Biology subjects

Cheng, X.

Publications and source records attributed to Cheng, X..

At least 73 records · Page 4Linked to original sources

bioRxiv2025

Epigenetic regulation of cilia stability and kidney by the chromatin remodeling SWI/SNF complexes

Cilia are important subcellular organelles, whose assembly are regulated by master regulator transcription factors including Foxj1 and Rfx proteins. However, whether and how cilia are regulated at epigenetic level remains unknown. We addressed this question by knocking down or knocking out of chromatin remodeling genes. Notably, depletion of multiple components of the switch/sucrose non-fermentable (SWI/SNF) complexes led to ciliopathy-like phenotypes in zebrafish embryos. Specifically, loss of Actl6a, an essential components of the SWI/SNF complexes, resulted in cilia disassembly and cystic kidney, without affectting cilia motility. Omics analyses revealed that in Actl6a-depleted pronephros or embryos, a set of cilia genes--including master regulators foxj1a and rfx2--were downregulated at transcriptional level, chromatin accessibility level and SWI/SNF binding level. Depletion of foxj1a or rfx2 in zebrafish also caused cilia disassembly and cystic kidney. Furthermore, overexpression of foxj1a or rfx2 mRNA partially rescued the cystic kidney and cilia disassembly phenotypes in actl6a mutants. Taken together, our study reveals that the SWI/SNF complexes maintain cilia stability and kidney homeostasis by directly modulating the expression of foxj1a or rfx2.

developmental biology↗

bioRxiv2025

Secondary structure transitions and dual PIP2 binding define cardiac KCNQ1-KCNE1 channel gating

The KCNQ1+KCNE1 potassium channel complex forms the slow delayed rectifier current (IKs) critical for cardiac repolarization. Loss-of-function variants in KCNQ1 and KCNE1 cause long QT syndrome types 1 and 5 (LQT1/LQT5), accounting for over one-third of clinical LQTS cases. Despite prior structural work on KCNQ1 and KCNQ1+KCNE3, the structural basis of KCNQ1+KCNE1 remains unresolved. Using cryo-EM and electrophysiology, we determined high-resolution (2.5-3.4 [A]) structures of human KCNQ1+KCNE1 in both closed and open states. KCNE1 occupies a pivotal position at the interface of three KCNQ1 subunits, inducing seven "helix-to-loop" transitions in KCNQ1 transmembrane segments. These structural rearrangements: 1) stabilize the closed pore and the conformation of the intermediate voltage-sensing domain, thereby determining channel gating, ion permeation, and single channel conductance; 2) enable a dual-PIP2 modulation mechanism, where one PIP2 occupies the canonical site, while the second PIP2 bridges the S4-S5 linker, KCNE1, and the adjacent S6, stabilizing channel opening; 3) create a fenestration capable of binding compounds specific for KCNQ1+KCNE1 (e.g., AC-1). Together, these findings reveal a previously unrecognized large-scale secondary structural transition during ion channel gating that fine-tunes IKs function and provides a foundation for targeted LQTS therapy development.

biophysics↗

bioRxiv2025

Establishing a Digital PCR-Based Reference Measurement Procedure for Monkeypox Virus: An Inter-laboratory Assessment and Standardization Study

The accurate detection of monkeypox virus (MPXV) is crucial for effective viral diagnosis and epidemic prevention. Currently, the field lacks standardized reference methods for MPXV quantification, as well as reliable pseudovirus reference materials (RMs) to ensure quality control throughout the detection process. To address this, we developed a droplet digital PCR (ddPCR) reference measurement procedure (RMP) for precise quantification of MPXV genes B6R, which demonstrates excellent performance with a wide dynamic range (11-1.24x104 copies/L), strong linearity (R2=0.9984), and a low limit of quantitation (11 copies/L, CV[≤]25%). Repeatability tests confirmed high precision, with inter-laboratory CVs <10% across nine labs using different dPCR platforms. recovery efficiencies for B6R and F3L were [~]69%, with uncertainties incorporated into final measurements. The homogeneity assessment showed good results (CV=2.94%), and stability studies confirmed the stability of the sample during -70 {degrees}C and short-term storage (4 {degrees}C/-20 {degrees}C). Mandels statistical data shows that the reproducibility between laboratories is consistent. This validated ddPCR RMP provides metrological traceability, ensuring reliable and comparable results for MPXV diagnosis and supporting public health efforts.

