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Sample records for affects cell division

  1. Oriented cell division affects the global stress and cell packing geometry of a monolayer under stretch.

    PubMed

    Xu, Guang-Kui; Liu, Yang; Zheng, Zhaoliang

    2016-02-08

    Cell division plays a vital role in tissue morphogenesis and homeostasis, and the division plane is crucial for cell fate. For isolated cells, extensive studies show that the orientation of divisions is sensitive to cell shape and the direction of extrinsic mechanical forces. However, it is poorly understood that how the cell divides within a cell monolayer and how the local stress change, due to the division, affects the global stress of epithelial monolayers. Here, we use the vertex dynamics models to investigate the effects of division orientation on the configurations and mechanics of a cell monolayer under stretch. We examine three scenarios of the divisions: dividing along the stretch axis, dividing along the geometric long axis of cells, and dividing at a random angle. It is found that the division along the long cell axis can induce the minimal energy difference, and the global stress of the monolayer after stretch releases more rapidly in this case. Moreover, the long-axis division can result in more random cell orientations and more isotropic cell shapes within the monolayer, comparing with other two cases. This study helps understand the division orientation of cells within a monolayer under mechanical stimuli, and may shed light on linking individual cell's behaviors to the global mechanics and patterns of tissues.

  2. Potato Snakin-1 Gene Silencing Affects Cell Division, Primary Metabolism, and Cell Wall Composition1[W

    PubMed Central

    Nahirñak, Vanesa; Almasia, Natalia Inés; Fernandez, Paula Virginia; Hopp, Horacio Esteban; Estevez, José Manuel; Carrari, Fernando; Vazquez-Rovere, Cecilia

    2012-01-01

    Snakin-1 (SN1) is an antimicrobial cysteine-rich peptide isolated from potato (Solanum tuberosum) that was classified as a member of the Snakin/Gibberellic Acid Stimulated in Arabidopsis protein family. In this work, a transgenic approach was used to study the role of SN1 in planta. Even when overexpressing SN1, potato lines did not show remarkable morphological differences from the wild type; SN1 silencing resulted in reduced height, which was accompanied by an overall reduction in leaf size and severe alterations of leaf shape. Analysis of the adaxial epidermis of mature leaves revealed that silenced lines had 70% to 90% increases in mean cell size with respect to wild-type leaves. Consequently, the number of epidermal cells was significantly reduced in these lines. Confocal microscopy analysis after agroinfiltration of Nicotiana benthamiana leaves showed that SN1-green fluorescent protein fusion protein was localized in plasma membrane, and bimolecular fluorescence complementation assays revealed that SN1 self-interacted in vivo. We further focused our study on leaf metabolism by applying a combination of gas chromatography coupled to mass spectrometry, Fourier transform infrared spectroscopy, and spectrophotometric techniques. These targeted analyses allowed a detailed examination of the changes occurring in 46 intermediate compounds from primary metabolic pathways and in seven cell wall constituents. We demonstrated that SN1 silencing affects cell division, leaf primary metabolism, and cell wall composition in potato plants, suggesting that SN1 has additional roles in growth and development beyond its previously assigned role in plant defense. PMID:22080603

  3. Cell division

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  4. BMP and Hh signaling affects primordial germ cell division in Drosophila.

    PubMed

    Sato, Takuya; Ogata, Jun; Niki, Yuzo

    2010-10-01

    The germline is segregated from the remainder of the soma during early embryonic development in metazoan species. In Drosophila, female primordial germ cells (PGCs) continue to proliferate during larval development, and become germline stem cells at the early pupal stage. To elucidate the roles of growth factors in larval PGC division, we examined expression patterns of a bone morphogenetic protein (BMP) growth factor, Decapentaplegic (Dpp), and Hedgehog (Hh), along with factors downstream of each, in the ovary during larval development. Dpp signaling appeared in the ovarian soma from early larval development, and was prominent in the terminal filament cells at late larval stage, whereas Hh appeared in the ovarian soma and PGCs from the third instar larval stage. The number of PGCs decreased when components of these signal transduction pathways were abrogated by RNAi in the PGCs, indicating that both Dpp and Hh signals directly regulate PGC proliferation. Experiments on the up- and down-regulation of Dpp and Hh with a tissue-specific Gal4 driver indicated that Dpp and Hh act as extrinsic and autocrine growth factors. Furthermore, heat-pulse experiments with hs-Gal4 showed that Dpp is active in PGC proliferation throughout larval development, whereas Hh has effects only during late larval development. In addition to Dpp, the reduction of Glass bottom boat (Gbb), another BMP molecule, caused a decrease in the number of PGCs and initiation of larval PGCs differentiation into cystocytes, indicating that Gbb functions to promote PGC division and repress differentiation.

  5. Ciprofloxacin Derivatives Affect Parasite Cell Division and Increase the Survival of Mice Infected with Toxoplasma gondii.

    PubMed

    Martins-Duarte, Erica S; Dubar, Faustine; Lawton, Philippe; da Silva, Cristiane França; Soeiro, Maria de Nazaré C; de Souza, Wanderley; Biot, Christophe; Vommaro, Rossiane C

    2015-01-01

    Toxoplasmosis, caused by the protozoan Toxoplasma gondii, is a worldwide disease whose clinical manifestations include encephalitis and congenital malformations in newborns. Previously, we described the synthesis of new ethyl-ester derivatives of the antibiotic ciprofloxacin with ~40-fold increased activity against T. gondii in vitro, compared with the original compound. Cipro derivatives are expected to target the parasite's DNA gyrase complex in the apicoplast. The activity of these compounds in vivo, as well as their mode of action, remained thus far uncharacterized. Here, we examined the activity of the Cipro derivatives in vivo, in a model of acute murine toxoplasmosis. In addition, we investigated the cellular effects T. gondii tachyzoites in vitro, by immunofluorescence and transmission electron microscopy (TEM). When compared with Cipro treatment, 7-day treatments with Cipro derivatives increased mouse survival significantly, with 13-25% of mice surviving for up to 60 days post-infection (vs. complete lethality 10 days post-infection, with Cipro treatment). Light microscopy examination early (6 and 24h) post-infection revealed that 6-h treatments with Cipro derivatives inhibited the initial event of parasite cell division inside host cells, in an irreversible manner. By TEM and immunofluorescence, the main cellular effects observed after treatment with Cipro derivatives and Cipro were cell scission inhibition--with the appearance of 'tethered' parasites--malformation of the inner membrane complex, and apicoplast enlargement and missegregation. Interestingly, tethered daughter cells resulting from Cipro derivatives, and also Cipro, treatment did not show MORN1 cap or centrocone localization. The biological activity of Cipro derivatives against C. parvum, an apicomplexan species that lacks the apicoplast, is, approximately, 50 fold lower than that in T. gondii tachyzoites, supporting that these compounds targets the apicoplast. Our results show that Cipro

  6. Ciprofloxacin Derivatives Affect Parasite Cell Division and Increase the Survival of Mice Infected with Toxoplasma gondii

    PubMed Central

    Martins-Duarte, Erica S.; Dubar, Faustine; Lawton, Philippe; França da Silva, Cristiane; C. Soeiro, Maria de Nazaré; de Souza, Wanderley; Biot, Christophe; Vommaro, Rossiane C.

    2015-01-01

    Toxoplasmosis, caused by the protozoan Toxoplasma gondii, is a worldwide disease whose clinical manifestations include encephalitis and congenital malformations in newborns. Previously, we described the synthesis of new ethyl-ester derivatives of the antibiotic ciprofloxacin with ~40-fold increased activity against T. gondii in vitro, compared with the original compound. Cipro derivatives are expected to target the parasite’s DNA gyrase complex in the apicoplast. The activity of these compounds in vivo, as well as their mode of action, remained thus far uncharacterized. Here, we examined the activity of the Cipro derivatives in vivo, in a model of acute murine toxoplasmosis. In addition, we investigated the cellular effects T. gondii tachyzoites in vitro, by immunofluorescence and transmission electron microscopy (TEM). When compared with Cipro treatment, 7-day treatments with Cipro derivatives increased mouse survival significantly, with 13–25% of mice surviving for up to 60 days post-infection (vs. complete lethality 10 days post-infection, with Cipro treatment). Light microscopy examination early (6 and 24h) post-infection revealed that 6-h treatments with Cipro derivatives inhibited the initial event of parasite cell division inside host cells, in an irreversible manner. By TEM and immunofluorescence, the main cellular effects observed after treatment with Cipro derivatives and Cipro were cell scission inhibition - with the appearance of ‘tethered’ parasites – malformation of the inner membrane complex, and apicoplast enlargement and missegregation. Interestingly, tethered daughter cells resulting from Cipro derivatives, and also Cipro, treatment did not show MORN1 cap or centrocone localization. The biological activity of Cipro derivatives against C. parvum, an apicomplexan species that lacks the apicoplast, is, approximately, 50 fold lower than that in T. gondii tachyzoites, supporting that these compounds targets the apicoplast. Our results show

  7. The Garlic Allelochemical Diallyl Disulfide Affects Tomato Root Growth by Influencing Cell Division, Phytohormone Balance and Expansin Gene Expression

    PubMed Central

    Cheng, Fang; Cheng, Zhihui; Meng, Huanwen; Tang, Xiangwei

    2016-01-01

    Diallyl disulfide (DADS) is a volatile organosulfur compound derived from garlic (Allium sativum L.), and it is known as an allelochemical responsible for the strong allelopathic potential of garlic. The anticancer properties of DADS have been studied in experimental animals and various types of cancer cells, but to date, little is known about its mode of action as an allelochemical at the cytological level. The current research presents further studies on the effects of DADS on tomato (Solanum lycopersicum L.) seed germination, root growth, mitotic index, and cell size in root meristem, as well as the phytohormone levels and expression profile of auxin biosynthesis genes (FZYs), auxin transport genes (SlPINs), and expansin genes (EXPs) in tomato root. The results showed a biphasic, dose-dependent effect on tomato seed germination and root growth under different DADS concentrations. Lower concentrations (0.01–0.62 mM) of DADS significantly promoted root growth, whereas higher levels (6.20–20.67 mM) showed inhibitory effects. Cytological observations showed that the cell length of root meristem was increased and that the mitotic activity of meristematic cells in seedling root tips was enhanced at lower concentrations of DADS. In contrast, DADS at higher concentrations inhibited root growth by affecting both the length and division activity of meristematic cells. However, the cell width of the root meristem was not affected. Additionally, DADS increased the IAA and ZR contents of seedling roots in a dose-dependent manner. The influence on IAA content may be mediated by the up-regulation of FZYs and PINs. Further investigation into the underlying mechanism revealed that the expression levels of tomato EXPs were significantly affected by DADS. The expression levels of EXPB2 and beta-expansin precursor were increased after 3 d, and those of EXP1, EXPB3 and EXLB1 were increased after 5 d of DADS treatment (0.41 mM). This result suggests that tomato root growth may be

  8. Artificial cell division.

    PubMed

    Mange, Daniel; Stauffer, André; Petraglio, Enrico; Tempesti, Gianluca

    2004-01-01

    After a survey of the theory and some realizations of self-replicating machines, this paper presents a novel self-replicating loop endowed with universal construction and computation properties. Based on the hardware implementation of the so-called Tom Thumb algorithm, the design of this loop leads to a new kind of cellular automaton made of a processing and a control units. The self-replication of the Swiss flag serves as an artificial cell division example of the loop which, according to autopoietic evaluation criteria, corresponds to a cell showing the phenomenology of a living system.

  9. A Genetic Screen for Mutations Affecting Cell Division in the Arabidopsis thaliana Embryo Identifies Seven Loci Required for Cytokinesis

    PubMed Central

    Gillmor, C. Stewart; Roeder, Adrienne H. K.; Sieber, Patrick; Somerville, Chris; Lukowitz, Wolfgang

    2016-01-01

    Cytokinesis in plants involves the formation of unique cellular structures such as the phragmoplast and the cell plate, both of which are required to divide the cell after nuclear division. In order to isolate genes that are involved in de novo cell wall formation, we performed a large-scale, microscope-based screen for Arabidopsis mutants that severely impair cytokinesis in the embryo. We recovered 35 mutations that form abnormally enlarged cells with multiple, often polyploid nuclei and incomplete cell walls. These mutants represent seven genes, four of which have previously been implicated in phragmoplast or cell plate function. Mutations in two loci show strongly reduced transmission through the haploid gametophytic generation. Molecular cloning of both corresponding genes reveals that one is represented by hypomorphic alleles of the kinesin-5 gene RADIALLY SWOLLEN 7 (homologous to tobacco kinesin-related protein TKRP125), and that the other gene corresponds to the Arabidopsis FUSED ortholog TWO-IN-ONE (originally identified based on its function in pollen development). No mutations that completely abolish the formation of cross walls in diploid cells were found. Our results support the idea that cytokinesis in the diploid and haploid generations involve similar mechanisms. PMID:26745275

  10. Repeated triggering of sporulation in Bacillus subtilis selects against a protein that affects the timing of cell division.

    PubMed

    Siebring, Jeroen; Elema, Matthijs J H; Drubi Vega, Fátima; Kovács, Akos T; Haccou, Patsy; Kuipers, Oscar P

    2014-01-01

    Bacillus subtilis sporulation is a last-resort phenotypical adaptation in response to starvation. The regulatory network underlying this developmental pathway has been studied extensively. However, how sporulation initiation is concerted in relation to the environmental nutrient availability is poorly understood. In a fed-batch fermentation set-up, in which sporulation of ultraviolet (UV)-mutagenized B. subtilis is repeatedly triggered by periods of starvation, fitter strains with mutated tagE evolved. These mutants display altered timing of phenotypical differentiation. The substrate for the wall teichoic acid (WTA)-modifying enzyme TagE, UDP-glucose, has recently been shown to be an intracellular proxy for nutrient availability, and influences the timing of cell division. Here we suggest that UDP-glucose also influences timing of cellular differentiation.

  11. Division rules for polygonal cells.

    PubMed

    Cowan, R; Morris, V B

    1988-03-07

    A number of fascinating mathematical problems concerning the division of two-dimensional space are formulated from questions about the planes of cell division in embryonic epithelia. Their solution aids in the quantitative description of cellular arrangement in epithelia. Cells, considered as polygons, site their division line according to stochastic rules, eventually forming a tessellation of the plane. The equilibrium distributions for the resulting mix of polygonal types are explored for a range of stochastic rules. We find surprising links with some classical distributions from the theory of probability.

  12. Alignment of cell division axes in directed epithelial cell migration

    NASA Astrophysics Data System (ADS)

    Marel, Anna-Kristina; Podewitz, Nils; Zorn, Matthias; Oskar Rädler, Joachim; Elgeti, Jens

    2014-11-01

    Cell division is an essential dynamic event in tissue remodeling during wound healing, cancer and embryogenesis. In collective migration, tensile stresses affect cell shape and polarity, hence, the orientation of the cell division axis is expected to depend on cellular flow patterns. Here, we study the degree of orientation of cell division axes in migrating and resting epithelial cell sheets. We use microstructured channels to create a defined scenario of directed cell invasion and compare this situation to resting but proliferating cell monolayers. In experiments, we find a strong alignment of the axis due to directed flow while resting sheets show very weak global order, but local flow gradients still correlate strongly with the cell division axis. We compare experimental results with a previously published mesoscopic particle based simulation model. Most of the observed effects are reproduced by the simulations.

  13. The physiology of bacterial cell division.

    PubMed

    Egan, Alexander J F; Vollmer, Waldemar

    2013-01-01

    Bacterial cell division is facilitated by the divisome, a dynamic multiprotein assembly localizing at mid-cell to synthesize the stress-bearing peptidoglycan and to constrict all cell envelope layers. Divisome assembly occurs in two steps and involves multiple interactions between more than 20 essential and accessory cell division proteins. Well before constriction and while the cell is still elongating, the tubulin-like FtsZ and early cell division proteins form a ring-like structure at mid-cell. Cell division starts once certain peptidoglycan enzymes and their activators have moved to the FtsZ-ring. Gram-negative bacteria like Escherichia coli simultaneously synthesize and cleave the septum peptidoglycan during division leading to a constriction. The outer membrane constricts together with the peptidoglycan layer with the help of the transenvelope spanning Tol-Pal system.

  14. Polarized Cell Division of Chlamydia trachomatis.

    PubMed

    Abdelrahman, Yasser; Ouellette, Scot P; Belland, Robert J; Cox, John V

    2016-08-01

    Bacterial cell division predominantly occurs by a highly conserved process, termed binary fission, that requires the bacterial homologue of tubulin, FtsZ. Other mechanisms of bacterial cell division that are independent of FtsZ are rare. Although the obligate intracellular human pathogen Chlamydia trachomatis, the leading bacterial cause of sexually transmitted infections and trachoma, lacks FtsZ, it has been assumed to divide by binary fission. We show here that Chlamydia divides by a polarized cell division process similar to the budding process of a subset of the Planctomycetes that also lack FtsZ. Prior to cell division, the major outer-membrane protein of Chlamydia is restricted to one pole of the cell, and the nascent daughter cell emerges from this pole by an asymmetric expansion of the membrane. Components of the chlamydial cell division machinery accumulate at the site of polar growth prior to the initiation of asymmetric membrane expansion and inhibitors that disrupt the polarity of C. trachomatis prevent cell division. The polarized cell division of C. trachomatis is the result of the unipolar growth and FtsZ-independent fission of this coccoid organism. This mechanism of cell division has not been documented in other human bacterial pathogens suggesting the potential for developing Chlamydia-specific therapeutic treatments.

  15. Sunlight and vitamin D affect DNA damage, cell division and cell death in human lymphocytes: a cross-sectional study in South Australia.

    PubMed

    Nair-Shalliker, Visalini; Fenech, Michael; Forder, Peta M; Clements, Mark S; Armstrong, Bruce K

    2012-09-01

    The ultraviolet (UV)-B spectrum in solar UV radiation is essential for stimulating the epidermal production of vitamin D but also damages DNA and causes cancer in exposed cells. We examined the role of solar UV in inducing DNA damage in blood lymphocytes and the possible modulation of this damage by serum 25-hydroxy vitamin D (25(OH)D) in 207 male and female participants from South Australia. Personal solar UV exposure was estimated from hours of outdoor exposure recalled at the time of blood collection for analysis of DNA damage in lymphocytes, using the cytokinesis-block micronucleus cytome (CBMN-cyt) assay and of serum 25(OH)D. We examined the association between solar UV exposure, serum 25(OH)D and DNA damage using multiple linear regression, with age, sex, body mass index and alcohol consumption as covariates. The frequency of cells with micronuclei (a biomarker of chromosome breakage or loss) increased with increasing sun exposure [% increase = 5.24; 95% confidence interval (CI): 0.35 to 10.37 P-value = 0.04] but cells with nucleoplasmic bridges (a biomarker of misrepair of DNA strand breaks or telomere end fusions) decreased (% increase = -8.38; 95% CI: -14.32 to -2.03 P-value = 0.01). There was also a fall in the nuclear division index (NDI) (% increase = -1.01; 95% CI: -2.00 to 0.00 P-value = 0.05), suggesting diminished mitogenic response and, possibly, immune suppression. There was no overall relationship between 25(OH)D and DNA damage. There were, however, weak modulating effects of 25(OH)D on the associations of solar UV exposure with micronucleus formation and with NDI (P-interaction = 0.03 and 0.05, respectively), where the increase in micronuclei and fall in NDI with increasing solar UV were greater at serum 25(OH)D levels <50 nmol/l. Thus, the influence of solar UV exposure in causing DNA damage or immune suppression in internal tissues may be stronger when vitamin D levels are low.

  16. Gravity and the orientation of cell division

    NASA Technical Reports Server (NTRS)

    Helmstetter, C. E.

    1997-01-01

    A novel culture system for mammalian cells was used to investigate division orientations in populations of Chinese hamster ovary cells and the influence of gravity on the positioning of division axes. The cells were tethered to adhesive sites, smaller in diameter than a newborn cell, distributed over a nonadhesive substrate positioned vertically. The cells grew and divided while attached to the sites, and the angles and directions of elongation during anaphase, projected in the vertical plane, were found to be random with respect to gravity. However, consecutive divisions of individual cells were generally along the same axis or at 90 degrees to the previous division, with equal probability. Thus, successive divisions were restricted to orthogonal planes, but the choice of plane appeared to be random, unlike the ordered sequence of cleavage orientations seen during early embryo development.

  17. Teaching Cell Division: Basics and Recommendations.

    ERIC Educational Resources Information Center

    Smith, Mike U.; Kindfield, Ann C. H.

    1999-01-01

    Presents a concise overview of cell division that includes only the essential concepts necessary for understanding genetics and evolution. Makes recommendations based on published research and teaching experiences that can be used to judge the merits of potential activities and materials for teaching cell division. Makes suggestions regarding the…

  18. Asymmetric stem cell division: lessons from Drosophila.

    PubMed

    Wu, Pao-Shu; Egger, Boris; Brand, Andrea H

    2008-06-01

    Asymmetric cell division is an important and conserved strategy in the generation of cellular diversity during animal development. Many of our insights into the underlying mechanisms of asymmetric cell division have been gained from Drosophila, including the establishment of polarity, orientation of mitotic spindles and segregation of cell fate determinants. Recent studies are also beginning to reveal the connection between the misregulation of asymmetric cell division and cancer. What we are learning from Drosophila as a model system has implication both for stem cell biology and also cancer research.

  19. Nanoengineering: Super symmetry in cell division

    NASA Astrophysics Data System (ADS)

    Huang, Kerwyn Casey

    2015-08-01

    Bacterial cells can be sculpted into different shapes using nanofabricated chambers and then used to explore the spatial adaptation of protein oscillations that play an important role in cell division.

  20. The centrosome and asymmetric cell division

    PubMed Central

    2009-01-01

    Asymmetric stem cell division is a mechanism widely employed by the cell to maintain tissue homeostasis, resulting in the production of one stem cell and one differentiating cell. However, asymmetric cell division is not limited to stem cells and is widely observed even in unicellular organisms as well as in cells that make up highly complex tissues. In asymmetric cell division, cells must organize their intracellular components along the axis of asymmetry (sometimes in the context of extracellular architecture). Recent studies have described cell asymmetry in many cell types and in many cases such asymmetry involves the centrosome (or spindle pole body in yeast) as the center of cytoskeleton organization. In this review, I summarize recent discoveries in cellular polarity that lead to an asymmetric outcome, with a focus on centrosome function. PMID:19458491

  1. The fencing problem and Coleochaete cell division.

    PubMed

    Wang, Yuandi; Dou, Mingya; Zhou, Zhigang

    2015-03-01

    The findings in this study suggest that the solution of a boundary value problem for differential equation system can be used to discuss the fencing problem in mathematics and Coleochaete, a green algae, cell division. This differential equation model in parametric expression is used to simulate the two kinds of cell division process, one is for the usual case and the case with a "dead" daughter cell.

  2. Impact of the cell division cycle on gene circuits

    NASA Astrophysics Data System (ADS)

    Bierbaum, Veronika; Klumpp, Stefan

    2015-12-01

    In growing cells, protein synthesis and cell growth are typically not synchronous, and, thus, protein concentrations vary over the cell division cycle. We have developed a theoretical description of genetic regulatory systems in bacteria that explicitly considers the cell division cycle to investigate its impact on gene expression. We calculate the cell-to-cell variations arising from cells being at different stages in the division cycle for unregulated genes and for basic regulatory mechanisms. These variations contribute to the extrinsic noise observed in single-cell experiments, and are most significant for proteins with short lifetimes. Negative autoregulation buffers against variation of protein concentration over the division cycle, but the effect is found to be relatively weak. Stronger buffering is achieved by an increased protein lifetime. Positive autoregulation can strongly amplify such variation if the parameters are set to values that lead to resonance-like behaviour. For cooperative positive autoregulation, the concentration variation over the division cycle diminishes the parameter region of bistability and modulates the switching times between the two stable states. The same effects are seen for a two-gene mutual-repression toggle switch. By contrast, an oscillatory circuit, the repressilator, is only weakly affected by the division cycle.

  3. Translational Control of Cell Division by Elongator

    PubMed Central

    Bauer, Fanelie; Matsuyama, Akihisa; Candiracci, Julie; Dieu, Marc; Scheliga, Judith; Wolf, Dieter A.; Yoshida, Minoru; Hermand, Damien

    2012-01-01

    SUMMARY Elongator is required for the synthesis of the mcm5s2 modification found on tRNAs recognizing AA-ending codons. In order to obtain a global picture of the role of Elongator in translation, we used reverse protein arrays to screen the fission yeast proteome for translation defects. Unexpectedly, this revealed that Elongator inactivation mainly affected three specific functional groups including proteins implicated in cell division. The absence of Elongator results in a delay in mitosis onset and cytokinesis defects. We demonstrate that the kinase Cdr2, which is a central regulator of mitosis and cytokinesis, is under translational control by Elongator due to the Lysine codon usage bias of the cdr2 coding sequence. These findings uncover a mechanism by which the codon usage, coupled to tRNA modifications, fundamentally contributes to gene expression and cellular functions. PMID:22768388

  4. Cell Division and Evolution of Biological Tissues

    NASA Astrophysics Data System (ADS)

    Rivier, Nicolas; Arcenegui-Siemens, Xavier; Schliecker, Gudrun

    A tissue is a geometrical, space-filling, random cellular network; it remains in this steady state while individual cells divide. Cell division (fragmentation) is a local, elementary topological transformation which establishes statistical equilibrium of the structure. Statistical equilibrium is characterized by observable relations (Lewis, Aboav) between cell shapes, sizes and those of their neighbours, obtained through maximum entropy and topological correlation extending to nearest neighbours only, i.e. maximal randomness. For a two-dimensional tissue (epithelium), the distribution of cell shapes and that of mother and daughter cells can be obtained from elementary geometrical and physical arguments, except for an exponential factor favouring division of larger cells, and exponential and combinatorial factors encouraging a most symmetric division. The resulting distributions are very narrow, and stationarity severely restricts the range of an adjustable structural parameter

  5. A New Essential Cell Division Protein in Caulobacter crescentus.

    PubMed

    Osorio, Aurora; Camarena, Laura; Cevallos, Miguel Angel; Poggio, Sebastian

    2017-04-15

    Bacterial cell division is a complex process that relies on a multiprotein complex composed of a core of widely conserved and generally essential proteins and on accessory proteins that vary in number and identity in different bacteria. The assembly of this complex and, particularly, the initiation of constriction are regulated processes that have come under intensive study. In this work, we characterize the function of DipI, a protein conserved in Alphaproteobacteria and Betaproteobacteria that is essential in Caulobacter crescentus Our results show that DipI is a periplasmic protein that is recruited late to the division site and that it is required for the initiation of constriction. The recruitment of the conserved cell division proteins is not affected by the absence of DipI, but localization of DipI to the division site occurs only after a mature divisome has formed. Yeast two-hybrid analysis showed that DipI strongly interacts with the FtsQLB complex, which has been recently implicated in regulating constriction initiation. A possible role of DipI in this process is discussed.IMPORTANCE Bacterial cell division is a complex process for which most bacterial cells assemble a multiprotein complex that consists of conserved proteins and of accessory proteins that differ among bacterial groups. In this work, we describe a new cell division protein (DipI) present only in a group of bacteria but essential in Caulobacter crescentus Cells devoid of DipI cannot constrict. Although a mature divisome is required for DipI recruitment, DipI is not needed for recruiting other division proteins. These results, together with the interaction of DipI with a protein complex that has been suggested to regulate cell wall synthesis during division, suggest that DipI may be part of the regulatory mechanism that controls constriction initiation.

  6. Bacterial cell division proteins as antibiotic targets.

    PubMed

    den Blaauwen, Tanneke; Andreu, José M; Monasterio, Octavio

    2014-08-01

    Proteins involved in bacterial cell division often do not have a counterpart in eukaryotic cells and they are essential for the survival of the bacteria. The genetic accessibility of many bacterial species in combination with the Green Fluorescence Protein revolution to study localization of proteins and the availability of crystal structures has increased our knowledge on bacterial cell division considerably in this century. Consequently, bacterial cell division proteins are more and more recognized as potential new antibiotic targets. An international effort to find small molecules that inhibit the cell division initiating protein FtsZ has yielded many compounds of which some are promising as leads for preclinical use. The essential transglycosylase activity of peptidoglycan synthases has recently become accessible to inhibitor screening. Enzymatic assays for and structural information on essential integral membrane proteins such as MraY and FtsW involved in lipid II (the peptidoglycan building block precursor) biosynthesis have put these proteins on the list of potential new targets. This review summarises and discusses the results and approaches to the development of lead compounds that inhibit bacterial cell division.

  7. Small GTPases as regulators of cell division.

    PubMed

    Militello, Rodrigo; Colombo, María I

    2013-09-01

    The superfamily of small GTPases serves as a signal transducer to regulate a diverse array of cellular functions. The members of this superfamily are structurally and functionally classified into at least 5 groups (Ras, Rho/Rac, Rab, Arf, and Ran) and they are involved in the control of cell proliferation and differentiation, regulation of the actin cytoskeleton, membrane trafficking, and nuclear transport. It is widely reported that members of the Rab family participate in the control of intracellular membrane trafficking through the interaction with specific effector molecules. However, many Rabs and other small GTPases have also been shown to function in cell division. In this review, we discuss current knowledge about Rab proteins regulating different stages of the cell cycle, such as the congregation and segregation of chromosomes (during metaphase) and the final stage of cell division known as cytokinesis, in which a cell is cleaved originating 2 daughter cells.

  8. Automated cell tracking identifies mechanically oriented cell divisions during Drosophila axis elongation.

    PubMed

    Wang, Michael F Z; Hunter, Miranda V; Wang, Gang; McFaul, Christopher; Yip, Christopher M; Fernandez-Gonzalez, Rodrigo

    2017-04-01

    Embryos extend their anterior-posterior (AP) axis in a conserved process known as axis elongation. Drosophila axis elongation occurs in an epithelial monolayer, the germband, and is driven by cell intercalation, cell shape changes, and oriented cell divisions at the posterior germband. Anterior germband cells also divide during axis elongation. We developed image analysis and pattern-recognition methods to track dividing cells from confocal microscopy movies in a generally applicable approach. Mesectoderm cells, forming the ventral midline, divided parallel to the AP axis, while lateral cells displayed a uniform distribution of division orientations. Mesectoderm cells did not intercalate and sustained increased AP strain before cell division. After division, mesectoderm cell density increased along the AP axis, thus relieving strain. We used laser ablation to isolate mesectoderm cells from the influence of other tissues. Uncoupling the mesectoderm from intercalating cells did not affect cell division orientation. Conversely, separating the mesectoderm from the anterior and posterior poles of the embryo resulted in uniformly oriented divisions. Our data suggest that mesectoderm cells align their division angle to reduce strain caused by mechanical forces along the AP axis of the embryo.

  9. Bacterial cell division and the septal ring.

    PubMed

    Weiss, David S

    2004-11-01

    Cell division in bacteria is mediated by the septal ring, a collection of about a dozen (known) proteins that localize to the division site, where they direct assembly of the division septum. The foundation of the septal ring is a polymer of the tubulin-like protein FtsZ. Recently, experiments using fluorescence recovery after photobleaching have revealed that the Z ring is extremely dynamic. FtsZ subunits exchange in and out of the ring on a time scale of seconds even while the overall morphology of the ring appears static. These findings, together with in vitro studies of purified FtsZ, suggest that the rate-limiting step in turnover of FtsZ polymers is GTP hydrolysis. Another component of the septal ring, FtsK, is involved in coordinating chromosome segregation with cell division. Recent studies have revealed that FtsK is a DNA translocase that facilitates decatenation of sister chromosomes by TopIV and resolution of chromosome dimers by the XerCD recombinase. Finally, two murein hydrolases, AmiC and EnvC, have been shown to localize to the septal ring of Escherichia coli, where they play an important role in separation of daughter cells.

  10. Regulation of cell division in higher plants

    SciTech Connect

    Jacobs, T.W.

    1992-01-01

    Cell division is arguably the most fundamental of all developmental processes. In higher plants, mitotic activity is largely confined to foci of patterned cell divisions called meristems. From these perpetually embryonic tissues arise the plant's essential organs of light capture, support, protection and reproduction. Once an adequate understanding of plant cell mitotic regulation is attained, unprecedented opportunities will ensue for analyzing and genetically controlling diverse aspects of development, including plant architecture, leaf shape, plant height, and root depth. The mitotic cycle in a variety of model eukaryotic systems in under the control of a regulatory network of striking evolutionary conservation. Homologues of the yeast cdc2 gene, its catalytic product, p34, and the cyclin regulatory subunits of the MPF complex have emerged as ubiquitous mitotic regulators. We have cloned cdc2-like and cyclin genes from pea. As in other eukaryotic model systems, p34 of Pisum sativum is a subunit of a high molecular weight complex which binds the fission yeast p13 protein and displays histone H1 kinase activity in vitro. Our primary objective in this study is to gain baseline information about the regulation of this higher plant cell division control complex in non-dividing, differentiated cells as well as in synchronous and asynchronous mitotic cells. We are investigating cdc2 and cyclin expression at the levels of protein abundance, protein phosphorylation and quaternary associations.

  11. Collective dynamics during cell division

    NASA Astrophysics Data System (ADS)

    Zapperi, Stefano; Bertalan, Zsolt; Budrikis, Zoe; La Porta, Caterina A. M.

    In order to correctly divide, cells have to move all their chromosomes at the center, a process known as congression. This task is performed by the combined action of molecular motors and randomly growing and shrinking microtubules. Chromosomes are captured by growing microtubules and transported by motors using the same microtubules as tracks. Coherent motion occurs as a result of a large collection of random and deterministic dynamical events. Understanding this process is important since a failure in chromosome segregation can lead to chromosomal instability one of the hallmarks of cancer. We describe this complex process in a three dimensional computational model involving thousands of microtubules. The results show that coherent and robust chromosome congression can only happen if the total number of microtubules is neither too small, nor too large. Our results allow for a coherent interpretation a variety of biological factors already associated in the past with chromosomal instability and related pathological conditions.

  12. Stem cell regulation: Implications when differentiated cells regulate symmetric stem cell division.

    PubMed

    Høyem, Marte Rørvik; Måløy, Frode; Jakobsen, Per; Brandsdal, Bjørn Olav

    2015-09-07

    We use a mathematical model to show that if symmetric stem cell division is regulated by differentiated cells, then changes in the population dynamics of the differentiated cells can lead to changes in the population dynamics of the stem cells. More precisely, the relative fitness of the stem cells can be affected by modifying the death rate of the differentiated cells. This result is interesting because stem cells are less sensitive than differentiated cells to environmental factors, such as medical therapy. Our result implies that stem cells can be manipulated indirectly by medical treatments that target the differentiated cells.

  13. Polarity in plant asymmetric cell division: Division orientation and cell fate differentiation.

    PubMed

    Shao, Wanchen; Dong, Juan

    2016-11-01

    Asymmetric cell division (ACD) is universally required for the development of multicellular organisms. Unlike animal cells, plant cells have a rigid cellulosic extracellular matrix, the cell wall, which provides physical support and forms communication routes. This fundamental difference leads to some unique mechanisms in plants for generating asymmetries during cell division. However, plants also utilize intrinsically polarized proteins to regulate asymmetric signaling and cell division, a strategy similar to the differentiation mechanism found in animals. Current progress suggests that common regulatory modes, i.e. protein spontaneous clustering and cytoskeleton reorganization, underlie protein polarization in both animal and plant cells. Despite these commonalities, it is important to note that intrinsic mechanisms in plants are heavily influenced by extrinsic cues. To control physical asymmetry in cell division, although our understanding is fragmentary thus far, plants might have evolved novel polarization strategies to orientate cell division plane. Recent studies also suggest that the phytohormone auxin, one of the most pivotal small molecules in plant development, regulates ACD in plants.

  14. Formative cell divisions: principal determinants of plant morphogenesis.

    PubMed

    Smolarkiewicz, Michalina; Dhonukshe, Pankaj

    2013-03-01

    Formative cell divisions utilizing precise rotations of cell division planes generate and spatially place asymmetric daughters to produce different cell layers. Therefore, by shaping tissues and organs, formative cell divisions dictate multicellular morphogenesis. In animal formative cell divisions, the orientation of the mitotic spindle and cell division planes relies on intrinsic and extrinsic cortical polarity cues. Plants lack known key players from animals, and cell division planes are determined prior to the mitotic spindle stage. Therefore, it appears that plants have evolved specialized mechanisms to execute formative cell divisions. Despite their profound influence on plant architecture, molecular players and cellular mechanisms regulating formative divisions in plants are not well understood. This is because formative cell divisions in plants have been difficult to track owing to their submerged positions and imprecise timings of occurrence. However, by identifying a spatiotemporally inducible cell division plane switch system applicable for advanced microscopy techniques, recent studies have begun to uncover molecular modules and mechanisms for formative cell divisions. The identified molecular modules comprise developmentally triggered transcriptional cascades feeding onto microtubule regulators that now allow dissection of the hierarchy of the events at better spatiotemporal resolutions. Here, we survey the current advances in understanding of formative cell divisions in plants in the context of embryogenesis, stem cell functionality and post-embryonic organ formation.

  15. Bestatin inhibits cell growth, cell division, and spore cell differentiation in Dictyostelium discoideum.

    PubMed

    Poloz, Yekaterina; Catalano, Andrew; O'Day, Danton H

    2012-04-01

    Bestatin methyl ester (BME) is an inhibitor of Zn(2+)-binding aminopeptidases that inhibits cell proliferation and induces apoptosis in normal and cancer cells. We have used Dictyostelium as a model organism to study the effects of BME. Only two Zn(2+)-binding aminopeptidases have been identified in Dictyostelium to date, puromycin-sensitive aminopeptidase A and B (PsaA and PsaB). PSA from other organisms is known to regulate cell division and differentiation. Here we show that PsaA is differentially expressed throughout growth and development of Dictyostelium, and its expression is regulated by developmental morphogens. We present evidence that BME specifically interacts with PsaA and inhibits its aminopeptidase activity. Treatment of cells with BME inhibited the rate of cell growth and the frequency of cell division in growing cells and inhibited spore cell differentiation during late development. Overexpression of PsaA-GFP (where GFP is green fluorescent protein) also inhibited spore cell differentiation but did not affect growth. Using chimeras, we have identified that nuclear versus cytoplasmic localization of PsaA affects the choice between stalk or spore cell differentiation pathway. Cells that overexpressed PsaA-GFP (primarily nuclear) differentiated into stalk cells, while cells that overexpressed PsaAΔNLS2-GFP (cytoplasmic) differentiated into spores. In conclusion, we have identified that BME inhibits cell growth, division, and differentiation in Dictyostelium likely through inhibition of PsaA.

  16. Cell Division Drives Epithelial Cell Rearrangements during Gastrulation in Chick.

    PubMed

    Firmino, Joao; Rocancourt, Didier; Saadaoui, Mehdi; Moreau, Chloe; Gros, Jerome

    2016-02-08

    During early embryonic development, cells are organized as cohesive epithelial sheets that are continuously growing and remodeled without losing their integrity, giving rise to a wide array of tissue shapes. Here, using live imaging in chick embryo, we investigate how epithelial cells rearrange during gastrulation. We find that cell division is a major rearrangement driver that powers dramatic epithelial cell intercalation events. We show that these cell division-mediated intercalations, which represent the majority of epithelial rearrangements within the early embryo, are absolutely necessary for the spatial patterning of gastrulation movements. Furthermore, we demonstrate that these intercalation events result from overall low cortical actomyosin accumulation within the epithelial cells of the embryo, which enables dividing cells to remodel junctions in their vicinity. These findings uncover a role for cell division as coordinator of epithelial growth and remodeling that might underlie various developmental, homeostatic, or pathological processes in amniotes.

  17. Cell biological regulation of division fate in vertebrate neuroepithelial cells.

    PubMed

    Willardsen, Minde I; Link, Brian A

    2011-08-01

    The developing nervous system derives from neuroepithelial progenitor cells that divide to generate all of the mature neuronal types. For the proper complement of cell types to form, the progenitors must produce postmitotic cells, yet also replenish the progenitor pool. Progenitor divisions can be classified into three general types: symmetric proliferative (producing two progenitors), asymmetric neurogenic (producing one progenitor and one postmitotic cell), and symmetric neurogenic (producing two postmitotic cells). The appropriate ratios for these modes of cell division require intrinsic polarity, which is one of the characteristics that define neuroepithelial progenitor cells. The type of division an individual progenitor undergoes can be influenced by cellular features, or behaviors, which are heterogeneous within the population of progenitors. Here we review three key cellular parameters, asymmetric inheritance, cell cycle kinetics, and interkinetic nuclear migration, and the possible mechanisms for how these features influence progenitor fates.

  18. Effects of Polyhydroxybutyrate Production on Cell Division

    NASA Technical Reports Server (NTRS)

    Miller, Kathleen; Rahman, Asif; Hadi, Masood Z.

    2015-01-01

    Synthetic biological engineering can be utilized to aide the advancement of improved long-term space flight. The potential to use synthetic biology as a platform to biomanufacture desired equipment on demand using the three dimensional (3D) printer on the International Space Station (ISS) gives long-term NASA missions the flexibility to produce materials as needed on site. Polyhydroxybutyrates (PHBs) are biodegradable, have properties similar to plastics, and can be produced in Escherichia coli using genetic engineering. Using PHBs during space flight could assist mission success by providing a valuable source of biomaterials that can have many potential applications, particularly through 3D printing. It is well documented that during PHB production E. coli cells can become significantly elongated. The elongation of cells reduces the ability of the cells to divide and thus to produce PHB. I aim to better understand cell division during PHB production, through the design, building, and testing of synthetic biological circuits, and identify how to potentially increase yields of PHB with FtsZ overexpression, the gene responsible for cell division. Ultimately, an increase in the yield will allow more products to be created using the 3D printer on the ISS and beyond, thus aiding astronauts in their missions.

  19. MioC and GidA proteins promote cell division in E. coli.

    PubMed

    Lies, Mark; Visser, Bryan J; Joshi, Mohan C; Magnan, David; Bates, David

    2015-01-01

    The well-conserved genes surrounding the E. coli replication origin, mioC and gidA, do not normally affect chromosome replication and have little known function. We report that mioC and gidA mutants exhibit a moderate cell division inhibition phenotype. Cell elongation is exacerbated by a fis deletion, likely owing to delayed replication and subsequent cell cycle stress. Measurements of replication initiation frequency and origin segregation indicate that mioC and gidA do not inhibit cell division through any effect on oriC function. Division inhibition is also independent of the two known replication/cell division checkpoints, SOS and nucleoid occlusion. Complementation analysis indicates that mioC and gidA affect cell division in trans, indicating their effect is at the protein level. Transcriptome analysis by RNA sequencing showed that expression of a cell division septum component, YmgF, is significantly altered in mioC and gidA mutants. Our data reveal new roles for the gene products of gidA and mioC in the division apparatus, and we propose that their expression, cyclically regulated by chromatin remodeling at oriC, is part of a cell cycle regulatory program coordinating replication initiation and cell division.

  20. Asymmetric cell division during T cell development controls downstream fate

    PubMed Central

    Pham, Kim; Shimoni, Raz; Charnley, Mirren; Ludford-Menting, Mandy J.; Hawkins, Edwin D.; Ramsbottom, Kelly; Oliaro, Jane; Izon, David; Ting, Stephen B.; Reynolds, Joseph; Lythe, Grant; Molina-Paris, Carmen; Melichar, Heather; Robey, Ellen; Humbert, Patrick O.; Gu, Min

    2015-01-01

    During mammalian T cell development, the requirement for expansion of many individual T cell clones, rather than merely expansion of the entire T cell population, suggests a possible role for asymmetric cell division (ACD). We show that ACD of developing T cells controls cell fate through differential inheritance of cell fate determinants Numb and α-Adaptin. ACD occurs specifically during the β-selection stage of T cell development, and subsequent divisions are predominantly symmetric. ACD is controlled by interaction with stromal cells and chemokine receptor signaling and uses a conserved network of polarity regulators. The disruption of polarity by deletion of the polarity regulator, Scribble, or the altered inheritance of fate determinants impacts subsequent fate decisions to influence the numbers of DN4 cells arising after the β-selection checkpoint. These findings indicate that ACD enables the thymic microenvironment to orchestrate fate decisions related to differentiation and self-renewal. PMID:26370500

  1. Cell division modulates prion accumulation in cultured cells.

    PubMed

    Ghaemmaghami, Sina; Phuan, Puay-Wah; Perkins, Beth; Ullman, Julie; May, Barnaby C H; Cohen, Fred E; Prusiner, Stanley B

    2007-11-13

    The phenotypic effect of prions on host cells is influenced by the physical properties of the prion strain and its level of accumulation. In mammalian cell cultures, prion accumulation is determined by the interplay between de novo prion formation, catabolism, cell division, and horizontal cell-to-cell transmission. Understanding this dynamic enables the analytical modeling of protein-based heritability and infectivity. Here, we quantitatively measured these competing effects in a subline of neuroblastoma (N2a) cells and propose a concordant reaction mechanism to explain the kinetics of prion propagation. Our results show that cell division leads to a predictable reduction in steady-state prion levels but not to complete clearance. Scrapie-infected N2a cells were capable of accumulating different steady-state levels of prions, dictated partly by the rate of cell division. We also show that prions in this subline of N2a cells are transmitted primarily from mother to daughter cells, rather than horizontal cell-to-cell transmission. We quantitatively modeled our kinetic results based on a mechanism that assumes a subpopulation of prions is capable of self-catalysis, and the levels of this subpopulation reach saturation in fully infected cells. Our results suggest that the apparent effectiveness of antiprion compounds in culture may be strongly influenced by the growth phase of the target cells.

  2. A new Escherichia coli cell division gene, ftsK.

    PubMed Central

    Begg, K J; Dewar, S J; Donachie, W D

    1995-01-01

    A mutation in a newly discovered Escherichia coli cell division gene, ftsK, causes a temperature-sensitive late-stage block in division but does not affect chromosome replication or segregation. This defect is specifically suppressed by deletion of dacA, coding for the peptidoglycan DD-carboxypeptidase, PBP 5. FtsK is a large polypeptide (147 kDa) consisting of an N-terminal domain with several predicted membrane-spanning regions, a proline-glutamine-rich domain, and a C-terminal domain with a nucleotide-binding consensus sequence. FtsK has extensive sequence identity with a family of proteins from a wide variety of prokaryotes and plasmids. The plasmid proteins are required for intercellular DNA transfer, and one of the bacterial proteins (the SpoIIIE protein of Bacillus subtilis) has also been implicated in intracellular chromosomal DNA transfer. PMID:7592387

  3. Polarized Cells, Polarized Views: Asymmetric Cell Division in Hematopoietic Cells

    PubMed Central

    Pham, Kim; Sacirbegovic, Faruk; Russell, Sarah M.

    2014-01-01

    It has long been recognized that alterations in cell shape and polarity play important roles in coordinating lymphocyte functions. In the last decade, a new aspect of lymphocyte polarity has attracted much attention, termed asymmetric cell division (ACD). ACD has previously been shown to dictate or influence many aspects of development in model organisms such as the worm and the fly, and to be disrupted in disease. Recent observations that ACD also occurs in lymphocytes led to exciting speculations that ACD might influence lymphocyte differentiation and function, and leukemia. Dissecting the role that ACD might play in these activities has not been straightforward, and the evidence to date for a functional role in lymphocyte fate determination has been controversial. In this review, we discuss the evidence to date for ACD in lymphocytes, and how it might influence lymphocyte fate. We also discuss current gaps in our knowledge, and suggest approaches to definitively test the physiological role of ACD in lymphocytes. PMID:24550912

  4. Kinetochore-microtubule interactions during cell division.

    PubMed

    Maiato, Helder; Sunkel, Claudio E

    2004-01-01

    Proper segregation of chromosomes during cell division is essential for the maintenance of genetic stability. During this process chromosomes must establish stable functional interactions with microtubules through the kinetochore, a specialized protein structure located on the surface of the centromeric heterochromatin. Stable attachment of kinetochores to a number of microtubules results in the formation of a kinetochore fibre that mediates chromosome movement. How the kinetochore fibre is formed and how chromosome motion is produced and regulated remain major questions in cell biology. Here we look at some of the history of research devoted to the study of kinetochore-microtubule interaction and attempt to identify significant advances in the knowledge of the basic processes. Ultrastructural work has provided substantial insights into the structure of the kinetochore and associated microtubules during different stages of mitosis. Also, recent in-vivo studies have probed deep into the dynamics of kinetochore-attached microtubules suggesting possible models for the way in which kinetochores harness the capacity of microtubules to do work and turn it into chromosome motion. Much of the research in recent years suggests that indeed multiple mechanisms are involved in both formation of the k-fibre and chromosome motion. Thus, rather than moving to a unified theory, it has become apparent that most cell types have the capacity to build the spindle using multiple and probably redundant mechanisms.

  5. Bacterial cell division: the mechanism and its precison.

    PubMed

    Harry, Elizabeth; Monahan, Leigh; Thompson, Lyndal

    2006-01-01

    The recent development of cell biology techniques for bacteria to allow visualization of fundamental processes in time and space, and their use in synchronous populations of cells, has resulted in a dramatic increase in our understanding of cell division and its regulation in these tiny cells. The first stage of cell division is the formation of a Z ring, composed of a polymerized tubulin-like protein, FtsZ, at the division site precisely at midcell. Several membrane-associated division proteins are then recruited to this ring to form a complex, the divisome, which causes invagination of the cell envelope layers to form a division septum. The Z ring marks the future division site, and the timing of assembly and positioning of this structure are important in determining where and when division will take place in the cell. Z ring assembly is controlled by many factors including negative regulatory mechanisms such as Min and nucleoid occlusion that influence Z ring positioning and FtsZ accessory proteins that bind to FtsZ directly and modulate its polymerization behavior. The replication status of the cell also influences the positioning of the Z ring, which may allow the tight coordination between DNA replication and cell division required to produce two identical newborn cells.

  6. Mechanical stretch triggers rapid epithelial cell division through Piezo1.

    PubMed

    Gudipaty, S A; Lindblom, J; Loftus, P D; Redd, M J; Edes, K; Davey, C F; Krishnegowda, V; Rosenblatt, J

    2017-03-02

    Despite acting as a barrier for the organs they encase, epithelial cells turn over at some of the fastest rates in the body. However, epithelial cell division must be tightly linked to cell death to preserve barrier function and prevent tumour formation. How does the number of dying cells match those dividing to maintain constant numbers? When epithelial cells become too crowded, they activate the stretch-activated channel Piezo1 to trigger extrusion of cells that later die. However, it is unclear how epithelial cell division is controlled to balance cell death at the steady state. Here we show that mammalian epithelial cell division occurs in regions of low cell density where cells are stretched. By experimentally stretching epithelia, we find that mechanical stretch itself rapidly stimulates cell division through activation of the Piezo1 channel. To stimulate cell division, stretch triggers cells that are paused in early G2 phase to activate calcium-dependent phosphorylation of ERK1/2, thereby activating the cyclin B transcription that is necessary to drive cells into mitosis. Although both epithelial cell division and cell extrusion require Piezo1 at the steady state, the type of mechanical force controls the outcome: stretch induces cell division, whereas crowding induces extrusion. How Piezo1-dependent calcium transients activate two opposing processes may depend on where and how Piezo1 is activated, as it accumulates in different subcellular sites with increasing cell density. In sparse epithelial regions in which cells divide, Piezo1 localizes to the plasma membrane and cytoplasm, whereas in dense regions in which cells extrude, it forms large cytoplasmic aggregates. Because Piezo1 senses both mechanical crowding and stretch, it may act as a homeostatic sensor to control epithelial cell numbers, triggering extrusion and apoptosis in crowded regions and cell division in sparse regions.

  7. Mitochondrial inheritance is mediated by microtubules in mammalian cell division.

    PubMed

    Lawrence, Elizabeth; Mandato, Craig

    2013-11-01

    The mitochondrial network fragments and becomes uniformly dispersed within the cytoplasm when mammalian cells enter mitosis. Such morphology and distribution of mitochondria was previously thought to facilitate the stochastic inheritance of mitochondria by daughter cells. In contrast, we recently reported that mitochondria in dividing mammalian cells are inherited by an ordered mechanism of inheritance mediated by microtubules. We showed that mitochondria are progressively enriched at the cell equator and depleted at the poles throughout division. Furthermore, the mitochondrial distribution during division is dependent on microtubules, indicating an ordered inheritance strategy. The microtubule-mediated positioning of mitochondria in dividing mammalian cells may have functional consequences for cell division and/or mitochondrial inheritance.

  8. Arginine methylation regulates antibody responses through modulating cell division and isotype switching in B cells.

    PubMed

    Hata, Kikumi; Mizuguchi, Junichiro

    2013-03-01

    Protein arginine methylation plays crucial roles, including signal transduction, transcriptional control, cell proliferation and/or differentiation. B cells undergo clonal division, isotype switching and differentiate into antibody forming cells following stimulation with Toll-like receptor-ligand, lipopolysaccharide (LPS) and T cell-derived signals, including CD40-ligand (CD40-L) and interleukin 4 (IL-4). Whether protein arginine methylation affects B cell division and/or isotype switching to IgG1 in response to LPS, IL-4, and CD40-L was examined using the arginine methyl transferase inhibitor adenosine-2',3'-dialdehyde (AdOx). Addition of AdOx substantially reduced the number of division cycles of stimulated B cells, whereas cell viability remained intact. Upon stimulation with LPS/IL-4/CD40-L, the proportion of surface IgG1 positive cells in each division cycle was slightly diminished by AdOx. However, the degree of expression of γ1 germ line transcript and activation-induced cytidine deaminase (AID) in response to LPS/IL-4/CD40-L were unaffected by addition of AdOx, suggesting that AdOx influences class switch recombination independent of AID expression through transcriptional control. Taken together, arginine methylation appears to be involved in B cell isotype switching, as well as in clonal expansion of B cells in response to LPS/IL-4/CD40-L.

  9. ASYMMETRIC CELL DIVISION: IMPLICATIONS FOR GLIOMA DEVELOPMENT AND TREATMENT.

    PubMed

    Lewis, Kate Marie; Petritsch, Claudia

    2013-12-01

    Glioma is a heterogeneous disease process with differential histology and treatment response. It was previously thought that the histological features of glial tumors indicated their cell of origin. However, the discovery of continuous neuro-gliogenesis in the normal adult brain and the identification of brain tumor stem cells within glioma have led to the hypothesis that these brain tumors originate from multipotent neural stem or progenitor cells, which primarily divide asymmetrically during the postnatal period. Asymmetric cell division allows these cell types to concurrently self-renew whilst also producing cells for the differentiation pathway. It has recently been shown that increased symmetrical cell division, favoring the self-renewal pathway, leads to oligodendroglioma formation from oligodendrocyte progenitor cells. In contrast, there is some evidence that asymmetric cell division maintenance in tumor stem-like cells within astrocytoma may lead to acquisition of treatment resistance. Therefore cell division mode in normal brain stem and progenitor cells may play a role in setting tumorigenic potential and the type of tumor formed. Moreover, heterogeneous tumor cell populations and their respective cell division mode may confer differential sensitivity to therapy. This review aims to shed light on the controllers of cell division mode which may be therapeutically targeted to prevent glioma formation and improve treatment response.

  10. Are There Really Animals Like That? No Cell Division.

    ERIC Educational Resources Information Center

    Blackwelder, R. E.; Garoian, G. S.

    1984-01-01

    Provides examples of animals in which growth occurs without cell division. Indicates that this phenomenon (called cell constancy or eutely) is an oddity of development that has arisen independently in several animal groups. (JN)

  11. Epithelial cell division in the Xenopus laevis embryo during gastrulation.

    PubMed

    Hatte, Guillaume; Tramier, Marc; Prigent, Claude; Tassan, Jean-Pierre

    2014-01-01

    How vertebrate epithelial cells divide in vivo and how the cellular environment influences cell division is currently poorly understood. A sine qua non condition to study cell division in situ is the ease of observation of cell division. This is fulfilled in the Xenopus embryo at the gastrula stage where polarized epithelial cells divide with a high frequency at the surface of the organism. Recently, using this model system, we have shown that epithelial cells divide by asymmetric furrowing and that the mode of cell division is regulated during development. Here, we further characterize epithelial cell division in situ. To this end, we used confocal microscopy to study epithelial cell division in the ectoderm of the Xenopus laevis gastrula. Cell division was followed either by indirect immunofluorescence in fixed embryos or by live imaging of embryos transiently expressing diverse fluorescent proteins. Here, we show that during cytokinesis, the plasma membranes of the two daughter cells are usually separated by a gap. For most divisions, daughter cells make contacts basally at a distance from the furrow tip which creates an inverted teardrop-like shaped volume tightly associated with the furrow. At the end of cytokinesis, the inverted teardrop is resorbed; thus it is a transient structure. Several proteins involved in cytokinesis are localized at the tip of the inverted teardrop suggesting that the formation of the gap could be an active process. We also show that intercalation of neighboring cells between daughter cells occasionally occurs during cytokinesis. Our results reveal an additional level of complexity in the relationship between dividing cells and also with their neighboring cells during cytokinesis in the Xenopus embryo epithelium.

  12. Cyclic AMP and cell division in Escherichia coli.

    PubMed Central

    D'Ari, R; Jaffé, A; Bouloc, P; Robin, A

    1988-01-01

    We examined several aspects of cell division regulation in Escherichia coli which have been thought to be controlled by cyclic AMP (cAMP) and its receptor protein (CAP). Mutants lacking adenyl cyclase (cya) or CAP (crp) were rod shaped, not spherical, during exponential growth in LB broth or glucose-Casamino Acids medium, and lateral wall elongation was normal; in broth, stationary-phase cells became ovoid. Cell mass was smaller for the mutants than for the wild type, but it remained appropriate for their slower growth rate and thus probably does not reflect early (uncontrolled) septation. The slow growth did not seem to reflect a gross metabolic disorder, since the mutants gave a normal yield on limiting glucose; surprisingly, however, the cya mutant (unlike crp) was unable to grow anaerobically on glucose, suggesting a role for cAMP (but not for CAP) in the expression of some fermentation enzyme. Both cya and crp mutants are known to be resistant to mecillinam, an antibiotic which inhibits penicillin-binding protein 2 (involved in lateral wall elongation) and also affects septation. This resistance does not reflect a lack of PBP2. Furthermore, it was not simply the result of slow growth and small cell mass, since small wild-type cells growing in acetate remained sensitive. The cAMP-CAP complex may regulate the synthesis of some link between PBP2 and the septation apparatus. The ftsZ gene, coding for a cell division protein, was expressed at a higher level in the absence of cAMP, as measured with an ftsZ::lacZ fusion, but the amount of protein per cell, shown by others to be invariable over a 10-fold range of cell mass, was independent of cAMP, suggesting that ftsZ expression is not regulated by the cAMP-CAP complex. Images PMID:2826407

  13. Cell Fate Decision Making through Oriented Cell Division

    PubMed Central

    Johnston, Christopher A.

    2016-01-01

    The ability to dictate cell fate decisions is critical during animal development. Moreover, faithful execution of this process ensures proper tissue homeostasis throughout adulthood, whereas defects in the molecular machinery involved may contribute to disease. Evolutionarily conserved protein complexes control cell fate decisions across diverse tissues. Maintaining proper daughter cell inheritance patterns of these determinants during mitosis is therefore a fundamental step of the cell fate decision-making process. In this review, we will discuss two key aspects of this fate determinant segregation activity, cortical cell polarity and mitotic spindle orientation, and how they operate together to produce oriented cell divisions that ultimately influence daughter cell fate. Our focus will be directed at the principal underlying molecular mechanisms and the specific cell fate decisions they have been shown to control. PMID:26844213

  14. Cell division ring, a new cell division protein and vertical inheritance of a bacterial organelle in anammox planctomycetes.

    PubMed

    van Niftrik, Laura; Geerts, Willie J C; van Donselaar, Elly G; Humbel, Bruno M; Webb, Richard I; Harhangi, Harry R; Camp, Huub J M Op den; Fuerst, John A; Verkleij, Arie J; Jetten, Mike S M; Strous, Marc

    2009-09-01

    Anammox bacteria are members of the phylum Planctomycetes that oxidize ammonium anaerobically and produce a significant part of the atmosphere's dinitrogen gas. They contain a unique bacterial organelle, the anammoxosome, which is the locus of anammox catabolism. While studying anammox cell and anammoxosome division with transmission electron microscopy including electron tomography, we observed a cell division ring in the outermost compartment of dividing anammox cells. In most Bacteria, GTP hydrolysis drives the tubulin-analogue FtsZ to assemble into a ring-like structure at the cell division site where it functions as a scaffold for the molecular machinery that performs cell division. However, the genome of the anammox bacterium 'Candidatus Kuenenia stuttgartiensis' does not encode ftsZ. Genomic analysis of open reading frames with potential GTPase activity indicated a possible novel cell division ring gene: kustd1438, which was unrelated to ftsZ. Immunogold localization specifically localized kustd1438 to the cell division ring. Genomic analyses of other members of the phyla Planctomycetes and Chlamydiae revealed no putative functional homologues of kustd1438, suggesting that it is specific to anammox bacteria. Electron tomography also revealed that the bacterial organelle was elongated along with the rest of the cell and divided equally among daughter cells during the cell division process.

  15. [Regulation of the Z ring positioning in bacterial cell division--a review].

    PubMed

    Sang, Yu; Tao, Jing; Yao, Yufeng

    2013-04-04

    The regulatory mechanism of bacterial cell division has long been a research focus. Forming a septum at the middle of the cell, the seemingly simple process is involved by multiple regulation factors. Zring (FtsZ ring) is the skeleton of the splitting complex. The locus where Z ring is formed is not only the position the septum formed but also determines the cell division site. Formation of Zring in the incorrect location results in inequality cell division. Several cell division regulation systems have been identified, including the Min system, nucleoid occlusion and the MipZ protein which effectively prevent Zring assembly by different mechanisms, ensuring formation of the fission complex at the correct position. Recent progresses about the formation process of Zring and regulation mechanism affecting the Z-ring positioning are summarized.

  16. Streptomyces: a screening tool for bacterial cell division inhibitors.

    PubMed

    Jani, Charul; Tocheva, Elitza I; McAuley, Scott; Craney, Arryn; Jensen, Grant J; Nodwell, Justin

    2015-02-01

    Cell division is essential for spore formation but not for viability in the filamentous streptomycetes bacteria. Failure to complete cell division instead blocks spore formation, a phenotype that can be visualized by the absence of gray (in Streptomyces coelicolor) and green (in Streptomyces venezuelae) spore-associated pigmentation. Despite the lack of essentiality, the streptomycetes divisome is similar to that of other prokaryotes. Therefore, the chemical inhibitors of sporulation in model streptomycetes may interfere with the cell division in rod-shaped bacteria as well. To test this, we investigated 196 compounds that inhibit sporulation in S. coelicolor. We show that 19 of these compounds cause filamentous growth in Bacillus subtilis, consistent with impaired cell division. One of the compounds is a DNA-damaging agent and inhibits cell division by activating the SOS response. The remaining 18 act independently of known stress responses and may therefore act on the divisome or on divisome positioning and stability. Three of the compounds (Fil-1, Fil-2, and Fil-3) confer distinct cell division defects on B. subtilis. They also block B. subtilis sporulation, which is mechanistically unrelated to the sporulation pathway of streptomycetes but is also dependent on the divisome. We discuss ways in which these differing phenotypes can be used in screens for cell division inhibitors.

  17. Towards a Minimal System for Cell Division

    NASA Astrophysics Data System (ADS)

    Schwille, Petra

    We have entered the "omics" era of the life sciences, meaning that our general knowledge about biological systems has become vast, complex, and almost impossible to fully comprehend. Consequently, the challenge for quantitative biology and biophysics is to identify appropriate procedures and protocols that allow the researcher to strip down the complexity of a biological system to a level that can be reliably modeled but still retains the essential features of its "real" counterpart. The virtue of physics has always been the reductionist approach, which allowed scientists to identify the underlying basic principles of seemingly complex phenomena, and subject them to rigorous mathematical treatment. Biological systems are obviously among the most complex phenomena we can think of, and it is fair to state that our rapidly increasing knowledge does not make it easier to identify a small set of fundamental principles of the big concept of "life" that can be defined and quantitatively understood. Nevertheless, it is becoming evident that only by tight cooperation and interdisciplinary exchange between the life sciences and quantitative sciences, and by applying intelligent reductionist approaches also to biology, will we be able to meet the intellectual challenges of the twenty-first century. These include not only the collection and proper categorization of the data, but also their true understanding and harnessing such that we can solve important practical problems imposed by medicine or the worldwide need for new energy sources. Many of these approaches are reflected by the modern buzz word "synthetic biology", therefore I briefly discuss this term in the first section. Further, I outline some endeavors of our and other groups to model minimal biological systems, with particular focus on the possibility of generating a minimal system for cell division.

  18. Ploidy-Dependent Unreductional Meiotic Cell Division in Polyploid Wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Meiosis includes one round of DNA replication and two successive nuclear divisions, i.e. meiosis I (reductional) and meiosis II (equational). This specialized cell division reduces chromosomes in half and generates haploid gametes in sexual reproduction of eukaryotes. It ensures faithful transmiss...

  19. WNT/β-catenin directs self-renewal symmetric cell division of hTERThigh prostate cancer stem cells.

    PubMed

    Zhang, Kai; Guo, Yanjing; Wang, Xue; Zhao, Huifang; Ji, Zhongzhong; Cheng, Chaping; Li, Li; Fang, Yuxiang; Xu, Dawei; Zhu, Helen He; Gao, Wei-Qiang

    2017-02-16

    Cancer stem-like cells (CSC) drive cancer progression and recurrence. Self-renewal expansion of CSC is achieved through symmetric cell division, yet how external stimuli affect intracellular regulatory programs of CSC division modes and stemness remains obscure. Here we report that hTERThigh prostate cancer (PCa) cells exhibit CSC properties, including a stem cell-associated gene expression signature, long term tumor-propagating capacity and epithelial-to-mensenchymal transition (EMT). In promoting the self-renewal symmetric division of hTERThigh PCa cells, WNT3a dramatically decreased the ratio of hTERThigh PCa cells undergoing asymmetric division. Increased WNT/β-catenin signal activation was detected also in hTERThigh PCa cells. hTERT-mediated CSC properties were at least partially dependent on β-catenin. These findings provide novel cellular and molecular mechanisms for the self-renewal of CSC orchestrated by tumor microenvironmental stimuli and CSC intracellular signals.

  20. Protein segregation between dividing hematopoietic progenitor cells in the determination of the symmetry/asymmetry of cell division.

    PubMed

    Nteliopoulos, Georgios; Gordon, Myrtle Y

    2012-09-20

    In the present study, we investigated how the symmetry/asymmetry of cell division in mitotic CD34(+) cells can be evaluated by determining the plane of cell division and the potential distribution of proteins between daughter cells. The orientation of the mitotic spindle is dependent upon the positioning of the centrosomes, which determine the plane of cell division and the sharing of proteins. If the functions of unequally shared proteins are relevant to the kinetics of cell division, they could determine whether the daughter cells undergo self-renewal or differentiation. The kinetic function of the proteins of interest was investigated using a colony-replating assay and carboxyfluorescein succinimidyl ester (CFSE) staining. We used Notch/Numb as a model system, since they have a role in balancing symmetric/asymmetric divisions. Mitotic cells were examined microscopically and centrosomal markers γ-tubulin/pericentrin were used with activated Notch-1 and Numb. We monitored the first crucial divisions by CFSE staining and found an inverse relationship between activated Notch and Numb expression, suggesting a reciprocal regulation. We suggest that the subpopulations expressing activated Notch or Numb have different cell fates. To determine the influence of Notch signaling on progenitor cell self-renewal, we used the γ-secretase inhibitor N-[N-(3,5-Difluorophenacetyl-L-alanyl)]-S-phenylglycine t-Butyl ester (DAPT). DAPT influences self-renewal/differentiation outcome by affecting the frequency of symmetric renewal divisions without affecting the rate of divisions. Overall, the purpose of this study was to establish a cellular system for predicting the symmetry/asymmetry of hematopoietic progenitor divisions at the level of centrosomes and protein distribution and to investigate the influence of these proteins on progenitor cell kinetics.

