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Taglietti V, Maroli G, Cermenati S, Monteverde S, Ferrante A, Rossi G, Cossu G, Beltrame M, Messina G. Nfix Induces a Switch in Sox6 Transcriptional Activity to Regulate MyHC-I Expression in Fetal Muscle. Cell Rep 2017; 17:2354-2366. [PMID: 27880909 PMCID: PMC5149531 DOI: 10.1016/j.celrep.2016.10.082] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 09/08/2016] [Accepted: 10/24/2016] [Indexed: 02/01/2023] Open
Abstract
Sox6 belongs to the Sox gene family and plays a pivotal role in fiber type differentiation, suppressing transcription of slow-fiber-specific genes during fetal development. Here, we show that Sox6 plays opposite roles in MyHC-I regulation, acting as a positive and negative regulator of MyHC-I expression during embryonic and fetal myogenesis, respectively. During embryonic myogenesis, Sox6 positively regulates MyHC-I via transcriptional activation of Mef2C, whereas during fetal myogenesis, Sox6 requires and cooperates with the transcription factor Nfix in repressing MyHC-I expression. Mechanistically, Nfix is necessary for Sox6 binding to the MyHC-I promoter and thus for Sox6 repressive function, revealing a key role for Nfix in driving Sox6 activity. This feature is evolutionarily conserved, since the orthologs Nfixa and Sox6 contribute to repression of the slow-twitch phenotype in zebrafish embryos. These data demonstrate functional cooperation between Sox6 and Nfix in regulating MyHC-I expression during prenatal muscle development. Sox6 has opposite roles in MyHC-I regulation during embryonic and fetal myogenesis In embryonic muscle, Sox6 enhances MyHC-I expression via regulation of Mef2C In fetal muscle, Nfix is required for Sox6-mediated repression of MyHC-I The Sox6 and Nfixa orthologs cooperate in repressing smyhc1 in zebrafish
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Affiliation(s)
| | - Giovanni Maroli
- Department of Biosciences, University of Milan, Milan 20133, Italy
| | - Solei Cermenati
- Department of Biosciences, University of Milan, Milan 20133, Italy
| | | | - Andrea Ferrante
- Department of Biosciences, University of Milan, Milan 20133, Italy
| | - Giuliana Rossi
- Department of Biosciences, University of Milan, Milan 20133, Italy
| | - Giulio Cossu
- Department of Biosciences, University of Milan, Milan 20133, Italy; Division of Cell Matrix Biology and Regenerative Medicine, University of Manchester, Oxford Road, M13 9PL Manchester, UK
| | - Monica Beltrame
- Department of Biosciences, University of Milan, Milan 20133, Italy
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Smith HK, Matthews KG, Oldham JM, Jeanplong F, Falconer SJ, Bass JJ, Senna-Salerno M, Bracegirdle JW, McMahon CD. Translational signalling, atrogenic and myogenic gene expression during unloading and reloading of skeletal muscle in myostatin-deficient mice. PLoS One 2014; 9:e94356. [PMID: 24718581 PMCID: PMC3981781 DOI: 10.1371/journal.pone.0094356] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Accepted: 03/14/2014] [Indexed: 11/18/2022] Open
Abstract
Skeletal muscles of myostatin null (Mstn(−/−)) mice are more susceptible to atrophy during hind limb suspension (HS) than are muscles of wild-type mice. Here we sought to elucidate the mechanism for this susceptibility and to determine if Mstn(−/−) mice can regain muscle mass after HS. Male Mstn(−/−) and wild-type mice were subjected to 0, 2 or 7 days of HS or 7 days of HS followed by 1, 3 or 7 days of reloading (n = 6 per group). Mstn(−/−) mice lost more mass from muscles expressing the fast type IIb myofibres during HS and muscle mass was recovered in both genotypes after reloading for 7 days. Concentrations of MAFbx and MuRF1 mRNA, crucial ligases regulating the ubiquitin-proteasome system, but not MUSA1, a BMP-regulated ubiquitin ligase, were increased more in muscles of Mstn(−/−) mice, compared with wild-type mice, during HS and concentrations decreased in both genotypes during reloading. Similarly, concentrations of LC3b, Gabarapl1 and Atg4b, key effectors of the autophagy-lysosomal system, were increased further in muscles of Mstn(−/−) mice, compared with wild-type mice, during HS and decreased in both genotypes during reloading. There was a greater abundance of 4E-BP1 and more bound to eIF4E in muscles of Mstn(−/−) compared with wild-type mice (P<0.001). The ratio of phosphorylated to total eIF2α increased during HS and decreased during reloading, while the opposite pattern was observed for rpS6. Concentrations of myogenic regulatory factors (MyoD, Myf5 and myogenin) mRNA were increased during HS in muscles of Mstn(−/−) mice compared with controls (P<0.001). We attribute the susceptibility of skeletal muscles of Mstn(−/−) mice to atrophy during HS to an up- and downregulation, respectively, of the mechanisms regulating atrophy of myofibres and translation of mRNA. These processes are reversed during reloading to aid a faster rate of recovery of muscle mass in Mstn(−/−) mice.
