Making sense of the limb-girdle muscular dystrophies

Morpholino-Mediated Exons 28-29 Skipping of Dysferlin and Characterization of Multiexon-skipped Dysferlin using RT-PCR, Immunoblotting, and Membrane Wounding Assay

Dysferlinopathies are a group of disabling muscular dystrophies  that includes limb girdle muscular dystrophy type 2B (LGMD2B), Miyoshi myopathy, and distal myopathy with anterior tibial onset (DMAT) as the main phenotypes. They are associated with molecular defects in DYSF, which encodes dysferlin, a key player in sarcolemmal homeostasis. Previous investigations have suggested that exon skipping may be a promising therapy for many patients with dysferlinopathies. It was reported that exons 28-29 of DYSF are dispensable for dysferlin functions. Here, we present a method for multiexon skipping of DYSF exons 28-29 using a cocktail of two phosphorodiamidate morpholino oligomers (PMOs) on cells derived from a dystrophinopathy patient. Also, we describe assays to characterize the multiexon skipped dysferlin at several levels by using one-step RT-PCR, immunoblotting, and a membrane wounding assay.

Bi-allelic loss-of-function OBSCN variants predispose individuals to severe recurrent rhabdomyolysis

Rhabdomyolysis is the acute breakdown of skeletal myofibres in response to an initiating factor, most commonly toxins and over exertion. A variety of genetic disorders predispose to rhabdomyolysis through different pathogenic mechanisms, particularly in patients with recurrent episodes. However, most cases remain without a genetic diagnosis. Here we present six patients who presented with severe and recurrent rhabdomyolysis, usually with onset in the teenage years; other features included a history of myalgia and muscle cramps. We identified ten bi-allelic loss-of-function variants in the gene encoding obscurin (OBSCN) predisposing individuals to recurrent rhabdomyolysis. We show reduced expression of OBSCN and loss of obscurin protein in patient muscle. Obscurin is proposed to be involved in SR function and Ca2+ handling. Patient cultured myoblasts appear more susceptible to starvation as evidenced by a greater decreased in SR Ca2+ content compared to control myoblasts. This likely reflects a lower efficiency when pumping Ca2+ back into the SR and/or a decrease in Ca2+ SR storage ability when metabolism is diminished. OSBCN variants have previously been associated with cardiomyopathies. None of the patients presented with a cardiomyopathy and cardiac examinations were normal in all cases in which cardiac function was assessed. There was also no history of cardiomyopathy in first degree relatives, in particular in any of the carrier parents. This cohort is relatively young, thus follow-up studies and the identification of additional cases with bi-allelic null OBSCN variants will further delineate OBSCN-related disease and the clinical course of disease.

Patient reported quality of life in limb girdle muscular dystrophy

This study determined the frequency and impact of symptoms on quality of life in patients diagnosed with limb girdle muscular dystrophy (LGMD). Participants with a diagnosis of LGMD in registries based at the Coalition to Cure Calpain-3, the Jain foundation, and the Global FKRP Registry competed a survey to report the frequency and relative impact of themes and symptoms of LGMD. Frequency, mean impact, and population impact scores were calculated, and responses were categorized by age, symptom duration, gender, employment status, use of assistive devices, and LGMD subtypes. 134 participants completed the survey. The most prevalent themes included an inability to do activities (100%), limitation with mobility (99.3%), and lower extremity weakness (97.0%). Themes with the greatest impact were: limitations with mobility, lower extremity weakness, and an inability to do activities. Symptom duration and the use of assistive devices were associated with the presence of multiple themes. Employment was associated with the impact of several themes with no differences in frequency. The prevalence and impact of these themes vary in the LMGD population. The most prevalent and impactful themes were related to weakness, but additional concerns related to emotional challenges should also be considered in clinical and research settings.

Sarcoglycanopathies: an update

Sarcoglycanopathies are the most severe forms of autosomal recessive limb-girdle muscular dystrophies (LGMDs), constituting about 10-25% of LGMDs. The clinical phenotype is variable, but onset is usually in the first decade of life. Patients present muscle hypertrophy, elevated CK, variable muscle weaknesses, and progressive loss of ambulation. Four subtypes are known: LGMDR3, LGMDR4, LGMDR5 and LGMDR6, caused, respectively, by mutations in the SGCA, SGCB,SGCG and SGCD genes. Their four coded proteins, α-SG, ß-SG, λ-SG and δ-SG are part of the dystrophin-glycoprotein complex (DGC) present in muscle sarcolemma, which acts as a linker between the cytoskeleton of the muscle fiber and the extracellular matrix, providing mechanical support to the sarcolemma during myofiber contraction. Many different mutations have already been identified in all the sarcoglycan genes, with a predominance of some mutations in different populations. The diagnosis is currently based on the molecular screening for these mutations. Therapeutic approaches include the strategy of gene replacement mediated by a vector derived from adeno-associated virus (AAV). Pre-clinical studies have shown detectable levels of SG proteins in the muscle, and some improvement in the phenotype, in animal models. Therapeutic trials in humans are ongoing.

Sarcotubular Myopathy Due to Novel TRIM32 Mutation in Association with Multiple Sclerosis

Azerbaijani 28-year-old female showed weakness (MRC (Medical Research Council Scale for Muscle Strength) grade 4 in the proximal part of the upper and MRC grade 2–3 in the lower extremities), difficulty in stair lifting, positive symptom of Hoover’s rising, «waddling gait», decline deep reflexes symmetrical, lack of surface reflexes, positive Babinsky’s reflex on the right, urinary incontinence during sneezing, prolonged walking and exercise from puberty. Additional methods made it possible to identify minor violations of conduction of the left ventricle, electromyography signs of primary muscular disease with predominant involvement of the proximal muscles of the lower extremities, elevation of serum creatine kinase (746.81 U/l), active foci of demyelination in the left frontal lobe, intrathecal synthesis of oligoclonal IgG bands (type 2) in cerebrospinal fluid, atrophy and fatty degeneration of all muscles of the shins, homozygous Variant of Uncertain Significance (VUS) c.1855C > T (p.Pro619Ser) in TRIM32 gene and heterozygous VUS c.2300C > G (p.Thr767Arg) in KIF5A, c.2840G > A (p.Arg947Lys) in MYH2, c.1502G > C (p.Gly501Ala) in POMT1 genes. Comparison of the phenotypes of the mutations that have been identified with the clinical picture of the patient suggests that VUS c.1855C > T (p.Pro619Ser) in the TRIM32 gene can be pathological. Summarizing, it can be argued that the cause of the identified disorders is a homozygous variant c.1855C > T (p.Pro619Ser) in TRIM32 gene that causes LGMDR8 in a patient with MS.

