Researchers from Delft University of Technology have made steps to explain how spatial patterns, like the stripes on a zebra, emerge in a population of cells. This enables them to predict certain spatial patterns without having complete information about what each of the millions of cells are doing. The researchers published their findings in Cell Systems on 25 November 2015.
Cells are composed of many different genes, proteins and other molecular parts. To make matters even more complicated, putting multiple cells together creates tissues and whole organisms such as human beings.
‘One of the major challenges that scientists face in modern biology and physics is somehow unravelling this complexity into ‘simple’ mathematical rules, like those of physics, that underlie and tie together disparate and complex living systems’, says Dr Hyun Youk, researcher at Delft University of Technology and the senior author of the publication in Cell Systems. ‘Motivated by previous experimental findings, we have now derived some mathematical rules that govern a wide range of multicellular systems.’
Youk and his former Master’s student and the first author of the work, Théo Maire, looked at a relatively simple class of cells that can both secrete and sense one particular molecule. This molecule can turn ‘on’ or turn ‘off’ a specific property of such a cell. ‘We show how putting two such cells together, and making them communicate with each other (through this molecule), alters each cell’s behaviour. We repeat this by putting together more and more cells that ‘talk’ to each other through this signalling molecule.’
‘We have derived rules with which we can now predict the emergence of certain spatial patterns in a group of cells. This could enable us to explain how spatial patterns (such as the stripes on a zebra) emerge in a population of cells, without us having the complete information about what each of the millions of cells are doing.’
Amount of freedom
Maire and Youk can now trace step-by-step, how complex behaviours of tissues and embryos can emerge from the simple interactions inside and between cells. ‘Our work thus explains a wide class of different biological entities that are important to the development and functioning of tissues and organs. We are able to show for the first time that concepts such as a cell’s ‘amount of freedom’, ‘amount of autonomy’, and ‘amount of collectiveness’ are quantifiable traits.’
Maire and Youk are also introducing the concept of ‘entropy of population’, a concept that can finally explain how spatial patterns emerge in a population of cells without having complete information about what each of the millions of cells are doing. This new concept makes a connection between disorderliness and orderliness of cells, with a new form of entropy that may be compared to the concept of entropy known in physics. This opens a door for exploring this intriguing link in more depth in the future.’
Title: "Molecular-level tuning of cellular autonomy controls the collective behaviors of cell populations".
Authors: Théo Maire, Hyun Youk.
Journal: Cell Systems
Published 25 November 2015
This fall, Hyun Youk was awarded an ERC starting grant for his research into how cells at different locations communicate using signalling molecules so that cells turn on the right genes at the right time and place.
More information on Hyun Youk and the Youk Lab – Physics of Cellular Systems
Hyun Youk, H.Youk@tudelft.nl
Ilona van den Brink (science information TU Delft), +31-15-2784259, firstname.lastname@example.org