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Sample records for cell nucleus division

  1. Cell division

    MedlinePlus Videos and Cool Tools

    ... hours after conception, the fertilized egg cell remains a single cell. After approximately 30 hours, it divides ... 3 days, the fertilized egg cell has become a berry-like structure made up of 16 cells. ...

  2. Cell division

    MedlinePlus Videos and Cool Tools

    ... structure made up of 16 cells. This structure is called a morula, which is Latin for mulberry. The cells continue to divide ... days following conception into a blastocyst. Although it is only the size of a pinhead, the blastocyst ...

  3. Cell nucleus in context

    SciTech Connect

    Lelievre, Sophie A.; Bissell, Mina J.; Pujuguet, Philippe

    1999-11-11

    The molecular pathways that participate in regulation of gene expression are being progressively unraveled. Extracellular signals, including the binding of extracellular matrix and soluble molecules to cell membrane receptors, activate specific signal transducers that convey information inside the cell and can alter gene products. Some of these transducers when translocated to the cell nucleus may bind to transcription complexes and thereby modify the transcriptional activity of specific genes. However, the basic molecules involved in the regulation of gene expression are found in many different cell and tissue types; thus the mechanisms underlying tissue-specific gene expression are still obscure. In this review, we focus on the study of signals that are conveyed to the nucleus. We propose that the way in which extracellular signals are integrated may account for tissue-specific gene expression. We argue that the integration of signals depends on the structural organization of cells ( i.e., extracellular matrix, cell membrane, cytoskeleton, nucleus) which a particular cell type within a tissue. Putting the nuclei in context allows us to envision gene expression as being regulated not only by the communication between the extracellular environment and the nucleus, but also by the influence of organized assemblies of cells on extracellular-nuclear communications.

  4. Optical micromanipulation inside the cell: a focus in cell division

    NASA Astrophysics Data System (ADS)

    Sacconi, Leonardo; Tolic-Nørrelykke, Iva M.; Stringari, Chiara; Pavone, Francesco S.

    2006-02-01

    In eukaryotic cells, proper position of the mitotic spindle and the division plane is necessary for successful cell division and development. In this work the nature of forces governing the positioning and elongation of the mitotic spindle and the spatio-temporal regulation of the division plane positioning in fission yeast was studied. By using a mechanical perturbations induced by laser dissection of the spindle and astral microtubules, we found that astral microtubules push on the spindle poles. Further, laser dissection of the spindle midzone induced spindle collapse inward. This suggests that the spindle is driven by the sliding apart of antiparallel microtubules in the spindle midzone. Exploiting a combination of non-linear microscopy and optical trapping, we performed an optical manipulation procedure designed to displace the cell nucleus away from its normal position in the center of the cell. After the laser-induced displacement, the nucleus typically returned towards the cell center, in a manner correlated with the extension of a microtubule from the nucleus to the closer tip of the cell. This observation suggests that the centering of the nucleus is provided by microtubule pushing force. Moreover the cells in which the nucleus was displaced during interphase displayed asymmetric division, whereas when the nucleus was displaced during late prophase or metaphase, the division plane formed at the cell center as in non-manipulated cells. This result suggests that in fission yeast the division plane is selected before pro-metaphase and that the signal is not provided by the mitotic spindle.

  5. The Arabidopsis Cell Division Cycle

    PubMed Central

    Gutierrez, Crisanto

    2009-01-01

    Plant cells have evolved a complex circuitry to regulate cell division. In many aspects, the plant cell cycle follows a basic strategy similar to other eukaryotes. However, several key issues are unique to plant cells. In this chapter, both the conserved and unique cellular and molecular properties of the plant cell cycle are reviewed. In addition to division of individual cells, the specific characteristic of plant organogenesis and development make that cell proliferation control is of primary importance during development. Therefore, special attention should be given to consider plant cell division control in a developmental context. Proper organogenesis depends on the formation of different cell types. In plants, many of the processes leading to cell differentiation rely on the occurrence of a different cycle, termed the endoreplication cycle, whereby cells undergo repeated full genome duplication events in the absence of mitosis and increase their ploidy. Recent findings are focusing on the relevance of changes in chromatin organization for a correct cell cycle progression and, conversely, in the relevance of a correct functioning of chromatin remodelling complexes to prevent alterations in both the cell cycle and the endocycle. PMID:22303246

  6. Circadian clocks and cell division

    PubMed Central

    2010-01-01

    Evolution has selected a system of two intertwined cell cycles: the cell division cycle (CDC) and the daily (circadian) biological clock. The circadian clock keeps track of solar time and programs biological processes to occur at environmentally appropriate times. One of these processes is the CDC, which is often gated by the circadian clock. The intermeshing of these two cell cycles is probably responsible for the observation that disruption of the circadian system enhances susceptibility to some kinds of cancer. The core mechanism underlying the circadian clockwork has been thought to be a transcription and translation feedback loop (TTFL), but recent evidence from studies with cyanobacteria, synthetic oscillators and immortalized cell lines suggests that the core circadian pacemaking mechanism that gates cell division in mammalian cells could be a post-translational oscillator (PTO). PMID:20890114

  7. Stochastic models for cell division

    NASA Astrophysics Data System (ADS)

    Stukalin, Evgeny; Sun, Sean

    2013-03-01

    The probability of cell division per unit time strongly depends of age of cells, i.e., time elapsed since their birth. The theory of cell populations in the age-time representation is systematically applied for modeling cell division for different spreads in generation times. We use stochastic simulations to address the same issue at the level of individual cells. Our approach unlike deterministic theory enables to analyze the size fluctuations of cell colonies at different growth conditions (in the absence and in the presence of cell death, for initially synchronized and asynchronous cell populations, for conditions of restricted growth). We find the simple quantitative relation between the asymptotic values of relative size fluctuations around mean values for initially synchronized cell populations under growth and the coefficients of variation of generation times. Effect of initial age distribution for asynchronous growth of cell cultures is also studied by simulations. The influence of constant cell death on fluctuations of sizes of cell populations is found to be essential even for small cell death rates, i.e., for realistic growth conditions. The stochastic model is generalized for biologically relevant case that involves both cell reproduction and cell differentiation.

  8. Actomyosin contractility rotates the cell nucleus

    PubMed Central

    Kumar, Abhishek; Maitra, Ananyo; Sumit, Madhuresh; Ramaswamy, Sriram; Shivashankar, G. V.

    2014-01-01

    The cell nucleus functions amidst active cytoskeletal filaments, but its response to their contractile stresses is largely unexplored. We study the dynamics of the nuclei of single fibroblasts, with cell migration suppressed by plating onto micro-fabricated patterns. We find the nucleus undergoes noisy but coherent rotational motion. We account for this observation through a hydrodynamic approach, treating the nucleus as a highly viscous inclusion residing in a less viscous fluid of orientable filaments endowed with active stresses. Lowering actin contractility selectively by introducing blebbistatin at low concentrations drastically reduced the speed and coherence of the angular motion of the nucleus. Time-lapse imaging of actin revealed a correlated hydrodynamic flow around the nucleus, with profile and magnitude consistent with the results of our theoretical approach. Coherent intracellular flows and consequent nuclear rotation thus appear to be an intrinsic property of cells. PMID:24445418

  9. Signaling to stomatal initiation and cell division

    PubMed Central

    Le, Jie; Zou, Junjie; Yang, Kezhen; Wang, Ming

    2014-01-01

    Stomata are two-celled valves that control epidermal pores whose opening and spacing optimizes shoot-atmosphere gas exchange. Arabidopsis stomatal formation involves at least one asymmetric division and one symmetric division. Stomatal formation and patterning are regulated by the frequency and placement of asymmetric divisions. This model system has already led to significant advances in developmental biology, such as the regulation of cell fate, division, differentiation, and patterning. Over the last 30 years, stomatal development has been found to be controlled by numerous intrinsic genetic and environmental factors. This mini review focuses on the signaling involved in stomatal initiation and in divisions in the cell lineage. PMID:25002867

  10. Signaling to stomatal initiation and cell division.

    PubMed

    Le, Jie; Zou, Junjie; Yang, Kezhen; Wang, Ming

    2014-01-01

    Stomata are two-celled valves that control epidermal pores whose opening and spacing optimizes shoot-atmosphere gas exchange. Arabidopsis stomatal formation involves at least one asymmetric division and one symmetric division. Stomatal formation and patterning are regulated by the frequency and placement of asymmetric divisions. This model system has already led to significant advances in developmental biology, such as the regulation of cell fate, division, differentiation, and patterning. Over the last 30 years, stomatal development has been found to be controlled by numerous intrinsic genetic and environmental factors. This mini review focuses on the signaling involved in stomatal initiation and in divisions in the cell lineage. PMID:25002867

  11. 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. PMID:27505160

  12. Polarized Cell Division of Chlamydia trachomatis

    PubMed Central

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

    2016-01-01

    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. PMID:27505160

  13. 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.

  14. 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…

  15. Isolation and characterization of neural stem cells from the neonatal rat cochlear nucleus.

    PubMed

    Rak, Kristen; Wasielewski, Natalia V; Radeloff, Andreas; Völkers, Johannes; Scherzed, Agmal; Jablonka, Sibylle; Hagen, Rudolf; Mlynski, Robert

    2011-03-01

    Neural stem cells have been identified in multiple parts of the postnatal mammalian brain, as well as in the inner ear. No investigation of potential neural stem cells in the cochlear nucleus has yet been performed. The aim of this study was to investigate potential neural stem cells from the cochlear nucleus by neurosphere assay and in histological sections to prove their capacity for self-renewal and for differentiation into progenitor cells and cells of the neuronal lineage. For this purpose, cells of the cochlear nucleus of postnatal day 6 rats were isolated and cultured for generation of primary neurospheres. Spheres were dissociated and cells analyzed for capacity for mitosis and differentiation. Cell division was detected by cell-counting assay and BrdU incorporation. Differentiated neural progenitor cells showed distinct labeling for Nestin and for Atoh1. Positive staining of ß-III Tubulin, glial fibrillary acid protein (GFAP) and myelin basic protein (MBP) showed differentiation into neurons, astrocytes and oligodendrocytes. Furthermore, Nestin- and BrdU-labeled cells could also be detected in histological sections. In conclusion, the isolated cells from the cochlear nucleus presented all the features of neural stem cells: cell division, presence of progenitor cells and differentiation into different cells of the neuronal lineage. The existence of neural stem cells may add to the understanding of developmental features in the cochlear nucleus. PMID:21258945

  16. 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.

  17. Nucleus-Specific Importin Alpha Proteins and Nucleoporins Regulate Protein Import and Nuclear Division in the Binucleate Tetrahymena thermophila▿ †

    PubMed Central

    Malone, Colin D.; Falkowska, Katarzyna A.; Li, Alanna Y.; Galanti, Sarah E.; Kanuru, Reshi C.; LaMont, Elizabeth G.; Mazzarella, Kate C.; Micev, Alan J.; Osman, Morwan M.; Piotrowski, Nicholas K.; Suszko, Jason W.; Timm, Adam C.; Xu, Ming-Ming; Liu, Lucy; Chalker, Douglas L.

    2008-01-01

    The ciliate Tetrahymena thermophila, having both germ line micronuclei and somatic macronuclei, must possess a specialized nucleocytoplasmic transport system to import proteins into the correct nucleus. To understand how Tetrahymena can target proteins to distinct nuclei, we first characterized FG repeat-containing nucleoporins and found that micro- and macronuclei utilize unique subsets of these proteins. This finding implicates these proteins in the differential permeability of the two nuclei and implies that nuclear pores with discrete specificities are assembled within a single cell. To identify the import machineries that interact with these different pores, we characterized the large families of karyopherin homologs encoded within the genome. Localization studies of 13 putative importin (imp) α- and 11 imp β-like proteins revealed that imp α-like proteins are nucleus specific—nine localized to the germ line micronucleus—but that most imp β-like proteins localized to both types of nuclei. These data suggest that micronucleus-specific proteins are transported by specific imp α adapters. The different imp α proteins exhibit substantial sequence divergence and do not appear to be simply redundant in function. Disruption of the IMA10 gene encoding an imp α-like protein that accumulates in dividing micronuclei results in nuclear division defects and lethality. Thus, nucleus-specific protein import and nuclear function in Tetrahymena are regulated by diverse, specialized karyopherins. PMID:18676955

  18. Asymmetric cell division in plant development.

    PubMed

    Heidstra, Renze

    2007-01-01

    Plant embryogenesis creates a seedling with a basic body plan. Post-embryonically the seedling elaborates with a lifelong ability to develop new tissues and organs. As a result asymmetric cell divisions serve essential roles during embryonic and postembryonic development to generate cell diversity. This review highlights selective cases of asymmetric division in the model plant Arabidopsis thaliana and describes the current knowledge on fate determinants and mechanisms involved. Common themes that emerge are: 1. role of the plant hormone auxin and its polar transport machinery; 2. a MAP kinase signaling cascade and; 3. asymmetric segregating transcription factors that are involved in several asymmetric cell divisions. PMID:17585494

  19. Lipid Microdomains in Cell Nucleus

    PubMed Central

    Cascianelli, Giacomo; Villani, Maristella; Tosti, Marcello; Marini, Francesca; Bartoccini, Elisa; Viola Magni, Mariapia

    2008-01-01

    It is known that nuclear lipids play a role in proliferation, differentiation, and apoptotic process. Cellular nuclei contain high levels of phosphatidylcholine and sphingomyelin, which are partially linked with cholesterol and proteins to form lipid–protein complexes. These lipids are also associated with transcription factors and newly synthesized RNA but, up to date, their organization is still unknown. The aim of the present work was to study if these specific lipid–protein interactions could be nuclear membrane microdomains and to evaluate their possible role. The results obtained demonstrate for the first time the existence of nuclear microdomains characterized by a specific lipid composition similar to that of intranuclear lipid–protein complexes previously described. Nuclear microdomain lipid composition changes during cell proliferation when the content of newly synthesized RNA increases. Because previous data show a correlation between nuclear lipids and transcription process, the role of nuclear microdomains in cellular functions is discussed. PMID:18923143

  20. Control of apoptosis by asymmetric cell division.

    PubMed

    Hatzold, Julia; Conradt, Barbara

    2008-04-01

    Asymmetric cell division and apoptosis (programmed cell death) are two fundamental processes that are important for the development and function of multicellular organisms. We have found that the processes of asymmetric cell division and apoptosis can be functionally linked. Specifically, we show that asymmetric cell division in the nematode Caenorhabditis elegans is mediated by a pathway involving three genes, dnj-11 MIDA1, ces-2 HLF, and ces-1 Snail, that directly control the enzymatic machinery responsible for apoptosis. Interestingly, the MIDA1-like protein GlsA of the alga Volvox carteri, as well as the Snail-related proteins Snail, Escargot, and Worniu of Drosophila melanogaster, have previously been implicated in asymmetric cell division. Therefore, C. elegans dnj-11 MIDA1, ces-2 HLF, and ces-1 Snail may be components of a pathway involved in asymmetric cell division that is conserved throughout the plant and animal kingdoms. Furthermore, based on our results, we propose that this pathway directly controls the apoptotic fate in C. elegans, and possibly other animals as well. PMID:18399720

  1. Physical role for the nucleus in cell migration

    NASA Astrophysics Data System (ADS)

    Fruleux, Antoine; Hawkins, Rhoda J.

    2016-09-01

    Cell migration is important for the function of many eukaryotic cells. Recently the nucleus has been shown to play an important role in cell motility. After giving an overview of cell motility mechanisms we review what is currently known about the mechanical properties of the nucleus and the connections between it and the cytoskeleton. We also discuss connections to the extracellular matrix and mechanotransduction. We identify key physical roles of the nucleus in cell migration.

  2. Physical role for the nucleus in cell migration.

    PubMed

    Fruleux, Antoine; Hawkins, Rhoda J

    2016-09-14

    Cell migration is important for the function of many eukaryotic cells. Recently the nucleus has been shown to play an important role in cell motility. After giving an overview of cell motility mechanisms we review what is currently known about the mechanical properties of the nucleus and the connections between it and the cytoskeleton. We also discuss connections to the extracellular matrix and mechanotransduction. We identify key physical roles of the nucleus in cell migration. PMID:27406341

  3. 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. PMID:23387408

  4. Small GTPases as regulators of cell division

    PubMed Central

    Militello, Rodrigo; Colombo, María I.

    2013-01-01

    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. PMID:24265858

  5. Suprachiasmatic Nucleus: Cell Autonomy and Network Properties

    PubMed Central

    Welsh, David K.; Takahashi, Joseph S.; Kay, Steve A.

    2013-01-01

    The suprachiasmatic nucleus (SCN) is the primary circadian pacemaker in mammals. Individual SCN neurons in dispersed culture can generate independent circadian oscillations of clock gene expression and neuronal firing. However, SCN rhythmicity depends on sufficient membrane depolarization and levels of intracellular calcium and cAMP. In the intact SCN, cellular oscillations are synchronized and reinforced by rhythmic synaptic input from other cells, resulting in a reproducible topographic pattern of distinct phases and amplitudes specified by SCN circuit organization. The SCN network synchronizes its component cellular oscillators, reinforces their oscillations, responds to light input by altering their phase distribution, increases their robustness to genetic perturbations, and enhances their precision. Thus, even though individual SCN neurons can be cell-autonomous circadian oscillators, neuronal network properties are integral to normal function of the SCN. PMID:20148688

  6. Nonlinear osmotic properties of the cell nucleus

    PubMed Central

    Finan, John D.; Chalut, Kevin J.; Wax, Adam; Guilak, Farshid

    2009-01-01

    Summary In the absence of active volume regulation processes, cell volume is inversely proportional to osmolarity, as predicted by the Boyle Van’t Hoff relation. In this study, we tested the hypothesis that nuclear volume has a similar relationship with extracellular osmolarity in articular chondrocytes, cells that are exposed to changes in the osmotic environment in vivo, and furthermore, we explored the mechanism of the relationships between osmolarity and nuclear size and shape. Nuclear size was quantified using two independent techniques, confocal laser scanning microscopy and angle-resolved low coherence interferometry. Nuclear volume was osmotically-sensitive but this relationship was not linear, showing a decline in the osmotic sensitivity in the hypo-osmotic range. Nuclear shape was also influenced by extracellular osmolarity, becoming smoother as the osmolarity decreased. The osmotically-induced changes in nuclear size paralleled the changes in nuclear shape, suggesting that shape and volume are interdependent. The osmotic sensitivity of shape and volume persisted after disruption of the actin cytoskeleton. Isolated nuclei contracted in response to physiologic changes in macromolecule concentration but not in response to physiologic changes in ion concentration, suggesting solute size has an important influence on the osmotic pressurization of the nucleus. This finding in turn implies that the diffusion barrier that causes osmotic effects is not a semi-permeable membrane, but rather due to size constraints that prevent large solute molecules from entering small spaces in the nucleus. As nuclear morphology has been associated previously with cell phenotype, these findings may provide new insight into the role of mechanical and osmotic signals in regulating cell physiology. PMID:19107599

  7. 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.

  8. 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.

  9. 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.

  10. Mechanics of cell division in fission yeast

    NASA Astrophysics Data System (ADS)

    Chang, Fred

    2012-02-01

    Cytokinesis is the stage of cell division in which a cell divides into two. A paradigm of cytokinesis in animal cells is that the actomyosin contractile ring provides the primary force to squeeze the cell into two. In the fission yeast Schizosaccharomyces pombe, cytokinesis also requires a actomyosin ring, which has been generally assumed to provide the force for cleavage. However, in contrast to animal cells, yeast cells assemble a cell wall septum concomitant with ring contraction and possess large (MPa) internal turgor pressure. Here, we show that the inward force generated by the division apparatus opposes turgor pressure; a decrease in effective turgor pressure leads to an increase in cleavage rate. We show that the ring cannot be the primary force generator. Scaling arguments indicate that the contractile ring can only provide a tiny fraction of the mechanical stress required to overcome turgor. Further, we show that cleavage can occur even in the absence of the contractile ring. Instead of the contractile ring, scaling arguments and modeling suggest that the large forces for cytokinesis are produced by the assembly of cell wall polymers in the growing septum.

  11. Cell division, differentiation and dynamic clustering

    NASA Astrophysics Data System (ADS)

    Kaneko, Kunihiko; Yomo, Tetsuya

    1994-08-01

    A novel mechanism for cell differentiation is proposed, based on the dynamic clustering in a globally coupled nonlinear system. A simple model with metabolic reaction, active transport of chemicals from media, and cell division is found to show three successive stages with the growth of the number of cells; coherent growth, dynamic clustering, and fixed cell differentiation. At the last stage, disparity in activities, germ line segregation, somatic cell differentiation, and homeochaotic stability against external perturbation are found. Our results, providing a simple interpretation of the experiments of the preceding paper, imply that cell differentiation can occur without a spatial pattern. From dynamical systems viewpoint, the new concept of “open chaos” is proposed, as a novel and general scenario for systems with growing numbers of elements, also seen in economics and sociology.

  12. Dorsal raphe nucleus projecting retinal ganglion cells: Why Y cells?

    PubMed Central

    Pickard, Gary E.; So, Kwok-Fai; Pu, Mingliang

    2015-01-01

    Retinal ganglion Y (alpha) cells are found in retinas ranging from frogs to mice to primates. The highly conserved nature of the large, fast conducting retinal Y cell is a testament to its fundamental task, although precisely what this task is remained ill-defined. The recent discovery that Y-alpha retinal ganglion cells send axon collaterals to the serotonergic dorsal raphe nucleus (DRN) in addition to the lateral geniculate nucleus (LGN), medial interlaminar nucleus (MIN), pretectum and the superior colliculus (SC) has offered new insights into the important survival tasks performed by these cells with highly branched axons. We propose that in addition to its role in visual perception, the Y-alpha retinal ganglion cell provides concurrent signals via axon collaterals to the DRN, the major source of serotonergic afferents to the forebrain, to dramatically inhibit 5-HT activity during orientation or alerting/escape responses, which dis-facilitates ongoing tonic motor activity while dis-inhibiting sensory information processing throughout the visual system. The new data provide a fresh view of these evolutionarily old retinal ganglion cells. PMID:26363667

  13. Dorsal raphe nucleus projecting retinal ganglion cells: Why Y cells?

    PubMed

    Pickard, Gary E; So, Kwok-Fai; Pu, Mingliang

    2015-10-01

    Retinal ganglion Y (alpha) cells are found in retinas ranging from frogs to mice to primates. The highly conserved nature of the large, fast conducting retinal Y cell is a testament to its fundamental task, although precisely what this task is remained ill-defined. The recent discovery that Y-alpha retinal ganglion cells send axon collaterals to the serotonergic dorsal raphe nucleus (DRN) in addition to the lateral geniculate nucleus (LGN), medial interlaminar nucleus (MIN), pretectum and the superior colliculus (SC) has offered new insights into the important survival tasks performed by these cells with highly branched axons. We propose that in addition to its role in visual perception, the Y-alpha retinal ganglion cell provides concurrent signals via axon collaterals to the DRN, the major source of serotonergic afferents to the forebrain, to dramatically inhibit 5-HT activity during orientation or alerting/escape responses, which dis-facilitates ongoing tonic motor activity while dis-inhibiting sensory information processing throughout the visual system. The new data provide a fresh view of these evolutionarily old retinal ganglion cells. PMID:26363667

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

    PubMed

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

    2016-02-01

    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. PMID:26859350

  15. 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.

  16. 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. PMID:24397934

  17. Physical association between a novel plasma-membrane structure and centrosome orients cell division.

    PubMed

    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. PMID:27502556

  18. Cell adhesion in regulation of asymmetric stem cell division

    PubMed Central

    Yamashita, Yukiko M.

    2010-01-01

    Adult stem cells inevitably communicate with their cellular neighbors within the tissues they sustain. Indeed, such communication, particularly with components of the stem cell niche, is essential for many aspects of stem cell behavior, including the maintenance of stem cell identity and asymmetric cell division. Cell adhesion mediates this communication by placing stem cells in close proximity to the signaling source and by providing a polarity cue that orients stem cells. Here, I review the recent discovery that cell adhesion molecules govern the behavior of stem cells. PMID:20724132

  19. 3-(Benzodioxan-2-ylmethoxy)-2,6-difluorobenzamides bearing hydrophobic substituents at the 7-position of the benzodioxane nucleus potently inhibit methicillin-resistant Sa and Mtb cell division.

    PubMed

    Straniero, Valentina; Pallavicini, Marco; Chiodini, Giuseppe; Zanotto, Carlo; Volontè, Luca; Radaelli, Antonia; Bolchi, Cristiano; Fumagalli, Laura; Sanguinetti, Maurizio; Menchinelli, Giulia; Delogu, Giovanni; Battah, Basem; De Giuli Morghen, Carlo; Valoti, Ermanno

    2016-09-14

    Lipophilic substituents at benzodioxane C (7) of 3-(benzodioxan-2-ylmethoxy)-2,6-difluorobenzamide improve the antibacterial activity against methicillin-resistant Staphylococcus aureus strains to MIC values in the range of 0.2-2.5 μg/mL, whereas hydrophilic substituents at the same position and modifications at the benzodioxane substructure, excepting for replacement with 2-cromanyl, are deleterious. Some of the lead compounds also exhibit good activity against Mtb. Parallel SARs to those of 3-(2-benzothiazol-2-ylmethoxy)-2,6-difluorobenzamide, well known FtsZ inhibitor, and cells alterations typical of FtsZ inhibition indicate such a protein as the target of these potent antibacterial benzodioxane-benzamides. PMID:27191617

  20. Synthetic cell division system: Controlling equal vs. unequal divisions by design

    PubMed Central

    Sato, Yoichi; Yasuhara, Kazuma; Kikuchi, Jun-ichi; Sato, Thomas N.

