Biology subjects

Chen, X.

Publications and source records attributed to Chen, X..

At least 1,081 records · Page 60Linked to original sources

bioRxiv2022

The Goldilocks Principle conferred by LDH isoenzymes controls murine T cell glycolysis and differentiation

Isoenzyme divergence is a prevalent mechanism governing tissue-specific and developmental stage-specific metabolism in mammals. The isoenzyme pattern (spectrum) of lactate dehydrogenase (LDH) reflects the status of glucose metabolism in different organs such as muscle, liver, and heart. T cells are highly dependent on glucose metabolism for survival, proliferation, and differentiation. However, the LDH isoenzyme spectrum in T cells and its potential impact on T cell-mediated immune response remain unclear. Here, we discovered that the LDH spectrum in murine T cells is characterized by three tetrameric isoenzymes composed of LDHA and LDHB (LDH-3/4/5). Genetic deletion of LDHA or LDHB altered the isoenzyme spectrum by removing all heterotetramers and leaving T cell with LDH-1 (the homotetramer of LDHB) or LDH-5 (the homotetramer of LDHA), respectively. Accordingly, altering the isoenzyme spectrum by deleting LDHA or LDHB compromises T cell metabolic fitness and effector cell differentiation in vivo. Unexpectedly, deleting LDHA suppressed glycolysis, whereas deleting LDHB further enhanced it, indicating that an optimal zone of glycolytic activity is critical to driving effector T cell differentiation. Mechanistically, the LDH isoenzyme spectrum imposed by LDHA and LDHB is required to optimize glycolysis to maintain a balanced NAD+/NADH pool, a hallmark of metabolic fitness. Together, our results suggest that the LDH isoenzyme spectrum enables "Goldilocks levels" of glycolytic and redox activity (i.e., not too high, not too low, but just right) to control T cell differentiation function.

immunology↗

bioRxiv2022

ISSAAC-seq enables sensitive and flexible multimodal profiling of chromatin accessibility and gene expression in single cells

Joint profiling of chromatin accessibility and gene expression from the same single cell/nucleus provides critical information about cell types in a tissue and cell states during a dynamic process. These emerging multi-omics techniques help the investigation of cell-type resolved gene regulatory mechanisms1-7. However, many methods are currently limited by low sensitivity, low throughput or complex workflow. Here, we developed in situ SHERRY after ATAC-seq (ISSAAC-seq), a highly sensitive and flexible single cell multi-omics method to interrogate chromatin accessibility and gene expression from the same single nucleus. We demonstrated that ISSAAC-seq is sensitive and provides high quality data with orders of magnitude more features than existing methods. Using the joint profiles from over 10,000 nuclei from the mouse cerebral cortex, we uncovered major and rare cell types and cell-type specific regulatory elements and identified heterogeneity at the chromatin level within established cell types defined by gene expression. Finally, we revealed distinct dynamics and relationships of gene expression and chromatin accessibility during an oligodendrocyte maturation trajectory.

genomics↗

bioRxiv2022

A Computational Method to Dissect Colonization Resistance of the Gut Microbiota against Pathogens

The indigenous gut microbes have co-evolved with their hosts for millions of years. Those gut microbes play a crucial role in host health and disease. In particular, they protect the host against incursion by exogenous and often harmful microorganisms, a mechanism known as colonization resistance (CR). Yet, identifying the exact microbes responsible for the gut microbiota-mediated CR against a particular pathogen remains a fundamental challenge in microbiome research. Here, we develop a computational method --- Generalized Microbe-Phenotype Triangulation (GMPT) to systematically identify causal microbes that directly influence the microbiota-mediated CR against a pathogen. We systematically validate GMPT using a classical population dynamics model in community ecology, and then apply it to microbiome data from two mouse studies on C. difficile infection. The developed method will not only significantly advance our understanding of CR mechanisms but also pave the way for the rational design of microbiome-based therapies for preventing and treating enteric infections.

bioinformatics↗

bioRxiv2022

Single-cell analysis of microglial transcriptomic diversity in subarachnoid hemorrhage

