In vivo expression patterns of MyoD, p21, and Rb proteins in myonuclei and satellite cells of denervated rat skeletal muscle

Abstract

MyoD, a myogenic regulatory factor, is rapidly expressed in adult skeletal muscles in response to denervation. However, the function(s) of MyoD expressed in denervated muscle has not been adequately elucidated. In vitro, it directly transactivates cyclin-dependent kinase inhibitor p21 (p21) and retinoblastoma protein (Rb), a downstream target of p21. These factors then act to regulate cell cycle withdrawal and antiapoptotic cell death. Using immunohistochemical approaches, we characterized cell types expressing MyoD, p21, and Rb and the relationship among these factors in the myonucleus of denervated muscles. In addition, we quantitatively examined the time course changes and expression patterns among distinct myofiber types of MyoD, p21, and Rb during denervation. Denervation induced MyoD expression in myonuclei and satellite cell nuclei, whereas p21 and Rb were found only in myonuclei. Furthermore, coexpression of MyoD, p21, and Rb was induced in the myonucleus, and quantitative analysis of these factors determined that there was no difference among the three myofiber types. These observations suggest that MyoD may function in myonuclei in response to denervation to protect against denervation-induced apoptosis via perhaps the activation of p21 and Rb, and function of MyoD expressed in satellite cell nuclei may be negatively regulated. The present study provides a molecular basis to further understand the function of MyoD expressed in the myonuclei and satellite cell nuclei of denervated skeletal muscle.

Growth factor and cytokine interactions in myogenesis. Part I. The effect of TNF-α and IFN-γ on IGF-I-dependent differentiation in mouse C2C12 myogenic cells

“…Myogenesis is controlled by members of a family of muscle-specific basic helix-loop-helix (bHLH) proteins that, in association with members of the ubiquitous E2A and myocyte enhancer factor-2 (MEF2) families, activate the differentiation program i.e. transcription of regulatory and structural muscle-specific genes (Ishido et al 2004). One of these factors, MyoD plays a specific role in muscle cell activation and in the transition from proliferation to differentiation, via cell cycle arrest and activation of the expression of multiple additional transcription factors and the muscle-specific genes in the differentiation program.…”

Neuronal control of myogenic regulatory factor accumulation in fetal muscle

“…The marked increases in MRF mRNAs that occur after adult denervation (Eftimie et al, 1991;Duclert et al, 1991;Witzemann and Sakmann, 1991;Buonanno et al, 1992;Voytik et al, 1993), are followed almost immediately by increases in myoD, myogenin and MRF4 proteins (Weis, 1994;Kostrominova et al, 2000;Weis et al, 2000;Hyatt et al, 2003;Ishido et al, 2004). This increase in protein is accompanied by changes in transcript accumulation for proteins encoded for by several MRF target genes (e.g., the nicotinic acetylcholine receptor subunits [cf.…”

“…While there are several studies of the effect of adult denervation on MRF proteins (Weis, 1994;Kostrominova et al, 2000;Weis et al, 2000;Ishido et al, 2004), almost all (save Hyatt et al, 2003) used immunohistochemistry, exclusively, for evaluation. Some have attempted to quantify levels of protein by counting the number of MRF-positive nuclei in denervated and innervated muscles, either with or without consideration of the intensity of immunostaining for the MRF.…”

“…myoD and myogenin mRNAs are preferentially expressed in adult rodent fast and slow twitch muscle fibers, respectively; however, there does not appear to be an absolute correlation between the accumulation of myoD and myogenin mRNAs and specific fiber types (Hughes et al, 1993(Hughes et al, , 1997Voytik et al, 1993;Kraus and Pette, 1997). Denervation of adult, rodent hindlimb muscles results in large increases in the mRNAs for all of the MRFs by ϳ2 days after denervation (Duclert et al, 1991;Eftimie et al, 1991;Witzemann and Sakmann, 1991;Buonanno et al, 1992;Voytik et al, 1993;Hyatt et al, 2003), followed almost immediately by increases in myoD, myogenin, and MRF4 proteins (Weis, 1994;Weis et al, 2000;Kostrominova et al, 2000;Hyatt et al, 2003;Ishido et al, 2004). While the changes in individual MRF mRNAs vary with the muscles studied and with the species of rodent evaluated, myogenin mRNA reportedly exhibits the greatest increase (levels of this transcript are 40-to 200-fold higher than in control muscle at 1-week after denervation).…”

Effect of tibiotarsal joint inflammation on gene expression and cross-sectional area in rat soleus muscle

“…MAFbx (also known as atrogin-1) and Muscle Ring Finger-1 (MuRF1) [13][14][15][16] . Muscle fiber CSA reduction is also followed by changes in the regulation of genes related to muscle differentiation and growth (MyoD) 17,18 mass regulation (myostatin) 19 and proinflammatory factors, such as p38 Mitogen-Activated Protein Kinase (p38MAPK), Nuclear Factor kappa B-dependent (NFκB), and Tumour Necrosis Factoralpha (TNF-alpha) [20][21][22] . According to a previous study, the carrageenan injection increases TNF-alpha 23 , a cytokine able to increase the gene expression of MuRF1 and atrogin-1 in rat skeletal muscle 20,24,25 through the NFκB 20 and MAPK 25 pathways, respectively.…”