H2AK119ub1 guides maternal inheritance and zygotic deposition of H3K27me3 in mouse embryos. H2AK119ub1 guides maternal inheritance and zygotic deposition of H3K27me3 in mouse embryos

Parental epigenomes are established during gametogenesis. While they are largely reset soon after fertilization in mammals, maternal histone H3 tri-methylation at lysine 27 (H3K27me3) is inherited by the next generation embryos. How H3K27me3 is properly established in oocytes and passed on to the embryos remains elusive. Furthermore, although polycomb repressive complex 2 (PRC2)-mediated H3K27me3 is known to interplay with PRC1-mediated mono-ubiquitination of histone H2A at lysine 119 (H2AK119ub1) to coordinate repressive polycomb domains in embryonic stem cells (ESCs), how they act in vivo remains unknown. To address these questions, here we profiled H2AK119ub1 dynamics during mouse oogenesis and preimplantation development, and investigated its functions in maternal inheritance of H3K27me3. Integrative analyses with H3K27me3 dynamics revealed that an unusually broad and distal-rich distribution of H2AK119ub1 is established during oogenesis and co-transmitted to embryos together with H3K27me3. On the other hand, an ESC-like canonical distribution of H2AK119ub1 is newly established at the 2-cell stage, a few days earlier than that of H3K27me3. Deficiency in polycomb group ring finger 1 (PCGF1) and PCGF6, essential components of variant PRC1 (vPRC1), leads to massive reduction of H2AK119ub1 and gene-selective loss of H3K27me3 in oocytes. The gene-selective deficient state of H3K27me3 is irreversibly inherited by embryos, which causes bi-allelic expression of H3K27me3-dependent imprinted genes, including Xist, embryonic sublethality, and placental enlargement at term. Collectively, our study not only revealed instructive in vivo dynamics of H2AK119ub1 for H3K27me3 establishment at the maternal-to-embryonic transition, but also identified PCGF1/6-PRC1 as an essential player for intergenerational epigenetic inheritance. Overall design: H2AK119ub1 CUT&RUN was performed in WT mouse oocytes and B6/PWK F1 hybrid preimplantation embryos. H2AK119ub1 and H3K27me3 CUT&RUN and RNAseq were performed in Pcgf1, Pcgf6, Pcgf1/6 CTR and KO oocytes. H3K27me3 CUT&RUN and RNAseq were performed in xPWK F1 hybrid Pcgf1/6 CTR and maternal KO late 2-cell, morula embryos. RNA-seq was performed in xPWK F1 hybrid Pcgff1/6 CTR and maternal KO extra-embryonic ectoderm.

亲本表观基因组在配子发生过程中得以建立。尽管在哺乳动物中，亲本表观基因组大多会在受精后快速重置，但母源组蛋白H3赖氨酸27三甲基化（histone H3 tri-methylation at lysine 27，H3K27me3）可传递给子代胚胎。目前尚不清楚H3K27me3如何在卵母细胞中被精准建立，并传递至胚胎中。此外，尽管已知多梳抑制复合体2（polycomb repressive complex 2，PRC2）介导的H3K27me3，可与多梳抑制复合体1（PRC1）介导的组蛋白H2A赖氨酸119单泛素化（mono-ubiquitination of histone H2A at lysine 119，H2AK119ub1）相互作用，以协同调控胚胎干细胞（embryonic stem cells，ESCs）中的沉默型多梳结构域，但二者在体内的具体作用机制仍不明确。为解答上述问题，本研究对小鼠卵发生及植入前发育过程中的H2AK119ub1动态变化进行了谱学分析，并探究了其在H3K27me3母源遗传中的功能。结合H3K27me3动态变化的整合分析显示，H2AK119ub1在卵发生过程中形成了异常宽泛且富含远端调控区域的分布模式，并与H3K27me3一同共传递至胚胎中。另一方面，H2AK119ub1的胚胎干细胞样经典分布模式在2细胞期重新建立，这一时间早于H3K27me3的模式建立约数天。多梳家族环指蛋白1（polycomb group ring finger 1，PCGF1）与PCGF6作为变异型多梳抑制复合体1（variant PRC1，vPRC1）的核心组分，其缺失会导致卵母细胞中H2AK119ub1的大量减少，以及基因选择性的H3K27me3丢失。这种基因选择性的H3K27me3缺失状态会被胚胎不可逆地继承，进而导致依赖H3K27me3的印记基因（包括Xist）出现双等位基因表达，引发胚胎亚致死及足月胎盘肥大。综上，本研究不仅揭示了母源向胚胎转换过程中，H2AK119ub1对H3K27me3建立具有指导意义的体内动态变化模式，还确定了PCGF1/6-PRC1是跨代表观遗传的关键调控因子。实验设计概述：对野生型（wild type，WT）小鼠卵母细胞及B6/PWK F1杂交子代植入前胚胎开展了H2AK119ub1靶标切割与释放测序（Cleavage Under Targets and Release Using Nuclease，CUT&RUN）；在Pcgf1、Pcgf6、Pcgf1/6对照组（control，CTR）及敲除（knockout，KO）卵母细胞中，分别进行了H2AK119ub1、H3K27me3的CUT&RUN测序及RNA测序（RNA-seq）；在xPWK F1杂交子代Pcgf1/6对照组及母源敲除晚期2细胞期、桑椹胚胚胎中，开展了H3K27me3的CUT&RUN测序及RNA-seq；在xPWK F1杂交子代Pcgf1/6对照组及母源敲除的胚外外胚层组织中开展了RNA-seq。