共查询到20条相似文献，搜索用时 15 毫秒
1.
Adult stem cells often divide asymmetrically to produce one self-renewed stem cell and one differentiating cell, thus maintaining both populations. The asymmetric outcome of stem cell divisions can be specified by an oriented spindle and local self-renewal signals from the stem cell niche. Here we show that developmentally programmed asymmetric behavior and inheritance of mother and daughter centrosomes underlies the stereotyped spindle orientation and asymmetric outcome of stem cell divisions in the Drosophila male germ line. The mother centrosome remains anchored near the niche while the daughter centrosome migrates to the opposite side of the cell before spindle formation. 相似文献
2.
Germination in spores of the fern Onoclea sensibilis is initiated by an asymmetric division that partitions the spore into two cells of unequal size. The unequal daughter cells differentiate immediately into distinct types. When spores are germinated on the surface of solutions of methanol, the initial division is symmetrical, and the daughter cells from this equal division develop into the same type of cell. The differentiation of a rhizoid from the smaller cell in untreated spores is suppressed by methanol treatment. 相似文献
3.
During cell division, chromosomes are distributed to daughter cells by the mitotic spindle. This system requires spatial cues to reproducibly self-organize. We report that such cues are provided by chromosome-mediated interaction gradients between the small guanosine triphosphatase (GTPase) Ran and importin-beta. This produces activity gradients that determine the spatial distribution of microtubule nucleation and stabilization around chromosomes and that are essential for the self-organization of microtubules into a bipolar spindle. 相似文献
4.
DP Doupé MP Alcolea A Roshan G Zhang AM Klein BD Simons PH Jones 《Science (New York, N.Y.)》2012,337(6098):1091-1093
Diseases of the esophageal epithelium (EE), such as reflux esophagitis and cancer, are rising in incidence. Despite this, the cellular behaviors underlying EE homeostasis and repair remain controversial. Here, we show that in mice, EE is maintained by a single population of cells that divide stochastically to generate proliferating and differentiating daughters with equal probability. In response to challenge with all-trans retinoic acid (atRA), the balance of daughter cell fate is unaltered, but the rate of cell division increases. However, after wounding, cells reversibly switch to producing an excess of proliferating daughters until the wound has closed. Such fate-switching enables a single progenitor population to both maintain and repair tissue without the need for a "reserve" slow-cycling stem cell pool. 相似文献
5.
Multiple unrelated polymer systems have evolved to partition DNA molecules between daughter cells at division. To better understand polymer-driven DNA segregation, we reconstituted the three-component segregation system of the R1 plasmid from purified components. We found that the ParR/parC complex can construct a simple bipolar spindle by binding the ends of ParM filaments, inhibiting dynamic instability, and acting as a ratchet permitting incorporation of new monomers and riding on the elongating filament ends. Under steady-state conditions, the dynamic instability of unattached ParM filaments provides the energy required to drive DNA segregation. 相似文献
6.
Chang JT Palanivel VR Kinjyo I Schambach F Intlekofer AM Banerjee A Longworth SA Vinup KE Mrass P Oliaro J Killeen N Orange JS Russell SM Weninger W Reiner SL 《Science (New York, N.Y.)》2007,315(5819):1687-1691
A hallmark of mammalian immunity is the heterogeneity of cell fate that exists among pathogen-experienced lymphocytes. We show that a dividing T lymphocyte initially responding to a microbe exhibits unequal partitioning of proteins that mediate signaling, cell fate specification, and asymmetric cell division. Asymmetric segregation of determinants appears to be coordinated by prolonged interaction between the T cell and its antigen-presenting cell before division. Additionally, the first two daughter T cells displayed phenotypic and functional indicators of being differentially fated toward effector and memory lineages. These results suggest a mechanism by which a single lymphocyte can apportion diverse cell fates necessary for adaptive immunity. 相似文献
7.
Colchicine-inhibited cilia regeneration: explanation for lack of effect in tris buffer medium 总被引：1，自引：0，他引：1
In Stentor coeruleus growth of new, daughter ciliates and experimentaly inducled regeneration of oral membranellar cilia are reversibly inhibited by low, nontoxic concentrations of colchicine. However, if the clulture medium containing colchicine (or Colcemid) is made up in tris(hydroxymethyl)aminomethane buffer, growth of ciliated daughters and regeneration of oral cilia proceed normally. The evidence suggests that the mechanism of this reversal of the effects of colchicine (or Colcemid) is due to a chemical reaction between tris(hydroxymethyl)-aminomethane (or its hydrochloride, or both) and colchicine (or Colcemid), wihich reduces the effective concentration of these mitotic spindle inhibitors reaching the stentors. 相似文献
8.
