DrosOmics: A Browser to Explore -omics Variation Across High-Quality Reference Genomes From Natural Populations of Drosophila melanogaster.

The advent of long-read sequencing technologies has allowed the generation of multiple high-quality de novo genome assemblies for multiple species, including well-known model species such as Drosophila melanogaster. Genome assemblies for multiple individuals of the same species are key to discover the genetic diversity present in natural populations, especially the one generated by transposable elements, the most common type of structural variant. Despite the availability of multiple genomic data sets for D. melanogaster populations, we lack an efficient visual tool to display different genome assemblies simultaneously. In this work, we present DrosOmics, a population genomic-oriented browser currently containing 52 high-quality reference genomes of D. melanogaster, including annotations from a highly reliable set of transposable elements, and functional transcriptomics and epigenomics data for 26 genomes. DrosOmics is based on JBrowse 2, a highly scalable platform, which allows the visualization of multiple assemblies at once, key to unraveling structural and functional features of D. melanogaster natural populations. DrosOmics is an open access browser and is freely available at http://gonzalezlab.eu/drosomics.

Hop stunt viroid infection induces heterochromatin reorganization.

Viroids are pathogenic noncoding RNAs that completely rely on their host molecular machinery to accomplish their life cycle. Several interactions between viroids and their host molecular machinery have been identified, including interference with epigenetic mechanisms such as DNA methylation. Despite this, whether viroids influence changes in other epigenetic marks such as histone modifications remained unknown. Epigenetic regulation is particularly important during pathogenesis processes because it might be a key regulator of the dynamism of the defense response. Here we have analyzed the changes taking place in Cucumis sativus (cucumber) facultative and constitutive heterochromatin during hop stunt viroid (HSVd) infection using chromatin immunoprecipitation (ChIP) of the two main heterochromatic marks: H3K9me2 and H3K27me3. We find that HSVd infection is associated with changes in both H3K27me3 and H3K9me2, with a tendency to decrease the levels of repressive epigenetic marks through infection progression. These epigenetic changes are connected to the transcriptional regulation of their expected targets, genes, and transposable elements. Indeed, several genes related to the defense response are targets of both epigenetic marks. Our results highlight another host regulatory mechanism affected by viroid infection, providing further information about the complexity of the multiple layers of interactions between pathogens/viroids and hosts/plants.

The Bivalent Genome: Characterization, Structure, and Regulation.

An intricate molecular machinery is at the core of gene expression regulation in every cell. During the initial stages of organismal development, the coordinated activation of diverse transcriptional programs is crucial and must be carefully executed to shape every organ and tissue. Bivalent promoters and poised enhancers are regulatory regions decorated with histone marks that are associated with both positive and negative transcriptional outcomes. These apparently contradictory signals are important for setting bivalent genes in a poised state, which is subsequently resolved during differentiation into either active or repressive states. We discuss the origins of bivalent promoters and the mechanisms implicated in their acquisition and maintenance. We further review how the presence of bivalent marks influences genome architecture. Finally, we highlight the potential link between bivalency and cancer which could drive biomedical research in disease etiology and treatment.

ASC proneural factors are necessary for chromatin remodeling during neuroectodermal to neuroblast fate transition to ensure the timely initiation of the neural stem cell program.

BACKGROUND: In both Drosophila and mammals, the achaete-scute (ASC/ASCL) proneural bHLH transcription factors are expressed in the developing central and peripheral nervous systems, where they function during specification and maintenance of the neural stem cells in opposition to Notch signaling. In addition to their role in nervous system development, ASC transcription factors are oncogenic and exhibit chromatin reprogramming activity; however, the impact of ASC on chromatin dynamics during neural stem cell generation remains elusive. Here, we investigate the chromatin changes accompanying neural commitment using an integrative genetics and genomics methodology. RESULTS: We found that ASC factors bind equally strongly to two distinct classes of cis-regulatory elements: open regions remodeled earlier during maternal to zygotic transition by Zelda and less accessible, Zelda-independent regions. Both classes of cis-elements exhibit enhanced chromatin accessibility during neural specification and correlate with transcriptional regulation of genes involved in a variety of biological processes necessary for neuroblast function/homeostasis. We identified an ASC-Notch regulated TF network that includes likely prime regulators of neuroblast function. Using a cohort of ASC target genes, we report that ASC null neuroblasts are defectively specified, remaining initially stalled, unable to divide, and lacking expression of many proneural targets. When mutant neuroblasts eventually start proliferating, they produce compromised progeny. Reporter lines driven by proneural-bound enhancers display ASC dependency, suggesting that the partial neuroblast identity seen in the absence of ASC genes is likely driven by other, proneural-independent, cis-elements. Neuroblast impairment and the late differentiation defects of ASC mutants are corrected by ectodermal induction of individual ASC genes but not by individual members of the TF network downstream of ASC. However, in wild-type embryos, the induction of individual members of this network induces CNS hyperplasia, suggesting that they synergize with the activating function of ASC to consolidate the chromatin dynamics that promote neural specification. CONCLUSIONS: We demonstrate that ASC proneural transcription factors are indispensable for the timely initiation of the neural stem cell program at the chromatin level by regulating a large number of enhancers in the vicinity of neural genes. This early chromatin remodeling is crucial for both neuroblast homeostasis as well as future progeny fidelity.

