Project description:In mammals, chromatin marks at imprinted genes are asymmetrically inherited from each parent to control gene expression. Many genomic imprints are determined by differentially methylated regions (DMRs), but these have not been comprehensively mapped physically or functionally in mouse preimplantation embryos. We here address this by integrating transcriptomic and epigenomic approaches. Transcriptome analysis of blastocysts from genetically distinguishable crosses identified 106 genes with previously unknown parent-of-origin-specific allelic bias (nBsX genes), and 71 novel imprinted genes with parent-of-origin-specific expression with an allelic ratio of 70:30 or greater (nBiX genes). Uniparental expression of tested nBsX and nBiX transcripts disappeared soon after implantation.
Project description:In mammals, chromatin marks at imprinted genes are asymmetrically inherited from each parent to control gene expression. Many genomic imprints are determined by differentially methylated regions (DMRs), but these have not been comprehensively mapped physically or functionally in mouse preimplantation embryos. To address this, we measured genome-wide DNA methylation in individual haploid uniparental parthenogenetic haploid (ph) and androgenetic haploid (ah) E3.5 blastocysts by micro-whole-genome bisulfite sequencing (µWGBS). For comparison, we also included ahESC and phESC lines in the analysis.Comparison of DNA methylomes from uniparental blastocysts with those of control blastocysts (produced by intracytoplasmic sperm injection) identified 859 DMRs. Haploid ES cells showed overall erosion of those DMRs, in contrast to diploid ES cells that relatively maintained differential methylation.
Project description:Polycomb repressive complexes 1 and 2 (PRC1/2) maintain transcriptional silencing of developmental genes largely by catalyzing mono-ubiquitination of histone H2A at lysine 119 (H2AK119ub1) and trimethylation of histone H3 at lysine 27 (H3K27me3), respectively. How Polycomb domains are reprogrammed during mammalian preimplantation development remains largely unclear. Here we show that, although H2AK119ub1 and H3K27me3 are highly colocalized in gametes, they undergo differential reprogramming dynamics following fertilization. H3K27me3 maintains thousands of maternally biased domains up to the blastocyst stage, whereas maternally biased H2AK119ub1 distribution in zygotes is largely equalized at the two-cell stage. Notably, while maternal PRC2 depletion has a limited effect on global H2AK119ub1 in early embryos, it disrupts allelic H2AK119ub1 at H3K27me3 imprinting loci including Xist. By contrast, acute H2AK119ub1 depletion in zygotes does not affect H3K27me3 imprinting maintenance, at least by the four-cell stage. Importantly, loss of H2AK119ub1, but not H3K27me3, causes premature activation of developmental genes during zygotic genome activation (ZGA) and subsequent embryonic arrest. Thus, our study reveals distinct dynamics and functions of H3K27me3 and H2AK119ub1 in mouse preimplantation embryos.
Project description:Purpose: The goals of this study are to define transcriptome (RNA-seq) of mouse preimplantation embryos at different stages of development under a range of different environmental conditions. Methods: Mouse preimplantation embro transcriptional profiles were generated using embryos at several different developmental stages using Smart-seq2. Results: RNA-seq analysis finds that there is a highly dynamic pattern of gene expression during the preimplantation period. The sensitiivty to nutrient conditions varies markedly at different stages of development, with 2C embryos more sensitive to pyruvate omission than later stage embryos. Conclusions: Our study represents a comprehensive analysis of the mouse preimplantation development transcriptome, and how pyruvate provision impacts different developmental stages.
Project description:Maternal imprinting at the Xist gene is essential to achieve paternal allele-specific imprinted X chromosome inactivation (XCI) in female mammals. However, the mechanism underlying the Xist imprinting is unclear. Here we show that the Xist gene is coated with H3K27me3 in mouse oocytes, which persists through preimplantation development. Ectopic removal of H3K27me3 induces maternal Xist expression and maternal XCI, indicating that maternal H3K27me3 is the imprinting mark of Xist.
Project description:Genomic imprinting is the parent-of-origin-specific allelic transcriptional silencing observed in mammals, which is governed by DNA methylation established in the gametes and maintained throughout the development. The frequency and extent of epimutations associated with the nine reported imprinting syndromes varies because it is evident that aberrant preimplantation maintenance of imprinted differentially methylated regions (DMRs) may affect multiple loci. Using a custom Illumina GoldenGate array targeting 27 imprinted DMRs, we profiled allelic methylation in 8 imprinting defect patients.
Project description:Purpose: The goals of this study are to establish a dynamic roadmap of imprinted X chromosome inactivation and the role of Xist by elucidation of the transcriptome of Xist KO embryos during mouse preimplantation development. Methods: mRNA profiles of the preimplantation embryos WT and KO for Xist were elucidated by RNA-seq at various stages. Trophoblasts isolated from blastocyst outgrowths were also included. The sequence reads for samples where gender could be determined and that passed quality filters were analyzed at the level of autosomes, X chromosome as well as single genes. Results: Female embryos fail to silence the X chromosome at late preimplantation development. General autosomal gene expression is not affected in embryos lacking Xist. Conclusions: Xist is crucial for iXCI. In preimplantation embryos, the main in vivo function of Xist is to regulate iXCI in females.