Access Of Transcription Factors Research Articles

Defining genome access of transcription factors.

Defining genome access of transcription factors.

MultiSC: a deep learning pipeline for analyzing multiomics single-cell data.

Single-cell technologies enable researchers to investigate cell functions at an individual cell level and study cellular processes with higher resolution. Several multi-omics single-cell sequencing techniques have been developed to explore various aspects of cellular behavior. Using NEAT-seq as an example, this method simultaneously obtains three kinds of omics data for each cell: gene expression, chromatin accessibility, and protein expression of transcription factors (TFs). Consequently, NEAT-seq offers a more comprehensive understanding of cellular activities in multiple modalities. However, there is a lack of tools available for effectively integrating the three types of omics data. To address this gap, we propose a novel pipeline called MultiSC for the analysis of MULTIomic Single-Cell data. Our pipeline leverages a multimodal constraint autoencoder (single-cell hierarchical constraint autoencoder) to integrate the multi-omics data during the clustering process and a matrix factorization-based model (scMF) to predict target genes regulated by a TF. Moreover, we utilize multivariate linear regression models to predict gene regulatory networks from the multi-omics data. Additional functionalities, including differential expression, mediation analysis, and causal inference, are also incorporated into the MultiSC pipeline. Extensive experiments were conducted to evaluate the performance of MultiSC. The results demonstrate that our pipeline enables researchers to gain a comprehensive view of cell activities and gene regulatory networks by fully leveraging the potential of multiomics single-cell data. By employing MultiSC, researchers can effectively integrate and analyze diverse omics data types, enhancing their understanding of cellular processes.

Abstract C072: Bmi1 expression is upregulated in response to injury/stress in the pancreas

Abstract Pancreatic homeostasis is regulated in part through epigenetic mechanisms that restrict or enable access of pancreatic lineage transcription factors to their target genes. These epigenetic protein cascades are also required for regeneration of the pancreas after injury. B-cell Moloney murine leukemia virus integration site 1 (Bmi1), a central protein in the Polycomb repressor complex 1 (PRC1), has been shown to be required for the regeneration of the pancreas after injury and its absence prevents pancreatic neoplasia in mice. Previous work also suggests that Bmi1 marks a subset of acinar cells contributing to pancreatic renewal and tissue maintenance. It remains unclear how Bmi1 expression levels are regulated in response to pancreatic stress and injury. Here we assess the baseline expression of Bmi1 in pancreatic tissue with a genetic reporter mouse model as well as changes in Bmi1 mRNA levels at different time points after the induction of pancreatitis in wild-type mice via RNA in situ hybridization (RNAscope). We also compare the ability of the murine pancreas to regenerate after acute pancreatitis in the presence and absence of Bmi1. Our data indicates that rather than a specific subpopulation, most, if not all, acinar cells in the pancreas express Bmi1 during their life and specific loss of Bmi1 in the pancreas impairs regeneration after acute pancreatitis. We also show an increase in Bmi1 mRNA levels within the pancreas shortly after the induction of acute pancreatitis which reduces as the pancreas resumes its normal histology. Altogether, our data indicate that Bmi1 expression is dynamic, responsive to injury and necessary for pancreatic homeostasis and regeneration. Citation Format: Nur Muhammad Renollet, Joyce K Thompson, Emily Wu, Osama Alkhalili, Nina Steele, Filip Bednar. Bmi1 expression is upregulated in response to injury/stress in the pancreas [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr C072.

