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Turner, D.

Publications and source records attributed to Turner, D..

30 records · Page 2Linked to original sources
bioRxiv2022

Candidatus Liberibacter asiaticus reduces callose and reactive oxygen species production in the phloem

Huanglongbing (HLB) causes significant economic loss in citrus production worldwide. HLB is caused by Candidatus Liberibacter asiaticus (CLas), a gram-negative bacterium which inhabits the phloem exclusively. CLas infection results in accumulation of callose and reactive oxygen species in the phloem of infected plants, but little is known about the specific processes that take place during infection because of the sparse distribution of bacteria and the inaccessibility of the phloem inside the tree. In this study, we used the seed vasculatures, which accumulate a high number of CLas, as a model tissue to study CLas-host cellular interactions. In vasculature where CLas is abundant, sieve pore callose and H2O2 concentration were reduced compared to healthy seed vasculature. The expression of callose synthases (CalS) and respiratory burst oxidase homolog (RBOH) genes were downregulated in infected seeds compared to healthy ones. In leaves of HLB-infected plants, H2O2 concentration and CalS expression increased compared to uninfected leaves, but cells with CLas had lower levels of sieve plate callose compared to cells without CLas. Our results provide evidence that the bacteria manipulate cell metabolism to disable plant defenses and suggests that HLB disease is the result of a constant arms-race between the pathogen and a defense response, which is ultimately harmful to the host plant.

plant biology↗
bioRxiv2021

The RNA m6A binding protein YTHDF2 promotes the B cell to plasma cell transition.

To identify roles of RNA binding proteins (RBPs) in the differentiation of B cells to antibody-secreting plasma cells we performed a CRISPR/Cas9 knockout screen of 1213 mouse RBPs for their ability to affect proliferation and/or survival, and the emergence of differentiated CD138+ cells in vitro. We identified RBPs that promoted the appearance of CD138+ cells including CSDE1 and STRAP, as well as RBPs that inhibited CD138+ cell appearance such as EIF3 subunits EIF3K and EIF3L. Furthermore, we identified RBPs that share the property of recruiting the CCR4-NOT complex to their target transcripts have the potential to mediate opposing outcomes on B cell differentiation. One such RBP, the m6A binding protein YTHDF2 promotes the appearance of CD138+ cells in vitro. In chimeric mouse models YTHDF2-deficient B cells formed germinal centers in a cell-autonomous manner, however plasma cells failed to accumulate.

immunology↗
bioRxiv2020

Diversity of carbapenem-resistant Acinetobacter baumannii and bacteriophage-mediated spread of the Oxa23 carbapenemase

Carbapenem-resistant A. baumannii are prevalent in low- and middle-income countries such as Egypt, but little is known about the molecular epidemiology and mechanisms of resistance in these settings. Here we characterise carbapenem-resistant A. baumannii from Alexandria, Egypt, and place it in a regional context. 54 carbapenem-resistant isolates from Alexandria Main University Hospital, Egypt, collected between 2010 and 2015 were genome sequenced using Illumina technology. Genomes were de novo assembled and annotated. Genomes for 36 isolates from the Middle East region were downloaded from GenBank. Core gene compliment was determined using Roary, and analyses of recombination were performed in Gubbins. MLST sequence type and antibiotic resistance genes were identified. The majority of Egyptian isolates belonged to one of 3 major clades, corresponding to Pasteur MLST clonal complex (CCPAS) 1, CCPAS2 and sequence type (STPAS) 158. Strains belonging to STPAS158 have been reported almost exclusively from North Africa, the Middle East and Pakistan, and may represent a region-specific lineage. All isolates carried an oxa23 gene, six carried blaNDM-1, and one carried blaNDM-2. The oxa23 gene was located on a variety of different mobile elements, with Tn2006 predominant in CCPAS2 strains, and Tn2008 predominant in other lineages. Of particular concern, in 8 of the 11 CCPAS1 strains, the carbapenemase gene was located in a temperate bacteriophage phiOXA, previously identified only once before in a CCPAS1 clone from the US military. The carbapenem-resistant A. baumannii population in Alexandria Main University hospital is very diverse, and indicates an endemic circulating population, including a region-specific lineage. The major mechanism for oxa23 dissemination in CCPAS1 isolates appears to be a bacteriophage, presenting new concerns about the ability of these carbapenemases to spread throughout the bacterial population. Data SummaryThe whole genome shotgun sequences of the isolates from this study have been deposited at DDBJ/ENA/GenBank under the BioProject accession number PRJNA659545. The individual genome accession numbers for each isolate are as follows: A1a, JACSUC000000000; A2, JACSUB000000000; A4, JACSVQ000000000; A5, JACSUA000000000; A6, JACSTZ000000000; A7-T, JACSVP000000000; A8-T, JACSVO000000000; A8a, JACSTY000000000; A9, JACSTX000000000; A10, JACSTW000000000; A10a, JACSTV000000000; A11a, JACSTU000000000; A13a, JACSTT000000000; A14a, JACSTS000000000; A15, JACSTR000000000; A16, JACSTQ000000000; A18, JACSTP000000000; A21, JACSVN000000000; A22, JACSTO000000000; A27, JACSTN000000000; A30, JACSTM000000000; A31, JACSTL000000000; A34, JACSTK000000000; A35, JACSTJ000000000; A36, JACSTI000000000; A39, JACSTH000000000; A40, JACSTG000000000; A41, JACSTF000000000; A42, JACSTE000000000; A43, JACSTD000000000; A44, JACSTC000000000; A45, JACSTB000000000; A46, JACSTA000000000; A64, JACSSZ000000000; A68, JACSSY000000000; A69, JACSSX000000000; A70, JACSSW000000000; A71, JACSVM000000000; A72, JACSSV000000000; A73, JACSSU000000000; A74, JACSST000000000; A75, JACSSS000000000; A78, JACSSR000000000; A82, JACSSQ000000000; A83, JACSVL000000000; A84, JACSSP000000000; A85, JACSSO000000000; A86, JACSVK000000000; A87, JACSSN000000000; A88, JACSSM000000000; A89, JACSSL000000000; A92, JACSSK000000000; A5910, JACSSJ000000000; A6135, JACSVJ000000000.

