Biology subjects

Ivanova, A.

Publications and source records attributed to Ivanova, A..

18 recordsLinked to original sources

bioRxiv2026

Spatially resolved gene expression and tumour-microenvironment interactions across malignant transformation in IDH-mutant glioma

Isocitrate dehydrogenase (IDH)-mutant gliomas represent most lower-grade diffuse gliomas in young adults. Although IDH-mutant gliomas initially behave indolently relative to IDH-wildtype counterparts, they undergo inevitable malignant transformation. The mechanisms driving this progression remain poorly defined. We analyzed a unique longitudinal cohort of two patients with IDH-mutant diffuse gliomas, each with matched WHO grade 2, 3, and 4 tumours. Spatial transcriptomics (NanoString GeoMx and 10X Visium), combined with differential expression, spatially variable gene analysis, and gene ontology enrichment, were used to define transcriptional programs underlying progression. Unexpectedly, across both patients, higher-grade tumours demonstrated reduced proliferation at the infiltrative margin as measured by Ki67. Spatial transcriptomic analysis identified an enrichment of invasion-associated genes associated with increasing tumour grade. In an independent bulk RNA-seq cohort, expression of this spatially derived program did not outperform grade-only PFS or OS analysis. These observations underscore the need to develop new metrics that account for spatial evolution that occurs across progression, but escapes detection in bulk analyses and provide the rationale for prioritizing migration-, cytoskeletal- and stress-associated programs for further investigation.

cancer biology↗

bioRxiv2025

Optimized protocol for processing murine tumor-bearing lung tissue for flow cytometry and single cell RNA-sequencing

NSCLC accounts for approximately 85% of lung cancers, and Kirsten rat sarcoma (KRAS) is the most commonly mutated gene in NSCLC. Although management of NSCLC has advanced markedly in recent years, its heterogeneity and plasticity remain incompletely understood. Single-cell RNA sequencing (scRNA-seq) has become an essential tool for dissecting cellular heterogeneity in complex tissues such as the lung. However, generating high-quality single-cell suspensions from tumor-bearing lung tissue is challenging, particularly during tumor formation when the tissue becomes fibrotic and heterogeneous. A key requirement for successful scRNA-seq is the preparation of viable single cells with minimal processing-induced stress or damage. Here, we present a detailed step-by-step protocol for isolating high-quality single-cell suspensions from both healthy and tumor-bearing mouse lung tissue in a KrasG12D; tdTomato reporter mouse model. The procedure includes tissue perfusion, controlled enzymatic digestion, gentle mechanical dissociation, red blood cell lysis, filtration, and viability assessment, and achieves >85% viable cells prior to scRNA-seq. Finally, the tdTomato+ tumor cells are efficiently isolated by FACS and can be detected as distinct clusters by scRNA-seq using this protocol. SUMMARYWe present a detailed protocol for isolating high-quality single-cell suspensions from both healthy and tumor-bearing murine lung tissue. This protocol can be applied to scRNA-seq, flow cytometry analysis, and primary cell isolation.

cell biology↗

bioRxiv2025

Assessing the feasibility of machine learning for ancient DNA age prediction: limitations and insights

We investigated the possibility of estimating the age of ancient biological samples directly from their DNA damage profiles using supervised machine learning. Traditional dating methods such as radiocarbon dating, dendrochronology rely on either material context or isotope composition, while our approach exploits intrinsic molecular degradation signatures. Using damage statistics obtained from ancient DNA sequencing data, we trained several regression models to predict sample age over a temporal range of up to 10,000 years. Despite initial correlations between specific damage features and age, cross-validation and external testing revealed no statistically significant predictive signal beyond mean-based baselines. These findings indicate that, in the current formulation, DNA damage information alone is insufficient for reliable age estimation. However, this negative result provides important methodological insight: environmental and biochemical factors appear to dominate damage variation, effectively masking chronological signal. We suggest that integrating contextual data, expanding labeled datasets, and incorporating physical models of DNA decay may improve future attempts. Our study thus contributes to a transparent assessment of the limitations and prospects of DNA-based fossil dating.

bioinformatics↗

bioRxiv2025

AMPK Repositions Early Endosomes via Gapex-5 to Promote Delivery of Iron to Mitochondria

