scholarly journals aPKC-mediated displacement and actomyosin-mediated retention polarize Miranda in Drosophila neuroblasts

2017 ◽  
Author(s):  
Matthew Hannaford ◽  
Anne Ramat ◽  
Nicolas Loyer ◽  
Jens Januschke
Keyword(s):  
Cell Cycle ◽  
Nervous System ◽  
Plasma Membrane ◽  
Cell Division ◽  
Nuclear Envelope ◽  
Cell Fate ◽  
Progenitor Cell ◽  
Unequal Distribution ◽  
Nuclear Envelope Breakdown ◽  
Differential Binding

SUMMARYCell fate generation can rely on the unequal distribution of molecules during progenitor cell division in the nervous system of vertebrates and invertebrates. Here we address asymmetric fate determinant localization in the developing Drosophila nervous system, focussing on the control of asymmetric Miranda distribution in larval neuroblasts. We used live imaging of neuroblast polarity reporters at endogenous levels of expression to address Miranda localization during the cell cycle. We reveal that the regulation and dynamics of cortical association of Miranda in interphase and mitosis are different. In interphase Miranda binds directly to the plasma membrane. At the onset of mitosis, Miranda is phosphorylated by aPKC and displaced from the PM. After nuclear envelope breakdown asymmetric localization of Miranda requires actomyosin activity. Therefore, Miranda phosphorylation by aPKC and differential binding to the actomyosin network are required at distinct phases of the cell cycle to polarize fate determinant localization.

scholarly journals aPKC-mediated displacement and actomyosin-mediated retention polarize Miranda in Drosophila neuroblasts

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Matthew Robert Hannaford ◽  
Anne Ramat ◽  
Nicolas Loyer ◽  
Jens Januschke
Keyword(s):  
Cell Cycle ◽  
Nervous System ◽  
Plasma Membrane ◽  
Nuclear Envelope ◽  
Cell Fate ◽  
Progenitor Cell ◽  
Adapter Protein ◽  
Unequal Distribution ◽  
Nuclear Envelope Breakdown ◽  
Differential Binding

Cell fate assignment in the nervous system of vertebrates and invertebrates often hinges on the unequal distribution of molecules during progenitor cell division. We address asymmetric fate determinant localization in the developing Drosophila nervous system, specifically the control of the polarized distribution of the cell fate adapter protein Miranda. We reveal a step-wise polarization of Miranda in larval neuroblasts and find that Miranda’s dynamics and cortical association are differently regulated between interphase and mitosis. In interphase, Miranda binds to the plasma membrane. Then, before nuclear envelope breakdown, Miranda is phosphorylated by aPKC and displaced into the cytoplasm. This clearance is necessary for the subsequent establishment of asymmetric Miranda localization. After nuclear envelope breakdown, actomyosin activity is required to maintain Miranda asymmetry. Therefore, phosphorylation by aPKC and differential binding to the actomyosin network are required at distinct phases of the cell cycle to polarize fate determinant localization in neuroblasts.

The pelota locus encodes a protein required for meiotic cell division: an analysis of G2/M arrest in Drosophila spermatogenesis

Development ◽  
1995 ◽  
Vol 121 (10) ◽  
pp. 3477-3486 ◽  
Author(s):  
C.G. Eberhart ◽  
S.A. Wasserman
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Nuclear Envelope ◽  
Germ Cells ◽  
Meiotic Division ◽  
Meiotic Cell ◽  
Spindle Formation ◽  
Nuclear Envelope Breakdown ◽  
G2 Phase

During Drosophila spermatogenesis, germ cells undergo four rounds of mitosis, an extended premeiotic G2 phase and two meiotic divisions. In males homozygous for mutations in pelota, the germline mitotic divisions are normal, but the cell cycle arrests prior to the first meiotic division; pelota males are therefore sterile. Chromosomes begin to condense in these mutants, but other meiotic processes, including nuclear envelope breakdown and spindle formation, do not occur. The arrest phenotype closely resembles that of mutations in the Drosophila cdc25 homolog twine. Although meiosis is blocked in pelota and twine homozygotes, spermatid differentiation continues. pelota is also required for patterning in the eye and mitotic divisions in the ovary. We have cloned the pelota locus and show it encodes a 44 × 10(3) M(r) protein with yeast, plant, worm and human homologs.

