Genomic editing of intronic enhancers unveils their role in fine-tuning tissue-specific gene expression in Arabidopsis thaliana

2021 ◽  
Author(s):  
Fanli Meng ◽  
Hainan Zhao ◽  
Bo Zhu ◽  
Tao Zhang ◽  
Mingyu Yang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Arabidopsis Thaliana ◽  
Transcriptional Repression ◽  
Regulation Of Gene Expression ◽  
Fine Tuning ◽  
Specific Gene ◽  
Open Chromatin ◽  
Floral Tissue ◽  
Deletion Lines ◽  
A Genome

Abstract Enhancers located in introns are abundant and play a major role in the regulation of gene expression in mammalian species. By contrast, the functions of intronic enhancers in plants have largely been unexplored and only a handful of plant intronic enhancers have been reported. We performed a genome-wide prediction of intronic enhancers in Arabidopsis thaliana using open chromatin signatures based on DNase I sequencing. We identified 941 candidate intronic enhancers associated with 806 genes in seedling tissue and 1,271 intronic enhancers associated with 1,069 genes in floral tissue. We validated the function of 15 of 21 (71%) of the predicted intronic enhancers in transgenic assays using a reporter gene. We also created deletion lines of three intronic enhancers associated with two different genes using CRISPR/Cas. Deletion of these enhancers, which span key transcription factor binding sites, did not abolish gene expression but caused varying levels of transcriptional repression of their cognate genes. Remarkably, the transcriptional repression of the deletion lines occurred at specific developmental stages and resulted in distinct phenotypic effects on plant morphology and development. Clearly, these three intronic enhancers are important in fine-tuning tissue- and development-specific expression of their cognate genes.

scholarly journals Pervasive promoter hypermethylation of silenced TERT alleles in human cancers

2020 ◽  
Vol 43 (5) ◽  
pp. 847-861 ◽  
Author(s):  
David Esopi ◽  
Mindy Kim Graham ◽  
Jacqueline A. Brosnan-Cashman ◽  
Jennifer Meyers ◽  
Ajay Vaghasia ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cancer Cells ◽  
Cell Lines ◽  
Cancer Cell ◽  
Transcriptional Repression ◽  
Cpg Island ◽  
Promoter Hypermethylation ◽  
Fine Tuning ◽  
Open Chromatin ◽  
Promoter Mutations

Abstract Background In cancers, maintenance of telomeres often occurs through activation of the catalytic subunit of telomerase, encoded by TERT. Yet, most cancers show only modest levels of TERT gene expression, even in the context of activating hotspot promoter mutations (C228T and C250T). The role of epigenetic mechanisms, including DNA methylation, in regulating TERT gene expression in cancer cells is as yet not fully understood. Methods Here, we have carried out the most comprehensive characterization to date of TERT promoter methylation using ultra-deep bisulfite sequencing spanning the CpG island surrounding the core TERT promoter in 96 different human cell lines, including primary, immortalized and cancer cell types, as well as in control and reference samples. Results In general, we observed that immortalized and cancer cell lines were hypermethylated in a region upstream of the recurrent C228T and C250T TERT promoter mutations, while non-malignant primary cells were comparatively hypomethylated in this region. However, at the allele-level, we generally found that hypermethylation of promoter sequences in cancer cells is associated with repressed expression, and the remaining unmethylated alleles marked with open chromatin are largely responsible for the observed TERT expression in cancer cells. Conclusions Our findings suggest that hypermethylation of the TERT promoter alleles signals transcriptional repression of those alleles, leading to attenuation of TERT activation in cancer cells. This type of fine tuning of TERT expression may account for the modest activation of TERT expression in most cancers.

scholarly journals In plants distal regulatory sequences overlap with unmethylated rather than low-methylated regions, in contrast to mammals

2020 ◽  
Author(s):  
Rurika Oka ◽  
Mattijs Bliek ◽  
Huub C.J. Hoefsloot ◽  
Maike Stam
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Arabidopsis Thaliana ◽  
Transcriptional Repression ◽  
Genome Stability ◽  
Regulation Of Gene Expression ◽  
Regulatory Sequences ◽  
Regulatory Regions ◽  
Plant Genomes ◽  
Underlying Mechanisms

