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Xu, Y.

Publications and source records attributed to Xu, Y..

At least 919 records · Page 51Linked to original sources

Transmission analysis of a large TB outbreak in London: mathematical modelling study using genomic data

Outbreaks of tuberculosis- such as the large isoniazid-resistant outbreak centered on London, United Kingdom, which originated in 1995- provide excellent opportunities to model transmission of this devastating disease. Transmission chains for tuberculosis are notoriously difficult to ascertain, but mathematical modelling approaches, combined with whole-genome sequencing (WGS) data, have strong potential to contribute to transmission analyses. Using such data, we aimed to reconstruct transmission histories for the outbreak using a Bayesian approach, and to use machine learning techniques with patient-level data to identify the key covariates associated with transmission. By using our transmission reconstruction method that accounts for phylogenetic uncertainty, we are able to identify 24 transmission events with reasonable confidence, 11 of which have zero single nucleotide polymorphism (SNP) distance, and as maximum distance of 3. Patient age, alcohol abuse and history of homelessness were found to be the most important predictors of being credible tuberculosis transmitters.

genomics↗

Divergent Cl-and H + pathways underlie transport coupling and gating in CLC exchangers and channels

The CLC family of anion transporting proteins is comprised of secondary active H+-coupled exchangers and of Cl- channels. Both functional subtypes play key roles in human physiology, and mutations causing their dysfunction lead to numerous genetic disorders. Current models suggest that the CLC exchangers do not utilize a classical ping-pong mechanism of antiport, where the transporter sequentially interacts with one substrate at a time. Rather, in the CLC exchangers both substrates bind and translocate simultaneously while moving through partially congruent pathways. How ions of opposite electrical charge bypass each other while moving in opposite directions through a shared permeation pathway remains unknown. Here, we use MD simulations in combination with biochemical and electrophysiological measurements to identify a pair of highly conserved phenylalanine residues that form an aromatic pathway, separate from the Cl- pore, whose dynamic rearrangements enable H+ movement. Mutations of these aromatic residues impair H+ transport and voltage-dependent gating in the CLC exchangers. Remarkably, the role of the aromatic pathway is evolutionarily conserved in CLC channels. Using atomic-scale mutagenesis we show that the electrostatic properties and conformational flexibility of these aromatic residues are essential determinants of channel gating. Our results suggest that Cl- and H+ move through physically distinct and evolutionarily conserved routes through the CLC channels and transporters. We propose a unifying mechanism that describes the gating mechanism of CLC exchangers and channels.

biochemistry↗

KIT ligand protects against both light-induced and genetic photoreceptor degeneration

Photoreceptor cell degeneration is a major cause of blindness and a considerable health burden during aging but effective therapeutic or preventive strategies have not so far become commercially available. Here we show in mouse models that signaling through the tyrosine kinase receptor KIT protects photoreceptor cells against both light-induced and inherited retinal degeneration. Upon light damage, photoreceptor cells upregulate Kit ligand (KITL) and activate KIT signaling, which in turn induces nuclear accumulation of the transcription factor NRF2 and stimulates the expression of the antioxidant gene Hmox1. Conversely, a viable Kit mutation promotes light-induced photoreceptor damage, which is reversed by experimental expression of Hmox1. Furthermore, overexpression of KITL from a viral AAV8 vector prevents photoreceptor cell death and partially restores retinal function after light damage or in genetic models of human retinitis pigmentosa. Hence, application of KITL may provide a novel therapeutic avenue for prevention or treatment of retinal degenerative diseases.

neuroscience↗

THE C99 FRAGMENT OF APP REGULATES CHOLESTEROL TRAFFICKING

The link between cholesterol homeostasis and the cleavage of the amyloid precursor protein (APP), and their relationship to the pathogenesis of Alzheimers disease (AD) is still unknown. Cellular cholesterol levels are regulated by a crosstalk between the plasma membrane (PM), where most of the cholesterol resides, and the endoplasmic reticulum (ER), where the protein machinery that regulates cholesterol resides. This crosstalk between PM and ER is believed to be regulated by lipid-sensing peptide(s) that can modulate the internalization of extracellular cholesterol and/or its de novo synthesis in the ER. Our data here indicates that the 99-aa C-terminal fragment of APP (C99), a cholesterol-binding peptide, regulates cholesterol trafficking between the PM and the ER. In AD models, increases in C99 provoke the upregulation of cholesterol internalization and its delivery to the ER, which in turn result into the loss of lipid homeostasis and the appearance of AD signatures, such as higher production of longer forms of amyloid {beta}. Our data suggest a novel role of C99 as mediator of cholesterol disturbances in AD, and as a potential early hallmark of the disease.