Conserved microRNAs and Flipons Shape Gene Expression during Development by Altering Promoter Conformations.

The classical view of gene regulation draws from prokaryotic models, where responses to environmental changes involve operons regulated by sequence-specific protein interactions with DNA, although it is now known that operons are also modulated by small RNAs. In eukaryotes, pathways based on microRNAs (miR) regulate the readout of genomic information from transcripts, while alternative nucleic acid structures encoded by flipons influence the readout of genetic programs from DNA. Here, we provide evidence that miR- and flipon-based mechanisms are deeply connected. We analyze the connection between flipon conformation and the 211 highly conserved human miR that are shared with other placental and other bilateral species. The direct interaction between conserved miR (c-miR) and flipons is supported by sequence alignments and the engagement of argonaute proteins by experimentally validated flipons as well as their enrichment in promoters of coding transcripts important in multicellular development, cell surface glycosylation and glutamatergic synapse specification with significant enrichments at false discovery rates as low as 10-116. We also identify a second subset of c-miR that targets flipons essential for retrotransposon replication, exploiting that vulnerability to limit their spread. We propose that miR can act in a combinatorial manner to regulate the readout of genetic information by specifying when and where flipons form non-B DNA (NoB) conformations, providing the interactions of the conserved hsa-miR-324-3p with RELA and the conserved hsa-miR-744 with ARHGAP5 genes as examples.

Insights into the Role of Histone Methylation in Brain Aging and Potential Therapeutic Interventions.

Epigenetic mechanisms play a primary role in the cellular damage associated with brain aging. Histone posttranslational modifications represent intrinsic molecular alterations essential for proper physiological functioning, while divergent expression and activity have been detected in several aspects of brain aging. Aberrant histone methylation has been involved in neural stem cell (NSC) quiescence, microglial deficits, inflammatory processes, memory impairment, cognitive decline, neurodegenerative diseases, and schizophrenia. Herein, we provide an overview of recent studies on epigenetic regulation of brain tissue aging, mainly focusing on the role of histone methylation in different cellular and functional aspects of the aging process. Emerging targeting strategies of histone methylation are further explored, including neuroprotective drugs, natural compounds, and lifestyle modifications with therapeutic potential towards the aging process of the brain.

Epigenetic regulation during meiosis and crossover.

Meiosis is a distinctive type of cell division that reorganizes genetic material between generations. The initial stages of meiosis consist of several crucial steps which include double strand break, homologous chromosome pairing, break repair and crossover. Crossover frequency varies depending on the position on the chromosome, higher at euchromatin region and rare at heterochromatin, centromeres, telomeres and ribosomal DNA. Crossover positioning is dependent on various factors, especially epigenetic modifications. DNA methylation, histone post-translational modifications, histone variants and non-coding RNAs are most probably playing an important role in positioning of crossovers on a chromosomal level as well as hotspot level. DNA methylation negatively regulates crossover frequency and its effect is visible in centromeres, pericentromeres and heterochromatin regions. Pericentromeric chromatin and heterochromatin mark studies have been a centre of attraction in meiosis. Crossover hotspots are associated with euchromatin regions having specific chromatin modifications such as H3K4me3, H2A.Z. and H3 acetylation. This review will provide the current understanding of the epigenetic role in plants during meiotic recombination, chromosome synapsis, double strand break and hotspots with special attention to euchromatin and heterochromatin marks. Further, the role of epigenetic modifications in regulating meiosis and crossover in other organisms is also discussed.