BackgroundSubarachnoid hemorrhage (SAH) is a severe stroke and the advanced treatment for SAH is still limited. Recent studies have shown that microglia-mediated neuroinflammation plays a critical role in the pathogenesis of SAH. Microglia can transform their states in response to central nervous system injury. However, the transcriptomic features of microglia remained unknown in SAH. Recent developed single-cell RNA sequencing (scRNA-seq) provides a possible way to solve this problem. MethodsEndovascular perforation (EVP) murine SAH model was established to reproduce experimental SAH. Microglia states are examined with immune staining and quantitate analysis. Post-SAH microglial single-cell suspension were harvest and sequenced using 10X scRNA-seq platform. Then, the detailed single-cell transcriptomic characterization of post-SAH microglia were analyzed with bioinformatics. ResultsTranscriptional analysis revealed at least ten diverse microglial subgroups, including SAH-associated microglia (SAM), inflammatory-associated microglia (IAM) and proliferation-associated microglia (PAM), which all exhibit distinct marker gene expression patterns. Microglia subsets interaction reveals the functional relationship between elevated signaling pathways and microglial sub-populations in SAH. Receptor-ligand pair analysis revealed that complex inter-cellular interactions exist between the microglia subsets and other cell types, and indicated that microglia are important mediators of neuroinflammation after SAH. Integrated analysis with normal microglia further proved the existence of these microglia subpopulations and different gene markers associated with SAH were clarified. ConclusionsCollectively, we first report the single-cell transcriptome of post-SAH microglia and found specific biomarkers related to the neuroinflammation in SAH. These results enhanced our understanding of the pathological mechanisms of microglial response to SAH, and may guide future development of SAH monitoring methods and therapeutics.

neuroscience↗

bioRxiv2022

Prelimbic proBDNF facilitates memory destabilization by regulation of neuronal function in juveniles

Fear regulation changes as a function of age and adolescence is a key developmental period for the continued maturation of fear neural circuitry. The involvement of prelimbic proBDNF in fear memory extinction and its mediated signaling were reported previously. Given the inherent high level of proBDNF during juvenile period, we tested whether prelimbic proBDNF regulated synaptic and neuronal functions allowing to influencing retrieval-dependent memory processing. By examining freezing behavior of auditory fear conditioned rats, we found high levels of prelimbic proBDNF in juvenile rats enhanced destabilization of the retrieval-dependent weak but not strong fear memory through activating p75NTR-GluN2B signaling. This modification was attributed to the increment in proportion of thin type spine and promotion in synaptic function, as evidence by facilitation of NMDA-mediated EPSCs and GluN2B-dependent synaptic depression. The strong prelimbic theta- and gamma-oscillation coupling predicted the suppressive effect of proBDNF on the recall of post-retrieval memory. Our results critically emphasize the importance of developmental proBDNF for modification of retrieval-dependent memory and provide a potential critical targeting to inhibit threaten memories associated with neurodevelopment disorders.

neuroscience↗

bioRxiv2021

Landscape of human spinal cord cell type diversity at midgestation

Understanding spinal cord generation and assembly is essential to elucidate how motor behavior is controlled and how disorders arise. The cellular landscape of the human spinal cord remains, however, insufficiently explored. Here, we profiled the midgestation human spinal cord with single cell-resolution and discovered, even at this fetal stage, remarkable heterogeneity across and within cell types. Glia displayed diversity related to positional identity along the dorso-ventral and rostro-caudal axes, while astrocytes with specialized transcriptional programs mapped onto distinct histological domains. We discovered a surprisingly early diversification of alpha () and gamma ({gamma}) motor neurons that control and modulate contraction of muscle fibers, which was suggestive of accelerated developmental timing in human spinal cord compared to rodents. Together with mapping of disease-related genes, this transcriptional profile of the developing human spinal cord opens new avenues for interrogating the cellular basis of motor control and related disorders in humans.

neuroscience↗

bioRxiv2021

APOBEC-mediated Editing of SARS-CoV-2 Genomic RNA Impacts Viral Replication and Fitness