TRIM32 and Malin in Neurological and Neuromuscular Rare Diseases

Tripartite motif (TRIM) proteins are RING E3 ubiquitin ligases defined by a shared domain structure. Several of them are implicated in rare genetic diseases, and mutations in TRIM32 and TRIM-like malin are associated with Limb-Girdle Muscular Dystrophy R8 and Lafora disease, respectively. These two proteins are evolutionary related, share a common ancestor, and both display NHL repeats at their C-terminus. Here, we revmniew the function of these two related E3 ubiquitin ligases discussing their intrinsic and possible common pathophysiological pathways.

Identification of a Novel Deep Intronic Mutation in CAPN3 Presenting a Promising Target for Therapeutic Splice Modulation

Calpainopathy, also known as limb girdle muscular dystrophy (LGMD) type 2A (LGMD2A) or LGMD R1 Calpain3-related, is one of the most common genetically characterized forms of limb-girdle muscular dystrophy with a wide range of phenotypic severity. We evaluated a consanguineous family with a clinical phenotype consistent with calpainopathy in whom conventional sequencing did not detect any mutations in the CAPN3 gene. Using whole exome sequencing paired with haplotype analysis, we identified a homozygous deep intronic single base pair deletion in CAPN3 (c.946-29delT). Familial segregation studies were consistent with recessive inheritance. Immunoblotting of muscle tissue from the patient showed complete absence of calpain 3. In silico analysis predicted the deletion to disrupt the branch point and subsequently alter splicing of exon 7. Studies of patient fibroblasts and muscle tissue confirmed altered splicing, resulting in an inclusion of a 389-bp intronic sequence upstream of exon 7, originating from a cryptic splice acceptor site in intron 6. This out-of-frame insertion results in a premature stop codon, leading to an apparent absence of protein likely due to degradation of the transcript via nonsense-mediated decay. We then designed phosphorodiamidate morpholino oligomers (PMOs) as splice modulators to block the new splice acceptor site. This approach successfully prevented the aberrant splicing - reverting the majority of the splice to the wildtype transcript. These results confirm the pathogenicity of this novel deep intronic mutation and provide a mutation-specific therapeutic strategy. Thus, deep intronic mutations in CAPN3 may be pathogenic and should be considered in the appropriate clinical setting. The identification of mutations which may be missed by traditional Sanger sequencing is essential as they may be excellent targets for individualized therapeutic strategies using RNA-directed splice modulation.

Comprehensive Assessment of Cardiac Involvement in Muscular Dystrophies by Cardiac MR Imaging

Muscular dystrophy is a group of genetically inherited diseases with irreversible and progressive muscle loss and is associated with cardiac involvement. Particularly in Duchenne and Becker dystrophies, cardiac disorders are the leading causes of mortality. Cardiovascular magnetic resonance imaging (CMR) can detect even incipient myocardial fibrosis (late gadolinium enhancement), which has prognostic significance in patients with preserved left ventricular function by echocardiogram and before the onset of symptoms. Early detection of cardiac abnormalities by CMR enables early cardioprotective treatment, leading to a better prognosis.

Limb-girdle muscular dystrophy type 2B: An unusual cause of proximal muscular weakness in Saudi Arabia

Dysferlinopathies encompass a group of neuromuscular diseases characterized by the absence of dysferlin in skeletal muscle. It is a genetic disorder caused by a mutation in the dysferlin gene (DYSF) with an autosomal recessive mode of inheritance. In this article, we report a case of Limb-girdle muscular dystrophy type 2B with a rare homozygous duplication c.164dupA, p.(Ile57Hisfs*8) (rs863225020) in DYSF in a Saudi patient. To the best of our knowledge, this is the first case from Saudi Arabia with complete clinical data, pathology findings, radiology findings, and genetic analysis. Although there is no curative treatment for this disease, an accurate diagnosis is important to avoid using steroids and immunosuppressive medications, which are not effective and may have several side effects. Further studies are needed to explore potential therapies for this rare condition.

Thrombospondin-1 and disease progression in dysferlinopathy

The purpose of this study was to determine whether thrombospondin (TSP)-1 promotes macrophage activity and disease progression in dysferlinopathy. First, we found that levels of TSP-1 are elevated in blood of non-ambulant dysferlinopathy patients compared with ambulant patients and healthy controls, supporting the idea that TSP-1 levels are correlated with disease progression. We then crossed dysferlinopathic BlaJ mice with TSP-1 knockout mice and assessed disease progression longitudinally with magnetic resonance imaging (MRI). In these mice, deletion of TSP-1 ameliorated loss in volume and mass of the moderately affected gluteal muscle but not of the severely affected psoas muscle. T2 MRI parameters revealed that loss of TSP-1 modestly inhibited inflammation only in gluteal muscle of male mice. Histological assessment indicated that deletion of TSP-1 reduced inflammatory cell infiltration of muscle fibers, but only early in disease progression. In addition, flow cytometry analysis revealed that, in males, TSP-1 knockout reduced macrophage infiltration and phagocytic activity, which is consistent with TSP-1-enhanced phagocytosis and pro-inflammatory cytokine induction in cultured macrophages. In summary, TSP-1 appears to play an accessory role in modulating Mp activity in BlaJ mice in a gender, age and muscle-dependent manner, but is unlikely a primary driver of disease progression of dysferlinopathy.

Dysferlinopathy Promotes an Intramuscle Expansion of Macrophages with a Cyto-Destructive Phenotype

Dysferlinopathies are a group of muscular dystrophies resulting from a genetic deficiency in Dysf. Macrophages, highly plastic cells that mediate tissue repair and destruction, are prominent within dystrophic skeletal muscles of dysferlinopathy patients. We hypothesized that Dysf-deficient muscle promotes recruitment, proliferation, and skewing of macrophages toward a cyto-destructive phenotype in dysferlinopathy. To track macrophage dynamics in dysferlinopathy, we adoptively transferred enhanced green fluorescent protein-labeled monocytes into Dysf-deficient BLA/J mice with age-related (2 to 10 months) muscle disease and Dysf-intact (C57BL/6 [B6]) mice. We detected an age- and disease-related increase in monocyte recruitment into Dysf-deficient muscles. Moreover, macrophages recruited into muscle proliferated locally and were skewed toward a cyto-destructive phenotype. By comparing Dysf-deficient and -intact monocytes, our data showed that Dysf in muscle, but not in macrophages, mediate intramuscle macrophage recruitment and proliferation. To further elucidate macrophage mechanisms related to dysferlinopathy, we investigated in vitro macrophage-myogenic cell interactions and found that Dysf-deficient muscle i) promotes macrophage proliferation, ii) skews macrophages toward a cyto-destructive phenotype, and iii) is more vulnerable to macrophage-mediated apoptosis. Taken together, our data suggest that the loss of Dysf expression in muscle, not macrophages, promotes the intramuscle expansion of cyto-destructive macrophages likely to contribute to dysferlinopathy. Identifying pathways within the Dysf-deficient muscle milieu that regulate cyto-destructive macrophages will potentially uncover therapeutic strategies for dysferlinopathies.

