Early clues to tumors and their microenvironments come from embryonic development. Here we review the literature and consider whether the embryonic brain and its pathologies can serve as a better model. Among embryonic organs, the brain is the most heterogenous and complex, with multiple lineages leading to wide spectrum of cell states and types. Its dysregulation promotes neurodevelopmental brain pathologies and pediatric tumors. Embryonic brain pathologies point to the crucial importance of spatial heterogeneity over time, akin to the tumor microenvironment. Tumors dedifferentiate through genetic mutations and epigenetic modulations; embryonic brains differentiate through epigenetic modulations. Our innovative review proposes learning developmental brain pathologies to target tumor evolution-and vice versa. We describe ways through which tumor pharmacology can learn from embryonic brains and their pathologies, and how learning tumor, and its microenvironment, can benefit targeting neurodevelopmental pathologies. Examples include pediatric low-grade versus high-grade brain tumors as in rhabdomyosarcomas and gliomas.

Chromatin regulation relies on "writer" enzymes that add posttranslational modifications to histone proteins. Variant polycomb repressive complex 1 (PRC1) exists as several subtypes, which are "writers" of ubiquitylation on histone H2A K118 and K119, crucial for transcriptional repression during development and cell identity determination. The mechanism by which dynamic chromatin exploration by variant PRC1 complexes couples to ubiquitin writing is unknown. Here, we developed a single-molecule approach to directly observe chromatin interactions and ubiquitylation by PRC1. We find that variant PRC1 transiently samples chromatin until it reaches a catalytically competent nucleosome-bound state, resulting in E2 recruitment and ubiquitin transfer. Variant PRC1 is weakly processive in ubiquitylating neighboring nucleosomes. Moreover, activity differences between PRC1 subtypes, containing either a PCGF1 or PCGF4 subunit, result from distinct probabilities of achieving a catalytically competent state. Our results thus demonstrate that the dynamic formation of an active complex between variant PRC1, E2, and chromatin is the critical determinant of subtype-specific variant PRC1 activity.

In order to advance personalized primary cancer prevention, surrogate endpoint biomarkers in distant, easy to access tissues (i.e., field defect indicators) reflecting field cancerization in the organ at risk are essential.

Here we utilized medroxyprogesterone acetate and 7,12-dimethylbenzanthracene to induce mammary gland cancers in mice. We assessed epigenetic signatures reflective of carcinogen exposure, cell-type composition, mitotic age, and methylation at progesterone receptor binding sites in both, the tissue at risk (normal mammary gland; field cancerization) and distant non-at-risk organs (cervix, oviduct, and blood; field defect indicators), in mice that did and did not develop mammary gland cancers.

We demonstrate that the anti-progestine mifepristone reduces the cancer risk by more than 50%. Importantly, the reduction in cancer risk is accompanied by a decline in both field cancerization and field defect indicators; specifically, epigenetic signatures in the cervix are predictive of mammary cancer formation but show tissue-specific directionality.

These data encourage further exploration of epigenetic biomarkers in certain field defect-indicating tissues with a view to monitor the efficacy of cancer prevention strategies in humans.

Aging is a key risk factor for many diseases, including cancer, and a better understanding of its underlying molecular mechanisms may help to prevent, delay, or treat age-related pathologies. Epigenetic alterations such as DNA methylation (DNAme) changes are a hallmark of aging and form the basis of so-called epigenetic clocks, yet their functional relevance and directionality in different organs during disease development is often unclear.

Here, we link cell-specific age-related DNAme changes with three key hallmarks of aging and cancer (senescence, promoter methylation in genes associated with stem cell fate, and dysregulated proliferation) to comprehensively dissect their association with current and future cancer development, carcinogen exposure or preventive measures, and mortality using data in different organs from over 12,510 human and 105 mouse samples, benchmarking against existing epigenetic clocks.

Our findings offer insights into the association of functionally enriched groups of age-related DNAme changes with cancer, identify sites perturbed earliest during carcinogenesis, as well as those distinct between cancer and reprogramming that could inform strategies to prevent teratoma formation upon in vivo reprogramming. Surprisingly, both mouse and human data reveal accelerated aging in breast cancer tissue but decelerated epigenetic aging in some non-cancer surrogate samples from breast cancer patients, in particular cervical samples.

This work provides evidence for discordant systemic tissue aging in breast cancer.

Burkitt lymphoma (BL) is an aggressive germinal center B-cell-derived malignancy. Historically, sporadic, endemic, and immunodeficiency-associated variants were distinguished, which differ in the frequency of Epstein-Barr virus (EBV) positivity. Aiming to identify subgroups based on DNA methylation patterns, we here profiled 96 BL cases, 17 BL cell lines, and six EBV-transformed lymphoblastoid cell lines using Illumina BeadChip arrays. DNA methylation analyses clustered the cases into four subgroups: two containing mostly EBV-positive cases (BL-mC1, BL-mC2) and two containing mostly EBV-negative cases (BL-mC3, BL-mC4). The subgroups BL-mC1/2, enriched for EBV-positive cases, showed increased DNA methylation, epigenetic age, and, in part, proliferation history compared to BL-mC3/4. CpGs hypermethylated in EBV-positive BLs were enriched for polycomb repressive complex 2 marks, while the CpGs hypomethylated in EBV-negative BLs were linked to, for example, B-cell receptor signaling. EBV-associated hypermethylation affected regulatory regions of genes frequently mutated in BL (e.g., CCND3, TP53) and impacted superenhancers. This finding suggests that hypermethylation may compensate for the lower mutational burden of pathogenic drivers in EBV-positive BLs. Though minor, significant differences were also observed between EBV-positive endemic and sporadic cases (e.g., at the SOX11 and RUNX1 loci). Our findings suggest that EBV status, rather than epidemiological variants, drives the DNA methylation-based subgrouping of BL.

