Embryo-maternal communication in bovine - strategies for deciphering a complex cross-talk

The role of IGF1 in the in vivo production of bovine embryos from superovulated donors

IGF1 plays an important role in bovine follicular growth, acquisition of oocyte competence and embryo viability. Current data also indicate a critical role for IGF1 in both the ovarian response and the embryo yield following the superovulatory treatments. IGF1 can have either positive or negative effects on embryo viability which is related to the concentration of IGF1 induced by superovulation treatment. These effects impact either on oocyte competence or directly on the embryo. Concentrations in the physiological range appear to result in the production of higher quality embryos, mainly due to the mitogenic and the anti-apoptotic activities of IGF1. However, high superovulatory responses are associated with decreased embryo viability and a concomitant increase in apoptosis. Studies in mice suggest that this increase in apoptosis is related to the downregulation of the IGF1 receptor in the embryo associated with high IGF1 concentrations. Strategies capable of controlling the IGF1 concentrations could be one approach to improve superovulation responses. A range of possible approaches for research within the IGF system in gonadotrophin-stimulated cattle is discussed in this review, including the possible use of superovulated female cattle as an alternative animal experimental model for research on reproductive disorders in humans associated with abnormal IGF1 concentrations.

Junior JC, Franciolli ALR, Martins DS, Pereira FTV, Favaron PO, Ambrósio CE, Miglino MA. Caracterização das membranas fetais em búfalas no terço inicial da gestação

Este estudo visou à caracterização das membranas fetais em búfalas (Bubalus bubalis, Linnaeus 1758) no terço inicial da gestação. As membranas fetais foram analisadas macroscópica e microscopicamente (luz e microscopia eletrônica de transmissão). O córion possui uma camada simples de células circulares, com núcleos de forma esférica, denominadas trofobláticas; há outro tipo celular, as células trofoblásticas gigantes, com dois ou mais núcleos. Ambas possuem uma grande quantidade de vesículas no citoplasma e retículo endoplasmático à microscopia de transmissão. O alantóide possui vasos preenchidos com eritrócitos, e contêm células alongadas, que formam um epitélio estratificado simples. O âmnion é uma membrana transparente, ou esbranquiçada; constituído por epitélio estratificado simples. A diferença principal entre o alantóide e o âmnion é que o último é avascular. O saco vitelínico é uma membrana opaca que desaparece durante a gestação; é a única membrana que não está em contato com as outras e apresenta três tipos diferentes de células que dão forma a três camadas distintas (endoderma, mesotélio, mesênquima).

Biological interpretations of transcriptomic profiles in mammalian oocytes and embryos

The characterization of gene-expression profiles in oocytes and embryos is critical to understand the influence of genetic and environmental factors on preimplantation and fetal development. Numerous gene-expression microarray studies using different platforms and species are offering insights into the biological processes extensively represented among the genes exhibiting differential expression. Major advances on understanding the direct relationship between gene expression and developmental competence are being reported. Integration of information across studies using meta-analysis techniques can increase the precision and accuracy to identify expression profiles associated with embryo development. Gene network and pathway analyses are offering insights into gene interactions and expression profiles of embryos. All these advances are cementing the way toward a comparative and systems approach to understanding the complex processes underlying vertebrate development.

Galectin 15 (LGALS15) functions in trophectoderm migration and attachment

Galectin 15 (LGALS15) is expressed specifically by the endometrial luminal epithelium (LE) of the ovine uterus in concert with blastocyst growth, elongation, and implantation. LGALS15 contains a predicted carbohydrate recognition domain (CRD) as well as LDV and RGD recognition sequences for integrin binding. Studies tested the hypothesis that LGALS15 is a secreted regulator of blastocyst development, as well as growth, migration, adhesion, and apoptosis of trophoblast. Bovine embryos were produced in vitro by standard conditions, and putative zygotes were cultured in the presence of recombinant ovine LGALS15. Rates of embryo cleavage and blastocyst formation were not affected by LGALS15. LGALS15 moderately increased proliferation of ovine trophectoderm (oTr) cells. Staurosporine elicited apoptosis of oTr cells, which could be partially inhibited by LGALS15. Migration of oTr cells was stimulated by LGALS15 that was dependent on Jun N-terminal kinase (JNK). A dose-dependent increase in oTr cell attachment to LGALS15 was found that could be inhibited by cyclic GRGDS, but not GRADS, peptides. Mutation of the LDVRGD integrin binding sequence of LGALS15 to LADRAD decreased its ability to promote oTr cell attachment, whereas mutation of the CRD had little effect. LGALS15 induced formation of robust focal adhesions in oTr cells that was abolished by mutation of the LDVRGD sequence. Collectively, these results support the hypothesis that LGALS15 stimulates trophectoderm cell migration and attachment via integrin binding and activation which are critical to blastocyst elongation and implantation.

