Rlim-Dependent and -Independent Pathways for X Chromosome Inactivation in Female ESCs

Publication date: 26 December 2017
Source:Cell Reports, Volume 21, Issue 13
Author(s): Feng Wang, Kurtis N. McCannell, Ana Bošković, Xiaochun Zhu, JongDae Shin, Jun Yu, Judith Gallant, Meg Byron, Jeanne B. Lawrence, Lihua J. Zhu, Stephen N. Jones, Oliver J. Rando, Thomas G. Fazzio, Ingolf Bach
During female mouse embryogenesis, two forms of X chromosome inactivation (XCI) ensure dosage compensation from sex chromosomes. Beginning at the four-cell stage, imprinted XCI (iXCI) exclusively silences the paternal X (Xp), and this pattern is maintained in extraembryonic cell types. Epiblast cells, which give rise to the embryo proper, reactivate the Xp (XCR) and undergo a random form of XCI (rXCI) around implantation. Both iXCI and rXCI depend on the long non-coding RNA Xist. The ubiquitin ligase RLIM is required for iXCI in vivo and occupies a central role in current models of rXCI. Here, we demonstrate the existence of Rlim-dependent and Rlim-independent pathways for rXCI in differentiating female ESCs. Upon uncoupling these pathways, we find more efficient Rlim-independent XCI in ESCs cultured under physiological oxygen conditions. Our results revise current models of rXCI and suggest that caution must be taken when comparing XCI studies in ESCs and mice.

Graphical abstract

Teaser

Embryonic stem cells are widely used for investigating X chromosome inactivation, the silencing of one X chromosome in females. Wang et al. show that this process is driven by two independent pathways, one that requires the ubiquitin ligase Rlim and another that functions independently of Rlim and is sensitive to environmental conditions.


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