Molecular features and expression kinetics of interleukin-10 gene from the marine teleost, Snubnose pompano (Trachinotus blochii).

Background: Interleukin 10 (IL-10) is uniquely positioned in the immune regulation of teleosts. Modifying the IL-10 pathway changes the teleost's disease susceptibility; however, there is no data on its post-transcriptional regulation. Trachinotus blochii is a high-value mariculture species.
Methods: The full-length tbil-10 gene was generated through the Rapid Amplification of cDNA Ends-PCR. After the detailed sequence analysis, the identified features were compared with other IL-10 sequences. The gene expressions in healthy and challenged (Vibrio harveyi) fish were studied.
Results: The sequence analysis showed an open reading frame of 564 bp and a 3' UTR (untranslated region) of 217 bp. The phylogram revealed an evolutionary distinction between marine and freshwater teleost IL-10. The shorter 3' UTR, additional conserved cysteines capable of forming stable disulphide bonds, and lesser mRNA instability moieties suggest the better structural stability of teleost IL-10 than tetrapods. Results identified 60 miRNA-mRNA duplexes that can regulate IL-10 3' UTR. Nine identified miRNAs are involved in immune response and seven are expressed in macrophages. The gills showed the highest gene expression in healthy fish. The study discovered two IL-10 mRNA transcripts that differed in 5' UTR lengths and thermodynamic ensemble's free energy. There was an increased expression of both tbil-10-mRNA transcripts from 2 to 48 h post-challenge which peaked at 24 h after the challenge, with higher expression of short mRNA transcript.
Conclusions: The results gave insights into the structural, functional, post-transcriptional regulatory mechanisms, and expression characteristics of the IL-10 gene in T. blochii.
Competing Interests: Declarations. Ethical approval: The ‘European Union’s Animal Experiments Directive 2010/63/E.U.’ and the ‘United Kingdom’s Animals (Scientific Procedures) Act (1986)’ were followed in the handling of live animals (2019). ICAR-CMFRI approved the methods (BT/AAQ/3/SP28267/2018). Consent to participate: Not applicable. Consent for publication: We confirmed that all the authors have read and approved the manuscript. Competing interests: The authors declare no competing interests.
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