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Results for “cell biology”

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 Read source abstracts and check manuscript versions; preprints are not peer reviewed.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 217 records · Page 12Linked to original sources

bioRxiv2019

De novo identification of toxicants that cause irreparable damage to parasitic nematode intestinal cells

Efforts to identify new drugs for therapeutic and preventive treatments against parasitic nematodes have gained increasing interest with expanding pathogen omics databases and drug databases from which new anthelmintic compounds might be identified. Here, a novel approach focused on integrating a pan-Nematoda multi-omics data targeted to a specific nematode organ system (the intestinal tract) with evidence-based filtering and chemogenomic screening was undertaken. Based on de novo computational target prioritization of the 3,564 conserved intestine genes in A. suum, exocytosis was identified as a high priority pathway, and predicted inhibitors of exocytosis were tested using the large roundworm (Ascaris suum larval stages), a filarial worm (Brugia pahangi adult and L3), a whipworm (Trichuris muris adult), and the non-parasitic nematode Caenorhabditis elegans. 10 of 13 inhibitors were found to cause rapid immotility in A. suum L3 larvae, and five inhibitors were effective against the three phylogenetically diverse parasitic nematode species, indicating potential for a broad spectrum anthelmintics. Several distinct pathologic phenotypes were resolved related to molting, motility, or intestinal cell and tissue damage using conventional and novel histologic methods. Pathologic profiles characteristic for each inhibitor will guide future research to uncover mechanisms of the anthelmintic effects and improve on drug designs. This progress firmly validates the focus on intestinal cell biology as a useful resource to develop novel anthelmintic strategies. Author summaryThe intestinal cells of parasitic nematodes are not known to regenerate, therefore disruption of essential processes that cause irreparable damage to intestinal cells is expected to promote worm expulsion. To facilitate improved methods of therapy we need to better understand the basic intestinal cell and tissue functions of this critical organ. To that end have undertaken a comprehensive analysis of multi-omics omics data and identify and prioritize intestinal genes/pathways with essential functions and associated drugs and established a foundational model of the STH intestinal system using the large roundworm Ascaris suum to test and validate inhibitors of these functions. We found 10 inhibitors to impacted motility, and seven of those showed severe pathology and an apparent irreparable damage to intestinal cells. Furthermore, five inhibitors were effective against the three phylogenetically diverse parasitic nematode species, indicating potential for a broad spectrum anthelmintics. Our results firmly validate the focus on intestinal cell biology as a useful resource to develop novel anthelmintic strategies.

pathology↗

bioRxiv2022

Influence of genetic ancestry on breast stromal cells provides biologic basis for increased incidence of metaplastic breast cancer in women of African descent

The biologic basis of genetic ancestry-dependent variability in disease incidence and outcome is just beginning to be explored. We recently reported enrichment of a population of ZEB1-expressing cells located adjacent to the ductal epithelial cells in the normal breast of women of African Ancestry (AA) compared to European Ancestry (EA). By establishing and characterizing cell lines corresponding to these cells and validating in vitro findings with tissue microarrays of healthy breast tissue from AA, EA and Latina Ancestry (LA) women, we demonstrate that these cells have the properties of fibroadipogenic/mesenchymal stromal cells that express PROCR and PDGFR. PROCR+/ZEB1+/PDGFR+ cells, hence renamed as PZP cells, are enriched in the normal breast tissues of AA compared to EA or LA women. In vitro, PZP cells trans-differentiated into adipocytes or osteocytes. In co-culture conditions, PZP:epithelial cell communication resulted in luminal epithelial cells acquiring basal/stem cell characteristics and increased expression of IL-6 suggesting the impact of this communication on breast epithelial hierarchy and the microenvironment. Consistent with this possibility, the level of phospho-STAT3, which is a downstream target of IL-6, was higher in the normal and cancerous breast tissues of AA compared to EA women. PZP cells transformed with HRasG12V {+/-} SV40-T/t antigens generated metaplastic carcinoma in NSG mice suggesting that these cells could be the cell-of-origin of metaplastic breast cancers. Collectively, these results identify a stromal cell component that could influence the biology of breast cancer in AA women.

