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Li R, Ferreira MP, Cooke MB, La Bounty P, Campbell B, Greenwood M, Willoughby DS, Kreider RB. Co-ingestion of carbohydrate with branched-chain amino acids or L-leucine does not preferentially increase serum IGF-1 and expression of myogenic-related genes in response to a single bout of resistance exercise. Amino Acids 2015; 47:1203-13. [PMID: 25740607 DOI: 10.1007/s00726-015-1947-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 02/16/2015] [Indexed: 12/23/2022]
Abstract
The purpose of this study was to determine if the co-ingestion of carbohydrate (CHO) with branched-chain amino acids (BCAA) or L-leucine (LEU) preferentially affected serum IGF-1 and the expression of myogenic-related genes in response to resistance exercise (RE). Forty-one college-age males were randomly assigned to 1 of 4 groups: CHO, CHO-BCAA, CHO-LEU, or placebo (PLC). Resistance exercise consisted of 4 sets of 10 repetitions of leg press and leg extension at 80 % 1RM. Supplements were ingested peri-exercise, and venous blood and muscle biopsies were obtained pre-exercise (PRE), and at 30, 120, and 360 min post-exercise. Serum IGF-1 was determined with ELISA, and skeletal muscle mRNA expression of myostatin, ACTRIIB, p21kip, p27kip, CDK2, cyclin B1, cyclin D1, Myo-D, myogenin, MRF-4, and myf5 was determined using real-time PCR. Results were analyzed by two-way ANOVA for serum IGF-1 and two-way MANOVA for mRNA expression. Serum IGF-1 in CHO + BCAA was greater than PLC (p < 0.05) but was not affected by RE (p > 0.05). A significant group × time interaction was located for cylin D1 (p < 0.05), but not for any other genes. However, significant time effects were noted for cyclin B1 and p21cip (p < 0.05). At 30, 120 and 360 min post-exercise, p21cip was significantly less than PRE. Cyclin D1 was greater than PRE and 30 min post-exercise at 120 and 360 min post-exercise, whereas cyclin B1 was significantly greater than PRE at 120 min post-exercise (p < 0.05). Unlike the co-ingestion of CHO with either BCAA or L-leucine in conjunction with RE, the expression of various myogenically related genes were up-regulated with RE.
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Affiliation(s)
- Rui Li
- Department of Health Sciences, Northeastern University, Boston, MA, 02115, USA,
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52
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Er H, Acar N, Kipmen-Korgun D, Celik-Ozenci C, Ustunel I, Asar M, Korgun ET. Determination of PCNA, cyclin D3, p27, p57 and apoptosis rate in normal and dexamethasone-induced intrauterine growth restricted rat placentas. Acta Histochem 2015; 117:137-47. [PMID: 25596037 DOI: 10.1016/j.acthis.2014.11.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 11/24/2014] [Accepted: 11/25/2014] [Indexed: 01/07/2023]
Abstract
Intrauterine growth restriction (IUGR) is a major clinical problem, which causes perinatal morbidity and mortality. One of the reasons for IUGR is abnormal placentation. In rats, fetal-placental exposure to maternally administered glucocorticoids decreases birth weight and placental weight. Proper placental development depends on the proliferation and differentiation of trophoblasts. Our knowledge about the mitotic regulators that play key roles in synchronizing these events is limited. Also the mechanisms underlying the placental growth inhibitory effects of glucocorticoids have not been elucidated. The aim of this study was to investigate the immunolocalization, mRNA and protein levels of proliferating cell nuclear antigen (PCNA), cyclin D3, p27 and p57 in normal and dexamethasone-induced IUGR Wistar rat placentas by reverse transcriptase polymerase chain reaction (RT-PCR), immunohistochemistry and Western blot. We also compared apoptotic cell numbers at the light microscopic level via terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL) and transmission electron microscopy. Glucocorticoid levels were higher in IUGR rats than in control rats after 60 and 120min of injection. We showed reduced gene and protein expressions of PCNA and cyclin D3 and increased expressions of p27 and p57 in IUGR placentas compared to control placentas. Apoptotic cell number was higher in the placentas of the IUGR group. In brief we found that maternal dexamethasone treatment led to a shift from cell proliferation to apoptosis in IUGR placentas. Dexamethasone induced placental and embryonal abnormalities which could be associated with reduced expressions of PCNA and cyclin D3, increased expressions of p27 and p57 and increased rate of apoptosis in IUGR placentas.
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Affiliation(s)
- Hakan Er
- Department of Histology and Embryology, Medical Faculty, Akdeniz University, 07070 Antalya, Turkey; Department of Biophysics, Medical Faculty, Akdeniz University, 07070 Antalya, Turkey
| | - Nuray Acar
- Department of Histology and Embryology, Medical Faculty, Akdeniz University, 07070 Antalya, Turkey
| | - Dijle Kipmen-Korgun
- Department of Biochemistry, Medical Faculty, Akdeniz University, 07070 Antalya, Turkey
| | - Ciler Celik-Ozenci
- Department of Histology and Embryology, Medical Faculty, Akdeniz University, 07070 Antalya, Turkey
| | - Ismail Ustunel
- Department of Histology and Embryology, Medical Faculty, Akdeniz University, 07070 Antalya, Turkey
| | - Mevlut Asar
- Department of Histology and Embryology, Medical Faculty, Akdeniz University, 07070 Antalya, Turkey
| | - Emin Turkay Korgun
- Department of Histology and Embryology, Medical Faculty, Akdeniz University, 07070 Antalya, Turkey.
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Abstract
Phosphoinositide 3-OH kinase (PI3K) regulates a number of developmental and physiologic processes in skeletal muscle; however, the contributions of individual PI3K p110 catalytic subunits to these processes are not well-defined. To address this question, we investigated the role of the 110-kDa PI3K catalytic subunit β (p110β) in myogenesis and metabolism. In C2C12 cells, pharmacological inhibition of p110β delayed differentiation. We next generated mice with conditional deletion of p110β in skeletal muscle (p110β muscle knockout [p110β-mKO] mice). While young p110β-mKO mice possessed a lower quadriceps mass and exhibited less strength than control littermates, no differences in muscle mass or strength were observed between genotypes in old mice. However, old p110β-mKO mice were less glucose tolerant than old control mice. Overexpression of p110β accelerated differentiation in C2C12 cells and primary human myoblasts through an Akt-dependent mechanism, while expression of kinase-inactive p110β had the opposite effect. p110β overexpression was unable to promote myoblast differentiation under conditions of p110α inhibition, but expression of p110α was able to promote differentiation under conditions of p110β inhibition. These findings reveal a role for p110β during myogenesis and demonstrate that long-term reduction of skeletal muscle p110β impairs whole-body glucose tolerance without affecting skeletal muscle size or strength in old mice.
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54
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Agius E, Bel-Vialar S, Bonnet F, Pituello F. Cell cycle and cell fate in the developing nervous system: the role of CDC25B phosphatase. Cell Tissue Res 2014; 359:201-13. [PMID: 25260908 DOI: 10.1007/s00441-014-1998-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 09/04/2014] [Indexed: 12/20/2022]
Abstract
Deciphering the core machinery of the cell cycle and cell division has been primarily the focus of cell biologists, while developmental biologists have identified the signaling pathways and transcriptional programs controlling cell fate choices. As a result, until recently, the interplay between these two fundamental aspects of biology have remained largely unexplored. Increasing data show that the cell cycle and regulators of the core cell cycle machinery are important players in cell fate decisions during neurogenesis. Here, we summarize recent data describing how cell cycle dynamics affect the switch between proliferation and differentiation, with an emphasis on the roles played by the cell cycle regulators, the CDC25 phosphatases.
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Affiliation(s)
- Eric Agius
- Université Toulouse 3; Centre de Biologie du Développement (CBD), 118 route de Narbonne, 31062, Toulouse, France
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55
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De Luca G, Ferretti R, Bruschi M, Mezzaroma E, Caruso M. Cyclin D3 critically regulates the balance between self-renewal and differentiation in skeletal muscle stem cells. Stem Cells 2014; 31:2478-91. [PMID: 23897741 PMCID: PMC3963451 DOI: 10.1002/stem.1487] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 05/26/2013] [Accepted: 06/21/2013] [Indexed: 12/28/2022]
Abstract
Satellite cells are mitotically quiescent myogenic stem cells resident beneath the basal lamina surrounding adult muscle myofibers. In response to injury, multiple extrinsic signals drive the entry of satellite cells into the cell cycle and then to proliferation, differentiation, and self-renewal of their downstream progeny. Because satellite cells must endure for a lifetime, their cell cycle activity must be carefully controlled to coordinate proliferative expansion and self-renewal with the onset of the differentiation program. In this study, we find that cyclin D3, a member of the family of mitogen-activated D-type cyclins, is critically required for proper developmental progression of myogenic progenitors. Using a cyclin D3-knockout mouse we determined that cyclin D3 deficiency leads to reduced myofiber size and impaired establishment of the satellite cell population within the adult muscle. Cyclin D3-null myogenic progenitors, studied ex vivo on isolated myofibers and in vitro, displayed impaired cell cycle progression, increased differentiation potential, and reduced self-renewal capability. Similarly, silencing of cyclin D3 in C2 myoblasts caused anticipated exit from the cell cycle and precocious onset of terminal differentiation. After induced muscle damage, cyclin D3-null myogenic progenitors exhibited proliferation deficits, a precocious ability to form newly generated myofibers and a reduced capability to repopulate the satellite cell niche at later stages of the regeneration process. These results indicate that cyclin D3 plays a cell-autonomous and nonredundant function in regulating the dynamic balance between proliferation, differentiation, and self-renewal that normally establishes an appropriate pool size of adult satellite cells.
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Affiliation(s)
- Giulia De Luca
- National Research Council, Institute of Cell Biology and Neurobiology, Fondazione Santa Lucia, Roma, Italy
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56
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Wu SL, Li GZ, Chou CY, Tsai MS, Chen YP, Li CJ, Liou GG, Chang WW, Chen SL, Wang SH. Double homeobox gene, Duxbl, promotes myoblast proliferation and abolishes myoblast differentiation by blocking MyoD transactivation. Cell Tissue Res 2014; 358:551-66. [PMID: 25130140 DOI: 10.1007/s00441-014-1974-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 07/21/2014] [Indexed: 01/08/2023]
Abstract
Homeobox genes encode transcription factors that regulate embryonic development programs including organogenesis, axis formation and limb development. Previously, we identified and cloned a mouse double homeobox gene, Duxbl, whose homeodomain exhibits the highest identity (67 %) to human DUX4, a candidate gene of facioscapulohumeral muscular dystrophy (FSHD). Duxbl proteins have been shown to be expressed in elongated myocytes and myotubes of trunk and limb muscles during embryogenesis. In this study, we found that Duxbl maintained low expression levels in various adult muscles. Duxbl proteins were induced to express in activated satellite cells and colocalized with MyoG, a myogenic differentiating marker. Furthermore, Duxbl proteins were not detected in quiescent satellite cells but detected in regenerated myocytes and colocalized with MyoD and MyoG following cardiotoxin-induced muscle injury. Ectopic Duxbl overexpressions in C2C12 myoblast cells promoted cell proliferation through mainly enhancing cyclin D1 and hyper-phosphorylated retinoblastoma protein but reducing p21 expression. However, Duxbl overexpression in C2C12 cells inhibited myogenic differentiation by decreasing MyoD downstream gene expressions, including M-cadherin, MyoG, p21 and cyclin D3 but not MyoD itself. Duxbl overexpressions also promoted cell proliferation but blocked MyoD-induced myogenic conversion in multipotent mesenchymal C3H10T1/2 cells. In addition, results of a luciferase reporter assay suggest that Duxbl negatively regulated MyoG promoter activity through the proximal two E boxes. In conclusion, these results indicate that Duxbl may play a crucial role in myogenesis and postnatal muscle regeneration by activating and proliferating satellite and myoblast cells.