Reporter genes for embryogenesis research in livestock species

Currently, our knowledge of early mammalian embryogenesis, stem cell differentiation and development is largely based on studies performed in mouse models. However, in important aspects, e.g. the timing of epigenetic reprogramming and embryonic genome activation, livestock species probably reflect far more closely the situation in men and other non-rodent mammals. A major challenge is the fact that in mammals, the development of individual zygotes is highly variable and vulnerable, and the outcome is uncertain. Valid indicators of the highly heterogeneous development and health status, and the actual developmental potential of individual oocytes, zygotes or embryos would be crucially important to tap the full power of holistic transcriptome and proteome analyses. Fluorescent reporter proteins opened new vistas for embryology and stem cell research: they can be used as reporters for the activity of gene promoters or tagged to functional proteins to study their intracellular localization in living cells, tissues and organisms. Fluorescent reporter genes may be used to microscopically observe key processes of early development. Thus, novel information related to developmental potential can be obtained from living embryos before processing them, e.g. for "-omic" studies. This review summarizes the main current reporter gene techniques and gene transfer approaches, which might be suitable for the investigation of early embryogenesis in livestock mammals. The potential of promoter reporter genes is exemplified by a bovine model system for quantitative monitoring of transcriptional reactivation of the so-called pluripotency gene POU5F1 in cloned bovine embryos.

Global gene expression analysis and regulation of the principal genes expressed in bovine placenta in relation to the transcription factor AP-2 family

BACKGROUND

Cell-cell communication is an important factor in feto-maternal units during placentogenesis. The placenta produces pivotal hormones and cytokines for communication between cotyledonary villi and the maternal caruncle. Gene expression in bovine placenta throughout pregnancy was comprehensively screened by a cDNA microarray, and we searched for a common transcription factor in a gene cluster that showed increasing expression throughout gestation in cotyledonary villi and caruncle.

METHODS

Placentomal tissues (villi and caruncle) were collected from Day 25 to Day 250 of gestation for microarray analysis. Global gene expression profiles were analyzed using the k-means clustering method. A consensus sequence cis-element that may control up-regulated genes in a characteristic cluster was examined in silico. The quantitative expression and localization of a specific transcription factor were investigated in each tissue using quantitative real-time RT-PCR and in situ hybridization.

RESULTS

The microarray expression profiles were classified into ten clusters. The genes with most markedly increased expression became concentrated in cluster 2 as gestation proceeded. Cluster 2 included placental lactogen (CSH1), pregnancy-associated glycoprotein-1 (PAG1), and sulfotransferase family 1E estrogen-preferring member 1 (SULT1E1), which were mainly detected in giant trophoblast binucleate cells (BNC). Consensus sequence analysis identified transcription factor AP-2 binding sites in some genes in this cluster. Quantitative real-time RT-PCR analysis confirmed that high level expression of transcription factor AP-2 alpha (TFAP2A) was common to cluster 2 genes during gestation. In contrast, the expression level of another AP-2 family gene, transcription factor AP-2 beta (TFAP2B), was extremely low over the same period. Another gene of the family, transcription factor AP-2 gamma (TFAP2C), was expressed at medium level compared with TFAP2A and TFAP2B. In situ hybridization showed that TFAP2A, TFAP2B and TFAP2C mRNAs were localized in trophoblast cells but were expressed by different cells. TFAP2A was expressed in cotyledonary epithelial cells including BNC, TFAP2B was specifically expressed in BNC, and TFAP2C in mononucleate cells.

CONCLUSION

We detected gestational-stage-specific gene expression profiles in bovine placentomes using a combination of microarray and in silico analysis. In silico analysis indicated that the AP-2 family may be a consensus regulator for the gene cluster that characteristically appears in bovine placenta as gestation progresses. In particular, TFAP2A and TFAP2B may be involved in regulating binucleate cell-specific genes such as CSH1, some PAG or SULT1E1. These results suggest that the AP-2 family is a specific transcription factor for clusters of crucial placental genes. This is the first evidence that TFAP2A may regulate the differentiation and specific functions of BNC in bovine placenta.

