佐藤 勝彦(サトウ カツヒコ) |

電子科学研究所 |

准教授 |

Last Updated :2020/10/09

- Schenz D, Nishigami Y, Sato K, Nakagaki TCurrent opinion in genetics & development 57 78 - 83 2019年08月 [査読有り][通常論文]
- Okuda S, Kuranaga E, Sato KBiophysical journal 116 6 1159 - 1170 2019年03月 [査読有り][通常論文]
**モジホコリ**高木 清二, 佐藤 勝彦, 中垣 俊之生物工学 96 8 488 - 492 2018年 [査読無し][招待有り]- Katsuhiko SatoDEVELOPMENT GROWTH & DIFFERENTIATION 59 5 317 - 328 2017年06月 [査読有り][通常論文]

During early embryonic development, epithelial cells form a monolayer sheet and migrate in a definite direction. This phenomenon, called epithelial cell migration, is an important topic in developmental biology. A characteristic feature of this process is attachment to adjacent cells during migration, which is necessary for maintaining the integrity of the sheet. However, it is unclear how these cohesive cells migrate without breaking their attachments. A mechanism for this phenomenon was recently proposed, in which direction-dependent contraction forces acting on cell boundaries induce unidirectional epithelial migration. In this review, we examine this proposed mechanism from various aspects and provide theoretical background for the collective migration of epithelial cells. This information may be helpful for investigators to realize the basic principles underlying collective epithelial migration and devise new mechanisms for it. - Dai Akita, Daniel Schenz, Shigeru Kuroda, Katsuhiko Sato, Kei-ichi Ueda, Toshiyuki NakagakiDEVELOPMENT GROWTH & DIFFERENTIATION 59 5 465 - 470 2017年06月 [査読有り][通常論文]

Vein networks span the whole body of the amoeboid organism in the plasmodial slime mould Physarum polycephalum, and the network topology is rearranged within an hour in response to spatio-temporal variations of the environment. It has been reported that this tube morphogenesis is capable of solving mazes, and a mathematical model, named the current reinforcement rule', was proposed based on the adaptability of the veins. Although it is known that this model works well for reproducing some key characters of the organism's maze-solving behaviour, one important issue is still open: In the real organism, the thick veins tend to trace the shortest possible route by cutting the corners at the turn of corridors, following a center-in-center trajectory, but it has not yet been examined whether this feature also appears in the mathematical model, using corridors of finite width. In this report, we confirm that the mathematical model reproduces the center-in-center trajectory of veins around corners observed in the maze-solving experiment. - K. Sato, I. Kunita, Y. Takikawa, D. Takeuchi, Y. Tanaka, T. Nakagaki, H. OriharaSOFT MATTER 13 14 2708 - 2716 2017年04月 [査読有り][通常論文]

Shear banding is frequently observed in complex fluids. However, the configuration of macromolecules in solutions undergoing shear banding has not yet been directly observed. In this study, by using the fact that F-actin solutions exhibit shear banding and actin filaments are visualized by fluorescent labels, we directly observed the intrinsic states of an actin solution undergoing shear banding. By combining the 3D imaging of labeled actin filaments and particle image velocimetry (PIV), we obtained orientation distributions of actin filaments in both high and low shear rate regions, whose quantitative differences are indicated. In addition, by using the orientation distributions and applying stress expression for rod-like polymers, we estimated stress tensors in both high and low shear rate regions. This evaluation indicates that different orientation distributions of filamentous macromolecules can exhibit a common shear stress. **Dynamic properties of bio-motile systems as a liquid-crystalline structure**S. Ishiwata, M. Miyazaki, K. Sato, K. Nakagome, S. A. Shintani, F. K, Shimozawa, N. Fukuda, K. Suzuki, J. Takagi, Y. Shimamoto, T. ItabashiMol. Cryst. Liq. Cryst. 647 127 - 150 2017年 [査読有り][招待有り]**Experimental models for Murray's law**D. Akita, I. Kunita, M. D. Fricker, S. Kuroda, K. Sato, T. NakagakiJ. Phys. D: Appl. Phys. 50 024001 2017年01月 [査読有り][通常論文]- Nakagome K, Sato K, Shintani SA, Ishiwata SBiophysics and physicobiology 13 217 - 226 2016年 [査読有り][通常論文]
- Katsuhiko Sato, Tetsuya Hiraiwa, Emi Maekawa, Ayako Isomura, Tatsuo Shibata, Erina KuranagaNATURE COMMUNICATIONS 6 10074 2015年12月 [査読有り][通常論文]