  1. Analysis of cell differentiation by division tracking cytometry.

    PubMed

    Ko, Kap-Hyoun; Odell, Ross; Nordon, Robert E

    2007-10-01

    We propose a quantitative method to characterize growth and differentiation dynamics of multipotent cells from time series carboxyfluorescein diacetate, succinimidyl ester (CFDA-SE) division tracking data. The dynamics of cell proliferation and differentiation was measured by combining (CFDA-SE) division tracking with phenotypic analysis. We define division tracking population statistics such as precursor cell frequency, generation time and renewal rate that characterize growth of various phenotypes in a heterogeneous culture system. This method is illustrated by study of the divisional recruitment of cord blood CD34(+) cells by hematopoietic growth factors. The technical issue of assigning the correct generation number to cells was addressed by employing high-resolution division tracking methodology and daily histogram analysis. We also quantified division-tracking artifacts such as CFDA-SE degeneration and cellular auto-fluorescence. Mitotic activation of cord blood CD34(+) cells by cytokines commenced after 2 days of cytokine stimulation. Mean generation number increased linearly thereafter, and it was conclusively shown that CD34(+) cells cycle slower than CD34(-) cells. Generation times for CD34(+) and CD34(-) cells were 24.7 +/- 0.8 h and 15.1 +/- 0.9 h (+/-SD, n = 5), respectively. The 20-fold increase in CD34(+) cell numbers at Day 6 could be attributed to a high CD34(+) cell renewal rate (91% +/- 2% per division). Although cultures were initiated with highly purified CD34(+) cells (approximately 96%), CD34(-) numbers had expanded rapidly by Day 6. This rapid expansion could be explained by their short generation time as well as a small fraction of CD34(+) cells (approximately 5%) that differentiated into CD34(-) cells. Multitype division tracking provides a detailed analysis of multipotent cell differentiation dynamics.

  2. Entrainment of cell division in phytoplankton with dynamic energy budgets

    NASA Astrophysics Data System (ADS)

    Muller, Erik B.; Ananthasubramaniam, Bharath; Klanjšček, Tin; Nisbet, Roger M.

    2011-11-01

    We explore the entrainment behavior of cell division in phytoplankton in the context of Dynamic Energy Budget (DEB) theory. In particular, we explore the range of DEB and environmental parameter values within which a cell divides at regular intervals in a periodic light environment with abundant nutrients and investigate the impact of parameter values on the phase of cell division. We consider three types of cells that differ in the evolution of surface area to volume ratio during the cell cycle: cells with a constant shape (isomorphs), cells with a constant surface area (V0-morphs) and cells with a constant surface area to volume ratio (V1-morphs), the latter being the default choice in studies on the population dynamics of unicellular organisms because of its desirable mathematical implications. Only in isomorphs and V0-morphs, however, cell division can be entrained to a periodic light. Regular cell division in V1 is purely coincidental, as it depends on exact choices for parameter values. We attribute this to the fact that V1-morphs lack the negative feedback of size on the dynamics of reserves in V0-morphs and isomorphs. Because entrained isomorphs and V0-morphs divide during the dark hours in our simulations, these two shapes can represent the division behavior of phytoplankton species that complete the cell cycle during the night, such as dinoflagellates and coccolithophores. A description of the division behavior of species completing the cell cycle during the day, such as silicon dependent diatoms and cyanobacteria, requires a more complex model than used in this paper. Furthermore, we explore the robustness of our findings by randomizing model parameters and introducing unevenness in biomass separation between daughter cells during cell division. We conclude that especially the entrainment in V0-morphs is relatively insensitive to perturbations.

  3. Mutations in the Borrelia burgdorferi Flagellar Type III Secretion System Genes fliH and fliI Profoundly Affect Spirochete Flagellar Assembly, Morphology, Motility, Structure, and Cell Division

    PubMed Central

    Gao, Lihui; Zhao, Xiaowei; Liu, Jun; Norris, Steven J.

    2015-01-01

    ABSTRACT The Lyme disease spirochete Borrelia burgdorferi migrates to distant sites in the tick vectors and mammalian hosts through robust motility and chemotaxis activities. FliH and FliI are two cytoplasmic proteins that play important roles in the type III secretion system (T3SS)-mediated export and assembly of flagellar structural proteins. However, detailed analyses of the roles of FliH and FliI in B. burgdorferi have not been reported. In this study, fliH and fliI transposon mutants were utilized to dissect the mechanism of the Borrelia type III secretion system. The fliH and fliI mutants exhibited rod-shaped or string-like morphology, greatly reduced motility, division defects (resulting in elongated organisms with incomplete division points), and noninfectivity in mice by needle inoculation. Mutants in fliH and fliI were incapable of translational motion in 1% methylcellulose or soft agar. Inactivation of either fliH or fliI resulted in the loss of the FliH-FliI complex from otherwise intact flagellar motors, as determined by cryo-electron tomography (cryo-ET). Flagellar assemblies were still present in the mutant cells, albeit in lower numbers than in wild-type cells and with truncated flagella. Genetic complementation of fliH and fliI mutants in trans restored their wild-type morphology, motility, and flagellar motor structure; however, full-length flagella and infectivity were not recovered in these complemented mutants. Based on these results, disruption of either fliH or fliI in B. burgdorferi results in a severe defect in flagellar structure and function and cell division but does not completely block the export and assembly of flagellar hook and filament proteins. PMID:25968649

  4. Repair of radiation-induced damage to the cell division mechanism of Escherichia coli.

    PubMed

    Adler, H I; Fisher, W D; Hardigree, A A; Stapleton, G E

    1966-02-01

    Adler, Howard I. (Oak Ridge National Laboratory, Oak Ridge, Tenn.), William D. Fisher, Alice A. Hardigree, and George E. Stapleton. Repair of radiation-induced damage to the cell division mechanism of Escherichia coli. J. Bacteriol. 91:737-742. 1966.-Microscopic observations of irradiated populations of filamentous Escherichia coli cells indicated that filaments can be induced to divide by a substance donated by neighboring cells. We have made this observation the basis for a quantitative technique in which filaments are incubated in the presence of nongrowing donor cells. The presence of "donor" organisms promotes division and subsequent colony formation in filaments. "Donor" bacteria do not affect nonfilamentous cells. An extract of "donor" cells retains the division-promoting activity. The extract has been partially fractionated, and consists of a heat-stable and a heat-labile component. The heat-stable component is inactive in promoting cell division, but enhances the activity of the heat-labile component. The division-promoting system is discussed as a radiation repair mechanism and as a normal component of the cell division system in E. coli.

  5. Oriented cell division shapes carnivorous pitcher leaves of Sarracenia purpurea.

    PubMed

    Fukushima, Kenji; Fujita, Hironori; Yamaguchi, Takahiro; Kawaguchi, Masayoshi; Tsukaya, Hirokazu; Hasebe, Mitsuyasu

    2015-03-16

    Complex morphology is an evolutionary outcome of phenotypic diversification. In some carnivorous plants, the ancestral planar leaf has been modified to form a pitcher shape. However, how leaf development was altered during evolution remains unknown. Here we show that the pitcher leaves of Sarracenia purpurea develop through cell division patterns of adaxial tissues that are distinct from those in bifacial and peltate leaves, subsequent to standard expression of adaxial and abaxial marker genes. Differences in the orientation of cell divisions in the adaxial domain cause bifacial growth in the distal region and adaxial ridge protrusion in the middle region. These different growth patterns establish pitcher morphology. A computer simulation suggests that the cell division plane is critical for the pitcher morphogenesis. Our results imply that tissue-specific changes in the orientation of cell division underlie the development of a morphologically complex leaf.

  6. Oriented cell division shapes carnivorous pitcher leaves of Sarracenia purpurea

    PubMed Central

    Fukushima, Kenji; Fujita, Hironori; Yamaguchi, Takahiro; Kawaguchi, Masayoshi; Tsukaya, Hirokazu; Hasebe, Mitsuyasu

    2015-01-01

    Complex morphology is an evolutionary outcome of phenotypic diversification. In some carnivorous plants, the ancestral planar leaf has been modified to form a pitcher shape. However, how leaf development was altered during evolution remains unknown. Here we show that the pitcher leaves of Sarracenia purpurea develop through cell division patterns of adaxial tissues that are distinct from those in bifacial and peltate leaves, subsequent to standard expression of adaxial and abaxial marker genes. Differences in the orientation of cell divisions in the adaxial domain cause bifacial growth in the distal region and adaxial ridge protrusion in the middle region. These different growth patterns establish pitcher morphology. A computer simulation suggests that the cell division plane is critical for the pitcher morphogenesis. Our results imply that tissue-specific changes in the orientation of cell division underlie the development of a morphologically complex leaf. PMID:25774486

  7. Synchronization of chromosome dynamics and cell division in bacteria.

    PubMed

    Thanbichler, Martin

    2010-01-01

    Bacterial cells have evolved a variety of regulatory circuits that tightly synchronize their chromosome replication and cell division cycles, thereby ensuring faithful transmission of genetic information to their offspring. Complex multicomponent signaling cascades are used to monitor the progress of cytokinesis and couple replication initiation to the separation of the two daughter cells. Moreover, the cell-division apparatus actively participates in chromosome partitioning and, particularly, in the resolution of topological problems that impede the segregation process, thus coordinating chromosome dynamics with cell constriction. Finally, bacteria have developed mechanisms that harness the cell-cycle-dependent positioning of individual chromosomal loci or the nucleoid to define the cell-division site and control the timing of divisome assembly. Each of these systems manages to integrate a complex set of spatial and temporal cues to regulate and execute critical steps in the bacterial cell cycle.

  8. Fluidization of tissues by cell division and apoptosis.

    PubMed

    Ranft, Jonas; Basan, Markus; Elgeti, Jens; Joanny, Jean-François; Prost, Jacques; Jülicher, Frank

    2010-12-07

    During the formation of tissues, cells organize collectively by cell division and apoptosis. The multicellular dynamics of such systems is influenced by mechanical conditions and can give rise to cell rearrangements and movements. We develop a continuum description of tissue dynamics, which describes the stress distribution and the cell flow field on large scales. In the absence of division and apoptosis, we consider the tissue to behave as an elastic solid. Cell division and apoptosis introduce stress sources that, in general, are anisotropic. By combining cell number balance with dynamic equations for the stress source, we show that the tissue effectively behaves as a viscoelastic fluid with a relaxation time set by the rates of division and apoptosis. If the system is confined in a fixed volume, it reaches a homeostatic state in which division and apoptosis balance. In this state, cells undergo a diffusive random motion driven by the stochasticity of division and apoptosis. We calculate the expression for the effective diffusion coefficient as a function of the tissue parameters and compare our results concerning both diffusion and viscosity to simulations of multicellular systems using dissipative particle dynamics.

  9. The involvement of phospholipases C and D in the asymmetric division of subsidiary cell mother cells of Zea mays.

    PubMed

    Apostolakos, Panagiotis; Panteris, Emmanuel; Galatis, Basil

    2008-11-01

    In the present study, the involvement of phospholipase C and D (PLC and PLD) pathways in the asymmetric divisions that produce the stomatal complexes of Zea mays was investigated. In particular, the polar organization of microtubules (MTs) and actin filaments (AFs) and the process of asymmetric division were studied in subsidiary cell mother cells (SMCs) treated with PLC and PLD modulators. In SMCs treated with butanol-1 (but-1), which blocks phosphatidic acid (PA) production via PLDs, AF-patch formation laterally to the inducing guard cell mother cell (GMC) and the subsequent asymmetric division were inhibited. In these SMCs, cell division plane determination, as expressed by MT preprophase band (MT-PPB) formation, was not disturbed. Exogenously applied PA partially relieved the but-1 effects on SMCs. In contrast to SMCs, but-1 did not affect the symmetric GMC division. Inhibition of the PLC catalytic activity by neomycin or U73122 resulted in inhibition of asymmetric SMC division, while AF-patch and MT-PPB were organized as in control SMCs. These data show that the PLC and PLD signaling pathways are involved in the transduction and/or perception of the inductive stimulus that is emitted by the GMCs and induces the polar AF organization and asymmetric SMC division. In contrast, division plane determination in SMCs, as expressed by MT-PPB formation, does not depend on PLC and PLD signaling pathways.

  10. Asymmetric cell division in polyploid giant cancer cells and low eukaryotic cells.

    PubMed

    Zhang, Dan; Wang, Yijia; Zhang, Shiwu

    2014-01-01

    Asymmetric cell division is critical for generating cell diversity in low eukaryotic organisms. We previously have reported that polyploid giant cancer cells (PGCCs) induced by cobalt chloride demonstrate the ability to use an evolutionarily conserved process for renewal and fast reproduction, which is normally confined to simpler organisms. The budding yeast, Saccharomyces cerevisiae, which reproduces by asymmetric cell division, has long been a model for asymmetric cell division studies. PGCCs produce daughter cells asymmetrically in a manner similar to yeast, in that both use budding for cell polarization and cytokinesis. Here, we review the results of recent studies and discuss the similarities in the budding process between yeast and PGCCs.

  11. Towards a bottom-up reconstitution of bacterial cell division.

    PubMed

    Martos, Ariadna; Jiménez, Mercedes; Rivas, Germán; Schwille, Petra

    2012-12-01

    The components of the bacterial division machinery assemble to form a dynamic ring at mid-cell that drives cytokinesis. The nature of most division proteins and their assembly pathway is known. Our knowledge about the biochemical activities and protein interactions of some key division elements, including those responsible for correct ring positioning, has progressed considerably during the past decade. These developments, together with new imaging and membrane reconstitution technologies, have triggered the 'bottom-up' synthetic approach aiming at reconstructing bacterial division in the test tube, which is required to support conclusions derived from cellular and molecular analysis. Here, we describe recent advances in reconstituting Escherichia coli minimal systems able to reproduce essential functions, such as the initial steps of division (proto-ring assembly) and one of the main positioning mechanisms (Min oscillating system), and discuss future perspectives and experimental challenges.

  12. M-cadherin-mediated intercellular interactions activate satellite cell division.

    PubMed

    Marti, Merce; Montserrat, Núria; Pardo, Cristina; Mulero, Lola; Miquel-Serra, Laia; Rodrigues, Alexandre Miguel Cavaco; Andrés Vaquero, José; Kuebler, Bernd; Morera, Cristina; Barrero, María José; Izpisua Belmonte, Juan Carlos

    2013-11-15

    Adult muscle stem cells and their committed myogenic precursors, commonly referred to as the satellite cell population, are involved in both muscle growth after birth and regeneration after damage. It has been previously proposed that, under these circumstances, satellite cells first become activated, divide and differentiate, and only later fuse to the existing myofiber through M-cadherin-mediated intercellular interactions. Our data show that satellite cells fuse with the myofiber concomitantly to cell division, and only when the nuclei of the daughter cells are inside the myofiber, do they complete the process of differentiation. Here we demonstrate that M-cadherin plays an important role in cell-to-cell recognition and fusion, and is crucial for cell division activation. Treatment of satellite cells with M-cadherin in vitro stimulates cell division, whereas addition of anti-M-cadherin antibodies reduces the cell division rate. Our results suggest an alternative model for the contribution of satellite cells to muscle development, which might be useful in understanding muscle regeneration, as well as muscle-related dystrophies.

  13. Mitochondrial inheritance is mediated by microtubules in mammalian cell division

    PubMed Central

    Lawrence, Elizabeth; Mandato, Craig

    2013-01-01

    The mitochondrial network fragments and becomes uniformly dispersed within the cytoplasm when mammalian cells enter mitosis. Such morphology and distribution of mitochondria was previously thought to facilitate the stochastic inheritance of mitochondria by daughter cells. In contrast, we recently reported that mitochondria in dividing mammalian cells are inherited by an ordered mechanism of inheritance mediated by microtubules. We showed that mitochondria are progressively enriched at the cell equator and depleted at the poles throughout division. Furthermore, the mitochondrial distribution during division is dependent on microtubules, indicating an ordered inheritance strategy. The microtubule-mediated positioning of mitochondria in dividing mammalian cells may have functional consequences for cell division and/or mitochondrial inheritance. PMID:24567781

  14. A mechanistic stochastic framework for regulating bacterial cell division

    PubMed Central

    Ghusinga, Khem Raj; Vargas-Garcia, Cesar A.; Singh, Abhyudai

    2016-01-01

    How exponentially growing cells maintain size homeostasis is an important fundamental problem. Recent single-cell studies in prokaryotes have uncovered the adder principle, where cells add a fixed size (volume) from birth to division, irrespective of their size at birth. To mechanistically explain the adder principle, we consider a timekeeper protein that begins to get stochastically expressed after cell birth at a rate proportional to the volume. Cell-division time is formulated as the first-passage time for protein copy numbers to hit a fixed threshold. Consistent with data, the model predicts that the noise in division timing increases with size at birth. Intriguingly, our results show that the distribution of the volume added between successive cell-division events is independent of the newborn cell size. This was dramatically seen in experimental studies, where histograms of the added volume corresponding to different newborn sizes collapsed on top of each other. The model provides further insights consistent with experimental observations: the distribution of the added volume when scaled by its mean becomes invariant of the growth rate. In summary, our simple yet elegant model explains key experimental findings and suggests a mechanism for regulating both the mean and fluctuations in cell-division timing for controlling size. PMID:27456660

  15. A mechanistic stochastic framework for regulating bacterial cell division.

    PubMed

    Ghusinga, Khem Raj; Vargas-Garcia, Cesar A; Singh, Abhyudai

    2016-07-26

    How exponentially growing cells maintain size homeostasis is an important fundamental problem. Recent single-cell studies in prokaryotes have uncovered the adder principle, where cells add a fixed size (volume) from birth to division, irrespective of their size at birth. To mechanistically explain the adder principle, we consider a timekeeper protein that begins to get stochastically expressed after cell birth at a rate proportional to the volume. Cell-division time is formulated as the first-passage time for protein copy numbers to hit a fixed threshold. Consistent with data, the model predicts that the noise in division timing increases with size at birth. Intriguingly, our results show that the distribution of the volume added between successive cell-division events is independent of the newborn cell size. This was dramatically seen in experimental studies, where histograms of the added volume corresponding to different newborn sizes collapsed on top of each other. The model provides further insights consistent with experimental observations: the distribution of the added volume when scaled by its mean becomes invariant of the growth rate. In summary, our simple yet elegant model explains key experimental findings and suggests a mechanism for regulating both the mean and fluctuations in cell-division timing for controlling size.

  16. Instructive simulation of the bacterial cell division cycle.

    PubMed

    Zaritsky, Arieh; Wang, Ping; Vischer, Norbert O E

    2011-07-01

    The coupling between chromosome replication and cell division includes temporal and spatial elements. In bacteria, these have globally been resolved during the last 40 years, but their full details and action mechanisms are still under intensive study. The physiology of growth and the cell cycle are reviewed in the light of an established dogma that has formed a framework for development of new ideas, as exemplified here, using the Cell Cycle Simulation (CCSim) program. CCSim, described here in detail for the first time, employs four parameters related to time (replication, division and inter-division) and size (cell mass at replication initiation) that together are sufficient to describe bacterial cells under various conditions and states, which can be manipulated environmentally and genetically. Testing the predictions of CCSim by analysis of time-lapse micrographs of Escherichia coli during designed manipulations of the rate of DNA replication identified aspects of both coupling elements. Enhanced frequencies of cell division were observed following an interval of reduced DNA replication rate, consistent with the prediction of a minimum possible distance between successive replisomes (an eclipse). As a corollary, the notion that cell poles are not always inert was confirmed by observed placement of division planes at perpendicular planes in monstrous and cuboidal cells containing multiple, segregating nucleoids.

  17. Orientation of endothelial cell division is regulated by VEGF signaling during blood vessel formation

    PubMed Central

    Zeng, Gefei; Taylor, Sarah M.; McColm, Janet R.; Kappas, Nicholas C.; Kearney, Joseph B.; Williams, Lucy H.; Hartnett, Mary E.; Bautch, Victoria L.

    2007-01-01

    New blood vessel formation requires the coordination of endothelial cell division and the morphogenetic movements of vessel expansion, but it is not known how this integration occurs. Here, we show that endothelial cells regulate division orientation during the earliest stages of blood vessel formation, in response to morphogenetic cues. In embryonic stem (ES) cell–derived vessels that do not experience flow, the plane of endothelial cytokinesis was oriented perpendicular to the vessel long axis. We also demonstrated regulated cleavage orientation in vivo, in flow-exposed forming retinal vessels. Daughter nuclei moved away from the cleavage plane after division, suggesting that regulation of endothelial division orientation effectively extends vessel length in these developing vascular beds. A gain-of-function mutation in VEGF signaling increased randomization of endothelial division orientation, and this effect was rescued by a transgene, indicating that regulation of division orientation is a novel mechanism whereby VEGF signaling affects vessel morphogenesis. Thus, our findings show that endothelial cell division and morphogenesis are integrated in developing vessels by flow-independent mechanisms that involve VEGF signaling, and this cross talk is likely to be critical to proper vessel morphogenesis. PMID:17068148

  18. On the chronology and topography of bacterial cell division.

    PubMed

    Vicente, M; Palacios, P; Dopazo, A; Garrido, T; Pla, J; Aldea, M

    1991-01-01

    Gene products that play a role in the formation of cell septum should be expected to be endowed with a set of specific properties. In principle, septal proteins should be located at the cell envelope. The expression of division genes should ensure the synthesis of septal proteins at levels commensurate with the needs of cell division at different rates of cell duplication. We have results indicating that some fts genes located within the 2.5-min cluster in the Escherichia coli chromosome conform to these predictions.

  19. Asymmetric cell division in Mycobacterium tuberculosis and its unique features.

    PubMed

    Vijay, Srinivasan; Nagaraja, Mukkayyan; Sebastian, Jees; Ajitkumar, Parthasarathi

    2014-03-01

    Recently, several reports showed that about 80 % of mid-log phase Mycobacterium smegmatis, Mycobacterium marinum, and Mycobacterium bovis BCG cells divide symmetrically with 5-10 % deviation in the septum position from the median. However, the mode of cell division of the pathogenic mycobacterial species, Mycobacterium tuberculosis, remained unclear. Therefore, in the present study, using electron microscopy, fluorescence microscopy of septum- and nucleoid-stained live and fixed cells, and live cell time-lapse imaging, we show the occurrence of asymmetric cell division with unusually deviated septum/constriction in 20 % of the 15 % septating M. tuberculosis cells in the mid-log phase population. The remaining 80 % of the 15 % septating cells divided symmetrically but with 2-5 % deviation in the septum/constriction position, as reported for M. smegmatis, M. marinum, and M. bovis BCG cells. Both the long and the short portions of the asymmetrically dividing M. tuberculosis cells with unusually deviated septum contained nucleoids, thereby generating viable short and long cells from each asymmetric division. M. tuberculosis short cells were acid fast positive and, like the long cells, further readily underwent growth and division to generate micro-colony, thereby showing that they were neither mini cells, spores nor dormant forms of mycobacteria. The freshly diagnosed pulmonary tuberculosis patients' sputum samples, which are known for the prevalence of oxidative stress conditions, also contained short cells at the same proportion as that in the mid-log phase population. The probable physiological significance of the generation of the short cells through unusually deviated asymmetric cell division is discussed.

  20. Intracellular viscoelasticity of HeLa cells during cell division studied by video particle-tracking microrheology.

    PubMed

    Chen, Yin-Quan; Kuo, Chia-Yu; Wei, Ming-Tzo; Wu, Kelly; Su, Pin-Tzu; Huang, Chien-Shiou; Chiou, Arthur

    2014-01-01

    Cell division plays an important role in regulating cell proliferation and differentiation. It is managed by a complex sequence of cytoskeleton alteration that induces dividing cells to change their morphology to facilitate their division. The change in cytoskeleton structure is expected to affect the intracellular viscoelasticity, which may also contribute to cellular dynamic deformation during cell division. However, the intracellular viscoelasticity during cell division is not yet well understood. In this study, we injected 100-nm (diameter) carboxylated polystyrene beads into the cytoplasm of HeLa cells and applied video particle tracking microrheology to measure their intracellular viscoelasticity at different phases during cell division. The Brownian motion of the intracellular nanoprobes was analyzed to compute the viscoelasticity of HeLa cells in terms of the elastic modulus and viscous modulus as a function of frequency. Our experimental results indicate that during the course of cell division, both intracellular elasticity and viscosity increase in the transition from the metaphase to the anaphase, plausibly due to the remodeling of cytoskeleton and redistributions of molecular motors, but remain approximately the same from the anaphase to the telophase.

  1. Stationary Size Distributions of Growing Cells with Binary and Multiple Cell Division

    NASA Astrophysics Data System (ADS)

    Rading, M. M.; Engel, T. A.; Lipowsky, R.; Valleriani, A.

    2011-10-01

    Populations of unicellular organisms that grow under constant environmental conditions are considered theoretically. The size distribution of these cells is calculated analytically, both for the usual process of binary division, in which one mother cell produces always two daughter cells, and for the more complex process of multiple division, in which one mother cell can produce 2 n daughter cells with n=1,2,3,… . The latter mode of division is inspired by the unicellular algae Chlamydomonas reinhardtii. The uniform response of the whole population to different environmental conditions is encoded in the individual rates of growth and division of the cells. The analytical treatment of the problem is based on size-dependent rules for cell growth and stochastic transition processes for cell division. The comparison between binary and multiple division shows that these different division processes lead to qualitatively different results for the size distribution and the population growth rates.

  2. An Arabidopsis Homolog of the Bacterial Cell Division Inhibitor SulA Is Involved in Plastid DivisionW⃞

    PubMed Central

    Raynaud, Cécile; Cassier-Chauvat, Corinne; Perennes, Claudette; Bergounioux, Catherine

    2004-01-01

    Plastids have evolved from an endosymbiosis between a cyanobacterial symbiont and a eukaryotic host cell. Their division is mediated both by proteins of the host cell and conserved bacterial division proteins. Here, we identified a new component of the plastid division machinery, Arabidopsis thaliana SulA. Disruption of its cyanobacterial homolog (SSulA) in Synechocystis and overexpression of an AtSulA-green fluorescent protein fusion in Arabidopsis demonstrate that these genes are involved in cell and plastid division, respectively. Overexpression of AtSulA inhibits plastid division in planta but rescues plastid division defects caused by overexpression of AtFtsZ1-1 and AtFtsZ2-1, demonstrating that its role in plastid division may involve an interaction with AtFtsZ1-1 and AtFtsZ2-1. PMID:15208387

  3. Mycobacterium tuberculosis CwsA overproduction modulates cell division and cell wall synthesis.

    PubMed

    Plocinski, P; Martinez, L; Sarva, K; Plocinska, R; Madiraju, M; Rajagopalan, M

    2013-12-01

    We recently showed that two small membrane proteins of Mycobacterium tuberculosis, CwsA and CrgA, interact with each other, and that loss of CwsA in M. smegmatis is associated with defects in the cell division and cell wall synthesis processes. Here we show that CwsA overproduction also affected growth, cell division and cell shape of M. smegmatis and M. tuberculosis. CwsA overproduction in M. tuberculosis led to increased sensitivity to cefsulodin, a penicillin-binding protein (PBP) 1A/1B targeting beta (β) -lactam, but was unaffected by other β-lactams and vancomycin. A M. smegmatis cwsA overexpressing strain showed bulgy cells, increased fluorescent vancomycin staining and altered localization of Wag31-mCherry fusion protein. However, the levels of phosphorylated Wag31, important for optimal peptidoglycan synthesis and growth in mycobacteria, were not affected. Interestingly, CwsA overproduction in E. coli led to the formation of large rounded cells that eventually lysed whereas the overproduction of FtsZ along with CwsA reversed this phenotype. Together, our results emphasize that optimal levels of CwsA are required for regulated cell wall synthesis, hence maintenance of cell shape, and that CwsA likely interacts with and modulates the activities of other cell wall synthetic components including PBPs.

  4. Male germline stem cell division and spermatocyte growth require insulin signaling in Drosophila.

    PubMed

    Ueishi, Satoru; Shimizu, Hanako; H Inoue, Yoshihiro

    2009-01-01

    Spermatogenesis in Drosophila commences with cell division of germline stem cells (GSCs) to produce male germline cells at the tip of the testis. However, molecular mechanisms inducing division of male GSCs have not been reported. Insulin-like peptides are known to play an essential role in stimulation of proliferation and growth of somatic cells, and it has recently been reported that such peptides promote cell division in female Drosophila GSCs. However, their effects on male germline cells have not been characterized. We found that inhibition of insulin production and insulin signaling mutations resulted in decreased numbers of germline cells in Drosophila testes. GSC numbers were maintained in young mutant males, with a gradual decrease in abundance of GSCs with age. Furthermore, in mutants, fewer germline cysts originated from GSCs and a lower frequency of GSC division was seen. Insulin signaling was found to promote cell cycle progression of the male GSCs at the G(2)/M phase. The cell volume of spermatocytes increases up to 25 times before initiation of meiosis in Drosophila. We examined whether insulin signaling extrinsically induces the greatest cell growth in Drosophila diploid cells and found that spermatocyte growth was affected in mutants. The results indicate that in addition to its function in somatic cells, insulin signaling plays an essential role in cell proliferation and growth during male Drosophila gametogenesis and that sperm production is regulated by hormonal control via insulin-like peptides.

  5. Constriction and septation during cell division in caulobacters.

    PubMed

    Poindexter, J S; Hagenzieker, J G

    1981-07-01

    Morphogenesis of the division site in caulobacters had been described as constrictive in Caulobacter spp. and septate in Asticcacaulis excentricus. However, subsequent studies of other gram-negative genera had implied that constrictive division was an artefact resulting from inadequate preservation of septa; exploration of alternatives to osmium fixation, particularly with aldehydes, was recommended. In this study, the appearance of sectioned division sites was reinvestigated in caulobacter cells prepared by 20 different procedures varying with respect to fixation agents, media, schedules, and temperatures, to dehydrating agents, and to embedding resins. Three types of division site morphogenesis were observed: constriction in C. bacteroides and C. crescentus, partial septation in C. leidyi, and complete, undivided septation in A. excentricus and A. biprosthecum. The anatomy of the division site depended on the bacterial strain, not on the method of preparation of the cells for sectioning. These studies confirm the earlier observations on osmium-fixed caulobacter cells and lead to the general conclusion that gram-negative bacteria with tapered poles probably divide by constriction, whereas septation results in blunt cell poles. A pattern of spiral, rather than circular, insertion of new envelope subunits at the cell equator is proposed as a basic developmental difference between constrictive and septate fission in gram-negative bacteria. Since caulobacter prosthecae can develop as extensions of tapered poles formed by constriction, whereas subpolar or lateral prosthecae occur in species with blunt poles resulting from septation, the site of formation of a thick septum appears unsuitable as a site of subsequent envelope outgrowth.

  6. Relevant parameters in models of cell division control

    NASA Astrophysics Data System (ADS)

    Grilli, Jacopo; Osella, Matteo; Kennard, Andrew S.; Lagomarsino, Marco Cosentino

    2017-03-01

    A recent burst of dynamic single-cell data makes it possible to characterize the stochastic dynamics of cell division control in bacteria. Different models were used to propose specific mechanisms, but the links between them are poorly explored. The lack of comparative studies makes it difficult to appreciate how well any particular mechanism is supported by the data. Here, we describe a simple and generic framework in which two common formalisms can be used interchangeably: (i) a continuous-time division process described by a hazard function and (ii) a discrete-time equation describing cell size across generations (where the unit of time is a cell cycle). In our framework, this second process is a discrete-time Langevin equation with simple physical analogues. By perturbative expansion around the mean initial size (or interdivision time), we show how this framework describes a wide range of division control mechanisms, including combinations of time and size control, as well as the constant added size mechanism recently found to capture several aspects of the cell division behavior of different bacteria. As we show by analytical estimates and numerical simulations, the available data are described precisely by the first-order approximation of this expansion, i.e., by a "linear response" regime for the correction of size fluctuations. Hence, a single dimensionless parameter defines the strength and action of the division control against cell-to-cell variability (quantified by a single "noise" parameter). However, the same strength of linear response may emerge from several mechanisms, which are distinguished only by higher-order terms in the perturbative expansion. Our analytical estimate of the sample size needed to distinguish between second-order effects shows that this value is close to but larger than the values of the current datasets. These results provide a unified framework for future studies and clarify the relevant parameters at play in the control of

  7. CD8 Memory Cells Develop Unique DNA Repair Mechanisms Favoring Productive Division

    PubMed Central

    Galgano, Alessia; Barinov, Aleksandr; Vasseur, Florence; de Villartay, Jean-Pierre; Rocha, Benedita

    2015-01-01

    Immune responses are efficient because the rare antigen-specific naïve cells are able to proliferate extensively and accumulate upon antigen stimulation. Moreover, differentiation into memory cells actually increases T cell accumulation, indicating improved productive division in secondary immune responses. These properties raise an important paradox: how T cells may survive the DNA lesions necessarily induced during their extensive division without undergoing transformation. We here present the first data addressing the DNA damage responses (DDRs) of CD8 T cells in vivo during exponential expansion in primary and secondary responses in mice. We show that during exponential division CD8 T cells engage unique DDRs, which are not present in other exponentially dividing cells, in T lymphocytes after UV or X irradiation or in non-metastatic tumor cells. While in other cell types a single DDR pathway is affected, all DDR pathways and cell cycle checkpoints are affected in dividing CD8 T cells. All DDR pathways collapse in secondary responses in the absence of CD4 help. CD8 T cells are driven to compulsive suicidal divisions preventing the propagation of DNA lesions. In contrast, in the presence of CD4 help all the DDR pathways are up regulated, resembling those present in metastatic tumors. However, this up regulation is present only during the expansion phase; i.e., their dependence on antigen stimulation prevents CD8 transformation. These results explain how CD8 T cells maintain genome integrity in spite of their extensive division, and highlight the fundamental role of DDRs in the efficiency of CD8 immune responses. PMID:26485718

  8. A novel cell division factor from tobacco 2B-13 cells that induced cell division in auxin-starved tobacco BY-2 cells

    NASA Astrophysics Data System (ADS)

    Shimizu, Takashi; Eguchi, Kentaro; Nishida, Ikuo; Laukens, Kris; Witters, Erwin; van Onckelen, Harry; Nagata, Toshiyuki

    2006-06-01

    Effects of auxin as plant hormones are widespread; in fact in almost all aspects of plant growth and development auxin plays a pivotal role. Although auxin is required for propagating cell division in plant cells, its effect upon cell division is least understood. If auxin is depleted from the culture medium, cultured cells cease to divide. It has been demonstrated in this context that the addition of auxin to auxin-starved nondividing tobacco BY-2 cells induced semisynchronous cell division. On the other hand, there are some cell lines, named habituated cells, that can grow without auxin. The cause and reason for the habituated cells have not been clarified. A habituated cell line named 2B-13 is derived from the tobacco BY-2 cell line, which has been most intensively studied among plant cell lines. When we tried to find the difference between two cell lines of BY-2 and 2B-13 cells, we found that the addition of culture filtrated from the auxin-habituated 2B-13 cells induced semisynchronous cell division in auxin-starved BY-2 cells. The cell division factor (CDF) that is responsible for inducing cell division in auxin-starved BY-2 cells was purified to near-homogeneity by sequential passage through a hydroxyapatite column, a ConA Sepharose column and a Sephadex gel filtration column. The resulting purified fraction appeared as a single band of high molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels by silver staining and was able to induce cell division in auxin-starved BY-2 cells. Identification of the protein by MALD-TOF-MS/MS revealed that it is structurally related to P-glycoprotein from Gossypioides kirkii, which belongs to ATP-binding cassette (ABC)-transporters. The significance of CDF as a possible ABC-transporter is discussed in relationship to auxin-autotrophic growth and auxin-signaling pathway.

  9. Process for control of cell division

    NASA Technical Reports Server (NTRS)

    Cone, C. D., Jr. (Inventor)

    1977-01-01

    A method of controlling mitosis of biological cells was developed, which involved inducing a change in the intracellular ionic hierarchy accompanying the cellular electrical transmembrane potential difference (Esubm) of the cells. The ionic hierarchy may be varied by imposing changes on the relative concentrations of Na(+), K(+) and Cl(-), or by directly imposing changes in the physical Esubm level across the cell surface.

  10. Asymmetric cell division of T cells upon antigen presentation uses multiple conserved mechanisms.

    PubMed

    Oliaro, Jane; Van Ham, Vanessa; Sacirbegovic, Faruk; Pasam, Anupama; Bomzon, Ze'ev; Pham, Kim; Ludford-Menting, Mandy J; Waterhouse, Nigel J; Bots, Michael; Hawkins, Edwin D; Watt, Sally V; Cluse, Leonie A; Clarke, Chris J P; Izon, David J; Chang, John T; Thompson, Natalie; Gu, Min; Johnstone, Ricky W; Smyth, Mark J; Humbert, Patrick O; Reiner, Steven L; Russell, Sarah M

    2010-07-01

    Asymmetric cell division is a potential means by which cell fate choices during an immune response are orchestrated. Defining the molecular mechanisms that underlie asymmetric division of T cells is paramount for determining the role of this process in the generation of effector and memory T cell subsets. In other cell types, asymmetric cell division is regulated by conserved polarity protein complexes that control the localization of cell fate determinants and spindle orientation during division. We have developed a tractable, in vitro model of naive CD8(+) T cells undergoing initial division while attached to dendritic cells during Ag presentation to investigate whether similar mechanisms might regulate asymmetric division of T cells. Using this system, we show that direct interactions with APCs provide the cue for polarization of T cells. Interestingly, the immunological synapse disseminates before division even though the T cells retain contact with the APC. The cue from the APC is translated into polarization of cell fate determinants via the polarity network of the Par3 and Scribble complexes, and orientation of the mitotic spindle during division is orchestrated by the partner of inscuteable/G protein complex. These findings suggest that T cells have selectively adapted a number of evolutionarily conserved mechanisms to generate diversity through asymmetric cell division.

  11. Defect driven shapes in nematic droplets: analogies with cell division

    NASA Astrophysics Data System (ADS)

    Leoni, Marco; Manyuhina, Oksana V.; Bowick, Mark J.; Marchetti, M. Cristina

    Building on the striking similarity between the structure of the spindle during mitosis in living cells and nematic textures in confined liquid crystals, we use a continuum model of two-dimensional nematic liquid crystal droplets, to examine the physical aspects of cell division. The model investigates the interplay between bulk elasticity of the microtubule assembly, described as a nematic liquid crystal, and surface elasticity of the cell cortex, modelled as a bounding flexible membrane, in controlling cell shape and division. The centrosomes at the spindle poles correspond to the cores of the topological defects required to accommodate nematic order in a closed geometry. We map out the progression of both healthy bipolar and faulty multi-polar division as a function of an effective parameter that incorporates active processes and controls centrosome separation. A robust prediction, independent of energetic considerations, is that the transition from a single cell to daughters cells occurs at critical value of this parameter. Our model additionally suggests that microtubule anchoring at the cell cortex may play an important role for successful bipolar division. This can be tested experimentally by regulating microtubule anchoring.

  12. Metabolic Maintenance of Cell Asymmetry following Division in Activated T Lymphocytes

    PubMed Central

    Verbist, Katherine C.; Guy, Cliff S; Milasta, Sandra; Liedmann, Swantje; Kamiński, Marcin M.; Wang, Ruoning; Green, Douglas R.

    2016-01-01

    Asymmetric cell division (ACD)—the partitioning of cellular components in response to polarizing cues during mitosis—plays roles in differentiation and development1. ACD is important for the self-renewal of neuroblasts in C. elegans and fertilized zygotes in Drosophila, and participates in the development of mammalian nervous and digestive systems1. T lymphocytes, upon activation by antigen-presenting cells (APC), can undergo ACD, wherein the daughter cell proximal to the APC is more likely to differentiate into an effector-like T cell and the distal daughter more likely to differentiate into a memory-like T cell2. Upon activation and prior to cell division, expression of the transcription factor c-Myc drives metabolic reprogramming, necessary for the subsequent proliferative burst3. We found that during the first division of an activated T cell, c-Myc can sort asymmetrically. Asymmetric amino acid transporter distribution, amino acid content, and TORC1 function correlate with c-Myc expression, and both amino acids and TORC1 activity sustain the differences in c-Myc expression in one daughter over the other. Asymmetric c-Myc levels in daughter T cells affect proliferation, metabolism, and differentiation, and these effects are altered by experimental manipulation of TORC1 activity or Myc expression. Therefore, metabolic signaling pathways cooperate with transcription programs to maintain differential cell fates following asymmetric T cell division. PMID:27064903

  13. Determining cell division symmetry through the dissection of dividing cells using single-cell expression analysis.

    PubMed

    Jasnos, Lukasz; Sawado, Tomoyuki

    2014-03-01

    Symmetric cell divisions give rise to two sister cells that are identical to each other, whereas asymmetric divisions produce two sister cells with distinctive phenotypes. Although cell division symmetry is usually determined on the basis of a few markers or biological functions, the overall similarity between sister cells has not been thoroughly examined at a molecular level. Here we provide a protocol to separate sister embryonic stem cells (ESCs) and to conduct multiplexed gene expression analyses at the single-cell level by using 48 ESC genes. The procedure includes the dissection of dividing, paired sister cells by micromanipulation, followed by cell lysis, reverse transcription, gene-specific cDNA amplification and multiplexed quantitative PCR analyses. This protocol can be completed in 10 d, and it can be readily adapted to other cell types that are able to grow in suspension culture.

  14. Local Cell Death Changes the Orientation of Cell Division in the Developing Drosophila Wing Imaginal Disc Without Using Fat or Dachsous as Orienting Signals

    PubMed Central

    Kale, Abhijit; Rimesso, Gerard; Baker, Nicholas E.

    2016-01-01

    Drosophila imaginal disc cells exhibit preferred cell division orientations according to location within the disc. These orientations are altered if cell death occurs within the epithelium, such as is caused by cell competition or by genotypes affecting cell survival. Both normal cell division orientations, and their orientations after cell death, depend on the Fat-Dachsous pathway of planar cell polarity (PCP). The hypothesis that cell death initiates a planar polarity signal was investigated. When clones homozygous for the pineapple eye (pie) mutation were made to initiate cell death, neither Dachsous nor Fat was required in pie cells for the re-orientation of nearby cells, indicating a distinct signal for this PCP pathway. Dpp and Wg were also not needed for pie clones to re-orient cell division. Cell shapes were evaluated in wild type and mosaic wing discs to assess mechanical consequences of cell loss. Although proximal wing disc cells and cells close to the dorso-ventral boundary were elongated in their preferred cell division axes in wild type discs, cell shapes in much of the wing pouch were symmetrical on average and did not predict their preferred division axis. Cells in pie mutant clones were slightly larger than their normal counterparts, consistent with mechanical stretching following cell loss, but no bias in cell shape was detected in the surrounding cells. These findings indicate that an unidentified signal influences PCP-dependent cell division orientation in imaginal discs. PMID:28030539

  15. Local Cell Death Changes the Orientation of Cell Division in the Developing Drosophila Wing Imaginal Disc Without Using Fat or Dachsous as Orienting Signals.

    PubMed

    Kale, Abhijit; Rimesso, Gerard; Baker, Nicholas E

    2016-01-01

    Drosophila imaginal disc cells exhibit preferred cell division orientations according to location within the disc. These orientations are altered if cell death occurs within the epithelium, such as is caused by cell competition or by genotypes affecting cell survival. Both normal cell division orientations, and their orientations after cell death, depend on the Fat-Dachsous pathway of planar cell polarity (PCP). The hypothesis that cell death initiates a planar polarity signal was investigated. When clones homozygous for the pineapple eye (pie) mutation were made to initiate cell death, neither Dachsous nor Fat was required in pie cells for the re-orientation of nearby cells, indicating a distinct signal for this PCP pathway. Dpp and Wg were also not needed for pie clones to re-orient cell division. Cell shapes were evaluated in wild type and mosaic wing discs to assess mechanical consequences of cell loss. Although proximal wing disc cells and cells close to the dorso-ventral boundary were elongated in their preferred cell division axes in wild type discs, cell shapes in much of the wing pouch were symmetrical on average and did not predict their preferred division axis. Cells in pie mutant clones were slightly larger than their normal counterparts, consistent with mechanical stretching following cell loss, but no bias in cell shape was detected in the surrounding cells. These findings indicate that an unidentified signal influences PCP-dependent cell division orientation in imaginal discs.

  16. Lineage tracing quantification reveals symmetric stem cell division in Drosophila male germline stem cells.

    PubMed

    Salzmann, Viktoria; Inaba, Mayu; Cheng, Jun; Yamashita, Yukiko M

    2013-12-01

    In the homeostatic state, adult stem cells divide either symmetrically to increase the stem cell number to compensate stem cell loss, or asymmetrically to maintain the population while producing differentiated cells. We have investigated the mode of stem cell division in the testes of Drosophila melanogaster by lineage tracing and confirm the presence of symmetric stem cell division in this system. We found that the rate of symmetric division is limited to 1-2% of total germline stem cell (GSC) divisions, but it increases with expression of a cell adhesion molecule, E-cadherin, or a regulator of the actin cytoskeleton, Moesin, which may modulate adhesiveness of germ cells to the stem cell niche. Our results indicate that the decision regarding asymmetric vs. symmetric division is a dynamically regulated process that contributes to tissue homeostasis, responding to the needs of the tissue.

  17. Harnessing single cell sorting to identify cell division genes and regulators in bacteria.

    PubMed

    Burke, Catherine; Liu, Michael; Britton, Warwick; Triccas, James A; Thomas, Torsten; Smith, Adrian L; Allen, Steven; Salomon, Robert; Harry, Elizabeth

    2013-01-01

    Cell division is an essential cellular process that requires an array of known and unknown proteins for its spatial and temporal regulation. Here we develop a novel, high-throughput screening method for the identification of bacterial cell division genes and regulators. The method combines the over-expression of a shotgun genomic expression library to perturb the cell division process with high-throughput flow cytometry sorting to screen many thousands of clones. Using this approach, we recovered clones with a filamentous morphology for the model bacterium, Escherichia coli. Genetic analysis revealed that our screen identified both known cell division genes, and genes that have not previously been identified to be involved in cell division. This novel screening strategy is applicable to a wide range of organisms, including pathogenic bacteria, where cell division genes and regulators are attractive drug targets for antibiotic development.

  18. Harnessing Single Cell Sorting to Identify Cell Division Genes and Regulators in Bacteria

    PubMed Central

    Burke, Catherine; Liu, Michael; Britton, Warwick; Triccas, James A.; Thomas, Torsten; Smith, Adrian L.; Allen, Steven; Salomon, Robert; Harry, Elizabeth

    2013-01-01

    Cell division is an essential cellular process that requires an array of known and unknown proteins for its spatial and temporal regulation. Here we develop a novel, high-throughput screening method for the identification of bacterial cell division genes and regulators. The method combines the over-expression of a shotgun genomic expression library to perturb the cell division process with high-throughput flow cytometry sorting to screen many thousands of clones. Using this approach, we recovered clones with a filamentous morphology for the model bacterium, Escherichia coli. Genetic analysis revealed that our screen identified both known cell division genes, and genes that have not previously been identified to be involved in cell division. This novel screening strategy is applicable to a wide range of organisms, including pathogenic bacteria, where cell division genes and regulators are attractive drug targets for antibiotic development. PMID:23565292

  19. Mitochondrial dynamics and inheritance during cell division, development and disease.

    PubMed

    Mishra, Prashant; Chan, David C

    2014-10-01

    During cell division, it is critical to properly partition functional sets of organelles to each daughter cell. The partitioning of mitochondria shares some common features with that of other organelles, particularly in the use of interactions with cytoskeletal elements to facilitate delivery to the daughter cells. However, mitochondria have unique features - including their own genome and a maternal mode of germline transmission - that place additional demands on this process. Consequently, mechanisms have evolved to regulate mitochondrial segregation during cell division, oogenesis, fertilization and tissue development, as well as to ensure the integrity of these organelles and their DNA, including fusion-fission dynamics, organelle transport, mitophagy and genetic selection of functional genomes. Defects in these processes can lead to cell and tissue pathologies.

  20. How to Foster an Understanding of Growth and Cell Division

    ERIC Educational Resources Information Center

    Kruger, Dirk; Fleige, Jennifer; Riemeier, Tanja

    2006-01-01

    The study presents the frequencies of students' conceptions of growth and cell division before and after one hour of instruction. The investigation supplements qualitative results by directing attention to those conceptions which might occur most frequently to students: teachers can then concentrate their preparation on practical requirements. A…

  1. Polyalkoxyflavonoids as inhibitors of cell division

    NASA Astrophysics Data System (ADS)

    Semenov, V. V.; Semenova, M. N.

    2015-02-01

    Being structural analogues of natural microtubule-destabilizing cytostatics, polyalkoxyflavonoids represent a promising class of compounds for anticancer drug design. The review covers synthetic routes to various polyalkoxyflavonoids and the results of biological assays in vitro on human cancer cells and in vivo using sea urchin embryos as a model. Mechanisms of action and structure-relationship activity for polyalkoxyflavonoids are discussed. The bibliography includes 151 references.

  2. A DNA damage checkpoint in Caulobacter crescentus inhibits cell division through a direct interaction with FtsW.

    PubMed

    Modell, Joshua W; Hopkins, Alexander C; Laub, Michael T

    2011-06-15

    Following DNA damage, cells typically delay cell cycle progression and inhibit cell division until their chromosomes have been repaired. The bacterial checkpoint systems responsible for these DNA damage responses are incompletely understood. Here, we show that Caulobacter crescentus responds to DNA damage by coordinately inducing an SOS regulon and inhibiting the master regulator CtrA. Included in the SOS regulon is sidA (SOS-induced inhibitor of cell division A), a membrane protein of only 29 amino acids that helps to delay cell division following DNA damage, but is dispensable in undamaged cells. SidA is sufficient, when overproduced, to block cell division. However, unlike many other regulators of bacterial cell division, SidA does not directly disrupt the assembly or stability of the cytokinetic ring protein FtsZ, nor does it affect the recruitment of other components of the cell division machinery. Instead, we provide evidence that SidA inhibits division by binding directly to FtsW to prevent the final constriction of the cytokinetic ring.

  3. Dielectric modelling of cell division for budding and fission yeast

    NASA Astrophysics Data System (ADS)

    Asami, Koji; Sekine, Katsuhisa

    2007-02-01

    The frequency dependence of complex permittivity or the dielectric spectrum of a system including a cell in cell division has been simulated by a numerical technique based on the three-dimensional finite difference method. Two different types of cell division characteristic of budding and fission yeast were examined. The yeast cells are both regarded as a body of rotation, and thus have anisotropic polarization, i.e. the effective permittivity of the cell depends on the orientation of the cell to the direction of an applied electric field. In the perpendicular orientation, where the rotational axis of the cell is perpendicular to the electric field direction, the dielectric spectra for both yeast cells included one dielectric relaxation and its intensity depended on the cell volume. In the parallel orientation, on the other hand, two dielectric relaxations appeared with bud growth for budding yeast and with septum formation for fission yeast. The low-frequency relaxation was shifted to a lower frequency region by narrowing the neck between the bud and the mother cell for budding yeast and by increasing the degree of septum formation for fission yeast. After cell separation, the low-frequency relaxation disappeared. The simulations well interpreted the oscillation of the relative permittivity of culture broth found for synchronous cell growth of budding yeast.

  4. Regulation of cell division in higher plants. Progress report

    SciTech Connect

    Jacobs, T.W.

    1992-07-01

    Cell division is arguably the most fundamental of all developmental processes. In higher plants, mitotic activity is largely confined to foci of patterned cell divisions called meristems. From these perpetually embryonic tissues arise the plant`s essential organs of light capture, support, protection and reproduction. Once an adequate understanding of plant cell mitotic regulation is attained, unprecedented opportunities will ensue for analyzing and genetically controlling diverse aspects of development, including plant architecture, leaf shape, plant height, and root depth. The mitotic cycle in a variety of model eukaryotic systems in under the control of a regulatory network of striking evolutionary conservation. Homologues of the yeast cdc2 gene, its catalytic product, p34, and the cyclin regulatory subunits of the MPF complex have emerged as ubiquitous mitotic regulators. We have cloned cdc2-like and cyclin genes from pea. As in other eukaryotic model systems, p34 of Pisum sativum is a subunit of a high molecular weight complex which binds the fission yeast p13 protein and displays histone H1 kinase activity in vitro. Our primary objective in this study is to gain baseline information about the regulation of this higher plant cell division control complex in non-dividing, differentiated cells as well as in synchronous and asynchronous mitotic cells. We are investigating cdc2 and cyclin expression at the levels of protein abundance, protein phosphorylation and quaternary associations.

  5. Asymmetric cell division of stem cells in the lung and other systems.

    PubMed

    Berika, Mohamed; Elgayyar, Marwa E; El-Hashash, Ahmed H K

    2014-01-01

    New insights have been added to identification, behavior and cellular properties of embryonic and tissue-specific stem cells over the last few years. The modes of stem cell division, asymmetric vs. symmetric, are tightly regulated during development and regeneration. The proper choice of a stem cell to divide asymmetrically or symmetrically has great consequences for development and disease because inappropriate asymmetric division disrupts organ morphogenesis, whereas uncontrolled symmetric division induces tumorigenesis. Therefore, understanding the behavior of lung stem cells could identify innovative solutions for restoring normal morphogenesis and/or regeneration of different organs. In this concise review, we describe recent studies in our laboratory about the mode of division of lung epithelial stem cells. We also compare asymmetric cell division (ACD) in the lung stem cells with other tissues in different organisms.

  6. Microenvironmental modulation of asymmetric cell division in human lung cancer cells.

    PubMed

    Pine, Sharon R; Ryan, Bríd M; Varticovski, Lyuba; Robles, Ana I; Harris, Curtis C

    2010-02-02

    Normal tissue homeostasis is maintained through asymmetric cell divisions that produce daughter cells with differing self-renewal and differentiation potentials. Certain tumor cell subfractions can self-renew and repopulate the heterogeneous tumor bulk, suggestive of asymmetric cell division, but an equally plausible explanation is that daughter cells of a symmetric division subsequently adopt differing cell fates. Cosegregation of template DNA during mitosis is one mechanism by which cellular components are segregated asymmetrically during cell division in fibroblast, muscle, mammary, intestinal, and neural cells. Asymmetric cell division of template DNA in tumor cells has remained elusive, however. Through pulse-chase experiments with halogenated thymidine analogs, we determined that a small population of cells within human lung cancer cell lines and primary tumor cell cultures asymmetrically divided their template DNA, which could be visualized in single cells and in real time. Template DNA cosegregation was enhanced by cell-cell contact. Its frequency was density-dependent and modulated by environmental changes, including serum deprivation and hypoxia. In addition, we found that isolated CD133(+) lung cancer cells were capable of tumor cell repopulation. Strikingly, during cell division, CD133 cosegregated with the template DNA, whereas the differentiation markers prosurfactant protein-C and pan-cytokeratins were passed to the opposing daughter cell, demonstrating that segregation of template DNA correlates with lung cancer cell fate. Our results demonstrate that human lung tumor cell fate decisions may be regulated during the cell division process. The characterization and modulation of asymmetric cell division in lung cancer can provide insight into tumor initiation, growth, and maintenance.

  7. Cell shape and Wnt signaling redundantly control the division axis of C. elegans epithelial stem cells.

    PubMed

    Wildwater, Marjolein; Sander, Nicholas; de Vreede, Geert; van den Heuvel, Sander

    2011-10-01

    Tissue-specific stem cells combine proliferative and asymmetric divisions to balance self-renewal with differentiation. Tight regulation of the orientation and plane of cell division is crucial in this process. Here, we study the reproducible pattern of anterior-posterior-oriented stem cell-like divisions in the Caenorhabditis elegans seam epithelium. In a genetic screen, we identified an alg-1 Argonaute mutant with additional and abnormally oriented seam cell divisions. ALG-1 is the main subunit of the microRNA-induced silencing complex (miRISC) and was previously shown to regulate the timing of postembryonic development. Time-lapse fluorescence microscopy of developing larvae revealed that reduced alg-1 function successively interferes with Wnt signaling, cell adhesion, cell shape and the orientation and timing of seam cell division. We found that Wnt inactivation, through mig-14 Wntless mutation, disrupts tissue polarity but not anterior-posterior division. However, combined Wnt inhibition and cell shape alteration resulted in disordered orientation of seam cell division, similar to the alg-1 mutant. Our findings reveal additional alg-1-regulated processes, uncover a previously unknown function of Wnt ligands in seam tissue polarity, and show that Wnt signaling and geometric cues redundantly control the seam cell division axis.

  8. The Significance of Microspore Division and Division Symmetry for Vegetative Cell-Specific Transcription and Generative Cell Differentiation.

    PubMed Central

    Eady, C.; Lindsey, K.; Twell, D.

    1995-01-01

    The significance of the onset and symmetry of pollen mitosis I (PMI) for the subsequent differentiation of the vegetative and generative cells was investigated by the in vitro maturation of isolated microspores of transgenic tobacco. Free uninucleate microspores of transgenic plants harboring the vegetative cell (VC)-specific late anther tomato lat52 promoter fused to the [beta]-glucuronidase (gus) gene showed normal asymmetric cell division at PMI and activated the lat52 promoter specifically in the nascent VC during in vitro maturation. In vitro maturation in the presence of high levels of colchicine effectively blocked PMI, resulting in the formation of uninucleate pollen grains in which the lat52 promoter was activated. Furthermore, matured uninucleate pollen grains were capable of germination and pollen tube growth despite the absence of a functional generative cell (GC). Lower levels of colchicine induced symmetric division at PMI, producing two similar daughter cells in which typical GC chromatin condensation was prevented. Similar cultures of transgenic microspores harboring the lat52 promoter driving the expression of a nuclear-targeted GUS fusion protein showed that lat52 promoter activation occurred in both symmetric daughter cells. These results directly demonstrate that division asymmetry at PMI is essential for correct GC differentiation and that activation of VC-specific transcription and functional VC maturation may be uncoupled from cytokinesis at PMI. These results are discussed in relation to models proposed to account for the role and distribution of factors controlling the differing fates of the vegetative and generative cells. PMID:12242352

  9. Bacterial cell division as a target for new antibiotics.

    PubMed

    Sass, Peter; Brötz-Oesterhelt, Heike

    2013-10-01

    Bacterial resistance to currently applied antibiotics complicates the treatment of infections and demands the evaluation of new strategies to counteract multidrug-resistant bacteria. In recent years, the inhibition of the bacterial divisome, mainly by targeting the central cell division mediator FtsZ, has been recognized as a promising strategy for antibiotic attack. New antibiotics were shown to either interfere with the natural dynamics and functions of FtsZ during the cell cycle or to activate a bacterial protease to degrade FtsZ and thus bring about bacterial death in a suicidal manner. Their efficacy in animal models of infection together with resistance-breaking properties prove the potential of such drugs and validate the inhibition of bacterial cell division as an attractive approach for antibiotic intervention.

  10. Chromosome replication, cell growth, division and shape: a personal perspective

    PubMed Central

    Zaritsky, Arieh; Woldringh, Conrad L.

    2015-01-01

    The origins of Molecular Biology and Bacterial Physiology are reviewed, from our personal standpoints, emphasizing the coupling between bacterial growth, chromosome replication and cell division, dimensions and shape. Current knowledge is discussed with historical perspective, summarizing past and present achievements and enlightening ideas for future studies. An interactive simulation program of the bacterial cell division cycle (BCD), described as “The Central Dogma in Bacteriology,” is briefly represented. The coupled process of transcription/translation of genes encoding membrane proteins and insertion into the membrane (so-called transertion) is invoked as the functional relationship between the only two unique macromolecules in the cell, DNA and peptidoglycan embodying the nucleoid and the sacculus respectively. We envision that the total amount of DNA associated with the replication terminus, so called “nucleoid complexity,” is directly related to cell size and shape through the transertion process. Accordingly, the primary signal for cell division transmitted by DNA dynamics (replication, transcription and segregation) to the peptidoglycan biosynthetic machinery is of a physico-chemical nature, e.g., stress in the plasma membrane, relieving nucleoid occlusion in the cell’s center hence enabling the divisome to assemble and function between segregated daughter nucleoids. PMID:26284044

  11. Formation of a cylindrical bridge in cell division

    NASA Astrophysics Data System (ADS)

    Citron, Daniel; Schmidt, Laura E.; Reichl, Elizabeth; Ren, Yixin; Robinson, Douglas; Zhang, Wendy W.

    2007-11-01

    In nature, the shape transition associated with the division of a mother cell into two daughter cells proceeds via a variety of routes. In the cylinder-thinning route, which has been observed in Dictyostelium and most animal cells, the mother cell first forms a broad bridge-like region, also known as a furrow, between two daughter cells. The furrow then rapidly evolves into a cylindrical bridge, which thins and eventually severs the mother cell into two. The fundamental mechanism underlying this division route is not understood. Recent experiments on Dictyostelium found that, while the cylinder-thinning route persists even when key actin cross-linking proteins are missing, it is disrupted by the removal of force-generating myosin-II proteins. Other measurements revealed that mutant cells lacking myosin-II have a much more uniform tension over the cell surface than wild-type cells. This suggests that tension variation may be important. Here we use a fluid model, previously shown to reproduce the thinning dynamics [Zhang & Robinson, PNAS 102, 7186 (2005)], to test this idea. Consistent with the experiments, the model shows that the cylinder formation process occurs regardless of the exact viscoelastic properties of the cell. In contrast to the experiments, a tension variation in the model hinders, rather then expedites, the cylinder formation.

  12. Size-independent symmetric division in extraordinarily long cells

    PubMed Central

    Pende, Nika; Leisch, Nikolaus; Gruber-Vodicka, Harald R.; Heindl, Niels R.; Ott, Jörg; den Blaauwen, Tanneke; Bulgheresi, Silvia

    2014-01-01

    Two long-standing paradigms in biology are that cells belonging to the same population exhibit little deviation from their average size and that symmetric cell division is size limited. Here, ultrastructural, morphometric and immunocytochemical analyses reveal that two Gammaproteobacteria attached to the cuticle of the marine nematodes Eubostrichus fertilis and E. dianeae reproduce by constricting a single FtsZ ring at midcell despite being 45 μm and 120 μm long, respectively. In the crescent-shaped bacteria coating E. fertilis, symmetric FtsZ-based fission occurs in cells with lengths spanning one order of magnitude. In the E. dianeae symbiont, formation of a single functional FtsZ ring makes this the longest unicellular organism in which symmetric division has ever been observed. In conclusion, the reproduction modes of two extraordinarily long bacterial cells indicate that size is not the primary trigger of division and that yet unknown mechanisms time the localization of both DNA and the septum. PMID:25221974

  13. Using Live-Cell Markers in Maize to Analyze Cell Division Orientation and Timing.

    PubMed

    Rasmussen, Carolyn G

    2016-01-01

    Recently developed live-cell markers provide an opportunity to explore the dynamics and localization of proteins in maize, an important crop and model for monocot development. A step-by-step method is outlined for observing and analyzing the process of division in maize cells. The steps include plant growth conditions, sample preparation, time-lapse setup, and calculation of division rates.

  14. Cell division control by the Chromosomal Passenger Complex

    SciTech Connect

    Waal, Maike S. van der; Hengeveld, Rutger C.C.; Horst, Armando van der; Lens, Susanne M.A.

    2012-07-15

    The Chromosomal Passenger Complex (CPC) consisting of Aurora B kinase, INCENP, Survivin and Borealin, is essential for genomic stability by controlling multiple processes during both nuclear and cytoplasmic division. In mitosis it ensures accurate segregation of the duplicated chromosomes by regulating the mitotic checkpoint, destabilizing incorrectly attached spindle microtubules and by promoting the axial shortening of chromosomal arms in anaphase. During cytokinesis the CPC most likely prevents chromosome damage by imposing an abscission delay when a chromosome bridge connects the two daughter cells. Moreover, by controlling proper cytoplasmic division, the CPC averts tetraploidization. This review describes recent insights on how the CPC is capable of conducting its various functions in the dividing cell to ensure chromosomal stability.

  15. Protein kinase C epsilon in cell division: control of abscission.

    PubMed

    Saurin, Adrian T; Brownlow, Nicola; Parker, Peter J

    2009-02-15

    Cell division requires the separation and partitioning of sister chromatids to opposite ends of the cell before an actomyosin ring contracts the membrane in between during cytokinesis. The final irreversible step occurs during abscission when the ring breaks down and the membrane is sealed in its place. The physical mechanics of contraction depend on RhoA, which is stimulated by a centralspindlin complex around the cell equator. However exactly how these events are reversed to allow actomyosin breakdown and abscission were not well understood. Here we will discuss new findings that implicate Protein Kinase C epsilon (PKCepsilon) as a regulator of RhoA signalling required for abscission.

  16. Bacterial cell division: experimental and theoretical approaches to the divisome.

    PubMed

    Broughton, Claire E; Roper, David I; Van Den Berg, Hugo A; Rodger, Alison

    2015-01-01

    Cell division is a key event in the bacterial life cycle. It involves constriction at the midcell, so that one cell can give rise to two daughter cells. This constriction is mediated by a ring composed offibrous multimers of the protein FtsZ. However a host of additional factors is involved in the formation and dynamics of this "Z-ring" and this complicated apparatus is collectively known as the "divisome". We review the literature, with an emphasis on mathematical modelling, and show how such theoretical efforts have helped experimentalists to make sense of the at times bewildering data, and plan further experiments.

  17. Rab24 is required for normal cell division.

    PubMed

    Militello, Rodrigo D; Munafó, Daniela B; Berón, Walter; López, Luis A; Monier, Solange; Goud, Bruno; Colombo, María I

    2013-05-01

    Rab24 is an atypical member of the Rab GTPase family whose distribution in interphase cells has been characterized; however, its function remains largely unknown. In this study, we have analyzed the distribution of Rab24 throughout cell division. We have observed that Rab24 was located at the mitotic spindle in metaphase, at the midbody during telophase and in the furrow during cytokinesis. We have also observed partial co-localization of Rab24 and tubulin and demonstrated its association to microtubules. Interestingly, more than 90% of transiently transfected HeLa cells with Rab24 presented abnormal nuclear connections (i.e., chromatin bridges). Furthermore, in CHO cells stably transfected with GFP-Rab24wt, we observed a large percentage of binucleated and multinucleated cells. In addition, these cells presented an extremely large size and multiple failures in mitosis, as aberrant spindle formation (metaphase), delayed chromosomes (telophase) and multiple cytokinesis. A marked increase in binucleated, multinucleated and multilobulated nucleus formation was observed in HeLa cells depleted of Rab24. We also present evidence that a fraction of Rab24 associates with microtubules. In addition, Rab24 knock down resulted in misalignment of chromosomes and abnormal spindle formation in metaphase leading to the appearance of delayed chromosomes during late telophase and failures in cytokinesis. Our findings suggest that an adequate level of Rab24 is necessary for normal cell division. In summary, Rab24 modulates several mitotic events, including chromosome segregation and cytokinesis, perhaps through the interaction with microtubules.

  18. Benzodioxane-benzamides as new bacterial cell division inhibitors.

    PubMed

    Chiodini, Giuseppe; Pallavicini, Marco; Zanotto, Carlo; Bissa, Massimiliano; Radaelli, Antonia; Straniero, Valentina; Bolchi, Cristiano; Fumagalli, Laura; Ruggeri, Paola; De Giuli Morghen, Carlo; Valoti, Ermanno

    2015-01-07

    A SAR study was performed on 3-substituted 2,6-difluorobenzamides, known inhibitors of the essential bacterial cell division protein FtsZ, through a series of modifications first of 2,6-difluoro-3-nonyloxybenzamide and then of its 3-pyridothiazolylmethoxy analogue PC190723. The study led to the identification of chiral 2,6-difluorobenzamides bearing 1,4-benzodioxane-2-methyl residue at the 3-position as potent antistaphylococcal compounds.

  19. Sara endosomes and the asymmetric division of intestinal stem cells.

    PubMed

    Montagne, Chrystelle; Gonzalez-Gaitan, Marcos

    2014-05-01

    Tissue homeostasis is maintained by adult stem cells, which self-renew and give rise to differentiating cells. The generation of daughter cells with different fates is mediated by signalling molecules coming from an external niche or being asymmetrically dispatched between the two daughters upon stem cell mitosis. In the adult Drosophila midgut, the intestinal stem cell (ISC) divides to generate a new ISC and an enteroblast (EB) differentiating daughter. Notch signalling activity restricted to the EB regulates intestinal cell fate decision. Here, we show that ISCs divide asymmetrically, and Sara endosomes in ISCs are specifically dispatched to the presumptive EB. During ISC mitosis, Notch and Delta traffic through Sara endosomes, thereby contributing to Notch signalling bias, as revealed in Sara mutants: Sara itself contributes to the control of the ISC asymmetric division. Our data uncover an intrinsic endosomal mechanism during ISC mitosis, which participates in the maintenance of the adult intestinal lineage.

  20. Oriented cell motility and division underlie early limb bud morphogenesis.

    PubMed

    Wyngaarden, Laurie A; Vogeli, Kevin M; Ciruna, Brian G; Wells, Mathew; Hadjantonakis, Anna-Katerina; Hopyan, Sevan

    2010-08-01

    The vertebrate limb bud arises from lateral plate mesoderm and its overlying ectoderm. Despite progress regarding the genetic requirements for limb development, morphogenetic mechanisms that generate early outgrowth remain relatively undefined. We show by live imaging and lineage tracing in different vertebrate models that the lateral plate contributes mesoderm to the early limb bud through directional cell movement. The direction of cell motion, longitudinal cell axes and bias in cell division planes lie largely parallel to one another along the rostrocaudal (head-tail) axis in lateral plate mesoderm. Transition of these parameters from a rostrocaudal to a mediolateral (outward from the body wall) orientation accompanies early limb bud outgrowth. Furthermore, we provide evidence that Wnt5a acts as a chemoattractant in the emerging limb bud where it contributes to the establishment of cell polarity that is likely to underlie the oriented cell behaviours.

