Homozygous Lamin A/C familial lipodystrophy R482Q mutation in autosomal recessive Emery Dreifuss muscular dystrophy

Autosomal recessive Emery Dreifuss muscular dystrophy (AR-EDMD) is rare, with few reports in the medical literature. We describe the first cases of AR-EDMD and autosomal dominant familial partial lipodystrophy (FPLD) in the Hutterite population resulting from homozygous or heterozygous R482Q mutations in the Lamin A/C gene (LMNA). Heterozygosity for LMNA R482Q mutation causes FPLD, which is associated with increased risk of hyperlipidemia and hypertension. The overall carrier frequency of the R482Q mutation in Dariusleut and Leherleut Hutterites in Alberta was found to be 1.45%. Homozygosity for this mutation has not been previously reported and here resulted in a combination of generalized lipodystrophy and EDMD. Knowledge that the LMNA R482Q mutation is present in this population is important for genetic counseling, surveillance, and management of the associated disorders.     

FKRP mutations cause congenital muscular dystrophy 1C and limb-girdle muscular dystrophy 2I in Asian patients

Mutation in the fukutin-related protein (FKRP) gene causes alpha-dystroglycanopathies, a group of autosomal recessive disorders associated with defective glycosylated alpha-dystroglycan (α-DG). The disease phenotype shows a broad spectrum, from the most severe congenital form involving brain and eye anomalies to milder limb-girdle form. FKRP-related alpha-dystroglycanopathies are common in European countries. However, a limited number of patients have been reported in Asian countries. Here, we presented the clinical, pathological, and genetic findings of nine patients with FKRP mutations identified at a single muscle repository center in Japan. Three and six patients were diagnosed with congenital muscular dystrophy type 1C and limb-girdle muscular dystrophy 2I, respectively. None of our Asian patients showed the most severe form of alpha-dystroglycanopathy. While all patients showed a reduction in glycosylated α-DG levels, to variable degrees, these levels did not correlate to clinical severity. Fifteen distinct pathogenic mutations were identified in our cohort, including five novel mutations. Unlike in the populations belonging to European countries, no common mutation was found in our cohort.     

A new mutation of the fukutin gene causing late-onset limb girdle muscular dystrophy

Defects in glycosylations of α-dystroglycan are associated with mutations in several genes, including the fukutin gene (FKTN). Hypoglycosylation of α-dystroglycan results in several forms of muscular dystrophy with variable phenotype. Outside Japan, the prevalence of muscular dystrophies related to aberrations of FKTN is rare, with only eight reported cases of limb girdle phenotype (LGMD2M). We describe the mildest affected patient outside Japan with genetically confirmed LGMD2M and onset of symptoms at age 14. She was brought to medical attention at age 12, not because of muscle weakness, but due to episodes of tachycardia caused by Wolff–Parkinson–White syndrome. On examination, she had rigid spine syndrome, a typical limb girdle dystrophy pattern of muscle weakness, cardiomyopathy, and serum CK levels >2000 IU/L (normal <150 IU/L). A homozygous, novel c.917A>G; p.Y306C mutation in the FKTN gene was found. The case confirms FKTN mutations as a cause of LGMD2M without mental retardation and expands the phenotypic spectrum for LGMD2M to include cardiomyopathy and rigid spine syndrome in the mildest affected non-Japanese patient reported so far.     

Detection of deletions within the dystrophin gene in Polish families affected with Duchenne/Becker muscular dystrophy

DNA analysis was performed in 190 cases of Duchenne and Becker muscular dystrophies (DMD/BMD), including 150 cases with DMD and 40 cases with BMD, using Southern blotting and PCR multiplex techniques with application of 25 pairs of primers. Deletions in the overall material were found in 109 cases: 81 (54%) in patients with DMD and 28 (70%) in patients with BMD. All the deletions in DMD were out of frame with the exception of two cases, whereas in BMD all the deletions but two were in frame. Junction fragments were detected in 12 cases of DMD. In five cases duplications were found: four in patients with DMD and one in a patient with BMD.     

