Expression of glycosylated α‐dystroglycan in newborn skeletal and cardiac muscles of fukutin related protein (FKRP) mutant mice

Introduction: Mutations in the Fukutin related protein (FKRP) gene are characterized by a lack of functionally glycosylated α‐dystroglycan (F‐α‐DG) in muscles. A small number of fibers retain the capacity to produce strong IIH6 reactive glycosylated‐α‐DG (g‐α‐DG) in muscles of both FKRP mutant animals and patients. Methods: We examined the expression of g‐α‐DG in limb, diaphragm, and cardiac muscles of newborn FKRP mutants and LARGE^myd mice with IIH6 antibody. Results: Near‐normal levels of g‐α‐DG were detected in all 3 muscles in the FKRP448LNeo‐ mutant. Expression was limited within the first 8 postnatal days with decreasing levels. No expression was identified in LARGE^myd mice. Conclusions: Temporary expression of glycosylated‐α‐DG in newborn FKRP mutant muscles is LARGE‐ and mutant FKRP‐dependent. The capability of mutant FKRP with a severe clinic phenotype to produce glycosylated‐α‐DG provides a new perspective for possible approaches to mitigate FKRP deficiency. Muscle Nerve 55 : 582–590, 2017     

Morphological and functional analyses of skeletal muscles from an immunodeficient animal model of limb‐girdle muscular dystrophy type 2E

Introduction: Limb‐girdle muscular dystrophy type 2E (LGMD2E) is caused by mutations in the β‐sarcoglycan gene, which is expressed in skeletal, cardiac, and smooth muscles. β‐Sarcoglycan‐deficient (Sgcb‐null) mice develop severe muscular dystrophy and cardiomyopathy with focal areas of necrosis. Methods: In this study we performed morphological (histological and cellular characterization) and functional (isometric tetanic force and fatigue) analyses in dystrophic mice. Comparison studies were carried out in 1‐month‐old (clinical onset of the disease) and 7‐month‐old control mice (C57Bl/6J, Rag2/γc‐null) and immunocompetent and immunodeficient dystrophic mice (Sgcb‐null and Sgcb/Rag2/γc‐null, respectively). Results: We found that the lack of an immunological system resulted in an increase of calcification in striated muscles without impairing extensor digitorum longus muscle performance. Sgcb/Rag2/γc‐null muscles showed a significant reduction of alkaline phosphate‐positive mesoangioblasts. Discussion: The immunological system counteracts skeletal muscle degeneration in the murine model of LGMD2E. Muscle Nerve 58 : 133–144, 2018     

Cardiopulmonary dysfunction in patients with limb‐girdle muscular dystrophy 2A

Introduction: Little is known about the frequency of cardiopulmonary failure in limb‐girdle muscular dystrophy type 2A (calpainopathy) patients, although some studies have reported severe cardiomyopathy or respiratory failure. Methods: To clarify the frequency of cardiopulmonary dysfunction in this patient population, we retrospectively reviewed the respiratory and cardiac function of 43 patients with calpainopathy. Results: Nine of the 43 patients had forced vital capacity (FVC) < 80%, and 3 used noninvasive positive pressure ventilation. Mean FVC was significantly lower in patients who were nonambulant and had normal creatine kinase levels. Only 1 patient had a prolonged QRS complex duration. Echocardiography revealed that 1 patient had very mild left ventricular dysfunction. Conclusions: These findings suggest that patients with calpainopathy may develop severe respiratory failure, but cardiac dysfunction is infrequent. Muscle Nerve 55 : 465–469, 2017     

LAMA2‐related myopathy: Frequency among congenital and limb‐girdle muscular dystrophies

Introduction: Muscular dystrophy caused by LAMA2‐gene mutations is an autosomal recessive disease typically presenting as a severe, early‐onset congenital muscular dystrophy (CMD). However, milder cases with a limb‐girdle type muscular dystrophy (LGMD) have been described. Methods: In this study, we assessed the frequency and phenotypic spectrum of LAMA2‐related muscular dystrophy in CMD (n = 18) and LGMD2 (n = 128) cohorts identified in the last 15 years in eastern Denmark. The medical history, brain‐MRI, muscle pathology, muscle laminin‐α2 expression, and genetic analyses were assessed. Results: Molecular genetics revealed 2 pathogenic LAMA2 mutations in 5 of 18 CMD and 3 of 128 LGMD patients, corresponding to a LAMA2‐mutation frequency of 28% in the CMD and 2.3% in the LGMD cohorts, respectively. Conclusions: This study demonstrates a wide clinical spectrum of LAMA2‐related muscular dystrophy and its prevalence in an LGMD2 cohort, which indicates that LAMA2 muscular dystrophy should be included in the LGMD2 nomenclature. Muscle Nerve 52: 547–553, 2015     

Diagnosis of limb‐girdle muscular dystrophy 2A by immunohistochemical techniques

The Western blot technique is currently the standard detection method for suspected limb girdle muscular dystrophy (LGMD) 2A (calpainopathy). This is the first report in the English literature of the successful application of immunohistochemical techniques to support a diagnosis of LGMD 2A. This approach is straightforward and appears to be reasonably specific. We propose that immunohistochemical methods should be re‐evaluated for the screening of undiagnosed patients with suspected LGMD 2A.     