438 DNA methylation patterns and transcriptional regulation during pig fetal skeletal muscle development

Abstract Fetal development is controlled by a complex cascade of highly regulated and coordinated gene expression patterns. Epigenetic mechanisms have important roles in regulating development and differentiation. Among such mechanisms, DNA methylation exhibits context-specific associations with gene expression and has been shown to be highly dynamic during developmental processes. We performed whole-genome bisulfite sequencing (WGBS) to assess DNA methylation in pig longissimus dorsi muscle at 41- and 70-d gestation (dg), as well as RNA- and small RNA-sequencing to identify coordinated changes in methylation and expression between myogenic stages. We identified 45,739 differentially methylated regions (DMRs) between stages, and the majority (n = 34,232) were hypomethylated at 70 vs. 41 dg. Developmental DMRs exhibited feature-specific enrichment in gene regulatory regions, as well as in regions proximal to micro-RNAs (miRNAs) that have known roles in myogenesis. Integration of methylation and transcriptomic data revealed strong associations between differential gene methylation and transcript abundance. We surveyed myogenic regulatory factor (MRF) genes to determine if differential methylation was present in expected genomic regions. Within the MYF5 and MYF6 locus, MYF5 was significantly promoter-hypermethylated at 70 dg, whereas MYF6 was significantly hypomethylated upstream of its transcription start site. MYF5 is the earliest MRF to be expressed and primarily functions in myoblast proliferation and determination, while MYF6 functions in muscle cell differentiation. Thus, these patterns were consistent with expected downregulation of MYF5 and upregulation of MYF6 as muscle development progresses and demonstrate that differential methylation is evident at myogenic transcription factors. Differential miRNA methylation was significantly negatively correlated with abundance, and dynamic expression of assayed miRNAs persisted postnatally. Motif analysis revealed significant enrichment of myogenic regulatory factor motifs among hypomethylated regions, suggesting that DNA hypomethylation may function to increase accessibility of muscle-specific transcription factors. We also show that developmental DMRs are enriched for GWAS SNPs associated with muscle physiology and meat quality traits, demonstrating the potential for epigenetic processes to influence phenotypic diversity. Our results enhance understanding of DNA methylation dynamics in pig fetal skeletal muscle and reveal putative cis-regulatory elements governed by epigenetic processes during porcine myogenesis.

Transcriptional activation domains interact with ATPase subunits of yeast chromatin remodelling complexes SWI/SNF, RSC and INO80

Chromatin remodelling complexes (CRC) are ATP-dependent molecular machines important for the dynamic organization of nucleosomes along eukaryotic DNA. CRCs SWI/SNF, RSC and INO80 can move positioned nucleosomes in promoter DNA, leading to nucleosome-depleted regions which facilitate access of general transcription factors. This function is strongly supported by transcriptional activators being able to interact with subunits of various CRCs. In this work we show that SWI/SNF subunits Swi1, Swi2, Snf5 and Snf6 can bind to activation domains of Ino2 required for expression of phospholipid biosynthetic genes in yeast. We identify an activator binding domain (ABD) of ATPase Swi2 and show that this ABD is functionally dispensable, presumably because ABDs of other SWI/SNF subunits can compensate for the loss. In contrast, mutational characterization of the ABD of the Swi2-related ATPase Sth1 revealed that some conserved basic and hydrophobic amino acids within this domain are essential for the function of Sth1. While ABDs of Swi2 and Sth1 define separate functional protein domains, mapping of an ABD within ATPase Ino80 showed co-localization with its HSA domain also required for binding actin-related proteins. Comparative interaction studies finally demonstrated that several unrelated activators each exhibit a specific binding pattern with ABDs of Swi2, Sth1 and Ino80.

Isolation and Partial Characterization of Novel, Structurally Uniform (Hfq6)n≥8 Assemblies Carrying Accessory Transcription and Translation Factors.

In growing E. coli cells, the transcription-translation complexes (TTCs) form characteristic foci; however, the exact molecular composition of these superstructures is not known with certainty. Herein, we report that, during our recently developed "fast" procedures for purification of E. coli RNA polymerase (RP), a fraction of the RP's α/RpoA subunits is displaced from the core RP complexes and copurifies with multiprotein superstructures carrying the nucleic acid-binding protein Hfq and the ribosomal protein S6. We show that the main components of these large multiprotein assemblies are fixed protein copy-number (Hfq6)n≥8 complexes; these complexes have a high level of structural uniformity and are distinctly unlike the previously described (Hfq6)n "head-to-tail" polymers. We describe purification of these novel, structurally uniform (Hfq6)n≥8 complexes to near homogeneity and show that they also contain small nonprotein molecules and accessory S6. We demonstrate that Hfq, S6, and RP have similar solubility profiles and present evidence pointing to a role of the Hfq C-termini in superstructure formation. Taken together, our data offer new insights into the composition of the macromolecular assemblies likely acting as scaffolds for transcription complexes and ribosomes during bacterial cells' active growth.

Genome-wide mapping of DNase I hypersensitive sites revealed differential chromatin accessibility and regulatory DNA elements under drought stress in rice cultivars.

