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Molecular adaptations in response to exercise training are associated with tissue-specific transcriptomic and epigenomic signatures.

Regular exercise has many physical and brain health benefits, yet the molecular mechanisms mediating exercise effects across tissues remain poorly understood. Here we analyzed 400 high-quality DNA methylation, ATAC-seq, and RNA-seq datasets from eight tissues from control and endurance exercise-trained (EET) rats. Integration of baseline datasets mapped the gene location dependence of epigenetic control features and identified differing regulatory landscapes in each tissue. The transcriptional responses to 8 weeks of EET showed little overlap across tissues and predominantly comprised tissue-type enriched genes. We identified sex differences in the transcriptomic and epigenomic changes induced by EET. However, the sex-biased gene responses were linked to shared signaling pathways. We found that many G protein-coupled receptor-encoding genes are regulated by EET, suggesting a role for these receptors in mediating the molecular adaptations to training across tissues. Our findings provide new insights into the mechanisms underlying EET-induced health benefits across organs.

Animals↗

ChromCall: assigning chromatin status to defined genomic regions using epigenomic profiling data.

MOTIVATION: Chromatin regulation is crucial for modulating gene expression and cellular function by altering DNA accessibility. Defining and understanding chromatin regulation across diverse biological conditions, including health and disease, requires quantification of both the presence and enrichment level of diverse DNA-binding factors and chromatin modifications across defined genomic regions. Existing approaches mainly rely on peak-based or genome-wide models, which identify high-signal regions but do not annotate chromatin status at predefined functional genomic regions, such as promoters or enhancers. This lack of region-based annotation limits downstream comparative and integrative analyses across multiple factors and datasets, prompting us to create ChromCall. RESULTS: ChromCall is an R package for region-based chromatin enrichment analysis that provides a robust and extensible foundation for transparent and reproducible epigenomic profiling at predefined genomic regions. We applied ChromCall to ChIP-seq data from glioblastoma (GBM) brain tumours and found that the promoters of genes implicated in treatment resistance are significantly more likely to exhibit a combination of histone marks associated with phenotypic plasticity. This highlights a potential novel mechanism of therapeutic escape in these deadly tumours. AVAILABILITY AND IMPLEMENTATION: The R package is available on https://github.com/GliomaGenomics/ChromCall and the version used in this paper is archived at https://doi.org/10.5281/zenodo.19580967.

Chromatin↗

Epigenome-Wide Analysis Identifies Pollution-Sensitive Loci in Fibrotic Interstitial Lung Disease.

Rationale: Particulate matter &#x2a7d;2.5 &#x3bc;m (PM2.5) adversely impacts patients with fibrotic interstitial lung disease (fILD). Objectives: We sought to determine whether PM2.5-associated epigenetic alterations contribute to the environmental pathogenesis of fILD. Methods: A retrospective two-cohort study applied satellite-derived PM2.5 and constituent exposure matching to the residential location of patients with fILD. Robust linear regressions were used to evaluate cohort-specific, epigenome-wide differential blood DNA methylation with increasing pollutant exposures (Illumina MethylationEPIC BeadChip). Cox and linear regressions were used to evaluate associations of cytosine-phosphate-guanine (CpG) loci with transplant-free survival and lung function. A Wilcoxon test was used to evaluate cartilage-associated protein (CRTAP) levels in fILD and control lungs. Measurements and Main Results: The University of Pittsburgh cohort (n&#x2009;=&#x2009;306) had 5-year median PM2.5 exposures of 12.1 &#x3bc;g/m3 compared with 5.1 &#x3bc;g/m3 in the University of British Columbia cohort (n&#x2009;=&#x2009;170). Higher pollutant exposures in the University of Pittsburgh cohort were associated with lower methylation at cg25354716, annotated to CRTAP, a critical extracellular matrix remodeling enzyme. Higher exposures in the University of British Columbia cohort were associated with higher methylation at cg01019301, annotated to TLN2 (talin-2), a cytoskeletal protein involved in fibroblast migration. A 10% increase in cg25354716 methylation was associated with a hazard ratio of 0.81 for death or lung transplantation in the meta-analyzed cohorts (95% confidence interval&#x2009;=&#x2009;0.69-0.96; P&#x2009;=&#x2009;0.01), whereas the same change in cg01019301 was associated with a hazard ratio of 1.36 (95% confidence interval&#x2009;= 1.07-1.74; P&#x2009;=&#x2009;0.01). CRTAP protein was more abundant in lungs from patients with fILD compared with those from donor controls (P&#x2009;<&#x2009;0.001). Conclusions: PM2.5 is associated with altered blood DNA methylation in fILD. This work identifies novel pollution-sensitive targets that hold potential for therapeutic modulation in fILD.

