351
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Ciani E, Calvanese V, Crochemore C, Bartesaghi R, Contestabile A. Proliferation of cerebellar precursor cells is negatively regulated by nitric oxide in newborn rat. J Cell Sci 2006; 119:3161-70. [PMID: 16835271 DOI: 10.1242/jcs.03042] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The diffusible messenger, nitric oxide plays multiple roles in neuroprotection, neurodegeneration and brain plasticity. Its involvement in neurogenesis has been disputed, on the basis of results on models in vivo and in culture. We report here that pharmacological blockade of nitric oxide production in rat pups resulted, during a restricted time window of the first three postnatal days, in increased cerebellar proliferation rate, as assessed through tritiated thymidine or BrdU incorporation into DNA. This was accompanied by increased expression of Myc, a transcription factor essential for cerebellar development, and of the cell cycle regulating gene, cyclin D1. These effects were mediated downstream by the nitric oxide-dependent second messenger, cGMP. Schedules of pharmacological NO deprivation targeted to later developmental stages (from postnatal day 3 to 7), no longer increased proliferation, probably because of partial escape of the cGMP level from nitric oxide control. Though limited to a brief temporal window, the proliferative effect of neonatal nitric oxide deprivation could be traced into adulthood. Indeed, the number of BrdU-labeled surviving cells, most of which were of neuronal phenotype, was larger in the cerebellum of 60-day-old rats that had been subjected to NO deprivation during the first three postnatal days than in control rats. Experiments on cell cultures from neonatal cerebellum confirmed that nitric oxide deprivation stimulated proliferation of cerebellar precursor cells and that this effect was not additive with the proliferative action of sonic hedgehog peptide. The finding that nitric oxide deprivation during early cerebellar neurogenesis, stimulates a brief increase in cell proliferation may contribute to a better understanding of the controversial role of nitric oxide in brain development.
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Affiliation(s)
- Elisabetta Ciani
- Department of Human and General Physiology, University of Bologna, Piazza di Porta San Donato 2, 40126 Bologna, Italy
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352
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Knoepfler PS, Zhang XY, Cheng PF, Gafken PR, McMahon SB, Eisenman RN. Myc influences global chromatin structure. EMBO J 2006; 25:2723-34. [PMID: 16724113 PMCID: PMC1500848 DOI: 10.1038/sj.emboj.7601152] [Citation(s) in RCA: 303] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2005] [Accepted: 04/27/2006] [Indexed: 01/15/2023] Open
Abstract
The family of myc proto-oncogenes encodes transcription factors (c-, N-, and L-Myc) that regulate cell growth and proliferation and are involved in the etiology of diverse cancers. Myc proteins are thought to function by binding and regulating specific target genes. Here we report that Myc proteins are required for the widespread maintenance of active chromatin. Disruption of N-myc in neuronal progenitors and other cell types leads to nuclear condensation accompanied by large-scale changes in histone modifications associated with chromatin inactivation, including hypoacetylation and altered methylation. These effects are largely reversed by exogenous Myc as well as by differentiation and are mimicked by the Myc antagonist Mad1. The first chromatin changes are evident within 6 h of Myc loss and lead to changes in chromatin structure. Myc widely influences chromatin in part through upregulation of the histone acetyltransferase GCN5. This study provides the first evidence for regulation of global chromatin structure by an oncoprotein and may explain the broad effects of Myc on cell behavior and tumorigenesis.
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Affiliation(s)
- Paul S Knoepfler
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Xiao-yong Zhang
- The Wistar Institute, Gene Expression and Regulation Program, Philadelphia, PA, USA
| | - Pei Feng Cheng
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Philip R Gafken
- Proteomics Facility, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Steven B McMahon
- The Wistar Institute, Gene Expression and Regulation Program, Philadelphia, PA, USA
| | - Robert N Eisenman
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
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353
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Taylor RM, Lee JP, Palacino JJ, Bower KA, Li J, Vanier MT, Wenger DA, Sidman RL, Snyder EY. Intrinsic resistance of neural stem cells to toxic metabolites may make them well suited for cell non-autonomous disorders: evidence from a mouse model of Krabbe leukodystrophy. J Neurochem 2006; 97:1585-99. [PMID: 16805770 DOI: 10.1111/j.1471-4159.2006.03986.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
While transplanted neural stem cells (NSCs) have been shown to hold promise for cell replacement in models of a number of neurological disorders, these examples have typically been under conditions where the host cells become dysfunctional due to a cell autonomous etiology, i.e. a 'sick' cell within a relatively supportive environment. It has long been held that cell replacement in a toxic milieu would not likely be possible; donor cells would succumb in much the same way as endogenous cells had. Many metabolic diseases are characterized by this situation, suggesting that they would be poor targets for cell replacement therapies. On the other hand, models of such diseases could prove ideal for testing the capacity for cell replacement under such challenging conditions. In the twitcher (twi ) mouse -- as in patients with Krabbe or globoid cell leukodystrophy (GLD), for which it serves as an authentic model -- loss of galactocerebrosidase (GalC) activity results in the accumulation of psychosine, a toxic glycolipid. Twi mice, like children with GLD, exhibit inexorable neurological deterioration presumably as a result of dysfunctional and ultimately degenerated oligodendrocytes with loss of myelin. It is believed that GLD pathophysiology is related to a psychosine-filled environment that kills not only host oligodendrocytes but theoretically any new cells placed into that milieu. Through the implantation of NSCs into the brains of both neonatal and juvenile/young adult twi mice, we have determined that widespread oligodendrocyte replacement and remyelination is feasible. NSCs appear to be intrinsically resistant to psychosine -- more so in their undifferentiated state than when directed ex vivo to become oligodendrocytes. This resistance can be enhanced by engineering the NSCs to over-express GalC. Some twi mice grafted with such engineered NSCs had thicker white tracts and lived 2-3 times longer than expected. While their brains had detectable levels of GalC, it was probably more significant that their psychosine levels were lower than in twi mice that died at a younger age. This concept of resistance based on differentiation state extended to human NSCs which could similarly survive within the twi brain. Taken together, these results suggest a number of points regarding cellular therapies against degenerative diseases with a prominent cell non-autonomous component: Cell replacement is possible if cells resistant to the toxic environment are employed. Furthermore, an important aspect of successful treatment will likely be not only cell replacement but also cross-correction of host cells to provide them with enzyme activity and hence resistance. While oligodendrocyte replacement alone was not a sufficient treatment for GLD (even when extensive), the replacement of both cells and molecules -- e.g. with NSCs that could both become oligodendrocytes and 'pumps' for GalC -- emerges as a promising basis for a multidisciplinary strategy. Most neurological disease are complex in this way and will likely require multifaceted approaches, perhaps with NSCs serving as the 'glue'.
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MESH Headings
- Animals
- Animals, Newborn
- Cell Differentiation/drug effects
- Cells, Cultured
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Galactosylceramidase/biosynthesis
- Galactosylceramidase/deficiency
- Genetic Therapy/methods
- Humans
- Immunohistochemistry
- Leukodystrophy, Globoid Cell/pathology
- Leukodystrophy, Globoid Cell/surgery
- Mice
- Mice, Mutant Strains
- Microscopy, Electron, Transmission/methods
- Myelin Basic Protein/metabolism
- Myelin Sheath/pathology
- Myelin Sheath/ultrastructure
- Neurons/drug effects
- Neurons/physiology
- Oligodendroglia/drug effects
- Oligodendroglia/physiology
- Psychosine/toxicity
- Stem Cell Transplantation/methods
- Stem Cells/drug effects
- Stem Cells/physiology
- Transduction, Genetic/methods
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Affiliation(s)
- Roseanne M Taylor
- Department of Animal Science, Faculty of Veterinary Science, University of Sydney and New South Wales, Australia
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354
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Pirity M, Blanck JK, Schreiber-Agus N. Lessons learned from Myc/Max/Mad knockout mice. Curr Top Microbiol Immunol 2006; 302:205-34. [PMID: 16620030 DOI: 10.1007/3-540-32952-8_8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The past two decades of gene targeting experiments have allowed us to make significant strides towards understanding how the Myc/Max/Mad network influences multiple aspects of cellular behavior during development. Here we summarize the findings obtained from the myc/max/mad knockout mice generated to date, namely those in which the N-myc, c-myc, L-myc, mad1, mxi1, mad3, mnt, or max genes have been targeted. A compilation of lessons we have learned from these myc/max/mad knockout mouse models, and suggestions as to where future efforts could be focused, are also presented.
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Affiliation(s)
- M Pirity
- Department of Molecular Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Ullmann 809, Bronx, NY 10461, USA
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355
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Kleine-Kohlbrecher D, Adhikary S, Eilers M. Mechanisms of transcriptional repression by Myc. Curr Top Microbiol Immunol 2006; 302:51-62. [PMID: 16620025 DOI: 10.1007/3-540-32952-8_3] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Myc proteins are nuclear proteins that exert their biological functions at least in part through the transcriptional regulation of large sets of target genes. Recent microarray analyses show that several percent of all genes may be directly regulated by Myc. A large body of data shows that Myc proteins both positively and negatively affect transcription. The basic mechanism underlying Myc's activation of transcription is well understood, but the mechanisms through which Myc negatively regulates or represses transcription are far less understood. In this chapter, we will review our current knowledge about this less-well-understood topic.
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Affiliation(s)
- D Kleine-Kohlbrecher
- Institute for Molecular Biology and Tumor Research, University of Marburg, 35033 Marburg, Germany
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356
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Abstract
Deregulation of Myc expression is a common feature in cancer and leads to tumor formation in experimental model systems. There are several potential barriers that Myc must overcome in order to promote tumorigenesis, including its propensity to sensitize many cell types to apoptotic cell death. Myc activities appear also to be constrained and fine-tuned by a set of proteins that include the Mxd (formerly named Mad) family and the related protein Mnt. Like Myc-family proteins, Mxd and Mnt proteins use Max as a cofactor for DNA binding. But Mnt-Max and Mxd-Max complexes are transcriptional repressors and can antagonize the transcriptional activation function of Myc-Max. Studies examining the relationship between Myc, Mxd and Mnt proteins suggest that whereas Mnt plays a general role as a Myc antagonist, Mxd proteins have more specialized roles as Myc antagonist that is probably related to their more restricted expression patterns. The interplay between these proteins is postulated to fine-tune Myc activity for cell-cycle entry and exit, proliferation rate and apoptosis.
