Epigenetics & Chromatin最新文献

DNA methylation is a conserved epigenetic modification that plays important roles in silencing transposable elements, regulating gene expression, and maintaining genome stability. In plants, DNA methylation is de novo established by the RNA-directed DNA methylation pathway and maintained during each cell cycle. It can be actively removed by the REPRESSOR OF SILENCING 1/DEMETER family proteins through the base excision repair pathway. Active DNA demethylation is essential for plant growth, development, reproduction and stress adaptation. During the past two decades, significant progress has been made in our understanding of active DNA demethylation. In this review, we will discuss the molecular mechanisms, regulation, and biological functions of active DNA demethylation in plants.

The TIP60 complex is an evolutionarily conserved, multifunctional chromatin remodeling complex involved in critical cellular processes, including DNA repair, transcription regulation, and cell cycle control. Although its molecular organization and functions have been extensively studied, a comparative synthesis of its context-specific roles across evolutionarily distant species and pathological conditions is important to fully grasp its biological and clinical significance. In this review, we provide an integrative overview of the TIP60 complex, emphasizing its composition and conserved functions in Homo sapiens and Drosophila melanogaster, with comparative insights from plant systems. We explore how TIP60 complex dysregulation contributes to the molecular pathology of cancer and neurodevelopmental disorders, highlighting recent mechanistic insights. We also examine the emerging interplay between TIP60 complex subunits and long non-coding RNAs, which are increasingly recognized as pivotal regulators of genome accessibility and transcriptional programs. Finally, in this intriguing scenario, we highlight the non-canonical functions of the TIP60 complex in mitosis and cytokinesis, underscoring its moonlighting roles in maintaining genomic and cellular integrity, beyond its established contribution to epigenetic regulation. By connecting these diverse aspects, our review aims to provide an integrated perspective on the TIP60 complex and its expanding functional landscape in health and disease.

Characterization of DNA binding sites for specific proteins is of fundamental importance in molecular biology. It is commonly addressed experimentally by chromatin immunoprecipitation and sequencing (ChIP-seq) of bulk samples (10³-10⁷ cells). We have developed an alternative method that uses a Chromatin Antibody-mediated Methylating Protein (ChAMP) composed of a GpC methyltransferase fused to protein G. By tethering ChAMP to a primary antibody directed against the DNA-binding protein of interest, and selectively switching on its enzymatic activity in situ, we generated distinct and identifiable methylation patterns adjacent to the protein binding sites. This method is compatible with methods of single-cell methylation-detection and single molecule methylation identification. Indeed, as every binding event generates multiple nearby methylations, we were able to confidently detect protein binding in long single molecules.

Background: Histone modifications are key epigenetic regulators of cell differentiation and have been intensively studied in many cell types and tissues. Nevertheless, we still lack a thorough understanding of how combinations of histone marks at the same genomic location, so-called chromatin states, are linked to gene expression, and how these states change in the process of differentiation. To receive insight into the epigenetic changes accompanying the differentiation along the chondrogenic lineage we analyzed two publicly available datasets representing (1) the early differentiation stages from embryonic stem cells into chondrogenic cells and (2) the direct differentiation of mature chondrocyte subtypes.

Results: We used ChromHMM to define chromatin states of 6 activating and repressive histone marks for each dataset and tracked the transitions between states that are associated with the progression of differentiation. As differentiation-associated state transitions are likely limited to a reduced set of genes, one challenge of such global analyses is the identification of these rare transitions within the large-scale data. To overcome this problem, we have developed a relativistic approach that quantitatively relates transitions of chromatin states on defined groups of tissue-specific genes to the background. In the early lineage, we found an increased transition rate into activating chromatin states on mesenchymal and chondrogenic genes while mature chondrocytes are mainly enriched in transition between activating states. Interestingly, we also detected a complex extension of the classical bivalent state (H3K4me3/H3K27me3) consisting of several activating promoter marks besides the repressive mark H3K27me3. Within the early lineage, mesenchymal and chondrogenic genes undergo transitions from this state into active promoter states, indicating that the initiation of gene expression utilizes this complex combination of activating and repressive marks. In contrast, at mature differentiation stages the inverse transition, the gain of H3K27me3 on active promoters, seems to be a critical parameter linked to the initiation of gene repression in the course of differentiation.

Conclusions: Our results emphasize the importance of a relative analysis of complex epigenetic data to identify chromatin state transitions associated with cell lineage progression. They further underline the importance of serial analysis of such transitions to uncover the diverse regulatory potential of distinct histone modifications like H3K27me3.

Background: Anopheles mosquitoes and the malaria parasites they transmit remain a significant global health problem. Most genomic and functional genomic studies of mosquitoes have focused on the protein-coding genome, and comparatively little is known about the importance of noncoding transcriptional enhancers in controlling their gene expression and phenotypic variation. Here we evaluate nine enhancers previously identified in a STARR-seq screen and present in a genetic locus that was identified as a major influence on susceptibility to malaria infection in wild Anopheles coluzzii mosquitoes.

Result: We developed an analytical pipeline to filter nine enhancers in the malaria susceptibility locus on chromosome 2L. First, ATAC-seq revealed that only three of the nine enhancers were located in open chromatin and thus likely to be active in somatic cells. Next, we cloned these three enhancers from malaria-susceptible and resistant mosquitoes and measured their enhancer activity by luciferase reporter assays. Only two of the three open-chromatin enhancers displayed significantly different enhancer activity between resistant and susceptible alleles. Finally, alleles of just one of these enhancers, ENH_2L-03, contained nucleotide variants which also segregated in wild mosquitoes, and ENH_2L-03 was prioritized for further study. A noncoding RNA was detected within ENH_2L-03, consistent with an enhancer RNA (eRNA), which we depleted in mosquitoes using RNAi in order to silence the enhancer activity. Transcriptional profiling of ENH_2L-03-silenced mosquitoes revealed 15 differentially expressed genes, which share a transcription factor binding motif suggestive of coordinate regulation. However, silencing ENH_2L-03 did not influence infection levels of either human or rodent malaria parasites.