molecular biology↗

The Clinical Significance and Biological Function of DPEP1 in B-cell Acute Lymphoblastic Leukemia

Dehydropeptidase-1 (DPEP1) is a zinc-dependent metalloproteinase abnormally expressed in many cancers. However, its potential role in adults with B-cell acute lymphoblastic leukaemia (ALL) is unknown.\n\nWe found that in adults with common-B-cell ALL high DPEP1 transcript levels at diagnosis was independently-associated with an increased CIR and worse RFS compared with subjects with low transcript levels. We show an increased proliferation and pro-survival role of DPEP1 in B-cell ALL cells via regulation of phosphCREB and p53 which may be the biological basis of the clinical correlation we report. Our data implicate DPEP1 expression in the biology of common B-cell ALL in adults. We report clinical correlates and provide a potential biological basis for these correlations. If confirmed, analyzing DPEP1 transcript levels at diagnosis could help predict therapy-outcomes. Moreover, regulation of DPEP1 expression could be a therapy target in B-cell ALL.

molecular biology↗

Radiation-Induced DNA Damage and Repair Effects on 3D Genome Organization

The three-dimensional structure of chromosomes plays an important role in gene expression regulation and also influences the repair of radiation-induced DNA damage. Genomic aberrations that disrupt chromosome spatial domains can lead to diseases including cancer, but how the 3D genome structure responds to DNA damage is poorly understood. Here, we investigate the impact of DNA damage response and repair on 3D genome folding using Hi-C experiments on wild type cells and ataxia telangiectasia mutated (ATM) patient cells. Fibroblasts, lymphoblasts, and ATM-deficient fibroblasts were irradiated with 5 Gy X-rays and Hi-C was performed after 30 minutes, 24 hours, or 5 days after irradiation. 3D genome changes after irradiation were cell type-specific, with lymphoblastoid cells generally showing more contact changes than irradiated fibroblasts. However, all tested repair-proficient cell types exhibited an increased segregation of topologically associating domains (TADs). This TAD boundary strengthening after irradiation was not observed in ATM deficient fibroblasts and may indicate the presence of a mechanism to protect 3D genome structure integrity during DNA damage repair.

genomics↗

Single Cell Transcriptional Signatures of the Human Placenta in Term and Preterm Parturition

More than 135 million births occur each year; yet, the molecular underpinnings of human parturition in gestational tissues, and in particular the placenta, are still poorly understood. The placenta is a complex heterogeneous organ including cells of both maternal and fetal origin, and insults that disrupt the maternal-fetal dialogue could result in adverse pregnancy outcomes such as preterm birth. There is limited knowledge of the cell type composition and transcriptional activity of the placenta and its compartments during physiologic and pathologic parturition. To fill this knowledge gap, we used scRNA-seq to profile the placental villous tree, basal plate, and chorioamniotic membranes of women with or without labor at term and those with preterm labor. Significant differences in cell type composition and transcriptional profiles were found among placental compartments and across study groups. For the first time, two cell types were identified: 1) lymphatic endothelial decidual cells in the chorioamniotic membranes, and 2) non-proliferative interstitial cytotrophoblasts in the placental villi. Maternal macrophages from the chorioamniotic membranes displayed the largest differences in gene expression (e.g. NFKB1) in both processes of labor; yet, specific gene expression changes were also detected in preterm labor. Importantly, several placental scRNA-seq transcriptional signatures were modulated with advancing gestation in the maternal circulation, and specific immune cell type signatures were increased with labor at term (NK-cell and activated T-cell) and with preterm labor (macrophage, monocyte, and activated T-cell). Herein, we provide a catalogue of cell types and transcriptional profiles in the human placenta, shedding light on the molecular underpinnings and non-invasive prediction of the physiologic and pathologic parturition.\n\nOne sentence summaryThe common molecular pathway of parturition for both term and preterm spontaneous labor is characterized using single cell gene expression analysis of the human placenta.

