Autosomal Recessive Limb-girdle Muscular Dystrophy Research Articles

Spectrum of muscular dystrophies associated with sarcolemmal-protein genetic defects

Muscular dystrophies are heterogeneous genetic disorders that share progressive muscle wasting. This may generate partial impairment of motility as well as a dramatic and fatal course. Less than 30years ago, the identification of the genetic basis of Duchenne muscular dystrophy opened a new era. An explosion of new information on the mechanisms of disease was witnessed, with many thousands of publications and the characterization of dozens of other genetic forms. Genes mutated in muscular dystrophies encode proteins of the plasma membrane and extracellular matrix, several of which are part of the dystrophin-associated complex. Other gene products localize at the sarcomere and Z band, or are nuclear membrane components.In the present review, we focus on muscular dystrophies caused by defects that affect the sarcolemmal and sub-sarcolemmal proteins. We summarize the nature of each disease, the genetic cause, and the pathogenic pathways that may suggest future treatment options. We examine X-linked Duchenne and Becker muscular dystrophies and the autosomal recessive limb-girdle muscular dystrophies caused by mutations in genes encoding sarcolemmal proteins. The mechanism of muscle damage is reviewed starting from disarray of the shock-absorbing dystrophin-associated complex at the sarcolemma and activation of inflammatory response up to the final stages of fibrosis. We trace only a part of the biochemical, physiopathological and clinical aspects of muscular dystrophy to avoid a lengthy list of different and conflicting observations. We attempt to provide a critical synthesis of what we consider important aspects to better understand the disease. In our opinion, it is becoming ever more important to go back to the bedside to validate and then translate each proposed mechanism. This article is part of a Special Issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis.

Carrier Frequency of the c.525delT Mutation in theSGCGGene and Estimated Prevalence of Limb Girdle Muscular Dystrophy Type 2C Among the Moroccan Population

Autosomal recessive limb-girdle muscular dystrophies (AR-LGMDs) are characterized by clinical and genetic heterogeneity. LGMD type 2C, or γ-sarcoglycanopathy, is the most frequent in North African populations as a result of the founder c.525delT mutation in the SGCG gene. Its epidemiology is poorly known in Morocco, and its prevalence among the Moroccan population has never been evaluated. This study screened 26 patients with a LGMD2C and 45 patients with an AR-LGMD phenotype for the c.525delT mutation. DNA extracted from umbilical cord blood samples of 250 newborns was tested for the same mutation. Molecular epidemiologic methods were used to calculate the frequency of heterozygotes for this mutation in Moroccan newborns and to estimate the prevalence of LGMD2C in the Moroccan population. The carrier frequency was estimated to be 1/250, which would imply that the prevalence of LGMD2C would be approximately 1/20,492 considering the effect of consanguinity. The homozygous c.525delT mutation was found in 65% of all patients with AR-LGMDs. These findings suggest that AR-LGMDs are prevalent in the Moroccan population and LGMD2C is one of the most common forms. This information might be useful for the development of diagnostic strategies on a large scale for better management of patients with AR-LGMD and genetic counseling of families.

Targeted Next-generation Sequencing Reveals a Homozygous Nonsense Mutation in CAPN3 that Causes Limb-girdle Muscular Dystrophy Type 2A First in Vietnam

Limb-girdle muscular dystrophy (LGMD) is a genetically heterogeneous entity characterized by progressive wasting of the shoulder and pelvic-girdle muscles. Diagnosing particular types of LGMD is still challenging, especially in developing countries, with targeted next-generation sequencing (NGS) emerging as the most advanced diagnostic tool. Here, a 15-year-old Vietnamese girl with proximal muscle weakness was examined for genetic cause via targeted NGS using the AmpliSeq Inherited Disease Ready-to-Use Panel on the Ion Torrent Personal Genome Machine of the detected nucleotide changes, a mutation in exon 3 of CAPN3 was considered to be the responsible mutation. In the readpile-ups, only T was observed at the 424th nucleotide, while only C was observed in the normal sample. The c.424 C>Ttransition in CAPN3 shifted glutamine to a stop codon at the 142nd amino acid residue (p.Q142X). The homozygous c.424C>T genotype was confirmed via XspI restriction enzyme digestion using polymerase chain reaction-amplified product from the index case encompassing exon 3.The patient was concluded to be autosomal recessive LGMD type 2A. XsaIdigestion of 100 control Vietnamese genomes disclosed one carrier of this mutation. Thus, LGMD type 2Awas first diagnosed in Vietnam, a developing country, via targeted NGS, avoiding invasive muscle biopsy.

