SMN1 and proximal spinal muscular atrophy: With advances in understanding of the genetic basis of SMA, potential drug strategies include replacement or correction of the mutated SMN1 gene, modulation of the low-functioning SMN2 “back-up gene” that is unique to humans, neuroprotection of the motor neurons affected by loss of SMN protein, and muscle protection to prevent or restore loss of muscle function in SMA [6, 12].