Animal Genomics, AgResearch, Hamilton, and Ovita Limited, Dunedin, New Zealand
Submitted 7 November 2003 ; accepted in final form 31 May 2004
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
myogenic regulatory factor; E-box; naked DNA
Myostatin expression is detected in myogenic precursors during early embryogenesis, and the expression continues in postnatal skeletal muscle (22, 26). Changes in muscle mass have been shown to be related to changes in myostatin expression. Recently, Roth et al. (32) reported that myostatin mRNA levels are reduced in response to heavy-resistance strength training in humans. On the other hand, higher levels of circulatory and muscle myostatin have been observed in humans with acquired immunodeficiency syndrome-related muscle wasting or age-associated sarcopenia (13, 25). Furthermore, chronic underfeeding in sheep and hindlimb suspension in rats resulted in increased levels of myostatin (6, 21, 42). Collectively, these results and those described in other reports indicate that myostatin expression is regulated at the transcription level.
Although the functional role of myostatin in controlling muscle mass has been delineated, much remains to be learned about the regulation of the myostatin gene at the transcription level. Recently, two studies (24, 37) have analyzed the human and bovine myostatin promoter. The 5' upstream regulatory sequences from human, bovine, porcine, and murine myostatin genes have considerable sequence homology and share many transcription factor binding motifs (37). The similarity between the human and bovine myostatin gene upstream region (1.6 kb) was 79%, and that between the bovine and murine was 68%. Among the factors influencing human myostatin promoter activity are glucocorticoid-responsive elements, which can upregulate the transcriptional activity of the myostatin promoter in response to dexamethasone treatment (24). In addition, multiple E-boxes, the consensus binding sequence of myogenic regulatory factors (MRF), have been identified in the myostatin promoter in different species (37). To date, these studies have been performed in cell cultures that are more or less a homogeneous population. Skeletal muscles are heterogeneous with respect to contractile properties, the fast and slow fiber types, which have distinct gene expression profiles (33). Muscle fiber types have been classified on the basis of the myosin heavy chain (MHC) isoform expression as 1) slow type I, 2) intermediate type IIA, 3) fast type IIX, and 4) fast type IIB. Myostatin expression is seen preferentially in the type IIB fibers (6). Similarly, MyoD expression predominates in fast type IIB/IIX muscle fibers (31). Furthermore, myostatin gene expression has been shown to be induced by MyoD (37), raising the possibility that the myostatin promoter may be responding to MyoD activity specifically in type IIB fibers. Hence, the purpose of this study was to determine the critical cis-acting regions within the myostatin promoter that drive fiber type-specific expression of this gene in vivo. In this report, the somatic transfer of naked DNA was used to analyze the myostatin promoter activity because this method offers a simple and efficient way of performing in vivo analysis of muscle-specific regulatory regions (36, 43) in a fiber type-specific manner (9, 38). The results obtained indicate that the promoter activity in vivo is species specific, as observed in the weaker activity of bovine myostatin promoter compared with the murine myostatin promoter in mouse. The results of the in vivo experiments also show that E-box E5 of the murine myostatin promoter plays a crucial role in the regulation of promoter activity. Furthermore, we demonstrate that among the MRF, MyoD preferentially activates the murine myostatin promoter and that this overlaps with the expression of reporter activity in type IIB fibers in vivo.
![]() |
MATERIALS AND METHODS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
Gel mobility shift assays. Recombinant MyoD, Myf5, and E47 were expressed and purified from Escherichia coli as described previously (37). The pQT-MyoD and pQT-E47 plasmids were kind gifts from Stephen F. Konieczny (Dept. of Biological Sciences, Purdue University, West Lafayette, IN) and Kyung-Sup Kim (Institute of Genetic Science, Dept. of Biochemistry and Molecular Biology, Yonsei University College of Medicine, Seoul, Korea). The pRSET-Myf5 plasmid was obtained by subcloning a Myf5 fragment from the expression plasmid pJM7 into the KpnI and EcoRI sites of pRSET A vector (Invitrogen).
