PTEN and proximal spinal muscular atrophy: We have previously shown that depleting PTEN protein levels improves survival and growth cone size in cultured primary Smn-/- motor neurons.16 Furthermore, intramuscular administration of AAV6-siPTEN to an SMA mouse model resulted in the successful targeting of motor neurons.16 Here, we demonstrate that systemic targeting of PTEN using viral vectors reduces disease severity and modestly improves survival in a mouse model of severe SMA.