BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Philip Maini (University of Oxford) DTSTART:20210927T153000Z DTEND:20210927T162000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/1 DESCRIPTION:Title: (Maini + Kulesa\, Part I) Modelling collective cell migration i n developmental biology\nby Philip Maini (University of Oxford) as par t of CMO - Modeling and Computational Approaches to Individual and Collect ive Cell Movement in Complex En\n\n\nAbstract\nOver the past decade\, in a n interdisciplinary collaboration between Philip Maini and colleagues in t he Wolfson Centre for Mathematical Biology and the Kulesa lab at The Stowe rs Institute for Medical Research\, we have developed a suite of cell-base d models in parallel with experiments to investigate the underlying dynami cs of collective cell migration. We focus on the highly invasive neural cr est cells that in the vertebrate embryo migrate in discrete streams along stereotypical pathways. In this talk\, we will review this work and show h ow it has led to new insights into the underlying biology. Specifically\, it will be shown how modelling\, combined with experiments\, led us to the identification of different cell phenotypes and phenotypic switching\, as well as generating hypotheses on how cells may be assembling and deformin g the extracellular matrix through which they migrate\, and how they may b e signalling to each other.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Paul Kulesa (Stowers Institute for Medical Research) DTSTART:20210927T163000Z DTEND:20210927T172000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/2 DESCRIPTION:Title: (Maini + Kulesa\, Part II) Modelling collective cell migration in developmental biology\nby Paul Kulesa (Stowers Institute for Medica l Research) as part of CMO - Modeling and Computational Approaches to Indi vidual and Collective Cell Movement in Complex En\n\n\nAbstract\nOver the past decade\, in an interdisciplinary collaboration between Philip Maini a nd colleagues in the Wolfson Centre for Mathematical Biology and the Kules a lab at The Stowers Institute for Medical Research\, we have developed a suite of cell-based models in parallel with experiments to investigate the underlying dynamics of collective cell migration. We focus on the highly invasive neural crest cells that in the vertebrate embryo migrate in discr ete streams along stereotypical pathways. In this talk\, we will review th is work and show how it has led to new insights into the underlying biolog y. Specifically\, it will be shown how modelling\, combined with experimen ts\, led us to the identification of different cell phenotypes and phenoty pic switching\, as well as generating hypotheses on how cells may be assem bling and deforming the extracellular matrix through which they migrate\, and how they may be signalling to each other.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Alex Mogilner (New York University) DTSTART:20210927T173000Z DTEND:20210927T182000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/3 DESCRIPTION:Title: Collective migration of one pair of cells in Ciona embryo\n by Alex Mogilner (New York University) as part of CMO - Modeling and Compu tational Approaches to Individual and Collective Cell Movement in Complex En\n\n\nAbstract\nDuring embryonic development\, cells often migrate colle ctively. The cardiogenic progenitors of \nthe ascidian Ciona provide one o f the simplest examples of collective migration: two \ncells migrate with defined leader-trailer polarity\, squeezed between stiff epidermis and\nde formable endoderm. The cells are also capable of migrating \nindividually\ , in a less persistent way. Two cells with upregulated protrusion migrate side by\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Qixuan Wang (UC Riverside) DTSTART:20210927T193000Z DTEND:20210927T202000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/4 DESCRIPTION:Title: Roles of cellular anisotropy and heterogeneity in cell movement \nby Qixuan Wang (UC Riverside) as part of CMO - Modeling and Computat ional Approaches to Individual and Collective Cell Movement in Complex En\ n\n\nAbstract\nCells can be structurally anisotropic\, and they can be het erogeneous\ndue to either genetic or environment clues. Cellular anisotrop y and\nheterogeneity might lead to interesting behaviors in individual or collective\ncell movement. In this talk we will discuss the roles of cellu lar anisotropy and\nheterogeneity in two systems. In the first part\, we w ill discuss how anisotropic\nflagella bending rigidity affects the flagell ar beating dynamics. Flagellar\nbeating is controlled by molecular motors that exert forces along the length of\nthe flagellum and are regulated by a feedback mechanism coupled to the flagellar\nmotion. We build on previou s work on sliding-controlled motor feedback to\ndevelop a fully three-dime nsional description of flagellar beating\, accounting\nfor both bending an d twist. We show that with isotropic bending\,\nthree-dimensional spiral m odes are spontaneously generated beyond a critical\nmolecular activity. On the other hand\, when a difference is introduced into the\nbending rigidi ty along orthogonal directions\, a preferential bending plane is\nestablis hed\, and we find that the generic three-dimensional spiral modes give\nwa y to planar beating along the soft axis as the difference in bending rigid ity\nincreases. In the second part\, we will discuss how hair follicle het erogeneous\nresponses to signals affect the cell flows which then regulate the follicle\ntemporal growth dynamics. Hair follicles are mini skin orga ns rich of stem\ncells\, and they undergo cyclic growth. The growing phase – anagen of a hair\nfollicle is tightly controlled by a group of epithe lial transient amplifying\n(TA) cells. Using an interdisciplinary approach combined of multi-scale modeling\nand lineage tracing experiments\, we sh ow that cellular heterogeneity based on\ncell division generations drive t he upward cell flows\, which guarantees the\nrefill of the follicle TA cel ls that prolongs the anagen.