Microtubule distribution and function in early Pelvetia development

1990 ◽  
Vol 97 (3) ◽  
pp. 545-552
Author(s):  
DARRYL L. KROFF ◽  
ANNA MADDOCK ◽  
DAVID L. GARD
Keyword(s):  
Mitotic Spindle ◽  
Immunofluorescence Microscopy ◽  
Cell Lineage ◽  
Cytochalasin D ◽  
Division Plane ◽  
Cell Cycles ◽  
Growth Axis ◽  
And Function ◽  
Proper Orientation ◽  
Peripheral Cytoplasm

We have used immunofluorescence microscopy to examine the distribution of microtubules (Mts) during the first two cell cycles in embryos of the brown alga, Pelvetia. Prior to germination of the zygote at 12 h post-fertilization, Mts radiated from the circumnuclear region into the peripheral cytoplasm. After rhizoid emergence, Mts resolved into two perinuclear microtubule organizing centers (MTOCs). The axis defined by the pair of MTOCs was oriented transverse to the growth axis, with Mts extending from each MTOC into the rhizoid. The axis defined by the MTOCs then reoriented by 90 degrees, and aligned with the growth axis. The first mitotic spindle formed between these MTOCs. The division plane bisected the spindle, giving rise to rhizoid and thallus cells with distinct developmental potentials. During the second cell cycle, the axis defined by MTOCs in the rhizoid cell again reoriented from an orthogonal to an axial alignment with respect to the growth axis. MTOC reorientation did not occur in the thallus cell, and the division planes in the rhizoid and thallus cells were orthogonal to one another. Zygotes treated with amiprophos methyl (APM) or taxol established an axis and initiated rhizoid outgrowth. However, treated zygotes ceased growing soon after germination and failed to divide. Cytochalasin D, which prevents establishment of the developmental axis, interfered with the proper orientation of the spindle. From these results we conclude that: (1) Mts are not required for establishment of the rhizoid-thallus axis or rhizoid germination; (2) an F-actin-dependent process, probably establishment of a developmental axis, is required for rotation of the axis defined by MTOCs; and (3) the alignment of perinuclear MTOCs dictates the orientation of spindle and subsequent division planes, and thereby controls cell lineage.

scholarly journals Plk1 regulates spindle orientation by phosphorylating NuMA in human cells

2018 ◽  
Vol 1 (6) ◽  
pp. e201800223 ◽  
Author(s):  
Shrividya Sana ◽  
Riya Keshri ◽  
Ashwathi Rajeevan ◽  
Sukriti Kapoor ◽  
Sachin Kotak
Keyword(s):  
Cell Division ◽  
Mitotic Spindle ◽  
Molecular Mechanisms ◽  
Spindle Pole ◽  
Spindle Orientation ◽  
Cell Cortex ◽  
Division Plane ◽  
Evolutionarily Conserved ◽  
Cortical Localization ◽  
Proper Orientation

Proper orientation of the mitotic spindle defines the correct division plane and is essential for accurate cell division and development. In metazoans, an evolutionarily conserved complex comprising of NuMA/LGN/Gαi regulates proper orientation of the mitotic spindle by orchestrating cortical dynein levels during metaphase. However, the molecular mechanisms that modulate the spatiotemporal dynamics of this complex during mitosis remain elusive. Here, we report that acute inactivation of Polo-like kinase 1 (Plk1) during metaphase enriches cortical levels of dynein/NuMA/LGN and thus influences spindle orientation. We establish that this impact of Plk1 on cortical levels of dynein/NuMA/LGN is through NuMA, but not via dynein/LGN. Moreover, we reveal that Plk1 inhibition alters the dynamic behavior of NuMA at the cell cortex. We further show that Plk1 directly interacts and phosphorylates NuMA. Notably, NuMA-phosphorylation by Plk1 impacts its cortical localization, and this is needed for precise spindle orientation during metaphase. Overall, our finding connects spindle-pole pool of Plk1 with cortical NuMA and answers a long-standing puzzle about how spindle-pole Plk1 gradient dictates proper spindle orientation for error-free mitosis.

