Transposition of native chromatin for fast and sensitive epigenomic profiling of open chromatin, DNA-binding proteins and nucleosome position

RNA Pol-II transcripts in nucleolar associated domains of cancer cell nucleoli

We performed a comparative study of the non-ribosomal gene content of nucleoli from seven cancer cell lines, using identical methods of purification and analysis. We identified unique chromosomal domains associated with the nucleolus (NADs) and genes within these domains (NAGs). Four cell lines have relatively few NAGs, which appears mostly transcriptionally inactive, consistent with literature. The remaining three lines formed a separate group with nucleoli with unique features and NADS. They constitute larger number of common NAGs, marked by ATAC-seq and having accessible promoters, with histone markers for transcriptional activity and detectable RNA Pol II bound at their promoters. The transcripts of these genes are almost entirely exported from the nucleolus. These results indicate that RNA Pol II dependent transcription in NADs can vary widely in different cell types, presumably dependent on the cell's developmental stage. Nucleolus-associated genes are likely to be distinguished marks reflecting the cell's metabolism.

Defining molecular circuits of CD8+ T cell responses in tissues during latent viral infection

Latent viral infections rely on a precise coordination of the immune response to control sporadic viral reactivation. CD8+ T cells play a crucial role in controlling viral latency by generating diverse memory responses in an epitope-specific manner. Among these distinct responses, conventional and inflationary memory responses have been described during herpesvirus infections. Using a newly generated TCR transgenic mouse strain, we investigated the transcriptomic and epigenetic remodeling of distinct epitope-specific CD8+ T cells during CMV infection across tissues at both population and single-cell levels. Our findings reveal that whereas the transcriptomic and epigenetic landscapes of conventional and inflationary memory responses diverge in the spleen and liver, these molecular programs converge in the salivary gland, a site of CMV persistence. Thus, we provide evidence that the dynamics of memory CD8+ T cell responses are distinct between tissues.

Unravelling early hematoendothelial development through the chick model: Insights and future perspectives

The chicken embryo has been an important model in advancing our understanding of early hematoendothelial development, particularly in the formation of hematopoietic stem cells (HSCs) and the endothelial-to-hematopoietic transition (EHT). The accessibility and ease of manipulation of chicken embryos have made them an invaluable tool for researching development of blood and endothelial cells. Early research using this model provided pivotal insights, demonstrating that intra-embryonic regions, such as the dorsal aorta (DA), are primary sources of HSCs, rather than the yolk sac (YS), as previously believed. The identification of intra-aortic hematopoietic clusters (IAHCs) and the process of EHT in the chicken embryo laid the foundation for similar discoveries in other vertebrate species, including mice and zebrafish. Recent advances in genetic tools, such as transgenic chickens expressing fluorescent proteins, have further enhanced the precision of cell lineage tracing and real-time imaging of dynamic cellular processes. This review highlights both historical contributions and contemporary advancements facilitated by the chicken model, underscoring its continued relevance in developmental biology. By examining key findings and methodological innovations, we aim to demonstrate the importance of the chicken embryo as a model system for understanding hematoendothelial development and its potential for informing therapeutic applications in regenerative medicine and blood disorders. Finally, we will underscore potential applications of the chicken model for comparative and omics-level studies in conjunction with other model systems and what future directions lie ahead.

Cardiac enhancers: Gateway to the regulatory mechanisms of heart regeneration

The adult mammalian heart has limited regenerative capacity. Cardiac injury, such as a myocardial infarction (MI), leads to permanent scarring and impaired heart function. In contrast, neonatal mice and zebrafish possess the ability to repair injured hearts. Cardiac regeneration is driven by profound transcriptional changes, which are controlled by gene regulatory elements, such as tissue regeneration enhancer elements (TREEs). Here, we review recent studies on cardiac injury/regeneration enhancers across species. We further explore regulatory mechanisms governing TREE activities and their associated binding regulators. We also discuss the potential of TREE engineering and how these enhancers can be utilized for heart repair. Decoding the regulatory logic of cardiac regeneration enhancers presents a promising avenue for understanding heart regeneration and advancing therapeutic strategies for heart failure.

How to analyze and understand the human immune system

To enhance our understanding of the pathogenesis of diseases, including rheumatic diseases, and to improve disease control, it is essential to attain a thorough understanding of the human immune system, alongside mouse immunology. Historically, the investigation of the human immune system has posed significant challenges due to methodological limitations. Nonetheless, recent advancements in genomic studies of multifactorial diseases have elucidated that numerous risk-associated genetic variants affecting quantitative differences in cell-specific gene expression. In light of these findings, we are currently examining individual genetic variations in both healthy individuals and patients, as well as categorizing cells into distinct subsets in order to construct a comprehensive dataset concerning the human immune system. This is accomplished by combining data on gene expression, factors influencing the expression mechanisms, protein expression, metabolomics, and environmental variables pertinent to immune functionality-such as gut microbiota. These datasets will facilitate the comprehensive characterization of the human immune system. Using these datasets and through the integrative analyses of data related to risk genetic variations and gene expression profiles of each disease and individual, we anticipate uncovering novel insights into the human immune system, the heterogeneity of diseases, immune function mechanisms, and their regulatory strategies that may not be achievable through murine models.

Identification and Functional Assessment of Candidate Causal Cis-Regulatory Variants Underlying Electrocardiographic QT Interval GWAS Loci

BACKGROUND

Identifying causal variants among tens or hundreds of associated variants at each locus in genome-wide association studies (GWAS) is challenging. As the vast majority of GWAS variants are noncoding, sequence variation at cis-regulatory elements (CREs) affecting transcriptional expression of specific genes is a widely accepted molecular hypothesis. Following this hypothesis, combined with the observation that open chromatin is a universal hallmark of all types of CREs, we aimed to identify candidate causal cis-regulatory variants underlying QT interval GWAS loci.

METHODS

Common variants in high linkage disequilibrium with genome-wide significant variants were identified using variant call format tools. Genome-wide maps of cardiac putative CREs were generated by MACS2-based peak calling in human cardiac left ventricular DNase I sequencing and Assay for Transposase-Accessible Chromatin using sequencing data sets (n=13). Variant-CRE overlap was performed using custom tracks in the Table Browser tool at the UCSC Genome Browser. Luciferase reporter-based enhancer assays for variant-centered test elements were performed in mouse HL1 cardiomyocyte cells. Reporter activities of allelic pairs were compared using a Student t test.

RESULTS

At a dozen GWAS loci, selected for higher effect sizes and better understanding of the likely causal genes, we identified all genome-wide significant variants (n=1401) and included all common variants (minor allele frequency >1%) in high linkage disequilibrium (r2>0.9) with them as candidate variants (n=3482). Candidate variants were filtered for overlap with cardiac left ventricular putative CREs to identify candidate causal cis-regulatory variants (n=476), which were further assessed for being a known cardiac expression quantitative trait locus variant as additional functional evidence (n=243). Functional evaluation of a subset of seven candidate variants by luciferase reporter-based enhancer assays in HL1 cells using variant-centered test elements led to the identification of 6 enhancer variants with significant allelic differences.

CONCLUSIONS

These efforts have generated a comprehensive set of candidate causal variants expected to be enriched for cis-regulatory potential and thereby, explaining the observed genetic associations.

