Limb-girdle muscular dystrophy / 中华神经科杂志

Limb girdle muscular dystrophy (LGMD) is characterized by progressive proximal muscle weakness with high genetic heterogeneity.LGMD is the fourth prevalent form of muscular dystrophies in the adult neurology department.Since most patients are juvenile-or adult-onset and present as limb muscle weakness,it would be easily misdiagnosed as myositis or metabolic myopathies.The final diagnosis depends on muscle immunohistochemical staining,Western blotting and genetic screening.In China,LGMD2B and LGMD2A are the most prevalent forms,accounting for 74.3％ in overall LGMD.Patients with LGMD2B usually have onset age between 19-27 years old.LGMD2B patients present as asymptomatic hyper creatine kinase emia (CK) at the early stage,and later develop to typical proximal muscle weakness with bilateral calf atrophy and extremely high serum CK.The onset age of LGMD2A patients is between 7-18 years old.LGMD2A patients presented as proximal muscle weakness with or without bilateral scapular winging and Achilles tendon contractures.Serum CK can be moderately or highly elevated.Current therapies are mainly supportive and the effective treatment is insufficient.The ongoing global elinical history study and gene therapy bring us new hope for treating LGMD in the coming future.

Expression levels of sarcolemmal membrane repair proteins following prolonged exercise training in mice.

Membrane repair is a conserved cellular process, where intracellular vesicles translocate to sites of plasma membrane injury to actively reseal membrane disruptions. Such membrane disruptions commonly occur in the course of normal physiology, particularly in skeletal muscles due to repeated contraction producing small tears in the sarcolemmal membrane. Here, we investigated whether prolonged exercise could produce adaptive changes in expression levels of proteins associated with the membrane repair process, including mitsugumin 53/tripartite motif-containing protein 72 (MG53/TRIM72), dysferlin and caveolin-3 (cav3). Mice were exercised using a treadmill running protocol and protein levels were measured by immunoblotting. The specificity of the antibodies used was established by immunoblot testing of various tissue lysates from both mice and rats. We found that MG53/TRIM72 immunostaining on isolated mouse skeletal muscle fibers showed protein localization at sites of membrane disruption created by the isolation of these muscle fibers. However, no significant changes in the expression levels of the tested membrane repair proteins were observed following prolonged treadmill running for eight weeks (30 to 80 min/day). These findings suggest that any compensation occurring in the membrane repair process in skeletal muscle following prolonged exercise does not affect the expression levels of these three key membrane repair proteins.

Heterogeneous Characteristics of Korean Patients with Dysferlinopathy

Dysferlinopathy is caused by mutations in the DYSF gene. To characterize the clinical spectrum, we investigated the characteristics of 31 Korean dysferlinopathy patients confirmed by immunohistochemistry. The mean age of symptom onset was 22.23 +/- 7.34 yr. The serum creatine kinase (CK) was highly increased (4- to 101-fold above normal). The pathological findings of muscle specimens showed nonspecific dystrophic features and frequent inflammatory cell infiltration. Muscle imaging studies showed fatty atrophic changes dominantly in the posterolateral muscles of the lower limb. The patients with dysferlinopathy were classified by initial muscle weakness: fifteen patients with Miyoshi myopathy phenotype (MM), thirteen patients with limb girdle muscular dystrophy 2B phenotype (LGMD2B), two patients with proximodistal phenotype, and one asymptomatic patient. There were no differences between LGMD2B and MM groups in terms of onset age, serum CK levels and pathological findings. Dysferlinopathy patients usually have young adult onset and high serum CK levels. However, heterogeneity of clinical presentations and pathologic findings upon routine staining makes it difficult to diagnose dysferlinopathy. These limitations make immunohistochemistry currently the most important method for the diagnosis of dysferlinopathy.

