In the early zebrafish embryo, the developing genome profile can be interfered with by exposure to pentachlorophenol, and some specific sets of genes are up-regulated or down-regulated. We used microarrays to detail the global program of gene expression underlying cellularisation and identified distinct classes of up-regulated genes during this process.
Pentachlorophenol exposure causes Warburg-like effects in zebrafish embryos at gastrulation stage.
Specimen part, Treatment
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Whole-transcriptome splicing profiling of E7.5 mouse primary germ layers reveals frequent alternative promoter usage during mouse early embryogenesis.
Specimen part
View SamplesAlternative splicing (AS) and alternative promoter (AP) usage expand the repertories of mammalian transcriptome profiles and thus diversify gene functions. However, our knowledge about the extent and functions of AS and AP usage in mouse early embryogenesis remains elusive. Here, by performing whole-transcriptome splicing profiling with high-throughput next generation sequencing, we report that AS extensively occurs in embryonic day (E) 7.5 mouse primary germ layers, and may be involved in multiple developmental processes. In addition, numerous RNA splicing factors are differentially expressed and alternatively spliced across the three germ layers, implying the potential importance of AS machinery in shaping early embryogenesis. Notably, AP usage is remarkably frequent at this stage, accounting for more than one quarter (430/1648) of the total significantly different AS events. Genes generating the 430 AP events participate in numerous biological processes, and include important regulators essential for mouse early embryogenesis, suggesting that AP usage is widely used and might be relevant to mouse germ layer specification. Our data underline the potential significance of AP usage in mouse gastrulation, providing a rich data source and opening another dimension for understanding the regulatory mechanisms of mammalian early development.
Whole-transcriptome splicing profiling of E7.5 mouse primary germ layers reveals frequent alternative promoter usage during mouse early embryogenesis.
Specimen part
View SamplesSirtuin 1 (SIRT1) is involved in both aging and circadian-clock regulation, yet the link between the two processes in relation to SIRT1 function is not clear. Using Sirt1-deficient mice, we found that Sirt1 and Period 2 (Per2) constitute a reciprocal negative regulation loop that plays important roles in modulating hepatic circadian rhythmicity and aging. Sirt1-deficient mice exhibited profound premature aging and enhanced acetylation of histone H4 on lysine16 (H4K16) in the promoter of Per2, the latter of which leads to its overexpression; in turn, Per2 suppresses Sirt1 transcription through binding to the Sirt1 promoter at the Clock/Bmal1 site. This negative reciprocal relationship between SIRT1 and PER2 was also observed in human hepatocytes. We further demonstrated that the absence of Sirt1 or the ectopic overexpression of Per2 in the liver resulted in a dysregulated pace of the circadian rhythm. The similar circadian rhythm was also observed in aged wild type mice. The interplay between Sirt1 and Per2 modulates aging gene expression and circadian-clock maintenance.
Negative reciprocal regulation between Sirt1 and Per2 modulates the circadian clock and aging.
Age, Specimen part
View SamplesZygotic genome activation (ZGA), which is according to the midblastula transition in zebrafish, is an important event during the maternal-zygotic transition in animals. Our preliminary study and other groups works indicate that epigenetic regulations play an essential role in ZGA.
Protein Arginine Methyltransferase 6 (Prmt6) Is Essential for Early Zebrafish Development through the Direct Suppression of gadd45αa Stress Sensor Gene.
Age, Specimen part
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Genome-wide uH2A localization analysis highlights Bmi1-dependent deposition of the mark at repressed genes.
Sex
View SamplesPolycomb group (PcG) proteins control organism development by regulating the expression of developmental genes. Transcriptional regulation by PcG proteins is achieved at least partly through the PRC2-mediated methylation on lysine 27 of histone H3 (H3K27) and PRC1-mediated ubiquitylation on lysine 119 of histone H2A (uH2A). As an integral component of PRC1, Bmi1 has been demonstrated to be critical for H2A ubiquitylation. Although recent studies have revealed the genome wide binding patterns of some of the PRC1 and PRC2 components, as well as the H3K27me3 mark, there have been no reports describing genome wide localization of uH2A. Using the recently developed ChIP-Seq technology, here we report genome wide localization of the Bmi1-dependent uH2A mark in MEF cells. Gene promoter averaging analysis indicates a peak of uH2A just inside the transcription start site (TSS) of well annotated genes. This peak is enriched at promoters containing the H3K27me3 mark and represents the least expressed genes in WT MEF cells. In addition, peak finding reveals regions of local uH2A enrichment throughout the mouse genome, including almost 700 gene promoters. Genes with promoter peaks of uH2A exhibit lower level expression when compared to genes that do not contain promoter peaks of uH2A. Moreover, we demonstrate that genes with uH2A peaks have increased expression upon Bmi1 knockout. Importantly, local enrichment of uH2A is not limited to regions containing the H3K27me3 mark. We provide evidence to suggest that DNA methylation is tightly linked to H2A ubiquitylation in high density CpG promoters. Thus, our work not only reveals Bmi1-dependent H2A ubiquitylation but also suggests that uH2A targeting in differentiated cells may employ a different mechanism from that in ES cells.
Genome-wide uH2A localization analysis highlights Bmi1-dependent deposition of the mark at repressed genes.
Sex
View SamplesPolycomb group (PcG) proteins are epigenetic silencers whose dysregulation is frequently linked to cancer via mechanisms that remain unclear. Using conditional knock-out mice in a colitis-associated colorectal cancer (CAC) model, we found that Bmi1 and Mel18 are important initiation and maintenance factors during CAC tumorigenesis. Epithelial depletion of both Bmi1 and Mel18, but not either gene alone, significantly reduces tumor growth and multiplicity.
BMI1 and MEL18 Promote Colitis-Associated Cancer in Mice via REG3B and STAT3.
Specimen part
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Dual functions of Tet1 in transcriptional regulation in mouse embryonic stem cells.
Specimen part, Disease, Treatment
View SamplesEpigenetic modification of the mammalian genome by DNA methylation (5-methylcytosine) has a profound impact on chromatin structure, gene expression and maintenance of cellular identity. Recent demonstration that members of the Ten-eleven translocation (Tet) family proteins can convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) raised the possibility that Tet proteins are capable of establishing a distinct epigenetic state. We have recently demonstrated that Tet1 is specifically expressed in murine embryonic stem (ES) cells and is required for ES cell self-renewal and maintenance. Using chromatin immunoprecipitation coupled with high-throughput DNA sequencing (ChIP-seq), here we show that Tet1 is preferentially bound to CpG-rich sequences at promoters of both transcriptionally active and Polycomb-repressed genes. Despite a general increase in levels of DNA methylation at Tet1 binding-sites, Tet1 depletion does not lead to down-regulation of all the Tet1 targets. Interestingly, while Tet1-mediated promoter hypomethylation is required for maintaining the expression of a group of transcriptionally active genes, it is also required for repression of Polycomb-targeted developmental regulators. Tet1 contributes to silencing of this group of genes by facilitating recruitment of PRC2 to CpG-rich gene promoters. Thus, our study not only establishes a role for Tet1 in modulating DNA methylation levels at CpG-rich promoters, but also reveals a dual function of Tet1 in promoting transcription of pluripotency factors as well as participating in the repression of Polycomb-targeted developmental regulators.
Dual functions of Tet1 in transcriptional regulation in mouse embryonic stem cells.
Specimen part
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