Chromatin structure and the inheritance of epigenetic information

Replication-coupled inheritance of chromatin states

During the development of eukaryote, faithful inheritance of chromatin states is central to the maintenance of cell fate. DNA replication poses a significant challenge for chromatin state inheritance because every nucleosome in the genome is disrupted as the replication fork passes. It has been found that many factors including DNA polymerases, histone chaperones, as well as, RNA Pol II and histone modifying enzymes coordinate spatially and temporally to maintain the epigenome during this progress. In this review, we provide a summary of the detailed mechanisms of replication-coupled nucleosome assembly and post-replication chromatin maturation, highlight the inheritance of chromatin states and epigenome during these processes, and discuss the future directions and challenges in this field.

Chromatin lysine acylation: On the path to chromatin homeostasis and genome integrity

The fundamental role of cells in safeguarding the genome's integrity against DNA double-strand breaks (DSBs) is crucial for maintaining chromatin homeostasis and the overall genomic stability. Aberrant responses to DNA damage, known as DNA damage responses (DDRs), can result in genomic instability and contribute significantly to tumorigenesis. Unraveling the intricate mechanisms underlying DDRs following severe damage holds the key to identify therapeutic targets for cancer. Chromatin lysine acylation, encompassing diverse modifications such as acetylation, lactylation, crotonylation, succinylation, malonylation, glutarylation, propionylation, and butyrylation, has been extensively studied in the context of DDRs and chromatin homeostasis. Here, we delve into the modifying enzymes and the pivotal roles of lysine acylation and their crosstalk in maintaining chromatin homeostasis and genome integrity in response to DDRs. Moreover, we offer a comprehensive perspective and overview of the latest insights, driven primarily by chromatin acylation modification and associated regulators.

Impact of HDAC inhibitors on macrophage polarization to enhance innate immunity against infections

Innate immunity plays an important role in host defense against pathogenic infections. It involves macrophage polarization into either the pro-inflammatory M1 or the anti-inflammatory M2 phenotype, influencing immune stimulation or suppression, respectively. Epigenetic changes during immune reactions contribute to long-term innate immunity imprinting on macrophage polarization. It is becoming increasingly evident that epigenetic modulators, such as histone deacetylase (HDAC) inhibitors (HDACi), enable the enhancement of innate immunity by tailoring macrophage polarization in response to immune stressors. In this review, we summarize current literature on the impact of HDACi and other epigenetic modulators on the functioning of macrophages during diseases that have a strong immune component, such as infections. Depending on the disease context and the chosen therapeutic intervention, HDAC1, HDAC2, HDAC3, HDAC6, or HDAC8 are particularly important in influencing macrophage polarization towards either M1 or M2 phenotypes. We anticipate that therapeutic strategies based on HDAC epigenetic mechanisms will provide a unique approach to boost immunity against disease challenges, including resistant infections.

Promoter DNA methylation and transcription factor condensation are linked to transcriptional memory in mammalian cells

The regulation of genes can be mathematically described by input-output functions that are typically assumed to be time invariant. This fundamental assumption underpins the design of synthetic gene circuits and the quantitative understanding of natural gene regulatory networks. Here, we found that this assumption is challenged in mammalian cells. We observed that a synthetic reporter gene can exhibit unexpected transcriptional memory, leading to a shift in the dose-response curve upon a second induction. Mechanistically, we investigated the cis-dependency of transcriptional memory, revealing the necessity of promoter DNA methylation in establishing memory. Furthermore, we showed that the synthetic transcription factor's effective DNA binding affinity underlies trans-dependency, which is associated with its capacity to undergo biomolecular condensation. These principles enabled modulating memory by perturbing either cis- or trans-regulation of genes. Together, our findings suggest the potential pervasiveness of transcriptional memory and implicate the need to model mammalian gene regulation with time-varying input-output functions. A record of this paper's transparent peer review process is included in the supplemental information.

A replisome-associated histone H3-H4 chaperone required for epigenetic inheritance

Faithful transfer of parental histones to newly replicated daughter DNA strands is critical for inheritance of epigenetic states. Although replication proteins that facilitate parental histone transfer have been identified, how intact histone H3-H4 tetramers travel from the front to the back of the replication fork remains unknown. Here, we use AlphaFold-Multimer structural predictions combined with biochemical and genetic approaches to identify the Mrc1/CLASPIN subunit of the replisome as a histone chaperone. Mrc1 contains a conserved histone-binding domain that forms a brace around the H3-H4 tetramer mimicking nucleosomal DNA and H2A-H2B histones, is required for heterochromatin inheritance, and promotes parental histone recycling during replication. We further identify binding sites for the FACT histone chaperone in Swi1/TIMELESS and DNA polymerase α that are required for heterochromatin inheritance. We propose that Mrc1, in concert with FACT acting as a mobile co-chaperone, coordinates the distribution of parental histones to newly replicated DNA.

Precision epigenetic editing: Technological advances, enduring challenges, and therapeutic applications

The epigenome is a complex framework through which gene expression is precisely and flexibly modulated to incorporate heritable memory and responses to environmental stimuli. It governs diverse cellular processes, including cell fate, disease, and aging. The need to understand this system and precisely control gene expression outputs for therapeutic purposes has precipitated the development of a diverse set of epigenetic editing tools. Here, we review the existing toolbox for targeted epigenetic editing, technical considerations of the current technologies, and opportunities for future development. We describe applications of therapeutic epigenetic editing and their potential for treating disease, with a discussion of ongoing delivery challenges that impede certain clinical interventions, particularly in the brain. With simultaneous advancements in available engineering tools and appropriate delivery technologies, we predict that epigenetic editing will increasingly cement itself as a powerful approach for safely treating a wide range of disorders in all tissues of the body.

Genetic and epigenetic instability as an underlying driver of progression and aggressive behavior in IDH-mutant astrocytoma

In recent years, the classification of adult-type diffuse gliomas has undergone a revolution, wherein specific molecular features now represent defining diagnostic criteria of IDH-wild-type glioblastomas, IDH-mutant astrocytomas, and IDH-mutant 1p/19q-codeleted oligodendrogliomas. With the introduction of the 2021 WHO CNS classification, additional molecular alterations are now integrated into the grading of these tumors, given equal weight to traditional histologic features. However, there remains a great deal of heterogeneity in patient outcome even within these established tumor subclassifications that is unexplained by currently codified molecular alterations, particularly in the IDH-mutant astrocytoma category. There is also significant intercellular genetic and epigenetic heterogeneity and plasticity with resulting phenotypic heterogeneity, making these tumors remarkably adaptable and robust, and presenting a significant barrier to the design of effective therapeutics. Herein, we review the mechanisms and consequences of genetic and epigenetic instability, including chromosomal instability (CIN), microsatellite instability (MSI)/mismatch repair (MMR) deficits, and epigenetic instability, in the underlying biology, tumorigenesis, and progression of IDH-mutant astrocytomas. We also discuss the contribution of recent high-resolution transcriptomics studies toward defining tumor heterogeneity with single-cell resolution. While intratumoral heterogeneity is a well-known feature of diffuse gliomas, the contribution of these various processes has only recently been considered as a potential driver of tumor aggressiveness. CIN has an independent, adverse effect on patient survival, similar to the effect of histologic grade and homozygous CDKN2A deletion, while MMR mutation is only associated with poor overall survival in univariate analysis but is highly correlated with higher histologic/molecular grade and other aggressive features. These forms of genomic instability, which may significantly affect the natural progression of these tumors, response to therapy, and ultimately clinical outcome for patients, are potentially measurable features which could aid in diagnosis, grading, prognosis, and development of personalized therapeutics.

