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Liu, T.

Publications and source records attributed to Liu, T..

At least 19 recordsLinked to original sources

The Effects of Global Signal Regression on Estimates of Resting-state BOLD fMRI and EEG Vigilance Correlations

Global signal regression (GSR) is a commonly used albeit controversial preprocessing approach in the analysis of resting-state BOLD fMRI data. While the effects of GSR on resting-state functional connectivity measures have received much attention, there has been relatively little attention devoted to its effects on studies looking at the relation between resting-state BOLD measures and independent measures of brain activity. In this study we used simultaneously acquired EEG-fMRI data in humans to examine the effects of GSR on the correlation between resting-state BOLD fluctuations and EEG vigilance measures. We show that GSR leads to a positive shift in the correlation between the BOLD and vigilance measures. This shift leads to a reduction in the spatial extent of negative correlations in widespread brain areas, including the visual cortex, but leads to the appearance of positive correlations in other areas, such as the cingulate gyrus. The results obtained using GSR are consistent with those of a temporal censoring process in which the correlation is computed using a temporal subset of the data. Since the data from these retained time points are unaffected by the censoring process, this finding suggests that the positive correlations in cingulate gyrus are not simply an artifact of GSR.

neuroscience

A heterochromatic histone methyltransferase lowers nucleosome occupancy at euchromatic promoters

H3K9me3 (histone H3 modified with tri-methylation at lysine 9) is a hallmark of transcriptional silencing and heterochromatin. However, its global effects on the genome, including euchromatin, are less well understood. Here we develop Formaldehyde-Assisted Identification of Regulatory Elements (FAIRE) for C. elegans to examine the chromatin configuration of mutants that lack virtually all H3K9me3, while leaving H3K9me1 and H3K9me2 intact. We find that nucleosomes are mildly disrupted, and levels of H3K9me2 and H3K27me3 rise in mutant embryos. In addition to these expected changes, the most dramatic change occurs in euchromatin: many regions encompassing transcription start sites (TSSs) gain an average of two nucleosomes in mutants. The affected regions normally lack H3K9me3, revealing a locus non-autonomous role for H3K9me3. Affected TSSs are associated with genes that are active in epithelia and muscles, and implicated in development, locomotion, morphogenesis and transcription. Mutant embryos develop normally under ideal laboratory conditions but die when challenged, with defects in morphogenesis and development. Our findings reveal that H3K9me3 protects transcription start sites within euchromatin from nucleosome deposition. These results may be relevant to mammals, where diseases that disrupt the nuclear lamina and heterochromatin can alter epithelial and muscle gene expression.

developmental biology

A wrappable microwire electrode for awake, chronic interfacing with small diameter autonomic peripheral nerves

Bioelectronic medicine requires the ability to monitor and modulate nerve activity in awake patients over time. The vagus nerve is a promising stimulation target, and preclinical models often use mice. However, an awake, chronic mouse vagus nerve interface has yet to be demonstrated. Here, we developed a functional wrappable microwire electrode to chronically interface with the small diameter mouse cervical vagus nerve ([~]100 m). In an acute setting, the wrappable microwire had similar recording performance to commercially available electrodes. A chronic, awake mouse model was then developed to record spontaneous compound action potentials (CAPs). Viable signal-to-noise ratios (SNRs) were obtained from the wrappable microwires between 30 and 60 days (n = 8). Weekly impedance measurements showed no correlation between SNR or time. The wrappable microwires successfully interfaced with small diameter nerves and has been validated in a chronic, awake preclinical model, which can better facilitate clinical translation for bioelectronic medicine.

bioengineering

Rapidly Assessing the Quality of Targeted Proteomics Experiments Through Monitoring Stable-isotope Labeled Standards

Targeted proteomics experiments based on selected reaction monitoring (SRM) have gained wide adoption in clinical biomarker, cellular modeling and numerous other biological experiments due to their highly accurate and reproducible quantification. The quantitative accuracy in targeted proteomics experiments is reliant on the stable-isotope, heavy-labeled peptide standards which are spiked into a sample and used as a reference when calculating the abundance of endogenous peptides. Therefore, the quality of measurement for these standards is a critical factor in determining whether data acquisition was successful. With improved MS instrumentation that enables the monitoring of hundreds of peptides in hundreds to thousands of samples, quality assessment is increasingly important and cannot be performed manually. We present Q4SRM, a software tool that rapidly checks the signal from all heavy labeled peptides and flags those that fail quality control metrics. Using four metrics, the tool detects problems both with individual SRM transitions and the collective group of transitions that monitor a single peptide. The programs speed enables its use at the point of data acquisition and can be ideally run immediately upon the completion of an LC-SRM-MS analysis.