Diagnostic challenge and therapeutic dilemma in necrotizing myopathy

Autosomal recessive limb-girdle muscular dystrophy (LGMD) 2L is caused by mutations in the anoctamin-5-gene ( ANO5 ) that encodes a calcium-activated chloride channel.1,2 Limb-girdle muscle weakness can also be caused by an immune-mediated necrotizing myopathy (IMNM) with antibodies against 3-hydroxy-3-methylglutaryl-coenzyme-A-reductase (HMGCR), which catalyzes a rate-limiting step in cholesterol biosynthesis and is inhibited by statins.3,4 We report on a patient with LGMD2L and HMGCR-associated IMNM without previous statin exposure. The authors thank the technical personnel of the Departments of Neuropathology, Neurology, and Radiology, RWTH University Aachen, Germany, for technical assistance; and Dr. A. Vigneron (D-Tek, Mons, Belgium, specialized in the development of diagnostic tests in autoimmune disorders) for performing the myositis-specific and myositis-associated antibody assays, including HMGCR.

A novel desmin mutation leading to autosomal recessive limb-girdle muscular dystrophy: distinct histopathological outcomes compared with desminopathies

BackgroundAutosomal recessive limb girdle muscular dystrophy (LGMD2) is a heterogeneous group of myopathies characterised by progressive muscle weakness involving proximal muscles of the shoulder and pelvic girdles including at least...

Limb-girdle Muscular Dystrophy Type 2A with Mutation in CAPN3: The First Report in Taiwan

The autosomal recessive limb-girdle muscular dystrophy type 2A (LGMD2A) is caused by mutations in the calpain 3 (CAPN3) gene, and it is characterized by selective atrophy and weakness of proximal limb and girdle muscles. We report a 33-year-old woman with initial presentations of exercise intolerance and running difficulty at age 15 years. At presentation, waddling gait, positive Gowers' sign, and marked muscle atrophy in pelvic and leg muscles were noted. Muscle computed tomography (CT) imaging demonstrated symmetric involvement of the posterior thigh muscles with relative sparing of vastus lateralis, sartorius, and gracilis. Muscle biopsy revealed a dystrophic change and many lobulated fibers on NADH-tetrazolium reductase staining. Genetic analysis of the CAPN3 gene identified a novel homozygous mutation of c2047_2050 del4, p.Lys683fs mutation, confirming the first LGMD2A patient in Taiwan.

Identification of Mutations in TMEM5 and ISPD as a Cause of Severe Cobblestone Lissencephaly

Cobblestone lissencephaly is a peculiar brain malformation with characteristic radiological anomalies. It is defined as cortical dysplasia that results when neuroglial overmigration into the arachnoid space forms an extracortical layer that produces agyria and/or a "cobblestone" brain surface and ventricular enlargement. Cobblestone lissencephaly is pathognomonic of a continuum of autosomal-recessive diseases characterized by cerebral, ocular, and muscular deficits. These include Walker-Warburg syndrome, muscle-eye-brain disease, and Fukuyama muscular dystrophy. Mutations in POMT1, POMT2, POMGNT1, LARGE, FKTN, and FKRP identified these diseases as alpha-dystroglycanopathies. Our exhaustive screening of these six genes, in a cohort of 90 fetal cases, led to the identification of a mutation in only 53% of the families, suggesting that other genes might also be involved. We therefore decided to perform a genome-wide study in two multiplex families. This allowed us to identify two additional genes: TMEM5 and ISPD. Because TMEM has a glycosyltransferase domain and ISPD has an isoprenoid synthase domain characteristic of nucleotide diP-sugar transferases, these two proteins are thought to be involved in the glycosylation of dystroglycan. Further screening of 40 families with cobblestone lissencephaly identified nonsense and frameshift mutations in another four unrelated cases for each gene, increasing the mutational rate to 64% in our cohort. All these cases displayed a severe phenotype of cobblestone lissencephaly A. TMEM5 mutations were frequently associated with gonadal dysgenesis and neural tube defects, and ISPD mutations were frequently associated with brain vascular anomalies.

