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:20260422T185218Z UID:CMO-21w5225/1 DESCRIPTION:Title: (Maini + Kulesa\, Part I) Modelling collective cell migration in devel opmental biology\nby Philip Maini (University of Oxford) as part of CM O - Modeling and Computational Approaches to Individual and Collective Cel l Movement in Complex En\n\n\nAbstract\nOver the past decade\, in an inter disciplinary collaboration between Philip Maini and colleagues in the Wolf son Centre for Mathematical Biology and the Kulesa lab at The Stowers Inst itute for Medical Research\, we have developed a suite of cell-based model s in parallel with experiments to investigate the underlying dynamics of c ollective cell migration. We focus on the highly invasive neural crest cel ls that in the vertebrate embryo migrate in discrete streams along stereot ypical pathways. In this talk\, we will review this work and show how it h as led to new insights into the underlying biology. Specifically\, it will be shown how modelling\, combined with experiments\, led us to the identi fication of different cell phenotypes and phenotypic switching\, as well a s generating hypotheses on how cells may be assembling and deforming the e xtracellular matrix through which they migrate\, and how they may be signa lling to each other.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Paul Kulesa (Stowers Institute for Medical Research) DTSTART:20210927T163000Z DTEND:20210927T172000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/2 DESCRIPTION:Title: (Maini + Kulesa\, Part II) Modelling collective cell migration in deve lopmental biology\nby Paul Kulesa (Stowers Institute for Medical Resea rch) as part of CMO - Modeling and Computational Approaches to Individual and Collective Cell Movement in Complex En\n\n\nAbstract\nOver the past de cade\, in an interdisciplinary collaboration between Philip Maini and coll eagues in the Wolfson Centre for Mathematical Biology and the Kulesa lab a t The Stowers Institute for Medical Research\, we have developed a suite o f cell-based models in parallel with experiments to investigate the underl ying dynamics of collective cell migration. We focus on the highly invasiv e neural crest cells that in the vertebrate embryo migrate in discrete str eams along stereotypical pathways. In this talk\, we will review this work and show how it has led to new insights into the underlying biology. Spec ifically\, it will be shown how modelling\, combined with experiments\, le d us to the identification of different cell phenotypes and phenotypic swi tching\, as well as generating hypotheses on how cells may be assembling a nd deforming the extracellular matrix through which they migrate\, and how they may be signalling to each other.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Alex Mogilner (New York University) DTSTART:20210927T173000Z DTEND:20210927T182000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/3 DESCRIPTION:Title: Collective migration of one pair of cells in Ciona embryo\nby Alex Mogilner (New York University) as part of CMO - Modeling and Computationa l Approaches to Individual and Collective Cell Movement in Complex En\n\n\ nAbstract\nDuring embryonic development\, cells often migrate collectively . The cardiogenic progenitors of \nthe ascidian Ciona provide one of the s implest examples of collective migration: two \ncells migrate with defined leader-trailer polarity\, squeezed between stiff epidermis and\ndeformabl e 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://researchseminars.org/talk/CMO-21w5225/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Qixuan Wang (UC Riverside) DTSTART:20210927T193000Z DTEND:20210927T202000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/4 DESCRIPTION:Title: Roles of cellular anisotropy and heterogeneity in cell movement\nb y Qixuan Wang (UC Riverside) as part of CMO - Modeling and Computational A pproaches to Individual and Collective Cell Movement in Complex En\n\n\nAb stract\nCells can be structurally anisotropic\, and they can be heterogene ous\ndue to either genetic or environment clues. Cellular anisotropy and\n heterogeneity might lead to interesting behaviors in individual or collect ive\ncell movement. In this talk we will discuss the roles of cellular ani sotropy and\nheterogeneity in two systems. In the first part\, we will dis cuss how anisotropic\nflagella bending rigidity affects the flagellar beat ing dynamics. Flagellar\nbeating is controlled by molecular motors that ex ert forces along the length of\nthe flagellum and are regulated by a feedb ack mechanism coupled to the flagellar\nmotion. We build on previous work on sliding-controlled motor feedback to\ndevelop a fully three-dimensional description of flagellar beating\, accounting\nfor both bending and twist . We show that with isotropic bending\,\nthree-dimensional spiral modes ar e spontaneously generated beyond a critical\nmolecular activity. On the ot her hand\, when a difference is introduced into the\nbending rigidity alon g orthogonal directions\, a preferential bending plane is\nestablished\, a nd we find that the generic three-dimensional spiral modes give\nway to pl anar beating along the soft axis as the difference in bending rigidity\nin creases. In the second part\, we will discuss how hair follicle heterogene ous\nresponses to signals affect the cell flows which then regulate the fo llicle\ntemporal growth dynamics. Hair follicles are mini skin organs rich of stem\ncells\, and they undergo cyclic growth. The growing phase – an agen of a hair\nfollicle is tightly controlled by a group of epithelial tr ansient amplifying\n(TA) cells. Using an interdisciplinary approach combin ed of multi-scale modeling\nand lineage tracing experiments\, we show that cellular heterogeneity based on\ncell division generations drive the upwa rd cell flows\, which guarantees the\nrefill of the follicle TA cells that prolongs the anagen.