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Corina I Schanzenbach, Sandra M Bernal-Ulloa, Vera A van der Weijden, Michael W Pfaffl, Mathias Büttner, Annegret Wünsch and Susanne E Ulbrich

Preimplantation bovine blastocyst supernatants exhibit sex-dependent antiviral activity, due to the ruminant pregnancy recognition signal interferon tau (IFNT). Differing potencies of IFNT variants have been supposed as cause, although evidence remains scarce. Here, we aimed at quantifying the sex-dependent IFNT production on transcriptional, translational and biological activity level in bovine blastocysts, to elucidate the origin of differences in antiviral activity between male and female blastocysts. Day 8 bovine blastocysts were co-cultured with endometrial stroma cells for 48 h. The embryonic IFNT mRNA expression was determined by quantitative reverse transcription followed by polymerase chain reaction (RT-qPCR). Additionally, the IFNT protein concentration was determined using a sensitive in-house developed IFNT-specific enzyme-linked immunosorbent assay (ELISA). The biological activity was assessed by quantifying the response of interferon-stimulated gene (ISG) expression in endometrial stroma cells. While the IFNT-specific ELISA displayed a limit of detection of 7.3 pg/mL, the stroma cell culture system showed to react to as little as 0.1 pg/mL IFNT in RT-qPCR analysis. The female blastocysts had a significant, 5.6-fold, 3.6-fold and 5.2-fold higher IFNT production than male blastocysts as determined by transcript abundance, protein concentration and, protein activity, respectively. Additionally, all parameters correlated positively, and therefore, we conclude that female blastocysts most likely have an increased IFNT gene and protein expression rather than expressing more potent IFNT variants.

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L Richardson, J P Hanrahan, T Tharmalingam, S D Carrington, P Lonergan, A C O Evans and S Fair

The aim of this study was to investigate the properties and to functionally characterize the cervical mucus that modulates sperm transport through the cervix by using ewe breeds with a divergent pregnancy rate (Belclare and Suffolk; high and low, respectively) following cervical insemination using frozen-thawed semen. Sperm number, as well as sialic acid and fucose content in both the channels and in the lumen of different regions of the cervix were quantified in inseminated Belclare and Suffolk ewes. Expression of glycosyltransferase and MUC genes, glycosidase activity and sialic acid speciation in follicular phase cervical tissue and mucus were assessed. More spermatozoa were found in the cervical channels in the region closest to the cervical os in Belclare than Suffolk ewes (P < 0.05) and Suffolk ewes had a higher sialic acid content in the cervical channels than Belclare ewes (P < 0.05) in all regions of cervix. Suffolk ewes had significantly higher expression of FUT1, ST6GAL1 and MUC5AC than Belclare ewes. There was no difference between the breeds in glycosidase activity (P > 0.05). Levels of Neu5Ac were higher in Belclare than Suffolk ewes (P < 0.05) and levels of Neu5Gc was higher in Suffolk than Belclare ewes (P < 0.05). Competitive sperm penetration assays demonstrated that frozen-thawed sperm progression increased when cervical mucus was incubated with sialyllactose prior to a sperm penetration test (P < 0.05). These results suggest that the difference between Belclare and Suffolk ewes in sperm transport with frozen-thawed semen is due to the higher concentration of sialic acid within channels, which binds to spermatozoa and reduces their ability to traverse the cervix.

Open access

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.

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María Luján Scalise, María Marta Amaral, Julieta Reppetti, Alicia E Damiano, Cristina Ibarra and Flavia Sacerdoti

Shiga toxin (Stx2) producing Escherichia coli infections during early gestation may impair placentation through a Stx2 damage of extravillous trophoblast (EVT) cells. We have previously demonstrated that Stx2 injected in rats in the early stage of pregnancy causes spontaneous abortion by a direct cytotoxic effect in the highly perfused feto-uteroplacental unit. The main aim was to evaluate the effects of Stx2 on EVT in order to understand the possible adverse effects that the toxin may have on trophoblast cells during early pregnancy. Swan 71 and HTR-8 cell lines were used as human EVT models. The presence of Stx2 receptor, globotriaosylceramide (Gb3), on Swan 71 and HTR-8 cells was evaluated by thin layer chromatography. The effects of Stx2 on cell viability were evaluated by neutral red uptake, migration by wound-healing assay and invasion was determined by the ‘transwell chamber’ assay. Metalloproteinase activity (MMP-2) was evaluated by zymography and tubulogenesis was analyzed by counting the total tube length and the number of branch formation. We have demonstrated that Swan 71 expresses high levels of Gb3 compared to HTR-8 cells. Stx2 decreased significantly Swan 71 viability in a dose-dependent manner after 72 h of toxin exposure. Furthermore, Stx2 impaired migration, invasion and tube-like formation of Swan 71 cells and decreased the MMP-2 activity. These cytotoxic effects were partially prevented by aminoguanidine, an inducible nitric oxide synthase inhibitor. These studies demonstrate that the function and viability of EVT cells may be altered by Stx2 and suggest that NO overexpression may be involved in the detrimental effects.