Humans↗

Distinct transcriptional and epigenomic programs define Hofbauer cells in term placenta.

Hofbauer cells (HBCs) are fetal macrophages located in the placenta that contribute to antimicrobial defense, angiogenesis, tissue remodeling, and metabolic processes within the chorionic villi. Although their roles in placental biology are increasingly recognized, the mechanisms that regulate HBC identity and function are not yet fully defined. This study aimed to define the core transcriptomic and epigenomic features of HBCs in term placentas and to examine their capacity for transcriptional responsiveness and phenotypic variation. Using chromatin accessibility profiling and bulk RNA-seq, we found that HBCs exhibit a unique gene expression and chromatin accessibility profile compared with other fetal and adult macrophages. We identified a coordinated transcriptional network involving nuclear receptors (NRs) NR4A1-3, the glucocorticoid receptor, and RFX family members (RFX1, RFX2, RFX5) that appears to shape HBC identity, particularly through pathways linked to lipid metabolism and angiogenesis. Although exploratory in nature, in vitro stimulation studies showed that HBCs exhibited increased transcriptional activity in response to combined IL-4 and rosiglitazone treatment, including induction of the lipid transporter CD36. Mass cytometry analysis revealed surface markers indicative of both immature and mature macrophage states. These results together indicate that HBCs are a distinct and diverse population of macrophages with a specialized, adaptable regulatory program in the human placenta.

Female↗

Targeted long-read genomic and epigenomic profiling enhances timely comprehensive variant discovery in hypotonia and muscle weakness.

BACKGROUND: Identifying the genetic basis of hypotonia and muscle weakness is critical for patient management and family counseling. However, diagnosis is often hindered by diverse genomic alterations, including repeat expansions, structural variants (SVs), and methylation defects. Standard-of-care testing, largely based on short-read sequencing, is limited in its ability to detect this heterogeneous variation landscape, leaving many patients undiagnosed or requiring lengthy sequential testing. Long-read sequencing represents a promising solution. However, its application as a first-tier diagnostic assay for hypotonia remains unexplored. METHODS: We retrospectively analyzed 227 patients with hypotonia to assess diagnostic yield, time-to-diagnosis, and costs associated with standard-of-care testing. A long-read whole-genome sequencing (LR-WGS) workflow with targeted analysis of hypotonia-associated genes was developed to detect and prioritize pathogenic SNVs, SVs, and CNVs, repeat expansions, and methylation changes at key disease loci. The workflow was validated in a reference-positive cohort with known diagnoses (n&#x2009;=&#x2009;15) and applied to an unsolved cohort (n&#x2009;=&#x2009;14). Variant interpretation followed ACMG guidelines and was confirmed with orthogonal methods. RESULTS: Standard-of-care testing achieved a diagnostic yield of 42% with an average time-to-diagnosis of 68.7&#xa0;days; however, 30% of diagnosed patients experienced significant delays (average 169&#xa0;days) due to sequential testing. The LR-WGS based approach identified all known pathogenic variants in the positive cohort, including SMN1 deletions, methylation defects at 15q11.2/Prader-Willi locus, FMR1 repeat expansions, and sequence and copy-number variants in&#x2009;>&#x2009;100 genes underlying myopathies and muscular dystrophies. The targeted long-read pipeline reduced prioritized variant calls by 97.9-99.9% and, in the unsolved cohort, yielded one definitive diagnosis (de novo COL6A3 deletion) and one possible diagnosis (aberrant methylation and copy number at POMK), for an additional 14% yield. Among patients diagnosed after sequential testing (n&#x2009;=&#x2009;29), LR-WGS is expected to reduce time-to-diagnosis by&#x2009;~&#x2009;85% and decrease cumulative diagnostic delays, with projected healthcare cost savings of $396,000-439,000. Across the entire 227 patient cohort, LR-WGS is anticipated to reduce testing costs by 6.5%, yielding an average savings of $105 per patient. CONCLUSIONS: LR-WGS enables comprehensive discovery of genomic and epigenomic variants in hypotonia and muscle weakness, improving diagnostic yield, shortening diagnostic timelines, and reducing costs compared with current standard-of-care testing.

