemizygous mutation and three females with heterozygous mutations in the MTM1 gene. The muscle biopsies were performed at 13–35years of age and a new histological marker, the necklace fibers, was described. Here, we report two siblings with the pathogenic c.664 C>T mutation in the MTM1 gene, presenting a severe muscle weakness and respiratory impairment requiring ventilatory support since the first months of life until death, at the age of 36months and 5months. In the older brother the muscle biopsy, performed at the age of 30months, showed almost 100% of necklace fibers, which were not present in the younger one submitted to muscle biopsy at 5months of age. Our findings confirm the necklace fibers can be a histopathological finding of MTM1 myopathies, even in the severe neonatal form, and suggest that the necklace fibers appear or increase in number over time.

Exome sequencing identifies KIAA1377 and C5orf42 as susceptibility genes for monomelic amyotrophy - Corrected Proof

2012-01-20

Abstract: Precise topographic localization, predominance in males mostly of Asian origin, and existence of some familial cases suggest a genetic background for monomelic amyotrophy. To identify susceptibility genes for monomelic amyotrophy, we performed whole-exome sequencing of four unrelated patients with monomelic amyotrophy and detected a total of 45 novel nonsynonymous single-nucleotide polymorphisms as unique variants to monomelic amyotrophy compared to control exomes. Genetic association analysis showed significant association with monomelic amyotrophy in the Gly668Ser variant of the KIAA1377 gene (odds ratio=4.62, P-value=0.0040) and the Pro1794Leu variant of the C5orf42 gene (odds ratio=4.63, P-value=0.0040). Moreover, the combination of two variants increased the risk of monomelic amyotrophy (P=1.4×10−5, OR=61.69, 95% confidence interval=9.62–394.94, in case of combination of two heterozygotes). These data suggest that KIAA1377 and C5orf42 synergistically play a role as susceptibility genes for monomelic amyotrophy.

Rippling muscle disease and facioscapulohumeral dystrophy-like phenotype in a patient carrying a heterozygous CAV3 T78M mutation and a D4Z4 partial deletion: Further evidence for “double trouble” overlapping syndromes - Corrected Proof

2012-01-16

Abstract: We report the first case of a heterozygous T78M mutation in the caveolin-3 gene (CAV3) associated with rippling muscle disease and proximal myopathy. The patient displayed also bilateral winged scapula with limited abduction of upper arms and marked asymmetric atrophy of leg muscles shown by magnetic resonance imaging. Immunohistochemistry on the patient’s muscle biopsy demonstrated a reduction of caveolin-3 staining, compatible with the diagnosis of caveolinopathy. Interestingly, consistent with the possible diagnosis of FSHD, the patient carried a 35kb D4Z4 allele on chromosome 4q35. We discuss the hypothesis that the two genetic mutations may exert a synergistic effect in determining the phenotype observed in this patient.

182nd ENMC International Workshop: RYR1-related myopathies, 15–17th April 2011, Naarden, The Netherlands - Corrected Proof

Heinz Jungbluth, James J. Dowling, Ana Ferreiro, Francesco Muntoni — 2012-01-09

Twenty clinicians and basic scientists from 10 countries convened for the 182nd ENMC sponsored Workshop on RYR1-related myopathies from the 15th to the 17th of April 2011 in Naarden, The Netherlands. RYR1-related myopathies are a clinically and pathologically heterogeneous group of conditions caused by mutations in the skeletal muscle ryanodine receptor (RYR1) gene, encoding the principal sarcoplasmic reticulum (SR) Ca2+ release channel (RyR1) with a crucial role in excitation–contraction (E–C) coupling. Myopathies with RYR1 involvement have been the topic of several previous ENMC workshops, namely the ENMC workshops on Central Core Disease (CCD) in January 2001 , on Multi-minicore Disease (MmD) in May 2000 and November 2002 , and on the various core myopathies in March 2007 , resulting in numerous productive collaborations between the various participants.