From shells to sequences: A proof-of-concept study for on-site analysis of hemolymphatic circulating cell-free DNA from sentinel mussels using Nanopore technology

Blue mussels are often abundant and widely distributed in polar marine coastal ecosystems. Because of their wide distribution, ecological importance, and relatively stationary lifestyle, bivalves have long been considered suitable indicators of ecosystem health and changes. Monitoring the population dynamics of blue mussels can provide information on the overall biodiversity, species interactions, and ecosystem functioning. In the present work, we combined the concept of liquid biopsy (LB), an emerging concept in medicine based on the sequencing of free circulating DNA, with the Oxford Nanopore Technologies (ONT) platform using a portable laboratory in a remote area. Our results demonstrate that this platform is ideally suited for sequencing hemolymphatic circulating cell-free DNA (ccfDNA) fragments found in blue mussels. The percentage of non-self ccfDNA accounted for >50 % of ccfDNA at certain sampling Sites, allowing the quick, on-site acquisition of a global view of the biodiversity of a coastal marine ecosystem. These ccfDNA fragments originated from viruses, bacteria, plants, arthropods, algae, and multiple Chordata. Aside from non-self ccfDNA, we found DNA fragments from all 14 blue mussel chromosomes, as well as those originating from the mitochondrial genomes. However, the distribution of nuclear and mitochondrial DNA was significantly different between Sites. Similarly, analyses between various sampling Sites showed that the biodiversity varied significantly within microhabitats. Our work shows that the ONT platform is well-suited for LB in sentinel blue mussels in remote and challenging conditions, enabling faster fieldwork for conservation strategies and resource management in diverse settings.

Epigenomic landscape of the human dorsal root ganglion: sex differences and transcriptional regulation of nociceptive genes

Gene expression is influenced by chromatin architecture via controlled access of regulatory factors to DNA. To better understand gene regulation in the human dorsal root ganglion (hDRG) we used bulk and spatial transposase-accessible chromatin technology followed by sequencing (ATAC-seq). Using bulk ATAC-seq, we detected that in females diverse differentially accessible chromatin regions (DARs) mapped to the X chromosome and in males to autosomal genes. EGR1/3 and SP1/4 transcription factor binding motifs were abundant within DARs in females, and JUN, FOS and other AP-1 factors in males. To dissect the open chromatin profile in hDRG neurons, we used spatial ATAC-seq. The neuron cluster showed higher chromatin accessibility in GABAergic, glutamatergic, and interferon-related genes in females, and in Ca2+- signaling-related genes in males. Sex differences in transcription factor binding sites in neuron-proximal barcodes were consistent with the trends observed in bulk ATAC-seq data. We validated that EGR1 expression is biased to female hDRG compared to male. Strikingly, XIST, the long-noncoding RNA responsible for X inactivation, hybridization signal was found to be highly dispersed in the female neuronal but not non-neuronal nuclei suggesting weak X inactivation in female hDRG neurons. Our findings point to baseline epigenomic sex differences in the hDRG that likely underlie divergent transcriptional responses that determine mechanistic sex differences in pain.

Motorized chain models of the ideal chromosome

An array of motor proteins consumes chemical energy in setting up the architectures of chromosomes. Here, we explore how the structure of ideal polymer chains is influenced by two classes of motors. The first class which we call "swimming motors" acts to propel the chromatin fiber through three-dimensional space. They represent a caricature of motors such as RNA polymerases. Previously, they have often been described by adding a persistent flow onto Brownian diffusion of the chain. The second class of motors, which we call "grappling motors" caricatures the loop extrusion processes in which segments of chromatin fibers some distance apart are brought together. We analyze these models using a self-consistent variational phonon approximation to a many-body Master equation incorporating motor activities. We show that whether the swimming motors lead to contraction or expansion depends on the susceptibility of the motors, that is, how their activity depends on the forces they must exert. Grappling motors in contrast to swimming motors lead to long-ranged correlations that resemble those first suggested for fractal globules and that are consistent with the effective interactions inferred by energy landscape analyses of Hi-C data on the interphase chromosome.

Deciphering epigenetic regulations in the inflammatory pathways of atopic dermatitis

Atopic dermatitis, commonly referred to as atopic eczema, is a persistent inflammatory skin disorder that predominantly manifests in children but may endure into adulthood. Its clinical management poses challenges due to the absence of a definitive cure, and its prevalence varies across ethnicities, genders, and geographic locations. The epigenetic landscape of AD includes changes in DNA methylation, changes in histone acetylation and methylation, and regulation by non-coding RNAs. These changes affect inflammatory and immune mechanisms, and research has identified AD-specific variations in DNA methylation, particularly in the affected epidermis. Histone modifications, including acetylation, have been associated with the disruption of skin barrier function in AD, suggesting the potential therapeutic benefit of histone deacetylase inhibitors such as belinostat. Furthermore, non-coding RNAs, particularly microRNAs and long non-coding RNAs (lncRNAs), have been implicated in modulating various cellular processes central to AD pathogenesis. Therapeutic implications in AD include the potential use of DNA methylation inhibitors and histone deacetylase inhibitors to correct aberrant methylation patterns and modulate gene expression related to immune responses and skin barrier functions. Additionally, the emerging role of lncRNAs suggests the possibility of using small interfering RNAs or antisense oligonucleotides to inhibit lncRNAs and adjust their regulatory impact on gene expression. In conclusion, the importance of epigenetic elements in AD is becoming increasingly clear as studies highlight the contribution of DNA methylation, histone modifications and, control by non-coding RNAs to the onset and progression of the disease. Understanding these epigenetic changes provides valuable insights for developing targeted therapeutic strategies.

Visualizing histone H4K20me1 in knock-in mice expressing the mCherry-tagged modification-specific intracellular antibody

During development and differentiation, histone modifications dynamically change locally and globally, associated with transcriptional regulation, DNA replication and repair, and chromosome condensation. The level of histone H4 Lys20 monomethylation (H4K20me1) increases during the G2 to M phases of the cell cycle and is enriched in facultative heterochromatin, such as inactive X chromosomes in cycling cells. To track the dynamic changes of H4K20me1 in living cells, we have developed a genetically encoded modification-specific intracellular antibody (mintbody) probe that specifically binds to the modification. Here, we report the generation of knock-in mice in which the coding sequence of the mCherry-tagged version of the H4K20me1-mintbody is inserted into the Rosa26 locus. The knock-in mice, which ubiquitously expressed the H4K20me1-mintbody, developed normally and were fertile, indicating that the expression of the probe does not disturb the cell growth, development, or differentiation. Various tissues isolated from the knock-in mice exhibited nuclear fluorescence without the need for fixation. The H4K20me1-mintbody was enriched in inactive X chromosomes in developing embryos and in XY bodies during spermatogenesis. The knock-in mice will be useful for the histochemical analysis of H4K20me1 in any cell types.