One microgram of MyoD or Myf5 protein was mixed with 100 ng of E47 protein and equilibrated at room temperature to form heterodimers for 10 min in binding buffer containing 10 mM HEPES (pH 7.9), 10% glycerol, 75 mM KCl, 5 mM MgCl2, 5 mM dithiothreitol (DTT), 0.5 µg of poly(dI-dC) (Roche), and 0.5% fetal calf serum.
Serial twofold dilutions of MyoD/E47 or Myf5/E47 heterodimers, from 600 ng to 33 pg, were mixed with DNA probe (10 pmol) in a final volume of 20 µl in binding buffer. After 30-min incubation at room temperature, samples were subjected to electrophoresis on a native 5% polyacrylamide gel in 0.5x Tris-borate-EDTA at 35 mA at room temperature. Gels were dried and exposed either to a film (Kodak X-Omat) at 80°C or to a PhosphorImager screen (Imaging Screen K-HD; Bio-Rad) for 3 h at room temperature and scanned on a PhosphorImager (Molecular Image FX; Bio-Rad). The relative optical density of bands corresponding to free and bound DNA was measured using Quantity One 4.2.2 software (Bio-Rad). The binding affinity was calculated as described elsewhere (7, 39). Because the protein concentrations did not take into account the fraction of inactive proteins, the data are referred to as apparent dissociation constants [Kd (app)].
Animals. Wild-type mouse strain C57BL/10 was bred at Ruakura Small Animal Colony (Hamilton, NZ). Animal handling and care was performed according to the specifications of the Ruakura Animal Ethics Committee.
Injection of naked DNA into muscles.
Four- to 5-week-old C57BL/10 mice were anesthetized with intraperitoneal injections of 0.1 ml/10 g body wt of Hypnorm (5 ml)/Hypnovel (2 ml) mix. A small incision (4 mm) was made in the hindlimb, and the quadriceps femoris muscle group exposed. Each quadriceps muscle was injected (i.e., the left and right quadriceps of each animal) with 50 µl (1 µg/µl DNA in sterile PBS) of either the bovine myostatin promoter construct 1.6b or the murine myostatin promoter constructs 2.5P, 1.7P, tE5, tE4, tE3, mE5, mE4, or mE3 or the control vector pGL3-B. For immunocytochemistry purposes, 4-wk-old mice were injected with 60 µl/muscle (1 µg/µl DNA in sterile PBS) of either the murine constructs 2.5P or tE5 or the control vector pGL3-B, mixed with a small amount of India ink to facilitate the localization of the injected DNA (3). The incisions were closed using stainless steel clips. Six animals per DNA construct underwent injection. For the experiment involving the murine 1.7P and the bovine 1.6b constructs, half of the mice were killed at day 3 and the remaining mice were killed at day 7 after the naked DNA injection, and the muscles (6 muscles/day/construct) were then processed for total luciferase activity. For the remaining experiments, all of the mice were killed at day 7 after naked DNA injection, and the muscles (12 muscles/construct) were then processed for total luciferase activity.
Total muscle luciferase and protein assay. Each muscle was frozen in liquid nitrogen and ground to a fine powder. The material was resuspended in 1 ml of cell lysis buffer [25 mM Tris-phosphate, pH 7.8, 2 mM DTT, 2 mM 2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (Sigma), 10% glycerol, and 1% Triton X-100], and processed as described for cell lysates. Ten microliters of undiluted muscle extract were used for luciferase assay. Five microliters (1:100 dilution in lysis buffer) of muscle extract were used for estimating total protein concentration by Bio-Rad protein assay reagent. The protein estimates were used to normalize the luciferase readings.
Immunocytochemistry. The muscles from mice injected with 2.5P, tE5, or pGL3-B DNA were collected and frozen in isopentane chilled in liquid nitrogen. Cryosections were cut at 10 µm, and the slides were frozen at 20°C until used.
