Characterizing the Role of daf-16/C. elegans FOXO in Lifespan and Healthspan

In Caenorhabditis elegans (C. elegans), there is a single FOXO transcription factor homolog, encoded by the gene, daf-16. As a central regulator for multiple pathways, DAF-16 integrates these signals to result in changes in longevity, development, fat storage, stress resistance, innate immunity, and reproduction. One of the main advantages of using C. elegans is the ability to study FOXO in the context of the whole animal. Therefore, manipulating the levels or the activity of daf-16 results in visible, scorable phenotypic changes. DAF-16 is the downstream target of the conserved insulin/IGF-1 signaling (IIS) pathway, a PI 3-kinase signaling cascade that ultimately controls its nuclear localization. Since the IIS pathway is a major regulator of lifespan, almost all studies of lifespan modulation examine the requirement of daf-16. More recently, lifespan analysis has been accompanied by healthspan analysis, referring to the time an animal is healthy. In this chapter, I will focus on the assays to assess lifespan and healthspan of C. elegans FOXO/daf-16, in the context of a whole animal.