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/4/ END:VEVENT BEGIN:VEVENT SUMMARY:John Dallon (Brigham Young University) DTSTART:20210927T203000Z DTEND:20210927T212000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/5 DESCRIPTION:Title: Modeling Amoeboidal Cell Motion – Force vs Speed\nby John Dallon (Brigham Young University) as part of CMO - Modeling and Computati onal Approaches to Individual and Collective Cell Movement in Complex En\n \n\nAbstract\nIn this talk I will discuss two models of cell motion. One assumes cells are ellipsoid and the other model makes no assumption about cell shape and focuses on cell adhesions. In the second model random swit ching terms are used to model the attachment and detachment of adhesions. In the first model formation the focus is on force and force transmission . In the second model the focus shifts to the dynamics of the adhesions a nd how they affect the cell speed.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Hillen (University of Alberta) DTSTART:20210927T213000Z DTEND:20210927T230000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/6 DESCRIPTION:Title: Free discussion in gathertown\nby Thomas Hillen (University of Alberta) as part of CMO - Modeling and Computational Approaches to Ind ividual and Collective Cell Movement in Complex En\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Luigi Preziosi (Politecnico di Torino) DTSTART:20210928T150000Z DTEND:20210928T155000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/7 DESCRIPTION:Title: (Preziosi + Loy\, Part I) Modelling cell re-orientation under s tretch\nby Luigi Preziosi (Politecnico di Torino) as part of CMO - Mod eling and Computational Approaches to Individual and Collective Cell Movem ent in Complex En\n\n\nAbstract\nThe active response of cells to mechanica l cues due to their interaction with the environment has been of increasin g interest\, since it is involved in many physiological phenomena\, pathol ogies\, and in tissue engineering. In particular\, several experiments hav e shown that\, if a substrate with overlying cells is cyclically stretched \, they will reorient with their main axis either perpendicular or at an o blique angle with respect to the main stretching direction.\nIn the first part of the seminar\, held by Luigi Preziosi\, the phenomenon is studied f rom the deterministic point of view working in the framework of continuum mechanics. First a nonlinear elastic energy for a quite general orthotropi c material is used and a complete bifurcation analysis is performed to exp lain the dependence of the reorientation angle on the applied strain. Then \, a linear viscoelastic model is proposed to describe the dependence on t he applied frequency.\nIn the second part of the seminar\, held by Nadia L oy\, stochastic effects are considered. In fact\, in many cases results ar e given in terms of the percentage of cells having an orientation in certa in intervals. With the aim of describing both the evolution and the statio nary state of the probability density function over cell orientations\, Fo kker-Planck equations are deduced starting from microscopic rules. connect ed with the continuum mechanics models previously introduced. In addition\ , we introduce a way of describing the microscopic re-orientation rule as a result of an optimal control internally activated by the cell.\nThe resu lts of both models compare very well with experimental results.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Nadia Loy (Politecnico di Torino) DTSTART:20210928T160000Z DTEND:20210928T165000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/8 DESCRIPTION:Title: (Preziosi + Loy\, Part II) Modelling cell re-orientation under stretch\nby Nadia Loy (Politecnico di Torino) as part of CMO - Modelin g and Computational Approaches to Individual and Collective Cell Movement in Complex En\n\n\nAbstract\nThe active response of cells to mechanical cu es due to their interaction with the environment has been of increasing in terest\, since it is involved in many physiological phenomena\, pathologie s\, and in tissue engineering. In particular\, several experiments have sh own that\, if a substrate with overlying cells is cyclically stretched\, t hey will reorient with their main axis either perpendicular or at an obliq ue angle with respect to the main stretching direction.\nIn the first part of the seminar\, held by Luigi Preziosi\, the phenomenon is studied from the deterministic point of view working in the framework of continuum mech anics. First a nonlinear elastic energy for a quite general orthotropic ma terial is used and a complete bifurcation analysis is performed to explain the dependence of the reorientation angle on the applied strain. Then\, a linear viscoelastic model is proposed to describe the dependence on the a pplied frequency.