The sections were permeabilized in PBS and 0.1% Triton X-100 for 30 min at room temperature and then incubated with primary anti-luciferase antibody (Promega) at 1:50 dilution in PBS, 5% normal goat serum, 1% BSA, and 0.1% Triton X-100 overnight at 4°C. After washing three times for 3 min each in PBS, the slides were incubated in PBS, 3% normal rabbit serum, 1% BSA, and 0.1% Triton X-100 for 1 h to reduce nonspecific binding of the secondary antibody. The sections were incubated with biotinylated secondary antibody (Amersham, Little Chalfont, UK) at 1:300 dilution for 1 h at room temperature. After being washed in PBS, the sections were finally incubated in streptavidin-conjugated fluorescein-labeled tertiary antibody (Alexa Fluor streptavidin; Molecular Probes, Eugene, OR) for 1 h at room temperature, washed in PBS, counterstained with 4',6-diamidino-2-phenylindole dihydrochloride (DAPI; Molecular Probes), mounted in fluorescent mounting medium (DAKO, Copenhagen, Denmark), and analyzed for reporter gene expression. For fiber typing, permeabilized serial sections were incubated with undiluted anti-fast type II fiber antibody N1.551 or anti-slow type I fiber antibody A4.840 (17, 18, 41) for 2 h at room temperature. Slides were washed in PBS and then blocked in PBS, 0.1% Triton X-100, and 5% normal sheep serum for 30 min at room temperature. Slides were then incubated with biotinylated secondary antibody (Amersham) and treated as described above. Control sections were incubated with either no primary antibody or mouse control IgG and then processed as described above.
Histochemical fiber typing of the muscle sections. For histochemical fiber typing of the muscle, a standard alkali ATPase method was used, as described by Guth and Samaha (15, 16). In summary, serial sections were fixed in a solution of 5.5% formaldehyde, 200 mM sodium cacodylate, 68 mM CaCl2, 340 mM sucrose for 5 min, and washed in Tris rinse solution (100 mM Tris, pH 7.4, and 18 mM CaCl2). The slides were then incubated in alkaline solution [100 mM 2-amino-2 methyl-1 propanol (AMIP; BDH Laboratory Supplies, Poole, UK), and 70 mM CaCl2, pH 10.4] for 15 min at room temperature, followed by washes in Tris rinse solution. The slides were transferred to staining reaction solution containing 100 mM AMIP, 18 mM CaCl2, and 2.7 mM ATP disodium salt (Boehringer Mannheim, Mannheim, Germany), preheated to 37°C, and incubated for 20 min. The slides were washed in 70 mM CaCl2, incubated in 2% CoCl2 for 3 min at room temperature, and washed in 100 mM AMIP. They were then transferred to a solution of 1% ammonium polysulfide [(NH4)2S; BDH] and incubated for 3 min at room temperature, followed by vigorous washing in water. The slides were counterstained with DAPI and mounted in DAKO faramount aqueous mounting medium.
Statistics. Normalized luciferase values from in vivo experiments were evaluated using analysis of variance of the log-transformed values with GenStat 6 software (VSN International, Hemel Hempstead, UK). Selected comparisons were tested for significance using Student's t-test and the pooled standard deviation. All in vitro assays were analyzed using Student's t-test.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
|
|
|
|
|
|
The muscles were recovered 7 days after the DNA injection, and the tissues were processed as described in MATERIALS AND METHODS. The resulting tissue sections were immunostained with various primary antibodies. Sections derived from the mice injected with the 2.5P construct were positive for luciferase expression (Fig. 8A), while sections from muscles injected with pGL3-B displayed no fluorescence when incubated with anti-luciferase antibody (data not shown). Serial sections from mice injected with the 2.5P construct were also immunostained with anti-slow type I fiber and anti-fast type II fiber antibodies, and the results were compared with those for luciferase antibody. The fibers that were positive for luciferase expression (Fig. 8A) colocalized with the fibers that were reactive with anti-fast type II fiber antibody (Fig. 8B) but not with fibers that were reactive with anti-slow type I antibody (Fig. 8C). This indicates that the myostatin promoter was restricting the expression of the reporter gene to fast type muscle fibers. However, the anti-fast type II antibody N1.551 was described as anti-fast type IIa in rats (41). To determine whether any of the fibers detected by N1.551 were type IIb, histochemical fiber typing was performed. The results show that most of the fibers positive for luciferase expression are darkly stained fibers, expected to be type IIb fibers (Fig. 8D). Control sections treated with no primary antibody or with mouse IgG did not display any fluorescence (data not shown). Interestingly, tE5 did not display fiber type-specific expression when injected into the muscle. As seen in Fig. 9A, a diffuse pattern of expression was observed when anti-luciferase antibody was used, and the luciferase-positive fibers colocalized with fibers reactive with anti-slow type I (Fig. 9B) as well as with anti-fast type II (Fig. 9C) antibodies. Although able to express the level of reporter gene activity similar to wild-type 2.5P construct both in vivo and in vitro, tE5 is unable to confer fiber type specificity.
