51
|
Vanderluit JL, Wylie CA, McClellan KA, Ghanem N, Fortin A, Callaghan S, MacLaurin JG, Park DS, Slack RS. The Retinoblastoma family member p107 regulates the rate of progenitor commitment to a neuronal fate. ACTA ACUST UNITED AC 2007; 178:129-39. [PMID: 17591923 PMCID: PMC2064429 DOI: 10.1083/jcb.200703176] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Retinoblastoma protein p107 regulates the neural precursor pool in both the developing and adult brain. As p107-deficient mice exhibit enhanced levels of Hes1, we questioned whether p107 regulates neural precursor self-renewal through the repression of Hes1. p107 represses transcription at the Hes1 promoter. Despite an expanded neural precursor population, p107-null mice exhibit a striking reduction in the number of cortical neurons. Hes1 deficiency rescues neurosphere numbers in p107-null embryos. We find that the loss of a single Hes1 allele in vivo restores the number of neural precursor cells at the ventricular zone. Neuronal birthdating analysis reveals a dramatic reduction in the rate of neurogenesis, demonstrating impairment in p107(-/-) progenitors to commit to a neuronal fate. The loss of a single Hes1 allele restores the number of newly generated neurons in p107-deficient brains. Together, we identify a novel function for p107 in promoting neural progenitor commitment to a neuronal fate.
Collapse
Affiliation(s)
- Jacqueline L Vanderluit
- Department of Cellular and Molecular Medicine, Ottawa Health Research Institute, Neuroscience Program, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | | | | | | | | | | | | | | | | |
Collapse
|
52
|
Ruzhynsky VA, McClellan KA, Vanderluit JL, Jeong Y, Furimsky M, Park DS, Epstein DJ, Wallace VA, Slack RS. Cell cycle regulator E2F4 is essential for the development of the ventral telencephalon. J Neurosci 2007; 27:5926-35. [PMID: 17537963 PMCID: PMC6672261 DOI: 10.1523/jneurosci.1538-07.2007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Early forebrain development is characterized by extensive proliferation of neural precursors coupled with complex structural transformations; however, little is known regarding the mechanisms by which these processes are integrated. Here, we show that deficiency of the cell cycle regulatory protein, E2F4, results in the loss of ventral telencephalic structures and impaired self-renewal of neural precursor cells. The mechanism underlying aberrant ventral patterning lies in a dramatic loss of Sonic hedgehog (Shh) expression specifically in this region. The E2F4-deficient phenotype can be recapitulated by interbreeding mice heterozygous for E2F4 with those lacking one allele of Shh, suggesting a genetic interaction between these pathways. Treatment of E2F4-deficient cells with a Hh agonist rescues stem cell self-renewal and cells expressing the homeodomain proteins that specify the ventral telencephalic structures. Finally, we show that E2F4 deficiency results in impaired activity of Shh forebrain-specific enhancers. In conclusion, these studies establish a novel requirement for the cell cycle regulatory protein, E2F4, in the development of the ventral telencephalon.