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Affiliation(s)
- Shey-Lin Wu
- Department of Neurology, Chang-Hua Christian Hospital, Changhua, Taiwan, Republic of China
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57
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Rajabi HN, Takahashi C, Ewen ME. Retinoblastoma protein and MyoD function together to effect the repression of Fra-1 and in turn cyclin D1 during terminal cell cycle arrest associated with myogenesis. J Biol Chem 2014; 289:23417-27. [PMID: 25006242 DOI: 10.1074/jbc.m113.532572] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The acquisition of skeletal muscle-specific function and terminal cell cycle arrest represent two important features of the myogenic differentiation program. These cellular processes are distinct and can be separated genetically. The lineage-specific transcription factor MyoD and the retinoblastoma protein pRb participate in both of these cellular events. Whether and how MyoD and pRb work together to effect terminal cell cycle arrest is uncertain. To address this question, we focused on cyclin D1, whose stable repression is required for terminal cell cycle arrest and execution of myogenesis. MyoD and pRb are both required for the repression of cyclin D1; their actions, however, were found not to be direct. Rather, they operate to regulate the immediate early gene Fra-1, a critical player in mitogen-dependent induction of cyclin D1. Two conserved MyoD-binding sites were identified in an intronic enhancer of Fra-1 and shown to be required for the stable repression of Fra-1 and, in turn, cyclin D1. Localization of MyoD alone to the intronic enhancer of Fra-1 in the absence of pRb was not sufficient to elicit a block to Fra-1 induction; pRb was also recruited to the intronic enhancer in a MyoD-dependent manner. These observations suggest that MyoD and pRb work together cooperatively at the level of the intronic enhancer of Fra-1 during terminal cell cycle arrest. This work reveals a previously unappreciated link between a lineage-specific transcription factor, a tumor suppressor, and a proto-oncogene in the control of an important facet of myogenic differentiation.
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Affiliation(s)
- Hasan N Rajabi
- From the Dana-Farber Cancer Institute, Boston, Massachusetts 02215
| | - Chiaki Takahashi
- From the Dana-Farber Cancer Institute, Boston, Massachusetts 02215, the Cancer Research Institute of Kanazawa University, 13-1 Takara-machi, Kanazawa 920-0934, Japan, and
| | - Mark E Ewen
- From the Dana-Farber Cancer Institute, Boston, Massachusetts 02215, the Molecular Oncology Research Institute, Tufts Medical Center, Boston, Massachusetts 02111
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58
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Ajioka I. Coordination of proliferation and neuronal differentiation by the retinoblastoma protein family. Dev Growth Differ 2014; 56:324-34. [PMID: 24697649 DOI: 10.1111/dgd.12127] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 02/13/2014] [Accepted: 02/16/2014] [Indexed: 12/23/2022]
Abstract
Once neurons enter the post-mitotic G0 phase during central nervous system (CNS) development, they lose their proliferative potential. When neurons re-enter the cell cycle during pathological situations such as neurodegeneration, they undergo cell death after S phase progression. Thus, the regulatory networks that drive cell proliferation and maintain neuronal differentiation are highly coordinated. In this review, the coordination of cell cycle control and neuronal differentiation during development are discussed, focusing on regulation by the Rb family of tumor suppressors (including p107 and p130), and the Cip/Kip family of cyclin dependent kinase (Cdk) inhibitors. Based on recent findings suggesting roles for these families in regulating neurogenesis and neuronal differentiation, I propose that the Rb family is essential for daughter cells of neuronal progenitors to enter the post-mitotic G0 phase without affecting the initiation of neuronal differentiation in most cases, while the Cip/Kip family regulates the timing of neuronal progenitor cell cycle exit and the initiation of neuronal differentiation at least in the progenitor cells of the cerebral cortex and the retina. Rb's lack of involvement in regulating the initiation of neuronal differentiation may explain why Rb family-deficient retinoblastomas characteristically exhibit neuronal features.
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Affiliation(s)
- Itsuki Ajioka
- Center for Brain Integration Research, Tokyo Medical and Dental University, 1-5-45 Yushima, Tokyo, 113-8510, Japan
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59
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Ohnishi Y, Watanabe M, Wato M, Tanaka A, Kakudo K, Nozaki M. Cyclin D1 expression is correlated with cell differentiation and cell proliferation in oral squamous cell carcinomas. Oncol Lett 2014; 7:1123-1127. [PMID: 24944679 PMCID: PMC3961451 DOI: 10.3892/ol.2014.1880] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 01/15/2014] [Indexed: 11/21/2022] Open
Abstract
The present study conducted an immunohistochemical investigation of cyclin D1 and Ki-67 expression in oral squamous cell carcinoma (SCC) to evaluate the correlations between cell differentiation, cell proliferation and metastasis, and the effect of anticancer drug medication and cyclin D1 expression. Cyclin D1 and Ki-67 were detected clearly in the nuclei of 35 SCC samples. No correlation between cyclin D1 protein expression and oral SCC differentiation was found. By contrast, the majority of metastatic foci (90%) exhibited strong cyclin D1 expression, whereas weak expression was observed in metastatic foci with pre-operative adjuvant therapy. Additionally, cyclin D1 and Ki-67 were expressed in basal to suprabasal cells of well-differentiated oral SCC, whereas cyclin D1-positive and Ki-67-negative cells were present in the highly-differentiated region, according to a double-immunostaining method. These results indicate that the expression of cyclin D1 protein plays a role in cell differentiation and cell proliferation in well-differentiated oral SCC.
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Affiliation(s)
- Yuichi Ohnishi
- Second Department of Oral and Maxillofacial Surgery, Osaka Dental University, Hirakata, Osaka 573-1121, Japan
| | - Masahiro Watanabe
- Second Department of Oral and Maxillofacial Surgery, Osaka Dental University, Hirakata, Osaka 573-1121, Japan
| | - Masahiro Wato
- Department of Oral Pathology, Osaka Dental University, Hirakata, Osaka 573-1121, Japan
| | - Akio Tanaka
- Department of Oral Pathology, Osaka Dental University, Hirakata, Osaka 573-1121, Japan
| | - Kenji Kakudo
- Second Department of Oral and Maxillofacial Surgery, Osaka Dental University, Hirakata, Osaka 573-1121, Japan
| | - Masami Nozaki
- Department of Cell Biology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
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60
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de Meester C, Timmermans AD, Balteau M, Ginion A, Roelants V, Noppe G, Porporato PE, Sonveaux P, Viollet B, Sakamoto K, Feron O, Horman S, Vanoverschelde JL, Beauloye C, Bertrand L. Role of AMP-activated protein kinase in regulating hypoxic survival and proliferation of mesenchymal stem cells. Cardiovasc Res 2013; 101:20-9. [PMID: 24104879 DOI: 10.1093/cvr/cvt227] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
AIMS Mesenchymal stem cells (MSCs) are widely used for cell therapy, particularly for the treatment of ischaemic heart disease. Mechanisms underlying control of their metabolism and proliferation capacity, critical elements for their survival and differentiation, have not been fully characterized. AMP-activated protein kinase (AMPK) is a key regulator known to metabolically protect cardiomyocytes against ischaemic injuries and, more generally, to inhibit cell proliferation. We hypothesized that AMPK plays a role in control of MSC metabolism and proliferation. METHODS AND RESULTS MSCs isolated from murine bone marrow exclusively expressed the AMPKα1 catalytic subunit. In contrast to cardiomyocytes, a chronic exposure of MSCs to hypoxia failed to induce cell death despite the absence of AMPK activation. This hypoxic tolerance was the consequence of a preference of MSC towards glycolytic metabolism independently of oxygen availability and AMPK signalling. On the other hand, A-769662, a well-characterized AMPK activator, was able to induce a robust and sustained AMPK activation. We showed that A-769662-induced AMPK activation inhibited MSC proliferation. Proliferation was not arrested in MSCs derived from AMPKα1-knockout mice, providing genetic evidence that AMPK is essential for this process. Among AMPK downstream targets proposed to regulate cell proliferation, we showed that neither the p70 ribosomal S6 protein kinase/eukaryotic elongation factor 2-dependent protein synthesis pathway nor p21 was involved, whereas p27 expression was increased by A-769662. Silencing p27 expression partially prevented the A-769662-dependent inhibition of MSC proliferation. CONCLUSION MSCs resist hypoxia independently of AMPK whereas chronic AMPK activation inhibits MSC proliferation, p27 being involved in this regulation.
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Affiliation(s)
- Carole de Meester
- Pôle de Recherche Cardiovasculaire, Université catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Avenue Hippocrate, 55, B1.55.05, Brussels B-1200, Belgium
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61
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Storer NY, White RM, Uong A, Price E, Nielsen GP, Langenau DM, Zon LI. Zebrafish rhabdomyosarcoma reflects the developmental stage of oncogene expression during myogenesis. Development 2013; 140:3040-50. [PMID: 23821038 DOI: 10.1242/dev.087858] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Rhabdomyosarcoma is a pediatric malignancy thought to arise from the uncontrolled proliferation of myogenic cells. Here, we have generated models of rhabdomyosarcoma in the zebrafish by inducing oncogenic KRAS(G12D) expression at different stages during muscle development. Several zebrafish promoters were used, including the cdh15 and rag2 promoters, which drive gene expression in early muscle progenitors, and the mylz2 promoter, which is expressed in differentiating myoblasts. The tumors that developed differed in their ability to recapitulate normal myogenesis. cdh15:KRAS(G12D) and rag2:KRAS(G12D) fish developed tumors that displayed an inability to complete muscle differentiation as determined by histological appearance and gene expression analyses. By contrast, mylz2:KRAS(G12D) tumors more closely resembled mature skeletal muscle and were most similar to well-differentiated human rhabdomyosarcoma in terms of gene expression. mylz2:KRAS(G12D) fish showed significantly improved survival compared with cdh15:KRAS(G12D) and rag2:KRAS(G12D) fish. Tumor-propagating activity was enriched in myf5-expressing cell populations within all of the tumor types. Our results demonstrate that oncogenic KRAS(G12D) expression at different stages during muscle development has profound effects on the ability of tumor cells to recapitulate normal myogenesis, altering the tumorigenic capability of these cells.