Expression of ten-eleven translocation 2 and glutathione-S-transferase pi in colorectal cancer patients with and without type 2 diabetes mellitus

AIMS

To highlight possible correlations of type 2 diabetes mellitus (T2DM) with microscopic / macroscopic characteristics of colorectal cancer tissues, along with the expression of Ten-Eleven Translocation 2 (TET2) and glutathione-S-transferase pi (GST-pi) proteins.

Epigenetic Regulation of Neural Stem Cells in Developmental and Adult Stages

The development of the nervous system is regulated by numerous intracellular molecules and cellular signals that interact temporally and spatially with the extracellular microenvironment. The three major cell types in the brain, i.e., neurons and two types of glial cells (astrocytes and oligodendrocytes), are generated from common multipotent neural stem cells (NSCs) throughout life. However, NSCs do not have this multipotentiality from the beginning. During cortical development, NSCs sequentially obtain abilities to differentiate into neurons and glial cells in response to combinations of spatiotemporally modulated cell-intrinsic epigenetic alterations and extrinsic factors. After the completion of brain development, a limited population of NSCs remains in the adult brain and continues to produce neurons (adult neurogenesis), thus contributing to learning and memory. Many biological aspects of brain development and adult neurogenesis are regulated by epigenetic changes via behavioral control of NSCs. Epigenetic dysregulation has also been implicated in the pathogenesis of various brain diseases. Here, we present recent advances in the epigenetic regulation of NSC behavior and its dysregulation in brain disorders.

DNA polymerase delta governs parental histone transfer to DNA replication lagging strand

Chromatin replication is intricately intertwined with the recycling of parental histones to the newly duplicated DNA strands for faithful genetic and epigenetic inheritance. The transfer of parental histones occurs through two distinct pathways: leading strand deposition, mediated by the DNA polymerase ε subunits Dpb3/Dpb4, and lagging strand deposition, facilitated by the MCM helicase subunit Mcm2. However, the mechanism of the facilitation of Mcm2 transferring parental histones to the lagging strand while moving along the leading strand remains unclear. Here, we show that the deletion of Pol32, a nonessential subunit of major lagging-strand DNA polymerase δ, results in a predominant transfer of parental histone H3-H4 to the leading strand during replication. Biochemical analyses further demonstrate that Pol32 can bind histone H3-H4 both in vivo and in vitro. The interaction of Pol32 with parental histone H3-H4 is disrupted through the mutation of the histone H3-H4 binding domain within Mcm2. Our findings identify the DNA polymerase δ subunit Pol32 as a critical histone chaperone downstream of Mcm2, mediating the transfer of parental histones to the lagging strand during DNA replication.

Dynamical phase transition in models that couple chromatin folding with histone modifications

Genomic regions can acquire heritable epigenetic states through unique histone modifications, which lead to stable gene expression patterns without altering the underlying DNA sequence. However, the relationship between chromatin conformational dynamics and epigenetic stability is poorly understood. In this paper, we propose kinetic models to investigate the dynamic fluctuations of histone modifications and the spatial interactions between nucleosomes. Our model explicitly incorporates the influence of chemical modifications on the structural stability of chromatin and the contribution of chromatin contacts to the cooperative nature of chemical reactions. Through stochastic simulations and analytical theory, we have discovered distinct steady-state outcomes in different kinetic regimes, resembling a dynamical phase transition. Importantly, we have validated that the emergence of this transition, which occurs on biologically relevant timescales, is robust against variations in model design and parameters. Our findings suggest that the viscoelastic properties of chromatin and the timescale at which it transitions from a gel-like to a liquidlike state significantly impact dynamic processes that occur along the one-dimensional DNA sequence.

Epigenetic Genome Modifications during Pregnancy: The Impact of Essential Nutritional Supplements on DNA Methylation

Pregnancy is an extremely stressful period in a pregnant woman's life. Currently, women's awareness of the proper course of pregnancy and its possible complications is constantly growing. Therefore, a significant percentage of women increasingly reach for various dietary supplements during gestation. Some of the most popular substances included in multi-ingredient supplements are folic acid and choline. Those substances are associated with positive effects on fetal intrauterine development and fewer possible pregnancy-associated complications. Recently, more and more attention has been paid to the impacts of specific environmental factors, such as diet, stress, physical activity, etc., on epigenetic modifications, understood as changes occurring in gene expression without the direct alteration of DNA sequences. Substances such as folic acid and choline may participate in epigenetic modifications by acting via a one-carbon cycle, leading to the methyl-group donor formation. Those nutrients may indirectly impact genome phenotype by influencing the process of DNA methylation. This review article presents the current state of knowledge on the use of folic acid and choline supplementation during pregnancy, taking into account their impacts on the maternal-fetal unit and possible pregnancy outcomes, and determining possible mechanisms of action, with particular emphasis on their possible impacts on epigenetic modifications.

Lysine Methylation-Dependent Proteolysis by the Malignant Brain Tumor (MBT) Domain Proteins

Lysine methylation is a major post-translational protein modification that occurs in both histones and non-histone proteins. Emerging studies show that the methylated lysine residues in non-histone proteins provide a proteolytic signal for ubiquitin-dependent proteolysis. The SET7 (SETD7) methyltransferase specifically transfers a methyl group from S-Adenosyl methionine to a specific lysine residue located in a methylation degron motif of a protein substrate to mark the methylated protein for ubiquitin-dependent proteolysis. LSD1 (Kdm1a) serves as a demethylase to dynamically remove the methyl group from the modified protein. The methylated lysine residue is specifically recognized by L3MBTL3, a methyl-lysine reader that contains the malignant brain tumor domain, to target the methylated proteins for proteolysis by the CRL4DCAF5 ubiquitin ligase complex. The methylated lysine residues are also recognized by PHF20L1 to protect the methylated proteins from proteolysis. The lysine methylation-mediated proteolysis regulates embryonic development, maintains pluripotency and self-renewal of embryonic stem cells and other stem cells such as neural stem cells and hematopoietic stem cells, and controls other biological processes. Dysregulation of the lysine methylation-dependent proteolysis is associated with various diseases, including cancers. Characterization of lysine methylation should reveal novel insights into how development and related diseases are regulated.

The epigenetic regulatory effect of histone acetylation and deacetylation on skeletal muscle metabolism-a review

Skeletal muscles, the largest organ responsible for energy metabolism in most mammals, play a vital role in maintaining the body's homeostasis. Epigenetic modification, specifically histone acetylation, serves as a crucial regulatory mechanism influencing the physiological processes and metabolic patterns within skeletal muscle metabolism. The intricate process of histone acetylation modification involves coordinated control of histone acetyltransferase and deacetylase levels, dynamically modulating histone acetylation levels, and precisely regulating the expression of genes associated with skeletal muscle metabolism. Consequently, this comprehensive review aims to elucidate the epigenetic regulatory impact of histone acetylation modification on skeletal muscle metabolism, providing invaluable insights into the intricate molecular mechanisms governing epigenetic modifications in skeletal muscle metabolism.