  1. Insights into cell division using Listeria monocytogenes infections of PtK2 renal epithelial cells.

    PubMed

    Sanger, Jean M; Sanger, Joseph W

    2012-11-01

    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.

  2. Replicating vesicles as models of primitive cell growth and division.

    PubMed

    Hanczyc, Martin M; Szostak, Jack W

    2004-12-01

    Primitive cells, lacking the complex bio-machinery present in modern cells, would have had to rely on the self-organizing properties of their components and on interactions with their environment to achieve basic cellular functions such as growth and division. Many bilayer-membrane vesicles, depending on their composition and environment, can exhibit complex morphological changes such as growth, fusion, fission, budding, internal vesicle assembly and vesicle-surface interactions. The rich dynamic properties of these vesicles provide interesting models of how primitive cellular replication might have occurred in response to purely physical and chemical forces.

  3. Microgravity effects during fertilization, cell division, development, and calcium metabolism in sea urchins

    NASA Technical Reports Server (NTRS)

    Schatten, Heide

    1996-01-01

    The overall objectives of this project are to explore the role of microgravity during fertilization, early development, cytoskeletal organization, and skeletal calcium deposition in a model development system: the sea urchin eggs and embryos. While pursuing these objectives, we have also helped to develop, test, and fly the Aquatic Research Facility (ARF) system. Cells were fixed at preselected time points to preserve the structures and organelles of interest with regards to cell biology events during development. The protocols used for the analysis of the results had been developed during the earlier part of this research and were applied for post-flight analysis using light and (immuno)fluorescence microscopy, scanning electron microscopy, and transmission electron microscopy. The structures of interest are: microtubules during fertilization, cell division, and cilia movement; microfilaments during cell surface restructuring and cell division; centrosomes and centrioles during cell division, cell differentiation, and cilia formation and movement; membranes, Golgi, endoplasmic reticulum, mitochondria, and chromosomes at all stages of development; and calcium deposits during spicule formation in late-stage embryos. In addition to further explore aspects important or living in space, several aspects of this research are also aimed at understanding diseases that affect humans on Earth which may be accelerated in space.

  4. Oriented cell division: new roles in guiding skin wound repair and regeneration.

    PubMed

    Yang, Shaowei; Ma, Kui; Geng, Zhijun; Sun, Xiaoyan; Fu, Xiaobing

    2015-11-18

    Tissue morphogenesis depends on precise regulation and timely co-ordination of cell division and also on the control of the direction of cell division. Establishment of polarity division axis, correct alignment of the mitotic spindle, segregation of fate determinants equally or unequally between daughter cells, are essential for the realization of oriented cell division. Furthermore, oriented cell division is regulated by intrinsic cues, extrinsic cues and other cues, such as cell geometry and polarity. However, dysregulation of cell division orientation could lead to abnormal tissue development and function. In the present study, we review recent studies on the molecular mechanism of cell division orientation and explain their new roles in skin repair and regeneration.

  5. Haspin has Multiple Functions in the Plant Cell Division Regulatory Network.

    PubMed

    Kozgunova, Elena; Suzuki, Takamasa; Ito, Masaki; Higashiyama, Tetsuya; Kurihara, Daisuke

    2016-04-01

    Progression of cell division is controlled by various mitotic kinases. In animal cells, phosphorylation of histone H3 at Thr3 by the kinase Haspin (haploid germ cell-specific nuclear protein kinase) promotes centromeric Aurora B localization to regulate chromosome segregation. However, less is known about the function of Haspin in regulatory networks in plant cells. Here, we show that inhibition of Haspin with 5-iodotubercidin (5-ITu) in Bright Yellow-2 (BY-2) cells delayed chromosome alignment. Haspin inhibition also prevented the centromeric localization of Aurora3 kinase (AUR3) and disrupted its function. This suggested that Haspin plays a role in the specific positioning of AUR3 on chromosomes in plant cells, a function conserved in animals. The results also indicated that Haspin and AUR3 are involved in the same pathway, which regulates chromosome alignment during prometaphase/metaphase. Remarkably, Haspin inhibition by 5-ITu also led to a severe cytokinesis defect, resulting in binuclear cells with a partially formed cell plate. The 5-ITu treatment did not affect microtubules, AUR1/2 or the NACK-PQR pathway; however, it did alter the distribution of actin filaments on the cell plate. Together, these results suggested that Haspin has several functions in regulating cell division in plant cells: in the localization of AUR3 on centromeres and in regulating late cell plate expansion during cytokinesis.

  6. Combination of Synthetic Chemistry and Live-Cell Imaging Identified a Rapid Cell Division Inhibitor in Tobacco and Arabidopsis thaliana.

    PubMed

    Nambo, Masakazu; Kurihara, Daisuke; Yamada, Tomomi; Nishiwaki-Ohkawa, Taeko; Kadofusa, Naoya; Kimata, Yusuke; Kuwata, Keiko; Umeda, Masaaki; Ueda, Minako

    2016-11-01

    Cell proliferation is crucial to the growth of multicellular organisms, and thus the proper control of cell division is important to prevent developmental arrest or overgrowth. Nevertheless, tools for controlling cell proliferation are still poor in plant. To develop novel tools, we focused on a specific compound family, triarylmethanes, whose members show various antiproliferative activities in animals. By combining organic chemistry to create novel and diverse compounds containing the triarylmethyl moiety and biological screens based on live-cell imaging of a fluorescently labeled tobacco Bright Yellow-2 (BY-2) culture cell line (Nicotiana tabacum), we isolated (3-furyl)diphenylmethane as a strong but partially reversible inhibitor of plant cell division. We also found that this agent had efficient antiproliferative activity in developing organs of Arabidopsis thaliana without causing secondary defects in cell morphology, and induced rapid cell division arrest independent of the cell cycle stage. Given that (3-furyl)diphenylmethane did not affect the growth of a human cell line (HeLa) and a budding yeast (Saccharomyces cerevisiae), it should act specifically on plants. Taking our results together, we propose that the combination of desired chemical synthesis and detailed biological analysis is an effective tool to create novel drugs, and that (3-furyl)diphenylmethane is a specific antiproliferative agent for plants.

  7. Label-free quantitative cell division monitoring of endothelial cells by digital holographic microscopy

    NASA Astrophysics Data System (ADS)

    Kemper, Björn; Bauwens, Andreas; Vollmer, Angelika; Ketelhut, Steffi; Langehanenberg, Patrik; Müthing, Johannes; Karch, Helge; von Bally, Gert

    2010-05-01

    Digital holographic microscopy (DHM) enables quantitative multifocus phase contrast imaging for nondestructive technical inspection and live cell analysis. Time-lapse investigations on human brain microvascular endothelial cells demonstrate the use of DHM for label-free dynamic quantitative monitoring of cell division of mother cells into daughter cells. Cytokinetic DHM analysis provides future applications in toxicology and cancer research.

  8. Asymmetric cell division in T lymphocyte fate diversification

    PubMed Central

    Arsenio, Janilyn; Metz, Patrick J.

    2015-01-01

    Immunological protection against microbial pathogens is dependent on robust generation of functionally diverse T lymphocyte subsets. Upon microbial infection, naïve CD4+ or CD8+ T lymphocytes can give rise to effector- and memory-fated progeny that together mediate a potent immune response. Recent advances in single-cell immunological and genomic profiling technologies have helped elucidate early and late diversification mechanisms that enable the generation of heterogeneity from single T lymphocytes. We discuss these findings here and argue that one such mechanism, asymmetric cell division, creates an early divergence in T lymphocyte fates by giving rise to daughter cells with a propensity towards the terminally differentiated effector or self-renewing memory lineages, with cell-intrinsic and -extrinsic cues from the microenvironment driving the final maturation steps. PMID:26474675

  9. Bacterial actin and tubulin homologs in cell growth and division.

    PubMed

    Busiek, Kimberly K; Margolin, William

    2015-03-16

    In contrast to the elaborate cytoskeletal machines harbored by eukaryotic cells, such as mitotic spindles, cytoskeletal structures detectable by typical negative stain electron microscopy are generally absent from bacterial cells. As a result, for decades it was thought that bacteria lacked cytoskeletal machines. Revolutions in genomics and fluorescence microscopy have confirmed the existence not only of smaller-scale cytoskeletal structures in bacteria, but also of widespread functional homologs of eukaryotic cytoskeletal proteins. The presence of actin, tubulin, and intermediate filament homologs in these relatively simple cells suggests that primitive cytoskeletons first arose in bacteria. In bacteria such as Escherichia coli, homologs of tubulin and actin directly interact with each other and are crucial for coordinating cell growth and division. The function and direct interactions between these proteins will be the focus of this review.

  10. The basal position of nuclei is one pre-requisite for asymmetric cell divisions in the early mouse embryo.

    PubMed

    Ajduk, Anna; Biswas Shivhare, Sourima; Zernicka-Goetz, Magdalena

    2014-08-15

    The early mouse embryo undertakes two types of cell division: symmetric that gives rise to the trophectoderm and then placenta or asymmetric that gives rise to inner cells that generate the embryo proper. Although cell division orientation is important, the mechanism regulating it has remained unclear. Here, we identify the relationship between the plane of cell division and the position of the nucleus and go towards identifying the mechanism behind it. We first find that as the 8-cell embryo progresses through the cell cycle, the nuclei of most - but not all - cells move from apical to more basal positions, in a microtubule- and kinesin-dependent manner. We then find that all asymmetric divisions happen when nuclei are located basally and, in contrast, all cells, in which nuclei remain apical, divide symmetrically. To understand the potential mechanism behind this, we determine the effects of modulating expression of Cdx2, a transcription factor key for trophectoderm formation and cell polarity. We find that increased expression of Cdx2 leads to an increase in a number of apical nuclei, whereas down-regulation of Cdx2 leads to more nuclei moving basally, which explains a previously identified relationship between Cdx2 and cell division orientation. Finally, we show that down-regulation of aPKC, involved in cell polarity, decreases the number of apical nuclei and doubles the number of asymmetric divisions. These results suggest a model in which the mutual interdependence of Cdx2 and cell polarity affects the cytoskeleton-dependent positioning of nuclei and, in consequence, the plane of cell division in the early mouse embryo.

  11. Endosymbiosis in trypanosomatid protozoa: the bacterium division is controlled during the host cell cycle.

    PubMed

    Catta-Preta, Carolina M C; Brum, Felipe L; da Silva, Camila C; Zuma, Aline A; Elias, Maria C; de Souza, Wanderley; Schenkman, Sergio; Motta, Maria Cristina M

    2015-01-01

    Mutualism is defined as a beneficial relationship for the associated partners and usually assumes that the symbiont number is controlled. Some trypanosomatid protozoa co-evolve with a bacterial symbiont that divides in coordination with the host in a way that results in its equal distribution between daughter cells. The mechanism that controls this synchrony is largely unknown, and its comprehension might provide clues to understand how eukaryotic cells evolved when acquiring symbionts that later became organelles. Here, we approached this question by studying the effects of inhibitors that affect the host exclusively in two symbiont-bearing trypanosomatids, Strigomonas culicis and Angomonas deanei. We found that inhibiting host protein synthesis using cycloheximide or host DNA replication using aphidicolin did not affect the duplication of bacterial DNA. Although the bacteria had autonomy to duplicate their DNA when host protein synthesis was blocked by cycloheximide, they could not complete cytokinesis. Aphidicolin promoted the inhibition of the trypanosomatid cell cycle in the G1/S phase, leading to symbiont filamentation in S. culicis but not in A. deanei. Treatment with camptothecin blocked the host protozoa cell cycle in the G2 phase and induced the formation of filamentous symbionts in both species. Oryzalin, which affects host microtubule polymerization, blocked trypanosomatid mitosis and abrogated symbiont division. Our results indicate that host factors produced during the cell division cycle are essential for symbiont segregation and may control the bacterial cell number.

  12. Endosymbiosis in trypanosomatid protozoa: the bacterium division is controlled during the host cell cycle

    PubMed Central

    Catta-Preta, Carolina M. C.; Brum, Felipe L.; da Silva, Camila C.; Zuma, Aline A.; Elias, Maria C.; de Souza, Wanderley; Schenkman, Sergio; Motta, Maria Cristina M.

    2015-01-01

    Mutualism is defined as a beneficial relationship for the associated partners and usually assumes that the symbiont number is controlled. Some trypanosomatid protozoa co-evolve with a bacterial symbiont that divides in coordination with the host in a way that results in its equal distribution between daughter cells. The mechanism that controls this synchrony is largely unknown, and its comprehension might provide clues to understand how eukaryotic cells evolved when acquiring symbionts that later became organelles. Here, we approached this question by studying the effects of inhibitors that affect the host exclusively in two symbiont-bearing trypanosomatids, Strigomonas culicis and Angomonas deanei. We found that inhibiting host protein synthesis using cycloheximide or host DNA replication using aphidicolin did not affect the duplication of bacterial DNA. Although the bacteria had autonomy to duplicate their DNA when host protein synthesis was blocked by cycloheximide, they could not complete cytokinesis. Aphidicolin promoted the inhibition of the trypanosomatid cell cycle in the G1/S phase, leading to symbiont filamentation in S. culicis but not in A. deanei. Treatment with camptothecin blocked the host protozoa cell cycle in the G2 phase and induced the formation of filamentous symbionts in both species. Oryzalin, which affects host microtubule polymerization, blocked trypanosomatid mitosis and abrogated symbiont division. Our results indicate that host factors produced during the cell division cycle are essential for symbiont segregation and may control the bacterial cell number. PMID:26082757

  13. Connecting the dots of the bacterial cell cycle: Coordinating chromosome replication and segregation with cell division.

    PubMed

    Hajduk, Isabella V; Rodrigues, Christopher D A; Harry, Elizabeth J

    2016-05-01

    Proper division site selection is crucial for the survival of all organisms. What still eludes us is how bacteria position their division site with high precision, and in tight coordination with chromosome replication and segregation. Until recently, the general belief, at least in the model organisms Bacillus subtilis and Escherichia coli, was that spatial regulation of division comes about by the combined negative regulatory mechanisms of the Min system and nucleoid occlusion. However, as we review here, these two systems cannot be solely responsible for division site selection and we highlight additional regulatory mechanisms that are at play. In this review, we put forward evidence of how chromosome replication and segregation may have direct links with cell division in these bacteria and the benefit of recent advances in chromosome conformation capture techniques in providing important information about how these three processes mechanistically work together to achieve accurate generation of progenitor cells.

  14. Common mechanisms regulating cell cortex properties during cell division and cell migration.

    PubMed

    Roubinet, Chantal; Tran, Phong T; Piel, Matthieu

    2012-11-01

    Single cell morphogenesis results from a balance of forces involving internal pressure (also called turgor pressure in plants and fungi) and the plastic and dynamic outer shell of the cell. Dominated by the cell wall in plants and fungi, mechanical properties of the outer shell of animal cells arise from the cell cortex, which is mostly composed of the plasma membrane (and membrane proteins) and the underlying meshwork of actin filaments and myosin motors (and associated proteins). In this review, following Bray and White [1988; Science 239:883-889], we draw a parallel between the regulation of the cell cortex during cell division and cell migration in animal cells. Starting from the similarities in shape changes and underlying mechanical properties, we further propose that the analogy between cell division and cell migration might run deeper, down to the basic molecular mechanisms driving cell cortex remodeling. We focus our attention on how an heterogeneous and dynamic cortex can be generated to allow cell shape changes while preserving cell integrity.

  15. Single-cell dynamics of the chromosome replication and cell division cycles in mycobacteria.

    PubMed

    Santi, Isabella; Dhar, Neeraj; Bousbaine, Djenet; Wakamoto, Yuichi; McKinney, John D

    2013-01-01

    During the bacterial cell cycle, chromosome replication and cell division must be coordinated with overall cell growth in order to maintain the correct ploidy and cell size. The spatial and temporal coordination of these processes in mycobacteria is not understood. Here we use microfluidics and time-lapse fluorescence microscopy to measure the dynamics of cell growth, division and chromosome replication in single cells of Mycobacterium smegmatis. We find that single-cell growth is size-dependent (large cells grow faster than small cells), which implicates a size-control mechanism in cell-size homoeostasis. Asymmetric division of mother cells gives rise to unequally sized sibling cells that grow at different velocities but show no differential sensitivity to antibiotics. Individual cells are restricted to one round of chromosome replication per cell division cycle, although replication usually initiates in the mother cell before cytokinesis and terminates in the daughter cells after cytokinesis. These studies reveal important differences between cell cycle organization in mycobacteria compared with better-studied model organisms.

  16. Dido3 PHD Modulates Cell Differentiation and Division

    PubMed Central

    Gatchalian, Jovylyn; Fütterer, Agnes; Rothbart, Scott B.; Tong, Qiong; Rincon-Arano, Hector; de Diego, Ainhoa Sánchez; Groudine, Mark; Strahl, Brian D.; Martínez-A, Carlos; van Wely, Karel H.M.; Kutateladze, Tatiana G.

    2014-01-01

    SUMMARY Death Inducer Obliterator 3 (Dido3) is implicated in the maintenance of stem cell genomic stability and tumorigenesis. Here, we show that Dido3 regulates the expression of stemness genes in embryonic stem cells through its plant homeodomain (PHD) finger. Binding of Dido3 PHD to histone H3K4me3 is disrupted by threonine phosphorylation that triggers Dido3 translocation from chromatin to the mitotic spindle. The crystal structure of Dido3 PHD in complex with H3K4me3 reveals an atypical aromatic-cage-like binding site that contains a histidine residue. Biochemical, structural, and mutational analyses of the binding mechanism identified the determinants of specificity and affinity and explained the inability of homologous PHF3 to bind H3K4me3. Together, our findings reveal a link between the transcriptional control in embryonic development and regulation of cell division. PMID:23831028

  17. Dynamics of gene regulatory networks with cell division cycle

    NASA Astrophysics Data System (ADS)

    Chen, Luonan; Wang, Ruiqi; Kobayashi, Tetsuya J.; Aihara, Kazuyuki

    2004-07-01

    This paper focuses on modeling and analyzing the nonlinear dynamics of gene regulatory networks with the consideration of a cell division cycle with duplication process of DNA , in particular for switches and oscillators of synthetic networks. We derive two models that may correspond to the eukaryotic and prokaryotic cells, respectively. A biologically plausible three-gene model ( lac,tetR , and cI ) and a repressilator as switch and oscillator examples are used to illustrate our theoretical results. We show that the cell cycle may play a significant role in gene regulation due to the nonlinear dynamics of a gene regulatory network although gene expressions are usually tightly controlled by transcriptional factors.

  18. Asymmetric cell division of stem and progenitor cells during homeostasis and cancer.

    PubMed

    Gómez-López, Sandra; Lerner, Robin G; Petritsch, Claudia

    2014-02-01

    Stem and progenitor cells are characterized by their ability to self-renew and produce differentiated progeny. A fine balance between these processes is achieved through controlled asymmetric divisions and is necessary to generate cellular diversity during development and to maintain adult tissue homeostasis. Disruption of this balance may result in premature depletion of the stem/progenitor cell pool, or abnormal growth. In many tissues, including the brain, dysregulated asymmetric divisions are associated with cancer. Whether there is a causal relationship between asymmetric cell division defects and cancer initiation is as yet not known. Here, we review the cellular and molecular mechanisms that regulate asymmetric cell divisions in the neural lineage and discuss the potential connections between this regulatory machinery and cancer.

  19. The Par complex and integrins direct asymmetric cell division in adult intestinal stem cells.

    PubMed

    Goulas, Spyros; Conder, Ryan; Knoblich, Juergen A

    2012-10-05

    The adult Drosophila midgut is maintained by intestinal stem cells (ISCs) that generate both self-renewing and differentiating daughter cells. How this asymmetry is generated is currently unclear. Here, we demonstrate that asymmetric ISC division is established by a unique combination of extracellular and intracellular polarity mechanisms. We show that Integrin-dependent adhesion to the basement membrane induces cell-intrinsic polarity and results in the asymmetric segregation of the Par proteins Par-3, Par-6, and aPKC into the apical daughter cell. Cell-specific knockdown and overexpression experiments suggest that increased activity of aPKC enhances Delta/Notch signaling in one of the two daughter cells to induce terminal differentiation. Perturbing this mechanism or altering the orientation of ISC division results in the formation of intestinal tumors. Our data indicate that mechanisms for intrinsically asymmetric cell division can be adapted to allow for the flexibility in lineage decisions that is required in adult stem cells.

  20. Evidence for equal size cell divisions during gametogenesis in a marine green alga Monostroma angicava

    PubMed Central

    Togashi, Tatsuya; Horinouchi, Yusuke; Sasaki, Hironobu; Yoshimura, Jin

    2015-01-01

    In cell divisions, relative size of daughter cells should play fundamental roles in gametogenesis and embryogenesis. Differences in gamete size between the two mating types underlie sexual selection. Size of daughter cells is a key factor to regulate cell divisions during cleavage. In cleavage, the form of cell divisions (equal/unequal in size) determines the developmental fate of each blastomere. However, strict validation of the form of cell divisions is rarely demonstrated. We cannot distinguish between equal and unequal cell divisions by analysing only the mean size of daughter cells, because their means can be the same. In contrast, the dispersion of daughter cell size depends on the forms of cell divisions. Based on this, we show that gametogenesis in the marine green alga, Monostroma angicava, exhibits equal size cell divisions. The variance and the mean of gamete size (volume) of each mating type measured agree closely with the prediction from synchronized equal size cell divisions. Gamete size actually takes only discrete values here. This is a key theoretical assumption made to explain the diversified evolution of isogamy and anisogamy in marine green algae. Our results suggest that germ cells adopt equal size cell divisions during gametogenesis. PMID:26333414

  1. Cell division resets polarity and motility for the bacterium Myxococcus xanthus.

    PubMed

    Harvey, Cameron W; Madukoma, Chinedu S; Mahserejian, Shant; Alber, Mark S; Shrout, Joshua D

    2014-11-01

    Links between cell division and other cellular processes are poorly understood. It is difficult to simultaneously examine division and function in most cell types. Most of the research probing aspects of cell division has experimented with stationary or immobilized cells or distinctly asymmetrical cells. Here we took an alternative approach by examining cell division events within motile groups of cells growing on solid medium by time-lapse microscopy. A total of 558 cell divisions were identified among approximately 12,000 cells. We found an interconnection of division, motility, and polarity in the bacterium Myxococcus xanthus. For every division event, motile cells stop moving to divide. Progeny cells of binary fission subsequently move in opposing directions. This behavior involves M. xanthus Frz proteins that regulate M. xanthus motility reversals but is independent of type IV pilus "S motility." The inheritance of opposing polarity is correlated with the distribution of the G protein RomR within these dividing cells. The constriction at the point of division limits the intracellular distribution of RomR. Thus, the asymmetric distribution of RomR at the parent cell poles becomes mirrored at new poles initiated at the site of division.

  2. Identification of Salmonella functions critical for bacterial cell division within eukaryotic cells.

    PubMed

    Henry, T; García-Del Portillo, F; Gorvel, J P

    2005-04-01

    Salmonella typhimurium multiplication inside eukaryotic host cells is critical for virulence. Salmonella typhimurium strain SL1344 appears as filaments upon growth in macrophages and MelJuSo cells, a human melanoma cell line, indicating a specific blockage in the bacterial cell division process. Several studies have investigated the host cell response impairing bacterial division. However, none looked at the bacterial factors involved in inhibition of Salmonella division inside eukaryotic cells. We show here that blockage in the bacterial division process is sulA-independent and takes place after FtsZ-ring assembly. Salmonella typhimurium genes in which mutations lead to filamentous growth within host cells were identified by a large scale mutagenesis approach on strain 12023, revealing bacterial functions crucial for cell division within eukaryotic cells. We finally demonstrate that SL1344 filamentation is a result of hisG mutation, requires the activity of an enzyme of the histidine biosynthetic pathway HisFH and is specific for the vacuolar environment.

  3. Autism as a sequence: from heterochronic germinal cell divisions to abnormalities of cell migration and cortical dysplasias

    PubMed Central

    Casanova, Manuel F.

    2014-01-01

    The considerable heterogeneity in the number and severity of symptoms observed in autism spectrum disorders (ASD) has been regarded as an obstacle to any future research. Some authors believe that clinical heterogeneity results from the complex interplay of the many genetic and environmental factors that themselves define a condition as multifactorial. However, it is important to note that neuropathological findings in both idiopathic and syndromic autism suggests a single pathophysiological mechanism acting during brain development: the heterochronic division of germinal cells and subsequent migrational abnormalities of daughter cells to their target fields. Multiple exogenous (e.g., viruses, drugs) and endogenous (e.g., genetic mutations) factors are known to disrupt the division of germinal cells and provide for an autism phenotype. The variety of endogenous and exogenous factors, their timing of action during brain development, and the genetic susceptibility of affected individuals (a Triple Hit hypothesis) may all account for the clinical heterogeneity of ASD. PMID:24780284

  4. Evidence of asymmetric cell division and centrosome inheritance in human neuroblastoma cells.

    PubMed

    Izumi, Hideki; Kaneko, Yasuhiko

    2012-10-30

    Asymmetric cell division (ACD) is believed to be a physiological event that occurs during development and tissue homeostasis in a large variety of organisms. ACD produces two unequal daughter cells, one of which resembles a multipotent stem and/or progenitor cell, whereas the other has potential for differentiation. Although recent studies have shown that the balance between self-renewal and differentiation potentials is precisely controlled and that alterations in the balance may lead to tumorigenesis in Drosophila neuroblasts, it is largely unknown whether human cancer cells directly show ACD in an evolutionarily conserved manner. Here, we show that the conserved polarity/spindle protein NuMA is preferentially localized to one side of the cell cortex during cell division, generating unequal inheritance of fate-altering molecules in human neuroblastoma cell lines. We also show that the cells with a single copy of MYCN showed significantly higher percentages of ACD than those with MYCN amplification. Moreover, suppression of MYCN in MYCN-amplified cells caused ACD, whereas expression of MYCN in MYCN-nonamplified cells enhanced symmetric cell division. Furthermore, we demonstrate that centrosome inheritance follows a definite rule in ACD: The daughter centrosome with younger mother centriole is inherited to the daughter cell with NuMA preferentially localized to the cell cortex, whereas the mother centrosome with the older mother centriole migrates to the other daughter cell. Thus, the mechanisms of cell division of ACD or symmetric cell division and centrosome inheritance are recapitulated in human cancer cells, and these findings may facilitate studies on cancer stem cells.

  5. Metabolic control of cell division in α-proteobacteria by a NAD-dependent glutamate dehydrogenase

    PubMed Central

    Beaufay, François; De Bolle, Xavier; Hallez, Régis

    2016-01-01

    ABSTRACT Prior to initiate energy-consuming processes, such as DNA replication or cell division, cells need to evaluate their metabolic status. We have recently identified and characterized a new connection between metabolism and cell division in the α-proteobacterium Caulobacter crescentus. We showed that an NAD-dependent glutamate dehydrogenase (GdhZ) coordinates growth with cell division according to its enzymatic activity. Here we report the conserved role of GdhZ in controlling cell division in another α-proteobacterium, the facultative intracellular pathogen Brucella abortus. We also discuss the importance of amino acids as a main carbon source for α-proteobacteria. PMID:27066186

  6. Celebrating Soft Matter's 10th Anniversary: Cell division: a source of active stress in cellular monolayers.

    PubMed

    Doostmohammadi, Amin; Thampi, Sumesh P; Saw, Thuan B; Lim, Chwee T; Ladoux, Benoit; Yeomans, Julia M

    2015-10-07

    We introduce the notion of cell division-induced activity and show that the cell division generates extensile forces and drives dynamical patterns in cell assemblies. Extending the hydrodynamic models of lyotropic active nematics we describe turbulent-like velocity fields that are generated by the cell division in a confluent monolayer of cells. We show that the experimentally measured flow field of dividing Madin-Darby Canine Kidney (MDCK) cells is reproduced by our modeling approach. Division-induced activity acts together with intrinsic activity of the cells in extensile and contractile cell assemblies to change the flow and director patterns and the density of topological defects. Finally we model the evolution of the boundary of a cellular colony and compare the fingering instabilities induced by cell division to experimental observations on the expansion of MDCK cell cultures.

  7. Arc Voltage Between Deion Grid Affected by Division of Arc in Magnetic Driven Arc

    NASA Astrophysics Data System (ADS)

    Inuzuka, Yutaro; Yamato, Takashi; Yamamoto, Shinji; Iwao, Toru

    2016-10-01

    Magnetic driven arc has been applied to DC breaker and fault current limiters. However, it has not been researched, especially stagnation and re-strike of the arc. In this paper, the arc voltage between deion grid affected by division of arc in magnetic driven arc and arc behavior are measured by using the oscilloscope and HSVC (High Speed Video Camera). As a result, arc voltage increased because of division of the arc. The arc mean moving speed increases with increasing the external magnetic field. However, when the arc was not stalemate, the arc moving speed does not change so much. The arc re-strike time increases and stalemate time decreases with increasing the external magnetic field. Therefore, the anode spot moving speed increases 8 times because arc re-strike occurs easily with the external magnetic field. Thus, the erosion of electrodes decreases and the arc movement becomes the smooth. When the arc is divided, the arc voltage increased because of the electrode fall voltage. Therefore, the arc voltage increases with increasing the number of deion grid.

  8. Treadmilling by FtsZ filaments drives peptidoglycan synthesis and bacterial cell division.

    PubMed

    Bisson-Filho, Alexandre W; Hsu, Yen-Pang; Squyres, Georgia R; Kuru, Erkin; Wu, Fabai; Jukes, Calum; Sun, Yingjie; Dekker, Cees; Holden, Seamus; VanNieuwenhze, Michael S; Brun, Yves V; Garner, Ethan C

    2017-02-17

    The mechanism by which bacteria divide is not well understood. Cell division is mediated by filaments of FtsZ and FtsA (FtsAZ) that recruit septal peptidoglycan-synthesizing enzymes to the division site. To understand how these components coordinate to divide cells, we visualized their movements relative to the dynamics of cell wall synthesis during cytokinesis. We found that the division septum was built at discrete sites that moved around the division plane. FtsAZ filaments treadmilled circumferentially around the division ring and drove the motions of the peptidoglycan-synthesizing enzymes. The FtsZ treadmilling rate controlled both the rate of peptidoglycan synthesis and cell division. Thus, FtsZ treadmilling guides the progressive insertion of new cell wall by building increasingly smaller concentric rings of peptidoglycan to divide the cell.

  9. Long-range ordered vorticity patterns in living tissue induced by cell division.

    PubMed

    Rossen, Ninna S; Tarp, Jens M; Mathiesen, Joachim; Jensen, Mogens H; Oddershede, Lene B

    2014-12-08

    In healthy blood vessels with a laminar blood flow, the endothelial cell division rate is low, only sufficient to replace apoptotic cells. The division rate significantly increases during embryonic development and under halted or turbulent flow. Cells in barrier tissue are connected and their motility is highly correlated. Here we investigate the long-range dynamics induced by cell division in an endothelial monolayer under non-flow conditions, mimicking the conditions during vessel formation or around blood clots. Cell divisions induce long-range, well-ordered vortex patterns extending several cell diameters away from the division site, in spite of the system's low Reynolds number. Our experimental results are reproduced by a hydrodynamic continuum model simulating division as a local pressure increase corresponding to a local tension decrease. Such long-range physical communication may be crucial for embryonic development and for healing tissue, for instance around blood clots.

  10. Long-range ordered vorticity patterns in living tissue induced by cell division

    PubMed Central

    Rossen, Ninna S.; Tarp, Jens M.; Mathiesen, Joachim; Jensen, Mogens H.; Oddershede, Lene B.

    2014-01-01

    In healthy blood vessels with a laminar blood flow, the endothelial cell division rate is low, only sufficient to replace apoptotic cells. The division rate significantly increases during embryonic development and under halted or turbulent flow. Cells in barrier tissue are connected and their motility is highly correlated. Here we investigate the long-range dynamics induced by cell division in an endothelial monolayer under non-flow conditions, mimicking the conditions during vessel formation or around blood clots. Cell divisions induce long-range, well-ordered vortex patterns extending several cell diameters away from the division site, in spite of the system’s low Reynolds number. Our experimental results are reproduced by a hydrodynamic continuum model simulating division as a local pressure increase corresponding to a local tension decrease. Such long-range physical communication may be crucial for embryonic development and for healing tissue, for instance around blood clots. PMID:25483750

  11. Disruption of the keratin filament network during epithelial cell division.

    PubMed Central

    Lane, E B; Goodman, S L; Trejdosiewicz, L K

    1982-01-01

    The behaviour of keratin filaments during cell division was examined in a wide range of epithelial lines from several species. Almost half of them show keratin disruption as described previously: by immunofluorescence, filaments are replaced during mitosis by a 'speckled' pattern of discrete cytoplasmic dots. In the electron microscope these ' speckles ' are seen as granules around the cell periphery, just below the actin cortical mesh, with no detectable 10 nm filament structure inside them and no keratin filament bundles in the rest of the cytoplasm. A time course of the filament reorganization was constructed from double immunofluorescence data; filaments are disrupted in prophase, and the filament network is intact again by cytokinesis. The phenomenon is restricted to cells rich in keratin filaments, such as keratinocytes; it is unrelated to the co-existence of vimentin in many of these cells, and vimentin is generally maintained as filaments while the keratin is restructured. Some resistance to the effect may be conferred by an extended cycle time. Filament reorganization takes place within minutes, so that a reversible mechanism seems more likely than one involving de novo protein synthesis, at this metabolically quiet stage of the cell cycle. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. PMID:6202508

  12. Regulation of cell division in higher plants. Final technical report

    SciTech Connect

    Jacobs, Thomas W.

    2000-02-29

    Research in the latter part of the grant period was divided into two parts: (1) expansion of the macromolecular tool kit for studying plant cell division; (2) experiments in which the roles played by plant cell cycle regulators were to be cast in the light of the emerging yeast and animal cell paradigm for molecular control of the mitotic cycle. The first objectives were accomplished to a very satisfactory degree. With regard to the second part of the project, we were driven to change our objectives for two reasons. First, the families of cell cycle control genes that we cloned encoded such closely related members that the prospects for success at raising distinguishing antisera against each were sufficiently dubious as to be impractical. Epitope tagging is not feasible in Pisum sativum, our experimental system, as this species is not realistically transformable. Therefore, differentiating the roles of diverse cyclins and cyclin-dependent kinases was problematic. Secondly, our procedure for generating mitotically synchronized pea root meristems for biochemical studies was far too labor intensive for the proposed experiments. We therefore shifted our objectives to identifying connections between the conserved proteins of the cell cycle engine and factors that interface it with plant physiology and development. In this, we have obtained some very exciting results.

  13. Division of shape-standardized tobacco cells reveals a limit to the occurrence of single-criterion-based selection of the plane of symmetric division.

    PubMed

    Asada, Tetsuhiro

    2013-06-01

    The plane of symmetric plant cell division tends to be selected so that the new cross-wall halving the cell volume has the least possible area, and several cases of such selection are best represented by a recently formulated model which promotes the view that the strength of the least area tendency is the only criterion for selecting the plane. To test this model, the present study examined the divisions of two types of shape-standardized tobacco BY-2 cell, oblate-spheroidal (os) cells prepared from protoplasts and spheri-cylindrical (sc) cells with unusual double-wall structures prepared from plasmolyzed cells. Measurements of cell shape parameters and division angles revealed that both cell types most frequently divide nearly along their short axes. While os cells did not exhibit any other division angle bias, sc cell division was characterized by another bias which made the frequency of longitudinal divisions secondarily high. The geometry of sc cells barely allows the longitudinal cross-walls to have locally minimum areas. Nevertheless, a comparison of detected and hypothetical standard divisions indicates that the frequency of longitudinal sc cell division can be significantly higher than that predicted when the longitudinal cross-walls are assumed to have locally minimum areas smaller than their original areas. These results suggest that, even in isolated plant cell types, the strength of the least area tendency is not the only criterion for selecting the division plane. The possibility that there is another basic, though often hidden, criterion is discussed.

  14. From HeLa cell division to infectious diarrhoea

    SciTech Connect

    Stephen, J.; Osborne, M.P.; Spencer, A.J.; Warley, A. )

    1990-09-01

    Hela S3 cells were grown in suspension both randomly and, synchronously using hydroxyurea which blocks cells at the G1/S interface. Cryosections were prepared, freeze-dried and analyzed by X-ray microanalysis. As cells moved into S and through M phases (Na) and (Cl) increased; both returned to normal levels upon re-entering G1 phase. The Na/K ratio was 1:1 in G1 phase. Infection of HeLa S3 cells in G1 phase with vaccinia virus resulted in no change in intracellular (Na). Infection of neonatal mice with murine rotavirus was localized to villus tip enterocytes and gave rise to diarrhoea which was maximal at 72h post-infection (p.i.). Diarrhoea was preceded by ischemia of villi (18-42h p.i.) and villus shortening (maximal at 42h p.i.), and was also coincident with a dramatic regrowth of villi. At 48h p.i. a proliferative zone of electron lucent cells was observed in villus base regions. Cryosections of infected gut, taken before, during, and after infection, together with corresponding age-matched controls, were freeze-dried and analysed by X-ray microanalysis. At 48h p.i. electron lucent villus base cells were shown to be more hydrated, and, to contain higher levels of both Na and Cl and lower levels of P, S, K and Mg than corresponding control cells. These studies increase confidence in the use of X-ray microanalysis in studying biological systems, provide some insight into the process of cell division, and constitute the basis of a new concept of diarrhoeal secretion.27 references.

  15. Addiction toxin Fst has unique effects on chromosome segregation and cell division in Enterococcus faecalis and Bacillus subtilis.

    PubMed

    Patel, S; Weaver, K E

    2006-08-01

    The Fst toxin of the Enterococcus faecalis pAD1-encoded par addiction module functions intracellularly to kill plasmid-free segregants. Previous results had shown that Fst induction results in membrane permeabilization and cessation of macromolecular synthesis, but only after 45 min. Electron micrographs of toxin-induced cells showed no obvious membrane abnormalities but did reveal defects in nucleoid segregation and cell division, begging the question of which is the primary effect of Fst. To distinguish the possibilities, division septae and nucleoids were visualized simultaneously with fluorescent vancomycin and a variety of DNA stains. Results showed that division and segregation defects occurred in some cells within 15 min after induction. At these early time points, affected cells remained resistant to membrane-impermeant DNA stains, suggesting that loss of membrane integrity is a secondary effect caused by ongoing division and/or segregation defects. Fst-resistant mutants showed greater variability in cell length and formed multiple septal rings even in the absence of Fst. Fst induction was also toxic to Bacillus subtilis. In this species, Fst induction caused only minor division abnormalities, but all cells showed a condensation of the nucleoid, suggesting that effects on the structure of the chromosomal DNA might be paramount.

  16. SOS-independent coupling between DNA replication and cell division in Escherichia coli.

    PubMed Central

    Jaffé, A; D'Ari, R; Norris, V

    1986-01-01

    Inhibition of DNA synthesis in Escherichia coli mutants in which the SOS-dependent division inhibitors SfiA and SfiC were unable to operate led to a partial arrest of cell division. This SOS-independent mechanism coupling DNA replication and cell division was characterized with respect to residual division, particle number, and DNA content. Whether DNA replication was blocked in the initiation or the elongation step, numerous normal-sized anucleate cells were produced (not minicells or filaments). Their production was used to evaluate the efficiency of this coupling mechanism, which seems to involve the cell division protein FtsZ (SulB), also known to be the target of the division inhibitors SfiA and SfiC. In the absence of DNA synthesis, the efficiency of coupling was modulated by the cyclic-AMP-cyclic-AMP receptor protein complex, which was required for anucleate cell production. Images PMID:3001034

  17. Physical Description of Mitotic Spindle Orientation During Cell Division

    NASA Astrophysics Data System (ADS)

    Jiménez-Dalmaroni, Andrea; Théry, Manuel; Racine, Victor; Bornens, Michel; Jülicher, Frank

    2009-03-01

    During cell division, the duplicated chromosomes are physically separated by the action of the mitotic spindle. The spindle is a dynamic structure of the cytoskeleton, which consists of two microtubule asters. Its orientation defines the axis along which the cell divides. Recent experiments show that the spindle orientation depends on the spatial distribution of cell adhesion sites. Here we show that the experimentally observed spindle orientation can be understood as the result of the action of cortical force generators acting on the spindle. We assume that the local activity of force generators is controlled by the spatial distribution of cell adhesion sites determined by the particular geometry of the adhesive substrate. We develop a simple physical description of the spindle mechanics, which allows us to calculate the torque acting on the spindle, as well as the energy profile and the angular distribution of spindle orientation. Our model accounts for the preferred spindle orientation, as well as the full shape of the angular distributions of spindle orientation observed in a large variety of pattern geometries. M. Th'ery, A. Jim'enez-Dalmaroni, et al., Nature 447, 493 (2007).

  18. Growth, Cell Division, and Fragmentation in a Species of Flexibacter

    PubMed Central

    Poos, Jocelyn C.; Turner, F. Rudolf; White, David; Simon, Gary D.; Bacon, Karen; Russell, Carl T.

    1972-01-01

    Flexibacter FS-1, a gram-negative gliding bacterium was grown in liquid culture as long (over 100-μm) filaments. The filaments possessed a triple-track wall which resembled that found in other gram-negative bacteria. Although phase-contrast microscopy indicated that the long filaments were nonseptate, electron microscopy revealed three or four septa along the length of each filament. The septa contained lysozyme-sensitive, electron-opaque material, presumed to be peptidoglycan, sandwiched between cell membranes. The outer triple track wall was not part of the septum. Mesosomes were seen in various areas of the cell and frequently were observed attached to septa in different stages of completion. Studies of the organism in slide culture revealed that individual filaments grew in an exponential fashion and divided in the middle despite the long length and multiseptate condition. When the temperature of a liquid culture growing exponentially with a generation time of 90 minutes was shifted from 30 to 35 C, the filaments fragmented into three or four shorter cells within 120 min. The short cells continued to grow exponentially at 35 C at approximately the same rate as at 30 C. When the culture was shifted back to 30 C, the cells immediately stopped dividing and began to elongate. After a period of 2 to 3 hr, cell division resumed. It is suggested that the shift-up in temperature induced the completion of the cross wall (centripetal growth of the triple-track wall) and cell separation at the sites of previously formed septa, whereas the shift-down in temperature caused a transient inhibition of cross-wall formation but not of growth. Fragmentation was inhibited by sodium azide but took place despite the inhibition of protein synthesis by chloramphenicol or the inhibition of deoxyribonucleic acid synthesis by mitomycin C. Images PMID:4118297

  19. Novel insights into mammalian embryonic neural stem cell division: focus on microtubules.

    PubMed

    Mora-Bermúdez, Felipe; Huttner, Wieland B

    2015-12-01

    During stem cell divisions, mitotic microtubules do more than just segregate the chromosomes. They also determine whether a cell divides virtually symmetrically or asymmetrically by establishing spindle orientation and the plane of cell division. This can be decisive for the fate of the stem cell progeny. Spindle defects have been linked to neurodevelopmental disorders, yet the role of spindle orientation for mammalian neurogenesis has remained controversial. Here we explore recent advances in understanding how the microtubule cytoskeleton influences mammalian neural stem cell division. Our focus is primarily on the role of spindle microtubules in the development of the cerebral cortex. We also highlight unique characteristics in the architecture and dynamics of cortical stem cells that are tightly linked to their mode of division. These features contribute to setting these cells apart as mitotic "rule breakers," control how asymmetric a division is, and, we argue, are sufficient to determine the fate of the neural stem cell progeny in mammals.

  20. Single-Cell Analysis of Growth and Cell Division of the Anaerobe Desulfovibrio vulgaris Hildenborough.

    PubMed

    Fievet, Anouchka; Ducret, Adrien; Mignot, Tâm; Valette, Odile; Robert, Lydia; Pardoux, Romain; Dolla, Alain R; Aubert, Corinne

    2015-01-01

    Recent years have seen significant progress in understanding basic bacterial cell cycle properties such as cell growth and cell division. While characterization and regulation of bacterial cell cycle is quite well-documented in the case of fast growing aerobic model organisms, no data has been so far reported for anaerobic bacteria. This lack of information in anaerobic microorganisms can mainly be explained by the absence of molecular and cellular tools such as single cell microscopy and fluorescent probes usable for anaerobes and essential to study cellular events and/or subcellular localization of the actors involved in cell cycle. In this study, single-cell microscopy has been adapted to study for the first time, in real time, the cell cycle of a bacterial anaerobe, Desulfovibrio vulgaris Hildenborough (DvH). This single-cell analysis provides mechanistic insights into the cell division cycle of DvH, which seems to be governed by the recently discussed so-called incremental model that generates remarkably homogeneous cell sizes. Furthermore, cell division was reversibly blocked during oxygen exposure. This may constitute a strategy for anaerobic cells to cope with transient exposure to oxygen that they may encounter in their natural environment, thereby contributing to their aerotolerance. This study lays the foundation for the first molecular, single-cell assay that will address factors that cannot otherwise be resolved in bulk assays and that will allow visualization of a wide range of molecular mechanisms within living anaerobic cells.

  1. Single-Cell Analysis of Growth and Cell Division of the Anaerobe Desulfovibrio vulgaris Hildenborough

    PubMed Central

    Fievet, Anouchka; Ducret, Adrien; Mignot, Tâm; Valette, Odile; Robert, Lydia; Pardoux, Romain; Dolla, Alain R.; Aubert, Corinne

    2015-01-01

    Recent years have seen significant progress in understanding basic bacterial cell cycle properties such as cell growth and cell division. While characterization and regulation of bacterial cell cycle is quite well-documented in the case of fast growing aerobic model organisms, no data has been so far reported for anaerobic bacteria. This lack of information in anaerobic microorganisms can mainly be explained by the absence of molecular and cellular tools such as single cell microscopy and fluorescent probes usable for anaerobes and essential to study cellular events and/or subcellular localization of the actors involved in cell cycle. In this study, single-cell microscopy has been adapted to study for the first time, in real time, the cell cycle of a bacterial anaerobe, Desulfovibrio vulgaris Hildenborough (DvH). This single-cell analysis provides mechanistic insights into the cell division cycle of DvH, which seems to be governed by the recently discussed so-called incremental model that generates remarkably homogeneous cell sizes. Furthermore, cell division was reversibly blocked during oxygen exposure. This may constitute a strategy for anaerobic cells to cope with transient exposure to oxygen that they may encounter in their natural environment, thereby contributing to their aerotolerance. This study lays the foundation for the first molecular, single-cell assay that will address factors that cannot otherwise be resolved in bulk assays and that will allow visualization of a wide range of molecular mechanisms within living anaerobic cells. PMID:26696987

  2. Transmission of persistent ionizing radiation-induced foci through cell division in human primary cells.

    PubMed

    Vaurijoux, Aurelie; Voisin, Pascale; Freneau, Amelie; Barquinero, Joan Francesc; Gruel, Gaetan

    2017-03-10

    Unrepaired DNA double-strand breaks (DSBs) induced by ionizing radiation are associated with lethal effects and genomic instability. After the initial breaks and chromatin destabilization, a set of post-translational modifications of histones occurs, including phosphorylation of serine 139 of histone H2AX (γH2AX), which leads to the formation of ionizing radiation-induced foci (IRIF). DSB repair results in the disappearance of most IRIF within hours after exposure, although some remain 24h after irradiation. Their relation to unrepaired DSBs is generally accepted but still controversial. This study evaluates the frequency and kinetics of persistent IRIF and analyzes their impact on cell proliferation. We observed persistent IRIF up to 7 days postirradiation, and more than 70% of cells exposed to 5Gy had at least one of these persistent IRIF 24h after exposure. Moreover we demonstrated that persistent IRIF did not block cell proliferation definitively. The frequency of IRIF was lower in daughter cells, due to asymmetric distribution of IRIF between some of them. We report a positive association between the presence of IRIF and the likelihood of DNA missegregation. Hence, the structure formed after the passage of a persistent IRI focus across the S and G2 phases may impede the correct segregation of the affected chromosome's sister chromatids. The ensuing abnormal resolution of anaphase might therefore cause the nature of IRIF in daughter-cell nuclei to differ before and after the first cell division. The resulting atypical chromosomal assembly may be lethal or result in a gene dosage imbalance and possibly enhanced genomic instability, in particular in the daughter cells.

  3. Fruit illumination stimulates cell division but has no detectable effect on fruit size in tomato (Solanum lycopersicum).

    PubMed

    Okello, Robert C O; Heuvelink, Ep; de Visser, Pieter H B; Lammers, Michiel; de Maagd, Ruud A; Marcelis, Leo F M; Struik, Paul C

    2015-05-01

    Light affects plant growth through assimilate availability and signals regulating development. The effects of light on growth of tomato fruit were studied using cuvettes with light-emitting diodes providing white, red or blue light to individual tomato trusses for different periods during daytime. Hypotheses tested were as follows: (1) light-grown fruits have stronger assimilate sinks than dark-grown fruits, and (2) responses depend on light treatment provided, and fruit development stage. Seven light treatments [dark, 12-h white, 24-h white, 24-h red and 24-h blue light, dark in the first 24 days after anthesis (DAA) followed by 24-h white light until breaker stage, and its reverse] were applied. Observations were made between anthesis and breaker stage at fruit, cell and gene levels. Fruit size and carbohydrate content did not respond to light treatments while cell division was strongly stimulated at the expense of cell expansion by light. The effects of light on cell number and volume were independent of the combination of light color and intensity. Increased cell division and decreased cell volume when fruits were grown in the presence of light were not clearly corroborated by the expression pattern of promoters and inhibitors of cell division and expansion analyzed in this study, implying a strong effect of posttranscriptional regulation. Results suggest the existence of a complex homeostatic regulatory system for fruit growth in which reduced cell division is compensated by enhanced cell expansion.

  4. Cell cycle and centromere FISH studies in premature centromere division

    PubMed Central

    Corona-Rivera, Alfredo; Salamanca-Gomez, Fabio; Bobadilla-Morales, Lucina; Corona-Rivera, Jorge R; Palomino-Cueva, Cesar; Garcia-Cobian, Teresa A; Corona-Rivera, Enrique

    2005-01-01

    Background Mitotic configurations consistent in split centromeres and splayed chromatids in all or most of the chromosomes or premature centromere division (PCD) have been described in three categories. (1) Low frequency of PCD observed in colchicines-treated lymphocyte cultures from normal individuals. (2) High frequency of PCD with mosaic variegated aneuploidy. (3) High frequency of PCD as a sole chromosome abnormality observed in individuals with no recognizable clinical pattern. We report four members of a family with the third category of PCD. Methods Cell cycle duration assessed by average generation time using differential sister chromatid stain analysis and FISH studies of DNA centromere sequences in PCD individuals, are included and compared with previously reported PCD individuals from 9 families. Results We observed PCD in colchicine-treated cultures from the propositus, his father, and two paternal aunts but not in his mother and four other paternal and maternal family members, as well as in untreated cultures from the propositus and his father. We observed cytological evidence of active centromeres by Cd stain. Significative cell cycle time reduction in anaphases of PCD individuals (average generation time of 21.8 h;SD 0.4) with respect to individuals without PCD (average generation time of 31.8 h;SD 3.9) was observed (P < 0.005, Student t-test for independent samples). Increased cell proliferation kinetics was observed in anaphasic cells of individuals with PCD, by differential sister chromatid stain analysis. FISH studies revealed the presence of alpha satellite DNA from chromosomes 1, 13, 21/18, X, all centromeres, and CENP-B box sequences in metaphasic and anaphasic cells from PCD individuals. Conclusion This report examines evidences of a functional relationship between PCD and cell cycle impairment. It seems that essential centromere integrity is present in these cases. PMID:16174301

  5. Stochastic modeling of cell growth with symmetric or asymmetric division

    NASA Astrophysics Data System (ADS)

    Marantan, Andrew; Amir, Ariel

    2016-07-01

    We consider a class of biologically motivated stochastic processes in which a unicellular organism divides its resources (volume or damaged proteins, in particular) symmetrically or asymmetrically between its progeny. Assuming the final amount of the resource is controlled by a growth policy and subject to additive and multiplicative noise, we derive the recursive integral equation describing the evolution of the resource distribution over subsequent generations and use it to study the properties of stable resource distributions. We find conditions under which a unique stable resource distribution exists and calculate its moments for the class of affine linear growth policies. Moreover, we apply an asymptotic analysis to elucidate the conditions under which the stable distribution (when it exists) has a power-law tail. Finally, we use the results of this asymptotic analysis along with the moment equations to draw a stability phase diagram for the system that reveals the counterintuitive result that asymmetry serves to increase stability while at the same time widening the stable distribution. We also briefly discuss how cells can divide damaged proteins asymmetrically between their progeny as a form of damage control. In the appendixes, motivated by the asymmetric division of cell volume in Saccharomyces cerevisiae, we extend our results to the case wherein mother and daughter cells follow different growth policies.

  6. Cell contacts orient some cell division axes in the Caenorhabditis elegans embryo

    PubMed Central

    1995-01-01

    Cells of the early Caenorhabditis elegans embryo divide in an invariant pattern. Here I show that the division axes of some early cells (EMS and E) are controlled by specific cell-cell contacts (EMS-P2 or E-P3 contact). Altering the orientation of contact between these cells alters the axis along which the mitotic spindle is established, and hence the orientation of cell division. Contact-dependent mitotic spindle orientation appears to work by establishing a site of the type described by Hyman and White (1987. J. Cell Biol. 105:2123-2135) in the cortex of the responding cell: one centrosome moves toward the site of cell-cell contact during centrosome rotation in both intact embryos and reoriented cell pairs. The effect is especially apparent when two donor cells are placed on one side of the responding cell: both centrosomes are "captured," pulling the nucleus to one side of the cell. No centrosome rotation occurs in the absence of cell-cell contact, nor in nocodazole-treated cell pairs. The results suggest that some of the cortical sites described by Hyman and White are established cell autonomously (in P1, P2, and P3), and some are established by cell-cell contact (in EMS and E). Additional evidence presented here suggests that in the EMS cell, contact-dependent spindle orientation ensures a cleavage plane that will partition developmental information, received by induction, to one of EMS's daughter cells. PMID:7744956

  7. Host actin polymerization tunes the cell division cycle of an intracellular pathogen.

    PubMed

    Siegrist, M Sloan; Aditham, Arjun K; Espaillat, Akbar; Cameron, Todd A; Whiteside, Sarah A; Cava, Felipe; Portnoy, Daniel A; Bertozzi, Carolyn R

    2015-04-28

    Growth and division are two of the most fundamental capabilities of a bacterial cell. While they are well described for model organisms growing in broth culture, very little is known about the cell division cycle of bacteria replicating in more complex environments. Using a D-alanine reporter strategy, we found that intracellular Listeria monocytogenes (Lm) spend a smaller proportion of their cell cycle dividing compared to Lm growing in broth culture. This alteration to the cell division cycle is independent of bacterial doubling time. Instead, polymerization of host-derived actin at the bacterial cell surface extends the non-dividing elongation period and compresses the division period. By decreasing the relative proportion of dividing Lm, actin polymerization biases the population toward cells with the highest propensity to form actin tails. Thus, there is a positive-feedback loop between the Lm cell division cycle and a physical interaction with the host cytoskeleton.

  8. Mammalian aPKC/Par polarity complex mediated regulation of epithelial division orientation and cell fate

    SciTech Connect

    Vorhagen, Susanne; Niessen, Carien M.

    2014-11-01

    Oriented cell division is a key regulator of tissue architecture and crucial for morphogenesis and homeostasis. Balanced regulation of proliferation and differentiation is an essential property of tissues not only to drive morphogenesis but also to maintain and restore homeostasis. In many tissues orientation of cell division is coupled to the regulation of differentiation producing daughters with similar (symmetric cell division, SCD) or differential fate (asymmetric cell division, ACD). This allows the organism to generate cell lineage diversity from a small pool of stem and progenitor cells. Division orientation and/or the ratio of ACD/SCD need to be tightly controlled. Loss of orientation or an altered ratio can promote overgrowth, alter tissue architecture and induce aberrant differentiation, and have been linked to morphogenetic diseases, cancer and aging. A key requirement for oriented division is the presence of a polarity axis, which can be established through cell intrinsic and/or extrinsic signals. Polarity proteins translate such internal and external cues to drive polarization. In this review we will focus on the role of the polarity complex aPKC/Par3/Par6 in the regulation of division orientation and cell fate in different mammalian epithelia. We will compare the conserved function of this complex in mitotic spindle orientation and distribution of cell fate determinants and highlight common and differential mechanisms in which this complex is used by tissues to adapt division orientation and cell fate to the specific properties of the epithelium.

  9. Mammalian aPKC/Par polarity complex mediated regulation of epithelial division orientation and cell fate.

    PubMed

    Vorhagen, Susanne; Niessen, Carien M

    2014-11-01

    Oriented cell division is a key regulator of tissue architecture and crucial for morphogenesis and homeostasis. Balanced regulation of proliferation and differentiation is an essential property of tissues not only to drive morphogenesis but also to maintain and restore homeostasis. In many tissues orientation of cell division is coupled to the regulation of differentiation producing daughters with similar (symmetric cell division, SCD) or differential fate (asymmetric cell division, ACD). This allows the organism to generate cell lineage diversity from a small pool of stem and progenitor cells. Division orientation and/or the ratio of ACD/SCD need to be tightly controlled. Loss of orientation or an altered ratio can promote overgrowth, alter tissue architecture and induce aberrant differentiation, and have been linked to morphogenetic diseases, cancer and aging. A key requirement for oriented division is the presence of a polarity axis, which can be established through cell intrinsic and/or extrinsic signals. Polarity proteins translate such internal and external cues to drive polarization. In this review we will focus on the role of the polarity complex aPKC/Par3/Par6 in the regulation of division orientation and cell fate in different mammalian epithelia. We will compare the conserved function of this complex in mitotic spindle orientation and distribution of cell fate determinants and highlight common and differential mechanisms in which this complex is used by tissues to adapt division orientation and cell fate to the specific properties of the epithelium.

  10. Uncovering the link between malfunctions in Drosophila neuroblast asymmetric cell division and tumorigenesis

    PubMed Central

    2012-01-01

    Asymmetric cell division is a developmental process utilized by several organisms. On the most basic level, an asymmetric division produces two daughter cells, each possessing a different identity or fate. Drosophila melanogaster progenitor cells, referred to as neuroblasts, undergo asymmetric division to produce a daughter neuroblast and another cell known as a ganglion mother cell (GMC). There are several features of asymmetric division in Drosophila that make it a very complex process, and these aspects will be discussed at length. The cell fate determinants that play a role in specifying daughter cell fate, as well as the mechanisms behind setting up cortical polarity within neuroblasts, have proved to be essential to ensuring that neurogenesis occurs properly. The role that mitotic spindle orientation plays in coordinating asymmetric division, as well as how cell cycle regulators influence asymmetric division machinery, will also be addressed. Most significantly, malfunctions during asymmetric cell division have shown to be causally linked with neoplastic growth and tumor formation. Therefore, it is imperative that the developmental repercussions as a result of asymmetric cell division gone awry be understood. PMID:23151376

  11. Differences in Cell Division Rates Drive the Evolution of Terminal Differentiation in Microbes

    PubMed Central

    Matias Rodrigues, João F.; Rankin, Daniel J.; Rossetti, Valentina; Wagner, Andreas; Bagheri, Homayoun C.

    2012-01-01

    Multicellular differentiated organisms are composed of cells that begin by developing from a single pluripotent germ cell. In many organisms, a proportion of cells differentiate into specialized somatic cells. Whether these cells lose their pluripotency or are able to reverse their differentiated state has important consequences. Reversibly differentiated cells can potentially regenerate parts of an organism and allow reproduction through fragmentation. In many organisms, however, somatic differentiation is terminal, thereby restricting the developmental paths to reproduction. The reason why terminal differentiation is a common developmental strategy remains unexplored. To understand the conditions that affect the evolution of terminal versus reversible differentiation, we developed a computational model inspired by differentiating cyanobacteria. We simulated the evolution of a population of two cell types –nitrogen fixing or photosynthetic– that exchange resources. The traits that control differentiation rates between cell types are allowed to evolve in the model. Although the topology of cell interactions and differentiation costs play a role in the evolution of terminal and reversible differentiation, the most important factor is the difference in division rates between cell types. Faster dividing cells always evolve to become the germ line. Our results explain why most multicellular differentiated cyanobacteria have terminally differentiated cells, while some have reversibly differentiated cells. We further observed that symbioses involving two cooperating lineages can evolve under conditions where aggregate size, connectivity, and differentiation costs are high. This may explain why plants engage in symbiotic interactions with diazotrophic bacteria. PMID:22511858

  12. Splitting the cell, building the organism: Mechanisms of cell division in metazoan embryos.

    PubMed

    Kumar, Megha; Pushpa, Kumari; Mylavarapu, Sivaram V S

    2015-07-01

    The unicellular metazoan zygote undergoes a series of cell divisions that are central to its development into an embryo. Differentiation of embryonic cells leads eventually to the development of a functional adult. Fate specification of pluripotent embryonic cells occurs during the early embryonic cleavage divisions in several animals. Early development is characterized by well-known stages of embryogenesis documented across animals--morulation, blastulation, and morphogenetic processes such as gastrulation, all of which contribute to differentiation and tissue specification. Despite this broad conservation, there exist clearly discernible morphological and functional differences across early embryonic stages in metazoans. Variations in the mitotic mechanisms of early embryonic cell divisions play key roles in governing these gross differences that eventually encode developmental patterns. In this review, we discuss molecular mechanisms of both karyokinesis (nuclear division) and cytokinesis (cytoplasmic separation) during early embryonic divisions. We outline the broadly conserved molecular pathways that operate in these two stages in early embryonic mitoses. In addition, we highlight mechanistic variations in these two stages across different organisms. We finally discuss outstanding questions of interest, answers to which would illuminate the role of divergent mitotic mechanisms in shaping early animal embryogenesis.

  13. Segrosome Complex Formation during DNA Trafficking in Bacterial Cell Division.

    PubMed

    Oliva, María A

    2016-01-01

    Bacterial extrachromosomal DNAs often contribute to virulence in pathogenic organisms or facilitate adaptation to particular environments. The transmission of genetic information from one generation to the next requires sufficient partitioning of DNA molecules to ensure that at least one copy reaches each side of the division plane and is inherited by the daughter cells. Segregation of the bacterial chromosome occurs during or after replication and probably involves a strategy in which several protein complexes participate to modify the folding pattern and distribution first of the origin domain and then of the rest of the chromosome. Low-copy number plasmids rely on specialized partitioning systems, which in some cases use a mechanism that show striking similarity to eukaryotic DNA segregation. Overall, there have been multiple systems implicated in the dynamic transport of DNA cargo to a new cellular position during the cell cycle but most seem to share a common initial DNA partitioning step, involving the formation of a nucleoprotein complex called the segrosome. The particular features and complex topologies of individual segrosomes depend on both the nature of the DNA binding protein involved and on the recognized centromeric DNA sequence, both of which vary across systems. The combination of in vivo and in vitro approaches, with structural biology has significantly furthered our understanding of the mechanisms underlying DNA trafficking in bacteria. Here, I discuss recent advances and the molecular details of the DNA segregation machinery, focusing on the formation of the segrosome complex.

  14. Probabilistic Model of Microbial Cell Growth, Division, and Mortality ▿

    PubMed Central

    Horowitz, Joseph; Normand, Mark D.; Corradini, Maria G.; Peleg, Micha

    2010-01-01

    After a short time interval of length δt during microbial growth, an individual cell can be found to be divided with probability Pd(t)δt, dead with probability Pm(t)δt, or alive but undivided with the probability 1 − [Pd(t) + Pm(t)]δt, where t is time, Pd(t) expresses the probability of division for an individual cell per unit of time, and Pm(t) expresses the probability of mortality per unit of time. These probabilities may change with the state of the population and the habitat's properties and are therefore functions of time. This scenario translates into a model that is presented in stochastic and deterministic versions. The first, a stochastic process model, monitors the fates of individual cells and determines cell numbers. It is particularly suitable for small populations such as those that may exist in the case of casual contamination of a food by a pathogen. The second, which can be regarded as a large-population limit of the stochastic model, is a continuous mathematical expression that describes the population's size as a function of time. It is suitable for large microbial populations such as those present in unprocessed foods. Exponential or logistic growth with or without lag, inactivation with or without a “shoulder,” and transitions between growth and inactivation are all manifestations of the underlying probability structure of the model. With temperature-dependent parameters, the model can be used to simulate nonisothermal growth and inactivation patterns. The same concept applies to other factors that promote or inhibit microorganisms, such as pH and the presence of antimicrobials, etc. With Pd(t) and Pm(t) in the form of logistic functions, the model can simulate all commonly observed growth/mortality patterns. Estimates of the changing probability parameters can be obtained with both the stochastic and deterministic versions of the model, as demonstrated with simulated data. PMID:19915038

  15. Asymmetric Numb distribution is critical for asymmetric cell division of mouse cerebral cortical stem cells and neuroblasts.

    PubMed

    Shen, Qin; Zhong, Weimin; Jan, Yuh Nung; Temple, Sally

    2002-10-01

    Stem cells and neuroblasts derived from mouse embryos undergo repeated asymmetric cell divisions, generating neural lineage trees similar to those of invertebrates. In Drosophila, unequal distribution of Numb protein during mitosis produces asymmetric cell divisions and consequently diverse neural cell fates. We investigated whether a mouse homologue m-numb had a similar role during mouse cortical development. Progenitor cells isolated from the embryonic mouse cortex were followed as they underwent their next cell division in vitro. Numb distribution was predominantly asymmetric during asymmetric cell divisions yielding a beta-tubulin III(-) progenitor and a beta-tubulin III(+) neuronal cell (P/N divisions) and predominantly symmetric during divisions producing two neurons (N/N divisions). Cells from the numb knockout mouse underwent significantly fewer asymmetric P/N divisions compared to wild type, indicating a causal role for Numb. When progenitor cells derived from early (E10) cortex undergo P/N divisions, both daughters express the progenitor marker Nestin, indicating their immature state, and Numb segregates into the P or N daughter with similar frequency. In contrast, when progenitor cells derived from later E13 cortex (during active neurogenesis in vivo) undergo P/N divisions they produce a Nestin(+) progenitor and a Nestin(-) neuronal daughter, and Numb segregates preferentially into the neuronal daughter. Thus during mouse cortical neurogenesis, as in Drosophila neurogenesis, asymmetric segregation of Numb could inhibit Notch activity in one daughter to induce neuronal differentiation. At terminal divisions generating two neurons, Numb was symmetrically distributed in approximately 80% of pairs and asymmetrically in 20%. We found a significant association between Numb distribution and morphology: most sisters of neuron pairs with symmetric Numb were similar and most with asymmetric Numb were different. Developing cortical neurons with Numb had longer

  16. Teaching Cell Division to Secondary School Students: An Investigation of Difficulties Experienced by Turkish Teachers

    ERIC Educational Resources Information Center

    Oztap, Haydar; Ozay, Esra; Oztap, Fulya

    2003-01-01

    This study examines the difficulties biology teachers face when teaching cell division in the secondary schools of the central part of the Erzurum province in Turkey. During this research, a questionnaire was distributed to a total of 36 secondary school biology teachers. Findings of the study indicate biology teachers perceive cell division as…

  17. Termination of DNA replication is required for cell division in Escherichia coli.

    PubMed Central

    Grossman, N; Rosner, E; Ron, E Z

    1989-01-01

    The correlation between termination of DNA replication and cell division in Escherichia coli was studied under conditions in which DNA replication was slowed down without inducing SOS functions. The experimental system used involved amino acid starvation of synchronized cells in the presence of methionine. The results further support the essential correlation between termination of DNA replication and initiation of division processes. PMID:2644214

  18. Matrix metalloproteinase-9 and cell division in neuroblastoma cells and bone marrow macrophages.

    PubMed

    Sans-Fons, M Gloria; Sole, Sonia; Sanfeliu, Coral; Planas, Anna M

    2010-12-01

    Matrix metalloproteinases (MMPs) degrade the extracellular matrix and carry out key functions in cell development, cancer, injury, and regeneration. In addition to its well recognized extracellular action, functional intracellular MMP activity under certain conditions is supported by increasing evidence. In this study, we observed higher gelatinase activity by in situ zymography and increased MMP-9 immunoreactivity in human neuroblastoma cells and in bone marrow macrophages undergoing mitosis compared with resting cells. We studied the pattern of immunoreactivity at the different stages of cell division by confocal microscopy. Immunostaining with different monoclonal antibodies against MMP-9 revealed a precise, dynamic, and well orchestrated localization of MMP-9 at the different stages of cell division. The cellular distribution of MMP-9 staining was studied in relation to that of microtubules. The spatial pattern of MMP-9 immunoreactivity suggested some participation in both the reorganization of the nuclear content and the process of chromatid segmentation. We then used several MMP-9 inhibitors to find out whether MMP-9 might be involved in the cell cycle. These drugs impaired the entry of cells into mitosis, as revealed by flow cytometry, and reduced cell culture growth. In addition, the silencing of MMP-9 expression with small interfering RNA also reduced cell growth. Taken together, these results suggest that intracellular MMP-9 is involved in the process of cell division in neuroblastoma cells and in primary cultures of macrophages.

