BACKGROUNDIn prokaryotic organisms, the mechanism responsible for the accurate partition of newly replicated chromosomes into daughter cells is incompletely understood. Segregation of the replication terminus of the circular prokaryotic chromosome poses special problems that have not previously been addressed. The aim of this study was to investigate the roles of several protein components (MreB, MreC, and MreD) of the prokaryotic cytoskeleton for the faithful transmission of the chromosomal terminus into daughter cells.

METHODSStrain LQ1 (mreB::cat), LQ2 (mreC::cat), and LQ3 (mreD::cat) were constructed using the Red recombination system. LQ11/pLAU53, LQ12/pLAU53, LQ13/pLAU53, LQ14/pLAU53, and LQ15/pLAU53 strains were generated by P1transduction of (tetO) 240 -Gm and (lacO) 240 -Km cassettes from strains IL2 and IL29. Fluorescence microscopy was performed to observe localization pattern of fluorescently-labeled origin and terminus foci in wild-type and mutant cells. SOS induction was monitored as gfp fluorescence from PsulA-gfp in log phase cells grown in Luria-Bertani medium at 37°C by measurement of emission at 525 nm with excitation at 470 nm in a microplate fluorescence reader.

RESULTSMutational deletion of the mreB, mreC, or mreD genes was associated with selective loss of the terminus region in approximately 40% of the cells within growing cultures. This was accompanied by significant induction of the SOS DNA damage response, suggesting that deletion of terminus sequences may have occurred by chromosomal cleavage, presumably caused by ingrowth of the division septum prior to segregation of the replicated terminal.

CONCLUSIONSThese results imply a role for the MreBCD cytoskeleton in the resolution of the final products of terminus replication and/or in the specific movement of newly replicated termini away from midcell prior to completion of septal ingrowth. This would identify a previously unrecognized stage in the overall process of chromosome segregation.

Chromosome Segregation ; genetics ; physiology ; Cytoskeleton ; metabolism ; Escherichia coli ; genetics ; metabolism

OBJECTIVETo explore the response of rat bone marrow mesenchymal stem cells (MSCs and calvarial osteoblasts to mechanical strain and the consequent changes of cytoskeleton F-actin.

METHODSBone marrow MSCs and calvarial osteoblasts were isolated from SD rats and cultured in vitro. Mechanical stretch was performed on passage 3 cells at 2 000 microepsilon for 0, 2, 6 and 12 hours using four-point bending system. The response of cells and the distribution of F-actin were observed using fluorescent staining under laser scanning confocal microscope and the morphological parameters were quantified using image analysis software Laserpix.

RESULTSUnder mechanical stretch, the fluorescent staining decreased obviously at both MSCs and osteoblasts, and F-actin filaments were rearranged and became tenuous, thinner, and abnormally distributed. The outline of nucleus became unclear and apoptotic changes were observed at some of both cells. Cellular size decreased more significantly in MSCs than in osteoblasts. Quantity analysis showed that total area of cells, total fluorescent density and green fluorescent density (F-actin) were all significantly decreased in MSCs (P < 0.05 or P < 0.01), and total fluorescent density, green fluorescent density and red fluorescent density (nuclei) did also in osteoblasts (P < 0.05 or P < 0.01).

CONCLUSIONMechanical stretch caused extensive response on both MSCs and osteoblasts which led to the rearrangement of F-actin filament and apoptosis in some of these cells. MSCs were more sensitive to mechanical strain than osteoblasts.

Actin Cytoskeleton ; metabolism ; Actins ; metabolism ; Animals ; Bone Marrow Cells ; Cells, Cultured ; Cytoskeleton ; Mesenchymal Stromal Cells ; Microtubules ; Osteoblasts ; Rats ; Stress, Mechanical

This article introduces the structure and function of the Sertoli cell cytoskeleton of the testis and the research progress in this aspect, focusing on the description of the function of vimentin, with some illustrations on the impact of physical and chemical factors on cytoskeleton, especially the structural changes of vimentin cell microfilament under simulated microgravity and space true microgravity. It for the first time proposes that the Sertoli cell cytoskeleton can be detected in semen, with a view to involving more researchers in further studies in this field.
Actin Cytoskeleton ; metabolism ; physiology ; Animals ; Apoptosis ; physiology ; Cytoskeleton ; metabolism ; physiology ; Humans ; Male ; Mice ; Rats ; Semen ; cytology ; metabolism ; Sertoli Cells ; cytology ; metabolism ; Testis ; cytology ; metabolism ; Vimentin ; metabolism

It is believed that there exists some relationship between the distribution and morphology of intracellular actin and cell adherence. Cells are likely to be deteched when the quantity of actin filament decreases. Actin filaments locate in the fringe of cancer cells and cells cultured in static state, so that these filaments can stretch out and form pseudopodia to adhere to the matrix. When these cells are stimulated their pseudopodia retract so that they can easily be detached from the matrix. When external forces are exerted on cells to adhere and deadhere from the matrix, the morphology and distribution of skeleton actin will change, so as the cells' morphology. The skeleton actins in cells are changed differently to adapt to different external forces which are imposed on the cells. It is obvious that the relationship between the mechanism of cell adhering to the matrix and the morphology & distribution of actins needs more attention.
Actin Cytoskeleton ; metabolism ; Actins ; metabolism ; Cell Adhesion ; Humans ; Neoplasms ; metabolism ; pathology ; Pseudopodia ; metabolism ; Shear Strength