\nIn the second part of the seminar\, held by Nadia Loy\, stochastic effects are considered. In fact\, in many cases results are gi ven in terms of the percentage of cells having an orientation in certain i ntervals. With the aim of describing both the evolution and the stationary state of the probability density function over cell orientations\, Fokker -Planck equations are deduced starting from microscopic rules. connected w ith the continuum mechanics models previously introduced. In addition\, we introduce a way of describing the microscopic re-orientation rule as a re sult of an optimal control internally activated by the cell.\nThe results of both models compare very well with experimental results.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Guillaume Charras (London Centre for Nanotechnology) DTSTART:20210928T170000Z DTEND:20210928T175000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/9 DESCRIPTION:Title: Dissecting the link between signalling and cell mechanics\n by Guillaume Charras (London Centre for Nanotechnology) as part of CMO - M odeling and Computational Approaches to Individual and Collective Cell Mov ement in Complex En\n\n\nAbstract\nThe submembranous actin cortex is the m ain determinant of cell shape. During mitosis and migration\, spatiotempor al changes in cortex mechanics give rise to shape changes. These result f rom tightly orchestrated global and local changes in RhoGTPase activity re gulated by recruitment of RhoGEFs and RhoGAPs to the cortex. Yet\, little is known about how signalling controls cell mechanics to drive shape chang e.\nI will present work investigating how signalling controls cell mechani cs. We use optogenetics to control the activity of RhoGTPases by relocalis ing a RhoGEF to the cortex and investigate the resulting temporal changes in surface tension using AFM. I will discuss how to coarse-grain signallin g downstream of RhoGTPases to link signalling to mechanics and shape chang e.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Jay Stotsky (University of Minnesota) DTSTART:20210928T190000Z DTEND:20210928T195000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/10 DESCRIPTION:Title: The Influence of the Cell Cortex on Cell Shape and Motion \nby Jay Stotsky (University of Minnesota) as part of CMO - Modeling and C omputational Approaches to Individual and Collective Cell Movement in Comp lex En\n\n\nAbstract\nBeneath the membrane of many cells lies the cell cor tex\, a composite layer of actin\, myosin\, and various cross-linking prot eins. The cell cortex is believed to have a strong influence on the abili ty of a cell to move about in its enviroment\, and in turn\, cell motility plays an important role in cancer metastasis and in many developmental pr ocesses. Cells can employ various strategies to move\, such as crawling or swimming\, and here I will discuss recent modeling and computational resu lts on how the forces\, applied externally or generated internally by the cellular cortex\, in conjunction with the mechanical properties of the cel l can lead to various shape changes and cell motion.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Gisell Estrada-Rodriguez (Sorbonne Universite) DTSTART:20210928T200000Z DTEND:20210928T205000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/11 DESCRIPTION:Title: Macroscopic description of nonlocal movement of biological sys tems in Rn and in networks\nby Gisell Estrada-Rodriguez (Sorbonne Univ ersite) as part of CMO - Modeling and Computational Approaches to Individu al and Collective Cell Movement in Complex En\n\n\nAbstract\nIn the presen ce of sparse attractants\, the movement of both cells and large organisms has been shown to be governed by long distance runs\, according to an appr oximate Levy distribution. In this talk we clarify the form of biologicall y relevant PDE descriptions for such movements. Motivated by experiments w e consider a microscopic velocity-jump model in which the motion of the in dividuals is characterized by long runs and long waiting times\, according to a heavy-tailed distribution.\n\nFurthermore\, this nonlocal movement o f individuals has been observed in more complex geometries\, e.g.\, the br ain. We propose to study the (nonlocal) diffusion using a network of subd omains\, corresponding to the nodes of a graph. I will introduce metaplex networks which are networks with internal structure\, and we will extend o ur analysis to two real world examples: a brain and a landscape network.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Hillen (University of Alberta) DTSTART:20210928T210000Z DTEND:20210928T223000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/12 DESCRIPTION:Title: Free discussion in gathertown\nby Thomas Hillen (Universit y of Alberta) as part of CMO - Modeling and Computational Approaches to In dividual and Collective Cell Movement in Complex En\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Helen Byrne (U California Santa Barbara) DTSTART:20210929T150000Z DTEND:20210929T155000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/13 DESCRIPTION:Title: (Byrne + Alarcon\, Part I) A multiscale model of complex endot helial cell dynamics in early angiogenesis\nby Helen Byrne (U Californ ia Santa Barbara) as part of CMO - Modeling and Computational Approaches t o Individual and Collective Cell Movement in Complex En\n\n\nAbstract\nWe introduce a hybrid two-dimensional multiscale model of angiogenesis\, the process by which endothelial cells (ECs) migrate from a pre-existing vascu lar bed in response