Congenital muscular dystrophy with primary partial laminin alpha2 chain deficiency: molecular study.

The authors report a case of congenital muscular dystrophy with mild nonprogressive muscle weakness, white matter hypodensity, and absence of the laminin alpha2 chain in muscle fibers with two antibodies, but not with four others. They identified mutations in LAMA2, which explain the partial laminin alpha2 deficiency. Analysis of this case and two others allows us to refine the epitopes of two of the commercial antibodies, and illustrate the importance of using antibodies directed against different domains of the protein.

Oppenheim's myatonia congenita.

In 1900 the famous German neurologist Hermann Oppenheim published a two-page article on "Myatonia congenita" which led to a long-lasting and confusing discussion in neurology and neuropediatrics, and which was extensively quoted throughout the 20th century. As this article is only available in German, an English translation is presented here. Further publications of Oppenheim on the same subject are mentioned and some comments are made on the impact of his seminal article. It had the merit of drawing the attention to the existence of congenital muscle diseases in children but its impact would be better understood by the influence Oppenheim had on his time, as he was one of the leading neurologists at the end of the 19th and beginning of the 20th century.

Age-related morphological changes of the deltoid muscle from 50 to 79 years of age.

A quantitative analysis of deltoid muscle biopsy specimens was performed by light microscopy in 26 males and 25 females aged 50-79 years without known neuromuscular disease. Muscle fibre size, fibre type distribution and increase in mitochondrial content in muscle fibres were examined using a semi-automatic image analysis system. This study showed significant age- and gender-related differences. In females, there was marked atrophy of type II fibres with increasing age, specially of type IIb fibres, but no significant change in muscle fibre type distribution. In males, there was diminution in the relative proportion of type IIb fibres with increasing age but no significant muscle fibre atrophy. Mitochondrial aggregates increased with age, and this increase was observed earlier in females than in males. The gender-related morphological changes observed in the present study differ somewhat from those reported in the literature. The differences between males and females may be partially related to gender differences in muscular activity and may reflect an earlier decline in deltoid muscle strength in females. The existence of these age and gender changes should be taken into account in the interpretation of muscle biopsies of aged individuals.

Oculopharyngeal MD among Bukhara Jews is due to a founder (GCG)9 mutation in the PABP2 gene.

OBJECTIVE: To determine whether all cases of oculopharyngeal muscular dystrophy (OPMD) among Bukhara Jews share the same founder mutation. BACKGROUND: Autosomal dominant OPMD is caused by a (GCG)8-13 repeat expansion in the polyadenylation binding protein 2 (PABP2) gene. The disease has a worldwide distribution but is particularly prevalent in Bukhara Jews and in French Canadians, in whom it was introduced by three sisters in 1648. METHODS: We established the size of the PABP2 mutation in 23 Bukhara Jewish patients belonging to eight unrelated families. In all families, we constructed haplotypes for the carrying chromosomes composed of the alleles for eight chromosome 14q polymorphic markers. RESULTS: All patients share a (GCG)9 PABP2 mutation and a four-marker haplotype. Furthermore, a shared intron single nucleotide polymorphism (SNP) in the PABP2 gene 2.6Kb from the mutation was not observed in 22 families with (GCG)9 mutations from nine different countries. The smaller size of the chromosomal region in linkage disequilibrium around the mutation in Bukhara Jews, as compared with French Canadians, suggests a founder effect that occurred more than 350 years ago. Based on the Luria-Delbrück corrected "genetic clock," we estimate that the mutation appeared or was introduced once in the Bukhara Jewish population between AD 872 and 1512 (mean, AD 1243). CONCLUSION: OPMD among Bukhara Jews is the result of a shared, historically distinct, PABP2 (GCG)9 mutation that likely arose or was introduced in this population at the time they first settled in Bukhara and Samarkand during the 13th or 14th centuries.

Nuclear inclusions in oculopharyngeal muscular dystrophy consist of poly(A) binding protein 2 aggregates which sequester poly(A) RNA.

