Biology subjects

Yin, S.

Publications and source records attributed to Yin, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Aquaporin-9 and aquaporin-10 but not aquaporin-3 confer susceptibility to dimethylarsinic acid genotoxicity in human cells

Human metabolism converts inorganic arsenic to the pentavalent methylated species MMA(V) and DMA(V), the forms most people excrete, and the forms long read as the end of a detoxification pathway. Whether a transporter sets how much of these metabolites reaches the genome has not been tested in a mammalian cell. We expressed human AQP3, AQP7, AQP9 or AQP10 in HEK293T and MRC5-SV40 cells and measured gamma-H2AX by flow cytometry across dose series of As(V), MMA(V) and DMA(V), pairing every aquaporin with a GFP-Tubulin control and an untransfected mock acquired in the same replicate. As(V) was inactive in HEK293T cells and only weakly active in MRC5-SV40 cells to 20 micromolar, and both methylated species damaged DNA only in the millimolar range, DMA(V) being the more potent of the two in both cell lines. Against that weak baseline, AQP9 and AQP10 raised DMA(V)-induced gamma-H2AX in HEK293T cells by roughly 17 percentage points over the matched control, more than doubling the damage the same exposure produced in control cells, whereas AQP3 and AQP7 changed it not at all. AQP9 alone remained active with MMA(V). The ranking held in MRC5-SV40 fibroblasts at one-sixth the size, and within single wells the damage rose with the amount of AQP9 a cell carried while the control was flat. Aquaglyceroporins therefore discriminate among arsenic species, and AQP9 and AQP10 turn a weakly genotoxic metabolite into a substantially more genotoxic one.

pharmacology and toxicology↗

bioRxiv2026

Aquaporin-3 amplifies arsenite genotoxicity as a dose-dependent gene-by-environment interaction in human cells

Chronic exposure to inorganic arsenic affects more than 200 million people, and disease outcome varies widely among individuals with comparable intake. Explanations have centered on arsenic metabolism, which acts on arsenite that is already inside the cell. Uptake sits upstream of metabolism and sets how much arsenite reaches the genome, yet whether it acts as a gene-by-environment modifier of genotoxicity has been asserted far more often than it has been measured. We expressed human aquaporin-3 (AQP3), its point mutants and the paralogues AQP7, AQP9 and AQP10 in three human cell lines, and measured DNA damage as {gamma}H2AX by flow cytometry against a damage threshold re-derived from mock-transfected cells in every experiment. In lung fibroblasts, AQP3 raised the {gamma}H2AX-high fraction 2.36-fold at 5 M arsenite. Because a gene-by-environment interaction widens the genotype gap with dose while an independent genotoxin would not, the combination exceeds what the two factors would produce if they simply added by 6.36 percentage points, which is an interaction. The response required the AQP3 sequence, was suppressed by N-acetylcysteine in proportion to arsenite dose, was absent in RKO cells, and was shared with AQP9 and AQP10, which created an arsenite dose-response in a cell line that had none of its own. Low-input RNA sequencing of 135 ten-cell pools located the effect inside the cell: at an identical 1 M applied dose and within a single batch, AQP3 raised HMOX1 (induced when trivalent arsenic modifies KEAP1 thiols, and so a report of intracellular rather than applied exposure) 3.3-fold, a shift equivalent to 40% of the 1-to-10 M interval on the measured dose-response, while AQP3 without arsenite was indistinguishable from untreated. Duplex sequencing detected no consistent change in somatic mutation frequency from arsenite alone at any dose to 10 M, in an assay that resolved a 26-fold response to N-ethyl-N-nitrosourea; the arsenite-induced mutation frequency at the EGFR locus nonetheless differed 1.61-fold by AQP3 genotype. The interaction is therefore not unique to AQP3, and aquaglyceroporin complement belongs alongside metabolism among the host factors that set arsenic susceptibility.

cell biology↗

bioRxiv2026

MINFLUX-nanoscopy of hNAIP/NLRC4 inflammasome activation in single human macrophages