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Affiliation(s)
- Heather K. Smith
- Department of Sport and Exercise Science, University of Auckland, Auckland, New Zealand
| | | | - Jenny M. Oldham
- AgResearch Ltd., Ruakura Agricultural Centre, Hamilton, New Zealand
| | - Ferenc Jeanplong
- AgResearch Ltd., Ruakura Agricultural Centre, Hamilton, New Zealand
| | | | - James J. Bass
- Liggins Institute, University of Auckland, Auckland, New Zealand
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Baldwin KM, Haddad F, Pandorf CE, Roy RR, Edgerton VR. Alterations in muscle mass and contractile phenotype in response to unloading models: role of transcriptional/pretranslational mechanisms. Front Physiol 2013; 4:284. [PMID: 24130531 PMCID: PMC3795307 DOI: 10.3389/fphys.2013.00284] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 09/18/2013] [Indexed: 01/30/2023] Open
Abstract
Skeletal muscle is the largest organ system in mammalian organisms providing postural control and movement patterns of varying intensity. Through evolution, skeletal muscle fibers have evolved into three phenotype clusters defined as a motor unit which consists of all muscle fibers innervated by a single motoneuron linking varying numbers of fibers of similar phenotype. This fundamental organization of the motor unit reflects the fact that there is a remarkable interdependence of gene regulation between the motoneurons and the muscle mainly via activity-dependent mechanisms. These fiber types can be classified via the primary type of myosin heavy chain (MHC) gene expressed in the motor unit. Four MHC gene encoded proteins have been identified in striated muscle: slow type I MHC and three fast MHC types, IIa, IIx, and IIb. These MHCs dictate the intrinsic contraction speed of the myofiber with the type I generating the slowest and IIb the fastest contractile speed. Over the last ~35 years, a large body of knowledge suggests that altered loading state cause both fiber atrophy/wasting and a slow to fast shift in the contractile phenotype in the target muscle(s). Hence, this review will examine findings from three different animal models of unloading: (1) space flight (SF), i.e., microgravity; (2) hindlimb suspension (HS), a procedure that chronically eliminates weight bearing of the lower limbs; and (3) spinal cord isolation (SI), a surgical procedure that eliminates neural activation of the motoneurons and associated muscles while maintaining neurotrophic motoneuron-muscle connectivity. The collective findings demonstrate: (1) all three models show a similar pattern of fiber atrophy with differences mainly in the magnitude and kinetics of alteration; (2) transcriptional/pretranslational processes play a major role in both the atrophy process and phenotype shifts; and (3) signaling pathways impacting these alterations appear to be similar in each of the models investigated.
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Affiliation(s)
- Kenneth M Baldwin
- Department of Physiology and Biophysics, University of California, Irvine, Irvine CA, USA
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Wittnich C, Tan L, Wallen J, Belanger M. Sex differences in myocardial metabolism and cardiac function: an emerging concept. Pflugers Arch 2013; 465:719-29. [DOI: 10.1007/s00424-013-1232-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 01/30/2013] [Indexed: 12/29/2022]
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An CI, Dong Y, Hagiwara N. Genome-wide mapping of Sox6 binding sites in skeletal muscle reveals both direct and indirect regulation of muscle terminal differentiation by Sox6. BMC DEVELOPMENTAL BIOLOGY 2011; 11:59. [PMID: 21985497 PMCID: PMC3239296 DOI: 10.1186/1471-213x-11-59] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2011] [Accepted: 10/10/2011] [Indexed: 01/06/2023]
Abstract
Background Sox6 is a multi-faceted transcription factor involved in the terminal differentiation of many different cell types in vertebrates. It has been suggested that in mice as well as in zebrafish Sox6 plays a role in the terminal differentiation of skeletal muscle by suppressing transcription of slow fiber specific genes. In order to understand how Sox6 coordinately regulates the transcription of multiple fiber type specific genes during muscle development, we have performed ChIP-seq analyses to identify Sox6 target genes in mouse fetal myotubes and generated muscle-specific Sox6 knockout (KO) mice to determine the Sox6 null muscle phenotype in adult mice. Results We have identified 1,066 Sox6 binding sites using mouse fetal myotubes. The Sox6 binding sites were found to be associated with slow fiber-specific, cardiac, and embryonic isoform genes that are expressed in the sarcomere as well as transcription factor genes known to play roles in muscle development. The concurrently performed RNA polymerase II (Pol II) ChIP-seq analysis revealed that 84% of the Sox6 peak-associated genes exhibited little to no binding of Pol II, suggesting that the majority of the Sox6 target genes are transcriptionally inactive. These results indicate that Sox6 directly regulates terminal differentiation of muscle by affecting the expression of sarcomere protein genes as well as indirectly through influencing the expression of transcription factors relevant to muscle development. Gene expression profiling of Sox6 KO skeletal and cardiac muscle revealed a significant increase in the expression of the genes associated with Sox6 binding. In the absence of the Sox6 gene, there was dramatic upregulation of slow fiber-specific, cardiac, and embryonic isoform gene expression in Sox6 KO skeletal muscle and fetal isoform gene expression in Sox6 KO cardiac muscle, thus confirming the role Sox6 plays as a transcriptional suppressor in muscle development. Conclusions Our present data indicate that during development, Sox6 functions as a transcriptional suppressor of fiber type-specific and developmental isoform genes to promote functional specification of muscle which is critical for optimum muscle performance and health.
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Affiliation(s)
- Chung-Il An
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, One Shields Avenue, Davis, California 95616, USA
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Lv H, Havari E, Pinto S, Gottumukkala RVSRK, Cornivelli L, Raddassi K, Matsui T, Rosenzweig A, Bronson RT, Smith R, Fletcher AL, Turley SJ, Wucherpfennig K, Kyewski B, Lipes MA. Impaired thymic tolerance to α-myosin directs autoimmunity to the heart in mice and humans. J Clin Invest 2011; 121:1561-73. [PMID: 21436590 DOI: 10.1172/jci44583] [Citation(s) in RCA: 166] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Accepted: 01/19/2011] [Indexed: 01/25/2023] Open
Abstract
Autoimmunity has long been linked to myocarditis and its sequela, dilated cardiomyopathy, the leading causes of heart failure in young patients. However, the underlying mechanisms are poorly defined, with most clinical investigations focused on humoral autoimmunity as the target for intervention. Here, we show that the α-isoform of myosin heavy chain (α-MyHC, which is encoded by the gene Myh6) is the pathogenic autoantigen for CD4+ T cells in a spontaneous mouse model of myocarditis. Further, we found that Myh6 transcripts were absent in mouse medullary thymic epithelial cells (mTECs) and peripheral lymphoid stromal cells, which have been implicated in mediating central and peripheral T cell tolerance, respectively. Transgenic expression of α-MyHC in thymic epithelium conferred tolerance to cardiac myosin and prevented myocarditis, demonstrating that α-MyHC is a primary autoantigen in this disease process. Remarkably, we found that humans also lacked α-MyHC in mTECs and had high frequencies of α-MyHC-specific T cells in peripheral blood, with markedly augmented T cell responses to α-MyHC in patients with myocarditis. Since α-MyHC constitutes a small fraction of MyHC in human heart, these findings challenge the longstanding notion that autoimmune targeting of MyHC is due to its cardiac abundance and instead suggest that it is targeted as a result of impaired T cell tolerance mechanisms. These results thus support a role for T cell-specific therapies for myocarditis.