KDM2A plays a dual role in regulating the expression of malignancy-related genes in esophageal squamous cell carcinoma.

KDM2A is a histone demethylase, which primarily catalyzes the demethylation of H3K36me2. Abnormal expression of KDM2A is observed in many types of cancers; however, the molecular events connected to KDM2A expression remain unclear. We report that KDM2A performs an oncogenic function in esophageal squamous cell carcinoma (ESCC) and is robustly expressed in ESCC cells. ShRNA-mediated knockdown of KDM2A resulted in a significant inhibition of the malignant phenotype of ESCC cell lines, whereas ectopic expression of KDM2A showed the opposite effect. We also analyzed the function of KDM2A using a CRISPR-CAS9 depletion system and subsequent rescue experiment, which also indicated a cancerous role of KDM2A. Interestingly, analysis of the gene expression network controlled by KDM2A using RNA-seq revealed an unexpected feature: KDM2A could induce expression of a set of well-documented oncogenic genes, including IL6 and LAT2, while simultaneously suppressing another set of oncogenes, including MAT2A and HMGCS1. Targeted inhibition of the upregulated oncogene in the KDM2A-depleted cells led to a synergistic suppressive effect on the malignant phenotype of ESCC cells. Our results revealed the dual role of KDM2A in ESCC cells, which may have therapeutic implications.

Prenatal exposure to arsenic promotes sterile inflammation through the Polycomb repressive element EZH2 and accelerates skin tumorigenesis in mouse.

Prenatal and postnatal life stress could be a potent programmer of phenotype or disease state of an individual in the later life. Prenatal arsenic exposure has been shown to promote developmental defects, low birth weight, immunotoxicity and is associated with various cancers including skin cancer in adulthood. To investigate the association between prenatal arsenic exposure and adult life skin carcinogenesis, we used a two-stage cutaneous carcinogenesis model in which BALB/c mice were prenatally exposed to 0.04 mg/kg and 0.4 mg/kg arsenic (As). Exposure to arsenic was sufficient to shorten the tumor latency period and promote epidermal hyperplasia in the offspring upon challenge with dimethylbenz[a]/12-O-tetradecanoylphorbol-13-acetate (DMBA/TPA). The levels of inflammatory and tissue microenvironment remodeling factors such as IL-1α and TNF-α were persistently elevated in the skin, and their inhibition through diacerein led to a significant decrease in the tumor response, suggesting their role in tumorigenesis. While there was overexpression of multiple epigenetic regulators at tissue level, we found decreased enrichment of Polycomb repressive complex 2 (PRC2) member EZH2 and H3K27me3 mark at the upstream of the affected inflammatory genes. The higher expression of the inflammatory genes suggests the gene specific selective nature of EZH2 repression which was also associated with increased binding of the activator KDM6a (demethylase). Further, arsenic conditioned basal keratinocytes cells (BKCs) showed increased migration and proliferation along with higher expression of tumor associated cytokines. Inhibition of EZH2 in the BKCs lead to their further upregulation suggesting that BKCs might be the potential cell type for the interaction of EZH2 and inflammatory cytokines. The present study provides new evidence for the role of PRC2 group regulators in inflammatory conditioning and development of skin cancer in offspring prenatally exposed to arsenic.

The Long Non-Coding RNA HOXA-AS2 Promotes Proliferation of Glioma Stem Cells and Modulates Their Inflammation Pathway Mainly through Post-Transcriptional Regulation.

Glioblastomas represent approximatively half of all gliomas and are the most deadly and aggressive form. Their therapeutic resistance and tumor relapse rely on a subpopulation of cells that are called Glioma Stem Cells (GSCs). Here, we investigated the role of the long non-coding RNA HOXA-AS2 in GSC biology using descriptive and functional analyses of glioma samples classified according to their isocitrate dehydrogenase (IDH) gene mutation status, and of GSC lines. We found that HOXA-AS2 is overexpressed only in aggressive (IDHwt) glioma and GSC lines. ShRNA-based depletion of HOXA-AS2 in GSCs decreased cell proliferation and altered the expression of several hundreds of genes. Integrative analysis revealed that these expression changes were not associated with changes in DNA methylation or chromatin signatures at the promoter of the majority of genes deregulated following HOXA-AS2 silencing in GSCs, suggesting a post-transcriptional regulation. In addition, transcription factor binding motif enrichment and correlation analyses indicated that HOXA-AS2 affects, directly or indirectly, the expression of key transcription factors implicated in GCS biology, including E2F8, E2F1, STAT1, and ATF3, thus contributing to GCS aggressiveness by promoting their proliferation and modulating the inflammation pathway.

