The protein kinase Cs (PKCs) are a family of Ser/Thr protein kinases categorized into three subfamilies: classical, novel, and atypical. The phosphorylation of PKC in germ cells is not well defined. In this study, we described the subcellular localization of phopho-PKC in the process of mouse oocyte maturation, fertilization, and early embryonic mitosis. Confocal microscopy revealed that phospho-PKC (pan) was distributed abundantly in the nucleus at the germinal vesicle stage. After germinal vesicle breakdown, phospho-PKC was localized in the vicinity of the condensed chromosomes, distributed in the whole meiotic spindle, and concentrated at the spindle poles. After metaphase I, phospho-PKC was translocated gradually to the spindle mid-zone during emission of the first polar body. After sperm penetration and electrical activation, the distribution of phospho-PKC was moved from the spindle poles to the spindle mid-zone. After the extrusion of the second polar body (PB2) phospho-PKC was localized in the area between the oocyte and the PB2. In fertilized eggs, phospho-PKC was concentrated in the pronuclei except for the nucleolus. Phospho-PKC was dispersed after pronuclear envelope breakdown, but distributed on the entire spindle at mitotic metaphase. The results suggest that PKC activation may play important roles in regulating spindle organization and stabilization, polar-body extrusion, and nuclear activity during mouse oocyte meiosis, fertilization, and early embryonic mitosis.
Zhen-Yu Zheng, Qing-Zhang Li, Da-Yuan Chen, Heide Schatten and Qing-Yuan Sun
Zhao-Jia Ge, Heide Schatten, Cui-Lian Zhang and Qing-Yuan Sun
It has become a current social trend for women to delay childbearing. However, the quality of oocytes from older females is compromised and the pregnancy rate of older women is lower. With the increased rate of delayed childbearing, it is becoming more and more crucial to understand the mechanisms underlying the compromised quality of oocytes from older women, including mitochondrial dysfunctions, aneuploidy and epigenetic changes. Establishing proper epigenetic modifications during oogenesis and early embryo development is an important aspect in reproduction. The reprogramming process may be influenced by external and internal factors that result in improper epigenetic changes in germ cells. Furthermore, germ cell epigenetic changes might be inherited by the next generations. In this review, we briefly summarise the effects of ageing on oocyte quality. We focus on discussing the relationship between ageing and epigenetic modifications, highlighting the epigenetic changes in oocytes from advanced-age females and in post-ovulatory aged oocytes as well as the possible underlying mechanisms.
Keqin Yan, Dingqing Feng, Jing Liang, Qing Wang, Lin Deng, Xiao Zhang, Bin Ling and Daishu Han
Viral infections of the ovary may perturb ovarian functions. However, the mechanisms underlying innate immune responses in the ovary are poorly understood. The present study demonstrates that cytosolic viral DNA sensor signaling initiates the innate immune response in mouse ovarian granulosa cells and affects endocrine function. The cytosolic DNA sensors p204 and cGAS and their common signaling adaptor stimulator of interferon (IFN) genes (STING) were constitutively expressed in granulosa cells. Transfection with VACV70, a synthetic vaccinia virus (VACV) DNA analog, induced the expression of type I interferons (IFNA/B) and major inflammatory cytokines (TNFA and IL6) through IRF3 and NF-κB activation respectively. Moreover, several IFN-inducible antiviral proteins, including 2′,5′-oligoadenylate synthetase, IFN-stimulating gene 15 and Mx GTPase 1, were also induced by VACV70 transfection. The innate immune responses in granulosa cells were significantly reduced by the transfection of specific small-interfering RNAs targeting p204, cGas or Sting. Notably, the VACV70-triggered innate immune responses affected steroidogenesis in vivo and in vitro. The data presented in this study describe the mechanism underlying ovarian immune responses to viral infection.
Jie Mei, Yuan Yan, Shi-Yuan Li, Wen-Jie Zhou, Qun Zhang, Ming-Qing Li and Hai-Xiang Sun
Decidualization renders the endometrium transiently receptive to an implanting blastocyst although the underlying mechanisms remain incompletely understood. The aim of this study was to determine the role of chemokine CXCL16 and its receptor CXCR6 in the decidualization during pregnancy. Here, the expression of CXCL16 was investigated in endometrial tissues, decidua and placenta in this study. Compared with endometrial tissue, protein expression of CXCL16 was significantly higher in tissues from the fertile control samples, especially in villus. Meanwhile, the primary trophoblast cells and decidual stromal cells (DSCs) secreted more CXCL16 and expressed higher CXCR6 compared to endometrial stromal cells (ESCs) in vitro. Stimulation with the inducer of decidualization (8-bromoadenosine 3′,5′-cyclic with medroxyprogesterone acetate, 8-Br-cAMP plus MPA) significantly upregulated the expression of CXCL16 and CXCR6 in ESCs in vitro. After treatment with exogenous recombinant human CXCL16 (rhCXCL16) or trophoblast-secreted CXLC16, decidualised ESCs showed a significant decidual response, mainly characterised by increased prolactin (PRL) secretion. Simultaneously, PI3K/PDK1/AKT/Cyclin D1 pathway in decidualised ESCs were activated by rhCXCL16, and AKT inhibitor GS 690693 abolished the PRL secretion of ESCs that was triggered by rhCXCL16. Finally, the impaired CXCL16/CXCR6 expression could be observed at the maternal–foetal interface from patients who have experienced spontaneous abortion. This study suggests that the CXCL16/CXCR6 axis contributes to the progression of ESC decidualization by activating PI3K/PDK1/AKT/Cyclin D1 pathway. It unveils a new paradigm at the maternal–foetal interface in which CXCL16 is an initiator for the molecular crosstalk that enhances decidualization of ESCs.