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Affiliation(s)
- Narie Y Storer
- Stem Cell Program and Division of Hematology/Oncology, Boston Children's Hospital and Dana-Farber Cancer Institute, Boston, MA 02115, USA
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62
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Gross SM, Rotwein P. Live cell imaging reveals marked variability in myoblast proliferation and fate. Skelet Muscle 2013; 3:10. [PMID: 23638706 PMCID: PMC3712004 DOI: 10.1186/2044-5040-3-10] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Accepted: 03/28/2013] [Indexed: 11/29/2022] Open
Abstract
Background During the process of muscle regeneration, activated stem cells termed satellite cells proliferate, and then differentiate to form new myofibers that restore the injured area. Yet not all satellite cells contribute to muscle repair. Some continue to proliferate, others die, and others become quiescent and are available for regeneration following subsequent injury. The mechanisms that regulate the adoption of different cell fates in a muscle cell precursor population remain unclear. Methods We have used live cell imaging and lineage tracing to study cell fate in the C2 myoblast line. Results Analyzing the behavior of individual myoblasts revealed marked variability in both cell cycle duration and viability, but similarities between cells derived from the same parental lineage. As a consequence, lineage sizes and outcomes differed dramatically, and individual lineages made uneven contributions toward the terminally differentiated population. Thus, the cohort of myoblasts undergoing differentiation at the end of an experiment differed dramatically from the lineages present at the beginning. Treatment with IGF-I increased myoblast number by maintaining viability and by stimulating a fraction of cells to complete one additional cell cycle in differentiation medium, and as a consequence reduced the variability of the terminal population compared with controls. Conclusion Our results reveal that heterogeneity of responses to external cues is an intrinsic property of cultured myoblasts that may be explained in part by parental lineage, and demonstrate the power of live cell imaging for understanding how muscle differentiation is regulated.
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Affiliation(s)
- Sean M Gross
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239-3098, USA.
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63
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Khanjyan MV, Yang J, Kayali R, Caldwell T, Bertoni C. A high-content, high-throughput siRNA screen identifies cyclin D2 as a potent regulator of muscle progenitor cell fusion and a target to enhance muscle regeneration. Hum Mol Genet 2013; 22:3283-95. [PMID: 23612904 DOI: 10.1093/hmg/ddt184] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Cell-mediated regenerative approaches using muscle progenitor cells hold promises for the treatment of many forms of muscle disorders. Their applicability in the clinic, however, is hindered by the low levels of regeneration obtained after transplantation and the large number of cells required to achieve an effect. To better understand the mechanisms that regulate the temporal switch of replicating muscle progenitor cells into terminally differentiated cells and to develop new strategies that could enhance muscle regeneration, we have developed and performed a high-throughput screening (HTS) capable of identifying genes that play active roles during myogenesis. Secondary and tertiary screens were used to confirm the effects of RNAi in vitro and in vivo and to select for candidate hits that significantly increase regeneration into skeletal muscles. Downregulation of cyclin D2 (CCND2) was shown to dramatically enhance myogenic differentiation of muscle progenitor cells and to induce a robust regeneration after cell transplantation into skeletal muscles of dystrophin-deficient mice. Protein interaction network and pathway analysis revealed that CCND2 directly interacts with the cyclin-dependent kinase Cdk4 to inhibit phosphorylation of the retinoblastoma protein (pRb), thus blocking the activation of the myogenic switch during fusion. These studies identify CCND2 as a new key regulator of terminal differentiation in muscle progenitor cells and open new possibilities for the treatment of many forms of muscle disorders characterized by impaired regeneration and loss of muscle mass.
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Affiliation(s)
- Michael V Khanjyan
- Department of Neurology, David Geffen School of Medicine, University of California Los Angeles, 710 Westwood Plaza, Los Angeles, CA 90095, USA
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64
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Li XH, Chen XJ, Ou WB, Zhang Q, Lv ZR, Zhan Y, Ma L, Huang T, Yan YB, Zhou HM. Knockdown of creatine kinase B inhibits ovarian cancer progression by decreasing glycolysis. Int J Biochem Cell Biol 2013; 45:979-86. [PMID: 23416112 DOI: 10.1016/j.biocel.2013.02.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 01/31/2013] [Accepted: 02/03/2013] [Indexed: 01/28/2023]
Abstract
Creatine kinase plays a key role in the energy homeostasis of vertebrate cells. Creatine kinase B (CKB), a cytosolic isoform of creatine kinase, shows upregulated expression in a variety of cancers. In this research, we confirmed that some ovarian cancer tissues had elevated CKB expression at the protein level. The functions of CKB in ovarian cancer progression were investigated in the ovarian cancer cell line Skov3, which has a high CKB expression. It was found that CKB knockdown inhibited Skov3 cell proliferation and induced apoptosis under hypoxia or hypoglycemia conditions. CKB depletion also sensitized Skov3 to chemotherapeutic agents. Furthermore, the CKB knockdown reduced glucose consumption and lactate production, and increased ROS production and oxygen consumption. This suggested that CKB knockdown decreased cytosolic glycolysis and resulted in a tumor suppressive metabolic state in Skov3 cells. Consequently, we found that the knockdown of CKB induced G2 arrest in cell cycle by elevating p21 expression and affected the PI3K/Akt and AMPK pathways. These findings provide new insights in the role of CKB in cancer cell survival and tumor progression. Our results also suggest that CKB depletion/inhibition in combination with chemotherapeutic agents might have synergistic effects in ovarian cancer therapy.
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Affiliation(s)
- Xu-Hui Li
- Beijing Key Laboratory of Protein Therapeutics, School of Life Sciences, Tsinghua University, Beijing, China
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65
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Kreslavsky T, Gleimer M, Miyazaki M, Choi Y, Gagnon E, Murre C, Sicinski P, von Boehmer H. β-Selection-induced proliferation is required for αβ T cell differentiation. Immunity 2013; 37:840-53. [PMID: 23159226 DOI: 10.1016/j.immuni.2012.08.020] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 08/02/2012] [Indexed: 10/27/2022]
Abstract
Proliferation and differentiation are tightly coordinated to produce an appropriate number of differentiated cells and often exhibit an antagonistic relationship. Developing T cells, which arise in the thymus from a minute number of bone-marrow-derived progenitors, undergo a major expansion upon pre-T cell receptor (TCR) expression. The burst of proliferation coincides with differentiation toward the αβ T cell lineage-but the two processes were previously thought to be independent from one another, although both were driven by signaling from pre-TCR and Notch receptors. Here we report that proliferation at this step was not only absolutely required for differentiation but also that its ectopic activation was sufficient to substantially rescue differentiation in the absence of Notch signaling. Consistently, pharmacological inhibition of the cell cycle machinery also blocked differentiation in vivo. Thus the proliferation step is strictly required prior to differentiation of immature thymocytes.
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Affiliation(s)
- Taras Kreslavsky
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
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66
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Wang L, Chen X, Zheng Y, Li F, Lu Z, Chen C, Liu J, Wang Y, Peng Y, Shen Z, Gao J, Zhu M, Chen H. MiR-23a inhibits myogenic differentiation through down regulation of fast myosin heavy chain isoforms. Exp Cell Res 2012; 318:2324-34. [PMID: 22771720 DOI: 10.1016/j.yexcr.2012.06.018] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 06/19/2012] [Accepted: 06/26/2012] [Indexed: 11/20/2022]
Abstract
MicroRNAs (miRNAs) are a class of small non-coding RNAs that repress the expression of their target genes post-transcriptionally. MiRNAs participate in the regulation of a variety of biological processes, including development and diseases. However, the functional role and molecular mechanism by which miRNAs regulate skeletal muscle development and differentiation are not fully understood. In this report, we identified miR-23a as a key regulator of skeletal muscle differentiation. Using bioinformatics analyses, miR-23a is predicted to target multiple adult fast myosin heavy chain (Myh) genes, including Myh 1, 2 and 4. Luciferase reporter assays show that miR-23a directly targets the 3' untranslated regions (UTRs) of these mRNAs. Interestingly, the expression level of mature miR-23a is inversely correlated with myogenic progression in mouse skeletal muscle. Both gain- and loss-of-function studies using C2C12 myoblasts demonstrate that miR-23a inhibits myogenic differentiation. These findings therefore reveal a novel role of miR-23a in regulating myogenic differentiation via inhibiting the expression of fast myosin heavy chain isoforms.
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Affiliation(s)
- Li Wang
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, No. 1 Wenyuan Road, Nanjing 210046, China
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Gurung R, Parnaik VK. Cyclin D3 promotes myogenic differentiation and Pax7 transcription. J Cell Biochem 2012; 113:209-19. [PMID: 21898542 DOI: 10.1002/jcb.23346] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Differentiation of skeletal muscle myoblasts involves activation of muscle-specific markers such as MyoD, Myf5, MRF4, and myogenin, followed by exit from the cell cycle, expression of structural proteins, and fusion into multinucleated myotubes. Cyclin D3 is upregulated during muscle differentiation, and expression of cyclin D3 in proliferating myoblasts causes early activation of myogenesis. In this study, we have identified the genes activated by cyclin D3 expression in C2C12 myoblasts and differentiated cells by real-time PCR analysis. Cyclin D3 expression induced faster differentiation kinetics and increase in levels of myogenic genes such as MyoD, Myf5, and myogenin at an early stage during the differentiation process, although long-term myogenic differentiation was not affected. Transcript levels of the transcription factor Pax7 that is expressed in muscle progenitors were enhanced by cyclin D3 expression in myoblasts. Components of a histone methyltransferase complex recruited by Pax7 to myogenic gene promoters were also regulated by cyclin D3. Further, the Pax7 promoter was upregulated in myoblasts expressing cyclin D3. Myoblasts that expressed cyclin D3 showed moderately higher levels of the cyclin-dependent kinase inhibitor p21 and were stalled in G2/M phase of the cell cycle. Our findings suggest that cyclin D3 primes myoblasts for differentiation by enhancing muscle specific gene expression and cell cycle exit.
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Affiliation(s)
- Ritika Gurung
- Centre for Cellular and Molecular Biology, Hyderabad, India
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68
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The p44/wdr77-dependent cellular proliferation process during lung development is reactivated in lung cancer. Oncogene 2012; 32:1888-900. [PMID: 22665061 DOI: 10.1038/onc.2012.207] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
During lung development, cells proliferate for a defined length of time before they begin to differentiate. Factors that control this proliferative process and how this growth process is related to lung cancer are currently unknown. Here, we found that the WD40-containing protein (p44/wdr77) was expressed in growing epithelial cells at the early stages of lung development. In contrast, p44/wdr77 expression was diminished in fully differentiated epithelial cells in the adult lung. Loss of p44/wdr77 gene expression led to cell growth arrest and differentiation. Re-expression of p44/wdr77 caused terminally differentiated cells to re-enter the cell cycle. Our findings suggest that p44/wdr77 is essential and sufficient for proliferation of lung epithelial cells. P44/Wdr77 was re-expressed in lung cancer, and silencing p44/wdr77 expression strongly inhibited growth of lung adenocarcinoma cells in tissue culture and abolished growth of lung adenocarcinoma tumor xenografts in mice. The growth arrest induced by loss of p44/wdr77 expression was partially through the p21-Rb signaling. Our results suggest that p44/wdr77 controls cellular proliferation during lung development, and this growth process is reactivated during lung tumorigenesis.
