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Zhang G, Fan N, Lv X, Liu Y, Guo J, Yang L, Peng B, Jiang H. Investigation of the Mechanical Properties of the Human Osteosarcoma Cell at Different Cell Cycle Stages †. MICROMACHINES 2017. [PMCID: PMC6190040 DOI: 10.3390/mi8030089] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The mechanical properties of a single cell play substantial roles in cell mitosis, differentiation, and carcinogenesis. According to the difference of elastic modulus between the benign cell and the tumor cell, it has been shown that the mechanical properties of cells, as special biomarkers, may contribute greatly to disease diagnosis and drug screening. However, the mechanical properties of cells at different cell cycle stages are still not clear, which may mislead us when we use them as biomarkers. In this paper, the target regions of the human osteosarcoma cell were precisely scanned without causing any cell damage by using an atomic force microscopy (AFM) for the first time. Then, the elasticity properties of the human osteosarcoma cells were investigated quantitatively at various regions and cell cycle stages. The 32 × 32 resolution map of the elasticity showed that the elastic modulus of the cells at the interphase was larger than that at the telophase of mitosis. Moreover, the elastic modulus of the cell in the peripheral region was larger than that in the nuclear region of the cell. This work provides an accurate approach to measure the elasticity properties of cells at different stages of the cell cycle for further application in the disease diagnosis.
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Affiliation(s)
- Guocheng Zhang
- School of Mechatronics Engineering, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China; (G.Z.); (N.F.); (J.G.); (L.Y.)
| | - Na Fan
- School of Mechatronics Engineering, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China; (G.Z.); (N.F.); (J.G.); (L.Y.)
| | - Xiaoying Lv
- School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China; (X.L.); (Y.L.)
| | - Yiyao Liu
- School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China; (X.L.); (Y.L.)
| | - Jian Guo
- School of Mechatronics Engineering, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China; (G.Z.); (N.F.); (J.G.); (L.Y.)
- School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, Hunan, China
| | - Longxiang Yang
- School of Mechatronics Engineering, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China; (G.Z.); (N.F.); (J.G.); (L.Y.)
| | - Bei Peng
- School of Mechatronics Engineering, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China; (G.Z.); (N.F.); (J.G.); (L.Y.)
- Center for Robotics, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China
- Correspondence: (B.P.); (H.J.); Tel.: +86-28-61831723 (B.P.); +86-28-61830242 (H.J.)
| | - Hai Jiang
- School of Mechatronics Engineering, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China; (G.Z.); (N.F.); (J.G.); (L.Y.)
- Correspondence: (B.P.); (H.J.); Tel.: +86-28-61831723 (B.P.); +86-28-61830242 (H.J.)
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Sanger JM, Sanger JW. Insights into cell division using Listeria monocytogenes infections of PtK2 renal epithelial cells. Cytoskeleton (Hoboken) 2012; 69:992-9. [PMID: 23027717 DOI: 10.1002/cm.21076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 09/11/2012] [Indexed: 12/18/2022]
Abstract
The assembly of actin into a cleavage furrow is accompanied by disassembly of the interphase actin cytoskeleton. A variation of this actin filament disassembly/assembly cycle is seen during cell division in PtK2 cells infected with the intracellular pathogen, Listeria monocytogenes, where F-actin associates with the bacteria either as a halo surrounding nonmoving bacteria, or as an array of filaments that encases the sides of moving baceteria and extends behind them like a tail. The moving Listeria are found both in the cytoplasm and in the distal ends of undulating filopodia. When infected cells enter mitosis, the distribution of moving and stationary bacteria changes. In the transition from prophase to metaphase, there is a decrease in the number of bacteria with tails of actin in the cytoplasm. The nonmoving bacteria surrounded with F-actin are excluded from the mitotic spindle and moving bacteria are seldom seen in the cytoplasm during mitosis, although small thin filopodia cluster at the edges of the cells. After completion of cytokinesis, strong tail reformation first becomes obvious in the filopodia with Listeria moving back into the cytoplasm as the daughter cells spread. In summary, the disassembly and reassembly of actin tails extending from Listeria in dividing cells is a variation of the changes in actin organization produced by stress fiber and myofibril disassembly/assembly cycles during cell division. We suggest that the same unknown factors that regulate the disassembly/assembly of stress fibers and myofibrils during mitosis and post cytokinesis also affect the movement of Listeria inside mitotic cells.
