Biology subjects

Nguyen, S. C.

Publications and source records attributed to Nguyen, S. C..

17 recordsLinked to original sources

bioRxiv2026

First-Trimester Non-Invasive Prediction of Preterm Birth Using Cell-Free DNA Fragmentomics

ObjectiveTo develop and validate a cell-free DNA (cfDNA) fragmentomic classifier for the early prediction of spontaneous preterm birth (PTB) using routine first-trimester non-invasive prenatal testing (NIPT) data. MethodsA nested case-control study was conducted within a prospective multicenter Vietnamese cohort comprising 286 pregnancies, including 82 spontaneous PTB cases and 204 term controls. Maternal plasma cfDNA collected during routine first-trimester NIPT (median gestational age, 12 weeks) was sequenced to a depth of approximately 20 million reads per sample. Five fragmentomic feature categories including copy number alterations, end-motif composition, nucleosome distance, fragment length, and joint fragment-lengthxend-motif were evaluated for PTB prediction. Machine learning classifiers were developed in a training cohort (n = 228, 65 PTB vs 163TB) and tested in a validation cohort (n = 58, 17 PTB vs 41 TB). ResultsAmong the five fragmentomic feature classes evaluated, 4-mer end-motif (EM) profiles exhibited the most pronounced differences between PTB and term control samples. Consistent with these findings, the EM-based classifier demonstrated the highest discriminative performance in the validation cohort, achieving an AUC of 0.970 (95% CI, 0.912-1.000). At a specificity >90%, the model achieved a sensitivity of 94% (95% CI, 78-100%). ConclusionThese findings demonstrate that cfDNA EM signatures derived from routine first-trimester NIPT can accurately identify pregnancies at risk of spontaneous preterm birth, without additional blood collection or sequencing, thereby extending the clinical utility of existing prenatal screening infrastructure. KEY POINTSO_ST_ABSWhat is already known about this topic?C_ST_ABSO_LICurrent first-trimester prediction strategies based on maternal characteristics, cervical length, and biochemical markers have limited predictive accuracy, particularly in nulliparous women. C_LIO_LIExisting cfDNA-based approaches have shown only modest performance or require additional assays, limiting clinical applicability. C_LI What does this study add?O_LIExisting NIPT sequencing data can be repurposed (without additional blood sampling or sequencing) for accurate prediction of spontaneous preterm birth (AUC=0.970). C_LIO_LIA classifier employing 4-mer end-motif (EM) profiles achieved an AUC of 0.970. At a specificity >90%, the model achieved a sensitivity of 94%. C_LI

genomics↗

bioRxiv2025

SWING domains prime chromatin for nuclear body mediated gene regulation

Nuclear speckles have long been recognized as RNA-rich nuclear bodies, yet their role in genome organization and gene regulation remains incompletely understood. Using a rapid dTAG-mediated degradation system to simultaneously deplete SON and SRRM2--the core structural components of nuclear speckles--we identify a novel class of genomic regions, which we term SWING regions. Upon speckle disruption, SWING regions relocate to the nuclear periphery and acquire repressive histone marks such as H3K9me3, accompanied by gene downregulation, particularly of genes involved in developmental pathways. Consistent with this, depletion of Lamin A reduces lamina association of SWING regions and enhances their association with nuclear speckles, supporting a bidirectional balance between these two nuclear compartments. Notably, human mutations in SON and SRRM2 are associated with neurodevelopmental disorders characterized by intellectual disability and global developmental delay. Patient-derived cells bearing such mutations similarly exhibit SWING-region relocalization and gene repression, underlining a role for speckles in developmental gene regulation. We also report that drug-induced speckle rejuvenation partially rescues aberrant SWING-region localization to the nuclear lamina in patient-derived cells and iPSCs with acute depletion of SON. These findings identify SWING regions as an intermediate chromatin state positioned between nuclear speckles and the lamina, maintained by opposing functions from both structures. Our work reveals a mechanism underlying the contribution of nuclear bodies to 3D genome organization, highlights the importance of nuclear speckles and SWING regions in developmental regulation, and provides a potential therapeutic intervention in speckle dysfunction. Impact StatementIdentification of nuclear speckles as determinants of specific 3D genome organization. Demonstration of functional interactions between opposing nuclear structures (speckle versus lamina) through SWING regions. Establishment of developmental and human disease relevance of speckle-mediated genome organization. Providing potential avenues for therapeutic intervention in speckleopathies.

genetics↗

bioRxiv2025

Mechanistic and Epigenetic Partitioning of Lamina-Associated Chromatin Revealed by a Genome-Wide Imaging Screen

