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Biology subjects

Lin, N.

Publications and source records attributed to Lin, N..

At least 19 recordsLinked to original sources

Synthesizing Mechanistic Hypotheses from Single-Cell Omics via Discretized Feature Attribution and Empirical Language Model Grounding

Single-cell multimodal omics offer unprecedented resolution of cellular networks, yet translating continuous computational attributions into structured, testable biological mechanisms remains a persistent bottleneck. To address this limitation, we introduce an analytical pipeline employing decision trees to discretize continuous neural network attributions into explicit regulatory thresholds. These boundaries then structurally constrain large language models, enabling them to integrate established literature with empirical data to synthesize context-specific hypotheses. Applying this continuous-to-discrete framework across sparse datasets yielded novel biological mechanisms. Specifically, the framework articulated a cytoskeletal gating hierarchy governing EGF-stimulated pathways, identified transcriptomic drivers of input resistance in cortical interneurons, and delineated translational logic predicting Ki-67 abundance within spatial transcriptomics. Retrospective benchmarking validated the frameworks capacity to autonomously reconstruct published regulatory logic. Supported by a locally deployable open-weight language model and a code-free interface, this approach establishes an auditable methodology to extract robust experimental hypotheses from high-dimensional single-cell data.

systems biology↗

The transcription factor Vca0578 (DsvR) mediated expression of ZapC is required to promote cell division during lytic transglycosylase insufficiency in Vibrio cholerae

The bacterial peptidoglycan (PG) cell wall, a polymer made of amino-acid-bearing glycan strands, maintains cell shape, provides structural integrity, and protects against osmotic lysis. PG maintenance is an active process that requires regulated PG breakdown to make space for insertion of new PG strands. PG breakdown is accomplished by autolysins, i.e. endogenous enzymes with cell wall cleavage activity. The lytic transglycosylases (LTGs), a class of autolysins, for example, cleave glycan strands during PG remodelling. LTGs are broadly conserved and are highly redundant in bacteria, but their physiological role is poorly-defined. In this study, we interrogated physiological consequences of LTG insufficiency in Vibrio cholerae using TnSeq to gain insights about roles of these enzymes. We identify an uncharacterized transcription factor, Vca0578, which alleviates defects associated with the {Delta}6LTG mutant. We demonstrate that Vca0578 positively regulates the expression of zapC, a typically non-essential Z-ring associated protein. In the absence of zapC, cell division was impaired during perturbations of cell envelope homeostasis caused by absence of LTGs, or by exposure to antibiotics inhibiting cell elongation; either condition rendered zapC conditionally essential. This essentiality could be overcome by increasing FtsZ levels. Lastly, we found that ZapC also contributes to both width and length homeostasis during normal growth. This work thus uncovers a novel transcriptional circuit that contributes to effective cell division in{Delta} 6LTG cells, and suggests an essential role for ZapC in cell division under stress conditions that cause perturbation of cell width homeostasis. AUTHOR SUMMARYBacteria must maintain their outer shell (the cell envelope) in the face of changes in the environment. For this, they use elaborate systems that remodel the cell envelope. How some of these systems work is not well understood. In this study, we describe a new gene circuit that is required to keep cells dividing when the cell envelope is compromised. We found that Vca0578, a putative transcription factor, controls expression of the zapC gene. The protein ZapC then helps bacteria grow and divide when the cell envelope is under stress, for example, in the presence of certain antibiotics. Thus, we have discovered a regulatory circuit that promotes bacterial growth and antibiotic resistance under stress.

microbiology↗

CAPZ, but not canonical autophagy, regulates the endosomal-exosomal trafficking of plasma membrane PD-L1

