Spinal muscular atrophy (SMA) is a devastating disorder primarily affecting newborns and young children. It is caused by reduced levels of the survival motor neuron (SMN) protein. Although normally present in all cells of the body, reduced levels of SMN protein results in degeneration of motor neurons, leading to muscle weakness and, in the case of severe disease, death. Our studies have uncovered that a small proportion of SMN protein is naturally released by cells in small "bubbles" called extracellular vesicles (EV). EV are normally involved in cell-to-cell communication, so EV released from one cell can be taken up by other cells elsewhere in the body. This raises the possibility of using EV to distribute SMN protein through the body. In this study, we will evaluate whether analysis of EV isolated from patient blood can be used as a marker for the disease state, which may allow us to develop a simple blood test to monitor the effectiveness of therapeutics. To explore the use of EV as a potential therapeutic, we will deliver a virus containing a good copy of the SMN gene to the liver of mice, such that the EV naturally produced by the liver will have enhanced levels of SMN protein for delivery to cells throughout the body. We will determine if this latter approach can lead to disease correction and extension of lifespan in the mouse model of SMA. Together, these studies will uncover novel approaches to disease management in patients with SMA.