microbiology↗
bioRxiv2020

Effectiveness of Growth Hormone Releasing Hormone Agonists (GHRH A) in Chronic Kidney Disease Induced Heart Failure with Preserved Ejection Fraction

BackgroundTherapies that improve morbidity and mortality in heart failure with preserved ejection fraction (HFpEF) are lacking. Growth hormone releasing hormone analogues (GHRH-A) reverse fibrosis and improve cardiac function in ischemic and non-ischemic animal models. We tested the hypothesis that GHRH-A treatment ameliorates chronic kidney disease (CKD)-induced HFpEF in a large animal model. MethodsFemale Yorkshire pigs (n=16) underwent 5/6 nephrectomy via renal artery embolization, which induced HFpEF, and 12-weeks later received daily subcutaneous injections of GHRH-A (n=8) or placebo (n=8). Kidney function, renal and cardiac MRI, pressure-volume loops, and electrical stimulation were assessed at baseline, 12-weeks, and 16-18 weeks post-embolization. ResultsThe CKD model was confirmed by increased creatinine and BUN. HFpEF was demonstrated at 12 weeks by maintenance of ejection fraction associated with increased left ventricular mass, relative wall thickening, end-diastolic pressure (EDP), end-diastolic pressure-volume relationship (EDPVR), and tau. After 6 weeks of treatment, diastolic function improved in the GHRH-A group, evidenced by normalization of EDP (p=0.03) associated with improved diastolic compliance as measured by EDP/EDV ratio (p=0.018). ConclusionA beneficial effect of GHRH-A in diastolic function was observed in a CKD large animal model that manifests the characteristics of HFpEF. These findings have important therapeutic implications for the HFpEF syndrome.

physiology↗
bioRxiv2019

Gene sharing networks to automate genome-based prokaryotic viral taxonomy

Viruses of bacteria and archaea are likely to be critical to all natural, engineered and human ecosystems, and yet their study is hampered by the lack of a universal or scalable taxonomic framework. Here, we introduce vConTACT 2.0, a network-based application to establish prokaryotic virus taxonomy that scales to thousands of uncultivated virus genomes, and integrates confidence scores for all taxonomic predictions. Performance tests using vConTACT 2.0 demonstrate near-identical correspondence to the current official viral taxonomy (>85% genus-rank assignments at 96% accuracy) through an integrated distance-based hierarchical clustering approach. Beyond "known viruses", we used vConTACT 2.0 to automatically assign 1,364 previously unclassified reference viruses to tentative taxa, and scaled it to modern metagenomic datasets for which the reference network was robust to adding 16,000 viral contigs. Together these efforts provide a systematic reference network and an accurate, scalable taxonomic analysis tool that is critically needed for the research community.

