51
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Aldiri I, Ajioka I, Xu B, Zhang J, Chen X, Benavente C, Finkelstein D, Johnson D, Akiyama J, Pennacchio LA, Dyer MA. Brg1 coordinates multiple processes during retinogenesis and is a tumor suppressor in retinoblastoma. Development 2016; 142:4092-106. [PMID: 26628093 PMCID: PMC4712833 DOI: 10.1242/dev.124800] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Retinal development requires precise temporal and spatial coordination of cell cycle exit, cell fate specification, cell migration and differentiation. When this process is disrupted, retinoblastoma, a developmental tumor of the retina, can form. Epigenetic modulators are central to precisely coordinating developmental events, and many epigenetic processes have been implicated in cancer. Studying epigenetic mechanisms in development is challenging because they often regulate multiple cellular processes; therefore, elucidating the primary molecular mechanisms involved can be difficult. Here we explore the role of Brg1 (Smarca4) in retinal development and retinoblastoma in mice using molecular and cellular approaches. Brg1 was found to regulate retinal size by controlling cell cycle length, cell cycle exit and cell survival during development. Brg1 was not required for cell fate specification but was required for photoreceptor differentiation and cell adhesion/polarity programs that contribute to proper retinal lamination during development. The combination of defective cell differentiation and lamination led to retinal degeneration in Brg1-deficient retinae. Despite the hypocellularity, premature cell cycle exit, increased cell death and extended cell cycle length, retinal progenitor cells persisted in Brg1-deficient retinae, making them more susceptible to retinoblastoma. ChIP-Seq analysis suggests that Brg1 might regulate gene expression through multiple mechanisms. Summary: The SWI/SNF protein Brg1 controls cell cycle length, cell cycle exit and cell survival, and is required for cell differentiation and retinal lamination, in the developing mouse retina.
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Affiliation(s)
- Issam Aldiri
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Itsuki Ajioka
- Center for Brain Integration Research (CBIR), Tokyo Medical and Dental University (TMDU), Tokyo 113-8510, Japan
| | - Beisi Xu
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jiakun Zhang
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Xiang Chen
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Claudia Benavente
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - David Finkelstein
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Dianna Johnson
- Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Jennifer Akiyama
- Lawrence Berkeley National Laboratory, Genomics Division, Berkeley, CA 94701, USA Department of Energy, Joint Genome Institute, Walnut Creek, CA 94598, USA
| | - Len A Pennacchio
- Lawrence Berkeley National Laboratory, Genomics Division, Berkeley, CA 94701, USA Department of Energy, Joint Genome Institute, Walnut Creek, CA 94598, USA
| | - Michael A Dyer
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN 38163, USA Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
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52
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Kohno S, Kitajima S, Sasaki N, Takahashi C. Retinoblastoma tumor suppressor functions shared by stem cell and cancer cell strategies. World J Stem Cells 2016; 8:170-84. [PMID: 27114748 PMCID: PMC4835675 DOI: 10.4252/wjsc.v8.i4.170] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 12/30/2015] [Accepted: 02/14/2016] [Indexed: 02/06/2023] Open
Abstract
Carcinogenic transformation of somatic cells resembles nuclear reprogramming toward the generation of pluripotent stem cells. These events share eternal escape from cellular senescence, continuous self-renewal in limited but certain population of cells, and refractoriness to terminal differentiation while maintaining the potential to differentiate into cells of one or multiple lineages. As represented by several oncogenes those appeared to be first keys to pluripotency, carcinogenesis and nuclear reprogramming seem to share a number of core mechanisms. The retinoblastoma tumor suppressor product retinoblastoma (RB) seems to be critically involved in both events in highly complicated manners. However, disentangling such complicated interactions has enabled us to better understand how stem cell strategies are shared by cancer cells. This review covers recent findings on RB functions related to stem cells and stem cell-like behaviors of cancer cells.
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Affiliation(s)
- Susumu Kohno
- Susumu Kohno, Chiaki Takahashi, Division of Oncology and Molecular Biology, Cancer Research Institute, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
| | - Shunsuke Kitajima
- Susumu Kohno, Chiaki Takahashi, Division of Oncology and Molecular Biology, Cancer Research Institute, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
| | - Nobunari Sasaki
- Susumu Kohno, Chiaki Takahashi, Division of Oncology and Molecular Biology, Cancer Research Institute, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
| | - Chiaki Takahashi
- Susumu Kohno, Chiaki Takahashi, Division of Oncology and Molecular Biology, Cancer Research Institute, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
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53
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Ajioka I. Biomaterial-engineering and neurobiological approaches for regenerating the injured cerebral cortex. Regen Ther 2016; 3:63-67. [PMID: 31245474 PMCID: PMC6581816 DOI: 10.1016/j.reth.2016.02.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Revised: 01/08/2016] [Accepted: 02/12/2016] [Indexed: 01/07/2023] Open
Abstract
The cerebral cortex is responsible for higher functions of the central nervous system (CNS), such as movement, sensation, and cognition. When the cerebral cortex is severely injured, these functions are irreversibly impaired. Although recent neurobiological studies reveal that the cortex has the potential for regeneration, therapies for functional recovery face some technological obstacles. Biomaterials have been used to evoke regenerative potential and promote regeneration in several tissues, including the CNS. This review presents a brief overview of new therapeutic strategies for cortical regeneration from the perspectives of neurobiology and biomaterial engineering, and discusses a promising technology for evoking the regenerative potential of the cerebral cortex.
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Affiliation(s)
- Itsuki Ajioka
- Center for Brain Integration Research (CBIR), Tokyo Medical and Dental University (TMDU), Tokyo 113-8510, Japan,The Japan Science and Technology Agency (JST), Precursory Research for Embryonic Science and Technology (PRESTO), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan,Center for Brain Integration Research, Tokyo Medical and Dental University, 1-5-45 Yushima, Tokyo 113-8510, Japan. Fax: +81 3 5803 4716.
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54
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Hazen JL, Faust GG, Rodriguez AR, Ferguson WC, Shumilina S, Clark RA, Boland MJ, Martin G, Chubukov P, Tsunemoto RK, Torkamani A, Kupriyanov S, Hall IM, Baldwin KK. The Complete Genome Sequences, Unique Mutational Spectra, and Developmental Potency of Adult Neurons Revealed by Cloning. Neuron 2016; 89:1223-1236. [PMID: 26948891 DOI: 10.1016/j.neuron.2016.02.004] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 12/14/2015] [Accepted: 01/13/2016] [Indexed: 02/07/2023]
Abstract
Somatic mutation in neurons is linked to neurologic disease and implicated in cell-type diversification. However, the origin, extent, and patterns of genomic mutation in neurons remain unknown. We established a nuclear transfer method to clonally amplify the genomes of neurons from adult mice for whole-genome sequencing. Comprehensive mutation detection and independent validation revealed that individual neurons harbor ∼100 unique mutations from all classes but lack recurrent rearrangements. Most neurons contain at least one gene-disrupting mutation and rare (0-2) mobile element insertions. The frequency and gene bias of neuronal mutations differ from other lineages, potentially due to novel mechanisms governing postmitotic mutation. Fertile mice were cloned from several neurons, establishing the compatibility of mutated adult neuronal genomes with reprogramming to pluripotency and development.
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Affiliation(s)
- Jennifer L Hazen
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N Torrey Pines Road, La Jolla CA 92037, USA
| | - Gregory G Faust
- Department of Biochemistry and Molecular Genetics, 1340 Jefferson Park Ave, University of Virginia School of Medicine, Charlottesville, VA 22901, USA
| | - Alberto R Rodriguez
- Mouse Genetics Core Facility, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - William C Ferguson
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N Torrey Pines Road, La Jolla CA 92037, USA
| | - Svetlana Shumilina
- Department of Biochemistry and Molecular Genetics, 1340 Jefferson Park Ave, University of Virginia School of Medicine, Charlottesville, VA 22901, USA
| | - Royden A Clark
- Department of Biochemistry and Molecular Genetics, 1340 Jefferson Park Ave, University of Virginia School of Medicine, Charlottesville, VA 22901, USA
| | - Michael J Boland
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N Torrey Pines Road, La Jolla CA 92037, USA
| | - Greg Martin
- Mouse Genetics Core Facility, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Pavel Chubukov
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N Torrey Pines Road, La Jolla CA 92037, USA.,Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Rachel K Tsunemoto
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N Torrey Pines Road, La Jolla CA 92037, USA.,Neuroscience Graduate Program, 9500 Gilman Drive, University of California San Diego, La Jolla, California, USA
| | - Ali Torkamani
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Sergey Kupriyanov
- Mouse Genetics Core Facility, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Ira M Hall
- McDonnell Genome Institute, Washington University School of Medicine, 4444 Forest Park Ave, St. Louis, MO 63108, USA.,Department of Medicine, Washington University School of Medicine, 660 S Euclid Ave, St. Louis, MO 63110, USA
| | - Kristin K Baldwin
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N Torrey Pines Road, La Jolla CA 92037, USA.,Neuroscience Graduate Program, 9500 Gilman Drive, University of California San Diego, La Jolla, California, USA
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55
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Naser R, Vandenbosch R, Omais S, Hayek D, Jaafar C, Al Lafi S, Saliba A, Baghdadi M, Skaf L, Ghanem N. Role of the Retinoblastoma protein, Rb, during adult neurogenesis in the olfactory bulb. Sci Rep 2016; 6:20230. [PMID: 26847607 PMCID: PMC4742828 DOI: 10.1038/srep20230] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 12/23/2015] [Indexed: 12/15/2022] Open
Abstract
Adult neural stem cells (aNSCs) are relatively quiescent populations that give rise to distinct neuronal subtypes throughout life, yet, at a very low rate and restricted differentiation potential. Thus, identifying the molecular mechanisms that control their cellular expansion is critical for regeneration after brain injury. Loss of the Retinoblastoma protein, Rb, leads to several defects in cell cycle as well as neuronal differentiation and migration during brain development. Here, we investigated the role of Rb during adult neurogenesis in the olfactory bulb (OB) by inducing its temporal deletion in aNSCs and progenitors. Loss of Rb was associated with increased proliferation of adult progenitors in the subventricular zone (SVZ) and the rostral migratory stream (RMS) but did not alter self-renewal of aNSCs or neuroblasts subsequent migration and terminal differentiation. Hence, one month after their birth, Rb-null neuroblasts were able to differentiate into distinct subtypes of GABAergic OB interneurons but were gradually lost after 3 months. Similarly, Rb controlled aNSCs/progenitors proliferation in vitro without affecting their differentiation capacity. This enhanced SVZ/OB neurogenesis associated with loss of Rb was only transient and negatively affected by increased apoptosis indicating a critical requirement for Rb in the long-term survival of adult-born OB interneurons.