Histone Marks in the 'Driver's Seat': Functional Roles in Steering the Transcription Cycle.

Particular chromatin modifications are associated with different states of gene transcription, yet our understanding of which modifications are causal 'drivers' in promoting transcription is incomplete. Here, we discuss new developments describing the ordered, mechanistic role of select histone marks occurring during distinct steps in the RNA polymerase II (Pol II) transcription cycle. In particular, we highlight the interplay between histone marks in specifying the 'next step' of transcription. While many studies have described correlative relationships between histone marks and their occupancy at distinct gene regions, we focus on studies that elucidate clear functional consequences of specific histone marks during different stages of transcription. These recent discoveries have refined our current mechanistic understanding of how histone marks promote Pol II transcriptional progression.

Chromatin Manipulation and Editing: Challenges, New Technologies and Their Use in Plants.

An ongoing challenge in functional epigenomics is to develop tools for precise manipulation of epigenetic marks. These tools would allow moving from correlation-based to causal-based findings, a necessary step to reach conclusions on mechanistic principles. In this review, we describe and discuss the advantages and limits of tools and technologies developed to impact epigenetic marks, and which could be employed to study their direct effect on nuclear and chromatin structure, on transcription, and their further genuine role in plant cell fate and development. On one hand, epigenome-wide approaches include drug inhibitors for chromatin modifiers or readers, nanobodies against histone marks or lines expressing modified histones or mutant chromatin effectors. On the other hand, locus-specific approaches consist in targeting precise regions on the chromatin, with engineered proteins able to modify epigenetic marks. Early systems use effectors in fusion with protein domains that recognize a specific DNA sequence (Zinc Finger or TALEs), while the more recent dCas9 approach operates through RNA-DNA interaction, thereby providing more flexibility and modularity for tool designs. Current developments of "second generation", chimeric dCas9 systems, aiming at better targeting efficiency and modifier capacity have recently been tested in plants and provided promising results. Finally, recent proof-of-concept studies forecast even finer tools, such as inducible/switchable systems, that will allow temporal analyses of the molecular events that follow a change in a specific chromatin mark.

Interplay of DNA and RNA N 6 -methyladenine with R-loops in regulating gene transcription in Arabidopsis.

R-loops and covalent modifications of N 6 -methyladenine on DNA (D-6 mA) or RNA (R-m6A) have been documented to function in various cellular processes in eukaryotes. However, the relationships between R-loops and both covalent modifications are still elusive in plants. Here, we integrated existing ssDRIP-seq with D-6 mA and R-m6A data from Arabidopsis thaliana. We found that the presence of either of both modifications facilitates R-loop formation and transcription of overlapping genes. Interestingly, our study suggests that the presence of R-m6A is key to affect R-loop intensity and positively regulate gene transcription. Moreover, the presence of D-6 mA plays an additive role to facilitate the effect of R-m6A on R-loop intensity, however, D-6 mA may negatively regulate gene transcription when coexisted with R-m6A. Our analyses indicate that D-6 mA, R-m6A, or histone marks may act individually and cooperatively with R-loops in regulating gene transcription. Our study is the first to link R-loops with D-6 mA and R-m6A in plants, thereby providing new insights into interactions between R-loops with D-6 mA, R-m6A, and histone marks for regulating gene transcription. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-01010-5.

Whole genome sequencing identified a 16 kilobase deletion on ECA13 associated with distichiasis in Friesian horses.

