scholarly journals Coordinated crosstalk between microtubules and actin by a spectraplakin regulates lumen formation and branching

2020 ◽  
Author(s):  
Delia Ricolo ◽  
Sofia J. Araújo
Keyword(s):  
Branching Processes ◽  
Single Cells ◽  
Membrane Dynamics ◽  
Direct Response ◽  
Tracheal System ◽  
Lumen Formation ◽  
Microtubule Organizing Centres ◽  
Branching Points ◽  
Key Players ◽  
Fgf Signalling

SUMMARYThe establishment of branched structures by single cells involves complex cytoskeletal remodelling events. In Drosophila, epithelial tracheal system terminal cells (TCs) and dendritic arborisation neurons are models for these subcellular branching processes. During tracheal embryonic development, the generation of subcellular branches is characterized by extensive remodelling of the microtubule (MT) network and actin cytoskeleton, followed by vesicular transport and membrane dynamics. We have previously shown that centrosomes are key players in the initiation of subcellular lumen formation where they act as microtubule organizing centres (MTOCs). However, not much is known on the events that lead to the growth of these subcellular luminal branches or what makes them progress through a particular trajectory within the cytoplasm of the TC. Here, we have identified that the spectraplakin Short-stop (Shot) promotes the crosstalk between MTs and actin, which leads to the extension and guidance of the subcellular lumen within the TC cytoplasm. Shot is enriched in cells undergoing the initial steps of subcellular branching as a direct response to FGF signalling. An excess of Shot induces ectopic acentrosomal branching points in the embryonic and larval tracheal TC leading to cells with extra subcellular lumina. These data provide the first evidence for a role for spectraplakins in subcellular lumen formation and branching.

scholarly journals Coordinated crosstalk between microtubules and actin by a spectraplakin regulates lumen formation and branching

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Delia Ricolo ◽  
Sofia J Araujo
Keyword(s):  
Drosophila Melanogaster ◽  
Single Cell ◽  
Single Cells ◽  
Terminal Cell ◽  
Direct Response ◽  
Lumen Formation ◽  
Cell Lumen ◽  
Branching Points ◽  
Key Players ◽  
Fgf Signalling

Subcellular lumen formation by single-cells involves complex cytoskeletal remodelling. We have previously shown that centrosomes are key players in the initiation of subcellular lumen formation in Drosophila melanogaster, but not much is known on the what leads to the growth of these subcellular luminal branches or makes them progress through a particular trajectory within the cytoplasm. Here, we have identified that the spectraplakin Short-stop (Shot) promotes the crosstalk between MTs and actin, which leads to the extension and guidance of the subcellular lumen within the tracheal terminal cell (TC) cytoplasm. Shot is enriched in cells undergoing the initial steps of subcellular branching as a direct response to FGF signalling. An excess of Shot induces ectopic acentrosomal luminal branching points in the embryonic and larval tracheal TC leading to cells with extra-subcellular lumina. These data provide the first evidence for a role for spectraplakins in single-cell lumen formation and branching.

scholarly journals Membrane dynamics of dividing cells imaged by lattice light-sheet microscopy

2016 ◽  
Vol 27 (22) ◽  
pp. 3418-3435 ◽  
Author(s):  
François Aguet ◽  
Srigokul Upadhyayula ◽  
Raphaël Gaudin ◽  
Yi-ying Chou ◽  
Emanuele Cocucci ◽  
...  
Keyword(s):  
Cell Surface ◽  
Cell Imaging ◽  
Single Cells ◽  
Light Sheet ◽  
Membrane Dynamics ◽  
Bottom Surface ◽  
Light Sheet Microscopy ◽  
Dividing Cells ◽  
Entire Cell ◽  
Membrane Bound

