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Das, S.

Publications and source records attributed to Das, S..

At least 361 records · Page 20Linked to original sources
bioRxiv2020

Development of a sensitive molecular diagnostic assay for detecting Borrelia burgdorferi DNA from blood of Lyme disease patients by digital PCR.

Lyme disease patients would benefit greatly from a timely, sensitive and specific molecular diagnostic test that can detect the causal agent, Borrelia burgdorferi, at the onset of symptoms. Currently available diagnostic methods recommended by the Centers for Disease Control and Prevention for Lyme disease, involve indirect serological tests that rely on the detection of a host-antibody response which often takes more than three weeks to develop. This results in non-detection of many genuine cases on a timely basis, preventing complete cure. In this study we have developed a digital PCR (polymerase chain reaction) assay that detects Lyme disease on clinical presentation at twice the sensitivity of the currently available diagnostic methods, using a cohort of patient samples collected from the Lyme disease endemic state of Connecticut, USA in 2016-2018. Digital PCR technology was chosen as it is more advanced and sensitive than other PCR techniques in detecting rare targets and the lower limit of detection of this diagnostic assay was found to be three genome copies of B. burgdorferi. The paucity of spirochetes in the bloodstream of Lyme disease patients that hinders the clinical adoption of PCR-based diagnostic tests, was overcome by using a comparatively larger sample volume, pre-analytical processing of blood samples and a pre-amplification step to enrich for B. burgdorferi-specific gene targets before using the digital PCR technology to analyze patient samples. Pre-analytical processing of blood samples from acute patients revealed that the best sample type for Lyme disease detection is platelet-rich plasma and not whole blood. If detected on time, Lyme disease can be cured completely limiting the overuse of antibiotics and associated morbidities.

molecular biology↗
bioRxiv2020

DNA glycosylase NEIL2 prevents Fusobacterium-mediated inflammation and DNA damage in colonic epithelial cells

Colorectal cancer (CRC) is the third most prevalent and deadly cancer. Approximately, 15-20 % of CRCs display microsatellite instability (MSI); however, the majority (80-85%) of cases are sporadic and known as microsatellite stable (MSS). Several recent studies indicated that infection and uncontrolled inflammation initiate DNA damage and lead to cancer progression. One of the major microbes, Fusobacterium nucleatum (Fn) is highly associated with CRC, but the role of DNA repair in microbe-associated CRC has been largely unknown. Here we show that NEIL2, an oxidized base-specific DNA glycosylase, is significantly downregulated among all the key DNA repair proteins involved in various DNA repair pathways, after infection of Fn with stem-cell-based enteroid-derived monolayers (EDMs) of murine and human healthy subjects. Furthermore, following Fn infection, NEIL2-null mouse-derived EDMs showed significantly higher level of DNA damage, including double strand breaks, and inflammatory cytokines.. Murine CRC model also showed downregulation of the NEIL2 transcript and accumulation of DNA damage. Importantly, analysis of publicly available transcriptomic data showed that the downregulation of NEIL2 is specific for MSS compared to MSI CRCs. We thus conclude that the pathogenic bacterial infection-induced downregulation of NEIL2, and consequent accumulation of DNA damage, play critical roles in the progression of CRC.

immunology↗
bioRxiv2020

A prevalent and culturable microbiota links ecological balance to clinical stability of the human lung after transplantation

There is accumulating evidence that the lower airway microbiota impacts lung health. However, the link between microbial community composition and lung homeostasis remains elusive. We combined amplicon sequencing and culturomics to characterize the viable bacterial community in 234 longitudinal bronchoalveolar lavage samples from 64 lung transplant recipients and established links to viral loads, host gene expression, lung function, and transplant health. We find that the lung microbiota post-transplant can be categorized into four distinct compositional states, pneumotypes. The predominant balanced pneumotype was characterized by a diverse bacterial community with moderate viral loads, and host gene expression profiles suggesting immune tolerance. The other three pneumotypes were characterized by being either microbiota-depleted, or dominated by potential pathogens, and were linked to increased immune activity, lower respiratory function, and increased risks of infection and rejection. Collectively, our findings establish a link between the lung microbial ecosytem, human lung function, and clinical stability post-transplant. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=191 SRC="FIGDIR/small/106211v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@1df2be3org.highwire.dtl.DTLVardef@ba839dorg.highwire.dtl.DTLVardef@116f657org.highwire.dtl.DTLVardef@86d8ac_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗
bioRxiv2020