Oculopharyngeal muscular dystrophy (OPMD) is an adult-onset disease characterized by progressive eyelid drooping, swallowing difficulties and proximal limb weakness. The autosomal dominant form of the disease is caused by short (GCG)(8-13) expansions in the PABP2 gene. This gene encodes the poly(A) binding protein 2 (PABP2), an abundant nuclear protein that binds with high affinity to nascent poly(A) tails, stimulating their extension and controlling their length. In this work we report that PABP2 is detected in filamentous nuclear inclusions, which are the pathological hallmark of OPMD. Using both immunoelectron microscopy and fluorescence confocal microscopy, the OPMD-specific nuclear inclusions appeared decorated by anti-PABP2 antibodies. In addition, the inclusions were labeled with antibodies directed against ubiquitin and the subunits of the proteasome and contained a form of PABP2 that was more resistant to salt extraction than the protein dispersed in the nucleoplasm. This suggests that the polyalanine expansions in PABP2 induce a misfolding and aggregation of the protein into insoluble inclusions, similarly to events in neurodegenerative diseases caused by CAG/polyglutamine expansions. No significant differences were observed in the steady-state poly(A) tail length in OPMD and normal myoblasts. However, the nuclear inclusions were shown to sequester poly(A) RNA. This raises the possibility that in OPMD the polyalanine expansions in the PABP2 protein may interfere with the cellular traffic of poly(A) RNA.

Molecular and genetic characterization of sarcospan: insights into sarcoglycan-sarcospan interactions.

Autosomal recessive limb girdle muscular dystrophies 2C-2F represent a family of diseases caused by primary mutations in the sarcoglycan genes. We show that sarcospan, a novel tetraspan-like protein, is also lost in patients with either a complete or partial loss of the sarcoglycans. In particular, sarcospan was absent in a gamma-sarcoglycanopathy patient with normal levels of alpha-, beta- and delta-sarcoglycan. Thus, it is likely that assembly of the complete, tetrameric sarcoglycan complex is a prerequisite for membrane targeting and localization of sarcospan. Based on our findings that sarcospan is integrally associated with the sarcoglycans, we screened >50 autosomal recessive muscular dystrophy cases for mutations in sarcospan. Although we identified three intragenic polymorphisms, we did not find any cases of muscular dystrophy associated with primary mutations in the sarcospan gene. Finally, we have identified an important case of limb girdle muscular dystrophy and cardiomyopathy with normal expression of sarcospan. This patient has a primary mutation in the gamma-sarcoglycan gene, which causes premature truncation of gamma-sarcoglycan without affecting assembly of the mutant gamma-sarcoglycan into a complex with alpha-, beta- and delta-sarcoglycan and sarcospan. This is the first demonstration that membrane expression of a mutant sarcoglycan-sarcospan complex is insufficient in preventing muscular dystrophy and cardiomyopathy and that the C-terminus of gamma-sarcoglycan is critical for the functioning of the entire sarcoglycan-sarcospan complex. These findings are important as they contribute to a greater understanding of the structural determinants required for proper sarcoglycan-sarcospan expression and function.

[Familial myopathy with desmin storage seen as a granulo-filamentar, electron-dense material with mutation of the alphaB-cristallin gene]. / Myopathie familiale avec surcharge en desmine, sous forme de matériel granulo-filamentaire dense en microscopie electronique, avec mutation dans le gêne de l'alphaB-cristalline.

Two familial cases of a myopathy remarkable by the presence of a granulo-filamentar, electron dense material were reported in 1978. In a second step, in 1988, it was demonstrated that this material contained an abnormally-phosphorylated desmin. During the last twenty years, the occurrence of new cases in this family confirmed the autosomal dominant inheritance of the disease, and made it potentially informative for molecular genetics studies. This allowed first to map the disease on chromosome11q21-23, and afterwards to identify a mutation within a gene coding for a chaperone protein, alphaBcrystallin. An extensive clinical, pathological and genetic study of this princeps family is herein reported in detail. First, it showed the possible detection of histopathological changes in presymptomatic patients. Second, it allowed to demonstrate the simultaneous occurrence of both alphaBcrystallin and desmin in the granulo-filamentar aggregates. Third, this study provided a precise knowledge of the evolution rate of the disease. The analysis of similar observations reported in the literature clearly shows the clinical, pathological and genetic heterogeneity of this new neuro-muscular disorder.

[Miyoshi distal myopathy: specific signs and incidence]. / Myopathie distale de type Miyoshi: séméiologie particulière et fréquence.