Transcription factors that define the epigenome structures and transcriptomes in microglia

Microglia, the resident macrophages of the brain, play critical roles in maintaining brain health. Recent genome-wide analyses, including ATAC-seq, ChIP-seq/CUT&RUN, and single-cell RNA-seq, have identified key transcription factors that define the transcriptome programs of microglia. Four transcription factors-PU.1, IRF8, SALL1, and SMAD4-form enhancer complexes and act as lineage-determining factors, shaping microglial identity. These factors co-bind with other lineage-determining transcription factors, directing one towards designated regions that program microglia while inhibiting the other from binding to DNA. Other transcription factors, such as BATF3 and MAFB, contribute to transcriptional cascades in microglia. TGF-β is a crucial cytokine driving these transcription factors to bind DNA and maintain homeostatic microglia. These findings provide insights into the physiological aspects of microglia and their roles in neuroinflammatory and neurodegenerative diseases. TEASER ABSTRACT: eTOC blurb: In this article, we compiled more than 100 transcription factors expressed in microglia. Our analysis illustrates that some transcription factors are under a distinct hierarchical rank and are sequentially activated to achieve microglia specific transcriptome programs. This article offers a new scope on the mechanistic foundation underlying microglia's complex activity.

Shaking culture attenuates circadian rhythms in induced pluripotent stem cells during osteogenic differentiation through the TEAD-Fbxl3-CRY axis

Circadian rhythms, which synchronize cellular and organismal activities with the Earth's 24-hour light-dark cycle, are controlled by clock genes. These genes not only regulate metabolic and physiological processes but also influence osteogenesis. Despite extensive research on the genetic control of circadian rhythms, little is known about the mechanisms by which mechanical factors in the extracellular environment affect these rhythms during the osteogenic differentiation of induced pluripotent stem cells (iPSCs). Shaking culture, which promotes the formation of three-dimensional organoid-like constructs from iPSC embryoid bodies (iPSC-EBs), introduces distinct biomechanical forces compared with static adherent culture. This raises the question of how these forces affect the circadian gene expression during osteogenic differentiation. In this study, we investigated the effects of shaking cultures on the circadian rhythm of key clock genes (Clock, Bmal1, and Npas2) in iPSC-EBs. In the adherent culture, iPSC-EBs displayed rhythmic oscillations of the clock genes, which were attenuated in the shaking culture. RNA-seq analysis revealed that the yes-associated protein (YAP)-transcriptional enhanced associate domain (TEAD) transcriptional cascade was activated in the shaking culture. Further investigations using assay for transposase-accessible chromatin with sequencing and chromatin immunoprecipitation assays identified Fbxl3 as a direct target of this transcriptional cascade. Fbxl3 upregulation in the shaking culture enhanced the degradation of CRY proteins, which are essential components of the circadian feedback loop, thereby suppressing clock gene oscillations. In addition, treatment with verteporfin, a YAP-TEAD inhibitor, restored circadian gene oscillations and increased the expression of osteogenic markers in shaking culture. These findings highlight a novel mechanistic link between biomechanical cues and circadian regulation and offer potential insights for optimizing tissue engineering strategies in regenerative medicine.

Angiopoietin-TIE2 feedforward circuit promotes PIK3CA-driven venous malformations

Venous malformations (VMs) are vascular anomalies lacking curative treatments, often caused by somatic PIK3CA mutations that hyperactivate the PI3Kα-AKT-mTOR signaling pathway. Here, we identify a venous-specific signaling circuit driving disease progression, where excessive PI3Kα activity amplifies upstream TIE2 receptor signaling through autocrine and paracrine mechanisms. In Pik3caH1047R-driven VM mouse models, single-cell transcriptomics and lineage tracking revealed clonal expansion of mutant endothelial cells with a post-capillary venous phenotype, characterized by suppression of the AKT-inhibited FOXO1 and its target genes, including the TIE2 antagonist ANGPT2. An imbalance in TIE2 ligands, likely exacerbated by aberrant recruitment of smooth muscle cells producing the agonist ANGPT1, increased TIE2 activity in both mouse and human VMs. While mTOR blockade had limited effects on advanced VMs in mice, inhibiting TIE2 or ANGPT effectively suppressed their growth. These findings uncover a PI3K-FOXO1-ANGPT-TIE2 circuit as a core driver of PIK3CA-related VMs and highlight TIE2 as a promising therapeutic target.

Massively parallel reporter assays and mouse transgenic assays provide correlated and complementary information about neuronal enhancer activity

High-throughput massively parallel reporter assays (MPRAs) and phenotype-rich in vivo transgenic mouse assays are two potentially complementary ways to study the impact of noncoding variants associated with psychiatric diseases. Here, we investigate the utility of combining these assays. Specifically, we carry out an MPRA in induced human neurons on over 50,000 sequences derived from fetal neuronal ATAC-seq datasets and enhancers validated in mouse assays. We also test the impact of over 20,000 variants, including synthetic mutations and 167 common variants associated with psychiatric disorders. We find a strong and specific correlation between MPRA and mouse neuronal enhancer activity. Four out of five tested variants with significant MPRA effects affected neuronal enhancer activity in mouse embryos. Mouse assays also reveal pleiotropic variant effects that could not be observed in MPRA. Our work provides a catalog of functional neuronal enhancers and variant effects and highlights the effectiveness of combining MPRAs and mouse transgenic assays.

An ATAC-seq protocol for neuroscience research

ATAC-seq (assay for transposase-accessible chromatin using sequencing) enables high resolution mapping of chromatin accessibility, providing critical insights into gene regulatory mechanisms in neuroscience research. This protocol presents an optimized approach for applying ATAC-seq to neural tissues and cells, addressing the unique challenges of preserving chromatin integrity in these delicate samples. We detail the key steps of tissue processing, nuclear isolation, transposition reactions, and library preparation specifically adapted for neural applications. The method requires minimal starting material (20,000-50,000 cells) while maintaining high sensitivity for detecting regulatory elements involved in neural development, plasticity, and neurological disorders. This tailored protocol facilitates robust investigation of neuroepigenomic regulation in diverse experimental contexts.

3D genome organization shapes DNA damage susceptibility to platinum-based drugs

Platinum (Pt) drugs are widely utilized in cancer chemotherapy. Although cytotoxic and resistance mechanisms of Pt drugs have been thoroughly explored, it remains elusive what factors affect the receptiveness of DNA to drug-induced damage in nuclei. Here, we demonstrate that nuclear locations of chromatin play a key role in Pt drug-induced DNA damage susceptibility in vivo. By integrating data from damage-seq experiments with 3D genome structure information, we show that nuclear locations of chromatin relative to specific nuclear bodies and compartments explain patterns of cisplatin DNA damage susceptibility. This aligns with observations of cisplatin enrichment in biomolecular condensates at certain nuclear bodies. Finally, 3D structure mapping of DNA damage reveals characteristic differences between nuclear distributions of oxaliplatin-induced DNA damage in drug resistant versus sensitive cells. DNA damage increases in gene-poor chromatin at the nuclear periphery, while it decreases in gene-rich regions located at nuclear speckles. This suggests a strategic redistribution of Pt drug-induced damage in nuclei during chemoresistance development.

Revealing long-range heterogeneous organization of nucleoproteins with 6mA footprinting by ipdTrimming

Enabled by long-read sequencing technologies, particularly Single Molecule, Real-Time sequencing, N6-methyladenine (6mA) footprinting is a transformative methodology for revealing the heterogenous and dynamic distribution of nucleosomes and other DNA-binding proteins. Here, we present ipdTrimming, a novel 6mA-calling pipeline that outperforms existing tools in both computational efficiency and accuracy. Utilizing this optimized experimental and computational framework, we are able to map nucleosome positioning and transcription factor occupancy in nuclear DNA and establish high-resolution, long-range binding events in mitochondrial DNA. Our study highlights the potential of 6mA footprinting to capture coordinated nucleoprotein binding and to unravel epigenetic heterogeneity.