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Affiliation(s)
- Jean M Sanger
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
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3
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Abstract
We review some of the problems in determining how myofibrils may be assembled and just as importantly how this contractile structure may be renewed by sarcomeric proteins moving between the sarcomere and the cytoplasm. We also address in this personal review the recent evidence that indicates that the assembly and dynamics of myofibrils are conserved whether the cells are analyzed in situ or in tissue culture conditions. We suggest that myofibrillogenesis is a fundamentally conserved process, comparable to protein synthesis, mitosis, or cytokinesis, whether examined in situ or in vitro.
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Du A, Sanger JM, Sanger JW. Cardiac myofibrillogenesis inside intact embryonic hearts. Dev Biol 2008; 318:236-46. [PMID: 18455713 DOI: 10.1016/j.ydbio.2008.03.011] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2007] [Revised: 03/06/2008] [Accepted: 03/07/2008] [Indexed: 01/27/2023]
Abstract
How proteins assemble into sarcomeric arrays to form myofibrils is controversial. Immunostaining and transfections of cultures of cardiomyocytes from 10-day avian embryos led us to propose that assembly proceeded in three stages beginning with the formation of premyofibrils followed by nascent myofibrils and culminating in mature myofibrils. However, premyofibril and nascent myofibril arrays have not been detected in early cardiomyocytes examined in situ in the forming avian heart suggesting that the mechanism for myofibrillogenesis differs in cultured and uncultured cells. To address this question of in situ myofibrillogenesis, we applied non-enzymatic procedures and deconvolution imaging techniques to examine early heart forming regions in situ at 2- to 13-somite stages (beating begins at the 9-somite stage), a time span of about 23 h. These approaches enabled us to detect the three myofibril stages in developing hearts supporting a three-step model of myofibrillogenesis in cardiomyocytes, whether they are present in situ, in organ cultures or in tissue culture. We have also discovered that before titin is organized the first muscle myosin filaments are about half the length of the 1.6 mum filaments present in mature A-bands. This supports the proposal that titin may play a role in length determination of myosin filaments.
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Affiliation(s)
- Aiping Du
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058, USA
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Sanger JW, Kang S, Siebrands CC, Freeman N, Du A, Wang J, Stout AL, Sanger JM. How to build a myofibril. J Muscle Res Cell Motil 2007; 26:343-54. [PMID: 16465476 DOI: 10.1007/s10974-005-9016-7] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Building a myofibril from its component proteins requires the interactions of many different proteins in a process whose details are not understood. Several models have been proposed to provide a framework for understanding the increasing data on new myofibrillar proteins and their localizations during muscle development. In this article we discuss four current models that seek to explain how the assembly occurs in vertebrate cross-striated muscles. The models hypothesize: (a) stress fiber-like structures as templates for the assembly of myofibrils, (b) assembly in which the actin filaments and Z-bands form subunits independently from A-band subunits, with the two subsequently joined together to form a myofibril, (c) premyofibrils as precursors of myofibrils, or (d) assembly occurring without any intermediary structures. The premyofibril model, proposed by the authors, is discussed in more detail as it could explain myofibrillogenesis under a variety of different conditions: in ovo, in explants, and in tissue culture studies on cardiac and skeletal muscles.
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Affiliation(s)
- Joseph W Sanger
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058, USA.