Relative expression of key genes involved in nucleic acids methylation in Anopheles gambiae sensu stricto

In vertebrates, enzymes responsible for DNA methylation, one of the epigenetic mechanisms, are encoded by genes falling into the cytosine methyltransferases genes family (Dnmt1, Dnmt3a,b and Dnmt3L). However, in Diptera, only the methyltransferase Dnmt2 was found, suggesting that DNA methylation might act differently for species in this order. Moreover, genes involved in epigenetic dynamics, such as Ten-eleven Translocation dioxygenases (TET) and Methyl-CpG-binding domain (MBDs), present in vertebrates, might play a role in insects. This work aimed at investigating nucleic acids methylation in the malaria vector Anopheles gambiae (Diptera: Culicidae) by analysing the expression of Dnmt2, TET2 and MBDs genes using quantitative real-time polymerase chain reaction (qRT-PCR) at pre-immature stages and in reproductive tissues of adult mosquitoes. In addition, the effect of two DNA methylation inhibitors on larval survival was evaluated. The qPCR results showed an overall low expression of Dnmt2 at all developmental stages and in adult reproductive tissues. In contrast, MBD and TET2 showed an overall higher expression. In adult mosquito reproductive tissues, the expression level of the three genes in males' testes was significantly higher than that in females' ovaries. The chemical treatments did not affect larval survival. The findings suggest that mechanisms other than DNA methylation underlie epigenetic regulation in An. gambiae.

Recapitulation of patient-specific 3D chromatin conformation using machine learning

Regulatory networks containing enhancer-gene edges define cellular states. Multiple efforts have revealed these networks for reference tissues and cell lines by integrating multi-omics data. However, the methods developed cannot be applied for large patient cohorts due to the infeasibility of chromatin immunoprecipitation sequencing (ChIP-seq) for limited biopsy material. We trained machine-learning models using chromatin interaction analysis with paired-end tag sequencing (ChIA-PET) and high-throughput chromosome conformation capture combined with chromatin immunoprecipitation (HiChIP) data that can predict connections using only assay for transposase-accessible chromatin using sequencing (ATAC-seq) and RNA-seq data as input, which can be generated from biopsies. Our method overcomes limitations of correlation-based approaches that cannot distinguish between distinct target genes of given enhancers or between active vs. poised states in different samples, a hallmark of network rewiring in cancer. Application of our model on 371 samples across 22 cancer types revealed 1,780 enhancer-gene connections for 602 cancer genes. Using CRISPR interference (CRISPRi), we validated enhancers predicted to regulate ESR1 in estrogen receptor (ER)+ breast cancer and A1CF in liver hepatocellular carcinoma.

Modeling epigenetic lesions that cause gliomas

Epigenetic lesions that disrupt regulatory elements represent potential cancer drivers. However, we lack experimental models for validating their tumorigenic impact. Here, we model aberrations arising in isocitrate dehydrogenase-mutant gliomas, which exhibit DNA hypermethylation. We focus on a CTCF insulator near the PDGFRA oncogene that is recurrently disrupted by methylation in these tumors. We demonstrate that disruption of the syntenic insulator in mouse oligodendrocyte progenitor cells (OPCs) allows an OPC-specific enhancer to contact and induce Pdgfra, thereby increasing proliferation. We show that a second lesion, methylation-dependent silencing of the Cdkn2a tumor suppressor, cooperates with insulator loss in OPCs. Coordinate inactivation of the Pdgfra insulator and Cdkn2a drives gliomagenesis in vivo. Despite locus synteny, the insulator is CpG-rich only in humans, a feature that may confer human glioma risk but complicates mouse modeling. Our study demonstrates the capacity of recurrent epigenetic lesions to drive OPC proliferation in vitro and gliomagenesis in vivo.

Remembering foods and foes: emerging principles of transcriptional memory

Transcriptional memory is characterized by a primed cellular state, induced by an external stimulus that results in an altered expression of primed genes upon re-exposure to the inducing signal. Intriguingly, the primed state is heritably maintained across somatic cell divisions even after the initial stimulus and target gene transcription cease. This phenomenon is widely observed across various organisms and appears to enable cells to retain a memory of external signals, thereby adapting to environmental changes. Signals range from nutrient supplies (food) to a variety of stress signals, including exposure to pathogens (foes), leading to long-term memory such as in the case of trained immunity in plants and mammals. Here, we review these priming phenomena and our current understanding of transcriptional memory. We consider different mechanistic models for how memory can work and discuss existing evidence for potential carriers of memory. Key molecular signatures include: the poising of RNA polymerase II machinery, maintenance of histone marks, as well as alterations in nuclear positioning and long-range chromatin interactions. Finally, we discuss the potential adaptive roles of transcriptional memory in the organismal response to its environment from nutrient sensing to trained immunity.

C4S DB: Comprehensive Collection and Comparison for ChIP-Seq Database

Combining multiple binding profiles, such as transcription factors and histone modifications, is a crucial step in revealing the functions of complex biological systems. Although a massive amount of chromatin immunoprecipitation followed by sequencing (ChIP-seq) data is available, existing ChIP-seq databases or repositories focus on individual experiments, and it is difficult to elucidate orchestrated regulation by DNA-binding elements. We developed the Comprehensive Collection and Comparison for ChIP-Seq Database (C4S DB) to provide researchers with insights into the combination of DNA binding elements based on quality-assessed public ChIP-seq data. The C4S DB is based on > 16,000 human ChIP-seq experiments and provides two main web interfaces to discover the relationships between ChIP-seq data. "Gene browser" illustrates the landscape of distributions of binding elements around a specified gene, and "global similarity," a hierarchical clustering heatmap based on a similarity between two ChIP-seq experiments, gives an overview of genome-wide relations of regulatory elements. These functions promote the identification or evaluation of both gene-specific and genome-wide colocalization or mutually exclusive localization. Modern web technologies allow users to search for and aggregate large-scale experimental data through interactive web interfaces with quick responses. The C4S DB is available at https://c4s.site.

Probiotics and Commensal Bacteria Metabolites Trigger Epigenetic Changes in the Gut and Influence Beneficial Mood Dispositions

The effect of the intestinal microbiome on the gut-brain axis has received considerable attention, strengthening the evidence that intestinal bacteria influence emotions and behavior. The colonic microbiome is important to health and the pattern of composition and concentration varies extensively in complexity from birth to adulthood. That is, host genetics and environmental factors are complicit in shaping the development of the intestinal microbiome to achieve immunological tolerance and metabolic homeostasis from birth. Given that the intestinal microbiome perseveres to maintain gut homeostasis throughout the life cycle, epigenetic actions may determine the effect on the gut-brain axis and the beneficial outcomes on mood. Probiotics are postulated to exhibit a range of positive health benefits including immunomodulating capabilities. Lactobacillus and Bifidobacterium are genera of bacteria found in the intestines and so far, the benefits afforded by ingesting bacteria such as these as probiotics to people with mood disorders have varied in efficacy. Most likely, the efficacy of probiotic bacteria at improving mood has a multifactorial dependency, relying namely on several factors that include the agents used, the dose, the pattern of dosing, the pharmacotherapy used, the characteristics of the host and the underlying luminal microbial environment (e.g., gut dysbiosis). Clarifying the pathways linking probiotics with improvements in mood may help identify the factors that efficacy is dependent upon. Adjunctive therapies with probiotics for mood disorders could, through DNA methylation molecular mechanisms, augment the intestinal microbial active cohort and endow its mammalian host with important and critical co-evolutionary redox signaling metabolic interactions, that are embedded in bacterial genomes, and that in turn can enhance beneficial mood dispositions.