186th ENMC International Workshop: Congenital myasthenic syndromes 24–26 June 2011, Naarden, The Netherlands - Corrected Proof

Amina Chaouch, David Beeson, Daniel Hantaï, Hanns Lochmüller — 2012-01-09

The ENMC hosted a group of 22 participants including parents, clinicians and scientists involved in the care or research of congenital myasthenic syndromes (CMS) patients. These represented different groups and centres from the United Kingdom, Germany, Spain, France, Bulgaria, Switzerland, and the United States. CMS are rare inherited disorders in which the safety margin of the neuromuscular transmission is compromised . Currently, full genetic testing for CMS is only available in 4 major centres (Rochester, Paris, Oxford, Munich) who have collectively diagnosed more than 1000 patients (). The objectives of the meeting were to provide an update on CMS both in the clinical and non-clinical domains and to promote more collaborative work.

Assessment of cardiac function in three mouse dystrophinopathies by magnetic resonance imaging - Corrected Proof

2012-01-03

Abstract: Lack of dystrophin results in skeletal muscle dystrophy and dilated cardiomyopathy in humans and animal models. To achieve a basic understanding of the natural development of cardiomyopathy in different dystrophinopathy mouse models, left and right ventricular heart function was assessed at different ages in three dystrophinopathy mouse models (mdx, mdx/utrn+/− model and mdx/utrn−/−) using magnetic resonance imaging. Left ventricular function was significantly decreased, already at 2months in the most severely affected mdx/utrn−/− mice. Furthermore, whereas heart function was stable in wild-type mice over time, both mdx and mdx/utrn+/− showed a clear decrease at 10months of age, most prominently in the right ventricle. Therefore magnetic resonance imaging is an adequate technique to determine heart function in dystrophinopathy mouse models and can be used to assess the effect of potential therapies.

N-Acetylcysteine treatment of dystrophic mdx mice results in protein thiol modifications and inhibition of exercise induced myofibre necrosis - Corrected Proof

Jessica R. Terrill, Hannah G. Radley-Crabb, Miranda D. Grounds, Peter G. Arthur — 2011-12-29

Abstract: Oxidative stress is implicated as a factor that increases necrosis of skeletal muscles in Duchenne Muscular Dystrophy (DMD) and the dystrophic mdx mouse. Consequently, drugs that minimize oxidative stress are potential treatments for muscular dystrophy. This study examined the in vivo benefits to mdx mice of an antioxidant treatment with the cysteine precursor N-acetylcysteine (NAC), administered in drinking water. NAC was completely effective in preventing treadmill exercise-induced myofibre necrosis (assessed histologically) and the increased blood creatine kinase levels (a measure of sarcolemma leakiness) following exercise were significantly lower in the NAC treated mice. While NAC had no effect on malondialdehyde level or protein carbonylation (two indicators of irreversible oxidative damage), treatment with NAC for one week significantly decreased the oxidation of glutathione and protein thiols, and enhanced muscle protein thiol content. These data provide in vivo evidence for protective benefits of NAC treatment on dystropathology, potentially via protein thiol modifications.

A missense mutation in the skeletal muscle chloride channel 1 (CLCN1) as candidate causal mutation for congenital myotonia in a New Forest pony - Corrected Proof

2011-12-26

Abstract: A 7-month-old New Forest foal presented for episodes of recumbency and stiffness with myotonic discharges on electromyography. The observed phenotype resembled congenital myotonia caused by CLCN1 mutations in goats and humans. Mutation of the CLCN1 gene was considered as possible cause and mutation analysis was performed. The affected foal was homozygous for a missense mutation (c.1775A>C, p.D592A) located in a well conserved domain of the CLCN1 gene. The mutation showed a recessive mode of inheritance within the reported pony family. Therefore, this CLCN1 polymorphism is considered to be a possible cause of congenital myotonia.

A Becker myotonia patient with compound heterozygosity for CLCN1 mutations and Prinzmetal angina pectoris - Corrected Proof

2011-12-26

Abstract: Becker myotonia is a recessive muscle disease with prevalence of >1:50,000. It is caused by markedly reduced function of the chloride channel encoded by CLCN1. We describe a Polish patient with severe myotonia, transient weakness, and muscle cramps who only responds to lidocaine. In addition, the patient has Prinzmetal angina pectoris and multiple lipomatosis. He is compound heterozygeous for a novel p.W303X and a frequent p.R894X CLCN1 mutation. CLCN1 exon number variation was excluded by MLPA. His son with latent myotonia was heterozygeous for p.R894X. We discuss the potential relations of the three rare diseases and the inheritance of p.R894X.