Morphogenetic epithelial movement occurs during embryogenesis and drives complex tissue formation. However, how epithelial cells coordinate their unidirectional movement while maintaining epithelial integrity is unclear. Here we propose a novel mechanism for collective epithelial cell movement based on Drosophila genitalia rotation, in which epithelial tissue rotates clockwise around the genitalia. We found that this cell movement occurs autonomously and requires myosin II. The moving cells exhibit repeated left-right-biased junction remodelling, while maintaining adhesion with their neighbours, in association with a polarized myosin II distribution. Reducing myosinID, known to cause counter-clockwise epithelial-tissue movement, reverses the myosin II distribution. Numerical simulations revealed that a left-right asymmetry in cell intercalation is sufficient to induce unidirectional cellular movement. The cellular movement direction is also associated with planar cell-shape chirality. These findings support a model in which left-right asymmetric cell intercalation within an epithelial sheet drives collective cellular movement in the same direction. - Katsuhiko Sato, Shin-ichiro ShimaPHYSICAL REVIEW E 92 4 042922 2015年10月 [査読有り][通常論文]

We investigate a phase model that includes both locally attractive and globally repulsive coupling in one dimension. This model exhibits nontrivial spatiotemporal patterns that have not been observed in systems that contain only local or global coupling. Depending on the relative strengths of the local and global coupling and on the form of global coupling, the system can show a spatially uniform state (in-phase synchronization), a monotonically increasing state (traveling wave), and three types of oscillations of relative phase difference. One of the oscillations of relative phase difference has the characteristic of being locally unstable but globally attractive. That is, any small perturbation to the periodic orbit in phase space destroys its periodic motion, but after a long time the system returns to the original periodic orbit. This behavior is closely related to the emergence of saddle two-cluster states for global coupling only, which are connected to each other by attractive heteroclinic orbits. The mechanism of occurrence of this type of oscillation is discussed. - Katsuhiko Sato, Tetsuya Hiraiwa, Tatsuo ShibataPHYSICAL REVIEW LETTERS 115 18 188102 2015年10月 [査読有り][通常論文]

During early development, epithelial cells form a monolayer sheet and migrate in a uniform direction. Here, we address how this collective migration can occur without breaking the cell-to-cell attachments. Repeated contraction and expansion of the cell-to-cell interfaces enables the cells to rearrange their positions autonomously within the sheet. We show that when the interface tension is strengthened in a direction that is tilted from the body axis, cell rearrangements occur in such a way that unidirectional movement is induced. We use a vertex model to demonstrate that such anisotropic tension can generate the unidirectional motion of cell sheets. Our results suggest that cell chirality facilitates collective cell migration during tissue morphogenesis. - Katsuhiko Sato, Yoshiki Kuramoto, Masako Ohtaki, Yuta Shimamoto, Shin'ichi IshiwataPHYSICAL REVIEW LETTERS 111 10 108104 2013年09月 [査読有り][通常論文]

At an intermediate activation level, striated muscle exhibits autonomous oscillations called SPOC, in which the basic contractile units, sarcomeres, oscillate in length, and various oscillatory patterns such as traveling waves and their disrupted forms appear in a myofibril. Here we show that these patterns are reproduced by mechanically connecting in series the unit model that explains characteristics of SPOC at the single-sarcomere level. We further reduce the connected model to phase equations, revealing that the combination of local and global couplings is crucial to the emergence of these patterns. - Itsuki Kunita, Katsuhiko Sato, Yoshimi Tanaka, Yoshinori Takikawa, Hiroshi Orihara, Toshiyuki NakagakiPHYSICAL REVIEW LETTERS 109 24 248303 2012年12月 [査読有り][通常論文]

