Biology subjects

Xie, X. S.

Publications and source records attributed to Xie, X. S..

At least 19 recordsLinked to original sources

bioRxiv2026

Prediction of Transcription Factor DNA Binding Affinity with High-Throughput Kd Measurements and Deep Learning

Transcription factors (TFs) regulate gene expression through specific interactions with genomic DNA. While TF binding motifs from public databases describe sequence preferences, quantifying genome-wide affinity (Kd) is highly desirable for a more accurate thermodynamic description. Here, we report ivtFOODIE (in vitro FOOtprinting with DeamInasE), an assay that leverages deaminase-mediated cytosine-to-uracil conversion to measure Kd values for a given TF across accessible genomic regions from human cells. By pre-training on TF binding sites from JASPAR and fine-tuning with our ivtFOODIE data from 46 TFs representing 13 different DNA-binding domains (DBDs), we developed Seq2Kd, a deep learning model capable of predicting a TFs absolute binding affinity on DNA sequences. Seq2Kd enables de novo motif discovery of [~]500 previously uncharacterized human TFs and reveals the effects of genetic variation both in TF-coding regions and DNA-binding sites on gene expression and disease susceptibility. By correlating predicted affinity changes with the sign and magnitude of expression quantitative trait locus (eQTL) effects, we stratified TFs into activator-like and repressor-like groups. Compared to clinically benign variants, pathogenic single-nucleotide variants (SNVs) within regulatory and protein-coding regions show significantly larger predicted shifts in Kd. We provide an interactive web portal, the ENcyclopedia of Transcription-factor Interactions with Regulatory Elements (ENTIRE), which integrates the Seq2Kd model with the ivtFOODIE dataset. This resource offers thermodynamic prediction for TF-DNA interactions for functional genomics and human disease.

biophysics↗

bioRxiv2026

Deep Learning of High-throughput Transcription Factor-DNA Binding Affinity Data: Quantitative Comparison with Pairwise-Additive Models

Transcription factors (TFs) regulate gene expression by binding to specific DNA sequences. Widely used models of TF-DNA binding, such as position weight matrices (PWMs) and position-specific affinity matrices (PSAMs), assume binding free energy is the sum of independent base contributions. However, there is ample evidence that non-additive effects significantly influence TF binding. Here, we utilize data from a high-throughput in vitro assay (ivtFOODIE) to generate genome-scale TF-DNA dissociation constants (Kd) and systematically evaluate sequence-to-affinity models of increasing complexity. We demonstrate that pairwise additive models exhibit systematic deviations from the measured affinity landscapes. Models incorporating adjacent dinucleotide interactions and deep learning architectures achieve markedly improved agreement with experimental Kd values. The magnitude of this non-pairwise-additivity depends strongly on the TF family. In silico mutation screening reveals widespread, TF-specific long-range interposition dependencies, highlighting the role of energetic coupling across distant positions in target recognition. These results provide a quantitative framework for comparing non-pairwise-additive energetic effects across diverse TFs.

biophysics↗

bioRxiv2026

Genome-wide maps of transcription factor footprints identify noncoding variants rewiring gene regulatory networks with varTFBridge

Genome-wide association studies have identified millions of noncoding loci linked to human traits, yet how these variants alter gene regulation remains a major challenge, particularly for rare variants where whole-genome sequencing cohorts and high-resolution functional annotations remain limited. Here we show that single-molecule deaminase footprinting (FOODIE) in K562 cells captures up to 103-fold heritability enrichment for erythroid traits despite covering 0.12% of the genome. We introduce varTFBridge, integrating FOODIE footprinting with AlphaGenome variant effect prediction to identify causal noncoding variants altering transcription factor (TF)-mediated regulation. Applied to 490,640 UK Biobank genomes across 13 erythrocyte traits, varTFBridge prioritises 113 high-confidence regulatory variants (104 common, 9 rare), encompassing 2,173 linkages along the variant-TF binding- gene-trait cascade across 64 TFs and 108 genes. varTFBridge recapitulates rs112233623 and resolves its mechanism: GATA1/TAL1 co-binding disruption at a CCND3 enhancer altering red blood cell count and volume.