Collapse
Affiliation(s)
- Vladimir A. Ruzhynsky
- Department of Cellular and Molecular Medicine, Ottawa Health Research Institute, Neuroscience Program, and
| | - Kelly A. McClellan
- Department of Cellular and Molecular Medicine, Ottawa Health Research Institute, Neuroscience Program, and
| | - Jacqueline L. Vanderluit
- Department of Cellular and Molecular Medicine, Ottawa Health Research Institute, Neuroscience Program, and
| | - Yongsu Jeong
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
| | - Marosh Furimsky
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
- Molecular Medicine Program and Vision Program, Ottawa Health Research Institute, Ottawa, Ontario, Canada K1H 8L6, and
| | - David S. Park
- Department of Cellular and Molecular Medicine, Ottawa Health Research Institute, Neuroscience Program, and
| | - Douglas J. Epstein
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
| | - Valerie A. Wallace
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
- Molecular Medicine Program and Vision Program, Ottawa Health Research Institute, Ottawa, Ontario, Canada K1H 8L6, and
| | - Ruth S. Slack
- Department of Cellular and Molecular Medicine, Ottawa Health Research Institute, Neuroscience Program, and
| |
Collapse
|
53
|
McClellan KA, Ruzhynsky VA, Douda DN, Vanderluit JL, Ferguson KL, Chen D, Bremner R, Park DS, Leone G, Slack RS. Unique requirement for Rb/E2F3 in neuronal migration: evidence for cell cycle-independent functions. Mol Cell Biol 2007; 27:4825-43. [PMID: 17452454 PMCID: PMC1951492 DOI: 10.1128/mcb.02100-06] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cell cycle regulatory retinoblastoma (Rb) protein is a key regulator of neural precursor proliferation; however, its role has been expanded to include a novel cell-autonomous role in mediating neuronal migration. We sought to determine the Rb-interacting factors that mediate both the cell cycle and migration defects. E2F1 and E2F3 are likely Rb-interacting candidates that we have shown to be deregulated in the absence of Rb. Using mice with compound null mutations of Rb and E2F1 or E2F3, we asked to what extent either E2F1 or E2F3 interacts with Rb in neurogenesis. Here, we report that E2F1 and E2F3 are both functionally relevant targets in neural precursor proliferation, cell cycle exit, and laminar patterning. Each also partially mediates the Rb requirement for neuronal survival. Neuronal migration, however, is specifically mediated through E2F3, beyond its role in cell cycle regulation. This study not only outlines overlapping and distinct functions for E2Fs in neurogenesis but also is the first to establish a physiologically relevant role for the Rb/E2F pathway beyond cell cycle regulation in vivo.
Collapse
Affiliation(s)
- Kelly A McClellan
- Department of Cellular and Molecular Medicine, Ottawa Health Research Institute, University of Ottawa, Ottawa, ON, Canada
| | | | | | | | | | | | | | | | | | | |
Collapse
|
54
|
Teng C, Guo Y, Zhang H, Zhang H, Ding M, Deng H. Identification and characterization of label-retaining cells in mouse pancreas. Differentiation 2007; 75:702-12. [PMID: 17381540 DOI: 10.1111/j.1432-0436.2007.00170.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Pancreatic stem cells (PSCs) may play an important role in maintaining and repairing pancreatic tissues. However, both the existence and localization of PSCs in adult mammalian pancreas still remain elusive. In order to locate the potential pancreatic progenitor/stem cells, we used the tracing label-retaining cells (LRCs) method and identified slow-cycling cells in mouse pancreas. Characterization of the LRCs revealed that the differentiation marker-negative LRCs were located not only within and around the islets but also around the acini and ducts. About 30% of the LRCs around the acini and ducts expressed c-Met, which is a putative pancreatic progenitor/stem cell marker. Moreover, the LRCs around the acini could be activated to form duct-like structures in response to pancreatic damage, and the involvement of these LRCs in the neogenesis of islets and focal areas could also be observed in acini. Our data suggest that the LRCs located around the acini and ducts may represent potential pancreatic progenitor/stem cells, and characterization of these cells may aid in further identification of the specific markers of pancreatic progenitor/stem cells.
Collapse
Affiliation(s)
- Chunbo Teng
- Laboratory of Chemical Genomics, Shenzhen Graduate School, Peking University, Shenzhen, China
| | | | | | | | | | | |
Collapse
|
55
|
A comparative genomics approach to identifying the plasticity transcriptome. BMC Neurosci 2007; 8:20. [PMID: 17355637 PMCID: PMC1831778 DOI: 10.1186/1471-2202-8-20] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2006] [Accepted: 03/13/2007] [Indexed: 02/04/2023] Open
Abstract
Background Neuronal activity regulates gene expression to control learning and memory, homeostasis of neuronal function, and pathological disease states such as epilepsy. A great deal of experimental evidence supports the involvement of two particular transcription factors in shaping the genomic response to neuronal activity and mediating plasticity: CREB and zif268 (egr-1, krox24, NGFI-A). The gene targets of these two transcription factors are of considerable interest, since they may help develop hypotheses about how neural activity is coupled to changes in neural function. Results We have developed a computational approach for identifying binding sites for these transcription factors within the promoter regions of annotated genes in the mouse, rat, and human genomes. By combining a robust search algorithm to identify discrete binding sites, a comparison of targets across species, and an analysis of binding site locations within promoter regions, we have defined a group of candidate genes that are strong CREB- or zif268 targets and are thus regulated by neural activity. Our analysis revealed that CREB and zif268 share a disproportionate number of targets in common and that these common targets are dominated by transcription factors. Conclusion These observations may enable a more detailed understanding of the regulatory networks that are induced by neural activity and contribute to the plasticity transcriptome. The target genes identified in this study will be a valuable resource for investigators who hope to define the functions of specific genes that underlie activity-dependent changes in neuronal properties.
