Biology subjects

Hwang, T.

Publications and source records attributed to Hwang, T..

16 recordsLinked to original sources

bioRxiv2026

A Neuronal Gene Expression Program Underlying Sustained Network Activity

Neurons function within interconnected networks and must continuously adjust their firing properties to maintain stable network activity. Although these adjustments require long-lasting molecular changes, the neuronal gene expression programs that support sustained network activity remain largely unknown. To address this, we developed CalTRAP-seq, a method for profiling gene expression in active neurons via calcium-dependent ribosome tagging. Applying CalTRAP-seq to primary neurons exhibiting synchronous network bursting revealed a gene expression program distinct from stimulus-induced immediate early gene responses, instead enriched for regulators of neuronal excitability. This program was accompanied by widespread alternative splicing of synaptic genes. Notably, neurons participating in network activity exhibited increased nuclear speckle formation, condensates implicated in splicing regulation. Disruption of nuclear speckles impaired synchronous burst dynamics. Together, these findings identify a gene expression program associated with sustained network activity that is complementary to stimulus-responsive gene expression, providing insight into how neurons coordinate gene expression to support stable network function.

neuroscience↗

bioRxiv2026

Allele-specific antisense oligonucleotide treatment rescues atad3-associated phenotype in zebrafish

Pathogenic variants in ATAD3A cause a spectrum of multisystem disorders, with a recurrent dominant-negative variant (c.1582C>T; p.Arg528Trp) associated with neurodevelopmental disease. Given the tolerance of ATAD3A to heterozygous loss of function variants, allele-specific transcript reduction represents a promising therapeutic strategy. We designed and optimized allele-specific antisense oligonucleotides (ASOs) targeting the c.1582C>T transcript and evaluated their efficacy and specificity in affected fibroblasts using allele-specific primers and amplicon-based next generation sequencing. Therapeutic potential was further assessed in vivo in zebrafish embryos expressing human wild-type or mutant ATAD3A transcripts. An optimized gapmer ASO selectively reduced mutant ATAD3A transcripts while relatively sparing the wild-type allele. In addition to RNase H-mediated degradation, the ASO induced exon skipping, leading to degradation of the aberrant transcript without production of a truncated protein. In zebrafish, expression of mutant human ATAD3A in embryos caused developmental abnormalities including reduced eye size, which were robustly rescued by co-injection of the optimized ASO. Our findings provide proof of concept for allele-targeted ASO therapy for dominant-negative ATAD3A variants. This work highlights the therapeutic potential of ASOs for rare dominant disorders involving genes tolerant to heterozygous loss-of-function, and establishes zebrafish as a versatile platform for in vivo ASO optimization.

genetics↗

bioRxiv2026

Deep Learning-Guided Holotomography Reveals Early Structural Remodelling During Pluripotency Exit

Real-time assessment of human pluripotent stem cell (hPSC) quality is critical for reproducibility and safety in regenerative medicine, yet current methods are invasive, labor-intensive, or highly operator-dependent. We present DeepHOPE (Deep-learning-guided Holotomography for Pluripotency Evaluation), a non-invasive, automatizable, and statistics-driven platform that integrates three-dimensional (3D) refractive index imaging with deep learning to assess pluripotency. DeepHOPE performs robustly across diverse contexts, including germ-layer differentiation, retinoic acid-induced differentiation, and mid-reprogramming cultures, enabling streamlined cell production workflows and improving the efficiency of midbrain dopaminergic neuron differentiation through informed colony selection. Mechanistically, DeepHOPE detects minute colony-scale topological changes that precede molecular loss of pluripotency. These early changes are associated with rapid F-actin remodeling, including apical-to-basal redistribution during early differentiation. Consistent with a functional role for cytoskeletal regulation in state transitions, sustained reduction of actomyosin tension decreases pluripotency, identifying cytoskeletal dynamics as an upstream determinant of early pluripotency exit. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/720508v1_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@1d73508org.highwire.dtl.DTLVardef@1dab29aorg.highwire.dtl.DTLVardef@1039f76org.highwire.dtl.DTLVardef@da29a1_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2026

Genetic architecture of miRNA expression in human brain and its contribution to brain disorders