Autosomal recessive Emery-Dreifuss muscular dystrophy caused by a novel mutation (R225Q) in the lamin A/C gene identified by exome sequencing

Introduction: The aim of this study is to describe a new mutation in the LMNA gene diagnosed by whole exome sequencing. Methods: A two‐generation kindred with recessive limb‐girdle muscular dystrophy was evaluated by exome sequencing of the proband's DNA. Results: Exome sequencing disclosed 194,618 variants (170,196 SNPs, 8482 MNPs, 7466 insertions, 8307 deletions, and 167 mixed combinations); 71,328 were homozygotic and 123,290 were heterozygotic, with 11,753 non‐synonymous, stop‐gain, stop‐loss, or frameshift mutations occurring in the coding region or nearby intronic region. The cross‐referencing of these mutations in candidate genes for muscular dystrophy showed a homozygote mutation c.G674A in exon 4 of LMNA causing a protein change R225Q in an arginine conserved from human to Xenopus tropicalis and in lamin B1. Conclusions: This technique will be preferred for studying patients with muscular dystrophy in the coming years. Muscle Nerve, 2012     

Skeletal muscle pathology in autosomal dominant Emery-Dreifuss muscular dystrophy with lamin A/C mutations

We present our observations on the skeletal muscle pathology of nine cases from seven families of autosomal dominant Emery-Dreifuss muscular dystrophy (ADEDMD) with identified mutations in the lamin A/C gene, aged 2-35 years at the time of biopsy. The severity of pathological change was moderate and the most common features were variation in fibre size (hypertrophy and atrophy), an increase in internal nuclei and smaller diameter fibres with high oxidative enzyme activity. Only one case showed necrosis, which was present in two separate samples taken from the quadriceps and tibialis anterior, at different ages. Immunocytochemistry detected an age-related reduction of laminin beta1 on the muscle fibres in adolescent and adult cases. Antibodies to lamins A and A/C, and emerin did not reveal any detectable differences from controls. Electron microscopy of two out of three cases showed an abnormal distribution of heterochromatin in many fibre nuclei. Our results show that dystrophic changes in skeletal muscle are not a major feature of ADEDMD, and that nuclear abnormalities may be detected with electron microscopy. Immunodetection of reduced laminin beta1 may be a useful secondary marker in adults with this disorder, as immunocytochemistry of lamins is not yet of diagnostic use.     

Extreme variability of skeletal and cardiac muscle involvement in patients with mutations in exon 11 of the lamin A/C gene

Mutations of the LMNA gene, encoding the nuclear envelope proteins lamins A and C, give rise to Emery-Dreifuss muscular dystrophy and to limb-girdle muscular dystrophy 1B (EDMD and LGMD1B). With one exception, all the reported EDMD and LGMD1B mutations are confined to the first 10 exons of the gene. We report four separate cases, with mutations in the same codon of LMNA exon 11, characterized by remarkable variability of clinical findings, in addition to features not previously reported. One patient had congenital weakness and died in early childhood. In two other patients, severe cardiac problems arose early and, in one of these, cardiac signs preceded by many years the onset of skeletal muscle weakness. The fourth case had a mild and late-onset LGMD1B phenotype. Our cases further expand the clinical spectrum associated with mutations in the LMNA gene and provide new evidence of the role played by the C-terminal domain of lamin A.     

A novel LMNA gene mutation Leu162Pro and the associated clinical characteristics in a family with autosomal-dominant emery-dreifuss muscular dystrophy

We report the clinical characteristics, genetic analysis, and muscle biopsy findings of a family with Emery-Dreifuss muscular dystrophy and a novel mutation (Leu162Pro) in the LMNA gene. Within this single family, the age of onset and disease severity varied among the family members. In addition, focal defects of nuclear membranes with chromatin blebs in endothelial cells was shown via electron microscopy.     

