Large variations in the proportion of intragenic deletion in the dystrophin gene have been observed in different populations. Although dystrophin gene deletion was extensively studied all over the world, only few studies were done on Egyptian population and there was no account on the dystrophin gene duplication. In this study, we present our results on the pattern of deletion of the dystrophin gene together with the usage of quantitative polymerase chain reaction (PCR) as a method for duplication analysis within the dystrophin gene in Egyptian patients. Forty one Duchene/Becker muscular dystrophy patients were included in this study. The diagnosis was based on detailed clinical assessment, serum creatine kinase (CK) level, neurophysiologic study and muscle biopsy for histopathological analysis. DNA was extracted from ten milliliter peripheral blood according to basic protocol, and multiplex polymerase chain reaction for dystrophin gene using both Chamberlin and Beggs sets of primers amplifying eighteen exons covering the two main dystrophin gene hot spots. In addition primers from Abbs set were used when it was necessary to check the exon borders. DNA from cases with no detectable deletion was analyzed for dystrophin gene duplication using quantitative PCR technique. We had a percentage of 61.1% deletion which is higher than data from previous Egyptian studies and most of the deletion was localized in the major hotspot region between exons 44 and 52 and we had 5% of the cases with duplication. Our results were compared with previous studies from Egypt and with studies from different populations especially with data recorded in the Middle East and North Africa.
Duchenne muscular dystrophy; multiplex PCR; quantitative PCR
Cells with myogenic potential are present in many tissues, and these cells readily form skeletal muscle in culture. We here focus on menstrual blood as another cell source for regenerative medicine. Menstrual blood-derived cells have high replicative ability, similar to progenitors or stem cells, and transdifferentiate or meta-differentiate into myocytes in vitro at unexpectedly high frequencies. This unique phenotype can be explained by histological and embryological aspects of the endometrium. The remarkable myogenic capability of these cells enables us to “rescue” dystrophied myocytes of the mdx model of Duchenne muscular dystrophy through cell fusion and transdifferentiation. Endometrial cells supplied as a form of menstrual blood-tissue mixture can be used for cell-based therapy in addition to a place for embryo implantation.
menstrual blood; mesenchymal stem cell; regenerative medicine
Cancer cachexia has a significant negative effect on quality of life, survival and the response to treatment. Recent in vitro and experimental animal studies have shown that myosin may be the primary target of the muscle wasting associated with cancer cachexia. In this study, we have extended these analyses to detailed studies of regulation of myofibrillar protein synthesis at the gene level, myofibrillar protein expression and regulation of muscle contraction at the muscle cell level in a 63-year old man with a newly diagnosed small cell lung cancer and a rapidly progressing lower extremity muscle wasting and paralysis. A significant preferential loss of the motor protein myosin together with a downregulation of protein synthesis at the transcriptional level was observed in the patient with cancer cachexia. This had a significant negative impact on muscle fiber size as well as maximum force normalized to muscle fiber cross-sectional area (specific tension).
Myosin; MuRF1; MAFBx; force generation capacity; skinned muscle fibers
Muscular dystrophies are a clinically and genetically heterogeneous group of disorders. Until recently most of the proteins associated with muscular dystrophies were believed to be proteins of the sarcolemma associated with reinforcing the plasma membrane or in facilitating its re-sealing following injury. In the last few years a novel and frequent pathogenic mechanism has been identified that involves the abnormal glycosylation of alpha-dystroglycan (ADG). This peripheral membrane protein undergoes complex and crucial glycosylation steps that enable it to interact with LG domain containing extracellular matrix proteins such as laminins, agrin and perlecan.
Mutations in six genes (POMT1, POMT2, POMGnT1, fukutin, FKRP and LARGE) have been identified in patients with reduced glycosylation of ADG. While initially a clear correlation between gene defect and phenotype was observed for each of these 6 genes (for example, Walker Warburg syndrome was associated with mutations in POMT1 and POMT2, Fukuyama congenital muscular dystrophy associated with fukutin mutations, and Muscle Eye Brain disease associated with POMGnT1 mutations), we have recently demonstrated that allelic mutations in each of these 6 genes can result in a much wider spectrum of clinical conditions. Thus, the crucial aspect in determining the phenotypic severity is not which gene is primarily mutated, but how severely the mutation affects the glycosylation of ADG.