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/4/ END:VEVENT BEGIN:VEVENT SUMMARY:John Dallon (Brigham Young University) DTSTART:20210927T203000Z DTEND:20210927T212000Z DTSTAMP:20260422T185218Z 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 Computational Ap proaches to Individual and Collective Cell Movement in Complex En\n\n\nAbs tract\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 sh ape and focuses on cell adhesions. In the second model random switching t erms are used to model the attachment and detachment of adhesions. In the first model formation the focus is on force and force transmission. In t he second model the focus shifts to the dynamics of the adhesions and how they affect the cell speed.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Hillen (University of Alberta) DTSTART:20210927T213000Z DTEND:20210927T230000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/6 DESCRIPTION:Title: Free discussion in gathertown\nby Thomas Hillen (University of Alb erta) as part of CMO - Modeling and Computational Approaches to Individual and Collective Cell Movement in Complex En\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Luigi Preziosi (Politecnico di Torino) DTSTART:20210928T150000Z DTEND:20210928T155000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/7 DESCRIPTION:Title: (Preziosi + Loy\, Part I) Modelling cell re-orientation under stretch< /a>\nby Luigi Preziosi (Politecnico di Torino) as part of CMO - Modeling a nd Computational Approaches to Individual and Collective Cell Movement in Complex En\n\n\nAbstract\nThe active response of cells to mechanical cues due to their interaction with the environment has been of increasing inter est\, since it is involved in many physiological phenomena\, pathologies\, and in tissue engineering. In particular\, several experiments have shown that\, if a substrate with overlying cells is cyclically stretched\, they will reorient with their main axis either perpendicular or at an oblique 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 mechani cs. First a nonlinear elastic energy for a quite general orthotropic mater ial is used and a complete bifurcation analysis is performed to explain th e dependence of the reorientation angle on the applied strain. Then\, a li near viscoelastic model is proposed to describe the dependence on the appl ied frequency.\nIn the second part of the seminar\, held by Nadia Loy\, st ochastic effects are considered. In fact\, in many cases results are given in terms of the percentage of cells having an orientation in certain inte rvals. With the aim of describing both the evolution and the stationary st ate of the probability density function over cell orientations\, Fokker-Pl anck equations are deduced starting from microscopic rules. connected with the continuum mechanics models previously introduced. In addition\, we in troduce a way of describing the microscopic re-orientation rule as a resul t of an optimal control internally activated by the cell.\nThe results of both models compare very well with experimental results.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Nadia Loy (Politecnico di Torino) DTSTART:20210928T160000Z DTEND:20210928T165000Z DTSTAMP:20260422T185218Z 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 - Modeling and C omputational Approaches to Individual and Collective Cell Movement in Comp lex En\n\n\nAbstract\nThe active response of cells to mechanical cues due to their interaction with the environment has been of increasing interest\ , since it is involved in many physiological phenomena\, pathologies\, and in tissue engineering. In particular\, several experiments have shown tha t\, if a substrate with overlying cells is cyclically stretched\, they wil l reorient with their main axis either perpendicular or at an oblique angl e with respect to the main stretching direction.\nIn the first part of the seminar\, held by Luigi Preziosi\, the phenomenon is studied from the det erministic point of view working in the framework of continuum mechanics. First a nonlinear elastic energy for a quite general orthotropic material is used and a complete bifurcation analysis is performed to explain the de pendence of the reorientation angle on the applied strain. Then\, a linear viscoelastic model is proposed to describe the dependence on the applied frequency.\nIn the second part of the seminar\, held by Nadia Loy\, stocha stic effects are considered. In fact\, in many cases results are given in terms of the percentage of cells having an orientation in certain interval s. 