During COVID-19 pandemic, mutations of SARS-CoV-2 produce new strains that can be more infectious or evade vaccines. Viral RNA mutations can arise from misincorporation by RNA-polymerases and modification by host factors. Analysis of SARS-CoV-2 sequence from patients showed a strong bias toward C-to-U mutation, suggesting a potential mutational role by host APOBEC cytosine deaminases that possess broad anti-viral activity. We report the first experimental evidence demonstrating that APOBEC3A, APOBEC1, and APOBEC3G can edit on specific sites of SARS-CoV-2 RNA to produce C-to-U mutations. However, SARS-CoV-2 replication and viral progeny production in Caco-2 cells are not inhibited by the expression of these APOBECs. Instead, expression of wild-type APOBEC3 greatly promotes viral replication/propagation, suggesting that SARS-CoV-2 utilizes the APOBEC-mediated mutations for fitness and evolution. Unlike the random mutations, this study suggests the predictability of all possible viral genome mutations by these APOBECs based on the UC/AC motifs and the viral genomic RNA structure. One-sentence summaryEfficient Editing of SARS-CoV-2 genomic RNA by Host APOBEC deaminases and Its Potential Impacts on the Viral Replication and Emergence of New Strains in COVID-19 Pandemic

microbiology↗

bioRxiv2021

Multiscale 3D Genome Reorganization during Skeletal Muscle Stem Cell Lineage Progression and Muscle Aging

3D genome rewiring is known to influence spatiotemporal expression of lineage-specific genes and cell fate transition during stem cell differentiation and aging processes. Yet it is unknown how 3D architecture remodels and orchestrates transcriptional changes during skeletal muscle stem cell (also called satellite cell, SC) activation, proliferation and differentiation course. Here, using in situ Hi-C we comprehensively map the 3D genome topology reorganization at multiscale levels during mouse SC lineage progression and integrate with transcriptional and chromatin signatures to elucidate how 3D genome rewiring dictates gene expression program. Specifically, rewiring at compartment level is most pronounced when SC becomes activated. Striking loss in TAD border insulation and chromatin looping also occurs during early activation process. Meanwhile, TADs can also form TAD clusters and super-enhancer containing TAD clusters orchestrate stage-specific gene expression during SC early activation. Furthermore, we elucidate 3D chromatin regulation of key transcription factor, PAX7 and identify cis-regulatory elements that are crucial for local chromatin architecture and Pax7 expression. Lastly, 3D genome remodeling is profiled in SCs isolated from naturally aging mice, unveiling that geriatric SCs display a prominent gain in long-range contacts and loss of TAD border insulation. Genome compartmentalization and chromatin looping are evidently altered in aged SC while geriatric SC display a more prominent loss in strength of TAD borders. Together, our results implicate 3D chromatin extensively reorganizes at multiple architectural levels and underpin the transcriptome remodeling during SC lineage development and SC aging.

cell biology↗

bioRxiv2021

Neuronal primary cilia regulate pyramidal cell positioning to the deep and superficial sublayers in the hippocampal CA1

Currently little is known about neuronal positioning and the roles of primary cilia in postnatal neurodevelopment. We show that primary cilia of principal neurons undergo marked changes in positioning and orientation, concurrent with postnatal neuron positioning in the mouse cerebral cortex. Primary cilia of early- and late-born principal neurons in compact layers display opposite orientations, while neuronal primary cilia in loose laminae are predominantly oriented toward the pia. In contrast, astrocytes and interneurons, and neurons in nucleated brain regions do not display specific cilia directionality. We further discovered that the cell bodies of principal neurons in inside-out laminated regions spanning from the hippocampal CA1 region to neocortex undergo a slow "reverse movement" for postnatal positioning and lamina refinement. Further, selective disruption of cilia function in the forebrain leads to altered lamination and gyrification in the retrosplenial cortex (RSC) that is formed by reverse movement. Collectively, this study identifies reverse movement as a fundamental process for principal cell positioning that refines lamination in the cerebral cortex and casts light on the evolutionary transition from 3-layered allocortices to 6-layered neocortices. Summary StatementGuided by cilia directionality, we discovered that the somata of principal neurons in inside-out laminated regions undergo a slow but substantial reverse movement for postnatal cell positioning, which refines cortical layering.

neuroscience↗

bioRxiv2021

Histone demethylase UTX regulates glioblastoma progression through affecting periostin expression