    2013-01-01

    Cell division is one of the most fundamental and evolutionarily conserved biological processes. Here, we report a synthetic system where we can control by design equal vs. unequal divisions. We synthesized a micro-scale inverse amphipathic droplet of which division is triggered by the increase of surface to volume ratio. Using this system, we succeeded in selectively inducing equal vs. unequal divisions of the droplet cells by adjusting the temperature or the viscosity of the solvent outside the droplet cell accordingly. Our synthetic division system may provide a platform for further development to a system where intracellular contents of the parent droplet cell could be divided into various ratios between the two daughter droplet cells to control their functions and fates. PMID:24327069

  1. (1) The Relationship of Protein Expression and Cell Division, (2) 3D Imaging of Cells Using Digital Holography, and (3) General Chemistry Enrollment at University of Michigan

    ERIC Educational Resources Information Center

    Matz, Rebecca L.

    2012-01-01

    Chapter 1: The role of cell division in protein expression is important to understand in order to guide the development of better nonviral gene delivery materials that can transport DNA to the nucleus with high efficiency for a variety of cell types, particularly when nondividing cells are targets of gene therapy. We evaluated the relationship…

  2. Cell Nucleus-Targeting Zwitterionic Carbon Dots

    PubMed Central

    Jung, Yun Kyung; Shin, Eeseul; Kim, Byeong-Su

    2015-01-01

    An innovative nucleus-targeting zwitterionic carbon dot (CD) vehicle has been developed for anticancer drug delivery and optical monitoring. The zwitterionic functional groups of the CDs introduced by a simple one-step synthesis using β-alanine as a passivating and zwitterionic ligand allow cytoplasmic uptake and subsequent nuclear translocation of the CDs. Moreover, multicolor fluorescence improves the accuracy of the CDs as an optical code. The CD-based drug delivery system constructed by non-covalent grafting of doxorubicin, exhibits superior antitumor efficacy owing to enhanced nuclear delivery in vitro and tumor accumulation in vivo, resulting in highly effective tumor growth inhibition. Since the zwitterionic CDs are highly biocompatible and effectively translocated into the nucleus, it provides a compelling solution to a multifunctional nanoparticle for substantially enhanced nuclear uptake of drugs and optical monitoring of translocation. PMID:26689549

  3. Estimated Radiation on Mars, Hits per Cell Nucleus

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This global map of Mars shows estimates for amounts of high-energy-particle cosmic radiation reaching the surface, a serious health concern for any future human exploration of the planet.

    The estimates are based on cosmic-radiation measurements made on the way to Mars by the Mars radiation environment experiment, an instrument on NASA's 2001 Mars Odyssey spacecraft, plus information about Mars' surface elevations from the laser altimeter instrument on NASA's Mars Global Surveyor. The areas of Mars expected to have least radiation are where elevation is lowest, because those areas have more atmosphere above them to block out some of the radiation. Earth's thick atmosphere shields us from most cosmic radiation, but Mars has a much thinner atmosphere than Earth does.

    Colors in the map refer to the estimated average number of times per year each cell nucleus in a human there would be hit by a high-energy cosmic ray particle. The range is generally from two hits (color-coded green), a moderate risk level, to eight hits (coded red), a high risk level.

    NASA's Jet Propulsion Laboratory, Pasadena, Calif. manages the 2001 Mars Odyssey and Mars Global Surveyor missions for NASA's Office of Space Science, Washington D.C. The Mars radiation environment experiment was developed by NASA's Johnson Space Center. Lockheed Martin Astronautics, Denver, is the prime contractor for Odyssey, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  4. Magnetic Manipulation of Nanorods in the Nucleus of Living Cells

    PubMed Central

    Celedon, Alfredo; Hale, Christopher M.; Wirtz, Denis

    2011-01-01

    The organization of chromatin in the cell nucleus is crucial for gene expression regulation. However, physically probing the nuclear interior is challenging because high forces have to be applied using minimally invasive techniques. Here, magnetic nanorods embedded in the nucleus of living cells are subjected to controlled rotational forces, producing micron-sized displacements in the nuclear interior. The resulting time-dependent rotation of the nanorods is analyzed in terms of viscoelastic parameters of the nucleus, in wild-type and Lamin A/C deficient cells. This method and analysis reveal that Lamin A/C knockout, together perhaps with other changes that result from the knockout, induce significant decreases in the nuclear viscosity and elasticity. PMID:22004741

  5. 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)

  6. Mechanisms of daughter cell-size control during cell division.

    PubMed

    Kiyomitsu, Tomomi

    2015-05-01

    Daughter cell size is tightly regulated during cell division. In animal cells, the position of the anaphase spindle specifies the cell cleavage site to dictate the relative size of the daughter cells. Although spindle orientation is regulated by dynein-dependent cortical pulling forces exerted on astral microtubules in many cell types, it was unclear how these forces are precisely regulated to center or displace the spindle. Recently, intrinsic signals derived from chromosomes or spindle poles have been demonstrated to regulate dynein-dependent pulling forces in symmetrically dividing cells. Unexpectedly, myosin-dependent contractile forces have also been shown to control spindle position by altering the cellular boundaries during anaphase. In this review, I discuss how dynein- and myosin-dependent forces are coordinately regulated to control daughter cell size. PMID:25548067

  7. 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

  8. Streptomyces: A Screening Tool for Bacterial Cell Division Inhibitors

    PubMed Central

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

    2016-01-01

    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. PMID:25256667

  9. 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.

  10. Pollen ultrastructure in anther cultures of Datura innoxia. I. Division of the presumptive vegetative cell.

    PubMed

    Dunwell, J M; Sunderland, N

    1976-12-01

    Ultrastructural features of embryogenic pollen in Datura innoxia are described, just prior to, during, and after completion of the first division of the presumptive vegetative cell. In anther cultures initiated towards the end of the microspore phase and incubated at 28 degrees C in darkness, the spores divide within 24 h and show features consistent with those of dividing spores in vivo. Cytokinesis is also normal in most of the spores and the gametophytic cell-plate curves round the presumptive generative nucleus in the usual highly ordered way. Further differentiation of the 2 gametophytic cells does not take place and the pollen either switches to embryogenesis or degenerates. After 48-72 h, the remaining viable pollen shows the vegetative cell in division. The cell, which has a large vacuole and thin layer of parietal cytoplasm carried over from the microspore, divides consistently in a plane parallel to the microspore division. The dividing wall follows a less-ordered course than the gametophytic wall and usually traverses the vacuole, small portions of which are incorporated into the daughter cell adjacent to the generative cell. The only structural changes in the vegetative cell associated with the change in programme appear to be an increase in electron density of both plastids and mitochondria and deposition of an electron-dense material (possibly lipid) on the tonoplast. The generative cell is attached to the intine when the vegetative cell divides. Ribosomal density increases in the generative cell and exceeds that in the vegetative cell. A thin electron-dense layer also appears in the generative-cell wall. It is concluded that embryogenesis commences as soon as the 2 gametophytic cells are laid down. Gene activity associated with postmitotic synthesis of RNA and protein in the vegetative cell is switched off. The data are discussed in relation to the first division of the embryogenic vegetative cells in Nicotiana tabacum. PMID:1018041

  11. 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...

  12. Barley disease susceptibility factor RACB acts in epidermal cell polarity and positioning of the nucleus

    PubMed Central

    Scheler, Björn; Schnepf, Vera; Galgenmüller, Carolina; Ranf, Stefanie; Hückelhoven, Ralph

    2016-01-01

    RHO GTPases are regulators of cell polarity and immunity in eukaryotes. In plants, RHO-like RAC/ROP GTPases are regulators of cell shaping, hormone responses, and responses to microbial pathogens. The barley (Hordeum vulgare L.) RAC/ROP protein RACB is required for full susceptibility to penetration by Blumeria graminis f.sp. hordei (Bgh), the barley powdery mildew fungus. Disease susceptibility factors often control host immune responses. Here we show that RACB does not interfere with early microbe-associated molecular pattern-triggered immune responses such as the oxidative burst or activation of mitogen-activated protein kinases. RACB also supports rather than restricts expression of defence-related genes in barley. Instead, silencing of RACB expression by RNAi leads to defects in cell polarity. In particular, initiation and maintenance of root hair growth and development of stomatal subsidiary cells by asymmetric cell division is affected by silencing expression of RACB. Nucleus migration is a common factor of developmental cell polarity and cell-autonomous interaction with Bgh. RACB is required for positioning of the nucleus near the site of attack from Bgh. We therefore suggest that Bgh profits from RACB’s function in cell polarity rather than from immunity-regulating functions of RACB. PMID:27056842

  13. Barley disease susceptibility factor RACB acts in epidermal cell polarity and positioning of the nucleus.

    PubMed

    Scheler, Björn; Schnepf, Vera; Galgenmüller, Carolina; Ranf, Stefanie; Hückelhoven, Ralph

    2016-05-01

    RHO GTPases are regulators of cell polarity and immunity in eukaryotes. In plants, RHO-like RAC/ROP GTPases are regulators of cell shaping, hormone responses, and responses to microbial pathogens. The barley (Hordeum vulgare L.) RAC/ROP protein RACB is required for full susceptibility to penetration by Blumeria graminis f.sp. hordei (Bgh), the barley powdery mildew fungus. Disease susceptibility factors often control host immune responses. Here we show that RACB does not interfere with early microbe-associated molecular pattern-triggered immune responses such as the oxidative burst or activation of mitogen-activated protein kinases. RACB also supports rather than restricts expression of defence-related genes in barley. Instead, silencing of RACB expression by RNAi leads to defects in cell polarity. In particular, initiation and maintenance of root hair growth and development of stomatal subsidiary cells by asymmetric cell division is affected by silencing expression of RACB. Nucleus migration is a common factor of developmental cell polarity and cell-autonomous interaction with Bgh RACB is required for positioning of the nucleus near the site of attack from Bgh We therefore suggest that Bgh profits from RACB's function in cell polarity rather than from immunity-regulating functions of RACB. PMID:27056842

  14. 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.

  15. Incorporation of mammalian actin into microfilaments in plant cell nucleus

    PubMed Central

    Paves, Heiti; Truve, Erkki

    2004-01-01

    Background Actin is an ancient molecule that shows more than 90% amino acid homology between mammalian and plant actins. The regions of the actin molecule that are involved in F-actin assembly are largely conserved, and it is likely that mammalian actin is able to incorporate into microfilaments in plant cells but there is no experimental evidence until now. Results Visualization of microfilaments in onion bulb scale epidermis cells by different techniques revealed that rhodamine-phalloidin stained F-actin besides cytoplasm also in the nuclei whereas GFP-mouse talin hybrid protein did not enter the nuclei. Microinjection of fluorescently labeled actin was applied to study the presence of nuclear microfilaments in plant cells. Ratio imaging of injected fluorescent rabbit skeletal muscle actin and phalloidin staining of the microinjected cells showed that mammalian actin was able to incorporate into plant F-actin. The incorporation occurred preferentially in the nucleus and in the perinuclear region of plant cells whereas part of plant microfilaments, mostly in the periphery of cytoplasm, did not incorporate mammalian actin. Conclusions Microinjected mammalian actin is able to enter plant cell's nucleus, whereas incorporation of mammalian actin into plant F-actin occurs preferentially in the nucleus and perinuclear area. PMID:15102327

  16. 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

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

    PubMed

    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

  18. Asymmetric Cell Division in Polyploid Giant Cancer Cells and Low Eukaryotic Cells

    PubMed Central

    Zhang, Dan; Wang, Yijia

    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. PMID:25045675

  19. Direct observation of nanoparticle-cancer cell nucleus interactions.

    PubMed

    Dam, Duncan Hieu M; Lee, Jung Heon; Sisco, Patrick N; Co, Dick T; Zhang, Ming; Wasielewski, Michael R; Odom, Teri W

    2012-04-24

    We report the direct visualization of interactions between drug-loaded nanoparticles and the cancer cell nucleus. Nanoconstructs composed of nucleolin-specific aptamers and gold nanostars were actively transported to the nucleus and induced major changes to the nuclear phenotype via nuclear envelope invaginations near the site of the construct. The number of local deformations could be increased by ultrafast, light-triggered release of the aptamers from the surface of the gold nanostars. Cancer cells with more nuclear envelope folding showed increased caspase 3 and 7 activity (apoptosis) as well as decreased cell viability. This newly revealed correlation between drug-induced changes in nuclear phenotype and increased therapeutic efficacy could provide new insight for nuclear-targeted cancer therapy. PMID:22424173

  20. Growth behavior of cochlear nucleus neuronal cells on semiconductor substrates.

    PubMed

    Rak, Kristen; Wasielewski, Natalia; Radeloff, Andreas; Scherzed, Agmal; Jablonka, Sibylle; Hagen, Rudolf; Mlynski, Robert

    2011-05-01

    Auditory brainstem implants provide sound information by direct stimulation of the cochlear nucleus to patients with dysfunctional or absent cranial nerve VIII. In contrast to patients with cochlear implants, the use of the auditory brainstem implants is less successful. This cannot be fully explained by the difference location of stimulation but a rather unspecific neuronal stimulation. The aim of this study was to further examine neuronal cells of the cochlear nucleus and to test their interactions with semiconductor substrates as a potential electrode material for improved auditory brainstem implants. The cochlear nuclei of postnatal day 7 rats were microsurgically dissected. The tissue was dissociated enzymatically and plated on coverslips as control and on the semiconductor substrates silicon or silicon nitride. After 4 days in culture the morphology and growth of dissociated cells was determined by fluorescence and scanning electron microscopy. Dissociated cells of the cochlear nucleus showed reduced cell growth on semiconductor substrates compared with controls. SEM analysis demonstrated close contact of neurons with supporting cells in culture and good adherence of neuronal growth cones on the used materials. These findings present basic knowledge for the development of neuron-electrode interfaces for future auditory brainstem implants. PMID:21370446

  1. Coordination between chromosome replication and cell division in Escherichia coli.

    PubMed Central

    Tang, M S; Helmstetter, C E

    1980-01-01

    Cell division properties of Escherichia coli B/r containing either a dnaC or a dnaI mutation were examined. Incubation at nonpermissive temperature resulted in the eventual production of cells of approximately normal size, or slightly smaller, which lacked chromosomal DNA. The cell division patterns in cultures which were grown at permissive temperature and then shifted to nonpermissive temperature were consistent with: first, division and equipartition of chromosomes by cells which were in the C and D periods at the time of the shift; second, an apparent delay in cell division; and third, commencement of the formation of chromosomeless cells. In glucose-grown cultures of the dnaI mutant, production of chromosomeless cells continued for at least 120 min, whereas in the dnaC mutant chromosomeless cells were formed during a single interval between 110 and 130 min after the temperature shift. The results are discussed in light of the hypothesis that replication of a specific chromosomal region is not an obligatory requirement for the initiation and completion of the processes leading to division in a cell which contains at least one functioning chromosome. PMID:6988405

  2. A unique cell division machinery in the Archaea

    PubMed Central

    Lindås, Ann-Christin; Karlsson, Erik A.; Lindgren, Maria T.; Ettema, Thijs J. G.; Bernander, Rolf

    2008-01-01

    In contrast to the cell division machineries of bacteria, euryarchaea, and eukaryotes, no division components have been identified in the second main archaeal phylum, Crenarchaeota. Here, we demonstrate that a three-gene operon, cdv, in the crenarchaeon Sulfolobus acidocaldarius, forms part of a unique cell division machinery. The operon is induced at the onset of genome segregation and division, and the Cdv proteins then polymerize between segregating nucleoids and persist throughout cell division, forming a successively smaller structure during constriction. The cdv operon is dramatically down-regulated after UV irradiation, indicating division inhibition in response to DNA damage, reminiscent of eukaryotic checkpoint systems. The cdv genes exhibit a complementary phylogenetic range relative to FtsZ-based archaeal division systems such that, in most archaeal lineages, either one or the other system is present. Two of the Cdv proteins, CdvB and CdvC, display homology to components of the eukaryotic ESCRT-III sorting complex involved in budding of luminal vesicles and HIV-1 virion release, suggesting mechanistic similarities and a common evolutionary origin. PMID:18987308

  3. 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

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

    PubMed

    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

  5. Cell autonomy and synchrony of suprachiasmatic nucleus circadian oscillators.

    PubMed

    Mohawk, Jennifer A; Takahashi, Joseph S

    2011-07-01

    The suprachiasmatic nucleus (SCN) of the hypothalamus is the site of the master circadian pacemaker in mammals. The individual cells of the SCN are capable of functioning independently from one another and therefore must form a cohesive circadian network through intercellular coupling. The network properties of the SCN lead to coordination of circadian rhythms among its neurons and neuronal subpopulations. There is increasing evidence for multiple interconnected oscillators within the SCN, and in this review we will highlight recent advances in our knowledge of the complex organization and function of the cellular and network-level SCN clock. Understanding the way in which synchrony is achieved between cells in the SCN will provide insight into the means by which this important nucleus orchestrates circadian rhythms throughout the organism. PMID:21665298

  6. Cell Autonomy and Synchrony of Suprachiasmatic Nucleus Circadian Oscillators

    PubMed Central

    Mohawk, Jennifer A.; Takahashi, Joseph S.

    2013-01-01

    The suprachiasmatic nucleus (SCN) of the hypothalamus is the site of the master circadian pacemaker in mammals. The individual cells of the SCN are capable of functioning independently from one another and therefore must form a cohesive circadian network through intercellular coupling. The network properties of the SCN lead to coordination of circadian rhythms among its neurons and neuronal subpopulations. There is increasing evidence for multiple interconnected oscillators within the SCN, and in this Review, we will highlight recent advances in our understanding of the complex organization and function of the cellular and network-level SCN clock. Understanding the way in which synchrony is achieved between cells in the SCN will provide insight into the means by which this important nucleus orchestrates circadian rhythms throughout the organism. PMID:21665298

  7. Ultrastructure and Membrane Traffic During Cell Division in the Marine Pennate Diatom Phaeodactylum tricornutum

    PubMed Central

    Tanaka, Atsuko; De Martino, Alessandra; Amato, Alberto; Montsant, Anton; Mathieu, Benjamin; Rostaing, Philippe; Tirichine, Leila; Bowler, Chris

    2015-01-01

    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. PMID:26386358

  8. 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.

  9. Physical plasticity of the nucleus in stem cell differentiation

    PubMed Central

    Pajerowski, J. David; Dahl, Kris Noel; Zhong, Franklin L.; Sammak, Paul J.; Discher, Dennis E.

    2007-01-01

    Cell differentiation in embryogenesis involves extensive changes in gene expression structural reorganization within the nucleus, including chromatin condensation and nucleoprotein immobilization. We hypothesized that nuclei in naive stem cells would therefore prove to be physically plastic and also more pliable than nuclei in differentiated cells. Micromanipulation methods indeed show that nuclei in human embryonic stem cells are highly deformable and stiffen 6-fold through terminal differentiation, and that nuclei in human adult stem cells possess an intermediate stiffness and deform irreversibly. Because the nucleo-skeletal component Lamin A/C is not expressed in either type of stem cell, we knocked down Lamin A/C in human epithelial cells and measured a deformability similar to that of adult hematopoietic stem cells. Rheologically, lamin-deficient states prove to be the most fluid-like, especially within the first ≈10 sec of deformation. Nuclear distortions that persist longer than this are irreversible, and fluorescence-imaged microdeformation with photobleaching confirms that chromatin indeed flows, distends, and reorganizes while the lamina stretches. The rheological character of the nucleus is thus set largely by nucleoplasm/chromatin, whereas the extent of deformation is modulated by the lamina. PMID:17893336

  10. Cell-Division Behavior in a Heterogeneous Swarm Environment.

    PubMed

    Erskine, Adam; Herrmann, J Michael

    2015-01-01

    We present a system of virtual particles that interact using simple kinetic rules. It is known that heterogeneous mixtures of particles can produce particularly interesting behaviors. Here we present a two-species three-dimensional swarm in which a behavior emerges that resembles cell division. We show that the dividing behavior exists across a narrow but finite band of parameters and for a wide range of population sizes. When executed in a two-dimensional environment the swarm's characteristics and dynamism manifest differently. In further experiments we show that repeated divisions can occur if the system is extended by a biased equilibrium process to control the split of populations. We propose that this repeated division behavior provides a simple model for cell-division mechanisms and is of interest for the formation of morphological structure and to swarm robotics. PMID:26545164

  11. 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

  12. Nucleus Morphometry in Cultured Epithelial Cells Correlates with Phenotype.

    PubMed

    Khan, Ayyad Z; Utheim, Tor P; Jackson, Catherine J; Reppe, Sjur; Lyberg, Torstein; Eidet, Jon R

    2016-06-01

    Phenotype of cultured ocular epithelial transplants has been shown to affect clinical success rates following transplantation to the cornea. The purpose of this study was to evaluate the relationship between cell nucleus morphometry and phenotype in three types of cultured epithelial cells. This study provides knowledge for the development of a non-invasive method of determining the phenotype of cultured epithelium before transplantation. Cultured human conjunctival epithelial cells (HCjE), human epidermal keratinocytes (HEK), and human retinal pigment epithelial cells (HRPE) were analyzed by quantitative immunofluorescence. Assessments of nucleus morphometry and nucleus-to-cytoplasm ratio (N/C ratio) were performed using ImageJ. Spearman's correlation coefficient was employed for statistical analysis. Levels of the proliferation marker PCNA in HCjE, HEK, and HRPE correlated positively with nuclear area. Nuclear area correlated significantly with levels of the undifferentiated cell marker ABCG2 in HCjE. Bmi1 levels, but not p63α levels, correlated significantly with nuclear area in HEK. The N/C ratio did not correlate significantly with any of the immunomarkers in HCjE (ABCG2, CK7, and PCNA) and HRPE (PCNA). In HEK, however, the N/C ratio was negatively correlated with levels of the undifferentiated cell marker CK14 and positively correlated with Bmi1 expression. The size of the nuclear area correlated positively with proliferation markers in all three epithelia. Morphometric indicators of phenotype in cultured epithelia can be identified using ImageJ. Conversely, the N/C ratio did not show a uniform relationship with phenotype in HCjE, HEK, or HRPE. N/C ratio therefore, may not be a useful morphometric marker for in vitro assessment of phenotype in these three epithelia. PMID:27329312

  13. Action at a Distance in the Cell's Nucleus

    NASA Astrophysics Data System (ADS)

    Kondev, Jane

    Various functions performed by chromosomes involve long-range communication between DNA sequences that are tens of thousands of bases apart along the genome, and microns apart in the nucleus. In this talk I will discuss experiments and theory relating to two distinct modes of long-range communication in the nucleus, chromosome looping and protein hopping along the chromosome, both in the context of DNA-break repair in yeast. Yeast is an excellent model system for studies that link chromosome conformations to their function as there is ample experimental evidence that yeast chromosome conformations are well described by a simple, random-walk polymer model. Using a combination of polymer physics theory and experiments on yeast cells, I will demonstrate that loss of polymer entropy due to chromosome looping is the driving force for homology search during repair of broken DNA by homologous recombination. I will also discuss the spread of histone modifications along the chromosome and away from the DNA break point in the context of simple physics models based on chromosome looping and kinase hopping, and show how combining physics theory and cell-biology experiment can be used to dissect the molecular mechanism of the spreading process. These examples demonstrate how combined theoretical and experimental studies can reveal physical principles of long-range communication in the nucleus, which play important roles in regulation of gene expression, DNA recombination, and chromatin modification. This work was supported by the NSF DMR-1206146.

  14. The PLASTID DIVISION1 and 2 Components of the Chloroplast Division Machinery Determine the Rate of Chloroplast Division in Land Plant Cell Differentiation[C][W

    PubMed Central

    Okazaki, Kumiko; Kabeya, Yukihiro; Suzuki, Kenji; Mori, Toshiyuki; Ichikawa, Takanari; Matsui, Minami; Nakanishi, Hiromitsu; Miyagishima, Shin-ya

    2009-01-01

    In most algae, the chloroplast division rate is held constant to maintain the proper number of chloroplasts per cell. By contrast, land plants evolved cell and chloroplast differentiation systems in which the size and number of chloroplasts change along with their respective cellular function by regulation of the division rate. Here, we show that PLASTID DIVISION (PDV) proteins, land plant–specific components of the division apparatus, determine the rate of chloroplast division. Overexpression of PDV proteins in the angiosperm Arabidopsis thaliana and the moss Physcomitrella patens increased the number but decreased the size of chloroplasts; reduction of PDV levels resulted in the opposite effect. The level of PDV proteins, but not other division components, decreased during leaf development, during which the chloroplast division rate also decreased. Exogenous cytokinins or overexpression of the cytokinin-responsive transcription factor CYTOKININ RESPONSE FACTOR2 increased the chloroplast division rate, where PDV proteins, but not other components of the division apparatus, were upregulated. These results suggest that the integration of PDV proteins into the division machinery enabled land plant cells to change chloroplast size and number in accord with the fate of cell differentiation. PMID:19567705

  15. 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.