AbstractBackgroundDNA methylation is an important factor in the regulation of gene expression and genome stability. High DNA methylation levels are associated with transcriptional repression. In mammalian systems, unmethylated, low methylated and fully methylated regions (UMRs, LMRs, and FMRs, respectively) can be distinguished. UMRs are associated with proximal regulatory regions, while LMRs are associated with distal regulatory regions. Although DNA methylation is mainly limited to the CG context in mammals, while it occurs in CG, CHG and CHH contexts in plants, UMRs and LMRs were expected to occupy similar genomic sequences in both mammals and plants.ResultsThis study investigated major model and crop plants such as Arabidopsis thaliana, tomato (Solanum lycopersicum), rice (Oryza sativa) and maize (Zea mays), and shows that plant genomes can also be subdivided in UMRs, LMRs and FMRs, but that LMRs are mainly present in the CHG context rather than the CG context. Strikingly, the identified CHG LMRs were enriched in transposable elements rather than regulatory regions. Maize candidate regulatory regions overlapped with UMRs. LMRs were enriched for heterochromatic histone modifications and depleted for DNase accessibility and H3K9 acetylation. CHG LMRs form a distinct, abundant cluster of loci, indicating they have a different role than FMRs.ConclusionsBoth mammalian and plant genomes can be segmented in three distinct classes of loci, UMRs, LMRs and FMRs, indicating similar underlying mechanisms. Unlike in mammals, distal regulatory sequences in plants appear to overlap with UMRs instead of LMRs. Our data indicate that LMRs in plants have a different function than those in mammals.

scholarly journals DNA Methylation of Enhancer Elements in Myeloid Neoplasms: Think Outside the Promoters?

Cancers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1424 ◽  
Author(s):  
Ordoñez ◽  
Martínez-Calle ◽  
Agirre ◽  
Prosper
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Epigenetic Modification ◽  
Myeloproliferative Neoplasms ◽  
Regulation Of Gene Expression ◽  
Fine Tuning ◽  
Specific Gene ◽  
Gene Promoters ◽  
Regulatory Regions ◽  
Genome Wide

Gene regulation through DNA methylation is a well described phenomenon that has a prominent role in physiological and pathological cell-states. This epigenetic modification is usually grouped in regions denominated CpG islands, which frequently co-localize with gene promoters, silencing the transcription of those genes. Recent genome-wide DNA methylation studies have challenged this paradigm, demonstrating that DNA methylation of regulatory regions outside promoters is able to influence cell-type specific gene expression programs under physiologic or pathologic conditions. Coupling genome-wide DNA methylation assays with histone mark annotation has allowed for the identification of specific epigenomic changes that affect enhancer regulatory regions, revealing an additional layer of complexity to the epigenetic regulation of gene expression. In this review, we summarize the novel evidence for the molecular and biological regulation of DNA methylation in enhancer regions and the dynamism of these changes contributing to the fine-tuning of gene expression. We also analyze the contribution of enhancer DNA methylation on the expression of relevant genes in acute myeloid leukemia and chronic myeloproliferative neoplasms. The characterization of the aberrant enhancer DNA methylation provides not only a novel pathogenic mechanism for different tumors but also highlights novel potential therapeutic targets for myeloid derived neoplasms.

scholarly journals ARID2 Chromatin Remodeler in Hepatocellular Carcinoma

Cells ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 2152
Author(s):  
Robin Loesch ◽  
Linda Chenane ◽  
Sabine Colnot
Keyword(s):  
Gene Expression ◽  
Hepatocellular Carcinoma ◽  
Associated Factors ◽  
Regulation Of Gene Expression ◽  
Specific Gene ◽  
Chromatin Remodeler ◽  
Chromatin Remodelers ◽  
Genes Encoding ◽  
Gene Alterations

Chromatin remodelers are found highly mutated in cancer including hepatocellular carcinoma. These mutations frequently occur in ARID (AT-rich Interactive Domain) genes, encoding subunits of the ATP-dependent SWI/SNF remodelers. The increasingly prevalent complexity that surrounds the functions and specificities of the highly modular BAF (BG1/BRM-associated factors) and PBAF (polybromo-associated BAF) complexes, including ARID1A/B or ARID2, is baffling. The involvement of the SWI/SNF complexes in diverse tissues and processes, and especially in the regulation of gene expression, multiplies the specific outcomes of specific gene alterations. A better understanding of the molecular consequences of specific mutations impairing chromatin remodelers is needed. In this review, we summarize what we know about the tumor-modulating properties of ARID2 in hepatocellular carcinoma.

scholarly journals Differential Regulation of Gene Expression of Alveolar Epithelial Cell Markers in Human Lung Adenocarcinoma-Derived A549 Clones

2015 ◽  
Vol 2015 ◽  
pp. 1-20 ◽  
Author(s):  
Hiroshi Kondo ◽  
Keiko Miyoshi ◽  
Shoji Sakiyama ◽  
Akira Tangoku ◽  
Takafumi Noma
Keyword(s):  
Gene Expression ◽  
Epithelial Cell ◽  
Mapk Pathway ◽  
Alveolar Epithelial Cell ◽  
Marker Gene ◽  
Regulation Of Gene Expression ◽  
Surfactant Protein ◽  
Specific Gene ◽  
Expression Levels ◽  
Alveolar Epithelial

