Biology subjects

Chu, C.

Publications and source records attributed to Chu, C..

At least 19 recordsLinked to original sources

bioRxiv2026

Telomeric G-Quadruplexes Formed by Six G-overhang Permutation Repeats

The single-stranded G-overhangs of vertebrate telomeres, composed of guanine (G)-rich hexanucleotide repeats, can adopt six register-dependent permutations: GGTTAG, GTTAGG, TTAGGG, TAGGGT, AGGGTA, and GGGTTA. Telomeric G-quadruplexes (G4s) formed by the first two repeat permutations, which are the most prevalent at human chromosome ends, have been largely overlooked. Here, G4 formation across all six permutations, each containing 4 to 9 repeats, are systematically investigated under varying cation conditions and molecular crowding environments. Our findings reveal that distinct repeat permutations yield markedly different G4 stabilities and folding topologies, which in turn modulate DNA polymerase activity. This expanded perspective on telomeric structural diversity provides new insights into telomere biology and suggests that multiple repeat patterns may cooperatively influence chromosome end protection and targeting.

biophysics↗

bioRxiv2026

MacaSurfer: unified surface-volume mapping of the macaque brain across the lifespan

Macaque brain MRI is central to translational and comparative neuroscience, yet multi-site, longitudinal, and cross-species analyses are hindered by a lack of unified, automated structural processing tools. Existing pipelines, mostly adapted from human neuroimaging or restricted to fragmented steps, fail to provide robust surface-volume representations across heterogeneous acquisitions and developmental stages. Here we introduce MacaSurfer, a fully automated, containerized framework for unified surface-volume mapping of the macaque brain across the lifespan. MacaSurfer features components tailored for macaque anatomy: a tissue segmentation model, a tissue-guided bias-field correction method optimizing structural mapping from T1-weighted images alone, topology-aware surface reconstruction, and surface-aware volumetric registration. Validated on 1,346 imaging sessions from 965 macaques across 39 international sites (spanning 2 weeks to 23 years of age), MacaSurfer demonstrated exceptional anatomical consistency, test-retest precision, and robustness against image degradation. Leveraging MacaSurfer-derived morphometry, we established normative trajectories from 835 macaques, providing a standardized reference for downstream individualized deviation analysis. MacaSurfer is openly available with source code, containers, and pretrained models, offering a reproducible ecosystem to accelerate developmental, translational, and comparative neuroimaging.

neuroscience↗

bioRxiv2026

Spatiotemporal unfolding of prefrontal neural response divergence in adolescent depression during naturalistic experience

Depression alters how emotional experience is interpreted and regulated, yet how depression-related neural divergence unfolds during ongoing experience remains poorly understood, leaving unresolved whether such divergence reflects stable trait-like abnormalities or state-dependent responses that emerge only at particular moments. This question is especially consequential in adolescence, when depression often emerges amid heightened social sensitivity and continuing maturation of prefrontal regulatory systems. Here, we used naturalistic film watching fMRI data of 36 adolescents with depression and 36 matched controls to map where, how, and when neural responses diverge between diagnostic groups. Neural polarization analysis localized group-level divergence to two prefrontal hubs, the dmPFC-rACC and left dlPFC, where individual similarity to the depression-group response pattern was associated with depressive symptom severity across the cohort. These local divergence sites were not spatially isolated. Seed-based inter-subject functional connectivity showed that they were embedded within distributed stimulus-locked coupling patterns spanning prefrontal control, salience, and subcortical reward circuits. Time-resolved phase synchrony further revealed that this divergence was not continuous, but arose at specific narrative moments, with the dmPFC-rACC diverging during socio-emotional events and the left dlPFC during cognitively demanding ones. Together, these findings move beyond static localization to reveal depression-related neural divergence as a spatially organized, network-embedded, and temporally gated response pattern shaped by the unfolding content of naturalistic experience.

neuroscience↗

bioRxiv2026

Accurate detection of mosaic mutations at short tandem repeats from bulk sequencing data

