Biology subjects

Levin, M.

Publications and source records attributed to Levin, M..

66 records · Page 4Linked to original sources

bioRxiv2019

A comprehensive conceptual and computational dynamics framework for Autonomous Regeneration Systems

This paper presents a new conceptual and computational dynamics framework for damage detection and regeneration in multicellular structures similar to living animals. The model uniquely achieves complete and accurate regeneration from any damage anywhere in the system. We demonstrated the efficacy of the proposed framework on an artificial organism consisting of three tissue structures corresponding to the head, body and tail of a worm. Each structure consists of a stem cell surrounded by a tissue of differentiated cells. We represent a tissue as an Auto-Associative Neural Network (AANN) with local interactions and stem cells as a self-repair network with long-range interactions. We also propose another new concept, Information Field which is a mathematical abstraction over traditional components of tissues, to keep minimum pattern information of the tissue structures to be accessed by stem cells in extreme cases of damage. Through entropy, a measure of communication between a stem cell and differentiated cells, stem cells monitor the tissue pattern integrity, violation of which triggers damage detection and tissue repair. Stem cell network monitors its state and invokes stem cell repair in the case of stem cell damage. The model accomplishes regeneration at two levels: In the first level, damaged tissues with intact stem cells regenerate themselves. Here, stem cell identifies entropy change and finds the damage and regenerates the tissue in collaboration with the AANN. In the second level, involving missing whole tissues and stem cells, the remaining stem cell(s) access the information field to restore the stem cell network and regenerate missing tissues. In the case of partial tissue damage with missing stem cells, the two levels collaborate to accurately restore the stem cell network and tissues. This comprehensive hypothetical framework offers a new way to conceptualise regeneration for better understanding the regeneration processes in living systems. It could also be useful in biology for regenerative medicine and in engineering for building self-repairing biobots.

synthetic biology↗

bioRxiv2019

Nervous System and Tissue Polarity Dynamically Adapt to New Morphologies in Planaria

The coordination of tissue-level polarity with organism-level polarity is crucial in development, disease, and regeneration. Exploiting the flexibility of the body plan in regenerating planarians, we used mirror duplication of the primary axis to show how established tissue-level polarity adapts to new organism-level polarity. Tracking of cilia-driven flow to characterize planar cell polarity of the epithelium revealed a remarkable reorientation of tissue polarity in double-headed planarians. This reorientation is driven by signals produced by the intact brain and is not hampered by radiation-induced removal of stem cells. The nervous system itself adapts its polarity to match the new organismal anatomy in these animals as revealed by distinct regenerative outcomes driven by polarized nerve transport. Thus, signals from the central nervous system can dynamically control and re-orient tissue-level polarity to match the organism-level anatomical configuration, illustrating a novel role of the nervous system in the regulation of patterning.

physiology↗

bioRxiv2019

Defined extracellular ionic solutions to study and manipulate the cellular resting membrane potential

All cells possess an electric potential across their plasma membranes. While familiar in the context of excitable cells such as neurons, healthy non-excitable cells are also able to generate and receive bioelectric signals. The cellular resting membrane potential (RMP) regulates many factors in cell homeostasis, such as cell proliferation, differentiation and apoptosis. It is therefore critical to develop simple strategies to measure, manipulate and characterize this feature. Current studies to evaluate RMP rely on the patch clamp approach, which is technically challenging, low-throughput and not widely available to the scientific community. Here, we present a relatively simple methodology to functionally study the role of RMP in non-excitable cells by modulating it pharmacologically, and using a voltage-sensitive dye to characterize the contribution of individual ions to the RMP. Specifically, we define protocols for using extracellular solutions in which permeable ions (Na+, Cl- and K+) are substituted with non-permeable ions (N-Methyl-D-glucamine (NMDG), gluconate, choline, SO42-) to study and manipulate RMP in vitro. The resulting RMP modifications were assessed with both patch clamp and a voltage sensitive dye. Using an epithelial and cancer cell line, we demonstrate that the proposed ionic solutions can determine the relative contribution of ionic species in setting the RMP and be used to actively and selectively modify the RMP. The proposed method is simple and reproducible and will make the study of bioelectricity more readily available to the cell biology community by enabling functional modulation of RMP in most cellular assays.\n\nAuthor Disclosure StatementsNo competing financial interests exist.

