Göran Erik Nilsson

• Lau, Gigi Yik Chee; Gerber, Lucie; Johansen, Anette; Dahl, Helge Andre; Torp, May-Kristin & Bates, Georgina [Show all 11 contributors for this article] (2026). Mitochondrial responses to anoxia-reoxygenation exposure in crucian carp (Carassius carassius). Journal of Experimental Biology. ISSN 0022-0949. 229(4). doi: 10.1242/jeb.251839. Full text in Research Archive
• Winklhofer, Magdalena; Nilsson, Göran Erik & Lefevre, Sjannie (2026). Long non-coding RNA transcripts in crucian carp brain – annotation and expression patterns in anoxia and reoxygenation. RNA Biology. ISSN 1547-6286. 23(1), p. 1–21. doi: 10.1080/15476286.2026.2643366. Full text in Research Archive Show summary

  Long non-coding RNA transcripts (lncRNAs) are important regulators of various cellular processes, including gene expression. However, whether they are involved in the regulation of anoxia-induced transcriptomic changes in crucian carp ( Carassius carassius ), a species that can survive without oxygen for months at low temperatures, has remained unexplored. The existing genome annotation includes mainly protein-coding genes, which are more straightforward to annotate than the lower-expressed lncRNAs. Therefore, this study aimed to annotate lncRNAs in the crucian carp genome, investigate their potential involvement in regulating mRNA abundance in response to anoxia and reoxygenation, and further characterize any differentially regulated lncRNAs and their potential interaction partners (nearby genes). Using next-generation RNA sequencing of brain samples from crucian carp across normoxia, anoxia, and reoxygenation conditions (n=10 per group), 145,264 transcripts were assembled with a reference-guided approach. Using the bioinformatic tools CPC2, CNCI, CPAT, and FEELnc, we identified 6,072 lncRNAs among the assembled transcripts. We observed a substantial transcriptomic response to anoxia, with a total of 56,440 differentially expressed (DE) transcripts (adjusted p-value < 0.05; | log2(fold change)| > 0.38), including 1,321 lncRNAs. The FEELnc classification module identified multiple proximal RNA transcripts that may help to predict lncRNA functions, and due to their proximity to potential interaction partners (IPs), were likely cis -acting. Most (60%) of the interaction sites between DElncRNAs and their targets were located between genes (intergenic), predominantly on the same strand in intergenic subtypes, and primarily nested in the genic context. The log2-fold changes in RNA abundance of DE predicted IPs exhibited a positive correlation with the log2-fold changes of their corresponding DElncRNAs. These findings indicate that lncRNAs are at least co-expressed with and may regulate transcription of specific genes in crucian carp during anoxia and reoxygenation.

• Scott, Mark Adam; Fagernes, Cathrine Elisabeth; Nilsson, Göran Erik & Stensløkken, Kåre-Olav (2024). Maintained mitochondrial integrity without oxygen in the anoxia-tolerant crucian carp. Journal of Experimental Biology. ISSN 0022-0949. 227(20). doi: 10.1242/jeb.247409. Full text in Research Archive Show summary

  Very few vertebrates survive without oxygen (anoxia) for more than a few minutes. Crucian carp (Carassius carassius) are one example, surviving months of anoxia at low temperatures, and we hypothesised that they maintain mitochondrial membrane potential and function. Isolated crucian carp cardiomyocytes indeed maintained mitochondrial membrane potential after blocking complex IV of the electron transport system with cyanide, while those of anoxia-intolerant trout depolarised. When complexes I–III were inhibited, crucian carp mitochondria depolarised, indicating that these complexes need to function during anoxia. Mitochondrial membrane potential depended on reversal of ATP synthase in chemical anoxia, as blocking with cyanide combined with oligomycin to inhibit ATP synthase led to depolarisation. ATP synthase activity was reduced in the heart after 1 week of anoxia in crucian carp, together with a downregulation of ATP synthase subunit gene expression. However, the morphology of cardiac mitochondria was not affected by 1 week of anoxia, even with a large increase in mitofusin 2 mRNA expression. Cardiac citrate synthase activity was not affected by anoxia, while cytochrome c oxidase activity was increased. We show how mitochondria respond to anoxia. A mechanistic understanding of how mitochondrial function can be maintained in anoxia may provide new perspectives to reduce mitochondrial damage in anoxia-sensitive organisms.

• Johansen, Anette; Thiede, Bernd; Anonsen, Jan Haug & Nilsson, Göran Erik (2024). Phosphoproteomic changes in response to anoxia are tissue-specific in the anoxia-tolerant crucian carp (Carassius carassius). Frontiers in Physiology. 15. doi: 10.3389/fphys.2024.1407834. Full text in Research Archive Show summary

  Crucian carp (Carassius carassius), a freshwater fish, can survive chronic anoxia for several months at low temperatures. Consequently, anoxia-related physiological and biochemical adaptations in this species have been studied for more than half a century. Still, despite for the well-known role of protein phosphorylation in regulating cellular processes, no studies have comprehensively characterized the phosphoproteome in crucian carp. In this study, we report the global phosphoproteome in crucian carp brain and liver during anoxia and reoxygenation. By applying a bottom-up proteomic approach on enriched phosphopeptides we found that the brain phosphoproteome shows surprisingly few changes during anoxia-reoxygenation exposure with only 109 out of 4200 phosphopeptides being differentially changed compared to normoxic controls. By contrast, in the liver 395 out of 1287 phosphopeptides changed. Although most changes occurred in the liver phosphoproteome, the pattern of changes indicated metabolic depression and decreased translation in both brain and liver. We also found changes in phosphoproteins involved in apoptotic regulation and reactive oxygen species handling in both tissues. In the brain, some of the most changed phosphopeptides belonged to proteins involved in central nervous system development and neuronal activity at the synaptic cleft. Changed phosphoproteins specific for liver tissue were related to glucose metabolism, such as glycolytic flux and glycogenolysis. In conclusion, protein phosphorylation in response to anoxia and reoxygenation showed both common and tissue-specific changes related to the functional differences between brain and liver.

• Gerber, Lucie; Torp, May-Kristin; Nilsson, Göran Erik; Lefevre, Sjannie & Stensløkken, Kåre-Olav (2024). Differential production of mitochondrial reactive oxygen species between mouse (Mus musculus) and crucian carp (Carassius carassius). Acta Physiologica. ISSN 1748-1708. 240(12). doi: 10.1111/apha.14244. Full text in Research Archive Show summary

  Aim In most vertebrates, oxygen deprivation and subsequent re-oxygenation are associated with mitochondrial impairment and excess production of reactive oxygen species (ROS) like hydrogen peroxide (H2O2). This in turn triggers a cascade of cell-damaging events in a temperature-dependent manner. The crucian carp (Carassius carassius) is one of few vertebrates that survives months without oxygen at cold temperatures and overcomes oxidative damage during re-oxygenation periods. Mitochondria of this anoxia-tolerant species therefore serve as an excellent model in translational research to study adaptation and resilience to low oxygen conditions and thermal variability. Methods Here, we used high-resolution respirometry on isolated mitochondria from hearts of crucian carp and the anoxia-intolerant mouse (Mus musculus), at 37 and 8°C; two temperatures relevant for transplantation medicine (i.e., graft preservation and subsequent rewarming). Results We find: (1) a striking difference in H2O2 release between the two species at 37°C despite comparable mitochondrial efficiency and capacity, (2) a massive H2O2 release after inhibition of complex V in mouse at 37°C that is absent in crucian carp, and prevented in mouse by incubation at 8°C or uncoupling with a protonophore at 37°C, and (3) indications that differences in mitochondrial complex I and II capacity and thermal sensitivity influence the release of mitochondrial H2O2 relative to respiration. Conclusion Our findings provide comparative insights into a spectrum of mitochondrial adaptations in vertebrates and the importance of thermal variability. Furthermore, the species- and temperature-related changes associated with mitochondria highlighted in this study may help identify mitochondria-based targets for translational medicine.

• Johansen, Anette; Thiede, Bernd; Anonsen, Jan Haug & Nilsson, Göran Erik (2023). Surviving without oxygen involves major tissue specific changes in the proteome of crucian carp (Carassius carassius). PeerJ. 11, p. 1–28. doi: 10.7717/peerj.14890. Full text in Research Archive Show summary

  The crucian carp ( Carassius carassius ) can survive complete oxygen depletion (anoxia) for several months at low temperatures, making it an excellent model for studying molecular adaptations to anoxia. Still, little is known about how its global proteome responds to anoxia and reoxygenation. By applying mass spectrometry-based proteome analyses on brain, heart and liver tissue from crucian carp exposed to normoxia, five days anoxia, and reoxygenation, we found major changes in particularly cardiac and hepatic protein levels in response to anoxia and reoxygenation. These included tissue-specific differences in mitochondrial proteins involved in aerobic respiration and mitochondrial membrane integrity. Enzymes in the electron transport system (ETS) decreased in heart and increased massively in liver during anoxia and reoxygenation but did not change in the brain. Importantly, the data support a special role for the liver in succinate handling upon reoxygenation, as suggested by a drastic increase of components of the ETS and uncoupling protein 2, which could allow for succinate metabolism without excessive formation of reactive oxygen species (ROS). Also during reoxygenation, the levels of proteins involved in the cristae junction organization of the mitochondria changed in the heart, possibly functioning to suppress ROS formation. Furthermore, proteins involved in immune (complement) system activation changed in the anoxic heart compared to normoxic controls. The results emphasize that responses to anoxia are highly tissue-specific and related to organ function.

• Gerber, Lucie Claire Lola; Resseguier, Julien Alain Andre; Helle-Valle, Tellef; Farhat, Elie; Nilsson, Göran Erik & Nilsson, Sjannie Lefevre (2023). Expression of prolyl hydroxylase domains, the upstream regulators of HIF, in the brain of the anoxia-tolerant crucian carp during anoxia-reoxygenation. American Journal of Physiology. Regulatory Integrative and Comparative Physiology. ISSN 0363-6119. 326(2), p. R184–R195. doi: 10.1152/ajpregu.00211.2023. Full text in Research Archive Show summary

  We report a profound upregulation of most egln paralog mRNA levels in anoxia and upon reoxygenation, with egln3ii showing the largest, a 17-fold increase, and highest relative mRNA abundance. The relative abundance of prolyl hydroxylase domain (PHD) proteins was maintained during anoxia and increased at reoxygenation. PHD immunoreactivity was localized to axonal branches with region-specific changes during anoxia-reoxygenation. These dynamic and regional changes in crucian carp, champion of anoxia tolerance, are most likely adaptive and call for further mechanistic studies.

• Lefevre, Sjannie & Nilsson, Göran E. (2023). Two decades of research on anoxia tolerance – mitochondria, -omics and physiological diversity. Journal of Experimental Biology. ISSN 0022-0949. 226(7), p. 1–10. doi: 10.1242/jeb.245584. Full text in Research Archive Show summary

  Just over two decades ago, Bob Boutilier published a much-cited Review in this journal on the mechanisms of cell survival in hypoxia and hypothermia. Here, we celebrate this important Review by describing how our knowledge of the mechanisms behind anoxia tolerance have progressed since 2001, including new key roles of mitochondria, something Boutilier had started exploring. Evidence now suggests that, in anoxia-tolerant brains, mitochondria initiate responses aimed at suppressing electrical activity and energy use. These responses are largely dependent on gamma-aminobutyric acid (GABA) release. Animals that survive anoxia must also tolerate reoxygenation – a major challenge that could cause a massive production of damaging reactive oxygen species (ROS). Here, the handling of succinate, which builds up during anoxia, is critical. Interestingly, there are clear species differences in succinate handling among anoxia-tolerant vertebrates (Trachemys and Chrysemys turtles and crucian carp, Carassius carassius). Trachemys turtles suppress succinate build-up during anoxia, presumably to limit ROS production during reoxygenation. By contrast, in crucian carp, reduction of fumarate to succinate during anoxia appears to be essential for keeping their mitochondria charged and viable. Consequently, during anoxia, crucian carp accumulate much more succinate than Trachemys turtles. Moreover, during anoxia, succinate is apparently transported from crucian carp brain and heart to the liver, which handles succinate upon reoxygenation. This is one example of the striking physiological diversity among vertebrates that survive long-term anoxia. More examples are given, and we argue that -omics approaches are, and will be, helpful in providing new insight and moving the field forward.

• Downie, Adam T.; Lefevre, Sjannie; Illing, Björn; Harris, Jessica; Jarrold, Michael D. & McMcormick, Mark I. [Show all 8 contributors for this article] (2023). Rapid physiological and transcriptomic changes associated with oxygen delivery in larval anemonefish suggest a role in adaptation to life on hypoxic coral reefs. PLoS Biology. ISSN 1544-9173. 21(5), p. 1–28. doi: 10.1371/journal.pbio.3002102. Full text in Research Archive Show summary

  Connectivity of coral reef fish populations relies on successful dispersal of a pelagic larval phase. Pelagic larvae must exhibit high swimming abilities to overcome ocean and reef currents, but once settling onto the reef, larvae transition to endure habitats that become hypoxic at night. Therefore, coral reef fish larvae must rapidly and dramatically shift their physiology over a short period of time. Taking an integrative, physiological approach, using swimming respirometry, and examining hypoxia tolerance and transcriptomics, we show that larvae of cinnamon anemonefish ( Amphiprion melanopus ) rapidly transition between “physiological extremes” at the end of their larval phase. Daily measurements of swimming larval anemonefish over their entire early development show that they initially have very high mass-specific oxygen uptake rates. However, oxygen uptake rates decrease midway through the larval phase. This occurs in conjunction with a switch in haemoglobin gene expression and increased expression of myoglobin, cytoglobin, and neuroglobin, which may all contribute to the observed increase in hypoxia tolerance. Our findings indicate that critical ontogenetic changes in the gene expression of oxygen-binding proteins may underpin the physiological mechanisms needed for successful larval recruitment to reefs.

• Dahl, Helge-Andre; Johansen, Anette; Nilsson, Göran Erik & Lefevre, Sjannie (2021). The Metabolomic Response of Crucian Carp (Carassius carassius) to Anoxia and Reoxygenation Differs between Tissues and Hints at Uncharacterized Survival Strategies. Metabolites. 11(7), p. 1–26. doi: 10.3390/metabo11070435. Full text in Research Archive Show summary

  The anoxia-tolerant crucian carp (Carassius carassius) has been studied in detail for numerous years, with particular focus on unravelling the underlying physiological mechanisms of anoxia tolerance. However, relatively little work has been focused on what occurs beyond anoxia, and often the focus is a single organ or tissue type. In this study, we quantified more than 100 metabolites by capillary electrophoresis-mass spectrometry (CE-MS) in brain, heart, liver, and blood plasma from four experimental groups, being normoxic (control) fish, anoxia-exposed fish, and two groups that had been exposed to anoxia followed by reoxygenation for either 3 h or 24 h. The heart, which maintains cardiac output during anoxia, unexpectedly, was slower to recover compared to the brain and liver, mainly due to a slower return to control concentrations of the energy-carrying compounds ATP, GTP, and phosphocreatine. Crucian carp accumulated amino acids in most tissues, and also surprisingly high levels of succinate in all tissues investigated during anoxia. Purine catabolism was enhanced, leading to accumulation of uric acid during anoxia and increasing urea formation that continued into 24 h of reoxygenation. These tissue-specific differences in accumulation and distribution of the metabolites may indicate an intricate system of transport between tissues, opening for new avenues of investigation of possible mechanisms aimed at reducing the generation of reactive oxygen species (ROS) and resultant tissue damage during reoxygenation.

