White Blood Cells, Hurricanes, and the Monkeys of Cayo Santiago
Citizen scientists help monitor monkey immune cells, providing a foundation for future work on stress, sociality, and aging.
Hannah joined The Scientist as an assistant editor in 2023. She earned her PhD in neuroscience from the University of Washington in 2017 and completed the Dalla Lana Fellowship in Global Journalism in 2020.
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Just off the east coast of Puerto Rico lies the diminutive island of Cayo Santiago. The island boasts about 1,500 inhabitants and—since it is only 0.05 square miles—it is lucky that almost all of them are 15-pound monkeys.
All of these free-ranging rhesus macaques are descendants of animals brought over from India in 1938 to establish a behavioral research colony. When Julie Horvath, a comparative genomics researcher at the Renaissance Computing Institute, joined the group more than a decade ago, she hoped to study associations between genes and behaviors. “But now,” she said, “we’ve realized that this is really challenging, because there isn’t just one gene that controls one behavior.”
Horvath, along with several collaborators, then became interested in how gene expression patterns in blood changed as the monkeys aged and how environmental factors might affect these transcription profiles. Since neither red blood cells nor platelets have nuclei, these patterns largely reflect gene expression in the various types of white blood cells.
“But depending on which cells you have more of in your blood, you're going to have different genes turning on or off,” said Horvath. Therefore, researchers need to determine the proportions of these different cell types to help make sense of differences in gene expression changes measured in blood. With thousands of blood smear images for each monkey, researchers are enlisting the help of citizen scientists to categorize the different cell types via the Monkey Health Explorer project.
In 2022, the team published their findings on how exposure to Hurricane Maria accelerated aging-like changes in immune system gene expression.1 Now, said Horvath, they want to know whether factors like social connectedness can normalize these patterns, bringing them back in line with the monkeys’ chronological age. Understanding the factors that speed up or slow down age-related changes in gene expression could one day provide insights into healthy aging strategies for humans.
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- Watowich MM et al. Proc Natl Acad Sci USA. 2022;119(8):e2121663119.