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6
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Miyoshi H, Satoh SK, Yamada E, Hamaguchi Y. Temporal change in local forces and total force all over the surface of the sea urchin egg during cytokinesis. ACTA ACUST UNITED AC 2006; 63:208-21. [PMID: 16470543 DOI: 10.1002/cm.20118] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We determined the tension over the entire surface of the sea urchin eggs during cytokinesis, on the basis of the intracellular pressure and cell shape. This allowed us to determine the temporal changes in both the distribution of local forces and the total force produced in the whole cell cortex. A spike-like peak at anaphase and a broader peak at the onset of furrowing were observed in the time-course of the total force. Treatment of the eggs with cytochalasin D, blebbistatin, ML-9, or ML-7 significantly lowered the total force when they inhibited cytokinesis, suggesting that the tension results mainly from the interaction between intact actin filaments and activated myosin II. Myosin II would function as a motor, not only in the furrow region, but over a wide area of the cell surface, because the sum of the tensions outside the furrow region was larger than that inside the furrow region throughout cytokinesis. The distribution of the local force revealed that a global increase in the cortical force started well before the onset of furrowing, and that the force inside the furrow region continued to increase despite the decrease in the force outside the furrow region after the onset of furrowing. The spatial and temporal patterns of the force over the entire surface support the hypothesis that there are two separate but coordinated actomyosin activation mechanisms, one of which induces global activation of the cortex and the other of which then maintains the contractility only inside the furrow region.
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Affiliation(s)
- Hiromi Miyoshi
- Department of Bioengineering, Tokyo Institute of Technology, O-okayama, Tokyo, Japan
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7
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Murthy K, Wadsworth P. Myosin-II-Dependent Localization and Dynamics of F-Actin during Cytokinesis. Curr Biol 2005; 15:724-31. [PMID: 15854904 DOI: 10.1016/j.cub.2005.02.055] [Citation(s) in RCA: 243] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2005] [Revised: 02/11/2005] [Accepted: 02/14/2005] [Indexed: 11/24/2022]
Abstract
BACKGROUND The assembly of an F-actin- and myosin-II-containing contractile ring (CR) is required for cytokinesis in eukaryotic cells. Interactions between myosin II and actin in the ring are believed to generate the force that constricts the cell into two daughters. The mechanism(s) that contribute to the spatially and temporally regulated assembly and disassembly of the CR at the cell equator are poorly understood. RESULTS We generated an LLCPK1 epithelial cell line that stably expresses GFP-actin. Live confocal imaging showed accumulation of GFP-actin in the equatorial cortex from late anaphase through cytokinesis. Fluorescence recovery after photobleaching (FRAP) experiments showed that actin in the CR is highly dynamic (t(1/2) = 26 s). In some cells, movement of GFP-actin toward the equatorial region was observed and contributed to FRAP. Blocking actin dynamic turnover with jasplakinolide demonstrates that dynamic actin is required for CR formation and cytokinesis. To test the role of myosin II in actin turnover and transport during CR formation, we inhibited myosin light-chain kinase with ML7 and myosin II ATPase activity with blebbistatin. Inhibition of myosin light-chain phosphorylation resulted in clearance of GFP-actin from the equatorial region, a reduction in myosin II in the furrow, and inhibition of cytokinesis. Treatment with blebbistatin did not block CR formation but reduced FRAP of GFP-actin and prevented completion of cytokinesis. CONCLUSIONS These results demonstrate that the majority of actin in the CR is highly dynamic and establish novel roles for myosin II in the retention and dynamic turnover of actin in the CR.
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Affiliation(s)
- Kausalya Murthy
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, 01003, USA
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8
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Ahuja P, Perriard E, Perriard JC, Ehler E. Sequential myofibrillar breakdown accompanies mitotic division of mammalian cardiomyocytes. J Cell Sci 2004; 117:3295-306. [PMID: 15226401 DOI: 10.1242/jcs.01159] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The contractile tissue of the heart is composed of individual cardiomyocytes. During mammalian embryonic development, heart growth is achieved by cell division while at the same time the heart is already exerting its essential pumping activity. There is still some debate whether the proliferative activity is carried out by a less differentiated, stem cell-like type of cardiomyocytes or whether embryonic cardiomyocytes are able to perform both of these completely different dynamic tasks, contraction and cell division. Our analysis of triple-stained specimen of cultured embryonic cardiomyocytes and of whole mount preparations of embryonic mouse hearts by confocal microscopy revealed that differentiated cardiomyocytes are indeed able to proliferate. However, to go through cell division, a disassembly of the contractile elements, the myofibrils, has to take place. This disassembly occurs in two steps with Z-disk and thin (actin)-filament-associated proteins getting disassembled before disassembly of the M-bands and the thick (myosin) filaments happens. After cytokinesis reassembly of the myofibrillar proteins to their mature cross-striated pattern can be seen. Another interesting observation was that the cell-cell contacts remain seemingly intact during division, probably reflecting the requirement of intact integration sites of the individual cells in the contractile tissue. Our results suggest that embryonic cardiomyocytes have developed an interesting strategy to deal with their major cytoskeletal elements, the myofibrils, during mitosis. The complex disassembly-reassembly process might also provide a mechanistic explanation, why cardiomyocytes cede to divide postnatally.