Entire CAPN3 gene deletion in a patient with limb‐girdle muscular dystrophy type 2A

Limb‐girdle muscular dystrophy type 2A (LGMD2A) due to mutations in the CAPN3 gene is one of the most common of autosomal recessive limb‐girdle muscular dystrophies. We describe a patient who had a typical LGMD2A phenotype and posterior compartment involvement on MRI. Different genetic analyses were performed, including microarray analysis. There was an apparently homozygous mutation in exon 24, c.2465G>T, p.(*822Leuext62*), and a lack of correlation in the disease segregation analyses. This suggested the presence of a genomic rearrangement. In fact, a heterozygous deletion of the entire CAPN3 gene was found. This novel deletion comprised the terminal region of the GANC gene and the entire CAPN3 gene. This finding points out the need to reconsider and adapt our current strategy of molecular diagnosis in order to detect these types of genomic rearrangements that escape standard mutation screening procedures. Muscle Nerve 50 : 448–453, 2014     

Homozygous α-sarcoglycan mutation in two siblings: One asymptomatic and one steroid-responsive mild limb–girdle muscular dystrophy patient

We describe a couple of siblings who have a homozygous mutation in the α-sarcoglycan gene and present a striking clinical difference in their phenotype; the brother is asymptomatic, and the sister is affected with mild limb–girdle muscular dystrophy. Drug therapy with a new steroid (deflazacort) was done over 6 months in the mild limb–girdle patient, and we observed objective benefit in muscle strength and in functional tests. Side effects were minimal. Immunohistochemistry for α-sarcoglycan showed reduced intensity of reaction in the limb–girdle dystrophy patient and was similar to normal in the asymptomatic case. A reduced amount of residual α-sarcoglycan protein level was found in their muscle biopsies. Unknown epigenetic or environmental factors may have an important role in determining protein and clinical phenotype expression. This is the first report of a patient with homozygous sarcoglycan gene mutation without overt muscle weakness in his adulthood. The spectrum of clinical phenotypes in sarcoglycanopathies is therefore wider than previously thought. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:769–775, 1998.     

Identification of a novel SGCA missense mutation in a case of limb‐girdle muscular dystrophy 2D with the absence of four sarcoglycan proteins

Limb‐girdle muscular dystrophy 2D (LGMD2D) is caused by mutations in the α‐sarcoglycan gene (SGCA). Due to lack of specificity, it is impossible to identify LGMD2D only by clinical symptoms and conventional immunohistochemical staining. The loss of any protein (α‐, β‐, γ‐, δ‐sarcoglycan) that represent sarcoglycanopathy may cause reduction or absence of the other three proteins. Here, we report a patient with a complete loss of all the four proteins. Next generation sequencing (NGS) results showed a missense mutation (C.218 C > T) and a partial heterozygous deletion containing exons 7 and 8 of SGCA, which led to the final diagnosis of the patient. The discovery of this new mutation could broaden the spectrum of SGCA mutations, which may be associated with putative LGMD2D, especially when all the four proteins are completely missing.     

A novel form of recessive limb girdle muscular dystrophy with mental retardation and abnormal expression of alpha-dystroglycan

The limb girdle muscular dystrophies are a heterogeneous group of conditions characterized by proximal muscle weakness and disease onset ranging from infancy to adulthood. We report here eight patients from seven unrelated families affected by a novel and relatively mild form of autosomal recessive limb girdle muscular dystrophy (LGMD2) with onset in the first decade of life and characterized by severe mental retardation but normal brain imaging. Immunocytochemical studies revealed a significant selective reduction of alpha-dystroglycan expression in the muscle biopsies. Linkage analysis excluded known loci for both limb girdle muscular dystrophy and congenital muscular dystrophies in the consanguineous families. We consider that this represents a novel form of muscular dystrophy with associated brain involvement. The biochemical studies suggest that it may belong to the growing number of muscular dystrophies with abnormal expression of alpha-dystroglycan.     

Limb-girdle muscular dystrophy type 2I: two Chinese families and a review in Asian patients

Background: Limb-girdle muscular dystrophy type 2I (LGMD2I) is an autosomal recessive hereditary disorder caused by mutations in the fukutin-related protein (FKRP) gene. Although the features of the disorder in European patients have been summarized, Asian patients with LGMD2I have rarely been reported. Thus, the clinical differences in LGMD2I between Asian and European patients and the associated genetic changes remain unclear.

Methods: We reported detailed clinical data as well as results from muscle biopsy, muscle MRI and genetic analysis of the FKRP gene in two unrelated Chinese families with LGMD2I. Additionally, a review of the literature focusing on the clinical and mutational features of LGMD2I in Asian patients was performed.

