Biology subjects

Li, Z.

Publications and source records attributed to Li, Z..

At least 523 records · Page 29Linked to original sources

bioRxiv2025

Decaying and expanding Erk gradients process memory of skeletal size during zebrafish fin regeneration

Regeneration of an amputated salamander limb or fish fin restores pre-injury size and structure, illustrating the phenomenon of positional memory. Although appreciated for centuries, the identity of position-dependent cues and how they control tissue growth are not resolved. Here, we quantify Erk signaling events in whole populations of osteoblasts during zebrafish fin regeneration. We find that osteoblast Erk activity is dependent on Fgf receptor signaling and organized into millimeter-long gradients that extend from the distal tip to the amputation site. Erk activity scales with the amount of tissue amputated, predicts the likelihood of osteoblast cycling, and predicts the size of regenerated skeletal structures. Mathematical modeling suggests gradients are established by the transient deposition of long-lived ligands that are transported by tissue growth. This concept is supported by the observed scaling of expression of the essential epidermal ligand fgf20a with extents of amputation. Our work provides evidence that localized, scaled expression of pro-regenerative ligands instructs long-range signaling and cycling to control skeletal size in regenerating appendages.

developmental biology↗

bioRxiv2025

Triple-effect correction for Cell Painting data with contrastive and domain-adversarial learning

Cell Painting (CP), as a high-throughput imaging technology, generates extensive cell-stained imaging data, providing unique morphological insights for biological research. However, CP data contains three types of technical effects, referred to as triple effects, including batch effects, gradient-influenced row and column effects (well position effects). The interaction of various technical effects can obscure true biological signals and complicate the characterization of CP data, making correction essential for reliable analysis. Here, we propose cpDistiller, a triple-effect correction method specially designed for CP data, which leverages a pre-trained segmentation model coupled with a semi-supervised Gaussian mixture variational autoencoder utilizing contrastive and domain-adversarial learning. Through extensive qualitative and quantitative experiments across various CP profiles, we demonstrate that cpDistiller effectively corrects triple effects, especially well position effects, a challenge that no current methods address, while preserving cellular heterogeneity. Moreover, cpDistiller effectively captures system-level phenotypic responses to genetic perturbations and reliably infers gene functions and interactions both when combined with scRNA-seq data and independently. cpDistiller also excels at identifying gene and compound targets, which is a critical step in drug discovery and broader biological research.

bioinformatics↗

bioRxiv2025

Mapping spatially-resolved transcriptomes in systemic sclerosis

Systemic sclerosis (SSc) is a prototypical fibrotic disease with high mortality and limited treatment options. Despite advances in single-cell RNA sequencing (scRNA-seq), the comprehensive understanding of cellular heterogeneity and cell-cell interaction within the fibrogenesis microenvironment remains limited. We generated spatially resolved transcriptome maps from healthy and SSc skin and built a scRNA-seq atlas to map the single-cell data to spatial space. This enabled us to identify a fibrotic niche, enriched with fibroblasts and macrophages, which is significantly expanded in SSc and correlated with clinical outcome. We revealed disease-specific cell states of fibroblasts and macrophages, and evaluated their spatial dependency on other cell types. We identified selective expression of ACKR3 in fibroblast progenitors that diminishes with SSc progression, which may serve to regulate CXCL12/CXCR4-mediated macrophage recruitment and fibrotic remodeling. Together, we provided an in-depth description at cellular and spatial levels of fine-tuned regulatory events occurring in SSc, offering spatiotemporal insights. One Sentence SummaryIntegrated spatial omics provide insight into the cellular and transcriptional landscape in spatially distinct microenvironments, which may drive fibrosis progression in SSc.

immunology↗

bioRxiv2025

Compromised 2-start zigzag chromatin folding in immature mouse retina cells driven by irregularly spaced nucleosomes with short DNA linkers.

