Pilot application of hepatic cDNA microarray of the sentinel fish striped sea bream as environmental biomarker

Feral organisms are affected by adverse environmental factors present in their habitat. It was hypothesized that transcript expression pattern in a suitable target organ of a sentinel feral organism compared to a reference transcript population may serve as a comprehensive biomarker of these adverse effects. This study was aimed at inquiring the applicability of such biomarker and establishing a procedure for its appropriate utilization. The examined system contains dual-labeled microarray-based evaluation of the hepatic transcript expression pattern in a sentinel fish sampled in two habitats, a polluted (Haifa Bay) and a clean (Dor) site, respectively, for two years. The hepatic expression patterns were compared to a reference RNA assumed to represent specimens that have no exposure history to pollution. The sentinel fish is Lithognathus mormyrus, which inhabits a marine coastal habitat along the Mediterranean coast of Israel. The hepatic transcript expression patterns were evaluated using a 1152-clone cDNA microarray, biased towards pollution-affected genes. The LIMMA software was used to calculate the log2 ratios of expressions (M) and to identify the differentially expressed genes in each sample (adjusted P<0.01). Keywords: Response of fish hepatic gene expression pattern to environmental conditions. Fish were sampled at each of two sites each year. All fish were hybridized to a common reference RNA population using a dye swap design. Hence, each fish was hybridized twice vs the reference RNA. The hybridization results were reanalysed by LIMMA using new division to samples.