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Lee, S.

Publications and source records attributed to Lee, S..

At least 649 records · Page 36Linked to original sources

Hepatocytic Prominin-1 protects liver fibrosis by stabilizing the SMAD7 protein

Background and AimsProminin-1 (PROM1) is known to be upregulated in hepatocytic progenitor cells (HPCs) and cholangiocytes of fibrotic livers. To understand the function of upregulated PROM1 during liver fibrosis, we analyzed liver fibrosis from global and liver-specific Prom1 knockout mice and investigated the molecular mechanism of how Prom1 protects the liver against liver fibrosis. MethodsWe analyzed PROM1 expression from human liver with mild and severe liver fibrosis (n=4-9). Liver fibrosis was induced by carbon tetrachloride (CCl4) treatment and bile duct ligation (BDL) from wild type and global and liver-specific knockout mice (n=3-13). The severity of liver fibrosis was determined by qRT-PCR, immunostaining and immunoblotting for fibrotic markers such as SMA, collagen. TGF{beta} signaling was also analyzed from fibrotic liver and primary hepatocytes of wild type and global and liver-specific knockout mice (n=3-5). Molecular interaction between PROM1 and SMAD7 was determined by endogenous and exogenous co-immunoprecipitation. ResultsPROM1 was found in the plasma membranes of both healthy and fibrotic hepatocytes and cholangiocytes. Global Prom1 knockout aggravated BDL- and CCl4-induced liver fibrosis. Prom1-/- hepatocytes showed increased TGF{beta} signaling due to reduced SMAD7 protein expression compared to that in wild-type hepatocytes. PROM1 prevented SMURF2-induced SMAD7 ubiquitination and degradation by interfering with the molecular association of SMAD7 with SMURF2. We also demonstrated that liver-specific Prom 1 knockout aggravated BDL-induced liver fibrosis due to reduced levels of SMAD7. ConclusionHepatocytic PROM1 stabilizes SMAD7, preventing TGF{beta} signaling. Thus, PROM1 is necessary for the negative regulation of TGF{beta} signaling during liver fibrosis.

cell biology↗

Measuring three-dimensional dynamics of platelet activation using 3-D quantitative phase imaging

Platelets, or thrombocytes, are anucleated tiny blood cells with an indispensable contribution to the hemostatic properties of whole blood, detecting injured sites at the surface of blood vessels and forming blood clots. Here, we quantitatively and non-invasively investigated the morphological and biochemical alterations of individual platelets during activation in the absence of exogenous agents by employing 3-D quantitative phase imaging (QPI). By reconstructing 3-D refractive index (RI) tomograms of individual platelets, we investigated alterations in platelet activation before and after the administration of various platelet agonists. Our results showed that while the integrity of collagen-stimulated platelets was preserved despite the existence of a few degranulated platelets with developed pseudopods, platelets stimulated by thrombin or thrombin receptor-activating peptide (TRAP) exhibited significantly lower cellular concentration and dry mass than did resting platelets. Our work provides a means to systematically investigate drug-respondents of individual platelets in a label-free and quantitative manner, and open a new avenue to the study of the activation of platelets.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=91 SRC=\"FIGDIR/small/827436v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (39K):\norg.highwire.dtl.DTLVardef@17fe91eorg.highwire.dtl.DTLVardef@a1b25dorg.highwire.dtl.DTLVardef@1c519d8org.highwire.dtl.DTLVardef@123b6dd_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

Comparative microbiomes of three species of laboratory-reared Periplaneta cockroaches

