MEIKIN expression and its C-terminal phosphorylation by PLK1 is closely related the metaphase-anaphase transition by affecting cyclin B1 and Securin stabilization in meiotic oocyte.

Oocyte meiotic maturation failure and chromosome abnormality is one of the main causes of infertility, abortion, and diseases. The mono-orientation of sister chromatids during the first meiosis is important for ensuring accurate chromosome segregation in oocytes. MEIKIN is a germ cell-specific protein that can regulate the mono-orientation of sister chromatids and the protection of the centromeric cohesin complex during meiosis I.

Rad9a is involved in chromatin decondensation and post-zygotic embryo development in mice.

Zygotic chromatin undergoes extensive reprogramming immediately after fertilization. It is generally accepted that maternal factors control this process. However, little is known about the underlying mechanisms.

CENP-A regulates chromosome segregation during the first meiosis of mouse oocytes.

Proper chromosome separation in both mitosis and meiosis depends on the correct connection between kinetochores of chromosomes and spindle microtubules. Kinetochore dysfunction can lead to unequal distribution of chromosomes during cell division and result in aneuploidy, thus kinetochores are critical for faithful segregation of chromosomes. Centromere protein A (CENP-A) is an important component of the inner kinetochore plate.

Protective effect of antioxidants on the pre-maturation aging of mouse oocytes.

Pre-maturation aging of immature oocytes may adversely affect the fate of an oocyte. Oxidative stress is one of the most detrimental factors affecting oocyte developmental competence and maturation during aging. In this study, experiments were designed to examine whether supplementation of antioxidants in a culture medium could protect immature mouse oocytes from damages caused by oxidative stress.

Rad9a is required for spermatogonia differentiation in mice.

Spermatogenesis in testes requires precise spermatogonia differentiation. Spermatocytes lacking the Rad9a gene are arrested in pachytene prophase, implying a possible role for RAD9A in spermatogonia differentiation. However, numerous RAD9A-positive pachytene spermatocytes are still observed in mouse testes following Rad9a excision using the Stra8-Cre system, and it is unclear whether Rad9a deletion in spermatogonia interrupts differentiation.

N6-Methyladenosine Sequencing Highlights the Involvement of mRNA Methylation in Oocyte Meiotic Maturation and Embryo Development by Regulating Translation in Xenopus laevis.

During the oogenesis of Xenopus laevis, oocytes accumulate maternal materials for early embryo development. As the transcription activity of the oocyte is silenced at the fully grown stage and the global genome is reactivated only by the mid-blastula embryo stage, the translation of maternal mRNAs accumulated during oocyte growth should be accurately regulated. Previous evidence has illustrated that the poly(A) tail length and RNA binding elements mediate RNA translation regulation in the oocyte.

Nek11 regulates asymmetric cell division during mouse oocyte meiotic maturation.

Nek11, a member of the never in mitosis gene A (NIMA) family, is activated in somatic cells associated with G1/S or G2/M arrest. However, its function in meiosis is unknown. In this research, the expression, localization and functions of NEK11 in the mouse oocyte meiotic maturation were examined.

Cep55 regulates spindle organization and cell cycle progression in meiotic oocyte.

Cep55 is a relatively novel member of the centrosomal protein family. Here, we show that Cep55 is expressed in mouse oocytes from the germinal vesicle (GV) to metaphase II (MII) stages. Immuostaining and confocal microscopy as well as time lapse live imaging after injection of mRNA encoding fusion protein of Cep55 and GFP identified that Cep55 was localized to the meiotic spindle, especially to the spindle poles at metaphase, while it was concentrated at the midbody in telophase in meiotic oocytes.

Cyclin B3 controls anaphase onset independent of spindle assembly checkpoint in meiotic oocytes.

Cyclin B3 is a relatively new member of the cyclin family whose functions are little known. We found that depletion of cyclin B3 inhibited metaphase-anaphase transition as indicated by a well-sustained MI spindle and cyclin B1 expression in meiotic oocytes after extended culture. This effect was independent of spindle assembly checkpoint activity, since both Bub3 and BubR1 signals were not observed at kinetochores in MI-arrested cells.

Nuf2 is required for chromosome segregation during mouse oocyte meiotic maturation.