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 with the continuum mechanics models previously introduced. In addition\, we introd uce a way of describing the microscopic re-orientation rule as a result of an optimal control internally activated by the cell.\nThe results of both models compare very well with experimental results.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Guillaume Charras (London Centre for Nanotechnology) DTSTART:20210928T170000Z DTEND:20210928T175000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/9 DESCRIPTION:Title: Dissecting the link between signalling and cell mechanics\nby Guil laume Charras (London Centre for Nanotechnology) as part of CMO - Modeling and Computational Approaches to Individual and Collective Cell Movement i n Complex En\n\n\nAbstract\nThe submembranous actin cortex is the main det erminant of cell shape. During mitosis and migration\, spatiotemporal chan ges in cortex mechanics give rise to shape changes. These result from tig htly orchestrated global and local changes in RhoGTPase activity regulated by recruitment of RhoGEFs and RhoGAPs to the cortex. Yet\, little is know n about how signalling controls cell mechanics to drive shape change.\nI w ill present work investigating how signalling controls cell mechanics. We use optogenetics to control the activity of RhoGTPases by relocalising a R hoGEF to the cortex and investigate the resulting temporal changes in surf ace tension using AFM. I will discuss how to coarse-grain signalling downs tream of RhoGTPases to link signalling to mechanics and shape change.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Jay Stotsky (University of Minnesota) DTSTART:20210928T190000Z DTEND:20210928T195000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/10 DESCRIPTION:Title: The Influence of the Cell Cortex on Cell Shape and Motion\nby Ja y Stotsky (University of Minnesota) as part of CMO - Modeling and Computat ional Approaches to Individual and Collective Cell Movement in Complex En\ n\n\nAbstract\nBeneath the membrane of many cells lies the cell cortex\, a composite layer of actin\, myosin\, and various cross-linking proteins. T he cell cortex is believed to have a strong influence on the ability 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 processes . Cells can employ various strategies to move\, such as crawling or swimmi ng\, and here I will discuss recent modeling and computational results on how the forces\, applied externally or generated internally by the cellula r cortex\, in conjunction with the mechanical properties of the cell can l ead to various shape changes and cell motion.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Gisell Estrada-Rodriguez (Sorbonne Universite) DTSTART:20210928T200000Z DTEND:20210928T205000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/11 DESCRIPTION:Title: Macroscopic description of nonlocal movement of biological systems in Rn and in networks\nby Gisell Estrada-Rodriguez (Sorbonne Universite) as part of CMO - Modeling and Computational Approaches to Individual and Collective Cell Movement in Complex En\n\n\nAbstract\nIn the presence of s parse attractants\, the movement of both cells and large organisms has bee n shown to be governed by long distance runs\, according to an approximate Levy distribution. In this talk we clarify the form of biologically relev ant PDE descriptions for such movements. Motivated by experiments we consi der a microscopic velocity-jump model in which the motion of the individua ls is characterized by long runs and long waiting times\, according to a h eavy-tailed distribution.\n\nFurthermore\, this nonlocal movement of indiv iduals has been observed in more complex geometries\, e.g.\, the brain. We propose to study the (nonlocal) diffusion using a network of subdomains\ , corresponding to the nodes of a graph. I will introduce metaplex network s which are networks with internal structure\, and we will extend our anal ysis to two real world examples: a brain and a landscape network.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Hillen (University of Alberta) DTSTART:20210928T210000Z DTEND:20210928T223000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/12 DESCRIPTION:Title: Free discussion in gathertown\nby Thomas Hillen (University of Al berta) as part of CMO - Modeling and Computational Approaches to Individua l and Collective Cell Movement in Complex En\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Helen Byrne (U California Santa Barbara) DTSTART:20210929T150000Z DTEND:20210929T155000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/13 DESCRIPTION:Title: (Byrne + Alarcon\, Part I) A multiscale model of complex endothelial cell dynamics in early angiogenesis\nby Helen Byrne (U California Sant a Barbara) as part of CMO - Modeling and Computational Approaches to Indiv idual and Collective Cell Movement in Complex En\n\n\nAbstract\nWe introdu ce a hybrid two-dimensional multiscale model of angiogenesis\, 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 c reate a new vascular network. Recent experimental studies have highlighted the central role of cell rearrangements in the formation of angiogenic ne tworks. Our model accounts for this phenomenon via the heterogeneous respo nse of ECs to their microenvironment. These cell rearrangements\, in turn\ , dynamically remodel the