Decoupling of H2Aub and H3K27me3 in early mammalian development

Polycomb group (PcG) proteins play critical roles during development. H2Aub and H3K27me3 are deposited by Polycomb-repressive Complex 1 and 2 (PRC1/2) respectively, and largely overlap in the genome due to mutual recruitment of the two complexes. However, whether PRC1/H2Aub and PRC2/H3K27me3 also function independently remains elusive. Here we uncovered a large-scale decoupling of H2Aub and H3K27me3 in preimplantation mouse embryos, at both canonical PcG targets and broad distal domains. H2Aub represses future bivalent genes without H3K27me3 but does not contribute to maintenance of H3K27me3-dependent non-canonical imprinting. Our study thus revealed their distinct and independent functions in early mammalian development. Mouse gametes and embryos were selected for H2AK119ub1 ChIP-seq profiling.