  19. Response of potato tuber cell division and growth to shade and elevated CO2.

    PubMed

    Chen, Chien-Teh; Setter, Tim L

    2003-02-01

    Plants adjust their sink-organ growth rates, development and distribution of dry matter in response to whole-plant photosynthate status. To advance understanding of these processes, potato (Solanum tuberosum L.) plants were subjected to CO(2) and light flux treatments, and early tuber growth was assessed. Atmospheric CO(2) (700 or 350 micro mol mol(-1)) and light flux (shade and control illumination) treatments were imposed at two growth stages: tuber initiation (TI) and tuber bulking (TB). Elevated CO(2) increased accumulation of total net biomass when imposed at both stages, and increased tuber growth rate by about 36 %, but did not increase the number of tubers. Elevated CO(2) increased the number of cells in tubers at both TI and TB stages, whereas shade substantially decreased the number of cells at both stages. Generally, treatments did not affect cell volume or the proportion of nuclei endoreduplicating (repeated nuclear DNA replication in the absence of cell division), but the shade treatment led to a decrease in cell volume at TB and a decrease in endoreduplication at TI. Elevated CO(2) increased, and shade decreased, glucose concentration and soluble invertase activity in the cambial zones at both TI and TB, whereas sucrose concentration and activities of glucokinase, fructokinase, cell-wall-bound invertase and thymidine kinase were unaffected. Modulation of tuber cell division was responsible for much of the growth response to whole-plant photosynthate status, and treatments affected cambial-zone glucose and soluble invertase in a pattern suggesting involvement of a glucose signalling pathway.

  20. Acentrosomal Drosophila epithelial cells exhibit abnormal cell division, leading to cell death and compensatory proliferation

    PubMed Central

    Poulton, John S; Cuningham, John C; Peifer, Mark

    2014-01-01

    Summary Mitotic spindles are critical for accurate chromosome segregation. Centrosomes, the primary microtubule nucleating centers of animal cells, play key roles in forming and orienting mitotic spindles. However, the survival of Drosophila without centrosomes suggested they are dispensable in somatic cells, challenging the canonical view. We used fly wing disc epithelia as a model to resolve these conflicting hypotheses, revealing that centrosomes play vital roles in spindle assembly, function, and orientation. Many acentrosomal cells exhibit prolonged spindle assembly, chromosome mis-segregation, DNA damage, misoriented divisions, and eventual apoptosis. We found that multiple mechanisms buffer the effects of centrosome loss, including alternative microtubule nucleation pathways and the Spindle Assembly Checkpoint. Apoptosis of acentrosomal cells is mediated by JNK signaling, which also drives compensatory proliferation to maintain tissue integrity and viability. These data reveal the importance of centrosomes in fly epithelia, but also demonstrate the robust compensatory mechanisms at the cellular and organismal level. PMID:25241934

  1. Highly Deviated Asymmetric Division in Very Low Proportion of Mycobacterial Mid-log Phase Cells.

    PubMed

    Vijay, Srinivasan; Mukkayyan, Nagaraja; Ajitkumar, Parthasarathi

    2014-01-01

    In this study, we show that about 20% of the septating Mycobacterium smegmatis and Mycobacterium xenopi cells in the exponential phase populationdivideasymmetrically, with an unusually high deviation (17 ± 4%) in the division site from the median, to generate short cells and long cells, thereby generating population heterogeneity. This mode of division is very different from the symmetric division of themajority (about 80%) of the septating cells in the Mycobacterium smegmatis, Mycobacterium marinum, and Mycobacterium bovis BCG exponential phase population, with 5-10% deviation in the division site from the mid-cell site, as reported by recent studies. The short cells and the long cells further grew and divided to generate a population. We speculate that the generation of the short cells and the long cells through the highly deviated asymmetric divisionin the low proportions of mycobacterial population may have a role in stress tolerance.

  2. A new class of cyclin dependent kinase in Chlamydomonas is required for coupling cell size to cell division.

    PubMed

    Li, Yubing; Liu, Dianyi; López-Paz, Cristina; Olson, Bradley Jsc; Umen, James G

    2016-03-25

    Proliferating cells actively control their size by mechanisms that are poorly understood. The unicellular green alga Chlamydomonas reinhardtii divides by multiple fission, wherein a 'counting' mechanism couples mother cell-size to cell division number allowing production of uniform-sized daughters. We identified a sizer protein, CDKG1, that acts through the retinoblastoma (RB) tumor suppressor pathway as a D-cyclin-dependent RB kinase to regulate mitotic counting. Loss of CDKG1 leads to fewer mitotic divisions and large daughters, while mis-expression of CDKG1 causes supernumerous mitotic divisions and small daughters. The concentration of nuclear-localized CDKG1 in pre-mitotic cells is set by mother cell size, and its progressive dilution and degradation with each round of cell division may provide a link between mother cell-size and mitotic division number. Cell-size-dependent accumulation of limiting cell cycle regulators such as CDKG1 is a potentially general mechanism for size control.

  3. Cell division cycle 20 overexpression predicts poor prognosis for patients with lung adenocarcinoma.

    PubMed

    Shi, Run; Sun, Qi; Sun, Jing; Wang, Xin; Xia, Wenjie; Dong, Gaochao; Wang, Anpeng; Jiang, Feng; Xu, Lin

    2017-03-01

    The cell division cycle 20, a key component of spindle assembly checkpoint, is an essential activator of the anaphase-promoting complex. Aberrant expression of cell division cycle 20 has been detected in various human cancers. However, its clinical significance has never been deeply investigated in non-small-cell lung cancer. By analyzing The Cancer Genome Atlas database and using some certain online databases, we validated overexpression of cell division cycle 20 in both messenger RNA and protein levels, explored its clinical significance, and evaluated the prognostic role of cell division cycle 20 in non-small-cell lung cancer. Cell division cycle 20 expression was significantly correlated with sex (p = 0.003), histological classification (p < 0.0001), and tumor size (p = 0.0116) in non-small-cell lung cancer patients. In lung adenocarcinoma patients, overexpression of cell division cycle 20 was significantly associated with bigger primary tumor size (p = 0.0023), higher MKI67 level (r = 0.7618, p < 0.0001), higher DNA ploidy level (p < 0.0001), and poor prognosis (hazard ratio = 2.39, confidence interval: 1.87-3.05, p < 0.0001). However, in lung squamous cell carcinoma patients, no significant association of cell division cycle 20 expression was observed with any clinical parameter or prognosis. Overexpression of cell division cycle 20 is associated with poor prognosis in lung adenocarcinoma patients, and its overexpression can also be used to identify high-risk groups. In conclusion, cell division cycle 20 might serve as a potential biomarker for lung adenocarcinoma patients.

  4. The Synchronization of Replication and Division Cycles in Individual E. coli Cells.

    PubMed

    Wallden, Mats; Fange, David; Lundius, Ebba Gregorsson; Baltekin, Özden; Elf, Johan

    2016-07-28

    Isogenic E. coli cells growing in a constant environment display significant variability in growth rates, division sizes, and generation times. The guiding principle appears to be that each cell, during one generation, adds a size increment that is uncorrelated to its birth size. Here, we investigate the mechanisms underlying this "adder" behavior by mapping the chromosome replication cycle to the division cycle of individual cells using fluorescence microscopy. We have found that initiation of chromosome replication is triggered at a fixed volume per chromosome independent of a cell's birth volume and growth rate. Each initiation event is coupled to a division event after a growth-rate-dependent time. We formalize our findings in a model showing that cell-to-cell variation in division timing and cell size is mainly driven by variations in growth rate. The model also explains why fast-growing cells display adder behavior and correctly predict deviations from the adder behavior at slow growth.

  5. Specific polar subpopulations of astral microtubules control spindle orientation and symmetric neural stem cell division.

    PubMed

    Mora-Bermúdez, Felipe; Matsuzaki, Fumio; Huttner, Wieland B

    2014-07-04

    Mitotic spindle orientation is crucial for symmetric vs asymmetric cell division and depends on astral microtubules. Here, we show that distinct subpopulations of astral microtubules exist, which have differential functions in regulating spindle orientation and division symmetry. Specifically, in polarized stem cells of developing mouse neocortex, astral microtubules reaching the apical and basal cell cortex, but not those reaching the central cell cortex, are more abundant in symmetrically than asymmetrically dividing cells and reduce spindle orientation variability. This promotes symmetric divisions by maintaining an apico-basal cleavage plane. The greater abundance of apical/basal astrals depends on a higher concentration, at the basal cell cortex, of LGN, a known spindle-cell cortex linker. Furthermore, newly developed specific microtubule perturbations that selectively decrease apical/basal astrals recapitulate the symmetric-to-asymmetric division switch and suffice to increase neurogenesis in vivo. Thus, our study identifies a novel link between cell polarity, astral microtubules, and spindle orientation in morphogenesis.

  6. Positioning of polarity formation by extracellular signaling during asymmetric cell division.

    PubMed

    Seirin Lee, Sungrim

    2016-07-07

    Anterior-posterior (AP) polarity formation of cell membrane proteins plays a crucial role in determining cell asymmetry, which ultimately generates cell diversity. In Caenorhabditis elegans, a single fertilized egg cell (P0), its daughter cell (P1), and the germline precursors (P2 and P3 cells) form two exclusive domains of different PAR proteins on the membrane along the anterior-posterior axis. However, the phenomenon of polarity reversal has been observed in which the axis of asymmetric cell division of the P2 and P3 cells is formed in an opposite manner to that of the P0 and P1 cells. The extracellular signal MES-1/SRC-1 has been shown to induce polarity reversal, but the detailed mechanism remains elusive. Here, using a mathematical model, I explore the mechanism by which MES-1/SRC-1 signaling can induce polarity reversal and ultimately affect the process of polarity formation. I show that a positive correlation between SRC-1 and the on-rate of PAR-2 is the essential mechanism underlying polarity reversal, providing a mathematical basis for the orientation of cell polarity patterns.

  7. Identification and Characterization of a Mutation Affecting the Division Arrest Signaling of the Pheromone Response Pathway in Saccharomyces Cerevisiae

    PubMed Central

    Fujimura, H. A.

    1990-01-01

    Mating pheromones, a- and α-factors, arrest the division of cells of opposite mating types, α and a cells, respectively. I have isolated a sterile mutant of Saccharomyces cerevisiae that is defective in division arrest in response to α-factor but not defective in morphological changes and agglutinin induction. The mutation was designated dac2 for division arrest control by mating pheromones. The dac2 mutation was closely linked to gal1 and was different from the previously identified cell type nonspecific sterile mutations (ste4, ste5, ste7, ste11, ste12, ste18 and dac1). Although dac2 cells had no phenotype in the absence of pheromones, they showed morphological alterations and divided continuously in the presence of pheromones. As a result, dac2 cells had a mating defect. The dac2 mutation could suppress the lethality caused by the disruption of the GPA1 gene (previously shown to encode a protein with similarity to the α subunit of mammalian G proteins). In addition, dac2 cells formed prezygotes with wild-type cells of opposite mating types, although they could not undergo cell fusion. These results suggest that the DAC2 product may control the signal for G-protein-mediated cell-cycle arrest and indicate that the synchronization of haploid yeast cell cycles by mating pheromones is essential for cell fusion during conjugation. PMID:2407613

  8. The equatorial position of the metaphase plate ensures symmetric cell divisions.

    PubMed

    Tan, Chia Huei; Gasic, Ivana; Huber-Reggi, Sabina P; Dudka, Damian; Barisic, Marin; Maiato, Helder; Meraldi, Patrick

    2015-07-18

    Chromosome alignment in the middle of the bipolar spindle is a hallmark of metazoan cell divisions. When we offset the metaphase plate position by creating an asymmetric centriole distribution on each pole, we find that metaphase plates relocate to the middle of the spindle before anaphase. The spindle assembly checkpoint enables this centering mechanism by providing cells enough time to correct metaphase plate position. The checkpoint responds to unstable kinetochore-microtubule attachments resulting from an imbalance in microtubule stability between the two half-spindles in cells with an asymmetric centriole distribution. Inactivation of the checkpoint prior to metaphase plate centering leads to asymmetric cell divisions and daughter cells of unequal size; in contrast, if the checkpoint is inactivated after the metaphase plate has centered its position, symmetric cell divisions ensue. This indicates that the equatorial position of the metaphase plate is essential for symmetric cell divisions.

  9. A theory of germinal center B cell selection, division, and exit.

    PubMed

    Meyer-Hermann, Michael; Mohr, Elodie; Pelletier, Nadége; Zhang, Yang; Victora, Gabriel D; Toellner, Kai-Michael

    2012-07-26

    High-affinity antibodies are generated in germinal centers in a process involving mutation and selection of B cells. Information processing in germinal center reactions has been investigated in a number of recent experiments. These have revealed cell migration patterns, asymmetric cell divisions, and cell-cell interaction characteristics, used here to develop a theory of germinal center B cell selection, division, and exit (the LEDA model). According to this model, B cells selected by T follicular helper cells on the basis of successful antigen processing always return to the dark zone for asymmetric division, and acquired antigen is inherited by one daughter cell only. Antigen-retaining B cells differentiate to plasma cells and leave the germinal center through the dark zone. This theory has implications for the functioning of germinal centers because compared to previous models, high-affinity antibodies appear one day earlier and the amount of derived plasma cells is considerably larger.

  10. Growth-Arrest-Specific Protein 2 Inhibits Cell Division in Xenopus Embryos

    PubMed Central

    Zhang, Tong; Dayanandan, Bama; Rouiller, Isabelle; Lawrence, Elizabeth J.; Mandato, Craig A.

    2011-01-01

    Background Growth-arrest-specific 2 gene was originally identified in murine fibroblasts under growth arrest conditions. Furthermore, serum stimulation of quiescent, non-dividing cells leads to the down-regulation of gas2 and results in re-entry into the cell cycle. Cytoskeleton rearrangements are critical for cell cycle progression and cell division and the Gas2 protein has been shown to co-localize with actin and microtubules in interphase mammalian cells. Despite these findings, direct evidence supporting a role for Gas2 in the mechanism of cell division has not been reported. Methodology and Principal Findings To determine whether the Gas2 protein plays a role in cell division, we over-expressed the full-length Gas2 protein and Gas2 truncations containing either the actin-binding CH domain or the tubulin-binding Gas2 domain in Xenopus laevis embryos. We found that both the full-length Gas2 protein and the Gas2 domain, but not the CH domain, inhibited cell division and resulted in multinucleated cells. The observation that Gas2 domain alone can arrest cell division suggests that Gas2 function is mediated by microtubule binding. Gas2 co-localized with microtubules at the cell cortex of Gas2-injected Xenopus embryos using cryo-confocal microscopy and co-sedimented with microtubules in cytoskeleton co-sedimentation assays. To investigate the mechanism of Gas2-induced cell division arrest, we showed, using a wound-induced contractile array assay, that Gas2 stabilized microtubules. Finally, electron microscopy studies demonstrated that Gas2 bundled microtubules into higher-order structures. Conclusion and Significance Our experiments show that Gas2 inhibits cell division in Xenopus embryos. We propose that Gas2 function is mediated by binding and bundling microtubules, leading to cell division arrest. PMID:21931817

  11. A plant cell division algorithm based on cell biomechanics and ellipse-fitting

    PubMed Central

    Abera, Metadel K.; Verboven, Pieter; Defraeye, Thijs; Fanta, Solomon Workneh; Hertog, Maarten L. A. T. M.; Carmeliet, Jan; Nicolai, Bart M.

    2014-01-01

    Background and Aims The importance of cell division models in cellular pattern studies has been acknowledged since the 19th century. Most of the available models developed to date are limited to symmetric cell division with isotropic growth. Often, the actual growth of the cell wall is either not considered or is updated intermittently on a separate time scale to the mechanics. This study presents a generic algorithm that accounts for both symmetrically and asymmetrically dividing cells with isotropic and anisotropic growth. Actual growth of the cell wall is simulated simultaneously with the mechanics. Methods The cell is considered as a closed, thin-walled structure, maintained in tension by turgor pressure. The cell walls are represented as linear elastic elements that obey Hooke's law. Cell expansion is induced by turgor pressure acting on the yielding cell-wall material. A system of differential equations for the positions and velocities of the cell vertices as well as for the actual growth of the cell wall is established. Readiness to divide is determined based on cell size. An ellipse-fitting algorithm is used to determine the position and orientation of the dividing wall. The cell vertices, walls and cell connectivity are then updated and cell expansion resumes. Comparisons are made with experimental data from the literature. Key Results The generic plant cell division algorithm has been implemented successfully. It can handle both symmetrically and asymmetrically dividing cells coupled with isotropic and anisotropic growth modes. Development of the algorithm highlighted the importance of ellipse-fitting to produce randomness (biological variability) even in symmetrically dividing cells. Unlike previous models, a differential equation is formulated for the resting length of the cell wall to simulate actual biological growth and is solved simultaneously with the position and velocity of the vertices. Conclusions The algorithm presented can produce different

  12. Local 3D matrix confinement determines division axis through cell shape.

    PubMed

    He, Lijuan; Chen, Weitong; Wu, Pei-Hsun; Jimenez, Angela; Wong, Bin Sheng; San, Angela; Konstantopoulos, Konstantinos; Wirtz, Denis

    2016-02-09

    How the division axis is determined in mammalian cells embedded in three-dimensional (3D) matrices remains elusive, despite that many types of cells divide in 3D environments. Cells on two-dimensional (2D) substrates typically round up completely to divide. Here, we show that in 3D collagen matrices, mammalian cells such as HT1080 human fibrosarcoma and MDA-MB-231 breast cancer cells exhibit division modes distinct from their Counterparts on 2D substrates, with a markedly higher fraction of cells remaining highly elongated through mitosis in 3D matrices. The long axis of elongated mitotic cells accurately predicts the division axis, independently of matrix density and cell-matrix interactions. This 3D-specific elongated division mode is determined by the local confinement produced by the matrix and the ability of cells to protrude and locally remodel the matrix via β1 integrin. Elongated division is readily recapitulated using collagen-coated microfabricated channels. Cells depleted of β1 integrin still divide in the elongated mode in microchannels, suggesting that 3D confinement is sufficient to induce the elongated cell-division phenotype.

  13. Timing mechanism dependent on cell division is invoked by Polycomb eviction in plant stem cells.

    PubMed

    Sun, Bo; Looi, Liang-Sheng; Guo, Siyi; He, Zemiao; Gan, Eng-Seng; Huang, Jiangbo; Xu, Yifeng; Wee, Wan-Yi; Ito, Toshiro

    2014-01-31

    Plant floral stem cells divide a limited number of times before they stop and terminally differentiate, but the mechanisms that control this timing remain unclear. The precise temporal induction of the Arabidopsis zinc finger repressor KNUCKLES (KNU) is essential for the coordinated growth and differentiation of floral stem cells. We identify an epigenetic mechanism in which the floral homeotic protein AGAMOUS (AG) induces KNU at ~2 days of delay. AG binding sites colocalize with a Polycomb response element in the KNU upstream region. AG binding to the KNU promoter causes the eviction of the Polycomb group proteins from the locus, leading to cell division-dependent induction. These analyses demonstrate that floral stem cells measure developmental timing by a division-dependent epigenetic timer triggered by Polycomb eviction.

  14. [Expression of CD48 as a live marker to distinguish division of hematopoietic stem cells].

    PubMed

    Yang, Xin; Zhang, Yu; Peng, Lu-Yun; Pang, Ya-Kun; Dong, Fang; Ji, Qing; Xu, Jing; Cheng, Tao; Yuan, Wei-Ping; Gao, Ying-Dai

    2014-06-01

    Hematopoietic stem cells are capable of self-renewal or differentiation when they divide. Three types of cell divisions exist. A dividing stem cell may generate 2 new stem cells (symmetrical renewal division), or 2 differentiating cells (symmetrical differentiation division), or 1 cell of each type (asymmetrical division). This study was aimed to explore an efficient and stable method to distinguish the way of cell division in hematopoietic stem cells. Previous studies showed that the distribution of Numb in a cell could be used to distinguish the type of cell division in various kinds of cells. Therefore, the distribution of Numb protein was detected by immunofluorescence in mitotic CD48(-)CD150(+)LSK cells of mice exploring the relationship between Numb protein and centrosomes. Since CD48 positive marks the HSC that have lost the ability to reconstitute the blood system in mice, CD48 marker could be used to distinguish cell fate decision between self-renewal and differentiation as a living marker. In this study, the CD48(-)CD150(+)LSK cells were sorted from bone marrow cells of mice and the cells were directly labeled with Alexa Fluor (AF) 488-conjugated anti-CD48 antibody in living cultures. After 3 days, the percentage of AF488(+) cells was evaluated under microscope and by FACS. Then colony forming cell assay (CFC) was performed and the ability of cell proliferation were compared between AF488(+) and AF488(-) cells. The results showed that Numb could be used to distinguish different cell division types of hematopoietic stem cells, which was symmetrically or asymmetrically segregated in mitotic CD48(-)CD150(+)LSK cells. The self-labeled fluorochrome could be detected both by FACS as well as microscope. There were about 40% AF488(+) cells after 3 day-cultures in medium titrated with self-labeled AF 488-conjugated anti-CD48 antibody, and the results were consistent between confocal fluorescence microscopy and flow cytometry analysis. The colony forming ability of

  15. Pesticide Roundup provokes cell division dysfunction at the level of CDK1/cyclin B activation.

    PubMed

    Marc, Julie; Mulner-Lorillon, Odile; Boulben, Sandrine; Hureau, Dorothée; Durand, Gaël; Bellé, Robert

    2002-03-01

    To assess human health risk from environmental chemicals, we have studied the effect on cell cycle regulation of the widely used glyphosate-containing pesticide Roundup. As a model system we have used sea urchin embryonic first divisions following fertilization, which are appropriate for the study of universal cell cycle regulation without interference with transcription. We show that 0.8% Roundup (containing 8 mM glyphosate) induces a delay in the kinetic of the first cell cleavage of sea urchin embryos. The delay is dependent on the concentration of Roundup. The delay in the cell cycle could be induced using increasing glyphosate concentrations (1-10 mM) in the presence of a subthreshold concentration of Roundup 0.2%, while glyphosate alone was ineffective, thus indicating synergy between glyphosate and Roundup formulation products. The effect of Roundup was not lethal and involved a delay in entry into M-phase of the cell cycle, as judged cytologically. Since CDK1/cyclin B regulates universally the M-phase of the cell cycle, we analyzed CDK1/cyclin B activation during the first division of early development. Roundup delayed the activation of CDK1/cyclin B in vivo. Roundup inhibited also the global protein synthetic rate without preventing the accumulation of cyclin B. In summary, Roundup affects cell cycle regulation by delaying activation of the CDK1/cyclin B complex, by synergic effect of glyphosate and formulation products. Considering the universality among species of the CDK1/cyclin B regulator, our results question the safety of glyphosate and Roundup on human health.

  16. CyDiv, a Conserved and Novel Filamentous Cyanobacterial Cell Division Protein Involved in Septum Localization

    PubMed Central

    Mandakovic, Dinka; Trigo, Carla; Andrade, Derly; Riquelme, Brenda; Gómez-Lillo, Gabriela; Soto-Liebe, Katia; Díez, Beatriz; Vásquez, Mónica

    2016-01-01

    Cell division in bacteria has been studied mostly in Escherichia coli and Bacillus subtilis, model organisms for Gram-negative and Gram-positive bacteria, respectively. However, cell division in filamentous cyanobacteria is poorly understood. Here, we identified a novel protein, named CyDiv (Cyanobacterial Division), encoded by the all2320 gene in Anabaena sp. PCC 7120. We show that CyDiv plays a key role during cell division. CyDiv has been previously described only as an exclusive and conserved hypothetical protein in filamentous cyanobacteria. Using polyclonal antibodies against CyDiv, we showed that it localizes at different positions depending on cell division timing: poles, septum, in both daughter cells, but also in only one of the daughter cells. The partial deletion of CyDiv gene generates partial defects in cell division, including severe membrane instability and anomalous septum localization during late division. The inability to complete knock out CyDiv strains suggests that it is an essential gene. In silico structural protein analyses and our experimental results suggest that CyDiv is an FtsB/DivIC-like protein, and could therefore, be part of an essential late divisome complex in Anabaena sp. PCC 7120. PMID:26903973

  17. CyDiv, a Conserved and Novel Filamentous Cyanobacterial Cell Division Protein Involved in Septum Localization.

    PubMed

    Mandakovic, Dinka; Trigo, Carla; Andrade, Derly; Riquelme, Brenda; Gómez-Lillo, Gabriela; Soto-Liebe, Katia; Díez, Beatriz; Vásquez, Mónica

    2016-01-01

    Cell division in bacteria has been studied mostly in Escherichia coli and Bacillus subtilis, model organisms for Gram-negative and Gram-positive bacteria, respectively. However, cell division in filamentous cyanobacteria is poorly understood. Here, we identified a novel protein, named CyDiv (Cyanobacterial Division), encoded by the all2320 gene in Anabaena sp. PCC 7120. We show that CyDiv plays a key role during cell division. CyDiv has been previously described only as an exclusive and conserved hypothetical protein in filamentous cyanobacteria. Using polyclonal antibodies against CyDiv, we showed that it localizes at different positions depending on cell division timing: poles, septum, in both daughter cells, but also in only one of the daughter cells. The partial deletion of CyDiv gene generates partial defects in cell division, including severe membrane instability and anomalous septum localization during late division. The inability to complete knock out CyDiv strains suggests that it is an essential gene. In silico structural protein analyses and our experimental results suggest that CyDiv is an FtsB/DivIC-like protein, and could therefore, be part of an essential late divisome complex in Anabaena sp. PCC 7120.

  18. The Arabidopsis Receptor Kinase ZAR1 Is Required for Zygote Asymmetric Division and Its Daughter Cell Fate

    PubMed Central

    Jia, Peng-Fei; Tang, Jun; Li, Hong-Ju; Liu, Jie; Yang, Wei-Cai

    2016-01-01

    Asymmetric division of zygote is critical for pattern formation during early embryogenesis in plants and animals. It requires integration of the intrinsic and extrinsic cues prior to and/or after fertilization. How these cues are translated into developmental signals is poorly understood. Here through genetic screen for mutations affecting early embryogenesis, we identified an Arabidopsis mutant, zygotic arrest 1 (zar1), in which zygote asymmetric division and the cell fate of its daughter cells were impaired. ZAR1 encodes a member of the RLK/Pelle kinase family. We demonstrated that ZAR1 physically interacts with Calmodulin and the heterotrimeric G protein Gβ, and ZAR1 kinase is activated by their binding as well. ZAR1 is specifically expressed micropylarly in the embryo sac at eight-nucleate stage and then in central cell, egg cell and synergids in the mature embryo sac. After fertilization, ZAR1 is accumulated in zygote and endosperm. The disruption of ZAR1 and AGB1 results in short basal cell and an apical cell with basal cell fate. These data suggest that ZAR1 functions as a membrane integrator for extrinsic cues, Ca2+ signal and G protein signaling to regulate the division of zygote and the cell fate of its daughter cells in Arabidopsis. PMID:27014878

  19. Receptor-like kinase ACR4 restricts formative cell divisions in the Arabidopsis root.

    PubMed

    De Smet, Ive; Vassileva, Valya; De Rybel, Bert; Levesque, Mitchell P; Grunewald, Wim; Van Damme, Daniël; Van Noorden, Giel; Naudts, Mirande; Van Isterdael, Gert; De Clercq, Rebecca; Wang, Jean Y; Meuli, Nicholas; Vanneste, Steffen; Friml, Jirí; Hilson, Pierre; Jürgens, Gerd; Ingram, Gwyneth C; Inzé, Dirk; Benfey, Philip N; Beeckman, Tom

    2008-10-24

    During the development of multicellular organisms, organogenesis and pattern formation depend on formative divisions to specify and maintain pools of stem cells. In higher plants, these activities are essential to shape the final root architecture because the functioning of root apical meristems and the de novo formation of lateral roots entirely rely on it. We used transcript profiling on sorted pericycle cells undergoing lateral root initiation to identify the receptor-like kinase ACR4 of Arabidopsis as a key factor both in promoting formative cell divisions in the pericycle and in constraining the number of these divisions once organogenesis has been started. In the root tip meristem, ACR4 shows a similar action by controlling cell proliferation activity in the columella cell lineage. Thus, ACR4 function reveals a common mechanism of formative cell division control in the main root tip meristem and during lateral root initiation.

  20. Molecular Insights into Division of Single Human Cancer Cells in On-Chip Transparent Microtubes

    PubMed Central

    2016-01-01

    In vivo, mammalian cells proliferate within 3D environments consisting of numerous microcavities and channels, which contain a variety of chemical and physical cues. External environments often differ between normal and pathological states, such as the unique spatial constraints that metastasizing cancer cells experience as they circulate the vasculature through arterioles and narrow capillaries, where they can divide and acquire elongated cylindrical shapes. While metastatic tumors cause most cancer deaths, factors impacting early cancer cell proliferation inside the vasculature and those that can promote the formation of secondary tumors remain largely unknown. Prior studies investigating confined mitosis have mainly used 2D cell culture systems. Here, we mimic aspects of metastasizing tumor cells dividing inside blood capillaries by investigating single-cell divisions of living human cancer cells, trapped inside 3D rolled-up, transparent nanomembranes. We assess the molecular effects of tubular confinement on key mitotic features, using optical high- and super-resolution microscopy. Our experiments show that tubular confinement affects the morphology and dynamics of the mitotic spindle, chromosome arrangements, and the organization of the cell cortex. Moreover, we reveal that membrane blebbing and/or associated processes act as a potential genome-safety mechanism, limiting the extent of genomic instability caused by mitosis in confined circumstances, especially in tubular 3D microenvironments. Collectively, our study demonstrates the potential of rolled-up nanomembranes for gaining molecular insights into key cellular events occurring in tubular 3D microenvironments in vivo. PMID:27267364

  1. Cell division plane orientation based on tensile stress in Arabidopsis thaliana

    PubMed Central

    Louveaux, Marion; Julien, Jean-Daniel; Mirabet, Vincent; Boudaoud, Arezki; Hamant, Olivier

    2016-01-01

    Cell geometry has long been proposed to play a key role in the orientation of symmetric cell division planes. In particular, the recently proposed Besson–Dumais rule generalizes Errera’s rule and predicts that cells divide along one of the local minima of plane area. However, this rule has been tested only on tissues with rather local spherical shape and homogeneous growth. Here, we tested the application of the Besson–Dumais rule to the divisions occurring in the Arabidopsis shoot apex, which contains domains with anisotropic curvature and differential growth. We found that the Besson–Dumais rule works well in the central part of the apex, but fails to account for cell division planes in the saddle-shaped boundary region. Because curvature anisotropy and differential growth prescribe directional tensile stress in that region, we tested the putative contribution of anisotropic stress fields to cell division plane orientation at the shoot apex. To do so, we compared two division rules: geometrical (new plane along the shortest path) and mechanical (new plane along maximal tension). The mechanical division rule reproduced the enrichment of long planes observed in the boundary region. Experimental perturbation of mechanical stress pattern further supported a contribution of anisotropic tensile stress in division plane orientation. Importantly, simulations of tissues growing in an isotropic stress field, and dividing along maximal tension, provided division plane distributions comparable to those obtained with the geometrical rule. We thus propose that division plane orientation by tensile stress offers a general rule for symmetric cell division in plants. PMID:27436908

  2. A role for katanin in plant cell division: microtubule organization in dividing root cells of fra2 and lue1Arabidopsis thaliana mutants.

    PubMed

    Panteris, Emmanuel; Adamakis, Ioannis-Dimosthenis S; Voulgari, Georgia; Papadopoulou, Galini

    2011-07-01

    Severing of microtubules by katanin has proven to be crucial for cortical microtubule organization in elongating and differentiating plant cells. On the contrary, katanin is currently not considered essential during cell division in plants as it is in animals. However, defects in cell patterning have been observed in katanin mutants, implying a role for it in dividing plant cells. Therefore, microtubule organization was studied in detail by immunofluorescence in dividing root cells of fra2 and lue1 katanin mutants of Arabidopsis thaliana. In both, early preprophase bands consisted of poorly aligned microtubules, prophase spindles were multipolar, and the microtubules of expanding phragmoplasts were elongated, bended toward and connected to the surface of daughter nuclei. Accordingly, severing by katanin seems to be necessary for the proper organization of these microtubule arrays. In both fra2 and lue1, metaphase/anaphase spindles and initiating phragmoplasts exhibited typical organization. However, they were obliquely oriented more frequently than in the wild type. It is proposed that this oblique orientation may be due to prophase spindle multipolarity and results in a failure of the cell plate to follow the predetermined division plane, during cytokinesis, producing oblique cell walls in the roots of both mutants. It is therefore concluded that, like in animal cells, katanin is important for plant cell division, influencing the organization of several microtubule arrays. Moreover, failure in microtubule severing indirectly affects the orientation of the division plane.

  3. RNA processing body (P-body) dynamics in mesophyll protoplasts re-initiating cell division.

    PubMed

    Bhullar, Dilbag S; Sheahan, Michael B; Rose, Ray J

    2016-12-07

    The ability of plants to regenerate lies in the capacity of differentiated cells to reprogram and re-enter the cell cycle. Reprogramming of cells requires changes in chromatin organisation and gene expression. However, there has been less focus on changes at the post transcription level. We have investigated P-bodies, sites of post transcriptional gene regulation, in plant cell reprogramming in cultured mesophyll protoplasts; by using a YFP-VARICOSE (YFP-VCSc) translational fusion. We showed an early increase in P-body number and volume, followed by a decline, then a subsequent continued increase in P-body number and volume as cell division was initiated and cell proliferation continued. We infer that plant P-bodies have a role to play in reprogramming the mature cell and re-initiating the cell division cycle. The timing of the first phase is consistent with the degredation of messages no longer required, as the cell transits to the division state, and may also be linked to the stress response associated with division induction in cultured cells. The subsequent increase in P-body formation, with partitioning to the daughter cells during the division process, suggests a role in the cell cycle and its re-initiation in daughter cells. P-bodies were shown to be mobile in the cytoplasm and show actin-based motility which facilitates their post-transcriptional role and partitioning to daughter cells.

  4. Chromosome segregation impacts on cell growth and division site selection in Corynebacterium glutamicum.

    PubMed

    Donovan, Catriona; Schauss, Astrid; Krämer, Reinhard; Bramkamp, Marc

    2013-01-01

    Spatial and temporal regulation of bacterial cell division is imperative for the production of viable offspring. In many rod-shaped bacteria, regulatory systems such as the Min system and nucleoid occlusion ensure the high fidelity of midcell divisome positioning. However, regulation of division site selection in bacteria lacking recognizable Min and nucleoid occlusion remains less well understood. Here, we describe one such rod-shaped organism, Corynebacterium glutamicum, which does not always place the division septum precisely at midcell. Here we now show at single cell level that cell growth and division site selection are spatially and temporally regulated by chromosome segregation. Mutants defective in chromosome segregation have more variable cell growth and aberrant placement of the division site. In these mutants, division septa constrict over and often guillotine the nucleoid, leading to nonviable, DNA-free cells. Our results suggest that chromosome segregation or some nucleoid associated factor influences growth and division site selection in C. glutamicum. Understanding growth and regulation of C. glutamicum cells will also be of importance to develop strains for industrial production of biomolecules, such as amino acids.

  5. Chromosome Segregation Impacts on Cell Growth and Division Site Selection in Corynebacterium glutamicum

    PubMed Central

    Donovan, Catriona; Schauss, Astrid; Krämer, Reinhard; Bramkamp, Marc

    2013-01-01

    Spatial and temporal regulation of bacterial cell division is imperative for the production of viable offspring. In many rod-shaped bacteria, regulatory systems such as the Min system and nucleoid occlusion ensure the high fidelity of midcell divisome positioning. However, regulation of division site selection in bacteria lacking recognizable Min and nucleoid occlusion remains less well understood. Here, we describe one such rod-shaped organism, Corynebacterium glutamicum, which does not always place the division septum precisely at midcell. Here we now show at single cell level that cell growth and division site selection are spatially and temporally regulated by chromosome segregation. Mutants defective in chromosome segregation have more variable cell growth and aberrant placement of the division site. In these mutants, division septa constrict over and often guillotine the nucleoid, leading to nonviable, DNA-free cells. Our results suggest that chromosome segregation or some nucleoid associated factor influences growth and division site selection in C. glutamicum. Understanding growth and regulation of C. glutamicum cells will also be of importance to develop strains for industrial production of biomolecules, such as amino acids. PMID:23405112

  6. ZapE is a novel cell division protein interacting with FtsZ and modulating the Z-ring dynamics.

    PubMed

    Marteyn, Benoit S; Karimova, Gouzel; Fenton, Andrew K; Gazi, Anastasia D; West, Nicholas; Touqui, Lhousseine; Prevost, Marie-Christine; Betton, Jean-Michel; Poyraz, Oemer; Ladant, Daniel; Gerdes, Kenn; Sansonetti, Philippe J; Tang, Christoph M

    2014-03-04

    Bacterial cell division requires the formation of a mature divisome complex positioned at the midcell. The localization of the divisome complex is determined by the correct positioning, assembly, and constriction of the FtsZ ring (Z-ring). Z-ring constriction control remains poorly understood and (to some extent) controversial, probably due to the fact that this phenomenon is transient and controlled by numerous factors. Here, we characterize ZapE, a novel ATPase found in Gram-negative bacteria, which is required for growth under conditions of low oxygen, while loss of zapE results in temperature-dependent elongation of cell shape. We found that ZapE is recruited to the Z-ring during late stages of the cell division process and correlates with constriction of the Z-ring. Overexpression or inactivation of zapE leads to elongation of Escherichia coli and affects the dynamics of the Z-ring during division. In vitro, ZapE destabilizes FtsZ polymers in an ATP-dependent manner. IMPORTANCE Bacterial cell division has mainly been characterized in vitro. In this report, we could identify ZapE as a novel cell division protein which is not essential in vitro but is required during an infectious process. The bacterial cell division process relies on the assembly, positioning, and constriction of FtsZ ring (the so-called Z-ring). Among nonessential cell division proteins recently identified, ZapE is the first in which detection at the Z-ring correlates with its constriction. We demonstrate that ZapE abundance has to be tightly regulated to allow cell division to occur; absence or overexpression of ZapE leads to bacterial filamentation. As zapE is not essential, we speculate that additional Z-ring destabilizing proteins transiently recruited during late cell division process might be identified in the future.

  7. Dimethyl sulfoxide can initiate cell divisions of arrested callus protoplasts by promoting cortical microtuble assembly

    SciTech Connect

    Hahne, G.; Hoffmann, F.

    1984-09-01

    A serious problem in the technology of plant cell culture is that isolated protoplasts from many species are reluctant to divide. We have succeeded in inducing consecutive divisions in a naturally arrested system i.e., protoplasts from a hibiscus cell line, which do not divide under standard conditions and in an artificially arrested system i.e., colchicine-inhibited callus protoplasts of Nicotiana glutinosa, which do readily divide in the absence of colchicine. In both cases, the reinstallation of a net of cortical microtubules, which had been affected either by colchicine or by the protoplast isolation procedure, resulted in continuous divisions of the formerly arrested protoplasts. Several compounds known to support microtubule assembly in vitro were tested for their ability to promote microtubule assembly in vivo. Best results were obtained by addition of dimethyl sulfoxide to the culture medium. Unlimited amounts of callus could be produced with the dimethyl sulfoxide method from protoplasts which never developed a single callus in control experiments. 30 references, 3 figures.

  8. Plant Cell Division Analyzed by Transient Agrobacterium-Mediated Transformation of Tobacco BY-2 Cells.

    PubMed

    Buschmann, Henrik

    2016-01-01

    The continuing analysis of plant cell division will require additional protein localization studies. This is greatly aided by GFP-technology, but plant transformation and the maintenance of transgenic lines can present a significant technical bottleneck. In this chapter I describe a method for the Agrobacterium-mediated genetic transformation of tobacco BY-2 cells. The method allows for the microscopic analysis of fluorescence-tagged proteins in dividing cells in within 2 days after starting a coculture. This transient transformation procedure requires only standard laboratory equipment. It is hoped that this rapid method would aid researchers conducting live-cell localization studies in plant mitosis and cytokinesis.

  9. Medicinal Plants: A Potential Source of Compounds for Targeting Cell Division

    PubMed Central

    Zulkipli, Ihsan N; David, Sheba R; Rajabalaya, Rajan; Idris, Adi

    2015-01-01

    Modern medicinal plant drug discovery has provided pharmacologically active compounds targeted against a multitude of conditions and diseases, such as infection, inflammation, and cancer. To date, natural products from medicinal plants remain a solid niche as a source from which cancer therapies can be derived. Among other properties, one favorable characteristic of an anticancer drug is its ability to block the uncontrollable process of cell division, as cancer cells are notorious for their abnormal cell division. There are numerous other documented works on the potential anticancer activity of drugs derived from medicinal plants, and their effects on cell division are an attractive and growing therapeutic target. Despite this, there remains a vast number of unidentified natural products that are potentially promising sources for medical applications. This mini review aims to revise the current knowledge of the effects of natural plant products on cell division. PMID:26106261

  10. Experimental systems to explore life origin: perspectives for understanding primitive mechanisms of cell division.

    PubMed

    Adamala, Katarzyna; Luisi, Pier Luigi

    2011-01-01

    Compartmentalization is a necessary element for the development of any cell cycle and the origin of speciation. Changes in shape and size of compartments might have been the first manifestation of development of so-called cell cycles. Cell growth and division, processes guided by biological reactions in modern cells, might have originated as purely physicochemical processes. Modern cells use enzymes to initiate and control all stages of cell cycle. Protocells, in the absence of advanced enzymatic machinery, might have needed to rely on physical properties of the membrane. As the division processes could not have been controlled by the cell's metabolism, the first protocells probably did not undergo regular cell cycles as we know it in cells of today. More likely, the division of protocells was triggered either by some inorganic catalyzing factor, such as porous surface, or protocells divided when the encapsulated contents reached some critical concentration.

  11. Nucleoid occlusion prevents cell division during replication fork arrest in Bacillus subtilis

    PubMed Central

    Bernard, Remi; Marquis, Kathleen A.; Rudner, David Z.

    2010-01-01

    Summary How bacteria respond to chromosome replication stress has been traditionally studied using temperature-sensitive mutants and chemical inhibitors. These methods inevitably arrest all replication and lead to induction of transcriptional responses and inhibition of cell division. Here, we used repressor proteins bound to operator arrays to generate a single stalled replication fork. These replication roadblocks impeded replisome progression on one arm, leaving replication of the other arm and re-initiation unaffected. Remarkably, despite robust generation of RecA-GFP filaments and a strong block to cell division during the roadblock, patterns of gene expression were not significantly altered. Consistent with these findings, division inhibition was not mediated by the SOS-induced regulator YneA nor by RecA-independent repression of ftsL. In support of the idea that nucleoid occlusion prevents inappropriate cell division during fork arrest, immature FtsZ-rings formed adjacent to the DNA mass but rarely on top of it. Furthermore, mild alterations in chromosome compaction resulted in cell division that guillotined the DNA. Strikingly, the nucleoid occlusion protein Noc had no discernable role in division inhibition. Our data indicate that Noc-independent nucleoid occlusion prevents inappropriate cell division during replication fork arrest. They further suggest that Bacillus subtilis normally manages replication stress rather than inducing a stress-response. PMID:20807205

  12. Interplay of cell shape and division orientation promotes robust morphogenesis of developing epithelia.

    PubMed

    Xiong, Fengzhu; Ma, Wenzhe; Hiscock, Tom W; Mosaliganti, Kishore R; Tentner, Andrea R; Brakke, Kenneth A; Rannou, Nicolas; Gelas, Arnaud; Souhait, Lydie; Swinburne, Ian A; Obholzer, Nikolaus D; Megason, Sean G

    2014-10-09

    Epithelial cells acquire functionally important shapes (e.g., squamous, cuboidal, columnar) during development. Here, we combine theory, quantitative imaging, and perturbations to analyze how tissue geometry, cell divisions, and mechanics interact to shape the presumptive enveloping layer (pre-EVL) on the zebrafish embryonic surface. We find that, under geometrical constraints, pre-EVL flattening is regulated by surface cell number changes following differentially oriented cell divisions. The division pattern is, in turn, determined by the cell shape distribution, which forms under geometrical constraints by cell-cell mechanical coupling. An integrated mathematical model of this shape-division feedback loop recapitulates empirical observations. Surprisingly, the model predicts that cell shape is robust to changes of tissue surface area, cell volume, and cell number, which we confirm in vivo. Further simulations and perturbations suggest the parameter linking cell shape and division orientation contributes to epithelial diversity. Together, our work identifies an evolvable design logic that enables robust cell-level regulation of tissue-level development.

  13. Transcription of the ftsZ gene and cell division in Escherichia coli.

    PubMed Central

    Robin, A; Joseleau-Petit, D; D'Ari, R

    1990-01-01

    The ftsZ gene of Escherichia coli, which lies in a cluster of cell division genes at 2 min on the genetic map, codes for a protein which is thought to play a key role in triggering cell division. Using an ftsZ::lacZ operon fusion, we have studied the transcription of the ftsZ gene under conditions in which cell division was either inhibited or synchronized in the bacterial population. In ftsZ, ftsA, ftsQ, and ftsI (or pbpB) mutants, there was no change in the differential rate of expression of the ftsZ gene in nonpermissive conditions, when cell division was completely blocked. Although the FtsZ protein is thought to be limiting for cell division, in synchronized cultures the ftsZ gene was expressed not only at the moment of septation initiation but throughout the cell cycle. Its expression, however, was not exponential but linear, with a rapid doubling in rate at a specific cell age; this age, about 20 min after division in a 60-min cycle, was different from the age at which the ftsZ::lacZ operon was duplicated. However, it was close to the age at which replication initiated and at which the rate of phospholipid synthesis doubled. During the transient division inhibition after a nutritional shift-up, ftsZ transcription again became linear, with two doublings in rate at intervals equal to the mass doubling time in the rich medium; it adopted the exponential rate typical of rich medium about 60 min after the shift-up, just before the bacterial population resumed cell division. The doubling in the rate of ftsZ transcription once per cycle in synchronized cultures and once per mass doubling time during the transition period after a nutritional shift-up reflects a new cell cycle event. PMID:2106510

  14. Asymmetric cell division and template DNA co-segregation in cancer stem cells.

    PubMed

    Pine, Sharon R; Liu, Wenyu

    2014-01-01

    During tissue homeostasis, normal stem cells self-renew and repopulate the diverse cell types found within the tissue via a series of carefully controlled symmetric and asymmetric cell divisions (ACDs). The notion that solid tumors comprise a subset of cancer stem cells (CSCs) with dysregulated self-renewal and excessive symmetric cell divisions has led to numerous studies aimed to elucidate the mechanisms regulating ACD under steady-state conditions, during stem-cell expansion and in cancer. In this perspective, we focus on a type of asymmetry that can be established during ACD, called non-random co-segregation of template DNA, which has been identified across numerous species, cell types, and cancers. We discuss the role of p53 loss in maintaining self-renewal in both normal and malignant cells. We then review our current knowledge of the mechanisms underlying co-segregation of template DNA strands and the stem-cell pathways associated with it in normal and CSCs.

  15. How-to-Do-It: Hands-on Activities that Relate Mendelian Genetics to Cell Division.

    ERIC Educational Resources Information Center

    McKean, Heather R.; Gibson, Linda S.

    1989-01-01

    Presented is an activity designed to connect Mendelian laws with the physical processes of cell division. Included are materials production, procedures and worksheets for the meiosis-mitosis game and a genetics game. (CW)

  16. Exclusive multipotency and preferential asymmetric divisions in post-embryonic neural stem cells of the fish retina.

    PubMed

    Centanin, Lázaro; Ander, Janina-J; Hoeckendorf, Burkhard; Lust, Katharina; Kellner, Tanja; Kraemer, Isabel; Urbany, Cedric; Hasel, Eva; Harris, William A; Simons, Benjamin D; Wittbrodt, Joachim

    2014-09-01

    The potency of post-embryonic stem cells can only be addressed in the living organism, by labeling single cells after embryonic development and following their descendants. Recently, transplantation experiments involving permanently labeled cells revealed multipotent neural stem cells (NSCs) of embryonic origin in the medaka retina. To analyze whether NSC potency is affected by developmental progression, as reported for the mammalian brain, we developed an inducible toolkit for clonal labeling and non-invasive fate tracking. We used this toolkit to address post-embryonic stem cells in different tissues and to functionally differentiate transient progenitor cells from permanent, bona fide stem cells in the retina. Using temporally controlled clonal induction, we showed that post-embryonic retinal NSCs are exclusively multipotent and give rise to the complete spectrum of cell types in the neural retina. Intriguingly, and in contrast to any other vertebrate stem cell system described so far, long-term analysis of clones indicates a preferential mode of asymmetric cell division. Moreover, following the behavior of clones before and after external stimuli, such as injuries, shows that NSCs in the retina maintained the preference for asymmetric cell division during regenerative responses. We present a comprehensive analysis of individual post-embryonic NSCs in their physiological environment and establish the teleost retina as an ideal model for studying adult stem cell biology at single cell resolution.

  17. Lin-28 promotes symmetric stem cell division and drives adaptive growth in the adult Drosophila intestine.

    PubMed

    Chen, Ching-Huan; Luhur, Arthur; Sokol, Nicholas

    2015-10-15

    Stem cells switch between asymmetric and symmetric division to expand in number as tissues grow during development and in response to environmental changes. The stem cell intrinsic proteins controlling this switch are largely unknown, but one candidate is the Lin-28 pluripotency factor. A conserved RNA-binding protein that is downregulated in most animals as they develop from embryos to adults, Lin-28 persists in populations of adult stem cells. Its function in these cells has not been previously characterized. Here, we report that Lin-28 is highly enriched in adult intestinal stem cells in the Drosophila intestine. lin-28 null mutants are homozygous viable but display defects in this population of cells, which fail to undergo a characteristic food-triggered expansion in number and have reduced rates of symmetric division as well as reduced insulin signaling. Immunoprecipitation of Lin-28-bound mRNAs identified Insulin-like Receptor (InR), forced expression of which completely rescues lin-28-associated defects in intestinal stem cell number and division pattern. Furthermore, this stem cell activity of lin-28 is independent of one well-known lin-28 target, the microRNA let-7, which has limited expression in the intestinal epithelium. These results identify Lin-28 as a stem cell intrinsic factor that boosts insulin signaling in intestinal progenitor cells and promotes their symmetric division in response to nutrients, defining a mechanism through which Lin-28 controls the adult stem cell division patterns that underlie tissue homeostasis and regeneration.

  18. The Relationship between Cell Number, Division Behavior and Developmental Potential of Cleavage Stage Human Embryos: A Time-Lapse Study.

    PubMed

    Kong, Xiangyi; Yang, Shuting; Gong, Fei; Lu, Changfu; Zhang, Shuoping; Lu, Guangxiu; Lin, Ge

    2016-01-01

    Day 3 cleavage embryo transfer is routine in many assisted reproductive technology centers today. Embryos are usually selected according to cell number, cell symmetry and fragmentation for transfer. Many studies have showed the relationship between cell number and embryo developmental potential. However, there is limited understanding of embryo division behavior and their association with embryo cell number and developmental potential. A retrospective and observational study was conducted to investigate how different division behaviors affect cell number and developmental potential of day 3 embryos by time-lapse imaging. Based on cell number at day 3, the embryos (from 104 IVF/intracytoplasmic sperm injection (ICSI) treatment cycles, n = 799) were classified as follows: less than 5 cells (< 5C; n = 111); 5-6 cells (5-6C; n = 97); 7-8 cells (7-8C; n = 442), 9-10 cells (9-10C; n = 107) and more than 10 cells (>10C; n = 42). Division behavior, morphokinetic parameters and blastocyst formation rate were analyzed in 5 groups of day 3 embryos with different cell numbers. In <5C and 5-6C embryos, fragmentation (FR; 62.2% and 30.9%, respectively) was the main cause for low cell number. The majority of 7-8C embryos exhibited obvious normal behaviors (NB; 85.7%) during development. However, the incidence of DC in 9-10C and >10C embryos increased compared to 7-8C embryos (45.8%, 33.3% vs. 11.1%, respectively). In ≥5C embryos, FR and DC significantly reduced developmental potential, whereas <5C embryos showed little potential irrespective of division behaviors. In NB embryos, the blastocyst formation rate increased with cell number from 7.4% (<5C) to 89.3% (>10C). In NB embryos, the cell cycle elongation or shortening was the main cause for abnormally low or high cell number, respectively. After excluding embryos with abnormal division behaviors, the developmental potential, implantation rate and live birth rate of day 3 embryos increased with cell number.

  19. ESCRT-III mediated cell division in Sulfolobus acidocaldarius - a reconstitution perspective.

    PubMed

    Härtel, Tobias; Schwille, Petra

    2014-01-01

    In the framework of synthetic biology, it has become an intriguing question what would be the minimal representation of cell division machinery. Thus, it seems appropriate to compare how cell division is realized in different microorganisms. In particular, the cell division system of Crenarchaeota lacks certain proteins found in most bacteria and Euryarchaeota, such as FtsZ, MreB or the Min system. The Sulfolobaceae family encodes functional homologs of the eukaryotic proteins vacuolar protein sorting 4 (Vps4) and endosomal sorting complex required for transport-III (ESCRT-III). ESCRT-III is essential for several eukaryotic pathways, e.g., budding of intraluminal vesicles, or cytokinesis, whereas Vps4 dissociates the ESCRT-III complex from the membrane. Cell Division A (CdvA) is required for the recruitment of crenarchaeal ESCRT-III proteins to the membrane at mid-cell. The proteins polymerize and form a smaller structure during constriction. Thus, ESCRT-III mediated cell division in Sulfolobus acidocaldarius shows functional analogies to the Z ring observed in prokaryotes like Escherichia coli, which has recently begun to be reconstituted in vitro. In this short perspective, we discuss the possibility of building such an in vitro cell division system on basis of archaeal ESCRT-III.

  20. Kinetics of large-scale chromosomal movement during asymmetric cell division in Escherichia coli

    PubMed Central

    Männik, Jaana; O’Neill, Jordan C.

    2017-01-01

    Coordination between cell division and chromosome replication is essential for a cell to produce viable progeny. In the commonly accepted view, Escherichia coli realize this coordination via the accurate positioning of its cell division apparatus relative to the nucleoids. However, E. coli lacking proper positioning of its cell division planes can still successfully propagate. Here, we characterize how these cells partition their chromosomes into daughters during such asymmetric divisions. Using quantitative time-lapse imaging, we show that DNA translocase, FtsK, can pump as much as 80% (3.7 Mb) of the chromosome between daughters at an average rate of 1700±800 bp/s. Pauses in DNA translocation are rare, and in no occasions did we observe reversals at experimental time scales of a few minutes. The majority of DNA movement occurs at the latest stages of cell division when the cell division protein ZipA has already dissociated from the septum, and the septum has closed to a narrow channel with a diameter much smaller than the resolution limit of the microscope (~250 nm). Our data suggest that the narrow constriction is necessary for effective translocation of DNA by FtsK. PMID:28234902

  1. Cell division in a minimal bacterium in the absence of ftsZ.

    PubMed

    Lluch-Senar, Maria; Querol, Enrique; Piñol, Jaume

    2010-10-01

    Mycoplasma genomes exhibit an impressively low amount of genes involved in cell division and some species even lack the ftsZ gene, which is found widespread in the microbial world and is considered essential for cell division by binary fission. We constructed a Mycoplasma genitalium ftsZ null mutant by gene replacement to investigate the role of this gene and the presence of alternative cell division mechanisms in this minimal bacterium. Our results demonstrate that ftsZ is non-essential for cell growth and reveal that, in the absence of the FtsZ protein, M. genitalium can manage feasible cell divisions and cytokinesis using the force generated by its motile machinery. This is an alternative mechanism, completely independent of the FtsZ protein, to perform cell division by binary fission in a microorganism. We also propose that the mycoplasma cytoskeleton, a complex network of proteins involved in many aspects of the biology of these microorganisms, may have taken over the function of many genes involved in cell division, allowing their loss in the regressive evolution of the streamlined mycoplasma genomes.

  2. The cytological changes of tobacco zygote and proembryo cells induced by beta-glucosyl Yariv reagent suggest the involvement of arabinogalactan proteins in cell division and cell plate formation

    PubMed Central

    2012-01-01

    Background In dicotyledonous plant, the first asymmetric zygotic division and subsequent several cell divisions are crucial for proembryo pattern formation and later embryo development. Arabinogalactan proteins (AGPs) are a family of extensively glycosylated cell surface proteins that are thought to have important roles in various aspects of plant growth and development, including embryogenesis. Previous results from our laboratory show that AGPs are concerned with tobacco egg cell fertilization and zygotic division. However, how AGPs interact with other factors involved in zygotic division and proembryo development remains unknown. Results In this study, we used the tobacco in vitro zygote culture system and series of meticulous cell biology techniques to investigate the roles of AGPs in zygote and proembryo cell division. For the first time, we examined tobacco proembryo division patterns detailed to every cell division. The bright-field images and statistical results both revealed that with the addition of an exogenous AGPs inhibitor, beta-glucosyl Yariv (beta-GlcY) reagent, the frequency of aberrant division increased remarkably in cultured tobacco zygotes and proembryos, and the cell plate specific locations of AGPs were greatly reduced after beta-GlcY treatment. In addition, the accumulations of new cell wall materials were also significantly affected by treating with beta-GlcY. Detection of cellulose components by Calcofluor white stain showed that strong fluorescence was located in the newly formed wall of daughter cells after the zygotic division of in vivo samples and the control samples from in vitro culture without beta-GlcY treatment; while there was only weak fluorescence in the newly formed cell walls with beta-GlcY treatment. Immunocytochemistry examination with JIM5 and JIM7 respectively against the low- and high-esterified pectins displayed that these two pectins located in opposite positions of zygotes and proembryos in vivo and the polarity was

  3. Mitochondrial growth and division during the cell cycle in HeLa cells

    PubMed Central

    Posakony, JW; England, JM; Attardi, G

    1977-01-01

    The growth and division of mitochondria during the cell cycle was investigated by a morphometric analysis of electron micrographs of synchronized HeLa cells. The ratio of total outer membrane contour length to cytoplasmic area did not vary significantly during the cell cycle, implying a continuous growth of the mitochondrial outer membrane. The mean fraction of cytoplasmic area occupied by mitochondrial profiles was likewise found to remain constant, indicating that the increase in total mitochondrial volume per cell occurs continuously during interphase, in such a way that the mitochondrial complement occupies a constant fraction( approximately 10-11(percent)) of the volume of the cytoplasm. The mean area, outer membrane contour length, and axis ratio of the mitochondrial profiles also did not vary appreciably during the cell cycle; furthermore, the close similarity of the frequency distributions of these parameters for the six experimental time-points suggested a stable mitochondrial shape distribution. The constancy of both the mean mitochondrial profile area and the number of mitochondrial profiles per unit of cytoplasmic area was interpreted to indicate the continuous division of mitochondria at the level of the cell population. Furthermore, no evidence was found for the occurrence of synchronous mitochondrial growth and division within individual cells. Thus, it appears that, in HeLa cells, there is no fixed temporal relationship between the growth and division of mitochondria and the events of the cell cycle. A number of statistical methods were developed for the purpose of making numerical estimates of certain three-dimensional cellular and mitochondrial parameters. Mean cellular and cytoplasmic volumes were calculated for the six time-points; both exhibited a nonlinear, approx. twofold increase. A comparison of the axis ratio distributions of the mitochondrial profiles with theoretical distributions expected from random sectioning of bodies of various

  4. A conformational switch controls cell wall-remodelling enzymes required for bacterial cell division.

    PubMed

    Yang, Desirée C; Tan, Kemin; Joachimiak, Andrzej; Bernhardt, Thomas G

    2012-08-01

    Remodelling of the peptidoglycan (PG) exoskeleton is intimately tied to the growth and division of bacteria. Enzymes that hydrolyse PG are critical for these processes, but their activities must be tightly regulated to prevent the generation of lethal breaches in the PG matrix. Despite their importance, the mechanisms regulating PG hydrolase activity have remained elusive. Here we investigate the control of cell division hydrolases called amidases (AmiA, AmiB and AmiC) required for Escherichia coli cell division. Poorly regulated amiB mutants were isolated encoding lytic AmiB variants with elevated basal PG hydrolase activities in vitro. The structure of an AmiB orthologue was also solved, revealing that the active site of AmiB is occluded by a conserved alpha helix. Strikingly, most of the amino acid substitutions in the lytic AmiB variants mapped to this domain and are predicted to disrupt its interaction with the active site. Our results therefore support a model in which cell separation is stimulated by the reversible relief of amidase autoinhibition governed by conserved subcomplexes within the cytokinetic ring. Analogous conformational control mechanisms are likely to be part of a general strategy used to control PG hydrolases present within multienzyme PG-remodelling machines.

  5. A subpopulation of adult skeletal muscle stem cells retains all template DNA strands after cell division.

    PubMed

    Rocheteau, Pierre; Gayraud-Morel, Barbara; Siegl-Cachedenier, Irene; Blasco, Maria A; Tajbakhsh, Shahragim

    2012-01-20

    Satellite cells are adult skeletal muscle stem cells that are quiescent and constitute a poorly defined heterogeneous population. Using transgenic Tg:Pax7-nGFP mice, we show that Pax7-nGFP(Hi) cells are less primed for commitment and have a lower metabolic status and delayed first mitosis compared to Pax7-nGFP(Lo) cells. Pax7-nGFP(Hi) can give rise to Pax7-nGFP(Lo) cells after serial transplantations. Proliferating Pax7-nGFP(Hi) cells exhibit lower metabolic activity, and the majority performs asymmetric DNA segregation during cell division, wherein daughter cells retaining template DNA strands express stem cell markers. Using chromosome orientation-fluorescence in situ hybridization, we demonstrate that all chromatids segregate asymmetrically, whereas Pax7-nGFP(Lo) cells perform random DNA segregation. Therefore, quiescent Pax7-nGFP(Hi) cells represent a reversible dormant stem cell state, and during muscle regeneration, Pax7-nGFP(Hi) cells generate distinct daughter cell fates by asymmetrically segregating template DNA strands to the stem cell. These findings provide major insights into the biology of stem cells that segregate DNA asymmetrically.

  6. The Escherichia coli datA site promotes proper regulation of cell division.

    PubMed

    Morigen, Morigen; Flåtten, Ingvild; Skarstad, Kirsten

    2014-04-01

    In Escherichia coli inhibition of replication leads to a block of cell division. This checkpoint mechanism ensures that no cell divides without having two complete copies of the genome to pass on to the two daughter cells. The chromosomal datA site is a 1 kb region that contains binding sites for the DnaA replication initiator protein, and which contributes to the inactivation of DnaA. An excess of datA sites provided on plasmids has been found to lead to both a delay in initiation of replication and in cell division during exponential growth. Here we have investigated the effect of datA on the cell division block that occurs upon inhibition of replication initiation in a dnaC2 mutant. We found that this checkpoint mechanism was aided by the presence of datA. In cells where datA was deleted or an excess of DnaA was provided, cell division occurred in the absence of replication and anucleate cells were formed. This finding indicates that loss of datA and/or excess of DnaA protein promote cell division. This conclusion was supported by the finding that the lethality of the division-compromised mutants ftsZ84 and ftsI23 was suppressed by deletion of datA, at the lowest non-permissive temperature. We propose that the cell division block that occurs upon inhibition of DNA replication is, at least in part, due to a drop in the concentration of the ATP-DnaA protein.

  7. Tumor-initiating label-retaining cancer cells in human gastrointestinal cancers undergo asymmetric cell division.

    PubMed

    Xin, Hong-Wu; Hari, Danielle M; Mullinax, John E; Ambe, Chenwi M; Koizumi, Tomotake; Ray, Satyajit; Anderson, Andrew J; Wiegand, Gordon W; Garfield, Susan H; Thorgeirsson, Snorri S; Avital, Itzhak

    2012-04-01

    Label-retaining cells (LRCs) have been proposed to represent adult tissue stem cells. LRCs are hypothesized to result from either slow cycling or asymmetric cell division (ACD). However, the stem cell nature and whether LRC undergo ACD remain controversial. Here, we demonstrate label-retaining cancer cells (LRCCs) in several gastrointestinal (GI) cancers including fresh surgical specimens. Using a novel method for isolation of live LRCC, we demonstrate that a subpopulation of LRCC is actively dividing and exhibits stem cells and pluripotency gene expression profiles. Using real-time confocal microscopic cinematography, we show live LRCC undergoing asymmetric nonrandom chromosomal cosegregation LRC division. Importantly, LRCCs have greater tumor-initiating capacity than non-LRCCs. Based on our data and that cancers develop in tissues that harbor normal-LRC, we propose that LRCC might represent a novel population of GI stem-like cancer cells. LRCC may provide novel mechanistic insights into the biology of cancer and regenerative medicine and present novel targets for cancer treatment.

  8. Control of cell division and the spatial localization of assembled gene products in Caulobacter crescentus

    SciTech Connect

    Nathan, P.D.

    1988-01-01

    Experiments are described that examine the role of penicillin-binding proteins (PBPs) in the regulation of cell division in Caulobacter crescentus; and the spatial localization of methyl-accepting chemotaxis proteins (MCPs) in C. crescentus swarmer and predivisional cells. In the analysis of PBP function, in vivo and in vitro assays are used to directly label C. crescentus PBPs with (/sup 3/H) penicillin G in wild type strain CB15, in a series of conditional cell division mutants and in new temperature sensitive cephalosporin C resistant mutants PC8002 and PC8003. 14 PBPs are characterized and a high molecular weight PBP (PBP 1B) that is required for cell division is identified. PBP 1B competes for ..beta..-lactams that induce filament formation and may be a high affinity binding protein. A second high molecular weight PBP (PBP 1C) is also associated with defective cell division. The examination of PBP patterns in synchronous swarmer cells reveals that the in vivo activity of PBP 1B and PBP 1C increases at the time that the cell division pathway is initiated. None of the PBPs, however, appear to be differentially localized in the C. crescentus cell. In the analysis of MCP localization, in vivo and in vitro assays are used to directly label C. crescentus MCPs with methyl-/sup 3/H. MCPs are examined in flagellated and non-flagellated vesicles prepared from cells by immunoaffinity chromatography.

  9. Transposon insertions in the Flavobacterium johnsoniae ftsX gene disrupt gliding motility and cell division.

    PubMed

    Kempf, M J; McBride, M J

    2000-03-01

    Flavobacterium johnsoniae is a gram-negative bacterium that exhibits gliding motility. To determine the mechanism of flavobacterial gliding motility, we isolated 33 nongliding mutants by Tn4351 mutagenesis. Seventeen of these mutants exhibited filamentous cell morphology. The region of DNA surrounding the transposon insertion in the filamentous mutant CJ101-207 was cloned and sequenced. The transposon was inserted in a gene that was similar to Escherichia coli ftsX. Two of the remaining 16 filamentous mutants also carried insertions in ftsX. Introduction of the wild-type F. johnsoniae ftsX gene restored motility and normal cell morphology to each of the three ftsX mutants. CJ101-207 appears to be blocked at a late stage of cell division, since the filaments produced cross walls but cells failed to separate. In E. coli, FtsX is thought to function with FtsE in translocating proteins involved in potassium transport, and perhaps proteins involved in cell division, into the cytoplasmic membrane. Mutations in F. johnsoniae ftsX may prevent translocation of proteins involved in cell division and proteins involved in gliding motility into the cytoplasmic membrane, thus resulting in defects in both processes. Alternatively, the loss of gliding motility may be an indirect result of the defect in cell division. The inability to complete cell division may alter the cell architecture and disrupt gliding motility by preventing the synthesis, assembly, or functioning of the motility apparatus.

