Ants provide "a natural system where there's a life span difference," Smith explains. "We can see where nature has leveraged these [epigenetic] pathways" to extend life.
In addition to questions of longevity, the genetic and epigenetic profiles of ants can provide interesting insights about metabolism. "Queens and workers have very different energy usage profiles," Smith notes. Ants' fat reserves seem to help determine behavior, he explains. "Worker ants don't have much to run on, so they run off to find more food." And because ants have insulin signaling pathways similar to those of humans, researchers might also be able to study crucial health issues such as metabolic syndrome and calorie use.
On a broader scale, drilling down into the ant genome could uncover some of the mechanisms of epigenetic shifts themselves. Environmental signals, such as the quality of food or ambient temperature, can influence how ants express different genes. "Those environmental signals get translated into higher or lower expression of a gene—and there's a big black box in the middle" that researchers are trying to crack open, Smith says.
Other ant genomes are slated for publication soon. And after working on a few of the forthcoming genomes, Smith thinks ants could be promising model organisms. Unlike genes of fruit flies, which have been common for genetic studies for decades, those of ants undergo DNA methylation, which is a key process by which many higher organisms, including mammals, regulate gene expression.
"Ants' true strength is an epigenetic system," Smith says. Mice also have a complex epigenetic profile, but they can be more troublesome for bigger studies because, as Smith notes of higher order experimental animals, "once you have a backbone, you have a lot of paperwork and expense."
In addition to cutting down on potential administrative headaches, ants draw particular interest because they are highly social organisms. "What we have been lacking," Smith notes "is a good invertebrate social model system" Although the honeybee genome was published in 2006, ants, he explains, "are a lot easier to keep in a lab."
But ants are by no means ideal. In fact, most species cannot be persuaded to reproduce in a laboratory setting. And Smith notes that he does not think the new paper with the two genome sequences "brings us any closer" to having a viable genetic ant model. This is in large part because H . saltator is "one of the very few species of ants that can stay alive and mate in the lab" and are currently only available for study in India, he notes.
Nevertheless, the new genomes show ants to be "a pretty great system to address epigenetic regulation," Berger says. And with a genetically modifiable ant, for instance, researchers could try knocking out a gene that regulates a life-extending enzyme (sirtuin) in female worker ants (a change noted in transition from worker to gamergate queen) to see if it might extend life span, she explains.
"It's going to take some time to fully exploit it as a model," Berger notes. She hopes, however, that someday soon, the ant model will provide a way to investigate the role of epigenetic change in development, longevity and behavior—a batch of attributes she calls the "triple whammy"—in insects as well as humans.
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