Evolutionary Changes Reproduced in the Lab by Manipulating Embryonic Development of Mice

Through small and gradual modifications in the embryonic development of mice teeth, produced in the laboratory, scientists have obtained teeth that morphologically are very similar to those observed in the fossil registry of rodent species that evolved from mice millions of years ago.

To modify the development of their teeth, the team from the Institute of Biotechnology of the University of Helsinki (Finland) worked with embryonic teeth cultures from mice not coded by the ectodysplasin A (EDA) protein, which regulates the formation of structures and differentiation of organs in the embryo throughout its development. The teeth obtained with these cultures which present this mutation develop into very fundamental forms, with very uniform crowns. Scientists gradually added different amounts of the EDA protein to the embryonic cells and let them develop.

The researchers observed that the teeth formed with different levels of complexity in their crown. The more primitive changes observed coincide with those which took place in animals of the Triassic period, some two hundred million years ago. The development of more posterior patterns corresponds with the different stages of evolution discovered in rodents that already became extinct in the Paleocene Epoch, approximately 60 million years ago. Researchers have therefore achieved the reproduction of the transitions observed in the fossil registry of mammal teeth.

The scientists were able to compare the shape of these teeth with a computer-generated prediction model created by Dr. Isaac Salazar-Ciudad, researcher at the Universitat Autònoma de Barcelona (UAB; Spain) and at the University of Helsinki, which reproduces how the tooth changes from a group of equal cells to a complicated three-dimensional (3D) structure, with the full shape of a molar tooth, computing the position of space of each cell. The model is capable of forecasting the changes in the morphology of the tooth when a gene is engineered, and therefore offers an explanation of the processes that cause these specific alterations to occur in the shape of teeth throughout evolution.

“Evolution has been explained as the ability of individuals to adapt to their environment in different ways,” Dr. Salazar-Ciudad stated, “But we do not know why or how individuals differ morphologically. The research helps to understand evolution, in each generation, as a game between the possible variations in form and natural selection.”

The research findings were published July 30, 2014, in the journal Nature.

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Institute of Biotechnology of the University of Helsinki
Universitat Autònoma de Barcelona