We report herein the first evidence that an F-actin solution shows shear banding, which is characterized by the spontaneous separation of homogeneous shear flow into two macroscopic domains of different definite shear rates. The constant shear stress observed in the F-actin solution is explained by the banded flow with volume fractions that obey the lever rule. Nonhomogenous reversible flows were observed in the F-actin solution with respect to upward and downward changes in the shear rate. This is the first time shear banding has been observed in a simple biomacromolecule. The biological implications and dynamic aspects of shear flow velocity characteristic patterns are discussed. - Daiki Endo, Katsuhiko Sato, Yoshinori HayakawaPhysical Review E - Statistical, Nonlinear, and Soft Matter Physics 86 1 016106 2012年07月11日 [査読有り][通常論文]

We performed experiments to investigate slow fracture in thin rubber films under uniaxial tension using high-viscosity oils. In this system we observed an oscillating instability in slowly propagating cracks for small applied strains. The transition between oscillatory and straight patterns occurred near the characteristic strain at which rubber exhibits a nonlinear stress-strain relation. This suggests that nonlinear elasticity plays an important role in the formation of the observed pattern. This was confirmed by numerical simulation for neo-Hookean and linear elasticity models. © 2012 American Physical Society. **Deformation of the equilibrium shape of a vesicle induced by enclosed flexible polymers**Y. Oya, K. Sato, T. KawakatsuEurophys. Lett. 94 68004 2011年06月 [査読有り][通常論文]- Katsuhiko Sato, Masako Ohtaki, Yuta Shimamoto, Shin'ichi IshiwataPROGRESS IN BIOPHYSICS & MOLECULAR BIOLOGY 105 3 199 - 207 2011年05月 [査読有り][通常論文]

It is widely accepted that muscle cells take either force-generating or relaxing state in an all-or-none fashion through the so-called excitation-contraction coupling. On the other hand, the membrane-less contractile apparatus takes the third state, i.e., the auto-oscillation (SPOC) state, at the activation level that is intermediate between full activation and relaxation. Here, to explain the dynamics of all three states of muscle, we construct a novel theoretical model based on the balance of forces not only parallel but also perpendicular to the long axis of myofibrils, taking into account the experimental fact that the spacing of myofilament lattice changes with sarcomere length and upon contraction. This theory presents a phase diagram composed of several states of the contractile apparatus and explains the dynamic behavior of SPOC, e.g., periodical changes in sarcomere length with the saw-tooth waveform. The appropriate selection of the constant of the molecular friction due to the cross-bridge formation can explain the difference in the SPOC periods observed under various activating conditions and in different muscle types, i.e., skeletal and cardiac. The theory also predicts the existence of a weak oscillation state at the boundary between SPOC and relaxation regions in the phase diagram. Thus, the present theory comprehensively explains the characteristics of auto-oscillation and contraction in the contractile system of striated muscle. (C) 2010 Elsevier Ltd. All rights reserved. - K. Sato, X. -F. Yuan, T. KawakatsuEUROPEAN PHYSICAL JOURNAL E 31 2 135 - 144 2010年02月 [査読有り][通常論文]

Numerous numerical and experimental evidence suggest that shear banding behavior looks like first-order phase transitions. In this paper, we demonstrate that this correspondence is actually established in the so-called non-local diffusive Johnson-Segalman model (the DJS model), a typical mechanical constitutive model that has been widely used for describing shear banding phenomena. In the neighborhood of the critical point, we apply the reduction procedure based on the center manifold theory to the governing equations of the DJS model. As a result, we obtain a time evolution equation of the flow field that is equivalent to the time-dependent Ginzburg-Landau (TDGL) equations for modeling thermodynamic first-order phase transitions. This result, for the first time, provides a mathematical proof that there is an analogy between the mechanical instability and thermodynamic phase transition at least in the vicinity of the critical point of the shear banding of DJS model. Within this framework, we can clearly distinguish the metastable branch in the stress-strain rate curve around the shear banding region from the globally stable branch. A simple extension of this analysis to a class of more general constitutive models is also discussed. Numerical simulations for the original DJS model and the reduced TDGL equation is performed to confirm the range of validity of our reduction theory. - Kunihiko Kaneko, Katsuhiko Sato, Tatsuo Michiue, Koji Okabayashi, Kiyoshi Ohnuma, Hiroki Danno, Makoto AsashimaJOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 310B 6 492 - 503 2008年09月 [査読有り][通常論文]