  10. Pixantrone induces cell death through mitotic perturbations and subsequent aberrant cell divisions

    PubMed Central

    Beeharry, Neil; Di Rora, Andrea Ghelli Luserna; Smith, Mitchell R; Yen, Timothy J

    2015-01-01

    Pixantrone is a novel aza-anthracenedione active against aggressive lymphoma and is being evaluated for use against various hematologic and solid tumors. The drug is an analog of mitoxantrone, but displays less cardiotoxicity than mitoxantrone or the more commonly used doxorubicin. Although pixantrone is purported to inhibit topoisomerase II activity and intercalate with DNA, exact mechanisms of how it induces cell death remain obscure. Here we evaluated the effect of pixantrone on a panel of solid tumor cell lines to understand its mechanism of cell killing. Initial experiments with pixantrone showed an apparent discrepancy between its anti-proliferative effects in MTS assays (short-term) compared with clonogenic assays (long-term). Using live cell videomicroscopy to track the fates of cells, we found that cells treated with pixantrone underwent multiple rounds of aberrant cell division before eventually dying after approximately 5 d post-treatment. Cells underwent abnormal mitosis in which chromosome segregation was impaired, generating chromatin bridges between cells or within cells containing micronuclei. While pixantrone-treated cells did not display γH2AX foci, a marker of DNA damage, in the main nuclei, such foci were often detected in the micronuclei. Using DNA content analysis, we found that pixantrone concentrations that induced cell death in a clonogenic assay did not impede cell cycle progression, further supporting the lack of canonical DNA damage signaling. These findings suggest pixantrone induces a latent type of DNA damage that impairs the fidelity of mitosis, without triggering DNA damage response or mitotic checkpoint activation, but is lethal after successive rounds of aberrant division. PMID:26177126

  11. Maf acts downstream of ComGA to arrest cell division in competent cells of B. subtilis.

    PubMed

    Briley, Kenneth; Prepiak, Peter; Dias, Miguel J; Hahn, Jeanette; Dubnau, David

    2011-07-01

    Transformable (competent) cells of Bacillus subtilis are blocked in cell division because the traffic ATPase ComGA prevents the formation of FtsZ rings. Although ComGA-deficient cells elongate and form FtsZ rings, cell division remains blocked at a later stage and the cells become mildly filamented. Here we show that the highly conserved protein Maf is synthesized predominantly in competent cells under the direct control of the transcription factor ComK and is solely responsible for the later block in cell division. In vivo and in vitro data show that Maf binds to both ComGA and DivIVA. A point mutation in maf that interferes with Maf binding to DivIVA also interferes with the ability of Maf to inhibit cell division. Based on these findings, we propose that Maf and ComGA mediate mechanisms for the inhibition of cell division in competent cells with Maf acting downstream of ComGA. We further suggest that Maf must interact with DivIVA to inhibit cell division.

  12. Maf acts downstream of ComGA to arrest cell division in competent cells of B. subtilis

    PubMed Central

    Briley, Kenneth; Prepiak, Peter; Dias, Miguel J.; Hahn, Jeanette; Dubnau, David

    2011-01-01

    Transformable (competent) cells of Bacillus subtilis are blocked in cell division because the traffic ATPase ComGA prevents the formation of FtsZ rings. Although ComGA-deficient cells elongate and form FtsZ rings, cell division remains blocked at a later stage and the cells become mildly filamented. Here we show that the highly conserved protein Maf is synthesized predominantly in competent cells under the direct control of the transcription factor ComK and is solely responsible for the later block in cell division. In vivo and in vitro data show that Maf binds to both ComGA and DivIVA. A point mutation in maf that interferes with Maf binding to DivIVA also interferes with the ability of Maf to inhibit cell division. Based on these findings, we propose that Maf and ComGA mediate mechanisms for the inhibition of cell division in competent cells with Maf acting downstream of ComGA. We further suggest that Maf must interact with DivIVA to inhibit cell division. PMID:21564336

  13. [Response of HeLa cells to mitomycine C. I. Cell division].

    PubMed

    Petrov, Iu P

    2013-01-01

    Using light microscopy, time-lapse imaging, and digital image analysis, the effect of mitomycine C (10 μg/ml) on HeLa-M cells has been studied. It has been shown that, after a 2 h contact with mitomycine, the cells could be separated into 2 groups: M-1--the functional cells surviving after division but non-entering mitosis any more; M-II--the cells entering mitosis but incapable to finish it; they are lost. Mitomycine C is known to specifically block DNA replication being located in the DNA minor groove. It should inhibit PHK synthesis if one follows the standard hypothesis of a transcription bubble formation. However, increasing the cell and nucleolus area during the M-I cell growth suggests that RNA and protein synthesis is not blocked. The author concludes that the presented data confirm his hypothesis about RNA synthesis in the major DNA groove (Petrov, 2006).

  14. Condensation of FtsZ filaments can drive bacterial cell division.

    PubMed

    Lan, Ganhui; Daniels, Brian R; Dobrowsky, Terrence M; Wirtz, Denis; Sun, Sean X

    2009-01-06

    Forces are important in biological systems for accomplishing key cell functions, such as motility, organelle transport, and cell division. Currently, known force generation mechanisms typically involve motor proteins. In bacterial cells, no known motor proteins are involved in cell division. Instead, a division ring (Z-ring) consists of mostly FtsZ, FtsA, and ZipA is used to exerting a contractile force. The mechanism of force generation in bacterial cell division is unknown. Using computational modeling, we show that Z-ring formation results from the colocalization of FtsZ and FtsA mediated by the favorable alignment of FtsZ polymers. The model predicts that the Z-ring undergoes a condensation transition from a low-density state to a high-density state and generates a sufficient contractile force to achieve division. FtsZ GTP hydrolysis facilitates monomer turnover during the condensation transition, but does not directly generate forces. In vivo fluorescence measurements show that FtsZ density increases during division, in accord with model results. The mechanism is akin to van der Waals picture of gas-liquid condensation, and shows that organisms can exploit microphase transitions to generate mechanical forces.

  15. Myo19 Ensures Symmetric Partitioning of Mitochondria and Coupling of Mitochondrial Segregation to Cell Division

    PubMed Central

    Rohn, Jennifer L.; Patel, Jigna V.; Neumann, Beate; Bulkescher, Jutta; Mchedlishvili, Nunu; McMullan, Rachel C.; Quintero, Omar A.; Ellenberg, Jan; Baum, Buzz

    2014-01-01

    Summary During animal cell division, an actin-based ring cleaves the cell into two. Problems with this process can cause chromosome missegregation and defects in cytoplasmic inheritance and the partitioning of organelles, which in turn are associated with human diseases [1–3]. Although much is known about how chromosome segregation is coupled to cell division, the way organelles coordinate their inheritance during partitioning to daughter cells is less well understood. Here, using a high-content live-imaging small interfering RNA screen, we identify Myosin-XIX (Myo19) as a novel regulator of cell division. Previously, this actin-based motor was shown to control the interphase movement of mitochondria [4]. Our analysis shows that Myo19 is indeed localized to mitochondria and that its silencing leads to defects in the distribution of mitochondria within cells and in mitochondrial partitioning at division. Furthermore, many Myo19 RNAi cells undergo stochastic division failure—a phenotype that can be mimicked using a treatment that blocks mitochondrial fission and rescued by decreasing mitochondrial fusion, implying that mitochondria can physically interfere with cytokinesis. Strikingly, using live imaging we also observe the inappropriate movement of mitochondria to the poles of spindles in cells depleted for Myo19 as they enter anaphase. Since this phenocopies the results of an acute loss of actin filaments in anaphase, these data support a model whereby the Myo19 actin-based motor helps to control mitochondrial movement to ensure their faithful segregation during division. The presence of DNA within mitochondria makes their inheritance an especially important aspect of symmetrical cell division. PMID:25447992

  16. Myo19 ensures symmetric partitioning of mitochondria and coupling of mitochondrial segregation to cell division.

    PubMed

    Rohn, Jennifer L; Patel, Jigna V; Neumann, Beate; Bulkescher, Jutta; Mchedlishvili, Nunu; McMullan, Rachel C; Quintero, Omar A; Ellenberg, Jan; Baum, Buzz

    2014-11-03

    During animal cell division, an actin-based ring cleaves the cell into two. Problems with this process can cause chromosome missegregation and defects in cytoplasmic inheritance and the partitioning of organelles, which in turn are associated with human diseases. Although much is known about how chromosome segregation is coupled to cell division, the way organelles coordinate their inheritance during partitioning to daughter cells is less well understood. Here, using a high-content live-imaging small interfering RNA screen, we identify Myosin-XIX (Myo19) as a novel regulator of cell division. Previously, this actin-based motor was shown to control the interphase movement of mitochondria. Our analysis shows that Myo19 is indeed localized to mitochondria and that its silencing leads to defects in the distribution of mitochondria within cells and in mitochondrial partitioning at division. Furthermore, many Myo19 RNAi cells undergo stochastic division failure--a phenotype that can be mimicked using a treatment that blocks mitochondrial fission and rescued by decreasing mitochondrial fusion, implying that mitochondria can physically interfere with cytokinesis. Strikingly, using live imaging we also observe the inappropriate movement of mitochondria to the poles of spindles in cells depleted for Myo19 as they enter anaphase. Since this phenocopies the results of an acute loss of actin filaments in anaphase, these data support a model whereby the Myo19 actin-based motor helps to control mitochondrial movement to ensure their faithful segregation during division. The presence of DNA within mitochondria makes their inheritance an especially important aspect of symmetrical cell division.

  17. Periplasmic Acid Stress Increases Cell Division Asymmetry (Polar Aging) of Escherichia coli.

    PubMed

    Clark, Michelle W; Yie, Anna M; Eder, Elizabeth K; Dennis, Richard G; Basting, Preston J; Martinez, Keith A; Jones, Brian D; Slonczewski, Joan L

    2015-01-01

    Under certain kinds of cytoplasmic stress, Escherichia coli selectively reproduce by distributing the newer cytoplasmic components to new-pole cells while sequestering older, damaged components in cells inheriting the old pole. This phenomenon is termed polar aging or cell division asymmetry. It is unknown whether cell division asymmetry can arise from a periplasmic stress, such as the stress of extracellular acid, which is mediated by the periplasm. We tested the effect of periplasmic acid stress on growth and division of adherent single cells. We tracked individual cell lineages over five or more generations, using fluorescence microscopy with ratiometric pHluorin to measure cytoplasmic pH. Adherent colonies were perfused continually with LBK medium buffered at pH 6.00 or at pH 7.50; the external pH determines periplasmic pH. In each experiment, cell lineages were mapped to correlate division time, pole age and cell generation number. In colonies perfused at pH 6.0, the cells inheriting the oldest pole divided significantly more slowly than the cells inheriting the newest pole. In colonies perfused at pH 7.50 (near or above cytoplasmic pH), no significant cell division asymmetry was observed. Under both conditions (periplasmic pH 6.0 or pH 7.5) the cells maintained cytoplasmic pH values at 7.2-7.3. No evidence of cytoplasmic protein aggregation was seen. Thus, periplasmic acid stress leads to cell division asymmetry with minimal cytoplasmic stress.

  18. Study of the mechanism of diatom cell division by means of 29Si isotope tracing

    NASA Astrophysics Data System (ADS)

    Audinot, J.-N.; Guignard, C.; Migeon, H.-N.; Hoffmann, L.

    2006-07-01

    Diatoms are delicate unicellular organisms enclosed in a silica frustule, that is made up of two valves. Multiplication of the diatoms occurs by ordinary mitotic cell division. During cell division each cell produces two daughter cells, each of them keeping one of the two valves of the mother cell and producing a new valve by absorbing the silicon present in the environment. The NanoSIMS 50 allows ion imaging to be performed on diatoms in order to determine the site of fixation of silicon. The aim of this study was to observe and compare the mechanism of the construction of the new valve after cell division. To this end, different types of diatoms have been transferred in a culture medium enriched with 29Si and after several days, the distribution of the different isotopes of silicon has been determined by NanoSIMS50 imaging. The construction of new valves has been observed and the isotopic ratio has been determined.

  19. Novel insights into mammalian embryonic neural stem cell division: focus on microtubules

    PubMed Central

    Mora-Bermúdez, Felipe; Huttner, Wieland B.

    2015-01-01

    During stem cell divisions, mitotic microtubules do more than just segregate the chromosomes. They also determine whether a cell divides virtually symmetrically or asymmetrically by establishing spindle orientation and the plane of cell division. This can be decisive for the fate of the stem cell progeny. Spindle defects have been linked to neurodevelopmental disorders, yet the role of spindle orientation for mammalian neurogenesis has remained controversial. Here we explore recent advances in understanding how the microtubule cytoskeleton influences mammalian neural stem cell division. Our focus is primarily on the role of spindle microtubules in the development of the cerebral cortex. We also highlight unique characteristics in the architecture and dynamics of cortical stem cells that are tightly linked to their mode of division. These features contribute to setting these cells apart as mitotic “rule breakers,” control how asymmetric a division is, and, we argue, are sufficient to determine the fate of the neural stem cell progeny in mammals. PMID:26628750

  20. Frizzled signalling controls orientation of asymmetric sense organ precursor cell divisions in Drosophila.

    PubMed

    Gho, M; Schweisguth, F

    1998-05-14

    During metazoan development, cell-fate diversity is brought about, in part, by asymmetric cell divisions. In Drosophila, bristle mechanosensory organs are composed of four different cells that originate from a single precursor cell, pI, after two rounds of asymmetric division. At each division, distinct fates are conferred on sister cells by the asymmetric segregation of Numb, a negative regulator of Notch signalling. Here we show that the orientation of the mitotic spindles and the localization of the Numb crescent follow a stereotyped pattern. Mitosis of pI is orientated parallel to the anteroposterior axis of the fly. We show that signalling mediated by the Frizzled receptor polarizes pI along this axis, thereby specifying the orientation of the mitotic spindle and positioning the Numb crescent. The mitoses of the two cells produced by mitosis of pI are orientated parallel and orthogonal, respectively, to the division axis of pI. This difference in cell-division orientation is largely independent of the identity of the secondary precursor cells, and is regulated by Frizzled-independent mechanisms.

  1. Asymmetric cell division of rice zygotes located in embryo sac and produced by in vitro fertilization.

    PubMed

    Sato, Akiko; Toyooka, Kiminori; Okamoto, Takashi

    2010-09-01

    In angiosperms, a zygote generally divides into an asymmetric two-celled embryo consisting of an apical and a basal cell. This unequal division of the zygote is a putative first step for formation of the apical-basal axis of plants and is a fundamental feature of early embryogenesis and morphogenesis in angiosperms. Because fertilization and subsequent embryogenesis occur in embryo sacs, which are deeply embedded in ovular tissue, in vitro fertilization of isolated gametes is a powerful system to dissect mechanisms of fertilization and post-fertilization events. Rice is an emerging molecular and experimental model plant, however, profile of the first zygotic division within embryo sac and thus origin of apical-basal embryo polarity has not been closely investigated. Therefore, in the present study, the division pattern of rice zygote in planta was first determined accurately by observations employing serial sections of the egg apparatus, zygotes and two-celled embryos in the embryo sac. The rice zygote divides asymmetrically into a two-celled embryo consisting of a statistically significantly smaller apical cell with dense cytoplasm and a larger vacuolated basal cell. Moreover, detailed observations of division profiles of zygotes prepared by in vitro fertilization indicate that the zygote also divides into an asymmetric two-celled embryo as in planta. Such observations suggest that in vitro-produced rice zygotes and two-celled embryos may be useful as experimental models for further investigations into the mechanism and control of asymmetric division of plant zygotes.

  2. ParA and ParB coordinate chromosome segregation with cell elongation and division during Streptomyces sporulation

    PubMed Central

    Donczew, Magdalena; Mackiewicz, Paweł; Wróbel, Agnieszka; Flärdh, Klas; Zakrzewska-Czerwińska, Jolanta

    2016-01-01

    In unicellular bacteria, the ParA and ParB proteins segregate chromosomes and coordinate this process with cell division and chromosome replication. During sporulation of mycelial Streptomyces, ParA and ParB uniformly distribute multiple chromosomes along the filamentous sporogenic hyphal compartment, which then differentiates into a chain of unigenomic spores. However, chromosome segregation must be coordinated with cell elongation and multiple divisions. Here, we addressed the question of whether ParA and ParB are involved in the synchronization of cell-cycle processes during sporulation in Streptomyces. To answer this question, we used time-lapse microscopy, which allows the monitoring of growth and division of single sporogenic hyphae. We showed that sporogenic hyphae stop extending at the time of ParA accumulation and Z-ring formation. We demonstrated that both ParA and ParB affect the rate of hyphal extension. Additionally, we showed that ParA promotes the formation of massive nucleoprotein complexes by ParB. We also showed that FtsZ ring assembly is affected by the ParB protein and/or unsegregated DNA. Our results indicate the existence of a checkpoint between the extension and septation of sporogenic hyphae that involves the ParA and ParB proteins. PMID:27248800

  3. ParA and ParB coordinate chromosome segregation with cell elongation and division during Streptomyces sporulation.

    PubMed

    Donczew, Magdalena; Mackiewicz, Paweł; Wróbel, Agnieszka; Flärdh, Klas; Zakrzewska-Czerwińska, Jolanta; Jakimowicz, Dagmara

    2016-04-01

    In unicellular bacteria, the ParA and ParB proteins segregate chromosomes and coordinate this process with cell division and chromosome replication. During sporulation of mycelial Streptomyces, ParA and ParB uniformly distribute multiple chromosomes along the filamentous sporogenic hyphal compartment, which then differentiates into a chain of unigenomic spores. However, chromosome segregation must be coordinated with cell elongation and multiple divisions. Here, we addressed the question of whether ParA and ParB are involved in the synchronization of cell-cycle processes during sporulation in Streptomyces To answer this question, we used time-lapse microscopy, which allows the monitoring of growth and division of single sporogenic hyphae. We showed that sporogenic hyphae stop extending at the time of ParA accumulation and Z-ring formation. We demonstrated that both ParA and ParB affect the rate of hyphal extension. Additionally, we showed that ParA promotes the formation of massive nucleoprotein complexes by ParB. We also showed that FtsZ ring assembly is affected by the ParB protein and/or unsegregated DNA. Our results indicate the existence of a checkpoint between the extension and septation of sporogenic hyphae that involves the ParA and ParB proteins.

  4. Omics and modelling approaches for understanding regulation of asymmetric cell divisions in arabidopsis and other angiosperm plants

    PubMed Central

    Kajala, Kaisa; Ramakrishna, Priya; Fisher, Adam; C. Bergmann, Dominique; De Smet, Ive; Sozzani, Rosangela; Weijers, Dolf; Brady, Siobhan M.

    2014-01-01

    Background Asymmetric cell divisions are formative divisions that generate daughter cells of distinct identity. These divisions are coordinated by either extrinsic (‘niche-controlled’) or intrinsic regulatory mechanisms and are fundamentally important in plant development. Scope This review describes how asymmetric cell divisions are regulated during development and in different cell types in both the root and the shoot of plants. It further highlights ways in which omics and modelling approaches have been used to elucidate these regulatory mechanisms. For example, the regulation of embryonic asymmetric divisions is described, including the first divisions of the zygote, formative vascular divisions and divisions that give rise to the root stem cell niche. Asymmetric divisions of the root cortex endodermis initial, pericycle cells that give rise to the lateral root primordium, procambium, cambium and stomatal cells are also discussed. Finally, a perspective is provided regarding the role of other hormones or regulatory molecules in asymmetric divisions, the presence of segregated determinants and the usefulness of modelling approaches in understanding network dynamics within these very special cells. Conclusions Asymmetric cell divisions define plant development. High-throughput genomic and modelling approaches can elucidate their regulation, which in turn could enable the engineering of plant traits such as stomatal density, lateral root development and wood formation. PMID:24825294

  5. Lineage correlations of single cell division time as a probe of cell-cycle dynamics.

    PubMed

    Sandler, Oded; Mizrahi, Sivan Pearl; Weiss, Noga; Agam, Oded; Simon, Itamar; Balaban, Nathalie Q

    2015-03-26

    Stochastic processes in cells are associated with fluctuations in mRNA, protein production and degradation, noisy partition of cellular components at division, and other cell processes. Variability within a clonal population of cells originates from such stochastic processes, which may be amplified or reduced by deterministic factors. Cell-to-cell variability, such as that seen in the heterogeneous response of bacteria to antibiotics, or of cancer cells to treatment, is understood as the inevitable consequence of stochasticity. Variability in cell-cycle duration was observed long ago; however, its sources are still unknown. A central question is whether the variance of the observed distribution originates from stochastic processes, or whether it arises mostly from a deterministic process that only appears to be random. A surprising feature of cell-cycle-duration inheritance is that it seems to be lost within one generation but to be still present in the next generation, generating poor correlation between mother and daughter cells but high correlation between cousin cells. This observation suggests the existence of underlying deterministic factors that determine the main part of cell-to-cell variability. We developed an experimental system that precisely measures the cell-cycle duration of thousands of mammalian cells along several generations and a mathematical framework that allows discrimination between stochastic and deterministic processes in lineages of cells. We show that the inter- and intra-generation correlations reveal complex inheritance of the cell-cycle duration. Finally, we build a deterministic nonlinear toy model for cell-cycle inheritance that reproduces the main features of our data. Our approach constitutes a general method to identify deterministic variability in lineages of cells or organisms, which may help to predict and, eventually, reduce cell-to-cell heterogeneity in various systems, such as cancer cells under treatment.

  6. In tobacco BY-2 cells xyloglucan oligosaccharides alter the expression of genes involved in cell wall metabolism, signalling, stress responses, cell division and transcriptional control.

    PubMed

    González-Pérez, Lien; Perrotta, Lara; Acosta, Alexis; Orellana, Esteban; Spadafora, Natasha; Bruno, Leonardo; Bitonti, Beatrice M; Albani, Diego; Cabrera, Juan Carlos; Francis, Dennis; Rogers, Hilary J

    2014-10-01

    Xyloglucan oligosaccharides (XGOs) are breakdown products of XGs, the most abundant hemicelluloses of the primary cell walls of non-Poalean species. Treatment of cell cultures or whole plants with XGOs results in accelerated cell elongation and cell division, changes in primary root growth, and a stimulation of defence responses. They may therefore act as signalling molecules regulating plant growth and development. Previous work suggests an interaction with auxins and effects on cell wall loosening, however their mode of action is not fully understood. The effect of an XGO extract from tamarind (Tamarindus indica) on global gene expression was therefore investigated in tobacco BY-2 cells using microarrays. Over 500 genes were differentially regulated with similar numbers and functional classes of genes up- and down-regulated, indicating a complex interaction with the cellular machinery. Up-regulation of a putative XG endotransglycosylase/hydrolase-related (XTH) gene supports the mechanism of XGO action through cell wall loosening. Differential expression of defence-related genes supports a role for XGOs as elicitors. Changes in the expression of genes related to mitotic control and differentiation also support previous work showing that XGOs are mitotic inducers. XGOs also affected expression of several receptor-like kinase genes and transcription factors. Hence, XGOs have significant effects on expression of genes related to cell wall metabolism, signalling, stress responses, cell division and transcriptional control.

  7. Determination of cell division axes in the early embryogenesis of Caenorhabditis elegans

    PubMed Central

    1987-01-01

    The establishment of cell division axes was examined in the early embryonic divisions of Caenorhabditis elegans. It has been shown previously that there are two different patterns of cleavage during early embryogenesis. In one set of cells, which undergo predominantly determinative divisions, the division axes are established successively in the same orientation, while division axes in the other set, which divide mainly proliferatively, have an orthogonal pattern of division. We have investigated the establishment of these axes by following the movement of the centrosomes. Centrosome separation follows a reproducible pattern in all cells, and this pattern by itself results in an orthogonal pattern of cleavage. In those cells that divide on the same axis, there is an additional directed rotation of pairs of centrosomes together with the nucleus through well-defined angles. Intact microtubules are required for rotation; rotation is prevented by inhibitors of polymerization and depolymerization of microtubules. We have examined the distribution of microtubules in fixed embryos during rotation. From these and other data we infer that microtubules running from the centrosome to the cortex have a central role in aligning the centrosome-nuclear complex. PMID:3680373

  8. Notch signaling acts before cell division to promote asymmetric cleavage and cell fate of neural precursor cells.

    PubMed

    Bhat, Krishna Moorthi

    2014-10-21

    Asymmetric cell divisions in the central nervous system generate neurons of diverse fates. In Drosophila melanogaster, the protein Numb localizes asymmetrically to dividing neural precursor cells such that only one daughter cell inherits Numb. Numb inhibits Notch signaling in this daughter cell, resulting in a different cell fate from the Notch-induced fate in the other-Numb-negative-daughter cell. Precursor cells undergo asymmetric cytokinesis generating daughter cells of different sizes. I found that inactivation of Notch in fly embryonic neural precursor cells disrupted the asymmetric positioning of the cleavage furrow and produced daughter cells of the same size and fate. Moreover, inactivation of Notch at different times altered the degree of asymmetric Numb localization, such that earlier inactivation of Notch caused symmetric distribution of Numb and later inactivation produced incomplete asymmetric localization of Numb. The extent of asymmetrically localized Numb positively correlated with the degree of asymmetric cytokinesis and the size disparity in daughter cells. Loss of Numb or expression of constitutively active Notch led to premature specification of the precursor cells into the fate of one of the daughter cells. Thus, in addition to its role in the specification of daughter cell fate after division, Notch controls Numb localization in the precursor cells to determine the size and fate of daughter cells. Numb also inhibits Notch signaling in precursor cells to prevent Notch-induced differentiation of the precursor cell, forming an autoregulatory loop.

  9. Polarity and cell division orientation in the cleavage embryo: from worm to human

    PubMed Central

    Ajduk, Anna; Zernicka-Goetz, Magdalena

    2016-01-01

    Cleavage is a period after fertilization, when a 1-cell embryo starts developing into a multicellular organism. Due to a series of mitotic divisions, the large volume of a fertilized egg is divided into numerous smaller, nucleated cells—blastomeres. Embryos of different phyla divide according to different patterns, but molecular mechanism of these early divisions remains surprisingly conserved. In the present paper, we describe how polarity cues, cytoskeleton and cell-to-cell communication interact with each other to regulate orientation of the early embryonic division planes in model animals such as Caenorhabditis elegans, Drosophila and mouse. We focus particularly on the Par pathway and the actin-driven cytoplasmic flows that accompany it. We also describe a unique interplay between Par proteins and the Hippo pathway in cleavage mammalian embryos. Moreover, we discuss the potential meaning of polarity, cytoplasmic dynamics and cell-to-cell communication as quality biomarkers of human embryos. PMID:26660321

  10. High frame-rate resolution of cell division during Candida albicans filamentation

    PubMed Central

    Thomson, Darren D.; Berman, Judith; Brand, Alexandra C.

    2016-01-01

    The commensal yeast, Candida albicans, is an opportunistic pathogen in humans and forms filaments called hyphae and pseudohyphae, in which cell division requires precise temporal and spatial control to produce mononuclear cell compartments. High-frame-rate live-cell imaging (1 frame/min) revealed that nuclear division did not occur across the septal plane. We detected the presence of nucleolar fragments that may be extrachromosomal molecules carrying the ribosomal RNA genes. Cells occasionally maintained multiple nucleoli, suggesting either polyploidy, multiple nuclei and/or aneuploidy of ChrR., while the migration pattern of sister nuclei differed between unbranched and branched hyphae. The presented movie challenges and extends previous concepts of C. albicans cell division. PMID:26854071

  11. High frame-rate resolution of cell division during Candida albicans filamentation.

    PubMed

    Thomson, Darren D; Berman, Judith; Brand, Alexandra C

    2016-03-01

    The commensal yeast, Candida albicans, is an opportunistic pathogen in humans and forms filaments called hyphae and pseudohyphae, in which cell division requires precise temporal and spatial control to produce mononuclear cell compartments. High-frame-rate live-cell imaging (1 frame/min) revealed that nuclear division did not occur across the septal plane. We detected the presence of nucleolar fragments that may be extrachromosomal molecules carrying the ribosomal RNA genes. Cells occasionally maintained multiple nucleoli, suggesting either polyploidy, multiple nuclei and/or aneuploidy of ChrR., while the migration pattern of sister nuclei differed between unbranched and branched hyphae. The presented movie challenges and extends previous concepts of C. albicans cell division.

  12. Supporting cell division is not required for regeneration of auditory hair cells after ototoxic injury in vitro.

    PubMed

    Shang, Jialin; Cafaro, Jon; Nehmer, Rachel; Stone, Jennifer

    2010-06-01

    In chickens, nonsensory supporting cells divide and regenerate auditory hair cells after injury. Anatomical evidence suggests that supporting cells can also transdifferentiate into hair cells without dividing. In this study, we characterized an organ culture model to study auditory hair cell regeneration, and we used these cultures to test if direct transdifferentiation alone can lead to significant hair cell regeneration. Control cultures (organs from posthatch chickens maintained without streptomycin) showed complete hair cell loss in the proximal (high-frequency) region by 5 days. In contrast, a 2-day treatment with streptomycin induced loss of hair cells from all regions by 3 days. Hair cell regeneration proceeded in culture, with the time course of supporting cell division and hair cell differentiation generally resembling in vivo patterns. The degree of supporting cell division depended upon the presence of streptomycin, the epithelial region, the type of culture media, and serum concentration. On average, 87% of the regenerated hair cells lacked the cell division marker BrdU despite its continuous presence, suggesting that most hair cells were regenerated via direct transdifferentiation. Addition of the DNA polymerase inhibitor aphidicolin to culture media prevented supporting cell division, but numerous hair cells were regenerated nonetheless. These hair cells showed signs of functional maturation, including stereociliary bundles and rapid uptake of FM1-43. These observations demonstrate that direct transdifferentiation is a significant mechanism of hair cell regeneration in the chicken auditory after streptomycin damage in vitro.

  13. Biased inheritance of mitochondria during asymmetric cell division in the mouse oocyte.

    PubMed

    Dalton, Caroline M; Carroll, John

    2013-07-01

    A fundamental rule of cell division is that daughter cells inherit half the DNA complement and an appropriate proportion of cellular organelles. The highly asymmetric cell divisions of female meiosis present a different challenge because one of the daughters, the polar body, is destined to degenerate, putting at risk essential maternally inherited organelles such as mitochondria. We have therefore investigated mitochondrial inheritance during the meiotic divisions of the mouse oocyte. We find that mitochondria are aggregated around the spindle by a dynein-mediated mechanism during meiosis I, and migrate together with the spindle towards the oocyte cortex. However, at cell division they are not equally segregated and move instead towards the oocyte-directed spindle pole and are excluded from the polar body. We show that this asymmetrical inheritance in favour of the oocyte is not caused by bias in the spindle itself but is dependent on an intact actin cytoskeleton, spindle-cortex proximity, and cell cycle progression. Thus, oocyte-biased inheritance of mitochondria is a variation on rules that normally govern organelle segregation at cell division, and ensures that essential maternally inherited mitochondria are retained to provide ATP for early mammalian development.

  14. Cell division patterns and chromosomal segregation defects in oral cancer stem cells.

    PubMed

    Kaseb, Hatem O; Lewis, Dale W; Saunders, William S; Gollin, Susanne M

    2016-09-01

    Oral squamous cell carcinoma (OSCC) is a serious public health problem caused primarily by smoking and alcohol consumption or human papillomavirus. The cancer stem cell (CSC) theory posits that CSCs show unique characteristics, including self-renewal and therapeutic resistance. Examining biomarkers and other features of CSCs is critical to better understanding their biology. To this end, the results show that cellular SOX2 immunostaining correlates with other CSC biomarkers in OSCC cell lines and marks the rare CSC population. To assess whether CSC division patterns are symmetrical, resulting in two CSC, or asymmetrical, leading to one CSC and one cancer cell, cell size and fluorescence intensity of mitotic cells stained with SOX2 were analyzed. Asymmetrical SOX2 distribution in ≈25% of the mitoses analyzed was detected. Chromosomal instability, some of which is caused by chromosome segregation defects (CSDs), is a feature of cancer cells that leads to altered gene copy numbers. We compare chromosomal instability (as measured by CSDs) between CSCs (SOX2+) and non-CSCs (SOX2-) from the same OSCC cell lines. CSDs were more common in non-CSCs (SOX2-) than CSCs (SOX2+) and in symmetrical CSC (SOX2+) mitotic pairs than asymmetrical CSC (SOX2+/SOX2-) mitotic pairs. CSCs showed fewer and different types of CSDs after ionizing radiation treatment than non-CSCs. Overall, these data are the first to demonstrate both symmetrical and asymmetrical cell divisions with CSDs in OSCC CSC. Further, the results suggest that CSCs may undergo altered behavior, including therapeutic resistance as a result of chromosomal instability due to chromosome segregation defects. © 2016 Wiley Periodicals, Inc.

  15. Isolated rat cortical progenitor cells are maintained in division in vitro by membrane-associated factors.

    PubMed

    Temple, S; Davis, A A

    1994-04-01

    Ventricular zone cells in the developing CNS undergo extensive cell division in vivo and under certain conditions in vitro. The culture conditions that promote cell division have been studied to determine the role that contact with cell membrane associated factors play in the proliferation of these cells. Progenitor cells have been taken from the ventricular zone of developing rat cerebral cortex and placed into microwells. Small clusters of these cells can generate large numbers of neurons and non-neuronal progeny. In contrast, single progenitor cells largely cease division, approximately 90% acquiring neuron-like characteristics by 1 day in vitro. DiI-labeled, single cells from embryonic day 14 cortex plated onto clusters of unmarked progenitor cells have a significantly higher probability (approximately 3-fold) of maintaining a progenitor cell phenotype than if plated onto the plastic substratum around 100 microns away from the clusters. Contact with purified astrocytes also promotes the progenitor cell phenotype, whereas contact with meningeal fibroblasts or balb3T3 cells promotes their differentiation. Membrane homogenates from cortical astrocytes stimulate significantly more incorporation of BrdU by E14 cortical progenitor cells than membrane homogenates from meningeal fibroblasts. These data indicate that the proliferation of rat cortical progenitor cells can be maintained by cell-type specific, membrane-associated factors.

  16. Evaluation of the Asymmetric Division of Drosophila Male Germline Stem Cells.

    PubMed

    Inaba, Mayu; Yamashita, Yukiko M

    2017-01-01

    Asymmetric cell division (ACD) is utilized in many stem cell systems to produce two daughter cells with different cell fates. Despite the fundamental importance of ACD during development and tissue homeostasis, the nature of ACD is far from being fully understood. Step-by-step observation of events during ACD allows us to understand processes that lead to ACD. Here we describe examples of how we evaluate ACD in vivo using the Drosophila male germline stem cell system.

  17. Cell division versus cell elongation: the control of radicle elongation during thermoinhibition of Tagetes minuta achenes.

    PubMed

    Taylor, Nicky J; Hills, Paul N; van Staden, Johannes

    2007-12-01

    Endogenous embryo factors, which act mainly in the radicle, prevent germination in Tagetes minuta at high temperatures. These factors act to prevent cell elongation, which is critical for radicle protrusion under optimal conditions. Once the radicle has emerged both cell elongation and cell division are required for post-germination growth. Germination can be induced at high temperatures by fusicoccin, which rapidly stimulates cell elongation. In addition, priming seeds at 25 degrees C on polyethylene glycol (PEG) 6000 and mannitol could also induce germination on water at 36 degrees C, indicating that priming prevents radicle protrusion at a point subsequent to the point of control in thermoinhibited achenes. Flow cytometry studies revealed that DNA synthesis occurs during thermoinhibition and the inhibition of DNA synthesis during this process inhibits subsequent germination on water under optimal conditions, suggesting a protective role for DNA synthesis in thermoinhibited achenes of T. minuta.

  18. Cell polarity, auxin transport, and cytoskeleton-mediated division planes: who comes first?

    PubMed

    Dhonukshe, Pankaj; Kleine-Vehn, Jürgen; Friml, Jiri

    2005-10-01

    In plants, cell polarity is an issue more recurring than in other systems, because plants, due to their adaptive and flexible development, often change cell polarity postembryonically according to intrinsic cues and demands of the environment. Recent findings on the directional movement of the plant signalling molecule auxin provide a unique connection between individual cell polarity and the establishment of polarity at the tissue, organ, and whole-plant levels. Decisions about the subcellular polar targeting of PIN auxin transport components determine the direction of auxin flow between cells and consequently mediate multiple developmental events. In addition, mutations or chemical interference with PIN-based auxin transport result in abnormal cell divisions. Thus, the complicated links between cell polarity establishment, auxin transport, cytoskeleton, and oriented cell divisions now begin to emerge. Here we review the available literature on the issues of cell polarity in both plants and animals to extend our understanding on the generation, maintenance, and transmission of cell polarity in plants.

  19. The role of cortical pattern in timing of cell division and morphogenesis in Stentor.

    PubMed

    De Terra, N

    1977-05-01

    This paper describes experiments involving reciprocal exchange of the oral apparatus between a large (L) and a small (S) strain of Stentor coeruleus. Mature L-strain stentors given and S-strain oral apparatus formed an oral primordium in response to the presence of abnormally small oral structures and mostly divided although a few reorganized instead. Conversely, when S-strain stentors in early division were given a large L-strain oral apparatus, they resorbed the developing primordium and returned to interphase. When combined with previous results, these findings provide evidence for the hypothesis that the time of cell division in Stentor is determined by a "critical" ratio between the size of the oral apparatus and the size of the cell body (somatic) cortex. This ratio develops because the somatic cortex grows during interphase and the oral apparatus does not. Cell division in Stentor therefore appears to be initiated by a cortical pattern change resulting from cell surface growth during interphase.

  20. MIRO1 influences the morphology and intracellular distribution of mitochondria during embryonic cell division in Arabidopsis.

    PubMed

    Yamaoka, Shohei; Nakajima, Masaki; Fujimoto, Masaru; Tsutsumi, Nobuhiro

    2011-02-01

    Regulating the morphology and intracellular distribution of mitochondria is essential for embryo development in animals. However, the importance of such regulation is not clearly defined in plants. The evolutionarily conserved Miro proteins are known to be involved in the regulation of mitochondrial morphology and motility. We previously demonstrated that MIRO1, an Arabidopsis thaliana orthologue of the Miro protein, is required for embryogenesis. An insertional mutation in the MIRO1 gene causes arrest of embryonic cell division, leading to abortion of the embryo at an early stage. Here we investigated the role of MIRO1 in the regulation of mitochondrial behaviour in egg cells and early-stage embryos using GFP-labeled mitochondria. Two-photon laser scanning microscopy revealed that, in miro1 mutant egg cells, mitochondria are abnormally enlarged, although egg cell formation is nearly unaffected. After fertilization and subsequent zygotic cell division, the homozygous miro1 mutant two-celled embryo contained a significantly reduced number of mitochondria in its apical cell compared with the wild type, suggesting that the miro1 mutation inhibits proper intracellular distribution of mitochondria, leading to an arrest of embryonic cell division. Our findings suggest that proper mitochondrial morphology and intracellular distribution are maintained by MIRO1 and are vital for embryonic cell division.

  1. Dystrophin expression in muscle stem cells regulates their polarity and asymmetric division.

    PubMed

    Dumont, Nicolas A; Wang, Yu Xin; von Maltzahn, Julia; Pasut, Alessandra; Bentzinger, C Florian; Brun, Caroline E; Rudnicki, Michael A

    2015-12-01

    Dystrophin is expressed in differentiated myofibers, in which it is required for sarcolemmal integrity, and loss-of-function mutations in the gene that encodes it result in Duchenne muscular dystrophy (DMD), a disease characterized by progressive and severe skeletal muscle degeneration. Here we found that dystrophin is also highly expressed in activated muscle stem cells (also known as satellite cells), in which it associates with the serine-threonine kinase Mark2 (also known as Par1b), an important regulator of cell polarity. In the absence of dystrophin, expression of Mark2 protein is downregulated, resulting in the inability to localize the cell polarity regulator Pard3 to the opposite side of the cell. Consequently, the number of asymmetric divisions is strikingly reduced in dystrophin-deficient satellite cells, which also display a loss of polarity, abnormal division patterns (including centrosome amplification), impaired mitotic spindle orientation and prolonged cell divisions. Altogether, these intrinsic defects strongly reduce the generation of myogenic progenitors that are needed for proper muscle regeneration. Therefore, we conclude that dystrophin has an essential role in the regulation of satellite cell polarity and asymmetric division. Our findings indicate that muscle wasting in DMD not only is caused by myofiber fragility, but also is exacerbated by impaired regeneration owing to intrinsic satellite cell dysfunction.

  2. Planar Cell Polarity Aligns Osteoblast Division in Response to Substrate Strain

    PubMed Central

    Galea, Gabriel L; Meakin, Lee B; Savery, Dawn; Taipaleenmaki, Hanna; Delisser, Peter; Stein, Gary S; Copp, Andrew J; van Wijnen, Andre J; Lanyon, Lance E; Price, Joanna S

    2015-01-01

    Exposure of bone to dynamic strain increases the rate of division of osteoblasts and also influences the directional organization of the cellular and molecular structure of the bone tissue that they produce. Here, we report that brief exposure to dynamic substrate strain (sufficient to rapidly stimulate cell division) influences the orientation of osteoblastic cell division. The initial proliferative response to strain involves canonical Wnt signaling and can be blocked by sclerostin. However, the strain-related orientation of cell division is independently influenced through the noncanonical Wnt/planar cell polarity (PCP) pathway. Blockade of Rho-associated coiled kinase (ROCK), a component of the PCP pathway, prevents strain-related orientation of division in osteoblast-like Saos-2 cells. Heterozygous loop-tail mutation of the core PCP component van Gogh-like 2 (Vangl2) in mouse osteoblasts impairs the orientation of division in response to strain. Examination of bones from Vangl2 loop-tail heterozygous mice by µCT and scanning electron microscopy reveals altered bone architecture and disorganized bone-forming surfaces. Hence, in addition to the well-accepted role of PCP involvement in response to developmental cues during skeletal morphogenesis, our data reveal that this pathway also acts postnatally, in parallel with canonical Wnt signaling, to transduce biomechanical cues into skeletal adaptive responses. The simultaneous and independent actions of these two pathways appear to influence both the rate and orientation of osteoblast division, thus fine-tuning bone architecture to meet the structural demands of functional loading. © 2014 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research. PMID:25264362

  3. Mutations in the Diageotropica (Dgt) gene uncouple patterned cell division during lateral root initiation from proliferative cell division in the pericycle.

    PubMed

    Ivanchenko, Maria G; Coffeen, Warren C; Lomax, Terri L; Dubrovsky, Joseph G

    2006-05-01

    In angiosperms, root branching requires a continuous re-initiation of new root meristems. Through some unknown mechanism, in most eudicots pericycle cells positioned against the protoxylem change identity and initiate patterned division, leading to formation of lateral root primordia that further develop into lateral roots. This process is auxin-regulated. We have observed that three mutations in the Diageotropica (Dgt) gene in tomato prevent primordium formation. Detailed analysis of one of these mutants, dgt1-1, demonstrated that the mutation does not abolish the proliferative capacity of the xylem-adjacent pericycle in the differentiated root portion. Files of shortened pericycle cells found in dgt1-1 roots were unrelated to primordium formation. Auxin application stimulated this unusual proliferation, leading to formation of a multi-layered xylem-adjacent pericycle, but did not rescue the primordium formation. In contrast to wild type, auxin could not induce any cell divisions in the pericycle of the most distal dgt1-1 root-tip portion. In wild-type roots, the Dgt gene promoter was expressed strongly in lateral root primordia starting from their initiation, and on auxin treatment was induced in the primary root meristem. Auxin level and distribution were altered in dgt1-1 root tissues, as judged by direct auxin measurements, and the tissue-specific expression of an auxin-response reporter was altered in transgenic plants. Together, our data demonstrate that the Dgt gene product, a type-A cyclophilin, is essential for morphogenesis of lateral root primordia, and that the dgt mutations uncouple patterned cell division in lateral root initiation from proliferative cell division in the pericycle.

  4. De novo cortical cell division triggered by the phytopathogen Rhodococcus fascians in tobacco.

    PubMed

    de O Manes, C L; Van Montagu, M; Prinsen, E; Goethals, K; Holsters, M

    2001-02-01

    Plant growth, development, and morphology can be affected by several environmental stimuli and by specific interactions with phytopathogens. In many cases, plants respond to pathogenic stimuli by adapting their hormone levels. Here, the interaction between the phytopathogen Rhodococcus fascians and one of its host plants, tobacco, was analyzed phenotypically and molecularly. To elucidate the basis of the cell division modulation and shoot primordia initiation caused by R. fascians, tobacco plants were infected at leaf axils and shoot apices. Adventitious meristems that gave rise to multiple-shoot primordia (leafy galls) were formed. The use of a transgenic line carrying the mitotic CycB1 promoter fused to the reporter gene coding for beta-glucuronidase from Escherichia coli (uidA), revealed that stem cortical cells were stimulated to divide in an initial phase of the leafy gall ontogenesis. Local cytokinin and auxin levels throughout the infection process as well as modulation of expression of the cell cycle regulator gene Nicta;CycD3;2 are discussed.

  5. Dystrophin expression in muscle stem cells regulates their polarity and asymmetric division

    PubMed Central

    Dumont, Nicolas A.; Wang, Yu Xin; von Maltzahn, Julia; Pasut, Alessandra; Bentzinger, C. Florian; Brun, Caroline E.; Rudnicki, Michael A.

    2016-01-01

    Dystrophin is expressed in differentiated myofibers where it is required for sarcolemmal integrity, and loss-of-function mutations in its gene result in Duchenne Muscular Dystrophy (DMD), a disease characterized by progressive and severe skeletal muscle degeneration. Here we found that dystrophin is also highly expressed in activated muscle stem cells (also known as satellite cells) where it associates with the Ser/Thr kinase Mark2 (also known as Par1b), an important regulator of cell polarity. In the absence of dystrophin, expression of Mark2 protein is downregulated, resulting in the inability to polarize Pard3 to the opposite side of the cell. Consequently, the number of asymmetric divisions is strikingly reduced in dystrophin-deficient satellite cells, while also displaying a loss of polarity, abnormal division patterns including centrosome amplification, impaired mitotic spindle orientation, and prolonged cell divisions. Altogether, these intrinsic defects strongly reduce the generation of myogenic progenitors needed for proper muscle regeneration. Therefore, we conclude that dystrophin has an essential role in the regulation of satellite cell polarity and asymmetric division. Our findings indicate that muscle wasting in DMD is not only caused by myofiber fragility, but is also exacerbated by impaired regeneration due to intrinsic satellite cell dysfunction. PMID:26569381

  6. Wnt signaling controls the stem cell-like asymmetric division of the epithelial seam cells during C. elegans larval development.

    PubMed

    Gleason, Julie E; Eisenmann, David M

    2010-12-01

    Metazoan stem cells repopulate tissues during adult life by dividing asymmetrically to generate another stem cell and a cell that terminally differentiates. Wnt signaling regulates the division pattern of stem cells in flies and vertebrates. While the short-lived nematode C. elegans has no adult somatic stem cells, the lateral epithelial seam cells divide in a stem cell-like manner in each larval stage, usually generating a posterior daughter that retains the seam cell fate and an anterior daughter that terminally differentiates. We show that while wild-type adult animals have 16 seam cells per side, animals with reduced function of the TCF homolog POP-1 have as many as 67 seam cells, and animals with reduced function of the β-catenins SYS-1 and WRM-1 have as few as three. Analysis of seam cell division patterns showed alterations in their stem cell-like divisions in the L2-L4 stages: reduced Wnt signaling caused both daughters to adopt non-seam fates, while activated Wnt signaling caused both daughters to adopt the seam fate. Therefore, our results indicate that Wnt signaling globally regulates the asymmetric, stem cell-like division of most or all somatic seam cells during C. elegans larval development, and that Wnt pathway regulation of stem cell-like behavior is conserved in nematodes.

  7. Evolutionary Cell Biology of Division Mode in the Bacterial Planctomycetes-Verrucomicrobia- Chlamydiae Superphylum.

    PubMed

    Rivas-Marín, Elena; Canosa, Inés; Devos, Damien P

    2016-01-01

    Bacteria from the Planctomycetes, Verrucomicrobia, and Chlamydiae (PVC) superphylum are exceptions to the otherwise dominant mode of division by binary fission, which is based on the interaction between the FtsZ protein and the peptidoglycan (PG) biosynthesis machinery. Some PVC bacteria are deprived of the FtsZ protein and were also thought to lack PG. How these bacteria divide is still one of the major mysteries of microbiology. The presence of PG has recently been revealed in Planctomycetes and Chlamydiae, and proteins related to PG synthesis have been shown to be implicated in the division process in Chlamydiae, providing important insights into PVC mechanisms of division. Here, we review the historical lack of observation of PG in PVC bacteria, its recent detection in two phyla and its involvement in chlamydial cell division. Based on the detection of PG-related proteins in PVC proteomes, we consider the possible evolution of the diverse division mechanisms in these bacteria. We conclude by summarizing what is known and what remains to be understood about the evolutionary cell biology of PVC division modes.

  8. Evolutionary Cell Biology of Division Mode in the Bacterial Planctomycetes-Verrucomicrobia- Chlamydiae Superphylum

    PubMed Central

    Rivas-Marín, Elena; Canosa, Inés; Devos, Damien P.

    2016-01-01

    Bacteria from the Planctomycetes, Verrucomicrobia, and Chlamydiae (PVC) superphylum are exceptions to the otherwise dominant mode of division by binary fission, which is based on the interaction between the FtsZ protein and the peptidoglycan (PG) biosynthesis machinery. Some PVC bacteria are deprived of the FtsZ protein and were also thought to lack PG. How these bacteria divide is still one of the major mysteries of microbiology. The presence of PG has recently been revealed in Planctomycetes and Chlamydiae, and proteins related to PG synthesis have been shown to be implicated in the division process in Chlamydiae, providing important insights into PVC mechanisms of division. Here, we review the historical lack of observation of PG in PVC bacteria, its recent detection in two phyla and its involvement in chlamydial cell division. Based on the detection of PG-related proteins in PVC proteomes, we consider the possible evolution of the diverse division mechanisms in these bacteria. We conclude by summarizing what is known and what remains to be understood about the evolutionary cell biology of PVC division modes. PMID:28018303

  9. Asymmetric division of Drosophila male germline stem cell shows asymmetric histone distribution.

    PubMed

    Tran, Vuong; Lim, Cindy; Xie, Jing; Chen, Xin

    2012-11-02

    Stem cells can self-renew and generate differentiating daughter cells. It is not known whether these cells maintain their epigenetic information during asymmetric division. Using a dual-color method to differentially label "old" versus "new" histones in Drosophila male germline stem cells (GSCs), we show that preexisting canonical H3, but not variant H3.3, histones are selectively segregated to the GSC, whereas newly synthesized histones incorporated during DNA replication are enriched in the differentiating daughter cell. The asymmetric histone distribution occurs in GSCs but not in symmetrically dividing progenitor cells. Furthermore, if GSCs are genetically manipulated to divide symmetrically, this asymmetric mode is lost. This work suggests that stem cells retain preexisting canonical histones during asymmetric cell divisions, probably as a mechanism to maintain their unique molecular properties.

  10. Glyphosate-based pesticides affect cell cycle regulation.

    PubMed

    Marc, Julie; Mulner-Lorillon, Odile; Bellé, Robert

    2004-04-01

    Cell-cycle dysregulation is a hallmark of tumor cells and human cancers. Failure in the cell-cycle checkpoints leads to genomic instability and subsequent development of cancers from the initial affected cell. A worldwide used product Roundup 3plus, based on glyphosate as the active herbicide, was suggested to be of human health concern since it induced cell cycle dysfunction as judged from analysis of the first cell division of sea urchin embryos, a recognized model for cell cycle studies. Several glyphosate-based pesticides from different manufacturers were assayed in comparison with Roundup 3plus for their ability to interfere with the cell cycle regulation. All the tested products, Amega, Cargly, Cosmic, and Roundup Biovert induced cell cycle dysfunction. The threshold concentration for induction of cell cycle dysfunction was evaluated for each product and suggests high risk by inhalation for people in the vicinity of the pesticide handling sprayed at 500 to 4000 times higher dose than the cell-cycle adverse concentration.

  11. Asymmetric cell divisions in flowering plants - one mother, "two-many" daughters.

    PubMed

    Ranganath, R M

    2005-09-01

    Plant development shows a fascinating range of asymmetric cell divisions. Over the years, however, cellular differentiation has been interpreted mostly in terms of a mother cell dividing mitotically to produce two daughter cells of different fates. This popular view has masked the significance of an entirely different cell fate specification pathway, where the mother cell first becomes a coenocyte and then cellularizes to simultaneously produce more than two specialized daughter cells. The "one mother - two different daughters" pathways rely on spindle-assisted mechanisms, such as translocation of the nucleus/spindle to a specific cellular site and orientation of the spindle, which are coordinated with cell-specific allocation of cell fate determinants and cytokinesis. By contrast, during "coenocyte-cellularization" pathways, the spindle-assisted mechanisms are irrelevant since cell fate specification emerges only after the nuclear divisions are complete, and the number of specialized daughter cells produced depends on the developmental context. The key events, such as the formation of a coenocyte and migration of the nuclei to specific cellular locations, are coordinated with cellularization by unique types of cell wall formation. Both one mother - two different daughters and the coenocyte-cellularization pathways are used by higher plants in precise spatial and time windows during development. In both the pathways, epigenetic regulation of gene expression is crucial not only for cell fate specification but also for its maintenance through cell lineage. In this review, the focus is on the coenocyte-cellularization pathways in the context of our current understanding of the asymmetric cell divisions. Instances where cell differentiation does not involve an asymmetric division are also discussed to provide a comprehensive account of cell differentiation.

  12. A new class of cyclin dependent kinase in Chlamydomonas is required for coupling cell size to cell division

    PubMed Central

    Li, Yubing; Liu, Dianyi; López-Paz, Cristina; Olson, Bradley JSC; Umen, James G

    2016-01-01

    Proliferating cells actively control their size by mechanisms that are poorly understood. The unicellular green alga Chlamydomonas reinhardtii divides by multiple fission, wherein a ‘counting’ mechanism couples mother cell-size to cell division number allowing production of uniform-sized daughters. We identified a sizer protein, CDKG1, that acts through the retinoblastoma (RB) tumor suppressor pathway as a D-cyclin-dependent RB kinase to regulate mitotic counting. Loss of CDKG1 leads to fewer mitotic divisions and large daughters, while mis-expression of CDKG1 causes supernumerous mitotic divisions and small daughters. The concentration of nuclear-localized CDKG1 in pre-mitotic cells is set by mother cell size, and its progressive dilution and degradation with each round of cell division may provide a link between mother cell-size and mitotic division number. Cell-size-dependent accumulation of limiting cell cycle regulators such as CDKG1 is a potentially general mechanism for size control. DOI: http://dx.doi.org/10.7554/eLife.10767.001 PMID:27015111

  13. The equatorial position of the metaphase plate ensures symmetric cell divisions

    PubMed Central

    Tan, Chia Huei; Gasic, Ivana; Huber-Reggi, Sabina P; Dudka, Damian; Barisic, Marin; Maiato, Helder; Meraldi, Patrick

    2015-01-01

    Chromosome alignment in the middle of the bipolar spindle is a hallmark of metazoan cell divisions. When we offset the metaphase plate position by creating an asymmetric centriole distribution on each pole, we find that metaphase plates relocate to the middle of the spindle before anaphase. The spindle assembly checkpoint enables this centering mechanism by providing cells enough time to correct metaphase plate position. The checkpoint responds to unstable kinetochore–microtubule attachments resulting from an imbalance in microtubule stability between the two half-spindles in cells with an asymmetric centriole distribution. Inactivation of the checkpoint prior to metaphase plate centering leads to asymmetric cell divisions and daughter cells of unequal size; in contrast, if the checkpoint is inactivated after the metaphase plate has centered its position, symmetric cell divisions ensue. This indicates that the equatorial position of the metaphase plate is essential for symmetric cell divisions. DOI: http://dx.doi.org/10.7554/eLife.05124.001 PMID:26188083

  14. Cortical PAR polarity proteins promote robust cytokinesis during asymmetric cell division

    PubMed Central

    Jordan, Shawn N.; Davies, Tim; Zhuravlev, Yelena; Dumont, Julien; Shirasu-Hiza, Mimi

    2016-01-01

    Cytokinesis, the physical division of one cell into two, is thought to be fundamentally similar in most animal cell divisions and driven by the constriction of a contractile ring positioned and controlled solely by the mitotic spindle. During asymmetric cell divisions, the core polarity machinery (partitioning defective [PAR] proteins) controls the unequal inheritance of key cell fate determinants. Here, we show that in asymmetrically dividing Caenorhabditis elegans embryos, the cortical PAR proteins (including the small guanosine triphosphatase CDC-42) have an active role in regulating recruitment of a critical component of the contractile ring, filamentous actin (F-actin). We found that the cortical PAR proteins are required for the retention of anillin and septin in the anterior pole, which are cytokinesis proteins that our genetic data suggest act as inhibitors of F-actin at the contractile ring. Collectively, our results suggest that the cortical PAR proteins coordinate the establishment of cell polarity with the physical process of cytokinesis during asymmetric cell division to ensure the fidelity of daughter cell formation. PMID:26728855

  15. A novel bacterial tyrosine kinase essential for cell division and differentiation

    PubMed Central

    Wu, Jianguo; Ohta, Noriko; Zhao, Ji-Liang; Newton, Austin

    1999-01-01

    Protein kinases play central roles in the regulation of eukaryotic and prokaryotic cell growth, division, and differentiation. The Caulobacter crescentus divL gene encodes a novel bacterial tyrosine kinase essential for cell viability and division. Although the DivL protein is homologous to the ubiquitous bacterial histidine protein kinases (HPKs), it differs from previously studied members of this protein kinase family in that it contains a tyrosine residue (Tyr-550) in the conserved H-box instead of a histidine residue, which is the expected site of autophosphorylation. DivL is autophosphorylated on Tyr-550 in vitro, and this tyrosine residue is essential for cell viability and regulation of the cell division cycle. Purified DivL also catalyzes phosphorylation of CtrA and activates transcription in vitro of the cell cycle-regulated fliF promoter. Suppressor mutations in ctrA bypass the conditional cell division phenotype of cold-sensitive divL mutants, providing genetic evidence that DivL function in cell cycle and developmental regulation is mediated, at least in part, by the global response regulator CtrA. DivL is the only reported HPK homologue whose function has been shown to require autophosphorylation on a tyrosine, and, thus, it represents a new class of kinases within this superfamily of protein kinases. PMID:10557274

  16. A model of membrane contraction predicting initiation and completion of bacterial cell division.

    PubMed

    Dow, Claire E; Rodger, Alison; Roper, David I; van den Berg, Hugo A

    2013-05-01

    Bacterial cell division involves a complex and dynamic sequence of events whereby polymers of the protein FtsZ assemble at the division plane and rearrange to achieve the goal of contracting the cell membrane at the site of cell division, thus dividing the parent cell into two daughter cells. We present a mathematical model (which we refer to as CAM-FF: Critical Accumulation of Membrane-bound FtsZ Fibres) of the assembly of the contractile ring in terms of the accumulation of short linear polymers of FtsZ that associate and dissociate from the cell membrane. In prokaryotes, the biochemical function of FtsZ is thought to underpin the assembly and at least the initial kinetic force of ring contraction. Our model extends earlier work of Surovtsev et al. [PLoS Comput. Biol., 2008, 4, e1000102] by adding (i) the kinetics of FtsZ accumulation on cell membrane anchor proteins and (ii) the physical forces required to deform the cell against its surface tension. Moreover, we provide a more rigorous treatment of intracellular diffusion and we revise some of the model parameter values in light of the experimental evidence now available. We derive a critical contraction parameter which links the chemical population dynamics of membrane-bound FtsZ molecules to the force of contraction. Using this parameter as a tool to predict the ability of the cell to initiate division, we are able to predict the division outcome in cells depleted of key FtsZ-binding proteins.

  17. Evolution of the Min Protein Oscillation in E. coli Bacteria During Cell Growth and Division

    NASA Astrophysics Data System (ADS)

    Baylis, Benjamin; Giuliani, Maximiliano; Dutcher, John

    2014-03-01

    Cell division is a key step in the life of a bacterium. This process is carefully controlled and regulated so that the cellular machinery is equally partitioned into two daughter cells of equal size. In E. coli, this is accomplished, in part, by the Min protein system, in which Min proteins oscillate along the long axis of the rod-shaped cells. We have used high magnification, time-resolved fluorescence microscopy to characterize in detail the oscillation in E. coli cells in which the MinD proteins are tagged with green fluorescent protein (GFP). We have used a microfluidic device to confine the bacteria into microchannels that allows us to track the evolution of the oscillation in cells as they grow and divide in LB growth media. In particular, we have tracked the loss of synchrony between the oscillations in the daughter cells following cell division.

  18. Asymmetric division of clonal muscle stem cells coordinates muscle regeneration in vivo.

    PubMed

    Gurevich, David B; Nguyen, Phong Dang; Siegel, Ashley L; Ehrlich, Ophelia V; Sonntag, Carmen; Phan, Jennifer M N; Berger, Silke; Ratnayake, Dhanushika; Hersey, Lucy; Berger, Joachim; Verkade, Heather; Hall, Thomas E; Currie, Peter D

    2016-07-08

    Skeletal muscle is an example of a tissue that deploys a self-renewing stem cell, the satellite cell, to effect regeneration. Recent in vitro studies have highlighted a role for asymmetric divisions in renewing rare "immortal" stem cells and generating a clonal population of differentiation-competent myoblasts. However, this model currently lacks in vivo validation. We define a zebrafish muscle stem cell population analogous to the mammalian satellite cell and image the entire process of muscle regeneration from injury to fiber replacement in vivo. This analysis reveals complex interactions between satellite cells and both injured and uninjured fibers and provides in vivo evidence for the asymmetric division of satellite cells driving both self-renewal and regeneration via a clonally restricted progenitor pool.

  19. Increase of sister chromatid exchanges and perturbations of cell division kinetics in human lymphocytes by benzene metabolites

    SciTech Connect

    Morimoto, K.; Wolff, S.

    1980-04-01

    Benzene, which has been associated with human cancers, is metabolized to produce several major metabolites that could be responsible for the biological effects. Tests have now been carried out on human lymphocytes in culture to determine if benzene or its metabolites, phenol, catechol, and hydroquinone, induce cytogenetic changes and affect the cell cycle. The results indicate that benzene itself does not induce sister chromatid exchanges or affect cell cycle kinetics over a wide range of doses. Catechol is a potent compound that induces sister chromatid exchanges and delays cell division very readily. Hydroquinone is also potent, but less so than catechol. Thus, the formation of catechol and hydroquinone is the most likely cause of benzene toxicity.

  20. Cleavage-like cell division and explosive increase in cell number of neonatal gonocytes.

    PubMed

    Sakai, Yasuhiro; Noce, Toshiaki; Yamashina, Shohei

    2004-02-01

    Based on previous conventional quantitative observations of rat testes, it was proposed that large numbers of gonocytes degenerate after birth and this notion was widely accepted. However, many studies show that neonatal gonocytes display high levels of mitotic activity. In order to resolve the apparent contradiction of increased mitotic activity in gonocytes despite a decrease in their numbers at the neonate stage, quantitative analysis using a marker of suitably higher resolution is required. It has been shown that the vasa protein could be used as a marker of germ cells. In this study, quantitative changes in gonocytes were re-examined using a germ-cell-specific marker in order to delineate more clearly the process of development from gonocytes to spermatogonia after birth. The vasa-positive cells, which correspond to gonocytes and spermatogonia, increased exponentially after birth. This observation suggests that all gonocyte divide actively after birth and do not degenerate as previously believed. Surprisingly, the cell volume of gonocytes decreased during their division. The largest population size was 2000-4000 micro3 at day 2, 1000-2000 micro3 at day 4 and 500-1000 micro3 at day 6. This finding suggests that gonocytes divide in a similar way to cleavage, which can be considered a special mode of fertilized eggs. Judging from the growth of seminiferous tubules and the degree of volume reduction, 60% of the contribution rate is estimated to be due to ordinal cell growth, and 40% due to volume reduction as in cleavage of a fertilized egg. This unique cleavage-like division may contribute to the supply of large numbers of spermatogonia.

  1. Three-dimensional patterns of cell division and expansion throughout the development of Arabidopsis thaliana leaves.

    PubMed

    Kalve, Shweta; Fotschki, Joanna; Beeckman, Tom; Vissenberg, Kris; Beemster, Gerrit T S

    2014-12-01

    Variations in size and shape of multicellular organs depend on spatio-temporal regulation of cell division and expansion. Here, cell division and expansion rates were quantified relative to the three spatial axes in the first leaf pair of Arabidopsis thaliana. The results show striking differences in expansion rates: the expansion rate in the petiole is higher than in the leaf blade; expansion rates in the lateral direction are higher than longitudinal rates between 5 and 10 days after stratification, but become equal at later stages of leaf blade development; and anticlinal expansion co-occurs with, but is an order of magnitude slower than periclinal expansion. Anticlinal expansion rates also differed greatly between tissues: the highest rates occurred in the spongy mesophyll and the lowest in the epidermis. Cell division rates were higher and continued for longer in the epidermis compared with the palisade mesophyll, causing a larger increase of palisade than epidermal cell area over the course of leaf development. The cellular dynamics underlying the effect of shading on petiole length and leaf thickness were then investigated. Low light reduced leaf expansion rates, which was partly compensated by increased duration of the growth phase. Inversely, shading enhanced expansion rates in the petiole, so that the blade to petiole ratio was reduced by 50%. Low light reduced leaf thickness by inhibiting anticlinal cell expansion rates. This effect on cell expansion was preceded by an effect on cell division, leading to one less layer of palisade cells. The two effects could be uncoupled by shifting plants to contrasting light conditions immediately after germination. This extended kinematic analysis maps the spatial and temporal heterogeneity of cell division and expansion, providing a framework for further research to understand the molecular regulatory mechanisms involved.

  2. Asymmetric distribution of histones during Drosophila male germline stem cell asymmetric divisions.

    PubMed

    Tran, Vuong; Feng, Lijuan; Chen, Xin

    2013-05-01

    It has long been known that epigenetic changes are inheritable. However, except for DNA methylation, little is known about the molecular mechanisms of epigenetic inheritance. Many types of stem cells undergo asymmetric cell divisions to generate self-renewed stem cells and daughter cells committed for differentiation. Still, whether and how stem cells retain their epigenetic memory remain questions to be elucidated. During the asymmetric division of Drosophila male germline stem cell (GSC), our recent studies revealed that the preexisting histone 3 (H3) are selectively segregated to the GSC, whereas newly synthesized H3 deposited during DNA replication are enriched in the differentiating daughter cell. We propose a two-step model to explain this asymmetric histone distribution. First, prior to mitosis, preexisting histones and newly synthesized histones are differentially distributed at two sets of sister chromatids. Next, during mitosis, the set of sister chromatids that mainly consist of preexisting histones are segregated to GSCs, while the other set of sister chromatids enriched with newly synthesized histones are partitioned to the daughter cell committed for differentiation. In this review, we apply current knowledge about epigenetic inheritance and asymmetric cell division to inform our discussion of potential molecular mechanisms and the cellular basis underlying this asymmetric histone distribution pattern. We will also discuss whether this phenomenon contributes to the maintenance of stem cell identity and resetting chromatin structure in the other daughter cell for differentiation.

  3. Novel roles of plant RETINOBLASTOMA-RELATED (RBR) protein in cell proliferation and asymmetric cell division.

    PubMed

    Desvoyes, Bénédicte; de Mendoza, Alex; Ruiz-Trillo, Iñaki; Gutierrez, Crisanto

    2014-06-01

    The retinoblastoma (Rb) protein was identified as a human tumour suppressor protein that controls various stages of cell proliferation through the interaction with members of the E2F family of transcription factors. It was originally thought to be specific to animals but plants contain homologues of Rb, called RETINOBLASTOMA-RELATED (RBR). In fact, the Rb-E2F module seems to be a very early acquisition of eukaryotes. The activity of RBR depends on phosphorylation of certain amino acid residues, which in most cases are well conserved between plant and animal proteins. In addition to its role in cell-cycle progression, RBR has been shown to participate in various cellular processes such as endoreplication, transcriptional regulation, chromatin remodelling, cell growth, stem cell biology, and differentiation. Here, we discuss the most recent advances to define the role of RBR in cell proliferation and asymmetric cell division. These and other reports clearly support the idea that RBR is used as a landing platform of a plethora of cellular proteins and complexes to control various aspects of cell physiology and plant development.

  4. Endocytosis restricts Arabidopsis KNOLLE syntaxin to the cell division plane during late cytokinesis.

    PubMed

    Boutté, Yohann; Frescatada-Rosa, Márcia; Men, Shuzhen; Chow, Cheung-Ming; Ebine, Kazuo; Gustavsson, Anna; Johansson, Lenore; Ueda, Takashi; Moore, Ian; Jürgens, Gerd; Grebe, Markus

    2010-02-03

    Cytokinesis represents the final stage of eukaryotic cell division during which the cytoplasm becomes partitioned between daughter cells. The process differs to some extent between animal and plant cells, but proteins of the syntaxin family mediate membrane fusion in the plane of cell division in diverse organisms. How syntaxin localization is kept in check remains elusive. Here, we report that localization of the Arabidopsis KNOLLE syntaxin in the plane of cell division is maintained by sterol-dependent endocytosis involving a clathrin- and DYNAMIN-RELATED PROTEIN1A-dependent mechanism. On genetic or pharmacological interference with endocytosis, KNOLLE mis-localizes to lateral plasma membranes after cell-plate fusion. Fluorescence-loss-in-photo-bleaching and fluorescence-recovery-after-photo-bleaching experiments reveal lateral diffusion of GFP-KNOLLE from the plane of division to lateral membranes. In an endocytosis-defective sterol biosynthesis mutant displaying lateral KNOLLE diffusion, KNOLLE secretory trafficking remains unaffected. Thus, restriction of lateral diffusion by endocytosis may serve to maintain specificity of syntaxin localization during late cytokinesis.