Acid phosphatase-positive globular inclusions is a good diagnostic marker for two patients with adult-onset Pompe disease lacking disease specific pathology - Corrected Proof

2011-12-23

Abstract: Diagnosis of adult-onset Pompe disease is sometimes challenging because of its clinical similarities to muscular dystrophy and the paucity of disease-specific vacuolated fibers in the skeletal muscle pathology. We describe two patients with adult-onset Pompe disease whose muscle pathology showed no typical vacuolated fibers but did show unique globular inclusions with acid phosphatase activity. The acid phosphatase-positive globular inclusions may be a useful diagnostic marker for adult-onset Pompe disease even when typical vacuolated fibers are absent.

Best practice guidelines on genetic diagnostics of Facioscapulohumeral muscular dystrophy: Workshop 9th June 2010, LUMC, Leiden, The Netherlands - Corrected Proof

2011-12-19

During the 171st European Neuromuscular Centre international workshop Standards of care and management of facioscapulohumeral muscular dystrophy (FSHD) in January 2010 , it was concluded that there was a need for further discussion to better define the “gold standard” for diagnostic procedures for FSHD. With the increasing complexity of the genetics of FSHD, it is important to reach an international consensus on the molecular testing methods. To this end, a meeting was held with 39 scientists from around the world at the Leiden University Medical Center on June 9, 2010 to establish consensus Best Practice Guidelines on Genetic Diagnosis of FSHD.

Multiple exon skipping strategies to by-pass dystrophin mutations - Corrected Proof

2011-12-19

Abstract: Manipulation of dystrophin pre-mRNA processing offers the potential to overcome mutations in the dystrophin gene that would otherwise lead to Duchenne muscular dystrophy. Dystrophin mutations will require the removal of one or more exons to restore the reading frame and in some cases, multiple exon skipping strategies exist to restore dystrophin expression. However, for some small intra-exonic mutations, a third strategy, not applicable to whole exon deletions, may be possible. The removal of only one frame-shifting exon flanking the mutation-carrying exon may restore the reading frame and allow synthesis of a functional dystrophin isoform, providing that no premature termination codons are encountered. For these mutations, the removal of only one exon offers a simpler, cheaper and more feasible alternative approach to the dual exon skipping that would otherwise be considered. We present strategies to by-pass intra-exonic dystrophin mutations that clearly demonstrate the importance of tailoring exon skipping strategies to specific patient mutations.

Tubular aggregates in skeletal muscle: Just a special type of protein aggregates? - Corrected Proof

Stefano Schiaffino — 2011-12-12

Abstract: Tubular aggregates are inclusions, usually found in type II muscle fibers and in males, consisting of regular arrays of tubules derived from the sarcoplasmic reticulum. Tubular aggregates are associated with a wide variety of muscle disorders, including poorly defined “tubular aggregate myopathies” characterized by weakness and/or myalgia and/or cramps, and are also present in different mouse models, including normal aging muscles. The mechanism(s) responsible for inducing the formation of these structures have not been identified, because of the slow time course of their development in vivo, several months in mice. However, identical structures are formed in a few hours in rat muscles kept in vitro in hypoxic medium. Here I suggest that tubular aggregates result from reshaping of sarcoplasmic reticulum caused by misfolding and aggregation of membrane proteins and thus represent a special type of “protein aggregates” due to altered proteostasis.

Focal myositis – A neurogenic phenomenon? - Corrected Proof

2011-12-12

Abstract: We report four cases of focal myositis. The patients, three men and one woman, had painful muscle hypertrophy, affecting four different sites. MRI confirmed the muscle enlargement and oedema. Electromyography revealed evidence of acute and chronic denervation in all four cases. Muscle biopsy was available in three and confirmed features suggestive of focal myositis. Based on our patient material, we suggest that chronic nerve irritation, such as compression, can lead to muscle hypertrophy which, when prolonged, provokes fibre necrosis and secondary inflammation. Our finding in four patients having hypertrophy involving four different sites, leads us further to suggest that this may be the common mechanism behind focal myositis.