The formation of condensed heterochromatin is critical for establishing cell-specific transcriptional programs. To reveal structural transitions underlying heterochromatin formation in maturing mouse rod photoreceptors, we apply cryo-EM tomography, AI-assisted deep denoising, and molecular modeling. We find that chromatin isolated from immature retina cells contains many closely apposed nucleosomes with extremely short or absent nucleosome linkers, which are inconsistent with the typical two-start zigzag chromatin folding. In mature retina cells, the fraction of short-linker nucleosomes is much lower, supporting stronger chromatin compaction. By Cryo-EM-assisted nucleosome interaction capture we observe that chromatin in immature retina is enriched with i{+/-}1 interactions while chromatin in mature retina contains predominantly i{+/-}2 interactions typical of the two-start zigzag. By mesoscale modeling and computational simulation, we clarify that the unusually short linkers typical of immature retina are sufficient to inhibit the two-start zigzag and chromatin compaction by the interference of very short linkers with linker DNA stems. We propose that this short linker composition renders nucleosome arrays more open in immature retina and that, as the linker DNA length increases in mature retina, chromatin fibers become globally condensed via tight zigzag folding. This mechanism may be broadly utilized to introduce higher chromatin folding entropy for epigenomic plasticity.

molecular biology↗

bioRxiv2025

Escherichia coli outer membrane vesicles encapsulating small molecule antibiotics improve drug function by facilitating transport

The development of novel antimicrobial agents that are effective against Gram-negative bacteria is hindered by the dual membrane cell wall structure of these bacteria. To reach their intracellular targets, most antibiotics must therefore pass through protein channels called porins; however, a common mechanism of acquired resistance is decreased expression of these proteins. Inspired by the ability of outer membrane vesicles (OMVs) to deliver cargo to the bacterial cytosol, we hypothesized that encapsulation of small molecule antibiotics within OMVs would improve the activity of the drugs by facilitating uptake. To test this, we investigated the ability of antibiotic- encapsulated OMVs to inhibit the growth of both Gram-negative and Gram-positive bacteria, including multidrug-resistant clinical isolates. We also demonstrated that this mechanism of delivery does not require porin expression. Together, our results demonstrate the potential of OMVs as novel antibiotic delivery vehicles to treat antibiotic-resistant bacterial infections.

bioengineering↗

bioRxiv2025

METTL3 Aggravates Intimal Hyperplasia by Facilitating the m6A-YTHDC1-dependent SGK1 Gene Transcription

BackgroundVascular smooth muscle cell (VSMC) migration and proliferation substantially contribute to neointimal hyperplasia related to in-stent restenosis. N6-methyladenosine (m6A) catalyzed by the methyltransferase-like 3 (METTL3)-involved methyltransferase complex is the most abundant RNA epigenetic modification in eukaryotes, but the role of m6A RNA methylation in VSMC migration and proliferation as well as neointima formation remains highly controversial. MethodsPrimary human and rat VSMCs were utilized for in vitro experiments. VSMC-specific METTL3 knockout mice (Mettl3flox/floxMyh11-CreERT2) were generated to explore wire injury in carotid arteries in vivo. Methylated RNA immunoprecipitation sequencing (MeRIP-Seq) was performed to screen for target genes by METTL3-catalyzed m6A RNA methylation. Methylation site mapping, MeRIP-quantitative PCR (MeRIP-qPCR), chromatin immunoprecipitation-qPCR (ChIP-qPCR) and reporter gene assays were applied to explore how METTL3 modulates its target gene expression. ResultsMETTL3 was consistently upregulated in the neointima from mice subjected to carotid wire injury and patients undergoing carotid endarterectomy. VSMC-specific METTL3 deficiency significantly attenuated neointima formation in carotid arteries following wire injury in mice. Accordingly, METTL3 ablation markedly repressed VSMC proliferation both in vitro and in vivo. Mechanistically, METTL3 directly catalyzed m6A methylation on serum/glucocorticoid regulated kinase 1 (SGK1) mRNA and subsequently facilitated its transcription, which relies on the established association between the SGK1 transcript and SGK1 promoter DNA by recruiting the m6A reader YTHDC1. Conversely, SGK1 overexpression abolished METTL3 deficiency-mediated suppression of VSMC proliferation and postinjury neointima formation. ConclusionsMETTL3-catalyzed m6A RNA methylation promoted VSMC proliferation and aggravated postinjury neointima formation by facilitating YTHDC1-dependent SGK1 gene transcription. Targeting the METTL3-YTHDC1-SGK1 axis to modulate VSMC proliferation may be a potential strategy for in-stent restenosis therapy.

