Distal Anterior Compartment Myopathy Research Articles

БИОХИМИЧЕСКИЕ И ПАТОФИЗИОЛОГИЧЕСКИЕ АСПЕКТЫ ДИСФЕРЛИН-АССОЦИИРОВАННЫХ МЫШЕЧНЫХ ДИСТРОФИЙ

Dysferlin is a transmembrane calcium-binding protein of the ferlin-1-like protein family, which includes myoferlin Fer1L3, otoferlin Fer1L2 and other ferlins Fer1L4, Fer1L5, and Fer1L6 along with dysferlin itself. Dysferlin is synthesized in all cells of the body, but most actively – in the symplasts of striated muscle tissue. The full range of functions performed by this protein is not fully clarified, but the following have been clearly shown: participation in the post-injury repair of sarcolemma and intracellular vesicular systems, generation and maintenance of the correct functioning of the sarcolemmal T-tubule system, regulation of endo- and exocytosis and inflammation, participation in phagocytosis. Mutations in the dysferlin gene lead to the development of a number of neuromuscular diseases of the autosomal recessive type of inheritance called dysferlinopathies: Miyoshi myopathy, limb-girdle muscular dystrophy type 2B, and distal anterior compartment myopathy. These diseases are characterized by the impaired expression of mRNA and/or the function of the protein dysferlin in skeletal muscles, which is caused by mutations in the DYSF (dystrophy-associated fer-1-like) gene. Although rare, dysferlinopathy is characterized by continuous progression causing severe disability, which explains the importance of research and development of appropriate treatments, including gene therapy. The article presents information on the structure of dysferlin, the mechanisms of its normal functions, as well as the biochemical basis of the pathogenesis of dysferlinopathies.

An Overview of Recent Advances and Clinical Applications of Exon Skipping and Splice Modulation for Muscular Dystrophy and Various Genetic Diseases.

Exon skipping is a therapeutic approach that is feasible for various genetic diseases and has been studied and developed for over two decades. This approach uses antisense oligonucleotides (AON) to modify the splicing of pre-mRNA to correct the mutation responsible for a disease, or to suppress a particular gene expression, as in allergic diseases. Antisense-mediated exon skipping is most extensively studied in Duchenne muscular dystrophy (DMD) and has developed from in vitro proof-of-concept studies to clinical trials targeting various single exons such as exon 45 (casimersen), exon 53 (NS-065/NCNP-01, golodirsen), and exon 51 (eteplirsen). Eteplirsen (brand name Exondys 51), is the first approved antisense therapy for DMD in the USA, and provides a treatment option for ~14% of all DMD patients, who are amenable to exon 51 skipping. Eteplirsen is granted accelerated approval and marketing authorization by the US Food and Drug Administration (FDA), on the condition that additional postapproval trials show clinical benefit. Permanent exon skipping achieved at the DNA level using clustered regularly interspaced short palindromic repeats (CRISPR) technology holds promise in current preclinical trials for DMD. In hopes of achieving clinical success parallel to DMD, exon skipping and splice modulation are also being studied in other muscular dystrophies, such as Fukuyama congenital muscular dystrophy (FCMD), dysferlinopathy including limb-girdle muscular dystrophy type 2B (LGMD2B), Miyoshi myopathy (MM), and distal anterior compartment myopathy (DMAT), myotonic dystrophy, and merosin-deficient congenital muscular dystrophy type 1A (MDC1A). This chapter also summarizes the development of antisense-mediated exon skipping therapy in diseases such as Usher syndrome, dystrophic epidermolysis bullosa, fibrodysplasia ossificans progressiva (FOP), and allergic diseases.