Cockroaches are the most primitive insects, and are often used as the basic insect model in many studies. Three species of Periplaneta cockroaches were raised in the laboratory for many generations under the same conditions. We conducted 16S rRNA-targeted high-throughput sequencing to evaluate the overall bacterial composition in the microbiomes of three species of cockroaches. The number of operational taxonomic units (OTUs) was not significantly different between the three cockroach species. With respect to the Shannon and Pielou indexes, the microbiome of Periplaneta americana presented higher values than that of either P. japonica or P. fulginosa. In terms of species composition, endosymbionts accounted for over half of all the bacterial species in P. japonica and P. fulginosa. The beta diversity analysis showed that P. japonica and P. fulginosa exhibit a similar microbiome composition, which is different from that of P. americana. However, we also identified that P. japonica and P. fulginosa are hosts to distinct bacterial species. Thus, although the composition of the microbiome may vary based on multiple conditions, it is possible to identify distinct compositions of the microbiome among the different Periplaneta cockroach species even when individuals are reared under the same conditions.\n\nImportanceCockroaches inhabit various habitats--which are known to be related to their microbiome--and exhibit different features depending on the species. It is expected that their microbiomes would vary according to species depending on these features. Cockroach microbiomes are known to vary based on the diet or environmental shifts. In this study, we compare the diversity of bacteria in the three cockroach species under conditions of reduced diet and environment shifts. This study can establish the basic microbiomes of three Periplaneta species and can be the basic data for cockroach research.

microbiology↗

Atomic structures determined from digitally defined nanocrystalline regions

Nanocrystallography has transformed our ability to interrogate the atomic structures of proteins, peptides, organic molecules and materials. By probing atomic level details in ordered sub-10 nm regions of nanocrystals, approaches in scanning nanobeam electron diffraction extend the reach of nanocrystallography and mitigate the need for diffraction from large portions of one or more crystals. We now apply scanning nanobeam electron diffraction to determine atomic structures from digitally defined regions of beam-sensitive peptide nanocrystals. Using a direct electron detector, we record thousands of sparse diffraction patterns over multiple crystal orientations. We assign each pattern to a specific location on a single nanocrystal with axial, lateral and angular coordinates. This approach yields a collection of patterns that represent a tilt series across an angular wedge of reciprocal space: a scanning nanobeam diffraction tomogram. From this diffraction tomogram, we can digitally extract intensities from any desired region of a scan in real or diffraction space, exclusive of all other scanned points. Intensities from multiple regions of a crystal or from multiple crystals can be merged to increase data completeness and mitigate missing wedges. Merged intensities from digitally defined regions of two crystals of a segment from the OsPYL/RCAR5 protein produce fragment-based ab-initio solutions that can be refined to atomic resolution, analogous to structures determined by selected area electron diffraction. In allowing atomic structures to now be determined from digitally outlined regions of a nanocrystal, scanning nanobeam diffraction tomography breaks new ground in nanocrystallography.

biophysics↗

Mitochondrial pyruvate carrier is required for optimal brown fat thermogenesis

Brown adipose tissue (BAT) is composed of thermogenic cells that convert chemical energy into heat to help maintain a constant body temperature and counteract metabolic disease in mammals. The metabolic adaptations required for thermogenesis are not fully understood. Here we explore how steady state levels of metabolic intermediates are altered in brown adipose tissue in response to cold exposure. Transcriptome and metabolome analysis revealed changes in pathways involved in amino acid, glucose, and TCA cycle metabolism. Using isotopic labeling experiments, we found that activated brown adipocytes increased labeling of pyruvate and TCA cycle intermediates from U13C-glucose. Although glucose oxidation has been implicated as being essential for thermogenesis, its requirement for efficient thermogenesis has not been directly tested. Here we show that mitochondrial pyruvate uptake is essential for optimal thermogenesis, as conditional deletion of Mpc1 in brown adipocytes leads to impaired cold adaptation. Isotopic labeling experiments using U13C-glucose showed that loss of MPC1 led to impaired labeling of TCA cycle intermediates, while labeling of glycolytic intermediates was unchanged. Loss of MPC1 in BAT increased 3-hydroxybutyrate levels in blood and BAT in response to the cold, suggesting that ketogenesis provides an alternative fuel source that partially compensates for impaired mitochondrial oxidation of cytosolic pyruvate. Collectively, these studies highlight that complete glucose oxidation is essential for optimal brown fat thermogenesis.

biochemistry↗

Compositional and functional differences of the mucosal microbiota along the intestine of healthy individuals