molecular biology↗

bioRxiv2025

Ammonia-mediated Conformational Dynamics in SCAP for SREBP Activation

Cholesterol homeostasis is regulated by the sterol regulatory element-binding protein (SREBP) pathway, with the membrane-embedded SREBP-cleavage-activating protein (SCAP) and insulin-inducible gene protein (Insig)-1/2 acting as sterol sensors. Our previous studies unveiled a critical role of ammonia in activating the SREBP pathway. Here, we performed extensive molecular dynamics (MD) simulations to elucidate the structural mechanisms through which ammonia binding triggers SCAP/Insig dissociation and subsequently activate SREBP. The SCAP S4 helix exists in two distinct conformations: a partially unfolded S4 and an intact S4; the transition between these states may constitute a crucial aspect of SCAP activation. We first studied the binding of ammonia to SCAP in different S4 conformational states. We then explored how the binding of ammonia or 25-hydroxycholesterol (25-HC) affects the conformational transition of S4 using targeted MD simulations. Finally, we performed comparative analysis of the 25-HC-bound inactive SCAP and the ammonia-bound active SCAP. Collectively, our findings highlight the importance of S4 helix conformation in activating the SCAP protein. Our simulations suggest that ammonia and 25-HC act as an agonist and antagonist of SCAP activation, respectively. Specifically, ammonia binding facilitates the transition of S4 from the unfolded to the straight conformation, triggering subsequent conformational changes in the transmembrane domain of SCAP. These changes eventually promote the SCAP/Insig dissociation and alter the position of the MELADL motif at the membrane surface. Significant StatementCellular cholesterol homeostasis is tightly regulated by the SREBP pathway, which relies on the membrane proteins SCAP and Insig to sense sterol levels. While ammonia has recently been identified as a novel activator of this pathway, its structural mechanism of action remained unknown. Here, extensive molecular dynamics simulations reveal that ammonia binding promotes a critical conformational transition in the SCAP S4 helix, facilitating SCAP activation and its dissociation from Insig. Our findings show that ammonia and cholesterol act as opposing modulators--agonist and antagonist--of SCAP activity. This work uncovers a previously unrecognized structural switch in SCAP and provides new molecular insight into small-molecule regulation of cholesterol sensing.

molecular biology↗

bioRxiv2025

Aptamer-Enabled Discovery and Clinical Analysis of Exosomal Surface Biomarkers in Hepatocellular Carcinoma

Exosomal membrane proteins hold promise as cancer biomarkers but face detection challenges due to low abundance and conformational sensitivity. We developed AptEx-ID, a microbead-displayed aptamer platform enabling high- throughput screening of hepatocellular carcinoma (HCC)-specific exosomal surface proteins. Aptamers, selected via competitive binding to tumor-derived versus healthy exosomes, demonstrated high affinity and specificity. Clinical validation using 50 HCC and 30 control plasma samples identified a 7-aptamer panel via machine learning, achieving 93.75% accuracy and 0.95 ROC-AUC. These aptamers further revealed HCC-associated biomarkers (e.g., IMPDH1, ASCC3, GTSE1), validated by siRNA knockdown and biophysical assays. Post-treatment monitoring showed aptamer signal reduction in responsive patients, highlighting their prognostic utility. This platform integrates biomarker discovery, diagnostics, and therapeutic monitoring, offering a robust approach for HCC management through exosomal surface proteome profiling.

molecular biology↗

bioRxiv2025

Promoting social connectedness through multi-person neurofeedback

Humans are inherently driven to build meaningful relationships, but attempts to socially connect with others are not always successful. This study investigates whether social connectedness can be improved by intentionally regulating inter-brain coupling, a neural correlate of successful social interactions. Using a multi-person neurofeedback system (i.e., a multi-brain computer interface), we showed dyads real-time visualizations of the extent to which their brainwaves (EEG signals) were "in sync". Our results showed that, compared to a sham control group, dyads who received multi-brain neurofeedback exhibited an increase in inter-brain coupling, and, critically, that this increase was associated with a higher sense of social connectedness. A chain mediation analysis suggested that this experience of enhanced social connectedness may have been driven by a sense of joint control and shared intentionality. Together, our findings showcase the potential for regulating inter-brain coupling to optimize human social relationships and behaviors.