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Affiliation(s)
- C William Hooker
- Shriners Hospitals for Children and Department of Cell and Developmental Biology, Oregon Health and Science University, 3101 SW Sam Jackson Park Rd, Portland, OR 97239, USA
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357
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Yan CT, Kaushal D, Murphy M, Zhang Y, Datta A, Chen C, Monroe B, Mostoslavsky G, Coakley K, Gao Y, Mills KD, Fazeli AP, Tepsuporn S, Hall G, Mulligan R, Fox E, Bronson R, De Girolami U, Lee C, Alt FW. XRCC4 suppresses medulloblastomas with recurrent translocations in p53-deficient mice. Proc Natl Acad Sci U S A 2006; 103:7378-83. [PMID: 16670198 PMCID: PMC1464348 DOI: 10.1073/pnas.0601938103] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Inactivation of the XRCC4 nonhomologous end-joining factor in the mouse germ line leads to embryonic lethality, in association with apoptosis of newly generated, postmitotic neurons. We now show that conditional inactivation of the XRCC4 in nestin-expressing neuronal progenitor cells, although leading to no obvious phenotype in a WT background, leads to early onset of neuronally differentiated medulloblastomas (MBs) in a p53-deficient background. A substantial proportion of the XRCC4/p53-deficient MBs have high-level N-myc gene amplification, often intrachromosomally in the context of complex translocations or other alterations of chromosome 12, on which N-myc resides, or extrachromosomally within double minutes. In addition, most XRCC4/p53-deficient MBs harbor clonal translocations of chromosome 13, which frequently involve chromosome 6 as a partner. One copy of the patched gene (Ptc), which lies on chromosome 13, was deleted in all tested XRCC4/p53-deficient MBs in the context of translocations or interstitial deletions. In addition, Cyclin D2, a chromosome 6 gene, was amplified in a subset of tumors. Notably, amplification of Myc-family or Cyclin D2 genes and deletion of Ptc also have been observed in human MBs. We therefore conclude that, in neuronal cells of mice, the nonhomologous end-joining pathway plays a critical role in suppressing genomic instability that, in a p53-deficient background, routinely contributes to genesis of MBs with recurrent chromosomal alterations.
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Affiliation(s)
- Catherine T. Yan
- *Howard Hughes Medical Institute, The Children's Hospital, CBR Institute for Biomedical Research
- Departments of Genetics
- Pediatrics, and
| | - Dhruv Kaushal
- *Howard Hughes Medical Institute, The Children's Hospital, CBR Institute for Biomedical Research
- Departments of Genetics
| | - Michael Murphy
- *Howard Hughes Medical Institute, The Children's Hospital, CBR Institute for Biomedical Research
- Departments of Genetics
| | - Yu Zhang
- *Howard Hughes Medical Institute, The Children's Hospital, CBR Institute for Biomedical Research
- Departments of Genetics
| | - Abhishek Datta
- *Howard Hughes Medical Institute, The Children's Hospital, CBR Institute for Biomedical Research
- Departments of Genetics
| | - Changzhong Chen
- Dana–Farber Microarray Core Facility, Dana–Farber Cancer Institute, Harvard Medical School, Boston, MA 02115
| | - Brianna Monroe
- *Howard Hughes Medical Institute, The Children's Hospital, CBR Institute for Biomedical Research
- Departments of Genetics
| | | | - Kristen Coakley
- *Howard Hughes Medical Institute, The Children's Hospital, CBR Institute for Biomedical Research
- Departments of Genetics
| | - Yijie Gao
- *Howard Hughes Medical Institute, The Children's Hospital, CBR Institute for Biomedical Research
- Departments of Genetics
| | - Kevin D. Mills
- *Howard Hughes Medical Institute, The Children's Hospital, CBR Institute for Biomedical Research
- Departments of Genetics
| | - Alex P. Fazeli
- *Howard Hughes Medical Institute, The Children's Hospital, CBR Institute for Biomedical Research
- Departments of Genetics
| | - Suprawee Tepsuporn
- *Howard Hughes Medical Institute, The Children's Hospital, CBR Institute for Biomedical Research
- Departments of Genetics
| | - Giles Hall
- Dana–Farber Microarray Core Facility, Dana–Farber Cancer Institute, Harvard Medical School, Boston, MA 02115
| | | | - Edward Fox
- Dana–Farber Microarray Core Facility, Dana–Farber Cancer Institute, Harvard Medical School, Boston, MA 02115
| | | | - Umberto De Girolami
- Department of Neuropathology, Brigham and Women's Hospital and Children's Hospital, Harvard Medical School, Boston, MA 02115; and
| | - Charles Lee
- **Pathology, Harvard Medical School, Boston, MA 02115
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115
| | - Frederick W. Alt
- *Howard Hughes Medical Institute, The Children's Hospital, CBR Institute for Biomedical Research
- Departments of Genetics
- To whom correspondence should be addressed. E-mail:
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358
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Park KI, Himes BT, Stieg PE, Tessler A, Fischer I, Snyder EY. Neural stem cells may be uniquely suited for combined gene therapy and cell replacement: Evidence from engraftment of Neurotrophin-3-expressing stem cells in hypoxic–ischemic brain injury. Exp Neurol 2006; 199:179-90. [PMID: 16714016 DOI: 10.1016/j.expneurol.2006.03.016] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2006] [Accepted: 03/15/2006] [Indexed: 11/19/2022]
Abstract
Previously, we reported that, when clonal neural stem cells (NSCs) were transplanted into brains of postnatal mice subjected to unilateral hypoxic-ischemic (HI) injury (optimally 3-7 days following infarction), donor-derived cells homed preferentially (from even distant locations) to and integrated extensively within the large ischemic areas that spanned the hemisphere. A subpopulation of NSCs and host cells, particularly in the penumbra, "shifted" their differentiation towards neurons and oligodendrocytes, the cell types typically damaged following asphyxia and least likely to regenerate spontaneously and in sufficient quantity in the "post-developmental" CNS. That no neurons and few oligodendrocytes were generated from the NSCs in intact postnatal cortex suggested that novel signals are transiently elaborated following HI to which NSCs might respond. The proportion of "replacement" neurons was approximately 5%. Neurotrophin-3 (NT-3) is known to play a role in inducing neuronal differentiation during development and perhaps following injury. We demonstrated that NSCs express functional TrkC receptors. Furthermore, the donor cells continued to express a foreign reporter transgene robustly within the damaged brain. Therefore, it appeared feasible that neuronal differentiation of exogenous NSCs (as well as endogenous progenitors) might be enhanced if donor NSCs were engineered prior to transplantation to (over)express a bioactive gene such as NT-3. A subclone of NSCs transduced with a retrovirus encoding NT-3 (yielding >90% neurons in vitro) was implanted into unilaterally asphyxiated postnatal day 7 mouse brain (emulating one of the common causes of cerebral palsy). The subclone expressed NT-3 efficiently in vivo. The proportion of NSC-derived neurons increased to approximately 20% in the infarction cavity and >80% in the penumbra. The neurons variously differentiated further into cholinergic, GABAergic, or glutamatergic subtypes, appropriate to the cortex. Donor-derived glia were rare, and astroglial scarring was blunted. NT-3 likely functioned not only on donor cells in an autocrine/paracrine fashion but also on host cells to enhance neuronal differentiation of both. Taken together, these observations suggest (1) the feasibility of taking a fundamental biological response to injury and augmenting it for repair purposes and (2) the potential use of migratory NSCs in some degenerative conditions for simultaneous combined gene therapy and cell replacement during the same procedure in the same recipient using the same cell (a unique property of cells with stem-like attributes).
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Affiliation(s)
- Kook In Park
- Department of Pediatrics, and the Brain Korea 21 Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea
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359
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Navarro-Galve B, Martinez-Serrano A. “Is there any need to argue…” about the nature and genetic signature of in vitro neural stem cells? Exp Neurol 2006; 199:20-5. [PMID: 16740262 DOI: 10.1016/j.expneurol.2006.03.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2005] [Accepted: 03/05/2006] [Indexed: 01/23/2023]
Affiliation(s)
- Beatriz Navarro-Galve
- Department of Molecular Biology and Center of Molecular Biology "Severo Ochoa", Laboratory CX-450, Autonomous University of Madrid and Spanish Council for Research [UAM-CSIC], Campus Cantoblanco, 28049-Madrid, Spain
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360
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Park KI, Hack MA, Ourednik J, Yandava B, Flax JD, Stieg PE, Gullans S, Jensen FE, Sidman RL, Ourednik V, Snyder EY. Acute injury directs the migration, proliferation, and differentiation of solid organ stem cells: Evidence from the effect of hypoxia–ischemia in the CNS on clonal “reporter” neural stem cells. Exp Neurol 2006; 199:156-78. [PMID: 16737696 DOI: 10.1016/j.expneurol.2006.04.002] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2006] [Accepted: 04/01/2006] [Indexed: 11/16/2022]
Abstract
Clonal neural cells with stem-like features integrate appropriately into the developing and degenerating central and peripheral nervous system throughout the neuraxis. In response to hypoxic-ischemic (HI) injury, previously engrafted, integrated, and quiescent clonal neural stem cells (NSCs) transiently re-enter the cell cycle, migrate preferentially to the site of ischemia, and differentiate into neurons and oligodendrocytes, the neural cell types typically lost following HI brain injury. They also replenish the supply of immature uncommitted resident stem/progenitor cells. Although they yield astrocytes, scarring is inhibited. These responses appear to occur most robustly within a 3-7 day "window" following HI during which signals are elaborated that upregulate genetic programs within the NSC that mediate proliferation, migration, survival, and differentiation, most of which appear to be terminated once the "window closes" and the chronic phase ensues, sending the NSCs into a quiescent state. These insights derived from using the stem cell in a novel role--as a "reporter" cell--to both track and probe the activity of endogenous stem cells as well as to "interrogate" and "report" the genes differentially induced by the acutely vs. chronically injured milieu. NSCs may be capable of the replacement of cells, genes, and non-diffusible factors in both a widespread or more circumscribed manner (depending on the therapeutic demands of the clinical situation). They may be uniquely responsive to some types of neurodegenerative conditions. We submit that these various capabilities are simply the normal expression of the basic homeostasis-preserving biologic properties and attributes of a stem cell which, if used rationally and in concert with this biology, may be exploited for therapeutic ends.