BACKGROUND: Distichiasis, an ocular disorder in which aberrant cilia (eyelashes) grow from the opening of the Meibomian glands of the eyelid, has been reported in Friesian horses. These misplaced cilia can cause discomfort, chronic keratitis, and corneal ulceration, potentially impacting vision due to corneal fibrosis, or, if secondary infection occurs, may lead to loss of the eye. Friesian horses represent the vast majority of reported cases of equine distichiasis, and as the breed is known to be affected with inherited monogenic disorders, this condition was hypothesized to be a simply inherited Mendelian trait. RESULTS: A genome wide association study (GWAS) was performed using the Axiom 670 k Equine Genotyping array (MNEc670k) utilizing 14 cases and 38 controls phenotyped for distichiasis. An additive single locus mixed linear model (EMMAX) approach identified a 1.83 Mb locus on ECA5 and a 1.34 Mb locus on ECA13 that reached genome-wide significance (pcorrected = 0.016 and 0.032, respectively). Only the locus on ECA13 withstood replication testing (p = 1.6 × 10- 5, cases: n = 5 and controls: n = 37). A 371 kb run of homozygosity (ROH) on ECA13 was found in 13 of the 14 cases, providing evidence for a recessive mode of inheritance. Haplotype analysis (hapQTL) narrowed the region of association on ECA13 to 163 kb. Whole-genome sequencing data from 3 cases and 2 controls identified a 16 kb deletion within the ECA13 associated haplotype (ECA13:g.178714_195130del). Functional annotation data supports a tissue-specific regulatory role of this locus. This deletion was associated with distichiasis, as 18 of the 19 cases were homozygous (p = 4.8 × 10- 13). Genotyping the deletion in 955 horses from 54 different breeds identified the deletion in only 11 non-Friesians, all of which were carriers, suggesting that this could be causal for this Friesian disorder. CONCLUSIONS: This study identified a 16 kb deletion on ECA13 in an intergenic region that was associated with distichiasis in Friesian horses. Further functional analysis in relevant tissues from cases and controls will help to clarify the precise role of this deletion in normal and abnormal eyelash development and investigate the hypothesis of incomplete penetrance.

Atypical chromatin structure of immune-related genes expressed in chicken erythrocytes.

The major biological role of red blood cells is to carry oxygen to the tissues in the body. However, another role of the erythroid cell is to participate in the immune response. Mature erythrocytes from chickens express Toll-like receptors and several cytokines in response to stimulation of the immune system. We previously reported the application of a biochemical fractionation protocol to isolate highly enriched transcribed DNA from polychromatic erythrocytes from chickens. In conjunction with next-generation DNA, RNA sequencing, chromatin immunoprecipitation-DNA sequencing, and formaldehyde-assisted isolation of regulatory elements (FAIRE) sequencing, we identified the active chromosomal compartments and determined their structural signatures in relation to expression levels. Here, we present the detailed chromatin characteristics of erythroid genes participating in the innate immune response. Our studies revealed an atypical chromatin structure for several genes coding for Toll-like receptors, interleukins, and interferon regulatory factors. The body of these genes had nucleosome-free regions intermingled with nucleosomes modified with H3K4me3 and H3K27ac, suggesting a dynamic unstable chromatin structure. We further show that human genes involved in cell identity have gene bodies with the same chromatin-instability features as the chicken polychromatic erythrocyte genes participating in the innate immune response.

Epigenomic and genomic landscape of Drosophila melanogaster heterochromatic genes.

Heterochromatin is associated with transcriptional repression. In contrast, several genes in the pericentromeric regions of Drosophila melanogaster are dependent on this heterochromatic environment for their expression. Here we present a comprehensive analysis of the epigenetic landscape of heterochromatic genes across all the developmental stages of Drosophila using the available histone modification and expression data from modENCODE. We find that heterochromatic genes exhibit combinations of active and inactive histone marks that correspond to their level of expression during development. We also show that Nuclear Matrix Associated Regions (MARs) are prominently present in the intergenic regions of heterochromatic genes during embryonic stages suggesting their plausible role in pericentromeric genome organization. Taken together, our meta-analysis of the various genomic datasets suggest that the epigenomic and genomic landscape of the heterochromatic genes are distinct which could be contributing to their unusual regulatory features as opposed to the surrounding heterochromatin, which is repressive in nature.

Small Molecules Targeting the Specific Domains of Histone-Mark Readers in Cancer Therapy.

