Biology subjects

Guo, S.

Publications and source records attributed to Guo, S..

15 recordsLinked to original sources

bioRxiv2018

The design, analysis and application of mouse clinical trials in oncology drug development

Mouse clinical trials (MCTs) are becoming widely used in pre-clinical oncology drug development. In this study, we provide some general guidelines on the design, analysis and application of MCTs. We first established empirical quantitative relationships between mouse number and measurement accuracy for both categorical and continuous efficacy endpoints, and showed that more mice are needed to achieve given accuracy for syngeneic models than for PDXs and CDXs. There is considerable disagreement between categorical methods on calling drug responses as objective response, indicating limitations of such approaches. We then introduced linear mixed models, or LMMs, to describe MCTs as clustered longitudinal studies, which explicitly model growth and drug response heterogeneities across mouse models and among mice within a mouse model. Several case studies were used to demonstrate the advantages of LMMs in discovering biomarkers and exploring a drugs mechanism of action. We also introduced the additive frailty models to perform survival analysis on MCTs, which more accurately estimate hazard ratios by modeling the clustered population structures in MCTs. We performed computational simulations for LMMs and frailty models to generate statistical power curves, and showed that statistical power is close for designs with similar total number of mice at given drug efficacy. Finally, we explained how MCTs can explain discrepant results in clinical trials, hence, MCTs are more than preclinical versions of clinical trials but possess their unique values. Results in the report will make MCTs a better tool for oncology drug development.

cancer biology↗

bioRxiv2018

Covalent Modification and Regulation of the Nuclear Receptor Nurr1 by a Dopamine Metabolite

Nurr1, a nuclear receptor essential for the development, maintenance, and survival of midbrain dopaminergic neurons, is a potential therapeutic target for Parkinsons disease, a neurological disorder characterized by the degeneration of these same neurons. Efforts to identify Nurr1 agonists have been hampered by the recognition that it lacks several classic regulatory elements of nuclear receptor function, including the canonical ligand-binding pocket. Here we report that the dopamine metabolite 5,6-dihydroxyindole (DHI) binds directly to and modulates the activity of Nurr1. Using biophysical assays and x-ray crystallography we show that DHI binds to the ligand binding domain within a non-canonical pocket, forming a covalent adduct with Cys566. In cultured cells and zebrafish, DHI stimulates Nurr1 activity, including the transcription of target genes underlying dopamine homeostasis. These findings suggest avenues for developing synthetic Nurr1 ligands to ameliorate the symptoms and progression of Parkinsons disease.

biophysics↗

bioRxiv2018

Protein Deacetylase CobB Interplays with c-di-GMP

As a ubiquitous bacterial secondary messenger, c-di-GMP plays key regulatory roles in processes such as bacterial motility and transcription regulation. CobB is the Sir2 family protein deacetylase that controls energy metabolism, chemotaxis and DNA supercoiling in many bacteria. Using an E.coli proteome microarray, we found that c-di-GMP strongly binds to CobB. Protein deacetylation assays showed that c-di-GMP inhibits CobB activity and thereby modulates the biogenesis of acetyl-CoA. Through mutagenesis studies, residues R8, R17 and E21 of CobB were shown to be required for c-di-GMP binding. Next, we found that CobB is an effective deacetylase of YdeH, a major diguanylate cyclase (DGC) of E.coli that is endogenously acetylated. Mass spectrometry analysis identified YdeH K4 as the major site of acetylation, and it could be deacetylated by CobB. Interestingly, deacetylation of YdeH enhances its stability and cyclase activity in c-di-GMP production. Thus, our work establishes a novel negative feedback loop linking c-di-GMP biogenesis and CobB-mediated protein deacetylation.

microbiology↗

bioRxiv2018

Identification of biomarker and HPV strain for Cervical Cancer from pre-existing RNAseq data