X-linked myotubular myopathy due to a complex rearrangement involving a duplication of MTM1 exon 10 - Corrected Proof

2011-12-12

Abstract: X-linked myotubular myopathy is a predominantly severe congenital myopathy with central nuclei on muscle biopsy due to mutations in the MTM1 gene encoding myotubularin. We report a boy with typical features of X-linked myotubular myopathy. Sequencing of the MTM1 gene did not reveal any causative mutations. Subsequent MLPA analysis identified a duplication of MTM1 exon 10 both in the patient and his mother. Additional quantitative fluorescent PCR and long-range PCR revealed an additional large deletion (2536bp) within intron 10, 143bp downstream of exon 10, and confirmed the duplication of exon 10. Our findings suggest that complex rearrangements have to be considered in typically affected males with X-linked myotubular myopathy.

5th Annual Dysferlin Conference 11–14 July 2011, Chicago, Illinois, USA - Corrected Proof

2011-12-09

The fifth Annual Dysferlin Conference, sponsored and organized by the Jain Foundation, was held from July 11 to 14, 2011 in Chicago, Illinois. Participants included 34 speakers, 31 poster presenters, 14 dysferlinopathy patients and family members, 5 representatives from other muscular dystrophy foundations, and 12 members of the Jain Foundation team. The objective of the dysferlin conference is to discuss progress towards developing therapies for the dysferlinopathies, Limb Girdle Muscular Dystrophy 2B (LGMD2B) and Miyoshi Myopathy (MMD1). These diseases manifest progressive muscle loss, usually beginning in the late teenage years, and are caused by mutations in the gene encoding dysferlin. The dysferlin protein is required for effective repair of muscle fiber membranes, but little is known about how this defect leads to the muscle loss experienced by patients, or if dysferlin is involved in other cellular processes that contribute to the pathology. The meeting addressed these and other issues specific to dysferlin deficiency, including the best tools for studying dysferlin and possible causes and interventions for the disease. Four dysferlinopathy patients from the Jain Foundation’s patient registry also shared their experiences with this disease, including the risk of misdiagnosis with polymyositis and the damaging outcome of prednisone treatment.

Correlation between muscle involvement, phenotype and D4Z4 fragment size in facioscapulohumeral muscular dystrophy - Corrected Proof

2011-12-09

Abstract: This study aimed to evaluate muscle involvement pattern and correlate the lesions on muscle imaging with clinical features and D4Z4 fragment size in 24 patients with facioscapulohumeral muscular dystrophy (ESHD). The grading of the muscle image detected by computed tomography (CT) was based on a four-point semi-quantitative visual scale. On muscle CT, the most affected muscle was trapezium, followed by hamstrings. CT image identified hamstrings involvement rather than shoulder-girdle in clinically asymptomatic subjects. CT image also showed that axial muscle was affected in one-third of patients which appeared even earlier than clinical manifestation. Strong correlations between CT findings, serum creatine kinase level and clinical severity scores were also found. Asymmetric involvement was more evident on CT image than it identified in manual muscle strength testing. Inverse correlation between CT grade and D4Z4 fragment size was clearly demonstrated. These findings suggest muscle CT will be helpful for the process of early intervention in FSHD, even in subjects in a preclinical status.

Density, calibre and ramification of muscle capillaries are altered in a mouse model of severe spinal muscular atrophy - Corrected Proof

E. Somers, Z. Stencel, T.M. Wishart, T.H. Gillingwater, S.H. Parson — 2011-12-09

Abstract: Spinal muscular atrophy (SMA) is traditionally described and characterised as a disease of the neuromuscular system. Recently, the vascular system has been implicated in SMA pathogenesis, but there are no reports on whether this impacts on skeletal muscle microvasculature. Using an established mouse model of severe SMA (Smn−/−;SMN2+/+), we examined the capillary bed in three different skeletal muscles using quantitative imaging and western blotting in late symptomatic mice (P5). We found a dramatic (45%) decrease in the density of the capillary bed in all muscles examined compared to littermate controls at early and late symptomatic time points, and reduced expression of a key endothelial protein, PECAM-1. In addition, capillary calibre was increased by 50% in SMA mice while ramification of capillaries into muscle was reduced. Investigation of earlier developmental time points revealed identical changes at an early symptomatic time point (P3), but significantly, no difference at a pre-symptomatic time point (P1). These changes are likely to have considerable impact on the ability of the muscle capillary bed to deliver oxygen and remove metabolites from muscle and may therefore contribute to pathogenesis in SMA.