Joint analysis of chromatin accessibility and gene expression in the same single cells reveals cancer-specific regulatory programs

Biological analyses conducted at the single-cell scale have revealed profound impacts of heterogeneity and plasticity of chromatin states and gene expression on physiology and cancer. Here, we developed Parallel-seq, a technology for simultaneously measuring chromatin accessibility and gene expression in the same single cells. By combining combinatorial cell indexing and droplet overloading, Parallel-seq generates high-quality data in an ultra-high-throughput fashion and at a cost two orders of magnitude lower than alternative technologies (10× Multiome and ISSAAC-seq). We applied Parallel-seq to 40 lung tumor and tumor-adjacent clinical samples and obtained over 200,000 high-quality joint scATAC-and-scRNA profiles. Leveraging this large dataset, we characterized copy-number variations (CNVs) and extrachromosomal circular DNA (eccDNA) heterogeneity in tumor cells, predicted hundreds of thousands of cell-type-specific regulatory events, and identified enhancer mutations affecting tumor progression. Our analyses highlight Parallel-seq's power in investigating epigenetic and genetic factors driving cancer development at the cell-type-specific level and its utility for revealing vulnerable therapeutic targets.

PBX1 and PBX3 transcription factors regulate SHH expression in the Frontonasal Ectodermal Zone through complementary mechanisms

Sonic hedgehog (SHH) signaling from the frontonasal ectodermal zone (FEZ) is a key regulator of craniofacial morphogenesis. Along with SHH, pre-B-cell leukemia homeobox (PBX) transcription factors regulate midfacial development. PBXs act in the epithelium during fusion of facial primordia, but their specific interactions with SHH have not been investigated. We hypothesized that PBX1/3 regulate SHH expression in the FEZ by activating or repressing transcription. The hypothesis was tested by manipulating PBX1/3 expression in chick embryos and profiling epigenomic landscapes at early developmental stages. PBX1/3 expression was perturbed in the chick face beginning at stage 10 (HH10) using RCAS viruses, and the resulting SHH expression was assessed at HH22. Overexpressing PBX1 expanded the SHH domain, while overexpressing PBX3 resulted in an opposite effect. Conversely, reducing PBX1 expression decreased SHH expression, but reducing PBX3 induced ectopic SHH expression. We performed ATAC-seq and mapped binding of PBX1 and PBX3 to DNA with ChIP-seq on the FEZ at HH22 to assess direct interactions of PBX1/3 with the SHH locus. These multi-omics approaches uncovered a 400 bp PBX1-enriched element within intron 1 of SHH (chr2:8,173,222-8,173,621). Enhancer activity of this element was demonstrated by electroporation of reporter constructs in ovo and luciferase reporter assays in vitro. When bound by PBX1, this element upregulates transcription, while it downregulates transcription when bound by PBX3. The present study identifies a cis-regulatory element, named SFE1, that interacts with PBX1/3 either directly or within a complex with cofactors to modulate SHH expression in the FEZ. This research establishes that PBX1 and PBX3 play complementary roles in SHH regulation during embryonic development.

Deciphering enhancers of hearing loss genes for efficient and targeted gene therapy of hereditary deafness

Hereditary hearing loss accounts for about 60% of congenital deafness. Although adeno-associated virus (AAV)-mediated gene therapy shows substantial potential for treating genetic hearing impairments, there remain significant concerns regarding the specificity and safety of AAV vectors. The sophisticated nature of the cochlea further complicates the challenge of precisely targeting gene delivery. Here, we introduced an AAV-reporter-based in vivo transcriptional enhancer reconstruction (ARBITER) workflow, enabling efficient and reliable dissection of enhancers. With ARBITER, we successfully demonstrated that the conserved non-coding elements (CNEs) within the gene locus collaboratively regulate the expression of Slc26a5, which was further validated using knockout mouse models. We also assessed the potential of identified enhancers to treat hereditary hearing loss by conducting gene therapy in Slc26a5 mutant mice. Based on the original Slc26a5 enhancer with limited efficiency, we engineered a highly efficient and outer hair cell (OHC)-specific enhancer, B8, which successfully restored hearing of Slc26a5 knockout mice.

Trajectories from single-cells to PAX5-driven leukemia reveal PAX5-MYC interplay in vivo

PAX5 acts as a master regulator of B-cell proliferation and differentiation. Its germline and somatic deregulation have both been implicated in the development of B-cell precursor acute lymphoblastic leukemia (BCP-ALL). However, the process how reduced PAX5 transcriptional activity mediates progression to BCP-ALL, is still poorly understood. Here, we characterized the longitudinal effects of PAX5 reduction on healthy, pre-leukemic and BCP-ALL cells at the single-cell level. Cell-surface marker analysis revealed a genotype-driven enrichment of the pre-BII population in healthy Pax5± mice. This population showed downregulated B-cell receptor signaling, while DNA replication/repair and cell-cycle signaling pathways were upregulated. Moreover, we observed a shift in the kappa/lambda light chain ratio toward lambda rearranged B-cells. Transplantation experiments further validated a delay of Pax5± pre-BII cells in maturation and transition to IgM-positivity. Additionally, single-cell RNA-Sequencing and bulk ATAC-Sequencing of different stages of BCP-ALL evolution showed that Pax5± pre-leukemic cells lose their B-cell identity and display Myc activation. Subsequently, BCP-ALLs acquired additional RAG-mediated aberrations and driver mutations in JAK-STAT and RAS-signaling pathways. Together, this study elucidates molecular and functional checkpoints in PAX5-mediated pre-leukemic cell progression exploitable for therapeutic intervention and demonstrates that PAX5 reduction is sufficient to initiate clonal evolution to BCP-ALL through activation of MYC.

Feedback regulation of m6A modification creates local auxin maxima essential for rice microsporogenesis

N6-methyladenosine (m6A) RNA modification and its effectors control various plant developmental processes, yet whether and how these effectors are transcriptionally controlled to confer functional specificity so far remain elusive. Herein, we show that a rice C2H2 zinc-finger protein, OsZAF, specifically activates the expression of OsFIP37 encoding a core component of the m6A methyltransferase complex during microsporogenesis in rice anthers. OsFIP37, in turn, facilitates m6A modification and stabilization of an auxin biosynthesis gene OsYUCCA3 to promote auxin biosynthesis in anthers. This elevates auxin levels coinciding with upregulation of an auxin response factor OsARF12 that positively controls OsZAF, thus creating a positive feedback circuit whereby OsFIP37 is continuously activated for local auxin production. Our findings suggest that OsZAF-dependent feedback regulation of m6A modification is integral to local auxin biosynthesis and signaling in anthers, which facilitates the timely generation of auxin maxima required for male meiosis in rice.

CREATE: cell-type-specific cis-regulatory element identification via discrete embedding

Cis-regulatory elements (CREs), including enhancers, silencers, promoters and insulators, play pivotal roles in orchestrating gene regulatory mechanisms that drive complex biological traits. However, current approaches for CRE identification are predominantly sequence-based and typically focus on individual CRE types, limiting insights into their cell-type-specific functions and regulatory dynamics. Here, we present CREATE, a multimodal deep learning framework based on Vector Quantized Variational AutoEncoder, tailored for comprehensive CRE identification and characterization. CREATE integrates genomic sequences, chromatin accessibility, and chromatin interaction data to generate discrete CRE embeddings, enabling accurate multi-class classification and robust characterization of CREs. CREATE excels in identifying cell-type-specific CREs, and provides quantitative and interpretable insights into CRE-specific features, uncovering the underlying regulatory codes. By facilitating large-scale prediction of CREs in specific cell types, CREATE enhances the recognition of disease- or phenotype-associated biological variabilities of CREs, thus advancing our understanding of gene regulatory landscapes and their roles in health and disease.