cancer biology↗

bioRxiv2023

Evolution of intracellular free radical load in colon adenocarcinoma cells over the course of butyrate-induced redifferentiation

Fluorescent nanodiamonds have exceptional optical properties and are highly biocompatible, which allows to use them as labels for long-term tracking of the cells. The research fields that make use of this application of nanodiamonds include stem cell biology and cancer biology, where quiescent and differentiating cells can be traced in vitro and in vivo. However, these studies focus on using nanodiamonds as simple labels, whereas they can serve as highly sensitive intracellular sensors for free radical species. In this study, we aimed to bring the two approaches together and to assess the free radical production in the cells over the course of their differentiation. We report on the successful enterocytic differentiation of HT-29 colon adenocarcinoma cells, pre-loaded with fluorescent nanodiamonds. The cells were cultured in butyrate-free or butyrate-supplemented medium for 13 days. Butyrate-treated cells developed the morphological and molecular traits, characteristic for normal enterocytes. Fluorescent nanodiamonds did not have a negative effect on the process of differentiation. Moreover, the particles could be found in the cytoplasm of both undifferentiated and re-differentiated cells even after 13 days of culture. The internalized nanodiamonds were used to assess the free radical load in the undifferentiated and re-differentiated HT-29 cells at different stages of the experiment. Consistently with previous findings, re-differentiated HT-29 cells showed higher free radical load than undifferentiated ones.

cell biology↗

bioRxiv2024

Influence of formaldehyde on signaling pathways when used in mammalian cell culture

Formaldehyde is the smallest existing aldehyde, a highly reactive color less gas at room temperature and ubiquitously present in our atmosphere. Because of its reactivity leading to the crosslinking of macromolecules like proteins, it is widely used in industrial applications, but also in cell biology in order to preserve cells and tissues for further analysis. In this work, we show that formaldehyde releasing solutions commonly used for fixation of cells, can diffuse via the gas phase to the neighboring well and influence signaling processes in the therein cultured cells. To analyze this effect, we utilized a stable reporter cell line for YAP signaling or a gene expression-based reporter for activation of the NF-{kappa}B pathway. Especially the stable reporter cell line can also be used as sensor for bioavailable formaldehyde. The observed impact of formaldehyde on cellular signaling underscores the need for careful planning of experimental protocols and emphasizes the importance of implementing proper controls when utilizing this reagent in cellular signaling analyses.

cell biology↗

bioRxiv2019

Cytoplasmic volume and limiting nucleoplasmin scale nuclear size during Xenopus laevis development

How nuclear size is regulated relative to cell size is a fundamental cell biological question. Reductions in both cell and nuclear sizes during Xenopus laevis embryogenesis provide a robust scaling system to study mechanisms of nuclear size regulation. To test if the volume of embryonic cytoplasm is limiting for nuclear growth, we encapsulated gastrula stage embryonic cytoplasm and nuclei in droplets of defined volume using microfluidics. Nuclei grew and reached new steady-state sizes as a function of cytoplasmic volume, supporting a limiting component mechanism of nuclear size control. Through biochemical fractionation, we identified the histone chaperone nucleoplasmin (Npm2) as a putative nuclear size-scaling factor. Cellular amounts of Npm2 decrease over development, and nuclear size was sensitive to Npm2 levels both in vitro and in vivo, affecting nuclear histone levels and chromatin organization. Thus, reductions in cell volume with concomitant decreases in Npm2 amounts represent a developmental mechanism of nuclear size-scaling that may also be relevant to cancers with increased nuclear size.

cell biology↗

bioRxiv2023

FREEDA: an automated computational pipeline guides experimental testing of protein innovation by detecting positive selection

