scholarly journals Actin blobs prefigure dendrite branching sites

2018 ◽  
Vol 217 (10) ◽  
pp. 3731-3746 ◽  
Author(s):  
Vanitha Nithianandam ◽  
Cheng-Ting Chien
Keyword(s):  
Actin Cytoskeleton ◽  
Structural Stability ◽  
In Vivo Imaging ◽  
Average Velocity ◽  
Morphological Changes ◽  
Dendritic Morphology ◽  
Actin Dynamics ◽  
Dendrite Branching ◽  
Neuronal Dendrites

The actin cytoskeleton provides structural stability and adaptability to the cell. Neuronal dendrites frequently undergo morphological changes by emanating, elongating, and withdrawing branches. However, the knowledge about actin dynamics in dendrites during these processes is limited. By performing in vivo imaging of F-actin markers, we found that F-actin was highly dynamic and heterogeneously distributed in dendritic shafts with enrichment at terminal dendrites. A dynamic F-actin population that we named actin blobs propagated bidirectionally at an average velocity of 1 µm/min. Interestingly, these actin blobs stalled at sites where new dendrites would branch out in minutes. Overstabilization of F-actin by the G15S mutant abolished actin blobs and dendrite branching. We identified the F-actin–severing protein Tsr/cofilin as a regulator of dynamic actin blobs and branching activity. Hence, actin blob localization at future branching sites represents a dendrite-branching mechanism to account for highly diversified dendritic morphology.

Inflammatory Disease and Abortive Platelet Shedding Caused by a Mutation in a Pivotal Regulator of Actin Dynamics in the redears Mouse.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1606-1606
Author(s):  
Monica J. Justice ◽  
Ben T. Kile ◽  
Lanette S. Woodward
Keyword(s):  
Actin Cytoskeleton ◽  
Inflammatory Disease ◽  
Critical Role ◽  
Neutrophil Infiltration ◽  
Blood Platelet ◽  
Forward Genetics ◽  
Actin Dynamics ◽  
Actin Depolymerization ◽  
Function Discovery

Abstract Mouse mutagenesis using forward genetics is valuable as a gene function discovery tool. We are looking for blood defects in a large ENU mutagenesis screen, and have isolated many new mouse mutants that reveal new mechanisms in hematopoiesis. One mutant mouse strain, called redears, is an intriguing model of inflammatory disease and thrombocytopenia. Animals homozygous for the redears (rd) mutation develop spontaneous inflammatory lesions of the ears and tail characterized by neutrophil infiltration and peripheral neutrophila. Unexpectedly, blood platelet numbers are dramatically reduced in rd/rd animals. A thorough analysis of platelet biogenesis shows that the platelet precursor cell, the megakaryocyte, undergoes abnormal maturation, which results in gross morphological abnormalities, increased ploidy and abortive platelet shedding. Here we report a mutation in a novel gene related to the yeast actin-interacting protein Aip1 in rd/rd mice. In yeast, Aip1 interacts with, and increases the activity of cofilin, a key regulator of actin depolymerization. Our data confirm that actin dynamics are dysregulated in rd/rd megakaryocytes and neutrophils. The massive cytoplasmic reorganization that is required for megakaryocyte maturation and platelet shedding has long been assumed to depend on the actin cytoskeleton. Intriguingly, recent studies suggest the process is caspase-dependent, and represents a form of ‘para-apoptosis’. With this in mind, we found that chemotaxis and apoptosis are perturbed in rd/rd neutrophils, suggesting that neutrophils are playing a key role in driving the inflammation. Disrupted actin depolymerization would provide an explanation for chemotactic deficiencies. Further, recent evidence implicating cofilin and other actin regulators in the initiation of apoptosis would suggest that this novel protein may play an essential role in neutrophil cell death. Thus, the redears mouse not only provides the first in vivo demonstration of the critical role of the actin cytoskeleton in megakaryocyte development and platelet production, but also represents a unique reagent to examine the relationship between actin dynamics, cellular maturation, inflammation and apoptosis. Our ongoing mutagenesis efforts continue to reveal new developmental mechanisms. New mutants, genetic tools, and resources can be found at www.mouse-genome.bcm.tmc.edu

scholarly journals Effect of Flumorph on F-Actin Dynamics in the Potato Late Blight Pathogen Phytophthora infestans

2015 ◽  
Vol 105 (4) ◽  
pp. 419-423 ◽  
Author(s):  
Chenlei Hua ◽  
Kiki Kots ◽  
Tijs Ketelaar ◽  
Francine Govers ◽  
Harold J. G. Meijer
Keyword(s):  
Actin Cytoskeleton ◽  
Phytophthora Infestans ◽  
Actin Filaments ◽  
Fluorescent Protein ◽  
Crop Protection ◽  
Hyphal Growth ◽  
Actin Dynamics ◽  
Protection Agent ◽  
Green Fluorescent