Short tandem repeats (STRs) are among the most mutable regions of the human genome, yet their somatic mosaicism remains poorly characterized due to the technical challenges of distinguishing genuine mutations from high intrinsic polymorphism and sequencing noise. Here, we introduce BulkMonSTR, a computational framework that combines STR-specific error modelling with machine-learning classification to enable accurate detection of mosaic STR mutations from bulk next-generation sequencing data. BulkMonSTR identifies nucleotide-resolution mutations--including insertions, deletions, and single-nucleotide variants (SNVs)--and supports both control-independent and case-control study designs. Leveraging a comprehensive training dataset derived from pedigree-based validation and in silico spike-in simulations, our random forest classifier effectively discriminates true mosaic events from germline variants and technical artifacts. Benchmarking on simulated and real datasets demonstrates that BulkMonSTR achieves substantially improved precision and F1 scores across diverse coverages and variant allele frequencies. In normal samples, cancer samples and controlled in silico mixing experiments, BulkMonSTR consistently outperforms existing methods, capturing a broader spectrum of STR mutations--including those arising on non-reference alleles--while achieving high validation rates. By enabling systematic, genome-wide interrogation of STR mosaicism, BulkMonSTR provides a scalable foundation for investigating the contributions of somatic STR mutations to aging and disease.

bioinformatics↗

bioRxiv2026

X-Cell: Scaling Causal Perturbation Prediction Across Diverse Cellular Contexts via Diffusion Language Models

Causal models of cellular systems hold the promise to empower broad biological discovery, including the systematic identification of novel targets for drug discovery. Predicting how genetic and pathway perturbations reshape gene expression across diverse cellular contexts is a prerequisite for building generalizable cellular foundation models. However, current methods typically fail to extrapolate beyond their training distributions because they rely predominantly on observational expression atlases rather than interventional perturbation data. We present X-Atlas/Pisces, the largest genome-wide CRISPRi Perturb-seq compendium to date, comprising 25.6 million perturbed single-cell transcriptomes across 16 biologically diverse contexts, including widely used cell lines, induced pluripotent stem cells (iPSCs), resting and CD3/CD28 activated Jurkat T lymphoma cells, and multi-lineage differentiating iPSCs. Leveraging this resource, we develop X-Cell, a diffusion language model that predicts perturbation responses by iteratively refining control-to-perturbed state transitions through cross-attention to multi-modal biological priors derived from natural language, protein language models, interaction networks, genetic dependency maps, and morphological profiles. X-Cell outperforms existing state-of-the-art models by up to five-fold on key metrics such as Pearson{Delta} (correlation between predicted and observed perturbation-induced log-fold changes), and demonstrates zero-shot prediction of T cell inactivating perturbations in stimulated Jurkat cells. We scale X-Cell to 4.9 billion parameters (X-Cell-Ultra), the largest causal perturbation model to date. We demonstrate for the first time that perturbation prediction follows power-law scaling with an exponent matching large language models. X-Cell-Ultra demonstrates zero-shot generalization to novel biological contexts, including unseen iPSC-derived melanocyte progenitors and primary human CD4+ T cells from multiple donors, and outperforms all baselines after self-supervised test-time adaptation. These results demonstrate that coordinated scaling of causal perturbation data and model capacity yields foundation models capable of generalizable perturbation prediction across cellular contexts, with potential applications for improving computational target identification, validation, and context-specific therapeutic prioritization.

systems biology↗

bioRxiv2026

In vivo-directed evolution identifies AAV-WM04 as a next-generation vector for potent and durable hearing restoration in DFNB9

Efficient and cell-specific gene delivery to cochlear inner hair cells (IHCs) remains a major challenge for inner ear gene therapy. Here, we identify and characterize a novel AAV2-derived capsid, AAV-WM04, that enables highly efficient and selective IHC transduction at low doses. Using an in vivo-directed evolution strategy, we generated a randomized AAV2 capsid library with 9-amino acid insertions and performed iterative selection in the adult mouse cochlea. Next-generation sequencing revealed enrichment of several variants, among which AAV-WM04 exhibited superior packaging efficiency and pronounced IHC tropism. AAV-WM04 achieved near-complete IHC transduction throughout the cochlear axis in adult mice, outperforming clinically relevant vectors with minimal off-target expression and no detectable ototoxicity. Robust and exclusive IHC transduction was further validated in non-human primates following round window membrane delivery, underscoring translational potential. Therapeutically, AAV-WM04 enabled efficient dual-AAV trans-splicing delivery of the large OTOF gene, resulting in uniform full-length otoferlin expression in IHCs. In a humanized Otof Q829X/Q829X mouse model, AAV-WM04 restored auditory function across a broad frequency range at relatively low doses and achieved durable hearing recovery. Collectively, these findings establish AAV-WM04 as a next-generation IHC-targeted vector with high efficiency, safety, and cross-species applicability for precision gene therapy of hereditary hearing loss.