genomics↗

Low FoxO expression in Drosophila somatosensory neurons protects dendrite growth under nutrient restriction

During prolonged nutrient restriction, developing animals redistribute vital nutrients to favor brain growth at the expense of other organs. In Drosophila, such brain sparing relies on a glia-derived growth factor to sustain proliferation of neural stem cells. However, whether other aspects of neural development are also spared under nutrient restriction is unknown. Here we show that dynamically growing somatosensory neurons in the Drosophila peripheral nervous system exhibit organ sparing at the level of arbor growth: Under nutrient stress, sensory dendrites preferentially grow as compared to neighboring non-neural tissues, resulting in dendrite overgrowth. Underlying this neuronal nutrient-insensitivity is the lower expression of the stress sensor FoxO in neurons. Consequently, nutrient restriction suppresses Tor signaling less and does not induce autophagy in neurons. Preferential dendrite growth is functional desirable because it results in heightened animal responses to sensory stimuli, indicative of a potential survival advantage under environmental challenges.

neuroscience↗

Kinetic Inference Resolves Epigenetic Mechanism of Drug Resistance in Melanoma

Drug-induced dedifferentiation towards a drug-tolerant persister state is a common mechanism cancer cells exploit to escape therapies, posing a significant obstacle to sustained therapeutic efficacy. The dynamic coordination of epigenomic and transcriptomic programs at the early-stage of drug exposure, which initiates and orchestrates these reversible dedifferentiation events, remains largely unexplored. Here we employ high-temporal-resolution multi-omics profiling, information-theoretic approaches, and dynamic system modeling to probe these processes in BRAF-mutant melanoma models and patient specimens. We uncover a hysteretic transition trajectory of melanoma cells in response to oncogene inhibition and subsequent release, driven by the sequential operation of two tightly coupled transcriptional waves, which orchestrate genome-scale chromatin state reconfiguration. Modeling of the transcriptional wave interactions predicts NF-{kappa}B/RelA-driven chromatin remodeling as the underlying mechanism of cell-state dedifferentiation, a finding we validate experimentally. Our results identify critical RelA-target genes that are epigenetically modulated to drive this process, establishing a quantitative epigenome gauge to measure cell-state plasticity in melanomas, which supports the potential use of drugs targeting epigenetic machineries to potentiate oncogene inhibition. Extending our investigation to other cancer models, we identify oxidative stress-mediated NF-{kappa}B/RelA activation as a common mechanism driving cellular transitions towards drug-tolerant persister states, revealing a novel and pivotal role for the NF-{kappa}B signaling axis in linking cellular oxidative stress to cancer progression.

cancer biology↗

Mitochondria branch within Alphaproteobacteria

It is well accepted that mitochondria originated from an alphaproteobacterial-like ancestor. However, the phylogenetic relationship of the mitochondrial endosymbiont to extant alphaproteobacteria remains a subject of discussion. The focus of much debate is whether the affiliation between mitochondria and fast-evolving alphaproteobacterial lineages reflects true homology or artifacts. Approaches such as protein-recoding and site-exclusion have been claimed to mitigate compositional heterogeneity between taxa but this comes at the cost of information loss and the reliability of such methods is so far unjustified. Here we demonstrate that site-exclusion methods produce erratic phylogenetic estimates of mitochondrial origin. We applied alternative strategies to reduce phylogenetic noise by taxon replacement and selective exclusion while keeping site substitution information intact. Cross-validation based on a series of trees placed mitochondria robustly within Alphaproteobacteria.

evolutionary biology↗

Temporal changes in genetic admixture are linked to heterozygosity and health diagnoses in humans

Reproduction between individuals from different ancestral populations creates genetically admixed offspring. Admixture can have positive and negative impacts on individual health, feeding back to population health. Historical and forced migrations, and recent mobility, have brought formerly disparate populations of humans together. Here we sought to better understand how temporal changes in genetic admixture influence levels of heterozygosity and health outcomes. We evaluated variation in ancestry over 100 birth years in 35,842 individuals from a genetic database linked to health records in a population in the Southeastern United States. Analysis of 2,678 ancestrally informative markers revealed increased admixture and heterozygosity for all clinically-defined race groups since 1990. Most groups also exhibited increasing long-range linkage disequilibrium over time. A phenome-wide association study of clinical outcomes detected protective associations with female reproductive disorders and increased risk for diseases with links to autoimmunity dysfunction. These mixed effects have important ramifications for human health.

