Toxicogenomic analysis of Caenorhabditis elegans reveals novel genes and pathways involved in the resistance to cadmium toxicity

Background: Exposure to cadmium is associated with a variety of human diseases. At low concentrations, cadmium activates the transcription of stress-responsive genes, which can prevent or repair the adverse effects caused by this metal. Results: Using Caenorhabditis elegans, 290 genes were identified that are differentially expressed (> 1.5- fold) following a 4 or 24 hour exposure to cadmium. Several of these genes are known to be involved in metal detoxification, including mtl-1, mtl-2, cdr-1 and ttm-1, confirming the efficacy of the study. The majority, however, were not previously associated with metal-responsiveness and are novel. Gene Ontology analysis mapped these genes to cellular/ion trafficking, metabolic enzymes and proteolysis categories. RNA interference-mediated inhibition of 50 cadmium-responsive genes resulted in an increased sensitivity to cadmium toxicity, demonstrating that these genes are involved in the resistance to cadmium toxicity. Several functional protein interacting networks were identified by interactome analysis. Within one network, the signaling protein KEL-8 was identified. Kel-8 protects C. elegans from cadmium toxicity in a mek-1 (MAPKK)-dependent manner. Conclusion: Because many C. elegans genes and signal transduction pathways are evolutionarily conserved, these results may contribute to the understanding of the functional roles of various genes in cadmium toxicity in higher organisms.