High cardiovascular morbidity and mortality in myofibrillar myopathies due to DES gene mutations: a 10-year longitudinal study - Corrected Proof

2011-12-07

Abstract: To determine incidence and type of major cardiac adverse events in patients with mutated desmin (DES) gene, we retrospectively reviewed baseline medical information, and examined the long-term outcomes of 28 DES patients (17 men, baseline mean age=37.7±14.4years [min=9, max=71]) from 19 families. Baseline studies revealed skeletal muscle involvement in 21 patients and cardiac abnormalities in all but one patient. Over a mean follow-up of 10.4±9.4years [min=1, max=35], cardiac death occurred in three patients, death due to cardiac comorbidities in two, one or more major cardiac adverse events in 13 patients. Among the 19 patients with mild conduction defects at baseline, eight developed high-degree conduction blocks requiring permanent pacing. Cardiac involvement was neither correlated with the type of DES mutation nor with the severity of skeletal muscle involvement. Our study underscores that in DES patients in-depth cardiac investigations are needed to prevent cardiac conduction system disease.

Sleep breathing disorders in 40 Italian patients with Myotonic dystrophy type 1 - Corrected Proof

2011-12-05

Abstract: The aim of this study was to estimate the prevalence and nature of sleep breathing disorders in Myotonic dystrophy type 1 (DM1). We wanted to determine whether there is a relationship between sleep breathing disorders and clinical parameters such as pulmonary function, degree of neuromuscular impairment, daytime sleepiness, and fatigue. This will help assess the prevalence of DM1 patients requiring nocturnal ventilatory treatments. We studied a random sample of 40 unrelated patients and found that 22/40 patients had obstructive sleep apnoea. Of these 22 patients, five showed also periodic breathing and four showed sleep hypoventilation. Nine patients were put on nocturnal ventilation following clinical and instrumental evaluations. Our study reveals that obstructive sleep apnoea is very common in these patients, but cannot be predicted on the basis of clinical–neurological features and diurnal functional respiratory tests. Our data emphasize that a periodical evaluation by polysomnography should be mandatory to ascertain, and treat if necessary, the presence of obstructive sleep apnoea, periodic breathing or nocturnal hypoventilation.

Quantitative muscle ultrasound is a promising longitudinal follow-up tool in Duchenne muscular dystrophy - Corrected Proof

2011-12-02

Abstract: Responsive outcome measures are needed to follow the disease status of Duchenne muscular dystrophy (DMD) patients, as new therapeutic approaches become available for affected boys. Quantitative muscle ultrasound (QMUS) is potentially an attractive follow up tool for DMD because it reflects the severity of the dystrophic process without the need for invasive procedures, by quantifying echo intensity (i.e. mean grey level of muscle images) and muscle thickness. We performed a longitudinal follow-up of lower and upper extremity QMUS in 18 DMD patients and compared this with physical functioning in 11 of these patients. QMUS could be performed in every patient, and no patient was subjected to more than a total of 20min of ultrasound scanning time for this study. As expected we found a significant increase of echo intensity with age, reflecting increasing dystrophic muscle changes. This increase was related to ambulatory status, functional grading, muscle strength and motor ability. Our study establishes QMUS as a practical and child-friendly tool for the longitudinal follow up of DMD patients.

Clinical features and new molecular findings in muscle phosphofructokinase deficiency (GSD type VII) - Corrected Proof

2011-12-02

Abstract: Muscle phosphofructokinase (PFKM) deficiency, a rare disorder of glycogen metabolism also known as glycogen storage disease type VII (GSDVII), is characterized by exercise intolerance, myalgias, cramps and episodic myoglobinuria associated with compensated hemolytic anaemia and hyperuricemia. We studied five patients with PFKM deficiency coming from different Italian regions. All probands showed exercise intolerance, hyperCKemia, cramps and myoglobinuria. One patient had a mild hypertrophic cardiomyopathy. Biochemical studies revealed residual PFK activity ranging from 1 to 5%. Molecular genetic analysis identified four novel mutations in the PFKM gene. In our series of patients, clinical and laboratory features were similar in all but one patient, who had an unusual phenotype characterized by 25years disease history, high CK levels, hypertrophic cardiomyopathy with paroxysmal atrial fibrillation without fixed muscle weakness.

