scholarly journals Cytokinesis and Midzone Microtubule Organization inCaenorhabditis elegans Require the Kinesin-like Protein ZEN-4

1998 ◽  
Vol 9 (8) ◽  
pp. 2037-2049 ◽  
Author(s):  
William B. Raich ◽  
Adrienne N. Moran ◽  
Joel H. Rothman ◽  
Jeff Hardin
Keyword(s):  
Cell Division ◽  
Null Allele ◽  
Time Lapse ◽  
Equatorial Region ◽  
Microtubule Organization ◽  
Dividing Cells ◽  
Spindle Midzone ◽  
Cross Links ◽  
Complete Cell

Members of the MKLP1 subfamily of kinesin motor proteins localize to the equatorial region of the spindle midzone and are capable of bundling antiparallel microtubules in vitro. Despite these intriguing characteristics, it is unclear what role these kinesins play in dividing cells, particularly within the context of a developing embryo. Here, we report the identification of a null allele ofzen-4, an MKLP1 homologue in the nematodeCaenorhabditis elegans, and demonstrate that ZEN-4 is essential for cytokinesis. Embryos deprived of ZEN-4 form multinucleate single-celled embryos as they continue to cycle through mitosis but fail to complete cell division. Initiation of the cytokinetic furrow occurs at the normal time and place, but furrow propagation halts prematurely. Time-lapse recordings and microtubule staining reveal that the cytokinesis defect is preceded by the dissociation of the midzone microtubules. We show that ZEN-4 protein localizes to the spindle midzone during anaphase and persists at the midbody region throughout cytokinesis. We propose that ZEN-4 directly cross-links the midzone microtubules and suggest that these microtubules are required for the completion of cytokinesis.

scholarly journals The Plastid of Toxoplasma gondii Is Divided by Association with the Centrosomes

2000 ◽  
Vol 151 (7) ◽  
pp. 1423-1434 ◽  
Author(s):  
Boris Striepen ◽  
Michael J. Crawford ◽  
Michael K. Shaw ◽  
Lewis G. Tilney ◽  
Frank Seeber ◽  
...  
Keyword(s):  
Cell Division ◽  
Toxoplasma Gondii ◽  
Genetic Manipulation ◽  
Fluorescent Proteins ◽  
Recombinant Expression ◽  
Molecular Genetic ◽  
Time Lapse ◽  
Microtubule Organization ◽  
Apicomplexan Parasites ◽  
Daughter Cells

Apicomplexan parasites harbor a single nonphotosynthetic plastid, the apicoplast, which is essential for parasite survival. Exploiting Toxoplasma gondii as an accessible system for cell biological analysis and molecular genetic manipulation, we have studied how these parasites ensure that the plastid and its 35-kb circular genome are faithfully segregated during cell division. Parasite organelles were labeled by recombinant expression of fluorescent proteins targeted to the plastid and the nucleus, and time-lapse video microscopy was used to image labeled organelles throughout the cell cycle. Apicoplast division is tightly associated with nuclear and cell division and is characterized by an elongated, dumbbell-shaped intermediate. The plastid genome is divided early in this process, associating with the ends of the elongated organelle. A centrin-specific antibody demonstrates that the ends of dividing apicoplast are closely linked to the centrosomes. Treatment with dinitroaniline herbicides (which disrupt microtubule organization) leads to the formation of multiple spindles and large reticulate plastids studded with centrosomes. The mitotic spindle and the pellicle of the forming daughter cells appear to generate the force required for apicoplast division in Toxoplasma gondii. These observations are discussed in the context of autonomous and FtsZ-dependent division of plastids in plants and algae.

scholarly journals Changes in the Min Oscillation Pattern before and after Cell Birth

2010 ◽  
Vol 192 (16) ◽  
pp. 4134-4142 ◽  
Author(s):  
Jennifer R. Juarez ◽  
William Margolin
Keyword(s):  
Cell Division ◽  
Fluorescent Protein ◽  
Time Lapse ◽  
The Other ◽  
Cell Pole ◽  
Daughter Cells ◽  
Division Site ◽  
Before And After ◽  
Dividing Cells ◽  
Green Fluorescent