Human papillomavirus (HPV) increased the risk of afflicting cervical cancer. Among over a hundred strains, HPV-16 and HPV-18 caused 70% of cervical cancers and precancerous cervical lesions (WHO 2018). To reveal the profile of HPV strains, HPViewer is designed by Hao et al. (2018) for metagenomic or human genomic shotgun sequencing data analysis. The application of HPViewer in detecting HPV strains in RNA sequencing data was assessed and results were communicated in the table. The performance of HPViewer in analyzing RNA sequencing data from multiple sources, demonstrated the potential of enlarging the application of HPViewer to RNA sequencing data. Furthermore, we attempted to verify the capability of a potential biomarker p16INK4a in detecting cervical cancer from precancerous lesions. Considering the protein nature of this biomarker, the experiment was designed to detect the differentially expressed gene, associating with this protein function group, in RNA-seq data from two articles. Compare to the findings from Royse et al. (2014), confirmatory result was reproduced that comparisons between both groups yielded insignificant outcome. Since data from single article was insufficient to provide meaningful clue, final dataset was collected from multiple sources. The results were compromised by batch effect, but they supported p16INK4a to be a prospective biomarker for cervical cancer diagnosis.

bioinformatics↗

bioRxiv2018

Sinking rates and export flux of transparent exopolymer particles (TEPs) in a eutrophic coastal sea: a case study in the Changjiang (Yangtze River) estuary

Transparent exopolymer particles (TEPs) are ubiquitous throughout the oceans, and their sedimentation is considered an efficient biological carbon sink pathway. However, the role TEPs play as a carbon sink in eutrophic coastal seas is not well studied. In order to investigate this issue, two cruises in the spring and summer of 2011 were carried out in the Changjiang (Yangtze River) estuary, a typical eutrophic coastal sea. The concentrations, sinking rates, and export flux of TEPs were studied. TEP concentrations ranged from 40.00 to 1040.00 g Xeq L-1 (mean = 209.70 {+/-} 240.93 g Xeq L-1) in spring and from 56.67 to 1423.33 g Xeq L-1 (mean = 433.33 {+/-} 393.02 g Xeq L-1) in summer. A significant positive correlation between TEP concentrations and chlorophyll (Chl) a concentrations was observed. TEP sinking rates ranged from 0.08 to 0.57 m d-1 (mean = 0.28 {+/-} 0.14 m d-1) in spring and from 0.10 to 1.08 m d-1 (mean = 0.34 {+/-} 0.31 m d-1) in summer. TEP sinking rates were always higher in the upper layers than in the deeper layers during both seasons. The export flux of TEPs was also calculated, and it ranged from 4.95 to 29.40 mg C m-2 d-1 in spring (mean = 14.66 {+/-} 8.83 mg C m-2 d-1) and from 6.80 to 30.45 mg C m-2 d-1 (mean = 15.71 {+/-} 8.73 mg C m-2 d-1) in summer. This study is the first study on TEP sinking in the Changjiang (Yangtze River) Estuary, and it confirmed that TEP plays a significant role as a carbon sink in the eutrophic coastal sea.

ecology↗

bioRxiv2018

High glucose-induced ubiquitylation of G6PD leads to the injury of podocyte

Oxidative stress contributes substantially to podocyte injury in diabetic kidney disease. The mechanism of hyperglycemia-induced oxidative stress in podocytes is not fully understood. Glucose-6-phosphate dehydrogenase is critical in maintaining NADPH, an important cofactor for antioxidant system. Here, we hypothesized that high glucose induces ubiquitylation and degradation of G6PD, which injures podocytes by reactive oxygen species (ROS) accumulation. We found that both G6PD protein expression and G6PD activity was decreased in kidneys of both diabetic patients and diabetic rodents. Overexpressing G6PD reversed redox imbalance and podocyte apoptosis induced by high glucose and palmitate. Inhibition of G6PD induced podocyte apoptosis. In G6PD deficient mice, podocyte apoptosis was also largely increased. High glucose had no effect on G6PD mRNA level but it caused decreased G6PD protein expression, which was mediated by the ubiquitin proteasome pathway. Furthermore, von Hippel-Lindau (VHL), an E3 ubiquitin ligase subunit, directly bound to G6PD and degraded G6PD through ubiquitylating G6PD on lysine residues 366/403. Our data suggest that high glucose induces ubiquitylation of G6PD by VHL, which leads to ROS accumulation and podocyte injury.

