Biology subjects

Lou, J.

Publications and source records attributed to Lou, J..

At least 19 recordsLinked to original sources

bioRxiv2026

Intrinsic immune receptor triggering mechanism informs rational chimeric receptor design

The T cell receptor (TCR) couple antigen recognition to T-cell activation and immune homeostasis. As an eight-subunit assembly, TCR activation operates as a highly coordinated, multi-subunit signaling event. However, which subunit serves as the primary trigger upon ligand engagement still remains unresolved. we identify CD3{varepsilon} as a triggering subunit whose intracellular domain (ICD) is released from the plasma membrane during TCR activation. Elevated membrane tension facilitates this transition from a membrane-proximal to a membrane-distal conformation. The released ICD forms condensates through phase separation with free or co-receptor-associated Lck. These condensates recruit additional CD3{varepsilon} ICDs from neighboring TCRs, triggering resting receptors and promoting further recruitment of TCRs and Lck to amplify proximal signaling. The CD3{varepsilon} ICD alone support robust T cell activation independently of its own ITAM. We observe a similar triggering mechanism in several activating receptors in T and nature killer (NK) cell. These findings support a unifying model in which designated subunits initiate multi-subunit immune receptor activation through phase separation with key kinases. Guided by this model, we engineered triggering molecules (TRIG) that lack canonical intracellular signaling modules. These TRIG molecules recruit endogenous immune receptors in a ligand-dependent manner and efficiently activate both T cells and NK cells. This mechanism provides a basis for designing chimeric receptors that activate immune cells through endogenous receptor signaling.

immunology↗

bioRxiv2026

A MultiOmics time-resolved systems map of gene regulation in Toxoplasma gondii

Understanding how T. gondii builds an invasion-competent cell has been limited by its rapid, asynchronous division cycle, incomplete gene function annotation, and studies that have examined one regulator or complex at a time. Here, we placed acute perturbation of 21 transcriptional and epigenetic factors, promoter occupancy, chromatin accessibility, and molecular validation on a common single-cell clock. The resulting consensus map links the lytic-cycle programs to candidate activating and repressive inputs, organizes genes into 108 co-regulated communities, and nominates regulatory partnerships that would not have emerged from any single data type. The work bridges three longstanding gaps: it resolves perturbation responses in cell-cycle time, distinguishes promoter occupancy from perturbation-linked regulation, and turns a large multidimensional dataset into an experimentally navigable map. We indeed confirmed known factor interactions such as MORC/HDAC3 and recovered combinations such as the Cdc5/SNIP1 and DMAP1/EPL1 as coregulatory nodes (that in other systems have been described to cooperate). Furthermore, we discovered a novel apicomplexan specific combination of AAF1/AP2XI-5 that provides mechanistic insights of the unique AP2 transcription factor family.

microbiology↗

bioRxiv2026

Long-range transport of biomolecular condensates by Marangoni effect

How mesoscale cargos such as biomolecular condensates are transported and spatially positioned within cells remains a fundamental question in cell biology. During Caenorhabditis elegans zygote polarization, a substantial fraction of P granules undergoes persistent anterior-to-posterior motion that cannot be fully explained by dissolution-recondensation. Here, combining microfluidic reconstitution, quantitative micropipette aspiration and live-cell imaging, we show that a MEG-3 concentration gradient generates interfacial-tension asymmetry and drives the directed transport of PGL-3-RNA co-condensates in vitro and P granules in vivo through the Marangoni effect. This framework enables parameter-free quantitative predictions of condensate transport. Orthogonal molecular perturbations abolish or reverse directional migration, directly linking interfacial properties to transport behavior and establishing the specificity of this mechanism. Together, our findings identify the Marangoni effect as a previously unrecognized mechanism for intracellular transport of biomolecular condensates and provide direct causal evidence that condensate emergent properties can contribute to physiological organization.