genetics↗

Phylogenomics provides new insights into gains and losses of selenoproteins among Archaeplastida

Selenoproteins that contain selenocysteine (Sec) are found in all kingdoms of life. Although they constitute a small proportion of the proteome, selenoproteins play essential roles in many organisms. In photosynthetic eukaryotes, selenoproteins have been found in algae but are missing in land plants (embryophytes). In this study, we explored the evolutionary dynamics of Sec incorporation by conveying a genomic search for the Sec machinery and selenoproteins across Archaeplastida. We identified a complete Sec machinery and variable sizes of selenoproteomes in the main algal lineages. However, the entire Sec machinery was missing in the BV clade (Bangiophyceae-Florideophyceae) of Rhodoplantae (red algae) and only partial machinery was found in three species of Archaeplastida, indicating parallel loss of Sec incorporation in different groups of algae. Further analysis of genome and transcriptome data suggests that all major lineages of streptophyte algae display a complete Sec machinery, although the number of selenoproteins is low in this group, especially in subaerial taxa. We conclude that selenoproteins tend to be lost in Archaeplastida upon adaptation to a subaerial or acidic environment. The high number of redox-active selenoproteins found in some bloom-forming marine microalgae may be related to defense against viral infections. Some of the selenoproteins in these organisms may have been gained by horizontal gene transfer from bacteria.

molecular biology↗

Prevalence of antimicrobial resistance genes and integrons in commensal Gram-negative bacteria in a college community

Although the human intestinal microbiome has been shown to harbor antimicrobial drug-resistance genes (ARG), the prevalence of such genes in a healthy population and their impact on extraintestinal infections that occur in that community are not well established. This study sought to identify ARG prevalence and their mobile elements in the intestines of a healthy community population at a California university, and compared these genes to those found in uropathogenic Escherichia coli isolated from patients with community-acquired urinary tract infection (CA-UTI). We isolated Gram-negative bacteria (GNB) from fecal samples of healthy volunteers and screened them by polymerase chain reaction (PCR) for ARG encoding resistance against ampicillin (AMP), trimethoprim-sulfamethoxazole (TMP-SMX), gentamicin (GENT), and colistin (COL). We found antimicrobial resistant GNB from 85 (83%) of 102 non-redundant rectal swab samples. Sixty-seven (66%) of these samples contained {beta}-lactamase genes (blaTEM, blaSHV, blaCTX-M, blaOXA, blaOXY), dihydrofolate reductase (DHFR) genes (dhfr-A17, dhfr-A7, dhfr-A5, dhfr-A21, dhfr-A1, dhfr-A15, and dhfr-B3), and aminoglycoside resistance genes (aadA5, aadA1, and aadB). Integron sequences were found in 37 fecal samples. These genes were found in 11 different GNB species isolated from the fecal samples. The same ARG were found in E. coli strains isolated from patients with CA-UTI examined at the college outpatient health clinic. The high prevalence of clinically-common ARG and integrons harbored by GNB in the intestine of a healthy population suggest that human intestines may serve as a major reservoir of these mobile ARG that appear in E. coli strains causing extraintestinal infections in the same community.\n\nImportanceIncreasing frequency of antimicrobial resistance (AMR) in human pathogenic bacteria has compromised our ability to treat infections. Since mobile antibiotic resistance genes (ARG) are readily exchanged between different species of bacteria through horizontal gene transfer, there is interest in investigating sources of these genes. The normal intestinal flora has been shown to contain a wide variety of ARG, which may have been introduced via food-containing AMR bacteria. We sought to assess the prevalence of ARG carriage in the intestines of a healthy population and determine if these ARG are found in E. coli strains that cause community-acquired urinary tract infection (CA-UTI) in the same community. Our findings indicate that the human intestine may serve as an important reservoir as well as a site in which ARG are transferred into E. coli that cause UTI. Further research is needed to reduce ARG carriage and devise new strategies to prevent AMR infections.

microbiology↗

Metagenomic Nanopore sequencing of influenza virus direct from clinical respiratory samples