ABSTRACT The Min system regulates the positioning of the cell division site in many bacteria. In Escherichia coli, MinD migrates rapidly from one cell pole to the other. In conjunction with MinC, MinD helps to prevent unwanted FtsZ rings from assembling at the poles and to stabilize their positioning at midcell. Using time-lapse microscopy of growing and dividing cells expressing a gfp-minD fusion, we show that green fluorescent protein (GFP)-MinD often paused at midcell in addition to at the poles, and the frequency of midcell pausing increased as cells grew longer and cell division approached. At later stages of septum formation, GFP-MinD often paused specifically on only one side of the septum, followed by migration to the other side of the septum or to a cell pole. About the time of septum closure, this irregular pattern often switched to a transient double pole-to-pole oscillation in the daughter cells, which ultimately became a stable double oscillation. The splitting of a single MinD zone into two depends on the developing septum and is a potential mechanism to explain how MinD is distributed equitably to both daughter cells. Septal pausing of GFP-MinD did not require MinC, suggesting that MinC-FtsZ interactions do not drive MinD-septal interactions, and instead MinD recognizes a specific geometric, lipid, and/or protein target at the developing septum. Finally, we observed regular end-to-end oscillation over very short distances along the long axes of minicells, supporting the importance of geometry in MinD localization.

scholarly journals Probing for Binding Regions of the FtsZ Protein Surface through Site-Directed Insertions: Discovery of Fully Functional FtsZ-Fluorescent Proteins

2016 ◽  
Vol 199 (1) ◽  
Author(s):  
Desmond A. Moore ◽  
Zakiya N. Whatley ◽  
Chandra P. Joshi ◽  
Masaki Osawa ◽  
Harold P. Erickson
Keyword(s):  
Cell Division ◽  
Fluorescent Proteins ◽  
Sole Source ◽  
Ring Structure ◽  
Content Type ◽  
Z Ring ◽  
Complete Cell ◽  
The Right

ABSTRACT FtsZ, a bacterial tubulin homologue, is a cytoskeletal protein that assembles into protofilaments that are one subunit thick. These protofilaments assemble further to form a “Z ring” at the center of prokaryotic cells. The Z ring generates a constriction force on the inner membrane and also serves as a scaffold to recruit cell wall remodeling proteins for complete cell division in vivo. One model of the Z ring proposes that protofilaments associate via lateral bonds to form ribbons; however, lateral bonds are still only hypothetical. To explore potential lateral bonding sites, we probed the surface of Escherichia coli FtsZ by inserting either small peptides or whole fluorescent proteins (FPs). Among the four lateral surfaces on FtsZ protofilaments, we obtained inserts on the front and back surfaces that were functional for cell division. We concluded that these faces are not sites of essential interactions. Inserts at two sites, G124 and R174, located on the left and right surfaces, completely blocked function, and these sites were identified as possible sites for essential lateral interactions. However, the insert at R174 did not interfere with association of protofilaments into sheets and bundles in vitro. Another goal was to find a location within FtsZ that supported insertion of FP reporter proteins while allowing the FtsZ-FPs to function as the sole source of FtsZ. We discovered one internal site, G55-Q56, where several different FPs could be inserted without impairing function. These FtsZ-FPs may provide advances for imaging Z-ring structure by superresolution techniques. IMPORTANCE One model for the Z-ring structure proposes that protofilaments are assembled into ribbons by lateral bonds between FtsZ subunits. Our study excluded the involvement of the front and back faces of the protofilament in essential interactions in vivo but pointed to two potential lateral bond sites, on the right and left sides. We also identified an FtsZ loop where various fluorescent proteins could be inserted without blocking function; these FtsZ-FPs functioned as the sole source of FtsZ. This advance provides improved tools for all fluorescence imaging of the Z ring and may be especially important for superresolution imaging.

scholarly journals Probing the Catalytic Activity of a Cell Division-Specific Transpeptidase In Vivo with β-Lactams

2003 ◽  
Vol 185 (13) ◽  
pp. 3726-3734 ◽  
Author(s):  
Christian Eberhardt ◽  
Lars Kuerschner ◽  
David S. Weiss
Keyword(s):  
Catalytic Activity ◽  
Cell Division ◽  
Penicillin Binding Protein ◽  
In Vitro System ◽  
New Findings ◽  
Peptidoglycan Cell Wall ◽  
Dividing Cells ◽  
A Cell

ABSTRACT Penicillin-binding protein 3 (PBP3; also called FtsI) is a transpeptidase that catalyzes cross-linking of the peptidoglycan cell wall in the division septum of Escherichia coli. To determine whether the catalytic activity of PBP3 is activated during division, we assayed acylation of PBP3 with three β-lactams (cephalexin, aztreonam, and piperacillin) in growing cells. Acylation of PBP3 with cephalexin, but not aztreonam or piperacillin, appeared to be stimulated by cell division. Specifically, cephalexin acylated PBP3 about 50% faster in a population of dividing cells than in a population of filamentous cells in which division was inhibited by inactivation or depletion of FtsZ, FtsA, FtsQ, FtsW, or FtsN. However, in a simpler in vitro system using isolated membranes, acylation with cephalexin was not impaired by depletion of FtsW or FtsN. A conflicting previous report that the ftsA3(Ts) allele interferes with acylation of PBP3 was found to be due to the presence of a thermolabile PBP3 in the strain used in that study. The new findings presented here are discussed in light of the hypothesis that the catalytic activity of PBP3 is stimulated by interaction(s) with other division proteins. We suggest that there might be allosteric activation of substrate binding.