bioinformatics

Characterization and mechanism of lead and zinc biosorption by growing Verticillium insectorum J3

Verticillium insectorum J3 was isolated from a local lead-zinc deposit tailing, and its biosorption characteristics and reaction to the toxicities of different Pb(II) and Zn(II) concentrations were investigated. SEM, FTIR, a pH test and a desorption experiment were carried out to identify a possible mechanism. The biosorption of J3 presented an inhibition trend at low concentrations (25-75 mg L-1) and promotion at high concentrations (100-300 mg L-1). J3 absorbed Pb(II) prior to Zn(II) and produced alkaline substances, while mycelial and pellet morphology modifications were important for the removal of Pb(II) and Zn(II) under different stressful conditions (SEM results). Both intracellular accumulation and extracellular absorption may contribute to the removal of Pb(II) at lower concentrations (25-50 mg L-1), although mainly extracellular biosorption occurred at higher concentrations (75-300 mg L-1). However, Zn(II) bioaccumulation occurred at all concentrations assayed. Verticillium insectorum J3 may have evolved active defenses to alleviate the toxicity of heavy metals and proved to be a highly efficient biosorbent, especially for Pb(II) at high concentrations. This study is a useful reference for the development of biotreatment technologies to mitigate heavy metal waste.

microbiology

Surge of Corticocardiac Coupling in SHRSP Rats Exposed to Forebrain Cerebral Ischemia

Sudden death is an important but under-recognized consequence of stroke. Acute stroke can disturb central control of autonomic function, and result in cardiac dysfunction and sudden death. Previous study showed that bilateral common carotid artery ligation (BCCAL) in spontaneously hypertensive stroke-prone rats (SHRSP) is a well-established model for forebrain ischemic sudden death. This study aims to investigate the temporal dynamic changes in electrical activities of the brain and heart and functional interactions between the two vital organs following forebrain ischemia. EEG and ECG signals were simultaneously collected from 9 SHRSP and 8 Wistar-Kyoto (WKY) rats. RR interval and cardiac arrhythmias were analyzed to investigate the cardiac response to brain ischemia. EEG power and coherence (CCoh) analysis were conducted to study the cortical response. Corticocardiac coherence (CCCoh) and directional connectivity (CCCon) were analyzed to determine brain-heart connection. Heart rate variability (HRV) was analyzed to evaluate autonomic functionality. BCCAL resulted in 100% mortality in SHRSP within 14 hours, whereas no mortality was observed in WKY. The functionality of both the brain and the heart were significantly altered in SHRSP compared to WKY after BCCAL. SHRSP rats, but not WKY rats, exhibited intermittent surge of CCCoh, which paralleled the elevated CCCon and reduced HRV, following the onset of ischemia until sudden death. Elevated brain-heart coupling invariably associated with the disruption of the autonomic nervous system and the risk of sudden death. This study may improve our understanding of the mechanism of ischemic stroke-induced sudden death.

physiology

Feasibility of constructing multi-dimensional genomic maps of juvenile idiopathic arthritis

