In many human societies, socioeconomic status is a strong predictor of health, even when controlling for tangible factors such as healthcare, smoking, and nutrition. It has been proposed that the psychological stress of being low-ranking in society could induce health problems. Among other things, my lab is interested in the biological pathway or pathways that link social status and health.
Studying these trends in animals can be useful because many of the previously mentioned factors, like smoking and healthcare, are controlled. It has been shown that, in many species of primates, low-ranking animals have higher levels of stress-related hormones than high-ranking animals.
So what’s the link between stress and health? One path might be through the amount of mitochondrial DNA, or mtDNA, in an individual’s somatic cells. A recent study found that subjecting mice to stress-inducing things like “foot shock” and “tail suspension” (!!!) increased the amount of mtDNA in their cells. A related study on humans found that subjects with major depression had higher levels of mtDNA than healthy subjects. My project is to investigate mtDNA levels in relation to social rank in rhesus macaques.
I don’t get to work with the macaques, unfortunately, but other members of the lab set up social groups at the Yerkes National Primate Research Center in Georgia. It has been found that order of introduction in a social group strongly predicts the eventual rank of a female macaque, so the lab was effectively able to “randomize” the ranks of the subjects. Each social group of five female macaques established a stable dominance hierarchy. The lab collected DNA samples from each macaque and then shuffled the groups around so that each macaque was in a group with four new group members. Once the new groups had stabilized, the lab collected another round of DNA samples.
My job is to conduct quantitative PCR, or qPCR, on the DNA samples. I obtain a cycle threshold value for each sample, which is an indicator of how much DNA was in the sample to begin with. I’ll calculate a ratio of mitochondrial DNA to nuclear DNA for each sample, because we don’t know exactly how many cells are in each sample, but we do know that each cell has one nucleus. And I’ll see if there is any relationship between an individual macaque’s social rank and the amount of mtDNA in its cells.