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Affiliation(s)
- Rayan Naser
- Department of Biology, American University of Beirut, Lebanon
| | - Renaud Vandenbosch
- Department of Cellular and Molecular Medicine, University of Ottawa, Canada
| | - Saad Omais
- Department of Biology, American University of Beirut, Lebanon
| | - Dayana Hayek
- Department of Biology, American University of Beirut, Lebanon
| | - Carine Jaafar
- Department of Biology, American University of Beirut, Lebanon
| | - Sawsan Al Lafi
- Department of Biology, American University of Beirut, Lebanon
| | - Afaf Saliba
- Department of Biology, American University of Beirut, Lebanon
| | | | - Larissa Skaf
- Department of Biology, American University of Beirut, Lebanon
| | - Noël Ghanem
- Department of Biology, American University of Beirut, Lebanon
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56
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Ruijtenberg S, van den Heuvel S. Coordinating cell proliferation and differentiation: Antagonism between cell cycle regulators and cell type-specific gene expression. Cell Cycle 2016; 15:196-212. [PMID: 26825227 PMCID: PMC4825819 DOI: 10.1080/15384101.2015.1120925] [Citation(s) in RCA: 368] [Impact Index Per Article: 46.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 10/04/2015] [Accepted: 11/12/2015] [Indexed: 11/25/2022] Open
Abstract
Cell proliferation and differentiation show a remarkable inverse relationship. Precursor cells continue division before acquiring a fully differentiated state, while terminal differentiation usually coincides with proliferation arrest and permanent exit from the division cycle. Mechanistic insight in the temporal coordination between cell cycle exit and differentiation has come from studies of cells in culture and genetic animal models. As initially described for skeletal muscle differentiation, temporal coordination involves mutual antagonism between cyclin-dependent kinases that promote cell cycle entry and transcription factors that induce tissue-specific gene expression. Recent insights highlight the contribution of chromatin-regulating complexes that act in conjunction with the transcription factors and determine their activity. In particular SWI/SNF chromatin remodelers contribute to dual regulation of cell cycle and tissue-specific gene expression during terminal differentiation. We review the concerted regulation of the cell cycle and cell type-specific transcription, and discuss common mutations in human cancer that emphasize the clinical importance of proliferation versus differentiation control.
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Affiliation(s)
- Suzan Ruijtenberg
- Developmental Biology, Department of Biology, Faculty of Sciences, Utrecht University, Utrecht, The Netherlands
| | - Sander van den Heuvel
- Developmental Biology, Department of Biology, Faculty of Sciences, Utrecht University, Utrecht, The Netherlands
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57
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Abstract
Neurons are usually regarded as postmitotic cells that undergo apoptosis in response to cell cycle reactivation. Nevertheless, recent evidence indicates the existence of a defined developmental program that induces DNA replication in specific populations of neurons, which remain in a tetraploid state for the rest of their adult life. Similarly, de novo neuronal tetraploidization has also been described in the adult brain as an early hallmark of neurodegeneration. The aim of this review is to integrate these recent developments in the context of cell cycle regulation and apoptotic cell death in neurons. We conclude that a variety of mechanisms exists in neuronal cells for G1/S and G2/M checkpoint regulation. These mechanisms, which are connected with the apoptotic machinery, can be modulated by environmental signals and the neuronal phenotype itself, thus resulting in a variety of outcomes ranging from cell death at the G1/S checkpoint to full proliferation of differentiated neurons.
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Key Words
- AD, Alzheimer disease
- BDNF, brain-derived neurotrophic factor
- BrdU, 5-bromo-2′-deoxyuridine
- CKI, Cdk-inhibitor
- CNS, central nervous system
- Cdk, cyclin-dependent kinase
- Cip/Kip, cyclin inhibitor protein/kinase inhibitor protein
- G0, quiescent state
- G1, growth phase 1
- G2, growth phase 2
- Ink, inhibitor of kinase
- Mcm2, minichromosome maintenance 2
- PCNA, proliferating cell nuclear antigen
- PD, Parkinson disease
- RGCs, retinal ganglion cells
- Rb, Retinoblastoma
- S-phase
- S-phase, synthesis phase.
- apoptosis
- cell cycle re-entry
- mitosis
- neuron
- p38MAPK, p38 mitogen-activated protein kinase
- p75NTR, neurotrophin receptor p75
- tetraploid
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Affiliation(s)
- José M Frade
- a Department of Molecular, Cellular and Developmental Neurobiology; Instituto Cajal; Consejo Superior de Investigaciones Científicas (IC-CSIC) ; Madrid , Spain
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58
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Characterization and pharmacologic targeting of EZH2, a fetal retinal protein and epigenetic regulator, in human retinoblastoma. J Transl Med 2015; 95:1278-90. [PMID: 26280220 PMCID: PMC4626270 DOI: 10.1038/labinvest.2015.104] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 07/01/2015] [Accepted: 07/07/2015] [Indexed: 12/31/2022] Open
Abstract
Retinoblastoma (RB) is the most common primary intraocular cancer in children, and the third most common cancer overall in infants. No molecular-targeted therapy for this lethal tumor exists. Since the tumor suppressor RB1, whose genetic inactivation underlies RB, is upstream of the epigenetic regulator EZH2, a pharmacologic target for many solid tumors, we reasoned that EZH2 might regulate human RB tumorigenesis. Histologic and immunohistochemical analyses were performed using an EZH2 antibody in sections from 43 samples of primary, formalin-fixed, paraffin-embedded human RB tissue, cryopreserved mouse retina, and in whole cell lysates from human RB cell lines (Y79 and WERI-Rb1), primary human fetal retinal pigment epithelium (RPE) and fetal and adult retina, mouse retina and embryonic stem (ES) cells. Although enriched during fetal human retinal development, EZH2 protein was not present in the normal postnatal retina. However, EZH2 was detected in all 43 analyzed human RB specimens, indicating that EZH2 is a fetal protein expressed in postnatal human RB. EZH2 expression marked single RB cell invasion into the optic nerve, a site of invasion whose involvement may influence the decision for systemic chemotherapy. To assess the role of EZH2 in RB cell survival, human RB and primary RPE cells were treated with two EZH2 inhibitors (EZH2i), GSK126 and SAH-EZH2 (SAH). EZH2i impaired intracellular adenosine triphosphate (ATP) production, an indicator of cell viability, in a time and dose-dependent manner, but did not affect primary human fetal RPE. Thus, aberrant expression of a histone methyltransferase protein is a feature of human RB. This is the first time this mechanism has been implicated for an eye, adnexal, or orbital tumor. The specificity of EZH2i toward human RB cells, but not RPE, warrants further in vivo testing in animal models of RB, especially those EZH2i currently in clinical trials for solid tumors and lymphoma.
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59
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Blixt MKE, Shirazi Fard S, All-Ericsson C, Hallböök F. Adding another piece to the retinoblastoma puzzle. Cell Death Dis 2015; 6:e1957. [PMID: 26512965 PMCID: PMC5399180 DOI: 10.1038/cddis.2015.317] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- M K E Blixt
- Department of Neuroscience, Biomedical Center, Uppsala University, Uppsala, Sweden
| | - S Shirazi Fard
- Department of Neuroscience, Biomedical Center, Uppsala University, Uppsala, Sweden
| | - C All-Ericsson
- S:t Eriks ögonsjukhus, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - F Hallböök
- Department of Neuroscience, Biomedical Center, Uppsala University, Uppsala, Sweden
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60
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Wade J, Alsop AT, Vertin NR, Yang H, Johnson MD, Bailey RC. Rapid, Multiplexed Phosphoprotein Profiling Using Silicon Photonic Sensor Arrays. ACS CENTRAL SCIENCE 2015; 1:374-382. [PMID: 26539563 PMCID: PMC4626792 DOI: 10.1021/acscentsci.5b00250] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Indexed: 05/04/2023]
Abstract
Extracellular signaling is commonly mediated through post-translational protein modifications that propagate messages from membrane-bound receptors to ultimately regulate gene expression. Signaling cascades are ubiquitously intertwined, and a full understanding of function can only be gleaned by observing dynamics across multiple key signaling nodes. Importantly, targets within signaling cascades often represent opportunities for therapeutic development or can serve as diagnostic biomarkers. Protein phosphorylation is a particularly important post-translational modification that controls many essential cellular signaling pathways. Not surprisingly, aberrant phosphorylation is found in many human diseases, including cancer, and phosphoprotein-based biomarker signatures hold unrealized promise for disease monitoring. Moreover, phosphoprotein analysis has wide-ranging applications across fundamental chemical biology, as many drug discovery efforts seek to target nodes within kinase signaling pathways. For both fundamental and translational applications, the analysis of phosphoprotein biomarker targets is limited by a reliance on labor-intensive and/or technically challenging methods, particularly when considering the simultaneous monitoring of multiplexed panels of phosphoprotein biomarkers. We have developed a technology based upon arrays of silicon photonic microring resonator sensors that fills this void, facilitating the rapid and automated analysis of multiple phosphoprotein levels from both cell lines and primary human tumor samples requiring only minimal sample preparation.
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Affiliation(s)
- James
H. Wade
- Department
of Chemistry, University of Illinois at
Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United
States
| | - Aurora T. Alsop
- Department
of Chemistry, University of Illinois at
Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United
States
| | - Nicholas R. Vertin
- Department
of Chemistry, University of Illinois at
Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United
States
| | - Hongwei Yang
- Department
of Neurological Surgery, Brigham and Women’s
Hospital and Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Mark D. Johnson
- Department
of Neurological Surgery, Brigham and Women’s
Hospital and Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Ryan C. Bailey
- Department
of Chemistry, University of Illinois at
Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United
States
- E-mail:
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61
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King BA, Parra C, Li Y, Helton KJ, Qaddoumi I, Wilson MW, Ogg RJ. Spatiotemporal Patterns of Tumor Occurrence in Children with Intraocular Retinoblastoma. PLoS One 2015; 10:e0132932. [PMID: 26230335 PMCID: PMC4521796 DOI: 10.1371/journal.pone.0132932] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 06/21/2015] [Indexed: 01/11/2023] Open
Abstract
PURPOSE To accurately map the retinal area covered by tumor in a prospectively enrolled cohort of children diagnosed with retinoblastoma. METHODS Orbital MRI in 106 consecutive retinoblastoma patients (44 bilateral) was analyzed. For MRI-visible tumors, the polar angle and angle of eccentricity of points defining tumor perimeter on the retina were determined by triangulation from images in three orthogonal planes. The centroid of the mapped area was calculated to approximate tumor origin, and the location and cumulative tumor burden were analyzed in relation to mutation type (germline vs. somatic), tumor area, and patient age at diagnosis. Location of small tumors undetected by MRI was approximated with fundoscopic images. RESULTS Mapping was successful for 129 tumors in 91 eyes from 67 patients (39 bilateral, 43 germline mutation). Cumulative tumor burden was highest within the macula and posterior pole and was asymmetrically higher within the inferonasal periphery. Tumor incidence was lowest in the superotemporal periphery. Tumor location varied with age at diagnosis in a complex pattern. Tumor location was concentrated in the macula and superonasal periphery in patients <5.6 months, in the inferotemporal quadrant of the posterior pole in patients 5.6-8.8 months, in the inferonasal quadrant in patients 8.8-13.2 months, and in the nasal and superotemporal periphery in patients >13.2 months. The distribution of MRI-invisible tumors was consistent with the asymmetry of mapped tumors. CONCLUSIONS MRI-based mapping revealed a previously unrecognized pattern of retinoblastoma localization that evolves with age at diagnosis. The structured spatiotemporal distribution of tumors may provide valuable clues about cellular or molecular events associated with tumorigenesis in the developing retina.