Dysferlin function in skeletal muscle: Possible pathological mechanisms and therapeutical targets in dysferlinopathies

Mutations in the dysferlin gene are linked to a group of muscular dystrophies known as dysferlinopathies. These myopathies are characterized by progressive atrophy. Studies in muscle tissue from dysferlinopathy patients or dysferlin-deficient mice point out its importance in membrane repair. However, expression of dysferlin homologous proteins that restore sarcolemma repair function in dysferlinopathy animal models fail to arrest muscle wasting, therefore suggesting that dysferlin plays other critical roles in muscle function. In the present review, we discuss dysferlin functions in the skeletal muscle, as well as pathological mechanisms related to dysferlin mutations. Particular focus is presented related the effect of dysferlin on cell membrane related function, which affect its repair, vesicle trafficking, as well as Ca(2+) homeostasis. Such mechanisms could provide accessible targets for pharmacological therapies.

TOR1AIP1 as a cause of cardiac failure and recessive limb-girdle muscular dystrophy

TorsinA-interacting protein 1 (TOR1AIP1) gene is a novel gene that has recently been described to cause limb-girdle muscular dystrophy (LGMD) with mild dilated cardiomyopathy. We report a family with mutations in TOR1AIP1 where the striking clinical feature is severe cardiac failure requiring cardiac transplant in two siblings, in addition to musculoskeletal weakness and muscular dystrophy. We demonstrate an absence of TOR1AIP1 protein expression in cardiac and skeletal muscles of affected siblings. We expand the phenotype of this gene to demonstrate the cardiac involvement and the importance of cardiac surveillance in patients with mutations in TOR1AIP1.

Identification of an intragenic deletion in the SGCB gene through a re-evaluation of negative next generation sequencing results

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504 myopathic patients have been screened by an NGS approach.

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A patient with a strong suspicion of sarcoglycanopathy, due to WB and immunohistochemical studies, was investigated.

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The absence of reads on the sixth exon of the β-sarcoglycan gene was identified by a careful re-evaluation of the NGS data.

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Subsequent array CGH analysis identified a novel 3.3 kb intragenic deletion in the SGCB gene.

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A strong collaboration between clinicians and molecular geneticists is crucial for a careful interpretation of NGS results.

A large mutation screening of 504 patients with muscular dystrophy or myopathy has been performed by next generation sequencing (NGS). Among this cohort of patients, we report a case with a severe form of muscular dystrophy with a proximal weakness in the limb-girdle muscles. Her biopsy revealed typical dystrophic features and immunohistochemistry for α- and γ-sarcoglycans showed an absent reaction, addressing the clinical diagnosis toward a sarcoglycanopathy. Considering that no causative point mutation was detected in any of the four sarcoglycan genes, we re-evaluated the NGS data by careful quantitative analysis of the specific reads mapping on the four sarcoglycan genes. A complete absence of reads from the sixth exon of the β-sarcoglycan gene was found. Subsequent array comparative genomic hybridization (CGH) analysis confirmed the result with the identification of a novel 3.3 kb intragenic deletion in the SGCB gene. This case illustrates the importance of a multidisciplinary approach involving clinicians and molecular geneticists and the need for a careful re-evaluation of NGS data.

Limb-girdle muscular dystrophy in the Agarwals: Utility of founder mutations in CAPN3 gene

Background and Purpose:

Diagnostic evaluation of limb-girdle muscular dystrophy type 2A (LGMD2A) involves specialized studies on muscle biopsy and mutation analysis. Mutation screening is the gold standard for diagnosis but is difficult as the gene is large and multiple mutations are known. This study evaluates the utility of two known founder mutations as a first-line diagnostic test for LGMD2A in the Agarwals.

Materials and Methods:

The Agarwals with limb-girdle muscular dystrophy (LGMD) phenotype were analyzed for two founder alleles (intron 18/exon 19 c.2051-1G>T and exon 22 c.2338G>C). Asymptomatic first-degree relatives of patients with genetically confirmed mutations and desirous of counseling were screened for founder mutations.

Results:

Founder alleles were detected in 26 out of 29 subjects with LGMD phenotype (89%). The most common genotype observed was homozygous for exon 22 c.2338 G>C mutation followed by compound heterozygosity. Single founder allele was identified in two. Single allele was detected in two of the five asymptomatic relatives.

Conclusion:

Eighty-nine percent of the Agarwals having LGMD phenotype have LGMD2A resulting from founder mutations. Founder allele analysis can be utilized as the initial noninvasive diagnostic step for index cases, carrier detection, and counseling.

Thrombospondin-1 levels correlate with macrophage activity and disease progression in dysferlin deficient mice

Dysferlinopathy is associated with accumulation of thrombospondin (TSP)-1 and macrophages, both of which may contribute to the pathogenesis of the disease. The purpose of this study was to determine whether TSP-1 levels can predict macrophage activity and disease progression in dysferlin deficient BlaJ mice, focusing on the early disease process. In 3 month-old BlaJ mice, muscle TSP-1 levels exhibited strong positive correlations with both accumulation of F4/80hi macrophages and with their in vivo phagocytic activity in psoas muscles as measured by magnetic resonance imaging and flow cytometry. Muscle TSP-1 levels also exhibited a strong negative correlation with muscle mass and strong positive correlations with histological measurements of muscle fiber infiltration and regeneration. Over the course of disease progression from 3 to 12 months of age, muscle TSP-1 levels showed more complicated relationships with macrophage activity and an inverse relationship with muscle mass. Importantly, blood TSP-1 levels showed strong correlations with macrophage activity and muscle degeneration, particularly early in disease progression in BlaJ mice. These data indicate that TSP-1 may contribute to a destructive macrophage response in dysferlinopathy and pose the intriguing possibility that TSP-1 levels may serve as a biomarker for disease progression.

Where do we stand in trial readiness for autosomal recessive limb girdle muscular dystrophies?

Autosomal recessive limb girdle muscular dystrophies (LGMD2) are a group of genetically heterogeneous diseases that are typically characterised by progressive weakness and wasting of the shoulder and pelvic girdle muscles. Many of the more than 20 different conditions show overlapping clinical features with other forms of muscular dystrophy, congenital, myofibrillar or even distal myopathies and also with acquired muscle diseases. Although individually extremely rare, all types of LGMD2 together form an important differential diagnostic group among neuromuscular diseases. Despite improved diagnostics and pathomechanistic insight, a curative therapy is currently lacking for any of these diseases. Medical care consists of the symptomatic treatment of complications, aiming to improve life expectancy and quality of life. Besides well characterised pre-clinical tools like animal models and cell culture assays, the determinants of successful drug development programmes for rare diseases include a good understanding of the phenotype and natural history of the disease, the existence of clinically relevant outcome measures, guidance on care standards, up to date patient registries, and, ideally, biomarkers that can help assess disease severity or drug response. Strong patient organisations driving research and successful partnerships between academia, advocacy, industry and regulatory authorities can also help accelerate the elaboration of clinical trials. All these determinants constitute aspects of translational research efforts and influence patient access to therapies. Here we review the current status of determinants of successful drug development programmes for LGMD2, and the challenges of translating promising therapeutic strategies into effective and accessible treatments for patients.

