Genome-wide Profiling Of Histone Modifications Research Articles

Abstract 4413: Identifying genome-wide histone profiles in patient derived models of AML for predictive biomarker development

Abstract Acute myeloid leukemia (AML) is a complex disease with highly individualized treatment plans for patients. Mostly these are based on genetic and phenotypic markers of the disease, but the patient’s overall condition is playing a significant role as well. To develop innovative drugs for a broad patient cohort, it is essential to understand the biological implications of these differences and to model them preclinically. In this study, we are assessing the utility of EpiCypher’s CUT&Tag-FFPE platform to characterize the epigenome of AML PDX samples. CUT&Tag-FFPE is an epigenome profiling assay that is compatible with Formalin-Fixed Paraffin-Embedded (FFPE) samples, enabling robust genome-wide profiling of histone modifications from limited clinical samples. We derived PDX model LEXFAM 2799 (NPM1 wt; FLT3 wt, t(8;21)) and LEXFAM 2966 (NPM1 mut; FLT3 wt) from treatment naïve patients and established in immunocompromised NSG mice. LEXFAM 2799 is a fast-growing model with passaging times of 33 days, whereas LEXFAM 2966 displays a passaging time of 140 days. We next treated with Standard of Care (SoC) agents Decitabine, Cytarabine and all-trans-retinoic acid (ATRA): LEXF 2966 was highly sensitive towards Decitabine leading to complete remission. Cytarabine induced a partial remission and ATRA had only minor effect on tumor growth. In contrast LEXFAM 2799 was resistant towards treatment with ATRA and showed only partial remission under treatment with Cytarabine or Decitabine. Using the CUT&Tag-FFPE platform we are analyzing FFPE slides from the above mentioned two AML PDX models to investigate differences in the genome-wide histone profile that relate to the different growth behavior as well as sensitivity towards SoC treatment. The goal of these studies is to identify tumor model specific profiles that correlated specifically with the sensitivity towards the hypomethylating agent Decitabine. In addition, we plan to analyze additional untreated as well as treated AML PD models to validate the identified signatures confirming them as predictive biomarkers for sensitivity towards current standard of care and prospectively as well innovative compounds. Citation Format: Alysha Simmons, Eva Oswald, Georg Kuales, Michael Keogh, Vishnu U. Kumary, Eva Brill, Martis W. Cowles, Bryan Venters, Julia B. Schueler. Identifying genome-wide histone profiles in patient derived models of AML for predictive biomarker development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4413.

Spatial-CUT&Tag: Spatially resolved chromatin modification profiling at the cellular level.

Spatial omics emerged as a new frontier of biological and biomedical research. Here, we present spatial-CUT&Tag for spatially resolved genome-wide profiling of histone modifications by combining in situ CUT&Tag chemistry, microfluidic deterministic barcoding, and next-generation sequencing. Spatially resolved chromatin states in mouse embryos revealed tissue-type-specific epigenetic regulations in concordance with ENCODE references and provide spatial information at tissue scale. Spatial-CUT&Tag revealed epigenetic control of the cortical layer development and spatial patterning of cell types determined by histone modification in mouse brain. Single-cell epigenomes can be derived in situ by identifying 20-micrometer pixels containing only one nucleus using immunofluorescence imaging. Spatial chromatin modification profiling in tissue may offer new opportunities to study epigenetic regulation, cell function, and fate decision in normal physiology and pathogenesis.

Rapid and Low-Input Profiling of Histone Marks in Plants Using Nucleus CUT&Tag.

Characterizing genome-wide histone posttranscriptional modifications and transcriptional factor occupancy is crucial for deciphering their biological functions. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) is a powerful method for genome-wide profiling of histone modifications and transcriptional factor-binding sites. However, the current ChIP-seq experimental procedure in plants requires significant material and several days for completion. CUT&Tag is an alternative method of ChIP-seq for low-sample and single-cell epigenomic profiling using protein A-Tn5 transposase fusion proteins (PAT). In this study, we developed a nucleus CUT&Tag (nCUT&Tag) protocol based on the live-cell CUT&Tag technology. Our results indicate that nCUT&Tag could be used for histone modifications profiling in both monocot rice and dicot rapeseed using crosslinked or fresh tissues. In addition, both active and repressive histone marks such as H3K4me3 and H3K9me2 can be identified using our nCUT&Tag. More importantly, all the steps in nCUT&Tag can be finished in only 1 day, and the assay can be performed with as little as 0.01 g of plant tissue as starting materials. Therefore, our results demonstrate that nCUT&Tag is an efficient alternative strategy for plant epigenomic studies.