local environment. The model reproduces characte ristic features of angiogenic sprouting that include branching\, chemotact ic sensitivity\, the brush border effect\, and cell mixing. These properti es\, rather than being hardwired into the model\, emerge naturally from th e gene expression patterns of individual cells. After calibrating and vali dating our model against experimental data\, we use 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 extrac ellular environment\, vary. In order to investigate the impact of cell rea rrangements on the vascular network structure\, we introduce the mixing me asure\, a scalar metric that quantifies cell mixing as the vascular networ k grows. We calculate the mixing measure for the simulated vascular networ ks generated by ECs of different lineages (wild-type cells and mutant cell s with impaired expression of a specific receptor). Our results show that the time evolution of the mixing measure is directly correlated to the gen eric features of the vascular branching pattern\, thus\, supporting the hy pothesis that cell rearrangements play an essential role in sprouting angi ogenesis. Furthermore\, we predict that lower cell rearrangement leads to an imbalance between branching and sprout elongation. Since the computatio n of this statistic requires only individual cell trajectories\, it can be computed for networks generated in biological experiments\, making it a p otential biomarker for pathological angiogenesis.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Tomás Alarcón (ICREA - Centre de Recerca de Matematica) DTSTART:20210929T160000Z DTEND:20210929T165000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/14 DESCRIPTION:Title: (Byrne + Alarcon\, Part II) A multiscale model of complex endothelial cell dynamics in early angiogenesis\nby Tomás Alarcón (ICREA - Cent re de Recerca de Matematica) as part of CMO - Modeling and Computational A pproaches to Individual and Collective Cell Movement in Complex En\n\n\nAb stract\nWe introduce a hybrid two-dimensional multiscale model of angiogen esis\, the process by which endothelial cells (ECs) migrate from a pre-exi sting vascular bed in response to local environmental cues and cell-cell i nteractions\, to create a new vascular network. Recent experimental studie s have highlighted the central role of cell rearrangements in the formatio n of angiogenic networks. Our model accounts for this phenomenon via the h eterogeneous response of ECs to their microenvironment. These cell rearran gements\, in turn\, dynamically remodel the local environment. The model r eproduces characteristic features of angiogenic sprouting that include bra nching\, chemotactic sensitivity\, the brush border effect\, and cell mixi ng. These properties\, rather than being hardwired into the model\, emerge naturally from the gene expression patterns of individual cells. After ca librating and validating our model against experimental data\, we use it t o predict how the structure of the vascular network changes as the baselin e gene expression levels of the VEGF-Delta-Notch pathway\, and the composi tion of the extracellular environment\, vary. In order to investigate the impact of cell rearrangements on the vascular network structure\, we intro duce the mixing measure\, a scalar metric that quantifies cell mixing as t he vascular network grows. We calculate the mixing measure for the simulat ed vascular networks generated by ECs of different lineages (wild-type cel ls and mutant cells with impaired expression of a specific receptor). Our results show that the time evolution of the mixing measure is directly cor related to the generic features of the vascular branching pattern\, thus\, supporting the hypothesis that cell rearrangements play an essential role in sprouting angiogenesis. Furthermore\, we predict that lower cell rearr angement leads to an imbalance between branching and sprout elongation. Si nce the computation of this statistic requires only individual cell trajec tories\, it can be computed for networks generated in biological experimen ts\, making it a potential biomarker for pathological angiogenesis.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Brian Camley (Johns Hopkins University) DTSTART:20210929T170000Z DTEND:20210929T175000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/15 DESCRIPTION:Title: Contact inhibition of locomotion and geometry\nby Brian Camley (J ohns Hopkins University) as part of CMO - Modeling and Computational Appro aches to Individual and Collective Cell Movement in Complex En\n\n\nAbstra ct\nFor cells to cooperate in healing a wound or work together to follow a signal\, they must coordinate their motion. One stereotyped behavior foun d in many cell types is "contact inhibition of locomotion" (CIL)\, in whic h cells that collide with one another repolarize away from contact. Experi ments studying CIL are often performed on flat rigid two-dimensional subst rates\, unlike the natural fibrous environment of many cells in vivo. How does extracellular matrix geometry and adhesivity affect CIL? First\, I wi ll talk about recent experiments by our collaborators in the Nain group\, which show that when cells are attached to single suspended nanofibers\, t he outcomes of CIL can be radically different\, with cells walking past ea ch other. Our modeling shows that this likely arises from the additional d egrees 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 discuss mo re recent modeling on how cell-cell collisions can be moderated by the geo metry of the cell-substrate contact angle.