N-Acetylcysteine Reduces Skeletal Muscles Oxidative Stress and Improves Grip Strength in Dysferlin-Deficient Bla/J Mice.

Dysferlinopathy is an autosomal recessive muscular dystrophy resulting from mutations in the dysferlin gene. Absence of dysferlin in the sarcolemma and progressive muscle wasting are hallmarks of this disease. Signs of oxidative stress have been observed in skeletal muscles of dysferlinopathy patients, as well as in dysferlin-deficient mice. However, the contribution of the redox imbalance to this pathology and the efficacy of antioxidant therapy remain unclear. Here, we evaluated the effect of 10 weeks diet supplementation with the antioxidant agent N-acetylcysteine (NAC, 1%) on measurements of oxidative damage, antioxidant enzymes, grip strength and body mass in 6 months-old dysferlin-deficient Bla/J mice and wild-type (WT) C57 BL/6 mice. We found that quadriceps and gastrocnemius muscles of Bla/J mice exhibit high levels of lipid peroxidation, protein carbonyls and superoxide dismutase and catalase activities, which were significantly reduced by NAC supplementation. By using the Kondziela's inverted screen test, we further demonstrated that NAC improved grip strength in dysferlin deficient animals, as compared with non-treated Bla/J mice, without affecting body mass. Together, these results indicate that this antioxidant agent improves skeletal muscle oxidative balance, as well as muscle strength and/or resistance to fatigue in dysferlin-deficient animals.

HNRNPDL-related muscular dystrophy: expanding the clinical, morphological and MRI phenotypes.

Autosomal dominant limb girdle muscular dystrophy D3 HNRNPDL-related is a rare dominant myopathy caused by mutations in HNRNPDL. Only three unrelated families have been described worldwide, a Brazilian and a Chinese carrying the mutation c.1132G>A p.(Asp378Asn), and one Uruguayan with the mutation c.1132G>C p. (Asp378His), both mutations occurring in the same codon. The present study enlarges the clinical, morphological and muscle MRI spectrum of AD-HNRNPDL-related myopathies demonstrating the significant particularities of the disease. We describe two new unrelated Argentinean families, carrying the previously reported c.1132G>C p.(Asp378His) HNRNPDL mutation. There was a wide phenotypic spectrum including oligo-symptomatic cases, pure limb girdle muscle involvement or distal lower limb muscle weakness. Scapular winging was the most common finding, observed in all patients. Muscle MRIs of the thigh, at different stages of the disease, showed particular involvement of adductor magnus and vastus besides a constant preservation of the rectus femoris and the adductor longus muscles, defining a novel MRI pattern. Muscle biopsy findings were characterized by the presence of numerous rimmed vacuoles, cytoplasmic bodies, and abundant autophagic material at the histochemistry and ultrastructural levels. HNRNPDL-related LGMD D3 results in a wide range of clinical phenotypes from the classic proximal form of LGMD to a more distal phenotype. Thigh MRI suggests a specific pattern. Codon 378 of HNRNPDL gene can be considered a mutation hotspot for HNRNPDL-related myopathy. Pathologically, the disease can be classified among the autophagic rimmed vacuolar myopathies as with the other multisystem proteinopathies.

Reliability of home-based, motor function measure in hereditary neuromuscular diseases.

Objective To evaluate the reliability of the motor function measure (MFM) scale in the assessment of disease severity and progression when administered at home and clinic and assess its correlation with the Paediatric Outcomes Data Collection Instrument (PODCI). Methods In this prospective study, two assessors rated children with hereditary neuromuscular diseases (HNMDs) using the MFM at the clinic and then 2 weeks later at the patients' home. Intraclass correlation coefficient (ICC) was calculated for the reliability of the MFM and its domains. The reliability of each item was assessed and the correlation between MFM and three domains of PODCI was evaluated. Results A total of 48 children (5-17 years of age) were assessed in both locations and the MFM scale demonstrated excellent inter-rater reliability (ICC, 0.98). Weighted kappa ranged from excellent to poor. Correlation of the home-based MFM with the PODCI domain 'basic mobility and transfers' was excellent, with the 'upper extremity' domain was moderate, but there was no correlation with the 'happiness' domain. Conclusion The MFM is a reliable tool for assessing patients with HNMD when used in a home-based setting.

Broadening the imaging phenotype of dysferlinopathy at different disease stages.

INTRODUCTION: MRI characterization of dysferlinopathy has been mostly limited to the lower limbs. We aimed to broaden the MRI description of dysferlinopathy and to correlate it with objective measures of motor dysfunction. METHODS: Sequential whole-body axial MRI was performed in 27 patients with genetically confirmed dysferlinopathy classified according to disease duration. Spearman correlations of fatty infiltration scores versus Motor Function Measure (MFM) were calculated. RESULTS: Significant fatty infiltration was symmetrically present in early stages mainly in the posterior compartments of legs and thighs, thigh adductors, pelvic girdle, and some paravertebral muscles and the subscapularis. Later, fatty infiltration involved leg and thigh anterior compartments, arms and forearms, paravertebral, and trunk muscles. MRI infiltration score correlated positively with disease duration and negatively with MFM scale. CONCLUSIONS: We expand MRI characterization of dysferlinopathy and provide evidence for use of MRI scoring combined with motor functional scales to assess the natural course of disease. Muscle Nerve, 2016 Muscle Nerve 54: 203-210, 2016.