Systematic mutation analysis of these 6 glycosyltransferases in patients with a dystroglycan glycosylation disorder identifies mutations in approximately 65% suggesting that more genes have yet to be identified.
Muscular dystrophy; glycoslyation; alpha dystroglycan; neuronal migration; glycosyltransferases
Idiopathic cardiomyopathy (ICM) is a primary cardiac disorder associated with abnormalities of ventricular wall thickness, size of ventricular cavity, contraction, relaxation, conduction and rhythm. Over the past two decades, molecular genetic analyses have revealed that mutations in the various genes cause ICM and such information concerning the genetic basis of ICM enables us to speculate the pathogenesis of this heterogeous cardiac disease. This review focuses on the molecular pathogenesis, i.e., genetic abnormalities and functional alterations due to the mutations especially in sarcomere/cytoskeletal components, in three characteristic features of ICM, hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM) and restrictive cardiomyopathy (RCM). Understanding the functional abnormalities of the sarcomere/cytoskeletal components, in ICM, has unraveled the function of these components not only as a contractile unit but also as a pivot for transduction of biochemical signals.
Idiopathic cardiomyopathy (ICM); mutation; cytoskeletal proteins
Glycosylation is the most common post-translational modification of proteins. The protein sequence data suggested that more than half of all proteins produced in mammalian cells are glycoproteins. Glycans of secreted glycoproteins affect many protein properties such as solubility, stability, protease sensitivity, and polarity, while glycans on cell surface glycoproteins are involved in various cellular functions including cell-cell and cell-matrix interactions during embryogenesis, immune reactions, and tumor development. The past decade of research on glycan function has revealed the etiology of a growing number of human genetic diseases with aberrant glycan formation. This review focuses upon the involvement of O-mannosylglycan in the molecular and cellular mechanisms of muscular dystrophies. Advances in glycobiology are expected to result in a better understanding and in improved treatments of a class of muscular dystrophies called α-dystroglycanopathies.
dystroglycan; O-mannosyl glycan; glycosyltransferase; muscular dystrophy
Distal myopathy with rimmed vacuoles (DMRV) or hereditary inclusion body myopathy (hIBM) is an adult onset slowly progressive myopathy secondary to mutations in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene that encodes a bifunctional enzyme which catalyzes the rate-limiting step in sialic acid biosynthesis. Many hypotheses have been proposed to explain why patients develop weakness and atrophy, but are most views are obscure and thus are still considered controversial, partly because of the lack of an appropriate model with which these theories could be clarified. In this review, we briefly summarize the progress in DMRV research, and highlight efforts of researchers in generating the animal model for this myopathy.
Amyloid; autophagy; muscular dystrophy
Mutations in the genes for nuclear envelope proteins of emerin (EMD) and lamin A/C (LMNA) are known to cause Emery-Dreifuss muscular dystrophy (EDMD) and limb girdle muscular dystrophy (LGMD). We compared clinical features of the muscular dystrophy patients associated with mutations in EMD (emerinopathy) and LMNA (laminopathy) in our series. The incidence of laminopathy was slightly higher than that of emerinopathy. The age at onset of the disease in emerinopathy was variable and significantly older than in laminopathy. The initial symptom of emerinopathy was also variable, whereas nearly all laminopathy patients presented initially with muscle weakness. Calf hypertrophy was often seen in laminopathy, underscoring the importance of mutation screening for LMNA in childhood muscular dystrophy with calf hypertrophy. The clinical spectrum of emerinopathy is actually wider than previously known including EDMD, LGMD, conduction defects with minimal muscle/joint involvement, and their intermittent forms. Pathologically, no marked difference was observed between emerinopathy and laminopathy. Increased number and variation in size of myonuclei were detected. More precise observations using electron microscopy is warranted to characterize the detailed nuclear changes in nuclear envelopathy.
