記述言語：英語   掲載種別：研究論文（学術雑誌）  

Phagocytosis is a cellular process for internalization of micron-sized large particles including pathogens. The Bin-Amphiphysin-Rvs167 (BAR) domain proteins, including the FCH-BAR (F-BAR) domain proteins, impose specific morphologies on lipid membranes. Most BAR domain proteins are thought to form membrane invaginations or protrusions by assembling into helical submicron-diameter filaments, such as on clathrin-coated pits, caveolae, and filopodia. However, the mechanism by which BAR domain proteins assemble into micron-scale phagocytic cups was unclear. Here, we show that the two-dimensional sheet-like assembly of Growth Arrest-Specific 7 (GAS7) plays a critical role in phagocytic cup formation in macrophages. GAS7 has the F-BAR domain that possesses unique hydrophilic loops for two-dimensional sheet formation on flat membranes. Super-resolution microscopy reveals the similar assemblies of GAS7 on phagocytic cups and liposomes. The mutations of the loops abolishes both the membrane localization of GAS7 and phagocytosis. Thus, the sheet-like assembly of GAS7 plays a significant role in phagocytosis.

DOI： 10.1038/s41467-019-12738-w

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掲載種別：論文集(書籍)内論文  

DOI： 10.1007/978-1-4939-9520-2_22

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掲載種別：研究論文（学術雑誌）  

DOI： 10.1371/journal.pcbi.1006152

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER PHYSICAL SOC  

A Markovian lattice model for photoreceptor cells is introduced to describe the growth of mosaic patterns on fish retina. The radial stripe pattern observed in wild-type zebrafish is shown to be selected naturally during retina growth, against the geometrically equivalent circular stripe pattern. The mechanism of such dynamical pattern selection is clarified on the basis of both numerical simulations and theoretical analyses, which find that the successive emergence of local defects plays a critical role in the realization of the wild-type pattern.

DOI： 10.1103/PhysRevE.96.032416

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATURE PUBLISHING GROUP  

Caveolae are abundant flask-shaped invaginations of plasma membranes that buffer membrane tension through their deformation. Few quantitative studies on the deformation of caveolae have been reported. Each caveola contains approximately 150 caveolin-1 proteins. In this study, we estimated the extent of caveolar deformation by measuring the density of caveolin-1 projected onto a two-dimensional (2D) plane. The caveolin-1 in a flattened caveola is assumed to have approximately one-quarter of the density of the caveolin-1 in a flask-shaped caveola. The proportion of one-quarter-density caveolin-1 increased after increasing the tension of the plasma membrane through hypo-osmotic treatment. The one-quarter-density caveolin-1 was soluble in detergent and formed a continuous population with the caveolin-1 in the caveolae of cells under isotonic culture. The distinct, dispersed lower-density caveolin-1 was soluble in detergent and increased after the application of tension, suggesting that the hypo-osmotic tension induced the dispersion of caveolin-1 from the caveolae, possibly through flattened caveolar intermediates.

DOI： 10.1038/s41598-017-08259-5

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATL ACAD SCIENCES  

The Golgi apparatus is a membrane-bounded organelle with the characteristic shape of a series of stacked flat cisternae. During mitosis in mammalian cells, the Golgi apparatus is once fragmented into small vesicles and then reassembled to form the characteristic shape again in each daughter cell. The mechanism and details of the reassembly process remain elusive. Here, by the physical simulation of a coarse-grained membrane model, we reconstructed the three-dimensional morphological dynamics of the Golgi reassembly process. Considering the stability of the interphase Golgi shape, we introduce two hypothetical mechanisms-the Golgi rim stabilizer protein and curvature-dependent restriction on membrane fusion-into the general biomembrane model. We show that the characteristic Golgi shape is spontaneously organized from the assembly of vesicles by proper tuning of the two additional mechanisms, i.e., the Golgi reassembly process is modeled as self-organization. We also demonstrate that the fine Golgi shape forms via a balance of three reaction speeds: vesicle aggregation, membrane fusion, and shape relaxation. Moreover, the membrane fusion activity decreases thickness and the number of stacked cisternae of the emerging shapes.

DOI： 10.1073/pnas.1619264114

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER PHYSICAL SOC  

We report molecular dynamics simulations of the segregation of two overlapping polymers motivated by chromosome segregation in biological cells. We investigate the relationship between polymer shapes and segregation dynamics and show that elongation and compaction make entangled polymers segregate rapidly. This result suggests that eukaryotic chromosomes take such a characteristic rod-shaped structure, which is induced by condensins, to achieve rapid segregation.

