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Zeng C, Shi H, Kirkpatrick LT, Ricome A, Park S, Scheffler JM, Hannon KM, Grant AL, Gerrard DE. Driving an Oxidative Phenotype Protects Myh4 Null Mice From Myofiber Loss During Postnatal Growth. Front Physiol 2022; 12:785151. [PMID: 35283757 PMCID: PMC8908108 DOI: 10.3389/fphys.2021.785151] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 12/28/2021] [Indexed: 12/17/2022] Open
Abstract
Postnatal muscle growth is accompanied by increases in fast fiber type compositions and hypertrophy, raising the possibility that a slow to fast transition may be partially requisite for increases in muscle mass. To test this hypothesis, we ablated the Myh4 gene, and thus myosin heavy chain IIB protein and corresponding fibers in mice, and examined its consequences on postnatal muscle growth. Wild-type and Myh4–/– mice had the same number of muscle fibers at 2 weeks postnatal. However, the gastrocnemius muscle lost up to 50% of its fibers between 2 and 4 weeks of age, though stabilizing thereafter. To compensate for the lack of functional IIB fibers, type I, IIA, and IIX(D) fibers increased in prevalence and size. To address whether slowing the slow-to-fast fiber transition process would rescue fiber loss in Myh4–/– mice, we stimulated the oxidative program in muscle of Myh4–/– mice either by overexpression of PGC-1α, a well-established model for fast-to-slow fiber transition, or by feeding mice AICAR, a potent AMP kinase agonist. Forcing an oxidative metabolism in muscle only partially protected the gastrocnemius muscle from loss of fibers in Myh4–/– mice. To explore whether traditional means of stimulating muscle hypertrophy could overcome the muscling deficits in postnatal Myh4–/– mice, myostatin null mice were bred with Myh4–/– mice, or Myh4–/– mice were fed the growth promotant clenbuterol. Interestingly, both genetic and pharmacological stimulations had little impact on mice lacking a functional Myh4 gene suggesting that the existing muscle fibers have maximized its capacity to enlarge to compensate for the lack of its neighboring IIB fibers. Curiously, however, cell signaling events responsible for IIB fiber formation remained intact in the tissue. These findings further show disrupting the slow-to-fast transition of muscle fibers compromises muscle growth postnatally and suggest that type IIB myosin heavy chain expression and its corresponding fiber type may be necessary for fiber maintenance, transition and hypertrophy in mice. The fact that forcing muscle metabolism toward a more oxidative phenotype can partially compensates for the lack of an intact Myh4 gene provides new avenues for attenuating the loss of fast-twitch fibers in aged or diseased muscles.
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Affiliation(s)
- Caiyun Zeng
- Department of Animal Sciences, Purdue University, West Lafayette, IN, United States
| | - Hao Shi
- Meat Science and Muscle Biology Research Group, Virginia Tech, Department of Animal and Poultry Sciences, Blacksburg, VA, United States
| | - Laila T. Kirkpatrick
- Meat Science and Muscle Biology Research Group, Virginia Tech, Department of Animal and Poultry Sciences, Blacksburg, VA, United States
| | - Aymeric Ricome
- Department of Animal Sciences, Purdue University, West Lafayette, IN, United States
| | - Sungkwon Park
- Department of Animal Sciences, Purdue University, West Lafayette, IN, United States
| | - Jason M. Scheffler
- Meat Science and Muscle Biology Research Group, Virginia Tech, Department of Animal and Poultry Sciences, Blacksburg, VA, United States
| | - Kevin M. Hannon
- Department of Basic Medical Sciences, Purdue University, West Lafayette, IN, United States
| | - Alan L. Grant
- Meat Science and Muscle Biology Research Group, Virginia Tech, Department of Animal and Poultry Sciences, Blacksburg, VA, United States
| | - David E. Gerrard
- Meat Science and Muscle Biology Research Group, Virginia Tech, Department of Animal and Poultry Sciences, Blacksburg, VA, United States
- *Correspondence: David E. Gerrard,
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Multiple transcription factors mediating the expressional regulation of myosin heavy chain gene involved in the indeterminate muscle growth of fish. Gene 2019; 687:308-318. [PMID: 30453072 DOI: 10.1016/j.gene.2018.11.040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 11/05/2018] [Accepted: 11/15/2018] [Indexed: 11/22/2022]
Abstract
Torafugu myosin heavy chain gene, MYHM2528-1, is specifically expressed in neonatal slow and fast muscle fibers, suggesting its functional role in indeterminate muscle growth in fish. However, the transcriptional regulatory mechanisms of MYHM2528-1 involved in indeterminate muscle growth in fish remained unknown. We previously isolated a 2100 bp 5'- flanking sequence of torafugu MYHM2528-1 that showed sufficient promoter activity to allow specific gene expression in neonatal muscle fibers of zebrafish. Here, we examined the cis-regulatory mechanism of 2100 bp 5'-flanking region of torafugu MYHM2528-1 using deletion-mutation analysis in zebrafish embryo. We discovered that myoblast determining factor (MyoD) binding elements play a key role and participate in the transcriptional regulation of MYHM2528-1 expression in zebrafish embryos. We further discovered that paired box protein (Pax3) are required for promoting MYHM2528-1 expression and myocyte enhancer factor-2 (MEF2) binding sites participate in the transcriptional regulation of MYHM2528-1 expression in slow/fast skeletal muscles. Our study also confirmed that the nuclear factor of activated T-cell (NFAT) binding sites take part in the transcriptional regulation of MYHM2528-1 expression in slow and fast muscles fiber in relation to indeterminate muscle growth. These results obviously confirmed that multiple cis-elements in the 5'-flanking region of MYHM2528-1 function in the transcriptional regulation of its expression.
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Tsukamoto S, Shibasaki A, Naka A, Saito H, Iida K. Lactate Promotes Myoblast Differentiation and Myotube Hypertrophy via a Pathway Involving MyoD In Vitro and Enhances Muscle Regeneration In Vivo. Int J Mol Sci 2018; 19:ijms19113649. [PMID: 30463265 PMCID: PMC6274869 DOI: 10.3390/ijms19113649] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Accepted: 11/16/2018] [Indexed: 12/25/2022] Open
Abstract
Lactate is a metabolic substrate mainly produced in muscles, especially during exercise. Recently, it was reported that lactate affects myoblast differentiation; however, the obtained results are inconsistent and the in vivo effect of lactate remains unclear. Our study thus aimed to evaluate the effects of lactate on myogenic differentiation and its underlying mechanism. The differentiation of C2C12 murine myogenic cells was accelerated in the presence of lactate and, consequently, myotube hypertrophy was achieved. Gene expression analysis of myogenic regulatory factors showed significantly increased myogenic determination protein (MyoD) gene expression in lactate-treated cells compared with that in untreated ones. Moreover, lactate enhanced gene and protein expression of myosin heavy chain (MHC). In particular, lactate increased gene expression of specific MHC isotypes, MHCIIb and IId/x, in a dose-dependent manner. Using a reporter assay, we showed that lactate increased promoter activity of the MHCIIb gene and that a MyoD binding site in the promoter region was necessary for the lactate-induced increase in activity. Finally, peritoneal injection of lactate in mice resulted in enhanced regeneration and fiber hypertrophy in glycerol-induced regenerating muscles. In conclusion, physiologically high lactate concentrations modulated muscle differentiation by regulating MyoD-associated networks, thereby enhancing MHC expression and myotube hypertrophy in vitro and, potentially, in vivo.
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Affiliation(s)
- Sakuka Tsukamoto
- Department of Nutrition and Food Science, Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1 Otsuka, Bunkyo, Tokyo 112-8610, Japan.
| | - Ayako Shibasaki
- Department of Nutrition and Food Science, Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1 Otsuka, Bunkyo, Tokyo 112-8610, Japan.
| | - Ayano Naka
- Laboratory of Applied Nutrition, Faculty of Human Life and Environmental Sciences, Ochanomizu University, Tokyo 112-8610, Japan..
| | - Hazuki Saito
- Department of Nutrition and Food Science, Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1 Otsuka, Bunkyo, Tokyo 112-8610, Japan.
| | - Kaoruko Iida
- Department of Nutrition and Food Science, Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1 Otsuka, Bunkyo, Tokyo 112-8610, Japan.
- The Institute for Human Life Innovation, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan.
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Yu H, Waddell JN, Kuang S, Tellam RL, Cockett NE, Bidwell CA. Identification of genes directly responding to DLK1 signaling in Callipyge sheep. BMC Genomics 2018; 19:283. [PMID: 29690867 PMCID: PMC5937834 DOI: 10.1186/s12864-018-4682-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 04/16/2018] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND In food animal agriculture, there is a need to identify the mechanisms that can improve the efficiency of muscle growth and protein accretion. Callipyge sheep provide excellent machinery since the up-regulation of DLK1 and RTL1 results in extreme postnatal muscle hypertrophy in distinct muscles. The aim of this study is to distinguish the genes that directly respond to DLK1 and RTL1 signaling from the genes that change as the result of muscle specific effects. RESULTS The quantitative PCR results indicated that DLK1 expression was significantly increased in hypertrophied muscles but not in non-hypertrophied muscles. However, RTL1 was up-regulated in both hypertrophied and non-hypertrophied muscles. Five genes, including PARK7, DNTTIP1, SLC22A3, METTL21E and PDE4D, were consistently co-expressed with DLK1, and therefore were possible transcriptional target genes responding to DLK1 signaling. Treatment of myoblast and myotubes with DLK1 protein induced an average of 1.6-fold and 1.4-fold increase in Dnttip1 and Pde4d expression respectively. Myh4 expression was significantly elevated in DLK1-treated myotubes, whereas the expression of Mettl21e was significantly increased in the DLK1-treated myoblasts but reduced in DLK1-treated myotubes. DLK1 treatment had no impact on Park7 expression. In addition, Park7 and Dnttip1 increased Myh4 and decreased Myh7 promoter activity, resemble to the effects of Dlk1. In contrast, expression of Mettl21e increased Myh7 and decreased Myh4 luciferase activity. CONCLUSION The study provided additional supports that RTL1 alone was insufficient to induce muscle hypertrophy and concluded that DLK1 was likely the primary effector of the hypertrophy phenotype. The results also suggested that DNTTIP1 and PDE4D were secondary effector genes responding to DLK1 signaling resulting in muscle fiber switch and muscular hypertrophy in callipyge lamb.
