Clinical and genetic analysis of a patient with Desminopathy manifesting initially with myalgia after lower limb activity / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical characteristics and genetic variant of a patient with desminopathy manifesting with atypical symptoms.@*METHODS@#A patient who was admitted to the Department of Neurology of Jing'an District Central Hospital on February 24, 2021 was selected as the study subject. Clinical data, laboratory tests, muscle pathology, muscle magnetic resonance imaging (MRI) and genetic testing of the patient were retrospectively analyzed.@*RESULTS@#The patient had developed myalgia after lower limb activity, and gradually developed asymmetrical muscle weakness and atrophy of the lower limbs. Cardiac examination revealed atrioventricular block and decreased left ventricular diastolic function. Muscle MRI showed that semitendinosus, sartorius, gracilis, fibula, gastronemius and supinator muscles were selectively involved at the early stage. Muscle biopsy confirmed pathological changes of desmin positive myofibrils. Genetic testing revealed that the patient has harbored a c.1024A>G (p.n342d) missense variant in exon 6 of the DES gene. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was rated as likely pathogenic (PS4_moderate+PM2_supporting+PP3_moderate+PP1).@*CONCLUSION@#Desmin disease has a great clinical heterogeneity. Postexercise myalgia of lower limbs is a rare clinical phenotype. For patients harboring the c.1024A>G (p.n342d) variant of the DES gene, in addition to semitendinosus and fibula, Cardiac involvement is relatively insidious and easy to be ignored in clinic. Timely muscle MRI, muscle biopsy and gene detection will help the early diagnosis of the disease.

Dynamic expression of desmin, α-SMA and TGF-β1 during hepatic fibrogenesis induced by selective bile duct ligation in young rats

We previously described a selective bile duct ligation model to elucidate the process of hepatic fibrogenesis in children with biliary atresia or intrahepatic biliary stenosis. Using this model, we identified changes in the expression of alpha smooth muscle actin (α-SMA) both in the obstructed parenchyma and in the hepatic parenchyma adjacent to the obstruction. However, the expression profiles of desmin and TGF-β1, molecules known to be involved in hepatic fibrogenesis, were unchanged when analyzed by semiquantitative polymerase chain reaction (RT-PCR). Thus, the molecular mechanisms involved in the modulation of liver fibrosis in this experimental model are not fully understood. This study aimed to evaluate the molecular changes in an experimental model of selective bile duct ligation and to compare the gene expression changes observed in RT-PCR and in real-time quantitative PCR (qRT‐PCR). Twenty-eight Wistar rats of both sexes and weaning age (21-23 days old) were used. The rats were separated into groups that were assessed 7 or 60 days after selective biliary duct ligation. The expression of desmin, α-SMA and TGF-β1 was examined in tissue from hepatic parenchyma with biliary obstruction (BO) and in hepatic parenchyma without biliary obstruction (WBO), using RT-PCR and qRT‐PCR. The results obtained in this study using these two methods were significantly different. The BO parenchyma had a more severe fibrogenic reaction, with increased α-SMA and TGF-β1 expression after 7 days. The WBO parenchyma presented a later, fibrotic response, with increased desmin expression 7 days after surgery and increased α-SMA 60 days after surgery. The qRT‐PCR technique was more sensitive to expression changes than the semiquantitative method.

The reno-protective effect of a phosphoinositide 3-kinase inhibitor wortmannin on streptozotocin-induced proteinuric renal disease rats

Diabetic nephropathy (DN) is a progressive kidney disease that is caused by injury to kidney glomeruli. Podocytes are glomerular epithelial cells and play critical roles in the glomerular filtration barrier. Recent studies have shown the importance of regulating the podocyte actin cytoskeleton in early DN. The phosphoinositide 3-kinase (PI3K) inhibitor, wortmannin, simultaneously regulates Rac1 and Cdc42, which destabilize the podocyte actin cytoskeleton during early DN. In this study, in order to evaluate the reno-protective effects of wortmannin in early DN by regulating Rac1 and Cdc42, streptozotocin (STZ)-induced proteinuric renal disease (SPRD) rats were treated with wortmannin. The albuminuria value of the SPRD group was 3.55 +/- 0.56 mg/day, whereas wortmannin group was 1.77 +/- 0.48 mg/day. Also, the albumin to creatinine ratio (ACR) value of the SPRD group was 53.08 +/- 10.82 mg/g, whereas wortmannin group was 20.27 +/- 6.41 mg/g. Changes in the expression level of nephrin, podocin and Rac1/Cdc42, which is related to actin cytoskeleton in podocytes, by wortmannin administration were confirmed by Western blotting. The expression levels of nephrin (79.66 +/- 0.02), podocin (87.81 +/- 0.03) and Rac1/Cdc42 (86.12 +/- 0.02) in the wortmannin group were higher than the expression levels of nephrin (55.32 +/- 0.03), podocin (53.40 +/- 0.06) and Rac1/Cdc42 (54.05 +/- 0.04) in the SPRD group. In addition, expression and localization of nephrin, podocin and desmin were confirmed by immunofluorescence. In summary, we found for the first time that wortmannin has a reno-protective effect on SPRD rats during the early DN. The beneficial effects of wortmannin in SPRD rats indicate that this compound could be used to delay the progression of the disease during the early DN stage.

Protein aggregate myopathies.