Collapse
|
56
|
Wenzel PL, Wu L, de Bruin A, Chong JL, Chen WY, Dureska G, Sites E, Pan T, Sharma A, Huang K, Ridgway R, Mosaliganti K, Sharp R, Machiraju R, Saltz J, Yamamoto H, Cross JC, Robinson ML, Leone G. Rb is critical in a mammalian tissue stem cell population. Genes Dev 2007; 21:85-97. [PMID: 17210791 PMCID: PMC1759903 DOI: 10.1101/gad.1485307] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The inactivation of the retinoblastoma (Rb) tumor suppressor gene in mice results in ectopic proliferation, apoptosis, and impaired differentiation in extraembryonic, neural, and erythroid lineages, culminating in fetal death by embryonic day 15.5 (E15.5). Here we show that the specific loss of Rb in trophoblast stem (TS) cells, but not in trophoblast derivatives, leads to an overexpansion of trophoblasts, a disruption of placental architecture, and fetal death by E15.5. Despite profound placental abnormalities, fetal tissues appeared remarkably normal, suggesting that the full manifestation of fetal phenotypes requires the loss of Rb in both extraembryonic and fetal tissues. Loss of Rb resulted in an increase of E2f3 expression, and the combined ablation of Rb and E2f3 significantly suppressed Rb mutant phenotypes. This rescue appears to be cell autonomous since the inactivation of Rb and E2f3 in TS cells restored placental development and extended the life of embryos to E17.5. Taken together, these results demonstrate that loss of Rb in TS cells is the defining event causing lethality of Rb(-/-) embryos and reveal the convergence of extraembryonic and fetal functions of Rb in neural and erythroid development. We conclude that the Rb pathway plays a critical role in the maintenance of a mammalian stem cell population.
Collapse
Affiliation(s)
- Pamela L. Wenzel
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Molecular Genetics, College of Biological Sciences, The Ohio State University, Columbus, Ohio 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
| | - Lizhao Wu
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Molecular Genetics, College of Biological Sciences, The Ohio State University, Columbus, Ohio 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
| | - Alain de Bruin
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Molecular Genetics, College of Biological Sciences, The Ohio State University, Columbus, Ohio 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
| | - Jean-Leon Chong
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Molecular Genetics, College of Biological Sciences, The Ohio State University, Columbus, Ohio 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
| | - Wen-Yi Chen
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Molecular Genetics, College of Biological Sciences, The Ohio State University, Columbus, Ohio 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
| | - Geoffrey Dureska
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Molecular Genetics, College of Biological Sciences, The Ohio State University, Columbus, Ohio 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
| | - Emily Sites
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Molecular Genetics, College of Biological Sciences, The Ohio State University, Columbus, Ohio 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
| | - Tony Pan
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
- Biomedical Informatics, Department of Pathology, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
| | - Ashish Sharma
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
- Biomedical Informatics, Department of Pathology, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
| | - Kun Huang
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
- Biomedical Informatics, Department of Pathology, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
| | - Randall Ridgway
- Department of Computer Science and Engineering, The Ohio State University, Columbus, Ohio 43210, USA
| | - Kishore Mosaliganti
- Department of Computer Science and Engineering, The Ohio State University, Columbus, Ohio 43210, USA
| | - Richard Sharp
- Department of Computer Science and Engineering, The Ohio State University, Columbus, Ohio 43210, USA
| | - Raghu Machiraju
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
- Biomedical Informatics, Department of Pathology, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Computer Science and Engineering, The Ohio State University, Columbus, Ohio 43210, USA
| | - Joel Saltz
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
- Biomedical Informatics, Department of Pathology, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
| | - Hideyuki Yamamoto