The regulation of the spatial organization of organelles within cells is critical for coordinating signaling, membrane traffic, and metabolite exchange. Metabolic cues regulate the position and function of lysosomes, yet whether and how metabolic signals may similarly regulate other organelles such as early endosomes (EEs) remains unclear. We find that AMP-activated protein kinase (AMPK), a key regulator of metabolic homeostasis activated in response to nutrient scarcity, triggers movement of EEs to the perinuclear region of cells, leading to enhanced proximity of endosomes to mitochondria and increased delivery of iron to mitochondria. The movement of EEs and increased mitochondrial iron content elicited by AMPK activation requires Gapex-5, a GEF for the early endosome Rab5 previously shown to be an AMPK substrate. These findings reveal a mechanism by which AMPK reprograms endosome positioning to facilitate inter-organelle communication and iron delivery to mitochondria to support metabolic adaptation under conditions of nutrient scarcity.

cell biology↗

bioRxiv2025

The mechanical properties of Arabidopsis thaliana roots adapt dynamically during development and to stress

Mechanical properties of plant cells and tissues change dynamically, influencing plant growth, development, and interactions with the environment. Despite their central roles in plant life, current knowledge of how these properties change in vivo is very limited. Here we have combined Brillouin microscopy and molecular rotors to investigate stiffness, viscosity and porosity in living Arabidopsis thaliana seedling roots during differentiation and in response to stress and genetic manipulation. We found that mechanical properties change in a cell- and tissue-specific manner. The properties change dynamically during differentiation to support directional cell expansion. Cell-type-specific adaptations are induced within hours in response to stress or changes in cell wall metabolism. The findings form the foundation for future studies to characterize regulatory mechanisms linking biochemical signaling and mechanical properties.

plant biology↗

bioRxiv2025

Secretion and signaling properties of Wnt11 and Wnt3 are determined by their N-terminus

Wnt proteins are evolutionarily conserved signaling molecules that control cell-cell communication in health and disease. While different Wnt proteins share a requirement for palmitoleoylation and the cargo receptor Evi/Wls for their secretion, they interact with diverse signaling receptors and co-receptors to elicit distinct outcomes in signal-receiving cells. The molecular mechanisms underlying this contrast between conserved post-translational modification and secretion and diverse receptor interactions remain poorly understood. Here, we demonstrate that Wnt11 maintains partial secretion capability in the absence of Evi/Wls. Unexpectedly, the secreted protein is also non-palmitoleoylated, yet retains its ability to activate downstream signaling in receiving cells through the Frizzled 6 receptor. We identify the N-terminus as the mediator of this unusual behavior, as Wnt3, which strictly requires Evi/Wls, becomes Evi/Wls-independent when its N-terminus is replaced with that of Wnt11. In different cell lines and in Xenopus laevis embryos, the chimeric Wnt11Nterm-Wnt3 protein recapitulates known Wnt11 phenotypes, demonstrating that the N-terminal portion of Wnt11 is sufficient to determine signaling specificity. Our findings reveal novel determinants of Wnt protein specificity and provide mechanistic insights into the molecular basis of Wnt secretion and downstream signaling.

cell biology↗

bioRxiv2025

Balancing Act: Groundwater microbiome''s resilience and vulnerability to hydroclimatic extremes

Groundwater health is increasingly threatened by climate change, which alters precipitation patterns, leading to groundwater recharge shifts. These shifts impact subsurface microbial communities, crucial for maintaining ecosystem functions. In this decade-long study of carbonate aquifers, we analyzed 815 bacterial 16S rRNA gene datasets, 226 dissolved organic matter (DOM) profiles, 387 metabolomic datasets, and 174 seepage microbiome sequences. Our findings reveal distinct short- and long-term temporal patterns of groundwater microbiomes driven by environmental fluctuations. Microbiomes of hydrologically connected aquifers exhibit lower temporal stability due to stochastic processes and greater susceptibility to surface disturbances, yet they demonstrate remarkable resilience. Conversely, isolated aquifer microbiomes show resistance to short-term changes, governed by deterministic processes, but exhibit reduced stability under prolonged stress. Variability in seepage-associated microorganisms, DOM, and metabolic diversity further drive microbiome dynamics. These findings highlight the dual vulnerability of groundwater systems to acute and chronic pressures, emphasizing the critical need for sustainable management strategies to mitigate the impacts of hydroclimatic extremes.

microbiology↗

bioRxiv2024

CACHE Challenge #1: targeting the WDR domain of LRRK2, a Parkinson's Disease associated protein.