scholarly journals A polo-like kinase modulates cytokinesis and flagella biogenesis in Giardia lamblia

2020 ◽  
Author(s):  
Eun-Ah Park ◽  
Juri Kim ◽  
Mee Young Shin ◽  
Soon-Jung Park
Keyword(s):  
Cell Division ◽  
Mitotic Index ◽  
Giardia Lamblia ◽  
Specific Inhibitor ◽  
Subcellular Fractionation ◽  
Immunofluorescence Assay ◽  
Kinase Assay ◽  
Nuclear Fraction ◽  
Dividing Cells

Abstract Background Polo-like kinases (PLKs) are conserved serine/threonine kinase, regulating cell cycle. Giardia lamblia PLK (GlPLK) role in its cell has not been yet studied. Here, the function of GlPLK was investigated to provide the insight of roles in Giardia cell division, especially during cytokinesis and in flagella formation. Methods To access the function of GlPLK, Giardia trophozoites were treated with PLK-specific inhibitor, GW843286X (GW) or anti-glplk morpholino, then growth of the cells was monitored and phenotypic characteristics of GlPLK-inhibited cells were observed by using mitotic index and flow cytometry assay. Transgenic G. lamblia expressing GlPLK as a hemagglutinin (HA)-tagging was constructed and used for immunofluorescence assay to detect the localization of GlPLK, followed by the subcellular fractionation. Furthermore, kinase assay was performed to assess the phosphorylation activities of GlPLK by purified proteins or in vitro synthesized proteins. To elucidate the role of phosphorylated GlPLK, the phosphorylation residues were mutated and expressed in Giardia trophozoites. Results After incubating trophozoites with 5 µM GW, the percentages of cells with four nuclei and/or longer flagella were increased. Immunofluorescence assays indicated that GlPLK was mainly localized at basal bodies and transiently localized at mitotic spindles in the dividing cells. Fractionation experiments demonstrated that GlPLK is present in the nuclear fraction, as did the centromeric histone H3. Morpholino-mediated GlPLK knockdown resulted in the same phenotypes as those observed in GW-treated cells, i.e., increased mitotic index and flagella length. Kinase assays using mutant recombinant GlPLKs indicated that mutation at Lys51 or at both Thr179 and Thr183 resulted in loss of kinase activity. Giardia expressing these mutant GlPLKs also demonstrated defects in cell growth, cytokinesis, and flagella. Conclusions These data indicated that GlPLK plays roles in Giardia cell division, especially during cytokinesis, and in flagella formation.

scholarly journals Critical role for cold shock protein YB-1 in cytokinesis

2020 ◽  
Author(s):  
Sunali Mehta ◽  
Michael Algie ◽  
Tariq Al-Jabri ◽  
Cushla McKinney ◽  
Srinivasaraghavan Kannan ◽  
...  
Keyword(s):  
Cell Division ◽  
Cancer Progression ◽  
Cold Shock ◽  
Binding Protein ◽  
Critical Role ◽  
Confocal Imaging ◽  
Cold Shock Protein ◽  
Microtubule Organization ◽  
Atomistic Modelling

ABSTRACTHigh levels of the cold shock protein Y-box-binding protein-1, YB-1, are tightly correlated with increased cell proliferation and cancer progression. However, the precise mechanism by which YB-1 regulates proliferation is unknown. Here, we found that YB-1 depletion in several cell lines resulted in cytokinesis failure, multinucleation and an increase in G1 transit time. Rescue experiments indicated that YB-1 was required for completion of cytokinesis. Using confocal imaging of cells undergoing cytokinesis both in vitro and in zebrafish embryos, we found that YB-1 was critical for microtubule organization during cytokinesis. Using mass spectrometry we identified multiple novel phosphorylation sites on YB-1. We show that phosphorylation of YB-1 at multiple serine residues was essential for its function during cytokinesis. Using atomistic modelling we show how multiple phosphorylations alter YB-1 conformation, allowing it to interact with protein partners. Our results establish phosphorylated YB-1 as a critical regulator of cytokinesis, defining for the first time precisely how YB-1 regulates cell division.SUMMARYY-box-binding protein-1, YB-1, is essential for cell division, but it is not clear how it functions. Using live imaging and confocal microscopy we show that YB-1 functions only in the last step of division, specifically being required to initiate cytokinesis.

