A major current focus is identifying endocrine pathways that coordinate aging and stress responses throughout the body. One study was undertaken to identify downstream pathways through which DAF-2 insulin receptor and AGE-1 PI3K signaling within a subset of cells regulates development and aging throughout the body. Our previous work suggested that DAF-2 and AGE-1 signaling regulated an endocrine output that controls aging and development in collaboration with DAF-16/FOXO, which is the major direct target of DAF-2 and AGE-1 signaling. To identify this parallel pathway, transcriptional microarrays were used to compared global gene expression in animals lacking AGE-1 PI3K signaling and two strains with AGE-1 PI3K-signaling restricted to specific tissues. This analysis identified specific transcripts that are regulated by endocrine outputs of AGE-1 PI3K signaling. Using RNA-interference and promoter deletion analysis, we are identifying the signaling pathways that couple to AGE-1 PI3K to regulate these targets. A second focus of our current work is defining molecular pathways that regulate the allocation of metabolic resources between somatic maintenance and other processes, such as reproduction. Aging can be slowed by processes that increase the maintenance and repair of the adult soma. Stressful conditions, such as nutrient depletion, activate these repair processes. Stress also impedes the distribution of resources to more costly processes, such as reproduction. Two active projects seek to identify pathways that regulate resource distribution under replete and stressful environments. One investigation has examined the factors that regulate synthesis of vitellogenin yolk proteins by intestinal cells. In reproductive adults, vitellogenins are synthesized by the intestine, transported to the gonad and stored by oocytes as a food source for developing embryos. Signaling by the DAF-2 insulin pathway regulates intestinal vitellogenin synthesis through unknown mechanisms. Our work has elucidated factors required for vitellogenin gene expression in response to DAF-2 signaling and other stimuli. In related work, we are examining cellular responses to nutrient stress. In several publications, we described a novel response to nutrient stress that could be visualized in C. elegans intestinal cells. This response is termed, FIRE, for Fasting-Induced Redistribution of Esterase activity. Under replete conditions with adequate nutrients, intestinal cells contain many cytoplasmic vesicles that are detectable by in situ esterase activity. When nutrients are removed, the cytoplasmic esterase activity is depleted and appears to redistribute to a nuclear, or perinuclear, localization. Using RNA-interference techniques, we have identified genes that regulate this cellular response to nutrient stress. These genes also affect growth, suggesting they provide a link between nutrient levels and growth processes. We are also examining the effects of aging on the FIRE response to determine whether FIRE-regulating genes might be altered during aging. Our work on xenobiotic response has focused on the bioactivity differences between methoxylated and hydroxylated stilbenes in C. elegans. We previously showed that methoxylation can enhance stilbene toxicity in C. elegans. We hypothesized that this may reflect differences in bioavailability and/or target interactions. To examine these possibilities, transcriptional microarrays were used to compare gene expression in response to short-term exposures at high concentrations of resveratrol, an hydroxylated stilbene, and pterostilbene, a methoxylated stilbene. Preliminary results indicate that a resveratrol and pterostilbene may regulate some overlapping targets, which would be consistent with the idea that their differing bioactivities reflect bioavailability differences. In addition, pterostilbene affects expression of additional genes unaffected by resveratrol, which may reflect target-specific differences in these compounds. Analysis of the microarray results is ongoing. Finally, we have characterized compounds with hormetic activity in C. elegans. Hormesis is the ability of a toxic compound to induce beneficial, protective effects at subtoxic doses. Using C. elegans, we conducted a small screen to identify natural products that exerted hormetic activity in a C. elegans lifespan assay. This screen identified one compound which extended lifespan at a non-toxic dose. A parallel screen was conducted by collaborators in the LNS to identify compounds that induce a Nrf transcriptional response in cultured mammalian cells. The Nrf response screen identified the same compound, suggesting that prolongevity activity in C. elegans may be mediated by the homologous gene. Current work aims to identify the structural aspects of this compound required for prolongevity activity. In addition, we are examining target genes induced in C. elegans by this compound.
| Wolkow, Catherine A (2010) New haystacks reveal new needles: using Caenorhabditis elegans to identify novel targets for ameliorating body composition changes during human aging. Interdiscip Top Gerontol 37:84-93 |
| Love, Dona C; Ghosh, Salil; Mondoux, Michelle A et al. (2010) Dynamic O-GlcNAc cycling at promoters of Caenorhabditis elegans genes regulating longevity, stress, and immunity. Proc Natl Acad Sci U S A 107:7413-8 |
| Shamir, Lior; Wolkow, Catherine A; Goldberg, Ilya G (2009) Quantitative measurement of aging using image texture entropy. Bioinformatics 25:3060-3 |
| Johnston, Josiah; Iser, Wendy B; Chow, David K et al. (2008) Quantitative image analysis reveals distinct structural transitions during aging in Caenorhabditis elegans tissues. PLoS One 3:e2821 |