Oomycetes are fungal-like pathogens that cause notorious diseases. Protecting crops against oomycetes requires regular spraying with chemicals, many with an unknown mode of action. In the 1990s, flumorph was identified as a novel crop protection agent. It was shown to inhibit the growth of oomycete pathogens including Phytophthora spp., presumably by targeting actin. We recently generated transgenic Phytophthora infestans strains that express Lifeact-enhanced green fluorescent protein (eGFP), which enabled us to monitor the actin cytoskeleton during hyphal growth. For analyzing effects of oomicides on the actin cytoskeleton in vivo, the P. infestans Lifeact-eGFP strain is an excellent tool. Here, we confirm that flumorph is an oomicide with growth inhibitory activity. Microscopic analyses showed that low flumorph concentrations provoked hyphal tip swellings accompanied by accumulation of actin plaques in the apex, a feature reminiscent of tips of nongrowing hyphae. At higher concentrations, swelling was more pronounced and accompanied by an increase in hyphal bursting events. However, in hyphae that remained intact, actin filaments were indistinguishable from those in nontreated, nongrowing hyphae. In contrast, in hyphae treated with the actin depolymerizing drug latrunculin B, no hyphal bursting was observed but the actin filaments were completely disrupted. This difference demonstrates that actin is not the primary target of flumorph.

scholarly journals Mammalian Adenylyl Cyclase-associated Protein 1 (CAP1) Regulates Cofilin Function, the Actin Cytoskeleton, and Cell Adhesion

2013 ◽  
Vol 288 (29) ◽  
pp. 20966-20977 ◽  
Author(s):  
Haitao Zhang ◽  
Pooja Ghai ◽  
Huhehasi Wu ◽  
Changhui Wang ◽  
Jeffrey Field ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Actin Cytoskeleton ◽  
Hela Cells ◽  
Actin Polymerization ◽  
Actin Dynamics ◽  
Ras Signaling ◽  
Filamentous Actin ◽  
Camp Pathway

CAP (adenylyl cyclase-associated protein) was first identified in yeast as a protein that regulates both the actin cytoskeleton and the Ras/cAMP pathway. Although the role in Ras signaling does not extend beyond yeast, evidence supports that CAP regulates the actin cytoskeleton in all eukaryotes including mammals. In vitro actin polymerization assays show that both mammalian and yeast CAP homologues facilitate cofilin-driven actin filament turnover. We generated HeLa cells with stable CAP1 knockdown using RNA interference. Depletion of CAP1 led to larger cell size and remarkably developed lamellipodia as well as accumulation of filamentous actin (F-actin). Moreover, we found that CAP1 depletion also led to changes in cofilin phosphorylation and localization as well as activation of focal adhesion kinase (FAK) and enhanced cell spreading. CAP1 forms complexes with the adhesion molecules FAK and Talin, which likely underlie the cell adhesion phenotypes through inside-out activation of integrin signaling. CAP1-depleted HeLa cells also had substantially elevated cell motility as well as invasion through Matrigel. In summary, in addition to generating in vitro and in vivo evidence further establishing the role of mammalian CAP1 in actin dynamics, we identified a novel cellular function for CAP1 in regulating cell adhesion.

Drosophila pupal macrophages – A versatile tool for combined ex vivo and in vivo imaging of actin dynamics at high resolution

2013 ◽  
Vol 92 (10-11) ◽  
pp. 349-354 ◽  
Author(s):  
Moritz Sander ◽  
Anna Julia Squarr ◽  
Benjamin Risse ◽  
Xiaoyi Jiang ◽  
Sven Bogdan
Keyword(s):  
High Resolution ◽  
In Vivo Imaging ◽  
Ex Vivo ◽  
Actin Dynamics ◽  
Versatile Tool

OPTICAL COHERENCE TOMOGRAPHY FOR BLADDER CANCER DIAGNOSIS: FROM ANIMAL STUDY TO CLINICAL DIAGNOSIS

2008 ◽  
Vol 01 (01) ◽  
pp. 125-140 ◽  
Author(s):  
ZHIJIA YUAN ◽  
HUGANG REN ◽  
WAYNE WALTZER ◽  
JASON KIM ◽  
JINGXUAN LIU ◽  
...  
Keyword(s):  
Bladder Cancer ◽  
Optical Coherence Tomography ◽  
Cancer Diagnosis ◽  
In Vivo Imaging ◽  
Laser Scanning ◽  
Dynamic Range ◽  
Morphological Changes ◽  
Optical Coherence ◽  
Cancerous Lesions