Plasma concentrations of pregnancy-associated glycoprotein-1 (PAG-1) in high producing dairy cows suffering early fetal loss during the warm season

The present study was designed to establish whether plasma pregnancy-associated glycoprotein-1 (PAG-1) measurements during the early fetal period can be associated with early fetal loss. Blood samples were obtained and ultrasound controls performed on days 35, 42, 49, 56, and 63 of gestation or until pregnancy loss from 98 lactating dairy cows. Radioimmunoassay systems were used to determine PAG-1 and progesterone concentrations. Of the 98 pregnancies investigated 18 (18.4%) suffered early fetal loss: 15 (18.5%) in cows carrying singletons, and 3 (16.7%) in twin pregnancies. In cows suffering pregnancy loss, all living embryos registered on day 35 seemed normal in size and development in all weekly ultrasound controls before fetal expulsion. Using analysis of variance, plasma PAG-1 and progesterone values were not different between no loss and fetal loss groups for every gestation period. Based on the odds ratio, and considering only PAG-1 values obtained on day 35 of gestation, the risk of fetal loss was 10 and 6.8 times more likely in cows with low (<2.5 ng/ml) and high (>4 ng/ml) PAG-1 values, respectively, than in cows with medium PAG-1 values, used as reference. Of the 10 inseminating bulls included in the study, one was related to increased fetal loss by odds ratio of 21.7, whereas one bull was attributed fetal loss rate reduced by odds ratio of 12.5 (1/0.08) These findings can have a clear clinical application: PAG-1 measurements from one single sample taken on day 35 of gestation provided more useful information than a series of values obtained from day 35 to 63 of gestation, and can be indicators of subsequent fetal loss.

A bovine oviduct epithelial cell suspension culture system suitable for studying embryo–maternal interactions: morphological and functional characterization

We established a short-term (24 h) culture system for bovine oviduct epithelial cells (BOECs), obtained on day 3.5 of the estrous cycle and evaluated the cells with respect to morphological criteria, marker gene expression, and hormone responsiveness. BOEC sheets were isolated mechanically from the ampulla with similar yields from oviducts ipsi- and contralateral to the ovulation site (57.9 ± 4.6 and 56.4 ± 8.0 × 106cells). BOECs showed > 95% purity and cells cultured for 24 h maintained morphological characteristics presentin vivo, as determined by light microscopy, scanning electron microscopy, and transmission electron microscopy. Both secretory cells with numerous secretory granules and ciliated cells with long, well-developed, and vigorously beating kinocilia were visible. Quantitative real-time PCR failed to detect significant differences in transcript levels between ipsi-and contralateral BOECs for the majority of marker genes (estrogen receptors α and β (ESR1andESR2), 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), oviductal glycoprotein 1 (OVGP1), progesterone receptor (PGR), and tumor rejection antigen 1 (TRA1)) throughout the 24 h culture period. However, the combined data of all time points for glutathione peroxidase 4 (GPX4), a gene previously shown to be expressed at higher levels in the ipsilateral oviductin vivo, also indicated significantly different mRNA levelsin vitro. The expression of marker genes remained stable after 6 h cell culture, indicating only a short adaptation period. Western blot analysis confirmed ESR1 and PGR protein expression throughout the culture period. In agreement with cyclic differencesin vivo, estradiol-17β stimulation increasedPGRtranscript abundance in BOECs. Our novel culture system provides functional BOECs in sufficient quantities for holistic transcriptome and proteome studies, e.g. for deciphering early embryo–maternal communication.

Effects of species and cellular activity of oviductal epithelial cells on their dialogue with co-cultured mouse embryos

