In association with microtubules, a variety of kinesins play important roles in cellular functions such as intracellular transport of organelles or vesicles, signal transduction, and cell division. In a previous study we revealed that human kinesin superfamily protein member 4 (KIF4) is a chromokinesin that binds to chromosomes. Since localization of several kinds of kinesin at midzone called central spindle, or midbody that connects two daughter cells, or both, suggests their implication in cell division, we investigated KIF4 localization of during mitosis and cytokinesis in Hela cells. In addition to association with segregating chromosomes through entire mitosis, it also localized to the midzone and to midbody at ana/telophase through cytokinesis. Especially in cells at cytokinesis, KIF4 appeared as a doublet facing each other at the apical ends of two daughter cells. Three- dimensional analysis of architectural relationship between microtubule bundles and KIF4 indicated that KIF4 forms a ring structure wrapping around the microtubule bundles. These results suggest that KIF4 is involved in cytokinesis, although direct evidence was not provided in this study.
Animals ; Cell Division/*physiology ; Hela Cells ; Humans ; Immunohistochemistry ; Kinesin/*metabolism ; Mitotic Spindle Apparatus/*metabolism ; Research Support, Non-U.S. Gov't

Spindle assembly checkpoint (SAC) is a protective mechanism for cells to undergo accurate mitosis. SAC prevented chromosome segregation when kinetochores were not, or incorrectly attached to microtubules in the anaphase of mitosis, thus avoiding aneuploid chromosomes in daughter cells. Aneuploidy and altered expression of SAC component proteins are common in different cancers, including lung cancer. Therefore, SAC is a potential new target for lung cancer therapy. Five small molecule inhibitors of monopolar spindle 1 (MPS1), an upstream component protein of SAC, have entered clinical trials. This article introduces the biological functions of SAC, summarizes the abnormal expression of SAC component proteins in various cancers and the research progress of MPS1 inhibitors, and expects to provide a reference for the future development of lung cancer therapeutic strategies targeting SAC components.
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Humans ; Cell Cycle Proteins/metabolism* ; Spindle Apparatus/metabolism* ; Protein Serine-Threonine Kinases/metabolism* ; M Phase Cell Cycle Checkpoints/genetics* ; Lung Neoplasms/metabolism*

OBJECTIVETo study the effect of maternal age on meiotic spindle and chromosome configuration of oocytes.

METHODSSpindle and chromosome configuration was examined in day 1 unfertilized human oocytes after in vitro fertilization (IVF) and intracytoplasmic sperm injection(ICSI) by immunocytochemistry and visualized by laser confocal microscopy.

RESULTSStatistically significant differences were observed on normal spindle and chromosome configurations of oocytes between 25-29 maternal age group (33% and 31%, respectively), and 30-34 age group (P< 0.05) as well as 35-40 age group(0%, P<0.01). The incidence of abnormal spindle and chromosome configurations of oocytes from 30-34 and 35-40 maternal age groups was much higher than that of oocytes from 25-29 age group (P<0.01, P<0.05).

CONCLUSIONIncidence of abnormal spindle and chromosome configuration of oocytes is related to maternal age. It could be an important reason of age related oocyte aneuploidy.

Adult ; Age Factors ; Chromosomes, Human ; metabolism ; Female ; Fertilization in Vitro ; Humans ; Immunohistochemistry ; Microscopy, Confocal ; Oocytes ; metabolism ; Sperm Injections, Intracytoplasmic ; Spindle Apparatus ; metabolism

The aim of the present study is to observe the dynamic changes of γ-tubulin in mouse somatic nuclear transferred (SCNT) embryos. The γ-tubulin was detected and analyzed in the enucleated oocyte and SCNT embryos by immunofluorescence and laser confocal microscopy. The results showed that γ-tubulin distributed in the cortex of the enucleated MII oocytes, and decreased in this area during the activation of oocytes. Meanwhile cytoplasmic asters appeared, but there was no spindle formed. Spindle formation could be observed in the enucleated oocytes which were injected with cumulus cells and activated by SrCl2. The spots-like γ-tubulin signals spread between chromosomes at the prophase, and the signals arrayed with spindle or aggregated at two poles of the spindle at the early metaphase. Furthermore, γ-tubulin signals were localized between the segregated sister chromatids at anaphase or telophase. Some reconstructed embryos exhibited advanced activation, showing abnormal spindles and aberrant distribution of γ-tubulin and chromosomes. Two spindles would be formed when the cumulus cell was injected into an intact oocyte, and the distribution of γ-tubulin was similar to that of the normal SCNT. Moreover, advanced activation also occurred in this case and formed either two small spindles or one big barrel-shaped spindle. These results suggest that γ-tubulin plays a pivotal role in spindle assembling in mouse SCNT embryos. The reconstructed oocytes were easily to be activated, and aberrant distribution of γ-tubulin is associated with formation of abnormal spindles and chromosome misalignment.
Animals ; Embryo, Mammalian ; metabolism ; Fluorescent Antibody Technique ; Metaphase ; Mice ; Microscopy, Confocal ; Nuclear Transfer Techniques ; Oocytes ; cytology ; Spindle Apparatus ; metabolism ; Telophase ; Tubulin ; metabolism