Humans↗

Clinical Relevance of Post-Treatment Circulating Tumor DNA Detection in Early Breast Cancer Using a Tissue-Free Epigenomic Assay: A 2-Year Landmark Analysis.

PURPOSE: Circulating tumor DNA (ctDNA) may serve as a biomarker to facilitate early identification of asymptomatic distant tumor spread in patients with breast cancer. The primary objective of this study was to assess clinical validity and prognostic value of post-treatment tissue-free ctDNA detection by evaluating its sensitivity for distant metastatic recurrence and its association with long-term outcomes. PATIENTS AND METHODS: Plasma samples were prospectively collected from patients with stage I-III early breast cancer who participated in the adjuvant SUCCESS-A phase III clinical trial (ClinicalTrials.gov identifier: NCT02181101). In this study, plasma samples collected approximately 2 years after completion of adjuvant chemotherapy from 313 SUCCESS A patients without evidence of prior disease recurrence were retrospectively analyzed using a tissue-free epigenomic ctDNA assay (Guardant Reveal). Survival analyses were performed using a landmark approach based on the time of sample collection. RESULTS: Overall, ctDNA was detected in 18 of 313 samples (5.8%). Of all ctDNA detected samples, 94% (17/18) were from patients who subsequently developed a distant recurrence, with ctDNA detected at a median interval of 7.9 months before recurrence. ctDNA positivity was strongly associated with a significantly shorter distant recurrence-free interval (hazard ratio [HR], 33.3 [95% CI, 4.12 to 268]; P < .0001) and poorer overall survival (HR, 27.3 [95% CI, 1.15 to 647]; P < .0001). The sensitivity for distant recurrence in patients who had a sample collected within 1 year before recurrence was 73% (11/15). The specificity in nonrecurred patients was 99.6% (267/268). CONCLUSION: Tissue-free detection of ctDNA 2 years after adjuvant chemotherapy was highly prognostic in an early-stage breast cancer cohort, and can be used to stratify patients with early-stage breast cancer at high risk for recurrence during follow-up who may benefit from early interventions.

Humans↗

Genomic and epigenomic diversity of breast cancer across Western and MENA populations: implications for precision oncology.

Breast cancer is the most common malignancy in women worldwide and is increasingly recognized as a biologically diverse disease shaped by both molecular and ancestral context. Women from the Middle East and North Africa (MENA) populations, including Saudi Arabia, often present at a younger age and with more aggressive subtypes such as HER2-positive and triple-negative breast cancer (TNBC) compared with Western cohorts. These clinical patterns reflect a distinctive genomic background marked by high consanguinity, founder mutations in key susceptibility genes, and population-specific somatic alterations that are not fully captured in global reference datasets. This review brings together current evidence on somatic, germline, transcriptomic, and epigenomic diversity in breast cancer across Western and MENA populations, with a focus on Saudi cohorts. Drawing on a previously published systematic review of more than 2,500 MENA breast cancer cases, TP53 accounted for approximately 24% and PIK3CA for roughly 10% of curated somatic mutation records pooled across 44 studies (proportions of mutation calls, not per-patient prevalence); in a separate single-center Saudi cohort, only 3.7% of patients underwent BRCA testing, and 37.5% of this clinically selected, testing-referred subgroup carried a pathogenic variant, a figure that should not be read as general-population BRCA prevalence. Variants of uncertain significance exceeded 20% across several regional genomic studies. We summarize conserved driver events, such as recurrent TP53 and PIK3CA mutations, while highlighting regional features, including unique stop-gain and loss-of-function variants, a high copy-number burden, and early-onset disease linked to ancestral architecture. We also discuss emerging data on MENA-specific regulatory signatures, including immune-enriched and basal-myo transcriptomic clusters, CIMP-like methylation patterns, and non-coding RNA networks; these associations are numerically suggestive in available cohorts but have not reached statistical significance in existing studies and warrant validation in larger, dedicated MENA/Saudi cohorts before being considered established determinants of treatment response and resistance. Finally, we examine the clinical implications of this diversity for biomarker development, pharmacogenomics, and access to targeted therapies, and outline practical steps toward ancestry-aware precision oncology in the region.