  16. Snapping magnetosome chains by asymmetric cell division in magnetotactic bacteria.

    PubMed

    Lin, Wei; Pan, Yongxin

    2011-12-01

    The mechanism by which prokaryotic cells organize and segregate their intracellular organelles during cell division has recently been the subject of substantial interest. Unlike other microorganisms, magnetotactic bacteria (MTB) form internal magnets (known as magnetosome chain) for magnetic orientation, and thus face an additional challenge of dividing and equipartitioning this magnetic receptor to their daughter cells. Although MTB have been investigated more than four decades, it is only recently that the basic mechanism of how MTB divide and segregate their magnetic organelles has been addressed. In this issue of Molecular Microbiology, the cell cycle of the model magnetotactic bacterium, Magnetospirillum gryphiswaldense is characterized by Katzmann and co-workers. The authors have found that M. gryphiswaldense undergoes an asymmetric cell division along two planes. A novel wedge-like type of cellular constriction is observed before separation of daughter cells and magnetosome chains, which is assumed to help cell cope with the magnetic force within the magnetosome chain. The data shows that the magnetosome chain becomes actively recruited to the cellular division site, in agreement with the previous suggestions described by Staniland et al. (2010), and the actin-like protein MamK is likely involved in this fast polar-to-midcell translocalization. With the use of cryo-electron tomography, an arc-shaped Z ring is observed near the division site, which is assumed to trigger the asymmetric septation of cell and magnetosome chain. PMID:22066928

  17. Spatial properties of koniocellular cells in the lateral geniculate nucleus of the marmoset Callithrix jacchus

    PubMed Central

    White, Andrew J R; Solomon, Samuel G; Martin, Paul R

    2001-01-01

    The receptive field dimensions, contrast sensitivity and linearity of spatial summation of koniocellular (KC), parvocellular (PC) and magnocellular (MC) cells in the lateral geniculate nucleus (LGN) of 11 adult marmosets were measured using achromatic sinusoidal gratings. The receptive field centre diameter of cells in each (PC, KC and MC) class increases with distance from the fovea. There is substantial overlap in centre size between the three cell classes at any eccentricity, but the PC cells have, on average, the smallest centres and the KC cells have the largest. Some PC and KC cells did not respond at all to the grating stimulus. The contrast sensitivity of the receptive field centre mechanism in KC cells decreases in proportion to the centre area. A similar trend was seen for the surround mechanism. These characteristics are common to PC and MC cells, suggesting that they originate at an early stage of visual processing in the retina. The KC cells showed, in general, lower peak evoked discharge rates than PC or MC cells. The spontaneous discharge rate of KC cells was lower than that of PC cells and similar to that of MC cells. The majority of cells in all divisions of the LGN show linear spatial summation. A few cells did show non-linear spatial summation; these cells were predominantly located in the MC and ventral KC layers. The ventral KC layers below and between the MC layers contain cells with larger and more transiently responding receptive fields than cells in the more dorsal KC layers. We conclude that many of the contrast-dependent spatial properties of cells in the marmoset LGN are common to PC, MC and KC cells. The main difference between KC cells and the other two classes is that there is more variability in their response properties, and they are less responsive to high spatial frequencies. PMID:11389209

  18. 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.

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

    PubMed

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

    2016-02-01

    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. PMID:26774292

  20. On robustness of phase resetting to cell division under entrainment.

    PubMed

    Ahmed, Hafiz; Ushirobira, Rosane; Efimov, Denis

    2015-12-21

    The problem of phase synchronization for a population of genetic oscillators (circadian clocks, synthetic oscillators, etc.) is considered in this paper, taking into account a cell division process and a common entrainment input in the population. The proposed analysis approach is based on the Phase Response Curve (PRC) model of an oscillator (the first order reduced model obtained for the linearized system and inputs with infinitesimal amplitude). The occurrence of cell division introduces state resetting in the model, placing it in the class of hybrid systems. It is shown that without common entraining input in all oscillators, the cell division acts as a disturbance causing phase drift, while the presence of entrainment guarantees boundedness of synchronization phase errors in the population. The performance of the obtained solutions is demonstrated via computer experiments for two different models of circadian/genetic oscillators (Neurospora׳s circadian oscillation model and the repressilator). PMID:26463679

  1. Blue Light Regulation of Cell Division in Chlamydomonas reinhardtii 1

    PubMed Central

    Münzner, Petra; Voigt, Jürgen

    1992-01-01

    A delay in cell division was observed when synchronized cultures of the unicellular green alga Chlamydomonas reinhardtii growing under heterotrophic conditions were exposed to white light during the second half of the growth period. This effect was also observed when photosynthesis was blocked by addition of the photosystem II inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Light pulses of 10 minutes were sufficient to induce a delay in cell division in the presence or absence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. A delay in cell division was induced by blue light but not by illumination with red or far-red light. The equal intensity action spectrum revealed two peaks at 400 and 500 nm. PMID:16669046

  2. Characteristics of near response cells projecting to the oculomotor nucleus.

    PubMed

    Zhang, Y; Mays, L E; Gamlin, P D

    1992-04-01

    1. Previous work has shown neurons just dorsal and lateral to the oculomotor nucleus that increase their firing rate with increases in the angle of ocular convergence. It has been suggested that the output of these midbrain near response cells might provide the vergence command needed by the medial rectus motoneurons. However, lens accommodation ordinarily accompanies convergence, and a subsequent study showed that only about one-half of these midbrain near response cells carried a signal related exclusively to vergence. One hypothesis suggested by this finding is that this subgroup of neurons might have a unique role in providing a "pure" vergence signal to the medial rectus motoneurons. 2. In the present study extracellular recordings were made from midbrain near response cells in monkeys while eye position and lens accommodation were measured. The monkeys viewed targets through an optical system that allowed the accommodative and ocular vergence demands to be manipulated independently. This approach was used to produce a partial dissociation of accommodative and vergence responses, so that an accommodative and vergence coefficient could be determined for each cell, by the use of the following equation FR = R0 + kda x AR + kdv x CR where FR is the firing rate of the near response cell, R0 is the predicted firing rate for a distant target, kda is the (dissociated) accommodation coefficient, AR is the accommodative response, kdv is the (dissociated) vergence coefficient, and CR is the convergence response. 3. The vergence and accommodation coefficients were determined for a large number of midbrain near response cells, including a subset that could be antidromically activated from the medial rectus subdivisions of the oculomotor nucleus. Some near response neurons were found with signals related exclusively to convergence (i.e., kdv greater than 0 and kda = 0), whereas several others had signals related exclusively to lens accommodation (i.e., kda greater than 0

  3. Covert Prepatterning of a Cell Division Wave.

    PubMed

    Veeman, Michael

    2016-04-18

    A directional wave of mitosis, progressing posterior to anterior across the epidermis, is important for neural tube closure in the invertebrate chordate Ciona intestinalis. In this issue of Developmental Cell, Ogura and Sasakura (2016) show that the patterning of this wave unexpectedly has complex origins in the previous cell cycle. PMID:27093077

  4. Microtubule networks for plant cell division.

    PubMed

    de Keijzer, Jeroen; Mulder, Bela M; Janson, Marcel E

    2014-09-01

    During cytokinesis the cytoplasm of a cell is divided to form two daughter cells. In animal cells, the existing plasma membrane is first constricted and then abscised to generate two individual plasma membranes. Plant cells on the other hand divide by forming an interior dividing wall, the so-called cell plate, which is constructed by localized deposition of membrane and cell wall material. Construction starts in the centre of the cell at the locus of the mitotic spindle and continues radially towards the existing plasma membrane. Finally the membrane of the cell plate and plasma membrane fuse to form two individual plasma membranes. Two microtubule-based cytoskeletal networks, the phragmoplast and the pre-prophase band (PPB), jointly control cytokinesis in plants. The bipolar microtubule array of the phragmoplast regulates cell plate deposition towards a cortical position that is templated by the ring-shaped microtubule array of the PPB. In contrast to most animal cells, plants do not use centrosomes as foci of microtubule growth initiation. Instead, plant microtubule networks are striking examples of self-organizing systems that emerge from physically constrained interactions of dispersed microtubules. Here we will discuss how microtubule-based activities including growth, shrinkage, severing, sliding, nucleation and bundling interrelate to jointly generate the required ordered structures. Evidence mounts that adapter proteins sense the local geometry of microtubules to locally modulate the activity of proteins involved in microtubule growth regulation and severing. Many of the proteins and mechanisms involved have roles in other microtubule assemblies as well, bestowing broader relevance to insights gained from plants. PMID:25136380

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

    PubMed Central

    Mishra, Prashant; Chan, David C.

    2014-01-01

    Preface 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 other organelles, particularly in their 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. We discuss the mechanisms regulating mitochondrial segregation during cell division, oogenesis, fertilization and tissue development. The mechanisms that ensure the integrity of these organelles and their DNA include fusion-fission dynamics, organelle transport, mitophagy, and genetic selection of functional genomes. Defects in these processes can lead to cell and tissue pathologies. PMID:25237825

  6. 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…

  7. 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.

  8. Microtubules contribute to maintain nucleus shape in epithelial cell monolayer

    NASA Astrophysics Data System (ADS)

    Tremblay, Dominique; Andrzejewski, Lukasz; Pelling, Andrew

    2013-03-01

    INTRODUCTION: Tissue strains can result in significant nuclear deformations and may regulate gene expression. However, the precise role of the cytoskeleton in regulating nuclear mechanics remains poorly understood. Here, we investigate the nuclear deformability of Madin-Darky canine kidney cells (MDCK) under various stretching conditions to clarify the role of the microtubules and actin network on the mechanical behavior of the nucleus. METHODS: A custom-built cell-stretching device allowing for real time imaging of MDCK nuclei was used. Cells were seeded on a silicone membrane coated with rat-tail collagen I. A nuclear stain, Hoechst-33342, was used to image nuclei during stretching. We exposed cells to a compressive and non-compressive stretching strain field of 25%. Nocodazole and cytochalasin-D were used to depolymerize the microtubules and actin network. RESULTS: Nuclei in control cells stretched more along their minor axis than major axis with a deformation of 5% and 2% respectively. This anisotropy vanished completely in microtubule-deprived cells and these cells showed a very high nuclear deformability along the minor axis when exposed to a compressive stretching strain field. CONCLUSIONS: The microtubules drive the anisotropic deformability of MDCK nuclei in a monolayer and maintain nuclear shape when exposed to compressive strain. Such intrinsic mechanical behavior indicates that microtubules are essential to maintain nuclear shape and may prevent down regulation of gene expression.

  9. 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.

  10. Fine-scale dissection of the subdomains of polarity protein BASL in stomatal asymmetric cell division

    PubMed Central

    Zhang, Ying; Bergmann, Dominique C.; Dong, Juan

    2016-01-01

    Cell polarity is a prerequisite for asymmetric cell divisions (ACDs) that generate cell type diversity during development of multicellular organisms. In Arabidopsis, stomatal lineage ACDs are regulated by the plant-specific protein BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE (BASL). BASL exhibits dynamic subcellular localization, accumulating initially in the nucleus, but then additionally in a highly polarized crescent at the cell cortex before division. BASL polarization requires a phosphorylation-mediated activation process, but how this is achieved remains unknown. In this study, we performed a fine-scale dissection of BASL protein subdomains and elucidated a nuclear localization sequence for nuclear import and a critical FxFP motif for cortical polarity formation, respectively. Artificially tethering BASL subdomains to the plasma membrane suggests that novel protein partner/s might exist and bind to an internal region of BASL. In addition, we suspect the existence of a protein degradation mechanism associated with the amino terminal domain of BASL that accounts for restricting its predominant expression to the stomatal lineage cells of the epidermis. Taken together, our results revealed that BASL, through its distinct subdomains, integrates multiple regulatory inputs to provide a mechanism that promotes difference during stomatal lineage ACDs. PMID:27422992

  11. 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.

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

    PubMed

    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

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

    PubMed Central

    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. PMID:25364740

  14. 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

  15. The Role of Symmetric Stem Cell Divisions in Tissue Homeostasis

    PubMed Central

    Yang, Jienian; Plikus, Maksim V.; Komarova, Natalia L.

    2015-01-01

    Successful maintenance of cellular lineages critically depends on the fate decision dynamics of stem cells (SCs) upon division. There are three possible strategies with respect to SC fate decision symmetry: (a) asymmetric mode, when each and every SC division produces one SC and one non-SC progeny; (b) symmetric mode, when 50% of all divisions produce two SCs and another 50%—two non-SC progeny; (c) mixed mode, when both the asymmetric and two types of symmetric SC divisions co-exist and are partitioned so that long-term net balance of the lineage output stays constant. Theoretically, either of these strategies can achieve lineage homeostasis. However, it remains unclear which strategy(s) are more advantageous and under what specific circumstances, and what minimal control mechanisms are required to operate them. Here we used stochastic modeling to analyze and quantify the ability of different types of divisions to maintain long-term lineage homeostasis, in the context of different control networks. Using the example of a two-component lineage, consisting of SCs and one type of non-SC progeny, we show that its tight homeostatic control is not necessarily associated with purely asymmetric divisions. Through stochastic analysis and simulations we show that asymmetric divisions can either stabilize or destabilize the lineage system, depending on the underlying control network. We further apply our computational model to biological observations in the context of a two-component lineage of mouse epidermis, where autonomous lineage control has been proposed and notable regional differences, in terms of symmetric division ratio, have been noted—higher in thickened epidermis of the paw skin as compared to ear and tail skin. By using our model we propose a possible explanation for the regional differences in epidermal lineage control strategies. We demonstrate how symmetric divisions can work to stabilize paw epidermis lineage, which experiences high level of micro

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

    PubMed

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

    2015-09-01

    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. PMID:25997796

  17. Cochlear nucleus whole mount explants promote the differentiation of neuronal stem cells from the cochlear nucleus in co-culture experiments.

    PubMed

    Rak, Kristen; Völker, Johannes; Jürgens, Lukas; Völker, Christine; Frenz, Silke; Scherzad, Agmal; Schendzielorz, Philipp; Jablonka, Sibylle; Mlynski, Robert; Radeloff, Andreas; Hagen, Rudolf

    2015-08-01

    The cochlear nucleus is the first brainstem nucleus to receive sensory input from the cochlea. Depriving this nucleus of auditory input leads to cellular and molecular disorganization which may potentially be counteracted by the activation or application of stem cells. Neuronal stem cells (NSCs) have recently been identified in the neonatal cochlear nucleus and a persistent neurogenic niche was demonstrated in this brainstem nucleus until adulthood. The present work investigates whether the neurogenic environment of the cochlear nucleus can promote the survival of engrafted NSCs and whether cochlear nucleus-derived NSCs can differentiate into neurons and glia in brain tissue. Therefore, cochlear nucleus whole-mount explants were co-cultured with NSCs extracted from either the cochlear nucleus or the hippocampus and compared to a second environment using whole-mount explants from the hippocampus. Factors that are known to induce neuronal differentiation were also investigated in these NSC-explant experiments. NSCs derived from the cochlear nucleus engrafted in the brain tissue and differentiated into all cells of the neuronal lineage. Hippocampal NSCs also immigrated in cochlear nucleus explants and differentiated into neurons, astrocytes and oligodendrocytes. Laminin expression was up-regulated in the cochlear nucleus whole-mounts and regulated the in vitro differentiation of NSCs from the cochlear nucleus. These experiments confirm a neurogenic environment in the cochlear nucleus and the capacity of cochlear nucleus-derived NSCs to differentiate into neurons and glia. Consequently, the presented results provide a first step for the possible application of stem cells to repair the disorganization of the cochlear nucleus, which occurs after hearing loss. PMID:25960344

  18. 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

  19. 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.

  20. Dissecting the cell to nucleus, perinucleus and cytosol

    PubMed Central

    Shaiken, Tattym E.; Opekun, Antone R.

    2014-01-01

    Cells have been described under the microscope as organelles containing cytoplasm and the nucleus. However, an unnoted structure exists between the cytoplasm and the nucleoplasm of eukaryotic cells. In addition to the nuclear envelope, there exists a perinuclear region (PNR or perinucleus) with unknown composition and function. Until now, an investigation of the role of the perinucleus has been restricted by the absence of a PNR isolation method. This manuscript describes a perinucleus isolation technique on the basis of its unique compact organization. The perinucleus was found to contain approximately 15 to 18% of the total proteins of the mammalian cell, almost half of the proteins of nuclei. Using four different normal and cancer cell lines, it was shown that the composition of PNR is highly dynamic. Application of the method showed that translocation of the p53 tumor-suppressor protein to the perinucleus in immortalized MEF cells is correlated with the translocation of p53-stabilizing protein, nucleophosmin (B23), to the PNR. Herein, the concept of the perinuclear region is advanced as a formal, identifiable structure. The roles of the perinucleus in maintaining genome integrity, regulation of gene expression and understanding of malignant transformation are discussed. PMID:24815916

  1. Auxin efflux carrier activity and auxin accumulation regulate cell division and polarity in tobacco cells.

    PubMed

    Petrásek, Jan; Elckner, Miroslav; Morris, David A; Zazímalová, Eva

    2002-12-01

    Division and growth of most types of in vitro-cultured plant cells require an external source of auxin. In such cultures, the ratio of external to internal auxin concentration is crucial for the regulation of the phases of the standard growth cycle. In this report the internal concentration of auxin in suspension-cultured cells of Nicotiana tabacum L., strain VBI-0, was manipulated either (i) by increasing 10-fold the normal concentration of 1-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid in the external medium; or (ii) by addition 1-N-naphthylphthalamic acid (NPA; an inhibitor of auxin efflux and of auxin efflux carrier traffic). Both treatments delayed the onset of cell division for 6-7 days without loss of cell viability. In both cases, cell division activity subsequently resumed coincident with a reduction in the ability of cells to accumulate [(3)H]NAA from an external medium. Following renewed cell division, a significant proportion of the NPA-treated cells but not those grown at high auxin concentration, exhibited changes in the orientation of new cell divisions and loss of polarity. We conclude that cell division, but not cell elongation, is prevented when the internal auxin concentration rises above a critical threshold value and that the directed traffic of auxin efflux carriers to the plasma membrane may regulate the orientation of cell divisions. PMID:12447544

  2. Models of chromatin spatial organisation in the cell nucleus

    NASA Astrophysics Data System (ADS)

    Nicodemi, Mario

    2014-03-01

    In the cell nucleus chromosomes have a complex architecture serving vital functional purposes. Recent experiments have started unveiling the interaction map of DNA sites genome-wide, revealing different levels of organisation at different scales. The principles, though, which orchestrate such a complex 3D structure remain still mysterious. I will overview the scenario emerging from some classical polymer physics models of the general aspect of chromatin spatial organisation. The available experimental data, which can be rationalised in a single framework, support a picture where chromatin is a complex mixture of differently folded regions, self-organised across spatial scales according to basic physical mechanisms. I will also discuss applications to specific DNA loci, e.g. the HoxB locus, where models informed with biological details, and tested against targeted experiments, can help identifying the determinants of folding.

  3. 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

  4. Inflammation Induces Irreversible Biophysical Changes in Isolated Nucleus Pulposus Cells

    PubMed Central

    Maidhof, Robert; Jacobsen, Timothy; Papatheodorou, Angelos; Chahine, Nadeen O.

    2014-01-01

    Intervertebral disc degeneration is accompanied by elevated levels of inflammatory cytokines that have been implicated in disease etiology and matrix degradation. While the effects of inflammatory stimulation on disc cell metabolism have been well-studied, their effects on cell biophysical properties have not been investigated. The hypothesis of this study is that inflammatory stimulation alters the biomechanical properties of isolated disc cells and volume responses to step osmotic loading. Cells from the nucleus pulposus (NP) of bovine discs were isolated and treated with either lipopolysaccharide (LPS), an inflammatory ligand, or with the recombinant cytokine TNF-α for 24 hours. We measured cellular volume regulation responses to osmotic loading either immediately after stimulation or after a 1 week recovery period from the inflammatory stimuli. Cells from each group were tested under step osmotic loading and the transient volume-response was captured via time-lapse microscopy. Volume-responses were analyzed using mixture theory framework to investigate two biomechanical properties of the cell, the intracellular water content and the hydraulic permeability. Intracellular water content did not vary between treatment groups, but hydraulic permeability increased significantly with inflammatory treatment. In the 1 week recovery group, hydraulic permeability remained elevated relative to the untreated recovery control. Cell radius was also significantly increased both after 24 hours of treatment and after 1 week recovery. A significant linear correlation was observed between hydraulic permeability and cell radius in untreated cells at 24 hours and at 1-week recovery, though not in the inflammatory stimulated groups at either time point. This loss of correlation between cell size and hydraulic permeability suggests that regulation of volume change is disrupted irreversibly due to inflammatory stimulation. Inflammatory treated cells exhibited altered F

  5. 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.

  6. Texture discrimination by cells in the cat lateral geniculate nucleus.

    PubMed

    Nothdurft, H C

    1990-01-01

    The spontaneous segregation of texture areas is an impressive perceptual phenomenon, the neural basis of which is not yet understood. In the texton concept (Julesz and Bergen 1983; Julesz 1984, 1986) it is assumed that the visual system analyzes a stimulus for certain features ('textons') the spatial distribution of which is pre-attentively registered and may provide the percept of dissected texture areas. Supposed textons are blobs of a given size, oriented lines, line intersections and line terminators, suggesting that texture analysis is exclusively mediated by form-specific filters at higher, e.g. cortical, processing levels. This paper investigates the contribution of cells in the cat lateral geniculate nucleus (LGN) to segregation of typical texton differences. The results indicate that LGN cells, though not resembling the supposed texton filters, often distinguished textured arrangements of such features on the basis of a variety of other visual cues, such as global or local variations in mean luminance or differences in spatial frequency composition. Thus, cells responded to texture borders between areas differing in the size or the density of texture elements and often revealed differential firing rates to textures differing by the crossing or the terminator feature. For textures with differences in line orientation, however, only small variations of the firing rate were seen. In summary, the observations suggest a means of texture representation in the cat LGN which is different from recent concepts of texture segregation in man. For a given pair of textures, cells with receptive fields larger than, or similar to the texture raster respond to global and local luminance variations between areas and, in particular, to differences in their spatial frequency composition. These cells, hence, may signal the global texture difference without encoding spatial details of the pattern from which texton features could be identified. Cells with receptive fields small

  7. Origin of the cell nucleus, mitosis and sex: roles of intracellular coevolution

    PubMed Central

    2010-01-01

    Background The transition from prokaryotes to eukaryotes was the most radical change in cell organisation since life began, with the largest ever burst of gene duplication and novelty. According to the coevolutionary theory of eukaryote origins, the fundamental innovations were the concerted origins of the endomembrane system and cytoskeleton, subsequently recruited to form the cell nucleus and coevolving mitotic apparatus, with numerous genetic eukaryotic novelties inevitable consequences of this compartmentation and novel DNA segregation mechanism. Physical and mutational mechanisms of origin of the nucleus are seldom considered beyond the long-standing assumption that it involved wrapping pre-existing endomembranes around chromatin. Discussions on the origin of sex typically overlook its association with protozoan entry into dormant walled cysts and the likely simultaneous coevolutionary, not sequential, origin of mitosis and meiosis. Results I elucidate nuclear and mitotic coevolution, explaining the origins of dicer and small centromeric RNAs for positionally controlling centromeric heterochromatin, and how 27 major features of the cell nucleus evolved in four logical stages, making both mechanisms and selective advantages explicit: two initial stages (origin of 30 nm chromatin fibres, enabling DNA compaction; and firmer attachment of endomembranes to heterochromatin) protected DNA and nascent RNA from shearing by novel molecular motors mediating vesicle transport, division, and cytoplasmic motility. Then octagonal nuclear pore complexes (NPCs) arguably evolved from COPII coated vesicle proteins trapped in clumps by Ran GTPase-mediated cisternal fusion that generated the fenestrated nuclear envelope, preventing lethal complete cisternal fusion, and allowing passive protein and RNA exchange. Finally, plugging NPC lumens by an FG-nucleoporin meshwork and adopting karyopherins for nucleocytoplasmic exchange conferred compartmentation advantages. These successive

  8. Patterns of Stem Cell Divisions Contribute to Plant Longevity.

    PubMed

    Burian, Agata; Barbier de Reuille, Pierre; Kuhlemeier, Cris

    2016-06-01

    The lifespan of plants ranges from a few weeks in annuals to thousands of years in trees. It is hard to explain such extreme longevity considering that DNA replication errors inevitably cause mutations. Without purging through meiotic recombination, the accumulation of somatic mutations will eventually result in mutational meltdown, a phenomenon known as Muller's ratchet. Nevertheless, the lifespan of trees is limited more often by incidental disease or structural damage than by genetic aging. The key determinants of tree architecture are the axillary meristems, which form in the axils of leaves and grow out to form branches. The number of branches is low in annual plants, but in perennial plants iterative branching can result in thousands of terminal branches. Here, we use stem cell ablation and quantitative cell-lineage analysis to show that axillary meristems are set aside early, analogous to the metazoan germline. While neighboring cells divide vigorously, axillary meristem precursors maintain a quiescent state, with only 7-9 cell divisions occurring between the apical and axillary meristem. During iterative branching, the number of branches increases exponentially, while the number of cell divisions increases linearly. Moreover, computational modeling shows that stem cell arrangement and positioning of axillary meristems distribute somatic mutations around the main shoot, preventing their fixation and maximizing genetic heterogeneity. These features slow down Muller's ratchet and thereby extend lifespan. PMID:27161504

  9. How PI3K-derived lipids control cell division

    PubMed Central

    Campa, Carlo C.; Martini, Miriam; De Santis, Maria C.; Hirsch, Emilio

    2015-01-01

    To succeed in cell division, intense cytoskeletal and membrane remodeling are required to allow accurate chromosome segregation and cytoplasm partitioning. Spatial restriction of the actin dynamics and vesicle trafficking define the cell symmetry and equivalent membrane scission events, respectively. Protein complexes coordinating mitosis are recruited to membrane microdomains characterized by the presence of the phosphatidylinositol lipid members (PtdIns), like PtdIns(3,4,5)P3,PtdIns(4,5)P2, and PtdIns(3)P. These PtdIns represent a minor component of cell membranes, defining membrane domain identity, ultimately controlling cytoskeleton and membrane dynamics during mitosis. The coordinated presence of PtdIns(3,4,5)P3 at the cell poles and PtdIns(4,5)P2 at the cleavage furrow controls the polarity of the actin cytoskeleton leading to symmetrical cell division. In the endosomal compartment, the trafficking of PtdIns(3)P positive vesicles allows the recruitment of the protein machinery required for the abscission. PMID:26484344

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

    PubMed Central

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

    2015-01-01

    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. PMID:26582817

  11. 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.

