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Liu, R.

Publications and source records attributed to Liu, R..

At least 91 records · Page 5Linked to original sources

DANCE 2.0: Transforming single-cell analysis from black box to transparent workflow

Preprocessing is a critical step in single-cell data analysis, yet current practices remain largely a black-box, trial-and-error process driven by user intuition, legacy defaults, and ad hoc heuristics. The optimal combination of steps such as normalization, gene selection, and dimensionality reduction varies across tasks, model architectures, and dataset characteristics, hindering reproducibility and method development. We present DANCE 2.0, an automated and interpretable preprocessing platform featuring two key modules: the Method-Aware Preprocessing (MAP) module, which discovers optimal pipelines for task-specific methods via hierarchical search, and the Dataset-Aware Preprocessing (DAP) module, which recommends pipelines for new datasets via similarity-based matching to a reference atlas. Together, MAP and DAP execute over 325,000 pipeline searches across six major tasks - clustering, cell type annotation, imputation, joint embedding, spatial domain identification, and cell type deconvolution - yielding robust and generalizable recommendations. MAP-recommended pipelines consistently outperform original method defaults, with substantial gains across all tasks. Beyond automation, DANCE 2.0 reveals interpretable preprocessing patterns across tasks, methods, and datasets, transforming preprocessing into a transparent, data-driven process. All resources are openly available at https://github.com/OmicsML/dance to support broad community adoption and future methodological advances.

bioinformatics↗

Development and Characterization of a Tunable PDMS Substrate Model for Investigating Elastic Properties and Mechanical Stretching in Intervertebral Disc Mechanobiology

BackgroundAberrant mechanical loading and altered extracellular matrix (ECM) composition favor catabolic cell responses, contributing to intervertebral disc (IVD) degeneration and ultimately impairing the integrity of the annulus fibrosus (AF). This highlights the need for new in vitro models to investigate the interplay of mechanical loading and cell-substrate interactions. Therefore, this study introduces a tunable stretching chamber platform to simultaneously study both factors in AF degeneration. MethodsTunable PDMS substrates were fabricated by adjusting ratios of Sylgard 184 and Sylgard 527, enabling molding into stretching chambers or well plates. Substrates underwent mechanical, optical and chemical characterization. Bovine AF cells were seeded onto the substrates and cultured under static conditions or subjected to cyclic strain (8% strain at 1 Hz). Substrate biocompatibility and cell morphology were assessed over 72 h in static cultures. Dynamic responses were assessed by cell viability and alignment. Digital Image Correlation (DIC) was employed to assess surface strain in custom-designed and commercial (STREX) stretching chambers at strains between 8 to 20%. ResultsPDMS formulations resulted in a stiffness (E modulus) range of 8.72 - 238.00 kPa, demonstrating distinct viscoelastic profiles. All substrate formulations supported AF cell adhesion and viability. DIC analysis revealed non-uniform axial and transverse strain distributions on membrane surfaces. Cyclic stretching showed that cells maintained viability up to 14 h. Additionally, cells responded to the applied strain by perpendicular alignment to the stretch axis at 6 h. ConclusionsThe PDMS based stretching platform offers a biocompatible and tunable mechanical environment that mimics physiological and pathophysiological elastic properties. It enables systematic investigations on how elastic properties and mechanical strain modulate AF cell behavior in IVD disease progression. Finally, this study raises the awareness of non-uniform and transverse strain components within the stretching chambers and highlights the discrepancy of effective strain transfer to the cell interaction surface.

bioengineering↗

Metagenomic analysis of antimicrobial resistance, virulence, and mobile genetic elements in the gut microbiota of Caprinae species

