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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.

Transportin3 (TNPO3) shuttles the SR proteins from the cytoplasm to the nucleus. The SR family includes essential splicing factors, such as SRSF1, that influence alternative splicing, controlling protein diversity in muscle and satellite cell differentiation. Given the importance of alternative splicing in the myogenic process and in the maintenance of healthy muscle, alterations in the splicing mechanism might contribute to the development of muscle disorders. Combining confocal, structured illumination and electron microscopy, we investigated the expression of TNPO3 and SRSF1 during myogenesis, looking at nuclear and cytoplasmic compartments. We investigated TNPO3 and its interaction with SRSF1 and we observed that SRSF1 remained mainly localized in the nucleus, while TNPO3 decreased in the cytoplasm and was strongly clustered in the nuclei of differentiated myotubes. In conclusion, combining different imaging techniques led us to describe the behavior of TNPO3 and SRSF1 during myogenesis, showing that their dynamics follow the myogenic process and could influence the proteomic network necessary during myogenesis. The combination of different high-, super- and ultra-resolution imaging techniques led us to describe the behavior of TNPO3 and its interaction with SRSF1, looking at nuclear and cytoplasmic compartments. These observations represent a first step in understanding the role of TNPO3 and SRFSF1 in complex mechanisms, such as myogenesis.

Metabolic myopathies comprise a clinically etiological diverse group of disorders caused by defects in cellular energy metabolism including the breakdown of carbohydrates and fatty acids, which include glycogen storage diseases and fatty acid oxidation disorders. Their wide clinical spectrum ranges from infantile severe multisystemic disorders to adult-onset myopathies. To suspect in adults these disorders, clinical features such as exercise intolerance and recurrent myoglobinuria need investigation while another group presents fixed weakness and cardiomyopathy as a clinical pattern.In metabolic myopathies, clinical manifestations are important to guide diagnostic tests used in order to lead to the correct diagnosis. The authors searched in literature the most recent techniques developed. The authors present an overview of the most common phenotypes of Pompe disease and what is currently known about the mechanism of ERT treatment. The most common disorders of lipid metabolism are overviewed, with their possible dietary or supplementary treatments.The clinical suspicion is the clue to conduct in-depth investigations in suspected cases of metabolic myopathies that lead to the final diagnosis with biochemical molecular studies and often nowadays by the use of Next Generation Sequencing (NGS) to determine gene mutations.

Becker muscular dystrophy (BMD) is an X-linked recessive disorder caused by dystrophin gene mutations. The phenotype and evolution of this muscle disorder are extremely clinical variable. In the last years, circulating biomarkers have acquired remarkable importance in their use as noninvasive biological indicators of prognosis and in monitoring muscle disease progression, especially when associated to muscle MRI imaging. We investigated the levels of circulating microRNAs (myo-miRNAs and inflammatory miRNAs) and of the proteins follistatin (FSTN) and myostatin (GDF-8) and compared results with clinical and radiological imaging data. In eight BMD patients, including two cases with evolving lower extremity weakness treated with deflazacort, we evaluated the expression level of 4 myo-miRNAs (miR-1, miR-206, miR-133a, and miR-133b), 3 inflammatory miRNAs (miR-146b, miR-155, and miR-221), FSTN, and GDF-8 proteins. In the two treated cases, there was pronounced posterior thigh and leg fibrofatty replacement assessed by muscle MRI by Mercuri score. The muscle-specific miR-206 was increased in all patients, and inflammatory miR-221 and miR-146b were variably elevated. A significant difference in myostatin expression was observed between steroid-treated and untreated patients. This study suggests that microRNAs and myostatin protein levels could be used to better understand the progression and management of the disease.

Aim Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease caused by the progressive degeneration of motor neurons. MicroRNAs are 17 - 27 nucleotide long molecules that regulate post-transcriptional mRNA expression. The aim of this study was to investigate the role of microRNAs in the skeletal muscle of ALS patients and correlate these results with the expression of histone deacetylase 4 (HDAC4) protein. Materials and methods We measured the expression levels of muscle-specific microRNAs (miR-1, miR-133a, miR-133b, miR-206), inflammatory micro-RNAs (miR-27a, miR-221, miR-155), and HDAC4 protein content on western blotting in muscle biopsies obtained for diagnostic reasons in 18 ALS patients: 8 genetic forms (C9-ALS and SOD1-ALS), 5 sporadic cases (SALS), and 5 ALS cases affected only by upper motor neuron disease (UMN). Results In muscle of patients with genetic forms of ALS, we found a strong upregulation of miR-206, a muscle-specific miRNA involved in neuromuscular junction (NMJ), regeneration and muscle atrophy, and a decreased expression of HDAC4 protein levels, which is involved both in denervation and regulation of miR-206 in ALS pathophysiology. In these patients, we also observed an increase of inflammatory miRNAs. Conclusion The different expression of miRNAs and HDAC4 in genetic ALS vs. SALS and UMN cases is likely to be correlated to different pathogenic mechanisms.