scholarly journals The Role of Phosphatases in Nuclear Envelope Disassembly and Reassembly and Their Relevance to Pathologies

Cells ◽  
2019 ◽  
Vol 8 (7) ◽  
pp. 687 ◽  
Author(s):  
Florentin Huguet ◽  
Shane Flynn ◽  
Paola Vagnarelli
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Nuclear Envelope ◽  
Current Understanding ◽  
The Past ◽  
Pathological Conditions ◽  
Regulation Of Cell Cycle

The role of kinases in the regulation of cell cycle transitions is very well established, however, over the past decade, studies have identified the ever-growing importance of phosphatases in these processes. It is well-known that an intact or otherwise non-deformed nuclear envelope (NE) is essential for maintaining healthy cells and any deviation from this can result in pathological conditions. This review aims at assessing the current understanding of how phosphatases contribute to the remodelling of the nuclear envelope during its disassembling and reformation after cell division and how errors in this process may lead to the development of diseases.

scholarly journals Role of spindle microtubules in the control of cell cycle timing.

1979 ◽  
Vol 80 (3) ◽  
pp. 674-691 ◽  
Author(s):  
G Sluder
Keyword(s):  
Cell Cycle ◽  
Nuclear Envelope ◽  
Sea Urchin ◽  
Control Cell ◽  
Microtubule Assembly ◽  
Nuclear Envelope Breakdown ◽  
Anaphase Onset ◽  
Spindle Cells ◽  
Spindle Microtubules

Sea urchin eggs are used to investigate the involvement of spindle microtubules in the mechanisms that control the timing of cell cycle events. Eggs are treated for 4 min with Colcemid at prophase of the first mitosis. No microtubules are assembled for at least 3 h, and the eggs do not divide. These eggs show repeated cycles of nuclear envelope breakdown (NEB) and nuclear envelope reformation (NER). Mitosis (NEB to NER) is twice as long in Colcemid-treated eggs as in the untreated controls. Interphase (NER to NEB) is the same in both. Thus, each cycle is prolonged entirely in mitosis. The chromosomes of treated eggs condense and eventually split into separate chromatids which do not move apart. This "canaphase" splitting is substantially delayed relative to anaphase onset in the control eggs. Treated eggs are irradiated after NEB with 366-nm light to inactivate the Colcemid. This allows the eggs to assemble normal spindles and divide. Up to 14 min after NEB, delays in the start of microtubule assembly give equal delays in anaphase onset, cleavage, and the events of the following cell cycle. Regardless of the delay, anaphase follows irradiation by the normal prometaphase duration. The quantity of spindle microtubules also influences the timing of mitotic events. Short Colcemid treatments administered in prophase of second division cause eggs to assemble small spindles. One blastomere is irradiated after NEB to provide a control cell with a normal-sized spindle. Cells with diminished spindles always initiate anaphase later than their controls. Telophase events are correspondingly delayed. This work demonstrates that spindle microtubules are involved in the mechanisms that control the time when the cell will initiate anaphase, finish mitosis, and start the next cell cycle.

