S. Fig, Immunofluorescence detection of Ezh2 using HP3-10 ES cells differentiated for 50 hours under the epiLCs protocol Bottom panel: DAPI staining. Middle panel: Ezh2 signal alone. Top panel: Ezh2 and DAPI surimposed. Cells with a single nuclear foci of Ezh2 as well as cells with two nuclear foci of Ezh2 are present

S. Video, A cell showing 2 Ezh2-Venus fluorescent nuclear territories performed 2 cell divisions over a 24-hours tracking. Cells of interest are pointed at certain times with an arrow

S. Video, Corresponding to Fig

S. Video, Corresponding to Fig

S. Video, Corresponding to Fig

S. Video, Corresponding to Fig

S. Video, Corresponding to S2 Fig

M. Lyon, Gene Action in the X-chromosome of the Mouse (Mus musculus L.), Nature, vol.91, issue.4773, pp.372-373, 1961.
DOI : 10.1016/0014-4827(60)90023-9

B. Payer and J. Lee, X Chromosome Dosage Compensation: How Mammals Keep the Balance, Annual Review of Genetics, vol.42, issue.1, pp.733-772, 2008.
DOI : 10.1146/annurev.genet.42.110807.091711

K. Plath, S. Mlynarczyk-evans, D. Nusinow, and B. Panning, RNA and the Mechanism of X Chromosome Inactivation, Annual Review of Genetics, vol.36, issue.1, pp.233-278, 2002.
DOI : 10.1146/annurev.genet.36.042902.092433

N. Brockdorff, A. Ashworth, G. Kay, V. Mccabe, and D. Norris, The product of the mouse Xist gene is a 15 kb inactive X-specific transcript containing no conserved ORF and located in the nucleus, Cell, vol.71, issue.3, pp.515-526, 1992.
DOI : 10.1016/0092-8674(92)90519-I

K. Ng, N. Daigle, A. Bancaud, T. Ohhata, and P. Humphreys, A system for imaging the regulatory noncoding Xist RNA in living mouse embryonic stem cells, Molecular Biology of the Cell, vol.22, issue.14, pp.2634-2645, 2005.
DOI : 10.1091/mbc.E11-02-0146

I. Okamoto and E. Heard, The dynamics of imprinted X inactivation during preimplantation development in mice, Cytogenetic and Genome Research, vol.127, issue.1-4, pp.318-324, 2006.
DOI : 10.1002/mrd.1126

Q. Ying, J. Wray, J. Nichols, L. Batlle-morera, and B. Doble, The ground state of embryonic stem cell self-renewal, Nature, vol.113, issue.7194, pp.519-523, 2008.
DOI : 10.1038/nature06968

I. Brons, L. Smithers, M. Trotter, P. Rugg-gunn, and B. Sun, Derivation of pluripotent epiblast stem cells from mammalian embryos, Nature, vol.24, issue.7150, pp.191-195, 2007.
DOI : 10.1128/MCB.15.1.141

P. Tesar, J. Chenoweth, F. Brook, T. Davies, and E. Evans, New cell lines from mouse epiblast share defining features with human embryonic stem cells, Nature, vol.12, issue.7150, pp.196-199, 2007.
DOI : 10.1038/nature05972

A. Minkovsky, S. Patel, and K. Plath, Concise Review: Pluripotency and the Transcriptional Inactivation of the Female Mammalian X Chromosome, STEM CELLS, vol.107, issue.1, pp.48-54, 2012.
DOI : 10.1073/pnas.1004584107

K. Hayashi, H. Ohta, K. Kurimoto, S. Aramaki, and M. Saitou, Reconstitution of the Mouse Germ Cell Specification Pathway in Culture by Pluripotent Stem Cells, Cell, vol.146, issue.4, pp.519-532, 2011.
DOI : 10.1016/j.cell.2011.06.052

E. Heard, P. Clerc, and P. Avner, X-CHROMOSOME INACTIVATION IN MAMMALS, Annual Review of Genetics, vol.31, issue.1, pp.571-610, 1997.
DOI : 10.1146/annurev.genet.31.1.571

J. Nichols, K. Jones, J. Phillips, S. Newland, and M. Roode, Validated germline-competent embryonic stem cell lines from nonobese diabetic mice, Nature Medicine, vol.21, issue.7, pp.814-818, 2009.
DOI : 10.4049/jimmunol.177.10.6603

Q. Ying and A. Smith, Defined Conditions for Neural Commitment and Differentiation, Methods Enzymol, vol.365, pp.327-341, 2003.
DOI : 10.1016/S0076-6879(03)65023-8

S. Vigneau, S. Augui, P. Navarro, P. Avner, and P. Clerc, An essential role for the DXPas34 tandem repeat and Tsix transcription in the counting process of X chromosome inactivation, Proceedings of the National Academy of Sciences, vol.386, issue.6622, pp.7390-7395, 2006.
DOI : 10.1038/386272a0

J. Chaumeil, L. Baccon, P. Wutz, A. Heard, and E. , A novel role for Xist RNA in the formation of a repressive nuclear compartment into which genes are recruited when silenced, Genes & Development, vol.20, issue.16, pp.2223-2237, 2006.
DOI : 10.1101/gad.380906

H. Hofemeister, G. Ciotta, J. Fu, P. Seibert, and A. Schulz, Recombineering, transfection, Western, IP and ChIP methods for protein tagging via gene targeting or BAC transgenesis, Methods, vol.53, issue.4, pp.437-452, 2011.
DOI : 10.1016/j.ymeth.2010.12.026

S. Schoeftner, A. Sengupta, S. Kubicek, K. Mechtler, and L. Spahn, Recruitment of PRC1 function at the initiation of X inactivation independent of PRC2 and silencing, The EMBO Journal, vol.7, issue.13, pp.3110-3122, 2006.
DOI : 10.1101/sqb.2004.69.309