MicroRNAs (miRNAs) regulate nearly all protein-coding genes and play critical roles in gene regulation, yet the mechanisms governing miRNA regulation remain poorly understood. Here, we examined the genetic architecture of miRNA expression in 995 human brain tissues spanning four regions and two ancestries (African and European) from neurotypical controls and individuals with three psychiatric disorders (schizophrenia, major depressive disorder, and bipolar disorder). We found that miRNA expression is highly dynamic across brain regions, with region-specific differences exceeding those attributable to ancestry or psychiatric diagnosis. Through miRNA expression quantitative trait loci (miR-eQTL) analyses, we identified genetic variants associated with miRNA expression in a region- and ancestry-dependent manner. Overall, miRNAs exhibited heritability levels comparable to protein-coding genes and were positively co-regulated with their host transcripts. Notably, miRNA-regulating genetic variants were enriched in enhancers active in oligodendrocytes and in binding sites of the transcription factor OLIG2, suggesting miRNA-mediated gene regulation in oligodendrocyte lineage. Finally, we identified 15 miRNAs as likely causative factors for psychiatric and neurodegenerative disorders such as major depressive disorder and Alzheimers disease. Together, our results reveal the genetic underpinnings of miRNA regulation in the human brain and suggest that miRNAs serve as key intermediaries linking genetic variation to complex neuropsychiatric and neurological phenotypes.

genomics↗

bioRxiv2025

Cytoskeleton remodeling caused by keratin dysregulation triggers tumor aggressiveness via promoting genomic instability and cellular adaption

Cellular architecture depends on keratin intermediate filament as a fundamental component, which offers essential mechanical support to fight environmental stresses. Our previous research demonstrated that keratin fusion variants increase tumor aggressiveness through enhanced cancer stemness in oral squamous cell carcinoma. The proper functioning of keratins plays an essential role in maintaining cell structure while determining cell fate. The present study demonstrates that keratin fusion variant drives genomic instability through cytokinesis defects, which results in the formation of polyaneuploid cancer cells (PACC). The cells expressing keratin fusion show elevated DNA damage repair gene expression, which serves as a key factor for mitotic slippage during cancer development. The PACCs generated by keratin fusion make cancer cells resistant to cisplatin treatment while simultaneously reducing {gamma}-H2AX induction and increasing survival rates. The Gene Set Enrichment Analysis results showed increased "regulation of actin cytoskeleton" activity in keratin fusion-expressing cells correlated with elevated actin filament networks and increased cell motility in these cells. In summary, the keratin fusion variant enhances cancer aggressiveness through three mechanisms: it creates genomic instability that leads to PACC formation and enables cancer cells to evade cGAS/STING-mediated death signals and modifies cytoskeleton structures, which results in drug resistance and metastasis.

cancer biology↗

bioRxiv2024

Comprehensive Whole Genome Sequencing Reveals Origins of Mutational Signatures Associated with Aging and Temozolomide Chemotherapy

In a comprehensive study to decipher the multi-layered response to the chemotherapeutic agent temozolomide (TMZ), we analyzed 427 genomes and determined mutational patterns in a collection of [~]40 isogenic DNA repair-deficient human TK6 lymphoblast cell lines. We demonstrate that the spontaneous mutational background is very similar to the aging-associated mutational signature SBS40 and mainly caused by polymerase zeta-mediated translesion synthesis (TLS). MSH2-/- mismatch repair knockout in conjunction with additional repair deficiencies uncovers cryptic mutational patterns. We report how distinct mutational signatures are induced by TMZ upon sequential inactivation of DNA repair pathways, mirroring the acquisition of chemotherapy resistance by glioblastomas. The most toxic adduct induced by TMZ, O6-meG, is directly repaired by the O6-methylguanine-DNA methyltransferase (MGMT). In MGMT-/- cells, mismatch repair (MMR) leads to cell death and limits mutagenesis. MMR deficiency results in TMZ resistance, allowing the accumulation of [~]105 C>T substitutions corresponding to signature SBS11. Under these conditions, N-alkylated bases, processed by base excision repair (BER), limit cell survival. Without BER, 3-meA is read through via error-prone TLS, causing T>A substitutions but not affecting survival. Blocking BER after abasic site formation results in large deletions and TMZ hypersensitization. Our findings reveal potential vulnerabilities of TMZ-resistant tumors.

genomics↗

bioRxiv2023

Design and validation of a high-throughput in vitro model of the outer Blood-Retinal Barrier (oBRB) using the Curiochips Microphysiological System