The nuclear periphery is a key site for heterochromatin organization in eukaryotic cells, where lamina-associated domains (LADs) promote transcriptional repression and genome stability. Despite their importance, the mechanisms governing LAD positioning in human cells remain poorly understood. To this end, we performed a genome-wide imaging-based siRNA screen and identified over 100 genes critical for perinuclear LAD localization, with a striking enrichment for RNA-binding proteins. Among these, hnRNPK emerged as a key regulator, required for the perinuclear positioning of approximately two-thirds of LADs genome-wide. Loss of hnRNPK led to LAD repositioning away from the nuclear periphery without altering their heterochromatin state, yet resulted in misexpression of genes within these domains. Notably, hnRNPK-sensitive LADs are uniquely marked by both H3K9me2 and H3K27me3, distinguishing them from hnRNPK-insensitive LADs that are enriched for H3K9me2 and H3K9me3. These findings reveal at least two mechanistically and epigenetically distinct LAD classes, suggesting that specialized pathways underlie their spatial organization. Our results uncover a pivotal role for hnRNPK in regulating the spatial organization of chromatin and highlight the broader diversity of LAD localization mechanisms.

cell biology↗

bioRxiv2025

RNA reinforces condensate nucleation on chromatin to amplify oncogenic transcription

Aberrant chromatin-associated condensates have emerged as drivers of transcriptional dysregulation in cancer. Although extensive studies have elucidated intrinsic protein sequence features governing their formation, how extrinsic factors within the chromatin environment modulate their assembly and pathogenic function remains poorly understood. Gain-of-function mutations in the histone acetylation reader ENL, found in pediatric leukemia and Wilms tumor, drive oncogenesis by inducing condensate formation at highly selective genomic loci. Here, we uncover a critical role for locally produced gene transcripts in reinforcing the nucleation, chromatin engagement, and oncogenic activity of ENL mutant condensates. Mutant ENL binds RNA in part through a conserved basic patch within its YEATS domain, and this interaction enhances condensate formation both in vitro and across diverse cellular contexts. Using a chemically inducible condensate displacement and re-nucleation system, we show that blocking ENL-RNA interactions or transcription impairs condensate reformation at endogenous targets. RNA interactions preferentially enhance mutant ENL occupancy at top-bound, condensate-permissive loci, leading to increased transcriptional bursting and robust gene activation at the single-cell and single-allele level. In mouse models, disrupting ENL-RNA interactions reduces condensate formation and oncogenic transcription in hematopoietic stem and progenitor cells, thereby suppressing ENL mutant-driven leukemogenesis. Together, these findings demonstrate that locally produced RNA transcripts can promote locus-specific nucleation of pathogenic condensates on chromatin, which in turn drive persistent and hyperactive transcription of oncogenic targets and lead to tumorigenesis.

molecular biology↗

bioRxiv2023

A nuclear architecture screen in Drosophila identifies Stonewall as a link between chromatin position at the nuclear periphery and germline stem cell fate

The association of genomic loci to the nuclear periphery is proposed to facilitate cell-type specific gene repression and influence cell fate decisions. However, the interplay between gene position and expression remains incompletely understood, in part because the proteins that position genomic loci at the nuclear periphery remain unidentified. Here, we used an Oligopaint-based HiDRO screen targeting [~]1000 genes to discover novel regulators of nuclear architecture in Drosophila cells. We identified the heterochromatin-associated protein, Stonewall (Stwl), as a factor promoting perinuclear chromatin positioning. In female germline stem cells (GSCs), Stwl binds and positions chromatin loci, including GSC differentiation genes, at the nuclear periphery. Strikingly, Stwl-dependent perinuclear positioning is associated with transcriptional repression, highlighting a likely mechanism for Stwls known role in GSC maintenance and ovary homeostasis. Thus, our study identifies perinuclear anchors in Drosophila and demonstrates the importance of gene repression at the nuclear periphery for cell fate.

cell biology↗

bioRxiv2023

Genome organization regulates nuclear pore complex formation and promotes differentiation during Drosophila oogenesis

Genome organization can regulate gene expression and promote cell fate transitions. The differentiation of germline stem cells (GSCs) to oocytes in Drosophila involves changes in genome organization mediated by heterochromatin and the nuclear pore complex (NPC). Heterochromatin represses germ-cell genes during differentiation and NPCs anchor these silenced genes to the nuclear periphery, maintaining silencing to allow for oocyte development. Surprisingly, we find that genome organization also contributes to NPC formation, mediated by the transcription factor Stonewall (Stwl). As GSCs differentiate, Stwl accumulates at boundaries between silenced and active gene compartments. Stwl at these boundaries plays a pivotal role in transitioning germ-cell genes into a silenced state and activating a group of oocyte genes and Nucleoporins (Nups). The upregulation of these Nups during differentiation is crucial for NPC formation and further genome organization. Thus, crosstalk between genome architecture and NPCs is essential for successful cell fate transitions.