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Affiliation(s)
- Huijuan Lv
- Joslin Diabetes Center, Boston, Massachusetts 02215, USA
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McCall GE, Haddad F, Roy RR, Zhong H, Edgerton VR, Baldwin KM. Transcriptional regulation of the myosin heavy chain IIb gene in inactive rat soleus. Muscle Nerve 2009; 40:411-9. [PMID: 19623632 DOI: 10.1002/mus.21361] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The myosin heavy chain (MHC) isoform composition of skeletal muscle is dependent, in part, on the functional demands of the muscle. The rat soleus muscle primarily expresses the slow-contracting type I MHC; however, chronic inactivity increases expression of the faster-contracting type II MHC isoforms. The purpose of this study was to identify the type IIb MHC promoter region(s) that regulate de novo transcription during chronic inactivity of the soleus induced by spinal cord isolation (SI; complete mid-thoracic and high sacral spinal cord transections plus deafferentation). Seven days after SI, transcription of IIb MHC was evidenced by increases in IIb pre-mRNA and mRNA. The activity of an approximately 2.2-kb IIb promoter-firefly luciferase reporter plasmid increased in SI soleus over control as compared to that of a promoterless plasmid. Deletion analyses indicated that the regions encompassing -2237 to -1431, -1048 to -461, and -192 to -161 basepairs (bp) each contributed to the increase in transcriptional activity. Moreover, deletions or mutations of AT-rich regions in the proximal -192 bp region abolished the increased promoter activity. These results provide important insights related to how proximal IIb MHC promoter elements regulate the increased expression of the IIb MHC gene in response to inactivity of a predominantly slow postural muscle as it undergoes a remodeling of its phenotype and functional characteristics.
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Affiliation(s)
- Gary E McCall
- Department of Physiology, University of California, Irvine, California, USA.
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Giger JM, Bodell PW, Zeng M, Baldwin KM, Haddad F. Rapid muscle atrophy response to unloading: pretranslational processes involving MHC and actin. J Appl Physiol (1985) 2009; 107:1204-12. [PMID: 19628726 DOI: 10.1152/japplphysiol.00344.2009] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Skeletal muscles, especially weight-bearing muscles, are very sensitive to changes in loading state. The aim of this paper was to characterize the dynamic changes in the unloaded soleus muscle in vivo following a short bout of hindlimb suspension (HS), testing the hypothesis that transcriptional events respond early to the atrophic stimulus. In fact, we observed that after only 1 day of HS, primary transcript levels of skeletal alpha-actin and type I myosin heavy chain (MHC) genes were significantly reduced by more than 50% compared with ground control levels. The degree of the decline for the mRNA expression of actin and type I MHC lagged behind that of the pre-mRNA levels after 1 day of HS, but by 2 and 7 days of HS, large decreases were observed. Although the faster MHC isoforms, IIx and IIb, began to be expressed in soleus after 1 day of HS, a relatively significant shift in mRNA expression from the slow MHC isoform type I toward these fast MHC isoforms did not emerge until 7 days of HS. One day of HS was sufficient to show significant decreases in mRNA levels of putative signaling factors serum response factor (SRF), suppressor of cytokine signaling-3 (SOCS3), and striated muscle activator of Rho signaling (STARS), although transcription factors yin-yang-1 (YY1) and transcriptional enhancing factor-1 (TEF-1) were not significantly affected by HS. The protein levels of actin and type I MHC were significantly decreased after 2 days of HS, and SRF protein was significantly decreased after 7 days HS. Our results show that after only 1 day of unloading, pre-mRNA and mRNA expression of muscle proteins and muscle-specific signaling factors are significantly reduced, suggesting that the downregulation of the synthesis side of the protein balance equation that occurs in atrophying muscle is initiated rapidly.
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Affiliation(s)
- Julia M Giger
- Departmentof Physiology and Biophysics, Univ. of California, Irvine, D-346, Med. Sci. I, Irvine, CA 92697, USA.
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Hagiwara N, Yeh M, Liu A. Sox6 is required for normal fiber type differentiation of fetal skeletal muscle in mice. Dev Dyn 2007; 236:2062-76. [PMID: 17584907 DOI: 10.1002/dvdy.21223] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Sox6, a member of the Sox family of transcription factors, is highly expressed in skeletal muscle. Despite its abundant expression, the role of Sox6 in muscle development is not well understood. We hypothesize that, in fetal muscle, Sox6 functions as a repressor of slow fiber type-specific genes. In the wild-type mouse, differentiation of fast and slow fibers becomes apparent during late fetal stages (after approximately embryonic day 16). However, in the Sox6 null-p(100H) mutant mouse, all fetal muscle fibers maintain slow fiber characteristics, as evidenced by expression of the slow myosin heavy chain MyHC-beta. Knockdown of Sox6 expression in wild-type myotubes results in a significant increase in MyHC-beta expression, supporting our hypothesis. Analysis of the MyHC-beta promoter revealed a Sox consensus sequence that likely functions as a negative cis-regulatory element. Together, our results suggest that Sox6 plays a critical role in the fiber type differentiation of fetal skeletal muscle.
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Affiliation(s)
- Nobuko Hagiwara
- University of California, Davis, Division of Cardiovascular Medicine/Rowe Program in Human Genetics, Davis, California 95616, USA.