Numerous diseases, including AMD (age-related macular degeneration), arise from the blood-retinal barrier and blood vessel abnormalities in the eye; unfortunately, there is a lack of reliable in-vitro models for their systematic study. This study describes a high-throughput microphysiological system (MPS) designed to model the outer Blood-Retinal Barrier (oBRB). The MPS platform is engineered to integrate seamlessly with high-content screening technologies, utilizing a design with a single oBRB model incorporating RPE (retina pigment epithelial cells) and endothelial cell co-culture to fit within a single 96-well. Arranged in the standard 96-well plate format, the platform allows high-throughput assessment of barrier integrity through 3D confocal imaging (ZO-1 staining), Trans Epithelial Electrical Resistance (TEER), and permeability measurements. The oBRB model enables the investigation of crosstalk among different cell types in co-culture. This includes assessing changes in the barrier integrity of the Retinal Pigment Epithelium (RPE) monolayer and investigating neovascularization events resulting from endothelial cell remodeling. The platform is positioned for utility in drug discovery and development efforts targeting diseases involving oBRB damage and choroidal neovascularization, such as age-related macular degeneration (AMD).

bioengineering↗

bioRxiv2023

Evaluation of the RNA-dependence of PRC2 binding to chromatin in human pluripotent stem cells

Polycomb Repressive Complex 2 (PRC2), an important histone modifier and epigenetic repressor, has been known to interact with RNA for almost two decades. In our previous publication (Long, Hwang et al. 2020), we presented data supporting the functional importance of RNA interaction in maintaining PRC2 occupancy on chromatin, using comprehensive approaches including an RNA-binding mutant of PRC2 and an rChIP-seq assay. Recently, concerns have been expressed regarding whether the RNA-binding mutant has impaired histone methyltransferase activity and whether the rChIP-seq assay can potentially generate artifacts. Here we provide new data that support a number of our original findings. First, we found the RNA-binding mutant to be fully capable of maintaining H3K27me3 levels in human induced pluripotent stem cells. The mutant had reduced methyltransferase activity in vitro, but only on some substrates at early time points. Second, we found that our rChIP-seq method gave consistent data across antibodies and cell lines. Third, we further optimized rChIP-seq by using lower concentrations of RNase A and incorporating a catalytically inactive mutant RNase A as a control, as well as using an alternative RNase (RNase T1). The EZH2 rChIP-seq results using the optimized protocols supported our original finding that RNA interaction contributes to the chromatin occupancy of PRC2.

molecular biology↗

bioRxiv2023

Calcium-permeable AMPA receptors govern PV neuron feature selectivity

The brain helps us survive by forming internal representations of the external world1,2. Excitatory cortical neurons are often precisely tuned to specific external stimuli3,4. However, inhibitory neurons, such as parvalbumin-positive (PV) interneurons, are generally less selective5. PV interneurons differ from excitatory cells in their neurotransmitter receptor subtypes, including AMPA receptors6,7. While excitatory neurons express calcium-impermeable AMPA receptors containing the GluA2 subunit, PV interneurons express receptors that lack the GluA2 subunit and are calcium-permeable (CP-AMPARs). Here we demonstrate a causal relationship between CP-AMPAR expression and the low feature selectivity of PV interneurons. We find a low expression stoichiometry of GluA2 mRNA relative to other subunits in PV interneurons which is conserved across ferrets, rodents, marmosets, and humans, causing abundant CP-AMPAR expression. Replacing CP-AMPARs in PV interneurons with calcium-impermeable AMPARs increased their orientation selectivity in the visual cortex. Sparse CP-AMPAR manipulations demonstrated that this increase was cell-autonomous and could occur well beyond development. Interestingly, excitatory-PV interneuron connectivity rates and unitary synaptic strength were unaltered by CP-AMPAR removal, suggesting that the selectivity of PV interneurons can be altered without drastically changing connectivity. In GluA2 knockout mice, where all AMPARs are calcium-permeable, excitatory neurons showed significantly reduced orientation selectivity, suggesting that CP-AMPARs are sufficient to drive lower selectivity regardless of cell type. Remarkably, hippocampal PV interneurons, which usually exhibit low spatial tuning, became more spatially selective after removing CP-AMPARs, indicating that CP-AMPARs suppress the feature selectivity of PV interneurons independent of modality. These results reveal a novel role of CP-AMPARs in maintaining a low-selectivity sensory representation in PV interneurons and suggest a conserved molecular mechanism that distinguishes the unique synaptic computations of inhibitory and excitatory neurons.