Catestatin (CST) is a key mediator of the immunoendocrine regulation of cardiovascular function

Hypertension (HTN) is associated with inflammation and excessive production of catecholamines. Hypertensive patients have reduced plasma levels of Catestatin (CST), a bioactive cleavage product of the prohormone Chromogranin A (CgA). In mouse models, HTN symptoms can be reduced by administration of CST, but the role of CST in the regulation of cardiovascular function is unknown. In this study, we generated mice with knockout (KO) of the region of the CgA gene coding for CST (CST-KO) and found that CST-KO mice are not only hypertensive as predicted, but also display left ventricular hypertrophy, have marked macrophage infiltration of the heart and adrenal gland, and have elevated levels of pro-inflammatory cytokines and catecholamines. Intraperitoneal injection with CST reversed these phenotypes, and ischemic pre-conditioning-induced cardioprotection was also abolished in CST-KO mice. Experiments with chlodronate depletion of macrophages and bone-marrow transfer showed that macrophages produce CST and that the anti-hypertensive effects of CST are mediated in part via CSTs immunosuppression of macrophages as a form of feedback inhibition. The data thus implicate CST as a key autocrine attenuator of the cardiac inflammation in HTN by reducing macrophage inflammation.

physiology↗
bioRxiv2020

Characterizations of SARS-CoV-2 mutational profile, spike protein stability and viral transmission

The recent pandemic of SARS-CoV-2 infection has affected more than 3.0 million people worldwide with more than 200 thousand reported deaths. The SARS-CoV-2 genome has a capability of gaining rapid mutations as the virus spreads. Whole genome sequencing data offers a wide range of opportunities to study the mutation dynamics. The advantage of increasing amount of whole genome sequence data of SARS-CoV-2 intrigued us to explore the mutation profile across the genome, to check the genome diversity and to investigate the implications of those mutations in protein stability and viral transmission. Four proteins, surface glycoprotein, nucleocapsid, ORF1ab and ORF8 showed frequent mutations, while envelop, membrane, ORF6 and ORF7a proteins showed conservation in terms of amino acid substitutions. Some of the mutations across different proteins showed co-occurrence, suggesting their functional cooperation in stability, transmission and adaptability. Combined analysis with the frequently mutated residues identified 20 viral variants, among which 12 specific combinations comprised more than 97% of the isolates considered for the analysis. Analysis of protein structure stability of surface glycoprotein mutants indicated viability of specific variants and are more prone to be temporally and spatially distributed across the globe. Similar empirical analysis of other proteins indicated existence of important functional implications of several variants. Analysis of co-occurred mutants indicated their structural and/or functional interaction among different SARS-COV-2 proteins. Identification of frequently mutated variants among COVID-19 patients might be useful for better clinical management, contact tracing and containment of the disease.

genomics↗
bioRxiv2020

Fruit bromelain derived peptides destabilize growth of amyloidal fibrils

{beta}-Amyloid deposition as fibrillar plaques in brain is the primary cause of Alzheimers disease. We report potency of cysteine protease fruit bromelain from pineapple in destabilising A{beta} fibrils. Bromelain peptide pool (Mw<500 Da) obtained mimicking human alimentary tract digestion inhibited fibrillation from monomeric and oligomeric states of A and irreversibly dissociated preformed fibrils into small oligomers of varied sizes. Time kinetics was followed by Thioflavin-T assay and microscopic imaging. Synthetic bromelain peptides corresponding to A{beta} sticky region found using ClustalW analysis revealed specificity of peptides in destabilisation of amyloidal structures. Spectra of different molecular states of A{beta} obtained from application of 8-anilino-1-naphthalenesulfonic acid, circular dichroism and Fourier-Transformed Infrared spectroscopy collectively indicated interaction dependent structural change. Probable mechanism for fibril dissociation was thus predicted. Peptides relieved A{beta} cytotoxicity on pheochromcytoma cells and dissociated plaques in AD-type rats prepared by bilateral intracerebroventricular administration of A{beta} in rat brain cortex. Pineapple being a phytoceutical, its efficiency to disaggregate amyloid bodies warrant further investigation. GRAPHICAL ABSTRACT O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

biochemistry↗
bioRxiv2020

Three adjacent nucleotide changes spanning two residues in SARS-CoV-2 nucleoprotein: possible homologous recombination from the transcription-regulating sequence

