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P. Perry, S. Sauer, N. Billon, W. Richardson, Mikhail Spivakov, G. Warnes, F. Livesey, M. Merkenschlager, A. Fisher, V. Azuara (2004)
A Dynamic Switch in the Replication Timing of Key Regulator Genes in Embryonic Stem Cells upon Neural InductionCell Cycle, 3
Chad Cowan, Jocelyn Atienza, D. Melton, K. Eggan (2005)
Nuclear Reprogramming of Somatic Cells After Fusion with Human Embryonic Stem CellsScience, 309
S. Yeo, Sangkyun Jeong, Janghwan Kim, Jee-Soo Han, Yong-Mahn Han, Yong-Kook Kang (2007)
Characterization of DNA methylation change in stem cell marker genes during differentiation of human embryonic stem cells.Biochemical and biophysical research communications, 359 3
N. Allen, S. Barton, K. Hilton, M. Norris, M. Surani (1994)
A functional analysis of imprinting in parthenogenetic embryonic stem cells.Development, 120 6
Takao Kuroda, M. Tada, H. Kubota, H. Kimura, S. Hatano, H. Suemori, N. Nakatsuji, T. Tada (2005)
Octamer and Sox Elements Are Required for Transcriptional cis Regulation of Nanog Gene ExpressionMolecular and Cellular Biology, 25
J. Rathjen, J. Lake, M. Bettess, J. Washington, G. Chapman, P. Rathjen (1999)
Formation of a primitive ectoderm like cell population, EPL cells, from ES cells in response to biologically derived factors.Journal of cell science, 112 ( Pt 5)
Kazutoshi Takahashi, K. Tanabe, M. Ohnuki, Megumi Narita, T. Ichisaka, K. Tomoda, S. Yamanaka (2007)
Induction of Pluripotent Stem Cells from Adult Human Fibroblasts by Defined FactorsCell, 131
S. Oh, H. Kim, Y. Park, H. Seol, Y. Kim, M. Cho, S. Ku, Y. Choi, Dong-Wook Kim, S. Moon (2005)
Methods for Expansion of Human Embryonic Stem CellsSTEM CELLS, 23
A. French, C. Adams, Lindam Anderson, J. Kitchen, M. Hughes, S. Wood (2008)
Development of Human Cloned Blastocysts Following Somatic Cell Nuclear Transfer with Adult FibroblastsSTEM CELLS, 26
Tong Lee, Richard Jenner, L. Boyer, M. Guenther, S. Levine, Roshan Kumar, B. Chevalier, S. Johnstone, Megan Cole, K. Isono, H. Koseki, Takuya Fuchikami, K. Abe, H. Murray, J. Zucker, Bingbing Yuan, G. Bell, Elizabeth Herbolsheimer, N. Hannett, K. Sun, D. Odom, A. Otte, T. Volkert, D. Bartel, D. Melton, D. Gifford, R. Jaenisch, R. Young (2006)
Control of Developmental Regulators by Polycomb in Human Embryonic Stem CellsCell, 125
W. Hwang, Y. Ryu, Jong Park, E. Park, E. Lee, J. Koo, H. Jeon, Byeong-chun Lee, S. Kang, Sun Kim, C. Ahn, J. Hwang, Ky Park, J. Cibelli, S. Moon (2004)
Evidence of a Pluripotent Human Embryonic Stem Cell Line Derived from a Cloned BlastocystScience, 303
T. Enver, S. Soneji, Chirag Joshi, John Brown, F. Iborra, T. Orntoft, T. Thykjaer, E. Maltby, Kath Smith, Raed Dawud, Mark Jones, M. Matin, P. Gokhale, J. Draper, P. Andrews (2005)
Cellular differentiation hierarchies in normal and culture-adapted human embryonic stem cells.Human molecular genetics, 14 21
V. Azuara, P. Perry, S. Sauer, M. Spivakov, H. Jørgensen, R. John, Mina Gouti, Miguel Casanova, G. Warnes, M. Merkenschlager, A. Fisher (2006)
Chromatin signatures of pluripotent cell linesNature Cell Biology, 8
S. Ko, Hyereen Kang, H. Lee, S. Han, S. Hong (2006)
Identification of Jmjd1a as a STAT3 downstream gene in mES cells.Cell structure and function, 31 2
N. Sato, L. Meijer, L. Skaltsounis, P. Greengard, A. Brivanlou (2004)
Maintenance of pluripotency in human and mouse embryonic stem cells through activation of Wnt signaling by a pharmacological GSK-3-specific inhibitorNature Medicine, 10
S. Mitalipov, Qi Zhou, James Byrne, Weizhi Ji, Robert Norgren, Don Wolf (2007)
Reprogramming following somatic cell nuclear transfer in primates is dependent upon nuclear remodeling.Human reproduction, 22 8
I. Hiratani, Amanda Leskovar, D. Gilbert (2004)
Differentiation-induced replication-timing changes are restricted to AT-rich/long interspersed nuclear element (LINE)-rich isochores.Proceedings of the National Academy of Sciences of the United States of America, 101 48
Takafusa Hikichi, S. Wakayama, E. Mizutani, Yasuhiro Takashima, S. Kishigami, N. Thuan, H. Ohta, Hong Bui, S. Nishikawa, T. Wakayama (2007)
Differentiation Potential of Parthenogenetic Embryonic Stem Cells Is Improved by Nuclear TransferSTEM CELLS, 25
Shelley Hough, Ian Clements, Peter Welch, Kristin Wiederholt (2006)
Differentiation of Mouse Embryonic Stem Cells after RNA Interference‐Mediated Silencing of OCT4 and NanogSTEM CELLS, 24
X. Qi, Teng-Guo Li, J. Hao, Jie Hu, Jing Wang, H. Simmons, Shigeto Miura, Y. Mishina, G. Zhao (2004)
BMP4 supports self-renewal of embryonic stem cells by inhibiting mitogen-activated protein kinase pathways.Proceedings of the National Academy of Sciences of the United States of America, 101 16
A. Suzuki, Á. Raya, Y. Kawakami, Masanobu Morita, Takaaki Matsui, K. Nakashima, F. Gage, Concepción Rodríguez-Esteban, J. Belmonte (2006)
Maintenance of embryonic stem cell pluripotency by Nanog-mediated reversal of mesoderm specificationNature Clinical Practice Cardiovascular Medicine, 3 Suppl 1
Marius Wernig, Jian-ping Zhao, J. Pruszak, E. Hedlund, Dongdong Fu, F. Soldner, V. Broccoli, M. Constantine‐Paton, O. Isacson, R. Jaenisch (2008)
Neurons derived from reprogrammed fibroblasts functionally integrate into the fetal brain and improve symptoms of rats with Parkinson's diseaseProceedings of the National Academy of Sciences, 105
L. Boyer, Tong Lee, Megan Cole, S. Johnstone, S. Levine, J. Zucker, M. Guenther, Roshan Kumar, H. Murray, Richard Jenner, D. Gifford, D. Melton, R. Jaenisch, R. Young (2005)
Core Transcriptional Regulatory Circuitry in Human Embryonic Stem CellsCell, 122
P. Cartwright, C. McLean, A. Sheppard, D. Rivett, K. Jones, S. Dalton (2005)
LIF/STAT3 controls ES cell self-renewal and pluripotency by a Myc-dependent mechanism, 132
Chunhui Xu, E. Rosler, Jianjie Jiang, J. Lebkowski, Joseph Gold, C. O'Sullivan, Karen Delavan-Boorsma, Michael Mok, Adrienne Bronstein, M. Carpenter (2005)
Basic Fibroblast Growth Factor Supports Undifferentiated Human Embryonic Stem Cell Growth Without Conditioned MediumSTEM CELLS, 23
A. Avilion, S. Nicolis, L. Pevny, Lidia Pérez, N. Vivian, R. Lovell-Badge (2003)
Multipotent cell lineages in early mouse development depend on SOX2 function.Genes & development, 17 1
I. Chambers, José Silva, Douglas Colby, J. Nichols, B. Nijmeijer, M. Robertson, J. Vrána, Kenneth Jones, L. Grotewold, Austin Smith (2007)
Nanog safeguards pluripotency and mediates germline developmentNature, 450
M. Tada, T. Tada (2006)
Nuclear Reprogramming of Somatic Nucleus Hybridized With Embryonic Stem Cells by ElectrofusionEmbryonic Stem Cell Protocols, 329
J. Nichols, B. Zevnik, K. Anastassiadis, H. Niwa, Daniela Klewe-Nebenius, I. Chambers, H. Schöler, Austin Smith (1998)
Formation of Pluripotent Stem Cells in the Mammalian Embryo Depends on the POU Transcription Factor Oct4Cell, 95
C. Taranger, A. Noer, Anita Sørensen, A. Håkelien, A. Boquest, P. Collas (2005)
Induction of dedifferentiation, genomewide transcriptional programming, and epigenetic reprogramming by extracts of carcinoma and embryonic stem cells.Molecular biology of the cell, 16 12
K. Kinoshita, Hiroki Ura, T. Akagi, M. Usuda, H. Koide, T. Yokota (2007)
GABPα regulates Oct-3/4 expression in mouse embryonic stem cellsBiochemical and Biophysical Research Communications, 353
Austin Smith, J. Heath, D. Donaldson, G. Wong, J. Moreau, M. Stahl, D. Rogers (1988)
Inhibition of pluripotential embryonic stem cell differentiation by purified polypeptidesNature, 336
Kitai Kim, K. Ng, P. Rugg-Gunn, J. Shieh, O. Kirak, R. Jaenisch, T. Wakayama, M. Moore, R. Pedersen, G. Daley (2007)
Recombination signatures distinguish embryonic stem cells derived by parthenogenesis and somatic cell nuclear transfer.Cell stem cell, 1 3
J. Nichols, I. Chambers, T. Taga, Austin Smith (2001)
Physiological rationale for responsiveness of mouse embryonic stem cells to gp130 cytokines.Development, 128 12
P. Tesar, Josh Chenoweth, F. Brook, T. Davies, E. Evans, David Mack, R. Gardner, R. McKay (2007)
New cell lines from mouse epiblast share defining features with human embryonic stem cellsNature, 448
S. Masui, Yuhki Nakatake, Yayoi Toyooka, Daisuke Shimosato, R. Yagi, Kazue Takahashi, H. Okochi, A. Okuda, R. Matoba, A. Sharov, M. Ko, H. Niwa (2007)
Pluripotency governed by Sox2 via regulation of Oct3/4 expression in mouse embryonic stem cellsNature Cell Biology, 9
Margaret Panning, D. Gilbert (2005)
Spatio‐temporal organization of DNA replication in murine embryonic stem, primary, and immortalized cellsJournal of Cellular Biochemistry, 95
L. Boyer, K. Plath, J. Zeitlinger, T. Brambrink, Lea Medeiros, Tong Lee, S. Levine, Marius Wernig, Adriana Tajonar, Mridula Ray, G. Bell, A. Otte, M. Vidal, D. Gifford, R. Young, R. Jaenisch (2006)
Polycomb complexes repress developmental regulators in murine embryonic stem cellsNature, 441
Annie Wiblin, W. Cui, A. Clark, W. Bickmore (2005)
Distinctive nuclear organisation of centromeres and regions involved in pluripotency in human embryonic stem cellsJournal of Cell Science, 118
R. Fundele, M. Norris, S. Barton, Monika Fehlau, Sarah Howlett, Walter Mills, M. Surani (1990)
Temporal and spatial selection against parthenogenetic cells during development of fetal chimeras.Development, 108 1
T. Brambrink, K. Hochedlinger, G. Bell, R. Jaenisch (2006)
ES cells derived from cloned and fertilized blastocysts are transcriptionally and functionally indistinguishable.Proceedings of the National Academy of Sciences of the United States of America, 103 4
T. Mikkelsen, Manching Ku, D. Jaffe, B. Issac, Erez Lieberman, G. Giannoukos, P. Alvarez, W. Brockman, Tae-Kyung Kim, R. Koche, William Lee, E. Mendenhall, Aisling O'Donovan, Aviva Presser, C. Russ, Xiaohui Xie, A. Meissner, Marius Wernig, R. Jaenisch, C. Nusbaum, E. Lander, B. Bernstein (2007)
Genome-wide maps of chromatin state in pluripotent and lineage-committed cellsNature, 448
D. Carlone, Jeong‐Heon Lee, Suzanne Young, Erika Dobrota, J. Butler, Joseph Ruiz, D. Skalnik (2005)
Reduced Genomic Cytosine Methylation and Defective Cellular Differentiation in Embryonic Stem Cells Lacking CpG Binding ProteinMolecular and Cellular Biology, 25
Jonghwan Kim, J. Chu, Xiaohua Shen, Jianlong Wang, S. Orkin (2008)
An Extended Transcriptional Network for Pluripotency of Embryonic Stem CellsCell, 132
S. Chamberlain, D. Yee, T. Magnuson (2008)
Polycomb Repressive Complex 2 Is Dispensable for Maintenance of Embryonic Stem Cell PluripotencySTEM CELLS, 26
J. Hipp, J. Mychaleckyj, J. Cibelli, J. Wininger, K. Grant, K. Vrana (2006)
Parthenogenetic Stem CellsReviews in Cell Biology and Molecular Medicine
J. Lake, J. Rathjen, J. Remiszewski, P. Rathjen (2000)