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10
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Doldo NA, Delmonico MJ, Bailey JA, Hand BD, Kostek MC, Rabon-Stith KM, Menon KS, Conway JM, Carignan CR, Hurley BF. Muscle-power quality: does sex or race affect movement velocity in older adults? J Aging Phys Act 2007; 14:411-22. [PMID: 17215559 DOI: 10.1123/japa.14.4.411] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
To determine sex and race differences in muscle power per unit of muscle contraction, knee-extensor muscle power normalized for knee-extensor muscle volume was measured in 79 middle-aged and older adults (30 men and 49 women, age range 50-85 years). Results revealed that women displayed a 38% faster peak movement velocity than men and African Americans had a 14% lower peak movement velocity than Whites of a similar age when expressed per unit of involved muscle (p < .001). As expected, men exhibited greater knee-extensor strength and peak power per unit of muscle than women, but women had a faster knee- extension movement velocity per unit of muscle than men at the same relative strength level. Moreover, African Americans had greater knee-extensor muscle volume than Whites but exhibited lower knee-extensor strength and lower movement velocity per unit of muscle when tested at the same relative strength levels.
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Affiliation(s)
- Neil A Doldo
- Dept. of Kinesiology, University of Maryland, College Park, MD, USA
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Cross-Doersen D, Isfort RJ. A novel cell-based system for evaluating skeletal muscle cell hypertrophy-inducing agents. In Vitro Cell Dev Biol Anim 2005; 39:407-12. [PMID: 14741040 DOI: 10.1290/1543-706x(2003)039<0407:ancsfe>2.0.co;2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Skeletal muscle is a tissue that adapts to increased use by increasing contractile protein gene expression and ultimately skeletal muscle mass (hypertrophy). To identify hypertrophy-inducing agents that may be potentially useful in the treatment of age-related muscle loss (sarcopenia) and to better understand hypertrophy signal transduction pathways, we have created a skeletal muscle cell-based hypertrophy-responsive system. This system was created by permanently modifying the relatively undifferentiated C2C12 cell line so that it contains the beta-myosin heavy chain (beta-MHC) gene promoter and enhancer regions fused to a luciferase reporter gene. This cell line responds, by increasing luciferase expression, to a variety of skeletal muscle hypertrophy-inducing agents, including insulin, insulin-like growth factor I, testosterone, and the beta-adrenergic receptor agonist isoproterenol, in both the undifferentiated and differentiated states. This cell-based system should be useful for identifying novel hypertrophy-inducing agents as well as understanding hypertrophy signal transduction.
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Affiliation(s)
- Doreen Cross-Doersen
- Research Division, Procter & Gamble Pharmaceuticals, Health Care Research Center, 8700 Mason-Montgomery Road, Mason, Ohio 45040-9317, USA
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Shanely RA, Van Gammeren D, Deruisseau KC, Zergeroglu AM, McKenzie MJ, Yarasheski KE, Powers SK. Mechanical ventilation depresses protein synthesis in the rat diaphragm. Am J Respir Crit Care Med 2004; 170:994-9. [PMID: 15297271 DOI: 10.1164/rccm.200304-575oc] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Prolonged mechanical ventilation results in diaphragmatic atrophy and contractile dysfunction in animals. We hypothesized that mechanical ventilation-induced diaphragmatic atrophy is associated with decreased synthesis of both mixed muscle protein and myosin heavy chain protein in the diaphragm. To test this postulate, adult rats were mechanically ventilated for 6, 12, or 18 hours and diaphragmatic protein synthesis was measured in vivo. Six hours of mechanical ventilation resulted in a 30% decrease (p < 0.05) in the rate of mixed muscle protein synthesis and a 65% decrease (p < 0.05) in the rate of myosin heavy chain protein synthesis; this depression in diaphragmatic protein synthesis persisted throughout 18 hours of mechanical ventilation. Real-time polymerase chain reaction analyses revealed that mechanical ventilation, in comparison with time-matched controls, did not alter diaphragmatic levels of Type I and IIx myosin heavy chain messenger ribonucleic acid levels in the diaphragm. These data support the hypothesis that mechanical ventilation results in a decrease in both mixed muscle protein and myosin heavy chain protein synthesis in the diaphragm. Further, the decline in myosin heavy chain protein synthesis does not appear to be associated with a decrease in myosin heavy chain messenger ribonucleic acid.
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Affiliation(s)
- R Andrew Shanely
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville 32611, USA
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Allegra S, Li J, Saez J, Langlois D. Terminal differentiation of Sol 8 myoblasts is retarded by a transforming growth factor-beta autocrine regulatory loop. Biochem J 2004; 381:429-36. [PMID: 15056073 PMCID: PMC1133849 DOI: 10.1042/bj20031008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2003] [Revised: 03/24/2004] [Accepted: 03/31/2004] [Indexed: 11/17/2022]
Abstract
In DM (differentiation medium), Sol 8 myoblasts spontaneously form myotubes and express the betaMHC (beta-myosin heavy chain), their main marker of terminal differentiation. This marker is detectable at 24 h, and increases up to 72 h. Our aim was to define temporal effects of TGFbeta (transforming growth factor beta) on betaMHC expression in Sol 8 cells. TGFbeta1 (1 ng/ml) added at time zero to DM decreased MyoD expression and completely inhibited betaMHC expression in Sol 8 cells. This inhibition of betaMHC expression was progressively lost when TGFbeta1 was added from 8 to 34 h. After 34 h, the cells were irreversibly differentiated, and TGFbeta1 did not inhibit betaMHC accumulation any longer. Two independent approaches showed that a TGFbeta autocrine regulatory loop retarded and partially impaired Sol 8 cell terminal differentiation. First, permanent immunoneutralization of the active TGFbetas released by the cells into DM increased betaMHC levels at 72 h compared with controls. Secondly, a dominant-negative mutant of the TGFbeta type II receptor was overexpressed in Sol 8 cells under the control of the betaMHC promoter. Both the dominant-negative receptor and the betaMHC gene were expressed after 24 h in DM. The delayed blocking of the TGFbeta signalling pathway by the dominant-negative receptor was as effective as permanent immunoneutralization to promote betaMHC expression. To conclude, TGFbeta inhibits Sol 8 cell terminal differentiation within a narrow time interval (24-34 h) that coincides with the onset of betaMHC expression.