This paper summarizes the recent technological development in our lab on cystoscopic optical coherence tomography (COCT) by integrating time-domain OCT (TDOCT) and spectral-domain OCT (SDOCT) with advanced MEMS-mirror technology for endoscopic laser scanning imaging. The COCT catheter can be integrated into the instrument channel of a commercial 22Fr rigid cystoscopic sheath for in vivo imaging of human bladder under the cystosocopic visual guidance; the axial/transverse resolutions of the COCT catheter are roughly 9 μm and 12 μm, respectively, and 2D COCT imaging can be performed with over 110dB dynamic range at 4–8 fps. To examine the utility and potential limitations of OCT for bladder cancer diagnosis, systemic ex vivo rat bladder carcinogenesis studies were performed to follow various morphological changes induced by tumor growth and in vivo porcine study was performed to examine the feasibility of COCT for in vivo imaging. Justified by promising results of the animal studies, preliminary clinical study was conducted on patients scheduled for operating-room cystoscopy for bladder cancers. Double-blind clinical results reveal that COCT can delineate detailed bladder architectures (e.g., urothelium, lamina propria, muscularis) at high resolution and detect bladder cancers based on enhanced urothelial heterogeneity as a result of excessive growing nature of bladder cancers. The diagnostic sensitivity and specificity can be enhanced to 92% and 85%, respectively. Results also suggest that due to reduced imaging depth of COCT in cancerous lesions, staging of bladder cancers may be limited to Ta or T1 for non-outgrowing cancerous lesions.

scholarly journals Drosophila Dendritic Arborisation Neurons: Fantastic Actin Dynamics and Where to Find Them

Cells ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2777
Author(s):  
Lukas Kilo ◽  
Tomke Stürner ◽  
Gaia Tavosanis ◽  
Anna B. Ziegler
Keyword(s):  
Time Course ◽  
Dendritic Tree ◽  
Morphological Diversity ◽  
Structural Diversity ◽  
Actin Dynamics ◽  
In Vivo Studies ◽  
Functional Requirements ◽  
Neuronal Dendrites ◽  
Dendrite Development

Neuronal dendrites receive, integrate, and process numerous inputs and therefore serve as the neuron’s “antennae”. Dendrites display extreme morphological diversity across different neuronal classes to match the neuron’s specific functional requirements. Understanding how this structural diversity is specified is therefore important for shedding light on information processing in the healthy and diseased nervous system. Popular models for in vivo studies of dendrite differentiation are the four classes of dendritic arborization (c1da–c4da) neurons of Drosophila larvae with their class-specific dendritic morphologies. Using da neurons, a combination of live-cell imaging and computational approaches have delivered information on the distinct phases and the time course of dendrite development from embryonic stages to the fully developed dendritic tree. With these data, we can start approaching the basic logic behind differential dendrite development. A major role in the definition of neuron-type specific morphologies is played by dynamic actin-rich processes and the regulation of their properties. This review presents the differences in the growth programs leading to morphologically different dendritic trees, with a focus on the key role of actin modulatory proteins. In addition, we summarize requirements and technological progress towards the visualization and manipulation of such actin regulators in vivo.

scholarly journals The influence of pseudoexfoliative syndrome on corneal morphology based on in vivo confocal microscopy

2017 ◽  
Vol 10 (2) ◽  
pp. 49-55 ◽  
Author(s):  
Vitaly V Potemkin ◽  
Tatyana S Varganova ◽  
Evgeniy L Akopov ◽  
Elena V Ageeva
Keyword(s):  
Dendritic Cells ◽  
Confocal Microscopy ◽  
Real Time ◽  
Cell Density ◽  
In Vivo Imaging ◽  
Morphological Changes ◽  
In Vivo Confocal Microscopy ◽  
Examination Method ◽  
Mode A

Confocal microscopy is a modern examination method, which provides in real-time mode a noninvasive in vivo imaging of the cornea, limb, and conjunctiva. Purpose. To evaluate main morphological changes observed by confocal microscopy in patients with pseudoexfoliation (PEX) syndrome. Methods. 21 patients were examined. 12 patients with PEX syndrome were enrolled as the main group, and 9 patients without PEX - as controls. Results. In patients with PEX, there was a decreased cell density in the epithelium and the stroma of the cornea, as well as a lot of hyperreflective intercellular microdeposits and dendritic cells (p < 0.05).

scholarly journals Endothelial-specific Crif1 deletion induces BBB maturation and disruption via the alteration of actin dynamics by impaired mitochondrial respiration

2020 ◽  
Vol 40 (7) ◽  
pp. 1546-1561
Author(s):  
Min Joung Lee ◽  
Yunseon Jang ◽  
Jeongsu Han ◽  
Soo J Kim ◽  
Xianshu Ju ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Motor Behavior ◽  
Actin Dynamics ◽  
Toxic Substances ◽  
Atp Production ◽  
Junctional Proteins ◽  
Peripheral Immune Cells

