CDEV Subgroup Contributed Talks

Bahti Zakirov

Francis Crick Institute

"Active Perception during Angiogenesis: Filopodia speed up Notch selection of Tip Cells in silico and in vivo"

How do cells make efficient collective decisions during tissue morphogenesis? Humans and other organisms use feedback between movement and sensing known as 'sensorimotor coordination' or 'active perception' to inform behaviour. Here we provide the first proof of concept in silico/in vivo study demonstrating that filopodia (actin-rich, dynamic, finger-like cell membrane protrusions) play an unexpected role in speeding up collective endothelial decisions during the time-constrained process of 'tip cell' selection during blood vessel formation (angiogenesis). We first validate simulation predictions in vivo with live imaging of zebrafish intersegmental vessel growth. Further simulation studies then indicate the effect is due to the feedback between movement and sensing on filopodia conferring a bistable switch-like property to Notch lateral inhibition, ensuring tip selection is a rapid and robust process. We then employ measures from computational neuroscience to assess whether filopodia function as a primitive (basal) form of active perception and find evidence in support. By viewing cell behaviour through the 'basal cognitive lens' we acquire a fresh perspective on the tip cell selection process, revealing a hidden, yet vital time-keeping role for filopodia. Finally, we discuss a myriad of new and exciting research directions stemming from our conceptual approach to interpreting cell behaviour.

Eva Deinum

Wageningen University

"Zebrastripes for life!"

The plant cell wall is a versatile material that can meet a wide range of mechanical requirements. The banded patterns in protoxylem form a striking example, enabling these vessels withstand substantial negative pressure and allow for extension at the same time. The required anisotropic material properties largely derive from the location and orientation of the constituting cellulose microfibrils. These, in turn are deposited along the cortical microtubule cytoskeleton. So, using the case of protoxylem as a model system for complex cell wall patterns, the question becomes how cortical microtubules can self-organize into banded patterns. This happens in interaction with another well-known patterning system, the ROP proteins. Studying their interaction provides interesting methodological challenges, as cortical microtubules are most often studied in ``particle based'' stochastic simulations, whereas ROPs, or their animal/yeast counterparts, are typically described in terms of partial differential equations. We, therefore, started by addressing both parts of the interaction in isolation: how can dynamic microtubules collectively adjust to a predefined ROP pattern and how can an –implicitly microtubule derived– field of diffusion anisotropy orient and change ROP patterns? Despite the very different modelling frameworks, our ROP work provided critical insights into a problem in the stochastic microtubule simulations.

Franziska Krämer

Buchmann Institute for Molecular Life Sciences

"Investigating Mechanical Force Dynamics of Extra-Embryonic Membranes in Tribolium castaneum (part 1)"

Efficient energy use and storage is crucial in living organisms. In the context of evolution, energy management is continuously optimized to ensure an individual's ability to successfully compete. This is especially true for oviparous species, as all required energy has to be provided at the moment of oviposition in order to give rise to a fully functional organism. Based on our preliminary imaging data in the emerging insect model Tribolium castaneum, we formulate the hypothesis that extra-embryonic serosa cells utilize shape change during gastrulation to allocate and store energy that is later on required for their extensive movement during dorsal closure. To investigate this possible functional connection, we want to gain further insights into the multi- scale effects of force propagation from cellular to tissue level. Spatial and temporal dynamics of forces are calculated using non-invasive Force Inference (FI). FI utilizes a biomechanical model, a mathematical inverse method and a Bayesian framework to estimate cell and tissue stress from segmented image data and for the whole system simultaneously. Here we highlight our workflow from obtaining 3D time-lapse light sheet-based fluorescent microscopy images of live Tribolium embryos to multi-scale estimation of tensions and pressures acting in the serosa membrane.

Zoë Lange

Frankfurt Institute for Advanced Studies

"Investigating Mechanical Force Dynamics of Extra-Embryonic Membranes in Tribolium castaneum (part 2)"

Efficient energy use and storage is crucial in living organisms. In the context of evolution, energy management is continuously optimized to ensure an individual's ability to successfully compete. This is especially true for oviparous species, as all required energy has to be provided at the moment of oviposition in order to give rise to a fully functional organism. Based on our preliminary imaging data in the emerging insect model Tribolium castaneum, we formulate the hypothesis that extra-embryonic serosa cells utilize shape change during gastrulation to allocate and store energy that is later on required for their extensive movement during dorsal closure. To investigate this possible functional connection, we want to gain further insights into the multi- scale effects of force propagation from cellular to tissue level. Spatial and temporal dynamics of forces are calculated using non-invasive Force Inference (FI). FI utilizes a biomechanical model, a mathematical inverse method and a Bayesian framework to estimate cell and tissue stress from segmented image data and for the whole system simultaneously. Here we highlight our workflow from obtaining 3D time-lapse light sheet-based fluorescent microscopy images of live Tribolium embryos to multi-scale estimation of tensions and pressures acting in the serosa membrane.