PFOS and F-53B disrupted inner cell mass development in mouse preimplantation embryo

Perfluorooctane sulfonic acid (PFOS) is a perfluoroalkyl and polyfluoroalkyl substance (PFAS) widely used in daily life. As its toxicity was confirmed, it has been gradually substituted by F-53B (chlorinated polyfluoroalkyl sulfonates, Cl-PFESAs) in China. PFOS exposure during prenatal development may hinder the development of preimplantation embryos, as indicated by recent epidemiological research and in vivo assays. However, the embryotoxicity data for F-53B are scarce. Furthermore, knowledge about the toxicity of F-53B and PFOS exposure to internal follicular fluid concentrations on early preimplantation embryo development remains limited. In this study, internal exposure concentrations of PFOS (10 nM) and F-53B (2 nM) in human follicular fluid were chosen to study the effects of PFAS on early mouse preimplantation embryo development. We found that both PFOS and F-53B treated zygotes exhibited higher ROS activity in 8-cell embryos but not in 2-cell stage embryos. PFOS and F-53B significantly affected the proportion and aggregation of the inner cell mass (ICM) in the blastocyst, but not the total cell number. Mouse embryonic stem cells (mESCs, isolated from the ICM) and embryoid body (EB) assays were employed to assess the toxicity of PFOS and F-53B on the development and differentiation of embryonic pluripotent cells. These results suggested that mESCs exhibited more DNA damage and abnormal germ layer differentiation after brief exposure to PFOS or F-53B. Finally, RNA-sequencing revealed that PFOS and F-53B exposure affected mESCs biosynthetic processes and chromatin-nucleosome assembly. Our results indicate that F-53B has potential risks as an alternative to PFOS, which disrupts ICM development and differentiation.

Does Trophectoderm Mitochondrial DNA Content Affect Embryo Developmental and Implantation Potential?

A retrospective case control study was undertaken at the molecular biology department of a private center for reproductive medicine in order to determine whether any correlation exists between the mitochondrial DNA (mtDNA) content of trophectoderm and embryo developmental potential. A total of 275 couples underwent IVF treatment, producing a total of 716 embryos. The trophectoderm was biopsied from each embryo at the blastocyst stage (day 5 or day 6 post-fertilization) subjected to low-pass next-generation sequencing (NGS), for the purpose of detecting aneuploidy. For each sample, the number of mtDNA reads obtained after analysis using NGS was divided by the number of reads attributable to the nuclear genome. The mtDNA copy number was found to be higher in aneuploid embryos than in those that were euploid (mean mtDNA ratio ± SD: 1.13 ± 1.37 versus 1.45 ± 1.78, p = 0.02) and in day 5 biopsies compared to day 6 biopsies (1.41 ± 1.66 vs. 1.19 ± 1.27, p = 0.001), whereas no statistically significant differences in mtDNA content were seen in relation to embryo morphology (1.58 ± 2.44 vs. 2.19 ± 2.89, p = 0.12), genetic sex (1.27 ± 1.29 vs. 1.27 ± 1.18, p = 0.99), maternal age (1.31 ± 1.41 vs. 1.33 ± 1.29, p = 0.43), or its ability to implant (1.14 ± 0.88 vs. 1.21 ± 1.16, p = 0.39). mtDNA has small potential to serve as an additional, independent biomarker for embryo selection.

ELOVL5 Participates in Embryonic Lipid Determination of Cellular Membranes and Cytoplasmic Droplets

Embryonic lipids are crucial for the formation of cellular membranes and dynamically participate in metabolic pathways. Cells can synthesize simple fatty acids, and the elongation of fatty acids facilitates the formation of complex lipids. The aim of this work was to investigate the involvement of the elongation of very long chain fatty acid enzyme 5 (ELOVL5) in embryonic development and lipid determination. Bovine embryos were produced in vitro using a standard protocol and randomly divided to receive one of three treatments at Day 4: morpholino (Mo) gene expression knockdown assay for ELOVL5 (ELOVL5-Mo), Mo antisense oligonucleotides for the thalassemic β-globulin human mRNA (technical control Mo), and placebo (biological control). The phenotypes of embryonic development, cell number, ELOVL5 protein abundance, lipid droplet deposits, and lipid fingerprint were investigated. No detrimental effects (p > 0.05) were observed on embryo development in terms of cleavage (59.4 ± 3.5%, 63.6 ± 4.1%, and 65.4 ± 2.2%), blastocyst production (31.3 ± 4.2%, 28.1 ± 4.9%, and 36.1 ± 2.1%), and blastocyst cell number (99.6 ± 7.7, 100.2 ± 6.2, 86.8 ± 5.6), respectively, for biological control, technical control Mo, and ELOVL5-Mo. ELOVL5 protein abundance and cytoplasmic lipid droplet deposition were increased (p < 0.05) in ELOVL5-Mo-derived blastocysts compared with the controls. However, seven lipid species, including phosphatidylcholines, phosphatidylethanolamines, and triacylglycerol, were downregulated in the ELOVL5-Mo-derived blastocysts compared with the biological control. Therefore, ELOVL5 is involved in the determination of embryonic lipid content and composition. Transient translational blockage of ELOVL5 reduced the expression of specific lipid species and promoted increased cytoplasmic lipid droplet deposition, but with no apparent deleterious effect on embryonic development and blastocyst cell number.

Polycomb Group Proteins Regulate Chromatin Architecture in Mouse Oocytes and Early Embryos

In mammals, chromatin organization undergoes drastic reorganization during oocyte development. However, the dynamics of three-dimensional chromatin structure in this process is poorly characterized. Using low-input Hi-C (genome-wide chromatin conformation capture), we found that a unique chromatin organization gradually appears during mouse oocyte growth. Oocytes at late stages show self-interacting, cohesin-independent compartmental domains marked by H3K27me3, therefore termed Polycomb-associating domains (PADs). PADs and inter-PAD (iPAD) regions form compartment-like structures with strong inter-domain interactions among nearby PADs. PADs disassemble upon meiotic resumption from diplotene arrest but briefly reappear on the maternal genome after fertilization. Upon maternal depletion of Eed, PADs are largely intact in oocytes, but their reestablishment after fertilization is compromised. By contrast, depletion of Polycomb repressive complex 1 (PRC1) proteins attenuates PADs in oocytes, which is associated with substantial gene de-repression in PADs. These data reveal a critical role of Polycomb in regulating chromatin architecture during mammalian oocyte growth and early development.

Small RNA-seq analysis of single porcine blastocysts revealed that maternal estradiol-17beta exposure does not affect miRNA isoform (isomiR) expression

BACKGROUND

The expression of microRNAs (miRNAs) is essential for the proper development of the mammalian embryo. A maternal exposure to endocrine disrupting chemicals during preimplantation bears the potential for transgenerational inheritance of disease through the epigenetic perturbation of the developing embryo. A comprehensive assembly of embryo-specific miRNAs and respective isoforms (isomiR) is lacking to date. We aimed at revealing the sex-specific miRNA expression profile of single porcine blastocysts developing in gilts orally exposed to exogenous estradiol-17 (E2). Therefore we analyzed the miRNA profile specifically focusing on isomiRs and potentially embryo-specific miRNAs.

RESULTS

Deep sequencing of small RNA (small RNA-seq) result in the detection of miRNA sequences mapping to known and predicted porcine miRNAs as well as novel miRNAs highly conserved in human and cattle. A set of highly abundant miRNAs and a large number of rarely expressed miRNAs were identified by using a small RNA analysis pipeline, which was integrated into a novel Galaxy workflow specifically benefits incompletely annotated species. In particular, orthologue species information increased the total number of annotated miRNAs, while mapping to other non-coding RNAs avoided falsely annotated miRNAs. Neither the low nor the high dose of E2 treatment (10 and 1000 µ E2/kg body weight daily, respectively) affected the miRNA profile in blastocysts despite the distinct differential mRNA expression and DNA methylation found in previous studies. The high number of generated sequence reads enabled a comprehensive analysis of the isomiR repertoire showing various templated and non-templated modifications. Furthermore, potentially blastocyst-specific miRNAs were identified.

CONCLUSIONS

In pre-implantation embryos, numerous distinct isomiRs were discovered indicating a high complexity of miRNA expression. Neither the sex of the embryo nor a maternal E2 exposure affected the miRNA expression profile of developing porcine blastocysts. The adaptation to the continuous duration of the E2 treatment might explain the lack of an effect.