The quest for effective cancer therapeutics has traditionally centered on targeting mutated or overexpressed oncogenic proteins. However, challenges arise in cancers with low mutational burden or when the mutated oncogene is not conventionally targetable, which are common situations in childhood cancers. This obstacle has sparked large-scale unbiased screens to identify collateral genetic dependencies crucial for cancer cell growth. These screens have revealed promising targets for therapeutic intervention in the form of lineage-selective dependency genes, which may have an expanded therapeutic window compared to pan-lethal dependencies. Many lineage-selective dependencies regulate gene expression and are closely tied to the developmental origins of pediatric tumors. Placing lineage-selective dependencies in a transcriptional network model is helpful for understanding their roles in driving malignant cell behaviors. Here, we discuss the identification of lineage-selective dependencies and how two transcriptional models, core regulatory circuits and gene regulatory networks, can serve as frameworks for understanding their individual and collective actions, particularly in cancers affecting children and young adults.

Aberrant upregulation or mutations of EZH2 frequently occur in human cancers. However, the clinical benefits of EZH2 inhibitors (EZH2i) remain unsatisfactory for majority of solid tumors. Therefore, there is an urgent need to develop new strategies to expand the therapeutic benefits of EZH2i. Nanocarriers have gained increased attention due to their advantages of prolonged blood circulation, enhanced cellular uptake, and active targeting capabilities. This study aims to address the challenges of EZH2i GSK126's limited efficacy and severe adverse effects against solid tumors.

A nano delivery system was developed by encapsulating GSK126 within albumin nanoparticles (GSK126 NPs).

The prepared GSK126 NPs exhibited a small spherical core with an average diameter of 30.09 nm ± 1.55 nm, high drug loading capacity (16.59% ± 2.86%) and good entrapment efficiency (99.53% ± 0.208%). GSK126 NPs decreased tumor weight and volume in the B16F10 xenograft mice, while such effects were not observed in the free GSK126 group. Subsequently, histological analysis demonstrated that GSK126 NPs significantly alleviated lipid-associated liver toxicity. Additionally, GSK126 NPs can partially counteract the effects of GSK126 on MDSCs, particularly by decreasing the infiltration of M-MDSCs into tumors.

Albumin-based EZH2i NPs have potent anti-cancer efficacy with tolerable adverse effects, providing promising opportunity for future clinical translation in treating solid tumors.

Embryonic DNA damage resulting from DNA repair deficiencies or exposure to ionizing radiation during early neurogenesis can lead to neurodevelopmental disorders, including microcephaly. This has been linked to an excessive DNA damage response in dorsal neural progenitor cells (NPCs), resulting in p53-dependent apoptosis and premature neuronal differentiation which culminates in depletion of the NPC pool. However, the effect of DNA damage on ventral forebrain NPCs, the origin of interneurons, remains unclear. In this study, we investigated the sequelae of irradiation of mouse fetuses at an early timepoint of forebrain neurogenesis. We focused on the neocortex (NCX) and medial ganglionic eminence (MGE), key regions for developing dorsal and ventral NPCs, respectively. Although both regions showed a typical p53-mediated DNA damage response consisting of cell cycle arrest, DNA repair and apoptosis, NCX cells displayed prolonged cell cycle arrest, while MGE cells exhibited more sustained apoptosis. Moreover, irradiation reduced the migration speed of interneurons in acute living brain slices and MGE explants, the latter indicating a cell-intrinsic component in the defect. RNA sequencing and protein analyses revealed disruptions in actin and microtubule cytoskeletal-related cellular machinery, particularly in MGE cells. Despite massive acute apoptosis and an obvious interneuron migration defect, prenatally irradiated animals did not show increased sensitivity to pentylenetetrazole-induced seizures, nor was there a reduction in cortical interneurons in young adult mice. This suggests a high plasticity of the developing brain to acute insults during early neurogenesis. Overall, our findings indicate that embryonic DNA damage induces region-specific responses, potentially linked to neurodevelopmental disorders.

The olfactory epithelium is one of the few regions of the nervous system that sustains neurogenesis throughout life. Its experimental accessibility makes it especially tractable for studying molecular mechanisms that drive neural regeneration in response to injury. In this study, we used single-cell sequencing to identify the transcriptional cascades and epigenetic processes involved in determining olfactory epithelial stem cell fate during injury-induced regeneration. By combining gene expression and accessible chromatin profiles of individual lineage-traced olfactory stem cells, we identified transcriptional heterogeneity among activated stem cells at a stage when cell fates are being specified. We further identified a subset of resting cells that appears poised for activation, characterized by accessible chromatin around wound response and lineage-specific genes prior to their later expression in response to injury. Together these results provide evidence for a latent activated stem cell state, in which a subset of quiescent olfactory epithelial stem cells are epigenetically primed to support injury-induced regeneration.

