Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Y04: Collective Behaviors in Biology IIRecordings Available
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Sponsoring Units: DBIO Chair: Brian Camley, Johns Hopkins University Room: McCormick Place W-176C |
Friday, March 18, 2022 8:00AM - 8:12AM |
Y04.00001: Sloppy Model Analysis of Bifurcations in Biochemical Networks Christian N Anderson, Mark K Transtrum The dynamic equations describing even simple biochemical networks have many parameters and exhibit a range of behaviors. Discovering and characterizing the bifurcation surfaces between these behavioral basins-of-attraction presents a substantial mathematical challenge, and closed-form solutions may not exist. Recent work has linked bifurcations to the renormalization group (RG), and the RG has been tied to sloppy analysis (or information geometry). This paper shows how sloppy analysis can apply directly to bifurcations, including the normal-form of all major types and multi-parameter multi-variable systems with no obvious simplifying reparameteriziation. The coarse-graining procedure employed allows analysis of either theoretical models or a data-driven approach. Sloppy analysis can therefore rapidly provide insight into otherwise difficult-to-characterize biochemical systems, and implies application to other forms of network analysis. |
Friday, March 18, 2022 8:12AM - 8:24AM |
Y04.00002: Excitable mechanics embodied in a walking cilium Matthew S Bull, Laurel A. A Kroo, Manu Prakash Rapid transduction of sensory stimulation to action is essential for an animal to survive. To this end, most animals use the sub-second excitable and multistable dynamics of a neuromuscular system. Here, studying an animal without neurons or muscles, we report analogous excitable and multistable dynamics embedded in the physics of a 'walking' cilium. We begin by showing that cilia can walk without specialized gait control and identify the characteristic scales of spatio-temporal height fluctuations of the tissue. With the addition of surface interaction, we construct a low-order dynamical model of this single-cilium sub-unit. En route to an emergent model for ciliary walking, we demonstrate the limits of substrate mediated synchronization between cilia. In the desynchronized limit, our model shows evidence of a multi-stability mediated by the crosstalk between locomotive forcing and height. The out-of-equilibrium mechanics directly control the locomotive forcing of a walking cilia bypassing the role of the synaptic junctions between neurons and muscles. We show a minimal mechanism -- trigger waves -- by which these walking cells may work together to achieve organism-scale collaboration, such as coordination of hunting strikes across 105 cells without central control. |
Friday, March 18, 2022 8:24AM - 8:36AM |
Y04.00003: Evolution of schooling and exploration strategies in the Mexican tetra fish Yaouen Fily, Adam Patch, Alexandra Paz, Karla J Holt, Erik R Duboué, Alex C Keene, Johanna E Kowalko The Mexican tetra fish is found in rivers as well as in subterranean caves. Each cave population is the result of the colonization of a cave by a surface population, followed by about 200,000 years of isolated adaptation to life in a dark, food-scarce environment. Thus, the Mexican tetra provides a fascinating window into the evolution of animal displacement patterns in response to changes in sensory inputs and food availability. In this talk I will present results on the collective dynamics of groups of fish from surface and cave populations and discuss the implications of the observed inter-population differences on the way each population explores its environment. |
Friday, March 18, 2022 8:36AM - 8:48AM |
Y04.00004: Riding the cAMP Wave: Maximizing Cell Migration by Slow Chemoattractant Waves Aravind Rao Karanam Chemotaxis is the motion of cells in response to chemical signals in the environment. While experiments have been done to understand various aspects of chemotaxis in eukaryotes, few experiments have probed the physical limits of the process. Using a microfluidic device to generate waves of the chemoattractant cyclic AMP (cAMP) of controlled size and speed, we were able to record cell migration speeds of individual cells of the social amoeba Dictyostelium that are significantly higher than in static gradients. This was coupled with the observation that these fast-moving cells were concentrated at a particular location on the back of a wave, much like surfing, given the right range of wave speeds. Cells that are 'riding the waves' rarely turn back, displaying very high persistence. Furthermore, cells that were not able to follow the first wave were typically able to ride the second wave. The experimental results were incorporated into a model, which aims to uncover the fundamental cellular processes that regulate the limits of chemotaxis and cell motility. This study may help us devise strategies to maximize cell migration efficiency. |
Friday, March 18, 2022 8:48AM - 9:00AM |
Y04.00005: Cellular crowd control: improving external control of collective cell migration by modulating existing cell-cell coordination Gawoon Shim, Daniel J Cohen, Danelle Devenport While there is increasing interest in approaches to reprogram collective cellular migration, a process critical for multicellular processes such as regeneration and development, little is known about what happens when external 'commands' conflict against natural collective behaviors of the collective system. In this study, we investigate two major questions: 1) how much does the strength of an endogenous collective behavior in a tissue limit our ability to control its collective cell migration, and 2) how can we circumvent such limitations? Using a bioelectric stimulus—electrotaxis—to externally program cell migration in large, cultured layers of primary mouse skin monolayers, we study how strong endogenous cell coordination created through strong cell-cell coupling via cadherin adhesion can compete with external migration commands, as well as methods that can be used to optimize external control of cellular collectives. We hope this study will pave the way for future approaches to better analyze, control, and synergize with existing collective behaviors. |
Friday, March 18, 2022 9:00AM - 9:12AM |
