Shared Transcriptional Signature in Caenorhabditis elegans Dauer Larvae and Long-lived daf-2 Mutants Implicates Detoxification System in Longevity Assurance

Abstract

In the nematode Caenorhabditis elegans, formation of the long-lived dauer larva and adult aging are both controlled by insulin/insulin-like growth factor-1 signaling. Potentially, increased adult life span in daf-2 insulin/insulin-like growth factor-1 receptor mutants results from mis-expression in the adult of a dauer larva longevity program. By using oligonucleotide microarray analysis, we identified a dauer transcriptional signature in daf-2 mutant adults. By means of a nonbiased statistical approach, we identified gene classes whose expression is altered similarly in dauers and daf-2 mutants, which represent potential determinants of life span. These include known determinants of longevity; the small heat shock protein/alpha-crystallins are up-regulated in both milieus. The cytochrome P450, short-chain dehydrogenase/reductase, UDP-glucuronosyltransferase, and glutathione S-transferase (in daf-2 mutants) gene classes were also up-regulated. These four gene classes act together in metabolism and excretion of toxic endobiotic and xenobiotic metabolites. This suggests that diverse toxic lipophilic and electrophilic metabolites, disposed of by phase 1 and phase 2 drug metabolism, may be the major determinants of the molecular damage that causes aging. In addition, we observed down-regulation of genes linked to nutrient uptake, including nhx-2 and pep-2. These work together in the uptake of dipeptides in the intestine, implying dietary restriction in daf-2 mutants. Some gene groups up-regulated in dauers and/or daf-2 were enriched for certain promoter elements as follows: the daf-16-binding element, the heat shock-response element, the heat shock-associated sequence, or the hif-1-response element. By contrast, the daf-16-associated element was enriched in genes down-regulated in dauers and daf-2 mutants. Thus, particular promoter elements appear longevity-associated or aging associated.