APE1 promotes lung adenocarcinoma through G4-mediated transcriptional reprogramming of urea cycle metabolism

Lung adenocarcinoma (LUAD) remains the leading cause of cancer deaths worldwide. Apurinic/apyrimidinic endonuclease 1 (APE1), an enzyme integral to DNA repair and redox signaling, is notably upregulated in LUAD. Here we reveal that APE1 amplification, primarily via allele duplication, strongly correlates with poor prognosis in LUAD patients. Using human LUAD cell lines and a KRAS-driven mouse model, we showed that APE1 deletion hampered cell proliferation and tumor growth, highlighting its role in tumorigenesis. Mechanistically, APE1 promoted the transcription of urea cycle genes CPS1 and ARG2 by modulating the presence of G-quadruplex (G4) structures in their promoter regions. APE1 loss disrupted the urea cycle and pyrimidine metabolism, inducing metabolic reprogramming and growth arrest, which could be rescued by CPS1 or pyrimidine restoration. These findings uncover APE1's role in transcriptional regulation of urea cycle metabolic reprogramming via G4 structure, providing a potential therapeutic target LUAD patients with elevated APE1 expression.

Normozoospermic infertile men possess subpopulations of sperm varying in DNA accessibility, relating to differing reproductive outcomes

STUDY QUESTION

Can a reliable assay be developed to quantify DNA accessibility in human sperm to help with the assessment of pre-implantation development affected by dense packaging of mammalian sperm's genetic material?

SUMMARY ANSWER

We adapted NicE-view, an assay that directly labels accessible DNA, for use in human sperm and applied it to examine spermatozoa from infertile individuals with distinct reproductive outcomes.

WHAT IS KNOWN ALREADY

Existing data suggest a connection between sperm chromatin compaction and reproductive outcomes. The assays used to generate this data, however, measure chromatin compaction indirectly and thus understanding their meaning is challenging.

STUDY DESIGN, SIZE, DURATION

Between April 2020 to December 2023, 60 normozoospermic infertile men were invited to participate in an experimental study and asked to provide a semen sample.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Among the 60 individuals forty had undergone at least one treatment with ART. Among these ART-treated participants, 20 were included in the study because after fertilization only one or no embryos developed during embryo culture (low blastocyst growth rate, LBGR). The other 20 men were included as at least 50% of cultured embryos developed to the blastocyst stage (high blastocyst growth rate). Additionally, 20 previously infertile individuals obtained a pregnancy naturally (NATP) and were included as well. Washed spermatozoa obtained from seminal plasma or prepared by swim-up procedure were processed for NicE-view to determine DNA accessibility as a marker of chromatin condensation using confocal microscopy. Images of more than 3 million spermatozoa were acquired. Computer-assisted image segmentation was used to identify individual sperm heads and DNA accessibility levels were then quantified in each. We also compared NicE-view to chromomycin A3 (CMA3), a conventional marker of chromatin de-condensation, and ATAC-see, an alternative assay for measuring DNA accessibility.

MAIN RESULTS AND THE ROLE OF CHANCE

Both semen and swim-up samples of participants contained two well-delineated subpopulations of spermatozoa with distinct DNA accessibility levels, the frequencies of which varied among individuals. Interestingly, individuals with high frequencies of highly accessible sperm DNA, as measured in semen, possessed decreased sperm concentrations. Moreover, participants with high frequency of highly accessible sperm DNA were more common in the LBGR sub-group. Surprisingly, selection of motile sperm by swim-up enriched for sperm with high DNA accessibility in participants from all three sub-groups. Chromatin accessibility measurements by Nice-view were distinct from DNA staining with the fluorescent CMA3 dye, and NicE-view allowed much clearer separation of sperm subpopulations than ATAC-see.

LIMITATIONS, REASONS FOR CAUTION

This was a single-centre study with a cohort of 60 individuals. Sperm samples containing very high frequencies of sperm with increased DNA accessibility were more common in the LBGR sub-group. The number of individuals with this pattern was, however, limited, even within this category.

WIDER IMPLICATIONS OF THE FINDINGS

High DNA accessibility is associated with poor pre-implantation embryonic development in vitro and NicE-view may be used for the prediction of abnormal embryonic development in ART. Further studies examining samples from larger cohorts of participants and the localization of accessible regions within the sperm genome are needed to fully evaluate the utility of this method.

STUDY FUNDING/COMPETING INTEREST(S)

Swiss National Science Foundation (Grant No. 189264), Swiss Center for Applied Human Toxicology (SCAHT) research (Grant No. 1 'male reproductive toxicity') (both to C.D.G.), and the Novartis Research Foundation (to A.H.F.M.P.). M.E.G., C.D.G., and A.H.F.M.P. are authors on a patent application (EP23210754.0) on the use of NicE-view for the assessment of sperm.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov ID NCT04256668.

HBV-driven host chromatin accessibility changes affect liver metabolic pathways, iron homeostasis and promote a preneoplastic phenotype

BACKROUND AND AIMS

Complex host-virus interactions account for adaptive and innate immunity dysfunctions and viral cccDNA mini-chromosome persistence, key features of HBV chronicity and challenges for HBV cure. The extent of HBV direct impact on liver transcriptome remains controversial. Transcriptional activation in eukaryotic cells is tightly linked with disruption of nucleosome organization at accessible genomic sites of remodeled chromatin. We sought to investigate the impact of HBV on chromatin accessibility and transcription.

METHODS

We used ATAC-seq (Assay for Transposase Accessible Chromatin followed by high throughput sequencing) to detect early changes in chromatin accessibility coupled with RNA-seq in HBV-infected Primary Human Hepatocytes (PHHs).

RESULTS

An increasing number of genomic sites change their nucleosome organization over time after HBV infection, with a prevalent, but not exclusive, reduction of chromatin accessibility at specific sites that is partially prevented by inhibiting HBV transcription and replication. ATAC-seq and RNA-seq integration showed that HBV infection impacts on liver fatty acids, bile acids, iron metabolism and liver cancer pathways. The upregulation of iron uptake genes leads to a significant increase of iron content in HBV-infected PHHs whereas iron chelation inhibits cccDNA transcription and viral replication. The chromatin accessibility and transcriptional changes imposed by HBV early after infection persist, as an epigenetic scar, in chronic HBV (CHB) patients and in HBV-related HCCs. These changes are to a large extent independent from viral replication levels and disease activity.

CONCLUSIONS

Altogether our results show that HBV infection impacts on host cell chromatin landscape and specific transcriptional programs including liver metabolism and liver cancer pathways. Re-wiring of iron metabolism boosts viral replication early after infection. The modulation of genes involved in cancer-related pathways may favor the development or the selection of a pro-neoplastic phenotype and persists in HBV-related HCCs.

