Researchers from Brandeis and the University of Pittsburgh recently confirmed Alan Turing's theory on how organisms develop their shapes and how identical cells differentiate into specialized cells.

Turing is most famous for his work in computer science and mathematics, but in particular, for cracking the Enigma code in World War II. In 1952, Turing also wrote a biology paper titled "The Chemical Basis of Morphogenesis." The paper describes how diffusion can interact with chemical reactions to make identical cells differentiate into specialized cells of the various parts of an organism, a process known as morphogenesis.

Scientists from Brandeis and the University of Pittsburgh have now provided the first experimental evidence confirming Turing's theory of morphogenesis. Profs. Seth Fraden (PHYS) and Irving Epstein (CHEM) have verified Turing's models through chemical experiments. The data from these experiments was analyzed by G. Bard Ermentrout, professor of computational biology and mathematics at the University of Pittsburgh. Nathan Tompkins (Ph.D., PHYS), Ning Li (Ph.D., PHYS) and Camille Girabawe (Ph.D., PHYS) also contributed to this research. Their findings were published in a paper titled "Testing Turing's theory of morphogenesis in chemical cells" in the Proceedings of the National Academy of Sciences on March 10.

Turing proposed a chemical process called intercellular reaction-diffusion to explain morphogenesis. This theory takes into consideration the effect of diffusion on chemical reactions. An inhibitory agent that suppresses the reaction and an excitatory agent that activates the reaction, diffuses around the system, over time causing the reaction to start in some places and stop in others. These oscillations give rise to patterns that result in chemically different groups of cells.

Fraden and Epstein created circular arrays of synthetic "cells" or droplets containing the reactants of an oscillatory reaction called the Belousov-Zhabotinsky reaction in order to test Turing's theories. They observed all six patterns predicted by Turing and an additional seventh pattern unpredicted by Turing. The team provides an understanding of this seventh pattern by modifying Turing's theory to take into consideration that the heterogeneity of chemical reactants is the differences in the phases of the reactants.

"It's not that Turing made a mistake," Fraden said in an interview with the Justice. "He simplified and the thing that he left out was heterogeneity."

In addition to contributing to the field of biological development and pattern formation, this research also has relevance to material science. "Throughout nature, in seashells and in porcupine quills, we see patterns emerge. So, why can't we make materials the same way?" said Fraden. "If we can understand this reaction-diffusion process and the conditions under which morphogenesis occurs, can we start building materials based on those principles?"

When asked about the future of this field of research, Epstein talked about studying evolutionary molecular self-organization. "The idea is to look for or make molecules that are capable of spontaneously organizing themselves into complex structures and also of catalyzing either their own production or their self-organization as a potential link to the origin of life." Building off of Turing's seminal work continues to inspire and inform the scientific community's understanding of many fields, including the basis of life itself.

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-Aishwarya Bhonsle