Biology subjects

Jung, I.

Publications and source records attributed to Jung, I..

16 recordsLinked to original sources

bioRxiv2026

Reprogramming Dedifferentiation Regulatory Networks Preserves Human Chondrocyte Phenotypes

Chondrocyte-based cartilage repair strategies such as autologous chondrocyte implantation (ACI) require extensive in vitro expansion to obtain clinically relevant cell numbers. However, this expansion step progressively drives chondrocyte dedifferentiation, reducing matrix-forming capacity and contributing to variable repair outcomes. To better understand this process, we used single-nucleus multiome profiling (snRNA-Seq + snATAC-Seq) to define the transcriptional and chromatin accessibility programs underlying human chondrocyte dedifferentiation during expansion. Multiome integration across passages revealed a continuous dedifferentiation trajectory accompanied by coordinated remodeling of gene expression and chromatin accessibility, identifying chromatin destabilization as an early regulatory event during phenotype loss. Guided by these regulatory signatures, we screened available small-molecule inhibitors targeting candidate pathways and found that Fludarabine most consistently preserved chondrocyte identity during early expansion. Fludarabine was associated with suppression of STAT1-related programs and early stabilization of the chromatin landscape prior to broader transcriptional recovery. Functionally, treated cells demonstrated enhanced matrix-forming capacity in chondrogenic pellet culture and significantly increased nascent protein synthesis in 3D hydrogel culture, with biosynthetic output approaching unexpanded controls by day 21. Together, these findings identify chromatin stability as a key regulatory determinant of expansion-associated chondrocyte dedifferentiation and establish a pharmacologic strategy to preserve chondrocyte functional potency during cell manufacturing for cartilage repair.

bioengineering↗

bioRxiv2026

A functional triangle relationship of topoisomerase IIβ, BARD1, and ERK2 in immediate early gene transcription

Immediate early genes (IEGs) encode master transcription factors, including EGR1, FOS, JUN, and MYC genes that drive robust transcription in the G1 phase of cell cycle. Our previous studies indicate that topoisomerase II{beta} (TOP2B) critically regulates IEG transcription and that the activities of TOP2B are dynamically controlled through post-translational modifications by BRCA1-BARD1 and ERKs. Here, we show that two E2 enzymes, UBCH5b and UBC13/MMS2, differentiate the effects and functions of TOP2B ubiquitination by BRCA1-BARD1. Comprehensive transcriptomics, proteomics, and biochemical and molecular cellular analyses revealed a close relationship between BARD1 and key mitogen-activated protein kinase pathway genes and identified activated ERK2 as a novel kinase that phosphorylates BARD1 at S391, a previously reported mitotic phosphorylation site, whose genetic mutation has been linked to tumorigenesis. Mechanistically, the catalytic activity of ERK2 stimulates TOP2B ubiquitination mediated by BRCA1-BARD1 in complex with UBCH5b and UBC13/MMS2, which controls the binding and function of TOP2B and BARD1 for transcriptional activation at representative IEGs. Taken together, our data propose that there is a functional regulatory circuit involving TOP2B, BARD1, and ERK2, three key transcriptional activators for IEG transcription, in which the gene association and catalytic activity of TOP2B are regulated through E2-differentiated ubiquitination by BRCA1-BARD1 and the phosphorylation of BARD1 by ERK2 for productive transcription.

molecular biology↗

bioRxiv2026

Age-Dependent Chromatin Remodeling Drives Inflammatory Dysregulation in Tendon Cells

