Biology subjects

Chi, Z.

Publications and source records attributed to Chi, Z..

12 recordsLinked to original sources

bioRxiv2026

Spatial Topology Reveals Biologically Distinct Recurrent Motifs in Colorectal Cancer

Most spatial transcriptomic analyses of solid tumors focus on individual cell states or single-sample spatial domains rather than on recurrent multicellular tissue architectures shared across patients, and typically depend on predefined cell-type annotations or compartment definitions. We developed STORM (Spatial Topology analysis of Recurrent Motifs), an unsupervised graph-attention variational autoencoder that learns recurrent spatial motifs directly from cell-level graph structure and molecular profiles without cell-type labels, manual annotation, or predefined compartments. We applied to 32 Xenium sections from 16 patients with paired early-onset (EOCRC) and average-onset (AOCRC) colorectal cancer, STORM identified 10 recurrent motifs that self-organized into tumor-parenchymal, stromal, and immune macro-compartments. Among these, the Desmoplastic Fibrotic Barrier (DFB) motif, a CAF- and ECM-rich boundary architecture, was associated with restricted CD8+ T-cell geodesic access to tumor cores independently of CD8+ abundance, as demonstrated by abundance-normalized neighborhood enrichment statistics and within-sample mixed-effects models. EOCRC selectively amplified this barrier-exclusion architecture, exhibiting tighter tumor parenchyma, denser DFB shells, and a DFB-specific ECM activation program that yielded an age-specific prognostic signature in TCGA-COAD. Translation of motif macro-classes to H&E images via a Vision Transformer classifier produced an image-derived DFB-barrier composite that predicted overall survival in advanced-stage TCGA colorectal cancer. STORM provides an annotation-free framework for discovering recurrent spatial motifs and identifies a fibroblast barrier architecture whose topological association with immune exclusion is independent of effector abundance, amplified in early-onset disease, and translatable to a deployable pathology-based prognostic biomarker.

bioinformatics↗

bioRxiv2026

Inflammatory Stromal Aging in Ulcerative Colitis and Colitis-Associated Cancer

ABSTRACTUlcerative colitis is a chronic inflammatory bowel disease that can progress from dysplasia to cancer. Inflammatory responses are critical drivers in this process, typically triggered by epithelial lesions and the ensuing infiltration of microbiota into the interstitial layer. Here, we focus on the pro-inflammatory state of the interstitial fibroblasts, which promotes immune infiltration and augments disease progression. The study aims to provide a mechanistic link how fibroblasts of the colitis-associated microenvironment integrate inflammatory signals, microbial infiltration and cellular memory. To this end, we investigated a large number of primary colon fibroblasts obtained from normal, colitis and colon cancer samples using a range of in vitro approaches and an in vivo co-inoculation cancer model. mRNA sequencing analysis identified that the disease-associated fibroblasts are exhibit a cellular inflammatory status, which involves the injury-induced senescence pathway. Using CXCL8, a potent chemokine upregulated in colitis and cancer colon fibroblasts, as a paradigm, this inflammatory status is triggered by the activation of the NF{kappa}B signaling via immune-derived cytokines (TNF, IL-1{beta}), bacterial signals (LPS) and the microbiome itself using mycoplasma as a paradigm. Finally, iPSC reprogramming studies indicate that fibroblasts from ulcerative colitis retain an epigenetic memory that sustains elevated CXCL8 expression. Together, our findings demonstrate that the senescence associated secretory phenotype of colon fibroblasts is a robust indicator for inflammation-driven colon tumorigenesis.