• Munday, Philip L.; Dixson, Danielle L.; Welch, Megan J; Chivers, Douglas P.; Domenici, Paolo & Grosell, Martin [Show all 13 contributors for this article] (2020). Methods matter in repeating ocean acidification studies. Nature. ISSN 0028-0836. 586, p. E20–E24. doi: 10.1038/s41586-020-2803-x. Full text in Research Archive
• Melleby, Arne Olav; Sandvik, Guro Katrine; Couturier, Christine Stephanie; Nilsson, Göran Erik & Stecyk, Jonathan Anthony William (2020). H2S-producing enzymes in anoxia-tolerant vertebrates: Effects of cold acclimation, anoxia exposure and reoxygenation on gene and protein expression. Comparative Biochemistry and Physiology - Part B: Biochemistry & Molecular Biology. ISSN 1096-4959. 243-244. doi: 10.1016/j.cbpb.2020.110430. Full text in Research Archive
• Thomsen, Mikkel T; Lefevre, Sjannie; Nilsson, Göran Erik; Wang, Tobias & Bayley, Mark (2019). Effects of lactate ions on the cardiorespiratory system in rainbow trout (Oncorhynchus mykiss). American Journal of Physiology. Regulatory Integrative and Comparative Physiology. ISSN 0363-6119. 316(5), p. R607–R620. doi: 10.1152/ajpregu.00395.2018. Full text in Research Archive Show summary

  Lactate ions are involved in several physiological processes, including a direct stimulation of the carotid body, causing increased ventilation in mammals. A similar mechanism eliciting ventilatory stimulation in other vertebrate classes has been demonstrated, but it remains to be thoroughly investigated. Here, we investigated the effects of lactate ions on the cardiorespiratory system in swimming rainbow trout by manipulating the blood lactate concentration. Lactate elicited a vigorous, dose-dependent elevation of ventilation and bradycardia at physiologically relevant concentrations at constant pH. After this initial confirmation, we examined the chiral specificity of the response and found that only l-lactate induced these effects. By removal of the afferent inputs from the first gill arch, the response was greatly attenuated, and a comparison of the responses to injections up- and downstream of the gills collectively demonstrated that the lactate response was initiated by branchial cells. Injection of specific receptor antagonists revealed that a blockade of serotonergic receptors, which are involved in the hypoxic ventilatory response, significantly reduced the lactate response. Finally, we identified two putative lactate receptors based on sequence homology and found that both were expressed at substantially higher levels in the gills. We propose that lactate ions modulate ventilation by stimulating branchial oxygen-sensing cells, thus eliciting a cardiorespiratory response through receptors likely to have originated early in vertebrate evolution.

• Vindas, Marco; Helland-Riise, Siri Helene; Nilsson, Göran Erik & Øverli, Øyvind (2019). Depression-like state behavioural outputs may confer beneficial outcomes in risky environments. Scientific Reports. 9, p. 1–8. doi: 10.1038/s41598-019-40390-3. Full text in Research Archive Show summary

  Recent theories in evolutionary medicine have suggested that behavioural outputs associated with depression-like states (DLS) could be an adaptation to unpredictable and precarious situations. In animal models, DLS are often linked to diverse and unpredictable stressors or adverse experiences. Theoretically, there are a range of potential fitness benefits associated with behavioural inhibition (typical to DLS), as opposed to more active/aggressive responses to adverse or uncontrollable events. This stance of evolutionary medicine has to our knowledge not been tested empirically. Here we address a possible key benefit of behavioural inhibition in a comparative model for social stress (territorial rainbow trout). By treating fish with the fast-acting antidepressant ketamine, we reversed the behavioural inhibition (i.e. stimulated an increase in activity level) in subordinate fish. During confrontation with a previously unfamiliar larger, aggressive and dominant individual, this increase in activity led to higher amounts of received aggression compared to sham-treated subordinates. This suggests that the behavioural inhibition characterizing animal models of DLS is indeed an effective coping strategy that reduces the risk of injuries in vulnerable social situations.

• Schunter, Celia; Rawasi, Timothy; Munday, Philip L. & Nilsson, Göran Erik (2019). Neural effects of elevated CO2 in fish may be amplified by a vicious cycle. Conservation Physiology. 7(1), p. 1–8. doi: 10.1093/conphys/coz100. Full text in Research Archive Show summary

  Lay summaries: The altered behaviours of fish exposed to elevated CO2 have been linked to changes in ion gradients and neurotransmitter function. To explain how relatively small changes in ion concentrations could have such profound neural effects, we propose that a vicious cycle can be triggered that amplifies the initial disturbance.

• Heuer, Rachael M.; Hamilton, Trevor J. & Nilsson, Göran Erik (2019). The physiology of behavioral impacts of high CO2. In Grosell, Martin; Munday, Philip L.; Farrell, P. & Brauner, Colin J. (Ed.), Carbon Dioxide. Elsevier. ISSN 9780128176092. p. 161–194. doi: 10.1016/bs.fp.2019.08.002. Full text in Research Archive
• Couturier, Christine Stephanie; Stecyk, Jonathan Anthony William; Ellefsen, Stian; Sandvik, Guro Katrine; Milton, Sarah L. & Prentice, Howard M. [Show all 7 contributors for this article] (2019). The expression of genes involved in excitatory and inhibitory neurotransmission in turtle (Trachemys scripta) brain during anoxic submergence at 21°C and 5°C reveals the importance of cold as a preparatory cue for anoxia survival. Comparative Biochemistry and Physiology - Part D:Genomics and Proteomics. ISSN 1744-117X. 30, p. 55–70. doi: 10.1016/j.cbd.2018.12.010. Full text in Research Archive Show summary

  We investigated if transcriptional responses are consistent with the arrest of synaptic activity in the anoxic turtle (Trachemys scripta) brain. Thirty-nine genes of key receptors, transporters, enzymes and regulatory proteins of inhibitory and excitatory neurotransmission were partially cloned and their expression in telencephalon of 21 °Cand 5 °C-acclimated normoxic, anoxic (24 h at 21 °C; 1 and 14 days at 5 °C) and reoxygenated (24 h at 21 °C; 13 days at 5 °C) turtles quantified by real-time RT-PCR. Gene expression was largely sustained with anoxia at 21 °C and 5 °C. However, the changes in gene expression that did occur were congruous with the decline in glutamatergic activity and the increase in GABAergic activity observed at cellular and whole organism levels. Moreover, at 21 °C, the alterations in gene expression with anoxia induced a distinct gene expression pattern compared to normoxia and reoxygenation. Strikingly, acclimation from 21 °C to 5 °C in normoxia effectuated substantial transcriptional responses. Most prominently, 56% of the excitatory neurotransmission genes were down-regulated, including most of the ones encoding the subunits composing excitatory N-methyl-D-aspartate (NMDA) and 3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) glutamate receptors. By contrast, only 26% of the inhibitory neurotransmission genes were down-regulated. Consequently, the gene expression pattern of 5 °C normoxic turtles was statistically distinct compared to that of 21 °C normoxic turtles. Overall, this study highlights that key transcriptional responses are consonant with the synaptic arrest that occurs in the anoxic turtle brain. In addition, the findings reveal that transcriptional remodelling induced by decreased temperature may serve to precondition the turtle brain for winter anoxia.

• Lefevre, Sjannie; McKenzie, David J. & Nilsson, Göran Erik (2018). In modelling effects of global warming, invalid assumptions lead to unrealistic projections. Global Change Biology. ISSN 1354-1013. 24(2), p. 553–556. doi: 10.1111/gcb.13978. Full text in Research Archive Show summary

  2017) provide new projections of future maximum fish weight (W∞). Based on criticism by Lefevre et al. (2017) they changed the scaling exponent for anabolism, dG. Here we find that changing both dG and the scaling exponent for catabolism, b, leads to the projection that fish may even become 98% smaller with a 1°C increase in temperature. This unrealistic outcome indicates that the current W∞ is unlikely to be explained by the Gill‐Oxygen Limitation Theory (GOLT) and, therefore, GOLT cannot be used as a mechanistic basis for model projections about fish size in a warmer world.

• Schunter, Celia; Welch, Megan J; Nilsson, Göran Erik; Rummer, Jodie L.; Munday, Philip L. & Ravasi, Timothy (2018). An interplay between plasticity and parental phenotype determines impacts of ocean acidification on a reef fish. Nature Ecology and Evolution. 2(2), p. 334–342. doi: 10.1038/s41559-017-0428-8. Full text in Research Archive
• Riggs, Claire L.; Summers, Amanda; Warren, Daniel E.; Nilsson, Göran Erik; Lefevre, Sjannie & Dowd, Wesley W. [Show all 8 contributors for this article] (2018). Small non-coding RNA expression and vertebrate anoxia tolerance. Frontiers in Genetics. 9:230, p. 1–22. doi: 10.3389/fgene.2018.00230. Full text in Research Archive Show summary

  Background: Extreme anoxia tolerance requires a metabolic depression whose modulation could involve small non-coding RNAs (small ncRNAs), which are specific, rapid, and reversible regulators of gene expression. A previous study of small ncRNA expression in embryos of the annual killifish Austrofundulus limnaeus, the most anoxia-tolerant vertebrate known, revealed a specific expression pattern of small ncRNAs that could play important roles in anoxia tolerance. Here, we conduct a comparative study on the presence and expression of small ncRNAs in the most anoxia-tolerant representatives of several major vertebrate lineages, to investigate the evolution of and mechanisms supporting extreme anoxia tolerance. The epaulette shark (Hemiscyllium ocellatum), crucian carp (Carassius carassius), western painted turtle (Chrysemys picta bellii), and leopard frog (Rana pipiens) were exposed to anoxia and recovery, and small ncRNAs were sequenced from the brain (one of the most anoxia-sensitive tissues) prior to, during, and following exposure to anoxia. Results: Small ncRNA profiles were broadly conserved among species under normoxic conditions, and these expression patterns were largely conserved during exposure to anoxia. In contrast, differentially expressed genes are mostly unique to each species, suggesting that each species may have evolved distinct small ncRNA expression patterns in response to anoxia. Mitochondria-derived small ncRNAs (mitosRNAs) which have a robust response to anoxia in A. limnaeus embryos, were identified in the other anoxia tolerant vertebrates here but did not display a similarly robust response to anoxia. Conclusion: These findings support an overall stabilization of the small ncRNA transcriptome during exposure to anoxic insults, but also suggest that multiple small ncRNA expression pathways may support anoxia tolerance, as no conserved small ncRNA response was identified among the anoxia-tolerant vertebrates studied. This may reflect divergent strategies to achieve the same endpoint: anoxia tolerance. However, it may also indicate that there are multiple cellular pathways that can trigger the same cellular and physiological survival processes, including hypometabolism.

• Boyd, Philip W.; Collins, Sinead; Dupont, Sam; Fabricius, Katharina; Gattuso, Jean-Pierre & Havenhand, Jonathan [Show all 21 contributors for this article] (2018). Experimental strategies to assess the biological ramifications of multiple drivers of global ocean change - A review. Global Change Biology. ISSN 1354-1013. 24(6), p. 2239–2261. doi: 10.1111/gcb.14102. Full text in Research Archive
• Nørstrud, Karoline Sletbak; Vindas, Marco; Nilsson, Göran Erik & Johansen, Ida Beitnes (2018). Short-term cortisol exposure alters cardiac hypertrophic and non-hypertrophic signalling in a time-dependent manner in rainbow trout. Biology Open. 7(12), p. 1–9. doi: 10.1242/bio.037853. Full text in Research Archive Show summary

  Cardiac disease is a growing concern in farmed animals, and stress has been implicated as a factor for myocardial dysfunction and mortality in commercial fish rearing. We recently showed that the stress hormone cortisol induces pathological cardiac remodelling in rainbow trout. Wild and farmed salmonids are exposed to fluctuations and sometimes prolonged episodes of increased cortisol levels. Thus, studying the timeframe of cortisol-induced cardiac remodelling is necessary to understand its role in the pathogenesis of cardiovascular disease in salmonids. We here establish that 3 weeks of cortisol exposure is sufficient to increase relative ventricular mass (RVM) by 20% in rainbow trout. Moreover, increased RVMs are associated with altered expression of hypertrophic and non-hypertrophic remodelling markers. Further, we characterised the time course of cortisol-induced cardiac remodelling by feeding rainbow trout cortisol-containing feed for 2, 7 and 21 days. We show that the effect of cortisol on expression of hypertrophic and non-hypertrophic remodelling markers is time-dependent and in some cases acute. Our data indicate that short-term stressors and life cycle transitions associated with elevated cortisol levels can potentially influence hypertrophic and non-hypertrophic remodelling of the trout heart.

• Fagernes, Cathrine Elisabeth; Stensløkken, Kåre-Olav; Kjendseth, Åsmund Røhr; Berenbrink, Michael; Ellefsen, Stian & Nilsson, Göran Erik (2017). Extreme anoxia tolerance in crucian carp and goldfish through neofunctionalization of duplicated genes creating a new ethanol- producing pyruvate decarboxylase pathway. Scientific Reports. doi: 10.1038/s41598-017-07385-4. Full text in Research Archive Show summary

  Without oxygen, most vertebrates die within minutes as they cannot meet cellular energy demands with anaerobic metabolism. However, fish of the genus Carassius (crucian carp and goldfish) have evolved a specialized metabolic system that allows them to survive prolonged periods without oxygen by producing ethanol as their metabolic end-product. Here we show that this has been made possible by the evolution of a pyruvate decarboxylase, analogous to that in brewer’s yeast and the first described in vertebrates, in addition to a specialized alcohol dehydrogenase. Whole-genome duplication events have provided additional gene copies of the pyruvate dehydrogenase multienzyme complex that have evolved into a pyruvate decarboxylase, while other copies retained the essential function of the parent enzymes. We reveal the key molecular substitution in duplicated pyruvate dehydrogenase genes that underpins one of the most extreme hypoxic survival strategies among vertebrates and that is highly deleterious in humans.