Dysferlinopathy in Switzerland: clinical phenotypes and potential founder effects

BackgroundDysferlin is reduced in patients with limb girdle muscular dystrophy type 2B, Miyoshi myopathy, distal anterior compartment myopathy, and in certain Ethnic clusters.MethodsWe evaluated clinical and genetic patient data from three different Swiss Neuromuscular Centers.ResultsThirteen patients from 6 non-related families were included. Age of onset was 18.8 ± 4.3 years. In all patients, diallelic disease-causing mutations were identified in the DYSF gene. Nine patients from 3 non-related families from Central Switzerland carried the identical homozygous mutation, c.3031 + 2T>C. A possible founder effect was confirmed by haplotype analysis. Three patients from two different families carried the heterozygous mutation, c.1064_1065delAA. Two novel mutations were identified (c.2869C>T (p.Gln957Stop), c.5928G>A (p.Trp1976Stop)).ConclusionsOur study confirms the phenotypic heterogeneity associated with DYSF mutations. Two mutations (c.3031 + 2T>C, c.1064_1065delAA) appear common in Switzerland. Haplotype analysis performed on one case (c. 3031 + 2T>C) suggested a possible founder effect.

Clinical heterogeneity and a high proportion of novel mutations in a Chinese cohort of patients with dysferlinopathy.

Dysferlinopathies are a group of autosomal recessive muscular dystrophies caused by mutations in the dysferlin gene. This study presents clinical features and the mutational spectrum in the largest cohort of Chinese patients analyzed to date. A total of 36 unrelated Chinese patients with diagnostic suspicion of dysferlinopathy were clinically and genetically characterized. Patients were divided into five phenotypes: 19 patients with limb girdle muscular dystrophy (LGMD) type 2B, 10 with Miyoshi myopathy (MM), 1 with distal anterior compartment myopathy (DACM), 3 with exercise intolerance, and 3 with asymptomatic hypercreatine phosphokinasemia (hyperCPKemia). Thirty-one patients showed an absence or drastic reduction of dysferlin expression by Westernblot. Forty-three mutations were identified in DYSF, including 31 novel. Our study underlines clinical heterogeneity and a high proportion of novel mutations in Chinese patients affected with dysferlinopathy.

Proteasomal Inhibition Restores Biological Function of Mis-sense Mutated Dysferlin in Patient-derived Muscle Cells

Dysferlin is a transmembrane protein implicated in surface membrane repair of muscle cells. Mutations in dysferlin cause the progressive muscular dystrophies Miyoshi myopathy, limb girdle muscular dystrophy 2B, and distal anterior compartment myopathy. Dysferlinopathies are inherited in an autosomal recessive manner, and many patients with this disease harbor mis-sense mutations in at least one of their two pathogenic DYSF alleles. These patients have significantly reduced or absent dysferlin levels in skeletal muscle, suggesting that dysferlin encoded by mis-sense alleles is rapidly degraded by the cellular quality control system. We reasoned that mis-sense mutated dysferlin, if salvaged from degradation, might be biologically functional. We used a dysferlin-deficient human myoblast culture harboring the common R555W mis-sense allele and a DYSF-null allele, as well as control human myoblast cultures harboring either two wild-type or two null alleles. We measured dysferlin protein and mRNA levels, resealing kinetics of laser-induced plasmalemmal wounds, myotube formation, and cellular viability after treatment of the human myoblast cultures with the proteasome inhibitors lactacystin or bortezomib (Velcade). We show that endogenous R555W mis-sense mutated dysferlin is degraded by the proteasomal system. Inhibition of the proteasome by lactacystin or Velcade increases the levels of R555W mis-sense mutated dysferlin. This salvaged protein is functional as it restores plasma membrane resealing in patient-derived myoblasts and reverses their deficit in myotube formation. Bortezomib and lactacystin did not cause cellular toxicity at the regimen used. Our results raise the possibility that inhibition of the degradation pathway of mis-sense mutated dysferlin could be used as a therapeutic strategy for patients harboring certain dysferlin mis-sense mutations.

