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The Polycomb group protein Eed protects the inactive X-chromosome from differentiation-induced reactivation

Nature Cell Biology volume 8, pages 195–202 (2006)Cite this article

Abstract

The Polycomb group (PcG) encodes an evolutionarily conserved set of chromatin-modifying proteins that are thought to maintain cellular transcriptional memory by stably silencing gene expression1. In mouse embryos that are mutated for the PcG protein Eed, X-chromosome inactivation (XCI) is not stably maintained in extra-embryonic tissues2. Eed is a component of a histone-methyltransferase complex that is thought to contribute to stable silencing in undifferentiated cells due to its enrichment on the inactive X-chromosome in cells of the early mouse embryo and in stem cells of the extra-embryonic trophectoderm lineage3,4,5,6,7,8. Here, we demonstrate that the inactive X-chromosome in Eed−/− trophoblast stem cells and in cells of the trophectoderm-derived extra-embryonic ectoderm in Eed−/− embryos remain transcriptionally silent, despite lacking the PcG-mediated histone modifications that normally characterize the facultative heterochromatin of the inactive X-chromosome. Whereas undifferentiated Eed−/− trophoblast stem cells maintained XCI, reactivation of the inactive X-chromosome occurred when these cells were differentiated. These results indicate that PcG complexes are not necessary to maintain transcriptional silencing of the inactive X-chromosome in undifferentiated stem cells. Instead, PcG proteins seem to propagate cellular memory by preventing transcriptional activation of facultative heterochromatin during differentiation.

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Figure 1: The paternal X-chromosome is active only in differentiating Eed−/− trophoblast stem cells.
Figure 2: All features of the inactive X-chromosome heterochromatin are absent in Eed−/− female trophoblast stem cells.
Figure 3: Xist RNA fails to coat the paternal X-chromosome in all Eed−/− trophoblast stem cells.
Figure 4: Absence of an epigenetic hallmark of active chromatin, H3-2mK4, from the paternal X-chromosome in Eed−/− trophoblast stem cells.
Figure 5: Lack of X-chromosome inactivation defects in the trophectoderm-derived undifferentiated extra-embryonic ectoderm and the differentiated derivatives of the primitive endoderm in Eed−/− embryos.

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Acknowledgements

We are grateful to T. Jenuwein for sharing the anti-H3-3mK27 antibody; and to K. Worringer, S. Mlynarczyk-Evans and A. Anderson for supplying Xist, Hprt, Mecp2 and Pgk1 FISH templates and probes. We also acknowledge S. Mlynarczyk-Evnas for technical advice on FISH. S.K. is a recipient of an American Cancer Society postdoctoral fellowship. This work was funded by a National Institutes of Health grant to T.M.

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Authors and Affiliations

  1. Department of Genetics and the Carolina Center for Genome Sciences, University of North Carolina, Chapel Hill, 27599-7264, NC, USA

    Sundeep Kalantry, Kyle C. Mills, Della Yee & Terry Magnuson

  2. Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, 1098 SM, The Netherlands

    Arie P. Otte

  3. Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, 94143, CA, USA

    Barbara Panning

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Correspondence to Terry Magnuson.

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Kalantry, S., Mills, K., Yee, D. et al. The Polycomb group protein Eed protects the inactive X-chromosome from differentiation-induced reactivation. Nat Cell Biol 8, 195–202 (2006). https://doi.org/10.1038/ncb1351

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