A Mathematical Model Connects the Evolution of Chickens, Fish and Frogs

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One of the most enduring, basic questions of life is: How does it happen? For instance, in human development, how do cells self-organize into skin, muscles or bones? How do they form a brain, a finger, a spine?

Although the answers to such questions remain unknown, one line of scientific inquiry lies in understanding gastrulation — the stage at which embryo cells develop from a single layer to a multidimensional structure with a main body axis. In humans, gastrulation happens around 14 days after conception.

It’s not possible to study human embryos at this stage, so researchers at the University of California San Diego, the University of Dundee (UK) and Harvard University were able to study gastrulation in chick embryos, which have many similarities to human embryos at this stage.

This research was conducted through what UC San Diego Assistant Professor of Physics Mattia Serra calls an ideal loop: an interdisciplinary, back-and-forth combination of theoretical and experimental science. Mattia is a theorist interested in finding emergent patterns in complex biophysical systems.

Here, he and his team built a mathematical model based on input from the University of Dundee biologists. The model was able to accurately predict the gastrulation flows — the motion of tens of thousands of cells in the entire chick embryo — observed under a microscope. This is the first time a self-organizing mathematical model has been able to reproduce these flows in chick embryos.

The biologists then wanted to see if the model could not just replicate what they knew experimentally to be true, but also predict what might happen under different conditions. Serra’s team “perturbed” the model — in other words, changing the initial conditions or the present parameters.