The biochemical and structural basis of NAIP/NLRC4 inflammasome activation is well understood. Far less well known are the spatiotemporal processes within cells that play a role in the activation of the NAIP/NLRC4 inflammasome. We used super-resolution imaging technology, including MINFLUX nanoscopy, to investigate the human hNAIP/hNLRC4 inflammasome in primary human macrophages following the phagocytosis of a specific Yersinia enterocolitica strain. hNAIP, which senses components of the bacterial type III secretion system (T3SS) and activates NLRC4, was recruited to bacteria-containing phagosomes after they were disrupted by the T3SS. Disruption of a single phagosome within a macrophage was sufficient to cause the accumulation of NLRC4 and NLRP3 (a sensor of another inflammasome), as well as the adapter protein ASC, in a dense condensate known as a speck. This subsequently led to plasma membrane permeation and pyroptosis. It appeared that, with increasing infection time, clusters containing NLRC4 and NLRP3/NLRC4 gradually acquired ASC for speck formation. MINFLUX-nanoscopy was able to visualise hNAIP at disrupted phagosomes with nanometre resolution, and also revealed the number and organisation of NLRC4 inflammasome discs within a speck, as well as their hNAIP content, for the first time. Surprisingly, the number of NLRC4 inflammasome discs varied considerably, ranging from 35 to 249 per speck. Also, only a small fraction of these seemed to contain hNAIP. Our results significantly improve our understanding of the process by which the hNAIP/NLRC4 inflammasome is activated in macrophages that have ingested bacteria containing a T3SS.

cell biology↗

bioRxiv2026

Parallel Arg/N-degron recognition systems regulate coenzyme A biosynthesis

Coenzyme A (CoA) is an essential metabolic cofactor whose biosynthesis is controlled by pantothenate kinases (PANKs), the rate-limiting enzymes in CoA synthesis. Although CoA production is extensively regulated, whether PANK abundance is controlled by selective protein degradation remains unknown. Here, we identify PANK1{beta} and PANK3 as substrates of the Arg/N-degron pathway. Two mechanistically distinct E3 ligase systems, UBR4-KCMF1 and MKLN1-CTLH, independently converge on a common N-terminal MK Arg/N-degron to promote PANK degradation and restrict CoA biosynthesis. UBR4-KCMF1 recognizes the MK Arg/N-degron through KCMF1 ZZ domain, whereas CTLH complex employs the B30.2-domain proteins RanBP9 and RanBP10 as previously unrecognized Arg/N-degron recognins. Structural, biochemical, and cellular analyses demonstrate that RanBP9 and RanBP10 recognize both Met-X and canonical Arg/N-degrons through their B30.2 domains, using a mechanism distinct from canonical UBR proteins. Together, these findings establish a new branch of the mammalian Arg/N-degron pathway and reveal ubiquitin-dependent control of PANK abundance in CoA homeostasis.

molecular biology↗

bioRxiv2026

MISSTE: a multiscale integrative spatial simulator for understanding the mechanisms underlying tissue ecosystems

Multiscale tissue ecosystems are governed by coupled intracellular decision-making, cell-cell interactions, and spatially structured microenvironmental signals, yet these scales are often studied separately. Here we present MISSTE, a modular framework that integrates Boolean intracellular state logic, agent-based modeling, and partial differential equation fields within a unified spatial simulation architecture. As a proof of concept, we applied MISSTE to CAR-T therapy in a solid tumor microenvironment. The model recapitulated emergent features of CAR-T behavior, including limited tumor penetration, stromal suppression, localized cytokine remodeling, hypoxia-associated constraint, and progressive functional exhaustion. Comparison of baseline and optimized conditions showed that coordinated enhancement of interaction range, migration, and cytotoxic function improved immune persistence and partial tumor control. Systematic parameter scans further identified effective immune-tumor contact as a stronger determinant of outcome than killing strength alone, highlighting spatial access as the dominant bottleneck. Guided by these results, we designed sequential intervention strategies and found that time-ordered enhancement of infiltration, killing, and late functional protection outperformed a static optimized regime. Together, these results establish MISSTE as a generalizable multiscale methodology for dissecting tissue ecosystems and for generating mechanistically grounded strategies for engineered cellular therapy design.

bioinformatics↗

bioRxiv2026

De novo Folding Mechanisms of Lasso Peptides

Lasso peptides adopt a distinctive [1]rotaxane conformation, yet the principles governing the folding of this kinetically trapped structure have remained elusive. Here, we integrated extensive molecular dynamics simulations and deep learning to elucidate the de novo folding mechanism of 20 lasso peptides lacking secondary post-translational modifications. We constructed Multi-Ensemble Markov Models for each lasso peptide and uncovered a universal uphill folding landscape with spontaneous folding probabilities consistently below 0.8%. Loop stability strongly correlated with folding propensity, and targeted experiments further validated that enhancing loop {beta}-hairpin formation promotes folding of microcin J25, the well-studied lasso peptide extensively characterized as an in vitro model. Additionally, the substantial entropy cost opposed lasso peptide folding. Simulations mimicking enzymatic spatial confinement reduced this penalty and stabilize folding. Leveraging Variational AutoEncoder-based pathway clustering, we resolved distinct pathway channels and representative folding pathways. Together, these findings establish representative folding models and fundamental thermodynamic and kinetic principles for rational engineering of lasso peptides.