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Key Words
- autocrine regulatory loop
- immunoneutralization
- sol 8 myoblasts
- terminal differentiation
- transforming growth factor β (tgfβ)
- dominant-negative tgfβ type ii receptor
- cmv, cytomegalovirus
- dm, differentiation medium
- dmem, dulbecco's modified eagle's medium
- egfp, enhanced green fluorescent protein
- fbs, fetal bovine serum
- gm, growth medium
- hs, horse serum
- βmhc, β-myosin heavy chain
- mrf, myogenic regulatory factor
- tgfβ, transforming growth factor β
- tβr(i/ii), type i/ii tgfβ receptor
- wt, wild-type
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Affiliation(s)
- Séverine Allegra
- UMR 369 INSERM/UCBL and IFR 62 Laënnec, Faculté de médecine, R.T.H. Laënnec, 7 rue G. Paradin, 69372 Lyon, Cedex 08, France
| | - Jacques Yuan Li
- UMR 369 INSERM/UCBL and IFR 62 Laënnec, Faculté de médecine, R.T.H. Laënnec, 7 rue G. Paradin, 69372 Lyon, Cedex 08, France
| | - José Maria Saez
- UMR 369 INSERM/UCBL and IFR 62 Laënnec, Faculté de médecine, R.T.H. Laënnec, 7 rue G. Paradin, 69372 Lyon, Cedex 08, France
| | - Dominique Langlois
- UMR 369 INSERM/UCBL and IFR 62 Laënnec, Faculté de médecine, R.T.H. Laënnec, 7 rue G. Paradin, 69372 Lyon, Cedex 08, France
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Polly P, Haddadi LM, Issa LL, Subramaniam N, Palmer SJ, Tay ESE, Hardeman EC. hMusTRD1alpha1 represses MEF2 activation of the troponin I slow enhancer. J Biol Chem 2003; 278:36603-10. [PMID: 12857748 DOI: 10.1074/jbc.m212814200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The novel transcription factor hMusTRD1alpha1 (human muscle TFII-I repeat domain-containing protein 1alpha1; previously named MusTRD1; O'Mahoney, J. V., Guven, K. L., Lin, J., Joya, J. E., Robinson, C. S., Wade, R. P., and Hardeman, E. C. (1998) Mol. Cell. Biol. 18, 6641-6652) was identified in a yeast one-hybrid screen as a protein that binds within an upstream enhancer-containing region of the skeletal muscle-specific gene, TNNI1 (human troponin I slow; hTnIslow). It has been proposed that hMusTRD1alpha1 may play an important role in fiber-specific muscle gene expression by virtue of its ability to bind to an Inr-like element (nucleotides -977 to -960) within the hTnIslow upstream enhancer-containing region that is necessary for slow fiber-specific expression. In this study we demonstrate that both MEF2C, a known regulator of slow fiber-specific genes, and hMusTRD1alpha1 regulate hTnIslow through the Inr-like element. Co-transfection assays in C2C12 cells and Cos-7 cells demonstrate that hMusTRD1alpha1 represses hTnIslow transcription and prevents MEF2C-mediated activation of hTnIslow transcription. Gel shift analysis shows that hMusTRD1alpha1 can abrogate MEF2C binding to its cognate site in the hTnIslow enhancer. Glutathione S-transferase pull-down assays demonstrate that hMusTRD1alpha1 can interact with both MEF2C and the nuclear receptor co-repressor. The data support the role of hMusTRD1alpha1 as a repressor of slow fiber-specific transcription through mechanisms involving direct interactions with MEF2C and the nuclear receptor co-repressor.
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Affiliation(s)
- Patsie Polly
- Muscle Development Unit, Children's Medical Research Institute, Wentworthville, New South Wales 2145, Australia
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Hogan PG, Chen L, Nardone J, Rao A. Transcriptional regulation by calcium, calcineurin, and NFAT. Genes Dev 2003; 17:2205-32. [PMID: 12975316 DOI: 10.1101/gad.1102703] [Citation(s) in RCA: 1546] [Impact Index Per Article: 70.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Patrick G Hogan
- The Center for Blood Research, Harvard Medical School, Boston, Massachusetts 02115, USA
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Hall TE, Cole NJ, Johnston IA. Temperature and the expression of seven muscle-specific protein genes during embryogenesis in the Atlantic cod Gadus morhua L. J Exp Biol 2003; 206:3187-200. [PMID: 12909700 DOI: 10.1242/jeb.00535] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Seven cDNA clones coding for different muscle-specific proteins (MSPs) were isolated from the fast muscle tissue of Atlantic cod Gadus morhua L. In situ hybridization using cRNA probes was used to characterize the temporal and spatial patterns of gene expression with respect to somite stage in embryos incubated at 4 degrees C, 7 degrees C and 10 degrees C. MyoD transcripts were first observed in the presomitic mesoderm prior to somite formation, and in the lateral compartment of the forming somites. MyoD expression was not observed in the adaxial cells that give rise to the slow muscle layer, and expression was undetectable by in situ hybridization in the lateral somitic mesoderm after the 35-somite stage, during development of the final approximately 15 somites. RT-PCR analysis, however, confirmed the presence of low levels of the transcript during these later stages. A phylogenetic comparison of the deduced aminoacid sequences of the full-length MyoD cDNA clone and those from other teleosts, and inference from the in situ expression pattern suggested homology with a second paralogue (MyoD2) recently isolated from the gilthead seabream Sparus aurata. Following MyoD expression, alpha-actin was the first structural gene to be switched on at the 16-somite stage, followed by myosin heavy chain, troponin T, troponin I and muscle creatine kinase. The final mRNA in the series to be expressed was troponin C. All genes were switched on prior to myofibril assembly. The troponin C sequence was unusual in that it showed the greatest sequence identity with the rainbow trout Oncorhynchus mykiss cardiac/slow form, but was expressed in the fast myotomal muscle and not in the heart. In addition, the third TnC calcium binding site showed a lower level of sequence conservation than the rest of the sequence. No differences were seen in the timing of appearance or rate of posterior progression (relative to somite stage) of any MSP transcripts between embryos raised at the different temperatures. It was concluded that myofibrillar genes are activated asynchronously in a distinct temporal order prior to myofibrillar assembly and that this process was highly canalized over the temperature range studied.