H4S47 O-GlcNAcylation regulates the activation of mammalian replication origins

The transmission and maintenance of genetic information in eukaryotic cells relies on the faithful duplication of the entire genome. In each round of division, excessive replication origins are licensed, with only a fraction activated to give rise to bi-directional replication forks in the context of chromatin. However, it remains elusive how eukaryotic replication origins are selectively activated. Here we demonstrate that O-GlcNAc transferase (OGT) enhances replication initiation by catalyzing H4S47 O-GlcNAcylation. Mutation of H4S47 impairs DBF4-dependent protein kinase (DDK) recruitment on chromatin, causing reduced phosphorylation of the replicative helicase mini-chromosome maintenance (MCM) complex and compromised DNA unwinding. Our short nascent-strand sequencing results further confirm the importance of H4S47 O-GlcNAcylation in origin activation. We propose that H4S47 O-GlcNAcylation directs origin activation through facilitating MCM phosphorylation, and this may shed light on the control of replication efficiency by chromatin environment.

Polymer folding through active processes recreates features of genome organization

From proteins to chromosomes, polymers fold into specific conformations that control their biological function. Polymer folding has long been studied with equilibrium thermodynamics, yet intracellular organization and regulation involve energy-consuming, active processes. Signatures of activity have been measured in the context of chromatin motion, which shows spatial correlations and enhanced subdiffusion only in the presence of adenosine triphosphate. Moreover, chromatin motion varies with genomic coordinate, pointing toward a heterogeneous pattern of active processes along the sequence. How do such patterns of activity affect the conformation of a polymer such as chromatin? We address this question by combining analytical theory and simulations to study a polymer subjected to sequence-dependent correlated active forces. Our analysis shows that a local increase in activity (larger active forces) can cause the polymer backbone to bend and expand, while less active segments straighten out and condense. Our simulations further predict that modest activity differences can drive compartmentalization of the polymer consistent with the patterns observed in chromosome conformation capture experiments. Moreover, segments of the polymer that show correlated active (sub)diffusion attract each other through effective long-ranged harmonic interactions, whereas anticorrelations lead to effective repulsions. Thus, our theory offers nonequilibrium mechanisms for forming genomic compartments, which cannot be distinguished from affinity-based folding using structural data alone. As a first step toward exploring whether active mechanisms contribute to shaping genome conformations, we discuss a data-driven approach.

Toward the Development of Epigenome Editing-Based Therapeutics: Potentials and Challenges

The advancement in epigenetics research over the past several decades has led to the potential application of epigenome-editing technologies for the treatment of various diseases. In particular, epigenome editing is potentially useful in the treatment of genetic and other related diseases, including rare imprinted diseases, as it can regulate the expression of the epigenome of the target region, and thereby the causative gene, with minimal or no modification of the genomic DNA. Various efforts are underway to successfully apply epigenome editing in vivo, such as improving target specificity, enzymatic activity, and drug delivery for the development of reliable therapeutics. In this review, we introduce the latest findings, summarize the current limitations and future challenges in the practical application of epigenome editing for disease therapy, and introduce important factors to consider, such as chromatin plasticity, for a more effective epigenome editing-based therapy.

BET proteins: Biological functions and therapeutic interventions

Bromodomain and extra-terminal (BET) family member proteins (BRD2, BRD3, BRD4 and BRDT) play a pivotal role in interpreting the epigenetic information of histone Kac modification, thus controlling gene expression, remodeling chromatin structures and avoid replicative stress-induced DNA damages. Abnormal activation of BET proteins is tightly correlated to various human diseases, including cancer. Therefore, BET bromodomain inhibitors (BBIs) were considered as promising therapeutics to treat BET-related diseases, raising >70 clinical trials in the past decades. Despite preliminary effects achieved, drug resistance and adverse events represent two major challenges for current BBIs development. In this review, we will introduce the biological functions of BET proteins in both physiological and pathological conditions; and summarize the progress in current BBI drug development. Moreover, we will also discuss the major challenges in the front of BET inhibitor development and provide rational strategies to overcome these obstacles.

Manifold epigenetics: A conceptual model that guides engineering strategies to improve whole-body regenerative health

Despite the promising advances in regenerative medicine, there is a critical need for improved therapies. For example, delaying aging and improving healthspan is an imminent societal challenge. Our ability to identify biological cues as well as communications between cells and organs are keys to enhance regenerative health and improve patient care. Epigenetics represents one of the major biological mechanisms involving in tissue regeneration, and therefore can be viewed as a systemic (body-wide) control. However, how epigenetic regulations concertedly lead to the development of biological memories at the whole-body level remains unclear. Here, we review the evolving definitions of epigenetics and identify missing links. We then propose our Manifold Epigenetic Model (MEMo) as a conceptual framework to explain how epigenetic memory arises and discuss what strategies can be applied to manipulate the body-wide memory. In summary we provide a conceptual roadmap for the development of new engineering approaches to improve regenerative health.

Nuclear architecture and the structural basis of mitotic memory

The nucleus is a complex organelle that hosts the genome and is essential for vital processes like DNA replication, DNA repair, transcription, and splicing. The genome is non-randomly organized in the three-dimensional space of the nucleus. This functional sub-compartmentalization was thought to be organized on the framework of nuclear matrix (NuMat), a non-chromatin scaffold that functions as a substratum for various molecular processes of the nucleus. More recently, nuclear bodies or membrane-less subcompartments of the nucleus are thought to arise due to phase separation of chromatin, RNA, and proteins. The nuclear architecture is an amalgamation of the relative organization of chromatin, epigenetic landscape, the nuclear bodies, and the nucleoskeleton in the three-dimensional space of the nucleus. During mitosis, the nucleus undergoes drastic changes in morphology to the degree that it ceases to exist as such; various nuclear components, including the envelope that defines the nucleus, disintegrate, and the chromatin acquires mitosis-specific epigenetic marks and condenses to form chromosome. Upon mitotic exit, chromosomes are decondensed, re-establish hierarchical genome organization, and regain epigenetic and transcriptional status similar to that of the mother cell. How this mitotic memory is inherited during cell division remains a puzzle. NuMat components that are a part of the mitotic chromosome in the form of mitotic chromosome scaffold (MiCS) could potentially be the seeds that guide the relative re-establishment of the epigenome, chromosome territories, and the nuclear bodies. Here, we synthesize the advances towards understanding cellular memory of nuclear architecture across mitosis and propose a hypothesis that a subset of NuMat proteome essential for nucleation of various nuclear bodies are retained in MiCS to serve as seeds of mitotic memory, thus ensuring the daughter cells re-establish the complex status of nuclear architecture similar to that of the mother cells, thereby maintaining the pre-mitotic transcriptional status.

High Expression of G9a Induces Cisplatin Resistance in Hepatocellular Carcinoma

OBJECTIVE

Chemotherapeutic drug resistance is the main obstacle that affects the efficacy of current therapies of hepatocellular carcinoma (HCC), which needs to be addressed urgently. High expression of histone methyltransferase G9a was reported to play a pivotal role in the progression of HCC. Regulatory mechanism of aberrant activation of G9a in HCC and the association with subsequent cisplatin (DDP) resistance still remains ambiguous. This study strived to investigate mechanism of G9a overexpression and its impact on cisplatin resistance in HCC cells.