The histone H3K27 demethylase UTX participates in regulating multiple cancer types. However, less is known about the UTX function in glioblastoma (GBM). This study aims to define the effect of UTX on GBM. GEPIA2 database analysis showed that UTX expression was significantly increased in GBM and inversely correlated with survival. Knockdown UTX inhibited GBM cell proliferation, migration, and invasion while promoting apoptosis. Moreover, knockdown UTX also hampered tumor growth in the heterotopic xenograft model. RNA-seq combined with qRT-PCR and ChIP-qPCR were used to identify the target genes. The results showed that the UTX-mediated genes were strongly associated with tumor progression and the extracellular environment. Protein-protein interaction analysis suggested that periostin (POSTN) interacted with most of the other UTX-mediated genes. POSTN supplement abolished the effect of UTX knockdown in GBM cells. Furthermore, silencing UTX exhibited similar antitumor effect in patient-derived glioblastoma stem-like cells, while UTX functions were partially restored after exposing POSTN. Our findings may reveal a new insight into the onset of gliomagenesis and progression, providing a promising therapeutic strategy for GBM treatment. Bullet PointsUTX correlates with survival in glioblastoma. Silencing UTX decreased the levels of H3K27 methylation in the POSTN gene, thereby suppressing POSTN expression. UTX-mediated POSTN expression is crucial for glioblastoma cell growth and tumorigenesis. O_LIUTX expression is increased in GBM and negatively correlated with survival. C_LIO_LIUTX knockdown influences proliferation and apoptosis in both GBM cells and GSCs. C_LIO_LIThe antitumor effect of UTX knockdown is achieved by suppressing POSTN expression. C_LI

cancer biology↗

bioRxiv2021

Classification and Regression Models for Genomic Selection of Skewed Phenotypes: A Case for Disease Resistance in Winter Wheat (Triticum aestivum L.)

Most genomic prediction models are linear regression models that assume continuous and normally distributed phenotypes, but responses to diseases such as stripe rust (caused by Puccinia striiformis f. sp. tritici) are commonly recorded in ordinal scales and percentages. Disease severity (SEV) and infection type (IT) data in germplasm screening nurseries generally do not follow these assumptions. On this regard, researchers may ignore the lack of normality, transform the phenotypes, use generalized linear models, or use supervised learning algorithms and classification models with no restriction on the distribution of response variables, which are less sensitive when modeling ordinal scores. The goal of this research was to compare classification and regression genomic selection models for skewed phenotypes using stripe rust SEV and IT in winter wheat. We extensively compared both regression and classification prediction models using two training populations composed of breeding lines phenotyped in four years (2016-2018, and 2020) and a diversity panel phenotyped in four years (2013-2016). The prediction models used 19,861 genotyping-by-sequencing single-nucleotide polymorphism markers. Overall, square root transformed phenotypes using rrBLUP and support vector machine regression models displayed the highest combination of accuracy and relative efficiency across the regression and classification models. Further, a classification system based on support vector machine and ordinal Bayesian models with a 2-Class scale for SEV reached the highest class accuracy of 0.99. This study showed that breeders can use linear and non-parametric regression models within their own breeding lines over combined years to accurately predict skewed phenotypes.

genetics↗

bioRxiv2021

Opposing regulation of short-term memory by basal ganglia direct and indirect pathways that are coactive during behavior

The basal ganglia direct and indirect pathways are viewed to mediate opposing functions in movement. However, this classic model is challenged by recent findings that both pathways are coactive during behavior. We examined the roles of direct (dSPNs) and indirect (iSPNs) pathway spiny projection neurons in a decision-making task with a short-term memory (STM) component. Optogenetic stimulation of cortical-input-defined dSPNs and iSPNs during STM oppositely biased upcoming licking choice, without affecting licking execution. Optogenetically identified dSPNs and iSPNs showed similar response patterns, although with quantitative difference in spatiotemporal organization. To understand how coactive dSPNs and iSPNs play opposing roles, we recorded population activity in frontal cortex and the basal ganglia output nucleus SNr. Stimulation of dSPNs and iSPNs bidirectionally regulated cortical decision variable through the differential modulation of SNr ramping activity. These results reconcile different views by demonstrating that coactive dSPNs and iSPNs precisely shape cortical activity in a push-pull balance.