neuroscience↗

bioRxiv2025

Development, validation, and evidence of frequent exchange of mating type HD alleles of Puccinia striiformis f. sp. tritici provide an insight into highly genetic diversity

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a worldwide destructive wheat disease. It possesses the potential to generate novel virulence races through sexual reproduction, which is the primary cause of its extensive epidemics. Mating type (MAT) of Pst lacks direct experimental evidence to account for the role of sexual recombination on high genetic diversity in evolution. Herein, we developed 11 pairs of HD alleles of Pst MAT genes, and 2 pairs HD alleles of P. striiformis f. sp. hordei (Psh, the causal agent of barley stripe rust) MAT genes. HD alleles in Pst are different from those in Psh. We tested that mating system of Pst is tetrapolar responsible for sexual genetic recombination via HD genes by experiments of selfing and sexual hybridization on alternate (secondary) hosts. Multiple HD gene types and HD gene recombination types were detected in Chinese natural Pst populations of 200 Pst isolates and 13 Psh isolates from 92 sampling sites in 11 provinces, supporting that sexual reproduction accounts for frequent emergence of new races and high genetic diversity of Pst population in northwestern oversummering variable region (hotspot) than other stripe rust-occurring regions in China. Overall, these results provide an insight into diverse types and frequent exchange of Ps MAT alleles, revealing the important role of sexual recombination via MAT alleles in virulence variation, high genetic diversity and epidemics of Pst, and also provide a basis for wheat stripe rust control in those regions where sexual reproduction occurs. Author summaryHeteroecism of the wheat stripe rust pathogen Puccinia striiformis f. sp. tritici (Pst) was discovered a decade ago. The significance of sexual reproduction in maintaining genetic diversity has emerged as a pressing concern in contemporary scientific discourse. In this study, we elucidated the presence of multiple HD gene types (HD1 linked to HD2) in Puccinia striiformis f. sp. tritici (Pst), distinguishing it from P. striiformis f. sp. hordei. Through biological experiments on sexual reproduction, we demonstrated that the mating system of Pst is tetrapolar. Furthermore, we observed that sexual reproduction, particularly selfing (individual race) and crossing (between two races), facilitates sexual recombination via HD genes, leading to pathogenic variation and a high level of genetic diversity. We established a model illustrating sexual reproduction of Pst by selfing and crossing, respectively. In China, we have observed that the Pst population exhibits a diverse range of HD gene types and HD gene recombination types. Notably, northwestern oversummering variable regions (hotspot) have a higher number of HD genes compared to other epidemic region. Population structure and cluster analyses based on HD genes indicate that Pst populations in Tibet and Xinjiang are distinct from those in other inland regions. These findings provide valuable insights into comprehending the intricate interplay between sexual reproduction and genetic diversity of Pst, thereby elucidating the reasons behind the high genetic diversity of the Chinese Pst population.

microbiology↗

bioRxiv2025

A SUMO-interacting motif in the guanine nucleotide exchange factor EPAC1 is required for subcellular targeting and function

Exchange protein directly activated by cAMP (EPAC1), a multifunctional intracellular cAMP receptor, dynamically localizes to various cellular loci, engaging with diverse molecular partners to maintain cellular homeostasis. The study investigates the role of the SUMO interacting motif (SIM) in the subcellular targeting and cellular functions of EPAC1. It reveals that the SIM is a critical structural element for EPAC1s association with RanBP2/Nup358, a nucleoporin of the cytoplasmic filament component of the nuclear pore complex (NPC). Mutational disruption of EPAC1 SIM interferes with EPAC1s ability to activate its canonical effectors, small GTPases, Rap1 and Rap2, and non-canonical functions, such as the formation of nuclear condensates and cellular SUMOylation. Because SIM is also directly involved in cAMP binding, RanBP2s association with EPAC1 with the SIM attenuates EPAC1s cAMP binding affinity to generate an EPAC1 signaling microdomain with reduced cAMP sensitivity around the NPC. The coupling between EPAC1s scaffold association and cAMP binding enables EPAC1 to tune its sensitivity to stress stimuli spatially depending on the cellular locations. These findings provide novel structural insights into EPAC1 signaling, highlighting the importance of SIM in EPAC1s cellular functions and potential novel strategies for therapeutically targeting EPAC1.

cell biology↗

bioRxiv2025

Entamoeba histolytica Gal/GalNAc lectin intermediate subunit promotes inflammation and epithelial damage in intestinal amebiasis through its C3 region.