cancer biology↗

bioRxiv2025

Form Follows Function: A New Paradigm of Pancreatic Cancer Progression

Pancreatic ductal adenocarcinoma (PDAC) exhibits a distinctive propensity to invade nearby organs and infiltrate large blood vessels, even in the absence of distant metastasis. While the genetic and transcriptomic drivers of PDAC progression have been well studied, the mechanisms by which these molecular changes translate into functional, invasive behavior remain largely unknown. Here, we uncover a striking level of tissue organization, characterized by previously unrecognized spatial and geometric properties within and among tumor structures. Leveraging the first large-scale, AI-assisted, human-curated PDAC atlas from hematoxylin and eosin (H&E) images, we annotated, classified, and characterized 144,474 malignant and normal structures from treatment-naive (n=118) and neoadjuvant-treated PDAC patients (n=50). Additionally, we developed a new computational tool, SHAPE, to investigate PDAC aggressiveness through a comprehensive "geometrization" of cancer progression. Using traditional H&E-stained slides and three-dimensional (3D) tissue reconstruction experiments, we observed that invading tumor structures display an eccentric morphology with pronounced local angular coherence. These geometric and spatial properties revealed coherent architectural patterns, with invasive structures closely tracking vessels and nerves as they infiltrate surrounding tissue. Mechanistically, integration of morphological features from 39,045 annotated tumor structures with whole-genome and RNA sequencing data revealed that PDACs with numerous eccentric structures exhibit increased copy number alterations (CNAs), loss of heterozygosity (LoH) on the p-arm of chromosome 17, and a quasi-mesenchymal/basal-like molecular subtype. Spatial transcriptomic analysis of 1,650 tumor structures from six additional PDAC patients further confirmed upregulation of invasive cellular programs within highly eccentric structures, such as epithelial-to-mesenchymal transition (EMT), angiogenesis, coagulation, and complement pathways, underscoring their infiltrative nature. Finally, cross-validation of our AI-based method enabled a fully automated, highly interpretable computational approach to assist pathologists and clinicians in evaluating neoadjuvant chemotherapy response, predicting patient survival, and guiding chemotherapy in adjuvant settings. Collectively, these findings deepen our understanding of PDAC progression, identify a new hallmark of tumor architecture, and pave the way for full integration of AI-driven morphology-based approaches into clinical workflows to improve the management of PDAC patients.

cancer biology↗

bioRxiv2025

Biomechanical Phenotyping Reveals Unique Mechanobiological Signatures of Early-Onset Colorectal Cancer

While both incidence and mortality of sporadic average-onset colorectal cancer (AO CRC, above 50 years of age) are in constant decline, sporadic early-onset colorectal cancer (EO CRC, under 50 years of age) is rising rapidly. Yet, the causes behind this rise remain poorly understood. Epidemiological studies indicate that lifestyle and environmental exposures may result in chronic inflammation, which is known to trigger tissue fibrosis. This study tests the hypothesis that fibrotic remodeling and biomechanical stiffening of colorectal tissues represent measurable hallmarks and potential drivers of EO CRC. Using primary human tissues, this work shows that EO CRC is associated with changes in collagen microstructure, increased stiffness and elevated viscosity of primary tumors. Spatial transcriptional profiling and immunostaining reveal pro-fibrotic signatures in stromal cells, alongside enhanced Yes-associated protein (YAP) mechanotransduction and proliferation in epithelial cells of EO CRC tissues. Mechanistically, increasing matrix stiffness in vitro promotes proliferation of epithelial cells in 2D and 3D colorectal cancer models. Together, these findings establish EO CRC as a disease marked by early and widespread biomechanical remodeling, suggesting that a fibrotic and stiffened tissue microenvironment may orchestrate EO CRC tumor initiation.

bioengineering↗

bioRxiv2025

The Arabidopsis WAVE/SCAR Protein BRICK1 Associates with Cell Edges and Plasmodesmata

Plasmodesmata (PD) are specialized structures in plant cell walls that mediate intercellular communication by regulating the trafficking of molecules between adjacent cells. The actin cytoskeleton plays a pivotal role in controlling PD permeability, but the molecular mechanisms underlying this regulation remain unclear. Here, we report that BRK1, a component of the WAVE/SCAR complex involved in Arp2/3-mediated actin nucleation, localizes to PD and primary pit fields in Arabidopsis cotyledons, leaves, and hypocotyls. Using a BRK1-YFP reporter line, we detected BRK1 enrichment at cell edges and in primary pit fields, identified by regions of reduced propidium iodide staining. We also observed colocalization between BRK1-YFP and the PD callose stain aniline blue, further supporting BRK1s association with PD. Together, these findings suggest that the WAVE/SCAR complex participates in PD regulation by promoting ARP2/3-dependent actin filament branching at PD, complementing the role of linear actin stabilization by formins.

plant biology↗

bioRxiv2025

U2-2 snRNA Mutations Alter the Transcriptome

Intron removal from pre-mRNA is catalyzed by the spliceosome, which comprises 5 snRNPs containing small nuclear RNAs (snRNAs). U2 snRNA makes critical RNA-RNA and RNA-protein contacts throughout the splicing cycle. Mutations in U2 snRNA, particularly at position C28, have been linked to cancers. To study gene expression changes mediated by mutated U2 snRNAs, U2-2 C28 mutants, U2-2 knockout (KO), and U2-2 overexpression (OE) cell lines were constructed followed by RNA sequencing. We observed significant changes in splicing and over 4,000 differentially expressed genes enriched in pathways like RNA processing and non-coding RNAs upon knocking out U2-2 snRNA. Splicing patterns were more influenced by U2-2 dosage than mutations alone. Therefore, the mutant exhibits a compound phenotype, resulting from reduced U2-2 levels (and thus mostly phenocopying the KO) and additional mutant-specific splicing changes. HIGHLIGHTSO_LIU2-2 snRNA BSL mutants alter splicing and the transcriptome C_LIO_LIU2-2 KO phenocopies most altered splice events in the mutants C_LIO_LIBoth U2-2 levels and mutations alter splicing C_LIO_LIMany altered splice events lead to NMD C_LI