neuroscience↗

bioRxiv2021

Fast, live-cell imaging of 15 intracellular compartments by deep learning segmentation of super-resolution data

The number of colors that can be used in fluorescence microscopy to image the live-cell anatomy and organelles interactions is far less than the number of intracellular organelles and compartments. Here, we report that deep convolutional neuronal networks can predict 15 subcellular structures from super-resolution spinning-disk microscopy images using only one dye, one laser excitation, and two detection channels. Comparing to the colocalization images, this method achieves pixel accuracies of over 91.7%, which not only bypasses the fundamental limitation of multi-color imaging but also accelerates the imaging speed by more than one order of magnitude.

cell biology↗

bioRxiv2021

Mechanical ventilation affects the microecology of the rat respiratory tract

BackgroundThe most common second strike in mechanically ventilated patients is a pulmonary infection caused by the ease with which bacteria can invade and colonize the lungs due to mechanical ventilation. At the same time, metastasis of lower airway microbiota may have significant implications in the development of intubation mechanical ventilation lung inflammation. Thus, we establish a rat model of tracheal intubation with mechanical ventilation and explore the effects of mechanical ventilation on lung injury and microbiological changes in rats. MethodsSprague-Dawley rats were randomized into control, Spontaneously Breathing (1, 3, 6 hours), Mechanical ventilation(1, 3, 6 hours) groups. Lung wet to dry weight ratio (W/D weight ratio) and Lung histopathological injury score were evaluated.16SrDNA sequencing was performed to explore respiratory flora changes. ResultsBacterial diversity was comparable between healthy and intubation mechanical ventilation rats, with time relation. Ordination analyses revealed that samples clustered more dispersing by tracheal intubation and mechanical ventilation. Finally, predicted metagenomes suggested a substantial increase in biofilm formation phenotype during early tracheal intubation and mechanical ventilation. ConclusionCollectively, these results establish a link between the duration of mechanical ventilation and alterations to the respiratory tract microecology. In future studies, we hope to discover the effectiveness of new immunomodulatory or probiotic bacteria to prevent airway diseases associated with ventilator therapy.

microbiology↗

bioRxiv2021

Distributed Feedforward and Feedback Processing across Perisylvian Cortex Supports Human Speech

Speech production is a complex human function requiring continuous feedforward commands together with reafferent feedback processing. These processes are carried out by distinct frontal and posterior cortical networks, but the degree and timing of their recruitment and dynamics remain unknown. We present a novel deep learning architecture that translates neural signals recorded directly from cortex to an interpretable representational space that can reconstruct speech. We leverage state-of-the-art learnt decoding networks to disentangle feedforward vs. feedback processing. Unlike prevailing models, we find a mixed cortical architecture in which frontal and temporal networks each process both feedforward and feedback information in tandem. We elucidate the timing of feedforward and feedback related processing by quantifying the derived receptive fields. Our approach provides evidence for a surprisingly mixed cortical architecture of speech circuitry together with decoding advances that have important implications for neural prosthetics.

neuroscience↗

bioRxiv2021

Serum Amyloid A promotes Acetaminophen-induced liverinjury by damaging sinusoidal endothelial cell and exacerbating platelet aggregation in liver

BackgroundAcetaminophen (APAP) is the most commonly used non-prescription antipyretic and analgesic drugs. Overuse of APAP can cause hepatotoxicity. Liver sinusoidal endothelial cells (LSECs) damage is an important early event in APAP-induced liver injury. Serum amyloid A (SAA) is an acute phase protein that mainly produced by hepatocytes, and promotes endothelial dysfunction via a pro-inflammatory and pro-thrombotic effect in atherosclerosis and renal disease. However, the role of SAA in APAP-induced liver injury remains unclear. MethodsIn this study, we used neutralizing antibody (anti-SAA) or antagonistic small peptide derived from sequence of human SAA1/2 (SAA-pep) to block the functional activity of Saa1/2 in mouse serum. Immunohistochemistry staining, Evans blue and platelet adhesion assays were performed to examine the liver damage, the integrity of sinusoidal endothelium and platelets accumulation in APAP-induce liver injury. ResultsOur study showed that in the early stage of APAP-induced acute liver injury in mice, the intrahepatic and serum Saa1/2 levels were significantly increased within 24 hours, and then gradually reduced to normal level from 3 days. Neutralization of Saa1/2 by antibodies or peptides effectively prevented the destruction of hepatic sinusoids, reduced the intrahepatic hemorrhage and platelet accumulation in liver, as well as increased the survival rate of mice treated with lethal dose of APAP. In vitro experiments showed that Saa1/2 aggravated LSECs death induced by APAP. Moreover, Saa1/2 promoted platelets adhesion on LSECs via Tlr2/Vcam-1 axis. ConclusionOur findings suggest that Saa1/2 promotes APAP-induced liver injury by damaged LSECs and exacerbated platelets aggregation. This study provides a potential target for intervention of acute liver injury/failure caused by hepatotoxic drugs such as APAP.