bioinformatics↗

bioRxiv2026

COUNTERING AGE-ASSOCIATED ALTERATIONS IN OLIGODENDROCYTE-DERIVED EXTRACELLULAR MATRIX REJUVENATES COGNITION

Efforts to rejuvenate age-related cognitive decline have predominantly targeted neurons, often overlooking non-neuronal cell types in the aging brain. Here, we show that countering alterations in oligodendrocyte-derived extracellular matrix (ECM) in the aging hippocampus restores cognition. We identify broad age-associated transcriptional and proteomic changes in oligodendrocytes, including dysregulation of the matrisome, with marked upregulation of ECM components and associated regulators with age. Among these, we detect an increase in Hyaluronan and proteoglycan link protein 2 (HAPLN2), an oligodendrocyte-derived core matrisome protein that locates specifically at the nodes of Ranvier, in the hippocampus of aged mice and older humans. Hapln2 overexpression in oligodendrocytes of young mice recapitulated age-related memory impairments. Conversely, abrogating the age-related increase in Hapln2 induced synaptic plasticity-related hippocampal transcriptional signatures and improved memory in aged mice. Together, these data define oligodendrocyte-derived ECM remodeling as a hallmark of brain aging that can be targeted to rescue cognitive decline.

neuroscience↗

bioRxiv2025

Single-cell Characterization of DNA Hydroxymethylation of the Mouse Brain During Aging

DNA methylation dynamics, including 5-hydroxymethylcytosine (5hmC) and 5-methylcytosine (5mC), critically regulate brain function, yet conventional methods cannot distinguish these modifications, obscuring their distinct roles in gene regulation and aging. We present Joint- Cabernet, a bisulfite-free single-cell platform enabling simultaneous profiling of 5hmC, 5mC, and transcriptomes. Applying Joint-Cabernet to 84,071 nuclei from adult and aged mouse brains, we resolved cell-type-specific DNA hydroxymethylation landscapes, revealing elevated 5hmCG and 5hmCH levels in transcriptionally active genes across neuronal subtypes and spatial gradients in cortical layers. During aging, 5hmCG accumulates globally but is selectively enriched at open chromatin loci, aligning with the upregulation of cell-type-specific genes in distinct brain cell types. This single-cell DNA methylation brain cell atlas provides a framework for studying methylation- driven mechanisms in brain aging and neurodegenerative diseases.

genetics↗

bioRxiv2024

Genome-wide Mapping Eukaryotic Open Chromatin Regions with Double-Stranded DNA Deaminase

A variety of methods such as ATAC-seq and CUT&Tag have been developed for probing chromatin states. However, enzymatic cleavage of DNA in these methods hinders their multi-omics integration with other DNA profiling techniques. Here, by extending our use of dsDNA deaminase (FOOtprinting with DeamInasE, FOODIE), we introduce two new methods for mapping Chromatin Open region by DeamInasE (ChrODIE) and histone modification by ANtibody-associated DeamInasE (ANDIE), respectively. Unlike cleavage-based methods, both ChrODIE and ANDIE leave genomic DNA after deamination unfragmented and amplifiable. This offers the potential for simultaneous or downstream integration with other genomic profiling methods, such as mapping 3D genome interactions.

genomics↗

bioRxiv2024

CGMFinder Identifies Correlated Gene Modules from 3H scRNA-seq Data

Correlated gene modules (CGMs) contain genes whose expression fluctuates together. Genes in CGMs are often functionally related and regulated by shared transcription factors. CGMs can be identified under steady-state conditions in populations of cells using single-cell RNA sequencing (scRNA-seq). Here, we introduce CGMFinder, a tool for CGM identification using "3H" scRNA-seq data (High mRNA capture efficiency, High cell numbers, and High sequencing depth). CGMFinder employs a graph-based filtering approach, first identifying CGM cores from highly-expressed genes and then linking noisy low-abundance genes to these cores. In lymphoblastoid cell line 3H datasets generated by in-lab and commercial protocols, CGMFinder accurately identifies CGMs enriched for gene ontologies or pathways. In cells grown under hypoxic conditions, CGMFinder successfully identified hypoxia-specific "glycolysis" and "response to oxygen levels" modules. Evaluations using ground truth correlation modules demonstrate that CGMFinder outperforms other CGM identification methods such as WGCNA and FastICA in scRNA-seq data.