Yong-Hai Li, Yi Hou, Wei Ma, Jin-Xiang Yuan, Dong Zhang, Qing-Yuan Sun and Wei-Hua Wang
CD9 is a cell surface protein that participates in many cellular processes, such as cell adhesion. Fertilization involves sperm and oocyte interactions including sperm binding to oocytes and sperm–oocyte fusion. Thus CD9 may play an essential role during fertilization in mammals. The present study was conducted to examine whether CD9 is present in porcine gametes and whether it participates in the regulation of sperm–oocyte interactions. The presence of CD9 in ovarian tissues, oocytes and spermatozoa was examined by immunohistochemistry, immunofluorescence and immunoblotting. Sperm binding and penetration of oocytes treated with CD9 antibody were examined by in vitro fertilization. The results showed that CD9 was present on the plasma membrane of oocytes at different developmental stages. A 24 kDa protein was found in oocytes during in vitro maturation by immunoblotting and its quantity was significantly (P < 0.001) increased as oocytes underwent maturation and reached the highest level after the oocytes had been cultured for 44 h. No positive CD9 staining was found in the spermatozoa. Both sperm binding to ooplasma and sperm penetration into oocytes were significantly (P < 0.01) reduced in anti-CD9 antibody-treated oocytes (1.2 ± 0.2 per oocyte and 16.6% respectively) as compared with oocytes in the controls (2.5 ± 0.4 per oocyte and 70.3% respectively). These results indicated that CD9 is expressed in pig oocytes during early growth and meiotic maturation and that it participates in sperm–oocyte interactions during fertilization.
Yun-Kao Cao, Zhi-Sheng Zhong, Da-Yuan Chen, Gui-Xue Zhang, Heide Schatten and Qing-Yuan Sun
The small GTPase Ran controls numerous cellular processes of the mitotic cell cycle. In this experiment, we investigated the localization and possible roles of Ran during mouse oocyte meiotic maturation, fertilization and early cleavage by using confocal laser scanning microscopy, antibody microinjection and microtubule disturbance. The results showed that Ran was localized mainly in the nucleus (except for the nucleolus) in the oocyte, zygote and early embryo. At pro-metaphase of meiosis I, Ran distributed throughout the cell, but predominantly concentrated around the condensed chromosomes. During the completion of meiosis I and meiosis II, it concentrated to the meiotic spindle microtubules except for the midbody region. After sperm penetration, Ran dispersed with the extrusion of the second polar body and gradually concentrated in the male and female pronuclei thereafter. Ran was also observed to exist diffusely in the cytoplasm in prophase; it concentrated at the mitotic spindle, and migrated to the nucleus during early cleavage. Ran’s concentration around the spindle disappeared when microtubule assembly was inhibited by colchicine, while it was concentrated around the chromosomes after microtubule stabilization with taxol treatment. Ran did not display any role in cytokinesis during division when pseudo-cleavage of germinal vesicle-intact oocytes was induced. Anti-Ran antibody microinjection decreased the germinal vesicle breakdown and the first polar body extrusion, and distorted spindle organization and chromosome alignment. Our results indicate that Ran has a cell cycle-dependent localization and may have regulatory roles in cell cycle progression and microtubule organization in mouse oocytes, fertilized eggs and early embryos.
Xiao-Qian Meng, Ke-Gang Zheng, Yong Yang, Man-Xi Jiang, Yan-Ling Zhang, Qing-Yuan Sun and Yun-Long Li
Microfilaments (actin filaments) regulate various dynamic events during meiotic maturation. Relatively, little is known about the regulation of microfilament organization in mammalian oocytes. Proline-rich tyrosine kinase2 (Pyk2), a protein tyrosine kinase related to focal adhesion kinase (FAK) is essential in actin filaments organization. The present study was to examine the expression and localization of Pyk2, and in particular, its function during rat oocyte maturation. For the first time, by using Western blot and confocal laser scanning microscopy, we detected the expression of Pyk2 in rat oocytes and found that Pyk2 and Try402 phospho-Pyk2 were localized uniformly at the cell cortex and surrounded the germinal vesicle (GV) or the condensed chromosomes at the GV stage or after GV breakdown. At the metaphase and the beginning of anaphase, Pyk2 distributed asymmetrically both in the ooplasm and the cortex with a marked staining associated with the chromosomes and the region overlying the meiotic spindle. At telophase, Pyk2 was observed in the cleavage furrows in addition to its cortex and cytoplasm localization. The dynamics of Pyk2 were similar to that of F-actin, and this kinase was found to co-localize with microfilaments in several developmental stages during rat oocyte maturation. Microinjection of Pyk2 antibody demolished the microfilaments assembly and also inhibited the first polar body (PB1) emission. These findings suggest an important role of Pyk2 for rat oocyte maturation by regulating the organization of actin filaments.