Dysferlin Expression in Skeletal muscles of Patients with Myopathy and Cultured Human Myoblast/Myotube

BACKGROUND: Dysferlin is a 230 kDa protein of the sarcolemma. This encoding gene is mutated in patients with dysferlinopathy (limb-girdle muscular dystrophy 2B and Miyoshi myopathy), which is characterized byan active muscle degeneration and regeneration process. Dysferlin is known to play an essential role in muscle signaling and muscle fiber repair. We studied the gene to define its functional role in muscle repair and differentiation in human skeletal muscle of the patients with myopathies and cultured human myoblast. METHODS: An immunohistochemical analysis of dysferlin and N-CAM in biopsied muscle tissue obtained from eleven patients with myopathies [six patients with Duchenne muscular dystrophy (DMD), two patients with dermatomyositis (DM), two patients with polymyositis (PM), and one patient with dysferlinopathy (MM)] and eight normal controls. Cultured human myoblast obtained from normal muscle tissue was also analyzed by the expression of dysferlin through immunocytochemical staining and western blot. RESULTS: The immunoreactivity of dysferlin was strongly expressed in regenerative muscle fibers of myopathies except dysferlinpathy, which was co-localization with N-CAM by double immunohistochemistry. By western blot analysis, the expression level of dysferlin was variable in myopathies compared to normal controls, but no expression in dyferlinopathy. The expression of dysferlin in myotubes was significantly increased compared to that in myoblast by immunostaining and western blot analysis. CONCLUSIONS: These results indicated that the expression of dysferlin increased in regenerative and degenerative muscle fibers and also increased in myoblast differentiation. Our study supports that dysferlin not only has a role in skeletal muscle development but also in regeneration/repair process.

Immunocytochemical and Western Blot Analysis in Miyoshi Myopathy

BACKGROUND: Recent genetic analyses have shown that Miyoshi myopathy (MM) is caused by a mutation in the DYSF, which induces the dysfunction of dysferlin. We identified the deficiency of dysferlin by immunohistochemistry and Western blot in four patients with clinically diagnosed MM, and investigated the clinical and pathological characteristics of MM. METHODS: A muscle biopsy was performed in four patients who were diagnosed with MM by clinical and electrophysiological study. Immunostaining of muscle specimens for dyferlin, dystrophin, alpha, beta, gamma, sigma-sarcoglycan, beta-dystroglycan, and caveolin-3 were performed in all four patients. We analyzed the quantitative analysis for dysferlin by Western blot in three of four patients. RESULTS: All four patients showed clinical onset during adolescence or early adulthood (15-26 year old), a slowly progressive course, and a relatively high serum creatine kinase level (2240-6400 IU/L). Routine pathological studies showed non-specific myopathic changes. On immunocytochemistry, there was negative immunoreacticity for dysferlin on muscle specimens in all patients. The immunoreactivities for dystrophin, alpha, beta, gamma, sigma-sarcoglycan, beta-dystroglycan, and caveolin-3 were normal. On Western blotting, complete loss of dysferlin was noted in all three patients with MM CONCLUSIONS: Identification of isolated deficiency of dysferlin on immunocytochemistry or Western blot is important for the confirmative diagnosis of MM.

Clinical and Pathological Characteristics of Four Korean Patients with Limb-Girdle Muscular Dystrophy type 2B

Limb-girdle muscular dystrophy type 2B (LGMD2B), a subtype of autosomal recessive limb-girdle muscular dystrophy (ARLGMD), is characterized by a relatively late onset and slow progressive course. LGMD2B is known to be caused by the loss of the dysferlin protein at sarcolemma in muscle fibers. In this study, the clinical and pathological characteristics of Korean LGMD2B patients were investigated. Seventeen patients with ARLGMD underwent muscle biopsy and the histochemical examination was performed. For the immunocytochemistry, a set of antibodies against dystrophin, alpha, beta, gamma, delta-sarcoglycans, dysferlin, caveolin-3, and beta-dystroglycan was used. Four patients (24%) showed selective loss of immunoreactivity against dysferlin at the sarcolemma on the muscle specimens. Therefore, they were classified into the LGMD2B category. The age at the onset of disease ranged from 9 yr to 33 yr, and none of the patients was wheelchair bound at the neurological examination. The serum creatine kinase (CK) was high in all the patients (4010-5310 IU/L). The pathologic examination showed mild to moderate dystrophic features. These are the first Korean LGMD2B cases with a dysferlin deficiency confirmed by immunocytochemistry. The clinical, pathological, and immunocytochemical findings of the patients with LGMD2B in this study were in accordance with those of other previous reports.