cell biology↗

bioRxiv2019

Developmental dynamics are a proxy for selective pressures on alternatively polyadenylated isoforms

Alternative polyadenylation (APA) leads to multiple transcripts from the same gene, yet their distinct functional attributes remain largely unknown. Here, we introduce APA-seq to detect the expression levels of APA isoforms from 3-end RNA-Seq data by exploiting both paired-end reads for gene isoform identification and quantification. Applying APA-seq, we detected the expression levels of APA isoforms from RNA-Seq data of single C. elegans embryos, and studied the patterns of 3 UTR isoform expression throughout embryogenesis. We found that global changes in APA usage demarcate developmental stages, suggesting a requirement for distinct 3 UTR isoforms throughout embryogenesis. We distinguished two classes of genes, depending upon the correlation between the temporal profiles of their isoforms: those with highly correlated isoforms (HCI) and those with lowly correlated isoforms (LCI) across time. This led us to hypothesize that variants produced with similar expression profiles may be the product of biological noise, while the LCI variants may be under tighter selection and consequently their distinct 3 UTR isoforms are more likely to have functional consequences. Supporting this notion, we found that LCI genes have significantly more miRNA binding sites, more correlated expression profiles with those of their targeting miRNAs and a relative lack of correspondence between their transcription and protein abundances. Collectively, our results suggest that a lack of coherence among the regulation of 3 UTR isoforms is a proxy for selective pressures acting upon APA usage and consequently for their functional relevance.

molecular biology↗

bioRxiv2019

Viral and bacterial infection elicit distinct changes in plasma lipids in febrile children

Fever is the most common reason that children present to Emergency Departments in the UK. Clinical signs and symptoms suggestive of bacterial infection are often non-specific, and there is no definitive test for the accurate diagnosis of infection. As a result, many children are prescribed antibiotics often unnecessarily, while others with life-threatening bacterial infections can remain untreated. The omics approaches to identifying biomarkers from the host-response to bacterial infection are promising. In this study, lipidomic analysis was carried out with plasma samples obtained from febrile children with confirmed bacterial infection (n=20) and confirmed viral infection (n=20). We show for the first time that bacterial and viral infection elicit distinct changes in the host lipidome. Glycerophosphoinositol, sphingomyelin, lysophosphotidylcholine and cholesterol sulfate were increased in the confirmed virus infected group, while fatty acids, glycerophosphocholine, glycerophosphoserine, lactosylceramide and bilirubin were increased in cases with confirmed bacterial infection. A combination of three lipids achieved the area under the receiver operating characteristic (ROC) curve of 0.918 (95% CI 0.835 to 1). This pilot study demonstrates the potential of metabolic biomarkers to assist clinicians in distinguishing bacterial from viral infection in febrile children, to facilitate effective clinical management and to the limit inappropriate use of antibiotics.

systems biology↗

bioRxiv2019

Lipocalin-2 is a Sensitive and Specific Marker of Bacterial Infection in Children

IntroductionBacterial infection is the leading cause of death in children globally. Clinical algorithms to identify children who are likely to benefit from antimicrobial treatment remain suboptimal. Biomarkers that accurately identify serious bacterial infection (SBI) could improve diagnosis and clinical management. Lipocalin 2 (LCN2) and neutrophil collagenase (MMP-8) are neutrophil-derived biomarkers associated with bacterial infection.\n\nMethodsWe evaluated LCN2 and MMP-8 as candidate biomarkers in 40 healthy controls and 151 febrile children categorised confirmed SBI, probable SBI, or viral infection. The diagnostic performance of LCN2 and MMP-8 to predict SBI was estimated by the area under the receiver operating characteristic curve (AUROC) and compared to the performance of C-reactive protein (CRP).\n\nResultsPlasma LCN2 and MMP-8 concentration were predictive of SBI. The AUROC (95% CI) for LCN2, MMP8 and CRP to predict SBI was 0.88 (0.82-0.94); 0.80 (0.72-0.87) and 0.89 (0.84-0.94), respectively. The diagnostic performance of LCN2 in combination with CRP was significantly superior to either marker alone: AUROC 0.92 (95% CI: 0.88-0.96).\n\nConclusionLCN2 is a sensitive and specific predictor of SBI in children which could be used to improve clinical management and antimicrobial stewardship. LCN2 should be further evaluated in prospective clinical studies.