G.P.44 Spectrum of mutations identified in the cohort of Czech LGMD patients

Limb girdle muscular dystrophies (LGMDs) represent a group of clinically and genetically heterogeneous disorders predominantly affecting shoulder and pelvic girdles. To date, 15 forms (2A-N) of autosomal recessive (AR) and eight forms (1A-H) of autosomal dominant LGMDs have been described. LGMD2A is the most frequent form of LGMD in many European countries, and is caused by mutations in the CAPN3 gene that encodes a muscle specific protease, calpain-3. Besides LGMD2A, we perform molecular genetic diagnostics of LGMD2I, LGMD2D, and LGMD2L caused by mutations in genes encoding fukutin-related protein (FKRP), alpha-sarcoglycan (SGCA) and anoctamin-5 (ANO5). Based on the results of clinical assessment and histopathological examination of muscle biopsies (including protein analysis using immunohistochemistry and immunoblotting), the mutational analysis of the CAPN3, FKRP, SGCA, and ANO5 genes was performed at the mRNA level (using reverse transcription-PCR-direct sequencing) and/or at the DNA level (using PCR-direct sequencing) in a cohort of Czech patients with a preliminary diagnosis of LGMD. In total, we screened 230 unrelated patients and mutations associated with the disease were determined in 70 of them (30.4%). Mutations in the CAPN3 gene were found in 55 patients, and LGMD2A was confirmed to represent the most frequent AR LGMD in the Czech Republic. The homozygous occurence of the most common mutation in the FKRP gene (p.Leu276Ile) associated with LGMD2I was determined in eight patients. Mutations in the SGCA and ANO5 genes were detected in 5 LGMD2D and 2 LGMD2L patients, respectively. This work was funded by the project “CEITEC – Central European Institute of Technology” (CZ.1.05/1.1.00/02.0068).

Sarcoglycan subcomplex: state of the art

sarcoglycan subcomplex: state of the art

P2.29 Autosomal recessive limb girdle muscular dystrophy in Saudi Arabia

Autosomal recessive limb-girdle muscular dystrophy (LGMD2) is a clinically and genetically heterogeneous disorder. So far 15 genes have been identified which are responsible for LGMD2.In Saudi Arabia, with high parental consanguinity rates; little is known about the genotype and phenotype of LGMD. So far we have studied seventeen consanguineous LGMD2 families. In this abstract we will present the clinical and genetic data on the completed families in our sample. This will consist of summary of fifteen families.

179th ENMC international workshop: Pregnancy in women with neuromuscular disorders: 5–7 November 2010, Naarden, The Netherlands

Sixteen doctors and scientists met in Naarden, The Netherlands, from 5 to 7 November 2010 to review current knowledge in the field of pregnancy in women with neuromuscular disease. The group was joined by three patients and their families. Participants were from eight countries, namely Belgium, Finland, France, Germany, Italy, Norway, The Netherlands and the United Kingdom. A variety of disciplines were represented, including neurology, clinical genetics, cardiology, respiratory medicine, obstetrics and gynaecology, epidemiology, ethics, a nurse specialist, and a representative from the ENMC research committee. Parenthood is a highly desirable aim in life for many couples, and increasingly this also applies to women affected by neuromuscular disorders (NMDs). Little is known about the effect of individual NMD on the course of pregnancy and delivery and conversely the effect of pregnancy on muscles themselves [1]. In the past, many patients have been discouraged from undertaking pregnancy for a variety of reasons. The overarching aim of the workshop was to harness knowledge about pregnancy in NMD with the intention of improving maternal and fetal outcomes. The workshop was structured to first review existing knowledge in the field, and second to propose practical recommendations for each stage of pregnancy, both in general terms and also specific to individual or groups of conditions, for use by all

Pitfall of identifying a disease locus by using low-resolution SNP arrays

Pitfall of identifying a disease locus by using low-resolution SNP arrays

Dysferlinopathy: Spectrum of pathological changes in skeletal muscle tissue

Dysferlinopathy is an autosomal recessive-limb girdle muscular dystrophy (AR-LGMD) caused due to the defect in gene encoding dysferlin, a sarcolemmal protein. Awareness of the variants and their relative frequency is essential for accurate diagnosis. To study the spectrum of morphologic changes in immunohistochemically proven cases of dysferlinopathies, to correlate the findings with clinical phenotype and durations of illness and determine the frequency. Dysferlinopathies seen over a period of 2 years at a tertiary neurological center were analyzed. Clinically, majority had Miyoshi phenotype (46.6%) with distal involvement and LGMD phenotype (40%) with proximal muscle involvement. In addition, a proximo-distal and tibial muscle phenotype was encountered. Morphologically, rimmed vacuoles were noted in the Miyoshi phenotype. The presence of ragged red fibers, lobulated fibers and inflammation had no preference to a particular phenotype. Significant atrophy and lobulated fibers were noted in patients with longer duration of illness. Dysferlinopathy was the second most common identifiable cause (21%) of LGMD next to sarcoglycanopathies (27%).