Engineering mtDNA deletions by reconstituting end joining in human mitochondria

Recent breakthroughs in the genetic manipulation of mitochondrial DNA (mtDNA) have enabled precise base substitutions and the efficient elimination of genomes carrying pathogenic mutations. However, reconstituting mtDNA deletions linked to mitochondrial myopathies remains challenging. Here, we engineered mtDNA deletions in human cells by co-expressing end-joining (EJ) machinery and targeted endonucleases. Using mitochondrial EJ (mito-EJ) and mito-ScaI, we generated a panel of clonal cell lines harboring a ∼3.5 kb mtDNA deletion across the full spectrum of heteroplasmy. Investigating these cells revealed a critical threshold of ∼75% deleted genomes, beyond which oxidative phosphorylation (OXPHOS) protein depletion, metabolic disruption, and impaired growth in galactose-containing media were observed. Single-cell multiomic profiling identified two distinct nuclear gene deregulation responses: one triggered at the deletion threshold and another progressively responding to heteroplasmy. Ultimately, we show that our method enables the modeling of disease-associated mtDNA deletions across cell types and could inform the development of targeted therapies.

Profiling regulatory elements in vivo by genome-wide methods

The biology of gene regulation in eukaryotic genomes is a mature field. The biochemical principles of factor binding to DNA are well-known from in vitro studies, as are the structural interactions in which specific domains of these proteins interface across a short stretch of DNA to confer sequence-specific recognition. Whereas the basic principles of binding and dissociation defined in vitro apply in vivo, the living nucleus is a dynamic compartment crowded with molecules, including motors that drive chromatin movements critical for the regulation of gene expression. Understanding these dynamics in vivo has spurred the development of cutting-edge technologies to observe factor-DNA interactions. The biological significance of chromatin dynamics is now revealed by a wide variety of high-resolution chromatin profiling methods.

The regulatory potential of transposable elements in maize

The genomes of flowering plants consist largely of transposable elements (TEs), some of which modulate gene regulation and function. However, the repetitive nature of TEs and difficulty of mapping individual TEs by short-read sequencing have hindered our understanding of their regulatory potential. Here we show that long-read chromatin fibre sequencing (Fiber-seq) comprehensively identifies accessible chromatin regions (ACRs) and CpG methylation across the maize genome. We uncover stereotypical ACR patterns at young TEs that degenerate with evolutionary age, resulting in TE enhancers preferentially marked by a novel plant-specific epigenetic feature: simultaneous hyper-CpG methylation and chromatin accessibility. We show that TE ACRs are co-opted as gene promoters and that ACR-containing TEs can facilitate gene amplification. Lastly, we uncover a pervasive epigenetic signature-hypo-5mCpG methylation and diffuse chromatin accessibility-directing TEs to specific loci, including the loci that sparked McClintock's discovery of TEs.

Predicting gene expression from DNA sequence using deep learning models

Transcription of genes is regulated by DNA elements such as promoters and enhancers, the activity of which are in turn controlled by many transcription factors. Owing to the highly complex combinatorial logic involved, it has been difficult to construct computational models that predict gene activity from DNA sequence. Recent advances in deep learning techniques applied to data from epigenome mapping and high-throughput reporter assays have made substantial progress towards addressing this complexity. Such models can capture the regulatory grammar with remarkable accuracy and show great promise in predicting the effects of non-coding variants, uncovering detailed molecular mechanisms of gene regulation and designing synthetic regulatory elements for biotechnology. Here, we discuss the principles of these approaches, the types of training data sets that are available and the strengths and limitations of different approaches.

Multi-omics integration identifies NK cell-mediated cytotoxicity as a therapeutic target in systemic lupus erythematosus

Background

Systemic lupus erythematosus (SLE) is an autoimmune condition that impacts various organs. Given the intricate clinical progression of SLE, it is imperative to explore novel avenues for precise diagnosis and treatment.

Methods

Peripheral blood mononuclear cells (PBMC) were isolated from 6 SLE patients before and after treatment, 7 healthy controls and 7 disease controls. Assay for Transposase Accessible Chromatin with high throughput Sequencing (ATAC-seq) was used to analyze the chromatin accessibility signatures and RNA-seq was used to identify the differentially expressed genes, mRNA, lncRNA, circRNA, miRNA. Then ATAC-seq and RNA-seq were integrated to further analyze hub genes and pathways. Finally, we validated gene expression levels and examined changes in key genes after treatment through in vitro experiments.

Results

Our analysis reveals dynamic changes in chromatin accessibility during the course of disease progression in SLE. Significantly higher numbers of differentially accessible regions, transcripts, genes, mRNA, lncRNA, circRNA, and miRNA were observed in SLE patients compared to other cohorts, with these variances markedly reduced post-treatment. Two gene clusters associated with SLE disease improvement were identified, with a total of 140 genes intersecting with ATAC results. Pathway analysis revealed that NK cell mediated cytotoxicity was the most differentiated and therapeutically altered pathway in SLE patients. Independent sample validation confirmed that the gene expression of this pathway was reduced in SLE patients and associated with disease activity, whereas hydroxychloroquine (HCQ) effectively elevated their expression in vitro.

Conclusion

Our findings suggest that these NK cell signature genes may be associated with the complex pathogenesis of SLE. The restoration of NK cell-mediated cytotoxicity may serve as a useful marker of improvement following SLE treatment.

Pre-existing epigenetic state and differential NF-κB activation shape type 2 immune cell responses

CD4+ T helper 2 (Th2) cells and group 2 innate lymphoid cells (ILC2s) drive type 2 immune responses via similar effector molecules that are primarily induced by different signals-interleukin (IL)-33 in ILC2s and TCR engagement in Th2 cells. Here, we examined the transcriptional regulation of type 2 immunity, focusing on the NF-κB pathway, which is differentially activated by TCR engagement or cytokine signaling. Conditional deletion of the NF-κB subunits c-Rel and p65 limited the expression of key type 2 genes, including Il13 and Il5, in ILC2s but not in Th2 cells. Genome-wide analysis revealed that the regulatory regions of such genes exist in an open chromatin state in ILC2s, allowing NF-κB binding upon IL-33 stimulation. These regions are less accessible in unstimulated Th2 cells, where NFAT plays a dominant role. Accordingly, p65 deletion impaired ILC2 activation and function during airway inflammation and helminth infection. Thus, innate and adaptive lymphocytes leverage distinct epigenetic landscapes and transcriptional regulators to control shared effector genes.

Identification of Loci with High Transgene Expression in CHO Cells

Chinese Hamster Ovary (CHO) cells are commonly used for producing therapeutic proteins in the biopharmaceutical industry. Targeted integration (TI) of therapeutic protein-encoding transgenes into predetermined high and stably expressing genomic loci can simplify the cell line development processes for biologics production. Establishing a successful TI system requires identifying genomic loci that allow a high expression of the integrated transgenes. In this work, we demonstrated that the Thousands of Reporters Integrated in Parallel (TRIP) technology can identify such transcriptional hotspots in CHO cells. TRIP simplifies screening for transcriptional hotspots since it utilizes randomly integrated barcoded reporters and uses each barcode as a unique identifier to track the genomic location and activity of the corresponding reporter by next-generation sequencing. Transcriptional hotspots identified by TRIP resulted in up to a 9.4-fold increase in mRNA levels and a 5.6-fold increase in fed-batch titers of a test molecule compared with a medium-expressing control locus. Moreover, single copy expression from one of the identified transcriptional hotspots resulted in up to a 1.6-fold higher titer in comparison to the piggyBac-mediated stable expression of the same molecule. Reporter expression levels from TRIP loci showed positive correlations with active chromatin marks; however, the proximity to active marks was not consistently deterministic. These results suggest that TRIP is a powerful functional screening method for identifying transcriptional hotspots in CHO cells without the need for more complex epigenomic analyses.