Aging impairs tissue function and tolerance to cellular stress by reprogramming the behavior of resident cells. With global increases in lifespan, the prevalence of chronic and degenerative musculoskeletal disorders, including tendon degeneration, continues to rise; however, effective interventions to counteract age-related decline remain limited. Here, we investigate how a central age-associated stressor, inflammation, differentially modulates tendon cell behavior derived from young and mature-aged donors. Using super-resolution microscopy to resolve nanoscale chromatin organization in conjunction with epigenomic and transcriptomic profiling, we identify age-dependent regulatory mechanisms that govern inflammatory responsiveness. Mature-aged tendon cells exhibit exaggerated pro-inflammatory and catabolic responses across chromatin, gene expression, and protein signaling levels, characterized by enhanced TNF receptor organization, elevated accessibility at pro-inflammatory regulatory elements, and robust induction of matrix-degrading enzymes. Notably, the AP-1 transcription factor family emerges as a central age-dependent regulator, displaying distinct motif accessibility patterns that bias mature tenocytes toward inflammatory and degenerative transcriptional programs. Taken together, our findings demonstrate that age-dependent epigenetic priming amplifies inflammatory sensitivity and constrains reparative gene regulation in mature tendon cells. This work provides a mechanistic framework linking chromatin remodeling to tendon degeneration and holds potential to identify epigenetic and transcriptional pathways as potential targets for rejuvenation strategies in aging musculoskeletal tissues.

bioengineering↗

bioRxiv2026

Hyperactive BMP and Mechanosignaling Remodel Chromatin to Drive Aberrant Osteogenesis in FOP

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder in which a recurrent ACVR1 (R206H) mutation drives progressive heterotopic ossification (HO). While aberrant BMP hypersensitivity has been studied, how this mutation enforces a persistent pro-osteogenic state remains unclear. Here, we combined super-resolution stochastic optical reconstruction microscopy (STORM), transposase-accessible chromatin with sequencing (ATAC-Seq), and RNA sequencing (RNA-Seq) to investigate how Acvr1R206H remodels chromatin to promote osteogenic transcriptional programs. Mutant mouse embryonic fibroblasts (MEFs) exhibited globally decondensed chromatin and increased accessibility at developmental and osteogenic loci enriched for HOX, TEAD, and RUNX motifs. Integration of ATAC-Seq and RNA-Seq data identified transcriptional networks primed for osteochondrogenic gene expression, including ossification, extracellular matrix organization, and cell adhesion pathways, consistent with enhanced BMP-SMAD and mechanotransduction activity. Time-course experiments revealed heightened responses to BMP ligands in Acvr1R206H/+ MEFs compared to wild-type, highlighting ligand hypersensitivity. Importantly, pharmacological modulation showed that chromatin alterations were dynamic and reversible: activation of Rho/ROCK in wild-type cells reproduced the mutant chromatin state, while inhibition of Rho/ROCK or BMP-SMAD signaling restored condensation to wild-type levels in mutant cells. Together, these findings establish that Acvr1R206H enforces a pro-osteogenic chromatin landscape through convergent BMP-SMAD and Rho/ROCK signaling, predisposing progenitors to aberrant differentiation trajectories. Our study reframes FOP as a disorder of persistent, but reversible, chromatin states and identifies novel therapeutic opportunities to restore mesenchymal cell homeostasis and prevent pathological bone formation. Significance StatementFibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder in which a mutation in ACVR1/ALK2 drives progressive heterotopic ossification. However, how this mutation enforces a persistent pro-osteogenic state is unclear. Here, we show that the Acvr1R206H mutation remodels chromatin architecture and accessibility through hyperactive BMP-SMAD and Rho/ROCK signaling, activating transcription factor networks that drive osteochondrogenic gene expression. These chromatin changes are dynamic and reversible with targeted pathway inhibition, revealing therapeutic potential to restore mesenchymal cell plasticity and prevent pathological bone formation.

bioengineering↗

bioRxiv2025

A gene regulatory element modulates myosin expression and controls cardiomyocyte response to stress

A hallmark of heart disease is gene dysregulation and reactivation of fetal gene programs. Reactivation of these fetal programs has compensatory effects during heart failure, depending on the type and stage of the underlying cardiomyopathy. Thousands of putative cardiac gene regulatory elements have been identified that may control these programs, but their functions are largely unknown. We profile genome-wide changes to gene expression and chromatin structure in cardiomyocytes derived from human pluripotent stem cells. We identify and characterize a gene regulatory element essential for the regulation of MYH6, which encodes human fetal myosin. Using chromatin conformation assays in combination with epigenome editing, we find that gene regulation is mediated by direct interaction between MYH6 and the enhancer. We also find that enhancer activation alters cardiomyocyte response to the hypertrophy-inducing peptide endothelin-1. Enhancer activation prevents polyploidization and changes in calcium dynamics following stress with endothelin-1. Collectively, these results identify regulatory mechanisms of cardiac gene expression programs that modulate cardiomyocyte maturation, cellular stress response, and could serve as potential therapeutic targets.