to local environmental cues and cell-cell interactions \, to create a new vascular network. Recent experimental studies have high lighted the central role of cell rearrangements in the formation of angiog enic networks. Our model accounts for this phenomenon via the heterogeneou s response of ECs to their microenvironment. These cell rearrangements\, i n turn\, dynamically remodel the local environment. The model reproduces c haracteristic features of angiogenic sprouting that include branching\, ch emotactic sensitivity\, the brush border effect\, and cell mixing. These p roperties\, rather than being hardwired into the model\, emerge naturally from the gene expression patterns of individual cells. After calibrating a nd validating our model against experimental data\, we use it to predict h ow the structure of the vascular network changes as the baseline gene expr ession levels of the VEGF-Delta-Notch pathway\, and the composition of the extracellular environment\, vary. In order to investigate the impact of c ell rearrangements on the vascular network structure\, we introduce the mi xing measure\, a scalar metric that quantifies cell mixing as the vascular network grows. We calculate the mixing measure for the simulated vascular networks generated by ECs of different lineages (wild-type cells and muta nt cells with impaired expression of a specific receptor). Our results sho w that the time evolution of the mixing measure is directly correlated to the generic features of the vascular branching pattern\, thus\, supporting the hypothesis that cell rearrangements play an essential role in sprouti ng angiogenesis. Furthermore\, we predict that lower cell rearrangement le ads to an imbalance between branching and sprout elongation. Since the com putation of this statistic requires only individual cell trajectories\, it can be computed for networks generated in biological experiments\, making it a potential biomarker for pathological angiogenesis.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Tomás Alarcón (ICREA - Centre de Recerca de Matematica) DTSTART:20210929T160000Z DTEND:20210929T165000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/14 DESCRIPTION:Title: (Byrne + Alarcon\, Part II) A multiscale model of complex endo thelial cell dynamics in early angiogenesis\nby Tomás Alarcón (ICREA - Centre de Recerca de Matematica) as part of CMO - Modeling and Computat ional Approaches to Individual and Collective Cell Movement in Complex En\ n\n\nAbstract\nWe introduce a hybrid two-dimensional multiscale model of a ngiogenesis\, the process by which endothelial cells (ECs) migrate from a pre-existing vascular bed in response to local environmental cues and cell -cell interactions\, to create a new vascular network. Recent experimental studies have highlighted the central role of cell rearrangements in the f ormation of angiogenic networks. Our model accounts for this phenomenon vi a the heterogeneous response of ECs to their microenvironment. These cell rearrangements\, in turn\, dynamically remodel the local environment. The model reproduces characteristic features of angiogenic sprouting that incl ude branching\, chemotactic sensitivity\, the brush border effect\, and ce ll mixing. These properties\, rather than being hardwired into the model\, emerge naturally from the gene expression patterns of individual cells. A fter calibrating and validating our model against experimental data\, we u se it to predict how the structure of the vascular network changes as the baseline gene expression levels of the VEGF-Delta-Notch pathway\, and the composition of the extracellular environment\, vary. In order to investiga te the impact of cell rearrangements on the vascular network structure\, w e introduce the mixing measure\, a scalar metric that quantifies cell mixi ng as the vascular network grows. We calculate the mixing measure for the simulated vascular networks generated by ECs of different lineages (wild-t ype cells and mutant cells with impaired expression of a specific receptor ). Our results show that the time evolution of the mixing measure is direc tly correlated to the generic features of the vascular branching pattern\, thus\, supporting the hypothesis that cell rearrangements play an essenti al role in sprouting angiogenesis. Furthermore\, we predict that lower cel l rearrangement leads to an imbalance between branching and sprout elongat ion. Since the computation of this statistic requires only individual cell trajectories\, it can be computed for networks generated in biological ex periments\, making it a potential biomarker for pathological angiogenesis. \n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Brian Camley (Johns Hopkins University) DTSTART:20210929T170000Z DTEND:20210929T175000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/15 DESCRIPTION:Title: Contact inhibition of locomotion and geometry\nby Brian Ca mley (Johns Hopkins University) as part of CMO - Modeling and Computationa l Approaches to Individual and Collective Cell Movement in Complex En\n\n\ nAbstract\nFor cells to cooperate in healing a wound or work together to f ollow a signal\, they must coordinate their motion. One stereotyped behavi or found in many cell types is "contact inhibition of locomotion" (CIL)\, in which cells that collide with one another repolarize away from contact. Experiments studying CIL are often performed on flat rigid two-dimensiona l substrates\, unlike the natural fibrous environment of many cells in viv o. How does extracellular matrix geometry and adhesivity affect CIL? First \, I will talk about recent experiments by our collaborators in the Nain g roup\, which show that when cells are attached to single suspended nanofib ers\, the outcomes of CIL can be radically different\, with cells walking past each other. Our modeling shows that this likely arises from the addit ional degrees of freedom that cells have to rotate around the fiber\, and can be abolished by forcing cells to attach to two fibers. I will also dis cuss more recent modeling on how cell-cell collisions can be moderated by the geometry of the cell-substrate contact angle.