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69
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Parker MH, von Maltzahn J, Bakkar N, Al-Joubori B, Ishibashi J, Guttridge D, Rudnicki MA. MyoD-dependent regulation of NF-κB activity couples cell-cycle withdrawal to myogenic differentiation. Skelet Muscle 2012; 2:6. [PMID: 22541644 PMCID: PMC3356597 DOI: 10.1186/2044-5040-2-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Accepted: 04/27/2012] [Indexed: 01/19/2023] Open
Abstract
Background Mice lacking MyoD exhibit delayed skeletal muscle regeneration and markedly enhanced numbers of satellite cells. Myoblasts isolated from MyoD-/- myoblasts proliferate more rapidly than wild type myoblasts, display a dramatic delay in differentiation, and continue to incorporate BrdU after serum withdrawal. Methods Primary myoblasts isolated from wild type and MyoD-/- mutant mice were examined by microarray analysis and further characterized by cell and molecular experiments in cell culture. Results We found that NF-κB, a key regulator of cell-cycle withdrawal and differentiation, aberrantly maintains nuclear localization and transcriptional activity in MyoD-/- myoblasts. As a result, expression of cyclin D is maintained during serum withdrawal, inhibiting expression of muscle-specific genes and progression through the differentiation program. Sustained nuclear localization of cyclin E, and a concomitant increase in cdk2 activity maintains S-phase entry in MyoD-/- myoblasts even in the absence of mitogens. Importantly, this deficit was rescued by forced expression of IκBαSR, a non-degradable mutant of IκBα, indicating that inhibition of NF-κB is sufficient to induce terminal myogenic differentiation in the absence of MyoD. Conclusion MyoD-induced cytoplasmic relocalization of NF-κB is an essential step in linking cell-cycle withdrawal to the terminal differentiation of skeletal myoblasts. These results provide important insight into the unique functions of MyoD in regulating the switch from progenitor proliferation to terminal differentiation.
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Affiliation(s)
- Maura H Parker
- Ottawa Hospital Research Institute, 501 Smyth Rd, Ottawa, ON, K1H 8L6, Canada.
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70
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Gagan J, Dey BK, Dutta A. MicroRNAs regulate and provide robustness to the myogenic transcriptional network. Curr Opin Pharmacol 2012; 12:383-8. [PMID: 22386695 DOI: 10.1016/j.coph.2012.02.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 01/31/2012] [Accepted: 02/02/2012] [Indexed: 11/19/2022]
Abstract
The genetics of skeletal muscle lineage commitment are deceptively complicated. MyoD overexpression is sufficient to convert fibroblasts into skeletal muscle myotubes. In vivo, there are a number of different steps of differentiation that require a large network of transcription factors that control differentiation and homeostasis of skeletal muscle progenitors. Each transcription factor has been shown to have the ability to promote the next factor in the cascade, but the mechanisms regulating the transitions remain incomplete. Recently, microRNAs have been shown to be important for a large number of developmental and oncogenic processes. In this review, we will discuss recent advances in the understanding of how microRNA is critical for skeletal muscle development by interacting with protein-coding genes that had previously been shown to be important for myogenesis.
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Affiliation(s)
- Jeffrey Gagan
- Department of Biochemistry and Molecular Genetics, University of Virginia, 1300 Jefferson Park Ave, Jordan Hall 1240, University of Virginia School of Medicine, Charlottesville, VA 22908, United States
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Huang SF, Cheng SD, Chuang WY, Chen IH, Liao CT, Wang HM, Hsieh LL. Cyclin D1 overexpression and poor clinical outcomes in Taiwanese oral cavity squamous cell carcinoma. World J Surg Oncol 2012; 10:40. [PMID: 22336657 PMCID: PMC3312822 DOI: 10.1186/1477-7819-10-40] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 02/16/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cyclin D1 gene regulates cell cycle and plays an important role in the tumorigenesis of human cancers. The association between cyclin D1, clinicopathologic parameters and prognosis in oral cavity squamous cell carcinoma (OSCC) is inconclusive. METHODS A total of 264 male OSCCs were examined for cyclin D1 protein expression using immunohistochemistry (IHC). The expression levels of cyclin D1 were defined as overexpression when more than 10% of tumor cells displayed nuclear staining with moderate to strong intensity. RESULTS Overexpression of cyclin D1 was found in 97 (36.7%) OSCCs. Cyclin D1 protein overexpression was significantly associated with lymph node metastasis (P = 0.002), tumor cell differentiation (P = 0.031) and tumor stage (P = 0.051), but not associated with age onset, cigarette smoking, alcohol drinking, or areca quid chewing. Overexpression of cyclin D1 was also significantly associated with poor clinical outcomes in terms of disease-free survival (DFS, P = 0.002) and overall survival (OS, P < 0.001). The effects of cyclin D1 protein overexpression on DFS (hazard ratio (HR) = 1.540; 95% confidence interval (CI), 1.068 - 2.222) and OS (HR = 1.702; 95% CI, 1.168 - 2.480) were still existed after adjusting for clinicopathological parameters (such as age, primary tumor status, tumor cell differentiation, and lymph node metastasis) using logistic multivariate analysis. CONCLUSION Cyclin D1 protein worked as an independent prognostic factor and can be as a biomarker for the aggressiveness of OSCC.
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Affiliation(s)
- Shiang-Fu Huang
- Department of Otolaryngology, Head and Neck Surgery, Chang Gung Memorial Hospital, Tao-Yuan, Taiwan
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72
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Wang X, Sistrunk C, Miliani de Marval PL, Kim Y, Rodriguez-Puebla ML. Combined effect of cyclin D3 expression and abrogation of cyclin D1 prevent mouse skin tumor development. Cell Cycle 2012; 11:335-42. [PMID: 22214766 DOI: 10.4161/cc.11.2.18774] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We have previously demonstrated that ras-mediated skin tumorigenesis depends on signaling pathways that act preferentially through cyclin D1 and D2. Interestingly, the expression of cyclin D3 inhibits skin tumor development, an observation that conflicts with the oncogenic role of D-type cyclins in the mouse epidermis. Here, we show that simultaneous up and downregulation of particular members of the D-type cyclin family is a valuable approach to reduce skin tumorigenesis. We developed the K5D3/cyclin D1(-/-) compound mouse, which overexpresses cyclin D3 but lacks expression of cyclin D1 in the skin. Similar to K5D3 transgenic mice, keratinocytes from K5D3/cyclin D1(-/-) compound mice show a significant reduction of cyclin D2 levels. Therefore, this model allows us to determine the effect of cyclin D3 expression when combined with reduced or absent expression of the remaining two members of the D-type cyclin family in mouse epidermis. Our data show that induced expression of cyclin D3 compensates for the reduced level of cyclin D1 and D2, resulting in normal keratinocyte proliferation. However, simultaneous ablation of cyclin D1 and downregulation of cyclin D2 via cyclin D3 expression resulted in a robust reduction in ras-mediated skin tumorigenesis. We conclude that modulation of the levels of particular members of the D-type cyclin family could be useful to inhibit tumor development and, in particular, ras-mediated tumorigenesis.
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Affiliation(s)
- Xian Wang
- Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA
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73
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Bai X, Wu X, Wang X, Liu X, Song Y, Gao F, Miao Y, Yu L, Tang B, Wang X, Radu B, Vallee I, Boireau P, Wang F, Zhao Y, Liu M. Inhibition of mammalian muscle differentiation by excretory secretory products of muscle larvae of Trichinella spiralis in vitro. Parasitol Res 2011; 110:2481-90. [DOI: 10.1007/s00436-011-2789-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 12/13/2011] [Indexed: 12/14/2022]
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74
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Tanaka S, Terada K, Nohno T. Canonical Wnt signaling is involved in switching from cell proliferation to myogenic differentiation of mouse myoblast cells. J Mol Signal 2011; 6:12. [PMID: 21970630 PMCID: PMC3198762 DOI: 10.1186/1750-2187-6-12] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Accepted: 10/05/2011] [Indexed: 11/29/2022] Open
Abstract
Background Wnt/β-catenin signaling is involved in various aspects of skeletal muscle development and regeneration. In addition, Wnt3a and β-catenin are required for muscle-specific gene transcription in embryonic carcinoma cells and satellite-cell proliferation during adult skeletal muscle regeneration. Downstream targets of canonical Wnt signaling are cyclin D1 and c-myc. However both target genes are suppressed during differentiation of mouse myoblast cells, C2C12. Underlying molecular mechanisms of β-catenin signaling during myogenic differentiation remain unknown. Results Using C2C12 cells, we examined intracellular signaling and gene transcription during myoblast proliferation and differentiation. We confirmed that several Wnt signaling components, including Wnt9a, Sfrp2 and porcupine, were consistently upregulated in differentiating C2C12 cells. Troponin T-positive myotubes were decreased by Wnt3a overexpression, but not Wnt4. TOP/FOP reporter assays revealed that co-expression with Wnt4 reduced Wnt3a-induced luciferase activity, suggesting that Wnt4 signaling counteracted Wnt3a signaling in myoblasts. FH535, a small-molecule inhibitor of β-catenin/Tcf complex formation, reduced basal β-catenin in the cytoplasm and decreased myoblast proliferation. K252a, a protein kinase inhibitor, increased both cytosolic and membrane-bound β-catenin and enhanced myoblast fusion. Treatments with K252a or Wnt4 resulted in increased cytoplasmic vesicles containing phosphorylated β-catenin (Tyr654) during myogenic differentiation. Conclusions These results suggest that various Wnt ligands control subcellular β-catenin localization, which regulate myoblast proliferation and myotube formation. Wnt signaling via β-catenin likely acts as a molecular switch that regulates the transition from cell proliferation to myogenic differentiation.
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Affiliation(s)
- Shingo Tanaka
- Department of Molecular and Developmental Biology, Kawasaki Medical School, Kurashiki, Okayama 701-0192, Japan.
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75
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The myogenic kinome: protein kinases critical to mammalian skeletal myogenesis. Skelet Muscle 2011; 1:29. [PMID: 21902831 PMCID: PMC3180440 DOI: 10.1186/2044-5040-1-29] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 09/08/2011] [Indexed: 12/13/2022] Open
Abstract
Myogenesis is a complex and tightly regulated process, the end result of which is the formation of a multinucleated myofibre with contractile capability. Typically, this process is described as being regulated by a coordinated transcriptional hierarchy. However, like any cellular process, myogenesis is also controlled by members of the protein kinase family, which transmit and execute signals initiated by promyogenic stimuli. In this review, we describe the various kinases involved in mammalian skeletal myogenesis: which step of myogenesis a particular kinase regulates, how it is activated (if known) and what its downstream effects are. We present a scheme of protein kinase activity, similar to that which exists for the myogenic transcription factors, to better clarify the complex signalling that underlies muscle development.
