Analysis of long-lived C. elegans daf-2 mutants using serial analysis of gene expression

Abstract

We have identified longevity-associated genes in a long-lived Caenorhabditis elegans daf-2 (insulin/IGF receptor) mutant using serial analysis of gene expression (SAGE), a method that efficiently quantifies large numbers of mRNA transcripts by sequencing short tags. Reduction of daf-2 signaling in these mutant worms leads to a doubling in mean lifespan. We prepared C. elegans SAGE libraries from 1, 6, and 10-d-old adult daf-2 and from 1 and 6-d-old control adults. Differences in gene expression between daf-2 libraries representing different ages and between daf-2 versus control libraries identified not only single genes, but whole gene families that were differentially regulated. These gene families are part of major metabolic pathways including lipid, protein, and energy metabolism, stress response, and cell structure. Similar expression patterns of closely related family members emphasize the importance of these genes in aging-related processes. Global analysis of metabolism-associated genes showed hypometabolic features in mid-life daf-2 mutants that diminish with advanced age. Comparison of our results to recent microarray studies highlights sets of overlapping genes that are highly conserved throughout evolution and thus represent strong candidate genes that control aging and longevity.

Genes that may modulate longevity in C. elegans in both dauer larvae and long-lived daf-2 adults

“…A general decrease in metabolic activity for daf-2 adults was detected in a previous study (Halaschek-Wiener et al, 2005;McElwee et al, 2006), and here we describe the affected pathways, in common between daf-2 adults and dauer larvae. There is an indication that transcripts for enzymes of the TCA cycle are lowered in both types of long-lived worms, although mechanisms that might compensate for reduced TCA cycle activity appear to involve different pathways, fermentation in dauer larvae versus the glyoxylate shunt in daf-2 adults.…”

“…Whereas McElwee et al (2004) used cDNA microarrays for a similar comparison, we used Serial Analysis of Gene Expression, or SAGE (Velculescu et al, 1995) to identify potential novel regulators of life span, and to characterize the expression profiles of different gene families that were previously shown to be associated with aging (Lund et al, 2002;Murphy et al, 2003). SAGE data for daf-2 and wild-type adults were compared in a previous study (Halaschek-Wiener et al, 2005), which showed general inhibition of metabolism in the middleaged daf-2 adults.…”

Genomic approaches for the understanding of aging in model organisms

“…Comparison of the transcriptional profiles of the dauer stage with that of long-lived daf-2 showed that many DAF-16-dependent genes are common in both transcriptional outputs (22). Hierarchical clustering of genes with altered expression during aging in wild-type N2 and long-lived daf-2 identified one functional group of genes that is common to both strains as well as one that is specific for the N2 strain (20,22,23). Heat shock genes are induced until mid-age and then reduced in later life in both strains.…”

Insulin activates the insulin receptor to downregulate the PTEN tumour suppressor

“…This is also consistent with several daf-2 microarray and serial analysis of gene expression (SAGE) experiments. [22][23][24] DAF-28/Insulin and DAF-2/IR negatively regulate DAF-18/PTEN in neurons and intestine To gain insight into what tissues the DAF-28/Insulin and DAF-2/IR negatively regulate DAF-18/PTEN, we performed an in situ antibody staining on these mutants. Consistent with our immunoblots, we found that wild-type animals have low levels of DAF-18/ PTEN and is not detected in neurons or intestinal cells.…”