bioinformatics↗
bioRxiv2018

661W photoreceptor cell line as a cell model for studying retinal ciliopathies

The retina contains several ciliated cell types, including the retinal pigment epithelium (RPE) and photoreceptor cells. The photoreceptor cilium is one of the most highly modified sensory cilia in the human body. The outer segment of the photoreceptor is a highly elaborate primary cilium, containing stacks or folds of membrane where the photopigment molecules are located. Perhaps unsurprisingly, defects in cilia often lead to retinal phenotypes, either as part of syndromic conditions involving other organs, or in isolation in the so-called retinal ciliopathies.\n\nThe study of retinal ciliopathies has been limited by a lack of retinal cell lines. RPE1 retinal pigment epithelial cell line is commonly used in such studies, but the existence of a photoreceptor cell line has largely been neglected in the retinal ciliopathy field. 661W cone photoreceptor cells, derived from mouse, have been widely used as a model for studying macular degeneration, but not described as a model for studying retinal ciliopathies such as retinitis pigmentosa.\n\nHere, we characterise the 661W cell line as a model for studying retinal ciliopathies. We fully characterise the expression profile of these cells over many passages, using whole transcriptome RNA sequencing, and provide this data on Gene Expression Omnibus (GEO) for the advantage of the scientific community. We show that these cells robustly express the majority of markers of cone cell origin, including short wave and medium wave opsin. Western blotting confirms expression of selected markers.\n\nUsing immunostaining and confocal microscopy, alongside scanning electron microscopy, we show that these cells grow long primary cilia, reminiscent of photoreceptor outer segments, and localise many cilium proteins to the axoneme, membrane and transition zone. Immunostaining shows that opsins are localised to the base of this primary cilium. We show that siRNA knockdown of cilia genes Ift88 results in loss of cilia, and that this can be assayed by high-throughput screening. We present evidence that the 661W cell line is a useful cell model for studying retinal ciliopathies.

cell biology↗
bioRxiv2018

Evaluation of the NCCN guidelines using the RIGHT Statement and AGREE II instrument: a cross-sectional review.

IntroductionRobust, clearly reported clinical practice guidelines (CPGs) are essential for evidence-based clinical practice. The Reporting Items for practice Guidelines in HealThcare (RIGHT) statement and Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument were published to improve the methodological and reporting quality in healthcare CPGs.\n\nMethodsWe applied the RIGHT statement checklist and AGREE II instrument to 48 National Comprehensive Cancer Network (NCCN) guidelines. Our primary objective was to assess the adherence to RIGHT and AGREE II items. Since neither RIGHT nor AGREE-II can judge the clinical usefulness of a guideline, our study is designed to only focus on the methodological and reporting quality of each guideline.\n\nResultsThe NCCN guidelines demonstrated notable strengths and weaknesses. For example, RIGHT statement items 19 (conflicts of interest), 7b (description of subgroups), and 13a (clear, precise recommendations) were fully reported in all guidelines. However, the guidelines inconsistently incorporated patient values and preferences and cost, nor did they consistently describe the method for assessing the quality and certainty of evidence. Regarding the AGREE II instrument, the NCCN guidelines scored highly on the domains 4 (clear, precise recommendations) and 6 (handling of conflicts of interest), but lowest on domain 2 (inclusion of all relevant stakeholders).\n\nConclusionsIn this investigation we found that NCCN CPGs demonstrate key strengths and weaknesses with respect to the reporting of key items essential to CPGs. We recommend the continued use of NCCN guidelines and adherence to the RIGHT and AGREE II items. Doing so serves to improve the evidence delivered to healthcare providers, thus potentially improving patient care.

epidemiology↗
bioRxiv2018

Treatment-Specific Composition of Gut Microbiota Is Associated with Disease Remission in a Pediatric Crohn’s Disease Cohort

BackgroundThe beneficial effects of antibiotics in Crohns disease (CD) depend in part on the gut microbiota but are inadequately understood. We investigated the impact of metronidazole (MET) and metronidazole plus azithromycin (MET+AZ) on the microbiota in pediatric CD, and the use of microbiota features as classifiers or predictors of disease remission.\n\nMethods16S rRNA-based microbiota profiling was performed on stool samples from 67 patients in a multinational, randomized, controlled, longitudinal, 12-week trial of MET vs. MET+AZ in children with mild to moderate CD. Profiles were analyzed together with disease activity, and then used to construct Random Forest models to classify remission or predict treatment response.\n\nResultsBoth MET and MET+AZ significantly decreased diversity of the microbiota and caused large treatment-specific shifts in microbiota structure at week 4. Disease remission was associated with a treatment-specific microbiota configuration. Random Forest models constructed from microbiota profiles pre- and during antibiotic treatment with metronidazole accurately classified disease remission in this treatment group (AUC of 0.879, 95% CI 0.683, 0.9877; sensitivity 0.7778; specificity 1.000, P < 0.001). A Random Forest model trained on preantibiotic microbiota profiles predicted disease remission at week 4 with modest accuracy (AUC of 0.8, P = 0.24).\n\nConclusionsMET and MET+AZ antibiotic regimens in pediatric CD lead to distinct gut microbiota structures at remission. It may be possible to classify and predict remission based in part on microbiota profiles, but larger cohorts will be needed to realize this goal.\n\nSummaryWe investigated the impact of metronidazole and metronidazole plus azithromycin on the gut microbiota in pediatric Crohns disease. Disease remission was associated with a treatment-specific microbiota configuration, and could be predicted based on pre-antibiotic microbiota profiles.