Upregulated IL-1β in dysferlin-deficient muscle attenuates regeneration by blunting the response to pro-inflammatory macrophages

BACKGROUND

Loss-of-function mutations in the dysferlin gene (DYSF) result in a family of muscle disorders known collectively as the dysferlinopathies. Dysferlin-deficient muscle is characterized by inflammatory foci and macrophage infiltration with subsequent decline in muscle function. Whereas macrophages function to remove necrotic tissue in acute injury, their prevalence in chronic myopathy is thought to inhibit resolution of muscle regeneration. Two major classes of macrophages, classical (M1) and alternative (M2a), play distinct roles during the acute injury process. However, their individual roles in chronic myopathy remain unclear and were explored in this study.

METHODS

To test the roles of the two macrophage phenotypes on regeneration in dysferlin-deficient muscle, we developed an in vitro co-culture model of macrophages and muscle cells. We assayed the co-cultures using ELISA and cytokine arrays to identify secreted factors and performed transcriptome analysis of molecular networks induced in the myoblasts.

RESULTS

Dysferlin-deficient muscle contained an excess of M1 macrophage markers, compared with WT, and regenerated poorly in response to toxin injury. Co-culturing macrophages with muscle cells showed that M1 macrophages inhibit muscle regeneration whereas M2a macrophages promote it, especially in dysferlin-deficient muscle cells. Examination of soluble factors released in the co-cultures and transcriptome analysis implicated two soluble factors in mediating the effects: IL-1β and IL-4, which during acute injury are secreted from M1 and M2a macrophages, respectively. To test the roles of these two factors in dysferlin-deficient muscle, myoblasts were treated with IL-4, which improved muscle differentiation, or IL-1β, which inhibited it. Importantly, blockade of IL-1β signaling significantly improved differentiation of dysferlin-deficient cells.

CONCLUSIONS

We propose that the inhibitory effects of M1 macrophages on myogenesis are mediated by IL-1β signals and suppression of the M1-mediated immune response may improve muscle regeneration in dysferlin deficiency. Our studies identify a potential therapeutic approach to promote muscle regeneration in dystrophic muscle.

Diagnosis of becker muscular dystrophy: Results of Re-analysis of DNA samples

INTRODUCTION

The phenotype of Becker muscular dystrophy (BMD) is highly variable, and the disease may be underdiagnosed. We searched for new mutations in the DMD gene in a cohort of previously undiagnosed patients who had been referred in the period 1985-1995.

METHODS

All requests for DNA analysis of the DMD gene in probands with suspected BMD were re-evaluated. If the phenotype was compatible with BMD, and no deletions or duplications were detected, DNA samples were screened for small mutations.

RESULTS

In 79 of 185 referrals, no mutation was found. Analysis could be performed on 31 DNA samples. Seven different mutations, including 3 novel ones, were found. Long-term clinical follow-up is described.

CONCLUSIONS

Refining DNA analysis in previously undiagnosed cases can identify mutations in the DMD gene and provide genetic diagnosis of BMD. A delayed diagnosis can still be valuable for the proband or the relatives of BMD patients.

Muscular dystrophy due to a sarcoglycan deficiency in a female Dobermann dog

A four-month-old female Dobermann presented with myalgia, dysphagia, progressive weakness and loss of body condition. Diagnostic evaluation at nine months of age revealed markedly elevated serum creatine kinase activity, electromyographic abnormalities and histological evidence of chronic-active muscle necrosis. Imaging confirmed dysphagia and aspiration pneumonia. Muscular dystrophy was suspected and immunohistochemical staining of muscle cryosections demonstrated reduced sarcoglycans. Treatment consisted of gastrostomy, and over the next 5 months the dog gained weight, despite continued loss of muscle mass. The dog died at 14 months of age after developing clinical signs of aspiration pneumonia. To the authors' knowledge, this is the first report of muscular dystrophy in a Dobermann and only the second detailed report of a canine sarcoglycanopathy. Supportive care resulted in an acceptable quality of life for 10 months after clinical signs were first observed.

Oxidative stress, NF-κB and the ubiquitin proteasomal pathway in the pathology of calpainopathy

The neuromuscular disorder, calpainopathy (LGMD 2A), is a major muscular dystrophy classified under limb girdle muscular dystrophies. Genetic mutations of the enzyme calpain 3 cause LGMD 2A. Calpainopathy is phenotypically observed as progressive muscle wasting and weakness. Pathomechanisms of muscle wasting of calpainopathy remain poorly understood. Oxidative stress, NF-κB and the ubiquitin proteasomal pathway underlie the pathology of several muscle wasting conditions but their role in calpainopathic dystrophy is not known. Oxidative and nitrosative stress, the source of reactive oxygen species, NF-κB signaling and protein ubiquitinylation were studied in 15 calpainopathic and 8 healthy control human muscle biopsies. Oxidative stress and NF-κB/IKK β signaling were increased in calpainopathic muscle and may contribute to increased protein ubiquitinylation and muscle protein loss. Preventing oxidative stress or inhibition of NF-κB signaling could be considered for treatment of LGMD 2A.

Rbfox1 downregulation and altered calpain 3 splicing by FRG1 in a mouse model of Facioscapulohumeral muscular dystrophy (FSHD)

Facioscapulohumeral muscular dystrophy (FSHD) is a common muscle disease whose molecular pathogenesis remains largely unknown. Over-expression of FSHD region gene 1 (FRG1) in mice, frogs, and worms perturbs muscle development and causes FSHD-like phenotypes. FRG1 has been implicated in splicing, and we asked how splicing might be involved in FSHD by conducting a genome-wide analysis in FRG1 mice. We find that splicing perturbations parallel the responses of different muscles to FRG1 over-expression and disease progression. Interestingly, binding sites for the Rbfox family of splicing factors are over-represented in a subset of FRG1-affected splicing events. Rbfox1 knockdown, over-expression, and RNA-IP confirm that these are direct Rbfox1 targets. We find that FRG1 is associated to the Rbfox1 RNA and decreases its stability. Consistent with this, Rbfox1 expression is down-regulated in mice and cells over-expressing FRG1 as well as in FSHD patients. Among the genes affected is Calpain 3, which is mutated in limb girdle muscular dystrophy, a disease phenotypically similar to FSHD. In FRG1 mice and FSHD patients, the Calpain 3 isoform lacking exon 6 (Capn3 E6-) is increased. Finally, Rbfox1 knockdown and over-expression of Capn3 E6- inhibit muscle differentiation. Collectively, our results suggest that a component of FSHD pathogenesis may arise by over-expression of FRG1, reducing Rbfox1 levels and leading to aberrant expression of an altered Calpain 3 protein through dysregulated splicing.

