Changes in miRNA Gene Expression Associated with ISA Virus Infection in Atlantic Salmon (Salmo salar)

Introduction: MicroRNAs (miRNAs) are an abundant class of endogenous small RNA molecules that downregulate gene expression at the posttranscriptional level. They play important roles in multiple biological processes by regulating genes that control developmental timing, growth, stem cell division and apoptosis by binding to the mRNA of target genes. We have recently identified and characterized miRNA genes in Atlantic salmon (Salmo salar). This has facilitated further studies on the role of miRNA genes in virus infections like ISA (Infectious Salmon Anaemia). In our present study we have studied changes in miRNA expression associated with ISA infection by analysis of miRNA expression levels in samples from nextgeneration sequencing (Illumina) followed by qPCR analysis of selected miRNAs. Four different tissues from ILA infected individuals were compared to tissue samples from healthy controls.  

Results: The miRNA expression profile of kidney, head kidney, gills and intestine showed that at least 20 miRNAs were expressed differently in infected versus healthy fish. Many of these miRNAs have been reported as associated with virus disease in other vertebrates. However, two miRNAs that were shown to be differentially expressed are novel to salmon, and thus, their function and target genes are still unknown.

 Conclusion: This is the first study showing association between ISA and miRNA expression. The miRNAs associated with ISA virus infection identified in this study provides a mean for better understanding the disease mechanisms.