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Affiliation(s)
- Benjamin A. King
- Department of Ophthalmology, Hamilton Eye Institute, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
- Department of Radiological Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Carlos Parra
- Department of Radiological Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
- Department of Biomedical Engineering, University of Memphis, Memphis, Tennessee, United States of America
| | - Yimei Li
- Department of Biostatistics, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Kathleen J. Helton
- Department of Radiological Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Ibrahim Qaddoumi
- Department of Oncology, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Matthew W. Wilson
- Department of Ophthalmology, Hamilton Eye Institute, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
- Department of Surgery, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Robert J. Ogg
- Department of Radiological Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
- * E-mail:
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62
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Lehman HL, Stairs DB. Single and Multiple Gene Manipulations in Mouse Models of Human Cancer. CANCER GROWTH AND METASTASIS 2015; 8:1-15. [PMID: 26380553 PMCID: PMC4558888 DOI: 10.4137/cgm.s21217] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 06/17/2015] [Accepted: 06/20/2015] [Indexed: 12/14/2022]
Abstract
Mouse models of human cancer play a critical role in understanding the molecular and cellular mechanisms of tumorigenesis. Advances continue to be made in modeling human disease in a mouse, though the relevance of a mouse model often relies on how closely it is able to mimic the histologic, molecular, and physiologic characteristics of the respective human cancer. A classic use of a genetically engineered mouse in studying cancer is through the overexpression or deletion of a gene. However, the manipulation of a single gene often falls short of mimicking all the characteristics of the carcinoma in humans; thus a multiple gene approach is needed. Here we review genetic mouse models of cancers and their abilities to recapitulate human carcinoma with single versus combinatorial approaches with genes commonly involved in cancer.
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Affiliation(s)
- Heather L Lehman
- Department of Pathology, The Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - Douglas B Stairs
- Department of Pathology, The Pennsylvania State University College of Medicine, Hershey, PA, USA
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63
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Miskovic J, Brekalo Z, Vukojevic K, Miskovic HR, Kraljevic D, Todorovic J, Soljic V. Co-expression of TTF-1 and neuroendocrine markers in the human fetal lung and pulmonary neuroendocrine tumors. Acta Histochem 2015; 117:451-9. [PMID: 25722034 DOI: 10.1016/j.acthis.2015.02.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Revised: 01/20/2015] [Accepted: 02/02/2015] [Indexed: 01/04/2023]
Abstract
The expression pattern of thyroid transcription factor 1 (TTF-1) and neuroendocrine markers, neuron cell adhesion molecule (NCAM; CD56), chromogranin A (CgA) and synaptophysin (Syp), of different lung cell lineages was histologically analyzed in 15 normal human fetal lungs and 12 neuroendocrine tumors (NETs) using immunohistochemical methods. During pseudoglandular phase strong nuclear TTF-1 staining was detected in the columnar nonciliated epithelial cells, while NCAM, CgA and Syp had a moderate expression in the proximal airways and mild expression in the distal airways. Neuroendocrine cells (NECs) in proximal lung airway were co-localizing TTF-1 and other neuroendocrine markers while neuroendocrine bodies (NEBs) exhibit only staining with NCAM and Syp. In the canalicular phase TTF-1 nuclear staining was expressed only in several epithelial cells in proximal airways, while budding airways epithelium showed strong TTF-1 expression. Expression of NCAM, CgA and Syp in this phase equals the one in pseudoglandular phase. NEBs cells were co-localizing TTF-1 and NCAM in proximal airways and few NECs in distal airway were co-localizing TTF-1 and Syp. TTF-1 staining in the saccular phase was limited to subsets of epithelial cells in the proximal airways with stronger positivity in the distal airways. NCAM expression is moderate only in proximal airways, while Syp and CgA show mild expression in proximal and distal airways. NECs were co-localizing TTF-1 and NCAM in proximal lung airway. With regard to NECs, all small cell lung cancer (SCLC) cells had strong TTF-1, NCAM, Syp and CgA positivity and TTF-1 co-localized with other neuroendocrine markers. All pulmonary typical carcinoids were TTF-1 negative, while pulmonary atypical carcinoids were focal positive for TTF-1 and some neoplastic cells co-localized TTF-1 with neuroendocrine markers. Our results indicate that TTF-1 expression in NECs suggests a possible role in their normal development and differentiation. Our results also indicate that possible cell of origin for poorly differentiated SCLC and some atypical carcinoid could be a progenitor cell in neuroendocrine lineage while in typical carcinoids possible cell of origin is localized in terminally differentiated NECs.
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Affiliation(s)
- Josip Miskovic
- Department of Surgery, University Hospital in Mostar, KraljaTvrtka bb, 88000 Mostar, Bosnia and Herzegovina
| | - Zdrinko Brekalo
- Department of Surgery, University Hospital in Mostar, KraljaTvrtka bb, 88000 Mostar, Bosnia and Herzegovina
| | - Katarina Vukojevic
- Laboratory for Early Human Development, Department of Anatomy, Histology and Embryology, School of Medicine, University of Split, Soltanska 2, 21000 Split, Croatia
| | - Helena Radic Miskovic
- Department of Neonatology, University Hospital in Mostar, Kralja Tvrtka bb, 88000 Mostar, Bosnia and Herzegovina
| | - Daniela Kraljevic
- Department of Pediatrics, University Hospital in Mostar, Kralja Tvrtka bb, 88000 Mostar, Bosnia and Herzegovina
| | - Jelena Todorovic
- Department of Pathology, Cytology and Forensic Medicine, University Hospital in Mostar, Kralja Tvrtka bb, 88000 Mostar, Bosnia and Herzegovina
| | - Violeta Soljic
- Department of Pathology, Cytology and Forensic Medicine, University Hospital in Mostar, Kralja Tvrtka bb, 88000 Mostar, Bosnia and Herzegovina; Department of Histology and Embryology, School of Medicine, University of Mostar, Bijeli brijeg bb, 88000 Mostar, Bosnia and Herzegovina.
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64
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Julian LM, Blais A. Transcriptional control of stem cell fate by E2Fs and pocket proteins. Front Genet 2015; 6:161. [PMID: 25972892 PMCID: PMC4412126 DOI: 10.3389/fgene.2015.00161] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Accepted: 04/08/2015] [Indexed: 01/04/2023] Open
Abstract
E2F transcription factors and their regulatory partners, the pocket proteins (PPs), have emerged as essential regulators of stem cell fate control in a number of lineages. In mammals, this role extends from both pluripotent stem cells to those encompassing all embryonic germ layers, as well as extra-embryonic lineages. E2F/PP-mediated regulation of stem cell decisions is highly evolutionarily conserved, and is likely a pivotal biological mechanism underlying stem cell homeostasis. This has immense implications for organismal development, tissue maintenance, and regeneration. In this article, we discuss the roles of E2F factors and PPs in stem cell populations, focusing on mammalian systems. We discuss emerging findings that position the E2F and PP families as widespread and dynamic epigenetic regulators of cell fate decisions. Additionally, we focus on the ever expanding landscape of E2F/PP target genes, and explore the possibility that E2Fs are not simply regulators of general ‘multi-purpose’ cell fate genes but can execute tissue- and cell type-specific gene regulatory programs.
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Affiliation(s)
- Lisa M Julian
- Sprott Centre for Stem Cell Research, Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON Canada
| | - Alexandre Blais
- Ottawa Institute of Systems Biology, Ottawa, ON Canada ; Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON Canada
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65
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Sengupta S, Lingnurkar R, Carey TS, Pomaville M, Kar P, Feig M, Wilson CA, Knott JG, Arnosti DN, Henry RW. The Evolutionarily Conserved C-terminal Domains in the Mammalian Retinoblastoma Tumor Suppressor Family Serve as Dual Regulators of Protein Stability and Transcriptional Potency. J Biol Chem 2015; 290:14462-75. [PMID: 25903125 DOI: 10.1074/jbc.m114.599993] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Indexed: 11/06/2022] Open
Abstract
The retinoblastoma (RB) tumor suppressor and related family of proteins play critical roles in development through their regulation of genes involved in cell fate. Multiple regulatory pathways impact RB function, including the ubiquitin-proteasome system with deregulated RB destruction frequently associated with pathogenesis. With the current study we explored the mechanisms connecting proteasome-mediated turnover of the RB family to the regulation of repressor activity. We find that steady state levels of all RB family members, RB, p107, and p130, were diminished during embryonic stem cell differentiation concomitant with their target gene acquisition. Proteasome-dependent turnover of the RB family is mediated by distinct and autonomously acting instability elements (IE) located in their C-terminal regulatory domains in a process that is sensitive to cyclin-dependent kinase (CDK4) perturbation. The IE regions include motifs that contribute to E2F-DP transcription factor interaction, and consistently, p107 and p130 repressor potency was reduced by IE deletion. The juxtaposition of degron sequences and E2F interaction motifs appears to be a conserved feature across the RB family, suggesting the potential for repressor ubiquitination and specific target gene regulation. These findings establish a mechanistic link between regulation of RB family repressor potency and the ubiquitin-proteasome system.
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Key Words
- retinoblastoma, RB, p107, p130, E2F-DP, cyclin, CDK, protein stability, proteasome, degron, transcriptional repression.