Dissecting Stem Cell Proliferation and Differentiation in Association with the Central Cell Cycle Regulator APC/CCdh1

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1236-1236 ◽  
Author(s):  
Daniel Ewerth ◽  
Andrea Schmidts ◽  
Birgit Kuegelgen ◽  
Dagmar Wider ◽  
Julia Schüler ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Stem Cell ◽  
Cell Division ◽  
Cell Fate ◽  
Myeloid Cells ◽  
Central Cell ◽  
Self Renewal ◽  
Cell Cycle Entry ◽  
Cell Cycle Regulator ◽  
Cd34 Cells

Abstract Abstract 1236 Hematopoietic stem cells (HSCs) and multipotent progenitor cells continuously maintain hematopoiesis by self-renewal and differentiation to all types of blood lineages. These unique processes are regulated by intrinsic and extrinsic signals (e.g. cytokines, cell-cell contacts) and strongly connects stem cell fate with the cell cycle. The ubiquitin-proteasome system regulates spatial and temporal abundance of proteins in the cell. During cell cycle, the anaphase-promoting complex or cyclosome (APC/C) with its co-activators Cdc20 and Cdh1 marks proteins for proteasomal degradation and thus controls their activity. Known targets of Cdh1, namely Skp2 and Id2, are involved in regulation of self-renewal and granulopoiesis (Wang et al., Blood 2011; Buitenhuis et al., Blood 2005). This raises the hypothesis that Cdh1 may be a critical upstream regulator of HSC differentiation. The analysis of human bone marrow cell subsets (CD34+, lymphoid and myeloid cells) revealed highest protein level of Cdh1 in CD34+ cells, lower expression in more mature lymphoid subsets (CD3+, CD19+) and only marginal expression in mature myeloid cells (CD41a+, CD11b+). These data suggest that Cdh1 is important to induce differentiation, but dispensable for maintaining the differentiated state. In vitro cultivation of G-CSF mobilized peripheral blood CD34+ cells under conditions resulting in either self-renewal (SCF, TPO, Flt3-l) or differentiation/granulopoiesis (SCF, G-CSF) showed downregulation of Cdh1 during culture compared to d0. Western blots did not only reveal decreasing levels of Cdh1, but also its inactivation by its specific inhibitor Emi1 which stabilized the ubiquitin ligase Skp2 and promoted cell cycle entry and proliferation by degrading the cyclin-dependent-kinase inhibitor p27. In addition, the APC/CCdh1 target cyclin B was upregulated. These data indicate that initial Cdh1 downregulation is required to promote cell cycle entry and proliferation of CD34+ HSCs under conditions mediating both self-renewal as well as differentiation. To analyze cell division/proliferation and self-renewal versus differentiation more closely, we used the fluorescent dye CFSE as an indicator of cell division in combination with CD34 to indicate the differentiation status. When cultured under self-renewal conditions using SCF, TPO and Flt3-l, CD34+cells showed enhanced proliferation with increased cells in higher generations, whereas using SCF and G-CSF to induce granulopoiesis, cells within lower generations were more prominent. These experiments also revealed a rapid decrease of CD34 expression in granulopoiesis after 3 cell divisions in contrast to a moderate decline under self-renewal conditions. This is consistent with more symmetric divisions into CD34+ daughter cells under self-renewal conditions and gradual cell cycle exit and differentiation under conditions that induce granulopoiesis. To further elucidate the role of Cdh1 for stem/progenitor cell fate, we used a lentiviral knockdown of Cdh1 in CD34+ cells. After 4 days of transduction and cell sorting, the cells were cultivated for 1 week in medium containing SCF, TPO and Flt3-l. Cdh1 depleted cells showed enhanced proliferation compared to the empty vector control and a higher expression of CD34. In colony forming unit (CFU) assays, we observed that CD34+ cells with Cdh1-knockdown were less efficient to differentiate to CFU-G, CFU-M and BFU-E. A higher potential to self-renew was validated by replating of these colonies, where the number with Cdh1-knockdown increased during serial replating. To validate our results in vivo, we have established a NOD/SCID/IL-2Rγ chain−/− (NSG) xenotransplant mouse model. The evaluation of engraftment capacity and differentiation potential of human Cdh1 depleted CD34+ cells in this model is ongoing. Our data establish the central cell cycle regulator APC/CCdh1 as a novel regulator of self-renewal and differentiation in CD34+ HSCs. Disclosures: No relevant conflicts of interest to declare.