Mutation in Exon 1f of PLEC, Leading to Disruption of Plectin Isoform 1f, Causes Autosomal-Recessive Limb-Girdle Muscular Dystrophy

Limb-girdle muscular dystrophy (LGMD) is a genetically heterogeneous group of inherited muscular disorders manifesting symmetric, proximal, and slowly progressive muscle weakness. Using Affymetrix 250K SNP Array genotyping and homozygosity mapping, we mapped an autosomal-recessive LGMD phenotype to the telomeric portion of chromosome 8q in a consanguineous Turkish family with three affected individuals. DNA sequence analysis of PLEC identified a homozygous c.1_9del mutation containing an initiation codon in exon 1f, which is an isoform-specific sequence of plectin isoform 1f. The same homozygous mutation was also detected in two additional families during the analysis of 72 independent LGMD2-affected families. Moreover, we showed that the expression of PLEC was reduced in the patient's muscle and that there was almost no expression for plectin 1f mRNA as a result of the mutation. In addition to dystrophic changes in muscle, ultrastructural alterations, such as membrane duplications, an enlarged space between the membrane and sarcomere, and misalignment of Z-disks, were observed by transmission electron microscopy. Unlike the control skeletal muscle, no sarcolemmal staining of plectin was detected in the patient's muscle. We conclude that as a result of plectin 1f deficiency, the linkage between the sarcolemma and sarcomere is broken, which could affect the structural organization of the myofiber. Our data show that one of the isoforms of plectin plays a key role in skeletal muscle function and that disruption of the plectin 1f can cause the LGMD2 phenotype without any dermatologic component as was previously reported with mutations in constant exons of PLEC.

Fukutin mutations in non-Japanese patients with congenital muscular dystrophy: Less severe mutations predominate in patients with a non-Walker-Warburg phenotype

Six genes including POMT1, POMT2, POMGNT1, FKRP, Fukutin (FKTN) and LARGE encode proteins involved in the glycosylation of α-dystroglycan (α-DG). Abnormal glycosylation of α-DG is a common finding in Walker-Warburg syndrome (WWS), muscle–eye–brain disease (MEB), Fukuyama congenital muscular dystrophy (FCMD), congenital muscular dystrophy types 1C and 1D and some forms of autosomal recessive limb-girdle muscular dystrophy (LGMD2I, LGMD2K, LGMD2M), and is associated with mutations in the above genes. FCMD, caused by mutations in Fukutin ( FKTN), is most frequent in Japan, but an increasing number of FKTN mutations are being reported outside of Japan. We describe four new patients with FKTN mutations and phenotypes ranging from: severe WWS in a Greek–Croatian patient, to congenital muscular dystrophy and cobblestone lissencephaly resembling MEB-FCMD in two Turkish patients, and limb-girdle muscular dystrophy and no mental retardation in a German patient. Four of the five different FKTN mutations have not been previously described.

P1.17 Limb-girdle muscular dystrophies in Czech Republic

Limb-girdle muscular dystrophies (LGMDs) represent a genetically and clinically heterogeneous group of muscular dystrophies predominantly affecting shoulder and pelvic girdles. To date, 15 forms of autosomal recessive (AR) and 7 forms of autosomal dominant (AD) LGMDs have been described. Mutations in many different genes encoding the sarcomeric, nuclear envelope, sarcolemmal and cytosolic proteins are responsible for the different forms of LGMDs. Involvement of genes causing posttranslational modifications of α-dystroglycan was demonstrated in the pathogenesis of several AR LGMDs.

Functional muscle analysis of the Tcap knockout mouse

Autosomal recessive limb‐girdle muscular dystrophy type 2G (LGMD2G) is an adult‐onset myopathy characterized by distal lower limb weakness, calf hypertrophy, and progressive decline in ambulation. The disease is caused by mutations in Tcap, a z‐disc protein of skeletal muscle, although the precise mechanisms resulting in clinical symptoms are unknown. To provide a model for preclinical trials and for mechanistic studies, we generated knockout mice carrying a null mutation in the TCAP gene. Here we present the first report of a Tcap knockout mouse model for LGMD2G and the results of an investigation into the effects of Tcap deficiency on skeletal muscle function in 4‐month‐ and 12‐month‐old mice. Muscle histology of Tcap‐null mice revealed abnormal myofiber size variation with central nucleation, similar to findings in the muscles of LGMD2G patients. An analysis of a Tcap binding protein, myostatin, showed that deletion of TCAP was accompanied by increased protein levels of myostatin. Our Tcap‐null mice exhibited a decline in the ability to maintain balance on a rotating rod, relative to wild‐type controls. No differences were detected in force or fatigue assays of isolated extensor digitorum longus (EDL) and soleus muscles. Finally, a mechanical investigation of EDL and soleus indicated an increase in muscle stiffness in knockout animals. We are the first to establish a viable knockout mouse model of Tcap deficiency and our model mice demonstrate a dystrophic phenotype comparable to humans with LGMD2G.Support: M.K. Childers Laboratory Startup Fund

