Project description:The transcriptional programs of ectothermic teleosts are directly influenced by water temperature. Although various cold-responsive transcriptional patterns have been determined in fishes, the systematic molecular networks governing the temperature responses are still unknown. We profiled the transcriptional responses in eight tissues of zebrafish exposed to graded cold temperatures, ranging from normal (28°C) to mild (18°C) and severe (10°C) cold, using RNA-seq. The tissues varied in the number of cold-responsive genes, of which the kidney appeared to be most sensitive, whereas the brain was the least. Fuzzy k-means clustering revealed 34 gene clusters of distinct expression patterns, demonstrating diverse tissue-specific responses in conjunction with multiple aspects of ubiquitous cross-tissue responses to cold. Thirty-one GO terms were over-represented upon cold treatment. These terms are involved in basic cellular processes, such as RNA splicing and proton transport, as well tissue-specific processes, such as ‘negative regulation of endopeptidase activity’ in the kidney. To identify the cis-regulatory elements governing the concerted cold responses, the promoters of the genes that demonstrated strong co-regulation were analyzed using an enriched motif discovery program, DREME. Eleven motifs, 6 known and 5 novel, were identified. These motifs belong to the genes corresponding to the 16 over-represented GO terms identified above. Some motifs, such as the AP-1 and STAT1 binding sites, are known to be stress responsive. By integrating comprehensive cold-induced transcriptional changes with a cis-motif identification tool, we identified genome-wide regulatory networks for the cold response in zebrafish. The identified networks provided new insights into molecular mechanisms of thermal responses in teleosts. Examination of gene expression of 24 samples (eight tissues at three temperatures)
Project description:Ambient temperature affects organisms comprehensively, however cold responses are different among tissues. Here, we adopt a transcript screening approach to explore and compare the cold responses in zebrafish gills and brain. Zebrafish were exposed to cold and the oligonucleotide-based microarray was used to identify cold-induced genes. Principle component analysis (PCA) of the gene expression profiles indicated that gills develop different strategies for the increasing of exposure period while brain relatively remained stable. Combining statistic and clustering methods, we found that gills showed higher protein metabolism and cell activity while brain showed higher stress responses and detoxification during cold acclimation. According to the microarray data sets, we extended the study on ionocyte- and isotocin neuron-related genes in gills and brain, respectively, and found these genes were broadly stimulated by cold. These data suggest that cold activates specific physiological functions in different tissues. Taken together, our results provide molecular evidences to elucidate the cold acclimation in zebrafish gills and brain. Keywords: Time course, Tissue types
Project description:The transcriptional programs of ectothermic teleosts are directly influenced by water temperature. Although various cold-responsive transcriptional patterns have been determined in fishes, the systematic molecular networks governing the temperature responses are still unknown. We profiled the transcriptional responses in eight tissues of zebrafish exposed to graded cold temperatures, ranging from normal (28°C) to mild (18°C) and severe (10°C) cold, using RNA-seq. The tissues varied in the number of cold-responsive genes, of which the kidney appeared to be most sensitive, whereas the brain was the least. Fuzzy k-means clustering revealed 34 gene clusters of distinct expression patterns, demonstrating diverse tissue-specific responses in conjunction with multiple aspects of ubiquitous cross-tissue responses to cold. Thirty-one GO terms were over-represented upon cold treatment. These terms are involved in basic cellular processes, such as RNA splicing and proton transport, as well tissue-specific processes, such as ‘negative regulation of endopeptidase activity’ in the kidney. To identify the cis-regulatory elements governing the concerted cold responses, the promoters of the genes that demonstrated strong co-regulation were analyzed using an enriched motif discovery program, DREME. Eleven motifs, 6 known and 5 novel, were identified. These motifs belong to the genes corresponding to the 16 over-represented GO terms identified above. Some motifs, such as the AP-1 and STAT1 binding sites, are known to be stress responsive. By integrating comprehensive cold-induced transcriptional changes with a cis-motif identification tool, we identified genome-wide regulatory networks for the cold response in zebrafish. The identified networks provided new insights into molecular mechanisms of thermal responses in teleosts.
Project description:Low temperatures may cause severe growth inhibition and mortality in fish. In order to understand the mechanism of cold tolerance, a transgenic zebrafish Tg (smyd1:m3ck) model was established to study the effect of energy homeostasis during cold stress. The muscle-specific promoter Smyd1 was used to express the carp muscle form III of creatine kinase (M3-CK), which maintained enzymatic activity at a relatively low temperature, in zebrafish skeletal muscle. In situ hybridization showed that M3-CK was expressed strongly in the skeletal muscle. When exposed to 13°C, Tg (smyd1:m3ck) fish maintained their swimming behavior, while the wild-type could not. Energy measurements showed that the concentration of ATP increased in Tg (smyd1:m3ck) versus wild-type fish at 28°C. After 2 h at 13°C, ATP concentrations were 2.16-fold higher in Tg (smyd1:m3ck) than in wild-type (P < 0.05). At 13°C, the ATP concentration in Tg (smyd1:m3ck) 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 Tg (smyd1:m3ck) 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.