We report 21 French patients (12 males and 9 females), presenting a distal myopathy of Miyoshi type. The main clinical features of these patients were 1) onset in late adolescence or early adulthood (mean age: 20.3 years), 2) early and predominant involvement of the posterior compartment muscles of legs, 3) marked elevation of serum CK (from 10 to 50 times the normal value), 4) dystrophic features with a necrotic regeneration pattern without vacuole in muscle biopsy. All cases were sporadic and a consanguinity of parents was found in five cases. The clinical course was relatively mild: twelve patients could walk without aid; However four patients were severely disabled. Four patients were initially considered as having polymyositis; corticosteroids and immunosuppressive drugs were always inefficient. A genetic linkage to chromosome 2 was ascertained in five cases. In our experience the Miyoshi distal myopathy is the most common form of distal myopathy, particularly in young patients.

Genetic heterogeneity of congenital muscular dystrophy with rigid spine syndrome.

Rigid spine syndrome is a neuromuscular disorder characterised by early rigidity of the spine due to axial muscle contractures, generally associated with muscle weakness, limb-joint contractures, and often respiratory failure. This phenotype may be associated with several muscular diseases. In cases of merosin-positive congenital muscular dystrophies (CMD) with rigid spine syndrome, we have recently identified a new locus (RSMD1) on chromosome 1p35-36. In the present study, we report the clinical, morphological and genetic analysis of other patients affected by a CMD with rigid spine syndrome from nine consanguineous families. Homozygosity mapping showed that the disease was linked to RSMD1 in one of the nine families. The other families were excluded from RSMD1, and the patients presented highly variable phenotypes suggesting the involvement of more than one gene defect in rigid spine syndrome. Nevertheless, a subgroup of patients who never walked, and had very early rigidity of the spine and scoliosis, may be considered for further genetic analysis.

Myoblast transplantations lead to the expression of the laminin alpha 2 chain in normal and dystrophic (dy/dy) mouse muscles.

Laminin-2 is part of the basement membrane of the skeletal muscle fibers. The laminin alpha 2 chain is absent or drastically reduced in a subgroup of congenital muscular dystrophy patients, and in the severely affected dystrophic dy/dy mouse. We previously reported that heterogeneous primary mouse muscle cell cultures conferred laminin alpha 2 chain expression in dy/dy mice muscles upon cell transplantation. In the present study we investigated whether pure myoblast cell lines were able to confer laminin alpha 2 chain expression in vivo. We observed that: (1) xeno-transplantation of non-immortalized human myoblast in SCID mouse muscles allows human laminin alpha 2 chain expression; (2) allotransplantation of the permanent G8 mouse myoblast cell line in dy/dy muscles allows the expression of the murine laminin alpha 2 chain; and (3) allo-transplantation of the D7 dystrophic dy/dy cell line allows the formation of new and hybrid muscle fibers in dy/dy muscle in the absence of laminin alpha 2 chain expression. We conclude that normal myoblasts are able to restore the expression of an extracellular skeletal muscle protein and that the absence of laminin-2 does not prevent transplanted muscle cells from participating in the formation of myofibers. Myoblasts are, therefore, attractive tools for further exploration of gene complementation strategies in the animal models of congenital muscular dystrophy.

The Peter Emil Becker Award lecture 1998. The saga of congenital muscular dystrophy.

The first credible descriptions of congenital muscular dystrophy (CMD) were made at the beginning of this century but the individuality of this condition had difficulty to be accepted because its distinction from other types of childhood neuromuscular disorders was far from clear. The reports of different clinico-pathological phenotypes of CMD and recently of immunocytochemical and molecular genetic studies allowed the precise definition of specific entities within the group of CMD. Here we present the historical background of CMD, its vicissitudes and the main steps leading to the individualisation of the merosin-deficient CMD to which the author has contributed. Mention is also made to major achievements in the characterisation of other types of CMD, namely the Fukuyama CMD, the muscle-eye-brain disease and a peculiar form of CMD with the rigidity of the spine. Animal models of merosin-deficient congenital muscular dystrophy were identified and their current study may lead to a better understanding of the pathogenesis of the human disease and to therapeutic strategies.

Homozygotes for oculopharyngeal muscular dystrophy have a severe form of the disease.