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Affiliation(s)
- Thomas E Hall
- Gatty Marine Laboratory, School of Biology, University of St Andrews, Fife, KY16 8LB, UK.
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17
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Trudel G, Jabi M, Uhthoff HK. Localized and adaptive synoviocyte proliferation characteristics in rat knee joint contractures secondary to immobility 11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated. Arch Phys Med Rehabil 2003; 84:1350-6. [PMID: 13680573 DOI: 10.1016/s0003-9993(03)00233-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
OBJECTIVE To investigate the proliferative activity of synoviocytes in joint contracture. DESIGN Experimental controlled trial. SETTING Laboratory in vivo study. ANIMALS Adult male Sprague-Dawley rats (avg weight, 340g). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES We immobilized the knee joints of 24 rats, in 135 degrees of flexion, for up to 32 weeks. Controls were 24 sham-operated and 5 unoperated rats. On sagittal sections, synoviocytes that stained with a proliferating cell nuclear antigen antibody were counted over the anterior and posterior synovial intima. The length of the synovial intima was also measured. RESULTS The absolute number of proliferating synoviocytes decreased markedly in the posterior capsule of knee joints immobilized for more than 2 weeks (2.4+/-1.0 vs 22.7+/-7.1 at week 16, P<.05), and so did the synovial intima length (1.4+/-0.1mm vs 8.6+/-0.5mm at week 16, P<.05). No change occurred anteriorly. CONCLUSION A decreased number of proliferating synoviocytes and increased intima adhesion in the posterior capsule characterized joint contractures. The data further suggest that the synovial intima adapted to the new position of the joint. Phenomena of mechanotransduction could explain the fact that adaptations were restricted to the posterior synovial intima.
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Affiliation(s)
- Guy Trudel
- Bone and Joint Laboratory, Department of Pathology, University of Ottawa, Ottawa, ON, Canada
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Pang L, Koren G, Wang Z, Nattel S. Tissue-specific expression of two human Ca(v)1.2 isoforms under the control of distinct 5' flanking regulatory elements. FEBS Lett 2003; 546:349-354. [PMID: 12832067 DOI: 10.1016/s0014-5793(03)00629-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Transcriptional regulation may be important for L-type Ca(2+) channel alpha(1C) subunit (Ca(v)1.2) gene expression. In this study, we found two human Ca(v)1.2 isoforms, one strongly and selectively expressed in heart and the other with apparently ubiquitous expression. The promoter for the cardiac isoform has an 'initiator' sequence, and is active in neonatal cardiomyocytes but not in cardiac fibroblasts, H9C2 cells, human aorta-vascular smooth muscle and HEK293 cells. The promoter for the ubiquitously expressed isoform is of the 'housekeeping' type and is active in all cell types examined. These data indicate specific expression patterns of two human Ca(v)1.2 isoforms under the control of distinct 5' flanking regulatory sequences.
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Affiliation(s)
- Li Pang
- Department of Medicine, Montreal Heart Institute, and University of Montreal, 5000 Belanger St East, Montreal, QC, Canada H1T 1C8
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19
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Huey KA, Haddad F, Qin AX, Baldwin KM. Transcriptional regulation of the type I myosin heavy chain gene in denervated rat soleus. Am J Physiol Cell Physiol 2003; 284:C738-48. [PMID: 12444021 DOI: 10.1152/ajpcell.00389.2002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Denervation (DEN) of rat soleus is associated with a decreased expression of slow type I myosin heavy chain (MHC) and an increased expression of the faster MHC isoforms. The molecular mechanisms behind these shifts remain unclear. We first investigated endogenous transcriptional activity of the type I MHC gene in normal and denervated soleus muscles via pre-mRNA analysis. Our results suggest that the type I MHC gene is regulated via transcriptional processes in the denervated soleus. Deletion and mutational analysis of the rat type I MHC promoter was then used to identify cis elements or regions of the promoter involved in this response. DEN significantly decreased in vivo activity of the -3,500, -2,500, -914, -408, -299, and -215 bp type I MHC promoters, relative to the alpha-skeletal actin promoter. In contrast, normalized -171 promoter activity was unchanged. Mutation of the betae3 element (-214/-190) in the -215 promoter and deletion of this element (-171 promoter) blunted type I downregulation with DEN. In contrast, betae3 mutation in the -408 promoters was not effective in attenuating the DEN response, suggesting the existence of additional DEN-responsive sites between -408 and -215. Western blotting and gel mobility supershift assays demonstrated decreased expression and DNA binding of transcription enhancer factor 1 (TEF-1) with DEN, suggesting that this decrease may contribute to type I MHC downregulation in denervated muscle.
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Affiliation(s)
- K A Huey
- Department of Physiology and Biophysics, University of California, Irvine 92697, USA
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20
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Tsika RW, McCarthy J, Karasseva N, Ou Y, Tsika GL. Divergence in species and regulatory role of beta -myosin heavy chain proximal promoter muscle-CAT elements. Am J Physiol Cell Physiol 2002; 283:C1761-75. [PMID: 12388056 DOI: 10.1152/ajpcell.00278.2002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We examined the functional role of distinct muscle-CAT (MCAT) elements during non-weight-bearing (NWB) regulation of a wild-type 293-base pair beta-myosin heavy chain (beta MyHC) transgene. Electrophoretic mobility shift assays (EMSA) revealed decreased NTEF-1, poly(ADP-ribose) polymerase, and Max binding at the human distal MCAT element when using NWB soleus vs. control soleus nuclear extract. Compared with the wild-type transgene, expression assays revealed that distal MCAT element mutation decreased basal transgene expression, which was decreased further in response to NWB. EMSA analysis of the human proximal MCAT (pMCAT) element revealed low levels of NTEF-1 binding that did not differ between control and NWB extract, whereas the rat pMCAT element displayed robust NTEF-1 binding that decreased when using NWB soleus extracts. Differences in binding between human and rat pMCAT elements were consistent whether using rat or mouse nuclear extract or in vitro synthesized human TEF-1 proteins. Our results provide the first evidence that 1) different binding properties and likely regulatory functions are served by the human and rat pMCAT elements, and 2) previously unrecognized beta MyHC proximal promoter elements contribute to NWB regulation.