P2.59 Lumbossacral paravertebral muscle MRI evaluation in dysferlinopathies

Dysferlinopathies are autosomal recessive muscular dystrophies secondary to mutations in the DYSF. Phenotypic expression can vary from assymptomatic HyperCKemias, Myioshy myopathy, LGMD2B, and other rarer presentations. Recently it has been reported that lumbossacral paravertebral muscles can also be early affected. To present the lumbossacral paravertebral, pelvic, girdle, thigh and leg muscle MRI and correlate lumbossacral paravertebral muscle findings with clinical findings in adult dysferlinopathy patients. The clinical, pathological and genetic findings of the patients with a dysferlinopathy were analysed. Lumbossacral, pelvic girdle, thigh and leg muscle MRI (1.5 Tesla) was performed. Dysferlinopathy diagnosis was made in 16 patients and MRI evaluation was done in 12. One patient had assymptomatic hyperCKemia, 1 had distal anterior compartment myopathy, 2 a Myioshy myopathy and 8 a LGMD2B. Parental consanguinity was reported in 7 patients. Their actual mean age is 46.4 years (28–75 years) and the mean age of first symptoms was 29.8 years (16–69 years). The mean time from first symptoms to genetic diagnosis was 11.5 years (3–43 years). Two are wheelchair bound. The mean CK value was 4717 UI/l. Genetic results revealed homozygous mutations in 7 patients, compound heterozygous mutations in 4 patients and a single pathogenic mutation was found in 1 patient. Muscle MRI revealed lumbossacral muscle adipose infiltration in 11 patients, slight in 2 patients and severe in 9. The patient with no lesion of the lumbossacral muscles is a symptomatic patient with a proximo-distal form of disease. One of the patients with slight degeneration of lumbossacral muscles is assymptomatic and the other is pauci-symptomatic. This study shows that lumbossacral muscles are affected in all stages and phenotypes of dysferlinopathy patients. Muscle MRI of the other segments will be discussed.

P1.19 Mutational spectrum and clinical features of Korean patients with dysferlinopathy

Background: Dysferlinopathy refers to a group of autosomal recessive muscular dystrophies caused by mutations in DYSF, which encodes dysferlin working for calcium-dependent membrane repair in skeletal muscle. The disease group includes three distinct disorders; limb-girdle muscular dystrophy type 2B (LGMD2B), Miyoshi myopathy (MM) and distal anterior compartment myopathy. Since dysferlinopathy is considered as a relatively common cause of muscular dystrophy in Korea, it is needed to characterize clinical and genetic features in Korean patients of dysferlinopathy.

Private dysferlin exon skipping mutation (c.5492G>A) with a founder effect reveals further alternative splicing involving exons 49–51

The allelic muscle disorders known as limb-girdle muscular dystrophy type 2B (LGMD2B), Miyoshi myopathy and distal anterior compartment myopathy result from defects in dysferlin-a sarcolemma-associated protein involved in membrane repair. Mutation screening in the dysferlin gene (DYSF) enabled the identification of seven Portuguese patients presenting the variant c.5492G>A, which was observed to promote skipping of exon 49 (p.Gly1802ValfsX17). Several residually expressed products of alternative splicing also involving exons 50 and 51 were detected in the leukocytes and muscle of both patients and normal controls. Quantitative transcript analysis confirmed these results and revealed that Delta49/Delta50 transcripts were predominant in blood. Although the patients were apparently unrelated, the c.5492G>A mutation was found in linkage disequilibrium with a particularly rare haplotype in the population, corroborating the hypothesis of a common origin. Despite the presence of the same mutation on the same haplotype background, onset of the disease was heterogeneous, with either proximal or distal muscle involvement.

Dysferlin Interacts with Tubulin and Microtubules in Mouse Skeletal Muscle

Dysferlin is a type II transmembrane protein implicated in surface membrane repair in muscle. Mutations in dysferlin lead to limb girdle muscular dystrophy 2B, Miyoshi Myopathy and distal anterior compartment myopathy. Dysferlin's mode of action is not well understood and only a few protein binding partners have thus far been identified. Using affinity purification followed by liquid chromatography/mass spectrometry, we identified alpha-tubulin as a novel binding partner for dysferlin. The association between dysferlin and alpha-tubulin, as well as between dysferlin and microtubules, was confirmed in vitro by glutathione S-transferase pulldown and microtubule binding assays. These interactions were confirmed in vivo by co-immunoprecipitation. Confocal microscopy revealed that dysferlin and alpha-tubulin co-localized in the perinuclear region and in vesicular structures in myoblasts, and along thin longitudinal structures reminiscent of microtubules in myotubes. We mapped dysferlin's alpha-tubulin-binding region to its C2A and C2B domains. Modulation of calcium levels did not affect dysferlin binding to alpha-tubulin, suggesting that this interaction is calcium-independent. Our studies identified a new binding partner for dysferlin and suggest a role for microtubules in dysferlin trafficking to the sarcolemma.