Gut mucosal microbes evolved closest to the host, developing specialized local communities. There is, however, insufficient knowledge of these communities as most studies have employed sequencing technologies to investigate faecal microbiota. This work used shotgun metagenomics of mucosal biopsies to explore the microbial communities compositions of terminal ileum and large intestine in 5 healthy individuals. Functional annotations and genome-scale metabolic modelling of selected species were then employed to identify local functional enrichments. While faecal metagenomics provided a good approximation of the average gut microbiome composition, mucosal biopsies allowed detecting the subtle variations of local microbial communities. Given their significant enrichment in the mucosal microbiota, we highlight the roles of Bacteroides species and describe the antimicrobial resistance biogeography along the intestine. We also detail which species, at which locations, are involved with the tryptophan/indole pathway, whose malfunctioning has been linked to pathologies including inflammatory bowel disease. Our study thus provides invaluable resources for investigating mechanisms connecting gut microbiota and host pathophysiology.

systems biology↗

A powerful subset-based gene-set analysis method identifies novel associations and improves interpretation in UK Biobank

Tests of association between a phenotype and a set of genes in a biological pathway can provide insights into the genetic architecture of complex phenotypes beyond those obtained from single variant or single gene association analysis. However, most existing gene set tests have limited power to detect gene set-phenotype association when a small fraction of the genes are associated with the phenotype, and no method exists which identifies the potentially "active" genes that might drive a gene-set-based association. To address these issues, we have developed Gene-set analysis Association Using Sparse Signals (GAUSS), a method for gene-set association analysis that requires only GWAS summary statistics. For each significantly associated gene set, GAUSS identifies the subset of genes that have the maximal evidence of association and can best account for the gene set association. Using pre-computed correlation structure among test statistics from a reference panel, our p-value calculation is substantially faster than other permutation or simulation-based approaches. In simulations with varying proportions of causal genes, we find that GAUSS effectively controls type 1 error rate and has greater power than several existing methods, particularly when a small proportion of genes account for the gene set signal. Using GAUSS, we analyzed UK Biobank GWAS summary statistics for 10,679 gene-sets and 1,403 binary phenotypes. We found that GAUSS is scalable and identified 13,466 phenotype and gene-set association pairs. Within these genes sets, we identify an average of 17.2 (max=405) genes that underlie these gene set associations.

genetics↗

Single-molecule study of the dynamic organization of Vascular Endothelial Growth Factor Receptor 2 on the endothelial cell surface

The nanoscale organization of cell surface receptors plays an important role in signaling. We determined this organization and its relation to receptor activation for VEGF Receptor-2 (VEGFR-2), a critical receptor tyrosine kinase in endothelial cells (ECs), by combining live-cell single-molecule imaging of endogenous VEGFR-2 with rigorous computational analysis. We found that surface VEGFR-2 can be mobile or immobile/confined, and monomeric or non-monomeric, with a complex interplay between the two. The mobility and interaction heterogeneity of VEGFR-2 in the basal state led to heterogeneity in the sequence of steps leading to VEGFR-2 activation by VEGF. Specifically, we found that VEGF can bind to both monomeric and non-monomeric VEGFR-2, and, when binding to monomeric VEGFR-2, promotes dimer formation but only for immobile/confined receptors. Overall, our study highlights the dynamic and heterogeneous nature of cell surface receptor organization and its complex relationships with receptor activation and signaling.

biophysics↗

Prominin-1-Radixin Axis controls hepatic gluconeogenesis by regulating PKA activity

Prominin-1 (Prom1) is a major cell surface marker of cancer stem cells, but its physiological functions in the liver have not been elucidated. We analyzed the levels of mRNA transcripts in serum-starved primary Prom1+/+ and Prom1-/- mouse hepatocytes using RNA-sequencing (RNA-seq) data, and found that CREB target genes were down-regulated. This initial observation led us to determine that the Prom1 deficiency inhibited cAMP response element binding protein (CREB) activation and gluconeogenesis, but not cyclic AMP (cAMP) accumulation, in glucagon-, epinephrine-, or forskolin-treated liver tissues and primary hepatocytes, and mitigated glucagon-induced hyperglycemia. Because Prom1 interacted with radixin, the Prom1 deficiency prevented radixin from localizing to the plasma membrane. Moreover, systemic adenoviral knockdown of radixin inhibited CREB activation and gluconeogenesis in glucagon-treated liver tissues and primary hepatocytes, and mitigated glucagon-elicited hyperglycemia. Based on these results, we conclude that Prom1 regulates hepatic PKA signaling via radixin functioning as an A kinase-anchored protein (AKAP).

cell biology↗

Neuromodulation of pelvic nerve during early phase of spinal cord injury in rats using implantable prototype devices - a preliminary study.

