Responses of threespine stickleback ( Gasterosteus aculeatus, L) transcriptome to hypoxia

Hypoxia is a naturally occurring phenomenon in aquatic systems. Its occurrence is potentiated by eutrophication caused by human actions and it may be made even more severe as a result of increasing temperatures due to climate change. Threespine stickleback ( Gasterosteus aculeatus) has previously been used by ecologists and evolutionary biologists, but has great potential also for physiological studies. We subjected threespine sticklebacks to hypoxia (air saturation 24–28%) or normoxia for 3 and 48 h. To study changes in the transcriptome, microarray determinations were carried out for the 48 h treatments and complementary real-time quantitative PCR was run on selected transcripts at both time points. The microarray results suggest downregulation of genes encoding proteins with functions typically inhibited by hypoxia, i.e., cell proliferation, DNA replication and repair, and protein degradation, and upregulation of transcripts with products having oxygenase and oxidase activities including two 2-oxoglutarate-deoxygenases. These transcripts encode for JmjC domain containing proteins JMJD6 and JMJD2C. JMJD6 transcription has not earlier been characterized to change in hypoxia. Cyp1A2 mRNA was also increased in the microarray and the upregulation could be confirmed on protein level by measuring ethoxyresorufin- O-deethlyase (EROD)-activity.