Joint profiling of histone modifications and transcriptome in single cells from mouse brain.

Genome-wide profiling of histone modifications can reveal not only the location and activity state of regulatory elements, but also the regulatory mechanisms involved in cell-type-specific gene expression during development and disease pathology. Conventional assays to profile histone modifications in bulk tissues lack single cell resolution. Here, we describe an ultra-high throughput method, Paired-Tag, for joint profiling of histone modifications and transcriptome in single cells to produce cell-type-resolved maps of chromatin state and transcriptome in complex tissues. We used this method to profile five histone modifications jointly with transcriptome in the adult mouse frontal cortex and hippocampus. Integrative analysis of the resulting maps identified distinct groups of genes subject to divergent epigenetic regulatory mechanisms. Our single cell multi-omics approach enables comprehensive analysis of chromatin state and gene regulation in complex tissues and characterization of gene regulatory programs in the constituent cell types.

Gene Regulatory Enhancers with Evolutionarily Conserved Activity Are More Pleiotropic than Those with Species-Specific Activity.

Studies of regulatory activity and gene expression have revealed an intriguing dichotomy: There is substantial turnover in the regulatory activity of orthologous sequences between species; however, the expression level of orthologous genes is largely conserved. Understanding how distal regulatory elements, for example, enhancers, evolve and function is critical, as alterations in gene expression levels can drive the development of both complex disease and functional divergence between species. In this study, we investigated determinants of the conservation of regulatory enhancer activity for orthologous sequences across mammalian evolution. Using liver enhancers identified from genome-wide histone modification profiles in ten diverse mammalian species, we compared orthologous sequences that exhibited regulatory activity in all species (conserved-activity enhancers) to shared sequences active only in a single species (species-specific-activity enhancers). Conserved-activity enhancers have greater regulatory potential than species-specific-activity enhancers, as quantified by both the density and diversity of transcription factor binding motifs. Consistent with their greater regulatory potential, conserved-activity enhancers have greater regulatory activity in humans than species-specific-activity enhancers: They are active across more cellular contexts, and they regulate more genes than species-specific-activity enhancers. Furthermore, the genes regulated by conserved-activity enhancers are expressed in more tissues and are less tolerant of loss-of-function mutations than those targeted by species-specific-activity enhancers. These consistent results across various stages of gene regulation demonstrate that conserved-activity enhancers are more pleiotropic than their species-specific-activity counterparts. This suggests that pleiotropy is associated with the conservation of regulatory across mammalian evolution.

Denoising genome-wide histone ChIP-seq with convolutional neural networks.

MotivationChromatin immune-precipitation sequencing (ChIP-seq) experiments are commonly used to obtain genome-wide profiles of histone modifications associated with different types of functional genomic elements. However, the quality of histone ChIP-seq data is affected by many experimental parameters such as the amount of input DNA, antibody specificity, ChIP enrichment and sequencing depth. Making accurate inferences from chromatin profiling experiments that involve diverse experimental parameters is challenging.ResultsWe introduce a convolutional denoising algorithm, Coda, that uses convolutional neural networks to learn a mapping from suboptimal to high-quality histone ChIP-seq data. This overcomes various sources of noise and variability, substantially enhancing and recovering signal when applied to low-quality chromatin profiling datasets across individuals, cell types and species. Our method has the potential to improve data quality at reduced costs. More broadly, this approach—using a high-dimensional discriminative model to encode a generative noise process—is generally applicable to other biological domains where it is easy to generate noisy data but difficult to analytically characterize the noise or underlying data distribution.Availability and implementation https://github.com/kundajelab/coda.

Abstract 3578: Methyl2Acetyl: predicting epigenetic and transcriptomic activity from DNA methylation

