Cohesin-based chromatin interactions enable regulated gene expression within preexisting architectural compartments
TL;DR: These findings indicate that cohesin-mediated long-range interactions facilitate discrete gene expression states within preexisting chromosomal compartments, suggesting an important role for cohesIn in genome organization.
Abstract: Chromosome conformation capture approaches have shown that interphase chromatin is partitioned into spatially segregated Mb-sized compartments and sub-Mb-sized topological domains. This compartmentalization is thought to facilitate the matching of genes and regulatory elements, but its precise function and mechanistic basis remain unknown. Cohesin controls chromosome topology to enable DNA repair and chromosome segregation in cycling cells. In addition, cohesin associates with active enhancers and promoters and with CTCF to form long-range interactions important for gene regulation. Although these findings suggest an important role for cohesin in genome organization, this role has not been assessed on a global scale. Unexpectedly, we find that architectural compartments are maintained in noncycling mouse thymocytes after genetic depletion of cohesin in vivo. Cohesin was, however, required for specific long-range interactions within compartments where cohesin-regulated genes reside. Cohesin depletion diminished interactions between cohesin-bound sites, whereas alternative interactions between chromatin features associated with transcriptional activation and repression became more prominent, with corresponding changes in gene expression. Our findings indicate that cohesin-mediated long-range interactions facilitate discrete gene expression states within preexisting chromosomal compartments.
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Baylor College of Medicine1, Stanford University2, Rice University3, Broad Institute4, Harvard University5, New York University6, University of California, San Diego7, Courant Institute of Mathematical Sciences8, New York University Shanghai9, National Institutes of Health10, Massachusetts Institute of Technology11
TL;DR: In this paper, the effects of degrading cohesin were explored, showing that loop domains can be eliminated and re-formed in under an hour, consistent with a model where loop extrusion is rapid.
1,290 citations
TL;DR: Although CTCF has been assigned various roles that are often contradictory, new results now help to draw a unifying model to explain the many functions of this protein.
Abstract: CCCTC-binding factor (CTCF) is a DNA-binding protein that has various, often seemingly contradictory, roles in gene regulation. This Review describes these disparate functions and how the context-dependent looping of DNA regions by CTCF is emerging as a potential unifying mechanism that underpins these diverse roles.
930 citations
TL;DR: It is shown that deletion of the cohesin-loading factor Nipbl in mouse liver leads to a marked reorganization of chromosomal folding, and the disappearance of TADs unmasks a finer compartment structure that accurately reflects the underlying epigenetic landscape.
Abstract: Imaging and chromosome conformation capture studies have revealed several layers of chromosome organization, including segregation into megabase-sized active and inactive compartments, and partitioning into sub-megabase domains (TADs) It remains unclear, however, how these layers of organization form, interact with one another and influence genome function Here we show that deletion of the cohesin-loading factor Nipbl in mouse liver leads to a marked reorganization of chromosomal folding TADs and associated Hi-C peaks vanish globally, even in the absence of transcriptional changes By contrast, compartmental segregation is preserved and even reinforced Strikingly, the disappearance of TADs unmasks a finer compartment structure that accurately reflects the underlying epigenetic landscape These observations demonstrate that the three-dimensional organization of the genome results from the interplay of two independent mechanisms: cohesin-independent segregation of the genome into fine-scale compartments, defined by chromatin state; and cohesin-dependent formation of TADs, possibly by loop extrusion, which helps to guide distant enhancers to their target genes
893 citations
TL;DR: The insights into chromatin architecture that have been gained through recent technological developments in quantitative biology, genomics and cell and molecular biology approaches are discussed and how these new concepts have been used to address important biological questions in development and disease are explained.
Abstract: Understanding how chromatin is organized within the nucleus and how this 3D architecture influences gene regulation, cell fate decisions and evolution are major questions in cell biology. Despite spectacular progress in this field, we still know remarkably little about the mechanisms underlying chromatin structure and how it can be established, reset and maintained. In this Review, we discuss the insights into chromatin architecture that have been gained through recent technological developments in quantitative biology, genomics and cell and molecular biology approaches and explain how these new concepts have been used to address important biological questions in development and disease.
810 citations
TL;DR: Insulated neighborhoods in T cell acute lymphoblastic leukemia (T-ALL) are mapped and it is found that tumor cell genomes contain recurrent microdeletions that eliminate the boundary sites of insulated neighborhoods containing prominent T-ALL proto-oncogenes.
Abstract: Oncogenes are activated through well-known chromosomal alterations such as gene fusion, translocation, and focal amplification. In light of recent evidence that the control of key genes depends on chromosome structures called insulated neighborhoods, we investigated whether proto-oncogenes occur within these structures and whether oncogene activation can occur via disruption of insulated neighborhood boundaries in cancer cells. We mapped insulated neighborhoods in T cell acute lymphoblastic leukemia (T-ALL) and found that tumor cell genomes contain recurrent microdeletions that eliminate the boundary sites of insulated neighborhoods containing prominent T-ALL proto-oncogenes. Perturbation of such boundaries in nonmalignant cells was sufficient to activate proto-oncogenes. Mutations affecting chromosome neighborhood boundaries were found in many types of cancer. Thus, oncogene activation can occur via genetic alterations that disrupt insulated neighborhoods in malignant cells.
800 citations
Cites background from "Cohesin-based chromatin interaction..."
...at the CD3 and GATA3 loci (41, 42) (Table S2A-B)....