Cerebral endothelial cells (ECs) require junctional proteins to maintain blood–brain barrier (BBB) integrity, restricting toxic substances and controlling peripheral immune cells with a higher concentration of mitochondria than ECs of peripheral capillaries. The mechanism underlying BBB disruption by defective mitochondrial oxidative phosphorylation (OxPhos) is unclear in a mitochondria-related gene-targeted animal model. To assess the role of EC mitochondrial OxPhos function in the maintenance of the BBB, we developed an EC-specific CR6-interactin factor1 ( Crif1) deletion mouse. We clearly observed defects in motor behavior, uncompacted myelin and leukocyte infiltration caused by BBB maturation and disruption in this mice. Furthermore, we investigated the alteration in the actin cytoskeleton, which interacts with junctional proteins to support BBB integrity. Loss of Crif1 led to reorganization of the actin cytoskeleton and a decrease in tight junction-associated protein expression through an ATP production defect in vitro and in vivo. Based on these results, we suggest that mitochondrial OxPhos is important for the maturation and maintenance of BBB integrity by supplying ATP to cerebral ECs.

New Angles on Neuronal Dendrites In Vivo

2007 ◽  
Vol 98 (6) ◽  
pp. 3770-3779 ◽  
Author(s):  
Werner Göbel ◽  
Fritjof Helmchen
Keyword(s):  
In Vivo Imaging ◽  
Laser Scanning ◽  
Pyramidal Neurons ◽  
Activity Patterns ◽  
Scanning Method ◽  
Two Photon Microscopy ◽  
Neuronal Dendrites ◽  
Tissue Surfaces ◽  
Image Planes

Imaging technologies are well suited to study neuronal dendrites, which are key elements for synaptic integration in the CNS. Dendrites are, however, frequently oriented perpendicular to tissue surfaces, impeding in vivo imaging approaches. Here we introduce novel laser-scanning modes for two-photon microscopy that enable in vivo imaging of spatiotemporal activity patterns in dendrites. First, we developed a method to image planes arbitrarily oriented in 3D, which proved particularly beneficial for calcium imaging of parallel fibers and Purkinje cell dendrites in rat cerebellar cortex. Second, we applied free linescans—either through multiple dendrites or along a single vertically oriented dendrite—to reveal fast dendritic calcium dynamics in neocortical pyramidal neurons. Finally, we invented a ribbon-type 3D scanning method for imaging user-defined convoluted planes enabling simultaneous measurements of calcium signals along multiple apical dendrites. These novel scanning modes will facilitate optical probing of dendritic function in vivo.

Regulation of actin dynamics is critical for endothelial barrier functions

2005 ◽  
Vol 288 (3) ◽  
pp. H1296-H1305 ◽  
Author(s):  
J. Waschke ◽  
F. E. Curry ◽  
R. H. Adamson ◽  
D. Drenckhahn
Keyword(s):  
Endothelial Cells ◽  
Actin Cytoskeleton ◽  
Cytochalasin D ◽  
Endothelial Barrier ◽  
Actin Dynamics ◽  
Intracellular Camp ◽  
Barrier Functions ◽  
Permeability Increase

We tested the hypothesis that the equilibrium between F- and G-actin in endothelial cells modulates the integrity of the actin cytoskeleton and is important for the maintenance of endothelial barrier functions in vivo and in vitro. We used the actin-depolymerizing agent cytochalasin D and jasplakinolide, an actin filament (F-actin) stabilizing and promoting substance, to modulate the actin cytoskeleton. Low doses of jasplakinolide (0.1 μM), which we have previously shown to reduce the permeability-increasing effect of cytochalasin D, had no influence on resting permeability of single-perfused mesenteric microvessels in vivo as well as on monolayer integrity. The F-actin content of cultured endothelial cells remained unchanged. In contrast, higher doses (10 μM) of jasplakinolide increased permeability (hydraulic conductivity) to the same extent as cytochalasin D and induced formation of intercellular gaps in cultured myocardial endothelial (MyEnd) cell monolayers. This was accompanied by a 34% increase of F-actin and pronounced disorganization of the actin cytoskeleton in MyEnd cells. Furthermore, we tested whether an increase of cAMP by forskolin and rolipram would prevent the cytochalasin D-induced barrier breakdown. Conditions that increase intracellular cAMP failed to block the cytochalasin D-induced permeability increase in vivo and the reduction of vascular endothelial cadherin-mediated adhesion in vitro. Taken together, these data support the hypothesis that the state of polymerization of the actin cytoskeleton is critical for maintenance of endothelial barrier functions and that both depolymerization by cytochalasin D and hyperpolymerization of actin by jasplakinolide resulted in an increase of microvessel permeability in vivo. However, cAMP, which is known to support endothelial barrier functions, seems to work by mechanisms other than stabilizing F-actin.

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