PROJECT SUMMARY Aging can be defined as the progressive gradual decline in physiological function. It is the major risk factor for human pathologies that lead to disease, morbidity and mortality. Therefore, a better understanding of aging and the processes that affect lifespan at the molecular level remains an important problem in modern biology and medicine. Recent observations have highlighted a potential new process as a possible driver of aging and age- associated disease. As an organism ages, retrotransposon mRNA expression increases. What is lacking, at this point, is an understanding of how this retrotransposon expression can cause aging and aging-related phenotypes. Drosophila has long served as a very useful model system to understand the molecular underpinnings of aging. In addition to a relatively short lifespan, Drosophila has well-developed genetic tools and a long history of observations of the effects of age on the organism. To complement this is a long history of work to understand transposon biology in this organism. This makes Drosophila particularly well-suited to set up a new model to understand the role of retrotransposon activity in aging and aging-related phenotypes. The goals of this project are to set up and characterize a Drosophila system to understand whether transposon activity is a cause or effect of aging.