Abstract
Imprinted X-inactivation silences genes exclusively on the paternally-inherited X-chromosome and is a paradigm of transgenerational epigenetic inheritance in mammals. Here, we test the role of maternal vs. zygotic Polycomb repressive complex 2 (PRC2) protein EED in orchestrating imprinted X-inactivation in mouse embryos. In maternal-null (Eedm-/-) but not zygotic-null (Eed-/-) early embryos, the maternal X-chromosome ectopically induced Xist and underwent inactivation. Eedm-/- females subsequently stochastically silenced Xist from one of the two X-chromosomes and displayed random X-inactivation. This effect was exacerbated in embryos lacking both maternal and zygotic EED (Eedmz-/-), suggesting that zygotic EED can also contribute to the onset of imprinted X-inactivation. Xist expression dynamics in Eedm-/- embryos resemble that of early human embryos, which lack oocyte-derived maternal PRC2 and only undergo random X-inactivation. Thus, expression of PRC2 in the oocyte and transmission of the gene products to the embryo may dictate the occurrence of imprinted X-inactivation in mammals.
Highlights
X-chromosome inactivation results in the mitotically-stable transcriptional inactivation of one of the two X-chromosomes in female mammals in order to equalize X-linked gene expression between males and females (Morey and Avner, 2011; Plath et al, 2002)
Polycomb repressive complex 2 (PRC2) proteins and H3K27me3 are first enriched on the prospective inactive paternal X-chromosome in the early mouse embryo at the 8–16 cell morula stage (Okamoto et al, 2004)
We assessed the accumulation of EED, H3K27me3, and Xist RNA by immunofluorescence (IF) combined with RNA fluorescent in situ hybridization (FISH) in wild-type (WT) embryonic day (E) 3.5 blastocyst embryos (Cloutier et al, 2018; Hinten et al, 2016), which are in the process of silencing paternal X-linked genes and establishing imprinted X-inactivation (Borensztein et al, 2017; Namekawa et al, 2010; Patrat et al, 2009; Wang et al, 2016)
Summary
X-chromosome inactivation results in the mitotically-stable transcriptional inactivation of one of the two X-chromosomes in female mammals in order to equalize X-linked gene expression between males and females (Morey and Avner, 2011; Plath et al, 2002). Without EED from the mother’s egg, early embryos failed to initiate imprinted X-inactivation and reverted instead to random X-inactivation, where either X-chromosome is chosen for silencing in female cells. This pattern resembles what happens in early human embryos, which are unable to undergo imprinted X-inactivation because a woman’s eggs lack the EED protein. Consistent with a role for PRC2 in X-inactivation, we and others previously showed that postimplantation female mouse embryos mutant for the Polycomb gene Eed fail to maintain silencing of paternal X-linked genes during imprinted X-inactivation (Kalantry and Magnuson, 2006; Kalantry et al, 2006; Wang et al, 2001). We test the hypothesis that oocyte-derived PRC2 orchestrates imprinted X-inactivation in the early embryo
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
