YBX1 Mediates Alternative Splicing and Maternal mRNA Decay During Pre-Implantation Development

Abstract

Background: In mammals, maternal gene products decay and zygotic genome activation (ZGA) during maternal to zygotic transition (MZT) is critical for pre-implantation. Y-box binding protein YBX1 plays vital roles in RNA stabilization and transcriptional regulation, but its roles in pre-implantation development remain to be elucidated. The objective of this study is to investigate the role and the molecular mechanisms of YBX1 during MZT.Methods: RNA-seq datasets in mice, human, bovine, and goat embryos were re-analyzed. YBX1 was knocked down by siRNA microinjection. The 8-cell stage embryos were collected for RNA-seq. The differentially expressed genes and alternative splicing (AS) events were identified using DESeq2 and rMATs, respectively. GO/KEGG/GSEA enrichment analysis was performed using clusterProfiler and enrichplot. Furthermore, 5-EU staining was performed to confirm the effect of YBX1 knockdown on transcriptional activity.Results: The expression of YBX1 was increased during MZT in goat, bovine, human, and mice. By microinjection of siRNA against YBX1, we successfully knocked down YBX1, and the embryo development was impaired in YBX1 knockdown embryos. Using RNA-seq, we identified 1623 up-regulated and 3531 down-regulated genes in the 8-cell stage YBX1 knockdown embryos. Of note, the down-regulated genes were enriched in regulation of RNA/mRNA stability and spliceosome, suggesting that YBX1 might medicate RNA stability and AS. To this end, we identified 3284 differential AS events and 1322 differentially expressed maternal mRNAs at the 8-cell stage YBX1 knockdown embryos. Meanwhile, the splicing factors and mRNA decay related showed aberrant expression. Moreover, the transcriptional activity during ZGA in goat and mice was compromised when YBX1 was knocked down.Conclusion: Our results identify that YBX1 serves an important role in maternal mRNA decay, alternative splicing, and the transcriptional activity required for early embryogenesis, which will broaden the current understanding of YBX1 functions during the stochastic reprogramming events.