genomics↗

bioRxiv2025

EZH1 Q571R-mediated chromatin compaction and its oncogenic potential in thyroid cancer

Dysregulation of Polycomb Repressive Complex 2 (PRC2) is established to contribute to cancer. Of its catalytic subunits, EZH1 and EZH2, EZH2 mutations in cancer have been extensively identified and studied, but the role of EZH1 in cancer remains largely unexplored. The recurrent presence of the EZH1Q571R mutation in follicular thyroid cancer suggests its involvement in tumor progression. Using EZH1 ChIP-seq, ATAC-seq, and H3K27me3 CUT&Tag, we demonstrated that EZH1Q571R enhances chromatin binding and compaction and stimulates PRC2-EZH1 catalytic activity, leading to increased H3K27me3 levels and repression of tumor suppressor genes. Purified PRC2-EZH1Q571R demonstrated a significant increase in histone methyltransferase activity compared to PRC2-EZH1WT via enhanced nucleosome binding and DNA compaction. Notably, this effect is particularly observed with EZH1Q571R but only to a lesser extent with the corresponding EZH2Q570R mutation, highlighting it as an EZH1-specific mechanism. We additionally demonstrated PRC2-EZH1Q571R to efficiently methylate H3K27 in pre-existing H3K36me2/3 nucleosomes, disrupting chromatin homeostasis. Our findings provide key insights into the molecular pathogenesis of EZH1Q571R-driven follicular thyroid cancer.

molecular biology↗

bioRxiv2025

Discovery of Epigenetically Silenced Tumor Suppressor Genes in Aggressive Breast Cancer Through a Computational Approach

Breast cancer is characterized by genetic and epigenetic deregulations, leading to aberrant expression of tissue-specific genes that are normally silent in healthy breast tissue. Our previous work identified the embryonic stem cell-specific gene DNMT3B, a de novo DNA methyltransferase, as aberrantly activated in breast cancer, correlating with aggressive tumour behaviour and high relapse risk, regardless of molecular subtype. Through integrative bioinformatic analyses of DNA methylation and transcriptomic data, we identified 154 genes downregulated via DNMT3B-driven promoter hypermethylation, many of which are associated with high relapse risk. Notably, the tumour suppressor gene GATA3 emerged as a primary target of functional inactivation through either loss-of-function mutations or DNMT3B-controlled hypermethylation, in a mutually exclusive manner. Both mechanisms of GATA3 inactivation were associated with similar molecular signatures linked to tumour progression, increased malignancy, and poorer prognosis. However, distinct differences were observed, with immune- and inflammation-related genes enriched in GATA3 hypermethylation cases but depleted in mutation-driven silencing. Additionally, our analysis uncovered other potential tumour suppressor genes epigenetically repressed in aggressive breast cancers. These findings underscore a broader role of GATA3 inactivation beyond genetic alterations and suggest therapeutic opportunities to target epigenetically silenced tumour suppressors in aggressive breast tumours.

bioinformatics↗

bioRxiv2024

Characterization of Newly Discovered Polyester Polyurethane-degrading Methylobacterium Aquaticum Strain A1

