Mathematical model links evolution of chickens, fish and frogs

One of life’s most enduring fundamental questions is: How does this happen? For example, 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 these questions remain unknown, one avenue of scientific research lies in understanding gastrulation, the stage at which embryonic cells develop from a single layer to a multidimensional structure with a main body axis. In humans, gastrulation occurs approximately 14 days after conception.

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

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

Here, he and his team built a mathematical model based on input from biologists at the University of Dundee. The model was able to accurately predict gastrulation flows – the movement of tens of thousands of cells in the entire chicken embryo – observed under a microscope. This is the first time that a self-organizing mathematical model has succeeded in reproducing these flows in chicken embryos.

The biologists then wanted to see if the model could not only reproduce what they experimentally knew to be true, but also predict what might happen under different conditions. Serra’s team “perturbed” the model, that is, changing the initial conditions or current parameters.

The results were surprising: the model generated cell flows that were not observed naturally in chicks, but were observed in two other vertebrate species: frogs and fish.

To ensure that these results are not a mathematical fantasy of the model, biology collaborators mimicked the model’s exact disruptions in the lab on the chicken embryo. Surprisingly, these manipulated chicken embryos also exhibited gastrulation flows naturally observed in fish and frogs.

These results, published in Scientists progresssuggest that the same physical principles behind multicellular self-organization may have evolved among vertebrate species.

“Fish, frogs and chicks all live in different environments, so over time, evolutionary pressure may have changed the parameters and initial conditions of embryo development,” Serra said. “But some of the fundamental principles of self-organization, at least at this early stage of gastrulation, may be the same in all three.”

Serra and his collaborators are currently studying other mechanisms that give rise to self-organization patterns at the embryo level. They hope this research could advance biomaterial design and regenerative medicine to help humans live longer, healthier lives.

“The human body is the most complex dynamic system in existence,” he said. “There are so many interesting biological, physical and mathematical questions about our bodies. It’s beautiful to contemplate. There is no end to the discoveries we can make.”