Disease relevance of Myog

• Because of the initial increase of immediate early gene c-fos mRNA and the subsequent increase of myogenic transcription factor myogenin mRNA, it appears that repetitive muscle stretch induces sequential progression of gene transcription toward muscle hypertrophy [1].
• Together, our results suggest that the transformed and undifferentiated phenotype of BA-Han-1C rhabdomyosarcoma cells is associated with the inactivation of the myogenic factor MyoD1 as well as lack of myogenin expression [2].
• EXPERIMENTAL DESIGN: To clarify the primary events in myogenic precursor cell activation, the expression of myogenin was examined in rats 1 to 48 hours after either a contusion injury to the gastrocnemius or after toxic injury to the soleus muscle [3].
• However, as revealed by changes in the expression levels of these two regulatory factors under conditions of hypothyroidism and chronic low-frequency stimulation (CLFS), MyoD and myogenin did not seem to be strictly correlated with fast and slow myosins, respectively [4].
• The unaltered levels of transcripts of myogenin, SkM2 of Na+ channels and gamma-subunit of AChR, confirm that there is no denervation-like prejunctional (nerve-related) component to explain the muscle weakness or the upregulation of AChRs at sites distant from burns [5].

Psychiatry related information on Myog

• It is likely that this maintained level of increased Id expression, in conjunction with the returning levels of myogenin and MRF4 expression, account for the reduced level of embryonic receptors in long-term denervated muscle [6].

High impact information on Myog

• Our data suggest that activation of myogenin gene expression and the establishment of the differentiated phenotype may require functional Myf-5 [7].
• The present investigation provides evidence that E1a interferes with the expression of myogenin and the activity of Myf-5, the two myogenic helix-loop-helix (HLH) proteins that are expressed in L6 muscle cells [7].
• The same inhibition by E1a can be shown for the other myogenic HLH proteins, MyoD, myogenin, and MRF4/Myf-6, that have been expressed in 10T1/2 fibroblasts [7].
• The Pan/E12,E47 proteins also show structural similarity with the Drosophila daughterless protein, MyoD, Myogenin, and Myf-5 [8].
• The virus converted cultured cardiac fibroblasts to skeletal muscle, indicated by expression of myogenin and skeletal myosin heavy chains (MHCs) [9].

Chemical compound and disease context of Myog

• Retinoic acid induces myogenin synthesis and myogenic differentiation in the rat rhabdomyosarcoma cell line BA-Han-1C [2].
• The relationship between myogenin or MyoD expression and hypertrophy of the rat soleus produced either by clenbuterol and 3,3', 5-triiodo-L-thyronine (CT) treatment or by surgical overload was examined [10].
• Male rats treated with dexamethasone for 14 days (1 mg per kg body weight) showed increased levels of MyoD1, myogenin and myf-5 compared to control male rats [11].

Biological context of Myog

• Insulin-like growth factor-I stimulates terminal myogenic differentiation by induction of myogenin gene expression [12].
• 3) Inhibitors of myogenesis also inhibit elevation of myogenin mRNA in response to IGF-I [12].
• We find that even in the presence of phosphorylated Akt, it is only when ERK1/2 phosphorylation is inhibited that IGF-I can stimulate myogenin mRNA expression [13].
• This widespread neural activity-independent influence on MyoD and myogenin expression was observed in myonuclei and satellite cells and was not specific for fast or slow fiber phenotypes [14].
• In fact, stable transfections of BA-Han-1C cells with myogenin expressing plasmids resulted in spontaneous differentiation [2].

Anatomical context of Myog

• Myogenin is a member of the recently discovered family of muscle determination genes that have been shown to induce myogenic differentiation in nonmuscle cells and to be closely correlated with terminal differentiation in myoblasts [15].
• Jun, Fos, MyoD1, and myogenin proteins are increased in skeletal muscle fiber nuclei after denervation [16].
• Fos, MyoD1, and Myogenin immunoreactivity was mostly confined to muscle cell nuclei, whereas Jun antibodies stained muscle cell and some interstitial cell nuclei [16].
• After 16 days of spaceflight, tibialis anterior, plantaris, medial gastrocnemius, and soleus muscles were removed from the hindlimb musculature and examined for the expression of MyoD-family transcription factors such as MyoD, myogenin, and MRF4 [17].
• This growth inhibitory response is followed by cell commitment to terminal differentiation with elevated expression of myogenin muscle determination genes, induction of muscle-specific proteins, and formation of multinucleated myotubes [18].