Reversible programming of pluripotent cell differentiation.Journal of cell science, 113 ( Pt 3)
S. Fouse, Yin Shen, M. Pellegrini, S. Cole, A. Meissner, L. Neste, R. Jaenisch, G. Fan (2008)
Promoter CpG methylation contributes to ES cell gene regulation in parallel with Oct4/Nanog, PcG complex, and histone H3 K4/K27 trimethylation.Cell stem cell, 2 2
K. Ogawa, Akira Saito, H. Matsui, Hiroshi Suzuki, S. Ohtsuka, Daisuke Shimosato, Y. Morishita, T. Watabe, H. Niwa, K. Miyazono (2006)
Activin-Nodal signaling is involved in propagation of mouse embryonic stem cellsJournal of Cell Science, 120
E. Meshorer, D. Yellajoshula, E. George, P. Scambler, David Brown, T. Misteli (2006)
Hyperdynamic plasticity of chromatin proteins in pluripotent embryonic stem cells.Developmental cell, 10 1
L. Vallier, Morgan Alexander, R. Pedersen (2005)
Activin/Nodal and FGF pathways cooperate to maintain pluripotency of human embryonic stem cellsJournal of Cell Science, 118
Tomoyuki Sumi, Norihiro Tsuneyoshi, N. Nakatsuji, H. Suemori (2007)
Apoptosis and differentiation of human embryonic stem cells induced by sustained activation of c-MycOncogene, 26
A. Tsumura, T. Hayakawa, Y. Kumaki, S. Takebayashi, M. Sakaue, Chisa Matsuoka, K. Shimotohno, F. Ishikawa, E. Li, Hiroki Ueda, J. Nakayama, M. Okano (2006)
Maintenance of self‐renewal ability of mouse embryonic stem cells in the absence of DNA methyltransferases Dnmt1, Dnmt3a and Dnmt3bGenes to Cells, 11
L. Armstrong, O. Hughes, S. Yung, L. Hyslop, R. Stewart, I. Wappler, H. Peters, T. Walter, P. Stojkovic, Jerome Evans, M. Stojkovic, M. Lako (2006)
The role of PI3K/AKT, MAPK/ERK and NFkappabeta signalling in the maintenance of human embryonic stem cell pluripotency and viability highlighted by transcriptional profiling and functional analysis.Human molecular genetics, 15 11
Jianming Jiang, Yun-Shen Chan, Y. Loh, Jun Cai, G. Tong, Ching-Aeng Lim, P. Robson, Sheng Zhong, H. Ng (2008)
A core Klf circuitry regulates self-renewal of embryonic stem cellsNature Cell Biology, 10
B. Panning, R. Jaenisch (1996)
DNA hypomethylation can activate Xist expression and silence X-linked genes.Genes & development, 10 16
M. Ramalho-Santos, Soonsang Yoon, Y. Matsuzaki, R. Mulligan, D. Melton (2002)
"Stemness": Transcriptional Profiling of Embryonic and Adult Stem CellsScience, 298
Junying Yu, M. Vodyanik, K. Smuga-Otto, Jessica Antosiewicz-Bourget, Jennifer Frane, Shulan Tian, Jeff Nie, Gudrun Jonsdottir, Victor Ruotti, R. Stewart, I. Slukvin, J. Thomson (2007)
Induced Pluripotent Stem Cell Lines Derived from Human Somatic CellsScience, 318
Kazutoshi Takahashi, S. Yamanaka (2006)
Induction of Pluripotent Stem Cells from Mouse Embryonic and Adult Fibroblast Cultures by Defined FactorsCell, 126
Y. Loh, Qiang Wu, Joon-Lin Chew, V. Vega, Weiwei Zhang, X. Chen, G. Bourque, J. George, Bernard Leong, Jun Liu, Kee‐Yew Wong, K. Sung, C. Lee, X. Zhao, K. Chiu, L. Lipovich, V. Kuznetsov, P. Robson, L. Stanton, Chia-Lin Wei, Y. Ruan, B. Lim, H. Ng (2006)
The Oct4 and Nanog transcription network regulates pluripotency in mouse embryonic stem cellsNature Genetics, 38
Jing-Yu Li, Mintie Pu, Ryutaro Hirasawa, Bin-zhong Li, Yan-Nv Huang, Rong Zeng, N. Jing, Taiping Chen, E. Li, H. Sasaki, Guo-Liang Xu (2007)
Synergistic Function of DNA Methyltransferases Dnmt3a and Dnmt3b in the Methylation of Oct4 and NanogMolecular and Cellular Biology, 27
Marius Wernig, A. Meissner, Ruth Foreman, T. Brambrink, Manching Ku, K. Hochedlinger, B. Bernstein, R. Jaenisch (2007)
In vitro reprogramming of fibroblasts into a pluripotent ES-cell-like stateNature, 448
Kitai Kim, P. Lerou, A. Yabuuchi, C. Lengerke, K. Ng, J. West, Andrew Kirby, M. Daly, G. Daley (2007)
Histocompatible Embryonic Stem Cells by ParthenogenesisScience, 315
L. Hyslop, M. Stojkovic, L. Armstrong, T. Walter, P. Stojkovic, S. Przyborski, M. Herbert, A. Murdoch, T. Strachan, M. Lako (2005)
Downregulation of NANOG Induces Differentiation of Human Embryonic Stem Cells to Extraembryonic LineagesSTEM CELLS, 23
M. Nakagawa, Michiyo Koyanagi, K. Tanabe, Kazutoshi Takahashi, T. Ichisaka, T. Aoi, K. Okita, Yuji Mochiduki, Nanako Takizawa, S. Yamanaka (2008)
Generation of induced pluripotent stem cells without Myc from mouse and human fibroblastsNature Biotechnology, 26
K. Okita, T. Ichisaka, S. Yamanaka (2007)
Generation of germline-competent induced pluripotent stem cellsNature, 448
N. Ivanova, John Dimos, C. Schaniel, J. Hackney, K. Moore, I. Lemischka (2002)
A Stem Cell Molecular SignatureScience, 298
L. Armstrong, M. Lako, W. Dean, M. Stojkovic (2006)
Epigenetic Modification Is Central to Genome Reprogramming in Somatic Cell Nuclear TransferSTEM CELLS, 24
J. Rathjen, B. Haines, Kathryn Hudson, A. Nesci, S. Dunn, P. Rathjen (2002)
Directed differentiation of pluripotent cells to neural lineages: homogeneous formation and differentiation of a neurectoderm population.Development, 129 11
I. Chambers, Douglas Colby, M. Robertson, J. Nichols, Sonia Lee, S. Tweedie, Austin Smith (2003)
Functional Expression Cloning of Nanog, a Pluripotency Sustaining Factor in Embryonic Stem CellsCell, 113
I. Wilmut, A. Schnieke, J. Mcwhir, A. Kind, K. Campbell (1997)
Viable offspring derived from fetal and adult mammalian cellsNature, 385
K. Mitsui, Yoshimi Tokuzawa, Hiroaki Itoh, K. Segawa, M. Murakami, Kazutoshi Takahashi, Masayoshi Maruyama, M. Maeda, S. Yamanaka (2003)
The Homeoprotein Nanog Is Required for Maintenance of Pluripotency in Mouse Epiblast and ES CellsCell, 113
Y. Park, Y. Kim, S. Oh, Sun Chung, S. Ku, S. Kim, Y. Choi, S. Moon (2008)
Alterations of proliferative and differentiation potentials of human embryonic stem cells during long-term cultureExperimental & Molecular Medicine, 40
H. Niwa, J. Miyazaki, Austin Smith (2000)
Quantitative expression of Oct-3/4 defines differentiation, dedifferentiation or self-renewal of ES cellsNature Genetics, 24
T. Pelton, M. Bettess, J. Lake, J. Rathjen, P. Rathjen (1998)
Developmental complexity of early mammalian pluripotent cell populations in vivo and in vitro.Reproduction, fertility, and development, 10 7-8
J. Cibelli, K. Grant, K. Chapman, K. Cunniff, Travis Worst, Heather Green, S. Walker, P. Gutin, L. Vilner, V. Tabar, T. Dominko, J. Kane, P. Wettstein, R. Lanza, L. Studer, K. Vrana, M. West (2002)
Parthenogenetic Stem Cells in Nonhuman PrimatesScience, 295
R. Humphrey, G. Beattie, Ana Lopez, N. Bucay, C. King, M. Firpo, S. Rose-John, A. Hayek (2004)
Maintenance of Pluripotency in Human Embryonic Stem Cells Is STAT3 IndependentSTEM CELLS, 22
W. Lowry, Laura Richter, Robin Yachechko, A. Pyle, J. Tchieu, Rupa Sridharan, A. Clark, K. Plath (2008)
Generation of human induced pluripotent stem cells from dermal fibroblastsProceedings of the National Academy of Sciences, 105
R.Lindsay Williams, D. Hilton, S. Pease, T. Willson, C. Stewart, D. Gearing, E. Wagner, D. Metcalf, N. Nicola, N. Gough (1988)
Myeloid leukaemia inhibitory factor maintains the developmental potential of embryonic stem cellsNature, 336
Y. Loh, Weiwei Zhang, X. Chen, J. George, H. Ng (2007)
Jmjd1a and Jmjd2c histone H3 Lys 9 demethylases regulate self-renewal in embryonic stem cells.Genes & development, 21 20
E. Revazova, N. Turovets, O. Kochetkova, L. Agapova, J. Sebastian, M. Pryzhkova, V. Smolnikova, L. Kuzmichev, J. Janus (2008)
HLA homozygous stem cell lines derived from human parthenogenetic blastocysts.Cloning and stem cells, 10 1
T. Hamazaki, Sarah Kehoe, T. Nakano, N. Terada (2006)
The Grb2/Mek Pathway Represses Nanog in Murine Embryonic Stem CellsMolecular and Cellular Biology, 26
In-Hyun Park, Rui Zhao, Jason West, A. Yabuuchi, Hongguang Huo, Tan Ince, P. Lerou, M. Lensch, George Daley (2008)
Reprogramming of human somatic cells to pluripotency with defined factorsNature, 451
K. Ogawa, R. Nishinakamura, Yuko Iwamatsu, Daisuke Shimosato, H. Niwa (2006)
Synergistic action of Wnt and LIF in maintaining pluripotency of mouse ES cells.Biochemical and biophysical research communications, 343 1
Henia Darr, Yoav Mayshar, N. Benvenisty (2006)
Overexpression of NANOG in human ES cells enables feeder-free growth while inducing primitive ectoderm features, 133
I. Brons, L. Smithers, M. Trotter, P. Rugg-Gunn, Bowen Sun, Susana Chuva, de Lopes, S. Howlett, A. Clarkson, L. Åhrlund-Richter, R. Pedersen, L. Vallier (2007)
Derivation of pluripotent epiblast stem cells from mammalian embryosNature, 448
Jianlong Wang, Sridhar Rao, J. Chu, Xiaohua Shen, D. Levasseur, T. Theunissen, S. Orkin (2006)
A protein interaction network for pluripotency of embryonic stem cellsNature, 444
Qi-Long Ying, J. Nichols, I. Chambers, Austin Smith (2003)
BMP Induction of Id Proteins Suppresses Differentiation and Sustains Embryonic Stem Cell Self-Renewal in Collaboration with STAT3Cell, 115
B. Bernstein, T. Mikkelsen, Xiaohui Xie, Michael Kamal, Dana Huebert, James Cuff, B. Fry, A. Meissner, Marius Wernig, K. Plath, R. Jaenisch, A. Wagschal, R. Feil, S. Schreiber, E. Lander (2006)
A Bivalent Chromatin Structure Marks Key Developmental Genes in Embryonic Stem CellsCell, 125
Hiroki Ura, M. Usuda, K. Kinoshita, Chuanhai Sun, Keitaro Mori, T. Akagi, T. Matsuda, H. Koide, T. Yokota (2008)
STAT3 and Oct-3/4 Control Histone Modification through Induction of Eed in Embryonic Stem Cells*Journal of Biological Chemistry, 283
S. Bendall, Morag Stewart, P. Menéndez, D. George, Kausalia Vijayaragavan, T. Werbowetski-Ogilvie, Verónica Ramos-Mejia, A. Rouleau, Jiabi Yang, M. Bossé, G. Lajoie, M. Bhatia (2007)
IGF and FGF cooperatively establish the regulatory stem cell niche of pluripotent human cells in vitroNature, 448
R. Xu, Xin Chen, D. Li, Rui Li, Gregory Addicks, Clay Glennon, T. Zwaka, J. Thomson (2002)
BMP4 initiates human embryonic stem cell differentiation to trophoblastNature Biotechnology, 20
Nimet Maherali, Rupa Sridharan, Wei Xie, J. Utikal, S. Eminli, Katrin Arnold, M. Stadtfeld, Robin Yachechko, J. Tchieu, R. Jaenisch, K. Plath, K. Hochedlinger (2007)
Directly reprogrammed fibroblasts show global epigenetic remodeling and widespread tissue contribution.Cell stem cell, 1 1
Shin-ya Yasuda, Norihiro Tsuneyoshi, Tomoyuki Sumi, Kouichi Hasegawa, T. Tada, N. Nakatsuji, H. Suemori (2006)
NANOG maintains self‐renewal of primate ES cells in the absence of a feeder layerGenes to Cells, 11
H. Wood, V. Episkopou (1999)
Comparative expression of the mouse Sox1, Sox2 and Sox3 genes from pre-gastrulation to early somite stagesMechanisms of Development, 86
J. Gurdon, J. Gurdon, J. Byrne (2004)
The First Half-Century of Nuclear TransplantationBioscience Reports, 24
Jing Liao, Zhao Wu, Ying Wang, L. Cheng, C. Cui, Yuan Gao, Taotao Chen, Lingjun Rao, Siye Chen, Nannan Jia, Huiming Dai, Shunmei Xin, Jiuhong Kang, G. Pei, Lei Xiao (2008)