  12. 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. PMID:25784047

  13. Asymmetric Cell Division in T Lymphocyte Fate Diversification.

    PubMed

    Arsenio, Janilyn; Metz, Patrick J; Chang, John T

    2015-11-01

    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

  14. Correlation between cationic lipid-based transfection and cell division.

    PubMed

    Kirchenbuechler, Inka; Kirchenbuechler, David; Elbaum, Michael

    2016-07-01

    We evaluate the temporal relation between protein expression by cationic lipid-mediated transfection and cell division using time lapse fluorescence microscopy. Detailed image analysis provides new insights on the single cell level while simultaneously achieving appropriate statistics. Earlier evidence by less direct methods such as flow cytometry indicates a primary route for transfection involving nuclear envelope breakdown, but also suggests the existence of a pathway independent of mitosis. We confirm and quantify both mechanisms. We found the timing for successful transfection to be unexpectedly flexible, contrary to assertions of a narrow time window. Specifically, cells dividing more than 24h after exposure to the transfection medium express the probed protein at a comparable level to cells in a mitotic state during or shortly after transfection. This finding can have a profound impact on the guidance and development of non-viral gene delivery materials. PMID:25556666

  15. The Cell Nucleus in Physiological and Experimentally Induced Hypometabolism

    NASA Astrophysics Data System (ADS)

    Malatesta, M.

    The main problem for manned space mission is, at present, represented by the mass penalty associated to the human presence. An efficient approach could be the induction of a hypometabolic stasis in the astronauts, thus drastically reducing the physical and psychological requirements of the crew. On the other hand, in the wild, a reduction in resource consumptions physiologi- cally occurs in certain animals which periodically enter hibernation, a hypometabolic state in which both the energy need and energy offer are kept at a minimum. During the last twelve years, we have been studying different tissues of hibernating dormice, with the aim of analyzing their features during the euthermia -hibernation-arousal cycle as well as getting insight into the mechanisms allowing adaptation to hypometabolism. We paid particular attention to the cell nucleus, as it is the site of chief metabolic functions, such as DNA replication and RNA transcription. Our observations revealed no significant modification in the basic features of cell nuclei during hibernation; however, the cell nuclei of hibernating dormice showed unusual nuclear bodies containing molecules involved in RNA pathways. Therefore, we supposed that they could represent storage/assembly sites of several factors for processing some RNA which could be slowly synthesised during hibernation and rapidly and abundantly released in early arousal in order to meet the increased metabolic needs of the cell. The nucleolus also underwent structural and molecular modifications during hibernation, maybe to continue important nucleolar functions, or, alternatively, permit a most efficient reactivation upon arousal. On the basis of the observations made in vivo , we recently tried to experimentally induce a reversible hypometabolic state in in vitro models, using cell lines derived from hibernating and non-hibernating species. By administering the synthetic opioid DADLE, we could significantly reduce both RNA transcrip- tion and

  16. Thermodynamic pathways to genome spatial organization in the cell nucleus.

    PubMed

    Nicodemi, Mario; Prisco, Antonella

    2009-03-18

    The architecture of the eukaryotic genome is characterized by a high degree of spatial organization. Chromosomes occupy preferred territories correlated to their state of activity and, yet, displace their genes to interact with remote sites in complex patterns requiring the orchestration of a huge number of DNA loci and molecular regulators. Far from random, this organization serves crucial functional purposes, but its governing principles remain elusive. By computer simulations of a statistical mechanics model, we show how architectural patterns spontaneously arise from the physical interaction between soluble binding molecules and chromosomes via collective thermodynamics mechanisms. Chromosomes colocalize, loops and territories form, and find their relative positions as stable thermodynamic states. These are selected by thermodynamic switches, which are regulated by concentrations/affinity of soluble mediators and by number/location of their attachment sites along chromosomes. Our thermodynamic switch model of nuclear architecture, thus, explains on quantitative grounds how well-known cell strategies of upregulation of DNA binding proteins or modification of chromatin structure can dynamically shape the organization of the nucleus. PMID:19289043

  17. Mathematical model of the cell division cycle of fission yeast.

    PubMed

    Novak, Bela; Pataki, Zsuzsa; Ciliberto, Andrea; Tyson, John J.

    2001-03-01

    Much is known about the genes and proteins controlling the cell cycle of fission yeast. Can these molecular components be spun together into a consistent mechanism that accounts for the observed behavior of growth and division in fission yeast cells? To answer this question, we propose a mechanism for the control system, convert it into a set of 14 differential and algebraic equations, study these equations by numerical simulation and bifurcation theory, and compare our results to the physiology of wild-type and mutant cells. In wild-type cells, progress through the cell cycle (G1-->S-->G2-->M) is related to cyclic progression around a hysteresis loop, driven by cell growth and chromosome alignment on the metaphase plate. However, the control system operates much differently in double-mutant cells, wee1(-) cdc25Delta, which are defective in progress through the latter half of the cell cycle (G2 and M phases). These cells exhibit "quantized" cycles (interdivision times clustering around 90, 160, and 230 min). We show that these quantized cycles are associated with a supercritical Hopf bifurcation in the mechanism, when the wee1 and cdc25 genes are disabled. (c) 2001 American Institute of Physics. PMID:12779461

  18. The Cell Birth Marker BrdU Does Not Affect Recruitment of Subsequent Cell Divisions in the Adult Avian Brain

    PubMed Central

    Cattan, Anat

    2015-01-01

    BrdU is commonly used to quantify neurogenesis but also causes mutation and has mitogenic, transcriptional, and translational effects. In mammalian studies, attention had been given to its dosage, but in birds such examination was not conducted. Our previous study suggested that BrdU might affect subsequent cell divisions and neuronal recruitment in the brain. Furthermore, this effect seemed to increase with time from treatment. Accordingly, we examined whether BrdU might alter neurogenesis in the adult avian brain. We compared recruitment of [3H]-thymidine+ neurons in brains of zebra finches (Taeniopygia guttata) when no BrdU was involved and when BrdU was given 1 or 3 months prior to [3H]-thymidine. In nidopallium caudale, HVC, and hippocampus, no differences were found between groups in densities and percentages of [3H]-thymidine+ neurons. The number of silver grains per [3H]-thymidine+ neuronal nucleus and their distribution were similar across groups. Additionally, time did not affect the results. The results indicate that the commonly used dosage of BrdU in birds has no long-term effects on subsequent cell divisions and neuronal recruitment. This conclusion is also important in neuronal replacement experiments, where BrdU and another cell birth marker are given, with relatively long intervals between them. PMID:25759813

  19. The cell birth marker BrdU does not affect recruitment of subsequent cell divisions in the adult avian brain.

    PubMed

    Cattan, Anat; Ayali, Amir; Barnea, Anat

    2015-01-01

    BrdU is commonly used to quantify neurogenesis but also causes mutation and has mitogenic, transcriptional, and translational effects. In mammalian studies, attention had been given to its dosage, but in birds such examination was not conducted. Our previous study suggested that BrdU might affect subsequent cell divisions and neuronal recruitment in the brain. Furthermore, this effect seemed to increase with time from treatment. Accordingly, we examined whether BrdU might alter neurogenesis in the adult avian brain. We compared recruitment of [(3)H]-thymidine(+) neurons in brains of zebra finches (Taeniopygia guttata) when no BrdU was involved and when BrdU was given 1 or 3 months prior to [(3)H]-thymidine. In nidopallium caudale, HVC, and hippocampus, no differences were found between groups in densities and percentages of [(3)H]-thymidine(+) neurons. The number of silver grains per [(3)H]-thymidine(+) neuronal nucleus and their distribution were similar across groups. Additionally, time did not affect the results. The results indicate that the commonly used dosage of BrdU in birds has no long-term effects on subsequent cell divisions and neuronal recruitment. This conclusion is also important in neuronal replacement experiments, where BrdU and another cell birth marker are given, with relatively long intervals between them. PMID:25759813

  20. Endopolyploidy in irradiated p53-deficient tumour cell lines: Persistence of cell division activity in giant cells expressing Aurora B- kinase

    PubMed Central

    Erenpreisa, Jekaterina; Ivanov, Andrei; Wheatley, Sally P; Kosmacek, Elizabeth A; Ianzini, Fiorenza; Anisimov, Alim P; Mackey, Michael; Davis, Paul J; Plakhins, Grigorijs; Illidge, Timothy M

    2008-01-01

    Recent findings including computerized live imaging suggest that polyploidy cells transiently emerging after severe genotoxic stress (and named ‘endopolyploid cells’) may have a role in tumour regrowth after anti-cancer treatment. Until now, mostly the factors enabling metaphase were studied in them. Here we investigate the mitotic activities and the role of Aurora B, in view of potential de-polyploidisation of these cells, because Aurora B- kinase is responsible for coordination and completion of mitosis. We observed that endopolyploid giant cells are formed in irradiated p53 tumours in several ways: (1) by division/fusion of daughter cells creating early multi-nucleated cells; (2) by asynchronous division/fusion of sub-nuclei of these multinucleated cells; (3) by a series of polyploidising mitoses reverting replicative interphase from aborted metaphase and forming giant cells with a single nucleus; (4) by micronucleation of arrested metaphases enclosing genome fragments; or (5) by incomplete division in the multipolar mitoses forming late multi-nucleated giant cells. We also observed that these activities are able to release para-diploid cells, although they do so infrequently. Although after a substantial delay, apoptosis typically occurs in these cells, we also found that roughly 2% of endopolyploid cells evade apoptosis and senescence arrest and continue mitotic activities. In this article we describe that catalytically active aurora B-kinase is expressed in the nuclei of many interphase endopolyploid cells, as well as being present at the centromeres, mitotic spindle and cleavage furrow during their mitotic efforts. The totally micronucleated giant cells (containing subgenomic fragments in multiple micronuclei) represented the only minor fraction, which failed to undergo mitosis and Aurora B was absent from it. These observations suggest that most endopolyploid tumour cells are not reproductively inert and that aurora B may contribute to the establishment

  1. Chromokinesin: Kinesin superfamily regulating cell division through chromosome and spindle.

    PubMed

    Zhong, Ai; Tan, Fu-Qing; Yang, Wan-Xi

    2016-09-01

    Material transportation is essential for appropriate cellular morphology and functions, especially during cell division. As a motor protein moving along microtubules, kinesin has several intracellular functions. Many kinesins play important roles in chromosome condensation and separation and spindle organization during the cell cycle. Some of them even can directly bind to chromosomes, as a result, these proteins are called chromokinesins. Kinesin-4 and kinesin-10 family are two major families of chromokinesin and many members can regulate some processes, both in mitosis and meiosis. Their functions have been widely studied. Here, we summarize current knowledge about known chromokinesins and introduce their intracellular features in accordance with different families. Furthermore, we have also introduced some new-found but unconfirmed kinesins which may have a relationship with chromosomes or the cell cycle. PMID:27196062

  2. Huntingtin regulates mammary stem cell division and differentiation.

    PubMed

    Elias, Salah; Thion, Morgane S; Yu, Hua; Sousa, Cristovao Marques; Lasgi, Charlène; Morin, Xavier; Humbert, Sandrine

    2014-04-01

    Little is known about the mechanisms of mitotic spindle orientation during mammary gland morphogenesis. Here, we report the presence of huntingtin, the protein mutated in Huntington's disease, in mouse mammary basal and luminal cells throughout mammogenesis. Keratin 5-driven depletion of huntingtin results in a decreased pool and specification of basal and luminal progenitors, and altered mammary morphogenesis. Analysis of mitosis in huntingtin-depleted basal progenitors reveals mitotic spindle misorientation. In mammary cell culture, huntingtin regulates spindle orientation in a dynein-dependent manner. Huntingtin is targeted to spindle poles through its interaction with dynein and promotes the accumulation of NUMA and LGN. Huntingtin is also essential for the cortical localization of dynein, dynactin, NUMA, and LGN by regulating their kinesin 1-dependent trafficking along astral microtubules. We thus suggest that huntingtin is a component of the pathway regulating the orientation of mammary stem cell division, with potential implications for their self-renewal and differentiation properties. PMID:24749073

  3. 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

  4. Single granule cells excite Golgi cells and evoke feedback inhibition in the cochlear nucleus.

    PubMed

    Yaeger, Daniel B; Trussell, Laurence O

    2015-03-18

    In cerebellum-like circuits, synapses from thousands of granule cells converge onto principal cells. This fact, combined with theoretical considerations, has led to the concept that granule cells encode afferent input as a population and that spiking in individual granule cells is relatively unimportant. However, granule cells also provide excitatory input to Golgi cells, each of which provide inhibition to hundreds of granule cells. We investigated whether spiking in individual granule cells could recruit Golgi cells and thereby trigger widespread inhibition in slices of mouse cochlear nucleus. Using paired whole-cell patch-clamp recordings, trains of action potentials at 100 Hz in single granule cells was sufficient to evoke spikes in Golgi cells in ∼40% of paired granule-to-Golgi cell recordings. High-frequency spiking in single granule cells evoked IPSCs in ∼5% of neighboring granule cells, indicating that bursts of activity in single granule cells can recruit feedback inhibition from Golgi cells. Moreover, IPSPs mediated by single Golgi cell action potentials paused granule cell firing, suggesting that inhibitory events recruited by activity in single granule cells were able to control granule cell firing. These results suggest a previously unappreciated relationship between population coding and bursting in single granule cells by which spiking in a small number of granule cells may have an impact on the activity of a much larger number of granule cells. PMID:25788690

  5. Cell Division Resets Polarity and Motility for the Bacterium Myxococcus xanthus

    PubMed Central

    Harvey, Cameron W.; Madukoma, Chinedu S.; Mahserejian, Shant; Alber, Mark S.

    2014-01-01

    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. PMID:25157084

  6. Quantitative measures to reveal coordinated cytoskeleton-nucleus reorganization during in vitro invasion of cancer cells

    NASA Astrophysics Data System (ADS)

    Dvir, Liron; Nissim, Ronen; Alvarez-Elizondo, Martha B.; Weihs, Daphne

    2015-04-01

    Metastasis formation is a major cause of mortality in cancer patients and includes tumor cell relocation to distant organs. A metastatic cell invades through other cells and extracellular matrix by biochemical attachment and mechanical force application. Force is used to move on or through a 2- or 3-dimensional (3D) environment, respectively, or to penetrate a 2D substrate. We have previously shown that even when a gel substrate is impenetrable, metastatic breast cancer cells can still indent it by applying force. Cells typically apply force through the acto-myosin network, which is mechanically connected to the nucleus. We develop a 3D image-analysis to reveal relative locations of the cell elements, and show that as cells apply force to the gel, a coordinated process occurs that involves cytoskeletal remodeling and repositioning of the nucleus. Our approach shows that the actin and microtubules reorganize in the cell, bringing the actin to the leading edge of the cell. In parallel, the nucleus is transported behind the actin, likely by the cytoskeleton, into the indentation dimple formed in the gel. The nucleus volume below the gel surface correlates with indentation depth, when metastatic breast cancer cells indent gels deeply. However, the nucleus always remains above the gel in benign cells, even when small indentations are observed. Determining mechanical processes during metastatic cell invasion can reveal how cells disseminate in the body and can uncover targets for diagnosis and treatment.

  7. Effects of brevetoxins on murine myeloma SP2/O cells: Aberrant cellular division

    USGS Publications Warehouse

    Han, T.K.; Derby, M.; Martin, D.F.; Wright, S.D.; Dao, M.L.

    2003-01-01

    Massive deaths of manatees (Trichechus manatus latirostris) during the red tide seasons have been attributed to brevetoxins produced by the dinoflagellate Karenia brevis (formerly Ptychodiscus breve and Gymnodinium breve). Although these toxins have been found in macrophages and lymphocytes in the lung, liver, and secondary lymphoid tissues of these animals, the molecular mechanisms of brevetoxicosis have not yet been identified. To investigate the effects of brevetoxins on immune cells, a murine myeloma cell line (SP2/O) was used as a model for in vitro studies. By adding brevetoxins to cultures of the SP2/O cells at concentrations ranging from 20 to 600 ng/ml, an apparent increase in proliferation was observed at around 2 hours post challenge as compared to the unchallenged cell cultures. This was followed by a drop in cell number at around 3 hours, suggesting an aberrant effect of brevetoxins on cellular division, the cells generated at 2 hours being apparently short-lived. In situ immunochemical staining of the SP2/O cells at 1 and 2 hour post challenge showed an accumulation of the toxins in the nucleus. A 21-kDa protein was subsequently isolated from the SP2/O cells as having brevetoxin-binding properties, and immunologically identified as p21, a nuclear factor known to down-regulate cellular proliferation through inhibition of cyclin-dependent kinases. These data are the first on a possible effect of brevetoxins on the cell cycle via binding to p21, a phenomenon that needs to be further investigated and validated in normal immune cells.

  8. Effects of brevetoxins on murine myeloma SP2/O cells: aberrant cellular division.

    PubMed

    Han, Thomas K; Derby, Melissa; Martin, Dean F; Wright, Scott D; Dao, My Lien

    2003-01-01

    Massive deaths of manatees (Trichechus manatus latirostris) during the red tide seasons have been attributed to brevetoxins produced by the dinoflagellate Karenia brevis (formerly Ptychodiscus breve and Gymnodinium breve). Although these toxins have been found in macrophages and lymphocytes in the lung, liver, and secondary lymphoid tissues of these animals, the molecular mechanisms of brevetoxicosis have not yet been identified. To investigate the effects of brevetoxins on immune cells, a murine myeloma cell line (SP2/O) was used as a model for in vitro studies. By adding brevetoxins to cultures of the SP2/O cells at concentrations ranging from 20 to 600 ng/ml, an apparent increase in proliferation was observed at around 2 hours post challenge as compared to the unchallenged cell cultures. This was followed by a drop in cell number at around 3 hours, suggesting an aberrant effect of brevetoxins on cellular division, the cells generated at 2 hours being apparently short-lived. In situ immunochemical staining of the SP2/O cells at 1 and 2 hour post challenge showed an accumulation of the toxins in the nucleus. A 21-kDa protein was subsequently isolated from the SP2/O cells as having brevetoxin-binding properties, and immunologically identified as p21, a nuclear factor known to down-regulate cellular proliferation through inhibition of cyclin-dependent kinases. These data are the first on a possible effect of brevetoxins on the cell cycle via binding to p21, a phenomenon that needs to be further investigated and validated in normal immune cells. PMID:12745987

  9. A MECHANISM FOR ASYMMETRIC CELL DIVISION RESULTING IN PROLIFERATIVE ASYNCHRONICITY

    PubMed Central

    Dey-Guha, Ipsita; Alves, Cleidson P.; Yeh, Albert C.; Salony; Sole, Xavier; Darp, Revati; Ramaswamy, Sridhar

    2014-01-01

    All cancers contain an admixture of rapidly and slowly proliferating cancer cells. This proliferative heterogeneity complicates the diagnosis and treatment of cancer patients because slow proliferators are hard to eradicate, can be difficult to detect, and may cause disease relapse sometimes years after apparently curative treatment. While clonal selection theory explains the presence and evolution of rapid proliferators within cancer cell populations, the circumstances and molecular details of how slow proliferators are produced is not well understood. Here, a β1-integrin/FAK/mTORC2/AKT1-associated signaling pathway is discovered that can be triggered for rapidly proliferating cancer cells to undergo asymmetric cell division and produce slowly proliferating AKT1low daughter cells. In addition, evidence indicates that the proliferative output of this signaling cascade involves a proteasome-dependent degradation process mediated by the E3 ubiquitin ligase TTC3. These findings reveal that proliferative heterogeneity within cancer cell populations, in part, is produced through a targetable signaling mechanism, with potential implications for understanding cancer progression, dormancy, and therapeutic resistance. PMID:25582703

  10. Quantitative analysis of protein dynamics during asymmetric cell division.

    PubMed

    Mayer, Bernd; Emery, Gregory; Berdnik, Daniela; Wirtz-Peitz, Frederik; Knoblich, Juergen A

    2005-10-25

    In dividing Drosophila sensory organ precursor (SOP) cells, the fate determinant Numb and its associated adaptor protein Pon localize asymmetrically and segregate into the anterior daughter cell, where Numb influences cell fate by repressing Notch signaling. Asymmetric localization of both proteins requires the protein kinase aPKC and its substrate Lethal (2) giant larvae (Lgl). Because both Numb and Pon localization require actin and myosin, lateral transport along the cell cortex has been proposed as a possible mechanism for their asymmetric distribution. Here, we use quantitative live analysis of GFP-Pon and Numb-GFP fluorescence and fluorescence recovery after photobleaching (FRAP) to characterize the dynamics of Numb and Pon localization during SOP division. We demonstrate that Numb and Pon rapidly exchange between a cytoplasmic pool and the cell cortex and that preferential recruitment from the cytoplasm is responsible for their asymmetric distribution during mitosis. Expression of a constitutively active form of aPKC impairs membrane recruitment of GFP-Pon. This defect can be rescued by coexpression of nonphosphorylatable Lgl, indicating that Lgl is the main target of aPKC. We propose that a high-affinity binding site is asymmetrically distributed by aPKC and Lgl and is responsible for asymmetric localization of cell-fate determinants during mitosis. PMID:16243032

  11. A factor that positively regulates cell division by activating transcription of the major cluster of essential cell division genes of Escherichia coli.

    PubMed Central

    Wang, X D; de Boer, P A; Rothfield, L I

    1991-01-01

    Cell division in Escherichia coli requires the products of the ftsQ, ftsA and ftsZ genes. It is not known how the cell regulates the cellular concentrations of these essential elements of the division system. We describe here a factor that activates cell division by specifically increasing transcription from one of the two promoters that lie immediately upstream of the ftsQAZ gene cluster. The trans-acting factor is the product of the sdiA gene, which was isolated on the basis of its ability to suppress the division inhibitory effect of the MinC/MinD division inhibitor. In addition, the sdiA gene product suppressed the action of other chromosomally encoded division inhibitors, induced minicell formation in wild type cells, and restored division activity to an ftsZ temperature-sensitive mutant grown under nonpermissive conditions. All of these properties were explained by the ability of the sdiA gene product specifically to increase transcription of the ftsQAZ gene cluster, resulting in an increase in cellular concentration of the FtsZ protein. The sdiA gene product is the first factor thus far identified that specifically regulates expression of this key group of cell division genes. Images PMID:1915297

  12. Internal dynamics of a living cell nucleus investigated by dynamic light scattering

    NASA Astrophysics Data System (ADS)

    Suissa, M.; Place, C.; Goillot, E.; Freyssingeas, E.

    2008-08-01

    Recent progresses in cellular biology have shown that the nucleus of a living cell is a structured integration of many functional domains with a complex spatial organization. This organization, as well as molecular and biochemical processes, is time regulated. In the past years many investigations have been performed using fluorescent microscopy techniques to study the internal dynamics of the nucleus of a living cell. These investigations, however, have never focussed on the global internal dynamics of the nucleus, which is still unknown. In this article we present an original light scattering experimental device that we built to investigate this dynamics during biological processes. By means of this experimental set-up, we investigated the global dynamics of the nucleus of a living cell treated with a DNA replication inhibitor. This dynamics presents different and independent kinds of relaxation well separated in time that vary as a function of the cell cycle phases.

  13. 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

  14. 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.

  15. 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  17. Construction of synthetic nucleoli and what it tells us about propagation of sub-nuclear domains through cell division

    PubMed Central

    Grob, Alice; McStay, Brian

    2014-01-01

    The cell nucleus is functionally compartmentalized into numerous membraneless and dynamic, yet defined, bodies. The cell cycle inheritance of these nuclear bodies (NBs) is poorly understood at the molecular level. In higher eukaryotes, their propagation is challenged by cell division through an “open” mitosis, where the nuclear envelope disassembles along with most NBs. A deeper understanding of the mechanisms involved can be achieved using the engineering principles of synthetic biology to construct artificial NBs. Successful biogenesis of such synthetic NBs demonstrates knowledge of the basic mechanisms involved. Application of this approach to the nucleolus, a paradigm of nuclear organization, has highlighted a key role for mitotic bookmarking in the cell cycle propagation of NBs. PMID:25486191

  18. 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.

  19. 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. PMID:26696987

  20. 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

  1. 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).

  2. Centromere Identity, Function, and Epigenetic Propagation Across Cell Divisions

    PubMed Central

    Black, Ben E.; Jansen, Lars E.T.; Foltz, Daniel R.; Cleveland, Don W.