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Affiliation(s)
- Kook In Park
- Department of Pediatrics and The Brain Korea 21 Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Korea
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361
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Browd SR, Kenney AM, Gottfried ON, Yoon JW, Walterhouse D, Pedone CA, Fults DW. N-myc can substitute for insulin-like growth factor signaling in a mouse model of sonic hedgehog-induced medulloblastoma. Cancer Res 2006; 66:2666-72. [PMID: 16510586 DOI: 10.1158/0008-5472.can-05-2198] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Medulloblastoma is a malignant brain tumor that arises in the cerebellum in children, presumably from granule neuron precursors (GNP). Advances in patient treatment have been hindered by a paucity of animal models that accurately reflect the molecular pathogenesis of human tumors. Aberrant activation of the Sonic hedgehog (Shh) and insulin-like growth factor (IGF) pathways is associated with human medulloblastomas. Both pathways are essential regulators of GNP proliferation during cerebellar development. In cultured GNPs, IGF signaling stabilizes the oncogenic transcription factor N-myc by inhibiting glycogen synthase kinase 3beta-dependent phosphorylation and consequent degradation of N-myc. However, determinants of Shh and IGF tumorigenicity in vivo remain unknown. Here we report a high frequency of medulloblastoma formation in mice following postnatal overexpression of Shh in cooperation with N-myc. Overexpression of N-myc, alone or in combination with IGF signaling mediators or with the Shh target Gli1, did not cause tumors. Thus, Shh has transforming functions in addition to induction of N-myc and Gli1. This tumor model will be useful for testing novel medulloblastoma therapies and providing insight into mechanisms of hedgehog-mediated transformation.
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Affiliation(s)
- Samuel R Browd
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, Utah 84132-2303, USA
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362
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Abstract
N-Myc is a member of the Myc family of proteins, which are best known for their potent oncogenic activities and association with a large proportion of human cancers. Intense scrutiny of the oncogenic properties of Myc family proteins over the last several decades has revealed a great deal about their transcriptional and oncogenic activities. Myc proteins have broad effects on transcription and can stimulate a variety of cell behaviors that contribute to the malignant phenotype. N-Myc and c-Myc also play essential functions during embryonic development, and loss of these proteins has deleterious effects in most, if not all, tissues and organ systems. What remains to be fully unraveled is the relationship between the diverse activities associated with deregulated and overexpressed Myc and their normal roles during embryonic development and tissue homeostasis. In this review I summarize our understanding of the transcriptional activities of Myc family proteins and the roles of N-myc in morphogenesis, particularly as they relate to cellular proliferation and apoptosis.
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Affiliation(s)
- Peter J Hurlin
- Shriners Hospitals for Children and the Department of Cell and Developmental Biology, Oregon Health Sciences University, Portland, Oregon 97201, USA.
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363
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Stearns D, Chaudhry A, Abel TW, Burger PC, Dang CV, Eberhart CG. c-myc overexpression causes anaplasia in medulloblastoma. Cancer Res 2006; 66:673-81. [PMID: 16423996 DOI: 10.1158/0008-5472.can-05-1580] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Both anaplasia and increased c-myc gene expression have been shown to be negative prognostic indicators for survival in medulloblastoma patients. myc gene amplification has been identified in many large cell/anaplastic medulloblastoma, but no causative link between c-myc and anaplastic changes has been established. To address this, we stably overexpressed c-myc in two medulloblastoma cell lines, DAOY and UW228, and examined the changes in growth characteristics. When analyzed in vitro, cell lines with increased levels of c-myc had higher rates of growth and apoptosis as well as significantly improved ability to form colonies in soft agar compared with control. When injected s.c. into nu/nu mice, flank xenograft tumors with high levels of c-myc in DAOY cell line background were 75% larger than those derived from control. Overexpression of c-myc was required for tumor formation by UW228 cells. Most remarkably, the histopathology of the Myc tumors was severely anaplastic, with large areas of necrosis/apoptosis, increased nuclear size, and macronucleoli. Indices of proliferation and apoptosis were also significantly higher in Myc xenografts. Thus, c-myc seems to play a causal role in inducing anaplasia in medulloblastoma. Because anaplastic changes are often observed in recurrent medulloblastoma, we propose that c-myc dysregulation is involved in the progression of these malignant embryonal neoplasms.
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Affiliation(s)
- Duncan Stearns
- Department of Neuropathology, Johns Hopkins University School of Medicine, 558 Ross Building, 720 Rutland Avenue, Baltimore, MD 21205, USA.
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364
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Bernard S, Eilers M. Control of cell proliferation and growth by Myc proteins. Results Probl Cell Differ 2006; 42:329-42. [PMID: 16903216 DOI: 10.1007/400_004] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Myc proteins act as signal transducers that alter cell proliferation in dependence on signals from the extracellular environment. In normal cells, the expression of MYC genes is therefore under tight control by growth factor dependent signals. The enormous interest in the function of these proteins is motivated by the observation that the close control of MYC expression is disrupted in a large percentage of human tumors, leading to deregulated expression of Myc proteins. A large body of evidence shows that this deregulation is a major driving force of human tumorigenesis; in cells with deregulated Myc, proliferation often takes place in the complete absence of external stimuli. We will discuss current models to understand Myc function and also potential avenues to selectively interfere with the proliferation of Myc-transformed cells.
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Affiliation(s)
- Sandra Bernard
- Institute for Molecular Biology and Tumor Research, University of Marburg, Germany
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365
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Uziel T, Zindy F, Xie S, Lee Y, Forget A, Magdaleno S, Rehg JE, Calabrese C, Solecki D, Eberhart CG, Sherr SE, Plimmer S, Clifford SC, Hatten ME, McKinnon PJ, Gilbertson RJ, Curran T, Sherr CJ, Roussel MF. The tumor suppressors Ink4c and p53 collaborate independently with Patched to suppress medulloblastoma formation. Genes Dev 2005; 19:2656-67. [PMID: 16260494 PMCID: PMC1283959 DOI: 10.1101/gad.1368605] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Accepted: 09/09/2005] [Indexed: 11/24/2022]
Abstract
Recurrent genetic alterations in human medulloblastoma (MB) include mutations in the sonic hedgehog (SHH) signaling pathway and TP53 inactivation (approximately 25% and 10% of cases, respectively). However, mouse models of MB, regardless of their initiating lesions, generally depend upon p53 inactivation for rapid onset and high penetrance. The gene encoding the cyclin-dependent kinase inhibitor p18(Ink4c) is transiently expressed in mouse cerebellar granule neuronal precursor cells (GNPs) as they exit the cell division cycle and differentiate. Coinactivation of Ink4c and p53 provided cultured GNPs with an additive proliferative advantage, either in the presence or absence of Shh, and induced MB with low penetrance but with greatly increased incidence following postnatal irradiation. In contrast, mice lacking one or two functional Ink4c alleles and one copy of Patched (Ptc1) encoding the Shh receptor rapidly developed MBs that retained wild-type p53. In tumor cells purified from double heterozygotes, the wild-type Ptc1 allele, but not Ink4c, was inactivated. Therefore, when combined with Ptc1 mutation, Ink4c is haploinsufficient for tumor suppression. Methylation of INK4C (CDKN2C) was observed in four of 23 human MBs, and p18(INK4C) protein expression was extinguished in 14 of 73 cases. Hence, p18(INK4C) loss may contribute to MB formation in children.
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Affiliation(s)
- Tamar Uziel
- Department of Tumor Cell Biology and Genetics, Memphis, Tennessee 38105, USA
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366
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Mill P, Mo R, Hu MC, Dagnino L, Rosenblum ND, Hui CC. Shh controls epithelial proliferation via independent pathways that converge on N-Myc. Dev Cell 2005; 9:293-303. [PMID: 16054035 DOI: 10.1016/j.devcel.2005.05.009] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2004] [Revised: 03/09/2005] [Accepted: 05/16/2005] [Indexed: 12/26/2022]
Abstract
Shh signaling induces proliferation of many cell types during development and disease, but how Gli transcription factors regulate these mitogenic responses remains unclear. By genetically altering levels of Gli activator and repressor functions in mice, we have demonstrated that both Gli functions are involved in the transcriptional control of N-myc and Cyclin D2 during embryonic hair follicle development. Our results also indicate that additional Gli-activator-dependent functions are required for robust mitogenic responses in regions of high Shh signaling. Through posttranscriptional mechanisms, including inhibition of GSK3-beta activity, Shh signaling leads to spatially restricted accumulation of N-myc and coordinated cell cycle progression. Furthermore, a temporal shift in the regulation of GSK3-beta activity occurs during embryonic hair follicle development, resulting in a synergy with beta-catenin signaling to promote coordinated proliferation. These findings demonstrate that Shh signaling controls the rapid and patterned expansion of epithelial progenitors through convergent Gli-mediated regulation.
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Affiliation(s)
- Pleasantine Mill
- Department of Medical and Molecular Genetics, University of Toronto, Toronto, Ontario M5G 1X8, Canada
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367
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Abstract
The entire vertebrate nervous system develops from a simple epithelial sheet, the neural plate which, along development, acquires the large number and wide variety of neuronal cell types required for the construction of a functional mature nervous system. These include processes of growth and pattern formation of the neural tube that are achieved through complicated and tightly regulated genetic interactions. Pattern formation, particularly in the vertebrate central nervous system, is one of the best examples of a morphogen-type of function. Cell cycle progression, however, is generally accepted to be dependent on cell-intrinsic factors. Recent studies have demonstrated that proliferation of neural precursors is also somehow controlled by secreted signaling molecules, well-known by their role as morphogens, such as fibroblast growth factor (FGF), vertebrate orthologs of the Drosophila wingless (Wnt), hedgehog (Hh), and transforming growth factor beta (TGF-beta) families, that in turn regulate the activity of factors controlling cell cycle progression. In this review we will summarize the experimental data that support the idea that classical morphogens can be reused to regulate proliferation of neural precursors.
