Superfund Research Program
Mechanisms and Impacts of PCB Resistant Fish
Project Leader: Mark E. Hahn (Woods Hole Oceanographic Institution)
Co-Investigators: Sibel I. Karchner (Woods Hole Oceanographic Institution), Neelakanteswar Aluru (Woods Hole Oceanographic Institution)
Grant Number: P42ES007381
Funding Period: 1995-2020
This year Mark Hahn, Ph.D., Sibel Karchner, Ph.D, Neel Aluru and colleagues provided new insights into the impact of long-term exposure to Superfund chemicals on natural populations, including the mechanisms involved in evolutionary adaptation of fish to extraordinarily high levels of PCBs in New Bedford Harbor. The researchers and their collaborators sequenced the genome of the Atlantic killifish (Fundulus heteroclitus) (Reid et al. 2017). Subsequently, they sequenced whole genomes of 43-50 individual fish from each of eight populations, including four populations of PCB-tolerant fish at Superfund sites. Genomic and transcriptomic analyses identified the aryl hydrocarbon receptor (AHR)-based signaling pathway as a key target of selection in all four tolerant populations (Reid et al. 2016). Four AHRs, AHR-interacting protein (AIP), and the AHR target gene CYP1A were shared targets of selection. However, distinct molecular variants contributed to adaptation in the different populations. There was also selection in signaling pathways connected to the AHR pathway, suggesting compensatory adaptations (Whitehead et al 2017). To better understand the function of AHRs and AIP, the researchers continued their efforts to use CRISPR-Cas9 to generate loss-of-function mutants in killifish and zebrafish. Additional studies characterized killifish genes involved in the response to hypoxia (low oxygen) (Townley et al. 2016) and examined the risk to terns feeding near the New Bedford Harbor Superfund site (Nacci et al. 2016). Overall, this research is helping to understand how natural populations of animals are affected by long-term exposure to toxic chemicals in the environment. The results illustrate the complex and extensive impact of exposure to mixtures of contaminants on the genetics of animal populations.