Pollution-affected fish hepatic transcriptome and its expression patterns on exposure to cadmium

Area of Science:

• Environmental toxicology
• Molecular biology
• Fish ecotoxicology

Background:

• Environmental pollution poses a significant threat to aquatic ecosystems.
• Assessing the impact of multiple pollutants on fish health requires sensitive and efficient methods.
• Gene expression profiling offers a powerful approach to understand toxicological responses in organisms.

Purpose of the Study:

• To develop and validate a multigene cDNA microarray for biomonitoring environmental pollutants in fish.
• To investigate the hepatic gene expression changes in *Lithognathus mormyrus* upon exposure to cadmium.
• To demonstrate the utility of the developed microarray as a tool for routine environmental threat assessment.

Main Methods:

• Construction of a *Lithognathus mormyrus* hepatic cDNA microarray using 4608 clones.
• Sequencing and annotation of cDNA clones to create a unique gene set.
• Exposure of fish to cadmium via feeding and injection, followed by microarray analysis of hepatic gene expression.
• Identification and analysis of differentially expressed genes.

Main Results:

• A microarray with 1494 unique annotated clones was successfully constructed.
• Cadmium exposure led to altered expression of 31 unique clones, with 23 genes downregulated.
• Key differentially expressed genes included metallothionein, cytochrome P450 2K5, and complement C31.
• The results suggest general toxicity due to intensive cadmium exposure.

Conclusions:

• A functional multigene cDNA microarray can be effectively used for routine biomonitoring of environmental threats.
• The developed tool demonstrates the capacity to identify specific toxicological responses in fish.
• This approach provides a foundation for developing biomarker indices for environmental risk assessment.