molecular biology↗

bioRxiv2025

Looking for the optimal pathway to stimulate hippocampus in human participants using transcranial ultrasound stimulation (TUS): a simulation study

At present, very limited methods can directly modulate the neural activities in deep brain structures in human participants. Low-intensity transcranial ultrasound stimulation (TUS), as an emerging and advanced modality of non-invasive brain stimulation (NIBS), has great potential for focally stimulating the subcortical structures that are related to sleep, emotion and the functions of motor of cognition. Due to the focality, the integration of various methods, including magnetic resonance imaging and possible pathways, is important to perform TUS intervention for precise targeting and dosing. Based on structural MRI scans, we constructed a simulation model of low-intensity TUS, with a particular focus on the optimal pathways of targeting hippocampus in human participants. Finally, we outlooked the future perspectives of TUS in clinical applications in neurological and psychiatric fields.

neuroscience↗

bioRxiv2025

The microtubule-severing enzyme spastin regulates spindle dynamics to promote chromosome segregation in Trypanosoma brucei

Microtubule-severing enzymes play essential roles in regulating diverse cellular processes, including mitosis and cytokinesis, by modulating microtubule dynamics. In the early branching protozoan parasite Trypanosoma brucei, microtubule-severing enzymes are involved in cytokinesis and flagellum length control during different life cycle stages, but none of them have been found to regulate mitosis in any life cycle form. Here, we report the biochemical and functional characterization of the microtubule-severing enzyme spastin in the procyclic form of T. brucei. We demonstrate that spastin catalyzes microtubule severing in vitro and ectopic overexpression of spastin disrupts spindle microtubules in vivo in trypanosome cells, leading to defective chromosome segregation. Knockdown of spastin impairs spindle integrity and disrupts chromosome alignment in metaphase and chromosome segregation in anaphase. We further show that the function of spastin requires the catalytic AAA-ATPase domain, the microtubule-binding domain, and the microtubule interacting and trafficking domain, and that the association of spastin with spindle depends on the microtubule-binding domain. Together, these results uncover an essential role for spastin in chromosome segregation by regulating spindle dynamics in this unicellular eukaryote.

cell biology↗

bioRxiv2025

Ether Rhodamines with Enhanced Hydrophilicity, Fluorogenicity, and Brightness for Super-Resolution Imaging

Rhodamine dyes are widely used fluorophores in super-resolution fluorescence imaging due to their exceptional optical properties and "aggregation-disaggregation" induced fluorogenic activation. However, their excessive lipophilicity often reduces brightness in aqueous environments and causes off-target staining, limiting their effectiveness in high-resolution imaging. To address these challenges, we introduce an ether-decorated N-terminal modification strategy for rhodamine and silicon-rhodamine (Si-rhodamine), replacing conventional N-alkyl groups. The ether chains enhance water solubility, decrease aggregate size, and improve fluorogenicity across a wide concentration range. Their flexible, hydrophilic structure forms a protective shield around the xanthene core, minimizing dye-water interactions and reducing fluorescence quenching. Additionally, the inductive effect of the ether chains decreases the electron-donating strength of the amino groups, suppressing quenching caused by twisted intramolecular charge transfer (TICT). These modifications collectively increase the quantum yields of ER and ESiR in water from 0.35 and 0.19 (for tetraethyl-substituted analogs) to 0.70 and 0.41, respectively. Probes derived from ER and ESiR exhibit outstanding fluorogenicity, enhanced signal-to-noise ratios, and improved resolution in complex aqueous environments, demonstrating superior performance in advanced super-resolution imaging techniques such as structured illumination microscopy (SIM), stimulated emission depletion (STED) microscopy, and single-molecule localization microscopy (SMLM). This work introduces an innovative strategy for fluorophore design, offering significant advancements for super-resolution imaging applications.

biochemistry↗

bioRxiv2024

Delineating the Spatial Patterns of Cell Type-Specific Stemness Using a Statistical Deconvolution Model