Drought stress (DS) is one of the major constraints limiting yield in crop plants including rice. Gene regulation under DS is largely governed by accessibility of the transcription factors (TFs) to their cognate cis-regulatory elements (CREs). In this study, we used DNase I hypersensitive assays followed by sequencing to identify the accessible chromatin regions under DS in a drought-sensitive (IR64) and a drought-tolerant (N22) rice cultivar. Our results indicated that DNase I hypersensitive sites (DHSs) were highly enriched at transcription start sites (TSSs) and numerous DHSs were detected in the promoter regions. DHSs were concurrent with epigenetic marks and the genes harboring DHSs in their TSS and promoter regions were highly expressed. In addition, DS induced changes in DHSs (∆DHSs) in TSS and promoter regions were positively correlated with upregulation of several genes involved in drought/abiotic stress response, those encoding TFs and located within drought-associated quantitative trait loci, much preferentially in the drought-tolerant cultivar. The CREs representing the binding sites of TFs involved in DS response were detected within the ∆DHSs, suggesting differential accessibility of TFs to their cognate sites under DS in different rice cultivars, which may be further deployed for enhancing drought tolerance in rice.

Abstract 3064: Distinct Regulatory Programs Govern Smooth Muscle Cell Fate In Atherosclerosis

Introduction: During atherosclerosis, some vascular smooth muscle cells (SMCs) undergo phenotypic modulation, de-differentiating and adopting a fibroblast-like (FMC) or a chondrocyte/osteoblast-like phenotype (CMC). Although FMCs and CMCs appear to occur in succession in single-cell RNAseq data, they occupy distinct locations within the lesion and are associated with protective and deleterious plaque features, respectively. Hypothesis: Smooth muscle cell transitions to FMC and CMC occur via discrete transcriptional pathways during atherosclerosis. Methods: We performed single-cell RNA-sequencing (scRNAseq) and assay for transposase-accessible chromatin with sequencing (ATAC-seq) on lineage-traced vascular SMCs isolated from the aortic root of ApoE mice (n=3). Our analysis included pseudotime and RNA velocity analyses of the scRNAseq data, which independently identified a subgroup of Vcam+Cd74+ modulated SMCs as a potential cell state from which FMCs and CMCs appear to originate, each following distinct trajectories. We explored lineage-specific gene expression using the TradeSeq R package and conducted Ingenuity Pathway Analysis on differentially expressed genes to identify relevant upstream transcription factors, which were assayed for lineage-specific motif accessibility. Results: Our analysis showed profound changes in gene expression between the two trajectories as well as differential activation and chromatin accessibility of specific transcription factors at the point where FMCs diverge from CMCs. Within the CMC lineage, we noted heightened activation and chromatin accessibility of transcription factors associated with cellular stress and inflammatory responses, including Tp53, Foxo4, and Irf1. In stark contrast, these factors exhibited diminished activity within the FMC lineage during the same pseudotime interval. Furthermore, coronary artery disease GWAS transcription factors Twist1 and Tcf21 displayed differential motif accessibility over the FMC and CMC trajectories. Conclusions: Our study provides valuable insights into the regulatory mechanisms governing SMC phenotypic transitions in atherosclerosis, and further underscores the importance of GWAS genes in influencing these transitions.

The role of SWI/SNF complexes in digestive system neoplasms.

Chromatin remodeling is a critical step in the DNA damage response, and the ATP-dependent chromatin remodelers are a group of epigenetic regulators that alter nucleosome assembly and regulate transcription factor accessibility to DNA, preventing genomic instability and tumorigenesis caused by DNA damage. The SWI/SNF chromatin remodeling complex is one of them, and mutations in the gene encoding the SWI/SNF subunit are frequently found in digestive tumors. We review the most recent literature on the role of SWI/SNF complexes in digestive tumorigenesis, with different SWI/SNF subunits playing different roles. They regulate the biological behavior of tumor cells, participate in multiple signaling pathways, interact with multiple genes, and have some correlation with the prognosis of patients. Their carcinogenic properties may help discover new therapeutic targets. Understanding the mutations and defects of SWI/SNF complexes, as well as the underlying functional mechanisms, may lead to new strategies for treating the digestive system by targeting relevant genes or modulating the tumor microenvironment.