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Denise Montell (U California Santa Barbara) DTSTART:20210929T190000Z DTEND:20210929T195000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/16 DESCRIPTION:Title: Orthogonal physical and chemical cues steer migrating Drosophila bord er cells\nby Denise Montell (U California Santa Barbara) as part of CM O - Modeling and Computational Approaches to Individual and Collective Cel l Movement in Complex En\n\n\nAbstract\nBorder cell migration in the Droso phila ovary is a relatively simple model for the study of collective\, coo perative\, cell-on cell migration in vivo that is amenable to live imaging \, genetic and optogenetic approaches. Decades of work have revealed the s ecreted signals that govern which 6 of the 850 epithelial cells acquire th e ability to migrate\, when during development they do so\, and where they go. In addition to biochemical signals\, moving cells also sense and resp ond to physical features of the microenvironment\; however\, the significa nce of tissue topography was unknown. We used Drosophila border cells to s tudy how chemical and physical information influences path selection. Alth ough chemical cues were thought to be sufficient\, live imaging\, genetics \, modeling\, and simulations show that microtopography is also important. Chemoattractants promote predominantly posterior movement\, whereas tissu e architecture presents orthogonal information\, a path of least resistanc e concentrated near the center of the egg chamber. E-cadherin supplies a p ermissive haptotactic cue. Our results provide insight into how cells inte grate and prioritize topographical\, adhesive\, and chemoattractant cues t o choose one path among many. New findings on the role of septin proteins in border cell morphology and migration will also be presented.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Gibin Powathil (Swansea University) DTSTART:20210929T200000Z DTEND:20210929T205000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/17 DESCRIPTION:Title: Multiscale Modelling of Cancer Progression and Treatment Responses\nby Gibin Powathil (Swansea University) as part of CMO - Modeling and Co mputational Approaches to Individual and Collective Cell Movement in Compl ex En\n\n\nAbstract\nBorder cell migration in the Drosophila ovary is a re latively simple model for the study of collective\, cooperative\, cell-on cell migration in vivo that is amenable to live imaging\, genetic and opto genetic approaches. Decades of work have revealed the secreted signals tha t govern which 6 of the 850 epithelial cells acquire the ability to migrat e\, when during development they do so\, and where they go. In addition to biochemical signals\, moving cells also sense and respond to physical fea tures of the microenvironment\; however\, the significance of tissue topog raphy was unknown. We used Drosophila border cells to study how chemical a nd physical information influences path selection. Although chemical cues were thought to be sufficient\, live imaging\, genetics\, modeling\, and s imulations show that microtopography is also important. Chemoattractants p romote predominantly posterior movement\, whereas tissue architecture pres ents orthogonal information\, a path of least resistance concentrated near the center of the egg chamber. E-cadherin supplies a permissive haptotact ic cue. Our results provide insight into how cells integrate and prioritiz e topographical\, adhesive\, and chemoattractant cues to choose one path a mong many. New findings on the role of septin proteins in border cell morp hology and migration will also be presented.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Hillen (University of Alberta) DTSTART:20210929T210000Z DTEND:20210929T223000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/18 DESCRIPTION:Title: Free discussion in gathertown\nby Thomas Hillen (University of Al berta) as part of CMO - Modeling and Computational Approaches to Individua l and Collective Cell Movement in Complex En\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Mark Chaplain (University of St. Andrews) DTSTART:20210930T150000Z DTEND:20210930T155000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/19 DESCRIPTION:Title: (Chaplain + Gerisch\, Part I) Mechanical models of pattern formation in biological tissues: the role of the stress-strain constitutive model\nby Mark Chaplain (University of St. Andrews) as part of CMO - Modeling and Computational Approaches to Individual and Collective Cell Movement in Complex En\n\n\nAbstract\nMechanical and mechanochemical models of patter n formation in biological tissues\nhave been used to study a variety of bi omedical systems\, particularly in\ndevelopmental biology\, and describe t he physical interactions between cells and\ntheir local surroundings. Thes e models in their original form consist of a\nbalance equation for the cel l density\, a balance equation for the density of the\nextracellular matri x (ECM)\, and a force-balance equation describing the\nmechanical equilibr ium of the cell-ECM system.