Cell biologists typically focus on conserved regions of a protein, overlooking innovations that can shape its function over evolutionary time. Computational analyses can reveal potential innovations by detecting statistical signatures of positive selection that leads to rapid accumulation of beneficial mutations. However, these approaches are not easily accessible to non-specialists, limiting their use in cell biology. Here, we present an automated computational pipeline FREEDA (Finder of Rapidly Evolving Exons in De novo Assemblies) that provides a simple graphical user interface requiring only a gene name, integrates widely used molecular evolution tools to detect positive selection, and maps results onto protein structures predicted by AlphaFold. Applying FREEDA to >100 mouse centromere proteins, we find evidence of positive selection in intrinsically disordered regions of ancient domains, suggesting innovation of essential functions. As a proof-of-principle experiment, we show innovation in centromere binding of CENP-O. Overall, we provide an accessible computational tool to guide cell biology research and apply it to experimentally demonstrate functional innovation.

cell biology↗

bioRxiv2024

Temperature-induced membrane trafficking drives antibody delivery to the brain

Despite quotidian occurrence of fever and hyperthermia, cell biological mechanisms underlying their effects remain unclear. Neurological complications of severe (>40{degrees}C) fever have been associated with increased blood-brain barrier (BBB) permeability due to structural disruption, while little is known about brain physiology of moderate fever. Here, we show that a temperature increase to 39-40{degrees}C increased fluid-phase uptake in PC12 cells and primary neurons. Uptake of selective cargoes showed that clathrin-mediated endocytosis and macropinocytosis were induced in a translation-dependent manner, consistent with a role for heat shock response. Exocytic recycling was also increased by hyperthermia, suggesting a comprehensive boost of membrane trafficking. Mild (<39{degrees}C) whole-body hyperthermia in vivo triggered fluid-phase uptake in various organs, notably enabling brain accumulation of an intravenously injected antibody that was blocked by dynamin inhibition. Taken together, our findings show that fever systemically regulates membrane trafficking, reveal dynamin-dependent endocytosis as a cell biological mechanism for temperature control of BBB permeability, and demonstrate a clinical potential of mild hyperthermia for facilitating brain delivery of biologic drugs. HighlightsO_LITemperature increase of 2-3{degrees}C upregulates endocytosis and exocytosis C_LIO_LITemperature-induced upregulation of membrane trafficking requires protein translation and dynamin function C_LIO_LIMild whole-body hyperthermia enhances fluid-phase endocytosis across the body C_LIO_LIMild hyperthermia enables delivery of an exogenous antibody from the bloodstream into the brain through a dynamin-dependent pathway C_LI

cell biology↗

bioRxiv2020

Fibrinogen anchors enable efficient multiplexed patterning of active proteins and subcellular control of membrane-receptor distribution

Protein micropatterning allows proteins to be precisely deposited onto a substrate of choice, and is now routinely used in cell biology and in vitro reconstitution. However, a drawback of current technology is that micropatterning efficiency can be variable between proteins, and that proteins may lose activity on the micropatterns. Here, we describe a general method to enable micropatterning of virtually any protein at high specificity and homogeneity while maintaining its activity. Our method is based on an anchor that micropatterns well, Fibrinogen, which we functionalized to bind to common purification tags. This enhances micropatterning on various substrates, facilitates multiplexed micropatterning, and dramatically improves the on-pattern activity of fragile proteins like molecular motors. Furthermore, it enhances the micropatterning of hard to micropattern cells. Last, this method enables subcellular micropatterning, whereby complex micropatterns simultaneously control cell shape and the distribution of transmembrane receptors within that cell. Altogether, these results open new avenues for cell biology.

cell biology↗

bioRxiv2022

Optimized fluorescent proteins for 4-color and photoconvertible live-cell imaging in Neurospora crassa