- Department of Biochemistry and Molecular Biology, University of Calgary Faculty of Medicine, Calgary, Alberta T2N 4N1, Canada
| | - James C. Cross
- Department of Biochemistry and Molecular Biology, University of Calgary Faculty of Medicine, Calgary, Alberta T2N 4N1, Canada
| | - Michael L. Robinson
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
- Division of Molecular and Human Genetics, Children’s Research Institute, Columbus, Ohio 43205, USA
- Department of Pediatrics, The Ohio State University, Columbus, Ohio 43210, USA
- E-MAIL ; FAX (513) 529-6900
| | - Gustavo Leone
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Molecular Genetics, College of Biological Sciences, The Ohio State University, Columbus, Ohio 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA
- Corresponding authors.E-MAIL ; FAX (614) 292-3312
| |
Collapse
|
57
|
Galderisi U, Cipollaro M, Giordano A. The retinoblastoma gene is involved in multiple aspects of stem cell biology. Oncogene 2006; 25:5250-6. [PMID: 16936744 DOI: 10.1038/sj.onc.1209736] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Genetic programs controlling self-renewal and multipotentiality of stem cells have overlapping pathways with cell cycle regulation. Components of cell cycle machinery can play a key role in regulating stem cell self-renewal, proliferation, differentiation and aging. Among the negative regulators of cell cycle progression, the RB family members play a prominent role in controlling several aspects of stem cell biology. Stem cells contribute to tissue homeostasis and must have molecular mechanisms that prevent senescence and hold 'stemness'. RB can induce senescence-associated changes in gene expression and its activity is downregulated in stem cells to preserve self-renewal. Several reports evidenced that RB could play a role in lineage specification of several types of stem cells. RB has a role in myogenesis as well as in cardiogenesis. These effects are not only related to its role in suppressing E2F-responsive genes but also to its ability to modulate the activity of tissue-specific transcription factors. RB is also involved in adipogenesis through a strict control of lineage commitment and differentiation of adipocytes as well in determining the switch between brown and white adipocytes. Also, hematopoietic progenitor cells utilize the RB pathway to modulate cell commitment and differentiation. In this review, we will also discuss the role of the other two RB family members: Rb2/p130 and p107 showing that they have both specific and overlapping functions with RB gene.
Collapse
Affiliation(s)
- U Galderisi
- Sbarro Institute for Cancer Research and Molecular Medicine, Center of Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA, USA.
| | | | | |
Collapse
|
58
|
Golestaneh N, Tang Y, Katuri V, Jogunoori W, Mishra L, Mishra B. Cell cycle deregulation and loss of stem cell phenotype in the subventricular zone of TGF-beta adaptor elf-/- mouse brain. Brain Res 2006; 1108:45-53. [PMID: 16884701 DOI: 10.1016/j.brainres.2006.05.113] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2005] [Revised: 05/11/2006] [Accepted: 05/15/2006] [Indexed: 01/19/2023]
Abstract
The mammalian forebrain subependyma contains neural stem cells and other proliferating progenitor cells. Recent studies have shown the importance of TGF-beta family members and their adaptor proteins in the inhibition of proliferation in the nervous system. Previously, we have demonstrated that TGF-beta induces phosphorylation and association of ELF (embryonic liver fodrin) with Smad3 and Smad4 resulting in nuclear translocation. Elf(-/-) mice manifest abnormal neuronal differentiation, with loss of neuroepithelial progenitor cell phenotype in the subventricular zone (SVZ) with dramatic marginal cell hyperplasia and loss of nestin expression. Here, we have analyzed the expression of cell cycle-associated proteins cdk4, mdm2, p21, and pRb family members in the brain of elf(-/-) mice to verify the role of elf in the regulation of neural precursor cells in the mammalian brain. Increased proliferation in SVZ cells of the mutant mice coincided with higher levels of cdk4 and mdm2 expression. A lesser degree of apoptosis was observed in the mutant mice compared to the wild-type control. Elf(-/-) embryos showed elevated levels of hyperphosphorylated forms of pRb, p130 and p107 and decreased level of p21 compared to the wild-type control. These results establish a critical role for elf in the development of a SVZ neuroepithelial stem cell phenotype and regulation of neuroepithelial cell proliferation, suggesting that a mutation in the elf locus renders the cells susceptible to a faster entry into S phase of cell cycle and resistance to senescence and apoptotic stimuli.
