Project description:The epigenomes of mammalian sperm and oocytes, characterized by gamete-specific 5-methylcytosine (5mC) patterns, are reprogrammed in early embryogenesis to establish full developmental potential. It is broadly accepted that the paternal genome is actively demethylated in the zygote while the maternal genome undergoes passive demethylation thanks to DNA replication over the subsequent cleavage divisions. Here we reveal that both maternal and paternal genomes undergo widespread active and passive demethylation in the pronuclear zygote before the first mitotic division. Whereas the passive demethylation requires DNA replication, the active demethylation relies on enzymatic oxidation of 5mC, as deletion of the DNA dioxygenase, Tet3, but not the inhibition of replication, blocks the active demethylation. At actively demethylated loci, 5mCs appear to be processed to unmodified cytosines in a manner independent of the DNA glycosylase TDG. These observations suggest the occurrence of genuine active demethylation in both parental genomes following fertilization. An extra supportive Tet3 knock-out female pronuclear sample related to experiment Series GSE56650.
Project description:During development, the inherited DNA methylation patterns from the parental gametes needs to be remodeled into a state compatible with embryonic pluripotency. In Zebrafish, this remodeling is achieved by the maternal methylome becoming hypomethylated to match the paternal methylome. However, how this is achieved in medaka (another teleost fish) is currently not known. Moreover, how DNA methylation remodeling is impacted in hybrid organisms, and the effects this may have on their development, is also not known. Here we address these questions by generation whole genome bisulfite sequencing data for zebrafish, medaka and zebrafish medaka embryos.
Project description:Single-cell epigenome sequencing techniques have recently been developed. However, the combination of different layers of epigenome sequencing in an individual cell has not yet been achieved. Here, we developed a single-cell multi-omics sequencing technology (single-cell COOL-seq) that can analyze the chromatin state/nucleosome positioning, DNA methylation, copy number variation and ploidy simultaneously from the same individual mammalian cell. We used this method to analyze the reprogramming of the chromatin state and DNA methylation in mouse preimplantation embryos. We found that within < 12 h of fertilization, each individual cell undergoes global genome demethylation together with the rapid and global reprogramming of both maternal and paternal genomes to a highly opened chromatin state. This was followed by decreased openness after the late zygote stage. Furthermore, from the late zygote to the 4-cell stage, the residual DNA methylation is preferentially preserved on intergenic regions of the paternal alleles and intragenic regions of maternal alleles in each individual blastomere. However, chromatin accessibility is similar between paternal and maternal alleles in each individual cell from the late zygote to the blastocyst stage. The binding motifs of several pluripotency regulators are enriched at distal nucleosome depleted regions from as early as the 2-cell stage. This indicates that the cis-regulatory elements of such target genes have been primed to an open state from the 2-cell stage onward, long before pluripotency is eventually established in the ICM of the blastocyst. Genes may be classified into homogeneously open, homogeneously closed and divergent states based on the chromatin accessibility of their promoter regions among individual cells. This can be traced to step-wise transitions during preimplantation development. Our study offers the first single-cell and parental allele-specific analysis of the genome-scale chromatin state and DNA methylation dynamics at single-base resolution in early mouse embryos and provides new insights into the heterogeneous yet highly ordered features of epigenomic reprogramming during this process.
Project description:With the exception of imprinted genes and certain repeats, DNA methylation is globally erased during pre-implantation development. Recent studies have suggested that Tet3-mediated oxidation of 5-methylcytosine (5mC) and DNA replication-dependent dilution both contribute to global paternal DNA demethylation, but demethylation of the maternal genome occurs via replication. Here we present genome-scale DNA methylation maps for both the paternal and maternal genomes of Tet3-depleted and/or DNA replication-inhibited zygotes. In both genomes, we found that inhibition of DNA replication blocks DNA demethylation independently from Tet3 function, and that Tet3 facilitates DNA demethylation by coupling with DNA replication. For both, our data indicate that replication-dependent dilution is the major contributor to demethylation, but Tet3 plays an important role, particularly at certain loci. Our study therefore both defines the respective functions of Tet3 and DNA replication in paternal DNA demethylation and reveals an unexpected contribution of Tet3 to demethylation of the maternal genome. In this data set, we include RRBS data of manually isolated paternal and maternal pronuclei from both WT and Tet3 CKO zygotes with or without aphidicolin treatment
Project description:The epigenomes of mammalian sperm and oocytes, characterized by gamete-specific 5-methylcytosine (5mC) patterns, are reprogrammed during early embryogenesis to establish full developmental potential. Previous studies have suggested that the paternal genome is actively demethylated in the zygote while the maternal genome undergoes subsequent passive demethylation via DNA replication during cleavage. Active demethylation is known to depend on 5mC oxidation by Tet dioxygenases and excision of oxidized bases by thymine DNA glycosylase (TDG). Here we show that both maternal and paternal genomes undergo widespread active and passive demethylation in zygotes before the first mitotic division. Passive demethylation was blocked by the replication inhibitor aphidicolin, and active demethylation was abrogated by deletion of Tet3 in both pronuclei. At actively demethylated loci, 5mCs were processed to unmodified cytosines. Surprisingly, the demethylation process was unaffected by the deletion of TDG from the zygote, suggesting the existence of other demethylation mechanisms downstream of Tet3-mediated oxidation. The dataset includes RRBS anlysis of 2 MII oocyte samples, 3 WT female pronuclei samples PN3-4 stage, 2 Tet3 KO female pronuclei samples and 2 Aphidicolin treated female pronuclei samples. Also as male counterpart, a Sperm sample, 2 WT male pronuclei samples PN3-4 stage, 2 Tet3 KO male pronuclei samples and 2 Aphidicolin treated male pronuclei samples were included.
