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Analysis of the gene expression pattern of bovine blastocysts at three stages of development

ABSTRACT: Blastocyst formation is a primordial event of pre-implantation development since it is required for pregnancy establishment and progression. The blastocyst plays a pivotal role because it is the stage at which the embryo is transferred and starts coordinated cross-talks with the mother. It is also the terminal step of pre-implantation developmentbefore transfer; it reflects all stresses the embryo may have faced during the process of in-vitro treatment. Achieving the formation of a morphologically healthy blastocyst following normal kinetics is a good sign but remains a poor indicator of embryo quality. Considering the limitation of the invasive methods for competence assessment, the analysis of blastocysts’ gene expression is a promising way to improve our understanding of blastocyst formation and to study the effects of different treatments on gene expression. Methods: Early, expanded and hatched blastocysts were collected for RNA extraction, amplification, and cDNA microarray hybridization. Gene candidates (IFNt, PLAC8, SSLP1, AKR1B1, HNRNPA2B1, ARGFX, NANOS, CCNB1) were selected and confirmed using Q-RT-PCR to validate the microarray data. Results: Our analysis show that hatched blastocysts are enriched in genes transcripts implicated in implantation, cell adhesion and extracellular matrix digestion. Early blastocysts expressed genes mainly involved in cell cycle control, transcription and translation. Q-RT-PCR validated most microarray results (87.5%). Some of the differentially expressed genes are interesting as potential markers of competence. Conclusions: Overall, our study provides new insights into the molecular regulation of blastocyst formation. In addition, it could help assess blastocyst staging and select better embryos based on the expression of quality markers.

ORGANISM(S): Bos taurus

PROVIDER: GSE25606 | GEO | 2011/02/17

SECONDARY ACCESSION(S): PRJNA134253

REPOSITORIES: GEO

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Project description:Blastocyst formation is a primordial event of pre-implantation development since it is required for pregnancy establishment and progression. The blastocyst plays a pivotal role because it is the stage at which the embryo is transferred and starts coordinated cross-talks with the mother. It is also the terminal step of pre-implantation developmentbefore transfer; it reflects all stresses the embryo may have faced during the process of in-vitro treatment. Achieving the formation of a morphologically healthy blastocyst following normal kinetics is a good sign but remains a poor indicator of embryo quality. Considering the limitation of the invasive methods for competence assessment, the analysis of blastocysts’ gene expression is a promising way to improve our understanding of blastocyst formation and to study the effects of different treatments on gene expression. Methods: Early, expanded and hatched blastocysts were collected for RNA extraction, amplification, and cDNA microarray hybridization. Gene candidates (IFNt, PLAC8, SSLP1, AKR1B1, HNRNPA2B1, ARGFX, NANOS, CCNB1) were selected and confirmed using Q-RT-PCR to validate the microarray data. Results: Our analysis show that hatched blastocysts are enriched in genes transcripts implicated in implantation, cell adhesion and extracellular matrix digestion. Early blastocysts expressed genes mainly involved in cell cycle control, transcription and translation. Q-RT-PCR validated most microarray results (87.5%). Some of the differentially expressed genes are interesting as potential markers of competence. Conclusions: Overall, our study provides new insights into the molecular regulation of blastocyst formation. In addition, it could help assess blastocyst staging and select better embryos based on the expression of quality markers. In the present study the Laval/Sirard_bovine_embryo_3K_V3.0 array was used to conduct a series of 18 hybridizations (for three Blastocysts stages (early, expended, hatched) with three biological replicates and dye swaps) in a loop design experiment.