Emerin; lamin A/C; muscular dystrophy
Myasthenia gravis (MG) is caused by the failure of neuromuscular transmission mediated by autoantibodies. That is, the binding of autoantibodies to postsynaptic membranes in neuromuscular junctions (NMJ) results in weakening of the ocular, bulbar and limb muscles and produces the characteristic syndrome of MG. This relatively rare disease serves as a model not only for study of the pathogenesis and treatment of all autoimmune disorders but also for understanding the basic mechanisms of neuromuscular transmission at the NMJ. About 80 to 85% of patients with MG have autoantibodies against acetylcholine receptors (AChR). Although a number of studies have shown the possible existence of other autoantibodies in the remaining ~20% of MG patients, the responsible autoantigens have remained elusive. However, antibodies against muscle-specific kinase (MuSK) have been found in 30% of MG patients without AChR antibodies. MuSK, a tyrosine kinase receptor, is required for the development of NMJ’s postsynaptic membranes. Still, the pathogenicity of MuSK antibodies as a cause of muscle weakness in patients with MG remains a matter of dispute, because the experimental autoimmune MG caused by MuSK antibodies in animals was absent. Here we describe recent progress toward understanding the pathogenic role of MuSK antibodies in the decline of muscle strength that typifies MG.
myasthenia gravis; experimental autoimmune MG; muscle-specific kinase
Exon skipping is one of the more promising therapeutic options for Duchenne Muscular Dystrophy (DMD). The idea is to use antisense oligonucleotides to splice out selected exons from the pre-mRNA, at or next to the mutation site, so as to generate a translatable transcript from the mutant dystrophin gene. In principle, the majority of DMD mutations can be rescued by targeting selected exons. Recent developments of antisense oligonucleotides (AOs) such as 2`O-methylated antisense oligonucleotides (2OMeAOs) or phosphorodiamidate morpholino oligomers (morpholinos, PMOs) have made it possible to restore dystrophin expression body-wide in dystrophic mice and dystrophic dogs by single or multi-exon skipping with no obvious side-effect. Since such treatment would, in many cases, require bespoke design of AOs, it is important to demonstrate treatment of a variety of mutations in dystrophic animals. In-frame deletion patterns usually result in a mix of Duchenne and milder Becker Muscular Dystrophy (BMD), but the ratio of Duchenne to Becker varies between patterns, and this provides useful information for selection of the exons that might most profitably be targeted. This review summarizes recent progress in exon skipping therapy and discusses future strategies.
Duchenne/Becker muscular dystrophy; dystrophin; revertant fibers; morpholinos
The purpose of the present study was to evaluate cardiac autonomic nervous system (ANS) in patients with myotonic dystrophy type 1 (DM1). The function of ANS was studied in 20 patients with DM1 and 15 healthy controls. All subjects were investigated by a battery of six cardiovascular autonomic tests and power spectral analysis of heart rate variability (HRV). Only one patient had normal autonomic function. Two (10%) patients had mild, 10 (50%) moderate and 7 (35%) severe autonomic dysfunction. Thirteen (65%) patients had vagal and 4 (20%) sympathetic hyperactivity. Seven (35%) patients had vagal and 15 (75%) sympathetic dysfunction. Eighteen (90%) patients had orthostatic hypotension. The 24-hour time domain parameters of SDNN (SD of the NN interval) and total power were significantly lower in DM1 patients than in healthy controls (p < 0.05). However, other parameters of HRV, such as SDANN (SD of the mean NN, 5-minute interval), low frequency (LF), high frequency (HF) power and the LF/HF ratio were somewhat lower in patients with DM1 than in controls, but this was not statistically significant. There was no significant relationship between autonomic dysfunction and the severity of the disease or CTG repeat length. There was also no correlation between HRV and age. Our findings suggest that sympathetic dysfunction and vagal predominance may both occur in patients with DM1.
