Nuclear and cytoplasmic dynamics of sperm penetration, pronuclear formation and microtubule organization during fertilization and early preimplantation development in the human

1995 ◽  
Vol 1 (5) ◽  
pp. 429-461 ◽  
Author(s):  
Jonathan Van Blerkom ◽  
Patrick Davis ◽  
John Merriam ◽  
Jane Sinclair
Keyword(s):  
Mitotic Spindle ◽  
Microtubule Organization ◽  
Cytoplasmic Microtubule ◽  
Spindle Formation ◽  
Sperm Tail ◽  
Relative Contribution ◽  
Human Fertilization ◽  
Sperm Penetration ◽  
Principal Piece

Abstract This report describes spatial and temporal aspects of sperm penetration and intracytoplasmic migration, pronuclear evolution and the specificity of presyngamic opposition, stage-specific changes in cytoskeletal organization and the relative contribution of maternal and paternal components to mitotic spindle formation. These studies involved observations of living human oocytes during conventional insemination in vitro and after intracytoplasmic deposition of spermatozoa, analysis of chromatin organization and distribution during pronuclear evolution, and detection of actin and α-, rβ- and γ-tubulin by confocal immuno-fluorescence microscopy. Immature and mature oocytes, penetrated but unfertilized oocytes, fertilized but arrested eggs, and cleavage-stage embryos from normal and dispermic fertilizations were examined. The results demonstrate that sperm nuclear migration to the maternal perinuclear region is rapid and linear, occurs in the absence of a detectable cytoskeletal system and appears to be assisted by an unusual configuration of the sperm tail principal piece which results from either retained intracytoplasmic motility or the process by which the sperm tail is progressively incorporated into the oocyte. Our findings also show a specificity of pronuclear alignment that is associated with a polarized distribution of both maternal and paternal chromatin, and with the position of the sperm centrosome and the presence of microtubules nucleated from this structure. The results also indicate that a maternal microtubule nucleating capacity is present in the immature oocyte but is apparently inactive until spindle formation. The poles of the first mitotic spindle appear to be derived from the sperm centrosome, although some maternal contribution cannot be excluded. The sperm tail and centrosome persist in a single cell through the cleavage stages, and the latter serves as a prominent site of cytoplasmic microtubule nucleation. The results provide a detailed understanding of the cellular and nuclear morphodynamics of the human fertilization process and indicate subtle defects that may be responsible for early developmental failure.

A novel structural component of the Dictyostelium centrosome

1996 ◽  
Vol 109 (13) ◽  
pp. 3103-3112 ◽  
Author(s):  
A. Kalt ◽  
M. Schliwa
Keyword(s):  
Mitotic Spindle ◽  
Structural Component ◽  
Myosin Ii ◽  
Live Cells ◽  
Microtubule Organizing Center ◽  
Direct Role ◽  
Cytoplasmic Microtubule ◽  
Interphase Cells ◽  
Organizing Center

The microtubule-organizing center of D. discoideum is a nucleus-associated body (NAB) that consists of a multilayered, box-shaped core embedded in an amorphous corona from which the microtubules emerge. The composition of the NAB is still largely unresolved. Here we have examined a high molecular mass component of the NAB which was identified by a monoclonal antibody raised against isolated nucleus/NAB complexes. This antibody recognized a 350 kDa component which is immunologically related to the D. discoideum heavy chain of myosin II. The 350 kDa antigen was localized only at the NAB in interphase cells, while in mitotic cells it may also be found in the vicinity of the NAB as well as in association with the mitotic spindle. Immunogold labeling experiments showed that the protein is part of the NAB corona. This association was not destroyed by treatment with 2 M urea or 0.6 M KCl. The 350 kDa antigen was part of the thiabendazole-induced cytoplasmic microtubule-organizing centers. A direct role in the polymerization of tubulin could not be determined in an in vitro microtubule nucleation assay, whereas antibody electroporation of live cells appeared to interfere with the generation of a normal microtubule system in a subset of cells. Our observations suggest that the 350 kDa antigen is a structural component of the NAB corona which could be involved in its stabilization.