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Affiliation(s)
- Preeti Ahuja
- Institute of Cell Biology, Swiss Federal Institute of Technology, ETH Hönggerberg, 8093 Zurich
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9
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Pielak RM, Gaysinskaya VA, Cohen WD. Formation and function of the polar body contractile ring in Spisula. Dev Biol 2004; 269:421-32. [PMID: 15110710 DOI: 10.1016/j.ydbio.2004.01.033] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2003] [Revised: 12/24/2003] [Accepted: 01/10/2004] [Indexed: 11/21/2022]
Abstract
Initial studies suggested that spatial organization of the putative polar body contractile ring was determined by the peripheral aster in Spisula [Biol. Bull. 205 (2003) 192]. Here we report detailed supporting observations, including testing of aster and ring function with inhibitors. The metaphase peripheral aster was confirmed to spread cortically in an umbrella-like pattern, with microtubule-poor center. The aster disassembled during anaphase, leaving the spindle docked at the F-actin-poor center of a newly generated cortical F-actin ring that closely approximated the aster in location, measured diameter range, and pattern. Cytochalasin D and latrunculin-B permitted all events except ring and polar body formation. Nocodazole disassembly or taxol stabilization of the peripheral aster produced poorly defined rings or bulging anaphase asters within the ring center, respectively, inhibiting polar body formation. Polar body extrusion occurred at the ring center, the diameter of which diminished. Ring contractility-previously assumed-was verified using blebbistatin, a myosin-II ATPase inhibitor that permitted ring assembly but blocked polar body extrusion. The data support the hypothesis that peripheral aster spreading, perhaps dynein-driven, is causally related to polar body contractile ring formation, with anaphase entry and aster disassembly also required for polar body biogenesis. Previously reported astral spreading during embryonic micromere formation suggests that related mechanisms are involved in asymmetric somatic cytokinesis.
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Affiliation(s)
- Rafal M Pielak
- Department of Biological Sciences, Hunter College, New York, NY 10021, USA
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10
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Silverman-Gavrila RV, Forer A. Myosin localization during meiosis I of crane-fly spermatocytes gives indications about its role in division. CELL MOTILITY AND THE CYTOSKELETON 2003; 55:97-113. [PMID: 12740871 DOI: 10.1002/cm.10112] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We showed previously that in crane-fly spermatocytes myosin is required for tubulin flux [Silverman-Gavrila and Forer, 2000a: J Cell Sci 113:597-609], and for normal anaphase chromosome movement and contractile ring contraction [Silverman-Gavrila and Forer, 2001: Cell Motil Cytoskeleton 50:180-197]. Neither the identity nor the distribution of myosin(s) were known. In the present work, we used immunofluorescence and confocal microscopy to study myosin during meiosis-I of crane-fly spermatocytes compared to tubulin, actin, and skeletor, a spindle matrix protein, in order to further understand how myosin might function during cell division. Antibodies to myosin II regulatory light chain and myosin II heavy chain gave similar staining patterns, both dependent on stage: myosin is associated with nuclei, asters, centrosomes, chromosomes, spindle microtubules, midbody microtubules, and contractile rings. Myosin and actin colocalization along kinetochore fibers from prometaphase to anaphase are consistent with suggestions that acto-myosin forces in these stages propel kinetochore fibres poleward and trigger tubulin flux in kinetochore fibres, contributing in this way to poleward chromosome movement. Myosin and actin colocalization at the cell equator in cytokinesis, similar to studies in other cells [e.g., Fujiwara and Pollard, 1978: J Cell Biol 77:182-195], supports a role of actin-myosin interactions in contractile ring function. Myosin and skeletor colocalization in prometaphase spindles is consistent with a role of these proteins in spindle formation. After microtubules or actin were disrupted, myosin remained in spindles and contractile rings, suggesting that the presence of myosin in these structures does not require the continued presence of microtubules or actin. BDM (2,3 butanedione, 2 monoxime) treatment that inhibits chromosome movement and cytokinesis also altered myosin distributions in anaphase spindles and contractile rings, consistent with the physiological effects, suggesting also that myosin needs to be active in order to be properly distributed.
