otic spindle adapts its orientation by sensing the matrix geometry. The statistics on spindle orientation of 
the HeLa cells cultured in various shaped matrix substantiates the conclusion that the metaphase spindle angle is influenced by the distribution of cortical F-actin. The main opinion on such influence of matrix towards spindle orientation is that the dynein-mediated astral microtubule-cortex interactions provide the pulling force to dynamically regulate mitotic spindle positioning and orientation. Knockdown of some proteins participating in this process such as MISP, results in more randomized spindle angles as the result of uncontrolled spindle orientation. Inhibiting the Mitotic Kinases Regulate F-Actin Dynamics polymerization of tubulin or actin by the treatment with Nocodazole or Latrunculin B results in metaphase arrest and abnormally rotated spindles. Collectively, these studies suggest a unique role of microtubule-F-actin interaction in spindle positioning and orientation. However, it remains elusive on how the cytoplasmic force rather than the cortical affects the spindle. One recent work suggests that Myosin 10 and cytoplasmic actin filaments in Xenopus Laevis embryos control spindle length and orientation. Persistently stabilized actin filaments may attenuate the connection between astral microtubules and cell cortex. But it becomes controversial that the reported cytoplasmic actin structure revolving around the spindle has a unique organization and motile pattern. Additionally, a ringlike actin structure related to spindle position and symmetric division is found in mouse zygote, but the dynamic of this structure remains unclear. Mathematical model drawing on the experimental data and model of previous works have been established to deal with the calculation of spindle-cytoskeleton dynamics. We inferred that actin filaments, together with Myosin play a pivotal role in the force chain, and inhibiting Myosin would weaken the interactions between mitotic spindle and cytoplasmic actin filament. In our experiment, we used specific chemical compounds to harness the enzymatic activities of kinases such as Plk1 and Mps1, motility of Myosin, and polymerization of PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19657107 F-actin. We observed that a CF-101 supplier ring-like F-actin structure forms in metaphase cells or maintains in MG132-arrested cells. Then we presented a model raising possible mechanism underlying the function of cytoplasmic actin filaments. We observed that the drugs perturb the formation of the ring-like F-actin structure, coupled with translated spindles and altered symmetric division. In summary, we characterized the formation of the ring-like F-actin structure as a mitotic event and developed a method to theoretically describe the relationships between mitotic spindle and cytoplasmic F-actin. block was over, cells were released about 8 hr for immunofluorescence and live-cell imaging. Drug Treatments HeLa cells were grown on coverslips in 24-well plates. For each drug treatment, we prepared 6 wells of cells. After the second release from Thymidine for 8 hours, cells were treated with aliquots of MG132, 10 minutes later, the first well of cells were collected, labeled as ” 0′ “and fixed for appropriate examination. Remaining wells of cells were exposed to DMSO, BI2536, Blebbistatin, Reversine and Lat B. We collected and fixed these cells every 10 minutes in a row. To collect anaphase cells for analysis of symmetric division, drugs were added 8 hours after release from Thymidine w
