Thus, we suppose that surface tension has a partial or slight effect on the determination of cell shape transformation, at least in some cell types. Conversely, our model based on Kc can explain the inhibition by the drugs because the increased stiffness around the polar regions can promote furrow ingression. Moreover, we found no or only slight defects in the spatial distribution of surface tension just before the arrest of furrow ingression in the zen-4 mutant cells, as far as we estimated surface tension on the basis of a surface tension model. Hence, it seems unlikely that the arrest of furrow ingression in the mutant cells arises from defects in surface tension control, although we cannot rule out the possibility that surface tension significantly contributes to furrow ingression, especially in phases other than the middle phase where the mutant cells are arrested. Similarly, it is possible that components other than Kc or surface tension may affect furrow ingression, e.g., astral microtubules and mechanical features of the cytoplasm. Although we do not know all of the mechanical components for cytokinesis, our simplified model based on Kc successfully explained the in vivo phenomena, 4-Hydroxyisoleucine the arrest in the mutant cells and the consequences of the local application of drugs. One of the advantages of our estimating method is that it allowed us to estimate Kc with a high spatio-temporal resolution, which has not been separable from contractility/surface tension in AFM. Actin-based cytoskeletal dynamics could be predicted through the estimation of Kc. In addition, our method only requires imaged cell shapes, and thus, it is easily applicable to microscopic images of cell shapes. Conversely, it should be noted that this method may be sensitive to several factors such as the spatial resolution of measurements of in vivo cell shapes and the smoothness cost for spatial changes in Kc. We did not detect any stiffer regions coinciding with the contractile ring, which may be due to an insufficiency in the spatial resolution of the furrow and/or the smoothness cost, which disfavors acute spatial changes in Kc. According to our estimation, Kc can spatially vary by,2 orders. Although there are no experimental data for Kc with a spatial resolution, Young’s modulus of cells measured by AFM spatially varied by,l-Chicoric-acid suggesting that cell surface stiffness can spatially change by this magnitude. The mechanics of cytokinesis remain enigmatic. Although many direct and indirect regulators of the cytoskeleton are involved in cytokinesis, their mechanical actions are poorly understood. The mechanical actions of several proteins are theoretically related to experimentally observed cytokinesis dynamics. Our method to estimate cell surface stiffness can be useful to predict the mechanical actions of proteins in a spatio-temporal manner. Human embryonic stem cells are pluripotent cells that can self-renew indefinitely and also generate cells representative of the three primary embryonic germ layers. The latter ability, termed pluripotency, makes hESC an ideal tool to develop cell replacement therapies. However, before the therapeutic potential of hESC can be fully realized, development of a culture system that enhances the production of undifferentiated hESC will be essential. Studies of the molecular mechanisms regulating hESC pluripotency could be helpful in this regard. Several transcription factors are known to be important regulators of pluripotency and self-renewal in hESC, including Oct4, Sox2 and Nanog. These three transcription factors are able to regulate the expression of each other, effectively forming a core transcriptional network governing pluripotency of hESC. A similar transcriptional network between Tcl1, Tbx3 and Esrrb also exist in mouse embryonic stem cells. However, whether there are other factors involved in regulating hESC pluripotency remains to be determined. Studies that address these questions could provide critical insights into the mechanisms regulating self-renewal and early differentiation of hESC.