Membrane remodeling is an essential part of transferring components to and from the cell surface and membrane-bound organelles and for changes in cell shape, which are particularly critical during cell division. Earlier analyses, based on classical optical live-cell imaging and mostly restricted by technical necessity to the attached bottom surface, showed persistent formation of endocytic clathrin pits and vesicles during mitosis. Taking advantage of the resolution, speed, and noninvasive illumination of the newly developed lattice light-sheet fluorescence microscope, we reexamined their assembly dynamics over the entire cell surface and found that clathrin pits form at a lower rate during late mitosis. Full-cell imaging measurements of cell surface area and volume throughout the cell cycle of single cells in culture and in zebrafish embryos showed that the total surface increased rapidly during the transition from telophase to cytokinesis, whereas cell volume increased slightly in metaphase and was relatively constant during cytokinesis. These applications demonstrate the advantage of lattice light-sheet microscopy and enable a new standard for imaging membrane dynamics in single cells and multicellular assemblies.

scholarly journals DTFLOW: Inference and Visualization of Single-cell Pseudo-temporal Trajectories Using Diffusion Propagation

2020 ◽  
Author(s):  
Jiangyong Wei ◽  
Tianshou Zhou ◽  
Xinan Zhang ◽  
Tianhai Tian
Keyword(s):  
Single Cell ◽  
Reduction Method ◽  
Developmental Trajectories ◽  
Branching Processes ◽  
Single Cells ◽  
New Method ◽  
Developmental States ◽  
Novel Approach ◽  
Cell Data

ABSTRACTOne of the major challenges in single-cell data analysis is the determination of cellular developmental trajectories using single-cell data. Although substantial studies have been conducted in recent years, more effective methods are still strongly needed to infer the developmental processes accurately. In this work we devise a new method, named DTFLOW, for determining the pseudo-temporal trajectories with multiple branches. This method consists of two major steps: namely a new dimension reduction method (i.e. Bhattacharyya kernel feature decomposition (BKFD)) and a novel approach, named Reverse Searching on kNN Graph (RSKG), to identify the underlying multi-branching processes of cellular differentiations. In BKFD we first establish a stationary distribution for each cell to represent the transition of cellular developmental states based on the random walk with restart algorithm and then propose a new distance metric for calculating pseudo-times of single-cells by introducing the Bhattacharyya kernel matrix. The effectiveness of DTFLOW is rigorously examined by using four single-cell datasets. We compare the efficiency of the new method with two state-of-the-art methods. Simulation results suggest that our proposed method has superior accuracy and strong robustness properties for constructing pseudo-time trajectories. Availability: DTFLOW is implemented in Python and available at https://github.com/statway/DTFLOW.

scholarly journals An optogenetic tool to raise intracellular pH in single cells and drive localized membrane dynamics

2021 ◽  
Author(s):  
Caitlin E. T. Donahue ◽  
Michael D. Siroky ◽  
Katharine A. White
Keyword(s):  
Single Cell ◽  
Intracellular Ph ◽  
Single Cells ◽  
Cell Polarization ◽  
Membrane Dynamics ◽  
Cell Physiology ◽  
Single Cell Level ◽  
Cell Level ◽  
Cell Behaviors ◽  
Membrane Ruffling

AbstractIntracellular pH (pHi) dynamics are critical for regulating normal cell physiology. For example, transient increases in pHi (7.2-7.6) regulate cell behaviors like cell polarization, actin cytoskeleton remodeling, and cell migration. Most studies on pH-dependent cell behaviors have been performed at the population level and use non-specific methods to manipulate pHi. The lack of tools to specifically manipulate pHi at the single-cell level has hindered investigation of the role of pHi dynamics in driving single cell behaviors. In this work, we show that Archaerhodopsin (ArchT), a light-driven outward proton pump, can be used to elicit robust and physiological pHi increases over the minutes timescale. We show that activation of ArchT is repeatable, enabling the maintenance of high pHi in single cells for approximately 45 minutes. We apply this spatiotemporal pHi manipulation tool to determine whether increased pHi is a sufficient driver of membrane ruffling in single cells. Using the ArchT tool, we show that increased pHi in single cells can drive localized membrane ruffling responses within seconds and increased membrane dynamics (both protrusion and retraction events) compared to control cells. Overall, this tool allows us to directly investigate the relationship between increased pHi and cell behaviors such as membrane ruffling. This tool will be transformative in facilitating the experiments required to determine if increased pHi is a driver of these cell behaviors at the single-cell level.