Sperm nuclear envelope: breakdown of intrinsic envelope and de novo formation in hamster oocytes or eggs

Zygote ◽  
1997 ◽  
Vol 5 (1) ◽  
pp. 35-46 ◽  
Author(s):  
Noriko Usui ◽  
Atsuo Ogura ◽  
Yasuyuki Kimura ◽  
Ryuzo Yanagimachi
Keyword(s):  
Cell Cycle ◽  
Nuclear Envelope ◽  
De Novo ◽  
Germinal Vesicle ◽  
Mature Oocyte ◽  
Sperm Nucleus ◽  
Sperm Chromatin ◽  
Early Prophase ◽  
Nuclear Envelope Breakdown ◽  
M Phase

SummaryDuring fertilisation of a fully mature oocyte, the sperm intrinsic nuclear envelope (SINE) disappears soon after sperm-oocyte fusion. A new nuclear envelope appears around the decondensed sperm chromatin when the oocyte reaches telophase II. Whether the SINE persists or rapidly disappears after sperm entery into immature oocytes or fertilised eggs has been controversial. Nuclear envelopes have been demonstrated around the sperm chromatin, which cannot be decondensed within the ooplasm of these oocytes or eggs, but whether these envelopes are persisting SINEs or newly formed envelopes has been apoint of dispute. To resolve this issue, the fate of the germinal vesicle stage(GV oocytes) or fertilised eggs at the pronuclear stage(PN eggs). The SINEs disappeared quikly within these oocytes or eggs, like those within maturing or mature oocytes, suggesting that the envelops around the sperm chromatin must be newly formed after SINE breakdown. To obtain further evidence, a detergent-treated, SINE-free sperm nucleus was injected into a PN egg. A new envelope appeared around the still-condensed or partially decondensed sperm chromatin within 3h after injection. Thus, disassembly of the SINE within ooplasm, unlike that of nuclear envelopes of other cells at prophase, is independent of the cell cycle stage of the oocyte or egg, whereas the ability of the ooplasm to assemble the new envelope is restricted to certain periods of the cycle. i.e. early prophase and telophase during meiosis and interphase, periods when active M-phase Promoting factor (MPF) is absent from the ooplasm.

scholarly journals Co-ordination of cell cycle and differentiation in the developing nervous system

2012 ◽  
Vol 444 (3) ◽  
pp. 375-382 ◽  
Author(s):  
Christopher Hindley ◽  
Anna Philpott
Keyword(s):  
Cell Cycle ◽  
Nervous System ◽  
Embryonic Development ◽  
Cell Fate ◽  
Cell Cycle Progression ◽  
Control Cell ◽  
Cell Cycle Regulators ◽  
Cyclin Dependent Kinases ◽  
Proliferation And Differentiation ◽  
Developing Nervous System

During embryonic development, cells must divide to produce appropriate numbers, but later must exit the cell cycle to allow differentiation. How these processes of proliferation and differentiation are co-ordinated during embryonic development has been poorly understood until recently. However, a number of studies have now given an insight into how the cell cycle machinery, including cyclins, CDKs (cyclin-dependent kinases), CDK inhibitors and other cell cycle regulators directly influence mechanisms that control cell fate and differentiation. Conversely, examples are emerging of transcriptional regulators that are better known for their role in driving the differentiated phenotype, which also play complementary roles in controlling cell cycle progression. The present review will summarise our current understanding of the mechanisms co-ordinating the cell cycle and differentiation in the developing nervous system, where these links have been, perhaps, most extensively studied.