cell biology↗

bioRxiv2018

Exogenous putrescine alleviates photoinhibition caused by salt stress through increasing cyclic electron flow in cucumber

When plants suffer from abiotic stresses, cyclic electron flow (CEF) is induced for photoprotection. Putrescine (Put), a main polyamine in chloroplasts, plays a critical role in stress tolerance. To elucidate the mechanism of Put regulating CEF for salt-tolerance in cucumber leaves, we measured chlorophyll fluorescence, P700 redox state, ATP and NADPH accumulation and so on. The maximum photochemical efficiency of PSII (Fv/Fm) was not influenced by NaCl and/or Put, but the activity of PSI reaction center (P700) was seriously inhibited by NaCl. Salt stress induced high level of CEF, moreover, NaCl and Put treated plants exhibited much higher CEF activity and ATP accumulation than single salt-treated plants to provide adequate ATP/NADPH ratio for plants growth. Furthermore, Put decreased the trans-membrane proton gradient ({Delta}pH), accompanied by reducing the pH-dependent non-photochemical quenching (qE) and increasing efficient quantum yield of PSII (Y(II)). The ratio of NADP+/NADPH in salt stressed leaves was significantly increased by Put, indicating that Put relieved over-reduction pressure at PSI accepter side. Taken together, our results suggest that exogenous Put enhances CEF to supply extra ATP for PSI recovery and CO2 assimilation, decreases {Delta}pH for electron transport related proteins staying active, and enable the non-photochemical quenching transformed into photochemical quenching.

plant biology↗

bioRxiv2018

Optical activation of TrkA signaling

Nerve growth factor/tropomyosin receptor kinase A (NGF/TrkA) signaling plays a key role in neuronal development, function, survival, and growth. The pathway is implicated in neurodegenerative disorders including Alzheimers disease, chronic pain, inflammation, and cancer. NGF binds the extracellular domain of TrkA, leading to the activation of the receptors intracellular kinase domain. TrkA signaling is highly dynamic, thus mechanistic studies would benefit from a tool with high spatial and temporal resolution. Here we present the design and evaluation of four strategies for light-inducible activation of TrkA in the absence of NGF. Our strategies involve the light-sensitive protein Arabidopsis cryptochrome 2 (CRY2) and its binding partner CIB1. We demonstrate successful recapitulation of native NGF/TrkA functions by optical induction of plasma membrane recruitment and homo-interaction of the intracellular domain of TrkA. This approach activates PI3K/AKT and Raf/ERK signaling pathways, promotes neurite growth in PC12 cells, and supports the survival of dorsal root ganglion neurons in the absence of NGF. This ability to activate TrkA using light bestows high spatial and temporal resolution for investigating NGF/TrkA signaling.

synthetic biology↗

bioRxiv2017

PrimerServer: a high-throughput primer design and specificity-checking platform

SummaryDesigning specific primers for multiple sites across the whole genome is still challenging, especially in species with complex genomes. Here we present PrimerServer, a high-throughput primer design and specificity-checking platform with both web and command-line interfaces. This platform efficiently integrates site selection, primer design, specificity checking and data presentation. In our case study, PrimerServer achieved high accuracy and a fast running speed for a large number of sites, suggesting its potential for molecular biology applications such as molecular breeding or medical testing.\n\nAvailability and ImplementationSource code for PrimerServer is available at https://github.com/billzt/PrimerServer. A demo server is freely accessible at https://primerserver.org, with all major browsers supported.\n\nContactzhangrui@caas.cn or guosandui@caas.cn

bioinformatics↗

bioRxiv2017

Karyotype stability and unbiased fractionation in the paleo-allotetraploid Cucurbita genomes