developmental biology↗

bioRxiv2023

CTCF/cohesin organize the ground state of chromatin-nuclear speckle association

The interchromatin space in the cell nucleus contains various membrane-less nuclear bodies. Recent findings indicate that nuclear speckles, comprising a distinct nuclear body, exhibit interactions with certain chromatin regions in a ground state. Key questions are how this ground state of chromatin-nuclear speckle association is established and what are the gene regulatory roles of this layer of nuclear organization. We report here that chromatin structural factors CTCF and cohesin are required for full ground state association between DNA and nuclear speckles. Disruption of ground state DNA-speckle contacts via either CTCF depletion or cohesin depletion had minor effects on basal level expression of speckle-associated genes, however we show strong negative effects on stimulus-dependent induction of speckle-associated genes. We identified a putative speckle targeting motif (STM) within cohesin subunit RAD21 and demonstrated that the STM is required for chromatin-nuclear speckle association. In contrast to reduction of CTCF or RAD21, depletion of the cohesin releasing factor WAPL stabilized cohesin on chromatin and DNA-speckle contacts, resulting in enhanced inducibility of speckle-associated genes. In addition, we observed disruption of chromatin-nuclear speckle association in patient derived cells with Cornelia de Lange syndrome (CdLS), a congenital neurodevelopmental diagnosis involving defective cohesin pathways, thus revealing nuclear speckles as an avenue for therapeutic inquiry. In summary, our findings reveal a mechanism to establish the ground organizational state of chromatin-speckle association, to promote gene inducibility, and with relevance to human disease.

genetics↗

bioRxiv2022

Remodeling and compaction of the inactive X is regulated by Xist during female B cell activation

X Chromosome Inactivation (XCI) equalizes X-linked gene expression between sexes. B cells exhibit unusually dynamic XCI, as Xist RNA/heterochromatic marks on the inactive X (Xi) are absent in naive B cells, but return following mitogenic stimulation. Xi gene expression analysis supports dosage compensation, but reveals high levels of XCI escape genes in both naive and activated B cells. Allele-specific OligoPaints indicate similar Xi and Xa territories in B cells that is less compact than in fibroblasts. Allele-specific Hi-C maps reveal a lack of TAD-like structures on the Xi of naive B cells, and alterations in TADs and stronger TAD boundaries at Xi escape genes after mitogenic stimulation. Notably, Xist deletion in B cells reduces Xi compaction and changes TAD boundaries, independent of its localization to the Xi. Our findings provide the first evidence that Xi compaction/small scale organization in lymphocytes impact XCI maintenance and female biased X-linked gene expression.

genetics↗

bioRxiv2022

NIPBL and WAPL balance cohesin activity to regulate chromatin folding and gene expression

The relationship between cohesin-mediated chromatin looping and gene expression remains unclear. We investigated the roles of NIPBL and WAPL, two regulators of cohesin activity, in chromatin folding and transcription in human cells. Consistent with their opposing roles in cohesin regulation, depletion of these factors showed opposite effects on levels of chromatin-bound cohesin and spatial insulation of neighboring domains. We find that NIPBL or WAPL depletion each alter the expression of ~2,000 genes, most of which are uniquely sensitive to either regulator. We find that each set of differentially expressed genes are enriched at chromatin loop anchors and clustered within the genome, suggesting there are genomic regions sensitive to either more or less cohesin. Remarkably, co-depletion of both regulators rescued chromatin misfolding and gene misexpression compared to either single knockdown. Taken together, we present a model in which the relative, rather than absolute, levels of NIPBL and WAPL are required to balance cohesin activity in chromatin folding to regulate transcription.

genetics↗

bioRxiv2022

High-throughput Oligopaint screen identifies druggable regulators of genome folding

Although the molecular rules governing genome organization are being quickly elucidated, relatively few proteins regulating this process have been identified. To address this gap, we developed a fully automated imaging pipeline, called HiDRO (high-throughput DNA or RNA labeling with optimized Oligopaints), that permits quantitative measurement of chromatin interactions across a large number of samples. Using HiDRO, we screened the human druggable genome and identified >300 factors that regulate chromatin folding during interphase, including 43 validated hits that either increase or decrease interactions between topological associating domains (TADs). We discovered that genetic or chemical inhibition of the ubiquitous kinase GSK3A enhances long-range interactions by dysregulating cohesin-mediated chromatin looping. Collectively, these results highlight a noncanonical role for GSK3A signaling in nuclear architecture and underscore the broader utility of HiDRO-based screening to identify novel mechanisms that drive the spatial organization of the genome.