Antiproliferative Effects of Ocimum basilicum Methanolic Extract and Fractions, Oleanolic Acid and 3-epi-Ursolic Acid

2020 ◽  
Vol 6 (2) ◽  
pp. 134-146 ◽  
Author(s):  
Kehkashan Arshad Qamar ◽  
Ahsana Dar Farooq ◽  
Bina S. Siddiqui ◽  
Nurul Kabir ◽  
Sabira Begum
Keyword(s):  
Ursolic Acid ◽  
Oleanolic Acid ◽  
Mitotic Spindle ◽  
Immunofluorescence Microscopy ◽  
Methanolic Extract ◽  
Folk Medicine ◽  
Ocimum Basilicum ◽  
Antiproliferative Effects ◽  
Ancient Times ◽  
Mcf 7

Aims: The aim of the current study was to identify active compound(s) responsible for the antiproliferative effects of O. basilicum and explore their underlying mechanism/s. Background: Plants have been the source of medicines for the treatment of various diseases since ancient times. Ocimum basilicum (Sweet Basil, Bobai Tulsi) has been used in the folk medicine for the treatment of human liver, spleen and stomach cancers. Background: Plants have been the source of medicines for the treatment of various diseases since ancient times. Ocimum basilicum (Sweet Basil, Bobai Tulsi) has been used in the folk medicine for the treatment of human liver, spleen and stomach cancers. Objective: To emphasize the importance of O. basilicum as a potential novel non-toxic alternative to the conventional anticancer therapy. Method: O. basilicum (aerial parts) methanolic extract and fractions were screened against HT-144, MCF-7, NCI-H460 and SF-268 human cancer cell lines using sulforhodamine B assay. The more active Petroleum Ether Insoluble (PEI) fraction was fractionated into six sub-fractions (OB-1 to OB-6). Four pure compounds (3-O-methyl ursolic acid, oleanolic acid, 3-epi-ursolic acid and ursolic acid) were isolated from the more potent sub-fraction OB- 6. Triple channel immunofluorescence microscopy was employed to observe the effects of methanolic extract, PEI fraction, sub-fractions OB-5 and OB-6, 3-epi-ursolic acid and oleanolic acid on the cytoskeleton and nuclei of MCF-7 cells. Result: The methanolic extract and the PEI fraction exhibited selectively greater growth inhibition against MCF-7 cell line (TGI: 56 and 36.2 µg/ml, respectively). By using triple channel immunofluorescence microscopy, it was observed that the methanolic extract, PEI fraction, sub-fraction OB-5 and 3-epi-ursolic acid induced irregular mitotic spindle formation and slowing of mitotic progression in MCF-7 cells while sub-fraction OB-6 induced mitotic arrest in the prophase stage. F-actin aggregation was also visible in PEI fraction, subfraction OB-5 and 3-epi-ursolic acid treated MCF-7 cells. Conclusion: These results emphasize the importance of O. basilicum as a potential novel non-toxic alternative to the conventional anticancer therapy and suggest that it inhibits the growth of MCF-7 cancer cells via multiple mechanisms such as interaction with the microtubules and mitotic spindle apparatus, and F-actin aggregation.

scholarly journals Steroidogenic Factor-1 (SF-1)-Driven Differentiation of Murine Embryonic Stem (ES) Cells into a Gonadal Lineage

Endocrinology ◽  
2011 ◽  
Vol 152 (7) ◽  
pp. 2870-2882 ◽  
Author(s):  
Unmesh Jadhav ◽  
J. Larry Jameson
Keyword(s):  
Target Genes ◽  
De Novo ◽  
Embryoid Body ◽  
Es Cells ◽  
Embryonic Stem ◽  
Cell Lineage ◽  
Culture Conditions ◽  
Steroidogenic Factor 1 ◽  
Lineage Differentiation ◽  
And Function