genomics↗

bioRxiv2024

Quantification and potential functional relevanceof binding cooperativity of adjacent transcriptionfactors on DNA

In eukaryotes, expression of a particular gene is regulated by a combination of transcription factors (TFs) bound on regulatory regions of the genomic DNA (promoters and enhancers). Recent advances in genomic sequencing technology have allowed measurements of TFs footprints and binding affinities on DNA at the single-molecule level, permitting the probing of binding cooperativity among adjacent TFs. This necessitates quantitative descriptions of TFs binding cooperativity and understanding of its potential functional relevance. In this study, we show that, thermodynamically, the binding affinities of two adjacent TFs can either increase together (positive cooperativity) or decrease together (negative cooperativity), rather than changing in opposite directions. Their binding cooperativity can be quantified by the{gamma} coefficient, which is independent of TF concentrations, and can be determined by single-molecule binding reads either from in vitro thermodynamic condition or cellular condition of non-equilibrium steady state (NESS). The functional relevance of positive cooperativity, which has been extensively discussed in the literature, is the sigmoidal binding curve around a TF concentration threshold (analogous to oxygen binding to hemoglobin), whereas the functional relevance of negative cooperativity is two-fold. First, mutual exclusion of the two TFs enables bidirectional gene switching similar to CI-Cro system in phage{lambda} . Second, under a non-equilibrium steady-state condition, in which TFs often exhibit intranuclear concentration fluctuations, negative binding cooperativity assures fast TF dissociation from DNA and hence rapid response for gene expression regulation. Significance StatementIn eukaryotes, multiple transcription factors (TFs) bind to regulatory regions of DNA to control gene expression. The binding affinity of one TF to a specific DNA site is influenced by the binding of another TF at an adjacent site, exhibiting either positive or negative cooperativity (the TFs either strengthen or weaken each others binding). Here we present metric for such cooperativity from experimental measurables. Functionally, positive cooperativity assures sensitive response above a threshold of TF concentrations, whereas functional roles for negative cooperativity might be two folds: First, mutual exclusion of TFs binding enables bidirectional gene switching. Second, as TF concentrations oscillate under non-equilibrium steady-state condition, negative binding cooperativity assures fast TF dissociation, hence rapid switching of transcription.

biophysics↗

bioRxiv2024

Single-cell proteomics of pre-implantation mouse embryos uncovers distinct asymmetry of certain proteins among early blastomeres

During pre-implantation mouse embryonic development, blastomeres undergo division and differentiation, reaching a distinctive level of heterogeneity, hence the completion of the first cell fate determination. However, when the initial asymmetry emerges and how this heterogeneity amplifies, particularly at the protein level, remain elusive. Here, by mass spectrometry-based single-blastomere proteomics, we identified proteins exhibiting significant heterogeneity in abundance among mouse blastomeres as early as the 2-cell stage. Differential gene expression among blastomeres, as indicated by intra-embryo variation in RNA abundance detected through single-cell RNA sequencing, was insufficient to fully explain the corresponding disparities in protein abundance. Instead, the asymmetric distribution of protein molecules during cell division was observed, serving as another mechanism contributing to protein heterogeneity, independent of RNA expression.

developmental biology↗

bioRxiv2024

Human transcription factor combinations mapped by genome-wide footprinting with deaminase

An individuals somatic cells have the same genome but exhibit cell-type-specific transcriptome regulated by a combination of transcription factors (TFs) for each gene. Mapping of TF sites on the human genome is critically important for understanding functional genomics. Here we report a novel technique to measure human TFs binding sites genome-wide with single-base resolution by footprinting with deaminase (FOODIE). Single-molecule sequencing reads from thousands of cells after in situ deamination yielded site-specific TF binding fractions and the cooperativity among adjacent TFs. In a human lymphoblastoid cell line, we found that genes in a correlated gene module (CGM) share TF(s) in their cis-regulatory elements to participate a particular biological function. Finally, single-cell resolved experiments (scFOODIE) allow cell-type-specific TF footprinting in heterogeneous brain tissues.