Colony-stimulating factor 2 enhances the developmental competence of yak (Poephagus grunniens) preimplantation embryos by modulating the expression of heat shock protein 70 kDa 1A

Colony-stimulating factor 2 (CSF₂) is known to promote the development and survival of rodents and ruminants preimplantation embryos; however, the effect of CSF₂ on yak embryos has not been reported. The objective of this study was to investigate the effects of CSF₂ on the developmental competence of yak embryos cultured in vitro in modified synthetic oviduct fluid (mSOF) medium and on the expression pattern of heat shock protein 70 kDa 1A (HSPA1A). In each experiment, cumulus-oocyte complexes (COCs) were matured in vitro and fertilized with frozen-thawed semen. Zygotes were treated with varying concentrations of CSF₂ (0, 10, 50, 100 ng/mL) until day 8 after fertilization. Embryo development was calculated as the percentage of oocytes that formed embryos at the 2-cell, 4-cell, 8-cell, 16-cell, morula and blastocyst stages. The total cell numbers (TCN) per blastocyst and their allocation to the inner cell mass (ICM) and trophectoderm (TE) lineages were determined using differential CDX2 staining. The expression of HSPA1A was examined by quantitative real-time PCR (qRT-PCR) and immunochemistry to determine the mRNA and protein levels. The results showed that treatment with 50 ng/mL CSF₂ significantly (P < 0.05) increased the rate of blastocyst formation (19.01% versus 9.93%) and the TCN per blastocyst (96.94 versus 81.41) compared to the control group. However, no significant differences were observed in the other stages of development. qRT-PCR analysis confirmed that treatment with 50 ng/mL CSF₂ significantly (P < 0.05) inhibited the expression of HSPA1A mRNA in blastocysts cultured in vitro relative to the control group, but there were no significant differences between the other treatment groups. Immunocytochemical analysis confirmed that HSPA1A protein accumulation was gradually reduced in yak blastocysts cultured in 0, 10, 100 or 50 ng/mL CSF₂, however, no significant differences were observed between the 10 and 100 ng/mL treatments (P > 0.05). In conclusion, these findings demonstrate that CSF₂ inhibits the expression of HSPA1A to facilitate yak blastocyst formation and increase cell numbers.

Immunological Staining of Global Changes in DNA Methylation in the Early Mammalian Embryo

The structural complexity of chromatin can make antibody access to some nuclear antigens energetically unfavorable. This can limit the usefulness and reliability of immunostaining unless validated methods of epitope retrieval are applied. We found that denaturation of chromatin by sequential use of acidification and tryptic digestion of fixed cells is required to reliably detect DNA methylation in the embryo. Using this method to unmask the epitope revealed an unexpected pattern of reprogramming of global patterns of DNA methylation in the preimplantation embryo. This paper provides a detailed description of the procedures required for immunological detection of 5-methylcytosine in the early embryo.

Single Cell Restriction Enzyme-Based Analysis of Methylation at Genomic Imprinted Regions in Preimplantation Mouse Embryos

The methylation of cytosines in DNA is a fundamental epigenetic regulatory mechanism. During preimplantation development, mammalian embryos undergo extensive epigenetic reprogramming, including the global erasure of germ cell-specific DNA methylation marks, to allow for the establishment of the pluripotent state of the epiblast. However, DNA methylation marks at specific regions, such as imprinted gene regions, escape this reprogramming process, as their inheritance from germline to soma is paramount for proper development. To study the dynamics of DNA methylation marks in single blastomeres of mouse preimplantation embryos, we devised a new approach-single cell restriction enzyme analysis of methylation (SCRAM). SCRAM allows for reliable, fast, and high-throughput analysis of DNA methylation states of multiple regions of interest from single cells. In the method described below, SCRAM is specifically used to address loss of DNA methylation at genomic imprints or other highly methylated regions of interest.

Validating reference microRNAs for normalizing qRT-PCR data in bovine oocytes and preimplantation embryos

BACKGROUND

MicroRNAs (miRNAs) are small noncoding RNAs that act as post-transcriptional regulators of gene targets. Accurate quantification of miRNA expression using validated internal controls should aid in the understanding of their role in epigenetic modification of genome function. To date, most studies that have examined miRNA expression levels have used the global mean expression of all expressed genes or the expression of reference mRNAs or nuclear RNAs for normalization.

RESULTS

We analyzed the suitability of a number of miRNAs as potential expression normalizers in bovine oocytes and early embryos, and porcine oocytes. The stages examined were bovine oocytes at the germinal vesicle (GV) and metaphase II stages, bovine zygotes, 2, 4 and 8 cell embryos, morulae and blastocysts, as well as porcine cumulus oocyte complexes, GV, metaphase I and II oocytes. qRT-PCR was performed to quantify expression of miR-93, miR-103, miR-26a, miR-191, miR-23b, Let-7a and U6 for bovine samples and miR-21, miR-26a, miR-93, miR-103, miR-148a, miR-182 and miR-191 for porcine oocytes. The average starting material for each sample was determined using specific standard curves for each primer set. Subsequently, geNorm and BestKeeper software were used to identify a set of stably expressed miRNAs. Stepwise removal to determine the optimum number of reference miRNAs identified miR-93 and miR-103 as the most stably expressed in bovine samples and miR-26a, miR-191 and miR-93 in porcine samples.

CONCLUSIONS

The combination of miR-93 and miR-103 is optimal for normalizing miRNA expression for qPCR experiments on bovine oocytes and preimplantation embryos; the preferred combination for porcine oocytes is miR-26a, miR-191 and miR-93.

Mitochondrial DNA content as a viability score in human euploid embryos: less is better

OBJECTIVE

To investigate the clinical relevance of mitochondrial DNA (mtDNA) content as a viability score in human euploid embryos.

DESIGN

Retrospective analysis of mtDNA content of transferred euploid embryos.

SETTING

Reproductive genetics laboratory.

PATIENT(S)

Single-embryo transfer in 270 patients who underwent preimplantation genetic screening (205 day-3 blastomere biopsies, and 65 day-5 trophectoderm biopsies), and 10 patients with double-embryo transfer (male-female).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Normalized mtDNA content versus nuclear DNA (nDNA) from transferred euploid embryos.

RESULT(S)

A high mtDNA copy number in euploid embryos is indicative of lower embryo viability and implantation. Using the normalized mtDNA content, we created the mitochondrial score or Mitoscore (Ms). Day-3 embryos with <34 (MsA) had an implantation rate (IR) of 59% (n = 51); those with 34-52 (MsB) had an IR of 44% (n = 52); those with 52-97 (MsC) had an IR of 42% (n = 50); and those with >97 (MsD) had an IR of 25% (n = 52). Embryos with Ms >160 (n = 22) never implanted. Day-5 embryos with <18.19 (MsA) had an IR of 81%; those with 18.19-24.15 (MsB) had an IR of 50% (n = 16); those with 24.15-50.58 (MsC) had an IR of 62% (n = 16); and those with levels >50.58 (MsD) had an IR of 18% (n = 17). Embryos with levels >60 (n = 7) never implanted.

CONCLUSION(S)

An increased amount of mtDNA in euploid embryos is related to poor implantation potential and may be indicative of reduced metabolic fuel during oocyte maturation. We are implementing Ms in our preimplantation genetic screening platform to prospectively analyze its clinical relevance.

Optimal single-embryo mass spectrometry fingerprinting

In pre-implantation embryos, lipids play key roles in determining viability, cryopreservation and implantation properties, but often their analysis is analytically challenging because of the few picograms of analytes present in each of them. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) allows obtaining individual phospholipid profiles of these microscopic organisms. This technique is sensitive enough to enable analysis of individual intact embryos and monitoring the changes in membrane lipid composition in the early stages of development serving as screening method for studies of biology and biotechnologies of reproduction. This article introduces an improved, more comprehensive MALDI-MS lipid fingerprinting approach that considerably increases the lipid information obtained from a single embryo. Using bovine embryos as a biological model, we have also tested optimal sample storage and handling conditions before the MALDI-MS analysis. Improved information at the molecular level is provided by the use of a binary matrix that enables phosphatidylcholines, sphingomyelins, phosphatidylserines, phosphatidylinositols and phosphoethanolamines to be detected via MALDI(±)-MS in both the positive and negative ion modes. An optimal MALDI-MS protocol for lipidomic monitoring of a single intact embryo is therefore reported with potential applications in human and animal reproduction, cell development and stem cell research.

Characterization of a diverse secretome generated by the mouse preimplantation embryo in vitro

This study investigates the suitability of surface-enhanced laser desorption and ionization time-of-flight (SELDI-TOF) and electrospray ionization (ESI) mass spectrometry for analysis of the proteins released by the mouse preimplantation embryo in vitro. SELDI-TOF analysis with CM10 or IMAC30 (but not Q10) protein chips detected a protein peak at m/z approximately 8570 released by both C57BL6 and hybrid embryos. No other peaks unique to the presence of the embryo were identified with this method. ESI mass spectrometry of tryptic digests of embryo-conditioned media identified a total of 20 proteins released during development from the zygote to blastocyst stage. Four proteins were expressed in at least 7 out of 8 cultures tested, one of these (lactate dehydrogenase B) was in all cultures. A further five proteins were in at least half of the cultures and 11 more proteins were in at least one culture. The expression of two of these proteins is essential for preimplantation embryo development (NLR family, pyrin domain containing 5 and peptidyl arginine deiminase, type VI). A further four proteins detected have roles in redox regulation of cells, and three others are capable of inducing post-translational modifications of proteins. This study shows the feasibility of ESI mass spectrometry for identifying the proteins secreted by the preimplantation embryo in vitro. This analysis identifies a range of targets that now require detailed functional analysis to assess whether their release by the embryo is an important property of early embryo development.