Entamoeba histolytica is a common enteric protozoan that sometimes transitions from a symbiont to a pathogen, causing intestinal amebiasis and extraintestinal abscesses in the host. The early-to-intermediate stages of intestinal amebiasis are characterized by an intense inflammatory response, during which host innate immune defenses play an important role. Here, using the cecal infection model of C3H/HeNCrl mice, we performed single-cell RNA sequencing of cecal tissues and identified the prominent pro-inflammatory function of host macrophages in intestinal amebiasis. On the amoebic cell surface, Igl is an intermediate subunit of galactose- and N-acetyl-D-galactosamine-inhibitable lectins, which contributes to parasite adherence. We proposed that E. histolytica Igl diffuses along with amoebic extracellular vesicles and contacts host macrophages, binding to the TLR4 co-receptor MD2 through its C3 region and initiating the TLR4/MyD88/NF-{kappa}B inflammatory signaling pathway in host cells. Moreover, by inducing macrophage inflammation and cytokine production, E. histolytica indirectly impairs intestinal epithelium integrity through the Igl protein. To our knowledge, this is the first report showing a host single-cell atlas in the field of amebiasis research. In response to the parasite invasion during intestinal amebiasis, our study provides new insights elucidating the inflammatory formation and epithelial damage of gut mucosal immune system, and also conduces to the identification of potential drug targets for these amoebas.

microbiology↗

bioRxiv2025

Uncovering Shared and Tissue-Specific Molecular Adaptations to Intermittent Fasting in Liver, Brain, and Muscle

Intermittent fasting (IF) has emerged as a powerful dietary intervention with profound metabolic benefits, yet the tissue-specific molecular mechanisms underlying these effects remain poorly understood. In this study, we employed comprehensive proteomics and transcriptomics analysis to investigate the systemic and organ-specific adaptations to IF in male C57BL/6 mice. Following a 16-hour daily fasting regimen (IF16) over four months, IF reduced blood glucose, HbA1c, and cholesterol levels while increasing ketone bodies, indicative of enhanced metabolic flexibility. Proteomic profiling of the liver, skeletal muscle, and cerebral cortex revealed tissue-specific responses, with the liver exhibiting the most pronounced changes, including upregulation of pathways involved in fatty acid oxidation, ketogenesis, and glycan degradation, and downregulation of steroid hormone and cholesterol metabolism. In muscle, IF enhanced pyruvate metabolism, fatty acid biosynthesis, and AMPK signaling, while suppressing oxidative phosphorylation and thermogenesis. The cerebral cortex displayed unique adaptations, with upregulation of autophagy, PPAR signaling, and metabolic pathways, and downregulation of TGF-beta and p53 signaling, suggesting a shift toward energy conservation and stress resilience. Notably, Serpin A1c emerged as the only protein commonly upregulated across all three tissues, highlighting its potential role in systemic adaptation to IF. Integrative transcriptomic and proteomic analyses revealed partial concordance between mRNA and protein expression, underscoring the complexity of post-transcriptional regulation. Shared biological signaling processes were identified across tissues, suggesting unifying mechanisms linking metabolic changes to cellular communication. Our findings reveal both conserved and tissue-specific responses by which IF may optimize energy utilization, enhance metabolic flexibility, and promote cellular resilience.

molecular biology↗

bioRxiv2025

SND1 Impairs Calcium Homeostasis in Right Ventricular Failure by Binding and Destabilizing SERCA2a in Cardiomyocytes