Myotonic dystrophy; autonomic nervous system; heart rate variability
Phosphofructokinase deficiency (Tarui disease) was the first disorder recognized to directly affect glycolysis. Since the discovery of the disease, in 1965, a wide range of biochemical, physiological and molecular studies have greatly contributed to our knowledge concerning not only phosphofructokinase function in normal muscle but also on the general control of glycolysis and glycogen metabolism. Studies on phosphofructokinase deficiency vastly enriched the field of glycogen storage diseases, making a relevant improvement also in the molecular genetic area. So far, more than one hundred patients have been described with prominent clinical symptoms characterized by muscle cramps, exercise intolerance, rhabdomyolysis and myo-globinuria, often associated with haemolytic anaemia and hyperuricaemia. The muscle phosphofructokinase gene is located on chromosome 12 and about 20 mutations have been described. Other glycogenoses have been recognised in the distal part of the glycolytic pathway: these are infrequent but some may induce muscle cramps, exercise intolerance and rhabdomyolysis. Phosphoglycerate Kinase, Phosphoglycerate Mutase, Lactate Dehydrogenase, β-Enolase and Aldolase A deficiencies have been described as distal glycogenoses. From the molecular point of view, the majority of these enzyme deficiencies are sustained by “private” mutations.
Phosphofructokinase deficiency; Tarui disease; Glycogen Storage Disease VII or GSD VII
This paper is a part of an introduction to authors’ study on systemic laminopathies and their role in human aging. Of special interest is progeria – a type of systemic laminopathy associated usually with mutation 1824 C > T and presenting phenotype of preliminary aging. The authors analyse the differences between the progeria and other syndrome of preliminary aging – Werner’s syndrome.
Aging; progeria; laminopathies; Werner’s syndrome
Charcot-Marie-Tooth type 4C4 disease (CMT4C4) is an early onset, autosomal recessive neuropathy with hoarseness caused by mutations in the GDAP1 gene which maps to the 8q13 region. To date, only 24 mutations in the GDAP1 gene have been reported. Neuropathological findings of sural nerve biopsies have been published for a limited number of CMT4C4 patients. Herein, a novel Pro153Leu mutation in the GDAP1 gene identified in a consanguineous Polish family is described and longitudinal clinical and electrophysiological studies as well as morphological findings are presented.
CMT; GDAP1 gene; genotype–phenotype correlations
Immunohistochemical and DNA results are described in a patient with sarcoglycanopathy. Immunostaining was comparatively normal for α-, attenuated for β- and δ-, and markedly attenuated for γ-sarcoglycan, thus sarcoglycanopathy was diagnosed, presumably a γ-sarcoglycanopathy. Unexpectedly, two α-SGP-related pathogenic mutations were identified in compound heterozygosity in the SGCA gene: c.229C > T (p.Arg77Cys) in exon 3 and c.850C > T (p.Arg284Cys) in exon 7. These are discussed together with six additional changes detected in SGCB, SGCG and SGCD.
Sarcoglycanopathy; α–sarcoglycan deficiency; γ–sarcoglycan deficiency
Deficiency of glycogen branching enzyme is causative of Glycogen Storage Disease type IV (GSD-IV), a rare autosomal recessive disorder of the glycogen synthesis, characterized by the accumulation of amylopectin-like polysaccharide, also known as polyglucosan, in almost all tissues. Its clinical presentation is variable and involves the liver or the neuromuscular system and different mutations in the GBE1 gene, located on chromosome 3, have been identified in both phenotypes. This review will addresses the neuromuscular clinical variants, focusing on the molecular genetics aspects of this disorder.
Glycogen storage disease; branching enzyme; GBE1 gene; metabolic myopathy
A systematic review of evidence for randomised controlled trials using pharmacologic and nutritional therapies in McArdle disease was undertaken. Primary outcome measures included any objective assessment of exercise endurance. Secondary outcome measures included changes in metabolic parameters, subjective measures such as quality of life scores and adverse outcomes. Ten randomised controlled trials were identified. Two trials low dose creatine (60 mg/kg/day) and oral sucrose 75 g prior to exercise demonstrated a positive effect.
McArdle disease; trials
Glycogen storage disease type II has a broad continuous clinical spectrum in terms of onset, involvement of organs and life expectancy.
