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Search indexed bioRxiv preprints in genomics, neuroscience, cell biology and bioinformatics. Read source abstracts and check manuscript versions; preprints are not peer reviewed.

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At least 415 records · Page 23Linked to original sources

bioRxiv2017

Uniform Resolution of Compact Identifiers for Biomedical Data

Most biomedical data repositories issue locally-unique accessions numbers, but do not provide globally unique, machine-resolvable, persistent identifiers for their datasets, as required by publishers wishing to implement data citation in accordance with widely accepted principles. Local accessions may however be prefixed with a namespace identifier, providing global uniqueness. Such \"compact identifiers\" have been widely used in biomedical informatics to support global resource identification with local identifier assignment.\n\nWe report here on our project to provide robust support for machine-resolvable, persistent compact identifiers in biomedical data citation, by harmonizing the Identifiers.org and N2T.net (Name-To-Thing) meta-resolvers and extending their capabilities. Identifiers.org services hosted at the European Molecular Biology Laboratory - European Bioinformatics Institute (EMBL-EBI), and N2T.net services hosted at the California Digital Library (CDL), can now resolve any given identifier from over 600 source databases to its original source on the Web, using a common registry of prefix-based redirection rules.\n\nWe believe these services will be of significant help to publishers and others implementing persistent, machine-resolvable citation of research data.

bioinformatics↗

bioRxiv2017

An extensible ontology for inference of emergent whole cell function from relationships between subcellular processes

Whole cell responses arise from coordinated interactions between diverse human gene products functioning within various pathways underlying sub-cellular processes (SCP). Lower level SCPs interact to form higher level SCPs, often in a context specific manner to give rise to whole cell function. We sought to determine if capturing such relationships enables us to describe the emergence of whole cell functions from interacting SCPs. We developed the \"Molecular Biology of the Cell\" ontology based on standard cell biology and biochemistry textbooks and review articles. Currently, our ontology contains 5,392 genes, 753 SCPs and 19,182 expertly curated gene-SCP associations. Our algorithm to populate the SCPs with genes enables extension of the ontology on demand and the adaption of the ontology to the continuously growing cell biological knowledge. Since whole cell responses most often arise from the coordinated activity of multiple SCPs, we developed a dynamic enrichment algorithm that flexibly predicts SCP-SCP relationships beyond the current taxonomy. This algorithm enables us to identify interactions between SCPs as a basis for higher order function in a context dependent manner, allowing us to provide a detailed description of how SCPs together can give rise to whole cell functions. We conclude that this ontology can, from omics data sets, enable the development of detailed multidimensional SCP networks for predictive modeling of emergent whole cell functions.

systems biology↗

bioRxiv2017

Combining Bayesian Approaches and Evolutionary Techniques for the Inference of Breast Cancer Networks

Gene and protein networks are very important to model complex large-scale systems in molecular biology. Inferring or reverseengineering such networks can be defined as the process of identifying gene/protein interactions from experimental data through computational analysis. However, this task is typically complicated by the enormously large scale of the unknowns in a rather small sample size. Furthermore, when the goal is to study causal relationships within the network, tools capable of overcoming the limitations of correlation networks are required. In this work, we make use of Bayesian Graphical Models to attach this problem and, specifically, we perform a comparative study of different state-of-the-art heuristics, analyzing their performance in inferring the structure of the Bayesian Network from breast cancer data.

bioinformatics↗

bioRxiv2017

Intra-protein binding peptide fragments have specific and intrinsic sequence patterns

The key finding in the DNA double helix model is the specific pairing or binding between nucleotides A-T and C-G, and the pairing rules are the molecule basis of genetic code. Unfortunately, no such rules have been discovered for proteins. Here we show that similar rules and intrinsic sequence patterns between intra-protein binding peptide fragments do exist, and they can be extracted using a deep learning algorithm. Multi-millions of binding and non-binding peptide fragments from currently available protein X-ray structures are classified with an accuracy of up to 93%. This discovery has the potential in helping solve protein folding and protein-protein interaction problems, two open and fundamental problems in molecular biology.\n\nOne Sentence SummaryClassification of binding and non-binding intra-protein peptide fragments using feed-forward neural network

bioinformatics↗

bioRxiv2017

Interdependence, Reflexivity, Fidelity, Impedance Matching, And The Evolution Of Genetic Coding

