Gene transcript changes in individual rainbow trout livers following an inflammatory stimulus

Area of Science:

• Comparative immunology
• Fish biology
• Molecular biology

Background:

• Inflammatory stimuli trigger the liver to produce acute phase proteins (APPs) for innate immunity and homeostasis.
• Understanding the conservation and variation of the acute phase response (APR) across vertebrates is crucial.

Purpose of the Study:

• To investigate transcriptional changes in rainbow trout liver following bacterial infection.
• To assess the extent of gene regulation affecting both cellular and plasma proteins during the APR.
• To explore the conservation and individual variation of the APR in vertebrates.

Main Methods:

• Rainbow trout (Oncorhynchus mykiss) were injected with Listonella (Vibrio) anguillarum bacterin.
• Transcriptional profiling of liver tissue was performed using microarray and quantitative RT-PCR.
• Gene expression changes were analyzed to identify up-regulated and down-regulated genes.

Main Results:

• Sixteen genes were up-regulated, including those involved in iron metabolism (hepcidin, haptoglobin, intelectin), suggesting iron sequestration as a key trout APR component.
• Twenty genes were down-regulated, unexpectedly including complement component 3 and alpha2-macroglobulin.
• Significant variations in gene expression were observed between individual fish, potentially explaining differences in disease susceptibility.

Conclusions:

• The capacity for an APR is conserved across vertebrates, but the specific genes involved vary significantly between species and individuals.
• Iron metabolism plays a critical role in the rainbow trout APR.
• Individual variation in gene expression during the APR may underlie natural differences in disease resistance.