An efficient co-culture system, especially with oviductal or uterine epithelial cells, is important not only for the production of high quality embryos, but also for the study of the molecular dialogue between embryos and their maternal environment. Although mouse embryos have been co-cultured successfully with oviductal epithelial cells (OECs) from several species, studies on the effects of species and functionality of OECs are few. Reports concerning the necessity of direct contact between the embryo and OECs and about the culture of mouse embryos in medium conditioned with heterologous OECs have been controversial. In this study, pronuclear embryos from Kunming mice, characterized by an obvious two-cell block in vitro, were co-cultured with mouse, goat, and chick OECs. The functionality of OECs was determined by analyzing the cell cycle, apoptosis, the numbers of mitochondria and cilia, and the ability both to support embryonic development and to remove hypoxanthine from the culture medium. The necessity of direct contact between OECs and embryos was studied by repeated renewal of culture medium with fresh conditioned medium, the culture of embryos in plastic wells connected by tunnels to wells with OEC monolayers, and the co-culture of embryos separated from OECs by a filter. Both goat and chick OECs supported mouse embryonic development, but their embryotrophic lifespan was shorter than that of the mouse OECs. Whereas media conditioned with mouse OECs supported mouse embryonic development satisfactorily, medium conditioned with goat OECs supported little development. Immediate dialogue between heterologous OECs and embryos was essential for efficient co-culture, whereas direct contact between the two cell types was not; neither dialogue nor contact was needed between isologous OECs and embryos. Embryotrophic activity and the ability to remove hypoxanthine from conditioned medium declined with time after confluence and number of passages of OECs, mainly because of apoptosis and dedifferentiation. Thus, the species and functionality of OECs have profound effects on their molecular dialogue with co-cultured embryos, and efficient co-culture depends upon both positive and negative conditioning.

Embryo-induced transcriptome changes in bovine endometrium reveal species-specific and common molecular markers of uterine receptivity

The endometrium plays a central role among the reproductive tissues in the context of early embryo–maternal communication and pregnancy. This study investigated transcriptome profiles of endometrium samples from day 18 pregnant vs non-pregnant heifers to get insight into the molecular mechanisms involved in conditioning the endometrium for embryo attachment and implantation. Using a combination of subtracted cDNA libraries and cDNA array hybridisation, 109 mRNAs with at least twofold higher abundance in endometrium of pregnant animals and 70 mRNAs with higher levels in the control group were identified. Among the mRNAs with higher abundance in pregnant animals, at least 41 are already described as induced by interferons. In addition, transcript levels of many new candidate genes involved in the regulation of transcription, cell adhesion, modulation of the maternal immune system and endometrial remodelling were found to be increased. The different expression level was confirmed with real-time PCR for nine genes. Localisation of mRNA expression in the endometrium was shown byin situhybridisation forAGRN,LGALS3BP,LGALS9,USP18,PARP12andBST2. A comparison with similar studies in humans, mice, and revealed species-specific and common molecular markers of uterine receptivity.

Monozygotic Twin Model Reveals Novel Embryo-Induced Transcriptome Changes of Bovine Endometrium in the Preattachment Period1

Initiation and maintenance of pregnancy are critically dependent on an intact embryo-maternal communication in the preimplantation period. To get new insights into molecular mechanisms underlying this complex dialog, a holistic transcriptome study of endometrium samples from Day 18 pregnant vs. nonpregnant twin cows was performed. This genetically defined model system facilitated the identification of specific conceptus-induced changes of the endometrium transcriptome. Using a combination of subtracted cDNA libraries and cDNA array hybridization, 87 different genes were identified as upregulated in pregnant animals. Almost one half of these genes are known to be stimulated by type I interferons. For the ISG15ylation system, which is assumed to play an important role in interferon tau (IFNT) signaling, mRNAs of four potential components (IFITM1, IFITM3, HSXIAPAF1, and DTX3L) were found at increased levels in addition to ISG15 and UBE1L. These results were further substantiated by colocalization of these mRNAs in the endometrium of pregnant animals shown by in situ hybridization. A functional classification of the identified genes revealed several different biological processes involved in the preparation of the endometrium for the attachment and implantation of the embryo. Specifically, elevated transcript levels were found for genes involved in modulation of the maternal immune system, genes relevant for cell adhesion, and for remodeling of the endometrium. This first systematic study of maternal transcriptome changes in response to the presence of an embryo on Day 18 of pregnancy in cattle is an important step toward deciphering the embryo-maternal dialog using a systems biology approach.