Functional muscle analysis of the Tcap knockout mouse

Autosomal recessive limb-girdle muscular dystrophy type 2G (LGMD2G) is an adult-onset myopathy characterized by distal lower limb weakness, calf hypertrophy and progressive decline in ambulation. The disease is caused by mutations in Tcap, a z-disc protein of skeletal muscle, although the precise mechanisms resulting in clinical symptoms are unknown. To provide a model for preclinical trials and for mechanistic studies, we generated knockout (KO) mice carrying a null mutation in the Tcap gene. Here we present the first report of a Tcap KO mouse model for LGMD2G and the results of an investigation into the effects of Tcap deficiency on skeletal muscle function in 4- and 12-month-old mice. Muscle histology of Tcap-null mice revealed abnormal myofiber size variation with central nucleation, similar to findings in the muscles of LGMD2G patients. An analysis of a Tcap binding protein, myostatin, showed that deletion of Tcap was accompanied by increased protein levels of myostatin. Our Tcap-null mice exhibited a decline in the ability to maintain balance on a rotating rod, relative to wild-type controls. No differences were detected in force or fatigue assays of isolated extensor digitorum longus (EDL) and soleus (SOL) muscles. Finally, a mechanical investigation of EDL and SOL indicated an increase in muscle stiffness in KO animals. We are the first to establish a viable KO mouse model of Tcap deficiency and our model mice demonstrate a dystrophic phenotype comparable to humans with LGMD2G.

Cardiomyopathy in a patient with limb-girdle muscular dystrophy type 2D: Pathomorphological aspects

Sarcoglycanopathies are a group of autosomal recessive limb-girdle muscular dystrophies caused by mutations in the genes encoding for α-, β-, γ- and δ-sarcoglycan, which are expressed in skeletal and cardiac muscle. Cardiomyopathy has rarely been reported in patients with mutations in the α-sarcoglycan gene and descriptions of heart pathology are lacking. To our knowledge, this is the first report on characteristic pathomorphological changes in cardiac muscle detected at autopsy in a patient with a proven mutation (nucleotide substitution 229C>T (R77C) in exon 3) in the α-sarcoglycan gene. The patient had the phenotype of Duchenne-like muscular dystrophy. Due to severe weakness of the respiratory muscles, permanent nocturnal mechanical ventilation via a tracheostomy had been necessary since the age of 24 years. The patient also suffered from mild pulmonary and systemic hypertension. At the age of 36, he lost consciousness and was brought to the emergency room in asystolia and unsuccessfully reanimated for half an hour. Gross heart examination disclosed scattered unsharply demarcated grey and yellow areas, characteristically localised in the outer (subepicardial) part of the lateral and posterior left ventricular wall, while the interventricular septum was spared. Similar changes were present in the apical region of the posterior right ventricular wall. Histopathological changes in focal subepicardial myocardial lesions in the free left ventricular wall consisted of myocardial degeneration in the absence of inflammatory infiltrates, fibrosis and fatty replacement of the myocardium, strikingly similar to changes in skeletal muscle. Since autopsy did not reveal any significant coronary stenosis or valvular pathology, both chronic myocardial ischemia and valvular disease could be excluded as causes of the above-described changes, which were ascribed to α-sarcoglycanopathy. Mild myocardial hypertrophy could be attributed to pulmonary and systemic hypertension. The progression of cardiomyopathy in α-sarcoglycanopathy was considered slow, since it had not reached the stage of dilated cardiomyopathy at the time of death. Focal subepicardial myocardial lesions, most pronounced in the posterobasal segment of the left ventricle, were characteristic of cardiomyopathy in α-sarcoglycanopathy. Since focal lesions may spread further, thorough cardiac monitoring is recommended in patients with α-sarcoglycanopathy.

Cardiac diseases in sarcoglycanopathies

Sarcoglycanopathies (SGs) are autosomal recessive limb-girdle muscular dystrophies (LGMD). These dystrophies are caused by mutations in any of the four sarcoglycan genes: α (LGMD 2D), β (LGMD 2E), γ (LGMD 2C) and δ (LGMD 2F). We discuss heart involvement in these diseases.