biophysics↗

bioRxiv2026

SMCHD1's DNA binding activity enables its stable retention on chromatin

Chromatin proteins play critical roles in gene regulation, yet frequently we do not fully understand how weak DNA binding affinity of such proteins contributes to their locus-specific actions. Here, we studied SMCHD1, a non-canonical SMC-family protein involved in three-dimensional genome organization and gene repression of the inactive X chromosome and its autosomal targets. We replaced endogenous SMCHD1 with GFP-tagged wild-type or hinge-domain DNA-binding mutant SMCHD1 to define the cellular role of DNA binding. The mutant showed reduced enrichment at the inactive X chromosome in female cells, while retaining stable binding at most autosomal binding sites. Impaired DNA binding weakens SMCHD1-mediated gene repression and chromatin-state regulation, producing hypomorphic effect. Multiple live-cell imaging methods reveal that DNA binding constrains SMCHD1 mobility and supports maintenance, rather than initial recruitment, of chromatin-bound SMCHD1 both during interphase and mitosis. Thus, SMCHD1's weak and sequence-independent DNA binding is a key determinant of its chromatin residence, localization and function. Our findings provide a framework for understanding SMCHD1 and other chromatin proteins with sequence-independent DNA binding activity.

genomics↗

bioRxiv2026

Cell cycle dependent regulation of mRNA export in response to replication stress

Nuclear export of mRNA is extensively coupled to transcription and processing of mRNA. How mRNA export is mechanistically regulated remains poorly understood. Here, we uncover a physical checkpoint at nuclear speckles that regulates mRNA export during DNA replication in S-phase of the cell cycle. Unbiased screening approaches identify WEE1 and CHK1 as novel mRNA export regulators. mRNA export complexes are recruited to sites of replication stress in S-phase. WEE1 inhibition prematurely activates CDK1 and PLK1, leading to accumulation of R-loop associated mRNA in large nuclear speckles, with late markers of replication stress present around their periphery. This recruitment is dependent on CDK1 activity. Phosphorylation of ALYREF by CDK1 and PLK1 regulates nuclear speckle accumulation of mRNA following replication stress. mRNA export factors including ALYREF are subsequently mis-localised from these speckles, preventing nuclear export of R-loop associated mRNA. Thus, WEE1, CDK1 and PLK1 enforce a cell cycle regulated checkpoint at nuclear speckles that serves to protect the cell from major sources of genome instability by ensuring that R-loop associated mature mRNA is not exported to the cytoplasm.

molecular biology↗

bioRxiv2026

Ionizable Lipids Promote Curvature Remodeling and Altered Fluctuation Dynamics in Endosomal Membranes

Inefficient endosomal escape is a crucial barrier to intracellular delivery of nucleic acid therapeutics using lipid nanoparticles (LNPs). The use of ionizable lipids (ILs) has significantly improved cargo delivery efficiency, yet the physical basis of their interaction with endosomal membranes and their role in endosomal escape remain unclear. It has been suggested that, as ILs become cationic during endosomal acidification, electrostatic affinity promotes fusion of the LNPs with the endosome. In this paper, we propose an additional mechanism in which ILs are redistributed from LNPs to host membranes, modulating the elastic properties and curvature of the membrane, lowering the energetic threshold for endosome disruption. To test this, we quantified the spontaneous curvature of clinically relevant ILs and ATP-binding lipids and measured the membrane mechanics of giant unilamellar vesicles (GUVs) with an endosome-relevant composition at endosome-relevant pH. Small-angle X-ray scattering (SAXS) measurements reveal that the incorporation of ILs and ATP lipids into endosome-mimetic membranes shifts the spontaneous curvature towards more negative values. Micropipette aspiration experiments indicated a decrease in the apparent area compressibility modulus of membranes doped with ILs and ATP lipids. In addition, membranes showed enhanced fluctuation amplitudes and altered relaxation behavior, consistent with membrane perturbations associated with lipid insertion and pH- or ATP-driven destabilization. Under conditions promoting the partitioning of ILs or ATP-binding lipids, we further observed reduced bending rigidity and increased heterogeneity in membrane tension. Together, these results support a model in which ILs (as well as newly developed ATP-binding lipids) partition into endosomal membranes, softening the membrane and generating local curvature frustration that facilitates endosomal disruption during the natural acidification process. By quantitatively linking lipid composition with changes in membrane elasticity and fluctuation dynamics, this work provides a biophysical framework for understanding how lipid redistribution may contribute to endosomal escape and improve delivery efficiency.

biophysics↗

bioRxiv2026

Modular counterplays shape condensation and signaling of chimeric antigen receptor