Hip abduction sign: a new clinical sign in sarcoglycanopathies

A new clinical sign in sarcoglycanopathies is described. Patients with sarcoglycanopathies showed a phase of abduction of the thighs while rising from the ground: the hip abduction sign. The sign results from selective weakness of hip adductors and comparative preservation of hip abductors. This sign had a sensitivity of 76.2%, specificity of 98%, and was most conspicuous between 3 and 10 years of disease duration. The hip abduction sign is an important clinical indicator of sarcoglycanopathies.

Dysferlin and animal models for dysferlinopathy

Dysferlin (DYSF) is involved in the membrane-repair process, in the intracellular vesicle system and in T-tubule development in skeletal muscle. It interacts with mitsugumin 53, annexins, caveolin-3, AHNAK, affixin, S100A10, calpain-3, tubulin and dihydropyridine receptor. Limb-girdle muscular dystrophy 2B (LGMD2B) and Miyoshi myopathy (MM) are muscular dystrophies associated with recessively inherited mutations in the DYSF gene. The diseases are characterized by weakness and muscle atrophy that progress slowly and symmetrically in the proximal muscles of the limb girdles. LGMD2B and MM, which are collectively termed “dysferlinopathy”, both lead to abnormalities in vesicle traffic and membrane repair at the plasma membrane in muscle fibers. SJL/J (SJL) and A/J mice are naturally occurring animal models for dysferlinopathy. Since there has been no an approach to therapy for dysferlinopathy, the immediate development of a therapeutic method for this genetic disorder is desirable. The murine models are useful in verification experiments for new therapies and they are valuable tools for identifying factors that accelerate dystrophic changes in skeletal muscle. It could be possible that the genetic or immunological background in SJL or A/J mice could modify muscle damage in experiments involving these models, because SJL and A/J mice show differences in the progress and prevalent sites of skeletal muscle lesions as well as in the gene-expression profiles of their skeletal muscle. In this review, we provide up-to-date information on the function of dysferlin, the development of possible therapies for muscle dystrophies (including dysferlinopathy) and the detection of new therapeutic targets for dysferlinopathy by means of experiments using animal models for dysferlinopathy.

1α,25(OH)(2)-Vitamin D3 increases dysferlin expression in vitro and in a human clinical trial

Dysferlinopathies are a heterogenous group of autosomal recessive inherited muscular dystrophies caused by mutations in DYSF gene. Dysferlin is expressed mainly in skeletal muscle and in monocytes and patients display a severe reduction or absence of protein in both tissues. Vitamin D3 promotes differentiation of the promyelocytic leukemia HL60 cells. We analyzed the effect of vitamin D3 on dysferlin expression in vitro using HL60 cells, monocytes and myotubes from controls and carriers of a single mutation in DYSF. We also performed an observational study with oral vitamin D3 in a cohort of 21 carriers. Fifteen subjects were treated for 1 year and dysferlin expression in monocytes was analysed before and after treatment. Treatment with vitamin D3 increased expression of dysferlin in vitro. The effect of vitamin D3 was mediated by both a nongenomic pathway through MEK/ERK and a genomic pathway involving binding of vitamin D3 receptor to the dysferlin promoter. Carriers treated with vitamin D3 had significantly increased expression of dysferlin in monocytes compared with nontreated carriers (P < 0.05). These findings will have important therapeutic implications since a combination of different molecular strategies together with vitamin D3 uptake could increase dysferlin expression to nonpathological protein levels.

Myogenesis in dysferlin-deficient myoblasts is inhibited by an intrinsic inflammatory response

Limb-girdle muscular dystrophy type 2B results from mutations in dysferlin, a membrane-associated protein involved in cellular membrane repair. Primary myoblast cultures derived from dysferlinopathy patients show reduced myogenic potential, suggesting that dysferlin may regulate myotube fusion and be required for muscle regeneration. These observations contrast with the findings that muscle develops normally in pre-symptomatic dysferlinopathy patients. To better understand the role of dysferlin in myogenesis, we investigated this process in vitro using cells derived from two mouse models of dysferlinopathy: SJL/J and A/J mice. We observed that myotubes derived from dysferlin-deficient muscle were of significantly smaller diameters, contained fewer myonuclei, and displayed reduced myogenic gene expression compared to dysferlin-sufficient cells. Together, these findings suggest that the absence of dysferlin from myoblasts is detrimental to myogenesis. Pro-inflammatory NFκB signaling was upregulated in dysferlin-deficient myotubes; the anti-inflammatory agent celastrol reduced the NFκB activation and improved myogenesis in dysferlin-deficient cultures. The results suggest that decreased myotube fusion in dysferlin deficiency is attributable to intrinsic inflammatory activation and can be improved using anti-inflammatory mediators.

Founder mutation for α-sarcoglycan-LGMD2D in a Magdalen Islands Acadian cluster

BACKGROUND

We have recruited a group of four living and reviewed the records of six deceased distantly related French-Canadians of Acadian descent affected by a childhood-onset form of recessive limb-girdle muscular dystrophy (LGMD). All cases originate from the small archipelago of the Magdalen Islands (population: 13,000) isolated in the Gulf of St-Lawrence.

METHODS

Based on the likely sharing of the same founder mutation we completed a 319K SNPs genome-wide scan to identify the disease locus and then screen candidate genes in this region.

RESULTS

All patients had normal initial motor milestones. They presented with limb girdle weakness at the average age of seven years (5-11). Progressive weakness led to loss of ambulation at a wide range of ages (10-39). Patients also developed macroglossia, large calves and mild to moderate contractures, hyperlordosis and decreased pulmonary function. Creatine kinase levels were elevated (1,800-10,000 U/L) in the first decades, but decreased with progression of disease. Homozygosity mapping uncovered a shared chromosomal region of 6.33Mb. The alpha sarcoglycan (SGCA) gene, mutated in LGMD2D, lay in this candidate interval. Sequencing of all SGCA exons uncovered a shared homozygous missense mutation (c. 229C>T, p.R77C), the most common SGCA mutation internationally reported. Using demographic data, we estimated a high carrier rate of 1/22.

CONCLUSION

The p.R77C mutation has also been observed in many populations, including in France and Spain (Basques). This corresponds to the first reported recessive founder disease for the Magdalen Islands, an archipelago settled in the XIXth century, largely by Acadian immigrants.

