Biology subjects

Cai, X.

Publications and source records attributed to Cai, X..

At least 55 records · Page 3Linked to original sources

bioRxiv2025

Spatiotemporal lineage mapping of tumor immune escape with eTRACER

The plasticity-first hypothesis posits that phenotypic plasticity emerges first in novel environments, followed by (epi)genetic changes that stabilize adaptive phenotypes. Whether tumor evolution follows this model, and how non-genetic mechanisms sustain long-term therapeutic resistance, remain unclear. Here, we develop eTRACER, an endogenously targeted, high-resolution and spatially-resolved CRISPR-Cas9 lineage-tracing system, to study tumor adaptation during longitudinal CD8+ T cell-mediated immunotherapy. Integrated clonal and single-cell transcriptomic analyses show that tumor immune evasion is governed by clonal state composition rather than clonal identity, arguing against selection from pre-existing genetic heterogeneity. Spatiotemporal lineage tracing reveals highly reversible state transitions prior to therapy, followed by consolidated epithelial-mesenchymal transition (EMT) during therapy. Single-cell multiomics identifies AP-1 as a key regulator of EMT stabilization and its inhibition enhances tumor sensitivity to immune killing. Together, these findings show that tumor plasticity precedes stable immune evasion, revealing an AP-1-centered mechanism underlying plasticity-first tumor evolution.

cancer biology↗

bioRxiv2025

Fish Show Genetic Evolutionary Responses to River Regulation

Eco-hydraulics traditionally aims at managing riverine systems in a semi-natural state while meeting human demands, assuming aquatic species are static. However, evidence of rapid evolution suggests that ignoring evolutionary dynamics of fish species might limit long-term effectiveness of eco-hydraulics frameworks. It remains unclear how freshwater fish adapt to human perturbation. Why are some fish populations more resilient to human perturbation than others? What are the genetic mechanisms behind it? To answer these questions, we genotyped eleven populations of three-spined stickleback in a regulated river system and collected data on river morphology, connectivity, flow regimes, physico-chemistry and parasite abundance through a combination of field surveys and modelling. Gene-environment association analysis detected strong signals of genetic divergence associated with hydraulic features. Gene ontology analysis revealed evolutionary responses that primarily involve functions in the nervous and sensory systems. These findings demonstrate that fish can evolve in response to river regulation, highlighting the need to transition from eco-hydraulics toward eco-evo-hydraulics.

evolutionary biology↗

bioRxiv2025

CD40 agonistic-monovalent streptavidin fusion antibody for targeted neoantigen peptide delivery and potent cancer vaccination

Cancer vaccines targeting patient-derived neoantigens offer great promise for personalized cancer therapy but face challenges in achieving targeted delivery to antigen-presenting cells (APCs) to elicit robust and durable cancer-specific immune responses. We synthesized an anti-mouse CD40 agonistic-monovalent streptavidin fusion antibody (CD40-mSAs), which enables targeted delivery of biotinylated neoantigen peptides to APCs in draining lymph nodes (dLNs). We confirmed mSA expression on the engineered antibody and its strong binding affinities to mouse CD40 and biotin. Advanced microscopy demonstrated that CD40-mSAs enhances homing to dLNs and intracellular delivery of neoantigen peptides to critical APC subsets, such as cDC1. The potent agonistic effects of CD40-mSAs on dendritic cell maturation, activation, and antigen presentation were verified through in vitro assays. Vaccination with CD40-mSAs elicited robust cancer-specific CD8 T cell responses, leading to significant tumor regression and prevention in a mouse tumor model. These results support CD40-mSAs as an all-in-one vaccine delivery platform with multifunctional immunopharmacological advantages and strong translational potential for personalized cancer vaccination. TeaserCD40-mSAs is an engineered anti-CD40 agonistic antibody designed to enhance cancer vaccine delivery.

immunology↗

bioRxiv2025

Visual-like Template Diffusion: Boosting Single-Sequence Protein Structure Prediction by Adapting Image Diffusion Models