Influenza is a major global public health threat as a result of its highly pathogenic variants, large zoonotic reservoir, and pandemic potential. Metagenomic viral sequencing offers the potential of a diagnostic test for influenza which also provides insights on transmission, evolution and drug resistance, and simultaneously detects other viruses. We therefore set out to apply Oxford Nanopore Technology to metagenomic sequencing of respiratory samples. We generated influenza reads down to a limit of detection of 102-103 genome copies/ml in pooled samples, observing a strong relationship between the viral titre and the proportion of influenza reads (p = 4.7x10-5). Applying our methods to clinical throat swabs, we generated influenza reads for 27/27 samples with high-to-mid viral titres (Cycle threshold (Ct) values <30) and 6/13 samples with low viral titres (Ct values 30-40). No false positive reads were generated from 10 influenza-negative samples. Thus Nanopore sequencing operated with 83% sensitivity (95% CI 67-93%) and 100% specificity (95% CI 69-100%) compared to the current diagnostic standard. Coverage of full length virus was dependent on sample composition, being negatively influenced by increased host and bacterial reads. However, at high influenza titres, we were able to reconstruct >99% complete sequence for all eight gene segments. We also detected Human Coronavirus and generated a near complete Human Metapneumovirus genome from clinical samples. While further optimisation is required to improve sensitivity, this approach shows promise for the Nanopore platform to be used in the diagnosis and genetic analysis of influenza and other respiratory viruses.

microbiology↗

Combining statistical and neural network approaches to derive energy functions for completely flexible protein backbone design

A designable protein backbone is one for which amino acid sequences that stably fold into it exist. To design such backbones, a general method is much needed for continuous sampling and optimization in the backbone conformational space without specific amino acid sequence information. The energy functions driving such sampling and optimization must faithfully recapitulate the characteristically coupled distributions of multiplexes of local and non-local conformational variables in designable backbones. It is also desired that the energy surfaces are continuous and smooth, with easily computable gradients. We combine statistical and neural network (NN) approaches to derive a model named SCUBA, standing for Side-Chain-Unspecialized-Backbone-Arrangement. In this approach, high-dimensional statistical energy surfaces learned from known protein structures are analytically represented as NNs. SCUBA is composed as a sum of NN terms describing local and non-local conformational energies, each NN term derived by first estimating the statistical energies in the corresponding multi-variable space via neighbor-counting (NC) with adaptive cutoffs, and then training the NN with the NC-estimated energies. To determine the relative weights of different energy terms, SCUBA-driven stochastic dynamics (SD) simulations of natural proteins are considered. As initial computational tests of SCUBA, we apply SD simulated annealing to automatically optimize artificially constructed polypeptide backbones of different fold classes. For a majority of the resulting backbones, structurally matching native backbones can be found with Dali Z-scores above 6 and less than 2 [A] displacements of main chain atoms in aligned secondary structures. The results suggest that SCUBA-driven sampling and optimization can be a general tool for protein backbone design with complete conformational flexibility. In addition, the NC-NN approach can be generally applied to develop continuous, noise-filtered multi-variable statistical models from structural data.\n\nLinux executables to setup and run SCUBA SD simulations are publicly available (http://biocomp.ustc.edu.cn/servers/download_scuba.php). Interested readers may contact the authors for source code availability.

bioinformatics↗

Clinically-relevant cell type cross-talk identified from a human lung tumor microenvironment interactome

Tumors comprise a complex microenvironment of interacting malignant and stromal cell types. Much of our understanding of the tumor microenvironment comes from in vitro studies isolating the interactions between malignant cells and a single stromal cell type, often along a single pathway. To develop a deeper understanding of the interactions between cells within human lung tumors we performed RNA-seq profiling of flow-sorted malignant cells, endothelial cells, immune cells, fibroblasts, and bulk cells from freshly resected human primary non-small-cell lung tumors. We mapped the cell-specific differential expression of prognostically-associated secreted factors and cell surface genes, and computationally reconstructed cross-talk between these cell types to generate a novel resource we call the Lung Tumor Microenvironment Interactome (LTMI). Using this resource, we identified and validated a prognostically unfavorable influence of Gremlin-1 production by fibroblasts on proliferation of malignant lung adenocarcinoma cells. We also found a prognostically favorable association between infiltration of mast cells and less aggressive tumor cell behavior. These results illustrate the utility of the LTMI as a resource for generating hypotheses concerning tumor-microenvironment interactions that may have prognostic and therapeutic relevance.\n\nSummaryRNA-seq profiling of sorted populations from primary lung cancer samples identifies prognostically relevant cross-talk between cell types in the tumor microenvironment.

cancer biology↗

The methyl cycle is a conserved regulator of biological clocks.