Pregnancy effects on distribution of progesterone receptors, oestrogen receptor α, glucocorticoid receptors, Ki-67 antigen and apoptosis in the bovine interplacentomal uterine wall and foetal membranes

Until recently, studies dealing with the uterus of the pregnant cow focus primarily on the placentome or on early and late pregnancy. Thus, there is a paucity of information about many aspects of the interplacentomal uterine wall including adherent foetal membranes. Corresponding tissue specimens were collected at the slaughterhouse and in animals undergoing premature caesarean section. Two specimens per month of pregnancy were assessed immunohistochemically for progesterone receptors, oestrogen receptor alpha and glucocorticoid receptors, Ki-67 protein and TUNEL procedure was performed. The latter two methods were employed in three animals each per months 1 and 2, 3 and 4, 7 and 8 and in six animals undergoing caesarean section at days 274 and 275 post insemination or during spontaneous labour. Results indicate that proliferation and apoptosis are of minor importance for tissue homeostasis since both can histochemically be detected only sporadically. Thus, at the sites investigated here, cellular hypertrophy plays an important role for tissue growth during pregnancy. Progesterone receptors, oestrogen receptor alpha and glucocorticoid receptors, however, exhibit cell type and pregnancy stage specific distribution patterns within the tissues assessed. Progesterone receptor immunoreactive scores remained fairly unchanged during pregnancy. Oestrogen receptor alpha scores, however, generally decreased and glucocorticoid receptors increased with ongoing gestation. Progesterone receptors and oestrogen receptor alpha were present in endometrial stroma and in myometrial smooth muscle cells during whole pregnancy. Oestrogen receptor alpha was detectable during whole pregnancy also in uterine glands. Progesterone receptors were, however, present at a very low level at the latter site only during months 1-3 and 6-9. Oestrogen receptor alpha and glucocorticoid receptors may also mediate uterine blood flow since they were present in the tunica media of uterine blood vessels. Results of the present study indicate, that progesterone and its receptor play an important role during whole gestation, mainly for uterine quiescence. Glucocorticoids and their receptors - possibly in cooperation with oestrogens and decreasing amounts of the oestrogen receptor alpha - should trigger processes initiating parturition, such as endometrial prostaglandin production. Further studies - including the periparturient period - should help to understand the exact role of the extraplacental compartment of the uterine wall for the initiation and progress of parturition.

Demilune cell and parotid protein from murine oviductal epithelium stimulates preimplantation embryo development

In mammals, fertilization and early preimplantation embryo development occur in the oviduct. We hypothesized that interaction exists between the developing embryos and the maternal genital tract, such that the embryos modulate the physiology and gene expression of the oviduct so that it is conducive to their development. By comparing the gene expression patterns in mouse oviducts containing transferred preimplantation embryos with those of oviducts containing oocytes, we report here the characterization of demilune cell and parotid protein (Dcpp), which was up-regulated in the embryo-containing oviduct. Dcpp mRNA was highly expressed in the oviductal epithelium at the estrus stage. The Dcpp gene codes for a protein of 150 amino acids and contains a signal peptide suggestive of secretory function. The Dcpp mRNA level was maintained in the oviductal epithelium of pregnant females but decreased continuously in those of pseudopregnant mice. Exogenous estrogen stimulated the expression of Dcpp mRNA and protein in ovariectomized mice. The effect was abolished by an estrogen antagonist, ICI 182,780. Dcpp protein was present in mouse oviductal fluid but not in uterine fluid. More importantly, Dcpp immunoreactivity was found in embryos recovered from the oviduct but not in mature oocytes from the ovary. Supplementation of Dcpp to culture medium stimulated the development of mouse embryos to the blastocyst stage. Anti-Dcpp antibody decreased the beneficial effect of Dcpp on implantation of two-cell mouse embryos transferred to the oviducts of the foster mothers. In summary, our data demonstrated that Dcpp is highly expressed in the oviductal lumen in the presence of preimplantation embryos. It stimulates the growth of preimplantation embryos and may play an important role in embryo-maternal dialogue.

Post-hatching development of the porcine and bovine embryo--defining criteria for expected development in vivo and in vitro

Particular attention has been paid to the pre-hatching period of embryonic development although blastocyst development is a poor indicator of embryo viability. Post-hatching embryonic development in vitro would allow for establishment of more accurate tools for evaluating developmental potential without the need for transfer to recipient animals. Such a system would require (1) definition of milestones of expected post-hatching embryonic development in vivo; and (2) development of adequate culture systems. We propose a stereomicroscopical staging system for post-hatching embryos defining the following stages: (1) Expanded hatched blastocyst stage where the embryo presents an inner cell mass (ICM) covered by trophoblast. (2) Pre-streak stage 1 where the embryonic disc is formed. (3) Pre-streak stage 2 where a crescent-shaped thickening of the caudal portion of the embryonic disk appears. (4) Primitive streak stage where the primitive streak has developed as an axis of cell ingression of cells for meso- and endoderm formation. (5) Neural groove stage where the neural groove is developing from the rostral pole of the embryo along with a proportional shortening of the primitive streak; and (6) Somite stage(s) where paraxial mesoderm gradually condensates to form somites. Post-hatching development of bovine embryos in vitro is compromised and although hatching occurs and elongation can be physically provoked by culture in agarose tunnels, the embryonic disk characterizing the pre-streak stage 1 is never established. Thus, particular focus should be placed on establishing culture conditions that support at least some of the above-mentioned critical phases of development that in vivo occur within the initial two (pig) to three (cattle) weeks.