Chimeric antigen receptor-engineered T (CAR T) cell therapy has achieved remarkable clinical efficacy against hematological malignancies but exhibits limited therapeutic outcomes in solid tumors, where immune checkpoint signaling is highly active. Here, we demonstrate that the second-generation CD28-CD3{zeta} (28Z) CAR undergoes liquid-liquid phase separation with the Src-family kinase LCK to assemble a signaling condensate crucial for CAR activation. PD-1, but not LAG3 or CTLA4, disrupts these CAR-LCK condensates through competitive binding to CAR rather than through its canonical phosphotase-dependent inhibitory pathway. Incorporation of a CD3{varepsilon} cytoplasmic module into the CAR introduces additional LCK interactions that reinforce CAR-LCK condensation, thus limited PD-1 incorporation and stabilize signalosome assembly. Consequently, the CD3{varepsilon}-engineered CAR (E-CAR) resists PD-1-mediated condensates disassembly, preserves immunological synapse organization, and sustains proximal signaling following PD-L1 engagement. E-CAR T cells are therefore resistant to PD-1-mediated functional suppression and maintain potent antitumor activity against PD-L1-positive solid tumors. Together, these findings identify disruption of CAR signaling condensates as a previously unrecognized mechanism of PD-1-mediated inhibition and establish CD3{varepsilon} modular signalosome engineering as a rational engineering strategy to overcome immune checkpoint suppression.

immunology↗

bioRxiv2026

A Microgel-Based Platform for Tunable Expansion and Function of γδ T-cells

Current {gamma}{delta} T-cell expansion protocols often sacrifice functionality for yield and largely ignore the context of activation. Here we utilize a tunable alginate microgel system functionalized with anti-CD3 and co-stimulatory antibodies (CD28 or CD2) to investigate the impact of biochemical signaling and substrate mechanics on {gamma}{delta} T-cell activation. Microgel-mediated expansion was compared to conventional soluble antibodies and TransAct beads. The microgels enhanced {gamma}{delta} T-cell expansion compared to soluble antibodies, allowed for controlled tuning of differentiation state, and promoted higher NKG2D, IFN-{gamma} and TNF- expression levels. Functionally, microgel-expanded {gamma}{delta} T-cells exhibited superior cytotoxicity against both solid and liquid tumor targets. This system also allowed elucidation of the differences in stimulation requirements for various donors, based on the starting phenotype. These findings establish a tunable platform for engineering {gamma}{delta} T-cells with improved therapeutic potential. Significance Statement{gamma}{delta} T-cells have shown promising therapeutic effects when used for T cell-based immunotherapy to treat solid tumor. However, achieving rapid expansion of {gamma}{delta} T-cells while maintaining their functionality remains a major challenge, especially given the heterogeneous responses from donors. We demonstrate that a tunable microgel system with flexible presentation of stimulatory cues improves {gamma}{delta} T-cell expansion while preserving cytotoxic function and reveal how starting phenotypes influence responses to activation. These understandings will provide design rationale to enable patient-specific treatment for optimal therapeutic outcomes.

bioengineering↗

bioRxiv2026

Comprehensive transcriptome data of melittin- and un-treated murine hepatoma Hepa 1-6 cells

Melittin, the principal bioactive peptide of bee venom, exerts potent antitumor activity against hepatocellular carcinoma (HCC). However, the comprehensive transcriptomic alterations it elicits in hepatoma cells remain poorly characterized. Here, we present an integrated transcriptome dataset from melittin- and un-treated murine Hepa 1-6 hepatoma cells, encompassing messenger RNA (mRNA) and microRNA (miRNA) expression profiles. Cells were exposed to 4 g/mL melittin in serum-free DMEM for 20 min, and total RNA was subjected to ribosomal RNA-depleted strand-specific RNA sequencing on an Illumina NovaSeq6000 platform (paired-end 150 bp) and small RNA sequencing on an Illumina HiSeq2500 platform (single-end 50 bp). Raw data were processed using Cutadapt to remove adapters and low-quality reads, yielding clean datasets with Q20 [≥] 99.85%, Q30 [≥] 98.48%, and valid data ratios exceeding 85%. All raw and processed sequencing data are publicly available. This transcriptomic resource provides a valuable resource and basis for elucidating the regulatory networks underlying melittin-induced anti-hepatoma effects. DatasetThe dataset can be accessed through the National Genomics Data Center, China National Center website by searching with the BioProject accession number PRJCA065485 Reviewers may use this link for anonymous access during the review process. Direct URL to data: Genome Sequence Archive-CNCB-NGDC. Dataset LicenseCC BY 4.0

