Maternal Eed knockout causes loss of H3K27me3 imprinting and random X inactivation in the extraembryonic cells

Abstract

Genomic imprinting is essential for mammalian development. Recent studies have revealed that maternal histone H3 Lys27 trimethylation (H3K27me3) can mediate DNA methylation-independent genomic imprinting. However, the regulatory mechanisms and functions of this new imprinting mechanism are largely unknown. Here we demonstrate that maternal Eed, an essential component of the Polycomb group complex 2 (PRC2), is required for establishing H3K27me3 imprinting. We found that all H3K27me3-imprinted genes, including Xist, lose their imprinted expression in Eed maternal knockout (matKO) embryos, resulting in male-biased lethality. Surprisingly, although maternal X-chromosome inactivation (XmCI) occurs in Eed matKO embryos at preimplantation due to loss of Xist imprinting, it is resolved at peri-implantation. Ultimately, both X chromosomes are reactivated in the embryonic cell lineage prior to random XCI, and only a single X chromosome undergoes random XCI in the extraembryonic cell lineage. Thus, our study not only demonstrates an essential role of Eed in H3K27me3 imprinting establishment but also reveals a unique XCI dynamic in the absence of Xist imprinting.

EZHIP constrains Polycomb Repressive Complex 2 activity in germ cells

“…Recent reports have shown that H3K27me3 on the maternal genome is important for the regulation of allele-specific gene expression 23 and therefore that disrupting PRC2 activity in oocyte through the deletion of Eed impairs, post-fertilization, the allelic expression of a subset of genes 53 . Conversely, it is tempting to speculate that PRC2 activity might be limited by EZHIP in order to prevent it from invading genomic regions and thus potentially promoting excessive imprinting.…”

Smchd1is a maternal effect gene required for autosomal imprinting

“…For example, loss of imprinting at the SNRPN cluster is responsible for Prader Willi syndrome or Angelman syndrome, and loss of imprinting at the IGF2/H19 and KCNQ1 clusters is responsible for Beckwith-Wiedemann syndrome (3)(4)(5)(6)(7)(8)(9)(10). Imprinted expression is enabled by germline DNA methylation or histone methylation imprints that resist preimplantation reprogramming and therefore retain their parent-oforigin specific marks (11)(12)(13)(14). Evidence to date suggests that proteins found in the oocyte establish the imprints and enable them to resist preimplantation reprogramming.…”

“…In this way these maternally derived proteins control imprinted expression. To date only a small number of such maternal effect genes have been identified, including Trim28, Zfp57, Stella, Rlim, Nlrp2, Dnmt3L, Dnmt1o and Eed (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23). Smchd1 is an epigenetic modifier, the zygotic form of which is required for both X chromosome inactivation (24,25) and silencing of clustered autosomal loci, including genes at the Snrpn and Igf2r-Airn imprinted clusters (26)(27)(28)(29).…”

Improved CUT&RUN chromatin profiling and analysis tools

“…Other advances based on our original CUT&RUN publication include CUT&RUN.Salt for fractionation of chromatin based on solubility (16) and CUT&RUN.ChIP for profiling specific protein components within complexes released by CUT&RUN digestion (17). CUT&RUN has also been adopted by others (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32), and since publication of our eLife paper we have distributed materials to >500 laboratories world-wide, with user questions and answers fielded interactively on our openaccess Protocols.io site (33).…”