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Affiliation(s)
- Jordi Cayuso
- Instituto de Biología Molecular de Barcelona (CSIC), Parc Cientific de Barcelona, C/ Josep Samitier 1-5, Barcelona 08028, Spain
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368
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Guerreiro JR, Winnischofer SMB, Bastos MF, Portaro FCV, Sogayar MC, de Camargo ACM, Hayashi MAF. Cloning and characterization of the human and rabbit NUDEL-oligopeptidase promoters and their negative regulation. ACTA ACUST UNITED AC 2005; 1730:77-84. [PMID: 16005531 DOI: 10.1016/j.bbaexp.2005.06.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2005] [Revised: 05/30/2005] [Accepted: 06/02/2005] [Indexed: 12/19/2022]
Abstract
NUDEL-oligopeptidase is a cytosolic cysteine peptidase, active towards oligopeptides and involved in the conversion and inactivation of a number of bioactive peptides. This protein interacts with neuronal proteins and is essential for brain development and cortical organization during embryogenesis. In this study, 5'-flanking sequences of the human and rabbit NUDEL-oligopeptidase gene were cloned into the pGL3 reporter gene vector and the promoter activity of the full-length fragment and deletions series was measured in transient transfection assays using two different cell lines, namely, C6 rat glioma and NH15 human neuroblastoma. Overall, a very similar pattern of promoter activity was obtained for both rabbit and human NUDEL-oligopeptidase promoter sequences, and their respective serial deletion constructs upon transient transfection into these cell lines. The only exception was for the longest rabbit upstream sequence that displayed about 1.8-fold higher luciferase expression upon transfection into NH15 neuronal cells than that observed upon transfection into C6 glioma cells. On the other hand, no significant difference was observed for the human longest sequence. These results are in good agreement with the expression pattern of NUDEL-oligopeptidase in human and rabbit tissues.
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Affiliation(s)
- Juliano R Guerreiro
- Laboratory for Applied Toxinology, Butantan Institute, São Paulo, 05503-900, Brazil
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369
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Parker MA, Anderson JK, Corliss DA, Abraria VE, Sidman RL, Park KI, Teng YD, Cotanche DA, Snyder EY. Expression profile of an operationally-defined neural stem cell clone. Exp Neurol 2005; 194:320-32. [PMID: 15992799 DOI: 10.1016/j.expneurol.2005.04.018] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2005] [Accepted: 04/28/2005] [Indexed: 01/15/2023]
Abstract
Neural stem cells (NSCs) are the most primordial and least committed cells of the nervous system, the cells that exist before regional specification develops. Because immunocytochemically-detectable markers that are sufficiently specific and sensitive to define an NSC have not yet been fully defined, we have taken the strong view that, to be termed a "stem cell" in the nervous system--in contrast to a "progenitor" or "precursor" (whose lineage commitment is further restricted)--a single neuroectodermally-derived cell must fulfill an operational definition that is essentially similar to that used in hematopoiesis. In other words, it must possess the following functional properties: (1) "Multipotency", i.e., the ability to yield mature cells in all three fundamental neural lineages throughout the nervous system--neurons (of all subtypes), astrocytes (of all types), oligodendrocytes--in multiple regional and developmental contexts and in a region and developmental stage-appropriate manner. (2) The ability to populate a developing region and/or repopulate an ablated or degenerated region of the nervous system with appropriate cell types. (3) The ability to be serially transplanted. (4) "Self-renewal", i.e., the ability to produce daughter cells (including new NSCs) with identical properties and potential. Having identified a murine neural cell clone that fulfills this strict operational definition--in contrast to other studies that used less rigorous or non-operational criteria for defining an NSC (e.g., the "neurosphere" assay)--we then examined, by comparing gene expression profiles, the relationship such a cell might have to (a) a multipotent somatic stem cell from another organ system (the hematopoietic stem cell [HSC]); (b) a pluripotent stem cell derived from the inner cell mass and hence without organ assignment (an embryonic stem cell); (c) neural cells isolated and maintained primarily as neurospheres but without having been subjected to the above mentioned operational screen ("CNS-derived neurospheres"). ESCs, HSCs, and operationally-defined NSCs--all of which have been identified not only by markers but by functional assays in their respective systems and whose state of differentiation could be synchronized--shared a large number of genes. Although, as expected, the most stem-like genes were expressed by ESCs, NSCs and HSCs shared a number of genes. CNS-derived neurospheres, on the other hand, expressed fewer "stem-like" genes held in common by the other operationally-defined stem cell populations. Rather they displayed a profile more consistent with differentiated neural cells. (Genes of neural identity were shared with the NSC clone.) Interestingly, when the operationally-defined NSC clone was cultured as a neurosphere (rather than in monolayer), its expression pattern shifted from a "stem-like" pattern towards a more "differentiated" one, suggesting that the neurosphere, without functional validation, may be a poor model for predicting stem cell attributes because it consists of heterogeneous populations of cells, only a small proportion of which are truly "stem-like". Furthermore, when operational definitions are employed, a common set of stem-like genes does emerge across both embryonic and somatic stem cells of various organ systems, including the nervous system.
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Affiliation(s)
- Mark A Parker
- Department of Otolaryngology, EN41, Children's Hospital-Boston, 300 Longwood Avenue, Boston, MA 02115, USA.
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370
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Sjostrom SK, Finn G, Hahn WC, Rowitch DH, Kenney AM. The Cdk1 Complex Plays a Prime Role in Regulating N-Myc Phosphorylation and Turnover in Neural Precursors. Dev Cell 2005; 9:327-38. [PMID: 16139224 DOI: 10.1016/j.devcel.2005.07.014] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2005] [Revised: 04/23/2005] [Accepted: 07/28/2005] [Indexed: 12/23/2022]
Abstract
Myc family transcription factors are destabilized by phosphorylation of a conserved amino-terminal GSK-3beta motif. In proliferating cerebellar granule neuron precursors (CGNPs), Sonic hedgehog signaling induces N-myc expression, and N-myc protein is stabilized by insulin-like growth factor-mediated suppression of GSK-3beta. N-myc phosphorylation-mediated degradation is a prerequisite for CGNP growth arrest and differentiation. We investigated whether N-myc phosphorylation and turnover are thus linked to cell cycle exit in primary mouse CGNP cultures and the developing cerebellum. We report that phosphorylation-induced turnover of endogenous N-myc protein in CGNPs increases during mitosis, due to increased priming phosphorylation of N-myc for GSK-3beta. The priming phosphorylation requires the Cdk1 complex, whose cyclin subunits are indirect Sonic hedgehog targets. These findings provide a mechanism for promoting growth arrest in the final cycle of neural precursor proliferation competency, or for resetting the cell cycle in the G1 phase, by destabilizing N-myc in mitosis.
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Affiliation(s)
- Sarah K Sjostrom
- Department of Pediatric Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115, USA
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371
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Shetty RS, Bose SC, Nickell MD, McIntyre JC, Hardin DH, Harris AM, McClintock TS. Transcriptional changes during neuronal death and replacement in the olfactory epithelium. Mol Cell Neurosci 2005; 30:90-107. [PMID: 16027002 DOI: 10.1016/j.mcn.2005.06.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 06/10/2005] [Accepted: 06/13/2005] [Indexed: 11/30/2022] Open
Abstract
The olfactory epithelium has the unusual ability to replace its neurons. We forced replacement of mouse olfactory sensory neurons by bulbectomy. Microarray, bioinformatics, and in situ hybridization techniques detected a rapid shift in favor of pro-apoptotic proteins, a progressive immune response by macrophages and dendritic cells, and identified or predicted 439 mRNAs enriched in olfactory sensory neurons, including gene silencing factors and sperm flagellar proteins. Transcripts encoding cell cycle regulators, axonogenesis proteins, and transcription factors and signaling proteins that promote proliferation and differentiation were increased at 5--7 days after bulbectomy and were expressed by basal progenitor cells or immature neurons. The transcription factors included Nhlh 1, Hes 6, Lmyc 1, c-Myc, Mxd 4, Id 1, Nmyc 1, Cited 2, c-Myb, Mybl 1, Tead 2, Dp 1, Gata 2, Lmo 1, and Sox1 1. The data reveal significant similarities with embryonic neurogenesis and make several mechanistic predictions, including the roles of the transcription factors in the olfactory sensory neuron lineage.
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Affiliation(s)
- Ranjit S Shetty
- Department of Physiology, Cellular and Molecular Neuroscience of Sensory Systems Training Program, University of Kentucky, 800 Rose Street, Lexington, KY 40536-0298, USA
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372
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Adhikary S, Eilers M. Transcriptional regulation and transformation by Myc proteins. Nat Rev Mol Cell Biol 2005; 6:635-45. [PMID: 16064138 DOI: 10.1038/nrm1703] [Citation(s) in RCA: 837] [Impact Index Per Article: 44.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Myc genes are key regulators of cell proliferation, and their deregulation contributes to the genesis of most human tumours. Recently, a wealth of data has shed new light on the biochemical functions of Myc proteins and on the mechanisms through which they function in cellular transformation.
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Affiliation(s)
- Sovana Adhikary
- Institute for Molecular Biology and Tumour Research, University of Marburg, Emil-Mannkopff-Strasse 2, 35033 Marburg, Germany
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373
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Kobayashi M, Hjerling-Leffler J, Ernfors P. Increased progenitor proliferation and apoptotic cell death in the sensory lineage of mice overexpressing N-myc. Cell Tissue Res 2005; 323:81-90. [PMID: 16133151 DOI: 10.1007/s00441-005-0011-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2005] [Accepted: 05/09/2005] [Indexed: 02/07/2023]
Abstract
N-myc, a member of the myc family of bHLH transcription factors, is expressed mainly in the nervous system, including derivatives of neural crest cells in the periphery during development, such as the sensory dorsal root ganglion (DRG). Previous studies suggest that N-myc is involved in the proliferation of progenitor cells in the sensory lineage. To address the role of N-myc in the development of peripheral sensory neurons, we have overexpressed N-myc in sensory progenitor cells. The overexpression of N-myc did not significantly affect the number of multipotent neural crest cells or glial differentiation but caused a brief and marked increase of both proliferation and apoptosis in the DRG at embryonic day 11 (E11), thus coinciding with the stage of cell-cycle exit. At E17, the total number of cells in the lumbar DRG of mice with forced expression of N-myc was significantly reduced compared with that in wild-type mice. Among the different DRG subpopulations examined, the number of parvalbumin-positive neurons representing large-diameter proprioceptive neurons increased significantly. Our results indicate that forced expression of N-myc in the sensory lineage leads to unscheduled cell-cycle re-entry and excessive apoptosis and show that N-myc can affect the composition of different functional subtypes of sensory neurons in the DRG.
