Characterization and transcript expression studies of interferon regulatory factors in Atlantic cod (Gadus morhua)

Inkpen, Sabrina M. (2014) Characterization and transcript expression studies of interferon regulatory factors in Atlantic cod (Gadus morhua). Masters thesis, Memorial University of Newfoundland.

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Abstract

The interferon regulatory factor (IRF) family of genes encode a group of transcription factors which have important roles not only in regulating the expression of Type I interferons (IFNs) and other genes in the interferon pathway, but also in growth, development and regulation of oncogenesis. In this study, several IRF family members in Atlantic cod (Gadus morhua) were characterized at the cDNA and putative amino acid level, allowing for phylogenetic analysis of these genes in teleost fish, and the development of paralogue specific PCR primers which were used in semi-quantitative RT-PCR and Quantitative PCR (QPCR) analyses. Two Atlantic cod Irf10 splice variants were identified and named Irf10-v1 and Irf10-v2, and their presence was confirmed by sequencing of the Irf10 genomic region. RT-PCR showed that Irf7, Irf8 and both Irf10 transcripts were detected in 15 cod tissues, while Irf4a and Irf4b appeared to be absent in some tissues. RT-PCR in embryo and larval samples showed unique transcript expression profiles of IRFs during development and indicated potential stage specific roles that will be investigated in future studies. QPCR analysis of spleen expression expanded upon previous studies, confirming that all transcripts were responsive to stimulation by the viral mimic poly(I:C) and showing that all except Irf4a were responsive to killed Aeromonas salmonicida (ASAL). Temperature was observed to affect the responsiveness of all except Irf4a to poly(I:C) and/or ASAL, supporting earlier studies. The effect of increased temperature on immune responsiveness to pathogens is of particular interest to Atlantic cod aquaculture in Newfoundland, where fish experience seasonal fluctuations in temperature.

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