BLACKSTONE, Neil; Northern Illinois University: Longevity and Environmental Signaling

The principal invertebrate model systems for studying longevity��worms and flies��have provided considerable insight into the molecular genetic mechanisms underlying aging. Nevertheless, these models have limitations: as adults, worms are completely post-mitotic and flies nearly so. Given the potential significance of stem cells as a therapeutic for aging, complementary model organisms would seem necessary, in particular, organisms that maintain active stem cell lineages for their entire ontogeny. In this context, colonial animals are of interest. Perhaps with the exception of the ascidians, colonial animals typically maintain active, multipotent stem cell lineages. In some environments, such animals may be extremely long lived. Such longevity may require the transduction of environmental signals into adaptive cellular and organismal responses utilizing stem cell populations. For instance, Podocoryna carnea, a colonial hydroid, modifies its growth and development in response to a range of environmental stimuli�light, temperature, food supply, substratum size, disturbance, competition, among others. At least two general mechanisms mediate cellular responses to these stimuli: shear stress and mitochondrial redox signaling. The former occurs in the cells lining the gastrovascular system in response to gastrovascular flow. The mitochondria-rich epitheliomuscular cells (EMCs) that are concentrated at polyp-stolon junctions mediate the latter. Since contractions of mitochondria-rich EMCs drive the gastrovascular flow, shear stress and redox signaling likely interact and typically reinforce each other to initiate adaptive cellular and organismal responses. In more complex animals, mechanisms for successful longevity may parallel these adaptive processes.