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76
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Kalchhauser I, Farley BM, Pauli S, Ryder SP, Ciosk R. FBF represses the Cip/Kip cell-cycle inhibitor CKI-2 to promote self-renewal of germline stem cells in C. elegans. EMBO J 2011; 30:3823-9. [PMID: 21822213 DOI: 10.1038/emboj.2011.263] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Accepted: 07/11/2011] [Indexed: 11/09/2022] Open
Abstract
Although the decision between stem cell self-renewal and differentiation has been linked to cell-cycle modifications, our understanding of cell-cycle regulation in stem cells is very limited. Here, we report that FBF/Pumilio, a conserved RNA-binding protein, promotes self-renewal of germline stem cells by repressing CKI-2(Cip/Kip), a Cyclin E/Cdk2 inhibitor. We have previously shown that repression of CYE-1 (Cyclin E) by another RNA-binding protein, GLD-1/Quaking, promotes germ cell differentiation. Together, these findings suggest that a post-transcriptional regulatory circuit involving FBF and GLD-1 controls the self-renewal versus differentiation decision in the germline by promoting high CYE-1/CDK-2 activity in stem cells, and inhibiting CYE-1/CDK-2 activity in differentiating cells.
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Affiliation(s)
- Irene Kalchhauser
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
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77
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Weintraub M, Kalebic T, Helman LJ, Bhatia KG. Disruption of the MyoD/p21 Pathway in Rhabdomyosarcoma. Sarcoma 2011; 1:135-41. [PMID: 18521215 PMCID: PMC2395370 DOI: 10.1080/13577149778218] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Purpose. Rhabdomyosarcoma (RMS) is an embryonal tumor thought to arise from skeletal muscle cells that fail to
differentiate terminally. The majority of RMSs express MyoD, a protein essential to the differentiation of skeletal muscle.
It was recently shown that during myogenesis, MyoD activates the expression of the cyclin-dependent kinase inhibitor
(CDKi), p21, which itself plays a critical role in normal muscle development. To investigate the integrity of the MyoD/p21
pathway in RMS, we analyzed p21 and its relationship to MyoD expression in RMS. Methods. A panel of RMS samples was assembled from primary biopsies and from cell lines. Integrity of p21 was analyzed
by single-strand conformation polymorphism (SSCP) and sequencing. Expression of p21 and MyoD was determined by
Northern blot analysis, and the ability of exogenous p21 to arrest the cell cycle of RMS cell line was determined by
transfection studies. Results. Our analysis indicates that although p21 is wild type in RMS, there is an inverse correlation between the levels
of p21 and MyoD in these tumors. Tumors that express significant amounts of MyoD fail to express p21. This does not
appear to be the result of mutations within the potential CACGTG sites present in the p21 promoter region or in the
coding region of p21. An additional group of RMSs express very high levels of p21 but express little, if any, MyoD.
Furthermore, RD, a RMS cell line which expresses high levels of endogenous p21, undergoes withdrawal from the cell
cycle following forced expression of p21, suggesting that the pathway which would lead to G1
arrest from endogenous p21 activity is defective. Discussion. These data suggest that the interaction between p21 and MyoD is defective in RMS although the precise
nature of the defect remains to be elucidated.
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Affiliation(s)
- M Weintraub
- Pediatric Branch National Cancer Institute National Institutes of Health Building 10, Room 13N240 Bethesda MD 20892 USA
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78
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Low-molecular-weight fucoidan regulates myogenic differentiation through the mitogen-activated protein kinase pathway in C2C12 cells. Br J Nutr 2011; 106:1836-44. [PMID: 21682942 DOI: 10.1017/s0007114511002534] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Low-molecular-weight fucoidan (LMWF) has been broadly studied in recent years due to its numerous biological properties. Nevertheless, there have been no reports about the effects of LMWF on myogenic differentiation (MyoD). The objective of the present study was to demonstrate the impact of LMWF on myogenesis in C2C12 cells. The ultimate aim was to establish whether LMWF regulates myogenesis similar to heparin as a partial regulator of myogenesis. LMWF was prepared at a minimal size by ultra-filtration compared with crude fucoidan. We treated C2C12 cells with LMWF and/or heparin during MyoD. The data from the present study are the first to suggest that LMWF suppresses the expression of the myogenic regulatory factors and the myocyte enhancer factors as well as the morphological changes that occur during differentiation. Additionally, the expression of the mitogen-activated protein kinase (MAPK) family was significantly inhibited by LMWF when compared with controls. The LMWF-treated group showed significantly decreased expression of reactive oxygen species (ROS) enzymes compared with control cells. Heparin was used as a positive control because it has been reported to activate MyoD. Taken together, these results suggest that LMWF might regulate MyoD through the MAPK pathway and by regulating ROS activity in C2C12 cells.
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PATHARE SWAPNALIM, GERSTUNG MORITZ, BEERENWINKEL NIKO, SCHÄFFER ALEJANDROA, KANNAN SADHANA, PAI PRATHAMESH, PATHAK KALOK, BORGES ANITAM, MAHIMKAR MANOJB. Clinicopathological and prognostic implications of genetic alterations in oral cancers. Oncol Lett 2011; 2:445-451. [PMID: 21546976 PMCID: PMC3085881 DOI: 10.3892/ol.2011.271] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Accepted: 02/17/2011] [Indexed: 11/05/2022] Open
Abstract
This study evaluated the clinicopathological and prognostic implications of genetic alterations characterizing oral squamous cell carcinoma(OSCC). Comparative genomic hybridization(CGH) was used to identify chromosomal alterations present in primary OSCCs obtained from 97 pateints. In this population, tobacco use was a significant risk factor for OSCC. By contrast, all 97 of our samples are negative for human papillomavirus (HPV) DNA integration, which is another known risk factor for OSCC in certain populations. Results of the Fisher's exact test followed by Benjamini-Hochberg correction for multiple testing, showed a correlation of 7p gain and 8p loss with node-positive OSCC (p≤0.04 for both genetic alterations) and association of 11q13 gain with high-grade OSCC (p≤0.05). Univariate Cox-proportional hazard models, also corrected for multiple testing, showed significant association of 11q13 gain and 18q loss with decreased survival (p≤0.05). These findings were supported by multivariate analysis which revealed that 11q13 gain and 18q loss together serve as a strong bivariate predictor of poor prognosis. In conclusion, our study has identified genetic alterations that correlate significantly with nodal status, grade, and poor survival status of OSCC. These potential biomarkers may aid the current TNM system for better prediction of clinical outcome.
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Affiliation(s)
- SWAPNALI M. PATHARE
- Cancer Research Institute, Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre (TMC), Kharghar Node, Navi Mumbai 410210
| | - MORITZ GERSTUNG
- Department of Biosystems Science and Engineering, ETH Zurich, Basel, Switzerland
| | - NIKO BEERENWINKEL
- Department of Biosystems Science and Engineering, ETH Zurich, Basel, Switzerland
| | - ALEJANDRO A. SCHÄFFER
- Computational Biology Branch, National Center for Biotechnology Information, NIH, DHHS, Bethesda, MD, USA
| | - SADHANA KANNAN
- ECTU, Advanced Centre for Treatment, Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre (TMC), Kharghar Node, Navi Mumbai 410210
| | - PRATHAMESH PAI
- Tata Memorial Hospital, Tata Memorial Centre (TMC), Mumbai 400012
| | | | - ANITA M. BORGES
- Department of Pathology and Laboratory Medicine, S.L. Raheja Hospital, Mumbai 400016, India
| | - MANOJ B. MAHIMKAR
- Cancer Research Institute, Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre (TMC), Kharghar Node, Navi Mumbai 410210
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Mu X, Li Y. Conditional TGF-β1 treatment increases stem cell-like cell population in myoblasts. J Cell Mol Med 2011; 15:679-90. [PMID: 20184662 PMCID: PMC3008543 DOI: 10.1111/j.1582-4934.2010.01042.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Accepted: 02/11/2010] [Indexed: 12/21/2022] Open
Abstract
The limitation in successfully acquiring large populations of stem cell has impeded their application. A new method based on the dedifferentiation of adult somatic cells to generate induced multipotent stem cells would allow us to obtain a large amount of autologous stem cells for regenerative medicine. The current work was proposed to induce a sub-population of cells with characteristics of muscle stem cells from myoblasts through conditional treatment of transforming growth factor (TGF)-β(1) . Our results show that a lower concentration of TGF-β(1) is able to promote C2C12 myoblasts to express stem cell markers as well as to repress myogenic proteins, which involves a mechanism of dedifferentiation. Moreover, TGF-β(1) treatment promoted the proliferation-arrested C2C12 myoblasts to re-enter the S-phase. We also investigated the multi-differentiation potentials of the dedifferentiated cells. TGF-β(1) pre-treated C2C12 myoblasts were implanted into mice to repair dystrophic skeletal muscle or injured bone. In addition to the C2C12 myoblasts, similar effects of TGF-β(1) were also observed in the primary myoblasts of mice. Our results suggest that TGF-β(1) is effective as a molecular trigger for the dedifferentiation of skeletal muscle myoblasts and could be used to generate a large pool of progenitor cells that collectively behave as multipotent stem cell-like cells for regenerative medicine applications.
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Affiliation(s)
- Xiaodong Mu
- The Laboratory of Molecular Pathology, Stem Cell Research Center (SCRC), Children’s Hospital of UPMCPittsburgh, PA, USA
- Department of Orthopaedic Surgery, University of PittsburghPittsburgh, PA, USA
| | - Yong Li
- The Laboratory of Molecular Pathology, Stem Cell Research Center (SCRC), Children’s Hospital of UPMCPittsburgh, PA, USA
- Department of Orthopaedic Surgery, University of PittsburghPittsburgh, PA, USA
- Department of Pathology, University of PittsburghPittsburgh, PA, USA
- Department of Bioengineering, University of PittsburghPittsburgh, PA, USA
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81
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Jin D, Hidaka K, Shirai M, Morisaki T. RNA-binding motif protein 24 regulates myogenin expression and promotes myogenic differentiation. Genes Cells 2011; 15:1158-67. [PMID: 20977548 DOI: 10.1111/j.1365-2443.2010.01446.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The formation of muscle fibers involves sequential expression of many proteins that regulate key steps during myoblast-to-myotube transition. Myogenin is a major player in the initiation and maintenance of myogenic differentiation in a mouse myoblast cell line, C2C12. RNA-binding proteins bind to specific target RNA sequences and regulate gene expression in a post-transcriptional manner. This study demonstrates that RNA-binding motif protein 24 (Rbm24) interacts with the 3'-untranslated region of myogenin mRNA and affects its half-life in C2C12 myogenesis. Knockdown of Rbm24 expression by RNA interference significantly decreased myogenin expression associated with the inhibition of myogenesis. In contrast, the overexpression of Rbm24 by stable transfection of a plasmid increased myogenin expression and had a positive effect on myogenic differentiation. Ectopic expression of myogenin was also able to restore myogenic differentiation in Rbm24-knockdown cells. Together, our results suggest that Rbm24 binds to myogenin mRNA and regulates its stability in C2C12 cells. Rbm24 plays a crucial role in myogenic differentiation at least in part through a myogenin-dependent post-transcriptional regulatory pathway.