ObjectivesThe bladder becomes retentive during the early phase of spinal cord injury, and requires proper bladder management to prevent damage to the lower urinary tract and kidney. We investigated the effects of on-demand pelvic nerve stimulation on the areflexive bladder during the earliest phase of complete spinal cord injury in rats and the use of pelvic nerve signals as a proxy to estimate intravesical pressure for closed-loop applications.\n\nMaterials and MethodsIn order to stimulate the pelvic nerves in female Sprague-Dawley rats with complete spinal cord transection (T7 level), a flexible electrode was implanted unilaterally on pelvic nerve, and electrical stimulation was provided by a custom-built nerve stimulator. Stimulation-evoked voiding was monitored in the awake state while size, capacity and spontaneous contractions of the bladder were analysed under anaesthesia. Separately, recordings of the pelvic nerve signals, external urethral sphincter activity and intravesical pressure were performed in animals with intact and transected spinal cord under anaesthesia.\n\nResultsSuccessful pelvic nerve stimulation enabled more frequent voiding, reduced overdistension of bladder, and preserved non-voiding spontaneous bladder contractions. Typical bladder management protocol for SCI rats (manual expression every 8 - 12 hours) resulted in more severe bladder overdistention. Signal processing of the recorded extraneural pelvic nerve signals successfully reconstructed changes in intravesical pressure, demonstrating their use in estimating the fullness and contractions of the bladder.\n\nConclusionsThe preliminary results suggest that pelvic nerve stimulators can serve as an alternative method for frequent emptying of the areflexive bladder. Simultaneous recording of the same pelvic nerve will be useful for development of a closed-loop neuroprosthesis.

neuroscience↗

Subjective value, not a grid-like code, describes neural activity in ventromedial prefrontal cortex during value-based decision-making

Across many studies, ventromedial prefrontal cortex (vmPFC) activity has been found to correlate with subjective value during value-based decision-making. Recently, however, vmPFC has also been shown to reflect a hexagonal gridlike code during navigation through physical and conceptual space. This raises the possibility that the subjective value correlates previously observed in vmPFC may have actually been a misconstrued gridlike signal. Here, we first show that, in theory, a hexagonal gridlike code of two-dimensional attribute space could mimic vmPFC activity previously attributed to subjective value. However, using fMRI data from a large number of subjects performing an intertemporal choice task, we show clear and unambiguous evidence that subjective value is a better description of vmPFC activity than a hexagonal gridlike code. In fact, we find no significant evidence at all for a hexagonal gridlike code in vmPFC activity during intertemporal choice. This result limits the generality of gridlike modulation as description of vmPFC activity. We suggest that vmPFC may flexibly switch representational schemes so as to encode the most relevant information for the current task.

neuroscience↗

Genomewide association study reveals transient loci underlying the genetic architecture of biomass accumulation under cold stress in Sorghum.

Sorghum bicolor is a promising cellulosic feedstock crop for bioenergy because of its potential for high biomass yields. However, in its early growth phases, sorghum is sensitive to cold stress, preventing early planting in temperate environments. Cold temperature adaptability is vital for the successful cultivation of both bioenergy and grain sorghum at higher latitudes and elevations, and for early season planting or to extend the growing season. Identification of genes and alleles that enhance biomass accumulation of sorghum grown under early cold stress would enable the development of improved bioenergy sorghum through breeding or genetic engineering. We conducted image-based phenotyping on 369 accessions from the sorghum Bioenergy Association Panel (BAP) in a controlled environment with early cold treatment. The BAP is a collection of densely genotyped and racially, geographically, and phenotypically diverse accessions. The plants were weighed, watered, and imaged daily to measure growth dynamics and water use efficiency (WUE). Daily, non-destructive imaging allowed for a temporal analysis of growth-related traits in response to cold stress. We performed a genome-wide association study (GWAS) to identify candidate genomic intervals and genes controlling response to early cold stress. GWAS identified transient quantitative trait loci (QTL) strongly associated with each growth-related trait, permitting an investigation into the genetic basis of cold stress response at different stages of development. The analysis identified a priori and novel candidate genes associated with growth-related traits and the temporal response to cold stress.\n\nSIGNIFICANCE STATEMENTGenome-wide association study of bioenergy sorghum accessions phenotyped under early season cold stress revealed transient QTLs for highly heritable biomass and growth-related traits that appeared as the temperature increased and plants developed. Sorghum accessions clustered into multiple groups for each heritable trait with distinct growth profiles. GWAS identified candidate genes associated with growth traits and cold stress responses. The top-performing accessions with the highest growth-related trait values over time and temperature shifts will be useful for further genetic analysis and breeding or engineering efforts directed at biomass yield enhancements.