|
|
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Murine vs. bovine myostatin promoter activity in murine skeletal muscle. To date, the 5' upstream sequences of the myostatin gene have been isolated from cattle, pig, mouse, and human (GenBank accession nos. AF348479, AF093798, AX139025, and AX058992, respectively). In the present study, the activity of promoter constructs from two different species, mouse and cattle, were examined in murine skeletal muscle. Interestingly, a comparison of the activity of the bovine and the murine myostatin promoter in vivo revealed that bovine promoter activity is significantly weaker than that of the murine promoter (Fig. 6). However, similar levels of reporter gene activity for these constructs were seen in C2C12 myoblasts. Previously, it was reported that 1.6 kb of bovine promoter is sufficient for the maximal promoter activity (37). The murine and bovine promoters share 68% homology within this region. However, the two promoters also display some distinct features, such as the number and arrangement of the E-boxes, the consensus binding sites for MRF, which are critical for muscle-specific gene expression. Because the in vivo system is more sensitive, these genetic differences between the bovine and murine promoters become more relevant. Furthermore, the murine sequence has a polyA tract (A20) between E-boxes E4 and E5 that is not present in the bovine sequence. PolyA sequences have been associated with DNA spatial conformation, and it has been argued that DNA curvature between motifs can lead to more efficient dimerization of proteins by bringing factors into proximity with each other (40). The presence of a polyA tract in the murine sequence could lead to a specific DNA conformation and therefore contribute to the level of promoter activity in vivo. Together, these differences might be sufficient to impair the ability of the bovine promoter to induce the reporter gene expression in murine skeletal muscle to the same level as that in C2C12 cells. Thus species specificity is a factor to be considered when generating transgenic mice for a particular gene promoter.
MyoD and Myf5 activate myostatin promoter differentially. MRF, in particular MyoD and Myf5, regulate their target genes by binding to E-boxes in the promoter region (1, 2, 8). Sequence analysis of the 2.5-kb fragment of the murine promoter revealed the presence of seven E-box motifs (Fig. 1). However, analysis of the murine myostatin promoter activity in C2C12 cells indicated that the first five E-boxes, in particular E-box E5, are sufficient for its maximal activity (Fig. 2). Furthermore, analysis of the induction of the murine promoter activity by these two MRF revealed that Myf5 is a weak activator, while MyoD appears to be a potent activator, of promoter activity (Fig. 3). Importantly, analysis of E-box activity in vivo confirmed the results obtained in vitro, where the presence of E-box E5 was sufficient to restore maximal promoter activity (Fig. 2 and 7). Moreover, mutation of E-box E5 decreased promoter activity (by 83%) to levels comparable to those observed in constructs lacking this E-box (Fig. 7), confirming the importance of E-box E5 for the activity of the murine promoter.
