Diaphragm displays early and progressive functional deficits in dysferlin‐deficient mice

Mouse lines with dysferlin deficiency are accepted animal models for limb girdle muscular dystrophy 2B and Miyoshi myopathy, yet slow progression of pathology prevents rapid screening of potential therapies for this disease. Our goal was to define a functional signature for skeletal muscles that lack dysferlin. Force generation and susceptibility to eccentric contractile injury measurements were performed in isolated limb muscles and the diaphragm from 10‐ and 36‐week‐old A/J and age‐matched control mice. Limb muscles had normal specific force at both 10 and 36 weeks, whereas the diaphragm had significant deficits in both specific force and susceptibility to eccentric contractile injury. Membrane ruptures in the diaphragm during eccentric contractions occurred predominantly in myosin heavy chain 2A‐expressing fibers. Dysferlin content did not vary significantly between wildtype muscles, suggesting that there was no correlation between disease severity and normal endogenous levels of the protein. These studies show that, unlike limb muscles, the diaphragm from the A/J mouse displays early deficits in function that may lower the age needed for evaluating potential therapies for dysferlinopathies. Muscle Nerve, 2010     

Variable reduction of caveolin-3 in patients with LGMD2B/MM

Abstract. Mutations in the human dysferlin gene (DYSF) cause autosomal recessive muscular dystrophies characterized by degeneration and weakness of proximal and/or distal muscles: limb girdle muscular dystrophy type 2B (LGMD2B) and Miyoshi myopathy (MM). Recently, an interaction between caveolin-3 and dysferlin in normal and dystrophic muscle (primary caveolin-3 deficiency; LGMD1C) was shown. In this study, clinical,morphological and genetic analysis was carried out in four independent LGMD2B/MM patients. All patients presented with an adult-onset, slowly progressive muscular dystrophy with variable involvement of proximal and distal muscles. We found complete lack of dysferlin in the four LGMD2B/MM patients. Secondary reduction of caveolin-3 was detected in three out of the four patients. Regular caveolae were detected along the basal lamina in two patients by electron microscopy. We provide further evidence that dysferlin and caveolin-3 interact in human skeletal muscle. It remains to be elucidated whether the loss of this interaction contributes to pathogenic events in muscular dystrophy.M. C. Walter and C. Braun contributed equally.     

无症状/轻症状高肌酸激酶血症20例临床研究

目的明确无症状/轻症状高肌酸激酶血症的病因及肌肉病理的诊断价值。方法对20例无症状/轻症状高肌酸激酶血症患者行肌肉病理检测,部分病例进一步行酶学和基因检测。结果纳入的20例患者中,病理异常17例(85.0%),提示诊断11例(55.0%):dysferlin相关肌病6例,dystrophin相关肌病4例,Pompe病1例;另3例分别确诊为calpain相关肌病、炎性肌病及药物相关肌病。共14例(70.0%)获得确诊。肌酸激酶2 000 U·L-1、2 000~10 000 U·L-1和10 000 U·L-1患者中分别确诊2/4例(50.0%)、9/13例(69.2%)和3/3例(100.0%)。结论肌肉活检对无症状/轻症状高肌酸激酶血症患者的诊断有重要价值;肌酸激酶水平与确诊率有一定关联。     

Diagnostic overview of blood‐based dysferlin protein assay for dysferlinopathies

Introduction: Dysferlin deficiency causes dysferlinopathies. Among peripheral blood mononuclear cells (PBMCs), the dysferlin protein is expressed specifically in CD14⁺ monocytes. Methods: We quantified dysferlin protein levels in PBMC lysates of 77 individuals suspected clinically of having a dysferlinopathy to screen for true positives. Subsequent molecular confirmation was done by Sanger sequencing and comparative genomic hybridization arrays to establish diagnosis. Results: Of the 44 individuals who had significantly reduced dysferlin levels (≤10%), 41 underwent molecular testing. We identified at least 1 mutation in 85% (35 of 41), and 2 mutations, establishing a dysferlinopathy diagnosis, in 61% (25 of 41) of these individuals. Among those with dysferlin protein levels of >10% (33 of 77), only 1 individual (of 14 who underwent molecular testing) had a detectable mutation. Conclusions: Our results suggest that dysferlin protein levels of ≤10% in PBMCs, are highly indicative of primary dysferlinopathies. However, this assay may not distinguish carriers from those with secondary dysferlin reduction. Muscle Nerve 50 : 333–339, 2014     

A case of dysferlinopathy presenting choreic movements.

Mutations in the dysferlin gene cause limb-girdle muscular dystrophy type 2B (LGMD2B). The involvement of the central nervous system in dysferlinopathy has not been described. We describe the clinical features of a patient with LGMD2B associated with dysferlin mutations (homozygous G3370T) who presented progressive choreic movements. The patient had no evidence of other causes of chorea. It is suggested that the chorea may be associated with the altered expression of the brain isoform of dysferlin.     

Novel sequence variants in dysferlin-deficient muscular dystrophy leading to mRNA decay and possible C2-domain misfolding

Mutations in the gene encoding dysferlin (DYSF) cause the allelic autosomal recessive disorders limb girdle muscular dystrophy 2B and Miyoshi myopathy. It encompasses 55 exons spanning 150 kb of genomic DNA. Dysferlin is involved in membrane repair in skeletal muscle. We identified three families with novel sequence variants in DYSF. All affected family members showed limb girdle weakness and had reduced or absent dysferlin protein on immunohistochemistry. All exons of DYSF were screened by genomic sequencing. Five novel variants in DYSF were found: two missense mutations (c.895G>A and c.4022T>C), one 5' donor splice-site variant (c.855+1delG), one nonsense mutation (c.1448C>A), and a variant in the 3'UTR of DYSF (c.*107T>A). All alterations were confirmed by restriction enzyme analysis and not found in 400 control alleles. Nonsense mediated RNA decay or changes in the three-dimensional protein structure resulting in intracellular dysferlin aggregates and finally the lack of dysferlin protein were identified as consequences of the novel DYSF variants.