185th ENMC International Workshop: Stem/precursor cells as a therapeutic strategy for muscular dystrophies 3–5 June 2011, Naarden, The Netherlands - Corrected Proof

Ketan Patel, Jennifer Morgan — 2011-11-30

The 185th ENMC Workshop on stem/precursor cells as a therapeutic strategy for muscular dystrophies was held at Naarden, The Netherlands, on 3–5 June 2011. Sixteen participants from seven countries (United Kingdom, The Netherlands, France, Germany, Italy, Spain and Singapore) with expertise in satellite cells, muscle stem cells, muscle development, muscular dystrophies, clinical trials and patients’ perspectives, attended.

Myasthenic tongue - Corrected Proof

Vasiliki Zouvelou, Michael Rentzos, Panagiotis Toulas, Ioannis Evdokimidis — 2011-11-28

In September 2010, a 55year-old male patient presented with fixed severe facial weakness, nasal speech, dysarthria and marked tongue atrophy with central furrowing, but good muscle bulk of the lateral tongue margins (A). There was no ocular, axial, limb or respiratory involvement. The bulbar deficits were fixed for many years and the present referral was not due to clinical deterioration. In 1969, at the age of 14 he received the diagnosis of juvenile generalized myasthenia gravis with ocular, bulbar and limb muscle involvement. He was treated with pyridostigmine (180mg qd) and prednisolone (20mg qd) for 11years with clinical improvement, concerning the ocular and limb muscle manifestations. For the last 30years he remained clinically stable and free of medication. Thymectomy was never performed. During the whole disease course there was no episode of myasthenic crisis or requirement for short-term immunotherapy (plasma exchange or intravenous immunoglobulin). At the present evaluation, repetitive nerve stimulation of nasalis, quadratus labii inferioris and trapezius muscles and single-fiber electromyography of orbicularis oris, were positive for myasthenia. Serum acetylcholine receptor antibodies were positive with a titer of 312nM (normal range<0.2nM). Serum anti-titin and anti-MuSK antibodies were negative. CT of the mediastinum was normal. MRI of the tongue demonstrated deep midline furrow and almost total fatty replacement of the tongue with predominant involvement of the intrinsic muscles (B–D).

A rapid immunohistochemical test to distinguish congenital myotonic dystrophy from X-linked myotubular myopathy - Corrected Proof

Caroline A. Sewry, Ros C.M. Quinlivan, Waney Squier, Glenn E. Morris, Ian Holt — 2011-11-23

Abstract: Severe forms of myotubular myopathy (MTM) and congenital myotonic dystrophy type 1 (CDM), both present as floppy infants with hypotonia, respiratory failure and bulbar insufficiency. Muscle biopsy is often performed as part of the diagnostic process, but these two disorders share very similar histopathological features. It is well documented that CDM muscle has nuclear foci that contain muscleblind-like 1 (MBNL1) protein. In muscle biopsies from eight neonates showing central nuclei, MBNL1 immunolocalisation identified discrete, intensely stained foci in three cases that were subsequently confirmed as CDM by DNA analysis. In the five remaining non-CDM patients and two controls, MBNL1 staining was heterogeneous in nuclei, not as foci. MBNL1 staining patterns in CDM were easily distinguishable from MTM. We suggest that in cases of hypotonia with suspected CDM or MTM, when biopsy has been taken, sections should additionally be stained for MBNL1 to provide a rapid indication of a CDM diagnosis.