The gut microbiota of livestock serves as a reservoir for antimicrobial resistance (AMR), yet Caprinae species remain understudied in this context. In this comprehensive metagenomic study, we analyzed 779 gut samples from Caprinae animals and reconstructed 17,023 high-quality metagenome-assembled genomes (MAGs). From these, we identified 4,685 antimicrobial resistance genes (ARGs) and 5,401 virulence factor genes (VFGs). Escherichia coli emerged as a major host carrying high burdens of both ARGs and VFGs. Strong positive correlations between ARGs, VFGs, and mobile genetic elements (MGEs) suggest potential co-selection and genetic linkage. Although MGEs were found in only 1.45% of MAGs, 23 ARGs were physically co-located with MGEs, indicating mobility potential. Additionally, three ARGs were embedded within viral genomes, two of which were associated with Myoviridae phages and one with an unclassified viral source, implicating phages in AMR dissemination. Comparative analyses revealed 292 ARG types shared between Caprinae and the human gut microbiota, including 20 genes representing six clinically critical resistance types: tetX1, tetX4, tmexD3, vanD, vanR, and vanS--conferring resistance to tigecycline, vancomycin, and polymyxins. These findings expand our understanding of the resistome and virulome in Caprinae animals and highlight potential zoonotic transmission pathways, underscoring the need for targeted AMR surveillance and mitigation strategies.

microbiology↗

Genome-wide extraction of differentially methylated DNA regions using adapter-anchored proximity primers

The epigenetic deregulation of CpG islands (CGIs) plays a crucial role in cancer initiation and progression. CGIs comprise 1-2% of the human genome and are rich in differentially methylated regions (DMRs) that can serve as cancer biomarkers in clinical samples and liquid biopsies. Focusing epigenetic sequencing on CpG-rich sequences, including CGIs and avoiding non-informative regions, offers an efficient and sensitive approach for cancer identification and tracking, especially within samples containing excess of unaltered, normal DNA. To this end, we have developed Adaptor-anchored Methylation amplification via Proximity Primers (aMAPP), a versatile PCR-based enrichment method. aMAPP employs specially designed primers to selectively enrich either methylated or unmethylated CpGs, depending on the upstream methylation conversion method employed. aMAPP achieves high coverage of genome-wide CGIs and detects hundreds of DMRs in tumor samples compared to adjacent normal tissue using ultra-low depth sequencing ([~]300,000 reads). It enables tracing of aberrant methylation down to allelic frequency 0.01% in dilutions of tumor DNA and in cell-free DNA samples, can be applied using picogram amounts of DNA, and can be adapted to enrich either small panels of cancer-specific DMRs, or the majority (>90%) of genomic CGIs and CpGs. aMAPP offers a simple, cost-effective, and highly sensitive approach for capturing the epigenetic footprint of genome-wide CpGs and identifying aberrantly methylated or un-methylated genomic regions. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/660377v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@b8b303org.highwire.dtl.DTLVardef@1f0a70corg.highwire.dtl.DTLVardef@67391dorg.highwire.dtl.DTLVardef@d6ac75_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

Tracing colorectal malignancy transformation from cell to tissue scale

The transformation of normal intestinal epithelium into colorectal cancer (CRC) involves coordinated changes across molecular, cellular, and architectural scales; yet, how these layers integrate remains poorly resolved. Here, we survey colorectal tumorigenesis by combining whole-transcriptome spatial molecular imaging (WTx CosMx SMI) with single-nucleus RNA-sequencing (snPATHO-seq) and digital histopathology on colon samples containing reference mucosa, adenomas and carcinomas, as well as a metastatic lymph node. Leveraging (discrete) histological annotations and (continuous) data-driven trajectories, we quantify the dynamics of cellular density, heterogeneity, function and signaling along the reference-adenoma-carcinoma axis, which is concordant in its spatial and molecular definition. This combination of analytical approaches across different data views let us chart tissue transformation across dimensions (physical/transcriptional) and scales (cell/tissue). We resolve [~]3.5 million cells into 43 epithelial, immune, and stromal subpopulations that exhibit a bi-furcating tumor evolution: On the one hand, LGR5+ stem-like epithelial cells are enriched in highly homogeneous proliferative tumor cores. On the other hand, MMP7+ fetal-like states are restricted to immunosuppressive invasive fronts, rich in cancer-associated fibroblasts (CAFs) and tumor-associated macrophages. These subpopulations form concentric spatial layers that organize transformed regions, and their compound aligns with histological malignancy. We further define transition crypts - single colonic crypts with divided histological and transcriptional makeup - that arise from rare crypt fusion or abrupt transformation events. Finally, we trace MMP7+ fetal-like tumor cell states and concomitant myofibroblast-like FAP+ CAFs to lymphovascular invasion sites and matched lymph node metastases, thereby recapitulating invasive programs at single-cell resolution and across sites. In all, we present single cell- and WTx-resolved spatial data that are among the first of their kind. These open up spatial-centric, out-of-the-box analytical avenues to resolve the molecular, cellular and architectural dynamics that attend tissue transformation during CRC onset, progression and dissemination.