MATERIALS AND METHODS

In this experimental study, we investigated effects of different concentrations of cisplatin in combination with BIX-01294 or PR-619 on viability and apoptosis of HuH7 and SNU387 cells via CCK-8 kit and flow cytometric analysis, respectively. Colony formation capacity was applied to evaluate effect of cisplatin with or without BIX-01294 on cell proliferation, and western blotting was used to verify expression level of the related proteins. Global mRNA expression profile analysis was adopted to identify differentially expressed genes associated with overexpression of G9a.

RESULTS

We observed that overexpression of G9a admittedly promoted cisplatin resistance in HCC cells. Global mRNA expression profile analysis after G9a inhibition showed that DNA repair and cell cycle progression were downregulated. Moreover, we identified that deubiquitination enzymes (DUBs) stabilized high expression of G9a in HCC through deubiquitination. Additionally, cisplatin could significantly inhibit proliferation of DUBs-deficient HCC cells, while promoting their apoptosis.

CONCLUSION

Collectively, our data indicated that DUBs stabilize G9a through deubiquitination, thereby participating in the cisplatin resistance of HCC cells. The elucidation of this mechanism contributes to propose a potential alternative intervention strategy for the treatment of HCC patients harboring high G9a levels.

Epigenetic regulation of embryonic ectoderm development in stem cell differentiation and transformation during ontogenesis

Dynamic chromatin accessibility regulates stem cell fate determination and tissue homeostasis via controlling gene expression. As a histone-modifying enzyme that predominantly mediates methylation of lysine 27 in histone H3 (H3K27me1/2/3), Polycomb repressive complex 2 (PRC2) plays the canonical role in targeting developmental regulators during stem cell differentiation and transformation. Embryonic ectoderm development (EED), the core scaffold subunit of PRC2 and as an H3K27me3-recognizing protein, has been broadly implicated with PRC2 stabilization and allosterically stimulated PRC2. Accumulating evidences from experimental data indicate that EED-associating epigenetic modifications are indispensable for stem cell maintenance and differentiation into specific cell lineages. In this review, we discuss the most updated advances to summarize the structural architecture of EED and its contributions and underlying mechanisms to mediating lineage differentiation of different stem cells during epigenetic modification to expand our understanding of PRC2.

Chromosome-level genome assembly reveals potential epigenetic mechanisms of the thermal tolerance in the oriental fruit fly, Bactrocera dorsalis

The oriental fruit fly, Bactrocera dorsalis (Hendel), has very strong ecological adaptability and phenotypic plasticity. Here, the genome of B. dorsalis was assembled into 549.45 Mb sequences with a contig N50 length of 12.81 Mb. Among, 95.67 % assembled genome sequences were anchored on six chromosomes with an N50 length of 94.63 Mb. According to the basic characteristics of the sex chromosomes of Tephritidae, the X chromosome of B. dorsalis was identified. Significant gene expansions were detected in several important gene families related to adaptability. In particular, we annotated 50 histone modification enzymes (HMEs) in this genome. A comparative transcriptome analysis indicated that 12 HME genes were differentially expressed in two thermo-tolerant strains (heat and cold). Interestingly, four and seven of the 12 HME genes responded to heat shock or cold hardening, respectively. These evidences suggested that the histone modification as an epigenetic modification may be involved in the thermal tolerance of B. dorsalis, but with different regulation mechanisms in thermal acclimation and hardening. The high quality genome of B. dorsalis provides an invaluable resource for further functional genomic study. Moreover, comparative genomic analysis will shed insights on revealing the mechanisms of adaptive evolution in this fly.

Schistosoma mansoni coactivator associated arginine methyltransferase 1 (SmCARM1) effect on parasite reproduction

Introduction

The human blood fluke parasite Schistosoma mansoni relies on diverse mechanisms to adapt to its diverse environments and hosts. Epigenetic mechanisms play a central role in gene expression regulation, culminating in such adaptations. Protein arginine methyltransferases (PRMTs) promote posttranslational modifications, modulating the function of histones and non-histone targets. The coactivator-associated arginine methyltransferase 1 (CARM1/PRMT4) is one of the S. mansoni proteins with the PRMT core domain.

Methods

We carried out in silico analyses to verify the expression of SmPRMTs in public datasets from different infection stages, single-sex versus mixed-worms, and cell types. The SmCARM1 function was evaluated by RNA interference. Gene expression levels were assessed, and phenotypic alterations were analyzed in vitro, in vivo, and ex vivo.

Results

The scRNAseq data showed that SmPRMTs expression is not enriched in any cell cluster in adult worms or schistosomula, except for Smcarm1 expression which is enriched in clusters of ambiguous cells and Smprmt1 in NDF+ neurons and stem/germinal cells from schistosomula. Smprmt1 is also enriched in S1 and late female germ cells from adult worms. After dsRNA exposure in vitro, we observed a Smcarm1 knockdown in schistosomula and adult worms, 83 and 69%, respectively. Smcarm1-knockdown resulted in reduced oviposition and no significant changes in the schistosomula or adult worm phenotypes. In vivo analysis after murine infection with Smcarm1 knocked-down schistosomula, showed no significant change in the number of worms recovered from mice, however, a significant reduction in the number of eggs recovered was detected. The ex vivo worms presented a significant decrease in the ovary area with a lower degree of cell differentiation, vitelline glands cell disorganization, and a decrease in the testicular lobe area. The worm tegument presented a lower number of tubercles, and the ventral sucker of the parasites presented a damaged tegument and points of detachment from the parasite body.

Discussion

This work brings the first functional characterization of SmCARM1 shedding light on its roles in S. mansoni biology and its potential as a drug target. Additional studies are necessary to investigate whether the reported effects of Smcarm1 knockdown are a consequence of the SmCARM1-mediated methylation of histone tails involved in DNA packaging or other non-histone proteins.

[New data on the pathophysiology of ischemic stroke: epigenetic mechanisms in focus]

Epigenetics is a branch of molecular biology that studies modifications able to change gene expression without changing the DNA sequence. Epigenetic modulations include DNA methylation, histone modifications, and noncoding RNAs. These heritable and modifiable gene changes can be caused by lifestyle and dietary factors. In recent years, epigenetic changes have been associated with the pathogenesis of a number of diseases, such as diabetes mellitus, obesity, renal pathology and various types of cancer. They were also associated with the pathogenesis of cardiovascular diseases, including ischemic stroke. In this regard, it is important to note that since epigenetic modifications are reversible processes, they can help in the development of new therapeutic approaches to treat human diseases. This mini-review presents the latest data on the influence of epigenetic modifications on the pathogenesis of ischemic stroke obtained both in animal models and in patients.

