Until now scientists have believed the variations in traits that exist along a continuum—height, skin color, tendency to gain weight or not, intelligence, tendency to develop certain diseases, etc.—come from both genetic and environmental factors. But they didn’t know how exactly these things worked together.
By studying ants, researchers have identified a key mechanism by which environmental (or epigenetic) factors influence the expression of all of these traits, as well as many more.
It’s a bit like an artist adding more or less white paint to black to create a palette of shades of gray. In effect, the study identifies the mechanism through which the environment interacts with specific genes, revealing environmental factors as an equal partner in determining complex traits.
“It’s a discovery that completely changes our understanding of how human variation comes to be,” says McGill University Professor Ehab Abouheif. “So many human traits, whether they are intelligence, height, or vulnerability to diseases such as cancer, exist along a continuum.
“If, as we believe, this epigenetic mechanism applies to a key gene in each area, the change is so enormous that it’s hard to even imagine right now how it will influence research in everything from health to cognitive development to farming.”
A team, led by Abouheif and Professor Moshe Szyf, has clearly identified a mechanism by which epigenetic factors—how the environment affects the expression of a single gene—have an overarching effect in creating quantitative variation in these kinds of complex traits.
The researchers arrived at this conclusion by conducting epigenetic experiments on ants from the species Camponotus floridanus (better known as the Florida carpenter ant).
Because there is little genetic influence in determining size variation of workers in a colony (they are on average 75 percent related), and because their genome has already been sequenced, it was possible for the researchers to focus on the effects of epigenetic factors in creating variations in size.
By increasing the degree of DNA methylation (a biochemical process that controls the expression of certain genes—a bit like a dimmer switch for a light bulb) of a gene involved in controlling growth called Egfr, they were able to create a spectrum of worker ant sizes despite the lack of genetic difference between one ant and the next.
Essentially, the researchers found that the more methylated the gene, the larger the size of the ants.
“Basically, what we found was a kind of cascading effect. By modifying the methylation of one particular gene that affects others, in this case the Egfr gene, we could affect all the other genes involved in cellular growth,” says Sebastian Alvarado, co-first author of the study in Nature Communications.
“We were working with ants, but it was a bit like discovering that we could create shorter or taller human beings.”
Source: McGill University