UBA1 and proximal spinal muscular atrophy: Because of the wide ranging therapeutic benefits of treatment with AAV9-UBA1 and the relevance of UBA1-mediated degeneration for multiple types of SMA, here, we set out to determine whether UBA1-dependent pathways are responsible for mediating defective sensory-motor connectivity in SMA and to identify UBA1 dependent mediators of degeneration.