Y04.00006: Cellular integration of physical and biochemical damage signals in the generation of tissue-level wound responses Aaron C Stevens, James O'Connor, Andrew Pumford, Hannah H Kim, Caroline E Howell, Lila S Nassar, Shane Hutson, Andrea Page-McCaw Laser wounds in Drosophila epithelia trigger calcium signaling – an early and conserved sign of wound detection – that includes an initial calcium influx into damaged cells within 0.1 s, a first expansion into adjacent cells over ~20 s, and a delayed second expansion to a much larger set of surrounding cells between 40-300 s. We have developed a computational model to test the plausibility of multiple hypothesized mechanisms driving these calcium signals and to further understand the underlying biology. The model exhibits collective behavior across multiple spatiotemporal scales by building up tissue-level calcium signaling from a coupled single-cell calcium signaling toolkit. The single-cell model includes calcium currents between each cell’s cytosol and its endoplasmic reticulum (ER), the extracellular space, and neighboring cells. These calcium currents are initiated in the model by cavitation-induced microtears in the plasma membranes of cells near the wound (initial influx), flow through gap junctions into adjacent cells (first expansion), and by the activation of G-protein coupled receptors via a wound-induced diffusible ligand (second expansion). The production, processing and propagation of the ligand is modeled using reaction-diffusion equations on a continuous, two-dimensional space. We will discuss how the model matches experimental observations and makes experimentally testable predictions. |
Friday, March 18, 2022 9:12AM - 9:24AM |
Y04.00007: A Celluar Potts Model for Collective Cell Migration Man Ho Tang, Wouter-Jan Rappel, Stephanie Fraley, William Leineweber, Sural Ranamukhaarachchi, Alyssa Walker Collective cell migration is a key process during various biological events such as embryonic morphogenesis, wound healing and cancer cell invasion. The coordinated cellular movement is regulated by numerous biophysical parameters (e.g., cell elasticity, interfacial surface tension and cell adhesion) as well as biochemical interactions (e.g., cell signaling, gradient sensing and matrix degradation). |
Friday, March 18, 2022 9:24AM - 9:36AM |
Y04.00008: Computational model for migration of human osteoblasts in direct current electric field Jonathan E Dawson, Tina Sellmann, Katrin Porath, Rainer Bader, Ursula van Rienen, Revathi Appali, Rüdiger Köhling Cell migration plays an important role in both physiological (development, regeneration) and pathological conditions (cancer metastasis). Cells migrate while sensing environmental cues in the form of mechanical, chemical or electrical stimuli. Although it is known that osteoblasts respond to exogenous electric fields, the underlying mechanism of electrotactic collective movement of human osteoblasts is unclear. Theoretical and computational approaches to study electrotactic cell migration until now did not consider the effect of electric field on single-cell motility, together with spatially dependent cell-to-cell interactions. Here, we present a computational model that takes into account cell interactions and describes cell migration in direct current electric field. We compare this model with in vitro experiments in which human primary osteoblasts are exposed to direct current electric field of varying field strength. Our results show that cell-cell interactions and fluctuations in the migration direction together lead to anode-directed collective migration of osteoblasts. |
Friday, March 18, 2022 9:36AM - 9:48AM |
Y04.00009: Collective curvature sensing and fluidity in three-dimentional multicellular systems Wenhui Tang, Dapeng(Max) Bi, Ming Guo Collective cell migration is an essential process throughout the lives of multicellular organisms, for example in embryonic development, wound healing, and tumor metastasis. Substrates or interfaces associated with these processes in situ are typically curved in three-dimensions (3D), with radii of curvatures comparable to many cell lengths, yet the role of substrate curvature at this scale in regulating collective cell migration remains virtually unknown. Using both fabricated hemispherical geometries and lung alveolospheres derived from human induced pluripotent stem cells, here we show that cells sense substrate curvature in a collective manner. As substrate curvature increases, cells reduce their collectiveness and the multicellular flow field becomes more dynamic. Furthermore, hexagonally shaped cells tend to aggregate in solid-like clusters surrounded by non-hexagonal cells that act as a background fluid. We propose a physical mechanism in which cells naturally form hexagonally organized clusters to minimize free energy, where the size of these clusters is limited by an elastic bending energy penalty induced by substrate curvature. Indeed, we observe that cluster size grows linearly as sphere radius increases, which further stabilizes the multicellular flow field and increases cell collectiveness. As a result, increasing curvature tends to promote the fluidity in multicellular monolayer. Together, these findings highlight the potential for a fundamental role of substrate curvature in regulating both spatial and temporal characteristics of three-dimensional multicellular systems in development, wound healing, and tumor formation. |
Friday, March 18, 2022 9:48AM - 10:00AM |
Y04.00010: Collective contact guidance triggers polar laning of turbulent epithelial monolayers Mathilde Lacroix, Bart Smeets, Carles Blanch-Mercader, Samuel Bell, Caroline Giuglaris, Jacques Prost, pascal silberzan Collective cell flows within tissues are central in biological processes such as morphogenesis, wound healing, or cancer progression. In vivo, cell migration is often influenced by oriented structures in the local environment, such as bundles of extra cellular matrix, that can be mimicked in vitro by topographical structures such as grooves and ridges. Although the ”contact guidance” of individual cells on such textured substrates has been thoroughly studied, little is known on the cell collective response to these cues. |
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