Dam identification (DamID) is a powerful technique to generate genome-wide maps of chromatin protein binding. Due to its high sensitivity it is particularly suited to study the genome interactions of chromatin proteins in small tissue samples in model organisms such as Drosophila. Here we report an intein-based approach to tune the expression level of Dam and Dam-fusion proteins in Drosophila by addition of a ligand to fly food. This helps to suppress toxic effects of Dam. In addition we describe a strategy for genetically controlled expression of Dam in a specific cell type in complex tissues. We demonstrate the utility of the latter by generating a glia-specific map of Polycomb in small samples of brain tissue. Overall design: RNA sequencing of 3 samples, each using 2 biological replicates.
Inducible DamID systems for genomic mapping of chromatin proteins in Drosophila.
Sex, Specimen part, Subject
View SamplesReporter genes integrated into the genome are a powerful tool to reveal effects of regulatory elements and local chromatin context on gene expression. However, so far such reporter assays have been of low throughput. Here we describe a multiplexing approach for the parallel monitoring of transcriptional activity of thousands of randomly integrated reporters. More than 27,000 distinct reporter integrations in mouse embryonic stem cells, obtained with two different promoters, show ~1,000-fold variation in expression levels. Data analysis indicates that lamina-associated domains act as attenuators of transcription, likely by reducing access of transcription factors to binding sites. Furthermore, chromatin compaction is predictive of reporter activity. We also found evidence for cross-talk between neighboring genes, and estimate that enhancers can influence gene expression on average over ~20 kb. The multiplexed reporter assay is highly flexible in design and can be modified to query a wide range of aspects of gene regulation. Overall design: mRNA profiles of 11 mouse embryonic cell lines each harboring multiple barcoded reporter constructs with mouse PGK promoter integrated at random positions in the genome, single replicate.
Chromatin position effects assayed by thousands of reporters integrated in parallel.
Specimen part, Cell line, Subject
View SamplesBackground.
A comprehensive gene expression atlas of sex- and tissue-specificity in the malaria vector, Anopheles gambiae.
Sex, Specimen part
View SamplesPurpose: mRNA translation into protein is highly regulated, but the role of mRNA isoforms, noncoding RNAs (ncRNAs), and genetic variants has yet to be systematically studied. Using high-throughput sequencing (RNA-seq), we have measured cellular levels of mRNAs and ncRNAs, and their isoforms, in lymphoblast cell lines (LCL) and in polysomal fractions, the latter shown to yield strong correlations of mRNAs with expressed protein levels. Analysis of allelic RNA ratios at heterozygous SNPs served to reveal genetic factors in ribosomal loading. Methods: RNA-seq was performed on cytosolic extracts and polysomal fractions (3 ribosomes or more) from three lymphoblastoid cell lines. As each RNA fraction was amplified (NuGen kit), and relative contributions from various RNA classes differed between cytosol and polysomes, the fraction of any given RNA species loaded onto polysomes was difficult to quantitate. Therefore, we focused on relative recovery of the various RNA classes and rank order of single RNAs compared to total RNA. Results: RNA-seq of coding and non-coding RNAs (including microRNAs) in three LCLs revealed significant differences in polysomal loading of individual RNAs and isoforms, and between RNA classes. Moreover, correlated distribution between protein-coding and non-coding RNAs suggests possible interactions between them. Allele-selective RNA recruitment revealed strong genetic influence on polysomal loading for multiple RNAs. Allelic effects can be attributed to generation of different RNA isoforms before polysomal loading or to differential loading onto polysomes, the latter defining a direct genetic effect on translation. Several variants and genes identified by this approach are also associated with RNA expression and clinical phenotypes in various databases. Conclusions: These results provide a novel approach using complete transcriptome RNA-seq to study polysomal RNA recruitment and regulatory variants affecting protein translation. Overall design: cells from 3 samples were grown to 5x105 cells/mL density in T75 tissue culture flask and harvested, total RNA and polysome bound RNA was sequenced by Ion Proton
Allele-Selective Transcriptome Recruitment to Polysomes Primed for Translation: Protein-Coding and Noncoding RNAs, and RNA Isoforms.
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KAP1 regulates gene networks controlling T-cell development and responsiveness.