Myopathy in a woman and her daughter associated with a novel splice site MTM1 mutation - Corrected Proof

2011-11-21

Abstract: We have investigated a woman and her daughter with an early onset, slowly progressive myopathy. Muscle biopsy showed in both cases severe atrophy with marked fatty replacement. Frequent fibers with internalized nuclei were present but no typical features of centronuclear myopathy. There were also many fibers with deep invaginations of the plasma membrane. The presence of necklace fibers provided clue to correct genetic diagnosis. Both patients had a novel heterozygous splice site mutation in the myotubularin gene, MTM1 (c.867+1G>T). Analysis of MTM1 cDNA revealed that the mutation resulted in aberrant splicing with variable exon skipping. The expression of normal transcripts was markedly reduced and there was reduced expression of myotubularin protein. Although the expression of the allele without the mutation was reduced we did not obtain evidence of skewed X-chromosome inactivation. Other factors than skewed X-inactivation may cause allele inactivation and manifestation of severe myopathy in heterozygous carriers of pathogenic MTM1 mutations.

Screening for mutations in Spanish families with myotonia. Functional analysis of novel mutations in CLCN1 gene - Corrected Proof

2011-11-17

Abstract: Myotonia congenita is an inherited muscle disorder caused by mutations in the CLCN1 gene, a voltage-gated chloride channel of skeletal muscle. We have studied 48 families with myotonia, 32 out of them carrying mutations in CLCN1 gene and eight carry mutations in SCN4A gene. We have found 26 different mutations in CLCN1 gene, including 13 not reported previously. Among those 26 mutations, c.180+3A>T in intron 1 is present in nearly one half of the Spanish families in this series, the largest one analyzed in Spain so far. Although scarce data have been published on the frequency of mutation c.180+3A>T in other populations, our data suggest that this mutation is more frequent in Spain than in other European populations. In addition, expression in HEK293 cells of the new missense mutants Tyr137Asp, Gly230Val, Gly233Val, Tyr302His, Gly416Glu, Arg421Cys, Asn567Lys and Gln788Pro, demonstrated that these DNA variants are disease-causing mutations that abrogate chloride currents.

Long-term follow-up of patients with congenital myasthenic syndrome caused by COLQ mutations - Corrected Proof

2011-11-16

Abstract: Congenital myasthenic syndromes (CMS) are clinically and genetically heterogeneous inherited disorders characterized by impaired neuromuscular transmission. Mutations in the acetylcholinesterase (AChE) collagen-like tail subunit gene (COlQ) cause recessive forms of synaptic CMS with end plate AChE deficiency. We present data on 15 COLQ -mutant CMS carrying 16 different mutations (9 novel ones identified) followed-up for an average period of 10years. The mean age at the first examination was 19years old (range from 3 to 48). We report relapses during short or long-term periods characterized by worsening of muscle weakness sometimes associated with respiratory crises. All the relapses ended spontaneously or with 3–4 DAP or ephedrine with no residual impairment. The triggering factors identified were esterase inhibitors, effort, puberty or pregnancy highlighting the importance of hormonal factors. There was no genotype–phenotype correlation. At the end of the follow-up, 80% of patients were ambulant and 87% of patients had no respiratory trouble in spite of severe relapses.

SETX gene mutation in a family diagnosed autosomal dominant proximal spinal muscular atrophy - Corrected Proof

Sabine Rudnik-Schöneborn, Larissa Arning, Jörg T. Epplen, Klaus Zerres — 2011-11-16

Abstract: Autosomal dominant proximal spinal muscular atrophy (ADSMA) is a rare disorder with unknown gene defects in the majority of families. Here we describe a family where the diagnosis of juvenile and adult onset ADSMA was made in three individuals. Because of retained tendon reflexes an atypical course of juvenile amyotrophic lateral sclerosis (ALS4) was considered. SETX gene sequencing revealed the previously reported heterozygous missense mutation c.1166T

Three cases of myasthenia gravis from one family with variations in clinical features and serum antibodies - Corrected Proof

Yuping Chen, Wei Wang, Dongning Wei, Li Yang — 2011-11-15

Abstract: Myasthenia gravis, an autoimmune disorder affecting neuromuscular transmission, is mainly sporadic while familial cases are very rare. Usually familial myasthenia gravis cases have uniform clinical symptoms as well as serum anti-acetylcholine receptor antibodies. Interestingly, in our cases varying clinical types of myasthenia gravis and seropositive/seronegative anti-acetylcholine receptor antibodies coexisted in the same family. The mother and her daughter both had ocular myasthenia gravis, detectable anti-acetylcholine receptor antibodies and non-detectable anti-muscle-specific kinase antibodies, and good responses to medications. The son displayed ocular symptoms at the onset, and then progressed into a generalized form after 1year. His serum anti-acetylcholine receptor antibodies and anti-muscle-specific kinase antibodies were both negative. Neither corticosteroids nor thymectomy alleviated his symptoms. Human leukocyte antigen DQA1*0301 allele sharing by the three patients may be involved in their genetic susceptibility to myasthenia gravis, and subtle differences in human leukocyte antigen DQB1 alleles may be associated with their variations in clinical features and serum antibodies.