Steroidogenic factor 1 (SF-1) is essential for the development and function of steroidogenic tissues. Stable incorporation of SF-1 into embryonic stem cells (SF-1-ES cells) has been shown to prime the cells for steroidogenesis. When provided with exogenous cholesterol substrate, and after treatment with retinoic acid and cAMP, SF-1-ES cells produce progesterone but do not produce other steroids such as cortisol, estradiol, or testosterone. In this study, we explored culture conditions that optimize SF-1-mediated differentiation of ES cells into defined steroidogenic lineages. When embryoid body formation was used to facilitate cell lineage differentiation, SF-1-ES cells were found to be restricted in their differentiation, with fewer cells entering neuronal pathways and a larger fraction entering the steroidogenic lineage. Among the differentiation protocols tested, leukemia inhibitory factor (LIF) removal, followed by prolonged cAMP treatment was most efficacious for inducing steroidogenesis in SF-1-ES cells. In this protocol, a subset of SF-1-ES cells survives after LIF withdrawal, undergoes morphologic differentiation, and recovers proliferative capacity. These cells are characterized by induction of steroidogenic enzyme genes, use of de novo cholesterol, and production of multiple steroids including estradiol and testosterone. Microarray studies identified additional pathways associated with SF-1 mediated differentiation. Using biotinylated SF-1 in chromatin immunoprecipitation assays, SF-1 was shown to bind directly to multiple target genes, with induction of binding to some targets after steroidogenic treatment. These studies indicate that SF-1 expression, followed by LIF removal and treatment with cAMP drives ES cells into a steroidogenic pathway characteristic of gonadal steroid-producing cells.

Cytoskeletal involvement in the modulation of cell-cell junctions by the protein kinase inhibitor H-7

1994 ◽  
Vol 107 (3) ◽  
pp. 683-692 ◽  
Author(s):  
S. Citi ◽  
T. Volberg ◽  
A.D. Bershadsky ◽  
N. Denisenko ◽  
B. Geiger
Keyword(s):  
Protein Kinase ◽  
Epithelial Cells ◽  
Immunofluorescence Microscopy ◽  
Kinase Inhibitor ◽  
Cytochalasin D ◽  
Extracellular Calcium ◽  
Protein Kinase Inhibitor ◽  
Madin Darby Canine Kidney ◽  
Darby Canine Kidney ◽  
Canine Kidney

The protein kinase inhibitor H-7 has been shown to block junction dissociation induced by low extracellular calcium in Madin Darby canine kidney epithelial cells (S. Citi, J. Cell Biol. (1992) 117, 169–178). To understand the basis of this effect, we have examined how H-7 affects the organization of junctions and the actin cytoskeleton in different types of epithelial cells in culture. Immunofluorescence microscopy showed that H-7 confers Ca2+ independence on cultured epithelial lens cells, which lack tight junctions and desmosomes but have microfilament-associated adherens junctions. In these cells, H-7 did not protect N-cadherin from trypsin digestion at low extracellular calcium, suggesting that H-7 does not stabilize the ‘active’ cadherin conformation. In cultured Madin Darby canine kidney cells, H-7 partially prevented the fall in transepithelial resistance induced by cytochalasin D, either alone or in conjunction with calcium chelators. Double-immunofluorescence microscopy showed that H-7 inhibits both the fragmentation of labeling for the tight junction protein cingulin and the condensation of actin into cytoplasmic foci induced by cytochalasin D. Taken together, these observations indicate that H-7 inhibits junction dissociation by affecting the contractility of the adherens junction-associated microfilaments following treatment with calcium chelators or cytochalasin D.

glsA, a Volvox gene required for asymmetric division and germ cell specification, encodes a chaperone-like protein

Development ◽  
1999 ◽  
Vol 126 (4) ◽  
pp. 649-658 ◽  
Author(s):  
S.M. Miller ◽  
D.L. Kirk
Keyword(s):  
Mitotic Spindle ◽  
Site Directed Mutagenesis ◽  
Cell Specification ◽  
Division Plane ◽  
Binding Domains ◽  
Acid Protein ◽  
Germ Cell Specification ◽  
Asymmetric Divisions ◽  
Dividing Cells ◽  
Amino Acid Protein

The gls genes of Volvox are required for the asymmetric divisions that set apart cells of the germ and somatic lineages during embryogenesis. Here we used transposon tagging to clone glsA, and then showed that it is expressed maximally in asymmetrically dividing embryos, and that it encodes a 748-amino acid protein with two potential protein-binding domains. Site-directed mutagenesis of one of these, the J domain (by which Hsp40-class chaperones bind to and activate specific Hsp70 partners) abolishes the capacity of glsA to rescue mutants. Based on this and other considerations, including the fact that the GlsA protein is associated with the mitotic spindle, we discuss how it might function, in conjunction with an Hsp70-type partner, to shift the division plane in asymmetrically dividing cells.

Carboxylesterase overexpression in the male reproductive tract: a universal safeguarding mechanism?