  5. Wood Formation in Trees Is Increased by Manipulating PXY-Regulated Cell Division.

    PubMed

    Etchells, J Peter; Mishra, Laxmi S; Kumar, Manoj; Campbell, Liam; Turner, Simon R

    2015-04-20

    The woody tissue of trees is composed of xylem cells that arise from divisions of stem cells within the cambial meristem. The rate of xylem cell formation is dependent upon the rate of cell division within the cambium and is controlled by both genetic and environmental factors. In the annual plant Arabidopsis, signaling between a peptide ligand CLE41 and a receptor kinase PXY controls cambial cell divisions; however, the pathway regulating secondary growth in trees has not been identified. Here, we show that an aspen receptor kinase PttPXY and its peptide ligand PttCLE41 are functional orthologs and act to control a multifunctional pathway that regulates both the rate of cambial cell division and woody tissue organization. Ectopic overexpression of PttPXY and PttCLE41 genes in hybrid aspen resulted in vascular tissue abnormalities and poor plant growth. In contrast, precise tissue-specific overexpression generated trees that exhibited a 2-fold increase in the rate of wood formation, were taller, and possessed larger leaves compared to the controls. Our results demonstrate that the PXY-CLE pathway has evolved to regulate secondary growth and manipulating this pathway can result in dramatically increased tree growth and productivity.

  6. Strigolactones inhibit caulonema elongation and cell division in the moss Physcomitrella patens.

    PubMed

    Hoffmann, Beate; Proust, Hélène; Belcram, Katia; Labrune, Cécile; Boyer, François-Didier; Rameau, Catherine; Bonhomme, Sandrine

    2014-01-01

    In vascular plants, strigolactones (SLs) are known for their hormonal role and for their role as signal molecules in the rhizosphere. SLs are also produced by the moss Physcomitrella patens, in which they act as signaling factors for controlling filament extension and possibly interaction with neighboring individuals. To gain a better understanding of SL action at the cellular level, we investigated the effect of exogenously added molecules (SLs or analogs) in moss growth media. We used the previously characterized Ppccd8 mutant that is deficient in SL synthesis and showed that SLs affect moss protonema extension by reducing caulonema cell elongation and mainly cell division rate, both in light and dark conditions. Based on this effect, we set up bioassays to examine chemical structure requirements for SL activity in moss. The results suggest that compounds GR24, GR5, and 5-deoxystrigol are active in moss (as in pea), while other analogs that are highly active in the control of pea branching show little activity in moss. Interestingly, the karrikinolide KAR1, which shares molecular features with SLs, did not have any effect on filament growth, even though the moss genome contains several genes homologous to KAI2 (encoding the KAR1 receptor) and no canonical homologue to D14 (encoding the SL receptor). Further studies should investigate whether SL signaling pathways have been conserved during land plant evolution.

  7. A P-Loop NTPase Regulates Quiescent Center Cell Division and Distal Stem Cell Identity through the Regulation of ROS Homeostasis in Arabidopsis Root

    PubMed Central

    Yu, Qianqian; Tian, Huiyu; Liu, Jiajia; Zhang, Bing; Li, Xugang; Ding, Zhaojun

    2016-01-01

    Reactive oxygen species (ROS) are recognized as important regulators of cell division and differentiation. The Arabidopsis thaliana P-loop NTPase encoded by APP1 affects root stem cell niche identity through its control of local ROS homeostasis. The disruption of APP1 is accompanied by a reduction in ROS level, a rise in the rate of cell division in the quiescent center (QC) and the promotion of root distal stem cell (DSC) differentiation. Both the higher level of ROS induced in the app1 mutant by exposure to methyl viologen (MV), and treatment with hydrogen peroxide (H2O2) rescued the mutant phenotype, implying that both the increased rate of cell division in the QC and the enhancement in root DSC differentiation can be attributed to a low level of ROS. APP1 is expressed in the root apical meristem cell mitochondria, and its product is associated with ATP hydrolase activity. The key transcription factors, which are defining root distal stem niche, such as SCARECROW (SCR) and SHORT ROOT (SHR) are both significantly down-regulated at both the transcriptional and protein level in the app1 mutant, indicating that SHR and SCR are important downstream targets of APP1-regulated ROS signaling to control the identity of root QC and DSCs. PMID:27583367

  8. Mutants of Saccharomyces cerevisiae unresponsive to cell division control by polypeptide mating hormone

    PubMed Central

    1980-01-01

    Temperature-sensitive mutations that produce insensitivity to division arrest by alpha-factor, a mating pheromone, were isolated in an MATa strain of Saccharomyces cerevisiae and shown by complementation studies to difine eight genes. All of these mutations (designated ste) produce sterility at the restrictive temperature in MATa cells, and mutations in seven of the genes produce sterility in MAT alpha cells. In no case was the sterility associated with these mutations coorectible by including wild-type cells of the same mating type in the mating test nor did nay of the mutants inhibit mating of the wild-type cells; the defect appears to be intrinsic to the cell for mutations in each of the genes. Apparently, none of the mutants is defective exclusively in division arrest by alpha-factor, as the sterility of none is suppressed by a temperature-sensitive cdc 28 mutation (the latter imposes division arrest at the correct cell cycle stage for mating). The mutants were examined for features that are inducible in MATa cells by alpha-factor (agglutinin synthesis as well as division arrest) and for the characteristics that constitutively distinguish MATa from MAT alpha cells (a-factor production, alpha-factor destruction). ste2 Mutants are defective specifically in the two inducible properties, whereas ste4, 5, 7, 8, 9, 11, and 12 mutants are defective, to varying degrees, in constitutive as well as inducible aspects. Mutations in ste8 and 9 assume a polar budding pattern unlike either MATa or MAT alpha cells but characteristic of MATa/alpha cells. This study defines seven genes that function in two cell types (MATa and alpha) to control the differentiation of cell type and one gene, ste2, that functions exclusively in MATa cells to mediate responsiveness to polypeptide hormone. PMID:6993497

  9. A NAD-dependent glutamate dehydrogenase coordinates metabolism with cell division in Caulobacter crescentus

    PubMed Central

    Beaufay, François; Coppine, Jérôme; Mayard, Aurélie; Laloux, Géraldine; De Bolle, Xavier; Hallez, Régis

    2015-01-01

    Coupling cell cycle with nutrient availability is a crucial process for all living cells. But how bacteria control cell division according to metabolic supplies remains poorly understood. Here, we describe a molecular mechanism that coordinates central metabolism with cell division in the α-proteobacterium Caulobacter crescentus. This mechanism involves the NAD-dependent glutamate dehydrogenase GdhZ and the oxidoreductase-like KidO. While enzymatically active GdhZ directly interferes with FtsZ polymerization by stimulating its GTPase activity, KidO bound to NADH destabilizes lateral interactions between FtsZ protofilaments. Both GdhZ and KidO share the same regulatory network to concomitantly stimulate the rapid disassembly of the Z-ring, necessary for the subsequent release of progeny cells. Thus, this mechanism illustrates how proteins initially dedicated to metabolism coordinate cell cycle progression with nutrient availability. PMID:25953831

  10. The bacterium endosymbiont of Crithidia deanei undergoes coordinated division with the host cell nucleus.

    PubMed

    Motta, Maria Cristina Machado; Catta-Preta, Carolina Moura Costa; Schenkman, Sergio; de Azevedo Martins, Allan Cezar; Miranda, Kildare; de Souza, Wanderley; Elias, Maria Carolina

    2010-08-26

    In trypanosomatids, cell division involves morphological changes and requires coordinated replication and segregation of the nucleus, kinetoplast and flagellum. In endosymbiont-containing trypanosomatids, like Crithidia deanei, this process is more complex, as each daughter cell contains only a single symbiotic bacterium, indicating that the prokaryote must replicate synchronically with the host protozoan. In this study, we used light and electron microscopy combined with three-dimensional reconstruction approaches to observe the endosymbiont shape and division during C. deanei cell cycle. We found that the bacterium replicates before the basal body and kinetoplast segregations and that the nucleus is the last organelle to divide, before cytokinesis. In addition, the endosymbiont is usually found close to the host cell nucleus, presenting different shapes during the protozoan cell cycle. Considering that the endosymbiosis in trypanosomatids is a mutualistic relationship, which resembles organelle acquisition during evolution, these findings establish an excellent model for the understanding of mechanisms related with the establishment of organelles in eukaryotic cells.

  11. Homeostatic response to blocking cell division in Drosophila imaginal discs: Role of the Fat/Dachsous (Ft/Ds) pathway.

    PubMed

    Montes, Antonio J; Morata, Ginés

    2017-03-11

    One major problem in developmental biology is the identification of the mechanisms that control the final size of tissues and organs. We are addressing this issue in the imaginal discs of Drosophila by analysing the response to blocking cell division in large domains in the wing and leg discs. The affected domains may be zones of restricted lineage like compartments, or zones of open lineage that may integrate cells from the surrounding territory. Our results reveal the existence of a powerful homeostatic mechanism that can compensate for gross differences in growth rates and builds structures of normal size. This mechanism functions at the level of whole discs, inducing additional cell proliferation to generate the cells that populate the cell division-arrested territory and generating an active recruitment process to integrate those cells. The activation of this response mechanism is mediated by alterations in the normal activity of PCP genes of the Fat/Ds system: in discs mutant for dachs, ds or four jointed the response mechanism is not activated.

  12. Real-time prediction of cell division timing in developing zebrafish embryo

    PubMed Central

    Kozawa, Satoshi; Akanuma, Takashi; Sato, Tetsuo; Sato, Yasuomi D.; Ikeda, Kazushi; Sato, Thomas N.

    2016-01-01

    Combination of live-imaging and live-manipulation of developing embryos in vivo provides a useful tool to study developmental processes. Identification and selection of target cells for an in vivo live-manipulation are generally performed by experience- and knowledge-based decision-making of the observer. Computer-assisted live-prediction method would be an additional approach to facilitate the identification and selection of the appropriate target cells. Herein we report such a method using developing zebrafish embryos. We choose V2 neural progenitor cells in developing zebrafish embryo as their successive shape changes can be visualized in real-time in vivo. We developed a relatively simple mathematical method of describing cellular geometry of V2 cells to predict cell division-timing based on their successively changing shapes in vivo. Using quantitatively measured 4D live-imaging data, features of V2 cell-shape at each time point prior to division were extracted and a statistical model capturing the successive changes of the V2 cell-shape was developed. By applying sequential Bayesian inference method to the model, we successfully predicted division-timing of randomly selected individual V2 cells while the cell behavior was being live-imaged. This system could assist pre-selecting target cells desirable for real-time manipulation–thus, presenting a new opportunity for in vivo experimental systems. PMID:27597656

  13. Real-time prediction of cell division timing in developing zebrafish embryo.

    PubMed

    Kozawa, Satoshi; Akanuma, Takashi; Sato, Tetsuo; Sato, Yasuomi D; Ikeda, Kazushi; Sato, Thomas N

    2016-09-06

    Combination of live-imaging and live-manipulation of developing embryos in vivo provides a useful tool to study developmental processes. Identification and selection of target cells for an in vivo live-manipulation are generally performed by experience- and knowledge-based decision-making of the observer. Computer-assisted live-prediction method would be an additional approach to facilitate the identification and selection of the appropriate target cells. Herein we report such a method using developing zebrafish embryos. We choose V2 neural progenitor cells in developing zebrafish embryo as their successive shape changes can be visualized in real-time in vivo. We developed a relatively simple mathematical method of describing cellular geometry of V2 cells to predict cell division-timing based on their successively changing shapes in vivo. Using quantitatively measured 4D live-imaging data, features of V2 cell-shape at each time point prior to division were extracted and a statistical model capturing the successive changes of the V2 cell-shape was developed. By applying sequential Bayesian inference method to the model, we successfully predicted division-timing of randomly selected individual V2 cells while the cell behavior was being live-imaged. This system could assist pre-selecting target cells desirable for real-time manipulation-thus, presenting a new opportunity for in vivo experimental systems.

  14. Real-time prediction of cell division timing in developing zebrafish embryo

    NASA Astrophysics Data System (ADS)

    Kozawa, Satoshi; Akanuma, Takashi; Sato, Tetsuo; Sato, Yasuomi D.; Ikeda, Kazushi; Sato, Thomas N.

    2016-09-01

    Combination of live-imaging and live-manipulation of developing embryos in vivo provides a useful tool to study developmental processes. Identification and selection of target cells for an in vivo live-manipulation are generally performed by experience- and knowledge-based decision-making of the observer. Computer-assisted live-prediction method would be an additional approach to facilitate the identification and selection of the appropriate target cells. Herein we report such a method using developing zebrafish embryos. We choose V2 neural progenitor cells in developing zebrafish embryo as their successive shape changes can be visualized in real-time in vivo. We developed a relatively simple mathematical method of describing cellular geometry of V2 cells to predict cell division-timing based on their successively changing shapes in vivo. Using quantitatively measured 4D live-imaging data, features of V2 cell-shape at each time point prior to division were extracted and a statistical model capturing the successive changes of the V2 cell-shape was developed. By applying sequential Bayesian inference method to the model, we successfully predicted division-timing of randomly selected individual V2 cells while the cell behavior was being live-imaged. This system could assist pre-selecting target cells desirable for real-time manipulation–thus, presenting a new opportunity for in vivo experimental systems.

  15. Isolation of Chinese hamster ovary cell mutants requiring the continuous presence of taxol for cell division

    PubMed Central

    1983-01-01

    Chinese hamster ovary (CHO) cell mutants resistant to the cytotoxic effects of taxol and requiring the drug for normal growth were isolated in a single step. One of these mutant cell lines, Tax-18, fails to divide in the absence of taxol; instead, the cells become larger, rounder, flatter, and multinucleated. Analysis by flow cytometry indicates that during taxol deprivation there is an accumulation of cells in G2 + M phase but that the cells are able to leak through the block in the absence of cell division and further increase their DNA content beyond the tetraploid amount. This interpretation is confirmed by karyotype analysis and by time-lapse studies that show cells rounded for mitosis two to five times longer than in wild-type cultures or in Tax-18 cultures grown in taxol. The cells finally attempt to undergo cytokinesis, fail, and spread out again, but as larger cells than before. Tax-18 has a normal growth rate and morphology when grown in taxol even at concentrations three to five times below the selecting concentration of the drug. The cells, however, have increased sensitivity to microtubule-disrupting drugs such as colcemid, griseofulvin, and D2O. The mutation for taxol auxotrophy behaves recessively in somatic cell hybridization experiments, and the phenotypic reversion rate is approximately 10(-5) in a nonmutagenized population. Both alpha- and beta-tubulin are present in apparently normal amounts and with normal electrophoretic mobilities on two- dimensional gels. The results suggest that Tax-18 lacks a factor necessary for mitosis and that taxol may be able to substitute for this factor. PMID:6134736

  16. Phased cell division, specific division rates and other biological observations of Dinophysis populations in sub-surface layers off the south coast of Ireland

    NASA Astrophysics Data System (ADS)

    Farrell, Hazel; Velo-Suarez, Lourdes; Reguera, Beatriz; Raine, Robin

    2014-03-01

    The proportions of viable cells of Dinophysis spp. that were paired (dividing) and recently divided during a cell cycle were measured on populations of D. acuta and D. acuminata observed off the south coast of Ireland in July 2007 and July 2009. Both species exhibited phased cell division in 2009 with maximum frequency of division (fmax) 2 h after sunrise. Different patterns of division (timing of fmax) were shown by D. acuta in 2007, when the population aggregated in a thin layer was transported by a coastal jet flow. High resolution (decimetre-scale) profiles within the thin layer showed large differences in the vertical distribution of biological properties (feeding status, mortality). Values of the specific growth rate μ were compared to estimates derived in similar fashion from observations on Dinophysis populations elsewhere. Different patterns exhibited by the same species in different regions may be attributed to adaptations to latitudinal differences (length of photoperiod). The question of whether phased cell division always occurs in Dinophysis populations, and the incorporation of the potential specific division rate into models of Dinophysis growth are discussed. Comprehensive field data sets demonstrate the impact of the results on the coherence of Dinophysis populations during their transport along the Irish coast in jet-like flows towards sites of intensive shellfish culture.

  17. Pseudomonas aeruginosa Transmigrates at Epithelial Cell-Cell Junctions, Exploiting Sites of Cell Division and Senescent Cell Extrusion

    PubMed Central

    Golovkine, Guillaume; Faudry, Eric; Bouillot, Stéphanie; Elsen, Sylvie; Attrée, Ina; Huber, Philippe

    2016-01-01

    To achieve systemic infection, bacterial pathogens must overcome the critical and challenging step of transmigration across epithelial barriers. This is particularly true for opportunistic pathogens such as Pseudomonas aeruginosa, an agent which causes nosocomial infections. Despite extensive study, details on the mechanisms used by this bacterium to transmigrate across epithelial tissues, as well as the entry sites it uses, remain speculative. Here, using real-time microscopy and a model epithelial barrier, we show that P. aeruginosa employs a paracellular transmigration route, taking advantage of altered cell-cell junctions at sites of cell division or when senescent cells are expelled from the cell layer. Once a bacterium transmigrates, it is followed by a cohort of bacteria using the same entry point. The basal compartment is then invaded radially from the initial penetration site. Effective transmigration and propagation require type 4 pili, the type 3 secretion system (T3SS) and a flagellum, although flagellum-deficient bacteria can occasionally invade the basal compartment from wounded areas. In the basal compartment, the bacteria inject the T3SS toxins into host cells, disrupting the cytoskeleton and focal contacts to allow their progression under the cells. Thus, P. aeruginosa exploits intrinsic host cell processes to breach the epithelium and invade the subcellular compartment. PMID:26727615

  18. Contribution of the FtsQ Transmembrane Segment to Localization to the Cell Division Site▿

    PubMed Central

    Scheffers, Dirk-Jan; Robichon, Carine; Haan, Gert Jan; den Blaauwen, Tanneke; Koningstein, Gregory; van Bloois, Edwin; Beckwith, Jon; Luirink, Joen

    2007-01-01

    The Escherichia coli cell division protein FtsQ is a central component of the divisome. FtsQ is a bitopic membrane protein with a large C-terminal periplasmic domain. In this work we investigated the role of the transmembrane segment (TMS) that anchors FtsQ in the cytoplasmic membrane. A set of TMS mutants was made and analyzed for the ability to complement an ftsQ mutant. Study of the various steps involved in FtsQ biogenesis revealed that one mutant (L29/32R;V38P) failed to functionally insert into the membrane, whereas another mutant (L29/32R) was correctly assembled and interacted with FtsB and FtsL but failed to localize efficiently to the cell division site. Our results indicate that the FtsQ TMS plays a role in FtsQ localization to the division site. PMID:17693520

  19. Pattern formation on membranes and its role in bacterial cell division.

    PubMed

    Kretschmer, Simon; Schwille, Petra

    2016-02-01

    Bacterial cell division is arguably one of the most central processes in biology. Despite the identification of many important molecular players, surprisingly little is yet known about the underlying physicochemical mechanisms. However, self-organized protein patterns play key roles during division of Escherichia coli, where division is initiated by the directed localization of FtsZ to the cell middle by an inhibitor gradient arising from pole-to-pole oscillations of MinCDE proteins. In vitro reconstitution studies have established that both the Min system and FtsZ with its membrane adaptor FtsA form dynamic energy-dependent patterns on membranes. Furthermore, recent in vivo and in vitro approaches have shown that Min patterns display rich dynamics in diverse geometries and respond to the progress of cytokinesis.

  20. ER-mitochondria contacts couple mtDNA synthesis with mitochondrial division in human cells.

    PubMed

    Lewis, Samantha C; Uchiyama, Lauren F; Nunnari, Jodi

    2016-07-15

    Mitochondrial DNA (mtDNA) encodes RNAs and proteins critical for cell function. In human cells, hundreds to thousands of mtDNA copies are replicated asynchronously, packaged into protein-DNA nucleoids, and distributed within a dynamic mitochondrial network. The mechanisms that govern how nucleoids are chosen for replication and distribution are not understood. Mitochondrial distribution depends on division, which occurs at endoplasmic reticulum (ER)-mitochondria contact sites. These sites were spatially linked to a subset of nucleoids selectively marked by mtDNA polymerase and engaged in mtDNA synthesis--events that occurred upstream of mitochondrial constriction and division machine assembly. Our data suggest that ER tubules proximal to nucleoids are necessary but not sufficient for mtDNA synthesis. Thus, ER-mitochondria contacts coordinate licensing of mtDNA synthesis with division to distribute newly replicated nucleoids to daughter mitochondria.

  1. The selection of S. cerevisiae mutants defective in the start event of cell division.

    PubMed

    Reed, S I

    1980-07-01

    Thirty-three temperature-sensitive mutations defective in the start event of the cell division cycle of Saccharomyces cerevisiae were isolated and subjected to preliminary characterization. Complementation studies assigned thes mutations to four complementation groups, one of which, cdc28, has been described previously. Genetic analysis revealed that these complementation groups define single nuclear genes, unlinked to one another. One of the three newly identified genes, cdc37, has been located in the yeast linkage map on chromosome IV, two meiotic map units distal to hom2.--Each mutation produces stage-specific arrest of cell division at start, the same point where mating pheromone interrupts division. After synchronization at start by incubation at the restrictive temperature, the mutants retain the capacity to enlarge and to conjugate.

  2. Intrinsic characteristics of Min proteins on the cell division of Helicobacter pylori.

    PubMed

    Nishida, Yoshie; Takeuchi, Hiroaki; Morimoto, Norihito; Umeda, Akiko; Kadota, Yoshu; Kira, Mizuki; Okazaki, Ami; Matsumura, Yoshihisa; Sugiura, Tetsuro

    2016-03-01

    Helicobacter pylori divides in the human stomach resulting in persistent infections and causing various disorders. Bacterial cell division is precisely coordinated by many molecules, including FtsZ and Min proteins. However, the role of Min proteins in H. pylori division is poorly understood. We investigated the functional characteristics of Min proteins in wild-type HPK5 and five HPK5-derivative mutants using morphological and genetic approaches. All mutants showed a filamentous shape. However, the bacterial cell growth and viability of three single-gene mutants (minC, minD, minE) were similar to that of the wild-type. The coccoid form number was lowest in the minE-disruptant, indicating that MinE contributes to the coccoid form conversion during the stationary phase. Immunofluorescence microscopic observations showed that FtsZ was dispersedly distributed throughout the bacterial cell irrespective of nucleoid position in only minD-disruptants, indicating that MinD is involved in the nucleoid occlusion system. A chase assay demonstrated that MinC loss suppressed FtsZ-degradation, indicating that FtsZ degrades in a MinC-dependent manner. Molecular interactions between FtsZ and Min proteins were confirmed by immunoprecipitation (IP)-western blotting (WB), suggesting the functional cooperation of these molecules during bacterial cell division. This study describes the intrinsic characteristics of Min proteins and provides new insights into H. pylori cell division.

  3. Cell Division by Longitudinal Scission in the Insect Endosymbiont Spiroplasma poulsonii

    PubMed Central

    Maclachlan, Catherine; Clerc-Rosset, Stéphanie; Knott, Graham W.

    2016-01-01

    ABSTRACT Spiroplasma bacteria are highly motile bacteria with no cell wall and a helical morphology. This clade includes many vertically transmitted insect endosymbionts, including Spiroplasma poulsonii, a natural endosymbiont of Drosophila melanogaster. S. poulsonii bacteria are mainly found in the hemolymph of infected female flies and exhibit efficient vertical transmission from mother to offspring. As is the case for many facultative endosymbionts, S. poulsonii can manipulate the reproduction of its host; in particular, S. poulsonii induces male killing in Drosophila melanogaster. Here, we analyze the morphology of S. poulsonii obtained from the hemolymph of infected Drosophila. This endosymbiont was not only found as long helical filaments, as previously described, but was also found in a Y-shaped form. The use of electron microscopy, immunogold staining of the FtsZ protein, and antibiotic treatment unambiguously linked the Y shape of S. poulsonii to cell division. Observation of the Y shape in another Spiroplasma, S. citri, and anecdotic observations from the literature suggest that cell division by longitudinal scission might be prevalent in the Spiroplasma clade. Our study is the first to report the Y-shape mode of cell division in an endosymbiotic bacterium and adds Spiroplasma to the so far limited group of bacteria known to utilize this cell division mode. PMID:27460796

  4. A Diguanylate Cyclase Acts as a Cell Division Inhibitor in a Two-Step Response to Reductive and Envelope Stresses

    PubMed Central

    Kim, Hyo Kyung

    2016-01-01

    ABSTRACT Cell division arrest is a universal checkpoint in response to environmental assaults that generate cellular stress. In bacteria, the cyclic di-GMP (c-di-GMP) signaling network is one of several signal transduction systems that regulate key processes in response to extra-/intracellular stimuli. Here, we find that the diguanylate cyclase YfiN acts as a bifunctional protein that produces c-di-GMP in response to reductive stress and then dynamically relocates to the division site to arrest cell division in response to envelope stress in Escherichia coli. YfiN localizes to the Z ring by interacting with early division proteins and stalls cell division by preventing the initiation of septal peptidoglycan synthesis. These studies reveal a new role for a diguanylate cyclase in responding to environmental change, as well as a novel mechanism for arresting cell division. PMID:27507823

  5. Morphological analysis of nuclear separation and cell division during the life cycle of Escherichia coli.

    PubMed Central

    Woldringh, C L

    1976-01-01

    Quantitative electron microscope observations were performed on Escherichia coli B/r after balanced growth with doubling times (tau) of 32 and 60 min. The experimental approach allowed the timing of morphological events during the cell cycle by classifying serially sectioned cells according to length. Visible separation of the nucleoplasm was found to coincide with the time of termination of chromosome replication as predicted by the Cooper-Helmstetter model. The duration of the process of constrictive cell division (10 min) appeared to be independent of the growth rate for tau equals 60 min or less but to increase with increase doubling time in more slowly growing cells. Physiological division, i.e., compartmentalization prior to physical separation of the cells, was only observed to occur in the last minute of the cell cycle. The morphological results indicate that cell elongation continues during the division process in cells with tau equals 32 min, but fails to continue in cells with tau equals 60 min. Images PMID:1107308

  6. FORMOSA controls cell division and expansion during floral development in Antirrhinum majus.

    PubMed

    Delgado-Benarroch, Luciana; Causier, Barry; Weiss, Julia; Egea-Cortines, Marcos

    2009-05-01

    Control of organ size is the product of coordinated cell division and expansion. In plants where one of these pathways is perturbed, organ size is often unaffected as compensation mechanisms are brought into play. The number of founder cells in organ primordia, dividing cells, and the period of cell proliferation determine cell number in lateral organs. We have identified the Antirrhinum FORMOSA (FO) gene as a specific regulator of floral size. Analysis of cell size and number in the fo mutant, which has increased flower size, indicates that FO is an organ-specific inhibitor of cell division and activator of cell expansion. Increased cell number in fo floral organs correlated with upregulation of genes involved in the cell cycle. In Arabidopsis the AINTEGUMENTA (ANT) gene promotes cell division. In the fo mutant increased cell number also correlates with upregulation of an Antirrhinum ANT-like gene (Am-ANT) in inflorescences that is very closely related to ANT and shares a similar expression pattern, suggesting that they may be functional equivalents. Increased cell proliferation is thought to be compensated for by reduced cell expansion to maintain organ size. In Arabidopsis petal cell expansion is inhibited by the BIGPETAL (BPE) gene, and in the fo mutant reduced cell size corresponded to upregulation of an Antirrhinum BPE-like gene (Am-BPE). Our data suggest that FO inhibits cell proliferation by negatively regulating Am-ANT, and acts upstream of Am-BPE to coordinate floral organ size. This demonstrates that organ size is modulated by the organ-specific control of both general and local gene networks.

  7. The Utilization during Mitotic Cell Division of Loci Controlling Meiotic Recombination and Disjunction in DROSOPHILA MELANOGASTER

    PubMed Central

    Baker, Bruce S.; Carpenter, Adelaide T. C.; Ripoll, P.

    1978-01-01

    To inquire whether the loci identified by recombination-defective and disjunction-defective meiotic mutants in Drosophila are also utilized during mitotic cell division, the effects of 18 meiotic mutants (representing 13 loci) on mitotic chromosome stability have been examined genetically. To do this, meiotic-mutant-bearing flies heterozygous for recessive somatic cell markers were examined for the frequencies and types of spontaneous clones expressing the cell markers. In such flies, marked clones can arise via mitotic recombination, mutation, chromosome breakage, nondisjunction or chromosome loss, and clones from these different origins can be distinguished. In addition, meiotic mutants at nine loci have been examined for their effects on sensitivity to killing by UV and X rays.—Mutants at six of the seven recombination-defective loci examined (mei-9, mei-41, c(3)G, mei-W68, mei-S282, mei-352, mei-218) cause mitotic chromosome instability in both sexes, whereas mutants at one locus (mei-218) do not affect mitotic chromosome stability. Thus many of the loci utilized during meiotic recombination also function in the chromosomal economy of mitotic cells.—The chromosome instability produced by mei-41 alleles is the consequence of chromosome breakage, that of mei-9 alleles is primarily due to chromosome breakage and, to a lesser extent, to an elevated frequency of mitotic recombination, whereas no predominant mechanism responsible for the instability caused by c(3)G alleles is discernible. Since these three loci are defective in their responses to mutagen damage, their effects on chromosome stability in nonmutagenized cells are interpreted as resulting from an inability to repair spontaneous lesions. Both mei-W68 and mei-S282 increase mitotic recombination (and in mei-W68, to a lesser extent, chromosome loss) in the abdomen but not the wing. In the abdomen, the primary effect on chromosome stability occurs during the larval period when the abdominal histoblasts

  8. FtsZ-less prokaryotic cell division as well as FtsZ- and dynamin-less chloroplast and non-photosynthetic plastid division

    PubMed Central

    Miyagishima, Shin-ya; Nakamura, Mami; Uzuka, Akihiro; Era, Atsuko

    2014-01-01

    The chloroplast division machinery is a mixture of a stromal FtsZ-based complex descended from a cyanobacterial ancestor of chloroplasts and a cytosolic dynamin-related protein (DRP) 5B-based complex derived from the eukaryotic host. Molecular genetic studies have shown that each component of the division machinery is normally essential for normal chloroplast division. However, several exceptions have been found. In the absence of the FtsZ ring, non-photosynthetic plastids are able to proliferate, likely by elongation and budding. Depletion of DRP5B impairs, but does not stop chloroplast division. Chloroplasts in glaucophytes, which possesses a peptidoglycan (PG) layer, divide without DRP5B. Certain parasitic eukaryotes possess non-photosynthetic plastids of secondary endosymbiotic origin, but neither FtsZ nor DRP5B is encoded in their genomes. Elucidation of the FtsZ- and/or DRP5B-less chloroplast division mechanism will lead to a better understanding of the function and evolution of the chloroplast division machinery and the finding of the as-yet-unknown mechanism that is likely involved in chloroplast division. Recent studies have shown that FtsZ was lost from a variety of prokaryotes, many of which lost PG by regressive evolution. In addition, even some of the FtsZ-bearing bacteria are able to divide when FtsZ and PG are depleted experimentally. In some cases, alternative mechanisms for cell division, such as budding by an increase of the cell surface-to-volume ratio, are proposed. Although PG is believed to have been lost from chloroplasts other than in glaucophytes, there is some indirect evidence for the existence of PG in chloroplasts. Such information is also useful for understanding how non-photosynthetic plastids are able to divide in FtsZ-depleted cells and the reason for the retention of FtsZ in chloroplast division. Here we summarize information to facilitate analyses of FtsZ- and/or DRP5B-less chloroplast and non-photosynthetic plastid division. PMID

  9. Gibberellin reactivates and maintains ovary-wall cell division causing fruit set in parthenocarpic Citrus species.

    PubMed

    Mesejo, Carlos; Yuste, Roberto; Reig, Carmina; Martínez-Fuentes, Amparo; Iglesias, Domingo J; Muñoz-Fambuena, Natalia; Bermejo, Almudena; Germanà, M Antonietta; Primo-Millo, Eduardo; Agustí, Manuel

    2016-06-01

    Citrus is a wide genus in which most of the cultivated species and cultivars are natural parthenocarpic mutants or hybrids (i.e. orange, mandarin, tangerine, grapefruit). The autonomous increase in GA1 ovary concentration during anthesis was suggested as being the stimulus responsible for parthenocarpy in Citrus regardless of the species. To determine the exact GA-role in parthenocarpic fruit set, the following hypothesis was tested: GA triggers and maintains cell division in ovary walls causing fruit set. Obligate and facultative parthenocarpic Citrus species were used as a model system because obligate parthenocarpic Citrus sp (i.e. Citrus unshiu) have higher GA levels and better natural parthenocarpic fruit set compared to other facultative parthenocarpic Citrus (i.e. Citrus clementina). The autonomous activation of GA synthesis in C. unshiu ovary preceded cell division and CYCA1.1 up-regulation (a G2-stage cell cycle regulator) at anthesis setting a high proportion of fruits, whereas C. clementina lacked this GA-biosynthesis and CYCA1.1 up-regulation failing in fruit set. In situ hybridization experiments revealed a tissue-specific expression of GA20ox2 only in the dividing tissues of the pericarp. Furthermore, CYCA1.1 expression correlated endogenous GA1 content with GA3 treatment, which stimulated cell division and ovary growth, mostly in C. clementina. Instead, paclobutrazol (GA biosynthesis inhibitor) negated cell division and reduced fruit set. Results suggest that in parthenocarpic citrus the specific GA synthesis in the ovary walls at anthesis triggers cell division and, thus, the necessary ovary growth rate to set fruit.

  10. Exploring Middle School Students' Conceptions of the Relationship between Genetic Inheritance and Cell Division

    ERIC Educational Resources Information Center

    Williams, Michelle; DeBarger, Angela Haydel; Montgomery, Beronda L.; Zhou, Xuechun; Tate, Erika

    2012-01-01

    This study examines students' understanding of the normative connections between key concepts of cell division, including both mitosis and meiosis, and underlying biological principles that are critical for an in-depth understanding of genetic inheritance. Using a structural equation modeling method, we examine middle school students'…

  11. Reflections from a Computer Simulations Program on Cell Division in Selected Kenyan Secondary Schools

    ERIC Educational Resources Information Center

    Ndirangu, Mwangi; Kiboss, Joel K.; Wekesa, Eric W.

    2005-01-01

    The application of computer technology in education is a relatively new approach that is trying to justify inclusion in the Kenyan school curriculum. Being abstract, with a dynamic nature that does not manifest itself visibly, the process of cell division has posed difficulties for teachers. Consequently, a computer simulation program, using…

  12. Do Online Labs Work? An Assessment of an Online Lab on Cell Division

    ERIC Educational Resources Information Center

    Gilman, Sharon L.

    2006-01-01

    Some studies show students successfully learning science through online courses. This study compared students doing an online and in-class lab exercise on cell division. Online students performed slightly but significantly better on a follow-up content quiz, however, about half those expressed a strong preference for in-class lab work.

  13. Drug discovery targeting cell division proteins, microtubules and FtsZ.

    PubMed

    Ojima, Iwao; Kumar, Kunal; Awasthi, Divya; Vineberg, Jacob G

    2014-09-15

    Eukaryotic cell division or cytokinesis has been a major target for anticancer drug discovery. After the huge success of paclitaxel and docetaxel, microtubule-stabilizing agents (MSAs) appear to have gained a premier status in the discovery of next-generation anticancer agents. However, the drug resistance caused by MDR, point mutations, and overexpression of tubulin subtypes, etc., is a serious issue associated with these agents. Accordingly, the discovery and development of new-generation MSAs that can obviate various drug resistances has a significant meaning. In sharp contrast, prokaryotic cell division has been largely unexploited for the discovery and development of antibacterial drugs. However, recent studies on the mechanism of bacterial cytokinesis revealed that the most abundant and highly conserved cell division protein, FtsZ, would be an excellent new target for the drug discovery of next-generation antibacterial agents that can circumvent drug-resistances to the commonly used drugs for tuberculosis, MRSA and other infections. This review describes an account of our research on these two fronts in drug discovery, targeting eukaryotic as well as prokaryotic cell division.

  14. A pseudokinase couples signaling pathways to enable asymmetric cell division in a bacterium

    PubMed Central

    Childers, W. S.; Shapiro, Lucy

    2014-01-01

    Bacteria face complex decisions when initiating developmental events such as sporulation, nodulation, virulence, and asymmetric cell division. These developmental decisions require global changes in genomic readout, and bacteria typically employ intricate (yet poorly understood) signaling networks that enable changes in cell function. The bacterium Caulobacter crescentus divides asymmetrically to yield two functionally distinct cells: a motile, chemotactic swarmer cell, and a sessile stalked cell with replication and division capabilities. Work from several Caulobacter labs has revealed that differentiation requires concerted regulation by several two-component system (TCS) signaling pathways that are differentially positioned at the poles of the predivisional cell (Figure 1). The strict unidirectional flow from histidine kinase (HK) to the response regulator (RR), observed in most studied TCS, is difficult to reconcile with the notion that information can be transmitted between two or more TCS signaling pathways. In this study, we uncovered a mechanism by which daughter cell fate, which is specified by the DivJ-DivK-PleC system and effectively encoded in the phosphorylation state of the single-domain RR DivK, is communicated to the CckA-ChpT-CtrA signaling pathway that regulates more than 100 genes for polar differentiation, replication initiation and cell division. Using structural biology and biochemical findings we proposed a mechanistic basis for TCS pathway coupling in which the DivL pseudokinase is repurposed as a sensor rather than participant in phosphotransduction.

  15. Formation of intracytoplasmic membrane system of mycobacteria related to cell division.

    PubMed

    IMAEDA, T; OGURA, M

    1963-01-01

    Imaeda, Tamotsu (Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela) and Mitua Ogura. Formation of intracytoplasmic membrane system of mycobacteria related to cell division. J. Bacteriol. 85:150-163. 1963.-Mycobacterium leprae, M. lepraemurium, and a Mycobacterium sp. were observed with an electron microscope. In these bacilli, the three-dimensional structure of the intracytoplasmic membrane system consists of tubular infoldings of the invaginated plasma membrane. The moderately dense substance, presumably representing the cell-wall precursor, is found in the membranous system, especially in the rapid growth phase of mycobacteria. This system always shows an intimate relationship with cell division. A low-density zone, probably corresponding to the low-density substance which coats the cell wall, appears in the connecting regions of the system and in the longitudinal portion of the cell wall. These zones extend centripetally, and the separation of the cell wall occurs after the two zones meet. Based on these results, we hypothesize that the intracytoplasmic membrane system may produce cell-wall material during cell division of mycobacteria.

  16. An EAR-Dependent Regulatory Module Promotes Male Germ Cell Division and Sperm Fertility in Arabidopsis.

    PubMed

    Borg, Michael; Rutley, Nicholas; Kagale, Sateesh; Hamamura, Yuki; Gherghinoiu, Mihai; Kumar, Sanjeev; Sari, Ugur; Esparza-Franco, Manuel A; Sakamoto, Wataru; Rozwadowski, Kevin; Higashiyama, Tetsuya; Twell, David

    2014-05-01

    The production of the sperm cells in angiosperms requires coordination of cell division and cell differentiation. In Arabidopsis thaliana, the germline-specific MYB protein DUO1 integrates these processes, but the regulatory hierarchy in which DUO1 functions is unknown. Here, we identify an essential role for two germline-specific DUO1 target genes, DAZ1 and DAZ2, which encode EAR motif-containing C2H2-type zinc finger proteins. We show that DAZ1/DAZ2 are required for germ cell division and for the proper accumulation of mitotic cyclins. Importantly, DAZ1/DAZ2 are sufficient to promote G2- to M-phase transition and germ cell division in the absence of DUO1. DAZ1/DAZ2 are also required for DUO1-dependent cell differentiation and are essential for gamete fusion at fertilization. We demonstrate that the two EAR motifs in DAZ1/DAZ2 mediate their function in the male germline and are required for transcriptional repression and for physical interaction with the corepressor TOPLESS. Our findings uncover an essential module in a regulatory hierarchy that drives mitotic transition in male germ cells and implicates gene repression pathways in sperm cell formation and fertility.

  17. Online CME Series Can Nutrition Simultaneously Affect Cancer and Aging? | Division of Cancer Prevention

    Cancer.gov

    Aging is considered by some scientists to be a normal physiological process, while others believe it is a disease. Increased cancer risk in the elderly raises the question regarding the common pathways for cancer and aging. Undeniably, nutrition plays an important role in both cases and this webinar will explore whether nutrition can simultaneously affect cancer and aging. |

  18. Klp10A, a stem cell centrosome-enriched kinesin, balances asymmetries in Drosophila male germline stem cell division.

    PubMed

    Chen, Cuie; Inaba, Mayu; Venkei, Zsolt G; Yamashita, Yukiko M

    2016-11-25

    Asymmetric stem cell division is often accompanied by stereotypical inheritance of the mother and daughter centrosomes. However, it remains unknown whether and how stem cell centrosomes are uniquely regulated and how this regulation may contribute to stem cell fate. Here we identify Klp10A, a microtubule-depolymerizing kinesin of the kinesin-13 family, as the first protein enriched in the stem cell centrosome in Drosophila male germline stem cells (GSCs). Depletion of klp10A results in abnormal elongation of the mother centrosomes in GSCs, suggesting the existence of a stem cell-specific centrosome regulation program. Concomitant with mother centrosome elongation, GSCs form asymmetric spindle, wherein the elongated mother centrosome organizes considerably larger half spindle than the other. This leads to asymmetric cell size, yielding a smaller differentiating daughter cell. We propose that klp10A functions to counteract undesirable asymmetries that may result as a by-product of achieving asymmetries essential for successful stem cell divisions.

  19. Social Comparison Affects Brain Responses to Fairness in Asset Division: An ERP Study with the Ultimatum Game

    PubMed Central

    Wu, Yin; Zhou, Yuqin; van Dijk, Eric; Leliveld, Marijke C.; Zhou, Xiaolin

    2011-01-01

    Previous studies have shown that social comparison influences individual’s fairness consideration and other-regarding behavior. However, it is not clear how social comparison affects the brain activity in evaluating fairness during asset distribution. In this study, participants, acting as recipients in the ultimatum game, were informed not only of offers to themselves but also of the average amount of offers in other allocator–recipient dyads. Behavioral results showed that the participants were more likely to reject division schemes when they were offered less than the other recipients, especially when the offers were highly unequal. Event-related brain potentials recorded from the participants showed that highly unequal offers elicited more negative-going medial frontal negativity than moderately unequal offers in an early time window (270–360 ms) and this effect was not significantly modulated by social comparison. In a later time window (450–650 ms), however, the late positive potential (LPP) was more positive for moderately unequal offers than for highly unequal offers when the other recipients were offered less than the participants, whereas this distinction disappeared when the other recipients were offered the same as or more than the participants. These findings suggest that the brain activity in evaluating fairness in asset division entails both an earlier (semi-) automatic process in which the brain responds to fairness at an abstract level and a later appraisal process in which factors related to social comparison and fairness norms come into play. PMID:22087088

  20. Dependency of Escherichia coli cell-division size, and independency of nucleoid segregation on the mode and level of ftsZ expression.

    PubMed

    Palacios, P; Vicente, M; Sánchez, M

    1996-06-01

    Expression of ftsZ in strain VIP205 is dissociated from its natural promoters, and is under the control of an inducible tac promoter. This abolishes the oscillation in ftsZ transcription observed in the wild type, allowing different levels of ftsZ expression. We demonstrate that this construction does not affect the expression of other genes, and has no effects on replication or nucleoid segregation. A shift in IPTG from 30 microM, that supports division at wild-type sizes, to lower (6 microM) or higher (100 microM) concentrations, indicates that VIP205 cells can divide within a broad range of FtsZ concentrations. Analysis of the morphological parameters during the transition from one IPTG concentration to another suggests that the correct timing of ftsZ expression, and the correct FtsZ concentration, are required for division to occur at normal cell sizes. After a transient division delay during the transition to lower IPTG concentrations, cells in which ftsZ is expressed continuously (yielding 80% of the wild-type FtsZ levels) divide with the same division time as the wild type, but at the expense of becoming 1.5 times larger. A precise control of ftsZ expression is required for normal division, but the existence of additional regulators to maintain the correct timing during the cell cycle cannot be ruled out.

  1. An intrinsically disordered linker plays a critical role in bacterial cell division.

    PubMed

    Buske, P J; Mittal, Anuradha; Pappu, Rohit V; Levin, Petra Anne

    2015-01-01

    In bacteria, animals, fungi, and many single celled eukaryotes, division is initiated by the formation of a ring of cytoskeletal protein at the nascent division site. In bacteria, the tubulin-like GTPase FtsZ serves as the foundation for the cytokinetic ring. A conserved feature of FtsZ is an intrinsically disordered peptide known as the C-terminal linker. Chimeric experiments suggest the linker acts as a flexible boom allowing FtsZ to associate with the membrane through a conserved C-terminal domain and also modulates interactions both between FtsZ subunits and between FtsZ and modulatory proteins in the cytoplasm.

  2. Dimer dynamics and filament organization of the bacterial cell division protein FtsA.

    PubMed

    Hsin, Jen; Fu, Rui; Huang, Kerwyn Casey

    2013-11-15

    FtsA is a bacterial actin homolog and one of the core proteins involved in cell division. While previous studies have demonstrated the capability of FtsA to polymerize, little is known about its polymerization state in vivo or if polymerization is necessary for FtsA function. Given that one function of FtsA is to tether FtsZ filaments to the membrane, in vivo polymerization of FtsA imposes geometric constraints and requires a specific polymer curvature direction. Here, we report a series of molecular dynamics simulations probing the structural dynamics of FtsA as a dimer and as a tetrameric single filament. We found that the FtsA polymer exhibits a preferred bending direction that would allow for its placement parallel with FtsZ polymers underneath the cytoplasmic membrane. We also identified key interfacial amino acids that mediate FtsA-FtsA interaction and propose that some amino acids play more critical roles than others. We performed in silico mutagenesis on FtsA and demonstrated that, while a moderate mutation at the polymerization interface does not significantly affect polymer properties such as bending direction and association strength, more drastic mutations change both features and could lead to non-functional FtsA.

  3. Ectopic Expression of WUS in Hypocotyl Promotes Cell Division via GRP23 in Arabidopsis

    PubMed Central

    Wang, Min; Li, Junhua; Guo, Xiaoyu; Chong, Kang; Xu, Yunyuan

    2013-01-01

    WUSCHEL (WUS) is essential for preventing stem cell differentiation in Arabidopsis. Here we report that in addition to its functions in meristematic stem cell maintenance, WUS is involved in the regulation of cell division. The WUS gain-of-function mutant, stem ectopic flowers (sef), displayed elongated hypocotyls, whereas the loss-of-function wus-1 mutant had shortened hypocotyls. The long hypocotyl in sef was due to the presence of more cells, rather than increased cell elongation. Microscopic observation, flow cytometry assays, quantitative RT-PCR (qRT-PCR), and histochemical staining of CycB1;1::GUS supported the hypothesis that ectopic cell division occurred in the sef hypocotyls after germination. Both immunoblot and qRT-PCR results showed that WUS was ectopically expressed in sef hypocotyls. Luciferase activity, chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift assay (EMSA) showed that GLUTAMINE-RICH PROTEIN 23 (GRP23) expression can be activated by WUS and that GRP23 is a direct target gene of WUS. The phenotypes of 35S::GRP23 plants and GRP23 knockdown lines supported the notion that GRP23 mediates the effects of WUS on hypocotyl length. Together, our data suggest that ectopic expression of WUS in hypocotyl controls cell division through its target gene GRP23. PMID:24086632

  4. The special case of hepatocytes: unique tissue architecture calls for a distinct mode of cell division.

    PubMed

    Slim, Christiaan L; van IJzendoorn, Sven C D; Lázaro-Diéguez, Francisco; Müsch, Anne

    2014-01-01

    Columnar epithelia (e.g., kidney, intestine) and hepatocytes embody the two major organizational phenotypes of non-stratified epithelial cells. Columnar epithelia establish their apical and basal domains at opposing poles and organize in monolayered cysts and tubules, in which their apical surfaces form a single continuous lumen whereas hepatocytes establish their apical domains in the midst of their basolateral domains and organize a highly branched capillary luminal network, the bile canaliculi, in which a single hepatocyte can engage in lumen formation with multiple neighbors. To maintain their distinct tissue architectures, columnar epithelial cells bisect their luminal domains during symmetric cell divisions, while the cleavage furrow in dividing hepatocytes avoids bisecting the bile canalicular domains. We discuss recently discovered molecular mechanisms that underlie the different cell division phenotypes in columnar and hepatocytic model cell lines. The serine/threonine kinase Par1b determines both the epithelial lumen polarity and cell division phenotype via cell adhesion signaling that converges on the small GTPase RhoA.

  5. Self-organized partitioning of dynamically localized proteins in bacterial cell division.

    PubMed

    Di Ventura, Barbara; Sourjik, Victor

    2011-01-04

    How cells manage to get equal distribution of their structures and molecules at cell division is a crucial issue in biology. In principle, a feedback mechanism could always ensure equality by measuring and correcting the distribution in the progeny. However, an elegant alternative could be a mechanism relying on self-organization, with the interplay between system properties and cell geometry leading to the emergence of equal partitioning. The problem is exemplified by the bacterial Min system that defines the division site by oscillating from pole to pole. Unequal partitioning of Min proteins at division could negatively impact system performance and cell growth because of loss of Min oscillations and imprecise mid-cell determination. In this study, we combine live cell and computational analyses to show that known properties of the Min system together with the gradual reduction of protein exchange through the constricting septum are sufficient to explain the observed highly precise spontaneous protein partitioning. Our findings reveal a novel and effective mechanism of protein partitioning in dividing cells and emphasize the importance of self-organization in basic cellular processes.

  6. miR-430 regulates oriented cell division during neural tube development in zebrafish.

    PubMed

    Takacs, Carter M; Giraldez, Antonio J

    2016-01-15

    MicroRNAs have emerged as critical regulators of gene expression. Originally shown to regulate developmental timing, microRNAs have since been implicated in a wide range of cellular functions including cell identity, migration and signaling. miRNA-430, the earliest expressed microRNA during zebrafish embryogenesis, is required to undergo morphogenesis and has previously been shown to regulate maternal mRNA clearance, Nodal signaling, and germ cell migration. The functions of miR-430 in brain morphogenesis, however, remain unclear. Herein we find that miR-430 instructs oriented cell divisions in the neural rod required for neural midline formation. Loss of miR-430 function results in mitotic spindle misorientation in the neural rod, failed neuroepithelial integration after cell division, and ectopic cell accumulation in the dorsal neural tube. We propose that miR-430, independently of canonical apicobasal and planar cell polarity (PCP) pathways, coordinates the stereotypical cell divisions that instruct neural tube morphogenesis.

  7. IFT proteins accumulate during cell division and localize to the cleavage furrow in Chlamydomonas.

    PubMed

    Wood, Christopher R; Wang, Zhaohui; Diener, Dennis; Zones, James Matt; Rosenbaum, Joel; Umen, James G

    2012-01-01

    Intraflagellar transport (IFT) proteins are well established as conserved mediators of flagellum/cilium assembly and disassembly. However, data has begun to accumulate in support of IFT protein involvement in other processes elsewhere in the cell. Here, we used synchronous cultures of Chlamydomonas to investigate the temporal patterns of accumulation and localization of IFT proteins during the cell cycle. Their mRNAs showed periodic expression that peaked during S and M phase (S/M). Unlike most proteins that are synthesized continuously during G1 phase, IFT27 and IFT46 levels were found to increase only during S/M phase. During cell division, IFT27, IFT46, IFT72, and IFT139 re-localized from the flagella and basal bodies to the cleavage furrow. IFT27 was further shown to be associated with membrane vesicles in this region. This localization pattern suggests a role for IFT in cell division.

  8. Accurate Cell Division in Bacteria: How Does a Bacterium Know Where its Middle Is?

    NASA Astrophysics Data System (ADS)

    Howard, Martin; Rutenberg, Andrew

    2004-03-01

    I will discuss the physical principles lying behind the acquisition of accurate positional information in bacteria. A good application of these ideas is to the rod-shaped bacterium E. coli which divides precisely at its cellular midplane. This positioning is controlled by the Min system of proteins. These proteins coherently oscillate from end to end of the bacterium. I will present a reaction-diffusion model that describes the diffusion of the Min proteins, and their binding/unbinding from the cell membrane. The system possesses an instability that spontaneously generates the Min oscillations, which control accurate placement of the midcell division site. I will then discuss the role of fluctuations in protein dynamics, and investigate whether fluctuations set optimal protein concentration levels. Finally I will examine cell division in a different bacteria, B. subtilis. where different physical principles are used to regulate accurate cell division. See: Howard, Rutenberg, de Vet: Dynamic compartmentalization of bacteria: accurate division in E. coli. Phys. Rev. Lett. 87 278102 (2001). Howard, Rutenberg: Pattern formation inside bacteria: fluctuations due to the low copy number of proteins. Phys. Rev. Lett. 90 128102 (2003). Howard: A mechanism for polar protein localization in bacteria. J. Mol. Biol. 335 655-663 (2004).

  9. Scaling laws governing stochastic growth and division of single bacterial cells.

    PubMed

    Iyer-Biswas, Srividya; Wright, Charles S; Henry, Jonathan T; Lo, Klevin; Burov, Stanislav; Lin, Yihan; Crooks, Gavin E; Crosson, Sean; Dinner, Aaron R; Scherer, Norbert F

    2014-11-11

    Uncovering the quantitative laws that govern the growth and division of single cells remains a major challenge. Using a unique combination of technologies that yields unprecedented statistical precision, we find that the sizes of individual Caulobacter crescentus cells increase exponentially in time. We also establish that they divide upon reaching a critical multiple (≈ 1.8) of their initial sizes, rather than an absolute size. We show that when the temperature is varied, the growth and division timescales scale proportionally with each other over the physiological temperature range. Strikingly, the cell-size and division-time distributions can both be rescaled by their mean values such that the condition-specific distributions collapse to universal curves. We account for these observations with a minimal stochastic model that is based on an autocatalytic cycle. It predicts the scalings, as well as specific functional forms for the universal curves. Our experimental and theoretical analysis reveals a simple physical principle governing these complex biological processes: a single temperature-dependent scale of cellular time governs the stochastic dynamics of growth and division in balanced growth conditions.

  10. Scaling laws governing stochastic growth and division of single bacterial cells

    PubMed Central

    Iyer-Biswas, Srividya; Wright, Charles S.; Henry, Jonathan T.; Lo, Klevin; Burov, Stanislav; Lin, Yihan; Crooks, Gavin E.; Crosson, Sean; Dinner, Aaron R.; Scherer, Norbert F.

    2014-01-01

    Uncovering the quantitative laws that govern the growth and division of single cells remains a major challenge. Using a unique combination of technologies that yields unprecedented statistical precision, we find that the sizes of individual Caulobacter crescentus cells increase exponentially in time. We also establish that they divide upon reaching a critical multiple (≈1.8) of their initial sizes, rather than an absolute size. We show that when the temperature is varied, the growth and division timescales scale proportionally with each other over the physiological temperature range. Strikingly, the cell-size and division-time distributions can both be rescaled by their mean values such that the condition-specific distributions collapse to universal curves. We account for these observations with a minimal stochastic model that is based on an autocatalytic cycle. It predicts the scalings, as well as specific functional forms for the universal curves. Our experimental and theoretical analysis reveals a simple physical principle governing these complex biological processes: a single temperature-dependent scale of cellular time governs the stochastic dynamics of growth and division in balanced growth conditions. PMID:25349411

  11. Radiation-induced division delay in Chinese hamster ovary fibroblast and carcinoma cells: dose effect and ploidy. [X-ray

    SciTech Connect

    Kimler, B.F.; Leeper, D.B.; Schneiderman, M.H.

    1981-02-01

    The mitotic selection procedure for cell cycle analysis was utilized to investigate the G/sub 2/ transition point for and the duration of radiation-induced division delay in diploid and tetraploid Chinese hamster ovary (CHO) fibroblasts and in Chinese hamster ovarian carcinoma cells. The location of the radiation-induced division delay transition point was dose independent at high doses and located approximately 42 min before division. At lower doses only an estimate of the point of blockade was possible; but the G/sub 2/ transition point appeared to be earlier in the cell cycle. The duration of radiation-induced division delay was dose dependent. This response is consistent with a sensitive population of cells in late G/sub 2/ that define the location of the transition point and the length of division delay. There was no difference observed in the dose response for radiation-induced division delay between the pseudotetraploid cell line of CHO and the pseudodiploid parent strain. However, in the cell line derived from a spontaneous Chinese hamster ovarian carcinoma the division delay was 39 +- 4 min/Gy. Therefore, radiation-induced division delay is independent of chromosome ploidy, but can show intraspecies cell line specificity.

  12. Fission yeast cells undergo nuclear division in the absence of spindle microtubules.

    PubMed

    Castagnetti, Stefania; Oliferenko, Snezhana; Nurse, Paul

    2010-10-12

    Mitosis in eukaryotic cells employs spindle microtubules to drive accurate chromosome segregation at cell division. Cells lacking spindle microtubules arrest in mitosis due to a spindle checkpoint that delays mitotic progression until all chromosomes have achieved stable bipolar attachment to spindle microtubules. In fission yeast, mitosis occurs within an intact nuclear membrane with the mitotic spindle elongating between the spindle pole bodies. We show here that in fission yeast interference with mitotic spindle formation delays mitosis only briefly and cells proceed to an unusual nuclear division process we term nuclear fission, during which cells perform some chromosome segregation and efficiently enter S-phase of the next cell cycle. Nuclear fission is blocked if spindle pole body maturation or sister chromatid separation cannot take place or if actin polymerization is inhibited. We suggest that this process exhibits vestiges of a primitive nuclear division process independent of spindle microtubules, possibly reflecting an evolutionary intermediate state between bacterial and Archeal chromosome segregation where the nucleoid divides without a spindle and a microtubule spindle-based eukaryotic mitosis.

  13. Incomplete Splicing, Cell Division Defects and Hematopoietic Blockage in dhx8 Mutant Zebrafish

    PubMed Central

    English, Milton A.; Lei, Lin; Blake, Trevor; Wincovitch, Stephen M.; Sood, Raman; Azuma, Mizuki; Hickstein, Dennis; Liu, P. Paul

    2012-01-01

    Vertebrate hematopoiesis is a complex developmental process that is controlled by genes in diverse pathways. To identify novel genes involved in early hematopoiesis, we conducted an ENU (N-ethyl-N-nitrosourea) mutagenesis screen in zebrafish. The mummy (mmy) line was investigated because of its multiple hematopoietic defects. Homozygous mmy embryos lacked circulating blood cells types and were dead by 30 hours post-fertilization (hpf). The mmy mutants did not express myeloid markers and had significantly decreased expression of progenitor and erythroid markers in primitive hematopoiesis. Through positional cloning, we identified a truncation mutation in dhx8 in the mmy fish. dhx8 is the zebrafish ortholog of the yeast splicing factor prp22, which is a DEAH-box RNA helicase. Mmy mutants had splicing defects in many genes, including several hematopoietic genes. Mmy embryos also showed cell division defects as characterized by disorganized mitotic spindles and formation of multiple spindle poles in mitotic cells. These cell division defects were confirmed by DHX8 knockdown in HeLa cells. Together, our results confirm that dhx8 is involved in mRNA splicing and suggest that it is also important for cell division during mitosis. This is the first vertebrate model for dhx8, whose function is essential for primitive hematopoiesis in developing embryos. PMID:22411201

  14. Ultrastructure and Membrane Traffic During Cell Division in the Marine Pennate Diatom Phaeodactylum tricornutum.

    PubMed

    Tanaka, Atsuko; De Martino, Alessandra; Amato, Alberto; Montsant, Anton; Mathieu, Benjamin; Rostaing, Philippe; Tirichine, Leila; Bowler, Chris

    2015-11-01

    The marine pennate diatom Phaeodactylum tricornutum has become a model for diatom biology, due to its ease of culture and accessibility to reverse genetics approaches. While several features underlying the molecular mechanisms of cell division have been described, morphological analyses are less advanced than they are in other diatoms. We therefore examined cell ultrastructure changes prior to and during cytokinesis. Following chloroplast division, cleavage furrows are formed at both longitudinal ends of the cell and are accompanied by significant vesicle transport. Although neither spindle nor microtubules were observed, the nucleus appeared to be split by the furrow after duplication of the Golgi apparatus. Finally, centripetal cytokinesis was completed by fusion of the furrows. Additionally, F-actin formed a ring structure and its diameter became smaller, accompanying the ingrowing furrows. To further analyse vesicular transport during cytokinesis, we generated transgenic cells expressing yellow fluorescent protein (YFP) fusions with putative diatom orthologs of small GTPase Sec4 and t-SNARE protein SyntaxinA. Time-lapse observations revealed that SyntaxinA-YFP localization expands from both cell tips toward the center, whereas Sec4-YFP was found in the Golgi and subsequently relocalizes to the future division plane. This work provides fundamental new information about cell replication processes in P. tricornutum.

  15. The novel herbicide oxaziclomefone inhibits cell expansion in maize cell cultures without affecting turgor pressure or wall acidification.

    PubMed

    O'Looney, Nichola; Fry, Stephen C

    2005-11-01

    Oxaziclomefone [OAC; IUPAC name 3-(1-(3,5-dichlorophenyl)-1-methylethyl)-3,4-dihydro-6-methyl-5-phenyl-2H-1,3-oxazin-4-one] is a new herbicide that inhibits cell expansion in grass roots. Its effects on cell cultures and mode of action were unknown. In principle, cell expansion could be inhibited by a decrease in either turgor pressure or wall extensibility. Cell expansion was estimated as settled cell volume; cell division was estimated by cell counting. Membrane permeability to water was measured by a novel method involving simultaneous assay of the efflux of (3)H(2)O and [(14)C]mannitol from a 'bed' of cultured cells. Osmotic potential was measured by depression of freezing point. OAC inhibited cell expansion in cultures of maize (Zea mays), spinach (Spinacia oleracea) and rose (Rosa sp.), with an ID(50) of 5, 30 and 250 nm, respectively. In maize cultures, OAC did not affect cell division for the first 40 h. It did not affect the osmotic potential of cell sap or culture medium, nor did it impede water transport across cell membranes. It did not affect cells' ability to acidify the apoplast (medium), which may be necessary for 'acid growth'. As OAC did not diminish turgor pressure, its ability to inhibit cell expansion must depend on changes in wall extensibility. It could be a valuable tool for studies on cell expansion.

  16. Dicer-1-dependent Dacapo suppression acts downstream of Insulin receptor in regulating cell division of Drosophila germline stem cells

    PubMed Central

    Yu, Jenn-Yah; Reynolds, Steven H.; Hatfield, Steve D.; Shcherbata, Halyna R.; Fischer, Karin A.; Ward, Ellen J.; Long, Dang; Ding, Ye; Ruohola-Baker, Hannele

    2009-01-01

    Summary It is important to understand the regulation of stem cell division because defects in this process can cause altered tissue homeostasis or cancer. The cyclin-dependent kinase inhibitor Dacapo (Dap), a p21/p27 homolog, acts downstream of the microRNA (miRNA) pathway to regulate the cell cycle in Drosophila melanogaster germline stem cells (GSCs). Tissue-extrinsic signals, including insulin, also regulate cell division of GSCs. We report that intrinsic and extrinsic regulators intersect in GSC division control; the Insulin receptor (InR) pathway regulates Dap levels through miRNAs, thereby controlling GSC division. Using GFP-dap 3′UTR sensors in vivo, we show that in GSCs the dap 3′UTR is responsive to Dicer-1, an RNA endonuclease III required for miRNA processing. Furthermore, the dap 3′UTR can be directly targeted by miR-7, miR-278 and miR-309 in luciferase assays. Consistent with this, miR-278 and miR-7 mutant GSCs are partially defective in GSC division and show abnormal cell cycle marker expression, respectively. These data suggest that the GSC cell cycle is regulated via the dap 3′UTR by multiple miRNAs. Furthermore, the GFP-dap 3′UTR sensors respond to InR but not to TGF-β signaling, suggesting that InR signaling utilizes Dap for GSC cell cycle regulation. We further demonstrate that the miRNA-based Dap regulation may act downstream of InR signaling; Dcr-1 and Dap are required for nutrition-dependent cell cycle regulation in GSCs and reduction of dap partially rescues the cell cycle defect of InR-deficient GSCs. These data suggest that miRNA- and Dap-based cell cycle regulation in GSCs can be controlled by InR signaling. PMID:19336466

  17. Dicer-1-dependent Dacapo suppression acts downstream of Insulin receptor in regulating cell division of Drosophila germline stem cells.

    PubMed

    Yu, Jenn-Yah; Reynolds, Steven H; Hatfield, Steve D; Shcherbata, Halyna R; Fischer, Karin A; Ward, Ellen J; Long, Dang; Ding, Ye; Ruohola-Baker, Hannele

    2009-05-01

    It is important to understand the regulation of stem cell division because defects in this process can cause altered tissue homeostasis or cancer. The cyclin-dependent kinase inhibitor Dacapo (Dap), a p21/p27 homolog, acts downstream of the microRNA (miRNA) pathway to regulate the cell cycle in Drosophila melanogaster germline stem cells (GSCs). Tissue-extrinsic signals, including insulin, also regulate cell division of GSCs. We report that intrinsic and extrinsic regulators intersect in GSC division control; the Insulin receptor (InR) pathway regulates Dap levels through miRNAs, thereby controlling GSC division. Using GFP-dap 3'UTR sensors in vivo, we show that in GSCs the dap 3'UTR is responsive to Dicer-1, an RNA endonuclease III required for miRNA processing. Furthermore, the dap 3'UTR can be directly targeted by miR-7, miR-278 and miR-309 in luciferase assays. Consistent with this, miR-278 and miR-7 mutant GSCs are partially defective in GSC division and show abnormal cell cycle marker expression, respectively. These data suggest that the GSC cell cycle is regulated via the dap 3'UTR by multiple miRNAs. Furthermore, the GFP-dap 3'UTR sensors respond to InR but not to TGF-beta signaling, suggesting that InR signaling utilizes Dap for GSC cell cycle regulation. We further demonstrate that the miRNA-based Dap regulation may act downstream of InR signaling; Dcr-1 and Dap are required for nutrition-dependent cell cycle regulation in GSCs and reduction of dap partially rescues the cell cycle defect of InR-deficient GSCs. These data suggest that miRNA- and Dap-based cell cycle regulation in GSCs can be controlled by InR signaling.

  18. DNA lesions, inducible DNA repair, and cell division: Three key factors in mutagenesis and carcinogenesis

    SciTech Connect

    Ames, B.N.; Shigenaga, M.K.; Gold, L.S.

    1993-12-01

    DNA lesions that escape repair have a certain probability of giving rise to mutations when the cell divides. Endogenous DNA damage is high: 10{sup 6} oxidative lesions are present per rat cell. An exogenous mutagen produces an increment in lesions over the background rate of endogenous lesions. The effectiveness of a particular lesion depends on whether it is excised by a DNA repair system and the probability that it gives rise to a mutation when the cell divides. When the cell divides, an unrepaired DNA lesion has a certain probability of giving rise to a mutation. Thus, an important factor in the mutagenic effect of an exogenous agent whether it is genotoxic or non-genotoxic, is the increment it causes over the background cell division rate (mitogenesis) in cells that appear to matter most in cancer, the stem cells, which are not on their way to being discarded. Increasing their cell division rate increases by high doses of chemicals. If both the rate of DNA lesions and cell division are increased, then there will be a multiplicative effect on mutagenesis (and carcinogenesis), for example, by high doses of a mutagen that also increases mitogenesis through cell killing. The defense system against reactive electrophilic mutagens, such as the glutathione transferases, are also almost all inducible and buffer cells against increments in active forms of chemicals that can cause DNA lesions. A variety of DNA repair defense systems, almost all inducible, buffer the cell against any increment in DNA lesions. Therefore, the effect of a particular chemical insult depends on the level of each defense, which in turn depends on the past history of exposure. Exogenous agents can influence the induction and effectiveness of these defenses. Defenses can be partially disabled by lack of particular micronutrients in the diet (e.g., antioxidants).