Polycomb Repressive Complex 2 (PRC2) is a central regulator of gene expression via the trimethylation of histone H3 on lysine 27. This epigenetic modification plays a crucial role in maintaining cell identity and controlling differentiation, while its dysregulation is closely linked to cancer progression. PRC2 silences tumor suppressor genes, promoting cell proliferation, metastasis, epithelial-mesenchymal transition, and cancer stem cell plasticity. Enhancement of zeste homolog 2 (EZH2) overexpression or gain-of-function mutations have been observed in several cancers, including lymphoma, breast, and prostate cancers, driving aggressive tumor behavior and drug resistance. In addition to EZH2, other PRC2 components, such as embryonic ectoderm development (EED) and suppressor of zeste 12, are essential for complex stability and function. EED, in particular, enhances EZH2 activity and has emerged as a therapeutic target. Inhibitors like MAK683 and EED226 disrupt EED's ability to maintain PRC2 activity, thereby reducing H3K27me3 levels and reactivating tumor suppressor genes. Valemetostat, a dual inhibitor of both EZH2 and EED, has shown promising results in aggressive cancers like diffuse large B-cell lymphoma and small-cell lung cancer, underlining the therapeutic potential of targeting multiple PRC2 components. PRC2's role extends beyond gene repression, as it contributes to metabolic reprogramming in tumors, regulating glycolysis and lipid synthesis to fuel cancer growth. Furthermore, PRC2 is implicated in chemoresistance, particularly by modulating DNA damage response and immune evasion. Tazemetostat, a selective EZH2 inhibitor, has demonstrated significant clinical efficacy in EZH2-mutant cancers, such as non-Hodgkin lymphomas and epithelioid sarcoma. However, the compensatory function of enhancer of zeste homolog 1 (EZH1) in some cancers requires dual inhibition strategies, as seen with agents like UNC1999 and Tulmimetostat, which target both EZH1 and EZH2. Given PRC2's multifaceted role in cancer biology, its inhibition represents a promising avenue for therapeutic intervention. The continued development of PRC2 inhibitors and exploration of their use in combination with standard chemotherapy or immunotherapy has great potential for improving patient outcomes in cancers driven by PRC2 dysregulation.

Mutations in the tumor suppressor genes BRCA1 and BRCA2 are associated with the triple-negative breast cancer phenotype, particularly aggressive and hard-to-treat tumors lacking estrogen, progesterone, and human epidermal growth factor receptor 2. This research aimed to understand the metabolic and genetic links behind BRCA1 and BRCA2 mutations and investigate their relationship with effective therapies. Using the Cytoscape software, two networks were generated through a bibliographic analysis of articles retrieved from the PubMed-NCBI database. We identified 98 genes deregulated by BRCA mutations, and 24 were modulated by therapies. In particular, BIRC5, SIRT1, MYC, EZH2, and CSN2 are influenced by BRCA1, while BCL2, BAX, and BRIP1 are influenced by BRCA2 mutation. Moreover, the study evaluated the efficacy of several promising therapies, targeting only BRCA1/BRCA2-mutated cells. In this context, CDDO-Imidazolide was shown to increase ROS levels and induce DNA damage. Similarly, resveratrol decreased the expression of the anti-apoptotic gene BIRC5 while it increased SIRT1 both in vitro and in vivo. Other specific drugs were found to induce apoptosis selectively in BRCA-mutated cells or block cell growth when the mutation occurs, i.e., 3-deazaneplanocin A, genistein or daidzein, and PARP inhibitors. Finally, over-representation analysis on the genes highlights ferroptosis and proteoglycan pathways as potential drug targets for more effective treatments.

Epigenetic modifications of chromatin are essential for the establishment of cell identities during embryogenesis. Between embryonic days 3.5-7.5 of murine development, major cell lineage decisions are made that discriminate extraembryonic and embryonic tissues, and the embryonic primary germ layers are formed, thereby laying down the basic body plan. In this review, we cover the contribution of dynamic chromatin modifications by DNA methylation, changes of chromatin accessibility, and histone modifications, that in combination with transcription factors control gene expression programs of different cell types. We highlight the differences in regulation of enhancer and promoter marks and discuss their requirement in cell lineage specification. Importantly, in many cases, lineage-specific targeting of epigenetic modifiers is carried out by pioneer or master transcription factors, that in sum mediate the chromatin landscape and thereby control the transcription of cell-type-specific gene programs and thus, cell identities.