The CACHE challenges are a series of prospective benchmarking exercises meant to evaluate progress in the field of computational hit-finding. Here we report the results of the inaugural CACHE #1 challenge in which 23 computational teams each selected up to 100 commercially available compounds that they predicted would bind to the WDR domain of the Parkinsons disease target LRRK2, a domain with no known ligand and only an apo structure in the PDB. The lack of known binding data and presumably low druggability of the target is a challenge to computational hit finding methods. Seventy-three of the 1955 procured molecules bound LRRK2 in an SPR assay with KD lower than 150 M and were advanced to a hit expansion phase where computational teams each selected up to 50 analogs each. Binding was observed in two orthogonal assays with affinities ranging from 18 to 140 M for seven chemically diverse series. The seven successful computational workflows varied in their screening strategies and techniques. Three used molecular dynamics to produce a conformational ensemble of the targeted site, three included a fragment docking step, three implemented a generative design strategy and five used one or more deep learning steps. CACHE #1 reflects a highly exploratory phase in computational drug design where participants sometimes adopted strikingly diverging screening strategies. Machine-learning accelerated methods achieved similar results to brute force (e.g. exhaustive) docking. First-in-class, experimentally confirmed compounds were rare and weakly potent, indicating that recent advances are not sufficient to effectively address challenging targets.

biochemistry↗

bioRxiv2024

Kinetic landscape of single virus-like particles highlights the efficacy of SARS-Cov-2 internalization

The efficiency of virus internalization into target cells is a major determinant of infectivity. SARS-CoV-2 internalization occurs via S-protein-mediated cell binding followed either by direct fusion with the plasma membrane or endocytosis and subsequent fusion with the endosomal membrane. Despite the crucial role of virus internalization, the precise kinetics of the processes involved remains elusive. We developed a pipeline, which combines live-cell microscopy and advanced image analysis, for measuring the rates of multiple internalization-associated molecular events of single SARS-CoV-2-virus-like particles (VLPs), including endosome ingression, pH change, and nucleocapsid release. Our live-cell imaging experiments demonstrate that only a few minutes after binding to the plasma membrane, VLPs ingress into Rab5-negative endosomes via Dynamin-dependent scission. Less than two minutes later, the pH of VLPs drops below 5 followed by an increase in VLP speed, yet these two events are not interrelated. Nucleocapsid release from the VLPs occurs with similar kinetics to the pH drop, suggesting that VLP fusion occurs during endosome acidification. Neither Omicron mutations nor abrogation of the S protein polybasic cleavage site altered the rate of VLP internalization events, indicating that they do not affect these processes. Finally, we observe that VLP internalization occurs two to three times faster in VeroE6 than in A549 cells, which may contribute to the greater susceptibility of the former cell line to SARS-CoV-2 infection. Taken together, our precise measurements of the kinetics of VLP internalization-associated processes shed light on their contribution to the effectiveness of SARS-CoV-2 propagation in cells. Time-lapse videos of the studied internalization events can be accessed in the dedicated COVIDynamics database.

cell biology↗

bioRxiv2023

FTSH3 facilitates complex I degradation through a direct interaction with the complex I subunit PSST

Complex I (NADH dehydrogenase), the largest complex involved in mitochondrial oxidative phosphorylation is composed of nuclear and mitochondrial encoded subunits. Its assembly requires sequential addition of subdomains and modules. As it is prone to oxidative damage, complex I subunits continually undergo proteolysis and turnover. We describe the mechanism by which complex I abundance is regulated in a complex I deficient mutant. Using a forward genetic approach we have identified that the complex I Q-module domain subunit PSST, interacts with FTSH3 (Filamentous Temperature Sensitive H3) to mediate the disassembly of the matrix arm domain module for proteolysis and turnover as a means of protein quality control. We show the direct interaction of FTSH3 with PSST and identify the amino acid residues required for this interaction. It is the ATPase function of FTSH3 that is required for the interaction, as the mutation can be compensated by a proteolytically inactive form of FTSH3. Furthermore, it cannot be compensated by FTSH10 that is also located in mitochondria, as the latter does not interact with PSST. This study reveals the mechanistic process at the resolution of the residues involved of how FTSH3 recognises complex I for degradation.

