The pluripotent genome in three dimensions is shaped around pluripotency factors
Ontology highlight
ABSTRACT: It is becoming increasingly clear that the shape of the genome importantly influences transcription regulation. Pluripotent stem cells (PSCs) such as embryonic stem cells (ESCs) were recently shown to organize their chromosomes into topological domains that are largely invariant between cell types. Here, we applied 4C technology and combined ChIP-seq with Hi-C data to demonstrate that inactive chromatin is unusually disorganized in PSC nuclei. We show that gene promoters engage in contacts between topological domains in a largely tissue-independent manner while enhancers have a more tissue-restricted interaction profile. Most strikingly, genomic clusters of pluripotency factor binding sites find each other very efficiently, in a manner that is strictly PSC-specific, dependent on the presence of Oct4 and Nanog protein and inducible upon artificial recruitment of Nanog to a selected chromosomal site. We conclude that pluripotent stem cells have a unique higher-order genome structure shaped by pluripotency factors. We speculate that this interactome enhances the robustness of the pluripotent state. 4C-seq was performed on a range of viewpoints in pluripotent (2x ESC, iPSC) and differentiated (neural precursor cells and astrocytes) cell lines.
Project description:3D-topology of DNA in the cell nucleus provides a level of transcription regulation beyond the sequence of the linear DNA. To study the relationship between transcriptional activity and spatial environment of a gene, we have used allele-specific 4C-technology to produce high-resolution topology maps of the active and inactive X-chromosomes in female cells. We found that loci on the active X form multiple long-range interactions, with spatial segregation of active and inactive chromatin. On the inactive X, silenced loci lack preferred interactions, suggesting a unique random organization inside the inactive territory. However, escapees, among which is Xist, are engaged in long-range contacts with each other, enabling identification of novel escapees. Deletion of Xist results in partial re-folding of the inactive X into a conformation resembling the active X, without affecting gene silencing or DNA methylation. Our data point to a role for Xist RNA in shaping the conformation of the inactive X-chromosome independently of transcription. Five or six 4C viewpoints were applied on the mouse female wild type active X-chromosome, the wild type inactive X-chromosome, the conditional Xist X-chromosome and the Xist knock out X-chromosome
Project description:Here, we show that the Kdm5c/Smcx member of the Jarid1 family of H3K4 demethylases is recruited to both enhancer and core promoter elements in ES and neuronal progenitor cells (NPC). Knockdown of Kdm5c deregulates transcription via a local increase in H3K4me3. While at core promoters the function of Kdm5c is to restrict transcription, loss of Kdm5c impairs enhancer function. Remarkably, an impaired enhancer function activates promoter activity from Kdm5c-bound intergenic regions. Our results demonstrate that the Kdm5c demethylase plays a crucial role in the functional identity and discrimination of enhancers and core promoters. We speculate that this is related to recruitment of H3K4me3 binders like the TFIID and NURF complexes6-8. Providing functional identity to genomic regions through balancing enzymes that deposit and remove histone modifications may prove to be a general epigenetic mechanism for the functional indexing of eukaryotic genomes. Examination of the KDM5C binding sites in mouse embryonic stem cells and in neuronal progenitor cells. Effect of KDM5C knock down on H3K4me3 and H3K4me1 levels and gene expression.
Project description:CTCF binding polarity determines chromatin looping CTCF ChIPseq was performed in E14 embryonic stem cells and neural precursor cells
Project description:We used single-cell RNA-sequencing to generate allele-resolution expression levels in individual cells that we used for inference of transcriptional burst kinetics.