  19. Illumination of growth, division and secretion by metabolic labeling of the bacterial cell surface

    PubMed Central

    Siegrist, M. Sloan; Swarts, Benjamin M.; Fox, Douglas M.; Lim, Shion An; Bertozzi, Carolyn R.

    2015-01-01

    The cell surface is the essential interface between a bacterium and its surroundings. Composed primarily of molecules that are not directly genetically encoded, this highly dynamic structure accommodates the basic cellular processes of growth and division as well as the transport of molecules between the cytoplasm and the extracellular milieu. In this review, we describe aspects of bacterial growth, division and secretion that have recently been uncovered by metabolic labeling of the cell envelope. Metabolite derivatives can be used to label a variety of macromolecules, from proteins to non-genetically-encoded glycans and lipids. The embedded metabolite enables precise tracking in time and space, and the versatility of newer chemoselective detection methods offers the ability to execute multiple experiments concurrently. In addition to reviewing the discoveries enabled by metabolic labeling of the bacterial cell envelope, we also discuss the potential of these techniques for translational applications. Finally, we offer some guidelines for implementing this emerging technology. PMID:25725012

  20. A distributed cell division counter reveals growth dynamics in the gut microbiota

    PubMed Central

    Myhrvold, Cameron; Kotula, Jonathan W.; Hicks, Wade M.; Conway, Nicholas J.; Silver, Pamela A.

    2015-01-01

    Microbial population growth is typically measured when cells can be directly observed, or when death is rare. However, neither of these conditions hold for the mammalian gut microbiota, and, therefore, standard approaches cannot accurately measure the growth dynamics of this community. Here we introduce a new method (distributed cell division counting, DCDC) that uses the accurate segregation at cell division of genetically encoded fluorescent particles to measure microbial growth rates. Using DCDC, we can measure the growth rate of Escherichia coli for >10 consecutive generations. We demonstrate experimentally and theoretically that DCDC is robust to error across a wide range of temperatures and conditions, including in the mammalian gut. Furthermore, our experimental observations inform a mathematical model of the population dynamics of the gut microbiota. DCDC can enable the study of microbial growth during infection, gut dysbiosis, antibiotic therapy or other situations relevant to human health. PMID:26615910

  1. Illumination of growth, division and secretion by metabolic labeling of the bacterial cell surface.

    PubMed

    Siegrist, M Sloan; Swarts, Benjamin M; Fox, Douglas M; Lim, Shion An; Bertozzi, Carolyn R

    2015-03-01

    The cell surface is the essential interface between a bacterium and its surroundings. Composed primarily of molecules that are not directly genetically encoded, this highly dynamic structure accommodates the basic cellular processes of growth and division as well as the transport of molecules between the cytoplasm and the extracellular milieu. In this review, we describe aspects of bacterial growth, division and secretion that have recently been uncovered by metabolic labeling of the cell envelope. Metabolite derivatives can be used to label a variety of macromolecules, from proteins to non-genetically-encoded glycans and lipids. The embedded metabolite enables precise tracking in time and space, and the versatility of newer chemoselective detection methods offers the ability to execute multiple experiments concurrently. In addition to reviewing the discoveries enabled by metabolic labeling of the bacterial cell envelope, we also discuss the potential of these techniques for translational applications. Finally, we offer some guidelines for implementing this emerging technology.

  2. Diurnal rhythm in the cell-division frequency of prochloron (prochlorophyta) in nature

    NASA Technical Reports Server (NTRS)

    Lewin, R. A.; Cheng, L.; Matta, J.

    1983-01-01

    Frequencies of cell division stages in suspensions of Prochloron cells, expressed at regular intervals throughout a natural day-night cycle from several colonies of four species of host didemnid, are given. The proportion of dividing cells of Prochloron living symbiotically in colonies of a didemnid, Diplosoma virens, rises from about 4% during the night (20.00-04.00 hrs.) to about 13% in the morning (0,.00-12.00 hrs.), and then falls again in the afternoon. Similiar, though less pronounced, changes were observed among Prochloron cells in two other symbiotic didemnids, Lissoclinum patella and L. voeltzkowi.

  3. Physical association between a novel plasma-membrane structure and centrosome orients cell division

    PubMed Central

    Negishi, Takefumi; Miyazaki, Naoyuki; Murata, Kazuyoshi; Yasuo, Hitoyoshi; Ueno, Naoto

    2016-01-01

    In the last mitotic division of the epidermal lineage in the ascidian embryo, the cells divide stereotypically along the anterior-posterior axis. During interphase, we found that a unique membrane structure invaginates from the posterior to the centre of the cell, in a microtubule-dependent manner. The invagination projects toward centrioles on the apical side of the nucleus and associates with one of them. Further, a cilium forms on the posterior side of the cell and its basal body remains associated with the invagination. A laser ablation experiment suggests that the invagination is under tensile force and promotes the posterior positioning of the centrosome. Finally, we showed that the orientation of the invaginations is coupled with the polarized dynamics of centrosome movements and the orientation of cell division. Based on these findings, we propose a model whereby this novel membrane structure orchestrates centrosome positioning and thus the orientation of cell division axis. DOI: http://dx.doi.org/10.7554/eLife.16550.001 PMID:27502556

  4. Brief Report: Single-Cell Analysis Reveals Cell Division-Independent Emergence of Megakaryocytes From Phenotypic Hematopoietic Stem Cells.

    PubMed

    Roch, Aline; Trachsel, Vincent; Lutolf, Matthias P

    2015-10-01

    Despite increasingly stringent methods to isolate hematopoietic stem cells (HSCs), considerable heterogeneity remains in terms of their long-term self-renewal and differentiation potential. Recently, the existence of long-lived, self-renewing, myeloid-restricted progenitors in the phenotypically defined HSC compartment has been revealed, but these cells remain poorly characterized. Here, we used an in vitro single-cell analysis approach to track the fate of 330 long-term HSCs (LT-HSC; Lin- cKit+ Sca-1+ CD150+ CD48- CD34-) cultured for 5 days under serum-free basal conditions. Our analysis revealed a highly heterogeneous behavior with approximately 15% of all phenotypic LT-HSCs giving rise to megakaryocytes (Mk). Surprisingly, in 65% of these cases, Mk development occurred in the absence of cell division. This observation suggests that myeloid-restricted progenitors may not derive directly from LT-HSCs but instead could share an identical cell surface marker repertoire.

  5. SepG coordinates sporulation-specific cell division and nucleoid organization in Streptomyces coelicolor.

    PubMed

    Zhang, Le; Willemse, Joost; Claessen, Dennis; van Wezel, Gilles P

    2016-04-01

    Bacterial cell division is a highly complex process that requires tight coordination between septum formation and chromosome replication and segregation. In bacteria that divide by binary fission a single septum is formed at mid-cell, a process that is coordinated by the conserved cell division scaffold protein FtsZ. In contrast, during sporulation-specific cell division in streptomycetes, up to a hundred rings of FtsZ (Z rings) are produced almost simultaneously, dividing the multinucleoid aerial hyphae into long chains of unigenomic spores. This involves the active recruitment of FtsZ by the SsgB protein, and at the same time requires sophisticated systems to regulate chromosome dynamics. Here, we show that SepG is required for the onset of sporulation and acts by ensuring that SsgB is localized to future septum sites. Förster resonance energy transfer imaging suggests direct interaction between SepG and SsgB. The beta-lactamase reporter system showed that SepG is a transmembrane protein with its central domain oriented towards the cytoplasm. Without SepG, SsgB fails to localize properly, consistent with a crucial role for SepG in the membrane localization of the SsgB-FtsZ complex. While SsgB remains associated with FtsZ, SepG re-localizes to the (pre)spore periphery. Expanded doughnut-shaped nucleoids are formed in sepG null mutants, suggesting that SepG is required for nucleoid compaction. Taken together, our work shows that SepG, encoded by one of the last genes in the conserved dcw cluster of cell division and cell-wall-related genes in Gram-positive bacteria whose function was still largely unresolved,coordinates septum synthesis and chromosome organization in Streptomyces.

  6. Natural synchronisation for the study of cell division in the green unicellular alga Ostreococcus tauri.

    PubMed

    Farinas, Benoît; Mary, Camille; de O Manes, Carmem-Lara; Bhaud, Yvonne; Peaucellier, Gérard; Moreau, Hervé

    2006-01-01

    Ostreococcus tauri (Prasinophyceae) is a marine unicellular green alga which diverged early in the green lineage. The interest of O. tauri as a potential model to study plant cell division is based on its key phylogenetic position, its simple binary division, a very simple cellular organisation and now the availability of the full genome sequence. In addition O. tauri has a minimal yet complete set of cell cycle control genes. Here we show that division can be naturally synchronised by light/dark cycles and that organelles divide before the nucleus. This natural synchronisation, although being only partial, enables the study of the expression of CDKs throughout the cell cycle. The expression patterns of OtCDKA and OtCDKB were determined both at the mRNA and protein levels. The single OtCDKA gene is constantly expressed throughout the cell cycle, whereas OtCDKB is highly regulated and expressed only in S/G2/M phases. More surprisingly, OtCDKA is not phosphorylated at the tyrosine residue, in contrast to OtCDKB which is strongly phosphorylated during cell division. OtCDKA kinase activity appears before the S phase, indicating a possible role of this protein in the G1/S transition. OtCDKB kinase activity occurs later than OtCDKA, and its tyrosine phosphorylation is correlated to G2/M, suggesting a possible control of the mitotic activity. To our knowledge this is the first organism in the green lineage which showed CDKB tyrosine phosphorylation during cell cycle progression.

  7. SepG coordinates sporulation-specific cell division and nucleoid organization in Streptomyces coelicolor

    PubMed Central

    Zhang, Le; Willemse, Joost; Claessen, Dennis; van Wezel, Gilles P.

    2016-01-01

    Bacterial cell division is a highly complex process that requires tight coordination between septum formation and chromosome replication and segregation. In bacteria that divide by binary fission a single septum is formed at mid-cell, a process that is coordinated by the conserved cell division scaffold protein FtsZ. In contrast, during sporulation-specific cell division in streptomycetes, up to a hundred rings of FtsZ (Z rings) are produced almost simultaneously, dividing the multinucleoid aerial hyphae into long chains of unigenomic spores. This involves the active recruitment of FtsZ by the SsgB protein, and at the same time requires sophisticated systems to regulate chromosome dynamics. Here, we show that SepG is required for the onset of sporulation and acts by ensuring that SsgB is localized to future septum sites. Förster resonance energy transfer imaging suggests direct interaction between SepG and SsgB. The beta-lactamase reporter system showed that SepG is a transmembrane protein with its central domain oriented towards the cytoplasm. Without SepG, SsgB fails to localize properly, consistent with a crucial role for SepG in the membrane localization of the SsgB–FtsZ complex. While SsgB remains associated with FtsZ, SepG re-localizes to the (pre)spore periphery. Expanded doughnut-shaped nucleoids are formed in sepG null mutants, suggesting that SepG is required for nucleoid compaction. Taken together, our work shows that SepG, encoded by one of the last genes in the conserved dcw cluster of cell division and cell-wall-related genes in Gram-positive bacteria whose function was still largely unresolved, coordinates septum synthesis and chromosome organization in Streptomyces. PMID:27053678

  8. The C. elegans engrailed homolog ceh-16 regulates the self-renewal expansion division of stem cell-like seam cells.

    PubMed

    Huang, Xinxin; Tian, E; Xu, Yanhua; Zhang, Hong

    2009-09-15

    Stem cells undergo symmetric and asymmetric division to maintain the dynamic equilibrium of the stem cell pool and also to generate a variety of differentiated cells. The homeostatic mechanism controlling the choice between self-renewal and differentiation of stem cells is poorly understood. We show here that ceh-16, encoding the C. elegans ortholog of the transcription factor Engrailed, controls symmetric and asymmetric division of stem cell-like seam cells. Loss of function of ceh-16 causes certain seam cells, which normally undergo symmetric self-renewal expansion division with both daughters adopting the seam cell fate, to divide asymmetrically with only one daughter retaining the seam cell fate. The human engrailed homolog En2 functionally substitutes the role of ceh-16 in promoting self-renewal expansion division of seam cells. Loss of function of apr-1, encoding the C. elegans homolog of the Wnt signaling component APC, results in transformation of self-renewal maintenance seam cell division to self-renewal expansion division, leading to seam cell hyperplasia. The apr-1 mutation suppresses the seam cell division defect in ceh-16 mutants. Our study reveals that ceh-16 interacts with the Wnt signaling pathway to control the choice between self-renewal expansion and maintenance division and also demonstrates an evolutionarily conserved function of engrailed in promoting cell proliferation.

  9. A plant U-box protein, PUB4, regulates asymmetric cell division and cell proliferation in the root meristem.

    PubMed

    Kinoshita, Atsuko; ten Hove, Colette A; Tabata, Ryo; Yamada, Masashi; Shimizu, Noriko; Ishida, Takashi; Yamaguchi, Katsushi; Shigenobu, Shuji; Takebayashi, Yumiko; Iuchi, Satoshi; Kobayashi, Masatomo; Kurata, Tetsuya; Wada, Takuji; Seo, Mitsunori; Hasebe, Mitsuyasu; Blilou, Ikram; Fukuda, Hiroo; Scheres, Ben; Heidstra, Renze; Kamiya, Yuji; Sawa, Shinichiro

    2015-02-01

    The root meristem (RM) is a fundamental structure that is responsible for postembryonic root growth. The RM contains the quiescent center (QC), stem cells and frequently dividing meristematic cells, in which the timing and the frequency of cell division are tightly regulated. In Arabidopsis thaliana, several gain-of-function analyses have demonstrated that peptide ligands of the Clavata3 (CLV3)/embryo surrounding region-related (CLE) family are important for maintaining RM size. Here, we demonstrate that a plant U-box E3 ubiquitin ligase, PUB4, is a novel downstream component of CLV3/CLE signaling in the RM. Mutations in PUB4 reduced the inhibitory effect of exogenous CLV3/CLE peptide on root cell proliferation and columella stem cell maintenance. Moreover, pub4 mutants grown without exogenous CLV3/CLE peptide exhibited characteristic phenotypes in the RM, such as enhanced root growth, increased number of cortex/endodermis stem cells and decreased number of columella layers. Our phenotypic and gene expression analyses indicated that PUB4 promotes expression of a cell cycle regulatory gene, CYCD6;1, and regulates formative periclinal asymmetric cell divisions in endodermis and cortex/endodermis initial daughters. These data suggest that PUB4 functions as a global regulator of cell proliferation and the timing of asymmetric cell division that are important for final root architecture.

  10. Centrosome-dependent asymmetric inheritance of the midbody ring in Drosophila germline stem cell division.

    PubMed

    Salzmann, Viktoria; Chen, Cuie; Chiang, C-Y Ason; Tiyaboonchai, Amita; Mayer, Michael; Yamashita, Yukiko M

    2014-01-01

    Many stem cells, including Drosophila germline stem cells (GSCs), divide asymmetrically, producing one stem cell and one differentiating daughter. Cytokinesis is often asymmetric, in that only one daughter cell inherits the midbody ring (MR) upon completion of abscission even in apparently symmetrically dividing cells. However, whether the asymmetry in cytokinesis correlates with cell fate or has functional relevance has been poorly explored. Here we show that the MR is asymmetrically segregated during GSC divisions in a centrosome age-dependent manner: male GSCs, which inherit the mother centrosome, exclude the MR, whereas female GSCs, which we here show inherit the daughter centrosome, inherit the MR. We further show that stem cell identity correlates with the mode of MR inheritance. Together our data suggest that the MR does not inherently dictate stem cell identity, although its stereotypical inheritance is under the control of stemness and potentially provides a platform for asymmetric segregation of certain factors.

  11. Individuality and universality in the growth-division laws of single E. coli cells

    NASA Astrophysics Data System (ADS)

    Kennard, Andrew S.; Osella, Matteo; Javer, Avelino; Grilli, Jacopo; Nghe, Philippe; Tans, Sander J.; Cicuta, Pietro; Cosentino Lagomarsino, Marco

    2016-01-01

    The mean size of exponentially dividing Escherichia coli cells in different nutrient conditions is known to depend on the mean growth rate only. However, the joint fluctuations relating cell size, doubling time, and individual growth rate are only starting to be characterized. Recent studies in bacteria reported a universal trend where the spread in both size and doubling times is a linear function of the population means of these variables. Here we combine experiments and theory and use scaling concepts to elucidate the constraints posed by the second observation on the division control mechanism and on the joint fluctuations of sizes and doubling times. We found that scaling relations based on the means collapse both size and doubling-time distributions across different conditions and explain how the shape of their joint fluctuations deviates from the means. Our data on these joint fluctuations highlight the importance of cell individuality: Single cells do not follow the dependence observed for the means between size and either growth rate or inverse doubling time. Our calculations show that these results emerge from a broad class of division control mechanisms requiring a certain scaling form of the "division hazard rate function," which defines the probability rate of dividing as a function of measurable parameters. This "model free" approach gives a rationale for the universal body-size distributions observed in microbial ecosystems across many microbial species, presumably dividing with multiple mechanisms. Additionally, our experiments show a crossover between fast and slow growth in the relation between individual-cell growth rate and division time, which can be understood in terms of different regimes of genome replication control.

  12. Individuality and universality in the growth-division laws of single E. coli cells.

    PubMed

    Kennard, Andrew S; Osella, Matteo; Javer, Avelino; Grilli, Jacopo; Nghe, Philippe; Tans, Sander J; Cicuta, Pietro; Cosentino Lagomarsino, Marco

    2016-01-01

    The mean size of exponentially dividing Escherichia coli cells in different nutrient conditions is known to depend on the mean growth rate only. However, the joint fluctuations relating cell size, doubling time, and individual growth rate are only starting to be characterized. Recent studies in bacteria reported a universal trend where the spread in both size and doubling times is a linear function of the population means of these variables. Here we combine experiments and theory and use scaling concepts to elucidate the constraints posed by the second observation on the division control mechanism and on the joint fluctuations of sizes and doubling times. We found that scaling relations based on the means collapse both size and doubling-time distributions across different conditions and explain how the shape of their joint fluctuations deviates from the means. Our data on these joint fluctuations highlight the importance of cell individuality: Single cells do not follow the dependence observed for the means between size and either growth rate or inverse doubling time. Our calculations show that these results emerge from a broad class of division control mechanisms requiring a certain scaling form of the "division hazard rate function," which defines the probability rate of dividing as a function of measurable parameters. This "model free" approach gives a rationale for the universal body-size distributions observed in microbial ecosystems across many microbial species, presumably dividing with multiple mechanisms. Additionally, our experiments show a crossover between fast and slow growth in the relation between individual-cell growth rate and division time, which can be understood in terms of different regimes of genome replication control.

  13. PP1-Dependent Formin Bnr1 Dephosphorylation and Delocalization from a Cell Division Site.

    PubMed

    Orii, Minami; Kono, Keiko; Wen, Hsin-I; Nakanishi, Makoto

    2016-01-01

    Cell cycle ends with cytokinesis that is the physical separation of a cell into two daughter cells. For faithful cytokinesis, cells integrate multiple processes, such as actomyosin ring formation, contraction and plasma membrane closure, into coherent responses. Linear actin assembly by formins is essential for formation and maintenance of actomyosin ring. Although budding yeast's two formins, Bni1 and Bnr1, are known to switch their subcellular localization at the division site prior to cytokinesis, the underlying mechanisms were not completely understood. Here, we provide evidence showing that Bnr1 is dephosphorylated concomitant with its release from the division site. Impaired PP1/Glc7 activity delayed Bnr1 release and dephosphorylation, Bni1 recruitment and actomyosin ring formation at the division site. These results suggest the involvement of Glc7 in this regulation. Further, we identified Ref2 as the PP1 regulatory subunit responsible for this regulation. Taken together, Glc7 and Ref2 may have a role in actomyosin ring formation by modulating the localization of formins during cytokinesis.

  14. PP1-Dependent Formin Bnr1 Dephosphorylation and Delocalization from a Cell Division Site

    PubMed Central

    Orii, Minami; Kono, Keiko; Wen, Hsin-I; Nakanishi, Makoto

    2016-01-01

    Cell cycle ends with cytokinesis that is the physical separation of a cell into two daughter cells. For faithful cytokinesis, cells integrate multiple processes, such as actomyosin ring formation, contraction and plasma membrane closure, into coherent responses. Linear actin assembly by formins is essential for formation and maintenance of actomyosin ring. Although budding yeast’s two formins, Bni1 and Bnr1, are known to switch their subcellular localization at the division site prior to cytokinesis, the underlying mechanisms were not completely understood. Here, we provide evidence showing that Bnr1 is dephosphorylated concomitant with its release from the division site. Impaired PP1/Glc7 activity delayed Bnr1 release and dephosphorylation, Bni1 recruitment and actomyosin ring formation at the division site. These results suggest the involvement of Glc7 in this regulation. Further, we identified Ref2 as the PP1 regulatory subunit responsible for this regulation. Taken together, Glc7 and Ref2 may have a role in actomyosin ring formation by modulating the localization of formins during cytokinesis. PMID:26771880

  15. Deletion of cdvB paralogous genes of Sulfolobus acidocaldarius impairs cell division.

    PubMed

    Yang, Nuan; Driessen, Arnold J M

    2014-03-01

    The majority of Crenarchaeota utilize the cell division system (Cdv) to divide. This system consists of three highly conserved genes, cdvA, cdvB and cdvC that are organized in an operon. CdvC is homologous to the AAA-type ATPase Vps4, involved in multivesicular body biogenesis in eukaryotes. CdvA is a unique archaeal protein that interacts with the membrane, while CdvB is homologous to the eukaryal Vps24 and forms helical filaments. Most Crenarcheota contain additional CdvB paralogs. In Sulfolobus acidocaldarius these are termed CdvB1-3. We have used a gene inactivation approach to determine the impact of these additional cdvB genes on cell division. Independent deletion mutants of these genes were analyzed for growth and protein localization. One of the deletion strains (ΔcdvB3) showed a severe growth defect on plates and delayed growth on liquid medium. It showed the formation of enlarged cells and a defect in DNA segregation. Since these defects are accompanied with an aberrant localization of CdvA and CdvB, we conclude that CdvB3 fulfills an important accessory role in cell division.

  16. NtDRP is necessary for accurate zygotic division orientation and differentiation of basal cell lineage toward suspensor formation.

    PubMed

    Zhao, Jing; Xin, Haiping; Cao, Lingyan; Huang, Xiaorong; Shi, Ce; Zhao, Peng; Fu, Ying; Sun, Meng-Xiang

    2016-11-01

    Plant embryogenesis begins with an asymmetric division of the zygote, producing apical and basal cells with distinct cell fates. The asymmetric zygote division is thought to be critical for embryo pattern formation; however, the molecular mechanisms regulating this process, especially maintaining the accurate position and proper orientation of cell division plane, remain poorly understood. Here, we report that a dynamin-related protein in Nicotiana tabacum, NtDRP, plays a critical role in maintaining orientation of zygotic division plane. Down-regulation of NtDRP caused zygotic cell division to occur in different, incorrect orientations and resulted in disruption of suspensor formation, and even development of twin embryos. The basal cell lineage totally integrated with the apical cell lineage into an embryo-like structure, suggesting that NtDRP is essential to accurate zygotic division orientation and differentiation of basal cell lineage toward suspensor formation. We also reveal that NtDRP plays its role by modulating microtubule spatial organization and spindle orientation during early embryogenesis. Thus, we revealed that NtDRP is involved in orientation of the asymmetric zygotic division and differentiation of distinct suspensor and embryo domains, as well as subsequent embryo pattern formation.

  17. Early B Cell Progenitors Deficient for GON4L Fail To Differentiate Due to a Block in Mitotic Cell Division.

    PubMed

    Barr, Jennifer Y; Goodfellow, Renee X; Colgan, Diana F; Colgan, John D

    2017-04-05

    B cell development in Justy mutant mice is blocked due to a precursor mRNA splicing defect that depletes the protein GON4-like (GON4L) in B cell progenitors. Genetic and biochemical studies have suggested that GON4L is a transcriptional regulator that coordinates cell division with differentiation, but its role in B cell development is unknown. To understand the function of GON4L, we characterized B cell differentiation, cell cycle control, and mitotic gene expression in GON4L-deficient B cell progenitors from Justy mice. We found that these cells established key aspects of the transcription factor network that guides B cell development and proliferation and rearranged the IgH gene locus. However, despite intact IL-7 signaling, GON4L-deficient pro-B cell stage precursors failed to undergo a characteristic IL-7-dependent proliferative burst. These cells also failed to upregulate genes required for mitotic division, including those encoding the G1/S cyclin D3 and E2F transcription factors and their targets. Additionally, GON4L-deficient B cell progenitors displayed defects in DNA synthesis and passage through the G1/S transition, contained fragmented DNA, and underwent apoptosis. These phenotypes were not suppressed by transgenic expression of prosurvival factors. However, transgenic expression of cyclin D3 or other regulators of the G1/S transition restored pro-B cell development from Justy progenitor cells, suggesting that GON4L acts at the beginning of the cell cycle. Together, our findings indicate that GON4L is essential for cell cycle progression and division during the early stages of B cell development.

  18. Influence of the circadian rhythm in cell division on radiation-induced mitotic delay in vivo

    SciTech Connect

    Rubin, N.H.

    1982-01-01

    Mitotic delay is described as a classical response to radiation; however, circadian rhythmicity in cell division in vivo has not been considered by many authors. The present study investigated the relation between fluctuations reported as mitotic delay and recovery in vivo and circadian oscillations in mitotic index in mouse corneal epithelium. One aspect involved single doses (approximately 600 rad) given to mice at different circadian stages. The normal circadian rhythm in cell division was never obliterated. Inhibition of mitosis was evident but unpredictable, ranging from 6 to 15 hr after irradiation. Recovery was evident only during the daily increase in mitotic index of controls. The classical interpretation of recovery from mitotic delay may be in an in vitro phenomenon not reflecting in vivo responses, which are apparently strongly circadian stage dependent. The second portion of the study demonstrated a dose-response effect on length of mitotic delay and, to a lesser extent, degree of recovery.

  19. Evolution of diverse cell division and vesicle formation systems in Archaea

    PubMed Central

    Makarova, Kira S.; Yutin, Natalya; Bell, Stephen D.; Koonin, Eugene V.

    2012-01-01

    Recently a novel cell division system comprised of homologues of eukaryotic ESCRT-III (endosomal sorting complex required for transport III) proteins was discovered in the hyperthermophilic crenarchaeote Sulfolobus acidocaldarius. On the basis of this discovery, we undertook a comparative genomic analysis of the machineries for cell division and vesicle formation in Archaea. Archaea possess at least three distinct membrane remodelling systems: the FtsZ-based bacterial-type system, the ESCRT-III-based eukaryote-like system and a putative novel system that uses an archaeal actin-related protein. Many archaeal genomes encode assortments of components from different systems. Evolutionary reconstruction from these findings suggests that the last common ancestor of the extant Archaea possessed a complex membrane remodelling apparatus, different components of which were lost during subsequent evolution of archaeal lineages. By contrast, eukaryotes seem to have inherited all three ancestral systems. PMID:20818414

  20. Linking asymmetric cell division to the terminal differentiation program of postmitotic neurons in C. elegans

    PubMed Central

    Bertrand, Vincent; Hobert, Oliver

    2009-01-01

    SUMMARY How asymmetric divisions are connected to the terminal differentiation program of neuronal subtypes is poorly understood. In C. elegans, two homeodomain transcription factors, TTX-3 (a LHX2/9 orthologue) and CEH-10 (a CHX10 orthologue), directly activate a large battery of terminal differentiation genes in the cholinergic interneuron AIY. We establish here a transcriptional cascade linking asymmetric division to this differentiation program. A transient lineage-specific input formed by the Zic factor REF-2 and the bHLH factor HLH-2 directly activates ttx-3 expression in the AIY mother. During the terminal division of the AIY mother, an asymmetric Wnt/β-catenin pathway cooperates with TTX-3 to directly restrict ceh-10 expression to only one of the two daughter cells. TTX-3 and CEH-10 automaintain their expression, thereby locking in the differentiation state. Our study establishes how transient lineage and asymmetric division inputs are integrated and suggests that the Wnt/β-catenin pathway is widely used to control the identity of neuronal lineages. PMID:19386265

  1. The influence of GAP-43 on orientation of cell division through G proteins.

    PubMed

    Huang, Rui; Zhao, Junpeng; Ju, Lili; Wen, Yujun; Xu, Qunyuan

    2015-12-01

    Recent studies have shown that GAP-43 is highly expressed in horizontally dividing neural progenitor cells, and G protein complex are required for proper mitotic-spindle orientation of those progenitors in the mammalian developing cortex. In order to verify the hypothesis that GAP-43 may influence the orientation of cell division through interacting with G proteins during neurogenesis, the GAP-43 RNA from adult C57 mouse was cloned into the pEGFP-N1 vector, which was then transfected into Madin-Darby Canine Kidney (MDCK) cells cultured in a three-dimensional (3D) cell culture system. The interaction of GAP-43 with Gαi was detected by co-immunoprecipitation (co-IP), while cystogenesis of 3D morphogenesis of MDCK cells and expression of GAP-43 and Gαi were determined by immunofluorescence and Western blotting. The results showed are as follows: After being transfected by pEGFP-N1-GAP-43, GAP-43 was localized on the cell membrane and co-localized with Gαi, and this dramatically induced a defective cystogenesis in 3D morphogenesis of MDCK cells. The functional interaction between GAP-43 and Gαi proteins was proven by the co-IP assay. It can be considered from the results that the GAP-43 is involved in the orientation of cell division by interacting with Gαi and this should be an important mechanism for neurogenesis in the mammalian brain.

  2. FtsZ and the division of prokaryotic cells and organelles.

    PubMed

    Margolin, William

    2005-11-01

    Binary fission of many prokaryotes as well as some eukaryotic organelles depends on the FtsZ protein, which self-assembles into a membrane-associated ring structure early in the division process. FtsZ is homologous to tubulin, the building block of the microtubule cytoskeleton in eukaryotes. Recent advances in genomics and cell-imaging techniques have paved the way for the remarkable progress in our understanding of fission in bacteria and organelles.

  3. A new model for cell division and migration with spontaneous topology changes.

    PubMed

    Mkrtchyan, Anna; Åström, Jan; Karttunen, Mikko

    2014-06-28

    Tissue topology, in particular proliferating epithelium topology, is remarkably similar between various species. Understanding the mechanisms that result in the observed topologies is needed for better insight into the processes governing tissue formation. We present a two-dimensional single-cell based model for cell divisions and tissue growth. The model accounts for cell mechanics and allows cell migration. Cells do not have pre-existing shapes or topologies. Shape changes and local rearrangements occur naturally as a response to the evolving cellular environment and cell-cell interactions. We show that the commonly observed tissue topologies arise spontaneously from this model. We consider different cellular rearrangements that accompany tissue growth and study their effects on tissue topology.

  4. Machine learning classification of cell-specific cardiac enhancers uncovers developmental subnetworks regulating progenitor cell division and cell fate specification.

    PubMed

    Ahmad, Shaad M; Busser, Brian W; Huang, Di; Cozart, Elizabeth J; Michaud, Sébastien; Zhu, Xianmin; Jeffries, Neal; Aboukhalil, Anton; Bulyk, Martha L; Ovcharenko, Ivan; Michelson, Alan M

    2014-02-01

    The Drosophila heart is composed of two distinct cell types, the contractile cardial cells (CCs) and the surrounding non-muscle pericardial cells (PCs), development of which is regulated by a network of conserved signaling molecules and transcription factors (TFs). Here, we used machine learning with array-based chromatin immunoprecipitation (ChIP) data and TF sequence motifs to computationally classify cell type-specific cardiac enhancers. Extensive testing of predicted enhancers at single-cell resolution revealed the added value of ChIP data for modeling cell type-specific activities. Furthermore, clustering the top-scoring classifier sequence features identified novel cardiac and cell type-specific regulatory motifs. For example, we found that the Myb motif learned by the classifier is crucial for CC activity, and the Myb TF acts in concert with two forkhead domain TFs and Polo kinase to regulate cardiac progenitor cell divisions. In addition, differential motif enrichment and cis-trans genetic studies revealed that the Notch signaling pathway TF Suppressor of Hairless [Su(H)] discriminates PC from CC enhancer activities. Collectively, these studies elucidate molecular pathways used in the regulatory decisions for proliferation and differentiation of cardiac progenitor cells, implicate Su(H) in regulating cell fate decisions of these progenitors, and document the utility of enhancer modeling in uncovering developmental regulatory subnetworks.

  5. Machine learning classification of cell-specific cardiac enhancers uncovers developmental subnetworks regulating progenitor cell division and cell fate specification

    PubMed Central

    Ahmad, Shaad M.; Busser, Brian W.; Huang, Di; Cozart, Elizabeth J.; Michaud, Sébastien; Zhu, Xianmin; Jeffries, Neal; Aboukhalil, Anton; Bulyk, Martha L.; Ovcharenko, Ivan; Michelson, Alan M.

    2014-01-01

    The Drosophila heart is composed of two distinct cell types, the contractile cardial cells (CCs) and the surrounding non-muscle pericardial cells (PCs), development of which is regulated by a network of conserved signaling molecules and transcription factors (TFs). Here, we used machine learning with array-based chromatin immunoprecipitation (ChIP) data and TF sequence motifs to computationally classify cell type-specific cardiac enhancers. Extensive testing of predicted enhancers at single-cell resolution revealed the added value of ChIP data for modeling cell type-specific activities. Furthermore, clustering the top-scoring classifier sequence features identified novel cardiac and cell type-specific regulatory motifs. For example, we found that the Myb motif learned by the classifier is crucial for CC activity, and the Myb TF acts in concert with two forkhead domain TFs and Polo kinase to regulate cardiac progenitor cell divisions. In addition, differential motif enrichment and cis-trans genetic studies revealed that the Notch signaling pathway TF Suppressor of Hairless [Su(H)] discriminates PC from CC enhancer activities. Collectively, these studies elucidate molecular pathways used in the regulatory decisions for proliferation and differentiation of cardiac progenitor cells, implicate Su(H) in regulating cell fate decisions of these progenitors, and document the utility of enhancer modeling in uncovering developmental regulatory subnetworks. PMID:24496624

  6. Cell division orientation is coupled to cell–cell adhesion by the E-cadherin/LGN complex

    PubMed Central

    Gloerich, Martijn; Bianchini, Julie M.; Siemers, Kathleen A.; Cohen, Daniel J.; Nelson, W. James

    2017-01-01

    Both cell–cell adhesion and oriented cell division play prominent roles in establishing tissue architecture, but it is unclear how they might be coordinated. Here, we demonstrate that the cell–cell adhesion protein E-cadherin functions as an instructive cue for cell division orientation. This is mediated by the evolutionarily conserved LGN/NuMA complex, which regulates cortical attachments of astral spindle microtubules. We show that LGN, which adopts a three-dimensional structure similar to cadherin-bound catenins, binds directly to the E-cadherin cytosolic tail and thereby localizes at cell–cell adhesions. On mitotic entry, NuMA is released from the nucleus and competes LGN from E-cadherin to locally form the LGN/NuMA complex. This mediates the stabilization of cortical associations of astral microtubules at cell–cell adhesions to orient the mitotic spindle. Our results show how E-cadherin instructs the assembly of the LGN/NuMA complex at cell–cell contacts, and define a mechanism that couples cell division orientation to intercellular adhesion. PMID:28045117

  7. Solanum lycopersicum AUXIN RESPONSE FACTOR 9 regulates cell division activity during early tomato fruit development.

    PubMed

    de Jong, Maaike; Wolters-Arts, Mieke; Schimmel, Bernardus C J; Stultiens, Catharina L M; de Groot, Peter F M; Powers, Stephen J; Tikunov, Yury M; Bovy, Arnoud G; Mariani, Celestina; Vriezen, Wim H; Rieu, Ivo

    2015-06-01

    The transformation of the ovary into a fruit after successful completion of pollination and fertilization has been associated with many changes at transcriptomic level. These changes are part of a dynamic and complex regulatory network that is controlled by phytohormones, with a major role for auxin. One of the auxin-related genes differentially expressed upon fruit set and early fruit development in tomato is Solanum lycopersicum AUXIN RESPONSE FACTOR 9 (SlARF9). Here, the functional analysis of this ARF is described. SlARF9 expression was found to be auxin-responsive and SlARF9 mRNA levels were high in the ovules, placenta, and pericarp of pollinated ovaries, but also in other plant tissues with high cell division activity, such as the axillary meristems and root meristems. Transgenic plants with increased SlARF9 mRNA levels formed fruits that were smaller than wild-type fruits because of reduced cell division activity, whereas transgenic lines in which SlARF9 mRNA levels were reduced showed the opposite phenotype. The expression analysis, together with the phenotype of the transgenic lines, suggests that, in tomato, ARF9 negatively controls cell division during early fruit development.

  8. Role of eukaryotic-like serine/threonine kinases in bacterial cell division and morphogenesis.

    PubMed

    Manuse, Sylvie; Fleurie, Aurore; Zucchini, Laure; Lesterlin, Christian; Grangeasse, Christophe

    2016-01-01

    Bacteria possess a repertoire of versatile protein kinases modulating diverse aspects of their physiology by phosphorylating proteins on various amino acids including histidine, cysteine, aspartic acid, arginine, serine, threonine and tyrosine. One class of membrane serine/threonine protein kinases possesses a catalytic domain sharing a common fold with eukaryotic protein kinases and an extracellular mosaic domain found in bacteria only, named PASTA for 'Penicillin binding proteins And Serine/Threonine kinase Associated'. Over the last decade, evidence has been accumulating that these protein kinases are involved in cell division, morphogenesis and developmental processes in Firmicutes and Actinobacteria. However, observations differ from one species to another suggesting that a general mechanism of activation of their kinase activity is unlikely and that species-specific regulation of cell division is at play. In this review, we survey the latest research on the structural aspects and the cellular functions of bacterial serine/threonine kinases with PASTA motifs to illustrate the diversity of the regulatory mechanisms controlling bacterial cell division and morphogenesis.

  9. Solanum lycopersicum AUXIN RESPONSE FACTOR 9 regulates cell division activity during early tomato fruit development

    PubMed Central

    de Jong, Maaike; Wolters-Arts, Mieke; Schimmel, Bernardus C. J.; Stultiens, Catharina L. M.; de Groot, Peter F. M.; Powers, Stephen J.; Tikunov, Yury M.; Bovy, Arnoud G.; Mariani, Celestina; Vriezen, Wim H.; Rieu, Ivo

    2015-01-01

    The transformation of the ovary into a fruit after successful completion of pollination and fertilization has been associated with many changes at transcriptomic level. These changes are part of a dynamic and complex regulatory network that is controlled by phytohormones, with a major role for auxin. One of the auxin-related genes differentially expressed upon fruit set and early fruit development in tomato is Solanum lycopersicum AUXIN RESPONSE FACTOR 9 (SlARF9). Here, the functional analysis of this ARF is described. SlARF9 expression was found to be auxin-responsive and SlARF9 mRNA levels were high in the ovules, placenta, and pericarp of pollinated ovaries, but also in other plant tissues with high cell division activity, such as the axillary meristems and root meristems. Transgenic plants with increased SlARF9 mRNA levels formed fruits that were smaller than wild-type fruits because of reduced cell division activity, whereas transgenic lines in which SlARF9 mRNA levels were reduced showed the opposite phenotype. The expression analysis, together with the phenotype of the transgenic lines, suggests that, in tomato, ARF9 negatively controls cell division during early fruit development. PMID:25883382

  10. Caffeine yields aneuploidy through asymmetrical cell division caused by misalignment of chromosomes.

    PubMed

    Katsuki, Yoko; Nakada, Shinichiro; Yokoyama, Tetsuji; Imoto, Issei; Inazawa, Johji; Nagasawa, Masayuki; Mizutani, Shuki

    2008-08-01

    Aneuploidy has been implicated as an important step leading to various neoplasias. Although genetic factors that block aneuploidy have been the subject of intense interest, the impact of pharmacological and environmental substances on the development of aneuploidy has not been studied. Here, we show that caffeine induces aneuploidy through asymmetrical cell division. Mitotic exits of HeLa, U2OS, and primary fibroblast cells were significantly delayed by 10 mmol/L caffeine. Most caffeine-treated mitotic cells showed misalignment of chromosomes at the metaphase plates, and were arrested at prometaphase. Mitoticarrest deficient 2 (MAD2) depletion rescued the caffeine-induced delay of mitotic exit, indicating that caffeine-induced prolongation of mitosis was caused by activation of a MAD2-dependent spindle checkpoint. Enumeration of centromeres by fluorescence in situ hybridization revealed that cell division in the presence of caffeine was not symmetrical and resulted in aneuploid cell production. Most of these cells survived and underwent DNA synthesis. Our findings reveal a novel pharmacological effect of a high concentration of caffeine on genomic stability in dividing cells.

  11. Structural characterization of the cell division cycle in Strigomonas culicis, an endosymbiont-bearing trypanosomatid.

    PubMed

    Brum, Felipe Lopes; Catta-Preta, Carolina Moura Costa; de Souza, Wanderley; Schenkman, Sergio; Elias, Maria Carolina; Motta, Maria Cristina Machado

    2014-02-01

    Strigomonas culicis (previously referred to as Blastocrithidia culicis) is a monoxenic trypanosomatid harboring a symbiotic bacterium, which maintains an obligatory relationship with the host protozoan. Investigations of the cell cycle in symbiont harboring trypanosomatids suggest that the bacterium divides in coordination with other host cell structures, particularly the nucleus. In this study we used light and electron microscopy followed by three-dimensional reconstruction to characterize the symbiont division during the cell cycle of S. culicis. We observed that during this process, the symbiotic bacterium presents different forms and is found at different positions in relationship to the host cell structures. At the G1/S phase of the protozoan cell cycle, the endosymbiont exhibits a constricted form that appears to elongate, resulting in the bacterium division, which occurs before kinetoplast and nucleus segregation. During cytokinesis, the symbionts are positioned close to each nucleus to ensure that each daughter cell will inherit a single copy of the bacterium. These observations indicated that the association of the bacterium with the protozoan nucleus coordinates the cell cycle in both organisms.

  12. Cytoskeleton dynamics control the first asymmetric cell division in Arabidopsis zygote

    PubMed Central

    Kimata, Yusuke; Higaki, Takumi; Kawashima, Tomokazu; Kurihara, Daisuke; Sato, Yoshikatsu; Yamada, Tomomi; Hasezawa, Seiichiro; Berger, Frederic; Higashiyama, Tetsuya

    2016-01-01

    The asymmetric cell division of the zygote is the initial and crucial developmental step in most multicellular organisms. In flowering plants, whether zygote polarity is inherited from the preexisting organization in the egg cell or reestablished after fertilization has remained elusive. How dynamically the intracellular organization is generated during zygote polarization is also unknown. Here, we used a live-cell imaging system with Arabidopsis zygotes to visualize the dynamics of the major elements of the cytoskeleton, microtubules (MTs), and actin filaments (F-actins), during the entire process of zygote polarization. By combining image analysis and pharmacological experiments using specific inhibitors of the cytoskeleton, we found features related to zygote polarization. The preexisting alignment of MTs and F-actin in the egg cell is lost on fertilization. Then, MTs organize into a transverse ring defining the zygote subapical region and driving cell outgrowth in the apical direction. F-actin forms an apical cap and longitudinal arrays and is required to position the nucleus to the apical region of the zygote, setting the plane of the first asymmetrical division. Our findings show that, in flowering plants, the preexisting cytoskeletal patterns in the egg cell are lost on fertilization and that the zygote reorients the cytoskeletons to perform directional cell elongation and polar nuclear migration. PMID:27911812

  13. ELECTRON MICROSCOPY OF AXIAL FIBRILS, OUTER ENVELOPE, AND CELL DIVISION OF CERTAIN ORAL SPIROCHETES

    PubMed Central

    Listgarten, M. A.; Socransky, S. S.

    1964-01-01

    Listgarten, M. A. (Harvard School of Dental Medicine and Forsyth Dental Center, Boston, Mass.), and S. S. Socransky. Electron microscopy of axial fibrils, outer envelope, and cell division of certain oral spirochetes. J. Bacteriol. 88:1087–1103. 1964.—The ultrastructure of axial fibrils and outer envelopes of a number of oral spirochetes was studied in thin sections and by negative contrast. The axial fibrils measured 150 to 200 A in diameter. Only one end of each fibril was inserted subterminally into the protoplasmic cylinder by means of a 400 A wide disc. The free ends of fibrils inserted near one end of the cylinder extended toward, and overlapped in close apposition, the free ends of fibrils inserted at the other end. In thin sections, some axial fibrils showed a substructure, suggestive of a dense central core. The outer envelopes of most spirochetes appeared to consist of 80 A wide polygonal structural subunits. However, in one large spirochete, the outer envelope demonstrated a “pin-striped” pattern. Cell division in a pure culture of Treponema microdentium was studied by negative contrast. Results suggested that this organism divides by transverse fission, the outer envelope being last to divide. During the course of division, new axial fibrils appeared to originate on either side of the point of constriction of the protoplasmic cylinder. Flagellalike extensions which were found in rapidly dividing organisms were due to protruding axial fibrils, and appeared to be the result of cell division. Some evidence is presented to support the concept of a homologous origin for axial fibrils and flagella. Images PMID:14219024

  14. Synthetic inhibitors of bacterial cell division targeting the GTP-binding site of FtsZ.

    PubMed

    Ruiz-Avila, Laura B; Huecas, Sonia; Artola, Marta; Vergoñós, Albert; Ramírez-Aportela, Erney; Cercenado, Emilia; Barasoain, Isabel; Vázquez-Villa, Henar; Martín-Fontecha, Mar; Chacón, Pablo; López-Rodríguez, María L; Andreu, José M

    2013-09-20

    Cell division protein FtsZ is the organizer of the cytokinetic Z-ring in most bacteria and a target for new antibiotics. FtsZ assembles with GTP into filaments that hydrolyze the nucleotide at the association interface between monomers and then disassemble. We have replaced FtsZ's GTP with non-nucleotide synthetic inhibitors of bacterial division. We searched for these small molecules among compounds from the literature, from virtual screening (VS), and from our in-house synthetic library (UCM), employing a fluorescence anisotropy primary assay. From these screens we have identified the polyhydroxy aromatic compound UCM05 and its simplified analogue UCM44 that specifically bind to Bacillus subtilis FtsZ monomers with micromolar affinities and perturb normal assembly, as examined with light scattering, polymer sedimentation, and negative stain electron microscopy. On the other hand, these ligands induce the cooperative assembly of nucleotide-devoid archaeal FtsZ into distinct well-ordered polymers, different from GTP-induced filaments. These FtsZ inhibitors impair localization of FtsZ into the Z-ring and inhibit bacterial cell division. The chlorinated analogue UCM53 inhibits the growth of clinical isolates of antibiotic-resistant Staphylococcus aureus and Enterococcus faecalis. We suggest that these interfacial inhibitors recapitulate binding and some assembly-inducing effects of GTP but impair the correct structural dynamics of FtsZ filaments and thus inhibit bacterial division, possibly by binding to a small fraction of the FtsZ molecules in a bacterial cell, which opens a new approach to FtsZ-based antibacterial drug discovery.

  15. Pregnancy persistently affects memory T cell populations.

    PubMed

    Kieffer, Tom E C; Faas, Marijke M; Scherjon, Sicco A; Prins, Jelmer R

    2017-02-01

    Pregnancy is an immune challenge to the maternal immune system. The effects of pregnancy on maternal immunity and particularly on memory T cells during and after pregnancy are not fully known. This observational study aims to show the short term and the long term effects of pregnancy on the constitution, size and activation status of peripheral human memory T-lymphocyte populations. Effector memory (EM) and central memory (CM) T-lymphocytes were analyzed using flow cytometry of peripheral blood from 14 nulligravid, 12 primigravid and 15 parous women that were on average 18 months postpartum. The short term effects were shown by the significantly higher CD4+ EM cell and activated CD4+ memory cell proportions in primigravid women compared to nulligravid women. The persistent effects found in this study were the significantly higher proportions of CD4+ EM, CD4+ CM and activated memory T cells in parous women compared to nulligravid women. In contrast to CD4+ cells, activation status of CD8+ memory cells did not differ between the groups. This study shows that pregnancy persistently affects the pre-pregnancy CD4+ memory cell pool in human peripheral blood. During pregnancy, CD4+ T-lymphocytes might differentiate into EM cells followed by persistent higher proportions of CD4+ CM and EM cells postpartum. The persistent effects of pregnancy on memory T cells found in this study support the hypothesis that memory T cells are generated during pregnancy and that these cells could be involved in the lower complication risks in multiparous pregnancies in humans.

  16. Functional Domain Analysis of the Cell Division Inhibitor EzrA

    PubMed Central

    Levin, Petra Anne

    2014-01-01

    The precise spatial and temporal control of bacterial cell division is achieved through the balanced actions of factors that inhibit assembly of the tubulin-like protein FtsZ at aberrant subcellular locations or promote its assembly at the future sites of division. In Bacillus subtilis, the membrane anchored cell division protein EzrA, interacts directly with FtsZ to prevent aberrant FtsZ assembly at cell poles and contributes to the inherently dynamic nature of the cytokinetic ring. Recent work suggests EzrA also serves as a scaffolding protein to coordinate lateral growth with cell wall biosynthesis through interactions with a host of proteins, a finding consistent with EzrA's four extensive coiled-coil domains. In a previous study we identified a conserved patch of residues near EzrA's C-terminus (the QNR motif) that are critical for maintenance of a dynamic cytokinetic ring, but dispensable for EzrA-mediated inhibition of FtsZ assembly at cell poles. In an extension of this work, here we report that EzrA's two C-terminal coiled-coils function in concert with the QNR motif to mediate interactions with FtsZ and maintain the dynamic nature of the cytokinetic ring. In contrast, EzrA's two N-terminal coiled-coils are dispensable for interaction between EzrA and FtsZ in vitro and in vivo, but required for EzrA mediated inhibition of FtsZ assembly at cell poles. Finally, chimeric analysis indicates that EzrA's transmembrane anchor plays a generic role: concentrating EzrA at the plasma membrane where presumably it can most effectively modulate FtsZ assembly. PMID:25068683

  17. Characterization of DicB by partially masking its potent inhibitory activity of cell division

    PubMed Central

    Yang, Shaoyuan; Pei, Hairun; Zhang, Xiaoying; Wei, Qiang; Zhu, Jia; Zheng, Jimin; Jia, Zongchao

    2016-01-01

    DicB, a protein encoded by the Kim (Qin) prophage in Escherichia coli, inhibits cell division through interaction with MinC. Thus far, characterization of DicB has been severely hampered owing to its potent activity which ceases cell division and leads to cell death. In this work, through fusing maltose-binding protein to the N-terminus of DicB (MBP–DicB), we successfully expressed and purified recombinant DicB that enabled in vitro analysis for the first time. More importantly, taking advantage of the reduced inhibitory activity of MBP–DicB, we were able to study its effects on cell growth and morphology. Inhibition of cell growth by MBP–DicB was systematically evaluated using various DicB constructs, and their corresponding effects on cell morphology were also investigated. Our results revealed that the N-terminal segment of DicB plays an essential functional role, in contrast to its C-terminal tail. The N-terminus of DicB is of critical importance as even the first amino acid (following the initial Met) could not be removed, although it could be mutated. This study provides the first glimpse of the molecular determinants underlying DicB's function. PMID:27466443

  18. Gα modulates salt-induced cellular senescence and cell division in rice and maize.

    PubMed

    Urano, Daisuke; Colaneri, Alejandro; Jones, Alan M

    2014-12-01

    The plant G-protein network, comprising Gα, Gβ, and Gγ core subunits, regulates development, senses sugar, and mediates biotic and abiotic stress responses. Here, we report G-protein signalling in the salt stress response using two crop models, rice and maize. Loss-of-function mutations in the corresponding genes encoding the Gα subunit attenuate growth inhibition and cellular senescence caused by sodium chloride (NaCl). Gα null mutations conferred reduced leaf senescence, chlorophyll degradation, and cytoplasm electrolyte leakage under NaCl stress. Sodium accumulated in both wild-type and Gα-mutant shoots to the same levels, suggesting that Gα signalling controls cell death in leaves rather than sodium exclusion in roots. Growth inhibition is probably initiated by osmotic change around root cells, because KCl and MgSO4 also suppressed seedling growth equally as well as NaCl. NaCl lowered rates of cell division and elongation in the wild-type leaf sheath to the level of the Gα-null mutants; however there was no NaCl-induced decrease in cell division in the Gα mutant, implying that the osmotic phase of salt stress suppresses cell proliferation through the inhibition of Gα-coupled signalling. These results reveal two distinct functions of Gα in NaCl stress in these grasses: attenuation of leaf senescence caused by sodium toxicity in leaves, and cell cycle regulation by osmotic/ionic stress.

  19. Gα modulates salt-induced cellular senescence and cell division in rice and maize

    DOE PAGES

    Urano, Daisuke; Colaneri, Alejandro; Jones, Alan M.

    2014-09-16

    The plant G-protein network, comprising Gα, Gβ, and Gγ core subunits, regulates development, senses sugar, and mediates biotic and abiotic stress responses. Here in this paper, we report G-protein signalling in the salt stress response using two crop models, rice and maize. Loss-of-function mutations in the corresponding genes encoding the Gα subunit attenuate growth inhibition and cellular senescence caused by sodium chloride (NaCl). Gα null mutations conferred reduced leaf senescence, chlorophyll degradation, and cytoplasm electrolyte leakage under NaCl stress. Sodium accumulated in both wild-type and Gα-mutant shoots to the same levels, suggesting that Gα signalling controls cell death in leavesmore » rather than sodium exclusion in roots. Growth inhibition is probably initiated by osmotic change around root cells, because KCl and MgSO4 also suppressed seedling growth equally as well as NaCl. NaCl lowered rates of cell division and elongation in the wild-type leaf sheath to the level of the Gα-null mutants; however there was no NaCl-induced decrease in cell division in the Gα mutant, implying that the osmotic phase of salt stress suppresses cell proliferation through the inhibition of Gα-coupled signalling. These results reveal two distinct functions of Gα in NaCl stress in these grasses: attenuation of leaf senescence caused by sodium toxicity in leaves, and cell cycle regulation by osmotic/ionic stress.« less

  20. The Bacterium Endosymbiont of Crithidia deanei Undergoes Coordinated Division with the Host Cell Nucleus

    PubMed Central

    Motta, Maria Cristina Machado; Catta-Preta, Carolina Moura Costa; Schenkman, Sergio; de Azevedo Martins, Allan Cezar; Miranda, Kildare; de Souza, Wanderley; Elias, Maria Carolina

    2010-01-01

    In trypanosomatids, cell division involves morphological changes and requires coordinated replication and segregation of the nucleus, kinetoplast and flagellum. In endosymbiont-containing trypanosomatids, like Crithidia deanei, this process is more complex, as each daughter cell contains only a single symbiotic bacterium, indicating that the prokaryote must replicate synchronically with the host protozoan. In this study, we used light and electron microscopy combined with three-dimensional reconstruction approaches to observe the endosymbiont shape and division during C. deanei cell cycle. We found that the bacterium replicates before the basal body and kinetoplast segregations and that the nucleus is the last organelle to divide, before cytokinesis. In addition, the endosymbiont is usually found close to the host cell nucleus, presenting different shapes during the protozoan cell cycle. Considering that the endosymbiosis in trypanosomatids is a mutualistic relationship, which resembles organelle acquisition during evolution, these findings establish an excellent model for the understanding of mechanisms related with the establishment of organelles in eukaryotic cells. PMID:20865129

  1. Gα modulates salt-induced cellular senescence and cell division in rice and maize

    SciTech Connect

    Urano, Daisuke; Colaneri, Alejandro; Jones, Alan M.

    2014-09-16

    The plant G-protein network, comprising Gα, Gβ, and Gγ core subunits, regulates development, senses sugar, and mediates biotic and abiotic stress responses. Here in this paper, we report G-protein signalling in the salt stress response using two crop models, rice and maize. Loss-of-function mutations in the corresponding genes encoding the Gα subunit attenuate growth inhibition and cellular senescence caused by sodium chloride (NaCl). Gα null mutations conferred reduced leaf senescence, chlorophyll degradation, and cytoplasm electrolyte leakage under NaCl stress. Sodium accumulated in both wild-type and Gα-mutant shoots to the same levels, suggesting that Gα signalling controls cell death in leaves rather than sodium exclusion in roots. Growth inhibition is probably initiated by osmotic change around root cells, because KCl and MgSO4 also suppressed seedling growth equally as well as NaCl. NaCl lowered rates of cell division and elongation in the wild-type leaf sheath to the level of the Gα-null mutants; however there was no NaCl-induced decrease in cell division in the Gα mutant, implying that the osmotic phase of salt stress suppresses cell proliferation through the inhibition of Gα-coupled signalling. These results reveal two distinct functions of Gα in NaCl stress in these grasses: attenuation of leaf senescence caused by sodium toxicity in leaves, and cell cycle regulation by osmotic/ionic stress.

  2. Gα modulates salt-induced cellular senescence and cell division in rice and maize

    PubMed Central

    Urano, Daisuke; Colaneri, Alejandro; Jones, Alan M.

    2014-01-01

    The plant G-protein network, comprising Gα, Gβ, and Gγ core subunits, regulates development, senses sugar, and mediates biotic and abiotic stress responses. Here, we report G-protein signalling in the salt stress response using two crop models, rice and maize. Loss-of-function mutations in the corresponding genes encoding the Gα subunit attenuate growth inhibition and cellular senescence caused by sodium chloride (NaCl). Gα null mutations conferred reduced leaf senescence, chlorophyll degradation, and cytoplasm electrolyte leakage under NaCl stress. Sodium accumulated in both wild-type and Gα-mutant shoots to the same levels, suggesting that Gα signalling controls cell death in leaves rather than sodium exclusion in roots. Growth inhibition is probably initiated by osmotic change around root cells, because KCl and MgSO4 also suppressed seedling growth equally as well as NaCl. NaCl lowered rates of cell division and elongation in the wild-type leaf sheath to the level of the Gα-null mutants; however there was no NaCl-induced decrease in cell division in the Gα mutant, implying that the osmotic phase of salt stress suppresses cell proliferation through the inhibition of Gα-coupled signalling. These results reveal two distinct functions of Gα in NaCl stress in these grasses: attenuation of leaf senescence caused by sodium toxicity in leaves, and cell cycle regulation by osmotic/ionic stress. PMID:25227951

  3. LocZ Is a New Cell Division Protein Involved in Proper Septum Placement in Streptococcus pneumoniae

    PubMed Central

    Holečková, Nela; Molle, Virginie; Buriánková, Karolína; Benada, Oldřich; Kofroňová, Olga; Ulrych, Aleš; Branny, Pavel

    2014-01-01

    ABSTRACT How bacteria control proper septum placement at midcell, to guarantee the generation of identical daughter cells, is still largely unknown. Although different systems involved in the selection of the division site have been described in selected species, these do not appear to be widely conserved. Here, we report that LocZ (Spr0334), a newly identified cell division protein, is involved in proper septum placement in Streptococcus pneumoniae. We show that locZ is not essential but that its deletion results in cell division defects and shape deformation, causing cells to divide asymmetrically and generate unequally sized, occasionally anucleated, daughter cells. LocZ has a unique localization profile. It arrives early at midcell, before FtsZ and FtsA, and leaves the septum early, apparently moving along with the equatorial rings that mark the future division sites. Consistently, cells lacking LocZ also show misplacement of the Z-ring, suggesting that it could act as a positive regulator to determine septum placement. LocZ was identified as a substrate of the Ser/Thr protein kinase StkP, which regulates cell division in S. pneumoniae. Interestingly, homologues of LocZ are found only in streptococci, lactococci, and enterococci, indicating that this close phylogenetically related group of bacteria evolved a specific solution to spatially regulate cell division. PMID:25550321

  4. Functional Analysis of the Cell Division Protein FtsW of Escherichia coli†

    PubMed Central

    Pastoret, Soumya; Fraipont, Claudine; den Blaauwen, Tanneke; Wolf, Benoît; Aarsman, Mirjam E. G.; Piette, André; Thomas, Annick; Brasseur, Robert; Nguyen-Distèche, Martine

    2004-01-01

    Site-directed mutagenesis experiments combined with fluorescence microscopy shed light on the role of Escherichia coli FtsW, a membrane protein belonging to the SEDS family that is involved in peptidoglycan assembly during cell elongation, division, and sporulation. This essential cell division protein has 10 transmembrane segments (TMSs). It is a late recruit to the division site and is required for subsequent recruitment of penicillin-binding protein 3 (PBP3) catalyzing peptide cross-linking. The results allow identification of several domains of the protein with distinct functions. The localization of PBP3 to the septum was found to be dependent on the periplasmic loop located between TMSs 9 and 10. The E240-A249 amphiphilic peptide in the periplasmic loop between TMSs 7 and 8 appears to be a key element in the functioning of FtsW in the septal peptidoglycan assembly machineries. The intracellular loop (containing the R166-F178 amphiphilic peptide) between TMSs 4 and 5 and Gly 311 in TMS 8 are important components of the amino acid sequence-folding information. PMID:15576787

  5. Novel mechanism of cell division inhibition associated with the SOS response in Escherichia coli.

    PubMed Central

    D'Ari, R; Huisman, O

    1983-01-01

    Certain Escherichia coli strains were shown to possess a novel system of cell division inhibition, called the SfiC+ phenotype. SfiC+ filamentation had a number of properties similar to those of sfiA-dependent division inhibition previously described: (i) both are associated with the SOS response induced by expression of the recA(Tif) mutation, (ii) both are associated with cell death, (iii) both are amplified in mutants lacking the Lon protease, and (iv) both are suppressed by sfiB mutations. SfiC+ filamentation and sfiA-dependent division inhibition differed in (i) the physiological conditions under which loss of viability is observed, (ii) the extent of amplification in lon mutants, (iii) their genetic regulation (SfiC+ filamentation is not under direct negative control of the LexA repressor), and (iv) their genetic determinants (SfiC+ filamentation depends on a locus, sfiC+, near 28 min on the E. coli map and distinct from sfiA). Images PMID:6352679

  6. Real-time three-dimensional imaging of cell division by differential interference contrast microscopy.

    PubMed

    Tsunoda, M; Isailovic, D; Yeung, E S

    2008-11-01

    Differential interference contrast (DIC) microscopy can provide information about subcellular components and organelles inside living cells. Applicability to date, however, has been limited to 2D imaging. Unfortunately, understanding of cellular dynamics is difficult to extract from these single optical sections. We demonstrate here that 3D differential interference contrast microscopy has sub-diffraction limit resolution both laterally and vertically, and can be used for following Madin Darby canine kidney cell division process in real time. This is made possible by optimization of the microscope optics and by incorporating computer-controlled vertical scanning of the microscope stage.

  7. Behavior of centrosomes during fertilization and cell division in mouse oocytes and in sea urchin eggs

    NASA Technical Reports Server (NTRS)

    Schatten, Heide; Schatten, Gerald; Balczon, Ron; Simerly, Calvin; Mazia, Daniel

    1986-01-01

    The behavior of centrosomes during the stages of fertilization and cell division in mouse oocytes and in sea urchin eggs was monitored in an immunofluorescence microscope, using autoimmune centrosomal antiserum derived from a patient with scleroderma to label the centrosomal material. These observations showed that centrosomes reproduce during the interphase and aggregate and separate during cell mitosis. Results supported the hypothesis of Mazia (1984), who proposed that centrosomes are 'flexible bodies'. It was also found that, while the sea urchin centrosomes are paternally inherited as was initially proposed by Bovery (1904), the mouse centrosomes are of maternal origin.

  8. Microtubule plus-end tracking proteins and their roles in cell division.

    PubMed

    Ferreira, Jorge G; Pereira, Ana L; Maiato, Helder

    2014-01-01

    Microtubules are cellular components that are required for a variety of essential processes such as cell motility, mitosis, and intracellular transport. This is possible because of the inherent dynamic properties of microtubules. Many of these properties are tightly regulated by a number of microtubule plus-end-binding proteins or +TIPs. These proteins recognize the distal end of microtubules and are thus in the right context to control microtubule dynamics. In this review, we address how microtubule dynamics are regulated by different +TIP families, focusing on how functionally diverse +TIPs spatially and temporally regulate microtubule dynamics during animal cell division.

  9. Knockdown of Dystrophin Dp71 Impairs PC12 Cells Cycle: Localization in the Spindle and Cytokinesis Structures Implies a Role for Dp71 in Cell Division

    PubMed Central

    Villarreal-Silva, Marcela; Centeno-Cruz, Federico; Suárez-Sánchez, Rocío; Garrido, Efraín; Cisneros, Bulmaro

    2011-01-01

    The function of dystrophin Dp71 in neuronal cells remains to be established. Previously, we revealed the involvement of this protein in both nerve growth factor (NGF)-induced neuronal differentiation and cell adhesion by isolation and characterization of PC12 neuronal cells with depleted levels of Dp71. In this work, a novel phenotype of Dp71-knockdown cells was characterized, which is their delayed growth rate. Cell cycle analyses revealed an altered behavior of Dp71-depleted cells, which consists of a delay in G0/G1 transition and an increase in apoptosis during nocodazole-induced mitotic arrest. Dp71 associates with lamin B1 and β-dystroglycan, proteins involved in aspects of the cell division cycle; therefore, we compared the distribution of Dp71 with that of lamin B1 and β-dystroglycan in PC12 cells at mitosis and cytokinesis by means of immunofluorescence and confocal microscopy analysis. All of these three proteins exhibited a similar immunostaining pattern, localized at mitotic spindle, cleavage furrow, and midbody. It is noteworthy that a drastic decreased staining in mitotic spindle, cleavage furrow, and midbody was observed for both lamin B1 and β-dystroglycan in Dp71-depleted cells. Furthermore, we demonstrated the interaction of Dp71 with lamin B1 in PC12 cells by immunoprecipitation and pull-down assays, and importantly, we revealed that knockdown of Dp71 expression caused a marked reduction in lamin B1 levels and altered localization of the nuclear envelope protein emerin. Our data indicate that Dp71 is a component of the mitotic spindle and cytokinesis multi-protein apparatuses that might modulate the cell division cycle by affecting lamin B1 and β-dystroglycan levels. PMID:21886794

  10. Asymmetric stem-cell division ensures sustained keratinocyte hyperproliferation in psoriatic skin lesions

    PubMed Central

    JIA, HAI-YAN; SHI, YING; LUO, LONG-FEI; JIANG, GUAN; ZHOU, QIONG; XU, SHI-ZHENG; LEI, TIE-CHI

    2016-01-01

    Excessive expansion of the transit-amplifying (TA) cell compartment is a distinct morphological characteristic of psoriatic epidermal hyperplasia. In order to examine the activation of basal stem cells and how they replenish such an enlarged compartment of TA cells in psoriatic epidermis, we utilized a BrdU labeling method to monitor mitotic stem cells in a mouse model of psoriasiform dermatitis, which was induced by imiquimod. Our results showed that perpendicular and parallel cell division characteristics of dividing stem cells existed in the inflamed epidermis. When we analyzed template-DNA strand segregation in trypsin-dissociated human psoriatic keratinocytes using BrdU pulse-chase labeling, we found that the percentage of asymmetric segregation of BrdU was significantly increased in the cell pairs of psoriatic epidermal cells compared with normal epidermal cells. Furthermore, we also examined the effects of both interleukin (IL)-17A and IL-22 cytokines on the differentiation status of cultured human keratinocytes. The results indicated that both cytokines had synergistic effects on passage-one epidermal cell sheets derived from skin explants and also on cultured keratinocytes, were involved in the maintenance of the undifferentiated stem cell phenotype, and these results suggest an efficient mechanism for preventing the premature loss of basal stem-cell pools in the pro-inflammatory cytokine-enriched milieu of the psoriatic epidermis. Our findings suggest that inhibition of hyperactive stem cells represents a potential therapeutic target to combat recalcitrant epidermal hyperplasia in psoriasis. PMID:26707630

  11. Fibroblasts Cultured on Nanowires Exhibit Low Motility, Impaired Cell Division, and DNA Damage

    PubMed Central

    Persson, Henrik; Købler, Carsten; Mølhave, Kristian; Samuelson, Lars; Tegenfeldt, Jonas O; Oredsson, Stina; Prinz, Christelle N

    2013-01-01

    Nanowires are commonly used as tools for interfacing living cells, acting as biomolecule-delivery vectors or electrodes. It is generally assumed that the small size of the nanowires ensures a minimal cellular perturbation, yet the effects of nanowires on cell migration and proliferation remain largely unknown. Fibroblast behaviour on vertical nanowire arrays is investigated, and it is shown that cell motility and proliferation rate are reduced on nanowires. Fibroblasts cultured on long nanowires exhibit failed cell division, DNA damage, increased ROS content and respiration. Using focused ion beam milling and scanning electron microscopy, highly curved but intact nuclear membranes are observed, showing no direct contact between the nanowires and the DNA. The nanowires possibly induce cellular stress and high respiration rates, which trigger the formation of ROS, which in turn results in DNA damage. These results are important guidelines to the design and interpretation of experiments involving nanowire-based transfection and electrical characterization of living cells. PMID:23813871

  12. Adherens junctions determine the apical position of the midbody during follicular epithelial cell division.

    PubMed

    Morais-de-Sá, Eurico; Sunkel, Claudio

    2013-08-01

    Cytokinesis is asymmetric along the apical-basal axis of epithelial cells, positioning the midbody near the apical domain. However, little is known about the mechanism and purpose of this asymmetry. We use live imaging of Drosophila follicle cell division to show that asymmetric cytokinesis does not result from intrinsic polarization of the main contractile ring components. We show that adherens junctions (AJs) maintain close contact with the apical side of the contractile ring during cytokinesis. Asymmetric distribution of AJ components within follicle cells and in the otherwise unpolarized S2 cells is sufficient to recruit the midbody, revealing that asymmetric cytokinesis is determined by apical AJs in the epithelia. We further show that ectopic midbody localization induces epithelial invaginations, shifting the position of the apical interface between daughter cells relative to the AB axis of the tissue. Thus, apical midbody localization is essential to maintain epithelial tissue architecture during proliferation.