The Cucurbita genus contains several economically important species in the Cucurbitaceae family. Interspecific hybrids between C. maxima and C. moschata are widely used as rootstocks for other cucurbit crops. We report high-quality genome sequences of C. maxima and C. moschata and provide evidence supporting an allotetraploidization event in Cucurbita. We are able to partition the genome into two homoeologous subgenomes based on different genetic distances to melon, cucumber and watermelon in the Benincaseae tribe. We estimate that the two diploid progenitors successively diverged from Benincaseae around 31 and 26 million years ago (Mya), and the allotetraploidization happened earlier than 3 Mya, when C. maxima and C. moschata diverged. The subgenomes have largely maintained the chromosome structures of their diploid progenitors. Such long-term karyotype stability after polyploidization is uncommon in plant polyploids. The two subgenomes have retained similar numbers of genes, and neither subgenome is globally dominant in gene expression. Allele-specific expression analysis in the C. maxima x C. moschata interspecific F1 hybrid and the two parents indicates the predominance of trans-regulatory effects underlying expression divergence of the parents, and detects transgressive gene expression changes in the hybrid correlated with heterosis in important agronomic traits. Our study provides insights into plant genome evolution and valuable resources for genetic improvement of cucurbit crops.

genomics↗

bioRxiv2017

GFF3sort: An efficient tool to sort GFF3 files for tabix indexing

BackgroundThe traditional method of visualizing gene annotation data in JBrowse is converting GFF3 files to JSON format, which is time-consuming. The latest version of JBrowse supports rendering sorted GFF3 files indexed by tabix, a novel strategy that is more convenient than the original conversion process. However, current tools available for GFF3 file sorting have some limitations and their sorting results would lead to erroneous rendering in JBrowse.\n\nResultsWe developed GFF3sort, a script to sort GFF3 files for tabix indexing. Specifically designed for JBrowse rendering, GFF3sort can properly deal with the order of features that have the same chromosome and start position, either by remembering their original orders or by conducting parent-child topology sorting. Based on our test datasets from seven species, GFF3sort produced accurate sorting results with acceptable efficiency compared with currently available tools.\n\nConclusionsGFF3sort is a novel tool to sort GFF3 files for tabix indexing. We anticipate that GFF3sort will be useful to help with genome annotation data processing and visualization.

bioinformatics↗

bioRxiv2017

Role Of Chymotrypsin-Like Elastase 1 In Lung Physiology And in α1-Antitrypsin Deficiency

1-antitrypsin (AAT) deficiency-related emphysema is the fourth leading indication for lung transplantation. We previously demonstrated that AAT covalently neutralizes chymotrypsin-like elastase 1 (Cela1) in vitro, that Cela1 is expressed during the alveolar stage of lung development in association with regions of lung elastin remodeling, and that lung stretch increases Cela1 expression and binding to lung elastin. Here we show that Cela1 is exclusively responsible for stretch-inducible lung elastase activity, reduces postnatal lung elastance, and is required for emphysema in an antisense oligo model of AAT deficiency. Cela1 mRNA is present in the human lung, and in the placental mammal lineage, Cela1 is more conserved than Cela2 or Cela3 with unique promoter and protein elements indicating a unique role for Cela1 in this lineage. These data demonstrate an adaptive role for Cela1 in placental mammal lung biology with physiologic relevance to AAT-deficient lung disease in humans.

physiology↗

bioRxiv2017

Prototyping And Implementation Of A Novel Feedforward Loop In A Cell-Free Transcription-Translation System And Cells