\n\nIn these models\, the stress-strain relatio n of the ECM is often described using\nthe Kelvin-Voigt model of linear vi scoelasticity. However\, due to the\nmultifaceted bio-physical nature of t he ECM constituents\, there are rheological\naspects that cannot be effect ively captured by this model and\, therefore\,\ndepending on the pattern f ormation process and the type of biological tissue\nconsidered\, other con stitutive models of linear viscoelasticity may be better\nSuited. (Co-auth ors: Chiara Villa and Tommaso Lorenzi.)\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Alf Gerisch (Technical University Darmstadt) DTSTART:20210930T160000Z DTEND:20210930T165000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/20 DESCRIPTION:Title: (Chaplain + Gerisch\, Part II) Mechanical models of pattern formation in biological tissues: the role of the stress-strain constitutive model\nby Alf Gerisch (Technical University Darmstadt) as part of CMO - Model ing and Computational Approaches to Individual and Collective Cell Movemen t in Complex En\n\n\nAbstract\nMechanical and mechanochemical models of pa ttern formation in biological tissues\nhave been used to study a variety o f biomedical systems\, particularly in\ndevelopmental biology\, and descri be the physical interactions between cells and\ntheir local surroundings. These models in their original form consist of a\nbalance equation for the cell density\, a balance equation for the density of the\nextracellular m atrix (ECM)\, and a force-balance equation describing the\nmechanical equi librium of the cell-ECM system.\n\nIn these models\, the stress-strain rel ation of the ECM is often described using\nthe Kelvin-Voigt model of linea r viscoelasticity. However\, due to the\nmultifaceted bio-physical nature of the ECM constituents\, there are rheological\naspects that cannot be ef fectively captured by this model and\, therefore\,\ndepending on the patte rn formation process and the type of biological tissue\nconsidered\, other constitutive models of linear viscoelasticity may be better\nsuited. Co-a uthors: Chiara Villa and Tommaso Lorenzi.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/20/ END:VEVENT BEGIN:VEVENT SUMMARY:Sean Sun (John Hopkins) DTSTART:20210930T170000Z DTEND:20210930T175000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/21 DESCRIPTION:Title: On the role of hydraulic resistance during cell migration\nby Sea n Sun (John Hopkins) as part of CMO - Modeling and Computational Approache s to Individual and Collective Cell Movement in Complex En\n\n\nAbstract\n Cells migrating in vivo can encounter microenvironments with varying physi cal properties. One such physical variable is the viscosity of the fluid s urrounding the cell. Increased fluid viscosity is expected to increase the hydraulic resistance experienced by the migrating cell and therefore decr ease 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 water dynam ics driven by ion channel activity. Results show that cells increased in a rea in high viscosity and actomyosin dynamics remained similar\, except th at actin retrograde flow speed is reduced. Inhibiting ion channel fluxes i n high viscosity media results in a large reduction in cell speed\, sugges ting that water flux contributes to the observed speed increase. Moreover\ , inhibiting actin-dependent vesicular trafficking that transports ion cha nnels from the ER to the cell boundary changes ion channel spatial positio ning and reduces cell speed in high viscosity media. Cells also displayed altered Ca2+-activity in high viscosity media\, and when cytoplasmic Ca2+ is sequestered\, cell speed reduction and altered ion channel positioning were observed. Taken together\, we find that the cell cytoplasmic actin-ph ase and water-phase are coupled during cell migration in high viscosity me dia. Directional water fluxes are mediated by ion channels whose position depend on actin-based vesicular trafficking. These results\, together with observed cell migration behavior in micro channels\, suggest that hydraul ic resistance and local hydraulic pressure are important mechanical variab les governing cell polarization and influence cell migration speed. A phys ical 2-phase model of cell migration incorporating actin and water dynamic s is presented to explain the experimental results.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/21/ END:VEVENT BEGIN:VEVENT SUMMARY:Tracy Stepien (University of Florida) DTSTART:20210930T190000Z DTEND:20210930T195000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/22 DESCRIPTION:Title: Collective cell migration in tissues with multiple cell types\nby Tracy Stepien (University of Florida) as part of CMO - Modeling and Compu tational Approaches to Individual and Collective Cell Movement in Complex En\n\n\nAbstract\nCollective cell migration plays an important role in man y processes including in the cohesion of epithelial cell monolayers\, in w ound healing\, and in embryonic development. In tissues with multiple cell types\, such as differentiating stem cells that spread in a single layer or epithelial and mesenchymal cells that spread in stratified layers\, con tinuum mechanical models may be used to understand the mechanisms involved . We develop PDE models to examine the spread and maturation of astrocytes in retinal development and the spread of multi-layer embryonic tissue exp lants in gastrulation\, and we compare numerical simulations to experiment al data to decipher the spatiotemporal distribution of cell types.