BackgroundJuvenile idiopathic arthritis (JIA) is one of the most common chronic conditions of childhood. Like many common chronic human illnesses, JIA likely involves complex interactions between genes and the environment, mediated by the epigenome. Such interactions are best understood through multi-dimensional genomic maps that identify critical genetic and epigenetic components of the disease. However, constructing such maps in a cost-effective way is challenging, and this challenge is further complicated by the challenge of obtaining biospecimens from pediatric patients at time of disease diagnosis, prior to therapy, as well as the limited quantity of biospecimen that can be obtained from children,particularly those who are unwell. In this paper, we demonstrate the feasibility and utility of creating multi-dimensional genomic maps for JIA from limited sample numbers.\n\nMethodsTo accomplish our aims, we used an approach similar to that used in the ENCODE and Roadmap Epigenomics projects, which used only 2 replicates for each component of the genomic maps. We used genome-wide DNA methylation sequencing, whole genome sequencing on the Illumina 10x platform, RNA sequencing, and chromatin immunoprecipitation-sequencing for informative histone marks (H3K4me1 and H3K27ac) to construct a multi-dimensional map of JIA neutrophils, a cell we have shown to be important in the pathobiology of JIA.\n\nResultsThe epigenomes of JIA neutrophils display numerous differences from those from healthy children. DNA methylation changes, however, had only a weak effect on differential gene expression. In contrast, H3K4me1 and H3K27ac, commonly associated with enhancer functions, strongly correlated with gene expression. Furthermore, although unique/novel enhancer marks were associated with insertion-deletion events (indels) identified on whole genome sequencing, we saw no strong association between epigenetic changes and underlying genetic variation. The initiation of treatment in JIA is associated with a re-ordering of both DNA methylation and histone modifications, demonstrating the plasticity of the epigenome in this setting.\n\nConclusionsThese findings, generated from a small number of patient samples, demonstrate how multidimensional genomic studies may yield new understandings of biology of JIA and provide insight into how therapy alters gene expression patterns.

genomics

HMMRATAC, the Hidden Markov ModeleR for ATAC-seq

ATAC-seq has been widely adopted to identify accessible chromatin regions across the genome. However, current data analysis still utilizes approaches initially designed for ChIP-seq or DNase-seq, without taking into account the transposase digested DNA fragments that contain additional nucleosome positioning information. We present the first dedicated ATAC-seq analysis tool, a semi-supervised machine learning approach named HMMRATAC. HMMRATAC splits a single ATAC-seq dataset into nucleosome-free and nucleosome-enriched signals, learns the unique chromatin structure around accessible regions, and then predicts accessible regions across the entire genome. We show that HMMRATAC outperforms the popular peak-calling algorithms on published human and mouse ATAC-seq datasets.

bioinformatics

TOXOPLASMA ACTIVATES HOST HYPOXIA INDUCIBLE FACTOR-1 BY CYTOPLASMIC TRAPPING AND LAMP1-DEPENDENT LYSOSOMAL DEGRADATION OF PROLYL-HYDROXYLASE 2

Hypoxia Inducible Factor-1 is a metazoan heterodimeric transcription factor that senses changes in O2 levels. HIF-1 subunit abundance is post-translationally regulated by prolyl-hydroxylase domain enzymes (PHDs), which use molecular O2 and -ketoglutarate to hydroxylate two prolyl-residues in HIF-1. Three PHDs have been identified and PHD2 is the most critical regulator of HIF-1. HIF-1 can also be activated independently of hypoxia and in some cases this is due to changes in PHD2 abundance through poorly understood mechanisms. Previously, we reported that under O2-replete conditions that the intracellular parasite Toxoplasma gondii activates HIF-1 by reducing PHD2 protein abundance. Here, we demonstrate that Toxoplasma regulates PHD2 through a multistep process. First, PHD2 is a nucleocytoplasmic protein and Toxoplasma induces PHD2 cytoplasmic accumulation to separate it from nuclear HIF-1. PHD2 is then degraded by lysosomes independently of the major autophagic processes, macroautophagy or chaperone-mediated autophagy. Rather, PHD2 interacts with the major lysosomal membrane protein, LAMP1, which is required for HIF-1 activation. These data therefore highlight for the first time that cytoplasmic trapping and subsequent lysosomal degradation of a host nucleocytoplasmic protein is a mechanism used by a microbial pathogen to regulate host gene expression.

cell biology

Open-pFind enables precise, comprehensive and rapid peptide identification in shotgun proteomics