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Affiliation(s)
- Miwako Kobayashi
- Unit of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Scheelesv. 1, 171 77 Stockholm, Sweden
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374
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Perini G, Diolaiti D, Porro A, Della Valle G. In vivo transcriptional regulation of N-Myc target genes is controlled by E-box methylation. Proc Natl Acad Sci U S A 2005; 102:12117-22. [PMID: 16093321 PMCID: PMC1184034 DOI: 10.1073/pnas.0409097102] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
N-Myc is a transcription factor that forms heterodimers with the protein Max and binds gene promoters by recognizing a DNA sequence, CACGTG, called E-box. The identification of N-myc target genes is an important step for understanding N-Myc biological functions in both physiological and pathological contexts. In this study, we describe the identification of N-Myc-responsive genes through chromatin immunoprecipitation and methylation-sensitive restriction analysis. Results show that N-Myc is a direct regulator of several identified genes, and that methylation of the CpG dinucleotide within the E-box prevents the access of N-Myc to gene promoters in vivo. Furthermore, methylation profile of the E-box within the promoters of EGFR and CASP8, two genes directly controlled by Myc, is cell type-specific, suggesting that differential E-box methylation may contribute to generating unique patterns of Myc-dependent transcription. This study illuminates a central role of DNA methylation in controlling N-Myc occupancy at gene promoters and modulating its transcriptional activity in cancer cells.
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Affiliation(s)
- Giovanni Perini
- Department of Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy
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375
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Kimura H, Stephen D, Joyner A, Curran T. Gli1 is important for medulloblastoma formation in Ptc1+/- mice. Oncogene 2005; 24:4026-36. [PMID: 15806168 DOI: 10.1038/sj.onc.1208567] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Germline mutations in the human homolog of the patched1 (PTCH1) are associated with basal cell nevus carcinoma syndrome (BCNS or Gorlin syndrome), which is characterized by developmental anomalies, radiation hypersensitivity and a predisposition to medulloblastomas and skin tumors. Patched1 (Ptc1) functions as a receptor for Sonic hedgehog (Shh) in a wide range of biological processes. Binding of Shh to Ptc1 results in activation of Smoothened (Smo), which in turn stimulates expression of downstream target genes including Ptc1 and Gli1. Gli1 is a member of a family of DNA-binding zinc-finger proteins, including Gli2 and Gli3, that function in transcription control. Here, we report that inactivation of both Gli1 alleles in Ptc1+/- mice significantly reduces spontaneous medulloblastoma formation. Therefore, Gli1 is not only a marker of pathway activation but also plays a functional role in medulloblastoma formation. Interestingly, Gli2 levels were elevated in medulloblastoma cells but not in normal granule neuron precursors during cerebellar development in mice lacking Gli1. In cultured fibroblasts, Gli1 was more potent than Gli2 at inducing cell transformation. These results demonstrate that Gli1 plays a central role in medulloblastoma formation in Ptc1+/- mice and that Gli2 may also contribute to oncogenesis.
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Affiliation(s)
- Hiromichi Kimura
- Department of Developmental Neurobiology, St Jude Children's Research Hospital, 332 North Lauderdale, Memphis, TN 38105, USA
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376
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Murphy MJ, Wilson A, Trumpp A. More than just proliferation: Myc function in stem cells. Trends Cell Biol 2005; 15:128-37. [PMID: 15752976 DOI: 10.1016/j.tcb.2005.01.008] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Adult stem cells are essential to maintain regenerative tissues such as skin epidermis, gastrointestinal mucosa or the hematopoietic system. Recent studies in mice suggest that the transcription factor and oncoprotein c-Myc has unexpected functions during both self-renewal and the differentiation of stem and early progenitor cells, particularly in interactions between stem cells and the local microenvironment or "niche". By incorporating recent findings on Myc and hematopoietic stem cells we propose a model in which "resting" hematopoietic stem cells are "activated" to self-renew and to differentiate at the interface between the niche and non-niche microenvironments.
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Affiliation(s)
- Mark J Murphy
- Genetics and Stem Cell Laboratory; Swiss Institute for Experimental Cancer Research (ISREC), Chemin des Boveresses 155, CH-1066 Epalinges, Switzerland
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377
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MYCN haploinsufficiency is associated with reduced brain size and intestinal atresias in Feingold syndrome. Nat Genet 2005; 37:465-7. [DOI: 10.1038/ng1546] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2004] [Accepted: 03/14/2005] [Indexed: 11/08/2022]
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378
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Williamson D, Lu YJ, Gordon T, Sciot R, Kelsey A, Fisher C, Poremba C, Anderson J, Pritchard-Jones K, Shipley J. Relationship between MYCN copy number and expression in rhabdomyosarcomas and correlation with adverse prognosis in the alveolar subtype. J Clin Oncol 2005; 23:880-8. [PMID: 15681534 DOI: 10.1200/jco.2005.11.078] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PURPOSE Amplification of the transcription factor MYCN is an important molecular diagnostic tool in stratifying treatment for neuroblastoma. Increased copy number and overexpression of MYCN in the pediatric cancer rhabdomyosarcoma has been described in a number of small studies with conflicting conclusions about its association with clinicopathologic characteristics. We aimed to study the phenomenon in the largest series to date. PATIENTS AND METHODS Using quantitative polymerase chain reaction, we measured MYCN copy number and expression levels in rhabdomyosarcoma samples from 113 and 92 individuals with a confirmed diagnosis of rhabdomyosarcoma, respectively. RESULTS Increased copy number of MYCN was found to be a feature of both the embryonal and alveolar subtypes. The copy number and expression levels were significantly greater in the alveolar subtype, although the range of expression in both subtypes spanned several orders of magnitude. MYCN copy number showed a significant correlation with expression in the alveolar subtype; this relationship between copy number and expression could be modeled as a logarithmic function. It is notable that relatively high expression frequently occurred in embryonal rhabdomyosarcoma without high copy number and that low expression was found in some cases with high copy number. In patients with alveolar rhabdomyosarcoma, overexpression (greater than median) or gain of genomic copies of MYCN were significantly associated with adverse outcome. CONCLUSION MYCN deregulation is a feature of rhabdomyosarcoma tumorigenesis, defines groups of patients with a poor prognosis, and is a potential target for novel therapies.
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Affiliation(s)
- Daniel Williamson
- Molecular Cytogenetics, The Institute of Cancer Research, Sutton, Surrey, United Kingdom
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379
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Grandori C, Gomez-Roman N, Felton-Edkins ZA, Ngouenet C, Galloway DA, Eisenman RN, White RJ. c-Myc binds to human ribosomal DNA and stimulates transcription of rRNA genes by RNA polymerase I. Nat Cell Biol 2005; 7:311-8. [PMID: 15723054 DOI: 10.1038/ncb1224] [Citation(s) in RCA: 487] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
c-Myc coordinates cell growth and division through a transcriptional programme that involves both RNA polymerase (Pol) II- and Pol III-transcribed genes. Here, we demonstrate that human c-Myc also directly enhances Pol I transcription of ribosomal RNA (rRNA) genes. rRNA synthesis and accumulation occurs rapidly following activation of a conditional MYC-ER allele (coding for a Myc-oestrogen-receptor fusion protein), is resistant to inhibition of Pol II transcription and is markedly reduced by c-MYC RNA interference. Furthermore, by using combined immunofluorescence and rRNA-FISH, we have detected endogenous c-Myc in nucleoli at sites of active ribosomal DNA (rDNA) transcription. Our data also show that c-Myc binds to specific consensus elements located in human rDNA and associates with the Pol I-specific factor SL1. The presence of c-Myc at specific sites on rDNA coincides with the recruitment of SL1 to the rDNA promoter and with increased histone acetylation. We propose that stimulation of rRNA synthesis by c-Myc is a key pathway driving cell growth and tumorigenesis.
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Affiliation(s)
- Carla Grandori
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024, USA.
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380
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Okubo T, Knoepfler PS, Eisenman RN, Hogan BLM. Nmyc plays an essential role during lung development as a dosage-sensitive regulator of progenitor cell proliferation and differentiation. Development 2005; 132:1363-74. [PMID: 15716345 DOI: 10.1242/dev.01678] [Citation(s) in RCA: 190] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Understanding how lung progenitor cells balance proliferation against differentiation is relevant to clinical disorders such as bronchopulmonary dysplasia of premature babies and lung cancer. Previous studies have established that lung development is severely disrupted in mouse mutants with reduced levels of the proto-oncogene Nmyc, but the precise mechanisms involved have not been explored. We show here that Nmyc expression in the embryonic lung is normally restricted to a distal population of undifferentiated epithelial cells, a high proportion of which are in the S phase of the cell cycle. Overexpression of NmycEGFP in the epithelium under the control of surfactant protein C (Sftpc) regulatory elements expands the domain of S phase cells and upregulates numerous genes associated with growth and metabolism, as shown by transcriptional microarray. In addition, there is marked inhibition of differentiation, coupled with an expanded domain of expression of Sox9 protein, which is also normally restricted to the distal epithelial compartment. By contrast, conditional deletion of Nmyc leads to reduced proliferation, epithelial differentiation and high levels of apoptosis in both epithelium and mesenchyme. Unexpectedly, about 50% of embryos in which only one copy of Nmyc is deleted die perinatally, with similarly abnormal lungs. We propose a model in which Nmyc is essential in the developing lung for maintaining a distal population of undifferentiated, proliferating progenitor cells.
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Affiliation(s)
- Tadashi Okubo
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
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381
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Cartwright P, McLean C, Sheppard A, Rivett D, Jones K, Dalton S. LIF/STAT3 controls ES cell self-renewal and pluripotency by a Myc-dependent mechanism. Development 2005; 132:885-96. [PMID: 15673569 DOI: 10.1242/dev.01670] [Citation(s) in RCA: 534] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Murine ES cells can be maintained as a pluripotent, self-renewing population by LIF/STAT3-dependent signaling. The downstream effectors of this pathway have not been previously defined. In this report, we identify a key target of the LIF self-renewal pathway by showing that STAT3 directly regulates the expression of the Myc transcription factor. Murine ES cells express elevated levels of Myc and following LIF withdrawal, Myc mRNA levels collapse and Myc protein becomes phosphorylated on threonine 58 (T58), triggering its GSK3beta dependent degradation. Maintained expression of stable Myc (T58A) renders self-renewal and maintenance of pluripotency independent of LIF. By contrast, expression of a dominant negative form of Myc antagonizes self-renewal and promotes differentiation. Transcriptional control by STAT3 and suppression of T58 phosphorylation are crucial for regulation of Myc activity in ES cells and therefore in promoting self-renewal. Together, our results establish a mechanism for how LIF and STAT3 regulate ES cell self-renewal and pluripotency.