• Lefevre, Sjannie; McKenzie, David J. & Nilsson, Göran E. (2017). Models projecting the fate of fish populations under climate change need to be based on valid physiological mechanisms. Global Change Biology. ISSN 1354-1013. 23(9), p. 3449–3459. doi: 10.1111/gcb.13652. Full text in Research Archive Show summary

  Some recent modelling papers projecting smaller fish sizes and catches in a warmer future are based on erroneous assumptions regarding (i) the scaling of gills with body mass and (ii) the energetic cost of ‘maintenance’. Assumption (i) posits that insurmountable geometric constraints prevent respiratory surface areas from growing as fast as body volume. It is argued that these constraints explain allometric scaling of energy metabolism, whereby larger fishes have relatively lower mass-specific metabolic rates. Assumption (ii) concludes that when fishes reach a certain size, basal oxygen demands will not be met, because of assumption (i). We here demonstrate unequivocally, by applying accepted physiological principles with reference to the existing literature, that these assumptions are not valid. Gills are folded surfaces, where the scaling of surface area to volume is not constrained by spherical geometry. The gill surface area can, in fact, increase linearly in proportion to gill volume and body mass. We cite the large body of evidence demonstrating that respiratory surface areas in fishes reflect metabolic needs, not vice versa, which explains the large interspecific variation in scaling of gill surface areas. Finally, we point out that future studies basing their predictions on models should incorporate factors for scaling of metabolic rate and for temperature effects on metabolism, which agree with measured values, and should account for interspecific variation in scaling and temperature effects. It is possible that some fishes will become smaller in the future, but to make reliable predictions the underlying mechanisms need to be identified and sought elsewhere than in geometric constraints on gill surface area. Furthermore, to ensure that useful information is conveyed to the public and policymakers about the possible effects of climate change, it is necessary to improve communication and congruity between fish physiologists and fisheries scientists. The final version of this research has been published in Global Change Biology. © 2017 Blackwell Publishing

• Lefevre, Sjannie; Stecyk, Jonathan Anthony William; Torp, May-Kristin; Løvold, Lisa Yuen; Sørensen, Christina & Johansen, Ida Beitnes [Show all 10 contributors for this article] (2017). Re-oxygenation after anoxia induces brain cell death and memory loss in the anoxia-tolerant crucian carp. Journal of Experimental Biology. ISSN 0022-0949. 220(21), p. 3883–3895. doi: 10.1242/jeb.165118. Full text in Research Archive Show summary

  Crucian carp (Carassius carassius) survive without oxygen for several months, but it is unknown whether they are able to protect themselves from cell death normally caused by the absence, and particularly return, of oxygen. Here, we quantified cell death in brain tissue from crucian carp exposed to anoxia and re-oxygenation using the terminal deoxy-nucleotidyl transferase dUTP nick-end labelling (TUNEL) assay, and cell proliferation by immunohistochemical staining for proliferating cell nuclear antigen (PCNA) as well as PCNA mRNA expression. We also measured mRNA and protein expression of the apoptosis executer protease caspase 3, in laboratory fish exposed to anoxia and re-oxygenation and fish exposed to seasonal anoxia and re-oxygenation in their natural habitat over the year. Finally, a behavioural experiment was used to assess the ability to learn and remember how to navigate in a maze to find food, before and after exposure to anoxia and re-oxygenation. The number of TUNEL-positive cells in the telencephalon increased after 1 day of re-oxygenation following 7 days of anoxia, indicating increased cell death. However, there were no consistent changes in whole-brain expression of caspase 3 in either laboratory-exposed or naturally exposed fish, indicating that cell death might occur via caspase-independent pathways or necrosis. Re-oxygenated crucian carp appeared to have lost the memory of how to navigate in a maze (learnt prior to anoxia exposure), while the ability to learn remained intact. PCNA mRNA was elevated after re-oxygenation, indicating increased neurogenesis. We conclude that anoxia tolerance involves not only protection from damage but also repair after re-oxygenation.

• Poleo, Antonio; Scholden, Joachim; Sørensen, Jørgen & Nilsson, Göran Erik (2017). The high tolerance to aluminum in crucian crap (Carcassius carcassius) is associated with its ability to avoid hypoxia. PLOS ONE. 12(6). doi: 10.1371/journal.pone.0179519. Full text in Research Archive Show summary

  It is well known that aluminium is the principle toxicant killing fish in acidified freshwater systems, and it has been shown that crucian carp (Carassius carassius) can survive exposures to aqueous aluminium levels toxic to most other freshwater fish species. The crucian carp has a remarkable ability to survive anoxic conditions, and the aim of the present study was to reveal if the tolerance to aluminium can be associated with the ability to survive prolonged anoxia. Crucian carps were exposed to either acidic Al-rich water (pH 5.8; 960 μg Al/l), acidic Al-poor water (pH 5.8; 50 μg Al/l) or untreated control water (pH 6.5; 50 μg Al/l). Blood, muscle and gill samples were collected from exposed fish, and closed respirometry was performed to measure critical O2-tension an normoxic O2-consumption. The results show an increased gill surface area in Al-exposed fish, while the critical O2-tension did not change. The normoxic O2-consumption was lower in Al-exposed fish and might be due to a reduced metabolic rate. The results suggest that crucian carp exposed to aluminium do not become hypoxic, since haematocrit, plasma lactate and blood ethanol did not differ from that of control fish after 14 days of exposure. We also observed an initial loss of plasma chloride and sodium, followed by a stabilisation of these ions at a lower level than in control fish. The decrease in plasma ions caused a transient increase in haematocrit and water content in muscle tissue, returning to control levels when the ion concentrations stabilised, suggesting that the water balance was restored. We conclude that the high tolerance to aluminium in crucian carp is associated with its ability to avoid hypoxia as well as an ability to counteract a continuous loss of plasma ions.

• Lai, Floriana; Fagernes, Cathrine Elisabeth; Bernier, Nicholas J; Miller, Gabrielle; Munday, Philip L & Nilsson, Göran Erik [Show all 7 contributors for this article] (2017). Responses of neurogenesis and neuroplasticity related genes to elevated CO2 levels in the brain of three teleost species. Biology Letters. ISSN 1744-9561. 13(8). doi: 10.1098/rsbl.2017.0240. Full text in Research Archive Show summary

  The continuous increase of anthropogenic CO2 in the atmosphere resulting in ocean acidification has been reported to affect brain function in some fishes. During adulthood, cell proliferation is fundamental for fish brain growth and for it to adapt in response to external stimuli, such as environmental changes. Here we report the first expression study of genes regulating neurogenesis and neuroplasticity in brains of three-spined stickleback (Gasterosteus aculeatus), cinnamon anemonefish (Amphiprion melanopus) and spiny damselfish (Acanthochromis polyacanthus) exposed to elevated CO2. The mRNA expression levels of the neurogenic differentiation factor (NeuroD) and doublecortin (DCX) were upregulated in three-spined stickleback exposed to high-CO2 compared with controls, while no changes were detected in the other species. The mRNA expression levels of the proliferating cell nuclear antigen (PCNA) and the brain-derived neurotrophic factor (BDNF) remained unaffected in the high-CO2 exposed groups compared to the control in all three species. These results indicate a species-specific regulation of genes involved in neurogenesis in response to elevated ambient CO2 levels. The higher expression of NeuroD and DCX mRNA transcripts in the brain of high-CO2–exposed three-spined stickleback, together with the lack of effects on mRNA levels in cinnamon anemonefish and spiny damselfish, indicate differences in coping mechanisms among fish in response to the predicted-future CO2 level.

• Lai, Floriana; Fagernes, Cathrine Elisabeth; Bernier, Nicholas J; Miller, Gabrielle; Munday, Philip L & Jutfelt, Fredrik [Show all 7 contributors for this article] (2017). Responses of neurogenesis and neuroplasticity related genes to elevated CO2 levels in the brain of three teleost species. Biology Letters. ISSN 1744-9561. doi: 10.1098/rsbl.2017.0240. Full text in Research Archive Show summary

  The continuous increase of anthropogenic CO2 in the atmosphere resulting in ocean acidification has been reported to affect brain function in some fishes. During adulthood, cell proliferation is fundamental for fish brain growth and for it to adapt in response to external stimuli, such as environmental changes. Here we report the first expression study of genes regulating neurogenesis and neuroplasticity in brains of three-spined stickleback (Gasterosteus aculeatus), cinnamon anemonefish (Amphiprion melanopus) and spiny damselfish (Acanthochromis polyacanthus) exposed to elevated CO2. The mRNA expression levels of the neurogenic differentiation factor (NeuroD) and doublecortin (DCX) were upregulated in three-spined stickleback exposed to high-CO2 compared with controls, while no changes were detected in the other species. The mRNA expression levels of the proliferating cell nuclear antigen (PCNA) and the brain-derived neurotrophic factor (BDNF) remained unaffected in the high-CO2 exposed groups compared to the control in all three species. These results indicate a species-specific regulation of genes involved in neurogenesis in response to elevated ambient CO2 levels. The higher expression of NeuroD and DCX mRNA transcripts in the brain of high-CO2–exposed three-spined stickleback, together with the lack of effects on mRNA levels in cinnamon anemonefish and spiny damselfish, indicate differences in coping mechanisms among fish in response to the predicted-future CO2 level.

• Johansen, Ida Beitnes; Sandblom, Erik; Skov, Peter V.; Gräns, Albin; Ekström, Andreas & Lunde, Ida Gjervold [Show all 13 contributors for this article] (2017). Bigger is not better: cortisol-induced cardiac growth and dysfunction in salmonids. Journal of Experimental Biology. ISSN 0022-0949. 220(14), p. 2545–2553. doi: 10.1242/jeb.135046. Full text in Research Archive Show summary

  Stress and elevated cortisol levels are associated with pathological heart growth and cardiovascular disease in humans and other mammals. We recently established a link between heritable variation in post-stress cortisol production and cardiac growth also in salmonid fish. A conserved stimulatory effect of the otherwise catabolic steroid hormone cortisol is likely implied, but has to date not been established experimentally. Furthermore, whereas cardiac growth is associated with failure of the mammalian heart, pathological cardiac hypertrophy has not previously been described in fish. Here we show that rainbow trout (Oncorhynchus mykiss) treated with cortisol in the food for 45 days have enlarged hearts with lower maximum stroke volume and cardiac output. In accordance with impaired cardiac performance, overall circulatory oxygen transporting capacity was diminished as indicated by reduced aerobic swimming performance. In contrast to the well-known adaptive/physiological heart growth observed in fish, cortisol-induced growth is maladaptive. Furthermore, the observed heart growth was associated with up-regulated signature genes of mammalian cardiac pathology, suggesting that signaling pathways mediating cortisol-induced cardiac remodeling in fish are conserved from fish to mammals. Altogether, we show that excessive cortisol can induce pathological cardiac remodeling. This is the first study to report and integrate the etiology, physiology and molecular biology of cortisol-induced pathological remodeling in fish.

• Schunter, Celia; Welch, Megan J; Ryu, Taewoo; Zhang, Huoming; Berumen, Michael L & Nilsson, Göran Erik [Show all 8 contributors for this article] (2016). Molecular signatures of transgenerational response to ocean acidification in a species of reef fish. Nature Climate Change. ISSN 1758-678X. 6(11), p. 1014–1018. doi: 10.1038/nclimate3087. Full text in Research Archive
• Nilsson, Göran Erik & Lefevre, Sjannie (2016). Physiological challenges to fishes in a warmer and acidified future. Physiology. ISSN 1548-9213. 31(6), p. 409–417. doi: 10.1152/physiol.00055.2015. Full text in Research Archive
• Mckenzie, David J.; Axelsson, Michael; Chabot, Denis; Claireaux, Guy; Cooke, Steven J. & Corner, Richard A. [Show all 29 contributors for this article] (2016). Conservation physiology of marine fishes: state of the art and prospects for policy. Conservation Physiology. 4(1). doi: 10.1093/conphys/cow046. Full text in Research Archive
• Lai, Floriana; Fagernes, Cathrine Elisabeth; Jutfelt, Fredrik & Nilsson, Göran Erik (2016). Expression of genes involved in brain GABAergic neurotransmission in three-spined stickleback exposed to near-future CO2. Conservation Physiology. 4(1). doi: 10.1093/conphys/cow068. Full text in Research Archive
• Regan, Matthew D.; Turko, Andy J.; Heras, Joseph; Andersen, Mads Kuhlmann; Lefevre, Sjannie & Wang, Tobias [Show all 11 contributors for this article] (2016). Ambient CO2, fish behaviour and altered GABAergic neurotransmission: Exploring the mechanism of CO2-altered behaviour by taking a hypercapnia dweller down to low CO2 levels. Journal of Experimental Biology. ISSN 0022-0949. 219(1), p. 109–118. doi: 10.1242/jeb.131375. Full text in Research Archive
• Lefevre, Sjannie; Watson, Sue-Ann; Munday, Philip L. & Nilsson, Göran Erik (2015). Will jumping snails prevail? Influence of near-future CO2, temperature and hypoxia on respiratory performance in the tropical conch Gibberulus gibberulus gibbosus. Journal of Experimental Biology. ISSN 0022-0949. 218(19), p. 2991–3001. doi: 10.1242/jeb.120717. Full text in Research Archive
• Nilsson, Göran Erik; Vaage, Ingvar Jarle & Stensløkken, Kåre-Olav (2015). Oxygen- and temperature-dependent expression of survival protein kinases in crucian carp (carassius carassius) heart and brain. American Journal of Physiology. Regulatory Integrative and Comparative Physiology. ISSN 0363-6119. 308(1), p. R50–R61. doi: 10.1152/ajpregu.00094.2014. Full text in Research Archive
• Lai, Floriana; Jutfelt, Fredrik & Nilsson, Goran Erik (2015). Altered neurotransmitter function in CO2-exposed stickleback (Gasterosteus aculeatus): a temperate model species for ocean acidification research. Conservation Physiology. 3(1), p. 1–6. doi: 10.1093/conphys/cov018. Full text in Research Archive Show summary

  Studies on the consequences of ocean acidification for the marine ecosystem have revealed behavioural changes in coral reef fishes exposed to sustained near-future CO2 levels. The changes have been linked to altered function of GABAergic neurotransmitter systems, because the behavioural alterations can be reversed rapidly by treatment with the GABAA receptor antagonist gabazine. Characterization of the molecular mechanisms involved would be greatly aided if these can be examined in a well-characterized model organism with a sequenced genome. It was recently shown that CO2-induced behavioural alterations are not confined to tropical species, but also affect the three-spined stickleback, although an involvement of the GABAA receptor was not examined. Here, we show that loss of lateralization in the stickleback can be restored rapidly and completely by gabazine treatment. This points towards a worrying universality of disturbed GABAA function after high-CO2 exposure in fishes from tropical to temperate marine habitats. Importantly, the stickleback is a model species with a sequenced and annotated genome, which greatly facilitates future studies on underlying molecular mechanisms.