SummaryCellular stemness is a cells ability to self-renew and differentiate into specialized cell types. In spatial transcriptomics (ST), researchers can use gene activity to quantify stemness and the associated spatial locations, allowing for the investigation of cellular profiles in their natural context. However, many ST platforms provide data with low resolution, and each data spot (i.e., spatial location) contains multiple cell types, which hinders the investigation of cell type-specific (CTS) behaviors, such as cell stemness, at different spatial locations. We developed a bivariate kernel-weighted regression method with constrained optimization to estimate CTS stemness as a function of spatial location and developed accompanying visualization tools. Through simulation studies and an application to real breast cancer ST data from the 10x Genomics Visium platform, we demonstrated that our method can accurately estimate CTS stemness and help shed light on the interplay among cell type, tissue structure, and stemness. Availability and implementationAn R Shiny app implementing the proposed method is available at GitHub (https://github.com/ericli0480/stemness-deconvolution/). Supplementary informationAvailable in a separate PDF file

bioinformatics↗

bioRxiv2024

CRISPR-Cas supervises diverse anti-phage defense systems

A variety of bacterial anti-phage systems have recently been discovered1-3, but how these systems synergize to defend against diverse phages remains poorly understood. Here, we report that the adaptive immune system CRISPR-Cas supervises the expression of diverse immune systems by exploiting the regulatory CRISPR RNA-like RNAs (crlRNAs). The crlRNAs target and inhibit the promoters of various immune systems, including the newly characterized Nezha and Gabija, as well as eight previously unrecognized systems that feature distinct defensive domains. Notably, CRISPR regulation balances the expression level of these systems to ensure effective anti-phage activity while avoiding their autoimmunity risks. In return, the supervised immune systems trigger abortive infections when CRISPR-Cas is inhibited by viral anti-CRISPR proteins, thereby offering an anti-anti-CRISPR protection at the population level. Moreover, these systems complement CRISPR immunity with a differing anti-phage profile. These findings highlight the pivotal role of CRISPR-Cas in orchestrating a diverse range of immune systems and showcase the delicate synergy among the multilayered defense strategies in prokaryotes.

microbiology↗

bioRxiv2024

Dorsolateral prefrontal cortex TMS evokes responses in the subgenual anterior cingulate cortex: Evidence from human intracranial EEG

Transcranial magnetic stimulation combined with intracranial local field potential recordings in humans (TMS-iEEG) represents a new method for investigating electrophysiologic effects of TMS with spatiotemporal precision. We applied TMS-iEEG to the dorsolateral prefrontal cortex (dlPFC) in two subjects and demonstrate evoked activity in the subgenual anterior cingulate cortex (sgACC). This study provides direct electrophysiologic evidence that dlPFC TMS, as targeted for depression treatment, can modulate brain activity in the sgACC.

neuroscience↗

bioRxiv2024

Dysregulation of Nitrosylation Dynamics Promotes Nitrosative Stress and Contributes to Cardiometabolic Heart Failure with Preserved Ejection Fraction