cancer biology↗

Regulation of essential hepatocyte functions and identity by super-enhancers in health and disease

Physiologically, hepatocytes perform an estimated 500 essential liver functions to ensure systemic homeostasis. The mechanisms how hepatocytes maintain these numerous crucial functions in response to physiological and pathophysiological challenges are largely unknown. In this study, we found that vital liver function genes (e.g., HNF4A, ALB, coagulation factors, and SLC2A2) in hepatocytes possess super-enhancers. Interfering with the super-enhancers by dCas9-sgRNA remarkably decreases the expression of these genes. Quiescent liver progenitor cells (LPCs) do not have active super-enhancers in vital liver function genes. In acute liver failure (ALF) caused by massive hepatic necrosis, activated LPCs perform liver function and differentiate into hepatocytes to rescue patients lives. We show that activated LPCs gradually form super-enhancers in liver function genes (e.g., HNF4A, ALB, and coagulation factors) during proliferation and differentiation. These super-enhancers are regulated by FOXA2 through the recruitment of HNF4 a, p300 and Mediators in most liver function genes, such as ALB and coagulation factors. However, super-enhancers in some genes (e.g., SLC2A2) are FOXA2-indenpendent. Hepatic FOXA2 expression is closely associated with the clinical outcome of ALF. In a cohort of ALF patients, robust FOXA2 is observed only in the surviving patients. Collectively, super-enhancers represent a critical epigenetic regulatory mechanism that enables rapidly enhanced transcription of liver function genes in response to pathophysiological challenges. In urgent clinical syndrome such as ALF, LPCs rescue liver function by rapid formation of super-enhancers in vital genes.

molecular biology↗

An autonomous AI agent for universal behavior analysis

Behavior analysis across species represents a fundamental challenge in neuroscience, psychology, and ethology, typically requiring extensive expert knowledge and labor-intensive processes that limit research scalability and accessibility. We introduce BehaveAgent, an autonomous multimodal AI agent designed to automate behavior analysis from video input without retraining or manual intervention. Unlike conventional methods that require manual behavior annotation, video segmentation, task-specific model training, BehaveAgent leverages the reasoning capabilities of multimodal large language models (LLM) to generalize across novel behavioral domains without need for additional training. It integrates LLMs, vision-language models (VLMs), and large-scale visual grounding modules, orchestrated through a multimodal context memory and goal-directed attention mechanism, to enable robust zero-shot visual reasoning across species and experimental paradigms, including plants, insects, rodents, primates, and humans. Upon receiving a video input, BehaveAgent autonomously identifies the correct analysis strategy and performs end-to-end behavior analysis and interpretation without human supervision. Leveraging vision-language representations, it performs general-purpose tracking, pose estimation and segmentation. We demonstrate BehaveAgents universal applicability to autonomously (1) identify the behavioral paradigm and develop an action plan specialized for the identified paradigm, (2) identify relevant subjects and objects, (3) track those features, (4) identify behavioral sequences with explicit reasoning, (5) generate and execute code for targeted analysis and (6) generate comprehensive research reports that integrate behavioral findings with relevant scientific literature. Through interpretable agentic reasoning, BehaveAgent makes its internal decision-making process transparent, clarifying why particular features are tracked or behaviors inferred. By reducing the time and expertise required for behavior analysis, BehaveAgent introduces a scalable, generalizable, and explainable paradigm for advancing biological and behavioral research.