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Affiliation(s)
- Donghao Jin
- Department of Bioscience, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
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82
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Ciemerych MA, Archacka K, Grabowska I, Przewoźniak M. Cell cycle regulation during proliferation and differentiation of mammalian muscle precursor cells. Results Probl Cell Differ 2011; 53:473-527. [PMID: 21630157 DOI: 10.1007/978-3-642-19065-0_20] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Proliferation and differentiation of muscle precursor cells are intensively studied not only in the developing mouse embryo but also using models of skeletal muscle regeneration or analyzing in vitro cultured cells. These analyses allowed to show the universality of the cell cycle regulation and also uncovered tissue-specific interplay between major cell cycle regulators and factors crucial for the myogenic differentiation. Examination of the events accompanying proliferation and differentiation leading to the formation of functional skeletal muscle fibers allows understanding the molecular basis not only of myogenesis but also of skeletal muscle regeneration. This chapter presents the basis of the cell cycle regulation in proliferating and differentiating muscle precursor cells during development and after muscle injury. It focuses at major cell cycle regulators, myogenic factors, and extracellular environment impacting on the skeletal muscle.
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Affiliation(s)
- Maria A Ciemerych
- Department of Cytology, Institute of Zoology, University of Warsaw, Miecznikowa 1, 02-096 Warsaw, Poland.
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83
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Saab R, Spunt SL, Skapek SX. Myogenesis and rhabdomyosarcoma the Jekyll and Hyde of skeletal muscle. Curr Top Dev Biol 2011; 94:197-234. [PMID: 21295688 DOI: 10.1016/b978-0-12-380916-2.00007-3] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Rhabdomyosarcoma, a neoplasm composed of skeletal myoblast-like cells, represents the most common soft tissue sarcoma in children. The application of intensive chemotherapeutics and refined surgical and radiation therapy approaches have improved survival for children with localized disease over the past 3 decades; however, these approaches have not improved the dismal outcome for children with metastatic and recurrent rhabdomyosarcoma. Elegant studies have defined the molecular mechanisms driving skeletal muscle lineage commitment and differentiation, and the machinery that couples differentiation with irreversible cell proliferation arrest. Further, detailed molecular analyses indicate that rhabdomyosarcoma cells have lost the capacity to fully differentiate when challenged to do so in experimental models. We review the intersection of normal skeletal muscle developmental biology and the molecular genetic defects in rhabdomyosarcoma with the underlying premise that understanding how the differentiation process has gone awry will lead to new treatment strategies aimed at promoting myogenic differentiation and concomitant cell cycle arrest.
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Affiliation(s)
- Raya Saab
- Children's Cancer Center of Lebanon, Department of Pediatrics, American University of Beirut, Beirut, Lebanon
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84
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Regulation of the p21 Sdi1/Cip1/Waf1DNA Synthesis Inhibitor in Senescent Human Diploid Fibroblasts. Can J Aging 2010. [DOI: 10.1017/s0714980800006772] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
ABSTRACTA large body of evidence has demonstrated that normal human fibroblasts have a limited division potential in culture and underwent senescence, a process whereby cells became arrested in the G1 phase of the cell cycle and overexpressed a DNA synthesis inhibitor(s). Cyclin-dependent kinase two (Cdk2) is required for the promotion of the Gi-to-S phase transition in human cells. Senescent fibroblasts contain intact cyclin-Cdk2 complexes but cannot induce Cdk2 protein kinase activity in response to mitogen stimulation. Recently, we cloned p21Sdi1, a potent inhibitor of DNA synthesis and Cdk2 kinase activity, from a senescent cell cDNA library and demonstrated that it was expressed at significantly higher levels in senescent cells than actively proliferating cells. In contrast to actively dividing cells, mitogen-stimulated senescent cells do not down-regulate the expression of p21Sdi1and do not express late G1 phase gene products that are required for entry into S phase. We suggest that the inability of mitogen-stimulated senescent cells to down-regulate p21Sdi1levels contributes to the resulting lack of late Gi gene expression and failure to traverse the G1/S phase boundary.
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85
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Bakkar N, Guttridge DC. NF-kappaB signaling: a tale of two pathways in skeletal myogenesis. Physiol Rev 2010; 90:495-511. [PMID: 20393192 DOI: 10.1152/physrev.00040.2009] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
NF-kappaB is a ubiquitiously expressed transcription factor that plays vital roles in innate immunity and other processes involving cellular survival, proliferation, and differentiation. Activation of NF-kappaB is controlled by an IkappaB kinase (IKK) complex that can direct either canonical (classical) NF-kappaB signaling by degrading the IkappaB inhibitor and releasing p65/p50 dimers to the nucleus, or causes p100 processing and nuclear translocation of RelB/p52 via a noncanonical (alternative) pathway. Under physiological conditions, NF-kappaB activity is transiently regulated, whereas constitutive activation of this transcription factor typically in the classical pathway is associated with a multitude of disease conditions, including those related to skeletal muscle. How NF-kappaB functions in muscle diseases is currently under intense investigation. Insight into this role of NF-kappaB may be gained by understanding at a more basic level how this transcription factor contributes to skeletal muscle cell differentiation. Recent data from knockout mice support that the classical NF-kappaB pathway functions as an inhibitor of skeletal myogenesis and muscle regeneration acting through multiple mechanisms. In contrast, alternative NF-kappaB signaling does not appear to be required for myofiber conversion, but instead functions in myotube homeostasis by regulating mitochondrial biogenesis. Additional knowledge of these signaling pathways in skeletal myogenesis should aid in the development of specific inhibitors that may be useful in treatments of muscle disorders.
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Affiliation(s)
- Nadine Bakkar
- Department of Molecular Virology, Immunology, and Medical Genetics, Arthur G. James Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
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86
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Abstract
Acute kidney injury (AKI) activates pathways of cell death and cell proliferation. Although seemingly discrete and unrelated mechanisms, these pathways can now be shown to be connected and even to be controlled by similar pathways. The dependence of the severity of renal-cell injury on cell cycle pathways can be used to control and perhaps to prevent acute kidney injury. This review is written to address the correlation between cellular life and death in kidney tubules, especially in acute kidney injury.
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Affiliation(s)
- Peter M Price
- Department of Internal Medicine, University of Arkansas for Medical Sciences, Central Arkansas Veterans Healthcare System, Little Rock, Arkansas, USA.
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87
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Salmon M, Owens GK, Zehner ZE. Over-expression of the transcription factor, ZBP-89, leads to enhancement of the C2C12 myogenic program. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1793:1144-55. [PMID: 19232372 PMCID: PMC2700214 DOI: 10.1016/j.bbamcr.2009.01.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Revised: 01/16/2009] [Accepted: 01/20/2009] [Indexed: 11/18/2022]
Abstract
Myogenesis involves the complex interplay between the down-regulation of non-muscle genes and the up-regulation of muscle-specific genes. This interplay is controlled by the myogenic regulatory factors Myf5, MRF4, MyoD and myogenin. To trigger the up-regulation of these muscle-specific factors, certain environmental cues, such as the removal of serum, signal C2C12 myoblast cells to withdraw from cell cycle, fuse and activate muscle-specific genes. Here, the level of ZBP-89 (zfp148), a Krüppel-like transcription factor, has been shown to increase during myogenesis. Over-expression of ZBP-89, via adenoviral infection, led to the enhancement of the myogenic program without requiring the removal of serum. Quantitative real-time PCR and ChIP assays documented that ZBP-89 promoted the down-regulation of Pax7 coupled with the up-regulation of MRF4 and MyoD to regulate C2C12 differentiation in vitro. In addition, ZBP-89 over-expression up-regulated p21 and Rb while promoting the down-regulation of cyclinA and cyclinD1. In converse, the diminution of ZBP-89 by siRNA promoted the retention of myogenic and cell cycle regulators at myoblast levels resulting in a concomitant delay of the myogenic program. From these studies we conclude that the transcription factor ZBP-89 plays an important role in the timing of the myogenic program.
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Affiliation(s)
- Morgan Salmon
- Department of Biochemistry and Molecular Biology and the Massey Cancer Center, School of Medicine, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0614, USA
| | - Gary K Owens
- Department of Physiology and Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908
| | - Zendra E. Zehner
- Department of Biochemistry and Molecular Biology and the Massey Cancer Center, School of Medicine, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0614, USA
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88
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Guo W, Zhang KM, Tu K, Li YX, Zhu L, Xiao HS, Yang Y, Wu JR. Adipogenesis licensing and execution are disparately linked to cell proliferation. Cell Res 2009; 19:216-23. [PMID: 19065151 DOI: 10.1038/cr.2008.319] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Coordination of cell differentiation and proliferation is a key issue in the development process of multi-cellular organisms and stem cells. Here we provide evidence that the establishment of adipocyte differentiation of 3T3-L1 cells requires two processes: the licensing of an adipogenesis gene-expression program within a particular growth-arrest stage, i.e., the contact-inhibition stage, and then the execution of this program in a cell-cycle-independent manner, by which the licensed progenitors are differentiated into adipocytes in the presence of inducing factors. Our results showed that differentiation licensing of 3T3-L1 cells during the contact-inhibition stage involved epigenetic modifications such as DNA methylation and histone modifications, whereas disturbing these epigenetic modifications by DNA methylation inhibitors or RNAi during the contact-inhibition stage significantly reduced adipogenesis efficiency. More importantly, when these licensed 3T3-L1 cells were re-cultured under non-differentiating conditions or treated only with insulin, this adipogenesis commitment could be maintained from one cell generation to the next, whereby the licensed program could be activated in a cell-cycle-independent manner once these cells were subjected to adipogenesis-inducing conditions. This result suggests that differentiation licensing and differentiation execution can be uncoupled and disparately linked to cell proliferation. Our findings deliver a new concept that cell-fate decision can be subdivided into at least two stages, licensing and execution, which might have different regulatory relationships with cell proliferation. In addition, this new concept may provide a clue for developing new strategies against obesity.
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Affiliation(s)
- Wei Guo
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China
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89
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Schiewer MJ, Morey LM, Burd CJ, Liu Y, Merry DE, Ho SM, Knudsen KE. Cyclin D1 repressor domain mediates proliferation and survival in prostate cancer. Oncogene 2009; 28:1016-27. [PMID: 19079343 PMCID: PMC2852245 DOI: 10.1038/onc.2008.446] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Revised: 10/16/2008] [Accepted: 11/07/2008] [Indexed: 12/15/2022]
Abstract
Regulation of the androgen receptor (AR) is critical to prostate cancer (PCa) development; therefore, AR is the first line therapeutic target for disseminated tumors. Cell cycle-dependent accumulation of cyclin D1 negatively modulates the transcriptional regulation of AR through discrete, CDK4-independent mechanisms. The transcriptional corepressor function of cyclin D1 resides within a defined motif termed repressor domain (RD), and it was hypothesized that this motif could be utilized as a platform to develop new strategies for blocking AR function. Here, we demonstrate that expression of the RD peptide is sufficient to disrupt AR transcriptional activation of multiple, prostate-specific AR target genes. Importantly, these actions are sufficient to specifically inhibit S-phase progression in AR-positive PCa cells, but not in AR-negative cells or tested AR-positive cells of other lineages. As expected, impaired cell cycle progression resulted in a suppression of cell doubling. Additionally, cell death was observed in AR-positive cells that maintain androgen dependence and in a subset of castrate-resistant PCa cells, dependent on Akt activation status. Lastly, the ability of RD to cooperate with existing hormone therapies was examined, which revealed that RD enhanced the cellular response to an AR antagonist. Together, these data demonstrate that RD is sufficient to disrupt AR-dependent transcriptional and proliferative responses in PCa, and can enhance efficacy of AR antagonists, thus establishing the impetus for development of RD-based mimetics.