Programmed death-ligand 1 (PD-L1) undergoes continuous endocytosis and intracellular trafficking that regulate its degradation, recycling, and exosomal release. Although PD-L1 internalization is known to depend on RAB5-mediated endocytosis, whether canonical autophagy contributes to its subsequent endosomal trafficking remains unclear. Here we show that the endosomal and exosomal trafficking of cell surface PD-L1 occurs independently of the canonical autophagy machinery. Genetic disruption of core autophagy components, including LC3B, ATG4B, ATG5, and ATG7, did not impair trafficking of internalized PD-L1 to early endosomes, multivesicular bodies, late endosomes, or extracellular vesicles. Pharmacologic inhibition of autophagosome-lysosome fusion enhanced accumulation of PD-L1 within RAB5-and CD63-positive compartments, but this effect persisted in cells lacking LC3B, ATG5, or ATG7, indicating that PD-L1 trafficking through the endosomal-exosomal pathway does not require canonical autophagy. Instead, we identify the actin-capping protein CAPZ as a key regulator of an endosomal maturation checkpoint that controls PD-L1 sorting. Loss of CAPZ impaired progression of PD-L1 from early to late endosomal compartments, reduced PD-L1 incorporation into multivesicular bodies and extracellular vesicles, and redirected PD-L1 toward RAB11-dependent recycling, resulting in increased plasma membrane PD-L1 abundance. These findings establish that PD-L1 membrane fate is determined by CAPZ-dependent endosomal maturation rather than canonical autophagy and identify endosomal trafficking machinery as a critical regulator of immune checkpoint distribution.

cell biology↗

Programmable artificial RNA condensates in mammalian cells

Artificial biomolecular condensates have emerged as powerful tools to control cellular behaviors. Here we introduce a method to build artificial condensates within living mammalian cells through the design of modular RNA motifs formed by a single, short strand of RNA. These condensates emerge spontaneously, creating RNA-rich compartments that remain separated from their surrounding environment. The RNA sequences include stem-loop domains that fold as the RNA is transcribed, and then condense in the nucleus and cytoplasm through loop-loop interactions. These sequences can be optimized and diversified, enabling the generation of distinct, non-mixing condensate populations and the programmable control of their subcellular localization. The RNA motifs can also be modified to recruit small molecules, proteins, and RNA molecules in a sequence-specific manner to the RNA-rich phase. By introducing additional RNAs that link two distinct types of condensates, we can create droplets with multiple subcompartments, whose organization can be controlled by tuning the stoichiometry of different RNA sequences. These artificial condensates provide a versatile platform for studying and manipulating molecular functions inside living cells.

synthetic biology↗

Multimodal AI for Single cfDNA Profiling and Cancer Screening

Cell-free DNA (cfDNA) serves as a non-invasive biomarker for cancer detection, but conventional methods face challenges due to the ultra-low abundance of tumor-derived cfDNA (ctDNA) among normal cfDNA. Though nucleosome-bound cfDNA harbors rich epigenomic features that could enable ctDNA identification by single-molecule multi-omics cross-validation, this remains unexplored due to methodological limits. Here, we developed a cfDNA sequencing approach integrating methylation, fragmentomics, and histone modifications at the single-molecule level; together with gene semantics and epigenomic annotations, these modalities were vectorized and fused to represent each cfDNA molecule. We trained a Transformer-based model (cfAI) to profile and evaluate ctDNA likelihood at molecule, gene, and sample levels. cfAI achieved [~]10-fold enrichment of cancer-derived signals over noise and reached 72.6% sensitivity at 93.1% specificity for multi-cancer detection. Our study establishes an innovative framework that overcomes the inherent signal-to-noise limitations of conventional assays and reveals biological features at molecular resolution for cancer detection.

bioinformatics↗

scPhoenix: A Contrastive Learning-based Framework with Aux-Core Feature Disentanglement Enhances Sparse Cellular Multi-omics Translation

Recent advances in single-cell multi-omics co-assays and spatiotemporal sequencing technologies have provided unprecedented opportunities for systematically characterizing cellular heterogeneity. However, severe sparsity and pronounced spatial heterogeneity--hallmark features of complex diseases and tumor microenvironment--remain major obstacles in deciphering cellular multi-omics data. Here, we present scPhoenix, a contrastive learning-based framework for single-cell cross-modality translation. scPhoenix adopts a two-stage Aux-Core strategy to disentangle modality-specific feature extraction from cross-modality feature interaction. Across diverse datasets, it preserves cellular heterogeneity during translation and demonstrates significant advantages for data with high sparsity. In addition, the framework integrates a contrastive learning framework with five effective data augmentation methods tailored to single-cell data. Moreover, scPhoenixs design supports extensions to unpaired data training and spatial multi-omics translation, enabling robust performance in scenarios with high spatial heterogeneity. scPhoenix is freely available at https://github.com/liwz-lab/scPhoenix.