A study of FHL1, BAG3, MATR3, PTRF and TCAP in Australian muscular dystrophy patients

FHL1, BAG3, MATR3 and PTRF are recently identified myopathy genes associated with phenotypes that overlap muscular dystrophy. TCAP is a rare reported cause of muscular dystrophy not routinely screened in most centres. We hypothesised that these genes may account for patients with undiagnosed forms of muscular dystrophy in Australia. We screened a large cohort of muscular dystrophy patients for abnormalities in FHL1 (n=102) and TCAP (n=100) and selected patients whose clinical features overlapped the phenotypes previously described for BAG3 (n=9), MATR3 (n=15) and PTRF (n=7). We found one FHL1 mutation (c.311G>A, p.C104Y) in a boy with rapidly progressive muscle weakness and reducing body myopathy who was initially diagnosed with muscular dystrophy. We identified no pathogenic mutations in BAG3, MATR3, PTRF or TCAP. In conclusion, we have excluded these five genes as common causes of muscular dystrophy in Australia. Patients with reducing body myopathy may be initially diagnosed as muscular dystrophy.

Phenotypic and immunohistochemical characterization of sarcoglycanopathies

INTRODUCTION

Limb-girdle muscular dystrophy presents with heterogeneous clinical and molecular features. The primary characteristic of this disorder is proximal muscular weakness with variable age of onset, speed of progression, and intensity of symptoms. Sarcoglycanopathies, which are a subgroup of the limb-girdle muscular dystrophies, are caused by mutations in sarcoglycan genes. Mutations in these genes cause secondary deficiencies in other proteins, due to the instability of the dystrophin-glycoprotein complex. Therefore, determining the etiology of a given sarcoglycanopathy requires costly and occasionally inaccessible molecular methods.

OBJECTIVE

The aim of this study was to identify phenotypic differences among limb-girdle muscular dystrophy patients who were grouped according to the immunohistochemical phenotypes for the four sarcoglycans.

METHODS

To identify phenotypic differences among patients with different types of sarcoglycanopathies, a questionnaire was used and the muscle strength and range of motion of nine joints in 45 patients recruited from the Department of Neurology--HC-FMUSP (Clinics Hospital of the Faculty of Medicine of the University of São Paulo) were evaluated. The findings obtained from these analyses were compared with the results of the immunohistochemical findings.

RESULTS

The patients were divided into the following groups based on the immunohistochemical findings: α-sarcoglycanopathies (16 patients), β-sarcoglycanopathies (1 patient), γ-sarcoglycanopathies (5 patients), and nonsarcoglycanopathies (23 patients). The muscle strength analysis revealed significant differences for both upper and lower limb muscles, particularly the shoulder and hip muscles, as expected. No pattern of joint contractures was found among the four groups analyzed, even within the same family. However, a high frequency of tiptoe gait was observed in patients with α-sarcoglycanopathies, while calf pseudo-hypertrophy was most common in patients with non-sarcoglycanopathies. The α-sarcoglycanopathy patients presented with more severe muscle weakness than did γ-sarcoglycanopathy patients.

CONCLUSION

The clinical differences observed in this study, which were associated with the immunohistochemical findings, may help to prioritize the mutational investigation of sarcoglycan genes.

Post-Natal knockdown of fukutin-related protein expression in muscle by long-termRNA interference induces dystrophic pathology [corrected]

Limb-girdle muscular dystrophy 2I (LGMD2I) is caused by mutations in the fukutin-related protein (FKRP) gene. Unlike its severe allelic forms, LGMD2I usually involves slower onset and milder course without defects in the central nervous system. The lack of viable animal models that closely recapitulate LGMD2I clinical phenotypes led us to use RNA interference technology to knock down FKRP expression via postnatal gene delivery so as to circumvent embryonic lethality. Specifically, an adeno-associated viral vector was used to deliver short hairpin (shRNA) genes to healthy ICR mice. Adeno-associated viral vectors expressing a single shRNA or two different shRNAs were injected one time into the hind limb muscles. We showed that FKRP expression at 10 months postinjection was reduced by about 50% with a single shRNA and by 75% with the dual shRNA cassette. Dual-cassette injection also reduced a-dystroglycan glycosylation and its affinity to laminin by up to 70% and induced α-dystrophic pathology, including fibrosis and central nucleation, in more than 50% of the myofibers at 10 months after injection. These results suggest that the reduction of approximately or more than 75% of the normal level of FKRP expression induces chronic dystrophic phenotypes in skeletal muscles. Furthermore, the restoration of about 25% of the normal FKRP level could be sufficient for LGMD2I therapy to correct the genetic deficiency effectively and prevent dystrophic pathology.

Partial dysferlin reconstitution by adult murine mesoangioblasts is sufficient for full functional recovery in a murine model of dysferlinopathy

Dysferlin deficiency leads to a peculiar form of muscular dystrophy due to a defect in sarcolemma repair and currently lacks a therapy. We developed a cell therapy protocol with wild-type adult murine mesoangioblasts. These cells differentiate with high efficiency into skeletal muscle in vitro but differ from satellite cells because they do not express Pax7. After intramuscular or intra-arterial administration to SCID/BlAJ mice, a novel model of dysferlinopathy, wild-type mesoangioblasts efficiently colonized dystrophic muscles and partially restored dysferlin expression. Nevertheless, functional assays performed on isolated single fibers from transplanted muscles showed a normal repairing ability of the membrane after laser-induced lesions; this result, which reflects gene correction of an enzymatic rather than a structural deficit, suggests that this myopathy may be easier to treat with cell or gene therapy than other forms of muscular dystrophies.

Role of thrombospondin 1 in macrophage inflammation in dysferlin myopathy

Muscle inflammation can be a prominent feature in several muscular dystrophies. In dysferlin myopathy, it is mainly composed of macrophages. To understand the origin of inflammation in dysferlin-deficient muscle, we analyzed soluble factors involved in monocyte chemotaxis released by myoblasts and myotubes from control and dysferlinopathy patients using a transwell system. Dysferlin-deficient myotubes released more soluble factors involved in monocyte chemotaxis compared with controls (p < 0.001). Messenger RNA microarray analysis showed a 3.2-fold increase of thrombospondin 1 (TSP-1) expression in dysferlin-deficient myotubes. Retrotranscriptasepolymerase chain reaction analysis, ELISA, and immunohistochemistry confirmed these results. Dysferlin mRNA knockdown with short-interfering RNA in normal myogenic cells resulted in TSP-1 mRNA upregulation and increased chemotaxis. Furthermore, monocyte chemotaxis was decreased when TSP-1 was blocked by specific antibodies. In muscle biopsies from dysferlinopathy patients, TSP-1 expression was increased in muscle fibers but not in biopsies of patientswith other myopathies with inflammation; TSP-1 was seen in some macrophages in all samples analyzed. Taken together, the data demonstrate that dysferlin-deficient muscle upregulates TSP-1 in vivoand in vitro and indicate that endogenous chemotactic factors arecrucial to the sustained inflammatory process observed in dysferlinopathies.

