Project description:DNA methylation is an important epigenetic modification that undergoes dynamic changes in mammalian embryogenesis, during which both parental genomes are reprogrammed. Despite the many immunostaining studies that have assessed global methylation, the gene-specific DNA methylation patterns in bovine preimplantation embryos are unknown. Using reduced representation bisulfite sequencing, we determined genome-scale DNA methylation patterns of bovine sperm and individual in vivo developed oocytes and preimplantation embryos. We show that: 1) the major wave of genome-wide demethylation was completed by the 8-cell stage; 2) promoter methylation was significantly and inversely correlated with gene expression at the 8-cell and blastocyst stages; 3) sperm and oocytes have numerous differentially methylated regions (DMRs) - DMRs specific for sperm were strongly enriched in long terminal repeats (LTRs) and rapidly lost methylation in embryos, while the oocyte-specific DMRs were more frequently localized in exons and CpG islands (CGIs) and demethylated gradually across cleavage stages; 4) a unique set of DMRs were found between in vivo and in vitro matured oocytes; and 5) differential methylation between bovine gametes was confirmed in some but not all known imprinted genes. Our data provide insights into deciphering the complex epigenetic reprogramming of bovine early embryos and will serve as an important model for investigating human development and the evolutionary and regulatory roles of DNA methylation.
Project description:Dynamic changes in DNA methylation are crucial in the epigenetic regulation of mammalian embryogenesis. Global DNA methylation studies in the bovine, however, remain mostly at the immunostaining level. We adopted the single-cell whole genome bisulfite sequencing (scWGBS) method to characterize stage-specific genome-wide DNA methylation in bovine sperm, individual oocytes derived in vivo and in vitro, as well as in vivo developed embryos at the 2-, 4-, 8- and 16-cell stages. This method allowed us to theoretically cover all CpG sites in the genome using single oocytes or embryos. We found that the major wave of genome-wide DNA demethylation was complete at the 8-cell stage when de novo methylation became prominent. Sperm and oocytes were differentially methylated in numerous regions (DMRs) which were enriched in intergenic regions, indicating these noncoding regions play important roles in gamete specification. DMRs were also identified between in vivo and in vitro matured oocytes. Moreover, X chromosome methylation followed the global dynamic patterns. Virtually no (less than 1.5%) DNA methylation was found in mitochondrial DNA. Finally, using our RNA-seq data generated from the same developmental stages, we revealed an inverse correlation between gene expression and promoter methylation. Our study provides the first fully comprehensive analysis of the global dynamics of DNA methylation in bovine gametes and single early embryos using scWGBS. These data provide insights into the critical features of the methylome of bovine embryos, and serve as an important reference for embryos produced by assisted reproduction, such as in vitro fertilization and cloning, and a model for human early embryo epigenetic regulation.
Project description:Compared to other mammalian species, porcine oocytes and embryos are characterized by large amounts of lipids stored mainly in the form of droplets in the cytoplasm. The amount and the morphology of LD change throughout the preimplantation development however, relatively little is known about expression of genes involved in lipid metabolism of early embryos. We compared porcine and bovine blastocyst stage embryos as well as dissected inner cell mass (ICM) and trophoblast (TE) cell populations with regard to lipid droplet storage and expression of genes functionally annotated to selected lipid Gene Ontology terms using RNA-seq. Comparing the number and the volume occupied by LD between bovine and porcine blastocysts, we have found significant differences both at the level of single embryo and a single blastomere. Aside from different lipid content we found that embryos regulate the lipid metabolism differentially at the gene expression level. Out of 125 genes, we have found 73 to be differentially expressed between entire porcine and bovine blastocyst, and 36 and 51 to be divergent between ICM and TE cell lines. We noticed significant involvement of cholesterol and ganglioside metabolism in preimplantation embryos as well as possible shift towards glucose rather than pyruvate dependence in bovine embryos. A number of genes like DGAT1, CD36 or NR1H3 may serve as lipid associated markers indicating distinct regulatory mechanisms while upregulated PLIN2, APOA1, SOAT1 indicate significant function during blastocyst formation and cell differentiation in both models.
Project description:Compared to other mammalian species, porcine oocytes and embryos are characterized by large amounts of lipids stored mainly in the form of droplets in the cytoplasm. The amount and the morphology of LD change throughout the preimplantation development however, relatively little is known about expression of genes involved in lipid metabolism of early embryos. We compared porcine and bovine blastocyst stage embryos as well as dissected inner cell mass (ICM) and trophoblast (TE) cell populations with regard to lipid droplet storage and expression of genes functionally annotated to selected lipid Gene Ontology terms using RNA-seq. Comparing the number and the volume occupied by LD between bovine and porcine blastocysts, we have found significant differences both at the level of single embryo and a single blastomere. Aside from different lipid content we found that embryos regulate the lipid metabolism differentially at the gene expression level. Out of 125 genes, we have found 73 to be differentially expressed between entire porcine and bovine blastocyst, and 36 and 51 to be divergent between ICM and TE cell lines. We noticed significant involvement of cholesterol and ganglioside metabolism in preimplantation embryos as well as possible shift towards glucose rather than pyruvate dependence in bovine embryos. A number of genes like DGAT1, CD36 or NR1H3 may serve as lipid associated markers indicating distinct regulatory mechanisms while upregulated PLIN2, APOA1, SOAT1 indicate significant function during blastocyst formation and cell differentiation in both models.
2020-09-07 | GSE156145 | GEO
Project description:The multiomics data on gametes and early embryos in bovine and porcine
Project description:Zygotic genome activation (ZGA) represents the inaugural post-fertilization transcription event. In mouse, RNA polymerase II (Pol II) initiates embryonic transcription through a step-wise transition, but the ZGA initiation process remains unclear in non-rodents. Here, Pol II profiling in bovine and porcine embryos, combined with multi-omics data across four mammalian species, revealed strong intergenic Pol II clusters, termed super Pol II domains (SPDs), that boost minor ZGA gene expression via chromatin interactions in bovine. Intriguingly, a similar strategy was found in human embryos, which also exhibit delayed ZGA followed by rapid up-regulation of minor ZGA genes. By contrast, these genes are precociously activated in porcine and mouse gametes before fertilization. Moreover, disruption of SPD structure, which decreases two minor ZGA genesKLF17orDUXAexpression, and knockdown them in bovine, leads to aberrant gene activation and impeded embryogenesis. Our findings highlight SPD enhancement as a species-specific evolutionary adaptation for initiating transcription in bovine and human embryos, thus illustrating previously underappreciated diversity in mammalian reproductive developmental strategies.
Project description:Zygotic genome activation (ZGA) represents the inaugural post-fertilization transcription event. In mouse, RNA polymerase II (Pol II) initiates embryonic transcription through a step-wise transition, but the ZGA initiation process remains unclear in non-rodents. Here, Pol II profiling in bovine and porcine embryos, combined with multi-omics data across four mammalian species, revealed strong intergenic Pol II clusters, termed super Pol II domains (SPDs), that boost minor ZGA gene expression via chromatin interactions in bovine. Intriguingly, a similar strategy was found in human embryos, which also exhibit delayed ZGA followed by rapid up-regulation of minor ZGA genes. By contrast, these genes are precociously activated in porcine and mouse gametes before fertilization. Moreover, disruption of SPD structure, which decreases two minor ZGA genes KLF17 or DUXA expression, and knockdown them in bovine, leads to aberrant gene activation and impeded embryogenesis. Our findings highlight SPD enhancement as a species-specific evolutionary adaptation for initiating transcription in bovine and human embryos, thus illustrating previously underappreciated diversity in mammalian reproductive developmental strategies.