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Affiliation(s)
- Satyaki Sengupta
- From the Department of Biochemistry and Molecular Biology, Graduate Program in Physiology, and
| | - Raj Lingnurkar
- From the Department of Biochemistry and Molecular Biology
| | | | | | - Parimal Kar
- From the Department of Biochemistry and Molecular Biology
| | - Michael Feig
- From the Department of Biochemistry and Molecular Biology
| | - Catherine A Wilson
- Department of Animal Science, Michigan State University, East Lansing, Michigan 48824
| | - Jason G Knott
- From the Department of Biochemistry and Molecular Biology, Department of Animal Science, Michigan State University, East Lansing, Michigan 48824
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66
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Nair RM, Vemuganti GK. Transgenic Models in Retinoblastoma Research. Ocul Oncol Pathol 2015; 1:207-13. [PMID: 27171579 DOI: 10.1159/000370157] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 11/26/2014] [Indexed: 01/10/2023] Open
Abstract
Understanding the mechanism of retinoblastoma (Rb) tumor initiation, development, progression and metastasis in vivo mandates the use of animal models that mimic this intraocular tumor in its genetic, anatomic, histologic and ultrastructural features. An early setback for developing mouse Rb models was that Rb mutations did not cause tumorigenesis in murine retinas. Subsequently, the discovery that the p107 protein takes over the role of pRb in mice led to the development of several animal models that phenotypically and histologically resemble the human form. This paper summarizes the transgenic models that have been developed over the last three decades.
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Affiliation(s)
- Rohini M Nair
- School of Medical Sciences, University of Hyderabad, Hyderabad, India
| | - Geeta K Vemuganti
- School of Medical Sciences, University of Hyderabad, Hyderabad, India
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67
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Onecut1 and Onecut2 transcription factors operate downstream of Pax6 to regulate horizontal cell development. Dev Biol 2015; 402:48-60. [PMID: 25794677 DOI: 10.1016/j.ydbio.2015.02.023] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 02/18/2015] [Accepted: 02/22/2015] [Indexed: 11/22/2022]
Abstract
Genetic studies of the last decades strongly indicated that generation of particular retinal cell types is governed by gene regulatory networks of transcription factors and their target genes. The paired and homeodomain transcription factor Pax6 plays a pivotal role in retinal development as its inactivation in the retinal progenitor cell population leads to abolished differentiation of all retinal cell types. However, until now, only a few transcription factors operating downstream of Pax6 responsible for generation of individual retinal cell types have been identified. In this study, we identified two transcription factors of the Onecut family, Onecut1 and Onecut2, as Pax6 downstream-acting factors. Onecut1 and Onecut2 were previously shown to be expressed in developing horizontal cells, retinal ganglion cells and cone photoreceptors; however, their role in differentiation of these cell types is poorly understood. In this study, we show that the horizontal cell genesis is severely disturbed in Onecut-deficient retinae. In single Onecut1 and Onecut2 mutants, the number of horizontal cells is dramatically reduced while horizontal cells are completely missing in the Onecut1/Onecut2 compound mutant. Analysis of genes involved in the horizontal cell genesis such as Foxn4, Ptf1a, Prox1 and Lim1 showed that although horizontal cells are initially formed, they are not maintained in Onecut-deficient retinae. Taken together, this study suggests the model in which Pax6 regulates the maintenance of horizontal cells through the activation of Onecut1 and Onecut2 transcription factors.
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68
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Chen X, Pappo A, Dyer MA. Pediatric solid tumor genomics and developmental pliancy. Oncogene 2015; 34:5207-15. [PMID: 25639868 PMCID: PMC4522402 DOI: 10.1038/onc.2014.474] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 12/09/2014] [Accepted: 12/09/2014] [Indexed: 12/13/2022]
Abstract
Pediatric solid tumors are remarkably diverse in their cellular origins, developmental timing and clinical features. Over the last 5 years, there have been significant advances in our understanding of the genetic lesions that contribute to the initiation and progression of pediatric solid tumors. To date, over 1000 pediatric solid tumors have been analyzed by Next-Generation Sequencing. These genomic data provide the foundation to launch new research efforts to address one of the fundamental questions in cancer biology—why are some cells more susceptible to malignant transformation by particular genetic lesions at discrete developmental stages than others? Because of their developmental, molecular, cellular and genetic diversity, pediatric solid tumors provide an ideal platform to begin to answer this question. In this review, we highlight the diversity of pediatric solid tumors and provide a new framework for studying the cellular and developmental origins of pediatric cancer. We also introduce a new unifying concept called cellular pliancy as a possible explanation for susceptibility to cancer and the developmental origins of pediatric solid tumors.
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Affiliation(s)
- X Chen
- Department of Computational Biology and Bioinformatics, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - A Pappo
- Department of Oncology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - M A Dyer
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
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69
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Fard SS, Blixt M, Hallböök F. The p53 co-activator Zac1 neither induces cell cycle arrest nor apoptosis in chicken Lim1 horizontal progenitor cells. Cell Death Discov 2015; 1:15023. [PMID: 27551456 PMCID: PMC4991769 DOI: 10.1038/cddiscovery.2015.23] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 07/07/2015] [Indexed: 11/22/2022] Open
Abstract
Chicken horizontal progenitor cells are able to enter their final mitosis even in the presence of DNA damage despite having a functional p53-p21 system. This suggests that they are resistant to DNA damage and that the regulation of the final cell cycle of horizontal progenitor cells is independent of the p53-p21 system. The activity of p53 is regulated by positive and negative modulators, including the zinc finger containing transcription factor Zac1 (zinc finger protein that regulates apoptosis and cell cycle arrest). Zac1 interacts with and enhances the activity of p53, thereby inducing cell cycle arrest and apoptosis. In this work, we use a gain-of-function assay in which mouse Zac1 (mZac1) is overexpressed in chicken retinal progenitor cells to study the effect on the final cell cycle of horizontal progenitor cells. The results showed that overexpression of mZac1 induced expression of p21 in a p53-dependent way and arrested the cell cycle as well as triggered apoptosis in chicken non-horizontal retinal progenitor cells. The negative regulation of the cell cycle by mZac1 is consistent with its proposed role as a tumour-suppressor gene. However, the horizontal cells were not affected by mZac1 overexpression. They progressed into S- and late G2/M-phase despite overexpression of mZac1. The inability of mZac1 to arrest the cell cycle in horizontal progenitor cells support the notion that the horizontal cells are less sensitive to events that triggers the p53 system during their terminal and neurogenic cell cycle, compared with other retinal cells. These properties are associated with a cell that has a propensity to become neoplastic and thus with a cell that may develop retinoblastoma.
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Affiliation(s)
- S Shirazi Fard
- Department of Neuroscience, Biomedical Center (BMC), Uppsala University , Uppsala, Sweden
| | - Mke Blixt
- Department of Neuroscience, Biomedical Center (BMC), Uppsala University , Uppsala, Sweden
| | - F Hallböök
- Department of Neuroscience, Biomedical Center (BMC), Uppsala University , Uppsala, Sweden
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70
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Benavente CA, Dyer MA. Genetically engineered mouse and orthotopic human tumor xenograft models of retinoblastoma. Methods Mol Biol 2015; 1267:307-17. [PMID: 25636476 DOI: 10.1007/978-1-4939-2297-0_15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Retinoblastoma is a rare pediatric cancer of the developing retina that initiates with biallelic inactivation of the RB1 gene. Murine models of retinoblastoma provide excellent tools for preclinical studies as well as for the study of the biological processes that drive tumorigenesis following Rb loss. In this chapter, we describe several genetically engineered mouse and orthotopic human xenograft models of retinoblastoma and discuss the advantages and disadvantages of these models.
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Affiliation(s)
- Claudia A Benavente
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, TN, 38105-3678, USA
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71
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Grossniklaus HE. Retinoblastoma. Fifty years of progress. The LXXI Edward Jackson Memorial Lecture. Am J Ophthalmol 2014; 158:875-91. [PMID: 25065496 PMCID: PMC4250440 DOI: 10.1016/j.ajo.2014.07.025] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 07/14/2014] [Accepted: 07/14/2014] [Indexed: 12/12/2022]
Abstract
PURPOSE To review the progress made in understanding the genetic basis, molecular pathology, and treatment of retinoblastoma since the previous Jackson lecture on the topic was published 50 years ago. DESIGN Perspective based on personal experience and the literature. METHODS The literature regarding retinoblastoma was reviewed since 1963. Advances in understanding the biology and treatment of retinoblastoma provided context through the author's clinical, pathologic, and research experiences. RESULTS Retinoblastoma was first identified in the 1500s and defined as a unique clinicopathologic entity in 1809. Until the mid-1900s, knowledge advanced sporadically, with technological developments of ophthalmoscopy and light microscopy, and with the introduction of surgical enucleation, chemotherapy, and radiation therapy. During the last 50 years, research and treatment have progressed at an unprecedented rate owing to innovations in molecular biology and the development of targeted therapies. During this time period, the retinoblastoma gene was discovered; techniques for genetic testing for retinoblastoma were developed; and plaque brachytherapy, chemoreduction, intra-arterial chemotherapy, and intraocular injections of chemotherapeutic agents were successfully introduced. CONCLUSIONS Nearly all patients with retinoblastoma in developed countries can now be cured of their primary cancer--a remarkable achievement for a childhood cancer that once was uniformly fatal. Much of this success is owed to deciphering the role of the Rb gene, and the benefits of targeted therapies, such as chemoreduction with consolidation as well as intra-arterial and intravitreal chemotherapies. Going forward, the main challenge will be ensuring that access to care is available for all children, particularly those in developing countries.
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Affiliation(s)
- Hans E Grossniklaus
- Departments of Ophthalmology and Pathology, Emory University School of Medicine, Atlanta, Georgia.
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72
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Organ size control is dominant over Rb family inactivation to restrict proliferation in vivo. Cell Rep 2014; 8:371-81. [PMID: 25017070 DOI: 10.1016/j.celrep.2014.06.025] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 05/05/2014] [Accepted: 06/17/2014] [Indexed: 12/19/2022] Open
Abstract
In mammals, a cell's decision to divide is thought to be under the control of the Rb/E2F pathway. We previously found that inactivation of the Rb family of cell cycle inhibitors (Rb, p107, and p130) in quiescent liver progenitors leads to uncontrolled division and cancer initiation. Here, we show that, in contrast, deletion of the entire Rb gene family in mature hepatocytes is not sufficient for their long-term proliferation. The cell cycle block in Rb family mutant hepatocytes is independent of the Arf/p53/p21 checkpoint but can be abrogated upon decreasing liver size. At the molecular level, we identify YAP, a transcriptional regulator involved in organ size control, as a factor required for the sustained expression of cell cycle genes in hepatocytes. These experiments identify a higher level of regulation of the cell cycle in vivo in which signals regulating organ size are dominant regulators of the core cell cycle machinery.