Enhanced efficiency of generating induced pluripotent stem (iPS) cells from human somatic cells by a combination of six transcription factorsCell Research, 18
J. Hanna, Marius Wernig, S. Markoulaki, Chiao‐Wang Sun, A. Meissner, John Cassady, C. Beard, T. Brambrink, Li-Chen Wu, T. Townes, R. Jaenisch (2007)
Treatment of Sickle Cell Anemia Mouse Model with iPS Cells Generated from Autologous SkinScience, 318
Diego Pasini, A. Bracken, J. Hansen, M. Capillo, K. Helin (2007)
The Polycomb Group Protein Suz12 Is Required for Embryonic Stem Cell DifferentiationMolecular and Cellular Biology, 27
Marius Wernig, A. Meissner, John Cassady, R. Jaenisch (2008)
c-Myc is dispensable for direct reprogramming of mouse fibroblasts.Cell stem cell, 2 1
Jian Li, Guangwen Wang, Chengyan Wang, Yang Zhao, Hong Zhang, Zhijia Tan, Zhihua Song, M. Ding, H. Deng (2007)
MEK/ERK signaling contributes to the maintenance of human embryonic stem cell self-renewal.Differentiation; research in biological diversity, 75 4
M. Tada, Y. Takahama, K. Abe, N. Nakatsuji, T. Tada (2001)
Nuclear reprogramming of somatic cells by in vitro hybridization with ES cellsCurrent Biology, 11
Abstract Embryonic stem (ES) cells have the capacity to proliferate indefinitely in culture while maintaining the ability to differentiate to form any of the cells of the body. This unique combination of functions suggests that these cells could provide a potentially unlimited source of differentiated cells for the treatment of disease and aging. Understanding the molecular processes that underpin these functions in ES cells will allow us to harness their potential and develop strategies that control their differentiation. Combination of controlled differentiation with ground-breaking technologies for the reversal of somatic cells to an ES cell-like state promise the generation of patient-derived pluripotent cell lines for the treatment of disease in the future. pluripotency, embryonic stem cell, early primitive ectoderm-like cell, cell reprogramming Introduction The ability of embryonic stem (ES) cells to give rise to all cells of the embryo and adult, in culture or within the context of the developing embryo, has been termed pluripotency. Pluripotency resides for a short period of time during the embryonic development of a mammal within the cells of the inner cell mass (ICM) of the blastocyst and the subsequent epiblast of the pre-gastrulation embryo, and is preserved in the primordial germ lineage during later development and into adulthood. In culture, pluripotent cells have been derived from all three embryonic populations. ES cells are derived from the embryonic ICM and maintain their pluripotency in culture. The maintenance of pluripotency within these cells requires extrinsic factors, either added to the growth medium or provided by growth on a feeder layer of differentiated cells (Smith et al., 1988; Williams et al., 1988), thereby creating an appropriate external signalling environment. It has become apparent that these factors are likely to be ultimately responsible for the maintenance of a network of key transcription factors within the cell that controls pluripotency. This network includes the homeodomain transcription factor Oct4 (Nichols et al., 1998; Niwa et al., 2000), the variant homeodomain transcription factor Nanog (Chambers et al., 2003; Mitsui et al., 2003; Kuroda et al., 2005; Hough et al., 2006) and the high mobility group (HMG)—box transcription factor Sox2 (Avilion et al., 2003). The identification of the many common targets and auto-regulatory networks established by these factors provides a current focus for understanding and controlling pluripotency. Pluripotency can also be re-established in a differentiated or non-pluripotent cell by exposure of the nucleus to external factors. The introduction of the nucleus of a somatic cell into an enucleated oocyte, termed Somatic Cell Nuclear Transfer (SCNT) results in a cell that is able to give rise to all cells of the mature organism, as demonstrated when this process was used to create Dolly the sheep and more than a dozen species of mammalian clones subsequently (Wilmut et al., 1997; reviewed in Gurdon and Byrne, 2004). More recently, the use of four specific transcription factors, c-myc, Sox2, Oct4 and Klf4, has been shown to induce pluripotency in both human and mouse somatic cells (Takahashi and Yamanaka, 2006; Takahashi et al., 2007; Lowry et al., 2008; Park et al., 2008a). These studies reveal that differentiation is reversible, and provide strong foundation for the development of technologies that will enable the generation of patient-derived pluripotent cells. Immunologically matched pluripotent cells are an ideal source for the generation of cells for transplantation, and patient-derived pluripotent cells may also be useful tools for the study of disease states and drug therapies. Loss of pluripotency and commitment to specific cell lineages results in changes in gene expression that include the down-regulation of the key pluripotency transcription factors and the up-regulation of regulators of differentiation (our unpublished data and Ivanova et al., 2002; Ramalho-Santos et al., 2002), and is accompanied by a range of epigenetic alterations including DNA methylation (Carlone et al., 2005; Li et al., 2007b; Yeo et al., 2007) and chromatin modifications (Azuara et al., 2006; Mikkelsen et al., 2007). Recent identification of specific combinations of epigenetic marks associated with pluripotency (Azuara et al., 2006; Bernstein et al., 2006) has highlighted the importance of epigenetic regulation in controlling cell fate. Subsequent modifications that occur on lineage specification are likely to require removal, or erasure to some degree, for pluripotency to be successfully re-established during cell reprogramming (Armstrong et al., 2006b). This review focuses on the signalling pathways required to maintain mouse and human ES cells in culture, recent advances in our understanding of the transcriptional networks maintaining pluripotency downstream of these pathways, mechanisms for the derivation of pluripotent cell lines and an overview of the epigenetic changes underlying these processes. We also discuss, briefly, the use of related pluripotent cell populations, early primitive ectoderm-like (EPL) cells (Rathjen et al., 1999) and the newly isolated EpiSC epiblast stem cells (Brons et al., 2007; Tesar et al., 2007), for understanding the molecular basis of pluripotency. ES cells—sending the right signal ES cells require extrinsic growth factors for maintenance of pluripotency in culture, suggesting that pluripotency is an inherently unstable cell state and that ES cells are ‘primed’ for rapid differentiation. Historically, ES cells were cultured in the presence of an underlying feeder layer of mitotically inactivated fetal fibroblast cells which provides an environment capable of supporting pluripotency. The requisite factor for self-renewal of mouse ES cells was subsequently determined to be leukaemia inhibitory factor (LIF), a cytokine able to maintain mouse ES cells in the absence of the fibroblast cell feeder layer (Williams et al., 1988). LIF is not required for pluripotency of the ICM in vivo (Nichols et al., 2001) and is unable to maintain pluripotency in human ES cells suggesting that alternative mechanisms function in the maintenance of pluripotency within these contexts. Serum is also important for mouse ES cell maintenance, although bone morphogenic protein 4 (BMP4) is able to replace this requirement (Ying et al., 2003; Qi et al., 2004). In addition, Wnt signalling has been found to act synergistically with LIF to maintain pluripotency in mouse ES cells and appears to have a role in human ES cells (Sato et al., 2004; Ogawa et al., 2006). Autocrine loops of Activin/Nodal signalling have also been implicated in the maintenance of mouse ES cells (Ogawa et al., 2007). Mouse and human ES cells exhibit distinct growth habits: doubling rates for human ES cells are characteristically longer than those recorded for mouse ES cells, between 30 and 40 h (Park et al., 2008b), human ES cells require maintenance of cell–cell contacts for propagation, and spontaneous differentiation within human ES cell colonies is initiated from central cells (Oh et al., 2005), whereas spontaneous differentiation of mouse ES cells occurs at the colony periphery. Human ES cells are routinely cultured on a fibroblast cell feeder layer, but their growth factor requirements also differ from those of mouse ES cells. The growth factors capable of promoting pluripotency in this system appear to be fibroblast growth factor (FGF2), produced by the feeder layer, and insulin-like growth factor (IGF), secreted by human ES cells, which setup interdependent paracrine loops (Bendall et al., 2007). Studies focusing on extrinsic signals required for maintaining human ES cells have found FGF2 is sufficient to support growth of these cells on Matrigel, a substrate made up predominantly of laminin and collagen but with additional unknown factors (Xu et al., 2005). It is likely extrinsic signals maintaining human ES cells will inhibit BMP signalling to sustain proliferation without differentiation. BMP4 has been shown to negatively regulate pluripotency and induce trophoblast-like cell formation from human ES cells (Xu et al., 2002). Activin/Nodal and FGF2 are capable of maintaining human ES cells in the absence of feeder layers and other exogenous factors (Vallier et al., 2005). One role of Activin A in the maintenance of human ES cells has been postulated as inhibition of the BMP4 signalling pathway mediators Smads 1 and 5. Activin A and Fgf2 have recently been shown to facilitate derivation and maintenance of pluripotent mouse epiblast-derived cell lines (Brons et al., 2007; Tesar et al., 2007). Although culture conditions and extrinsic growth factors that can support pluripotent cell maintenance have been identified, how the signalling pathways controlled by these factors act to maintain the intrinsic transcription factor network required for pluripotency is poorly understood. In mouse ES cells, LIF activates JAK/STAT signalling and mitogen activated protein kinase (MapK) pathways. The choice between pluripotency and differentiation is dependent on a balance between Stat3 and extracellular signal regulated kinase (ERK) MapK activity, respectively. In mouse ES cells, BMP4 prevents differentiation through the inhibition of ERK (Qi et al., 2004) and induction of other inhibitors of differentiation such as Ids (Ying et al., 2003). Stat3 activates a number of genes that play important roles in pluripotency, including