Project description:CTCF binding polarity determines chromatin looping CTCF ChIPseq was performed in E14 embryonic stem cells and neural precursor cells
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:DamID LaminB1 data were generated in POU2F1-/- MEFs to study the potential role of POU2F1/Oct1 in genome - nuclear lamina interactions. DamID LaminA data were generated in NPCs and Astrocytes to study similarities/differences between LaminA and LaminB1 binding. Comparison of MEF wt versus MEF POU2F1-/-. Comparison of LaminA (NPC & AC) with LaminB1 (NPC & AC data in GSE17051)
Project description:Despite recent progress in genome topology knowledge, the role of repeats, comprising the majority of mammalian genomes, remains elusive. Satellites are highly abundant sequences that cluster around centromeres, attract pericentromeric heterochromatin and aggregate into nuclear chromocenters that are assumed to form a repressive compartment in the nucleus to which genes are recruited for silencing. Here we designed a strategy for genome-wide identification of pericentromere-associated domains (PADs) in different mouse cell types. The ~1000 PADs and non-PADs have similar chromatin states in embryonic stem cells. During lineage commitment however chromocenters progressively overlap with constitutively inactive genomic regions at the nuclear periphery. This suggests that chromocenters do not actively recruit PADs but are themselves attracted to inactive chromatin compartments. However, we also found that experimentally induced proximity of an active locus to chromocenters was sufficient to cause gene repression. Collectively, our data suggests that rather than being a driver of nuclear organization, pericentromeric satellite repeats mostly co-segregate with inactive genomic regions to nuclear compartments where they can contribute to stably maintaining the repressed status of proximal chromosomal regions. We performed satellite 4C (sat4C) on mouse primary thymus tissue, pluripotent mouse embryonic stem cells (ESC) and neural precursor cells (NPC) and terminally differentiated astrocytes (AC) that were sequentially derived from these ESC in vitro
Project description:Primitive neural stem cells (NSCs) could be derived from pluripotent mouse embryonic stem (ES) cells, and then differentiate into definitive-type neural stem cells which resemble NSCs obtained from the central nervous system. Hence, primitive NSCs define an early stage of neural induction and provide a model to understand the mechanism that controls initial neural commitment. In this study, we performed microarray assay to analyze the global transcriptional profiles in mouse ES cell-derived primitive and definitive NSCs and to depict the molecular changes during the multi-staged neural differentiation process. Primitive NSCs derived directly from ESCs in Lif (p-NSC_L), primitive NSCs that were sub-cultured in the presence of Lif and FGF (p-NSC_LF), as well as definitive NSCs derived from primitive NSCs in medium containing FGF and EGF, were collected for RNA extraction and hybridization on Affymetrix microarrays. Mouse ESCs and NSCs obtained from mouse embryonic brain (E11.5) were included for controls. For each cell type, we collected two biological replicate samples for microarray analysis.
Project description:BCR–ABL1+ precursor B-cell acute lymphoblastic leukemia (BCR– ABL1+ B-ALL) is an aggressive hematopoietic neoplasm characterized by a block in differentiation due in part to the somatic loss of transcription factors required for B-cell development. We hypothesized that overcoming this differentiation block by forcing cells to reprogram to the myeloid lineage would reduce the leukemogenicity of these cells. We found that primary human BCR–ABL1+ B-ALL cells could be induced to reprogram into macrophage-like cells by exposure to myeloid differentiation-promoting cytokines in vitro or by transient expression of the myeloid transcription factor C/EBPα or PU.1. The resultant cells were clonally related to the primary leukemic blasts but resembled normal macrophages in appearance, immunophenotype, gene expression, and function. Most importantly, these macrophage-like cells were unable to establish disease in xenograft hosts, indicating that lineage reprogramming eliminates the leukemogenicity of BCR–ABL1+ B-ALL cells, and suggesting a previously unidentified therapeutic strategy for this disease. Finally, we determined that myeloid reprogramming may occur to some degree in human patients by identifying primary CD14+ monocytes/ macrophages in BCR–ABL1+ B-ALL patient samples that possess the BCR–ABL1+ translocation and clonally recombined VDJ regions. We obtained the expression profiles of 5 human B-ALL samples using Afymmetrix U133A2 microarrays. Blasts were either analyzed without culture, or cultured in the presence of myeloid cytokines and sorted into CD14+ and CD19+ populations.
