Danon disease is a severe multisystem disorder clinically characterized by hypertrophic cardiomyopathy, skeletal myopathy and mental retardation in male patients, and by a milder phenotype ...(predominantly involving cardiac muscle) in female patients. The disease is inherited as an X‐linked dominant trait. The primary deficiency of lysosome‐associated membrane protein‐2 (LAMP‐2) causes disruption of autophagy, leading to an impaired fusion of lysosomes to autophagosomes and biogenesis of lysosomes. We surveyed over 500 Danon disease patients reported in the literature from the first description to the present, in order to summarize the clinical, pathological and molecular data and treatment perspectives. An early molecular diagnosis is of crucial importance for genetic counselling and for therapeutic interventions: in male patients, the prognosis is poor due to rapid progression towards heart failure, and only heart transplantation modifies the disease course.
Regulated removal of proteins and organelles by autophagy-lysosome system is critical for muscle homeostasis. Excessive activation of autophagy-dependent degradation contributes to muscle atrophy and ...cachexia. Conversely, inhibition of autophagy causes accumulation of protein aggregates and abnormal organelles, leading to myofiber degeneration and myopathy. Defects in lysosomal function result in severe muscle disorders such as Pompe (glycogen storage disease type II (GSDII)) disease, characterized by an accumulation of autophagosomes. However, whether autophagy is detrimental or not in muscle function of Pompe patients is unclear. We studied infantile and late-onset GSDII patients and correlated impairment of autophagy with muscle wasting. We also monitored autophagy in patients who received recombinant α-glucosidase. Our data show that infantile and late-onset patients have different levels of autophagic flux, accumulation of p62-positive protein aggregates and expression of atrophy-related genes. Although the infantile patients show impaired autophagic function, the late-onset patients display an interesting correlation among autophagy impairment, atrophy and disease progression. Moreover, reactivation of autophagy in vitro contributes to acid α-glucosidase maturation in both healthy and diseased myotubes. Together, our data suggest that autophagy protects myofibers from disease progression and atrophy in late-onset patients.
Update on polyglucosan storage diseases Cenacchi, Giovanna; Papa, V.; Costa, R. ...
Virchows Archiv : an international journal of pathology,
12/2019, Letnik:
475, Številka:
6
Journal Article
Recenzirano
An abnormal structural form of glycogen (with less branching points or amylopectin-like polysaccharide) called polyglucosan (PG) may accumulate in various tissues such as striated and smooth muscles, ...brain, nerve, liver and skin, and cause a group of nine different genetic disorders manifesting with a variety of clinical phenotypes that affect mainly the nervous system (Lafora disease, adult PG body disease), the heart (glycogen storage disease type XV, hypertrophic cardiomyopathy type 6, PG body myopathy type 1) and the skeletal muscle (glycogen storage disease type IV, glycogen storage disease type VII, PG body myopathy type 2), depending on the organs which are mostly affected by the PG aggregates. The pathological feature of PG storage in tissues is a hallmark of these disorders. Whole-genome sequencing has allowed to obtain a diagnosis in a large number of patients with a previously unrecognized disorder. We describe the clinical, pathological and molecular features of these genetic disorders, for many of which the pathological mechanisms underlying the corresponding mutant gene have been investigated and, at least in part, understood.
Myosin heavy chain 7 (MYH7)-related myopathies are emerging as an important group of muscle diseases of childhood and adulthood, with variable clinical and histopathological expression depending on ...the type and location of the mutation. Mutations in the head and neck domains are a well-established cause of hypertrophic cardiomyopathy whereas mutation in the distal regions have been associated with a range of skeletal myopathies with or without cardiac involvement, including Laing distal myopathy and Myosin storage myopathy. Recently the spectrum of clinical phenotypes associated with mutations in MYH7 has increased, blurring this scheme and adding further phenotypes to the list. A broader disease spectrum could lead to misdiagnosis of different congenital myopathies, neurogenic atrophy and other neuromuscular conditions.
As a result of a multicenter Italian study we collected clinical, histopathological and imaging data from a population of 21 cases from 15 families, carrying reported or novel mutations in MYH7. Patients displayed a variable phenotype including atypical pictures, as dropped head and bent spine, which cannot be classified in previously described groups. Half of the patients showed congenital or early infantile weakness with predominant distal weakness. Conversely, patients with later onset present prevalent proximal weakness. Seven patients were also affected by cardiomyopathy mostly in the form of non-compacted left ventricle. Muscle biopsy was consistent with minicores myopathy in numerous cases. Muscle MRI was meaningful in delineating a shared pattern of selective involvement of tibialis anterior muscles, with relative sparing of quadriceps.
This work adds to the genotype-phenotype correlation of MYH7-relatedmyopathies confirming the complexity of the disorder.
Aims
The peculiar clinical features and the pathogenic mechanism related to calpain‐3 deficiency (impaired sarcomere remodelling) suggest that the ubiquitin‐proteasome degradation pathway may have a ...crucial role in Limb Girdle Muscular Dystrophy 2A (LGMD2A). We therefore investigated muscle atrophy and the role of the ubiquitin‐proteasome and lysosomal‐autophagic degradation pathways.
Methods
We selected 25 adult male LGMD2A patients (and seven controls), classified them using clinical severity score, analysed muscle fibre size by morphometry and protein and/or transcriptional expression levels of the most important atrophy‐ and autophagy‐related genes (MuRF1, atrogin1, LC3, p62, Bnip3).