BackgroundRecent reports suggest increased myocardial iNOS expression leads to excessive protein s-nitrosylation, contributing to the pathophysiology of HFpEF. However, the relationship between NO bioavailability, dynamic regulation of protein s-nitrosylation by trans- and de-nitrosylases, and HFpEF pathophysiology has not been elucidated. Here, we provide novel insights into the delicate interplay between NO bioavailability and protein s-nitrosylation in HFpEF. MethodsPlasma nitrite, nitrosothiols (RsNO), and 3-nitrotyrosine (3-NT) were measured in HFpEF patients and in controls. Studies in WKY or ZSF1 obese rats were performed to evaluate HFpEF severity, NO signaling, and total nitroso-species (Rx(s)NO) levels. snRNA sequencing was performed to identify key genes involved in NO signaling and s-nitrosylation regulation. ResultsIn HFpEF patients, circulating RsNO and 3-NT were significantly elevated while nitrite, a biomarker for NO bioavailability, remained unchanged. In ZSF1 obese rats, NO bioavailability was significantly reduced while Rx(s)NO levels exhibited an age-dependent increase as HFpEF progressed. snRNA seq highlighted significant upregulation of a trans-nitrosylase, hemoglobin-beta subunit (HBb), which was corroborated in human HFpEF hearts1. Subsequent experiments confirmed HBb upregulation and revealed significant reductions in enzyme activity of two major de-nitrosylases, Trx2 and GSNOR in ZSF1 obese hearts. Further, elevated RxNO levels, increased HBb expression, and reduced activity of Trx2 and GSNOR were identified in the kidney and liver of the ZSF1 obese rats. ConclusionsOur data reveal circulating markers of nitrosative stress (RsNO and 3-NT) are significantly elevated in HFpEF patients. Data from the ZSF1 obese rat model mirror the results from HFpEF patients and reveal that pathological accumulation of RxNO/nitrosative stress in HFpEF may be in part, due to the upregulation of the trans-nitrosylase, HBb, and impaired activity of the de-nitrosylases, Trx2 and GSNOR. Our data suggest that dysregulated protein nitrosylation dynamics in the heart, liver, and kidney contribute to the pathogenesis of cardiometabolic HFpEF. Translational PerspectiveOur findings describe for the first time that circulating RsNO and 3-NT are significantly upregulated in HFpEF patients suggesting systemic nitrosative stress in HFpEF, and demonstrate a profound disconnect between insufficient physiological NO signaling and pathological nitrosative stress in HFpEF, which is in stark contrast to HFrEF in which both NO bioavailability and protein s-nitrosylation are attenuated. Further, this study provides novel mechanistic insights into a critical molecular feature of HFpEF in humans and animal models: nitrosative stress arises predominantly from imbalance of trans-nitrosylases and de-nitrosylases, thereby leading to impaired NO bioavailability concomitant with increased protein s-nitrosylation. Importantly, these perturbations extend beyond the heart to the kidney and liver, suggesting HFpEF is characterized by a systemic derangement in trans- and de-nitrosylase activity and providing a unifying molecular lesion for the systemic presentation of HFpEF pathophysiology. These findings have direct clinical implications for the modulation of NO levels in the HFpEF patient, and indicate that restoring the balance between trans- and denitrosylases may be novel therapeutic targets to ameliorate disease symptoms in HFpEF patients.

physiology↗

bioRxiv2024

Attention field as a cognitive-behavioral marker for demarcating internet- but not smoking-addiction from reward

Attentional effect (AE), attention profile (AP), and attention field (AF) have been studied extensively, however, their roles in addiction and demarcating addiction from rewards remain unclear. Using a modified Posner-paradigm with two types of pre-rewarded-cues (addiction-related and addiction-unrelated) and four groups (smoking-dependents, internet-dependents, and respective HCs), we found that both AEs and APs were independent of either cue type or group, while AFs were interactively modulated by the two. AFs of addiction-related cues were narrower than those of addiction-unrelated cues for internet-dependents, but not for either smoking-dependents or HCs; AFs of internet-dependents (not smoking-dependents) were narrower than those of HCs for addiction-related cues, but not for addiction-unrelated cues. Significantly, internet-dependents reduced AFs can be simulated by the divisive-normalization computation, both of which closely tracked their addictive severities. Our findings identify a cognitive-behavioral marker for demarcating internet-addiction from rewarding, arguing against the notion that internet-addiction, or, more generally, non-substance-addiction, is ill-posed.

neuroscience↗

bioRxiv2024

EpiAgent: Foundation model for single-cell epigenomic data

Large-scale foundation models have recently opened new avenues for artificial general intelligence. Such a research paradigm has recently shown considerable promise in the analysis of single-cell sequencing data, while to date, efforts have centered on transcriptome. In contrast to gene expression, chromatin accessibility provides more decisive insights into cell states, shaping the chromatin regulatory landscapes that control transcription in distinct cell types. Yet, challenges also persist due to the abundance of features, high data sparsity, and the quasi-binary nature of these data. Here, we introduce EpiAgent, the first foundation model for single-cell epigenomic data, pretrained on a large-scale Human-scATAC-Corpus comprising approximately 5 million cells and 35 billion tokens. EpiAgent encodes chromatin accessibility patterns of cells as concise "cell sentences," and employs bidirectional attention to capture cellular heterogeneity behind regulatory networks. With comprehensive benchmarks, we demonstrate that EpiAgent excels in typical downstream tasks, including unsupervised feature extraction, supervised cell annotation, and data imputation. By incorporating external embeddings, EpiAgent facilitates the prediction of cellular responses to both out-of-sample stimulated and unseen genetic perturbations, as well as reference data integration and query data mapping. By simulating the knockout of key cis-regulatory elements, EpiAgent enables in-silico treatment for cancer analysis. We further extended zero-shot capabilities of EpiAgent, allowing direct cell type annotation on newly sequenced datasets without additional training.