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Denise Montell (U California Santa Barbara) DTSTART:20210929T190000Z DTEND:20210929T195000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/16 DESCRIPTION:Title: Orthogonal physical and chemical cues steer migrating Drosophi la border cells\nby Denise Montell (U California Santa Barbara) as par t of CMO - Modeling and Computational Approaches to Individual and Collect ive Cell Movement in Complex En\n\n\nAbstract\nBorder cell migration in th e Drosophila ovary is a relatively simple model for the study of collectiv e\, cooperative\, cell-on cell migration in vivo that is amenable to live imaging\, genetic and optogenetic approaches. Decades of work have reveale d the secreted signals that govern which 6 of the 850 epithelial cells acq uire the ability to migrate\, when during development they do so\, and whe re they go. In addition to biochemical signals\, moving cells also sense a nd respond to physical features of the microenvironment\; however\, the si gnificance of tissue topography was unknown. We used Drosophila border cel ls to study how chemical and physical information influences path selectio n. Although chemical cues were thought to be sufficient\, live imaging\, g enetics\, modeling\, and simulations show that microtopography is also imp ortant. Chemoattractants promote predominantly posterior movement\, wherea s tissue architecture presents orthogonal information\, a path of least re sistance concentrated near the center of the egg chamber. E-cadherin suppl ies a permissive haptotactic cue. Our results provide insight into how cel ls integrate and prioritize topographical\, adhesive\, and chemoattractant cues to choose one path among many. New findings on the role of septin pr oteins in border cell morphology and migration will also be presented.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Gibin Powathil (Swansea University) DTSTART:20210929T200000Z DTEND:20210929T205000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/17 DESCRIPTION:Title: Multiscale Modelling of Cancer Progression and Treatment Respo nses\nby Gibin Powathil (Swansea University) as part of CMO - Modeling and Computational Approaches to Individual and Collective Cell Movement i n Complex En\n\n\nAbstract\nBorder cell migration in the Drosophila ovary is a relatively simple model for the study of collective\, cooperative\, c ell-on cell migration in vivo that is amenable to live imaging\, genetic a nd optogenetic approaches. Decades of work have revealed the secreted sign als that govern which 6 of the 850 epithelial cells acquire the ability to migrate\, when during development they do so\, and where they go. In addi tion to biochemical signals\, moving cells also sense and respond to physi cal features of the microenvironment\; however\, the significance of tissu e topography was unknown. We used Drosophila border cells to study how che mical and physical information influences path selection. Although chemica l cues were thought to be sufficient\, live imaging\, genetics\, modeling\ , and simulations show that microtopography is also important. Chemoattrac tants promote predominantly posterior movement\, whereas tissue architectu re presents orthogonal information\, a path of least resistance concentrat ed near the center of the egg chamber. E-cadherin supplies a permissive ha ptotactic cue. Our results provide insight into how cells integrate and pr ioritize topographical\, adhesive\, and chemoattractant cues to choose one path among many. New findings on the role of septin proteins in border ce ll morphology and migration will also be presented.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Hillen (University of Alberta) DTSTART:20210929T210000Z DTEND:20210929T223000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/18 DESCRIPTION:Title: Free discussion in gathertown\nby Thomas Hillen (Universit y of Alberta) as part of CMO - Modeling and Computational Approaches to In dividual and Collective Cell Movement in Complex En\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Mark Chaplain (University of St. Andrews) DTSTART:20210930T150000Z DTEND:20210930T155000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/19 DESCRIPTION:Title: (Chaplain + Gerisch\, Part I) Mechanical models of pattern for mation in biological tissues: the role of the stress-strain constitutive m odel\nby Mark Chaplain (University of St. Andrews) as part of CMO - Mo deling and Computational Approaches to Individual and Collective Cell Move ment in Complex En\n\n\nAbstract\nMechanical and mechanochemical models of pattern formation in biological tissues\nhave been used to study a variet y of biomedical systems\, particularly in\ndevelopmental biology\, and des cribe the physical interactions between cells and\ntheir local surrounding s. These models in their original form consist of a\nbalance equation for the cell density\, a balance equation for the density of the\nextracellula r matrix (ECM)\, and a force-balance equation describing the\nmechanical e quilibrium of the cell-ECM system.