genomics↗

bioRxiv2023

Single-cell bisulfite-free 5mC and 5hmC sequencing with high sensitivity and scalability

Existing single cell bisulfite-based DNA methylation analysis is limited by low DNA recovery, and the measurement of 5hmC at single-base resolution remains challenging. Here we present a bisulfite-free single-cell whole-genome 5mC and 5hmC profiling technique, named Cabernet, which can characterize 5mC and 5hmC at single-base resolution with high genomic coverage. Cabernet utilizes Tn5 transposome for DNA fragmentation, which enables the discrimination between different alleles for measuring hemi-methylation status. Using Cabernet, we revealed the 5mC, hemi-5mC and 5hmC dynamics during early mouse embryo development, uncovering genomic regions exclusively governed by active or passive demethylation. We show that hemi-methylation status can be used to distinguish between pre- and post-replication cells, enabling more efficient cell grouping when integrated with 5mC profile. The property of Tn5 naturally enables Cabernet to achieve high-throughput single-cell methylome profiling, where we probed mouse cortical neurons and embryonic day 7.5 (E7.5) embryos, and constructed the library for thousands of single cells at high efficiency, demonstrating its potential for analyzing complex tissues at substantially low cost. Together, we present a new way of high-throughput methylome and hydroxymethylome detection at single-cell resolution, enabling efficient analysis of epigenetic status of biological systems with complicated nature such as neurons and cancer cells. Significance StatementMost of current methylation profiling techniques rely on bisulfite treatment, which suffers low DNA recovery. The technique proposed in this study, named Cabernet, can be used to measure 5mC and 5hmC at single-base resolution with high genomic coverage. By using Tn5 transposome, hemi-methylation status can be measured and high-throughput methylome profiling can be achieved. Together, it provides an efficient way to analyze the epigenetic landscape of complicated biological systems.

genomics↗

bioRxiv2023

Repeated Omicron infection alleviates SARS-CoV-2 immune imprinting

The continuous emergence of highly immune evasive SARS-CoV-2 variants, like XBB.1.51,2 and XBB.1.163,4, highlights the need to update COVID-19 vaccine compositions. However, immune imprinting induced by wildtype (WT)-based vaccination would compromise the antibody response to Omicron-based boosters5-9. Vaccination strategies that can counter immune imprinting are critically needed. In this study, we investigated the degree and dynamics of immune imprinting in mouse models and human cohorts, especially focusing on the role of repeated Omicron stimulation. Our results show that in mice, the efficacy of single Omicron-boosting is heavily limited by immune imprinting, especially when using variants antigenically distinct from WT, like XBB, while the concerning situation could be largely mitigated by a second Omicron booster. Similarly, in humans, we found that repeated Omicron infections could also alleviate WT-vaccination-induced immune imprinting and generate high neutralizing titers against XBB.1.5 and XBB.1.16 in both plasma and nasal mucosa. By isolating 781 RBD-targeting mAbs from repeated Omicron infection cohorts, we revealed that double Omicron exposure alleviates immune imprinting by generating a large proportion of highly matured and potent Omicron-specific antibodies. Importantly, epitope characterization using deep mutational scanning (DMS) showed that these Omicron-specific antibodies target distinct RBD epitopes compared to WT-induced antibodies, and the bias towards non-neutralizing epitopes observed in single Omicron exposures due to imprinting was largely restored after repeated Omicron stimulation, together leading to a substantial neutralizing epitope shift. Based on the DMS profiles, we identified evolution hotspots of XBB.1.5 RBD and demonstrated the combinations of these mutations could further boost XBB.1.5s immune-evasion capability while maintaining high ACE2 binding affinity. Our findings suggest the WT component should be abandoned when updating COVID-19 vaccine antigen compositions to XBB lineages, and those who havent been exposed to Omicron yet should receive two updated vaccine boosters.