The MRF have been shown to bind to an E-box in complex with ubiquitous helix-loop-helix E-proteins, including E12 and E47. It has been suggested that MyoD/E47 heterodimers cooperate in binding to promoters containing multiple E-boxes (4) and that MyoD/E12 heterodimer binding affinity to DNA targets containing multiple E-boxes is much higher than that observed in interactions with targets containing a single E-box (10). On the other hand, under certain experimental conditions, a single E-box motif is capable of binding a specific MRF and confer activity (12, 35).
The results reported here indicate that MyoD preferentially activates myostatin promoter activity, which is consistent with findings of the previous study by Spiller et al. (37). To further investigate the basis of higher activation of the promoter by MyoD compared with Myf5, we examined the DNA binding of MyoD/E47 and Myf5/E47 to E-box E5 of the murine myostatin promoter in vitro. The E-box E5 was chosen for the EMSA experiments on the basis of its crucial nature in the activation of the myostatin promoter (Fig. 2 and 7). Our in vitro results indicate a difference, although small, between the binding affinity of MyoD/E47 to the DNA compared with that of Myf5/E47. The relatively higher binding affinity of MyoD could be contributing to the stronger activation of the myostatin promoter by MyoD than that by Myf5 in the transient transfections (Fig. 3). Furthermore, the presence of more than one E-box in the transfected constructs may also help the activation by MyoD. Previously, the murine sarcoma virus (MSV) promoter-enhancer containing six E-boxes was tested for MyoD-E12 and myogenin-E12 interactions. The report demonstrated that DNA sequences containing multiple E-boxes have higher binding affinity to MyoD/E12 and Myogenin/E12 DNA than DNA fragments containing a single E-box (10). Furthermore, it was shown that MyoD-E12 has higher affinity for the MSV enhancer and bound to the DNA with higher cooperativity than did myogenin-E12. On the basis of these results, we postulated that multiple E-boxes in the promoter region could not only contribute to high-affinity DNA binding but also confer MyoD and myogenin DNA recognition specificity (10).
Myostatin promoter activity is fiber type specific. Because myostatin expression has been described in association with fast-twitch muscle fibers (6, 23), we assessed the capacity of myostatin promoter constructs 2.5P and tE5 to render fiber-type specificity to reporter gene expression in vivo. Corin et al. (9) showed the expression of injected troponin I slow isoform (TnIs)-luciferase constructs in slow fibers and inferred that chromosomal integration was not a primary requirement to achieve appropriate fiber type-specific gene regulation. It was postulated that the DNA sequence of the injected promoter conveyed the necessary information for fiber type-specific TnIs gene expression in the adult skeletal muscle. Similarly, Swoap (38) reported the fast fiber type-specific expression of the MHC type IIB promoter in vivo using somatic gene transfer. The results of our study demonstrate that the 2.5P fragment of the murine myostatin promoter is sufficient to drive the expression of the reporter gene in a fiber type-specific manner in 4-wk-old mice. Interestingly, MyoD has also been shown to be expressed preferentially in fast-twitch muscle fibers (19, 20), and myostatin and MyoD expression overlap during embryogenesis (30). Furthermore, although the levels of MyoD decrease in the adult muscle, it is still highly expressed in 4-wk-old mice (28), coinciding with the manifestation of fiber type-specific properties, mainly the switch from embryonic and neonatal MHC to MHC types IIA, IIB, and IIX that develop by 34 wk of age in mice (5). Also, Wheeler et al. (43) demonstrated that the presence of a functional E-box within the MHC type IIB promoter is essential for the expression of the reporter gene in vivo in a fiber type-specific manner. These results also support our finding that the absence of the sequences upstream of E-box E5 in tE5 leads to loss of fiber-specific expression, as is evident in the expression of luciferase activity in both types I and II fibers (Fig. 9). It is noteworthy that the sequences upstream of E5 E-box contain two additional E-boxes, E6 and E7, that are present in the 2.5P construct (Fig. 1A).