Stem cell therapy appears to be promising for restoring damaged or irreparable lung tissue. However, establishing a simple and reproducible protocol for preparing lung progenitor populations is difficult because the molecular basis for alveolar epithelial cell differentiation is not fully understood. We investigated anin vitrosystem to analyze the regulatory mechanisms of alveolus-specific gene expression using a human alveolar epithelial type II (ATII) cell line, A549. After cloning A549 subpopulations, each clone was classified into five groups according to cell morphology and marker gene expression. Two clones (B7 and H12) were further analyzed. Under serum-free culture conditions,surfactant protein C(SPC), an ATII marker, was upregulated in both H12 and B7.Aquaporin 5(AQP5), an ATI marker, was upregulated in H12 and significantly induced in B7. When the RAS/MAPK pathway was inhibited,SPCandthyroid transcription factor-1(TTF-1) expression levels were enhanced. After treatment with dexamethasone (DEX), 8-bromoadenosine 3′5′-cyclic monophosphate (8-Br-cAMP), 3-isobutyl-1-methylxanthine (IBMX), and keratinocyte growth factor (KGF),surfactant protein BandTTF-1expression levels were enhanced. We found that A549-derived clones have plasticity in gene expression of alveolar epithelial differentiation markers and could be useful in studying ATII maintenance and differentiation.

scholarly journals Cold priming uncouples light- and cold-regulation of gene expression in Arabidopsis thaliana

2020 ◽  
Author(s):  
Andras Bittner ◽  
Jörn van Buer ◽  
Margarete Baier
Keyword(s):  
Gene Expression ◽  
Arabidopsis Thaliana ◽  
Plant Pathogens ◽  
Cold Treatment ◽  
Regulation Of Gene Expression ◽  
Light Regulation ◽  
High Light ◽  
Cold Stimulus ◽  
Expression Of Genes ◽  
Specific Manner

Abstract Background: The majority of stress-sensitive genes responds to cold and high light in the same direction, if plants face the stresses for the first time. As shown recently for a small selection of genes of the core environmental stress response cluster, pre-treatment of Arabidopsis thaliana with a 24 h long 4 °C cold stimulus modifies cold regulation of gene expression for up to a week at 20 °C, although the primary cold effects are reverted within the first 24 h. Such memory-based regulation is called priming. Here, we analyse the effect of 24 h cold priming on cold regulation of gene expression on a transcriptome-wide scale and investigate if and how cold priming affects light regulation of gene expression.Results: Cold-priming affected cold and excess light regulation of a small subset of genes. In contrast to the strong gene co-regulation observed upon cold and light stress in not-primed plants, most priming-sensitive genes were regulated in a stressor-specific manner in cold-primed plant. Furthermore, almost as much genes were inversely regulated as co-regulated by a 24 h long 4 °C cold treatment and exposure to heat-filtered high light (800 µmol quanta m-2 s-1). Gene ontology enrichment analysis revealed that cold priming preferentially supports expression of genes involved in the defence against plant pathogens upon cold triggering. The regulation took place on the cost of the expression of genes involved in growth regulation and transport. On the contrary, cold priming resulted in stronger expression of genes regulating metabolism and development and weaker expression of defence genes in response to high light triggering. qPCR with independently cultivated and treated replicates confirmed the trends observed in the RNASeq guide experiment.Conclusion: A 24 h long priming cold stimulus activates a several days lasting stress memory that controls cold and light regulation of gene expression and adjusts growth and defence regulation in a stressor-specific manner.

A repressor controls the timing and spatial localisation of stalk cell-specific gene expression in Dictyostelium

Development ◽  
1993 ◽  
Vol 118 (4) ◽  
pp. 1041-1048 ◽  
Author(s):  
A.J. Harwood ◽  
A. Early ◽  
J.G. Williams
Keyword(s):  
Gene Expression ◽  
Transcriptional Repression ◽  
Consensus Sequence ◽  
Matrix Proteins ◽  
Stalk Cell ◽  
Specific Gene ◽  
Gene Mutant ◽  
Dependent Protein ◽  
Apical Papilla ◽  
Repressor Element