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Affiliation(s)
- Hui Yu
- Department of Animal Sciences, Purdue University, 270 South Russell Street, West Lafayette, IN, 47907, USA. .,Department of Molecular and Integrative Physiology, University of Michigan, 1000 Wall Street, Ann Arbor, MI, 48105, USA.
| | - Jolena N Waddell
- Department of Animal Sciences, Purdue University, 270 South Russell Street, West Lafayette, IN, 47907, USA.,Department of Animal Science & Veterinary Technology, Tarleton State University, Stephenville, TX, USA
| | - Shihuan Kuang
- Department of Animal Sciences, Purdue University, 270 South Russell Street, West Lafayette, IN, 47907, USA.,Center for Cancer Research, Purdue University, West Lafayette, IN, USA
| | - Ross L Tellam
- CSIRO Animal, Food and Health Sciences, St. Lucia, QLD, Australia
| | - Noelle E Cockett
- Department of Animal, Dairy and Veterinary Sciences, Utah State University, Logan, UT, USA
| | - Christopher A Bidwell
- Department of Animal Sciences, Purdue University, 270 South Russell Street, West Lafayette, IN, 47907, USA.
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Expression of the myosin heavy chain IIB gene in porcine skeletal muscle: the role of the CArG-Box promoter response element. PLoS One 2014; 9:e114365. [PMID: 25469802 PMCID: PMC4255089 DOI: 10.1371/journal.pone.0114365] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 11/07/2014] [Indexed: 01/09/2023] Open
Abstract
Due to its similarity to humans, the pig is increasingly being considered as a good animal model for studying a range of human diseases. Despite their physiological similarities, differential expression of the myosin heavy chain (MyHC) IIB gene (MYH4) exists in the skeletal muscles of these species, which is associated with a different muscle phenotype. The expression of different MyHC isoforms is a critical determinant of the contractile and metabolic characteristics of the muscle fibre. We aimed to elucidate whether a genomic mechanism was responsible for the drastically different expression of MYH4 between pigs and humans, thus improving our understanding of the pig as a model for human skeletal muscle research. We utilized approximately 1 kb of the MYH4 promoter from a domestic pig and a human (which do and do not express MYH4, respectively) to elucidate the role of the promoter sequence in regulating the high expression of MYH4 in porcine skeletal muscle. We identified a 3 bp genomic difference within the proximal CArG and E-box region of the MYH4 promoter of pigs and humans that dictates the differential activity of these promoters during myogenesis. Subtle species-specific genomic differences within the CArG-box region caused differential protein-DNA interactions at this site and is likely accountable for the differential MYH4 promoter activity between pigs and humans. We propose that the genomic differences identified herein explain the differential activity of the MYH4 promoter of pigs and humans, which may contribute to the differential expression patterns displayed in these otherwise physiologically similar mammals. Further, we report that both the pig and human MYH4 promoters can be induced by MyoD over-expression, but the capacity to activate the MYH4 promoter is largely influenced by the 3 bp difference located within the CArG-box region of the proximal MYH4 promoter.
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6
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Wang L, Liu X, Niu F, Wang H, He H, Gu Y. Single nucleotide polymorphisms, haplotypes and combined genotypes in MYH₃ gene and their associations with growth and carcass traits in Qinchuan cattle. Mol Biol Rep 2012; 40:417-26. [PMID: 23073773 PMCID: PMC3518803 DOI: 10.1007/s11033-012-2076-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2012] [Accepted: 10/03/2012] [Indexed: 10/27/2022]
Abstract
MYH₃ is a major contractile protein which converts chemical energy into mechanical energy through the ATP hydrolysis. MYH₃ is mainly expressed in the skeletal muscle in different stages especially embryonic period, and it has a role in the development of skeletal muscle and heart. In this study, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was applied to analyze the genetic variations of the MYH₃ gene and verify the effect on growth and carcass traits in a total of 365 Qinchuan cattles. The PCR product was digested with some restriction enzyme and demonstrated the polymorphism in the population, the single nucleotide polymorphisms (SNPs) at nucleotides g. +1215T>C, g. +3377C>T, and g. +28625C>T were in linkage disequilibrium with each other. The result of haplotype analysis showed that nineteen different haplotypes were identified among the five SNPs. The statistical analyses indicated that the five SNPs were significant association with growth and carcass traits (P < 0.05, N = 365); whereas the five SNPs were no significant association between 18 combined genotypes of MYH₃ gene and growth and carcass traits. Taken together, our results provide the evidence that polymorphisms in MYH₃ are associated with growth and carcass traits in Qinchuan cattle, and may be used as a possible candidate for marker-assisted selection and management in beef cattle breeding program.
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Affiliation(s)
- Lijun Wang
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, People's Republic of China
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7
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Asaduzzaman M, Kinoshita S, Siddique BS, Asakawa S, Watabe S. Multiple cis-elements in the 5'-flanking region of embryonic/larval fast-type of the myosin heavy chain gene of torafugu, MYH(M743-2), function in the transcriptional regulation of its expression. Gene 2011; 489:41-54. [PMID: 21893174 DOI: 10.1016/j.gene.2011.08.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Revised: 08/10/2011] [Accepted: 08/17/2011] [Indexed: 01/10/2023]
Abstract
The myosin heavy chain gene, MYH(M743-2), is highly expressed in fast muscle fibers of torafugu embryos and larvae, suggesting its functional roles for embryonic and larval muscle development. However, the transcriptional regulatory mechanism involved in its expression remained unknown. Here, we analyzed the 2075bp 5'-flanking region of torafugu MYH(M743-2) to examine the spatial and temporal regulation by using transgenic and transient expression techniques in zebrafish embryos. Combining both transient and transgenic analyses, we demonstrated that the 2075bp 5'-flanking sequences was sufficient for its expression in skeletal, craniofacial and pectoral fin muscles. The immunohistochemical observation revealed that the zebrafish larvae from the stable transgenic line consistently expressed enhanced green fluorescent protein (EGFP) in fast muscle fibers. Promoter deletion analyses demonstrated that the minimum 468bp promoter region could direct MYH(M743-2) expression in zebrafish larvae. We discovered that the serum response factor (SRF)-like binding sites are required for promoting MYH(M743-2) expression and myoblast determining factor (MyoD) and myocyte enhancer factor-2 (MEF2) binding sites participate in the transcriptional control of MYH(M743-2) expression in fast skeletal muscles. We further discovered that MyoD binding sites, but not MEF2, participate in the transcriptional regulation of MYH(M743-2) expression in pectoral fin and craniofacial muscles. These results clearly demonstrated that multiple cis-elements in the 5'-flanking region of MYH(M743-2) function in the transcriptional control of its expression.
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Affiliation(s)
- Md Asaduzzaman
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan
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IIb or not IIb? Regulation of myosin heavy chain gene expression in mice and men. Skelet Muscle 2011; 1:5. [PMID: 21798083 PMCID: PMC3143903 DOI: 10.1186/2044-5040-1-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Accepted: 02/01/2011] [Indexed: 11/18/2022] Open
Abstract
Background While the myosin heavy chain IIb isoform (MyHC-IIb) is the predominant motor protein in most skeletal muscles of rats and mice, the messenger RNA (mRNA) for this isoform is only expressed in a very small subset of specialized muscles in adult large mammals, including humans. Results We identify the DNA sequences limiting MyHC-IIb expression in humans and explore the activation of this gene in human skeletal muscle. We demonstrate that the transcriptional activity of ~1.0 kb of the human MyHC-IIb promoter is greatly reduced compared to that of the corresponding mouse sequence in both mouse and human myotubes in vitro and show that nucleotide differences that eliminate binding sites for myocyte enhancer factor 2 (MEF2) and serum response factor (SRF) account for this difference. Despite these differences, we show that MyHC-IIb mRNA is expressed in fetal human muscle cells and that MyHC-IIb mRNA is significantly up-regulated in the skeletal muscle of Duchene muscular dystrophy patients. Conclusions These data identify the genetic basis for a key phenotypic difference between the muscles of large and small mammals, and demonstrate that mRNA expression of the MyHC-IIb gene can be re-activated in human limb muscle undergoing profound degeneration/regeneration.
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9
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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: 0.5] [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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10
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Shanely RA, Zwetsloot KA, Childs TE, Lees SJ, Tsika RW, Booth FW. IGF-I activates the mouse type IIb myosin heavy chain gene. Am J Physiol Cell Physiol 2009; 297:C1019-27. [PMID: 19657059 DOI: 10.1152/ajpcell.00169.2009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
IGF-I increases skeletal muscle mass, but whether IGF-I increases type IIb myosin heavy chain (MyHC) transcriptional activity is not known. C2C12 myotubes were cultured with or without IGF-I to determine whether IGF-I increases type IIb MyHC promoter activity, and if so, what region of the promoter might IGF-I signaling regulate. At differentiation days 3 and 4, IGF-I increased type IIb MyHC mRNA and mouse 3.0-kb type IIb MyHC promoter activity. Deletion construct studies identified a potential IGF-I-responsive region between 1.25 and 1.2 kb of the type IIb MyHC promoter, which contained an exact 6-bp T-cell factor/lymphoid enhancer factor (Tcf/Lef) binding site at position -1206 to -1201. Site-specific mutation of the putative Tcf/Lef binding site reduced IGF-I-induced 1.3-kb type IIb MyHC promoter activity. To identify potential IGF-I signaling molecules, the phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin and LY-294002 were both found to markedly attenuate IGF-I activation of the 1.3-kb type IIb MyHC promoter. Downstream signaling of IGF-I can phosphorylate and inactivate GSK-3beta, thereby enhancing beta-catenin protein. The GSK-3beta inhibitor, LiCl, dramatically enhanced IGF-I induction of the 1.3-kb type IIb MyHC promoter, and constitutively active GSK-3beta attenuated IGF-I-induced 1.3-kb type IIb MyHC promoter activity. Finally, IGF-I increased nuclear beta-catenin protein, and small interfering RNA knockdown of beta-catenin attenuated IGF-I-induced 1.3-kb type IIb MyHC promoter activity and type IIb MyHC mRNA. In summary, IGF-I stimulation of C2C12 myotubes increases mouse type IIb MyHC promoter activity, likely through signaling of PI3K, GSK-3beta, beta-catenin, and a Tcf/Lef binding site at -1,206 to -1,201 bp in the promoter.
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Affiliation(s)
- R Andrew Shanely
- Department of Biomedical Sciences, University of Missouri-Columbia, Columbia, Missouri 65211, USA
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11
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Shi H, Scheffler JM, Zeng C, Pleitner JM, Hannon KM, Grant AL, Gerrard DE. Mitogen-activated protein kinase signaling is necessary for the maintenance of skeletal muscle mass. Am J Physiol Cell Physiol 2009; 296:C1040-8. [DOI: 10.1152/ajpcell.00475.2008] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The signal transduction cascades that maintain muscle mass remain to be fully defined. Herein, we report that inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) signaling in vitro decreases myotube size and protein content after 3-day treatment with a MEK inhibitor. Neither p38 nor JNK inhibitors had any effect on myotube size or morphology. ERK1/2 inhibition also upregulated gene transcription of atrogin-1 and muscle-specific RING finger protein 1 and downregulated the phosphorylation of Akt and its downstream kinases. Forced expression of enhanced green fluorescent protein-tagged MAPK phosphatase 1 (MKP-1) in soleus and gastrocnemius muscles decreased both fiber size and reporter activity. This atrophic effect of MKP-1 was time dependent. Analysis of the reporter activity in vivo revealed that the activities of nuclear factor-κB and 26S proteasome were differentially activated in slow and fast muscles, suggesting muscle type-specific mechanisms may be utilized. Together, these findings suggest that MAPK signaling is necessary for the maintenance of skeletal muscle mass because inhibition of these signaling cascades elicits muscle atrophy in vitro and in vivo.
