SMN1 and proximal spinal muscular atrophy: Previous studies have identified loss of nerve/muscle connectivity at the NMJ as one of the earliest and most important pathological events in SMA.23,24 We therefore examined the effect of targeting PTEN on NMJ pathology in SMN2+/+; SMNΔ7+/+; Smn-/- (SMNΔ7) mice, a well-characterized model of SMA.25 We injected 1010 vector genome of AAV6-siPTEN (n = 4 mice) or AAV6-scrambled-siPTEN (n = 4 mice) vectors into the levator auris longus (LAL) muscle of postnatal day 1 SMNΔ7 mice.