microbiology↗

bioRxiv2019

Identification of reduced host transcriptomic signatures for tuberculosis and digital PCR-based validation and quantification

Recently, host whole blood gene expression signatures have been identified for diagnosis of tuberculosis (TB). Absolute quantification of the concentrations of signature transcripts in blood have not been reported, but would facilitate the development of diagnostic tests.\n\nTo identify minimal transcript signatures, we applied a novel transcript selection procedure to microarray data from African adults comprising 536 patients with TB, other diseases (OD) and latent TB (LTBI), divided into training and test sets. Signatures were validated using reverse transcriptase (RT) - digital PCR (dPCR).\n\nA four-transcript signature (GBP6, TMCC1, PRDM1, ARG1) measured using RT-dPCR distinguished TB patients from those with OD (area under the curve (AUC) 93.8% (CI95% 82.2 - 100%). A three-transcript signature (FCGR1A, ZNF296, C1QB) differentiated TB from LTBI (AUC 97.3%, CI95%: 93.3 - 100%), regardless of HIV.\n\nThese signatures have been validated across platforms and across samples offering strong, quantitative support for their use as diagnostic biomarkers for TB.

molecular biology↗

bioRxiv2018

PCF11 connects alternative polyadenylation to formation and spontaneous regression of neuroblastoma

Diversification at the transcriptome 3end is an important and evolutionarily conserved layer of gene regulation associated with differentiation and dedifferentiation processes. However the underlying mechanisms and functional consequences are poorly defined. Here, we identify extensive transcriptome-3end-alterations in neuroblastoma, a tumour entity with a paucity of recurrent somatic mutations and an unusually high frequency of spontaneous regression. Utilising extensive RNAi-screening we reveal the landscape and drivers of transcriptome-3end-diversification, discovering PCF11 as critical regulator, directing alternative polyadenylation (APA) of hundreds of transcripts including a differentiation RNA-operon. PCF11 shapes inputs converging on WNT-signalling, and governs cell cycle, proliferation, apoptosis and neurodifferentiation. Postnatal PCF11 down-regulation induces a neurodifferentiation program, and low-level PCF11 in neuroblastoma associates with favourable outcome and spontaneous tumour regression. Our findings document a critical role for APA in tumourigenesis and describe a novel mechanism for cell fate reprogramming in neuroblastoma with important clinical implications. An interactive data repository of transcriptome-wide APA covering >170 RNAis, and an APA-network map with regulatory hubs is provided.

developmental biology↗

bioRxiv2018

Estimating parasite load dynamics to reveal novel resistance mechanisms to human malaria

Improved methods are needed to identify host mechanisms which directly protect against human infectious diseases in order to develop better vaccines and therapeutics1,2. Pathogen load determines the outcome of many infections3, and is a consequence of pathogen multiplication rate, duration of the infection, and inhibition or killing of pathogen by the host (resistance). If these determinants of pathogen load could be quantified then their mechanistic correlates might be determined. In humans the timing of infection is rarely known and treatment cannot usually be withheld to monitor serial changes in pathogen load and host response. Here we present an approach to overcome this and identify potential mechanisms of resistance which control parasite load in Plasmodium falciparum malaria. Using a mathematical model of longitudinal infection dynamics for orientation, we made individualized estimates of parasite multiplication and growth inhibition in Gambian children at presentation with acute malaria and used whole blood RNA-sequencing to identify their correlates. We identified novel roles for secreted proteases cathepsin G and matrix metallopeptidase 9 (MMP9) as direct effector molecules which inhibit P. falciparum growth. Cathepsin G acts on the erythrocyte membrane, cleaving surface receptors required for parasite invasion, whilst MMP9 acts on the parasite. In contrast, the type 1 interferon response and expression of CXCL10 (IFN-{gamma}-inducible protein of 10 kDa, IP-10) were detrimental to control of parasite growth. Natural variation in iron status and plasma levels of complement factor H were determinants of parasite multiplication rate. Our findings demonstrate the importance of accounting for the dynamic interaction between host and pathogen when seeking to identify correlates of protection, and reveal novel mechanisms controlling parasite growth in humans. This approach could be extended to identify additional mechanistic correlates of natural- and vaccine-induced immunity to malaria and other infections.

