Unknown,Transcriptomics,Genomics,Proteomics

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Embryonic transcription is controlled by maternally defined chromatin state

ABSTRACT: During development histone modifying enzymes are required for cell identity and lineage commitment, however little is known about the regulatory origins of the epigenome during embryonic development. Here we generate a comprehensive set of embryonic epigenome reference maps, which we use to determine the extent to which maternal factors shape chromatin state in Xenopus embryos. Using Î±-amanitin to inhibit zygotic transcription, we find that the majority of H3K4me3 and H3K27me3-enriched regions form a maternally defined epigenetic regulatory space with an underlying logic of hypomethylated islands. This maternal regulatory space extends to a substantial proportion of neurula stage-activated promoters. In contrast, p300-recruitment to distal regulatory regions requires embryonic transcription at most loci. The results show that H3K4me3 and H3K27me3 are part of a regulatory space that exerts an extended maternal control well into post-gastrulation development, and highlight the combinatorial action of maternal and zygotic factors through proximal and distal regulatory sequences. We have performed ChIP-sequencing of eight histone modifications, RNA polymerase II (RNAPII) and the enhancer protein p300 at five stages of development: blastula (st. 9), gastrula (st. 10.5, 12.5), neurula (st. 16) and tailbud (st. 30). These experiments allow identification of enhancers (H3K4me1, p300), promoters (H3K4me3, H3K9ac), transcribed regions (H3K36me3, RNAPII) and repressed and heterochromatic domains (H3K27me3, H3K9me2, H3K9me3, H4K20me3). In addition we generated pre-MBT (st. 8) maps for three histone modifications (H3K4me3, H3K9ac, H3K27me3) and single-base resolution DNA methylome maps using whole genome bisulfite sequencing of blastula and gastrula (st. 9 and 10.5) embryos. To determine the maternal and zygotic contributions to chromatin state, we used alpha-amanitin to block embryonic transcription. Fertilised eggs were injected with 2.3 nl of 2.67 ng/ul alpha-amanitin and developed until the control embryos reached mid-gastrulation. Alpha-amanitin and control embryos were used for RNA-seq and ChIP-seq of RNAPII, H3K4me3, H3K27me3 and p300. For all ChIP-seq samples of the epigenome reference maps and RNAPII ChIP-seq samples of the Î±-amanitin experiments three biological replicates of different chromatin isolations of 45 embryos were pooled. Two biological replicates for H3K4me3 (Î±-amanitin injected: resp. 90 and 56 embryo equivalents (eeq); control: resp. 45 and 67 eeq), H3K27me3 (Î±-amanitin injected: resp. 90 and 180 eeq; control: resp. 45 and 202 eeq) and p300 (Î±-amanitin injected: resp. 112 and 56 eeq; control: resp. 112 and 67 eeq) ChIP-seq samples of the Î±-amanitin experiments were generated. For RNA-seq samples of the Î±-amanitin experiments RNA from 5 embryos from one biological replicate was isolated and depleted of ribosomal RNA

