Nav: Home

IRCM researchers explain how evolution has equipped our hands with 5 fingers

October 05, 2016

October 5, 2016, 1 p.m. ET. - Have you ever wondered why our hands have exactly five fingers? Dr. Marie Kmita's team certainly has. The researchers at the Institut de recherches cliniques de Montréal and Université de Montréal have uncovered a part of this mystery, and their remarkable discovery has just been published in the prestigious journal Nature.

A matter of evolution

We have known for several years that the limbs of vertebrates, including our arms and legs, stem from fish fins. The evolution that led to the appearance of limbs, and in particular the emergence of fingers in vertebrates, reflects a change in the body plan associated with a change of habitat, the transition from an aquatic environment to a terrestrial environment. How this evolution occurred is a fascinating question that goes all the way back to the work of Charles Darwin.

This August, researchers in Chicago, Dr. Neil Shubin and his team, demonstrated that two genes--hoxa13 and hoxd13--are responsible for the formation of fin rays and our fingers. "This result is very exciting, because it clearly establishes a molecular link between fin rays and fingers," said Yacine Kherdjemil, a doctoral student in Marie Kmita's laboratory and first author of the article published in Nature.

However, the transition from fin to limb was not accomplished overnight. The fossil record indicates that our ancestors were polydactyl, meaning that they had more than five fingers, which raises another key question. Through what mechanism did evolution favor pentadactyly (five fingers) among current species?

One observation in particular caught the attention of Dr. Kmita's team: "During development, in mice and humans, the hoxa11 and hoxa13 genes are activated in separate domains of the limb bud, while in fish, these genes are activated in overlapping domains of the developing fin," said Marie Kmita, Director of the Institut de recherches cliniques de Montréal'S Genetics and Development research unit and Associate Research Professor in the Department of Medicine at the Université de Montréal.

In trying to understand the significance of this difference, Yacine Kherdjemil demonstrated that by reproducing the fish-type regulation for the hoxa11 gene, mice develop up to seven digits per paw, i.e., a return to ancestral status. Dr. Marie Kmita's team also discovered the sequence of DNA responsible for the transition between fish- and mouse-type regulation for the hoxa11 gene. "It suggests that this major morphological change did not occur through the acquisition of new genes but by simply modifying their activities," added Dr. Marie Kmita.

From a clinical point of view, this discovery reinforces the notion that malformations during fetal development are not only due to mutations in the genes and may come from mutations in sequences of DNA known as regulatory sequences. "At present, technical constraints do not allow for identifying this type of mutation directly in patients, hence the importance of basic research using animal models", said Marie Kmita.
-end-
About the study

The research project was conducted at the IRCM's Genetics and Development research unit by Yacine Kherdjemil, Rushikesh Sheth, Annie Dumouchel, Gemma de Martino and Marie Kmita. Robert L. Lalonde and Marie-Andrée Akimenko, from the University of Ottawa, Kyriel M. Pineault and Deneen M. Wellik, from the University of Michigan, as well as H. Scott Stadler, from Shriners Hospital for Children, also collaborated on the study.

The research was funded by the Canadian Institutes of Health Research, the Canada Research Chairs Program, the Natural Sciences and Engineering Research Council and a grant from Shriners Hospital Research. Yacine Kherdjemil also received the IRCM - Michel-Bélanger Scholarship from the IRCM Foundation and a scholarship from the molecular biology program at the Université de Montréal.

About Marie Kmita

Marie Kmita obtained a PhD in cell and molecular biology from the Université de Reims in France. She is Associate IRCM Research Professor and Director of the Genetics and Development research unit. Dr. Kmita is also Associate Research Professor in the Department of Medicine (accreditation in molecular biology) at the Université de Montréal, as well as an Adjunct Professor in the Department of Medicine (Division of Experimental Medicine) at McGill University. Dr. Kmita holds the Canada Research Chair in Molecular Embryology and Genetics. For more information, visit http://www.ircm.qc.ca/kmita.

About the IRCM

Founded in 1967, the Institut de recherches cliniques de Montréal (IRCM) is a non-profit organization that conducts fundamental and clinical biomedical research in addition to training high-level young scientists. With its cutting-edge technology facilities, the institute brings together 33 research teams, which work in cancer, immunology, neuroscience, cardiovascular and metabolic diseases, systems biology and medicinal chemistry. The IRCM also operates a research clinic specialized in hypertension, cholesterol, diabetes and cystic fibrosis, as well as a research centre on rare and genetic diseases in adults. The IRCM is affiliated with the Université de Montréal and associated with McGill University. Its clinic is affiliated with the Centre hospitalier de l'Université de Montréal (CHUM). The IRCM is supported by the Ministère de l'Économie, de la Science et de l'Innovation (Quebec ministry of Economy, Science and Innovation).

About Université de Montréal

Université de Montréal and its two affiliated schools, École Polytechnique (engineering) and HEC Montréal (business), are amongst the world's top 100 universities, according to international rankings. Founded in 1878, the campus today has over 66,000 students and 2,600 professors, making Université de Montréal the second largest university in Canada. Its students are drawn to the university by its deep roots in cosmopolitan Montreal and in consideration of its tenacious dedication to its international mission. umontreal.ca/english

University of Montreal

Related Evolution Articles:

Prebiotic evolution: Hairpins help each other out
The evolution of cells and organisms is thought to have been preceded by a phase in which informational molecules like DNA could be replicated selectively.
How to be a winner in the game of evolution
A new study by University of Arizona biologists helps explain why different groups of animals differ dramatically in their number of species, and how this is related to differences in their body forms and ways of life.
The galloping evolution in seahorses
A genome project, comprising six evolutionary biologists from Professor Axel Meyer's research team from Konstanz and researchers from China and Singapore, sequenced and analyzed the genome of the tiger tail seahorse.
Fast evolution affects everyone, everywhere
Rapid evolution of other species happens all around us all the time -- and many of the most extreme examples are associated with human influences.
Landscape evolution and hazards
Landscapes are formed by a combination of uplift and erosion.
New insight into enzyme evolution
How enzymes -- the biological proteins that act as catalysts and help complex reactions occur -- are 'tuned' to work at a particular temperature is described in new research from groups in New Zealand and the UK, including the University of Bristol.
The evolution of Dark-fly
On Nov. 11, 1954, Syuiti Mori turned out the lights on a small group of fruit flies.
A look into the evolution of the eye
A team of researchers, among them a zoologist from the University of Cologne, has succeeded in reconstructing a 160 million year old compound eye of a fossil crustacean found in southeastern France visible.
Is evolution more intelligent than we thought?
Evolution may be more intelligent than we thought, according to a University of Southampton professor.
The evolution of antievolution policies
Organized opposition to the teaching of evolution in public schoolsin the United States began in the 1920s, leading to the famous Scopes Monkey trial.

Related Evolution Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".