The effects of time of first cleavage, developmental stage, and delipidation of nuclear-transferred porcine blastocysts on survival following vitrification

The effect of removing cytoplasmic lipid droplets (delipidation) at the 2-cell and developmental stages on the survival of porcine somatic cell nuclear-transferred blastocysts developed from the enucleated oocytes receiving somatic cells from kidney of an adult female after cryopreservation was examined. Vitrification was performed using the Cryoloop method with a small volume of medium (0.5 microl). To select 2-cell embryos with a high potential to develop into blastocysts, the relationship between the timing of the first cleavage and the developmental potential was examined. The potential of nuclear-transferred oocytes to develop into blastocysts in the intermediate-cleavage group (20-24h after activation, 25%) was slightly or significantly (P<0.05) higher than that in fast-cleavage (<20 h after activation, 13%) and slow-cleavage groups (>24h after activation, 5%). Most non-delipidated blastocysts did not survive after thawing (0% for early-stage and 9% for advanced-stage blastocysts), but the survival rate of delipidated blastocysts 48 h after culture (54% and 72%, respectively) was not significantly different from that of non-vitrified blastocysts (80% and 92%, respectively). The survival rate of advanced-stage blastocysts after vitrification was slightly higher than that of early-stage blastocysts. The present study demonstrates that somatic cell nuclear-transferred porcine blastocysts developed from embryos selected at the 2-cell stage can be preserved by vitrification with a small volume of medium if the lipid droplets of the embryos are first removed.

Development and calcium level changes in pre-implantation porcine nuclear transfer embryos activated with 6-DMAP after fusion

This study investigated the effect of treatment with 6-dimethylaminopurine (6-DMAP) following fusion on in vitro development of porcine nuclear transfer (NT) embryos. Frozen thawed ear skin cells were transferred into the perivitelline space of enucleated oocytes. Reconstructed oocytes were fused and activated with electric pulse in 0.3 M mannitol supplemented with either 0.1 or 1.0 mM CaCl(2). In each calcium concentration, activated oocytes were divided into three groups. Two groups of them were exposed to either ionomycin (I + 6-DMAP or 6-DMAP alone. In experiment 2, fused NT embryos in 0.3 M mannitol containing 1.0 mM CaCl(2) were exposed to 6-DMAP either immediately or 20 min after fusion/activation. For 0.1 mM CaCl(2), oocytes activated with either I + 6-DMAP or 6-DMAP alone showed a higher (P < 0.05) developmental rate to the blastocyst stage than those activated with an electric pulse alone (26.7 and 22.5 vs. 12.5%). For 1.0 mM CaCl(2), oocytes activated with either I + 6-DMAP or 6-DMAP alone showed significantly higher (P < 0.05) developmental rate to the blastocyst stage (35.6 and 28.3 vs. 19.8%). Developmental rate to the blastocyst stage was (P < 0.05) increased in NT embryos activated with 6-DMAP 20 min after fusion. 6-DMAP made a higher and wider Ca(2+) transient compared to that induced by electric pulses (Fig. 3). The fluctuation lasted during the time that oocytes were cultured in 6-DMAP. Regardless of Ca(2+) concentration in fusion medium, activation with 6-DMAP following electric pulses supported more development of porcine NT embryos. Activation of NT embryos with 6-DMAP after fusion in the presence of 1.0 mM CaCl(2) could support better developmental rate to the blastocyst stage.

Production of transgenic porcine blastocysts by hand-made cloning

Recently, a zona-free technique for bovine somatic cell nuclear transfer (NT) with no requirement for micromanipulation (i.e. hand-made cloning (HMC)) has been described. The present study demonstrates the application of the HMC technique in the production of transgenic porcine blastocysts. In vitro-matured zona-free porcine oocytes were bisected manually using a microblade and halves containing no chromatin (i.e. the cytoplasts) were selected. Two cytoplasts were electrofused with one transgenic fibroblast expressing enhanced green fluorescent protein and reconstructed embryos were activated in calcium ionophore (A23187) followed by 6-dimethylaminopurine. Subsequently, embryos were cultured in NCSU-23 medium supplemented with 4 mg mL(-1) bovine serum albumin for 7 days. In five replicates, 93.0 +/- 7.0% (mean +/- s.e.m.) of attempted reconstructed embryos fused and survived activation (31/31, 15/23, 28/28, 37/37 and 28/28). On Day 7 after activation, the respective blastocyst rates (per successfully reconstructed embryos) were 6% (2/31), 7% (1/15), 7% (2/28), 3% (1/37) and 7% (2/28), resulting in an average of 6.0 +/- 0.8%. Enhanced green fluorescent protein was expressed in all cells of all eight developing blastocysts. Efforts are now directed towards the production of offspring from such transgenic NT blastocysts.

Centrosomal protein centrin is not detectable during early pre-implantation development but reappears during late blastocyst stage in porcine embryos

Centrin is an evolutionarily conserved 20 kDa, Ca+2-binding, calmodulin-related protein associated with centrioles and basal bodies of phylogenetically diverse eukaryotic cells. Earlier studies have shown that residual centrosomes of non-rodent mammalian spermatozoa retain centrin and, in theory, could contribute this protein for the reconstruction of the zygotic centrosome after fertilization. The present work shows that CEN2 and CEN3 mRNA were detected in germinal vesicle-stage (GV) oocytes, MII oocytes, and pre-implantation embryos from the two-cell through the blastocyst stage, but not in spermatozoa. Boar ejaculated spermatozoa possess centrin as revealed by immunofluorescence microscopy and western blotting. Immature, GV oocytes possess speckles of centrin particles in the perinuclear area, visualized by immunofluorescence microscopy and exhibit a 19 kDa band revealed by western blotting. Mature MII stage oocytes lacked centrin that could be detected by immunofluorescence or western blotting. The sperm centrin was lost in zygotes after in vitro fertilization. It was not detectable in embryos by immunofluorescence microscopy until the late blastocyst stage. Embryonic centrin first appeared as fine speckles in the perinuclear area of some interphase blastocyst cells and as putative centrosomes of the spindle poles of dividing cells. The cells of the hatched blastocysts developed centrin spots comparable with those of the cultured cells. Some blastomeres displayed undefined curved plate-like centrin-labeled structures. Anti-centrin antibody labeled interphase centrosomes of cultured pig embryonic fibroblast cells as distinct spots in the juxtanuclear area. Enucleated pig oocytes reconstructed by electrofusion with pig fibroblasts displayed centrin of the donor cell during the early stages of nuclear decondensation but became undetectable in the late pronuclear or cleavage stages. These observations suggest that porcine zygotes and pre-blastocyst embryonic cells lack centrin and do not retain exogenously incorporated centrin. The early embryonic centrosomes function without centrin. Centrin in the blastocyst stage embryos is likely a result of de novo synthesis at the onset of differentiation of the pluripotent blastomeres.

Molecular dynamics of heterochromatin protein 1beta, HP1beta, during mouse preimplantation development

To elucidate the molecular dynamics of HP1beta in mouse preimplantation embryos, we examined the localization, dynamics, and mobility of HP1beta in the (pro)nucleus by live cell imaging. Time-lapse observation revealed that the chromatin association of HP1beta is regulated in a cell cycle-dependent manner. HP1beta was localized in the interphase nucleus and was dynamically dissociated from the nucleus during the metaphase stage. The HP1beta assembly and clustered heterochromatin structure were both found in the nuclei of 2-cell and later-stage embryos. Moreover, fluorescent recovery after photobleaching analysis implied that HP1beta is more freely mobile in the pronucleus of the 1-cell embryo than in the 4-cell nucleus. These results suggest that the chromatin configuration may be regulated by the stability and mobility of chromatin-associated proteins including HP1beta during early embryonic stages.

