Abstract Previous studies have investigated the physiological responses in the liver of Synechogobius hasta exposed to waterborne zinc (Zn). However, at present, very little is known about the underlying molecular mechanisms of these responses. In this study, RNA sequencing (RNA-seq) was performed to analyse the differences in the hepatic transcriptomes between control and Zn-exposed S . hasta . A total of 36,339 unigenes and 1,615 bp of unigene N50 were detected. These genes were further annotated to the Nonredundant protein (NR), Nonredundant nucleotide (Nt), Swiss-Prot, Kyoto Encyclopedia of Genes and Genomes (KEGG), Clusters of Orthologous Groups (COG) and Gene Ontology (GO) databases. After 60 days of Zn exposure, 708 and 237 genes were significantly up- and down-regulated, respectively. Many differentially expressed genes (DEGs) involved in energy metabolic pathways were identified, and their expression profiles suggested increased catabolic processes and reduced biosynthetic processes. These changes indicated that waterborne Zn exposure increased the energy production and requirement, which was related to the activation of the AMPK signalling pathway. Furthermore, using the primary hepatocytes of S . hasta , we identified the role of the AMPK signalling pathway in Zn-influenced energy metabolism.
Abstract DNA methylation and demethylation are crucial epigenetic modification and regulation for animal development, and their dynamic changes may affect skeletal muscle development. The ten-eleven translocation (Tet) family proteins are demethylases which are involved in the dynamic changes of DNA methylation. However, the expression pattern of Tet family genes and their role in myogenesis in fish remains unclear. In this study, the temporal and spatial expression profiles of Tet1 , Tet2 and Tet3 were assayed with RT-qPCR techniques in Chinese perch, Siniperca chuatsi . The obtained data showed that the expressions of three Tet family genes were differentially expressed at different development stages. Tet1 was expressed low at blastula stage, but highly expressed at gastrula stage, then remained low until hatching. The expressions of Tet2 and Tet3 were significantly increased at late gastrula and kept high expression before hatching stage. At the spatial level, the Tet1 expression was highest in gill tissue, moderate level in brain and slow muscle. Tet2 was similar to that of Tet1 except that it was expressed at a lower level in slow muscle, and Tet3 exhibited a higher expression level in gill and brain, a moderate level in fast muscle. Cosinor analysis turned out that the expression of Tet1 and Tet2 displayed a significant daily rhythm in fast muscle, but Tet3 did not show daily rhythmicity. Inhibiting the activity of Tet1/2 proteins by injecting Bobcat339 significantly reduced the expression of MyoD and MRF4 , but not MyoG and Myf5 , by which leads to the increase of the number of satellite cells and proliferating myoblasts. Together, the results suggest that Tet1/2 may target to MyoD and MRF4 resulted in DNA demethylation and promote their expression, and therefore stimulate myoblast differentiation.
Chinese perch (Siniperca chuatsi) is one of the commercially important fish species. Understanding the molecular mechanisms of skeletal muscle growth and development is helpful for selection breeding and improving the growth rate of Chinese perch. In this study, the histological and transcriptome differences in fast muscle of Chinese perch between 30 days post hatching (dph) and 60 dph were analyzed using histological section and high-throughput RNA-Seq. The results showed that the diameter of muscle fibers was primarily distributed in the range of 30-40 μm at 30 dph Chinese perch, whereas the diameter of muscle fibers was primarily distributed in the range of 40-50 μm at 60 dph, indicating that the diameter of muscle fibers was increased at 60 dph. A total of 465 differentially expressed genes (DEGs) were identified, including 136 up-regulated and 329 down-regulated genes. The down-regulated genes including Myh4, Eno3, Fos and Igfn1 are associated with muscle cell differentiation and fusion in Chinese perch. The up-regulated gene Tnni2 is closely related to fast muscle growth and development, and may be an important gene in regulating fast muscle growth of Chinese perch during 30 dph to 60 dph. The analysis of the protein-protein interaction network of DEGs also revealed that Fos, Junb and Egr1 may involve in the development of fast muscle in Chinese perch. The KEGG enrichment results showed that the significantly up-regulated genes in the 60 dph group were involved in several pathways related to fast muscle metabolism and protein synthesis, such as glycosphingolipid biosynthesis-globo and isoglobo series, glycosphingolipid biosynthesis-ganglio series and aminoacyl-tRNA biosynthesis. The transcriptome analysis suggests that the accumulation of proteins in the cytoplasm may be the main reason for the increase in fast muscle diameter in Chinese perch from 30 dph to 60 dph.
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