Unusual chromatin status and organization of the inactive X chromosome in murine trophoblast giant cells

• DOI: 10.1242/dev.087429
• Publication Date: 2013-01-29T15:01:23Z
• Authors: Catherine Corbel; Patricia Diabango...; Anne-Valerie Gendrel; Jennifer C. Chow; Edith Heard
• Keywords: XIST; Dosage compensation; Skewed X-inactivation

Mammalian X-chromosome inactivation (XCI) enables dosage compensation between XX females and XY males. It is an essential process its absence in individuals results early lethality due primarily to extra-embryonic defects. This sensitivity X-linked gene tissues difficult reconcile with the reported tendency of escape from XCI these tissues. The precise transcriptional status inactive X chromosome different lineages has mainly been examined using transgenes or vitro differentiated stem cells degree which endogenous genes are silenced embryonic during postimplantation stages unclear. Here we investigate temporal lineage-specific X-inactivation several mouse embryos. We find stable silencing most lineages, significant levels one cell type: trophoblast giant (TGCs). To basis this epigenetic instability, chromatin structure organization TGCs obtained ectoplacental cone explants. that Xist RNA-coated a highly unusual content TGCs, presenting both heterochromatic marks such as H3K27me3 euchromatic histone H4 acetylation H3K4 methylation. Strikingly, RNA does not form overt silent nuclear compartment Cot1 hole cells. combination active features likely reflect, might underlie, partial activity TGCs.