The mutation status of the lysine demethylase 6 A (KDM6A), a gene antagonist to Enhancer of zeste homolog 2 (EZH2), is closely related to the therapeutic efficacy of EZH2 inhibitors in several malignancies. However, the mutational landscape of KDM6A and the therapeutic targetability of EZH2 inhibitors in esophageal squamous carcinoma (ESCC) remain unreported. Here, we found that approximately 9.18% (9/98) of our study ESCC tissues had KDM6A mutations of which 7 cases resulted in a complete loss of expression and consequent loss of demethylase function. We found that KDM6A-deficient ESCC cells exhibited increased sensitivity to EZH2 inhibitor, and the radiosensitizing activity of EZH2 inhibitor was evident in KDM6A-dficient ESCC cells. Further transcriptome analysis revealed that ferroptosis is implicated in the radiosensitizing effect exerted by EZH2 inhibition on KDM6A-deficient ESCC cells. The following Chromatin Immunoprecipitation (ChIP), co-immunoprecipitation, and luciferase reporter assays demonstrated that in KDM6A-deficient ESCC cells, (1) Acyl-CoA Synthetase Long Chain Family Member 4 (ACSL4) is the target gene for EZH2 to regulate ferroptosis; (2) The IR-induced hypoxia inducible factor 1 subunit alpha (HIF-1α) is a predominant mediator of EZH2 to repress ACSL4; (3) the HRE7-8 regions of the ACSL4 promoter are required for the repressive function of EZH2 on ACSL4; (4) EZH2 regulates ACSL4 by forming a co-repressive complex with HIF-1α. Our study provides preclinical evidence supporting that EZH2 inhibitors may confer therapeutic benefit in KDM6A-deficient ESCC patients.

Chromatin immunoprecipitation coupled with next-generation sequencing (ChIP-seq) is a crucial method for examining transcription factor binding and histone modifications across the entire genome. This is a key step in deciphering the complex mechanisms that control cancer immunosurveillance. Here, we provide a comprehensive protocol covering all the steps needed to obtain DNA for ChIP-seq library preparation, starting from tissue dissection, followed by fixation, chromatin preparation, immunoprecipitation, and finally DNA purification. The protocol is optimized for frozen mice tissues, but can be easily adapted for use with any model organism. The resulting immunoprecipitated chromatin is suitable for library preparation and sequencing on an Illumina platform.

Polycomb group (PcG) proteins play key roles in development by repressing thousands of targets through histone modifications. However, how PcG is recruited to specific targets is poorly understood. In Arabidopsis, certain noncoding RNAs are necessary for recruiting the PcG protein CURLY LEAF (CLF) to its target sites. However, RNAs associated with CLF have not been analyzed on a genomic scale; thus, it is unknown whether long noncoding RNA (lncRNA)-mediated PcG recruitment is a widespread mechanism. Here, we systematically searched for CLF-associated RNAs by RNA immunoprecipitation followed by deep sequencing. We identified 1,299 genic and 138 intergenic regions that produced CLF-associated mRNAs and putative lncRNAs, respectively. The genes producing CLF-associated RNAs are depleted in PcG targets, carry active chromatin marks, and are highly expressed, suggesting that CLF may have a nonspecific or promiscuous RNA-binding affinity, similar to animal PcG proteins. Notably, a significant portion of the CLF-associated lncRNAs is derived from the nuclear mitochondrial sequence, which is extensively marked by H3K27me3. These findings indicate that, while CLF-RNA interactions are widespread, they may not always correlate with PcG target sites, highlighting the complexity of PcG recruitment mechanisms in Arabidopsis.

Polycomb Repressive Complex 1 (PRC1) and CCCTC-binding factor (CTCF) are critical regulators of 3D chromatin architecture that influence cellular transcriptional programs. Spatial chromatin structures comprise conserved compartments, topologically associating domains (TADs), and dynamic, cell-type-specific chromatin loops. Although the role of CTCF in chromatin organization is well-known, the involvement of PRC1 is less understood. In this study, we identified an unexpected, essential role for the canonical Pcgf2-containing PRC1 complex (cPRC1.2), a known transcriptional repressor, in activating bivalent genes during differentiation. Our Hi-C analysis revealed that cPRC1.2 forms chromatin loops at bivalent promoters, rendering them silent yet poised for activation. Using mouse embryonic stem cells (ESCs) with CRISPR/Cas9-mediated gene editing, we found that the loss of Pcgf2, though not affecting the global level of H2AK119ub1, disrupts these cPRC1.2 loops in ESCs and impairs the transcriptional induction of crucial target genes necessary for neuronal differentiation. Furthermore, we identified CTCF enrichment at cPRC1.2 loop anchors and at Polycomb group (PcG) bodies, nuclear foci with concentrated PRC1 and its tethered chromatin domains, suggesting that PRC1 and CTCF cooperatively shape chromatin loop structures. Through virtual 4C and other genomic analyses, we discovered that establishing neuronal progenitor cell (NPC) identity involves a switch from cPRC1.2-mediated chromatin loops to CTCF-mediated active loops, enabling the expression of critical lineage-specific factors. This study uncovers a novel mechanism by which pre-formed PRC1 and CTCF loops at lineage-specific genes maintain a poised state for subsequent gene activation, advancing our understanding of the role of chromatin architecture in controlling cell fate transitions.

Ovarian cancer (OC) is a common gynecological disease with a high mortality rate worldwide due to its insidious nature and undetectability at an early stage. The standard treatment, combining platinum‑based chemotherapy with cytoreductive surgery, has suboptimal results. Therefore, early diagnosis of OC is crucial. All cell types secrete extracellular vesicles, particularly exosomes. Exosomes, which contain lipids, proteins, DNA and non‑coding RNAs (ncRNAs), are novel methods of intercellular communication that participate in tumor development and progression. ncRNAs are categorized by size into long ncRNAs (lncRNAs) and small ncRNAs (sncRNAs). sncRNAs further include transfer RNAs, small nucleolar RNAs, PIWI‑interacting RNAs and microRNAs (miRNAs). miRNAs inhibit protein translation and promote messenger RNA (mRNA) cleavage to suppress gene expression. By sponging downstream miRNAs, lncRNAs and circular RNAs can regulate target gene expression, thereby weakening the interactions between miRNAs and mRNAs. Exosomes and exosomal ncRNAs, commonly present in human biological fluids, are promising biomarkers for OC. The present article aimed to review the potential role of exosomal ncRNAs in the diagnosis and prognosis of OC by summarizing the characteristics, processes, roles and isolation methods of exosomes and exosomal ncRNAs.