biophysics↗

bioRxiv2026

UFMylation of Pyruvate Dehydrogenase Regulates Mitochondrial Metabolism

The ubiquitin-fold modifier 1 (UFM1) post-translational modification (PTM), or UFMylation, regulates protein homeostasis and is essential for human development. Yet the roles of the de-UFMylase, UFM1-specific peptidase 2 (UFSP2), which removes UFM1 from UFMylated proteins, remain poorly characterized. Here, we demonstrate that UFMylation and UFSP2 regulate mitochondrial metabolism. Quantitative proteomics in UFSP2-deficient cells revealed the accumulation of many proteins previously unknown to be impacted by UFMylation. These included components of the mitochondrial ribosome, electron transport chain (ETC), and pyruvate dehydrogenase (PDH) complex. Functional analyses demonstrated that excessive UFMylation in UFSP2-deficient cells increases mitochondrial respiration, glucose oxidation in the tricarboxylic acid (TCA) cycle, and PDH enzymatic activity. We identified dihydrolipoamide S-acetyltransferase (DLAT), the E2 component of PDH, as a direct UFMylation substrate, with lysine 118 (K118) as the primary conjugation site. Mutating K118 to arginine (K118R) abolished DLAT UFMylation and reduced pyruvate oxidation, identifying this modification as an activator of PDH. These findings reveal a UFMylation-based regulatory mechanism that controls mitochondrial function by inducing utilization of pyruvate as a TCA cycle fuel.

biochemistry↗

bioRxiv2026

HIRA-mediated H3.3 deposition preserves hepatocyte cell identity during liver aging

Age-associated functional decline is partly driven by progressive chromatin degeneration. Maintenance of chromatin integrity preserves cell identity and promotes healthy aging, but through different mechanisms in proliferating and non-proliferating cells. However, specific mechanisms of chromatin maintenance and their compensatory capacity in proliferating and non-proliferating cells are undefined. The histone chaperone HIRA deposits the histone variant H3.3 in a DNA replication-independent manner, leading to its accumulation in aging, non-proliferating cells. Here, we show that hepatocyte-specific loss of HIRA causes loss of cell identity, metabolic dysfunction, and accelerated fibrotic pathology with age. Transcriptomic and epigenomic analyses indicate that HIRA-H3.3 preserves chromatin integrity and sustains transcription of highly expressed genes, including cell identity genes. Partial hepatectomy, associated with induced proliferation, restores identity of HIRA knockout livers with compensatory deposition of canonical histones H3.1/2. Together, these results demonstrate that HIRA-mediated H3.3 deposition is essential for safeguarding cell identity and tissue function during aging of non-proliferating cells, but this function can be rescued by tissue regeneration and associated cell proliferation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=124 SRC="FIGDIR/small/710643v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@a2a26aorg.highwire.dtl.DTLVardef@154e5aeorg.highwire.dtl.DTLVardef@b315a7org.highwire.dtl.DTLVardef@152bca4_HPS_FORMAT_FIGEXP M_FIG C_FIG

genomics↗

bioRxiv2026

AAV-Mediated Dual-Gene Therapy Restores Metabolic Function in Mice with Propionic Acidemi

Background and AimsPropionic acidemia (PA) is a rare autosomal recessive disorder caused by mutations in PCCA or PCCB, which encode the two subunits of propionyl-CoA carboxylase (PCC). PCC deficiency causes toxic metabolite accumulation and multi-organ damage. Current management, including dietary restriction, pharmacological support, and liver transplantation, does not restore enzymatic activity. We developed a dual-gene adeno-associated virus (AAV) therapy that delivers both PCC subunits to treat both PA subtypes. MethodsWe generated a clinically relevant PCCA-R73W knock-in mouse model and administered AAV8 vectors encoding native human PCCA and PCCB under the control of a liver-specific thyroxine-binding globulin promoter (AAV8-TBG-hPCCA-P2A-hPCCB). Metabolite levels and organ safety were longitudinally assessed. ResultsDual-gene therapy produced dose-dependent reductions in plasma C3/C2 ratio, 3-hydroxypropionic acid, 2-methylcitric acid, and propionylglycine, and significantly outperformed single-gene (PCCA-only) therapy. Neonatal facial-vein injection achieved metabolic correction comparable to or better than adult treatment. The longitudinal follow-up revealed sustained efficacy over a 16-week period, with no signs of hepatotoxicity or adverse effects. ConclusionsSingle-dose, dual-gene AAV therapy achieves sustained metabolic correction and demonstrates long-term safety in a clinically relevant PA model, supporting its translational potential for both type I and type II propionic acidemia.