molecular biology↗

bioRxiv2024

Negative Selection Allows DNA Mismatch Repair-Deficient Mouse Fibroblasts In Vitro to Tolerate High Levels of Somatic Mutations

Substantial numbers of somatic mutations have been found to accumulate with age in different human tissues. Clonal cellular amplification of some of these mutations can cause cancer and other diseases. However, it is as yet unclear if and to what extent an increased burden of random mutations can affect cellular function without clonal amplification. We tested this in cell culture, which avoids the limitation that an increased mutation burden in vivo typically leads to cancer. We performed single-cell whole-genome sequencing of primary fibroblasts from DNA mismatch repair (MMR) deficient Msh2-/- mice and littermate control animals after long-term passaging. Apart from analyzing somatic mutation burden we analyzed clonality, mutational signatures, and hotspots in the genome, characterizing the complete landscape of somatic mutagenesis in normal and MMR-deficient mouse primary fibroblasts during passaging. While growth rate of Msh2-/-fibroblasts was not significantly different from the controls, the number of de novo single-nucleotide variants (SNVs) increased linearly up until at least 30,000 SNVs per cell, with the frequency of small insertions and deletions (INDELs) plateauing in the Msh2-/- fibroblasts to about 10,000 INDELS per cell. We provide evidence for negative selection and large-scale mutation-driven population changes, including significant clonal expansion of preexisting mutations and widespread cell-strain-specific hotspots. Overall, our results provide evidence that increased somatic mutation burden drives significant cell evolutionary changes in a dynamic cell culture system without significant effects on growth. Since similar selection processes against mutations preventing organ and tissue dysfunction during aging are difficult to envision, these results suggest that increased somatic mutation burden can play a causal role in aging and diseases other than cancer.

genomics↗

bioRxiv2023

A biosensor encompassing fusarinine C-magnetic nanoparticles and aptamer-red/green carbon dots for dual-channel fluorescent and RGB discrimination of Campylobacter and Aliarcobacter

The diarrhea pathogens Campylobacter and Aliarcobacter are similar in morphology and their resulting symptoms, making them difficult to be differentially diagnosed. Herein, we report a biosensor with two newly-synthesized modules to differentiate the genera-representative species of C. jejuni and A. butzleri. Module 1 was fusarinine C-decorated magnetic nanoparticles; module 2 consisted of C. jejuni-specific aptamer modified with red-emitting carbon dots (CDs) and A. butzleri-specific aptamer-modified green-emitting CDs. These two CDs had non-interfering spectra. Module 1 was used to selectively capture C. jejuni and A. butzleri from an un-cultured sample, and the specific CDs in module 2 would then recognize and bind to their counterpart bacteria when subjected to the collected module 1-bacteria complex. By measuring the fluorescence intensities from each CDs, the existence and abundance of each bacterium could be differentially indicated. This biosensor exhibited a wide detection range of up to 1 x 107 CFU/mL and the lowest limit of detection (LOD) of 1 CFU/mL, for each bacterium. Thus, the biosensor with dual-fluorescent channels facilitated a culture-independent, ultrasensitive and discriminative detection of C. jejuni and A. butzleri. Remarkably, this fluorescent detection could be transformed into RGB color indication to render the visual discrimination. After integrating the microfluidics, this biosensor offered RGB differentiation of the two bacteria in human stool or chicken broilers with a LOD of 5 CFU/mL and turnaround time of 65 min. This work suggested a new biosensor-based methodology for the discrimination of Campylobacter and Aliarcobacter in real samples.

bioengineering↗

bioRxiv2021

Heptanol-mediated phase separation determines phase preference of molecules in live cell membranes