Yan et al. (44) demonstrated that an intragenic E-box present in the myoglobin gene restricted the expression of the reporter gene to slow oxidative fibers. Mutation of this E-box increased the expression of the reporter gene in the mainly fast glycolytic extensor digitorum longus muscle threefold compared with the wild-type construct. Interestingly, the same mutation did not significantly alter the activity of the promoter in the slow oxidative soleus muscle. They postulated that basic helix-loop-helix proteins such as MyoD can form complexes with corepressors to negatively regulate gene expression in certain cell backgrounds. Similarly, mutation of three different E-boxes in the promoter region of the muscle creatine kinase gene led to distinct expression patterns in slow and fast skeletal, cardiac, and tongue muscles of transgenic mice (11, 29, 34).
Although other factors may also be involved in conferring fiber-type specificity to the murine myostatin promoter, the in vivo results together with the results obtained in vitro (EMSA and cotransfection experiments) make it attractive to propose that MyoD could control the muscle-specific and fiber type-specific transcription of myostatin in skeletal muscle.
![]() |
GRANTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
![]() |
ACKNOWLEDGMENTS |
---|
The antibodies N1.551 and A4.840, developed by Helen M. Blau, were obtained from the Developmental Studies Hybridoma Bank, University of Iowa, Ames, IA.
Current address of D. Forbes: Liggins Institute, Faculty of Medicine and Health Sciences, University of Auckland, Auckland, New Zealand.
![]() |
FOOTNOTES |
---|
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
2. Apone S and Hauschka SD. Muscle gene E-box control elements: evidence for quantitatively different transcriptional activities and the binding of distinct regulatory factors. J Biol Chem 270: 2142021427, 1995.
3. Ashley WW Jr and Russell B. Tenotomy decreases reporter protein synthesis via the 3'-untranslated region of the -myosin heavy chain mRNA. Am J Physiol Cell Physiol 279: C257C265, 2000.
4. Bengal E, Flores O, Rangarajan PN, Chen A, Weintraub H, and Verma IM. Positive control mutations in the MyoD basic region fail to show cooperative DNA binding and transcriptional activation in vitro. Proc Natl Acad Sci USA 91: 62216225, 1994.[Abstract]
5. Calvo S, Venepally P, Cheng J, and Buonanno A. Fiber-type-specific transcription of the troponin I slow gene is regulated by multiple elements. Mol Cell Biol 19: 515525, 1999.
6. Carlson CJ, Booth FW, and Gordon SE. Skeletal muscle myostatin mRNA expression is fiber-type specific and increases during hindlimb unloading. Am J Physiol Regul Integr Comp Physiol 277: R601R606, 1999.
7. Carrey J. Gel retardation at low pH resolves trp repressor-DNA complexes for quantitative study. Proc Natl Acad Sci USA 85: 975979, 1988.[Abstract]
8. Catala F, Wanner R, Barton P, Cohen A, Wright W, and Buckingham M. A skeletal muscle-specific enhancer regulated by factors binding to E and CArG boxes is present in the promoter of the mouse myosin light-chain 1A gene. Mol Cell Biol 15: 45854596, 1995.[Abstract]
9. Corin SJ, Levitt LK, O'Mahoney JV, Joya JE, Hardeman EC, and Wade R. Delineation of a slow-twitch-myofiber-specific transcriptional element by using in vivo somatic gene transfer. Proc Natl Acad Sci USA 92: 61856189, 1995.
10. Czernik PJ, Peterson CA, and Hurlburt BK. Preferential binding of MyoD-E12 versus myogenin-E12 to the murine sarcoma virus enhancer in vitro. J Biol Chem 271: 91419149, 1996.
11. Donoviel DB, Shield MA, Buskin JN, Haugen HS, Clegg CH, and Hauschka SD. Analysis of muscle creatine kinase gene regulatory elements in skeletal and cardiac muscles of transgenic mice. Mol Cell Biol 16: 16491658, 1996.[Abstract]
12. Edmondson DG, Lyons GE, Martin JF, and Olson EN. Mef2 gene expression marks the cardiac and skeletal muscle lineages during mouse embryogenesis. Development 120: 12511263, 1994.
