Epithelial Sheet Dynamics during Primitive Streak formation as Active Matter

Lead Research Organisation: University of Bristol
Department Name: Mathematics

Abstract

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

Planned Impact

The research proposed here investigates the mechanisms governing gastrulation, a central process in the development of all higher animals. Findings made here will greatly increase our understanding of how cell-cell signalling directs cellular events, like differentiation, proliferation and migration. This is important for understanding development and the origin and cause of many congenital defects. Gastrulation is core material in many Life Sciences and Medical textbooks. Key research findings made here could become textbook material and therefore affect students of the medical and life sciences.
Soft and active matter are recent directions within the physical sciences. They are specifically set up to deal with out of equilibrium, living systems and the patterns they form. As such, the research proposed here forms part of a concerted effort to construct a general theory of living things, in this case the collective properties of cells behaving as a tissue. Development, with its germ layers, patterning and segmentation, and geometrical constraints, is one of the most promising areas for this approach. Research findings from this proposal are expected to find their way into teaching materials for students in the new, interdisciplinary field of biological physics / quantitative biology.
The key processes of gastrulation such as directed collective migration, ingression and EMT are also central to other biological processes using similar cellular mechanisms like wound healing, tissue repair and regeneration. Failure to properly control these is key to the development of autoimmune diseases and metastasis of cancer cells. Therefore findings made here will be directly relevant to these areas. Understanding these developmental processes is also essential for the rational use of embryonic stem cells in regenerative medicine. It is by no means clear how embryonic stem cells migrate to the right positions and organise themselves correctly to repair defects in-situ. Clearly, successful manipulation of stem cells will require understanding of directed cell migration, cell-cell interactions and interactions between behaviour and signalling. Therefore, in the 5-10 year term, the research proposed here will undoubtedly have practical applications in these increasingly important areas of medicine and healthcare, affecting researchers and practitioners in both the academic and the commercial sector.
An important aspect of the proposed research is that it will strengthen links between the Biology and Physics communities. This closer integration will be beneficial to both: Biology will benefit from the depth of modelling experience, and wealth of analytical and numerical techniques developed in the statistical mechanics community, and Physics will benefit from opening up to a new community and gaining impact on a rapidly developing area. A vital aspect here is the development of a productive interdisciplinary culture. Though this is accepted reality, current undergraduate and postgraduate training remains largely monodisciplinary. Important interdisciplinary training will be provided to the PDRAs involved as well as associated PhD and master students. For example, Dr Manli Chuai was trained as a medical doctor but is now also trained in methods of advanced LSFM and large scale data analysis. Hence, an important added benefit of our proposed research will be to develop careers within an interdisciplinary culture.
The Life Sciences sector has an important economic impact in Dundee, contributing around 16% of the city's GDP. A range of activities and organisations in the city connect scientists with the public. In recognition of the economic and social impact of these interactions, the College of Life Sciences won the BBSRC "Excellence with Impact" Award in 2011.
Finally, this research generates exquisite experimental and simulated images. These have been and will be part of exhibitions at the local, national and international level.

Publications

10 25 50
 
Title Active drawing machine 
Description In collaboration with Manchester-based Daksha Patel (http://dakshapatel.co.uk/), I am currently developing an active drawing machine. 
Type Of Art Artwork 
Year Produced 2019 
Impact (still being created) 
 
Description One of the earliest steps in the development of animals is gastrulation, where the early embryo turns inside-out to begin forming an inside and an outside. In this award, using a microscopic model, we have thoroughly analysed different mechanical pathways to generate stresses inside these cell sheets.

We are able to explain how, starting from as slight in pulling asymmetry, the feedback loop between contractile junctions and the microscopic viscoelastic properties of the cells can lead to polarisation of a tissue, so that it will contract asymmetrically in one direction and expands in another. A key part of this mechanism are active T1 transitions, where groups of 4 cells exchange neighbours and rearrange against the direction of applied stress.

This convergence-extension flow has been shown to be crucial to gastrulation and to germ band extension in drosophila, and our experimental sister grant has shown that convergence-extension flows also drive chick embryo gastrulation.

While we have a qualitative model of this process, a direct quantitative comparison with experiment is still outstanding. A modelling paper that focusses on the mechanism of an active T1 event is close to submission. It shows that our actomyosin feeback engine that leads to contraction at the single junction level can generate a T1 in a mechanically polarised tissue. We quantify the amount of convergence-extension flow generated by such a T1 and show that the mechanism is robust for a wide range of myosin response and viscoelastic time scales.
Exploitation Route We hope that our mechanical pathway to stress generation and convergence-extension flows will lead to more realistic in-silico models of development, and so ultimately benefit the bioengineering of tissues and organisms.
Sectors Digital/Communication/Information Technologies (including Software),Pharmaceuticals and Medical Biotechnology

 
Description Some Theoretical Models of Active Matter
Amount £56,000 (GBP)
Funding ID 2278414 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 09/2019 
End 09/2023
 
Description Glassy mechanics of epithelial cell sheets 
Organisation University of Grenoble
Country France 
Sector Academic/University 
PI Contribution We have an ongoing collaboration to understand the glassy mechanics of epithelial cell sheets: For our paper Soft Matter 'Cell division and death inhibit glassy behaviour of confluent tissues', our SAMoS computational package was used (by myself) to carry out and analyse part of the simulations. I have visited Grenoble twice in the past two years, and contributed to making their ongoing research more focused on epithelial sheets, and contributed soft matter theoretical arguments.
Collaborator Contribution In Grenoble, Kirsten Martens, Jean-Louis Barrat and then-postdoc Daniel Matoz-Fernandez had an ongoing project about division in epithelial cell sheets. In collaboration, we adapted their project and merged it with the SAMoS model to produce a coherent picture of how division and death preclude glassy physics in such cell sheets. The large-scale simulations in the paper were carried out using Daniel's purpose-built GPU code, after a careful calibration of both codes during a week-long visit of his to Aberdeen.
Impact Cell division and death inhibit glassy behaviour of confluent tissues, DA Matoz-Fernandez, K Martens, R Sknepnek, JL Barrat, S Henkes, Soft matter 13 (17), 3205-3212 (2017), PhD project funding for Magali Le Geoff in Grenoble to work, among other tools, with the active vertex model of SAMoS. Confinement-induced transition between wavelike collective cell migration modes, Vanni Petrolli, Magali Le Goff, Monika Tadrous, Kirsten Martens, Cédric Allier, Ondrej Mandula, Lionel Hervé, Silke Henkes, Rastko Sknepnek, Thomas Boudou, Giovanni Cappello, Martial Balland, Physical Review Letters 122 (16), 168101 (2019) Dense active matter model of motion patterns in confluent cell monolayers, S Henkes, K Kostanjevec, R Sknepnek, JM Collinson and E Bertin, accepted for publication in Nature Communications (March 2020)
Start Year 2015
 
Description Activer [drawing] matter. Collaborative arts / science project with Daksha Patel, a Manchester-based artist (http://dakshapatel.co.uk/), in which we constructed a vibrating table with moving chalks, to demonstrate active motion. The table was exhibited at Creative Reactions 2019 (Bristol), and it was professionally filmed last summer. 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact An estimate of several hundred visitors saw the vibrating table during the month-long exhibition. The video of the moving chalks has been in several exhibitions and been entered for several drawing prizes by Daksha Patel.
Year(s) Of Engagement Activity 2019,2020
URL https://mathsart.blogs.bristol.ac.uk/