Single-sequence protein structure prediction has drawn increasing attention due to the high computational costs associated with obtaining homologous information. Here, we propose a visual-like 2D geometric template* diffusion method, named TDFold, to generate high-quality pairwise geometries (including pairwise distances and orientations) for achieving accurate and highly efficient single-sequence 3D structure prediction for proteins. Given a protein sequence, TDFold initially generates high-quality inter-residue geometries from a probabilistic diffusion perspective. Since inter-residue geometries can be encoded as multi-channel feature matrices, analogous to image feature maps, we construct an image-level 2D geometric template diffusion module by adapting the stable diffusion (SD) model from text-vision generation to sequencegeometry diffusion for proteins. Subsequently, a lightweight sequencegeometry collaborative learning (SCL) network is constructed to facilitate accurate and efficient protein structure prediction. As a result, TDFold possesses three highlights: (i) better single-sequence prediction performance: TDFold greatly outperforms existing protein language models (PLMs, e.g. ESMFold and OmegaFold) and homology-based methods (e.g. AlphaFold2, AlphaFold3 and RoseTTAFold) on homologyinsufficient datasets such as Orphan and Orphan25, while also achieving promising results on the popular CASP14, CASP15 and CASP16 benchmarks; (ii) low resource consumption: By utilizing the lightweight SCL architecture, the GPU memory consumption of TDFold is generally lower than that of popular methods such as AlphaFold2 and ESMFold; (iii) higher efficiency in training and inference: TDFold can be trained within a week using a single NVIDIA 4090 GPU. Furthermore, the inference time of TDFold is significantly shorter (about 10x to 100x) than that of existing methods (ESMFold, AlphaFold2 and AlphaFold3) for long protein sequences. This work demonstrates the effectiveness of leveraging powerful vision diffusion models to enhance protein 2D geometric template generation, thereby establishing a new paradigm for single-sequence protein structure prediction. It also accelerates protein-related research, particularly for resource-limited universities and academic institutions. The code has been released to speed up biological research.

bioinformatics↗

bioRxiv2025

A global genetic interaction map of a human cell reveals conserved principles of genetic networks

We generated a genome-scale, genetic interaction network from the analysis of more than 4 million double mutants in the haploid human cell line, HAP1. The network maps [~]90,000 genetic interactions, including thousands of extreme synthetic lethal and genetic suppression interactions. Genetic interaction profiles enabled assembly of a hierarchical model of cell function, including modules corresponding to protein complexes, pathways, biological processes, and cellular compartments. Comparative analyses showed that general principles of genetic networks are conserved from yeast to human cells. A genetic interaction network mapped in a single genetic background complements the DepMap gene co-essentiality network, recapitulating many of the same biological connections and also capturing unique functional information to reveal roles of uncharacterized genes and molecular determinants of specific cancer cell line genetic dependencies.

systems biology↗

bioRxiv2025

Pp6-Pfkfb1 axis modulates intracellular bacterial proliferation by orchestrating host-pathogen metabolic crosstalk

Intracellular bacterial pathogens exhibit heterogeneous replication rates within host macrophages, but the mechanisms by which they manipulate host factors for survival remain incompletely understood. Using a fluorescence-dilution reporter system in Salmonella typhimurium (Salmonella)-infected macrophages, we found that Protein Phosphatase 6 (Pp6) was downregulated in macrophages harboring growing bacteria. Conditional knockout of Pp6 elevated host susceptibility to Salmonella-mediated lethality due to compromised antimicrobial defenses. MicroRNA-31 (miR-31) was identified as a negative regulator of Pp6, and its conditional ablation enhanced bacterial clearance. Yeast two-hybrid screening identified 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 1 (Pfkfb1), a metabolic regulator, as a substrate of Pp6. Pp6 deficiency resulted in significantly elevated expression of Pfkfb1, which was highly expressed in macrophages containing replicating Salmonella. Pfkfb1 deletion restricted bacterial proliferation by promoting nitric oxide (NO) production while concurrently suppressing arginase-1 (Arg-1) expression and impairing arginine metabolism in macrophages. Collectively, these results establish the Pp6-Pfkfb1 axis as a key regulator of host metabolic adaptation and intracellular bacterial survival, offering potential therapeutic targets against multidrug-resistant pathogens. Author summaryIntracellular pathogens secrete effector proteins that intercept and modify host cells to usurp host defenses and establish habitable intracellular niches, yet the host factors they manipulate for survival and virulence are not fully understood. Using a fluorescence-dilution reporter system in Salmonella typhimurium (Salmonella)-infected macrophages, we found Protein Phosphatase 6 (Pp6) was significantly decreased in macrophages harboring replicating Salmonella and its deficiency indulged bacterial growth in macrophages. However, the deletion of microRNA-31 (miR-31), a negative regulator of Pp6, enhanced Salmonella clearance. Furthermore, through yeast two- hybrid screening, we identified 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 1 (Pfkfb1) is a substrate of Pp6. And we demonstrated Pfkfb1, abundantly expressed in macrophages containing growing bacteria, is crucial for Salmonella proliferation by regulating nitric oxide (NO) levels, arginase-1 (Arg-1) expression and arginine metabolism. Overall, the molecular changes in Pp6-Pfkfb1 axis drive host metabolic adaptations that enable intracellular bacterial survival.