【目的】 研究高产奶牛与优秀种公牛关系,追踪高产奶牛系谱,找出优秀种公牛,为牛场挑选优秀种公牛冻精提供理论依据。【方法】 统计泌乳牛305 d产奶量超过万千克的种公牛女儿,并通过输精记录匹配其女儿父号,将种公牛女儿305 d产奶量过万千克头数与女儿总数比值排名在前18头优秀种公牛通过中国奶牛数据中心查询其后代女儿生产性能,并对其女儿生产性能数据进行分析。【结果】 65610339号种公牛女儿305 d产奶量超过万千克占其所有女儿总数比例最高,达到57.14%。将挑选的18头优秀种公牛通过中国奶牛数据中心查询,65382019号种公牛女儿平均蛋白率最高,为3.32%。65382094号种公牛女儿平均305 d乳脂量最高,为4.04%。65908265号种公牛女儿平均305 d产奶量最高,为10 644 kg。【结论】 追踪高产奶牛父号系谱,其有共同血缘,且大部分源于北美优秀种公牛。优秀种公牛女儿测定的优秀率非常高,经过严格筛选的种公牛冻精在遗传上更具有优势。 相似文献
9.
The construction of multicellular organisms depends on stem cells-cells that can both regenerate and produce daughter cells that undergo differentiation. Here, we show that the gaseous messenger ethylene modulates cell division in the cells of the quiescent center, which act as a source of stem cells in the seedling root. The cells formed through these ethylene-induced divisions express quiescent center-specific genes and can repress differentiation of surrounding initial cells, showing that quiescence is not required for these cells to signal to adjacent stem cells. We propose that ethylene is part of a signaling pathway that modulates cell division in the quiescent center in the stem cell niche during the postembryonic development of the root system. 相似文献
10.
Nasmyth K 《Science (New York, N.Y.)》2002,297(5581):559-565
During cell division, each daughter cell inherits one copy of every chromosome. Accurate transmission of chromosomes requires that the sister DNA molecules created during DNA replication are disentangled and then pulled to opposite poles of the cell before division. Defects in chromosome segregation produce cells that are aneuploid (containing an abnormal number of chromosomes)-a situation that can have dire consequences. Aneuploidy is a leading cause of spontaneous miscarriages in humans and is also a hallmark of many human cancer cells. Recent work with yeast, Xenopus, and other model systems has provided new information about the proteins that control chromosome segregation during cell division and how the activities of these proteins are coordinated with the cell cycle. 相似文献
11.
Aldridge BB Fernandez-Suarez M Heller D Ambravaneswaran V Irimia D Toner M Fortune SM 《Science (New York, N.Y.)》2012,335(6064):100-104
Cells use both deterministic and stochastic mechanisms to generate cell-to-cell heterogeneity, which enables the population to better withstand environmental stress. Here we show that, within a clonal population of mycobacteria, there is deterministic heterogeneity in elongation rate that arises because mycobacteria grow in an unusual, unipolar fashion. Division of the asymmetrically growing mother cell gives rise to daughter cells that differ in elongation rate and size. Because the mycobacterial cell division cycle is governed by time, not cell size, rapidly elongating cells do not divide more frequently than slowly elongating cells. The physiologically distinct subpopulations of cells that arise through asymmetric growth and division are differentially susceptible to clinically important classes of antibiotics. 相似文献
12.
Yoshida S Kono K Lowery DM Bartolini S Yaffe MB Ohya Y Pellman D 《Science (New York, N.Y.)》2006,313(5783):108-111
The links between the cell cycle machinery and the cytoskeletal proteins controlling cytokinesis are poorly understood. The small guanine nucleotide triphosphate (GTP)-binding protein RhoA stimulates type II myosin contractility and formin-dependent assembly of the cytokinetic actin contractile ring. We found that budding yeast Polo-like kinase Cdc5 controls the targeting and activation of Rho1 (RhoA) at the division site via Rho1 guanine nucleotide exchange factors. This role of Cdc5 (Polo-like kinase) in regulating Rho1 is likely to be relevant to cytokinesis and asymmetric cell division in other organisms. 相似文献
13.