• Wilkie, Michael; Stecyk, Jonathan Anthony William; Couturier, Christine Stephanie; Sidhu, Sanya; Sandvik, Guro Katrine & Nilsson, Göran Erik (2015). Reversible brain swelling in crucian carp (Carassius carassius) and goldfish (Carassius auratus) in response to high external ammonia and anoxia. Comparative Biochemistry and Physiology A. ISSN 1095-6433. 184, p. 65–75. doi: 10.1016/j.cbpa.2014.12.038. Full text in Research Archive
• Lefevre, Sjannie; Damsgaard, Christian; Pascale, Desirae R.; Nilsson, Göran Erik & Stecyk, Jonathan Anthony William (2014). Air breathing in the Arctic: influence of temperature, hypoxia, activity and restricted air access on respiratory physiology of the Alaska blackfish Dallia pectoralis. Journal of Experimental Biology. ISSN 0022-0949. 217(24), p. 4387–4398. doi: 10.1242/jeb.105023. Full text in Research Archive
• Anttila, K; Couturier, Christine Stephanie; Øverli, Øyvind; Johnsen, Arild; Marthinsen, Gunnhild & Nilsson, Göran Erik [Show all 7 contributors for this article] (2014). Atlantic salmon show capability for cardiac acclimation to warm temperatures. Nature Communications. 5. doi: 10.1038/ncomms5252. Full text in Research Archive
• Bowden, A.J.; Gardiner, N.M.; Couturier, Christine Stephanie; Stecyk, Jonathan Anthony William; Nilsson, Göran Erik & Munday, P.L. [Show all 7 contributors for this article] (2014). Alterations in gill structure in tropical reef fishes as a result of elevated temperatures. Comparative Biochemistry and Physiology A. ISSN 1095-6433. 175(1), p. 64–71. doi: 10.1016/j.cbpa.2014.05.011. Full text in Research Archive
• Chung, Wen-Sung; Marshall, N. Justin; Watson, Sue-Ann; Munday, Philip L. & Nilsson, Göran Erik (2014). Ocean acidification slows retinal function in a damselfish through interference with GABAA receptors. Journal of Experimental Biology. ISSN 0022-0949. 217(3), p. 323–326. doi: 10.1242/jeb.092478. Full text in Research Archive
• Stensløkken, Kåre-Olav; Ellefsen, Stian; Vasieva, Olga; Fang, Youhan; Farrell, Anthony P. & Olohan, Lisa [Show all 9 contributors for this article] (2014). Life without Oxygen: Gene Regulatory Responses of the Crucian Carp (Carassius carassius) Heart Subjected to Chronic Anoxia. PLOS ONE. 9(11). doi: 10.1371/journal.pone.0109978. Full text in Research Archive Show summary

  Crucian carp are unusual among vertebrates in surviving extended periods in the complete absence of molecular oxygen. During this time cardiac output is maintained though these mechanisms are not well understood. Using a high-density cDNA microarray, we have defined the genome-wide gene expression responses of cardiac tissue after exposing the fish at two temperatures (8 and 13uC) to one and seven days of anoxia, followed by seven days after restoration to normoxia. At 8uC, using a false discovery rate of 5%, neither anoxia nor re-oxygenation elicited appreciable changes in gene expression. By contrast, at 13uC, 777 unique genes responded strongly. Up-regulated genes included those involved in protein turnover, the pentose phosphate pathway and cell morphogenesis while down-regulated gene categories included RNA splicing and transcription. Most genes were affected between one and seven days of anoxia, indicating gene regulation over the medium term but with few early response genes. Re-oxygenation for 7 days was sufficient to completely reverse these responses. Glycolysis displayed more complex responses with anoxia up-regulated transcripts for the key regulatory enzymes, hexokinase and phosphofructokinase, but with down-regulation of most of the non-regulatory genes. This complex pattern of responses in genomic transcription patterns indicates divergent cardiac responses to anoxia, with the transcriptionally driven reprogramming of cardiac function seen at 13uC being largely completed at 8uC.

• Sørensen, Christina; Munday, Philip L. & Nilsson, Göran Erik (2014). Aerobic vs. anaerobic scope: Sibling species of fish indicate that temperature dependence of hypoxia tolerance can predict future survival. Global Change Biology. ISSN 1354-1013. 20(3), p. 724–729. doi: 10.1111/gcb.12399. Full text in Research Archive
• Rummer, Jodie L.; Couturier, Christine Stephanie; Stecyk, Jonathan Anthony William; Gardiner, N.M.; Kinch, Jeff P. & Nilsson, Göran Erik [Show all 7 contributors for this article] (2014). Life on the edge: thermal optima for aerobic scope of equatorial reef fishes are close to current day temperatures. Global Change Biology. ISSN 1354-1013. 20(4), p. 1055–1066. doi: 10.1111/gcb.12455. Full text in Research Archive
• Chivers, Douglas P.; McCormick, Mark I.; Nilsson, Göran Erik; Munday, Philip L.; Watson, Sue-Ann & Meekan, Mark G. [Show all 9 contributors for this article] (2014). Impaired learning of predators and lower prey survival under elevated CO2: a consequence of neurotransmitter interference. Global Change Biology. ISSN 1354-1013. 20(2), p. 515–522. doi: 10.1111/gcb.12291. Full text in Research Archive
• Tomter, Ane Berg; Zoppellaro, Giorgio; Andersen, Niels Højmark; Hersleth, Hans-Petter; Hammerstad, Marta & Røhr, Åsmund Kjendseth [Show all 15 contributors for this article] (2013). Ribonucleotide reductase class I with different radical generating clusters. Coordination chemistry reviews. ISSN 0010-8545. 257(1), p. 3–26. doi: 10.1016/j.ccr.2012.05.021. Full text in Research Archive Show summary

  Ribonucleotide reductase (RNR) catalyzes the rate limiting step in DNA synthesis where ribonucleotides are reduced to their corresponding deoxyribonucleotides. They are formed through a radical-induced reduction of ribonucleotides. Three classes of RNR generate the catalytically active site thiyl radical using different co-factors: a tyrosyl-radical in most cases (class I), homolytic cleavage of deoxyadenosyl-cobalamin (class II), or a glycyl-radical (class III), respectively. Class I RNR has a larger subunit R1/R1E containing the active site and a smaller subunit R2/R2F with (the thiyl-generating power from) a tyrosyl radical or an oxidized iron-manganese cluster and is reviewed herein. Class I is divided into subclasses, Ia (tyrosyl-radical and di-iron-oxygen cluster), Ib (tyrosyl-radical and di-manganese-oxygen cluster) and Ic (an iron-manganese cluster). Presented here is an overview of recent developments in the understanding of class I RNR: metal-ion cluster identities, novel 3D structures, magnetic-optical properties, and reaction mechanisms. It became clear in the last years that the primitive bacterial RNR sources can utilize different metal-ion clusters to fulfil function. Within class Ia that includes members from eukaryotes (mammalians, fish) and some viruses species, the presence of hydrogen bonding interactions from water at different distances with the tyrosyl-radical site can occur. This demonstrates a large versatility in the mechanism to form the thiyl radical.

• Thompson, John W.; Nilsson, Göran Erik & Perez-Pinzon, Miguel A (2013). Anoxia resistance in lower and higher vertebrates. In Gidday, Jeffrey M; Perez-Pinzon, Miguel A & Zhang, John H. (Ed.), Innate Tolerance in the CNS. Springer. ISSN 9781441996947. p. 19–35. doi: 10.1007/978-1-4419-9695-4_2. Full text in Research Archive
• Wilson, Christopher M.; Stecyk, Jonathan Anthony William; Couturier, Christine Stephanie; Nilsson, Göran Erik & Farrell, Anthony P. (2013). Phylogeny and effects of anoxia on hyperpolarization-activated cyclic nucleotide-gated channel gene expression in the heart of a primitive chordate, the Pacific hagfish (Eptatretus stoutii). Journal of Experimental Biology. ISSN 0022-0949. 216(23), p. 4462–4472. Full text in Research Archive Show summary

  The aneural heart of the Pacific hagfish, Eptatretus stoutii, varies heart rate fourfold during recovery from anoxia. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which play an important role in establishing the pacemaker rate of vertebrate hearts, were postulated to be present in this ancestral vertebrate heart, and it was also theorized that changes in hagfish heart rate with oxygen availability involved altered HCN expression. Partial gene cloning revealed six HCN isoforms in the hagfish heart. Hagfish representatives of HCN2, HCN3 and HCN4 were discovered, with HCN2 and HCN3 existing as isoforms designated as HCN2a, HCN2b, HCN3a, two paralogs of HCN3b, and HCN3c. Phylogenetic analysis revealed HCN3b and HCN3c to be ancestral, followed by HCN3a, HCN4 and HCN2. Moreover, HCN3a expression was dominant in both the atrial and ventricular chambers, suggesting that the HCN4 dominance in adult mammalian hearts appeared after hagfish divergence. HCN expression was higher in the atrium than in the ventricle, as might be expected given that atrial beating rate is known to be faster than the ventricular rate. In addition, mRNA expression under normoxic conditions was compared with that following 24 h of anoxia, and either a 2-h or 36-h recovery in normoxic water. In the ventricle, anoxia decreased HCN3a but not HCN4 expression. In contrast, atrial HCN3a expression significantly increased following 2 h of recovery, before returning to control levels following 36 h of recovery, possibly contributing to heart rate changes previously observed under these conditions.

• Rummer, Jodie L.; Stecyk, Jonathan Anthony William; Couturier, Christine Stephanie; Watson, Sue-Ann; Nilsson, Göran Erik & Munday, Philip L. (2013). Elevated CO2 enhances aerobic scope of a coral reef fish. Conservation Physiology. 1(1). doi: 10.1093/conphys/cot023. Full text in Research Archive Show summary

  The uptake of anthropogenic CO2 by the ocean has been suggested to impact marine ecosystems by decreasing the respiratory capacity of fish and other water breathers. We investigated the aerobic metabolic scope of the spiny damselfish, Acanthochromis polyacanthus, from the Great Barrier Reef, Australia when exposed for 17 days to CO2 conditions predicted for the end of the century (946 μatm CO2). Surprisingly, resting O2 consumption rates were significantly lower and maximal O2 consumption rates significantly higher in high-CO2-exposed fish compared with control fish (451 μatm CO2). Consequently, high-CO2-exposed fish exhibited an unexpected increase in absolute (38%) and factorial aerobic scopes (47%). Haematological and muscle water changes associated with exercise were not affected by CO2 treatment. Thus, contrary to predictions, our results suggest that elevated CO2 may enhance aerobic scope of some fish species. Long-term experiments are now required to assess the response to elevated CO2 further, because developmental and transgenerational effects can be dramatic in fish. Ultimately, understanding the variability among species regarding the effects of CO2 on aerobic scope will be critical in predicting the impacts of ocean acidification on marine communities and ecosystems.

• Wilson, Christopher M.; Stecyk, Jonathan Anthony William; Couturier, Christine Stephanie; Nilsson, Göran Erik & Farrell, Anthony P. (2013). Research article phylogeny and effects of anoxia on hyperpolarization- activated cyclic nucleotidegated channel gene expression in the heart of a primitive chordate, the pacific hagfish (eptatretus stoutii). Journal of Experimental Biology. ISSN 0022-0949. 216(23), p. 4462–4472. doi: 10.1242/jeb.094912. Full text in Research Archive
• Watson, Sue; Lefevre, Sjannie; McCormick, Mark I.; Domenici, Paolo; Nilsson, Göran Erik & Munday, Philip L. (2013). Marine mollusc predator-escape behaviour altered by near-future carbon dioxide levels. Proceedings of the Royal Society of London. Biological Sciences. ISSN 0962-8452. 281(1774). doi: 10.1098/rspb.2013.2377. Full text in Research Archive
• Couturier, Christine Stephanie; Stecyk, Jonathan Anthony William; Rummer, Jodie L.; Munday, Philip L. & Nilsson, Göran Erik (2013). Species-specific effects of near-future CO2 on the respiratory performance of two tropical prey fish and their predator. Comparative Biochemistry and Physiology A. ISSN 1095-6433. 166(3), p. 482–489. doi: 10.1016/j.cbpa.2013.07.025. Full text in Research Archive
• Lardon, Isabelle; Nilsson, Göran Erik; Stecyk, Jonathan Anthony William; Vu, Trung Nghia; Laukens, Kris & Dommisse, Roger [Show all 7 contributors for this article] (2013). H-1-NMR study of the metabolome of an exceptionally anoxia tolerant vertebrate, the crucian carp (Carassius carassius). Metabolomics. ISSN 1573-3882. 9(2), p. 311–323. doi: 10.1007/s11306-012-0448-y. Full text in Research Archive
• Sandvik, Guro Katrine; Nilsson, Göran Erik & Jensen, Frank B. (2012). Dramatic increase of nitrite levels in hearts of anoxia-exposed crucian carp supporting a role in cardioprotection. American Journal of Physiology. Regulatory Integrative and Comparative Physiology. ISSN 0363-6119. 302(4), p. R468–R477. doi: 10.1152/ajpregu.00538.2011. Full text in Research Archive
• Nilsson, Göran Erik; Dymowska, Agnieszka Karolina & Stecyk, Jonathan Anthony William (2012). New insights into the plasticity of gill structure. Respiratory Physiology & Neurobiology (RESPNB). ISSN 1569-9048. 184(3), p. 214–222. doi: 10.1016/j.resp.2012.07.012. Full text in Research Archive
• Nilsson, Göran Erik; Dixson, Danielle L.; Domenici, Paolo; McCormick, Mark I.; Sørensen, Christina & Watson, Sue-Ann [Show all 7 contributors for this article] (2012). Near-future carbon dioxide levels alter fish behaviour by interfering with neurotransmitter function. Nature Climate Change. ISSN 1758-678X. 2(3), p. 201–204. doi: 10.1038/NCLIMATE1352. Full text in Research Archive
• Ellefsen, Stian; Bliksøen, Marte; Rutkovskiy, Arkady; Johansen, Ida Beitnes; Kaljusto, Mari-Liis & Nilsson, Göran Erik [Show all 8 contributors for this article] (2012). Per-unit-living tissue normalization of real-time RT-PCR data in ischemic rat hearts. Physiological Genomics. ISSN 1094-8341. 44(12), p. 651–656. doi: 10.1152/physiolgenomics.00004.2012. Full text in Research Archive
• Sørensen, Christina; Nilsson, Göran Erik; Summers, Cliff H. & Øverli, Øyvind (2012). Social stress reduces forebrain cell proliferation in rainbow trout (Oncorhynchus mykiss). Behavioural Brain Research. ISSN 0166-4328. 227(2), p. 311–318. doi: 10.1016/j.bbr.2011.01.041. Full text in Research Archive
• Johansen, Ida Beitnes; Sørensen, Christina; Sandvik, Guro Katrine; Nilsson, Göran Erik; Höglund, Erik & Bakken, Morten [Show all 7 contributors for this article] (2012). Neural plasticity is affected by stress and heritable variation in stress coping style. Comparative Biochemistry and Physiology - Part D:Genomics and Proteomics. ISSN 1744-117X. 7(2), p. 161–171. doi: 10.1016/j.cbd.2012.01.002. Full text in Research Archive
• Sandvik, Guro Katrine; Tomter, Ane Berg; Bergan, Jonas; Zoppellaro, Giorgio; Barra, Anne-Laure & Røhr, Åsmund Kjendseth [Show all 10 contributors for this article] (2012). Studies of Ribonucleotide Reductase in Crucian Carp-An Oxygen Dependent Enzyme in an Anoxia Tolerant Vertebrate. PLOS ONE. 7(8). doi: 10.1371/journal.pone.0042784. Full text in Research Archive Show summary

  The enzyme ribonucleotide reductase (RNR) catalyzes the conversion of ribonucleotides to deoxyribonucleotides, the precursors for DNA. RNR requires a thiyl radical to activate the substrate. In RNR of eukaryotes (class Ia RNR), this radical originates from a tyrosyl radical formed in reaction with oxygen (O2) and a ferrous di-iron center in RNR. The crucian carp (Carassius carassius) is one of very few vertebrates that can tolerate several months completely without oxygen (anoxia), a trait that enables this fish to survive under the ice in small ponds that become anoxic during the winter. Previous studies have found indications of cell division in this fish after 7 days of anoxia. This appears nearly impossible, as DNA synthesis requires the production of new deoxyribonucleotides and therefore active RNR. We have here characterized RNR in crucian carp, to search for adaptations to anoxia. We report the full-length sequences of two paralogs of each of the RNR subunits (R1i, R1ii, R2i, R2ii, p53R2i and p53R2ii), obtained by cloning and sequencing. The mRNA levels of these subunits were measured with quantitative PCR and were generally well maintained in hypoxia and anoxia in heart and brain. We also report maintained or increased mRNA levels of the cell division markers proliferating cell nuclear antigen (PCNA), brain derived neurotrophic factor (BDNF) and Ki67 in anoxic hearts and brains. Electron paramagnetic resonance (EPR) measurements on in vitro expressed crucian carp R2 and p53R2 proteins gave spectra similar to mammalian RNRs, including previously unpublished human and mouse p53R2 EPR spectra. However, the radicals in crucian carp RNR small subunits, especially in the p53R2ii subunit, were very stable at 0 °C. A long half-life of the tyrosyl radical during wintertime anoxia could allow for continued cell division in crucian carp.