pharmacology and toxicology↗

bioRxiv2021

Epigenetic and Transcriptional Dysregulation in CD4+ T cells of Patients with Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common skin disorders in children. Disease etiology involves genetic and environmental factors, with the 29 independent AD risk loci enriched for risk allele-dependent gene expression in the skin and CD4+ T cell compartments. We investigated epigenetic mechanisms that may account for genetic susceptibility in CD4+ T cells. To understand gene regulatory activity differences in peripheral blood T cells in AD, we measured chromatin accessibility (ATAC-seq), NFKB1 binding (ChIP-seq), and gene expression (RNA-seq) in stimulated CD4+ T cells from subjects with active moderate-to-severe AD and age-matched, non-allergic controls. Open chromatin regions in stimulated CD4+ T cells were highly enriched for AD genetic risk variants, with almost half of AD risk loci overlapping with AD-dependent ATAC-seq peaks. AD-specific open chromatin regions were strongly enriched for NF{kappa}B DNA binding motifs. ChIP-seq identified hundreds of NFKB1-occupied genomic loci that were AD-specific or Control-specific. As expected, the AD-specific ChIP-seq peaks were strongly enriched for NF{kappa}B DNA binding motifs. Surprisingly, Control-specific NKFB1 ChIP-seq peaks were not enriched for NFKB1 motifs, instead containing motifs for other classes of human TFs, suggesting a mechanism involving altered indirect NFKB1 binding. Using DNA sequencing data, we identified 63 instances of genotype-dependent chromatin accessibility at 36 AD risk variants (30% of AD risk loci) that could lead to genotype-dependent expression at these loci. We propose that CD4+ T cells respond to stimulation in an AD-specific manner, resulting in disease and genotype-dependent chromatin accessibility involving NFKB binding. AUTHOR SUMMARYStimulated CD4+ T cells from patients with atopic dermatitis have disease-dependent regulation of how gene expression is regulated. This regulation is disease dependent and the way the DNA is accessible and the transcription factor NFKB1 binds is enriched for genetic risk variants. Clinically, the CD4+ T cells in the peripheral blood of patients with AD respond to stimulation in a disease and genotype-dependent manner.

genomics↗

bioRxiv2021

Representation of Drosophila larval behaviors by muscle activity patterns

How muscle actions are coordinated to realize animal movement is a fundamental question in behavioral study. To obtain the overall muscular activity patterns accompanying behaviors at high spatiotemporal resolution is technically difficult. In this work, we used light sheet microscopy to simultaneously image and analyze the activity, length and orientation of Drosophila larval muscles across body segments at single muscle resolution in nearly free behaviors. For typical behavioral modes such as peristalsis, head cast and turning, larval muscles showed behavioral mode specific activity patterns. Unexpectedly, reorientation of larval head involves muscle tone in the apparently motionless posterior segments. With a STGCN(spatial temporal graph convolution neural network)-Generator model, sequence of larval behavioral poses outlined by morphological patterns of muscles could be accurately predicted based on the time series of ventral but not dorsal muscle activities, and vice versa. Laser ablation of ventral but not dorsal muscles interrupted peristaltic wave and undermined head cast in both frequency and amplitude. Our results provide a simplified muscle activity representation of soft body motion that can be used for probing the key components of animal motor control.

neuroscience↗