BackgroundGenetic variations across the SARS-CoV-2 genome may influence transmissibility of the virus and the hosts anti-viral immune response, in turn affecting the frequency of variants over-time. In this study, we examined the adjacent amino acid polymorphisms in the nucleocapsid (R203K/G204R) of SARS-CoV-2 that arose on the background of the spike D614G change and describe how strains harboring these changes became dominant circulating strains globally. MethodsDeep sequencing data of SARS-CoV-2 from public databases and from clinical samples were analyzed to identify and map genetic variants and sub-genomic RNA transcripts across the genome. ResultsSequence analysis suggests that the three adjacent nucleotide changes that result in the K203/R204 variant have arisen by homologous recombination from the core sequence (CS) of the leader transcription-regulating sequence (TRS) rather than by stepwise mutation. The resulting sequence changes generate a novel sub-genomic RNA transcript for the C-terminal dimerization domain of nucleocapsid. Deep sequencing data from 981 clinical samples confirmed the presence of the novel TRS-CS-dimerization domain RNA in individuals with the K203/R204 variant. Quantification of sub-genomic RNA indicates that viruses with the K203/R204 variant may also have increased expression of sub-genomic RNA from other open reading frames. ConclusionsThe finding that homologous recombination from the TRS may have occurred since the introduction of SARS-CoV-2 in humans resulting in both coding changes and novel sub-genomic RNA transcripts suggests this as a mechanism for diversification and adaptation within its new host.

microbiology↗
bioRxiv2020

Engineering multiple species-like genetic incompatibilities in insects

Speciation constrains the flow of genetic information between populations of sexually reproducing organisms. Gaining control over mechanisms of speciation would enable new strategies to manage wild populations of disease vectors, agricultural pests, and invasive species. Additionally, such control would provide safe biocontainment of transgenes and gene drives. Natural speciation can be driven by pre-zygotic barriers that prevent fertilization or by post-zygotic genetic incompatibilities that render the hybrid progeny inviable or sterile. Here we demonstrate a general approach to create engineered genetic incompatibilities (EGIs) in the model insect Drosophila melanogaster. Our system couples a dominant lethal transgene with a recessive resistance allele. EGI strains that are homozygous for both elements are fertile and fecund when they mate with similarly engineered strains, but incompatible with wild-type strains that lack resistant alleles. We show that EGI genotypes can be tuned to cause hybrid lethality at different developmental life-stages. Further, we demonstrate that multiple orthogonal EGI strains of D. melanogaster can be engineered to be mutually incompatible with wild-type and with each other. Our approach to create EGI organisms is simple, robust, and functional in multiple sexually reproducing organisms.

synthetic biology↗
bioRxiv2020

DNA methylation classification in diffuse glioma shows little spatial heterogeneity after adjusting for tumor purity

Intratumoral heterogeneity is a hallmark of diffuse gliomas. We used neuronavigation to acquire 133 image-guided and spatially-separated stereotactic biopsy samples from 16 adult patients with a diffuse glioma, which we characterized using DNA methylation arrays. Samples were obtained from regions with and without imaging abnormalities. Methylation profiles were analyzed to devise a three-dimensional reconstruction of genetic and epigenetic heterogeneity. Molecular aberrations indicated that tumor was found outside imaging abnormalities, underlining the infiltrative nature of this tumor and the limitations of current routine imaging modalities. We demonstrate that tumor purity is highly variable between samples and largely explains apparent epigenetic spatial heterogeneity. Indeed, we observed that DNA methylation subtypes are highly conserved in space after adjusting for tumor purity. Genome-wide heterogeneity analysis showed equal or increased heterogeneity among normal tissue when compared to tumor. These findings were validated in a separate cohort of 61 multi-sector tumor and 64 normal samples. Our findings underscore the infiltrative nature of diffuse gliomas and suggest that heterogeneity in DNA methylation is innate to somatic cells and not a characteristic feature of this tumor type.