Intragenic viral silencer element regulates HTLV-1 latency via RUNX complex recruitment

Retroviruses integrate their genetic material into the host genome, enabling persistent infection. Human T cell leukaemia virus type 1 (HTLV-1) and human immunodeficiency virus type 1 (HIV-1) share similarities in genome structure and target cells, yet their infection dynamics differ drastically. While HIV-1 leads to high viral replication and immune system collapse, HTLV-1 establishes latency, promoting the survival of infected cells and, in some cases, leading to leukaemia. The mechanisms underlying this latency preference remain unclear. Here we analyse blood samples from people with HTLV-1 and identify an open chromatin region within the HTLV-1 provirus that functions as a transcriptional silencer and regulates transcriptional burst. The host transcription factor RUNX1 binds to this open chromatin region, repressing viral expression. Mutation of this silencer enhances HTLV-1 replication and immunogenicity, while its insertion into HIV-1 suppresses viral production. These findings reveal a strategy by which HTLV-1 ensures long-term persistence, offering potential insights into retroviral evolution and therapeutic targets.

Deciphering the role of RNA in regulating CTCF's DNA binding affinity in leukemia cells

BACKGROUND

CTCF, a highly studied transcription factor, is essential for chromatin interaction maintenance. Several independent studies report that CTCF interacts with RNAs in vitro and in cells. Yet continuous debates about the authenticity of the RNA-binding affinity of CTCF and its biological role remain in large part due to limited research techniques available, such as CLIP-seq.

RESULT

Here, we investigate RNA's role in CTCF's transcription factor function through its chromatin occupancy. To systematically explore whether RNAs affect CTCF's ability to bind DNA, we perturb CTCF-RNA interactions by three independent approaches and examine CTCF genome occupancy by ChIP-seq. Although RNase A and triptolide treatment each affect a certain number of CTCF-binding peaks, few peaks overlap between treatment groups indicating the effect of RNA in regulating CTCF's DNA binding affinity is variable between loci. In addition, limited transcriptional or chromatin accessibility changes occur between cells expressing wild-type CTCF or CTCF lacking the RNA binding region.

CONCLUSION

Our data provide a complementary approach and in silico evidence to consider the significance of RNA affecting CTCF's DNA binding affinity globally.

Repeat-element RNAs integrate a neuronal growth circuit

Neuronal growth and regeneration are regulated by local translation of mRNAs in axons. We examined RNA polyadenylation changes upon sensory neuron injury and found upregulation of a subset of polyadenylated B2-SINE repeat elements, hereby termed GI-SINEs (growth-inducing B2-SINEs). GI-SINEs are induced from ATF3 and other AP-1 promoter-associated extragenic loci in injured sensory neurons but are not upregulated in lesioned retinal ganglion neurons. Exogenous GI-SINE expression elicited axonal growth in injured sensory, retinal, and corticospinal tract neurons. GI-SINEs interact with ribosomal proteins and nucleolin, an axon-growth-regulating RNA-binding protein, to regulate translation in neuronal cytoplasm. Finally, antisense oligos against GI-SINEs perturb sensory neuron outgrowth and nucleolin-ribosome interactions. Thus, a specific subfamily of transposable elements is integral to a physiological circuit linking AP-1 transcription with localized RNA translation.

Leveraging chicken embryos for studying human enhancers

The dynamic activity of complex gene regulatory networks stands at the core of all cellular functions that define cell identity and behaviour. Gene regulatory networks comprise transcriptional enhancers, acted upon by cell-specific transcription factors to control gene expression in a spatial and temporal specific manner. Enhancers are found in the non-coding genome; pathogenic variants can disrupt enhancer activity and lead to disease. Correlating non-coding variants with aberrant enhancer activity remains a significant challenge. Due to their clinical significance, there is a longstanding interest in understanding enhancer function during early embryogenesis. With the onset of the omics era, it is now feasible to identify putative tissue-specific enhancers from epigenome data. However, such predictions in vivo require validation. The early stages of chick embryogenesis closely parallel those of human, offering an accessible in vivo model in which to assess the activity of putative human enhancer sequences. This review explores the unique advantages and recent advancements in employing chicken embryos to elucidate the activity of human transcriptional enhancers and the potential implications of these findings in human disease.

Basal-shift transformation leads to EGFR therapy-resistance in human lung adenocarcinoma

Although EGFR tyrosine kinase inhibitors (EGFR-TKIs) are effective for EGFR-mutant lung adenocarcinoma (LUAD), resistance inevitably develops through diverse mechanisms, including secondary genetic mutations, amplifications and as-yet undefined processes. To comprehensively unravel the mechanisms of EGFR-TKI resistance, we establish a biobank of patient-derived EGFR-mutant lung cancer organoids, encompassing cases previously treated with EGFR-TKIs. Through comprehensive molecular profiling including single-cell analysis, here we identify a subgroup of EGFR-TKI-resistant LUAD organoids that lacks known resistance-related genetic lesions and instead exhibits a basal-shift phenotype characterized by the hybrid expression of LUAD- and squamous cell carcinoma-related genes. Prospective gene engineering demonstrates that NKX2-1 knockout induces the basal-shift transformation along with EGFR-target therapy resistance. Basal-shift LUADs frequently harbor CDKN2A/B loss and are sensitive to CDK4/6 inhibitors. Our EGFR-mutant lung cancer organoid library not only offers a valuable resource for lung cancer research but also provides insights into molecular underpinnings of EGFR-TKI resistance, facilitating the development of therapeutic strategies.

Epigenetic perspectives on wheat speciation, adaptation, and development

Bread wheat (Triticum aestivum) has undergone a complex evolutionary history shaped by polyploidization, domestication, and adaptation. Recent advances in multiomics approaches have shed light on the role of epigenetic mechanisms, including DNA methylation, histone modification, chromatin accessibility, and noncoding RNAs, in regulating gene expression throughout these processes. Epigenomic reprogramming contributes to genome stability and subgenome differentiation and modulates key agronomic traits by influencing flowering time, environmental responses, and developmental programs. This review synthesizes current insights into epigenetic regulation of wheat speciation, adaptation, and development, highlighting their potential applications in crop improvement. A deeper understanding of these mechanisms will facilitate targeted breeding strategies leveraging epigenetic variations to enhance wheat resilience and productivity in the face of changing environments.

ChromActivity: integrative epigenomic and functional characterization assay based annotation of regulatory activity across diverse human cell types

We introduce ChromActivity, a computational framework for predicting and annotating regulatory activity across the genome through integration of multiple epigenomic maps and various functional characterization datasets. ChromActivity generates genomewide predictions of regulatory activity associated with each functional characterization dataset across many cell types based on available epigenomic data. It then for each cell type produces ChromScoreHMM genome annotations based on the combinatorial and spatial patterns within these predictions and ChromScore tracks of overall predicted regulatory activity. ChromActivity provides a resource for analyzing and interpreting the human regulatory genome across diverse cell types.

