Limb-girdle Dystrophy Type Research Articles

Tips to Design Effective Splice-Switching Antisense Oligonucleotides for Exon Skipping and Exon Inclusion.

Antisense-mediated exon skipping and exon inclusion have proven to be powerful tools for treating neuromuscular diseases. The approval of Exondys 51 (eteplirsen) and Spinraza (nusinersen) for the treatment of patients with Duchenne muscular dystrophy (DMD) and spinal muscular atrophy (SMA) was the most noteworthy accomplishment in 2016. Exon skipping uses short DNA-like molecules called antisense oligonucleotides (AONs) to correct the disrupted reading frame, allowing the production of functional quasi-dystrophin proteins, and ameliorate the progression of the disease. Exon inclusion for SMA employs an AON targeting an intronic splice silencer site to include an exon which is otherwise spliced out. Recently, these strategies have also been explored in many other genetic disorders, including dysferlin-deficient muscular dystrophy (e.g., Miyoshi myopathy; MM, limb-girdle muscular dystrophy type 2B; LGMD2B, and distal myopathy with anterior tibial onset; DMAT), laminin α2 chain (merosin)-deficient congenital muscular dystrophy (MDC1A), sarcoglycanopathy (e.g., limb-girdle muscular dystrophy type 2C; LGMD2C), and Fukuyama congenital muscular dystrophy (FCMD). A major challenge in exon skipping and exon inclusion is the difficulty in designing effective AONs. The mechanism of mRNA splicing is highly complex, and the efficacy of AONs is often unpredictable. We will discuss the design of effective AONs for exon skipping and exon inclusion in this chapter.

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.

Left ventricular deformation abnormalities in a patient with calpainopathy-a case from the three-dimensional speckle-tracking echocardiographic MAGYAR-Path Study.

Calpainopathy or limb-girdle muscular dystrophy type 2A (LGMD2A) is the most common type of autosomal recessive limb-girdle muscular dystrophies. The disease is caused by mutations in the CAPN3 gene encoding calpain, a protein involved in muscle membrane remodeling and repair. This paper gives an overview of the genetic background, clinical course, and diagnosis of the disease, and presents the first case of calpainopathy in which cardiac deformation mechanics was investigated. Three-dimensional speckle-tracking echocardiography (3DSTE) demonstrated reduced left ventricular (LV) strains and increased LV apical rotation and twist, suggestive of asymptomatic subclinical LV dysfunction. Cardiac involvement has not been previously reported in calpainopathy.

Impaired regeneration in calpain-3 null muscle is associated with perturbations in mTORC1 signaling and defective mitochondrial biogenesis

BackgroundPrevious studies in patients with limb-girdle muscular dystrophy type 2A (LGMD2A) have suggested that calpain-3 (CAPN3) mutations result in aberrant regeneration in muscle.MethodsTo gain insight into pathogenesis of aberrant muscle regeneration in LGMD2A, we used a paradigm of cardiotoxin (CTX)-induced cycles of muscle necrosis and regeneration in the CAPN3-KO mice to simulate the early features of the dystrophic process in LGMD2A. The temporal evolution of the regeneration process was followed by assessing the oxidative state, size, and the number of metabolic fiber types at 4 and 12 weeks after last CTX injection. Muscles isolated at these time points were further investigated for the key regulators of the pathways involved in various cellular processes such as protein synthesis, cellular energy status, metabolism, and cell stress to include Akt/mTORC1 signaling, mitochondrial biogenesis, and AMPK signaling. TGF-β and microRNA (miR-1, miR-206, miR-133a) regulation were also assessed. Additional studies included in vitro assays for quantifying fusion index of myoblasts from CAPN3-KO mice and development of an in vivo gene therapy paradigm for restoration of impaired regeneration using the adeno-associated virus vector carrying CAPN3 gene in the muscle.ResultsAt 4 and 12 weeks after last CTX injection, we found impaired regeneration in CAPN3-KO muscle characterized by excessive numbers of small lobulated fibers belonging to oxidative metabolic type (slow twitch) and increased connective tissue. TGF-β transcription levels in the regenerating CAPN3-KO muscles were significantly increased along with microRNA dysregulation compared to wild type (WT), and the attenuated radial growth of muscle fibers was accompanied by perturbed Akt/mTORC1 signaling, uncoupled from protein synthesis, through activation of AMPK pathway, thought to be triggered by energy shortage in the CAPN3-KO muscle. This was associated with failure to increase mitochondria content, PGC-1α, and ATP5D transcripts in the regenerating CAPN3-KO muscles compared to WT. In vitro studies showed defective myotube fusion in CAPN3-KO myoblast cultures. Replacement of CAPN3 by gene therapy in vivo increased the fiber size and decreased the number of small oxidative fibers.ConclusionOur findings provide insights into understanding of the impaired radial growth phase of regeneration in calpainopathy.