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73
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Ajioka I. Coordination of proliferation and neuronal differentiation by the retinoblastoma protein family. Dev Growth Differ 2014; 56:324-34. [PMID: 24697649 DOI: 10.1111/dgd.12127] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 02/13/2014] [Accepted: 02/16/2014] [Indexed: 12/23/2022]
Abstract
Once neurons enter the post-mitotic G0 phase during central nervous system (CNS) development, they lose their proliferative potential. When neurons re-enter the cell cycle during pathological situations such as neurodegeneration, they undergo cell death after S phase progression. Thus, the regulatory networks that drive cell proliferation and maintain neuronal differentiation are highly coordinated. In this review, the coordination of cell cycle control and neuronal differentiation during development are discussed, focusing on regulation by the Rb family of tumor suppressors (including p107 and p130), and the Cip/Kip family of cyclin dependent kinase (Cdk) inhibitors. Based on recent findings suggesting roles for these families in regulating neurogenesis and neuronal differentiation, I propose that the Rb family is essential for daughter cells of neuronal progenitors to enter the post-mitotic G0 phase without affecting the initiation of neuronal differentiation in most cases, while the Cip/Kip family regulates the timing of neuronal progenitor cell cycle exit and the initiation of neuronal differentiation at least in the progenitor cells of the cerebral cortex and the retina. Rb's lack of involvement in regulating the initiation of neuronal differentiation may explain why Rb family-deficient retinoblastomas characteristically exhibit neuronal features.
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Affiliation(s)
- Itsuki Ajioka
- Center for Brain Integration Research, Tokyo Medical and Dental University, 1-5-45 Yushima, Tokyo, 113-8510, Japan
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74
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Fujita H, Aoki H, Ajioka I, Yamazaki M, Abe M, Oh-Nishi A, Sakimura K, Sugihara I. Detailed expression pattern of aldolase C (Aldoc) in the cerebellum, retina and other areas of the CNS studied in Aldoc-Venus knock-in mice. PLoS One 2014; 9:e86679. [PMID: 24475166 PMCID: PMC3903578 DOI: 10.1371/journal.pone.0086679] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 12/13/2013] [Indexed: 11/22/2022] Open
Abstract
Aldolase C (Aldoc, also known as "zebrin II"), a brain type isozyme of a glycolysis enzyme, is expressed heterogeneously in subpopulations of cerebellar Purkinje cells (PCs) that are arranged longitudinally in a complex striped pattern in the cerebellar cortex, a pattern which is closely related to the topography of input and output axonal projections. Here, we generated knock-in Aldoc-Venus mice in which Aldoc expression is visualized by expression of a fluorescent protein, Venus. Since there was no obvious phenotypes in general brain morphology and in the striped pattern of the cerebellum in mutants, we made detailed observation of Aldoc expression pattern in the nervous system by using Venus expression in Aldoc-Venus heterozygotes. High levels of Venus expression were observed in cerebellar PCs, cartwheel cells in the dorsal cochlear nucleus, sensory epithelium of the inner ear and in all major types of retinal cells, while moderate levels of Venus expression were observed in astrocytes and satellite cells in the dorsal root ganglion. The striped arrangement of PCs that express Venus to different degrees was carefully traced with serial section alignment analysis and mapped on the unfolded scheme of the entire cerebellar cortex to re-identify all individual Aldoc stripes. A longitudinally striped boundary of Aldoc expression was first identified in the mouse flocculus, and was correlated with the climbing fiber projection pattern and expression of another compartmental marker molecule, heat shock protein 25 (HSP25). As in the rat, the cerebellar nuclei were divided into the rostrodorsal negative and the caudoventral positive portions by distinct projections of Aldoc-positive and negative PC axons in the mouse. Identification of the cerebellar Aldoc stripes in this study, as indicated in sample coronal and horizontal sections as well as in sample surface photos of whole-mount preparations, can be referred to in future experiments.
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Affiliation(s)
- Hirofumi Fujita
- Department of Systems Neurophysiology, Tokyo Medical and Dental University Graduate School, Bunkyo-ku, Tokyo, Japan
- Systems Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, California, United States of America
- Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Hanako Aoki
- Department of Systems Neurophysiology, Tokyo Medical and Dental University Graduate School, Bunkyo-ku, Tokyo, Japan
| | - Itsuki Ajioka
- Center for Brain Integration Research, Tokyo Medical and Dental University Graduate School, Bunkyo-ku, Tokyo, Japan
| | - Maya Yamazaki
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Manabu Abe
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Arata Oh-Nishi
- Molecular Neuroimaging Program, Molecular Imaging Center, National Institute of Radiological Sciences, Inage-ku, Chiba, Japan
| | - Kenji Sakimura
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Izumi Sugihara
- Department of Systems Neurophysiology, Tokyo Medical and Dental University Graduate School, Bunkyo-ku, Tokyo, Japan
- Center for Brain Integration Research, Tokyo Medical and Dental University Graduate School, Bunkyo-ku, Tokyo, Japan
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75
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Pentimalli F, Indovina P, Giordano A. Retinoblastoma beyondRB1: recent advances in genetic biomarkers. EXPERT REVIEW OF OPHTHALMOLOGY 2014. [DOI: 10.1586/eop.10.75] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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76
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Shirazi Fard S, All-Ericsson C, Hallböök F. The heterogenic final cell cycle of chicken retinal Lim1 horizontal cells is not regulated by the DNA damage response pathway. Cell Cycle 2013; 13:408-17. [PMID: 24247150 DOI: 10.4161/cc.27200] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cells with aberrations in chromosomal ploidy are normally removed by apoptosis. However, aneuploid neurons have been shown to remain functional and active both in the cortex and in the retina. Lim1 horizontal progenitor cells in the chicken retina have a heterogenic final cell cycle, producing some cells that enter S-phase without proceeding into M-phase. The cells become heteroploid but do not undergo developmental cell death. This prompted us to investigate if the final cell cycle of these cells is under the regulation of an active DNA damage response. Our results show that the DNA damage response pathway, including γ-H2AX and Rad51 foci, is not triggered during any phase of the different final cell cycles of horizontal progenitor cells. However, chemically inducing DNA adducts or double-strand breaks in Lim1 horizontal progenitor cells activated the DNA damage response pathway, showing that the cells are capable of a functional response to DNA damage. Moreover, manipulation of the DNA damage response pathway during the final cell cycle using inhibitors of ATM/ATR, Chk1/2, and p38MAPK, neither induced apoptosis nor mitosis in the Lim1 horizontal progenitor cells. We conclude that the DNA damage response pathway is functional in the Lim1 horizontal progenitor cells, but that it is not directly involved in the regulation of the final cell cycle that gives rise to the heteroploid horizontal cell population.
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Affiliation(s)
| | | | - Finn Hallböök
- Department of Neuroscience; BMC Uppsala University; Uppsala, Sweden
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77
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Abstract
Advances in animal models of retinoblastoma have accelerated research in this field, aiding in understanding tumor progression and assessing therapeutic modalities. The distinct pattern of mutations and specific location of this unique intraocular tumor have paved the way for two types of models- those based on genetic mutations, and xenograft models. Retinoblastoma gene knockouts with an additional loss of p107, p130, p53 and using promoters of Nestin, Chx10, and Pax6 genes show histological phenotypic changes close to the human form of retinoblastoma. Conditional knockout in specific layers of the developing retina has thrown light on the origin of this tumor. The use of xenograft models has overcome the obstacle of time delay in the presentation of symptoms, which remains a crucial drawback of genetic models. With the advances in molecular and imaging technologies, the current research aims to develop models that mimic all the features of retinoblastoma inclusive of its initiation, progression and metastasis. The combination of genetic and xenograft models in retinoblastoma research has and will help to pave way for better understanding of retinoblastoma tumor biology and also in designing and testing effective diagnostic and treatment modalities.
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Affiliation(s)
- Rohini M Nair
- School of Medical Sciences, University of Hyderabad, Hyderabad, India
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78
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Luo C, Deng YP. Retinoblastoma: concerning its initiation and treatment. Int J Ophthalmol 2013; 6:397-401. [PMID: 23826540 DOI: 10.3980/j.issn.2222-3959.2013.03.26] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 03/22/2013] [Indexed: 02/05/2023] Open
Abstract
Retinoblastoma (RB) is the most common intraocular cancer of infancy and childhood. This cancer is initiated by mutation on RB1, the tumor suppressor gene that is responsible for the regulation of both cell cycle and gnome stability in retinal cells. Patients with a constitutional mutation on RB1 can be inherited. RB occurs approximately 1 in every 15 000-20 000 live births. The worldwide mortality for this cancer is about 5%-11%. However, this rate rises to about 40%-70% in developing countries due to a delay in diagnosis. A wide variety of options are available for the treatment, but often a combination of therapies is adopted to optimize individualized care.
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Affiliation(s)
- Chang Luo
- Department of Ophthalmology, West China Hospital, Sichuan University, 37# Guo Xue Xiang, Chengdu 610041, Sichuan Province, China
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79
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Kapatai G, Brundler MA, Jenkinson H, Kearns P, Parulekar M, Peet AC, McConville CM. Gene expression profiling identifies different sub-types of retinoblastoma. Br J Cancer 2013; 109:512-25. [PMID: 23756868 PMCID: PMC3721394 DOI: 10.1038/bjc.2013.283] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 05/16/2013] [Accepted: 05/16/2013] [Indexed: 02/06/2023] Open
Abstract
Background: Mutation of the RB1 gene is necessary but not sufficient for the development of retinoblastoma. The nature of events occurring subsequent to RB1 mutation is unclear, as is the retinal cell-of-origin of this tumour. Methods: Gene expression profiling of 21 retinoblastomas was carried out to identify genetic events that contribute to tumorigenesis and to obtain information about tumour histogenesis. Results: Expression analysis showed a clear separation of retinoblastomas into two groups. Group 1 retinoblastomas express genes associated with a range of different retinal cell types, suggesting derivation from a retinal progenitor cell type. Recurrent chromosomal alterations typical of retinoblastoma, for example, chromosome 1q and 6p gain and 16q loss were also a feature of this group, and clinically they were characterised by an invasive pattern of tumour growth. In contrast, group 2 retinoblastomas were found to retain many characteristics of cone photoreceptor cells and appear to exploit the high metabolic capacity of this cell type in order to promote tumour proliferation. Conclusion: Retinoblastoma is a heterogeneous tumour with variable biology and clinical characteristics.
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Affiliation(s)
- G Kapatai
- School of Cancer Sciences, Vincent Drive, University of Birmingham, Birmingham, UK
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80
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Bassett EA, Korol A, Deschamps PA, Buettner R, Wallace VA, Williams T, West-Mays JA. Overlapping expression patterns and redundant roles for AP-2 transcription factors in the developing mammalian retina. Dev Dyn 2013; 241:814-29. [PMID: 22411557 DOI: 10.1002/dvdy.23762] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND We have previously shown that the transcription factor AP-2α (Tcfap2a) is expressed in postmitotic developing amacrine cells in the mouse retina. Although retina-specific deletion of Tcfap2a did not affect retinogenesis, two other family members, AP-2β and AP-2γ, showed expression patterns similar to AP-2α. RESULTS Here we show that, in addition to their highly overlapping expression patterns in amacrine cells, AP-2α and AP-2β are also co-expressed in developing horizontal cells. AP-2γ expression is restricted to amacrine cells, in a subset that is partially distinct from the AP-2α/β-immunopositive population. To address possible redundant roles for AP-2α and AP-2β during retinogenesis, Tcfap2a/b-deficient retinas were examined. These double mutants showed a striking loss of horizontal cells and an altered staining pattern in amacrine cells that were not detected upon deletion of either family member alone. CONCLUSIONS These studies have uncovered critical roles for AP-2 activity in retinogenesis, delineating the overlapping expression patterns of Tcfap2a, Tcfap2b, and Tcfap2c in the neural retina, and revealing a redundant requirement for Tcfap2a and Tcfap2b in horizontal and amacrine cell development.