genetics↗

bioRxiv2019

H3K9me2 orchestrates inheritance of spatial positioning of peripheral heterochromatin through mitosis

Cell-type-specific 3D organization of the genome is unrecognizable during mitosis. It remains unclear how essential positional information is transmitted through cell division such that a daughter cell recapitulates the spatial genome organization of the parent. Lamina-associated domains (LADs) are regions of repressive heterochromatin positioned at the nuclear periphery that vary by cell type and contribute to cell-specific gene expression and identity. Here we show that histone 3 lysine 9 dimethylation (H3K9me2) is an evolutionarily conserved, specific mark of nuclear peripheral heterochromatin and that it is retained through mitosis. During mitosis, phosphorylation of histone 3 serine 10 temporarily shields the H3K9me2 mark allowing for dissociation of chromatin from the nuclear lamina. Using high-resolution 3D immuno-oligoFISH, we demonstrate that H3K9me2-enriched genomic regions, which are positioned at the nuclear lamina in interphase cells prior to mitosis, re-associate with the forming nuclear lamina before mitotic exit. The H3K9me2 modification of peripheral heterochromatin ensures that positional information is safeguarded through cell division such that individual LADs are re-established at the nuclear periphery in daughter nuclei. Thus, H3K9me2 acts as a 3D architectural mitotic guidepost. Our data establish a mechanism for epigenetic memory and inheritance of spatial organization of the genome.

cell biology↗

bioRxiv2018

The genome-wide, multi-layered architecture of chromosome pairing in early Drosophila embryos

Genome organization involves cis and trans chromosomal interactions, both implicated in gene regulation, development, and disease. Here, we focused on trans interactions in Drosophila, where homologous chromosomes are paired in somatic cells from embryogenesis through adulthood. We first addressed the long-standing question of whether pairing extends genome-wide and, to this end, developed a haplotype-resolved Hi-C approach that uses a new strategy to minimize homolog misassignment and thus robustly distinguish trans-homolog from cis contacts. This approach revealed striking genome-wide pairing in Drosophila embryos. Moreover, we discovered pairing to be surprisingly structured, with trans-homolog domains and interaction peaks, many coinciding with the positions of analogous cis features. We also found a significant correlation between pairing and the chromatin accessibility mediated by the pioneer factor Zelda. Our findings reveal a complex, highly structured organization underlying homolog pairing, first discovered more than a century ago.\n\nOne Sentence SummaryA robust approach for haplotype-resolved Hi-C reveals highly-structured homolog pairing in early stage Drosophila embryos.

genetics↗

bioRxiv2018

Highly Structured Homolog Pairing Reflects Functional Organization of the Drosophila Genome

Trans-homolog interactions encompass potent regulatory functions, which have been studied extensively in Drosophila, where homologs are paired in somatic cells and pairing-dependent gene regulation, or transvection, is well-documented. Nevertheless, the structure of pairing and whether its functional impact is genome-wide have eluded analysis. Accordingly, we generated a diploid cell line from divergent parents and applied haplotype-resolved Hi-C, discovering that homologs pair relatively precisely genome-wide in addition to establishing trans-homolog domains and compartments. We also elucidated the structure of pairing with unprecedented detail, documenting significant variation across the genome. In particular, we characterized two forms: tight pairing, consisting of contiguous small domains, and loose pairing, consisting of single larger domains. Strikingly, active genomic regions (A-type compartments, active chromatin, expressed genes) correlated with tight pairing, suggesting that pairing has a functional role genome-wide. Finally, using RNAi and haplotype-resolved Hi-C, we show that disruption of pairing-promoting factors results in global changes in pairing.\n\nOne Sentence SummaryHaplotype-resolved Hi-C reveals structures of homolog pairing and global implications for gene activity in hybrid PnM cells.