Comparison of 4', 6'-diamidino-2-phenylindole and Giemsa stainings in preimplantation mouse embryos micronucleus assay including a triple dose study

Analysis of micronuclei (MN) in preimplantation embryos is a good method for the evaluation of cytogenetic damage induced by occupational and environmental mutagen during early pregnancy. To examine whether conventional Giemsa staining produced the same accuracy of micronuclei as the DNA-specific 4', 6'-diamidino-2-phenylindole (DAPI) staining in preimplantation embryo induced by maternal exposure to chlorpyrifos, we conducted assays on 469 mouse (3 groups) preimplantation embryos micronucleus. Slides were stained with DAPI. After DAPI staining, the slides were de-stained and restained with Giemsa. Giemsa staining showed similar frequencies in MN to DNA-specific DAPI staining in all three groups. Both staining techniques revealed significant increases in frequency of MN in the treated group in comparison to the control group. Both methods showed a statistically significant correlation between MN frequency and the dose of chlorpyrifos. Compared with DAPI staining, the sensitivity of Giemsa staining was 85.0%, 86.0% and 90.9% for control, 40 mg/kg, and 80 mg/kg chlorpyrifos treated group, respectively. The specificity was 97.9%, 91.4% and 96.5% for control, 40 mg/kg, and 80 mg/kg chlorpyrifos treated group, respectively. Thus, we recommend that Giemsa staining technique be a standard staining method in detecting MN of preimplantation embryos induced by occupational or environmental hazards.

Cryosurvival of bovine blastocysts is enhanced by culture with trans-10 cis-12 conjugated linoleic acid (10t,12c CLA)

An excessive lipid content in embryo cells is a consequence of embryo culture in the presence of serum which is suggested to be responsible for their high susceptibility to cryopreservation. The objective of the present study was to examine the effects of supplementing serum-containing culture media with trans-10 cis-12 conjugated linoleic acid (10t,12c CLA) on embryo lipid accumulation and its subsequent cryopreservation. Abattoir-derived oocytes were matured and fertilized in vitro (IVF=day 0). On day 1, presumptive zygotes (n=3390) were randomly placed in: (I) (MS), granulosa cell monolayer cultured with M199 and 10% serum; (II) (SCLA), granulosa cell monolayer cultured with M199, 10% serum and 100 microM 10t,12c CLA and (III) (SOF), modified synthetic oviduct fluid, where embryo culture proceeded for 8 days. Cleavage rates or D7/D8 embryo quality did not vary among treatments. D7/D8 embryo production rate was significantly (P<0.001) lower in SOF (17.9+/-1.6%) than in groups MS (29.8+/-2.5%) and SCLA (27.8+/-2.0%). After cytoplasmic lipid droplets observation under Nomarski microscopy, classified embryos were the leanest when cultured in SOF, intermediate in SCLA and the fattest in MS (P<0.02). Post-thawing intact blastocyst rates where significantly higher in the SCLA group (84.7+/-4.1%) than in SOCS (50.3+/-4.8%, P=0.0007) or SOF (65.3+/-6.9%, P=0.03) groups. Post-thawing re-expanding rates were significantly lower when embryos were cultured in MS (34.7+/-3.7%) than in SCLA (63.7+/-5.3%, P=0.0006) or SOF (49.0+/-4.6%, P=0.04). Moreover, re-expanding rates were lower (P=0.05) in SOF than in SCLA cultured embryos. These results clearly show that addition of CLA to serum-containing media reduced lipid accumulation during in vitro culture and significantly improved cryopreservation survival.

Time-lapse and retrospective analysis of DNA methylation in mouse preimplantation embryos by live cell imaging

Genome-wide change of DNA methylation in preimplantation embryos is known to be important for the nuclear reprogramming process. A synthetic RNA encoding enhanced green fluorescence protein fused to the methyl-CpG-binding domain and nuclear localization signal of human MBD1 was microinjected into metaphase II-arrested or fertilized oocytes, and the localization of methylated DNA was monitored by live cell imaging. Both the central part of decondensing sperm nucleus and the rim region of the nucleolus in the male pronucleus were highly DNA-methylated during pronuclear formation. The methylated paternal genome undergoing active DNA demethylation in the enlarging pronucleus was dispersed, assembled, and then migrated to the nucleolar rim. The female pronucleus contained methylated DNA predominantly in the nucleoplasm. When the localization of methylated DNA in preimplantation embryos was examined, a configurational change of methylated chromatin dramatically occurred during the transition of 2-cell to 4-cell embryos. Moreover, retrospective analysis demonstrated that a noticeable number of the oocytes reconstructed by round spermatid injection (ROSI) possess small, bright dots of methylated chromatin in the nucleoplasm of male pronucleus. These ROSI oocytes showed a significantly low rate of 2-cell formation, thus suggesting that the poor embryonic development of the ROSI oocytes may result from the abnormal localization of methylated chromatin.

Expression of extracellular matrix metalloproteinase inducer and matrix metalloproteinases during mouse embryonic development

Mouse embryo implantation is a highly invasive and controlled process that involves remodeling and degradation of the extracellular matrix of the uterus. Matrix metalloproteinases (MMPs) are the main proteinases facilitating this process. Extracellular matrix metalloproteinase inducer (EMMPRIN) can stimulate the production of MMPs and is required for successful implantation in the mouse. The aims of the present study were to examine the expression profiles of mRNA and proteins for EMMPRIN and MMPs in the developing mouse embryoin vitro, and to study whether EMMPRIN protein induces the production of MMPs by mouse blastocysts. EMMPRIN mRNA, detected by RT-PCR, was present at all stages of embryo development from the one-cell to the blastocyst outgrowth. EMMPRIN protein, observed by confocal microscopy, was present on the cell surface at the same stages of development as was the mRNA. Of seven MMPs studied, murine collagenase-like A (Mcol-A), murine collagenase-like B (Mcol-B) and gelatinase A (MMP-2) mRNAs were detected only in blastocyst outgrowths by RT-PCR. Gelatinase B (MMP-9) mRNA was detected both in expanded blastocysts and blastocyst outgrowths. MMP-2 and -9 proteins were detected in the cytoplasm of outgrowing trophoblast cells. Collagenase-2 (MMP-8), collagenase-3 (MMP-13), or stromelysin-1 (MMP-3) mRNAs were not present at any stage of pre- or peri-implantation mouse embryo development. Quantitative RT-PCR analyses showed that recombinant EMMPRIN protein did not stimulate MMP-2 or -9 expression by mouse blastocyst outgrowths. These data suggest that EMMPRIN may regulate physiological functions other than MMP production by mouse embryos during implantation.

Dynamic changes in the localization of five members of the methyl binding domain (MBD) gene family during murine and bovine preimplantation embryo development

There are five methyl binding domain (MBD) proteins characterized by a methyl CpG-binding domain. Four MBD proteins (MeCP2 and MBDs 1-3) are linked to transcriptional repression and one (MBD4), to DNA repair. During preimplantation development, the embryo undergoes global demethylation following fertilization and selective remethylation following the maternal to zygotic transition (MZT). This study characterized changes in MBD mRNA expression and protein localization during both murine and bovine preimplantation development. These species were selected because they undergo MZT at different developmental stages. Gene expression profiling during preimplantation development detected the presence of all MBDs examined, although stage and species-specific differences were observed. MBD2 was not expressed in murine or bovine oocytes and MeCP2 was not detected in murine blastocysts, subcellular protein localization was found to vary at time points critical in development. Most MBDs showed species-specificity in localization patterns and differences were found between individual MBDs. MBD1 localization is consistent with a novel role during MZT for both species. MBD3, known to play a crucial role in murine embryogenesis, was highly localized to the nucleus before and after, but not during the MZT in the bovine. MBD2, MBD4, and MeCP2 show varying patterns of localization which indicate possible roles in the early cleavage stages and in inner cell mass differentiation. Further experiments are currently underway to define discreet functional roles for specific MBDs during bovine preimplantation embryogenesis.

In vitro development and cell allocation of porcine blastocysts derived by aggregation of in vitro fertilized embryos

In pigs, the morphology and cell number of in vitro-produced blastocysts are inferior to those of their in vivo counterparts. The objective of this study was to increase developmental competence and to gain an understanding of cell allocation in blastocysts derived from the aggregation of four-cell stage porcine embryos produced in vitro. After removal of the zona pellucida, two (2x) and three (3x) four-cell stage embryos were aggregated by co-culturing them in aggregation plates. Five days after aggregation, the developmental ability and the number of cells in the aggregated embryos were determined. The percentage of blastocysts was higher (P < 0.05) in both the 2x and 3x aggregated embryos (66.6% and 72.0%, respectively) compared to that of the 1x embryos and the intact controls (43.1% and 36.4%, respectively). The total cell number of blastocysts also increased in aggregated embryos compared to that of intact controls (2.6-fold for 2x and 3.4-fold for 3x) (P < 0.05). The cells of two differentially stained embryos were started to mix at 72 hr after aggregation. In vitro-fertilized porcine aggregates (2x) were developed to blastocyst with a random distribution of cells from each embryo. The mRNA levels for the oct-4, bcl-xL and connexin 43 genes were higher (P < 0.05) and bak gene were lower (P < 0.05) in both the 2x and 3x aggregated embryos than the intact controls. Therefore, the aggregation of the four-cell stage embryos could be used to improve the quality of porcine preimplantation stage embryos produced in vitro.