microbiology↗

bioRxiv2025

SR9009 Regulates Macrophage Polarization via the NR1D1/NF-κB Axis to Ameliorate Obesity Associated Ulcerative Colitis

ObjectiveThe incidence of ulcerative colitis (UC) and obesity has risen in recent years, potentially linked through metabolic dysregulation and chronic inflammation. The nuclear receptor NR1D1 is pivotal in regulating circadian rhythms and plays a significant role in inflammation and metabolism. This study investigates the therapeutic effects and mechanisms of the NR1D1 agonist SR9009 on obesity-related UC. MethodsWe established a mouse model of obesity-induced UC utilizing a high-fat diet alongside dextran sulfate sodium (DSS). 32 male C57BL/6 mice were divided into four groups: control (DZ), high-fat diet (GZ), obesity associated UC model group (UC), and SR9009 intervention group (JD), with eight mice each. We evaluated body weight, blood lipids, colonic tissue alterations, IL-1{beta}, IL-18, macrophage polarization, and NR1D1 expression levels. ResultsMice in the UC group demonstrated significantly elevated body weight, spleen index, TG, CHOL and inflammatory markers (P<0.01). Pathological scores of colonic tissues increased markedly (P=0.000), with a rise in M1 macrophages (CD68) and a decline in M2 macrophages (CD206) (P<0.001). NR1D1 expression was notably downregulated (P<0.01). Post-SR9009 intervention, the JD group showed significantly reduced serum TG and CHOL levels (P=0.001, 0.011), IL-1{beta} and IL-18 (P<0.001), improved colonic pathology (P=0.000), a decrease in M1 macrophages, an increase in M2 macrophages, and an enhanced M1/M2 ratio (P<0.001). ConclusionSR9009 mitigates intestinal inflammation in obesity associated UC by activating NR1D1, inhibiting the NF-{kappa}B pathway, and modulating macrophage polarization (suppressing M1 and enhancing M2). These findings propose a novel strategy for targeting NR1D1 in the treatment of obesity-related ulcerative colitis.

molecular biology↗

bioRxiv2025

Diffusion Neuroimaging of Speech Acquisition in Infants

How multisystem white-matter maturation supports early speech acquisition in infancy remains unclear. Using longitudinal diffusion MRI from the Baby Con-nectome Project, we quantified neurite density maturation from birth to 24 months across 33 white-matter tracts spanning motor, auditory, visual, ventral-language, and dorsal-language systems. Maturation was coordinated across systems rather than confined to canonical language pathways: dorsal-language association tracts began relatively immature near birth but showed steep postnatal growth, pro-gressively rebalancing with motor and sensory systems. Tract-behavior coupling was likewise distributed across developmental domains, with broadly positive age-adjusted associations for motor outcomes, a sparser, partly motor-like profile for gesture-related phrase comprehension, and predominantly negative associa-tions for lexical speech-related outcomes. Exploratory follow-up analyses further suggested motor and social precursor capacities that may help mediate these in-direct developmental routes from structural maturation to later speech-related outcomes. These findings support a multisystem developmental account in which early speech acquisition emerges not from an isolated language pathway, but from coordinated maturation across multiple systems and the precursor skills that link them.

neuroscience↗

bioRxiv2025

Balanced Permeability Index is a Strong Predictor of Intestinal Absorption and Oral Bioavailability for Heterobifunctional Ligand-Directed Degraders