Limb girdle muscular dystrophy due to mutations in POMT2

BackgroundMutations in the gene coding for protein O-mannosyl-transferase 2 (POMT2) are known to cause severe congenital muscular dystrophy, and recently, mutations in POMT2 have also been linked to a milder...

Limb-girdle muscular dystrophy type 2I: two Chinese families and a review in Asian patients

ABSTRACTBackground: Limb-girdle muscular dystrophy type 2I (LGMD2I) is an autosomal recessive hereditary disorder caused by mutations in the fukutin-related protein (FKRP) gene. Although the features of the disorder in European patients have been summarized, Asian patients with LGMD2I have rarely been reported. Thus, the clinical differences in LGMD2I between Asian and European patients and the associated genetic changes remain unclear.Methods: We reported detailed clinical data as well as results from muscle biopsy, muscle MRI and genetic analysis of the FKRP gene in two unrelated Chinese families with LGMD2I. Additionally, a review of the literature focusing on the clinical and mutational features of LGMD2I in Asian patients was performed.Results: The muscle biopsy results showed dystrophic features. Immunohistochemical staining revealed decreased glycosylations on α-dystroglycan. The muscle MRI results showed that the gluteus maximus, adductor, biceps femoris, vastus intermedius and vastus lateralis were severely affected. The patients in the two families harbored the same compound heterozygous mutations (c.545A>G and c.948delC). One patient showed significant clinical improvement after corticosteroid treatment.Conclusion: Our study expanded the reported spectrum of Asian LGMD2I patients. Our literature review revealed that pathogenic mutations in the FKRP gene in Asian LGMD2I patients are compound heterozygous rather than homozygous. Compound heterozygous Asian patients have a mild phenotype but frequently show respiratory and cardiac impairments. Corticosteroids may be beneficial for the treatment of LGMD2I and should be further investigated.

P.36 - Limb girdle muscular dystrophy type 2I: Lack of correlation between clinical severity, histopathological alterations and levels of glycosylated α-dystroglycan in patients homozygous for the common FKRP mutation

Limb girdle musclular dystrophy type 2I (LGMD2I) is a progressive disorder caused by mutations in the FuKutin-Related Protein gene (FKRP). LGMD2I displays clinical heterogeneity with onset of severe symptoms in early childhood to mild calf and thigh hypertrophy in the second or third decade. Patients homozygous for the common FKRP mutation c.826C > A (p.Leu276Ile) show phenotypes within the milder end of the clinical spectrum. However, this group also manifests substantial clinical variability. FKRP deficiency causes hypoglycosylation of α-dystroglycan; a component of the dystrophin associated glycoprotein complex. α-Dystroglycan hypoglycosylation is in turn associated with loss of interaction with -, and hence, depletion of laminin α2. Here, we have attempted to clarify if the clinical variability seen in patients homozygous for c.826C > A, is related to alterations in muscle fiber pathology, α-DG glycosylation levels, levels of laminin α2 as well as the capacity of α-DG to bind to laminin. We have assessed vastus lateralis muscle biopsies from 25 LGMD2I patients harboring the c.826C > A/c.826C > A genotype by histological examination, immunohistochemistry and immunoblotting. No clear correlation was found between clinical severity, as determined by self-reported walking function, and the above features, suggesting that more complex molecular processes are contributing to the progression of disease.

