A differentially expressed enolase gene isolated from the gilthead sea bream (Sparus aurata) under high-density conditions is up-regulated in brain after in vivo lipopolysaccharide challenge

To investigate the effect of different population densities on gene transcription in the sea bream brain (Sparus aurata), the messenger RNA (mRNA) differential display (DD) technique was used to analyse gene expression. Sea bream were held at different densities, 6 or 26 kg m(-3), over a period of 14 days. We identified seven differentially expressed sequences of which one sequence was functionally identified. The S. aurata enolase gene homologue (S-enolase), pertaining to the alpha non-neuronal enolase group of the enzyme superfamily, was up-regulated in the brain of fish in the high-density population group. S-enolase mRNA expression was also found in other tissues including heart, liver and head kidney suggesting a ubiquitous nature. Furthermore, brain S-enolase mRNA is highly up-regulated 48 h after intra-peritoneal bacterial lipopolysaccharide (LPS) administration. Therefore, S-enolase gene expression is linked to the incidence of different stressors, density and infective agents, in the sea bream and may be a potential molecular biomarker for stress diagnosis in this fish. (C) 2004 Published by Elsevier B.V.