Fungal cells are quite unique among life in their organization and structure, and yet implementation of many tools recently developed for fluorescence imaging in animal systems and yeast has been slow in filamentous fungi. Here we present analysis of properties of fluorescent proteins in Neurospora crassa as well as describing genetic tools for the expression of these proteins that may be useful beyond cell biology applications. The efficacy of ten different fluorescent protein tags were compared in a constant context of genomic and intracellular location; six different promoters are described for the assessment of the fluorescent proteins and varying levels of expression, as well as a customizable bidirectional promoter system. We present an array of fluorescent proteins suitable for use across the visible light spectrum to allow for 4-color imaging, in addition to a photoconvertible fluorescent protein that enables a change in the color of a small subset of proteins in the cell. These tools build on the rich history of cell biology research in filamentous fungi and provide new tools to help expand research capabilities.

cell biology↗

bioRxiv2016

Multiplex shRNA Screening of Germ Cell Development by in vivo Transfection of Mouse Testis

Spermatozoa are one of the few mammalian cells types that cannot be fully derived in vitro, severely limiting the application of modern genomic techniques to study germ cell biology. The current gold standard approach of characterizing single gene knockout mice is slow as generation of each mutant line can take 6-9 months. Here, we describe an in vivo approach to rapid functional screening of germline genes based on a new non-surgical, non-viral in vivo transfection method to deliver nucleic acids into testicular germ cells. By coupling multiplex transfection of short hairpin RNA constructs with pooled amplicon sequencing as a readout, we were able to screen many genes for spermatogenesis function in a quick and inexpensive experiment. We transfected nine mouse testes with a pilot pool of RNAi against well-characterized genes to show that this system is highly reproducible and accurate. With a false negative rate of 18% and a false positive rate of 12%, this method has similar performance as other RNAi screens in the well-described Drosophila model system. In a separate experiment, we screened 26 uncharacterized genes computationally predicted to be essential for spermatogenesis and found numerous candidates for follow up studies. Further, by characterizing the effect of both libraries on neuronal N2a cells, we show that our screening results from testis are tissue-specific. Our calculations indicate that the current implementation of this approach could be used to screen thousands of protein-coding genes simultaneously in a single mouse testis. The experimental protocols and analysis scripts provided will enable other groups to use this procedure to study diverse aspects of germ cell biology ranging from epigenetics to cell physiology. This approach also has great promise as an applied tool for validating diagnoses made from medical genome sequencing, or designing synthetic biological sequences that act as potent and highly specific male contraceptives.

Genomics↗

bioRxiv2025

Methods for simulations with thousands of interacting objects to model mass transport in the brain

Clearance of toxic species that may cause neurodegenerative diseases relies on convection and diffusion of mass around cells in the central nervous system. In this manuscript, methods that allow the nanoscale modeling of mass transport around cells in the brain at a resolution of 8 nm are described. The cells are modeled as surface meshes and a parallelization scheme is used to solve the diffusion equation directly on the surface mesh of each biological cell independently. This is followed by mass exchange between biological cells that are in direct contact. The analysis volume size is fixed at 4 m x 4 m x 4 m but arrays of analysis volumes of arbitrary size may be analyzed, with fluxes across analysis volume boundaries updated at each time step by a semi-implicit formulation. Setup of the discretized equations is described, along with the face matching that allows mass transfer between cells. Parallelization is via a manager/worker framework. One-sided RMA communication in MPI is used to coordinate the efforts of multiple workers, with common information handled by the manager. This specialized framework is suitable for analyzing diffusional transport around thousands of interacting objects simultaneously. The framework is implemented with custom code developed in Julia, which is used here as a rapid prototyping language. Using model geometries, the accuracy of the discretization methods are demonstrated, with limitations and next steps described. Authors summaryThe methods that enable modeling diffusional mass transport around thousands of objects in parallel are described. The accuracy of the method with model objects is demonstrated.

bioengineering↗

bioRxiv2024

Novel Nuclear Roles for Testis-Specific ACTL7A and ACTL7B Supported by In Vivo Characterizations and AI Facilitated In Silico Mechanistic Modeling with Implications for Epigenetic Regulation in Spermiogenesis.