Collapse
Affiliation(s)
- Nady Golestaneh
- Laboratory of Developmental Neurobiology, Georgetown University School of Medicine, 3900 Reservoir Road NW, Medical/Dental Building, Room NW 209-213, Washington, DC 20007, USA
| | | | | | | | | | | |
Collapse
|
59
|
Young KM, Bartlett PF, Coulson EJ. Neural progenitor number is regulated by nuclear factor-kappaB p65 and p50 subunit-dependent proliferation rather than cell survival. J Neurosci Res 2006; 83:39-49. [PMID: 16307445 DOI: 10.1002/jnr.20702] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The number of cells generated by a proliferating stem or precursor cell can be influenced both by proliferation and by the degree of cell death/survival of the progeny generated. In this study, the extent to which cell survival controls progenitor number was examined by comparing the growth characteristics of neurosphere cultures derived from mice lacking genes for the death-inducing Bcl-2 homologue Hara Kiri (Hrk), apoptosis-associated protein 1 (Apaf1), or the prosurvival nuclear factor-kappaB (NFkappaB) subunits p65, p50, or c-rel. We found no evidence that Hrk or Apaf1, and by inference the mitochondrial cell death pathway, are involved in regulating the number of neurosphere-derived progeny. However, we identified the p65p50 NFkappaB dimer as being required for the normal growth and expansion of neurosphere cultures. Genetic loss of both p65 and p50 NFkappaB subunits resulted in a reduced number of progeny but an increased proportion of neurons. No effect on cell survival was observed. This suggests that the number and fate of neural progenitor cells are more strongly regulated by cell cycle control than survival.
Collapse
Affiliation(s)
- Kaylene M Young
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | | | | |
Collapse
|
60
|
Piltti K, Kerosuo L, Hakanen J, Eriksson M, Angers-Loustau A, Leppä S, Salminen M, Sariola H, Wartiovaara K. E6/E7 oncogenes increase and tumor suppressors decrease the proportion of self-renewing neural progenitor cells. Oncogene 2006; 25:4880-9. [PMID: 16532024 DOI: 10.1038/sj.onc.1209492] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Many if not most tissues need a controlled number of stem cells to maintain normal function. Cancer can be seen as a process of disturbed tissue homeostasis, in which too many cells have or acquire too primitive identity. Here we measured how oncogenes and tumour suppressors affect the differentiation capacity, proportion and characteristics of progenitor cells in a model tissue. Neural progenitor cells (NPCs) were exposed to human papilloma virus E6, E7 or E6/E7 oncogenes, which degrade tumour suppressors p53 and pRb family members, respectively. E6/E7-expressing or p53-/- NPCs were able to differentiate, but simultaneously retained high capacity for self-renewal, proliferation, ability to remain multipotent in conditions promoting differentiation and showed delayed cell cycle exit. These functions were mediated through p53 and pRb family, and involved MEK-ERK signalling. Decreased amount of p53 increased self-renewal and proliferation, whereas pRb affected only proliferation. Our results suggest that the oncogenes increase whereas p53 and pRb family tumour suppressors decrease the number and proportion of progenitor cells. These findings provide one explanation how oncogenes and tumour suppressors control tissue homeostasis and highlight their importance in stem cell self- renewal, linked both to cancer and life-long tissue turnover.
Collapse
Affiliation(s)
- K Piltti
- Developmental Biology, Institute of Biomedicine, University of Helsinki, and HUCH Laboratory Diagnostics, Helsinki University Central Hospital, Finland
| | | | | | | | | | | | | | | | | |
Collapse
|
61
|
Wildwater M, Campilho A, Perez-Perez JM, Heidstra R, Blilou I, Korthout H, Chatterjee J, Mariconti L, Gruissem W, Scheres B. The RETINOBLASTOMA-RELATED gene regulates stem cell maintenance in Arabidopsis roots. Cell 2006; 123:1337-49. [PMID: 16377572 DOI: 10.1016/j.cell.2005.09.042] [Citation(s) in RCA: 251] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Revised: 08/19/2005] [Accepted: 09/20/2005] [Indexed: 12/16/2022]
Abstract
The maintenance of stem cells in defined locations is crucial for all multicellular organisms. Although intrinsic factors and signals for stem cell fate have been identified in several species, it has remained unclear how these connect to the ability to reenter the cell cycle that is one of the defining properties of stem cells. We show that local reduction of expression of the RETINOBLASTOMA-RELATED (RBR) gene in Arabidopsis roots increases the amount of stem cells without affecting cell cycle duration in mitotically active cells. Conversely, induced RBR overexpression dissipates stem cells prior to arresting other mitotic cells. Overexpression of D cyclins, KIP-related proteins, and E2F factors also affects root stem cell pool size, and genetic interactions suggest that these factors function in a canonical RBR pathway to regulate somatic stem cells. Expression analysis and genetic interactions position RBR-mediated regulation of the stem cell state downstream of the patterning gene SCARECROW.