Leptin has concentration and stage-dependent effects on embryonic development in vitro

There is accumulating evidence that leptin may be directly involved in pre-implantation embryonic development, however, it is unclear whether there is a concentration and stage-dependent regulatory pattern. In this study, the addition of 10 ng/ml human recombinant leptin to the culture medium significantly increased the percentage of two-cell mouse embryos that developed into blastocysts and hatched blastocysts, whereas in the presence of 100 ng/ml leptin, the development rate was significantly inhibited. The total cell numbers in the hatched blastocysts were significantly higher in the presence of 10 ng/ml leptin compared with controls and higher concentrations. The differential sensitivity to leptin was found to vary among embryos at different stages of development. Supplementation of leptin (10 ng/ml) to culture medium at two- to eight-cell stages resulted in a consistent stimulatory effect on embryo development. Most interestingly, the inhibitory effect of high leptin concentration (100 ng/ml) on embryo development was diminished when it was added to the culture medium at the eight-cell stage of development. The concentration-dependent regulation pattern was confirmed using sheep embryos, under similar conditions although sheep embryos appeared to be more sensitive in responding to leptin. Having established the effect of exogenous leptin on embryo development, the expression pattern of leptin and its receptors were also investigated. Leptin mRNA was not detected in mouse two-, four-, eight-cell and blastocyst stage embryos, whereas three isoforms of leptin receptor (Ob-Ra, Ob-Rb and Ob-Re) were identified in these cells, indicating that leptin is likely to modulate embryo development via a paracrine signalling system.

Construction and characteristics of 3-end enriched cDNA library from individual embryos of cattle

To analyze stage-specific gene expression profiles of pre-implantation embryos and evaluate potential viability, techniques were adapted to generate 3-end enriched cDNA libraries from individual embryos of cattle based on RT-PCR methodology. The reproducibility of constructing a cDNA library was tested by five independent PCR experiments with specific primers for the presence of several rare genes such as DNMT1 (DNA methylation transferase 1), DNMT2, DNMT3A, Oct-4/3 (octmer-binding transcription factor), IFN-iota, IGF-2r (insulin like growth factor 2 receptor), and the housekeeping genes, H2A and beta-actin. Results indicated repeatability and that a proportion of expressed genes in the cDNA library from an individual embryo was not affected by limited PCR amplification. From the cDNA library, 134 clones were randomly selected for sequencing and showed that structure related elements accounted for 33.5% of transcripts and the energy- and metabolism-related genes were also an important component being 11.9% in the cDNA library. Approximately 14% of genes in the library were functionally unknown including greater than 5% of genes that were likely novel because there was no identity in Genbank. The frequency of structure-related genes such as beta-actin and ribosomal proteins in the cDNA library corresponded to other reports and suggested that the cDNA library constructed by RT-PCR might be proportional to the mRNA populations. The cDNA libraries constructed from different stage embryos will provide a powerful tool to explore novel genes relevant to embryogenesis, determine the profiling of stage-specific gene expression, and evaluate the potential viability of embryos.

The Bysl gene product, bystin, is essential for survival of mouse embryos

Human bystin is a cytoplasmic protein directly binding to trophinin, a cell adhesion molecule potentially involved in human embryo implantation. The present study shows that bystin is expressed in luminal and glandular epithelia in the mouse uterus at peri-implantation stages. In fertilized embryos, bystin was not seen until blastocyst stage. Bystin expression started during hatching and increased in expanded blastocyst. However, bystin apparently disappeared from the blastocyst during implantation. After implantation bystin re-appeared in the epiblast. Targeted disruption of the mouse bystin gene, Bysl, resulted in embryonic lethality shortly after implantation, indicating that bystin is essential for survival of mouse embryos.

Esg1, expressed exclusively in preimplantation embryos, germline, and embryonic stem cells, is a putative RNA-binding protein with broad RNA targets

In our earlier attempt to identify genes involved in the maintenance of cellular pluripotency, we found that KH-domain protein Embryonal stem cell-specific gene 1 (Esg1) showed similar expression patterns to those of Oct3/4 (Pou5f1), whereas the forced repression of Oct3/4 in mouse embryonic stem cells immediately downregulated the expression of Esg1. Here we further confirm this overlap by in situ hybridization and immunohistochemical analyses. Both Esg1 transcript and protein exist in the egg and preimplantation embryos. At embryonic day 3.5, blastocyst stage, however, ESG1 protein was more abundant in the inner cell mass (ICM) than in trophectoderm (TE), whereas Esg1 transcript was detected in both the ICM and the TE, particularly in the polar trophectoderm. The presence of an RNA-binding KH-domain in ESG1 led us to search for and identify 902 target transcripts by microarray analysis of immunoprecipitated ESG1 complex. Interaction of 20 target mRNA with ESG1, including Cdc25a, Cdc42, Ezh2, Nfyc and Nr5a2, was further validated by reverse transcriptase-polymerase chain reaction of the immunoprecipitation material, supporting the notion that ESG1 is an RNA-binding protein which associates with specific target transcripts.

Nuclear and cytoplasmic localization of interferon-tau in in vitro-produced bovine blastocysts

Experiments were conducted to detect interferon-tau in bovine in vitro-derived blastocysts by transmission electron (TEM) and confocal microscopy. TEM showed the presence of IFN-tau in the cytoplasm and the nuclei of expanded blastocysts. Confocal microscopy similarly confirmed the presence of IFN-tau in the trophectoderm of blastocysts. The distribution of IFN-tau appeared variable with some cells showing strong labeling while others appeared to be devoid of the protein.

Analysis of Development-Related Gene Expression in Cloned Bovine Blastocysts with Different Developmental Potential

The high incidence of abnormalities in cloned calves is a most serious problem for bovine somatic cell nuclear transfer (NT) technology. Because there is little information on the differences in mRNA expression in cloned blastocysts with donor cells of different sex and origin, we compared development-related gene expression in two types of cloned bovine blastocysts with different potentials to develop into normal calves, a female adult cumulus cell line (high potential to develop into live calves) and a male fibroblast cell line (low potential to develop into live calves) to examine the correlation between the normality of cloned calves and blastocyst mRNA expression patterns. We analyzed 12 genes involved in apoptosis, growth factor signaling, metabolism, and DNA methylation in blastocysts originating from two types of donor cells and in vitro-fertilized blastocysts using quantitative real-time polymerase chain reaction. Expression of the pro-apoptotic Bax gene and anti-apoptotic Bcl-2 and Glut-1 genes in fibroblast-derived blastocysts was significantly higher than in cumulus cell-derived and in vitro-fertilized blastocysts. The high Bcl-2 and Glut-1 gene expression suggests that some embryonic cells with damaged DNA in fibroblast-derived blastocysts are not removed, and their descendants later manifest abnormal placenta or fetus formation. Transfer of pre-selected cloned blastocysts into recipients is required, however, to determine whether the expression pattern of these apoptosis-related genes reflects differences in the potential to develop into normal calves.

Expression of leptin ligand and receptor and effect of exogenous leptin supplement on in vitro development of porcine embryos

The present study investigated the expression of ligand and receptor for leptin, and the effect of leptin supplementation on preimplantation development of porcine in vitro fertilized (IVF) and somatic cell nuclear transfer (SCNT) embryos. The IVF embryos were produced using frozen boar semen and SCNT embryos were obtained by nuclear transfer of fetal fibroblasts into enucleated oocytes. The protein expression of leptin ligand and receptor was investigated in in vitro matured oocytes, 2-, 4- and 8-cell embryos, morulae and blastocysts derived from IVF and SCNT using immunofluorescence. Both the ligand and receptor were detected in in vitro matured oocytes and all stage of IVF and SCNT embryos. The IVF and SCNT embryos were cultured in modified North Carolina State University (mNCSU)-23 medium supplemented with various concentrations (0, 1, 10, 100 or 1000 ng/mL) of leptin. The rates of cleavage at day 2 and blastocyst formation at day 7, and cell number of blastocysts were monitored as experimental parameters. In SCNT embryos, supplementing with 1000 ng/mL leptin significantly (P<0.05) increased the rate of blastocysts formation (20.2% versus 12.9%) and total cell number (54.6+/-17.4 versus 45.1+/-15.2) compared to the control group. In IVF embryos, leptin supplementation did not affect preimplantation embryo development and cell number in blastocysts. In conclusion, the present study demonstrated the expression of leptin ligand and receptor and the embryotropic effect of leptin in SCNT embryos.

