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The American Journal of Pathology Jun 1995Myasthenia gravis is an autoimmune disorder characterized in most cases by serological antibody against the acetylcholine receptor (AChR). Evidence for intrathymic...
Myasthenia gravis is an autoimmune disorder characterized in most cases by serological antibody against the acetylcholine receptor (AChR). Evidence for intrathymic localization of AChR suggests that the thymus has an important role in the pathogenesis of this disorder. Using reverse transcription followed by the polymerase chain reaction, we have demonstrated AChR alpha-subunit mRNA in thymuses and thymomas from patients with and without myasthenia gravis. We have also studied the expression of myogenin which is known to be involved in the regulation of AChR expression. By using the reverse transcription polymerase chain reaction, we found myogenin mRNAs in all of the thymuses and thymomas. Thus, both AChR alpha-subunit and myogenin mRNA are present in all of these specimens. By immunohistochemistry myoid cells (desmin and myoglobin positive) were present in all (four of four) thymuses studied and in two of five thymomas. Thus, in thymomas, nonmyoid cells might express both AChR and myogenin. These results indicate that cells within the thymus and thymoma express AChR and its regulatory protein myogenin and that such cells, under certain conditions, might play a role in the triggering of myasthenia gravis.
Topics: Adolescent; Adult; Aged; Blotting, Northern; Female; Humans; Immunohistochemistry; Infant; Male; Middle Aged; Myasthenia Gravis; Myogenin; Nucleic Acid Hybridization; Polymerase Chain Reaction; RNA, Messenger; Receptors, Cholinergic; Thymoma; Thymus Gland; Thymus Neoplasms
PubMed: 7778671
DOI: No ID Found -
Scientific Reports Jun 2019Muscle differentiation is controlled by adhesion and growth factor-dependent signalling through common effectors that regulate muscle-specific transcriptional programs....
Muscle differentiation is controlled by adhesion and growth factor-dependent signalling through common effectors that regulate muscle-specific transcriptional programs. Here we report that mDiaphanous1, an effector of adhesion-dependent RhoA-signalling, negatively regulates myogenesis at the level of Myogenin expression. In myotubes, over-expression of mDia1ΔN3, a RhoA-independent mutant, suppresses Myogenin promoter activity and expression. We investigated mDia1-interacting proteins that may counteract mDia1 to permit Myogenin expression and timely differentiation. Using yeast two-hybrid and mass-spectrometric analysis, we report that mDia1 has a stage-specific interactome, including Prohibitin2, MyoD, Akt2, and β-Catenin, along with a number of proteosomal and mitochondrial components. Of these interacting partners, Prohibitin2 colocalises with mDia1 in cytoplasmic punctae in myotubes. We mapped the interacting domains of mDia1 and Phb2, and used interacting (mDia1ΔN3/Phb2 FL or mDia1ΔN3/Phb2-Carboxy) and non-interacting pairs (mDia1H + P/Phb2 FL or mDia1ΔN3/Phb2-Amino) to dissect the functional consequences of this partnership on Myogenin promoter activity. Co-expression of full-length as well as mDia1-interacting domains of Prohibitin2 reverse the anti-myogenic effects of mDia1ΔN3, while non-interacting regions do not. Our results suggest that Prohibitin2 sequesters mDia1, dampens its anti-myogenic activity and fine-tunes RhoA-mDia1 signalling to promote differentiation. Overall, we report that mDia1 is multi-functional signalling effector whose anti-myogenic activity is modulated by a differentiation-dependent interactome. The data have been deposited to the ProteomeXchange with identifier PXD012257.
Topics: Animals; Cell Differentiation; Cytoplasm; Formins; HEK293 Cells; Humans; Mice; Muscle Development; Muscle Fibers, Skeletal; Mutation; MyoD Protein; Myogenin; Prohibitins; Promoter Regions, Genetic; Protein Binding; Protein Domains; Repressor Proteins; Signal Transduction; Two-Hybrid System Techniques; rhoA GTP-Binding Protein
PubMed: 31165762
DOI: 10.1038/s41598-019-44749-4 -
Journal of Orthopaedic Research :... Nov 2012Angiogenesis and myogenesis occur in the surrounding skeletal muscles following distraction osteogenesis, but their molecular mechanisms remain unclear. The present...