In this study, we present Methylobacterium aquaticum A1, a novel strain capable of degrading polyester polyurethane (PE-PUR). The attachment of M. aquaticum A1 to PE-PUR and its degradation capabilities were verified using Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FT-IR). Analysis of the reference genome of M. aquaticum revealed genes encoding enzymes with potential PE-PUR degrading activity, including esterases, lipase, proteases and amidase such as tesA, pgpB, aes, aprE, lon, degQ, and gatA. An esterase activity assay using p-nitrophenyl acetate (p-NPA) showed increased ester bond-cleaving activity when M. aquaticum A1 was exposed to polyurethane diol (PU-diol), suggesting inducible enzymatic activity involved in PE-PUR degradation. These findings highlight the potential of M. aquaticum A1 as a promising biocatalyst for PE-PUR degradation. IMPORTANCEMicrobial biodegradation is increasingly recognized as a sustainable approach to addressing microplastic pollution. This study introduces M. aquaticum A1, a newly isolated strain capable of adhering to and degrading polyester polyurethane (PE-PUR), one of the most widely utilized plastics. To our knowledge, this is the first report of PE-PUR degradation by a member of the Methylobacterium genus. This paper provides a detailed characterization of M. aquaticum A1 and identifies several enzyme candidates--tesA, pgpB, aes, aprE, lon, degQ, and gatA--as potentially involved in the degradation process. Given that Methylobacterium species are known to be ecologically beneficial and inhabit diverse environments, the capacity of M. aquaticum A1 to degrade PE-PUR presents a promising strategy for mitigating microplastic pollution across a range of ecosystems.

microbiology↗

bioRxiv2024

Inhibiting EZH2 complements steroid effects in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a devastating X-linked disorder caused by mutations in the dystrophin gene. Despite recent advances in understanding the disease etiology and applying emerging treatment methodologies, glucocorticoid derivatives remain the only general therapeutic option that can slow disease development. However, the precise molecular mechanism of glucocorticoid action remains unclear, and there is still need for additional remedies to complement the treatment. Here, using single-nucleus RNA-sequencing and spatial transcriptome analyses of human and mouse muscles, we investigated pathogenic features in DMD patients and palliative effects of glucocorticoids. Our approach further illuminated the importance of proliferating satellite cells, and revealed increased activity of a signal transduction pathway involving EZH2 in the patient cells. Subsequent administration of EZH2 inhibitors to Dmd mutant mice resulted in improved muscle phenotype through maintaining the immune-suppressing effect but overriding the muscle weakness and fibrogenic effects exerted by glucocorticoids. Our analysis reveals pathogenic mechanisms that can be readily targeted by extant therapeutic options for DMD. TeaserA survey of DMD tissues in human and mouse suggests EZH2 as a critical factor in DMD satellite cells; its inhibition resulted in better prognosis.

genetics↗

bioRxiv2022

Characterization of altered molecular mechanisms in Parkinson disease through cell type-resolved multi-omics analyses

Parkinsons disease (PD) is a progressive neurodegenerative disorder. However, cell type-dependent transcriptional regulatory programs responsible for PD pathogenesis remain elusive. Here, we establish transcriptomic and epigenomic landscapes of the substantia nigra (SN) by profiling 87,733 nuclei obtained from healthy controls and PD patients. Our multi-omic data integration provides functional annotation of 128,724 cis-regulatory elements (cREs) and uncovers cell-type specific dysregulated cREs with a strong transcriptional influence on genes implicated in PD. The establishment of high-resolution three-dimensional chromatin contact maps identifies 656 target genes of dysregulated cREs and genetic risk loci, including both novel candidates and known PD risk genes. Notably, these new PD candidate genes exhibit modular gene expression patterns with unique molecular signatures in distinct cell types. Thus, our single-cell transcriptome and epigenome uncover cell type-specific disrupted transcriptional regulations in PD. TeaserSingle-cell transcriptome and epigenome uncover cell type-specific disrupted transcriptional regulations in Parkinsons disease.

genomics↗

bioRxiv2021

Clinical and immunological signatures of severe COVID-19 in previously healthy patients with clonal hematopoiesis

Identifying additional risk factors for COVID-19 severity in numerous previously healthy patients without canonical clinical risk factors remains challenging. In this study, we investigate whether clonal hematopoiesis of indeterminate potential (CHIP), a common aging-related process that predisposes various inflammatory responses, may exert COVID-19 severity. We examine the clinical impact of CHIP in 143 laboratory-confirmed COVID-19 patients. Both stratified analyses and logistic regression including the interaction between canonical risk factors and CHIP show that CHIP is an independent risk factor for severe COVID-19, especially in previously healthy patients. Analyses of 60,310 single-cell immune transcriptome profiles identify distinct immunological signatures for CHIP (+) severe COVID-19 patients, particularly in classical monocytes, with a marked increase in pro-inflammatory cytokine responses and potent IFN-{gamma} mediated hyperinflammation signature. We further demonstrate that the enhanced expression of CHIP (+) specific IFN-{gamma} response genes is attributed to the CHIP mutation-dependent epigenetic reprogramming of poised or bivalent cis-regulatory elements. Our results highlight a unique immunopathogenic mechanism of CHIP in the progression of severe COVID-19, which could be extended to elucidate how CHIP contributes to a variety of human infectious diseases.