genetics↗

bioRxiv2025

The Hippo Pathway Regulates Corneal Endothelial Regeneration

Corneal endothelial cells (CECs) have limited regeneration capacity in primates while display a potent restorative capability in some species such as rodents after wounding. The mechanism which determines the regenerative capability of CECs remains poorly understood. Here, we identify that the Hippo signaling pathway is inhibited and the downstream effector YAP is activated during CEC wound healing in rabbit and mouse. Knockdown of Yap1 and pharmacological inhibition of YAP suppresses CECs wound healing in rodents in both in vitro and in vivo models. XMU-MP-1, a specific small molecular inhibitor for Hippo signaling pathway, can promote the corneal endothelial regeneration in rodents and corneal endothelial proliferation in cultured primate CECs, as well as in vivo non-human primate CEC wounding model. These findings suggest that Hippo pathway serves as a conserved signal to regulate corneal endothelial regeneration among various species, providing a novel target for non-invasive treatment of corneal endothelium decompensation.

cell biology↗

bioRxiv2025

3D Hybrid Bioprinting for Complex Multi-Tissue Engineering

3D bioprinting has revolutionized tissue engineering, enabling intricate, physiologically relevant constructs unattainable with conventional techniques, yet it remains limited in integrating soft and rigid multifunctional components for complex multi-tissue applications. In this study, we introduce a 3D hybrid bioprinting approach implementing the Hybprinter platform, which integrates multiple 3D printing modules under optimized conditions for a continuous bioprinting process with multiple soft and hard biomaterials. This approach demonstrates robust biocompatibility and broad tissue engineering potential for modeling and therapeutic applications. The capacity to fabricate multi-hydrogel hybrid constructs is illustrated by representative examples highlighting vascularization, multifunctionality, mechanical robustness, and implant suturability. Notably, compared with commonly fabricated hydrogel-only constructs, the resulting hybrid constructs achieve over a 1000-fold increase in mechanical strength, and demonstrated enhanced osteogenic differentiation, underscoring their suitability for load-bearing musculoskeletal and orthopedic tissue engineering. Additionally, cell-laden hydrogel constructs demonstrated robust chondrogenic differentiation, highlighting the capacity for lineage-specific tissue development in vitro. Beyond these outcomes, the presented hybrid bioprinting approach integrates essential tissue engineering attributes that unites mechanical robustness and suturable capacity with multi-material integration, gradient property design, incorporation of bioactive agents, and support for multi-cell loading. This versatile platform advances complex tissue engineering and holds promise for patient specific, organ-on-demand applications.

bioengineering↗

bioRxiv2025

Multi-platform framework for mapping somatic retrotransposition in human tissues

Mobile element insertions (MEI) shape the human genome in both germline and somatic tissues. While inherited MEIs are well characterized, mapping somatic MEIs (sMEI) in non-cancer tissues remains challenging due to their low allelic fraction and repetitive nature. We established an integrative framework for sMEI analysis leveraging modern sequencing technologies and analytical innovations. We first benchmarked sMEI detection and demonstrated advantages of long-read and MEI-targeted sequencing for ultra-low-frequency events using a mixture of well-established cell lines. We then showed that haplotype phasing and donor-specific assemblies refine sMEI detection, effectively distinguishing from germline and false signals in in-silico tumor-normal mixtures. We further developed a source-tracing strategy based on internal sequence variation, expanding the catalogue of active source elements beyond traditional transduction-based methods. Applying this framework to donor tissues, we identified 18 rare somatic L1 insertions, revealing structural and source diversity. Our work provides a foundational framework and biological insight into sMEIs.