plant biology↗

bioRxiv2022

APOE Expression and Secretion are Modulated by Copper-Dependent and -Independent Mitochondrial Dysfunction

Mitochondria influence cellular function through both cell-autonomous and non-cell autonomous mechanisms, such as production of paracrine and endocrine factors. Here, we demonstrate that mitochondrial regulation of the secretome is more extensive than previously appreciated, as both genetic and pharmacological disruption of the electron transport chain caused upregulation of the Alzheimers disease risk factor apolipoprotein E (APOE) and other secretome components. This upregulation of secretory proteins was of a similar extent as modifications to the mitochondrial annotated proteome. Indirect disruption of the electron transport chain by gene editing of SLC25A mitochondrial membrane transporters as well as direct genetic and pharmacological disruption of either complexes I, III, or the copper-containing complex IV of the electron transport chain, elicited upregulation of APOE transcript, protein, and secretion, up to 49-fold. These APOE phenotypes were robustly expressed in diverse cell types and iPSC-derived human astrocytes as part of an inflammatory gene expression program. Moreover, age- and genotype-dependent decline in brain levels of respiratory complex I preceded an increase in APOE in the 5xFAD mouse model. We propose that mitochondria act as novel upstream regulators of APOE-dependent cellular processes in health and disease.

cell biology↗

bioRxiv2022

The language network reliably 'tracks' naturalistic meaningful non-verbal stimuli

The language network, comprised of brain regions in the left frontal and temporal cortex, responds robustly and reliably during language comprehension but shows little or no response during many non-linguistic cognitive tasks (e.g., Fedorenko & Blank, 2020). However, one domain whose relationship with language remains debated is semantics--our conceptual knowledge of the world. Given that the language network responds strongly to meaningful linguistic stimuli, could some of this response be driven by the presence of rich conceptual representations encoded in linguistic inputs? In this study, we used a naturalistic cognition paradigm to test whether the cognitive and neural resources that are responsible for language processing are also recruited for processing semantically rich non-verbal stimuli. To do so, we measured BOLD responses to a set of [~]5-minute-long video and audio clips that consisted of meaningful event sequences but did not contain any linguistic content. We then used the inter-subject correlation (ISC) approach (Hasson et al., 2004) to examine the extent to which the language network tracks these stimuli, i.e. exhibits stimulus-related variation. Across all the regions of the language network, non-verbal meaningful stimuli elicited reliable ISCs. These ISCs were higher than the ISCs elicited by semantically impoverished non-verbal stimuli (e.g., a music clip), but substantially lower than the ISCs elicited by linguistic stimuli. Our results complement earlier findings from controlled experiments (e.g., Ivanova et al., 2021) in providing further evidence that the language network shows some sensitivity to semantic content in non-verbal stimuli.

neuroscience↗

bioRxiv2022

LanA (Language Atlas): A probabilistic atlas for the language network based on fMRI data from >800 individuals

Two analytic traditions characterize fMRI language research. One relies on averaging activations voxel-wise across individuals. This approach has limitations: because of inter-individual variability in the locations of language areas, a location in a common brain space cannot be meaningfully linked to function. An alternative approach relies on identifying language areas in each individual using a functional localizer. Because of its greater sensitivity, functional resolution, and interpretability, functional localization is gaining popularity, but it is not always feasible, and cannot be applied retroactively to past studies. We provide a solution for bridging these currently disjoint approaches in the form of a probabilistic functional atlas created from fMRI data for an extensively validated language localizer in 806 individuals. This atlas enables estimating the probability that any given location in a common brain space belongs to the language network, and thus can help interpret group-level peaks and meta-analyses of such peaks, and lesion locations in patient investigations. More meaningful comparisons of findings across studies should increase robustness and replicability in language research.