Luteotrophic influence of early bovine embryos and the relationship between plasma progesterone concentrations and embryo survival

This study was carried out to evaluate the luteotrophic influence of early (before Day 7 as well as after Day 7; Day 0=estrus) bovine embryos and the relationship between plasma progesterone (P4) concentrations and embryo survival. Virgin Holstein dairy heifers (n=325) from a single herd were randomly allocated to be nonbred, bred by artificial insemination (AI) or by embryo transfer (ET). Bred heifers were either treated with 1500 IU human chorionic gonadotrophin (hCG) on Day 7 of the estrous cycle or received no hCG treatment. Plasma P4 concentrations on Days 0, 5, 7, 10, 13, 15, 17, 19 and 21 were similar in pregnant AI- and ET-bred heifers and, this was observed in both hCG-treated and untreated females. Nonbred, AI- and ET-bred nonpregnant heifers (both hCG-treated and untreated) presented similar plasma P4 concentrations. Plasma P4 concentrations of pregnant heifers significantly deviated from those of nonpregnant and nonbred heifers on Day 17. In hCG-treated heifers, plasma P4 concentrations and Day 28 pregnancy rate were significantly higher in females with an induced accessory corpus luteum (CL) than in those females without an induced accessory CL. Treatment with hCG, although inducing the formation of accessory CL and significantly increasing plasma P4 concentrations had no significant effect on Day 28 pregnancy rate. In conclusion, this study does not support the existence of any peripherally detectable luteotrophic influence from early embryos (Days 5-7). Plasma P4 was only significantly related to embryo survival on Day 17, the time of expected onset of luteolysis.

Holistic differential analysis of embryo-induced alterations in the proteome of bovine endometrium in the preattachment period

During the peri-implantation period, molecular signaling between embryo and endometrium (layer of tissue lining the uterus lumen) is supposed to be crucial for the maintenance of pregnancy. To investigate embryo-induced alterations in the proteome of bovine endometrium in the preattachment period (day 18), we used monozygotic cattle twins (generated by embryo splitting) as a model eliminating genetic variability as a source for proteome differences. One of the twins was pregnant after the transfer of two in vitro produced blastocysts, while the corresponding twin received a sham-transfer and served as a nonpregnant control. The two-dimensional fluorescence difference gel electrophoresis (2-D DIGE) analysis of the endometrium samples of three twin pairs (pregnant/nonpregnant) revealed four proteins with significantly higher abundance (p < 10(-9)) in each sample derived from the pregnant animals: Rho GDP dissociation inhibitor beta; 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD); soluble NADP(+)-dependent isocitrate dehydrogenase 1; and acyl-CoA-binding protein. To verify the accuracy of the 2-D DIGE quantification, the abundances of 20 alpha-HSD were quantified by a targeted cleavable isotope-coded affinity tag (ICAT) approach. The mass spectrometry-based ICAT quantification matched perfectly the results obtained by 2-D DIGE quantification, demonstrating the accuracy of our data. These results demonstrate that our model (monozygotic twins) in combination with the appropriate analytical tools is particularly suitable for the detection of the proteins involved in the embryo-maternal interactions.

Phospholipid transfer protein (PLTP) mRNA expression is stimulated by developing embryos in the oviduct