microbiology↗
bioRxiv2018

Convergent evolution of psilocybin biosynthesis by psychedelic mushrooms

Psilocybin is a psychoactive compound with clinical applications produced by dozens of mushroom species1. There has been a longstanding interest in psilocybin research with regard to treatment for addiction2, depression3, and end-of-life suffering4. However, until recently very little was known about psilocybin biosynthesis and its ecological role. Here we confirm and refine recent findings5 about the genes underpinning psilocybin biosynthesis, discover that there is more than one psilocybin biosynthesis cluster in mushrooms, and we provide the first data directly addressing psilocybins ecological role. By analysing independent genome assemblies for the hallucinogenic mushrooms Psilocybe cyanescens and Pluteus salicinus we recapture the recently discovered psilocybin biosynthesis cluster5,6 and show that a transcription factor previously implicated in its regulation is actually not part of the cluster. Further, we show that the mushroom Inocybe corydalina produces psilocybin but does not contain the established biosynthetic cluster, and we present an alternative cluster. Finally, a meta-transcriptome analysis of wild-collected mushrooms provides evidence for intra-mushroom insect gene expression of flies whose larvae grow inside Psilocybe cyanescens. These larvae were successfully reared into adults. Our results show that psilocybin does not confer complete protection against insect mycophagy, and the hypothesis that it is produced as an adaptive defense compound may need to be reconsidered.

evolutionary biology↗
bioRxiv2017

Juicebox.js provides a cloud-based visualization system for Hi-C data

Contact mapping experiments such as Hi-C explore how genomes fold in 3D. Here, we introduce Juicebox.js, a cloud-based web application for exploring the resulting datasets. Like the original Juicebox application, Juicebox.js allows users to zoom in and out of such datasets using an interface similar to Google Earth. Furthermore, Juicebox.js encodes the exact state of the browser in a shareable URL. Creating a public browser for a new Hi-C dataset does not require coding and can be accomplished in under a minute.

bioinformatics↗
bioRxiv2017

Gastruloids develop the three body axes in the absence of extraembryonic tissues and spatially localised signalling

Establishment of the three body axes is a critical step during animal development. In mammals, genetic studies have shown that a combination of precisely deployed signals from extraembryonic tissues position the anteroposterior axis (AP) within the embryo and lead to the emergence of the dorsoventral (DV) and left-right (LR) axes. We have used Gastruloids, embryonic organoids, as a model system to understand this process and find that they are able to develop AP, DV and LR axes as well as to undergo axial elongation in a manner that mirror embryos. The Gastruloids can be grown for 160 hours and form derivatives from ectoderm, mesoderm and endoderm. We focus on the AP axis and show that in the Gastruloids this axis is registered in the expression of T/Bra at one pole that corresponds to the tip of the elongation. We find that localisation of T/Bra expression depends on the combined activities of Wnt/{beta}-Catenin and Nodal/Smad2,3 signalling, and that BMP signalling is dispensable for this process. Furthermore, AP axis specification occurs in the absence of both extraembryonic tissues and of localised sources of signalling. Our experiments show that Nodal, together with Wnt/{beta}-Catenin signalling, is essential for the expression of T/Bra but that Wnt signalling has a separable activity in the elongation of the axis. The results lead us to suggest that, in the embryo, the role of the extraembryonic tissues might not be to induce the axes but to bias an intrinsic ability of the embryo to break its initial symmetry and organise its axes.\n\nOne sentence summaryCulture of aggregates of defined number of Embryonic Stem cells leads to self-organised embryo-like structures which, in the absence of localised signalling from extra embryonic tissues and under the autonomous influence of Wnt and Nodal signalling, develop the three main axes of the body.

developmental biology↗