Project description:Dysfunction of the dystrophin-glycoprotein complex (DGC) is a frequent cause of hereditary forms of muscular dystrophy. Although DGC function in maintaining skeletal muscle integrity has been well characterized, little is known about how the DGC complex is coordinately regulated at the transcriptional level. To test this hypothesis, we engineered HDAC4 stably overexpressing and control myotubes in an in vitro model of muscle differentiation. Here we present evidence that HDAC4, a neural activity-responsive histone deacetylase, is a critical transcriptional regulator of the DGC complex. We show that HDAC4 can repress multiple components of the DGC complex, including dystrophin and sarcoglycan family members in both cultured myotubes. To confirm this finding, the protein levels of core DGC complex members including dystrophin, sarcoglycan complex members, and additional dystrophin-associated proteins were evaluated in differentiated myotubes by western analysis. C2C12 mouse myotubes were infected with either a HDAC4 expressing or control (Neo) retroviruses. After stable selection, myotubes were differentiated at 90% confluency in 2% horse serum (Hyclone) for 4 days. At this time point, RNA was extracted and the two types of cells compared in a microarray analysis.
Project description:Dysfunction of the dystrophin-glycoprotein complex (DGC) is a frequent cause of hereditary forms of muscular dystrophy. Although DGC function in maintaining skeletal muscle integrity has been well characterized, little is known about how the DGC complex is coordinately regulated at the transcriptional level. To test this hypothesis, we engineered HDAC4 stably overexpressing and control myotubes in an in vitro model of muscle differentiation. Here we present evidence that HDAC4, a neural activity-responsive histone deacetylase, is a critical transcriptional regulator of the DGC complex. We show that HDAC4 can repress multiple components of the DGC complex, including dystrophin and sarcoglycan family members in both cultured myotubes. To confirm this finding, the protein levels of core DGC complex members including dystrophin, sarcoglycan complex members, and additional dystrophin-associated proteins were evaluated in differentiated myotubes by western analysis. Keywords: genetic modification and cell type comparison of muscle cells
Project description:Goal was to assess protein linkers between microtubules and dystrophin (specifically dystrophin regions R4-15 and R20-23). Two paired 10-plex TMT experiments were used to compare sixteen unique Dystrophin Glycoprotein Complex (or microtubule) enrichments (four genotypes, each with n=4) plus four pooled samples to allow comparison across the two individual 10-plex experiments for microtubules or DGC. A pair of 10-plex TMT(20 tags total) for the DGC enrichements, and a second pair of TMT (20 tags) for the MT enrichments. Samples are gastroc skeletal muscle from mouse.
Project description:Deficiencies in the human dystrophin glycoprotein complex (DGC), which links the extracellular matrix with the intracellular cytoskeleton, cause muscular dystrophies, a group of incurable disorders associated with heterogeneous muscle, brain and eye abnormalities. Stresses such as nutrient deprivation and aging cause muscle wasting, which can be exacerbated by reduced levels of the DGC in membranes, the integrity of which is vital for muscle health and function. Moreover, the DGC operates in multiple signaling pathways, demonstrating an important function in gene expression regulation. To advance disease diagnostics and treatment strategies, we strive to understand the genetic pathways that are perturbed by DGC mutations. Here, we utilize a Drosophila model to investigate the transcriptomic changes in mutants of four DGC components under temperature and metabolic stress. We identify DGC-dependent genes, stress-dependent genes and genes dependent on the DGC for a proper stress response, confirming a novel function of the DGC in stress-response signaling. This perspective yields new insights into the etiology of muscular dystrophy symptoms, possible treatment directions and a better understanding of DGC signaling and regulation under normal and stress conditions.