Ligand-directed degraders (LDDs) are heterobifunctional molecules that degrade proteins by engaging the ubiquitin-protein ligase (E3) system. LDDs consist of a target-engaging moiety, an E3 ligase-binding moiety and a bridging linker. Due to their size and physicochemical complexity these molecules do not adhere to well-established rules of lead optimization. The optimization of passive permeability remains a key challenge to develop orally bioavailable LDDs. To overcome this challenge, in this study we demonstrate that the Balanced Permeability Index (BPI)--a new metric that combines size, polarity and lipophilicity--is highly predictive of oral bioavailability for LDDs. Here, we introduce an additional parameter--called smallest maximum intramo-lecular distance (SMID)--to the original BPI index to account for cross sectional area of LDDs, termed BPILDD. With this new parameter, BPILDD can differentiate oral bioavailability of LDDs in our dataset more effectively than polarity, lipophilicity, or size separately. In addition, BPILDD is also more effective at identifying orally bioavailable LDDs than some in vitro measurements of cell permeability that traditionally inform bioavailability. This finding opens the possibility of employing BPILDD for the design and optimization of orally bioavailable LDDs to improve their drug metabolism and pharmacokinetics properties.

pharmacology and toxicology↗

bioRxiv2025

Particular Amino Acid on Lateral Interface Maintains FtsZ Function Under Acid Stress in Streptococcus mutans

FtsZ is the core protein for cell division in bacteria that can polymerize into Z-rings and drive cytokinesis. Understanding how bacteria maintain the correct function of FtsZ under various environmental stresses is crucial for novel antibacterial drug discovery. Our previous study revealed that the FtsZ in S. mutans has higher self-assembly and GTPase activity under acidic stress, which may be responsible for the cariogenesis of S. mutans. However, the mechanism is still unknown. Here, we further reported the crystal structure of S. mutans FtsZ, revealing a unique lateral interface. Through protein polymerization and GTPase ability assay, we experimentally demonstrated that mutation of Arg68 on this lateral interface significantly reduced the functional activity of FtsZ in an acidic environment. The phenotype assay and rat caries model further showed that mutation of Arg68 effectively inhibited the acid resistance of S. mutans and the occurrence and progress of dental caries in vivo. By employing a molecular dynamics simulation analysis, we conclude that mutation of Arg68 disrupts the conformation change necessary for SmFtsZ polymerization under acidic conditions. Our study proposes a novel mechanism to maintain FtsZ function in bacteria and could be a potential target for antimicrobial drugs to inhibit the growth of S. mutans in an acidic environment. Significance StatementFtsZ is the core protein that drives cytokinesis. Maintaining the self-assembly and GTPase activity of FtsZ plays a critical role in cell growth under environmental stress. Currently, research on FtsZ function maintenance under stress mainly focuses on model organisms, with less on other pathogenic bacteria. This study reveals a novel structural mechanism for the acidic tolerance of FtsZ in S. mutans which survives in strongly acidic surroundings. Meanwhile, Arg68 on the lateral interface of SmFtsZ may be a potential therapeutic target to regulate microecology and combat S. mutans-associated dental caries.

microbiology↗

bioRxiv2025

Concurrent PIK3CA mutant drives cachexia through inflammatory signaling in EGFR mutant lung cancer

PIK3CA mutation is frequently concurrent with known oncogenic drivers such as EGFR mutation in lung cancer, raising an interesting question about its real function. Cachexia is a systemic disease involving complex interaction between primary tumors and distant organs, significantly contributing to cancer-related mortality. Through integrative study of genetically engineered mouse models (GEMMs) and clinical data, we find concurrent PIK3CA mutant preferentially drives cachexia in EGFR-mutant lung cancer, promoting malignant progression instead of cancer initiation. PIK3CA mutant-mediated cachexia could be overcome by osimertinib (Osi) treatment in Osi-sensitive GEMM. In contrast, chemotherapy, routinely used in clinic for those relapsed from Osi therapy, fails to ameliorate cachexia in Osi-resistant GEMM despite notable tumor suppression. PIK3CA mutant-driven cachexia is mediated through NF-{kappa}B activation and could be dampened by combined aspirin treatment. This work uncovers the biological function of PIK3CA mutant and mechanism behinds its clinical impacts, and proposes a potentially effective strategy for clinical management.