O-154 First mitotic spindle formation led by sperm centrosome-dependent microtubule organising centres may cause high incidence of zygotic division errors in humans

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
Y Kai ◽  
H Kawano ◽  
N Yamashita
Keyword(s):  
Mitotic Spindle ◽  
High Frequency ◽  
Live Cell Imaging ◽  
Cell Imaging ◽  
Immunofluorescence Assay ◽  
Live Cell ◽  
Microtubule Assembly ◽  
Cell Stage ◽  
Spindle Formation

Abstract Study question Why do multinucleated blastomeres appear at high frequency in two-cell-stage embryos in humans? Summary answer Failure in microtubule assembly during the first mitotic spindle body formation by sperm centrosome-dependent microtubule organising centres (MTOCs) may lead to chromosomal instability. What is known already Unlike that in mice, multinucleated blastomeres appear at high frequency in two-cell-stage embryos in humans. However, the underlying mechanism remains elusive. In mice, multiple acentriolar MTOCs appear around the male and female pronuclei after pronuclear disappearance and contribute to dual-spindle formation, engulfing each parental chromosome. This spindle formation may ensure an error-free division, keeping the chromosomes stable during the first cleavage, as observed in mice, but it is unclear whether a similar mechanism exists in humans. Study design, size, duration To examine how sperm centrosomes contribute to MTOC formation in humans, two types of 3PN zygotes derived fromeither conventional in vitro fertilization (c-IVF, n = 30) or intracytoplasmic sperm injection (ICSI, n = 10) were used. The zygotes were collected from October 2018 to January 2020. MTOC and mitotic spindle formation at consecutive stages of development during the first cleavage were analysed under static and dynamic conditions using immunofluorescence assay and fluorescent live-cell imaging. Participants/materials, setting, methods Under ethics approval, 3PN zygotes were donated by infertile couples undergoing c-IVF or ICSI cycles at the Yamashita Shonan Yume Clinic in Japan. All participants provided informed consent. Immunofluorescence assay was performed using antibodies against α-tubulin, pericentrin, and H3K9me3 after fixation with MTSB-XF solution. Fluorescent live-cell imaging was performed using TagGFP2-H2B mRNA (chromosome marker) and FusionRed-MAP4 mRNA (microtubule marker). Main results and the role of chance Immunofluorescence revealed that while 3PN zygotes derived from c-IVF showed four pericentrin dots, those derived from ICSI exhibited two pericentrin dots. In pro-metaphase, an independent group of chromosomes derived from each pronucleus and MTOCs were formed by the sperm centrosome at the core. Microtubules from each MTOC extended toward the chromosomes in the early metaphase; a quadrupolar spindle was formed in the c-IVF-derived zygotes, and a bipolar spindle was formed in the ICSI-derived zygotes by the MTOCs at the zygote apex after chromosome alignment. In pro-metaphase, the microtubules extended from the MTOCs to the nearest chromosome. Since microtubule assembly was found on oocyte-derived chromosomes, we hypothesised that whether a chromosome is surrounded by microtubules depends on the location of the MTOCs, irrespective of its origin. Live-cell imaging of histone H2B and MAP4 revealed that four MTOCs appeared around the three pronuclei just before the disappearance of the pronuclear membrane; microtubules then extended from the MTOCs toward the chromosomes, beginning to form a mitotic spindle as the chromosomes moved to the centre of the oocyte. Interestingly, one of the three assembled chromosome groups showed no microtubule assembly in the pro-metaphase. Similar results were obtained in all six 3PN zygotes subjected. Limitations, reasons for caution We demonstrated the high risk of developing bare chromosomes not surrounded by microtubules during the formation of the first mitotic spindle, using human tripronuclear zygotes. However, owing to unavailability of normal fertilized oocytes for this study because of the clinical use, we were unable to confirm this in normal zygotes. Wider implications of the findings Although two sperm centrosome-dependent MTOCs are expected to be formed in normal fertilized oocytes, these MTOCs are not sufficient to completely enclose physically separated female and male chromosomes with the microtubules. This explains the high frequency of zygotic division errors that lead to unstable human chromosomes. Trial registration number not applicable

scholarly journals Fission Yeast mto2p Regulates Microtubule Nucleation by the Centrosomin-related Protein mto1p

2005 ◽  
Vol 16 (6) ◽  
pp. 3040-3051 ◽  
Author(s):  
Itaru Samejima ◽  
Paula C. C. Lourenço ◽  
Hilary A. Snaith ◽  
Kenneth E. Sawin
Keyword(s):  
Fission Yeast ◽  
Insertional Mutagenesis ◽  
Spindle Pole ◽  
Related Protein ◽  
Microtubule Nucleation ◽  
Microtubule Organization ◽  
Cytoplasmic Microtubule ◽  
Division Site ◽  
Cell Extracts