In mammal, fertilization and early preimplantation embryo development occurs in the oviduct. Evidence is accumulating that the oviductal epithelia secrete various biomolecules to the lumen during the secretory phase of the estrus cycle to enhance embryo development. This secretory activity of the oviduct is under the regulation of steroid hormones. Observations also suggested that the gametes and embryos modulate the physiology and gene-expressing pattern of the oviduct. However, the underlying molecular changes remain elusive. We hypothesize that the developing embryos interact with the surrounding environment and affect the gene expression patterns of the oviduct, thereby modulating the oviductal secretory activity conducive to the preimplantation embryo development. To test this hypothesis, suppression subtractive hybridization (SSH) was used to compare the gene expressions in mouse oviduct containing transferred in vitro cultured preimplantation embryos with that of oviduct containing oocytes during the preimplantation period. We reported here the identification and characterization of phospholipids transfer protein (PLTP), which is highly expressed in the embryo-containing oviduct and localized at the oviductal epithelium by in situ hybridization. PLTP contains signal peptide putative for secretory function. More importantly, PLTP mRNA increases in the oviductal epithelia of pregnant, but not pseudo-pregnant mice when assayed by real-time PCR. Taken together, our data suggested that PLTP may play important role(s) during in vivo preimplantation embryo development. This molecule would be a target to delineate the mechanisms and the roles of oviductal secretory proteins on early embryonic development.

Effect of interferon-tau on prostaglandin biosynthesis, transport, and signaling at the time of maternal recognition of pregnancy in cattle: evidence of polycrine actions of prostaglandin E2

Recognition and establishment of pregnancy involve several molecular and cellular interactions among the conceptus, uterus, and corpus luteum (CL). In ruminants, interferon-tau (IFNtau) of embryonic origin is recognized as the pregnancy recognition signal. Endometrial prostaglandin F(2alpha) (PGF(2alpha)) is the luteolysin, whereas PGE(2) is considered a luteoprotective or luteotrophic mediator at the time of establishment of pregnancy. The interplay between IFNtau and endometrial PGs production, transport, and signaling at the time of maternal recognition of pregnancy (MRP) is not well understood. We have studied the expression of enzymes involved in metabolism of PGE(2) and PGF(2alpha), cyclooxygenase-1 (COX-1) and COX-2, PG synthases (PGES and PGFS), PG 15-dehydrogenase, and PG transporter as well as PGE(2) (EP2 and EP3) and PGF(2alpha) receptors. IFNtau influences cell-specific expression of COX-2, PGFS, EP2, and EP3 in endometrium, myometrium, and CL in a spatio-temporal and tissue-specific manner, whereas it does not alter COX-1, PGES, PG 15-dehydrogenase, PG transporter, or PGF(2alpha) receptor expression in any of these tissues. In endometrium, IFNtau decreases PGFS in epithelial cells and increases EP2 in stroma. In myometrium, IFNtau decreases PGFS and increases EP2 in smooth muscle cells. In CL, IFNtau increases PGES and decreases EP3. Together, our results show that IFNtau directly or indirectly increases PGE(2) biosynthesis and EP2-associated signaling in endometrium, myometrium, and CL during MRP. Thus, PGE(2) may play pivotal roles in endometrial receptivity, myometrial quiescence, and luteal maintenance, indicating polycrine (endocrine, exocrine, paracrine, and autocrine) actions of PGE(2) at the time of MRP. Therefore, the establishment of pregnancy may depend not only on inhibition of endometrial PGF(2alpha), but also on increased PGE(2) production in cattle.

Protein patterns of pig oocytes during in vitro maturation

In vitro maturation (IVM) of fully grown mammalian oocytes is characterized by initial germinal vesicle (GV) breakdown and rearrangement of microtubule network during the first meiosis (MI), followed by extrusion of the first polar body and block of the oocytes in metaphase of the second meiosis (MII). Only fully matured oocytes are capable of undergoing fertilization and the initiation of zygotic development. These observations are mostly based on morphological evaluation; however, the molecular events responsible for these processes are not known. In this study, we have launched the analysis of pig oocytes during in vitro maturation using a proteomics approach. First, oocyte proteins have been separated by two-dimensional gel electrophoresis and identified by mass spectrometry. Remarkably, several proteins, including peroxiredoxins, ubiquitin carboxyl-terminal hydrolase isozyme L1, and spermine synthase, are even more abundant than actin, usually the most abundant protein in somatic cells. Furthermore, we have initiated comparative analysis of the oocytes at different stages of maturation to characterize candidate proteins, which are differentially expressed during in vitro maturation. To date, we have identified antiquitin (D7A1), the member of aldehyde dehydrogenase family7 that has been significantly increased in MI and MII stages compared with GV oocytes. To our knowledge, this is the first pig oocyte proteome available so far that may be used as a reference map. The proteins that are differentially regulated during IVM may present potential biomarkers of oocyte maturation and quality. It is a useful inventory toward a deeper understanding of the mechanisms underlying reproduction and development.