bioinformatics↗

bioRxiv2024

Transcriptomic disruption and functional hypoactivity in DYT-SGCE MGE-patterned inhibitory neurons

Myoclonus Dystonia is a dystonic movement disorder caused by SGCE mutations, the underlying pathophysiology for which remains unclear. Here, we evaluated the impact of SGCE mutations on medial ganglionic eminence (MGE)-derived GABAergic neurons using patient-derived induced pluripotent and gene edited embryonic stem cell lines, each compared to their isogenic wild-type control. No significant differences were observed in markers of neuronal development however, single-cell RNA sequencing demonstrated transcriptomic dysregulation in genes related to axonal organization, synaptic signalling, and action potential generation in the SGCE -mutation harbouring neurons. Functional assays demonstrated reduced neurite outgrowth, lower calcium responses to GABA, and decreased neuronal excitability and network activity in the SGCE -mutant neurons. These findings contrast with the hyperexcitable phenotype previously observed in SGCE -mutant cortical glutamatergic neurons. Collectively, this supports loss of neuronal inhibitory activity, and disruption to the neuronal excitatory/inhibitory balance in motor circuits, in contributing to the overall hyperkinetic clinical phenotype in Myoclonus Dystonia.

neuroscience↗

bioRxiv2024

Unexpected Activities of CYP152 Peroxygenases towards Non-carboxylic Substrates Reveal Novel Substrate Recognition Mechanism and Catalytic Versatility

Exploring and exploiting the catalytic promiscuity of enzymes is a central topic and captivating challenge in enzymology. CYP152 peroxygenases are attractive biocatalysts for diverse reactions under mild conditions using H2O2 as cofactor. However, their substrate scope is limited by a carboxyl group required for acid-base catalysis, following the well-accepted principle that heme-dependent H2O2-utilizing enzymes employ a carboxyl group within their active sites to facilitate H2O2 activation. Herein, we reveal for the first time that several CYP152 family members can directly degrade various aromatic pollutants without any carboxyl group, exhibiting novel aromatic hydroxylation and dehalogenation activities. Through crystal structure analysis, isotope tracing experiments, and QM/MM calculations, we elucidate that the phenolic hydroxyl group activated by electron-withdrawing substituent(s) functionally replaces the carboxyl group, forming hydrogen bonds with the conserved arginine leading to Compound I formation. The oxygen atom of the newly formed hydroxyl group originates from water, bypassing the conventional oxygen rebound step. These findings provide first insights into the mechanisms of P450 peroxygenases towards non-carboxylic substrates, expanding our knowledge of biological C-H activation and C-halogen bond cleavage beyond canonical P450 reactions. This discovery holds immense potential for harnessing these enzymes in innovative strategies for industrial biocatalysis and environmental remediation.

biochemistry↗

bioRxiv2024

Deaminase-mediated chromatin accessibility profiling with single-allele resolution

Binding of transcription factors (TFs) at gene regulatory elements controls cellular epigenetic state and gene expression. Current genome-wide chromatin profiling approaches have inherently limited resolution, complicating assessment of TF occupancy and co-occupancy, especially at individual alleles. In this work, we introduce Accessible Chromatin by Cytosine Editing Site Sequencing with ATAC-seq (ACCESS-ATAC), which harnesses a double-stranded DNA cytosine deaminase (Ddd) enzyme to stencil TF binding locations within accessible chromatin regions. We optimize bulk and single-cell ACCESS-ATAC protocols and develop computational methods to show that the increased resolution compared with ATAC-seq improves the accuracy of TF binding site prediction. We use ACCESS-ATAC to perform genome-wide allelic occupancy and co-occupancy imputation for 64 TFs each in HepG2 and K562, revealing that the propensity of a majority of TFs to co-occupy nearby motifs oscillates with a period approximating the helical turn of DNA. Altogether, ACCESS-ATAC expands the resolution and capabilities of bulk and single-cell epigenomic profiling.

genomics↗