Dysferlin associates with the developing T‐tubule system in rodent and human skeletal muscle

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.

New aspects on patients affected by dysferlin deficient muscular dystrophy

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...

Pattern of skeletal muscle involvement in primary dysferlinopathies: a whole-body 3.0-T magnetic resonance imaging study

Mutations in the gene encoding dysferlin cause limb girdle muscular dystrophy type 2B (LGMD2B), distal Miyoshi myopathy (MM), and a rare form of distal anterior compartment myopathy. To study the correlations between clinical manifestations and muscle imaging changes we conducted a 3.0-T magnetic resonance imaging (MRI) study in six German patients with primary dysferlinopathies defined by absence of dysferlin expression in muscle (MM, n = 3; LGMD2B, n = 2; hyperCKemia without clinical symptoms, n = 1). Patients with manifest myopathy had widespread muscular pathology. In analogy to previous imaging studies, we confirmed an involvement of the anterior and posterior thigh compartments and a predominant involvement of posterior lower legs. However, our whole-body MRI study further provided evidence of signal alterations in the glutei, erector spinae and shoulder girdle muscles. Correlation of clinical findings with imaging demonstrated the potential of MRI to detect subclinical muscle pathology. Whole-body 3.0-T MRI is a non-invasive method to demonstrate various degrees of skeletal muscle alterations and disease progression in muscular dystrophies. Furthermore, whole-body high-field MRI may serve as a helpful diagnostic tool in differentiating primary dysferlinopathies from other forms of LGMD and distal myopathies.

G.P.10.10 Dysferlin does not play an essential role in skeletal myoblast fusion

Mutations in the dysferlin gene cause limb-girdle muscular dystrophy type 2B, Miyoshi myopathy and distal anterior compartment myopathy, collectively known as dysferlinopathy. The dysferlin protein containing six C2 domains and one transmembrane domain has been implicated in the membrane resealing step of sarcolemma repair and myoblast fusion. However, the mechanism of the disease and the function of dysferlin in this process are still largely unknown. To investigate the function of dysferlin in myoblast differentiation, primary cultures and skeletal muscle tissue from wild type C57BL10, dysferlin-deficient C57BL10.SJL-dysf and dystrophin-deficient mdx mice were analysed for growth and fusion as well as protein expression during differentiation. The primary myoblasts generated from C57BL10.SJL-dysf have a similar division rate and fusion index compared to C57BL10 and mdx mice. In C57BL10 and mdx, dysferlin is expressed at the sites of membrane fusion and cell membrane after differentiation. No significant difference was found in myogenin expression in C57BL10.SJL-dysf myoculture compared to C57BL10 and mdx myoculture. We observed 20–30% of wild type levels of the dysferlin protein in C57BL10.SJL-dysf neonatal muscle tissue and primary myoblasts generated from neonatal mice by Western blot. However, the truncated dysferlin protein in C57BL10.SJL-dysf fails to correctly localise at the sites of membrane fusion and cell membrane in primary culture and skeletal muscle indicating that it is not functional. The lack of functional dysferlin and the same differentiation efficiency in C57BL10.SJL-dysf suggests that dysferlin does not play an essential role in myoblast fusion.

Late onset in dysferlinopathy widens the clinical spectrum

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.

Dysferlin Homozygous Mutation G1418D Causes Limb-Girdle Type 2B in a Mexican Family

Dysferlin protein (DYSF) is a ferlin family member found in sarcolemma and is involved in membrane repair, muscle differentiation, membrane fusion, etc. The deficiency of DYSF due to mutations is associated with different pathologic phenotypes including the autosomal recessive limb-girdle type 2B phenotype (LGMD2B), a distal anterior compartment myopathy (DMAT), and the Miyoshi myopathy (MM). In this study, we determined a missense mutation c.4253G>A on the DYSF gene in a Mexican family from an endogamic population. This mutation was assumed to be the cause of dystrophy because only homozygous individuals of the family manifest a clinical phenotype. Structural implications caused by G/D substitution at amino acid position 1418 are discussed in terms of potential importance of the dysferlin neighboring sequence.

