Dynamic landscapes of H3K27ac in mouse preimplantation embryos

Histone acetylation H3K27ac is a well-established chromatin marker for active enhancers and promoters. However, reprogramming dynamics of H3K27ac during maternal-to-zygotic transition (MZT) in mammalian embryos has not been well studied. By profiling the allelic landscape of H3K27ac during mouse MZT, here we show that H3K27ac undergoes three waves of rapid global transitions from oocyte to 2-cell stages. Notably, germinal vesicle (GV) oocyte and zygote are globally hyperacetylated by forming noncanonical broad H3K27ac domains that correlate with broad H3K4me3 and open chromatin. H3K27ac also marks genomic regions primed for activation including ZGA gene promoters, retrotransposons, and active alleles of imprinted genes. Importantly, both CBP/p300 and HDAC activities play important roles in regulating the H3K27ac dynamics and are essential for pre-implantation development. Specifically, CBP/p300 deposits broad H3K27ac domains in zygotes and open condensed chromatin at putative enhancers to ensure proper ZGA. In contrast, HDACs mediate the broad to canonical H3K27ac transition to safeguard ZGA by preventing premature expression of developmental genes and promoting ZGA gene activation. Our study demonstrates that coordinated activities of CBP/p300 and HDACs during mouse MZT are essential for ZGA and mouse pre-implantation development. Overall design: We profiled the allelic landscape of H3K27ac in mouse early embryos using low-input CUT&RUN, by crossing B6D2F1/J female mice and PWK/PhJ male mice. The role of CBP/p300 and HDACs activities in regulating H3K27ac dynamics and ZGA in mouse early preimplantation embryos were studied using A485 and TSA treatment followed by RNA-seq and ATAC-seq comparisons.