Biology subjects

Takei, N.

Publications and source records attributed to Takei, N..

4 recordsLinked to original sources

bioRxiv2026

Mouse oocytes organize mRNA-protein assemblies and ER-associated translation hubs to drive meiosis

Oocyte meiosis in animals is essential for producing fertilizable eggs. As transcription becomes largely quiescent, meiotic progression depends on temporally regulated translation of accumulated maternal mRNAs. However, the underlying mechanisms remain unclear. Here, we identified diverse and highly organized mRNA-protein assemblies in mouse oocytes that coordinate cytoplasmic mRNA regulation and enable spatiotemporal translation to drive oocyte meiosis. Twelve RNA-binding proteins (RBPs), including DDX4/VASA, HDLBP/Vigilin, and TDRD3, were assembled into widely distributed aggregates in germinal vesicle (GV)-stage oocytes. We depleted DDX4 and HDLBP using Trim-Away and found that these RBPs regulate the precise assembly of RNA granules and protein aggregates through distinct mechanisms, promoting temporal protein synthesis at cortical translation factories with the endoplasmic reticulum, termed CORTE. All 12 RBPs formed distinct mRNA-protein assemblies, whose size and distribution changed upon meiotic initiation. These findings reveal the molecular basis of spatiotemporal mRNA-protein-organelle networks underlying animal reproduction and development.

cell biology↗

bioRxiv2021

Tdrd3 regulates the progression of meiosis II through translational control of Emi2 mRNA in mouse oocytes

After completion of meiosis I, the oocyte immediately enters meiosis II and forms a metaphase II (MII) spindle without an interphase, which is fundamental for generating a haploid gamete. Here, we identify tudor domain-containing protein 3 (Tdrd3) as a novel regulator of oocyte meiosis. Although early mitotic inhibitor 2 (Emi2) protein has been shown to ensure the meiosis I to II transition and the subsequent MII spindle formation by inhibiting the anaphase-promoting complex/cyclosome (APC/C), how it accumulates after meiosis I has remained unresolved. We isolated Tdrd3 as a protein directly binding to Emi2 mRNA. In GV-stage mouse oocytes, Emi2 mRNA assembled into RNA granules containing Tdrd3, while cyclin B1 mRNA, which was translated in early meiosis I, formed different granules. Knockdown of Tdrd3 attenuated Emi2 synthesis in meiosis II without affecting cyclin B1 synthesis in meiosis I. Moreover, Tdrd3-deficient oocytes entered interphase and failed to form an MII spindle after completion of meiosis I. Taken together, our results indicate the importance of Tdrd3-mediated translational control of Emi2 mRNA, which promotes Emi2 synthesis in meiosis II, for the progression of meiosis.

developmental biology↗

bioRxiv2020

Changes in subcellular structures and states of Pumilio1 regulate the translation of target Mad2 and Cyclin B1 mRNAs

Temporal and spatial control of mRNA translation has emerged as a major mechanism for promoting diverse biological processes. However, the molecular nature of temporal control of translation remains unclear. In oocytes, many mRNAs are deposited as a translationally repressed form and are translated at appropriate timings to promote the progression of meiosis and development. Here, we show that changes in structures and states of the RNA-binding protein Pumilio1 regulate the translation of target mRNAs and progression of oocyte maturation. Pumilio1 was shown to bind to Mad2 and Cyclin B1 mRNAs, assemble highly clustered solid-like aggregates, and surround Mad2 and Cyclin B1 RNA granules in mouse oocytes. These Pumilio1 aggregates were dissolved by phosphorylation prior to the translational activation of target mRNAs. Stabilization of Pumilio1 aggregates prevented the translational activation of target mRNAs and oocyte maturation. Together, our results provide an aggregation-dissolution model for the temporal and spatial control of translation.

cell biology↗

bioRxiv2017

Changes in levels of major yolk protein in the coelomic fluid and gonad during the reproductive cycle in wild sea urchins, Mesocentrotus nudus

Both female and male sea urchins accumulate the major yolk protein (MYP) in the nutritive phagocytes of immature gonads before gametogenesis, and MYP is the most abundant protein in the coelomic fluid of both sexes. In females, MYP in the coelomic fluid is taken up by the nutritive phagocytes and transported to the growing oocytes. This study examined quantitative changes of MYP in the coelomic fluid of both sexes during the reproductive cycle of wild sea urchins, Mesocentrotus nudus. Levels of MYP in the coelomic fluid of females increased and reached a peak at the histological pre-mature stage of gonad activity (i.e. Stage 3), and positive correlation between the MYP level and the gonadosomatic index (GSI) was observed. In male sea urchins the level of MYP in the coelomic fluid increased at the pre-mature stage, though positive correlation between the MYP level and GSI was not observed. These results indicate that MYP in the coelomic fluid is suitable as a biomarker of the onset and progression of sexual maturity in female sea urchins.

physiology↗