Nuclear envelope alterations in fibroblasts from patients with muscular dystrophy, cardiomyopathy, and partial lipodystrophy carrying lamin A/C gene mutations

Mutations in LMNA, the gene that encodes nuclear lamins A and C, cause up to eight different diseases collectively referred to as "laminopathies." These diseases affect striated muscle, adipose tissue, peripheral nerve, and bone, or cause features of premature aging. We investigated the consequences of LMNA mutations on nuclear architecture in skin fibroblasts from 13 patients with different laminopathies. Western-blotting showed that none of the mutations examined led to a decrease in cellular levels of lamin A or C. Regardless of the disease, we observed honeycomb nuclear structures and nuclear envelope blebs in cells examined by immunofluorescence microscopy. Concentrated foci of lamin A/C in the nucleoplasm were also observed. Only mutations in the head and tail domains of lamins A and C significantly altered the nuclear architecture of patient fibroblasts. These results confirm that mutations in lamins A and C may lead to a weakening of a structural support network in the nuclear envelope in fibroblasts and that nuclear architecture changes depend upon the location of the mutation in different domains of lamin A/C.     

Muscle imaging analogies in a cohort of patients with different clinical phenotypes caused by LMNA gene mutations

Laminopathies are a heterogeneous group of LMNA‐gene‐mutation–related clinical disorders associated with alterations of cardiac and skeletal muscle and peripheral nerves, metabolic defects, and premature aging. Leg muscle imaging investigations were performed in a cohort of patients with LMNA gene alterations who were suffering from Emery–Dreifuss muscular dystrophy, limb‐girdle muscular dystrophy type 1B, isolated cardiac disorders or a phenotype of cardiac disorders, and lipodystrophy, including one individual with peripheral neuropathy. Leg muscle imaging revealed varying degrees of alteration in the soleus and medial head of gastrocnemius in each subject. This study demonstrates that LMNA‐gene‐mutated patients devoid of any clinically detectable skeletal muscle involvement have the same pattern of leg muscle involvement as patients with overt skeletal muscle compromise. This finding suggests the presence of a continuum of skeletal muscle involvement among phenotypes of LMNA‐gene‐mutation–related skeletalmyopathy and cardiomyopathy. Muscle Nerve, 2010     

Co-morbidity of Emery–Dreifuss muscular dystrophy and a congenital myasthenic syndrome possibly affecting the phenotype in a large Bedouin kindred

Emery–Dreifuss muscular dystrophy (EDMD) is an X-linked humero-peroneal muscular dystrophy associated with contractures and cardiomyopathy. In a 90 member family, we found 11 affected male individuals, three of whom displayed areflexia and neurogenic electromyographic changes. Muscle biopsy performed in one case demonstrated type grouping suggestive of a neurogenic disorder. These three individuals and another family member, who suffers from mild, static limb weakness but is clinically and genetically unaffected by EDMD showed an abnormal incremental response of over 100% to tetanic stimulation. In contrast, one affected family member showed myopathic features on needle electromyography and no definite pathology in repetitive stimulation studies. The diagnosis of EDMD was established by demonstrating a 1712_1713insTGGGC mutation in the emerin gene. This family apparently expresses co-morbidity of EDMD with an exceptionally mild form of pre-synaptic congenital myasthenic syndrome resembling the Lambert–Eaton myasthenic syndrome (LEMS). The superimposed pre-synaptic disorder may have contributed to the development of the neurogenic features demonstrated in these patients.     

Duchenne/Becker muscular dystrophy: A report on clinical,biochemical, and genetic study in Gujarat population,India

Objective:

In India, various groups have studied different regions to find out deletion pattern of dystrophin gene. We have investigated its deletion pattern among Duchenne/Becker muscular dystrophy (D/BMD) patients across Gujarat. Moreover, in this study we also correlate the same with reading frame rule. However, we too consider various clinicopathological features to establish as adjunct indices when deletion detection fails.

Materials and Methods:

In this pilot study, a total of 88 D/BMD patients consulting at our centers in Gujarat, India were included. All patients were reviewed on basis of their clinical characteristics, tested by three primer sets of 10-plex, 9-plex, and 7-plex polymerase chain reaction (PCR) for genetic analysis; whereas, biochemical indices were measured using automated biochemical analyzers.