systems biology↗

bioRxiv2018

Cellular Migration May Exhibit Intrinsic Left-Right Asymmetries: A meta-analysis

The intracellular model of embryonic left-right (LR) asymmetry proposes that body laterality originates from intrinsic chiral properties of individual cells, and several recent studies identified consistent chirality in the behavior of cells in vitro. Here, we explored one prediction of the intrinsic asymmetry model: that LR asymmetries would be present in a wide range of mammalian cells, manifesting in the form of LR-biased migration toward an attractant. We mined data from published papers on galvanotaxis and chemotaxis and quantitatively analyzed the migration trajectories of adult somatic cells, stem cells, and cancer cells to determine whether they display significant consistent LR biases in their movements toward migration targets. We found that several cell types exhibited LR biases during galvanotaxis and chemotaxis, and that treatments inhibiting cytoskeletal remodeling or targeting ion channel activity both abolished these LR biases. While we cannot conclusively rule out the existence of subtle biasing cues in the apparatus of some of the studies, the analysis of this dataset suggests specific assays and cell types for further investigation into the chiral aspects of intrinsic cell behavior.\n\nFundingThis work was funded by the American Heart Association Established Investigator grant 0740088N and NIH grants R01-GM077425 (to ML) and NRSA grant 1F32GM087107 (to LNV). M.L. is also supported by the G. Harold and Leila Y. Mathers Charitable Foundation.

cell biology↗

bioRxiv2017

Effects of Ivermectin exposure on regeneration of D. dorotocephala planaria

The ability of cells to communicate is essential during pattern formation, as they make decisions that drive growth and form. One mode of cellular signaling is via bioelectrical properties determined by the activity of ion channels. Several studies have shown a role for bioelectric signaling in planarian regeneration, but these have focused on D. japonica and S. mediterranea. It is not known how the alterations of ion channel activity would affect regeneration in other species of planaria. Here, we tested the effect of ivermectin (IVM), a chloride channel opener drug commonly used to combat heart worms, on regeneration in a new species of planaria: D. dorotocephala. Exposure to IVM during regeneration resulted in patterning abnormalities, such as bifurcated tails with partial heads, as well as delayed regeneration. By testing the effect of drugs that target resting potential on regenerative repair in novel model species, additional insight is gained on the comparative roles of ionic signaling across taxa.

developmental biology↗

bioRxiv2017

Integrated pathogen load and dual transcriptome analysis of systemic host-pathogen interactions in severe malaria

The pathogenesis of severe Plasmodium falciparum malaria is incompletely understood. Since the pathogenic stage of the parasite is restricted to blood, dual RNA-sequencing of host and parasite transcripts in blood can reveal their interactions at a systemic scale. Here we identify human and parasite gene expression associated with severe disease features in Gambian children. Differences in parasite load explained up to 99% of differential expression of human genes but only a third of the differential expression of parasite genes. Co-expression analyses showed a remarkable co-regulation of host and parasite genes controlling translation, and host granulopoiesis genes uniquely co-regulated and differentially expressed in severe malaria. Our results indicate that high parasite load is the proximal stimulus for severe P. falciparum malaria, that there is an unappreciated role for many parasite genes in determining virulence, and hint at a molecular arms-race between host and parasite to synthesise protein products.

systems biology↗