Epigenetic factors are crucial for ensuring proper chromatin dynamics during the initial stages of embryo development. Among these factors, the Polycomb group (PcG) of proteins plays a key role in establishing correct transcriptional programmes during mouse embryogenesis. PcG proteins are classified into two complexes: Polycomb repressive complex 1 (PRC1) and PRC2. Both complexes decorate histone proteins with distinct post-translational modifications (PTMs) that are predictive of a silent transcriptional chromatin state. In recent years, a critical adaptation of the classical techniques to analyse chromatin profiles and to study biochemical interactions at low-input resolution has allowed us to deeply explore PcG molecular mechanisms in the very early stages of mouse embryo development– from fertilisation to gastrulation, and from zygotic genome activation (ZGA) to specific lineages differentiation. These advancements provide a foundation for a deeper understanding of the fundamental role Polycomb complexes play in early development and have elucidated the mechanistic dynamics of PRC1 and PRC2. In this review, we discuss the functions and molecular mechanisms of both PRC1 and PRC2 during early mouse embryo development, integrating new studies with existing knowledge. Furthermore, we highlight the molecular functionality of Polycomb complexes from ZGA through gastrulation, with a particular focus on non-canonical imprinted and bivalent genes, and Hox cluster regulation.

表观遗传因素对于确保胚胎发育初始阶段适当的染色质动态至关重要。在这些因素中，多梳蛋白组 (PcG) 在小鼠胚胎发生过程中建立正确的转录程序中起着关键作用。 PcG 蛋白分为两种复合物：Polycomb 抑制复合物 1 (PRC1) 和 PRC2。这两种复合物都用独特的翻译后修饰 (PTM) 装饰组蛋白，这些修饰可预测沉默转录染色质状态。近年来，对分析染色质谱和低输入分辨率下生化相互作用的经典技术进行了关键的改造，使我们能够深入探索小鼠胚胎发育早期阶段（从受精到原肠胚形成）的 PcG 分子机制。从合子基因组激活（ZGA）到特定谱系分化。这些进展为更深入地了解 Polycomb 复合物在早期发育中所发挥的基本作用奠定了基础，并阐明了 PRC1 和 PRC2 的机制动力学。在这篇综述中，我们讨论了 PRC1 和 PRC2 在小鼠早期胚胎发育过程中的功能和分子机制，将新的研究与现有知识相结合。此外，我们还重点介绍了 ZGA 通过原肠胚形成的 Polycomb 复合物的分子功能，特别关注非规范印记基因和二价基因以及 Hox 簇调控。