Translational regulation plays a pivotal role during pre-implantation development. However, the mechanisms by which messenger RNAs (mRNAs) are selectively regulated over time, along with their dynamic utilization and fate during this period, remain largely unknown. Here, we performed fraction-resolved polysome profiling and characterized translational dynamics across oocytes and early embryo development. This approach allowed us to examine the changes in translation during pre-implantation development in high resolution and uncover previously unrecognized modes of translational selectivity. We observed a stage-specific delay in translation, characterized by the postponed recruitment of stored mRNAs-either unbound or associated with light ribosomal fractions-into actively translating polysomes (heavy fraction). Comparative analysis of translatome with proteomics, RNA N6-methyladenosine modifications, and mRNA features further revealed both coordinated and distinct regulatory mechanisms during pre-implantation development. Furthermore, we identified a eukaryotic initiation factor 1A domain containing 3, Eif1ad3, which is exclusively translated at the two-cell stage and is essential for embryonic development by regulating ribosome biogenesis and protein synthesis. Collectively, our study provides a valuable resource of spatiotemporal translational regulation in mammalian pre-implantation development and highlights a previously uncharacterized translation initiation factor critical for early embryos.

• MeSH
• Adenosine analogs & derivatives   metabolism   MeSH
• Blastocyst metabolism   MeSH
• Embryonic Development * genetics   MeSH
• Eukaryotic Initiation Factor-1 metabolism   genetics   MeSH
• RNA, Messenger * metabolism   genetics   MeSH
• Mice MeSH
• Oocytes metabolism   growth & development   MeSH
• Polyribosomes metabolism   genetics   MeSH
• Protein Biosynthesis * MeSH
• Ribosomes metabolism   MeSH
• Gene Expression Regulation, Developmental * MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Adenosine MeSH
• Eukaryotic Initiation Factor-1 MeSH
• RNA, Messenger * MeSH
• N-methyladenosine MeSH Browser

Translational regulation is pivotal during preimplantation development. However, how mRNAs are selected for temporal regulation and their dynamic utilization and fate during this period are still unknown. Using a high-resolution ribosome profiling approach, we analyzed the transcriptome, as well as monosome- and polysome-bound RNAs of mouse oocytes and embryos, defining an unprecedented extent of spatiotemporal translational landscapes during this rapid developmental phase. We observed previously unknown mechanisms of translational selectivity, i.e., stage-wise deferral of loading monosome-bound mRNAs to polysome for active translation, continuous translation of both monosome and polysome-bound mRNAs at the same developmental stage, and priming to monosomes after initial activation. We showed that a eukaryotic initiation factor Eif1ad3, which is exclusively translated in the 2-Cell embryo, is required for ribosome biogenesis post embryonic genome activation. Our study thus provides genome-wide datasets and analyses of spatiotemporal translational dynamics accompanying mammalian germ cell and embryonic development and reveals the contribution of a novel translation initiation factor to mammalian pre-implantation development.

• Publication type
• Journal Article MeSH
• Preprint MeSH

Translation is critical for development as transcription in the oocyte and early embryo is silenced. To illustrate the translational changes during meiosis and consecutive two mitoses of the oocyte and early embryo, we performed a genome-wide translatome analysis. Acquired data showed significant and uniform activation of key translational initiation and elongation axes specific to M-phases. Although global protein synthesis decreases in M-phases, translation initiation and elongation activity increases in a uniformly fluctuating manner, leading to qualitative changes in translation regulation via the mTOR1/4F/eEF2 axis. Overall, we have uncovered a highly dynamic and oscillatory pattern of translational reprogramming that contributes to the translational regulation of specific mRNAs with different modes of polysomal occupancy/translation that are important for oocyte and embryo developmental competence. Our results provide new insights into the regulation of gene expression during oocyte meiosis as well as the first two embryonic mitoses and show how temporal translation can be optimized. This study is the first step towards a comprehensive analysis of the molecular mechanisms that not only control translation during early development, but also regulate translation-related networks employed in the oocyte-to-embryo transition and embryonic genome activation.

• MeSH
• Embryonic Development * MeSH
• Meiosis MeSH
• RNA, Messenger genetics   metabolism   MeSH
• Mice MeSH
• Oocytes * cytology   growth & development   metabolism   MeSH
• Protein Biosynthesis * MeSH
• Gene Expression Regulation, Developmental MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• RNA, Messenger MeSH