Plasma membranes contain diverse nanoscale assemblies of lipid and protein domains. Specific localization of lipids and proteins in these domains is often essential for membrane function and integrity. Due to the nanoscale size and dynamic nature of membrane domains, identification of molecules residing in domains either is not possible with modern imaging techniques or requires advanced methods with high spatiotemporal resolution. Such methods need expensive equipment making these approaches inaccessible and thus difficult to implement at large scale. Here, we present a novel membrane fluidizer-induced clustering (MFIC) approach to identify the phase-preference of molecules in intact cell membranes. Experiments in phase-separated bilayers and live cells on molecules with known phase preference demonstrate that heptanol hyperfluidizes the membrane and stabilizes phase separation in cell membranes. The domain stabilization results in a transition of nano-to micron-sized clusters of associated molecules and allows identification of molecules localized in domains using routine microscopy techniques. This assay can be carried out on both genetically and extrinsically labelled molecules in live cell membranes, does not require any invasive sample preparation and can be carried out in 10-15 minutes. This inexpensive and easy to implement assay can be conducted at large-scale and will allow easy identification of molecules partitioning into domains.

biophysics↗

bioRxiv2021

Remarkable Adsorption Performance of Rutile TiO2 (110) Nanosheet for DNA Nucleobases: A First-Principles Study

The remarkable biocompatibility and supreme physical properties of nanostructured TiO2 have promised itself a strong future for biomedical applications. The present study reported a theoretical study on the adsorption of rutile TiO2 (110) nanosheet for DNA nucleobases using first-principles calculations. The calculations of the binding energy and work function demonstrate that the TiO2 nanosheet has remarkable adsorption strength to the DNA nucleobases, being more than 20 times larger than that of graphene and its derivatives. Further electronic band structure and density of state calculations elucidate the interaction mechanisms, which originate from dramatically reduced energy levels and strong hybridization of the 2p orbital of C, N and/or O with 3d orbital of Ti atoms near the Fermi level. The study directs a promising material at applications in DNA sensors and sequencers.

bioengineering↗

bioRxiv2020

Ratio of the interferon-γ signature to the immunosuppression signature predicts anti-PD-1 therapy response in melanoma

Immune checkpoint inhibitor (ICI) treatments produce clinical benefit in many patients. However, better pretreatment predictive biomarkers for ICI are still needed to help match individual patients to the treatment most likely to be of benefit. Existing gene expression profiling (GEP)-based biomarkers for ICI are primarily focused on measuring a T cell-inflamed tumour microenvironment that contributes positively to the response to ICI. Here, we identified an immunosuppression signature (IMS) through analysing RNA sequencing data from a combined discovery cohort (n = 120) consisting of three publicly available melanoma datasets. Using the ratio of an established IFN-{gamma} signature and IMS led to consistently better prediction of the ICI therapy outcome compared to a collection of nine published GEP signatures from the literature on a newly generated internal validation cohort (n = 55) and three published datasets of metastatic melanoma treated with anti-PD-1 (n = 48) and anti-CTLA-4 (n = 42) as well as in patients with gastric cancer treated with antiPD-1 (n = 45), demonstrating the potential utility of IMS as a predictive/prognostic biomarker that complements existing GEP signatures for immunotherapy.

immunology↗

bioRxiv2019

Single-cell whole-genome sequencing reveals mutational landscapes of DNA mismatch repair deficiency in mouse primary fibroblasts

DNA Mismatch repair (MMR) deficiency is a major cause of hereditary non-polyposis colorectal cancer, and is also associated with increased risk of several other cancers. This is generally ascribed to the role of MMR in avoiding mutations by correcting DNA replication errors. In MMR knockout mice very high frequencies of somatic mutations, up until 100-fold of background, have been reported. However, these results have been obtained using bacterial reporter transgenes, which are not representative for the genome overall, and mutational patterns of MMR deficiency remain largely unknown. To fill this knowledge gap, we performed single-cell whole-genome sequencing of lung fibroblasts of Msh2-/- and wild-type mice. We observed a 4-fold increase of somatic single nucleotide variants (SNVs) in the fibroblasts of Msh2-/- mice compared to those of wild-type mice. The SNV signature of Msh2 deficiency was found to be driven by C>T and T>C transitions. By comparing it to human cancer signatures, we not only confirmed the inferred MMR-deficiency-related etiology of several cancer signatures but also suggested that MMR deficiency is likely the cause of a cancer signature with its etiology previously unknown. We also observed a 7-fold increase of somatic small insertions and deletions (INDELs) in the Msh2-/- mice. An elevated INDEL frequency has also been found in human MMR-related cancers. INDELs and SNVs distributed differently across genomic features in the Msh2-/- and control cells, with evidence of selection pressure and repair preference. These results provide insights into the landscape of somatic mutations in normal somatic cells caused by MMR deficiency.\n\nSignificanceOur results show that MMR deficiency in the mouse is associated with a much lower elevation of somatic mutation rates than previously reported and provides the first MMR whole-genome mutational landscapes in normal somatic cells in vivo.

genomics↗