VGLL2 and TEAD1 fusion proteins identified in human sarcoma drive YAP/TAZ-independent tumorigenesis by engaging EP300

Studies on Hippo pathway regulation of tumorigenesis largely center on YAP and TAZ, the transcriptional co-regulators of TEADs. Here, we present an oncogenic mechanism involving VGLL and TEAD fusions that is Hippo pathway-related but YAP/TAZ-independent. We characterize two recurrent fusions, VGLL2-NCOA2 and TEAD1-NCOA2, recently identified in human spindle cell rhabdomyosarcoma. We demonstrate that in contrast to VGLL2 and TEAD1 the fusion proteins are potent activators of TEAD-dependent transcription, and the function of these fusion proteins does not require YAP/TAZ. Furthermore, we identify that VGLL2 and TEAD1 fusions engage specific epigenetic regulation by recruiting histone acetyltransferase EP300 to control TEAD-mediated transcriptional and epigenetic landscapes. We show that small-molecule EP300 inhibition can suppress fusion protein-induced oncogenic transformation both in vitro and in vivo in mouse models. Overall, our study reveals a molecular basis for VGLL involvement in cancer and provides a framework for targeting tumors carrying VGLL, TEAD, or NCOA translocations.

Genomic analysis of progenitors in viral infection implicates glucocorticoids as suppressors of plasmacytoid dendritic cell generation

Plasmacytoid Dendritic cells (pDCs) are the most potent producers of interferons, which are critical antiviral cytokines. pDC development is, however, compromised following a viral infection, and this phenomenon, as well as its relationship to conventional (c)DC development is still incompletely understood. By using lymphocytic choriomeningitis virus (LCMV) infection in mice as a model system, we observed that DC progenitors skewed away from pDC and toward cDC development during in vivo viral infection. Subsequent characterization of the transcriptional and epigenetic landscape of fms-like tyrosine kinase 3+ (Flt3+) DC progenitors and follow-up studies revealed increased apoptosis and reduced proliferation in different individual DC-progenitors as well as a profound type I interferon (IFN-I)-dependent ablation of pre-pDCs, but not pre-DC precursors, after both acute and chronic LCMV infections. In addition, integrated genomic analysis identified altered activity of 34 transcription factors in Flt3+ DC progenitors from infected mice, including two regulators of Glucocorticoid (GC) responses. Subsequent studies demonstrated that addition of GCs to DC progenitors led to downregulated pDC-primed-genes while upregulating cDC-primed-genes, and that endogenous GCs selectively decreased pDC, but not cDC, numbers upon in vivo LCMV infection. These findings demonstrate a significant ablation of pre-pDCs in infected mice and identify GCs as suppressors of pDC generation from early progenitors. This provides a potential explanation for the impaired pDC development following viral infection and links pDC numbers to the hypothalamic-pituitary-adrenal axis.

The context-dependent epigenetic and organogenesis programs determine 3D vs. 2D cellular fitness of MYC-driven murine liver cancer cells

3D cellular-specific epigenetic and transcriptomic reprogramming is critical to organogenesis and tumorigenesis. Here, we dissect the distinct cell fitness in 2D (normoxia vs. chronic hypoxia) vs 3D (normoxia) culture conditions for an MYC-driven murine liver cancer model. We identify over 600 shared essential genes and additional context-specific fitness genes and pathways. Knockout of the VHL-HIF1 pathway results in incompatible fitness defects under normoxia vs. 1% oxygen or 3D culture conditions. Moreover, deletion of each of the mitochondrial respiratory electron transport chain complex has distinct fitness outcomes. Notably, multicellular organogenesis signaling pathways including TGFβ-SMAD, which is upregulated in 3D culture, specifically constrict the uncontrolled cell proliferation in 3D while inactivation of epigenetic modifiers (Bcor, Kmt2d, Mettl3, and Mettl14) has opposite outcomes in 2D vs. 3D. We further identify a 3D-dependent synthetic lethality with partial loss of Prmt5 due to a reduction of Mtap expression resulting from 3D-specific epigenetic reprogramming. Our study highlights unique epigenetic, metabolic, and organogenesis signaling dependencies under different cellular settings.

Mapping the Simultaneously Accessible and ssDNA-Containing Genome With KAS-ATAC Sequencing

The KAS-ATAC assay provides a method to capture genomic DNA fragments that are simultaneously physically accessible and contain single-stranded DNA (ssDNA) bubbles. These are characteristic features of two of the key processes involved in regulating and expressing genes-on one hand, the activity of cis-regulatory elements (cREs), which are typically devoid of nucleosomes when active and occupied by transcription factors, and on the other, the association of RNA polymerases with DNA, which results in the presence of ssDNA structures. Here, we present a detailed protocol for carrying out KAS-ATAC as well as basic processing of KAS-ATAC datasets and discuss the key considerations for its successful application. Key features • Allows mapping of simultaneously accessible and ssDNA-containing DNA fragments. • Describes the execution of N3-kethoxal labeling and transposition of native chromatin. • Describes the pulldown of biotin-labeled DNA fragments and library generation. • Describes basic KAS-ATAC data processing steps.

Comprehensive secretome profiling and CRISPR screen identifies SFRP1 as a key inhibitor of epidermal progenitor proliferation

Secreted proteins are crucial for the structure and functions of the human epidermis, but the full repertoire of the keratinocyte secretome has not been experimentally defined. In this study, we performed mass spectrometry on conditioned media from primary human keratinocytes, identifying 406 proteins with diverse roles in adhesion, migration, proliferation, proteolysis, signal transduction, and innate immunity. To leverage this new dataset, we developed a novel colony formation assay-based CRISPR screen to investigate the functions of uncharacterized secreted proteins on epidermal stem cells. The screen identified six candidate proteins that promoted proliferation of epidermal progenitors and two proteins that inhibited it. Secreted frizzled-related protein-1 (SFRP1) was the most potent inhibitor. We discovered that SFRP1 restrained clonogenic keratinocyte proliferation by inhibiting Wnt signaling as well as blocking ectopic expression of leukemia inhibitory factor (LIF). Collectively, our study expands our knowledge of the keratinocyte secretome, establishes a novel CRISPR screen to assess the function of non-cell autonomous factors, and highlights SFRP1's role in regulating epidermal balance.

PAX8 Interacts with the SWI/SNF Complex at Enhancers to Drive Proliferation in Ovarian Cancer

Activation of lineage-specific gene expression programs is mediated by the recruitment of lineage-specific transcription factors and their coactivators to chromatin. The lineage factor PAX8 drives essential gene expression in ovarian cancer cells and is required for tumor proliferation. However, the molecular details surrounding cofactor recruitment and specific activation of transcription by PAX8 remain unknown. Here, we identify an important functional interaction between PAX8 and the switch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complex. We show that PAX8 can recruit SWI/SNF complexes to DNA, in which they function to open chromatin and facilitate the expression of PAX8 target genes. Genetic deletion of PAX8 results in loss of SWI/SNF from PAX8-bound enhancers, loss of expression of associated target genes, and reduced proliferation. These results can be phenocopied by pharmacological inhibition of SWI/SNF ATPase activity. These data indicate that PAX8 mediates the expression of an essential ovarian cancer proliferative program in part by the recruitment of the SWI/SNF complex, highlighting a novel vulnerability in PAX8-dependent ovarian cancer. Implications: PAX8 recruits SWI/SNF complexes to enhancers to mediate the expression of genes essential for ovarian cancer proliferation.

Dynamic activity changes in transcription factors: Unlocking the mechanisms regulating physiological changes in the brain

Transcription factors (TFs) regulate the establishment and modulation of the transcriptome within cells, thereby playing a crucial role in various aspects of cellular physiology throughout the body. Quantitative measurement of TF activity during the development, function, and dysfunction of the brain is essential for gaining a deeper understanding of the regulatory mechanisms governing gene expression during these processes. Due to their role as regulators of gene expression, assessing and modulating detailed TF activity contributes to the development of practical methods to intervene in these processes, potentially offering more efficient treatments for diseases. Recent methodologies have revealed that TF activity is dynamically regulated within cells and organisms, including the adult brain. This review summarizes the regulatory mechanisms of TF activities and the methodologies used to assess them, emphasizing their importance in both fundamental research and clinical applications.