Angiogenesis and myogenesis occur in the surrounding skeletal muscles following distraction osteogenesis, but their molecular mechanisms remain unclear. The present study investigated morphological features of lengthened muscles and the time course change of vascular endothelial growth factor (VEGF), its receptors (VEGFR-1 and VEGFR-2) and myogenin gene expression profiles related to angiogenesis and myogenesis in tibialis anterior (TA) muscles with a mouse model of distraction osteogenesis, which involves 1 week of waiting period (latency phase), 2 weeks of intermittent distraction (distraction phase), and 5 weeks of remodeling period (consolidation phase). Macroscopic findings showed that lengthened TA muscles increased to approximately 42% longer and 10% heavier at the end of the process when compared to pre-surgery. During the distraction phase, VEGF and its receptors were induced in the vascular endothelial cells, myogenin-positive satellite cells and myocytes, and subsequently, capillary progression and myogenesis were increased. Real-time RT-PCR showed that Vegf, Vegfr-1, Vegfr-2, and myogenin genes expression was enhanced during the muscle lengthening. Vegf and Vegfr-1 were upregulated following the recession of angiogenesis at the consolidation phase. We conclude that upregulation of VEGF and its receptors by mechanical tension-stress could be involved in the process of angiogenesis and myogenesis in lengthened muscles.
Topics: Animals; Capillaries; Gene Expression; Immunohistochemistry; Male; Mice; Mice, Inbred C57BL; Models, Animal; Muscle Development; Muscle, Skeletal; Myogenin; Neovascularization, Physiologic; Osteogenesis, Distraction; Real-Time Polymerase Chain Reaction; Receptors, Vascular Endothelial Growth Factor; Reverse Transcriptase Polymerase Chain Reaction; Vascular Endothelial Growth Factor A
PubMed: 22528802
DOI: 10.1002/jor.22136 -
Journal of Applied Physiology... Mar 2021Little is known about the molecular responses to power resistance exercise that lead to skeletal muscle remodeling and enhanced athletic performance. We assessed the...
Little is known about the molecular responses to power resistance exercise that lead to skeletal muscle remodeling and enhanced athletic performance. We assessed the expression of titin-linked putative mechanosensing proteins implicated in muscle remodeling: muscle ankyrin repeat proteins (Ankrd 1, Ankrd 2, and Ankrd 23), muscle-LIM proteins (MLPs), muscle RING-finger protein-1 (MuRF-1), and associated myogenic proteins (MyoD1, myogenin, and myostatin) in skeletal muscle in response to power resistance exercise with or without a postexercise meal, in fed, resistance-trained men. A muscle sample was obtained from the vastus lateralis of seven healthy men on separate days, 3 h after 90 min of rest (Rest) or power resistance exercise with (Ex + Meal) or without (Ex) a postexercise meal to quantify mRNA and protein levels. The levels of phosphorylated HSP27 (pHSP27-Ser15) and cytoskeletal proteins in muscle and creatine kinase activity in serum were also assessed. The exercise increased ( ≤ 0.05) pHSP27-Ser15 (∼6-fold) and creatine kinase (∼50%), whereas cytoskeletal protein levels were unchanged ( > 0.05). Ankrd 1 (∼15-fold) and MLP (∼2-fold) mRNA increased, whereas Ankrd 2, Ankrd 23, MuRF-1, MyoD1, and myostatin mRNA were unchanged. Ankrd 1 (∼3-fold, Ex) and MLPb (∼20-fold, Ex + Meal) protein increased, but MLPa, Ankrd 2, Ankrd 23, and the myogenic proteins were unchanged. The postexercise meal did not affect the responses observed. Power resistance exercise, as performed in practice, induced subtle early responses in the expression of MLP and Ankrd 1 yet had little effect on the other proteins investigated. These findings suggest possible roles for MLP and Ankrd 1 in the remodeling of skeletal muscle in individuals who regularly perform this type of exercise. This is the first study to assess the early changes in the expression of titin-linked putative mechanosensing proteins and associated myogenic regulatory factors in skeletal muscle after power resistance exercise in fed, resistance-trained men. We report that power resistance exercise induces subtle early responses in the expression of Ankrd 1 and MLP, suggesting these proteins play a role in the remodeling of skeletal muscle in individuals who regularly perform this type of exercise.