    2011-01-01

    The key to understanding centromere identity is likely to lie in the chromatin containing the histone H3 variant, CENP-A. CENP-A is the prime candidate to carry the epigenetic information that specifies the chromosomal location of the centromere in nearly all eukaryotic species, raising questions fundamental to understanding chromosome inheritance: How is the epigenetic centromere mark propagated? What physical properties of CENP-A-containing complexes are important for epigenetically marking centromeres? What are the molecules that recognize centromeric chromatin and serve as the foundation for the mitotic kinetochore? We discuss recent advances from our research groups that have yielded substantial insight into these questions and present our current understanding of the centromere. Future work promises an understanding of the molecular processes that confer fidelity to genome transmission at cell division. PMID:21467140

  3. Emergence of homeostatic epithelial packing and stress dissipation through divisions oriented along the long cell axis

    PubMed Central

    Wyatt, Tom P. J.; Harris, Andrew R.; Lam, Maxine; Cheng, Qian; Bellis, Julien; Dimitracopoulos, Andrea; Kabla, Alexandre J.; Charras, Guillaume T.; Baum, Buzz

    2015-01-01

    Cell division plays an important role in animal tissue morphogenesis, which depends, critically, on the orientation of divisions. In isolated adherent cells, the orientation of mitotic spindles is sensitive to interphase cell shape and the direction of extrinsic mechanical forces. In epithelia, the relative importance of these two factors is challenging to assess. To do this, we used suspended monolayers devoid of ECM, where divisions become oriented following a stretch, allowing the regulation and function of epithelial division orientation in stress relaxation to be characterized. Using this system, we found that divisions align better with the long, interphase cell axis than with the monolayer stress axis. Nevertheless, because the application of stretch induces a global realignment of interphase long axes along the direction of extension, this is sufficient to bias the orientation of divisions in the direction of stretch. Each division redistributes the mother cell mass along the axis of division. Thus, the global bias in division orientation enables cells to act collectively to redistribute mass along the axis of stretch, helping to return the monolayer to its resting state. Further, this behavior could be quantitatively reproduced using a model designed to assess the impact of autonomous changes in mitotic cell mechanics within a stretched monolayer. In summary, the propensity of cells to divide along their long axis preserves epithelial homeostasis by facilitating both stress relaxation and isotropic growth without the need for cells to read or transduce mechanical signals. PMID:25908119

  4. RETINOBLASTOMA RELATED1 Regulates Asymmetric Cell Divisions in Arabidopsis[C][W][OA

    PubMed Central

    Weimer, Annika K.; Nowack, Moritz K.; Bouyer, Daniel; Zhao, Xin’Ai; Harashima, Hirofumi; Naseer, Sadaf; De Winter, Freya; Dissmeyer, Nico; Geldner, Niko; Schnittger, Arp

    2012-01-01

    Formative, also called asymmetric, cell divisions produce daughter cells with different identities. Like other divisions, formative divisions rely first of all on the cell cycle machinery with centrally acting cyclin-dependent kinases (CDKs) and their cyclin partners to control progression through the cell cycle. However, it is still largely obscure how developmental cues are translated at the cellular level to promote asymmetric divisions. Here, we show that formative divisions in the shoot and root of the flowering plant Arabidopsis thaliana are controlled by a common mechanism that relies on the activity level of the Cdk1 homolog CDKA;1, with medium levels being sufficient for symmetric divisions but high levels being required for formative divisions. We reveal that the function of CDKA;1 in asymmetric cell divisions operates through a transcriptional regulation system that is mediated by the Arabidopsis Retinoblastoma homolog RBR1. RBR1 regulates not only cell cycle genes, but also, independent of the cell cycle transcription factor E2F, genes required for formative divisions and cell fate acquisition, thus directly linking cell proliferation with differentiation. This mechanism allows the implementation of spatial information, in the form of high kinase activity, with intracellular gating of developmental decisions. PMID:23104828

  5. Radioisotopic Method for Measuring Cell Division Rates of Individual Species of Diatoms from Natural Populations †

    PubMed Central

    Rivkin, Richard B.

    1986-01-01

    Silicon is an essential element for diatom frustule synthesis and is usually taken up only by dividing cells. With 68Ge, a radioactive analog of Si, the cell cycle marker event of frustule formation was identified for individual species of diatom. The frequency of cells within a population undergoing this division event was estimated, and the cell division rate was calculated. In laboratory cultures, these rates of cell division and those calculated from changes in cell numbers were similar. By dual labeling with 68Ge(OH)4 and NaH14CO3, rates of cell division and photosynthesis were coincidently measured for diatoms both in laboratory cultures and when isolated from natural populations in estuarine, offshore, and polar environments. These techniques permit the coupling between photosynthesis and cell division to be examined in situ for individual species of diatom. PMID:16347039

  6. Systematic study of cell isolation from bovine nucleus pulposus: Improving cell yield and experiment reliability.

    PubMed

    Lee, Juliana T Y; Cheung, Kenneth M C; Leung, Victor Y L

    2015-12-01

    Differences in matrix compositions in human nucleus pulposus (NP) clinical samples demand different cell isolation protocols for optimal results but there is no clear guide about this to date. Sub-optimal protocols may result in low cell yield, limited reliability of results or even failure of experiments. Cell yield, viability and attachment of cells isolated from bovine NP tissue with different protocols were estimated by cell counting, Trypan blue staining and cell culturing respectively. RNA was extracted from isolated cells and quantified by Nanodrop spectrometry and RT-qPCR. Higher collagenase concentration, longer digestion duration and pronase pre-treatment increased the cell yield. Cell viability remained high (<5% dead cells) even after 0.2% collagenase treatment for overnight. NP cells remained to have high ACAN, COL2A1, CDH2, KRT18, and KRT19 expression compared to muscle cells for different cell isolation conditions tested. Digestion by collagenase alone without the use of pronase could isolate cells from human degenerated NP tissue but clusters of cells were observed. We suggest the use of the disappearance of tissue as an indirect measure of cells released. This study provides a guide for researchers to decide the parameters involved in NP cell isolation for optimal outcome. PMID:26036782

  7. A DNA damage-induced, SOS-independent checkpoint regulates cell division in Caulobacter crescentus.

    PubMed

    Modell, Joshua W; Kambara, Tracy K; Perchuk, Barrett S; Laub, Michael T

    2014-10-01

    Cells must coordinate DNA replication with cell division, especially during episodes of DNA damage. The paradigm for cell division control following DNA damage in bacteria involves the SOS response where cleavage of the transcriptional repressor LexA induces a division inhibitor. However, in Caulobacter crescentus, cells lacking the primary SOS-regulated inhibitor, sidA, can often still delay division post-damage. Here we identify didA, a second cell division inhibitor that is induced by DNA damage, but in an SOS-independent manner. Together, DidA and SidA inhibit division, such that cells lacking both inhibitors divide prematurely following DNA damage, with lethal consequences. We show that DidA does not disrupt assembly of the division machinery and instead binds the essential division protein FtsN to block cytokinesis. Intriguingly, mutations in FtsW and FtsI, which drive the synthesis of septal cell wall material, can suppress the activity of both SidA and DidA, likely by causing the FtsW/I/N complex to hyperactively initiate cell division. Finally, we identify a transcription factor, DriD, that drives the SOS-independent transcription of didA following DNA damage. PMID:25350732

  8. A DNA Damage-Induced, SOS-Independent Checkpoint Regulates Cell Division in Caulobacter crescentus

    PubMed Central

    Modell, Joshua W.; Kambara, Tracy K.; Perchuk, Barrett S.; Laub, Michael T.

    2014-01-01

    Cells must coordinate DNA replication with cell division, especially during episodes of DNA damage. The paradigm for cell division control following DNA damage in bacteria involves the SOS response where cleavage of the transcriptional repressor LexA induces a division inhibitor. However, in Caulobacter crescentus, cells lacking the primary SOS-regulated inhibitor, sidA, can often still delay division post-damage. Here we identify didA, a second cell division inhibitor that is induced by DNA damage, but in an SOS-independent manner. Together, DidA and SidA inhibit division, such that cells lacking both inhibitors divide prematurely following DNA damage, with lethal consequences. We show that DidA does not disrupt assembly of the division machinery and instead binds the essential division protein FtsN to block cytokinesis. Intriguingly, mutations in FtsW and FtsI, which drive the synthesis of septal cell wall material, can suppress the activity of both SidA and DidA, likely by causing the FtsW/I/N complex to hyperactively initiate cell division. Finally, we identify a transcription factor, DriD, that drives the SOS-independent transcription of didA following DNA damage. PMID:25350732

  9. 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

  10. Regulation of the Cell Division Cycle in Trypanosoma brucei

    PubMed Central

    2012-01-01

    The cell division cycle is tightly regulated by the activation and inactivation of a series of proteins that control the replication and segregation of organelles to the daughter cells. During the past decade, we have witnessed significant advances in our understanding of the cell cycle in Trypanosoma brucei and how the cycle is regulated by various regulatory proteins. However, many other regulators, especially those unique to trypanosomes, remain to be identified, and we are just beginning to delineate the signaling pathways that drive the transitions through different cell cycle stages, such as the G1/S transition, G2/M transition, and mitosis-cytokinesis transition. Trypanosomes appear to employ both evolutionarily conserved and trypanosome-specific molecules to regulate the various stages of its cell cycle, including DNA replication initiation, spindle assembly, chromosome segregation, and cytokinesis initiation and completion. Strikingly, trypanosomes lack some crucial regulators that are well conserved across evolution, such as Cdc6 and Cdt1, which are involved in DNA replication licensing, the spindle motor kinesin-5, which is required for spindle assembly, the central spindlin complex, which has been implicated in cytokinesis initiation, and the actomyosin contractile ring, which is located at the cleavage furrow. Conversely, trypanosomes possess certain regulators, such as cyclins, cyclin-dependent kinases, and mitotic centromere-associated kinesins, that are greatly expanded and likely play diverse cellular functions. Overall, trypanosomes apparently have integrated unique regulators into the evolutionarily conserved pathways to compensate for the absence of those conserved molecules and, additionally, have evolved certain cell cycle regulatory pathways that are either different from its human host or distinct between its own life cycle forms. PMID:22865501

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

    PubMed

    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. PMID:27575162

  12. 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.

  13. In situ label-free cell viability assessment of nucleus pulposus tissue.

    PubMed

    Dittmar, Roman; van Dijk, Bart G M; van Zandvoort, Marc A M J; Ito, Keita

    2014-04-01

    Regenerative medicine approaches aiming at treating degenerating intervertebral discs, a major cause of back pain, are increasingly tested in ex-vivo disc explant models mimicking in-vivo conditions. For assessing the efficacy of regenerative therapies, cell viability is commonly measured requiring specific labels to stain cells. Here, we demonstrate and evaluate how cellular auto-fluorescence can be utilized to non-invasively assess viability in disc tissue in-situ using label-free two-photon microscopy. Live and dead bovine disc cells (0% and 100% cell viability) from the nucleus pulposus were seeded into collagen gels and auto-fluorescence was characterized. Subsequently, nucleus pulposus explants were cultured for 6 days in media with different glucose supplementation (0, 0.25, 0.5, and 1 g/L) to induce different degrees of cell death. Then, samples were split and viability was assessed using label-free two-photon microscopy and conventional staining. Results show that live and dead nucleus pulposus cells systematically emit auto-fluorescent light with distinct characteristics. Cell viability values obtained with label-free microscopy did not significantly differ from those acquired with staining. In summary, monitoring auto-fluorescence facilitates accurate cell viability assessment in nucleus tissue requiring no additional dyes. Thus, this technique may be suitable for pre-clinical testing of regenerative therapies in nucleus pulposus cultures. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:545-550, 2014. PMID:24391094

  14. Continuous nucleus extraction by optically-induced cell lysis on a batch-type microfluidic platform.

    PubMed

    Huang, Shih-Hsuan; Hung, Lien-Yu; Lee, Gwo-Bin

    2016-04-12

    The extraction of a cell's nucleus is an essential technique required for a number of procedures, such as disease diagnosis, genetic replication, and animal cloning. However, existing nucleus extraction techniques are relatively inefficient and labor-intensive. Therefore, this study presents an innovative, microfluidics-based approach featuring optically-induced cell lysis (OICL) for nucleus extraction and collection in an automatic format. In comparison to previous micro-devices designed for nucleus extraction, the new OICL device designed herein is superior in terms of flexibility, selectivity, and efficiency. To facilitate this OICL module for continuous nucleus extraction, we further integrated an optically-induced dielectrophoresis (ODEP) module with the OICL device within the microfluidic chip. This on-chip integration circumvents the need for highly trained personnel and expensive, cumbersome equipment. Specifically, this microfluidic system automates four steps by 1) automatically focusing and transporting cells, 2) releasing the nuclei on the OICL module, 3) isolating the nuclei on the ODEP module, and 4) collecting the nuclei in the outlet chamber. The efficiency of cell membrane lysis and the ODEP nucleus separation was measured to be 78.04 ± 5.70% and 80.90 ± 5.98%, respectively, leading to an overall nucleus extraction efficiency of 58.21 ± 2.21%. These results demonstrate that this microfluidics-based system can successfully perform nucleus extraction, and the integrated platform is therefore promising in cell fusion technology with the goal of achieving genetic replication, or even animal cloning, in the near future. PMID:26987542

  15. 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.

  16. Analytical model for macromolecular partitioning during yeast cell division

    PubMed Central

    2014-01-01

    Background Asymmetric cell division, whereby a parent cell generates two sibling cells with unequal content and thereby distinct fates, is central to cell differentiation, organism development and ageing. Unequal partitioning of the macromolecular content of the parent cell — which includes proteins, DNA, RNA, large proteinaceous assemblies and organelles — can be achieved by both passive (e.g. diffusion, localized retention sites) and active (e.g. motor-driven transport) processes operating in the presence of external polarity cues, internal asymmetries, spontaneous symmetry breaking, or stochastic effects. However, the quantitative contribution of different processes to the partitioning of macromolecular content is difficult to evaluate. Results Here we developed an analytical model that allows rapid quantitative assessment of partitioning as a function of various parameters in the budding yeast Saccharomyces cerevisiae. This model exposes quantitative degeneracies among the physical parameters that govern macromolecular partitioning, and reveals regions of the solution space where diffusion is sufficient to drive asymmetric partitioning and regions where asymmetric partitioning can only be achieved through additional processes such as motor-driven transport. Application of the model to different macromolecular assemblies suggests that partitioning of protein aggregates and episomes, but not prions, is diffusion-limited in yeast, consistent with previous reports. Conclusions In contrast to computationally intensive stochastic simulations of particular scenarios, our analytical model provides an efficient and comprehensive overview of partitioning as a function of global and macromolecule-specific parameters. Identification of quantitative degeneracies among these parameters highlights the importance of their careful measurement for a given macromolecular species in order to understand the dominant processes responsible for its observed partitioning. PMID

  17. Emp is a component of the nuclear matrix of mammalian cells and undergoes dynamic rearrangements during cell division

    SciTech Connect

    Bala, Shashi; Kumar, Ajay; Soni, Shivani; Sinha, Sudha; Hanspal, Manjit . E-mail: manjit.hanspal@tufts.edu

    2006-04-21

    Emp, originally detected in erythroblastic islands, is expressed in numerous cell types and tissues suggesting a functionality not limited to hematopoiesis. To study the function of Emp in non-hematopoietic cells, an epitope-tagged recombinant human Emp was expressed in HEK cells. Preliminary studies revealed that Emp partitioned into both the nuclear and Triton X-100-insoluble cytoskeletal fractions in approximately a 4:1 ratio. In this study, we report investigations of Emp in the nucleus. Sequential extractions of interphase nuclei showed that recombinant Emp was present predominantly in the nuclear matrix. Immunofluorescence microscopy showed that Emp was present in typical nuclear speckles enriched with the spliceosome assembly factor SC35 and partially co-localized with actin staining. Coimmunoprecipitation and GST-pull-down assays confirmed the apparent close association of Emp with nuclear actin. During mitosis, Emp was detected at the mitotic spindle/spindle poles, as well as in the contractile ring during cytokinesis. These results suggest that Emp undergoes dynamic rearrangements within the nuclear architecture that are correlated with cell division.

  18. N-Cadherin-Mediated Signaling Regulates Cell Phenotype for Nucleus Pulposus Cells of the Intervertebral Disc

    PubMed Central

    Hwang, Priscilla Y.; Jing, Liufang; Michael, Keith W.; Richardson, William J.; Chen, Jun; Setton, Lori A.

    2015-01-01

    Juvenile nucleus pulposus (NP) cells of the intervertebral disc (IVD) are large, vacuolated cells that form cell clusters with strong cell–cell interactions. With maturation and aging, NP cells lose their ability to form these cell clusters, with aging-associated changes in NP cell phenotype, morphology, and proteoglycan synthesis that may contribute to IVD degeneration. Therefore, it is important to understand the mechanisms governing juvenile NP cell cluster behavior towards the goal of revealing factors that can promote juvenile, healthy NP cell phenotypes. N-cadherin has been identified as a cell–cell adhesion marker that is present in juvenile NP cells, but disappears with age. The goal of this study was to reveal the importance of N-cadherin in regulating cell–cell interactions in juvenile NP cell cluster formation and test for a regulatory role in maintaining a juvenile NP phenotype in vitro. Juvenile porcine IVD cells, of notochordal origin, were promoted to form cell clusters in vitro, and analyzed for preservation of the juvenile NP phenotype. Additionally, cadherin-blocking experiments were performed to prevent cluster formation in order to study the importance of cluster formation in NP cell signaling. Findings reveal N-cadherin-mediated cell–cell contacts promote cell clustering behavior and regulate NP cell matrix production and preservation of NP-specific markers. Inhibition of N-cadherin-mediated contacts resulted in loss of all features of the juvenile NP cell. These results establish a regulatory role for N-cadherin in juvenile NP cells, and suggest that preservation of the N-cadherin mediated cell–cell contact is important for preserving juvenile NP cell phenotype and morphology. PMID:25848407

  19. The DYRK-family kinase Pom1 phosphorylates the F-BAR protein Cdc15 to prevent division at cell poles

    PubMed Central

    Ullal, Pranav; McDonald, Nathan A.; Chen, Jun-Song; Lo Presti, Libera; Roberts-Galbraith, Rachel H.; Gould, Kathleen L.

    2015-01-01

    Division site positioning is critical for both symmetric and asymmetric cell divisions. In many organisms, positive and negative signals cooperate to position the contractile actin ring for cytokinesis. In rod-shaped fission yeast Schizosaccharomyces pombe cells, division at midcell is achieved through positive Mid1/anillin-dependent signaling emanating from the central nucleus and negative signals from the dual-specificity tyrosine phosphorylation-regulated kinase family kinase Pom1 at the cell poles. In this study, we show that Pom1 directly phosphorylates the F-BAR protein Cdc15, a central component of the cytokinetic ring. Pom1-dependent phosphorylation blocks Cdc15 binding to paxillin Pxl1 and C2 domain protein Fic1 and enhances Cdc15 dynamics. This promotes ring sliding from cell poles, which prevents septum assembly at the ends of cells with a displaced nucleus or lacking Mid1. Pom1 also slows down ring constriction. These results indicate that a strong negative signal from the Pom1 kinase at cell poles converts Cdc15 to its closed state, destabilizes the actomyosin ring, and thus promotes medial septation. PMID:26553932

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

    PubMed Central

    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. PMID:26074904

  1. Control of Asymmetric Cell Divisions during Root Ground Tissue Maturation

    PubMed Central

    Choi, Ji Won; Lim, Jun

    2016-01-01

    Controlling the production of diverse cell/tissue types is essential for the development of multicellular organisms such as animals and plants. The Arabidopsis thaliana root, which contains distinct cells/tissues along longitudinal and radial axes, has served as an elegant model to investigate how genetic programs and environmental signals interact to produce different cell/tissue types. In the root, a series of asymmetric cell divisions (ACDs) give rise to three ground tissue layers at maturity (endodermis, middle cortex, and cortex). Because the middle cortex is formed by a periclinal (parallel to the axis) ACD of the endodermis around 7 to 14 days post-germination, middle cortex formation is used as a parameter to assess maturation of the root ground tissue. Molecular, genetic, and physiological studies have revealed that the control of the timing and extent of middle cortex formation during root maturation relies on the interaction of plant hormones and transcription factors. In particular, abscisic acid and gibberellin act synergistically to regulate the timing and extent of middle cortex formation, unlike their typical antagonism. The SHORT-ROOT, SCARECROW, SCARECROW-LIKE 3, and DELLA transcription factors, all of which belong to the plant-specific GRAS family, play key roles in the regulation of middle cortex formation. Recently, two additional transcription factors, SEUSS and GA- AND ABA-RESPONSIVE ZINC FINGER, have also been characterized during ground tissue maturation. In this review, we provide a detailed account of the regulatory networks that control the timing and extent of middle cortex formation during post-embryonic root development. PMID:27306644

  2. 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…

  3. The Analysis of Cell Cycle, Proliferation, and Asymmetric Cell Division by Imaging Flow Cytometry.

    PubMed

    Filby, Andrew; Day, William; Purewal, Sukhveer; Martinez-Martin, Nuria

    2016-01-01

    Measuring cellular DNA content by conventional flow cytometry (CFC) and fluorescent DNA-binding dyes is a highly robust method for analysing cell cycle distributions within heterogeneous populations. However, any conclusions drawn from single-parameter DNA analysis alone can often be confounded by the asynchronous nature of cell proliferation. We have shown that by combining fluorescent DNA stains with proliferation tracking dyes and antigenic staining for mitotic cells one can elucidate the division history and cell cycle position of any cell within an asynchronously dividing population. Furthermore if one applies this panel to an imaging flow cytometry (IFC) system then the spatial information allows resolution of the four main mitotic phases and the ability to study molecular distributions within these populations. We have employed such an approach to study the prevalence of asymmetric cell division (ACD) within activated immune cells by measuring the distribution of key fate determining molecules across the plane of cytokinesis in a high-throughput, objective, and internally controlled manner. Moreover the ability to perform high-resolution, temporal dissection of the cell division process lends itself perfectly to investigating the influence chemotherapeutic agents exert on the proliferative capacity of transformed cell lines. Here we describe the method in detail and its application to both ACD and general cell cycle analysis. PMID:27460238

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

    PubMed Central

    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. PMID:24949109

  5. Control of cell growth, division and death: information processing in living cells

    PubMed Central

    Tyson, John J.; Novak, Bela

    2014-01-01

    By way of surface receptor molecules and internal surveillance mechanisms, the living cell receives information about its external environment and internal state. In light of this information, the cell must determine its most appropriate course of action under the circumstances and initiate the relevant response pathways. Typical responses include growth and division, sexual reproduction, movement, differentiation and programmed cell death. Similar to a digital computer that uses bistable electrical switches to store and process information, the living cell uses bistable biochemical switches to implement its decision-making capabilities. In this review article, we describe some of the lines of thought that led, over the last 50 years, to our current understanding of cellular information processing, particularly related to cell growth, division and death. PMID:24904735

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

    PubMed

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

    2014-01-01

    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. PMID:24996848

  7. Arabidopsis  SABRE and CLASP interact to stabilize cell division plane orientation and planar polarity

    PubMed Central

    Pietra, Stefano; Gustavsson, Anna; Kiefer, Christian; Kalmbach, Lothar; Hörstedt, Per; Ikeda, Yoshihisa; Stepanova, Anna N.; Alonso, Jose M.; Grebe, Markus

    2013-01-01

    The orientation of cell division and the coordination of cell polarity within the plane of the tissue layer (planar polarity) contribute to shape diverse multicellular organisms. The root of Arabidopsis thaliana displays regularly oriented cell divisions, cell elongation and planar polarity providing a plant model system to study these processes. Here we report that the SABRE protein, which shares similarity with proteins of unknown function throughout eukaryotes, has important roles in orienting cell division and planar polarity. SABRE localizes at the plasma membrane, endomembranes, mitotic spindle and cell plate. SABRE stabilizes the orientation of CLASP-labelled preprophase band microtubules predicting the cell division plane, and of cortical microtubules driving cell elongation. During planar polarity establishment, sabre is epistatic to clasp at directing polar membrane domains of Rho-of-plant GTPases. Our findings mechanistically link SABRE to CLASP-dependent microtubule organization, shedding new light on the function of SABRE-related proteins in eukaryotes. PMID:24240534

  8. Light can rescue auxin-dependent synchrony of cell division in a tobacco cell line

    PubMed Central

    Qiao, Fei; Petrášek, Jan; Nick, Peter

    2010-01-01

    Pattern formation in plants has to cope with ambient variability and therefore must integrate environmental cues such as light. Synchrony of cell divisions was previously observed in cell files of tobacco suspension cultures, which represents a simple case of pattern formation. To develop cellular approaches for light-dependent patterning, light-responsive tobacco cell lines were screened from the cell line Nicotiana tabacum L. cv. Virginia Bright Italia 0 (VBI-0). The light responsive and auxin-autonomous cell line VBI-3 was isolated. As in the progenitor line VBI-0, cell divisions are synchronized in VBI-3 during exponential growth phase. This synchrony can be inhibited by 1-N-naphthylphthalamic acid, an auxin transport inhibitor, and this process was accompanied by the disassembly of actin filaments. However, the synchrony could be rescued when the cells were cultured under white light or with exogenous indolyl-3-acetic acid. The rescue was most efficient for continuous far-red light followed by continuous blue light, whereas continuous red light was least effective. These findings are discussed in the context of phytochrome-induced auxin biosynthesis and auxin-dependent synchrony of cell division. PMID:19884227

  9. Mitotic spindle rotation and mode of cell division in the developing telencephalon.

    PubMed

    Haydar, Tarik F; Ang, Eugenius; Rakic, Pasko

    2003-03-01

    The mode of neural stem cell division in the forebrain proliferative zones profoundly influences neocortical growth by regulating the number and diversity of neurons and glia. Long-term time-lapse multiphoton microscopy of embryonic mouse cortex reveals new details of the complex three-dimensional rotation and oscillation of the mitotic spindle before stem cell division. Importantly, the duration and amplitude of spindle movement predicts and specifies the eventual mode of mitotic division. These technological advances have provided dramatic data and insights into the kinetics of neural stem cell division by elucidating the involvement of spindle rotation in selection of the cleavage plane and the mode of neural stem cell division that together determine the size of the mammalian neocortex. PMID:12589023

  10. 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

    2015-01-01

    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. PMID:26188083

  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. Temperature-induced labelling of Fluo-3 AM selectively yields brighter nucleus in adherent cells

    SciTech Connect

    Meng, Guixian; Pan, Leiting; Li, Cunbo; Hu, Fen; Shi, Xuechen; Lee, Imshik; Drevenšek-Olenik, Irena; Zhang, Xinzheng; Xu, Jingjun

    2014-01-17

    Highlights: •We detailedly examine temperature effects of Fluo-3 AM labelling in adherent cells. •4 °C Loading and 20 °C de-esterification of Fluo-3 AM yields brighter nuclei. •Brighter nuclei labelling by Fluo-3 AM also depends on cell adhesion quality. •A qualitative model of the brighter nucleus is proposed. -- Abstract: Fluo-3 is widely used to study cell calcium. Two traditional approaches: (1) direct injection and (2) Fluo-3 acetoxymethyl ester (AM) loading, often bring conflicting results in cytoplasmic calcium ([Ca{sup 2+}]{sub c}) and nuclear calcium ([Ca{sup 2+}]{sub n}) imaging. AM loading usually yields a darker nucleus than in cytoplasm, while direct injection always induces a brighter nucleus which is more responsive to [Ca{sup 2+}]{sub n} detection. In this work, we detailedly investigated the effects of loading and de-esterification temperatures on the fluorescence intensity of Fluo-3 in response to [Ca{sup 2+}]{sub n} and [Ca{sup 2+}]{sub c} in adherent cells, including osteoblast, HeLa and BV2 cells. Interestingly, it showed that fluorescence intensity of nucleus in osteoblast cells was about two times larger than that of cytoplasm when cells were loaded with Fluo-3 AM at 4 °C and allowed a subsequent step for de-esterification at 20 °C. Brighter nuclei were also acquired in HeLa and BV2 cells using the same experimental condition. Furthermore, loading time and adhesion quality of cells had effect on fluorescence intensity. Taken together, cold loading and room temperature de-esterification treatment of Fluo-3 AM selectively yielded brighter nucleus in adherent cells.