The methyl cycle is a universally conserved metabolic pathway operating in prokaryotes and eukaryotes. In this pathway, the amino acid methionine is used to synthesize S-adenosylmethionine, the methyl donor co-substrate in the methylation of nucleic acids, histone and non-histone proteins and many other molecules within the cell. The methylation of nucleic acids and proteins is the foundation of epigenetic and epitranscriptomic regulations of gene expression, but whether the methyl cycle centrally regulates gene expression and function by controlling the availability of methyl moieties is poorly understood.\n\nFrom cyanobacteria to humans, a circadian clock that involves an exquisitely regulated transcription-translation-feedback loop driving oscillations in gene expression and orchestrating physiology and behavior has been described. We reported previously that inhibition of the methyl cycle in mammalian cells caused the lengthening of the period of these oscillations, suggesting the methyl cycle may indeed act as a central regulator of gene expression, at least in mammals. Here, we investigated whether the methyl cycle, given its universal presence among living beings, regulates the circadian clock in species across the phylogenetic tree of life.\n\nWe reveal a remarkable evolutionary conservation of the link between the methyl cycle and the circadian clock. Moreover, we show that the methyl cycle also regulates the somite segmentation clock, another transcription-translation negative feedback loop-based timing mechanism that orchestrate embryonic development in vertebrates, highlighting the methyl cycle as a master regulator of biological clocks.\n\nSIGNIFICANCE STATEMENTHere we reveal that the methyl cycle, a universal metabolic pathway leading to the synthesis of S-adenosylmethionine, the methyl donor co-substrate in virtually all transmethylation reactions within the cell, is a conserved regulator of biological clocks. These discoveries highlight the methyl cycle as a metabolic hub that regulates gene expression via the availability of methyl moieties for the methylation of nucleic acids, proteins and many other molecules with the cell.

evolutionary biology↗

The Salt-Inducible Kinase inhibitor YKL-05-099 suppresses MEF2C function and acute myeloid leukemia progression in vivo

Lineage-defining transcription factors (TFs) are compelling targets for leukemia therapy, yet they are among the most challenging proteins to modulate directly with small molecules. We previously used CRISPR screening to identify a Salt-Inducible Kinase 3 (SIK3) requirement for the growth of acute myeloid leukemia (AML) cell lines that overexpress the lineage TF MEF2C. In this context, SIK3 maintains MEF2C function by directly phosphorylating histone deacetylase 4 (HDAC4), a repressive cofactor of MEF2C. Here, we evaluated whether inhibition of SIK3 with the tool compound YKL-05-099 can suppress MEF2C function and attenuate disease progression in animal models of AML. Genetic targeting of SIK3 or MEF2C selectively suppressed the growth of transformed hematopoietic cells under in vitro and in vivo conditions. Similar phenotypes were obtained when exposing cells to YKL-05-099, which caused cell cycle arrest and apoptosis in MEF2C-expressing AML cell lines. An epigenomic analysis revealed that YKL-05-099 rapidly suppressed MEF2C function by altering the phosphorylation state and nuclear localization of HDAC4. Using a gatekeeper allele of SIK3, we found that the anti-proliferative effects of YKL-05-099 occurred through on-target inhibition of SIK3 kinase activity. Based on these findings, we treated two different mouse models of MLL-AF9 AML with YKL-05-099, which attenuated disease progression in vivo and extended animal survival at well-tolerated doses. These findings validate SIK3 as a therapeutic target in MEF2C-positive AML and provide a rationale for developing drug-like inhibitors of SIK3 for definitive pre-clinical investigation and for studies in human patients with leukemia.\n\nKey PointsAML cells are uniquely sensitive to genetic or chemical inhibition of Salt-Inducible Kinase 3 in vitro and in vivo.\n\nA SIK inhibitor YKL-05-099 suppresses MEF2C function and AML in vivo.

cancer biology↗