Results:

The diagnosis of D/BMD was confirmed by multiplex-PCR (M-PCR) in D/BMD patients. A number of 65 (73.86%) out of 88 patients showed deletion in dystrophin gene. The exon 50 (58.46%) was the most frequent deletion found in our study. The mean age of onset of DMD and BMD was 4.09 ± 0.15 and 7.14 ± 0.55 years, respectively. In patients, mean creatine phosphokinase (CPK), lactate dehydrogenase (LDH), and myoglobin levels were elevated significantly (P < 0.05) in comparison to controls. Addition to CPK, LDH and myoglobin are good adjunct when deletion detection failed. These data are further in accordance with world literature when correlated with frame rule.

Conclusion:

The analysis has been carried out for the first time for a total of 88 D/BMD patients particularly from Gujarat, India. More research is essential to elucidate specific mutation pattern in association with management and therapies of proband.     

Pathological changes of the myonuclear fibrous lamina and internal nuclear membrane in two cases of autosomal dominant limb-girdle muscular dystrophy with atrioventricular conduction disturbance (LGMD1B)

Mutations in the lamin A/C gene have been reported in a variety of disorders including autosomal dominant Emery-Dreifuss muscular dystrophy and autosomal dominant limb girdle muscular dystrophy with cardiac conduction block or limb girdle muscular dystrophy type 1B (LGMD1B). However, how these mutations are involved in developing these diseases is not known. We examined morphological changes of the skeletal muscle in two cases of LGMD1B in a family, directing our attention to the nuclear envelope and its underlying structures where lamin A/C is located. Although conventional fluorescence microscope revealed no discernible abnormality in the distribution of emerin and lamin A/C, a serial multi-layer scanning with confocal laser scanning microscope showed an attenuated and uneven distribution of lamin A/C. Furthermore, under an electron microscope, the nuclear fibrous lamina and inner nuclear membrane were relatively indistinct compared to controls. These changes in the myonuclei may be related to pathomechanisms of the present cases.     

Molecular analysis of the duchenne muscular dystrophy gene in patients with becker muscular dystrophy presenting with dilated cardiomyopathy

Molecular analysis of the Duchenne muscular dystrophy (DMD) gene was performed on 4 unrelated patients with Becker muscular dystrophy (BMD) presenting with dilated cardiomyopathy. Two patients with a deletion involving exon 1 were quite unique in that they developed fatal myocardial involvement in their teens, despite the absence of significant muscular weakness. The deletion found in these patients comprised the 3′-end of exon 1 and the greater part of intron 1. Two other patients with a deletion of exon 47 showed progressive muscular atrophy and weakness; they were considered to be typical BMD in both clinical features and the type of gene deletion. We speculate that a deletion around exon 1 may severely damage the expression and/or the function of dystrophin selectively in cardiac muscle, but not in skeletal muscle. © 1993 John Wiley & Sons, Inc.     

MLPA based detection of mutations in the dystrophin gene of 180 Polish families with Duchenne/Becker muscular dystrophy

Duchenne/Becker muscular dystrophy (DMD/BMD) is a recessive, X-linked disorder caused by a mutation in the dystrophin gene. Deletions account for approximately 60–65% of mutations, duplications for 5–10%. The remaining cases are mainly point mutations. According to Monaco theory clinical form of the disease depends on maintaining or disrupting the reading frame. The purpose of the study was to determine frequency and location of deletions and duplications in the dystrophin gene, to determine the compliance between maintaining/disrupting the reading frame and clinical form of the disease and to check the effectiveness of MLPA (multiplex ligation-dependent probe amplification) in the detection of these mutations in hemizygous patients and heterozygous female carriers. The material is composed of combined results of molecular diagnosis carried out in years 2009–2012 in 180 unrelated patients referred with the diagnosis of DMD/BMD tested by use of MLPA. We identified 110 deletions, 22 duplication (in one patient two different duplications were detected) and 2 point mutations. Deletions involved mainly exons 45–54 and 3–21, whereas most duplications involved exons 3–18. The compliance with Monaco theory was 95% for deletions and 76% for duplications. Most of mutations in the dystrophin gene were localized in the hot spots – different for deletions and duplications. MLPA enabled their quick identification, exact localization and determination whether or not they maintained or disrupted the reading frame. MLPA was also effective in detection of deletions and duplications in female carriers.     