cancer biology↗
bioRxiv2020

DDX5 targets tissue-specific RNAs to promote intestine tumorigenesis

Tumorigenesis in different segments of the intestinal tract involves tissue-specific oncogenic drivers. In the colon, complement component 3 (C3) activation is a major contributor to inflammation and malignancies. By contrast, tumorigenesis in the small intestine involves fatty acid-binding protein 1 (FABP1). However, little is known of the upstream mechanisms driving their expressions in different segments of the intestinal tract. Here, we report that an RNA binding protein DDX5 augments C3 and FABP1 expressions post-transcriptionally to promote tumorigenesis in the colon and small intestine, respectively. Mice with epithelial-specific knockout of DDX5 are protected from intestine tumorigenesis. The identification of DDX5 as the common upstream regulator of tissue-specific oncogenic molecules provides a new therapeutic target for intestine cancers.

cancer biology↗
bioRxiv2020

Finding associations in a heterogeneous setting: Statistical test for aberration enrichment

Most two-group statistical tests are implicitly looking for a broad pattern such as an overall shift in mean, median or variance between the two groups. Therefore, they operate best in settings where the effect of interest is uniformly affecting everyone in one group versus the other. In real-world applications, there are many scenarios where the effect of interest is heterogeneous. For example, a drug that works very well on only a proportion of patients and is equivalent to a placebo on the remaining patients, or a disease associated gene expression dysregulation that only occurs in a proportion of cases whereas the remaining cases have expression levels indistinguishable from the controls for the considered gene. In these examples with heterogeneous effect, we believe that using classical two-group statistical tests may not be the most powerful way to detect the signal. In this paper, we developed a statistical test targeting heterogeneous effects and demonstrated its power in a controlled simulation setting compared to existing methods. We focused on the problem of finding meaningful associations in complex genetic diseases using omics data such as gene expression, miRNA expression, and DNA methylation. In simulated and real data, we showed that our test is complementary to the traditionally used statistical tests and is able to detect disease-relevant genes with heterogeneous effects which would not be detectable with previous approaches.

bioinformatics↗
bioRxiv2020

CATH functional families predict protein functional sites

MotivationIdentification of functional sites in proteins is essential for functional characterisation, variant interpretation and drug design. Several methods are available for predicting either a generic functional site, or specific types of functional site. Here, we present FunSite, a machine learning predictor that identifies catalytic, ligand-binding and protein-protein interaction functional sites using features derived from protein sequence and structure, and evolutionary data from CATH functional families (FunFams). ResultsFunSites prediction performance was rigorously benchmarked using cross-validation and a holdout dataset. FunSite outperformed all publicly-available functional site prediction methods. We show that conserved residues in FunFams are enriched in functional sites. We found FunSites performance depends greatly on the quality of functional site annotations and the information content of FunFams in the training data. Finally, we analyse which structural and evolutionary features are most predictive for functional sites. AvailabilityThe datasets and prediction models are available on request. Contactc.orengo@ucl.ac.uk Supplementary informationSupplementary data are available at Bioinformatics online.

