Prairie voles are humble creatures, slightly smaller than chipmunks, with dishwater-brown fur. But because of their highly social behavior, they offer a remarkable window into a complex universe of human traits and are ideal models for studying behavioral epigenetics, says UVA psychology professor Jessica Connelly. Ultimately, this research could help UVA scientists better understand why humans are susceptible to certain disorders of the brain and why humans differ in their range of social abilities.
Behavioral epigenetics explores how your cells read DNA when responding to the outside environment. Here’s how it works: Every cell in your body contains a complete set of your DNA that tells it what to do from the outset. But outside factors—including emotional stressors—can change how your cells decode that genetic information, even though the DNA code itself does not change. And some researchers believe that those extra-genetic changes—epigenetic tags or marks, on top of the DNA—can be carried down to future generations.
Connelly and her team work to define epigenetic marks that they can track easily in humans, through blood tests. She and her collaborator, fellow UVA psychology professor James Morris, published a paper last year in the Proceedings of the National Academy of Sciences on their work to identify such a tag in young adults. Their work aims to shed light on how the epigenome contributes to the way typical people respond to their social world, which will help the team better understand the epigenetic associations they’ve established with autism spectrum disorders, postpartum depression and schizophrenia.
But how does all of this connect to those little prairie voles? They have parenting and mating behaviors remarkably similar to those of humans. When pups receive substandard parental care, it plays out in their social behavior—and sets up epigenetic marks on particular genes.
Specifically, the UVA researchers measure oxytocin, the so-called love hormone that promotes bonding and feelings of contentment, and reduces anxiety. They found that voles raised by two parents who spend little time with them experience DNA methylation—picture it as a chemical cap placed on a DNA molecule—at the oxytocin receptor gene. “Methylation turns down the gene,” rendering it less effective, says Kelly Wroblewski (Grad ’20), a psychology Ph.D. candidate who works with Connelly. Those pups cannot properly process the hormone, causing them higher stress—and the malfunction continues into their adulthood, when they have trouble finding mates and can’t properly bond with or care for their own pups, researchers found.
For the gene that Connelly and Wroblewski study, humans have the same DNA methylation sites as do voles. “In humans, we look at how those sites vary by individual and relate that to how each person’s brain responds to different social stimuli,” Connelly says. “We have found that people who are low in DNA methylation at these sites actually attenuate their brain’s response to threatening stimuli. This could be part of the explanation for why some people are naturally very good in social situations and others just aren’t.”
Whether epigenetic marks can be passed down to the next generation is a matter of impassioned debate among researchers, but some scientists theorize that, say, a trauma experienced by your great-grandmother could be locked in your own cellular library, making you more susceptible to depression, anxiety or any number of fear responses.
Connelly suspects that epigenetic modifications are inherited in some form, “though how this happens is still contentious,” she says. Although epigenetics has been around for more than half a century, the research has exploded in the past decade. “It’s a very young field,” she says. “There is still a lot to learn.”