A mechanistic role for nuclear function of testis-specific actin related proteins (ARPs) is proposed here through contributions of ARP subunit swapping in canonical chromatin regulatory complexes. This is significant to our understanding of both mechanisms controlling regulation of spermiogenesis, and the expanding functional roles of the ARPs in cell biology. Among these roles, actins and ARPs are pivotal not only in cytoskeletal regulation, but also in intranuclear chromatin organization, influencing gene regulation and nucleosome remodeling. This study focuses on two testis-specific ARPs, ACTL7A and ACTL7B, exploring their intranuclear activities and broader implications utilizing combined in vivo, in vitro, and in silico approaches. ACTL7A and ACTL7B, previously associated with structural roles, are hypothesized here to serve in chromatin regulation during germline development. This study confirms the intranuclear presence of ACTL7B in spermatocytes and round spermatids, revealing a potential role in intranuclear processes, and identifies a putative nuclear localization sequence conserved across mammalian ACTL7B, indicating a potentially unique mode of nuclear transport which differs from conventional actin. Ablation of ACTL7B leads to varied transcriptional changes reported here. Additionally, in the absence of ACTL7A or ACTL7B there is a loss of intranuclear localization of HDAC1 and HDAC3, which are known regulators of epigenetic associated acetylation changes that in turn regulate gene expression. Thus, these HDACs are implicated as contributors to the aberrant gene expression observed in the KO mouse testis transcriptomic analysis. Furthermore, this study employed and confirmed the accuracy of in silico models to predict ARP interactions with Helicase-SANT-associated (HSA) domains, uncovering putative roles for testis-specific ARPs in nucleosome remodeling complexes. In these models, ACTL7A and ACTL7B were found capable of binding to INO80 and SWI/SNF nucleosome remodeler family members in a manner akin to nuclear actin and ACTL6A. These models thus implicate germline-specific ARP subunit swapping within chromatin regulatory complexes as a potential regulatory mechanism for chromatin and associated molecular machinery adaptations in nuclear reorganizations required during spermiogenesis. These results hold implications for male fertility and epigenetic programing in the male-germline that warrant significant future investigation. In summary, this study reveals that ACTL7A and ACTL7B play intranuclear gene regulation roles in male gametogenesis, adding to the multifaceted roles identified also spanning structural, acrosomal, and flagellar stability. ACTL7A and ACTL7B unique nuclear transport, impact on HDAC nuclear associations, impact on transcriptional processes, and proposed mechanism for involvement in nucleosome remodeling complexes supported by AI facilitated in silico modeling contribute to a more comprehensive understanding of the indispensable functions of ARPs broadly in cell biology, and specifically in male fertility.

cell biology↗

bioRxiv2022

ALIBY: ALFA Nanobody-Based Toolkit for Imaging and Biochemistry in Yeast

Specialized epitope tags continue to be an integral component in various biochemical and cell biological applications such as fluorescence microscopy, immunoblotting, immunoprecipitation, and protein purification. However, until recently, no single tag could offer this complete set of functionalities on its own. Here, we present a plasmid-based toolkit named ALIBY (ALFA Toolkit for Imaging and Biochemistry in Yeast) that provides a universal workflow to adopt the versatile ALFA tag/NbALFA system within the well-established model organism Saccharomyces cerevisiae. The kit comprises of tagging plasmids for labelling a protein-of-interest with the ALFA tag, and detection plasmids encoding a fluorescent protein-tagged NbALFA for live-cell imaging purposes. We demonstrate the suitability of ALIBY for visualizing the spatiotemporal localization of yeast proteins (i.e., cytoskeleton, nucleus, centrosome, divisome and exocyst) in live cells. Our approach has yielded an excellent signal-to-noise ratio without off-targeting or effect on cell growth. In summary, our yeast-specific toolkit aims to simplify and further advance the live-cell imaging of differentially abundant yeast proteins while also being suitable for biochemical applications. ImportanceIn yeast research, conventional fluorescent protein tags and small epitope tags are widely used to study the spatiotemporal dynamics and activity of proteins. Though proven to be efficient, these tags lack the versatility for usage across different cell biological and biochemical studies of a given protein-of-interest. Therefore, there is an urgent need for a unified platform for visualization, biochemical, and functional analyses of proteins-of-interest in yeast. Herein, we have engineered ALIBY, a plasmid-based toolkit which expands the benefits of the recently developed ALFA tag/NbALFA system to studies in the well-established model organism Saccharomyces cerevisiae. We demonstrate that ALIBY provides a simple and versatile strain construction workflow for long duration live-cell imaging and biochemical applications in yeast.

