BAR HARBOR, MAINE – A team of scientists that includes senior staff scientist Ben King and visiting faculty members at the MDI Biological Laboratory has identified the genes and regulatory networks that enable organisms to alter themselves physically in response to changes in their environment.
The paper was published in the journal Molecular Biology and Evolution and was named one of the “papers of the month” by the National Institute of Environmental Health Sciences.
“By furthering our knowledge of how organisms adapt to changing environments, our findings have implications for how we understand molecular evolution and areas of science ranging from climate change to medicine,” says King. “The results are particularly relevant to the fields of regeneration and wound healing, where cells often must change their identity and function to create healthy new tissue.”
The research team studied how the Atlantic killifish, a common, small fish, modifies its gills to live in freshwater or saltwater. While some of the structures used to maintain salt balance were already known, this new study sheds light on how the killifish coordinates the many changes necessary for their gills to transition from one form to the other.
The team found a surprising level of uniformity among individual fish in the genetic response to changing salinity, indicating that the genes and regulatory networks involved have been tightly controlled by evolutionary processes. Among populations of killifish that are less likely to encounter changes in salinity—that live, for example, at the salty mouth of a bay as opposed to the tidal estuaries where fresh and salt water mingle—the regulatory networks, no longer so necessary for survival, were less tightly controlled.
Joe Shaw, Ph.D., associate professor at the School of Public and Environment Affairs at Indiana University, led the study along with co-author Bruce Stanton, Ph.D., professor of microbiology and immunology at the Geisel School of Medicine at Dartmouth. Both Shaw and Stanton are members of the MDI Biological Laboratory’s visiting faculty. Shaw and co-author John Colbourne, Ph.D., chair of environmental genomics at the University of Birmingham, UK, are co-directors of the environmental genomics course at the MDI Biological Laboratory. The study’s other co-authors have participated in the environmental genomics course or conducted research at the MDI Biological Laboratory.
To track changes in genetic activity during the study, the researchers added arsenic to the fish’s water. Previous studies of fish living in polluted environments had demonstrated that arsenic interferes with the fish’s ability to adapt to changing levels of salinity. Stanton and Shaw conducted some of those studies at the Callahan Mine Superfund site in Brooksville, Maine. Using arsenic provided a point of contrast with fish in untreated water.
Follow-up research planned by the study’s authors demonstrate the wide applicability of this study’s findings. Stanton, who is also director of the Dartmouth Toxic Metals Superfund Research Program and the Dartmouth Lung Biology Center, will study the effect of arsenic on immune response and lung disease. Shaw will conduct experiments involving populations of killifish that evolved under different conditions in order to increase our understanding of species that can withstand changes in their environment, including climate change. King is investigating the role microRNAs, small regulatory molecules, play in these adaptive mechanisms. MicroRNAs play a critical role in regeneration, and killifish are able to regenerate most of their tissues and organs.