genomics↗

bioRxiv2025

Fast Dynamic Whole-Body In Vivo Cytometry Using Magnetic Particle Imaging

Rapid quantification of the immediate organ accumulation of injected stem cells remains a major challenge. We performed in vivo cytometry (non-invasive cell counting) with magnetic particle imaging (MPI) to track magnetically labeled cells in real-time on a time scale of minutes with high sensitivity, zero background signal, and simple linear quantification. Human mesenchymal stem cells (hMSCs, [~]25 {micro}m in diameter) and human neural precursor cells (hNPCs, [~]10 {micro}m in diameter) were labeled with ferucarbotran or Synomag(R)-D70 as superparamagnetic iron oxide (SPIOs), and tracked with MPI in mice to map their whole-body cell biodistribution after intravenous (IV) or intra-arterial (IA) injection. The organ site of cell accumulation and retention were dependent on cell type, injection route, and frequency of administration, with the lung and liver acting as the major entrapment organs. In vivo MPI enabled quantitative tracking of the dynamic clearance and redistribution of labeled cells, showing major differences between larger hMSCs and smaller hNPCs. Co-registered MRI/CT and histological validation confirmed the anatomical localization of SPIO-labeled cells including the brain following IA injection. Integrating MPI cytometry with preclinical and translational studies may aid in further optimization of the route, dose, and frequency of stem cell administration. One Sentence SummaryFast whole-body in vivo cytometry using MPI is able to dynamically track and quantify therapeutic stem cell accumulation.

bioengineering↗

bioRxiv2025

Visual Regularities Underlie Hierarchical Object Representations in the Human Brain and Self-supervised DNN

NeuroAI develops the interplay of neuroscience and artificial intelligence, especially on visual processing. Human visual system organizes objects based on a representational hierarchy. However, it remains unclear whether this hierarchy arises from visual or semantic information. One hypothesis posits that the visual system is structured around statistical regularities of visual information. Here, we test this hypothesis using the THINGS datasets and pure-visual deep neural networks (DNN). We constructed a low-dimensional object space based on multiple abstract object properties, reflecting statistical patterns of visual regularities. By applying voxelwise encoding models, we identified clusters in the higher visual cortex based on their property tuning, and they were found to support specific object categories. These clusters serve as the middle level to reveal a property-cluster-object hierarchical organization. Subsequently, we investigated whether this hierarchical structure could be captured by a self-supervised DNN. Through activity similarity analysis, we mapped the brain clusters onto the DNN and independently found that the DNNs clusters exhibited distinct property tuning and influenced the classification accuracy of corresponding object categories, mirroring the effects observed in the human brain. Our results demonstrate similar hierarchical structures in the human brain and self-supervised DNN, suggesting that the visual regularities shape neural architecture of visual system. This study highlights the great potential of neural computational model in neuroscience study. Index Terms Visual Processing, Abstract Property, Hierarchical Representation, Self-supervised Visual DNN

neuroscience↗

bioRxiv2025

SRRM1 coordinates an alternative splicing program that promotes expression of oncogenic protein isoforms.

The alternative splicing of the adapter protein NUMB is dysregulated in multiple cancer types, regulating its functional divergence towards either tumor suppression or oncogenesis in an isoform-dependant manner. Here we utilized a NUMB exon 9 (E9) splicing reporter in a genome-wide CRISPR screen to identify splicing regulators SRRM1 and SRSF11 that promote NUMB oncogenic splicing in colorectal, lung and breast cancer cell lines. We show that SRRM1 and SRSF11 share common protein interactors, RNA targets and effects on an oncogenic splicing program which favors the expression of pro-tumorigenic isoforms. In addition to NUMB E9, SRRM1 regulates cancer-associated splicing events in genes encoding signaling proteins, transcription factors and actin cytoskeleton regulators, many of which are also developmentally regulated, including CD44, MKNK2, ECT2, DIAPH1, KAT5, TCF7L2, FOXM1 and TBX3. Loss of SRRM1 in colorectal and lung cancer cells reduces cell proliferation, colony formation and invasion capabilities, as well as expression of tumour promoters Cyclin D1, Notum, and PRDX2. Our data indicate that SRRM1 regulation of alternative splicing represents a node to target multiple properties of malignant cells, with broad effects on cellular signaling, proliferation, EMT, apoptosis resistance and stemness.