bioinformatics↗

Measurement Quality Metrics to Improve Absolute Microbial Cell Counting

Total and viable microbial cell counts are increasingly important for applications including live biotherapeutic products, food safety, and probiotics. In microbiology, cells are quantified using methods such as colony forming unit (CFU), flow cytometry, and polymerase chain reaction (PCR), but different methods measure different aspects of the cells (measurands), and results may not be directly comparable across methods. In the absence of a ground-truth reference material for cell count, one cannot quantify the accuracy of any cell counting method, which limits method performance assessments and comparisons. Herein, a modified analysis of cell counting methods based on the ISO 20391-2:2019 standard was developed and demonstrated for microbial cell samples diluted over a log-scale range of concentrations. Escherichia coli samples ranging in concentration from approximately 5 x 105 cells/mL to 2 x 107 cells/mL were quantified using CFU, Coulter principle, fluorescence flow cytometry, and impedance flow cytometry. Quality metrics modified from the ISO standard were calculated for each method and shown to be repeatable across replicate experiments. The quality metrics illustrate large differences in proportionality and variability across methods, with total cell counts in good agreement and viable cell count having more variability. As the ISO standard is meant to guide fit-for-purpose method selection, interpretation of the results and quality metrics can drive method choice and optimization. The framework introduced here will help researchers select fit-for-purpose counting methods for quantification of microbial total and viable cells across a range of applications.

microbiology↗

Feature similarity: a sensitive method to capture the functional interaction of brain regions and networks to support flexible behavior

The brain is a dynamic system where complex behaviours emerge from interactions across distributed regions. Accurately linking brain function to cognition requires tools that are sensitive to these dynamics. We introduce a novel technique, Feature Similarity (FS), which represents a conceptual advancement in measuring brain region interactions by integrating multiple features across various measures, moving beyond traditional methods that focus on a single measure. Our results show that FS can capture functional brain organisation: regions within the same functional network have greater FS compared to those in different networks, and FS also identifies the principal gradient that spans from unimodal to transmodal cortices. FS demonstrated greater sensitivity to task modulation than traditional functional connectivity (FC) and 46 out of 49 statistical measures of pairwise interactions (SPIs). Specifically, FS reveals interaction patterns missed by FC and most SPIs, such as a double dissociation in Dorsal Attention Network: greater interaction with Visual network during working memory tasks and greater interaction with default mode network during long-term memory tasks. These findings position FS as a powerful tool for capturing task-specific brain network dynamics and advancing our understanding of cognitive flexibility. Using FS to reanalyse existing fMRI data could resolve inconsistencies, lead to novel insights, and prompt revisions of existing theories or the development of new theoretical frameworks.

neuroscience↗

Three Open Questions in Polygenic Score Portability

A major obstacle hindering the broad adoption of polygenic scores (PGS) is their lack of "portability" to people that differ--in genetic ancestry or other characteristics--from the GWAS samples in which genetic effects were estimated. Here, we use the UK Biobank to measure the change in PGS prediction accuracy as a continuous function of individuals genome-wide genetic dissimilarity to the GWAS sample ("genetic distance"). Our results highlight three gaps in our understanding of PGS portability. First, prediction accuracy is extremely noisy at the individual level and not well predicted by genetic distance. In fact, variance in prediction accuracy is explained comparably well by socioeconomic measures. Second, trends of portability vary across traits. For several immunity-related traits, prediction accuracy drops near zero quickly even at intermediate levels of genetic distance. This quick drop may reflect GWAS associations being more ancestry-specific in immunity-related traits than in other traits. Third, we show that even qualitative trends of portability can de pend on the measure of prediction accuracy used. For instance, for type 2 diabetes, precision stays roughly constant, while recall surprisingly increases, with genetic distance. Together, our results show that portability cannot be understood through global ancestry groupings alone. There are other, understudied factors influencing portability, such as the specifics of the evolution of the trait and its genetic architecture, social context, and the construction of the polygenic score. Addressing these gaps can aid in the development and application of PGS and inform more equitable genomic research.

