From Fins To Limbs - How We Got Our Fingers And Toes
December 15, 2012

Genetics And Mathematics Come Together To Describe How We Got Our Fingers And Toes

April Flowers for - Your Universe Online

A multidisciplinary international research project has identified the mechanism responsible for generating our fingers and toes.

Dr. Maria Kmita and her colleagues at the Intitut de Recherches Cliniques de Montreal (IRCM) took part in the groundbreaking study that has revealed the importance of gene regulation in the transition from fins to limbs during evolution.

The team, which also included members from CRG Barcelona, the University of Catabria, and the European Molecular Biology Laboratory (EMBL), provided experimental evidence supporting a theoretical model for pattern formation by combining genetic studies with mathematical modeling. The theoretical model they used is known as the Turing mechanism. In 1952, Alan Turing, a mathematician best known for his work in early computer science and cryptanalysis — specifically the decryption of the German Enigma machine during World War II, proposed mathematical equations for pattern formation. These equations 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 long remained under debate, mostly due to the lack of experimental data supporting it,” explains Dr. Rushikesh Sheth, postdoctoral fellow in Dr. Kmita´s laboratory. “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.”

"Architect" genes known as Hox genes control embryonic development in humans, as in other mammals. Hox genes are essential for the proper positioning of the body's architecture, defining 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.”

The Canadian Institutes of Health Research and the Canada Research Chairs Program funded the study.

The findings of this study were recently published in the journal Science.