Results: The muscle biopsy results showed dystrophic features. Immunohistochemical staining revealed decreased glycosylations on α-dystroglycan. The muscle MRI results showed that the gluteus maximus, adductor, biceps femoris, vastus intermedius and vastus lateralis were severely affected. The patients in the two families harbored the same compound heterozygous mutations (c.545A>G and c.948delC). One patient showed significant clinical improvement after corticosteroid treatment.

Conclusion: Our study expanded the reported spectrum of Asian LGMD2I patients. Our literature review revealed that pathogenic mutations in the FKRP gene in Asian LGMD2I patients are compound heterozygous rather than homozygous. Compound heterozygous Asian patients have a mild phenotype but frequently show respiratory and cardiac impairments. Corticosteroids may be beneficial for the treatment of LGMD2I and should be further investigated.     

Fukutin gene mutations in an Italian patient with early onset muscular dystrophy but no central nervous system involvement

Hypoglycosylation of α‐dystroglycan characterizes a subgroup of muscular dystrophies of variable severity, including Fukuyama congenital muscular dystrophy. We found fukutin gene mutations in a 4.5‐year‐old Italian patient, with reduced α‐dystroglycan expression, dystrophic features on muscle biopsy, hypotonia since birth, mild myopathy, but no brain involvement. Mutations in the fukutin gene can be associated with much milder phenotypes than classical Fukuyama congenital muscular dystrophy, and, although rare, can occur in non‐Japanese. Muscle Nerve, 2009     

Dysferlin aggregation in limb‐girdle muscular dystrophy type 2B/myoshi myopathy necessitates mutational screen for diagnosis

Introduction: Diagnosis of the limb‐girdle muscular dystrophies (LGMDs) has been facilitated by the use of immunofluorescence microscopy, Western blot analysis, and rapid genetic testing. Methods: We identified 7 patients with LGMD2B or Miyoshi myopathy (MM) phenotypes and performed detailed history, physical examination, and mutation analyses of genomic DNA. Results: Ten disease‐causing variants of the dysferlin gene (DYSF) were detected, 4 of which were novel and predicted to be pathogenic (IVS33+9G>T, c.1343T>C, c.4747T>G, and c.5066dupC). Two of these mutations (c.1343T>C and IVS33+9G>T) were associated with a reduction in sarcolemmal dysferlin expression, despite increased total mRNA and protein in mixed muscle homogenates, due to a pathological retention of the mutated polypeptide in the cytoplasm. Conclusions: Considering that protein‐based assays may yield false negative test results and that dysferlin aggregation may be present in other LGMDs, mutational screening is necessary for specific diagnosis in primary dysferlinopathy patients exhibiting this phenotype. Muscle Nerve 47: 740–747, 2013     

Diagnostic value of muscle MRI in differentiating LGMD2I from other LGMDs

Mutations in the fukutin–related protein (FKRP) have recently been demonstrated to cause limb girdle muscular dystrophy type 2I (LGMD2I), one of the most common forms of the autosomal recessive LGMDs in Europe. We performed a systematic clinical and muscle MRI assessment in 6 LGMD2I patients and compared these findings with those of 14 patients with genetically confirmed diagnosis of other forms of autosomal recessive LGMDs or dystrophinopathies. All LGMD2I patients had a characteristic clinical phenotype with predominant weakness of hip flexion and adduction, knee flexion and ankle dorsiflexion. These findings were also mirrored on MRI of the lower extremities which demonstrated marked signal changes in the adductor muscles, the posterior thigh and posterior calf muscles. This characteristic clinical and MRI phenotype was also seen in LGMD2A. However, in LGMD2A there was a selective involvement of the medial gastrocnemius and soleus muscle in the lower legs which was not seen in LGMD2I. The pattern in LGMD2A and LGMD2I were clearly different from the one seen in alpha–sarcoglycanopathy and dystrophinopathy type Becker which showed marked signal abnormalities in the anterior thigh muscles. Our results indicate that muscular MRI is a powerful tool for differentiating LGMD2I from other forms of autosomal recessive LGMDs and dystrophinopathies.     

Phenotypic aspects of FKRP-linked muscular dystrophy type 2I in a series of eleven patients

INTRODUCTION: Limb-girdle muscular dystrophy type 2I (LGMD2I) is caused by mutations in the fukutin related protein gene (FKRP gene). This study tries to evaluate clinical, biological and mutational characteristics of LGMD2I. PATIENTS AND METHODS: Eleven patients belonging to 9 families from the North of France were selected. We reported demographic data, and results of muscular testing, cardiac, and respiratory examination, as well as the histopathological features of muscle tissue and a genetic analysis of FKRP gene for each patient. RESULTS: There were 6 females and 5 males. Mean age at onset was 9.7 years old. Six had Duchenne like phenotype, 5 Becker like phenotype. Nine patients suffered from restrictive respiratory failure, two males had severe dilated cardiomyopathy. Ten patients had the common L276I mutation. Three mutations had not been previously identified: L322V, L489R and R275G heterozygous mutations associated with the L276I mutation. CONCLUSION: This study underlines inter and intra familial phenotypic variability in LGMD2I, preponderance of cardiomyopathy in males and restrictive respiratory insufficiency in female.