  13. Cryptococcal Cell Morphology Affects Host Cell Interactions and Pathogenicity

    PubMed Central

    Nielsen, Judith N.; Charlier, Caroline; Baltes, Nicholas J.; Chrétien, Fabrice; Heitman, Joseph; Dromer, Françoise; Nielsen, Kirsten

    2010-01-01

    Cryptococcus neoformans is a common life-threatening human fungal pathogen. The size of cryptococcal cells is typically 5 to 10 µm. Cell enlargement was observed in vivo, producing cells up to 100 µm. These morphological changes in cell size affected pathogenicity via reducing phagocytosis by host mononuclear cells, increasing resistance to oxidative and nitrosative stress, and correlated with reduced penetration of the central nervous system. Cell enlargement was stimulated by coinfection with strains of opposite mating type, and ste3aΔ pheromone receptor mutant strains had reduced cell enlargement. Finally, analysis of DNA content in this novel cell type revealed that these enlarged cells were polyploid, uninucleate, and produced daughter cells in vivo. These results describe a novel mechanism by which C. neoformans evades host phagocytosis to allow survival of a subset of the population at early stages of infection. Thus, morphological changes play unique and specialized roles during infection. PMID:20585559

  14. The Arabidopsis CLASP gene encodes a microtubule-associated protein involved in cell expansion and division.

    PubMed

    Ambrose, J Christian; Shoji, Tsubasa; Kotzer, Amanda M; Pighin, Jamie A; Wasteneys, Geoffrey O

    2007-09-01

    Controlling microtubule dynamics and spatial organization is a fundamental requirement of eukaryotic cell function. Members of the ORBIT/MAST/CLASP family of microtubule-associated proteins associate with the plus ends of microtubules, where they promote the addition of tubulin subunits into attached kinetochore fibers during mitosis and stabilize microtubules in the vicinity of the plasma membrane during interphase. To date, nothing is known about their function in plants. Here, we show that the Arabidopsis thaliana CLASP protein is a microtubule-associated protein that is involved in both cell division and cell expansion. Green fluorescent protein-CLASP localizes along the full length of microtubules and shows enrichment at growing plus ends. Our analysis suggests that CLASP promotes microtubule stability. clasp-1 T-DNA insertion mutants are hypersensitive to microtubule-destabilizing drugs and exhibit more sparsely populated, yet well ordered, root cortical microtubule arrays. Overexpression of CLASP promotes microtubule bundles that are resistant to depolymerization with oryzalin. Furthermore, clasp-1 mutants have aberrant microtubule preprophase bands, mitotic spindles, and phragmoplasts, indicating a role for At CLASP in stabilizing mitotic arrays. clasp-1 plants are dwarf, have significantly reduced cell numbers in the root division zone, and have defects in directional cell expansion. We discuss possible mechanisms of CLASP function in higher plants.

  15. Ex vivo Live Imaging of Single Cell Divisions in Mouse Neuroepithelium

    PubMed Central

    Piotrowska-Nitsche, Karolina; Caspary, Tamara

    2013-01-01

    We developed a system that integrates live imaging of fluorescent markers and culturing slices of embryonic mouse neuroepithelium. We took advantage of existing mouse lines for genetic cell lineage tracing: a tamoxifen-inducible Cre line and a Cre reporter line expressing dsRed upon Cre-mediated recombination. By using a relatively low level of tamoxifen, we were able to induce recombination in a small number of cells, permitting us to follow individual cell divisions. Additionally, we observed the transcriptional response to Sonic Hedgehog (Shh) signaling using an Olig2-eGFP transgenic line 1-3 and we monitored formation of cilia by infecting the cultured slice with virus expressing the cilia marker, Sstr3-GFP 4. In order to image the neuroepithelium, we harvested embryos at E8.5, isolated the neural tube, mounted the neural slice in proper culturing conditions into the imaging chamber and performed time-lapse confocal imaging. Our ex vivo live imaging method enables us to trace single cell divisions to assess the relative timing of primary cilia formation and Shh response in a physiologically relevant manner. This method can be easily adapted using distinct fluorescent markers and provides the field the tools with which to monitor cell behavior in situ and in real time. PMID:23666396

  16. ABI domain-containing proteins contribute to surface protein display and cell division in Staphylococcus aureus.

    PubMed

    Frankel, Matthew B; Wojcik, Brandon M; DeDent, Andrea C; Missiakas, Dominique M; Schneewind, Olaf

    2010-10-01

    The human pathogen Staphylococcus aureus requires cell wall anchored surface proteins to cause disease. During cell division, surface proteins with YSIRK signal peptides are secreted into the cross-wall, a layer of newly synthesized peptidoglycan between separating daughter cells. The molecular determinants for the trafficking of surface proteins are, however, still unknown. We screened mutants with non-redundant transposon insertions by fluorescence-activated cell sorting for reduced deposition of protein A (SpA) into the staphylococcal envelope. Three mutants, each of which harboured transposon insertions in genes for transmembrane proteins, displayed greatly reduced envelope abundance of SpA and surface proteins with YSIRK signal peptides. Characterization of the corresponding mutations identified three transmembrane proteins with abortive infectivity (ABI) domains, elements first described in lactococci for their role in phage exclusion. Mutations in genes for ABI domain proteins, designated spdA, spdB and spdC (surface protein display), diminish the expression of surface proteins with YSIRK signal peptides, but not of precursor proteins with conventional signal peptides. spdA, spdB and spdC mutants display an increase in the thickness of cross-walls and in the relative abundance of staphylococci with cross-walls, suggesting that spd mutations may represent a possible link between staphylococcal cell division and protein secretion.

  17. Brassinosteroid signaling directs formative cell divisions and protophloem differentiation in Arabidopsis root meristems.

    PubMed

    Kang, Yeon Hee; Breda, Alice; Hardtke, Christian S

    2017-01-15

    Brassinosteroids (BRs) trigger an intracellular signaling cascade through its receptors BR INSENSITIVE 1 (BRI1), BRI1-LIKE 1 (BRL1) and BRL3. Recent studies suggest that BR-independent inputs related to vascular differentiation, for instance root protophloem development, modulate downstream BR signaling components. Here, we report that protophloem sieve element differentiation is indeed impaired in bri1 brl1 brl3 mutants, although this effect might not be mediated by canonical downstream BR signaling components. We also found that their small meristem size is entirely explained by reduced cell elongation, which is, however, accompanied by supernumerary formative cell divisions in the radial dimension. Thus, reduced cell expansion in conjunction with growth retardation, because of the need to accommodate supernumerary formative divisions, can account for the overall short root phenotype of BR signaling mutants. Tissue-specific re-addition of BRI1 activity partially rescued subsets of these defects through partly cell-autonomous, partly non-cell-autonomous effects. However, protophloem-specific BRI1 expression essentially rescued all major bri1 brl1 brl3 root meristem phenotypes. Our data suggest that BR perception in the protophloem is sufficient to systemically convey BR action in the root meristem context.

  18. Late assembly of the Vibrio cholerae cell division machinery postpones septation to the last 10% of the cell cycle

    PubMed Central

    Galli, Elisa; Paly, Evelyne; Barre, François-Xavier

    2017-01-01

    Bacterial cell division is a highly regulated process, which involves the formation of a complex apparatus, the divisome, by over a dozen proteins. In the few model bacteria in which the division process was detailed, divisome assembly occurs in two distinct steps: a few proteins, including the FtsZ tubulin-like protein, form a membrane associated contractile ring, the Z-ring, at ~30% of the cell cycle. The Z-ring serves as a scaffold for the recruitment of a second series of proteins, including integral membrane and periplasmic cell wall remodelling enzymes, at ~50% of the cell cycle. Actual septation occupies most of the remaining half of the cell cycle. In contrast, we present evidence suggesting that early pre-divisional Z-rings form between 40 and 50% of the cell cycle and mature into fully assembled divisome at about 80% of the cell cycle in Vibrio cholerae. Thus, actual septation is restricted to a very short amount of time. Our results further suggest that late assembly of the divisome probably helps maintain the asymmetric polar organisation of V. cholerae cells by limiting the accumulation of a cell pole marker, HubP, at the nascent cell poles. PMID:28300142

  19. Borrelia burgdorferi ftsZ Plays a Role in Cell Division

    PubMed Central

    Dubytska, Lydia; Godfrey, Henry P.; Cabello, Felipe C.

    2006-01-01

    ftsZ is essential for cell division in many microorganisms. In Escherichia coli and Bacillus subtilis, FtsZ plays a role in ring formation at the leading edge of the cell division septum. An ftsZ homologue is present in the Borrelia burgdorferi genome (ftsZBbu). Its gene product (FtsZBbu) is strongly homologous to other bacterial FtsZ proteins, but its function has not been established. Because loss-of-function mutants of ftsZBbu might be lethal, the tetR/tetO system was adapted for regulated control of this gene in B. burgdorferi. Sixty-two nucleotides of an ftsZBbu antisense DNA sequence under the control of a tetracycline-responsive modified hybrid borrelial promoter were cloned into pKFSS1. This construct was electroporated into a B. burgdorferi host strain carrying a chromosomally located tetR under the control of the B. burgdorferi flaB promoter. After induction by anhydrotetracycline, expression of antisense ftsZ RNA resulted in generation of filamentous B. burgdorferi that were unable to divide and grew more slowly than uninduced cells. To determine whether FtsZBbu could interfere with the function of E. coli FtsZ, ftsZBbu was amplified from chromosomal DNA and placed under the control of the tetracycline-regulated hybrid promoter. After introduction of the construct into E. coli and induction with anhydrotetracycline, overexpression of ftsZBbu generated a filamentous phenotype. This suggested interference of ftsZBbu with E. coli FtsZ function and confirmed the role of ftsZBbu in cell division. This is the first report of the generation of a B. burgdorferi conditional lethal mutant equivalent by tetracycline-controlled expression of antisense RNA. PMID:16484209

  20. Force-balance model of suppression of multipolar division in cancer cells with extra centrosomes

    NASA Astrophysics Data System (ADS)

    Zhu, Jie

    2013-03-01

    Cancer cells often possess extra centrosomes which have the potential to cause cell death due to catastrophic multipolar division. Many cancer cells, however, are able to escape multipolar mitosis by clustering the extra centrosomes to form bipolar spindles. The mechanism of centrosome clustering is therefore of great interest to the development of anti-cancer drugs because the de-clustering of extra centrosomes provides an appealing way to eliminate cancer cells while keeping healthy cells intact. We present a physical model assuming 1) dynamic centrosomal microtubules interact with chromosomes by both pushing on chromosome arms and pulling along kinetochores; 2) these microtubules interact with force generators associated with actin/adhesion structures at the cell boundary; and 3) motors act on anti-parallel microtubules from different centrosomes. We find via computer simulations that chromosomes tend to aggregate near the cell center while centrosomes can be either clustered to form bipolar spindles or scattered to form multipolar spindles, depending on the strengths of relative forces, cell shape and adhesion geometry. The model predictions agree with data from cells plated on adhesive micropatterns and from biochemically or genetically perturbed cells. Furthermore, our model is able to explain various microtubule distributions in interphase cells on patterned substrates. This work was supported by NSF

  1. Accelerated cell divisions drive the outgrowth of the regenerating spinal cord in axolotls

    PubMed Central

    Rost, Fabian; Albors, Aida Rodrigo; Mazurov, Vladimir; Brusch, Lutz; Deutsch, Andreas

    2016-01-01

    Axolotls are unique in their ability to regenerate the spinal cord. However, the mechanisms that underlie this phenomenon remain poorly understood. Previously, we showed that regenerating stem cells in the axolotl spinal cord revert to a molecular state resembling embryonic neuroepithelial cells and functionally acquire rapid proliferative divisions (Rodrigo Albors et al., 2015). Here, we refine the analysis of cell proliferation in space and time and identify a high-proliferation zone in the regenerating spinal cord that shifts posteriorly over time. By tracking sparsely-labeled cells, we also quantify cell influx into the regenerate. Taking a mathematical modeling approach, we integrate these quantitative datasets of cell proliferation, neural stem cell activation and cell influx, to predict regenerative tissue outgrowth. Our model shows that while cell influx and neural stem cell activation play a minor role, the acceleration of the cell cycle is the major driver of regenerative spinal cord outgrowth in axolotls. DOI: http://dx.doi.org/10.7554/eLife.20357.001 PMID:27885987

  2. A Millifluidic Study of Cell-to-Cell Heterogeneity in Growth-Rate and Cell-Division Capability in Populations of Isogenic Cells of Chlamydomonas reinhardtii

    PubMed Central

    Damodaran, Shima P.; Eberhard, Stephan; Boitard, Laurent; Rodriguez, Jairo Garnica; Wang, Yuxing; Bremond, Nicolas; Baudry, Jean; Bibette, Jérôme; Wollman, Francis-André

    2015-01-01

    To address possible cell-to-cell heterogeneity in growth dynamics of isogenic cell populations of Chlamydomonas reinhardtii, we developed a millifluidic drop-based device that not only allows the analysis of populations grown from single cells over periods of a week, but is also able to sort and collect drops of interest, containing viable and healthy cells, which can be used for further experimentation. In this study, we used isogenic algal cells that were first synchronized in mixotrophic growth conditions. We show that these synchronized cells, when placed in droplets and kept in mixotrophic growth conditions, exhibit mostly homogeneous growth statistics, but with two distinct subpopulations: a major population with a short doubling-time (fast-growers) and a significant subpopulation of slowly dividing cells (slow-growers). These observations suggest that algal cells from an isogenic population may be present in either of two states, a state of restricted division and a state of active division. When isogenic cells were allowed to propagate for about 1000 generations on solid agar plates, they displayed an increased heterogeneity in their growth dynamics. Although we could still identify the original populations of slow- and fast-growers, drops inoculated with a single progenitor cell now displayed a wider diversity of doubling-times. Moreover, populations dividing with the same growth-rate often reached different cell numbers in stationary phase, suggesting that the progenitor cells differed in the number of cell divisions they could undertake. We discuss possible explanations for these cell-to-cell heterogeneities in growth dynamics, such as mutations, differential aging or stochastic variations in metabolites and macromolecules yielding molecular switches, in the light of single-cell heterogeneities that have been reported among isogenic populations of other eu- and prokaryotes. PMID:25760649

  3. A millifluidic study of cell-to-cell heterogeneity in growth-rate and cell-division capability in populations of isogenic cells of Chlamydomonas reinhardtii.

    PubMed

    Damodaran, Shima P; Eberhard, Stephan; Boitard, Laurent; Rodriguez, Jairo Garnica; Wang, Yuxing; Bremond, Nicolas; Baudry, Jean; Bibette, Jérôme; Wollman, Francis-André

    2015-01-01

    To address possible cell-to-cell heterogeneity in growth dynamics of isogenic cell populations of Chlamydomonas reinhardtii, we developed a millifluidic drop-based device that not only allows the analysis of populations grown from single cells over periods of a week, but is also able to sort and collect drops of interest, containing viable and healthy cells, which can be used for further experimentation. In this study, we used isogenic algal cells that were first synchronized in mixotrophic growth conditions. We show that these synchronized cells, when placed in droplets and kept in mixotrophic growth conditions, exhibit mostly homogeneous growth statistics, but with two distinct subpopulations: a major population with a short doubling-time (fast-growers) and a significant subpopulation of slowly dividing cells (slow-growers). These observations suggest that algal cells from an isogenic population may be present in either of two states, a state of restricted division and a state of active division. When isogenic cells were allowed to propagate for about 1000 generations on solid agar plates, they displayed an increased heterogeneity in their growth dynamics. Although we could still identify the original populations of slow- and fast-growers, drops inoculated with a single progenitor cell now displayed a wider diversity of doubling-times. Moreover, populations dividing with the same growth-rate often reached different cell numbers in stationary phase, suggesting that the progenitor cells differed in the number of cell divisions they could undertake. We discuss possible explanations for these cell-to-cell heterogeneities in growth dynamics, such as mutations, differential aging or stochastic variations in metabolites and macromolecules yielding molecular switches, in the light of single-cell heterogeneities that have been reported among isogenic populations of other eu- and prokaryotes.

  4. Egf Signaling Directs Neoblast Repopulation by Regulating Asymmetric Cell Division in Planarians.

    PubMed

    Lei, Kai; Thi-Kim Vu, Hanh; Mohan, Ryan D; McKinney, Sean A; Seidel, Chris W; Alexander, Richard; Gotting, Kirsten; Workman, Jerry L; Sánchez Alvarado, Alejandro

    2016-08-22

    A large population of proliferative stem cells (neoblasts) is required for physiological tissue homeostasis and post-injury regeneration in planarians. Recent studies indicate that survival of a few neoblasts after sublethal irradiation results in the clonal expansion of the surviving stem cells and the eventual restoration of tissue homeostasis and regenerative capacity. However, the precise mechanisms regulating the population dynamics of neoblasts remain largely unknown. Here, we uncovered a central role for epidermal growth factor (EGF) signaling during in vivo neoblast expansion mediated by Smed-egfr-3 (egfr-3) and its putative ligand Smed-neuregulin-7 (nrg-7). Furthermore, the EGF receptor-3 protein localizes asymmetrically on the cytoplasmic membrane of neoblasts, and the ratio of asymmetric to symmetric cell divisions decreases significantly in egfr-3(RNAi) worms. Our results not only provide the first molecular evidence of asymmetric stem cell divisions in planarians, but also demonstrate that EGF signaling likely functions as an essential regulator of neoblast clonal expansion.

  5. EzrA: a spectrin-like scaffold in the bacterial cell division machinery

    PubMed Central

    Cleverley, Robert; Lewis, Richard

    2015-01-01

    Much progress has been made in identifying the components of the divisome, the assembly of proteins that undertakes the vital process of cell division in bacteria. However, how the highly interdependent processes on either side of the membrane are coordinated during division is a major unresolved question. How is the degradation and synthesis of the cell wall on the outside of the cell coordinated with cytokinesis and membrane fission, which are driven from the inside of the cell by the tubulin homologue FtsZ? A possible key mediator of such coordination is the membrane protein EzrA, as it interacts both with FtsZ and the penicillin binding proteins (PBPs) that synthesize peptidoglycan. Cleverley et al. [Nature Communications (2014) 5, 5421] have recently solved the crystal structure of the cytoplasmic domain of B. subtilis EzrA, which points to an important scaffolding role for EzrA in the divisome. The structure resembles the eukaryotic, cytoskeletal spectrin proteins, which link actin filaments in the cytoskeleton and also connect the actin cytoskeleton to membrane-bound integrin proteins.

  6. Morphology and ultrastructure of Interfilum and Klebsormidium (Klebsormidiales, Streptophyta) with special reference to cell division and thallus formation

    PubMed Central

    Mikhailyuk, Tatiana; Holzinger, Andreas; Massalski, Andrzej; Karsten, Ulf

    2014-01-01

    Representatives of the closely related genera, Interfilum and Klebsormidium, are characterized by unicells, dyads or packets in Interfilum and contrasting uniseriate filaments in Klebsormidium. According to the literature, these distinct thallus forms originate by different types of cell division, sporulation (cytogony) versus vegetative cell division (cytotomy), but investigations of their morphology and ultrastructure show a high degree of similarity. Cell walls of both genera are characterized by triangular spaces between cell walls of neighbouring cells and the parental wall or central space among the walls of a cell packet, exfoliations and projections of the parental wall and cap-like and H-like fragments of the cell wall. In both genera, each cell has its individual cell wall and it also has part of the common parental wall or its remnants. Therefore, vegetative cells of Interfilum and Klebsormidium probably divide by the same type of cell division (sporulation-like). Various strains representing different species of the two genera are characterized by differences in cell wall ultrastructure, particularly the level of preservation, rupture or gelatinization of the parental wall surrounding the daughter cells. The differing morphologies of representatives of various lineages result from features of the parental wall during cell separation and detachment. Cell division in three planes (usual in Interfilum and a rare event in Klebsormidium) takes place in spherical or short cylindrical cells, with the chloroplast positioned perpendicularly or obliquely to the filament (dyad) axis. The morphological differences are mainly a consequence of differing fates of the parental wall after cell division and detachment. The development of different morphologies within the two genera mostly depends on characters such as the shape of cells, texture of cell walls, mechanical interactions between cells and the influence of environmental conditions. PMID:26504365

  7. Gene transcription is coordinated with, but not dependent on, cell divisions during C. elegans embryonic fate specification.

    PubMed

    Nair, Gautham; Walton, Travis; Murray, John Isaac; Raj, Arjun

    2013-08-01

    Cell differentiation and proliferation are coordinated during animal development, but the link between them remains uncharacterized. To examine this relationship, we combined single-molecule RNA imaging with time-lapse microscopy to generate high-resolution measurements of transcriptional dynamics in Caenorhabditis elegans embryogenesis. We found that globally slowing the overall development rate of the embryo by altering temperature or by mutation resulted in cell proliferation and transcription slowing, but maintaining, their relative timings, suggesting that cell division may directly control transcription. However, using mutants with specific defects in cell cycle pathways that lead to abnormal lineages, we found that the order between cell divisions and expression onset can switch, showing that expression of developmental regulators is not strictly dependent on cell division. Delaying cell divisions resulted in only slight changes in absolute expression time, suggesting that expression and proliferation are independently entrained to a separate clock-like process. These changes in relative timing can change the number of cells expressing a gene at a given time, suggesting that timing may help determine which cells adopt particular transcriptional patterns. Our results place limits on the types of mechanisms that are used during normal development to ensure that division timing and fate specification occur at appropriate times.

  8. Regulation of cell divisions and differentiation by MALE STERILITY32 is required for anther development in maize.

    PubMed

    Moon, Jihyun; Skibbe, David; Timofejeva, Ljudmilla; Wang, Chung-Ju Rachel; Kelliher, Timothy; Kremling, Karl; Walbot, Virginia; Cande, William Zacheus

    2013-11-01

    Male fertility in flowering plants relies on proper division and differentiation of cells in the anther, a process that gives rise to four somatic layers surrounding central germinal cells. The maize gene male sterility32 (ms32) encodes a basic helix-loop-helix (bHLH) transcription factor, which functions as an important regulator of both division and differentiation during anther development. After the four somatic cell layers are generated properly through successive periclinal divisions, in the ms32 mutant, tapetal precursor cells fail to differentiate, and, instead, undergo additional periclinal divisions to form extra layers of cells. These cells become vacuolated and expand, and lead to failure in pollen mother cell development. ms32 expression is specific to the pre-meiotic anthers and is distributed initially broadly in the four lobes, but as the anther develops, its expression becomes restricted to the innermost somatic layer, the tapetum. The ms32-ref mac1-1 double mutant is unable to form tapetal precursors and also exhibits excessive somatic proliferation leading to numerous, disorganized cell layers, suggesting a synergistic interaction between ms32 and mac1. Altogether, our results show that MS32 is a major regulator in maize anther development that promotes tapetum differentiation and inhibits periclinal division once a tapetal cell is specified.

  9. Klp10A, a stem cell centrosome-enriched kinesin, balances asymmetries in Drosophila male germline stem cell division

    PubMed Central

    Chen, Cuie; Inaba, Mayu; Venkei, Zsolt G; Yamashita, Yukiko M

    2016-01-01

    Asymmetric stem cell division is often accompanied by stereotypical inheritance of the mother and daughter centrosomes. However, it remains unknown whether and how stem cell centrosomes are uniquely regulated and how this regulation may contribute to stem cell fate. Here we identify Klp10A, a microtubule-depolymerizing kinesin of the kinesin-13 family, as the first protein enriched in the stem cell centrosome in Drosophila male germline stem cells (GSCs). Depletion of klp10A results in abnormal elongation of the mother centrosomes in GSCs, suggesting the existence of a stem cell-specific centrosome regulation program. Concomitant with mother centrosome elongation, GSCs form asymmetric spindle, wherein the elongated mother centrosome organizes considerably larger half spindle than the other. This leads to asymmetric cell size, yielding a smaller differentiating daughter cell. We propose that klp10A functions to counteract undesirable asymmetries that may result as a by-product of achieving asymmetries essential for successful stem cell divisions. DOI: http://dx.doi.org/10.7554/eLife.20977.001 PMID:27885983

  10. Nuclear and cell division in Bacillus subtilis: dormant nucleoids in stationary-phase cells and their activation.

    PubMed Central

    Van Iterson, W; Michels, P A; Vyth-Dreese, F; Aten, J A

    1975-01-01

    The morphology of nucleoids and mesosomes of Bacillus subtilis in stationary-and lag-phase cultures was studied by making three-dimensional cell reconstructions in plastic of electron micrographs of serial sections. In cells from stationary cultures, the dormant nucleoids are frequently, but not always, spherical and the mesosomes are small and compact. It is suggested that the spherical nucleoids represent the resting stage in which replication and segregation have been completed. In cells from lag-phase cultures, the compact mesosomes develop into an elaborate system of tubes and wider sacs which become wrapped around the elongating nucleoids and invade the nucleoplasm in preparation for division. Images PMID:803960

  11. Effect of microgravity environment on cell wall regeneration, cell divisions, growth, and differentiation of plants from protoplasts (7-IML-1)

    NASA Technical Reports Server (NTRS)

    Rasmussen, Ole

    1992-01-01

    The primary goal of this project is to investigate if microgravity has any influence on growth and differentiation of protoplasts. Formation of new cell walls on rapeseed protoplasts takes place within the first 24 hours after isolation. Cell division can be observed after 2-4 days and formation of cell aggregates after 5-7 days. Therefore, it is possible during the 7 day IML-1 Mission to investigate if cell wall formation, cell division, and cell differentiation are influenced by microgravity. Protoplasts of rapeseeds and carrot will be prepared shortly before launch and injected into 0.6 ml polyethylene bags. Eight bags are placed in an aluminum block inside the ESA Type 1 container. The containers are placed at 4 C in PTCU's and transferred to orbiter mid-deck. At 4 C all cell processes are slowed down, including cell wall formation. Latest access to the shuttle will be 12 hours before launch. In orbit the containers will be transferred from the PTC box to the 22 C Biorack incubator. The installation of a 1 g centrifuge in Biorack will make it possible to distinguish between effects of near weightlessness and effects caused by cosmic radiation and other space flight factors including vibrations. Parallel control experiments will be carried out on the ground. Other aspects of the experiment are discussed.

  12. Novel DNA damage checkpoint in mitosis: Mitotic DNA damage induces re-replication without cell division in various cancer cells.

    PubMed

    Hyun, Sun-Yi; Rosen, Eliot M; Jang, Young-Joo

    2012-07-06

    DNA damage induces multiple checkpoint pathways to arrest cell cycle progression until damage is repaired. In our previous reports, when DNA damage occurred in prometaphase, cells were accumulated in 4 N-DNA G1 phase, and mitosis-specific kinases were inactivated in dependent on ATM/Chk1 after a short incubation for repair. We investigated whether or not mitotic DNA damage causes cells to skip-over late mitotic periods under prolonged incubation in a time-lapse study. 4 N-DNA-damaged cells re-replicated without cell division and accumulated in 8 N-DNA content, and the activities of apoptotic factors were increased. The inhibition of DNA replication reduced the 8 N-DNA cell population dramatically. Induction of replication without cell division was not observed upon depletion of Chk1 or ATM. Finally, mitotic DNA damage induces mitotic slippage and that cells enter G1 phase with 4 N-DNA content and then DNA replication is occurred to 8 N-DNA content before completion of mitosis in the ATM/Chk1-dependent manner, followed by caspase-dependent apoptosis during long-term repair.

  13. The role of a cell surface inhibitor in early signal transduction associated with the regulation of cell division and differentiation

    NASA Technical Reports Server (NTRS)

    Johnson, T. C.; Enebo, D. J.; Moos, P. J.; Fattaey, H. K.; Spooner, B. S. (Principal Investigator)

    1992-01-01

    Serum stimulation of quiescent human fibroblast cultures resulted in a hyperphosphorylation of the nuclear retinoblastoma gene susceptibility product (RB). However, serum stimulation in the presence of 9 x 10(-8) M of a purified bovine sialoglycopeptide (SGP) cell surface inhibitor abrogated the hyperphosphorylation of the RB protein and the subsequent progression of cells through the mitotic cycle. The experimental results suggest that the SGP mediated its cell cycle arrest at a site in the cell cycle that was at the time of RB phosphorylation or somewhat upstream of the modification of this regulatory protein of cell division. Both cells serum-deprived and serum stimulated in the presence of the SGP displayed only a hypophosphorylated RB protein, consistent with the SGP-mediated cell cycle arrest point being near the G1/S interface.

  14. Asymmetric cell divisions in the early embryo of the leech Helobdella robusta.

    PubMed

    Weisblat, David A

    2007-01-01

    The small glossiphoniid leech Helobdella robusta is among the best-studied representatives of the super-phylum Lophotrochozoa in terms of early development. The Helobdella embryo undergoes a modified version of spiral cleavage, characterized by stereotyped cell lineages comprising multiple examples of equal and unequal divisions, many of which are well-conserved with respect to those of other clitellate annelids, such as the oligochaete Tubifex. Here, we review the early development of Helobdella, focusing on the variety of unequal cell divisions. We then summarize an experimental analysis of the mechanisms underlying the unequal first cleavage in Helobdella, concluding that the unequal first cleavages in Helobdella and Tubifex proceed by different mechanisms. This result demonstrates the evolvability of the basic cell biological mechanisms underlying well-conserved developmental processes. Finally, we propose a model in which the unequal second cleavage in Helobdella may be regulated by the polarized distribution of PAR protein homologs, convergent with the unequal first cleavage of the nematode Caenorhabditis elegans (super-phylum Ecdysozoa).

  15. Mechanics of kinetochore microtubules and their interactions with chromosomes during cell division

    NASA Astrophysics Data System (ADS)

    Nazockdast, Ehssan; Fürthauer, Sebastian; Redemann, Stephanie; Baumgart, Johannes; Lindow, Norbert; Kratz, Andrea; Prohaska, Steffen; Müller-Reichert, Thomas; Shelley, Michael

    2016-11-01

    The accurate segregation of chromosomes, and subsequent cell division, in Eukaryotic cells is achieved by the interactions of an assembly of microtubules (MTs) and motor-proteins, known as the mitotic spindle. We use a combination of our computational platform for simulating cytoskeletal assemblies and our structural data from high-resolution electron tomography of the mitotic spindle, to study the kinetics and mechanics of MTs in the spindle, and their interactions with chromosomes during chromosome segregation in the first cell division in C.elegans embryo. We focus on kinetochore MTs, or KMTs, which have one end attached to a chromosome. KMTs are thought to be a key mechanical component in chromosome segregation. Using exploratory simulations of MT growth, bending, hydrodynamic interactions, and attachment to chromosomes, we propose a mechanical model for KMT-chromosome interactions that reproduces observed KMT length and shape distributions from electron tomography. We find that including detailed hydrodynamic interactions between KMTs is essential for agreement with the experimental observations.

  16. Signaling networks during development: the case of asymmetric cell division in the Drosophila nervous system.

    PubMed

    Carmena, Ana

    2008-09-01

    Remarkable progress in genetics and molecular biology has made possible the sequencing of the genomes from numerous species. In the post-genomic era, technical developments in the fields of proteomics and bioinformatics are poised to further catapult our understanding of protein structure, function and organization into complex signaling networks. One of the greatest challenges in the field now is to unravel the functional signaling networks and their spatio-temporal regulation in living cells. Here, the need for such in vivo system-wide level approach is illustrated in relation to the mechanisms that underlie the biological process of asymmetric cell division. Genomic, post-genomic and live imaging techniques are reviewed in light of the huge impact they are having on this field for the discovering of new proteins and for the in vivo analysis of asymmetric cell division. The proteins, signals and the emerging networking of functional connections that is arising between them during this process in the Drosophila nervous system will be also discussed.

  17. Bistability of a coupled Aurora B kinase-phosphatase system in cell division

    PubMed Central

    Zaytsev, Anatoly V; Segura-Peña, Dario; Godzi, Maxim; Calderon, Abram; Ballister, Edward R; Stamatov, Rumen; Mayo, Alyssa M; Peterson, Laura; Black, Ben E; Ataullakhanov, Fazly I; Lampson, Michael A; Grishchuk, Ekaterina L

    2016-01-01

    Aurora B kinase, a key regulator of cell division, localizes to specific cellular locations, but the regulatory mechanisms responsible for phosphorylation of substrates located remotely from kinase enrichment sites are unclear. Here, we provide evidence that this activity at a distance depends on both sites of high kinase concentration and the bistability of a coupled kinase-phosphatase system. We reconstitute this bistable behavior and hysteresis using purified components to reveal co-existence of distinct high and low Aurora B activity states, sustained by a two-component kinase autoactivation mechanism. Furthermore, we demonstrate these non-linear regimes in live cells using a FRET-based phosphorylation sensor, and provide a mechanistic theoretical model for spatial regulation of Aurora B phosphorylation. We propose that bistability of an Aurora B-phosphatase system underlies formation of spatial phosphorylation patterns, which are generated and spread from sites of kinase autoactivation, thereby regulating cell division. DOI: http://dx.doi.org/10.7554/eLife.10644.001 PMID:26765564

  18. Phytochemicals as inhibitors of bacterial cell division protein FtsZ: coumarins are promising candidates.

    PubMed

    Duggirala, Sridevi; Nankar, Rakesh P; Rajendran, Selvakumar; Doble, Mukesh

    2014-09-01

    Naturally occurring phytochemicals with reported antibacterial activity were screened for their ability to inhibit the bacterial cell division protein Escherichia coli FtsZ. Among the representative compounds, coumarins inhibit the GTPase and polymerization activities of this protein effectively. Further screening with ten coumarin analogs we identified two promising candidates, scopoletin and daphnetin. The former is found to inhibit the GTPase activity of the protein in a noncompetitive manner. Docking of these coumarins with the modeled protein indicate that they bind to T7 loop, which is different from the GTP-binding site (active site), thereby supporting the experimental data. Lowest binding energy is obtained with scopoletin. 3D QSAR indicates the need for groups such as hydroxyl, diethyl, or dimethyl amino in the 7th carbon for enhanced activity. None of the coumarins exhibited cytotoxicity against NIH/3T3 and human embryonic kidney cell lines. The length of Bacillus subtilis increases in the presence of these compounds probably due to the lack of septum formation. Results of this study indicate the role of coumarins in halting the first step of bacterial cell division process.

  19. Hydrocarbons Are Essential for Optimal Cell Size, Division, and Growth of Cyanobacteria1[OPEN

    PubMed Central

    Lea-Smith, David J.; Nürnberg, Dennis J.; Baers, Laura L.; Davey, Matthew P.; Parolini, Lucia; Huber, Roland G.; Cotton, Charles A. R.; Mastroianni, Giulia; Bombelli, Paolo; Ungerer, Petra; Stevens, Tim J.; Howe, Christopher J.

    2016-01-01

    Cyanobacteria are intricately organized, incorporating an array of internal thylakoid membranes, the site of photosynthesis, into cells no larger than other bacteria. They also synthesize C15-C19 alkanes and alkenes, which results in substantial production of hydrocarbons in the environment. All sequenced cyanobacteria encode hydrocarbon biosynthesis pathways, suggesting an important, undefined physiological role for these compounds. Here, we demonstrate that hydrocarbon-deficient mutants of Synechococcus sp. PCC 7002 and Synechocystis sp. PCC 6803 exhibit significant phenotypic differences from wild type, including enlarged cell size, reduced growth, and increased division defects. Photosynthetic rates were similar between strains, although a minor reduction in energy transfer between the soluble light harvesting phycobilisome complex and membrane-bound photosystems was observed. Hydrocarbons were shown to accumulate in thylakoid and cytoplasmic membranes. Modeling of membranes suggests these compounds aggregate in the center of the lipid bilayer, potentially promoting membrane flexibility and facilitating curvature. In vivo measurements confirmed that Synechococcus sp. PCC 7002 mutants lacking hydrocarbons exhibit reduced thylakoid membrane curvature compared to wild type. We propose that hydrocarbons may have a role in inducing the flexibility in membranes required for optimal cell division, size, and growth, and efficient association of soluble and membrane bound proteins. The recent identification of C15-C17 alkanes and alkenes in microalgal species suggests hydrocarbons may serve a similar function in a broad range of photosynthetic organisms. PMID:27707888

  20. Spatiotemporally modulated Vestigial gradient by Wingless signaling adaptively regulates cell division for precise wing size control.

    PubMed

    Zhu, Hao

    2011-01-07

    In animal development, the growth of a tissue or organ is timely arrested when it reaches the stereotyped correct size. How this is robustly controlled remains poorly understood. The prevalent viewpoint, which is that morphogen gradients, due to their organizing roles in development, are directly responsible for growth arrest, cannot explain a number of observations. Recent findings from studies of the Drosophila wing have revealed that the interpretation of the Wingless gradient requires signaling-induced self-inhibition and that cell proliferation is controlled by graded vestigial expression. These findings highlight a growth control mechanism that involves Wingless regulated vestigial expression, but a question is whether they can quantitatively explain the observed precision and robustness of wing size control. Quantitative and systematic investigation into Wingless signaling using a mathematical model has elucidated two points. First, negative regulation of the Vestigial gradient by Wingless signaling makes vestigial expression precise and robust. Second, weak Wingless signaling in a primarily small wing pouch causes a short and steep Vestigial gradient, which stimulates more cell divisions and leads to a significant expansion of the wing pouch; however, strong Wingless signaling in a primarily large wing pouch causes a long and smooth Vestigial gradient, which stimulates fewer cell divisions and results in a slight expansion of the wing pouch. These results substantially decipher an inherent mechanism of tissue and organ size control. Our model explains, and is supported by, a number of experimental observations.

  1. Developmental stratification of the mammary epithelium occurs through symmetry-breaking vertical divisions of apically positioned luminal cells.

    PubMed

    Huebner, Robert J; Lechler, Terry; Ewald, Andrew J

    2014-03-01

    Mammary ducts are elongated during development by stratified epithelial structures, known as terminal end buds (TEBs). TEBs exhibit reduced apicobasal polarity and extensive proliferation. A major unanswered question concerns the mechanism by which the simple ductal epithelium stratifies during TEB formation. We sought to elucidate this mechanism using real-time imaging of growth factor-induced stratification in 3D cultures of mouse primary epithelial organoids. We hypothesized that stratification could result from vertical divisions in either the apically positioned luminal epithelial cells or the basally positioned myoepithelial cells. Stratification initiated exclusively from vertical apical cell divisions, both in 3D culture and in vivo. During vertical apical divisions, only the mother cell retained tight junctions and segregated apical membranes. Vertical daughter cells initiated an unpolarized cell population located between the luminal and myoepithelial cells, similar to the unpolarized body cells in the TEB. As stratification and loss of apicobasal polarity are early hallmarks of cancer, we next determined the cellular mechanism of oncogenic stratification. Expression of activated ERBB2 induced neoplastic stratification through analogous vertical divisions of apically positioned luminal epithelial cells. However, ERBB2-induced stratification was accompanied by tissue overgrowth and acute loss of both tight junctions and apical polarity. Expression of phosphomimetic MEK (MEK1DD), a major ERBB2 effector, also induced stratification through vertical apical cell divisions. However, MEK1DD-expressing organoids exhibited normal levels of growth and retained apicobasal polarity. We conclude that both normal and neoplastic stratification are accomplished through receptor tyrosine kinase signaling dependent vertical cell divisions within the luminal epithelial cell layer.

  2. The TCP4 transcription factor of Arabidopsis blocks cell division in yeast at G1 {yields} S transition

    SciTech Connect

    Aggarwal, Pooja; Padmanabhan, Bhavna; Bhat, Abhay; Sarvepalli, Kavitha; Sadhale, Parag P.; Nath, Utpal

    2011-07-01

    Highlights: {yields} TCP4 is a class II TCP transcription factor, that represses cell division in Arabidopsis. {yields} TCP4 expression in yeast retards cell division by blocking G1 {yields} S transition. {yields} Genome-wide expression studies and Western analysis reveals stabilization of cell cycle inhibitor Sic1, as possible mechanism. -- Abstract: The TCP transcription factors control important aspects of plant development. Members of class I TCP proteins promote cell cycle by regulating genes directly involved in cell proliferation. In contrast, members of class II TCP proteins repress cell division. While it has been postulated that class II proteins induce differentiation signal, their exact role on cell cycle has not been studied. Here, we report that TCP4, a class II TCP protein from Arabidopsis that repress cell proliferation in developing leaves, inhibits cell division by blocking G1 {yields} S transition in budding yeast. Cells expressing TCP4 protein with increased transcriptional activity fail to progress beyond G1 phase. By analyzing global transcriptional status of these cells, we show that expression of a number of cell cycle genes is altered. The possible mechanism of G1 {yields} S arrest is discussed.

  3. Stimulation of cell division by argon and Nd:YAG laser trabeculoplasty in cynomolgus monkeys

    SciTech Connect

    Dueker, D.K.; Norberg, M.; Johnson, D.H.; Tschumper, R.C.; Feeney-Burns, L. )

    1990-01-01

    Although laser treatment of the trabecular meshwork is the most common form of surgery for glaucoma, the tissue response to this therapy is still incompletely understood. We applied argon or Nd:YAG laser to the trabecular meshwork of six monkeys. Cell division was identified by injecting tritiated thymidine into the anterior chamber 24 hr after laser application. Autoradiography of tissue sections revealed significantly more labelled cells in eyes treated with laser than in the untreated controls. In addition, cells in neighboring tissues such as iris, ciliary body and sclera showed labelling in association with laser application. Furthermore, comparison of argon-induced lesions with those caused by pulsed Nd:YAG suggests that there are quantitative and qualitative differences in the response of trabecular meshwork and surrounding tissues to these two forms of laser energy.

  4. The spindle position checkpoint: how to deal with spindle misalignment during asymmetric cell division in budding yeast.

    PubMed

    Fraschini, Roberta; Venturetti, Marianna; Chiroli, Elena; Piatti, Simonetta

    2008-06-01

    During asymmetric cell division, spindle positioning is critical to ensure the unequal segregation of polarity factors and generate daughter cells with different sizes or fates. In budding yeast the boundary between mother and daughter cell resides at the bud neck, where cytokinesis takes place at the end of the cell cycle. Since budding and bud neck formation occur much earlier than bipolar spindle formation, spindle positioning is a finely regulated process. A surveillance device called the SPOC (spindle position checkpoint) oversees this process and delays mitotic exit and cytokinesis until the spindle is properly oriented along the division axis, thus ensuring genome stability.

  5. Roles of the essential protein FtsA in cell growth and division in Streptococcus pneumoniae.

    PubMed

    Mura, Andrea; Fadda, Daniela; Perez, Amilcar J; Danforth, Madeline L; Musu, Daniela; Rico, Ana Isabel; Krupka, Marcin; Denapaite, Dalia; Tsui, Ho-Ching T; Winkler, Malcolm E; Branny, Pavel; Vicente, Miguel; Margolin, William; Massidda, Orietta

    2016-11-21

    Streptococcus pneumoniae is an ovoid-shaped Gram-positive bacterium that grows by carrying out peripheral and septal peptidoglycan (PG) synthesis, analogous to model bacilli such as Escherichia coli and Bacillus subtilis In the model bacilli, FtsZ and FtsA proteins assemble into a ring at midcell and are dedicated to septal PG synthesis, but not peripheral PG synthesis; hence inactivation of FtsZ or FtsA results in long filamentous cells unable to divide. Here we demonstrate that FtsA and FtsZ colocalize at midcell in S. pneumoniae and that partial depletion of FtsA perturbs septum synthesis, resulting in elongated cells with multiple FtsZ rings that fail to complete septation. Unexpectedly, complete depletion of FtsA resulted in delocalization of FtsZ rings and ultimately cell ballooning and lysis. In contrast, depletion or deletion of gpsB and sepF, which in B. subtilis are synthetically lethal with ftsA, resulted in enlarged and elongated cells, with multiple FtsZ rings, the latter mimicking partial depletion of FtsA. Notably, cell ballooning was not observed, consistent with later recruitment of these proteins to midcell after Z ring assembly. Overproduction of FtsA stimulates septation and suppresses the cell division defects caused by deletion of sepF and gpsB under some conditions, supporting the notion that FtsA shares overlapping functions with GpsB and SepF at later steps in the division process. Our results indicate that, in S. pneumoniae, both GpsB and SepF are involved in septal PG synthesis, whereas FtsA and FtsZ coordinate both peripheral and septal PG synthesis and are codependent for localization at midcell.

  6. Two Forkhead transcription factors regulate the division of cardiac progenitor cells by a Polo-dependent pathway

    PubMed Central

    Ahmad, Shaad M.; Tansey, Terese R.; Busser, Brian W.; Nolte, Michael T.; Jeffries, Neal; Gisselbrecht, Stephen S.; Rusan, Nasser M.; Michelson, Alan M.

    2012-01-01

    SUMMARY The development of a complex organ requires the specification of appropriate numbers of each of its constituent cell types, as well as their proper differentiation and correct positioning relative to each other. During Drosophila cardiogenesis, all three of these processes are controlled by jumeau (jumu) and Checkpoint suppressor homologue (CHES-1-like), two genes encoding forkhead transcription factors that we discovered utilizing an integrated genetic, genomic and computational strategy for identifying genes expressed in the developing Drosophila heart. Both jumu and CHES-1-like are required during asymmetric cell division for the derivation of two distinct cardiac cell types from their mutual precursor, and in symmetric cell divisions that produce yet a third type of heart cell. jumu and CHES-1-like control the division of cardiac progenitors by regulating the activity of Polo, a kinase involved in multiple steps of mitosis. This pathway demonstrates how transcription factors integrate diverse developmental processes during organogenesis. PMID:22814603

  7. Self-organization and advective transport in the cell polarity formation for asymmetric cell division.

    PubMed

    Seirin Lee, Sungrim; Shibata, Tatsuo

    2015-10-07

    Anterior-Posterior (AP) polarity formation of cell membrane proteins plays a crucial role in determining cell asymmetry, which depends not only on the several genetic process but also biochemical and biophysical interactions. The mechanism of AP formation of Caenorhabditis elegans embryo is characterized into the three processes: (i) membrane association and dissociation of posterior and anterior proteins, (ii) diffusion into the membrane and cytosol, and (iii) active cortical and cytoplasmic flows induced by the contraction of the acto-myosin cortex. We explored the mechanism of symmetry breaking and AP polarity formation using self-recruitment model of posterior proteins. We found that the AP polarity pattern is established over wide range in the total mass of polarity proteins and the diffusion ratio in the cytosol to the membrane. We also showed that the advective transport in both membrane and cytosol during the establishment phase affects optimal time interval of establishment and positioning of the posterior domain, and plays a role to increase the robustness in the AP polarity formation by reducing the number of posterior domains for the sensitivity of initial conditions. We also demonstrated that a proper ratio of the total mass to cell size robustly regulate the length scale of the posterior domain.

  8. YneA, an SOS-Induced Inhibitor of Cell Division in Bacillus subtilis, Is Regulated Posttranslationally and Requires the Transmembrane Region for Activity▿ †

    PubMed Central

    Mo, Allison H.; Burkholder, William F.

    2010-01-01

    Cell viability depends on the stable transmission of genetic information to each successive generation. Therefore, in the event of intrinsic or extrinsic DNA damage, it is important that cell division be delayed until DNA repair has been completed. In Bacillus subtilis, this is accomplished in part by YneA, an inhibitor of division that is induced as part of the SOS response. We sought to gain insight into the mechanism by which YneA blocks cell division and the processes involved in shutting off YneA activity. Our data suggest that YneA is able to inhibit daughter cell separation as well as septum formation. YneA contains a LysM peptidoglycan binding domain and is predicted to be exported. We established that the YneA signal peptide is rapidly cleaved, resulting in secretion of YneA into the medium. Mutations within YneA affect both the rate of signal sequence cleavage and the activity of YneA. YneA does not stably associate with the cell wall and is rapidly degraded by extracellular proteases. Based on these results, we hypothesize that exported YneA is active prior to signal peptide cleavage and that proteolysis contributes to the inactivation of YneA. Finally, we identified mutations in the transmembrane segment of YneA that abolish the ability of YneA to inhibit cell division, while having little or no effect on YneA export or stability. These data suggest that protein-protein interactions mediated by the transmembrane region may be required for YneA activity. PMID:20400548

  9. whmD is an essential mycobacterial gene required for proper septation and cell division

    PubMed Central

    Gomez, James E.; Bishai, William R.

    2000-01-01

    A study of potential mycobacterial regulatory genes led to the isolation of the Mycobacterium smegmatis whmD gene, which encodes a homologue of WhiB, a Streptomyces coelicolor protein required for sporulation. Unlike its Streptomyces homologue, WhmD is essential in M. smegmatis. The whmD gene could be disrupted only in the presence of a plasmid supplying whmD in trans. A plasmid that allowed chemically regulated expression of the WhmD protein was used to generate a conditional whmD mutant. On withdrawal of the inducer, the conditional whmD mutant exhibited irreversible, filamentous, branched growth with diminished septum formation and aberrant septal placement, whereas WhmD overexpression resulted in growth retardation and hyperseptation. Nucleic acid synthesis and levels of the essential cell division protein FtsZ were unaltered by WhmD deficiency. Together, these phenotypes indicate a role for WhmD in mycobacterial septum formation and cell division. PMID:10880571

  10. The Type IVa Pilus Machinery Is Recruited to Sites of Future Cell Division.

    PubMed

    Carter, Tyson; Buensuceso, Ryan N C; Tammam, Stephanie; Lamers, Ryan P; Harvey, Hanjeong; Howell, P Lynne; Burrows, Lori L

    2017-01-31

    Type IVa pili (T4aP) are ubiquitous microbial appendages used for adherence, twitching motility, DNA uptake, and electron transfer. Many of these functions depend on dynamic assembly and disassembly of the pilus by a megadalton-sized, cell envelope-spanning protein complex located at the poles of rod-shaped bacteria. How the T4aP assembly complex becomes integrated into the cell envelope in the absence of dedicated peptidoglycan (PG) hydrolases is unknown. After ruling out the potential involvement of housekeeping PG hydrolases in the installation of the T4aP machinery in Pseudomonas aeruginosa, we discovered that key components of inner (PilMNOP) and outer (PilQ) membrane subcomplexes are recruited to future sites of cell division. Midcell recruitment of a fluorescently tagged alignment subcomplex component, mCherry-PilO, depended on PilQ secretin monomers-specifically, their N-terminal PG-binding AMIN domains. PilP, which connects PilO to PilQ, was required for recruitment, while PilM, which is structurally similar to divisome component FtsA, was not. Recruitment preceded secretin oligomerization in the outer membrane, as loss of the PilQ pilotin PilF had no effect on localization. These results were confirmed in cells chemically blocked for cell division prior to outer membrane invagination. The hub protein FimV and a component of the polar organelle coordinator complex-PocA-were independently required for midcell recruitment of PilO and PilQ. Together, these data suggest an integrated, energy-efficient strategy for the targeting and preinstallation-rather than retrofitting-of the T4aP system into nascent poles, without the need for dedicated PG-remodeling enzymes.

  11. The Type IVa Pilus Machinery Is Recruited to Sites of Future Cell Division

    PubMed Central

    Carter, Tyson; Buensuceso, Ryan N. C.; Tammam, Stephanie; Lamers, Ryan P.; Harvey, Hanjeong

    2017-01-01

    ABSTRACT Type IVa pili (T4aP) are ubiquitous microbial appendages used for adherence, twitching motility, DNA uptake, and electron transfer. Many of these functions depend on dynamic assembly and disassembly of the pilus by a megadalton-sized, cell envelope-spanning protein complex located at the poles of rod-shaped bacteria. How the T4aP assembly complex becomes integrated into the cell envelope in the absence of dedicated peptidoglycan (PG) hydrolases is unknown. After ruling out the potential involvement of housekeeping PG hydrolases in the installation of the T4aP machinery in Pseudomonas aeruginosa, we discovered that key components of inner (PilMNOP) and outer (PilQ) membrane subcomplexes are recruited to future sites of cell division. Midcell recruitment of a fluorescently tagged alignment subcomplex component, mCherry-PilO, depended on PilQ secretin monomers—specifically, their N-terminal PG-binding AMIN domains. PilP, which connects PilO to PilQ, was required for recruitment, while PilM, which is structurally similar to divisome component FtsA, was not. Recruitment preceded secretin oligomerization in the outer membrane, as loss of the PilQ pilotin PilF had no effect on localization. These results were confirmed in cells chemically blocked for cell division prior to outer membrane invagination. The hub protein FimV and a component of the polar organelle coordinator complex—PocA—were independently required for midcell recruitment of PilO and PilQ. Together, these data suggest an integrated, energy-efficient strategy for the targeting and preinstallation—rather than retrofitting—of the T4aP system into nascent poles, without the need for dedicated PG-remodeling enzymes. PMID:28143978

  12. Mating-defective ste mutations are suppressed by cell division cycle start mutations in Saccharomyces cerevisiae.

    PubMed Central

    Shuster, J R

    1982-01-01

    Temperature-sensitive mutants which arrest in the G1 phase of the cell cycle have been described for the yeast Saccharomyces cerevisiae. One class of these mutants (carrying cdc28, cdc36, cdc37, or cdc39) forms a shmoo morphology at restrictive temperature, characteristic of mating pheromone-arrested wild-type cells. Therefore, one hypothesis to explain the control of cell division by mating factors states that mating pheromones arrest wild-type cells by inactivating one or more of these CDC gene products. A class of mutants (carrying ste4, ste5, ste7, ste11, or ste12) which is insensitive to mating pheromone and sterile has also been described. One possible function of the STE gene products is the inactivation of the CDC gene products in the presence of a mating pheromone. A model incorporating these two hypotheses predicts that such STE gene products will not be required for mating in strains carrying an appropriate cdc lesion. This prediction was tested by assaying the mating abilities of double mutants for all of the pairwise combinations of cdc and ste mutations. Lesions in either cdc36 or cdc39 suppressed the mating defect due to ste4 and ste5. Allele specificity was observed in the suppression of both ste4 and ste5. The results indicate that the CDC36, CDC39, STE4, and STE5 gene products interact functionally or physically or both in the regulation of cell division mediated by the presence or absence of mating pheromones. The cdc36 and cdc39 mutations did not suppress ste7, ste11, or ste12. Lesions in cdc28 or cdc37 did not suppress any of the ste mutations. Other models of CDC and STE gene action which predicted that some of the cdc and ste mutations would be alleles of the same locus were tested. None of the cdc mutations was allelic to the ste mutations and, therefore, these models were eliminated. PMID:6757719

  13. A pulse-chase strategy for EdU labelling assay is able to rapidly quantify cell division orientation.

    PubMed

    Yin, Xiaofeng; Tsukaya, Hirokazu

    2016-09-01

    Measurement of the direction of cell division is an important, yet difficult, task to analyse how a plant organ acquires its final shape from an initially small group of cells. We introduce a method that rapidly and easily quantifies cell division direction and is applicable to all plant species. A pulse-chase strategy for 5-ethynyl-2'-deoxyuridine (EdU) labelling assay was established and was shown to be successful for leaves of Arabidopsis thaliana (Arabidopsis) and Juncus prismatocarpus. By optimization of the pulse and chase periods, most of the signals obtained were sets of daughter nuclei. For Arabidopsis, the optimal time was a 45-min pulse and a 7-h chase. For J. prismatocarpus, the optimal time was a 2-h pulse and a 13.5-h chase. The positions of the daughter nuclei were used to quantify cell division direction in the Arabidopsis leaf primordia. Overall, cell division along the proximal-distal axis was more frequent than along the medial-lateral axis. In petiole, major vein, minor vein and margin areas, the major cell division direction seemed to be coincident with the direction of auxin flow. The advantages of our method over the few methods used previously are discussed. We anticipate that it will provide opportunities to study plant development in the near future.

  14. Three-Dimensional Analysis of Cell Division Orientation in Epidermal Basal Layer Using Intravital Two-Photon Microscopy

    PubMed Central

    Nemoto, Tomomi

    2016-01-01

    Epidermal structures are different among body sites, and proliferative keratinocytes in the epidermis play an important role in the maintenance of the epidermal structures. In recent years, intravital skin imaging has been used in mammalian skin research for the investigation of cell behaviors, but most of these experiments were performed with rodent ears. Here, we established a non-invasive intravital imaging approach for dorsal, ear, hind paw, or tail skin using R26H2BEGFP hairless mice. Using four-dimensional (x, y, z, and time) imaging, we successfully visualized mitotic cell division in epidermal basal cells. A comparison of cell division orientation relative to the basement membrane in each body site revealed that most divisions in dorsal and ear epidermis occurred in parallel, whereas the cell divisions in hind paw and tail epidermis occurred both in parallel and oblique orientations. Based on the quantitative analysis of the four-dimensional images, we showed that the epidermal thickness correlated with the basal cell density and the rate of the oblique divisions. PMID:27657513

  15. Positioning the Flagellum at the Center of a Dividing Cell To Combine Bacterial Division with Magnetic Polarity

    PubMed Central

    Bennet, Mathieu; Klumpp, Stefan

    2015-01-01

    ABSTRACT Faithful replication of all structural features is a sine qua non condition for the success of bacterial reproduction by binary fission. For some species, a key challenge is to replicate and organize structures with multiple polarities. Polarly flagellated magnetotactic bacteria are the prime example of organisms dealing with such a dichotomy; they have the challenge of bequeathing two types of polarities to their daughter cells: magnetic and flagellar polarities. Indeed, these microorganisms align and move in the Earth’s magnetic field using an intracellular chain of nano-magnets that imparts a magnetic dipole to the cell. The paradox is that, after division occurs in cells, if the new flagellum is positioned opposite to the old pole devoid of a flagellum during cell division, the two daughter cells will have opposite magnetic polarities with respect to the positions of their flagella. Here we show that magnetotactic bacteria of the class Gammaproteobacteria pragmatically solve this problem by synthesizing a new flagellum at the division site. In addition, we model this particular structural inheritance during cell division. This finding opens up new questions regarding the molecular aspects of the new division mechanism, the way other polarly flagellated magnetotactic bacteria control the rotational direction of their flagella, and the positioning of organelles. PMID:25714711

  16. Asymmetric division triggers cell-specific gene expression through coupled capture and stabilization of a phosphatase.

    PubMed

    Bradshaw, Niels; Losick, Richard

    2015-10-14

    Formation of a division septum near a randomly chosen pole during sporulation in Bacillus subtilis creates unequal sized daughter cells with dissimilar programs of gene expression. An unanswered question is how polar septation activates a transcription factor (σ(F)) selectively in the small cell. We present evidence that the upstream regulator of σ(F), the phosphatase SpoIIE, is compartmentalized in the small cell by transfer from the polar septum to the adjacent cell pole where SpoIIE is protected from proteolysis and activated. Polar recognition, protection from proteolysis, and stimulation of phosphatase activity are linked to oligomerization of SpoIIE. This mechanism for initiating cell-specific gene expression is independent of additional sporulation proteins; vegetative cells engineered to divide near a pole sequester SpoIIE and activate σ(F) in small cells. Thus, a simple model explains how SpoIIE responds to a stochastically-generated cue to activate σ(F) at the right time and in the right place.

  17. Cytoplasm-to-nucleus translocation of a herpesvirus tegument protein during cell division.

    PubMed

    Elliott, G; O'Hare, P

    2000-03-01

    We have previously shown that the herpes simplex virus tegument protein VP22 localizes predominantly to the cytoplasm of expressing cells. We have also shown that VP22 has the unusual property of intercellular spread, which involves the movement of VP22 from the cytoplasm of these expressing cells into the nuclei of nonexpressing cells. Thus, VP22 can localize in two distinct subcellular patterns. By utilizing time-lapse confocal microscopy of live cells expressing a green fluorescent protein-tagged protein, we now report in detail the intracellular trafficking properties of VP22 in expressing cells, as opposed to the intercellular trafficking of VP22 between expressing and nonexpressing cells. Our results show that during interphase VP22 appears to be targeted exclusively to the cytoplasm of the expressing cell. However, at the early stages of mitosis VP22 translocates from the cytoplasm to the nucleus, where it immediately binds to the condensing cellular chromatin and remains bound there through all stages of mitosis and chromatin decondensation into the G(1) stage of the next cycle. Hence, in VP22-expressing cells the subcellular localization of the protein is regulated by the cell cycle such that initially cytoplasmic protein becomes nuclear during cell division, resulting in a gradual increase over time in the number of nuclear VP22-expressing cells. Importantly, we demonstrate that this process is a feature not only of VP22 expressed in isolation but also of VP22 expressed during virus infection. Thus, VP22 utilizes an unusual pathway for nuclear targeting in cells expressing the protein which differs from the nuclear targeting pathway used during intercellular trafficking.

  18. Mathematical models of tissue stem and transit target cell divisions and the risk of radiation- or smoking-associated cancer

    PubMed Central

    Hendry, Jolyon H.

    2017-01-01

    proliferation and differentiation in the partially transformed stem and transit cell population are allowed for, nor is any difference made if one assumes that transit cells require an extra mutation to confer malignancy from the number required by stem cells. The probability of a cancer being mutagen-induced correlates across cancer sites with the estimated cumulative number of stem cell divisions in the associated tissue (p<0.05), although in some cases there is sensitivity of findings to removal of high-leverage outliers and in some cases only modest variation in probability, but these issues do not affect the validity of the findings. There are no significant correlations (p>0.3) between lifetime cancer-site specific radiation risk and the probability of that cancer being mutagen-induced. These results do not depend on the assumed critical number of mutations leading to cancer, or on the assumed mutagen-associated mutation rate, within the generally-accepted ranges tested. However, there are borderline significant negative correlations (p = 0.08) between the smoking-associated mortality rate difference (current vs former smokers) and the probability of cancer being mutagen-induced. This is only the case where values of the critical number of mutations leading to cancer, k, is 3 or 4 and not for smaller values (1 or 2), but does not strongly depend on the assumed mutagen-associated mutation rate. PMID:28196079

  19. Mathematical models of tissue stem and transit target cell divisions and the risk of radiation- or smoking-associated cancer.

    PubMed

    Little, Mark P; Hendry, Jolyon H

    2017-02-01

    proliferation and differentiation in the partially transformed stem and transit cell population are allowed for, nor is any difference made if one assumes that transit cells require an extra mutation to confer malignancy from the number required by stem cells. The probability of a cancer being mutagen-induced correlates across cancer sites with the estimated cumulative number of stem cell divisions in the associated tissue (p<0.05), although in some cases there is sensitivity of findings to removal of high-leverage outliers and in some cases only modest variation in probability, but these issues do not affect the validity of the findings. There are no significant correlations (p>0.3) between lifetime cancer-site specific radiation risk and the probability of that cancer being mutagen-induced. These results do not depend on the assumed critical number of mutations leading to cancer, or on the assumed mutagen-associated mutation rate, within the generally-accepted ranges tested. However, there are borderline significant negative correlations (p = 0.08) between the smoking-associated mortality rate difference (current vs former smokers) and the probability of cancer being mutagen-induced. This is only the case where values of the critical number of mutations leading to cancer, k, is 3 or 4 and not for smaller values (1 or 2), but does not strongly depend on the assumed mutagen-associated mutation rate.

  20. Pattern reorganization occurs independently of cell division during Drosophila wing disc regeneration in situ.

    PubMed

    Díaz-García, Sandra; Baonza, Antonio

    2013-08-06

    One of the most intriguing problems in developmental biology is how an organism can replace missing organs or portions of its body after injury. This capacity, known as regeneration, is conserved across different phyla. The imaginal discs of Drosophila melanogaster provide a particularly well-characterized model for analyzing regeneration. We have developed a unique method to study organ regeneration under physiological conditions using the imaginal discs of Drosophila. Using this method, we revisited different aspects of organ regeneration. The results presented in this report suggest that during the initial stages of regeneration, different processes occur, including wound healing, a temporary loss of markers of cell-fate commitment, and pattern reorganization. We present evidence indicating that all of these processes occur even when cell division has been arrested. Our data also suggested that Wingless is not required during the early stages of disc regeneration.

  1. Pattern reorganization occurs independently of cell division during Drosophila wing disc regeneration in situ

    PubMed Central

    Díaz-García, Sandra; Baonza, Antonio

    2013-01-01

    One of the most intriguing problems in developmental biology is how an organism can replace missing organs or portions of its body after injury. This capacity, known as regeneration, is conserved across different phyla. The imaginal discs of Drosophila melanogaster provide a particularly well-characterized model for analyzing regeneration. We have developed a unique method to study organ regeneration under physiological conditions using the imaginal discs of Drosophila. Using this method, we revisited different aspects of organ regeneration. The results presented in this report suggest that during the initial stages of regeneration, different processes occur, including wound healing, a temporary loss of markers of cell-fate commitment, and pattern reorganization. We present evidence indicating that all of these processes occur even when cell division has been arrested. Our data also suggested that Wingless is not required during the early stages of disc regeneration. PMID:23878228

  2. Dynamics of phragmoplastin in living cells during cell plate formation and uncoupling of cell elongation from the plane of cell division.

    PubMed Central

    Gu, X; Verma, D P

    1997-01-01

    The cell plate is formed by the fusion of Golgi apparatus-derived vesicles in the center of the phragmoplast during cytokinesis in plant cells. A dynamin-like protein, phragmoplastin, has been isolated and shown to be associated with cell plate formation in soybean by using immunocytochemistry. In this article, we demonstrate that similar to dynamin, phragmoplastin polymerizes to form oligomers. We fused soybean phragmoplastin with the green fluorescence protein (GFP) and introduced it into tobacco BY-2 cells to monitor the dynamics of early events in cell plate formation. We demonstrate that the chimeric protein is functional and targeted to the cell plate during cytokinesis in transgenic cells. GFP-phragmoplastin was found to appear first in the center of the forming cell plate, and as the cell plate grew outward, it redistributed to the growing margins of the cell plate. The redistribution of phragmoplastin may require microtubule reorganization because the microtubule-stabilizing drug taxol inhibited phragmoplastin redistribution. Our data show that throughout the entire process of cytokinesis, phragmoplastin is concentrated in the area in which membrane fusion is active, suggesting that phragmoplastin participates in an early membrane fusion event during cell plate formation. Based on the dynamics of GFP-phragmoplastin, it appears that the process of cell plate formation is completed in two phases. The first phase is confined to the cylinder of the phragmoplast proper and is followed by a second phase that deposits phragmoplast vesicles in a concentric fashion, resulting in a ring of fluorescence, with the concentration of vesicles being higher at the periphery. In addition, overexpression of GFP-phragmoplastin appears to act as a dominant negative, slowing down the completion of cell plate formation, and often results in an oblique cell plate. The latter appears to uncouple cell elongation from the plane of cell division, forming twisted and elongated cells

  3. High Antioxidant Activity Facilitates Maintenance of Cell Division in Leaves of Drought Tolerant Maize Hybrids

    PubMed Central

    Avramova, Viktoriya; AbdElgawad, Hamada; Vasileva, Ivanina; Petrova, Alexandra S.; Holek, Anna; Mariën, Joachim; Asard, Han; Beemster, Gerrit T. S.

    2017-01-01

    We studied the impact of drought on growth regulation in leaves of 13 maize varieties with different drought sensitivity and geographic origins (Western Europe, Egypt, South Africa) and the inbred line B73. Combining kinematic analysis of the maize leaf growth zone with biochemical measurements at a high spatial resolution allowed us to examine the correlation between the regulation of the cellular processes cell division and elongation, and the molecular redox-regulation in response to drought. Moreover, we demonstrated differences in the response of the maize lines to mild and severe levels of water deficit. Kinematic analysis indicated that drought tolerant lines experienced less impact on leaf elongation rate due to a smaller reduction of cell production, which, in turn, was due to a smaller decrease of meristem size and number of cells in the leaf meristem. Clear differences in growth responses between the groups of lines with