NSF Award
2420167
Water temperatures in the polar oceans can drop below the freezing point of animal tissues, resulting in the formation of ice crystals that can cause potentially fatal tissue damage. To survive in the frozen polar oceans, some fish species produce antifreeze proteins, which suppress the formation of ice crystals. These proteins must be maintained at high concentrations in the blood to be effective, but they are small enough to be filtered by the kidney and lost in urine. Their active re-absorption would be an energetically costly process. Antifreeze producing fishes have adapted to either seasonally or permanently disrupt the primary unit of filtration in the kidney, the glomerulus. Understanding how the vertebrate kidney responds to the need to maintain antifreeze proteins will address questions central to polar, evolutionary, biomedical, and developmental biology. This study aims to employ genomic techniques to discover the mechanisms that regulate seasonal changes to kidney morphology and function in several species of high latitude cod, a commercially and ecologically important group of polar fishes. Results will advance our fundamental understanding of how fishes have adapted to seasonally variable polar environments. Broader impacts of the project seek to enhance understanding of polar adaptation across multiple academic levels by improving undergraduate and K-12 STEM education and increase the participation of underrepresented populations in STEM.<br/><br/>The study system will focus on four ecologically important species of cod; the polar cod, Boreogadus saida, pacific cod, Gadus macrocephalus, walleye pollock, Gadus chalcogrammus, and saffron cod, Eleginus gracilis. Observation of seasonal changes to kidney morphology will be accomplished through histological inspection of kidney tissues from cods kept at 0°C (winter conditions) and 8°C (summer condition) at a NOAA cold water culture facility in Newport, Oregon. Seasonal cell-type specific changes in response to antifreeze protein production will be determined through gene expression patterns in the kidney of Eleginus using single-nucleus RNA sequencing. Reconstruction of the changes to cis-regulatory regions that enabled the evolution of seasonal polyphenism in Eleginus kidney will be accomplished using a combination of ATAC-seq and comparative evolutionary genetics. Candidate regulatory networks identified by the analyses will be modeled in zebrafish (Danio rerio). Bioinformatic pipelines, histological imagery, and molecular sequence data will be publicly posted and shared with the polar research community.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