Lamin A/C mediates microglial activation by modulating cell proliferation and immune response

Lamin A/C is involved in macrophage activation and premature aging, also known as progeria. As the resident macrophage in brain, overactivation of microglia causes brain inflammation, promoting aging and brain disease. In this study, we investigated the role of Lamin A/C in microglial activation and its impact on progeria using Lmna^−/− mice, primary microglia, Lmna knockout (Lmna-KO) and Lmna-knockdown (Lmna-KD) BV2 cell lines. We found that the microglial activation signatures, including cell proliferation, morphology changes, and proinflammatory cytokine secretion (IL-1β, IL-6, and TNF-α), were significantly suppressed in all Lamin A/C-deficient models when stimulated with LPS. TMT-based quantitative proteomic and bioinformatic analysis were further applied to explore the mechanism of Lamin A/C-regulated microglia activation from the proteome level. The results revealed that immune response and phagocytosis were impaired in Lmna^−/− microglia. Stat1 was identified as the hub protein in the mechanism by which Lamin A/C regulates microglial activation. Additionally, DNA replication, chromatin organization, and mRNA processing were also altered by Lamin A/C, with Ki67 fulfilling the main hub function. Lamin A/C is a mechanosensitive protein and, the immune- and proliferation-related biological processes are also regulated by mechanotransduction. We speculate that Lamin A/C-mediated mechanotransduction is required for microglial activation. Our study proposes a novel mechanism for microglial activation mediated by Lamin A/C.     

A point mutation in the glycerol kinase gene associated with a deletion in the dystrophin gene in a familial X-linked muscular dystrophy: non-contiguous gene syndrome involving Becker muscular dystrophy and glycerol kinase loci

We report a family with an X-linked recessive muscular dystrophy characterised by exercise-induced myalgia, recurrent pigmenturia and mild proximal muscle involvement. Immunocytochemical and immunoblotting analysis in muscle, using the antibody directed against the rod domain of dystrophin, revealed a loss of immunoreactivity, but the immunolabelling using the antibodies directed against the COOH and NH₂ domains of dystrophin were almost normal. The immunoreactions for -sarcoglycan, γ-sarcoglycan and β-dystroglycan were normal. In the five male patients of this family with increased serum creatine kinase levels (from ×8 to ×50), mass spectrometry screening of the urine revealed a large increase in glycerol elimination which was quantified by enzymatic assay (from ×14 to ×39). An in-frame deletion of the dystrophin gene (exons 13–29) was found in the same five males and in three carrier females. All the deleted chromosomes also carried a missense mutation at nucleotide 947 of the Xp glycerol kinase (GK) gene resulting in a Thr to Met substitution at codon 278. These findings indicate that the two mutations cosegregate on the same chromosome in this family. This is the first reported case of two physically independent mutations, within the DMD and GK genes, which are contiguous but several hundred kilobases apart.     

Clinical,pathological, and genetic features of limb-girdle muscular dystrophy type 2A with new calpain 3 gene mutations in seven patients from three Japanese families

We report on the clinical, pathological, and genetic features of 7 patients with limb-girdle muscular dystrophy type 2A (LGMD2A) from three Japanese families. The mean age of onset was 9.7 ± 3.1 years (mean ± SD), and loss of ambulance occurred at 38.5 ± 2.1 years. Muscle atrophy was predominant in the pelvic and shoulder girdles, and proximal limb muscles. Muscle pathology revealed dystrophic changes. In two families, an identical G to C mutation at position 1080 the in calpain 3 gene was identified, and a frameshift mutation (1796insA) was found in the third family. The former mutation results in a W360R substitution in the proteolytic site of calpain 3, and the latter in a deletion of the Ca²⁺-binding domain. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21: 1493–1501, 1998