Shotgun proteomics has grown rapidly in recent decades, but a large fraction of tandem mass spectrometry (MS/MS) data in shotgun proteomics are not successfully identified. We have developed a novel database search algorithm, Open-pFind, to efficiently identify peptides even in an ultra-large search space which takes into account unexpected modifications, amino acid mutations, semi- or non-specific digestion and co-eluting peptides. Tested on two metabolically labeled MS/MS datasets, Open-pFind reported 50.5-117.0% more peptide-spectrum matches (PSMs) than the seven other advanced algorithms. More importantly, the Open-pFind results were more credible judged by the verification experiments using stable isotopic labeling. Tested on four additional large-scale datasets, 70-85% of the spectra were confidently identified, and high-quality spectra were nearly completely interpreted by Open-pFind. Further, Open-pFind was over 40 times faster than the other three open search algorithms and 2-3 times faster than three restricted search algorithms. Re-analysis of an entire human proteome dataset consisting of [~]25 million spectra using Open-pFind identified a total of 14,064 proteins encoded by 12,723 genes by requiring at least two uniquely identified peptides. In this search results, Open-pFind also excelled in an independent test for false positives based on the presence or absence of olfactory receptors. Thus, a practical use of the open search strategy has been realized by Open-pFind for the truly global-scale proteomics experiments of today and in the future.

bioinformatics

Dynamic virulence-related regions of the fungal plant pathogen Verticillium dahliae display remarkably enhanced sequence conservation

Selection pressure impacts genomes unevenly, as different genes adapt with differential speed to establish an organisms optimal fitness. Plant pathogens co-evolve with their hosts, which implies continuously adaption to evade host immunity. Effectors are secreted proteins that mediate immunity evasion, but may also typically become recognized by host immune receptors. To facilitate effector repertoire alterations, in many pathogens, effector genes reside in dynamic genomic regions that are thought to display accelerated evolution, a phenomenon that is captured by the two-speed genome hypothesis. The genome of the vascular wilt pathogen Verticillium dahliae has been proposed to obey to a similar two-speed regime with dynamic, lineage-specific regions that are characterized by genomic rearrangements, increased transposable element activity and enrichment in in planta-induced effector genes. However, little is known of the origin of, and sequence diversification within, these lineage-specific regions. Based on comparative genomics among Verticillium spp. we now show differential sequence divergence between core and lineage-specific genomic regions of V. dahliae. Surprisingly, we observed that lineage-specific regions display markedly increased sequence conservation. Since single nucleotide diversity is reduced in these regions, host adaptation seems to be merely achieved through presence/absence polymorphisms. Increased sequence conservation of genomic regions important for pathogenicity is an unprecedented finding for filamentous plant pathogens and signifies the diversity of genomic dynamics in host-pathogen co-evolution.

microbiology

Thermoneutrality induces skeletal muscle myopathy via brown adipose tissue in an IRF4- and myostatin-dependent manner

Skeletal muscle and brown adipose tissue (BAT) share a common lineage and have been functionally linked, as exercise increases browning through the actions of various myokines. It is unknown, however, whether BAT can affect skeletal muscle function. Our prior work has shown that loss of the transcription factor IRF4 in BAT (BATI4KO) reduces adaptive thermogenesis. Here, we note that these mice also have reduced exercise capacity relative to wild-type littermates, associated with diminished mitochondrial function, ribosomal protein synthesis, and mTOR signaling in muscle, in addition to the signature ultrastructural abnormalities of tubular aggregate myopathy. Within brown adipose tissue, loss of IRF4 caused the induction of a myogenic gene expression signature, which includes an increase in the secreted factor myostatin, a known inhibitor of muscle function. Reduction of myostatin activity by the injection of neutralizing antibodies or soluble ActRIIB receptor rescued the exercise capacity of BATI4KO mice. Additionally, overexpression of IRF4 in brown adipocytes reduced serum myostatin and increased mitochondrial function and exercise capacity in muscle. A physiological role for this system is suggested by the observation that mice housed at thermoneutrality show lower exercise capacity with increased serum myostatin; both of these abnormalities are corrected by surgical removal of BAT. Collectively, our data point to an unsuspected level of BAT-muscle cross-talk driven by IRF4 and myostatin.\n\nHighlightsO_LIMice lacking IRF4 in BAT have a decrease in exercise capacity, accompanied by histological, ultrastructural, signaling, gene expression, and bioenergetic evidence of myopathy in white vastus.\nC_LIO_LILoss of IRF4 promotes the expression of a myogenic signature in BAT, including the myokine myostatin.\nC_LIO_LINeutralization of serum myostatin rescues the ability of BATI4KO mice to exercise normally, while overexpression of IRF4 in BAT allows mice to run better than wild-type counterparts.\nC_LIO_LIThermoneutrality reduces the level of IRF4 in BAT of WT mice, resulting in a myopathic phenotype that can be reversed by surgical excision of BAT.\nC_LI

physiology

Differential role of prefrontal and parietal cortices in controlling level of consciousness