neuroscience↗

bioRxiv2022

Massively Parallel Dissection of RNA in RNA-protein interactions in vivo

Many of the biological functions performed by RNA are mediated by RNA-binding proteins (RBPs), and understanding the molecular basis of these interactions is fundamental to molecular biology. Here, we present MPRNA-immunoprecipitation (MPRNA-IP), an adaptation of the previously developed massively parallel RNA assay (MPRNA), and a new avenue for in vivo high-throughput dissection of RNA-protein interactions. By using custom pools of tens of thousands of RNA sequences containing systematically designed truncations and mutations, we are able to identify RNA domains, sequences, and secondary structures necessary and sufficient for protein binding in a single experiment. We show that this approach is successful for multiple RNAs of interest including NORAD, MS2, and human telomerase RNA, and we describe statistical models for identifying RNA domains and parsing the structural contributions of RNA in these interactions. By blending modern and classical approaches, MPRNA-IP provides a novel high-throughput way to elucidate RNA-based mechanisms behind RNA-protein interactions.

genomics↗

bioRxiv2021

A distributed residue network permits conformational binding specificity in a conserved family of actin remodelers

Metazoan proteomes contain many paralogous proteins that have evolved distinct functions. The Ena/VASP family of actin regulators consists of three members that share an EVH1 interaction domain with a 100% conserved binding site. A proteome-wide screen revealed ciliary protein PCARE as a high-affinity ligand for ENAH EVH1. Here we report the surprising observation that PCARE is ~100-fold specific for ENAH over paralogs VASP and EVL and can selectively bind and inhibit ENAH-dependent adhesion in cells. Specificity arises from a mechanism whereby PCARE stabilizes a conformation of the ENAH EVH1 domain that is inaccessible to family members VASP and EVL. Structure-based modeling rapidly identified seven residues distributed throughout EVL that are sufficient to differentiate binding by ENAH vs. EVL. By exploiting the ENAH-specific conformation, we rationally designed the tightest and most selective ENAH binder to date. Our work uncovers a conformational mechanism of interaction specificity that distinguishes highly similar paralogs and establishes tools for dissecting specific Ena/VASP functions in processes including cancer cell invasion.

biochemistry↗

bioRxiv2021

A proteome-wide screen uncovers diverse roles for sequence context surrounding proline-rich motifs in Ena/VASP molecular recognition

The human proteome is replete with short linear motifs (SLiMs) of 4-6 residues that are critical for protein-protein interactions, yet the importance of the sequence surrounding such motifs is underexplored. We devised a proteomic screen to systematically examine the influence of SLiM sequence context on protein-protein interactions. Focusing on the EVH1 domain of ENAH, an actin regulator that is upregulated in invasive cancers, we screened 36-residue proteome-derived peptides for binding. We discovered a pocket on the ENAH EVH1 domain that diverged from its orthologs to recognize extended SLiMs, and we found that proteins with two EVH1-binding SLiMs can wrap around a single domain. We also found that the ciliary protein PCARE uses an extended 23-residue region to obtain higher affinity than any known ENAH EVH1-binding motif. Our screen provides a way to uncover the effects of broader proteomic context on motif-mediated interactions, revealing diverse mechanisms of contextual control over EVH1 interactions and establishing that SLiMs cant be fully understood outside of their native context.

biochemistry↗

bioRxiv2019

The Firre locus produces a trans-acting RNA molecule that functions in hematopoiesis

RNA has been classically known to play central roles in biology, including maintaining telomeres1, protein synthesis2, and in sex chromosome compensation in certain species3,4. At the center of these important biological systems are noncoding RNAs. While thousands of long noncoding RNAs (lncRNAs) have been identified in mammalian genomes5-8, attributing RNA-based roles to lncRNA loci requires an assessment of whether the observed effect could be due to DNA regulatory elements, the act of transcription, or the lncRNA transcript. Here, we use the syntenically conserved lncRNA locus, Functional intergenic repeating RNA element (Firre), that is located on the X chromosome as a model to discriminate between DNA- and RNA-mediated effects in vivo. To this end, we generated genetically defined loss-of-function, gain-of-function, and rescue mouse models for Firre and provide genetic evidence that the Firre locus produces a trans-acting RNA. We report that: (i) Firre mutant mice have cell-specific defects during hematopoiesis and changes in gene expression that can be rescued by induction of Firre RNA from a transgene in the Firre knockout background, (ii) mice overexpressing Firre from a transgene exhibit increased levels of pro-inflammatory cytokines and impaired survival upon exposure to lipopolysaccharide, and (iii) deletion of the Firre locus did not result in changes in local gene expression on the X chromosome in 9 different biological contexts, suggesting that Firre does not function by cis-acting RNA or DNA elements. Together, our results provide genetic evidence that the Firre locus produces a trans-acting lncRNA that has physiological roles in hematopoiesis and immune function.