BackgroundRight ventricular failure (RVF) is a major contributor to a poor prognosis in patients with pulmonary arterial hypertension (PAH); however, its underlying molecular mechanisms remain incompletely understood. We identified a significant upregulation of the cardiac fetal gene SND1 in the right ventricular myocardium of RVF rats. This upregulation may be a key component of cardiac fetal reprogramming and play a critical role in RVF progression. However, the precise molecular mechanisms by which SND1 contributes to RVF remain unelucidated. MethodsRat models of PAH were established by intraperitoneal injection of monocrotaline (MCT). The pulmonary artery pressure and right ventricular function of rats were assessed using transthoracic echocardiography combined with right heart catheterization. Weighted gene co-expression network analysis (WGCNA) of proteomic data identified a significant association between SND1 upregulation and RVF progression. Calcium transient and contractility measurements in single cardiomyocytes were performed to evaluate the effect of SND1 on sarcoplasmic reticulum (SR) function. Liquid chromatography with mass spectrometry/mass spectrometry analysis combined with co-immunoprecipitation (Co-IP) was used to identify sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 2A (SERCA2a) as the protein interacting with SND1. The effect of SND1 on the progression of RVF was validated using cardiomyocyte-specific SND1 conditional knockout rats. ResultsProteomic and molecular analyses revealed that the cardiac fetal gene SND1 is reactivated in RVF and may contribute to disease progression. In vitro, SND1 knockdown in neonatal rat ventricular myocytes (NRVMs) enhanced contractility, improved calcium transient amplitude and velocity, and increased cell survival under calcium overload. Mechanistically, SND1 interacts with SERCA2a and promotes its proteasomal degradation, impairing SR calcium reuptake. SND1 knockdown restored SERCA2a stability. In vivo, cardiomyocyte-specific SND1 knockout improved right ventricular function, reduced SERCA2a degradation and apoptosis, and increased survival in RVF rats. ConclusionOur study revealed that SND1 reactivation (a fetal gene) contributes to the progression of RVF by promoting SERCA2a degradation and impairing calcium handling. Targeted suppression of SND1 enhances cardiomyocyte contractility and survival, highlighting SND1 as a potential therapeutic target for improving right ventricular function in PAH. Clinical perspectiveO_ST_ABSWhat Is New?C_ST_ABSO_LIThis study identifies SND1, a reactivated fetal gene, as a key contributor to right ventricular failure (RVF) progression in pulmonary arterial hypertension (PAH). C_LIO_LISND1 interacts with SERCA2a, promoting its proteasomal degradation, which disrupts sarcoplasmic reticulum calcium reuptake and weakens cardiomyocyte contractility. C_LIO_LICardiomyocyte-specific SND1 deletion restores SERCA2a levels, improves calcium handling, enhances right ventricular function, and increases survival in RVF rats. C_LI What Are the Clinical Implications?O_LIThe reactivation of fetal genes such as SND1 is not just a marker but a pathogenic driver in maladaptive right ventricular remodeling. C_LIO_LITargeting SND1 represents a novel therapeutic approach to improve right ventricular contractility and prevent heart failure progression in patients with PAH. C_LIO_LIThese findings may inform the development of gene- or protein-targeted therapies aimed at stabilizing SERCA2a and preserving right heart function in high-risk populations. C_LI

cell biology↗

bioRxiv2025

Breathe in, breathe out: Bacterial density determines collective migration in aerotaxis

Bacteria navigate their environment by biasing their swimming direction toward beneficial chemicals and away from harmful ones. Out of all the chemicals bacteria respond to, oxygen stands out due to its ubiquitous presence, distinct influence on bacterial metabolism and motility, and historical role in chemotaxis research. However, a coherent understanding of bacterial motility in oxygen gradients, known as aerotaxis, remains elusive, as evidenced by conflicting reports on the migration direction of the model organism Escherichia coli in self-generated oxygen gradients. Here, by combining experiments, simulations, and theory, we provide a unified framework elucidating the fundamental biophysical principle governing bacterial aerotaxis. We track the migration of bacteria in a capillary channel under self-generated oxygen gradients and show that the migration direction depends on the overall bacterial density. At high densities, bacteria migrate toward regions of higher oxygen concentration, whereas at low densities, they move in the opposite direction. We identify a critical bacterial density at which collective migration ceases, despite the presence of oxygen gradients. A kinetic theory, based on the assumption that bacteria seek an optimal oxygen concentration, is then developed to quantitatively explain our experimental findings. We validate this hypothesis by demonstrating the biased movement of individual bacteria in a dense suspension and proposing a signaling pathway that enables this behavior. Thus, by bridging the molecular level understanding of the signaling pathway, the motility of single bacteria in oxygen gradients, and the collective population dynamics shaped by oxygen diffusion and consumption, our study provides a comprehensive understanding of aerotaxis, addressing the long-standing controversy over how bacteria response to non-uniform oxygen distributions pervasive in microbial habitats.