genetics↗

Functional and multi-omic aging rejuvenation with GLP-1R agonism

Identifying readily implementable methods that can effectively counteract aging is urgently needed for tackling age-related degenerative disorders. Here, we conducted functional assessments and deep molecular phenotyping in the aging mouse to demonstrate that glucagon-like peptide-1 receptor agonist (GLP-1RA) treatment attenuates body-wide age-related changes. Apart from improvements in physical and cognitive performance, the age-counteracting effects are prominently evident at multiple omic levels. These span the transcriptomes and DNA methylomes of various tissues, organs and circulating white blood cells, as well as the plasma metabolome. Importantly, the beneficial effects are specific to aged mice, not young adults, and are achieved with a low dosage of GLP-1RA which has a negligible impact on food consumption and body weight. The molecular rejuvenation effects exhibit organ-specific characteristics, which are generally heavily dependent on hypothalamic GLP-1R. We benchmarked the GLP-1RA age-counteracting effects against those of mTOR inhibition, a well-established anti-aging intervention, observing a strong resemblance across the two strategies. Our findings have broad implications for understanding the mechanistic basis of the clinically observed pleiotropic effects of GLP-1RAs, the design of intervention trials for age-related diseases, and the development of anti-aging-based therapeutics.

systems biology↗

An Open-Source Membrane Stretcher for Simultaneous Mechanical and Structural Characterizations of Soft Materials and Biological Tissues

The ability to simultaneously measure material mechanics and structure is central for understanding their nonlinear relationship that underlies the mechanical properties of materials, such as hysteresis, strain-stiffening and -softening, and plasticity. This experimental capability is also critical in biomechanics and mechanobiology research, as it enables direct characterizations of the intricate interplay between cellular responses and tissue mechanics. Stretching devices developed over the past few decades, however, do not often allow simultaneous measurements of the structural and mechanical responses of the sample. In this work, we introduce an open-source stretching system that can apply uniaxial strain at a submicron resolution, report the tensile force response of the sample, and be mounted on an inverted microscope for real-time imaging. Our system consists of a pair of stepper-based linear motors that stretch the sample symmetrically, a force transducer that records the sample tensile force, and an optically clear sample holder that allows for high-magnification microscopy. Using polymer samples and cellular specimens, we characterized the motion control accuracy, force measurement robustness, and microscopy compatibility of our stretching system. We envision that this uniaxial stretching system will be a valuable tool for characterizing soft and living materials.

bioengineering↗

Regulation of Chromatin Modifications through Coordination of Nucleus Size and Epithelial Cell Morphology Heterogeneity

Cell morphology heterogeneity is pervasive in epithelial collectives, yet the underlying mechanisms driving such heterogeneity and its consequential biological ramifications remain elusive. Here, we observed a consistent correlation between the epithelial cell morphology and nucleus morphology during crowding, revealing a persistent log-normal probability distribution characterizing both cell and nucleus areas across diverse epithelial model systems. We further showed that this morphological diversity arises from asymmetric partitioning during cell division. Moreover, we provide insights into the impact of nucleus morphology on chromatin modifications. We demonstrated that constraining nucleus leads to downregulation of the euchromatic mark H3K9ac and upregulation of the heterochromatic mark H3K27me3. Furthermore, we showed that nucleus size regulates H3K27me3 levels through histone demethylase UTX. These findings highlight the significance of cell morphology heterogeneity as a driver of chromatin state diversity, shaping functional variability within epithelial tissues.

biophysics↗

Image-based Strain Analysis Reveals Intracellular Strain Controlled by Nucleo-Cytoskeletal Coupling