Repetitive sperm-induced Ca2+ transients in mouse oocytes are cell cycle dependent

Development ◽  
1995 ◽  
Vol 121 (10) ◽  
pp. 3259-3266 ◽  
Author(s):  
K.T. Jones ◽  
J. Carroll ◽  
J.A. Merriman ◽  
D.G. Whittingham ◽  
T. Kono
Keyword(s):  
Cell Cycle ◽  
Nuclear Envelope ◽  
Dependent Manner ◽  
Nuclear Envelope Breakdown ◽  
Mouse Oocytes ◽  
A Cell ◽  
Mature Mouse ◽  
Cycle Dependent ◽  
Stage 1

Mature mouse oocytes are arrested at metaphase of the second meiotic division. Completion of meiosis and a block to polyspermy is caused by a series of repetitive Ca2+ transients triggered by the sperm at fertilization. These Ca2+ transients have been widely reported to last for a number of hours but when, or why, they cease is not known. Here we show that Ca2+ transients cease during entry into interphase, at the time when pronuclei are forming. In fertilized oocytes arrested at metaphase using colcemid, Ca2+ transients continued for as long as measurements were made, up to 18 hours after fertilization. Therefore sperm is able to induce Ca2+ transients during metaphase but not during interphase. In addition metaphase II oocytes, but not pronuclear stage 1-cell embryos showed highly repetitive Ca2+ oscillations in response to microinjection of inositol trisphosphate. This was explored further by treating in vitro maturing oocytes at metaphase I for 4–5 hours with cycloheximide, which induced nuclear progression to interphase (nucleus formation) and subsequent re-entry to metaphase (nuclear envelope breakdown). Fertilization of cycloheximide-treated oocytes revealed that continuous Ca2+ oscillations in response to sperm were observed after nuclear envelope breakdown but not during interphase. However interphase oocytes were able to generate Ca2+ transients in response to thimerosal. This data suggests that the ability of the sperm to trigger repetitive Ca2+ transients in oocytes is modulated in a cell cycle-dependent manner.

Two proteins that cycle asynchronously between centrosomes and nuclear structures: Drosophila CP60 and CP190

1997 ◽  
Vol 110 (14) ◽  
pp. 1573-1583 ◽  
Author(s):  
K. Oegema ◽  
W.F. Marshall ◽  
J.W. Sedat ◽  
B.M. Alberts
Keyword(s):  
Cell Cycle ◽  
Nuclear Envelope ◽  
Wide Field ◽  
Dependent Manner ◽  
Independent Manner ◽  
Nuclear Envelope Breakdown ◽  
Nuclear Structures ◽  
Dynamic Structures ◽  
Cycle Dependent

Both the nucleus and the centrosome are complex, dynamic structures whose architectures undergo cell cycle-specific rearrangements. CP190 and CP60 are two Drosophila proteins of unknown function that shuttle between centrosomes and nuclei in a cell cycle-dependent manner. These two proteins are associated in vitro, and localize to centrosomes in a microtubule independent manner. We injected fluorescently labeled, bacterially expressed CP190 and CP60 into living Drosophila embryos and followed their behavior during the rapid syncytial blastoderm divisions (nuclear cycles 10–13). Using quantitative 3-D wide-field fluorescence microscopy, we show that CP190 and CP60 cycle between nuclei and centrosomes asynchronously with the accumulation of CP190 leading that of CP60 both at centrosomes and in nuclei. During interphase, CP190 is found in nuclei. Immediately following nuclear envelope breakdown, CP190 localizes to centrosomes where it remains until telophase, thereafter accumulating in reforming nuclei. Unlike CP190, CP60 accumulates at centrosomes primarily during anaphase, where it remains into early interphase. During nuclear cycles 10 and 11, CP60 accumulates in nuclei simultaneous with nuclear envelope breakdown, suggesting that CP60 binds to an unknown nuclear structure that persists into mitosis. During nuclear cycles 12 and 13, CP60 accumulates gradually in nuclei during interphase, reaching peak levels just before nuclear envelope breakdown. Once in the nucleus, both CP190 and CP60 appear to form fibrous intranuclear networks that remain coherent even after nuclear envelope breakdown. The CP190 and CP60 networks do not co-localize extensively with each other or with DNA. This work provides direct evidence, in living cells, of a coherent protein network that may represent a nuclear skeleton.

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