Abstract DNA methylation and histone modifications are interconnected and interdependent epigenetic mechanisms that regulate chromatin accessibility in cells. They establish cell’s developmental identity and modulate individual response to endogenous developmental stimuli and environmental changes. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) is a popular assay to study genomewide histone modification profiles. However, ChIP-seq assays require relatively large amounts of starting materials (ranging from ~105 cells using a low cell number protocol to 107 cells in a standard protocol), which remains as a major obstacle for precious biological samples including primary tumor specimens. On the other hand, tagmentation-based whole genome bisulfite sequencing (TWGBS) protocol enables unbiased assessment of the genomewide methylation pattern using ~3,000 cells. Therefore, a quantitative relationship between DNA methylation and epigenetic/transcriptomic activity is in great demand. In the current study, we developed Methyl2Acetyl, a machine learning framework to infer promoter epigenetic activities (e.g. H3K27Ac enrichment) using TWGBS data as input. The proposed model utilizes random forest learners, which allow automatic extraction of complex interactions among DNA methylation features surrounding transcription start sites. We applied Methyl2Acetyl to a set of pediatric solid tumor samples with high quality H3K27Ac ChIPseq data to evaluate its performance. The model accurately predicted promoter H3K27Ac enrichment in independent test samples (Pearson correlation against measured enrichment: 0.81 ± 0.02). To further test the robustness of our model, we trained a Methyl2Acetyl model on solid tumors and applied it to a set of 10 pediatric leukemia samples. Despite dramatic global methylome differences between solid tumors and leukemia, Methyl2Acetyl predicted promoter H3K27Ac enrichment showed strong concordance with target gene expression level in the same sample (Pearson correlation: 0.75 ± 0.02, classification AUC: 0.89 ± 0.01). Collectively, our data suggested that DNA methylation is predictive of promoter active histone modification enrichment and gene expression activity. Epigenetically active promoters can be imputed from TWGBS data in samples with limiting starting materials. Citation Format: Xiang Chen. Methyl2Acetyl: predicting epigenetic and transcriptomic activity from DNA methylation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3578. doi:10.1158/1538-7445.AM2017-3578

Dynamic Transcriptional and Epigenetic Regulation of Human Epidermal Keratinocyte Differentiation

SummaryHuman skin is maintained by the differentiation and maturation of interfollicular stem and progenitors cells. We used DeepCAGE, genome-wide profiling of histone modifications and retroviral integration analysis, to map transcripts, promoters, enhancers, and super-enhancers (SEs) in prospectively isolated keratinocytes and transit-amplifying progenitors, and retrospectively defined keratinocyte stem cells. We show that >95% of the active promoters are in common and differentially regulated in progenitors and differentiated keratinocytes, while approximately half of the enhancers and SEs are stage specific and account for most of the epigenetic changes occurring during differentiation. Transcription factor (TF) motif identification and correlation with TF binding site maps allowed the identification of TF circuitries acting on enhancers and SEs during differentiation. Overall, our study provides a broad, genome-wide description of chromatin dynamics and differential enhancer and promoter usage during epithelial differentiation, and describes a novel approach to identify active regulatory elements in rare stem cell populations.

Development of primer sets that can verify the enrichment of histone modifications, and their application to examining vernalization-mediated chromatin changes in Brassica rapa L.

Epigenetic regulation is crucial for the development of plants and for adaptation to a changing environment. Recently, genome-wide profiles of histone modifications have been determined by a combination of chromatin immunoprecipitation (ChIP) and genomic tiling arrays (ChIP on chip) or ChIP and high-throughput sequencing (ChIP-seq) in species including Arabidopsis thaliana, rice and maize. Validation of ChIP analysis by PCR or qPCR using positive and negative regions of histone modification is necessary. In contrast, information about histone modifications is limited in Chinese cabbage, Brassica rapa. The aim of this study was to develop positive and negative control primer sets for H3K4me3 (trimethylation of the 4(th) lysine of H3), H3K9me2, H3K27me3 and H3K36me3 in B. rapa. The expression and histone modification of four FLC paralogs in B. rapa, before and after vernalization, were examined using the method developed here. After vernalization, expression of all four BrFLC genes was reduced, and accumulation of H3K27me3 was observed in three of them. As with A. thaliana, the vernalization response and stability of FLC repression correlated with the accumulation of H3K27me3. These results suggest that the epigenetic state during vernalization is important for high bolting resistance in B. rapa. The positive and negative control primer sets developed here revealed positive and negative histone modifications in B. rapa that can be used as a control for future studies.

A Multiplexed System for Quantitative Comparisons of Chromatin Landscapes

Genome-wide profiling of histone modifications can provide systematic insight into the regulatory elements and programs engaged in a given cell type. However, conventional chromatin immunoprecipitation and sequencing (ChIP-seq) does not capture quantitative information on histone modification levels, requires large amounts of starting material, and involves tedious processing of each individual sample. Here, we address these limitations with a technology that leverages DNA barcoding to profile chromatin quantitatively and in multiplexed format. We concurrently map relative levels of multiple histone modifications across multiple samples, each comprising as few as a thousand cells. We demonstrate the technology by monitoring dynamic changes following inhibition of p300, EZH2, or KDM5, by linking altered epigenetic landscapes to chromatin regulator mutations, and by mapping active and repressive marks in purified human hematopoietic stem cells. Hence, this technology enables quantitative studies of chromatin state dynamics across rare cell types, genotypes, environmental conditions, and drug treatments.