Topics: Connectin; Exercise; Humans; Male; Muscle, Skeletal; Myogenin; Resistance Training
PubMed: 33356984
DOI: 10.1152/japplphysiol.00711.2020 -
Developmental Biology Apr 1999The myogenic basic helix-loop-helix transcription factor myogenin plays an essential role in the differentiation of skeletal muscle and, secondarily, in rib and sternum...
The myogenic basic helix-loop-helix transcription factor myogenin plays an essential role in the differentiation of skeletal muscle and, secondarily, in rib and sternum formation during mouse development. However, virtually nothing is known about the quantitative requirements for myogenin in these processes. Here, we describe the generation of mice carrying a hypomorphic allele of myogenin, which expresses myogenin transcripts at approximately one-fourth the level of the wild-type myogenin allele. The hypomorphic allele in combination with wild-type and myogenin-null alleles was used to create an allelic series. Embryos representing the complete range of genotypes from homozygous wild type to homozygous null were analyzed for their viability, ability to form normal ribs and sternum, and extent of skeletal muscle differentiation. Embryos carrying the hypomorphic myogenin allele over a wild-type allele were normal. In embryos bearing homozygous hypomorphic alleles, the sternum developed normally and extensive skeletal muscle differentiation occurred. However, muscle hypoplasia and reduced muscle-specific gene expression were apparent in these embryos, and the mice were not viable as neonates. When the hypomorphic allele was placed over a myogenin-null allele, the resulting embryos had sternum defects resembling homozygous myogenin-null embryos, and there was severe muscle hypoplasia. Our results demonstrate that skeletal muscle formation is highly sensitive to the absolute levels of myogenin and that correct sternum formation, skeletal muscle differentiation, and viability each require distinct threshold levels of myogenin.
Topics: Alleles; Animals; Embryonic and Fetal Development; Gene Dosage; Gene Expression Regulation, Developmental; Helix-Loop-Helix Motifs; Immunohistochemistry; Mice; Muscle Development; Muscle, Skeletal; Mutation; Myogenin; Phenotype; RNA, Messenger; Sternum; Transcription Factors
PubMed: 10075840
DOI: 10.1006/dbio.1998.9182 -
Journal of Cachexia, Sarcopenia and... Aug 2018Skeletal muscle is characterized by an efficient regeneration potential that is often impaired during myopathies. Understanding the molecular players involved in muscle...
BACKGROUND
Skeletal muscle is characterized by an efficient regeneration potential that is often impaired during myopathies. Understanding the molecular players involved in muscle homeostasis and regeneration could help to find new therapies against muscle degenerative disorders. Previous studies revealed that the Ser/Thr kinase p21 protein-activated kinase 1 (Pak1) was specifically down-regulated in the atrophying gastrocnemius of Yoshida hepatoma-bearing rats. In this study, we evaluated the role of group I Paks during cancer-related atrophy and muscle regeneration.
METHODS
We examined Pak1 expression levels in the mouse Tibialis Anterior muscles during cancer cachexia induced by grafting colon adenocarcinoma C26 cells and in vitro by dexamethasone treatment. We investigated whether the overexpression of Pak1 counteracts muscle wasting in C26-bearing mice and in vitro also during interleukin-6 (IL6)-induced or dexamethasone-induced C2C12 atrophy. Moreover, we analysed the involvement of group I Paks on myogenic differentiation in vivo and in vitro using the group I chemical inhibitor IPA-3.
RESULTS
We found that Pak1 expression levels are reduced during cancer-induced cachexia in the Tibialis Anterior muscles of colon adenocarcinoma C26-bearing mice and in vitro during dexamethasone-induced myotube atrophy. Electroporation of muscles of C26-bearing mice with plasmids directing the synthesis of PAK1 preserves fiber size in cachectic muscles by restraining the expression of atrogin-1 and MuRF1 and possibly by inducing myogenin expression. Consistently, the overexpression of PAK1 reduces the dexamethasone-induced expression of MuRF1 in myotubes and increases the phospho-FOXO3/FOXO3 ratio. Interestingly, the ectopic expression of PAK1 counteracts atrophy in vitro by restraining the IL6-Stat3 signalling pathway measured in luciferase-based assays and by reducing rates of protein degradation in atrophying myotubes exposed to IL6. On the other hand, we observed that the inhibition of group I Paks has no effect on myotube atrophy in vitro and is associated with impaired muscle regeneration in vivo and in vitro. In fact, we found that mice treated with the group I inhibitor IPA-3 display a delayed recovery from cardiotoxin-induced muscle injury. This is consistent with in vitro experiments showing that IPA-3 impairs myogenin expression and myotube formation in vessel-associated myogenic progenitors, C2C12 myoblasts, and satellite cells. Finally, we observed that IPA-3 reduces p38α/β phosphorylation that is required to proceed through various stages of satellite cells differentiation: activation, asymmetric division, and ultimately myotube formation.
