[Show abstract][Hide abstract] ABSTRACT: We previously discovered the human 10T-->C (Trp4Arg) missense mutation in exon 2 of the muscle LIM protein (MLP, CSRP3) gene.
We sought to study the effects of this single-nucleotide polymorphism in the in vivo situation.
We now report the generation and detailed analysis of the corresponding Mlp(W4R/+) and Mlp(W4R/W4R) knock-in animals, which develop an age- and gene dosage-dependent hypertrophic cardiomyopathy and heart failure phenotype, characterized by almost complete loss of contractile reserve under catecholamine induced stress. In addition, evidence for skeletal muscle pathology, which might have implications for human mutation carriers, was observed. Importantly, we found significantly reduced MLP mRNA and MLP protein expression levels in hearts of heterozygous and homozygous W4R-MLP knock-in animals. We also detected a weaker in vitro interaction of telethonin with W4R-MLP than with wild-type MLP. These alterations may contribute to an increased nuclear localization of W4R-MLP, which was observed by immunohistochemistry.
Given the well-known high frequency of this mutation in Caucasians of up to 1%, our data suggest that (W4R-MLP) might contribute significantly to human cardiovascular disease.
Circulation Research 03/2010; 106(4):695-704. DOI:10.1161/CIRCRESAHA.109.206243 · 11.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mutations in the dysferlin gene cause limb-girdle muscular dystrophy type 2B, Miyoshi myopathy, and distal anterior compartment myopathy. Dysferlin mainly localizes to the sarcolemma in mature skeletal muscle where it is implicated in membrane fusion and repair. In different forms of muscular dystrophy, a predominantly cytoplasmic localization of dysferlin can be observed in regenerating myofibers, but the subcellular compartment responsible for this labeling pattern is not yet known. We have previously demonstrated an association of dysferlin with the developing T-tubule system in vitro. To investigate the role of dysferlin in adult skeletal muscle regeneration, we studied dysferlin localization at high resolution in a rat model of regeneration and found that the subcellular labeling of dysferlin colocalizes with the developing T-tubule system. Furthermore, ultrastructural analysis of dysferlin-deficient muscle revealed primary T-tubule anomalies similar to those seen in caveolin-3–deficient muscle. These findings indicate that dysferlin is necessary for correct T-tubule formation, and dysferlin-deficient skeletal muscle is characterized by abnormally configured T-tubules. Muscle Nerve : 166–173, 2010
[Show abstract][Hide abstract] ABSTRACT: Mutations in the dysferlin gene lead to limb girdle muscular dystrophy 2B, Miyoshi myopathy and distal anterior compartment myopathy. A cohort of 36 patients affected by dysferlinopathy is described, in the first UK study of clinical, genetic, pathological and biochemical data. The diagnosis was established by reduction of dysferlin in the muscle biopsy and subsequent mutational analysis of the dysferlin gene. Seventeen mutations were novel; the majority of mutations were small deletions/insertions, and no mutational hotspots were identified. Sixty-one per cent of patients (22 patients) initially presented with limb girdle muscular dystrophy 2B, 31% (11 patients) with a Miyoshi phenotype, one patient with proximodistal mode of onset, one patient with muscle stiffness after exercise and one patient as a symptomatic carrier. A wider range of age of onset was noted than previously reported, with 25% of patients having first symptoms before the age of 13 years. Independent of the initial mode of presentation, in our cohort of patients the gastrocnemius muscle was the most severely affected muscle leading to an inability to stand on tiptoes, and lower limbs were affected more severely than upper limbs. As previous anecdotal evidence on patients affected by dysferlinopathy suggests good muscle prowess before onset of symptoms, we also investigated pre-symptomatic fitness levels of the patients. Fifty-three per cent of the patients were very active and sporty before the onset of symptoms which makes the clinical course of dysferlinopathy unusual within the different forms of muscular dystrophy and provides a challenge to understanding the underlying pathomechanisms in this disease.
Journal of neurology, neurosurgery, and psychiatry 07/2009; 81(9):946-53. DOI:10.1136/jnnp.2009.178038 · 6.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Skeletal muscle requires an efficient and active membrane repair system to overcome the rigours of frequent contraction. Dysferlin is a component of that system and absence of dysferlin causes muscular dystrophy (dysferlinopathy) characterized by adult onset muscle weakness, high serum creatine kinase levels and a prominent inflammatory infiltrate. We have observed that dysferlinopathy patient biopsies show an excess of immature fibres and therefore investigated the role of dysferlin in muscle regeneration. Using notexin-induced muscle damage, we have shown that regeneration is attenuated in a mouse model of dysferlinopathy, with delayed removal of necrotic fibres, an extended inflammatory phase and delayed functional recovery. Satellite cell activation and myoblast fusion appear normal, but there is a reduction in early neutrophil recruitment in regenerating and also needle wounded muscle in dysferlin-deficient mice. Primary mouse dysferlinopathy myoblast cultures show reduced cytokine release upon stimulation, indicating that the secretion of chemotactic molecules is impaired. We suggest an extension to the muscle membrane repair model, where in addition to fusing patch repair vesicles with the sarcolemma dysferlin is also involved in the release of chemotactic agents. Reduced neutrophil recruitment results in incomplete cycles of regeneration in dysferlinopathy which combines with the membrane repair deficit to ultimately trigger dystrophic pathology. This study reveals a novel pathomechanism affecting muscle regeneration and maintenance in dysferlinopathy and highlights enhancement of the neutrophil response as a potential therapeutic avenue in these disorders.