immunology↗

bioRxiv2023

Opposing, spatially-determined epigenetic forces impose restrictions on stochastic olfactory receptor choice

Olfactory receptor (OR) choice represents an example of genetically hardwired stochasticity, where every olfactory neuron expresses one out of [~]2000 OR alleles in a probabilistic, yet stereotypic fashion. Here, we propose that topographic restrictions in OR expression are established in neuronal progenitors by two opposing forces: polygenic transcription and genomic silencing, both of which are influenced by dorsoventral gradients of transcription factors NFIA, B, and X. Polygenic transcription of OR genes may define spatially constrained OR repertoires, among which one OR allele is selected for singular expression later in development. Heterochromatin assembly and genomic compartmentalization of OR alleles also vary across the axes of the olfactory epithelium and may preferentially eliminate ectopically expressed ORs with more dorsal expression destinations from this "privileged" repertoire. Our experiments identify early transcription as a potential "epigenetic" contributor to future developmental patterning and reveal how two spatially responsive probabilistic processes may act in concert to establish deterministic, precise, and reproducible territories of stochastic gene expression.

genomics↗

bioRxiv2023

Extruding transcription elongation loops observed in high-resolution single-cell 3D genomes

Inside human nuclei, genes are transcribed within a highly packed genome, whose organization is facilitated by cohesin-mediated loop extrusion. However, whether cohesin-mediated loop extrusion participates in transcription is unknown. Here we report that the cohesin-mediated loop extrusion participates in transcription by forming a topoisomerases-regulated transcription elongation loop (TEL), in which cohesin is stalled at the transcription start site (TSS) and gradually extrudes loops asymmetrically until reaching the transcription termination site (TTS). By improving the spatial resolution of single-cell 3D genome mapping to 5 kb with micrococcal nuclease (MNase) in our new single-cell Micro-C (scMicro-C) method, we directly observed the loop expansion of TELs. Furthermore, TELs biological function is to ensure high transcriptional burst frequencies by fast re-initiation of RNA Pol II. One-Sentence SummarySingle-cell high-resolution 3D genome structures reveal that cohesin-mediated loop extrusion participates in transcription.

genomics↗

bioRxiv2022

Correlated protein modules reflecting functional coordination of interacting proteins are uncovered by single-cell proteomics

Single-cell proteomics has attracted a lot of attention in recent years because it offers more functional relevance than single-cell transcriptomics. However, most work to date focused on cell typing, which has been widely accomplished by single-cell transcriptomics. Here we report the use of single-cell proteomics to measure the correlations between the translational levels of any pair of proteins in a single mammalian cell. In measuring pairwise correlations among [~]1,000 proteins in a population of homogeneous K562 cells in a steady-state condition, we observed multiple correlated protein modules (CPMs), each containing a group of highly positively correlated proteins that are functionally interacting and collectively involved in certain biological functions, such as protein synthesis and oxidative phosphorylation. Some CPMs are shared across different cell types while others are cell-type specific. Widely studied in omics analyses, pairwise correlations are often measured by introducing perturbations to bulk samples. However, some correlations of gene or protein expression in steady-state condition would be masked by perturbation. The single-cell correlations probed in our experiment reflect intrinsic steady-state fluctuations in the absence of perturbation. We note that observed correlations between proteins are experimentally more distinct and functionally more relevant than those between corresponding mRNAs measured in single-cell transcriptomics. By virtue of single-cell proteomics, functional coordination of proteins is manifested through CPMs. Table of Contents Image O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/520903v2_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@10e27corg.highwire.dtl.DTLVardef@857044org.highwire.dtl.DTLVardef@8d9731org.highwire.dtl.DTLVardef@1c149a4_HPS_FORMAT_FIGEXP M_FIG C_FIG