Cancer Biology↗

bioRxiv2026

PD-1 remodels SHP2 dynamics and drives the non-catalytic inhibition of T cell activation

The inhibitory receptor programmed cell death protein 1 (PD-1) suppresses T cell activation primarily by recruiting the src homology 2 domain-containing phosphatase 2 (SHP2), thereby unleashing its phosphatase activity. However, a purely enzymatic model struggles to fully explain the rapid and robust disruption of proximal T cell receptor (TCR) and CD28 signaling. Here, by integrating X-ray crystallography, single-molecule magnetic tweezers, supported lipid bilayers, TIRF imaging, liquid-liquid phase separation, and cellular assays, we uncover a dual-layered inhibitory mechanism of the PD-1/SHP2 axis. Mechanistically, we determine the crystal structure of SHP2 in complex with dually phosphorylated PD-1 cytoplasmic motifs (pPD-1), revealing a ligand-induced open conformation, which is distinct from the oncogenic E76K-associated state. We further directly resolve the closed-to-open conformational dynamics of individual SHP2 molecules, characterized by an 8-nm transition amplitude, and demonstrate that pPD-1 accelerates the transition by at least 94-fold. Crucially, the pPD-1-mediated highly open conformation exposes the tandem SH2 (t-SH2) domains to function as a biophysical barrier. Independent of phosphatase activity, these domains directly dismantle pTCR and pCD28 signaling condensates to suppress T cell activation. Together, our findings establish a model in which pPD-1 remodels SHP2 structural dynamics and drives a non-catalytic inhibitory mechanism of TCR and CD28 signaling, suggesting next-generation immunotherapy design to reverse T cell suppression.

immunology↗

bioRxiv2026

CellPulse: A Foundation Model of Coordinated Gene Dynamics Simulating Viral Infectious Diseases

Understanding how cells respond to perturbations like viral infections requires models capturing coordinated gene dynamics. However, current gene expression foundation models are predominantly reliant on single-cell data and static gene expression, limiting their applicability in real clinical scenarios. We present CellPulse, a direction-aware foundation model trained on the Virus Stimulated Atlas (VISTA), a newly curated atlas of over 23 million bulk RNA-sequencing differential expression profiles from viral infections. CellPulse models the direction and magnitude of gene expression changes via a structured representation of differential expression and a direction-aware attention mechanism, enabling the learning of coherent regulatory programs. It shows powerful diagnosing capability by accurately classifying 31 distinct virus types across diverse clinical and laboratory samples, solely from host transcriptional signatures. Crucially, without prior knowledge injection, CellPulses interpretability reveals virus-associated host factors that mediate infection. Using a selection of host factors for in silico drug screening yielded numerous compounds with confirmed efficacies in wet-lab assays, while cell-based and animal experiments further verified the causal relationship between host targets and viral infections. Overall, CellPulse represents a generalizable foundation model for deciphering coordinated gene dynamics from bulk transcriptomics, bridging host response modeling with clinical relevance and therapeutic discovery for infectious diseases and beyond.

bioinformatics↗

bioRxiv2026

Interpretable Biological Sequence Clustering with iClust

Biological sequence clustering is a fundamental problem in bioinformatics, yet most existing methods mainly optimize clustering quality or efficiency while offering limited insight into why sequences are grouped together. This restricts their usefulness in downstream analysis, where representative sequences and clear cluster boundaries are often needed. To address this issue, we propose iClust, an interpretable clustering method that characterizes each cluster by a representative prototype and an adaptive radius. By adapting to local sequence structure rather than relying on a single global threshold, iClust produces clusters that are both meaningful and explainable. A final consolidation step further reduces tiny fragments and improves structural stability. Experiments on simulated and real biological sequence datasets show that iClust achieves competitive clustering performance while providing clearer cluster-level explanations than conventional threshold-based methods. In addition to its empirical impact as a practical clustering method for biological sequences, this article opens up new avenues for developing biological sequence clustering approaches from the viewpoint of interpretable machine learning.

bioinformatics↗

bioRxiv2026

CD28 Co-stimulation Is Organized by Signaling Condensates and Counteracted by PD-1