Project description:The Ca2+ oscillations initiated by the fertilizing sperm (but terminating concomitant with pronucleus formation) apparently ensure that the events constituting egg activation occur in the correct temporal order; early events (e.g., cortical granule exocytosis) require fewer oscillations than later events (e.g., recruitment of maternal mRNA). Whether the Ca2+ signaling events impact long-term development, in particular development to term, is unknown. Using fertilized eggs that have undergone the first few Ca2+ oscillations, we developed procedures that result either in inhibiting or stimulating the natural pattern of Ca2+ signaling of inseminated eggs. Although the incidence of development to the blastocyst stage is unaltered by these procedures, fewer offspring are born following embryo transfer, indicating that developmental competence of the blastocysts is reduced. Interestingly, embryo transfer experiments reveal that when the natural regime of Ca2+ oscillations is precociously interrupted, the incidence of implantation is compromised whereas hyper-stimulation of Ca2+ signaling events compromises post-implantation development. Moreover, although there was no major difference in the overall growth rates of the offspring, those obtained following hyper-stimulation exhibited a far greater variability in their weight. Analysis of global patterns of gene expression by microarray analysis revealed that approximately 20% of the transcripts are mis-regulated when too few oscillations are experienced by the embryo and EASE analysis indicates that genes preferentially involved in RNA processing and polymerase II transcription are differentially affected. In addition, a set of genes involved in cell adhesion is also mis-expressed and could thus be mechanistically linked to the observed reduced implantation. Only about 3% of the transcripts were mis-regulated following hyper-stimulation, and EASE analysis indicates that genes preferentially involved in metabolism are differentially affected. In toto, these results indicate that a range Ca2+ signaling events following fertilization (an excess or reduction) has long-term effects on both gene expression and development to term. Experiment Overall Design: We profiled the global gene expression in the blastocysts by treatment of Ca2+ oscillations, and identified the genes differentially expressed.

Project description:Objective: To study the uptake by human embryos of extracellular vesicles secreted by the maternal endometrium, and to investigate their miRNA cargo, in order to describe their role in implantation and early embryo development. Design: Prospective descriptive study. Subjects: Healthy women oocyte donors with confirmed fertility and day 5 human blastocysts. Intervention: Endometrial biopsies were collected from healthy oocyte donors undergoing transvaginal ultrasound-guided cyst aspiration for oocyte retrieval. Main Outcome Measures: Extracellular vesicle were isolated from culture media of primary human endometrial epithelial cells by ultracentrifugation. Concentration and size were analyzed by nanoparticle tracking analysis, their morphology visualized by transmission electron microscopy and extracellular vesicle protein markers expression was determined by western blotting. Vesicles were fluorescently labelled with Bodipy-TR ceramide, and their uptake by human blastocysts was analyzed using confocal microscopy. Analysis of the miRNA cargo of extracellular vesicles was performed using miRNAseq, target genes of the most expressed miRNAs were annotated and functional enrichment analysis was performed. Results: Extracellular vesicle characterization revealed a size within 100-300 nm, and expression of extracellular vesicle protein markers HSP70, TSG101, CD9 and CD81. Fluorescent microscopy showed an efficient extracellular vesicle internalization by human blastocysts within 1-2h, being the fluorescent signal stronger in the hatched area of the embryo. miRNAseq described 149 annotated miRNAs and top 37 most expressed miRNAs targeted 6,592 genes. Functional enrichment analysis of these targeted genes indicated that they participate in several processes related to embryo development, oxygen metabolism, cell cycle, cell differentiation, apoptosis, metabolism, cellular organization or gene expression. Among miRNAs contained in these EVs, hsa-miR-92a-3p, hsa-let-7b-5p, hsa-miR-30a-5p, hsa-miR-24-3p, hsa-miR-21-5p and hsa-let-7a-5p were highly implicated in all these biological processes. Conclusion: Data suggest that extracellular vesicles secreted by human endometrial epithelial cells are internalized by human blastocysts, and transport miRNAs to modulate biological processes related to implantation events and early embryo development. Knowledge of the communication system between human endometrium and embryo via miRNA cargo of these vesicles could describe new biomarkers of implantation success and embryo competence.

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Analysis of the gene expression pattern of bovine blastocysts at three stages of development

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