neuroscience↗

Expanding the chicken gut virome: Uncovering viral diversity, host interactions, and regional variations across the intestinal tract

Chicken gastrointestinal virome comprises a complex and diverse viral community with significant implications for host health and microbiome function. We analyzed 3,312 publicly available chicken gut metagenomic datasets to establish the chicken gastrointestinal virome collection (CGVD), which includes 39,380 non-redundant viral operational taxonomic units (vOTUs); notably, 84.90% (33,433/39,380) represent novel sequences absent from current databases. Over half of the CGVD vOTUs were classified as bacteriophages, predominantly from the order Caudovirales. The predicted hosts were mainly prokaryotes, particularly Bacillota and Bacteroidota, revealing a multifaceted landscape of virus-host interactions. Many vOTUs infected multiple bacterial phyla, indicating high adaptability and broad ecological impact. In addition, lifestyle prediction showed that 28.28% (11,137 /39,380) of the vOTUs in CGVD were identified as lytic phages. Functional annotation demonstrated that viral genes contribute to key metabolic processes, including nucleotide and amino acid metabolism, thereby facilitating viral replication and host adaptation. The detection of auxiliary metabolic genes and carbohydrate-active enzymes underscores the role of viruses in modulating the gut microbiome. Although antibiotic resistance genes and mobile genetic elements were present, their contribution to horizontal gene transfer appears limited. Additionally, marked regional differences in virome composition were observed between the small and large intestines, particularly in the abundance of families such as Siphoviridae and Myoviridae. CGVD not only highlights the key role of viruses in shaping the chicken gut microbiome and influencing microbial dynamics and metabolic pathways, but also provides new resources and insights for future research.

microbiology↗

TIR immune signaling is blocked by phosphorylation to maintain plant growth

Toll/interleukin-1 receptor (TIR) domain proteins are immune signaling components and function as NAD+-cleaving enzymes to activate defense responses. Activation of TIRs represses growth and drives cell death in plants and promotes axon degeneration in animals, but how plant TIRs are repressed remains unclear. Here, we show that TIR NADase activity requires a conserved serine residue spatially close to the catalytic glutamate. The plant Ca2+-dependent protein kinases (CPKs), the mammalian Ca2+/calmodulin-dependent protein kinase II delta (CAMK2D) and TANK binding kinase 1 (TBK1) phosphorylate TIR domains at this conserved serine, which blocks TIR NADase activities and functions and thus maintains growth in plants and suppresses SARM1 TIR signaling in animals, respectively. Our findings define a fundamental molecular mechanism by which phosphorylation at a conserved serine residue blocks TIR signaling to balance growth and defense trade-offs.

plant biology↗

In Situ Graphene-Seq: Spatial Transcriptomics and Chronic Electrophysiological Characterization of Tissue Microenvironments

Biological systems are composed of diverse, interconnected cell types, yet capturing both their functional dynamics and molecular identities at high spatiotemporal resolution remains challenging. While electrophysiological measurements provide real-time insights into cellular activities, they cannot fully describe the molecular architecture and states of the measured cells. Conversely, transcriptomics reveals cell gene expression patterns but does not capture functional states. Bridging these modalities is essential for a holistic understanding of the molecular mechanisms driving functional changes. In this study, we introduce in situ graphene-sequencing (graphene-seq), a unique platform that seamlessly integrates chronic electrophysiology with imaging-based, spatially resolved 3D transcriptomics, overcoming longstanding limitations of current multimodal approaches. This system leverages stretchable mesh nanoelectronics for long-term, single-cell-level interfacing and incorporates transparent graphene/PEDOT:PSS electrodes, enabling seamless integration of electrical recordings and optical imaging. By combining electrophysiology with high-throughput, imaging-based in situ sequencing, this platform allows comprehensive multimodal, spatially resolved analysis of cell microenvironment within spatially heterogeneous tissues. We validate in situ graphene-seq by charting multimodal profiles of human-induced pluripotent stem cell-derived cardiomyocyte and endothelial cell co-cultures, examining how spatial heterogeneity in cell composition influences both electrophysiological activity and gene expression. This scalable, integrated approach offers a powerful tool for studying the complex interplay between cellular function and molecular identity. It also provides insights into how tissue microenvironments shape cell behavior and molecular states, advancing applications in regenerative medicine, stem cell therapy, and disease modeling.