Wen-Qing Shi, Shi-En Zhu, Dong Zhang, Wei-Hua Wang, Guo-Liang Tang, Yun-Peng Hou and Shu-Jun Tian
This study was designed to examine the effect of Taxol pretreatment on vitrification of porcine oocytes matured in vitro by an open pulled straw (OPS) method. In the first experiment, the effect of Taxol pretreatment and fluorescein diacetate (FDA) staining on parthenogenetic development of oocytes was evaluated. In the second experiment, viability, microtubule organization and embryo development of oocytes were assessed after oocytes were exposed to vitrification/warming solutions or after vitrification with or without Taxol pretreatment. The results showed that Taxol pretreatment and/or FDA staining did not negatively influence the oocyte’s developmental competence after parthenogenetic activation. After being exposed to vitrification/warming solutions, the survival rate (83.3%) of the oocytes was significantly (P < 0.05) reduced as compared with that in the control (100%). Vitrification/warming procedures further reduced the survival rates of oocytes regardless of oocytes being treated with (62.1%) or without (53.8%) Taxol. The proportions of oocytes with normal spindle configuration were significantly reduced after the oocytes were exposed to vitrification/warming solutions (38.5%) or after vitrification with (10.3%) or without (4.1%) Taxol pretreatment as compared with that in control (76.8%). The rates of two-cell-stage (5.6–53.2%) embryos at 48 h and blastocysts (0–3.8%) at 144 h after activation were significantly reduced after exposure to vitrification/warming solutions or after vitrification as compared with control (90.9% and 26.6% respectively). However, the proportion of vitrified oocytes developed to two-cell stage was significantly higher when oocytes were pretreated with (24.3%) than without (5.6%) Taxol. These results indicate that pretreatment of oocytes with Taxol before vitrification helps to reduce the damage induced by vitrification and is a potential way to improve the development of vitrified porcine oocytes.
Ruizhi Deng, Chengquan Han, Lu Zhao, Qing Zhang, Beifen Yan, Rui Cheng, Biao Wei, Peng Meng, Tingchao Mao, Yong Zhang and Jun Liu
Endogenous retroviruses (ERVs), which are abundant in mammalian genomes, can modulate the expression of nearby genes, and their expression is dynamic and stage-specific during early embryonic development in mice and humans. However, the functions and mechanisms of ERV elements in regulating embryonic development remain unclear. Here, we utilized several methods to determine the contribution of ERVs to the makeup and regulation of transcripts during embryonic genome activation (EGA). We constructed an ERV library and embryo RNA-seq library (IVF_2c and IVF_8c) of goat to serve as our research basis. The GO and KEGG analysis of nearby ERV genes revealed that some ERV elements may be associated with embryonic development. RNA-seq results were consistent with the features of EGA. To obtain the transcripts derived from the ERV sequences, we blasted the ERV sequences with embryonic transcripts and identified three lncRNAs and one mRNA that were highly expressed in IVF-8c rather than in IVF-2c (q-value <0.05). Then, we validated the expression patterns of nine ERV-related transcripts during early developmental stages and knocked down three high-expression transcripts in EGA. The knockdown of lncRNA TCONS_00460156 or mRNA HSD17B11 significantly decreased the developmental rate of IVF embryos. Our findings suggested that some transcripts from ERVs are essential for the early embryonic development of goat, and analyzing the ERV expression profile during goat EGA may help elucidate the molecular mechanisms of ERV in regulating embryonic development.
Zi-gang Shen, Wei He, Ji Zhang, Hai-yang He, Xia Yang, Zheng-qiong Chen, Ping Yang, Jian Li, Zhi-qing Liang, Yu-zhang Wu and Jin-tao Li
SPINLW1 (previously known as eppin (epididymal protease inhibitor)) is a target under intense scrutiny in the study of male contraceptive vaccines. B-cell-dominant epitopes are now recognized as key parts of the induction of humoral immune responses against target antigens. The generation of robust humoral responses in vivo has become a crucial problem in the development of modern vaccines. In this study, we developed a completely novel B-cell-dominant-epitope-based mimovirus vaccine, which is a kind of virus-size particulate antigen delivery system. The mimovirus successfully self-assembled from a cationic peptide containing a cell-penetrating peptide of TAT49–57 and a plasmid DNA encoding both three SPINLW1 (103–115) copies and adjuvant C3d3. The male mice were immunized with the epitope-based mimovirus vaccine, which resulted in a gradual elevation of specific serum IgG antibody levels. These reached a peak at week 4. Mating for the fertility assay showed that the mimovirus vaccine had accomplished a moderate fertility inhibition effect and investigation into the mechanism of action showed that it did so by interfering with the reproductive function of the sperm but that it did not damage the structures of the testes or cause serum testosterone to decline. Our results suggest an ideal protocol for suppressing fertility in mice by an engineered mimovirus vaccine.