• Munday, Philip L.; McCormick, Mark I. & Nilsson, Göran Erik (2012). Impact of global warming and rising CO2 levels on coral reef fishes: what hope for the future? Journal of Experimental Biology. ISSN 0022-0949. 215(22), p. 3865–3873. doi: 10.1242/jeb.074765. Full text in Research Archive
• Stecyk, Jonathan Anthony William; Couturier, Christine; Fagernes, Cathrine Elisabeth; Ellefsen, Stian & Nilsson, Göran Erik (2012). Quantification of heat shock protein mRNA expression in warm and cold anoxic turtles (Trachemys scripta) using an external RNA control for normalization. Comparative Biochemistry and Physiology - Part D:Genomics and Proteomics. ISSN 1744-117X. 7(1), p. 59–72. doi: 10.1016/j.cbd.2011.11.001. Full text in Research Archive
• Stecyk, Jonathan Anthony William; Larsen, Bent Collert & Nilsson, Göran Erik (2011). Intrinsic contractile properties of the crucian carp (Carassius carassius) heart during anoxic and acidotic stress. American Journal of Physiology. Regulatory Integrative and Comparative Physiology. ISSN 0363-6119. 301(4), p. R1132–R1142. doi: 10.1152/ajpregu.00372.2010. Full text in Research Archive
• Sørensen, Christina; Bohlin, Linda Catrine; Øverli, Øyvind & Nilsson, Göran Erik (2011). Cortisol reduces cell proliferation in the telencephalon of rainbow trout (Oncorhynchus mykiss). Physiology and Behavior. ISSN 0031-9384. 102(5), p. 518–523. doi: 10.1016/j.physbeh.2010.12.023. Full text in Research Archive
• Johansen, Ida Beitnes; Lunde, Ida Gjervold; Røsjø, Helge; Christensen, Geir Arve; Nilsson, Göran Erik & Bakken, Morten [Show all 7 contributors for this article] (2011). Cortisol response to stress is associated with myocardial remodeling in salmonid fishes. Journal of Experimental Biology. ISSN 0022-0949. 214(8), p. 1313–1321. doi: 10.1242/jeb.053058. Full text in Research Archive
• Johansen, Ida Beitnes; Sandvik, Guro Katrine; Nilsson, Göran Erik; Bakken, Morten & Øverli, Øyvind (2011). Cortisol receptor expression differs in the brains of rainbow trout selected for divergent cortisol responses. Comparative Biochemistry and Physiology - Part D:Genomics and Proteomics. ISSN 1744-117X. 6(2), p. 126–132. doi: 10.1016/j.cbd.2010.11.002. Full text in Research Archive
• Donelson, Jennifer M.; Munday, Philip L.; McCormick, Mark I. & Nilsson, Göran Erik (2011). Acclimation to predicted ocean warming through developmental plasticity in a tropical reef fish. Global Change Biology. ISSN 1354-1013. 17(4), p. 1712–1719. doi: 10.1111/j.1365-2486.2010.02339.x. Full text in Research Archive
• Stecyk, Jonathan Anthony William; Skovgaard, Nini; Nilsson, Göran Erik & Wang, Tobias (2010). Vasoactivity of hydrogen sulfide in normoxic and anoxic turtles (Trachemys scripta). American Journal of Physiology. Regulatory Integrative and Comparative Physiology. ISSN 0363-6119. 298(5), p. R1225–R1239. doi: 10.1152/ajpregu.00521.2009. Full text in Research Archive
• Utne-Palm, Anne Christine; Salvanes, Anne Gro Vea; Currie, Bronwen; Kaartvedt, Stein; Nilsson, Göran Erik & Braithwaite, Victoria Anne [Show all 19 contributors for this article] (2010). Trophic Structure and Community Stability in an Overfished Ecosystem. Science. ISSN 0036-8075. 329(5989), p. 333–336. doi: 10.1126/science.1190708. Full text in Research Archive
• Nilsson, Gøran Erik (2010). Surviving without any oxygen. In Nilsson, Gøran Erik (Eds.), Respiratory Physiology of Vertebrates. Cambridge University Press. ISSN 9780521878548. p. 300–328. Full text in Research Archive
• Nilsson, Gøran Erik & Randall, David J. (2010). Adaptations to hypoxia in fishes. In Nilsson, Gøran Erik (Eds.), Respiratory Physiology of Vertebrates. Cambridge University Press. ISSN 9780521878548. p. 131–173. Full text in Research Archive
• Krogh, Kristine von; Sørensen, Christina; Nilsson, Göran Erik & Øverli, Øyvind (2010). Forebrain cell proliferation, behavior, and physiology of zebrafish, Danio rerio, kept in enriched or barren environments. Physiology and Behavior. ISSN 0031-9384. 101(1), p. 32–39. doi: 10.1016/j.physbeh.2010.04.003. Full text in Research Archive
• Lopez-Barneo, J; Nurse, C.A.; Nilsson, Göran Erik; Buck, L.T.; Gassmann, Max & Bogdanova, A. Yu. (2010). First Aid Kit for Hypoxic Survival: Sensors and Strategies. Physiological and Biochemical Zoology. ISSN 1522-2152. 83(5), p. 753–763. doi: 10.1086/651584. Full text in Research Archive
• Gorr, Thomas A.; Wichmann, D; Hu, J; Hermes-Lima, M; Welker, AF & Terwilliger, N [Show all 13 contributors for this article] (2010). Hypoxia Tolerance in Animals: Biology and Application. Physiological and Biochemical Zoology. ISSN 1522-2152. 83(5), p. 733–752. doi: 10.1086/648581. Full text in Research Archive
• Gardiner, NM; Munday, Philip L. & Nilsson, Göran Erik (2010). Counter-Gradient Variation in Respiratory Performance of Coral Reef Fishes at Elevated Temperatures. PLOS ONE. 5(10). doi: 10.1371/journal.pone.0013299. Full text in Research Archive
• Stensløkken, Kåre-Olav; Ellefsen, Stian; Larsen, Helene Kile; Vaage, Ingvar Jarle & Nilsson, Göran Erik (2010). Expression of heat shock proteins in anoxic crucian carp (Carassius carassius): support for cold as a preparatory cue for anoxia. American Journal of Physiology. Regulatory Integrative and Comparative Physiology. ISSN 0363-6119. 298(6), p. R1499–R1508. doi: 10.1152/ajpregu.00675.2009. Full text in Research Archive
• Nilsson, Göran Erik; Nilsson, Sara Østlund & Munday, PL (2010). Effects of elevated temperature on coral reef fishes: Loss of hypoxia tolerance and inability to acclimate. Comparative Biochemistry and Physiology A. ISSN 1095-6433. 156(4), p. 389–393. doi: 10.1016/j.cbpa.2010.03.009. Full text in Research Archive
• Nilsson, Gøran Erik (2010). Introduction: why we need oxygen. In Nilsson, Gøran Erik (Eds.), Respiratory Physiology of Vertebrates. Cambridge University Press. ISSN 9780521878548. p. 3–13. Full text in Research Archive
• Mitrovic, Dejana; Dymowska, Agnieszka Karolina; Nilsson, Gøran Erik & Perry, Steve F. (2009). Physiological consequences of gill remodeling in goldfish (Carassius auratus) during exposure to long-term hypoxia. American Journal of Physiology. Regulatory Integrative and Comparative Physiology. ISSN 0363-6119. 297, p. R224–R234. doi: 10.1152/ajpregu.00189.2009. Full text in Research Archive
• Nilsson, Gøran Erik; Crawley, Natalie; Lunde, Ida Gjervold & Munday, Philip L. (2009). Elevated temperature reduces the respiratory scope of coral reef fishes. Global Change Biology. ISSN 1354-1013. 15(6), p. 1405–1412. doi: 10.1111/j.1365-2486.2008.01767.x. Full text in Research Archive
• Munday, Philip L; Crawley, Natalie & Nilsson, Gøran Erik (2009). Interacting effects of elevated temperature and ocean acidification on the aerobic performance of coral reef fishes. Marine Ecology Progress Series. ISSN 0171-8630. 388, p. 235–242. doi: 10.3354/meps08137. Full text in Research Archive
• Smith, Richard W; Cash, Phil; Ellefsen, Stian & Nilsson, Gøran Erik (2009). Proteomic changes in the crucian carp brain during exposure to anoxia. Proteomics. ISSN 1615-9853. 9(8), p. 2217–2229. doi: 10.1002/pmic.200800662. Full text in Research Archive
• Nilsson, Gøran Erik; Crawley, Natalie; Lunde, Ida Gjervold & Munday, Philip L (2009). Elevated temperature reduces the respiratory scope of coral reef fishes. Global Change Biology. ISSN 1354-1013. 15(6), p. 1405–1412. doi: 10.1111/j.1365-2486.2008.01767.x. Full text in Research Archive
• Vornanen, Matti; Stecyk, Jonathan A. .W. & Nilsson, Gøran Erik (2009). The anoxia-tolerant crucian carp (Carassius carassius L.). In Richards, Jeffrey; Farrell, Anthony P. & Brauner, Colin (Ed.), Fish Physiology Volume 27, Hypoxia. Elsevier. ISSN 9780123746320. p. 397–441. Full text in Research Archive
• Ellefsen, Stian; Stensløkken, Kåre-Olav; Fagernes, Cathrine Elisabeth; Kristensen, Tom & Nilsson, Gøran Erik (2009). Expression of genes involved in GABAergic neurotransmission in anoxic crucian carp brain (Carassius carassius). Physiological Genomics. ISSN 1094-8341. 36(2), p. 61–68. doi: 10.1152/physiolgenomics.90301.2008. Full text in Research Archive
• Nilsson, Göran Erik & Nilsson, Sara Østlund (2008). Hypoxic survival in two extremes: under the ice and on coral reefs. In Sebert, Philippe; Onyango, D. E. & Kapoor, B. G. (Ed.), Fish Life in Special Environments. Science Publishers Inc.. ISSN 9781578083879. Full text in Research Archive
• Ellefsen, Stian; Stenslokken, KO; Sandvik, Guro Katrine; Kristensen, Tom & Nilsson, Gøran Erik (2008). Improved normalization of real-time reverse transcriptase polymerase chain reaction data using an external RNA control. Analytical Biochemistry. ISSN 0003-2697. 376. doi: 10.1016/j.ab.2008.01.028. Full text in Research Archive
• Nilsson, Gøran Erik & Nilsson, Sara Østlund (2008). Hypoxic survival in two extremes: under the ice and on coral reefs. In Sebert, Philippe; Onyango, D. E. & Kapoor, B. G. (Ed.), Fish Life in Special Environments. Science Publishers Inc.. ISSN 9781578083879. p. 169–191. Full text in Research Archive
• Stensløkken, Kåre-Olav; Ellefsen, Stian; Stecyk, Jonathan Anthony William; Dahl, Mai Britt; Nilsson, Gøran Erik & Vaage, Jarle (2008). Differential regulation of AMP-activated kinase and AKT kinase in response to oxygen availability in crucian carp (Carassius carassius). American Journal of Physiology. Regulatory Integrative and Comparative Physiology. ISSN 0363-6119. 295(6), p. R1803–R1814. doi: 10.1152/ajpregu.90590.2008. Full text in Research Archive
• Stensløkken, Kåre-Olav; Milton, SL; Lutz, PL; Sundin, L; Renshaw, GMC & Stecyk, Jonathan Anthony William [Show all 7 contributors for this article] (2008). Effect of anoxia on the electroretinogram of three anoxia-tolerant vertebrates. Comparative Biochemistry and Physiology A. ISSN 1095-6433. 150, p. 395–403. doi: 10.1016/j.cbpa.2008.03.022. Full text in Research Archive
• Ellefsen, Stian; Sandvik, Guro Katrine; Larsen, Helene Kile; Stensløkken, Kåre-Olav; Hov, Dag Are Steenhoff & Kristensen, Tom [Show all 7 contributors for this article] (2008). Expression of genes involved in excitatory neurotransmission in anoxic crucian carp (Carassius carassius) brain. Physiological Genomics. ISSN 1094-8341. 35, p. 5–17. Full text in Research Archive
• Nilsson, Gøran Erik & Nilsson, Sara Østlund (2008). Does size matter for hypoxia tolerance in fish? Biological Reviews. ISSN 1464-7931. 83, p. 173–189. doi: 10.1111/j.1469-185X.2008.00038.x. Full text in Research Archive

View all works in NVA

• Nilsson, Gøran Erik (2010). Respiratory Physiology of Vertebrates. Cambridge University Press. ISBN 9780521878548. 334 p. Full text in Research Archive

View all works in NVA

• Lefevre, Sjannie & Nilsson, Göran Erik (2024). Case study: The anoxia-tolerant crucian carp, Encyclopedia of Fish Physiology (Second Edition). Elsevier. ISSN 9780323997614. p. 148–158. doi: 10.1016/B978-0-323-90801-6.00105-1. Full text in Research Archive
• Gerber, Lucie Claire Lola; Lundeberg, Jenny; Farhat, Elie; Nilsson, Göran Erik & Lefevre, Sjannie (2024). The key to living without oxygen? Succinate transport in the anoxia tolerant crucian carp. Full text in Research Archive
• Gerber, Lucie Claire Lola; Torp, May-Kristin; Nilsson, Göran Erik; Lefevre, Sjannie & Stensløkken, Kåre-Olav (2023). Comparison of Cardiac Mitochondrial Function of an Anoxia Tolerant and Intolerant Vertebrate. Full text in Research Archive
• Lefevre, Sjannie; Downie, Adam; Rummer, Jodie L. & Nilsson, Göran Erik (2022). Changes in haemoglobin gene expression during development of a coral reef fish. Full text in Research Archive Show summary

  Tropical reef fishes, such as the orange clownfish and other anemonefishes share a particular life history: The larvae hatch at the reef, go through a pelagic stage, after which the larvae return to the reef for settlement and maturation into adults. The two environments – coral reef and open sea – are vastly different, and poses unique challenges to the physiology of the fish. It has been shown that several species start out by having high maximum oxygen consumptions rates as larvae, but low hypoxia tolerance, a pattern that then reverses before or during the time of settlement. It has been hypothesised that shifting from low-affinity to high-affinity haemoglobin could be responsible for this pattern, but due to the very small size of the larvae, it has been difficult to investigate. In this study we used RNA sequencing to look at transcriptomic changes during larval development of the cinnamon clownfish (Amphiprion melanopus), focusing on the haemoglobin genes, which have different paralogs of the alpha and beta subunits. Larvae were bred and hatched in the lab, and sampled at 4, 6 and 9 days post-hatch. We found a clear shift from 4 to 9 days in the paralogs dominating the expression of both alpha and beta subunits. While investigation of the functional properties are still necessary to confirm that they switch from low- to high-affinity isoforms, specifically, the data supports the hypothesis that haemoglobin isoform switching occurs just before the larvae settle on the reef.