Human Molecular Genetics 04/2009; 18(11):1976-89. DOI:10.1093/hmg/ddp121 · 6.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Muscle immunoanalysis of the sarcoglycan complex is an important part of the diagnostic evaluation of muscle biopsies in patients with autosomal recessive limb-girdle muscular dystrophy. Reduced or absent sarcolemmal expression of one or all of the four sarcoglycans (alpha-, beta-, gamma-, delta-sarcoglycan) can be found in patients with limb-girdle muscular dystrophy 2C-F (LGMD2C-F) and also in patients with Duchenne and Becker muscular dystrophy (DMD/BMD). It has previously been suggested that different patterns of sarcoglycan expression could predict the primary genetic defect, and that genetic analysis could be directed by these patterns. In this first UK study we studied 24 genetically characterized patients with sarcoglycan deficient LGMD, in 22 of whom muscle immunoanalysis data were available. Thirteen patients showed alpha-sarcoglycan deficient LGMD2D, 7 patients beta-sarcoglycan deficient LGMD2E, 3 patients gamma-sarcoglycan deficient LGDM2C, and one patient delta-sarcoglycan deficient LGMD2F. Muscle biopsies were analysed in one centre without knowledge of the established genetic diagnosis. Our results demonstrated that residual sarcoglycan expression is highly variable and does not enable an accurate prediction of the genotype. Considering previous reports of sarcoglycanopathy patients with an isolated loss of one sarcoglycan we recommend to use antibodies against all four sarcoglycans for immunoanalysis of skeletal muscle sections. A concomitant reduction of dystrophin and beta-dystroglycan was observed more frequently than previously reported and illustrates the important differential diagnosis of DMD and BMD for sarcoglycan deficient LGMD.
[Show abstract][Hide abstract] ABSTRACT: LGMD2B, Miyoshi Myopathy and Distal Anterior Compartment Myopathy are caused by mutations in the dysferlin gene (DYSF) leading to progressive muscular weakness and wasting with onset usually within the second or third decade of life. We here present a patient with disease onset at 73 years. The presenting symptom was exercise-induced stiffness of the trunk and proximal leg muscles without major progression over a period of 12 years. Gastrocnemius muscle biopsy revealed dystrophic morphology and biochemical depletion of dysferlin, while sequence analysis revealed compound heterozygous splicing mutations of the dysferlin gene. This case represents the eldest age of onset of dysferlinopathy reported so far and widens the clinical spectrum of this disease.
[Show abstract][Hide abstract] ABSTRACT: The dysferlin gene is mutated in limb-girdle muscular dystrophy type 2B, Miyoshi myopathy, and distal anterior compartment myopathy. In mature skeletal muscle, dysferlin is located predominantly at the sarcolemma, where it plays a role in membrane fusion and repair. To investigate the role of dysferlin during early muscle differentiation, its localization was studied at high resolution in a muscle cell line. This demonstrated that dysferlin is not expressed at the plasmalemma of myotubes but mostly localizes to the T-tubule network. However, dysferlin translocated to the site of injury and toward the plasma membrane in a Ca2+-dependent fashion in response to a newly designed in vitro wounding assay. This reaction was specific to the full-length protein, as heterologously expressed deletion mutants of distinct C2 domains of dysferlin did not show this response. These results shed light on the dynamics of muscle membrane repair and are highly indicative of a specific role of dysferlin in this process in early myogenesis.
The FASEB Journal 07/2007; 21(8):1768-76. DOI:10.1096/fj.06-7659com · 5.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: While much is known about the clinical course of adult FSHD, the third most common inherited muscular dystrophy, data on the "infantile phenotype" and especially on the progression of the disease in children are limited. We have followed a cohort of 7 patients with infantile FSHD for 9-25 years and here report the clinical and genetic findings in this group. Infantile FSHD is relatively rare, amounting to 4% of all of our FSHD patients. Despite some variability in the progression, infantile FSHD has a more consistent phenotype than adult FSHD. Although they had normal motor milestones, all patients showed facial weakness from early childhood, and subsequently were severely affected with rapid progression of the disease, marked muscular wasting, weakness, and hyperlordosis. None of the patients have shown signs of nocturnal hypoventilation or cardiomyopathy so far. No correlation was found between sex and the severity of phenotype whereas all but one patient had very short fragment sizes of the D4Z4 repeat. Only two patients had a de novo mutation: 3 patients inherited the mutation from a parent with somatic mosaicism, and one was inherited from a parent with classical adult FSHD. One patient was unusual in having one allele inherited from his father who showed somatic mosaicism and one allele with an additional de novo mutation. We conclude that infantile FSHD is a severe and rapidly progressive disease, and this needs to be taken into account in the advice given to patients diagnosed in early childhood. However, our data also suggest that the risk to an individual with classical FSHD of having a child with the infantile form is low.