cancer biology↗

bioRxiv2025

High-pressure Golgi neuronal staining for X-ray whole-brain imaging

Whole-brain imaging has revolutionized neuroscience research, providing comprehensive insights into neural networks across the entire brain. This powerful approach has greatly advanced our understanding of brain functions and the mechanisms underlying various diseases. One primary challenge in whole-brain imaging technology is to achieve high-resolution observation of neural networks at large scales. Although Golgi method allows labeling random neurons in their entirety in the brain, visualizing individual dendritic trees, and tracing long-distance axonal projections, the lengthy processing time pose a limit on its use, i.e., staining a mouse whole-brain sample of just 300 mm3 takes over two weeks. Here, we developed a rapid staining technique for whole-brain neurons using high-pressure assisted Golgi (HP Golgi). This method significantly reduced the staining time for mouse whole-brain neurons from 16 days to only 4 days. We demonstrated the broad applicability of the HP Golgi method across various model organisms, achieving whole-brain neuronal staining in zebrafish, mice, and rats. Further, we successfully performed rapid staining of hippocampal neurons in an intact pig brain, which is difficult to achieve with the classic Golgi-Cox method. We also demonstrated that the combination of the HP Golgi method with synchrotron-based X-ray microscopy for high-resolution imaging of whole-brain neurons in mice. This HP Golgi method enables fast and high-resolution neuronal imaging in large model organisms, showcasing its broad applicability for diverse applications.

biophysics↗

bioRxiv2025

Auditory tract maturation in early infancy: Links to speech production

Infants exhibit remarkable language acquisition abilities, supported by highly plastic neural substrates that dynamically interact with early speech experiences. However, the developmental mechanisms of these neural substrates and their specific role in speech acquisition remain incompletely understood. Here, we present NeoAudi Tract (NAT), a robust automated toolbox for extracting the full set of auditory tracts in infants from birth to 24 months using 3T diffusion MRI data. By characterizing the microstructural changes in these tracts, we demonstrate a gradual and continuous maturation process of the auditory system. Additionally, we identify significant correlations between auditory tract maturation and both fine-motor skills and expressive language t-scores from the Mullen Scales of Early Learning tests. Our findings highlight the role of the auditory system in speech production and indicate the intertwined development of auditory and motor systems that underlies speech acquisition, particularly during perceptual reorganization.

neuroscience↗

bioRxiv2024

Dynamic Grouping of Ongoing Activity in V1 Hypercolumns

Neurons spontaneous activity provides rich information about the brain. A single neurons activity has close relationships with the local network. In order to understand such relationships, we studied the spontaneous activity of thousands of neurons in macaque V1 and V2 with two-photon calcium imaging. In V1, the ongoing activity was dominated by global fluctuations in which the activity of majority of neurons were correlated. Neurons activity also relied on their relative locations within the local functional architectures, including ocular dominance, orientation, and color maps. Neurons with similar preferences dynamically grouped into co-activating ensembles and exhibited spatial patterns resembling the local functional maps. Different ensembles had different strengths and frequencies. This observation was consistent across all hypercolumn-sized V1 locations we examined. In V2, different imaging sites had different orientation and color features. However, the spontaneous activity in the sampled regions also correlated with the underlying functional architectures. These results indicate that functional architectures play an essential role in influencing neurons spontaneous activity, and can be explained by a network model that integrates diverse horizontal connections among similar functional domains.

neuroscience↗

bioRxiv2024

Innervation density governs crosstalk of GPCR-based norepinephrine and dopamine sensors

GPCR-based fluorescent sensors are widely used to correlate neuromodulatory signaling with brain function. While experiments in transfected cells often reveal selectivity for individual neurotransmitters, sensor specificity in the brain frequently remains uncertain. Pursuing experiments in brain slices and in vivo, we find that norepinephrine and dopamine cross-activate the respective sensors. Non-specific activation occurred when innervation of the cross-reacting transmitter was high, and silencing of specific innervation was indispensable for interpreting sensor fluorescence.

neuroscience↗

bioRxiv2024

Key contribution of prefrontal inhibition to passive coping behaviour: chronic stress and fast-acting antidepressant

