ABSTRACT/SUMMARY Inhibitors of the mTOR pathway are among the most promising interventions to target age-related dysfunction, however, there is a critical need to further define the pro longevity effects to facilitate clinical development of mTOR inhibitors. The current proposal will significantly advance this effort providing new targets for intervention and novel markers to monitor individual responses to mTOR inhibition. The overarching goal of this research program is to develop a mechanistic understanding of novel downstream targets of rapamycin, in order to facilitate safer and more effective strategies to promote healthy aging. Cellular senescence occurs in both somatic and stem cell populations and contributes to age-related dysfunction, and our laboratory has shown that mTOR inhibition using rapamycin, can prevent entry into the senescent state. The mTOR pathway also regulates senescence a n d pluripotency in a variety of stem cell populations. The central hypothesis of the application is that mTOR inhibition by rapamycin prevents senescence and enhances pluripotency by increasing the lncRNA H19. The rationale for this hypothesis is our observation that rapamycin increases levels of the non- coding RNA (lncRNA) H19. We find that levels of H19 decrease during senescence and in pluripotent cells. H19 plays a central role during development and differentiation, and maintenance of adult stem cell populations. Rapamycin increases H19 levels, prevents senescence and maintains pluripotency. The results suggest that increasing H19 levels in response to mTOR inhibition may play a dual role, inhibiting senescence while simultaneously increasing pluripotency in adult stem cell populations. The proposed work will provide transformative data regarding a novel mechanism for lifespan extension and improvement of late-life function in multiple tissues.