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Affiliation(s)
- Peter Cartwright
- University of Georgia, Rhodes Center, 425 River Road, Athens, GA 30602-2771, USA
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382
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Sitcheran R, Gupta P, Fisher PB, Baldwin AS. Positive and negative regulation of EAAT2 by NF-kappaB: a role for N-myc in TNFalpha-controlled repression. EMBO J 2005; 24:510-20. [PMID: 15660126 PMCID: PMC548660 DOI: 10.1038/sj.emboj.7600555] [Citation(s) in RCA: 188] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2004] [Accepted: 12/21/2004] [Indexed: 01/15/2023] Open
Abstract
The glutamate transporter gene, EAAT2/GLT-1, is induced by epidermal growth factor (EGF) and downregulated by tumor necrosis factor alpha (TNFalpha). While TNFalpha is generally recognized as a positive regulator of NF-kappaB-dependent gene expression, its ability to control transcriptional repression is not well characterized. Additionally, the regulation of NF-kappaB by EGF is poorly understood. Herein, we demonstrate that both TNFalpha-mediated repression and EGF-mediated activation of EAAT2 expression require NF-kappaB. We show that EGF activates NF-kappaB independently of signaling to IkappaB. Furthermore, TNFalpha can abrogate IKKbeta- and p65-mediated activation of EAAT2. Our results suggest that NF-kappaB can intrinsically activate EAAT2 and that TNFalpha mediates repression through a distinct pathway also requiring NF-kappaB. Consistently, we find that N-myc is recruited to the EAAT2 promoter with TNFalpha and that N-myc-binding sites are required for TNFalpha-mediated repression. Moreover, N-myc overexpression inhibits both basal and p65-induced activation of EAAT2. Our data highlight the remarkable specificity of NF-kappaB activity to regulate gene expression in response to diverse cellular signals and have implications for glutamate homeostasis and neurodegenerative disease.
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Affiliation(s)
- Raquel Sitcheran
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, NC, USA
| | - Pankaj Gupta
- Department of Pathology, College of Physicians and Surgeons, Columbia University Medical Center, New York, NY, USA
| | - Paul B Fisher
- Department of Pathology, College of Physicians and Surgeons, Columbia University Medical Center, New York, NY, USA
- Departments of Neurosurgery and Urology, College of Physicians and Surgeons, Columbia University Medical Center, New York, NY, USA
| | - Albert S Baldwin
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, NC, USA
- Department of Biology, University of North Carolina at Chapel Hill, NC, USA
- 22-000 Lineberger Comprehensive Cancer Center, CB#7295, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7295, USA. Tel.: +1 919 966 3652; Fax: +1 919 966 0444; E-mail: or
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383
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Savill RM, Scotting PJ, Coyle B. Strategies to investigate gene expression and function in granule cells. CEREBELLUM (LONDON, ENGLAND) 2005; 4:271-8. [PMID: 16321883 DOI: 10.1080/14734220500367790] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Studying gene expression in granule cells is a major route to understanding the factors required for many key cellular processes such as specification, proliferation, migration, differentiation, apoptosis, tumour formation and neurodegeneration. A greater understanding of these processes will not only provide insight into cerebellum development, but also diseases of the cerebellum. Granule cells can be readily grown in culture and both viral and non-viral strategies have been optimised to allow gene transfer and expression in cultured cells. However, granule cell migration and maturation are inherent parts of cerebellum development and these rely on interactions with other cells. Hence, a true picture of gene function in these cells can only be obtained when tissue context is maintained. Studies of gene function in this context can be achieved by creation of mouse models. Conditional mouse models, where loss of gene expression is restricted as far as possible to granule cells, are by far the most informative resource in this respect. Despite their obvious benefits, the production of mouse models is both costly and time-consuming and this may be further compounded by a potential lack of phenotype due to redundancy of gene function. Organotypic slice cultures, on the other hand, are a comparatively cheap and accessible model for studies of gene function where tissue context is maintained. Recent technologies have provided the means to manipulate gene expression in such systems and are beginning to yield valuable insights into the molecular regulation of cerebellum development.
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Affiliation(s)
- Rebecca M Savill
- Children's Brain Tumour Research Centre, Institute of Genetics, School of Biology, University of Nottingham, UK
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384
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Laeng P, Pitts RL, Lemire AL, Drabik CE, Weiner A, Tang H, Thyagarajan R, Mallon BS, Altar CA. The mood stabilizer valproic acid stimulates GABA neurogenesis from rat forebrain stem cells. J Neurochem 2004; 91:238-51. [PMID: 15379904 DOI: 10.1111/j.1471-4159.2004.02725.x] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Valproate, an anticonvulsant drug used to treat bipolar disorder, was studied for its ability to promote neurogenesis from embryonic rat cortical or striatal primordial stem cells. Six days of valproate exposure increased by up to fivefold the number and percentage of tubulin beta III-immunopositive neurons, increased neurite outgrowth, and decreased by fivefold the number of astrocytes without changing the number of cells. Valproate also promoted neuronal differentiation in human fetal forebrain stem cell cultures. The neurogenic effects of valproate on rat stem cells exceeded those obtained with the neurotrophins brain-derived growth factor (BDNF) or NT-3, and slightly exceeded the effects obtained with another mood stabilizer, lithium. No effect was observed with carbamazepine. Most of the newly formed neurons were GABAergic, as shown by 10-fold increases in neurons that immunostained for GABA and the GABA-synthesizing enzyme GAD65/67. Double immunostaining for bromodeoxyuridine and tubulin beta III showed that valproate increased by four- to fivefold the proliferation of neuronal progenitors derived from rat stem cells and increased cyclin D2 expression. Valproate also regulated the expression of survival genes, Bad and Bcl-2, at different times of treatment. The expression of prostaglandin E synthase, analyzed by quantitative RT-PCR, was increased by ninefold as early as 6 h into treatment by valproate. The enhancement of GABAergic neuron numbers, neurite outgrowth, and phenotypic expression via increases in the neuronal differentiation of neural stem cell may contribute to the therapeutic effects of valproate in the treatment of bipolar disorder.
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Affiliation(s)
- Pascal Laeng
- Gene Discovery, Psychiatric Genomics, Inc., Gaithersburg, Maryland 20878, USA.
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385
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Corrales JD, Rocco GL, Blaess S, Guo Q, Joyner AL. Spatial pattern of sonic hedgehog signaling through Gli genes during cerebellum development. Development 2004; 131:5581-90. [PMID: 15496441 DOI: 10.1242/dev.01438] [Citation(s) in RCA: 213] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cerebellum consists of a highly organized set of folia that are largely generated postnatally during expansion of the granule cell precursor (GCP)pool. Since the secreted factor sonic hedgehog (Shh) is expressed in Purkinje cells and functions as a GCP mitogen in vitro, it is possible that Shh influences foliation during cerebellum development by regulating the position and/or size of lobes. We studied how Shh and its transcriptional mediators,the Gli proteins, regulate GCP proliferation in vivo, and tested whether they influence foliation. We demonstrate that Shh expression correlates spatially and temporally with foliation. Expression of the Shh target gene Gli1 is also highest in the anterior medial cerebellum, but is restricted to proliferating GCPs and Bergmann glia. By contrast, Gli2is expressed uniformly in all cells in the developing cerebellum except Purkinje cells and Gli3 is broadly expressed along the anteroposterior axis. Whereas Gli mutants have a normal cerebellum, Gli2 mutants have greatly reduced foliation at birth and a decrease in GCPs. In a complementary study using transgenic mice, we show that overexpressing Shh in the normal domain does not grossly alter the basic foliation pattern, but does lead to prolonged proliferation of GCPs and an increase in the overall size of the cerebellum. Taken together, these studies demonstrate that positive Shh signaling through Gli2 is required to generate a sufficient number of GCPs for proper lobe growth.
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Affiliation(s)
- JoMichelle D Corrales
- Howard Hughes Medical Institute and Developmental Genetics Program, Skirball Institute of Biomolecular Medicine, 540 First Avenue, New York, NY 10016, USA
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386
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Abstract
Our knowledge of the causes of brain tumors has steadily increased and is leading to a refined understanding of the signaling pathways that may be essential for tumor formation. At the same time, we are gaining insights into the developmental processes that regulate the formation of the diverse range of cell types in the normal brain. Interestingly, many of these pathways seem to overlap and suggest common mechanisms regulating tumor formation and cellular development. This overlap may also inform us about the nature of the cell of origin for different types of brain tumors. By appreciating the inter-relationship between tumor formation and development, we maybe able to design new therapeutics targeting tumors for new modes of treatment.
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Affiliation(s)
- Alan H Shih
- Department of Cancer Biology and Genetics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
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387
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Contestabile A, Ciani E. Role of nitric oxide in the regulation of neuronal proliferation, survival and differentiation. Neurochem Int 2004; 45:903-14. [PMID: 15312985 DOI: 10.1016/j.neuint.2004.03.021] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Nitric oxide (NO), an important cellular messenger, has been linked to both neurodegenerative and neuroprotective actions. In the present review, we focus on recent data establishing a survival and differentiation role for NO in several neural in vitro and in vivo models. Nitric oxide has been found to be essential for survival of neuronal cell lines and primary neurons in culture under various death challenges. Furthermore, its lack may aggravate some neuropathological conditions in experimental animals. Several cellular pathways and signaling systems subserving this neuroprotective role of NO are considered in the review. Survey of recent data related to the developmental role of NO mainly focus on its action as a negative regulator of neuronal precursor cells proliferation and on its role of promotion of neuronal differentiation. Discussion on discrepancies arising from the literature is focused on the Janus-faced properties of the molecule and it is proposed that most controversial results are related to the intrinsic property of NO to compensate among functionally opposed effects. As an example, the increased proliferation of neural cell precursors under conditions of NO shortage may be, later on in the development, compensated by increased elimination through programmed cell death as a consequence of the lack of the survival-promoting action of the molecule. To elucidate these complex, and possibly contrasting, effects of NO is indicated as an important task for future researches.