[Show abstract][Hide abstract] ABSTRACT: Infantile Pompe disease (IPD) is a fatal, autosomal recessive muscle-wasting disorder. Due to a deficiency of the lysosomal enzyme acid alpha-glucosidase patients develop a generalized myopathy, diaphragmatic weakness, and cardiomyopathy leading to death usually within the first year of life. So far there is no therapy available. We report on the safety and efficacy of transgenically derived recombinant human precursor acid alpha-glucosidase (rhGAA) in a 10-month follow-up study in two children with IPD who previously completed a 48-week course of enzyme replacement therapy (ERT) with the same medication at the same dose in a phase II clinical trial. Under this therapy cardiac status and muscle strength had improved, leading to survival beyond the age of one year. These results, together with data from two other phase II clinical trials encouraged further evaluation of the long-term safety and efficacy of enzyme replacement therapy in patients with infantile-onset Pompe disease. During the 10-month follow-up period, ERT was well-tolerated and neither patient experienced a single infusion-associated reaction. The initial improvements in cardiac size and function, as measured by left ventricular mass index and the fractional shortening, were maintained in both patients, and a continued improvement of motor function, as measured by the Alberta infant motor scale, was observed.
[Show abstract][Hide abstract] ABSTRACT: Pompe disease is an autosomal recessive muscle-wasting disorder caused by the deficiency of the lysosomal enzyme acid alpha-glucosidase. Due to virtual absence of acid alpha-glucosidase, patients with classical infantile Pompe disease develop progressive cardiomyopathy, skeletal muscle weakness and respiratory insufficiency leading to death in early infancy. We report on the results of a phase II clinical trial including two patients with classical infantile Pompe disease receiving enzyme replacement therapy over a period of 48 weeks by weekly infusions. Recombinant acid alpha-glucosidase was derived from the milk of transgenic rabbits. Safety was evaluated by recording adverse events while clinical efficacy was evaluated by ventilator-free survival, left ventricular mass index, motor development as well as histologic and biochemical analysis of muscle biopsies. This therapy was in general well-tolerated. There was an overall improvement in left ventricular mass, cardiac function, skeletal muscle function and histological appearance of skeletal muscle.
[Show abstract][Hide abstract] ABSTRACT: Facilitated glucose transporter isoform 1 deficiency syndrome (GLUT1 DS), caused by impaired GLUT1-mediated glucose transport into the brain, is characterized by hypoglycorrhachia. The defect in the facilitative glucose transporter isoform 1 (GLUT1) can be confirmed by functional, quantitative, and molecular analyses. Diagnostic difficulties arise when these analyses are normal and hypoglycorrhachia remains unexplained. Three infants presenting with seizures and hypoglycorrhachia at 2, 4, and 6 weeks of age, which suggests GLUT1 deficiency syndrome, are reported. The seizures responded to a ketogenic diet in Patients 1 and 3 and phenobarbitone in Patient 2. Repeated GLUT1 analyses were normal. When treatment was discontinued, all patients remained seizure-free and developed normally. Subsequent lumbar punctures showed the return to normoglycorrhachia. We conclude that these cases might represent a transient disturbance in GLUT1-mediated glucose transport. The biomolecular basis for this clinical observation remains unknown. Though no treatment is required, clinical follow-up and repeated lumbar punctures are necessary to distinguish this benign condition from the original GLUT1 deficiency syndrome.
[Show abstract][Hide abstract] ABSTRACT: Microcephalic osteodysplastic primordial dwarfism (MOPD) is defined as a syndrome presenting with intrauterine and postnatal growth retardation, typical facial appearance, skeletal dysplasia and brain abnormalities. Autosomal-recessive inheritance is suspected. Sharing clinical manifestations, the former type III has been accepted to be the same entity as type I. We present the case of a male infant with MOPD I and micrencephaly with simplified gyral pattern to a degree defining it as microlissencephaly (MLIS). The brain abnormalities in MOPD I have not yet been classified. Reviewing the literature, we conclude that microlissencephaly appears to be the distinct developmental brain abnormality in MOPD I. Conversely, osteodysplastic changes have to be taken into consideration in the differential diagnosis of microlissencephaly. In addition, our patient suffered from acute lymphatic leukaemia which has not previously been described in association with MOPD I.