Identification of a Dysferlin Gene Mutation in a Korean Case with Miyoshi Myopathy

Recent genetic and immunohistochemical analyses have shown that Miyoshi myopathy (MM) is caused by a mutation in the DYSF gene, which induces dysfunction of dysferlin. The author described one patient showing characteristic MM phenotype with deficiency of dysferlin on immunohistochemistry. Direct DNA sequencing of whole exons of DYSF gene revealed one homozygous missense mutation (G1165C) on exon 12, which let to an amino acid substitution from the glutamic acid to glutamine at the 389 of the peptide sequence in this patient. This is the first reported case of MM confirmed by immunohistochemical and genetic analyses in Korea.

Dysferlin in a hyperCKaemic patient with caveolin 3 mutation and in C2C12 cells after p38 MAP kinase inhibition

Dysferlin is a plasma membrane protein of skeletal muscle whose deficiency causes Miyoshi myopathy, limb girdle muscular dystrophy 2B and distal anterior compartment myopathy. Recent studies have reported that dysferlin is implicated in membrane repair mechanism and coimmunoprecipitates with caveolin 3 in human skeletal muscle. Caveolin 3 is a principal structural protein of caveolae membrane domains in striated muscle cells and cardiac myocytes. Mutations of caveolin 3 gene (CAV3) cause different diseases and where caveolin 3 expression is defective, dysferlin localization is abnormal. We describe the alteration of dysferlin expression and localization in skeletal muscle from a patient with raised serum creatine kinase (hyperCKaemia), whose reduction of caveolin 3 is caused by a CAV3 P28L mutation. Moreover, we performed a study on dysferlin interaction with caveolin 3 in C2C12 cells. We show the association of dysferlin to cellular membrane of C2C12 myotubes and the low affinity link between dysferlin and caveolin 3 by immunoprecipitation techniques. We also reproduced caveolinopathy conditions in C2C12 cells by a selective p38 MAP kinase inhibition with SB203580, which blocks the expression of caveolin 3. In this model, myoblasts do not fuse into myotubes and we found that dysferlin expression is reduced. These results underline the importance of dysferlin-caveolin 3 relationship for skeletal muscle integrity and propose a cellular model to clarify the dysferlin alteration mechanisms in caveolinopathies.

Clinical and pathological features of Miyoshi myopathy with dysferlin protein deficient / 临床神经病学杂志

Objective To investigate the clinical and pathological features of Miyoshi myopathy(MM) with dysferlin protein deficient. Methods The clinical and pathological data of the 3 patients with MM were analysed. Results 3 patients were onset at youngster.The clinical manifestation were myastheria and myoatrophy in distal of lower limbs.1 case combined myalgia and tumefaction in lower limbs at early stage of onset;1 case showed myathenia in proximal of lower limbs.The level of serum creatine phosphokinase (CK) was significantly ligher in the 3 cases (7543 IU/L, 5657 IU/L, 8721 IU/L respectively). The level of serum lactic dehydrogenase (LDH) was significantly higher in the 2 cases (456 IU/L ,636 IU/L respectively).The result of muscle pathology was showed myogenic damage in all the cases. The expression of dysferlin protain in membrane of muscle cells was completely deficient, although the expression of dystrophin was normal. Inflammatory cells infiltration was found in 1 case's muscle tissue. Conclusions The clinical characters of MM patient are onset at youngster,myasthenia and myoatrophy in lower limbs.The deficit of dysferlin protain can be found by pathology.