\n\nIn these models\, the stress-strain relation of the ECM is often described using\nthe Kelvin-Voigt model of li near viscoelasticity. However\, due to the\nmultifaceted bio-physical natu re of the ECM constituents\, there are rheological\naspects that cannot be effectively captured by this model and\, therefore\,\ndepending on the pa ttern formation process and the type of biological tissue\nconsidered\, ot her constitutive models of linear viscoelasticity may be better\nSuited. ( Co-authors: Chiara Villa and Tommaso Lorenzi.)\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Alf Gerisch (Technical University Darmstadt) DTSTART:20210930T160000Z DTEND:20210930T165000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/20 DESCRIPTION:Title: (Chaplain + Gerisch\, Part II) Mechanical models of pattern fo rmation in biological tissues: the role of the stress-strain constitutive model\nby Alf Gerisch (Technical University Darmstadt) as part of CMO - Modeling and Computational Approaches to Individual and Collective Cell Movement in Complex En\n\n\nAbstract\nMechanical and mechanochemical model s of pattern formation in biological tissues\nhave been used to study a va riety of biomedical systems\, particularly in\ndevelopmental biology\, and describe the physical interactions between cells and\ntheir local surroun dings. These models in their original form consist of a\nbalance equation for the cell density\, a balance equation for the density of the\nextracel lular matrix (ECM)\, and a force-balance equation describing the\nmechanic al equilibrium of the cell-ECM system.\n\nIn these models\, the stress-str ain relation of the ECM is often described using\nthe Kelvin-Voigt model o f linear viscoelasticity. However\, due to the\nmultifaceted bio-physical nature of the ECM constituents\, there are rheological\naspects that canno t be effectively captured by this model and\, therefore\,\ndepending on th e pattern formation process and the type of biological tissue\nconsidered\ , other constitutive models of linear viscoelasticity may be better\nsuite d. Co-authors: Chiara Villa and Tommaso Lorenzi.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/20/ END:VEVENT BEGIN:VEVENT SUMMARY:Sean Sun (John Hopkins) DTSTART:20210930T170000Z DTEND:20210930T175000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/21 DESCRIPTION:Title: On the role of hydraulic resistance during cell migration\ nby Sean Sun (John Hopkins) as part of CMO - Modeling and Computational Ap proaches to Individual and Collective Cell Movement in Complex En\n\n\nAbs tract\nCells migrating in vivo can encounter microenvironments with varyin g physical properties. One such physical variable is the viscosity of the fluid surrounding the cell. Increased fluid viscosity is expected to incre ase the hydraulic resistance experienced by the migrating cell and therefo re decrease the cell speed. We demonstrate that contrary to this expected result\, cells migrate faster in high viscosity media on 2D substrates. To reveal the molecular mechanism\, we examined both actin dynamics and wate r dynamics driven by ion channel activity. Results show that cells increas ed in area in high viscosity and actomyosin dynamics remained similar\, ex cept that actin retrograde flow speed is reduced. Inhibiting ion channel f luxes in high viscosity media results in a large reduction in cell speed\, suggesting that water flux contributes to the observed speed increase. Mo reover\, inhibiting actin-dependent vesicular trafficking that transports ion channels from the ER to the cell boundary changes ion channel spatial positioning and reduces cell speed in high viscosity media. Cells also dis played altered Ca2+-activity in high viscosity media\, and when cytoplasmi c Ca2+ is sequestered\, cell speed reduction and altered ion channel posit ioning were observed. Taken together\, we find that the cell cytoplasmic a ctin-phase and water-phase are coupled during cell migration in high visco sity media. Directional water fluxes are mediated by ion channels whose po sition depend on actin-based vesicular trafficking. These results\, togeth er with observed cell migration behavior in micro channels\, suggest that hydraulic resistance and local hydraulic pressure are important mechanical variables governing cell polarization and influence cell migration speed. A physical 2-phase model of cell migration incorporating actin and water dynamics is presented to explain the experimental results.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/21/ END:VEVENT BEGIN:VEVENT SUMMARY:Tracy Stepien (University of Florida) DTSTART:20210930T190000Z DTEND:20210930T195000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/22 DESCRIPTION:Title: Collective cell migration in tissues with multiple cell types< /a>\nby Tracy Stepien (University of Florida) as part of CMO - Modeling an d Computational Approaches to Individual and Collective Cell Movement in C omplex En\n\n\nAbstract\nCollective cell migration plays an important role in many processes including in the cohesion of epithelial cell monolayers \, in wound healing\, and in embryonic development. In tissues with multip le cell types\, such as differentiating stem cells that spread in a single layer or epithelial and mesenchymal cells that spread in stratified layer s\, continuum mechanical models may be used to understand the mechanisms i nvolved. We develop PDE models to examine the spread and maturation of ast rocytes in retinal development and the spread of multi-layer embryonic tis sue explants in gastrulation\, and we compare numerical simulations to exp erimental data to decipher the spatiotemporal distribution of cell types.