Abstract 2627: PanCancer epigenetic regulators of lymphocyte activation states

Abstract Several immune cell types have been successfully targeted for immunomodulatory therapy; however, the efficacies of such therapies are hindered by incompatible immune cell activation states. CD8+ T-cell exhaustion is one of the most studied T-cell states in the context of cancer and was shown to limit checkpoint blockade efficacy. Although CD8+ T-cell exhaustion studies in mice showed this state is tightly regulated by chromatin accessibility of cis-regulatory elements (CREs) and transcription factor activation, the exploration of these mechanisms, their prevalence, and their specificity in human cancers remains limited. In addition, chromatin accessibility signatures of other lymphocyte (CD4+ and NK) states frequently found in solid tumors have not been carefully characterized in a pan-cancer setting. Here we introduce the first single-nuclei atlas of pan-cancer and disease-specific cis- and trans-regulatory elements in tumor infiltrating lymphocytes. We profiled ~140K T-cell and NK cell nuclei with snATAC-seq and snRNA-seq from 227 tumor and normal samples from eleven cancer types. We distinguished two major subpopulations among exhausted CD8+ T-cells: GZMK expressing (CD8+ GZMK+ Tex) and ITGAE+ tissue-resident (CD8+ Trm ex). CD8+ GZMK+ Tex was enriched in clear cell renal cell carcinoma, while CD8+ Trm ex was found in all other cancers. Both exhausted groups featured high motif accessibility and expression of NR4A1, NFATC2, and NFKB2 transcription factors (previously reported to regulate exhaustion), but differed in EOMES motif accessibility and gene expression. We have identified other lymphocyte subpopulations showing exhaustion signatures, including CD4+ follicular helpers (CD4+ Tfh), CD4+ regulatory cells (CD4+ Tregs), and weakly cytotoxic tissue-resident NK cells (trNK weak). All these subpopulations showed increased expression and motif accessibility of the NR4A1 transcription factor, highlighting its role in regulating dysfunctional states not only in CD8+ T-cells, but also in CD4+ and NK cells. Additionally, CD4+ Tfh and Tregs showed enhanced activity of NFKB1, NFKB2, and POU2F2, and trNK weak cells had increased activity of NR4A2 and NR2F2. To put our results into clinical perspective, we have collected cohorts of renal cancer, melanoma and triple-negative breast tumors treated with immunotherapy in clinical trial settings, and showed elevated GZMK expression in exhausted T-cells in responders compared to non-responders. Citation Format: Alla Karpova, Nadezhda V. Terekhanova, Siqi Chen, Reyka G. Jayasinghe, Andrew Houston, Wagma Caravan, Ryan C. Fields, Li Ding. PanCancer epigenetic regulators of lymphocyte activation states [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 2627.

Chromatin phase separated nanoregions explored by polymer cross-linker models and reconstructed from single particle trajectories.

Phase separated domains (PSDs) are ubiquitous in cell biology, representing nanoregions of high molecular concentration. PSDs appear at diverse cellular domains, such as neuronal synapses but also in eukaryotic cell nucleus, limiting the access of transcription factors and thus preventing gene expression. We develop a generalized cross-linker polymer model, to study PSDs: we show that increasing the number of cross-linkers induces a polymer condensation, preventing access of diffusing molecules. To investigate how the PSDs restrict the motion of diffusing molecules, we compute the mean residence and first escaping times. Finally, we develop a method based on mean-square-displacement of single particle trajectories to reconstruct the properties of PSDs from the continuum range of anomalous exponents. We also show here that PSD generated by polymers do not induces a long-range attracting field (potential well), in contrast with nanodomains at neuronal synapses. To conclude, PSDs can result from condensed chromatin organization, where the number of cross-linkers controls molecular access.

Distinct guard cell-specific remodeling of chromatin accessibility during abscisic acid- and CO2-dependent stomatal regulation.