bioengineering↗

Integrated spatial morpho-transcriptomics predicts functional traits in pancreatic cancer

Analyses of patient-derived cell lines have greatly enhanced discovery of molecular biomarkers and therapeutic targets. However, characterization of cellular morphological properties is limited. We studied cell morphologies of human pancreatic adenocarcinoma (PDAC) cell lines and their associations with drug sensitivity, gene expression, and functional properties. By integrating live cell and spatial mRNA imaging, we identified KRAS inhibitor-induced morphological changes specific for drug-resistant cells that correlated with gene expression changes. We then categorized a large panel of patient-derived PDAC cell lines into morphological (e.g., polygonal, irregular, spheroid) and organizational (e.g., tightly aggregated, multilayered, dispersed) subtypes and found differences in gene expression, therapeutic targeting potential, and metastatic proclivity. In human PDAC tissues, we identified prognostic expression signatures associated with distinct cancer cell organization patterns. In summary, we highlight the potential of cell morphological information in rapid, cost-effective assays to aid precision oncology efforts leveraging patient-derived in vitro models and tissues.

cancer biology↗

Comprehensive profiling of N6-methyladnosine (m6A) readouts reveals novel m6A readers that regulate human embryonic stem cell differentiation

N6-methyladenosine (m6A) methylation has emerged as a prevalent RNA modification that extensively impacts various physiological and pathological processes via various post-transcriptional readout effects in mammals. High-throughput methylome profiling has outlined the landscape of m6A modification sites, but their downstream readouts require comprehensive investigation. To this end, we systematically assessed the effects of m6A on mRNA half-life, translation efficiency, and alternative splicing across five cell lines (A549, HEK293T, HUVEC, JURKAT, and human embryonic stem cells (hESCs)) using actinomycin D-disrupted temporal transcriptome sequencing, ribosome sequencing, and ultra-high-depth transcriptome sequencing, respectively. Our analysis, coupled with the integration of public and re-profiled m6A methylome data, revealed high cell type specificity in m6A readouts where m6A level alone is insufficient to predict m6A readouts. Machine learning models focused on the RNA binding protein (RBP) binding context of m6A sites demonstrated substantial predictive ability of m6A readouts while prioritizing putative m6A readers from their informative RBP features. Four novel m6A readers (DDX6, FUBP3, FXR2, and L1TD1) were identified and validated through m6A RNA pull-down assays and transcriptome-wide RBP binding site mapping. Notably, FUBP3, FXR2 and L1TD1 were found to regulate hESC differentiation without impairing self-renewal, underscoring their critical roles in stem cell biology. Together, this study bridges the gap in understanding m6A functional readouts and lays the groundwork for future research on m6A-mediated stem cell fate decisions.

genomics↗

Deciphering Ibogaines Matrix Pharmacology: Multiple Transporter Modulation at Serotonin Synapses