13. Gonzalez-Cadavid NF, Taylor WE, Yarasheski K, Sinha-Hikim I, Ma K, Ezzat S, Shen R, Lalani R, Asa S, Mamita M, Nair G, Arver S, and Bhasin S. Organization of the human myostatin gene and expression in healthy men and HIV-infected men with muscle wasting. Proc Natl Acad Sci USA 95: 1493814943, 1998.
14. Grobet LML, Poncelet D, Pirottin D, Brouwers B, Riquet J, Schoeberlein A, Dunner S, Menissier F, Massabanda J, Fries R, Hanset R, and Georges M. A deletion in the bovine myostatin gene causes the double-muscled phenotype in cattle. Nat Genet 17: 7174, 1997.[ISI][Medline]
15. Guth L and Samaha F. Qualitative differences between actomyosin ATPase of slow and fast mammalian muscle. Exp Neurol 25: 138152, 1969.[ISI][Medline]
16. Guth L and Samaha F. Procedure for the histochemical demonstration of actomyosin ATPase. Exp Neurol 28: 365367, 1970.[ISI][Medline]
17. Hughes SM and Blau H. Muscle fiber pattern is independent of cell lineage in postnatal rodent development. Cell 68: 659671, 1992.[ISI][Medline]
18. Hughes SM, Cho M, Karsch-Mizrachi I, Travis M, Silberstein L, Leinwand LA, and Blau HM. Three slow myosin heavy chains sequentially expressed in developing mammalian skeletal muscle. Dev Biol 158: 183199, 1993.[CrossRef][ISI][Medline]
19. Hughes SM, Koishi K, Rudnicki M, and Maggs AM. MyoD protein is differentially accumulated in fast and slow skeletal muscle fibers and required for normal fiber type balance in rodents. Mech Dev 61: 151163, 1997.[CrossRef][ISI][Medline]
20. Hughes SM, Taylor JM, Tapscott SJ, Gurley CM, Carter WJ, and Peterson CA. Selective accumulation of MyoD and myogenin mRNAs in fast and slow adult skeletal muscle is controlled by innervation and hormones. Development 118: 11371147, 1993.
21. Jeanplong F, Bass JJ, Smith HK, Kirk SP, Kambadur R, Sharma M, and Oldham JM. Prolonged underfeeding of sheep increases myostatin and myogenic regulatory factor Myf-5 in skeletal muscle while IGF-I and myogenin are repressed. J Endocrinol 176: 425437, 2003.
22. Kambadur R, Sharma M, Smith TP, and Bass JJ. Mutations in myostatin (GDF8) in double-muscled Belgian Blue and Piedmontese cattle. Genome Res 7: 910916, 1997.
23. Kirk S, Oldham J, Kambadur R, Sharma M, Dobbie P, and Bass J. Myostatin regulation during skeletal muscle regeneration. J Cell Physiol 184: 356363, 2000.[CrossRef][ISI][Medline]
24. Ma K, Mallidis C, Artaza J, Taylor W, Gonzalez-Cadavid N, and Bhasin S. Characterization of 5'-regulatory region of human myostatin gene: regulation by dexamethasone in vitro. Am J Physiol Endocrinol Metab 281: E1128E1136, 2001.
25. Mallidis C, Bhasin S, Matsumoto A, Shen R, and Gonzalez-Cadavid NF. Skeletal muscle myostatin in a rat model of aging-associated sarcopenia. In: Proceedings of the 81st Annual Meeting of The Endocrine Society, San Diego, CA, 1999. Chevy Chase, MD: The Endocrine Society, 1999, p.73.
26. McPherron AC, Lawler AM, and Lee SJ. Regulation of skeletal muscle mass in mice by a new TGF- superfamily member. Nature 387: 8390, 1997.[CrossRef][ISI][Medline]
27. McPherron AC and Lee SJ. Double muscling in cattle due to mutations in the myostatin gene. Proc Natl Acad Sci USA 94: 1245712461, 1997.