G.P.4.06 Dysferlinopathy with very late onset and untypical clinical presentation

Mutations in the dysferlin gene cause LGMD2B, Miyoshi Myopathy and distal anterior compartment myopathy. The age of onset is generally in the late teens to mid-twenties. Although phenotypic heterogeneity is a common feature in this entity, patients with LGMD2B usually present with weakness in proximal muscle groups, whereas patients with Myioshi Myopathy and distal anterior compartment myopathy usually show distal weakness as the presenting symptom. Here we present a patient who showed first symptoms at the age of 73 years with gradual onset of stiffness affecting her trunk and lower limb girdle.

Dysferlinopathy in the Jews of the Caucasus: A frequent mutation in the dysferlin gene

Dysferlin encoding gene (DYS) is mutated in the autosomal recessive disorders Miyoshi myopathy, Limb Girdle Muscular Dystrophy type 2B (LGMD2B) and distal anterior compartment myopathy, causing dysferlin deficiency in muscle biopsy. Three ethnic clusters have previously been described in Dysferlinopathy: the Libyan Jewish population originating in the area of Tripoli, Italian and Spanish populations. We report another cluster of this muscular dystrophy in Israel among Jews of the Caucasus region. A genomic analysis of the dysferlin coding sequence performed in patients from this ethnic group, who demonstrated an absence of dysferlin expression in muscle biopsy, revealed a homozygous frameshift mutation of G deletion at codon 927 (2779delG) predicting a truncated protein and a complete loss of functional protein. The possible existence of a founder effect is strengthened by our finding of a 4% carrier frequency in this community. These findings are important for genetic counseling and also enable a molecular diagnosis of LGMD2B in Jews of the Caucasus region.

Distal anterior compartment myopathy with early ankle contractures

Dysferlinopathies exhibit marked heterogeneity in the initial distribution of muscle involvement at the onset of the disease. We describe a Japanese patient with dysferlinopathy who exhibited distal anterior compartment myopathy (DACM) with early contractures of the ankle, whose pedigree included patients with two other types of dysferlinopathy. The existence of three phenotypes of dysferlinopathy in one pedigree is reported, indicating the involvement of molecules other than dysferlin in the pathogenesis.

From T‐tubule to sarcolemma: damage‐induced dysferlin translocation in early myogenesis

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.

AHNAK a novel component of the dysferlin protein complex, redistributes to the cytoplasm with dysferlin during skeletal muscle regeneration

Mutations in dysferlin cause limb girdle muscular dystrophy 2B, Miyoshi myopathy and distal anterior compartment myopathy. Dysferlin is proposed to play a role in muscle membrane repair. To gain functional insight into the molecular mechanisms of dysferlin, we have searched for dysferlin-interacting proteins in skeletal muscle. By coimmunoprecipitation coupled with mass spectrometry, we demonstrate that AHNAK interacts with dysferlin. We defined the binding sites in dysferlin and AHNAK as the C2A domain in dysferlin and the carboxyterminal domain of AHNAK by glutathione S-transferase (GST)-pull down assays. As expected, the N-terminal domain of myoferlin also interacts with the carboxyterminal domain of AHNAK. In normal skeletal muscle, dysferlin and AHNAK colocalize at the sarcolemmal membrane and T-tubules. In dysferlinopathies, reduction or absence of dysferlin correlates with a secondary muscle-specific loss of AHNAK. Moreover, in regenerating rat muscle, dysferlin and AHNAK showed a marked increase and cytoplasmic localization, consistent with the direct interaction between them. Our data suggest that dysferlin participates in the recruitment and stabilization of AHNAK to the sarcolemma and that AHNAK plays a role in dysferlin membrane repair process. It may also have significant implications for understanding the biology of AHNAK-containing exocytotic vesicles, "enlargosomes," in plasma membrane remodeling and repair.