bioinformatics↗
bioRxiv2020

IDH1 Mutations Induce Organelle Defects Via Dysregulated Phospholipids

Cytosolic IDH1 enzyme plays a key, but currently unexplored, role in lipid biosynthesis. Using Raman imaging microscopy, we identified heterogeneous lipid profiles in cellular organelles attributed uniquely to IDH1 mutations. Via organelle lipidomics, we found an increase in saturated and monounsaturated fatty acids in the endoplasmic reticulum of IDH1mut cells compared with IDHWT glioma. We showed that these fatty acids incorporate into phospholipids and induce organelle dysfunctions, with prominent dilation of Golgi apparatus, which can be restored by transient knockdown of stearyl-CoA desaturase or inhibition of D-2-hydroxyglutarate (D-2HG) formation. We validated these findings using tissue from patients with glioma. Oleic acid addition led to increased sensitivity to apoptosis of IDH1mut cells compared with IDHWT. Addition of D-2HG to U251WT cells lead in increased ER and Golgi apparatus dilation. Collectively, these studies provide clinically relevant insights into the functional link between IDH1mut-induced lipid alterations and organelle dysfunction, with therapeutic implications. SignificanceGliomas are devastating tumors, with the most aggressive form--glioblastoma multiforme-- correlated with a mean patient survival of 14.5 months. No curative treatment exists to date. Low-grade glioma (LGG) with the isocitrate dehydrogenase 1 (IDH1) mutation, R132H, provides a survival benefit to patients. Understanding the unique metabolic profile of IDH1mut could provide clues regarding its association with longer survival and information about therapeutic targets. Herein, we identified lipid imbalances in organelles, generated by IDHmut in cells and patient tissue, that were responsible for Golgi dilation and that correlated with increased survival. Addition of oleic acid, which tilted the balance towards elevated levels of monounsaturated fatty acids produced IDH1mut-specific cellular apoptosis. HighlightsO_LISingle-organelle omics revealed unique alterations in lipid metabolism due to IDH1-mutations. C_LIO_LIIDH mutation leads to organelle-wide structural defects. C_LIO_LIIDH1 mutation leads to increased monounsaturated fatty acids levels in glioma cells and oligodendroglioma patient samples. C_LIO_LILipid alterations affect the membrane integrity of the Golgi apparatus. C_LIO_LIIncreased D-2HG induced SCD expression and elevated monounsaturated fatty acids C_LIO_LITilting the balance toward more-abundant monounsaturated fatty acids leads to specific IDH1mut glioma apoptosis. C_LI

cancer biology↗
bioRxiv2020

Creation of an Open Science Dataset from PREVENT-AD, a Longitudinal Cohort Study of Pre-symptomatic Alzheimer's Disease.

To move Alzheimer Disease (AD) research forward it is essential to collect data from large cohorts, but also make such data available to the global research community. We describe the creation of an open science dataset from the PREVENT-AD (PResymptomatic EValuation of Experimental or Novel Treatments for AD) cohort, composed of cognitively unimpaired older individuals with a parental or multiple-sibling history of AD. From 2011 to 2017, 386 participants were enrolled (mean age 63 years old {+/-} 5) for sustained investigation among whom 349 have retrospectively agreed to share their data openly. Repositories are findable through the unified interface of the Canadian Open Neuroscience Platform (https://portal.conp.ca/) and contain up to five years of longitudinal imaging data, cerebral fluid biochemistry, neurosensory capacities, cognitive, genetic, and medical information. Imaging data can be accessed openly at https://openpreventad.loris.ca while most of the other information, sensitive by nature, is accessible by qualified researchers at https://registeredpreventad.loris.ca. In addition to being a living resource for continued data acquisition, PREVENT-AD offers opportunities to facilitate understanding of AD pathogenesis.

neuroscience↗
bioRxiv2020

Lysophosphatidic acid-mediated GPR35 signaling in CX3CR1+ macrophages regulates the intestinal cytokine milieu

Single nucleotide polymorphisms in the gene encoding G protein-coupled receptor 35 (GPR35) are associated with increased risk of inflammatory bowel disease. However, the mechanism(s) by which GPR35 modulates the intestinal milieu remain undefined. Here we demonstrate in zebrafish and mice that expression of Gpr35 is microbiota-dependent and is enhanced upon inflammation. We identify a GPR35+ colonic macrophage population in mice that is characterized by increased production of pro-inflammatory cytokines, and determine that lysophosphatidic acid (LPA) acts as an endogenous GPR35 ligand to induce Tnf expression. Mice lacking Gpr35 in CX3CR1+ macrophages have aggravated colitis when exposed to dextran sodium sulfate, have decreased transcript levels of the corticosterone-generating gene Cyp11b1, and reduced levels of macrophage-derived TNF. Administration of TNF in these mice restores Cyp11b1 expression and intestinal corticosterone production, and ameliorates DSS-induced colitis. These findings suggest that LPA signals through GPR35 in CX3CR1+ macrophages to control the intestinal cytokine milieu. HighlightsO_LIInflammatory cues and the microbiota modulate Gpr35 expression across species C_LIO_LILPA modulates GPR35-dependent functions in zebrafish and mice macrophages C_LIO_LIGPR35 expressing macrophages have a protective role during intestinal inflammation C_LIO_LIGPR35 control intestinal inflammation by inducing TNF and corticosterone synthesis C_LI eTOC BlurbGPR35 have been associated with IBD, but how GPR35 may influence macrophage-mediated intestinal homeostasis remains unclear. Using zebrafish and mice genetic tools, Niess, Villablanca, and colleagues have identified that LPA triggers GPR35 activity, and loss of macrophage GPR35 signaling confers intrinsic dysfunctions with effects on cytokine production and intestinal homeostasis.