scholarly journals Contributions of Intrinsic Membrane Dynamics to Fast Network Oscillations With Irregular Neuronal Discharges

2005 ◽  
Vol 94 (6) ◽  
pp. 4344-4361 ◽  
Author(s):  
Caroline Geisler ◽  
Nicolas Brunel ◽  
Xiao-Jing Wang
Keyword(s):  
Single Cell ◽  
Single Cells ◽  
Membrane Dynamics ◽  
Membrane Properties ◽  
Synaptic Current ◽  
Substantial Impact ◽  
Integrate And Fire ◽  
Sinusoidal Input ◽  
Fast Oscillations ◽  
Oscillatory Cycle

During fast oscillations in the local field potential (40–100 Hz gamma, 100–200 Hz sharp-wave ripples) single cortical neurons typically fire irregularly at rates that are much lower than the oscillation frequency. Recent computational studies have provided a mathematical description of such fast oscillations, using the leaky integrate-and-fire (LIF) neuron model. Here, we extend this theoretical framework to populations of more realistic Hodgkin–Huxley-type conductance-based neurons. In a noisy network of GABAergic neurons that are connected randomly and sparsely by chemical synapses, coherent oscillations emerge with a frequency that depends sensitively on the single cell's membrane dynamics. The population frequency can be predicted analytically from the synaptic time constants and the preferred phase of discharge during the oscillatory cycle of a single cell subjected to noisy sinusoidal input. The latter depends significantly on the single cell's membrane properties and can be understood in the context of the simplified exponential integrate-and-fire (EIF) neuron. We find that 200-Hz oscillations can be generated, provided the effective input conductance of single cells is large, so that the single neuron's phase shift is sufficiently small. In a two-population network of excitatory pyramidal cells and inhibitory neurons, recurrent excitation can either decrease or increase the population rhythmic frequency, depending on whether in a neuron the excitatory synaptic current follows or precedes the inhibitory synaptic current in an oscillatory cycle. Detailed single-cell properties have a substantial impact on population oscillations, even though rhythmicity does not originate from pacemaker neurons and is an emergent network phenomenon.

scholarly journals A feedback mechanism converts individual cell features into a supracellular ECM structure in Drosophila trachea

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Arzu Öztürk-Çolak ◽  
Bernard Moussian ◽  
Sofia J Araújo ◽  
Jordi Casanova
Keyword(s):  
Extracellular Matrix ◽  
Individual Cell ◽  
Active Role ◽  
Feedback Mechanism ◽  
Cell Junctions ◽  
Complex Relationship ◽  
Tracheal System ◽  
Key Players ◽  
Active Feedback ◽  
Drosophila Trachea

The extracellular matrix (ECM), a structure contributed to and commonly shared by many cells in an organism, plays an active role during morphogenesis. Here, we used the Drosophila tracheal system to study the complex relationship between the ECM and epithelial cells during development. We show that there is an active feedback mechanism between the apical ECM (aECM) and the apical F-actin in tracheal cells. Furthermore, we reveal that cell-cell junctions are key players in this aECM patterning and organisation and that individual cells contribute autonomously to their aECM. Strikingly, changes in the aECM influence the levels of phosphorylated Src42A (pSrc) at cell junctions. Therefore, we propose that Src42A phosphorylation levels provide a link for the ECM environment to ensure proper cytoskeletal organisation.