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Affiliation(s)
- Erin A Bassett
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
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81
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Oshikawa M, Okada K, Nakajima K, Ajioka I. Cortical excitatory neurons become protected from cell division during neurogenesis in an Rb family-dependent manner. Development 2013; 140:2310-20. [PMID: 23615279 DOI: 10.1242/dev.095653] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cell cycle dysregulation leads to abnormal proliferation and cell death in a context-specific manner. Cell cycle progression driven via the Rb pathway forces neurons to undergo S-phase, resulting in cell death associated with the progression of neuronal degeneration. Nevertheless, some Rb- and Rb family (Rb, p107 and p130)-deficient differentiating neurons can proliferate and form tumors. Here, we found in mouse that differentiating cerebral cortical excitatory neurons underwent S-phase progression but not cell division after acute Rb family inactivation in differentiating neurons. However, the differentiating neurons underwent cell division and proliferated when Rb family members were inactivated in cortical progenitors. Differentiating neurons generated from Rb(-/-); p107(-/-); p130(-/-) (Rb-TKO) progenitors, but not acutely inactivated Rb-TKO differentiating neurons, activated the DNA double-strand break (DSB) repair pathway without increasing trimethylation at lysine 20 of histone H4 (H4K20), which has a role in protection against DNA damage. The activation of the DSB repair pathway was essential for the cell division of Rb-TKO differentiating neurons. These results suggest that newly born cortical neurons from progenitors become epigenetically protected from DNA damage and cell division in an Rb family-dependent manner.
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Affiliation(s)
- Mio Oshikawa
- Center for Brain Integration Research, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
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82
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Li T, Lewallen M, Chen S, Yu W, Zhang N, Xie T. Multipotent stem cells isolated from the adult mouse retina are capable of producing functional photoreceptor cells. Cell Res 2013; 23:788-802. [PMID: 23567557 DOI: 10.1038/cr.2013.48] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Various stem cell types have been tested for their potential application in treating photoreceptor degenerative diseases, such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD). Only embryonic stem cells (ESCs) have so far been shown to generate functional photoreceptor cells restoring light response of photoreceptor-deficient mice, but there is still some concern of tumor formation. In this study, we have successfully cultured Nestin(+)Sox2(+)Pax6(+) multipotent retinal stem cells (RSCs) from the adult mouse retina, which are capable of producing functional photoreceptor cells that restore the light response of photoreceptor-deficient rd1 mutant mice following transplantation. After they have been expanded for over 35 passages in the presence of FGF and EGF, the cultured RSCs still maintain stable proliferation and differentiation potential. Under proper differentiation conditions, they can differentiate into all the major retinal cell types found in the adult retina. More importantly, they can efficiently differentiate into photoreceptor cells under optimized differentiation conditions. Following transplantation into the subretinal space of slowly degenerating rd7 mutant eyes, RSC-derived photoreceptor cells integrate into the retina, morphologically resembling endogenous photoreceptors and forming synapases with resident retinal neurons. When transplanted into eyes of photoreceptor-deficient rd1 mutant mice, a RP model, RSC-derived photoreceptors can partially restore light response, indicating that those RSC-derived photoreceptors are functional. Finally, there is no evidence for tumor formation in the photoreceptor-transplanted eyes. Therefore, this study has demonstrated that RSCs isolated from the adult retina have the potential of producing functional photoreceptor cells that can potentially restore lost vision caused by loss of photoreceptor cells in RP and AMD.
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Affiliation(s)
- Tianqing Li
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
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83
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Andrusiak MG, Vandenbosch R, Dick FA, Park DS, Slack RS. LXCXE-independent chromatin remodeling by Rb/E2f mediates neuronal quiescence. Cell Cycle 2013; 12:1416-23. [PMID: 23574720 DOI: 10.4161/cc.24527] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Neuronal survival is dependent upon the retinoblastoma family members, Rb1 (Rb) and Rb2 (p130). Rb is thought to regulate gene repression, in part, through direct recruitment of chromatin modifying enzymes to its conserved LXCXE binding domain. We sought to examine the mechanisms that Rb employs to mediate cell cycle gene repression in terminally differentiated cortical neurons. Here, we report that Rb loss converts chromatin at the promoters of E2f-target genes to an activated state. We established a mouse model system in which Rb-LXCXE interactions could be induciblely disabled. Surprisingly, this had no effect on survival or gene silencing in neuronal quiescence. Absence of the Rb LXCXE-binding domain in neurons is compatible with gene repression and long-term survival, unlike Rb deficiency. Finally, we are able to show that chromatin activation following Rb deletion occurs at the level of E2fs. Blocking E2f-mediated transcription downstream of Rb loss is sufficient to maintain chromatin in an inactive state. Taken together our results suggest a model whereby Rb-E2f interactions are sufficient to maintain gene repression irrespective of LXCXE-dependent chromatin remodeling.
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Affiliation(s)
- Matthew G Andrusiak
- Department of Cellular & Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
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84
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Rodríguez-Aznar E, Barrallo-Gimeno A, Nieto MA. Scratch2 prevents cell cycle re-entry by repressing miR-25 in postmitotic primary neurons. J Neurosci 2013; 33:5095-105. [PMID: 23516276 PMCID: PMC6704984 DOI: 10.1523/jneurosci.4459-12.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Revised: 01/02/2013] [Accepted: 01/30/2013] [Indexed: 01/25/2023] Open
Abstract
During the development of the nervous system the regulation of cell cycle, differentiation, and survival is tightly interlinked. Newly generated neurons must keep cell cycle components under strict control, as cell cycle re-entry leads to neuronal degeneration and death. However, despite their relevance, the mechanisms controlling this process remain largely unexplored. Here we show that Scratch2 is involved in the control of the cell cycle in neurons in the developing spinal cord of the zebrafish embryo. scratch2 knockdown induces postmitotic neurons to re-enter mitosis. Scratch2 prevents cell cycle re-entry by maintaining high levels of the cycle inhibitor p57 through the downregulation of miR-25. Thus, Scratch2 appears to safeguard the homeostasis of postmitotic primary neurons by preventing cell cycle re-entry.
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Affiliation(s)
| | | | - M. Angela Nieto
- Instituto de Neurociencias, CSIC-UMH, San Juan de Alicante 03550, Spain
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85
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Shirazi Fard S, Jarrin M, Boije H, Fillon V, All-Eriksson C, Hallböök F. Heterogenic final cell cycle by chicken retinal Lim1 horizontal progenitor cells leads to heteroploid cells with a remaining replicated genome. PLoS One 2013; 8:e59133. [PMID: 23527113 PMCID: PMC3602602 DOI: 10.1371/journal.pone.0059133] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 02/13/2013] [Indexed: 12/24/2022] Open
Abstract
Retinal progenitor cells undergo apical mitoses during the process of interkinetic nuclear migration and newly generated post-mitotic neurons migrate to their prospective retinal layer. Whereas this is valid for most types of retinal neurons, chicken horizontal cells are generated by delayed non-apical mitoses from dedicated progenitors. The regulation of such final cell cycle is not well understood and we have studied how Lim1 expressing horizontal progenitor cells (HPCs) exit the cell cycle. We have used markers for S- and G2/M-phase in combination with markers for cell cycle regulators Rb1, cyclin B1, cdc25C and p27Kip1 to characterise the final cell cycle of HPCs. The results show that Lim1+ HPCs are heterogenic with regards to when and during what phase they leave the final cell cycle. Not all horizontal cells were generated by a non-apical (basal) mitosis; instead, the HPCs exhibited three different behaviours during the final cell cycle. Thirty-five percent of the Lim1+ horizontal cells was estimated to be generated by non-apical mitoses. The other horizontal cells were either generated by an interkinetic nuclear migration with an apical mitosis or by a cell cycle with an S-phase that was not followed by any mitosis. Such cells remain with replicated DNA and may be regarded as somatic heteroploids. The observed heterogeneity of the final cell cycle was also seen in the expression of Rb1, cyclin B1, cdc25C and p27Kip1. Phosphorylated Rb1-Ser608 was restricted to the Lim1+ cells that entered S-phase while cyclin B1 and cdc25C were exclusively expressed in HPCs having a basal mitosis. Only HPCs that leave the cell cycle after an apical mitosis expressed p27Kip1. We speculate that the cell cycle heterogeneity with formation of heteroploid cells may present a cellular context that contributes to the suggested propensity of these cells to generate cancer when the retinoblastoma gene is mutated.
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Affiliation(s)
| | - Miguel Jarrin
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Henrik Boije
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Valerie Fillon
- Laboratoire de Génétique Cellulaire, Institut National de la Recherche Agronomique, Castanet-Tolosan, France
| | | | - Finn Hallböök
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
- * E-mail:
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86
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Morin A, Bardot B, Simeonova I, Lejour V, Bouarich-Bourimi R, Toledo F. Of mice and men: fuzzy tandem repeats and divergent p53 transcriptional repertoires. Transcription 2013; 4:67-71. [PMID: 23412358 DOI: 10.4161/trns.23772] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The clinical importance of tumor suppressor p53 makes it one of the most studied transcription factors. A comparison of mammalian p53 transcriptional repertoires may help identify fundamental principles in genome evolution and better understand cancer processes. Here we summarize mechanisms underlying the divergence of mammalian p53 transcriptional repertoires, with an emphasis on the rapid evolution of fuzzy tandem repeats containing p53 response elements.
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87
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Bartesaghi S, Salomoni P. Tumor suppressive pathways in the control of neurogenesis. Cell Mol Life Sci 2013; 70:581-97. [PMID: 22802124 PMCID: PMC11113109 DOI: 10.1007/s00018-012-1063-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 06/16/2012] [Accepted: 06/18/2012] [Indexed: 12/16/2022]
Abstract
The generation of specialized neural cells in the developing and postnatal central nervous system is a highly regulated process, whereby neural stem cells divide to generate committed neuronal progenitors, which then withdraw from the cell cycle and start to differentiate. Cell cycle checkpoints play a major role in regulating the balance between neural stem cell expansion and differentiation. Loss of tumor suppressors involved in checkpoint control can lead to dramatic alterations of neurogenesis, thus contributing to neoplastic transformation. Here we summarize and critically discuss the existing literature on the role of tumor suppressive pathways and their regulatory networks in the control of neurogenesis and transformation.
