Scientists Double The Size Of Ants
Variations in traits like height, skin color, body weight, and vulnerability to diseases fall along a spectrum, and they’re all the results of genetics combined with the environment. Now, researchers working with ants have identified a key chemical process that allows environmental factors to interact with the genes that code for these sorts of quantitative traits. In the process, they’ve created ants who run the gamut from miniscule to (relatively) gargantuan. The findings are published in Nature Communications this week.
The environment affects the expression of genes through what’s called epigenetics. Specific biochemical reactions can turn parts of the genome on or off, and one of the most well-studied of these mechanisms is DNA methylation. That’s when molecules called methyl groups are added to sections of DNA sequences.
Well, a McGill team led by Ehab Abouheif and Moshe Szyf conducted epigenetic experiments on Florida carpenter ants (Camponotus floridanus) collected from Tallahassee. Their genome had already been sequenced. Queens, workers, and soldiers in an ant nest share similar genetics—yet they display a huge range of sizes that corresponds to their duties to the colony. That’s because early in their development, differences in nutrition and chemical cues trigger various parts of their genome, and you end up with adult ants who are specialized to perform specific tasks. Since there’s little genetic influence on worker size, the researchers were able to focus on epigenetic factors.
They exposed ant larvae to drugs that either increased or decreased the degree of DNA methylation of a gene involved in controlling growth called Egfr. “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,” first author Sebastian Alvarado now of Stanford explains in a news release.
As a result, the team created a continuous spectrum of worker ant sizes: They shrank ants to sizes smaller than those that exist in nature, while almost doubling the size of others. The more methylated the gene, they found, the larger the size of ants: A 20 percent modification in DNA methylation, for example, yielded a 20 percent change in body size. «This helps explain at a molecular level how continuums exist between two very discrete variables,» Alvarado says in a university statement.
“We were working with ants,” he adds, “but it was a bit like discovering that we could create shorter or taller human beings.” The findings could one day help researchers influence how much (or how little) of a gene gets expressed, potentially limiting the growth of cancer cells or our different tendencies to develop certain diseases.