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12
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Tsika RW, Schramm C, Simmer G, Fitzsimons DP, Moss RL, Ji J. Overexpression of TEAD-1 in transgenic mouse striated muscles produces a slower skeletal muscle contractile phenotype. J Biol Chem 2008; 283:36154-67. [PMID: 18978355 DOI: 10.1074/jbc.m807461200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
TEA domain (TEAD) transcription factors serve important functional roles during embryonic development and in striated muscle gene expression. Our previous work has implicated a role for TEAD-1 in the fast-to-slow fiber-type transition in response to mechanical overload. To investigate whether TEAD-1 is a modulator of slow muscle gene expression in vivo, we developed transgenic mice expressing hemagglutinin (HA)-tagged TEAD-1 under the control of the muscle creatine kinase promoter. We show that striated muscle-restricted HA-TEAD-1 expression induced a transition toward a slow muscle contractile protein phenotype, slower shortening velocity (Vmax), and longer contraction and relaxation times in adult fast twitch extensor digitalis longus muscle. Notably, HA-TEAD-1 overexpression resulted in an unexpected activation of GSK-3alpha/beta and decreased nuclear beta-catenin and NFATc1/c3 protein. These effects could be reversed in vivo by mechanical overload, which decreased muscle creatine kinase-driven TEAD-1 transgene expression, and in cultured satellite cells by TEAD-1-specific small interfering RNA. These novel in vivo data support a role for TEAD-1 in modulating slow muscle gene expression.
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Affiliation(s)
- Richard W Tsika
- Department of Biochemistry, School of Medicine, University of Missouri, Columbia, Missouri 65211, USA.
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13
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Rinaldi C, Haddad F, Bodell PW, Qin AX, Jiang W, Baldwin KM. Intergenic bidirectional promoter and cooperative regulation of the IIx and IIb MHC genes in fast skeletal muscle. Am J Physiol Regul Integr Comp Physiol 2008; 295:R208-18. [PMID: 18434443 DOI: 10.1152/ajpregu.00134.2008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study investigated the dynamic regulation of IIx-IIb MHC genes in the fast white medial gastrocnemius (WMG) muscle in response to intermittent resistance exercise training (RE), a model associated with a rapid shift from IIb to IIx expression (11). We investigated the effect of 4 days of RE on the transcriptional activity across the skeletal MHC gene locus in the WMG in female Sprague-Dawley rats. Our results show that RE resulted in significant shifts from IIb to IIx observed at both the pre-mRNA and mRNA levels. An antisense RNA (xII NAT) was detected in the intergenic (IG) region between IIx and IIb, extending across the entire IIx gene and into its promoter. The expression of the xII NAT was positively correlated with IIb pre-mRNA (R = +0.8), and negatively correlated with IIx pre-mRNA (R = -0.8). Transcription mapping of the IIx-IIb IG region revealed the generation of sense IIb and xII NATs from a single promoter region. This bidirectional promoter is highly conserved among species and contains several regulatory elements that may be implicated in its regulation. These results suggest that the IIx and the IIb genes are physically and functionally linked via the bidirectional promoter. In order for the IIx MHC gene to be regulated, a feedback mechanism from the IG xII NAT is needed. In conclusion, the IG bidirectional promoter generating antisense RNA appears to be essential for the coordinated regulation of the skeletal muscle MHC genes during dynamic phenotype shifts.
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Affiliation(s)
- Chiara Rinaldi
- Physiology and Biophysics Department, University of California Irvine, Irvine, CA, USA
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14
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Shi H, Scheffler JM, Pleitner JM, Zeng C, Park S, Hannon KM, Grant AL, Gerrard DE. Modulation of skeletal muscle fiber type by mitogen‐activated protein kinase signaling. FASEB J 2008; 22:2990-3000. [DOI: 10.1096/fj.07-097600] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Hao Shi
- Department of Animal SciencesPurdue UniversityWest LafayetteIndianaUSA
| | | | | | - Caiyun Zeng
- Department of Animal SciencesPurdue UniversityWest LafayetteIndianaUSA
| | - Sungkwon Park
- Department of Animal SciencesPurdue UniversityWest LafayetteIndianaUSA
| | - Kevin M. Hannon
- Department of Basic Medical SciencesPurdue UniversityWest LafayetteIndianaUSA
| | - Alan L. Grant
- Department of Animal SciencesPurdue UniversityWest LafayetteIndianaUSA
| | - David E. Gerrard
- Department of Animal SciencesPurdue UniversityWest LafayetteIndianaUSA
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15
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Liang CS, Ikeda D, Kinoshita S, Shimizu A, Sasaki T, Asakawa S, Shimizu N, Watabe S. Myocyte enhancer factor 2 regulates expression of medaka Oryzias latipes fast skeletal myosin heavy chain genes in a temperature-dependent manner. Gene 2008; 407:42-53. [DOI: 10.1016/j.gene.2007.09.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Revised: 09/19/2007] [Accepted: 09/25/2007] [Indexed: 10/22/2022]
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16
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Kumai Y, Ito T, Miyamaru S, Yumoto E. Modulation of MyoD- and Ki-67-Positive Satellite Cells in the Short-Term Denervated Rat Thyroarytenoid Muscle. Laryngoscope 2007; 117:2063-7. [PMID: 17828047 DOI: 10.1097/mlg.0b013e318133a13c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES To evaluate the effects of short-term denervation on the kinetics of satellite cells (SCs) and myocytes in the rat thyroarytenoid (TA) muscle using immunohistochemistry for a myogenic regulatory factor, MyoD, and a cell proliferation marker, Ki-67. STUDY DESIGN Quantitative immunohistochemical assessment of MyoD and Ki-67 expression in SCs and myocytes after denervation. METHODS The left recurrent laryngeal nerve (RLN) was transected in 15 adult Wistar rats, which were sacrificed 1, 3, or 7 days after the treatment (n = 5, each group). Fluorescein immunostaining was used to visualize the localization of MyoD+ and Ki-67+ SCs in combination with M-cadherin immunostaining for detection of SCs. We examined the temporal changes of the ratios of MyoD+ and Ki-67+ SCs for all of the counted muscle fibers and M-cadherin+ cells in both the denervated and the contralateral control TA muscle. RESULTS On the denervated side, the TA muscle contained 3.8 +/- 0.4% MyoD+ SCs and 1.3 +/- 0.4% Ki-67+ SCs. Of the SCs, 22.6 +/- 2.2% were MyoD+, and 14.5 +/- 4.4% were Ki-67+, whereas SCs on the control side did not express these markers. CONCLUSIONS In the rat TA muscle, denervation induces SC activation, and some SCs enter the cell cycle, whereas others are involved in the differentiation process. The number of activated SCs is relatively small compared with all M-cadherin+ SCs. Therefore, SCs might be good targets for a therapy to prevent TA muscle atrophy after RLN paralysis.
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Affiliation(s)
- Yoshihiko Kumai
- Department of Otolaryngology Head and Neck Surgery, Kumamoto University, Graduate School of Medicine, Honjo, Kumamoto, Japan.
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17
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Characterization and functional analysis of the 5' flanking region of myosin light chain-2 gene expressed in white muscle of the gilthead sea bream (Sparus aurata). COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2007; 2:187-99. [PMID: 20483292 DOI: 10.1016/j.cbd.2007.04.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Revised: 04/01/2007] [Accepted: 04/02/2007] [Indexed: 11/22/2022]
Abstract
The promoter region ( approximately 1400 bp) of myosin light chain 2 gene of fast skeletal muscle from the marine fish Sparus aurata was cloned, sequenced and characterized. It contains a consensus sequence for TATA box, six perfect E-boxes known as binding sites to myogenic basic helix-loop-helix transcription factors and four putative MEF2-binding sites. Three genomic fragments (truncated at their upstream region) of 244, 650 and 1400 bp showed promoter activity evidenced by muscle-specific reporter gene activity using transient expression of green fluorescent protein in microinjected zebrafish embryos and in skeletal muscle of S. aurata fry following intramuscularly injection of plasmid DNA. The three genomic fragments also directed luciferase activity in skeletal muscle of S. aurata fry following intramuscularly injection of plasmid DNA showing a 60 to 150-fold higher luciferase activity compared to that obtained with pGL3-Basic. These experiments show that the three genomic fragments are functional muscle-specific promoters which will be useful for directing myostatin and follistatin expression in fish muscle in order to study their effect on fish muscle growth.
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18
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Shi H, Zeng C, Ricome A, Hannon KM, Grant AL, Gerrard DE. Extracellular signal-regulated kinase pathway is differentially involved in beta-agonist-induced hypertrophy in slow and fast muscles. Am J Physiol Cell Physiol 2006; 292:C1681-9. [PMID: 17151143 DOI: 10.1152/ajpcell.00466.2006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The molecular mechanisms controlling beta-adrenergic receptor agonist (BA)-induced skeletal muscle hypertrophy are not well known. We presently report that BA exerts a distinct muscle- and muscle fiber type-specific hypertrophy. Moreover, we have shown that pharmacologically or genetically attenuating extracellular signal-regulated kinase (ERK) signaling in muscle fibers resulted in decreases (P < 0.05) in fast but not slow fiber type-specific reporter gene expressions in response to BA exposure in vitro and in vivo. Consistent with these data, forced expression of MAPK phosphatase 1, a nuclear protein that dephosphorylates ERK1/2, in fast-twitch skeletal muscle ablated (P < 0.05) the hypertrophic effects of BA feeding (clenbuterol, 20 parts per million in water) in vivo. Further analysis has shown that BA-induced phosphorylation and activation of ERK occurred to a greater (P < 0.05) extent in fast myofibers than in slow myofibers. Analysis of the basal level of ERK activity in slow and fast muscles revealed that ERK1/2 is activated to a greater extent in fast- than in slow-twitch muscles. These data indicate that ERK signaling is differentially involved in BA-induced hypertrophy in slow and fast skeletal muscles, suggesting that the increased abundance of phospho-ERK1/2 and ERK activity found in fast-twitch myofibers, compared with their slow-twitch counterparts, may account, at least in part, for the fiber type-specific hypertrophy induced by BA stimulation. These data suggest that fast myofibers are pivotal in the adaptation of muscle to environmental cues and that the mechanism underlying this change is partially mediated by the MAPK signaling cascade.