The ecmA and ecmB genes of Dictyostelium encode related extracellular matrix proteins and both are induced by DIF, the stalk cell-specific morphogen. The ecmA gene is expressed throughout the prestalk region of the migrating slug but only later, at culmination, do the prestalk cells express the ecmB gene. Expression of the ecmB gene is induced at the entrance to the stalk tube and we have identified two, apparently redundant, promoter elements that control this process. They act as repressors, preventing transcription in the tip of the migrating slug and the apical papilla of the culminant. They have a semi-palindromic consensus sequence TTGnCAA, where n is in one case 2 and in the other 4 bp. Either element alone is able to repress ecmB promoter activity in prestalk cells. Introduction of a single repressor element into the promoter of the ecmA gene changes its expression pattern to resemble that of the ecmB gene. Mutant elements, where n is altered, cause repression during the slug stage but allow premature ecmB expression during culmination; suggesting that the effective strength of the inductive signal may increase during culmination. Inhibition of cAMP-dependent protein kinase (PKA) in prestalk cells blocks both stalk cell maturation and ecmB gene expression. We show that the block to gene expression correlates precisely with the presence of a functional repressor element and this is consistent with the notion that expression of the ecmB gene is controlled by a PKA-dependent release from transcriptional repression.

scholarly journals Inducible cell-specific mouse models for paired epigenetic and transcriptomic studies of microglia and astroglia

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Ana J. Chucair-Elliott ◽  
Sarah R. Ocañas ◽  
David R. Stanford ◽  
Victor A. Ansere ◽  
Kyla B. Buettner ◽  
...  
Keyword(s):  
Gene Expression ◽  
Affinity Purification ◽  
Regulation Of Gene Expression ◽  
Cell Types ◽  
Tissue Level ◽  
Cell Phenotype ◽  
Specific Gene ◽  
Cell Type ◽  
A Cell ◽  
Cell Type Specific

AbstractEpigenetic regulation of gene expression occurs in a cell type-specific manner. Current cell-type specific neuroepigenetic studies rely on cell sorting methods that can alter cell phenotype and introduce potential confounds. Here we demonstrate and validate a Nuclear Tagging and Translating Ribosome Affinity Purification (NuTRAP) approach for temporally controlled labeling and isolation of ribosomes and nuclei, and thus RNA and DNA, from specific central nervous system cell types. Analysis of gene expression and DNA modifications in astrocytes or microglia from the same animal demonstrates differential usage of DNA methylation and hydroxymethylation in CpG and non-CpG contexts that corresponds to cell type-specific gene expression. Application of this approach in LPS treated mice uncovers microglia-specific transcriptome and epigenome changes in inflammatory pathways that cannot be detected with tissue-level analysis. The NuTRAP model and the validation approaches presented can be applied to any brain cell type for which a cell type-specific cre is available.

scholarly journals Cohesin-dependent regulation of gene expression during differentiation is lost in cohesin-mutated myeloid malignancies

Blood ◽  
2019 ◽  
Vol 134 (24) ◽  
pp. 2195-2208 ◽  
Author(s):  
Daniel Sasca ◽  
Haiyang Yun ◽  
George Giotopoulos ◽  
Jakub Szybinski ◽  
Theo Evan ◽  
...  
Keyword(s):  
Gene Expression ◽  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
Potential Role ◽  
Regulation Of Gene Expression ◽  
Specific Gene ◽  
Myeloid Malignancy ◽  
Erythroid Maturation ◽  
Acute Myeloid

Cohesin mutations are common in myeloid malignancy. Sasca et al elucidate the potential role of cohesin loss in myelodysplastic syndrome and acute myeloid leukemia (MDS/AML). They demonstrate that cohesin binding is critical for erythroid-specific gene expression and that reduction in cohesin impairs terminal erythroid maturation and promotes myeloid malignancy.

scholarly journals Limit cycle dynamics can guide the evolution of gene regulatory networks towards point attractors

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Stuart P. Wilson ◽  
Sebastian S. James ◽  
Daniel J. Whiteley ◽  
Leah A. Krubitzer
Keyword(s):  
Gene Expression ◽  
Limit Cycles ◽  
Gene Networks ◽  
Regulatory Networks ◽  
Expression Patterns ◽  
Specific Gene ◽  
Boolean Models ◽  
A Genome ◽  
Order Of Magnitude ◽  
Accelerate Evolution

AbstractDevelopmental dynamics in Boolean models of gene networks self-organize, either into point attractors (stable repeating patterns of gene expression) or limit cycles (stable repeating sequences of patterns), depending on the network interactions specified by a genome of evolvable bits. Genome specifications for dynamics that can map specific gene expression patterns in early development onto specific point attractor patterns in later development are essentially impossible to discover by chance mutation alone, even for small networks. We show that selection for approximate mappings, dynamically maintained in the states comprising limit cycles, can accelerate evolution by at least an order of magnitude. These results suggest that self-organizing dynamics that occur within lifetimes can, in principle, guide natural selection across lifetimes.

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