genetics↗

bioRxiv2018

Diversification and collapse of a telomere elongation mechanism

In virtually all eukaryotes, telomerase counteracts chromosome erosion by adding repetitive sequence to terminal ends. Drosophila melanogaster instead relies on specialized retrotransposons that insert preferentially at telomeres. This exchange of goods between host and mobile element--wherein the mobile element provides an essential genome service and the host provides a hospitable niche for mobile element propagation--has been called a genomic symbiosis. However, these telomere-specialized, jockey family elements may actually evolve to selfishly over-replicate in the genomes that they ostensibly serve. Under this intra-genomic conflict model, we expect rapid diversification of telomere-specialized retrotransposon lineages and possibly, the breakdown of this tenuous relationship. Here we report data consistent with both predictions. Searching the raw reads of the 15-million-year-old melanogaster species group, we generated de novo jockey retrotransposon consensus sequences and used phylogenetic tree-building to delineate four distinct telomere-associated lineages. Recurrent gains, losses, and replacements account for this striking retrotransposon lineage diversity. Moreover, an ancestrally telomere-specialized element has escaped, residing now throughout the genome of D. rhopaloa. In D. biarmipes, telomere-specialized elements have disappeared completely. De novo assembly of long-reads and cytogenetics confirmed this species-specific collapse of retrotransposon-dependent telomere elongation. Instead, telomere-restricted satellite DNA and DNA transposon fragments occupy its terminal ends. We infer that D. biarmipes relies instead on a recombination-based mechanism conserved from yeast to flies to humans. Combined with previous reports of adaptive evolution at host proteins that regulate telomere length, telomere-associated retrotransposon diversification and disappearance offer compelling evidence that intra-genomic conflict shapes Drosophila telomere evolution.

evolutionary biology↗

bioRxiv2018

A Multiplexed DNA FISH strategy for Assessing Genome Architecture in C. elegans

Eukaryotic DNA is highly organized within nuclei and this genomic organization is important for genome function. Fluorescent in situ hybridization (FISH) approaches allow the 3D architecture of genomes to be visualized. Scalable FISH technologies, which can be applied to whole animals, are needed to help unravel how genomic architecture regulates, or is regulated by, development, growth, reproduction, and aging. Here, we describe a multiplexed DNA FISH Oligopaint library that targets the entire C. elegans genome at chromosome, three megabase, and 500 kb scales. We describe a hybridization strategy that provides flexibility to DNA FISH experiments by coupling a single primary probe synthesis reaction to dye conjugated detection oligos via bridge oligos, eliminating the time and cost typically associated with labeling probe sets for individual DNA FISH experiments. The approach allows visualization of genome organization at varying scales in all/most cells across all stages of development in an intact animal model system.

cell biology↗

bioRxiv2018

Walking along chromosomes with super-resolution imaging, contact maps, and integrative modeling

Chromosome structure is thought to be crucial for proper functioning of the nucleus. Here, we present a method for visualizing chromosomal DNA at super-resolution and then integrating Hi-C data to produce three-dimensional models of chromosome organization. We begin by applying Oligopaint probes and the single-molecule localization microscopy methods of OligoSTORM and OligoDNA-PAINT to image 8 megabases of human chromosome 19, discovering that chromosomal regions contributing to compartments can form distinct structures. Intriguingly, our data also suggest that homologous maternal and paternal regions may be differentially organized. Finally, we integrate imaging data with Hi-C and restraint-based modeling using a method called integrative modeling of genomic regions (IMGR) to increase the genomic resolution of our traces to 10 kb.\n\nOne Sentence SummarySuper-resolution genome tracing, contact maps, and integrative modeling enable 10 kb resolution glimpses of chromosome folding.

genetics↗

bioRxiv2017

OligoMiner: A rapid, flexible environment for the design of genome-scale oligonucleotide in situ hybridization probes

Oligonucleotide (oligo)-based fluorescence in situ hybridization (FISH) has emerged as an important tool for the study of chromosome organization and gene expression and has been empowered by the commercial availability of highly complex pools of oligos. However, a dedicated bioinformatic design utility has yet to be created specifically for the purpose of identifying optimal oligo FISH probe sequences on the genome-wide scale. Here, we introduce OligoMiner, a rapid and robust computational pipeline for the genome-scale design of oligo FISH probes that affords the scientist exact control over the parameters of each probe. Our streamlined method uses standard bioinformatic file formats, allowing users to seamlessly integrate existing and new utilities into the pipeline as desired, and introduces a novel method for evaluating the specificity of each probe molecule that connects simulated hybridization energetics to rapidly generated sequence alignments using supervised learning. We demonstrate the scalability of our approach by performing genome-scale probe discovery in numerous model organism genomes and showcase the performance of the resulting probes with both diffraction-limited and single-molecule super-resolution imaging of chromosomal and RNA targets. We anticipate this pipeline will make the FISH probe design process much more accessible and will more broadly facilitate the design of pools of hybridization probes for a variety of applications.

bioinformatics↗