BRCA↗

Viability of X-autosome translocations in mammals: an epigenomic hypothesis from a rodent case-study.

X-autosome translocations are highly deleterious chromosomal rearrangements due to meiotic disruption, the effects of X-inactivation on the autosome, and the necessity of maintaining different replication timing patterns between the two segments. In spite of this, X-autosome translocations are not uncommon. We here focus on the genus Taterillus (Rodentia, Gerbillinae) which provides two sister lineages differing by two autosome-gonosome translocations. Despite the recent and dramatic chromosomal repatterning characterising these lineages, the X-autosome translocated species all display intercalary heterochromatic blocks (IHBs) between the autosomal and the ancestral sexual segments. These blocks, composed of highly amplified telomeric repeats and rDNA clusters, are not observed on the chromosomes of the non-translocated species, nor the Y1 and Y2 of the translocated species. Such IHBs are found in all mammals documented for X-autosome translocation. We propose an epigenomic hypothesis which explains the viability of X-autosome translocations in mammals. This posits that constitutive heterochromatin is probably selected for in X-autosome translocations since it may (1) prevent facultative heterochromatinization of the inactivated X from spreading to the autosomal part, and (2) allow for the independent regulation of replication timing of the sex and autosomal segments.

Animals↗

Epigenomic mapping in Arabidopsis using tiling microarrays.

In addition to genetic information, chromosomes transmit epigenetic information from cell to cell during division, and sometimes from generation to generation. While genetic information is encoded directly in the DNA sequence, epigenetic information is not, although it is usually associated with specific chromosomal regions. Epigenetic modifications in plants include cytosine methylation as well as modification of histones and other chromosomal proteins. Small interfering RNA play major roles in targeting these modifications to specific regions. Genomic tiling microarrays are powerful tools for analysing epigenetic information, and we review their application in building epigenomic maps in the model plant, Arabidopsis.

Arabidopsis↗

Genome-wide epigenomic atlas and multi-omics responses of Eriocheir sinensis to natural extreme heat.

BACKGROUND: Global climate warming has led to increasingly frequent and prolonged extreme summer heat events, posing severe environmental challenges to aquaculture systems. Extreme summer heat can disrupt the performance of pond-cultured ectotherms. The Chinese mitten crab (Eriocheir sinensis) is an economically important freshwater crustacean, but coordinated molecular differences following contrasting natural summers remain incompletely characterized. RESULTS: We performed a comprehensive multi-omics analysis integrating meteorological monitoring, mRNA/lncRNA transcriptomics, small-RNA profiling of miRNAs, DNA methylomics, and LC-MS metabolomics in E. sinensis populations collected from Yancheng, China, between 2020 and 2024. Across the ten farms, survival was significantly lower in 2024, whereas yield and the proportion of large individuals showed nonsignificant downward trends. Gene-set analyses showed negative enrichment of cellular heat-response, protein-folding, oxidative-phosphorylation, and mitochondrial ATP-production terms in the 2024 cohort at the time of sampling. The integrated transcript annotation contained 72,240 lncRNAs and 63,833 mRNAs, and CpG was the predominant methylation context. Differential methylation analysis identified 73 regions and 185 cytosines, with hypomethylated events predominating within the significant subset. Metabolomic profiles differed between annual cohorts and mapped to carbohydrate, lipid, and amino-acid pathways. Cross-omics integration prioritized eight candidate genes-ADCY9, UNC79, UBN1, IFT52, ACO2, LOC126986070, LOC127001126, and LOC126997895-and qPCR reproduced the reported directions of expression for selected RNAs. CONCLUSION: This study provides the first integrative multi-omics framework for understanding chronic heat adaptation in E. sinensis. By linking transcriptomic, epigenomic, and metabolic remodeling, we elucidate the molecular mechanisms underlying energy imbalance, epigenetic reprogramming, and immune dysregulation during prolonged thermal stress. These findings offer valuable insights and genomic resources for breeding heat-tolerant crab strains and improving aquaculture resilience under ongoing climate change.