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...Previous studies have established that CTCF is bound at the anchor sites of chromosome loop structures, but not every CTCF-bound site in the genome is involved in looping interactions, and the CTCF-bound sites that are detected at the boundaries at looping interactions tend to be co-bound by cohesin (8, 9, 11, 24, 40, 42, 63-66)....
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...To define a second control set of non-boundary CTCF sites (“control set 2”), we used previous evidence that the CTCF-bound sites that are detected at the boundaries at looping interactions tend to be co-bound by cohesin (8, 9, 11, 24, 40, 42, 63-66)....
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References
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TL;DR: Burrows-Wheeler Alignment tool (BWA) is implemented, a new read alignment package that is based on backward search with Burrows–Wheeler Transform (BWT), to efficiently align short sequencing reads against a large reference sequence such as the human genome, allowing mismatches and gaps.
Abstract: Motivation: The enormous amount of short reads generated by the new DNA sequencing technologies call for the development of fast and accurate read alignment programs. A first generation of hash table-based methods has been developed, including MAQ, which is accurate, feature rich and fast enough to align short reads from a single individual. However, MAQ does not support gapped alignment for single-end reads, which makes it unsuitable for alignment of longer reads where indels may occur frequently. The speed of MAQ is also a concern when the alignment is scaled up to the resequencing of hundreds of individuals.
Results: We implemented Burrows-Wheeler Alignment tool (BWA), a new read alignment package that is based on backward search with Burrows–Wheeler Transform (BWT), to efficiently align short sequencing reads against a large reference sequence such as the human genome, allowing mismatches and gaps. BWA supports both base space reads, e.g. from Illumina sequencing machines, and color space reads from AB SOLiD machines. Evaluations on both simulated and real data suggest that BWA is ~10–20× faster than MAQ, while achieving similar accuracy. In addition, BWA outputs alignment in the new standard SAM (Sequence Alignment/Map) format. Variant calling and other downstream analyses after the alignment can be achieved with the open source SAMtools software package.
Availability: http://maq.sourceforge.net
Contact: [email protected]
43,862 citations
"Cohesin-based chromatin interaction..." refers background or methods in this paper
...Trimmed reads were aligned independently to the mouse reference genome assembly (NCBI37/mm9) using BWA (Li and Durbin 2009)....
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...There was a highly significant overlap of 502 differential interactions between replicates (P < 10 15, odds ratio of 5.25 for 224 increased interactions and 9.96 for...
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...Rather, cohesin enables discrete gene expression states by promoting cohesin-based interac- tions within a preexisting architectural framework....
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TL;DR: Bowtie extends previous Burrows-Wheeler techniques with a novel quality-aware backtracking algorithm that permits mismatches and can be used simultaneously to achieve even greater alignment speeds.
Abstract: Bowtie is an ultrafast, memory-efficient alignment program for aligning short DNA sequence reads to large genomes. For the human genome, Burrows-Wheeler indexing allows Bowtie to align more than 25 million reads per CPU hour with a memory footprint of approximately 1.3 gigabytes. Bowtie extends previous Burrows-Wheeler techniques with a novel quality-aware backtracking algorithm that permits mismatches. Multiple processor cores can be used simultaneously to achieve even greater alignment speeds. Bowtie is open source http://bowtie.cbcb.umd.edu.
20,335 citations
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01 Dec 2010
TL;DR: A guide to using S environments to perform statistical analyses providing both an introduction to the use of S and a course in modern statistical methods.
Abstract: A guide to using S environments to perform statistical analyses providing both an introduction to the use of S and a course in modern statistical methods The emphasis is on presenting practical problems and full analyses of real data sets
18,346 citations
"Cohesin-based chromatin interaction..." refers background in this paper
...3D), indicating that most are direct targets of cohesin-mediated regulation....
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TL;DR: A method based on the negative binomial distribution, with variance and mean linked by local regression, is proposed and an implementation, DESeq, as an R/Bioconductor package is presented.
Abstract: High-throughput sequencing assays such as RNA-Seq, ChIP-Seq or barcode counting provide quantitative readouts in the form of count data. To infer differential signal in such data correctly and with good statistical power, estimation of data variability throughout the dynamic range and a suitable error model are required. We propose a method based on the negative binomial distribution, with variance and mean linked by local regression and present an implementation, DESeq, as an R/Bioconductor package.
13,356 citations
"Cohesin-based chromatin interaction..." refers background or methods in this paper
...We used the Bioconductor R package DESeq version 1.6.1 (Anders and Huber 2010) to determine significantly differentially expressed genes in cohesin-deficient thymocytes versus control cells (FDR = 0.05)....
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...1 (Anders and Huber 2010) to determine significantly differentially expressed genes in cohesin-deficient thymocytes versus control cells (FDR = 0....
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TL;DR: It is demonstrated in macrophages and B cells that collaborative interactions of the common factor PU.1 with small sets of macrophage- or B cell lineage-determining transcription factors establish cell-specific binding sites that are associated with the majority of promoter-distal H3K4me1-marked genomic regions.
9,620 citations
"Cohesin-based chromatin interaction..." refers methods in this paper
...…compart- Genome Research 2067 www.genome.org Cohesin-based chromatin interactions Cohesin binding predicts perturbed long-range interactions in cohesin-deficient thymocytes We applied the HOMER pipeline (Heinz et al. 2010) to our Hi-C data (see Methods, section on Hi-C data analysis, for details)....
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...We applied the HOMER pipeline (Heinz et al. 2010) to our Hi-C data (see Methods, section on Hi-C data analysis, for details)....
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