28. Musaro A, Cusella De Angelis MG, Germani A, Ciccarelli C, Molinaro M, and Zani BM. Enhanced expression of myogenic regulatory genes in aging skeletal muscle. Exp Cell Res 221: 241248, 1995.[CrossRef][ISI][Medline]
29. Nguyen QG, Buskin JN, Himeda CL, Shield MA, and Hauschka SD. Differences in the function of three conserved E-boxes of the muscle creatine kinase gene in cultured myocytes and in transgenic mouse skeletal and cardiac muscle. J Biol Chem 278: 4649446505, 2003.
30. Oldham JM, Martyn JAK, Sharma M, Jeanplong F, Kambadur R, and Bass JJ. Molecular expression of myostatin and MyoD is greater in double-muscled than normal-muscled cattle fetuses. Am J Physiol Regul Integr Comp Physiol 280: R1488R1493, 2001.
31. Petropoulos CJ, Payne W, Salter DW, and Hughes SH. Appropriate in vivo expression of a muscle-specific promoter by using avian retroviral vectors for gene transfer. J Virol 66: 33913397, 1992.[Abstract]
32. Roth SM, Martel GF, Ferrell RE, Metter EJ, Hurley BF, and Rogers MA. Myostatin gene expression is reduced in humans with heavy-resistance strength training: a brief communication. Exp Biol Med 228: 706709, 2003.
33. Schiaffino S and Reggiani C. Molecular diversity of myofibrillar proteins: gene regulation and functional significance. Physiol Rev 76: 371423, 1996.
34. Shield MA, Haugen HS, Clegg CH, and Hauschka SD. E-box sites and a proximal regulatory region of the muscle creatine kinase gene differentially regulate expression in diverse skeletal muscles and cardiac muscle of transgenic mice. Mol Cell Biol 16: 50585068, 1996.[Abstract]
35. Simon AM and Burden SJ. An E box mediates activation and repression of the acetylcholine receptor -subunit gene during myogenesis. Mol Cell Biol 13: 51335140, 1993.[Abstract]
36. Skarli M, Kiri A, Vrbova G, Lee CA, and Goldspink G. Myosin regulatory elements as vectors for gene transfer by intramuscular injection. Gene Ther 5: 514520, 1998.[CrossRef][ISI][Medline]
37. Spiller MP, Kambadur R, Jeanplong F, Thomas M, Martyn JK, Bass JJ, and Sharma M. The myostatin gene is a downstream target gene of basic helix-loop-helix transcription factor MyoD. Mol Cell Biol 22: 70667082, 2002.
38. Swoap SJ. In vivo analysis of the myosin heavy chain IIB promoter region. Am J Physiol Cell Physiol 274: C681C687, 1998.
39. Truscott M, Raynal L, Premdas P, Goulet B, Leduy L, Berube G, and Nepveu A. CDP/Cux stimulates transcription from the DNA polymerase gene promoter. Mol Cell Biol 23: 30133028, 2003.
40. Wada-Kiyama Y, Kuwabara K, Sakuma Y, Onishi Y, Trifonov EN, and Kiyama R. Localization of curved DNA and its association with nucleosome phasing in the promoter region of the human estrogen receptor gene. FEBS Lett 444: 117124, 1999.[CrossRef][ISI][Medline]
41. Webster C, Silberstein L, Hays AP, and Blau HM. Fast muscle fibers are preferentially affected in Duchenne muscular dystrophy. Cell 52: 503513, 1988.[ISI][Medline]
42. Wehling M, Cai B, and Tidball JG. Modulation of myostatin expression during modified muscle use. FASEB J 14: 103110, 2000.
43. Wheeler MT, Snyder EC, Patterson MN, and Swoap SJ. An E-box within the MHC IIB gene is bound by MyoD and is required for gene expression in fast muscle. Am J Physiol Cell Physiol 276: C1069C1078, 1999.
44. Yan Z, Serrano AL, Schiaffino S, Bassel-Duby R, and Williams RS. Regulatory elements governing transcription in specialized myofiber subtypes. J Biol Chem 276: 1736117366, 2001.
|
HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Visit Other APS Journals Online |