TELP, a sensitive and versatile library construction method for next-generation sequencing.

Next-generation sequencing has been widely used for the genome-wide profiling of histone modifications, transcription factor binding and gene expression through chromatin immunoprecipitated DNA sequencing (ChIP-seq) and cDNA sequencing (RNA-seq). Here, we describe a versatile library construction method that can be applied to both ChIP-seq and RNA-seq on the widely used Illumina platforms. Standard methods for ChIP-seq library construction require nanograms of starting DNA, substantially limiting its application to rare cell types or limited clinical samples. By minimizing the DNA purification steps that cause major sample loss, our method achieved a high sensitivity in ChIP-seq library preparation. Using this method, we achieved the following: (i) generated high-quality epigenomic and transcription factor-binding maps using ChIP-seq for murine adipocytes; (ii) successfully prepared a ChIP-seq library from as little as 25 pg of starting DNA; (iii) achieved paired-end sequencing of the ChIP-seq libraries; (iv) systematically profiled gene expression dynamics during murine adipogenesis using RNA-seq and (v) preserved the strand specificity of the transcripts in RNA-seq. Given its sensitivity and versatility in both double-stranded and single-stranded DNA library construction, this method has wide applications in genomic, epigenomic, transcriptomic and interactomic studies.

Epigenomic analysis of primary human T cells reveals enhancers associated with TH2 memory cell differentiation and asthma susceptibility.

A characteristic feature of asthma is the aberrant accumulation, differentiation or function of memory CD4(+) T cells that produce type 2 cytokines (TH2 cells). By mapping genome-wide histone modification profiles for subsets of T cells isolated from peripheral blood of healthy and asthmatic individuals, we identified enhancers with known and potential roles in the normal differentiation of human TH1 cells and TH2 cells. We discovered disease-specific enhancers in T cells that differ between healthy and asthmatic individuals. Enhancers that gained the histone H3 Lys4 dimethyl (H3K4me2) mark during TH2 cell development showed the highest enrichment for asthma-associated single nucleotide polymorphisms (SNPs), which supported a pathogenic role for TH2 cells in asthma. In silico analysis of cell-specific enhancers revealed transcription factors, microRNAs and genes potentially linked to human TH2 cell differentiation. Our results establish the feasibility and utility of enhancer profiling in well-defined populations of specialized cell types involved in disease pathogenesis.

Genome-wide histone state profiling of fibroblasts from the opossum, Monodelphis domestica, identifies the first marsupial-specific imprinted gene

BackgroundImprinted genes have been extensively documented in eutherian mammals and found to exhibit significant interspecific variation in the suites of genes that are imprinted and in their regulation between tissues and developmental stages. Much less is known about imprinted loci in metatherian (marsupial) mammals, wherein studies have been limited to a small number of genes previously known to be imprinted in eutherians. We describe the first ab initio search for imprinted marsupial genes, in fibroblasts from the opossum, Monodelphis domestica, based on a genome-wide ChIP-seq strategy to identify promoters that are simultaneously marked by mutually exclusive, transcriptionally opposing histone modifications.ResultsWe identified a novel imprinted gene (Meis1) and two additional monoallelically expressed genes, one of which (Cstb) showed allele-specific, but non-imprinted expression. Imprinted vs. allele-specific expression could not be resolved for the third monoallelically expressed gene (Rpl17). Transcriptionally opposing histone modifications H3K4me3, H3K9Ac, and H3K9me3 were found at the promoters of all three genes, but differential DNA methylation was not detected at CpG islands at any of these promoters.ConclusionsIn generating the first genome-wide histone modification profiles for a marsupial, we identified the first gene that is imprinted in a marsupial but not in eutherian mammals. This outcome demonstrates the practicality of an ab initio discovery strategy and implicates histone modification, but not differential DNA methylation, as a conserved mechanism for marking imprinted genes in all therian mammals. Our findings suggest that marsupials use multiple epigenetic mechanisms for imprinting and support the concept that lineage-specific selective forces can produce sets of imprinted genes that differ between metatherian and eutherian lines.

Histone Modification Patterns and Their Responses to Environment

Histone modifications play important roles in the epigenetic regulation of gene expression. Recent genome-wide profiling of histone modifications with deep sequencing-based methods provides novel insights of crosstalk between histone modifications, leading to recent proposals of histone “language” or “web” as an alternative of “code” to appreciate combinatorial modification patterns. Environmental factor–altered histone modifications now may be addressed dynamically and systematically with the recognition and use of these interesting combinatorial patterns.