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Silverman-Gavrila RV, Forer A. Effects of anti-myosin drugs on anaphase chromosome movement and cytokinesis in crane-fly primary spermatocytes. CELL MOTILITY AND THE CYTOSKELETON 2001; 50:180-97. [PMID: 11807939 DOI: 10.1002/cm.10006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
To investigate whether myosin is involved in crane-fly primary spermatocyte division, we studied the effects of myosin inhibitors on chromosome movement and on cytokinesis. With respect to chromosome movement, the myosin ATPase inhibitor 2,3-butanedione 2-monoxime (BDM) added during autosomal anaphase reversibly perturbed the movements of all autosomes: autosomes stopped, slowed, or moved backwards during treatment. BDM added before anaphase onset altered chromosome movement less than when BDM was added during anaphase: chromosome movements only rarely were stopped. They often were normal initially and then, if altered at all, were slowed. To confirm that the effects of BDM were due to myosin inhibition, we treated cells with ML-7, a drug that inhibits myosin light chain kinase (MLCK), an enzyme necessary to activate myosin. ML-7 affected anaphase movement only when added in early prometaphase: this treatment prevented chromosome attachment to the spindle. We treated cells with H-7 as a control for possible non-myosin effects of ML-7. H-7, which has a lower affinity than ML-7 for MLCK but a higher affinity than ML-7 for other potential targets, had no effect. These data confirm that the BDM effect is on myosin and indicate that the myosin used for chromosome movement is activated near the start of prometaphase. With respect to cytokinesis, BDM did not block furrow initiation but did block subsequent contraction of the contractile ring. When BDM was added after initiation of the furrow, the contractile ring either stalled or relaxed. ML-7 blocked contractile ring contraction when added at all stages after autosomal anaphase onset, including when added during cytokinesis. H-7 had no effect. These results confirm that the effects of BDM are on myosin and indicate that the myosin used for cytokinesis is activated starting from autosomal anaphase and continuing throughout cytokinesis.
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Bi E. Cytokinesis in budding yeast: the relationship between actomyosin ring function and septum formation. Cell Struct Funct 2001; 26:529-37. [PMID: 11942606 DOI: 10.1247/csf.26.529] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cytokinesis in budding yeast is accomplished by the concerted action of actomyosin ring function and septum formation. The actomyosin ring is not essential for cell viability, but it is required for efficient cell division. Deletion of the actomyosin ring results in abnormal septum formation, and a delay in cytokinesis and cell separation. In contrast, septum formation is essential for cell viability. Block of septum formation prevents the contraction, but not the formation of the actomyosin ring. Here we review and provide additional evidence that defines the functional and molecular relationship between actomyosin ring function and septum formation.
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Affiliation(s)
- E Bi
- Department of Cell & Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia 19104-6058, USA.