Project description:In the diploid genome, genes come in two copies, which can have different DNA sequence and where one is maternal and one is paternal. In a particular cell, a gene could potentially be expressed from both copies (biallelic expression) or only one (monoallelic). We performed RNA-Sequencing on individual cells, from zygote to the cells of the late blastocyst, and also individual cells from the adult liver. Using first generation crosses between two distantly related mouse strains, CAST/Ei and C57BL/6, we determined the expression separately from the maternal and paternal alleles. We found that half of the genes were expressed by only one allele, randomly so that some cells would express the paternal allele, some the maternal and a few cell both alleles. We also observed the spread of the progressive inactivation of the paternal X chromosome. First generation mouse strain crosses were used to study monoallelic expression on the single cell level
Project description:The epigenomes of mammalian sperm and oocytes, characterized by gamete-specific 5-methylcytosine (5mC) patterns, are reprogrammed in early embryogenesis to establish full developmental potential. It is broadly accepted that the paternal genome is actively demethylated in the zygote while the maternal genome undergoes passive demethylation thanks to DNA replication over the subsequent cleavage divisions. Here we reveal that both maternal and paternal genomes undergo widespread active and passive demethylation in the pronuclear zygote before the first mitotic division. Whereas the passive demethylation requires DNA replication, the active demethylation relies on enzymatic oxidation of 5mC, as deletion of the DNA dioxygenase, Tet3, but not the inhibition of replication, blocks the active demethylation. At actively demethylated loci, 5mCs appear to be processed to unmodified cytosines in a manner independent of the DNA glycosylase TDG. These observations suggest the occurrence of genuine active demethylation in both parental genomes following fertilization.
Project description:PGC7 is a primordial germ cell (PGCs)-specific protein involved in epigenetic chromatin reprogramming in the zygote following fertilization. TET3 is a dioxygenase that catalyzes the conversion of the modified genomic base 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC) and plays a key role in epigenetic chromatin reprogramming in the zygote following fertilization. PGC7 participates in protection of DNA methylation in the maternal pronucleus by preventing conversion of 5mC to 5hmC by TET3 oxidization subsequent DNA demethylation. Thus we tested the co-localization of PGC7 and TET3 in specific loci by ChIP-seq assays.
Project description:It is known that both maternal and paternal health/disease can influence the early development and later metabolic homeostasis of the offspring. We investigated whether maternal exercise during gestation alone could protect the offspring from the adverse effects of either maternal or paternal obesity induced by high-fat diet (HFD). To understand the underlying mechanisms we performed transcriptomics, whole-genome DNA methylation and targeted DNA methylation analysis at the metabolic master regulator, peroxisome proliferator-activated receptor g coactivator-1a (Pgc-1a) promoter in the adult offspring skeletal muscle. Both maternal and paternal HFD resulted in impaired glucose tolerance in the offspring at 9 months of age. Maternal exercise during gestation completely mitigated this metabolic impairment induced by either maternal or paternal HFD. Adult offspring exposed to either maternal or paternal HFD without exercise during gestation had skeletal muscle transcriptional profiles enriched in genes regulating inflammation and immune responses, whereas maternal exercise resulted in a transcriptional profile that was more similar to control offspring from normal chow fed parents. Changes in promoter and CpG DNA methylation were detected between the groups but did not explain the transcriptional changes. Maternal HFD increased methylation of the Pgc-1α promoter at CpG -260, which was prevented by maternal exercise. Paternal HFD did not affect the methylation of the Pgc-1α promoter. These findings demonstrate the negative consequences of maternal and paternal obesity for the offspring’s metabolic outcomes later in life and the clear benefits of maternal exercise during gestation. The mechanisms involve transcriptional regulation of skeletal muscle likely through multiple types of epigenetic modifications.
Project description:It is known that both maternal and paternal health/disease can influence the early development and later metabolic homeostasis of the offspring. We investigated whether maternal exercise during gestation alone could protect the offspring from the adverse effects of either maternal or paternal obesity induced by high-fat diet (HFD). To understand the underlying mechanisms we performed transcriptomics, whole-genome DNA methylation and targeted DNA methylation analysis at the metabolic master regulator, peroxisome proliferator-activated receptor g coactivator-1a (Pgc-1a) promoter in the adult offspring skeletal muscle. Both maternal and paternal HFD resulted in impaired glucose tolerance in the offspring at 9 months of age. Maternal exercise during gestation completely mitigated this metabolic impairment induced by either maternal or paternal HFD. Adult offspring exposed to either maternal or paternal HFD without exercise during gestation had skeletal muscle transcriptional profiles enriched in genes regulating inflammation and immune responses, whereas maternal exercise resulted in a transcriptional profile that was more similar to control offspring from normal chow fed parents. Changes in promoter and CpG DNA methylation were detected between the groups but did not explain the transcriptional changes. Maternal HFD increased methylation of the Pgc-1α promoter at CpG -260, which was prevented by maternal exercise. Paternal HFD did not affect the methylation of the Pgc-1α promoter. These findings demonstrate the negative consequences of maternal and paternal obesity for the offspring’s metabolic outcomes later in life and the clear benefits of maternal exercise during gestation. The mechanisms involve transcriptional regulation of skeletal muscle likely through multiple types of epigenetic modifications.