P.434 - ActiMyo home monitoring in adult patients with limb girdle muscular dystrophy type 2B and facioscapulohumeral muscular dystrophy in study ATYR 1940-C-004

To evaluate the feasibility of home-monitoring changes in functional activity using ActiMyo in a subset of patients with LGMD2B and FSHD in study ATYR 1940-C-004. ActiMyo is composed of two watch-like devices that record magneto-inertial sensors used to compute activity and gait variables in controlled and non-controlled setting. ATYR1940-C-004 is a multicenter, open-label study evaluating intra-patient dose escalations of intravenous ATYR1940 in patients with genetically confirmed FSHD and LGMD2B. ActiMyo was provided to patients at baseline. Patients wore the device every day at home for the duration of the study (approximately four months). For each patient, gait variables were calculated from the data recorded in 30-day sub-periods using the ActiMyo sensor worn at the ankle, and the wrist. For each sub-period, gait parameters were compared between FSHD and LGMD2B patients using a non-parametric Mann-Whitney test. Change from baseline over the four month period was assessed using Friedman analysis of variance for paired samples. Of the eighteen patients enrolled in the study, ten were ambulant and sufficiently compliant for analysis. Median step speed and step length were significantly lower in FSHD patients compared to LGMD2B patients at baseline. Longitudinal analyses of those completing the assessment showed a visit effect with a mild decrement of median step speed after 3 months in 8 patients (p = 0.03) and after 4 months in 6 patients (p = 0.04). In contrast, cumulative variables such as total number of meters/step were highly variable from month to month, and no visit effect were found in this variable, or other like duration of walking episodes, step length or step height. The present study shows the feasibility of monitoring gait activity at home in ambulant FSHD and LGMD2B patients. In this limited number of patients, Actimyo could detect statistically significant mild decreases in median step speed over a four month period.

P.144 - Turnover studies on DNAJB6 and the CASA pathway proteins

Limb-girdle muscular dystrophy type 1D (LGMD1D) results from dominant mutations in the co-chaperone DNAJB6. The mutations confer toxic properties to the short cytoplasmic isoform DNAJB6b, and slow down the turnover of mutant DNAJB6, as well as that of the co-expressed wild-type protein. We have previously shown that DNAJB6 interacts with the chaperone-assisted selective autophagy (CASA) system. This macroautophagy pathway, important for muscle maintenance, depends on the co-chaperone BAG3, together with HSPA8 (Hsc70) and HSPB8 (Hsp22). Interestingly, overexpression of BAG3 increases DNAJB6b toxicity in zebrafish – an effect not seen with the BAG3 myopathy mutant P209L – suggesting an active role for BAG3 in LGMD1D pathogenesis. The role of altered DNAJB6 turnover in the pathogenesis of LGMD1D, and its relationship with the CASA proteins is unknown. BAG3 could increase the toxicity of mutant DNAJB6b by aggravating its turnover block. Alternatively, if BAG3 and HSPB8 lie downstream of DNAJB6b mutations, also their turnover rates could be affected. To explore these possibilities, we have carried out cell-culture based protein turnover studies. In our setup, proteins of interest are expressed in a tetracycline-inducible system, and their turnover is followed after tetracycline removal. Coexpression or knockdown allows identification of modulating effects of other proteins. Unexpectedly, while wild-type BAG3 had little effect, BAG3 P209L blocked the turnover of both wild-type and mutant DNAJB6b. This correlated with a shift of DNAJB6b to the insoluble fraction, suggesting that mutant BAG3 may sequester DNAJB6b into an insoluble pool that is resistant to normal degradation. Our results reinforce a functional interaction between DNAJB6 and BAG3, provide a possible explanation for the different effects of wild-type and P209L BAG3 on DNAJB6 toxicity, and place DNAJB6 downstream of the BAG3 P209L mutation, potentially linking the pathomechanisms of LGMD1D and BAG3 myopathy.

P.395 - Identification of new inhibitors of misfolded alpha-sarcoglycan degradation by high-throughput screening

Several genetic diseases are caused by missense mutations leading to the proteasomal degradation of misfolded proteins through the endoplasmic reticulum quality control process (ERQC). Among these diseases, limb-girdle muscular dystrophies type 2D (LGMD2D) is characterized by a progressive proximal muscle weakness. Molecularly, LGMD2D is due to mutations in the gene encoding alpha–sarcoglycan (alpha-SG), a dystrophin-associated glycoprotein. Recent findings described the positive impact of ERQC inhibitors on alpha-SG localization to the plasma membrane leading to the development of new therapeutical perspectives. Here, we report the development of a new in vitro high-throughput screening assay that allow to monitor the proper localization of the most frequent mutant form of alpha-SG (R77C substitution). Using this pharmacological assay, a library of 2200 FDA-approved drugs was tested identifying a list of new drug candidates potentially repurposable to LGMD2D.