Epigenetic adaptations in drug-tolerant tumor cells

Traditional chemotherapy against cancer is often severely hampered by acquired resistance to the drug. Epigenetic alterations and other mechanisms like drug efflux, drug metabolism, and engagement of survival pathways are crucial in evading drug pressure. Herein, growing evidence suggests that a subpopulation of tumor cells can often tolerate drug onslaught by entering a "persister" state with minimal proliferation. The molecular features of these persister cells are gradually unraveling. Notably, the "persisters" act as a cache of cells that can eventually re-populate the tumor post-withdrawal drug pressure and contribute to acquiring stable drug-resistant features. This underlines the clinical significance of the tolerant cells. Accumulating evidence highlights the importance of modulation of the epigenome as a critical adaptive strategy for evading drug pressure. Chromatin remodeling, altered DNA methylation, and de-regulation of non-coding RNA expression and function contribute significantly to this persister state. No wonder targeting adaptive epigenetic modifications is increasingly recognized as an appropriate therapeutic strategy to sensitize them and restore drug sensitivity. Furthermore, manipulating the tumor microenvironment and "drug holiday" is also explored to maneuver the epigenome. However, heterogeneity in adaptive strategies and lack of targeted therapies have significantly hindered the translation of epigenetic therapy to the clinics. In this review, we comprehensively analyze the epigenetic alterations adapted by the drug-tolerant cells, the therapeutic strategies employed to date, and their limitations and future prospects.

Microglia and Brain Macrophages as Drivers of Glioma Progression

Evidence is accumulating that the tumour microenvironment (TME) has a key role in the progression of gliomas. Non-neoplastic cells in addition to the tumour cells are therefore finding increasing attention. Microglia and other glioma-associated macrophages are at the centre of this interest especially in the context of therapeutic considerations. New ideas have emerged regarding the role of microglia and, more recently, blood-derived brain macrophages in glioblastoma (GBM) progression. We are now beginning to understand the mechanisms that allow malignant glioma cells to weaken microglia and brain macrophage defence mechanisms. Surface molecules and cytokines have a prominent role in microglia/macrophage-glioma cell interactions, and we discuss them in detail. The involvement of exosomes and microRNAs forms another focus of this review. In addition, certain microglia and glioma cell pathways deserve special attention. These "synergistic" (we suggest calling them "Janus") pathways are active in both glioma cells and microglia/macrophages where they act in concert supporting malignant glioma progression. Examples include CCN4 (WISP1)/Integrin α6β1/Akt and CHI3L1/PI3K/Akt/mTOR. They represent attractive therapeutic targets.

The assembly of mammalian SWI/SNF chromatin remodeling complexes is regulated by lysine-methylation dependent proteolysis

The assembly of mammalian SWI/SNF chromatin remodeling complexes is developmentally programed, and loss/mutations of SWI/SNF subunits alter the levels of other components through proteolysis, causing cancers. Here, we show that mouse Lsd1/Kdm1a deletion causes dramatic dissolution of SWI/SNF complexes and that LSD1 demethylates the methylated lysine residues in SMARCC1 and SMARCC2 to preserve the structural integrity of SWI/SNF complexes. The methylated SMARCC1/SMARCC2 are targeted for proteolysis by L3MBTL3 and the CRL4DCAF5 ubiquitin ligase complex. We identify SMARCC1 as the critical target of LSD1 and L3MBTL3 to maintain the pluripotency and self-renewal of embryonic stem cells. L3MBTL3 also regulates SMARCC1/SMARCC2 proteolysis induced by the loss of SWI/SNF subunits. Consistently, mouse L3mbtl3 deletion causes striking accumulation of SWI/SNF components, associated with embryonic lethality. Our studies reveal that the assembly/disassembly of SWI/SNF complexes is dynamically controlled by a lysine-methylation dependent proteolytic mechanism to maintain the integrity of the SWI/SNF complexes.

Mechanisms of chromatin-based epigenetic inheritance

Multi-cellular organisms such as humans contain hundreds of cell types that share the same genetic information (DNA sequences), and yet have different cellular traits and functions. While how genetic information is passed through generations has been extensively characterized, it remains largely obscure how epigenetic information encoded by chromatin regulates the passage of certain traits, gene expression states and cell identity during mitotic cell divisions, and even through meiosis. In this review, we will summarize the recent advances on molecular mechanisms of epigenetic inheritance, discuss the potential impacts of epigenetic inheritance during normal development and in some disease conditions, and outline future research directions for this challenging, but exciting field.

Missing Causality and Heritability of Autoimmune Hepatitis

BACKGROUND

Autoimmune hepatitis has an unknown cause and genetic associations that are not disease-specific or always present. Clarification of its missing causality and heritability could improve prevention and management strategies.

AIMS

Describe the key epigenetic and genetic mechanisms that could account for missing causality and heritability in autoimmune hepatitis; indicate the prospects of these mechanisms as pivotal factors; and encourage investigations of their pathogenic role and therapeutic potential.

METHODS

English abstracts were identified in PubMed using multiple key search phases. Several hundred abstracts and 210 full-length articles were reviewed.

RESULTS

Environmental induction of epigenetic changes is the prime candidate for explaining the missing causality of autoimmune hepatitis. Environmental factors (diet, toxic exposures) can alter chromatin structure and the production of micro-ribonucleic acids that affect gene expression. Epistatic interaction between unsuspected genes is the prime candidate for explaining the missing heritability. The non-additive, interactive effects of multiple genes could enhance their impact on the propensity and phenotype of autoimmune hepatitis. Transgenerational inheritance of acquired epigenetic marks constitutes another mechanism of transmitting parental adaptations that could affect susceptibility. Management strategies could range from lifestyle adjustments and nutritional supplements to precision editing of the epigenetic landscape.

CONCLUSIONS

Autoimmune hepatitis has a missing causality that might be explained by epigenetic changes induced by environmental factors and a missing heritability that might reflect epistatic gene interactions or transgenerational transmission of acquired epigenetic marks. These unassessed or under-evaluated areas warrant investigation.

Liquid Crystal Droplet-Based Biosensors: Promising for Point-of-Care Testing

The development of biosensing platforms has been impressively accelerated by advancements in liquid crystal (LC) technology. High response rate, easy operation, and good stability of the LC droplet-based biosensors are all benefits of the long-range order of LC molecules. Bioprobes emerged when LC droplets were combined with biotechnology, and these bioprobes are used extensively for disease diagnosis, food safety, and environmental monitoring. The LC droplet biosensors have high sensitivity and excellent selectivity, making them an attractive tool for the label-free, economical, and real-time detection of different targets. Portable devices work well as the accessory kits for LC droplet-based biosensors to make them easier to use by anyone for on-site monitoring of targets. Herein, we offer a review of the latest developments in the design of LC droplet-based biosensors for qualitative target monitoring and quantitative target analysis.

Painters in chromatin: a unified quantitative framework to systematically characterize epigenome regulation and memory

In eukaryotes, many stable and heritable phenotypes arise from the same DNA sequence, owing to epigenetic regulatory mechanisms relying on the molecular cooperativity of 'reader-writer' enzymes. In this work, we focus on the fundamental, generic mechanisms behind the epigenome memory encoded by post-translational modifications of histone tails. Based on experimental knowledge, we introduce a unified modeling framework, the painter model, describing the mechanistic interplay between sequence-specific recruitment of chromatin regulators, chromatin-state-specific reader-writer processes and long-range spreading mechanisms. A systematic analysis of the model building blocks highlights the crucial impact of tridimensional chromatin organization and state-specific recruitment of enzymes on the stability of epigenomic domains and on gene expression. In particular, we show that enhanced 3D compaction of the genome and enzyme limitation facilitate the formation of ultra-stable, confined chromatin domains. The model also captures how chromatin state dynamics impact the intrinsic transcriptional properties of the region, slower kinetics leading to noisier expression. We finally apply our framework to analyze experimental data, from the propagation of γH2AX around DNA breaks in human cells to the maintenance of heterochromatin in fission yeast, illustrating how the painter model can be used to extract quantitative information on epigenomic molecular processes.