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/22/ END:VEVENT BEGIN:VEVENT SUMMARY:Meghan Rhodes (University of Alberta) DTSTART:20210930T200000Z DTEND:20210930T205000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/23 DESCRIPTION:Title: Comparing the effects of linear and one-term Ogden elasticity in a mo del of glioblastoma invasion\nby Meghan Rhodes (University of Alberta) as part of CMO - Modeling and Computational Approaches to Individual and Collective Cell Movement in Complex En\n\n\nAbstract\nWe present a model o f glioblastoma (GBM) invasion which includes mass effects and tissue mecha nics. Furthermore\, we show how different brain tissue elasticity models a ffect the dynamics and invasion wave speed. Inspired by Budday et al. (201 7) who mechanically tested brain tissue to determine an appropriate consti tutive model of brain tissue mechanics\, we explore two models: The linear elasticity model\, and the one-term Ogden model. In a simplified 1D versi on of the model\, we show the existence of travelling wave solutions. The traveling waves can be viewed as the invasion of GBM tumor cells into the surrounding healthy brain tissue. Thus\, identifying the speed of the wave and how it is affected by model components and parameters is useful in de termining what drives invasion. We show that although the wave speed is in dependent of the chosen mechanical model\, the dynamics of GBM spread and the effects on surrounding brain tissue differ significantly between the l inear and one-term Ogden elasticity models. (joint with T. Hillen)\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/23/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Hillen (University of Alberta) DTSTART:20210930T210000Z DTEND:20210930T223000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/24 DESCRIPTION:Title: Free discussion in gathertown\nby Thomas Hillen (University of Al berta) as part of CMO - Modeling and Computational Approaches to Individua l and Collective Cell Movement in Complex En\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/24/ END:VEVENT BEGIN:VEVENT SUMMARY:Dietmar Oelz (University of Queensland) DTSTART:20211001T150000Z DTEND:20211001T155000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/25 DESCRIPTION:Title: Protein Friction and F-Actin Bending Promote Contraction of Disordere d Actomyosin Networks\nby Dietmar Oelz (University of Queensland) as p art of CMO - Modeling and Computational Approaches to Individual and Colle ctive Cell Movement in Complex En\n\n\nAbstract\nThe origins of disordered actomyosin network contraction such as in the cellular cortex remain an a ctive topic of research.\nWe derive a mathematical model for the evolution of two-dimensional networks. A major advantage of our approach is that it \nenables direct calculation of the network stress tensor\, which provides a quantitative measure of contractility. Exploiting this\, we\nuse repeat ed simulations of disordered networks to confirm that both protein frictio n and actin filament bending are required\nfor contraction. We also show t hat actin filament turnover is necessary to sustain contraction and preven t pattern formation.\nWe then consider a toy-model version of the model fo r only two filaments immersed in an actomyosin network.\nUsing asymptotic analysis numerical simulation of the resulting PDE and numerical solutions \, we find that bending facilitates contraction by inducing a geometric as ymmetry that enables motors to move faster close to filament plus-ends\, i nhibiting expansion.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/25/ END:VEVENT BEGIN:VEVENT SUMMARY:Satoshi Sawai (University of Tokyo) DTSTART:20211001T160000Z DTEND:20211001T165000Z DTSTAMP:20260422T185218Z 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 Computat ional Approaches to Individual and Collective Cell Movement in Complex En\ n\n\nAbstract\nIn fast moving cells such as amoeba and immune cells\, dend ritic actin filaments are spatio-temporally regulated to shape large-scale plasma membrane protrusions. Through quantitative image analysis of Dict yostelium on micro-fabricated surfaces\, we show that there is a distinct mode of topographical guidance directed by the macropinocytic membrane cup . Unlike other topographic guidance known to date that depends on nanomet er-scale curvature sensing protein or stress fibers\, the macropinocytic m embrane cup is driven by the Ras/PI3K/F-actin signaling patch and its depe ndency on the micrometer-scale topographic features\; namely PI3K/F-actin- independent accumulation of Ras-GTP at the convex curved surface\, PI3K-de pendent patch propagation along the convex edge and its actomyosin-depende nt constriction at the concave edge. We will introduce a basic mathematic al model of macropinocytic cup formation and closure and apply it to study this newly discovered mode of directed cell migration. Our simulations d emonstrate that the topographically-dependent initiation in combination wi th the mutually-defining patch patterning and the membrane deformation giv es rise to the topographical guidance. The results suggest that macropino cytic 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 faithfully tra ce bent and bifurcating ridges for particle ingestion and cell guidance.