Conclusion: Despite the absence of an ENH_2L-03 effect on infection outcome, multiple enhancers can cooperate to influence a phenotype, and further examination of this enhancer is warranted. Overall, we provide a pipeline for the in vivo functional study of transcriptional enhancers in Anopheles, towards understanding how enhancer function may control important vector phenotypes.

Epigenetic factors underlie cellular identity through the regulation of transcriptional networks that establish a cell's phenotype and function. Cell conversions are directed by transcription factor binding at target DNA which induce changes to identity-specific gene regulatory programs. The degree of cell plasticity is determined by the interplay of epigenetic mechanisms to create a landscape susceptible to such binding events. 5-hydroxymethylcytosine, a key intermediate during the process of DNA demethylation, is an epigenetic modification involved in controlling these epigenetic dynamics related to cell identity. Here, the role of 5-hydroxcymethylcytosine during cell identity conversions, including its relationship with other main epigenetic mechanisms, is reviewed.

DNA methylation is a fundamental epigenetic modification that regulates gene expression and maintains genomic stability. Consequently, DNA methylation remains a key biomarker in cancer research, playing a vital role in diagnosis, prognosis, and tailored treatment strategies. Aberrant methylation patterns enable early cancer detection and therapeutic stratification; however, their complex patterns necessitates advanced analytical tools. Recent advances in artificial intelligence (AI) and machine learning (ML), including deep learning networks and graph-based models, have revolutionized cancer epigenomics by enabling rapid, high-resolution analysis of DNA methylation profiles. Moreover, these technologies are accelerating the development of Multi-Cancer Early Detection (MCED) tests, such as GRAIL's Galleri and CancerSEEK, which improve diagnostic accuracy across diverse cancer types. In this review, we explore the synergy between AI and DNA methylation profiling to advance precision oncology. We first examine the role of DNA methylation as a biomarker in cancer, followed by an overview of DNA profiling technologies. We then assess how AI-driven approaches transform clinical practice by enabling early detection and accurate classification. Despite their promise, challenges remain, including limited sensitivity for early-stage cancers, the black-box nature of many AI algorithms, and the need for validation across diverse populations to ensure equitable implementation. Future directions include integrating multi-omics data, developing explainable AI frameworks, and addressing ethical concerns, such as data privacy and algorithmic bias. By overcoming these gaps, AI-powered epigenetic diagnostics can enable earlier detection, more effective treatments, and improved patient outcomes, globally. In summary, this review synthesizes current advancements in the field and envisions a future where AI and epigenomics converge to redefine cancer diagnostics and therapy.

Oocyte maturation involves both nuclear and cytoplasmic processes that are critical for the acquisition of oocyte competence. Granulosa cells, surrounding the oocyte, play a pivotal role in the maturation process, with mechanisms such as cAMP signaling significantly influencing oocyte development. Epigenetic mechanisms - including DNA methylation and its oxidative derivatives, histone post-translational modifications and chromatin remodeling - interfere with the accessibility of transcription factors to regulatory regions of the genome, such as promoter regions of genes, hence generally regulating gene expression profiles; however, in oocytes, transcription is largely independent of DNA methylation patterns. Here we highlight epigenetic reprogramming events occurring during oocyte development and ageing, focusing on the establishment of gamete-specific epigenetic marks, including DNA modifications at imprinted regions, and age-related epigenetic changes. We focus on the mechanisms of DNA methylation and demethylation during mouse and human oocyte maturation, alongside an exploration of how ageing impacts the oocyte epigenome and its implications for reproductive success. By providing a comprehensive analysis of the role of epigenetics in oocyte development and maturation, this review addresses the importance of comprehending these processes to enhance in vitro fertilization treatments and improve reproductive outcomes.

Background: Cohesin is a major regulator of three-dimensional genome organization and gene expression. Cohesin associates with DNA and dynamically extrudes a DNA loop, often bringing two cis-regulatory elements physically close together. Extruding cohesin molecules can be stalled or stabilized when they encounter a CTCF insulator protein on DNA, thereby anchoring a DNA loop. However, many enhancer-promoter loops that are bound by cohesin lack CTCF and it is not clear how cohesin is stabilized at or recruited to these sites in the genome.

Results: Here, we investigated the localization of cohesin with common chromatin regulators and transcription factors on the mouse embryonic stem cell genome. The SP1 and NFYA transcription factors are ubiquitously expressed proteins known to regulate expression of genes associated with a variety of cellular processes, while WDR5 is a ubiquitous core component of multiple chromatin regulatory complexes. We found that cohesin co-bound promoters and enhancers with WDR5, with SP1, or with NFYA in mESCs. Cohesin physically interacted with and colocalized with WDR5, with SP1, or with NFYA on the same molecule of chromatin. Strikingly, depletion of WDR5, SP1, or NFYA caused a decrease in cohesin binding at shared binding sites, while depletion of cohesin did not alter binding of WDR5, SP1, or NFYA on the genome.

Conclusions: These results indicate that common transcription factors and chromatin regulators stabilize cohesin at specific sites in chromatin and may thereby serve as structural regulators of enhancer-promoter loops via the stabilization of cohesin.