The immunosuppressive function of regulatory T (Treg) cells is essential for maintaining immune homeostasis. Enhancer of zeste homolog 2 (EZH2), a histone H3 lysine 27 (H3K27) methyltransferase, plays a key role in maintaining Treg cell function upon CD28 co-stimulation, and Ezh2 deletion in Treg cells causes autoimmunity. Here, we assess whether increasing H3K27me3 levels, by using an Ezh2Y641F gain-of-function mutation, will improve Treg cell function. We find that Treg cells expressing Ezh2Y641F display an effector Treg phenotype, are poised for improved homing to organ tissues, and can accelerate remission from autoimmunity. The H3K27me3 landscape and transcriptome of naive Ezh2Y641F Treg cells exhibit a redistribution of H3K27me3 modifications that recapitulates the gene expression profile of activated Ezh2WT Treg cells after CD28 co-stimulation. Altogether, increased H3K27me3 levels promote the differentiation of effector Treg cells that can better suppress autoimmunity.

Pediatric low grade brain tumors and neurodevelopmental disorders share proteins, signaling pathways, and networks. They also share germline mutations and an impaired prenatal differentiation origin. They may differ in the timing of the events and proliferation. We suggest that their pivotal distinct, albeit partially overlapping, outcomes relate to the cell states, which depend on their spatial location, and timing of gene expression during brain development. These attributes are crucial as the brain develops sequentially, and single-cell spatial organization influences cell state, thus function. Our underlying premise is that the root cause in neurodevelopmental disorders and pediatric tumors is impaired prenatal differentiation. Data related to pediatric brain tumors, neurodevelopmental disorders, brain cell (sub)types, locations, and timing of expression in the developing brain are scant. However, emerging single cell technologies, including transcriptomic, spatial biology, spatial high-resolution imaging performed over the brain developmental time, could be transformational in deciphering brain pathologies thereby pharmacology.

The Lys mutation of the canonical histone H3.1 Glu97 residue (H3E97K) is found in cancer cells. Previous biochemical analyses revealed that the nucleosome containing the H3E97K mutation is extremely unstable as compared to the wild-type nucleosome. However, the mechanism by which the H3E97K mutation causes nucleosome instability has not been clarified yet. In the present study, the cryo-electron microscopy structure of the nucleosome containing the H3E97K mutation revealed that the entry/exit DNA regions of the H3E97K nucleosome are disordered, probably by detachment of the nucleosomal DNA from the H3 N-terminal regions. This may change the intra-molecular amino acid interactions with the replaced H3 Lys97 residue, inducing structural distortion around the mutated position in the nucleosome. Consistent with the nucleosomal DNA end flexibility and the nucleosome instability, the H3E97K mutation exhibited reduced binding of linker histone H1 to the nucleosome, defective activation of PRC2 (the essential methyltransferase for facultative heterochromatin formation) with a poly-nucleosome, and enhanced nucleosome transcription by RNA polymerase II.

Monkeypox virus (MPV) is known to inflict injuries and, in some cases, lead to fatalities in humans. However, the underlying mechanisms responsible for its pathogenicity remain poorly understood. We investigated functions of MPV core proteins, H3L, A35R, A29L, and I1L, and discovered that H3L induced transcriptional perturbations and injuries. We substantiated that H3L upregulated IL1A expression. IL1A, in consequence, caused cellular injuries, and this detrimental effect was mitigated when countered with IL1A blockage. We also observed that H3L significantly perturbed the transcriptions of genes in cardiac system. Mechanistically, H3L occupied the promoters of genes governing cellular injury, leading to alterations in the binding patterns of H3K27me3 and H3K4me3 histone marks, ultimately resulting in expression perturbations. In vivo and in vitro models confirmed that H3L induced transcriptional disturbances and cardiac dysfunction, which were ameliorated when IL1A was blocked or repressed. Our study provides valuable insights into comprehensive understanding of MPV pathogenicity, highlights the significant roles of H3L in inducing injuries, and potentially paves the way for the development of therapeutic strategies targeting IL1A.

Animal body plans are established during embryonic development by the Hox genes. This patterning process relies on the differential expression of Hox genes along the head-to-tail axis. Hox spatial collinearity refers to the relationship between the organization of Hox genes in clusters and the differential Hox expression, whereby the relative order of the Hox genes within a cluster mirrors the spatial sequence of expression in the developing embryo. In vertebrates, the cluster organization is also associated with the timing of Hox activation, which harmonizes Hox expression with the progressive emergence of axial tissues. Thereby, in vertebrates, Hox temporal collinearity is intimately linked to Hox spatial collinearity. Understanding the mechanisms contributing to Hox temporal and spatial collinearity is thus key to the comprehension of vertebrate patterning. Here, we provide an overview of the main discoveries pertaining to the mechanisms of Hox spatial-temporal collinearity.