  13. Targeted delivery of peptide-conjugated biocompatible gold nanoparticles into cancer cell nucleus

    NASA Astrophysics Data System (ADS)

    Qian, Wei; Curry, Taeyjuana; Che, Yong; Kopelman, Raoul

    2013-02-01

    Nucleus remains a significant target for nanoparticles with diagnostic and therapeutic applications because both genetic information of the cell and transcription machinery reside there. Novel therapeutic strategies (for example, gene therapy), enabled by safe and efficient delivery of nanoparticles and drug molecules into the nucleus, are heralded by many as the ultimate treatment for severe and intractable diseases. However, most nanomaterials and macromolecules are incapable of reaching the cell nucleus on their own, because of biological barriers carefully honed by evolution including cellular membrane and nuclear envelope. In this paper, we have demonstrated an approach of fabrication of biocompatible gold nanoparticle (Au NP)-based vehicles which can entering into cancer cell nucleus by modifying Au NPs with both PEG 5000 and two different peptides (RGD and nuclear localization signal (NLS) peptide). The Au NPs used were fabricated via femtosecond laser ablation of Au bulk target in deionized water. The Au NPs produced by this method provide chemical free, virgin surface, which allows us to carry out "Sequential Conjugation" to modify their surface with PEG 5000, RGD, and NLS. "Sequential Conjugation" described in this presentation is very critical for the fabrication of Au NP-based vehicles capable of entering into cancer cell nucleus as it enables the engineering and tuning surface chemistries of Au NPs by independently adjusting amounts of PEG and peptides bound onto surface of Au NPs so as to maximize their nuclear targeting performance and biocompatibility regarding the cell line of interest. Both optical microscopy and transmission electron microscopy (TEM) are used to confirm the in vitro targeted nuclear delivery of peptide-conjugated biocompatible Au NPs by showing their presence in the cancer cell nucleus.

  14. Single cell lineage tracing reveals that oriented cell division contributes to trabecular morphogenesis and regional specification

    PubMed Central

    Li, Jingjing; Miao, Lianjie; Shieh, David; Spiotto, Ernest; Li, Jian; Zhou, Bin; Paul, Antoni; Schwartz, Robert J.; Firulli, Anthony B.; Singer, Harold A.; Huang, Guoying; Wu, Mingfu

    2016-01-01

    Summary The cardiac trabeculae are sheet-like structures extending from the myocardium that function to increase surface area. A lack of trabeculation causes embryonic lethality due to compromised cardiac function. To understand the cellular and molecular mechanisms of trabecular formation, we genetically labeled individual cardiomyocytes prior to trabeculation via the brainbow multicolor system, and traced and analyzed the labeled cells during trabeculation by whole-embryo clearing and imaging. The clones derived from labeled single cells displayed four different geometric patterns that are derived from different patterns of oriented cell division (OCD) and migration. Of the four types of clones, the inner, transmural, and mixed clones contributed to trabecular cardiomyocytes. Further studies showed that perpendicular OCD is an extrinsic asymmetric cell division that putatively contributes to trabecular regional specification. Furthermore, N-Cadherin deletion in labeled clones disrupted the clonal patterns. In summary, our data demonstrate that OCD contributes to trabecular morphogenesis and specification. PMID:27052172

  15. Effect of the Min System on Timing of Cell Division in Escherichia coli

    PubMed Central

    Jia, Shuxin; Keilberg, Daniela; Hot, Edina; Thanbichler, Martin; Søgaard-Andersen, Lotte; Lenz, Peter

    2014-01-01

    In Escherichia coli the Min protein system plays an important role in positioning the division site. We show that this system also has an effect on timing of cell division. We do this in a quantitative way by measuring the cell division waiting time (defined as time difference between appearance of a division site and the division event) and the Z-ring existence time. Both quantities are found to be different in WT and cells without functional Min system. We develop a series of theoretical models whose predictions are compared with the experimental findings. Continuous improvement leads to a final model that is able to explain all relevant experimental observations. In particular, it shows that the chromosome segregation defect caused by the absence of Min proteins has an important influence on timing of cell division. Our results indicate that the Min system affects the septum formation rate. In the absence of the Min proteins this rate is reduced, leading to the observed strongly randomized cell division events and the longer division waiting times. PMID:25090009

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

    PubMed Central

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

    2016-01-01

    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. PMID:26515603

  17. Cell Division and Targeted Cell Cycle Arrest Opens and Stabilizes Basement Membrane Gaps

    PubMed Central

    Matus, David Q.; Chang, Emily; Makohon-Moore, Sasha C.; Hagedorn, Mary A.; Chi, Qiuyi; Sherwood, David R.

    2014-01-01

    Large gaps in basement membrane (BM) occur during organ remodeling and cancer cell invasion. Whether dividing cells, which temporarily reduce their attachment to BM, influence these breaches is unknown. Here we analyse uterine-vulval attachment during development across 21 species of rhabditid nematodes and find that the BM gap that forms between these organs is always bounded by a non-dividing vulval cell. Through cell cycle manipulation and live cell imaging in Caenorhabditis elegans, we show that actively dividing vulval cells facilitate enlargement of this breach by promoting BM movement. In contrast, targeted cell-cycle arrest halts BM movement and limits gap opening. Further, we demonstrate that the BM component laminin accumulates at the BM gap edge and promotes increased integrin levels in non-dividing vulval cells, stabilizing gap position. Together, these studies reveal that cell division can be used as a mechanism to regulate BM breaches, thus controlling the exchange of cells between tissues. PMID:24924309

  18. Genome-scale RNAi profiling of cell division in human tissue culture cells.

    PubMed

    Kittler, Ralf; Pelletier, Laurence; Heninger, Anne-Kristine; Slabicki, Mikolaj; Theis, Mirko; Miroslaw, Lukasz; Poser, Ina; Lawo, Steffen; Grabner, Hannes; Kozak, Karol; Wagner, Jan; Surendranath, Vineeth; Richter, Constance; Bowen, Wayne; Jackson, Aimee L; Habermann, Bianca; Hyman, Anthony A; Buchholz, Frank

    2007-12-01

    Cell division is fundamental for all organisms. Here we report a genome-scale RNA-mediated interference screen in HeLa cells designed to identify human genes that are important for cell division. We have used a library of endoribonuclease-prepared short interfering RNAs for gene silencing and have used DNA content analysis to identify genes that induced cell cycle arrest or altered ploidy on silencing. Validation and secondary assays were performed to generate a nine-parameter loss-of-function phenoprint for each of the genes. These phenotypic signatures allowed the assignment of genes to specific functional classes by combining hierarchical clustering, cross-species analysis and proteomic data mining. We highlight the richness of our dataset by ascribing novel functions to genes in mitosis and cytokinesis. In particular, we identify two evolutionarily conserved transcriptional regulatory networks that govern cytokinesis. Our work provides an experimental framework from which the systematic analysis of novel genes necessary for cell division in human cells can begin. PMID:17994010

  19. Evaluation of rapid cell division in non-uniform cell cycles.

    PubMed

    Lee, Juyun; Jeon, Wonju; Chang, Man; Han, Myung-Soo

    2015-10-01

    To better understand the mechanisms of development of harmful algal blooms (HABs), accurate estimates of species-specific in situ growth rates are needed. HABs are caused by rapid cell division by the causative microorganisms. To accurately estimate the in situ growth rates of harmful algae having non-uniform and/or irregular cell cycles, we modified a standard equation based on the cell cycle, and calculated the in situ growth rate to describe the process of bloom development in nature. Sampling of a developing bloom of Heterosigma akashiwo in Pohang Bay, Korea, was conducted every 3 h from 15:00 on August 2 to 07:00 on August 4, 2006. The amount of H. akashiwo DNA was measured using flow cytometry following tyramide signal amplification-fluorescence in situ hybridization. On August 2, the percentage of G1 phase cells decreased from 15:00 to 19:00 then increased until 22:00; it then decreased until 07:00 on August 3, followed by an increase to 10:00. This indicates the ability of the cells in nature to undergo more than one round of division per day. During the following night two rounds of division did not occur. The in situ growth rates estimated using the modified equation ranged from 0.31 to 0.53 d(-1) . We conclude that the use of this equation enables more accurate estimates of bloom formation by rapidly dividing cells. PMID:26175341

  20. 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

  1. Effect of vertebroplasty filler materials on viability and gene expression of human nucleus pulposus cells.

    PubMed

    Lazáry, Aron; Speer, Gábor; Varga, Péter Pál; Balla, Bernadett; Bácsi, Krisztián; Kósa, János P; Nagy, Zsolt; Takács, István; Lakatos, Péter

    2008-05-01

    Consequences of intradiscal cement leakage--often occurring after vertebral cement augmentation for the treatment of vertebral compression fractures--are still unknown. In this study, we have investigated the influences of vertebroplasty filler materials (polymethylmethacrylate-, calcium phosphate- and calcium sulfate-based bone cement) on isolated nucleus pulposus cells. Cell viability of cultured human nucleus pulposus cells were measured after treatment with vertebroplasty filler materials. Gene expression profile of selected genes was determined with quantitative real-time PCR. The widely used polymethylmethacrylate and calcium phosphate cement significantly decreased cell number in a dose- and time-dependent manner while calcium sulfate cement affected cell viability less. Expression of genes involved in matrix metabolism of nucleus pulposus--aggrecan, collagens, small proteoglycans--as well as important transcription factors have also significantly changed due to treatment (e.g., 2.5-fold decrease in aggrecan expression was determined in cultures due to polymethylmethacrylate treatment). Our results suggest that vertebroplasty filler materials--depending on the type of applied material--can accelerate the degeneration of nucleus pulposus cells resulting in a less flexible disc in case of intradiscal cement leakage. This process may increase the risk of a subsequent new vertebral fracture, the main complication of vertebral augmentation. PMID:18176942

  2. Bacterial cell division: a moving MinE sweeper boggles the MinD.

    PubMed

    Margolin, W

    2001-05-15

    Placement of the division site in Escherichia coli is determined in part by three Min proteins. Recent studies have shown that MinE, previously thought to form a static ring near the division site at the midcell position, actually joins MinC and MinD in their rapid oscillation between the cell poles. PMID:11378404

  3. Stem and progenitor cell division kinetics during postnatal mouse mammary gland development.

    PubMed

    Giraddi, Rajshekhar R; Shehata, Mona; Gallardo, Mercedes; Blasco, Maria A; Simons, Benjamin D; Stingl, John

    2015-01-01

    The cycling properties of mammary stem and progenitor cells is not well understood. To determine the division properties of these cells, we administered synthetic nucleosides for varying periods of time to mice at different stages of postnatal development and monitored the rate of uptake of these nucleosides in the different mammary cell compartments. Here we show that most cell division in the adult virgin gland is restricted to the oestrogen receptor-expressing luminal cell lineage. Our data also demonstrate that the oestrogen receptor-expressing, milk and basal cell subpopulations have telomere lengths and cell division kinetics that are not compatible with these cells being hierarchically organized; instead, our data indicate that in the adult homeostatic gland, each cell type is largely maintained by its own restricted progenitors. We also observe that transplantable stem cells are largely quiescent during oestrus, but are cycling during dioestrus when progesterone levels are high. PMID:26511661

  4. Nanomolar pyrophosphate detection and nucleus staining in living cells with simple terpyridine-Zn(II) complexes.

    PubMed

    Chao, Duobin; Ni, Shitan

    2016-01-01

    Great efforts have been made to develop fluorescent probes for pyrophosphate (PPi) detection. Nucleus staining with fluorescence microscopy has been also widely investigated. But fluorescent probes for PPi detection with high sensitivity in water medium and nucleus staining with low-cost non-precious metal complexes in living cells are still challenging. Herein, we report simple terpyridine-Zn(II) complexes for selective nanomolar PPi detection over ATP and ADP in water based on aggregation induced emission (AIE) and intramolecular charge transfer (ICT). In addition, these terpyridine-Zn(II) complexes were successfully employed for nucleus staining in living cells. These results demonstrated simply obtained terpyridine-Zn(II) complexes are powerful tool for PPi detection and the development of PPi-related studies. PMID:27198968

  5. Nanomolar pyrophosphate detection and nucleus staining in living cells with simple terpyridine–Zn(II) complexes

    NASA Astrophysics Data System (ADS)

    Chao, Duobin; Ni, Shitan

    2016-05-01

    Great efforts have been made to develop fluorescent probes for pyrophosphate (PPi) detection. Nucleus staining with fluorescence microscopy has been also widely investigated. But fluorescent probes for PPi detection with high sensitivity in water medium and nucleus staining with low–cost non–precious metal complexes in living cells are still challenging. Herein, we report simple terpyridine–Zn(II) complexes for selective nanomolar PPi detection over ATP and ADP in water based on aggregation induced emission (AIE) and intramolecular charge transfer (ICT). In addition, these terpyridine–Zn(II) complexes were successfully employed for nucleus staining in living cells. These results demonstrated simply obtained terpyridine–Zn(II) complexes are powerful tool for PPi detection and the development of PPi–related studies.

  6. Nanomolar pyrophosphate detection and nucleus staining in living cells with simple terpyridine–Zn(II) complexes

    PubMed Central

    Chao, Duobin; Ni, Shitan

    2016-01-01

    Great efforts have been made to develop fluorescent probes for pyrophosphate (PPi) detection. Nucleus staining with fluorescence microscopy has been also widely investigated. But fluorescent probes for PPi detection with high sensitivity in water medium and nucleus staining with low–cost non–precious metal complexes in living cells are still challenging. Herein, we report simple terpyridine–Zn(II) complexes for selective nanomolar PPi detection over ATP and ADP in water based on aggregation induced emission (AIE) and intramolecular charge transfer (ICT). In addition, these terpyridine–Zn(II) complexes were successfully employed for nucleus staining in living cells. These results demonstrated simply obtained terpyridine–Zn(II) complexes are powerful tool for PPi detection and the development of PPi–related studies. PMID:27198968

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

    PubMed

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

    2016-07-26

    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

  8. 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

  9. Computational prediction of strain-dependent diffusion of transcription factors through the cell nucleus.

    PubMed

    Nava, Michele M; Fedele, Roberto; Raimondi, Manuela T

    2016-08-01

    Nuclear spreading plays a crucial role in stem cell fate determination. In previous works, we reported evidence of multipotency maintenance for mesenchymal stromal cells cultured on three-dimensional engineered niche substrates, fabricated via two-photon laser polymerization. We correlated maintenance of multipotency to a more roundish morphology of these cells with respect to those cultured on conventional flat substrates. To interpret these findings, here we present a multiphysics model coupling nuclear strains induced by cell adhesion to passive diffusion across the cell nucleus. Fully three-dimensional reconstructions of cultured cells were developed on the basis of confocal images: in particular, the level of nuclear spreading resulted significantly dependent on the cell localization within the niche architecture. We assumed that the cell diffusivity varies as a function of the local volumetric strain. The model predictions indicate that the higher the level of spreading of the cell, the higher the flux across the nucleus of small solutes such as transcription factors. Our results point toward nuclear spreading as a primary mechanism by which the stem cell translates its shape into a fate decision, i.e., by amplifying the diffusive flow of transcriptional activators into the nucleus. PMID:26476736

  10. Noise and Epigenetic Inheritance of Single-Cell Division Times Influence Population Fitness.

    PubMed

    Cerulus, Bram; New, Aaron M; Pougach, Ksenia; Verstrepen, Kevin J

    2016-05-01

    The fitness effect of biological noise remains unclear. For example, even within clonal microbial populations, individual cells grow at different speeds. Although it is known that the individuals' mean growth speed can affect population-level fitness, it is unclear how or whether growth speed heterogeneity itself is subject to natural selection. Here, we show that noisy single-cell division times can significantly affect population-level growth rate. Using time-lapse microscopy to measure the division times of thousands of individual S. cerevisiae cells across different genetic and environmental backgrounds, we find that the length of individual cells' division times can vary substantially between clonal individuals and that sublineages often show epigenetic inheritance of division times. By combining these experimental measurements with mathematical modeling, we find that, for a given mean division time, increasing heterogeneity and epigenetic inheritance of division times increases the population growth rate. Furthermore, we demonstrate that the heterogeneity and epigenetic inheritance of single-cell division times can be linked with variation in the expression of catabolic genes. Taken together, our results reveal how a change in noisy single-cell behaviors can directly influence fitness through dynamics that operate independently of effects caused by changes to the mean. These results not only allow a better understanding of microbial fitness but also help to more accurately predict fitness in other clonal populations, such as tumors. PMID:27068419

  11. MiR-27a Regulates Apoptosis in Nucleus Pulposus Cells by Targeting PI3K

    PubMed Central

    Chen, Huajiang; Yuan, Wen; Wang, Jianxi; Tang, Xianye

    2013-01-01

    The precise role of apoptosis in the pathogenesis of intervertebral disc degeneration (IDD) remains to be elucidated. We analyzed degenerative nucleus pulposus (NP) cells and found that the expression of miR-27a was increased. The overexpression of miR-27a was further verified using real-time RT-PCR. Bioinformatics target prediction identified phosphoinositide-3 kinases (PI3K) as putative targets of miR-27a. Furthermore, miR-27a inhibited PI3K expression by directly targeting their 3’-UTRs, and this inhibition was abolished by mutation of the miR-27a binding sites. Various cellular processes including cell growth, proliferation, migration and adhesion are regulated by activation of the PI3K/AKT signaling pathway, and nucleus pulposus cells are known to strongly express the phosphorylated survival protein AKT. Our results identify PI3K as a novel target of miR-27a. Upregulation of miR-27a thus targets PI3K, initiating apoptosis of nucleus pulposus cells. This present study revealed that downregulated miR-27a might develop a novel intervention for IDD treatment through the prevention of apoptosis in Nucleus pulposus Cells. PMID:24086481

  12. MiR-27a regulates apoptosis in nucleus pulposus cells by targeting PI3K.

    PubMed

    Liu, Gang; Cao, Peng; Chen, Huajiang; Yuan, Wen; Wang, Jianxi; Tang, Xianye

    2013-01-01

    The precise role of apoptosis in the pathogenesis of intervertebral disc degeneration (IDD) remains to be elucidated. We analyzed degenerative nucleus pulposus (NP) cells and found that the expression of miR-27a was increased. The overexpression of miR-27a was further verified using real-time RT-PCR. Bioinformatics target prediction identified phosphoinositide-3 kinases (PI3K) as putative targets of miR-27a. Furthermore, miR-27a inhibited PI3K expression by directly targeting their 3'-UTRs, and this inhibition was abolished by mutation of the miR-27a binding sites. Various cellular processes including cell growth, proliferation, migration and adhesion are regulated by activation of the PI3K/AKT signaling pathway, and nucleus pulposus cells are known to strongly express the phosphorylated survival protein AKT. Our results identify PI3K as a novel target of miR-27a. Upregulation of miR-27a thus targets PI3K, initiating apoptosis of nucleus pulposus cells. This present study revealed that downregulated miR-27a might develop a novel intervention for IDD treatment through the prevention of apoptosis in Nucleus pulposus Cells. PMID:24086481

  13. Implication of the nucleus in excitation contraction coupling of heart cells.

    PubMed

    Bkaily, G; Gros-Louis, N; Naik, R; Jaalouk, D; Pothier, P

    1996-01-26

    In the present study, Fluo-3 Ca2+ measurement and confocal microscopy techniques were used in order to localize cytosolic []c and nuclear []n free Ca2+ distribution in resting and spontaneously contracting single heart cells from 10-day-old chick embryos. In resting single cells, the concentration of Ca2+ in the cytoplasm was lower than that in the nucleus. Increasing cytosolic free Ca2+ from 100-1600 nM gradually increased [Ca2+]n with a maximum capacity near 1200 nM. Results from Fura-2 microfluorometry and Fluo-3 confocal microscopy suggest a potential cross talk between the increase of cytosolic free Ca2+ and the uptake and release of Ca2+ by the nucleus during spontaneous contraction of single myocytes. Calcium waves in spontaneously contracting cells were found to spread from one cell to the next with the nucleus acting as a fluorescent beacon in which Ca2+ levels remained elevated for several milliseconds even after cytosolic Ca2+ had returned to near basal values. These results strongly suggest that the nucleus plays a negative and positive feedback role in controlling cytosolic free Ca2+ concentration during excitation-contraction coupling in heart cells. PMID:8717425

  14. Metabolic maintenance of cell asymmetry following division in activated T lymphocytes.

    PubMed

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

    2016-04-21

    Asymmetric cell division, the partitioning of cellular components in response to polarizing cues during mitosis, has roles in differentiation and development. It is important for the self-renewal of fertilized zygotes in Caenorhabditis elegans and neuroblasts in Drosophila, and in the development of mammalian nervous and digestive systems. T lymphocytes, upon activation by antigen-presenting cells (APCs), can undergo asymmetric cell division, wherein the daughter cell proximal to the APC is more likely to differentiate into an effector-like T cell and the distal daughter is more likely to differentiate into a memory-like T cell. Upon activation and before cell division, expression of the transcription factor c-Myc drives metabolic reprogramming, necessary for the subsequent proliferative burst. Here we find that during the first division of an activated T cell in mice, c-Myc can sort asymmetrically. Asymmetric distribution of amino acid transporters, amino acid content, and activity of mammalian target of rapamycin complex 1 (mTORC1) is correlated with c-Myc expression, and both amino acids and mTORC1 activity sustain the differences in c-Myc expression in one daughter cell compared to the other. Asymmetric c-Myc levels in daughter T cells affect proliferation, metabolism, and differentiation, and these effects are altered by experimental manipulation of mTORC1 activity or c-Myc expression. Therefore, metabolic signalling pathways cooperate with transcription programs to maintain differential cell fates following asymmetric T-cell division. PMID:27064903

  15. Microdissection studies on the polarity of unequal division in grasshopper neuroblasts. I. Subsequent divisions in neuroblast-type cells produced against the polarity by micromanipulation.

    PubMed

    Yamashiki, N; Kawamura, K

    1986-09-01

    Equal or unequal division against the polarity of normal division was induced in grasshopper neuroblasts by means of a microdissection technique. The subsequent cell divisions were traced in order to analyse the factors that determine the polarity. Daughter cells of two types (neuroblast-type and ganglion cell type) were produced by operations in which the mitotic apparatus was rotated or shifted. Cell types were classified by such characteristics as nuclear shape, mitotic activity, and inequality or equality of the subsequent cytokinesis. It became evident that the fate of daughter cells was determined simply by the cytoplasmic volume. In 27 cases out of 40 microdissecting operations, both sister cells were recognized as of neuroblast type. Mitosis of these neuroblast-type sister cells proceeded asynchronously. The time required for neuroblast-type cells to reach metaphase of the second division depended on their volume. It is considered that the polarity of unequal division in grasshopper neuroblasts may be maintained by a joint action of the cap cells attaching to one of the polar regions of the cell and the cortex differentiated in the previous cell division. PMID:3743651

  16. Concentration Sensing by the Moving Nucleus in Cell Fate Determination: A Computational Analysis.

    PubMed

    Aggarwal, Varun; Dickinson, Richard B; Lele, Tanmay P

    2016-01-01

    During development of the vertebrate neuroepithelium, the nucleus in neural progenitor cells (NPCs) moves from the apex toward the base and returns to the apex (called interkinetic nuclear migration) at which point the cell divides. The fate of the resulting daughter cells is thought to depend on the sampling by the moving nucleus of a spatial concentration profile of the cytoplasmic Notch intracellular domain (NICD). However, the nucleus executes complex stochastic motions including random waiting and back and forth motions, which can expose the nucleus to randomly varying levels of cytoplasmic NICD. How nuclear position can determine daughter cell fate despite the stochastic nature of nuclear migration is not clear. Here we derived a mathematical model for reaction, diffusion, and nuclear accumulation of NICD in NPCs during interkinetic nuclear migration (INM). Using experimentally measured trajectory-dependent probabilities of nuclear turning, nuclear waiting times and average nuclear speeds in NPCs in the developing zebrafish retina, we performed stochastic simulations to compute the nuclear trajectory-dependent probabilities of NPC differentiation. Comparison with experimentally measured nuclear NICD concentrations and trajectory-dependent probabilities of differentiation allowed estimation of the NICD cytoplasmic gradient. Spatially polarized production of NICD, rapid NICD cytoplasmic consumption and the time-averaging effect of nuclear import/export kinetics are sufficient to explain the experimentally observed differentiation probabilities. Our computational studies lend quantitative support to the feasibility of the nuclear concentration-sensing mechanism for NPC fate determination in zebrafish retina. PMID:26872214

  17. Concentration Sensing by the Moving Nucleus in Cell Fate Determination: A Computational Analysis

    PubMed Central

    Aggarwal, Varun; Dickinson, Richard B.; Lele, Tanmay P.