Sorafenib Inhibits Epithelial-Mesenchymal Transition through an Epigenetic-Based Mechanism in Human Lung Epithelial Cells

The epithelial to mesenchymal transition (EMT) has been well recognized for many decades as an essential early step in the progression of primary tumors towards metastases. Widespread epigenetic reprogramming of DNA and histone modifications tightly regulates gene expression and cellular activity during carcinogenesis, and epigenetic therapy has been developed to design efficient strategies for cancer treatment. As the first oral agent approved for the clinical treatment of cancer, sorafenib has significant inhibitory effects on tumor growth and EMT. However, a detailed understanding of the underlying epigenetic mechanism remains elusive. In this manuscript, we performed a ChIP-seq assay to evaluate the activity of sorafenib on the genome-wide profiling of histone modifications. We demonstrate that sorafenib largely reverses the changes in histone modifications that occur during EMT in A549 alveolar epithelial cells. Sorafenib also significantly reduces the coordinated epigenetic switching of critical EMT-associated genes in accordance with their expression levels. Furthermore, we show that sorafenib potentiates histone acetylation by regulating the expression levels of histone-modifying enzymes. Collectively, these findings provide the first evidence that sorafenib inhibits the EMT process through an epigenetic mechanism, which holds enormous promise for identifying novel epigenetic candidate diagnostic markers and drug targets for the treatment of human malignancies.

Epigenomic Annotation of Enhancers Predicts Transcriptional Regulators of Human Neural Crest

Neural crest cells (NCC) are a transient, embryonic cell population characterized by unusual migratory ability and developmental plasticity. To annotate and characterize cis-regulatory elements utilized by the human NCC, we coupled a hESC differentiation model with genome-wide profiling of histone modifications and of coactivator and transcription factor (TF) occupancy. Sequence analysis predicted major TFs binding at epigenomically annotated hNCC enhancers, including a master NC regulator, TFAP2A, and nuclear receptors NR2F1 and NR2F2. Although many TF binding events occur outside enhancers, sites coinciding with enhancer chromatin signatures show significantly higher sequence constraint, nucleosomal depletion, correlation with gene expression, and functional conservation in NCC isolated from chicken embryos. Simultaneous co-occupancy by TFAP2A and NR2F1/F2 is associated with permissive enhancer chromatin states, characterized by high levels of p300 and H3K27ac. Our results provide global insights into human NC chromatin landscapes and a rich resource for studies of craniofacial development and disease.

Cancer associated epigenetic transitions identified by genome-wide histone methylation binding profiles in human colorectal cancer samples and paired normal mucosa

BackgroundDespite their well-established functional roles, histone modifications have received less attention than DNA methylation in the cancer field. In order to evaluate their importance in colorectal cancer (CRC), we generated the first genome-wide histone modification profiles in paired normal colon mucosa and tumor samples.MethodsChromatin immunoprecipitation and microarray hybridization (ChIP-chip) was used to identify promoters enriched for histone H3 trimethylated on lysine 4 (H3K4me3) and lysine 27 (H3K27me3) in paired normal colon mucosa and tumor samples from two CRC patients and for the CRC cell line HT29.ResultsBy comparing histone modification patterns in normal mucosa and tumors, we found that alterations predicted to have major functional consequences were quite rare. Furthermore, when normal or tumor tissue samples were compared to HT29, high similarities were observed for H3K4me3. However, the differences found for H3K27me3, which is important in determining cellular identity, indicates that cell lines do not represent optimal tissue models. Finally, using public expression data, we uncovered previously unknown changes in CRC expression patterns. Genes positive for H3K4me3 in normal and/or tumor samples, which are typically already active in normal mucosa, became hyperactivated in tumors, while genes with H3K27me3 in normal and/or tumor samples and which are expressed at low levels in normal mucosa, became hypersilenced in tumors.ConclusionsGenome wide histone modification profiles can be used to find epigenetic aberrations in genes associated with cancer. This strategy gives further insights into the epigenetic contribution to the oncogenic process and may identify new biomarkers.

Dynamic protein methylation in chromatin biology.

.Post-translational modification of chromatin is emerging as an increasingly important regulator of chromosomal processes. In particular, histone lysine and arginine methylation play important roles in regulating transcription, maintaining genomic integrity, and contributing to epigenetic memory. Recently, the use of new approaches to analyse histone methylation, the generation of genetic model systems, and the ability to interrogate genome wide histone modification profiles has aided in defining how histone methylation contributes to these processes. Here we focus on the recent advances in our understanding of the histone methylation system and examine how dynamic histone methylation contributes to normal cellular function in mammals.