immunology↗

bioRxiv2019

Characterizing the nuclear and cytoplasmic transcriptomes in developing and mature human cortex uncovers new insight into psychiatric disease gene regulation

Transcriptome compartmentalization by the nuclear membrane provides both stochastic and functional buffering of transcript activity in the cytoplasm and has recently been implicated in neurodegenerative disease processes. Although many mechanisms regulating transcript compartmentalization are also prevalent in brain development, the extent to which subcellular localization differs as the brain matures has yet to be addressed. To characterize the nuclear and cytoplasmic transcriptomes during brain development, we sequenced both RNA fractions from homogenate prenatal and adult human postmortem cortex using PolyA+ and RiboZero library preparation methods. We find that while many genes are differentially expressed by fraction and developmental expression changes are similarly detectable in nuclear and cytoplasmic RNA, the compartmented transcriptomes become more distinct as the brain matures, perhaps reflecting increased utilization of nuclear retention as a regulatory strategy in adult brain. We examined potential mechanisms of this developmental divergence including alternative splicing, RNA editing, nuclear pore composition, RNA binding protein motif enrichment, and RNA secondary structure. Intron retention is associated with greater nuclear abundance in a subset of transcripts, as is enrichment for several splicing factor binding motifs. Finally, we examined disease association with fraction-regulated gene sets and found nuclear-enriched genes were also preferentially enriched in gene sets associated with neurodevelopmental psychiatric diseases. These results suggest that although gene-level expression is globally comparable between fractions, nuclear retention of transcripts may play an underappreciated role in developmental regulation of gene expression in brain, particularly in genes whose dysregulation is related to neuropsychiatric disorders.

neuroscience↗

bioRxiv2019

The Tug1 Locus is Essential for Male Fertility

BackgroundSeveral long noncoding RNAs (lncRNAs) have been shown to function as central components of molecular machines that play fundamental roles in biology. While the number of annotated lncRNAs in mammalian genomes has greatly expanded, their functions remain largely uncharacterized. This is compounded by the fact that identifying lncRNA loci that have robust and reproducible phenotypes when mutated has been a challenge. ResultsWe previously generated a cohort of 20 lncRNA loci knockout mice. Here, we extend our initial study and provide a more detailed analysis of the highly conserved lncRNA locus, Taurine Upregulated Gene 1 (Tug1). We report that Tug1 knockout male mice are sterile with complete penetrance due to a low sperm count and abnormal sperm morphology. Having identified a lncRNA loci with a robust phenotype, we wanted to determine which, if any, potential elements contained in the Tug1 genomic region (DNA, RNA, protein, or the act of transcription) have activity. Using engineered mouse models and cell-based assays, we provide evidence that the Tug1 locus harbors three distinct regulatory activities - two noncoding and one coding: (i) a cis DNA repressor that regulates many neighboring genes, (ii) a lncRNA that can regulate genes by a trans-based function, and finally (iii) Tug1 encodes an evolutionary conserved peptide that when overexpressed impacts mitochondrial membrane potential. ConclusionsOur results reveal an essential role for the Tug1 locus in male fertility and uncover three distinct regulatory activities in the Tug1 locus, thus highlighting the complexity present at lncRNA loci.

genomics↗

bioRxiv2018

Integrative analysis of DNA methylation suggests down-regulation of oncogenic pathways and reduced de-novo mutation in survival outliers of glioblastoma

The study of survival outliers of glioblastoma (GBM) can have important implications on gliomagenesis as well as in the identification of ways to alter clinical course on this almost uniformly lethal cancer type. However, current studied epigenetic and genetic signatures of the GBM outliers have failed to identify unifying criteria to characterize this unique group of patients. In this study, we profiled the global DNA methylation pattern of mainly IDH1 wild type survival outliers of glioblastoma and performed comprehensive enrichment analyses with genomic and epigenomic signatures. We found that the genome of long-term survivors in glioblastoma is differentially methylated relative to short-term survivor patients depending on CpG density: hypermethylation near CpG islands (CGIs) and hypomethylation far from CGIs. Interestingly, these two patterns are associated with distinct oncogenic aspects in gliomagenesis. The hypomethylation pattern at the region distant from CGI is associated with lower rates of de novo mutations while the hypermethylation at CGIs correlates with transcriptional downregulation of genes involved in cancer progression pathways. These results extend our understanding of DNA methylation of survival outliers in glioblastoma in a genome-wide level, and provide insight on the potential impact of DNA hypomethylation in cancer genome.

cancer biology↗