Distinct dynamics and functions of H2AK119ub and H3K27me3 in mouse preimplantation embryos (CUT&RUN)

Polycomb repressive complexes 1 and 2 (PRC1/2) maintain transcriptional silencing of developmental genes largely by catalyzing mono-ubiquitination of histone H2A at lysine 119 (H2AK119ub1) and trimethylation of histone H3 at lysine 27 (H3K27me3), respectively. How Polycomb domains are reprogrammed during mammalian preimplantation development remains largely unclear. Here we show that, although H2AK119ub1 and H3K27me3 are highly colocalized in gametes, they undergo differential reprogramming dynamics following fertilization. H3K27me3 maintains thousands of maternally biased domains up to the blastocyst stage, whereas maternally biased H2AK119ub1 distribution in zygotes is largely equalized at the two-cell stage. Notably, while maternal PRC2 depletion has a limited effect on global H2AK119ub1 in early embryos, it disrupts allelic H2AK119ub1 at H3K27me3 imprinting loci including Xist. By contrast, acute H2AK119ub1 depletion in zygotes does not affect H3K27me3 imprinting maintenance, at least by the four-cell stage. Importantly, loss of H2AK119ub1, but not H3K27me3, causes premature activation of developmental genes during zygotic genome activation (ZGA) and subsequent embryonic arrest. Thus, our study reveals distinct dynamics and functions of H3K27me3 and H2AK119ub1 in mouse preimplantation embryos. To determine H2Aub reprogramming dynamics, H2Aub was profiled using CUT&RUN in mouse germinal vesicle (GV) (2 rep) and metaphase II (MII) oocytes (2 rep), zygotes (2 rep), 2-cell (3 rep), 4-cell (2 rep), morula (2 rep), inner cell mass (ICM) (1 rep) from blastocysts, and epiblast (2 rep) from embryonic day 6.5 (E6.5) embryos. STAR-ChIP was used to profile H2Aub in sperm. To assess how loss of H3K27me3 may affect H2Aub, H2Aub CUT&RUN was performed in Eed KO oocytes (2 rep) and Eed maternal KO 4-cell (2 rep) and morula embryos (2 rep). To determine how loss of H2Aub affects H3K27me3, H3K27me3 CUT&RUN was performed in H2Aub-depleted 4-cell embryos (2 rep for control, 2 rep for depletion). CUT&RUN was also performed to conirm that H2Aub was depleted in 4-cell embryos (1 rep for control and 1 rep for depletion).