Autosomal dominant oculopharyngeal muscular dystrophy (OPMD) usually begins with ptosis or dysphagia during the fifth or sixth decade of life. We studied 7 patients with OPMD symptoms starting before the age of 36 years. All were found to be homozygotes for the dominant (GCG)9 OPMD mutation. On average, disease onset was 18 years earlier than in heterozygotes, and patients had a significantly larger number of muscle nuclei containing intranuclear inclusions (INIs) (9.4 vs 4.9%).

Oculopharyngeal muscular dystrophy.

Autosomal dominant oculopharyngeal muscular dystrophy (OPMD) is an adult-onset disease with worldwide distribution. It usually presents in the fifth or sixth decades with progressive dysphagia, eyelid ptosis, and proximal limb weakness. Unique intranuclear filament inclusions in skeletal muscle fibers are its morphological hallmark. Surgical correction of the ptosis and cricopharyngeal myotomy are the only therapies available. Autosomal dominant OPMD is caused by short (GCG)8-13 riplet-repeat expansions in the polyadenylation binding protein 2 (PABP2) gene, which is localized in chromosome 14q11. Autosomal recessive OPMD is caused by a double dose of a (GCG)7 PABP2 allele. The GCG expansions cause lengthening of a predicted polyalanine tract in the protein. The expanded polyalanine domains may cause polyalanine nuclear toxicity by accumulating as nondegradable nuclear filaments.

Hereditary inclusion body myopathies.

Hereditary inclusion body myopathies comprise autosomal recessive and autosomal dominant muscle disorders that have a variable clinical phenotype but share similar morphological features. These include rimmed vacuoles within muscle fibres and collections of intrasarcoplasmic and intranuclear tubulofilamentous inclusions, 16-18 nm in external diameter. The resemblances and the differences between the sporadic and the hereditary inclusion body myopathies are discussed. Recent advances in the identification of various proteins involved in these diseases are mentioned because they have provided better insight into their underlying pathophysiological mechanisms. Linkage studies have allowed the localization of the genetic defect of some hereditary inclusion body myopathies and related disorders, contributing to their individualization.

Characterization of monoclonal antibodies to calpain 3 and protein expression in muscle from patients with limb-girdle muscular dystrophy type 2A.

Monoclonal antibodies were raised to two regions of calpain 3 (muscle-specific calcium-activated neutral protease), which is the product of the gene that is defective in limb-girdle muscular dystrophy type 2A. The antibodies produced characteristic patterns of bands on Western blots: normal calpain 3 protein was represented by bands at 94 kd, plus additional fragments at approximately 60 or 30 kd, according to the antibody used. Specificity was confirmed by the loss of all bands in patients with null gene mutations. The "normal" profile of bands was observed in muscle from 33 control subjects and 70 disease-control patients. Calpain 3 protein was found to be extremely stable in fresh human muscle, with full-size protein being detected 8 hours after the muscle had been removed. Blots of muscle from nine limb-girdle muscular dystrophy type 2A patients with defined mutations showed variation in protein expression, with seven showing a clear reduction in the abundance of protein detected. No simple relationship was found between the abundance and clinical severity. Two patients showed normal expression of the full-size 94 kd band accompanied by a clear reduction in the smaller fragments. This pattern was also observed in one patient with an undefined form of limb-girdle dystrophy. These results indicate that immunodiagnosis is feasible, but caution will need to be exercised with the interpretation of near-normal protein profiles.

Autosomal recessive oculopharyngodistal myopathy in light of distal myopathy with rimmed vacuoles and oculopharyngeal muscular dystrophy.

We investigated two Japanese siblings presenting with oculopharyngodistal myopathy, whose healthy parents were consanguineous. To clarify their disease characteristics, we compared them with four patients with distal myopathy with rimmed vacuoles linked to chromosome 9p1-q1, and 36 patients with oculopharyngeal muscular dystrophy linked to 14q11.2-q13. The first symptom in the patients with autosomal recessive oculopharyngodistal myopathy was weakness of the tibialis anterior muscle. Their biceps muscles showed initial and advanced myogenic changes, with rimmed vacuoles in 3% and 6% of the muscle fibers, respectively. In contrast, patients with distal myopathy with rimmed vacuoles revealed many rimmed vacuoles, on average in 20% of the fibers, and their oculopharyngeal muscles were spared. None of the patients with oculopharyngeal muscular dystrophy showed distal dominant weakness and the occurrence of rimmed vacuoles was rare. Ultrastructural studies in groups of autosomal recessive oculopharyngodistal myopathy and distal myopathy with rimmed vacuoles disclosed a collection of cytoplasmic filaments of 16-18 nm, but oculopharyngeal muscular dystrophy-specific intranuclear inclusions of 8.5 nm were not found. Thus, the phenotype of autosomal recessive oculopharyngodistal myopathy is distinct from distal myopathy with rimmed vacuoles and oculopharyngeal muscular dystrophy, but shares some ultrastructural characteristics with distal myopathy with rimmed vacuoles and hereditary inclusion body myopathy.