In plants, epidermal guard cells integrate and respond to numerous environmental signals to control stomatal pore apertures, thereby regulating gas exchange. Chromatin structure controls transcription factor (TF) access to the genome, but whether large-scale chromatin remodeling occurs in guard cells during stomatal movements, and in response to the hormone abscisic acid (ABA) in general, remains unknown. Here, we isolate guard cell nuclei from Arabidopsis thaliana plants to examine whether the physiological signals, ABA and CO2 (carbon dioxide), regulate guard cell chromatin during stomatal movements. Our cell type-specific analyses uncover patterns of chromatin accessibility specific to guard cells and define cis-regulatory sequences supporting guard cell-specific gene expression. We find that ABA triggers extensive and dynamic chromatin remodeling in guard cells, roots, and mesophyll cells with clear patterns of cell type specificity. DNA motif analyses uncover binding sites for distinct TFs enriched in ABA-induced and ABA-repressed chromatin. We identify the Abscisic Acid Response Element (ABRE) Binding Factor (ABF) bZIP-type TFs that are required for ABA-triggered chromatin opening in guard cells and roots and implicate the inhibition of a clade of bHLH-type TFs in controlling ABA-repressed chromatin. Moreover, we demonstrate that ABA and CO2 induce distinct programs of chromatin remodeling, whereby elevated atmospheric CO2 had only minimal impact on chromatin dynamics. We provide insight into the control of guard cell chromatin dynamics and propose that ABA-induced chromatin remodeling primes the genome for abiotic stress resistance.

Dissecting Lineage and Cell State-Specific Epigenetic Evolution in Relapsed Acute Myeloid Leukemia

Introduction: The prognosis for relapsed Acute Myeloid Leukemia (AML) following initial treatment and remission remains poor, largely due to a limited number of therapies with proven clinical efficacy. Epigenetic states and evolution are known to contribute to the initiation of AML, however, the role of epigenetic evolution in relapse remains understudied, and the effects of lineage-specific epigenetic changes at relapse are unknown. We hypothesized that epigenetic modifications confined to specific lineages or differentiation states may contribute to disease resistance and relapse. To test this, we generated single cell ATACseq data from four AML patients at initial diagnosis and at relapse post-induction chemotherapy. We utilized mapping of AML scATACseq to scATAC-derived healthy hematopoietic chromatin states, lineage trajectory analysis, and gene and transcription factor accessibility analysis to identify epigenetic changes occurring at discrete points in different AML differentiation trajectories. Methods: Malignant AML cells were purified from paired samples collected from four patients at diagnosis and relapse via FACS and were sequenced using the 10x chromium scATAC platform. ArchR, Monocle3, and custom R scripts were used for all analyses. AML cell scATAC data was mapped to a healthy hematopoietic scATAC reference using Latent Semantic Indexing (LSI) and projection onto a single cell ATAC-seq manifold derived from healthy hematopoietic cell types. Closest healthy cell types were identified for each AML cell, differentiation trajectories were generated using monocole3, and gene and transcription factor accessibility was quantified across the different AML differentiation states and lineages. Results: Our analysis showed varying patterns of lineage bias across AMLs. Some samples exhibited changes in differentiation state at relapse, becoming either less differentiated or less myeloid-like. Analysis of differences in TF activity between diagnosis and relapse within myeloid and lymphoid trajectories revealed lineage-specific and differentiation state-specific changes in TF activity. In patient SU360, overall differentiation states did not change, and AML cells at both diagnosis and relapse were primarily myeloid-like with a smaller lymphoid-like population. In this sample, GATA family TFs, which were active in progenitor-like cells at diagnosis, became significantly more active in terminally differentiated AML cells at relapse. No specific chromatin changes were observed in lymphoid-like AML cells at relapse. In patient SU484, where diagnosis cells were myeloid-differentiated and relapse cells were more progenitor-like, GATA and RUNX family TF activity, which was restricted to progenitor cells at diagnosis, showed broad activation in all cells at relapse, aligning with the overall de-differentiation observed in the AML. In SU142, a case with no significant change in overall chromatin or differentiation state at relapse, multiple SP family transcription factors showed significant activation specifically in progenitor-like AML cells at relapse. Conclusion: Our study of four distinct AMLs suggests the existence of lineage-specific epigenetic evolution in some relapsed AMLs. We found that epigenetic activation of specific transcription factors, such as GATA and RUNX, was restricted to certain steps of myeloid differentiation, suggesting that epigenetic changes contributing to resistance and relapse are relevant in specific AML lineages and differentiation states. Notably, we found that even in AMLs where overall epigenetic state remains stable, there is activation of specific TFs (e.g. SP1) in progenitor cells at relapse, consistent with literature demonstrating SP family TF relevance in Leukemic Stem Cell (LSC) drug resistance. These observations suggest that epigenetic modifications in less-differentiated AML cells may reflect changes occurring in LSCs, potentially contributing to resistance and relapse. Our study is limited due to a small sample size that precludes broad generalizations, but our findings provide a foundation for further characterization of AML relapse epigenetics. Ultimately, these findings suggest the existence of specific epigenetic changes at certain points in the AML differentiation hierarchy that contribute to relapse, warranting further exploration of cell state-specific epigenetic evolution.