CONCLUSIONS
Our data provide novel evidence that is consistent with group I Paks playing a central role in the regulation of muscle homeostasis, atrophy and myogenesis.
Topics: Animals; Cachexia; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Cytokines; Disease Models, Animal; Gene Expression; Male; Mice; Muscle Fibers, Skeletal; Muscle, Skeletal; Muscular Atrophy; Myoblasts; Myogenin; Neoplasms; Phosphorylation; Regeneration; Satellite Cells, Skeletal Muscle; p21-Activated Kinases; p38 Mitogen-Activated Protein Kinases
PubMed: 29781585
DOI: 10.1002/jcsm.12303 -
ELife Oct 2021Non-centrosomal microtubule-organizing centers (MTOCs) are pivotal for the function of multiple cell types, but the processes initiating their formation are unknown....
Non-centrosomal microtubule-organizing centers (MTOCs) are pivotal for the function of multiple cell types, but the processes initiating their formation are unknown. Here, we find that the transcription factor myogenin is required in murine myoblasts for the localization of MTOC proteins to the nuclear envelope. Moreover, myogenin is sufficient in fibroblasts for nuclear envelope MTOC (NE-MTOC) formation and centrosome attenuation. Bioinformatics combined with loss- and gain-of-function experiments identified induction of AKAP6 expression as one central mechanism for myogenin-mediated NE-MTOC formation. Promoter studies indicate that myogenin preferentially induces the transcription of muscle- and NE-MTOC-specific isoforms of and , which encodes nesprin-1α, the NE-MTOC anchor protein in muscle cells. Overexpression of AKAP6β and nesprin-1α was sufficient to recruit endogenous MTOC proteins to the nuclear envelope of myoblasts in the absence of myogenin. Taken together, our results illuminate how mammals transcriptionally control the switch from a centrosomal MTOC to an NE-MTOC and identify AKAP6 as a novel NE-MTOC component in muscle cells.
Topics: 3T3 Cells; A Kinase Anchor Proteins; Animals; Cell Line; HEK293 Cells; Humans; Mice; Microtubule-Organizing Center; Muscle Cells; Myogenin; Nuclear Envelope
PubMed: 34605406
DOI: 10.7554/eLife.65672 -
The Journal of Biological Chemistry Mar 2007Many studies have examined transcriptional regulation during the initiation of skeletal muscle differentiation; however, there is less information regarding...
Many studies have examined transcriptional regulation during the initiation of skeletal muscle differentiation; however, there is less information regarding transcriptional control during adult myogenesis and during the maintenance of the differentiated state. MyoD and the mammalian SWI/SNF chromatin-remodeling enzymes containing the Brg1 ATPase are necessary to induce myogenesis in cell culture models and in developing embryonic tissue, whereas myogenin and Brg1 are critical for the expression of the late genes that induce terminal muscle differentiation. Here, we demonstrate that myogenin also binds to its own promoter during the late stages of embryonic muscle development. As is the case during embryonic myogenesis, MyoD and Brg1 co-localize to the myogenin promoter in primary adult muscle satellite cells. However, in mature myofibers, myogenin and Brg1 are preferentially co-localized to the myogenin promoter. Thus, the myogenin promoter is occupied by different myogenic factors at different times of myogenesis. The relevance of myogenin in the continued expression from its own promoter is demonstrated in culture, where we show that myogenin, in the absence of MyoD, is capable of maintaining its own expression by recruiting the Brg1 ATPase to modify promoter chromatin structure and facilitate myogenin expression. Finally, we utilized in vivo electroporation to demonstrate that Brg1 is required for the continued production of the myogenin protein in newborn skeletal muscle tissue. These findings strongly suggest that the skeletal muscle phenotype is maintained by myogenin and the continuous activity of Brg1-based SWI/SNF chromatin-remodeling enzymes.