SPTSSA Is a Prognostic Marker for Glioblastoma Associated with Tumor-Infiltrating Immune Cells and Oxidative Stress

Background. SPTSSA encodes the small subunit A of serine palmitoyltransferase. It catalyzes the formation of sphingoid long-chain base backbone of sphingolipids. Its role in glioma prognosis and tumor-infiltrating immune cells remains unclear. Methods. We analyzed SPTSSA expression and association with clinical prognosis using GEPIA and CGGA database. Then, GSEA was performed to identify relevant biological functions of SPTSSA. The correlations between SPTSSA expression and tumor immune infiltrates were investigated using CIBERSORT and TIMER. Finally, IHC and IF were performed to confirm the value of prognosis and the correlation with immune infiltration. Results. SPTSSA expression was significantly upregulated in diffuse glioma compared to normal tissues and associated with poor survival in GEPIA and CGGA database. Then, we identified biological processes and signaling pathways associated with SPTSSA expression. The result showed that SPTSSA enriched in the GO term like oxidative stress. Finally, we showed that SPTSSA expression was significantly associated with tumor-infiltrating immune cells and overall survival via IHC. Conclusion. These findings suggest that SPTSSA expression might be used as a prognostic biomarker for glioma and potential target for novel glioma therapy.

An Epigenetic Role of Mitochondria in Cancer

Mitochondria are not only the main energy supplier but are also the cell metabolic center regulating multiple key metaborates that play pivotal roles in epigenetics regulation. These metabolites include acetyl-CoA, α-ketoglutarate (α-KG), S-adenosyl methionine (SAM), NAD⁺, and O-linked beta-N-acetylglucosamine (O-GlcNAc), which are the main substrates for DNA methylation and histone post-translation modifications, essential for gene transcriptional regulation and cell fate determination. Tumorigenesis is attributed to many factors, including gene mutations and tumor microenvironment. Mitochondria and epigenetics play essential roles in tumor initiation, evolution, metastasis, and recurrence. Targeting mitochondrial metabolism and epigenetics are promising therapeutic strategies for tumor treatment. In this review, we summarize the roles of mitochondria in key metabolites required for epigenetics modification and in cell fate regulation and discuss the current strategy in cancer therapies via targeting epigenetic modifiers and related enzymes in metabolic regulation. This review is an important contribution to the understanding of the current metabolic-epigenetic-tumorigenesis concept.

A simple pipeline for cell cycle kinetic studies in the root apical meristem

Root system architecture ultimately depends on precise signaling between different cells and tissues in the root apical meristem (RAM) and integration with environmental cues. This study describes a simple pipeline to simultaneously determine cellular parameters, nucleus geometry, and cell cycle kinetics in the RAM. The method uses marker-free techniques for nucleus and cell boundary detection, and 5-ethynyl-2'-deoxyuridine (EdU) staining for DNA replication quantification. Based on this approach, we characterized differences in cell volume, nucleus volume, and nucleus shape across different domains of the Arabidopsis RAM. We found that DNA replication patterns were cell layer and region dependent. G2 phase duration, which varied from 3.5 h in the pericycle to more than 4.5 h in the epidermis, was found to be associated with some features of nucleus geometry. Endocycle duration was determined as the time required to achieve 100% EdU-positive cells in the elongation zone and, as such, it was estimated to be in the region of 5 h for the epidermis and cortex. This experimental pipeline could be used to precisely map cell cycle duration in the RAM of mutants and in response to environmental stress in several plant species without the need for introgressing molecular cell cycle markers.

Connections between metabolism and epigenetics: mechanisms and novel anti-cancer strategy

Cancer cells undergo metabolic adaptations to sustain their growth and proliferation under several stress conditions thereby displaying metabolic plasticity. Epigenetic modification is known to occur at the DNA, histone, and RNA level, which can alter chromatin state. For almost a century, our focus in cancer biology is dominated by oncogenic mutations. Until recently, the connection between metabolism and epigenetics in a reciprocal manner was spotlighted. Explicitly, several metabolites serve as substrates and co-factors of epigenetic enzymes to carry out post-translational modifications of DNA and histone. Genetic mutations in metabolic enzymes facilitate the production of oncometabolites that ultimately impact epigenetics. Numerous evidences also indicate epigenome is sensitive to cancer metabolism. Conversely, epigenetic dysfunction is certified to alter metabolic enzymes leading to tumorigenesis. Further, the bidirectional relationship between epigenetics and metabolism can impact directly and indirectly on immune microenvironment, which might create a new avenue for drug discovery. Here we summarize the effects of metabolism reprogramming on epigenetic modification, and vice versa; and the latest advances in targeting metabolism-epigenetic crosstalk. We also discuss the principles linking cancer metabolism, epigenetics and immunity, and seek optimal immunotherapy-based combinations.

Liquid-liquid phase separation in tumor biology

Liquid–liquid phase separation (LLPS) is a novel principle for explaining the precise spatial and temporal regulation in living cells. LLPS compartmentalizes proteins and nucleic acids into micron-scale, liquid-like, membraneless bodies with specific functions, which were recently termed biomolecular condensates. Biomolecular condensates are executors underlying the intracellular spatiotemporal coordination of various biological activities, including chromatin organization, genomic stability, DNA damage response and repair, transcription, and signal transduction. Dysregulation of these cellular processes is a key event in the initiation and/or evolution of cancer, and emerging evidence has linked the formation and regulation of LLPS to malignant transformations in tumor biology. In this review, we comprehensively summarize the detailed mechanisms of biomolecular condensate formation and biophysical function and review the recent major advances toward elucidating the multiple mechanisms involved in cancer cell pathology driven by aberrant LLPS. In addition, we discuss the therapeutic perspectives of LLPS in cancer research and the most recently developed drug candidates targeting LLPS modulation that can be used to combat tumorigenesis.

Studying Epigenetics of Cardiovascular Diseases on Chip Guide

Epigenetics is defined as the study of inheritable changes in the gene expressions and phenotypes that occurs without altering the normal DNA sequence. These changes are mainly due to an alteration in chromatin or its packaging, which changes the DNA accessibility. DNA methylation, histone modification, and noncoding or microRNAs can best explain the mechanism of epigenetics. There are various DNA methylated enzymes, histone-modifying enzymes, and microRNAs involved in the cause of various CVDs (cardiovascular diseases) such as cardiac hypertrophy, heart failure, and hypertension. Moreover, various CVD risk factors such as diabetes mellitus, hypoxia, aging, dyslipidemia, and their epigenetics are also discussed together with CVDs such as CHD (coronary heart disease) and PAH (pulmonary arterial hypertension). Furthermore, different techniques involved in epigenetic chromatin mapping are explained. Among these techniques, the ChIP-on-chip guide is explained with regard to its role in cardiac hypertrophy, a final form of heart failure. This review focuses on different epigenetic factors that are involved in causing cardiovascular diseases.