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Affiliation(s)
- Antonio Contestabile
- Department of Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy.
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388
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Abstract
N-myc has emerged as a member of a transcriptional regulatory network which impinges directly on the machinery of cell growth and proliferation. Critical during neural crest embryogenesis, N-myc is rapidly down-regulated as tissues become terminally differentiated and growth-arrested. The involvement of N-myc in these fundamental cellular processes necessitates an intricate strategy for its regulation, which is still being elucidated. Deregulated N-myc over-expression has clear transforming ability in vitro and in vivo. The transcriptional target genes responsible for this activity are beginning to be unravelled.
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Affiliation(s)
- Wayne D Thomas
- Children's Cancer Institute Australia for Medical Research, Randwick, NSW, Australia.
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389
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Abstract
Proteins from the Polycomb group (PcG) are epigenetic chromatin modifiers involved in cancer development and also in the maintenance of embryonic and adult stem cells. The therapeutic potential of stem cells and the growing conviction that tumors contain stem cells highlights the importance of understanding the extrinsic and intrinsic circuitry controlling stem cell fate and their connections to cancer.
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Affiliation(s)
- Merel E Valk-Lingbeek
- The Netherlands Cancer Institute, Department of Molecular Genetics, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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390
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Raivich G, Bohatschek M, Da Costa C, Iwata O, Galiano M, Hristova M, Nateri AS, Makwana M, Riera-Sans L, Wolfer DP, Lipp HP, Aguzzi A, Wagner EF, Behrens A. The AP-1 transcription factor c-Jun is required for efficient axonal regeneration. Neuron 2004; 43:57-67. [PMID: 15233917 DOI: 10.1016/j.neuron.2004.06.005] [Citation(s) in RCA: 357] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2003] [Revised: 04/27/2004] [Accepted: 06/04/2004] [Indexed: 01/06/2023]
Abstract
Nerve injury triggers numerous changes in the injured neurons and surrounding nonneuronal cells that ultimately result in successful target reinnervation or cell death. c-Jun is a component of the heterodimeric AP-1 transcription factor, and c-Jun is highly expressed in response to neuronal trauma. Here we have investigated the role of c-jun during axonal regeneration using mice lacking c-jun in the central nervous system. After transection of the facial nerve, the absence of c-Jun caused severe defects in several aspects of the axonal response, including perineuronal sprouting, lymphocyte recruitment, and microglial activation. c-Jun-deficient motorneurons were atrophic, resistant to axotomy-induced cell death, and showed reduced target muscle reinnervation. Expression of CD44, galanin, and alpha7beta1 integrin, molecules known to be involved in regeneration, was greatly impaired, suggesting a mechanism for c-Jun-mediated axonal growth. Taken together, our results identify c-Jun as an important regulator of axonal regeneration in the injured central nervous system.
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Affiliation(s)
- Gennadij Raivich
- Perinatal Brain Repair Group, Department of Obstetrics and Gynaecology, University College London, 86-96 Chenies Mews, London WC1E 6HX, United Kingdom
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391
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Ciani E, Severi S, Contestabile A, Bartesaghi R, Contestabile A. Nitric oxide negatively regulates proliferation and promotes neuronal differentiation through N-Myc downregulation. J Cell Sci 2004; 117:4727-37. [PMID: 15331636 DOI: 10.1242/jcs.01348] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nitric oxide (NO) has been found to act as an important negative regulator of cell proliferation in several systems. We report here that NO negatively regulates proliferation of neuronal cell precursors and promotes their differentiation by downregulating the oncogene N-Myc. We have studied this regulatory function of NO in neuroblastoma cell lines (SK-N-BE) and in primary cerebellar granule cell cultures. In a neuronal NO synthase (nNOS) overexpressing neuroblastoma cell line exposed to the differentiative action of retinoic acid, NO slowed down proliferation and accelerated differentiation towards a neuronal phenotype. This effect was accompanied by a parallel decrease of N-Myc expression. Similar results could be obtained in parental SK-N-BE cells by providing an exogenous source of NO. Pharmacological controls demonstrated that NO's regulatory actions on cell proliferation and N-Myc expression were mediated by cGMP as an intermediate messenger. Furthermore, NO was found to modulate the transcriptional activity of N-Myc gene promoter by acting on the E2F regulatory region, possibly through the control of Rb phosphorylation state, that we found to be negatively regulated by NO. In cerebellar granule cell cultures, NOS inhibition increased the division rate of neuronal precursors, in parallel with augmented N-Myc expression. Because a high N-Myc expression level is essential for neuroblastoma progression as well as for proliferation of neuronal precursors, its negative regulation by NO highlights a novel physiopathological function of this important messenger molecule.
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Affiliation(s)
- Elisabetta Ciani
- Department of Human and General Physiology, University of Bologna, Piazza di Porta San Donato 2, 40127, Bologna, Italy.
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392
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Bouchard C, Marquardt J, Brás A, Medema RH, Eilers M. Myc-induced proliferation and transformation require Akt-mediated phosphorylation of FoxO proteins. EMBO J 2004; 23:2830-40. [PMID: 15241468 PMCID: PMC514943 DOI: 10.1038/sj.emboj.7600279] [Citation(s) in RCA: 164] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2004] [Accepted: 05/25/2004] [Indexed: 11/08/2022] Open
Abstract
Myc synergizes with Ras and PI3-kinase in cell transformation, yet the molecular basis for this behavior is poorly understood. We now show that Myc recruits TFIIH, P-TEFb and Mediator to the cyclin D2 and other target promoters, while the PI3-kinase pathway controls formation of the pre-initiation complex and loading of RNA polymerase II. The PI3-kinase pathway involves Akt-mediated phosphorylation of FoxO transcription factors. In a nonphosphorylated state, FoxO factors inhibit induction of multiple Myc target genes, Myc-induced cell proliferation and transformation by Myc and Ras. Abrogation of FoxO function enables Myc to activate target genes in the absence of PI3-kinase activity and to induce foci formation in primary cells in the absence of oncogenic Ras. We suggest that the cooperativity between Myc and Ras is at least in part due to the fact that Myc and FoxO proteins control distinct steps in the activation of an overlapping set of critical target genes.
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Affiliation(s)
- Caroline Bouchard
- Institute for Molecular Biology and Tumor Research, Marburg, Germany
| | - Judith Marquardt
- Institute for Molecular Biology and Tumor Research, Marburg, Germany
| | - Alexandra Brás
- Dutch Cancer Institute (NKI-H8), Plesmanlaan, Amsterdam, Netherlands
| | - René H Medema
- Dutch Cancer Institute (NKI-H8), Plesmanlaan, Amsterdam, Netherlands
| | - Martin Eilers
- Institute for Molecular Biology and Tumor Research, Marburg, Germany
- Inst. f. Molekularbiologie & Tumorf., Universität Marburg, Emil-Mannkopff-Str. 2, 35033 Marburg, Germany. Tel.: +49 6421 286 6410/6768; Fax: +49 6421 286 5196; E-mail:
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393
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Li Y, Zhang H, Choi SC, Litingtung Y, Chiang C. Sonic hedgehog signaling regulates Gli3 processing, mesenchymal proliferation, and differentiation during mouse lung organogenesis. Dev Biol 2004; 270:214-31. [PMID: 15136151 DOI: 10.1016/j.ydbio.2004.03.009] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2004] [Revised: 03/03/2004] [Accepted: 03/08/2004] [Indexed: 01/17/2023]
Abstract
Lack of Sonic hedgehog (Shh) signaling, mediated by the Gli proteins, leads to severe pulmonary hypoplasia. However, the precise role of Gli genes in lung development is not well established. We show Shh signaling prevents Gli3 proteolysis to generate its repressor forms (Gli3R) in the developing murine lung. In Shh(-/-) or cyclopamine-treated wild-type (WT) lung, we found that Gli3R level is elevated, and this upregulation appears to contribute to defects in proliferation and differentiation observed in the Shh(-/-) mesenchyme, where Gli3 is normally expressed. In agreement, we found Shh(-/-);Gli3(-/-) lungs exhibit enhanced growth potential. Vasculogenesis is also enhanced; in contrast, bronchial myogenesis remains absent in Shh(-/-);Gli3(-/-) compared with Shh(-/-) lungs. Genes upregulated in Shh(-/-);Gli3(-/-) relative to Shh(-/-) lung include Wnt2 and, surprisingly, Foxf1 whose expression has been reported to be Shh-dependent. Cyclins D1, D2, and D3 antibody labelings also reveal distinct expression patterns in the normal and mutant lungs. We found significant repression of Tbx2 and Tbx3, both linked to inhibition of cellular senescence, in Shh(-/-) and partial derepression in Shh(-/-); Gli3(-/-) lungs, while Tbx4 and Tbx5 expressions are less affected in the mutants. Our findings shed light on the role of Shh signaling on Gli3 processing in lung growth and differentiation by regulating several critical genes.
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Affiliation(s)
- Yina Li
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232-8240, USA
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394
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Canzoniere D, Farioli-Vecchioli S, Conti F, Ciotti MT, Tata AM, Augusti-Tocco G, Mattei E, Lakshmana MK, Krizhanovsky V, Reeves SA, Giovannoni R, Castano F, Servadio A, Ben-Arie N, Tirone F. Dual control of neurogenesis by PC3 through cell cycle inhibition and induction of Math1. J Neurosci 2004; 24:3355-69. [PMID: 15056715 PMCID: PMC6730030 DOI: 10.1523/jneurosci.3860-03.2004] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Growing evidence indicates that cell cycle arrest and neurogenesis are highly coordinated and interactive processes, governed by cell cycle genes and neural transcription factors. The gene PC3 (Tis21/BTG2) is expressed in the neuroblast throughout the neural tube and inhibits cell cycle progression at the G1 checkpoint by repressing cyclin D1 transcription. We generated inducible mouse models in which the expression of PC3 was upregulated in neuronal precursors of the neural tube and of the cerebellum. These mice exhibited a marked increase in the production of postmitotic neurons and impairment of cerebellar development. Cerebellar granule precursors of PC3 transgenic mice displayed inhibition of cyclin D1 expression and a strong increase in the expression of Math1, a transcription factor required for their differentiation. Furthermore, PC3, encoded by a recombinant adenovirus, also induced Math1 in postmitotic granule cells in vitro and stimulated the Math1 promoter activity. In contrast, PC3 expression was unaffected in the cerebellar primordium of Math1 null mice, suggesting that PC3 acts upstream to Math1. As a whole, our data suggest that cell cycle exit of cerebellar granule cell precursors and the onset of cerebellar neurogenesis are coordinated by PC3 through transcriptional control of cyclin D1 and Math1, respectively.