Genetic coding is generally thought to have required ribozymes whose functions were taken over by polypeptide aminoacyl-tRNA synthetases (aaRS). Two discoveries about aaRS and their tRNA substrates now furnish a unifying rationale for the opposite conclusion: that the key processes of the Central Dogma of molecular biology emerged simultaneously and naturally from simple origins in a peptide*RNA partnership, eliminating the epistemological need for a prior RNA world. First, the two aaRS classes likely arose from opposite strands of the same ancestral gene, implying a simple genetic alphabet. Inversion symmetries in aaRS structural biology arising from genetic complementarity would have stabilized the initial and subsequent differentiation of coding specificities and hence rapidly promoted diversity in the proteome. Second, amino acid physical chemistry maps onto tRNA identity elements, establishing reflexivity in protein aaRS. Bootstrapping of increasingly detailed coding is thus intrinsic to polypeptide aaRS, but impossible in an RNA world. These notions underline the following concepts that contradict gradual replacement of ribozymal aaRS by polypeptide aaRS: (i) any set of aaRS must be interdependent; (ii) reflexivity intrinsic to polypeptide aaRS production dynamics promotes bootstrapping; (iii) takeover of RNA-catalyzed aminoacylation by enzymes will necessarily degrade specificity; (iv) the Central Dogmas emergence is most probable when replication and translation error rates remain comparable. These characteristics are necessary and sufficient for the essentially de novo emergence of a coupled gene-replicase-translatase system of genetic coding that would have continuously preserved the functional meaning of genetically encoded protein genes whose phylogenetic relationships match those observed today.

evolutionary biology↗

bioRxiv2017

Insuperable Problems Of The Genetic Code Initially Emerging In An RNA World

Differential equations for error-prone information transfer (template replication, transcription or translation) are developed in order to consider, within the theory of autocatalysis, the advent of coded protein synthesis. Variations of these equations furnish a basis for comparing the plausibility of contrasting scenarios for the emergence of tRNA aminoacylation, ultimately by enzymes, and the relationship of this process with the origin of the universal system of molecular biological information processing embodied in the Central Dogma. The hypothetical RNA World does not furnish an adequate basis for explaining how this system came into being, but principles of self-organisation that transcend Darwinian natural selection furnish an unexpectedly robust basis for a rapid, concerted transition to genetic coding from a peptide*RNA world.

evolutionary biology↗

bioRxiv2017

A Varroa Destructor Protein Atlas Reveals Molecular Underpinnings Of Developmental Transitions And Sexual Differentiation

Varroa destructor is the most economically damaging honey bee pest, weakening colonies by simultaneously parasitizing bees and transmitting harmful viruses. Despite these impacts on honey bee health, surprisingly little is known about its fundamental molecular biology. Here we present a Varroa protein atlas crossing all major developmental stages (egg, protonymph, deutonymph and adult) for both male and female mites as a web-based interactive tool (http://foster.nce.ubc.ca/varroa/index.html). By intensity-based label-free quantitation, 1,433 proteins were differentially expressed across developmental stages, including two distinct viral polyproteins. Enzymes for processing carbohydrates and amino acids were among many of these differences as well as proteins involved in cuticle formation. Lipid transport involving vitellogenin was the most significantly enriched biological process in the foundress (reproductive female) and young mites. In addition, we found that 101 proteins were sexually regulated and functional enrichment analysis suggests that chromatin remodeling may be a key feature of sex determination. In a proteogenomic effort, we identified 519 protein-coding regions (169 of which were differentially expressed) supported by 1,464 peptides which were previously unannotated. Since this is a recurring trend with annotating genomes of non-model species, we analyzed their amino acid and nucleotide composition as well as their orthology to other species to suggest reasons why they may have been missed initially. Overall, this work provides a first-of-its-kind interrogation of the patterns of gene expression that govern the Varroa life cycle and the tools we have developed will support further research on this threatening honey bee pest.

developmental biology↗

bioRxiv2017

Simple, single-step, and scar-free mutagenesis of bacterial genes

The need for generating precisely designed mutations is common in genetics, biochemistry, and molecular biology. Here, I describe a new {lambda} Red recombineering method (Direct and Inverted Repeat stimulated excision; DIRex) for fast and easy generation of single point mutations, small insertions or replacements as well as deletions of any size, in bacterial genes. The method does not leave any resistance marker or scar sequence and requires only one transformation to generate a semi-stable intermediate insertion mutant. Spontaneous excision of the intermediate efficiently and accurately generates the final mutant. In addition, the intermediate is transferable between strains by generalized transductions, enabling transfer of the mutation into multiple strains without repeating the recombineering step. Existing methods that can be used to accomplish similar results are either (i) more complicated to design, (ii) more limited in what mutation types can be made, or (iii) require expression of extrinsic factors in addition to {lambda} Red. I demonstrate the utility of the method by generating several deletions, small insertions/replacements, and single nucleotide exchanges in Escherichia coli and Salmonella enterica. Furthermore, the design parameters that influence the excision frequency and the success rate of generating desired point mutations have been examined to determine design guidelines for optimal efficiency.