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Affiliation(s)
- Stefano Bartesaghi
- Samantha Dickson Brain Cancer Unit, UCL Cancer Institute, 72 Huntley Street, London, WC1E 6DD UK
| | - Paolo Salomoni
- Samantha Dickson Brain Cancer Unit, UCL Cancer Institute, 72 Huntley Street, London, WC1E 6DD UK
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88
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Balla MMS, Kusumbe AP, Vemuganti GK, Bapat SA. Cancer Stem Cells. Regen Med 2013. [DOI: 10.1007/978-94-007-5690-8_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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89
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Mitosis in neurons: Roughex and APC/C maintain cell cycle exit to prevent cytokinetic and axonal defects in Drosophila photoreceptor neurons. PLoS Genet 2012; 8:e1003049. [PMID: 23209426 PMCID: PMC3510051 DOI: 10.1371/journal.pgen.1003049] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 09/11/2012] [Indexed: 02/02/2023] Open
Abstract
The mechanisms of cell cycle exit by neurons remain poorly understood. Through genetic and developmental analysis of Drosophila eye development, we found that the cyclin-dependent kinase-inhibitor Roughex maintains G1 cell cycle exit during differentiation of the R8 class of photoreceptor neurons. The roughex mutant neurons re-enter the mitotic cell cycle and progress without executing cytokinesis, unlike non-neuronal cells in the roughex mutant that perform complete cell divisions. After mitosis, the binucleated R8 neurons usually transport one daughter nucleus away from the cell body into the developing axon towards the brain in a kinesin-dependent manner resembling anterograde axonal trafficking. Similar cell cycle and photoreceptor neuron defects occurred in mutants for components of the Anaphase Promoting Complex/Cyclosome. These findings indicate a neuron-specific defect in cytokinesis and demonstrate a critical role for mitotic cyclin downregulation both to maintain cell cycle exit during neuronal differentiation and to prevent axonal defects following failed cytokinesis. Neurons generally differentiate and never divide again. One barrier to understanding the mechanisms has been the paucity of genetic mutations that result in neuronal cell cycles. Here we show that mutation in three genes lead to cell cycle re-entry by a particular class of developing photoreceptor neurons in the fly retina. Strikingly, these neurons do not complete cell division but only divide their nuclei. The binucleated neurons then typically retain one nucleus in its normal location in the cell body, while transporting the other into the growing axon like other axonal material. Our findings identify Cyclin A regulation as crucial to maintaining cell cycle exit by at least some neurons and identify a neuron-specific defect in cell division as a further barrier to neuron proliferation. Because defects in transporting axonal material have been implicated in the origin of multiple neurodegenerative diseases, our findings also suggest a possible connection between defective cell cycle regulation and neuronal cell death.
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90
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Behesti H, Bhagat H, Dubuc AM, Taylor MD, Marino S. Bmi1 overexpression in the cerebellar granule cell lineage of mice affects cell proliferation and survival without initiating medulloblastoma formation. Dis Model Mech 2012; 6:49-63. [PMID: 23065639 PMCID: PMC3529338 DOI: 10.1242/dmm.009506] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
BMI1 is a potent inducer of neural stem cell self-renewal and neural progenitor cell proliferation during development and in adult tissue homeostasis. It is overexpressed in numerous human cancers – including medulloblastomas, in which its functional role is unclear. We generated transgenic mouse lines with targeted overexpression of Bmi1 in the cerebellar granule cell lineage, a cell type that has been shown to act as a cell of origin for medulloblastomas. Overexpression of Bmi1 in granule cell progenitors (GCPs) led to a decrease in cerebellar size due to decreased GCP proliferation and repression of the expression of cyclin genes, whereas Bmi1 overexpression in postmitotic granule cells improved cell survival in response to stress by altering the expression of genes in the mitochondrial cell death pathway and of Myc and Lef-1. Although no medulloblastomas developed in ageing cohorts of transgenic mice, crosses with Trp53−/− mice resulted in a low incidence of medulloblastoma formation. Furthermore, analysis of a large collection of primary human medulloblastomas revealed that tumours with a BMI1high TP53low molecular profile are significantly enriched in Group 4 human medulloblastomas. Our data suggest that different levels and timing of Bmi1 overexpression yield distinct cellular outcomes within the same cellular lineage. Importantly, Bmi1 overexpression at the GCP stage does not induce tumour formation, suggesting that BMI1 overexpression in GCP-derived human medulloblastomas probably occurs during later stages of oncogenesis and might serve to enhance tumour cell survival.
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Affiliation(s)
- Hourinaz Behesti
- Blizard Institute of Cell and Molecular Science, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, 4 Newark Street, London, E1 2AT, UK
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91
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Donovan SL, Corbo JC. Retinal horizontal cells lacking Rb1 sustain persistent DNA damage and survive as polyploid giant cells. Mol Biol Cell 2012; 23:4362-72. [PMID: 23015754 PMCID: PMC3496610 DOI: 10.1091/mbc.e12-04-0293] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The retinoblastoma tumor susceptibility gene, Rb1, is a key regulator of the cell cycle, and mutations in this gene have been found in many human cancers. Prior studies showed that retina-specific knockout of Rb1 in the mouse results in the formation of abnormally large horizontal cells, but the development, fate, and genomic status of these cells remain unknown. In this study, we conditionally inactivate Rb1 in early retinal progenitors and show that the loss of Rb1 leads to the rapid degeneration of most retinal cells except horizontal cells, which persist as giant cells with aberrant centrosome content, DNA damage, and polyploidy/aneuploidy. We observed inappropriate cell cycle entry of Rb1-deficient horizontal cells during the first postnatal weeks, which dropped off abruptly by P30. Despite extensive DNA damage in Rb1-deficient horizontal cells, these cells can still enter mitosis. Adult Rb1-deficient horizontal cells display elevated DNA content (5N-34N) that varied continuously, suggesting the presence of aneuploidy. We also found evidence of supernumerary and disoriented centrosomes in a rare population of mitotic cells in the mutant retinas. Overall our data demonstrate that horizontal cells are a remarkably robust cell type and can survive for months despite extensive DNA damage and elevated genome content.
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Affiliation(s)
- Stacy L Donovan
- Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO 63110, USA
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92
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Abstract
Stem cells play a critical role during embryonic development and in the maintenance of homeostasis in adult individuals. A better understanding of stem cell biology, including embryonic and adult stem cells, will allow the scientific community to better comprehend a number of pathologies and possibly design novel approaches to treat patients with a variety of diseases. The retinoblastoma tumor suppressor RB controls the proliferation, differentiation, and survival of cells, and accumulating evidence points to a central role for RB activity in the biology of stem and progenitor cells. In some contexts, loss of RB function in stem or progenitor cells is a key event in the initiation of cancer and determines the subtype of cancer arising from these pluripotent cells by altering their fate. In other cases, RB inactivation is often not sufficient to initiate cancer but may still lead to some stem cell expansion, raising the possibility that strategies aimed at transiently inactivating RB might provide a novel way to expand functional stem cell populations. Future experiments dedicated to better understanding how RB and the RB pathway control a stem cell's decisions to divide, self-renew, or give rise to differentiated progeny may eventually increase our capacity to control these decisions to enhance regeneration or help prevent cancer development.
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Affiliation(s)
- Julien Sage
- Department of Pediatrics, Department of Genetics, Stanford Institute for Stem Cell Biology and Regenerative Medicine, Stanford Cancer Institute, Stanford, California 94305, USA.
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93
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Simeonova I, Lejour V, Bardot B, Bouarich-Bourimi R, Morin A, Fang M, Charbonnier L, Toledo F. Fuzzy tandem repeats containing p53 response elements may define species-specific p53 target genes. PLoS Genet 2012; 8:e1002731. [PMID: 22761580 PMCID: PMC3386156 DOI: 10.1371/journal.pgen.1002731] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 04/11/2012] [Indexed: 12/21/2022] Open
Abstract
Evolutionary forces that shape regulatory networks remain poorly understood. In mammals, the Rb pathway is a classic example of species-specific gene regulation, as a germline mutation in one Rb allele promotes retinoblastoma in humans, but not in mice. Here we show that p53 transactivates the Retinoblastoma-like 2 (Rbl2) gene to produce p130 in murine, but not human, cells. We found intronic fuzzy tandem repeats containing perfect p53 response elements to be important for this regulation. We next identified two other murine genes regulated by p53 via fuzzy tandem repeats: Ncoa1 and Klhl26. The repeats are poorly conserved in evolution, and the p53-dependent regulation of the murine genes is lost in humans. Our results indicate a role for the rapid evolution of tandem repeats in shaping differences in p53 regulatory networks between mammalian species. TP53, the gene encoding p53, is mutated in more than half of human cancers. Consequently, p53 is one of the most studied transcription factors, shown to directly regulate more than 150 genes. The mouse is a model of choice to study p53 mutants and cancer. However, differences were found between tumorigenesis in mice and humans, and these should be investigated to improve the relevance of mouse models. The distinct mutational events required to initiate retinoblastomas in these species constitute a classic example of such differences. Here we show that p53 regulates the Retinoblastoma-like 2 (Rbl2) gene, encoding tumor suppressor p130, in murine but not human cells. The p53-dependent regulation of murine Rbl2/p130 relies on clustered p53 response elements, located within tandem repeats poorly conserved in evolution. A similar situation was found for two other genes, also p53 targets in mice but not in humans. Thus, tandem repeats may shape differences in mammalian p53 regulatory networks. By uncovering differences in p53 target gene repertoires between mice and humans, our findings may help to improve mice as models of human disease. In addition, the role of tandem repeats in shaping the target gene repertoires of other mammalian transcription factors should be considered.