Molecular diagnosis of muscular dystrophies, focused on limb girdle muscular dystrophies

BACKGROUND

Muscular dystrophies include a spectrum of muscle disorders, some of which are phenotypically well characterized. The identification of dystrophin as the causative factor in Duchenne muscular dystrophy has led to the development of molecular genetics and has facilitated the division of muscular dystrophies into distinct groups, among which are the 'limb girdle muscular dystrophies'.

OBJECTIVES

This article reviews the methodology to be used in the diagnosis of muscular dystrophies, focused on the groups of limb girdle muscular dystrophies, and the development of new strategies to reach a final molecular diagnosis.

METHOD

A literature review (Medline) from 1985 to the present.

CONCLUSION

Immunohistochemistry and western blotting analyses of the proteins involved in the various forms of muscular dystrophies have permitted a refined pathological approach necessary to conduct genetic studies and to offer appropriate genetic counseling. The application of molecular medicine in genetic muscular dystrophies also brings great hope to the therapeutic management of these patients.

Measurement of the functional status of patients with different types of muscular dystrophy

Muscular dystrophy (MD) comprises a group of diseases characterized by progressive muscle weakness that induces functional deterioration. Clinical management requires the use of a well-designed scale to measure patients' functional status. This study aimed to investigate the quality of the functional scales used to assess patients with different types of MD. The Brooke scale and the Vignos scale were used to grade arm and leg function, respectively. The Barthel Index was used to evaluate the function of daily living activity. We performed tests to assess the acceptability of these scales. The characteristics of the different types of MD are discussed. This was a multicenter study and included patients diagnosed with Duchenne muscular dystrophy (DMD) (classified as severely progressive MD), Becker muscular dystrophy (BMD), limb girdle muscular dystrophy (LGMD) and facioscapulohumeral muscular dystrophy (FSHD). BMD, LGMD, and FSHD were classified as slowly progressive MD. The results demonstrated that the Brooke scale was acceptable for grading arm function in DMD, but was unable to discriminate between differing levels of severity in slowly progressive MD. The floor effect was large for all types of slowly progressive MD (range, 20.0-61.9), and was especially high for BMD. The floor effect was also large for BMD (23.8%) and FSHD (50.0%) using the Vignos scale. Grades 6-8 of the Vignos scale were inapplicable because they included items involving the use of long leg braces for walking or standing, and some patients did not use long leg braces. In the Barthel Index, a ceiling effect was prominent for slowly progressive MD (58.9%), while a floor effect existed for DMD (17.9%). Among the slowly progressive MDs, FSHD patients had the best level of functioning; they had better leg function and their daily living activities were less affected than patients with other forms of slowly progressive MD. The results of this study demonstrate the acceptability of the different applications used for measuring functional status in patients with different types of MD. Some of the limitations of these measures as applied to MD should be carefully considered, especially in patients with slowly progressive MD. We suggest that these applications be used in combination with other measures, or that a complicated instrument capable of evaluating the various levels of functional status be used.

Detecting copy number variations in autosomal recessive limb-girdle muscular dystrophies using a multiplex ligation-dependent probe amplification (MLPA) assay

Pathogenic mutations in the four sarcoglycan genes, designated SGCA, SGCB, SGCD and SGCG, are responsible for a subgroup of autosomal, recessive limb-girdle muscular dystrophies (LGMD 2C-F), also called sarcoglycanopathies. For the present study, we designed a multiplex ligation-dependent probe amplification (MLPA) assay, targeting all 30 coding exons and a non-coding exon of these four genes. The assay uses synthetic probes and two colours, such that as many as 28 probes can be combined into one reaction. The set of probes was established for routine application, in order to diagnostically screen patients for large duplications or deletions. In 14 of the 94 cases (15%) tested, we detected changes in copy number. Mutations in gene SGCG accounted for 7 of the 94 cases (8%), suggesting that the size of the gene makes it vulnerable to large exonic deletions. The results suggested that all cases of sarcoglycanopathy should be screened for changes in copy number. The MLPA was shown to be a rapid, robust and reliable method to screen for copy number variations (CNVs). The present synthetic probe-approach overcomes the limitations associated with cloning procedures and is particularly applicable to a range of diseases for which the number of patients to be tested is small.

Revised spectrum of mutations in sarcoglycanopathies

To define the spectrum of mutations in alpha-, beta-, gamma-, and delta-sarcoglycan (SG) genes, we analyzed these genes in 69 probands with clinical and biological criteria compatible with the diagnosis of autosomal recessive limb-girdle muscular dystrophy. For 48 patients, muscle biopsies were available and multiplex western blot analysis of muscle proteins showed significant abnormalities of alpha- and gamma-SG. Our diagnostic strategy includes multiplex western blot, sequencing of SG genes, multiplex quantitative-fluorescent PCR and RT-PCR analyses. Mutations were detected in 57 patients and homozygous or compound heterozygous mutations were identified in 75% (36/48) of the patients with abnormal western blot, and in 52% (11/21) of the patients without muscle biopsy. Involvement of alpha-SG was demonstrated in 55.3% of cases (26/47), whereas gamma- and beta-SG were implicated in 25.5% (12/47) and in 17% (8/47) of cases, respectively. Interestingly, we identified 25 novel mutations, and a significant proportion of these mutations correspond to deletions (identified in 14 patients) of complete exon(s) of alpha- or gamma-SG genes, and partial duplications (identified in 5 patients) of exon 1 of beta-SG gene. This study highlights the high frequency of exonic deletions of alpha- and gamma-SG genes, as well as the presence of a hotspot of duplications affecting exon 1 of the beta-SG gene. In addition, protein analysis by multiplex western blot in combination with mutation screening and genotyping results allowed to propose a comprehensive and efficient diagnostic strategy and strongly suggested the implication of additional genes, yet to be identified, in sarcoglycanopathy-like disorders.