Persistent passive coping behaviour is a hallmark feature in major depression and is reversed by fast-acting antidepressants (such as ketamine). This behaviour is regulated by a specific cortico-midbrain circuit. However, whether the prefrontal cortex (PFC), especially inhibition in PFC, contributes to the modulation of passive coping, and whether this modulation is important for mediating the impacts of chronic stress and/or fast-acting antidepressants, are poorly understood. Here, we found that rostral prelimbic cortex (rPL) bidirectionally controls the occurrence of passive coping behaviour where excitatory and inhibitory neurons play opposite roles. Chronic stress leads to reduced excitation/inhibition (E/I) ratio, reflected as alterations in in vivo spiking rate, synaptic inputs and intrinsic excitability of both excitatory and inhibitory neurons. A fast-acting antidepressant, (2R, 6R)-hydroxynorketamine (HNK), reduced passive coping behaviour, restored rPL E/I ratio and partially reversed altered properties in rPL neurons, in chronically stressed mice. Importantly, chronic stress and HNK mostly affected fast-spiking/parvalbumin inhibitory neurons instead of other inhibitory neurons, indicating the important role of this subtype of inhibitory neurons in the above processes. These findings demonstrate the importance of rPL E/I balance in regulating passive coping, which can be modulated by chronic stress and rapidly restored by fast-acting antidepressant.

neuroscience↗

bioRxiv2024

Ternary representation of contextual information along the CA1 transverse axis

Episodic memory refers to the recollection of personally experienced events anchored in spatial contexts. Salient objects within a navigation environment serve as both landmarks and event cues; however, the nuanced integration of these elements during episodic memory formation is not well understood. The mnemonic functions of the hippocampal CA1 region are partially organized along its transverse axis, with proximal and distal subregions preferentially processing spatial and non-spatial information, respectively. Based on comprehensive analysis of neuronal responses along the CA1 proximodistal axis to manipulations of environmental cues and object features, we identified an event-like population coding within CA1 following object displacement. In addition, the neuronal responses at both initial and relocated object locations were shaped by distinct convergent inputs. These findings highlight the specific roles that objects may play in spatial navigation and memory encoding, providing novel insights into the selective processing of object-related information within the entorhinal-hippocampal network. Significance StatementSalient objects within a navigation environment serve as both landmarks and event cues critical for episodic memory. However, the enigmatic contribution of objects to the "where" and "what" components of episodic memory remains poorly understood. Here we comprehensively analyzed the neuronal responses in the hippocampal CA1 region along its transverse axis, to manipulations of environmental cues and object features. Our results revealed an event-like population coding within CA1 following object displacement, suggesting a minimal landmark role these objects play during memory formation. This study provides novel insights into the selective and flexible processing of object-related information within the entorhinal-hippocampal network.

neuroscience↗

bioRxiv2024

Correlative multiscale 3D imaging of mouse primary and metastatic tumors by sequential light sheet and confocal fluorescence microscopy

Three-dimensional (3D) optical microscopy, combined with advanced tissue clearing, permits in situ interrogation of the tumor microenvironment (TME) in large volumetric tumors for preclinical cancer research. Light sheet (also known as ultramicroscopy) and confocal fluorescence microscopy are often used to achieve macroscopic and microscopic 3D images of optically cleared tumor tissues, respectively. Although each technique offers distinct fields of view (FOVs) and spatial resolution, the combination of these two optical microscopy techniques to obtain correlative multiscale 3D images from the same tumor tissues has not yet been explored. To establish correlative multiscale 3D optical microscopy, we developed a method for optically marking defined regions of interest (ROIs) within a cleared mouse tumor by employing a UV light-activated visible dye and Z-axis position-selective UV irradiation in a light sheet microscope system. By integrating this method with subsequent tissue processing, including physical ROI marking, reversal of tissue clearing, tissue macrosectioning, and multiplex immunofluorescence, we established a workflow that enables the tracking and 3D imaging of ROIs within tumor tissues through sequential light sheet and confocal fluorescence microscopy. This approach allowed for quantitative 3D spatial analysis of the immune response in the TME of a mouse mammary tumor following cancer immunotherapy at multiple spatial scales. The workflow also facilitated the direct localization of a metastatic lesion within a whole mouse brain. These results demonstrate that our ROI tracking method and its associated workflow offer a novel approach for correlative multiscale 3D optical microscopy, with the potential to provide new insights into tumor heterogeneity, metastasis, and response to therapy at various spatial levels.

cancer biology↗