DNA methylation↗

A new map for navigating the yeast epigenome.

The posttranslational modification of histones by acetylation or methylation regulates chromatin structure and can determine how a DNA sequence is interpreted by, for example, the transcriptional machinery. In this issue of Cell, Pokholok and colleagues (2005) describe a new and reliable genome-wide microarray study of histone modifications and gene expression in yeast. Their epigenetic map can be used to guide further research on the epigenome.

Chromosome Mapping↗

Genomes: epigenomics and the future of genome sciences.

Emerging data from diverse organisms indicate that we are only at the threshold of our understanding of the genome-wide implications of epigenetics. This relatively new field, entitled epigenomics, will be advanced by the recently completed sequence of the Tetrahymena thermophila macronuclear genome.

Animals↗

Profound flanking sequence preference of Dnmt3a and Dnmt3b mammalian DNA methyltransferases shape the human epigenome.

Mammalian DNA methyltransferases methylate cytosine residues within CG dinucleotides. By statistical analysis of published data of the Human Epigenome Project we have determined flanking sequences of up to +/-four base-pairs surrounding the central CG site that are characteristic of high (5'-CTTGCGCAAG-3') and low (5'-TGTTCGGTGG-3') levels of methylation in human genomic DNA. We have investigated the influence of flanking sequence on the catalytic activity of the Dnmt3a and Dnmt3b de novo DNA methyltransferases using a set of synthetic oligonucleotide substrates that covers all possible +/-1 flanks in quantitative terms. Methylation kinetics experiments revealed a >13-fold difference between the preferred (RCGY) and disfavored +/-1 flanking base-pairs (YCGR). In addition, AT-rich flanks are preferred over GC-rich ones. These experimental preferences coincide with the genomic methylation patterns. Therefore, we have expanded our experimental analysis and found a >500-fold difference in the methylation rates of the consensus sequences for high and low levels of methylation in the genome. This result demonstrates a very pronounced flanking sequence preference of Dnmt3a and Dnmt3b. It suggests that the methylation pattern of human DNA is due, in part, to the flanking sequence preferences of the de novo DNA MTases and that flanking sequence preferences could be involved in the origin of CG islands. Furthermore, similar flanking sequence preferences have been found for the stimulation of the immune system by unmethylated CGs, suggesting a co-evolution of DNA MTases and the immune system.

Base Sequence↗

Mammalian epigenomics: reprogramming the genome for development and therapy.

Epigenetic modifications of DNA and chromatin are important for genome function during development and in adults. DNA and chromatin modifications have central importance for genomic imprinting and other aspects of epigenetic control of gene expression. In somatic lineages, modifications are generally stably maintained and are characteristic of different specialized tissues. The mammalian genome undergoes major reprogramming of modification patterns in germ cells and in the early embryo. Some of the factors that are involved both in maintenance and in reprogramming, such as methyltransferases, are being identified. Epigenetic reprogramming is deficient in animal cloning, which is a major explanation for the inefficiency of the cloning procedure. Deficiencies in reprogramming are likely to underlie the occurrence of epimutations and of epigenetic inheritance. Environmental factors can alter epigenetic modifications and may thus have long-lasting effects on phenotype. Epigenomics methods are being developed to catalogue genome modifications under normal and pathological conditions. Epigenetic engineering is likely to play an important role in medicine in the future.

Animals↗

Epigenomics and epigenetic therapy of cancer.

Epigenetic inactivation of genes that are crucial for the control of normal cell growth is a hallmark of cancer cells. These epigenetic mechanisms include crosstalk between DNA methylation, histone modification and other components of chromatin higher-order structure, and lead to the regulation of gene transcription. Re-expression of genes epigenetically inactivated can result in the suppression of tumour growth or sensitization to other anticancer therapies. Small molecules that reverse epigenetic inactivation are now undergoing clinical trials in cancer patients. This, together with epigenomic analysis of chromatin alterations such as DNA methylation and histone acetylation, opens up the potential both to define epigenetic patterns of gene inactivation in tumours and to use drugs that target epigenetic silencing.