DOI： 10.1103/PhysRevE.94.042403

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

Most of the land plants generally have dorsoventrally flat leaves, maximizing the surface area of both upper (adaxial) side and lower (abaxial) side. The former is specialized for light capturing for photosynthesis and the latter is specialized for gas exchange. From findings of molecular genetics, it has been considered that the coupled dynamics between tissue morphogenesis and gene regulation for cell identity is responsible for making flat leaves. The hypothesis claims that a flat leaf is generated under two assumptions, (i) two mutually recessive groups of genes specify adaxial and abaxial sides of a leaf, (ii) cell divisions are induced at the limited region in the leaf margin where both of two groups are expressed. We examined the plausibility and possibility of this hypothesis from the dynamical point of view. We studied a mathematical model where two processes are coupled, tissue morphogenesis induced by cell division and deformation, and dynamics of gene regulations. From the analysis of the model we found that the classically believed hypothesis is not sufficient to generate flat leaves with high probability. We examined several different modifications and revision of the model. Then we found that a simple additional rule of polarized cell division facilitates flat leaf formation. The result of our analysis gives prediction of possible mechanism, which can be easily verified in experiments. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jtbi.2016.06.005

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

The filamentous cyanobacterium, Anabaena sp. PCC 7120, is one of the simplest models of a multicellular system showing cellular differentiation. In nitrogen-deprived culture, undifferentiated vegetative cells differentiate into heterocysts at similar to 10-cell intervals along the cellular filament. As undifferentiated cells divide, the number of cells between heterocysts (segment length) increases, and a new heterocyst appears in the intermediate region.
To understand how the heterocyst pattern is formed and maintained, we constructed a one-dimensional cellular automaton (CA) model of the heterocyst pattern formation. The dynamics of vegetative cells is modeled by a stochastic transition process including cell division, differentiation and increase of cell age (maturation). Cell division and differentiation depend on the time elapsed after the last cell division, the "cell age". The model dynamics was mathematically analyzed by a two-step Markov approximation. In the first step, we determined steady state of cell age distribution among vegetative cell population. In the second step, we determined steady state distribution of segment length among segment population. The analytical solution was consistent with the results of numerical simulations. We then compared the analytical solution with the experimental data, and quantitatively estimated the immeasurable intercellular kinetics. We found that differentiation is initially independent of cellular maturation, but becomes dependent on maturation as the pattern formation evolves. Our mathematical model and analysis enabled us to quantify the internal cellular dynamics at various stages of the heterocyst pattern formation. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jtbi.2015.01.034

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

The cytoplasms of ameboid cells are nonlinearly viscous. The cell controls this viscosity by modulating the amount, localization and interactions of bio-polymers. Here we investigated how the nonlinearity infers the cellular behaviors and whether nonlinearity-specific behaviors exist. We modeled the developed plasmodium of the slime mold Physarum polycephalum as a network of branching tubes and examined the linear and nonlinear viscous cytoplasm flows in the tubes. We found that the nonlinearity in the cytoplasm's viscosity induces a novel type of symmetry breaking in the protoplasmic flow. We also show that symmetry breaking can play an important role in adaptive behaviors, namely, connection of behavioral modes implemented on different time scales and transportation of molecular signals from the front to the rear of the cell during cellular locomotion. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jtbi.2014.09.023

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

Inhomogeneous distribution of auxin is essential in various differentiation processes of plant development. Auxin transfer between cells by efflux carrier protein called PINFORMED (PIN) has been considered to be responsible for inhomogeneous distribution of auxin. Two major types of auxin distribution patterns are "spot" patterns and "passage" patterns, which are responsible for determining the position of the primordia of a leaf or flower in shoot apical meristem and formation of leaf veins, respectively.
In this study, we studied the pattern formation of auxin distribution mediated by polarization of PIN using mathematical methods. We developed several different models which show possible interaction mechanisms between auxin and PIN on 2-dimentional hexagonal cellular lattice, (1) Basic auxin flux model, (2) auxin-dependent PIN degradation model and (3) auxin self-feedback model.
We analyzed these models by numerical calculation and mathematical analysis. From intensive numerical calculations under different conditions, we found that some models show three different types of pattern formations in dynamics, (a) homogeneous, (b) passage and (c) spot pattern depending on parameter condition. We analyzed these models mathematically using approximation of 1-dimensional periodic space. We determined the conditions that passage and spot patterns are generated in each model, respectively. After these analyses, we propose possible mechanisms by which plants switch passage and spot patterns in different organs by small modification. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jtbi.2014.09.039

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掲載種別：研究論文（国際会議プロシーディングス）  

The objective of our research was to predict cell fates of a multicellular system, accompanied by cellular differentiation. To fulfill this objective, we sought to distinguish the differentiated and undifferentiated cells of filamentous cyanobacteria (Anabaena sp. PCC 7120) using Raman imaging. This technique indicated Raman bands of the cellular system, in which several bands were assigned to vibrations of β-carotene and scytonemin. We applied principal component analysis (PCA) to the Raman spectra to determine the PC1 and PC2 loading plots and their scores. The data points obtained for heterocyst tended to converge along the bottom of the scatterplot whereas those for vegetative cells were more widely distributed in the PC plane. This indicates that the chemical compositions of a heterocyst were relatively stable. As vegetative cells are capable of proliferation or differentiation, they may transit and exist in several states including the pseudo-differentiated state. The results suggest that the chemical compositions of a vegetative cell fluctuated according to its cellular condition. In conclusion, the results of Raman imaging indicate that the diverse states of vegetative cells are localized in a specific state through differentiation. © 2013 SPIE.