278 EFFECT OF FOLLICULAR WAVE SYNCHRONIZATION AND SUPERSTIMULATION ON THE NORMALITY OF BOVINE EMBRYOS PRODUCED IN VITRO

2010 ◽  
Vol 22 (1) ◽  
pp. 296 ◽  
Author(s):  
K. Imai ◽  
T. Somfai ◽  
M. Ohtake ◽  
Y. Inaba ◽  
Y. Aikawa ◽  
...  
Keyword(s):  
Cell Division ◽  
Development Program ◽  
Time Lapse ◽  
Oocyte Quality ◽  
Blastocyst Stage ◽  
In Vitro Production ◽  
Cell Stage ◽  
Follicular Wave ◽  
Significant Difference

We previously reported that follicular wave synchronization by dominant follicle removal on Day 5 and the start of a superstimulatory treatment on Day 7 after ovum pick-up (OPU) was effective to increase oocyte quality (Imai et al. 2008 Reprod. Fertil. Dev. 20, 182). The present study was designed to examine the effect of superstimulatory treatment-induced follicular wave synchronization on quality of embryos obtained by OPU and in vitro production. Japanese Black cows were reared under the same feeding and environmental conditions and 2 OPU sessions were conducted in each cow. The first OPU session was performed in 7 cows at arbitrary days of estrous cycle using a 7.5-MHz linear transducer with needle connected to an ultrasound scanner. Then, follicles larger than 8 mm in diameter were aspirated and CIDR was inserted on Day 5 (the day of first OPU session = Day 0). The cows then received 30 mg of FSH twice a day from Days 7 to 10 in decreasing doses (4, 4, 3, 3, 2, 2, 1, 1 mg per shot) by i.m. injections. Cloprostenol (PGF; 0.75 mg) was administered in the morning of Day 9. The second OPU session was performed 48 h after PGF administration (Day 11) and only follicles larger than 5 mm in diameter were aspirated. The CIDR was removed from the cows just before OPU. Grade 1 and 2 cumulus oocyte complexes were in vitro matured, fertilized (IVF), and cultured as described by Imai et al. (2006 J. Reprod. Dev. 52, Suppl. S19-29). Some zygotes were fixed and stained to check their sperm penetration. Embryo development was monitored by time-lapse cinematography for 168 h after IVF. Cleavage pattern of embryos was classified morphologically into normal and abnormal (including those with multiple fragments, protrusions, 3 to 4 blastomeres, and uneven cell division) groups at their first cleavage. Normal penetration rate of second OPU session was significantly (P < 0.05) higher than that of the first OPU session. There were no differences in the mean percentage of total blastocyst and grade 1 blastocyst rates between the first (45.2 and 46.9%, respectively) and second (47.5 and 41.8%, respectively) OPU sessions. However, the rates of blastocysts developing from embryos that were beyond the 4-cell stage at 48 h after IVF was significantly (P < 0.05) higher after the second OPU session (81.2%) than after the first OPU session (67.4%). Furthermore, a significant difference (P < 0.05) was found in the rates of normal cleavage at the first cell division in embryos that developed to the blastocyst stage between the first and second OPU sessions (53.3% and 73.9%, respectively). These results indicate that superstimulatory treatment-induced follicular wave synchronization improved the normality of fertilization and development of cattle oocytes obtained by OPU. This work was supported by the Research and Development Program for New Bio-industry Initiatives.

scholarly journals Isolation of cardiomyocytes undergoing mitosis with complete cytokinesis

2019 ◽  
Author(s):  
Hsiao-yun Y. Milliron ◽  
Matthew J. Weiland ◽  
Eric J. Kort ◽  
Stefan Jovinge
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Content ◽  
Cell Cycle Progression ◽  
Time Lapse ◽  
Heart Tissue ◽  
Molecular Beacons ◽  
Human Cardiomyocytes ◽  
Complete Cell ◽  
Proliferation Assays