Infantile onset is the most severe form, presenting with prominent cardiomyopathy, hypotonia, hepatomegaly and death before 12 months of life. Late onset form has onset at any age, lack of severe (or absence of) cardiac involvement, progressive skeletal muscle dysfunction and less dismal short-term prognosis.
In addition to muscle and heart involvement, other tissues are affected liver, spleen, endothelium, lung, brain, anterior horns, peripheral nerves.
In fact some patients with infantile form have hearing loss, abnormal brain myelination and central fever and some adult patients show aneurysms of brain arteries due to accumulation of glycogen in vessels.
As for other treatable lysosomal diseases, the advent of enzyme replacement therapy will change the natural history of this disease and also will increase our knowledge concerning clinical heterogeneity.
Alpha-galactosidase; cardiomyopathy; myopathy
Deficiency of debrancher enzyme causes Glycogen Storage Disease (GSD) type III, an autosomal recessive disorder, characterized by tissue accumulation of abnormally structured glycogen. This report reviews current clinical and molecular knowledge about this disorder and describes the variability at phenotype and genotype levels of a large group of Italian GSDIII patients.
Glycogen storage disease; AGL; metabolic myopathy
McArdle’s disease is caused by genetic defects of the musclespecific isozyme of glycogen phosphorylase, which block ATP formation from glycogen in skeletal muscle. Creatine supplementation and ketogenic diet have been tested as potential supplements for muscle energy metabolism which may improve muscle symptomatic. Outcome measures were clinical scores describing muscle symptomatic and parameters derived from 31P-MRS examinations on working muscle. In two placebo controlled cross-over studies low dose creatine showed beneficial effects on muscle symptoms and performance whereas high dose creatine distinctly worsened muscle symptomatic in patients. In both studies, however, the absence of an elevation in phosphocreatine indicated the absence of a creatine uptake by the muscle fibre. The effects of creatine on muscle symptomatic may be independent from energy metabolism in muscle. In a case study, ketogenic diet improved muscle symptomatic and performance. However, these effects again did not result in 31PMRS visible changes in muscle energy metabolism.
McArdle disease; creatine supplementation; ketogenic diet
Replicative aging and oxidative stress are two plausible theories explaining the etiology of muscular dystrophy. The first theory indicates that replicative aging of myogenic cells (satellite cells), owing to enhanced myofiber turnover, is a plausible explanation of the progression of Duchenne muscular dystrophy (DMD). The oxidative stress theory indicates that failure of muscle regeneration to keep up with the ongoing apoptosis and necrosis following oxidative stress, that normally associates muscular exercise, leads to muscle atrophy in DMD.
To test for these two theories, markers of replicative aging and oxidative stress were assessed in the blood of 30 DMD patients vs. 20 normal healthy age matching controls. Markers of replicative aging showed significantly lower telomerase activity, significantly increased expression of receptors for advanced glycation end products (RAGEs) mRNA and Bax mRNA (an apoptotic gene) in DMD compared to controls. There was a significant increase in markers of oxidative stress among DMD patients compared to controls, measured in terms of increased apoptotic percentage in circulating mononuclear cells, increased lipid peroxidation measured in terms of plasma malondialdehyde (MDA) and increased protein carbonyls. Levels of plasma nitric oxide (NO), which neutralizes oxygen radicals, and expression of inducible nitric oxide synthase (iNOS) mRNA in neutrophils was significantly lower among DMD compared to controls.
Biostimulation of WBC by helium neon (He:Ne) laser irradiation induced a significant increase in the expression of iNOS mRNA and plasma NO levels, but still at a lower level compared to controls. He:Ne laser irradiation induced a marked decrease in markers of oxidative stress among DMD patients compared to their level before irradiation, measured in terms of decreased plasma protein carbonyls, decreased plasma MDA, and decreased apoptosis percentage.
Conclusion: This study points to that oxidative stress is the prime cause for muscle degeneration in DMD and points out to the possible ameliorative effect of He:Ne laser on this stress.
Apoptosis; Bax mRNA; He:Ne laser; lipid peroxidation; nitric oxide; nitric oxide synthase; receptors for advanced glycation end products (RAGEs); telomerase reverse transcriptase