Meeting Abstract

59-7  Sunday, Jan. 5 14:30 – 14:45  Characterizing the Hypoxia-Inducible Factor-1 Pathway in Response to Acute Thermal Stress and Hypoxia in Antarctic Notothenioid Fishes RIX, AS*; O’BRIEN, KM; University of Alaska Fairbanks and Institute of Arctic Biology, Fairbanks, AK; University of Alaska Fairbanks and Institute of Arctic Biology, Fairbanks, AK asrix@alaska.edu

The master regulator of oxygen homeostasis in most metazoans is the transcription factor, hypoxia-inducible factor-1 (HIF-1), a heterodimer of HIF-1α and HIF-1β subunits. In Antarctic notothenioid fishes, HIF-1α has a polyglutamine/glutamic acid (polyQ/E) insert that varies in length with phylogeny and is longest in members of the most derived family, the Channichthyidae (icefishes), lacking hemoglobin. The impact of this insert on the function of HIF-1 is unknown. We sought to determine if the HIF-1 pathway is activated in hearts of the red-blooded notothenioid, Notothenia coriiceps, and the icefish, Chaenocephalus aceratus, in response to exposure to their critical thermal maximum (CT_MAX) or hypoxia of 5.0 mg L^-1 O₂ for two hours. Additionally, N. coriiceps was exposed to a longer, more severe hypoxia of 2.3 mg L^-1 O₂ for 12 hours. Levels of HIF-1α protein were quantified in nuclei using western blotting and mRNA levels of several genes regulated by HIF-1 were quantified using quantitative real-time PCR. Only severe hypoxia resulted in an increase of HIF-1α levels in N. coriiceps; despite this increase, mRNA levels of genes known to be regulated by HIF-1 did not increase. However, mRNA levels of lactate dehydrogenase-A decreased in C. aceratus exposed to mild hypoxia. Together, these results suggest that in notothenioids HIF-1α accumulates and translocates into the nucleus in response to hypoxia but may not transactivate gene expression.