Development is a complex process that involves differentiation into a variety of cell types. In spite of its complexity, the macroscopic pattern and cell types are robust to environmental and developmental perturbations. Even in vitro far from normal developmental conditions, ten normal tissues have been generated from Xenopus animal caps by successive treatment with activin and retinoic acid (RA). To describe both normal development and in vitro organogenesis, we introduce developmental potential following the pioneering Study by Waddington. This potential value represents changeability of a cellular state, which decreases toward a local minimum through development. The attraction to a particular cell type through development is described as a process to decrease the potential value to its local minimum. By choosing an explicit potential form as a function of the concentrations of treated activin and RA, the concentration dependence of in vitro organogenesis is reproduced. The potential landscape is shown to have several local minima, each of which represents a stable cell type. This potential also explains why the induction of given tissues requires more treatment of activin at, later stages. The consequences of the developmental potential hypothesis encompass the robustness of each tissue generation. the loss of competence through development, and the order Of tissues in induction by tissues, which we have confirmed experimentally for in vitro organogenesis. The developmental potential hypothesis for a global description of early development is crucial to understanding the robustness of morphogenesis and explains the achievement of in vitro organogenesis using few molecules as well. - Katsuhiko Sato, Kunihiko KanekoPHYSICAL REVIEW E 75 6 061909 2007年06月 [査読有り][通常論文]

An equation describing the evolution of phenotypic distribution is derived using methods developed in statistical physics. The equation is solved by using the singular perturbation method, and assuming that the number of bases in the genetic sequence is large. Applying the equation to the mutation-selection model by Eigen provides the critical mutation rate for the error catastrophe. Phenotypic fluctuation of clones (individuals sharing the same gene) is introduced into this evolution equation. With this formalism, it is found that the critical mutation rate is sometimes increased by the phenotypic fluctuations, i.e., noise can enhance robustness of a fitted state to mutation. Our formalism is systematic and general, while approximations to derive more tractable evolution equations are also discussed. - K Sato, K KanekoPHYSICAL BIOLOGY 3 1 74 - 82 2006年03月 [査読有り][通常論文]

Characterizing a cell state by measuring the degree of gene expression as well as its noise has gathered much attention. The distribution of such state values (e.g., abundances of some proteins) over cells has been measured, and is not only a result of intracellular process, but is also influenced by the growth in cell number that depends on the state. By incorporating the growth-death process into the standard Fokker-Planck equation, a nonlinear temporal evolution equation of distribution is derived and then solved by means of eigenfunction expansions. This general formalism is applied to the linear relaxation case. First, when the growth rate of a cell increases linearly with the state value x, the shift of the average x due to the growth effect is shown to be proportional to the variance of x and the relaxation time, similar to the biological fluctuation-response relationship. Second, when there is a threshold value of x for growth, the existence of a critical growth rate, represented again by the variance and the relaxation time, is demonstrated. The relevance of the results to the analysis of biological data on the distribution of cell states, as obtained for example by flow cytometry, is discussed. - K Sato, Y Ito, T Yomo, K KanekoPROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 100 24 14086 - 14090 2003年11月 [査読有り][通常論文]

A general relationship between fluctuation and response in a biological system is presented. The fluctuation is given by the variance of some quantity, whereas the response is given as the average change of that quantity for a given parameter change. We propose a relationship where the two are proportional, in a similar way to the fluctuation-dissipation theorem in physics. By studying an evolution experiment where fluorescence of protein in bacteria increases, we confirm our relation by observing a positive correlation between the speed of fluorescence evolution and the phenotypic fluctuation of the fluorescence over clone bacteria. The generality of the relationship as well as its relevance to evolution is discussed.