cancer biology↗

bioRxiv2025

LINE-1 ORF1p is a shared and immunogenic antigen in cancer

BackgroundRecent clinical trials are beginning to show the potential for therapeutic cancer vaccines directed against tumor associated antigens. However, there is a limited set of well-defined antigens that are shared across tumors. Noncanonical coding elements in the genome that are usually silenced in normal cells potentially represent a rich source of "dark" antigens when expressed and presented to the immune system. LINE-1 elements are repetitive, virus-like genomic sequences that can copy themselves to new genomic loci, and which are reactivated in many cancers. In this study, we explore ORF1p, a protein encoded by LINE-1 elements, as a potential shared cancer vaccine antigen. MethodsWe assessed the tumor specificity of LINE-1 expression in large scale public RNA-seq data sets and in a curated database of public immunopeptidomics studies. We validated these findings using cell line and tissue data and performed an in vitro vaccination assay using healthy donor PBMCs to test the immunogenicity of ORF1p. ResultsWe found widespread RNA expression of LINE-1 across many tumor types with esophageal cancer showing the most highly elevated expression. We also found widespread MHC class I presentation of ORF1p-derived peptides in a range of tumor types, including esophageal cancer. We validated the tumor specific protein expression of ORF1p in a small set of 5 tumor, 5 matched normal, and 5 healthy esophageal samples. Finally, we demonstrated that dendritic cells pulsed with ORF1p peptides were able to induce interferon gamma production in healthy donor human T cells after repeated stimulation in vitro. ConclusionsWe present data demonstrating that dark antigens derived from LINE-1 elements are 1) expressed in a cancer tissue-specific manner, 2) detected in immunopeptidomics data (both publicly available and newly generated for this study) and 3) immunogenic in vitro. The tumor specificity and immunogenicity of ORF1p peptides point to their potential as a cancer vaccine antigen.

cancer biology↗

bioRxiv2025

X-Atlas/Orion: Genome-wide Perturb-seq Datasets via a Scalable Fix-Cryopreserve Platform for Training Dose-Dependent Biological Foundation Models

The rapid expansion of massively parallel sequencing technologies has enabled the development of foundation models to uncover novel biological findings. While these have the potential to significantly accelerate scientific discoveries by creating AI-driven virtual cell models, their progress has been greatly limited by the lack of large-scale high-quality perturbation data, which remains constrained due to scalability bottlenecks and assay variability. Here, we introduce "Fix-Cryopreserve-ScRNAseq" (FiCS) Perturb-seq, an industrialized platform for scalable Perturb-seq data generation. We demonstrate that FiCS Perturb-seq exhibits high sensitivity and low batch effects, effectively capturing perturbation-induced transcriptomic changes and recapitulating known biological pathways and protein complexes. In addition, we release X-Atlas: Orion edition (X-Atlas/Orion), the largest publicly available Perturb-seq atlas. This atlas, generated from two genome-wide FiCS Perturb-seq experiments targeting all human protein-coding genes, comprises eight million cells deeply sequenced to over 16,000 unique molecular identifiers (UMIs) per cell. Furthermore, we show that single guide RNA (sgRNA) abundance can serve as a proxy for gene knockdown (KD) efficacy. Leveraging the deep sequencing and substantial cell numbers per perturbation, we also show that stratification by sgRNA expression can reveal dose-dependent genetic effects. Taken together, we demonstrate that FiCS Perturb-seq is an efficient and scalable platform for high-throughput Perturb-seq screens. Through the release of X-Atlas/Orion, we highlight the potential of FiCS Perturb-seq to address current scalability and variability challenges in data generation, advance foundation model development that incorporates gene-dosage effects, and accelerate biological discoveries.

genomics↗

bioRxiv2025

OPTRACE: Optical Imaging Guided Transplantation and Tracking of Cells in the Mouse Brain

Intracerebral cell transplantation holds great promise for treating stroke and other neurological disorders, but progress is hindered by challenges in precise cell delivery and limited methods for monitoring post-engraftment dynamics. To address these limitations, we introduce OPTRACE (OPtical imaging-guided Transplantation and tRAcking of CElls), a two-step framework that integrates precision delivery with longitudinal in vivo tracking to advance cell therapy. During transplantation, OPTRACE enables real-time visualization using cost-effective translucent glass micropipettes, guided by predictive modeling to optimize delivery parameters. A novel pulse-elevation injection technique further enhances the precision of superficial cortical engraftment. Following transplantation, multicolor labeling combined with two-photon fluorescence microscopy permits longitudinal single-cell tracking, revealing host microglial responses, and altered neuronal calcium signaling at the graft interface. By unifying high-resolution delivery and tracking strategies, OPTRACE provides a powerful platform for elucidating engraftment biology and accelerating the development of effective cell-based interventions for neurological diseases.