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Affiliation(s)
- Matthew J. Schiewer
- Department of Cancer Biology, Thomas Jefferson University, Philadelphia, PA 19107-5541, USA
| | - Lisa M. Morey
- Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0056, USA
| | - Craig J. Burd
- Laboratory of Molecular Carcinogenesis, NIEHS, Research Triangle Park, NC 27709-2233 USA
| | - Yuhong Liu
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107-5541, USA
| | - Diane E. Merry
- Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107-5541, USA
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107-5541, USA
| | - Shuk-Mei Ho
- Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0056, USA
- Center for Environmental Genetics, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0056, USA
- UC Barrett Cancer Center, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0056, USA
| | - Karen E. Knudsen
- Department of Cancer Biology, Thomas Jefferson University, Philadelphia, PA 19107-5541, USA
- Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107-5541, USA
- Department of Urology, Thomas Jefferson University, Philadelphia, PA 19107-5541, USA
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90
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Yang Y, Xu Y, Li W, Wang G, Song Y, Yang G, Han X, Du Z, Sun L, Ma K. STAT3 induces muscle stem cell differentiation by interaction with myoD. Cytokine 2009; 46:137-41. [PMID: 19223199 DOI: 10.1016/j.cyto.2008.12.015] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2008] [Accepted: 12/29/2008] [Indexed: 11/17/2022]
Abstract
Signal transducers and activators of transcription (STAT) family proteins transduce pivotal biological effects of various cytokines and hormones. STAT3 proteins are known to play a central role in the regulation of growth, differentiation, and survival of many types of cells. However, the function of STAT3 in myogenesis still remains largely unknown. We now provided direct evidence that STAT3 could induce myogenic differentiation and this effect might be mediated by interaction with MyoD--the essential transcription factor during myogenic differentiation. Furthermore, leukemia inhibitory factor (LIF) might be the upstream factor which activated JAK2/STAT3 pathway to stimulate muscle cell differentiation. Taken together, these results provide a molecular basis for further understanding of the muscle regeneration mechanism.
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Affiliation(s)
- Yanping Yang
- Department of Hematology and Oncology, The First Hospital, Jilin University, 71 Xinmin Street, Changchun 130021, China
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91
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Abstract
Prostate cancer (PCa) cell proliferation is dependent on activation of the androgen receptor (AR), a ligand-dependent transcription factor. AR activation controls G1-S phase progression through fostering enhanced translation of the D-type cyclins, which promote cell cycle progression through activation of CDK4/6. However, the D-type cyclins harbor additional, CDK4/6 kinase-independent, functions through manipulation of transcription factors, including AR. It was previously established that cyclins D1 and D3 have the potential to modulate AR, and with regard to cyclin D1, disruption of this function occurs in human tumors. Therefore, it was essential to interrogate cyclin D3 function in this tumor type. Here, we show that cyclin D3 is found in association with AR in PCa cells, as mediated through a conserved motif. Cyclin D3 functions to attenuate AR activity through defined mechanisms that include modulation of ligand-dependent conformational changes and modulation of chromatin binding activity. Accumulated cyclin D3 slows cell proliferation in AR-dependent cells, thus suggesting that androgen-induced D-type cyclin production serves to temper the mitogenic response to androgen. Supporting this hypothesis, it is shown that cyclin D3 expression is reduced in primary PCas as a function of tumor grade, and inversely correlates with the proliferative index. In total, these data identify cyclin D3 as a critical modulator of the androgen response, whose deregulation may foster unchecked AR activity in PCa.
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92
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Bascones-Ilundain C, Gonzalez-Moles MA, Esparza G, Gil-Montoya JA, Bascones-Martinez A. Significance of liquefaction degeneration in oral lichen planus: a study of its relationship with apoptosis and cell cycle arrest markers. Clin Exp Dermatol 2007; 32:556-63. [PMID: 17608758 DOI: 10.1111/j.1365-2230.2007.02457.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To assess the utility of liquefaction degeneration as a marker of apoptosis in oral lichen planus (OLP). METHODS TdT-mediated dUTP-biotin nick-end labelling (TUNEL) assay and immunohistochemical methods were used to detect p21 proteins and the active form of caspase 3 in 32 tissue samples of oral mucosa with OLP and 20 samples of normal oral mucosa. RESULTS Liquefaction degeneration was moderate or intense in 27.5% (n=8) and slight in 72.4% (n=21) of OLP samples. There was low expression of apoptosis markers (TUNEL, active caspase 3 form), which was not significantly associated with liquefaction degeneration of the basal cell layer. Basal and suprabasal expression of p21 was significantly more frequent in samples with more intense liquefaction degeneration of basal cells (P<0.01). CONCLUSIONS Our results demonstrate that liquefaction degeneration, as a morphological expression of T lymphocyte attack, does not unequivocally indicate apoptosis. Attacked basal cells more frequently respond with cell-cycle arrest or senescence than with apoptosis.
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Affiliation(s)
- C Bascones-Ilundain
- Department of Periodontics and Dentistry, Complutense University, Madrid, Spain
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93
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Phillips DC, Hunt JT, Moneypenny CG, Maclean KH, McKenzie PP, Harris LC, Houghton JA. Ceramide-induced G2 arrest in rhabdomyosarcoma (RMS) cells requires p21Cip1/Waf1 induction and is prevented by MDM2 overexpression. Cell Death Differ 2007; 14:1780-91. [PMID: 17627285 DOI: 10.1038/sj.cdd.4402198] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The sphingoplipid ceramide is responsible for a diverse range of biochemical and cellular responses including a putative role in modulating cell cycle progression. Herein, we describe that an accumulation of ceramide, achieved through the exogenous application of C(6)-ceramide or exposure to sphingomyelinase, induces a G(2) arrest in Rhabdomyosarcoma (RMS) cell lines. Utilizing the RMS cell line RD, we show that this G(2) arrest required the rapid induction of p21(Cip1/Waf1) independent of DNA damage. This was followed at later time points (48 h) by the commitment to apoptosis. Apoptosis was prevented by Bcl-2 overexpression, but permitted the maintenance of elevated p21(Cip1/Waf1) protein expression and the stabilization of the G(2) arrest response. Inhibition of p21(Cip1/Waf1) protein synthesis with cyclohexamide (CHX) or silencing of p21(Cip1/Waf1) with siRNA, prevented ceramide-mediated G(2) arrest and the late induction of apoptosis. Further, adopting the recent discovery that murine double minute 2 (MDM2) controls p21(Cip1/Waf1) expression by presenting this CDK inhibitor to the proteasome for degradation, RD cells overexpressing MDM2 abrogated ceramide-mediated p21(Cip1/Waf1) induction, G(2) arrest and the late ensuing apoptosis. Collectively, these data further support the notion that ceramide accumulation can modulate cell cycle progression. Additionally, these observations highlight MDM2 expression and proteasomal activity as key determinants of the cellular response to ceramide accumulation.
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Affiliation(s)
- D C Phillips
- Division of Molecular Therapeutics, Department of Oncology, St. Jude Children's Research Hospital, 332 North Lauderdale, Memphis, TN 38105, USA
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94
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Abstract
Ubiquitin-dependent proteolysis plays an important role in regulating fundamental biological functions, including cell division and cellular differentiation. Previous studies implicate the ubiquitin-proteasome system (UPS) in myogenic differentiation through regulating cell cycle progression and modulating myogenic factors such as MyoD and Myf5. Certain ubiquitin protein ligases, including the SCF complex and APC, have been suggested to govern terminal muscle differentiation. However, the underlying mechanism of regulation of both the cell cycle and myogenic factors by the UPS during this process remains unclear. We have dissected the role of the UPS in myogenic differentiation using an in vitro muscle differentiation system based on C2C12 cells. We demonstrate that Cdh1-APC regulates two critical proteins, Skp2 and Myf5, for proteolysis during muscle differentiation. The targeting of Skp2 by Cdh1-APC for destruction results in elevation of p21 and p27, which are crucial for coordinating cellular division and differentiation. Degradation of Myf5 by Cdh1-APC facilitates myogenic fusion. Knockdown of Cdh1 by siRNA significantly attenuates muscle differentiation. Taken together, Cdh1-APC is an important ubiquitin E3 ligase that modulates muscle differentiation through coordinating cell cycle progression and initiating the myogenic differentiation program.
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Affiliation(s)
- Wenqi Li
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine and University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213, USA
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95
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Chen Y, Takita J, Mizuguchi M, Tanaka K, Ida K, Koh K, Igarashi T, Hanada R, Tanaka Y, Park MJ, Hayashi Y. Mutation and expression analyses of the MET and CDKN2A genes in rhabdomyosarcoma with emphasis on MET overexpression. Genes Chromosomes Cancer 2007; 46:348-58. [PMID: 17243166 DOI: 10.1002/gcc.20416] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma of childhood. The simultaneous loss of Ink4a/Arf function and disruption of Met signaling in Ink4a/Arf-/- mice transgenic for hepatocyte growth factor/scatter factor (HGF/SF) induces RMS with extremely high penetrance and short latency. To address the roles of MET and CDKN2A (p16INK4A/p14ARF) in human RMS, we performed mutational analyses in 39 samples of RMS by PCR-SSCP. No mutations were detected in exons 14-21 of MET whereas a nonsense mutation at codon 80 of p16(INK4A) was identified in an alveolar RMS cell line. We also quantified the relative expression levels and DNA copy numbers of these genes in seven cell lines and 17 fresh tumors by real-time quantitative PCR. Expression of MET was detected in all samples; however, more than 10-fold difference was found in the samples with higher or lower expression level, despite a normal DNA copy number. The protein expression level was consistent with that of mRNA, and in cell lines with a higher expression level, MET was constitutively activated. Notably, the expression level of MET was significantly higher in patients who died (P = 0.02), in patients with stage IV (P = 0.04), as well as in patients with PAX3-FKHR chimeric transcript (P = 0.04). On the other hand, reduced or absent expression of p16INK4A and/or p14(ARF) showed no significant correlation with the clinicopathological parameters, except for the age at diagnosis. Our data suggest that MET plays a role in the progression of RMS.