P.164 - Novel binding partner of dysferlin is required for plasma-membrane repair

Mutations in the dysferlin gene are responsible for adult-onset, progressive, and recessively inherited muscular dystrophies called dysferlinopathy, which has two main phenotypes: Miyoshi myopathy and limb-girdle muscular dystrophy type 2B. The dysferlin is composed of 55 exons encoding for 2,080 amino acids. The dysferlin protein is expressed in the plasma membrane of skeletal muscles and has been reported to be involved in calcium-mediated membrane fusion and repair. We previously reported over 50 different mutations across the entire dysferlin and are focusing on these dysferlin and dysferlin-related proteins. To identify the binding partners of dysferlin, which can be working as the similar functional role, would be possible therapeutic targets to compensate the functional loss of the mutated dysferlin. Using a proteomics approach combined with a recombinant maltose-binding protein, we found a protein X that binds to a specific region of dysferlin. Next, using an ex vivo laser-injury experiment, we revealed that protein X is essential for the membrane repair of sarcolemmal damage in skeletal muscle fiber. Moreover, the injury-triggered subsarcolemmal accumulation of the protein X was regulated by dysferlin. Finally, an X-activating compound rescued the impairment of the damaged membrane repair in immortalized myoblasts established from the dysferlin-deficient patients. Collectively, the protein X is required for plasma-membrane repair and a potential therapeutic target for dysferlinopathy.

P.151 - Limb girdle muscular dystrophy 2G in a religious minority of Bulgarian muslims homozygous for the c.75G>A, p.Trp25* TCAP mutation

Mutations in TCAP gene cause autosomal recessive limb-girdle muscular dystrophy type 2G (LGMD2G), congenital muscular dystrophy and dilated and hypertrophic cardiomyopathy. To describe the phenotypic spectrum of LGMD 2G in a genetically homogeneous group of patients, belonging to a religious minority of Bulgarian muslims. Sixteen affected individuals (11 male and 5 female) from 10 pedigrees underwent neurological examination, including manual muscle testing, electromyography (EMG), cardiac evaluation, ventillatory assessment, evaluation of serum creatine kinase levels (CK) and molecular-genetic testing. The pattern of muscle involvement in the lower limbs was assessed in 2 patients by 3T MRI. Fifteen of the affected were homozygous for the c.75G>A, p.Trp25*mutation, whereas one was compound heterozygous, carrying Glu132Val in exon 2 as second mutation. The mean age at onset was 17.94 ± 3.97 years, ranging between 10 and 25 years. The initial manifestations in 12 patients included proximal muscle weakness in the lower limbs, followed by difficulties in ankle dorsiflexion. In 4 of the affected the proximal and distal weakness in the legs occurred simultaneously. The proximal muscles of the upper limbs became involved 5–9 years after the disease onset. Scapular winging and lumbar hyperlordosis developed late in the course of the disease. Respiratory and cardiac functions were spared. On the MRI the muscles in all three compartments of the thigh and anterior leg ones were predominantly affected, while m. sartorius, gracilis remained relatively spared. Homozygosity for c.75G>A, p.Trp25*mutation is associated with a homogeneous clinical presentation in terms of pattern of muscle involvement. The clinical course and severity of the disease however show inter- and intra-familial variation despite the mutation homogeneity.

Generation of an induced pluripotent stem cell line (CSCRMi001-A) from a patient with a new type of limb-girdle muscular dystrophy (LGMD) due to a missense mutation in POGLUT1 (Rumi)

Recently, a new type of limb-girdle muscular dystrophy (LGMD type 2Z) has been identified due to a missense mutation in POGLUT1 (protein O-glucosyltransferase-Rumi), an enzyme capable of adding glucose to a distinct serine residue of epidermal growth factor-like repeats containing a C-X-S-X-(P/A)-C consensus sequence such as Notch receptors. Affected patients demonstrate reduced Notch signaling, decreased muscle stem cell pool and hypoglycosylation of α-dystroglycan, leading to LGMD phenotype. Here we report the generation and characterization of an iPSC line (CSCRMi001-A) from a LGMD-2Z patient with missense mutation in POGLUT1 which can be used for in vitro disease modeling.

Natural disease history of mouse models for limb girdle muscular dystrophy types 2D and 2F.