bioengineering↗

bioRxiv2025

Arcuate Fasciculus: Evolutionary Convergence in Marmosets and Humans

The marmoset is a highly vocal platyrrhine monkey that shares key anatomical and functional features with humans, offering insights into the evolution of brain connectivity. Although similarities in vocalization features with humans have been reported, it remains unclear whether marmosets possess an arcuate fasciculus (af) homolog. This study delineated white matter tracts in marmosets, establishing homologies with those observed in other primates, including macaques, chimpanzees, and humans. The presence of an af homolog in marmosets was confirmed by tracer and ultra-high-resolution diffusion magnetic resonance imaging datasets. We compared cortical connectivity patterns across these species and found the af in marmosets terminates in the ventral frontal cortex, with greater similarity to humans than macaques. Furthermore, we linked af connectivity with vocalization-related brain activation in both marmosets and humans. Collectively, our findings suggest that a dorsal pathway, which emerged early in marmoset evolution, has evolved convergently with humans, despite their distant phylogenetic kinship.

neuroscience↗

bioRxiv2025

A unified eIF1A+ luminal cells-centered hypoxic and "cold" tumor microenvironment promotes PCa progression among different subtypes

PCa is a malignancy with high heterogeneity arises from both tumor microenvironment (TME) and histological subtypes. To achieve superior clinical efficacy, it is imperative to identify unified progression drivers within such heterogeneity in PCa, thereby enabling the development of more consistent and effective therapeutic strategies. In this study, we applied imaging mass cytometry to stain 39 proteins on 71 tissues comprising para-cancer, low-grade acinar adenocarcinoma (LgPAC), high-grade PAC (HgPAC), intraductal carcinoma (IDC) and ductal adenocarcinoma (DAC) tissues, obtaining the spatial proteomic landscape of 345,233 single cells. We discovered a hypoxic eIF1A+ luminal epithelial (LE) cluster exhibiting both translational activation and immunosuppressive properties, which was enriched in high-risk PCa including HgPAC, IDC and DAC, and associated which tumor progression and unfavorable prognosis. Additionally, eIF1A+ LE orchestrates the formation of an immunologically "cold" TME, characterized by the low infiltration of anti-cancer immune cells including PD1- T cells CD163- macrophages. Through in vivo validation and investigator-initiated study, we further found that Homoharringtonine, an inhibitor targeting protein translation process, effectively inhibited PCa growth, alleviated hypoxic microenvironment, and enhanced immune cell infiltration. This study is the first to apply spatial proteomics to delineate consistent molecular features across histological subtypes, providing transformative insights for clinical management of PCa.

cancer biology↗

bioRxiv2025

Changes in nuclear and actin mechanics from G1 to G2 affect nuclear integrity

The structural integrity of the nucleus is dependent on nuclear mechanical elements of chromatin and lamins to resist antagonistic actin cytoskeleton forces. Imbalance results in nuclear blebbing, rupture, and cellular dysfunction found in many human diseases. We used Fluorescent Ubiquitin Cell Cycle Indicator (FUCCI) cells to determine how cell cycle changes affect the nucleus and actin force balance. While nuclear blebs are present equally throughout interphase, nuclear blebs form predominantly in G1 and then persist into G2 due to increased actin-based nuclear confinement and focal adhesion density in G1 vs. G2 cells. Upon artificial confinement, G2 nuclei ruptured more than G1 nuclei. Single nucleus micromanipulation force measurements confirmed that G1 nuclei are stronger than G2 nuclei in both the chromatin-based and lamin-based nuclear stiffness regimes. Decreased nuclear stiffness can be explained by loss of peripheral H3K9me3 from G1 to G2, recapitulated by H3K9me3 inhibition via Chaetocin. Cell cycle-based changes in nuclear and actin mechanics impact nuclear integrity and shape.

cell biology↗