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Affiliation(s)
- Daniela Canzoniere
- Istituto Neurobiologia e Medicina Molecolare and Istituto Biologia e Patologia Molecolare, Consiglio Nazionale delle Ricerche, 00156 Rome, Italy
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395
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West AB, Kapatos G, O'Farrell C, Gonzalez-de-Chavez F, Chiu K, Farrer MJ, Maidment NT. N-myc regulates parkin expression. J Biol Chem 2004; 279:28896-902. [PMID: 15078880 DOI: 10.1074/jbc.m400126200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in the parkin gene are common in early-onset and familial Parkinson's disease (PD), and the parkin protein interacts in the ubiquitin-proteasome system as an E3 ligase. However, the regulatory pathways that govern parkin expression are unknown. In this study, we showed that a phylogenetically conserved N-myc binding site in the bi-directional parkin promoter interacted with myc-family transcription factors in reporter assays, and N-myc bound to the parkin promoter in chromatin immunoprecipitation assays and repressed transcription activity. Parkin expression was inversely correlated with N-myc levels in the developing mouse and human brain, in human neuroblastoma cell lines with various levels of n-myc amplification, and in an inducible N-myc cell line. Although parkin and N-myc expression were dramatically altered upon retinoic acid-induced differentiation of a human neuroblastoma cell line, modulation of parkin expression did not significantly affect either rates of cellular proliferation or levels of cyclin E. Analysis of additional genes associated with familial PD revealed a shared basis of transcription regulation mediated by N-myc and the cell cycle. Our results, in combination with functional knowledge of the proteins encoded by these genes, suggest a common pathway linking together PD, the ubiquitin-proteasome system, and cell cycle control.
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Affiliation(s)
- Andrew B West
- Morris K Udall Center for Parkinson's Disease Research, UCLA Neuropsychiatric Institute, Los Angeles, California 90024, USA.
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396
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Leung C, Lingbeek M, Shakhova O, Liu J, Tanger E, Saremaslani P, Van Lohuizen M, Marino S. Bmi1 is essential for cerebellar development and is overexpressed in human medulloblastomas. Nature 2004; 428:337-41. [PMID: 15029199 DOI: 10.1038/nature02385] [Citation(s) in RCA: 666] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Accepted: 02/02/2004] [Indexed: 11/08/2022]
Abstract
Overexpression of the polycomb group gene Bmi1 promotes cell proliferation and induces leukaemia through repression of Cdkn2a (also known as ink4a/Arf) tumour suppressors. Conversely, loss of Bmi1 leads to haematological defects and severe progressive neurological abnormalities in which de-repression of the ink4a/Arf locus is critically implicated. Here, we show that Bmi1 is strongly expressed in proliferating cerebellar precursor cells in mice and humans. Using Bmi1-null mice we demonstrate a crucial role for Bmi1 in clonal expansion of granule cell precursors both in vivo and in vitro. Deregulated proliferation of these progenitor cells, by activation of the sonic hedgehog (Shh) pathway, leads to medulloblastoma development. We also demonstrate linked overexpression of BMI1 and patched (PTCH), suggestive of SHH pathway activation, in a substantial fraction of primary human medulloblastomas. Together with the rapid induction of Bmi1 expression on addition of Shh or on overexpression of the Shh target Gli1 in cerebellar granule cell cultures, these findings implicate BMI1 overexpression as an alternative or additive mechanism in the pathogenesis of medulloblastomas, and highlight a role for Bmi1-containing polycomb complexes in proliferation of cerebellar precursor cells.
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Affiliation(s)
- Carly Leung
- Institute of Clinical Pathology, Department of Pathology, University of Zürich, Schmelzbergstrasse 12, 8091 Zürich, Switzerland
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397
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Edsjö A, Nilsson H, Vandesompele J, Karlsson J, Pattyn F, Culp LA, Speleman F, Påhlman S. Neuroblastoma cells with overexpressed MYCN retain their capacity to undergo neuronal differentiation. J Transl Med 2004; 84:406-17. [PMID: 14767491 DOI: 10.1038/labinvest.3700061] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Amplification of MYCN in neuroblastoma strongly correlates to unfavorable outcome, but little is known of how the high MYCN expression translates into an aggressive tumor phenotype. More aggressive neuroblastomas are generally immature and overexpression of exogenous MYCN in cultured neuroblastoma cells and other neuronal cell types has been reported to inhibit induced differentiation, suggesting a link between high MYCN expression and an immature phenotype. However, we show here that MYCN is expressed in human neuroblasts of sympathetic chain ganglia at fetal week 8.5, a developmental stage at which these neuroblasts express a number of sympathetic neuronal differentiation marker genes. Analyses of 28 neuroblastoma tumor specimens and 27 cell lines for the expression of MYCN and a panel of neuronal differentiation marker genes did not reveal any correlation between MYCN and marker gene expression levels. Finally, we tested five separate differentiation protocols and show that MYCN overexpressing neuroblastoma cells with a neuronal phenotype, derived from the non-MYCN-amplified human neuroblastoma cell line SK-N-SH, retain their capacity to differentiate despite constitutive MYCN overexpression. Our results show that high MYCN expression and sympathetic differentiation are compatible, and indirectly our findings lend support to previously published MYCN neuroblastoma tumor data, which suggest that in single MYCN copy neuroblastomas there is no direct correlation between a high cellular MYCN protein content and aggressive tumor cell behavior.
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Affiliation(s)
- Anders Edsjö
- Department of Laboratory Medicine, Molecular Medicine, Lund University, University Hospital MAS, S-20502 Malmö, Sweden
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398
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Gebauer S, Yu AL, Omura-Minamisawa M, Batova A, Diccianni MB. Expression profiles and clinical relationships ofID2,CDKN1B, andCDKN2A in primary neuroblastoma. Genes Chromosomes Cancer 2004; 41:297-308. [PMID: 15390183 DOI: 10.1002/gcc.20096] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Despite considerable research into the etiology of neuroblastoma, the molecular basis of this disease has remained elusive. In contrast to the absence of expression of the known tumor suppressor CDKN2A (also known as p16 and INK4A) in a wide variety of tumor types we have found in previous studies that CDKN2A protein is paradoxically highly expressed in many advanced stage neuroblastomas and unrelated to RB1 status. In the present study, we sought to identify the mechanistic relationships that might influence CDKN2A expression and negate its influence on tumor cell proliferation. In this regard, we examined the role of the tumor-suppressor gene CDKN1B (also known as p27 and Kip1) and the oncogene ID2 in relationship to CDKN2A expression, MYCN amplification, and neuroblastoma pathogenesis in 17 neuroblastoma cell lines and 129 samples of primary tumors of all stages. All neuroblastoma cell lines expressed the ID2 transcript and protein. However, although the majority of primary neuroblastomas also expressed the ID2 transcript, expression of the ID2 protein was undetectable or only barely detectable, regardless of transcript expression. In both cell lines and primary tumors, ID2 expression was independent of both CDKN2A and MYCN expression. In primary neuroblastomas, CDKN1B protein was expressed in significantly fewer advanced-stage neuroblastomas than early-stage neuroblastomas, but its expression had no relationship with CDKN2A expression or MYCN amplification. We concluded that the paradoxical expression of CDKN2A in neuroblastoma cannot be explained by inactivation of the tumor-suppressor gene CDKN1B or overexpression of the oncogene ID2. We further concluded that ID2 is not a target of MYCN regulation nor is it a prognostic factor for neuroblastoma. Finally, the loss of CDKN1B in advanced-stage neuroblastoma suggests this protein may play a role in the neuroblastoma disease process.
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Affiliation(s)
- Sigrun Gebauer
- Division of Pediatric Hematology/Oncology, UCSD Medical Center, 200 West Arbor Drive, San Diego, CA 92103-8447, USA
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399
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Hurlin PJ, Dezfouli S. Functions of myc:max in the control of cell proliferation and tumorigenesis. INTERNATIONAL REVIEW OF CYTOLOGY 2004; 238:183-226. [PMID: 15364199 DOI: 10.1016/s0074-7696(04)38004-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Deregulation and elevated expression of members of the Myc family of bHLHZip transcription factors are observed in a high percentage of tumors. This close association with human cancers has led to a tremendous effort to define their biological and biochemical activities. Although Myc family proteins have the capacity to elicit a wide range of cell behaviors, their principal function appears to be to drive cells into the cell cycle and to keep them there. However, forced expression of Myc profoundly sensitizes normal cells to apoptosis. Therefore, tumor formation caused by deregulated Myc expression requires cooperating events that disrupt pathways that mediate apoptosis. Myc-dependent tumor formation may also be impeded by a set of related bHLHZip proteins with the demonstrated potential to act as Myc antagonists in cell culture experiments. In this review, we examine the complex activities of Myc family proteins and how their actions might be regulated in the context of a network of bHLHZip proteins.
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Affiliation(s)
- Peter J Hurlin
- Portland Shriners Hospitals for Children and Department of Cell and Developmental Biology Oregon Health Sciences University, Portland, Oregon 97201, USA
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400
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Inatani M, Irie F, Plump AS, Tessier-Lavigne M, Yamaguchi Y. Mammalian brain morphogenesis and midline axon guidance require heparan sulfate. Science 2003; 302:1044-6. [PMID: 14605369 DOI: 10.1126/science.1090497] [Citation(s) in RCA: 335] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Heparan sulfate (HS) is required for morphogen signaling during Drosophila pattern formation, but little is known about its physiological importance in mammalian development. To define the developmental role of HS in mammalian species, we conditionally disrupted the HS-polymerizing enzyme EXT1 in the embryonic mouse brain. The EXT1-null brain exhibited patterning defects that are composites of those caused by mutations of multiple HS-binding morphogens. Furthermore, the EXT1-null brain displayed severe guidance errors in major commissural tracts, revealing a pivotal role of HS in midline axon guidance. These findings demonstrate that HS is essential for mammalian brain development.
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Affiliation(s)
- Masaru Inatani
- The Burnham Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
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