From an insertional mutagenesis screen, we isolated a novel gene, mto2+, involved in microtubule organization in fission yeast. mto2Δ strains are viable but exhibit defects in interphase microtubule nucleation and in formation of the postanaphase microtubule array at the end of mitosis. The mto2Δ defects represent a subset of the defects displayed by cells deleted for mto1+ (also known as mod20+ and mbo1+), a centrosomin-related protein required to recruit the γ-tubulin complex to cytoplasmic microtubule-organizing centers (MTOCs). We show that mto2p colocalizes with mto1p at MTOCs throughout the cell cycle and that mto1p and mto2p coimmunoprecipitate from cytoplasmic extracts. In vitro studies suggest that mto2p binds directly to mto1p. In mto2Δ mutants, although some aspects of mto1p localization are perturbed, mto1p can still localize to spindle pole bodies and the cell division site and to “satellite” particles on interphase microtubules. In mto1Δ mutants, localization of mto2p to all of these MTOCs is strongly reduced or absent. We also find that in mto2Δ mutants, cytoplasmic forms of the γ-tubulin complex are mislocalized, and the γ-tubulin complex no longer coimmunoprecipitates with mto1p from cell extracts. These experiments establish mto2p as a major regulator of mto1p-mediated microtubule nucleation by the γ-tubulin complex.

scholarly journals In vitro reconstitution of branched microtubule nucleation

2019 ◽  
Author(s):  
Ammarah Tariq ◽  
Lucy Green ◽  
J Charles G. Jeynes ◽  
Christian Soeller ◽  
James G. Wakefield
Keyword(s):  
Mitotic Spindle ◽  
Eukaryotic Cell ◽  
Synthetic Approach ◽  
Dependent Manner ◽  
Spindle Formation ◽  
In Vitro Reconstitution ◽  
A Cell ◽  
One Step ◽  
Cycle Dependent

AbstractEukaryotic cell division requires the mitotic spindle, a microtubule (MT)-based structure which accurately aligns and segregates duplicated chromosomes. The dynamics of spindle formation are determined primarily by correctly localising the MT nucleator, γ-Tubulin Ring Complex (γ-TuRC)1-4, within the cell. A conserved MT-associated protein complex, Augmin, recruits γ-TuRC to pre-existing spindle MTs, amplifying their number, in an essential cellular phenomenon termed “branched” MT nucleation5-9. Here, we purify endogenous, GFP-tagged Augmin and γ-TuRC from Drosophila embryos to near homogeneity using a novel one-step affinity technique. We demonstrate that, in vitro, while Augmin alone does not affect Tubulin polymerisation dynamics, it stimulates γ-TuRC-dependent MT nucleation in a cell cycle-dependent manner. We also assemble and visualise the MT-Augmin-γ-TuRC-MT junction using light microscopy. Our work therefore conclusively reconstitutes branched MT nucleation. It also provides a powerful synthetic approach with which to investigate the emergence of cellular phenomena, such as mitotic spindle formation, from component parts.

scholarly journals Characterization of proteins immunologically related to brain microtubule-associated protein MAP-1B in non-neural cells

1989 ◽  
Vol 92 (4) ◽  
pp. 607-620
Author(s):  
J. Diaz-Nido ◽  
J. Avila
Keyword(s):  
Mitotic Spindle ◽  
Polyclonal Antibodies ◽  
Microtubule Assembly ◽  
Neural Cells ◽  
Microtubule Network ◽  
Cytoplasmic Microtubule ◽  
Protein Map ◽  
Dividing Cells

Brain microtubule-associated protein MAP-1 is composed of at least two polypeptides, MAP-1A and MAP-1B, which are among the main components of the neural cytoskeleton. Specific monoclonal and polyclonal antibodies against MAP-1B stain nuclei, mitotic spindles, centrosomes and the cytoplasmic microtubule network of different non-neural cells studied by immunofluorescence microscopy. It appears that these cells contain two proteins of 325K and 220K (K = 10(3) Mr), which are immunologically related to brain MAP-1B. The 325K protein, which is localized to the cytoplasmic microtubule network, the centrosome and the mitotic spindle, seems to be structurally related to the neural MAP-1B, as judged from their similar peptide maps and phosphorylation patterns. The 220K protein, which is localized to the nuclear matrix in interphase cells and to the mitotic spindle in dividing cells, has a proteolytic profile different from that of neural MAP-1B and is phosphorylated to a much lesser extent than the 325K protein. Both proteins bind tubulin in vitro, which suggests that they may participate in microtubule assembly in vivo; the 325K protein could perform such a role during the entire cell cycle, while the 220K protein could be implicated in the formation of the mitotic spindle.