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Affiliation(s)
- Iva Simeonova
- Institut Curie, Centre de Recherche, Paris, France
- UPMC Univ Paris 06, Paris, France
- CNRS UMR 3244, Paris, France
| | - Vincent Lejour
- Institut Curie, Centre de Recherche, Paris, France
- UPMC Univ Paris 06, Paris, France
- CNRS UMR 3244, Paris, France
| | - Boris Bardot
- Institut Curie, Centre de Recherche, Paris, France
- UPMC Univ Paris 06, Paris, France
- CNRS UMR 3244, Paris, France
| | - Rachida Bouarich-Bourimi
- Institut Curie, Centre de Recherche, Paris, France
- UPMC Univ Paris 06, Paris, France
- CNRS UMR 3244, Paris, France
| | - Aurélie Morin
- Institut Curie, Centre de Recherche, Paris, France
- UPMC Univ Paris 06, Paris, France
- CNRS UMR 3244, Paris, France
| | - Ming Fang
- Institut Curie, Centre de Recherche, Paris, France
- UPMC Univ Paris 06, Paris, France
- CNRS UMR 3244, Paris, France
| | - Laure Charbonnier
- Institut Curie, Centre de Recherche, Paris, France
- UPMC Univ Paris 06, Paris, France
- CNRS UMR 3244, Paris, France
| | - Franck Toledo
- Institut Curie, Centre de Recherche, Paris, France
- UPMC Univ Paris 06, Paris, France
- CNRS UMR 3244, Paris, France
- * E-mail:
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94
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Wadhwa L, Bond WS, Perlaky L, Overbeek PA, Hurwitz MY, Chévez-Barrios P, Hurwitz RL. Embryonic retinal tumors in SV40 T-Ag transgenic mice contain CD133+ tumor-initiating cells. Invest Ophthalmol Vis Sci 2012; 53:3454-62. [PMID: 22562503 DOI: 10.1167/iovs.12-9549] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
PURPOSE Human retinoblastomas form during the proliferative phase of retina development and are caused by mutations that result in absent or functionally defective Rb protein. Similar tumors occur in mice only when multiple Rb gene family members are absent. We asked if retinal tumors can arise from an undifferentiated retinal cell. The tumor-initiating cells isolated from these tumors that formed in early embryonic murine retinas were characterized. METHODS Transgenic mice were created using a Pax6 promoter to target expression of SV40 large T-antigen (T-Ag) in the undifferentiated murine embryonic retina. T-Ag, which sequesters all Rb family proteins and p53, is expressed in the retina and lens by murine embryonic day 10 (E10) and tumors are observed by E12.5. A cell line that is adherent in serum-containing media and forms neurospheres in supplemented serum-free media was developed from retinal tumors isolated on postnatal day 7. RESULTS In all, 1.5% of attached cells form neurospheres when transferred to serum-free medium. All cultured cells express T-Ag, confirming that they derive from the original tumors; 0.5% of adherent cells express detectable levels of CD133. CD133+ FACS-sorted cells cultured in serum-free medium form 3-fold more neurospheres than do CD133- cells. Six of seven mice injected with CD133+ cells and one of seven mice injected with CD133- cells formed tumors during a 6-month period. Unlike primary adherent cells, primary and secondary tumors heterogeneously express markers of stem cells and differentiation similar to human retinoblastoma. CONCLUSIONS CD133+ tumor-initiating cells can originate from proliferating undifferentiated precursor cells.
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Affiliation(s)
- Lalita Wadhwa
- Texas Children's Cancer and Hematology Centers, Texas Children's Hospital, Baylor College of Medicine, Houston, Texas, USA
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95
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Abstract
Various studies have demonstrated that somatic differentiated cells can be reprogrammed into other differentiated states or into pluripotency, thus showing that the differentiated cellular state is not irreversible. These findings have generated intense interest in the process of reprogramming and in mechanisms that govern the pluripotent state. However, the realization that differentiated cells can be triggered to switch to considerably different lineages also emphasizes that we need to understand how the identity of mature cells is normally maintained. Here we review recent studies on how the differentiated state is controlled at the transcriptional level and discuss how new insights have begun to elucidate mechanisms underlying the stable maintenance of mature cell identities.
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Affiliation(s)
- Johan Holmberg
- Ludwig Institute for Cancer Research Ltd, BOX 240, Karolinska Institutet, S-171 77 Stockholm, Sweden.
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96
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Takahashi C, Sasaki N, Kitajima S. Twists in views on RB functions in cellular signaling, metabolism and stem cells. Cancer Sci 2012; 103:1182-8. [PMID: 22448711 DOI: 10.1111/j.1349-7006.2012.02284.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 03/13/2012] [Indexed: 12/15/2022] Open
Abstract
One-quarter of a century ago, identification of the human retinoblastoma gene (RB) loci proved Knudson's 'two-hit theory' that tumor suppressor genes exist. Since then, numerous works delineated crucial roles for the RB protein (pRB)-E2F transcription factor complex in G1-S phase transition. In addition, discovering the relationship between pRB and tissue-specific transcription factors enabled a better understanding of how cell cycle exit and terminal differentiation are coupled. Recent works provoked many exciting twists in views on pRB functions during cancer initiation and progression beyond its previously well-appreciated roles. Various mitogenic and cytostatic cellular signals appeared to modulate pRB functions and thus affect a wide variety of effector molecules. In addition, genetic studies in mice as well as other creatures incessantly force us to revise our views on pRB functions. This review will focus particularly on the roles of pRB in regulating intracellular signaling, cell metabolism, chromatin function, stem cells and cancer stem cells.
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Affiliation(s)
- Chiaki Takahashi
- Kanazawa University Cancer Research Institute, Kanazawa, Ishikawa, Japan.
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97
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Devès M, Bourrat F. Transcriptional mechanisms of developmental cell cycle arrest: problems and models. Semin Cell Dev Biol 2012; 23:290-7. [PMID: 22464972 DOI: 10.1016/j.semcdb.2012.03.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 02/02/2012] [Accepted: 03/01/2012] [Indexed: 12/30/2022]
Abstract
Metazoans begin their life as a single cell. Then, this cell enters a more or less protracted period of active cell proliferation, which can be considered as the default cellular state. A crucial event, the developmental cell cycle exit, occurs thereafter. This phenomenon allows for differentiation to happen and regulates the final size of organs and organisms. Its control is still poorly understood. Herein, we review some transcriptional mechanisms of cell cycle exit in animals, and propose to use cellular conveyor belts as model systems for its study. We finally point to evidence that suggests that the mechanisms of developmental cell cycle arrest may have to be maintained in adult tissues.
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98
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Yaguchi H, Okumura F, Takahashi H, Kano T, Kameda H, Uchigashima M, Tanaka S, Watanabe M, Sasaki H, Hatakeyama S. TRIM67 protein negatively regulates Ras activity through degradation of 80K-H and induces neuritogenesis. J Biol Chem 2012; 287:12050-9. [PMID: 22337885 DOI: 10.1074/jbc.m111.307678] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Tripartite motif (TRIM)-containing proteins, which are defined by the presence of a common domain structure composed of a RING finger, one or two B-box motifs and a coiled-coil motif, are involved in many biological processes including innate immunity, viral infection, carcinogenesis, and development. Here we show that TRIM67, which has a TRIM motif, an FN3 domain and a SPRY domain, is highly expressed in the cerebellum and that TRIM67 interacts with PRG-1 and 80K-H, which is involved in the Ras-mediated signaling pathway. Ectopic expression of TRIM67 results in degradation of endogenous 80K-H and attenuation of cell proliferation and enhances neuritogenesis in the neuroblastoma cell line N1E-115. Furthermore, morphological and biological changes caused by knockdown of 80K-H are similar to those observed by overexpression of TRIM67. These findings suggest that TRIM67 regulates Ras signaling via degradation of 80K-H, leading to neural differentiation including neuritogenesis.
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Affiliation(s)
- Hiroaki Yaguchi
- Department of Biochemistry, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido 060-8638, Japan
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99
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Abstract
The retinoblastoma (RB) tumor suppressor belongs to a cellular pathway that plays a crucial role in restricting the G1-S transition of the cell cycle in response to a large number of extracellular and intracellular cues. Research in the last decade has highlighted the complexity of regulatory networks that ensure proper cell cycle progression, and has also identified multiple cellular functions beyond cell cycle regulation for RB and its two family members, p107 and p130. Here we review some of the recent evidence pointing to a role of RB as a molecular adaptor at the crossroads of multiple pathways, ensuring cellular homeostasis in different contexts. In particular, we discuss the pro- and anti-tumorigenic roles of RB during the early stages of cancer, as well as the importance of the RB pathway in stem cells and cell fate decisions.
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Affiliation(s)
- Patrick Viatour
- Department of Genetics, Stanford University, Stanford, CA 94305, USA.
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100
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Caenorhabditis elegans cyclin D/CDK4 and cyclin E/CDK2 induce distinct cell cycle re-entry programs in differentiated muscle cells. PLoS Genet 2011; 7:e1002362. [PMID: 22102824 PMCID: PMC3213155 DOI: 10.1371/journal.pgen.1002362] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 09/12/2011] [Indexed: 11/19/2022] Open
Abstract
Cell proliferation and differentiation are regulated in a highly coordinated and inverse manner during development and tissue homeostasis. Terminal differentiation usually coincides with cell cycle exit and is thought to engage stable transcriptional repression of cell cycle genes. Here, we examine the robustness of the post-mitotic state, using Caenorhabditis elegans muscle cells as a model. We found that expression of a G1 Cyclin and CDK initiates cell cycle re-entry in muscle cells without interfering with the differentiated state. Cyclin D/CDK4 (CYD-1/CDK-4) expression was sufficient to induce DNA synthesis in muscle cells, in contrast to Cyclin E/CDK2 (CYE-1/CDK-2), which triggered mitotic events. Tissue-specific gene-expression profiling and single molecule FISH experiments revealed that Cyclin D and E kinases activate an extensive and overlapping set of cell cycle genes in muscle, yet failed to induce some key activators of G1/S progression. Surprisingly, CYD-1/CDK-4 also induced an additional set of genes primarily associated with growth and metabolism, which were not activated by CYE-1/CDK-2. Moreover, CYD-1/CDK-4 expression also down-regulated a large number of genes enriched for catabolic functions. These results highlight distinct functions for the two G1 Cyclin/CDK complexes and reveal a previously unknown activity of Cyclin D/CDK-4 in regulating metabolic gene expression. Furthermore, our data demonstrate that many cell cycle genes can still be transcriptionally induced in post-mitotic muscle cells, while maintenance of the post-mitotic state might depend on stable repression of a limited number of critical cell cycle regulators. During development, cells face the important decision whether to continue to proliferate, or to exit the cell-division cycle and fully differentiate. Improved insight into the molecular mechanisms that arrest the cell cycle during terminal differentiation is important for our understanding of normal development, as well as for cancer research and regenerative medicine. To investigate the arrested state of terminally differentiated cells, we examined muscle cells in the model organism C. elegans, which is known for its reproducible cell-division pattern. We found that expression of a single cell cycle kinase with its regulatory partner (Cyclin) induced many cell division genes in muscle. While Cyclin D and E kinases often act similarly, only Cyclin D with CDK-4 triggered DNA replication in muscle, and this combination induced a much broader transcriptional response than Cyclin E/CDK-2. Despite activation of a substantial cell cycle program, Cyclin/CDK expression did not induce complete muscle cell division and failed to induce some key cell cycle regulators. Our results highlight distinct activities of Cyclin D and Cyclin E kinases, and they indicate that cell-cycle gene expression remains remarkably flexible in differentiated cells. We propose that the post-mitotic state of differentiated cells is maintained by tight control of a few regulatory genes.
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