1999 ◽  
Vol 11 (3) ◽  
pp. 133 ◽  
Author(s):  
A. T. Mikhailov ◽  
M. Torrado
Keyword(s):  
Reproductive Tract ◽  
Expression Patterns ◽  
Cell Lineage ◽  
Environmental Chemicals ◽  
Male Reproductive Tract ◽  
Morphological Organization ◽  
Associated Functions ◽  
And Function ◽  
Hypothetical Explanation

Data on expression patterns of carboxylesterases in the male reproductive tract of different animal groups (i.e. bivalve mollusks, fruitflies and rodents) are summarized to highlight some particularly interesting questions in the context of sperm differentiation, maturation and function. The male reproduc-tive system, in spite of extreme variation in the anatomical/morphological organization in different species, is characterized by similar patterns of male-dependent carboxylesterase overexpression. The phenomenon of conserved carboxylesterase overexpression indicates similar male sex-associated functions of the enzymes. There is possible evidence of carboxylesterase recruitment by male reproductive-tract tissues indi-cating that it could be adaptive for spermatogenesis, sperm maturation and sperm use. Moreover, this idea can be extended to include a sperm cell lineage protection. This issue is discussed in the light of recent data on environmental reproductive xenobiotics that can provide a basis for a hypothetical explanation of car-boxylesterase overexpression in the male reproductive tract. Based on a well-known role of car-boxylesterases in detoxification of environmental chemicals such as organophosphate pesticides, it is proposed that various male genital tract carboxylesterases may be characterized by a similar physiological function to protect the male reproductive system against xenobiotic influences that could provoke its dys-function, thus altering sperm differentiation and maturation.

scholarly journals The mitotic spindle protein CKAP2 potently increases formation and stability of microtubules

eLife ◽  
2022 ◽  
Vol 11 ◽  
Author(s):  
Thomas S McAlear ◽  
Susanne Bechstedt
Keyword(s):  
Cell Division ◽  
Growth Factor ◽  
Mitotic Spindle ◽  
Apparent Rate Constant ◽  
Microtubule Dynamics ◽  
Proliferation Marker ◽  
Microtubule Growth ◽  
Large Rearrangements ◽  
And Function

Cells increase microtubule dynamics to make large rearrangements to their microtubule cytoskeleton during cell division. Changes in microtubule dynamics are essential for the formation and function of the mitotic spindle, and misregulation can lead to aneuploidy and cancer. Using in vitro reconstitution assays we show that the mitotic spindle protein Cytoskeleton-Associated Protein 2 (CKAP2) has a strong effect on nucleation of microtubules by lowering the critical tubulin concentration 100-fold. CKAP2 increases the apparent rate constant ka of microtubule growth by 50-fold and increases microtubule growth rates. In addition, CKAP2 strongly suppresses catastrophes. Our results identify CKAP2 as the most potent microtubule growth factor to date. These finding help explain CKAP2's role as an important spindle protein, proliferation marker, and oncogene.

An analysis of the response to gut induction in the C. elegans embryo

Development ◽  
1995 ◽  
Vol 121 (4) ◽  
pp. 1227-1236 ◽  
Author(s):  
B. Goldstein
Keyword(s):  
Body Wall ◽  
Cell Lineage ◽  
Muscle Cells ◽  
The Other ◽  
Cell Stage ◽  
Pharyngeal Muscle ◽  
Cell Cycles ◽  
Sister Cell ◽  
C Elegans ◽  
Cell Diversity

Establishment of the gut founder cell (E) in C. elegans involves an interaction between the P2 and the EMS cell at the four cell stage. Here I show that the fate of only one daughter of EMS, the E cell, is affected by this induction. In the absence of the P2-EMS interaction, both E and its sister cell, MS, produce pharyngeal muscle cells and body wall muscle cells, much as MS normally does. By cell manipulations and inhibitor studies, I show first that EMS loses the competence to respond before it divides even once, but P2 presents an inducing signal for at least three cell cycles. Second, induction on one side of the EMS cell usually blocks the other side from responding to a second P2-derived signal. Third, microfilaments and microtubules may be required near the time of the interaction for subsequent gut differentiation. Lastly, cell manipulations in pie-1 mutant embryos, in which the P2 cell is transformed to an EMS-like fate and produces a gut cell lineage, revealed that gut fate is segregated to one of P2's daughters cell-autonomously. The results contrast with previous results from similar experiments on the response to other inductions, and suggest that this induction may generate cell diversity by a different mechanism.