Chromatin↗

Rapid and reversible epigenome editing by endogenous chromatin regulators.

Understanding the causal link between epigenetic marks and gene regulation remains a central question in chromatin biology. To edit the epigenome we developed the FIRE-Cas9 system for rapid and reversible recruitment of endogenous chromatin regulators to specific genomic loci. We enhanced the dCas9-MS2 anchor for genome targeting with Fkbp/Frb dimerizing fusion proteins to allow chemical-induced proximity of a desired chromatin regulator. We find that mSWI/SNF (BAF) complex recruitment is sufficient to oppose Polycomb within minutes, leading to activation of bivalent gene transcription in mouse embryonic stem cells. Furthermore, Hp1/Suv39h1 heterochromatin complex recruitment to active promoters deposits H3K9me3 domains, resulting in gene silencing that can be reversed upon washout of the chemical dimerizer. This inducible recruitment strategy provides precise kinetic information to model epigenetic memory and plasticity. It is broadly applicable to mechanistic studies of chromatin in mammalian cells and is particularly suited to the analysis of endogenous multi-subunit chromatin regulator complexes.Understanding the link between epigenetic marks and gene regulation requires the development of new tools to directly manipulate chromatin. Here the authors demonstrate a Cas9-based system to recruit chromatin remodelers to loci of interest, allowing rapid, reversible manipulation of epigenetic states.

CRISPR-Cas Systems↗

3D epigenome of glial cell types in developing human cortex.

The human cortex is complex and heterogeneous, undergoing extensive expansion during development1,2. Our&#xa0;prior study of neurogenesis, including radial glia (RG), intermediate progenitor cells, excitatory neurons and interneurons demonstrated that chromatin looping underlies transcriptional regulation for lineage-specific genes, shedding light on how non-coding genetic variants contribute to neuropsychiatric disorders by means of cell-type-specific gene regulation3. RG have a crucial role in generating cellular diversity through both neurogenesis and gliogenesis and can be further classified into ventricular RG (vRG) and outer RG (oRG)4,5. Given their significance in cortical development, we conducted a comprehensive three-dimensional (3D) epigenomic analysis of four main glial populations, including vRG, oRG, oligodendrocyte precursor cells and microglia, from the mid-gestational human neocortex. By integrating gene expression, chromatin accessibility, DNA methylation and 3D chromatin interactions, we identified cell-type-specific candidate cis-regulatory elements (cCREs) and validated their regulatory function using transgenic mouse embryos. Using machine learning, we prioritized 112 schizophrenia risk variants within glia cCREs and further confirmed the predicted vRG enhancer disruption by&#xa0;the rs4449074 risk allele in vivo. Finally, oRG cCREs are enriched for human accelerated regions compared with other cCREs and a subset of human accelerated regions show activity differences from their chimpanzee orthologues that interact with genes involved in neuronal development. Our findings advance the understanding of human-specific gene regulation during corticogenesis.

Journal Article↗

The profile of repeat-associated histone lysine methylation states in the mouse epigenome.

Histone lysine methylation has been shown to index silenced chromatin regions at, for example, pericentric heterochromatin or of the inactive X chromosome. Here, we examined the distribution of repressive histone lysine methylation states over the entire family of DNA repeats in the mouse genome. Using chromatin immunoprecipitation in a cluster analysis representing repetitive elements, our data demonstrate the selective enrichment of distinct H3-K9, H3-K27 and H4-K20 methylation marks across tandem repeats (e.g. major and minor satellites), DNA transposons, retrotransposons, long interspersed nucleotide elements and short interspersed nucleotide elements. Tandem repeats, but not the other repetitive elements, give rise to double-stranded (ds) RNAs that are further elevated in embryonic stem (ES) cells lacking the H3-K9-specific Suv39h histone methyltransferases. Importantly, although H3-K9 tri- and H4-K20 trimethylation appear stable at the satellite repeats, many of the other repeat-associated repressive marks vary in chromatin of differentiated ES cells or of embryonic trophoblasts and fibroblasts. Our data define a profile of repressive histone lysine methylation states for the repetitive complement of four distinct mouse epigenomes and suggest tandem repeats and dsRNA as primary triggers for more stable chromatin imprints.

Animals↗