Single-cell epigenetic, transcriptional, and protein profiling of latent and active HIV-1 reservoir revealed that IKZF3 promotes HIV-1 persistence

Understanding how HIV-1-infected cells proliferate and persist is key to HIV-1 eradication, but the heterogeneity and rarity of HIV-1-infected cells hamper mechanistic interrogations. Here, we used single-cell DOGMA-seq to simultaneously capture transcription factor accessibility, transcriptome, surface proteins, HIV-1 DNA, and HIV-1 RNA in memory CD4+ Tcells from six people living with HIV-1 during viremia and after suppressive antiretroviral therapy. We identified increased transcription factor accessibility in latent HIV-1-infected cells (RORC) and transcriptionally active HIV-1-infected cells (interferon regulatory transcription factor [IRF] and activator protein 1 [AP-1]). A proliferation program (IKZF3, IL21, BIRC5, and MKI67 co-expression) promoted the survival of transcriptionally active HIV-1-infected cells. Both latent and transcriptionally active HIV-1-infected cells had increased IKZF3 (Aiolos) expression. Distinct epigenetic programs drove the heterogeneous cellular states of HIV-1-infected cells: IRF:activation, Eomes:cytotoxic effector differentiation, AP-1:migration, and cell death. Our study revealed the single-cell epigenetic, transcriptional, and protein states of latent and transcriptionally active HIV-1-infected cells and cellular programs promoting HIV-1 persistence.

Chromatin gatekeeper and modifier CHD proteins in development, and in autism and other neurological disorders.

Chromatin, a protein-DNA complex, is a dynamic structure that stores genetic information within the nucleus and responds to molecular/cellular changes in its structure, providing conditional access to the genetic machinery. ATP-dependent chromatin modifiers regulate access of transcription factors and RNA polymerases to DNA by either "opening" or "closing" the structure of chromatin, and its aberrant regulation leads to a variety of neurodevelopmental disorders. The chromodomain helicase DNA-binding (CHD) proteins are ATP-dependent chromatin modifiers involved in the organization of chromatin structure, act as gatekeepers of genomic access, and deposit histone variants required for gene regulation. In this review, we first discuss the structural and functional domains of the CHD proteins, and their binding sites, and phosphorylation, acetylation, and methylation sites. The conservation of important amino acids in SWItch/sucrose non-fermenting (SWI/SNF) domains, and their protein and mRNA tissue expression profiles are discussed. Next, we convey the important binding partners of CHD proteins, their protein complexes and activities, and their involvements in epigenetic regulation. We also show the ChIP-seq binding dynamics for CHD1, CHD2, CHD4, and CHD7 proteins at promoter regions of histone genes, as well as several genes that are critical for neurodevelopment. The role of CHD proteins in development is also discussed. Finally, this review provides information about CHD protein mutations reported in autism and neurodevelopmental disorders, and their pathogenicity. Overall, this review provides information on the progress of research into CHD proteins, their structural and functional domains, epigenetics, and their role in stem cell, development, and neurological disorders.

Quantification of Global Histone Post Translational Modifications Using Intranuclear Flow Cytometry in Isolated Mouse Brain Microglia.

Gene expression control occurs partially by modifications in chromatin structure, including the addition and removal of posttranslational modifications to histone tails. Histone post-translational modifications (HPTMs) can either facilitate gene expression or repression. For example, acetylation of histone tail lysine residues neutralizes the positive charge and reduces interactions between the tail and negatively charged DNA. The decrease in histone tail-DNA interactions results in increased accessibility of the underlying DNA, allowing for increased transcription factor access. The acetylation mark also serves as a recognition site for bromodomain-containing transcriptional activators, together resulting in enhanced gene expression. Histone marks can be dynamically regulated during cell differentiation and in response to different cellular environments and stimuli. While next-generation sequencing approaches have begun to characterize genomic locations for individual histone modifications, only one modification can be examined concurrently. Given that there are hundreds of different HPTMs, we have developed a high throughput, quantitative measure of global HPTMs that can be used to screen histone modifications prior to conducting more extensive genome sequencing approaches. This protocol describes a flow cytometry-based method to detect global HPTMs and can be conducted using cells in culture or isolated cells from in vivo tissues. We present example data from isolated mouse brain microglia to demonstrate the sensitivity of the assay to detect global shifts in HPTMs in response to a bacteria-derived immune stimulus (lipopolysaccharide). This protocol allows for the rapid and quantitative assessment of HPTMs and can be applied to any transcriptional or epigenetic regulator that can be detected by an antibody.

