Aging is a degenerative process characterized by a progressive deterioration of cellular components and organelles resulting in mortality. The nematode Caenorhabditis elegans has been used extensively to study the biology of aging, and several determinants of C. elegans longevity are conserved in higher order organisms. The specific mechanisms of longevity in C. elegans have not been completely identified and many pathways are still poorly understood. Dietary restriction is one promising pro-longevity intervention, though like other aspects of longevity, its mechanism is also poorly defined. DR, a reduction in caloric intake in the absence of malnutrition, extends lifespan and has been found to delay the onset of age-associated disease, not only in C. elegans, but in a wide range of species including yeast, flies, mice, and primates. We are performing a genome-wide screen of the Vidal RNA interference (RNAi) Library, which has a catalog of 11,511 clones. By knocking down specific genes within the C. elegans genome through RNAi, we are able to observe an extension or reduction in longevity in response to DR. We will follow up on our collected data by measuring the full lifespans of all mutants that respond strongly in the screen. By screening such a large number of genes, the widespread effect, and hopefully mechanism, of DR will be elucidated. We hope to see genes significantly affected by DR cluster into groups with common functionality, or along the same pathway, and then follow up on those specific pathways to clarify the mechanisms underlying DR. If these pathways are conserved, research findings relating to C. elegans may be applicable to other organisms. We hope to confirm these results and further investigate the interaction between DR and other potential longevity pathways.

Although aging has been studied extensively, the molecular mechanisms of longevity are unclear. Dietary restriction (DR), a reduction in calories without malnutrition, increases lifespan in most model organisms tested, including rats, flies, and the round worm, Caenorhabditis elegans. Although DR is the most proven longevity-promoting intervention, the mechanism by which it works has not been fully elucidated. A reduction of metabolic rate and reduction of insulin signaling have been implicated in longevity, though neither appear to be sufficient on their own. Another highly supported mechanism of longevity includes the link between TOR (Target of Rapamycin) signaling and DR. Recent data suggests that TOR and DR act along the same pathway in respect to longevity; however, it is widely accepted that DR influences other pathways in addition to TOR. There are many approaches to DR in C. elegans. Using a bacterium carrying an RNAi plasmid, we feed the worms from egg through the first four days of adulthood and are therefore able to knockout specific genes in temperature sterile nematodes. The worms are then transferred to a liquid medium in the absence of the bacterial food. This process allows us to test the effects of dietary restriction on specific genes and determine whether the mutants will respond synergistically or antagonistically to the intervention. These results will be followed up to determine common pathways relating to longevity. Caloric intake was believed to be the sole mechanism of lifespan extension in DR; however recent data supports the idea that different mechanisms appear to be involved. This screen will provide us with a basis of which knockouts extend or shorten lifespan allowing us to relate the biology of DR with the pathways recognized as determinants of aging. If these pathways are conserved, these research findings may be applicable to other organisms.

Oxidative stress and aggregation of misfolded proteins have been linked to aging in a range of model organisms, including the nematode Caenorhabditis elegans. Reduced expression of genes involved in mitochondrial respiration, such as those coding for electron transport chain (ETC) components, have been found to ameliorate these decreases in lifespan. This rescue is thought to act through upregulation of the mitochondrial unfolded protein response (UPRmt) in a cell-non-autonomous manner. Induction of the UPRmt is essential for degradation of misfolded mitochondrial proteins, and has been correlated with longevity in ETC mutant worms. While the mechanism underlying the UPRmt and its effect on gene expression knockdown is not well understood, there is evidence that knockdown induces the UPRmt. Previous studies demonstrate that knockdown of ETC components, as well as knockdown of a subset of mitochondrial proteins both induce the GFP reporters for the mitochondrial chaperone, hsp-6. To identify novel genes involved in the UPRmt, we are performing a forward genome-wide RNAi screen using the hsp-6::GFP reporter and measuring the UPRmt activity by fluorescent microscopy. We expect genes induced by the UPRmt to cluster into groups with common functionality, or along the same metabolic pathways. These hits may include genes coding for the ETC or other mitochondrial proteins, as well as genes outside of the mitochondrion. We will follow up on our screen data results by sequence verifying RNAi mutants and completing full lifespans to elucidate the interaction between the UPRmt and gene knockdown.