cell biology↗

bioRxiv2022

Navigating Multiple Environments with Emergent Grid Cell Remapping

Animals employ a neural system to map physical environmental position to neural activity and encode allocentric location. Grid cells, proposedly a vital component of this system, form a population code of space by firing in characteristic tessellated triangles of locations. This population code remaps across environments and behavioural states, independently of specific sensory inputs, pointing to a substrate of standard computation across environments, which many speculate to be path integration. However, testing whether these cells are crucial for path integration is outside the scope of current experiments and calls for complementary methods, possibly given by computational models. Recently, normative artificial neural network models have shown that path integration and grid-cell-like activity can be found in recurrent neural networks (RNNs) trained to navigate in a simulated two-dimensional environment. Remarkably, the emergent spatial profile of these grid-like cells is similar to biological cell responses in that they set up a toroidal structure. Here, we extend the RNN normative model to multiple environments and show that cells that form the toroidal structure are crucial for path integration. However, cells selected through the grid cell score, a common defining property of grid cells, are much less important and comparable to randomly selected cells. Moreover, we show that the model can navigate multiple environments and that toroidal cells remap across environments in a biologically plausible way. Results demonstrate a causal relation between toroidal cells and path integration in virtual agents and propose a mechanism of remapping in grid cells based on remapping in place cells. The work is anticipated to impact both experimental and computational neuroscience and machine learning due to the methods employed and the evaluation of results. For example, we propose explicit experiments that can evaluate both the models validity and the role of grid cells in navigation. Moreover, the model may elucidate how high-dimensional data is mapped to low-dimensional structures, possibly providing a substrate for interpolation.

neuroscience↗

bioRxiv2021

mTOR controls neurotoxic lysosome exocytosis in inflammatory reactive astrocytes

Astrocytes respond and contribute to neuroinflammation by adopting inflammatory reactive states. Although recent efforts have characterized the gene expression signatures associated with these reactive states, the cell biology underlying inflammatory reactive astrocyte phenotypes remains under-explored. Here, we used CRISPR-based screening in human iPSC-derived astrocytes to identify mTOR activation a driver of cytokine-induced endolysosomal system remodeling, manifesting as alkalinization of endolysosomal compartments, decreased autophagic flux, and increased exocytosis of certain endolysosomal cargos. Through endolysosomal proteomics, we identified and focused on one such cargo - IL-32, a disease-associated pro-inflammatory cytokine not present in rodents, whose secretion mechanism is not well understood. We found that IL-32 was partially secreted in extracellular vesicles likely to be exosomes. Furthermore, we found that IL-32 was involved in the polarization of inflammatory reactive astrocyte states, was upregulated in astrocytes in multiple sclerosis lesions, and preferentially co-localized with astrocytes in hypoxic-ischemic encephalopathy. We believe that our results advance our understanding of cell biological pathways underlying inflammatory reactive astrocyte phenotypes and identify potential therapeutic targets.

cell biology↗

bioRxiv2025

Specialized Molecular Pathways Drive the Formation of Light-Scattering Assemblies in Leucophores