Protein aggregate myopathies (PAM) are an emerging group of muscle diseases characterized by structural abnormalities. Protein aggregate myopathies are marked by the aggregation of intrinsic proteins within muscle fibers and fall into four major groups or conditions: (1) desmin-related myopathies (DRM) that include desminopathies, a-B crystallinopathies, selenoproteinopathies caused by mutations in the, a-B crystallin and selenoprotein N1 genes, (2) hereditary inclusion body myopathies, several of which have been linked to different chromosomal gene loci, but with as yet unidentified protein product, (3) actinopathies marked by mutations in the sarcomeric ACTA1 gene, and (4) myosinopathy marked by a mutation in the MYH-7 gene. While PAM forms 1 and 2 are probably based on impaired extralysosomal protein degradation, resulting in the accumulation of numerous and diverse proteins (in familial types in addition to respective mutant proteins), PAM forms 3 and 4 may represent anabolic or developmental defects because of preservation of sarcomeres outside of the actin and myosin aggregates and dearth or absence of other proteins in these actin or myosin aggregates, respectively. The pathogenetic principles governing protein aggregation within muscle fibers and subsequent structural sarcomeres are still largely unknown in both the putative catabolic and anabolic forms of PAM. Presence of inclusions and their protein composition in other congenital myopathies such as reducing bodies, cylindrical spirals, tubular aggregates and others await clarification. The hitherto described PAMs were first identified by immunohistochemistry of proteins and subsequently by molecular analysis of their genes.

Changes in cell shape and desmin intermediate filament distribution are associated with down-regulation of desmin expression in C2C12 myoblasts grown in the absence of extracellular Ca2+

Desmin is the main intermediate filament (IF) protein of muscle cells. In skeletal muscle, desmin IFs form a scaffold that interconnects the entire contractile apparatus with the subsarcolemmal cytoskeleton and cytoplasmic organelles. The interaction between desmin and the sarcolemma is mediated by a number of membrane proteins, many of which are Ca2+-sensitive. In the present study, we analyzed the effects of the Ca2+ chelator EGTA (1.75 mM) on the expression and distribution of desmin in C2C12 myoblasts grown in culture. We used indirect immunofluorescence microscopy and reverse transcription polymerase chain reaction (RT-PCR) to analyze desmin distribution and expression in C2C12 cells grown in the presence or absence of EGTA. Control C2C12 myoblasts showed a well-spread morphology after a few hours in culture and became bipolar when grown for 24 h in the presence of EGTA. Control C2C12 cells showed a dense network of desmin from the perinuclear region to the cell periphery, whereas EGTA-treated cells showed desmin aggregates in the cytoplasm. RT-PCR analysis revealed a down-regulation of desmin expression in EGTA-treated C2C12 cells compared to untreated cells. The present results suggest that extracellular Ca2+ availability plays a role in the regulation of desmin expression and in the spatial distribution of desmin IFs in myoblasts, and is involved in the generation and maintenance of myoblast cell shape.

Desmin-related myopathy: report of a rare case.

The Protein Surplus Myopathies (PSM) are characterized by accumulation of protein aggregates, identifiable ultrastructurally, resulting due to mutations of the encoding genes. Desmin-related myopathies (DRM) are a form of PSM characterized by mutations of the desmin gene resulting in the formation of protein aggregates comprising mutant protein desmin and disturbance of the regular desmin intermediate network in the muscle fibers. We describe a rare case of DRM in a 23-year-old man who presented with complaints of difficulty in climbing stairs and running since the age of 5 years. EMG studies revealed a myopathic pattern. Muscle biopsy showed the features of muscular dystrophy with bluish rimmed vacuoles and sarcoplasmic inclusions, which were immunoreactive to desmin. Ultrastructural examination showed sarcoplasmic bodies and granulofilamentous inclusions. Although rare, the possibility of DRM/desminopathy should be considered in the presence of bluish rimmed vacuoles on light microscopy and characteristic ultrastructural inclusions. To the best of our knowledge this is the first case of DRM/desminopathy reported from India.

Desmin: molecular interactions and putative functions of the muscle intermediate filament protein

Desmin is the intermediate filament (IF) protein occurring exclusively in muscle and endothelial cells. There are other IF proteins in muscle such as nestin, peripherin, and vimentin, besides the ubiquitous lamins, but they are not unique to muscle. Desmin was purified in 1977, the desmin gene was characterized in 1989, and knock-out animals were generated in 1996. Several isoforms have been described. Desmin IFs are present throughout smooth, cardiac and skeletal muscle cells, but can be more concentrated in some particular structures, such as dense bodies, around the nuclei, around the Z-line or in costameres. Desmin is up-regulated in muscle-derived cellular adaptations, including conductive fibers in the heart, electric organs, some myopathies, and experimental treatments with drugs that induce muscle degeneration, like phorbol esters. Many molecules have been reported to associate with desmin, such as other IF proteins (including members of the membrane dystroglycan complex), nebulin, the actin and tubulin binding protein plectin, the molecular motor dynein, the gene regulatory protein MyoD, DNA, the chaperone alphaB-crystallin, and proteases such as calpain and caspase. Desmin has an important medical role, since it is used as a marker of tumors' origin. More recently, several myopathies have been described, with accumulation of desmin deposits. Yet, after almost 30 years since its identification, the function of desmin is still unclear. Suggested functions include myofibrillogenesis, mechanical support for the muscle, mitochondrial localization, gene expression regulation, and intracellular signaling. This review focuses on the biochemical interactions of desmin, with a discussion of its putative functions.