synthetic biology↗

bioRxiv2017

Producing Hfq/Sm Proteins and sRNAs for Structural and Biophysical Studies of Ribonucleoprotein Assembly

Hfq is a bacterial RNA-binding protein that plays key roles in the post-transcriptional regulation of gene expression. Like other Sm proteins, Hfq assembles into toroidal discs that bind RNAs with varying affinities and degrees of sequence specificity. By simultaneously binding to a regulatory small RNA (sRNA) and an mRNA target, Hfq hexamers facilitate productive RNA[···]RNA interactions; the generic nature of this chaperone-like functionality makes Hfq a hub in many sRNA-based regulatory networks. That Hfq is crucial in diverse cellular pathways--including stress response, quorum sensing and biofilm formation-- has motivated genetic and RNAomic studies of its function and physiology (in vivo), as well as biochemical and structural analyses of Hfq[···]RNA interactions (in vitro). Indeed, crystallographic and bio-physical studies first established Hfq as a member of the phylogenetically-conserved Sm superfamily. Crystallography and other biophysical methodologies enable the RNA-binding properties of Hfq to be elucidated in atomic detail, but such approaches have stringent sample requirements, viz.: reconstituting and characterizing an Hfq*RNA complex requires ample quantities of well-behaved (sufficient purity, homogeneity) specimens of Hfq and RNA (sRNA, mRNA fragments, short oligoribonucleotides, or even single nucleotides). The production of such materials is covered in this Chapter, with a particular focus on recombinant Hfq proteins for crystallization experiments.\n\nAbbreviations\n\nJournal formatMethods in Molecular Biology (Springer Protocols series); this volume is entitled \"Bacterial Regulatory RNA: Methods and Protocols\"; an author guide is linked at http://www.springer.com/series/7651

biochemistry↗

bioRxiv2017

Beyond Homology Transfer: Deep Learning for Automated Annotation of Proteins

Accurate annotation of protein functions is important for a profound understanding of molecular biology. A large number of proteins remain uncharacterized because of the sparsity of available supporting information. For a large set of uncharacterized proteins, the only type of information available is their amino acid sequence. In this paper, we propose DeepSeq - a deep learning architecture - that utilizes only the protein sequence information to predict its associated functions. The prediction process does not require handcrafted features; rather, the architecture automatically extracts representations from the input sequence data. Results of our experiments with DeepSeq indicate significant improvements in terms of prediction accuracy when compared with other sequence-based methods. Our deep learning model achieves an overall validation accuracy of 86.72%, with an F1 score of 71.13%. Moreover, using the automatically learned features and without any changes to DeepSeq, we successfully solved a different problem i.e. protein function localization, with no human intervention. Finally, we discuss how this same architecture can be used to solve even more complicated problems such as prediction of 2D and 3D structure as well as protein-protein interactions.

bioinformatics↗

bioRxiv2017

Flexible, multi-use, PCR-based nucleic acid integrity assays based on the ubiquitin C gene

Nucleic acid integrity assessment is an important aspect of quality control for many applications in molecular biology. A number of methods exist (electrophoresis- or PCR-based), but they are not universally applicable. Some of them need huge amounts of input, process certain amount of samples, require expensive equipment, only work specifically on (c)DNA, (m)RNA, certain species or certain tissues, or produce fragments covering a small length range. We investigated if the ubiquitin C gene (UBC) could be used to develop flexible, multi-use PCR-based (deoxy)ribonucleic acid integrity assays. UBC gene analysis (in human, mouse, pig, cow, horse, sheep, dog and cat) shows that UBC is a highly conserved and ubiquitously expressed gene (reference gene in RT-qPCR), that encodes a polyubiquitin precursor (containing tandem repeats of at least 5 ubiquitin monomers of 228 bp) in a single exon. On average, ubiquitin monomers show a nucleic acid sequence identity of 96% at intraspecies level and 93% at interspecies level. Based on a multiple alignment of all monomer ubiquitin sequences of all investigated species, we could design a single degenerated primer pair generating PCR amplicons of 137, 365, 593 and 821 bp on low amounts of high quality DNA of all investigated species (down to 10 pg) and on cDNA reverse transcribed from high quality RNA from different tissues (e.g. heart, liver, brain, kidney). Increasing levels of nucleic acid degradation resulted in a decrease of amplification products starting with the longer amplicons. We conclude that UBC is suited to develop a single, cheap, universal assay to estimate the presence, integrity and amplificability of native mammalian nucleic acids. In addition, we used the same strategy to design a similar assay to check the quality of bisulfite treated mammalian DNA.