T cell activation relies on the coordinated integration of TCR and co-signaling pathways, yet how these signals are physically organized remains unclear. Here, we demonstrate that CD28 co-stimulation is driven by a phase-separation mechanism in which the CD28 intracellular domain (ICD) forms signaling condensates with the Src-family kinase Lck. Ligand engagement promotes the CD28 ICD accessibility, and triggers rapid CD28/Lck condensation, enhancing CD28 phosphorylation, cytoskeletal polarization, and cytokine production. We further identify PD-1 as a graded regulator of this process: monophosphorylated PD-1 is recruited into CD28/Lck condensates, whereas di-phosphorylated PD-1 competitively binds the CD28 ICD and dissolves these assemblies. CD28 and PD-1 ICDs also undergo condensation directly, revealing a dynamic and compositionally heterogeneous signaling system. Guided by this competitive phase-separation mechanism, we engineer CD28 ICD mutants that preserve Lck condensation while resisting PD-1-mediated disruption. Incorporation of these condensation-selective mutants into CAR constructs confers resistance to inhibitory signaling and enhances antitumor efficacy in vivo. These findings establish phase separation as a central organizing principle of CD28 co-stimulation and provide a biophysical framework for engineering more resilient therapeutic T cells.

immunology↗

bioRxiv2026

RVPSD: A comprehensive and user-friendly web database for RNA viral protein structures

Protein structures are central to understanding the diversity and biological function of RNA viruses. However, few experimentally validated structures of RNA viruses are currently available. To address this gap, we established the RNA Viral Protein Structure Database (RVPSD) that comprises diverse RNA viral protein structures predicted using AlphaFold2. RVPSD integrates taxonomic classification, viral nucleotide and protein sequences, functional annotations, and predicted three-dimensional protein structures to support a systematic exploration of the RNA viral proteomes. Currently, RVPSD comprises a total of 154,716 AlphaFold2-predicted RNA viral protein structures from 5,263 RNA virus species, with 84.9% exhibiting high pLDDT scores (>70) and representing a large-scale and comprehensive resource for RNA viral protein structures. RVPSD also provides a user-friendly web interface, with advanced search, sequence- and structure-based retrieval, interactive 3D visualization, and access and downloading structural data, enabling researchers to perform comparative structural analyses and functional annotation of viral "dark matter".

microbiology↗

bioRxiv2026

TCRAD: An End-to-End Framework for Antigen-Targeted T Cell Receptor Design

Understanding and engineering T-cell receptor (TCR) specificity is central to personalized immunotherapy and antigen discovery. However, while antigen-conditioned TCR design approaches have begun to emerge, most frameworks still focus on scoring candidate TCR-pMHC pairs, and achieving high hit rates in designing functional, target-reactive TCRs remains a key bottleneck. Here, we present TCRAD, a deep learning pipeline that performs de novo design of TCR CDR3{beta} sequences conditioned on antigenic peptides. TCRAD comprises three modules: Sequence Generation, Sequence Filtration, and Structure Prediction. TCRAD can effectively generate antigen-specific CDR3{beta} sequences, discriminate functional binders with high accuracy, and predict bound and unbound structures with performance comparable to or exceeding state-of-art methods. Experimental validation using the 1G4/NY-ESO-1 system demonstrated that the model can design novel functional TCRs capable of surface expression, specific pMHC binding, and that 17.2% candidates (5 of 29) elicit antigen-induced activation. Together, these results establish TCRAD as a powerful framework for TCR sequence design, offering a scalable path toward rational engineering of antigen-specific TCRs for cancer immunotherapy, vaccine development, and personalized immunotherapeutics.

bioinformatics↗

bioRxiv2026

Quantitative Full-length transcriptome analysis by nanopore sequencing with Error-Aware UMI mapping