scholarly journals METTL3 Modulates Osteoclast Differentiation and Function by Controlling RNA Stability and Nuclear Export

2020 ◽  
Vol 21 (5) ◽  
pp. 1660 ◽  
Author(s):  
Di Li ◽  
Luhui Cai ◽  
Runsha Meng ◽  
Zhihui Feng ◽  
Qiong Xu
Keyword(s):  
Nuclear Export ◽  
Osteoclast Differentiation ◽  
Rna Stability ◽  
Cell Lineage ◽  
Specific Gene ◽  
Bone Homeostasis ◽  
Protein Levels ◽  
Lineage Differentiation ◽  
And Function ◽  
Skeletal Integrity

Osteoclast differentiation and function are crucial for maintaining bone homeostasis and preserving skeletal integrity. N6-methyladenosine (m6A) is an abundant mRNA modification that has recently been shown to be important in regulating cell lineage differentiation. Nevertheless, the effect of m6A on osteoclast differentiation remains unknown. In the present study, we observed that the m6A level and methyltransferase METTL3 expression increased during osteoclast differentiation. Mettl3 knockdown resulted in an increased size but a decreased bone-resorbing ability of osteoclasts. The expression of osteoclast-specific genes (Nfatc1, c-Fos, Ctsk, Acp5 and Dcstamp) was inhibited by Mettl3 depletion, while the expression of the cellular fusion-specific gene Atp6v0d2 was upregulated. Mechanistically, Mettl3 knockdown elevated the mRNA stability of Atp6v0d2 and the same result was obtained when the m6A-binding protein YTHDF2 was silenced. Moreover, the phosphorylation levels of key molecules in the MAPK, NF-κB and PI3K-AKT signaling pathways were reduced upon Mettl3 deficiency. Depletion of Mettl3 maintained the retention of Traf6 mRNA in the nucleus and reduced the protein levels of TRAF6. Taken together, our data suggest that METTL3 regulates osteoclast differentiation and function through different mechanisms involving Atp6v0d2 mRNA degradation mediated by YTHDF2 and Traf6 mRNA nuclear export. These findings elucidate the molecular basis of RNA epigenetic regulation in osteoclast development.

scholarly journals Analysis of the myogenin promoter reveals an indirect pathway for positive autoregulation mediated by the muscle-specific enhancer factor MEF-2.

1992 ◽  
Vol 12 (9) ◽  
pp. 3665-3677 ◽  
Author(s):  
D G Edmondson ◽  
T C Cheng ◽  
P Cserjesi ◽  
T Chakraborty ◽  
E N Olson
Keyword(s):  
Cell Fate ◽  
Consensus Sequence ◽  
Cell Lineage ◽  
Mammalian Development ◽  
Indirect Pathway ◽  
Binding Factor ◽  
Nonmuscle Cells ◽  
And Function ◽  
Myod Gene

Transcriptional cascades that specify cell fate have been well described in invertebrates. In mammalian development, however, gene hierarchies involved in determination of cell lineage are not understood. With the recent cloning of the MyoD family of myogenic regulatory factors, a model system has become available with which to study the dynamics of muscle determination in mammalian development. Myogenin, along with other members of the MyoD gene family, possesses the apparent ability to redirect nonmuscle cells into the myogenic lineage. This ability appears to be due to the direct activation of an array of subordinate or downstream genes which are responsible for formation and function of the muscle contractile apparatus. Myogenin-directed transcription has been shown to occur through interaction with a DNA consensus sequence known as an E box (CANNTG) present in the control regions of numerous downstream genes. In addition to activating the transcription of subordinate genes, members of the MyoD family positively regulate their own expression and cross-activate one another's expression. These autoregulatory interactions have been suggested as a mechanism for induction and maintenance of the myogenic phenotype, but the molecular details of the autoregulatory circuits are undefined. Here we show that the myogenin promoter contains a binding site for the myocyte-specific enhancer-binding factor, MEF-2, which can function as an intermediary of myogenin autoactivation. Since MEF-2 can be induced by myogenin, these results suggest that myogenin and MEF-2 participate in a transcriptional cascade in which MEF-2, once induced by myogenin, acts to amplify and maintain the myogenic phenotype by acting as a positive regulator of myogenin expression.

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