immunology↗
bioRxiv2020

Serotonin signaling by maternal neurons upon stress ensures progeny survival

Germ cells are vulnerable to stress. Therefore, how organisms protect their future progeny from damage in a fluctuating environment is a fundamental question in biology. We show that in Caenorhabditis elegans, serotonin released by maternal neurons during stress ensures the viability and stress tolerance of future offspring by enabling the transcription factor HSF1 to alter chromatin in soon-to-be fertilized germ cells by recruiting the histone chaperone FACT, displacing histones, and initiating protective gene expression. Without maternal serotonin signaling by neurons, FACT is not recruited by HSF1 in germ cells, transcription occurs but is delayed, and progeny of stressed C. elegans mothers fail to complete development. Serotonin acts through a signal transduction pathway conserved between C. elegans and mammalian cells to facilitate HSF1 to recruit FACT. These studies uncover a novel mechanism by which stress sensing by neurons is coupled to transcription response times of germ cells to protect future offspring.

cell biology↗
bioRxiv2020

Retromer retrieves the Wilson Disease protein, ATP7B from lysosomes in a copper-dependent mode

ATP7B utilizes lysosomal exocytosis to export copper from hepatocytes. We investigated the fate of ATP7B, post-copper export. At high copper ATP7B traffics to lysosomes and upon subsequent copper chelation, returns to Trans Golgi Network. At high copper, ATP7B co-localizes with lysosomal marker, Lamp1 and the core member of retromer complex, Vps35. Knocking down VPS35 did not alter copper-responsive vesicularization of ATP7B; rather upon subsequent copper chelation, ATP7B failed to relocalize to TGN that could be rescued by overexpressing wtVPS35. Using super-resolution microscopy and proximity ligation assays we demonstrate that VPS35 and ATP7B are juxtaposed on the same lysosomal compartment and their interaction is indirect. Utilizing in-cell photoamino acid-based UV-crosslinking and subsequent immunoprecipitation, we detected ATP7B and retromer subunits, VPS35 and VPS26 in a large complex in high copper conditions, hence confirming their interaction. We demonstrate that retromer regulates lysosome to TGN trafficking of the copper transporter ATP7B and it is dependent upon cellular copper level.

cell biology↗
bioRxiv2019

Coarse-Grained Modeling of DNA Plectoneme Formation in the Presence of Base-Pair Mismatches

Damaged or mismatched DNA bases result in the formation of physical defects in double-stranded DNA. In vivo, defects in DNA must be rapidly and efficiently repaired to maintain cellular function and integrity. Defects can also alter the mechanical response of DNA to bending and twisting constraints, both of which are important in defining the mechanics of DNA supercoiling. Here, we use coarse-grained molecular dynamics (MD) simulation and supporting statistical-mechanical theory to study the effect of mismatched base pairs on DNA supercoiling. Our simulations show that plectoneme pinning at the mismatch site is deterministic under conditions of relatively high force (> 2 pN) and high salt concentration (> 0.5 M NaCl). Under physiologically relevant conditions of lower force (0.3 pN) and lower salt concentration (0.2 M NaCl), we find that plectoneme pinning becomes probabilistic and the pinning probability increases with the mismatch size. These findings are in line with experimental observations. The simulation framework, validated with experimental results and supported by the theoretical predictions, provides a way to study the effect of defects on DNA supercoiling and the dynamics of supercoiling in molecular detail.

biophysics↗