The two species were chosen for comparison because of their marked differences in behavioral structure. "Harpegnathos is more primitive and Camponotus is more advanced in terms of social organization," explains Berger. "Camponotus has different worker castes that specialize their behavior and Harpegnathos has only one worker caste, but those workers have plasticity in their fertility." When a Harpegnathos queen dies, other worker ants can actually transform and take over her role, preserving the colony, while the death of a Camponotus queen means the end of that particular colony. The group believes that comparing the flexibility of the less specialized, less advanced Harpegnathos with the more rigid, specialized Camponotus will provide a way of determining whether such changes are controlled by epigenetic modifications.
Citing entomologist E. O. Wilson's observation that an ant colony can be viewed as a single "superorganism," Berger compares the different castes of species to human cell differentiation, the processes that determine whether an embryonic stem cell ultimately becomes, for example, a liver cell rather than a neuron in the brain. "It's these epigenetic changes that are regulating, in part, all of these different cell types in our bodies. The ants -- the different castes -- are the same genome, so there must be epigenetic regulation. "
Within that genome, the researchers found all of the gene families that correspond to major epigenetic regulators in mammals. "This makes ants an excellent model for studying epigenetic regulatory mechanisms," says Berger.
Co-author Reinberg studied the ants' DNA methylation levelsa key epigenetic mechanism that changes DNA expression and found that the more primitive Harpegnathos has lower levels of DNA methylation than the more advanced Camponotus. Studying the ant genomes, the research team also found genes corresponding to enzymes that chemic
|Contact: Karen Kreeger|
University of Pennsylvania School of Medicine