c-myc (Cartwright et al., 2005), nanog (Chambers et al., 2003; Mitsui et al., 2003; Darr et al., 2006; Suzuki et al., 2006), eed (Ura et al., 2008), jmjd1a (Ko et al., 2006) and GABPα, which appears to be required for the maintenance of Oct4 expression (Kinoshita et al., 2007). Neither STAT3 nor BMP4 activity are implicated in pluripotency of human ES cells (Xu et al., 2002; Humphrey et al., 2004), while ERK activity is required for the maintenance of pluripotency (Armstrong et al., 2006a; Li et al., 2007a). Moreover, sustained activation of c-Myc in human ES cells induces differentiation and apoptosis (Sumi et al., 2007). Thus, consistent with the differing extrinsic requirements, the intracellular signals regulating pluripotency in mouse and human ES cells appear to share little commonality, despite the conservation of the core transcription factor networks (see below) and functional similarity of the cells. Transcriptional regulation of pluripotency—key players in the network A major advance in understanding the pluripotent state has come with the identification of a network of auto- and cross-regulatory control mediated by three key transcription factors—Oct4, Nanog and Sox2 (see below; Boyer et al., 2005; Loh et al., 2006). Each of these factors is required for pluripotency both in vivo and in vitro. Loss of Oct4 or Nanog results in the loss of pluripotency and the spontaneous differentiation of cells to trophectoderm and primitive endoderm respectively (Nichols et al., 1998; Niwa et al., 2000; Chambers et al., 2003; Mitsui et al., 2003; Hough et al., 2006). Overexpression of Nanog, but not Oct4, is able to maintain pluripotency in the absence of LIF in mouse ES cells (Chambers et al., 2003; Mitsui et al., 2003) and in the absence of a feeder layer in human and primate ES cells, although the cells appear to exhibit primitive ectoderm-like characteristics (Darr et al., 2006; Yasuda et al., 2006). Sox2 is expressed in both ICM and early primitive ectoderm (Wood and Episkopou, 1999; Avilion et al., 2003) and Sox2−/− mouse embryos arrest at a similar time to Oct4−/− and Nanog−/− embryos (Avilion et al., 2003). Recently, two groups have applied chromatin immuno-precipitation (ChIP) using antibodies directed against these key transcriptional regulators to determine target genes in both mouse and human ES cells. These studies showed that many target genes were bounded by the combinations of Oct4, Nanog and Sox2 in human ES cells (Boyer et al., 2005) and Oct4 and Nanog in mouse ES cells (Sox2 was not examined; Loh et al., 2006). The results also confirmed the numerous earlier studies describing direct regulation of the key regulators by each other and auto-regulation of the factors themselves. The targets described included both actively transcribed genes and inactive genes, consistent with a role for these regulatory factors in the maintenance of pluripotency via both active and repressive mechanisms. Substantial differences were observed between Oct4/Nanog/Sox2 targets in mouse and human ES cells; these differences have been the subject of much speculation. It may be that core regulatory mechanisms are conserved although many direct target genes of the pluripotency regulating factors clearly are not. These three transcription factors bind to many hundreds of promoters in ES cells, and the transcriptional activity of the genes varies. This suggests that, while Oct4, Sox2 and Nanog impose a general program for maintaining pluripotency, other factors act with them to control expression of individual genes. Recent analysis of an extended Oct4, Sox2, Nanog transcription factor network in mouse ES cells included the Oct4- or Nanog-interacting proteins Rex1, Dax1, Zpf281 and Nac1 (Wang et al., 2006; Kim et al., 2008) and two pluripotency-associated factors c-Myc (Cartwright et al., 2005), and Klf4 (Jiang et al., 2008). This genome-wide screen of promoters bound by each of the factors found that many promoters (∼800) were occupied by multiple, common factors. Moreover, promoters bound by few of the factors were generally inactive, whereas those bound by four or more of the factors were more likely to be active in ES cells and repressed on differentiation (Kim et al., 2008). The second major finding was that genes bound by Myc and Rex1 were distinct from those bound by the other factors (Kim et al., 2008), with Myc-association correlating more highly with expressed genes, suggesting that Myc regulation differs from that of the other pluripotency factors. This work also proposes a hierarchy of factors, where Klf4 is an upstream regulator of larger feed-forward loops containing Oct4 and Sox2, a regulator of common targets including Nanog and a potential regulator of Myc, as it binds the c-Myc promoter (Fig. 1). Figure 1: View largeDownload slide Proposed hierarchy of key pluripotency network transcription factors showing auto-regulatory and cross-regulatory transcriptional loops (arrows). These factors are also able to induce pluripotency in somatic cells. Figure 1: View largeDownload slide Proposed hierarchy of key pluripotency network transcription factors showing auto-regulatory and cross-regulatory transcriptional loops (arrows). These factors are also able to induce pluripotency in somatic cells. Although a role for Sox2 in pluripotency has been established, the major function of this factor in the stable network appears to be maintaining Oct4 expression (Masui et al., 2007). However, an additional role for Sox2 in establishing a pluripotent transcriptional network cannot be overlooked (Takahashi and Yamanaka, 2006; Okita et al., 2007; Wernig et al., 2007). New work has also questioned the requirement for Nanog in maintaining pluripotency, as mouse ES cells with no detectable Nanog expression can proliferate as pluripotent stem cells (Chambers et al., 2007). Rather, Nanog may act to suppress differentiation and stabilize the pluripotent state. This and other work (Enver et al., 2005) suggest that ES cell populations are heterogeneous and cells fluctuate between states with no loss in potency. Epigenetic regulation of pluripotency—poised and ready for differentiation Examination of the epigenetic status of pluripotent cells has identified a number of pluripotent cell-specific properties that provide some insight into how pluripotent cells maintain potential while preserving the ability to respond rapidly to differentiation signals. Although the large-scale organization of genomes at the level of chromosomes is not significantly different in ES and differentiated cells, ES cell nuclei appear to have a distinct nuclear structure at key loci involved in the maintenance of pluripotency or in the process of differentiation. For example, NANOG is localized significantly more centrally in the nuclei of human ES cells compared with a more peripheral location in B cells, and OCT4 loops out from the chromosome territory in human ES cells (Wiblin et al., 2005). Replication timing analyses support these observations. Patterns of replication timing generally reflect global genome organization with actively transcribed genes commonly replicated early in S-phase and silenced genes usually replicated later. Global replication patterns are essentially identical between pluripotent murine ES and differentiated cells (Panning and Gilbert, 2005). However, the replication timing of certain stem cell- and lineage-specific genes has been shown to correlate with their expression. The ES cell-specific genes examined replicated early in ES cells but their time of replication was delayed after induction of neural differentiation, consistent with down-regulation of their expression (Hiratani et al., 2004; Perry et al., 2004). Conversely, several neuronal genes, including Sox3 and Mash1, switch to early replication on neural induction, accompanying up-regulation of their expression (Azuara et al., 2006). Although a subset of lineage-specific genes change their replication timing from late to early upon activation, a large number of lineage-specific genes, such as Ikaros, Myog and Math1, are already early replicating in ES cells even though they are not actively transcribed (Azuara et al., 2006). This led to the notion that many lineage-specific genes may be ‘primed’ for activation in ES cells. Pluripotent cells such as ES and P19 cells (a primitive ectoderm-like transformed cell line) also appear to have a unique chromatin state. Referred to as hyperdynamic or ‘breathing’ chromatin, this state is characterized by the rapid turnover of a subset of proteins associated with chromatin, including the H2B and H3 core histones when compared with non-pluripotent cells (Meshorer et al., 2006). Generation of a mutant form of histone H1, which bound stably to chromatin and reduced the dynamic exchange, blocked differentiation of ES cells and the cells eventually died on prolonged culture (Meshorer et al., 2006). These findings are consistent with a model whereby pluripotent cells have regions of unique chromatin that may be in a ‘primed state’ and in which the dynamic chromatin facilitates the rapid implementation of specific developmental programs and shutting down of programs that are not required in response to differentiation cues. Further evidence for a ‘primed state’ existing in pluripotent cells comes from the observation that large regions of chromatin in ES cells contain epigenetic marks which are characteristically associated with both repression and activation. These ‘bivalent domains’ consist of regions with histone 3 lysine 4 tri-methylation (H3K4me3), an active mark, within more extensive regions of histone 3 lysine 27 tri-methylation (H3K27me3), which is a repressive mark. Bivalent domains are often associated with regions encoding developmentally important transcription factors which are not expressed, or expressed at low levels, in ES cells (Azuara et al., 2006; Bernstein et al., 2006). In addition, ∼50% of bivalent domains contain OCT4, NANOG or SOX2 binding sites (Bernstein et al., 2006). Almost all of the genes encoding developmental regulators that were occupied by OCT4, SOX2 and NANOG and repressed in the regulatory circuitry highlighted in Boyer et al. (2005) were also shown to be the targets of Polycomb Repressive Complex 2 (PRC2). A further study identified over 200 genes in human ES cells that are bound by PRC2, display H3K27me3 marks and are transcriptionally repressed (Lee et al., 2006), and similar results were found when mouse ES cells were examined (Boyer et al., 2006). Expansion of the pluripotent factor network to include Dax1 and Klf4 showed that their transcriptional targets were also enriched