Pigmentation plays a vital role in the survival of organisms, supporting functions such as camouflage, communication, and mate attraction. In vertebrates, these functions are mediated by specialized pigment cells known as chromatophores of which, uric acid crystal-forming leucophores remain the least understood, with little known about their molecular mechanisms. A key question in pigment cell biology is whether different crystal chemistries require distinct molecular pathways, or whether similar cellular processes drive the formation of diverse crystals. This study was designed to unravel the uncharacterized process of uric acid crystallization in leucophores and compare them to guanine crystal formation in iridophores and pterin formation in xanthophores. The results of our transcriptomic, ultrastructural, and metabolomic analyses, demonstrate that leucophores share molecular pathways with iridophores, particularly those connected to organelle organization and purine metabolism, but express discrete genes involved in uric acid biosynthesis and storage. Additionally, leucophores share intracellular trafficking and pterin biosynthesis genes with xanthophores, suggesting universally conserved processes. Ultrastructural studies reveal star-like fibrous structures in leucosomes, which likely serve as scaffolds for unique one-dimensional uric acid assemblies that radiate from the core and act as efficient light scatterers. These findings provide new insights into leucophore cell biology and the specialized mechanisms driving molecular crystalline assembly, and reveal that while some cellular processes are conserved, the specific chemistry of each crystal type drives the evolution of distinct molecular pathways.

cell biology↗

bioRxiv2024

Engineering fluorescent reporters in human pluripotent cells and strategies for live imaging human neurogenesis

Investigation of cell behaviour and cell biological processes underlying human development is facilitated by creation of fluorescent reporters in human pluripotent stem cells, which can be differentiated into cell types of choice. Here we report use of a piggyBac transposon-mediated stable integration strategy to engineer human pluripotent stem cell reporter lines. These express a plasma membrane localised protein tagged with the fluorescent proteins eGFP or mKate2, the photoconvertible nuclear marker H2B-mEos3.2, or the cytoskeletal protein F-tractin tagged with mKate2. Focussing on neural development these lines were used to live image and quantify cell behaviours, including cell cycle progression and cell division orientation in spinal cord rosettes. Further, lipofection-mediated introduction of piggyBac constructs into human neural progenitors labelled single cells and small cell groups within rosettes, allowing individual cell behaviours including neuronal delamination to be monitored. Finally, using the F-tractin-mKate2 hiPSC line, novel actin dynamics were captured during proliferation in cortical neural rosettes. This study presents and validates new tools and techniques with which to interrogate human cell behaviour and cell biology using live imaging approaches.

developmental biology↗

bioRxiv2018

Fission Yeast Cells Grow Approximately Exponentially

How the rate of cell growth is influenced by cell size is a fundamental question of cell biology. The simple model that cell growth is proportional to cell size, based on the proposition that larger cells have proportionally greater synthetic capacity than smaller cells, leads to the predication that the rate of cell growth increases exponentially with cell size. However, other modes of cell growth, including bilinear growth, have been reported. The distinction between exponential and bilinear growth has been explored in particular detail in the fission yeast Schizosaccharomyces pombe. We have revisited the mode of fission yeast cell growth using high-resolution time-lapse microscopy and find, as previously reported, that these two growth models are difficult to distinguish both because of the similarity in shapes between exponential and bilinear curves over the two-fold change in length of a normal cell cycle and because of the substantial biological and experimental noise inherent to these experiments. Therefore, we contrived to have cells grow more than two fold, by holding them in G2 for up to eight hours. Over this extended growth period, in which cells grow up to 5.5-fold, the two growth models diverge to the point that we can confidently exclude bilinear growth as a general model for fission yeast growth. Although the growth we observe is clearly more complicated than predicted by simple exponential growth, we find that exponential growth is a robust approximation of fission yeast growth, both during an unperturbed cell cycle and during extended periods of growth.

cell biology↗