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MESH Headings
- Adrenergic beta-Agonists/pharmacology
- Animals
- Cell Cycle Proteins/genetics
- Cell Cycle Proteins/metabolism
- Cell Line
- Clenbuterol
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Dual Specificity Phosphatase 1
- Extracellular Signal-Regulated MAP Kinases/metabolism
- Gene Expression/drug effects
- Hypertrophy
- Immediate-Early Proteins/genetics
- Immediate-Early Proteins/metabolism
- Isoproterenol/pharmacology
- MAP Kinase Signaling System/drug effects
- Male
- Mice
- Mice, Inbred C57BL
- Mitogen-Activated Protein Kinase 1/metabolism
- Mitogen-Activated Protein Kinase 3/metabolism
- Muscle Fibers, Fast-Twitch/drug effects
- Muscle Fibers, Fast-Twitch/metabolism
- Muscle Fibers, Fast-Twitch/pathology
- Muscle Fibers, Slow-Twitch/drug effects
- Muscle Fibers, Slow-Twitch/metabolism
- Muscle Fibers, Slow-Twitch/pathology
- Muscular Diseases/chemically induced
- Muscular Diseases/genetics
- Muscular Diseases/metabolism
- Muscular Diseases/pathology
- Organ Size
- Phosphoprotein Phosphatases/genetics
- Phosphoprotein Phosphatases/metabolism
- Phosphorylation
- Protein Phosphatase 1
- Protein Tyrosine Phosphatases/genetics
- Protein Tyrosine Phosphatases/metabolism
- Rats
- Rats, Sprague-Dawley
- Transfection
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Affiliation(s)
- H Shi
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA
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19
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Cuellar H, Kim JA, Unguez GA. Evidence of post-transcriptional regulation in the maintenance of a partial muscle phenotype by electrogenic cells of S. macrurus. FASEB J 2006; 20:2540. [PMID: 17077280 DOI: 10.1096/fj.06-6474fje] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Electrocytes, the current-producing cells of electric organs (EOs) in electric fish, are unique in that they derive from striated muscle and they possess biochemical characteristics of both muscle and non-muscle cells. In the freshwater teleost Sternopygus macrurus, electrocytes are multinucleated cells that do not contract yet retain expression of some proteins common to skeletal muscle cells. Given the role that transcriptional regulation plays in the activation of the myogenic program in vertebrates, we examined the expression patterns of several genes associated with multiple functions of skeletal muscle in mature electrocytes of S. macrurus. Our expression analyses detected transcripts for alpha-actin, alpha-acetylcholine (ACh) receptor (alpha-AChR), desmin, muscle creatine kinase (MCK), myosin heavy chain (MHC) isoforms, titin, tropomyosin, and troponin-T genes in the EO. However, immunolabeling studies revealed that electrocytes do not contain MCK, MHCs, or tropomyosin or troponin-T proteins. These results underscore the contribution of gene regulatory mechanisms in the maintenance of the muscle-like phenotype of EO that may be transcriptional-independent. We also report the classification and frequency of distinct transcripts from a random selection of 420 clones from an EO cDNA library. This is the first characterization of expressed genes in an EO, and it is an important step toward identifying mechanisms that affect different muscle protein systems for the evolution of highly specialized noncontractile tissues. Evidence of post-transcriptional regulation in the maintenance of a partial muscle phenotype by electrogenic cells of S. macrurus.
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Affiliation(s)
- Heriberto Cuellar
- Department of Biology, Foster Hall, New Mexico State University, Las Cruces, NM 88003, USA
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20
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Lees SJ, Rathbone CR, Booth FW. Age-associated decrease in muscle precursor cell differentiation. Am J Physiol Cell Physiol 2005; 290:C609-15. [PMID: 16192302 DOI: 10.1152/ajpcell.00408.2005] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Muscle precursor cells (MPCs) are required for the regrowth, regeneration, and/or hypertrophy of skeletal muscle, which are deficient in sarcopenia. In the present investigation, we have addressed the issue of age-associated changes in MPC differentiation. MPCs, including satellite cells, were isolated from both young and old rat skeletal muscle with a high degree of myogenic purity (>90% MyoD and desmin positive). MPCs isolated from skeletal muscle of 32-mo-old rats exhibited decreased differentiation into myotubes and demonstrated decreased myosin heavy chain (MHC) and muscle creatine kinase (CK-M) expression compared with MPCs isolated from 3-mo-old rats. p27(Kip1) is a cyclin-dependent kinase inhibitor that has been shown to enhance muscle differentiation in culture. Herein we describe our finding that p27(Kip1) protein was lower in differentiating MPCs from skeletal muscle of 32-mo-old rats than in 3-mo-old rat skeletal muscle. Although MHC and CK-M expression were approximately 50% lower in differentiating MPCs isolated from 32-mo-old rats, MyoD protein content was not different and myogenin protein concentration was twofold higher. These data suggest that there are inherent differences in cell signaling during the transition from cell cycle arrest to the formation of myotubes in MPCs isolated from sarcopenic muscle. Furthermore, there is an age-associated decrease in muscle-specific protein expression in differentiating MPCs despite normal MyoD and elevated myogenin levels.
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Affiliation(s)
- Simon J Lees
- Dept. of Biomedical Sciences, Univ. of Missouri-Columbia, Veterinary Medicine Bldg., 1600 East Rollins, Rm. E102, Columbia, MO 65211, USA.
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21
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De Arcangelis V, Coletti D, Canato M, Molinaro M, Adamo S, Reggiani C, Naro F. Hypertrophy and transcriptional regulation induced in myogenic cell line L6-C5 by an increase of extracellular calcium. J Cell Physiol 2005; 202:787-95. [PMID: 15389566 DOI: 10.1002/jcp.20174] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Calcium plays a pivotal role in the establishment of the differentiated phenotype in myogenic cells but the involved molecular mechanisms are still matter of debate. Here we studied the effects of exposing L6-C5 myogenic cells to high extracellular Ca2+ concentration ([Ca2+]o), which induces an increase of intracellular calcium ([Ca2+]i) without involving Ca2+ release from the intracellular stores but exclusively due to plasma membrane influx (Naro et al., 2003). Exposure of L6-C5 cells to [Ca2+]o up to 20 mM for 30 min, before shifting them into a differentiative medium, induced the appearance of multinucleated, myosin-positive myotubes, much larger than in control cells with an increased protein/DNA ratio. These large myotubes showed nuclear accumulation of the hypertrophy marker GATA-2. The hypertrophic growth of these cells was blocked by cyclosporin A (CsA), FK506, or overexpression of a calcineurin-dominant negative protein, suggesting the involvement in this process of the Ca2+ responsive phosphatase calcineurin. Furthermore, transient exposure of L6-C5 cells to high [Ca2+]o increased the expression of luciferase reporter driven by myoglobin (Mb) and beta-MHC promoters but not IIB-MHC and MCK promoters. Luciferase transcription driven by CK promoter was, instead, enhanced by mobilizing Ca2+ from the intracellular stores. These data indicate that a transient increase of [Ca2+]i due to plasma-membrane influx is sufficient to induce a hypertrophic phenotype and an increased expression of slow-fiber genes but not fast-fiber genes.
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Affiliation(s)
- V De Arcangelis
- Dipartimento di Istologia ed Embriologia Medica, Università di Roma La Sapienza, Italy
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22
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Giger JM, Haddad F, Qin AX, Zeng M, Baldwin KM. Effect of unloading on type I myosin heavy chain gene regulation in rat soleus muscle. J Appl Physiol (1985) 2004; 98:1185-94. [PMID: 15591287 DOI: 10.1152/japplphysiol.01099.2004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Slow-twitch soleus, a weight-bearing hindlimb muscle, predominantly expresses the type I myosin heavy chain (MHC) isoform. However, under unloading conditions, a transition in MHC expression occurs from slow type I toward the fast-type isoforms. Transcriptional processes are believed to be involved in this adaptation. To test the hypothesis that the downregulation of MHC1 in soleus muscle following unloading is controlled through cis element(s) in the proximal region of the promoter, the MHC1 promoter was injected into soleus muscles of control rats and those subjected to 7 days of hindlimb suspension. Mutation analyses of six putative regulatory elements within the -408-bp region demonstrated that three elements, an A/T-rich, the proximal muscle-type CAT (betae3), and an E-box (-63 bp), play an important role in the basal level of MHC1 gene activity in the control soleus and function as unloading-responsive elements. Gel mobility shift assays revealed a diminished level of complex formation of the betae3 and E-box probes with nuclear extract from hindlimb suspension soleus compared with control soleus. Supershift assays indicated that transcriptional enhancer factor 1 and myogenin factors bind the betae3 and E-box elements, respectively, in the control soleus. Western blots showed that the relative concentrations of the transcriptional enhancer factor 1 and myogenin factors were significantly attenuated in the unloaded soleus compared with the control muscle. We conclude that the downregulation of MHC1 in response to unloading is due, in part, to a significant decrease in the concentration of these transcription factors available for binding the positive regulatory elements.
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Affiliation(s)
- Julia M Giger
- Dept. of Physiology and Biophysics, Univ. of California-Irvine, D-346, Med Sci I, Irvine, CA 92697, USA
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23
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Akimoto T, Sorg BS, Yan Z. Real-time imaging of peroxisome proliferator-activated receptor-γ coactivator-1α promoter activity in skeletal muscles of living mice. Am J Physiol Cell Physiol 2004; 287:C790-6. [PMID: 15151904 DOI: 10.1152/ajpcell.00425.2003] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In response to sustained increase in contractile activity, mammalian skeletal muscle undergoes adaptation with enhanced mitochondrial biogenesis and fiber type switching. The peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) was recently identified as a key regulator for these adaptive processes. To investigate the sequence elements in the PGC-1α gene that are responsible for activity-dependent transcriptional activation, we have established a unique system to analyze promoter activity in skeletal muscle of living mice. Expression of PGC-1α-firefly luciferase reporter gene in mouse tibialis anterior muscle transfected by electric pulse-mediated gene transfer was assessed repeatedly in the same muscle by using optical bioluminescence imaging analysis before and after low-frequency (10 Hz) motor nerve stimulation. Nerve stimulation (2 h) resulted in a transient 3-fold increase ( P < 0.05) in PGC-1α promoter activity along with a 1.6-fold increase ( P < 0.05) in endogenous PGC-1α mRNA. Mutation of two consensus myocyte enhancer factor 2 (MEF2) binding sites (−2901 and −1539) or a cAMP response element (CRE) (−222) completely abolished nerve stimulation-induced increase in PGC-1α promoter activity. These findings provide direct evidence that contractile activity-induced PGC-1α promoter activity in skeletal muscle is dependent on the MEF2 and the CRE sequence elements. The experimental methods used in the present study have general applicability to studies of gene regulation in muscle.
