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

Mammalian oocyte development depends on the temporally controlled translation of maternal transcripts, particularly in the coordination of meiotic and early embryonic development when transcription has ceased. The translation of mRNA is regulated by various RNA-binding proteins. We show that the absence of cytoplasmic polyadenylation element-binding protein 3 (CPEB3) negatively affects female reproductive fitness. CPEB3-depleted oocytes undergo meiosis normally but experience early embryonic arrest due to a disrupted transcriptome, leading to aberrant protein expression and the subsequent failure of embryonic transcription initiation. We found that CPEB3 stabilizes a subset of mRNAs with a significantly longer 3'UTR that is enriched in its distal region with cytoplasmic polyadenylation elements. Overall, our results suggest that CPEB3 is an important maternal factor that regulates the stability and translation of a subclass of mRNAs that are essential for the initiation of embryonic transcription and thus for embryonic development.

• Keywords
• embryo, mRNA, oocyte, translation,
• MeSH
• 3' Untranslated Regions genetics   MeSH
• Embryonic Development genetics   MeSH
• Meiosis genetics   MeSH
• RNA, Messenger genetics   metabolism   MeSH
• Mice MeSH
• Oocytes * metabolism   MeSH
• Polyadenylation MeSH
• RNA-Binding Proteins * metabolism   genetics   MeSH
• RNA Stability genetics   MeSH
• Gene Expression Regulation, Developmental MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• 3' Untranslated Regions MeSH
• Cpeb3 protein, mouse MeSH Browser
• RNA, Messenger MeSH
• RNA-Binding Proteins * 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

A serine/threonine-specific protein kinase B (PKB), also known as Akt, is a key factor in the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway that regulates cell survival, metabolism and proliferation. Akt phosphorylates many downstream specific substrates, which subsequently control the nuclear envelope breakdown (NEBD), centrosome maturation, spindle assembly, chromosome segregation, and cytokinesis. In vertebrates, Akt is also an important player during oogenesis and preimplantation development. In the signaling pathways regulating mRNA translation, Akt is involved in the control of mammalian target of rapamycin complex 1 (mTORC1) and thereby regulates the activity of a translational repressor, the eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1). In this review, we summarize the functions of Akt in mitosis, meiosis and early embryonic development. Additionally, the role of Akt in the regulation of mRNA translation is addressed with respect to the significance of this process during early development.

• Keywords
• Akt kinase, early embryo, mRNA translation, mTORC1, meiosis, mitosis, oocyte, spindle,
• MeSH
• Phosphatidylinositol 3-Kinase metabolism   MeSH
• Embryonic Development MeSH
• Phosphatidylinositol 3-Kinases * metabolism   MeSH
• Phosphoproteins metabolism   MeSH
• Phosphorylation genetics   MeSH
• Oocytes metabolism   MeSH
• Oogenesis MeSH
• Protein Serine-Threonine Kinases metabolism   MeSH
• Proto-Oncogene Proteins c-akt * metabolism   MeSH
• Mammals metabolism   MeSH
• Signal Transduction MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Phosphatidylinositol 3-Kinase MeSH
• Phosphatidylinositol 3-Kinases * MeSH
• Phosphoproteins MeSH
• Protein Serine-Threonine Kinases MeSH
• Proto-Oncogene Proteins c-akt * MeSH

Cyclin dependent kinase 1 (CDK1) has been primarily identified as a key cell cycle regulator in both mitosis and meiosis. Recently, an extramitotic function of CDK1 emerged when evidence was found that CDK1 is involved in many cellular events that are essential for cell proliferation and survival. In this review we summarize the involvement of CDK1 in the initiation and elongation steps of protein synthesis in the cell. During its activation, CDK1 influences the initiation of protein synthesis, promotes the activity of specific translational initiation factors and affects the functioning of a subset of elongation factors. Our review provides insights into gene expression regulation during the transcriptionally silent M-phase and describes quantitative and qualitative translational changes based on the extramitotic role of the cell cycle master regulator CDK1 to optimize temporal synthesis of proteins to sustain the division-related processes: mitosis and cytokinesis.