for bivalent marks (Kim et al., 2008). PRC2 catalyses tri-methylation of H3K27. Disruption of key components of PRC2 in ES cells resulted in loss of H3K27me3, derepression of most target genes examined and inappropriate expression of developmental regulators and differentiation-specific genes (Azuara et al., 2006; Boyer et al., 2006; Pasini et al., 2007; Chamberlain et al., 2008). This suggests a role for PRC2 in repressing ‘primed state’ genes, which may help stabilize the pluripotent state. It is apparent, however, that H3K27me3 repressive marks are not required for the maintenance of pluripotency, but are important for subsequent differentiation (Pasini et al., 2007; Chamberlain et al., 2008). Although maintenance of a ‘primed state’ may be necessary for correct implementation of differentiation programs, epigenetic modifiers have a role to play in maintaining pluripotency. The histone 3 lysine 9 (H3K9) histone demethylases jmjd1a and jmjd2c have been shown to be required for the continued expression of pluripotent regulators in mouse ES cells, with depletion of these enzymes leading to loss of self-renewal and ES cell differentiation (Loh et al., 2007). The contribution of DNA methylation to the maintenance of pluripotency has also been examined. DNA methylation-deficient mouse ES cells are able to self-renew and proliferate (Tsumura et al., 2006), but cell death is induced on differentiation (Panning and Jaenisch, 1996). Genome-wide mapping of promoter CpG methylation patterns in mouse ES cells and correlation with gene expression, bivalent marks and Oct4, Polycomb or Nanog binding found that ∼87% of genes that lack both H3K4me3 and H3K27me3 modifications are DNA methylated (Fouse et al., 2008). Furthermore, looking in methylase mutant ES cells, Fouse et al. (2008) found that ∼1.7% of genes were expressed at significantly elevated levels compared with control ES cells and that tissue-specific genes were over-represented in this cohort. A similar comparison in fibroblasts showed that roughly 10% of genes showed increased expression. These findings suggest that DNA methylation is not a major contributor to pluripotency and supports the notion that ES cells use several different mechanisms to repress differentiation-associated genes. It will be interesting to see whether similar methylation patterns are observed in human ES cells. Like DNA methylation, genomic imprinting does not appear to play an important role in pluripotency, as the successful derivation of ES cell lines from parthenogenetic human, mouse and non-human primate embryos demonstrates (Cibelli et al., 2002; Kim et al., 2007a,b; Revazova et al., 2007). Parthenogenetic ES (pES) cells are produced from embryos that result from artificial oocyte activation without fertilization. These entirely maternally derived ES cells lack paternal imprinting but are capable of differentiation to form a broad range of cell types, as assessed by in vitro differentiation, teratoma formation and contribution to tissues in chimeric mice (Allen et al., 1994; Cibelli et al., 2002; Hikichi et al., 2007; Revazova et al., 2007, 2008). However, lower levels of contribution in chimeric mice and reduced rates of in vitro differentiation of pES cell lines have been reported (Fundele et al., 1990; Allen et al., 1994; Hikichi et al., 2007), suggesting some impairment in these cells. This may be due, at least in part, to an aberrant epigenetic state, as some improvement is observed when pES cells are subjected to reprogramming by nuclear transfer and ES cell lines are then re-derived (Hikichi et al., 2007). Many of the distinctive epigenetic signatures found in ES cells to date are important for the process of differentiation, probably to ensure the continued silencing of alternative fates once lineage choice has been made. The epigenetic modifications acquired as cells subsequently differentiate then act to enforce the stability of those cell fate decisions. Primitive ectoderm-like cells—a differentiation step in the right direction A comprehensive understanding of pluripotency and its regulation will only be gained through a broadening of research to include the primitive ectoderm, a pluripotent derivative of the ICM in the embryo. This population of cells undergoes gastrulation to form the three germ layers (progenitor cell-types) of the embryo from which differentiated tissues are subsequently derived. As such, these cells may hold the key to understanding and directing the earliest steps of cell fate choice. There are currently two in vitro models of primitive ectoderm: EPL cells and epiblast stem cells (EpiSCs). EPL cells are formed from mouse ES cells and share many of the features characteristic of primitive ectoderm including the expression of specific gene markers and a reduced ability to form extra-embryonic tissues (Pelton et al., 1998; Rathjen et al., 1999, 2002; Lake et al., 2000). EPL cells are generated via addition of conditioned media from HepG2 cells, believed to mimic signals arising from the primitive endoderm in vivo, to stimulate a controlled transition of ES cells to the EPL cell type. Several lines of evidence suggest key regulators of pluripotency are controlled by distinct mechanisms in primitive ectoderm and EPL cells compared with ICM and ES cells. Klf4 expression is down-regulated on the formation of EPL cells, suggesting major changes in the transcription factor network (our unpublished data). Nanog expression decreases in much of the primitive ectoderm (Chambers et al., 2003) and on generation of EPL cells (our unpublished data). However, a concomitant increase in Gata6 expression is not observed (our unpublished data) as is seen on loss of Nanog in ES cells (Mitsui et al., 2003; Hyslop et al., 2005; Hamazaki et al., 2006; Hough et al., 2006). Epiblast stem cell (EpiSC) lines, isolated from post-implantation mouse embryos (Brons et al., 2007; Tesar et al., 2007), also represent a post-ICM/ES cell pluripotent population. Initial characterization of these cell lines demonstrate that they are LIF-independent, requiring either Fgf2 or Activin A depending on the method of derivation. These cells express the core pluripotency-associated transcription factors Oct4, Nanog and Sox2, but have a gene expression profile similar to that of the late epiblast and distinct from ICM and ES cells. Similarly, some Oct4 target genes and epigenetic marks at specific loci also differed in ES cells and EpiSCs. Interestingly, these features of EpiSCs more closely resembled those of human ES cells, raising the possibility that human ES cells are more similar to epiblast-like cells than ICM. An investigation of the differences between ES, EPL and EpiSC cells at the level of signalling, transcriptional regulation and epigenetics will provide information on how pluripotency is maintained in distinct but directly related cell types. Ultimately, a greater understanding of the ES to EPL cell transition and manipulation of the differentiation potential of EPL cells and EpiSCs will enhance our ability to direct the differentiation of pluripotent cells toward the cell types we desire. Somatic cell reprogramming—new sources of pluripotent cells Despite the complexity of the transcriptional network in pluripotent cells, the ability to generate ES cell lines, as well as whole organisms, from somatic nuclei demonstrates the network can be re-established. Interestingly, it is the failure to completely re-set the epigenetic code that appears to reduce the efficiency of reprogramming (Armstrong et al., 2006b). A number of methods for reprogramming differentiated cells are being investigated, including fusion of differentiated cells with pluripotent cells (Tada et al., 2001; Cowan et al., 2005; Tada and Tada, 2006), and treatment of differentiated cells with extracts from pluripotent cells (Taranger et al., 2005). Currently, the most effective and reproducible methods for producing ES-like cells are SCNT and the generation of induced pluripotent stem (iPS) cells using specific transcription factors. Mouse ES cell lines have been derived by introducing nuclei from various somatic donor cell types into an enucleated oocyte and harvesting ES cells from the resulting cloned blastocyst. ES cells derived from this procedure (Fig. 2B) have been shown to express a profile of genes which is also present in ES cells derived from fertilized embryos (Brambrink et al., 2006). SCNT has been used successfully to form non-human primate blastocysts (Mitalipov et al., 2007) and, more recently, human blastocysts (French et al., 2008). However, currently no successful generation of a human ES cell line by this method has been reported. A well publicized claim was subsequently retracted (Hwang et al., 2004), and the cell line has since been shown to have been derived by parthenogenesis (Kim et al., 2007b). Figure 2: View largeDownload slide Methods for generating pluripotent stem cells. (A) Blastocyst derivation of an ES cell line. Mouse embryonic stem cells are conventionally derived from a mouse blastocyst in culture. Blastocysts can be obtained from fertilized oocytes or from parthenogenetic activation of unfertilized oocytes. ES cells from other species are similarly derived. (B) Somatic Cell Nuclear Transfer (SCNT). SCNT entails: (i) enucleation of a somatic cell (green with yellow nucleus); (ii) enucleation of an oocyte (light pink with pink nucleus); (iii) introduction of the nucleus of the somatic cell into the enucleated oocyte. The resulting cell may be propagated to the blastocyst stage and ES cell lines derived in the normal manner (as described in A). Alternatively, the blastocyst can be used to produce a cloned organism. (C) Generation of induced pluripotent stem (iPS) cells. Transduction of somatic cells with retroviral vectors expressing four transcription factors (c-Myc, Oct4, Klf4 and Sox2) was sufficient to generate a pluripotent-like cell capable of contributing to all three germ layers and to tissues in chimeric mice when re-introduced into the blastocyst. These cells represent a pluripotent-like cell with features resembling those of ES cells. Figure 2: View largeDownload slide Methods for generating pluripotent stem cells. (A) Blastocyst derivation of an ES cell line. Mouse embryonic stem cells are conventionally derived from a mouse blastocyst in culture. Blastocysts can be obtained from fertilized oocytes or from parthenogenetic activation of unfertilized oocytes. ES cells from other species are similarly derived. (B) Somatic Cell Nuclear Transfer (SCNT). SCNT entails: (i) enucleation of a somatic cell (green with yellow nucleus); (ii) enucleation of an oocyte (light pink with pink nucleus); (iii) introduction of the nucleus of the somatic cell into the enucleated oocyte. The resulting cell may be propagated to the blastocyst stage and ES cell lines derived in the normal manner (as described in A). Alternatively, the blastocyst can be used to produce a cloned organism. (C) Generation of induced pluripotent stem (iPS) cells. Transduction of somatic cells with retroviral vectors expressing four transcription factors (c-Myc, Oct4, Klf4 and Sox2) was sufficient to generate a pluripotent-like cell capable of contributing to all three germ layers and to tissues in chimeric mice when re-introduced into the blastocyst. These cells represent a pluripotent-like cell with features resembling those of ES cells. The cytoplasm of the enucleated oocyte is able to re-establish the pluripotent state via a mechanism dependent on epigenetic changes. However, the identities of the oocyte factors (and pluripotent cell factors in the cell fusion and extracts methods) that mediate this process are largely undefined. The best insight into the molecular mediators of reprogramming comes from the generation of iPS cells. This innovative technology was borne out of a radical approach in which candidate genes associated with pluripotency were expressed in non-pluripotent cells to re-establish a pluripotent state (Takahashi and Yamanaka, 2006; Fig. 2C). Mouse fibroblast cells were transduced with a combination of retroviral vectors, each encoding cDNA for a prospective reprogramming protein, and initially assayed for the ability to activate a reporter gene that is specifically expressed in mouse ES cells. More rigorous tests followed to confirm pluripotency, including in vitro differentiation and teratoma formation to produce cells derived from all three germ layers, as well injection into blastocysts and subsequent contribution to chimeric mice (Maherali et al., 2007; Okita et al., 2007; Wernig et al., 2007). Takahashi and Yamanaka (2006) identified a minimal set of four cDNAs required to produce an ‘ES-like’ iPS cell: Oct4, Sox2, Klf4 and c-myc. As discussed above, Oct4, Sox2 and Klf4 form part of a core group of pluripotency regulators that appear to work in a highly combinatorial manner to control a pluripotent-specific program of gene expression and repression (Boyer et al., 2005; Loh et al., 2006; Kim et al., 2008). c-Myc appears to lie outside this core group as its targets are generally distinct from those of the other factors (Kim et al., 2008). In addition, promoters occupied by c-Myc are likely to have the ‘active’ H3K4me3 mark, lack H3K27me3 and be expressed in ES cells, suggesting c-Myc binding is associated with chromatin modifications that support gene expression. c-Myc expression has now been shown to be dispensable for iPS cell formation, but its presence dramatically enhances the timing and efficiency of reprogramming (Nakagawa et al., 2008; Wernig et al., 2008a), consistent with a role in promoting changes in chromatin accessibility. Since the iPS cell technique was first published in mid-2006, the field has flourished. Human cells have been reprogrammed successfully (Takahashi et al., 2007; Liao et al., 2008; Lowry et al., 2008; Nakagawa et al., 2008; Park et al., 2008a), additional and alternative reprogramming factors have been identified (Yu et al., 2007; Liao et al., 2008; Nakagawa et al., 2008) and mouse models of human disease treated with cells of iPS cell origin (Hanna et al., 2007; Wernig et al., 2008b). The potential of these cells appears to match that of ES cells, with the added advantages of ease of derivation and no requirement for oocytes. However, despite the rapid pace and promise, significant hurdles remain in the race to the clinic. These include safety issues surrounding the clinical application of iPS cells due to use of genome-integrating viral vectors for the introduction and expression of the reprogramming factors. The random integration site and presence of promoter sequences increase the possibility of inappropriately inactivating or activating genes. Similarly, the use of proto-oncogenes such as myc and Klf4 correlate with an increased risk of tumour formation. In addition, caveats remain over the completeness of reprogramming of both iPS cells and SCNT-derived ES cells, with the cell line variability in differentiation potential and functionality and stability of the ‘re-differentiated’ cells still to be rigorously examined. Conclusions Understanding the molecular basis of pluripotency and the earliest differentiation processes will provide the knowledge needed to grow and manipulate pluripotent cells efficiently, reproducibly and in a manner appropriate for clinical applications. Despite differences in growth factor requirements, gene expression profiles and Oct4/Nanog/Sox2 targets in mouse and human ES cells, apparent conservation of epigenetic features, transcription factor networks and the ability of the same four factors to induce pluripotency imply that common mechanisms underlie pluripotency in mouse and human cells. Although considerable advances have been made in identifying the complex networks involved, we do not yet understand how these factors maintain pluripotency (repression of differentiation-specific genes does not appear to be required), how growth factors control and stabilize these networks or how these cells respond so precisely to differentiation cues. Similarly, the exciting prospect of generating pluripotent cells from any source warrants a deep understanding of the reprogramming process. This will lead to improvements in efficiency and methods of generation and ensure the safety of the cells for therapeutic use. Funding This work was funded by the University of Adelaide, the University of Melbourne, the Australian Stem Cell Centre and the Australian Research Council Special Centre for the Molecular Genetics of Development. References Allen ND, Barton SC, Hilton K, Norris ML, Surani MA. A functional analysis of imprinting in parthenogenetic embryonic stem cells, Development , 1994, vol. 120 (pg. 1473- 1482) Google Scholar PubMed Armstrong L, Hughes O, Yung S, Hyslop L, Stewart R, Wappler I, Peters H, Walter T, Stojkovic P, Evans J, et al. The role of PI3K/AKT, MAPK/ERK and NFkappabeta signalling in the maintenance of human embryonic stem cell pluripotency and viability highlighted by transcriptional profiling and functional analysis, Hum Mol Genet , 2006, vol. a 15 (pg. 1894- 1913) Google Scholar CrossRef Search ADS PubMed Armstrong L, Lako M, Dean W, Stojkovic M. Epigenetic modification is central to genome reprogramming in somatic cell nuclear transfer, Stem Cells , 2006, vol. b 24 (pg. 805- 814) Google Scholar CrossRef Search ADS PubMed Avilion AA, Nicolis SK, Pevny LH, Perez L, Vivian N, Lovell-Badge R. Multipotent cell lineages in early mouse development depend on SOX2 function, Genes Dev , 2003, vol. 17 (pg. 126- 140) Google Scholar CrossRef Search ADS PubMed Azuara V, Perry P, Sauer S, Spivakov M, Jorgensen HF, John RM, Gouti M, Casanova M, Warnes G, Merkenschlager M, et al. Chromatin signatures of pluripotent cell lines, Nat Cell Biol , 2006, vol. 8 (pg. 532- 538) Google Scholar CrossRef Search ADS PubMed Bendall SC, Stewart MH, Menendez P, George D, Vijayaragavan K, Werbowetski-Ogilvie T, Ramos-Mejia V, Rouleau A, Yang J, Bosse M, et al. IGF and FGF cooperatively establish the regulatory stem cell niche of pluripotent human cells in vitro, Nature , 2007, vol. 448 (pg. 1015- 1021) Google Scholar CrossRef Search ADS PubMed Bernstein BE, Mikkelsen TS, Xie X, Kamal M, Huebert DJ, Cuff J, Fry B, Meissner A, Wernig M, Plath K, et al. A bivalent chromatin structure marks key developmental genes in embryonic stem cells, Cell , 2006, vol. 125 (pg. 315- 326) Google Scholar CrossRef Search ADS PubMed Boyer LA, Lee TI, Cole MF, Johnstone SE, Levine SS, Zucker JP, Guenther MG, Kumar RM, Murray HL, Jenner RG, et al. Core transcriptional regulatory circuitry in human embryonic stem cells, Cell , 2005, vol. 122 (pg. 947- 956) Google Scholar CrossRef Search ADS PubMed Boyer LA, Plath K, Zeitlinger J, Brambrink T, Medeiros LA, Lee TI, Levine SS, Wernig M, Tajonar A, Ray MK, et al. Polycomb complexes repress developmental regulators in murine embryonic stem cells, Nature , 2006, vol. 441 (pg. 349- 353) Google Scholar CrossRef Search ADS PubMed Brambrink T, Hochedlinger K, Bell G, Jaenisch R. ES cells derived from cloned and fertilized blastocysts are transcriptionally and functionally indistinguishable, Proc Natl Acad Sci USA , 2006, vol. 103 (pg. 933- 938) Google Scholar CrossRef Search ADS PubMed Brons IG, Smithers LE, Trotter MW, Rugg-Gunn P, Sun B, Chuva de Sousa Lopes SM, Howlett SK, Clarkson A, Ahrlund-Richter L, Pedersen RA, et al. Derivation of pluripotent epiblast stem cells from mammalian embryos, Nature , 2007, vol. 448 (pg. 191- 195) Google Scholar CrossRef Search ADS PubMed Carlone DL, Lee JH, Young SR, Dobrota E, Butler JS, Ruiz J, Skalnik DG. Reduced genomic cytosine methylation and defective cellular differentiation in embryonic stem cells lacking CpG binding protein, Mol Cell Biol , 2005, vol. 25 (pg. 4881- 4891) Google Scholar CrossRef Search ADS PubMed Cartwright P, McLean C, Sheppard A, Rivett D, Jones K, Dalton S. LIF/STAT3 controls ES cell self-renewal and pluripotency by a Myc-dependent mechanism, Development , 2005, vol. 132 (pg. 885- 896) Google Scholar CrossRef Search ADS PubMed Chamberlain SJ, Yee D, Magnuson T. Polycomb repressive complex 2 is dispensable for maintenance of embryonic stem cell pluripotency, Stem Cells , 2008, vol. 26 (pg. 1496- 1505) Google Scholar CrossRef Search ADS PubMed Chambers I, Colby D, Robertson M, Nichols J, Lee S, Tweedie S, Smith A. Functional expression cloning of Nanog, a pluripotency sustaining factor in embryonic stem cells, Cell , 2003, vol. 113 (pg. 643- 655) Google Scholar CrossRef Search ADS PubMed Chambers I, Silva J, Colby D, Nichols J, Nijmeijer B, Robertson M, Vrana J, Jones K, Grotewold L, Smith A. Nanog safeguards pluripotency and mediates germline development, Nature , 2007, vol. 450 (pg. 1230- 1234) Google Scholar CrossRef Search ADS PubMed Cibelli JB, Grant KA, Chapman KB, Cunniff K, Worst T, Green HL, Walker SJ, Gutin PH, Vilner L, Tabar V, et al. Parthenogenetic stem cells in nonhuman primates, Science , 2002, vol. 295 pg. 819 Google Scholar CrossRef Search ADS PubMed Cowan CA, Atienza J, Melton DA, Eggan K. Nuclear reprogramming of somatic cells after fusion with human embryonic stem cells, Science , 2005, vol. 309 (pg. 1369- 1373) Google Scholar CrossRef Search ADS PubMed Darr H, Mayshar Y, Benvenisty N. Overexpression of NANOG in human