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Affiliation(s)
- Takayuki Akimoto
- Division of Cardiology, Dept. of Medicine, Duke University Medical Center, 4321 Medical Park Drive, Suite 200, Duke Univ. Independence Park Facility, Durham, NC 27704, USA
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24
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Acharyya S, Ladner KJ, Nelsen LL, Damrauer J, Reiser PJ, Swoap S, Guttridge DC. Cancer cachexia is regulated by selective targeting of skeletal muscle gene products. J Clin Invest 2004; 114:370-8. [PMID: 15286803 PMCID: PMC484974 DOI: 10.1172/jci20174] [Citation(s) in RCA: 197] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2003] [Accepted: 06/03/2004] [Indexed: 02/06/2023] Open
Abstract
Cachexia is a syndrome characterized by wasting of skeletal muscle and contributes to nearly one-third of all cancer deaths. Cytokines and tumor factors mediate wasting by suppressing muscle gene products, but exactly which products are targeted by these cachectic factors is not well understood. Because of their functional relevance to muscle architecture, such targets are presumed to represent myofibrillar proteins, but whether these proteins are regulated in a general or a selective manner is also unclear. Here we demonstrate, using in vitro and in vivo models of muscle wasting, that cachectic factors are remarkably selective in targeting myosin heavy chain. In myotubes and mouse muscles, TNF-alpha plus IFN-gamma strongly reduced myosin expression through an RNA-dependent mechanism. Likewise, colon-26 tumors in mice caused the selective reduction of this myofibrillar protein, and this reduction correlated with wasting. Under these conditions, however, loss of myosin was associated with the ubiquitin-dependent proteasome pathway, which suggests that mechanisms used to regulate the expression of muscle proteins may be cachectic factor specific. These results shed new light on cancer cachexia by revealing that wasting does not result from a general downregulation of muscle proteins but rather is highly selective as to which proteins are targeted during the wasting state.
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Affiliation(s)
- Swarnali Acharyya
- Division of Human Cancer Genetics, Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University, Columbus 43210, USA
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25
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Acharyya S, Ladner KJ, Nelsen LL, Damrauer J, Reiser PJ, Swoap S, Guttridge DC. Cancer cachexia is regulated by selective targeting of skeletal muscle gene products. J Clin Invest 2004. [DOI: 10.1172/jci200420174] [Citation(s) in RCA: 351] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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26
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McCullagh KJA, Calabria E, Pallafacchina G, Ciciliot S, Serrano AL, Argentini C, Kalhovde JM, Lømo T, Schiaffino S. NFAT is a nerve activity sensor in skeletal muscle and controls activity-dependent myosin switching. Proc Natl Acad Sci U S A 2004; 101:10590-5. [PMID: 15247427 PMCID: PMC489979 DOI: 10.1073/pnas.0308035101] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Calcineurin (Cn) signaling has been implicated in nerve activity-dependent fiber type specification in skeletal muscle, but the downstream effector pathway has not been established. We have investigated the role of the transcription factor nuclear factor of activated T cells (NFAT), a major target of Cn, by using an in vivo transfection approach in regenerating and adult rat muscles. NFAT transcriptional activity was monitored with two different NFAT-dependent reporters and was found to be higher in slow compared to fast muscles. NFAT activity is decreased by denervation in slow muscles and is increased by electrostimulation of denervated muscles with a tonic low-frequency impulse pattern, mimicking the firing pattern of slow motor neurons, but not with a phasic high-frequency pattern typical of fast motor neurons. To determine the role of NFAT, we transfected regenerating and adult rat muscles with a plasmid coding for VIVIT, a specific peptide inhibitor of Cn-mediated NFAT activation. VIVIT was found to block the expression of slow myosin heavy chain (MyHC-slow) induced by slow motor neuron activity in regenerating slow soleus muscle and to inhibit the expression of MyHC-slow transcripts and the activity of a MyHC-slow promoter in adult soleus. The role of NFAT was confirmed by the finding that a constitutively active NFATc1 mutant stimulates the MyHC-slow, inhibits the fast MyHC-2B promoter in adult fast muscles, and induces MyHC-slow expression in regenerating muscles. These results support the notion that Cn-NFAT signaling acts as a nerve activity sensor in skeletal muscle in vivo and controls nerve activity-dependent myosin switching.
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Affiliation(s)
- Karl J A McCullagh
- Department of Biomedical Sciences, Consiglio Nazionale delle Ricerche Institute of Neurosciences, University of Padua, 35121 Padua, Italy
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27
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Salerno MS, Thomas M, Forbes D, Watson T, Kambadur R, Sharma M. Molecular analysis of fiber type-specific expression of murine myostatin promoter. Am J Physiol Cell Physiol 2004; 287:C1031-40. [PMID: 15189813 DOI: 10.1152/ajpcell.00492.2003] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Myostatin is a negative regulator of muscle growth, and absence of the functional myostatin protein leads to the heavy muscle phenotype in both mouse and cattle. Although the role of myostatin in controlling muscle mass is established, little is known of the mechanisms regulating the expression of the myostatin gene. In this study, we have characterized the murine myostatin promoter in vivo. Various constructs of the murine myostatin promoter were injected into the quadriceps muscle of mice, and the reporter luciferase activity was analyzed. The results indicate that of the seven E-boxes present in the 2.5-kb fragment of the murine myostatin promoter, the E5 E-box plays an important role in the regulation of promoter activity in vivo. Furthermore, the in vitro studies demonstrated that MyoD preferentially binds and upregulates the murine myostatin promoter activity. We also analyzed the activity of the bovine and murine promoters in murine skeletal muscle and showed that, despite displaying comparable levels of activity in murine myoblast cultures, bovine myostatin promoter activity is much weaker than murine myostatin promoter in mice. Finally, we demonstrate that in vivo, the 2.5-kb region of the murine myostatin promoter is sufficient to drive the activity of the reporter gene in a fiber type-specific manner.
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Affiliation(s)
- Mônica Senna Salerno
- Animal Genomics, AgResearch, Ruakura Research Centre, Private Bag 3123, East St., Hamilton, New Zealand
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28
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Riquet FB, Rodriguez M, Guigal N, Dromaint S, Naime I, Boutin JA, Galizzi JP. In vivo characterisation of the human UCP3 gene minimal promoter in mice tibialis anterior muscles. Biochem Biophys Res Commun 2004; 311:583-91. [PMID: 14623310 DOI: 10.1016/j.bbrc.2003.10.034] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Transcriptional mechanisms controlling human UCP3 gene expression in skeletal muscle remain poorly understood. Experiments based on plasmid electrotransfer into tibialis anterior muscle of C57/BL6 male mice were set up in order to functionally analyze the hUCP3 gene promoter. These transfection experiments showed that a 6300 bp region upstream of the transcription initiation site was sufficient to mediate maximal promoter activity. Further analyses with a series of 5(')-deleted constructs demonstrated that the hUCP3 gene minimal promoter was located between nucleotides -284 and -40. Furthermore, an essential region was identified between nucleotides -284 and -224. The analysis of this region revealed a putative response element for PPAR located between nucleotides -281 and -269. Finally, mutations of potential cis-acting elements within the hUCP3 minimal promoter showed the presence of two TATA boxes (-198/-194 and -45/-41) required for constitutive UCP3 gene expression. To our knowledge, this is the first time that molecular characterization of the UCP3 promoter has been achieved using an in vivo experimental model.
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Affiliation(s)
- Franck B Riquet
- Institut de Recherches Servier, Division de Pharmacologie Moléculaire et Cellulaire, 125, Chemin de Ronde, 78290 Croissy-sur-Seine, France
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29
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Hyatt JPK, Roy RR, Baldwin KM, Edgerton VR. Nerve activity-independent regulation of skeletal muscle atrophy: role of MyoD and myogenin in satellite cells and myonuclei. Am J Physiol Cell Physiol 2003; 285:C1161-73. [PMID: 12839833 DOI: 10.1152/ajpcell.00128.2003] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Electrical activity is thought to be the primary neural stimulus regulating muscle mass, expression of myogenic regulatory factor genes, and cellular activity within skeletal muscle. However, the relative contribution of neural influences that are activity-dependent and -independent in modulating these characteristics is unclear. Comparisons of denervation (no neural influence) and spinal cord isolation (SI, neural influence with minimal activity) after 3, 14, and 28 days of treatment were used to demonstrate whether there are neural influences on muscle that are activity independent. Furthermore, the effects of these manipulations were compared for a fast ankle extensor (medial gastrocnemius) and a fast ankle flexor (tibialis anterior). The mass of both muscles plateaued at approximately 60% of control 2 wk after SI, whereas both muscles progressively atrophied to <25% of initial mass at this same time point after denervation. A rapid increase in myogenin and, to a lesser extent, MyoD mRNAs and proteins was observed in denervated and SI muscles: at the later time points, these myogenic regulatory factors remained elevated in denervated, but not in SI, muscles. 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. Mitotic activity of satellite and connective tissue cells also was consistently lower in SI than in denervated muscles. These results demonstrate a neural effect independent of electrical activity that 1) helps preserve muscle mass, 2) regulates muscle-specific genes, and 3) potentially spares the satellite cell pool in inactive muscles.
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Affiliation(s)
- Jon-Philippe K Hyatt
- Department of Physiological Science, University of California-Los Angeles, 621 Charles E. Young Drive, Los Angeles, CA 90095, USA
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30
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Stevenson EJ, Giresi PG, Koncarevic A, Kandarian SC. Global analysis of gene expression patterns during disuse atrophy in rat skeletal muscle. J Physiol 2003; 551:33-48. [PMID: 12844509 PMCID: PMC2343139 DOI: 10.1113/jphysiol.2003.044701] [Citation(s) in RCA: 216] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Muscular inactivity leads to atrophy, weakness, and decreased fatigue resistance. In order to provide a window into the dynamic processes that underlie muscle atrophy, we performed global gene expression analysis of rat soleus muscles using Affymetrix GeneChips at 1, 4, 7 and 14 days of hindlimb unloading. Expression of 309 known genes was significantly changed by at least 2-fold (212 upregulated, 97 downregulated). K-means clustering was used to divide these genes into co-regulated clusters based on the similarity of temporal expression patterns. This allowed the development of a timeline of the atrophy process with respect to the behaviour of genes in a broad array of functional categories. Regulatory genes were often upregulated early, in either a transient or sustained manner, but they also populated clusters with later patterns of activation, suggesting different phases of molecular adaptations. Other early events were the activation of ubiquitination genes and downregulation of protein chaperones. In comparison, clusters representing slightly delayed activation patterns included genes involved in fast contraction, glycolysis, translational inhibition, oxidative stress, protein degradation, and amino acid catabolism. Downregulated genes exhibited fewer unique expression patterns and included structural and regulatory genes of the extracellular matrix and cytoskeleton, and genes that define a slow-oxidative phenotype. Other novel findings include the tight co-activation of proteasome subunit and ubiquitination genes, differential regulation of serine proteases and serine protease inhibitors, and the identification of transcriptional, signalling, growth and cell cycle genes that probably play a role in the atrophy process. The present work has uncovered temporal patterns of gene expression that highlight the molecular processes that underlie muscle atrophy and provide new avenues for study.