Cells can sense and transduce mechanical forces, such as stretching, and convert these signals into diverse cell biological events. While much effort has been devoted to identifying the downstream biochemical and cellular responses, it is equally crucial to pinpoint the mechanical stimuli within a cell driving these responses. Specifically, much remains unknown about how intracellular strains are distributed and controlled during mechanical deformation. In this study, we developed a microscopy-based intracellular strain measurement technique. Utilizing the intrapopulation mechanical heterogeneity of epithelial monolayers, we observed an inverse relationship between cytoplasmic and nuclear strains. We found that this anti-correlation is abolished by the inhibition of Linker of Nucleoskeleton and Cytoskeleton (LINC) complex, suggesting that nucleo-cytoskeletal coupling controls intracellular strain distribution. We discovered a direct connection between cytoplasmic strain and stretch-induced nucleus size changes, implying that molecular events arising from cytoplasmic deformation may drive nuclear remodeling during stretching. By conducting multivariable analyses, we found that the intracellular strain can be inferred from cell morphology. Overall, our experimental platform and findings provide a foundation for unraveling the relationship between mechanotransduction pathways and upstream intracellular strain. SIGNIFICANCEMechanical stimuli exert influence on epithelial cells, not only orchestrating embryogenesis and regeneration, but also regulating cancer progression and inflammatory conditions. Despite efforts to identify mechanically activated molecular events, understanding how deformation is distributed within cells to induce subcellular responses remains limited. Specifically, the control of subcellular strain distribution during mechanical stretch is unclear. In this study, we developed a microscopy-based method to measure subcellular strain and observed an inverse relationship between cytoplasmic and nuclear strains. Disrupting nucleo-cytoplasmic coupling abolished this relationship, suggesting its role in controlling strain distribution. Additionally, we found that cytoplasmic strain correlates with nucleus size changes during stretching, indicating cytoplasmic events influence nucleus remodeling.

biophysics↗

A cell-type-specific nitric oxide-cGMP pathway regulates proprioceptor morphology

Neurons show remarkable morphological diversity facilitated by transcriptional regulation during development and fitting with their connectivity and function. Second messenger pathways mediated by cyclic 3,5 adenosine or guanosine monophosphate (cAMP or cGMP) may serve to integrate extrinsic signals and regulate branching and growth of neurites. We investigated the regulation of cGMP signaling in neuronal morphogenesis in Drosophila somatosensory neurons and found cell type-specificity in expression of the enzyme soluble guanylate cyclase (sGC) in different sensory neuron classes. sGC is responsible for the production of cGMP in response to the diffusible free radical messenger nitric oxide (NO) such that different levels of sGC impart cell type-specific sensitivity to NO. Supporting a role for the NO-cGMP pathway in neuronal morphogenesis, we find that knockout of sGC or nitric oxide synthase (NOS) impacts the morphology of multidendritic proprioceptors. The homeodomain transcription factor Cut shows different levels of expression in different somatosensory neuron types and we find that Cut regulates the level of cGMP signaling via repression of sGC expression. Thus, transcription factor levels contribute to cell type diversification by regulating levels of a signaling pathway to mediate somatosensory neuron morphogenesis.

neuroscience↗

Microwell-based flow culture reduces hypoxia-induced phenotype and restores drug response in prostate cancer spheroids

3D cancer spheroids represent a highly promising model for study of cancer progression and therapeutic development. Wide-scale adoption of cancer spheroids, however, remains a challenge due to the lack of control over hypoxic gradients that may cloud the assessment of cell morphology and drug response. Here, we present a Microwell Flow Device (MFD) that generates in-well laminar flow around 3D tissues via repetitive tissue sedimentation. Using a prostate cancer cell line, we demonstrate the spheroids in the MFD exhibit improved cell growth, reduced necrotic core formation, enhanced structural integrity, and down-regulated expression of cell stress genes. The flow-cultured spheroids also exhibit an improved sensitivity to chemotherapy with greater transcriptional response. These results demonstrate how fluidic stimuli reveal the cellular phenotype previously masked by severe necrosis. Our platform advances 3D cellular models and enables study into hypoxia modulation, cancer metabolism, and drug screening within pathophysiological conditions.

