Hypoxia factor (HIF-1): new insight into its physiological role and regulation in marine fish and snailsDoris Abele, Alfred-Wegener-Institute for Polar and Marine Research, Section: Shelf Sea Ecology, Am Handelshafen 12, 27570 Bremerhaven; Doris.Abele@awi.deThroughout the animal kingdom, hypoxia inducible factor has been recognized as a central regulator of gene transcription under severe oxygen deprivation. Discovered in 1995 by Wang & Semenza as the protein inducing erythropoietin expression under hypoxia, HIFs are now recognized as a highly conserved basic-helix-loop-helix (bHLH)/PAS1 transcription factor family that confers multifaceted adaptive responses to cellular oxygen shortage on the level of gene expression. HIF is a heterodimer, composed of a HIF-α and a HIF-ß (=ARNT) subunit. HIF-α is degraded in an oxygen dependent manner in mammalian cells above 1 kPa (1% oxygen) tissue po2. Interestingly, in fish HIF-expression seems to be constitutive in various tissues, and in isolated trout hepatocytes HIF-α stabilized at po2 levels as high as 5 kPa, i.e. way into the normoxic range for liver cells. Therefore, fish-HIF-researchers are now discussing alternative roles for hypoxia factor in fish, and generally for marine ectotherms, which involve response to cooling and cobalt. In my talk I will present results from recent studies of hypoxia inducible factor in polar and Antarctic eelpout (Aalmuttern) exposed in vivo to acute and prolonged cooling and warming. I will talk about the biochemical changes occurring in the liver of the fish under conditions of HIF induction and under conditions in which the response is abrogated during acute heat stress. A main focus in our work was on whether or not reactive oxygen species are involved in HIF-α subunit regulation in fish, and I will give my current view of possible HIF-ROS interactions. Further, I will present conspicuous changes in HIF-1α sequences in eurythermal, stenothermal and high Antarctic fish on a latitudinal cline and summarize methods and tools available in our lab for the investigation of HIF expression and function in ectotherms. I should like to shortly present our on-going research on HIF function in Antarctic limpets.