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Affiliation(s)
- Eric J Stevenson
- Department of Health Sciences, Boston University, 635 Commonwealth Avenue, Boston, MA 02215, USA
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31
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Green CD. Psychology strikes out: Coleman R. Griffith and the Chicago Cubs. HISTORY OF PSYCHOLOGY 2003; 6:267-283. [PMID: 14506818 DOI: 10.1037/1093-4510.6.3.267] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Coleman R. Griffith is widely known as the father of sport psychology in the United States. He directed the Research in Athletics Laboratory at the University of Illinois in the late 1920s and early 1930s and produced many articles and books on the psychology of sport. In 1938, P. K. Wrigley, owner of the Chicago Cubs, hired him to help improve the team's performance. Griffith and an assistant filmed and measured the players' skills, attempting to build a "scientific" training program for the team. Many of Griffith's subjects, most notably the managers, objected to his interference (as they saw it) and attempted to undermine his work. Griffith wrote more than 600 pages of reports on his work with the Cubs between 1938 and 1940. This article examines the content of those reports and the reasons for the failure of Griffith's project.
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Affiliation(s)
- Christopher D Green
- Department of Psychology, York University, Toronto, Ontario M3J 1P3, Canada.
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32
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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: 1.4] [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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33
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Abstract
SUMMARY
Extraocular muscle exhibits higher-velocity and lower-tension contractions than other vertebrate striated muscles. These distinctive physiological properties are associated with the expression of a novel extraocular myosin heavy chain (MYH). Encoded by the MYH13 gene, the extraocular myosin heavy chain is a member of the fast/developmental MYH gene cluster on human chromosome 17 and the syntenic MYH cluster on mouse chromosome 11. Comparison of cDNA sequences reveals that MYH13 also encodes the atypical MYH identified in laryngeal muscles, which have similar fast contractile properties. Comparing the MYH13 sequence with the other members of the fast/developmental cluster, the slow/cardiac MYH genes and two orphan skeletal MYH genes in the human genome provides insights into the origins of specialization in striated muscle myosins. Specifically, these studies indicate (i) that the extraocular myosin is not derived from the adult fast skeletal muscle myosins, but was the first member of the fast/developmental MYH gene cluster to diverge and specialize, (ii) that the motor and rod domains of the MYH13 have evolved under different selective pressures and (iii) that the MYH13 gene has been largely insulated from genomic events that have shaped other members of the fast/developmental cluster. In addition, phylogenetic footprinting suggests that regulation of the extraocular MYH gene is not governed primarily by myogenic factors, but by a hierarchical network of regulatory factors that relate its expression to the development of extraocular muscles.
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Affiliation(s)
- Fred Schachat
- Department of Cell Biology, Division of Physiology, Duke University Medical School, Durham, NC 27710, USA.
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34
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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: 1.1] [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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35
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Allen DL, Sartorius CA, Sycuro LK, Leinwand LA. Different pathways regulate expression of the skeletal myosin heavy chain genes. J Biol Chem 2001; 276:43524-33. [PMID: 11551968 DOI: 10.1074/jbc.m108017200] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mammalian skeletal muscles are a mosaic of different fiber types largely defined by differential myosin heavy chain (MyHC) expression. Little is known about the molecular mechanisms regulating expression of the MyHC gene family members in different fiber types. In this work, we identified several cis- and trans-elements that regulate expression of the three adult fast MyHC genes. Despite multiple DNA-binding motifs for well characterized muscle transcription factors upstream of all three fast MyHC genes, expression of MyoD/Myf-5, calcineurin, or NFAT3 had different effects on the three promoters. MyoD or Myf-5 overexpression preferentially activated the IIb promoter, whereas NFAT or activated calcineurin overexpression preferentially activated the IIa promoter. Calcineurin had a 50-100-fold stimulatory effect on the IIa promoter, and the known downstream effectors of calcineurin (myocyte enhancer factor-2 and NFAT) cannot completely account for this activation. Finally, we identified two elements critical for regulating MyHC-IId/x expression: a 130-base pair enhancer element and a CArG-like element that inhibited IId/x promoter activity in vitro. Thus, we have found specific regulatory pathways that are distinct for the three adult fast MyHC genes. These elements are logical candidates for fiber-specific control of skeletal muscle gene expression in vivo.
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Affiliation(s)
- D L Allen
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309-0347, USA
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36
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Horton MJ, Brandon CA, Morris TJ, Braun TW, Yaw KM, Sciote JJ. Abundant expression of myosin heavy-chain IIB RNA in a subset of human masseter muscle fibres. Arch Oral Biol 2001; 46:1039-50. [PMID: 11543711 PMCID: PMC3848045 DOI: 10.1016/s0003-9969(01)00066-8] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Type IIB fast fibres are typically demonstrated in human skeletal muscle by histochemical staining for the ATPase activity of myosin heavy-chain (MyHC) isoforms. However, the monoclonal antibody specific for the mammalian IIB isoform does not detect MyHC IIB protein in man and MyHC IIX RNA is found in histochemically identified IIB fibres, suggesting that the IIB protein isoform may not be present in man; if this is not so, jaw-closing muscles, which express a diversity of isoforms, are likely candidates for their presence. ATPase histochemistry, immunohistochemistry polyacrylamide gel electrophoresis and in situ hybridization, which included a MyHC IIB-specific mRNA riboprobe, were used to compare the composition and RNA expression of MyHC isoforms in a human jaw-closing muscle, the masseter, an upper limb muscle, the triceps, an abdominal muscle, the external oblique, and a lower limb muscle, the gastrocnemius. The external oblique contained a mixture of histochemically defined type I, IIA and IIB fibres distributed in a mosaic pattern, while the triceps and gastrocnemius contained only type I and IIA fibres. Typical of limb muscle fibres, the MyHC I-specific mRNA probes hybridized with histochemically defined type I fibres, the IIA-specific probes with type IIA fibres and the IIX-specific probes with type IIB fibres. The MyHC IIB mRNA probe hybridized only with a few histochemically defined type I fibres in the sample from the external oblique; in addition to this IIB message, these fibres also expressed RNAs for MyHC I, IIA and IIX. MyHC IIB RNA was abundantly expressed in histochemical and immunohistochemical type IIA fibres of the masseter, together with transcripts for IIA and in some cases IIX. No MyHC IIB protein was detected in fibres and extracts of either the external oblique or masseter by immunohistochemistry, immunoblotting and electrophoresis. Thus, IIB RNA, but not protein, was found in the fibres of two different human skeletal muscles. It is believed this is the first report of the substantial expression of IIB mRNA in man as demonstrated in a subset of masseter fibres, but rarely in limb muscle, and in only a few fibres of the external oblique. These findings provide further evidence for the complexity of myosin gene expression, especially in jaw-closing muscles.
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MESH Headings
- Abdominal Muscles/metabolism
- Abdominal Muscles/ultrastructure
- Adenosine Triphosphatases
- Adolescent
- Adult
- Electrophoresis, Polyacrylamide Gel
- Female
- Gene Expression
- Humans
- Immunoblotting
- In Situ Hybridization
- Male
- Masseter Muscle/metabolism
- Masseter Muscle/ultrastructure
- Middle Aged
- Muscle Fibers, Fast-Twitch/metabolism
- Muscle Fibers, Fast-Twitch/ultrastructure
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/ultrastructure
- Muscle Fibers, Slow-Twitch/metabolism
- Muscle Fibers, Slow-Twitch/ultrastructure
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/ultrastructure
- Myosin Heavy Chains/analysis
- Myosin Heavy Chains/genetics
- Myosin Type I/analysis
- Myosin Type I/genetics
- Myosin Type II/analysis
- Myosin Type II/genetics
- Nonmuscle Myosin Type IIA/analysis
- Nonmuscle Myosin Type IIA/genetics
- Nonmuscle Myosin Type IIB/analysis
- Nonmuscle Myosin Type IIB/genetics
- Phenotype
- Protein Isoforms/analysis
- Protein Isoforms/genetics
- RNA Probes
- RNA, Messenger/analysis
- RNA, Messenger/genetics
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Affiliation(s)
- Michael J. Horton
- Department of Orthodontics, School of Dental Medicine, University of Pittsburgh, 3501 Terrace Street, Pittsburgh, PA 15261, USA
| | - Carla A. Brandon
- Department of Orthodontics, School of Dental Medicine, University of Pittsburgh, 3501 Terrace Street, Pittsburgh, PA 15261, USA
| | - Terence J. Morris
- Department of Orthodontics, School of Dental Medicine, University of Pittsburgh, 3501 Terrace Street, Pittsburgh, PA 15261, USA
| | - Thomas W. Braun
- Department of Oral Surgery, School of Dental Medicine, University of Pittsburgh, 3501 Terrace Street, Pittsburgh, PA 15261, USA
| | - Kenneth M. Yaw
- Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, 3471 Fifth Ave., Pittsburgh, PA 15213, USA
| | - James J. Sciote
- Department of Orthodontics, School of Dental Medicine, University of Pittsburgh, 3501 Terrace Street, Pittsburgh, PA 15261, USA
- Corresponding author. Tel.: +1-412-648-8419; fax: +1-412-648-8817. (J.J. Sciote)
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37
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Swoap SJ, Hunter RB, Stevenson EJ, Felton HM, Kansagra NV, Lang JM, Esser KA, Kandarian SC. The calcineurin-NFAT pathway and muscle fiber-type gene expression. Am J Physiol Cell Physiol 2000; 279:C915-24. [PMID: 11003571 DOI: 10.1152/ajpcell.2000.279.4.c915] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To test for a role of the calcineurin-NFAT (nuclear factor of activated T cells) pathway in the regulation of fiber type-specific gene expression, slow and fast muscle-specific promoters were examined in C2C12 myotubes and in slow and fast muscle in the presence of calcineurin or NFAT2 expression plasmids. Overexpression of active calcineurin in myotubes induced both fast and slow muscle-specific promoters but not non-muscle-specific reporters. Overexpression of NFAT2 in myotubes did not activate muscle-specific promoters, although it strongly activated an NFAT reporter. Thus overexpression of active calcineurin activates transcription of muscle-specific promoters in vitro but likely not via the NFAT2 transcription factor. Slow myosin light chain 2 (MLC2) and fast sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA1) reporter genes injected into rat soleus (slow) and extensor digitorum longus (EDL) (fast) muscles were not activated by coinjection of activated calcineurin or NFAT2 expression plasmids. However, an NFAT reporter was strongly activated by overexpression of NFAT2 in both muscle types. Calcineurin and NFAT protein expression and binding activity to NFAT oligonucleotides were different in slow vs. fast muscle. Taken together, these results indicate that neither calcineurin nor NFAT appear to have dominant roles in the induction and/or maintenance of slow or fast fiber type in adult skeletal muscle. Furthermore, different pathways may be involved in muscle-specific gene expression in vitro vs. in vivo.