Comprehensive transcriptome profiling is essential for understanding RNA diversity and regulation, yet accurate identification and quantification of full-length transcript isoforms remain challenging with short-read sequencing technologies. Nanopore sequencing enables direct sequencing of long cDNA molecules and thus offers a powerful solution for full-length transcriptome analysis, but its application to quantitative transcriptomics is limited by PCR amplification bias and the difficulty of unique molecular identifier (UMI) recognition under high sequencing error rates. Here, we developed UMImap, a dedicated pipeline for robust UMI identification, error correction, and deduplication in nanopore data. By integrating transcript-aware UMI correction with long-read isoform assembly, UMImap substantially improves UMI recognition accuracy compared with existing methods and effectively mitigates PCR-induced duplication bias. Using this framework, we identified tens of thousands of full-length transcript isoforms, including a large fraction of previously unannotated isoforms that are significantly longer than reference annotations. Quantitative analyses demonstrate the reliability of UMImap for transcript-level quantification. Functional and pathway enrichment analyses of highly expressed novel isoforms revealed coherent and biologically meaningful patterns, including strong enrichment in RNA processing, splicing, and translation pathways. Our results establish UMImap as an effective solution for UMI-based quantification in nanopore full-length transcriptome sequencing and highlight the potential of long-read sequencing to simultaneously achieve accurate isoform discovery and expression analysis in complex transcriptomes.

bioinformatics↗

bioRxiv2025

UC Irvine Brain Initiative Cell Atlas Network (BICAN) Brain Procurement Program for the Center for Multiomic Human Brain Cell Atlas Project

High-quality neurotypical postmortem human brain tissue is essential but difficult to obtain for constructing comprehensive human brain cell atlases. Here we describe the establishment of UC Irvines Brain Procurement Program, a coordinated initiative to collect and process neurotypical donor brains for multiomic mapping studies within the NIH BRAIN Initiative Cell Atlas Network (BICAN) consortium. Through partnerships with the Orange County Coroners Office, the UC Irvine Willed Body Program, UCI Medical Center, and the Childrens Hospital of Orange County, we have developed standardized workflows encompassing donor identification, postmortem brain recovery and processing, region-of-interest dissection, neurotypical donor selection, and data management. Our experience demonstrates the feasibility of a community-based, multi-institutional procurement framework while highlighting challenges in recruiting neurotypical donors and ensuring demographic representation reflective of Southern California. We further identify opportunities to strengthen outreach and donation pathways. This program provides a scalable model for advancing population-reflective, high-quality human brain cell atlas efforts. HighlightsO_LIEstablish a multi-site pipeline for procuring high-quality neurotypical human brains. C_LIO_LIDemonstrate feasibility of donor collection across childhood to adulthood. C_LIO_LIIdentify barriers and propose strategies to improve broad donor recruitment. C_LI

neuroscience↗

bioRxiv2025

Human progenitor T-cell differentiation regulated by the mechanical resistance of thymus-mimetic extracellular matrices

Therapeutic T-cell engineering ex vivo from human hematopoietic stem cells (HSCs) focuses on recapitulating notch1-signaling and 4{beta}1-integrin-mediated adhesion within the thymic niche with supportive stromal cell feeder-layers or surface-immobilized recombinant protein-based engineered thymic niches (ETNs). The relevant Notch1-DLL-4 and 4{beta}1-integrin-VCAM-1 interactions are known to respond to mechanical forces that regulate their bond dissociation behaviors and downstream signal transduction, yet manipulating the mechanosensitive features of these key receptor-ligand interactions in thymopoiesis has been largely ignored in current ETN designs. Here, we demonstrate that human T-cell development from cord blood-derived CD34+ HSCs is regulated via molecular cooperativity in notch1 and integrin-mediated mechanotransduction. Mechanically confining interpenetrating network (IPN) hydrogel-based 3D cell culture comprised of collagen type I and alginate polysaccharides functionalized with DLL-4 and VCAM-1 is used as a model viscoelastic 3D ETN to manipulate human progenitor (pro)T-cell differentiation. This ETN enables orthogonal control of the mechanical and biomolecular features of the thymic niche, including thymopoietic ligand density, modulus, and viscoelastic properties (e.g., stress relaxation kinetics). We identify that soft, viscous matrices that enhance activation of the notch1-pathway, and subsequently notch1 intracellular domain (NICD) nuclear import sustain the T-cell development gene regulatory network during proT-cell differentiation. Conversely, stiff, elastic matrices inhibit HSC commitment to the T-lineage, and rather promotes Myeloid-cell differentiation. Our observations indicate mechanical reciprocity in signaling pathways indispensable to thymopoiesis, and highlights extracellular matrix mechanics as a variable in controlling hematopoietic stem cell fate decisions.

bioengineering↗