Project description:Signaling through the insulin receptor governs central physiological functions related to cell growth and metabolism. Here we show by tandem native protein complex purification approach and super-resolution STED microscopy that insulin receptor activity requires association with the fundamental structural module in muscle, the dystrophin glycoprotein complex (DGC), and the desmosomal component plakoglobin (g-catenin). The integrity of this high-molecular-mass assembly renders skeletal muscle susceptibility to insulin because DGC-insulin receptor dissociation by plakoglobin downregulation reduced insulin signaling and caused atrophy. Furthermore, low insulin receptor activity in muscles from transgenic or fasted mice decreased plakoglobin-DGC-insulin receptor content on the plasma membrane, but not when plakoglobin was overexpressed. By masking b-dystroglycan LIR domains, plakoglobin prevents autophagic clearance of plakoglobin-DGC-insulin receptor co-assemblies and maintains their function. Our findings establish DGC as a signaling hub, and provide a possible mechanism for the insulin resistance in Duchenne Muscular Dystrophy, and for the cardiomyopathies seen with plakoglobin mutations.
Project description:Mutations in genes encoding components of the sarcolemmal dystrophin-glycoprotein complex (DGC) are responsible for a large number of muscular dystrophies. As such, molecular dissection of the DGC is expected to both reveal pathological mechanisms, and provides a biological framework for validating new DGC components. Establishment of the molecular composition of plasma-membrane protein complexes has been hampered by a lack of suitable biochemical approaches. Here we present an analytical workflow based upon the principles of protein correlation profiling that has enabled us to model the molecular composition of plasma-membrane protein complexes in mouse skeletal muscle. We also report our analysis of protein complexes in mice harboring mutations in DGC components, which implicates cell-adhesion pathways directly targeted by NFκB in the pathophysiology of DGC-related muscular dystrophies. Our study suggests that inflammatory and compensatory mechanisms are activated in these diseases. Additionally, it provides a molecular framework that will facilitate refinement of our understanding of the DGC, identification of protein biomarkers of neuromuscular disease, and pharmacological interrogation of the DGC in adult skeletal muscle.
Project description:Mutations in genes encoding components of the sarcolemmal dystrophin-glycoprotein complex (DGC) are responsible for a large number of muscular dystrophies. As such, molecular dissection of the DGC is expected to both reveal pathological mechanisms, and provides a biological framework for validating new DGC components. Establishment of the molecular composition of plasma-membrane protein complexes has been hampered by a lack of suitable biochemical approaches. Here we present an analytical workflow based upon the principles of protein correlation profiling that has enabled us to model the molecular composition of plasma-membrane protein complexes in mouse skeletal muscle. We also report our analysis of protein complexes in mice harboring mutations in DGC components, which implicates cell-adhesion pathways directly targeted by NFκB in the pathophysiology of DGC-related muscular dystrophies. Our study suggests that inflammatory and compensatory mechanisms are activated in these diseases. Additionally, it provides a molecular framework that will facilitate refinement of our understanding of the DGC, identification of protein biomarkers of neuromuscular disease, and pharmacological interrogation of the DGC in adult skeletal muscle.
Project description:Duchenne Muscular Dystrophy (DMD) is a devastating genetic disease leading to degeneration of skeletal muscles and premature death. How dystrophin absence leads to muscle wasting remains unclear. Here, we describe an optimized protocol to differentiate human induced Pluripotent Stem Cells (iPSC) to a late myogenic stage. This allows to recapitulate classical DMD phenotypes (mislocalization of proteins of the Dystrophin glycoprotein associated complex (DGC), increased fusion, myofiber branching, force contraction defects and calcium hyperactivation) in isogenic DMD-mutant iPSC lines in vitro. Treatment of the myogenic cultures with prednisolone (the standard of care for DMD) can dramatically rescue force contraction, fusion and branching defects in DMD iPSC lines. This argues that prednisolone acts directly on myofibers, challenging the largely prevalent view that its beneficial effects are due to anti-inflammatory properties. Our work introduces a new human in vitro model to study the onset of DMD pathology and test novel therapeutic approaches.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.