There is current controversy regarding the role of prefrontal versus posterior cortices in consciousness. Clinical and correlative data have been used both to support and refute a causal role for prefrontal cortex in the level of consciousness, but a definitive relationship has not been demonstrated. We used anesthetic-induced unconsciousness as a model system to study the effect of cholinergic and noradrenergic stimulation of rat prefrontal and posterior parietal cortices on the level of consciousness. We demonstrate that cholinergic stimulation of prefrontal cortex, but not parietal cortical areas, restored wakefulness in rats despite continuous exposure to sevoflurane anesthesia. Noradrenergic stimulation of the prefrontal or parietal areas did not reverse the anesthetized state. We conclude that cholinergic mechanisms in prefrontal cortex can control the level of consciousness.\n\nOne Sentence SummaryPrefrontal cholinergic stimulation restores consciousness in rats despite continuous exposure to sevoflurane anesthesia

neuroscience

Characterization of mannitol metabolism genes in Saccharina explains its key role in mannitol biosynthesis and evolutionary significance in Laminariales

As a unique photosynthetic product in brown algae, mannitol exhibits high synthesis and accumulation in Saccharina japonica. Mannitol acts as a carbon-storage compound and is an osmoprotectant, imparting increased tolerance to osmotic stress. However, the underlying biochemical and molecular mechanisms in macroalgae have not been studied. Analysis of genomic and transcriptomic data has shown that mannitol metabolism in S. japonica is a circular pathway composed of four steps. In this study, one S. japonica mannitol-1-phosphate dehydrogenase (M1PDH2) and two mannitol-1-phosphatase (M1Pase) proteins were recombinantly expressed to analysis enzyme biochemical properties. RNA sequencing and droplet digital polymerase chain reaction were used to analyze the gene expression patterns of mannitol metabolism in different generations, tissues, sexes, and abiotic stresses. Our findings revealed insights into the mannitol synthesis pathways in brown algae. All genes were constitutively expressed in all samples, allowing maintenance of basic mannitol anabolism and dynamic maintenance of the \"saccharide pool\" in vivo as the main storage and antistress mechanism. Enzyme assays confirmed that the recombinant proteins produced mannitol, with the specific activity of SjaM1Pase1 being 1.8-4831 times that of other algal enzymes. Combined with the transcriptional analysis, SjaM1Pase1 was shown to be the dominant gene of mannitol metabolism. Mannitol metabolism genes in multicellular filamentous (gametophyte) and large parenchyma thallus (sporophyte) generations had different expression levels and responded differently under environmental stresses (hyposaline and hyperthermia) in gametophytes and sporophytes. The considerable variation in enzyme characteristics and expression of mannitol synthesis genes suggest their important ecophysiological significance in the evolution of complex systems (filamentous and thallus) and environmental adaptation of Laminariales.

molecular biology

The brown alga Saccharina japonica features distinct vanadium-dependent bromoperoxidases and iodoperoxidases

Marine algae have an extraordinary ability to absorb halogens which provide algae with an inorganic antioxidant impacting atmospheric chemistry. Although brown algal Laminariales species are the most efficient iodine accumulators among all living systems, and Saccharina japonica is the primary material used for iodine extraction, the functions and regulatory mechanisms of these species have not been fully documented. In this study, a functional genomics analysis of the algal vanadium-dependent haloperoxidase (vHPO) gene family was conducted; there genes can introduce halogen atoms into organic compounds. The comprehensive analyses regarding the bioinformatics and phylogenetics of novel genomic and transcriptomic sequencing data of 21 Rhodophyta and 19 Ochrophyta marine algal species revealed that brown algal vHPOs have two gene types, vanadium-dependent bromoperoxidase (vBPO) and vanadium-dependent iodoperoxidase (vIPO), with secondary endosymbiotic host origin. The enzyme activity of S. japonica vBPO and vIPO were verified for the first time and were quite stable in a wide range of temperature and pH values. However, the specific activity and optimal conditions were considerably different between vBPO and vIPO. The transcript expression analysis in different S. japonica tissues (including rhizoids), generations (sporophytes and gametophytes), sexes (male and female), and stress conditions (hyposaline and hyperthermia) also showed great differences between vBPOs and vIPOs. Most of the vBPOs were constitutively expressed with higher expression dose, which may be responsible for basal halogen metabolism. On the contrary, vIPOs mainly showed specific expression, which may be involved in tissue differentiation, generation differentiation, sex differentiation, and stress regulation. Comprehensive analysis of gene family evolution, enzyme biochemical characteristics, and complex transcriptional mechanisms were conducive to the environmental adaptation and sophisticated system evolution of Laminariales. The successful bromination of small-molecule compound substrate by SjavBPO provided high activity and efficient enzymatic tools for artificial synthesis of halogenated compounds.