genetics↗

bioRxiv2026

Individualized network topography in pre-adolescent children and adults using naturalistic precision fMRI

Group-averaged network definitions, commonly used in developmental functional connectivity research, limit our understanding of how network topography may change with age and can lead to inaccurate estimates of age effects on intra- and inter-network functional connectivity. Here, we collected a precision fMRI dataset from 24 parent-child pairs (children 6 to 8 years, 13 females; adults 33 to 47 years, 12 females) during passive video viewing and derived individual template-matched functional network maps from 60 minutes of motion-censored data per participant. Overall, large-scale network architecture was broadly shared between children and adults, with no age-effects observed for network-level surface area, few age differences in network boundaries and generally lower assignment confidence in children. Considering inter-individual similarity in network topography, association networks showed stronger within-family similarity and no overall effect of age on similarity of networks between pairs of individuals. We further asked how individualized network definitions might impact estimates of age effects on dense functional connectivity. While all approaches pointed to greater within-network functional connectivity in adults, we found that individualized approaches had larger age effects and lower sensitivity to head motion. Together, our results suggest that, relative to adults, pre-adolescent children show reduced network assignment confidence and weaker within-network connectivity, but limited differences in network borders and size, and underscore the value of individualized mapping for increasing sensitivity to age effects.

neuroscience↗

bioRxiv2025

Aging-induced hepatocyte CD44 drives IL6/STAT3 signaling and associates with impaired neighboring T cell function.

Liver cancer incidences increase dramatically beyond 55 years of age, suggesting that age-associated changes contribute critically to tumor initiation. However, the mechanisms linking liver aging and cancer initiation are not well defined. This study investigates the role of CD44, a marker of liver tumor-initiating cells (TIC), in age-associated liver pathophysiology. Aged livers showed accumulation of CD44-expressing hepatocytes exhibiting enrichment of immune modulatory genes and activation of the immunosuppressive IL6/JAK/STAT3 pathway. Indeed, in adoptive transfer assays, antigen-exposed CD8+ T cells mounted a lower IFN-{gamma} response in aged livers than in young livers, indicating an immunosuppressive aged milieu. Concordantly, spatial analyses showed that the proximal neighbourhoods of Cd44-expressing hepatocytes are enriched in T cells exhibiting reduced cytokine and chemokine gene expression. Finally, hepatocyte-specific knock out of Cd44 mitigated the IL6/JAK/STAT3 gene signature in aged livers. Overall, these findings suggest that CD44 expression in aged hepatocytes promotes activation of the immunosuppressive IL6/JAK/STAT3 pathway and this is associated with impaired T cell effector function.

cell biology↗

bioRxiv2025

Towards CRISPR-based editing of the mitochondrial genome in yeast

Mitochondria, which evolved from symbiotic bacteria, possess their own genomes (mtDNA) and support independent transcription and translation within the organelle. Given the essential role of mtDNA in energy production, metabolism, as well as cellular homeostasis, and the high density of confirmed pathogenic mutations that map to mtDNA, there is a pressing need for versatile methods to study and manipulate this genome. Although CRISPR technology has revolutionized the editing of nuclear genomes, it has not been successfully extended to mtDNA, primarily due to the challenge of delivering single guide RNAs (sgRNAs) across both outer and inner mitochondrial membranes. Here we develop a survival-based reporter in Saccharomyces cerevisiae to screen for potential RNA import motifs. We identify a 40-nucleotide aptamer (IM83) that facilitates sgRNA entry into the mitochondrial matrix, enabling CRISPR editing by a mitochondrially-localized adenine base editor. We show that mitochondrial import of IM83 is ATP-dependent and enhanced by the tRNA synthetase Msk1. Further investigations identify barriers to efficient CRISPR editing of mtDNA, including loss of membrane potential associated with mitochondrial targeting of the base editor. These insights lay the groundwork for future improvements in CRISPR-based editing of mtDNA in eukaryotes.