In eukaryotes, DNA is packaged into chromatin with the help of highly conserved histone proteins. Together with DNA-binding proteins, posttranslational modifications (PTMs) on these histones play crucial roles in regulating genome function, cell fate determination, inheritance of acquired traits, cellular states, and diseases. While most studies have focused on individual DNA-binding proteins, chromatin proteins, or histone PTMs in bulk cell populations, such chromatin features co-occur and potentially act cooperatively to accomplish specific functions in a given cell. This review discusses state-of-the-art techniques for the simultaneous profiling of multiple chromatin features in low-input samples and single cells, focusing on histone PTMs, DNA-binding, and chromatin proteins. We cover the origins of the currently available toolkits, compare and contrast their characteristic features, and discuss challenges and perspectives for future applications. Studying the co-occurrence of histone PTMs, DNA-binding proteins, and chromatin proteins in single cells will be central for a better understanding of the biological relevance of combinatorial chromatin features, their impact on genomic output, and cellular heterogeneity.

Cell fate determination is an intricate process which is orchestrated by multiple regulatory layers including signal pathways, transcriptional factors, epigenetic modifications, and metabolic rewiring. Among the sophisticated epigenetic modulations, the repressive mark H3K27me3, deposited by PRC2 (polycomb repressive complex 2) and removed by demethylase KDM6, plays a pivotal role in mediating the cellular identity transition through its dynamic and precise alterations. Herein, we overview and discuss how H3K27me3 and its modifiers regulate pluripotency maintenance and early lineage differentiation. We primarily highlight the following four aspects: 1) the two subcomplexes PRC2.1 and PRC2.2 and the distribution of genomic H3K27 methylation; 2) PRC2 as a critical regulator in pluripotency maintenance and exit; 3) the emerging role of the eraser KDM6 in early differentiation; 4) newly identified additional factors influencing H3K27me3. We present a comprehensive insight into the molecular principles of the dynamic regulation of H3K27me3, as well as how this epigenetic mark participates in pluripotent stem cell-centered cell fate determination.

The Polycomb Repressive Complex 2 (PRC2) regulates corticogenesis, yet the consequences of mutations to this epigenetic modifier in the mature brain are poorly defined. Importantly, PRC2 core genes are haploinsufficient and causative of several human neurodevelopmental disorders. To address the role of PRC2 in mature cortical structure and function, we conditionally deleted the PRC2 gene Eed from the developing mouse dorsal telencephalon. Adult homozygotes displayed smaller forebrain structures. Single-nucleus transcriptomics revealed that glutamatergic neurons were particularly affected, exhibiting dysregulated gene expression profiles, accompanied by aberrations in neuronal morphology and connectivity. Remarkably, homozygous mice performed well on challenging cognitive tasks. In contrast, while heterozygous mice did not exhibit clear anatomical or behavioral differences, they displayed dysregulation of neuronal genes and altered neuronal morphology that was strikingly different from homozygous phenotypes. Collectively, these data reveal how alterations to PRC2 function shape the mature brain and reveal a dose-specific role for PRC2 in determining glutamatergic neuron identity.

DNA methylation is an epigenetic mark that plays an important role in defining cancer phenotypes, with global hypomethylation and focal hypermethylation at CpG islands observed in tumors. These methylation marks can also be used to define tumor types and provide an avenue for biomarker identification. The homeobox gene class is one that has potential for this use, as well as other genes that are Polycomb Repressive Complex 2 targets. To begin to unravel this relationship, we performed a pan-cancer DNA methylation analysis using sixteen Illumina HM450k array datasets from TCGA, delving into cancer-specific qualities and commonalities between tumor types with a focus on homeobox genes. Our comparisons of tumor to normal samples suggest that homeobox genes commonly harbor significant hypermethylated differentially methylated regions. We identified two homeobox genes, HOXA3 and HOXD10, that are hypermethylated in all 16 cancer types. Furthermore, we identified several potential homeobox gene biomarkers from our analysis that are uniquely methylated in only one tumor type and that could be used as screening tools in the future. Overall, our study demonstrates unique patterns of DNA methylation in multiple tumor types and expands on the interplay between the homeobox gene class and oncogenesis.

Tobacco use is a major modifiable risk factor for adverse health outcomes, including cancer, and elicits profound epigenetic changes thought to be associated with long-term cancer risk. While electronic cigarettes (e-cigarettes) have been advocated as harm reduction alternatives to tobacco products, recent studies have revealed potential detrimental effects, highlighting the urgent need for further research into the molecular and health impacts of e-cigarettes. Here, we applied computational deconvolution methods to dissect the cell- and tissue-specific epigenetic effects of tobacco or e-cigarette use on DNA methylation (DNAme) in over 3,500 buccal/saliva, cervical, or blood samples, spanning epithelial and immune cells at directly and indirectly exposed sites. The 535 identified smoking-related DNAme loci [cytosine-phosphate-guanine sites (CpG)] clustered into four functional groups, including detoxification or growth signaling, based on cell type and anatomic site. Loci hypermethylated in buccal epithelial cells of smokers associated with NOTCH1/RUNX3/growth factor receptor signaling also exhibited elevated methylation in cancer tissue and progressing lung carcinoma in situ lesions, and hypermethylation of these sites predicted lung cancer development in buccal samples collected from smokers up to 22 years prior to diagnosis, suggesting a potential role in driving carcinogenesis. Alarmingly, these CpGs were also hypermethylated in e-cigarette users with a limited smoking history. This study sheds light on the cell type-specific changes to the epigenetic landscape induced by smoking-related products.