Associations of Myog with chemical compounds

• The hypertrophic myotubes dramatically increased expression of myogenin, muscle creatine kinase, beta-enolase, and IGF binding protein 5 and activated the myocyte enhancer factor 2C gene which is normally silent in this cell line [19].
• Myogenic events like the induction of myogenin and of glucose carrier GLUT4 were also blocked and myoblasts could not exit the cell cycle, as measured by the lack of mRNA induction of p21 cyclin-dependent kinase inhibitor [20].
• Nitrotyrosine treatment prevented synthesis or activation of markers of myogenic differentiation, including muscle-specific myosin, alpha-actin, integrin alpha(7), and myogenin [21].
• Myogenin mRNA expression was studied by Northern blot hybridizations, and the results were correlated with the onsets of the mitotic activity (i.e., incorporation of bromodeoxyuridine) of the satellite cells and of the production of the myogenin and MyoD1 proteins, as well as muscle-specific intermediate filament protein, desmin [3].
• We show that in the presence of serum, lithium induced the differentiation of H9c2 cells as measured by multinucleated myotube formation and expression of the muscle-specific proteins, myogenin and skeletal alpha-actin [22].

Regulatory relationships of Myog

• Highly specific inhibition of IGF-I-stimulated differentiation by an antisense oligodeoxyribonucleotide to myogenin mRNA. No effects on other actions of IGF-T [15].
• Elevation of myogenin mRNA is blocked by TGF-beta 1 added at the time of the shift [23].
• The skeletal alpha-actin promoter contains E box and serum response element (SRE) regulatory regions which are directly or indirectly activated by myogenin (or MyoD) and IGF-I proteins, respectively [24].
• In addition, calpastatin appears to modulate myogenic gene expression, as indicated by the lack of myogenin (a transcription factor expressed in differentiating myoblasts) in myoblasts overexpressing calpastatin [25].
• In contrast, we provide evidence that calcium/calmodulin-activated protein kinase II participates in mediating the effects of muscle depolarization on nAChR and myogenin gene expression [26].

Other interactions of Myog

• 1) Myogenin mRNA is elevated by IGF-I, with a concentration dependency that parallels the stimulation of differentiation, including a decrease in stimulation at higher concentrations [12].
• 2) The time course of elevation of myogenin mRNA is consistent with its acting as an intermediate in the signalling pathway between occupancy of the IGF-I receptor and induction of expression of muscle-specific genes [12].
• IGF-I, des(1-3)IGF-I, or IGF-II induced L6E9 skeletal muscle cell differentiation as measured by myotube formation, myogenin gene expression, and GLUT4 glucose carrier induction [27].
• However, TGF-beta 1 can also block myogenic differentiation in cells transfected with the myogenin gene under the control of a constitutive SV40 viral promoter [23].
• Contrary to its weak mitogenic activity, FGFR4 effectively mediates the inhibition of myogenic differentiation in L6E9 cells and also suppresses the expression of the myogenic regulatory protein myogenin [28].

Analytical, diagnostic and therapeutic context of Myog

• After denervation, mRNA levels of the jun and fos protooncogenes and of the muscular differentiation factors myoD1 and myogenin are increased [16].
• The ratio of myogenin to MyoD mRNA content estimated by RT-PCR in TR animals was 28% higher than that in Con animals (P < 0.05) [29].
• Protein expression levels of myogenin and MyoD were measured by Western blots [29].
• MAIN OUTCOME MEASURES: After repetitive stretch, total ribonucleic acid (RNA) was extracted from the muscles and Northern blotting was carried out using c-fos and myogenin oligonucleotide as probes [1].
• We used immunofluorescence and RT-PCR to demonstrate the expression of the skeletal muscle-specific regulatory genes MyoD and myogenin, and of several skeletal muscle-specific structural genes in cultures of the established rat smooth muscle cell lines PAC1, A10, and A7r5 [30].

References