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Affiliation(s)
- Yuyan Chen
- Department of Pediatrics, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
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96
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Yahi H, Philipot O, Guasconi V, Fritsch L, Ait-Si-Ali S. Chromatin modification and muscle differentiation. Expert Opin Ther Targets 2007; 10:923-34. [PMID: 17105377 DOI: 10.1517/14728222.10.6.923] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Skeletal muscle differentiation is a multistep process, which begins with the commitment of multi-potent mesodermal precursor cells to the muscle fate. These committed cells, the myoblasts, then differentiate and fuse into multinucleated myotubes. The final step of muscle differentiation is the maturation of differentiated myotubes into myofibres. Skeletal muscle development requires the coordinated expression of various transcription factors like the members of the myocyte enhancer binding-factor 2 family and the muscle regulatory factors. These transcription factors, in collaboration with chromatin-remodelling complexes, act in specific combinations and within complex transcriptional regulatory networks to achieve skeletal myogenesis. Additional factors involved in the epigenetic regulation of this process continue to be discovered. In this review, the authors discuss the recent discoveries in the epigenetic regulation of myogenesis. They also summarise the role of chromatin-modifying enzymes regulating muscle gene expression. These different factors are often involved in multiple steps of muscle differentiation and have redundant activities. Altogether, the recent findings have allowed a better understanding of myogenesis and have raised new hopes for the pharmacological development of new therapies aimed at muscle degeneration diseases, such as myotonic dystrophy or Duchenne muscular dystrophy.
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Affiliation(s)
- Hakima Yahi
- Institut André Lwoff, Laboratoire Epigénétique et Cancer, FRE 2944, CNRS, 7 rue Guy Moquet, 94800 Villejuif, France
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97
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Perdiguero E, Ruiz-Bonilla V, Gresh L, Hui L, Ballestar E, Sousa-Victor P, Baeza-Raja B, Jardí M, Bosch-Comas A, Esteller M, Caelles C, Serrano AL, Wagner EF, Muñoz-Cánoves P. Genetic analysis of p38 MAP kinases in myogenesis: fundamental role of p38alpha in abrogating myoblast proliferation. EMBO J 2007; 26:1245-56. [PMID: 17304211 PMCID: PMC1817635 DOI: 10.1038/sj.emboj.7601587] [Citation(s) in RCA: 201] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Accepted: 01/10/2007] [Indexed: 02/06/2023] Open
Abstract
The p38 mitogen-activated protein kinase (MAPK) pathway plays a critical role in skeletal muscle differentiation. However, the relative contribution of the four p38 MAPKs (p38alpha, p38beta, p38gamma and p38delta) to this process is unknown. Here we show that myoblasts lacking p38alpha, but not those lacking p38beta or p38delta, are unable to differentiate and form multinucleated myotubes, whereas p38gamma-deficient myoblasts exhibit an attenuated fusion capacity. The defective myogenesis in the absence of p38alpha is caused by delayed cell-cycle exit and continuous proliferation in differentiation-promoting conditions. Indeed, activation of JNK/cJun was enhanced in p38alpha-deficient myoblasts leading to increased cyclin D1 transcription, whereas inhibition of JNK activity rescued the proliferation phenotype. Thus, p38alpha controls myogenesis by antagonizing the activation of the JNK proliferation-promoting pathway, before its direct effect on muscle differentiation-specific gene transcription. More importantly, in agreement with the defective myogenesis of cultured p38alpha(Delta/Delta) myoblasts, neonatal muscle deficient in p38alpha shows cellular hyperproliferation and delayed maturation. This study provides novel evidence of a fundamental role of p38alpha in muscle formation in vitro and in vivo.
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Affiliation(s)
- Eusebio Perdiguero
- Differentiation and Cancer Program, Center for Genomic Regulation (CRG-PRBB), Barcelona, Spain
| | - Vanessa Ruiz-Bonilla
- Differentiation and Cancer Program, Center for Genomic Regulation (CRG-PRBB), Barcelona, Spain
| | - Lionel Gresh
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
| | - Lijian Hui
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
| | | | - Pedro Sousa-Victor
- Differentiation and Cancer Program, Center for Genomic Regulation (CRG-PRBB), Barcelona, Spain
| | - Bernat Baeza-Raja
- Differentiation and Cancer Program, Center for Genomic Regulation (CRG-PRBB), Barcelona, Spain
| | - Mercè Jardí
- Differentiation and Cancer Program, Center for Genomic Regulation (CRG-PRBB), Barcelona, Spain
| | - Anna Bosch-Comas
- Differentiation and Cancer Program, Center for Genomic Regulation (CRG-PRBB), Barcelona, Spain
| | | | - Carme Caelles
- Biomedical Research Institute (IRB-PCB), Barcelona, Spain
| | - Antonio L Serrano
- Differentiation and Cancer Program, Center for Genomic Regulation (CRG-PRBB), Barcelona, Spain
| | - Erwin F Wagner
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
| | - Pura Muñoz-Cánoves
- Differentiation and Cancer Program, Center for Genomic Regulation (CRG-PRBB), Barcelona, Spain
- Center for Genomic Regulation (CRG), Program on Differentiation and Cancer, Dr Aiguader, 88, Barcelona 08003, Spain. Tel.: +34 93 3160133; Fax: +34 93 3160099; E-mail:
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98
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Wu G, Glickstein S, Liu W, Fujita T, Li W, Yang Q, Duvoisin R, Wan Y. The anaphase-promoting complex coordinates initiation of lens differentiation. Mol Biol Cell 2007; 18:1018-29. [PMID: 17215516 PMCID: PMC1805114 DOI: 10.1091/mbc.e06-09-0809] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Lens development requires the precise coordination of cell division and differentiation. The mechanisms by which the differentiation program is initiated after cell cycle arrest remains not well understood. Cyclin-dependent kinase inhibitors (CKIs), such as p15 and p21, have been suggested to be critical components that inhibit G1 progression and therefore, their activation is necessary for quiescence and important for the onset of differentiation. Regulation of p15 and p21 is principally governed by transforming growth factor (TGF)-beta-signaling pathway. We have identified that Cdh1/APC, a critical ubiquitin protein ligase, plays an important role in regulating lens differentiation by facilitating TGF-beta-induced degradation of SnoN, a transcriptional corepressor that needs to be removed for transcriptional activation of p15 and p21. The depletion of Cdh1 by RNA interference attenuates the TGF-beta-mediated induction of p15 and p21 and significantly blocks lens differentiation. Expression of nondegradable SnoN also noticeably attenuates lens induction. Furthermore, we have shown that Cdh1 and SnoN form a complex at the onset of lens differentiation. In vivo histological analysis confirms our biochemical and genetic results. Thus, Cdh1/APC is crucial to the coordination of cell cycle progression and the initiation of lens differentiation through mediating TGF-beta-signaling-induced destruction of SnoN.
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Affiliation(s)
- George Wu
- *University of Pittsburgh Cancer Institute, Pittsburgh, PA 15312
- Weill Medical College of Cornell University, New York, NY 10021; and
| | - Sara Glickstein
- Weill Medical College of Cornell University, New York, NY 10021; and
| | - Weijun Liu
- *University of Pittsburgh Cancer Institute, Pittsburgh, PA 15312
- Department of Cell Biology and Physiology, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261
| | - Takeo Fujita
- *University of Pittsburgh Cancer Institute, Pittsburgh, PA 15312
- Department of Cell Biology and Physiology, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261
| | - Wenqi Li
- *University of Pittsburgh Cancer Institute, Pittsburgh, PA 15312
- Department of Cell Biology and Physiology, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261
| | - Qi Yang
- *University of Pittsburgh Cancer Institute, Pittsburgh, PA 15312
| | - Robert Duvoisin
- Neurological Sciences Institute, Oregon Health and Science University, Beaverton, OR 97006
| | - Yong Wan
- *University of Pittsburgh Cancer Institute, Pittsburgh, PA 15312
- Department of Cell Biology and Physiology, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261
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99
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Cyclin D1 expression in oral squamous cell carcinoma and verrucous carcinoma: correlation with histological differentiation. ACTA ACUST UNITED AC 2007; 103:e30-5. [PMID: 17197212 DOI: 10.1016/j.tripleo.2006.09.011] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2005] [Revised: 07/04/2006] [Accepted: 09/18/2006] [Indexed: 12/25/2022]
Abstract
OBJECTIVE To assess the expression of cyclin D1 in oral squamous cell carcinoma (OSCC) and verrucous carcinoma (VC), to compare its expression in both of these carcinomas, and to investigate the possible correlation of cyclin D1 expression in different histological grades of OSCC. STUDY DESIGN Paraffin embedded tissues from 71 cases of OSCC and VC were studied immunohistochemically. Expression of protein was correlated between the 2 entities and in different grades of OSCC. RESULTS Cyclin D1 overexpression was seen in 29 cases (70.7%) of OSCC and in 19 cases (63.3%) of verrucous carcinoma. Statistical significance at the 5% level was observed for cyclin D1 expression between all categories of squamous cell carcinoma (SCC), that is, between well-differentiated and moderately differentiated carcinomas, and between moderate and poorly differentiated carcinomas, and well and poorly differentiated squamous carcinomas. No statistical significance was observed in cyclin D1 expression between SCC and oral verrucous carcinoma; however, statistical significance was seen between oral VC and poorly differentiated squamous cell carcinoma. CONCLUSION Increased expression of cyclin D1 significantly correlated with lack of differentiation in these malignant epithelial neoplasms.
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100
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Upton JW, Speck SH. Evidence for CDK-dependent and CDK-independent functions of the murine gammaherpesvirus 68 v-cyclin. J Virol 2006; 80:11946-59. [PMID: 17005668 PMCID: PMC1676255 DOI: 10.1128/jvi.01722-06] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gamma-2 herpesviruses encode homologues of mammalian D-type cyclins (v-cyclins), which likely function to manipulate the cell cycle, thereby providing a cellular environment conducive to virus replication and/or reactivation from latency. We have previously shown that the v-cyclin of murine gammaherpesvirus 68 is an oncogene that binds and activates cellular cyclin-dependent kinases (CDKs) and is required for efficient reactivation from latency. To determine the contribution of v-cyclin-mediated cell cycle regulation to the viral life cycle, recombinant viruses in which specific point mutations (E133V or K104E) were introduced into the v-cyclin open reading frame were generated, resulting in the disruption of CDK binding and activation. While in vitro growth of these mutant viruses was unaffected, lytic replication in the lungs following low-dose intranasal inoculation was attenuated for both mutants deficient in CDK binding as well as virus in which the entire v-cyclin open reading frame was disrupted by the insertion of a translation termination codon. This replication defect was not apparent in spleens of mice following intraperitoneal inoculation, suggesting a cell type- and/or route-specific dependence on v-cyclin-CDK interactions during the acute phase of virus infection. Notably, although a v-cyclin-null virus was highly attenuated for reactivation from latency, the E133V v-cyclin CDK-binding mutant exhibited only a modest defect in virus reactivation from splenocytes, and neither the E133V nor K104E v-cyclin mutants were compromised in reactivation from peritoneal exudate cells. Taken together, these data suggest that lytic replication and reactivation in vivo are differentially regulated by CDK-dependent and CDK-independent functions of v-cyclin, respectively.
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Affiliation(s)
- Jason W Upton
- Department of Microbiology and Immunology, Emory University School of Medicine, 1462 Clifton Road, Suite 429, Atlanta, GA 30322, USA
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