\ n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/22/ END:VEVENT BEGIN:VEVENT SUMMARY:Meghan Rhodes (University of Alberta) DTSTART:20210930T200000Z DTEND:20210930T205000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/23 DESCRIPTION:Title: Comparing the effects of linear and one-term Ogden elasticity in a model of glioblastoma invasion\nby Meghan Rhodes (University of A lberta) as part of CMO - Modeling and Computational Approaches to Individu al and Collective Cell Movement in Complex En\n\n\nAbstract\nWe present a model of glioblastoma (GBM) invasion which includes mass effects and tissu e mechanics. Furthermore\, we show how different brain tissue elasticity m odels affect the dynamics and invasion wave speed. Inspired by Budday et a l. (2017) who mechanically tested brain tissue to determine an appropriate constitutive model of brain tissue mechanics\, we explore two models: The linear elasticity model\, and the one-term Ogden model. In a simplified 1 D version of the model\, we show the existence of travelling wave solution s. The traveling waves can be viewed as the invasion of GBM tumor cells in to the surrounding healthy brain tissue. Thus\, identifying the speed of t he wave and how it is affected by model components and parameters is usefu l in determining what drives invasion. We show that although the wave spee d is independent of the chosen mechanical model\, the dynamics of GBM spre ad and the effects on surrounding brain tissue differ significantly betwee n the linear and one-term Ogden elasticity models. (joint with T. Hillen)\ n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/23/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Hillen (University of Alberta) DTSTART:20210930T210000Z DTEND:20210930T223000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/24 DESCRIPTION:Title: Free discussion in gathertown\nby Thomas Hillen (Universit y of Alberta) as part of CMO - Modeling and Computational Approaches to In dividual and Collective Cell Movement in Complex En\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/24/ END:VEVENT BEGIN:VEVENT SUMMARY:Dietmar Oelz (University of Queensland) DTSTART:20211001T150000Z DTEND:20211001T155000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/25 DESCRIPTION:Title: Protein Friction and F-Actin Bending Promote Contraction of Di sordered Actomyosin Networks\nby Dietmar Oelz (University of Queenslan d) as part of CMO - Modeling and Computational Approaches to Individual an d Collective Cell Movement in Complex En\n\n\nAbstract\nThe origins of dis ordered actomyosin network contraction such as in the cellular cortex rema in an active topic of research.\nWe derive a mathematical model for the ev olution of two-dimensional networks. A major advantage of our approach is that it\nenables direct calculation of the network stress tensor\, which p rovides a quantitative measure of contractility. Exploiting this\, we\nuse repeated simulations of disordered networks to confirm that both protein friction and actin filament bending are required\nfor contraction. We also show that actin filament turnover is necessary to sustain contraction and prevent pattern formation.\nWe then consider a toy-model version of the m odel for only two filaments immersed in an actomyosin network.\nUsing asym ptotic analysis numerical simulation of the resulting PDE and numerical so lutions\, we find that bending facilitates contraction by inducing a geome tric asymmetry that enables motors to move faster close to filament plus-e nds\, inhibiting expansion.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/25/ END:VEVENT BEGIN:VEVENT SUMMARY:Satoshi Sawai (University of Tokyo) DTSTART:20211001T160000Z DTEND:20211001T165000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/26 DESCRIPTION:Title: Macropinocytic cup formation and topographical cell guidance\nby Satoshi Sawai (University of Tokyo) as part of CMO - Modeling and C omputational Approaches to Individual and Collective Cell Movement in Comp lex En\n\n\nAbstract\nIn fast moving cells such as amoeba and immune cells \, dendritic actin filaments are spatio-temporally regulated to shape larg e-scale plasma membrane protrusions. Through quantitative image analysis of Dictyostelium on micro-fabricated surfaces\, we show that there is a di stinct mode of topographical guidance directed by the macropinocytic membr ane cup. Unlike other topographic guidance known to date that depends on nanometer-scale curvature sensing protein or stress fibers\, the macropino cytic membrane cup is driven by the Ras/PI3K/F-actin signaling patch and i ts dependency on the micrometer-scale topographic features\; namely PI3K/F -actin-independent accumulation of Ras-GTP at the convex curved surface\, PI3K-dependent patch propagation along the convex edge and its actomyosin- dependent constriction at the concave edge. We will introduce a basic mat hematical model of macropinocytic cup formation and closure and apply it t o study this newly discovered mode of directed cell migration. Our simula tions demonstrate that the topographically-dependent initiation in combina tion with the mutually-defining patch patterning and the membrane deformat ion gives rise to the topographical guidance. The results suggest that ma cropinocytic cup serves as a global surveyor of substrate topology. It is a self-enclosing structure that can support liquid ingestion by default\, however in the presence of structured surfaces\, it is directed to faithfu lly trace bent and bifurcating ridges for particle ingestion and cell guid ance.