ES cells enables feeder-free growth while inducing primitive ectoderm features, Development , 2006, vol. 133 (pg. 1193- 1201) Google Scholar CrossRef Search ADS PubMed Enver T, Soneji S, Joshi C, Brown J, Iborra F, Orntoft T, Thykjaer T, Maltby E, Smith K, Dawud RA, et al. Cellular differentiation hierarchies in normal and culture-adapted human embryonic stem cells, Hum Mol Genet , 2005, vol. 14 (pg. 3129- 3140) Google Scholar CrossRef Search ADS PubMed Fouse SD, Shen Y, Pellegrini M, Cole S, Meissner A, Van Neste L, Jaenisch R, Fan G. Promoter CpG methylation contributes to ES cell gene regulation in parallel with Oct4/Nanog, PcG complex, and histone H3 K4/K27 trimethylation, Cell Stem Cell , 2008, vol. 2 (pg. 160- 169) Google Scholar CrossRef Search ADS PubMed French AJ, Adams CA, Anderson LS, Kitchen JR, Hughes MR, Wood SH. Development of human cloned blastocysts following somatic cell nuclear transfer with adult fibroblasts, Stem Cells , 2008, vol. 26 (pg. 485- 493) Google Scholar CrossRef Search ADS PubMed Fundele RH, Norris ML, Barton SC, Fehlau M, Howlett SK, Mills WE, Surani MA. Temporal and spatial selection against parthenogenetic cells during development of fetal chimeras, Development , 1990, vol. 108 (pg. 203- 211) Google Scholar PubMed Gurdon JB, Byrne JA. The first half-century of nuclear transplantation, Biosci Rep , 2004, vol. 24 (pg. 545- 557) Google Scholar CrossRef Search ADS PubMed Hamazaki T, Kehoe SM, Nakano T, Terada N. The Grb2/Mek pathway represses Nanog in murine embryonic stem cells, Mol Cell Biol , 2006, vol. 26 (pg. 7539- 7549) Google Scholar CrossRef Search ADS PubMed Hanna J, Wernig M, Markoulaki S, Sun CW, Meissner A, Cassady JP, Beard C, Brambrink T, Wu LC, Townes TM, et al. Treatment of sickle cell anemia mouse model with iPS cells generated from autologous skin, Science , 2007, vol. 318 (pg. 1920- 1923) Google Scholar CrossRef Search ADS PubMed Hikichi T, Wakayama S, Mizutani E, Takashima Y, Kishigami S, Van Thuan N, Ohta H, Thuy Bui H, Nishikawa S, Wakayama T. Differentiation potential of parthenogenetic embryonic stem cells is improved by nuclear transfer, Stem Cells , 2007, vol. 25 (pg. 46- 53) Google Scholar CrossRef Search ADS PubMed Hiratani I, Leskovar A, Gilbert DM. Differentiation-induced replication-timing changes are restricted to AT-rich/long interspersed nuclear element (LINE)-rich isochores, Proc Natl Acad Sci USA , 2004, vol. 101 (pg. 16861- 16866) Google Scholar CrossRef Search ADS PubMed Hough SR, Clements I, Welch PJ, Wiederholt KA. Differentiation of mouse embryonic stem cells after RNA interference-mediated silencing of OCT4 and Nanog, Stem Cells , 2006, vol. 24 (pg. 1467- 1475) Google Scholar CrossRef Search ADS PubMed Humphrey RK, Beattie GM, Lopez AD, Bucay N, King CC, Firpo MT, Rose-John S, Hayek A. Maintenance of pluripotency in human embryonic stem cells is STAT3 independent, Stem Cells , 2004, vol. 22 (pg. 522- 530) Google Scholar CrossRef Search ADS PubMed Hwang WS, Ryu YJ, Park JH, Park ES, Lee EG, Koo JM, Jeon HY, Lee BC, Kang SK, Kim SJ, et al. Evidence of a pluripotent human embryonic stem cell line derived from a cloned blastocyst, Science , 2004, vol. 303 (pg. 1669- 1674) Google Scholar CrossRef Search ADS PubMed Hyslop L, Stojkovic M, Armstrong L, Walter T, Stojkovic P, Przyborski S, Herbert M, Murdoch A, Strachan T, Lako M. Downregulation of NANOG induces differentiation of human embryonic stem cells to extraembryonic lineages, Stem Cells , 2005, vol. 23 (pg. 1035- 1043) Google Scholar CrossRef Search ADS PubMed Ivanova NB, Dimos JT, Schaniel C, Hackney JA, Moore KA, Lemischka IR. A stem cell molecular signature, Science , 2002, vol. 298 (pg. 601- 604) Google Scholar CrossRef Search ADS PubMed Jiang J, Chan YS, Loh YH, Cai J, Tong GQ, Lim CA, Robson P, Zhong S, Ng HH. A core Klf circuitry regulates self-renewal of embryonic stem cells, Nat Cell Biol , 2008, vol. 10 (pg. 353- 360) Google Scholar CrossRef Search ADS PubMed Kim K, Lerou P, Yabuuchi A, Lengerke C, Ng K, West J, Kirby A, Daly MJ, Daley GQ. Histocompatible embryonic stem cells by parthenogenesis, Science , 2007, vol. a 315 (pg. 482- 486) Google Scholar CrossRef Search ADS PubMed Kim K, Ng K, Rugg-Gunn PJ, Shieh JH, Kirak O, Jaenisch R, Wakayama T, Moore MA, Pedersen RA, Daley GQ. Recombination signatures distinguish embryonic stem cells derived by parthenogenesis and somatic cell nuclear transfer, Cell Stem Cell , 2007, vol. b 1 (pg. 346- 352) Google Scholar CrossRef Search ADS Kim J, Chu J, Shen X, Wang J, Orkin SH. An extended transcriptional network for pluripotency of embryonic stem cells, Cell , 2008, vol. 132 (pg. 1049- 1061) Google Scholar CrossRef Search ADS PubMed Kinoshita K, Ura H, Akagi T, Usuda M, Koide H, Yokota T. GABPalpha regulates Oct-3/4 expression in mouse embryonic stem cells, Biochem Biophys Res Commun , 2007, vol. 353 (pg. 686- 691) Google Scholar CrossRef Search ADS PubMed Ko SY, Kang HY, Lee HS, Han SY, Hong SH. Identification of Jmjd1a as a STAT3 downstream gene in mES cells, Cell Struct Funct , 2006, vol. 31 (pg. 53- 62) Google Scholar CrossRef Search ADS PubMed Kuroda T, Tada M, Kubota H, Kimura H, Hatano SY, Suemori H, Nakatsuji N, Tada T. Octamer and Sox elements are required for transcriptional cis regulation of Nanog gene expression, Mol Cell Biol , 2005, vol. 25 (pg. 2475- 2485) Google Scholar CrossRef Search ADS PubMed Lake J, Rathjen J, Remiszewski J, Rathjen PD. Reversible programming of pluripotent cell differentiation, J Cell Sci , 2000, vol. 113 (pg. 555- 566) Google Scholar PubMed Lee TI, Jenner RG, Boyer LA, Guenther MG, Levine SS, Kumar RM, Chevalier B, Johnstone SE, Cole MF, Isono K, et al. Control of developmental regulators by Polycomb in human embryonic stem cells, Cell , 2006, vol. 125 (pg. 301- 313) Google Scholar CrossRef Search ADS PubMed Li J, Wang G, Wang C, Zhao Y, Zhang H, Tan Z, Song Z, Ding M, Deng H. MEK/ERK signaling contributes to the maintenance of human embryonic stem cell self-renewal, Differentiation , 2007, vol. a 75 (pg. 299- 307) Google Scholar CrossRef Search ADS PubMed Li JY, Pu MT, Hirasawa R, Li BZ, Huang YN, Zeng R, Jing NH, Chen T, Li E, Sasaki H, et al. Synergistic function of DNA methyltransferases Dnmt3a and Dnmt3b in the methylation of Oct4 and Nanog, Mol Cell Biol , 2007, vol. b 27 (pg. 8748- 8759) Google Scholar CrossRef Search ADS Liao J, Wu Z, Wang Y, Cheng L, Cui C, Gao Y, Chen T, Rao L, Chen S, Jia N, et al. Enhanced efficiency of generating induced pluripotent stem (iPS) cells from human somatic cells by a combination of six transcription factors, Cell Res , 2008, vol. 18 (pg. 600- 603) Google Scholar CrossRef Search ADS PubMed Loh YH, Wu Q, Chew JL, Vega VB, Zhang W, Chen X, Bourque G, George J, Leong B, Liu J, et al. The Oct4 and Nanog transcription network regulates pluripotency in mouse embryonic stem cells, Nat Genet , 2006, vol. 38 (pg. 431- 440) Google Scholar CrossRef Search ADS PubMed Loh YH, Zhang W, Chen X, George J, Ng HH. Jmjd1a and Jmjd2c histone H3 Lys 9 demethylases regulate self-renewal in embryonic stem cells, Genes Dev , 2007, vol. 21 (pg. 2545- 2557) Google Scholar CrossRef Search ADS PubMed Lowry WE, Richter L, Yachechko R, Pyle AD, Tchieu J, Sridharan R, Clark AT, Plath K. Generation of human induced pluripotent stem cells from dermal fibroblasts, Proc Natl Acad Sci USA , 2008, vol. 105 (pg. 2883- 2888) Google Scholar CrossRef Search ADS PubMed Maherali N, Sridharan R, Xie W, Utikal J, Eminli S, Arnold K, Stadtfeld M, Yachechko R, Tchieu J, Jaenisch R, et al. Directly reprogrammed fibroblasts show global epigenetic remodeling and widespread tissue contribution, Cell Stem Cells , 2007, vol. 1 (pg. 55- 70) Google Scholar CrossRef Search ADS Masui S, Nakatake Y, Toyooka Y, Shimosato D, Yagi R, Takahashi K, Okochi H, Okuda A, Matoba R, Sharov AA, et al. Pluripotency governed by Sox2 via regulation of Oct3/4 expression in mouse embryonic stem cells, Nat Cell Biol , 2007, vol. 9 (pg. 625- 635) Google Scholar CrossRef Search ADS PubMed Meshorer E, Yellajoshula D, George E, Scambler PJ, Brown DT, Misteli T. Hyperdynamic plasticity of chromatin proteins in pluripotent embryonic stem cells, Dev Cell , 2006, vol. 10 (pg. 105- 116) Google Scholar CrossRef Search ADS PubMed Mikkelsen TS, Ku M, Jaffe DB, Issac B, Lieberman E, Giannoukos G, Alvarez P, Brockman W, Kim TK, Koche RP, et al. Genome-wide maps of chromatin state in pluripotent and lineage-committed cells, Nature , 2007, vol. 448 (pg. 553- 560) Google Scholar CrossRef Search ADS PubMed Mitalipov SM, Zhou Q, Byrne JA, Ji WZ, Norgren RB, Wolf DP. Reprogramming following somatic cell nuclear transfer in primates is dependent upon nuclear remodeling, Hum Reprod , 2007, vol. 22 (pg. 2232- 2242) Google Scholar CrossRef Search ADS PubMed Mitsui K, Tokuzawa Y, Itoh H, Segawa K, Murakami M, Takahashi K, Maruyama M, Maeda M, Yamanaka S. The homeoprotein Nanog is required for maintenance of pluripotency in mouse epiblast and ES cells, Cell , 2003, vol. 113 (pg. 631- 642) Google Scholar CrossRef Search ADS PubMed Nakagawa M, Koyanagi M, Tanabe K, Takahashi K, Ichisaka T, Aoi T, Okita K, Mochiduki Y, Takizawa N, Yamanaka S. Generation of induced pluripotent stem cells without Myc from mouse and human fibroblasts, Nat Biotechnol , 2008, vol. 26 (pg. 101- 106) Google Scholar CrossRef Search ADS PubMed Nichols J, Zevnik B, Anastassiadis K, Niwa H, Klewe-Nebenius D, Chambers I, Scholer H, Smith A. Formation of pluripotent stem cells in the mammalian embryo depends on the POU transcription factor Oct4, Cell , 1998, vol. 95 (pg. 379- 391) Google Scholar CrossRef Search ADS PubMed Nichols J, Chambers I, Taga T, Smith A. Physiological rationale for responsiveness of mouse embryonic stem cells to gp130 cytokines, Development , 2001, vol. 128 (pg. 2333- 2339) Google Scholar PubMed Niwa H, Miyazaki J, Smith AG. Quantitative expression of Oct-3/4 defines differentiation, dedifferentiation or self-renewal of ES cells, Nat Genet , 2000, vol. 24 (pg. 372- 376) Google Scholar CrossRef Search ADS PubMed Ogawa K, Nishinakamura R, Iwamatsu Y, Shimosato D, Niwa H. Synergistic action of Wnt and LIF in maintaining pluripotency of mouse ES cells, Biochem Biophys Res Commun , 2006, vol. 343 (pg. 159- 166) Google Scholar CrossRef Search ADS PubMed Ogawa K, Saito A, Matsui H, Suzuki H, Ohtsuka S, Shimosato D, Morishita Y, Watabe T, Niwa H, Miyazono K. Activin-Nodal signaling is involved in propagation of mouse embryonic stem cells, J Cell Sci , 2007, vol. 120 (pg. 55- 65) Google Scholar CrossRef Search ADS PubMed Oh SK, Kim HS, Park YB, Seol HW, Kim YY, Cho MS, Ku SY, Choi YM, Kim DW, Moon SY. Methods for expansion of human embryonic stem cells, Stem