neuroscience↗

bioRxiv2021

Analysis of 329,942 SARS-CoV-2 records retrieved from GISAID database

BackgroundThe 31st of December 2019 was when the World Health Organization received a report about an outbreak of pneumonia of unknown etiology in the Chinese city of Wuhan. The outbreak was the result of the novel virus labeled as SARS-CoV-2, which spread to about 220 countries and caused approximately 3,311,780 deaths, infecting more than 159,319,384 people by May 12th, of 2021. The virus caused a worldwide pandemic leading to panic, quarantines, and lockdowns - although none of its predecessors from the coronavirus family have ever achieved such a scale. The key to understanding the global success of SARS-CoV-2 is hidden in its genome. Materials and MethodsWe retrieved data for 329,942 SARS-CoV-2 records uploaded to the GISAID database from the beginning of the pandemic until the 8th of January 2021. To process the data, a Python variant detection script was developed, using pairwise2 from the BioPython library. Pandas, Matplotlib, and Seaborn, were applied to visualize the data. Genomic coordinates were obtained from the UCSC Genome Browser (https://genome.ucsc.edu/). Sequence alignments were performed for every gene separately. Genomes less than 26,000 nucleotides long were excluded from the research. Clustering was performed using HDBScan. ResultsHere, we addressed the genetic variability of SARS-CoV-2 using 329,942 worldwide samples. The analysis yielded 155 genome variations (SNPs and deletions) in more than 0.3% of the sequences. Nine common SNPs were present in more than 20% of the samples. Clustering results suggested that a proportion of people (2.46%) were infected with a distinct subtype of the B.1.1.7 variant. The subtype may be characterized by four to six additional mutations, with four being a more frequent option (G28881A, G28882A, and G28883[C] in the N gene, A23403G in S, A28095T in ORF8, G25437T in ORF3a). Two clusters were formed by mutations in the samples uploaded predominantly by Denmark and Australia, which may indicate the emergence of "Danish" and "Australian" variants. Five clusters were linked to increased/decreased age, shifted gender ratio, or both. According to a correlation coefficient matrix, 69 mutations correlate with at least one other mutation (correlation coefficient greater than 0.7). We also addressed the completeness of the GISAID database, where between 77% and 93% of the fields were either left blank or filled incorrectly. Metadata mining analysis has led to a hypothesis about gender inequality in medical care in certain countries. Finally, we found ORF6 and E as the most conserved genes (96.15% and 94.66% of the sequences totally match the reference, respectively), making them potential targets for vaccines and treatment. Our results indicate areas of the SARS-CoV-2 genome that researchers can focus on for further structural and functional analysis.

bioinformatics↗

bioRxiv2021

Sequential in vivo labeling of insulin secretory granule pools in INS-SNAP transgenic pigs

{beta}-cells produce, store and secrete insulin upon elevated blood glucose levels. Insulin secretion is a highly regulated process. The probability for insulin secretory granules to undergo fusion with the plasma membrane or being degraded is correlated with their age. However, the molecular features and stimuli connected to this behavior have not yet been fully understood. Furthermore, our understanding of {beta}-cell function is mostly derived from studies of ex vivo isolated islets and/or rodent models. To overcome this translational gap and study insulin secretory granule turnover in vivo, we have generated a transgenic pig model with the SNAP-tag fused to insulin. We demonstrate the correct targeting and processing of the tagged insulin and normal glycemic control of the pig model. Furthermore, we show specific single- and dual-color granular labeling of in vivo labeled pig pancreas. This model may provide unprecedented insights into the in vivo insulin secretory granule behavior in an animal close to humans.

cell biology↗

bioRxiv2020

The root of the transmissible cancer: first description of a widespread Mytilus trossulus-derived cancer lineage in M. trossulus

Two lineages of bivalve transmissible neoplasia (BTN), BTN1 and BTN2, are known in blue mussels Mytilus. Both lineages derive from the Pacific mussel M. trossulus and are identified primarily by the unique genotypes of the nuclear gene EF1. BTN1 is found in populations of M. trossulus from the Northeast Pacific, while BTN2 has been detected in populations of other Mytilus species worldwide but not in M. trossulus itself. The aim of our study was to examine mussels M. trossulus from the Sea of Japan (Northwest Pacific) for the presence of BTN. Using hemocytology and flow cytometry of the hemolymph, we confirmed disseminated neoplasia in our specimens. Cancerous mussels possessed the unique BTN2 EF1 genotype and two mitochondrial haplotypes with different recombinant control regions, similar to that of common BTN2 lineages. This is the first report of BTN2 in its original host species M. trossulus populations in West Pacific may be the birthplace of BTN2 and a natural reservoir where it is maintained and whence it spreads worldwide. A comparison of all available BTN and M. trossulus COI sequences suggests a common and recent, though presumably prehistoric origin of BTN2 diversity in populations of M. trossulus outside the Northeast Pacific.