Toward an objective measure of functional disability in dysferlinopathy.

INTRODUCTION: Understanding the natural history of dysferlinopathy is essential to design and quantify novel therapeutic protocols. Our aim in this study was to assess, clinically and functionally, a cohort of patients with dysferlinopathy, using validated scales. METHODS: Thirty-one patients with genetically confirmed dysferlinopathy were assessed using the motor function measure (MFM), Modified Rankin Scale (MRS), Muscle Research Council (MRC) scale, serum creatine kinase (CK) assessment, baseline spirometry data, and echocardiographic and electrophysiologic studies. RESULTS: MFM and MRC scores showed a significant negative correlation with disease duration and inverse correlation with MRS, but not with onset age, clinical phenotype, or CK levels. Percent forced vital capacity (%FVC) correlated negatively with disease duration and onset age. Eight known pathogenic mutations were identified recurrently, 4 of which accounted for 79% of the total. CONCLUSIONS: The results suggest that MFM is a reliable outcome measure that may be useful for longitudinal follow-up in dysferlinopathy. Recurrent mutations suggest a founder effect in the Chilean population.

A new evidence for the maintenance of the sarcoglycan complex in muscle sarcolemma in spite of the primary absence of delta-SG protein.

delta-Sarcoglycan (delta-SG) is one of the first proteins of the sarcoglycan complex (SGC) to be expressed during muscle development, and it has been considered fundamental for the assembling and insertion of the SGC in the sarcolemma. Studies using heterologous cell systems and co-precipitation have demonstrated that SGC assembly was dependent on the simultaneous synthesis of all four sarcoglycan proteins. Mutations in any one of sarcoglycan genes, including the common disease causing mutation c.656delC in the delta-SG gene, block complex formation and its insertion in the plasma membrane. Failure in complex assembly in patients with this mutation would be therefore expected. In this study, we provide evidence for the possibility of preservation of part of the SG complex in the sarcolemma, even in the absence of delta-SG. This is based on the study of one mildly affected patient with limb-girdle muscular dystrophy type 2F (LGMD2F) due to the homozygous c.656delC mutation in the delta-SG gene. Protein analysis in his muscle biopsy presented a significant deficiency of only delta-SG with retention of the other three SG proteins in the sarcolemma. RNA expression analysis showed that zeta-SG, a functionally homologous to delta-SG, is not atypically upregulated in his muscle and would not replace the absent delta-SG, retaining the complex alpha-beta-gamma-zeta. The patient started clinical manifestation at age 25, with frequent falls, but he is currently able to walk unassisted at age 42. His clinical course is significantly milder when compared to several other affected patients carrying the same mutation associated with a total deficiency of the four SG proteins in the muscle studied by our group and confirmed in other patients. Therefore, our results add a new in vivo evidence that alpha-, beta-, and gamma-SG proteins can be maintained in the sarcolemma without delta-SG. Additionally, LGMD2F, with retention of the part of the SGC, might be associated to a milder clinical course, which has important implications for clinical prognosis and genetic counseling of the family.

Mutation analysis in the FKRP gene provides an explanation for a rare cause of intrafamilial clinical variability in LGMD2I.

We report a limb-girdle muscular dystrophy 2I family with three affected sisters and a highly variable clinical course. FKRP gene sequencing showed that all three sisters carried a nonsense paternal mutation (W225X). The two oldest sisters with a severe phenotype carried two maternal mutations V79M and P89A. However, the youngest sister with a milder course carried the paternal and only the V79M maternal mutation, due to an intragenic recombination.

A family with McLeod syndrome and calpainopathy with clinically overlapping diseases.

The authors describe a family with six patients with muscular dystrophy with a variable course. One is a compound heterozygote for CAPN3 mutations (calpainopathy) and the others have a single CAPN3 mutation. Linkage analysis and sequencing revealed a XK gene mutation (McLeod syndrome). This illustrates the variable phenotype of XK mutations and suggests the possibility that CAPN3 heterozygotes may have their condition caused by nonallelic mutations in other unrelated genes.

A new form of autosomal dominant limb-girdle muscular dystrophy (LGMD1G) with progressive fingers and toes flexion limitation maps to chromosome 4p21.

Limb-girdle muscular dystrophy (LGMD) is a genetic disorder characterized by progressive weakness of pelvic and scapular girdles and great clinical variability. It is a highly heterogeneous disease with 16 identified loci: six of them autosomal dominant (AD) (LGMD1) and 10 autosomal recessive (AR) (LGMD2). The responsible genes are known for three of the AD-LGMD and for all 10 AR-LGMD. Linkage analysis excluded these 16 loci in a Brazilian-Caucasian family with 12 patients affected by AD late-onset LGMD associated with progressive fingers and toes flexion limitation. Biceps muscle biopsy from one of the patients showed a predominantly myopathic histopathological pattern, associated with rimmed vacuoles. A genomewide scan was performed which mapped a new locus for this disorder at 4p21 with a maximum two-point lod score of 6.62 for marker D4S2964. Flanking markers place this locus between D4S2947 and D4S2409, within an interval of 9 cM. We propose to classify this AD form of LGMD as LGMD1G.