The use of both cigarettes and e-cigarettes elicits cell- and exposure-specific epigenetic effects that are predictive of carcinogenesis, suggesting caution when broadly recommending e-cigarettes as aids for smoking cessation.

Familial Dysautonomia (FD) is a rare disease caused by ELP1 exon 20 skipping. Here we clarify the role of RNA Polymerase II (RNAPII) and chromatin on this splicing event. A slow RNAPII mutant and chromatin-modifying chemicals that reduce the rate of RNAPII elongation induce exon skipping whereas chemicals that create a more relaxed chromatin exon inclusion. In the brain of a mouse transgenic for the human FD-ELP1 we observed on this gene an age-dependent decrease in the RNAPII density profile that was most pronounced on the alternative exon, a robust increase in the repressive marks H3K27me3 and H3K9me3 and a decrease of H3K27Ac, together with a progressive reduction in ELP1 exon 20 inclusion level. In HEK 293T cells, selective drug-induced demethylation of H3K27 increased RNAPII elongation on ELP1 and SMN2, promoted the inclusion of the corresponding alternative exons, and, by RNA-sequencing analysis, induced changes in several alternative splicing events. These data suggest a co-transcriptional model of splicing regulation in which age-dependent changes in H3K27me3/Ac modify the rate of RNAPII elongation and affect processing of ELP1 alternative exon 20.

The regulation of PD-L1 is the key question, which largely determines the outcome of the immune checkpoint inhibitors (ICIs) based therapy. However, besides the transcription level, the protein stability of PD-L1 is closely correlated with its function and has drawn increasing attention. In this study, EZH2 inhibition enhances PD-L1 expression and protein stability, and the deubiquitinase ubiquitin-specific peptidase 22 (USP22) is identified as a key mediator in this process. EZH2 inhibition transcriptionally upregulates USP22 expression, and upregulated USP22 further stabilizes PD-L1. Importantly, a combination of EZH2 inhibitors with anti-PD-1 immune checkpoint blockade therapy improves the tumor microenvironment, enhances sensitivity to immunotherapy, and exerts synergistic anticancer effects. In addition, knocking down USP22 can potentially enhance the therapeutic efficacy of EZH2 inhibitors on colon cancer. These findings unveil the novel role of EZH2 inhibitors in tumor immune evasion by upregulating PD-L1, and this drawback can be compensated by combining ICI immunotherapy. Therefore, these findings provide valuable insights into the EZH2-USP22-PD-L1 regulatory axis, shedding light on the optimization of combining both immune checkpoint blockade and EZH2 inhibitor-based epigenetic therapies to achieve more efficacies and accuracy in cancer treatment.

This review article critically examines the pivotal role of chromatin organization in gene regulation, cellular differentiation, disease progression and aging. It explores the dynamic between the euchromatin and heterochromatin, coded by a complex array of histone modifications that orchestrate essential cellular processes. We discuss the pathological impacts of chromatin state misregulation, particularly in cancer and accelerated aging conditions such as progeroid syndromes, and highlight the innovative role of epigenetic therapies and artificial intelligence (AI) in comprehending and harnessing the histone code toward personalized medicine. In the context of aging, this review explores the use of AI and advanced machine learning (ML) algorithms to parse vast biological datasets, leading to the development of predictive models for epigenetic modifications and providing a framework for understanding complex regulatory mechanisms, such as those governing cell identity genes. It supports innovative platforms like CEFCIG for high-accuracy predictions and tools like GridGO for tailored ChIP-Seq analysis, which are vital for deciphering the epigenetic landscape. The review also casts a vision on the prospects of AI and ML in oncology, particularly in the personalization of cancer therapy, including early diagnostics and treatment optimization for diseases like head and neck and colorectal cancers by harnessing computational methods, AI advancements and integrated clinical data for a transformative impact on healthcare outcomes.

The three-dimensional organization of the genome plays a central role in the regulation of cellular functions, particularly in the human brain. This review explores the intricacies of chromatin organization, highlighting the distinct structural patterns observed between neuronal and non-neuronal brain cells. We integrate findings from recent studies to elucidate the characteristics of various levels of chromatin organization, from differential compartmentalization and topologically associating domains (TADs) to chromatin loop formation. By defining the unique chromatin landscapes of neuronal and non-neuronal brain cells, these distinct structures contribute to the regulation of gene expression specific to each cell type. In particular, we discuss potential functional implications of unique neuronal chromatin organization characteristics, such as weaker compartmentalization, neuron-specific TAD boundaries enriched with active histone marks, and an increased number of chromatin loops. Additionally, we explore the role of Polycomb group (PcG) proteins in shaping cell-type-specific chromatin patterns. This review further emphasizes the impact of variations in chromatin architecture between neuronal and non-neuronal cells on brain development and the onset of neurological disorders. It highlights the need for further research to elucidate the details of chromatin organization in the human brain in order to unravel the complexities of brain function and the genetic mechanisms underlying neurological disorders. This research will help bridge a significant gap in our comprehension of the interplay between chromatin structure and cell functions.