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Affiliation(s)
- S J Swoap
- Department of Biology, Williams College, Williamstown, Massachusetts 01267, USA
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38
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Briggs MM, Schachat F. Early specialization of the superfast myosin in extraocular and laryngeal muscles. J Exp Biol 2000; 203:2485-94. [PMID: 10903163 DOI: 10.1242/jeb.203.16.2485] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Extraocular muscle (EOM) exhibits high-velocity, low-tension contractions compared with other vertebrate striated muscles. These distinctive properties have been associated with a novel myosin heavy chain (MyHC) isoform, MyHC-EO. An atypical MyHC, MyHC IIL, has also been identified in laryngeal muscles that have similarly fast contractile properties. It co-migrates with MyHC-EO on high-resolution SDS gels, but appeared to be encoded by a different mRNA. We combined CNBr peptide maps and full-length cDNA sequences to show that rabbit muscle EO and IIL MyHCs are identical. Analysis of the 5; untranslated region (5;UTR) of the mRNAs identified three variants that result from a combination of alternative splicing and multiple transcription initiation sites. This complex pattern of 5;UTRs has not been reported previously for MyHC genes. We identified the human homologue of the MyHC-EO gene in GenBank, and analyzed the 5; upstream region, which revealed a paucity of muscle-specific transcription factor binding sites compared with the other MyHC genes. These features are likely to be critical to the unique regulation and tissue-specific expression of the MyHC-EO/IIL gene.Phylogenetic analysis indicates that MyHC-EO/IIL diverged from an ancestral MyHC gene to generate the first specialized fast myosin. The catalytic S1 head domain is more closely related to the fast MyHCs, while the rod is more closely related to the slow/cardiac MyHCs. The exon boundaries of the MyHC-EO are identical to those of the embryonic MyHC gene and virtually identical to those of the α and (β) cardiac genes. This implies that most of the current exon boundaries were present in the ancestral gene, predating the duplications that generated the family of skeletal and cardiac myosin genes.
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Affiliation(s)
- M M Briggs
- Department of Cell Biology, Box 3011, Duke University Medical Center, Durham, NC 27710, USA.
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39
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Fitts RH, Riley DR, Widrick JJ. Physiology of a microgravity environment invited review: microgravity and skeletal muscle. J Appl Physiol (1985) 2000; 89:823-39. [PMID: 10926670 DOI: 10.1152/jappl.2000.89.2.823] [Citation(s) in RCA: 334] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spaceflight (SF) has been shown to cause skeletal muscle atrophy; a loss in force and power; and, in the first few weeks, a preferential atrophy of extensors over flexors. The atrophy primarily results from a reduced protein synthesis that is likely triggered by the removal of the antigravity load. Contractile proteins are lost out of proportion to other cellular proteins, and the actin thin filament is lost disproportionately to the myosin thick filament. The decline in contractile protein explains the decrease in force per cross-sectional area, whereas the thin-filament loss may explain the observed postflight increase in the maximal velocity of shortening in the type I and IIa fiber types. Importantly, the microgravity-induced decline in peak power is partially offset by the increased fiber velocity. Muscle velocity is further increased by the microgravity-induced expression of fast-type myosin isozymes in slow fibers (hybrid I/II fibers) and by the increased expression of fast type II fiber types. SF increases the susceptibility of skeletal muscle to damage, with the actual damage elicited during postflight reloading. Evidence in rats indicates that SF increases fatigability and reduces the capacity for fat oxidation in skeletal muscles. Future studies will be required to establish the cellular and molecular mechanisms of the SF-induced muscle atrophy and functional loss and to develop effective exercise countermeasures.
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Affiliation(s)
- R H Fitts
- Department of Biology, Marquette University, Milwaukee, WI 53201, USA.
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40
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Giger JM, Haddad F, Qin AX, Baldwin KM. In vivo regulation of the beta-myosin heavy chain gene in soleus muscle of suspended and weight-bearing rats. Am J Physiol Cell Physiol 2000; 278:C1153-61. [PMID: 10837343 DOI: 10.1152/ajpcell.2000.278.6.c1153] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the weight-bearing hindlimb soleus muscle of the rat, approximately 90% of muscle fibers express the beta-myosin heavy chain (beta-MHC) isoform protein. Hindlimb suspension (HS) causes the MHC isoform population to shift from beta toward the fast MHC isoforms. Our aim was to establish a model to test the hypothesis that this shift in expression is transcriptionally regulated through specific cis elements of the beta-MHC promoter. With the use of a direct gene transfer approach, we determined the activity of different length beta-MHC promoter fragments, linked to a firefly luciferase reporter gene, in soleus muscle of control and HS rats. In weight-bearing rats, the relative luciferase activity of the longest beta-promoter fragment (-3500 bp) was threefold higher than the shorter promoter constructs, which suggests that an enhancer sequence is present in the upstream promoter region. After 1 wk of HS, the reporter activities of the -3500-, -914-, and -408-bp promoter constructs were significantly reduced ( approximately 40%), compared with the control muscles. However, using the -215-bp construct, no differences in promoter activity were observed between HS and control muscles, which indicates that the response to HS in the rodent appears to be regulated within the -408 and -215 bp of the promoter.
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Affiliation(s)
- J M Giger
- Department of Physiology and Biophysics, University of California, Irvine 92697, USA
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41
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Hallauer PL, Karpati G, Hastings KE. Skeletal muscle gene transfer: regeneration-associated deregulation of fast troponin I fiber type specificity. Am J Physiol Cell Physiol 2000; 278:C1266-74. [PMID: 10837355 DOI: 10.1152/ajpcell.2000.278.6.c1266] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Direct gene transfer into skeletal muscle in vivo presents a convenient experimental approach for studies of adult muscle gene regulatory mechanisms, including fast vs. slow fiber type specificity. Previous studies have reported preferential expression of fast myosin heavy chain and slow myosin light chain and troponin I (TnIslow) gene constructs in muscles enriched in the appropriate fiber type. We now report a troponin I fast (TnIfast) direct gene transfer study. We injected into the mouse soleus muscle plasmid DNA or recombinant adenovirus carrying a TnIfast/ beta-galactosidase (beta-gal) reporter construct that had previously been shown to be expressed specifically in fast fibers in transgenic mice. Surprisingly, microscopic histochemical analysis 1 and 4 wk postinjection showed similar TnIfast/beta-gal expression in fast and slow fibers. A low but significant level of muscle fiber segmental regeneration was evident in muscles 1 wk postinjection, and TnIfast/beta-gal expression was preferentially targeted to regenerating fiber segments. This finding can explain why TnIfast constructs are deregulated with regard to fiber type specificity, whereas the myosin constructs previously studied are not. The involvement of regenerating fiber segments in transduction by plasmid DNA and recombinant adenoviruses injected into intact normal adult muscle is an unanticipated factor that should be taken into account in the planning and interpretation of direct gene transfer experiments.
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Affiliation(s)
- P L Hallauer
- Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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42
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Abstract
In this review, the adaptations in myosin heavy chain (MHC) isoform expression induced by chronic reductions in neuromuscular activity (including electrical activation and load bearing) of the intact neuromuscular unit are summarized and evaluated. Several different animal models and human clinical conditions of reduced neuromuscular activity are categorized based on the manner and extent to which they alter the levels of electrical activation and load bearing, resulting in three main categories of reduced activity. These are: 1) reduced activation and load bearing (including spinal cord injury, spinal cord transection, and limb immobilization with the muscle in a shortened position); 2) reduced loading (including spaceflight, hindlimb unloading, bed rest, and unilateral limb unloading); and 3) inactivity (including spinal cord isolation and blockage of motoneuron action potential conduction by tetrodotoxin). All of the models discussed resulted in increased expression of fast MHC isoforms at the protein and/or mRNA levels in slow and fast muscles (with the possible exception of unilateral limb unloading in humans). However, the specific fast MHC isoforms that are induced (usually the MHC-IIx isoform in slow muscle and the MHC-IIb isoform in fast muscle) and the degree and rate of adaptation are dependent upon the animal species and the specific model or condition that is being studied. Recent studies designed to elucidate the mechanisms by which electrical activation and load bearing alter expression of MHC isoforms at the cellular and genetic levels are also reviewed. Two main mechanisms have been proposed, the myogenin:MyoD and calcineurin:NF-AT pathways. Collectively, the data suggest that the regulation of MHC isoform expression involves a complex interaction of multiple control mechanisms including the myogenin:MyoD and calcineurin:NF-AT pathways; however, other intracellular signaling pathways are likely to contribute.
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Affiliation(s)
- R J Talmadge
- Department of Human Nutrition, Foods and Exercise, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0430, USA.
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43
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Adams GR, Haddad F, McCue SA, Bodell PW, Zeng M, Qin L, Qin AX, Baldwin KM. Effects of spaceflight and thyroid deficiency on rat hindlimb development. II. Expression of MHC isoforms. J Appl Physiol (1985) 2000; 88:904-16. [PMID: 10710385 DOI: 10.1152/jappl.2000.88.3.904] [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: 11/22/2022] Open
Abstract
Both slow-twitch and fast-twitch muscles are undifferentiated after birth as to their contractile protein phenotype. Thus we examined the separate and combined effects of spaceflight (SF) and thyroid deficiency (TD) on myosin heavy chain (MHC) gene expression (protein and mRNA) in muscles of neonatal rats (7 and 14 days of age at launch) exposed to SF for 16 days. Spaceflight markedly reduced expression of the slow, type I MHC gene by approximately 55%, whereas it augmented expression of the fast IIx and IIb MHCs in antigravity skeletal muscles. In fast muscles, SF caused subtle increases in the fast IIb MHC relative to the other adult MHCs. In contrast, TD prevented the normal expression of the fast MHC phenotype, particularly the IIb MHC, whereas TD maintained expression of the embryonic/neonatal MHC isoforms; this response occurred independently of gravity. Collectively, these results suggest that normal expression of the type I MHC gene requires signals associated with weight-bearing activity, whereas normal expression of the IIb MHC requires an intact thyroid state acting independently of the weight-bearing activities typically encountered during neonatal development of laboratory rodents. Finally, MHC expression in developing muscles is chiefly regulated by pretranslational processes based on the tight relationship between the MHC protein and mRNA data.