genetics↗

bioRxiv2025

Aging alters tumor cell - T cell crosstalk to promote breast cancer progression

Age is a dominant risk factor for all major breast cancer subtypes. However, the mechanisms by which aging influences tumor development remain unclear. Using a novel mouse model whereby breast cancer is induced in situ in young and old wild-type mice via intraductal delivery of a lentivirus encoding the HER2/neu oncogene, we found that old mice exhibited a higher oncogene-induced tumor burden than young mice. Old tumor cells showed reduced expression of interferon-related genes, particularly the T cell-recruiting chemokines Cxcl9 and Cxcl10, linked to their altered chromatin accessibility. CXCL9/10 expression also declined with age in human HER2+ tumors. Correspondingly, old tumors exhibited fewer T cells within tumor lesions. Targeted interventions showed that decreased expression of Cxcl9/10 is responsible for reduced T cell infiltration and weakened anti-tumor immunity. These results show how aged tumor cells are impaired in their recruitment of immune cells, leading to a defective anti-tumor immune response.

cancer biology↗

bioRxiv2025

CFMF: A Clustering-Free Cell Marker Finder for Single-Cell Transcriptomic Data

BackgroundAccurate identification of marker genes is essential in single-cell RNA sequencing (scRNA-seq) analysis. However, conventional clustering-based annotation is constrained by resolution parameter selection and predefined marker gene databases. MethodsWe developed Clustering-Free Cell Marker Finder (CFMF), a novel computational framework that enables the discovery of marker genes without clustering. CFMF was validated using multiple scRNA-seq datasets and systematically benchmarked against widely used gene selection methods. ResultsWe first validated CFMF using the PBMC3K dataset and found that it not only recovered canonical markers, but also uncovered novel marker genes. When validating with glioblastoma datasets, CFMF successfully recapitulated established subtype signatures. Using scRNA-seq data of human normal lung, we demonstrated its superior sensitivity in rare cell detection even at very low prevalence. We applied CFMF to perform integrative analysis on colorectal cancer scRNA-seq data and defined seven transcriptionally distinct subclones, which includes an LGR5+ population that is strongly associated with metastasis. ConclusionCFMF represents a versatile and robust strategy for marker gene discovery, rare cell detection, and integrative dissection of tumor heterogeneity, thereby advancing single-cell research and facilitating the identification of previously unrecognized cell types.

bioinformatics↗

bioRxiv2025

STED-FCS in subdiffraction limit volumes reveals altered diffusion in live cell applications

Fluorescence correlation spectroscopy (FCS) is a widely established light microscopy technique for investigating physiological parameters such as diffusion states, particle numbers, and viscosity in biological samples. Combining FCS with stimulated emission depletion (STED-FCS) has enabled the investigation of molecular diffusion to sub diffraction-limited volumes. However, the full potential of STED-FCS for biomedical applications remains underexplored. Here, we present proof-of-principle studies with novel implementations of STED-FCS for investigating biological processes in living samples. Specifically, we demonstrate the impact of STED-FCS analyses in three distinct biomedical assays. Firstly, we prove that STED-FCS is capable of observing dynamic changes in autophagy-related protein microtubule-associated protein 1 light chain 3b (LC3b) along neuronal axons. Secondly, we show that STED-FCS can resolve alterations in the carbohydrate chain lengths of glycoproteins in melanoma cells. Finally, we demonstrate that STED-FCS can measure the reduced mobility of lipids within the plasma membrane of neuronal cells treated with the Alzheimers disease-associated, aggregation-prone toxic peptide amyloid-beta 1-42 (A{beta}42). We believe that this study will inspire researchers to utilize STED-FCS to address critical questions in their bio-imaging studies, particularly regarding the super-resolution assessment of dynamic processes in living cells.

biophysics↗

bioRxiv2025

Feasibility of a parent-delivered attention and working memory intervention for early school-aged children born preterm