AbstractRationale-Adult human cardiomyocytes (CMs) do not complete cytokinesis despite passing through the S-phase of the cell cycle. As a result polyploidization and multinucleation occur. In order to get a deeper understanding of the mechanisms surrounding division of CMs there is a crucial need for a technique to isolate CMs that complete cell division/cytokinesis.Objective-Markers of cell cycle progression based on DNA content cannot distinguish between mitotic CMs that fail to complete cytokinesis from those cells that undergo true cell division. With the use of molecular beacons (MB) targeting specific mRNAs we aimed to identify truly proliferative CMs derived from hiPSCs.Methods and Results-Fluorescence activated cell-sorting combined with molecular beacons was performed to sort CM populations enriched for mitotic cells. Expressions of cell-cycle specific genes were confirmed by means of RT-qPCR, single-cell RNA sequencing (scRNA-seq). We further characterized the sorted groups by proliferation assays and time-lapse microscopy which confirmed the proliferative advantage of MB-positive cell populations relative to MB-negative and G2/M populations. Gene expression analysis revealed that the MB-positive CM subpopulation exhibited patterns consistent with the biological processes of nuclear division, chromosome segregation, and transition from M to G1 phase. The use of dual-MBs targeting CDC20 and SPG20 mRNAs (CDC20+SPG20+) enabled the enrichment of cytokinetic events. Interestingly, cells that did not complete cytokinesis and remained binucleated were found to be CDC20−SPG20+ while polyploid CMs that replicated DNA but failed to complete karyokinesis were found to be CDC20−SPG20−.Conclusions-This study demonstrates a novel alternative to existing DNA content-based approaches for sorting CMs with true mitotic potential that can be used to study in detail the unique dynamics of CM nuclei during mitosis. Together with high-throughput scRNA-seq, our technique for sorting live CMs undergoing cytokinesis would provide a basis for future studies to uncover mechanisms underlying the development and regeneration of heart tissue.

DNA Polymerase in Avian Erythroid Cells

1972 ◽  
Vol 11 (3) ◽  
pp. 785-798
Author(s):  
A. F. WILLIAMS
Keyword(s):  
Cell Division ◽  
Dna Synthesis ◽  
Dna Polymerase ◽  
Cell Types ◽  
Polymerase Activity ◽  
Erythroid Cells ◽  
Isolated Nuclei ◽  
Dividing Cells ◽  
Different Cell Types

The level and properties of DNA polymerase activity assayable in extracts of avian erythroid cells was studied. The enzyme was detectable in the dividing cells (erythroblasts) of the erythropoietic series and also the immature non-dividing erythrocytes. It could not be assayed in mature erythrocytes. Investigations showed that activity began to decline at the time of the last cell division of the erythroid series. Properties of the enzyme did change in different cell types; however, the changes did not correlate with cessation of DNA synthesis. Some preliminary results on DNA synthesis by isolated nuclei are also reported and these showed that only nuclei from erythroblasts could synthesize DNA in vitro in the absence of primer.

Cardiomyocyte binucleation is associated with aberrant mitotic microtubule distribution, mislocalization of RhoA and IQGAP3, as well as defective actomyosin ring anchorage and cleavage furrow ingression

2018 ◽  
Vol 114 (8) ◽  
pp. 1115-1131 ◽  
Author(s):  
Marina Leone ◽  
Gentian Musa ◽  
Felix Benedikt Engel
Keyword(s):  
Time Lapse ◽  
Equatorial Region ◽  
Central Component ◽  
Cleavage Furrow ◽  
Cardiomyocyte Proliferation ◽  
The Difference ◽  
Time Lapse Imaging ◽  
Regenerative Therapies

Abstract Aims After birth mammalian cardiomyocytes initiate a last cell cycle which results in binucleation due to cytokinesis failure. Despite its importance for cardiac regenerative therapies, this process is poorly understood. Here, we aimed at a better understanding of the difference between cardiomyocyte proliferation and binucleation and providing a new tool to distinguish these two processes. Methods and results Monitoring of cell division by time-lapse imaging revealed that rat cardiomyocyte binucleation stems from a failure to properly ingress the cleavage furrow. Astral microtubule required for actomyosin ring anchorage and thus furrow ingression were not symmetrically distributed at the periphery of the equatorial region during anaphase in binucleating cardiomyocytes. Consequently, RhoA, the master regulator of actomyosin ring formation and constriction, non-muscle myosin IIB, a central component of the actomyosin ring, as well as IQGAP3 were abnormally localized during cytokinesis. In agreement with improper furrow ingression, binucleation in vitro and in vivo was associated with a failure of RhoA and IQGAP3 to localize to the stembody of the midbody. Conclusion Taken together, these results indicate that naturally occurring cytokinesis failure in primary cardiomyocytes is due to an aberrant mitotic microtubule apparatus resulting in inefficient anchorage of the actomyosin ring to the plasma cell membrane. Thus, cardiomyocyte binucleation and division can be discriminated by the analysis of RhoA as well as IQGAP3 localization.

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