Collapse
Affiliation(s)
- Marjolein Wildwater
- Department of Molecular Cell Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | | | | | | | | | | | | | | | | | | |
Collapse
|
62
|
Ricard J, Salinas J, Garcia L, Liebl DJ. EphrinB3 regulates cell proliferation and survival in adult neurogenesis. Mol Cell Neurosci 2006; 31:713-22. [PMID: 16483793 DOI: 10.1016/j.mcn.2006.01.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2005] [Revised: 12/07/2005] [Accepted: 01/02/2006] [Indexed: 12/26/2022] Open
Abstract
Interactions between ephrins and their receptors have been implicated in many processes during central nervous system development. In the adult, ephrins and Eph receptors have been implicated in controlling cell proliferation and neuroblast migration, although there is no direct evidence for the role of ephrinB3 in these functions. In addition, activation of Eph receptors has been shown to regulate transduction pathways important in cell cycle control as well as cell death. We show that ephrinB3 contributes to the control of cell proliferation and survival in the adult subventricular zone (SVZ). EphrinB3(-/-) mice exhibit a significant increase in dividing cells along the lateral ventricle, and altered expression of proteins involved in cell cycle regulation. Gain-of-function approach by infusing soluble ephrinB3-Fc molecules in ephrinB3(-/-) can suppress cell proliferation to wild type levels. At the same time, ephrinB3 also regulates cell survival as greater numbers of cells die in the SVZ of ephrinB3(-/-) mice. Together, our results suggest that ephrinB3 negatively regulates cell cycle progression and cell apoptosis in the adult subventricular zone.
Collapse
Affiliation(s)
- Jerome Ricard
- The Miami Project to Cure Paralysis and Department of Neurosurgery, University of Miami School of Medicine, 1095 NW 14th Terrace, R-48, Miami, FL 33136, USA
| | | | | | | |
Collapse
|
63
|
Scimè A, Grenier G, Huh MS, Gillespie MA, Bevilacqua L, Harper ME, Rudnicki MA. Rb and p107 regulate preadipocyte differentiation into white versus brown fat through repression of PGC-1alpha. Cell Metab 2005; 2:283-95. [PMID: 16271529 DOI: 10.1016/j.cmet.2005.10.002] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2005] [Revised: 06/28/2005] [Accepted: 10/11/2005] [Indexed: 10/25/2022]
Abstract
The Rb family, Rb, p107, and p130, play important roles in cell cycle control and cellular differentiation, and Rb has been suggested to regulate adipocyte differentiation. We report here that mice lacking p107 displayed a uniform replacement of white adipose tissue (WAT) with brown adipose tissue (BAT). Mutant WAT depots contained mutilocular adipocytes that expressed elevated levels of PGC-1alpha and UCP-1 typical of BAT. WAT from p107-/- mice contained markedly elevated numbers of adipogenic precursors that displayed downregulated expression of pRb. Consistent with the hypothesis that pRb is required for adult adipocyte differentiation, Cre-mediated deletion of Rb in adult primary preadipocytes blocked their differentiation into white adipocytes. Importantly, pRb was observed to bind the PGC-1alpha promoter and repress transcription. Therefore, p107 and pRb regulate PGC-1alpha expression to control the switch between white and brown adipocyte differentiation from a common pool of presumptive adult progenitors in fat tissue.