• Lefevre, Sjannie; Downie, Adam; Rummer, Jodie L. & Nilsson, Göran Erik (2022). Changes in haemoglobin gene expression during development of a coral reef fish. Full text in Research Archive
• Gerber, Lucie; Torp, May-Kristin; Nilsson, Göran Erik; Lefevre, Sjannie & Stensløkken, Kåre-Olav (2022). Improving organ preservation: Another lesson from the champion of anoxia tolerance, the crucian carp (C. carassius). Full text in Research Archive
• Gerber, Lucie; Torp, May-Kristin; Nilsson, Göran Erik; Stensløkken, Kåre-Olav & Lefevre, Sjannie (2022). Mitochondrial Functions in the Anoxia Tolerant Crucian Carp. Full text in Research Archive
• Gerber, Lucie; Torp, May-Kristin; Nilsson, Göran Erik; Lefevre, Sjannie & Stensløkken, Kåre-Olav (2022). Improving organ preservation: Another lesson from the champion of anoxia tolerance, the crucian carp (C. carassius). Full text in Research Archive
• Gerber, Lucie; Helle-Valle, Tellef; Resseguier, Julien Alain Andre; Torp, May-Kristin; Dahl, Helge Andre & Nilsson, Göran Erik [Show all 8 contributors for this article] (2022). Prolyl Hydroxylase Domains in the Anoxia Tolerant Crucian Carp (c. carassius): Insights into the Regulation of the HIF Response to Anoxia-Reoxygenation. Full text in Research Archive
• Gerber, Lucie; Helle-Valle, Tellef; Resseguier, Julien Alain Andre; Torp, May-Kristin; Dahl, Helge Andre & Nilsson, Göran Erik [Show all 8 contributors for this article] (2022). Prolyl Hydroxylase Domains in the Anoxia Tolerant Crucian Carp (c. carassius): Insights into the Regulation of the HIF Response to Anoxia-Reoxygenation. Full text in Research Archive
• Gerber, Lucie; Nilsson, Göran Erik & Lefevre, Sjannie (2021). Kan en fisk fra Nordmarka hjelpe oss? Full text in Research Archive
• Nilsson, Göran Erik; Dixson, Danielle L.; Domenici, Paolo; McCormick, Mark I.; Sørensen, Christina & Watson, Sue-Ann [Show all 7 contributors for this article] (2020). Author Correction: Near-future carbon dioxide levels alter fish behaviour by interfering with neurotransmitter function (Nature Climate Change, (2012), 2, 3, (201-204), 10.1038/nclimate1352). Nature Climate Change. ISSN 1758-678X. 10(8), p. 790–790. doi: 10.1038/s41558-020-0836-7. Full text in Research Archive
• Lefevre, Sjannie; Lau, Gigi Yik Chee; Dahl, Helge-Andre & Nilsson, Göran Erik (2019). Crucian carp: mitochondria, anoxia and reoxygenation. Full text in Research Archive
• Lefevre, Sjannie; Lau, Gigi Yik Chee; Dahl, Helge-Andre & Nilsson, Göran Erik (2019). Re-oxygenation resilience - the other aspect of the crucian carp’s anoxia tolerance. Full text in Research Archive
• Lefevre, Sjannie; McKenzie, David J. & Nilsson, Göran Erik (2019). Global warming and future fish size: thoughts on the gill-oxygen limitation hypothesis. Full text in Research Archive
• Jutfelt, Fredrik; Norin, Tommy; Ern, Rasmus; Overgaard, Johannes; Wang, Tobias & McKenzie, David J. [Show all 28 contributors for this article] (2018). Oxygen- and capacity-limited thermal tolerance: blurring ecology and physiology. Journal of Experimental Biology. ISSN 0022-0949. 221(1). doi: 10.1242/jeb.169615. Full text in Research Archive
• Nilsson, Göran Erik (2015). Vertebrates that survive without oxygen - what help do they get from gene expression, genes and genomes? Full text in Research Archive
• Nilsson, Göran Erik (2014). Cardiorespiratory Performance in Anoxia Tolerant Fish and Reptiles. Full text in Research Archive
• Lefevre, Sjannie; Stecyk, Jonathan A. W.; Torp, May-Kristin & Nilsson, Göran Erik (2014). HOW TOLERANT IS AN ANOXIA-TOLERANT VERTEBRATE? Full text in Research Archive Show summary

  The crucian carp Carassius carassius is capable of surviving without oxygen for several months, by carefully matching ATP supply and demand. It does so by exploiting its unique ability to produce ethanol as an anaerobic end-product and undergo partial metabolic rate suppression, shutting down non-vital functions such as vision. Even so, it is unknown if crucian carp are fully able to protect themselves from the damage (i.e. cell death), normally caused by absence and particularly re-entrance of oxygen. Here, we investigated the occurrence of apoptosis in brain of crucian carp exposed to normoxia, anoxia and re-oxygenation in the laboratory, using Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). We also measured mRNA and protein levels of the apoptosis executer protein Caspase 3 using quantitative real-time PCR and Western blotting. Additionally, Caspase 3 expression levels were measured in brains from crucian carp captured in their natural habitat at different months of the year. Overall, crucian carp appear to maintain apoptotic activity in anoxia, but there is a transient increase in the early re-oxygenation phase. In its natural habitat transcription of Caspase 3 is generally much down-regulated during the winter, but protein levels are maintained, with only a slight increase in the spring.

• Munday, Philip L.; Watson, Sue-Ann; Chung, Wen-Sung; Marshall, N. Justin & Nilsson, Göran Erik (2014). Response to 'The importance of accurate CO2 dosing and measurement in ocean acidification studies'. Journal of Experimental Biology. ISSN 0022-0949. 217(10), p. 1828–1829. doi: 10.1242/jeb.105890. Full text in Research Archive
• Lefevre, Sjannie; Watson, Sue-Ann; Munday, Philip L. & Nilsson, Göran Erik (2014). Golbal warming: Will jumping snails prevail? Full text in Research Archive
• Hammerstad, Marta; Tomter, Ane Berg; Hersleth, Hans-Petter; Røhr, Åsmund Kjendseth; Zoppellaro, Giorgio & Andersen, Niels Højmark [Show all 12 contributors for this article] (2013). Studies of the tyrosyl radicals and metal clusters in R2 of class Ia and Ib ribonucleotide reductase. Full text in Research Archive
• Tomter, Ane Berg; Zoppellaro, Giorgio; Hammerstad, Marta; Barra, Anne-Laure; Sandvik, Guro Katrine & Andersen, Niels Højmark [Show all 15 contributors for this article] (2013). Spectroscopic and DFT studies of the tyrosyl radicals in R2F/R2/p53R2 subunits of ribonucleotide reductase. Full text in Research Archive Show summary

  Spectroscopic and dft studies of the tyrosyl radicals in R2F/R2/p53R2 subunits of ribonucleotide reductase Ane B. Tomter1; Giorgio Zoppellaro1; Marta Hammerstad1; Niels H. Andersen1;Anne-Laure Barra2; Guro K. Sandvik1; Åsmund K. Roehr1; Jonas Bergan1; Stian Ellefsen1; Göran E. Nilsson1;Caleb B. Bell III 3; Florian Schmitzberger4; Pär Nordlund4; Edward I. Solomon4; and K. Kristoffer Andersson1* 1 Department of Molecular Biosciences, University of Oslo, NO-0316 Oslo (Norway), 2 Grenoble High Magnetic Field Laboratory, CNRS, Grenoble ,France 3Departmen of Chemistry, Stanford University, Stanford, CA ,USA 4Department of Med. Biochem. & Biophys., Karolinska Institutet, Stockholm, Sweden k.k.andersson@imbv.uio.no The Ribonucleotide reductase (RNR) catalyzes the conversion of ribonucleotides to the deoxyribonucleotides. Class I RNR is oxygen dependent and consists of two non-identical homodimeric subunits, named R1 and R2. The small subunit R2 carries a stable tyrosyl radical which is necessary for enzymatic activity [1]. We have studied the reduced state of the class Ib RNR R2F enzyme from Bacillus cereus, an opportunistic pathogen causing food poisoning, by CD, MCD, and VTVH-MCD spectroscopy [2]. Different tyrosyl radicals were analysed by electron paramagnetic resonance (EPR/HF-EPR) [3] and resonance Raman (rRaman) spectroscopy also of RNR from an anoxia tolerant vertebrate (crucian carp) and a virus. We have published structures of mouse R2 protein and integer spin EPR of di-nuclear Co and Fe clusters [4]. In the B. cereus R2, the rRaman fingerprints, and g-tensor values of tyrosyl radical is similar those featured by E. coli R2. In other R2s differences can be seen especially in the hyperfine A-tensor and g-values values, which indicate a different rotational conformation of the phenoxyl ring and presence of sometime hydrogen bonds to phenyl-oxygens. We can also observe a tyrosyl-radical interacting with a di-manganese cluster in B. cereus R2F with help of NrdI [5,6], similar to other class Ib R2F [6,7]. The manganase R2F [8, 9] has higher specific activity than iron form with natural reductant. It seems we can obtain tyrosyl-radical interacting magnetically with other metal ions as well like Co(II). The results will be compared to the studies of E. coli R2 (class Ia and Ib), mouse R2 [4], Epstein Barr Virus R2 [10], carp R2 [11,12] and p53R2 [11,12, 13]. References. [1] K.K. Andersson (Ed.), Ribonucleotide reductase, Nova Science Publishers, Inc. Hauppauge, NY, USA, ISBN: 978-1-60456-199-9, 2008; [2] A.B. Tomter, et al., Biochemistry 2008; 47, 11300; [3] K.K. Andersson, et al., J. Biol. Inorg. Chem. 2003, 8, 23; [4] K.R. Strand, et al., J. Biol. Chem., 2002, 277, 34229; 2004, 279, 46794; . Biochemistry 2003, 42, 12223; [5] Å.K. Røhr et al., Angew. Chem. Int. Ed.. 2010, 49, 2324; [6] J.A. Cortruvo and J. Stubbe, Biochemistry 2010, 49, 1297; [7] Cox et al., J. Am. Chem. Soc. 2010, 132, 11197; [8] A.B. Tomter, et al. PLoS ONE 2012, 7, e33436; [9] Crona et al, J. Biol. Chem. 2011, 286, 33053; [10] A.B. Tomter, et al., PloS ONE 2011, 6, e25022; [11] A.B. Tomter, et al. Coordin. Chem. Rev. 2013, 257, 3-26 , doi: 10.1016/j.ccr.2012.05.021; [12] G.K. Sandvik, et al. PLoS ONE. 2012, 8, e42784; [13] Wei et al., Biochemistry 2006; 45; 14043

• Tomter, Ane Berg; Zoppellaro, Giorgio; Hersleth, Hans-Petter; Andersen, Niels Højmark; Barra, Anne-Laure & Sandvik, Guro Katrine [Show all 13 contributors for this article] (2013). Spectroscopic, structural and DFT studies of the tyrosyl radicals in R2F/R2/p53R2 subunits of ribonucleotide reductase. NBS-nytt. ISSN 0801-3535. 1, p. 74–74. Full text in Research Archive Show summary

  Abstract M53 Spectroscopic, structural and DFT studies of the tyrosyl radicals in R2F/R2/p53R2 subunits of ribonucleotide reductase Ane B. Tomter1, Giorgio Zoppellaro1, Marta Hammerstad1, Hans-Petter Hersleth1, Niels H. Andersen1, Anne-Laure Barra2, Guro K. Sandvik1, Åsmund Kjendseth Røhr1, Göran E. Nilsson1, Caleb B. Bell III3, Florian Schmitzberger4, Pär Nordlund4, Edward I. Solomon4 and K. Kristoffer Andersson1 1Department of Biosciences, University of Oslo, NO-0316 Oslo, Norway 2Grenoble High Magnetic Field Laboratory, CNRS, Grenoble, France 3Department of Chemistry, Stanford University, Stanford, CA , USA 4Department of Med. Biochem. & Biophys., Karolinska Institutet, Stockholm, Sweden The Ribonucleotide reductase (RNR) catalyzes the conversion of ribonucleotides to the deoxyribonucleotides. Class I RNR is oxygen dependent and consists of two non-identical subunits. The small class I subunit R2 carries a stable tyrosyl radical which is necessary for enzymatic activity. Different tyrosyl radicals were analysed by electron paramagnetic resonance (EPR/HF-EPR/DFT) and resonance Raman (rRaman) spectroscopy also of RNR from an anoxia tolerant vertebrate (crucian carp) and a virus. In the B. cereus R2, the rRaman fingerprints, and g-tensor values of tyrosyl radical is similar those featured by E. coli R2. The results will be compared to the studies of mouse R2, Epstein Barr Virus R2, carp R2 and p53R2. We can also observe a tyrosyl-radical magnetically interacting with di-manganese/di-cobalt clusters in B. cereus R2F with help of NrdI, similar to other class Ib R2F. A.B. Tomter, et al., Coordin. Chem. Rev. 2013.

