Super Pol II Domains enhance minor ZGA through 3D-interaction to ensure the integrity of major transcriptional waves in ZGA delayed mammals (RNA-Seq)

Zygotic genome activation (ZGA) represents the inaugural post-fertilization transcription event. In mouse, RNA polymerase II (Pol II) initiates embryonic transcription through a step-wise transition, but the ZGA initiation process remains unclear in non-rodents. Here, Pol II profiling in bovine and porcine embryos, combined with multi-omics data across four mammalian species, revealed strong intergenic Pol II clusters, termed super Pol II domains (SPDs), that boost minor ZGA gene expression via chromatin interactions in bovine. Intriguingly, a similar strategy was found in human embryos, which also exhibit delayed ZGA followed by rapid up-regulation of minor ZGA genes. By contrast, these genes are precociously activated in porcine and mouse gametes before fertilization. Moreover, disruption of SPD structure, which decreases two minor ZGA genesKLF17orDUXAexpression, and knockdown them in bovine, leads to aberrant gene activation and impeded embryogenesis. Our findings highlight SPD enhancement as a species-specific evolutionary adaptation for initiating transcription in bovine and human embryos, thus illustrating previously underappreciated diversity in mammalian reproductive developmental strategies.