In long-lived mutant animals with decreased insulin/IGF-1 signaling activity, expression of many longevity-associated genes requires the forkhead transcription factor DAF-16/FOXO [1]. In order to understand the regulatory mechanisms for longevity control by DAF-16/FOXO, we have analyzed how DAF-16/FOXO functions in animal''s tissues to control the expression of its downstream target genes. We have found that DAF-16/FOXO acts in a cell-autonomous fashion to up- or down-regulate many of its target genes in long-lived
daf-2 mutant animals. In our analysis of
dod-8, a target gene that is regulated cell autonomously by DAF-16/FOXO, we find that DAF-16/FOXO can bind to both DAF-16/FOXO-associated element (DAE) [1] and other non-canonical sub-optimal sites that are located within the
dod-8 promoter. Moreover, the DAE site is essential for in vivo expression of
dod-8 in
daf-2 mutant animals. Interestingly, we have also found that nematode GATA factors also bind to the DAE site. We are currently addressing potential co-regulation of dod genes by DAF-16/FOXO and GATA factors. Long-lived animals with activation of DAF-16/FOXO only in the intestine display enhanced locomotion behavior at mid-age and increased lifespan [2]. In accordance with such benefits, we have found that intestinal DAF-16/FOXO activity acts cell non-autonomously to protect muscles that lack
daf-16/foxo from the deterioration that accompanies normal aging. Thus, intestinal DAF-16 must regulate certain signaling pathway(s) that influence the rate of aging of other tissues. Using RFP fusions, we showed that intestinal DAF-16/FOXO can turn on expression of certain DAF-16-regulated genes in
daf-16(-) tissues. Such cell non-autonomous regulation likely underlies the ability of intestinal DAF-16/FOXO to promote the survival of
daf-16(-) tissues. We are currently analyzing candidate RNAi clones that perturb the cell non-autonomous gene regulation by DAF-16/FOXO to identify the downstream signaling pathway(s) that mediate tissue crosstalk and longevity control. Reference: 1)Murphy, C. et al. (2003) Genes that act downstream of DAF-16 to influence the lifespan of Caenorhabditis elegans. Nature 427:277-83. 2)Libina, N., Berman, J., and Kenyon, C. (2003) Tissue-specific activities of C. elegans DAF-16 in the regulation of lifespan. Cell 115:489-502.