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Baltic salmon (Salmo salar) yolk-sac fry mortality is associated with disturbances in the function of hypoxia-inducible transcription factor (HIF-1α) and consecutive gene expression
Vuori, K.A.M.; Soitamo, A.; Vuorinen, P.J.; Nikinmaa, M. (2004). Baltic salmon (Salmo salar) yolk-sac fry mortality is associated with disturbances in the function of hypoxia-inducible transcription factor (HIF-1α) and consecutive gene expression. Aquat. Toxicol. 68(4): 301-313. dx.doi.org/10.1016/j.aquatox.2004.03.019
In: Aquatic Toxicology. Elsevier Science: Tokyo; New York; London; Amsterdam. ISSN 0166-445X, more
Peer reviewed article  

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Keywords
    Deficiency diseases; Marine fish; Mortality; Marine

Authors  Top 
  • Vuori, K.A.M.
  • Soitamo, A.
  • Vuorinen, P.J.
  • Nikinmaa, M.

Abstract
    Baltic salmon (Salmo salar) suffer from abnormally high yolk-sac fry mortality designated as M74-syndrome. In 1990s, 25-80% of salmon females, which ascended rivers to spawn, produced yolk-sac fry suffering from the syndrome. Symptoms of M74-affected fry include neurological disturbances, impaired vascular development and abnormal haemorrhages. The latter symptoms are observed in mammalian embryos if the function of hypoxia inducible transcription factor (HIF-1α), its dimerization partner aryl hydrocarbon nuclear translocator (ARNT) or target gene vascular endothelial growth factor (VEGF) is disturbed. To study the possible involvement of HIF-1α and its target gene VEGF in the development of the syndrome, we collected healthy and M74-affected wild Baltic salmon yolk-sac fry and analyzed HIF-1 mRNA and protein expression, HIF-1α DNA-binding, target gene VEGF protein expression, and blood vessel density in both groups at different stages of yolk-sac fry development. In addition, since Baltic salmon females contain organochlorine contaminants, which have been suggested to be the cause of M74 syndrome via the aryl hydrocarbon receptor (AhR)-dependent gene expression pathway, we studied AhR protein expression, AhR DNA-binding and target gene CYP1A protein expression. Since the parents of both healthy and M74-affected wild fry will have experienced the organochlorine load from the Baltic Sea, hatchery-reared fry were included in the studies as an additional control. The results show that the vascular defects observed in fry suffering from M74 are associated with reduced DNA-binding activity of HIF-1α and subsequent downregulation of its target gene vascular endothelial growth factor (VEGF). In addition, also AhR function is decreased in diseased fry making it unlikely that symptoms of M74-affected fry would be caused by an upregulation of xenobiotically induced AhR-dependent gene expression pathway.

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