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/26/ END:VEVENT BEGIN:VEVENT SUMMARY:Kevin Painter (Politecnico di Torino) DTSTART:20211001T170000Z DTEND:20211001T175000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/27 DESCRIPTION:Title: Models for the collective navigation: from cells to whales \nby Kevin Painter (Politecnico di Torino) as part of CMO - Modeling and C omputational Approaches to Individual and Collective Cell Movement in Comp lex En\n\n\nAbstract\nIn collective navigation\, a population travels as a group from an origin to a destination. Famous examples include the migrat ions of birds\, between their winter and summer grounds\, but collective m ovements also extend down to microorganisms and cell populations. Collecti ve navigation is believed to improve the efficiency of migration\, for exa mple through the presence of more knowledgeable individuals that guide nai ve members ("leader-follower behaviour") or through the averaging out of i ndividual undertainty ("many wrongs"). In this talk I will describe indivi dual and continuous approaches for modelling collective navigation. The in dividual based model is predicated on a random walk model\, where individu als supplement their own inherent guidance information with information ac quired from other group members. The continuous model is based on a nonlo cal hyperbolic PDE system. We investigate the point at which group informa tion becomes beneficial to migration and how it can help a population navi gate through "information voids"\, i.e. areas with negligible guidance inf ormation. We also explore the effectiveness of different modes through whi ch a leader can herd a group of naïve followers.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/27/ END:VEVENT BEGIN:VEVENT SUMMARY:Andreas Buttenschoen (University of British Columbia) DTSTART:20211001T190000Z DTEND:20211001T195000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/28 DESCRIPTION:Title: Spatio-temporal heterogeneities in a mechano-chemical model of collective cell migration\nby Andreas Buttenschoen (University of Bri tish Columbia) as part of CMO - Modeling and Computational Approaches to I ndividual and Collective Cell Movement in Complex En\n\n\nAbstract\nSmall GTPases\, such as Rac and Rho\, are well known central regulators of cell morphology and motility\, whose dynamics also play a role in coordinating collective cell migration. Experiments have shown GTPase dynamics to be af fected by both chemical and mechanical cues\, but also to be spatially and temporally heterogeneous. This heterogeneity is found both within a singl e cell\, and between cells in a tissue. For example\, sometimes the leader and follower cells display an inverted GTPase configuration. While progre ss on understanding GTPase dynamics in single cells has been made\, a majo r remaining challenge is to understand the role of GTPase heterogeneity in collective cell migration.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/28/ END:VEVENT BEGIN:VEVENT SUMMARY:Stefanie Sonner (Radboud University\, Nijmegen) DTSTART:20211001T200000Z DTEND:20211001T205000Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/29 DESCRIPTION:Title: A coupled ODE-PDE system modelling the growth of cellulolytic biofilms\nby Stefanie Sonner (Radboud University\, Nijmegen) as part o f CMO - Modeling and Computational Approaches to Individual and Collective Cell Movement in Complex En\n\n\nAbstract\nWe discuss a mathematical mode l for the growth of cellulolytic biofilms. Cellulolytic biofilms play an i mportant role in the production of cellulosic ethanol\, a biofuel with lar ge economic potential. Different from traditional models where the biofilm grows into the aqueous phase and nutrients are transported by diffusion\, bacteria colonize\, consume and degrade a cellulosic substratum that supp orts them. Hence\, the nutrients are immobilized and modelled by an ODE. T he ODE is coupled to a two-fold degenerate reaction diffusion equation for the biomass density that exhibits a polynomial degeneracy (as known from the porous medium equation) and a singularity as the biomass density appro aches its maximum value (fast diffusion effect).\nWe show the well-posedne ss of the model and prove the existence of travelling wave solutions. Inva ding fronts had been observed in biological experiments as well as in nume rical simulations of the model.\nThis is joint work with Hermann Eberl\, J ack Hughes and Koondanibha Mitra.\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/29/ END:VEVENT BEGIN:VEVENT SUMMARY:Hans Othmer (University of Minnesota) DTSTART:20211001T210000Z DTEND:20211001T211500Z DTSTAMP:20260404T060946Z UID:CMO-21w5225/30 DESCRIPTION:Title: (Othmer\, Hillen) Closing\nby Hans Othmer (University of M innesota) as part of CMO - Modeling and Computational Approaches to Indivi dual and Collective Cell Movement in Complex En\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/CMO-21w5225/30/ END:VEVENT END:VCALENDAR