Purpose: We aimed at evaluating the feasibility of using MicroRNA (miR)-34a and miR-29b to detect inner ear damage in patients with mitochondrial disease (MD) and sensorineural hearing loss (SNHL)....

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.

Limb-girdle muscular dystrophies (LGMDs) encompass a clinically heterogeneous group of rare, genetic progressive muscle disorders presenting with weakness and atrophy of predominant pelvic and shoulder muscles. The spectrum of disease severity ranges from severe childhood-onset muscular dystrophy to adult-onset dystrophy. Areas covered: The review presents an update of the clinical phenotypes and diagnostic options for LGMD including both dominant and recessive LGMD and consider their differential clinical and histopathological features. An overview of most common phenotypes and of possible complications is given. The management of the main clinical respiratory, cardiac, and central nervous system complications are covered. The instrumental, muscle imaging, and laboratory exams to assess and reach diagnosis are described. The use of recent genetic techniques such as next generation sequencing (NGS), whole-exome sequencing compared to other techniques (e.g. DNA sequencing, protein analysis) is covered. Currently available drugs or gene therapy and rehabilitation management are focused on. Expert commentary: Many LGMD cases, which for a long time previously remained without a molecular diagnosis, can now be investigated by NGS. Gene mutation analysis is always required to obtain a certain molecular diagnosis, fundamental to select homogeneous group of patients for future pharmaceutical and gene trials.

Background Neutral lipid storage disease with myopathy (NLSDM) is a rare lipid metabolism disorder. In this study, we evaluated some circulating miRNAs levels in serum samples and the MRI of three affected siblings. Methods Three members of one NLSDM family were identified: two brothers and one sister. Muscles of lower and right upper extremities were studied by MRI. Expression profile of miRNAs, obtained from serum samples, was detected using qRT‐PCR. Results Two brothers presented with progressive skeletal myopathy, while the sister had severe hepatosteatosis and diabetes. NLSDM patients showed a significant increase of muscle‐specific miRNAs expression compared with healthy subjects. We found a correlation between hepatic damage and elevation of miRNAs expression profile of liver origin. Conclusions The dysregulation of miRNAs might represent an indicator of skeletal and hepatic damage and it might be useful to monitor the progression of NLSDM.

We describe a family with a novel TNPO3 mutation of limb–girdle muscular dystrophy D2 (or LGMD 1F), a rare muscle disorder with autosomal dominant inheritance, first identified in an Italo-Spanish family where the causative defect has been found to be due to TNPO3 gene mutation, encoding transportin-3 protein (TNPO3). We present the clinical, histopathological and muscle magnetic resonance imaging (MRI) features in two patients, mother and son Hungarian origin, affected by LGMD D2 and correlate their clinical, MRI and histopathological data found in this condition. The affected son presented early pelvic girdle muscle weakness and thin muscles similar to a congenital myopathy; the mother was less compromised and had an LGMD phenotype. Muscle MRI showed a very pronounced lower limb muscle atrophy in both patients. The most relevant change obtained in the child muscle biopsy was a generalized type 1 fibre atrophy. The two patients presented the same mutation, but a different phenotype has been observed in mother and son.

Aim To evaluate the feasibility of microRNAs (miR) in clinical use to fill in the gap of current methodology commonly used to test hearing impairment in MELAS patients. Material and method A literature review was performed using the following keywords, i.e., MELAS, Hearing Loss, Hearing Impairment, Temporal Bone, Otoacustic Emission (OTOAE), Auditory Brain Response (ABR), and microRNA. We reviewed the literature and focused on the aspect of the temporal bone, the results of electrophysiological tests in human clinical studies, and the use of miR for detecting lesions in the cochlea in patients with MELAS. Results In patients with MELAS, Spiral Ganglions (SG), stria vascularis (SV), and hair cells are damaged, and these damages affect in different ways various structures of the temporal bone. The function of these cells is typically investigated using OTOAE and ABR, but in patients with MELAS these tests provide inconsistent results, since OTOAE response is absent and ABR is normal. The normal ABR responses are unexpected given the SG loss in the temporal bone. Recent studies in humans and animals have shown that miRs, and in particular miRs 34a, 29b, 76, 96, and 431, can detect damage in the cells of the cochlea with high sensitivity. Studies that focus on the temporal bone aspects have reported that miRs increase is correlated with the death of specific cells of the inner ear. MiR − 9/9* was identified as a biomarker of human brain damage, miRs levels increase might be related to damage in the central auditory pathways and these increased levels could identify the damage with higher sensitivity and several months before than electrophysiological testing. Conclusion We suggest that due to their accuracy and sensitivity, miRs might help monitor the progression of SNHL in patients with MELAS.