Intrinsically disordered domain of transcription factor TCF-1 is required for T cell developmental fidelity.

In development, pioneer transcription factors access silent chromatin to reveal lineage-specific gene programs. The structured DNA-binding domains of pioneer factors have been well characterized, but whether and how intrinsically disordered regions affect chromatin and control cell fate is unclear. Here, we report that deletion of an intrinsically disordered region of the pioneer factor TCF-1 (termed L1) leads to an early developmental block in T cells. The few T cells that develop from progenitors expressing TCF-1 lacking L1 exhibit lineage infidelity distinct from the lineage diversion of TCF-1-deficient cells. Mechanistically, L1 is required for activation of T cell genes and repression of GATA2-driven genes, normally reserved to the mast cell and dendritic cell lineages. Underlying this lineage diversion, L1 mediates binding of TCF-1 to its earliest target genes, which are subject to repression as T cells develop. These data suggest that the intrinsically disordered N terminus of TCF-1 maintains T cell lineage fidelity.

Multiple roles and regulatory mechanisms of the transcription factor HNF4 in the intestine.

Hepatocyte nuclear factor 4-alpha (HNF4α) drives a complex array of transcriptional programs across multiple organs. Beyond its previously documented function in the liver, HNF4α has crucial roles in the kidney, intestine, and pancreas. In the intestine, a multitude of functions have been attributed to HNF4 and its accessory transcription factors, including but not limited to, intestinal maturation, differentiation, regeneration, and stem cell renewal. Functional redundancy between HNF4α and its intestine-restricted paralog HNF4γ, and co-regulation with other transcription factors drive these functions. Dysregulated expression of HNF4 results in a wide range of disease manifestations, including the development of a chronic inflammatory state in the intestine. In this review, we focus on the multiple molecular mechanisms of HNF4 in the intestine and explore translational opportunities. We aim to introduce new perspectives in understanding intestinal genetics and the complexity of gastrointestinal disorders through the lens of HNF4 transcription factors.

Chromatin accessibility memory of donor cells disrupts bovine somatic cell nuclear transfer blastocysts development.

The post-transfer developmental capacity of bovine somatic cell nuclear transfer (SCNT) blastocysts is reduced, implying that abnormalities in gene expression regulation are present at blastocyst stage. Chromatin accessibility, as an indicator for transcriptional regulatory elements mediating gene transcription activity, has heretofore been largely unexplored in SCNT embryos, especially at blastocyst stage. In the present study, single-cell sequencing assay for transposase-accessible chromatin (scATAC-seq) of in vivo and SCNT blastocysts were conducted to segregate lineages and demonstrate the aberrant chromatin accessibility of transcription factors (TFs) related to inner cell mass (ICM) development in SCNT blastocysts. Pseudotime analysis of lineage segregation further reflected dysregulated chromatin accessibility dynamics of TFs in the ICM of SCNT blastocysts compared to their in vivo counterparts. ATAC- and ChIP-seq results of SCNT donor cells revealed that the aberrant chromatin accessibility in the ICM of SCNT blastocysts was due to the persistence of chromatin accessibility memory at corresponding loci in the donor cells, with strong enrichment of trimethylation of histone H3 at lysine 4 (H3K4me3) at these loci. Correction of the aberrant chromatin accessibility through demethylation of H3K4me3 by KDM5B diminished the expression of related genes (e.g., BCL11B) and significantly improved the ICM proliferation in SCNT blastocysts. This effect was confirmed by knocking down BCL11B in SCNT embryos to down-regulate p21 and alleviate the inhibition of ICM proliferation. These findings expand our understanding of the chromatin accessibility abnormalities in SCNT blastocysts and BCL11B may be a potential target to improve SCNT efficiency.

Exercise intervention during pregnancy induces DNA methylation alterations in maternal blood and cord blood.

Exercise intervention during pregnancy induces DNA methylation alterations in maternal blood and cord blood.