genetics↗

bioRxiv2017

Biosensor libraries harness large classes of binding domains for allosteric transcription regulators

Bacterias ability to specifically sense small molecules in their environment and trigger metabolic responses in accordance is an invaluable biotechnological resource. While many transcription factors (TFs) mediating these processes have been studied, only a handful has been leveraged for molecular biology applications. To expand this panel of biotechnologically important sensors here we present a strategy for the construction and testing of chimeric TF libraries, based on the fusion of highly soluble periplasmic binding proteins (PBPs) with DNA-binding domains (DBDs). We validated this strategy by constructing and functionally testing two unique sense-and-response regulators for benzoate, an environmentally and industrially relevant metabolite. This work will enable the development of tailored biosensors for synthetic regulatory circuits.

synthetic biology↗

bioRxiv2019

M-current downregulation leads to stellate ganglia sympathetic hyperactivity associated with hypertension

The activity of cardiac sympathetic nerves from the stellate ganglia is increased in many cardiovascular diseases contributing to the pathophysiology, however the mechanisms underlying this are unknown. Moreover, clinical studies show their surgical removal is an effective treatment, despite the biophysical properties of these neurons being largely unstudied. Here we demonstrate that stellate ganglia neurons from prehypertensive spontaneously hypertensive rats are hyperactive and describe in detail their electrophysiological phenotype guided by single cell RNA-sequencing, molecular biology and perforated patch-clamp to uncover the underlying mechanism. The expression of key transcripts was confirmed in human stellate ganglia. We further demonstrate the contribution of a plethora of ion channels to stellate ganglia neuronal firing, and show that hyperexcitability was curbed by M-current activators, non-selective sodium current blockers or inhibition of Nav1.1-1.3, Nav1.6 or INaP. These findings have implications for target discovery to reduce cardiac sympathetic activity without resorting to surgery.

neuroscience↗

bioRxiv2020

NAChRDB: A Web Resource of Structure-Function Annotations to Unravel the Allostery of Nicotinic Acetylcholine Receptors

SummaryDue to their paramount importance, near-ubiquitous presence, and complex nature, nicotinic acetylcholine receptors (nAChRs) have remained the focus of intensive research for over 50 years. The vast amount of knowledge accumulated on the topic has become extremely difficult to navigate. NAChRDB addresses this challenge by providing web-based, real-time access to curated residue-level functional annotations of neuromuscular nAChRs with interactive 3D visualization and sequence alignment. NAChRDB provides systematic access to experimental observations and predictions from computational studies reported in the literature or performed specifically to complement current knowledge, which allows new findings to be interpreted in a more holistic context, both from a structural and a functional perspective. NAChRDB aims to serve as an invaluable resource for identifying gaps in knowledge and for guiding discovery through structural and molecular biology experiments, especially when exploring the allosteric mechanisms underlying neuromuscular nAChR function and pathology. Availability and ImplementationNAChRDB is freely available online, with a self-explanatory interface and useful tool tips (https://crocodile.ncbr.muni.cz/Apps/NAChRDB/). No installation or user registration is required. NAChRDB content is stored in .json format, queried using Python, and rendered in browser using Javascript and WebGL (LiteMol). NAChRDB is highly responsive and accessible through any modern Internet browser on desktop and mobile devices. Contactjkoca@ceitec.cz Supplementary informationSupplementary data are available online.

bioinformatics↗

bioRxiv2020

Computational front end to diverse therapeutic phage cocktails

New therapies are necessary to combat increasingly antibiotic-resistant bacterial pathogens. We have developed a technology platform of computational, molecular biology, and microbiology tools which together enable on-demand production of phages that target virtually any given bacterial isolate. Two complementary computational tools that identify and precisely map prophages and other integrative genetic elements (IGEs) in bacterial genomes are used to identify prophage-laden bacteria that are close relatives of the target strain. Phage genomes are engineered to disable lysogeny, through use of long amplicon PCR and Gibson assembly. Finally, the engineered phage genomes are introduced into host bacteria for phage production. As an initial demonstration, we used this approach to produce a phage cocktail against the opportunistic pathogen Pseudomonas aeruginosa PAO1. Two prophage-laden P. aeruginosa strains closely related to PAO1 were identified, ATCC 39324 and ATCC 27853. Deep sequencing revealed that mitomycin C treatment of these strains induced seven phages that grow on P. aeruginosa PAO1. The most diverse five of these were engineered for non-lysogeny by deleting the integrase gene (int), which is readily identifiable and typically conveniently located at one end of the prophage. The {Delta}int phages, individually and in cocktails, showed killing of P. aeruginosa PAO1 in vitro as well as in a waxworm (Galleria mellonella) model of infection. SIGNIFICANCE STATEMENTThe antibiotic-resistance crisis in medicine and agriculture has led to renewed interest in phage therapy as an alternative means of treating infection. However, conventional methods for isolating pathogen-specific phage are slow, labor-intensive, and frequently unsuccessful. We have demonstrated that prophages carried by near-neighbor bacteria can serve as starting material for production of engineered phages that kill the target pathogen. Our approach and technology platform offer new opportunity for rapid development of phage therapies against most, if not all, bacterial pathogens, a foundational advance for use of phage in treating infectious disease.