    2016-01-01

    During development of the vertebrate neuroepithelium, the nucleus in neural progenitor cells (NPCs) moves from the apex toward the base and returns to the apex (called interkinetic nuclear migration) at which point the cell divides. The fate of the resulting daughter cells is thought to depend on the sampling by the moving nucleus of a spatial concentration profile of the cytoplasmic Notch intracellular domain (NICD). However, the nucleus executes complex stochastic motions including random waiting and back and forth motions, which can expose the nucleus to randomly varying levels of cytoplasmic NICD. How nuclear position can determine daughter cell fate despite the stochastic nature of nuclear migration is not clear. Here we derived a mathematical model for reaction, diffusion, and nuclear accumulation of NICD in NPCs during interkinetic nuclear migration (INM). Using experimentally measured trajectory-dependent probabilities of nuclear turning, nuclear waiting times and average nuclear speeds in NPCs in the developing zebrafish retina, we performed stochastic simulations to compute the nuclear trajectory-dependent probabilities of NPC differentiation. Comparison with experimentally measured nuclear NICD concentrations and trajectory-dependent probabilities of differentiation allowed estimation of the NICD cytoplasmic gradient. Spatially polarized production of NICD, rapid NICD cytoplasmic consumption and the time-averaging effect of nuclear import/export kinetics are sufficient to explain the experimentally observed differentiation probabilities. Our computational studies lend quantitative support to the feasibility of the nuclear concentration-sensing mechanism for NPC fate determination in zebrafish retina. PMID:26872214

  18. miR-21 promotes human nucleus pulposus cell proliferation through PTEN/AKT signaling.

    PubMed

    Liu, Hongzhe; Huang, Xiangwang; Liu, Xiangyang; Xiao, Sheng; Zhang, Yi; Xiang, Tiecheng; Shen, Xiongjie; Wang, Guoping; Sheng, Bin

    2014-01-01

    The precise role of nucleus pulposus cell proliferation in the pathogenesis of intervertebral disc degeneration remains to be elucidated. Recent findings have revealed that microRNAs, a class of small noncoding RNAs, may regulate cell proliferation in many pathological conditions. Here, we showed that miR-21 was significantly upregulated in degenerative nucleus pulposus tissues when compared with nucleus pulposus tissues that were isolated from patients with idiopathic scoliosis and that miR-10b levels were associated with disc degeneration grade. Moreover, bioinformatics target prediction identified PTEN as a putative target of miR-21. miR-21 inhibited PTEN expression by directly targeting the 3'UTR, and this inhibition was abolished through miR-21 binding site mutations. miR-21 overexpression stimulated cell proliferation and AKT signaling pathway activation, which led to cyclin D1 translation. Additionally, the increase in proliferation and cyclin D1 expression induced by miR-21 overexpression was almost completely blocked by Ly294002, an AKT inhibitor. Taken together, aberrant miR-21 upregulation in intervertebral disc degeneration could target PTEN, which would contribute to abnormal nucleus pulposus cell proliferation through derepressing the Akt pathway. Our study also underscores the potential of miR-21 and the PTEN/Akt pathway as novel therapeutic targets in intervertebral disc degeneration. PMID:24603539

  19. miR-21 Promotes Human Nucleus Pulposus Cell Proliferation through PTEN/AKT Signaling

    PubMed Central

    Liu, Hongzhe; Huang, Xiangwang; Liu, Xiangyang; Xiao, Sheng; Zhang, Yi; Xiang, Tiecheng; Shen, Xiongjie; Wang, Guoping; Sheng, Bin

    2014-01-01

    The precise role of nucleus pulposus cell proliferation in the pathogenesis of intervertebral disc degeneration remains to be elucidated. Recent findings have revealed that microRNAs, a class of small noncoding RNAs, may regulate cell proliferation in many pathological conditions. Here, we showed that miR-21 was significantly upregulated in degenerative nucleus pulposus tissues when compared with nucleus pulposus tissues that were isolated from patients with idiopathic scoliosis and that miR-10b levels were associated with disc degeneration grade. Moreover, bioinformatics target prediction identified PTEN as a putative target of miR-21. miR-21 inhibited PTEN expression by directly targeting the 3′UTR, and this inhibition was abolished through miR-21 binding site mutations. miR-21 overexpression stimulated cell proliferation and AKT signaling pathway activation, which led to cyclin D1 translation. Additionally, the increase in proliferation and cyclin D1 expression induced by miR-21 overexpression was almost completely blocked by Ly294002, an AKT inhibitor. Taken together, aberrant miR-21 upregulation in intervertebral disc degeneration could target PTEN, which would contribute to abnormal nucleus pulposus cell proliferation through derepressing the Akt pathway. Our study also underscores the potential of miR-21 and the PTEN/Akt pathway as novel therapeutic targets in intervertebral disc degeneration. PMID:24603539

  20. Wnt and the Cancer Niche: Paracrine Interactions with Gastrointestinal Cancer Cells Undergoing Asymmetric Cell Division

    PubMed Central

    Xin, Hong-Wu; Ambe, Chenwi M.; Ray, Satyajit; Kim, Bo-Kyu; Koizumi, Tomotake; Wiegand, Gordon W.; Hari, Danielle; Mullinax, John E.; Jaiswal, Kshama R.; Garfield, Susan H.; Stojadinovic, Alexander; Rudloff, Udo; Thorgeirsson, Snorri S.; Avital, Itzhak

    2013-01-01

    Objective: Stem-like cancer cells contribute to cancer initiation and maintenance. Stem cells can self-renew by asymmetric cell division (ACD). ACD with non-random chromosomal cosegregation (ACD-NRCC) is one possible self-renewal mechanism. There is a paucity of evidence supporting ACD-NRCC in human cancer. Our aim was to investigate ACD-NRCC and its potential interactions with the cancer niche (microenvironment) in gastrointestinal cancers. Design: We used DNA double and single labeling approaches with FACS to isolate live cells undergoing ACD-NRCC. Results: Gastrointestinal cancers contain rare subpopulations of cells capable of ACD-NRCC. ACD-NRCC was detected preferentially in subpopulations of cells previously suggested to be stem-like/tumor-initiating cancer cells. ACD-NRCC was independent of cell-to-cell contact, and was regulated by the cancer niche in a heat-sensitive paracrine fashion. Wnt pathway genes and proteins are differentially expressed in cells undergoing ACD-NRCC vs. symmetric cell division. Blocking the Wnt pathway with IWP2 (WNT antagonist) or siRNA-TCF4 resulted in suppression of ACD-NRCC. However, using a Wnt-agonist did not increase the relative proportion of cells undergoing ACD-NRCC. Conclusion: Gastrointestinal cancers contain subpopulations of cells capable of ACD-NRCC. Here we show for the first time that ACD-NRCC can be regulated by the Wnt pathway, and by the cancer niche in a paracrine fashion. However, whether ACD-NRCC is exclusively associated with stem-like cancer cells remains to be determined. Further study of these findings might generate novel insights into stem cell and cancer biology. Targeting the mechanism of ACD-NRCC might engender novel approaches for cancer therapy. PMID:23901343

  1. The Protective Role of Symmetric Stem Cell Division on the Accumulation of Heritable Damage

    PubMed Central

    McHale, Peter T.; Lander, Arthur D.

    2014-01-01

    Stem cell divisions are either asymmetric—in which one daughter cell remains a stem cell and one does not—or symmetric, in which both daughter cells adopt the same fate, either stem or non-stem. Recent studies show that in many tissues operating under homeostatic conditions stem cell division patterns are strongly biased toward the symmetric outcome, raising the question of whether symmetry confers some benefit. Here, we show that symmetry, via extinction of damaged stem-cell clones, reduces the lifetime risk of accumulating phenotypically silent heritable damage (mutations or aberrant epigenetic changes) in individual stem cells. This effect is greatest in rapidly cycling tissues subject to accelerating rates of damage accumulation over time, a scenario that describes the progression of many cancers. A decrease in the rate of cellular damage accumulation may be an important factor favoring symmetric patterns of stem cell division. PMID:25121484

  2. The protective role of symmetric stem cell division on the accumulation of heritable damage.

    PubMed

    McHale, Peter T; Lander, Arthur D

    2014-08-01

    Stem cell divisions are either asymmetric-in which one daughter cell remains a stem cell and one does not-or symmetric, in which both daughter cells adopt the same fate, either stem or non-stem. Recent studies show that in many tissues operating under homeostatic conditions stem cell division patterns are strongly biased toward the symmetric outcome, raising the question of whether symmetry confers some benefit. Here, we show that symmetry, via extinction of damaged stem-cell clones, reduces the lifetime risk of accumulating phenotypically silent heritable damage (mutations or aberrant epigenetic changes) in individual stem cells. This effect is greatest in rapidly cycling tissues subject to accelerating rates of damage accumulation over time, a scenario that describes the progression of many cancers. A decrease in the rate of cellular damage accumulation may be an important factor favoring symmetric patterns of stem cell division. PMID:25121484

  3. 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. PMID:26487778

  4. Fatostatin Inhibits Cancer Cell Proliferation by Affecting Mitotic Microtubule Spindle Assembly and Cell Division.

    PubMed

    Gholkar, Ankur A; Cheung, Keith; Williams, Kevin J; Lo, Yu-Chen; Hamideh, Shadia A; Nnebe, Chelsea; Khuu, Cindy; Bensinger, Steven J; Torres, Jorge Z

    2016-08-12

    The sterol regulatory element-binding protein (SREBP) transcription factors have become attractive targets for pharmacological inhibition in the treatment of metabolic diseases and cancer. SREBPs are critical for the production and metabolism of lipids and cholesterol, which are essential for cellular homeostasis and cell proliferation. Fatostatin was recently discovered as a specific inhibitor of SREBP cleavage-activating protein (SCAP), which is required for SREBP activation. Fatostatin possesses antitumor properties including the inhibition of cancer cell proliferation, invasion, and migration, and it arrests cancer cells in G2/M phase. Although Fatostatin has been viewed as an antitumor agent due to its inhibition of SREBP and its effect on lipid metabolism, we show that Fatostatin's anticancer properties can also be attributed to its inhibition of cell division. We analyzed the effect of SREBP activity inhibitors including Fatostatin, PF-429242, and Betulin on the cell cycle and determined that only Fatostatin possessed antimitotic properties. Fatostatin inhibited tubulin polymerization, arrested cells in mitosis, activated the spindle assembly checkpoint, and triggered mitotic catastrophe and reduced cell viability. Thus Fatostatin's ability to inhibit SREBP activity and cell division could prove beneficial in treating aggressive types of cancers such as glioblastomas that have elevated lipid metabolism and fast proliferation rates and often develop resistance to current anticancer therapies. PMID:27378817

  5. 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)

  6. Synergistic Targeting of Cell Membrane, Cytoplasm and Nucleus of Cancer Cells using Rod-Shaped Nanoparticles

    PubMed Central

    Barua, Sutapa; Mitragotri, Samir

    2014-01-01

    Design of carriers for effective delivery and targeting of drugs to cellular and sub-cellular compartments is an unmet need in medicine. Here, we report pure drug nanoparticles comprising camptothecin (CPT), trastuzumab (TTZ) and doxorubicin (DOX) to enable cell-specific interactions, subcellular accumulation and growth inhibition of breast cancer cells. CPT is formulated in the form of nanorods which are coated with TTZ. DOX is encapsulated in the TTZ corona around the CPT nanoparticle. Our results show that TTZ/DOX-coated CPT nanorods exhibit cell-specific internalization in BT-474 breast cancer cells, after which TTZ is recycled to the plasma membrane leaving CPT nanorods in the perinuclear region and delivering DOX into the nucleus of the cells. The effects of CPT-TTZ-DOX nanoparticles on growth inhibition are synergistic (combination index = 0.17±0.03) showing 10-10,000 fold lower inhibitory concentrations (IC50) compared to those of individual drugs. The design of antibody-targeted pure drug nanoparticles offers a promising design strategy to facilitate intracellular delivery and therapeutic efficiency of anticancer drugs. PMID:24053162

  7. The Multiple Functions of T Stellate/Multipolar/Chopper Cells in the Ventral Cochlear Nucleus

    PubMed Central

    Oertel, Donata; Wright, Samantha; Cao, Xiao-Jie; Ferragamo, Michael; Bal, Ramazan

    2010-01-01

    Acoustic information is brought to the brain by auditory nerve fibers, all of which terminate in the cochlear nuclei, and is passed up the auditory pathway through the principal cells of the cochlear nuclei. A population of neurons variously known as T stellate, type I multipolar, planar multipolar, or chopper cells forms one of the major ascending auditory pathways through the brain stem. T Stellate cells are sharply tuned; as a population they encode the spectrum of sounds. In these neurons, phasic excitation from the auditory nerve is made more tonic by feed forward excitation, coactivation of inhibitory with excitatory inputs, relatively large excitatory currents through NMDA receptors, and relatively little synaptic depression. The mechanisms that make firing tonic also obscure the fine structure of sounds that is represented in the excitatory inputs from the auditory nerve and account for the characteristic chopping response patterns with which T stellate cells respond to tones. In contrast with other principal cells of the ventral cochlear nucleus (VCN), T stellate cells lack a low-voltage-activated potassium conductance and are therefore sensitive to small, steady, neuromodulating currents. The presence of cholinergic, serotonergic and noradrenergic receptors allows the excitability of these cells to be modulated by medial olivocochlear efferent neurons and by neuronal circuits associated with arousal. T Stellate cells deliver acoustic information to the ipsilateral dorsal cochlear nucleus (DCN), ventral nucleus of the trapezoid body (VNTB), periolivary regions around the lateral superior olivary nucleus (LSO), and to the contralateral ventral lemniscal nuclei (VNLL) and inferior colliculus (IC). It is likely that T stellate cells participate in feedback loops through both medial and lateral olivocochlear efferent neurons and they may be a source of ipsilateral excitation of the LSO. PMID:21056098

  8. Hydrodynamic stimulation and long term cultivation of nucleus pulposus cells: a new bioreactor system to induce extracellular matrix synthesis by nucleus pulposus cells dependent on intermittent hydrostatic pressure.

    PubMed

    Gokorsch, S; Nehring, D; Grottke, C; Czermak, P

    2004-11-01

    A novel bioreactor system was constructed to induce extracellular matrix (ECM) synthesis by intervertebral disc (ID) cells due to intermittent hydrostatic pressure. The developed system is completely sterilizable and reusable. It is viable for cultivation, immobilization, and stimulation of various other cell types and tissues especially for cartilage. The custom made lid allows long-run cultivation through semi-continuous operation. Manual interferences and therefore the risk of contamination are reduced. Sampling, medium changing and addition of supplements are easily performed from the connected conditioning vessel, which could be placed in an incubator. For the present investigations nucleus pulposus cells from pigs were taken and immobilized in agarose to obtain three-dimensional cell matrix constructs which were subjected to intermittent hydrostatic pressure. Afterwards the construct was biochemically examined. The proven constituents of ECM were found to be released in dependence of the magnitude and profile of the applied pressure. PMID:15636054

  9. Raman spectroscopy for DNA quantification in cell nucleus.

    PubMed

    Okotrub, K A; Surovtsev, N V; Semeshin, V F; Omelyanchuk, L V

    2015-01-01

    Here we demonstrate the feasibility of a novel approach to quantify DNA in cell nuclei. This approach is based on spectroscopy analysis of Raman light scattering, and avoids the problem of nonstoichiometric binding of dyes to DNA, as it directly measures the signal from DNA. Quantitative analysis of nuclear DNA contribution to Raman spectrum could be reliably performed using intensity of a phosphate mode at 1096 cm(-1) . When compared to the known DNA standards from cells of different animals, our results matched those values at error of 10%. We therefore suggest that this approach will be useful to expand the list of DNA standards, to properly adjust the duration of hydrolysis in Feulgen staining, to assay the applicability of fuchsines for DNA quantification, as well as to measure DNA content in cells with complex hydrolysis patterns, when Feulgen densitometry is inappropriate. PMID:25355529

  10. Communication Between the Cell Membrane and the Nucleus: Role of Protein Compartmentalization

    SciTech Connect

    Lelievre, Sophie A; Bissell, Mina J

    1998-10-21

    Understanding how the information is conveyed from outside to inside the cell is a critical challenge for all biologists involved in signal transduction. The flow of information initiated by cell-cell and cell-extracellular matrix contacts is mediated by the formation of adhesion complexes involving multiple proteins. Inside adhesion complexes, connective membrane skeleton (CMS) proteins are signal transducers that bind to adhesion molecules, organize the cytoskeleton, and initiate biochemical cascades. Adhesion complex-mediated signal transduction ultimately directs the formation of supramolecular structures in the cell nucleus, as illustrated by the establishment of multi complexes of DNA-bound transcription factors, and the redistribution of nuclear structural proteins to form nuclear subdomains. Recently, several CMS proteins have been observed to travel to the cell nucleus, suggesting a distinctive role for these proteins in signal transduction. This review focuses on the nuclear translocation of structural signal transducers of the membrane skeleton and also extends our analysis to possible translocation of resident nuclear proteins to the membrane skeleton. This leads us to envision the communication between spatially distant cellular compartments (i.e., membrane skeleton and cell nucleus) as a bidirectional flow of information (a dynamic reciprocity) based on subtle multilevel structural and biochemical equilibria. At one level, it is mediated by the interaction between structural signal transducers and their binding partners, at another level it may be mediated by the balance and integration of signal transducers in different cellular compartments.

  11. A conformational switch controls cell wall remodeling enzymes required for bacterial cell division

    PubMed Central

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

    2012-01-01

    Summary Remodeling of the peptidoglycan (PG) exoskeleton is intimately tied to the growth and division of bacteria. Enzymes that hydrolyze 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 ortholog 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 auto-inhibition governed by conserved sub-complexes within the cytokinetic ring. Analogous conformational control mechanisms are likely to be part of a general strategy used to control PG hydrolases present within multi-enzyme PG remodeling machines. PMID:22715947

  12. 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. PMID:22331764

  13. Perturbation of nucleo-cytoplasmic transport affects size of nucleus and nucleolus in human cells.

    PubMed

    Ganguly, Abira; Bhattacharjee, Chumki; Bhave, Madhura; Kailaje, Vaishali; Jain, Bhawik K; Sengupta, Isha; Rangarajan, Annapoorni; Bhattacharyya, Dibyendu

    2016-03-01

    Size regulation of human cell nucleus and nucleolus are poorly understood subjects. 3D reconstruction of live image shows that the karyoplasmic ratio (KR) increases by 30-80% in transformed cell lines compared to their immortalized counterpart. The attenuation of nucleo-cytoplasmic transport causes the KR value to increase by 30-50% in immortalized cell lines. Nucleolus volumes are significantly increased in transformed cell lines and the attenuation of nucleo-cytoplasmic transport causes a significant increase in the nucleolus volume of immortalized cell lines. A cytosol and nuclear fraction swapping experiment emphasizes the potential role of unknown cytosolic factors in nuclear and nucleolar size regulation. PMID:26813731

  14. HEK293 cells express dystrophin Dp71 with nucleus-specific localization of Dp71ab.

    PubMed

    Nishida, Atsushi; Yasuno, Sato; Takeuchi, Atsuko; Awano, Hiroyuki; Lee, Tomoko; Niba, Emma Tabe Eko; Fujimoto, Takahiro; Itoh, Kyoko; Takeshima, Yasuhiro; Nishio, Hisahide; Matsuo, Masafumi

    2016-09-01

    The dystrophin gene consists of 79 exons and encodes tissue-specific isoforms. Mutations in the dystrophin gene cause Duchenne muscular dystrophy, of which a substantial proportion of cases are complicated by non-progressive mental retardation. Abnormalities of Dp71, an isoform transcribed from a promoter in intron 62, are a suspected cause of mental retardation. However, the roles of Dp71 in human brain have not been fully elucidated. Here, we characterized dystrophin in human HEK293 cells with the neuronal lineage. Reverse transcription-PCR amplification of the full-length dystrophin transcript revealed the absence of fragments covering the 5' part of the dystrophin cDNA. In contrast, fragments covering exons 64-79 were present. The Dp71 promoter-specific exon G1 was shown spliced to exon 63. We demonstrated that the Dp71 transcript comprised two subisoforms: one lacking exon 78 (Dp71b) and the other lacking both exons 71 and 78 (Dp71ab). Western blotting of cell lysates using an antibody against the dystrophin C-terminal region revealed two bands, corresponding to Dp71b and Dp71ab. Immunohistochemical examination with the dystrophin antibody revealed scattered punctate signals in the cytoplasm and the nucleus. Western blotting revealed one band corresponding to Dp71b in the cytoplasm and two bands corresponding to Dp71b and Dp71ab in the nucleus, with Dp71b being predominant. These results indicated that Dp71ab is a nucleus-specific subisoform. We concluded that Dp71, comprising Dp71b and Dp71ab, was expressed exclusively in HEK293 cells and that Dp71ab was specifically localized to the nucleus. Our findings suggest that Dp71ab in the nucleus contributes to the diverse functions of HEK293 cells. PMID:27109495

  15. 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.

  16. 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. PMID:25762143

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

    PubMed Central

    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. PMID:26713733

  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. Cell Division During Inhibition of Deoxyribonucleic Acid Synthesis in Escherichia coli

    PubMed Central

    Helmstetter, Charles E.; Pierucci, Olga

    1968-01-01

    When cultures of Escherichia coli B/r growing at various rates were exposed to ultraviolet light, mitomycin C, or nalidixic acid, deoxyribonucleic acid (DNA) synthesis stopped but cell division continued for at least 20 min. The chromosome configurations in the cells which divided were estimated by determining the rate of DNA synthesis during the division cycle. The cultures were pulse-labeled with 14C-thymidine, and the amount of label incorporated into cells of different ages was found by measuring the radioactivity in cells born subsequent to the labeling period. The cells which divided in the absence of DNA synthesis were those which had completed a round of chromosome replication prior to the treatments. It was concluded that completion of a round of replication is a necessary and sufficient condition of DNA synthesis for cell division. PMID:4870278

  20. 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

  1. DNA damage-induced translocation of S100A11 into the nucleus regulates cell proliferation

    PubMed Central

    2010-01-01

    Background Proteins are able to react in response to distinct stress stimuli by alteration of their subcellular distribution. The stress-responsive protein S100A11 belongs to the family of multifunctional S100 proteins which have been implicated in several key biological processes. Previously, we have shown that S100A11 is directly involved in DNA repair processes at damaged chromatin in the nucleus. To gain further insight into the underlying mechanism subcellular trafficking of S100A11 in response to DNA damage was analyzed. Results We show that DNA damage induces a nucleolin-mediated translocation of S100A11 from the cytoplasm into the nucleus. This translocation is impeded by inhibition of the phosphorylation activity of PKCα. Translocation of S100A11 into the nucleus correlates with an increased cellular p21 protein level. Depletion of nucleolin by siRNA severely impairs translocation of S100A11 into the nucleus resulting in a decreased p21 protein level. Additionally, cells lacking nucleolin showed a reduced colony forming capacity. Conclusions These observations suggest that regulation of the subcellular distribution of S100A11 plays an important role in the DNA damage response and p21-mediated cell cycle control. PMID:21167017

  2. Mechanisms of Regulating Cell Topology in Proliferating Epithelia: Impact of Division Plane, Mechanical Forces, and Cell Memory

    PubMed Central

    Li, Yingzi; Naveed, Hammad; Kachalo, Sema; Xu, Lisa X.; Liang, Jie

    2012-01-01

    Regulation of cell growth and cell division has a fundamental role in tissue formation, organ development, and cancer progression. Remarkable similarities in the topological distributions were found in a variety of proliferating epithelia in both animals and plants. At the same time, there are species with significantly varied frequency of hexagonal cells. Moreover, local topology has been shown to be disturbed on the boundary between proliferating and quiescent cells, where cells have fewer sides than natural proliferating epithelia. The mechanisms of regulating these topological changes remain poorly understood. In this study, we use a mechanical model to examine the effects of orientation of division plane, differential proliferation, and mechanical forces on animal epithelial cells. We find that regardless of orientation of division plane, our model can reproduce the commonly observed topological distributions of cells in natural proliferating animal epithelia with the consideration of cell rearrangements. In addition, with different schemes of division plane, we are able to generate different frequency of hexagonal cells, which is consistent with experimental observations. In proliferating cells interfacing quiescent cells, our results show that differential proliferation alone is insufficient to reproduce the local changes in cell topology. Rather, increased tension on the boundary, in conjunction with differential proliferation, can reproduce the observed topological changes. We conclude that both division plane orientation and mechanical forces play important roles in cell topology in animal proliferating epithelia. Moreover, cell memory is also essential for generating specific topological distributions. PMID:22912800

  3. Monodisperse magnetite nanoparticles coupled with nuclear localization signal peptide for cell-nucleus targeting.

    PubMed

    Xu, Chenjie; Xie, Jin; Kohler, Nathan; Walsh, Edward G; Chin, Y Eugene; Sun, Shouheng

    2008-03-01

    Functionalization of monodisperse superparamagnetic magnetite (Fe(3)O(4)) nanoparticles for cell specific targeting is crucial for cancer diagnostics and therapeutics. Targeted magnetic nanoparticles can be used to enhance the tissue contrast in magnetic resonance imaging (MRI), to improve the efficiency in anticancer drug delivery, and to eliminate tumor cells by magnetic fluid hyperthermia. Herein we report the nucleus-targeting Fe(3)O(4) nanoparticles functionalized with protein and nuclear localization signal (NLS) peptide. These NLS-coated nanoparticles were introduced into the HeLa cell cytoplasm and nucleus, where the particles were monodispersed and non-aggregated. The success of labeling was examined and identified by fluorescence microscopy and MRI. The work demonstrates that monodisperse magnetic nanoparticles can be readily functionalized and stabilized for potential diagnostic and therapeutic applications. PMID:18080259

  4. Formation of tRNA granules in the nucleus of heat-induced human cells

    SciTech Connect

    Miyagawa, Ryu; Mizuno, Rie; Watanabe, Kazunori; Ijiri, Kenichi

    2012-02-03

    Highlights: Black-Right-Pointing-Pointer tRNAs are tranlocated into the nucleus in heat-induced HeLa cells. Black-Right-Pointing-Pointer tRNAs form the unique granules in the nucleus. Black-Right-Pointing-Pointer tRNA ganules overlap with nuclear stress granules. -- Abstract: The stress response, which can trigger various physiological phenomena, is important for living organisms. For instance, a number of stress-induced granules such as P-body and stress granule have been identified. These granules are formed in the cytoplasm under stress conditions and are associated with translational inhibition and mRNA decay. In the nucleus, there is a focus named nuclear stress body (nSB) that distinguishes these structures from cytoplasmic stress granules. Many splicing factors and long non-coding RNA species localize in nSBs as a result of stress. Indeed, tRNAs respond to several kinds of stress such as heat, oxidation or starvation. Although nuclear accumulation of tRNAs occurs in starved Saccharomyces cerevisiae, this phenomenon is not found in mammalian cells. We observed that initiator tRNA{sup Met} (Meti) is actively translocated into the nucleus of human cells under heat stress. During this study, we identified unique granules of Meti that overlapped with nSBs. Similarly, elongator tRNA{sup Met} was translocated into the nucleus and formed granules during heat stress. Formation of tRNA granules is closely related to the translocation ratio. Then, all tRNAs may form the specific granules.