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13
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Noguchi T, Arai R, Motegi F, Nakano K, Mabuchi I. Contractile ring formation in Xenopus egg and fission yeast. Cell Struct Funct 2001; 26:545-54. [PMID: 11942608 DOI: 10.1247/csf.26.545] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
How actin filaments (F-actin) and myosin II (myosin) assemble to form the contractile ring was investigated with fission yeast and Xenopus egg. In fission yeast cells, an aster-like structure composed of F-actin cables is formed at the medial cortex of the cell during prophase to metaphase, and a single F-actin cable(s) extends from this structure, which seems to be a structural basis of the contractile ring. In early mitosis, myosin localizes as dots in the medial cortex independently of F-actin. Then they fuse with each other and are packed into a thin contractile ring. At the growing ends of the cleavage furrow of Xenopus eggs, F-actin at first assembles to form patches. Next they fuse with each other to form short F-actin bundles. The short bundles then form long bundles. Myosin seems to be transported by the cortical movement to the growing end and assembles there as spots earlier than F-actin. Actin polymerization into the patches is likely to occur after accumulation of myosin. The myosin spots and the F-actin patches are simultaneously reorganized to form the contractile ring bundles. The idea that a Ca signal triggers cleavage furrow formation was tested with Xenopus eggs during the first cleavage. We could not detect any Ca signals such as a Ca wave, Ca puffs or even Ca blips at the growing end of the cleavage furrow. Furthermore, cleavages are not affected by Ca-chelators injected into the eggs at concentrations sufficient to suppress the Ca waves. Thus we conclude that formation of the contractile ring is not induced by a Ca signal at the growing end of the cleavage furrow.
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Affiliation(s)
- T Noguchi
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Japan
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14
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Wöllert T, DePina AS, Sandberg LA, Langford GM. Reconstitution of active pseudo-contractile rings and myosin-II-mediated vesicle transport in extracts of clam oocytes. THE BIOLOGICAL BULLETIN 2001; 201:241-243. [PMID: 11687401 DOI: 10.2307/1543344] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Affiliation(s)
- T Wöllert
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA
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15
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Yumura S. Myosin II dynamics and cortical flow during contractile ring formation in Dictyostelium cells. J Cell Biol 2001; 154:137-46. [PMID: 11448996 PMCID: PMC2196877 DOI: 10.1083/jcb.200011013] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2000] [Revised: 05/30/2001] [Accepted: 06/05/2001] [Indexed: 11/22/2022] Open
Abstract
Myosin II is a major component of a contractile ring. To examine if myosin II turns over in contractile rings, fluorescence of GFP-myosin II expressed in Dictyostelium cells was bleached locally by laser illumination, and the recovery was monitored. The fluorescence recovered with a half time of 7.01 +/- 2.62 s. This recovery was not caused by lateral movement of myosin II from the nonbleached area, but by an exchange with endoplasmic myosin II. Similar experiments were performed in cells expressing GFP-3ALA myosin II, of which three phosphorylatable threonine residues were replaced with alanine residues. In this case, recovery was not detected within a comparable time range. These results indicate that myosin II in the contractile ring performs dynamic turnover via its heavy chain phosphorylation. Because GFP-3ALA myosin II did not show the recovery, it served as a useful marker of myosin II movement, which enabled us to demonstrate cortical flow of myosin II toward the equator for the first time. Thus, cortical flow accompanies the dynamic exchange of myosin II during the formation of contractile rings.
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Affiliation(s)
- S Yumura
- Department of Biology, Faculty of Science, Yamaguchi University, Yoshida 1677-1, Yamaguchi 753-8512, Japan.
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16
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Matzke R, Jacobson K, Radmacher M. Direct, high-resolution measurement of furrow stiffening during division of adherent cells. Nat Cell Biol 2001; 3:607-10. [PMID: 11389447 DOI: 10.1038/35078583] [Citation(s) in RCA: 260] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
It is unclear whether cell division is driven by cortical relaxation outside the equatorial region or cortical contractility within the developing furrow alone. To approach this question, a technique is required that can monitor spatially-resolved changes in cortical stiffness with good time resolution. We employed atomic force microscopy (AFM), in force-mapping mode, to track dynamic changes in the stiffness of the cortex of adherent cultured cells along a single scan-line during M phase, from metaphase to cytokinesis. Video microscopy, which we used to correlate the AFM data with mitotic events identified by light microscopy, indicated that the AFM force-mapping technique does not perturb dividing cells. Here we show that cortical stiffening occurs over the equatorial region about 160 seconds before any furrow appears, and that this stiffening markedly increases as the furrow starts. By contrast, polar relaxation of cells does not seem to be an obligatory event for cell division to occur.
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Affiliation(s)
- R Matzke
- Center for Nanoscience, Ludwig Maximilians Universität München, Amalienstrasse 54, D-80799 München, Germany
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