Ibogaine is the main psychoactive alkaloid produced by the iboga tree (Tabernanthe iboga) that has a unique therapeutic potential across multiple indications, including opioid dependence, substance use disorders, depression, anxiety, posttraumatic stress disorder (PTSD), and traumatic brain injury (TBI). We systematically examined the effects of ibogaine, its main metabolite noribogaine, and a series of iboga analogs at monoamine neurotransmitter transporters, some which have been linked to the oneiric and therapeutic effects of these substances. We report that ibogaine and noribogaine inhibit the transport function of the vesicular monoamine transporter 2 (VMAT2) with sub-micromolar potency in cell-based fluorimetry assays and at individual synaptic vesicle clusters in mouse brain as demonstrated via two-photon microscopy. The iboga compounds also inhibit the plasma membrane monoamine transporters (MATs), prominently including the serotonin transporter (SERT), and a novel iboga target, the organic cation transporter 2 (OCT2). SERT transport inhibition was demonstrated in serotonin axons and soma in the brain and in rat brain synaptosomes, where ibogaine and its analogs did not act as substrate-type serotonin releasers. Noribogaine showed dual inhibition of VMAT2 and SERT with comparable potency, providing an explanatory model for the known neurochemical effects of ibogaine in rodents. Together, the updated profile of the monoamine transporter modulation offers insight into the complexity of the iboga pharmacology, which we termed "matrix pharmacology". The matrix pharmacology concept is outlined and used to explain why ibogaine and noribogaine do not induce catalepsy, as demonstrated in our study, in contrast to other VMAT2 inhibitors. TOC Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/641351v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@a1cacaorg.highwire.dtl.DTLVardef@8be27org.highwire.dtl.DTLVardef@1fc320forg.highwire.dtl.DTLVardef@3a8837_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

HIV-Induced Sialoglycans on Infected Cells Promote Immune Evasion from Myeloid Cell-Mediated Killing

Sialic acid-containing glycans (sialoglycans) on pathological cells interact with Siglecs, glyco-immune checkpoint receptors expressed on myeloid cells such as monocytes and neutrophils. This interaction suppresses the cytotoxic functions of these immune cells. We show that HIV infection reprograms the glycosylation machinery of infected cells to increase the expression of specific sialoglycan ligands for Siglecs-3, -7, and -9. These ligands engage Siglecs on myeloid cells, impairing their ability to target HIV-infected cells. Selective disruption of these interactions using 10-1074-Sia, an HIV-specific antibody conjugated to sialidase--an enzyme that removes sialic acids--significantly enhances monocyte- and neutrophil-mediated killing of HIV-infected cells in autologous assays. Treatment with 10-1074-Sia in humanized mice infected with HIV reduces viral load and decreases inflammation. These findings reveal a novel immune evasion mechanism exploited by HIV to evade myeloid cell immune surveillance and highlight the potential of targeting sialoglycan-Siglec interactions to improve immune clearance of HIV-infected cells.

immunology↗

A synthetic chlorophagy receptor promotes plant fitness by mediating chloroplast microautophagy

Chloroplasts are major photosynthetic and protein-containing organelles in green plants and algae. Unwanted chloroplast proteins and entire chloroplasts are cleared through various degradation pathways including autophagy. Nevertheless, canonical chlorophagy receptors remain unidentified, and whether and to what extent chlorophagy can be enhanced to benefect the plants remain unknown. Here we designed and validated a synthetic chloroplast autophagy receptor using biochemical, genetical, and imaging approaches. This synthetic receptor, LIR-SNT-BFP, was constructed by fusing a fragment containing the LC3-interacting region (LIR) of the selective autophagy receptor NBR1 and the N-terminal amphipathic -helix of the chloroplast outer envelope protein SFR2. The fusion protein LIR-SNT-BFP coated the chloroplast and attracted ATG8a in planta. Upon induction, the synthetic receptor elicited vacuole-mediated microautophagy of entire chloroplasts independent of the ATG8 conjugation machinery proteins ATG5 or ATG7. Meanwhile, it induced chloroplast division; however the induced chlorophagy was independent of PDV2. Notably, moderate chlorophagy improves rosette growth, but excessive levels are detrimental. Furthermore, induced chlorophagy partially protects against herbicide-induced leaf chlorosis. This study demonstrates controlled chloroplast degradation using a synthetic chlorophagy receptor.

plant biology↗

Enrichment of halogenated organic compounds and their degrading microorganisms in the deepest ocean