Nuf2 plays an important role in kinetochore-microtubule attachment and thus is involved in regulation of the spindle assembly checkpoint in mitosis. In this study, we examined the localization and function of Nuf2 during mouse oocyte meiotic maturation. Myc6-Nuf2 mRNA injection and immunofluorescent staining showed that Nuf2 localized to kinetochores from germinal vesicle breakdown to metaphase I stages, while it disappeared from the kinetochores at the anaphase I stage, but relocated to kinetochores at the MII stage.

Casein kinase 1 (α, δ and ε) localize at the spindle poles, but may not be essential for mammalian oocyte meiotic progression.

CK1 (casein kinase 1) is a family of serine/threonine protein kinase that is ubiquitously expressed in eukaryotic organism. CK1 members are involved in the regulation of many cellular processes. Particularly, CK1 was reported to phosphorylate Rec8 subunits of cohesin complex and regulate chromosome segregation in meiosis in budding yeast and fission yeast.

Deletion of Mylk1 in oocytes causes delayed morula-to-blastocyst transition and reduced fertility without affecting folliculogenesis and oocyte maturation in mice.

The mammalian oocyte undergoes two rounds of asymmetric cell divisions during meiotic maturation and fertilization. Acentric spindle positioning and cortical polarity are two major factors involved in asymmetric cell division, both of which are thought to depend on the dynamic interaction between myosin II and actin filaments. Myosin light chain kinase (MLCK), encoded by the Mylk1 gene, could directly phosphorylate and activate myosin II.

Arrested human embryos are more likely to have abnormal chromosomes than developing embryos from women of advanced maternal age.

Background: Aneuploidy is one of the major factors that result in low efficiency in human infertility treatment by in vitro fertilization (IVF). The development of DNA microarray technology allows for aneuploidy screening by analyzing all 23 pairs of chromosomes in human embryos. All chromosome screening for aneuploidy is more accurate than partial chromosome screening, as errors can occur in any chromosome.

Scaffold subunit Aalpha of PP2A is essential for female meiosis and fertility in mice.

Ppp2r1a encodes the scaffold subunit Aalpha of protein phosphatase 2A (PP2A), which is an important and ubiquitously expressed serine threonine phosphatase family and plays a critical role in many fundamental cellular processes. To identify the physiological role of PP2A in female germ cell meiosis, we selectively disrupted Ppp2r1a expression in oocytes by using the Cre-Loxp conditional knockout system. Here we report for the first time that oocyte-specific deletion of Ppp2r1a led to severe female subfertility without affecting follicle survival, growth, and ovulation.

Maternal diabetes causes abnormal dynamic changes of endoplasmic reticulum during mouse oocyte maturation and early embryo development.

Background: The adverse effects of maternal diabetes on oocyte maturation and embryo development have been reported.

Methods: In this study, we used time-lapse live cell imaging confocal microscopy to investigate the dynamic changes of ER and the effects of diabetes on the ER's structural dynamics during oocyte maturation, fertilization and early embryo development.

Results: We report that the ER first became remodeled into a dense ring around the developing MI spindle, and then surrounded the spindle during migration to the cortex.

Overexpression of SETβ, a protein localizing to centromeres, causes precocious separation of chromatids during the first meiosis of mouse oocytes.

Chromosome segregation in mammalian oocyte meiosis is an error-prone process, and any mistake in this process may result in aneuploidy, which is the main cause of infertility, abortion and many genetic diseases. It is now well known that shugoshin and protein phosphatase 2A (PP2A) play important roles in the protection of centromeric cohesion during the first meiosis. PP2A can antagonize the phosphorylation of rec8, a member of the cohesin complex, at the centromeres and thus prevent cleavage of rec8 and so maintain the cohesion of chromatids.

The distribution and possible role of ERK8 in mouse oocyte meiotic maturation and early embryo cleavage.

It is well known that extracellular signal-regulated kinase 8 (ERK8) plays pivotal roles in various mitotic events. But its physiological roles in oocyte meiotic maturation remain unclear. In this study, we found that although no specific ERK8 signal was detected in oocyte at the germinal vesicle stage, ERK8 began to migrate to the periphery of chromosomes shortly after germinal vesicle breakdown.