Free access

Xiang Xiao, Yue Yang, Baiping Mao, C Yan Cheng and Ya Ni

SRC family kinases (SFKs) are known regulators of multiple cellular events, including cell movement, differentiation, proliferation, survival and apoptosis. SFKs are expressed virtually by all mammalian cells. They are non-receptor protein kinases that phosphorylate a variety of cellular proteins on tyrosine, leading to the activation of protein targets in response to environmental stimuli. Among SFKs, SRC, YES and FYN are the ubiquitously expressed and best studied members. In fact, SRC, the prototypical SFK, was the first tyrosine kinase identified in mammalian cells. Studies have shown that SFKs are regulators of cell junctions, and function in endocytosis and membrane trafficking to regulate junction restructuring events. Herein, we briefly summarize the recent findings in the field regarding the role of SFKs in the testis in regulating spermatogenesis, particularly in Sertoli–Sertoli and Sertoli–germ cell adhesion. While it is almost 50 years since the identification of the oncogene v-Src encoded by Rous sarcoma transforming virus, the understanding of SFK involvement during spermatogenesis in the testis remains far behind that in other epithelia and tissues. The goal of this review is to bridge this gap.

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Peter Smith, Jo-Ann L Stanton, Laurel Quirke and Jennifer L Juengel

The aim of this study was to examine the relationships between gestational nutrition, fetal ovarian development and offspring fertility in female sheep and to highlight the potential mechanisms underlying these relationships. Adult sheep (n = 79) were fed either a maintenance or 0.6 of maintenance plane of nutrition for the first 55 days of gestation and thereafter fed ad libitum. Fetuses were collected for analysis at days 55 and 75 of gestation. Female offspring were monitored from birth until 19 months of age. Effects of restricted nutrition were observed on maternal plasma concentrations of progesterone, creatinine, albumin and Ca2+ at day 55 and creatinine at day 75. Concentrations of metabolic factors and steroid hormones in day 75 fetal plasma were not affected by the restricted maternal plane of nutrition. At day 55 of gestation, fetal ovarian germ cell development was not affected by maternal plane of nutrition. At day 75 of gestation ovaries from fetuses whose dams were exposed to restricted nutrition contained more germ cells but had lower germ cell proliferation rates than controls. For female offspring at 8 months of age, the dams gestational plane of nutrition did not affect the onset of puberty, ovulation rate (OR) and antral follicle counts (AFC). At 19 months of age, ewes from dams exposed to the restricted plane of gestational nutrition had higher OR, AFC and progesterone concentrations while concentrations of FSH were lower. In conclusion, while effects on fertility per se are yet to be determined, a reduced maternal plane of gestational nutrition can improve indicators of fertility in female offspring.

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Zhe-Long Jin, Xing-Hui Shen, Liang Shuang, Jeong-woo Kwon, Min-Jeong Seong and Nam-Hyung Kim

Homologous recombination (HR) plays a critical role in facilitating replication fork progression when the polymerase complex encounters a blocking DNA lesion, and it also serves as the primary mechanism for error-free DNA repair of double-stranded breaks. DNA repair protein RAD51 homolog 1 (RAD51) plays a central role in HR. However, the role of RAD51 during porcine early embryo development is unknown. In the present study, we examined whether RAD51 is involved in the regulation of early embryonic development of porcine parthenotes. We found that inhibition of RAD51 delayed cleavage and ceased development before the blastocyst stage. Disrupting RAD51 activity with RNAi or an inhibitor induces sustained DNA damage, as demonstrated by the formation of distinct γH2AX foci in nuclei of four-cell embryos. Inhibiting RAD51 triggers a DNA damage checkpoint by activating the ataxia telangiectasia mutated (ATM)–p53–p21 pathway. Furthermore, RAD51 inhibition caused apoptosis, reactive oxygen species accumulation, abnormal mitochondrial distribution and decreased pluripotent gene expression in blastocysts. Thus, our results indicate that RAD51 is required for proper porcine parthenogenetic activation (PA) embryo development.

