SMN1 and proximal spinal muscular atrophy: Furthermore, the application of NAC to the SMN-knockdown cultures (from day 13 to day 24) significantly mitigated the reduction of the percentage of motile mitochondria (Fig. S1B) and the number and area of mitochondria in axons (Fig. S2B,D), confirming the protective effects of NAC against mitochondrial defects in both iPSC- and hESC-based SMA models.