A common disease-associated missense mutation in alpha-sarcoglycan fails to cause muscular dystrophy in mice

Limb-girdle muscular dystrophy type 2D (LGMD2D) is caused by autosomal recessive mutations in the alpha-sarcoglycan gene. An R77C substitution is the most prevalent cause of the disease, leading to disruption of the sarcoglycan-sarcospan complex. To model this common mutation, we generated knock-in mice with an H77C substitution in alpha-sarcoglycan. The floxed neomycin (Neo)-cassette retained at the targeted H77C alpha-sarcoglycan locus caused a loss of alpha-sarcoglycan expression, resulting in muscular dystrophy in homozygotes, whereas Cre-mediated deletion of the floxed Neo-cassette led to recovered H77C alpha-sarcoglycan expression. Contrary to expectations, mice homozygous for the H77C-encoding allele expressed both this mutant alpha-sarcoglycan and the other components of the sarcoglycan-sarcospan complex in striated muscle, and did not develop muscular dystrophy. Accordingly, conditional rescued expression of the H77C protein in striated muscle of the alpha-sarcoglycan-deficient mice prevented the disease. Adding to the case that the behavior of mutant alpha-sarcoglycan is different between humans and mice, mutant human R77C alpha-sarcoglycan restored the expression of the sarcoglycan-sarcospan complex when introduced by adenoviral vector into the skeletal muscle of previously created alpha-sarcoglycan null mice. These findings indicate that the alpha-sarcoglycan with the most frequent missense mutation in LGMD2D is correctly processed, is transported to the sarcolemma, and is fully functional in mouse muscle. Our study presents an unexpected difference in the behavior of a missense-mutated protein in mice versus human patients, and emphasizes the need to understand species-specific protein quality control systems.

EFNS guideline on diagnosis and management of limb girdle muscular dystrophies

The limb girdle muscular dystrophies (LGMD) are termed as such as they share the characteristic feature of muscle weakness predominantly affecting the shoulder and pelvic girdles; their classification has been completely revised in recent years because of elucidation of many of the underlying genetic and protein alterations in the various subtypes. An array of diagnostic measures is possible but with varying ease of use and availability. Several aspects of muscle cell function appear to be involved in the causation of muscle pathology. These cellular variations may confer some specific clinical features thus permitting recognition of the LGMD subtype and hence directing appropriate levels of monitoring and intervention. Despite an extensive literature on the individual limb girdle dystrophies, these publications may be impenetrable for the general neurologist in this increasingly complex field. The proposed guidelines suggest an approach to the diagnosis and monitoring of the limb girdle dystrophies in a manner accessible to general neurologists.

Limb-girdle muscular dystrophy: diagnostic evaluation, frequency and clues to pathogenesis

We characterized the frequency of limb-girdle muscular dystrophy (LGMD) subtypes in a cohort of 76 Australian muscular dystrophy patients using protein and DNA sequence analysis. Calpainopathies (8%) and dysferlinopathies (5%) are the most common causes of LGMD in Australia. In contrast to European populations, cases of LGMD2I (due to mutations in FKRP) are rare in Australasia (3%). We have identified a cohort of patients in whom all common disease candidates have been excluded, providing a valuable resource for identification of new disease genes. Cytoplasmic localization of dysferlin correlates with fiber regeneration in a subset of muscular dystrophy patients. In addition, we have identified a group of patients with unidentified forms of LGMD and with markedly abnormal dysferlin localization that does not correlate with fiber regeneration. This pattern is mimicked in primary caveolinopathy, suggesting a subset of these patients may also possess mutations within proteins required for membrane targeting of dysferlin.

Living with muscular dystrophy: health related quality of life consequences for children and adults

Background

Muscular dystrophies are chronic diseases manifesting with progressive muscle weakness leading to decreasing activities and participation. To understand the impact on daily life, it is important to determine patients' quality of life.

Objective

To investigate Health Related Quality of Life (HRQoL) of children and adults with muscular dystrophy (MD), and to study the influence of type and severity of MD on HRQoL in adult patients.

Methods

Age-related HRQoL questionnaires were administered to 40 children (8–17 years), and 67 adult patients with muscular dystrophies.

Results

Significant differences in HRQoL were found in children and adults with MD compared to healthy controls. Patients with Becker muscular dystrophy reported a better HRQoL on the several scales compared to patients with other MDs. Severity was associated with worse fine motor functioning and social functioning in adult patients.

Conclusion

This is one of the first studies describing HRQoL of patients with MD using validated instruments in different age groups. The results indicate that having MD negatively influences the HRQoL on several domains.

MRI for the demonstration of subclinical muscle involvement in muscular dystrophy

AIM

To compare magnetic resonance imaging (MRI) with clinical examination for the detection of muscle abnormality in patients with muscular dystrophy.

METHODS

Muscle power in 20 patients with a variety of forms of muscular dystrophy was examined clinically using the Medical Research Council (MRC) grading scale, and patients were subsequently imaged with MRI. MRI and clinical examination for the detection of muscle normality and abnormality were compared using a McNemar chi-squared test to examine differences between the two methods.

RESULTS

MRI demonstrated radiological evidence of muscle abnormality more often than clinical examination; 50% of movements assessed as normal on clinical examination were associated with muscle abnormalities on MRI, including a significant proportion where there was severe radiological abnormality, indicating that focally advanced disease may be undetectable clinically.

CONCLUSION

The combination of clinical examination and MRI could improve the accuracy of phenotypic characterization of patients with muscular dystrophy, and this in turn could allow a more focussed molecular analysis through muscle biopsy or genetic investigation. This may also be very helpful in the assessment of the degree of muscle compromise not only in the early phases of the disease but especially during follow-up and can be used in therapeutic trials.

Calpains and human disease

Calpains, particularly conventional dimeric calpains, have claimed to be involved in the cell degeneration processes that characterize numerous disease conditions linked to dysfunctions of cellular Ca2+ homeostasis. The evidence supporting their involvement has traditionally been indirect and circumstantial, but recent work has added more solid evidence supporting the role of ubiquitous dimeric calpains in the process of neurodegeneration. The only disease condition in which a calpain defect has been conclusively involved concerns an atypical monomeric calpain: the muscle specific calpain-3, also known as p94. Inactivating defects in its gene cause a muscular dystrophy termed LGMD-2A. The molecular mechanism by which the absence of the proteolytic activity of calpain-3 causes the dystrophic process is unknown. Another atypical calpain, which has been characterized recently as a Ca2(+)-dependent protease, calpain 10, appears To be involved in the etiology of type 2 diabetes. The involvement has been inferred essentially from genetic evidence. Also in the case of type 2 diabetes the molecular mechanisms that could link the disease to calpain 10 are unknown.

Dysferlin expression in monocytes: A source of mRNA for mutation analysis

Dysferlin protein is expressed in peripheral blood monocytes. The genomic analysis of the DYSF gene has proved to be time consuming because it has 55 exons. We designed a mutational screening strategy based on cDNA from monocytes to find out whether the mutational analysis could be performed in mRNA from a source less invasive than the muscle biopsy. We studied 34 patients from 23 families diagnosed with dysferlinopathy. The diagnosis was based on clinical findings and on the absence of protein expression using either immunohistochemistry or Western blot of skeletal muscle and/or monocytes. We identified 28 different mutations, 13 of which were novel. The DYSF mutations in both alleles were found in 30 patients and only in one allele in four. The results were confirmed using genomic DNA in 26/34 patients. This is the first report to furnish evidence of reliable mutational analysis using monocytes cDNA and constitutes a good alternative to genomic DNA analysis.