Limb-girdle muscular dystrophy types 2D and 2F (LGMD 2D and 2F) are autosomal recessive disorders caused by mutations in the alpha- and delta sarcoglycan genes, respectively, leading to severe muscle weakness and degeneration. The cause of the disease has been well characterized and a number of animal models are available for pre-clinical studies to test potential therapeutic interventions. To facilitate transition from drug discovery to clinical trials, standardized procedures and natural disease history data were collected for these mouse models. Implementing the TREAD-NMD standardized operating procedures, we here subjected LGMD2D (SGCA-null), LGMD2F (SGCD-null) and wild type (C57BL/6J) mice to five functional tests from the age of 4 to 32 weeks. To assess whether the functional test regime interfered with disease pathology, sedentary groups were taken along. Muscle physiology testing of tibialis anterior muscle was performed at the age of 34 weeks. Muscle histopathology and gene expression was analysed in skeletal muscles and heart.Muscle histopathology and gene expression was analysed in skeletal muscles and heart. Mice successfully accomplished the functional tests, which did not interfere with disease pathology. Muscle function of SGCA- and SGCD-null mice was impaired and declined over time. Interestingly, female SGCD-null mice outperformed males in the two and four limb hanging tests, which proved the most suitable non-invasive tests to assess muscle function. Muscle physiology testing of tibialis anterior muscle revealed lower specific force and higher susceptibility to eccentric-induced damage in LGMD mice. Analyzing muscle histopathology and gene expression, we identified the diaphragm as the most affected muscle in LGMD strains. Cardiac fibrosis was found in SGCD-null mice, being more severe in males than in females. Our study offers a comprehensive natural history dataset which will be useful to design standardized tests and future pre-clinical studies in LGMD2D and 2F mice.

Treadmill Training with HAL Exoskeleton-A Novel Approach for Symptomatic Therapy in Patients with Limb-Girdle Muscular Dystrophy-Preliminary Study.

Purpose: Exoskeletons have been developed for rehabilitation of patients with walking impairment due to neurological disorders. Recent studies have shown that the voluntary-driven exoskeleton HAL® (hybrid assistive limb) can improve walking functions in spinal cord injury and stroke. The aim of this study was to assess safety and effects on walking function of HAL® supported treadmill therapy in patients with limb-girdle muscular dystrophy (LGMD).Materials and Methods: Three LGMD patients received 8 weeks of treadmill training with HAL® 3 times a week. Outcome parameters were 10-meter walk test (10 MWT), 6-minute walk test, and timed-up-and-go test (TUG). Parameters were assessed pre and post training and 6 weeks later (follow-up).Results: All patients completed the therapy without adverse reactions and reported about improvement in endurance. Improvements in outcome parameters after 8 weeks could be demonstrated. Persisting effects were observed after 6 weeks for the 10 MWT and TUG test (follow-up).Conclusions: HAL® treadmill training in LGMD patients can be performed safely and enables an intensive highly repetitive locomotor training. All patients benefitted from this innovative method. Upcoming controlled studies with larger cohorts should prove its effects in different types of LGMD and other myopathies.

Novel fukutin mutations in limb-girdle muscular dystrophy type 2M with childhood onset

Novel fukutin mutations in limb-girdle muscular dystrophy type 2M with childhood onset

Treatment with Recombinant Human MG53 Protein Increases Membrane Integrity in a Mouse Model of Limb Girdle Muscular Dystrophy 2B

Limb girdle muscular dystrophy type 2B (LGMD2B) and other dysferlinopathies are degenerative muscle diseases that result from mutations in the dysferlin gene and have limited treatment options. The dysferlin protein has been linked to multiple cellular functions including a Ca2+-dependent membrane repair process that reseals disruptions in the sarcolemmal membrane. Recombinant human MG53 protein (rhMG53) can increase the membrane repair process in multiple cell types both invitro and invivo. Here, we tested whether rhMG53 protein can improve membrane repair in a dysferlin-deficient mouse model of LGMD2B (B6.129-Dysftm1Kcam/J). We found that rhMG53 can increase the integrity of the sarcolemmal membrane of isolated muscle fibers and whole muscles in a Ca2+-independent fashion when assayed by a multi-photon laser wounding assay. Intraperitoneal injection of rhMG53 into mice before acute eccentric treadmill exercise can decrease the release of intracellular enzymes from skeletal muscle and decrease the entry of immunoglobulin G and Evans blue dye into muscle fibers invivo. These results indicate that short-term rhMG53 treatment can ameliorate one of the underlying defects in dysferlin-deficient muscle by increasing sarcolemmal membrane integrity. We also provide evidence that rhMG53 protein increases membrane integrity independently of the canonical dysferlin-mediated, Ca2+-dependent pathway known to be important for sarcolemmal membrane repair.