  5. Vasopressin-immunoreactive cell bodies in the bed nucleus of the stria terminalis of the rat.

    PubMed

    van Leeuwen, F; Caffé, R

    1983-01-01

    In the dorsal and ventral portions of the bed nucleus of the stria terminalis of the rat numerous cell bodies immunoreactive for vasopressin and neurophysin II were found after colchicin pretreatment. These cells are predominantly multipolar but sometimes also bipolar, and have a width and length of approximately 9 and 16 microns, respectively. In the homozygous Brattleboro rat, which is deficient in vasopressin, no immunoreactive vasopressin was found in these cells. Following incubation with anti-oxytocin and anti-bovine neurophysin I, only magnocellular immunoreactive cell bodies were found in the septal region. The consequences of these results concerning the vasopressin fiber pathways in the brain are discussed. PMID:6339062

  6. 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

  7. From cell differentiation to cell collectives: Bacillus subtilis uses division of labor to migrate.

    PubMed

    van Gestel, Jordi; Vlamakis, Hera; Kolter, Roberto

    2015-04-01

    The organization of cells, emerging from cell-cell interactions, can give rise to collective properties. These properties are adaptive when together cells can face environmental challenges that they separately cannot. One particular challenge that is important for microorganisms is migration. In this study, we show how flagellum-independent migration is driven by the division of labor of two cell types that appear during Bacillus subtilis sliding motility. Cell collectives organize themselves into bundles (called "van Gogh bundles") of tightly aligned cell chains that form filamentous loops at the colony edge. We show, by time-course microscopy, that these loops migrate by pushing themselves away from the colony. The formation of van Gogh bundles depends critically on the synergistic interaction of surfactin-producing and matrix-producing cells. We propose that surfactin-producing cells reduce the friction between cells and their substrate, thereby facilitating matrix-producing cells to form bundles. The folding properties of these bundles determine the rate of colony expansion. Our study illustrates how the simple organization of cells within a community can yield a strong ecological advantage. This is a key factor underlying the diverse origins of multicellularity. PMID:25894589

  8. An ultradian clock controls locomotor behaviour and cell division in isolated cells of Paramecium tetraurelia.

    PubMed

    Kippert, F

    1996-04-01

    An ultradian clock operates in fast growing cells of the large ciliate, Paramecium tetraurelia. The period of around 70 minutes is well temperature-compensated over the temperature range tested, i.e. between 18 degrees C and 33 degrees C. The Q10 between 18 degrees C and 27 degrees C is 1.08; above 27 degrees C there is a slight overcompensation. The investigation of individual cells has revealed that two different cellular functions are under temporal control by this ultradian clock. First, locomotor behaviour, which is an alternation between a phase of fast swimming with only infrequent turning, and a phase of slow swimming with frequent spontaneous changes of direction. In addition, the ultradian clock is involved in the timing of cell division. Generation times are not randomly distributed, but occur in well separated clusters. At all of the six temperatures tested, the clusters are separated by around 70 minutes which corresponds well to the period of the locomotor behaviour rhythm at the respective temperatures. Whereas the interdivision times were gradually lengthened both above and below the optimum growth temperature, the underlying periodicity remained unaffected. Also cells of different clonal age had identical periods, suggesting that neither the differences in DNA content, not other changes associated with ageing in Paramecium have an effect on the clock. A constant phase relationship was observed between the rhythm in locomotor behaviour and the time window for cell division; this strongly suggests that the same ultradian clock exerts temporal control over both processes. PMID:8718678

  9. Effects of Nitrogen on Mesophyll Cell Division and Epidermal Cell Elongation in Tall Fescue Leaf Blades 1

    PubMed Central

    MacAdam, Jennifer W.; Volenec, Jeffrey J.; Nelson, Curtis J.

    1989-01-01

    Leaf elongation rate (LER) in grasses is dependent on epidermal cell supply (number) and on rate and duration of epidermal cell elongation. Nitrogen (N) fertilization increases LER. Longitudinal sections from two genotypes of tall fescue (Festuca arundinacea Schreb.), which differ by 50% in LER, were used to quantify the effects of N on the components of epidermal cell elongation and on mesophyll cell division. Rate and duration of epidermal cell elongation were determined by using a relationship between cell length and displacement velocity derived from the continuity equation. Rate of epidermal cell elongation was exponential. Relative rates of epidermal cell elongation increased by 9% with high N, even though high N increased LER by 89%. Duration of cell elongation was approximately 20 h longer in the high- than in the low-LER genotype regardless of N treatment. The percentage of mesophyll cells in division was greater in the high- than in the low-LER genotype. This increased with high N in both genotypes, indicating that LER increased with cell supply. Division of mesophyll cells adjacent to abaxial epidermal cells continued after epidermal cell division stopped, until epidermal cells had elongated to a mean length of 40 micrometers in the high-LER and a mean length of 50 micrometers in the low-LER genotype. The cell cycle length for mesophyll cells was calculated to be 12 to 13 hours. Nitrogen increased mesophyll cell number more than epidermal cell number: in both genotypes, the final number of mesophyll cells adjacent to each abaxial epidermal cell was 10 with low N and 14 with high N. A spatial model is used to describe three cell development processes relevant to leaf growth. It illustrates the overlap of mesophyll cell division and epidermal cell elongation, and the transition from epidermal cell elongation to secondary cell wall deposition. PMID:16666581

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

    NASA Astrophysics Data System (ADS)

    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.

  11. EMBO workshop report. An eclipse over the cell nucleus functional organization of the cell nucleus Prague, August 9-12, 1999.

    PubMed

    Raska, I; Aebi, U; Earnshaw, W C

    2000-08-01

    The EMBO workshop 'Functional Organization of the Cell Nucleus' held in Prague at the Hotel of the Postgraduate School of Medicine was attended by 110 participants (49 invited speakers and 61 selected participants) from 22 countries. Such a full range of topics devoted to the cell biology of the nucleus has not been discussed previously in such an intimate meeting in Europe. The workshop not only offered an opportunity for junior scientists to benefit from having an international meeting within Europe and a chance to discuss their work with internationally recognized experts, but it also offered a unique opportunity for interactions among the more established investigators. The fruits of a number of presentations are gathered together in a Special Issue of the Journal of Structural Biology which appeared in spring 2000. Last but not least, it is worth mentioning that while stepping through a packed scientific program, the participants did find the time to observe the solar eclipse just before the lunch break of August 11. PMID:10921866

  12. Real-Time Lineage Analysis to Study Cell Division Orientation in the Arabidopsis Shoot Meristem.

    PubMed

    Tobin, Cory J; Meyerowitz, Elliot M

    2016-01-01

    Cells in the Arabidopsis shoot apical meristem are small and divide frequently throughout the life-time of the organism making them good candidates for studying the mechanisms of cell division in plants. But tracking these cell divisions requires multiple images to be taken of the same specimen over time which means the specimen must stay alive throughout the process. This chapter provides details on how to prepare plants for live imaging, keep them alive and growing through multiple time points, and how to process the data to extract cell boundary coordinates from three-dimensional images. PMID:26659961

  13. Dominant negative mutants of the Cdc2 kinase uncouple cell division from iterative plant development.

    PubMed Central

    Hemerly, A; Engler, J de A; Bergounioux, C; Van Montagu, M; Engler, G; Inzé, D; Ferreira, P

    1995-01-01

    Because plant cells do not move and are surrounded by a rigid cell wall, cell division rates and patterns are believed to be directly responsible for generating new structures throughout development. To study the relationship between cell division and morphogenesis, transgenic tobacco and Arabidopsis plants were constructed expressing dominant mutations in a key regulator of the Arabidopsis cell cycle, the Cdc2a kinase. Plants constitutively overproducing the wild-type Cdc2a or the mutant form predicted to accelerate the cell cycle did not exhibit a significantly altered development. In contrast, a mutation expected to arrest the cell cycle abolished cell division when expressed in Arabidopsis, whereas some tobacco plants constitutively producing this mutant protein were recovered. These plants had a reduced histone H1 kinase activity and contained considerably fewer cells. These cells were, however, much larger and underwent normal differentiation. Morphogenesis, histogenesis and developmental timing were unaffected. The results indicate that, in plants, the developmental controls defining shape can act independently from cell division rates. Images PMID:7664733

  14. Serial interactome capture of the human cell nucleus

    PubMed Central

    Conrad, Thomas; Albrecht, Anne-Susann; de Melo Costa, Veronica Rodrigues; Sauer, Sascha; Meierhofer, David; Ørom, Ulf Andersson

    2016-01-01

    Novel RNA-guided cellular functions are paralleled by an increasing number of RNA-binding proteins (RBPs). Here we present ‘serial RNA interactome capture' (serIC), a multiple purification procedure of ultraviolet-crosslinked poly(A)–RNA–protein complexes that enables global RBP detection with high specificity. We apply serIC to the nuclei of proliferating K562 cells to obtain the first human nuclear RNA interactome. The domain composition of the 382 identified nuclear RBPs markedly differs from previous IC experiments, including few factors without known RNA-binding domains that are in good agreement with computationally predicted RNA binding. serIC extends the number of DNA–RNA-binding proteins (DRBPs), and reveals a network of RBPs involved in p53 signalling and double-strand break repair. serIC is an effective tool to couple global RBP capture with additional selection or labelling steps for specific detection of highly purified RBPs. PMID:27040163

  15. Imaging and quantification of amyloid fibrillation in the cell nucleus.

    PubMed

    Arnhold, Florian; Scharf, Andrea; von Mikecz, Anna

    2015-01-01

    Xenobiotics, as well as intrinsic processes such as cellular aging, contribute to an environment that constantly challenges nuclear organization and function. While it becomes increasingly clear that proteasome-dependent proteolysis is a major player, the topology and molecular mechanisms of nuclear protein homeostasis remain largely unknown. We have shown previously that (1) proteasome-dependent protein degradation is organized in focal microenvironments throughout the nucleoplasm and (2) heavy metals as well as nanoparticles induce nuclear protein fibrillation with amyloid characteristics. Here, we describe methods to characterize the landscape of intranuclear amyloid on the global and local level in different systems such as cultures of mammalian cells and the soil nematode Caenorhabditis elegans. Application of discrete mathematics to imaging data is introduced as a tool to develop pattern recognition of intracellular protein fibrillation. Since stepwise fibrillation of otherwise soluble proteins to insoluble amyloid-like protein aggregates is a hallmark of neurodegenerative protein-misfolding disorders including Alzheimer's disease, CAG repeat diseases, and the prion encephalopathies, investigation of intracellular amyloid may likewise aid to a better understanding of the pathomechanisms involved. We consider aggregate profiling as an important experimental approach to determine if nuclear amyloid has toxic or protective roles in various disease processes. PMID:25311131

  16. 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. PMID:26854071

  17. 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. PMID:27123539

  18. From Cell Differentiation to Cell Collectives: Bacillus subtilis Uses Division of Labor to Migrate

    PubMed Central

    van Gestel, Jordi; Vlamakis, Hera; Kolter, Roberto

    2015-01-01

    The organization of cells, emerging from cell–cell interactions, can give rise to collective properties. These properties are adaptive when together cells can face environmental challenges that they separately cannot. One particular challenge that is important for microorganisms is migration. In this study, we show how flagellum-independent migration is driven by the division of labor of two cell types that appear during Bacillus subtilis sliding motility. Cell collectives organize themselves into bundles (called “van Gogh bundles”) of tightly aligned cell chains that form filamentous loops at the colony edge. We show, by time-course microscopy, that these loops migrate by pushing themselves away from the colony. The formation of van Gogh bundles depends critically on the synergistic interaction of surfactin-producing and matrix-producing cells. We propose that surfactin-producing cells reduce the friction between cells and their substrate, thereby facilitating matrix-producing cells to form bundles. The folding properties of these bundles determine the rate of colony expansion. Our study illustrates how the simple organization of cells within a community can yield a strong ecological advantage. This is a key factor underlying the diverse origins of multicellularity. PMID:25894589

  19. 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. PMID:17360069

  20. Mini-F plasmid genes that couple host cell division to plasmid proliferation.

    PubMed Central

    Ogura, T; Hiraga, S

    1983-01-01

    A mechanism for stable maintenance of plasmids, besides the replication and partition mechanisms, has been found to be specified by genes of a mini-F plasmid. An oriC plasmid carrying both a mini-F segment necessary for partition [coordinates 46.4-49.4 kilobase pairs (kb) on the F map] and another segment (42.9-43.6 kb), designated ccd (coupled cell division), is more stably maintained than are oriC plasmids carrying only the partition segment; the stability is comparable to that of the parental mini-F plasmid. When replication of a plasmid carrying ccd is prevented and the plasmid copy number decreases, to as few as one per cell, host cell division is inhibited, but not increase of turbidity or chromosome replication. Appearance of plasmid-free segregants is therefore effectively prevented under such conditions. Experimental results suggest that reduction of the copy number of plasmids carrying the ccd region causes an inhibition of cell division and that the ccd region can be dissected into two functional regions; one (ccdB) inhibits cell division and the other (ccdA) releases the inhibition. The interplay of the ccdA and ccdB genes promotes stable plasmid maintenance by coupling host cell division to plasmid proliferation. PMID:6308648

  1. Segmentation of White Blood Cells through Nucleus Mark Watershed Operations and Mean Shift Clustering

    PubMed Central

    Liu, Zhi; Liu, Jing; Xiao, Xiaoyan; Yuan, Hui; Li, Xiaomei; Chang, Jun; Zheng, Chengyun

    2015-01-01

    This paper presents a novel method for segmentation of white blood cells (WBCs) in peripheral blood and bone marrow images under different lights through mean shift clustering, color space conversion and nucleus mark watershed operation (NMWO). The proposed method focuses on obtaining seed points. First, color space transformation and image enhancement techniques are used to obtain nucleus groups as inside seeds. Second, mean shift clustering, selection of the C channel component in the CMYK model, and illumination intensity adjustment are employed to acquire WBCs as outside seeds. Third, the seeds and NMWO are employed to precisely determine WBCs and solve the cell adhesion problem. Morphological operations are further used to improve segmentation accuracy. Experimental results demonstrate that the algorithm exhibits higher segmentation accuracy and robustness compared with traditional methods. PMID:26370995

  2. Activated STAT1 Transcription Factors Conduct Distinct Saltatory Movements in the Cell Nucleus

    PubMed Central

    Speil, Jasmin; Baumgart, Eugen; Siebrasse, Jan-Peter; Veith, Roman; Vinkemeier, Uwe; Kubitscheck, Ulrich

    2011-01-01

    The activation of STAT transcription factors is a critical determinant of their subcellular distribution and their ability to regulate gene expression. Yet, it is not known how activation affects the behavior of individual STAT molecules in the cytoplasm and nucleus. To investigate this issue, we injected fluorescently labeled STAT1 in living HeLa cells and traced them by single-molecule microscopy. We determined that STAT1 moved stochastically in the cytoplasm and nucleus with very short residence times (<0.03 s) before activation. Upon activation, STAT1 mobility in the cytoplasm decreased ∼2.5-fold, indicating reduced movement of STAT1/importinα/β complexes to the nucleus. In the nucleus, activated STAT1 displayed a distinct saltatory mobility, with residence times of up to 5 s and intermittent diffusive motion. In this manner, activated STAT1 factors can occupy their putative chromatin target sites within ∼2 s. These results provide a better understanding of the timescales on which cellular signaling and regulated gene transcription operate at the single-molecule level. PMID:22261046

  3. Symmetric cell division in pseudohyphae of the yeast Saccharomyces cerevisiae.

    PubMed Central

    Kron, S J; Styles, C A; Fink, G R

    1994-01-01

    Laboratory strains of Saccharomyces cerevisiae are dimorphic; in response to nitrogen starvation they switch from a yeast form (YF) to a filamentous pseudohyphal (PH) form. Time-lapse video microscopy of dividing cells reveals that YF and PH cells differ in their cell cycles and budding polarity. The YF cell cycle is controlled at the G1/S transition by the cell-size checkpoint Start. YF cells divide asymmetrically, producing small daughters from full-sized mothers. As a result, mothers and daughters bud asynchronously. Mothers bud immediately but daughters grow in G1 until they achieve a critical cell size. By contrast, PH cells divide symmetrically, restricting mitosis until the bud grows to the size of the mother. Thus, mother and daughter bud synchronously in the next cycle, without a G1 delay before Start. YF and PH cells also exhibit distinct bud-site selection patterns. YF cells are bipolar, producing their second and subsequent buds at either pole. PH cells are unipolar, producing their second and subsequent buds only from the end opposite the junction with their mother. We propose that in PH cells a G2 cell-size checkpoint delays mitosis until bud size reaches that of the mother cell. We conclude that yeast and PH forms are distinct cell types each with a unique cell cycle, budding pattern, and cell shape. Images PMID:7841518

  4. Label-free three-dimensional imaging of cell nucleus using third-harmonic generation microscopy

    SciTech Connect

    Lin, Jian; Zheng, Wei; Wang, Zi; Huang, Zhiwei

    2014-09-08

    We report the implementation of the combined third-harmonic generation (THG) and two-photon excited fluorescence (TPEF) microscopy for label-free three-dimensional (3-D) imaging of cell nucleus morphological changes in liver tissue. THG imaging shows regular spherical shapes of normal hepatocytes nuclei with inner chromatin structures while revealing the condensation of chromatins and nuclear fragmentations in hepatocytes of diseased liver tissue. Colocalized THG and TPEF imaging provides complementary information of cell nuclei and cytoplasm in tissue. This work suggests that 3-D THG microscopy has the potential for quantitative analysis of nuclear morphology in cells at a submicron-resolution without the need for DNA staining.

  5. Label-free three-dimensional imaging of cell nucleus using third-harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Lin, Jian; Zheng, Wei; Wang, Zi; Huang, Zhiwei

    2014-09-01

    We report the implementation of the combined third-harmonic generation (THG) and two-photon excited fluorescence (TPEF) microscopy for label-free three-dimensional (3-D) imaging of cell nucleus morphological changes in liver tissue. THG imaging shows regular spherical shapes of normal hepatocytes nuclei with inner chromatin structures while revealing the condensation of chromatins and nuclear fragmentations in hepatocytes of diseased liver tissue. Colocalized THG and TPEF imaging provides complementary information of cell nuclei and cytoplasm in tissue. This work suggests that 3-D THG microscopy has the potential for quantitative analysis of nuclear morphology in cells at a submicron-resolution without the need for DNA staining.

  6. Protective effect of cannabidiol on hydrogen peroxide‑induced apoptosis, inflammation and oxidative stress in nucleus pulposus cells.

    PubMed

    Chen, Jie; Hou, Chen; Chen, Xin; Wang, Dong; Yang, Pinglin; He, Xijing; Zhou, Jinsong; Li, Haopeng

    2016-09-01

    Cannabidiol, a major component of marijuana, protects nerves, and exerts antispasmodic, anti-inflammatory and anti‑anxiety effects. In the current study, the protective effect of cannabidiol was observed to prevent hydrogen peroxide (H2O2)‑induced apoptosis, inflammation and oxidative stress in nucleus pulposus cells. Nucleus pulposus cells were isolated from rats and cultured in vitro, and H2O2 was used to construct the nucleus pulposus cell model. Cell viability of the nucleus pulposus cells was assessed using a 3‑(4,5-dimethylthiazol-2-yl)-2,5‑diphenyltetrazolium bromide assay. The ratio of apoptotic cells, and caspase‑3 or cyclooxygenase‑2 (COX‑2) mRNA expression was analyzed by annexin V‑fluorescein isothiocyanate/propidium‑iodide staining and reverse transcription‑quantitative polymerase chain reaction, respectively. The quantities of interleukin (IL)‑1β and interleukin‑6 were measured using a series of assay kits. B-cell lymphoma 2 (Bcl‑2) and inducible nitric oxide synthase (iNOS) protein expression levels were analyzed using western blotting. The present study identified that cannabidiol enhanced cell viability and reduced apoptosis in H2O2‑treated nucleus pulposus cells in vitro using a lumbar disc herniation (LDH) model. In addition, cannabidiol reduced caspase‑3 gene expression and augmented the Bcl‑2 protein expression levels in the nucleus pulposus cells following H2O2 exposure. Pre‑treatment with cannabidiol suppressed the promotion of COX‑2, iNOS, IL‑1β and IL‑6 expression in the nucleus pulposus cells following H2O2 exposure. Taken together, these results suggest that cannabidiol potentially exerts its protective effect on LDH via the suppression of anti‑apoptosis, anti‑inflammation and anti‑oxidative activities in nucleus pulposus cells. PMID:27430346

  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. Phosphorus Deficiency Inhibits Cell Division But Not Growth in the Dinoflagellate Amphidinium carterae.

    PubMed

    Li, Meizhen; Shi, Xinguo; Guo, Chentao; Lin, Senjie

    2016-01-01

    Phosphorus (P) is an essential nutrient element for the growth of phytoplankton. How P deficiency affects population growth and the cell division cycle in dinoflagellates has only been studied in some species, and how it affects photosynthesis and cell growth remains poorly understood. In the present study, we investigated the impact of P deficiency on the cell division cycle, the abundance of the carbon-fixing enzyme Rubisco, and other cellular characteristics in the Gymnodiniales peridinin-plastid species Amphidinium carterae. We found that under P-replete condition, the cell cycle actively progressed in the culture in a 24-h diel cycle with daily growth rates markedly higher than the P-deficient cultures, in which cells were arrested in the G1 phase and cell size significantly enlarged. The results suggest that, as in previously studied dinoflagellates, P deficiency likely disenables A. carterae to complete DNA duplication or check-point protein phosphorylation. We further found that under P-deficient condition, overall photosystem II quantum efficiency (Fv/Fm ratio) and Rubisco abundance decreased but not significantly, while cellular contents of carbon, nitrogen, and proteins increased significantly. These observations indicated that under P-deficiency, this dinoflagellate was able to continue photosynthesis and carbon fixation, such that proteins and photosynthetically fixed carbon could accumulate resulting in continued cell growth in the absence of division. This is likely an adaptive strategy thereby P-limited cells can be ready to resume the cell division cycle upon resupply of phosphorus. PMID:27313570

  9. Phosphorus Deficiency Inhibits Cell Division But Not Growth in the Dinoflagellate Amphidinium carterae

    PubMed Central

    Li, Meizhen; Shi, Xinguo; Guo, Chentao; Lin, Senjie

    2016-01-01

    Phosphorus (P) is an essential nutrient element for the growth of phytoplankton. How P deficiency affects population growth and the cell division cycle in dinoflagellates has only been studied in some species, and how it affects photosynthesis and cell growth remains poorly understood. In the present study, we investigated the impact of P deficiency on the cell division cycle, the abundance of the carbon-fixing enzyme Rubisco, and other cellular characteristics in the Gymnodiniales peridinin-plastid species Amphidinium carterae. We found that under P-replete condition, the cell cycle actively progressed in the culture in a 24-h diel cycle with daily growth rates markedly higher than the P-deficient cultures, in which cells were arrested in the G1 phase and cell size significantly enlarged. The results suggest that, as in previously studied dinoflagellates, P deficiency likely disenables A. carterae to complete DNA duplication or check-point protein phosphorylation. We further found that under P-deficient condition, overall photosystem II quantum efficiency (Fv/Fm ratio) and Rubisco abundance decreased but not significantly, while cellular contents of carbon, nitrogen, and proteins increased significantly. These observations indicated that under P-deficiency, this dinoflagellate was able to continue photosynthesis and carbon fixation, such that proteins and photosynthetically fixed carbon could accumulate resulting in continued cell growth in the absence of division. This is likely an adaptive strategy thereby P-limited cells can be ready to resume the cell division cycle upon resupply of phosphorus. PMID:27313570

  10. The BASL Polarity Protein Controls a MAPK Signaling Feedback Loop in Asymmetric Cell Division

    PubMed Central

    Zhang, Ying; Wang, Pengcheng; Shao, Wanchen; Zhu, Jian-Kang; Dong, Juan

    2015-01-01

    SUMMARY Cell polarization is linked to fate determination during asymmetric division of plant stem cells, but the underlying molecular mechanisms remain unknown. In Arabidopsis, BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE (BASL) is polarized to control stomatal asymmetric division. A MITOGEN-ACTIVATED PROTEIN KINASE (MAPK) cascade determines terminal stomatal fate by promoting the degradation of the lineage determinant SPEECHLESS (SPCH). Here we demonstrate that a positive feedback loop between BASL and the MAPK pathway constitutes a polarity module at the cortex. Cortical localization of BASL requires phosphorylation mediated by MPK3/6. Phosphorylated BASL functions as a scaffold and recruits the MAPKKK YODA and MPK3/6 to spatially concentrate signaling at the cortex. Activated MPK3/6 reinforces the feedback loop by phosphorylating BASL, and inhibits stomatal fate by phosphorylating SPCH. Polarization of the BASL-MAPK signaling feedback module represents a mechanism connecting cell polarity to fate differentiation during asymmetric stem cell division in plants. PMID:25843888