Epigenetic modifications (or epigenetic tags) on DNA and histones not only alter the chromatin structure, but also provide a recognition platform for subsequent protein recruitment and enable them to acquire executive instructions to carry out specific intracellular biological processes. In cells, different epigenetic-tags on DNA and histones are often recognized by the specific domains in proteins (readers), such as bromodomain (BRD), chromodomain (CHD), plant homeodomain (PHD), Tudor domain, Pro-Trp-Trp-Pro (PWWP) domain and malignant brain tumor (MBT) domain. Recent accumulating data reveal that abnormal intracellular histone modifications (histone marks) caused by tumors can be modulated by small molecule-mediated changes in the activity of the above domains, suggesting that small molecules targeting histone-mark reader domains may be the trend of new anticancer drug development. Here, we summarize the protein domains involved in histone-mark recognition, and introduce recent research findings about small molecules targeting histone-mark readers in cancer therapy.

Enhancer DNA methylation in acute myeloid leukemia and myelodysplastic syndromes.

DNA methylation (CpG methylation) exerts an important role in normal differentiation and proliferation of hematopoietic stem cells and their differentiated progeny, while it has also the ability to regulate myeloid versus lymphoid fate. Mutations of the epigenetic machinery are observed in hematological malignancies including acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) resulting in hyper- or hypo-methylation affecting several different pathways. Enhancers are cis-regulatory elements which promote transcription activation and are characterized by histone marks including H3K27ac and H3K4me1/2. These gene subunits are target gene expression 'fine-tuners', are differentially used during the hematopoietic differentiation, and, in contrast to promoters, are not shared by the different hematopoietic cell types. Although the interaction between gene promoters and DNA methylation has extensively been studied, much less is known about the interplay between enhancers and DNA methylation. In hematopoiesis, DNA methylation at enhancers has the potential to discriminate between fetal and adult erythropoiesis, and also is a regulatory mechanism in granulopoiesis through repression of neutrophil-specific enhancers in progenitor cells during maturation. The interplay between DNA methylation at enhancers is disrupted in AML and MDS and mainly hyper-methylation at enhancers raising early during myeloid lineage commitment is acquired during malignant transformation. Interactions between mutated epigenetic drivers and other oncogenic mutations also affect enhancers' activity with final result, myeloid differentiation block. In this review, we have assembled recent data regarding DNA methylation and enhancers' activity in normal and mainly myeloid malignancies.

Regulation of the Genes Encoding the ppN/OFQ and NOP Receptor.

Over the years, the ability of N/OFQ-NOP receptor system in modulating several physiological functions, including the release of neurotransmitters, anxiety-like behavior responses, modulation of the reward circuitry, inflammatory signaling, nociception, and motor function, has been examined in several brain regions and at spinal level. This chapter collects information related to the genes encoding the ppN/OFQ and NOP receptor, their regulation, and relative transcriptional control mechanisms. Furthermore, genetic manipulations, polymorphisms, and epigenetic alterations associated with different pathological conditions are discussed. The evidence here collected indicates that the study of ppN/OFQ and NOP receptor gene expression may offer novel opportunities in the field of personalized therapies and highlights this system as a good "druggable target" for different pathological conditions.

Propagation of trimethylated H3K27 regulated by polycomb protein EED is required for embryogenesis, hematopoietic maintenance, and tumor suppression.

Polycomb repressive complex 2 (PRC2) catalyzes the monomethylation, dimethylation, and trimethylation of histone H3 Lys27 (H3K27) and acts as a central epigenetic regulator that marks the repressive chromatin domain. Embryonic ectoderm development (EED), an essential component of PRC2, interacts with trimethylated H3K27 (H3K27me3) through the aromatic cage structure composed of its three aromatic amino acids, Phe97, Trp364, and Tyr365. This interaction allosterically activates the histone methyltransferase activity of PRC2 and thereby propagates repressive histone marks. In this study, we report the analysis of knock-in mice harboring the myeloid disorder-associated EED Ile363Met (I363M) mutation, analogous to the EED aromatic cage mutants. The I363M homozygotes displayed a remarkable and preferential reduction of H3K27me3 and died at midgestation. The heterozygotes increased the clonogenic capacity and bone marrow repopulating activity of hematopoietic stem/progenitor cells (HSPCs) and were susceptible to leukemia. Lgals3, a PRC2 target gene encoding a multifunctional galactose-binding lectin, was derepressed in I363M heterozygotes, which enhanced the stemness of HSPCs. Thus, our work provides in vivo evidence that the structural integrity of EED to H3K27me3 propagation is critical, especially for embryonic development and hematopoietic homeostasis, and that its perturbation increases the predisposition to hematologic malignancies.