Building novel synthetic biological devices is a time-consuming task because of the lengthy cell-based testing and optimization processes. Recent progress made in the cell-free field suggests that the utilization of mathematical models and cell-free transcription-translation testing platforms to systematically design and test novel synthetic biocircuits may help streamline some of the processes. Here we present a study of building a novel functional biological network motif from scratch with the aid of the mathematical modeling and the cell-free prototyping. In this work, we demonstrated that we were able to make a 3-promoter feedforward circuit from a concept to a working biocircuit in cells within a month. We started with performing simulations with a cell-free transcription-translation simulation toolbox. After verifying the feasibility of the circuit design, we used a fast assembling method to build the constructs and used the linear DNAs directly in the cell-free system for prototyping. After additional tests and assemblies, we implemented the circuit in plasmid forms in cells and showed that the in vivo results were consistent with the simulations and the outcomes in the cell-free platform. This study showed the usefulness of modeling and prototyping in building synthetic biocircuits and that we can use these tools to help streamline the process of circuit optimizations in future studies.

bioengineering↗

bioRxiv2017

Implementation and System Identification of a Phosphorylation-Based Insulator in a Cell-Free Transcription-Translation System

An outstanding challenge in the design of synthetic biocircuits is the development of a robust and efficient strategy for interconnecting functional modules. Recent work demonstrated that a phosphorylation-based insulator (PBI) implementing a dual strategy of high gain and strong negative feedback can be used as a device to attenuate retroactivity. This paper describes the implementation of such a biological circuit in a cell-free transcription-translation system and the structural identifiability of the PBI in the system. We first show that the retroactivity also exists in the cell-free system by testing a simple negative regulation circuit. Then we demonstrate that the PBI circuit helps attenuate the retroactivity significantly compared to the control. We consider a complex model that provides an intricate description of all chemical reactions and leveraging specific physiologically plausible assumptions. We derive a rigorous simplified model that captures the output dynamics of the PBI. We perform standard system identification analysis and determine that the model is globally identifiable with respect to three critical parameters. These three parameters are identifiable under specific experimental conditions and we perform these experiments to estimate the parameters. Our experimental results suggest that the functional form of our simplified model is sufficient to describe the reporter dynamics and enable parameter estimation. In general, this research illustrates the utility of the cell-free expression system as an alternate platform for biocircuit implementation and system identification and it can provide helpful insights into future biological circuit designs.

bioengineering↗

bioRxiv2017

Expressing Biologically Active Membrane Proteins in a Cell-Free Transcription-Translation Platform

Cell-free transcription-translation platforms have been widely utilized to express soluble proteins in basic synthetic biological circuit prototyping. From a synthetic biology point of view, it is critical to express membrane proteins in cell-free transcription-translation systems, and use them directly in biocircuits, considering the fact that histidine kinases, G-protein coupled receptors (GPCRs) and other important biosensors are all membrane proteins. Previous studies have expressed membrane proteins in cell-free systems with the help of detergents, liposomes or nanodiscs, but have not demonstrated the ability to prototype circuit behavior for the purpose of testing more complex circuit functions involving membrane-bound proteins. Built on previous efforts, in this work we demonstrated that we could co-translationally express solubilized and active membrane proteins in our cell-free TX-TL platform with membrane-like materials. We first tested the expression of several constructs with {beta}1 and {beta}2 adrenergic receptors in TX-TL and observed significant insoluble membrane protein production. The addition of nanodiscs to the cell free expression system enabled solubilization of membrane proteins. Nanodisc is lipoprotein-based membrane-like material. The activity of {beta}2 adrenergic receptor was tested with both fluorescence and Surface Plasmon Resonance (SPR) binding assays by monitoring the specific binding response of small-molecule binders, carazolol and norepinephrine. Our results suggest that it is promising to use cell-free expression systems to prototype synthetic biocircuits involving single chain membrane proteins without extra procedures. This data made us one step closer to testing complex membrane protein circuits in cell-free environment.

bioengineering↗