Towards a consensus atlas of human and mouse adipose tissue at single-cell resolution

Adipose tissue (AT) is a complex connective tissue with a high relative proportion of adipocytes, which are specialized cells with the ability to store lipids in large droplets. AT is found in multiple discrete depots throughout the body, where it serves as the primary repository for excess calories. In addition, AT has an important role in functions as diverse as insulation, immunity and regulation of metabolic homeostasis. The Human Cell Atlas Adipose Bionetwork was established to support the generation of single-cell atlases of human AT as well as the development of unified approaches and consensus for cell annotation. Here, we provide a first roadmap from this bionetwork, including our suggested cell annotations for humans and mice, with the aim of describing the state of the field and providing guidelines for the production, analysis, interpretation and presentation of AT single-cell data.

Induction of a transcriptional adaptation response by RNA destabilization events

Transcriptional adaptation (TA) is a cellular process whereby mRNA-destabilizing mutations are associated with the transcriptional upregulation of so-called adapting genes. The nature of the TA-triggering factor(s) remains unclear, namely whether an mRNA-borne premature termination codon or the subsequent mRNA decay process, and/or its products, elicits TA. Here, working with mouse Actg1, we first establish two types of perturbations that lead to mRNA destabilization: Cas9-induced mutations predicted to lead to mutant mRNA decay, and Cas13d-mediated mRNA cleavage. We find that both types of perturbations are effective in degrading Actg1 mRNA, and that they both upregulate Actg2. Notably, increased chromatin accessibility at the Actg2 locus was observed only in the Cas9-induced mutant cells but not in the Cas13d-targeted cells, suggesting that chromatin remodeling is not required for Actg2 upregulation. We further show that ribozyme-mediated Actg1 pre-mRNA cleavage also leads to a robust upregulation of Actg2, and that this upregulation is again independent of chromatin remodeling. Together, these data highlight the critical role of RNA destabilization events as a trigger for TA, or at least a TA-like response.

Novel Approach to Overcome Osimertinib Resistance Using Bromodomain and Extra-Terminal Domain Inhibitors

Osimertinib, a third-generation EGFR-tyrosine kinase inhibitor, is the first-line therapy for lung cancer harboring EGFR mutations. The mechanisms underlying osimertinib resistance are diverse, with approximately half remaining unknown. Epigenetic dysregulation is implicated in drug resistance; however, the mechanisms remain unclear. Therefore, we investigated epigenetic involvement in osimertinib resistance and its therapeutic potential. We established osimertinib-resistant cells and used an assay for transposase-accessible chromatin using sequencing to evaluate chromatin accessibility, finding significant changes post-resistance. Combining the assay for transposase-accessible chromatin and RNA sequencing data, we identified FGF1 as a resistance-related gene regulated by histone modifications. FGF1 induced osimertinib resistance, and its suppression attenuated resistance. Bromodomain and extra-terminal domain inhibitors combined with osimertinib overcame osimertinib resistance by reducing FGF1 expression. Increased FGF1 expression was observed in osimertinib-resistant clinical samples. This combination therapy was effective in cell lines and mouse xenograft models. These results suggest targeting histone modifications using bromodomain and extra-terminal domain inhibitors as a novel approach to overcoming osimertinib resistance.

Matrix-producing neutrophils populate and shield the skin

Defence from environmental threats is provided by physical barriers that confer mechanical protection and prevent the entry of microorganisms1. If microorganisms overcome those barriers, however, innate immune cells use toxic chemicals to kill the invading cells2,3. Here we examine immune diversity across tissues and identify a population of neutrophils in the skin that expresses a broad repertoire of proteins and enzymes needed to build the extracellular matrix. In the naive skin, these matrix-producing neutrophils contribute to the composition and structure of the extracellular matrix, reinforce its mechanical properties and promote barrier function. After injury, these neutrophils build 'rings' of matrix around wounds, which shield against foreign molecules and bacteria. This structural program relies on TGFβ signalling; disabling the TGFβ receptor in neutrophils impaired ring formation around wounds and facilitated bacterial invasion. We infer that the innate immune system has evolved diverse strategies for defence, including one that physically shields the host from the outside world.

Chromatin Accessibility and Translational Landscapes of Bermudagrass (Cynodon dactylon) Under Chilling Stress

Cold tolerance in plants is a complex trait regulated by a network of transcription factors (TFs) and their downstream genes. While C-repeat binding factors (CBFs) are well-known for their role in cold tolerance, other regulatory networks remain largely unexplored. This study utilizes a combined approach of Assay for Transposase-Accessible Chromatin with Sequencing (ATAC-seq) and RNA-seq to identify cold-responsive TFs in Cynodon dactylon (Bermudagrass), a species widely grown in southern China but limited by cold stress. Early-stage cold stress was found to induce dynamic changes in 331 differentially accessible regions (DARs), with over 45% located in gene promoter regions. Key TFs, including CAMTA1, CAMTA2, WRKY43, WRKY48, WRKY21, and DREB1G, were associated with gained DARs, highlighting their roles in cold response regulation. In contrast, several Heat Shock Factor (HSF) family members, such as HSFA6B, HSFB2A, HSFC1, and HSFB2B, were linked to lost DARs, underscoring their involvement in cold stress regulation. The correlation between chromatin accessibility and gene expression emphasizes the critical role of TFs in plant cold stress adaptation. This study highlights the potential of ATAC-seq and RNA-seq as powerful tools for uncovering novel TFs essential for cold tolerance in plants, offering insights for future research and breeding efforts.

Tri-omic single-cell mapping of the 3D epigenome and transcriptome in whole mouse brains throughout the lifespan

Exploring the genomic basis of transcriptional programs has been a long-standing research focus. Here we report a single-cell method, ChAIR, to map chromatin accessibility, chromatin interactions and RNA expression simultaneously. After validating in cultured cells, we applied ChAIR to whole mouse brains and delineated the concerted dynamics of epigenome, three-dimensional (3D) genome and transcriptome during maturation and aging. In particular, gene-centric chromatin interactions and open chromatin states provided 3D epigenomic mechanism underlying cell-type-specific transcription and revealed spatially resolved specificity. Importantly, the composition of short-range and ultralong chromatin contacts in individual cells is remarkably correlated with transcriptional activity, open chromatin state and genome folding density. This genomic property, along with associated cellular properties, differs in neurons and non-neuronal cells across different anatomic regions throughout the lifespan, implying divergent nuclear mechano-genomic mechanisms at play in brain cells. Our results demonstrate ChAIR's robustness in revealing single-cell 3D epigenomic states of cell-type-specific transcription in complex tissues.

Advances in Spatial Omics Technologies

Rapidly developing spatial omics technologies provide us with new approaches to deeply understanding the diversity and functions of cell types within organisms. Unlike traditional approaches, spatial omics technologies enable researchers to dissect the complex relationships between tissue structure and function at the cellular or even subcellular level. The application of spatial omics technologies provides new perspectives on key biological processes such as nervous system development, organ development, and tumor microenvironment. This review focuses on the advancements and strategies of spatial omics technologies, summarizes their applications in biomedical research, and highlights the power of spatial omics technologies in advancing the understanding of life sciences related to development and disease.