Objective To investigate the effects of lipopolysaccharide (LPS) on human pulmonary vascular endothelial cells (HPVECs) cytoskeleton and perform biological analysis of the microRNA (miRNA) spectrum. Methods The morphology of HPVECs was observed by microscope, the cytoskeleton by FITC-phalloidin staining, and the expression of VE-cadherin was detected by immunofluorescence cytochemical staining; the tube formation assay was conducted to examine the angiogenesis, along with cell migration test to detect the migration, and JC-1 mitochondrial membrane potential to detect the apoptosis. Illumina small-RNA sequencing was used to identify differentially expressed miRNAs in NC and LPS group. The target genes of differentially expressed miRNAs were predicted by miRanda and TargetScan, and the functional and pathway enrichment analysis was performed on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Further biological analysis of related miRNAs was carried out. Results After the LPS got induced, the cells became round and the integrity of cytoskeleton was destroyed. The decreased expression of VE-cadherin was also observed, along with the decreased ability of angiogenesis and migration, and increased apoptosis. Sequencing results showed a total of 229 differential miRNAs, of which 84 miRNA were up-regulated and 145 miRNA were down-regulated. The target gene prediction and functional enrichment analysis of these differential miRNA showed that they were mainly concentrated in pathways related to cell connection and cytoskeleton regulation, cell adhesion process and inflammation. Conclusion In vitro model of lung injury, multiple miRNAs are involved in the process of HPVECs cytoskeleton remodeling, the reduction of barrier function, angiogenesis, migration and apoptosis.
Humans ; Lipopolysaccharides/pharmacology* ; Endothelial Cells/metabolism* ; MicroRNAs/metabolism* ; Lung/metabolism* ; Cytoskeleton ; Gene Expression Profiling

Microenvironmental biophysical factors play a fundamental role in controlling cell behaviors including cell morphology, proliferation, adhesion and differentiation, and even determining the cell fate. Cells are able to actively sense the surrounding mechanical microenvironment and change their cellular morphology to adapt to it. Although cell morphological changes have been considered to be the first and most important step in the interaction between cells and their mechanical microenvironment, their regulatory network is not completely clear. In the current study, we generated silicon-based elastomer polydimethylsiloxane (PDMS) substrates with stiff (15:1, PDMS elastomer vs. curing agent) and soft (45:1) stiffnesses, which showed the Young's moduli of ~450 kPa and 46 kPa, respectively, and elucidated a new path in cytoskeleton re-organization in chondrocytes in response to changed substrate stiffnesses by characterizing the axis shift from the secreted extracellular protein laminin β1, focal adhesion complex protein FAK to microfilament bundling. We first showed the cellular cytoskeleton changes in chondrocytes by characterizing the cell spreading area and cellular synapses. We then found the changes of secreted extracellular linkage protein, laminin β1, and focal adhesion complex protein, FAK, in chondrocytes in response to different substrate stiffnesses. These two proteins were shown to be directly interacted by Co-IP and colocalization. We next showed that impact of FAK on the cytoskeleton organization by showing the changes of microfilament bundles and found the potential intermediate regulators. Taking together, this modulation axis of laminin β1-FAK-microfilament could enlarge our understanding about the interdependence among mechanosensing, mechanotransduction, and cytoskeleton re-organization.
Cell Adhesion ; Chondrocytes ; Cytoskeleton/metabolism* ; Elastomers/metabolism* ; Laminin/metabolism* ; Mechanotransduction, Cellular

OBJECTIVETo investigate the effect of cytomegalovirus (CMV) infection on actin and microfilament in human embryo fibroblast cells (HF) and its relationship with CMV replication.

METHODSCell morphology was observed after the infection of CMV. Western-blot was used to measure the expression levels of beta-actin, G-actin and F-actin proteins. CMV immediately early antigen (CMV IE) in HF cells was analyzed by indirect immunofluorescence assay. Microfilament alteration was determined by cytoskeleton fluorescence probe.

RESULTCMV IE was demonstrated in more than 95% of HF cells after infection, which was primarily located in nucleus. The shape of HF cells changed from thin shuttle like to round and thick ball like, even escaping from wall after infection by CMV. Compared with control group, the expression of G-actin protein increased at 24 h of CMV infection (0.941 +/-0.061 compared with 0.714 +/-0.119, P <0.05), then decreased at 72 h, 96 h respectively(0.218 +/-.035, 0.230 +/-0.055 compared with 0.714 +/-0.119, P <0.05). The levels of F-actin in infected cells gradually decreased at 24 h, 72 h and 96 h compared with control HF cells (0.256 +/-0.021, 0.127 +/-0.032, 0.026 +/-0.008 compared with 0.373 +/-0.050, P<0.05). In infected HF cells, microfilaments were found ruptured, arranged turbulently. Cells fused and fluorescence density of microfilament markedly reduced.