immunology↗

bioRxiv2021

CHD4 conceals aberrant CTCF-binding sites at TAD interiors by regulating chromatin accessibility in mESCs

CTCF plays a critical role in the 3D chromatin organization by determining the TAD borders. Although CTCF primarily binds at the TAD borders, there also exist putative CTCF-binding sites within TADs, which are spread throughout the genome by retrotransposition. However, the detailed mechanism responsible for masking these putative CTCF-binding sites remains elusive. Here, we show that the ATP-dependent chromatin remodeler, CHD4, regulates chromatin accessibility to conceal aberrant CTCF-binding sites embedded in H3K9me3-enriched heterochromatic B2 SINEs in mouse embryonic stem cells (mESCs). Upon CHD4 depletion, these aberrant CTCF-binding sites become accessible, and aberrant CTCF recruitment occurs at the TAD interiors, resulting in disorganization of the local TADs. Furthermore, RNA-binding intrinsically disordered domains of CHD4 is required to prevent the aberrant CTCF bindings. Lastly, CHD4 is required for the repression of B2 SINE transcripts. These results highlight the CHD4-mediated mechanism that safeguards the appropriate CTCF bindings and associated TAD organizations in mESCs.

molecular biology↗

bioRxiv2020

Simultaneous, cell-intrinsic downregulation of PD-1 and TIGIT enhances the effector function of CD19-targeting CAR T cells and promotes an early-memory phenotype

CD19-targeting chimeric antigen receptor (CAR) T cells have become an important therapeutic option for patients with relapsed and refractory B cell malignancies. However, recent clinical data indicate that a significant portion of patients still do not benefit from the therapy owing to various resistance mechanisms, including high expression of multiple inhibitory immune checkpoint receptors on activated CAR T cells. Here, we report a lentiviral two-in-one CAR T approach in which two checkpoint receptors are downregulated simultaneously by a dual short-hairpin RNA (shRNA) cassette integrated into a CAR vector. Using this system, we evaluated CD19-targeting CAR T cells in the context of four different checkpoint combinations--PD-1/TIM-3, PD-1/LAG-3, PD-1/CTLA-4 and PD-1/TIGIT--and found that CAR T cells with PD-1/TIGIT downregulation uniquely exerted synergistic antitumor effects in mouse xenograft models compared with PD-1 single downregulation, and maintained cytolytic and proliferative capacity upon repeated antigen exposure. Importantly, functional and phenotypic analyses of CAR T cells as well as analyses of transcriptomic profiles suggested that downregulation of PD-1 enhances short-term effector function, whereas downregulation of TIGIT is primarily responsible for maintaining a less-differentiated/exhausted state, providing a potential mechanism for the observed synergy. The PD-1/TIGIT-downregulated CAR T cells generated from diffuse large B-cell lymphoma patient-derived T cells using a clinically applicable manufacturing process also showed robust antitumor activity and significantly improved persistence in vivo compared with conventional CD19-targeting CAR T cells. Overall, our results demonstrate that the cell-intrinsic PD-1/TIGIT dual downregulation strategy may prove effective in overcoming immune checkpoint-mediated resistance in CAR T therapy.

immunology↗

bioRxiv2018

A new class of constitutively active super-enhancers is associated with fast recovery of 3D chromatin loops