The adult Drosophila midgut contains multipotent intestinal stem cells (ISCs) scattered along its basement membrane that have been shown by lineage analysis to generate both enterocytes and enteroendocrine cells. ISCs containing high levels of cytoplasmic Delta-rich vesicles activate the canonical Notch pathway and down-regulate Delta within their daughters, a process that programs these daughters to become enterocytes. ISCs that express little vesiculate Delta, or are genetically impaired in Notch signaling, specify their daughters to become enteroendocrine cells. Thus, ISCs control daughter cell fate by modulating Notch signaling over time. Our studies suggest that ISCs actively coordinate cell production with local tissue requirements by this mechanism. 相似文献
14.
Lee L Tirnauer JS Li J Schuyler SC Liu JY Pellman D 《Science (New York, N.Y.)》2000,287(5461):2260-2262
Correct positioning of the mitotic spindle is critical for cell division and development. Spindle positioning involves a search-and-capture mechanism whereby dynamic microtubules find and then interact with specific sites on the submembrane cortex. Genetic, biochemical, and imaging experiments suggest a mechanism for cortical-microtubule capture. Bim1p, located at microtubule distal ends, bound Kar9p, a protein associated with the daughter cell cortex. Bim1p is the yeast ortholog of human EB1, a binding partner for the adenomatous polyposis coli tumor suppressor. EB1 family proteins may have a general role in linking the microtubule cytoskeleton to cortical polarity determinants. 相似文献
15.
16.
M. A. Eremina 《Russian Agricultural Sciences》2011,37(2):160-162
A 2.2% decrease of the homozygosity level in daughter cows of four bull sires led to an increase of their milk yield by 487.2
kg or by 7.5%. Minimum genetic similarity and maximum distance were established in daughters of bulls with a highest lactation
milk yield >7000 kg. 相似文献
17.
Abnormal cytokinesis in cells deficient in the breast cancer susceptibility protein BRCA2 总被引：1，自引：0，他引：1
Germ-line mutations inactivating BRCA2 predispose to cancer. BRCA2-deficient cells exhibit alterations in chromosome number (aneuploidy), as well as structurally aberrant chromosomes. Here, we show that BRCA2 deficiency impairs the completion of cell division by cytokinesis. BRCA2 inactivation in murine embryo fibroblasts (MEFs) and HeLa cells by targeted gene disruption or RNA interference delays and prevents cell cleavage. Impeded cell separation is accompanied by abnormalities in myosin II organization during the late stages in cytokinesis. BRCA2 may have a role in regulating these events, as it localizes to the cytokinetic midbody. Our findings thus link cytokinetic abnormalities to a hereditary cancer syndrome characterized by chromosomal instability and may help to explain why BRCA2-deficient tumors are frequently aneuploid. 相似文献
18.
Animals and fungi assemble a contractile ring of actin filaments and the motor protein myosin to separate into individual daughter cells during cytokinesis. We used fluorescence microscopy of live fission yeast cells to observe that membrane-bound nodes containing myosin were broadly distributed around the cell equator and assembled into a contractile ring through stochastic motions, after a meshwork of dynamic actin filaments appeared. Analysis of node motions and numerical simulations supported a mechanism whereby transient connections are established when myosins in one node capture and exert force on actin filaments growing from other nodes. 相似文献
19.
Kapoor TM Lampson MA Hergert P Cameron L Cimini D Salmon ED McEwen BF Khodjakov A 《Science (New York, N.Y.)》2006,311(5759):388-391
The stable propagation of genetic material during cell division depends on the congression of chromosomes to the spindle equator before the cell initiates anaphase. It is generally assumed that congression requires that chromosomes are connected to the opposite poles of the bipolar spindle ("bioriented"). In mammalian cells, we found that chromosomes can congress before becoming bioriented. By combining the use of reversible chemical inhibitors, live-cell light microscopy, and correlative electron microscopy, we found that monooriented chromosomes could glide toward the spindle equator alongside kinetochore fibers attached to other already bioriented chromosomes. This congression mechanism depended on the kinetochore-associated, plus end-directed microtubule motor CENP-E (kinesin-7). 相似文献
20.
The mitotic spindle: a self-made machine 总被引：1，自引：0，他引：1
The mitotic spindle is a highly dynamic molecular machine composed of tubulin, motors, and other molecules. It assembles around the chromosomes and distributes the duplicated genome to the daughter cells during mitosis. The biochemical and physical principles that govern the assembly of this machine are still unclear. However, accumulated discoveries indicate that chromosomes play a key role. Apparently, they generate a local cytoplasmic state that supports the nucleation and growth of microtubules. Then soluble and chromosome-associated molecular motors sort them into a bipolar array. The emerging picture is that spindle assembly is governed by a combination of modular principles and that their relative contribution may vary in different cell types and in various organisms. 相似文献