microbiology↗

bioRxiv2020

Genome-wide analyses of chromatin interactions after the loss of Pol I, Pol II and Pol III

BackgroundThe relationship between transcription and the 3D genome organization is one of the most important questions in molecular biology, but the roles of transcription in 3D chromatin remain controversial. Multiple groups showed that transcription affects global Cohesin binding and genome 3D structures. At the same time, several studies have indicated that transcription inhibition does not affect global chromatin interactions. ResultsHere, we provide the most comprehensive evidence to date to demonstrate that transcription plays a marginal role in organizing the 3D genome in mammalian cells: 1) degraded Pol I, Pol II and Pol III proteins in mESCs, and showed their loss results in little or no changes of global 3D chromatin structures for the first time; 2) selected RNA polymerases high abundance binding sites-associated interactions and found they still persist after the degradation; 3) generated higher resolution chromatin interaction maps and revealed that transcription inhibition mildly alters small loop domains; 4) identified Pol II bound but CTCF and Cohesin unbound loops and disclosed that they are largely resistant to transcription inhibition. Interestingly, Pol II depletion for a longer time significantly affects the chromatin accessibility and Cohesin occupancy, suggesting RNA polymerases are capable of affecting the 3D genome indirectly. So, the direct and indirect effects of transcription inhibition explain the previous confusing effects on the 3D genome. ConclusionsWe conclude that Pol I, Pol II, and Pol III loss only mildly alter chromatin interactions in mammalian cells, suggesting the 3D chromatin structures are pre-established and relatively stable.

genomics↗

bioRxiv2020

Developing bio-technical reliability among future researchers and industrial work-force in developing countries: a success story

A common problem in the biotech sector of developing countries is that a large portion of students attain a poor conceptual understanding of the basic theory and/or lack proficiency in basic laboratory skills even as they complete higher studies such as a masters degree. A small scale solution was developed in the form of a unique post-graduate diploma program that imparted reliable skills in students with good theoretical knowledge. The course of 6 to 8 months duration, with an optional 6 months internship, was successfully conducted for 8 batches. Most students of this course inculcated the right laboratory practices. This was evident by safe operations, and precise as well as accurate results of quantitative experiments conducted by them. They learned to work independently as well as in teams. They could create and follow standard operating procedures, and contribute to general laboratory maintenance. Every student also designed, prepared and conducted routine molecular biology experiments. The following aspects are suggested for successfully dealing with the patchy and varied capacities of life science students during higher (post bachelors) studies: a) careful selection of students, b) training with prioritized objectives, c) attention to basic lab-practices, d) opportunities to self-learn, e) structured group discussions, f) teacher(s) with genuine interest and passion, g) reasonable infrastructure, and h) maintaining a good student-instructor ratio. The course objectives, structure, teaching methods, and experiences are presented here along with some of the relevant data, including statistics about improvement in the precision and accuracy in experimental results by students. Limitations in this course and a general critical perspective of the routine higher education have also been discussed briefly.

scientific communication and education↗

bioRxiv2020

A one-tube method for rapid and reliable plant genomic DNA isolation for PCR analysis

BackgroundConsistent isolation of high quality plant genomic DNA is a prerequisite for successful PCR analysis. Time consumption, ease of operation and procedure cost are important secondary considerations for selecting an effective DNA extraction method. The simple, reliable and rapid DNA extraction method developed by Edwards and colleagues in 1991 [1] has proven to be the gold standard. ResultsThrough modification of the Edwards method of extraction, we have developed a one-tube protocol that greatly improves the efficiency of plant DNA extraction and reduces the potential for sample contamination while simultaneously yielding high quality DNA suitable for PCR analysis. We further show that DNA extracts prepared with this method are stable at room temperature for at least three months. ConclusionThe one-tube extraction method yields high quality plant DNA with improved efficiency while greatly minimizing the potential for cross contamination. This low-cost and environment-friendly method is widely applicable for plant molecular biology research.

plant biology↗