Project description:CCCTC-binding factor (CTCF) is an architectural protein involved in the three-dimensional organization of chromatin. In this study, we systematically assayed the 3D genomic contact profiles of hundreds of CTCF binding sites in multiple tissues with high-resolution 4C-seq. We find both developmentally stable and dynamic chromatin loops. As recently reported, our data also suggest that chromatin loops preferentially form between CTCF binding sites oriented in a convergent manner. To directly test this, we used CRISPR-Cas9 genome editing to delete core CTCF binding sites in three loci, including the CTCF site in the Sox2 super-enhancer. In all instances, CTCF and cohesin recruitment were lost, and chromatin loops with distal CTCF sites were disrupted or destabilized. Re-insertion of oppositely oriented CTCF recognition sequences restored CTCF and cohesin recruitment, but did not re-establish chromatin loops. We conclude that CTCF binding polarity plays a functional role in the formation of higher order chromatin structure. 4C-seq was performed on a large number of viewpoints in E14 embryonic stem cells, neural precursor cells and primary fetal liver cells
Project description:Background: During early embryonic development, one of the two X chromosomes in mammalian female cells is inactivated to compensate for a potential imbalance in transcript levels with male cells containing a single X chromosome. We use mouse female Embryonic Stem Cells (ESCs) with nonrandom XCI and polymorphic X chromosomes to study the dynamics of gene silencing over the inactive X chromosome (Xi) by high-resolution allele-specific RNA-Seq. Results: Induction of XCI by differentiation of female ESCs shows that genes proximal to the X-inactivation center (XIC) are silenced earlier than distal genes, while lowly expressed genes show faster XCI dynamics than highly expressed genes. The active X chromosome shows a minor but significant increase in gene activity during differentiation, resulting in complete dosage compensation in differentiated cell types. Genes escaping XCI show little or no silencing during early propagation of XCI. Using allele-specific RNA-Seq of Neural Progenitor Cells (NPCs) generated from the female ESCs, we identify three regions distal to the XIC that stably escape XCI during differentiation of the female ESCs, as well as during propagation of the NPCs. These regions coincide with Topologically Associated Domains (TADs) as determined in the undifferentiated female ESCs. Also the previously characterized human gene clusters escaping XCI correlate with TADs. Conclusions: Together, the dynamics of gene silencing observed over the Xi during XCI provide further insight in the formation and maintenance of the repressive Xi complex. The association of regions of escape with TADs, in mouse and human, suggests a regulatory role for TADs during propagation of XCI. 19 RNA-Seq profiles of mouse ESCs, EpiSCs and NPCs, mostly from distant crosses to allow allele specific mapping. 1 HiC profile of an undifferentiated mouse female ESC line containing a Tsix mutation. Mainly focusing on X inactivation.
Project description:Human tissue based proteomics projects are challenging due to low abundance of proteins and tissue specificity of protein expression. In this study, we aimed to develop a cell-based approach to profile the male specific region of the Y chromosome (MSY) proteins. First, we profiled the expression of 23 Y chromosome genes and 15 of their X-linked homologues during neural cell differentiation from NT2 cells at three different developmental stages using qRT-PCR, western blotting and immunofluorescent (IF) techniques. The expression level of 12 Y-linked genes significantly increased over neural differentiation. Including RBMY1, EIF1AY, DDX3Y1, HSFY1, BPY2, PCDH11Y, UTY, RPS4Y1, USP9Y, SRY, PRY, and ZFY. Subsequently, DDX3Y was selected as a candidate for knockdown as it was significantly expressed in neural progenitor cells and it is known to be expressed in a gender specific manner and play a role in spermatogenesis. A siRNA-mediated DDX3Y knockdown in neural progenitor cells impaired cell cycle progression and increased apoptosis, consequently interrupting differentiation. Label-free quantitative shotgun proteomics based on a spectral counting approach was then used to characterize the proteomic profile of the cells after DDX3Y knockdown. Among 920 reproducibly identified proteins detected, 74 proteins were differentially expressed following DDX3Y siRNA treatment compared to mock treated cells. Functional grouping indicated these proteins were associated with cell cycle, cell-to-cell signaling, apoptosis and other important networks such as RNA processing and transcription regulation. Disease-based analysis confirmed DDX3Y involvement primarily in neurological and RNA metabolism disorders. Our results confirm that MSY genes are expressed in male neuronal cells, and demonstrate that Y linked DDX3 (DDX3Y) could play a multifunctional role in neural cell development in a sexually dimorphic manner.