• Keywords
• 4E-BP1, CDK1, M-phase, mRNA, mTOR, translation,
• MeSH
• Cell Cycle genetics   physiology   MeSH
• Humans MeSH
• RNA, Messenger genetics   metabolism   MeSH
• CDC2 Protein Kinase genetics   metabolism   MeSH
• Cell Cycle Proteins genetics   metabolism   MeSH
• TOR Serine-Threonine Kinases genetics   metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• RNA, Messenger MeSH
• CDC2 Protein Kinase MeSH
• Cell Cycle Proteins MeSH
• TOR Serine-Threonine Kinases MeSH

In the absence of transcription, the regulation of gene expression in oocytes is controlled almost exclusively at the level of transcriptome and proteome stabilization, and translation. A subset of maternal transcripts is stored in a translationally dormant state in the oocyte, and temporally driven translation of specific mRNAs propel meiotic progression, oocyte-to-embryo transition and early embryo development. We identified Ank2.3 as the only transcript variant present in the mouse oocyte and discovered that it is translated after nuclear envelope breakdown. Here we show that Ank2.3 mRNA is localized in higher concentration in the oocyte nucleoplasm and, after nuclear envelope breakdown, in the newly forming spindle where its translation occurs. Furthermore, we reveal that Ank2.3 mRNA contains an oligo-pyrimidine motif at 5'UTR that predetermines its translation through a cap-dependent pathway. Lastly, we show that prevention of ANK2 translation leads to abnormalities in oocyte cytokinesis.

• MeSH
• Ankyrins genetics   metabolism   MeSH
• Spatio-Temporal Analysis * MeSH
• Cytokinesis * MeSH
• Embryo, Mammalian cytology   physiology   MeSH
• Meiosis * MeSH
• RNA, Messenger genetics   metabolism   MeSH
• Mice MeSH
• Oocytes cytology   physiology   MeSH
• Oogenesis MeSH
• Gene Expression Regulation, Developmental * MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Ank2 protein, mouse MeSH Browser
• Ankyrins MeSH
• RNA, Messenger MeSH

The tight correlation between mRNA distribution and subsequent protein localization and function indicate a major role for mRNA localization within the cell. RNA localization, followed by local translation, presents a mechanism for spatial and temporal gene expression regulation utilized by various cell types. However, little is known about mRNA localization and translation in the mammalian oocyte and early embryo. Importantly, fully-grown oocyte becomes transcriptionally inactive and only utilizes transcripts previously synthesized and stored during earlier development. We discovered an abundant RNA population in the oocyte and early embryo nucleus together with RNA binding proteins. We also characterized specific ribosomal proteins, which contribute to translation in the oocyte and embryo. By applying selected markers to mouse and human oocytes, we found that there might be a similar mechanism of RNA metabolism in both species. In conclusion, we visualized the localization of RNAs and translation machinery in the oocyte, that could shed light on this terra incognita of these unique cell types in mouse and human.

• MeSH
• Embryo, Mammalian metabolism   ultrastructure   MeSH
• Cells, Cultured MeSH
• Humans MeSH
• RNA, Messenger analysis   genetics   MeSH
• Mice MeSH
• Oocytes metabolism   ultrastructure   MeSH
• RNA-Binding Proteins analysis   genetics   MeSH
• Protein Biosynthesis * MeSH
• Transcriptome MeSH
• Gene Expression Regulation, Developmental * MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• RNA, Messenger MeSH
• RNA-Binding Proteins MeSH

Although the involvement of the extracellular signal-regulated kinases 1 and 2 (ERK1/2) pathway in the regulation of cytostatic factor (CSF) activity; as well as in microtubules organization during meiotic maturation of oocytes; has already been described in detail; rather less attention has been paid to the role of ERK1/2 in the regulation of mRNA translation. However; important data on the role of ERK1/2 in translation during oocyte meiosis have been documented. This review focuses on recent findings regarding the regulation of translation and the role of ERK1/2 in this process in the meiotic cycle of mammalian oocytes. The specific role of ERK1/2 in the regulation of mammalian target of rapamycin (mTOR); eukaryotic translation initiation factor 4E (eIF4E) and cytoplasmic polyadenylation element binding protein 1 (CPEB1) activity is addressed along with additional focus on the other key players involved in protein translation.