Morphological characterization of pre- and peri-implantation in vitro cultured, somatic cell nuclear transfer and in vivo derived ovine embryos

The processes of cellular differentiation were studied in somatic cell nuclear transfer (SCNT), in vitro cultured (IVC) and in vivo developed (in vivo) ovine embryos on days 7, 9, 11, 13, 17 and 19. SCNT embryos were constructed from in vitro matured oocytes and granulosa cells, and IVC embryos were produced by in vitro culture of in vivo fertilized zygotes. Most SCNT and IVC embryos were transferred to recipients on day 6 while some remained in culture for day 7 processing. In vivo embryos were collected as zygotes, transferred to intermediate recipients and retransferred to final recipients on day 6. All embryos were processed for examination by light and transmission electron microscopy or immunohistochemical labelling for alpha-1-fetoprotein and vimentin. Overall, morphological development of in vivo embryos was superior to IVC and SCNT embryos. Day 7 and particularly day 9 IVC and SCNT embryos had impaired hypoblast development, some lacking identifiable inner cell masses. On day 11, only in vivo and IVC embryos had developed an embryonic disc, and gastrulation was evident in half of in vivo embryos and one IVC embryo. By day 13, all in vivo embryos had completed gastrulation whereas IVC and SCNT embryos remained retarded. On days 17 and 19, in vivo embryos had significantly more somites and a more developed allantois than IVC and SCNT embryos. We conclude that IVC and particularly SCNT procedures cause a retardation of embryo development and cell differentiation at days 7-19 of gestation.

Gram-negative bacterial LPS induced poor uterine receptivity and implantation failure in mouse: alterations in IL-1beta expression in the preimplantation embryo and uterine horns

Genito-urinary tract or systemic infections of the gram-negative bacteria in pregnant women, causes abortions, preterm labor, and several other perinatal complications. LPS is the most potent antigenic component of the gram-negative bacterial cell wall and is known to modulate the expression of various proinflammatory cytokines. Here we investigate the role of the soluble form of IL-1 i.e., IL-1beta in the 'minimum dose' of LPS induced pregnancy loss in mice. Uterine cross-sections on each day of the preimplantation period of pregnancy were examined histopathologically for finding out LPS induced changes in the uterine preparation for embryo implantation. The expression of IL-1beta in the various stages of the preimplantation period of pregnancy was studied by RT-PCR in the embryos and the uterine horns of the LPS treated and normal pregnant mice. We found that LPS significantly alters the proliferation of the glandular epithelium, luminal epithelium and stroma during the preimplantation period. We also found large infiltration of macrophages into the uterine horns of the LPS treated animals. The level and pattern of IL-1beta expression in the preimplantation embryos and uterine horns were also altered in LPS treated animals. These observations indicate that LPS can alter the uterine preparation for blastocyst implantation, which could be due to the change in the IL-1beta expression in the uterine horns. However, a change in the expression pattern of IL-1beta in the preimplantation embryos underlines the significance of this molecule in LPS induced pregnancy loss or implantation failure in mouse.

Production of a cloned calf using zona-free serial nuclear transfer

The efficiency of generating cloned animals following somatic cell nuclear transfer appears to have reached a plateau, despite ongoing research to improve developmental outcomes. A major limitation appears in the restricted nature of the adult/donor cell to de-differentiate to form a totipotent nucleus. Serial nuclear transfer, a modified cloning technique, has increased the developmental competence of amphibian, murine and porcine cloned embryos. This procedure involves a second nuclear transfer step; pronuclear-like cloned nuclei are transferred into pronuclear stage zygotic cytoplasts. The present study reports on the development of a serial nuclear transfer technique in the bovine, based on a zona-free method (hand-made cloning), resulting in the birth of a cloned calf. Comparisons were made between embryos produced by hand-made cloning and serial nuclear transfer. There were no differences between in vitro development or differential cell counts in the blastocysts produced. Transfer of 16 serial hand-made cloned blastocysts resulted in the production of one healthy calf (6%), whereas hand-made cloning resulted in the birth of 1 calf from 23 transferred blastocysts (4%). One serial nuclear transfer pre-term fetus had renal and hepatic abnormalities (previously observed in clones from this cell line). Although it may not be as beneficial in the bovine as in other species, normal placentation (size, placentomes and umbilicus) was encouraging. Refinement of this technique may help to identify species-specific differences in zygotic competence that affect reprogramming of donor cell nuclei and that may improve efficiency.

Angiopoietin-1 and -2 mRNA and protein expression in mouse preimplantation embryos and uteri suggests a role in angiogenesis during implantation

After attachment and migration through the endometrial epithelium, the embryo must induce angiogenesis within the endometrial stroma to successfully complete the implantation process. Growth factors have been shown to play an important role in embryo implantation and placentation. The aim of the study was to investigate the expression of angiopoietin-1 and -2 (Ang-1 and -2) mRNA and protein expression during the development of single preimplantation mouse embryos and of possible complementary expression in mouse uteri. Angiopoietin-1 mRNA was expressed throughout development in 78% of zygotes, 66% of 2-cell-embryos, 71% of 4-cell-embryos, 70% of 8-cell-embryos, 60% of morula stages, 48% of early blastocysts and 78% of late blastocysts. The number of Ang-1-expressing embryos in the early-blastocyst group was significantly different in comparison with zygotes, 4-cell-embryos, 8-cell-embryos and late blastocysts. Angiopoietin-2 mRNA and protein expression could not be detected in preimplantation embryos. Examination of the uteri revealed Ang-2 mRNA and protein expression in the oestrogen-dominated cycling phase and the progesterone-dominated mated phase, whereas Ang-1 expression was restricted to the mated phase. Herein, Ang-1 expression in preimplantation mouse embryos as well as Ang-1 and -2 expression in mouse uteri is demonstrated, suggesting a possible role for angiopoietins in the embryo–maternal dialogue of the implantation process via an enhancement of the vascular remodelling in favour of an implanting conceptus.

Expression of IGF-II mRNA-binding proteins (IMPs) in gonads and testicular cancer

Insulin-like growth factor-II mRNA-binding proteins 1, 2 and 3 (IMP1, IMP2 and IMP3) belong to a family of RNA-binding proteins implicated in mRNA localization, turnover and translational control. We examined their expression pattern during development of murine and human testis and ovaries. In the mouse, IMPs were expressed in male and female gonadal cells at embryonic day 12.5 (E12.5). From E16.5, IMP1 and IMP3 became restricted to the developing germ cells, whereas IMP2 expression persisted in the interstitial cells. In mature mouse and human ovaries, IMP1, IMP2 and IMP3 were detected in resting and growing oocytes and in the granulosa cells. In testis, IMP1 and IMP3 were found mainly in the spermatogonia, whereas IMP2 was expressed in the immature Leydig cells. Moreover, all three IMPs were detected in human semen. The developmental expression pattern of IMP1 and IMP3 in the human testis prompted us to examine their possible involvement in testicular neoplasia. IMPs were detected primarily in germ-cell neoplasms, including preinvasive testicular carcinoma in situ, classical and spermatocytic seminoma, and nonseminomas, with particularly high expression in undifferentiated embryonal carcinoma. The relative expression of IMP1, IMP2 and IMP3 varied among tumor types and only IMP1 was detected in all carcinoma in situ cells. Thus IMPs, and in particular IMP1, may be useful auxiliary markers of testicular neoplasia.

Differential Expression of Alternatively Spliced Transcripts of HLA-G in Human Preimplantation Embryos and Inner Cell Masses

It has been reported that preimplantation human embryos secrete HLA-G, and the levels may be predictive of their ability to implant. However, it is not known which of the membrane-bound (HLA-G 1-4) and soluble (HLA-G 5-6) alternatively spliced forms are present, nor the developmental stage at which they appear. Therefore, we have investigated HLA-G mRNA isoform expression on single embryos at the two-, four-, six-, and eight-cell, morula, and blastocyst stages. The percentage of embryos expressing each HLA-G isoform mRNA increased with developmental stage, but contrary to expectation, HLA-G5 mRNA was not detected in single two- to eight-cell embryos and was only expressed by 20% of morulae and blastocysts. Similarly, soluble HLA-G6 mRNA was not detected until the blastocyst stage and then in only one-third of embryos. In contrast, labeling with MEM G/9 Ab (specific for HLA-G1 and -G5) was observed in 15 of 20 two- to eight-cell embryos and 5 of 5 blastocysts. This disparity between mRNA and protein may be due to HLA-G protein remaining from maternal oocyte stores produced before embryonic genome activation and brings into question the measurement of soluble HLA-G for clinical evaluation of embryo quality. Although HLA-G is expressed in the preimplantation embryo, later it is primarily expressed in the invasive trophoblast of the placenta rather than the fetus. Therefore, we have investigated whether down-regulation of HLA-G first occurs in the inner cell mass (precursor fetal cells) of the blastocyst and, in support of this concept, have shown the absence HLA-G1 and -G5 protein and mRNA.