Project description:To gain genome wide information on the association of EZH2 with promoter regions in HeLa cells, DamID experiments and subsequent analysis by promoter arrays (Affymetrix GeneChip Human Promoter 1.0R ) were performed. The DamID method uses fusions of the bacterial Dam DNA methylase and the protein of interest, to direct the enzymatic activity to the proteinM-bM-^@M-^Ys genomic binding sites, where the DNA is methylated. Methylated DNA is then extracted, enriched and further analysed by microarray. EZH2 is the enzymatic subunit of the Polycomb Repressive Complex 2, which deposits the H3K27me3 mark on chromatin. This mark is associated with low gene expression, either in polycomb repressed regions or, in combination with methylation of H3K4, at poised promoters. An EZH2-T416A mutant (EZH2-mTP5) fails to bind to NIPP1, a factor implied in the regulation of PRC2 binding to a subset of target regions. To obtain a genome wide picture of differential binding of EZH2-WT and the EZH2-mTP5 mutant to promoter regions, the mutant was subjected to DamID/microanalysis as well. DamID of EZH2-WT (2 replicates) and EZH2-mTP5(T416A)(2 replicates) vs. control (Dam without fused protein)(4 samples)
Project description:Protein phosphatase 1 (PP1) is a Ser/Thr phosphatase that has been implicated in many key cellular functions including transcriptional regulation. Due to its involvement these many processes, it becomes difficult to directly link PP1 to transcriptional regulation on the chromatin level as no direct genomic binding sites have been identified. Previous work has failed to address this as the most common method used, namely chromatin immunoprecipitation (ChIP), is an antibody-dependent technique and currently no ChIP-grade PP1 antibodies have been developed. Using DamID, an alternative to ChIP, we have identified PP1 isoform-specific binding sites on the promoter regions of genes. We also identified the binding sites of three main PP1 regulatory subunits (R-subunits) in order to identify potential PP1 holo-enzymes binding sites. Our study revealed the full extent of PP1 isoform specific binding an allowed us to investigate the dependency of the R-subunits on PP1 for chromatin targeting. This data establishes PP1 as a chromatin interactor and allow for the identification of direct effects PP1 can have on the regulation of the genes on whose promoter it is bound. HeLa stable cell lines were created using constructs derived from pIND-(V5)-EcoDam. These constructs express trace amounts of Dam or C-terminal fusions with PP1α, PP1β, PP1γ and three R-subunits, PNUTS, NIPP1 and RepoMan, both wildtype (WT) and their PP1-binding mutants (RATA). Two independent stable cell lines were set up for each of the constructs. DamID-DNA was labeled and hybridized to a GeneChip Human Promoter 1.0R Array (Affymetrix, Santa Clara, CA, USA). The tiling array readouts were analyzed with the “model-based analysis of tiling arrays” (MAT) algorithm (version 1.0.0) against the hg19 reference genome. We normalized two biological replicates of each Dam-fusion over two Dam-only biological replicates. Each biological repeat consisted of 2 technical repeats pooled together prior to hybridization to the tiling array.
Project description:The onset and progression of breast cancer are linked to genetic and epigenetic changes that alter the normal programming of cells. Epigenetic modifications of DNA and histones contribute to chromatin structure that results in the activation or repression of gene expression. Several epigenetic pathways have been shown to be highly deregulated in cancer cells. Targeting specific histone modifications represents a viable strategy to prevent oncogenic transformation, tumor growth or metastasis. Methylation of histone H3 lysine 4 has been extensively studied and shown to mark genes for expression; however this residue can also be acetylated and the specific function of this alteration is less well known. To define the relative roles of histone H3 methylation (H3K4me3) and acetylation (H3K4ac) in breast cancer, we determined genomic regions enriched for both marks in normal-like (MCF10A), transformed (MCF7) and metastatic (MDA-MB-231) cells using a genome-wide ChIP-Seq approach. Our data revealed a genome-wide gain of H3K4ac associated with both early and late breast cancer cell phenotypes, while gain of H3K4me3 was predominantly associated with late stage cancer cells. Enrichment of H3K4ac was overrepresented at promoters of genes associated with cancer-related phenotypic traits, such as estrogen response and epithelial-to-mesenchymal transition pathways. Our findings highlight an important role for H3K4ac in predicting epigenetic changes associated with early stages of transformation. In addition, our data provide a valuable resource for understanding epigenetic signatures that correlate with known breast cancer-associated oncogenic pathways. RNA-Seq of cell lines MCF10A, MCF7 and MDA-MB-231.
Project description:These RNA-seq data were generated to correlate with genomic interaction data in a related Hi-C analysis. MCF10A is a normal-like mammary epithelial cell line and MCF7 is a transformed estrogen responsive breast cancer cell line derived from a metastatic site; both are commonly used in models of breast cancer progression. Analysis revealed a set of genes related to repression of WNT signalling that were both up-regulated in MCF7 and located in genomic regions that had transitioned from closed to open structure in MCF7. RNA-seq of MCF10A and MCF7 cells. 3 replicates each. Sequencing was strand-specific and conducted on ribo-depleted RNA.