Identification of a new locus for a peculiar form of congenital muscular dystrophy with early rigidity of the spine, on chromosome 1p35-36.

Classical congenital muscular dystrophies (CMDs) are autosomal recessive neuromuscular disorders characterized by early onset of hypotonia and weakness, atrophy of limbs and trunk muscles, contractures, and dystrophic changes in the muscle biopsy. So far, only one gene, LAMA2 (6q2), which encodes the laminin alpha2 chain (or merosin), has been identified in these disorders. Mutations in LAMA2 cause CMD with complete or partial merosin deficiency, detectable by immunocytochemistry on muscle biopsies, and account for approximately 50% of CMD cases. In a large consanguineous family (11 siblings) comprising three children affected by CMD without merosin deficiency, we undertook a genomewide search by homozygosity mapping and analyzed 380 microsatellite markers. The affected children were homozygous for several markers on chromosome 1p35-36. We identified two additional consanguineous families with affected children who also showed linkage to this locus. A maximum cumulative LOD score of 4.48, at a recombination fraction of .00, was obtained with D1S2885. A consistent feature in these three families was the presence of early rigidity of the spine, scoliosis, and reduced vital capacity, as found in rigid-spine syndrome (RSS). This study is the first description of a locus for a merosin-positive CMD and will help to better define the nosology of RSS.

PCR based mutation screening of the laminin alpha2 chain gene (LAMA2): application to prenatal diagnosis and search for founder effects in congenital muscular dystrophy.

Classical congenital muscular dystrophy with merosin deficiency is caused by mutations in the laminin alpha2 chain gene (LAMA2). Extended sequencing of the introns flanking the 64 LAMA2 exons was carried out and, based on these sequences, oligonucleotide primers were designed to amplify the coding region of each exon separately. By PCR-SSCP analysis, we identified eight new mutations in nine families originating from various countries. All induced a premature truncation of the protein, either in the short arm or in the globular C-terminal domain. A 2 bp deletion in exon 13, 2098delAG, was found in three French non-consanguineous families and a nonsense mutation of exon 20, Cys967stop, in two other non-consanguineous families originating from Italy. Determination of rare intragenic polymorphisms permitted us to show evidence of founder effects for these two mutations suggesting a remote degree of consanguinity between the families. Other, more frequent polymorphisms, G to A 1905 (exon 12), A to G 2848 (exon 19), A to G 5551 (exon 37), and G to A 6286 (exon 42), were used as intragenic markers for prenatal diagnosis. This study provides valuable methods for determining the molecular defects in LAMA2 causing merosin deficient congenital muscular dystrophy.

Short GCG expansions in the PABP2 gene cause oculopharyngeal muscular dystrophy.

Autosomal dominant oculopharyngeal muscular dystrophy (OPMD) is an adult-onset disease with a world-wide distribution. It usually presents in the sixth decade with progressive swallowing difficulties (dysphagia), eyelid drooping (ptosis) and proximal limb weakness. Unique nuclear filament inclusions in skeletal muscle fibres are its pathological hallmark. We isolated the poly(A) binding protein 2 gene (PABP2) from a 217-kb candidate interval on chromosome 14q11 (B.B. et al., manuscript submitted). A (GCG)6 repeat encoding a polyalanine tract located at the N terminus of the protein was expanded to (GCG)8-13 in the 144 OPMD families screened. More severe phenotypes were observed in compound heterozygotes for the (GCG)9 mutation and a (GCG)7 allele that is found in 2% of the population, whereas homozygosity for the (GCG)7 allele leads to autosomal recessive OPMD. Thus the (GCG)7 allele is an example of a polymorphism which can act either as a modifier of a dominant phenotype or as a recessive mutation. Pathological expansions of the polyalanine tract may cause mutated PABP2 oligomers to accumulate as filament inclusions in nuclei.