Environmental factors, and not just the genes, may play a crucial role in determining complex traits such as height, skin colour, weight and intelligence, researchers, including one of Indian-origin, have found.
Until now scientists have believed that the variations in such traits were a result of both genetic and environmental factors. But they did not 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, along with many more.
They believe that, by identifying a key gene for each trait and how it is affected epigenetically (by the environment), it is potentially possible to influence the degree of its expression - and so create variation in how specific traits are expressed.
It is the discovery of the mechanism through which the environment interacts with specific genes, revealing environmental factors as an equal partner in determining complex traits, researchers said.
A McGill University team led by Professors Moshe Szyf and Ehab Abouheif 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 per cent 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 can turn a light up or down) 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," said Sebastian Alvarado, co-first author on the study.
"We were working with ants, but it was a bit like discovering that we could create shorter or taller human beings," said Alvarado.
"In the case of growth in ants, it was the Egfr gene which was determinant," said Rajendhran Rajakumar, co-first author of the paper.
The study was published in the journal Nature Communications.