plant biology↗

A supragranular nexus for the effects of neocortical beta events on human tactile perception

Transient neocortical events with high spectral power in the 15-29Hz beta band are among the most reliable predictors of sensory perception: High prestimulus beta event rates in primary somatosensory lead to sensory suppression, most effective at 100-300ms prestimulus latency. However, the synaptic and neuronal mechanisms inducing betas perceptual effects have not been completely localized. We combined human MEG with neural modeling designed to account for these macroscale signals to interpret the cellular and circuit mechanisms that underlie the influence of beta on tactile detection. Extending prior studies, we modeled the hypothesis that higher-order thalamic bursts, sufficient for beta event generation in cortex, recruit supragranular GABAB inhibition acting on a 300ms time scale to suppress sensory information. Consistency between model and MEG data supported this hypothesis and led to a further prediction, validated in our data, that stimuli are perceived when beta events occur simultaneously with tactile stimulation. The post-event suppressive mechanism explains an array of studies that associate beta with decreased processing, while the during-event mechanism may demand a reinterpretation of the role of beta events in the context of coincident timing.\n\nSignificance statementSomatosensory beta events - transient 15-29Hz oscillations in electromagnetic recordings - are thought to be generated when \"top-down\" bursts of spikes presumably originating in higher-order thalamus arrive in upper layers of somatosensory cortex. Physiological evidence had shown that the immediate action of these top-down projections should be excitatory; however, after a beta event, sensory perception is noticeably inhibited for approximately 300ms. The source of this post-event sensory suppression, in particular, had been unresolved. Using a detailed computational model of somatosensory cortex, we find evidence for the hypothesis that these bursts couple indirectly to GABAB inhibition in upper layers of cortex, and that beta events first briefly disinhibit sensory relay before a longer period of inhibition.

neuroscience↗

Loss of BubR1 Acetylation instigates Replication Stress leading to Complex Chromosomal Rearrangement in tumors

Chromosome number and structure instability is the hallmark of cancer. Equal chromosome segregation is guaranteed by the spindle assembly checkpoint (SAC), thus defective SAC leads to chromosome instability. However, aneuploidy alone is not oncogenic, and whether compromised SAC is associated with structure instability remains elusive. BubR1 is a core component of SAC, which is acetylated at lysine 250 in mitosis. Previously, we showed that deficiency of BubR1 acetylation in mice (K243R/+) leads to spontaneous tumorigenesis via chromosome mis-segregation. Here, we asked whether loss of BubR1 acetylation is associated with chromosome structure instability by examining K243R/+ mice intercrossed to p53-deficient mice. Genome-wide sequencing and spectral karyotyping of the double mutant mouse tumors revealed that BubR1 acetylation deficiency leads to complex chromosome rearrangements, including Robertsonian-like whole-arm translocations and premature sister-chromatid separations (PMSCS). In primary MEFs, replication stress was markedly increased in telomeres and centromeres, suggesting that the replication stress underlies the significant increase of DNA damage and subsequent chromosome rearrangements. Furthermore, defects in BubR1 acetylation at K250 were detected in human cancers as well. Collectively, we propose that chromosome mis-segregation by the loss of BubR1 acetylation causes chromosome structure instability, leading to massive chromosome rearrangements through the induction of replication stress.

cancer biology↗

Epigenetics biomarkers of delirium: immune response, inflammatory response and cholinergic synaptic involvement evidenced by genome-wide DNA methylation analysis of delirious inpatients