Centrosome Aberrations, Disturbed Mitotic Spindle Formation and G1 Arrest in Normal and Leukemic Cells Treated with the SRC/ABL Inhibitor Dasatinib.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2167-2167
Author(s):  
Alice Fabarius ◽  
Michelle Giehl ◽  
Alwin Kraemer ◽  
Oliver Frank ◽  
Martin C. Mueller ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Lines ◽  
Mitotic Spindle ◽  
Cell Cycle Progression ◽  
Dermal Fibroblasts ◽  
G1 Arrest ◽  
Osteosarcoma Cell ◽  
Cycle Progression ◽  
Spindle Formation

Abstract Multitargeted ABL inhibitors have been developed to simultaneously inhibit various pathways associated with proliferation in BCR-ABL+ diseases. Dasatinib (Bristol Myers Squibb) is a potent inhibitor targeting ABL, SRC, and other tyrosine kinases. SRC kinases are required for progression through the initial phase of mitosis. Centrosomes play a fundamental role in mitotic spindle organization, chromosome segregation and genetic stability. We sought to evaluate the activity of dasatinib on proliferation, centrosome status, spindle formation, and cell cycle progression in vitro and in vivo. Normal human dermal fibroblasts (NHDF), Chinese hamster embryonal fibroblasts (CHE), and the human osteosarcoma cell line U2OS were treated with serial concentrations (1nM-10μM) of dasatinib for 3 weeks. Effects of dasatinib were compared with data achieved with the ABL inhibitors imatinib (Novartis, 5–20μM) and nilotinib (Novartis, 0.5–20μM), the specific SRC inhibitor PP2 (Calbiochem-Novabiochem, 0.1–2μM), the ABL/LYN inhibitor INNO-406 (Innovive, 0.1–2μM), and solvent control. Bone marrow and peripheral blood samples from 18 patients (pts, 10 m, 8 f; median age 57 yrs, range 26–75) treated with dasatinib (70mg bid) after imatinib failure for a median of 11 mo (range, 3–16) were investigated. 17 pts had chronic myeloid leukemia (CML) in chronic phase. One patient suffered from a gastrointestinal stromal tumor. For comparison, 3 untreated CML pts and 3 healthy individuals were evaluated. Cell proliferation was determined in liquid culture incubated with serial dilutions of the inhibitor. Centrosome morphology and spindle formation were evaluated after pericentrin and α-tubulin staining, respectively. Cell cycle progression was analyzed by FACS and expression of EG5 by immunofluorescence microscopy. Dasatinib induced a G1 cell cycle arrest in all cell lines tested and in pts associated with a shift to 1n DNA ploidy and absence of EG5 as a marker for G2 phase/mitosis. In vitro, centrosomal aberrations and delay of spindle formation were observed in a dose dependent fashion. In pts, centrosome alterations were found in a median of 17% (range, 10–15) of cells. Disturbed spindle formation was observed in 9/18 pts. In comparison, incubation with imatinib and nilotinib was associated with centrosome aberrations but not with defects of spindle formation and G1 arrest. PP2 induced S-phase arrest; centrosome aberrations were observed at higher dosages (1–2 μM) only, spindle formation was not affected. INNO-406 was associated with both centrosome aberrations and disturbed spindle formation. In pharmacological doses, proliferation of BCR-ABL neg. cell lines was inhibited after dasatinib treatment, but not after incubation with imatinib, nilotinib, PP2, or INNO-406. In conclusion, dasatinib blocks the G1/S transition and thereby inhibits cell growth in normal and neoplastic cells. In addition, it induces both centrosomal and spindle aberrations. Effects of dasatinib are not based on SRC inhibition alone but may be associated with the combination of SRC and ABL inhibition or with non-specific effects on multiple kinases. Therefore, dasatinib should be defined as a cytostatic drug with a strong targeted component resulting in a preferential inhibition of cells harboring a specific target, like BCR-ABL.

scholarly journals Cytoplasmic dynein plays a role in mammalian mitotic spindle formation.

1993 ◽  
Vol 123 (4) ◽  
pp. 849-858 ◽  
Author(s):  
E A Vaisberg ◽  
M P Koonce ◽  
J R McIntosh
Keyword(s):  
Mitotic Spindle ◽  
Mammalian Cells ◽  
Cytoplasmic Dynein ◽  
Detectable Effect ◽  
Spindle Formation ◽  
Bipolar Spindle ◽  
Dynein Motor ◽  
Motor Enzymes ◽  
Chromosome Attachment