• Keywords
• CPEB1, ERK1/2, MAP kinase, eIF4E, mTOR, oocyte, translation,
• MeSH
• Cytoplasm genetics   metabolism   MeSH
• Eukaryotic Initiation Factor-4E metabolism   MeSH
• mRNA Cleavage and Polyadenylation Factors metabolism   MeSH
• Phosphatidylinositol 3-Kinases metabolism   MeSH
• Humans MeSH
• Meiosis * MeSH
• RNA, Messenger genetics   metabolism   MeSH
• Mitogen-Activated Protein Kinase 1 metabolism   MeSH
• Mitogen-Activated Protein Kinase 3 metabolism   MeSH
• Mitogen-Activated Protein Kinases metabolism   MeSH
• Oocytes metabolism   MeSH
• Polyadenylation MeSH
• Protein Biosynthesis * MeSH
• Signal Transduction MeSH
• TOR Serine-Threonine Kinases metabolism   MeSH
• Protein Binding MeSH
• Gene Expression Regulation, Developmental MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Eukaryotic Initiation Factor-4E MeSH
• mRNA Cleavage and Polyadenylation Factors MeSH
• RNA, Messenger MeSH
• Mitogen-Activated Protein Kinase 1 MeSH
• Mitogen-Activated Protein Kinase 3 MeSH
• Mitogen-Activated Protein Kinases MeSH
• TOR Serine-Threonine Kinases MeSH

Fully grown mammalian oocytes utilize transcripts synthetized and stored during earlier development. RNA localization followed by a local translation is a mechanism responsible for the regulation of spatial and temporal gene expression. Here we show that the mouse oocyte contains 3 forms of cap-dependent translational repressor expressed on the mRNA level: 4E-BP1, 4E-BP2 and 4E-BP3. However, only 4E-BP1 is present as a protein in oocytes, it becomes inactivated by phosphorylation after nuclear envelope breakdown and as such it promotes cap-dependent translation after NEBD. Phosphorylation of 4E-BP1 can be seen in the oocytes after resumption of meiosis but it is not detected in the surrounding cumulus cells, indicating that 4E-BP1 promotes translation at a specific cell cycle stage. Our immunofluorescence analyses of 4E-BP1 in oocytes during meiosis I showed an even localization of global 4E-BP1, as well as of its 4E-BP1 (Thr37/46) phosphorylated form. On the other hand, 4E-BP1 phosphorylated on Ser65 is localized at the spindle poles, and 4E-BP1 phosphorylated on Thr70 localizes on the spindle. We further show that the main positive regulators of 4E-BP1 phosphorylation after NEBD are mTOR and CDK1 kinases, but not PLK1 kinase. CDK1 exerts its activity toward 4E-BP1 phosphorylation via phosphorylation and activation of mTOR. Moreover, both CDK1 and phosphorylated mTOR co-localize with 4E-BP1 phosphorylated on Thr70 on the spindle at the onset of meiotic resumption. Expression of the dominant negative 4E-BP1 mutant adversely affects translation and results in spindle abnormality. Taken together, our results show that the phosphorylation of 4E-BP1 promotes translation at the onset of meiosis to support the spindle assembly and suggest an important role of CDK1 and mTOR kinases in this process. We also show that the mTOR regulatory pathway is present in human oocytes and is likely to function in a similar way as in mouse oocytes.

• Keywords
• 4E-BP1, CDK1, cumulus cells, kinase, mRNA, mTOR, meiosis, oocyte, spindle, translation,
• MeSH
• Adaptor Proteins, Signal Transducing MeSH
• Spindle Apparatus genetics   MeSH
• Cell Cycle genetics   MeSH
• Eukaryotic Initiation Factors MeSH
• Phosphoproteins genetics   metabolism   MeSH
• Phosphorylation MeSH
• Humans MeSH
• Mice MeSH
• Oocytes growth & development   metabolism   MeSH
• CDC2 Protein Kinase genetics   MeSH
• Cell Cycle Proteins MeSH
• Protein Biosynthesis MeSH
• TOR Serine-Threonine Kinases genetics   MeSH
• Carrier Proteins genetics   metabolism   MeSH
• Gene Expression Regulation, Developmental MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Adaptor Proteins, Signal Transducing MeSH
• Eif4ebp1 protein, mouse MeSH Browser
• Eukaryotic Initiation Factors MeSH
• Phosphoproteins MeSH
• mTOR protein, mouse MeSH Browser
• CDC2 Protein Kinase MeSH
• Cell Cycle Proteins MeSH
• TOR Serine-Threonine Kinases MeSH
• Carrier Proteins MeSH