Preterm birth is a common neurodevelopmental condition that can have lasting impacts on cognition, including attention and working memory. Interventions that strengthen these skills in early childhood could support school readiness. Dino Island is a tablet-based intervention that combines process-specific practice of attention and working memory skills with a compensatory component that teaches metacognitive skills to scaffold learning. In this pilot study, we evaluated the feasibility of parent-delivered Dino Island in young children born preterm (N=10), alongside a control group who played educational games (N=12). Both groups were instructed to play 2-3 times per week for approximately 20 minutes over a 12-week period. Attention and working memory on untrained tasks were assessed before and after completing the intervention. Parents provided fidelity data through tracking sheets and participated in exit interviews to offer feedback and identify barriers and facilitators. We found that the Dino Island program was successfully delivered by parents with high fidelity. Attrition was higher in the Dino Island group, likely reflecting the challenges of delivering cognitive remediation in home settings. Comparison of attention and working memory scores on untrained tasks pre- and post-showed practice effects but no specific benefit of Dino Island. However, parent reports suggested behavioral improvements specific to the Dino Island group, noting far-transfer effects where children applied metacognitive strategies in other contexts. Overall, this work shows feasibility and tolerability of Dino Island in young children born preterm. Future research should examine its potential impact on school readiness and longer-term academic outcomes in this population.

neuroscience↗

bioRxiv2025

Integrating Mutation and Stop Signals for Improved RNA Structure Analysis and Insight Discovery

BackgroundUnderstanding RNA structures is essential for exploring its diverse cellular roles. Chemical modification-based RNA structure probing remains a key approach to revealing RNA structures in complex in vivo conditions. Practically, chemical modifications generate both mutation and stop signals during reverse transcription within a single experiment. However, traditional analysis pipelines often rely on only one of the two signals without fully leveraging both. ResultsTo address this, we developed a machine learning-based approach, STONE, that integrates both signals from a single experiment. STONE improved RNA structure analysis across multiple independent validation regions, notably 28S rRNA, viral RNA and regulatory RNAs. In genome-wide datasets, especially single-cell data, STONE significantly increased nucleotide coverage per transcript and improved gene detection reliability. In genome-wide datasets, especially single-cell data, STONE substantially enhanced structural information coverage at both transcript and nucleotide levels. This maximized signal utilization, yielding RNA structures in single-cell data comparable to those from bulk datasets. Furthermore, STONE-derived structural scores allow direct identification of RNA-binding protein binding sites directly from a single probing experiment, with results on RNAs such as U1 snRNA, RNase P RNA, and XIST lncRNA closely matching established techniques like CLIP-seq and RNP-MaP. ConclusionsBy integrating mutation and stop signals from one single experiment, STONE advances RNA structure analysis accuracy, extends nucleotide coverage, and facilitates complex RNA-protein interaction studies, broadening the methods applications in RNA-based research.

bioinformatics↗

bioRxiv2025

Theta and gamma transcranial alternating current stimulation modulate Mandarin consonant and lexical tone perception

A theta/gamma oscillatory neural mechanism has been postulated to explain the auditory sampling of hierarchical syllable-phoneme structure with corresponding speech rates or linguistic hierarchies (theta for syllable and gamma for phoneme). Yet, whether such a mechanism is generalizable to Mandarin Chinese, a language that both has suprasegmental phonemes in the form of lexical tones and contains more monosyllabic words, which may lead to higher reliance on either phonemic-level or syllabic-level perceptual representations, is unclear. In this study, we applied transcranial electric stimulation with either theta or gamma alternating currents (tACS) to bilateral auditory cortices in healthy Mandarin-speaking participants during a consonant or tone identification task in quiet or noisy environments. Results showed that theta tACS impaired consonant identification in quiet, specifically, and generally prolonged reaction times across tasks and environments. Gamma tACS, however, only delayed tone identification in quiet. Besides, both theta and gamma tACS modulated perceptual decision-making parameters, leading to increased boundary thresholds (cautiousness of decision) and altered response biases in the perceptual decision of both consonants and tones, as evidenced by the hierarchical drift-diffusion model (HDDM). These findings indicate that theta oscillations causally support the perception of Mandarin syllables, with consonants and lexical tones presumably embedded in syllable-level representations, regardless of task difficulty. Gamma activity, however, is presumably engaged in supporting fast-changing and fine-grained acoustic features in a modulatory manner. Significance StatementHow the brain samples speech features for perception is a key question in language neuroscience. Previous research has shown that theta and gamma brain activity support the perception of suprasegmental syllables and segmental phonemes, corresponding to their length or linguistic hierarchy. However, for Mandarin, the existence of suprasegmental phonemes (lexical tones) and the large number of monosyllabic words can either lead to higher reliance on gamma oscillations for phoneme perception, or higher dependence on theta oscillations for holistic syllable integration. With the combination of brain stimulation to selectively modulate theta/gamma auditory activity and phoneme identification tasks, this study reveals a causal role of theta activity in supporting holistic syllable-based Mandarin phoneme perception, yet gamma engagement is modulatory.

neuroscience↗