Knockdown of UCHL5IP causes abnormalities in γ-tubulin localisation, spindle organisation and chromosome alignment in mouse oocyte meiotic maturation.

UCHL5IP is one of the subunits of the haus complex, which is important for microtubule generation, spindle bipolarity and accurate chromosome segregation in Drosophila and human mitotic cells. In this study, the expression and localisation of UCHL5IP were explored, as well as its functions in mouse oocyte meiotic maturation. The results showed that the UCHL5IP protein level was consistent during oocyte maturation and it was localised to the meiotic spindle in MI and MII stages.

Nek9 regulates spindle organization and cell cycle progression during mouse oocyte meiosis and its location in early embryo mitosis.

Nek9 (also known as Nercc1), a member of the NIMA (never in mitosis A) family of protein kinases, regulates spindle formation, chromosome alignment and segregation in mitosis. Here, we showed that Nek9 protein was expressed from germinal vesicle (GV) to metaphase II (MII) stages in mouse oocytes with no detectable changes. Confocal microscopy identified that Nek9 was localized to the spindle poles at the metaphase stages and associated with the midbody at anaphase or telophase stage in both meiotic oocytes and the first mitotic embyros.

The roles of parathyroid hormone-like hormone during mouse preimplantation embryonic development.

Parathyroid hormone-like hormone (PTHLH) was first identified as a parathyroid hormone (PTH)-like factor responsible for humoral hypercalcemia in malignancies in the 1980s. Previous studies demonstrated that PTHLH is expressed in multiple tissues and is an important regulator of cellular and organ growth, development, migration, differentiation, and survival. However, there is a lack of data on the expression and function of PTHLH during preimplantation embryonic development.

The G protein coupled receptor 3 is involved in cAMP and cGMP signaling and maintenance of meiotic arrest in porcine oocytes.

The arrest of meiotic prophase in mammalian oocytes within fully grown follicles is dependent on cyclic adenosine monophosphate (cAMP) regulation. A large part of cAMP is produced by the Gs-linked G-protein-coupled receptor (GPR) pathway. In the present study, we examined whether GPR3 is involved in the maintenance of meiotic arrest in porcine oocytes.

Checkpoint kinase 1 is essential for meiotic cell cycle regulation in mouse oocytes.

Checkpoint kinase 1 (Chk1) plays key roles in all currently defined cell cycle checkpoints, but its functions in mouse oocyte meiosis remain unclear. In this study, we report the expression, localization and functions of Chk1 in mouse oocyte meiosis. Chk1 was expressed from germinal vesicle (GV) to metaphase II (MII) stages and localized to the spindle from pro-metaphase I (pro-MI) to MII stages in mouse oocytes.

Localization and function of the Ska complex during mouse oocyte meiotic maturation.

The Ska (spindle and kinetochore-associated) complex is composed of three proteins: Ska1, Ska2 and Ska3. It is required for stabilizing kinetochore-microtubule (KT-MT) interactions and silencing spindle checkpoint during mitosis. However, its roles in meiosis remain unclear.

Synaptotagmin1 is required for spindle stability and metaphase-to-anaphase transition in mouse oocytes.

Synaptotagmin1, a calcium sensor for exocytosis, forms the 7S complex, or so-called SNARE protein complex, together with SNAP -25, syntaxin and synaptobrevin to mediate docking and fusion of synaptic vesicles to the plasma membrane of the nerve terminal. Here, we identified the unique localization, expression and function of Syt1 during mouse oocyte meiotic maturation by using confocal microscopy, western blotting, Morpholino-based knockdown and time-lapse live cell imaging. We showed that Syt1 expression was gradually increased during oocyte maturation.

Septin1 is required for spindle assembly and chromosome congression in mouse oocytes.

The bipolar spindle is a complex molecular machinery that drives chromosome congression and segregation. During meiosis in the mouse multiple microtubule organizing centers aggregate to form a bipolar intermediate followed by elongation and establishment of the barrel-shaped acentriolar meiotic spindle. Previous studies have shown that septin1 is localized to spindle poles in mitosis, suggesting its possible involvement in spindle assembly.