Adverse effects of retinoic acid on embryo development and the selective expression of retinoic acid receptors in mouse blastocysts

BACKGROUND

All-trans retinoic acid (RA), the oxidative metabolite of vitamin A, is essential for normal development. In addition, high levels of RA are teratogenic in many species. We have previously shown that excess RA results in immediate effects on the preimplantation embryo and on blastocyst development. This study was conducted to clarify the long-term survival of mouse blastocyst and the effect of RA on gene expression.

METHODS AND RESULTS

Using an in vitro model, we identified the immediate adverse impact of RA on mouse blastocyst development. This involved an inhibition of cell proliferation and growth retardation. Using an in vivo model, we also identified the resorption of postimplanted blastocysts that had been treated with excess RA. Analysis of RA-mediated gene induction was also included. The retinoic acid receptors RARalpha and RARgamma were constitutively expressed in the blastocyst and the inner cell mass, whereas RARbeta was induced upon RA treatment.

CONCLUSIONS

This is the first evidence to show the impacts of RA on mouse blastocysts in vitro and any carry-over effects in the uterus. There is a retardation of early postimplantation blastocyst development and then subsequent blastocyst death. Our findings also show that there is some degree of selective induction of retinoic acid receptors when excess RA is administered to the blastocysts.

Orphan nuclear receptor LRH-1 is required to maintain Oct4 expression at the epiblast stage of embryonic development

Oct4 plays an essential role in maintaining the inner cell mass and pluripotence of embryonic stem (ES) cells. The expression of Oct4 is regulated by the proximal enhancer and promoter in the epiblast and by the distal enhancer and promoter at all other stages in the pluripotent cell lineage. Here we report that the orphan nuclear receptor LRH-1, which is expressed in undifferentiated ES cells, can bind to SF-1 response elements in the proximal promoter and proximal enhancer of the Oct4 gene and activate Oct4 reporter gene expression. LRH-1 is colocalized with Oct4 in the inner cell mass and the epiblast of embryos at early developmental stages. Disruption of the LRH-1 gene results in loss of Oct4 expression at the epiblast stage and early embryonic death. Using LRH-1(-/-) ES cells, we also show that LRH-1 is required to maintain Oct4 expression at early differentiation time points. In vitro and in vivo results show that LRH-1 plays an essential role in the maintenance of Oct4 expression in ES cells at the epiblast stage of embryonic development, thereby maintaining pluripotence at this crucial developmental stage prior to segregation of the primordial germ cell lineage at gastrulation.

Leptin receptors are down-regulated in uterine implantation sites compared to interimplantation sites

Leptin is a circulating hormone that plays an important role in the regulation of metabolism, obesity, and reproduction. Leptin binds to its receptors on the cell membrane and is involved in the activation of STAT3. Recently, endometrium was suggested to be a novel target for leptin recently. We, therefore, examined the expression of leptin, leptin receptors, and STAT3 in the mouse uterus (implantation and interimplantation sites) to investigate the role of the leptin system during the early implantation period. Leptin mRNA was not detected in mouse uterine tissues or blastocysts, although adipose tissue, the positive control, showed a strong signal. Both of the receptor splice variants were expressed in the uterus and blastocysts, but the mRNA level was much lower in implantation sites compared to interimplantation sites. The mRNA expression of leptin receptors was determined to be higher in stromal cells than in the luminal epithelium using laser capture microdissection (LCM) analysis. Using immunohistochemistry, leptin was detected as a strong signal in the luminal epithelium and embryo, whereas the receptor was detected in subepithelial stromal cells rather than the luminal epithelium. As leptin itself was not detected by RT-PCR, the immunohistologically detected leptin may originate elsewhere, such as in adipose tissue. The differential expression of leptin receptors in implantation sites compared to interimplantation sites suggests that the leptin/leptin receptor system may be a delicate regulator of the implantation process.

Serine-threonine kinases and transcription factors active in signal transduction are detected at high levels of phosphorylation during mitosis in preimplantation embryos and trophoblast stem cells

Serine-threonine kinases and transcription factors play important roles in the G1-S phase progression of the cell cycle. Assays that use quantitative fluorescence by immunocytochemical means, or that measure band strength during Western blot analysis, may have confused interpretations if the intention is to measure G1-S phase commitment of a small subpopulation of phosphorylated proteins, when a larger conversion of the same population of proteins can occur during late G2 and M phases. In mouse trophoblast stem cells (TSC), a human placental cell line (HTR), and/or mouse preimplantation embryos, 8/19 serine-threonine and tyrosine kinases, 3/8 transcription factors, and 8/14 phospho substrate and miscellaneous proteins were phosphorylated at higher levels in M phase than in interphase. Most phosphoproteins appeared to associate with the spindle complex during M phase, but one (p38MAPK) associated with the spindle pole and five (Cdx2, MEK1, 2, p27, and RSK1) associated with the DNA. Phosphorylation was detected throughout apparent metaphase, anaphase and telophase for some proteins, or for only one of these segments for others. The phosphorylation was from 2.1- to 6.2-fold higher during M phase compared with interphase. These data suggest that, when planning and interpreting quantitative data and perturbation experiments, consideration must be given to the role of serine-threonine kinases and transcription factors during decision making in M phase as well as in G1-S phase.

Two insulin-responsive glucose transporter isoforms and the insulin receptor are developmentally expressed in rabbit preimplantation embryos

Glucose is the most important energy substrate for mammalian blastocysts. Its uptake is mediated by glucose transporters (GLUT). In muscle and adipocyte cells insulin stimulates glucose uptake by activation of the insulin receptor (IR) pathway and translocation of GLUT4. GLUT4 is expressed in bovine preimplantation embryos. A new insulin-responsive isoform, GLUT8, was recently described in mouse blastocysts. Thus, potentially, two insulin-responsive isoforms are expressed in early embryos. The mechanism of insulin action on embryonic cells, however, is still not clear. In the present study expression of IR, GLUT1, 2, 3, 4, 5 and 8 was studied in rabbit preimplantation embryos using RT-PCR, Western blotting and immunohistochemistry. The rabbit mRNA sequences for the complete coding region of IR, GLUT4 and a partial GLUT8 sequence were determined by RACE-PCR and sequencing. GLUT4 was expressed in 3-day-old morulae and in 4- and 6-day-old blastocysts. IR and GLUT8 transcripts were detectable only in blastocysts. Blastocysts also expressed GLUT1 and 3, but not GLUT2 and 5. Transcript numbers of GLUT4 and 8 were higher in trophoblast than in embryoblast cells. Translation of IR, GLUT4 and 8 proteins in blastocysts was confirmed by Western blotting. GLUT4 was localized mainly in the membrane and in the perinuclear region in trophoblast cells while in embryoblast cells its localization was predominantly in the perinuclear cytoplasm. The possible function(s) of two insulin-responsive isoforms, GLUT4 and GLUT8, in rabbit preimplantation embryos needs further investigation. It may not necessarily be linked to insulin-stimulated glucose transport.

The role of gonadotropin-releasing hormone (GnRH) and its receptor in development of porcine preimplantation embryos derived from in vitro fertilization

This study was performed to investigate the expression of embryo-derived gonadotropin-releasing hormone (GnRH) and its receptor, and to determine the role of GnRH in porcine preimplantation embryos. In Experiment 1, porcine blastocysts derived from in vitro fertilization (IVF) and cultured in North Carolina State University (NCSU)-23 medium were subjected to reverse transcription polymerase chain reaction (RT-PCR) amplification with specific primers for GnRH and its receptor. The results showed that GnRH and its receptor were expressed in porcine IVF blastocysts. In order to investigate the role of GnRH in embryo development, porcine IVF embryos were cultured in NCSU-23 supplemented with different concentrations (0, 0.1, 1, or 10 microM) of a GnRH agonist (leuprolide, Experiment 2) or GnRH antagonist (antide, Experiment 3). Supplementing the culture medium with 0.1 or 1 microM leuprolide increased the rate of blastocyst formation (28.5 or 27.6% versus 20.2%) and mean total cell number (129 versus 104) compared to the control group. In contrast, antide significantly decreased the rate of blastocyst formation [12.6% (0.1 microM), 10.2% (1.0 microM), or 8.9% (10.0 microM) versus 22.8% (control)] and total cell number [69 (1 microM) or 68 (10 microM) versus 104 (control)]. In Experiment 4, porcine IVF embryos were cultured in NCSU-23 medium containing 1 microM antide plus 1 microM leuprolide. The embryotrophic effect of GnRH agonist was reversed by co-supplementing with GnRH antagonist. In conclusion, the present study demonstrated that supplementing a culture medium with GnRH agonist can improve blastocyst formation and the quality of porcine IVF embryos, and that this action was mediated through GnRH receptors.

EGF and IGF-I as predictors of ICSI outcome in human preimplantation embryo cultures

PURPOSE OF INVESTIGATION

Detection of EGF and IGF-I in human embryo cultures and their effect on ICSI outcome.