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Affiliation(s)
- G R Adams
- Department of Physiology and Biophysics, University of California, Irvine, California 92697-4560, USA
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44
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di Maso NA, Haddad F, Zeng M, McCue SA, Baldwin KM. Role of denervation in modulating IIb MHC gene expression in response to T(3) plus unloading state. J Appl Physiol (1985) 2000; 88:682-9. [PMID: 10658038 DOI: 10.1152/jappl.2000.88.2.682] [Citation(s) in RCA: 25] [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] Open
Abstract
Previously, we have reported that the combination of hindlimb suspension (HS) and thyroid hormone [triiodothyronine (T(3))] treatment induces the de novo expression of the fast IIb myosin heavy chain (MHC) gene in the soleus. Thus we tested the hypotheses that the induction of IIb MHC expression with HS + T(3) is prevented with denervation and that this IIb induction is regulated by transcriptional processes. Adult female rats were subjected to 2 wk of combined HS + T(3) in which one side of the lower leg was simultaneously denervated. HS + T(3) caused decreased expression of the slow type I MHC and concomitant increases in both the fast type IIx and IIb MHC isoforms in the intact soleus muscle. Denervation prevented the endogenous expression of the IIb MHC gene at both the protein and mRNA levels. Although HS + T(3) intervention was able to markedly increase the expression of the 2.6-kb IIb MHC promoter-reporter construct using direct gene transfer, this induction, however, was not inhibited by denervation. These findings collectively suggest that normal innervation is essential for inducing the unique expression of the IIb MHC in a slow muscle in response to HS + T(3); however, in the denervated muscle, there is a discordance between the regulation of the endogenous IIb MHC gene relative to the exogenous IIb MHC promoter-reporter construct.
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Affiliation(s)
- N A di Maso
- Department of Physiology and Biophysics, University of California, Irvine, California 92697, USA
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Carson JA, Wei L. Integrin signaling's potential for mediating gene expression in hypertrophying skeletal muscle. J Appl Physiol (1985) 2000; 88:337-43. [PMID: 10642399 DOI: 10.1152/jappl.2000.88.1.337] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Overloaded skeletal muscle undergoes dramatic shifts in gene expression, which alter both the phenotype and mass. Molecular biology techniques employing both in vivo and in vitro hypertrophy models have demonstrated that mechanical forces can alter skeletal muscle gene regulation. This review's purpose is to support integrin-mediated signaling as a candidate for mechanical load-induced hypertrophy. Research quantifying components of the integrin-signaling pathway in overloaded skeletal muscle have been integrated with knowledge regarding integrins role during development and cardiac hypertrophy, with the hope of demonstrating the pathway's importance. The role of integrin signaling as an integrator of mechanical forces and growth factor signaling during hypertrophy is discussed. Specific components of integrin signaling, including focal adhesion kinase and low-molecular-weight GTPase Rho are mentioned as downstream targets of this signaling pathway. There is a need for additional mechanistic studies capable of providing a stronger linkage between integrin-mediated signaling and skeletal muscle hypertrophy; however, there appears to be abundant justification for this type of research.
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Affiliation(s)
- J A Carson
- Exercise Science Department, University of South Carolina, Columbia, South Carolina 29208, USA.
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Mitchell-Felton H, Kandarian SC. Normalization of muscle plasmid uptake by Southern blot: application to SERCA1 promoter analysis. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:C1269-76. [PMID: 10600779 DOI: 10.1152/ajpcell.1999.277.6.c1269] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Direct injection of plasmid DNA into muscle allows the study of promoters in a physiological environment. Because of the variability of reporter gene activity, attempts have been made to normalize activity to muscle plasmid uptake by coinjection of a second "control" plasmid whose reporter gene is constitutively expressed by a viral promoter. The purpose of this study was to evaluate the use of a control plasmid vs. Southern blot to normalize for differences in uptake of plasmids containing promoter fragments of the skeletal muscle-specific sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA1) gene. Results showed that the correlation of luciferase activity from control vs. SERCA1 plasmids is poor and that normalization by a virally driven control plasmid increased variability of SERCA1 luciferase activity. In several cases, the presence of a control plasmid inhibited SERCA1 reporter expression. When Southern blot analysis was used to normalize for differences in plasmid uptake there was less variability than with coinjection, and correlations between plasmid uptake and SERCA1 luciferase activity were better. Moreover, there were no inhibitory effects of a control plasmid allowing for optimization of injection conditions of the SERCA1 deletion constructs. The use of Southern analysis is suggested to determine whether plasmid uptake is differentially affected by physiological stimuli, muscle types, or plasmid sizes under study.
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Affiliation(s)
- H Mitchell-Felton
- Department of Health Sciences, Boston University, Boston, Massachusetts 02215, USA
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Freyssenet D, Connor MK, Takahashi M, Hood DA. Cytochrome c transcriptional activation and mRNA stability during contractile activity in skeletal muscle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:E26-32. [PMID: 10409124 DOI: 10.1152/ajpendo.1999.277.1.e26] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We evaluated contractile activity-induced alterations in cytochrome c transcriptional activation and mRNA stability with unilateral chronic stimulation (10 Hz, 3 h/day) of the rat tibialis anterior (TA) muscle for 1, 2, 3, 4, 5, and 7 days (n = 3-11/group). Transcriptional activation was assessed by direct plasmid DNA injection into the TA with a chloramphenicol acetyltransferase (CAT) reporter gene linked to 326 bp of the cytochrome c promoter. Cytochrome c mRNA in stimulated muscles increased by 1.3- to 1. 7-fold above control between 1 and 7 days. Cytochrome c protein was increased after 5 days of stimulation to reach levels that were 1. 9-fold higher than control by 7 days. Cytochrome c mRNA stability, determined with an in vitro decay assay, was greater in stimulated TA than in control between 2 and 4 days, likely mediated by the induction of a cytosolic factor. In contrast, cytochrome c transcriptional activation was elevated only after 5 days of stimulation when mRNA stability had returned to control levels. Thus the contractile activity-induced increase in cytochrome c mRNA was due to an early increase in mRNA stability, followed by an elevation in transcriptional activation, leading to an eventual increase in cytochrome c protein levels.
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Affiliation(s)
- D Freyssenet
- Department of Biology, York University, Toronto, Ontario, Canada M3J 1P3
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Abstract
The effects of a chronic (up to 360 days) reduction in neuromuscular activity (defined as electrical activation and loading) on myosin heavy chain (MHC) isoform expression in the rat soleus muscle were studied. A complete mid-thoracic (T7-T8) spinal cord transection (ST) was used to induce a reduction in soleus muscle neuromuscular activity. Electrophoretic analyses revealed that MHC-I was progressively decreased after ST, accounting for approx. 90% of the total soleus MHC in controls and only approx. 12% 1 year after ST. The reductions in the proportion of MHC-I were countered by increases in MHC-IIa and MHC-IIx with the increase in MHC-IIx preceding the increase in MHC-IIa. Curiously, MHC-IIb was expressed only at very low levels. Thus, a complete transformation from predominantly MHC-I to MHC-IIb did not occur. Many fibers (up to approx. 80%) contained multiple MHCs (hybrid fibers) after ST. The proportion of hybrid fibers was maintained at a high level (approx. 50%) 1 year after ST. These data suggest that: 1) a prolonged reduction in neuromuscular activity was not sufficient to induce high level MHC-IIb expression by the soleus muscle; and 2) hybrid fibers were not simply transitional fibers. Thus, it appears that under appropriate conditions hybrid fibers may represent a "stable" fiber phenotype.
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Affiliation(s)
- R J Talmadge
- Department of Human Nutrition, Foods & Exercise, Virginia Polytechnic Institute and State University, Blacksburg 24061-0430, USA.
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Abstract
The model of chronic low-frequency stimulation for the study of muscle plasticity was developed over 30 years ago. This protocol leads to a transformation of fast, fatigable muscles toward slower, fatigue-resistant ones. It involves qualitative and quantitative changes of all elements of the muscle fiber studied so far. The multitude of stimulation-induced changes makes it possible to establish the full adaptive potential of skeletal muscle. Both functional and structural alterations are caused by orchestrated exchanges of fast protein isoforms with their slow counterparts, as well as by altered levels of expression. This remodeling of the muscle fiber encompasses the major, myofibrillar proteins, membrane-bound and soluble proteins involved in Ca2+ dynamics, and mitochondrial and cytosolic enzymes of energy metabolism. Most transitions occur in a coordinated, time-dependent manner and result from altered gene expression, including transcriptional and posttranscriptional processes. This review summarizes the advantages of chronic low-frequency stimulation for studying activity-induced changes in phenotype, and its potential for investigating regulatory mechanisms of gene expression. The potential clinical relevance or utility of the technique is also considered.
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Affiliation(s)
- D Pette
- Faculty of Biology, University of Konstanz, Germany
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Peters DG, Mitchell-Felton H, Kandarian SC. Unloading induces transcriptional activation of the sarco(endo)plasmic reticulum Ca2+-ATPase 1 gene in muscle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:C1218-25. [PMID: 10329971 DOI: 10.1152/ajpcell.1999.276.5.c1218] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Previous work showed that protein and mRNA levels of the "fast" isoform of the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA1) are markedly increased in unloaded slow-twitch soleus muscles, suggesting pretranslational control of gene expression [L. M. Schulte, J. Navarro, and S. C. Kandarian. Am. J. Physiol. 264 (Cell Physiol. 33): C1308-C1315, 1993]. However, because of the difficulty of measuring transcription rates from whole muscle, transcriptional activation of the SERCA1 gene with unloading has not been confirmed. Because SERCA1 pre-mRNA levels can reflect transcriptional activity, in the present study SERCA1 introns were sequenced to allow intron-directed RT-PCR measurement of SERCA1 pre-mRNA. These data were then compared with changes in SERCA1 mRNA expression in control and unloaded soleus muscles. After 2, 4, and 10 days of unloading, SERCA1 pre-mRNA and mRNA transcript levels increased significantly by two-, three-, and sevenfold, respectively (P < 0.01). Parallel increases in SERCA1 pre-mRNA and mRNA suggest transcriptional activation of the endogenous SERCA1 gene by muscle unloading. SERCA2, the cardiac/slow-twitch skeletal muscle isoform, was not markedly increased by unloading, and RNase protection assays showed no change in alternative splicing of SERCA1 or SERCA2 primary transcripts. With use of in vivo plasmid injection, the activity of a reporter gene driven by 3.6 kb of the SERCA1 5'-flanking region increased fivefold in 7-day-unloaded soleus muscles. Comparison of the magnitude of transcriptional activation of endogenous and constructed SERCA1 genes by unloading confirms the fidelity of using intronic RT-PCR to examine muscle gene transcription rates and suggests that cis-acting elements sufficient for regulating unloading-induced transcriptional activation are contained in this promoter construct.
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Affiliation(s)
- D G Peters
- Department of Health Sciences, Boston University, Boston, Massachusetts 02215, USA
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