bioengineering↗

Benzo(a)pyrene regulates chaperone-mediated autophagy via heat shock protein 90

The Benzo(a)pyrene (Bap) exposure induced oxidative damage, DNA damage and autophagy. To explore the molecular mechanism of BaP-induced autophagy. In these studies, we first found that heat shock protein 90 (HSP90), heat shock cognate 70 (HSC70) and lysosomal-associated membrane protein type 2 receptor (Lamp-2a) expressions of C57BL mice lung tissue and A549 cells exposed to BaP were significant increase, as well as Bap induced DNA double-strand breaks (DSBs) and activated DNA damage responses, as evidenced by comet assay and {gamma}-H2AX foci analysis in A549 cells. Our results demonstrated BaP induced CMA and caused DNA damage. Next, we knocked down HSP90 expression by the HSP90 Inhibitor, NVP-AUY 922, exposed or HSP90 shRNA lentivirus transduction in A549 cells. HSC70 and Lamp-2a expressions of these cells exposed to BaP were not significant increase, which showed that BaP inducted CMA was mediated by HSP90. Further, HSP90 shRNA prevented BaP induced of Bap which suggested BaP regulated CMA and caused DNA damage by HSP90. Our results elucidated a new mechanism of BaP regulated CMA through HSP90.

biochemistry↗

A novel PLS1 c.981+1G>A variant causes autosomal-dominant hereditary hearing loss in a family via up-regulation of the PI3K-Akt signaling pathway

BackgroundThe fimbrin protein family contains a variety of proteins, of which Plastin1 (PLS1) is an important member. The latest researches show that variations in the coding region of PLS1 gene is related to the development of deafness. However, it remains unknown about the molecular mechanism of deafness caused by PLS1 gene variants. Methodswhole exome sequencing was performed on the affected family members and healthy ones to identify the pathogenic variants, followed by sanger sequencing. Minigene assay was conducted to investigate the impact of the variant on PLS1 mRNA splicing. The pathogenicity of the variant was further investigated in zebrafish. RNA-sequencing (RNA-seq) was done for analyzing the dysregulated downstream signaling pathways caused by knockdown of PLS1 expression. ResultsWe identified a novel variant PLS1 c.981+1G>A in a large Chinese family with hearing loss and demonstrated that the variant is responsible for the occurrence of hearing loss by inducing Exon8 skipping or deletion of Exon8 (47bp). The variant caused abnormal inner ear phenotypes, characterized by decreased mean otolith distance, anterior otolith diameter, posterior otolith diameter, and cochlear diameter, swimming speed and distance in zebrafish. Furthermore, silencing PLS1 expression significantly upregulated genes in the PI3K-Akt signaling pathway, including Col6a3, Spp1, Itgb3 and Hgf. ConclusionsPLS1 c.981+1G>A is a novel pathogenic variant for hearing loss by inducing Exon8 skipping or deletion of Exon8 (47bp). Up-regulation of the PI3K-Akt signaling pathway plays an important role in the pathogenesis of PLS-1 gene.

genetics↗

Phylogenomic analyses using genomes and transcriptomes do not resolve relationships among major clades in Phrymaceae

Premise of the studyPhylogenomic datasets using genomes and transcriptomes provide rich opportunities beyond resolving bifurcating phylogenetic relationships. Monkeyflower (Phrymaceae) is a model system for evolutionary ecology. However, it lacks a well-supported phylogeny for a stable taxonomy and for macroevolutionary comparisons. MethodsWe sampled 24 genomes and transcriptomes in Phrymaceae and closely related families, including eight newly sequenced transcriptomes. We reconstructed the phylogeny using IQ-TREE and ASTRAL, evaluated gene tree discordance using PhyParts, Quartet Sampling, and cloudogram, and carried out phylogenetic network analyses using PhyloNet and HyDe. We searched for whole genome duplication (WGD) events using chromosome numbers, synonymous distance, and gene duplication events. Key resultsMost gene trees support the monophyly of Phrymaceae and each of its tribes. Most gene trees also support the tribe Mimuleae being sister to Phrymeae + Diplaceae + Leucocarpeae, with extensive gene tree discordance among the latter three. Despite the discordance, polyphyly of Mimulus s.l. is strongly supported, and no particular reticulation event among the Phrymaceae tribes is well supported. Reticulation likely occurred among Erythranthe bicolor and close relatives. No ancient WGD event was detected in Phrymaceae. Instead, small-scale duplications are among potential drivers of macroevolutionary diversification of Phrymaceae. ConclusionsWe show that analysis of reticulate evolution is sensitive to taxon sampling and methods used. We also demonstrate that genome-scale data do not always fully "resolve" phylogenetic relationships. They present rich opportunities to investigate reticulate evolution, and gene and genome evolution involved in lineage diversification and adaptation.

evolutionary biology↗