molecular biology

Template-based prediction of vigilance fluctuations in resting-state fMRI

Changes in vigilance or alertness during a typical resting state fMRI scan are inevitable and have been found to affect measures of functional brain connectivity. Since it is not often feasible to monitor vigilance with EEG during fMRI scans, it would be of great value to have methods for estimating vigilance levels from fMRI data alone. A recent study, conducted in macaque monkeys, proposed a template-based approach for fMRI-based estimation of vigilance fluctuations. Here, we use simultaneously acquired EEG/fMRI data to investigate whether the same template-based approach can be employed to estimate vigilance fluctuations of awake humans across different resting-state conditions. We first demonstrate that the spatial pattern of correlations between EEG-defined vigilance and fMRI in our data is consistent with the previous literature. Notably, however, we observed a significant difference between the eyes-closed (EC) and eyes-open (EO) conditions finding stronger negative correlations with vigilance in regions forming the default mode network and higher positive correlations in thalamus and insula in the EC condition when compared to the EO condition. Taking these correlation maps as \"templates\" for vigilance estimation, we found that the template-based approach produced fMRI-based vigilance estimates that were significantly correlated with EEG-based vigilance measures, indicating its generalizability from macaques to humans. We also demonstrate that the performance of this method was related to the overall amount of variability in a subjects vigilance state, and that the template-based approach outperformed the use of the global signal as a vigilance estimator. In addition, we show that the template-based approach can be used to estimate the variability across scans in the amplitude of the vigilance fluctuations. We discuss the benefits and tradeoffs of using the template-based approach in future fMRI studies.

neuroscience

Cerebral blood flow predicts differential neurotransmitter activity

Application of metabolic magnetic resonance imaging measures such as cerebral blood flow in translational medicine is limited by the unknown link of observed alterations to specific neurophysiological processes. In particular, the sensitivity of cerebral blood flow to activity changes in specific neurotransmitter systems remains unclear. We address this question by probing cerebral blood flow in healthy volunteers using seven established drugs with known dopaminergic, serotonergic, glutamatergic and GABAergic mechanisms of action. We use a novel framework aimed at disentangling the observed effects to contribution from underlying neurotransmitter systems. We find for all evaluated compounds a reliable spatial link of respective cerebral blood flow changes with underlying neurotransmitter receptor densities corresponding to their primary mechanisms of action. The strength of these associations with receptor density is mediated by respective drug affinities. These findings suggest that cerebral blood flow is a sensitive brain-wide in-vivo assay of metabolic demands across a variety of neurotransmitter systems in humans.

neuroscience

SPIN1 promotes tumorigenesis by blocking the uL18-MDM2-p53 pathway

Ribosomal proteins (RPs) play important roles in modulating the MDM2-p53 pathway. However, less is known about the upstream regulators of the RPs. Here we identify SPIN1 (Spindlin 1) as a novel binding partner of human RPL5/uL18 that is important for this pathway. SPIN1 ablation activates p53, suppresses cell growth, reduces clonogenic ability, and induces apoptosis of cancer cells by sequestering uL18 in the nucleolus, preventing it from interacting with MDM2, and thereby alleviating uL18-mediated inhibition of MDM2 ubiquitin ligase activity towards p53. SPIN1 deficiency increases ribosome-free uL18 and uL5 (human RPL11), which are required for SPIN1 depletion-induced p53 activation. Analysis of cancer genomic databases suggests that SPIN1 is highly expressed in several human cancers, and its overexpression is positively correlated with poor prognosis in cancer patients. Altogether, our findings reveal that the oncogenic property of SPIN1 is highly attributed to its negative regulation of uL18, leading to p53 inactivation.

cancer biology