Epigenetic changes are known to accrue in normal cells as a result of ageing and cumulative exposure to cancer risk factors. Increasing evidence points towards age-related epigenetic changes being acquired in a quasi-stochastic manner, and that they may play a causal role in cancer development. Here, I describe the quasi-stochastic nature of DNA methylation (DNAm) changes in ageing cells as well as in normal cells at risk of neoplastic transformation, discussing the implications of this stochasticity for developing cancer risk prediction strategies, and in particular, how it may require a conceptual paradigm shift in how we select cancer risk markers. I also describe the mounting evidence that a significant proportion of DNAm changes in ageing and cancer development are related to cell proliferation, reflecting tissue-turnover and the opportunity this offers for predicting cancer risk via the development of epigenetic mitotic-like clocks. Finally, I describe how age-associated DNAm changes may be causally implicated in cancer development via an irreversible suppression of tissue-specific transcription factors that increases epigenetic and transcriptomic entropy, promoting a more plastic yet aberrant cancer stem-cell state. This article is part of a discussion meeting issue 'Causes and consequences of stochastic processes in development and disease'.

The immunosuppressive function of regulatory T (Treg) cells is essential for maintaining immune homeostasis. Enhancer of zeste homolog 2 (EZH2), a histone H3 lysine 27 (H3K27) methyltransferase, plays a key role in maintaining Treg cell function upon CD28 co-stimulation, and Ezh2 deletion in Treg cells causes autoimmunity. Here we assessed whether increased EZH2 activity in Treg cells would improve Treg cell function. Using an Ezh2 gain-of-function mutation, Ezh2 Y641F , we found that Treg cells expressing Ezh2 Y641F displayed an increased effector Treg phenotype and were poised for improved homing to organ tissues. Expression of Ezh2 Y641F in Treg cells led to more rapid remission from autoimmunity. H3K27me3 profiling and transcriptomic analysis revealed a redistribution of H3K27me3, which prompted a gene expression profile in naïve Ezh2 Y641F Treg cells that recapitulated aspects of CD28-activated Ezh2 WT Treg cells. Altogether, increased EZH2 activity promotes the differentiation of effector Treg cells that can better suppress autoimmunity.

EZH2 function promotes effector differentiation of Treg cells.EZH2 function promotes Treg cell migration to organ tissues.EZH2 function in Treg cells improves remission from autoimmunity.EZH2 function poises naïve Treg cells to adopt a CD28-activated phenotype.

Epigenetic regulation of gene expression plays a crucial role in plant development and environmental adaptation. The H3K4me3 and H3K27me3 have not only been discovered in the regulation of gene expression in multiple biological processes but also in responses to abiotic stresses in plants. However, evidence for the presence of both H3K4me3 and H3K27me3 on the same nucleosome is sporadic. Cold-induced deposition of bivalent H3K4me3-H3K27me3 modifications and nucleosome depletion over a considerable number of active genes is documented in potato tubers and provides clues on an additional role of the bivalent modifications. Limited by the available information of genes encoding PcG/TrxG proteins as well as their corresponding mutants in potatoes, the molecular mechanism underlying the cold-induced deposition of the bivalent mark remains elusive. In this study, we found a similar deposition of the bivalent H3K4me3-H3K27me3 mark over 2129 active genes in cold-treated Arabidopsis Col-0 seedlings. The expression levels of the bivalent mark-associated genes tend to be independent of bivalent modification levels. However, these genes were associated with greater chromatin accessibility, presumably to provide a distinct chromatin environment for gene expression. In mutants clf28 and lhp1, failure to deposit H3K27me3 in active genes upon cold treatment implies that the CLF is potentially involved in cold-induced deposition of H3K27me3, with assistance from LHP1. Failure to deposit H3K4me3 during cold treatment in atx1-2 suggests a regulatory role of ATX1 in the deposition of H3K4me3. In addition, we observed a cold-induced global reduction in nucleosome occupancy, which is potentially mediated by LHP1 in an H3K27me3-dependent manner.

Polycomb repressive complexes 1 and 2 (PRC1 and PRC2) are transcriptional repressor complexes that play a fundamental role in epigenomic regulation and the cell-fate decision; these complexes are widely conserved in multicellular organisms. PRC1 is an E3 ubiquitin (ub) ligase that generates histone H2A ubiquitinated at lysine (K) 119 (H2AK119ub1), whereas PRC2 is a histone methyltransferase that specifically catalyzes tri-methylation of histone H3K27 (H3K27me3). Genome-wide analyses have confirmed that these two key epigenetic marks highly overlap across the genome and contribute to gene repression. We are now beginning to understand the molecular mechanisms that enable PRC1 and PRC2 to identify their target sites in the genome and communicate through feedback mechanisms to create Polycomb chromatin domains. Recently, it has become apparent that PRC1-induced H2AK119ub1 not only serves as a docking site for PRC2 but also affects the dynamics of the H3 tail, both of which enhance PRC2 activity, suggesting that trans-tail communication between H2A and H3 facilitates the formation of the Polycomb chromatin domain. In this review, we discuss the emerging principles that define how PRC1 and PRC2 establish the Polycomb chromatin domain and regulate gene expression in mammals.