Project description:Histone acetylation H3K27ac is a well-established chromatin marker for active enhancers and promoters. However, reprogramming dynamics of H3K27ac during maternal-to-zygotic transition (MZT) in mammalian embryos has not been well studied. By profiling the allelic landscape of H3K27ac during mouse MZT, here we show that H3K27ac undergoes three waves of rapid global transitions from oocyte to 2-cell stages. Notably, germinal vesicle (GV) oocyte and zygote are globally hyperacetylated by forming noncanonical broad H3K27ac domains that correlate with broad H3K4me3 and open chromatin. H3K27ac also marks genomic regions primed for activation including ZGA gene promoters, retrotransposons, and active alleles of imprinted genes. Importantly, both CBP/p300 and HDAC activities play important roles in regulating the H3K27ac dynamics and are essential for pre-implantation development. Specifically, CBP/p300 deposits broad H3K27ac domains in zygotes and open condensed chromatin at putative enhancers to ensure proper ZGA. In contrast, HDACs mediate the broad to canonical H3K27ac transition to safeguard ZGA by preventing premature expression of developmental genes and promoting ZGA gene activation. Our study demonstrates that coordinated activities of CBP/p300 and HDACs during mouse MZT are essential for ZGA and mouse pre-implantation development.
Project description:Profiles of H3K4me3, H3K27ac, H3K27me3 and H3K9me3 in bovine GV oocytes and preimplantation embryos, and the characterization of chromatin accessibility in bovine blastocyst, inner cell mass and trophectoderm.
Project description:The epigenetic regulation containing DNA methylation and chromatin accessibility have been extensively explored in human preimplantation development. However, the dynamic of demethylation in this crucial process remains largely unknown. In this study, we use CLEVER-seq to quantify the DNA 5-formylcytosine (5fC) level of human early embryos. The distribution of 5fC exhibits genomic region preference and are enriched in L1 and ERVK, subfamily of repeat element. Unlike in mice, the paired pronuclei presents inconsistent 5fC level although the male pronuclei experiences stronger demethylation. And the centre of 5fC shows less accessible genome especially in proximal region. Collectively, our work offers new insight into the understanding of the complex demethylation in early human embryo development.
Project description:In mammals, all somatic development originates from lineage segregation in early embryos. However, the dynamics of transcriptomes and epigenomes in concert with initial cell fate commitment remains poorly characterized. Here, we report comprehensive investigation of transcriptomes and base-resolution methylomes for early lineages in peri- and postimplantation mouse embryos. We found allele- and lineage-specific de novo methylation at CG and CH sites, leading to differential methylation between embryonic and extraembryonic lineages at promoters of lineage regulators, gene bodies, and DNA methylation valleys. By determining chromatin architecture using Hi-C across the same developmental period, we showed both global demethylation and remethylation in early development correlate with chromatin compartments. Dynamic local methylation is evident during gastrulation, which revealed maps of putative regulatory elements. Finally, we found that de novo methylation patterning does not strictly require implantation. These data unveiled dynamic transcriptomes, DNA methylomes, and 3D chromatin landscapes during the earliest mammalian lineage specification.
Project description:Although the DNA methylome of human early embryos has been analyzed, some of the key features have not been addressed to date. Here, we performed single-cell DNA methylome sequencing for human preimplantation embryos and found that tens of thousands of genomic loci exhibited de novo DNA methylation. This finding indicates that genome-wide DNA methylation reprogramming during preimplantation development is a dynamic balance between strong global demethylation and significant focused re-methylation. Furthermore, the demethylation of the paternal genome is much faster and thorough than that of the maternal genome. From the 2-cell to post-implantation stage, methylation of the paternal genome is consistently lower than that on the maternal genome. We also showed that the genetic lineage of the early blastomeres could be traced by DNA methylation analysis. Our work paves the way for deciphering the secrets of DNA methylation reprogramming in human early embryos.
Project description:Differential gene expression in preimplantation embryos has been documented, but few focused studies have been done to compare differential expression in human embryos after embryonic genome activation and specifically how they relate to blastocyst development. We hypothesized that blastocyst stage embryos would differentially express genes in pathways important in cell division, mobilization, and processes important in embryo implantation including endometrial apposition, adhesion, and invasion. We analyzed gene expression in 6 preimplantation human embryos. Embryos studied were previously cryopreserved, supernumerary human embryos donated by couples who completed their family building through in vitro fertilization and had given specific consent for use in research. Embryos cryopreserved at the pronuclear stage were thawed and cultured to cleavage (Day 3) or blastocyst (Day 5) stage. Differential gene expression was first obtained through Affymetrix gene expression microarrays and then validated both in silico using the Gene Expression Omnibus and in vitro with RT-qPCR. Compared to cleavage stage embryos, blastocyst stage embryos differentially expressed 51 genes (p < 0.001), with overrepresentation in amoebiasis pathways and pathways in cancer.
Project description:Sperm-derived tsRNAs could act as acquired epigenetic factors and contribute to offspring phenotypes. However, the roles of specific tsRNAs in early embryo development remain to be elucidated. Here, by using pigs as a research model, we probed the tsRNA dynamics during spermatogenesis and sperm maturation, and demonstrated the delivery of tsRNAs from semen-derived exosomes to spermatozoa. By microinjection of the antisense sequence into in vitro fertilized oocytes and subsequent single-cell RNA-sequencing of embryos, we identified a specific functional tsRNA group (Gln-TTGs) that participate in the early cleavage of porcine preimplantation embryos, probably by regulating cell cycle-associated genes. Thus, specific tsRNAs present in mature spermatozoa play significant roles during preimplantation embryo development.