The formation and functioning of a mitotic spindle depends not only on the assembly/disassembly of microtubules but also on the action of motor enzymes. Cytoplasmic dynein has been localized to spindles, but whether or how it functions in mitotic processes is not yet known. We have cloned and expressed DNA fragments that encode the putative ATP-hydrolytic sites of the cytoplasmic dynein heavy chain from HeLa cells and from Dictyostelium. Monospecific antibodies have been raised to the resulting polypeptides, and these inhibit dynein motor activity in vitro. Their injection into mitotic mammalian cells blocks the formation of spindles in prophase or during recovery from nocodazole treatment at later stages of mitosis. Cells become arrested with unseparated centrosomes and form monopolar spindles. The injected antibodies have no detectable effect on chromosome attachment to a bipolar spindle or on motions during anaphase. These data suggest that cytoplasmic dynein plays a unique and important role in the initial events of bipolar spindle formation, while any later roles that it may play are redundant. Possible mechanisms of dynein's involvement in mitosis are discussed.

scholarly journals The Catastrophe-promoting Activity of Ectopic Op18/Stathmin Is Required for Disruption of Mitotic Spindles But Not Interphase Microtubules

2001 ◽  
Vol 12 (1) ◽  
pp. 73-83 ◽  
Author(s):  
Per Holmfeldt ◽  
Niklas Larsson ◽  
Bo Segerman ◽  
Bonnie Howell ◽  
Justin Morabito ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Polymerization Rate ◽  
Terminal Region ◽  
Phosphorylation Sites ◽  
Mitotic Spindles ◽  
Intact Cells ◽  
Spindle Formation ◽  
Tubulin Binding

Oncoprotein18/stathmin (Op18) is a microtubule (MT) destabilizing protein that is inactivated during mitosis by phosphorylation at four Ser-residues. Op18 has at least two functions; the N-terminal region is required for catastrophe-promotion (i.e., transition from elongation to shortening), while the C-terminal region is required to inhibit MT-polymerization rate in vitro. We show here that a “pseudophosphorylation” derivative of Op18 (i.e., four Ser- to Glu-substitutions at phosphorylation sites) exhibits a selective loss of catastrophe-promoting activity. This is contrasted to authentic phosphorylation, which efficiently attenuates all activities except tubulin binding. In intact cells, overexpression of pseudophosphorylated Op18, which is not phosphorylated by endogenous kinases, is shown to destabilize interphase MTs but to leave spindle formation untouched. To test if the mitotic spindle is sensitive only to the catastrophe-promoting activity of Op18 and resistant to C-terminally associated activities, N- and C-terminal truncations with defined activity-profiles were employed. The cell-cycle phenotypes of nonphosphorylatable mutants (i.e., four Ser- to Ala-substitutions) of these truncation derivatives demonstrated that catastrophe promotion is required for interference with the mitotic spindle, while the C-terminally associated activities are sufficient to destabilize interphase MTs. These results demonstrate that specific Op18 derivatives with defined activity-profiles can be used as probes to distinguish interphase and mitotic MTs.

scholarly journals Novel roles of Kinesin-13 and Kinesin-8 during cell growth and division in the moss Physcomitrella patens

2019 ◽  
Author(s):  
Shu Yao Leong ◽  
Tomoya Edzuka ◽  
Gohta Goshima ◽  
Moé Yamada
Keyword(s):  
Cell Growth ◽  
Mitotic Spindle ◽  
Tip Growth ◽  
Physcomitrella Patens ◽  
Microtubule Dynamics ◽  
Chromosome Movement ◽  
Spindle Formation ◽  
Tip Cells ◽  
Null Mutants

AbstractKinesin-13 and -8 are well-known microtubule (MT) depolymerases that regulate MT length and chromosome movement in animal mitosis. While much is unknown about plant Kinesin-8, Arabidopsis and rice Kinesin-13 have been shown to depolymerise MTs in vitro. However, mitotic function of both kinesins has yet to be understood in plants. Here, we generated the complete null mutants in plants of Kinesin-13 and -8 in the moss Physcomitrella patens. Both kinesins were found to be non-essential for viability, but the Kinesin-13 knockout (KO) line had increased mitotic duration and reduced spindle length, whereas the Kinesin-8 KO line did not display obvious mitotic defects. Surprisingly, spindle MT poleward flux, for which Kinesin-13 is responsible for in animals, was retained in the absence of Kinesin-13. Concurrently, MT depolymerase activity of either moss kinesins could not be observed, with MT catastrophe inducing (Kinesin-13) or MT gliding (Kinesin-8) activity observed in vitro. Interestingly, both KO lines showed waviness in their protonema filaments, which correlated with positional instability of the MT foci in their tip cells. Taken together, the results suggest that plant Kinesin-13 and -8 have diverged in both mitotic function and molecular activity, acquiring new roles in regulating MT foci positioning for directed tip-growth.One sentence summaryThis study uncovered the roles of Kinesin-13 and Kinesin-8 in regulating microtubule dynamics for mitotic spindle formation and straight tip cell growth in the moss Physcomitrella patens

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