DOI： 10.1117/12.2018694

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY  

Nonisochronicity (frequency change caused by amplitude deviation) is the essential trait that differentiates limit cycle oscillators from phase oscillators. We studied networks of nonisochronic limit cycle oscillators, and demonstrated that the frequencies assume distributed values in a sustainable manner. We observed two complex phenomena in the networks: stationary distributed frequencies at a regular interval (quantization of frequencies), and continuous irregular modulation of frequencies. In the analysis we reveal the mechanisms by which the frequencies are distributed, and show how the nonisochronicity produces these complex phenomena. We also illustrate that the topology of the networks determines the behavior of the system. Copyright (C) EPLA, 2010

DOI： 10.1209/0295-5075/92/20005

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

Mathematical models to describe period-memorizing behavior in Physarum plasmodium are reported. In constructing the model, we first examine the basic characteristics required for the class of models, then create a minimal linear model to fulfill these requirements. We also propose two modifications of the minimal model, nonlinearization and noise addition, which improve the reproducibility of experimental evidences. Differences in the mechanisms and in the reproducibility of experiments between our models and the previous models are discussed. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jtbi.2010.01.005

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PUBLIC LIBRARY SCIENCE  

Ecological systems are always subjected to various environmental fluctuations. They evolve under these fluctuations and the resulting systems are robust against them. The diversity in ecological systems is also acquired through the evolution. How do the fluctuations affect the evolutionary processes? Do the fluctuations have direct impact on the species diversity in ecological systems? In the present paper, we investigate the relation between the environmental fluctuation and the evolution of species diversity with a mathematical model of evolutionary ecology. In the model, individual organisms compete for a single restricted resource and the temporal fluctuation in the resource supply is introduced as the environmental fluctuation. The evolutionary process is represented by the mutational change of genotypes which determines their resource utilization strategies. We found that when the environmental state is switched form static to fluctuating conditions, the initial closely related population distributed around the genotype adapted for the static environment is destabilized and divided into two groups in the genotype space; i.e., the evolutionary branching is induced by the environmental fluctuation. The consequent multiple species structures is evolutionary stable at the presence of the fluctuation. We perform the evolutionary invasion analysis for the phenomena and illustrate the mechanisms of the branchings. The results indicate a novel process of increasing the species diversity via evolutionary branching, and the analysis reveals the mechanisims of the branching preocess as the response to the environmental fluctuation. The robustness of the evolutionary process is also discussed.

DOI： 10.1371/journal.pone.0003925

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Population dynamics on two sites of ecological fields are studied. Each site shows oscillatory dynamics with a heteroclinic cycle ora limit cycle attractor, and Populations migrate between two sites diffusively. In this system, frequency locking states with specific ratios between the oscillations of two sites are observed. The selection of the ratios are explained with the symmetry of the phase space. Other properties of the locking states as behaviors intrinsic to heteroclinic cycles are also discussed. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cam.2005.12.037

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY  

A coupled phase-oscillator model where each oscillator has an angular velocity that varies due to the interaction with other oscillators is studied. This model is proposed to give a novel example of a wide variety of time scales as complex systems. It is found that initial conditions close to a one-cluster state self-organize into multiple clusters with different angular velocities, i.e. diversification of the time scales emerges through the multi clustering process in phases. Analyses for the clusters solution, the stability of the solution and the mechanism determining the time scales are reported. Copyright (C) EPLA, 2007.

DOI： 10.1209/0295-5075/78/20004

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

A open flow system with chaotic behavior in local elemets is studied. As novel phenomena in the system, we report a simple bistable pattern is arised in the downstream though the spatially coherent chaotic oscillation is observed in the upstream domain. The two patterns are characterized by Lyapunov analysis.

DOI： 10.1143/PTPS.161.352

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

A square lattice distribution of coupled oscillators that have heteroclinic cycle attractors is studied. In this system, we find a novel type of patterns that is spatially disordered and periodic in time. These patterns are limit cycle attractors in the ambient phase space (i.e. not chaotic), and there exsit many limit cycles, dividing the phase space into their basins. The patterns emerge from a local law concerning the difference between the phases of oscillators. The number of patterns grows exponentially as a function of the number of oscillators.

DOI： 10.1143/PTP.109.133

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

Coupled heteroclinic cycles are introduced as a new class of coupled oscillator systems. As an example, we study a square lattice distribution of heteroclinic cycles and show the emergence of non-chaotic disordered patterns. A short analysis of them is also reported.

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記述言語：日本語  

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