Stem cells use asymmetric and symmetric cell division to generate progeny. Symmetric cell division is defined as the generation of daughter cells that are destined to acquire the same fate. Stem cells divide asymmetrically to generate one daughter with a stem-cell fate and one daughter with different fate. Disruption of the machinery that regulates asymmetric division may be a reason for the generation of cancer. The asymmetric mechanism is maintained by cell polarity factors, cell fate determinants, and the spindle apparatus. The mutation or dysregulation of these factors may change stem cells from asymmetric to symmetric cell division, then leading to tumorigenesis. Therefore, further study is needed on the mechanisms of stem cell control between asymmetric and symmetric cell division, as well as the relationships among stem cells, cancer stem cells, and tumor cells. It may bring us a new approach for the resistance, recurrence, and metastasis of tumors.
Animals ; Cell Division ; physiology ; Cell Polarity ; Cell Transformation, Neoplastic ; Drosophila ; cytology ; Humans ; Neoplasms ; pathology ; Neoplastic Stem Cells ; pathology ; Neurons ; cytology ; Spindle Apparatus ; metabolism ; Tumor Suppressor Proteins ; metabolism

Animals ; Autoantigens ; genetics ; metabolism ; physiology ; Centromere Protein A ; Chromosomal Instability ; Chromosomal Proteins, Non-Histone ; genetics ; metabolism ; physiology ; Gene Expression Regulation, Neoplastic ; Humans ; Kinetochores ; metabolism ; Mitosis ; physiology ; Rectal Neoplasms ; genetics ; metabolism ; pathology ; Spindle Apparatus ; metabolism

BubR1 gene is a homologue of the mitotic checkpoint gene Mad3 in budding yeast which is highly conserved in mammalian. BubR1 protein is a key component mediating spindle assembly checkpoint activation. BubR1 safeguards accurate chromosome segregation during cell division by monitoring kinetochore-microtubule attachments and kinetochore tension. There is a dose-dependent effect between the level of BubR1 expression and the function of spindle assembly checkpoint. BubR1-deficient would lead to mitotic progression with compromised spindle assembly checkpoint because cells become progressively aneuploid. Recently, it has been reported that BubR1 also plays important roles in meiotic, DNA damage response, cancer, infertility, and early aging. This review briefly summarizes the current progresses in studies of BubR1 function.
Cell Cycle Proteins ; genetics ; metabolism ; physiology ; Chromosome Segregation ; genetics ; physiology ; Kinetochores ; metabolism ; physiology ; Mitosis ; genetics ; physiology ; Protein-Serine-Threonine Kinases ; genetics ; metabolism ; physiology ; Saccharomycetales ; genetics ; physiology ; Spindle Apparatus ; genetics ; metabolism ; physiology

Multinucleated cells resulted from mitosis defect have been noted in pathophysiological states of the cells such as inflammation, senescence and cancer. Since oxidative stress has been known to correlate with these pathophysiological conditions, we tested the effect of H2O2 on the cell cycle progression and formation of multinucleated cells. H2O2 induced a significant delay in cell cycle progression in Chang liver cells. Interestingly, H2O2 actively induced hyperamplification of centrosomes (> or =3) and multipolar spindle formation during mitosis and subsequently increased the generation of multinucleated cells. A significant increase of the phospho-ERK level was observed upon H2O2 treatment but PD98059, an MEK1/2 inhibitor, didn't reduce the frequency of cells with hyperamplified centrosomes. On the other hand, treatment of either H2O2 or adriamycin increased intracellular ROS levels and multinucleated cells, which were significantly suppressed by antioxidants, N-acetylcysteine and PDTC. Thus, our results suggest that oxidative stress can trigger centrosome hyperamplification and multinucleated cell formation, which may promote pathophysiological progression.
Cell Line ; Cell Nucleus/*drug effects/*metabolism ; Centrosome/*drug effects/*metabolism ; Gene Amplification ; Humans ; Hydrogen Peroxide/*pharmacology ; MAP Kinase Signaling System ; Mitotic Spindle Apparatus/drug effects ; Phenotype ; Reactive Oxygen Species/metabolism ; Research Support, Non-U.S. Gov't

Sec13p has been known as an endoplasmic reticulum-Golgi transport protein. Recently, it has also been shown to be required for the formation of septation in the fission yeast Schizosaccharomyces pombe. In the present study, we focused on the role of a human homolog of Saccharomyces cerevisiae SEC13, Sec13 protein during mitosis in U2OS cells. We found that the expression of Sec13 was constant throughout the cell cycle, and localized to the kinetochores at metaphase during mitosis. By using green fluorescent protein technology, we observed that Sec13 is required for evasion of mitotic arrest in response to spindle damage, leading to G1-like phase and apoptotic cell death. In addition, cells expressing exogenous Sec13 showed giant nuclei compared to endogenous ones in the absence of nocodazole. These results demonstrate that Sec13 is involved in the regulation of the metaphase/anaphase transition and may be functionally associated with mitotic machinery to maintain genomic stability during mitosis.
Anaphase ; Antineoplastic Agents/pharmacology ; Cell Line, Tumor/drug effects/metabolism/pathology ; *G1 Phase ; *Genomic Instability ; Green Fluorescent Proteins/metabolism ; Humans ; Kinetochores/metabolism ; Membrane Proteins/*genetics/metabolism ; Metaphase ; Mitosis/*physiology ; *Mitotic Spindle Apparatus ; Nocodazole/pharmacology ; Osteosarcoma/genetics/metabolism/pathology ; Research Support, Non-U.S. Gov't