Transgenic inactivation of murine myostatin does not decrease the severity of disease in a model of Spinal Muscular Atrophy - Corrected Proof

2011-11-14

Abstract: Spinal Muscular Atrophy (SMA) is a devastating neurodegenerative disease and is a leading genetic cause of infantile death. SMA is caused by the homozygous loss of Survival Motor Neuron-1 (SMN1). The presence of a nearly identical copy gene called SMN2 has led to the development of several strategies that are designed to elevate SMN levels, and it is clear that SMN2 is an important modifier gene. However, the possibility exists that SMN-independent strategies to lessen the severity of the SMA phenotype could provide insight into disease development as well as aid in the identification of potential therapeutic targets. Muscle enhancement has been considered an interesting target for a variety of neurodegenerative diseases, including SMA. Previously we have shown in SMA mice that delivery of recombinant follistatin resulted in an extension in survival and a general lessening of disease severity. Follistatin is known to functionally block myostatin (MSTN), a potent inhibitor of muscle development. However, follistatin is a multifaceted protein involved in a variety of cellular pathways. To determine whether MSTN inhibition was the primary pathway associated with the previously reported follistatin results, we generated an animal model of SMA in which Mstn was genetically inactivated. In this report we characterize the novel SMA/Mstn model and demonstrate that Mstn inactivation does not significantly enhance muscle development in neonatal animals, nor does it result in an amelioration of the SMA phenotype.

Blood glutathione decrease in subjects carrying lamin A/C gene mutations is an early marker of cardiac involvement - Corrected Proof

2011-11-09

Abstract: Dominant inherited Emery-Dreifuss muscular dystrophy and limb-girdle muscular dystrophy type 1B are due to mutations in the LMNA gene encoding lamin A/C and present similar life-threatening cardiac disease, the early diagnosis of which lacks reliable biomarkers. Glutathione depletion characterizes subjects with cardiac diseases of non-genetic aetiology. We examined blood glutathione in 22 LMNA-mutated subjects without altered left ventricular ejection fraction (LVEF>40%) measured by conventional echocardiography. Left and right ventricular (LV/RV) contractility was evaluated using echocardiography implemented with tissue-Doppler echography. Blood glutathione was positively correlated with LV and RV contractility (p<0.05), and was decreased by 23% in subjects with reduced LV/RV contractility compared to subjects with normal contractility. ROC analysis showed that blood glutathione reliably detected reduced LV/RV contractility (AUC-95% CI: 0.90 [0.76–1.04]; p=0.01). Blood glutathione decrease may allow the detection of reduced contractility in muscular dystrophic LMNA-mutated patients with still preserved LVEF.

A critical Smn threshold in mice dictates onset of an intermediate spinal muscular atrophy phenotype associated with a distinct neuromuscular junction pathology - Corrected Proof

2011-11-09

Abstract: Spinal muscular atrophy (SMA) is caused by mutations/deletions within the SMN1 gene and characterized by loss of lower motor neurons and skeletal muscle atrophy. SMA is clinically heterogeneous, with disease ranging from severe to mild. Here, we identify a critical threshold of Smn that dictates onset of SMA in the intermediate Smn2B/− mouse model. With about 15% normal level of Smn protein, Smn2B/− mice display reduced body weight, motor neuron loss and motor defects. Importantly, these mice are phenotype-free until P10 with a median life expectancy of 28days. They show neuromuscular junction (NMJ) pathology with an inter-muscular differential vulnerability and an association between pre- and post-synaptic defects. Our work suggests that increasing Smn protein levels only minimally could be of significant benefit since Smn2B/2B mice are phenotypically normal. Further, the finding that NMJ pathology varies between severe and intermediate SMA mouse models, suggests that future therapies be adapted to the severity of SMA.