• Johansen, Ida Beitnes; Lunde, Ida Gjervold; Vindas, Marco Antonio; Stecyk, Jonathan Anthony William; Røsjø, Helge & Christensen, Geir Arve [Show all 9 contributors for this article] (2012). Stresshormonet kortisol induserer hjertevekst hos laksefisk. Full text in Research Archive
• Couturier, Christine Stephanie; Øverli, Øyvind & Nilsson, Göran Erik (2012). Aerob kapasitet hos laks i en varmere fremtid: En sammenligning mellom norske og franske laksepopulasjoner. Full text in Research Archive
• Tomter, Ane Berg; Zoppellaro, Giorgio; Hammerstad, Marta; Barra, Anne-Laure; Sandvik, Guro Katrine & Andersen, Niels Højmark [Show all 11 contributors for this article] (2012). Spectroscopic and dft studies of the tyrosyl radicals in R2F/R2/p53R2 subunits of ribonucleotide reductase. Full text in Research Archive Show summary

  Spectroscopic and dft studies of the tyrosyl radicals in R2F/R2/p53R2 subunits of ribonucleotide reductase Ane B. Tomter; Giorgio Zoppellaro; Marta Hammerstad, Anne-Laure Barra; Guro K. Sandvik; Niels H. Andersen; Åsmund K. Roehr; Jonas Bergan; Stian Ellefsen; Göran E. Nilsson; Caleb B. Bell III; Florian Schmitzberger; Pär Nordlund; Edward I. Solomon; and K. Kristoffer Andersson Department of Molecular Biosciences, University of Oslo, NO-0316 Oslo (Norway), Grenoble High Magnetic Field Laboratory, CNRS, Grenoble ,France Departmen of Chemistry, Stanford University, Stanford, CA ,USA Department of Med. Biochem. and Biophys., Karolinska Institutet, Stockholm, Sweden The Ribonucleotide reductase (RNR) catalyzes the conversion of ribonucleotides to the deoxyribonucleotides. Class I RNR is oxygen dependent and consists of two non-identical homodimeric subunits, named R1 and R2. The small subunit R2 carries a stable tyrosyl radical which is necessary for enzymatic activity [1]. We have studied the reduced state of the class Ib RNR R2F enzyme from Bacillus cereus, an opportunistic pathogen causing food poisoning, by CD, MCD, and VTVH-MCD spectroscopy [2]. Different tyrosyl radicals were analysed by electron paramagnetic resonance (EPR/HF-EPR) [3] and resonance Raman (rRaman) spectroscopy also of RNR from an anoxia tolerant vertebrate (crucian carp) and a virus. We have published structures of mouse R2 protein and integer spin EPR of di-nuclear Co and Fe clusters [4]. In the B. cereus R2, the rRaman fingerprints, and g-tensor values of tyrosyl radical is similar those featured by E. coli R2. In other R2s differences can be seen especially in the hyperfine A-tensor and g-values values, which indicate a different rotational conformation of the phenoxyl ring and presence of sometime hydrogen bonds to phenyl-oxygens. We can also observe a tyrosyl-radical interacting with a di-manganese cluster in B. cereus R2F with help of NrdI [5,6], similar to other class Ib R2F [6,7]. The manganase R2F [8, 9] has higher specific activity than iron form with natural reductant. It seems we can obtain tyrosyl-radical interacting magnetically with other metal ions. The results will be compared to the studies of E. coli R2 (class Ia and Ib), mouse R2 [4], Epstein Barr Virus R2 [10], carp R2 [11,12] and p53R2 [11,12]. References. [1] K.K. Andersson (Ed.), Ribonucleotide reductase, Nova Science Publishers, Inc. Hauppauge, NY, USA, ISBN: 978-1-60456-199-9, 2008; [2] A.B. Tomter, et al., Biochemistry 2008; 47, 11300; [3] K.K. Andersson, et al., J. Biol. Inorg. Chem. 2003, 8, 23; [4] K.R. Strand, et al., J. Biol. Chem., 2002, 277, 34229; 2004, 279, 46794; [5] Å.K. Røhr et al., Angew. Chem. Int. Ed.. 2010, 49, 2324; [6] J.A. Cortruvo, J. Stubbe, Biochemistry 2010, 49, 1297; [7] Cox et al., J. Am. Chem. Soc. 2010, 132, 11197; [8] A.B. Tomter, et al. PLoS ONE 2012, 7(3), e33436; [9] Crona et al, J. Biol. Chem. 2011, 286, 33053; [10] A.B. Tomter, et al., PloS ONE 2011, 6 (9), e25022; [11] A.B. Tomter, et al. Coordin. Chem. Rev. 2012, (in press); [12] G.K. Sandvik, et al. PLoS ONE. 2012, (in press)

• Andersson, K. Kristoffer; Tomter, Ane Berg; Zoppellaro, Giorgio; Barra, Anne-Laure; Sandvik, Guro Katrine & Andersen, Niels Højmark [Show all 14 contributors for this article] (2011). Spectroscopic and DFT Studies of the Tyrosyl Radicals and the Binuclear Metal-ion Sites in R2F/R2 subunits of Ribonucleotide Reductase. JBIC Journal of Biological Inorganic Chemistry. ISSN 0949-8257. 16, p. S417–S417. doi: 10.1007/s00775-011-0862-z. Full text in Research Archive Show summary

  Ribonucleotide reductase (RNR) catalyzes the conversion of ribonucleotides to the deoxyribonucleotides. Class I RNR is oxygen dependent and consists of two non-identical homodimeric subunits, named R1 and R2. The small subunit R2 carries a stable tyrosyl radical which is necessary for enzymatic activity (1). We have studied the reduced state of the class Ib RNR R2F enzyme from Bacillus cereus, an opportunistic pathogen causing food poisoning, by CD, MCD, and VTVH-MCD spectroscopy (2). Different tyrosyl radicals were analysed by electron paramagnetic resonance (EPR/HF-EPR) (3) and resonance Raman (rRaman) spectroscopy also of RNR from an anoxia tolerant vertebrate (crucian carp) and a virus. We have published structures of mouse R2 protein and integer spin EPR of di-nuclear Co and Fe clusters (4). In the B. cereus R2, the rRaman fingerprints, and g-tensor values of tyrosyl radical is similar those featured by E. coli R2. In other R2s differences can be seen especially in the hyperfine A-tensor and g-values values, which indicate a different rotational conformation of the phenoxyl ring and presence of sometime hydrogen bonds to phenyl-oxygens. We can also observe a radical in the manganese substituted B. cereus R2F with help of NrdI (5), similar to other class Ib R2F (6), it seems we can obtain radical with other metal ions. The results will be compared to the studies of E. coli R2 (class Ia and Ib), mouse R2, and p53R2. (1) M. Kolberg et al, Biochim. Biophys. Acta 2004, 1699, 1; K.K. Andersson (Ed.) Ribonucleotide reductase 2008, Nova Science, New York. (2) A.B. Tomter, et al. Biochemistry 2008, 47, 11300 (3) K.K. Andersson & A.-L. Barra Spectrochim. Acta (A) Mol. Biomol. Spectrosc. 2002, 58, 1101; K.K. Andersson, et a., J. Biol. Inorg. Chem. 2003, 8, 23; A.-L. Barra et al., In Very High Frequency (VHR) ESR/EPR. Biol. Magn. Resonance 2004, 22, 145 (4) K.R. Strand et al., J. Biol. Chem., 2002, 277, 34229; K.R. Strand et al., J. Biol. Chem., 2004, 279, 46794 (5) Å.K. Røhr et al., Angew. Chem. Int. Ed.. 2010, 49, 2324 (6) J.A. Cortruvo & J. Stubbe, Biochemistry 2010, 49, 1297

• Sandvik, Guro Katrine; Tomter, Ane Berg; Røhr, Åsmund Kjendseth; Zoppellaro, Giorgio; Andersen, Niels Højmark & Bergan, Jonas [Show all 10 contributors for this article] (2010). Class I Ribonucleotide reductase in an anoxia tolerant vertebrate, the crucian carp. Full text in Research Archive Show summary

  Class I Ribonucleotide reductase in an anoxia tolerant vertebrate, the crucian carp Guro K. Sandvik1, Ane B. Tomter1, Åsmund K. Røhr, Giorgio Zoppellaro1, Niels H. Andersen1, Jonas Bergan1, Stian Ellefsen1, Anne-Laure Barra2, Göran E. Nilsson1 and K. Kristoffer Andersson1 1Department of Molecular Biosciences, University of Oslo, POBox 1041, NO-0316 Oslo, NORWAY 2 Grenoble High Magentic Field Laboratory, LCMI-CNRS, B.P. 166, FR- 38042 Grenoble cedex 9 FRANCE The fish crucian carp (Carrassius carrassius) can survive several months in anoxia, partly because of its extraordinary ability to convert lactate to ethanol, which allows it to avoid lactate accumulation. Consequently, the crucian carp are able to survive on anaerobic metabolism through the winter, when the pond they are living in gets covered with ice and snow, blocking oxygen exchange with the air. Remarkably, previous studies in our group have shown cell division in severe hypoxic crucian carp (in water with <0.1 mg O2/L). This led us to investigate the enzyme ribonucleotide reductase (RNR), because RNR is required for production of new nucleotides and is oxygen dependent in all vertebrates studied so far. RNR in crucian carp must therefore be exceptional in some way, possibly by forming an unusually stable radical, or by having an extremely high oxygen affinity. We have cloned and sequenced several variants of class I RNR in the crucian carp: two variants of the large RNR (R1) subunit, two variants of the small RNR (R2) subunit and two variants of the p53R2 subunit. Interestingly, quantitative real-time PCR measurements in normoxic and severe hypoxic crucian carp revealed that the expression of the small RNR subunit (R2), which is the subunit activated by oxygen, was maintained in severe hypoxia. In mammals, this subunit is normally only expressed in mitotically active cells, suggesting that the crucian carp may have a functional RNR in severe hypoxia. RNR proteins were also in vitro expressed in E. coli for structural and enzymatic studies. Amino acid analysis, EPR (electron paramagnetic resonance), HF-EPR and Raman spectroscopy show that the crucian carp RNR variants are structurally similar to mammalian RNR, but ongoing studies will reveal if their oxygen affinity or stability in hypoxia or anoxia are different. Supported by the Research Council of Norway.

• Sandvik, Guro Katrine; Tomter, Ane Berg; Røhr, Åsmund Kjendseth; Zoppellaro, Giorgio; Andersen, Niels Højmark & Bergan, Jonas [Show all 10 contributors for this article] (2010). Class I Ribonucleotide reductase in an anoxia tolerant vertebrate, the crucian carp. Full text in Research Archive Show summary

  Guro K. Sandvik1, Ane B. Tomter1, Åsmund K. Røhr, Giorgio Zoppellaro1, Niels H. Andersen1, Jonas Bergan1, Stian Ellefsen1, Anne-Laure Barra2, Göran E. Nilsson1 and K. Kristoffer Andersson1 1Department of Molecular Biosciences, University of Oslo, POBox 1041, NO-0316 Oslo, NORWAY 2 Grenoble High Magentic Field Laboratory, LCMI-CNRS, B.P. 166, FR- 38042 Grenoble cedex 9 FRANCE The fish crucian carp (Carrassius carrassius) can survive several months in anoxia, partly because of its extraordinary ability to convert lactate to ethanol, which allows it to avoid lactate accumulation. Consequently, the crucian carp are able to survive on anaerobic metabolism through the winter, when the pond they are living in gets covered with ice and snow, blocking oxygen exchange with the air. Remarkably, previous studies in our group have shown cell division in severe hypoxic crucian carp (in water with <0.1 mg O2/L). This led us to investigate the enzyme ribonucleotide reductase (RNR), because RNR is required for production of new nucleotides and is oxygen dependent in all vertebrates studied so far. RNR in crucian carp must therefore be exceptional in some way, possibly by forming an unusually stable radical, or by having an extremely high oxygen affinity. We have cloned and sequenced several variants of class I RNR in the crucian carp: two variants of the large RNR (R1) subunit, two variants of the small RNR (R2) subunit and two variants of the p53R2 subunit. Interestingly, quantitative real-time PCR measurements in normoxic and severe hypoxic crucian carp revealed that the expression of the small RNR subunit (R2), which is the subunit activated by oxygen, was maintained in severe hypoxia. In mammals, this subunit is normally only expressed in mitotically active cells, suggesting that the crucian carp may have a functional RNR in severe hypoxia. RNR proteins were also in vitro expressed in E. coli for structural and enzymatic studies. Amino acid analysis, EPR (electron paramagnetic resonance), HF-EPR and Raman spectroscopy show that the crucian carp RNR variants are structurally similar to mammalian RNR, but ongoing studies will reveal if their oxygen affinity or stability in hypoxia or anoxia are different. Supported by the Research Council of Norway.

• Mommsen, Thomas P.; Nilsson, Gøran Erik & Walsh, Patrick J. (2010). CBP turns fifty. Comparative Biochemistry and Physiology - Part D:Genomics and Proteomics. ISSN 1744-117X. 5(1), p. 10–11. doi: 10.1016/j.cbd.2009.12.002. Full text in Research Archive
• Mommsen, TP; Nilsson, Gøran Erik & Walsh, PJ (2010). CBP turns fifty. Comparative Biochemistry and Physiology A. ISSN 1095-6433. 155(1), p. 10–11. doi: 10.1016/j.cbpa.2009.10.028. Full text in Research Archive
• Tomter, Ane Berg; Barra, Anne-Laure; Sandvik, Guro Katrine; Zoppellaro, Giorgio; Andersen, Niels Højmark & Røhr, Åsmund Kjendseth [Show all 14 contributors for this article] (2010). Spectroscopic and HF-EPR studies of the tyrosyl radical and the binuclear iron site of the R2F/R2 subunits of ribonucleotide reductase. Full text in Research Archive Show summary