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Wei Cui, Chelsea Marcho, Yongsheng Wang, Rinat Degani, Morgane Golan, Kimberly D Tremblay, Jaime A Rivera-Pérez and Jesse Mager

Mediator is an evolutionarily conserved multi-subunit complex, bridging transcriptional activators and repressors to the general RNA polymerase II (Pol II) initiation machinery. Though the Mediator complex is crucial for the transcription of almost all Pol II promoters in eukaryotic organisms, the phenotypes of individual Mediator subunit mutants are each distinct. Here, we report for the first time, the essential role of subunit MED20 in early mammalian embryo development. Although Med20 mutant mouse embryos exhibit normal morphology at E3.5 blastocyst stage, they cannot be recovered at early post-gastrulation stages. Outgrowth assays show that mutant blastocysts cannot hatch from the zona pellucida, indicating impaired blastocyst function. Assessments of cell death and cell lineage specification reveal that apoptosis, inner cell mass, trophectoderm and primitive endoderm markers are normal in mutant blastocysts. However, the epiblast marker NANOG is ectopically expressed in the trophectoderm of Med20 mutants, indicative of defects in trophoblast specification. These results suggest that MED20 specifically, and the Mediator complex in general, are essential for the earliest steps of mammalian development and cell lineage specification.

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Vijay Pratap Singh, Wei-Ting Yueh, Jennifer L Gerton and Francesca E Duncan

Eighteen histone deacetylases exist in mammals. The class 1 histone deacetylases HDAC1 and HDAC2 are important for oogenesis and fertility in mice, likely via their effects on histones. The reproductive function of HDAC8, another class 1 enzyme, has not been explored. One key target of HDAC8 is the SMC3 subunit of cohesin, an essential complex mediating sister chromatid cohesion and chromosome segregation. In current models, HDAC8 activity is required for SMC3 recycling, but this function should be dispensable in oocytes since cohesion is established during pre-meiotic S phase and maintained until meiotic resumption during ovulation. Whether other oocyte-specific HDAC8-mediated deacetylation events are required for oogenesis and female fertility is unknown. We used two Cre drivers to remove Hdac8 at specific stages of oocyte development to address whether HDAC8 is required for female fertility in mice. When HDAC8 was knocked out in oocytes in primary and later stage follicles (Zp3-Cre), oogenesis and folliculogenesis appeared normal and mice were fertile. However, females were subfertile when HDAC8 was knocked out prior to pre-meiotic S phase and cohesion establishment (Vasa-Cre). This subfertility was independent of chromosome segregation errors during meiosis but rather appeared to be the result of defects in oogenesis that resulted in smaller fully grown oocytes with a reduced ability to resume meiosis. In all cases, we did not observe compensatory changes in HDAC1, HDAC2 and HDAC3 levels. Thus, although oocyte-specific expression of HDAC8 is not essential for mouse oogenesis after meiotic S phase, it contributes to optimal fertility. We infer that oocyte-specific expression of the deacetylase HDAC8 is required early in oogenesis for optimal fertility.

Free access

Parag A Parekh, Thomas X Garcia and Marie-Claude Hofmann

Sertoli cells regulate male germ cell proliferation and differentiation and are a critical component of the spermatogonial stem cell (SSC) niche, where homeostasis is maintained by the interplay of several signaling pathways and growth factors. These factors are secreted by Sertoli cells located within the seminiferous epithelium, and by interstitial cells residing between the seminiferous tubules. Sertoli cells and peritubular myoid cells produce glial cell line-derived neurotrophic factor (GDNF), which binds to the RET/GFRA1 receptor complex at the surface of undifferentiated spermatogonia. GDNF is known for its ability to drive SSC self-renewal and proliferation of their direct cell progeny. Even though the effects of GDNF are well studied, our understanding of the regulation its expression is still limited. The purpose of this review is to discuss how GDNF expression in Sertoli cells is modulated within the niche, and how these mechanisms impact germ cell homeostasis.