H. Marks, T. Kalkan, R. Menafra, S. Denissov, and K. Jones, The Transcriptional and Epigenomic Foundations of Ground State Pluripotency, Cell, vol.149, issue.3, pp.590-604, 2012.
DOI : 10.1016/j.cell.2012.03.026

P. Clerc and P. Avner, Role of the region 3??? to Xist exon 6 in the counting process of X-chromosome inactivation, Nature Genetics, vol.5, issue.3, pp.249-253, 1998.
DOI : 10.1007/BF00357001

C. Kress, S. Vandormael-pournin, P. Baldacci, M. Cohen-tannoudji, and C. Babinet, Nonpermissiveness for mouse embryonic stem (ES) cell derivation circumvented by a single backcross to 129/Sv strain: establishment of ES cell lines bearing the Om d conditional lethal mutation, Mammalian Genome, vol.9, issue.12, pp.998-1001, 1998.
DOI : 10.1007/s003359900914

G. Penny, G. Kay, S. Sheardown, S. Rastan, and N. Brockdorff, Requirement for Xist in X chromosome inactivation, Nature, vol.379, issue.6561, pp.131-137, 1996.
DOI : 10.1038/379131a0

P. Johnston and B. Cattanach, Controlling elements in the mouse: IV. Evidence of non-random X-inactivation, Genetical Research, vol.20, issue.02, pp.151-160, 1981.
DOI : 10.1016/0092-8674(77)90151-9

S. Augui, G. Filion, S. Huart, E. Nora, and M. Guggiari, Sensing X Chromosome Pairs Before X Inactivation via a Novel X-Pairing Region of the Xic, Science, vol.309, issue.5735, pp.1632-1636, 2007.
DOI : 10.1126/science.1113673

S. Maenner, M. Blaud, L. Fouillen, A. Savoye, and V. Marchand, 2-D Structure of the A Region of Xist RNA and Its Implication for PRC2 Association, PLoS Biology, vol.276, issue.1, p.1000276, 2010.
DOI : 10.1371/journal.pbio.1000276.s010

K. Monkhorst, I. Jonkers, E. Rentmeester, F. Grosveld, and J. Gribnau, X Inactivation Counting and Choice Is a Stochastic Process: Evidence for Involvement of an X-Linked Activator, Cell, vol.132, issue.3, pp.410-421, 2008.
DOI : 10.1016/j.cell.2007.12.036

M. Donohoe, S. Silva, S. Pinter, N. Xu, and J. Lee, The pluripotency factor Oct4 interacts with Ctcf and also controls X-chromosome pairing and counting, Nature, vol.135, issue.7251, pp.128-132, 2009.
DOI : 10.1038/nature08098

M. Escamilla-del-arenal, S. Da-rocha, and E. Heard, Evolutionary diversity and developmental regulation of X-chromosome inactivation, Human Genetics, vol.40, issue.2, pp.307-327, 2011.
DOI : 10.1016/j.molcel.2010.12.011

P. Burgoyne, A. Thornhill, S. Boudrean, S. Darling, and C. Bishop, The Genetic Basis of XX-XY Differences Present before Gonadal Sex Differentiation in the Mouse [and Discussion], Philosophical Transactions of the Royal Society B: Biological Sciences, vol.350, issue.1333, pp.253-260, 1995.
DOI : 10.1098/rstb.1995.0159

U. Mittwoch, Blastocysts prepare for the race to be male, Human Reproduction, vol.8, issue.10, pp.1550-1555, 1993.
DOI : 10.1093/oxfordjournals.humrep.a137889

A. Soma, K. Sato, and T. Nakanishi, Visualization of inactive X chromosome in preimplantation embryos utilizing MacroH2A-EGFP transgenic mouse, genesis, vol.130, issue.4, pp.259-267, 2013.
DOI : 10.1007/s00439-011-1014-9

K. Plath, J. Fang, S. Mlynarczyk-evans, R. Cao, and K. Worringer, Role of Histone H3 Lysine 27 Methylation in X Inactivation, Science, vol.300, issue.5616, pp.131-135, 2003.
DOI : 10.1126/science.1084274

W. Mak, J. Baxter, J. Silva, A. Newall, and A. Otte, Mitotically Stable Association of Polycomb Group Proteins Eed and Enx1 with the Inactive X Chromosome in Trophoblast Stem Cells, Current Biology, vol.12, issue.12, pp.1016-1020, 2002.
DOI : 10.1016/S0960-9822(02)00892-8

J. Silva, W. Mak, I. Zvetkova, R. Appanah, and T. Nesterova, Establishment of Histone H3 Methylation on the Inactive X Chromosome Requires Transient Recruitment of Eed-Enx1 Polycomb Group Complexes, Developmental Cell, vol.4, issue.4, pp.481-495, 2003.
DOI : 10.1016/S1534-5807(03)00068-6

J. Shin, M. Wallingford, J. Gallant, C. Marcho, and B. Jiao, RLIM is dispensable for Xchromosome inactivation in the mouse embryonic epiblast, Nature, 2014.

S. Bao, N. Miyoshi, I. Okamoto, T. Jenuwein, and E. Heard, Initiation of epigenetic reprogramming of the X chromosome in somatic nuclei transplanted to a mouse oocyte, EMBO reports, vol.127, issue.8, pp.748-754, 2005.
DOI : 10.1038/256640a0

I. Okamoto, S. Tan, and N. Takagi, X-chromosome inactivation in XX androgenetic mouse embryos surviving implantation, Development, vol.127, pp.4137-4145, 2000.