ORGANISM(S): Xenopus (Silurana) tropicalis

SUBMITTER: Saartje Hontelez

PROVIDER: E-GEOD-67974 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Histone variants complement and integrate histone post-translational modifications in regulating transcription. The histone variant macroH2A1 (mH2A1) is almost three times the size of its canonical H2A counterpart due to the presence of a ~25kDa evolutionarily conserved non-histone macro domain. Strikingly, mH2A1 can mediate both gene repression and activation. However, the molecular determinants conferring these alternative functions remain elusive. Here, we report that mH2A1.2 is required for the activation of the myogenic gene regulatory network and muscle cell differentiation. H3K27 acetylation at prospective enhancers is exquisitely sensitive to mH2A1.2, indicating a role of mH2A1.2 in imparting enhancer activation. Both H3K27 acetylation and recruitment of the transcription factor Pbx1 at prospective enhancers are regulated by mH2A1.2. Overall, our findings indicate a role of mH2A1.2 in marking regulatory regions for activation. To establish the role of the histone variant mH2A1.2 in skeletal muscle differentiation we employed the mouse skeletal muscle C2C12 cell line and examined the genome wide distribution mH2A1.2 in myoblast (MB) and myotube (MT) (two replicates). We intersected the distribution of mH2A1.2 with active (H3K4me3 and H3K4me1 from published dataset, and H3K27ac, two replicates) and repressive (H3K27me3, two replicates) epigenetic marks in MB and MT. To gain insite on how chromatin accessibility is remodelled when muscle cells are induced to differentiate, we performed ATAC-seq in C2C12 MB and MT (2 replicates). We then evaluated whether mH2A1.2 was involved in conferring H3K27 acetylation during skeletal muscle differentiation by performing H3K27ac ChIP-seq (two replicates) upon mH2A1.2i in MB and MT. We also prefomred the ChIP-Seq for transcription factor Pbx1 in control and mH2A1.2i cells in MT to address the potential role of mH2A in recruitment of Pbx1. RNA-seq experiments were performed in control and mH2A1.2i C2C12 cells at the stage of MB and MT (three replicates). When mH2A1.2i C2C12 MB were induced to differentiate, a global effect on transcription was observed.

Project description:Purpose: The aim of this study is (1) to identify the chromatin occupancy of the epigenetic regulator Smchd1 in neural stem cells (NSCs) derived from E14.5 mouse brain; (2) to profile key epigenetic marks H3K4me3, H3K27me3 and DNA methylation in wild type and Smchd1 null NSCs; (3) to identify the chromatin occupancy of Ctcf in wild type and Smchd1 null NSCs. Methods: Chromatin immunoprecipitation for Smchd1, H3K4me3, H3K27me3 and Ctcf was performed essentially as in (Nelson et al. 2006). Briefly, nuclei were isolated from formaldehyde crosslinked NSCs and chromatin was fragmented by sonication. Chromatin immunoprecipitation was performed with corresponding antibodies for Smchd1, H3K4me3 and H3K27me3. DNA was extracted from the immunoprecipitated fraction following reverse-crosslinking. Isolated DNA was used to generate sequencing libraries with Illumina's TruSeq DNA Sample Preparation Kit or Ovation Ultralow system (NuGen) according to manufacturer's instruction. Libraries were pooled and sequenced on the Illumina HiSeq 2000 platform for 100 bp single-end reads. Image analysis was performed in real time by the HiSeq Control Software (HCS) v1.4.8 and Real Time Analysis (RTA) v1.12.4.2, running on the instrument computer. Real-time base calling on the HiSeq instrument computer was performed with the RTA software. Illumina CASAVA1.8 pipeline was used to generate the sequence data. To examine the level of DNA methylation, genomic DNA was extracted using an AllPrep DNA/RNA Mini Kit (Qiagen) and methylated DNA was isolated via binding to the methyl-CpG binding domain of human MBD2 protein coupled beads using the MethylMiner methylated DNA enrichment kit (Life Technologies) according to the manufacturer’s instructions. Isolated DNA was used to generate sequencing libraries as for the ChIP-seq experiment with Illumina’s TruSeq DNA Sample Preparation Kit according to manufacturer's instruction and sequenced on the Illumina HiSeq 2000 platform for 49 bp single-end reads. Sequencing analysis was performed as described for the ChIP-seq experiments. Chromatin occupancy of the epigenetic regulator Smchd1 in neural stem cells (NSCs) derived from E14.5 mouse brain was determined by Smchd1 ChIP-seq. Enrichment of H3K4me3 and H3K27me3 in wild type and Smchd1 null NSCs were assessed by H3K4me3 and H3K27me3 ChIP-seq, respectively. DNA methylation in wild type and Smchd1 null NSCs was assessed by MBD-seq. Chromatin occupancy of Ctcf in wild type and Smchd1 null NSCs was determined by by Ctcf ChIP-seq.

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Embryonic transcription is controlled by maternally defined chromatin state

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