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Affiliation(s)
- Richard W Tsika
- Department of Biochemistry, School of Medicine, University of Missouri-Columbia, Columbia, Missouri 65211, USA.
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22
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Giger JM, Haddad F, Qin AX, Baldwin KM. Functional overload increases beta-MHC promoter activity in rodent fast muscle via the proximal MCAT (betae3) site. Am J Physiol Cell Physiol 2002; 282:C518-27. [PMID: 11832337 DOI: 10.1152/ajpcell.00444.2001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Functional overload (OL) of the rat plantaris muscle by the removal of synergistic muscles induces a shift in the myosin heavy chain (MHC) isoform expression profile from the fast isoforms toward the slow type I, or, beta-MHC isoform. Different length rat beta-MHC promoters were linked to a firefly luciferase reporter gene and injected in control and OL plantaris muscles. Reporter activities of -3,500, -914, -408, and -215 bp promoters increased in response to 1 wk of OL. The smallest -171 bp promoter was not responsive to OL. Mutation analyses of putative regulatory elements within the -171 and -408 bp region were performed. The -408 bp promoters containing mutations of the betae1, distal muscle CAT (MCAT; betae2), CACC, or A/T-rich (GATA), were still responsive to OL. Only the proximal MCAT (betae3) mutation abolished the OL response. Gel mobility shift assays revealed a significantly higher level of complex formation of the betae3 probe with nuclear protein from OL plantaris compared with control plantaris. These results suggest that the betae3 site functions as a putative OL-responsive element in the rat beta-MHC gene promoter.
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Affiliation(s)
- Julia M Giger
- Department of Physiology and Biophysics, University of California-Irvine, Irvine, CA 92697, USA
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Huey KA, Roy RR, Haddad F, Edgerton VR, Baldwin KM. Transcriptional regulation of the type I myosin heavy chain promoter in inactive rat soleus. Am J Physiol Cell Physiol 2002; 282:C528-37. [PMID: 11832338 DOI: 10.1152/ajpcell.00355.2001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chronic muscle inactivity with spinal cord isolation (SI) decreases expression of slow type I myosin heavy chain (MHC) while increasing expression of the faster MHC isoforms, primarily IIx. The purpose of this study was to determine whether type I MHC downregulation in the soleus muscle of SI rats is regulated transcriptionally and to identify cis-acting elements or regions of the rat type I MHC gene promoter involved in this response. One week of SI significantly decreased in vivo activity of the -3500-, -408-, -299-, -215-, and -171-bp type I MHC promoters. The activity of all tested deletions of the type I MHC promoter, relative to the human skeletal alpha-actin promoter, were significantly reduced in the SI soleus, except activity of the -171-bp promoter, which increased. Mutation of the betae3 element (-214/-190 bp) in the -215- and -408-bp promoters and deletion of this element (-171-bp promoter) attenuated type I downregulation with SI. Gel mobility shift assays demonstrated a decrease in transcription enhancer factor-1 binding to the betae3 element with SI, despite an increase in total binding to this region. These results demonstrate that type I MHC downregulation with SI is transcriptionally regulated and suggest that interactions between transcription enhancer factor-1 and the betae3 element are likely involved in this response.
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Affiliation(s)
- K A Huey
- Department of Physiology and Biophysics, University of California-Irvine, Irvine, CA 92697, USA
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Helguera G, Olcese R, Song M, Toro L, Stefani E. Tissue-specific regulation of Ca(2+) channel protein expression by sex hormones. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1569:59-66. [PMID: 11853958 DOI: 10.1016/s0304-4165(01)00234-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The L-type Ca(2+) channel pore-forming alpha subunit, alpha(1C) can be detected in brain and heart as two proteins with molecular masses of approximately 240 kDa and approximately 190 kDa known as alpha(1C-long) and alpha(1C-short), respectively. In brain, the alpha(1C-short) is thought to be the product of a approximately 50 kDa C-terminus calpain-mediated proteolytic deletion. We now show that uterine smooth muscle also possesses alpha(1C-long) and alpha(1C-short) isoforms, and that the relative expression of these two forms is regulated by sex hormones in a tissue-specific manner. Protein expression of alpha(1C) L-type Ca(2+) channels was examined in uterine smooth muscle, brain and heart, comparing non-pregnant (NP) estrus vs. late-pregnant (21 days) rats. The two forms of alpha(1C) were detected in all studied tissues. In late-pregnant uterus, alpha(1C-long) doubled the expression of alpha(1C-short); in NP uterus the opposite occurred. However, these changes were restricted to the uterine muscle, with no changes in brain and heart. To investigate the mechanism of such regulation, ovariectomized rats were treated with sex hormones, progesterone (P4) and/or 17beta-estradiol (estrogen, E2). P4 treatment, which yielded P4 plasma levels of 5 +/- 1 ng/ml and a high P4/E2 ratio (3 +/- 1.5 x 10(3)) similar to the ratio in late-pregnant uterus (1.5 +/- 0.3 x10(3)), facilitated alpha(1C-long) expression. In contrast, E2 or E2+P4 treatment that increased E2 plasma levels to 60 +/- 8 pg/ml and 75 +/- 24 pg/ml, produced low P4/E2 ratios of 0.03 +/- 0.006 and 0.2 +/- 0.1, respectively. These low P4/E2 ratios also found in NP rats at estrus (0.3 +/- 0.1) favored the expression of alpha(1C-short) form in myometrium. Neither hormone treatment altered alpha(1C) expression in brain or heart. Our results indicate that expression of alpha(1C) isoforms depends on P4/E2 ratios. Plasma P4/E2 ratios <1 x 10(3) favor the expression of the alpha(1C-short); whereas ratios >1 x 10(3) facilitate the expression of the alpha(1C-long) form. This regulation is tissue-specific for myometrium since it did not occur in heart and brain tissues.
