Analyzing Cold Tolerance Mechanism in Transgenic Zebrafish (<i>Danio rerio</i>)

<div><p>Low temperatures may cause severe growth inhibition and mortality in fish. In order to understand the mechanism of cold tolerance, a transgenic zebrafish <i>Tg</i> (<i>smyd1:m3ck</i>) model was established to study the effect of energy homeostasis during cold stress. The muscle-specific promoter <i>Smyd1</i> was used to express the carp muscle form III of creatine kinase (<i>M3</i>-<i>CK</i>), which maintained enzymatic activity at a relatively low temperature, in zebrafish skeletal muscle. <i>In situ</i> hybridization showed that <i>M3</i>-<i>CK</i> was expressed strongly in the skeletal muscle. When exposed to 13°C, <i>Tg</i> (<i>smyd1:m3ck</i>) fish maintained their swimming behavior, while the wild-type could not. Energy measurements showed that the concentration of ATP increased in <i>Tg</i> (<i>smyd1:m3ck</i>) versus wild-type fish at 28°C. After 2 h at 13°C, ATP concentrations were 2.16-fold higher in <i>Tg</i> (<i>smyd1:m3ck</i>) than in wild-type (<i>P</i><0.05). At 13°C, the ATP concentration in <i>Tg</i> (<i>smyd1:m3ck</i>) fish and wild-type fish was 63.3% and 20.0%, respectively, of that in wild-type fish at 28°C. Microarray analysis revealed differential expression of 1249 transcripts in <i>Tg</i> (<i>smyd1:m3ck</i>) versus wild-type fish under cold stress. Biological processes that were significantly overrepresented in this group included circadian rhythm, energy metabolism, lipid transport, and metabolism. These results are clues to understanding the mechanisms underlying temperature acclimation in fish.</p>