Some Contributions to the Theory of Near-Critical Bisexual Branching Processes

2007 ◽  
Vol 44 (02) ◽  
pp. 492-505
Author(s):  
M. Molina ◽  
M. Mota ◽  
A. Ramos
Keyword(s):  
Branching Process ◽  
Branching Processes ◽  
Sufficient Conditions ◽  
Positive Probability ◽  
Limit Laws ◽  
Bisexual Branching Processes ◽  
Probabilistic Evolution

We investigate the probabilistic evolution of a near-critical bisexual branching process with mating depending on the number of couples in the population. We determine sufficient conditions which guarantee either the almost sure extinction of such a process or its survival with positive probability. We also establish some limiting results concerning the sequences of couples, females, and males, suitably normalized. In particular, gamma, normal, and degenerate distributions are proved to be limit laws. The results also hold for bisexual Bienaymé–Galton–Watson processes, and can be adapted to other classes of near-critical bisexual branching processes.

Effects of carbamylcholine on chick embryo aggregate retina cell cultures

1988 ◽  
Vol 46 ◽  
pp. 350-351
Author(s):  
Glenn M. Cohen ◽  
Radharaman Ray
Keyword(s):  
Cell Cultures ◽  
Single Cells ◽  
Retinal Cell ◽  
Cell Aggregates ◽  
High Concentration ◽  
In Ovo ◽  
Sterile Culture ◽  
Retinal Tissue ◽  
Synaptic Junctions ◽  
And Control

Retinal,cell aggregates develop in culture in a pattern similar to the in ovo retina, forming neurites first and then synapses. In the present study, we continuously exposed chick retinal cell aggregates to a high concentration (1 mM) of carbamylcholine (carbachol), an acetylcholine (ACh) analog that resists hydrolysis by acetylcholinesterase (AChE). This situation is similar to organophosphorus anticholinesterase poisoning in which the ACh level is elevated at synaptic junctions due to inhibition of AChE, Our objective was to determine whether continuous carbachol exposure either damaged cholino- ceptive neurites, cell bodies, and synaptic elements of the aggregates or influenced (hastened or retarded) their development.The retinal tissue was isolated aseptically from 11 day embryonic White Leghorn chicks and then enzymatically (trypsin) and mechanically (trituration) dissociated into single cells. After washing the cells by repeated suspension and low (about 200 x G) centrifugation twice, aggregate cell cultures (about l0 cells/culture) were initiated in 1.5 ml medium (BME, GIBCO) in 35 mm sterile culture dishes and maintained as experimental (containing 10-3 M carbachol) and control specimens.

Ultrastructure of myoepithelial cell in parotid gland

1988 ◽  
Vol 46 ◽  
pp. 342-343
Author(s):  
C. N. Sun
Keyword(s):  
Parotid Gland ◽  
Osmium Tetroxide ◽  
Individual Cell ◽  
Branching Processes ◽  
Muscle Cells ◽  
Myoepithelial Cells ◽  
Uranyl Acetate ◽  
Thin Sections ◽  
Gland Carcinoma ◽  
Parotid Gland Carcinoma

Myoepithelial cells have been observed in the prostate, harderian, apocrine, exocrine sweat and mammary glands. Such cells and their numerous branching processes form basket-like structures around the glandular acini. Their shapes are quite different from structures seen either in spindleshaped smooth muscle cells or skeletal muscle cells. These myoepithelial cells lie on the epithelial side of the basement membrane in the glands. This presentation describes the ultrastructure of such myoepithelial cells which have been found also in the parotid gland carcinoma from a 45-year old patient.Specimens were cut into small pieces about 1 mm3 and immediately fixed in 4 percent glutaraldehyde in phosphate buffer for two hours, then post-fixed in 1 percent buffered osmium tetroxide for 1 hour. After dehydration, tissues were embedded in Epon 812. Thin sections were stained with uranyl acetate and lead citrate. Ultrastructurally, the pattern of each individual cell showed wide variations.

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