Super-enhancers or stretch enhancers are clusters of active enhancers that often coordinate cell-type specific gene regulation. However, little is known about the function of super-enhancers beyond gene regulation. In this study, through a comprehensive analysis of super-enhancers in 30 human cell/tissue types, we identified a new class of super-enhancers which are constitutively active across most cell/tissue types. These common super-enhancers are associated with universally highly expressed genes in contrast to the canonical definition of super-enhancers that assert cell-type specific gene regulation. In addition, the genome sequence of these super-enhancers is highly conserved by evolution and among humans, advocating their universal function in genome regulation. Integrative analysis of 3D chromatin loops demonstrates that, in comparison to the cell-type specific super-enhancers, the cell-type common super-enhancers present a striking association with rapidly recovering loops. We propose that a new class of super-enhancers may play an important role in the early establishment of 3D chromatin structure.\n\nBackgroundSuper-enhancers or stretch enhancers are defined by a strong enrichment of mediators and transcription-regulating proteins, appearing to play a deterministic role in cellular identity by controlling the expression of cell-type specific genes[1, 2]. Previous studies have revealed the critical function of super-enhancers during development and differentiation[3]. The enrichment of disease-associated single nucleotide polymorphism (SNP) in super-enhancers compared to that of typical enhancers proposed a substantial link between super-enhancers and many complex human diseases[2]. In addition, a set of recent studies have proposed potential functions of super-enhancers in the extremely long-range chromatin communications and the establishment of 3D chromatin loops[4]. These results suggest a more universal role of super-enhancers in genome regulation apart from cell-type specific gene regulation, but little is known about the mechanisms underlying these various functions. To extend the current knowledge of super-enhancers and their biological roles, we conducted a comprehensive analysis of super-enhancer activities across 30 human cell/tissue types. Our analysis suggests that a substantial number of super-enhancers exhibits prevalent activities across cell-types in terms of H3K27ac signals, and that these non-canonical super-enhancers are involved in the formation of fast recovering chromatin loops.\n\nNoteA genome browser session has been set up for visualization of the super-enhancer domains described in the current study- https://genome.ucsc.edu/cgi-bin/hgTracks?hgS-doOtherUser=submit&hgS-otherUserName=abundantiavosliberabit&hgS-otherUserSessionName=SuperEnhancerDomain

genomics↗

bioRxiv2017

Histone H3 Lysine 4 methyltransferases MLL3 and MLL4 Modulate Long-range Chromatin Interactions at Enhancers

Regulation of gene expression in mammalian cells depends on long-range chromatin interactions between enhancers and promoters. Currently, the exact mechanisms that connect distal enhancers to their specific target promoters remain to be fully elucidated. Here we show that the histone H3 Lysine 4 monomethylation (H3K4me1) writer proteins MLL3 and MLL4 (MLL3/4) play an active role in this process. We demonstrate that in differentiating mouse embryonic stem cells, MLL3/4-dependent deposition of H3K4me1 at enhancers correlates with increased levels of chromatin interactions, whereas loss of MLL3/4 leads to greatly reduced frequencies of chromatin interactions and failure of lineage-specific gene expression programs. We further show that H3K4me1 facilitates recruitment of the Cohesin complex to chromatin in vitro and in vivo, providing a potential mechanism for MLL3/4 to promote chromatin looping. Taken together, our results support an active role for MLL3/4 in modulating chromatin organization at enhancers in mammalian cells.

genomics↗

bioRxiv2016

The human functional genome defined by genetic diversity

Large scale efforts to sequence whole human genomes provide extensive data on the non-coding portion of the genome. We used variation information from 11,257 human genomes to describe the spectrum of sequence conservation in the population. We established the genome-wide variability for each nucleotide in the context of the surrounding sequence in order to identify departure from expectation at the population level (context-dependent conservation). We characterized the population diversity for functional elements in the genome and identified the coordination of conserved sequences of distal and cis enhancers, chromatin marks, promoters, coding and intronic regions. The most context-dependent conserved regions of the genome are associated with unique functional annotations and a genomic organization that spreads up to one megabase. Importantly, these regions are enriched by over 100-fold of non-coding pathogenic variants. This analysis of human genetic diversity thus provides a detailed view of sequence conservation, functional constraint and genomic organization of the human genome. Specifically, it identifies highly conserved non-coding sequences that are not captured by analysis of interspecies conservation and are greatly enriched in disease variants.

genomics↗