Identification of DAF-16/FoxO targets associated with longevity

FoxO transcription factors can promote longevity in invertebrates and mammals. In C.elegans, the FoxO family member DAF-16 is required for lifespan extension in the contexts of daf-2/IGFR mutation and germline ablation. The daf-16 genomic locus encodes three distinct groups of transcripts (a,b, and d/f/h). In animals with reduced insulin signaling or ablated germlines, mutations that reduce daf-16a and d/f/h levels without affecting daf-16b reduce lifespan to the same extent as daf-16 null mutations. We reasoned that identifying a set of targets of the daf-16a and d/f/h isoforms that are differentially regulated in two contexts of reduced insulin signaling and in germline ablated animals would enrich for the daf-16 transcriptional targets that are required for longevity. We identified targets that were differentially regulated in daf-2(e1368) and daf-2(e1370) mutants relative to wild-type, and differentially regulated in the opposite direction from WT in compound mutants with both daf-16(mg54), which eliminates the a and d/f/h isoforms, and daf-16(mu86) which is a predicted null allele. We performed a similar analysis in glp-1(e2141) germline ablated animals (omitting the wild-type comparison). We then identified daf-16 targets associated with longevity (dal genes) which were found in all three sets of comparisons. Overall design: 10 strains were profiled, with 5 biological samples of each strain, for a total of 50 samples. Synchronized populations were grown to day 1 of adulthood, then harvested for RNA. Animals were grown at 15C for the first 72 hours to permit dauer bypass, then upshifted to 20C, except for glp-1 strains which were grown at 25C to ablate the germline. Lifespan analysis was performed on a cohort from each sample to confirm expected phenotypes. Strains were wild-type (WT), daf-2(e1370), daf-16(mg54);daf-2(e1370), daf-16(mu86);daf-2(e1370), daf-2(e1368), daf-16(mg54);daf-2(e1368), daf-16(mu86);daf-2(e1368), glp-1(e2141), daf-16(mg54);glp-1(e2141), daf-16(mu86);glp-1(e2141).

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