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/26/ END:VEVENT BEGIN:VEVENT SUMMARY:Kevin Painter (Politecnico di Torino) DTSTART:20211001T170000Z DTEND:20211001T175000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/27 DESCRIPTION:Title: Models for the collective navigation: from cells to whales\nby Ke vin Painter (Politecnico di Torino) as part of CMO - Modeling and Computat ional Approaches to Individual and Collective Cell Movement in Complex En\ n\n\nAbstract\nIn collective navigation\, a population travels as a group from an origin to a destination. Famous examples include the migrations of birds\, between their winter and summer grounds\, but collective movement s also extend down to microorganisms and cell populations. Collective navi gation is believed to improve the efficiency of migration\, for example th rough the presence of more knowledgeable individuals that guide naive memb ers ("leader-follower behaviour") or through the averaging out of individu al undertainty ("many wrongs"). In this talk I will describe individual an d continuous approaches for modelling collective navigation. The individua l based model is predicated on a random walk model\, where individuals sup plement their own inherent guidance information with information acquired from other group members. The continuous model is based on a nonlocal hyp erbolic PDE system. We investigate the point at which group information be comes beneficial to migration and how it can help a population navigate th rough "information voids"\, i.e. areas with negligible guidance informatio n. We also explore the effectiveness of different modes through which a le ader can herd a group of naïve followers.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/27/ END:VEVENT BEGIN:VEVENT SUMMARY:Andreas Buttenschoen (University of British Columbia) DTSTART:20211001T190000Z DTEND:20211001T195000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/28 DESCRIPTION:Title: Spatio-temporal heterogeneities in a mechano-chemical model of collec tive cell migration\nby Andreas Buttenschoen (University of British Co lumbia) as part of CMO - Modeling and Computational Approaches to Individu al and Collective Cell Movement in Complex En\n\n\nAbstract\nSmall GTPases \, such as Rac and Rho\, are well known central regulators of cell morphol ogy and motility\, whose dynamics also play a role in coordinating collect ive cell migration. Experiments have shown GTPase dynamics to be affected by both chemical and mechanical cues\, but also to be spatially and tempor ally heterogeneous. This heterogeneity is found both within a single cell\ , and between cells in a tissue. For example\, sometimes the leader and fo llower cells display an inverted GTPase configuration. While progress on u nderstanding GTPase dynamics in single cells has been made\, a major remai ning challenge is to understand the role of GTPase heterogeneity in collec tive cell migration.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/28/ END:VEVENT BEGIN:VEVENT SUMMARY:Stefanie Sonner (Radboud University\, Nijmegen) DTSTART:20211001T200000Z DTEND:20211001T205000Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/29 DESCRIPTION:Title: A coupled ODE-PDE system modelling the growth of cellulolytic biofilm s\nby Stefanie Sonner (Radboud University\, Nijmegen) as part of CMO - Modeling and Computational Approaches to Individual and Collective Cell M ovement in Complex En\n\n\nAbstract\nWe discuss a mathematical model for t he growth of cellulolytic biofilms. Cellulolytic biofilms play an importan t role in the production of cellulosic ethanol\, a biofuel with large econ omic potential. Different from traditional models where the biofilm grows into the aqueous phase and nutrients are transported by diffusion\, bacter ia colonize\, consume and degrade a cellulosic substratum that supports th em. Hence\, the nutrients are immobilized and modelled by an ODE. The ODE is coupled to a two-fold degenerate reaction diffusion equation for the bi omass density that exhibits a polynomial degeneracy (as known from the por ous medium equation) and a singularity as the biomass density approaches i ts maximum value (fast diffusion effect).\nWe show the well-posedness of t he model and prove the existence of travelling wave solutions. Invading fr onts had been observed in biological experiments as well as in numerical s imulations of the model.\nThis is joint work with Hermann Eberl\, Jack Hug hes and Koondanibha Mitra.\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/29/ END:VEVENT BEGIN:VEVENT SUMMARY:Hans Othmer (University of Minnesota) DTSTART:20211001T210000Z DTEND:20211001T211500Z DTSTAMP:20260422T185218Z UID:CMO-21w5225/30 DESCRIPTION:Title: (Othmer\, Hillen) Closing\nby Hans Othmer (University of Minnesot a) as part of CMO - Modeling and Computational Approaches to Individual an d Collective Cell Movement in Complex En\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CMO-21w5225/30/ END:VEVENT END:VCALENDAR