A project has identified the mechanism responsible for generating our fingers and toes, and revealed the importance of gene regulation in the transition of fins to limbs during evolution.  

Their conclusion involves a theoretical model for pattern formation known as the Turing mechanism. In 1952, mathematician Alan Turing proposed equations for pattern formation, which describe how two uniformly-distributed substances, an activator and a repressor, trigger the formation of complex shapes and structures from initially-equivalent cells. 

The Turing model for pattern formation has been a source of speculation and debate due to the lack of experimental data supporting it.

"By studying the role of Hox genes during limb development, we were able to show, for the first time, that the patterning process that generates our fingers and toes relies on a Turing-like mechanism," says Dr. Rushikesh Sheth, postdoctoral fellow at Institut de recherches cliniques de MontrĂ©al (IRCM) and co-first author of the study.   

In humans, as in other mammals, the embryo's development is controlled, in part, by "architectual" Hox genes. These genes are essential to the proper positioning of the body's architecture, and define the nature and function of cells that form organs and skeletal elements.

"Our genetic study suggested that Hox genes act as modulators of a Turing-like mechanism, which was further supported by mathematical tests performed by our collaborators, Dr. James Sharpe and his team," adds Dr. Marie Kmita, Director of the Genetics and Development research unit at the IRCM. "Moreover, we showed that drastically reducing the dose of Hox genes in mice transforms fingers into structures reminiscent of the extremities of fish fins.

"These findings further support the key role of Hox genes in the transition of fins to limbs during evolution, one of the most important anatomical innovations associated with the transition from aquatic to terrestrial life."


Published in Science.