Cells , 2005, vol. 23 (pg. 605- 609) Google Scholar CrossRef Search ADS PubMed Okita K, Ichisaka T, Yamanaka S. Generation of germline-competent induced pluripotent stem cells, Nature , 2007, vol. 448 (pg. 313- 317) Google Scholar CrossRef Search ADS PubMed Panning B, Jaenisch R. DNA hypomethylation can activate Xist expression and silence X-linked genes, Genes Dev , 1996, vol. 10 (pg. 1991- 2002) Google Scholar CrossRef Search ADS PubMed Panning MM, Gilbert DM. Spatio-temporal organization of DNA replication in murine embryonic stem, primary, and immortalized cells, J Cell Biochem , 2005, vol. 95 (pg. 74- 82) Google Scholar CrossRef Search ADS PubMed Park IH, Zhao R, West JA, Yabuuchi A, Huo H, Ince TA, Lerou PH, Lensch MW, Daley GQ. Reprogramming of human somatic cells to pluripotency with defined factors, Nature , 2008, vol. a 451 (pg. 141- 146) Google Scholar CrossRef Search ADS PubMed Park YB, Kim YY, Oh SK, Chung SG, Ku SY, Kim SH, Choi YM, Moon SY. Alterations of proliferative and differentiation potentials of human embryonic stem cells during long-term culture, Exp Mol Med , 2008, vol. b 40 (pg. 98- 108) Google Scholar CrossRef Search ADS Pasini D, Bracken AP, Hansen JB, Capillo M, Helin K. The polycomb group protein Suz12 is required for embryonic stem cell differentiation, Mol Cell Biol , 2007, vol. 27 (pg. 3769- 3779) Google Scholar CrossRef Search ADS PubMed Pelton TA, Bettess MD, Lake J, Rathjen J, Rathjen PD. Developmental complexity of early mammalian pluripotent cell populations in vivo and in vitro, Reprod Fertil Dev , 1998, vol. 10 (pg. 535- 549) Google Scholar CrossRef Search ADS PubMed Perry P, Sauer S, Billon N, Richardson WD, Spivakov M, Warnes G, Livesey FJ, Merkenschlager M, Fisher AG, Azuara V. A dynamic switch in the replication timing of key regulator genes in embryonic stem cells upon neural induction, Cell Cycle , 2004, vol. 3 (pg. 1645- 1650) Google Scholar CrossRef Search ADS PubMed Qi X, Li TG, Hao J, Hu J, Wang J, Simmons H, Miura S, Mishina Y, Zhao GQ. BMP4 supports self-renewal of embryonic stem cells by inhibiting mitogen-activated protein kinase pathways, Proc Natl Acad Sci USA , 2004, vol. 101 (pg. 6027- 6032) Google Scholar CrossRef Search ADS PubMed Ramalho-Santos M, Yoon S, Matsuzaki Y, Mulligan RC, Melton DA. “Stemness”: transcriptional profiling of embryonic and adult stem cells, Science , 2002, vol. 298 (pg. 597- 600) Google Scholar CrossRef Search ADS PubMed Rathjen J, Lake JA, Bettess MD, Washington JM, Chapman G, Rathjen PD. Formation of a primitive ectoderm like cell population, EPL cells, from ES cells in response to biologically derived factors, J Cell Sci , 1999, vol. 112 (pg. 601- 612) Google Scholar PubMed Rathjen J, Haines BP, Hudson KM, Nesci A, Dunn S, Rathjen PD. Directed differentiation of pluripotent cells to neural lineages: homogeneous formation and differentiation of a neurectoderm population, Development , 2002, vol. 129 (pg. 2649- 2661) Google Scholar PubMed Revazova ES, Turovets NA, Kochetkova OD, Kindarova LB, Kuzmichev LN, Janus JD, Pryzhkova MV. Patient-specific stem cell lines derived from human parthenogenetic blastocysts, Cloning Stem Cells , 2007, vol. 9 (pg. 432- 449) Google Scholar CrossRef Search ADS PubMed Revazova ES, Turovets NA, Kochetkova OD, Agapova LS, Sebastian JL, Pryzhkova MV, Smolnikova VI, Kuzmichev LN, Janus JD. HLA homozygous stem cell lines derived from human parthenogenetic blastocysts, Cloning Stem Cells , 2008, vol. 10 (pg. 11- 24) Google Scholar CrossRef Search ADS PubMed Sato N, Meijer L, Skaltsounis L, Greengard P, Brivanlou AH. Maintenance of pluripotency in human and mouse embryonic stem cells through activation of Wnt signaling by a pharmacological GSK-3-specific inhibitor, Nat Med , 2004, vol. 10 (pg. 55- 63) Google Scholar CrossRef Search ADS PubMed Smith AG, Heath JK, Donaldson DD, Wong GG, Moreau J, Stahl M, Rogers D. Inhibition of pluripotential embryonic stem cell differentiation by purified polypeptides, Nature , 1988, vol. 336 (pg. 688- 690) Google Scholar CrossRef Search ADS PubMed Sumi T, Tsuneyoshi N, Nakatsuji N, Suemori H. Apoptosis and differentiation of human embryonic stem cells induced by sustained activation of c-Myc, Oncogene , 2007, vol. 26 (pg. 5564- 5576) Google Scholar CrossRef Search ADS PubMed Suzuki A, Raya A, Kawakami Y, Morita M, Matsui T, Nakashima K, Gage FH, Rodriguez-Esteban C, Belmonte JC. Maintenance of embryonic stem cell pluripotency by Nanog-mediated reversal of mesoderm specification, Nat Clin Pract Cardiovasc Med , 2006, vol. 3 Suppl. 1(pg. S114- S122) Google Scholar CrossRef Search ADS PubMed Tada M, Tada T. Nuclear reprogramming of somatic nucleus hybridized with embryonic stem cells by electrofusion, Methods Mol Biol , 2006, vol. 329 (pg. 411- 420) Google Scholar PubMed Tada M, Takahama Y, Abe K, Nakatsuji N, Tada T. Nuclear reprogramming of somatic cells by in vitro hybridization with ES cells, Curr Biol , 2001, vol. 11 (pg. 1553- 1558) Google Scholar CrossRef Search ADS PubMed Takahashi K, Yamanaka S. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors, Cell , 2006, vol. 126 (pg. 663- 676) Google Scholar CrossRef Search ADS PubMed Takahashi K, Tanabe K, Ohnuki M, Narita M, Ichisaka T, Tomoda K, Yamanaka S. Induction of pluripotent stem cells from adult human fibroblasts by defined factors, Cell , 2007, vol. 131 (pg. 861- 872) Google Scholar CrossRef Search ADS PubMed Taranger CK, Noer A, Sorensen AL, Hakelien AM, Boquest AC, Collas P. Induction of dedifferentiation, genomewide transcriptional programming, and epigenetic reprogramming by extracts of carcinoma and embryonic stem cells, Mol Biol Cell , 2005, vol. 16 (pg. 5719- 5735) Google Scholar CrossRef Search ADS PubMed Tesar PJ, Chenoweth JG, Brook FA, Davies TJ, Evans EP, Mack DL, Gardner RL, McKay RD. New cell lines from mouse epiblast share defining features with human embryonic stem cells, Nature , 2007, vol. 448 (pg. 196- 199) Google Scholar CrossRef Search ADS PubMed Tsumura A, Hayakawa T, Kumaki Y, Takebayashi S, Sakaue M, Matsuoka C, Shimotohno K, Ishikawa F, Li E, Ueda HR, et al. Maintenance of self-renewal ability of mouse embryonic stem cells in the absence of DNA methyltransferases Dnmt1, Dnmt3a and Dnmt3b, Genes Cells , 2006, vol. 11 (pg. 805- 814) Google Scholar CrossRef Search ADS PubMed Ura H, Usuda M, Kinoshita K, Sun C, Mori K, Akagi T, Matsuda T, Koide H, Yokota T. STAT3 and Oct-3/4 Control Histone Modification through Induction of Eed in Embryonic Stem Cells, J Biol Chem , 2008, vol. 283 (pg. 9713- 9723) Google Scholar CrossRef Search ADS PubMed Vallier L, Alexander M, Pedersen RA. Activin/Nodal and FGF pathways cooperate to maintain pluripotency of human embryonic stem cells, J Cell Sci , 2005, vol. 118 (pg. 4495- 4509) Google Scholar CrossRef Search ADS PubMed Wang J, Rao S, Chu J, Shen X, Levasseur DN, Theunissen TW, Orkin SH. A protein interaction network for pluripotency of embryonic stem cells, Nature , 2006, vol. 444 (pg. 364- 368) Google Scholar CrossRef Search ADS PubMed Wernig M, Meissner A, Foreman R, Brambrink T, Ku M, Hochedlinger K, Bernstein BE, Jaenisch R. In vitro reprogramming of fibroblasts into a pluripotent ES-cell-like state, Nature , 2007, vol. 448 (pg. 318- 324) Google Scholar CrossRef Search ADS PubMed Wernig M, Meissner A, Cassady JP, Jaenisch R. c-Myc is dispensable for direct reprogramming of mouse fibroblasts, Cell Stem Cell , 2008, vol. a 2 (pg. 10- 12) Google Scholar CrossRef Search ADS PubMed Wernig M, Zhao JP, Pruszak J, Hedlund E, Fu D, Soldner F, Broccoli V, Constantine-Paton M, Isacson O, Jaenisch R. Neurons derived from reprogrammed fibroblasts functionally integrate into the fetal brain and improve symptoms of rats with Parkinson's disease, Proc Natl Acad Sci USA , 2008, vol. b 105 (pg. 5856- 5861) Google Scholar CrossRef Search ADS Wiblin AE, Cui W, Clark AJ, Bickmore WA. Distinctive nuclear organisation of centromeres and regions involved in pluripotency in human embryonic stem cells, J Cell Sci , 2005, vol. 118 (pg. 3861- 3868) Google Scholar CrossRef Search ADS PubMed Williams RL, Hilton DJ, Pease S, Willson TA, Stewart CL, Gearing DP, Wagner EF, Metcalf D, Nicola NA, Gough NM. Myeloid leukaemia inhibitory factor maintains the developmental potential of embryonic stem cells, Nature , 1988, vol. 336 (pg. 684- 687) Google Scholar CrossRef Search ADS PubMed Wilmut I, Schnieke AE, McWhir J, Kind AJ, Campbell KH. Viable offspring derived from fetal and adult mammalian cells, Nature , 1997, vol. 385 (pg. 810- 813) Google Scholar CrossRef Search ADS PubMed Wood HB, Episkopou V. Comparative expression of the mouse Sox1, Sox2 and Sox3 genes from pre-gastrulation to early somite stages, Mech Dev , 1999, vol. 86 (pg. 197- 201) Google Scholar CrossRef Search ADS PubMed Xu RH, Chen X, Li DS, Li R, Addicks GC, Glennon C, Zwaka TP, Thomson JA. BMP4 initiates human embryonic stem cell differentiation to trophoblast, Nat Biotechnol , 2002, vol. 20 (pg. 1261- 1264) Google Scholar CrossRef Search ADS PubMed Xu C, Rosler E, Jiang J, Lebkowski JS, Gold JD, O'Sullivan C, Delavan-Boorsma K, Mok M, Bronstein A, Carpenter MK. Basic fibroblast growth factor supports undifferentiated human embryonic stem cell growth without conditioned medium, Stem Cells , 2005, vol. 23 (pg. 315- 323) Google Scholar CrossRef Search ADS PubMed Yasuda SY, Tsuneyoshi N, Sumi T, Hasegawa K, Tada T, Nakatsuji N, Suemori H. NANOG maintains self-renewal of primate ES cells in the absence of a feeder layer, Genes Cells , 2006, vol. 11 (pg. 1115- 1123) Google Scholar CrossRef Search ADS PubMed Yeo S, Jeong S, Kim J, Han JS, Han YM, Kang YK. Characterization of DNA methylation change in stem cell marker genes during differentiation of human embryonic stem cells, Biochem Biophys Res Commun , 2007, vol. 359 (pg. 536- 542) Google Scholar CrossRef Search ADS PubMed Ying QL, Nichols J, Chambers I, Smith A. BMP induction of Id proteins suppresses differentiation and sustains embryonic stem cell self-renewal in collaboration with STAT3, Cell , 2003, vol. 115 (pg. 281- 292) Google Scholar CrossRef Search ADS PubMed Yu J, Vodyanik MA, Smuga-Otto K, Antosiewicz-Bourget J, Frane JL, Tian S, Nie J, Jonsdottir GA, Ruotti V, Stewart R, et al. Induced pluripotent stem cell lines derived from human somatic cells, Science , 2007, vol. 318 (pg. 1917- 1920) Google Scholar CrossRef Search ADS PubMed © The Author 2008. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Molecular Human Reproduction – Oxford University Press
Published: Aug 20, 2008
Keywords: Keywords pluripotency embryonic stem cell early primitive ectoderm-like cell cell reprogramming
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