Topics: Animals; Cell Line; Chromosomal Proteins, Non-Histone; DNA Helicases; Embryo, Mammalian; Gene Expression Regulation, Developmental; Mice; Muscle Development; Muscle, Skeletal; MyoD Protein; Myogenin; Nuclear Proteins; Promoter Regions, Genetic; Transcription Factors
PubMed: 17194702
DOI: 10.1074/jbc.M608898200 -
Cells Oct 2022Muscle injuries, degenerative diseases and other lesions negatively affect functioning of human skeletomuscular system and thus quality of life. Therefore, the...
Muscle injuries, degenerative diseases and other lesions negatively affect functioning of human skeletomuscular system and thus quality of life. Therefore, the investigation of molecular mechanisms, stimulating myogenic differentiation of primary skeletal-muscle-derived mesenchymal stem/stromal cells (SM-MSCs), is actual and needed. The aim of the present study was to investigate the myogenic differentiation of CD56 (neural cell adhesion molecule, NCAM)-positive and -negative SM-MSCs and their response to the non-cytotoxic heat stimulus. The SM-MSCs were isolated from the post operation muscle tissue, sorted by flow cytometer according to the CD56 biomarker and morphology, surface profile, proliferation and myogenic differentiation has been investigated. Data show that CD56(+) cells were smaller in size, better proliferated and had significantly higher levels of CD146 (MCAM) and CD318 (CDCP1) compared with the CD56(-) cells. At control level, CD56(+) cells significantly more expressed myogenic differentiation markers and myogenin ( and better differentiated to the myogenic direction. The non-cytotoxic heat stimulus significantly stronger stimulated expression of myogenic markers in CD56(+) than in CD56(-) cells that correlated with the multinucleated cell formation. Data show that regenerative properties of CD56(+) SM-MSCs can be stimulated by an extracellular stimulus and be used as a promising skeletal muscle regenerating tool in vivo.
Topics: Humans; Myogenin; CD146 Antigen; Quality of Life; Mesenchymal Stem Cells; Muscle, Skeletal; Heat-Shock Response; Biomarkers; Neural Cell Adhesion Molecules; Antigens, Neoplasm; Cell Adhesion Molecules
PubMed: 36291076
DOI: 10.3390/cells11203209 -
American Journal of Physiology.... Jul 2000Myogenin is a muscle-specific transcription factor participating in denervation-induced increases in nicotinic ACh receptor (nAChR) gene expression. Although myogenin... (Comparative Study)
Comparative Study
Myogenin is a muscle-specific transcription factor participating in denervation-induced increases in nicotinic ACh receptor (nAChR) gene expression. Although myogenin RNA expression in denervated muscle is well documented, surprisingly little is known about myogenin protein expression. Therefore, we assayed myogenin protein and RNA in innervated and denervated muscles from young (4 mo) and old (24-32 mo) rats and compared this expression to that of the nAChR alpha-subunit RNA. These assays revealed increased myogenin protein expression within 1 day of denervation, preceding detectable increases in nAChR RNA. By 3 days of denervation, myogenin and nAChR alpha-subunit RNA were increased 500- and 130-fold, respectively, whereas myogenin protein increased 14-fold. Interestingly, old rats (32 mo) had 6-fold higher myogenin protein and approximately 80-fold higher mRNA levels than young rats. However, after denervation, expression levels were similar for young and old animals. The increased myogenin expression during aging, which tends to localize to small fibers, likely reflects spontaneous denervation and/or regeneration. Our results show that increased myogenin protein in denervated muscles correlates with the upregulation of its mRNA.
Topics: Aging; Animals; Blotting, Western; Cell Nucleus; Immunohistochemistry; Muscle Denervation; Muscle Fibers, Skeletal; Muscle, Skeletal; Myogenin; RNA, Messenger; Rats; Rats, Wistar; Receptors, Cholinergic
PubMed: 10896880
DOI: 10.1152/ajpregu.2000.279.1.R179