pathology↗

bioRxiv2018

Astroplastic: A start-to-finish process for polyhydroxybutyrate production from solid human waste using genetically engineered bacteria to address the challenges for future manned Mars missions

Space exploration has long been a source of inspiration, challenging scientists and engineers to find innovative solutions to various problems. One of the current focuses in space exploration is to send humans to Mars. However, the challenge of transporting materials to Mars and the need for waste management processes are two major obstacles for these long-duration missions.\n\nTo address these two challenges a process called Astroplastic was developed that produces polyhydroxybutyrate (PHB) from solid human waste, which can be used to 3D print useful items for astronauts. PHB granules are naturally produced by bacteria such as Ralstonia eutropha and Pseudomonas aeruginosa for carbon and energy storage. The phaJ, phaC, and phaCBA genes were cloned from these native PHB-producing bacteria into Escherichia coli. These genes code for enzymes that aid in PHB production by converting products of glycolysis and {beta}-oxidation pathways, such as acetyl-CoA and enoyl-CoA, into PHB. To ensure a continuous PHB production system and to eliminate the need for cell lysis to extract PHB, recombinant E. coli was engineered to use the genes in its natural type I secretion system to secrete PHB. The C-terminal of the HlyA secretion tag was fused to phasin (PhaP), a protein originally from R. eutropha. Phasin-HlyA electrostatically binds PHB granules and transports them outside of the cell.\n\nIn addition to genetically engineering bacteria, a concept for start-to-finish PHB production process was designed. Integrating expert feedback and experimental results, conditions for each step of the process including the collection and storage of waste, volatile fatty acid (VFA) fermentation, VFA extraction, PHB fermentation, and PHB extraction were optimized. The optimized system will provide a sustainable and continuous PHB production system, which will address the problems of transportation costs and waste management for future space missions.\n\nFinancial DisclosureMindfuel Science Alberta Foundation Genome Alberta GenScript Polyferm Canada GeekStarter Alberta Integrated DNA Technologies University of Calgary University of Calgary Cumming School of Medicine University of Calgary Bachelor of Sciences University of Calgary Schulich School of Engineering University of Calgary OBrien Centre for the Bachelor of Health Sciences City of Calgary Alberta Innovates The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.\n\nCompeting InterestsThe authors have declared that no competing interests exist.\n\nEthics StatementN/A\n\nData AvailabilityAll data are freely available without restriction.

synthetic biology↗

bioRxiv2017

Loss of Wt1 in the murine spinal cord alters interneuron composition and locomotion

Rhythmic and patterned locomotion is driven by spinal cord neurons that form neuronal circuits, referred to as central pattern generators (CPGs). Recently, dI6 neurons were suggested to participate in the control of locomotion. The dI6 neurons can be subdivided into three populations, one of which expresses the Wilms tumor suppressor gene Wt1. However, the role that Wt1 exerts on these cells is not understood. Here, we aimed to identify behavioral changes and cellular alterations in the spinal cord associated with Wt1 deletion. Locomotion analyses of mice with neuron-specific Wt1 deletion revealed that these mice ran slower than controls with a decreased stride frequency and an increased stride length. These mice showed changes in their fore-hindlimb coordination, which were accompanied by a loss of contralateral projections in the spinal cord. Neonates with Wt1 deletion displayed an increase in uncoordinated hindlimb movements and their motor neuron output was arrhythmic with a decreased frequency. The population size of dI6, V0 and V2a neurons in the developing spinal cord of conditional Wt1 mutants was significantly altered. These results show that the development of particular dI6 neurons depends on Wt1 expression and loss of Wt1 is associated with alterations in locomotion.

neuroscience↗