METHODS

Collection of culture medium from embryos of 50 women under ICSI program. EGF and IGF-I were measured via enzyme immunoassay.

RESULTS

ICSI outcome was independent of age, infertility years, FSH, LH, prolactine and E2. EGF detection was higher in 48- (32%), than in 72-hour embryos (14%) (p < 0.001). EGF negative embryos are likely to be arrested at the morula stage (p < 0.001) and are associated with poor pregnancy rates (p < 0.05). IGF-I was undetected in 48-hour embryos.

CONCLUSIONS

For the first time human embryos were surveyed from fertilization until embryo transfer, regarding EGF and IGF-I production. IGF-I is not a predictor of ICSI outcome. EGF is present in one-third of human embryo cultures at 48 hours, but this ratio wanes at the morula stage. EGF negative embryos are associated with lower pregnancy rates.

PGD for autosomal dominant polycystic kidney disease type 1

Autosomal dominant polycystic kidney disease (ADPKD) is primarily characterized by renal cysts and progression to renal failure. It is a genetically heterogeneous disease, with mutations in the PKD1 gene accounting for the majority of cases. Direct mutation detection for PKD1-linked ADPKD or type 1 is complicated by the large size and complex genomic structure of PKD1. This paper describes a microsatellite marker-based assay for PGD in couples at risk of transmitting ADPKD type 1. During PGD, genetic analysis is carried out on single blastomeres biopsied from preimplantation embryos obtained after IVF, and only embryos unaffected by the disease under investigation are selected for transfer. Single-cell genetic analysis relied on a fluorescent duplex-PCR of linked polymorphic markers followed by fragment length determination on an automated sequencer. The co-amplification of the intragenic KG8 and the extragenic D16S291 marker at the single-cell level was evaluated in pre-clinical tests on lymphoblasts and research blastomeres. The developed assay proved to be efficient (96.1% amplification) and accurate (1.4% allele drop-out and 4.3% contamination), and can be applied in all informative ADPKD type 1 couples. From five clinical cycles carried out for three couples, two pregnancies ensued, resulting in the birth of two healthy children.

Accumulation and distribution of neutral lipid droplets is non-uniform in ovine blastocysts produced in vitro in either the presence or absence of serum

Sheep zygotes were cultured in serum-free or serum-supplemented media to determine effects on blastocyst yields and within-blastocyst abundance and distribution of neutral lipid droplets. Embryos cultured in synthetic oviduct fluid supplemented with bovine serum albumin (0.4% w/v) (SBSA) generated similar blastocyst yields (mean ± s.e.m. = 20% ± 5) to those in synthetic oviduct fluid supplemented with serum (10% v/v) from ewes fed a diet containing 0% (SZFO; 26% ± 2) or 3% fish oil (S3FO; 23% ± 3). SBSA zygotes generated more good-quality blastocysts than their SZFO or S3FO counterparts (P < 0.05). Within-blastocyst abundance of neutral lipid droplets was non-uniform; data were collected from discrete embryo sectors (each = 2700 µm2) representing highest (H), intermediate (I) and lowest (L) densities of accumulation. For all sectors, area (µm2) occupied by lipid droplets in SBSA blastocysts (mean H = 470; I = 370; L = 245) was smaller (P < 0.01) than occupied in others (SBSA : SZFO = 1 : 1.41, 1 : 1.48 and 1 : 1.42; SBSA : S3FO = 1 : 1.36, 1 : 1.30 and 1 : 1.31; data for H, I and L, respectively). Among S3FO blastocysts only, inferior quality was associated with greater lipid abundance. Overall, embryo culture in the presence of serum increased neutral lipid droplet abundance but accumulation was non-uniform.

Mouse granulocyte-macrophage colony-stimulating factor enhances viability of porcine embryos in defined culture conditions

The aim of this study was to determine the effects of mouse granulocyte-macrophage colony-stimulating factor (mGM-CSF) on development of porcine parthenotes and nuclear transferred embryos, and on their expression of implantation-related genes. In the presence of bovine serum albumin, mGM-CSF did not increase the percentage of oocytes that developed to the blastocyst stage and at day 7 did not increase cell numbers of embryos. Addition of 2 ng/ml GM-CSF to protein-free culture medium significantly increased the compaction and blastocoel formation of 1- to 2-cell parthenotes developing in vitro. However, total cell numbers were not increased when they were cultured in the presence of GM-CSF. Semi-quantitative reverse transcriptase polymerase chain reaction revealed that mGM-CSF enhances mRNA expression of the leukemia inhibitory factor receptor, but does not influence interleukin-6 or sodium/glucose co-transporter protein gene expression in blastocyst stage parthenotes. These results suggest that mGM-CSF may enhance viability of porcine embryos developing in vitro in a defined culture medium.

Exogenous interferon-γ alters murine inner cell mass and trophoblast development. Effect on the expression of ErbB1, ErbB4 and heparan sulfate proteoglycan (perlecan)

Implantation is a crucial event in human pregnancy. The participation of cytokines in the implantation process has been widely documented, although the role of many of these molecules is still a matter of controversy. In a previous report from our laboratory, we demonstrated that addition of interferon-γ to the culture medium produces deleterious effects on mouse embryo development. In this study we investigated the effect of this cytokine on outgrowing embryo morphology and on the expression of epidermal growth factor receptors (ErbBs) and heparan sulfate proteoglycan (perlecan) in mouse embryos culturedin vitro. Morphological assessment of inner cell mass and trophoblast development was carried onin-situfixed and stained outgrowths. Localization of ErbB1, ErbB4 and perlecan on pre- and peri-implantation embryos was investigated by immunocytochemistry. Addition of interferon-γ produced a deleterious effect on both inner cell mass and trophoblast morphology. Immunostaining demonstrated that ErbB1, ErbB4 and perlecan are present on pre-implantation embryos and blasto-cysts; interferon-γ altered the expression of ErbB4 and Perlecan at the blastocyst stage. We propose that the effects produced by this cytokine could be related to the altered acquisition of adhesion competence and low implantation rates observed in certain reproductive immunological disorders.

Sexing of murine and bovine embryos by developmental arrest induced by high-titer H-Y antisera

Murine and bovine embryos at the late morula stage were cultured in medium containing high-titer rat H-Y antisera. After 12h of incubation, embryos blocked at the late morulae stage were classified as males and those at the blastocyst stage were classified as females. Sexing of murine embryos by PCR and cytogenetics revealed that 83% of the embryos classified as males and 82% of those classified as females had their sex correctly predicted (P < 0.05). Bovine embryos were transferred to recipient females. Pregnancy rates were 71.4% (10/14) for embryos classified as males and 68.8% (11/16) for embryos classified as females. The sex was correctly predicted for 80% (8/10) of the embryos classified as males and for 81.8% (9/11) of those classified as females (overall accuracy, 80.9%, P < 0.05). Therefore, the induction of developmental arrest by high-titer male-specific antisera was an efficient strategy for non-invasive embryo sexing. The procedure was straightforward and has considerable commercial potential for sexing bovine embryos.

Effects of oxygen tension on the development and quality of porcine in vitro fertilized embryos

The present study was conducted to examine the effect of oxygen tension during in vitro culture (IVC) of porcine oocytes/embryos on their development and quality using two different culture systems. Porcine cumulus oocyte complexes (COCs) were matured (IVM) and fertilized (IVF) in vitro, and subsequently cultured for 6 days in a simple and economical portable incubator or a standard CO(2) incubator. While the same temperature (38.5 degrees C) and CO(2) concentration (5%) were used in the both systems, the portable incubator was operated in a negative air pressure (- 300 mmHg) to create an O(2) level at 8-10% (low O(2) concentration), or in a positive air pressure (high O(2) concentration). To compare the two culture systems, IVM and IVF of COCs and subsequent IVC of in vitro produced (IVP) embryos were carried out in the portable incubator with a low O(2) concentration (Group I) or in the standard incubator with a high O(2) concentration (Group II). To assess the effect of O(2) concentration on IVC of IVP embryos, some oocytes that had been cultured in the standard incubator for IVM and IVF were subsequently cultured in the portable incubator with a low O(2) concentration (Group III) or a high O(2) concentration (Group IV). The occurrence of DNA fragmentation in the blastocysts produced under different culture conditions was examined by TUNEL staining to assess embryo quality. The rates of oocytes that reached MII and were penetrated by spermatozoa following IVF did not differ between the two incubation systems. In contrast, the proportions of development to blastocysts and the mean cell number of blastocysts in Group I were higher than those in Group II and Group IV. The index of DNA-fragmented nucleus in the blastocysts of Group I was significantly lower than that in the blastocysts of Group II. Therefore, low oxygen tension during IVM, IVF and IVC enhanced the subsequent development of IVP embryos to the blastocyst stage and improved their quality.