Collapse
Affiliation(s)
- Anthony Scimè
- Molecular Medicine Program, Ottawa Health Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada
| | | | | | | | | | | | | |
Collapse
|
64
|
Balciunaite E, Spektor A, Lents NH, Cam H, Te Riele H, Scime A, Rudnicki MA, Young R, Dynlacht BD. Pocket protein complexes are recruited to distinct targets in quiescent and proliferating cells. Mol Cell Biol 2005; 25:8166-78. [PMID: 16135806 PMCID: PMC1234327 DOI: 10.1128/mcb.25.18.8166-8178.2005] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Revised: 05/26/2005] [Accepted: 06/27/2005] [Indexed: 01/24/2023] Open
Abstract
Biochemical and genetic studies have determined that retinoblastoma protein (pRB) tumor suppressor family members have overlapping functions. However, these studies have largely failed to distinguish functional differences between the highly related p107 and p130 proteins. Moreover, most studies pertaining to the pRB family and its principal target, the E2F transcription factor, have focused on cells that have reinitiated a cell cycle from quiescence, although recent studies suggest that cycling cells exhibit layers of regulation distinct from mitogenically stimulated cells. Using genome-wide chromatin immunoprecipitation, we show that there are distinct classes of genes directly regulated by unique combinations of E2F4, p107, and p130, including a group of genes specifically regulated in cycling cells. These groups exhibit both distinct histone acetylation signatures and patterns of mammalian Sin3B corepressor recruitment. Our findings suggest that cell cycle-dependent repression results from recruitment of an unexpected array of diverse complexes and reveals specific differences between transcriptional regulation in cycling and quiescent cells. In addition, factor location analyses have, for the first time, allowed the identification of novel and specific targets of the highly related transcriptional regulators p107 and p130, suggesting new and distinct regulatory networks engaged by each protein in continuously cycling cells.
Collapse
Affiliation(s)
- Egle Balciunaite
- Department of Pathology, MSB 504, New York University School of Medicine and New York University Cancer Institute, 550 First Avenue, New York, NY 10016, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
65
|
Abstract
The retinoblastoma protein (pRB) and the pRB-related p107 and p130 comprise the 'pocket protein' family of cell cycle regulators. These proteins are best known for their roles in restraining the G1-S transition through the regulation of E2F-responsive genes. pRB and the p107/p130 pair are required for the repression of distinct sets of genes, potentially due to their selective interactions with E2Fs that are engaged at specific promoter elements. In addition to regulating E2F-responsive genes in a reversible manner, pocket proteins contribute to silencing of such genes in cells that are undergoing senescence or differentiation. Pocket proteins also affect the G1-S transition through E2F-independent mechanisms, such as by inhibiting Cdk2 or by stabilizing p27(Kip1), and they are implicated in the control of G0 exit, the spatial organization of replication, and genomic rereplication. New insights into pocket protein regulation have also been obtained. Kinases previously thought to be crucial to pocket protein phosphorylation have been shown to be redundant, and new modes of phosphorylation and dephosphorylation have been identified. Despite these advances, much remains to be learned about the pocket proteins, particularly with regard to their developmental and tumor suppressor functions. Thus continues the story of the pocket proteins and the cell cycle.
Collapse
Affiliation(s)
- David Cobrinik
- Dyson Vision Research Institute and Department of Ophthalmology, Weill Medical College of Cornell University, 1300 York Avenue, LC303, New York, NY 10021, USA.
| |
Collapse
|
66
|
Abstract
For most of the past century, the prospect of replacing lost or damaged cells in the central nervous system (CNS) was hampered by the opinion that the adult mammalian CNS was incapable of generating new nerve cells. This belief, like most dogmas, was essentially founded on a lack of experimental evidence to the contrary. The overturning of this 'no new neuron' hypothesis began midway through the twentieth century with a series of reports documenting neurogenesis in the postnatal and adult brain, continued with the isolation and in vitro culture of neurogenic cells from the adult mammalian brain, and culminated in the discovery of a population of multipotent, self-renewing cells in the adult CNS (that is, bona fide neural stem cells). Although a variety of techniques were initially used, the neurosphere assay (NSA) rapidly emerged as the assay of choice and has since become a valuable tool for isolating, and understanding the biology of, embryonic and adult CNS stem cells. Like all technologies, it is not without its limitations. In this article we will highlight several shortcomings of the assay related to its application and interpretation that we believe have led to a significant body of research whose conclusions may well be misleading.
Collapse
Affiliation(s)
- Brent A Reynolds
- Laboratory for Neural Stem Cell Biology, Queensland Brain Institute, University of Queensland Brisbane, Queensland 4072, Australia.
| | | |
Collapse
|