BackgroundThe authors previously hypothesized the role of epigenetics in pathophysiology of delirium, and tested DNA methylation (DNAm) change among pro-inflammatory cytokines along with aging in blood, glia and neuron. The authors reported that DNAm level of the TNF-alpha decreases along with aging in blood and glia, but not in neuron; however, DNAm differences between delirium cases and non-delirium controls have not been investigated directly. Therefore, in the present study, DNAm differences in blood between delirium patients and controls without delirium were examined.\n\nMethodsA case-control study with 92 subjects was conducted. Whole blood samples were collected and genome-wide DNAm was measured by the Infinium HumanMethylationEPIC BeadChip arrays. The correlation between DNAm levels in the TNF-alpha and age, network analysis, and the correlation between age and DNAm age were tested.\n\nResultsOnly delirium cases showed 3 CpGs sites in the TNF-alpha significantly correlated to age after multiple corrections. A genome-wide significant CpG site near the gene of LDLRAD4 was identified. In addition, network analysis showed several significant pathways with false discovery rate adjusted p-value < 0.05. The top pathway with GO was immune response, and the second top pathway with KEGG was cholinergic synapse. Although there was no statistically significant difference, DNAm age among non-delirium controls showed \"slower aging\" compared to delirium cases.\n\nConclusionsDNAm differences were shown both at gene and network levels between delirium cases and non-delirium controls. This finding indicates that DNAm status in blood has a potential to be used as epigenetic biomarkers for delirium.

neuroscience↗

DNA methylation change in neurotrophic genes with aging and delirium evidenced from three independent cohorts

INTRODUCTIONWe previously reported the association between DNA methylation (DNAm) of pro-inflammatory cytokine genes and aging. Neurotrophic factors are also known to be associated with aging and neurocognitive disorders. Thus, we hypothesized that DNAm of neurotrophic genes change with aging, especially in delirium patients.\n\nMETHODSDNAm were analyzed using HumanMethylationEPIC BeadChip Kit in 3 independent cohorts; blood from 383 Grady Trauma Project subjects, brain from 21 neurosurgery patients, and blood from 87 inpatients with and without delirium.\n\nRESULTSBoth blood and brain samples showed that most of the DNAm of neurotrophic genes were positively correlated with aging. Furthermore, DNAm of neurotrophic genes were positively correlated with aging in delirium cases than in non-delirium controls.\n\nDISCUSSIONThese findings support our hypothesis that the neurotrophic genes may be epigenetically modulated with aging, and this process may be contributing to the pathophysiology of delirium.

neuroscience↗

Lipid droplet accumulating microglia represent a dysfunctional and pro-inflammatory state in the aging brain

Microglia become progressively activated and seemingly dysfunctional with age, and genetic studies have linked these cells to the pathogenesis of a growing number of neurodegenerative diseases. Here we report a striking buildup of lipid droplets in microglia with aging in mouse and human brains. These cells, which we call lipid droplet-accumulating microglia (LAM), are defective in phagocytosis, produce high levels of reactive oxygen species, and secrete pro-inflammatory cytokines. RNA sequencing analysis of LAM revealed a transcriptional profile driven by innate inflammation distinct from previously reported microglial states. An unbiased CRISPR-Cas9 screen identified genetic modifiers of lipid droplet formation; surprisingly, variants of several of these genes, including progranulin, are causes of autosomal dominant forms of human neurodegenerative diseases. We thus propose that LAM contribute to age-related and genetic forms of neurodegeneration.

neuroscience↗

Convolutional neural network model to predict causal risk factors that share complex regulatory features

Major progress in disease genetics has been made through genome-wide association studies (GWASs). One of the key tasks for post-GWAS analyses is to identify causal noncoding variants with regulatory function. Here, on the basis of > 2,000 functional features, we developed a convolutional neural network framework for combinatorial, nonlinear modeling of complex patterns shared by risk variants scattered among multiple associated loci. When applied for major psychiatric disorders and autoimmune diseases, neural and immune features, respectively, exhibited high explanatory power while reflecting the pathophysiology of the relevant disease. The predicted causal variants were concentrated in active regulatory regions of relevant cell types and tended to be in physical contact with transcription factors while residing in evolutionarily conserved regions and resulting in expression changes of genes related to the given disease. We demonstrate some examples of novel candidate causal variants and associated genes. Our method is expected to contribute to the identification and functional interpretation of causal noncoding variants in post-GWAS analyses.

genetics↗