Autologous intramuscular transplantation of engineered satellite cells induces exosome-mediated systemic expression of Fukutin-related protein and rescues disease phenotype in a murine model of limb-girdle muscular dystrophy type 2I.

α-Dystroglycanopathies are a group of muscular dystrophies characterized by α-DG hypoglycosylation and reduced extracellular ligand-binding affinity. Among other genes involved in the α-DG glycosylation process, fukutin related protein (FKRP) gene mutations generate a wide range of pathologies from mild limb girdle muscular dystrophy 2I (LGMD2I), severe congenital muscular dystrophy 1C (MDC1C), to Walker-Warburg Syndrome and Muscle-Eye-Brain disease. FKRP gene encodes for a glycosyltransferase that in vivo transfers a ribitol phosphate group from a CDP –ribitol present in muscles to α-DG, while in vitro it can be secreted as monomer of 60kDa. Consistently, new evidences reported glycosyltransferases in the blood, freely circulating or wrapped within vesicles. Although the physiological function of blood stream glycosyltransferases remains unclear, they are likely released from blood borne or distant cells. Thus, we hypothesized that freely or wrapped FKRP might circulate as an extracellular glycosyltransferase, able to exert a “glycan remodelling” process, even at distal compartments. Interestingly, we firstly demonstrated a successful transduction of MDC1C blood-derived CD133+ cells and FKRP L276IKI mouse derived satellite cells by a lentiviral vector expressing the wild-type of human FKRP gene. Moreover, we showed that LV-FKRP cells were driven to release exosomes carrying FKRP. Similarly, we observed the presence of FKRP positive exosomes in the plasma of FKRP L276IKI mice intramuscularly injected with engineered satellite cells. The distribution of FKRP protein boosted by exosomes determined its restoration within muscle tissues, an overall recovery of α-DG glycosylation and improved muscle strength, suggesting a systemic supply of FKRP protein acting as glycosyltransferase.

Abnormal spontaneous activity in primary myopathic disorders.

Reproducible non-insertional spontaneous activity (SA), with the exception of endplate activity, is an unequivocal sign of abnormality and is one of the most useful findings obtained on electromyography. In this retrospective study we analyzed occurrence and distribution of abnormal SA in 151 patients with genetically confirmed myopathies. Complex repetitive discharges (CRDs) occurred more frequently than fibrillation potentials (fibs) and positive sharp waves (PSWs) in centronuclear myopathy (CNM) and limb-girdle muscular dystrophy type 2A (LGMD-2A), whereas fibs/PSWs were observed more often in desminopathy and facioscapulohumeral dystrophy (FSHD). Abnormal SA was commonly found in CNM (66.7%) and desminopathy (61.5%), occasionally in Duchenne (DMD) and Becker muscular dystrophy (BMD) (45.2% and 27.6%, respectively), but rarely in FSHD (14.9%) and LGMD-2A (12.0%). Abnormal SA probably occurs more frequently in disorders associated with structural changes in muscle fibers. Screening for SA may be a valuable tool for diagnosis of non-myotonic myopathies. Muscle Nerve 56: 427-432, 2017.

Hyperckemia and myalgia are common presentations of anoctamin-5-related myopathy in French patients.

Patients with anoctamin-5 (ANO5) mutations may present not only with limb-girdle muscular dystrophy type 2L or adult-onset Miyoshi-type myopathy but also with asymptomatic hyperCKemia, exercise intolerance, or rhabdomyolysis. Data from 38 patients in France with ANO5 mutations with and without muscle weakness on first examination were compared. Twenty patients presented without muscle weakness. Median age at symptom onset or discovery of hyperCKemia was 23 years. Creatine kinase levels ranged from 200 to 40,000 U/L. Electromyography showed a myopathic pattern in 5 patients, and muscle imaging showed involvement of posterior calf muscles in 10 patients. Mild cardiac involvement was observed in 2 patients. Sixteen patients remain free of weakness after a median follow-up period of 5 years. Asymptomatic, sometimes mild hyperCKemia or exercise intolerance is a presentation of ANO5-related myopathy and may remain isolated or precede muscle weakness by many years. Muscle Nerve 56: 1096-1100, 2017.