Specimen part
View SamplesThe modulation of chromatin status at specific genomic loci controls lymphoid differentiation. Here, we investigated the role played in this process by KAP1, the universal cofactor of KRAB-containing Zinc Finger Proteins (KRAB-ZFPs), a tetrapod-restricted family of transcriptional repressors. T cell-specific Kap1 knockout mice displayed a significant expansion of immature thymocytes and imbalances in the ratios of mature T cells in the thymus and the spleen, with impaired responses to TCR stimulation. Transcriptome and chromatin studies revealed that KAP1 directly controls the expression of a number of genes involved in TCR and cytokine signalling, among which Traf1 and FoxO1, and is strongly associated with cis-acting regulatory elements marked by the H3K9me3 repressive mark on the genome of thymic T cells. Likely responsible for tethering KAP1 to at least part of its genomic targets, a small number of KRAB/ZFPs are selectively expressed in T lymphoid cells. These results reveal the so far unsuspected yet important role of KRAB/KAP1-mediated epigenetic regulation in T lymphocyte differentiation and activation.
KAP1 regulates gene networks controlling T-cell development and responsiveness.
No sample metadata fields
View SamplesGlobal heterochromatin reduction, which is one of the hallmarks of aging cells, is associated with reduced transposable element repression and increased risk of chromatin instability. To ensure genomic integrity, the irreparable cells in a population exit permanently from the cell cycle, and this process is termed “senescence”. However, senescence only blocks the expansion of unwanted cells, and the aberrant chromatin of senescent cells remains unstable. Serendipitously, we found that the transient ectopic expression of a repressive epigenetic modulator, DNA methyltransferase 3-like (DNMT3L) was sufficient to delay the premature senescence progression of late-passage mouse embryonic fibroblasts (MEFs) associated with a tightened global chromatin structure. DNMT3L induces more repressive H3K9 methylation on endogenous retroviruses and downregulates the derepressed transposons in aging MEFs. In addition, we found that a pulse of ectopic DNMT3L resulted in the reestablishment of H3K27me3 on polycomb repressive complex 2 (PRC2)-target genes that were derepressed in old MEFs. We demonstrated that ectopic DNMT3L interacted with PRC2 in MEFs. Our data also suggested that ectopic DNMT3L might guide PRC2 to redress deregulated chromatin regions in aging cells. This study might lead to an epigenetic reinforcement strategy for overcoming aging-associated epimutation and senescence.
Transient DNMT3L Expression Reinforces Chromatin Surveillance to Halt Senescence Progression in Mouse Embryonic Fibroblast.
Specimen part
View SamplesThis SuperSeries is composed of the SubSeries listed below.
KAP1 regulates gene networks controlling mouse B-lymphoid cell differentiation and function.
Specimen part
View SamplesChromatin remodeling is fundamental for B cell differentiation. Here, we explored the role in this process of KAP1, the cofactor of KRAB-ZFP transcriptional repressors. B lymphoid-specific Kap1 knockout mice displayed reduced numbers of mature B cells, lower steady-state levels of antibodies and accelerated rates of decay of neutralizing antibodies following viral immunization. Transcriptome analyses of Kap1-deleted B splenocytes revealed an upregulation of PTEN, the enzymatic counter-actor of PIK3 signaling, and of genes encoding DNA damage response factors, cell-cycle regulators and chemokine receptors. ChIP/seq studies established that KAP1 bound at or close to a number of these genes, and controlled chromatin status at their promoters. Genome-wide, KAP1-binding sites avoided active B cell-specific enhancers and were enriched in repressive histone marks, further supporting a role for this molecule in gene silencing in vivo. Likely responsible for tethering KAP1 to at least some of these targets, a discrete subset of KRAB-ZFPs is enriched in B lymphocytes. This work thus reveals the role of KRAB/KAP1-mediated epigenetic regulation in B cell development and homeostasis.
KAP1 regulates gene networks controlling mouse B-lymphoid cell differentiation and function.
Specimen part
View SamplesE-cadherin, a protein encoded by the CDH1 gene is the dominant epithelial cell adhesion molecule playing a crucial role in epithelial tissue polarity and structural integrity. The progression of 90% or more carcinomas is believed to be mediated by disruption of normal E-cadherin expression, subcellular localization or function. Despite the strong correlation between E-cadherin loss and malignancy the mechanism through how this occurs is not known in most sporadic and hereditary epithelial carcinomas. Previous works have shown the importance of CDH1 intron 2 sequences for proper gene and protein expression supporting the possibility of these being cis-modulators of E-cadherin expression/function. but when co-expressed it led to reduced cell-cell adhesiveness, increased invasion and angiogenesis. By expression array analysis, IFITM1 and IFI27 levels were found to be increased upon CDH1a overexpression. Importantly, CDH1a was found to be de novo expressed in gastric cancer cell lines when compared to normal stomach.
Transcription initiation arising from E-cadherin/CDH1 intron2: a novel protein isoform that increases gastric cancer cell invasion and angiogenesis.
Specimen part, Cell line
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