systems biology↗

bioRxiv2022

Imprinted SARS-CoV-2 humoral immunity induces converging Omicron RBD evolution

Continuous evolution of Omicron has led to a rapid and simultaneous emergence of numerous variants that display growth advantages over BA. 5. Despite their divergent evolutionary courses, mutations on their receptor-binding domain (RBD) converge on several hotspots. The driving force and destination of such convergent evolution and its impact on humoral immunity remain unclear. Here, we demonstrate that these convergent mutations can cause striking evasion of neutralizing antibody (NAb) drugs and convalescent plasma, including those from BA.5 breakthrough infection, while maintaining sufficient ACE2 binding capability. BQ.1.1.10, BA.4.6.3, XBB, and CH. 1.1 are the most antibody-evasive strain tested, even exceeding SARS-CoV-1 level. To delineate the origin of the convergent evolution, we determined the escape mutation profiles and neutralization activity of monoclonal antibodies (mAbs) isolated from BA.2 and BA.5 breakthrough-infection convalescents. Importantly, due to humoral immune imprinting, BA.2 and especially BA.5 breakthrough infection caused significant reductions in the epitope diversity of NAbs and increased proportion of non-neutralizing mAbs, which in turn concentrated humoral immune pressure and promoted convergent evolution. Moreover, we showed that the convergent RBD mutations could be accurately inferred by integrated deep mutational scanning (DMS) profiles, and the evolution trends of BA.2.75/BA.5 subvariants could be well-simulated through constructed convergent pseudovirus mutants. Together, our results suggest current herd immunity and BA.5 vaccine boosters may not provide good protection against infection. Broad-spectrum SARS-CoV-2 vaccines and NAb drugs development should be highly prioritized, and the constructed mutants could help to examine their effectiveness in advance.

immunology↗

bioRxiv2022

Further humoral immunity evasion of emerging SARS-CoV-2 BA.4 and BA.5 subvariants

Multiple BA.4 and BA.5 subvariants with R346 mutations on the spike glycoprotein have been identified in various countries, such as BA.4.6/BF.7 harboring R346T, BA.4.7 harboring R346S, and BA.5.9 harboring R346I. These subvariants, especially BA.4.6, exhibit substantial growth advantages compared to BA.4/BA.5. In this study, we showed that BA.4.6, BA.4.7, and BA.5.9 displayed higher humoral immunity evasion capability than BA.4/BA.5, causing 1.5 to 1.9-fold decrease in NT50 of the plasma from BA.1 and BA.2 breakthrough-infection convalescents compared to BA.4/BA.5. Importantly, plasma from BA.5 breakthrough-infection convalescents also exhibits significant neutralization activity decrease against BA.4.6, BA.4.7, and BA.5.9 than BA.4/BA.5, showing on average 2.4 to 2.6-fold decrease in NT50. For neutralizing antibody drugs, Bebtelovimab remains potent, while Evusheld is completely escaped by these subvariants. Together, our results rationalize the prevailing advantages of the R346 mutated BA.4/BA.5 subvariants and urge the close monitoring of these mutants, which could lead to the next wave of the pandemic.

immunology↗

bioRxiv2022

Rational identification of potent and broad sarbecovirus-neutralizing antibody cocktails from SARS convalescents

SARS-CoV-2 Omicron sublineages have escaped most RBD-targeting therapeutic neutralizing antibodies (NAbs), which proves the previous NAb drug screening strategies deficient against the fast-evolving SARS-CoV-2. Better broad NAb drug candidate selection methods are needed. Here, we describe a rational approach for identifying RBD-targeting broad SARS-CoV-2 NAb cocktails. Based on high-throughput epitope determination, we propose that broad NAb drugs should target non-immunodominant RBD epitopes to avoid herd immunity-directed escape mutations. Also, their interacting antigen residues should focus on sarbecovirus conserved sites and associate with critical viral functions, making the antibody-escaping mutations less likely to appear. Following the criteria, a featured non-competing antibody cocktail, SA55+SA58, is identified from a large collection of broad sarbecovirus NAbs isolated from SARS convalescents. SA55+SA58 potently neutralizes ACE2-utilizing sarbecoviruses, including circulating Omicron variants, and could serve as broad SARS-CoV-2 prophylactics to offer long-term protection. Our screening strategy can also be applied to identify broad-spectrum NAb drugs against other fast-evolving viruses, such as influenza viruses.

immunology↗