CONCLUSIONCytomegalovirus can induce alteration of actins and microfilament, which may be associated with its infection, replication and reactivity in host cells.

Actin Cytoskeleton ; metabolism ; Actins ; biosynthesis ; genetics ; Antigens, Viral ; analysis ; Cells, Cultured ; Cytomegalovirus ; Cytoskeleton ; metabolism ; Embryo, Mammalian ; Fibroblasts ; metabolism ; ultrastructure ; virology ; Humans ; Immediate-Early Proteins ; analysis

OBJECTIVEInvestigations were carried out to understand the effect of 50 Hz power frequency magnetic field on microfilament assembly of human amniotic cells and on expression of actin and epidermal growth factor receptor.

METHODSHuman amnion FL cells were exposed to 0.1, 0.2, 0.3, 0.4, 0.5 mT power frequency magnetic field for 30 minutes. Microfilaments were marked using Phalloidin-TRITC, and then were observed under a fluorescence microscope. An optical method was used to detect the relative content of microfilament in cells. A scanning electron microscope was used to detect the cell shape. The content of actin and epidermal growth factor receptor in the preparation of the detergent-insoluble cytoskeleton were measured by western-blotting to analyse the potential mechanism of the change induced by magnetic field.

RESULTSIntracellular stress fibers were found to decrease after exposing cells to a 0.2 mT power frequency magnetic field for 30 minutes. New microfilament and filopodia bundles appeared at the cell periphery after exposure, but the detected total F-actin content per cell was not significantly changed, detected by a F-actin-specific dye. The change in the amount of microfilaments caused by the field could be recovered 2 hours later when the field was withdrawn. The mean height of microfilament cytoskeleton decreased from (12.37 +/- 1.28) microm to (9.97 +/- 0.38) microm (t = 6.96, P > 0.05) after exposure using a confocal microscope. The cell shapes became more flat and lamellipodia appeared after exposure observed by a scanning electron microscope. By using Western blotting method, the intracellular contents of epidermal growth factor receptor and of actin in the preparation of the detergent-insoluble cytoskeleton which are associated with high-affinity epidermal growth factor receptors, increased about (31.2 +/- 4.1)% (t = 17.10, P < 0.05) and (16.8 +/- 2.3)% (t = 16.68, P < 0.05) respectively, compared with that of the control.

CONCLUSIONThese results suggest that a short time exposure to a 0.2 mT power frequency magnetic field induces re-organization of microfilament in human amnion FL cells. These changes could be recovered by field withdraw and may have something with the clustering of epidermal growth factor receptors induced by magnetic field.

Actin Cytoskeleton ; metabolism ; Amnion ; cytology ; radiation effects ; Cell Line ; Cell Movement ; Cytoskeleton ; metabolism ; radiation effects ; Electromagnetic Fields ; Humans ; Receptor, Epidermal Growth Factor ; metabolism ; Signal Transduction

Epilepsy is a common, chronic neurological disorder that has been associated with impaired neurodevelopment and immunity. The chemokine receptor CXCR5 is involved in seizures via an unknown mechanism. Here, we first determined the expression pattern and distribution of the CXCR5 gene in the mouse brain during different stages of development and the brain tissue of patients with epilepsy. Subsequently, we found that the knockdown of CXCR5 increased the susceptibility of mice to pentylenetetrazol- and kainic acid-induced seizures, whereas CXCR5 overexpression had the opposite effect. CXCR5 knockdown in mouse embryos via viral vector electrotransfer negatively influenced the motility and multipolar-to-bipolar transition of migratory neurons. Using a human-derived induced an in vitro multipotential stem cell neurodevelopmental model, we determined that CXCR5 regulates neuronal migration and polarization by stabilizing the actin cytoskeleton during various stages of neurodevelopment. Electrophysiological experiments demonstrated that the knockdown of CXCR5 induced neuronal hyperexcitability, resulting in an increased number of seizures. Finally, our results suggested that CXCR5 deficiency triggers seizure-related electrical activity through a previously unknown mechanism, namely, the disruption of neuronal polarity.
Animals ; Humans ; Mice ; Actin Cytoskeleton/metabolism* ; Actins/metabolism* ; Epilepsy/metabolism* ; Neurons/metabolism* ; Receptors, CXCR5/metabolism* ; Seizures/metabolism*

Rho-associated coiled-coil protein kinase (ROCK) is a serine/threonine kinase that belongs to AGC family of kinases. By inducing the formation of stress fibers and reorganizing the cytoskeleton, it is involved in many biological behaviors of cells including cell contraction, cell migration, cell division, and morphological changes, and thus exerts important roles in regulating the multiple functions of cells.
Cell Division ; Cell Movement ; Cytoskeleton ; metabolism ; Humans ; rho-Associated Kinases ; metabolism ; physiology