biophysics↗

bioRxiv2025

Structural basis of substrate specificity of Helix pomatia AMP deaminase and a chimeric ADGF adenosine deaminase

HPAMPD, an enzyme enriched in the foot muscle of the mollusk Helix pomatia, exhibits deaminase activity on adenosine-5-monophosphate (AMP). HPAMPD is the first member of the adenosine deaminase-related growth factor (ADGF) family to prefer the nucleotide, AMP, over the nucleoside, adenosine. To investigate the substrate selectivity of HPAMPD, we determined its structure in the apo form and in complex with the adenosine analogs pentostatin (2- deoxycoformycin) and pentostatin-5-monophosphate. Structurally, HPAMPD adopts a fold similar to human ADA2, an ADGF family member. HPAMPD has acquired the ability to interact with the 5-monophosphate group of AMP through polar and charged residues located in three key structural elements: (1) the loop immediately following strand {beta}1, (2) the loop between helices H and I, and (3) the end of strand {beta}5 and its adjacent loop. We engineered a chimeric deaminase by integrating these elements from HPAMPD into another related mollusk nucleoside adenosine deaminase, the A. californica ADGF. The chimeric enzyme efficiently deaminates AMP, demonstrating a gained substrate specificity, while retaining the adenosine deamination activity of Aplysia ADGF. The phosphate-binding feature of HPAMPD is a hallmark of nucleotide deaminases, conserved among AMP and N6-methyl-AMP (6mAMP) deaminases. We discuss the human adenosine deaminases each with distinct substrate specificities for the nucleoside, the nucleotide (AMP), and the methylated form, 6mAMP. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=85 SRC="FIGDIR/small/645602v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@be415forg.highwire.dtl.DTLVardef@b5f7a5org.highwire.dtl.DTLVardef@957514org.highwire.dtl.DTLVardef@397e9a_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2025

Energy inefficiency underpinning brain state dysregulation in individuals with major depressive disorder

Disruptions in brain state dynamics are a hallmark of major depressive disorder (MDD), yet their underlying mechanisms remain unclear. This study, building on network control theory, revealed that decreased state stability and increased state-switching frequency in MDD are driven by elevated energy costs and reduced control stability, indicating energy inefficiency. Key brain regions, including the left dorsolateral prefrontal cortex, exhibited impaired energy regulation capacity, and these region-specific energy patterns were correlated with depressive symptom severity. Neurotransmitter and gene expression association analyses linked these energy deficits to intrinsic biological factors, notably the 5-HT2a receptor and excitatory-inhibitory balance. These findings shed light on the energetic mechanism underlying brain state dysregulation in MDD and its associated biological underpinnings, highlighting brain energy dynamics as a potential biomarker by which to explore therapeutic targets and advance precise interventions for restoring healthy brain dynamics in depression.

neuroscience↗

bioRxiv2025

Mapping human cerebral blood flow with high-density, multi-channel speckle contrast optical spectroscopy

Recently, speckle contrast optical spectroscopy (SCOS) enabled non-invasive, high signal-to-noise-ratio (SNR) human cerebral blood flow (CBF) measurements, relevant for both neuroscience and clinical monitoring of diseases with CBF dysregulation. Single channel SCOS measurements limit the information obtained to only one location on the head. In this work, we develop a multi-channel SCOS system to map spatial heterogeneity in CBF changes during human brain activation. Using a galvanometer, we temporally multiplexed a free-space laser to 7 source fibers positioned at different locations on the head. Diffuse light collected from the tissue is captured by fiber bundles projecting to 17 complementary metal-oxide semiconductor (CMOS) cameras, resulting in 50 source-detector channels measuring optical density (OD) and relative CBF changes covering an area of 7.6 cm by 6.6 cm on the head. We validated the spatial specificity and stability of the system using a liquid flow phantom. We then measured brain activity during a word-color Stroop task in 15 subjects and obtained brain activation maps. The average signal changes in the channel showing the largest activation were 1.7 x 10-2 in {Delta}OD and 6.6% in CBF.