The hadal trenches, the deepest regions of the ocean, serve as the final resting place for marine particles and as "tunnels" for material exchange between the ocean and Earths interior. Despite their extreme conditions, the trenches contain high content of organic carbon (OC) and active microbial carbon turnover, are hotspots for deep-sea OC degradation and unique microbial processes. However, little is known about the OC components and microbial metabolisms driving the OC degradation in the trenches. This study reveals unexpectedly high concentrations of halogenated organic compounds (HOCs) in the Mariana Trench sediments, with about 1 halogen per 58 carbon atoms in the OC pool. Systematic analysis of deep-sequenced metagenomes and metagenome-assembled-genomes from the global ocean shows significantly higher abundance of the genes for biodegradation of HOCs (dehalogenation) in trench microbes, with microorganisms capable of dehalogenation belonging to 16 phyla and 52 orders, 75% of which identified as HOCs degraders for the first time. Microcosms simulating trench conditions showed rapid degradation of typical HOCs and transcription of genes related with HOCs metabolisms, demonstrating the active HOCs degradation by the trench microorganisms. The findings suggest the HOCs metabolism as an important process in the OC remineralization of deep-sea trenches, advancing understanding of deep-sea carbon cycling and microbial survival strategies.

microbiology↗

Structural Basis for OAS2 Regulation and its Antiviral Function

Oligoadenylate synthetase (OAS) proteins are immune sensors for double-stranded RNA and critical for restricting viruses. OAS2 comprises two OAS domains, only one of which can synthesize 2-5-oligoadenylates for RNase L activation. Existing structures of OAS1 provide a model for enzyme activation, but do not explain how multiple OAS domains discriminate RNA length. Here, we discover that OAS2 exists in an autoinhibited state as a zinc-mediated dimer and present a mechanism for RNA length discrimination: the catalytically deficient domain acts as a molecular ruler that prevents autoreactivity to short RNAs. We demonstrate that dimerization and myristoylation localize OAS2 to Golgi membranes and that this is required for OAS2 activation and restriction of viruses that exploit the endomembrane system for replication, e.g. coronaviruses. Finally, our results highlight the non-redundant role of OAS proteins and emphasize the clinical relevance of OAS2 by identifying a patient with a loss-of-function mutation leading to autoimmune disease.

biochemistry↗

Building Foundation Models to Characterize Cellular Interactions via Geometric Self-Supervised Learning on Spatial Genomics

Cellular interactions form the fundamental/core circuits that drive development, physiology, and disease within tissues. Advances in spatial genomics (SG) and artificial intelligence (AI) offer unprecedented opportunities to computationally analyze and predict the behavior of cell intricate networks, and to identify interactions that drive disease states. However, challenges arise in both methodology and scalability: (i) how to computationally characterize complicated cellular interactions of multi-scale nature where chemical genes/circuits in individual cells process information and drive interactions among large numbers of diverse cell types, and (ii) how to scale up the pipeline to accommodate the increasing volumes of SG data that map transcriptome-scale gene expression and spatial proximity across millions of cells. In this paper, we introduce the Cellular Interaction Foundation Model (CI-FM), an AI foundation model functioning to analyze and simulate cellular interactions within living tissues. In the CI-FM pipeline, we explicitly capture and embed cellular interactions within microenvironments by leveraging the powerful and scalable geometric graph neural network model, and optimize the characterization of cellular interactions with a novel self-supervised learning objective - we train it to infer gene expressions of cells based upon their interacting microenvironment. As a result, we construct CI-FM with 100 million parameters by consuming SG data of 23 million cells. Our benchmarking experiments show CI-FM effectively infers gene expressions conditional on the microenvironmental contexts: we achieve a high correlation and a low mismatch error (MSE of 1.1% relative to the square median expression), with 79.4% of cells on average being annotated as the similar cell type based on their predicted and actual expressions. We demonstrate the downstream utility of CI-FM by: (i) applying CI-FM to embed tumor samples to capture cellular interactions within tumor microenvironments (ROC-AUC score of 0.76 on classifying sample conditions via linear probing on embeddings), and identifying shared signatures across samples; and (ii) using CI-FM to simulate changes in microenvironmental composition in response to T cell infiltration, which highlights how CI-FM can be leveraged to model cellular responses to tissue perturbations - an essential step toward constructing "AI virtual tissues". Our model is open source and publicly accessible at https://huggingface.co/ynyou/CIFM.

bioinformatics↗