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Affiliation(s)
- Gustavo Helguera
- Department of Anestesiology, University of California Los Angeles, 90095-1778, USA
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Wright CE, Bodell PW, Haddad F, Qin AX, Baldwin KM. In vivo regulation of the beta-myosin heavy chain gene in hypertensive rodent heart. Am J Physiol Cell Physiol 2001; 280:C1262-76. [PMID: 11287340 DOI: 10.1152/ajpcell.2001.280.5.c1262] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The main goal of this study was to examine the transcriptional activity of different-length beta-myosin heavy chain (beta-MHC) promoters in the hypertensive rodent heart using the direct gene transfer approach. A hypertensive state was induced by abdominal aortic constriction (AbCon) sufficient to elevate mean arterial pressure by approximately 45% relative to control. Results show that beta-MHC promoter activity of all tested wild-type constructs, i.e., -3500, -408, -299, -215, -171, and -71 bp, was significantly increased in AbCon hearts. In the normal control hearts, expression of the -71-bp construct was comparable to that of the promoterless vector, but its induction by AbCon was comparable to that of the other constructs. Additional results, based on mutation analysis and DNA gel mobility shift assays targeting betae1, betae2, GATA, and betae3 elements, show that these previously defined cis-elements in the proximal promoter are indeed involved in maintaining basal promoter activity; however, none of these elements, either individually or collectively, appear to be major players in mediating the hypertension response of the beta-MHC gene. Collectively, these results indicate that three separate regions on the beta-MHC promoter are involved in the induction of the gene in response to hypertension: 1) a distal region between -408 and -3500 bp, 2) a proximal region between -299 and -215 bp, and 3) a basal region within -71 bp of the transcription start site. Future research needs to further characterize these responsive regions to more fully delineate beta-MHC transcriptional regulation in response to pressure overload.
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Affiliation(s)
- C E Wright
- Department of Physiology and Biophysics, University of California, Irvine, California 92697, USA
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Huey KA, Roy RR, Baldwin KM, Edgerton VR. Temporal effects of inactivty on myosin heavy chain gene expression in rat slow muscle. Muscle Nerve 2001; 24:517-26. [PMID: 11268024 DOI: 10.1002/mus.1035] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Myosin heavy chain (MHC) mRNA and protein profiles in adult rat soleus and adductor longus were determined after 4, 8, 15, 30, 60, and 90 days of spinal cord isolation (SI). SI results in complete neuromuscular inactivity while leaving the motoneuron-muscle fiber connections intact. From 15 to 90 days, type I MHC mRNA was significantly decreased, whereas type I MHC protein did not significantly decrease until 30 and 60 days in the soleus and adductor longus, respectively. However, in both muscles, slow MHC downregulation was offset by significant upregulation of the faster MHC isoforms, primarily IIx. From 60 to 90 days, type I MHC was almost completely replaced with faster isoforms at the mRNA and protein levels. Thus, chronic inactivity and unloading of slow rat hindlimb muscles shifted the MHC profile from predominately type I to type IIx MHC mRNA and protein.
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Affiliation(s)
- K A Huey
- Department of Physiology and Biophysics, University of California, 346-D Medical Sciences I, Irvine, California 92697, USA.
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27
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Baldwin KM, Haddad F. Effects of different activity and inactivity paradigms on myosin heavy chain gene expression in striated muscle. J Appl Physiol (1985) 2001; 90:345-57. [PMID: 11133928 DOI: 10.1152/jappl.2001.90.1.345] [Citation(s) in RCA: 203] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The goal of this mini-review is to summarize findings concerning the role that different models of muscular activity and inactivity play in altering gene expression of the myosin heavy chain (MHC) family of motor proteins in mammalian cardiac and skeletal muscle. This was done in the context of examining parallel findings concerning the role that thyroid hormone (T(3), 3,5,3'-triiodothyronine) plays in MHC expression. Findings show that both cardiac and skeletal muscles of experimental animals are initially undifferentiated at birth and then undergo a marked level of growth and differentiation in attaining the adult MHC phenotype in a T(3)/activity level-dependent fashion. Cardiac MHC expression in small mammals is highly sensitive to thyroid deficiency, diabetes, energy deprivation, and hypertension; each of these interventions induces upregulation of the beta-MHC isoform, which functions to economize circulatory function in the face of altered energy demand. In skeletal muscle, hyperthyroidism, as well as interventions that unload or reduce the weight-bearing activity of the muscle, causes slow to fast MHC conversions. Fast to slow conversions, however, are seen under hypothyroidism or when the muscles either become chronically overloaded or subjected to intermittent loading as occurs during resistance training and endurance exercise. The regulation of MHC gene expression by T(3) or mechanical stimuli appears to be strongly regulated by transcriptional events, based on recent findings on transgenic models and animals transfected with promoter-reporter constructs. However, the mechanisms by which T(3) and mechanical stimuli exert their control on transcriptional processes appear to be different. Additional findings show that individual skeletal muscle fibers have the genetic machinery to express simultaneously all of the adult MHCs, e.g., slow type I and fast IIa, IIx, and IIb, in unique combinations under certain experimental conditions. This degree of heterogeneity among the individual fibers would ensure a large functional diversity in performing complex movement patterns. Future studies must now focus on 1) the signaling pathways and the underlying mechanisms governing the transcriptional/translational machinery that control this marked degree of plasticity and 2) the morphological organization and functional implications of the muscle fiber's capacity to express such a diversity of motor proteins.
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Affiliation(s)
- K M Baldwin
- Department of Physiology and Biophysics, University of California, Irvine, California 92697, USA.
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