  Spectroscopic and HF-EPR Studies of the Tyrosyl Radical and the Binuclear Iron Site of the R2F/R2 subunits of Ribonucleotide Reductase Ane B. Tomter1, Anne-Laure Barra2, Guro K. Sandvik1, Giorgio Zoppellaro1, Niels H. Andersen1, Åsmund K. Røhr1, Jonas Bergan1, Stian Ellefsen1, Göran E. Nilsson1, Caleb B. Bell III3, Florian Schmitzberger4, Pär Nordlund4, Edward I. Solomon3, and K. Kristoffer Andersson1 1 Department of Molecular Biosciences, University of Oslo, Norway 2 Grenoble High Magnetic Field Laboratory, CNRS, Grenoble, France 3 Chemistry Department, Stanford University, Stanford, CA, USA 4 Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden Ribonucleotide reductase (RNR) catalyzes the conversion of ribonucleotides to the corresponding deoxyribonucleotides in all living organisms, thereby providing and controlling the pool of building blocks necessary for DNA synthesis and repair. Class I RNR is oxygen dependent and consists of two non-identical homodimeric subunits, named R1 and R2 which can be assembled into enzymatically active tetramers (R12R22). As shown in Figure 1, the ribonucleotide binding and active site A is located in R1, while the small subunit R2 carries a stable tyrosyl radical which is necessary for enzymatic activity, close to a diiron metal site. The radical generated in the R2 subunit is shuttled to the active site of R1 subunit, about 35 Å from the radical iron cluster, through a conserved array of hydrogen bonded amino acids [1]. We have studied the reduced state of the class Ib RNR R2F enzyme from Bacillus cereus, an opportunistic pathogen causing food poisoning, using a combination of circular dichroism (CD), magnetic circular dichroism (MCD), and variable-temperature variable-field (VTVH) MCD spectroscopy [2]. Furthermore, the tyrosyl radical in the ferric active state was analysed by electron paramagnetic resonance (EPR/HF-EPR) [3] and resonance Raman (rR) spectroscopy of RNR from an anoxia tolerant vertebrate (crucian carp) and a virus. In the B. cereus R2, the rR fingerprints and g-tensor values of tyrosyl radical resemble those featured by E. coli R2, although differences can be seen especially in the hyperfine A-tensor values, which indicate a different rotational conformation of the phenoxyl ring. We can also observe a radical in the manganese substituted B. cereus R2F with help of NrdI [4], similar to what has been observed for E. coli R2F [5]. The results have been compared to the studies of E. coli R2, mouse R2, and p53R2 which all are of RNR class Ia. [1] (a) M. Kolberg, K.R. Strand, P. Graff, K.K. Andersson Biochim. Biophys. Acta 2004, 1699, 1-34. (b) Andersson K. K. Ed. in Ribonucleotide reductase 2008, Nova Science, New York. [2] A.B.Tomter, C.B. Bell, Å.K. Røhr, K.K. Andersson, E.I. Solomon Biochemistry 2008, 47, 11300-11309. [3] (a) K.K. Andersson, A.-L. Barra (2002) Spectrochim. Acta (A) Mol. Biomol. Spectrosc. 2002, 58, 1101-1112; (b) K.K. Andersson, P. P. Schmidt, B. Katterle, K.R. Stand, A. Palmer, S.-K. Lee, E. I. Solomon, A. Gräslund, A.-L. Barra (2003) J. Biol. Inorg. Chem. 2003, 8, 235-247(c) Barra A.-L., A. Gräslund and K. K. Andersson (2004) In Very High Frequency (VHR) ESR/EPR. Biol. Magn. Resonance 22, 145-164 [4] Å.K. Røhr, H.-P. Hersleth, K.K. Andersson, Angew. Chem. Int. Ed.. 2010, 49, 2324-2327 [5] J.A. Cortruvo, J. Stubbe, Biochemistry 2010, 49, 1297-1309

• Mommsen, TP; Nilsson, Gøran Erik & Walsh, PJ (2010). CBP turns fifty. Comparative Biochemistry and Physiology - Part B: Biochemistry & Molecular Biology. ISSN 1096-4959. 155(1), p. 10–11. doi: 10.1016/j.cbpb.2009.10.011. Full text in Research Archive
• Stecyk, Jonathan Anthony William; Larsen, Bent Collert & Nilsson, Gøran Erik (2009). Crucian carp heart performance during anoxia and acidosis. Comparative Biochemistry and Physiology A. ISSN 1095-6433. 153A(2), p. S98–S98. doi: 10.1016/j.cbpa.2009.04.116. Full text in Research Archive
• Tomter, Ane Berg; Røhr, Åsmund Kjendseth; Zoppellaro, Giorgio; Sandvik, Guro Katrine; Bergan, Jonas & Barra, Anne-Laure [Show all 14 contributors for this article] (2009). Ribonucleotide reductase spectroscopy and structure of class I proteins from bacteria, virus, mammals and fish. Full text in Research Archive Show summary

  Ribonucleotide reductase spectroscopy and structure of class I proteins from bacteria, virus, mammals and fish. Ane B. Tomter(a), Åsmund K. Røhr(a), Giorgio Zoppellaro(a), Guro K. Sandvik(a), Jonas Bergan(a), Anne-Laure Barra(b), Florian Schmitzberger(c), Caleb Bell III(d), Pin-Pin Wei(d), Göran E. Nilsson(a), Pär Nordlund(c), Edward I. Solomon(d), Kari R. Strand(a) and K. Kristoffer Andersson(a) (a)Department of Molecular Biosciences (IMBV), University of Oslo, NO-0316 Oslo, NO; k.k.andersson@imbv.uio.no, Fax; +4722856041, (b)Grenoble High Magnetic Field Laboratory, CNRS, Grenoble, FR, (c)Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, SE, (d)Department of Chemistry, Stanford University, Stanford, CA, US Ribonucleotide reductase (RNR) is the enzyme that converts ribonucleotides to their corresponding deoxyribonucleotides. The R2 subunit (class Ia and b) have a diferric iron-oxygen cluster and a tyrosyl radical that is essential for enzymatic activity [1,2]. The p53R2 is proposed to be involved in DNA repair and mitochondrial DNA synthesis. The human (Class Ia) p53R2/ R2, the Bacillus cereus (Class Ib) R2, the Epstein Barr virus (Class Ia) R2, Karp R2 (Class Ia) and the murine (Class Ia) p53R2 proteins have been studied by electron paramagnetic resonance (EPR/HF-EPR), Raman, magnetic circular dichroism (MCD) [3] and circular dichroism [3]. While the studies of the active diferric iron-oxygen cluster and the tyrosyl radical together with the mixed valent form (Fe(II)-Fe(III) cluster) shows little or no variation between mammalian the R2, fish and p53R2 subunits, the MCD and X-band integer spin EPR studies reveals a difference diferrous forms. The p53R2 and Bacillus cereus R2 [3] lack the cooperatively binding of Fe(II) and Co(II) shown for the mouse R2. Taken together the interaction with the R1 subunit of RNR are similar for mammalian, fish R2 and p53R2 active and possibly also mixed valent forms. Novel 3D structures have been determined of other RNR related proteins from Bacillus cereus. 1. Andersson K.K. (ed.) (2008) Ribonucleotide reductase, Nova Science Publishers, Inc. Hauppauge, N.Y. USA. ISBN: 978-1-60456-199-9. 2 Kolberg M., Strand K.R., Graff P., Andersson K.K. (2004) Radicals in Three Different Classes of Ribonucleotide Reductases: Structural and Functional Basis. Biochim. Biophys. Acta 1699; 1-34. 3. Tomter A.B, Bell III C.B, Røhr A.K., Andersson K.K., Solomon E.I. (2008) Circular dichroism and magnetic circular dichroism studies of the reduced biferrous site of the R2F subunit of the class Ib ribonucleotide reductase from Bacillus cereus: Comparison to the class Ia R2s form E. coli and mouse. Biochemistry 47, 11300-11309.

• Nilsson, Gøran Erik (2009). Karussens liv under isen. [TV]. NRK1 Ut i Naturen. Full text in Research Archive
• Walsh, PJ; Mommsen, TP & Nilsson, Gøran Erik (2009). The do's and don't's of submitting scientific papers. Comparative Biochemistry and Physiology - Part C: Toxicology & Pharmacology. ISSN 1532-0456. 149(3), p. 267–268. doi: 10.1016/j.cbpc.2008.12.007. Full text in Research Archive
• Walsh, PJ; Mommsen, TP & Nilsson, Gøran Erik (2009). The do's and don't's of submitting scientific papers. Comparative Biochemistry and Physiology - Part D:Genomics and Proteomics. ISSN 1744-117X. 4(1), p. 1–2. doi: 10.1016/j.cbd.2008.12.005. Full text in Research Archive
• Walsh, PJ; Mommsen, TP & Nilsson, Gøran Erik (2009). The do's and don't's of submitting scientific papers. Comparative Biochemistry and Physiology - Part B: Biochemistry & Molecular Biology. ISSN 1096-4959. 152(3), p. 203–204. doi: 10.1016/j.cbpb.2008.12.010. Full text in Research Archive
• Walsh, PJ; Mommsen, TP & Nilsson, Gøran Erik (2009). The do's and don't's of submitting scientific papers. Comparative Biochemistry and Physiology A. ISSN 1095-6433. 152(3), p. 291–292. doi: 10.1016/j.cbpa.2008.12.007. Full text in Research Archive
• Sandvik, Guro Katrine; Bergan, Jonas; Ellefsen, Stian; Tomter, Ane Berg; Andersson, K. Kristoffer & Nilsson, Gøran Erik (2009). Ribonucleotide reductase in an anoxia tolerant vertebrate, the crucian carp. Full text in Research Archive
• Sandvik, Guro Katrine; Bergan, Jonas; Ellefsen, Stian; Tomter, Ane Berg; Røhr, Åsmund Kjendseth & Andersson, K. Kristoffer [Show all 7 contributors for this article] (2009). Class I ribonucleotide reductase in an anoxia tolerant fish. Full text in Research Archive
• Johansen, Ida Beitnes; Sandvik, Guro Katrine; Nilsson, Gøran Erik & Øverli, Øyvind (2009). Effect of selection for stress responsiveness on neural plasticity: A gene expression study. Comparative Biochemistry and Physiology A. ISSN 1095-6433. 153A(2), p. S92–S92. doi: 10.1016/j.cbpa.2009.04.094. Full text in Research Archive
• Couturier, Christine; Nilsson, Gøran Erik; Prentice, HM; Milton, SL; Fagernes, Cathrine Elisabeth & Stecyk, Jonathan Anthony William [Show all 9 contributors for this article] (2009). Gene expression in anoxic turtle brain. Comparative Biochemistry and Physiology A. ISSN 1095-6433. 153A(2), p. S101–S101. doi: 10.1016/j.cbpa.2009.04.127. Full text in Research Archive
• Røhr, Åsmund Kjendseth; Tomter, Ane Berg; Sandvik, Guro Katrine; Bergan, Jonas; Barra, Anne-Laure & Nilsson, Gøran Erik [Show all 8 contributors for this article] (2008). Spectroscopic and structural studies of ion center and tyrosyl radical in mammalian, fish and bacterial ribonucleotide reductase. Full text in Research Archive
• Tomter, Ane Berg; Røhr, Åsmund Kjendseth; Sandvik, Guro Katrine; Bergan, Jonas; Barra, Anne-Laure & Nilsson, Gøran Erik [Show all 8 contributors for this article] (2008). HF and X-band EPR and structural studies of ion center and tyrosyl radical in mammalian, fish and bacterial ribonucleotide reductase. Full text in Research Archive
• Nilsson, Gøran Erik; Oijordsbakken, M; Ellefsen, Stian; Stenslokken, K & Stecyk, J (2008). Hypoxia inducible factor (HIF) - A threat to hypoxic survival? Comparative Biochemistry and Physiology A. ISSN 1095-6433. 150, p. S118–S119. doi: 10.1016/j.cbpa.2008.04.270. Full text in Research Archive
• Sandvik, G; Bergan, J; Ellefsen, Stian & Nilsson, Gøran Erik (2008). Is the presumably oxygen-dependent enzyme ribonucleotide reductase functioning in anoxic crucian carp? Comparative Biochemistry and Physiology A. ISSN 1095-6433. 150, p. S120–S120. doi: 10.1016/j.cbpa.2008.04.277. Full text in Research Archive
• Stecyk, J; Skovgaard, N; Nilsson, Gøran Erik & Wang, T (2008). Effects of hydrogen sulfide on the cardiovascular system of normoxic and anoxic turtles (Trachemys scripta). Comparative Biochemistry and Physiology A. ISSN 1095-6433. 150, p. S99–S99. doi: 10.1016/j.cbpa.2008.04.198. Full text in Research Archive
• Dymowska, Agnieszka Karolina; Stecyk, J & Nilsson, Gøran Erik (2008). Localization of ionocytes in crucian carp (Carassius carassius) gills during hypoxic remodelling. Comparative Biochemistry and Physiology A. ISSN 1095-6433. 150, p. S103–S103. doi: 10.1016/j.cbpa.2008.04.213. Full text in Research Archive
• Fagemes, C; Ellefsen, Stian; Stenslokken, K; Berenbrink, M & Nilsson, Gøran Erik (2008). Molecular background to ethanol production in crucian carp (Carassius carassius). Comparative Biochemistry and Physiology A. ISSN 1095-6433. 150, p. S112–S112. doi: 10.1016/j.cbpa.2008.04.246. Full text in Research Archive
• Boyd, Philip W.; Collins, Sinead; Dupont, Sam; Fabricius, Katharina; Gattuso, Jean-Pierre & Havenhand, Jonathan [Show all 21 contributors for this article] (2019). SCOR WG149 Handbook to support the SCOR Best Practice Guide for ‘Multiple Drivers’ Marine Research. University of Tasmania, on behalf of Scientific Committee on Oceanic Research (SCOR). ISSN 9781925646726. Full text in Research Archive
• Fagernes, Cathrine Elisabeth; Ellefsen, Stian & Nilsson, Göran Erik (2014). Molecular background of ethanol production in anoxia tolerant fish. Akademika forlag. Full text in Research Archive
• Sørensen, Christina; Øverli, Øyvind & Nilsson, Göran Erik (2011). Regulation of brain cell proliferation in fish. Faculty of Mathematics and Natural Sciences. Full text in Research Archive
• Fagernes, Cathrine Elisabeth; Ellefsen, Stian & Nilsson, Göran Erik (2008). Molecular background to ethanol production in crucian carp (Carassius carassius). Universitetet i Oslo. Full text in Research Archive Show summary

  Crucian carp (Carassius carassius) avoids lactic acidosis during prolonged periods of anoxia by producing ethanol as the main anaerobic end-product. Apparently, this is made possible by adaptations in the pyruvate dehydrogenase complex (PDHc), which seems to leak acetaldehyde. The acetaldehyde can subsequently be converted to ethanol by alcohol dehydrogenase, a conversion that seems to be restricted to skeletal muscle. The PDHc is a multienzyme complex, consisting of three main units (E1, E2 and E3). I have cloned the E1-subunits E1α and E1β and the E2 enzyme in crucian carp and some related cyprinid fishes, and investigated their sequences and mRNA expression in brain, heart, liver and red muscle using real-time RT PCR. For the E1 subunits, multiple paralogs were found, E1α1-3 and E1β1-2. The extensively deviating E1α3 and E1β2 forms were exclusively expressed in red muscle, where they dominated the expression, making up >94% of the overall E1α- and E1β-subunit expression in this tissue. E1α3 was also found in the ethanol producing goldfish (Carassius auratus) but not in other cyprinid fish studied (zebrafish, roach and common carp). By contrast E1α1,2 and E1β1 were expressed at comparable levels in all investigated tissues, including red muscle. For the E2 enzyme, only one paralog was found. This paralog was also expressed at comparable levels in all investigated tissues. The ubiquitous E1α1,2 and E1β1 paralogs are probably responsible for the normal acetyl-CoA synthesis involved in oxidative ATP production. It is suggested that the muscle-specific E1α3 and E1β2 paralogs are involved in ethanol production in crucian carp, by forming E1 enzymes that produce acetaldehyde.

View all works in NVA