Results
Muscle fibre size was significantly lower in LGMD2A than in controls and it was significantly correlated with patients' clinical disability score recorded at the time of biopsy, suggesting that functional and structural muscle impairment are dependent. The large majority of atrophic fibres originate from a mechanism different from regeneration, as assessed by neonatal myosin immunolabelling. As compared with controls, LGMD2A muscles have higher MuRF1 (but not atrogin1) protein and MuRF1 gene expression levels, and MuRF1 protein levels significantly correlated with both muscle fibre size and clinical disability score. LGMD2A muscles have slightly increased levels of LC3‐II and p62 proteins and a significant up‐regulation of p62 and Bnip3 gene expression.
Conclusions
In LGMD2A muscles the activation of the atrophy programme appeared to depend mainly upon induction of the ubiquitin‐proteasome system and, to a lesser extent, the autophagic‐lysosomal degradation pathway.
Muscle pathology in dysferlin deficiency Fanin, M.; Angelini, C.
Neuropathology and applied neurobiology,
December 2002, Letnik:
28, Številka:
6
Journal Article
Recenzirano
Dysferlin deficiency is being increasingly recognized in limb‐girdle dystrophy and distal myopathy but its role in the development of muscle pathology is still poorly understood. For this purpose, 26 ...muscle biopsies from 25 dysferlinopathy patients were analysed by routine histochemistry and by immunohistochemistry with eight different antibodies, and scored for inflammatory response and type of cell infiltrate, fibre degeneration and regeneration, fibre type composition and severity of histopathological changes. In cases with an advanced‐stage dystrophic pattern we observed type 1 fibre predominance exceeding 80%, suggesting a selective loss of type 2 fibres or a conversion process.
The extent of muscle fibre regeneration and degeneration in dysferlinopathy was intermediate between sarcoglycanopathy and Duchenne dystrophy or myositis, suggesting a rather aggressive course of the disease. An increased inflammatory response was observed in the majority of our patients (16/26), who also showed an active dystrophic pattern. Type and localization of cellular infiltrates suggest that inflammatory reaction is secondary to necrosis. Major histocompatibility complex (MHC) class I molecules were overexpressed in dysferlinopathy, mainly in association with fibre phagocytosis and regeneration; their occasional expression in non‐necrotic fibres might represent a marker of ongoing necrosis. Muscle inflammation might be triggered by the structurally altered membrane consequent to dysferlin defect.
The frequency of various limb-girdle muscular dystrophy (LGMD) molecular diagnoses has previously been investigated only in cohorts of patients presenting LGMD phenotype.
A total of 550 muscle ...biopsies underwent multiple protein screening (including calpain-3 functional assay) and extensive gene mutation analysis to examine the frequency of LGMD subtypes in patients with distinct clinical phenotypes (severe childhood-onset LGMD, adult-onset LGMD, distoproximal myopathy, and asymptomatic hyperCKemia).
The percentage of molecularly ascertained cases directly relates with the degree of clinical involvement: 60% of total LGMD (77% of childhood-onset, 46% of adult-onset, 66% of distoproximal myopathy) and 14% of hyperCKemia. The higher number of molecular diagnoses in severe phenotypes might suggest that genes selected for our screening are those more frequently associated with severe LGMD, and that the hyperCKemia group includes heterogeneous diagnoses. The probability of obtaining a molecular diagnosis increases when a protein defect is found in a muscle biopsy: in such cases, we diagnosed 87% of LGMD and 76% of hyperCKemia.
Diagnosing 77% of childhood-onset limb-girdle muscular dystrophy (LGMD) and 60% of total LGMD is an important result. The missing identification of gene mutations in about 40% of patients with typical LGMD phenotype suggests that unknown genetic or nongenetic etiologies are still to be recognized. Dysferlin, caveolin-3, and emerin protein defects invariably corresponded to primary disorders (100%), whereas a lower correlation was found for sarcoglycans (77%) and calpain-3 (84%). The different efficiency of genetic diagnosis after the identification of a protein defect in the various disorders is possibly due to different pathogenetic effects of mutations.
Aims: We compared myopathological features in myasthenia gravis (MG) patients with antibodies against AChR (seropositive) and muscle‐specific tyrosin‐kinase (MuSK). While the immunopathogenesis of ...seropositive MG is well known, there is a lack of pathological studies in anti‐MuSK antibody‐positive (MuSK+) MG. Methods: We analysed skeletal muscle biopsy features of 13 MG patients: 6 MuSK+ (all women) and 7 anti‐AchR antibody‐positive (AChR+) (2 women and 5 men). In our histopathological examination, we quantified the atrophy factor of both fibre types, and the extent of minicores, myofibrillar disarray, cytochrome c oxidase (COX)‐negative fibres, mitochondrial aggregates and fibre type grouping. Results: Mean muscle fibre atrophy factor was higher in AChR+ MG than MuSK+ MG, both in type I fibres (494 vs. 210) and particularly in type II fibres (1023 vs. 300). Fibre type grouping was observed in AChR+ MG whereas COX‐negative fibres were common in MuSK+ MG. Bulbar muscles were more severely affected in MuSK+ MG and the disease was more severe: the onset was usually earlier (39 years) with Myasthenia Gravis Foundation of America score III in MuSK+ MG, and score II was found in AChR+ MG (62 years). Conclusions: Muscle biopsies of MuSK+ MG show myopathic signs with prominent mitochondrial abnormalities, whereas neurogenic features and atrophy are more frequently found in AChR+ MG. The mitochondrial impairment could explain the oculo‐bulbar involvement in MuSK+ MG.
PDF