bioengineering↗

bioRxiv2025

Inwardly rectifying potassium channels regulate membrane potential polarization and direction sensing during neutrophil chemotaxis

Potassium channels regulate membrane potential and diverse physiological processes, including cell migration. However, the specific function of the inwardly rectifying potassium channels in immune cell chemotaxis is unknown. Here, we identified that the inwardly rectifying potassium channel Kir7.1 (KCNJ13) maintains the resting membrane potential and is required for directional sensing during neutrophil chemotaxis. Pharmacological or genetic inhibition of Kir7.1 in neutrophils impaired direction sensing toward various chemoattractants without affecting cell polarization in multiple neutrophil models. Using genetically encoded voltage indicators, we observed oscillating depolarization of the membrane potential in protrusions in zebrafish neutrophils, and Kir7.1 is required for polarized depolarization towards the chemokine source. Focal depolarization with optogenetic tools biases pseudopod selection and induces de novo protrusions. Global hyperpolarizing neutrophils stalled cell migration. Furthermore, Kir7.1 regulates GPCR signaling activation. This work adds membrane potential to the intricate feedforward mechanism, coupling the adaptive and excitable network required to steer immune cells in complex tissue environments.

cell biology↗

bioRxiv2025

Housekeeping genes are enriched in rheumatoid arthritis-related genes

Housekeeping genes are often considered to be stably expressed in any tissue, cell, or disease state, and the relationship between housekeeping genes and rheumatoid arthritis (RA) has never been systematically analyzed. Therefore we aimed to explore whether housekeeping genes are abnormally expressed in RA by analyzing 15 datasets that were filtered from 140 gene expression profiles. By cumulative hypergeometric test, for 73.3% (11/15) of the datasets, housekeeping genes were significantly (p < 0.05) enriched in differentially expressed genes (DEGs) between RA patients and healthy controls. Using the relative enrichment factor (Re) as an effect size, a Meta-analysis strategy was adopted to integrate the individual results. The logarithmic Re estimation for multiple studies was 0.48 with the 95% confidence interval ranging from 0.17 to 0.80. The combined effect size was significantly higher than that of the randomized case (p = 0.0012) suggesting a consistent result with the hypergeometric test. The robustness of results was verified by sensitivity and subgroup analyses. Furthermore, the expression fluctuation of housekeeping genes was higher in RA patients than healthy controls and the correlation between DNA methylation and gene expression of housekeeping genes was significantly higher than that of non-housekeeping genes, which indicates the potential epigenetic regulation relationship between housekeeping genes and the pathogenesis of RA. This study identified for the first time a significant enrichment of housekeeping genes in DEGs of RA, which might provide new perspectives for understanding the potential role of housekeeping genes in RA.

bioinformatics↗

bioRxiv2025

Molecular Mechanism of pH Sensing and Activation in GPR4 Reveals Proton-Mediated GPCR Signaling

Maintaining pH homeostasis is critical for cellular function across all living organisms. Proton-sensing G protein-coupled receptors (GPCRs), particularly GPR4, play a pivotal role in cellular responses to pH changes, yet the molecular mechanisms underlying their proton sensing and activation remain incompletely understood. Here we present high-resolution cryo-electron microscopy structures of GPR4 in complex with G proteins under physiological and acidic pH conditions. Our structures expose an intricate proton-sensing mechanism driven by a sophisticated histidine network in the receptors extracellular domain. Upon protonation of key histidines under acidic conditions, a remarkable conformational cascade is initiated, propagating from the extracellular region to the intracellular G protein-coupling interface. This dynamic process involves precise transmembrane helix rearrangements and conformational shifts of conserved motifs, mediated by strategically positioned water molecules. Notably, we discovered a bound bioactive lipid, lysophosphatidylcholine, which has positive allosteric effects on GPR4 activation. These findings provide a comprehensive framework for understanding proton sensing in GPCRs and the interplay between pH sensing and lipid regulation, offering insights into cellular pH homeostasis and potential therapies for pH-related disorders.

molecular biology↗